Submitted on November 16, 2007
Accepted on February 12, 2008
Effect of diazoxide on flavoprotein oxidation and ROS generation during ischemia-reperfusion: a study on Langendorff-perfused rat hearts using optic fibers
Philippe Pasdois1, Bertrand Beauvoit2, Liliane Tariosse1, Beatrice Vinassa3, Simone Bonoron-Adele1, and Pierre Dos Santos4*
1 U.828, Inserm, Pessac, France
2 University of Bordeaux 2, Bordeaux, France
3 U.828, Inserm, Pessac, France; University of Bordeaux 2, Bordeaux, France
4 U.828, Inserm, Pessac, France; University Hospital of Bordeaux, Bordeaux, France; University of Bordeaux 2, Bordeaux, France
* To whom correspondence should be addressed. E-mail: pierre.dossantos{at}wanadoo.fr.
This study analyzed the oxidant generation during ischemia-reperfusion protocols of Langendorff-perfused rat hearts, preconditioned with a mitoKATP opener (i.e. the diazoxide). The autofluorescence of mitochondrial flavoproteins, and that of the total NAD(P)H pool on one hand, and the fluorescence of dyes sensitive to H2O2 or O2
- (i.e. the dihydrodichlorofluoroscein and dihydroethidine, respectively) on the other, were non-invasively measured at the surface of the left ventricular wall by means of optic fibers. Isolated perfused rat hearts were subjected to an ischemia-reperfusion protocol. Opening mitoKATP with diazoxide (100 µM) (i) improved the recovery of rate-pressure product after reperfusion (72 ± 2% vs. 16.8 ± 2.5% of baseline value in control group, p < 0.01), (ii) attenuated the oxidant generation during both ischemic (-46 ± 5% H2DCF oxidation and -40 ± 3% DHE oxidation vs. control group, p < 0.01) and reperfusion (-26 ± 2% H2DCF oxidation and -23 ± 2% DHE oxidation vs. control group, p<0.01) periods. All these effects were abolished by coperfusion of 5-hydroxydecanoic acid (5HD, 500 µM), a mitoKATP blocker. During the preconditioning phase, diazoxide induced a transient, reversible, and 5HD-sensitive flavoprotein and dihydrodichlorofluoroscein (but not dihydroethidine) oxidation. In conclusion, the diazoxide-mediated cardioprotection is supported by a moderate H2O2 production during the preconditioning phase and a strong decrease in oxidant generation during the subsequent ischemic and reperfusion phases.
