Resveratrol decreases high glucose‑induced apoptosis in renal tubular cells via suppressing endoplasmic reticulum stress

Abstract

Diabetic nephropathy (DN) is the second most common complication of diabetes mellitus after cardiovascular complications. Endoplasmic reticulum (ER) stress is known to be associated with DN. Resveratrol (RSV) exhibits anti‑oxidative, anti‑inflammatory and cytoprotective effects. Therefore, the aims of the present study were to investigate the role of RSV in the inhibition of high concentration glucose (HG)‑induced apoptosis in renal tubular cells, as well as to examine the protective effects of RSV against diabetes‑mediated renal damage via inhibition of ER stress in DN. RSV was orally administered to diabetic db/db mice once a day for 12 consecutive weeks. Compared with untreated db/db mice, treating db/db mice with RSV significantly decreased urine albumin excretion and the urine albumin to creatinine ratio, and attenuated renal histopathological injury. Furthermore, RSV treatment resulted in decreased expression levels of glucose‑regulated protein of 78 kDa and C/EBP‑homologous protein (two ER stress markers) and caspase12 in murine kidneys. RSV administration also inhibited the apoptosis of NRK‑52E cells and activation of the ER stress signal transduction pathway induced by HG treatment in vitro. Collectively, the present results indicated that RSV protected renal tubular cells against HG‑induced apoptosis in DN by suppressing ER stress.

Figure 1.

RSV attenuates renal injury in db/db mice. (A) Body weight, (B) blood glucose, (C) urine albumin and creatinine ratio and (D) urine albumin excretion levels in db/db mice were decreased by RSV treatment. Data are presented as the mean ± SEM. *P<0.05 vs. db/m group; ^#P<0.05 vs. db/db group. RSV, resveratrol.

Figure 2.

Histological morphology of the kidney. Representative images of H&E, PAS and Masson-stained renal tissue sections in each group at 20 weeks of age. Scale bar, 20 µm. H&E, hematoxylin and eosin; PAS, periodic acid-Schiff; RSV, resveratrol.

Figure 3.

RSV suppresses ER stress-induced apoptosis in the kidneys of db/db mice. (A) Protein expression levels of GRP78, CHOP, cleaved caspase12 and β-actin were measured using western blotting. Semi-quantification of protein expression levels of (B) GRP78, (C) CHOP and (D) cleaved caspase12. Data are presented as the mean ± SEM. *P<0.05 vs. db/m group; ^#P<0.05 vs. db/db group. RSV, resveratrol; GRP78, glucose-regulated protein of 78 kDa; CHOP, C/EBP-homologous protein.

Figure 4.

RSV inhibits GRP78 and CHOP expression levels in the kidneys of db/db mice. (A) GRP78 and CHOP expression levels were determined via immunohistochemical staining in the renal tissues of mice in each group. Scale bar, 20 µm. Semi-quantitative bar graphs of renal (B) GRP78 and (C) CHOP in different groups. Data are presented as the mean ± SEM. *P<0.05 vs. db/m group; ^#P<0.05 vs. db/db group. RSV, resveratrol; GRP78, glucose-regulated protein of 78 kDa; CHOP, C/EBP-homologous protein.

Figure 5.

RSV decreases the apoptotic rate in renal cells of db/db mice. (A) Representative images of apoptotic renal cells in mice of each group determined using TUNEL assay. (B) Semi-quantitative bar graphs of TUNEL-positive stained tubular cells in different groups. Scale bar, 20 µm. Data are presented as the mean ± SEM. *P<0.05 vs. db/m group; ^#P<0.05 vs. db/db group. RSV, resveratrol.

Figure 6.

RSV inhibits high concentration glucose-induced apoptosis in NRK-52E cells. NRK-52E cells were pretreated with 20 µM RSV for 6 h, followed by incubation with NG (5.5 mM), HM or HG (30 mM) for another 24 h. (A) Representative images of apoptotic NRK-52E cells determined via flow cytometry. (B) Quantification of apoptotic NRK-52E cells. Data are presented as the mean ± SEM. *P<0.05 vs. NG group ^#P<0.05 vs. HG group. RSV, resveratrol; NG, normal glucose; HG, high glucose; HM, high concentration mannitol.

Figure 7.

RSV prevents high concentration glucose-induced ER stress in NRK-52E cells. NRK-52E cells were pretreated with 20 µM RSV for 6 h, followed by incubation with NG (5.5 mM), HM or HG (30 mM) for another 24 h. The expression levels of GRP78 and CHOP in NRK-52E cells were determined via (A) western blotting and (B) reverse transcription-quantitative PCR. Data are presented as the mean ± SEM. *P<0.05 vs. NG group ^#P<0.05 vs. HG group. RSV, resveratrol; NG, normal glucose; HG, high glucose; HM, high concentration mannitol; GRP78, glucose-regulated protein of 78 kDa; CHOP, C/EBP-homologous protein.