The protective effects of oligomeric proanthocyanidins (OP) on myocardial injury induced by long-time and intensive exercise and its potential mechanisms were investigated in this study.Wistar rats were subjected to six consecutive weeks of excessive swimming exercise training,in which two groups were gavaged with 50 mg/kg OP (OP50 group) and 100 mg/kg OP (OP100 group) daily,respectively,the model group (Mod) received an equal volume of saline,and the normal group (Nor) was used as control.Results showed that the serum levels of lactate dehydrogenase (LDH),creatine kinase (CK) and cardiac troponin (cTnI),the common markers of exercise-induced myocardial injury,were significantly elevated in the Mod group,and myocardial tissues showed obvious pathological morphology,and a marked inflammatory cell infiltration.In the OP50 and OP100 groups,LDH,CK and cTnI were significantly down-regulated,and the pathological changes in myocardial tissue were significantly reduced (P<0.05).In the Mod group,malondialdehyde (MDA) increased significantly in the myocardial tissues,the antioxidant enzymes glutathione (GSH) and superoxide dismutase (SOD) decreased,and the nuclear factor E2 related factor 2 (Nrf2) / heme oxygenase-1 (HO-1) (Nrf2/HO-1) signaling pathway was inhibited.In the OP50 and OP100 groups,the level of GSH and SOD was significantly up-regulated,and the expression of proteins in the Nrf2/HO-1 pathway was significantly increased (P<0.05).The levels of inflammatory indicators,tumor necrosis factor-α(TNF-α),interleukin-6 (IL-6) and interleukin-1β (IL-1β),were significantly increased in the Mod group,and the expression of key proteins in the thioredoxin-interacting protein/NOD-like receptor thermal protein domain associated protein 3 (TXNIP/NLRP3) inflammatory response signaling pathway was significantly increased.The levels of the inflammatory factors were significantly down-regulated in both the OP50 and OP100 groups,and the expression of proteins in the TXNIP/NLRP3 pathway was significantly decreased in the OP100 group (P<0.05).In summary,OP supplementation has a significant protective effect on exercise-induced myocardial injury in rats,and this protective mechanism is involved in enhancing the myocardial Nrf2/HO-1 antioxidant pathway and inhibiting the TXNIP/NLRP3 inflammatory response signaling pathway.

"> proanthocyanidins, exercise-induced myocardial injury, oxidative stress, Nrf2/HO-1 antioxidant pathway, inflammatory response, TXNIP/NLRP3 pro-inflammation pathway