INTERLEUKIN-1-BETA MESSENGER-RNA EXPRESSION IN ISCHEMIC RAT CORTEX

Background and Purpose: Interleukin-1beta is a proinflammatory cytokine produced by blood-borne and resident brain inflammatory cells. The present study was conducted to determine if interleukin-1beta mRNA was produced in the brain of rats subjected to permanent focal ischemia. Methods: Rat interleukin-1beta cDNA, synthesized from stimulated rat peritoneal macrophage RNA by reverse transcription and polymerase chain reaction and cloned in plasmid Bluescript KS+, was used to evaluate the expression of interleukin-1beta mRNA in cerebral cortex from spontaneously hypertensive rats and normotensive rats subjected to permanent middle cerebral artery occlusion. Interleukin-1beta mRNA was quantified by Northern blot analysis and compared with rat macrophage RNA standard. To correct for gel loading, blots were also analyzed with cyclophilin cDNA, which encodes an abundant, conserved protein that was unchanged by the experimental conditions. Results: Interleukin-1beta mRNA produced in the ischemic zone was significantly increased from 6 hours to 120 hours, with a maximum of 211+/-24% of interleukin-1beta reference standard, ie, 0.2 ng stimulated rat macrophage RNA, mRNA compared with the level in nonischemic cortices (4+/-2%) at 12 hours after ischemia (P<.01; n=6). Interleukin-1beta mRNA at 12 hours after ischemia was markedly elevated in hypertensive rats over levels, found in two normotensive rat strains. Neurological deficits were also apparent only in the hypertensive rats. Conclusions: Brain interleukin-1beta mRNA is elevated acutely after permanent focal ischemia and especially in hypertensive rats. These data suggest that this, potent proinflammatory and procoagulant cytokine might have a role in brain damage following ischemia.