Rac1-independent methuosis mediates maduramicin-induced cardiotoxicity
摘要：Maduramicin often causes severe cardiotoxicity in target and nontarget animals. Apoptotic and non-apoptotic cell death mediate the cardiotoxicity induced by maduramicin. The effect and mechanism of non-apoptotic cell death are largely unknown. To understand the role of non-apoptotic cell death in maduramicin-induced cardiotoxicity, the rat cardiomyocytes（H9 c2） were used as an in vitro model in present study. We found maduramicin induced a large number of cytoplasm vacuoles in H9 c2 cells, which were time-dependent and concentration-dependent. The vacuoles were phase-lucentcoated with monolayer membrane. In a certain time range, the vacuolation of H9 c2 cells induced by maduramicin is reversible. Organelle staining showed that the cytoplasmic vacuoles induced by maduramicin did not originate from the swelling of mitochondria, endoplasmic reticulum and Golgi apparatus, but there was partial co-localization between vacuoles and lysosomes. The dextran uptake assay indicated that the cytoplasmic vacuoles mainlygenerated from macropinocytosis. However, there was no obvious co-localization between maduramicin-induced cytoplasm vacuoles and early endosome marker protein EEA1, late endosome marker protein Rab7, lysosome marker protein LAMP1 as well as autophagy marker protein LC3 B. H-Ras and Rac1 were significantly upregulated（P＜0.05 or P＜0.01） after maduramicin treatment for 24 h-72 h, along with the significant increased expression of activated Rac1. After silencing Rac1 gene, the death rate of H9 c2 cells was significant reduced, but the number of cytoplasm vacuolesdid not decrease. These findings demonstrate a non-apoptotic cell death type methuosis mediates mduramicin-induced severe cardiotoxicity in Rac1-independent way.