Regulatory effect of curcumin on renal apoptosis and its mechanism in overtraining rats

Abstract

To study the effects and mechanisms of curcumin alleviating oxidative stress induced by overtraining and inhibiting renal apoptosis in rats. Male Wistar rats of 7 weeks old were divided into control group (C group, 12), overtraining group (OM group, 11), curcumin + overtraining group (COM group, 14). Group C did not undergo any exercise intervention. Rats in OM group and COM group underwent 8-week incremental load swimming training. During the training, the COM group was treated with curcumin at the dose of 200 mg/(kg·d) in the volume as 5 ml/kg by intragastric administration, and the other groups was treated with an equal volume of 0.5% carboxymethylcellulose. Twenty-four hours after the last training, renal histopathological changes were observed by light microscopy, related biochemical indicators in blood and renal tissue were detected. The results showed that after 8 weeks of incremental load swimming training, the renal tissue structure of group C was normal under light microscope; histopathological changes were observed in OM group; COM group was significantly relieved compared with OM group. Compared with group C, serum levels of corticosterone (Cor), creatinine (Cr) and blood urea nitrogen (BUN) in OM group were increased (P<0.01), serum level of testosterone (T) was lower (P<0.01); the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) was not changed significantly (P>0.05), while the expression of heme oxygenase-1 (HO-1) was decreased (P<0.05), total antioxidant capacity (T-AOC) and superoxide dismutase (SOD) activity were decreased (P<0.01), malondialdehyde (MDA) concentration was increased (P<0.01); the renal apoptosis was increased (P<0.01), the expression of anti-apoptotic B cell lymphoma-2 protein (Bcl-2) was decreased (P<0.01), and the expression of proapoptotic Bcl-2 associated X protein (Bax) was increased (P<0.01). Compared with the OM group, Cor level was decreased (P<0.01) in the COM group, T level was increased (P<0.01), Cr and BUN levels were lower (P<0.05); the expression of Nrf2 and HO-1 were increased (P<0.05), T-AOC and SOD activity were increased (P<0.01), MDA concentration was decreased (P<0.05); the renal apoptosis was decreased (P<0.05), the expression of Bcl-2 was increased (P<0.05), and the expression of Bax was decreased (P<0.01). The trend of testosterone/corticosterone ratio between groups was consistent with testosterone change, and the change trend of Bcl-2/Bax ratio was consistent with the change of Bcl-2. The 8-week incremental load swimming training triggered excessive training in rats, aggravated oxidative stress and accelerated renal apoptosis, leading to pathological changes and dysfunction of kidney. Curcumin can up-regulate expression of Nrf2 and HO-1, effectively alleviates oxidative stress induced by overtraining, thereby increasing Bcl-2 expression, decreasing Bax expression, inhibiting renal apoptosis and protecting renal tissue structure and function properly.