Application of real-time polymerase chain reaction to quantitate induced expression of interleukin-1β mRNA in ischemic brain tolerance

A short duration of ischemia (i.e., ischemic preconditioning) was shown to result in significant tolerance to subsequent ischemic injury. Since previous reports suggest that interleukin-1 beta (IL-1 beta) may be involved in both ischemic damage and neuroprotection, the present work examined the expression of li-1 beta mRNA in cortical brain tissue after an established preconditioning (PC) stimulus known to produce significant brain tolerance to focal stroke after 1-7 days. Significant induction of IL-1 beta mRNA was observed in the ipsilateral cortex at 6 hr (87 +/- 9 copies of the mRNA per microgram of brain tissue compared to 16 +/- 5 copies in sham-operated samples, P < 0.001, n = 4) and 8 hr (46 +/- 4 copies, P < 0.01, n = 4) after PC by means of real-time Taqman polymerase chain reaction (PCR). The peak expression of IL-1 beta mRNA after PC was significantly (P < 0.01) lower than that after permanent occlusion of the middle cerebral artery MCAO), i.e., 87 +/- 9 and 546 +/- 92 copies of RNA per microgram tissue at peak levels for PC and focal stroke, respectively. Immunohistochemistry studies revealed a parallel induction of IL-1 beta in the ipsilateral cortex after PC. The maximal expression of IL-1 beta was observed during the first week post-PC, showing marked parallelism with the duration of ischemic tolerance. These data suggest that the significant but low levels of IL-1 beta induction after PC may contribute to ischemic brain tolerance. (C) 2000 Wiley-Liss, Inc.