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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]

Abstract The liver is an important iron storage site and a primary MC-LR target. C57BL/6 and Hfe −/− mice were used to investigate effects and mechanisms of MC-LR on systematic iron homeostasis. Body weight, tissue iron content, hematological and serological indexes, and histopathological were evaluated. Ultrastructure and iron metabolism-related genes and proteins were analyzed. MC-LR induced dose-dependent increases in red blood cells, hemoglobin, and hematocrit. In contrast MC-LR-induced dose-dependent decreases in mean corpuscular volume, hemoglobin, and hemoglobin concentration were observed both C57BL/6 and Hfe −/− mice. In both mouse species, serological indexes increased. Aggravated liver and spleen iron were observed in C57BL/6 mice, consistent with Perls' Prussian blue staining. However, an opposite trend was observed in Hfe −/− mice. C57BL/6 mice had lower Hamp1 (Hepcidn), Bmp6 , Il-6 , and Tmprss6. Significant increased Hjv , Hif-1α and Hif-2α were observed in both C57BL/6 and Hfe −/− mice. MC-LR-induced pathological lesions were dose-dependent increase in C57BL/6 mice. More severe pathological injuries in MC-LR groups (25 μg/kg) were observed in Hfe −/− mice than in C57BL/6 mice. In Hfe −/− mice, upon exposure to 25 μg/kg MC-LR, mitochondrial membranes were damaged and mitochondrial counts increased with significant swelling. These results indicated that MC-LR can induce the accumulation of iron in C57BL/6 mice with the occurrence of anemia, similar to thalassemia. Moreover, dysregulation of iron homeostasis may be due to MC-LR-induced Hamp1 downregulation, possibly mediated by hypoxia or the IL6–STAT3 and BMP–SMAD signaling pathways. Highlights • MC-LR induced the accumulation of iron in C57BL/6 mice with the occurrence of anemia that similar to thalassemia. • MC-LR reduced the expression of hepcidin that is the central hormone in regulating iron homeostasis in the body. • The downregulation of hepcidin induced by MC-LR may be related to hypoxia, IL-6-STAT3, and BMP-SMAD signaling pathway and HIFs play important roles. [ABSTRACT FROM AUTHOR]