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Peripheral benzodiazepine receptor agonist Ro5--4864 inhibits mitochondrial permeability transition in rat heart

Li Jingyuan, Wang Junke, Zeng Yinming

Department of Anesthesiology, the First Affiliated Hospital, China Medical University.Shenyang 110001,Liaoning；China

Abstract

Opening of mitochondrial permeability transition （MPT） pores leads to mitochondrial injury during oxidative stress. The peripheral benzodiazepine receptor （PBR） located at mitochondrial outer-membrane has been shown to be involved in several mitochondrial functions. In the present study, we used Ro5-4864, a PBR agonist, to test if activation of PBR could prevent MPT pore opening during Ca~(2+) overloading. Cardiac mitochondria isolated from Sprague-Dawley rats were treated by 150 #mu#mol/L Ca~(2+) to induce MPT. Ro5-4864 （50, 100 and 200 #mu#mol/L） was added into incubation buffer before adding 150 #mu#mol/L Ca~(2+). In additional group, atractyloside （ATR, 20 #mu#mol/L）, an opener of MPT pores was added 5 min before the addition of 100 #mu#mol/L Ro5-4864. The change of absorbance at 520 nm was monitored with a spectrophotometer at 30℃ for 10 min. Western blot was used to detect cytochrome C loss. The mitochondrial membrane potential was monitored with the fluorescence dye JC-1. Ro5-4864 inhibited the decrease of absorbance at 520 nm compared to that in the untreated Ca~(2+) group （P〈0.01, P〈0.05）. In the presence of ATR, Ro5-4864 was not able to prevent MPT anymore. Opening of MPT pores by Ca~(2+) decreased the content of cytochrome C in mitochondria, but increased cytochrome C content in cytosol. Ro5- 4864 preserved cytochrome C content in mitochondria and led to less cytochrome C release to cytosol. ATR treatment reversed the protective effect of Ro5-4864 on cytochrome C content. Opening of MPT pores led to mitochondrial depolarization, whereas Ro5-4864 treatment maintained mitochondrial membrane potential. Thus, prevention of MPT by activation of PBR during calcium overloading maintains mitochondrial cytochrome C content and membrane potential. Activation of PBR during cardiac ischemia and reperfusion may be an alternative way for cardioprotection.

Key words: peripheral benzodiazepine receptor;Ro5-4864;mitochondrial permeability transition

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Citing This Article：

Li Jingyuan, Wang Junke, Zeng Yinming. Peripheral benzodiazepine receptor agonist Ro5--4864 inhibits mitochondrial permeability transition in rat heart. Acta Physiol Sin 2007; 59 (1): 13-18 (in Chinese with English abstract).