POLYMORPHONUCLEAR LEUKOCYTE (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, produ ced in a range of up to 5.4 ng/ml; TNF-alpha and IL-1 beta were produc ed in a range of up to 1 ng/ml. During normoxia, LPS was the most pote nt 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 h ad an overall inhibitory effect on cytokine release except for PMA-ind uced IL-1 beta release, and hypoxia/reoxygenation had a significant up regulating effect except for a further inhibition of fMLP-induced rele ase of TNF-alpha. Integrin-matrix protein ligation differentiated both spontaneous and externally induced cytokine release and its sensitivi ty to alteration in oxygen tension. Thus the process of PMN elaboratio n. of inflammatory cytokines is controlled on multiple levels of signa l transduction, differentiated by integrin-extracellular matrix intera ctions, and is sensitive to alterations in microenvironmental oxygen t ension.