Abstract 137: The Effect Of Mitophagy During Transient Ischemic Brain In Rats
Background and Purpose: Mitochondria provides energy to maintain normal cell functioning. Mitophagy is one of mitochondria functions, which can clear out injured mitochondria, ensure stability of mitochondria and promote cell survival in hostile environment. However, if mitophagy occurs during cerebral ischemia is unknown. The present study explored dynamic mitophagy, the effect of promoting mitophagy, and the molecular mechanisms of mitophagy during cerebral ischemia/reperfusion.
Methods: Adult male SD rats underwent 2h middle cerebral artery occlusion (MCAO) followed by 6 to 72h reperfusion. Dynamic changes of mitophagy were determined by LC3 immunostaining, Western blot analysis, and transmission electron microscope. To study the impact of mitophagy, we injected rapamycin, a mitophagy stimulator, into the left ventricle in rats underwent transient MCAO. To evaluate the effect of mitophagy, neuronal death and neurological deficits were determined. To explore the effect of mitophagy on mitochondria function, the number of mitochondria, the levels of MDA, ATP, and JC-1 were examined. To study the mechanism of mitophagy, mitochondrial Beclin-1 and p62 expression were also determined.
Results: We demonstrated that autophagy was mainly detected in mitochondria in the peri-focal area of ischemic cortex after ischemia/reperfusion. Mitophagy was increased at 6h (p<0.05), peaked at 24h (p<0.05), gradually reduced at 48h (p<0.05), and returned to normal at 72h of transient MCAO. Pre-treatment with rapamycin greatly enhanced mitophagy, reduced infarct volume, and improved neurological outcomes compared to the control (p<0.05). We found that the number of mitochondria and mtDNA copy, mitochondria ATP synthesis level, and JC-1 were increased (p<0.05), and MDA was reduced in rapamycin treated rats (p<0.05). We further demonstrated that rapamycin pre-treatment enhanced mitochondrial Beclin-1and p62 in mitochondria.
Conclusion: We demonstrated ischemia could induce mitophagy in brain cells. Rapamycin attenuated ischemic brain injury, which was via stimulating mitophagy that can reduce oxidative stress and improve mitochondria function. The mechanism of rapamycin promoting mitophagy was through increasing Beclin-1 and p62 expression.
- © 2012 by American Heart Association, Inc.