Triptolide (TP),an oxygenated diterpene,has a variety of beneficial pharmacodynamic activities but its clinical applications are restricted due to severe testicular injury.This study aimed to delineate the molecular mechanisms of TP-induced testicular injury in vitro and in vivo.TP (5-50000 nmol/L) dose-dependently decreased the viability of TM4 Sertoli cells with an IC5o value of 669.5-269.45 nmol/L at 24 h.TP (125,250,and 500 nmol/L) dose-dependently increased the accumulation of ROS,the phosphorylation of JNK,mitochondrial dysfunction and activation of the intrinsic apoptosis pathway in TM4 cells.These processes were attenuated by co-treatment with the antioxidant N-acetyl cysteine (NAC,1 mmol/L).Furthermore,TP treatment inhibited the translocation of Nrf2 from cytoplasm into the nucleus as well as the expression of downstream genes NAD(P)H quinone oxidoreductase1 (NQ01),catalase (CAT) and hemeoxygenase 1 (HO-1),thus abrogating Nrf2-mediated defense mechanisms against oxidative stress.Moreover,siRNA knockdown of Nrf2 significantly potentiated TP-induced apoptosis of TM4 cells.The above results from in vitro experiments were further validated in male mice after oral administration of TP (30,60,and 120 mg·k~1·d1,for 14 d),as evidenced bythe detected indexes,including dose-dependently decreased SDH activity,increased MDA concentration,altered testicle histomorphology,elevated caspase-3 activation,apoptosis induction,increased phosphorylation of JNK,and decreased gene expression of NQ01,CAT and HO-1 as well as nuclear protein expression of Nrf2 in testicular tissue.Our results demonstrate that TP activates apoptosis of Sertoli cells and injury of the testis via the ROS/JNK-mediated mitochondrial-dependent apoptosis pathway and down-regulates Nrf2 activation.