Ethanol metabolism and effects: nitric oxide and its interaction

Ethanol (EtOH) in alcoholic beverages is consumed by a large number of individuals and its elimination is primarily by oxidation. The role of nitric oxide (NO) in EtOH's effects is important since NO is one of the most prominent biological factors in mammals. NO is constantly formed endogenously from L-arginine. Dose and length of EtOH exposure, and cell type are the main factors affecting EtOH effects on NO production. Either acute or chronic EtOH ingestion affects inducible NO synthase (iNOS) activity. However it seems that EtOH suppresses induced-NO production by inhibition of iNOS in different cells. On the other hand, it is clear that acute low doses of EtOH increase both the release of NO and endothelial NOS (eNOS) expression, and augment endothelium-mediated vasodilatation, whereas higher doses impair endothelial functions. EtOH selectively affects neuronal NOS (nNOS) activity in different brain cells, which may relate to various behavioral interactions. Therefore, there is an excellent chance for EtOH and NO to react with each other. Effects of EtOH on NO production and NOS activity may be important to EtOH modification of cell or organ function. Nitrosated compounds (alkyl nitrites) are often found as the interaction products, which might be one of the minor pathways of EtOH metabolism. NO also inhibits EtOH metabolizing enzymes. Furthermore, NO is involved in EtOH induced liver damage and has a role in fetal development during EtOH exposure in pregnancy. The mechanisms underlying these effects are only partially understood. Hence, the current discussion of the interaction of EtOH and NO is presented.