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Extraocular, limb and diaphragm muscle group-specific antioxidant enzyme activity patterns in control and mdx mice
R J Ragusa1, C K Chow, D K St Clair
1Department of Anatomy and Neurobiology, University of Kentucky Medical Center 40536-0084, USA.
Abstract:
The mechanisms primarily responsible for the degenerative processes occurring in dystrophic skeletal muscle remain unresolved. The identification of the mechanisms that lead to the complete sparing of extraocular muscle in dystrophinopathies is of particular interest. A number of studies have provided evidence to suggest that the muscle pathology that characterizes muscular dystrophy may be, in part, free radical mediated. In the present study, we examined the antioxidant enzyme status of extraocular, diaphragm and gastrocnemius muscles in control strain and mdx mice. Our results revealed that in the control strain, both extraocular and diaphragm muscles had higher copper/zinc superoxide dismutase, manganese superoxide dismutase and selenium dependent glutathione peroxidase activities as compared to the gastrocnemius. Furthermore, the diaphragm had higher glutathione reductase activity as compared to the gastrocnemius. These findings indicate that the highly aerobic extraocular and diaphragm muscles have higher antioxidant enzyme capacity than the gastrocnemius, a muscle more dependent on anaerobic energy metabolism. Changes in the antioxidant enzyme status of the mdx mouse correlated, in part, with the degree of histopathological involvement of the three muscle groups assessed.
Insights
This study investigated antioxidant enzymes in mouse muscles, finding that aerobic muscles have higher capacity. These antioxidant differences may explain why some muscles are spared in muscular dystrophy.
Area of Science:
- Biochemistry
- Muscle Physiology
- Molecular Biology
Background:
- Muscular dystrophy involves skeletal muscle degeneration, but mechanisms remain unclear.
- Extraocular muscles are often spared in dystrophinopathies, a key area of interest.
- Free radicals are implicated in muscular dystrophy pathology.
Purpose of the Study:
- To compare antioxidant enzyme status across different muscle types in normal and dystrophic mice.
- To investigate the role of antioxidant defenses in muscle sparing within muscular dystrophy models.
Main Methods:
- Assessed antioxidant enzyme activities (superoxide dismutase, glutathione peroxidase, glutathione reductase) in extraocular, diaphragm, and gastrocnemius muscles.
- Utilized control and mdx (dystrophin-deficient) mouse models.
- Correlated enzyme status with histopathological findings.
Main Results:
- Control mice showed higher antioxidant enzyme activity in aerobic extraocular and diaphragm muscles compared to the gastrocnemius.
- Diaphragm muscles exhibited greater glutathione reductase activity than gastrocnemius.
- Antioxidant enzyme changes in mdx mice partially aligned with muscle damage severity.
Conclusions:
- Aerobic muscles possess a higher intrinsic antioxidant capacity than anaerobic muscles.
- Differences in antioxidant enzyme profiles may contribute to the differential susceptibility of muscles in muscular dystrophy.
- Antioxidant status is altered in mdx mice, correlating with disease progression.