Fibrinogen-dependent neutrophil activation is mediated by tyrosine kinases.

RUBEL, CAROLINA; FERNÁNDEZ, GABRIELA; BEIGIER-BOMPADRE, MACARENA; DRAN, GRACIELA; BARRIONUEVO, PAULA; PALERMO, MARINA

Punta del Este, Uruguay.

Congreso; Vº Congreso Latinoamericano de Inmunología.; 1999

Asociación Latinoamericana de Inmunología (ALAI).

In a previous study we have shown that soluble fibrinogen (Fbg) induced the activation of human neutrophils (PMN) through the binding to the asubunit of the b2 integrin:CD11b/CD18. This activation was evaluated by the upregulation of CD11b and CD66b and the inhibition of spontaneous apoptosis. Considering that tyrosine phosphorilation of several proteins, including the Src family, have been implicated in adhesion mediated by b2 integrins and spreading of PMN, we now examined the role of protein tyrosine phosphorilation in Fbg-dependent activation of human PMN. We evaluated the effect of different kinase inhibitors on the upregulation of CD66b, CD11b, and inhibition of spontaneous apoptosis induced by soluble Fbg. The tyrosine kinase inhibitors (TKI) used were Genistein, a competitive inhibitor to ATP; Herbimicyn, wich attacks critical sulfhydril groups in tyrosine kinases; PP2, a selective TKI for Src family and H7, a serine kinase inhibitor. We observed that Fbg-induced upregulation of CD66b was blocked by Genistein, Herbimicyn and PP2 (control: 82 ± 11; +Fbg: 285 ± 72; +Gen+Fbg: 166 ± 40; +Herb+Fbg: 125 ± 25; +PP2+Fbg: 137 ± 31) but not by H7: (+Fbg+H7: 415 ± 122). Phorbol esters-induced degranulations, an stimulus notmediated by tyrosine kinases, was not affected. TKI also abolished Fbg delay of apoptosis (control: 47 ± 13; +Fbg: 16 ± 5; +Gen+Fbg: 44 ± 11; +Herb+Fbg: 42 ± 9; +PP2+Fbg: 40 ± 13). On the other hand, CD11b upregulation by Fbg was unafected by treatment with these inhibitors. It appears that Fbg dependent degranulation and inhibition of apoptosis are madiated by tyrosine kinases and at least Src family plays an important role in both functions. On the contrary, CD11b upregulation seems not to be regulated by tyrosine kinases suggesting the involvement of other signaling pathways in this Fbg effect. The knowledge of the mechanisms involved in the control of neutrophils activation might be critical for the resolution of the immflamatory focus.