Advanced Glycation End Products Increase Collagen-specific Chaperone Protein in Mouse Diabetic Nephropathy

Abstract

Advanced glycation end products (AGEs) appear to contribute to the diabetic complications. This study reports the inhibitory effect of OPB-9195 (OPB), an inhibitor of AGEs formation, and the role of a collagen-specific molecular chaperone, a 47-kDa heat shock protein (HSP47) in diabetic nephropathy. Transgenic mice carrying nitric-oxide synthase cDNA fused with insulin promoter (iNOSTg) leads to diabetes mellitus. The iNOSTg mice at 6 months of age represented diffuse glomerulosclerosis, and the expression of HSP47 was markedly increased in the mesangial area in parallel with increased expression of types I and IV collagens. OPB treatment ameliorated glomerulosclerosis in the iNOSTg mice associated with the decreased expression of HSP47 and types I and IV collagens. The expression of transforming growth factor-β (TGF-β) was increased in glomeruli of iNOSTg mice and decreased after treatment with OPB. To confirm these mechanisms, cultured mesangial cells were stimulated with AGEs. AGEs significantly increased the expression of HSP47, type IV collagen, and TGF-β mRNA. Neutralizing antibody for TGF-β inhibited the overexpression of both HSP47 and type IV collagen in vitro. In conclusion, AGEs increase the expression of HSP47 in association with collagens, both in vivo and in vitro. The processes may be mediated by TGF-β. Advanced glycation end products (AGEs) appear to contribute to the diabetic complications. This study reports the inhibitory effect of OPB-9195 (OPB), an inhibitor of AGEs formation, and the role of a collagen-specific molecular chaperone, a 47-kDa heat shock protein (HSP47) in diabetic nephropathy. Transgenic mice carrying nitric-oxide synthase cDNA fused with insulin promoter (iNOSTg) leads to diabetes mellitus. The iNOSTg mice at 6 months of age represented diffuse glomerulosclerosis, and the expression of HSP47 was markedly increased in the mesangial area in parallel with increased expression of types I and IV collagens. OPB treatment ameliorated glomerulosclerosis in the iNOSTg mice associated with the decreased expression of HSP47 and types I and IV collagens. The expression of transforming growth factor-β (TGF-β) was increased in glomeruli of iNOSTg mice and decreased after treatment with OPB. To confirm these mechanisms, cultured mesangial cells were stimulated with AGEs. AGEs significantly increased the expression of HSP47, type IV collagen, and TGF-β mRNA. Neutralizing antibody for TGF-β inhibited the overexpression of both HSP47 and type IV collagen in vitro. In conclusion, AGEs increase the expression of HSP47 in association with collagens, both in vivo and in vitro. The processes may be mediated by TGF-β. Nephropathy is a morbid complication associated with diabetes mellitus and is the leading cause of end-stage renal disease (1Bojestig M. Arnqvist H.J. Hermansson G. Karlberg B.E. Ludvigsson J. N. Engl. J. Med. 1994; 330: 15-18Crossref PubMed Scopus (420) Google Scholar). Diabetic nephropathy is characterized by a mesangial expansion followed by glomerulosclerosis. The mechanism of these processes remains unknown. Advanced glycation end products (AGEs) 1The abbreviations used are: AGEs, advanced glycation end-products; HSP47, 47-kDa heat shock protein; iNOS, inducible nitric-oxide synthase; OPB, OPB-9195; TGF, transforming growth factor; CML, carboxymethyllysine; BSA, bovine serum albumin; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; siRNA, small interfering RNA. 1The abbreviations used are: AGEs, advanced glycation end-products; HSP47, 47-kDa heat shock protein; iNOS, inducible nitric-oxide synthase; OPB, OPB-9195; TGF, transforming growth factor; CML, carboxymethyllysine; BSA, bovine serum albumin; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; siRNA, small interfering RNA. have been recently reported to play an important role in the pathogenesis of diabetic complications, particularly in the progression of retinopathy and nephropathy (2Vlassara H. Bucala R. Striker L. Lab. Investig. 1994; 70