Purpose Chronic ethanol (EtOH) ingestion increases the incidence of the acute respiratory distress syndrome (ARDS), a severe form of acute lung injury. Based on previous evidence that chronic EtOH stimulation increased endothelial nitric oxide synthase (eNOS) expression and activity in pulmonary endothelial cells in vitro, we hypothesize that chronic EtOH ingestion would increase lung eNOS expression and activity in a well-established rat model of chronic EtOH ingestion.
Methods Male Sprague-Dawley rats were fed liquid diets containing EtOH (36% of calories) or maltose-dextrin as an isocaloric substitution for EtOH (control) for 6 weeks. Selected animals were also treated with the angiotensin-converting enzyme (ACE) inhibitor lisinopril (3 mg/L) for 6 weeks. Lung tissue was prepared for analysis of H2O2 production, NOS activity, cGMP production, eNOS expression, and eNOS interactions with its regulatory proteins.
Results Compared with control rats, H2O2 production, eNOS expression, lungNOS activity, and cGMP levels were significantly increased in EtOH-treated rats, effects attenuated by lisinopril. Chronic EtOH ingestion also increased lung levels of heat shock protein 90 (hsp90) while having no effect on caveolin 1 expression, and in co-immunoprecipitation studies decreased caveolin 1-eNOS interactions while having no effect on hsp90-eNOS interaction.
Conclusions These results indicate that chronic EtOH ingestion increases lung eNOS expression and activity. The increased eNOS activity appears related in part to EtOH-induced alterations in the interaction of eNOS with regulatory proteins. Along with our previous reports, these findings provide new insight into mechanisms by which EtOH ingestion alters cell function in vivo and implicates EtOH-mediated increases in reactive oxygen and nitrogen species as important mediators.