Utrophin A Upregulation by FDA-Approved Drugs for the Treatment of Duchenne Muscular Dystrophy

Abstract

Duchenne Muscular Dystrophy (DMD) is a disorder caused by mutations in the dystrophin gene, preventing the production of the functional dystrophin protein which assures maintenance of the myofiber integrity throughout muscle contraction. A lack of dystrophin results in severe muscle degeneration and regeneration accompanied by a loss of muscle function. Many pre-clinical and clinical studies are focused on developing strategies to counteract the detrimental effects of DMD; however, there is no cure. One such approach consists of upregulating the endogenous protein utrophin A in dystrophic muscle, which, once highly expressed at the sarcolemma, could functionally compensate for the lack of dystrophin. Recent evidence demonstrates that utrophin A expression is regulated at its 3’ and 5’UTR through post-transcriptional and translational events. Therefore, in the work presented here, we hypothesized that repurposing FDA-approved drugs that target the signaling pathways involved in post-transcriptional and translational regulation of utrophin A will be an efficient approach in rapidly bringing new therapeutic interventions for DMD. In this work, we repurposed four promising FDA-approved drugs able to stimulate utrophin A expression levels in dystrophic muscles: the anti-coagulant drug Heparin, the anti-inflammatory drug Celecoxib, the β-adrenergic receptor blocking agent Betaxolol and the cholesterol-lowering drug Pravastatin. These drugs induce significant improvements in the dystrophic phenotype of mdx mice. This includes amelioration of muscle fiber integrity and muscle function as well as promoting morphological and fiber type changes in mdx mice muscles. Collectively, this thesis describes the potential of a repurposing approach to activate key post-transcriptional and translational pathways involved in utrophin A’s regulation in the hopes of developing new therapeutics for the treatment of DMD.