MORPHOLOGICAL POLARIZATION OF HUMAN POLYMORPHONUCLEAR LEUKOCYTES IN RESPONSE TO 3 DIFFERENT CHEMOATTRACTANTS - AN EFFECTOR RESPONSE INDEPENDENT OF CALCIUM RISE AND TYROSINE KINASES

Chemoattractants such as interleukin-8, C5a and N-formylmethionyl-leuc yl-phenylalanine induce a cytosolic calcium rise involved in triggerin g the secretory functions of human polymorphonuclear leucocytes. We st udied the possible role of calcium rise in membrane ruffling, actin po lymerization, filamentous actin distribution, and morphological polari zation, which are all events contributing to chemotaxis, Membrane ruff ling was assessed by right-angle light-scatter changes, the cellular c ontent of polymerized actin by fluorescence of bodipy phallacidin, the intracellular distribution of filamentous actin by fluorescence micro scopy and image digitization, and morphological polarization by scanni ng electron microscopy, Pretreatment of polymorphonuclear leucocytes w ith 50 mu M BAPTA/AM, an intracellular calcium chelator, lowered the b asal level in cell calcium and inhibited the transient calcium rise st imulated by 2 nM interleukin-8, 2 nM C5a, and 10 nM N-formylmethionyl- leucyl-phenylalanine. However, BAPTA pretreatment of polymorphonuclear leucocytes did not modify membrane ruffling, actin polymerization, fi lamentous actin distribution, and morphological polarization stimulate d by chemoattractants. Downstream effecters may be protein tyrosine ki nases. However, the tyrosine kinase inhibitor tyrphostin did not affec t the cytoskeletal characteristics elicited by chemoattractants. Taken together, our results suggest that the transductional pathway leading to cytoskeleton organization and morphological polarization of polymo rphonuclear leucocytes is different from that leading to secretion.