Cytotoxicity by nitrite inhalants is not related to peroxynitrite formation

Nitrite inhalant abuse has been correlated with HIV and Kaposi's sarcoma. Mouse models of inhalant exposure show immunosuppression and loss of immune cells. In the present study, isobutyl nitrite caused a dose-dependent loss of viability of a macrophage cell line. In the absence of cells, isobutyl nitrite reacted with hydrogen peroxide to form peroxynitrite. However, assays of mitochondrial respiration and nitration that detect peroxynitrite indicated that very little was present in cell cultures following exposure to the inhalants. Isobutyl, isoamyl, and butyl nitrites inhibited mitochondrial respiration, but only at high concentrations. Similarly, the nitrating activity of isobutyl nitrite occurred only at high concentrations and was not affected by the presence of hydrogen peroxide. Western blots showed that the inhalant did not increase nitrotyrosine formation in RAW cells or in peritoneal exudate macrophages (PEM) from exposed mice. Thus, the toxicity induced by isobutyl nitrite was probably not due to peroxynitrite formation.