INHIBITION OF TUMOUR NECROSIS FACTOR PRODUCTION IN ENDOTOXIN-STIMULATED HUMAN MONONUCLEAR LEUKOCYTES BY THE PROSTACYCLIN ANALOGUE ILOPROST: CELLULAR MECHANISMS

Abstract

The prostacyclin analogue iloprost has been shown to inhibit effectively TNF-α 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-α synthesis by iloprost. Healthy human PBMC were challenged withEscherichia coliLPS and assessed for TNF-α gene transcription, mRNA stability and protein secretion. Iloprost reduced both steady-state TNF-α 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-α transcriptional activity (as evaluated by nuclear run-on transcription analysis) and a decrease in TNF-α mRNA stability (as assessed by serial Northern blot analysis of TNF-α mRNA content in PBMC blocked with actinomycin D). When collectively assessed, these data demonstrate that iloprost regulates TNF-α synthesis at both transcriptional and post-transcriptional level.