Involvement of tyrosine protein kinase in INF-gamma-induced human endothelial cell apoptosis

Although it is well recognized that interferon-gamma (IFN-gamma) is involve d in the development of systemic inflammatory response syndrome, a conditio n characterized by loss of endothelial barrier function, whether or not IFN -gamma has any direct effect on endothelial cell (EC) death is unclear. Fur thermore, which signal transduction pathway involved in IFN-gamma-induced E C apoptosis remains to be elucidated. To answer these questions, we investi gated the effect of IFN-gamma on EC death (apoptosis versus necrosis) and t he underlying signal transduction pathway responsible for IFN-gamma-induced EC apoptosis. IFN-gamma resulted in a dose-dependent increase in EC apopto sis after 24 h incubation (p < .05). However, IFN-gamma did not induce EC n ecrosis. Tumor necrosis factor-alpha (TNF-alpha), but not lipopolysaccharid e (LPS), had a augmentative effect on IFN-gamma-induced EC apoptosis (p < . 05), while both of them alone failed to induce EC apoptosis. These results indicate that exposure of EC to IFN-gamma can cause apoptosis rather than n ecrosis. Both calcium ionophore, A23187, and the protein kinase C (PKC) act ivator phorbol-myristate-acetate (PMA) had a synergistic effect on IFN-gamm a-induced EC apoptosis (p < .05). However, neither the calcium chelator 1,2 -bis 2-aminophenoxy ethane-N,N,N',N'-tetraacetic acid (BAPTA), nor the PKC inhibitor 1 -5-isoquinolinysulfonyl 2-methyl piperazine (H-7) attenuated IF N-gamma-induced EC apoptosis. Three specific tyrosine protein kinase (TPK) inhibitors, herbimycin A, tyrphostin, and genistein, significantly inhibite d IFN-gamma-induced EC apoptosis in a dose-dependent fashion (p < .05). Fur thermore, the activation of TPK in EC by IFN-gamma was completely abrogated by these TPK inhibitors. These findings suggest that the signal transducti on pathway required for induction of EC apoptosis by IFN-gamma is TPK depen dent and is independent of calcium and PKC.