Carbonic anhydrase inhibitors' effects on dystrophin-deficient mouse muscle

Object: The aim of this study was to show that Caenorhabditis elegans (C. elegans) is a suitable screening model allowing the identification of potential therapeutic substances out of already proved drug compounds in mouse models. Therefore, we analysed the effect of two substances that rescued the muscular degenerative phenotype of a Dys-deficient C. elegans mutant in the mdx mouse model.

Introduction: Duchenne muscular dystrophy (DMD) is an X-linked degenerative muscular wasting disease. In C. elegans mutations of the dys-1 gene in association with a mild MyoD mutation result in a muscular degenerative phenotype. This model shows a nearly immobilized phenotype and was used to screen for molecules able to rescue this phenotype. Invertebrate animal models allow for high-throughput screening of a multitude of drugs in a physiological context. A screen of about 1000 compounds identified several substances that rescue the C. elegans Dys-deficient phenotype. Two of this effective substances, methazolamide and dichlorophenamide, are carbonic anhydrase inhibitors used for anti-glaucoma, benign intracranial hypertension and hypocalemic periodic paralysis therapy. Carbonic anhydrase catalyzes the rapid conversion of carbon dioxide to bicarbonate and protons. Feeding experiments with food containing methazolamide and dichlorophenamide were performed in mdx mice. The mdx mouse presents the most common murine model for DMD. A point mutation in the dystrophin gene at position 3185 results in a premature stop codon.

Methods: We conducted feeding experiments for the duration of 120 days with food containing methazolamide and dichlorophenamide in mdx mice. Histological appearance of three muscles M. tibialis anterior, diaphragm and M. soleus of treated and control animals was examined, and correlated to muscle force in isolated M. extensor digitorum longus (EDL).

Results: Dichlorophenamide reduced the number of centrally nucleated and round fibres in diaphragm significantly. In TA and Sol we observed a shift of the fibre perimeter variation towards larger hypertrophic fibres. Specific tetanic muscle force increased significantly by 20–30% in the treated EDL muscle group for both substances. However, both treatments failed to increase resistance of muscle fibres to eccentric contractions.

Conclusions: The results demonstrate that C. elegans represents a good screening model and is suitable for identification of drugs with therapeutic potential.