Inhibition of tumour necrosis factor production in endotoxin-stimulated human mononuclear leukocytes by the prostacyclin analogue iloprost: cellular mechanisms.

The prostacyclin analogue iloprost has been shown to inhibit effectively TNF-alpha production in human peripheral blood mononuclear leukocytes (PBMC) stimulated with bacterial lipopolysaccharide (LPS). The current paper set out to analyse further the possible mechanisms involved in the regulation of TNF-alpha synthesis by iloprost. Healthy human PBMC were challenged with Escherichia coli LPS and assessed for TNF-alpha gene transcription, mRNA stability and protein secretion. Iloprost reduced both steady-state TNF-alpha mRNA expression and protein release as assessed by Northern blot analysis, polymerase chain reaction and enzyme immunoassay. This effect was related both to a reduction of TNF-alpha transcriptional activity (as evaluated by nuclear run-on transcription analysis) and a decrease in TNF-alpha mRNA stability (as assessed by serial Northern blot analysis of TNF-alpha mRNA content in PBMC blocked with actinomycin D). When collectively assessed, these data demonstrate that iloprost regulates TNF-alpha synthesis at both transcriptional and post-transcriptional level.