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

The kinetics of IL-8, tumour necrosis factor-alpha (TNF-alpha and IL-1 beta release by PMN adhered to fibronectin, laminin or plastic for 24 h in response to continuous stimulation with lipopolysaccharide (LPS; 50 ng/ml), N-formyl-Met-Leu-Phe (fMLP; 100 mM), or phorbol myristate acetate (PMA; 10 ng/ml), was investigated under altered oxygen tension conditions. Cell supernatants were sampled for cytokine content every 6 h and measured by ELISA. IL-8 was the most abundant cytokine, produced in a range of up to 5.4 ng/ml; TNF-alpha and IL-1 beta were produced in a range of up to 1 ng/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-1 beta production and markedly inhibited TNF-alpha production. PMA markedly suppressed IL-8 and IL-1 beta release and failed to induce any release of TNF-alpha. Hypoxia had an overall inhibitory effect on cytokine release except for PMA-induced IL-1 beta release, and hypoxia/reoxygenation had a significant upregulating effect except for a further inhibition of fMLP-induced release of TNF-alpha. 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.