Effects of ethanol on neutrophil recruitment and lung host defense in nitric oxide synthase I and nitric oxide synthase II knockout mice

Background: Ethanol (ETOH) inhibits Escherichia coli endotoxin [lipopolysac charide (LPS)]-mediated induction of nitric oxide (NO) synthase (NOS) trans cription and translation in macrophages and neutrophils [polymorphonuclear (PMN) cells] within the lung. ETOH also inhibits PMN recruitment into the l ung and enhances NOS I-mediated production of NO. The contribution of the i ndividual NOS isozymes to ETOH-mediated suppression of the host defense res ponse to lung infection has not been defined. Methods: We evaluated the role of constitutive NOS I and NOS II in ETOH-med iated inhibition of PMN recruitment into the lung and ETOH-mediated suppres sion of lung clearance of inhaled Klebsiella pneumonia (K: pneumoniae) in f emale, homozygous transgenic mice deficient in the genes for NOS I (nNOS-KO ) or NOS II (iNOS-KO) and their wild-type controls (WT). Results: Four hours after intratracheal administration of LPS or aerosol in halation of IL pneumoniae, the lung content of PMNs obtained by bronchoalve olar lavage from WT mice was significantly reduced when compared with that obtained from the lungs of nNOS-KO and iNOS-KO mice. Pretreatment of WT mic e with the NOS ii inhibitor L-N6-iminoethyllysine (L-NIL; 10 mg/kg, ip) or with the NOS I inhibitor 7-nitroindazole (7-NI) (10, 25, or 40 mg/kg, ip) 3 0 min before LPS administration enhanced the lung content of PMNs recoverab le by bronchoalveolar lavage. However, pretreatment of iNOS-KO with L-ML di d not affect lung recruitment of PMNs. Moreover, administration of 25 or 40 mg/kg, ip of 7-NI to nNOS-KO mice resulted in death of all the animals wit hin 10 min. Pretreatment of nNOS-KO with 7-NI (10 mg/kg) did not affect LPS -stimulated PMN recruitment. Pretreatment of mice with ETOH (4.5 g/kg, ip) produced a greater inhibition of LPS-stimulated lung recruitment of PMNs in iNOS-KO mice than in WT mice. In contrast, pretreatment of nNOS-KO with ET OH produced little inhibition of LPS-stimulated lung recruitment of PMNs wh en compared with that measured in WT mice. Finally, 4 hr after aerosol inha lation of It pneumoniae, lung clearance of this bacteria was enhanced in iN OS-KO when compared with WT and inhibited in nNOS-KO when compared with WT mice. ETOH-mediated suppression of lung clearance of It pneumoniae was unaf fected in nNOS-KO mice and enhanced in the iNOS-KO mice, when compared with that obtained in WT mice. ETOH-stimulated the production of NOS I-derived nitrate and nitrite production by rat brain and lung and inhibited LPS-indu ced NOS II mRNA, protein, and production of nitrate and nitrite anion. Fina lly, inhibition of NOS I and NOS I deletion inhibited the in vivo metabolis m of ETOH. Conclusions: We conclude that constitutive NOS I is involved in protection of the lung from stressor-induced lung injury. NOS I within the PMNs may li mit PMN recruitment into the lung. Speculatively, NOS II-derived NO may als o limit PMN-induced lung damage at the expense of a slower clearance of the bacterial burden.