Nitrite inhalation in rats elevates tissue NOSIII expression and alters tyrosine nitration and phosphorylation

Organic nitrites are nitric oxide (NO) donors that are used predominantly a s inhalent drugs of abuse and have been shown to have immunomodulating effe cts. NO donors can modulate NOS activity and expression, thus altering the level of endogenous NO production. NO can react with superoxide (O-2(.-)) t o form peroxynitrite (ONOO-), which can nitrate tyrosine residues in protei ns and alter tyrosine phosphorylation. We investigated the effects of inhal ed isobutyl nitrite (ISBN) on NOS expression, tyrosine nitration, and tyros ine phosphorylation in selected organs of rats. Following exposures of 109 and 1517 ppm ISBN for 4 h, the lung, spleen, liver, and kidney were removed and assayed by SDS-PAGE for NOS III (eNOS), NOS EI (iNOS), nitrotyrosine ( NT)- and phosphotyrosine (PT)-immunoreactive proteins using specific antibo dies, ISBN at 1517 ppm, but not 109 ppm, caused an increase in NOS III expr ession in the liver and kidney, but not in the lung and spleen, No apparent effect on NOS II expression was observed in these organs. The expressions of NT and PT protein bands (30-200 kDa) were increased in the liver and kid ney, but not in the lung and spleen. This increase in NT persisted for 24 h post-exposure. Increased NOS III expression in the liver and kidney may pr omote peroxynitrite formation and contribute to the increase in NT and PT i mmunoreactivity. ISBN inhalation may thus cause changes in cellular signali ng involving tyrosine phosphorylation. These findings may suggest a mechani stic basis for the apparent immunotoxicity associated with nitrite abuse. ( C) 2000 Academic Press.