Role of PKC and tyrosine kinase in ethanol-mediated inhibition of LPS-inducible nitric oxide synthase.
Ethanol increases human and animal susceptibility to opportunistic lung infections in part by suppression of endotoxin (LPS) and bacteria-mediated upregulation of inducible nitric oxide synthase (iNOS) in alveolar macrophages (AM). LPS and cytokine-induced NOS mRNA are dependent on NF-kappaB/Rel (NFkappaB) and Activator Protein-1 (AP-1), which are regulated in turn by protein kinase C and tyrosine kinase-dependent phosphorylation. ETOH does not directly inhibit NFkappaB or AP-1, in vivo, but rather inhibits LPS-induced activation of the MEKK/MAP kinase system and inhibition of inhibitory protein IkappaBalpha required for formation of AP-1 and NFkappaB, respectively. in AM. Both transcription factors are involved iNOS mRNA transcription. LPS-induced upregulation of MEKK/MAP tyrosine kinase upregulates NADPH oxidase activity and oxygen free radical formation required for activation of NFkappaB and AP-1 and phosphorylation of IkappaBalpha. LPS downregulates endogenous calcium-sensitive PKC isozymes (PKCdelta), which repress iNOS mRNA expression. ETOH inhibits LPS-induced upregulation of iNOS mRNA by preventing its ability to decrease PKCdelta and upregulate tyrosine kinase-mediated phosphorylation. This effect of ETOH is prevented by inhibitors of PKC and tyrosine kinase. The data support the hypothesis that ETOH inhibits LPS-induced upregulation of iNOS mRNA by interfering with the phosphorylation processes involved in activation of the nuclear transcription factors NFkappaB and AP-1.
Greenberg
S S
SS
Alcohol Research Center, Department of Medicine, Louisiana State University Medical Center, New Orleans 70112, USA.
Jie
O
O
Zhao
X
X
Wang
J F
JF
D000818:Animals; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D000431:Ethanol / Q000494:pharmacology*; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology*; D016676:Macrophages, Alveolar / Q000201:enzymology; D016328:NF-kappa B / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D052247:Nitric Oxide Synthase Type II; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D018808:Transcription Factor AP-1 / Q000494:pharmacology
D004791:Enzyme Inhibitors; D008070:Lipopolysaccharides; D016328:NF-kappa B; D018808:Transcription Factor AP-1; D000431:Ethanol; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C