Ethanol inhibits cytokine-induced iNOS and sPLA2 in immortalized astrocytes: Evidence for posttranscriptional site of ethanol action

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Abstract
Chronic and excessive ethanol consumption is known to alter neuron and glial cell functions in the central nervous system (CNS). Astrocytes comprise the major cell type in the brain. These immune active cells are capable of responding to proinflammatory cytokines and endotoxins, which stimulate transcriptional pathways leading to induction of genes, including the inducible nitric oxide synthase (iNOS) and secretory phospholipase A2 (sPLA2). In this study, we investigate the effects of ethanol on cytokine-induced iNOS and sPLA2 in immortalized astrocytes (DITNC). When DITNC cells were exposed to ethanol (0–200 mM) for 4 h prior to subsequent stimulation with cytokines for 16 h, NO production decreased with increasing ethanol concentrations starting from 50 mM. At ethanol concentrations higher than 100 mM, ethanol also inhibited cytokine-induced sPLA2 release into the culture medium. The inhibitory effect of ethanol on NO production corresponds well with the decrease in iNOS protein and NOS enzyme activity, but not with iNOS and sPLA2 mRNA nor binding of NF-κB to DNA. The inhibition of cytokine-induced NO production by ethanol was also dependent on the time of ethanol exposure to the cells, but addition of acetaldehyde up to 200 µM did not elicit any changes. Taken together, these results provide evidence for a posttranscriptional mode of ethanol action on the cytokine induction pathway for NO production in astrocytes.