Cardioprotection by the TSPO ligand 4′-chlorodiazepam is associated with inhibition of mitochondrial accumulation of cholesterol at reperfusion

Abstract

AimsThe translocator protein (TSPO) is located on the outer mitochondrial membrane where it is responsible for the uptake of cholesterol into mitochondria of steroidogenic organs. TSPO is also present in the heart where its role remains uncertain. We recently showed that TSPO ligands reduced infarct size and improved mitochondrial functions after ischaemia-reperfusion. This study, thus, sought to determine whether cholesterol could play a role in the cardioprotective effect of TSPO ligands. Methods and resultsIn a model of 30 min coronary occlusion/15 min reperfusion in Wistar rat, we showed that reperfusion induced lipid peroxidation as demonstrated by the increase in conjugated diene and thiobarbituric acid reactive substance formation and altered mitochondrial function (decrease in oxidative phosphorylation and increase in the sensitivity of mitochondrial permeability transition pore opening) in ex-vivo isolated mitochondria. This was associated with an increase in mitochondrial cholesterol uptake (89.5 + 12.2 vs. 39.9 + 3.51 nmol/mg protein in controls, P , 0.01) and a subsequent strong generation of auto-oxidized oxysterols, i.e. 7a-and 7b-hydroxycholesterol, 7-ketocholesterol, cholesterol-5a,6a-epoxide, and 5b,6b-epoxide (+173, +149, +165, +165, and +193% vs. controls, respectively; P , 0.01). Administration of the selective TSPO ligand 4 ′ -chlorodiazepam inhibited oxidative stress, improved mitochondrial function, and abolished both mitochondrial cholesterol accumulation and oxysterol production. This was also observed with the new TSPO ligand TRO40303. ConclusionThese data suggest that 4 ′ -chlorodiazepam inhibits oxidative stress and oxysterol formation by reducing the accumulation of cholesterol in the mitochondrial matrix at reperfusion and prevents mitochondrial injury. This new and original mechanism may contribute to the cardioprotective properties of TSPO ligands.--

Exercise‐induced heart mitochondrial cholesterol depletion influences the inhibition of mitochondrial swelling

“…Administration of the selective TSPO ligands inhibited oxidative stress, improved mitochondrial function, and abolished both mitochondrial cholesterol accumulation and oxysterol production induced by ischaemia–reperfusion. These data showed that reduction of cholesterol accumulation in heart mitochondria by modulation of TSPO activity prevents mitochondrial injury (Paradis et al 2013). To the best of our knowledge, the effect of exercise on the action of TSPO in the heart has not been shown.…”

“…The mechanism responsible for removal of cholesterol from mitochondrial membranes remains unknown, but involvement of 18 kDa mitochondrial translocator protein (TSPO) in this mechanism must be taken into consideration. This protein is responsible for the uptake of cholesterol into mitochondria of steroidogenic organs, but also in heart (Paradis et al 2013). Also, as an element of the mitochondrial outer membrane, cholesterol is associated with the outer/inner mitochondrial membrane contact sites (Rone et al 2009).…”

Metabolic control of cell death

“…The cardiac damage inflicted by ischemia-reperfusion damage is accompanied by an increase in cholesterol uptake by mitochondria and the generation of auto-oxidized oxysterols, a phenomenon that can be avoided by ligands of translocator protein (18kDa) (TSPO), an OMM protein that interacts with VDAC1 and has been suggested to regulate MPT (123). …”

The changing landscape in translocator protein (TSPO) function

“…Other studies have associated the effects of TSPO-binding chemicals with membrane cholesterol accumulation/modulation [49,50] and steroidogenesis [51], but in the light of our recent shift in understanding, whether these observations are indeed mediated through TSPO is a question that needs confirmation.…”