CEREBRAL INTERLEUKIN-6 IS NEUROPROTECTIVE DURING PERMANENT FOCAL CEREBRAL-ISCHEMIA IN THE RAT

Interleukin-6 (IL-6) is a neurotrophic cytokine expressed in both neur ons and glia. The present study shows that cerebral ischemia produced by permanent occlusion of the middle cerebral artery (MCAO) produces a dramatic increase in IL-6 bioactivity in the ischemic hemisphere with in 2 hours of MCAO (167 +/- 55 IU versus sham: 50 +/- 35 IU), with fur ther increases at 8 hours (3,456 +/- 1,162 IU) and 24 hours (6,008 +/- 1,772 IU), In a separate series of experiments. intracerebroventricul ar injection of recombinant IL-6 (3,100 or 31,000 IU) significantly re duced ischemic brain damage Lifter MCAO (to 52% and 65% of controls, r espectively). The large increase in endogenous IL-6 bioactivity in res ponse to ischemia, together with the marked neuroprotection produced b y exogenous IL-6 suggest that this cytokine is an important endogenous inhibitor of neuronal death during cerebral ischemia.