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Background: Ethanol (EtOH) is known to alter host immune responses and cytokine production. Acute EtOH exposure can suppress tumor necrosis factor (TNF)-[alpha] production, which attenuates pulmonary defense against infection. Previous studies in our laboratory show that acute EtOH inhibited TNF-[alpha] production by a posttranscriptional process, namely suppression of TNF-[alpha]-converting, enzyme-mediated, ectodomain shedding. However, chronic EtOH has been shown to augment TNF-[alpha] production, and this has been associated with EtOH-induced liver injury. To further characterize this paradoxical effect of EtOH on TNF-[alpha] production, we developed an in vitro model by using Mono Mac 6 cells, a human monocytic cell line.

Methods: Mono Mac 6 cells were treated with EtOH (0-75 mM) for 1 to 7 days. TNF-[alpha] production was induced by lipopolysaccharide and phorbol myristate acetate and quantitated by enzyme-linked immunosorbent assay. Generation of reactive oxygen species (ROS) was assayed by using a specific fluorogenic reagent.

Results: Acute EtOH initially inhibited lipopolysaccharide/phorbol myristate acetate-induced TNF-[alpha] production in Mono Mac 6 cells. However, during chronic EtOH exposure, this inhibition was reversed gradually over time. By day 6 after EtOH treatment, Mono Mac 6 cells demonstrated significant up-regulation of TNF-[alpha] production. Moreover, chronic EtOH induced the generation of ROS in these Mono Mac 6 cells. Scavenging ROS by Mn(III)tetrakis(1-methyl-4pyridyl)porphyrin pentachloride and N-acetyl-L-cysteine attenuated chronic EtOH-enhanced TNF-[alpha] production.

Conclusion: These results suggest that ROS induction is involved in EtOH-enhanced TNF-[alpha] production by monocytes. This study also provides insight into the mechanisms of alteration of TNF-[alpha] production in different EtOH exposure settings.

(C) 2001 Lippincott Williams & Wilkins, Inc.