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Interleukin-1 beta mRNA expression in ischemic rat cortex
T Liu1, P C McDonnell, P R Young
1Department of Cardiovascular Pharmacology, SmithKline Beecham Pharmaceuticals, King of Prussia, PA 19406.
Background And Purpose:
Interleukin-1 beta is a proinflammatory cytokine produced by blood-borne and resident brain inflammatory cells. The present study was conducted to determine if interleukin-1 beta mRNA was produced in the brain of rats subjected to permanent focal ischemia.
Methods:
Rat interleukin-1 beta 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-1 beta mRNA in cerebral cortex from spontaneously hypertensive rats and normotensive rats subjected to permanent middle cerebral artery occlusion. Interleukin-1 beta 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-1 beta mRNA produced in the ischemic zone was significantly increased from 6 hours to 120 hours, with a maximum of 211 +/- 24% of interleukin-1 beta 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-1 beta 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-1 beta 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.
Insights
Interleukin-1 beta mRNA significantly increased in rat brains after focal ischemia, particularly in hypertensive rats. This suggests a role for this cytokine in ischemic brain damage.
Area of Science:
- Neuroscience
- Inflammation Research
- Ischemic Stroke Models
Background:
- Interleukin-1 beta (IL-1β) is a key proinflammatory cytokine.
- It is produced by both blood-borne and resident brain inflammatory cells.
- Its role in ischemic brain injury requires further investigation.
Purpose of the Study:
- To determine if interleukin-1 beta mRNA is produced in the brain following permanent focal ischemia in rats.
- To investigate the temporal expression of IL-1β mRNA post-ischemia.
- To compare IL-1β mRNA levels in hypertensive versus normotensive rats.
Main Methods:
- Utilized rat IL-1β cDNA for expression analysis.
- Quantified IL-1β mRNA in rat cerebral cortex using Northern blot analysis.
- Employed cyclophilin cDNA for normalization to correct for gel loading variations.
Main Results:
- IL-1β mRNA levels in the ischemic zone significantly increased from 6 to 120 hours post-occlusion.
- A maximum increase of 211% was observed at 12 hours compared to non-ischemic tissue.
- Hypertensive rats exhibited markedly elevated IL-1β mRNA levels and neurological deficits compared to normotensive rats.
Conclusions:
- Brain IL-1β mRNA is acutely upregulated following permanent focal ischemia.
- This upregulation is particularly pronounced in hypertensive rats.
- These findings suggest a potential role for IL-1β in mediating ischemic brain damage.