Premature senescence is a key process in the progression of diabetic nephropathy (DN). In our study, we hypothesized that receptors for advanced glycation end-products (RAGE) mediate endoplasmic reticulum (ER) stress to induce premature senescence via p21 signaling activation in diabetic nephropathy. Here, we demonstrated that elevated expression of RAGE, ER stress marker glucose-regulated protein 78 (GRP78), and cell-cycle regulator p21 was all positively correlated with enhanced senescence-associated-β-galactosidase (SA-β-gal) activity in DN patients. In addition, the fraction of SA-β-gal or cells in the G0G1 phase were enhanced in cultured mouse proximal tubular epithelial cells (PTECs) and the expression of RAGE, GRP78 and p21 was up-regulated by advanced glycation end-products (AGEs) in a dose- and time-dependent manner. Interestingly, ER stress inducers or RAGE overexpression mimicked AGEs induced-premature senescence, and this was significantly suppressed by p21 gene silencing. However, RAGE blocking successfully attenuated AGEs-induced ER stress and p21 expression, as well as premature senescence. Moreover, ER stress inducers directly caused p21 activation, premature senescence, and also enhanced RAGE expression by positive feedback. These observations suggest that RAGE promotes premature senescence of PTECs by activation of ER stress-dependent p21 signaling.
Keywords: 4-PBA; 4-phenylbutyrate; 4′,6-diamidino-2-phenylindole; AGEs; BSA; DAPI; DN; Diabetic nephropathy; ER; ER stress; GFP; GRP78; Green fluorescent protein; MOI; PTECs; Premature senescence; RAGE; SA-β-gal; SAHF; TG; TM; advanced glycation end-products; bovine serum albumin; diabetic nephropathy; endoplasmic reticulum; glucose-regulated protein 78; multiplicity of infection; p21; proximal tubular epithelial cells; receptor for advanced glycation end-products; senescence-associated heterochromatic foci; senescence-associated-β-galactosidase; thapsigargin; tunicamycin.
© 2013.