Role

apoptosis, atherosclerosis, cancer, cellcycle, diabetes, differentiation, inflammation, ligand-independent roles, others, starvation

review articles (Rosen and Spiegelman 2001)

            1.  overview

                        a)  PPARg is a member of the ARF6 complex, a heterodimer of PPARg and RXRa which regulates the aP2 enhancer (Tontonoz, Graves et al. 1994)

            2.  expression

                        a)  fat cells (Lambe and Tugwood 1996)

                                    1)  white adipose tissue of the adult rat (Braissant, Foufelle et al. 1996)

                                    2)  expressed highly in adipose tissue (Dreyer, Krey et al. 1992)

                        b)  intestinal tissue

                                    1)  large intestine (Lambe and Tugwood 1996)

                                    2)  site specific expression

                                                a)  increased amounts along crypt to lumen (Mansen, Guardiola-Diaz et al. 1996)

                                    3)  expressed in M-S colon carcinoma cells (Gupta, Brockman et al. 2001)

                        c)  immune tissue (Braissant, Foufelle et al. 1996)

                                    1)  monocytes (Lambe and Tugwood 1996)

                                                a)  expression is lower in monocytes, but increases as the cells differentiate to macrophages in vitro (Thieringer, Fenyk-Melody et al. 2000)

                                                b)  monocytes treated with anti-ICAM-3, LPS, and PMA have induced PPARg expression (Pontsler, St Hilaire et al. 2002)

                                    2)  macrophages

                                                a)  human macrophages after differentiation [[Chinetti, 2000 #920], 1998 #747]

                                                            1)  resides in the nucleus of differentiating monocytes

                                                            2)  is responsive to ligand treatment, and activates reporters (Chinetti, Griglio et al. 1998)

                                                            3)  detected by Northern and Western blots           

                                                b)  activated macrophages (Ricote, Li et al. 1998)

                                                c)  macrophages from resting bone marrow have lower levels of PPARg mRNA (Ricote, Li et al. 1998)

                                                d)  activated peritoneal mps have high levels of PPARg mRNA (Ricote, Li et al. 1998)

                                                e)  macrophages, strong expression (Tontonoz, Nagy et al. 1998)check this reference

                                                f)  resting bone-marrow-derived macrhophages have low levels of PPARg mRNA (Ricote, Li et al. 1998)

                                                g)  primary macrophages and monocytic cell lines

                                                            1)  activated by oxLDL, M-CSF, and GM-CSF (Ricote, Huang et al. 1999)-25

                                                h)  human cultured mast cells express PPARg1 and PPARg2 mRNA (Sugiyama, Nonaka et al. 2000)

                                                i)  pancreatic stellate cells

                                                            1)  express transcriptionally active PPARg as measured by reporter assay (Masamune, Kikuta et al. 2002)

                                    3)  lymphoid tissues

                                                a)  spleen (red and white pulp) (Vidal-Puig, Jimenez-Linan et al. 1996)167

                                                b)  Peyer’s patches (Vidal-Puig, Jimenez-Linan et al. 1996)-168

                                    4)  T cells (Clark 2002)-86

                                                a)  human peripheral blood T cells (Clark 2002)-87

                                                b)  peripheral T lymphocytes (Wang, Frauwirth et al. 2002)

                                                            1)  increased expression of mRNA upon T cell stimulation (Wang, Frauwirth et al. 2002)

                        d)  retina (Braissant, Foufelle et al. 1996)

                        e)  skeletal muscle (Vidal-Puig, Jimenez-Linan et al. 1996)

                        f)  liver (Vidal-Puig, Jimenez-Linan et al. 1996)

                                    1)  hepatic stellate cells (Everett, Galli et al. 2000)-9

                                                a)  level is decreased upon plate on plastic (Everett, Galli et al. 2000)-9

                        g)  atherosclerotic lesions (Ricote, Huang et al. 1998; Tontonoz, Nagy et al. 1998)

                        l)  expression during rat embryonic development (Braissant and Wahli 1998)

                                    1)  E13.5 – first detected in CNS only, hindbrain

                                    2)  E15.5 – expressed in CNS,

                                    3)  E18.5 – mRNAs found only in BAT, at high levels

                        m)  adipogenesis (Saladin, Fajas et al. 1999)

                                    1)  3-6 fold increase of PPARg2 mRNA in the first 24 hours

                                    2)  PPARg1 mRNA is unchanged in first 24 hours of adipogenesis

                        n)  subcellular localization

                                    1)  PPARg is expressed primarily in the nucleus of macrophages (Chinetti, Griglio et al. 1998)

                        o)  placental development

                                    1)  PPARg is required for placental development, because the knockouts lack this (Lowell 1999)-(Barak 1999, Kubota 1999)

                                    2)  similar phenotype to the RXRa and RXRa/RXRb double knockouts

                        p)  foam cells

                                    1)  highly expressed in human and murine atherosclerotic lesions (Ricote, Huang et al. 1999)-25,29,30

                        q)  brown adipose tissue (Valmaseda, Carmona et al. 1999)

                                    1)  PPARg expression is maintained (maybe slight increase) as the cells differentiate in culture (Valmaseda, Carmona et al. 1999)

                        r)  rat adult expression (Braissant, Foufelle et al. 1996)

                                    1)  adipose tissue, immune system

                        s)  colon adneocarcinoma, human colonic mucosa, and cultured colon cancer cells (Yang and Frucht 2001)-14,15

                        t)  pancreatic cells

                                    1)  human pancreatic islet a-cells (Schinner, Dellas et al. 2002)

                                    2)  pancreatic cancer cell lines:  MIAPaca-2, PANC-1, and BxPC-3 cells all express PPARg (Toyota, Miyazaki et al. 2002)

                                                a)  express a functional PPARg, induced reporter activity in these cells (Toyota, Miyazaki et al. 2002)

                        u)  VSMCs (Sugawara, Uruno et al. 2002)-15

                        v)  fibroblast cells, synovial

                                    1)  RTPCR confirmed expression of PPARg in human synovial cells, and PPARg is transcriptionally active (Fahmi, Pelletier et al. 2002)

                        w)  leukemic cells

                                    1)  PPARg is expressed in leukemic cell lines (Yamakawa-Karakida, Sugita et al. 2002)

                        x)  prostate cancer cells

                                    1)  expressed in prostate cancer and prostatic intraepithelial neoplasia patients, but not in normal prostate cells (Segawa, Yoshimura et al. 2002)

            3.  PPARg mutations

                        a)  P12A, P115Q mutations have little effect on insulin sensitivity (Kersten, Desvergne et al. 2000)

                        b)  dominant negative at 290 and 467 (Barroso, Gurnell et al. 1999)

                                    1)  severe insulin resistance

                        c)  K319A or L469A

                                    1)  mutation of K319A or L469A prevents ligand binding (Chen, Johnson et al. 2000)

                        d)  L468A/E471A  - acts as a dominant negative forms

                                    1)  PPARg L468A/E471A can bind to ligand and DNA but not to coactivators (Wang, Fu et al. 2001)-26

Role Inflammation

role in GI tract in inflammation (Auwerx 2002)

review of antiinflammation role (Welch, Ricote et al. 2003)

            1.  suppression of inflammatory cytokines (Jiang, Ting et al. 1998; Ricote, Li et al. 1998)

                        a)  PPARg stops inflammatory product production

                                    1)  stimulation with 15-d-PGJ2 stops production of inflammatory products (Jiang, Ting et al. 1998) by mononuclear cells irt PMA treatment

                                                a)  inhibits expression of iNOS, gelatinase B (MMP-9), and scavenger receptor A genes in response to 15d-PGJ2 and synthetic PPARg ligands (Ricote, Li et al. 1998)

                                                b)  lowers induction of nitrite production (Ricote, Li et al. 1998)

                                    2)  troglitazone and 15d-PGJ2 inhibit induction of TNFa by LPS, phorbol ester, and okadaic acid in human monocytes (Jiang, Ting et al. 1998)

                                    3)  PPARg agonists inhibit monocyte elaboration of inflammatory cytokines at agonist levels similar to those which promote adipogenesis (Jiang, Ting et al. 1998)

                                    4)  NSAIDs inhibit cytokines (Jiang, Ting et al. 1998)

                                                a)  TNFa, IL-1b, and IL-6

                                    5)  PPARg ligands in primary human monocytes block phorbol ester induction of TNFa, IL-6, and IL1b (Ricote, Huang et al. 1999)-27

                                    6)  PPARg ligands inhibit induction of iNOS, gelatinase B (MMP-9) and scavenger receptor A transcription (Ricote, Li et al. 1998; Chinetti, Fruchart et al. 2000)-64

                                    10)  inhibit the expression of E-selectin of human vascular endothelial cells in response to TNFa (Nawa, Nawa et al. 2000)

                                                a)  troglitzaone, pioglitazone, a-clofibrate, and PGJ2 inhibited expression of an E-selectin reporter

                                                b)  LRF/ATF3 (liver regenerating factor 1/activating transcription factor 3) bound to the NF-ELAM1 site and repressed transcription of E-selectin in response to TNFa

                        b)  PPARg inhibits TNFa production

                                    1)  inhibits TNFa production induced by PMA treatment in peripheral blood mononuclear cells (Jiang, Ting et al. 1998)

                                                a)  appears to be regulated through inhibition of TNFa mRNA expression (Jiang, Ting et al. 1998)

                                                            1)  promoter luciferase construct and cotreatment with troglitazone, PGJ2, and PMA

                        c)  may antagonize AP-1, STAT, and NFkB  families of transcription factors (Chinetti, Griglio et al. 1998)-38

                                    1)  PPARg can bind and inactivate NFkB to stop inflammatory responses (Ricote, Li et al. 1998)

                                    2)  PPARg interferes with NFkB in reporter assays in human macrophages (Chinetti, Griglio et al. 1998)

                                    3)  PPARg inhibits AP-1, NFkB, STAT1, and Ets transcription factors (Ricote, Huang et al. 1999)-23,28 (reviewed in (Ricote, Huang et al. 1999))

                                    4)  reduce binding of AP-1 upstream of MMP-1 gene, preventing its transcription (Fahmi, Pelletier et al. 2002)

                                                a)  MMP-1 secretion is decreased in cells treated with increasing PPARg ligand concentration (Fahmi, Pelletier et al. 2002)

                                                b)  PMA induction of MMP-1 is still inhibited by 10mM PGJ2

                                    5)  expression of constitutively active isoform of PPARg in endothelial cells lowers AP-1 activation (Wang, Verna et al. 2002)

                        d)  iNOS

                                    3)  not induced upon PPARg treatment (Ricote, Li et al. 1998)

                                    4)  PPARg inhibits iNOS by antagonizing AP-1, STAT, and NFkB (Ricote, Li et al. 1998)

                                    5)  coinjection of PPARg ligands with LPS (10ug) and IFNg (10ug) into a rat brain prevents the induction of iNOS usually seen with just injection of LPS and IFNg (Heneka, Klockgether et al. 2000)

                                                a)  iNOS expressed primarily in CGCs, and not glial cells

                                                b)  protective effects were stimulated by ibuprofen, troglitazone, or 15d-PGJ2

                                    6)  PPARg activation inhibits antracellular signaling cascades like NFkB that regulate inflammation and apoptosis (Gupta, Polk et al. 2001)-28,29

                                    7)  NOS-2 RNA production in response to LPS/IFNg treatment in RAW cells is inhibited by some PPARg ligands (Castrillo, Mojena et al. 2001)

                                                a)  RAW cells pretreated with PPARg ligand for 5 minutes, followed by 18 hours with LPS and IFNg

                                                b)  15dPGJ2 and L796,449 inhibited some, while rosiglitazone at single-digit micromolar concentrations did not

                        e)  NFkB

                                    1)  NFkB binding activity in response to LPS/IFNg treatment of RAW cells is decreased by pGJ2 and L796,449, but not rosiglitazone (Castrillo, Mojena et al. 2001)

                                                a)  conversely, IkB protein levels are not decreased as much in the presence of 15dPGJ2 and L796,449 (Castrillo, Mojena et al. 2001)

                                                b)  NFkB-mediated reporter activity in RAW 264.7 cells was lowered by both 15dPGJ2 and L796,449 but not 10mM rosiglitazone (Castrillo, Mojena et al. 2001)

                                    3)  expression of a constitutively active isoform of PPARg in endothelial cells represses AP-1 and NFkB activity (Wang, Verna et al. 2002)

                        e)  TGFb signaling

                                    1)  PPARg inhibits TGFb induced gene expression by inhibiting Smad3 signaling (Fu, Zhang et al. 2001)

                                                a)  PPARg activators inhibit TGFb-induced CTGF expression in human aortic smooth muscle cells (Fu, Zhang et al. 2001)

                                                            1)  reversed by PPARg antagonist treatment

                                                            2)  reversed by Smad3 overexpression (Fu, Zhang et al. 2001)

            2.  inhibits inflammation caused by LPS

                        a)  15d-PGJ2 has no effect on inflammation induced by LPS (Jiang, Ting et al. 1998)

                        b)  no effect on inflammation

                                    1)  PPAR agonists had no effect on the production of IL-6 and TNFa in cultured human macrophages and monocytes in response to LPS or PMA treatment (Thieringer, Fenyk-Melody et al. 2000)

                        c)  rosiglitazone at 1uM inhibits a large number of LPS target genes (Welch, Ricote et al. 2003)

                                    1)  PPARg dependent at 1uM, but at higher concentrations seems to be PPARd dependent

                                    2)  inhibits genes involved in acquired immunity including IL-12, IP-10, and monokine induced by IFNg (Welch, Ricote et al. 2003)

                        d)  PPARg expression pattern reflects its inhibition of inflammation, since it is highly expressed in macrophages recovered from peritoneal exudates after 3 days of inflammatory stimulus, but not in resident macrophages (Welch, Ricote et al. 2003)-16

            3.  PPARg reduces nitritie production

                        a)  reduce nitrite production

                                    1)  in RAW264.7 murine mps, PG-J2 and Wy reduce nitrite accumulation

                        b)  some PPARg ligands stop NO synthesis in RAW cells following 18 hours of LPS/IFNg treatement (Castrillo, Mojena et al. 2001)

                                    1)  macrophages treated pretreated with PPARg ligands for 5 mins, followed by treatment with 200ng

                                    2)  Rosiglitazone did not stop

                                    L796,449, L165,041, and 15dPGJ2 all stopped

            4.  MMP-9 - matrx metalloprotein 9

                        a)   PPARg ligands inhibit the induction of this gene (Chinetti, Fruchart et al. 2000)-64

                        b)  PPARg ligands sotp this excretion of this gene also (Chinetti, Fruchart et al. 2000)-24, 26

                                    1)  inhibit the induction of MMP-9 promoter activity (Ricote, Li et al. 1998)

                        c)   function – is excreted in response to inflammatory cytokines and degrades the ECM, leading to atherosclerotic plaque rupture and thrombosis in the artery plaques 


            5.  effect of PPARg agonists on macrophage cytokine production (table 1 from (Moore, Fitzgerald et al. 2001))

 

Stimulus

Effect of PPARg Stimulation

PPARg ligand

Conc.

Species

Cellular System

Ref

LPS

No change:  TNF

Troglitazone

30mM

human

monocytes

8

 

No change:  IL-6, TNFa

L-165,041

L165,461

L-796,449

AD05075

1-100mM

Human

monocytes, macrophages

10

 

Increased:  TNFa

Rosiglitazone

1-100mM

rat

peritoneal macrophages

19

 

Increased TNFa, IL6

AD-5075

10mg/kg 5 days

mouse

in vivo:  db/db mice, C57/BL6J mice

10

 

Decreased:  TNFa, IL6

Troglitazone

Rosiglitazone

Ciglitazone

60mM

100mM

50mM

Mouse

ES-derived macrophages

7

PMA

Decreased:  TNFa, IL-6

Trogrlitazone

1-100mM

Human

Monocytes

8

 

Increased:  IL-6

Troglitazone

10-30mM

Mouse

ES-derived macrophages

6

 

No change:  IL-6, TNFa

L-165,041

L-165,461

L796,449

AD-5075

1-100mM

 

Human

monocytes, macrophages

10

 

 

 

 

 

 

 

            6.  inflammatory bowel disease

                        a)  ligands for PPARg seem to have benerficial effects in inflammatory bowel disease (Lazar 2002)-(Su 1999, Desreumaux 2001)

            7.  inhibits pancreatic stellate cells from causing fibrosis

                        a)  PSC proliferation in response to PDGF is inhibited by cotreatment with PPARg ligands [Masamune, 2002

                        b)  inhibits MCP-1 expression [Masamune, 2002 #1204]

            8.  epithelial cells

                        a)  15d-PGJ2 induces epithelial cell apoptosis (Clark 2002)-75

                        b)  thiazolidinedione decreases levels of IL-8, MCP-1 in human aortic epithelial cells (Clark 2002)-76

                        c)  troglitazone increases basal ICAM-1 expression but inhibits TNFa induced ICAM-1 expression (Clark 2002)-77

            9.  endothelial cells

                        a)  adenovirus-mediated expression of a constitutively active PPARg (Wang, Verna et al. 2002)

                                    1)  significant activation of PPARg target genes

                                    2)  suppressed expression of vascular adhesion molecules in ECs and ensuing leukocyte recruitment

                                    3)  downregulation of AP-1 and NFkB activity

Role Differentiation

            1.  differentiation of adipocytes (A. Transcription Factors)

                        **   reviews (Spiegelman 1998)

                        a)  PPARg is required for adipogenesis

                                    1)  fibroblasts from PPARg wt or knockout embryos (Lowell 1999)-(Kubota 1999) or ES cells ((Lowell 1999)-Rosen 1999) express normal C/EBPb and d in response to differentiation protocol, but have low C/EBPa levels, no aP2 or leptin, and don’t accumulate lipid

                                    2)  PPARg knockouts infected with PPARg2 recover adipogenesis, but C/EBPa do not (Rosen, Hsu et al. 2002)

                                    3)  C/EBPa cannot induce adipogenesis in the absence of PPARg2 (Rosen, Hsu et al. 2002)

                                    4)  3T3-L1 adipocytes with overexpressed dominant negative mutant that lacks the 16 carboxyl terminal aminoacids inhibits adipogenesis

                                                a)  reduced cell size, intracellular TAG content, increased lipolysis, reduced FFA uptake, reduced mRNA for free fatty acid metabolism enzymes, lower GLUT4, lower IR, lower insulin receptor substrate (IRS), lower c/EBP mRNAs, reduced IRS2 concentration, and lower insulin-stimulated glucose uptake (Tamori 2002 2045)

                        b)  PPARg overexpression in fibroblasts can induce differentiation into lipid-storing adipocytes (Tontonoz, Graves et al. 1994; Tontonoz, Hu et al. 1994; Hu, Tontonoz et al. 1995; MacDougald and Lane 1995; Tontonoz, Hu et al. 1995)

                        c)  expression of PPARg2 during differentiation of 3T3-L1 preadipocytes

                                    1)  PPARg2 protein increases only 2-fold during 3T3-L1 preadipocyte differentiation (Thuillier, Baillie et al. 1998)

                                    2)  as 3T3-L1 cells began to differentiate, PPARg2 accumulated around developing lipid droplets (Thuillier, Baillie et al. 1998)

                                    3)  RXRa protein accumulates upon fat cell differentiation by several fold (Thuillier, Baillie et al. 1998)

                                                a)  this is what seems to be important for PPARg signaling

                                                b)  mRNA levels are static

                                    4)  PPARg target aFABP increases earlier than normal when cells are cotreated with pioglitazone in addition to insulin (Thuillier, Baillie et al. 1998)

                        d)  PPARg ligands can induce differentiation

                                    1)  pRB knockout mice (Hansen, Petersen et al. 1999) (see pRB sectionRb)

                                    2)  PPAR can induce the differentiation of adipocytes (202 Spiegelman 1997)

                        e)  PPARg activation can also induce brown adipocyte differentiation from precursors (Tai, Jennermann et al. 1996)

                        f)  forced PPARg and C/EBPa expression in myoblastic cells treated with PPARg ligands suppresses osteoblastic differentiation of bone marrow stromal cells (Bar-Tana 2001)-(Gimble 1996)

                        g)  human data

                                    1)  TZDs cause increase in adipose mass in humans in vivo (Bar-Tana 2001)-(Mori 1999, Akazawa 2000)

                        h)  thiazolidinediones convert the differentiation of myoblasts to adipocytes instead (Grimaldi, Teboul et al. 1997)

                        i)  only PPARg2 (not PPARg1) is required for adipocyte differentiation

                                    *  see review article also (Lazar 2002)

                                    a) retroviral expression of PPARg1 in ZFP54-overexpressing cells (ZFP54 stops PPARg1 and PPARg2 transcription) does not recover adipocyte differentiation, although PPARg2 does (Ren, Collingwood et al. 2002)

                        j)  NIH 3T3 non-adipocyte cells

                                    1)  when infected with PPARg retrovirus, cells were able to differentiate to adipocytes (Okuno, Arimoto et al. 2002)

                        k)  PPARg1 forced expression in PPARg -/- cells can respond to rosiglitazone treatment to cause adipocyte differentiation (Mueller, Drori et al. 2002)

                                    1)  activate the same target genes, same fatty acid uptake also (Mueller, Drori et al. 2002)

                                    2)  at lower ligand concentrations, PPARg1 is less efficient at causing differentiation, although they have similar ligand binding ability  (Mueller, Drori et al. 2002)

            2.  monocyte and macrophage differentiation (Ricote, Huang et al. 1998; Tontonoz, Nagy et al. 1998)

                        a)  prostaglandin D2 synthase is expressed in these cells as well

                                    1)  required for 15d-PGJ2 synthesis

                                    2)  predominantly expressed in macrophages and specialized APCs (Ricote, Li et al. 1998)-11

                        b)  activation with PPARg and/or RXR ligands causes induction of CD14, a marker of monocyte differentiation (Ricote, Huang et al. 1999)-30,36

                        c)  not required for macrophage development

                                    1)  macrophage growth factors stimulated the PPARg deficient embryonic stem cells to become macrophages without defects (Moore, Fitzgerald et al. 2001)-6,7

                                    2)  macrophage functions such as phagocytosis and cytokine production were unaffeceted in the knockout cells (Moore, Fitzgerald et al. 2001)-6

                        d)  PPARg is important for monocyte differentation

                                    1)  PPARg is induced during myelomonocytic differentiation

                                    2)  PPARg ligands promote differentiation of myelomonocytic cells

                        e)  expression in 3T3-L1 fibroblasts causes differentiation into adipocytes (Tontonoz, Hu et al. 1994; Brun, Tontonoz et al. 1996)

                        f)  C/EBPb and C/EBPd regulate PPARg, which regulates C/EBPa (reviewed in (Lowell 1999))

                                    1)  PPARg knockout cannot differentiate into adipocytes (Lowell 1999)-(Kubota 1999 and Rosen 1999)

                        g)  activation of myelomonocytic cells causes changes in monocytic differentiation, promotes oxLDL uptake through activation of CD36 (Tontonoz, Nagy et al. 1998)

                        h)  PPARg null macrophages are not deficient in mp differentiation, or for phagocytosis and inflammatory cytokine production (Clark 2002)

            3.  muscle cells

                        a)  although pGJ2 prevents differentiation of precursors to muscle cells, it is not through a PPARg-dependent mechanism (Hunter, van Delft et al. 2001)

                        b)  L-805645 and ciglitazone did not repress the myogenic program or reduce expression of endogenous MyoD in C2C12 cells (Hunter, van Delft et al. 2001)

                        c)  overexpression of PPARg in precursors does prevent the differentiation to muscle cells (Hunter, van Delft et al. 2001)

            4.  mouse placenta

                        a)  at day 10.0 during embryonic development, there are clear placental alterations (Michalik, Desvergne et al. 2002)-(Barak 1999, Kubota 1999)

                                    1)  vascular problems – fetal vesels do not properly invade the labyrinth, and maternal vessels are dilated and ruptured (Michalik, Desvergne et al. 2002)-(Barak 1999)

                                    2)  do not accumulate lipids in the labyrinthine barrier

            5.  adipogenic steatosis

                        a)  PPARa knockout cells infected with adenovirus PPARg1 expressing virus model system (Yu, Matsusue et al. 2003)

                                    1)  had steatosis of the liver, large induction of fatty acid genes in these cells

                                    2)  steatosis was different than that induced by starvation

            6.  anti-osteogenic

                        a)  genistein activation of PPARg at higher doses prevents the ostergenesis seen at lower doses (Dang, Audinot et al. 2003)

                                    1)  in KS483 cells, peat at 1uM, followed by decrease at lower levels due to PPARg activation (Dang, Audinot et al. 2003)

Cell cycle and apoptosis

            1.  PPARg stops proliferation

                        a)  activation of PPARg inhibits proliferation of some cell lines and blocks growth of some tumors in mice (Altiok, Xu et al. 1997; Tontonoz, Singer et al. 1997; Mueller, Sarraf et al. 1998; Sarraf, Mueller et al. 1998)

                        e)  THP-1 monocytes express PPARg.  When exposed to oxidized low-density lipoproteins, differentiate into lipid-accumulating macrophages (Ricote, Huang et al. 1998; Tontonoz, Nagy et al. 1998)

                        f)  MCF-7 cells stop proliferating in response to PGJ2 treatment (Wang, Fu et al. 2001)

                                    1)  higher G1 phase after 48 hr treat with 10uM PGJ2

                                    2)  lower Rb phosphorylation

                                    3)  abolished by overexpression of cyclin D1

                        i)  induces growth arrest of fibroblasts (Altiok, Xu et al. 1997)

                                    1)  growth arrest correlates with rise in E2F (Altiok, Xu et al. 1997)

                        j)  ciglitazone and PGJ2 inhibit the cell proliferation in response to PDGF (Everett, Galli et al. 2000)-9

                        k)  p21 half-life is shortened by TRO and RSG treatment (Wakino 2001 47650)

                                    1)  PPARg ligands attenuate mitogen-induced p21Cip1 expression at the post-translational level by enhancing PTPase activity, and decreasing PKCd phosphorylation and activity in rat aaortc smooth muscle cells (Wakino 2001 47650)

                                    2)  PPARg ligands lower PKCd activity in response to PPARg ligand treatment (Wakino 2001 47650)

                                    3)  overexpression of PKCd removes the inhibition in response to PPARg ligands (Wakino 2001 47650)

                        l)  B cell proliferation is inhibited by PPARg (Setoguchi, Misaki et al. 2001)

                                    1)  haploinsufficiency results in enhanced B cell proliferation in response to LPS and antibody stimulation (Setoguchi, Misaki et al. 2001)

                                    2)  treatment with PPARg reduced apoptosis (Setoguchi, Misaki et al. 2001)

                                    3)  NFkB levels were constitutively higher in B cells taken from haploinsufficient PPARg mice (Setoguchi, Misaki et al. 2001)

                        n)  T cells treated with PMA at the same time as PPARg agonists don’t show as much activation as T cells treated with PMA alone (Clark 2002)-88

                                    1)  15d-PGJ2 was more efficacious than other PPARg ligands (3-100uM versus 25-100mM)

                                    2)  possibly mediated through PPARg-dependent inhibition of IL-2 secretion (Clark 2002)-86,87

                        o)  rosiglitazone inhibits capillary endothelial cell proliferation at low doses in vitro, but does not affect tumor cells (Panigrahy, Singer et al. 2002)

            2.  PPARg induces apoptosis

                        a)  BRL49653 and PG-J2 (20nM and 100nM) induce cell death (Chinetti, Griglio et al. 1998)

                                    1)  TUNEL assay

                        b)  cotreatment with TNFa/IFNg and PPARg ligands caused higher cell death (Chinetti, Griglio et al. 1998)

                        c)  colon cancer cells (HT-29) treated with PPARg ligands (ciglitazone 10mM) undergo apoptosis (Yang and Frucht 2001)

                                    1)  three day treatment have apoptosis

                                    2)  potentiation with cotreatment with 9-cis-RA

                                    3)  caspase inhibition with ZVAD-fmk inhibits ciglitazone (10mM)-mediated induction of apoptosis in a dose-dependent manner (Yang and Frucht 2001)

                        d)  treatment of T cells with 10uM PGJ2 or 100uM ciglitazone induces apoptosis (Wang, Frauwirth et al. 2002)

            3.  PPARg affects LPS/IFNg induced apoptosis

                        a)  ibuprofen and troglitazone both partially inhibit apoptosis induced by LPS and IFNg

                                    1)  injection of LPS and IFNg induces apoptosis and necrosis of brain tissue in rats, as measured by TUNEL staining and chromatin condensation (Heneka, Klockgether et al. 2000)

                                    2)  this effect was not seen when coinjection of a COX inhibitor (instead of PPARg ligand) was performed (Heneka, Klockgether et al. 2000)

            4.  mechanism of PPARg inhibition of cell cycle

                        a)  ligand activation of 3T3 fibroblasts or HIB-1B adipocyte line stops expression of PP2A, which prevents dephosphorylation of its targets including transcription factors E2F/DP which leads to cell cycle withdrawal (Altiok, Xu et al. 1997)

            5.  anti-cancer roles

                        b)  TZD cause differentiation and withdrawal from the cell-cycle of human liposarcoma cells (Tontonoz, Singer et al. 1997)

                        c)  TZD treatment in breast cancer cell lines causes lipid accumulation, expression of genes associated with a more differentiated state, and reduction in the growth rates and clonogenic capacities of cells (Mueller, Sarraf et al. 1998)

                        d)  combined treatment of MCF7 breast tumors in immunodeficient BNX mice with TZDs and all-trans retinoic acid causes apoptosis and fibrosis of the cells (Koshizuka 1998 8806)

                        g)  troglitazone strongly inhibits tumor cell line growth (Sarraf, Mueller et al. 1998)

                        m)  pancreatic cancer cell replication is inhibited by PPARg ligand treatment (Toyota, Miyazaki et al. 2002)

                                    1)  Tro causes a reduction in Thymidin incorporation and increases G1 phase presence (Toyota, Miyazaki et al. 2002)

                                    2)  Tro inhibits Cyclin D1 expression, and E2F (Toyota, Miyazaki et al. 2002)

            6.  anti-apoptosis effects

                        a)  FL5.12 cells withdrawn from IL-3 exposure undergo apoptosis, but this is inhibited by the presence of PPARg and more by presence of ligand (Wang, Frauwirth et al. 2002)

                                    1)  seems correlated with enhanced PPARg reporter activity (Wang, Frauwirth et al. 2002)

                                    2)  delays death for a number of hours, esp in presence of ligand (Wang, Frauwirth et al. 2002)

                                    3)  prevents drop in mt membrane potential that normally occurs upon withdrawal of IL-3 from these cells

 

Role in Cancer

            brief review in (Ricote, Huang et al. 1999), noting few articles on this subject

            1.  colorectal cancer

                        a)  PPARg agonists inhibit colorectal cancer

                                    1)  PPARg agonists inhibit the growth of human colorectal cancer cells (Wang, Fu et al. 2001)-8,55

                                    2)  PPARg ligands induce differentiation and inhibit growth (Ricote, Huang et al. 1999)-83

                                                a)  BRL49653 and troglitazone inhibit growth of a number of different colon cancer cell lines

                                                b)  increase four genes repressed in malignancy

                                                c)  reduce tumor size in troglitazone-treated nude mice

                                    3)  PPARg ligands inhibit cell proliferation and anchorage-independent growth (Burris, Pelton et al. 1999)

                                    4)  PPARg heterozygotes are more susceptible to azoxymethane-induced colon cancer than wild type counterparts (Girnun, Smith et al. 2002)

                        b)  PPARg agonists promote colorectal cancer

                                    1)  PPARg agonists promote intestinal tumorigenesis in the Min mouse (Wang, Fu et al. 2001)-39,53

                                                a) perhaps PPARg, by inhibiting inflammation, reduced tumor survieillance

                                    2)  PPARg ligands augment colon carcinoma (Ricote, Huang et al. 1999)-85,86

                                                a)  increase in size and number of polyps in troglitazone treated Min mice (heterozygous for APC)

                                    3)  mice lacking one copy of the APC tumor suppressor (Min+/-) have a modest increase in spontaneous colon tumors when treated with PPARg activators (Lefebvre, Chen et al. 1998; Saez, Tontonoz et al. 1998)

                                                a)  5X increase in tumor multiplicity in the colon after treatment for 8 weeks with BRL-49,653 at 20mg/kg/day (Lefebvre, Chen et al. 1998)

                                                b)  3X increase with troglitazone treatment at 150mg/kg/day for 8 weeks in Min+/- mice (Lefebvre, Chen et al. 1998)

                                    4)  PPARg ligands cause increased colon tumor cell line growth (Saez, Tontonoz et al. 1998)

                                    5)  TZD promotes colonic tumor formation in APCmin/+ (adenomatous polyposis coli) mice (Lefebvre, Chen et al. 1998; Saez, Tontonoz et al. 1998; Sarraf, Mueller et al. 1998)

                        c)  expression (controversial role in cancer)

                                    1)  overexpression in tumor relative to normal mucosa in four patients (Ricote, Huang et al. 1999)-35

                                    2)  PPARg is highly expressed in almost all colon cancer lines and at nearly equal levels in normal tissue and colonic tumors (Ricote, Huang et al. 1999)-83

                                    3)  increasing expression crypt to villus in normal mucosa, highest expression in differentiated cells (Ricote, Huang et al. 1999)-82

                                    4)  increasing expression villus to crypt in normal mucosa, mostly in proliferating cells of the crypts, and no expression in the differentiated cells (Ricote, Huang et al. 1999)-85

                        d)  cancer during infection with H. pflori

                                    1)  H. pflori causes an increase in cell proliferation and inhibition of apoptosis in the epithelial tissue of infected patients

                                                a)  increased in H. pylori-induced pre-malignant and malignant lesions (Gupta, Polk et al. 2001)-38-40

                                    2)  role of COX-2

                                                a)  increased expression of COX-2, implying that prostaglandins play a role in host response to H. pylori (Gupta, Polk et al. 2001)-34-37

                                                b)  chronic use of aspirin that inhibit COX-2 decrease the risk for distal gastric cancer (Gupta, Polk et al. 2001)-41-43

                                                c)  H. pylori-indeced apoptosis is augmented in the presence of COX-2 inhibitors in vitro (Gupta, Polk et al. 2001)-44

                                                d)  H. pylori-induced apoptosis is augmented in COX-2 knockout mice  (Gupta, Polk et al. 2001)-45

                                    3)  PPARg activation prevents death induced by H. pylori

                                                a)  cell lines have reduced apoptosis, DNA fragmentation

                                                b)  stops the nuclear translocation of NFkB that is induced by H. pylori  (Gupta, Polk et al. 2001)

                                                            1)  IkB phosphorylation is inhibited

                                                            2)  IKK activity is inhibited

                                                c)  stops IL-8 release, which is downstream of NFkB activation

            2.  prostate cells

                        a)  BRL49653 inhibits growth of three prostate carcinoma cell lines, and causes selective necrosis of prostate carcinoma versus normal tissue (Ricote, Huang et al. 1999)-33

                        b)  15S-HETE activates PPARg and seems to prevent the growth of Pca’s (prostate carcinomas) (Shappell, Gupta et al. 2001)

                        c)  BRL-49653 and 15S-HETE both cause a delay in cell cycle progression in liquid cultures (Shappell, Gupta et al. 2001)

                                    1)  previous expts didn’t see this (Shappell, Gupta et al. 2001)-12

                                    2)  PGJ2 caused an accumulation of Pca cells in the S phase at 48 hours (Shappell, Gupta et al. 2001)-17

                        d)  clinical results show that serum prostate-specific antigen decreases in 33% of patients with androgen-dependent Pca and 14% with androgen-independent Pca (Shappell, Gupta et al. 2001)-28

            3.  keratinocytes

                        a)  k-Ras transformed epithelial cells

                                    1)  activation of PPARg has antineoplastic effects in Ras-transformed cells (Shao, Sheng et al. 2002)

                                                a)  causes a long delay in transit through G1 phase associated with inhibition of PI3K/Akt activity and reduction in cyclin D1 expression (Shao, Sheng et al. 2002)

            4.  leukemia

                        a)  inhibit growth of leukemia cells

                                    1)  treatment of leukemia cells with 15dPGJ2 or troglitazone inhibits proliferation and induces apoptosis in serum-free cultures (Yamakawa-Karakida, Sugita et al. 2002)

            5.  angiogenesis

                        a)  rosiglitazone stops in vivo angiogenesis in CAM and bFGF-induced corneal neovascularization (Panigrahy, Singer et al. 2002)

            6.  leiomyomas – smooth muscle tumors of the uterine myometrium

                        a)  PPARg ligands docosahexaenoic acid, 15dpgj2, troglitazone, and ciglitazone inhibit 17b-estradiol-stimulated cell proliferation (Houston, Copland et al. 2003)

                                    1)  appears to be mediated through negative crosstalk between PPARg and the estrogen receptor (Houston, Copland et al. 2003)

            7.  pituitary tumors

                        a)  PPARg is expressed in all tumors examined (Heaney, Fernando et al. 2003)

                        b)  PPARg activation causes cell cycle arrest and apoptosis (Heaney, Fernando et al. 2003)

                        c)  in vivo growth of tumors was suppressed rosi treated mice (Heaney, Fernando et al. 2003)

Role in Starvation and Diabetes

            1.  diabetic mice

                        1)  insulin treatment of diabetic mice partly restores PPARg mRNA levels in epididymal fat cells (Vidal-Puig, Jimenez-Linan et al. 1996)

                                    a)  and in human adipocyte cell lines (Vidal-Puig, Considine et al. 1997)

                        2)  TZD treatment increases insulin sensitivity and decreases hyperglycemia in diabetic mice (Burant 1997 2900)

            2.  starvation and insulin effects on expression

                        a)  PPARg1/2 are decreased in rodents by fasting and insulin deficiencies (Cusin, Terrettaz et al. 1990; Appel and Fried 1992; Girard, Perdereau et al. 1994; O'Brien and Granner 1996; Vidal, Auboeuf et al. 1996)

                        b)  insulin effects on PPARg function

                                    1)  insulin can alter the transactivation abilities of PPARg (Hu, Kim et al. 1996; Zhang, Berger et al. 1996; Werman, Hollenberg et al. 1997)

            3.  PPARg ligands like antidiabetic thiazolidinediones (TZDs) e.g.  Rezulin (Spiegelman 1998)

                        a)  lower glucose levels in rodent models of insulin resistance

                        b)  lower circulating levels of FAs

                        c)  mediate these effects through PPARg interactions (Lehmann, Moore et al. 1995; Willson, Cobb et al. 1996)

                        d)  enhance insulin sensitivity in humans (Saltiel and Olefsky 1996; Willson, Cobb et al. 1996)

            4.  PPARg modifies glucorocorticoid

                        a)  PPARg ligands modify glucocorticoid

                                    1)  chronic treatment of mice with rosiglitazone caused a significant decrease of plasma corticosterone levels (Berger, Tanen et al. 2001)

                                                a)  this may stop the glucocorticoid induction of adipogenesis

                                    2)  chronic treatment of Zucker rats with rosiglitazone caused an increase in corticosterone levels in fatty Zucker rats (Berger, Tanen et al. 2001)-46

            5.  PPARg’s big picture role

                        a)  PPARg is a thrifty gene, promoting fat storage to survive starvation under scarce food, and promoting excessive fat storage when food is plentiful (reviewed in (Lowell 1999))

                                    1)  PPARg increases the number of small adipocytes, stimulating adipogenesis, and creasing the number of large adipocytes

                                                a)  large adipocytes produce excess TNFa and free FAs

                                    2)  PPARg haploinsufficiency limits adipocyte hypertrophy probably through increased leptin expression

                        b)  antidiabetic PPARg agonists sensitize peripheral tissue to the action of insulin resulting in decreases in hyperglycemia, hyperlipidemia, and hyperinsulinemia seen in type 2 diabetes

                        c)  antidiabetic PPARg agonists cause a decrease in intra-abdominal and an increase in subcutaneous adiposity in diabetic animals and NIDDM subjects (Berger, Tanen et al. 2001)-42,43

                                    1)  visceral fat is closely associated with the development of insulin resistance and other disturbances associated with NIDDM (Berger, Tanen et al. 2001)-44

                        d)  high fat diet AND PPARg expression effect proposal (Yamauchi, Waki et al. 2001)

                                    1)  HF diet, normal amounts of PPARg/RXR activity cause increase TG content in WAT, skeletal muscle, and liver due to increased fatty acid influx to these tissues, and HF diet-induced leptin resistance, causing insulin resistance associated with obesity (Yamauchi, Waki et al. 2001)

                                    2)  reduction of PPARg/RXR activity due to HX531 or BADGE treatment, or lower expression of PPARg, limit FA influx to WAT and skeletal muscle, increased leptin expression by antagonism of PPARg/RXR-mediated suppression of the gene, and reduced expression of lipogenic genes (Yamauchi, Waki et al. 2001)

                                                a)  consequent induction of PPARa pathway in liver, BAT, and skeletal muscle, expression of UCP2 and b-oxidation enzymes

                                    3)  severe reduction of PPARg/RXR activity depletes WAT due to decreased flux of FFA into the WAT by marked suppression of PPARg target genes, causing increased FA flux into liver/muscle and leptin deficiency and decreased effects of PPARa pathways

                                                a)  increased expression of lipogenic enzymes and decreased expression of enzymes involved in b-oxidation and UCP2, increasing skeletal muscle and liver tissue TG content (Yamauchi, Waki et al. 2001)

                        e)  another high fat/PPARg expression proposal effects on obesity and diabetes (Yamauchi, Kamon et al. 2001)

                                    *  what are the effects of high fat diet and/or troglitazone treatment on wt or PPARg-heterozygotic mice?

                                    1)  normal mice, HF diet

                                                a)  increased TG content in WAT, skeletal muscle, and liver due to increased fatty acid influx into WAT, skeletal muscle, and liver

                                                b)  leptin resistance, leading to insulin resistance and obesity

                                                c)  increase in FFA (Yamauchi, Kamon et al. 2001)-15 and TNFa (Yamauchi, Kamon et al. 2001)-16, and decrease in insulin-sensitiszing hormones, like adiponectin (Yamauchi, Kamon et al. 2001)-17

                                    2)  normal mice, HF diet, treatment with TZD

                                                a)  stimulation of adipogenesis, promoting flux of FFA from the liver and muscle into WAT, leading to lower TG in the liver and muscle, and improved insulin sensitivity, increased obesity

                                                b)  adipocyte differetiation and apoptosis, increasing small adipocyte formation, which alleviate insulin resistance through a decrease in molecules causing insulin resistance, such as FFA and TNFa, and upregulation of insulin-sensitizing hormone adiponectin

                                    3)  heterozygotic mice, HF diet

                                                a)  reduction of PPARg activity

                                                b)  decreased TG content in WAT, skeletal muscle, and liver

                                                c)  increased leptin expression by antagonism of PPARg-mediated leptin expression, reducing lipogenic enzymes, and consequent activation of PPARa pathway in liver, BAT, and skeletal muscle, causing increases in UCP2 and enzymes involved in b-oxidation

            6.  PPARg antagonism stops HF diet-induced obesity, insulin resistance, and diabetes (Yamauchi, Waki et al. 2001)

                        a)  reduce TG content in WAT, skeletal muscle, and liver

            7.  proposed mechanism of action (Kersten, Desvergne et al. 2000)

                        a)  TZDs divert fatty acids away from skeletal muscle by increasing their uptake in adipose tissue

                                    1)  this reduces the deleterious effects of FA on muscle insulin action

                                    2)  however, mice without adipose tissue still benefit from TZD treatment

            8.  PPARg role in pancreatic beta cells

                        a)  PPARg is expressed in INS-1 pancreatic beta cell line (Kawai, Hirose et al. 2002)

                                    1)  troglitazone enhances insulin secretion in response to glucose stimulus (Kawai, Hirose et al. 2002)

                                    2)   FFA-induced lipotoxicity of these cells is reduced by cotreatment with troglitazone (Kawai, Hirose et al. 2002)

                        b)  PPARg antagonist prevents UCP-2 overexpression in pancreatic beta cells, allowing normal insulin secretion in diabetics (Patane, Anello et al. 2002)

                                    1)  high FFA and high glucose both stimulate insulin production

                                    2)  high FFA also induces PPARg expression, and UCP-2 expression in turn, which prevents efficient ATP production in pancreatic beta cells, lowering insulin secretion (Patane, Anello et al. 2002)

Role in atherosclerosis

reviewed in (Takano and Komuro 2002)

            VI.  Atherosclerosis

            1.  PPARg ligands inhibit the growth of VSMCs

                        a)  troglitazone inhibits human aortic smooth muscle cell growth and proliferation (Ricote, Huang et al. 1999)-74

                        b)  troglitazone suppresses rat VSMC growth induced by basic fibroblast growth factor (Ricote, Huang et al. 1999)-75

                        c)  troglitazone reduces the migration of VSMC induced by PDGF-BB (Ricote, Huang et al. 1999)-73,75

                        d)  troglitazone treatment for 3 months have reduced intimal and medial complex thickness in the common carotid artery in vivo human studies (Ricote, Huang et al. 1999)-81

                        e)  in vitro, PPARg ligands prevent the G1-S transition in RASMC (Wakino, Kintscher et al. 2000)

                                    1)  stop the phosphorylation of Rb in these cells

                                    2)  p21 expression is downregulated by rosi and trog

            2.   inhibit atherosclerosis in general

                        a)  PPARg ligands decrease lesion formation in male but not female mice (Tordjman, Bernal-Mizrachi et al. 2001)-16

                        b)  PPARg ligands decrease several cardio risk factors, like blood pressure, hyperlipidemia, and oxidation of LDL

                        c)  reduce carotid artery thickness in humans and neointimal formation after balloon injury in rats (Moore, Fitzgerald et al. 2001)-38-40

                        d)  GW7845 treatment effects on a high-fat high-cholesterol diet show PPARg-agonists retard atherosclerosis development in male but not female mice (Moore, Fitzgerald et al. 2001)-22

                                    1)  cause an increase in CD36 mRNA in the lesions of the mice treated with PPARg-agonist, and no decrease in SR-A (Moore, Fitzgerald et al. 2001)-22

                                    2)  markers of inflammation were lower in male mice treated with the PPARg agonists (Moore, Fitzgerald et al. 2001)-22

                        e)  suppress expression of plasminogen activator inhibitor type 1 in vascular endothelial cells (Sugawara, Uruno et al. 2002)-16 and matrix metalloproteinase-9 in VSMCs (Sugawara, Uruno et al. 2002)-15

                        f)  implication is that PPARg is antiatherogenic because it facilitates the removal of cholesterol from macrophages via cholesterol transporter proteins, such as ABCA1 

                        g)  TZD treatment, or 15D-PGJ2 and PGA1 treatment cause a reduction in myocardial infarct size (Wayman, Hattori et al. 2002)

            3.  LDL receptor null mice

                        a)  troglitazone treatment inhibits the development of atherosclerotic lesions under both hypercholesterolemia or hypercholesterolemia and insulin resistance (Moore, Fitzgerald et al. 2001)-41

                        b)  decrease in macrophage content of the atherosclerotic lesions under both dietary conditions (Moore, Fitzgerald et al. 2001)-41

                        c)  troglitazone inhibits the transendothelial migration of THP-1 monocytes in response to MCP-1 (Moore, Fitzgerald et al. 2001)-41

                        d)  apoE knockout mice

                                    1)  troglitazone had a positive effect on athersclerotic lesion size in these mice under conditions of hypercholesterolemia and mild insulin resistance (Moore, Fitzgerald et al. 2001)-42

                        e)  PPARg null studies

                                    1)  transplant of PPARg knockout marrow into LDL-null mice showed increased lesion size after 8 weeks on the high fat diet (Moore, Fitzgerald et al. 2001)-31

            4.  foam cell generation

                        a)  troglitazone does not increase receptor-mediated uptake of oxidized LDL and cholesterol (Moore, Fitzgerald et al. 2001)-6

                                    1)  does upregulate CD36 expression, but lowers SR-A (Moore, Fitzgerald et al. 2001)-6

                        b)  increase the expression of ABCA1, mRNA, and cellular efflux resulting from expression (Moore, Fitzgerald et al. 2001)-31,32

            5.  activation of cholesterol efflux

                        a)  PPARg ligands induce cholesterol efflux from macrophages

                                    1)  likely mechanism is enhanced transcription of LXRa which targets the cholesterol efflux genes (Oram and Lawn 2001)-57,58

            6.  PPARg expression in atherosclerosis

                        a)  in human cadavers, expressed at lowest levels in diffuse intimal thickening, more in the fatty streak, and more in the atheromatous plaque (Sueyoshi, Yamada et al. 2001)

pGJ2 Effects Independent of PPARg Activation

            1.  apoptosis of hepatic myofibroblasts by 15-d-PGJ2

                        a)  5mM can induce apoptosis in serunm starved cells (Li, Tao et al. 2001)

                                    1)  caspase-dependent (Li, Tao et al. 2001)

                                    2)  dependent on the formation of H2O2 radicals (Li, Tao et al. 2001)

                        b)  other PPARg ligands (ciglitazone and troglitazone) did not cause apoptosis (Li, Tao et al. 2001)

            2.  troglitazone can act independently of PPARg (Akiyama, Sakai et al. 2002)

                        a)  inhibited ABCA1 expression in both PPARg deficient and wild-type macrophages (Akiyama, Sakai et al. 2002)

                        b)  Egr-1 induction

                                    1)  induced by TGZ, but not by other PPARg ligands (Baek, Wilson et al. 2003)

                                                a)  increases mRNA and protein stability

                                    2)  inhibition of ERK phosphorylation in HCT-116 cells stops Egr-1 induction by TGZ (Baek, Wilson et al. 2003)

            3.  inactivation of IKK2 subunit of IKK

                        a)  cyclopentenone PGs, including 15d-PGJ2, directly inhibit and modify the IKK2 subunit of IKK (Clark 2002)-98

                                    1)  this prevents phosphoyrlation of inhibitor IkB proteins that then target these proteins for ubiquitin conjugation and degradation (Clark 2002)-99

                        b)  RAW 264.7 mps treated with LPS and IFNa, incubation with 15d-PGJ2 causes a sig inhjibition of IKK2 activity and inhibition of degradation of inhibitory IkB proteins (Clark 2002)-99

                                    1)  downstream NFkB targets were also inhibited as well, including type-2 NOS and COX2 (Clark 2002)-99

                                    2)  also confirmed by (Clark 2002)-100

            4.  anti-inflammation effects of pGJ2 in macrophages does not depend on PPARg (Clark 2002)-97

                        a)  15d-PGJ2 and thiazolidinediones have anti-inflammatory effects that are independent on PPARg (Clark 2002)-97

            5.  MAPK pathway is PPARg-independently activated by pGJ2 (Lennon, Ramauge et al. 2002)

                        a)  cultured primary astrocytes have MAPK pathways activated by .5 hours following stimulation with PGJ2 in a dose-dependent manner (Lennon, Ramauge et al. 2002)

                                    1)  ROS scavengers inhibit this induction

                        b)  ciglitazone also induces MAPK in a ROS-dependent manner (Lennon, Ramauge et al. 2002)

            6.  overlap with PPARd function

                        a)  rosiglitazone induces several residual PPARg target genes in knockout mice, and a similar pattern is seen with GW0742 treatment in those mice (Welch, Ricote et al. 2003)

Other Roles

            1.  side effects of treatment

                        a)  weight gain in human patients (Kersten 2001)-(Fuchtenbusch 2000)

                                    1)  heterozygous PPARg mice have smaller fat stores on a high fat diet (Kersten 2001)-(Kubota 1999, Miles 2000)

            2.  metabolic roles

                        a)  key regulator of glucose and lipid homeostasis (Lehmann, Moore et al. 1995; Willson, Cobb et al. 1996)

                        b)  hyperglycemia and hypertriglyceridemia

                                    1)  both are reduced when PPARg is activated with non-thiazolidinedioine PPARg agonists (Berger, Leibowitz et al. 1999)

            3.  response to peroxisome proliferators (PPARa activators)

                        a)  PPARa activators can still cause cell proliferation even in PPARg knockout mice (Gonzalez and Peters 2001)

            4.  protein kinase C

                        a)  PPARg ligands can inhibit signaling through PKC pathways (Wakino 2001 47650)-15,16

            5.  cardiac hypertrophy is decreased by PPARg

                        a)  model system bands the primary artery or treats with angiotensin II, causing hypertrophy to maintain the flow of blood

                        b)  PPARg activation lowers the development of cardiac hypertrophy (Asakawa, Takano et al. 2002)

                                    1)  pretreatment of cardiac myocytes for 30 minutes, followed by Ang II treatment for 48 hours shows reduced expression of skeletal actina, a marker of hypertrophy (Asakawa, Takano et al. 2002)

                                    2)  lowers the increase in muscle cell surface area in response to AngII

            6.  T cell response

                        a)  PPARg ligands inhibit antigen responses of T cell clones and inhibit anti-CD3 antibody-stimualted proliferative responses of T cell clones and T cell enriched splenocytes (Clark 2002)

                        b)  IL-2 induced proliferation of T cells is not inhibited by PPARg ligand treatment (Clark 2002)

                        c)  phytohemagglutinin-induced proliferation, IL-2 production, and IL-2 mRNA expression in human peripheral blood T cells is inhibited by PPARg ligands in a dose-dependent manner (Clark 2002)-87

            7.  glucose uptake

                        a)  astrocytes

                                    1)  pioglitazone causes increased glucose consumption in time and dose-dependent manner (Dello Russo, Gavrilyuk et al. 2003)