The cyclophilin inhibitor Debio 025 normalizes mitochondrial function, muscle apoptosis and ultrastructural defects in Col6a1^−/− myopathic mice

Abstract

-/-mice, a model of muscular dystrophies due to defects of collagen VI. Experimental approach: We studied calcineurin activity based on NFAT translocation; T cell activation based on expression of CD69 and CD25; propensity to open the permeability transition pore in mitochondria and skeletal muscle fibres based on the ability to retain Ca 2+ and on membrane potential, respectively; muscle ultrastructure by electronmicroscopy; and apoptotic rates by terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling assays in Col6a1 -/-mice before after treatment with Debio 025. Key results: Debio 025 did not inhibit calcineurin activity, yet it desensitizes the mitochondrial permeability transition pore in vivo. Treatment with Debio 025 prevented the mitochondrial dysfunction and normalized the apoptotic rates and ultrastructural lesions of myopathic Col6a1 -/-mice. Conclusions and implications:Desensitization of the mitochondrial permeability transition pore can be achieved by selective inhibition of matrix cyclophilin D without inhibition of calcineurin, resulting in an effective therapy of Col6a1 -/-myopathic mice. These findings provide an important proof of principle that collagen VI muscular dystrophies can be treated with Debio 025. They represent an essential step towards an effective therapy for Ullrich Congenital Muscular Dystrophy and Bethlem Myopathy, because Debio 025 does not expose patients to the potentially harmful effects of immunosuppression.

A Calcineurin-Independent Mechanism of Angiogenesis Inhibition by a Nonimmunosuppressive Cyclosporin A Analog

“…Mitochondrial permeability transition pore formation promotes cell death and is prevented by CsA and nonimmunosuppressive analogs, presumably through CyPD inhibition (Kim et al, 2003). The potential of CyPD inhibition by nonimmunosuppressive CsA analogs is being pursued as a therapeutic strategy in a number of diseases including muscular dystrophy (Tiepolo et al, 2009;Wissing et al, 2010). It is possible that CyP inhibition in antiangiogenesis may develop as a similarly viable target.…”

Mitochondrial Dysfunction and Defective Autophagy in the Pathogenesis of Collagen VI Muscular Dystrophies

“…The resting mitochondrial membrane potential was not affected by lack of ColVI, yet mitochondria depolarized after addition of the F1FO ATP synthase inhibitor oligomycin or of the respiratory chain complex I inhibitor rotenone only in cells from ColVIdeficient individuals (Irwin et al 2003;Angelin et al 2007Angelin et al , 2008Palma et al 2009;Tiepolo et al 2009;Sabatelli et al 2012). Neither response is normal because, in the short term at least, (1) inhibition of ATP synthesis by oligomycin should cause hyperpolarization, and (2) inhibition of respiration should still allow the membrane potential to be maintained by proton pumping by the ATP synthase running "in reverse" and utilizing glycolytic ATP as fuel (see, e.g., Porcelli et al 2009).…”

“…Neither response is normal because, in the short term at least, (1) inhibition of ATP synthesis by oligomycin should cause hyperpolarization, and (2) inhibition of respiration should still allow the membrane potential to be maintained by proton pumping by the ATP synthase running "in reverse" and utilizing glycolytic ATP as fuel (see, e.g., Porcelli et al 2009). Of note, cells from ColVI-defective genotypes also displayed increased rates of apoptosis that could be prevented by plating on ColVI or by addition of cyclosporin A (CsA), treatments that also normalized the mitochondrial response to oligomycin and/ or rotenone (Irwin et al 2003;Angelin et al 2007Angelin et al , 2008Palma et al 2009;Tiepolo et al 2009;Sabatelli et al 2012). These findings, which we shall discuss further below, (1) suggest the existence of a latent (compensated) mitochondrial dysfunction that may worsen (and decompensate) with time, which is consistent with the chronic and progressive features of ColVI muscular dystrophies; and (2) indicate that the underlying mitochondrial dysfunction, and possibly the disease, can be cured with CsA.…”

Congenital Muscular Dystrophy

“…In a study of 5 patients with collagen VI myopathy, a trial of oral CsA largely normalised mitochondrial dysfunction apoptosis and increased muscle regeneration (347). An analogue of CsA, Debio 025, which selectively inhibits cyclophilin D (rather than calcineurin and cyclophilins as in the case of CsA) has also been tested in col6a1 -/-mice with positive findings including normalisation of mitochondrial function in skeletal muscle fibres, significant reduction in ultrastructural damage and decreased incidence of apoptosis in diaphragm muscle fibres (348,349).…”