Role of Transforming Growth Factor beta Induced by Podocyte in the Pathogenesis of Diabetic Nephropathy / 대한신장학회잡지

ABSTRACT

BACKGROUND: According to the development of methods in podocyte cell culture several studies for the role of podocyte in the progression of glomerulosclerosis have been recently reported. But there is few report for the regulation of TGFbeta1 synthesis and type IV collagen production in podocyte in diabetic nephropathy. We investigated the effects of high glucose and TGFbeta1 in culture medium on TGFbeta1 and type IV collagen production and whether their production is dependent on protein kinase C (PKC) pathway in cultured mouse podocyte cell line. METHODS: Conditionally immortalized mouse podocytes with a temperature-sensitive variant of SV40 large T antigen were cultivated. To propagate podocytes, cells were cultivated at 33 degrees C and treated with gamma-interferon (permissive condition). And to induce differentiation, podocytes were changed at 37 degrees C and deprived of gamma-interferon (non-permissive condition). The effects of high glucose and TGFbeta1 in culture media on procollagen alpha1 (PCalpha1 (IV)) and their relationships to PKC pathway were examined. The mRNA expression and protein production of TGFbeta1 and PCalpha1 (IV) were assayed by reverse transcription - polymerase chain reaction (RT-PCR) and western analysis. RESULTS: Compared with normal glucose (NG, 5.5 mM), high glucose exposure (HG, 15, 30 mM) increased the mRNA expression and protein production of TGFbeta1 and PCalpha1 (IV), but without a statistic significance: TGFbeta1 (after 6 hours 69.62+/-9.00 vs 83.48+/-7.82 vs 74.49+/-24.73, after 24 hours 65.06+/-20.55 vs 68.01+/-24.35 vs 94.23+/-13.14), PCalpha1 (IV) (after 6 hours 109.94+/-10.43 vs 102.00+/-6.68 vs 138.65+/-39.83, after 24 hours 105.88+/-9.53 vs 83.95+/-1.12 vs 109.14+/-3.29, after 72 hours 99.18+/-5.30 vs 92.93+/-6.33 vs 109.25+/-4.11). TGFbeta1 significantly decreased the expression of PCalpha1 (IV). Calphostin C treatment further stimulated the increase of PCalpha1 (IV) production induced by HG and inhibited the decreased mRNA expression of PCalpha1 (IV) induced by TGFbeta1 administration. CONCLUSION: We suggest that TGFbeta1 have an important role in podocyte in the pathogenesis of diabetic nephropathy. The HG-induced increases of procollagen alpha1 type IV collagen seems to be negatively regulated by TGFbeta1 and PKC pathway and possibly another pathway will positively regulate the production of PCalpha1 (IV), and these pathways may have a different effect on collagen synthesis dependent on the renal cell type.