The metalloporphyrin FeTPPS but not by cyclosporin A antagonizes the interaction of peroxynitrate and hydrogen peroxide on cardiomyocyte cell death

The objective of this study was to determine whether the metalloporphyrin, 5,10,15,20-tetrakis(4-sulfonatophenyl) porphyrinato iron (III) chloride (FeTPPS), antagonized the effect of peroxynitrite, oxygen-free radicals, and the combination of the two, on cardiomyocyte cell viability. We further sought to compare the effects of FeTPPS to an inhibitor of the mitochondrial transmembrane permeability transition pores (PTP)—cyclosporin A. Cardiomyocytes from embryonic chick heart were treated with 3-morpholinosydnonimine (SIN-1), which decomposes to liberate NO and superoxide anion (O₂ ⁻) which in turn generates peroxynitrite. FeTPPS antagonized cell death induced by either SIN-1 or H₂O₂. The combination of H₂O₂ plus SIN-1 further enhanced the amount of cell death over SIN-1 alone. FeTPPS rescued cells from almost complete cell death with the combination of SIN-1 plus H₂O₂. SIN-1 induced cardiac protein nitration, including mitochondrial proteins as demonstrated by Western blotting with nitrotyrosine-specific antibodies. FeTPPS reduced cellular protein nitration. SIN-1-induced loss of mitochondrial transmembrane permeability transition pores potential was visualized with fluorescent dye staining and was reversed by FeTPPS. In contrast, the mitochondrial PTP blocker cyclosporin A did not alter SIN-1-induced cell death. In summary, these data demonstrate the enhanced cellular lethality of the combination of peroxynitrite and reactive oxygen species from hydrogen peroxide. A mitochondrial death pathway was implicated as nitration of mitochondrial proteins was induced by peroxynitrite that also induced a loss of ΔΨm that was prevented by FeTPPS. In contrast, cyclosporin did not antagonize the effects of SIN-1. The ability of FeTPPS to reduce reactive nitrogen-induced cell death, and protein nitration suggests that FeTPPS is a useful agent to maintain cell viability and is better than cyclosporin in this situation.