REGULATION OF POLYMORPHONUCLEAR NEUTROPHIL CD16 AND CD11B CD18 EXPRESSION BY MATRIX PROTEINS DURING HYPOXIA IS VLA-5, VLA-6 DEPENDENT/

We investigated the effects of hypoxia on matrix protein regulation of polymorphonuclear neutrophil (PMN) CD16 and CD11b/ CD18 expression. A dherence of PMN to fibronectin increased CD16 expression during hypoxi a over levels seen during normoxia, while adherence of PMN to either f ibronectin or laminin increased CD11b/CD18 expression during hypoxia o ver levels seen during normoxia. Kinetics assays demonstrated a t(1/2) approximate to 60 min and 30 min of hypoxia for maximal up-regulation of CD16 and CD11b/CD18, respectively. Incubation of fluid-phase PMN w ith anti-VLA-5 (alpha(5)/beta(1)) and anti-VLA-6 (alpha(6)/beta(1)) mA bs blocked the effect of fibronectin and laminin on CD16 and CD11b/CD1 8 expression. Cross-linking of both fluid-phase and adherent PMN VLA-5 and VLA-6 receptors resulted in a progressive increase in CD16 and CD 11b/CD18 expression during hypoxia, but not normoxia. Increases in CD1 6 and CD11b/CD18 expression resulted in increased E anti-Fc gamma RIII and EC3bi resetting. Inhibition of G(PLC) activity and IP3 production with U73122 and cyclopiazonic acid blocked the ability of fibronectin to increase CD16 expression and E anti-Fc gamma RIII resetting. Inhib ition of protein tyrosine kinase with genistein and herbimycin A block ed the ability of laminin to increase CD11b/CD18 expression and EC3bi resetting. Depletion of intracellular Ca2+ abrogated the effects of fi bronectin and laminin on CD16 and CD11b/CD18 expression, while restora tion of intracellular Ca2+ restored the ability of fibronectin and lam inin to increase CD16 and CD11b/CD18 expression. These results demonst rate that during hypoxia integrin signaling via alpha(5)/beta(1) and a lpha(6)/beta(1) results in the increased expression of CD16 and CD11b/ CD18. This increase in receptor expression results in biologically act ive receptors and is dependent upon intracellular Ca2+, G(PLC), and pr otein tyrosine kinase activity.