A natural PPAR-gamma agonist, 15-deoxy-delta 12,14-prostaglandin J2, may act as an enhancer of PAI-1 in human proximal renal tubular cells under hypoxic and inflammatory conditions.
BACKGROUND
Hypoxia and inflammation, an unavoidable milieu for renal tubular cells during the development of renal fibrosis, reportedly up-regulate production of plasminogen activator inhibitor-1 (PAI-1), a promoter of tissue fibrosis. Peroxisome proliferator-activated receptor (PPAR)-gamma agonists may modulate renal fibrosis progression via their anti-inflammatory effects in a PPAR-gamma-dependent or -independent manner. However, no information is known about the effects of PPAR-gamma agonists on PAI-1 expression in human proximal renal tubular cells (HPTECs) under hypoxia and/or inflammation.


METHODS
Confluent HPTECs were exposed to normoxia (18% O(2)), hypoxia (1% O(2)) and/or TNF-alpha at 10 ng/mL for up to 48 h. The cells were incubated with two PPAR-gamma agonists, 15-deoxy-delta 12,14-prostaglandin J2 (15d-PGJ2) and pioglitazone. Precise amounts of PAI-1 mRNA and protein were measured by TaqMan quantitative PCR and immunoassay, respectively. PPAR response element (PPRE) activity induced by 15d-PGJ2 was measured by transfection with PPRE-luciferase construct.


RESULTS
Basal PAI-1 was significantly increased, in a dose-dependent manner, by 15d-PGJ2. It also enhanced hypoxia-, TNF-alpha- and hypoxia plus TNF-alpha-stimulated PAI-1 expression at the mRNA and protein levels. Pioglitazone had no influence on PAI-1 protein production. Although 15d-PGJ2 enhanced PPRE activity significantly in the HPTECs expressing PPAR-gamma, a specific inhibitor for PPAR-gamma, GW9662, did not diminish 15d-PGJ2-induced PAI-1 expression. In contrast, a non-selective tyrosine kinase (TK) inhibitor, genisteine or a MEK1 (MAPK kinase) inhibitor, PD98059, inhibited 15d-PGJ2-induced PAI-1 production completely.


CONCLUSIONS
The endogenous PPAR-gamma agonist, 15d-PGJ2, increased PAI-1 expression independently of PPAR-gamma via the activation of TK or MAP kinase in HPTECs and may act as an enhancer of PAI-1 production in the kidney under hypoxic and inflammatory conditions.
Kimura
Hideki
H
Division of Nephrology, Department of General Medicine, School of Medicine, Faculty of Medical Sciences, University of Fukui, Yoshida, Fukui 910-1193, Japan. hkimura@u-fukui.ac.jp
Li
Xuan
X
Torii
Kunio
K
Okada
Toshiharu
T
Takahashi
Naoki
N
Fujii
Hiroshi
H
Ishihara
Shunji
S
Yoshida
Haruyoshi
H
D015687:Cell Hypoxia; D002478:Cells, Cultured; D005419:Flavonoids / Q000494:pharmacology; D019833:Genistein / Q000494:pharmacology; D006801:Humans; D007249:Inflammation / Q000378:metabolism / Q000473:pathology; D007687:Kidney Tubules, Proximal / Q000187:drug effects* / Q000378:metabolism* / Q000473:pathology; D048369:MAP Kinase Kinase 1 / Q000037:antagonists & inhibitors; D047495:PPAR gamma / Q000819:agonists*; D000077205:Pioglitazone; D017395:Plasminogen Activator Inhibitor 1 / Q000096:biosynthesis* / Q000235:genetics; D015230:Prostaglandin D2 / Q000031:analogs & derivatives* / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D045162:Thiazolidinediones / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
C097240:15-deoxy-delta(12,14)-prostaglandin J2; D005419:Flavonoids; D047495:PPAR gamma; D017395:Plasminogen Activator Inhibitor 1; D047428:Protein Kinase Inhibitors; C051321:SERPINE1 protein, human; D045162:Thiazolidinediones; D014409:Tumor Necrosis Factor-alpha; D019833:Genistein; D011505:Protein-Tyrosine Kinases; D048369:MAP Kinase Kinase 1; C482125:MAP2K1 protein, human; D015230:Prostaglandin D2; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; D000077205:Pioglitazone