A nitric oxide synthase transgene ameliorates muscular dystrophy in mdx mice

Abstract

Dystrophin-deficient muscles experience large reductions in expression of nitric oxide synthase (NOS), which suggests that NO deficiency may influence the dystrophic pathology. Because NO can function as an antiinflammatory and cytoprotective molecule, we propose that the loss of NOS from dystrophic muscle exacerbates muscle inflammation and fiber damage by inflammatory cells. Analysis of transgenic mdx mice that were null mutants for dystrophin, but expressed normal levels of NO in muscle, showed that the normalization of NO production caused large reductions in macrophage concentrations in the mdx muscle. Expression of the NOS transgene in mdx muscle also prevented the majority of muscle membrane injury that is detectable in vivo, and resulted in large decreases in serum creatine kinase concentrations. Furthermore, our data show that mdx muscle macrophages are cytolytic at concentrations that occur in dystrophic, NOS-deficient muscle, but are not cytolytic at concentrations that occur in dystrophic mice that express the NOS transgene in muscle. Finally, our data show that antibody depletions of macrophages from mdx mice cause significant reductions in muscle membrane injury. Together, these findings indicate that macrophages promote injury of dystrophin-deficient muscle, and the loss of normal levels of NO production by dystrophic muscle exacerbates inflammation and membrane injury in muscular dystrophy.

A canine minidystrophin is functional and therapeutic in mdx mice

“…21 However, forced overexpression of nNOS is reported to reduce muscle pathology in mdx mice primarily by keeping inflammation in check. 24 In DMD and mdx muscles, the nNOS has lost its submembrane anchor and become diffused and diminished in the cytoplasma of the myofibers. After minidystrophin gene expression in the mdx muscle, we have observed profound improvement in dystrophic pathology.…”

“…The N-and C-terminal portions of the canine minidystrophin genes were then joined in-frame by a PCR-mediated strategy. Similar to the human minidystrophin gene, the in-frame deleted minidystrophin cDNA contained the N terminus, hinge1, rods (1,2,22,23,24), hinge 4 and CR domain (Figure 1a). The final construction was carefully sequenced and all the essential domains were verified according to the reported canine dystrophin cDNA (GeneBank AF070485).…”

Expression of the skeletal muscle dystrophin–dystroglycan complex and syntrophin-nitric oxide synthase complex is severely affected in the type 2 diabetic Goto–Kakizaki rat

“…Loss of nNOS may also result in aberrant regulation of adrenergic vasoconstriction (Thomas et al, 1998). In addition, nitric oxide represents an anti-inflammatory and cytoprotective factor (Wehling et al, 2001) suggesting that a reduction in nNOS may trigger muscle pathology (Rando, 2001). This has been shown to be the case in sarcoglycan-deficient muscles from patients afflicted with limb-girdle muscular dystrophy (Crosbie et al, 2002).…”

A Multidisciplinary Evaluation of the Effectiveness of Cyclosporine A in Dystrophic Mdx Mice

“…This leads to a complex and still not fully understood network of interconnected pathogenic events responsible for progressive muscle degeneration; these events involve the increased entrance of calcium, the activation of proteases, and the occurrence of a functional ischemic state. [1][2][3][4] Recent evidence suggests that a chronic inflammatory state is a secondary reaction that strongly contributes to the progression of the pathology. A significant overexpression of inflammatory and immune response genes has been described by microarray in muscle of dystrophic subjects.…”