Hypercholesterolemia is a major risk factor for coronary artery diseases and cardiac ischemic events. Cholesterol per se could also have negative effects on the myocardium, independently from hypercholesterolemia. Previously, we reported that myocardial ischemia–reperfusion induces a deleterious build-up of mitochondrial cholesterol and oxysterols, which is potentiated by hypercholesterolemia and prevented by translocator protein (TSPO) ligands. Here, we studied the mechanism by which sterols accumulate in cardiac mitochondria and promote mitochondrial dysfunction. We performed myocardial ischemia–reperfusion in rats to evaluate mitochondrial function, TSPO, and steroidogenic acute regulatory protein (STAR) levels and the related mitochondrial concentrations of sterols. Rats were treated with the cholesterol synthesis inhibitor pravastatin or the TSPO ligand 4’-chlorodiazepam. We used Tspo deleted rats, which were phenotypically characterized. Inhibition of cholesterol synthesis reduced mitochondrial sterol accumulation and protected mitochondria during myocardial ischemia–reperfusion. We found that cardiac mitochondrial sterol accumulation is the consequence of enhanced influx of cholesterol and not of the inhibition of its mitochondrial metabolism during ischemia–reperfusion. Mitochondrial cholesterol accumulation at reperfusion was related to an increase in mitochondrial STAR but not to changes in TSPO levels. 4’-Chlorodiazepam inhibited this mechanism and prevented mitochondrial sterol accumulation and mitochondrial ischemia–reperfusion injury, underlying the close cooperation between STAR and TSPO. Conversely, Tspo deletion, which did not alter cardiac phenotype, abolished the effects of 4’-chlorodiazepam. This study reveals a novel mitochondrial interaction between TSPO and STAR to promote cholesterol and deleterious sterol mitochondrial accumulation during myocardial ischemia–reperfusion. This interaction regulates mitochondrial homeostasis and plays a key role during mitochondrial injury.

高胆固醇血症是冠状动脉疾病和心脏缺血事件的主要危险因素。胆固醇本身也可能对心肌产生负面影响，这与高胆固醇血症无关。以前，我们报道了心肌缺血再灌注诱导线粒体胆固醇和氧甾醇的有害积累，高胆固醇血症会增强这种积累，而转运蛋白 （TSPO） 配体会阻止这种积累。在这里，我们研究了甾醇在心脏线粒体中积累并促进线粒体功能障碍的机制。我们对大鼠进行了心肌缺血再灌注，以评估线粒体功能、 TSPO 和类固醇生成急性调节蛋白 （STAR） 水平以及甾醇的相关线粒体浓度。大鼠用胆固醇合成抑制剂普伐他汀或 TSPO 配体 4'-氯二氮泮治疗。我们使用了 Tspo 缺失的大鼠，这些大鼠具有表型特征。抑制胆固醇合成减少了线粒体甾醇积累，并在心肌缺血再灌注期间保护了线粒体。我们发现心脏线粒体甾醇积累是胆固醇内流增加的结果，而不是缺血再灌注期间线粒体代谢抑制的结果。再灌注时线粒体胆固醇积累与线粒体 STAR 的增加有关，但与 TSPO 水平的变化无关。4'-氯地西泮抑制了这种机制，并阻止了线粒体甾醇积累和线粒体缺血再灌注损伤，这是 STAR 和 TSPO 密切合作的基础。相反，不改变心脏表型的 Tspo 缺失消除了 4'-氯二氮泮的作用。 本研究揭示了 TSPO 和 STAR 之间的一种新的线粒体相互作用，在心肌缺血再灌注期间促进胆固醇和有害的甾醇线粒体积累。这种相互作用调节线粒体稳态，在线粒体损伤过程中起关键作用。