Control of the Opening of mPTP by Ex Vivo Measurements on Permeabilized Muscle Fibers (COMMEF)

Overview

mPTP (Mitochondrial Permeability Transition Pore) is a channel formed by a protein complex integrated into the inner membrane of mitochondria. Its opening is related to the elevation of the intra-mitochondrial calcium concentration and will result in: a mitochondrial decoupling, a rupture of the metabolic gradient and the release of pro-apoptotic factors. The objective of this study is the development of a new ex vivo technique for characterizing mPTP by a dual measurement combining oxygraphy and fluorimetry on permeabilized skeletal muscle fibers.

The development of new expertise in the study of mPTP is part of an approach to optimize the processing of muscle samples. The aim of this work is to evaluate the feasibility and reproducibility of a method of analysis on muscle fibers only permeabilized, while coupling two complementary techniques, oxygraphy and fluorimetry. Its principle is based on the knowledge that the opening of the mPTP leads to an inhibition of respiration at the level of the complex I of the respiratory chain. This inhibition is the consequence of the escape from mitochondria of the reduced form of nicotinamide adenine dinucleotide (NADH, i.e. substrate of complex I) concomitant with the opening of mPTP. Thus, the oxygraphy must allow the observation of the inhibition of respiration synonymous with the non-availability of the substrate of the complex I and thus indirectly reflect the opening of the mPTP. For its part, the fluorimetry must allow, in the presence of a fluorescent calcium indicator (i.e. Calcium Green), the observation of the release of calcium synonymous with the opening of the mPTP. Once validated, this technique should make it possible to evaluate in situ the sensitivity of mPTP to calcium. In a context of application within clinical protocols, the evaluation of the mPTP calcium sensitivity should contribute to a better understanding of the physiological and physio-pathological mechanisms of adaptation of muscle tissue.

Conditions