Ischemic preconditioning-induced neuroprotection is associated with differential expression of IL-1β and IL-1 receptor antagonist in the ischemic cortex

Ischemic preconditioning (IP) is a phenomenon that organs develop a tolerance toward subsequent lethal ischemic insults. Among the factors that are involved in IP, IL-1β and its endogenous receptor antagonist IL-1ra have been identified as important players in the induction of IP. The present study investigated whether IP affects the levels of these two antagonistic proteins during tolerance and reperfusion periods after ischemic stroke. The IP 24 h prior to ischemic stroke resulted in neuroprotection in the cortex. IP-induced protection is accompanied by increased IL-1β gene and IL-1ra gene and protein levels during the tolerance period. In the post-ischemic cortex, IP resulted in the suppression of IL-1β mRNA and protein levels at 6 h without affecting IL-1ra expression and the up-regulation of IL-1ra protein at 24 h. These findings demonstrate that IP differentially regulates cortical IL-1β and IL-1ra expression before and after ischemic stroke and suggest that the shift toward an anti-inflammatory state in the post-ischemic cortex may contribute to IP-induced neuroprotection.