title: The effect of high glucose and PPAR-gamma agonists on PPAR-gamma expression and function in HK-2 cells.
abstract: Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) are ligand-activated transcription factors that regulate cell growth, inflammation, lipid metabolism, and insulin sensitivity. PPAR-gamma in the human kidney has been described. However, the role of PPAR-gamma in proximal tubular cells with respect to cell growth and inflammation in diabetic nephropathy is largely unknown. We evaluated the effect of high (30 mM) D-glucose, thiazolidinedione pioglitazone (10 microM), and the selective PPAR-gamma agonist L-805645 (8 microM) on PPAR-gamma expression, growth, and inflammatory parameters in the proximal tubular model of HK-2 cells. PPAR-gamma was present in HK-2 cells and upregulated with 30 mM D-glucose to 177 +/- 31.2% of control (P < 0.05). PPAR-gamma activation was induced by pioglitazone to a similar level to that observed by exposure to high glucose but maximally induced by the selective agonist L-805645. However, L-805645 reduced cell viability in both 5 and 30 mM d-glucose to 73.8 +/- 3.1 and 77.6 +/- 1.4% of control (both P < 0.0001). In parallel, thymidine incorporation was reduced with L-805645 in both 5 and 30 mM D-glucose to 33.3 +/- 3.4 and 37.9 +/- 2.2%, respectively (both P < 0.0001). Flow cytometry demonstrated increased apoptosis and G(1) phase arrest in association with an increase in p21(cip1/waf1) in cells exposed to L-805645. Exposure to 30 mM D-glucose did not significantly change AP-1 promoter activity (89.0 +/- 5.5% of control); however, the addition of L-805645 significantly reduced it to 62.2 +/- 2.7% of control (P < 0.0001). Thirty nanomolar D-glucose induced transforming growth factor-beta(1) to 137.7 +/- 16.9% of control (P < 0.05), and L-805645 was able to suppress this to 68.7 +/- 5.7% of control (P < 0.01 vs. d-glucose). Exposure to 30 mM D-glucose reduced monocyte chemoattractant protein 1 levels to 78.6 +/- 7.1% (P < 0.05) of control, with the reduction more marked in the presence of either pioglitazone (P < 0.01) or L-805645 (P < 0.01). In summary, high glucose upregulates PPAR-gamma and when significantly induced demonstrates anti-proliferative and anti-inflammatory effects.
authors.affiliation: Department of Medicine, The University of Sydney, Renal Research Group, Kolling Institute of Medical Research, Royal North Shore Hospital, New South Wales 2065, Australia.
authors.forename: U
authors.initials: U
authors.lastname: Panchapakesan
authors.forename: C A
authors.initials: CA
authors.lastname: Pollock
authors.forename: X M
authors.initials: XM
authors.lastname: Chen
mesh_terms: D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D018932:Chemokine CCL2 / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism; D003928:Diabetic Nephropathies / Q000378:metabolism; D005434:Flow Cytometry; D005947:Glucose / Q000494:pharmacology*; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology; D007687:Kidney Tubules, Proximal / Q000166:cytology* / Q000378:metabolism; D000077205:Pioglitazone; D011401:Promoter Regions, Genetic / Q000502:physiology; D018160:Receptors, Cytoplasmic and Nuclear / Q000819:agonists* / Q000235:genetics / Q000378:metabolism*; D045162:Thiazolidinediones / Q000494:pharmacology; D013936:Thymidine / Q000493:pharmacokinetics; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014157:Transcription Factors / Q000819:agonists* / Q000235:genetics / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000378:metabolism; D053773:Transforming Growth Factor beta1; D014316:Tritium
chemical_list: C493956:CDKN1A protein, human; D018932:Chemokine CCL2; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D007004:Hypoglycemic Agents; D018160:Receptors, Cytoplasmic and Nuclear; C508960:TGFB1 protein, human; D045162:Thiazolidinediones; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D014316:Tritium; D005947:Glucose; D013936:Thymidine; D000077205:Pioglitazone