A history of abuse of nitrite inhalants has been correlated with HIV seropositivity and Kaposi's sarcoma. A series of 14 daily, 45-min exposures of mice to 900-ppm isobutyl nitrite in an inhalation chamber reduced the number of peritoneal exudate macrophages (PEM) by 35% and the number of resident peritoneal macrophages (RPM) by 18%. Although the tumoricidal activity of RPM was not affected by the inhalant, the cytotoxicity of PEM was reduced by 26%. The induction of nitric oxide (NO) and the inducible NO synthase (iNOS) protein in PEM were inhibited by the inhalant to a similar extent. Inhibition of NF-kappaB activation in PEM from mice exposed to the inhalant corresponded to reduced degradation of the NF-kappaB inhibitor, IkappaB alpha. Proteasome-associated, enzymatic activity was compromised in PEM from inhalant-exposed mice, suggesting that inhaled isobutyl nitrite compromised macrophage, tumoricidal activity by inhibiting proteasomal degradation of the NF-kappaB inhibitor, IkappaB alpha.
