Objective: To study the mechanisms of curcumin alleviating oxidative stress and spleen apoptosis induced by overtraining in rats by regulating Kelch-like ECH-associated protein-1 (Keap1)-nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant response element (ARE) signaling pathway.
Methods: 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). The C Group did not undergo any exercise intervention. The OM and COM group underwent 8-week incremental load swimming training. During the training, rats in the COM group were treated with curcumin at the dose of 200 mg/(kg·d) in the volume of 5 ml/kg by gavage, and rats in the other groups were given an equal volume of solvent, 0.5% sodium carboxymethylcellulose. Twenty-four hours after the last training, the spleen index was calculated by weighing, the pathological changes of the spleen were observed by light microscopy, and the biochemical indicators of blood and spleen were detected.
Results: The spleen structure of C group was normal under light microscope; the spleen index of OM group was significantly lower than that of C group (P＜0.01) and pathological changes were obvious; the spleen index of COM group was significantly higher than that of OM group (P＜0.05) and histomorphological changes were relieved. Compared with C group, in OM group, serum corticosterone (Cor) level, spleen apoptosis level, malondialdehyde (MDA) concentration and the expression of proapoptotic Bcl-2 associated X protein (Bax) in spleen were increased (P＜0.05 or P＜0.01); the body weight, serum testosterone (T), superoxide dismutase (SOD) activity, the expressions of heme oxygenase-1 (HO-1) and anti-apoptotic B cell lymphoma-2 protein (Bcl-2) in spleen were decreased (P＜0.05 or P＜0.01); the expression of Nrf2 was not changed significantly (P＞ 0.05). Compared with OM group, in COM group, there were no significant changes in body weight (P＞0.05), serum T level, SOD activity, the expressions of Bcl-2, Nrf2 and HO-1 in spleen were increased (P＜0.05 or P＜0.01); serum Cor level, spleen apoptosis level, MDA concentration and the expression of Bax were decreased (P＜0.05 or P＜0.01). The change trend of T/Cor ratio between groups was consistent with the change of testosterone, and the change trend of Bcl-2/Bax ratio was consistent with the change of Bcl-2.
Conclusion: The 8-week incremental load excessive swimming training aggravated spleen apoptosis, led to pathological changes and dysfunction of spleen. Curcumin can up-regulate expression of Nrf2 and HO-1, alleviate oxidative stress induced by overtraining, enhance Bcl-2 expression and attenuate Bax expression, thereby inhibiting excessive spleen apoptosis of rats, protecting the structure and function of spleen.