Glycated albumin induces superoxide generation in mesangial cells.

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-alpha and -alpha1, 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-á-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.