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

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 mmol/L Ca(2+) to induce MPT. Ro5-4864 (50, 100 and 200 micromol/L) was added into incubation buffer before adding 150 micromol/L Ca(2+). In additional group, atractyloside (ATR, 20 micromol/L), an opener of MPT pores was added 5 min before the addition of 100 micromol/L Ro5-4864. The change of absorbance at 520 nm was monitored with a spectrophotometer at 30 degrees C 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.