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Biochem J. 1997 Nov 1;327 ( Pt 3):819-23.

Differential regulation of nitric oxide synthase mRNA expression by lipopolysaccharide and pro-inflammatory cytokines in fetal hepatocytes treated with cycloheximide.

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Instituto de Bioquímica (CSIC-UCM), Facultad de Farmacia, Universidad Complutense, 28040 Madrid, Spain.


The effect of cycloheximide (CHX) on the mRNA expression of the cytokine-inducible, calcium-independent nitric oxide synthase (iNOS) was investigated in fetal hepatocytes stimulated with lipopolysaccharide (LPS) or pro-inflammatory cytokines. In the presence of CHX the LPS-dependent iNOS mRNA levels were reduced, whereas the response to pro-inflammatory cytokines was enhanced. Because iNOS transcription is highly dependent on the activation of nuclear factor kappaB (NF-kappaB), this factor was evaluated by electrophoretic mobility shift assays, and a close correlation between NF-kappaB activity and iNOS mRNA levels was observed. CHX itself potentiated the degradation of the IkappaB alpha and IkappaB beta inhibitory subunits (IkappaB is inhibitory kappaB) of the NF-kappaB complex, and therefore the loss of LPS-dependent iNOS mRNA expression cannot be attributed to a blockage in the activation of NF-kappaB. These results suggest the existence of a CHX-sensitive pathway in the expression of iNOS mediated by LPS, a mechanism that is not involved in the response to pro-inflammatory cytokines.

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