iNOS expression in dystrophinopathies can be reduced by somatic gene transfer of dystrophin or utrophin

Background: Nitric oxide (NO) is an inorganic gas produced by a family of NO synthase (NOS) proteins. The presence and the distribution of inducible-NOS (NC)S II or iNOS), and NADPH-diaphorase (NADPH-d), a marker for NOS catalytic activity, were determined in muscle sections from control, DMD, and BMD patients. Materials and Methods: NADPH-d reactivity, iNOS- and nNOS (NOS I)-immunolocalization were studied in muscles from mdx mice before and after somatic gene transfer of dystrophin or utrophin. Results: In control patients, few fibers (<2%) demonstrated focal accumulation of iNOS in sarcolemma. In DMD patients, a strong iNOS immunoreactivity was observed in some necrotic muscle fibers as well as in some mononuclear cells, and regenerating muscle fibers had diffusely positive iNOS immunoreactivity. In DMD patients, NADPH-d reactivity was increased and mainly localized in regenerating muscle fibers. In mdx mice quadriceps, iNOS expression was mainly observed in regenerating muscle fibers, but not prior to 4 weeks postnatal, and was still present 8 weeks after birth. The expression of dystrophin and the overexpression of utrophin using adenovirus-mediated constructs reduced the number of iNOS-positive fibers in mdx quadriceps muscles. The correction of some pathology in mdx by dystrophin expression or utrophin overexpression was independent of the presence of nNOS. Conclusions: These results suggest that iNOS could play a role in the physiopathology of DMD and that the abnormal expression of iNOS could be corrected by gene therapy.