Advanced Glycation End Product-Induced Peroxisome Proliferator-Activated Receptor γ Gene Expression in the Cultured Mesangial Cells

Abstract

We identified the AGEs-induced expression of peroxisome proliferator-activated γ (PPAR γ) in the cultured mesangial cells using reverse transcription-polymerase chain reaction, electrophoretic mobility shift assay (EMSA), and Western immunoblotting. Administration of AGEs-BSA into the cultured mesangial cells resulted in an increase in the levels of mRNA and proteins for PPAR γ in a dose-dependent manner. Specific bands which indicate the protein binding to PPAR γ responsive element (PPRE) in the nuclear extracts were also detected in AGEs-BSA-treated mesangial cells, but not found in BSA-treated cells by EMSA. Antioxidants, NAC, PDTC, and aminoguanidine, attenuated the gene expression and activity of PPAR γ induced by AGEs. These results indicate that PPAR γ was induced and activated by the oxidative signal(s) evoked by AGEs-ligand-receptor interactions. AGEs-induced gene expression of PPAR γ and the signal intensity of PPAR γ and PPRE complex were attenuated furthermore by protein kinase C inhibitors, calphostin C and staurospolin, but not abolished completely, indicating that both signal transduction pathways through the induction of PKC activation and independent of PKC activation were involved in the AGEs-mediated expression and activation process of PPAR γ. AGEs also increased the gene expression of smooth muscle α-actin, which is a marker for phenotypic change in mesangial cells. It is suggested therefore that AGEs-induced transcription factor as the oxidative stress may have a role in the differentiation of mesangial cells.