Glycated Albumin Induces Superoxide Generation in Mesangial Cells

Abstract

Background/Aims: Reactive oxygen species are involved in the pathogenesis of diabetic nephropathy. Amadori-modified glycated albumin modulates signaling pathways in mesangial cells that contribute to the development of diabetic nephropathy. However, the effects of glycated albumin on mesangial cell superoxide (O₂^-) production are unknown. Thus, we examined whether glycated albumin induces mesangial cell O₂^- generation and whether increased O₂^- production elicits cell growth. Methods: Quiescent human mesangial cells (HMC) were exposed to bovine serum albumin (BSA) or glycated BSA (Gly-BSA) with or without diphenylene iodonium (DPI) or apocynin, inhibitors of NAD(P)H oxidase, GF109203X (GFX), a protein kinase C (PKC) inhibitor. Results: Gly-BSA increased PKC activity, particularly PKC-α and -α1, within 15 min of incubation with HMC, which decreased to the control value at 2 h. Gly-BSA incubated with HMC increased O₂^- production by 2 times vis-à-vis BSA-treated cells. The Gly-BSA-induced increased O₂^- generation was suppressed by DPI or GFX. Gly-BSA significantly increased mesangial [³H]-leucine incorporation, whereas these processes were abrogated by DPI, apocynin or GFX. Conclusions: Gly-BSA induces PKC/NAD(P)H oxidase-dependent O₂^- production in HMC, which in turn results in cell hypertrophy. Thus, O₂^- induced by glycated albumin might cause mesangial cell alterations in diabetes participating in the pathophysiology of diabetic nephropathy.