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Salinomycin, as a polyether ionophore antibiotic, is extensively used as a feed additive against coccidiosis in poultry and as a growth promoter of ruminants worldwide. Owing to its narrow therapeutic index, numerous intoxication have been reported in target/non-target animals by overdosage, misuse or drug interactions as well as human who consumed salinomycin accidently. Salinomycin-induced cardiotoxicity in chicken and non-target animals is considered as a major contributor to animal death. In the current study, we aim to elucidate the underlying mechanism of its myocardial toxicity using primary chicken myocardial cell as an in vitro model. The results showed that salinomycin altered cellular morphology and induced cell death in a concentration-dependent manner. Salinomycin treatment elevated the permeability of the cell membrane and leaded to the efflux of enzymes, including creatine kinase (CK) and lactate dehydrogenase (LDH). Flow cytometry analysis indicated the number of apoptotic cells increased significantly by salinomycin exposure. Furthermore, caspase-3 and caspase-9 were activated at gene and protein level rather than caspase-8, along with the up-regulation of apoptosis genes Bax, Cytochrome C, Apoptotic peptidase activating factor 1 (Apaf-1) and the down-regulation of Bcl-2. Salinomycin-induced mitochondrial dysfunction was accompanied by the significant decrease of mitochondrial membrane potential (MMP) and the severe ultrastructure damage. In conclusion, these findings suggest that the toxic dose of salinomycin induces severe cardiomyocytes death through mitochondria mediated apoptosis pathway., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Maduramicin is one of the most extensively used anticoccidial drugs for the treatment of Eimeria spp. infections. However, overdosage, misuse and drug interactions have resulted in the development of ionophore toxic syndrome. Heart and skeletal muscles have been identified as the main target organs of toxicity. In the present study, primary chicken myocardial cells were isolated to investigate the toxicity and underlying mechanisms of maduramicin. Our results showed that maduramicin causes morphological changes and a decrease in the viability of chicken myocardial cells. Annexin V-FITC/PI and 4′,6-diamidino-2-phenylindole (DAPI) staining showed a significant increase in the number of apoptotic cells. Furthermore, caspases-3/8/9 were activated at the gene and protein levels and this was accompanied by the upregulation of apoptosis-related genes, including bcl-2 , bax , and cytochrome C . Treatment with the pan-caspase inhibitor N -benzyloxycarbonyl-Val-Ala-Asp (O-Me) fluoromethyl ketone (z-VAD-fmk) ameliorated the apoptosis and cytotoxicity. Furthermore, intracellular Ca 2+ and reactive oxygen species (ROS) were elevated, whereas mitochondrial membrane potential (MMP) and intracellular glutathione (GSH) decreased with exposure to maduramicin. The antioxidant N -acetyl-cysteine (NAC) had no significant effect on maduramicin-induced cytotoxicity and apoptosis. Taken together, our findings demonstrate that maduramicin is cytotoxic to primary chicken myocardial cells via caspase dependent and independent apoptotic pathways. [ABSTRACT FROM AUTHOR]