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Microcystin‐leucine arginine (MC‐LR) is a cyclic heptapeptide, produced by aquatic cyanobacteria such as microcystis, with strong reproductive toxicity which poses greater threat to the reproductive abilities of humans and animals. By exploring the role of trimethylation of histone H3 at lysine 4 (H3K4me3) and the role of oxidative stress in MC‐LR‐induced apoptosis in testicular Sertoli cells in Sprague‐Dawley (SD) rats, this study indicated that MC‐LR increased the expression levels of apoptosis‐related genes by raising the levels of H3K4me3. 5′‐Deoxy‐5′‐methylthioadenosine (MTA), the inhibitor of H3K4me3, reduced apoptosis, indicating for the first time that epigenetic modification is closely related to the testicular reproductive toxicity induced by MC‐LR. MC‐LR also induced oxidative stress by stimulating the generation of reactive oxygen species (ROS), and subsequently triggering mitochondria‐mediated apoptotic pathway by decreasing mitochondrial membrane potential and increasing the levels of Bax, Bcl‐2, Caspase‐3, and so on. MC‐LR‐induced apoptosis of testicular cells could be decreased after pretreatment with oxidative stress inhibitor N‐acetyl‐cysteine (NAC). Furthermore, the pathological damage to mitochondria and testes were observed in SD rats. These results show that MC‐LR can induce apoptosis by raising the levels of H3K4me3, and pretreatment with MTA can ameliorate the MC‐LR‐induced apoptosis of cocultured cells by lowering the levels of H3K4me3. Furthermore, NAC has a protective effect on MC‐LR‐induced apoptosis of testicular cells in SD rats by inhibiting the oxidative stress. [ABSTRACT FROM AUTHOR]

Microcystin‐LR (MC‐LR), a potent endotoxin, can induce reproductive toxicity. In order to investigate the role and mechanisms of apoptosis (p53‐dependent and mitochondrial pathways) of germ cells induced by MC‐LR, the co‐cultured primary Sertoli‐germ cells from Sprague‐Dawley rats were used for the experiments. Expression levels of proteins, genes, and mitochondrial membrane potential (MMP) were obtained after exposing co‐cultured Sertoli‐germ cells to MC‐LR with or without the addition of the p53 inhibitor, pifithrin‐α (PFT‐α), and MMP inhibitor, cyclosporin A (CsA). Results indicated that MC‐LR could activate p53‐dependent pathway‐associated proteins in Sertoli‐germ cells, leading to a decrease in MMP (indicating the opening of mitochondrial permeability transition pore [mPTP] and the release of Cytochrome‐c [Cyt‐c]) from the mitochondria into the cytoplasm and eventually the induction of apoptosis. PFT‐α inhibited the expression ofp53, ameliorated the MMP of the co‐cultured Sertoli‐germ cells, and prevented the release of Cyt‐c from the mitochondria into the cytoplasm, which reduces the occurrence of apoptosis. Similarly, the decreased release of Cyt‐c from the mitochondria into the cytoplasm and the declined level of apoptosis in Sertoli‐germ cells induced by MC‐LR were observed after the addition of CsA. These results indicated that the apoptosis of the co‐cultured Sertoli‐germ cells induced by MC‐LR was mediated by the p53‐dependent pathway, with the involvement of the opening of mPTP. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the MC-LR induced oxidative injury and apoptosis in Chinese hamster ovary (CHO) cells, and the protective effects of N-acetylcysteine (NAC) on these cells. Cell viability was determined by MTT assay after exposure to NAC at various concentrations (0, 1, 5, 10, 20, 30, 40, 50, 60 and 80 mmol/L) alone, or NAC (0, 1 and 5 mmol/L) plus MC-LR (0, 2.5, 5 and 10 μg/ml) for 24 h. The reactive oxygen species (ROS) in CHO cells were measured by DCFH-DA, mitochondrial membrane potential (MMP) by fluorescence probe JC-1 staining, and apoptosis index determined by Annexin V-PI staining. Results showed, following exposure to NAC alone for 24 h, cell viability remains higher than 80% at 1 and 5 mmol/L. After exposure to NAC at different concentrations plus MC-LR, cell viability increased, ROS decreased, MMP elevated, and apoptosis index reduced to a certain extent. In conclusion, MC-LR may induce the apoptosis of CHO cells by inducing ROS production which is protected by NAC.