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Menadione mimics the infarct-limiting effect of preconditioning in isolated rat hearts
1Department of Cell Biology and Neuroscience, University of South Alabama, College of Medicine, Mobile, Alabama 36688, USA.
Abstract:
The role of mitochondrial free radicals in the cardioprotective effect of ischemic preconditioning was examined in isolated buffer-perfused rat hearts. Infarct size in control rat hearts subjected to 30 min of regional ischemia and 120 min of reperfusion was 32.6 +/- 3.4% of the risk zone. Ischemic preconditioning (3 cycles of 5-min global ischemia/5-min reperfusion) before the same regional ischemia and reperfusion protocol significantly reduced infarct size to 2.6 +/- 0.8% of the risk zone. Perfusion with menadione (3.0 microM), a generator of mitochondrial free radicals, in lieu of preconditioning ischemia significantly reduced infarction to 10.9 +/- 2.7%. N-2-mercaptopropionylglycine (1.0 mM), a free radical scavenger, blocked the protection of menadione, significantly increasing infarction to 23.5 +/- 1.1%. Myxothiazol (0.6 microM), a site III mitochondrial inhibitor, blocked the protection of menadione and significantly increased infarction to 25.2 +/- 3.8%. The infarct-limiting effect of menadione was attenuated to 19.7 +/- 1.5% of the risk zone by 10 microM SB203580, a p38 mitogen-activated protein kinase (MAPK) inhibitor. Furthermore, menadione significantly increased p38 MAPK phosphorylation to a level 5.6-fold over basal. These results indicate that free radicals that originate within mitochondria can activate p38 MAPK and protect hearts against infarction.
Insights
Mitochondrial free radicals, generated by menadione, protect hearts from infarction by activating p38 mitogen-activated protein kinase (MAPK). This finding reveals a novel mechanism for ischemic preconditioning
Area of Science:
- Cardiovascular Physiology
- Mitochondrial Biology
- Cell Signaling
Background:
- Ischemic preconditioning (IP) confers cardioprotection against myocardial infarction.
- The precise mechanisms underlying IP, particularly the role of mitochondrial free radicals, remain incompletely understood.
- Mitochondria are key organelles in cellular energy production and signaling pathways.
Purpose of the Study:
- To investigate the role of mitochondrial free radicals in the cardioprotective effects of ischemic preconditioning.
- To elucidate the signaling pathways activated by mitochondrial free radicals in the heart.
- To determine if p38 mitogen-activated protein kinase (MAPK) is involved in this protective mechanism.
Main Methods:
- Isolated buffer-perfused rat hearts were used to model myocardial ischemia and reperfusion.
- Infarct size was measured following regional ischemia and reperfusion.
- Hearts were treated with menadione (mitochondrial free radical generator), N-2-mercaptopropionylglycine (free radical scavenger), myxothiazol (mitochondrial inhibitor), or SB203580 (p38 MAPK inhibitor).
- Western blotting was used to assess p38 MAPK phosphorylation.
Main Results:
- Ischemic preconditioning significantly reduced infarct size from 32.6% to 2.6%.
- Menadione perfusion mimicked preconditioning, reducing infarct size to 10.9%.
- Free radical scavenger and mitochondrial inhibitor blocked menadione's protective effect.
- p38 MAPK inhibitor attenuated menadione's infarct-limiting effect, and menadione increased p38 MAPK phosphorylation.
Conclusions:
- Mitochondrial free radicals play a crucial role in mediating the cardioprotective effects of ischemic preconditioning.
- These mitochondrial free radicals activate the p38 MAPK signaling pathway.
- Targeting mitochondrial free radical generation and p38 MAPK activation may offer therapeutic strategies for myocardial protection.