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Evaluation of Coronary Flow Reserve After Myocardial Ischemia Reperfusion in Rats
Published on: June 28, 2019
Changes in rat myocardium associated with modulation of ischemic tolerance by diazoxide
P Simoncíková1, T Ravingerová, E Andelová
1Institute for Heart Research, Slovak Academy of Sciences, Dúbravská cesta 9, 840 05 Bratislava 45, Slovakia.
Abstract:
Pretreatment with diazoxide, mitochondrial K(ATP) channel opener, was found to protect the rat heart against ischemia/reperfusion injury. Our aim was also to characterize the effects of diazoxide on the alterations of regulatory myocardial proteins, on mitochondrial ultrastructure, integrity and induction of apoptotic responses. Isolated rat hearts were Langendorff perfused and subjected to index ischemia (II) induced by 25 min global ischemia and 35 min reperfusion. In diazoxide- treated hearts, diazoxide (50 micromol/l) was applied 15 min before II. The levels and activation of specific proteins were determined using specific antibodies, activities of matrix metalloproteinases by zymography using gelatin as a substrate. The ultrastructure of mitochondria was investigated by electron microscopy of ultrathin sections of mitochondrial fractions embedded in Epon812. In rat hearts pretreated with diazoxide we found better recovery of contractile function after II. Electron microscopy studies revealed that application of diazoxide was connected with better preservation of mitochondrial integrity at basal conditions and after II in comparison to control hearts. Ischemia induced activation of caspase-3 as well as decrease of mitochondria-associated Bcl-2 levels but diazoxide treatment did not significantly influence these changes. On the other hand, diazoxide pretreatment reduced the cytosolic levels of pro-apoptotic Bax protein. Western blot analysis revealed that application of diazoxide increased activation of both ERK-1 and ERK-2 as compared with control hearts. ERK-2 activities were also higher in diazoxide-treated hearts after II when compared to control hearts. Moreover, application of diazoxide inhibited the activities of tissue matrix metalloproteinases (MMP-2). The results suggest that the cardioprotection mediated by diazoxide in rats is associated with preservation of mitochondrial integrity and function. The effect of diazoxide on ERK pathway points to the involvement of this signaling cascade in diazoxide-mediated adaptive responses of myocardium to ischemia.
Insights
Diazoxide, a mitochondrial K(ATP) channel opener, protects rat hearts from ischemia/reperfusion injury by preserving mitochondrial integrity and function. It also influences protein signaling pathways, suggesting adaptive responses to ischemia.
Area of Science:
- Cardiovascular Research
- Mitochondrial Biology
- Cellular Signaling
Background:
- Ischemia/reperfusion (I/R) injury is a significant cause of heart damage.
- Mitochondrial dysfunction plays a key role in I/R injury.
- Targeting mitochondrial K(ATP) channels may offer cardioprotective strategies.
Purpose of the Study:
- To investigate the cardioprotective effects of diazoxide against I/R injury in isolated rat hearts.
- To characterize diazoxide's impact on myocardial regulatory proteins, mitochondrial ultrastructure, and apoptosis.
- To explore the involvement of signaling pathways like ERK in diazoxide-mediated protection.
Main Methods:
- Langendorff-perfused isolated rat hearts subjected to global ischemia and reperfusion.
- Pretreatment with diazoxide (mitochondrial K(ATP) channel opener).
- Assessment of contractile function, mitochondrial integrity (electron microscopy), protein levels/activation (Western blot, zymography), and apoptotic markers (caspase-3, Bcl-2, Bax).
Main Results:
- Diazoxide pretreatment improved recovery of cardiac contractile function post-I/R.
- Mitochondrial integrity was better preserved in diazoxide-treated hearts.
- Diazoxide reduced cytosolic Bax levels but did not significantly alter caspase-3 or Bcl-2.
- Increased activation of ERK-1/ERK-2 and inhibition of MMP-2 were observed with diazoxide treatment.
Conclusions:
- Cardioprotection by diazoxide is linked to preserved mitochondrial integrity and function.
- The ERK signaling pathway is implicated in diazoxide-induced adaptive responses to myocardial ischemia.
- Diazoxide demonstrates potential as a therapeutic agent for I/R injury.
