Cell-surface heparan sulfate proteoglycan-mediated regulation of human neutrophil migration by the serpin antithrombin III

The serpin antithrombin III (AT III) is reported to have hemostasis-regulat ing and anti-inflammatory properties. To determine its ability to influence thrombin-independent leukocyte responses, the direct effects of the AT III concentrate Kybernin P and a monoclonal antibody-purified AT III on neutro phil migration were studied. Chemotactic activity of human neutrophils isol ated from the blood of healthy donors was determined in modified Boyden mic rochemotaxis chambers, and binding studies were performed according to stan dard experimental protocols. Preincubation in vitro of neutrophils with Kyb ernin P or immune-adsorbed AT iii significantly deactivated migration towar d fMet-Leu-Phe, or interleukin-8 (IL-8), in a concentration-dependent manne r. In the absence of additional attractants, neutrophils exhibited a migrat ory response toward gradients of AT III preparations. True chemotaxis was c onfirmed in checkerboard assays. Analyses revealed that the AT III heparin- binding site interacts with neutrophil membrane-associated heparan sulfate proteoglycan receptors, Mechanisms of intracellular signaling differed; the deactivation of IL-8-induced chemotaxis resulted from tyrphostin-sensitive interactions of AT Ill-signaling with the IL-8 signal transduction pathway , whereas AT III-induced chemotaxis involved protein kinase C and phosphodi esterases. Signaling similarities between AT III and the proteoglycan synde can-4 may suggest the binding of AT III to this novel type of membrane rece ptor. Under physiological conditions, AT III may prevent neutrophils from p remature activation. Moreover, the systemic administration of AT III concen trate could have beneficial effects in combating systemic inflammation. (c) 2001 by The American Society of Hematology