Cytotoxicity of cytokines in cerebral microvascular endothelial cell

Abstract

Objective: Several studies reported that the levels of proinflammatory cytokines such as TNF-α, IL-1β, IL-6, and IL-8 are elevated in the cerebrospinal fluid (CSF) of patients after subarachnoid hemorrhage (SAH). Cytokines in CSF may contribute to the development of vasospasm and cerebral ischemia. In the present study, we investigated the possible cytotoxic effects of these cytokines on cultured cerebral microvascular endothelial cells. Method: The effects of TNF-α, IL-1β, IL-6, and IL-8 were tested using cell viability assay, DNA fragmentation analysis (DNA laddering), Western blot analysis (Anti-poly-(ADP-ribose) polymerase [PARP] antibody), and caspase-3 activity. Results: TNF-α and IL-1β, but not IL-6 or IL-8, caused cell detachment in a dose-dependent manner ( p<0.05). TNF-α (200 pg/ml) and IL-1β (150 pg/ml) produced DNA ladders at 24–72 h. TNF-α but not IL-1β cleaved the PARP from 116- to 85-kDa fragments and enhanced caspase-3 activity at 24–72 h after incubation with endothelial cells. Caspase-3 inhibitor at 10 μmol/l significantly prevented TNF-α-induced cell detachment ( p<0.05). Discussion: TNF-α induces apoptosis in cultured cerebral endothelial cells through the cleavage of caspase-3. IL-1β decreases the adherent cells, produces DNA ladders, but fails to cleave PARP or increase caspase-3 activity. IL-1β may induce apoptosis in cerebral endothelial cells through different pathway from that of TNF-α.