Aldanondo, G. 1 , Toral-Ojeda, I. 1, 2 , Lasa-Elgarresta, J. . 1 , Irastorza, A. 3 , Ferrón, P. 3 , Miranda, J. I. . 3 , Aizpurua, J. M. . 3 , Lopez de Munain, A. 1, 2, 5, 6 & Vallejo-Illarramendi, A. 1, 2, 4
1 Neuroscience Area, Biodonostia Research Institute, San Sebastian, Spain
2 CIBERNED, Instituto de Salud Carlos III, Madrid, Spain
3 University of the Basque Country, Faculty of Chemistry, San Sebastian, Spain
4 Euskampus
5 Department of Neuroscience, University of the Basque Country, San Sebastian, Spain
6 Department of Neurology, Donostia Hospital, San Sebastian, Spain
The sarcoplasmic reticulum receptor RyR1 is abnormally nitrosylated within the skeletal muscle of mdx and Sgcb-/- dystrophic mice, which results in calstabin1 depletion from the RyR macromolecular complex and a subsequent calcium leak to the cytosol. RyR1 modulators such as S107, have recently demonstrated their efficacy in vivo by ameliorating muscle damage and improving muscle function in these mice.
In this work we have studied the effect of A6, a novel RyR1 modulator designed and synthesized by our group that shows less in vitro citotoxicity than S107. During a 5-week experiment, limb strength, CK and LDH serum levels were assessed weekly in 3 groups of mice: control, non-treated mdx and A6-treated mdx. At the end of the experiment mice were sacrificed and muscles were dissected for histological analysis. We also analyzed intracellular calcium levels in isolated fibres from flexor digitorum brevis muscles of these mice. We found that in mdx isolated fibres, A6 treatment reduces significantly basal cytosolic calcium concentration to the levels observed in control fibres. Furthermore, we observed that A6 treatment reduces histological evidence of muscle damage and improves muscle function.
In conclusion, our study shows that A6 is effective in reducing cytosolic calcium levels and improving muscular function in mdx mice. In addition, it consolidates RyR1-calstabin1 interaction as a useful therapeutic target for drug development against muscular dystrophies.