Duchenne muscular dystrophy: pathogenesis and pharmacology

Altered contents of tocopherols in chickens with inherited muscular dystrophy

Oxidative damage has been hypothesized as the basis for some of the changes in enzymatic functions and physical properties of membranes in inherited muscular dystrophy. The contents of alpha- and gamma-tocopherol (vitamin E) and their oxidation products, the tocopheryl quinones, were measured at 1 to 4 weeks after hatching in the muscle and other tissues of chickens with inherited muscular dystrophy. Analyses at these early ages minimized the potential influence of pathological changes on the measured parameters. The affected muscle (pectoralis major) of dystrophic birds contained significantly higher levels of alpha-tocopheryl quinone and a decreased ratio of alpha- to gamma-tocopherol. Consistent changes in these parameters were not observed in other tissues. Although their basis remains unclear, these changes in the tocopherols are suggestive of oxidative stress in dystrophic muscle membranes. Lipid extracts of tissues of normal and dystrophic birds exhibited no significant differences in the content of conjugated dienes or lipofuscins, two other indices of oxidative stress. These data do not consistently support the hypothesis that oxidative stress plays a causal role in damage to dystrophic muscle, although it remains possible that free-radical damage is involved in the secondary alterations associated with muscular dystrophy.

Studies of water permeability and proteins of erythrocyte membranes in patients with Duchenne muscular dystrophy

The characteristics of water permeability of erythrocytes from 54 Duchenne muscular dystrophy (DMD) patients and age-matched controls have been determined by a pulse nuclear magnetic resonance (NMR) technique. A decreased permeability of erythrocyte membrane in DMD was definitely found at all temperatures between 15 and 42 degrees C, with normal values for the activation energy of water diffusion. No differences between DMD and control subjects in the pattern of erythrocyte membrane polypeptides separated by two-dimensional electrophoresis could be detected. The findings are discussed in relation to the molecular mechanisms of water diffusion across erythrocyte membrane and the problem of erythrocyte membrane abnormalities in DMD. A new interpretation of erythrocyte membrane alterations is proposed based on the recent findings regarding the molecular pathology of DMD.

Oxidative stress and muscular dystrophy

Oxidative stress may be the fundamental basis of many of the structural, functional and biochemical changes characteristic of the inherited muscular dystrophies in animals and humans. The presence of by-products of oxidative damage, and the compensatory increases in cellular antioxidants, both indicate oxidative stress may be occurring in dystrophic muscle. Changes in the proportions and metabolism of cellular lipids, abnormal functions of cellular membranes, altered activity of membrane-bound enzymes such as the SR Ca2+-ATPase, disturbances in cellular protein turnover and energy production and a variety of other changes all indicate that these inherited muscular dystrophies appear more like the results of oxidative stress to muscle than any other type of underlying muscle disturbance. Particular details of these altered characteristics of dystrophic muscle, in combination with current knowledge on the processes of oxidative damage to cells, may provide some insight into the underlying biochemical defect responsible for the disease, as well as direct research towards the ultimate goal of an effective treatment.