Polymorphonuclear leucocyte (PMN)-derived inflammatory cytokines—regulation by oxygen tension and extracellular matrix

Abstract

Abstract The kinetics of IL-8, tumour necrosis factor-alpha (TNF-α) and IL-1β release by PMN adhered to fibronectin, laminin or plastic for 24h in response to continuousstimulation with lipopolysaccharide (LPS; 50ng/ml), n-formyl-Met-Leu-Phe (fMLP; 100mm), or phorbol myristate acetate (PMA; 10ng/ml), was investigated under altered oxygen tension conditions. Cell supernatants were sampled for cytokine content every 6h and measured by ELISA. IL-8 was the most abundant cytokine, produced in a range of up to 5.4ng/ml; TNF-α and IL-1β were produced in a range of up to 1ng/ml. During normoxia, LPS was the most potent stimulus, inducing the release of each cytokine, while fMLP showed a less pronounced effect on IL-8 and IL-1β production and markedly inhibited TNF-α production. PMA markedly suppressed IL-8 and IL-1β release and failed to induce any release of TNF-α. Hypoxia had an overall inhibitory effect on cytokine release except for PMA-induced IL-1β release, and hypoxia/reoxygenation had a significant up-regulating effect except for a further inhibition of fMLP-induced release of TNF-α. Integrin–matrix protein ligation differentiated both spontaneous and externally induced cytokine release and its sensitivity to alteration in oxygen tension. Thus the process of PMN elaboration of inflammatory cytokines is controlled on multiple levels of signal transduction, differentiated by integrin–extracellular matrix interactions, and is sensitive to alterations in microenvironmental oxygen tension.