Expression of interleukin-6 is suppressed by inhibition of voltage-sensitive Na⁺/Ca²⁺ channels after cerebral ischemia

Expression of interleukin-6 (IL-6), a neurotrophic cytokine, is up-regulated after cerebral ischemia, but the underlying mechanism of the up-regulation remains unclear. NS-7 is a novel blocker of voltage-sensitive Ca²⁺ and Na⁺ channels and is known to reduce cerebral damage by ischemia. The present study was undertaken to examine the association between increases in intracellular Ca²⁺ concentration induced by membrane depolarization and IL-6 induction. IL-6 expression in rat brain was investigated by immunohistochemistry and Western blot analysis following 3.5-48 h of reperfusion after 1.5 h of occlusion of the middle cerebral artery. NS-7 (1 mg/kg; NS-7 group) or saline (saline group) was injected i.v. 5 min after the start of reperfusion. The saline group showed clear IL-6 expression in various cortical regions, which peaked at 24h of reperfusion. By contrast, IL-6 expression was significantly suppressed in the NS-7 group throughout the reperfusion period. Microglia activation was also reduced in the NS-7 group. These findings suggest that IL-6 expression may be up-regulated by the increased intracellular Ca²⁺ concentration triggered by membrane depolarization after cerebral ischemia. (C) 2000 Lippincott Williams and Wilkins.