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Gene expression after short periods of coronary occlusion
1Max-Planck-Institute for Physiological and Clinical Research, Department of Experimental Cardiology, Bad Nauheim, Germany.
Abstract:
Brief periods of coronary occlusion render the affected myocardium more tolerant to the otherwise devastating effects of long coronary occlusion. Besides this phenomena, called ischemic preconditioning, short periods of ischemia cause a regional dysfunction, namely myocardial stunning. The molecular mechanisms of both syndromes are not very well understood. We therefore investigated the expression of genes which may be involved in cardioprotection or repair processes. Using our porcine model of ischemia and reperfusion we were able to show an induction of genes coding for transcription factors (proto-oncogenes), for proteins involved in repair processes (heat shock genes), for proteins implicated in the calcium homeostasis (calcium-handling genes) and for growth factors. We could show that the increased mRNA levels are due to an enhanced transcriptional activity and not to a prolonged half-life of the transcripts. The angiogenic growth factor vascular endothelial growth factor (VEGF) represents an exception. It exhibits--in addition to a HIF-motif (Hypoxia Inducible Factor) in its promoter/enhancer--a protein binding region in its 3' UTR which when occupied renders the mRNA more stable. However to what extent the expression of the distinct genes contributes to the cardioprotective effect of ischemic preconditioning or myocardial stunning can only be presumed. Increased mRNA stability can be confered via adenosine which is produced during ischemia by ATP-breakdown. The demasking of unknown genes--via differential display reverse transcription polymerase chain reaction (DDRT-PCR)--should provide a more comprehensive view of the mechanisms underlying both processes.
Insights
Ischemic preconditioning and myocardial stunning involve gene expression changes. Researchers found increased mRNA levels for genes related to cardioprotection and repair, primarily due to enhanced transcription, not mRNA stability.
Area of Science:
- Cardiovascular Biology
- Molecular Cardiology
- Gene Expression Regulation
Background:
- Ischemic preconditioning confers myocardial tolerance to ischemia.
- Myocardial stunning results from short ischemic periods.
- Molecular mechanisms underlying these phenomena remain unclear.
Purpose of the Study:
- Investigate gene expression changes during ischemia-reperfusion.
- Identify genes involved in cardioprotection and repair.
- Elucidate mechanisms of mRNA regulation in these processes.
Main Methods:
- Utilized a porcine model of ischemia and reperfusion.
- Analyzed gene expression of transcription factors, heat shock proteins, calcium-handling genes, and growth factors.
- Employed differential display reverse transcription polymerase chain reaction (DDRT-PCR).
Main Results:
- Demonstrated induction of genes for transcription factors, repair proteins, calcium-handling proteins, and growth factors.
- Showed increased mRNA levels result from enhanced transcriptional activity, except for VEGF.
- VEGF mRNA stability is regulated by its 3' UTR and Hypoxia Inducible Factor (HIF) motif.
Conclusions:
- Gene expression changes contribute to cardioprotection and myocardial stunning.
- Enhanced transcriptional activity is the primary driver of increased mRNA levels.
- Further research is needed to fully understand the role of specific genes and mRNA stability in these processes.