Prolonged ethanol treatment enhances lipopolysaccharide/phorbol myristate acetate-induced tumor necrosis factor-alpha production in human monocytic cells.
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.


CONCLUSIONS
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.
Zhang
Z
Z
Department of Pediatrics, Louisiana State University School of Medicine, New Orleans, USA.
Bagby
G J
GJ
Stoltz
D
D
Oliver
P
P
Schwarzenberger
P O
PO
Kolls
J K
JK
D002273:Carcinogens; D002460:Cell Line; D002492:Central Nervous System Depressants / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D000431:Ethanol / Q000494:pharmacology*; D006801:Humans; D008070:Lipopolysaccharides; D009000:Monocytes / Q000187:drug effects* / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate; D014409:Tumor Necrosis Factor-alpha / Q000187:drug effects* / Q000378:metabolism
D002273:Carcinogens; D002492:Central Nervous System Depressants; D008070:Lipopolysaccharides; D017382:Reactive Oxygen Species; D014409:Tumor Necrosis Factor-alpha; D000431:Ethanol; D013755:Tetradecanoylphorbol Acetate