Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0026850 (muscular dystrophy)
 5,870 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Allopurinol lowers peripheral vascular resistance in dogs, and it has beneficial effects upon muscular dystrophy patients. Since it has been suggested that muscular dystrophy may result from muscle ischemia, we decided to investigate the effects of allopurinol on skeletal muscle blood flow in normal and dystrophic mice. Arterioloar red cell velocity and diameters were measured in the cremaster muscle and used to calculate blood flow. Allopurinol (5 mg/kg, i.p.) resulted in an 81% increase in arteriolar blood flow in normal mice and a 102% increase in dystrophic mice. Such an increase in microcirculatory perfusion could be a mechanism contributing to the clinical effects of allopurinol.
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PMID:The effects of allopurinol on skeletal muscle microcirculation in normal and dystrophic mice. 52 75

Skeletal muscle blood vessels from eight patients with documented Duchenne type muscular dystrophy were examined by light and electron microscopy, with particular attention to the capillary-venous bed. The characteristic lesions of vasoactive amine injury were not present. Endothelial degeneration and regeneration also were absent. Lamellation of capillary basement membranes was noted without true hypertrophy or evidence of discontunuities. Thrombus formation and platelet interaction were absent. Lumenal obliteration was not noted at the arterial level. Rarely, venous obliteration was present in association with nodular connective tissue overgrowth. The minimal abnormalities appear to be nonspecific and do not substantiate postulated vascular injury by vasoactive mediators or ischemia. The role of a nonspecific chronic inflammatory reaction with phagocytes derived from the vascular compartment should be considered with respect to those described basement membrane changes.
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PMID:Blood vessel structure in Duchenne muscular dystrophy. I. Light and electron microscopic observations in resting muscle. 56 43

The vascular hypothesis of the cause of muscular dystrophy suggests that ischemia is responsible for the muscle fiber necrosis. A xenon 133 clearance study of muscle blood flow in Duchenne and other muscular dystrophies showed no obvious difference between the response to exercise and arterial occlusion compared with control subjects. Radioautographic study of distribution of 4-125l-antipyrine in skeletal muscle of mice with muscular dystrophy showed no abnormal areas of ischemia. A statistical examination was also made of the grouping of damaged fibers, one of the observations on which the vascular hypothesis was based. Only 0.9% of fibers undergoing phagocytosis occurred in groups of four or more fibers in greater frequency than would have been expected by chance, and 70% of such fibers were isolated. These studies argue strongly against the vascular hypothesis of the cause of muscular dystrophy.
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PMID:Failure to confirm a vascular cause of muscular dystrophy. 113 13

In the presence of O2, Fe(III) or Cu(II), and an appropriate electron donor, a number of enzymic and nonenzymic oxygen free radical-generating systems are able to catalyze the oxidative modification of proteins. Whereas random, global modification of many different amino acid residues and extensive fragmentation occurs when proteins are exposed to oxygen radicals produced by high energy radiation, only one or a few amino acid residues are modified and relatively little peptide bond cleavage occurs when proteins are exposed to metal-catalyzed oxidation (MCO) systems. The available evidence indicates that the MCO systems catalyze the reduction of Fe(III) to Fe(II) and of O2 to H2O2 and that these products react at metal-binding sites on the protein to produce active oxygen (free radical?) species (viz; OH, ferryl ion) which attack the side chains of amino acid residues at the metal-binding site. Among other modifications, carbonyl derivatives of some amino acid residues are formed; prolyl and arginyl residues are converted to glutamylsemialdehyde residues, lysyl residues are likely converted to 2-amino-adipylsemialdehyde residues; histidyl residues are converted to asparagine and/or aspartyl residues; prolyl residues are converted to glutamyl or pyroglutamyl residues; methionyl residues are converted to methionylsulfoxide residues; and cysteinyl residues to mixed-disulfide derivatives. The biological significance of these metal ion-catalyzed reactions is highlighted by the demonstration: (i) that oxidative modification of proteins "marks" them for degradation by most common proteases and especially by the cytosolic multicatalytic proteinase from mammalian cells; (ii) protein oxidation contributes substantially to the intracellular pool of catalytically inactive and less active, thermolabile forms of enzymes which accumulate in cells during aging, oxidative stress, and in various pathological states, including premature aging diseases (progeria, Werner's syndrome), muscular dystrophy, rheumatoid arthritis, cataractogenesis, chronic alcohol toxicity, pulmonary emphysema, and during tissue injury provoked by ischemia-reperfusion. Furthermore, the metal ion-catalyzed protein oxidation is the basis of biological mechanisms for regulating changes in enzyme levels in response to shifts from anaerobic to aerobic metabolism, and probably from one nutritional state to another. It is also involved in the killing of bacteria by neutrophils and in the loss of neutrophil function following repeated cycles of respiratory burst activity.
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PMID:Metal ion-catalyzed oxidation of proteins: biochemical mechanism and biological consequences. 228 87

Just before I became an editor of Biochemical and Biophysical Research Communications in 1977 we published our first paper in this same journal on the study of tiny perfused rat hearts by (31)P NMR. In this article I trace the development of this in vivo NMR approach from the study of small rat and mouse hearts to human investigations. With the advent of molecular genetics the mouse became a key model organism for understanding and characterizing the function of human genes. I illustrate this by some of our recent work on Duchenne and Becker muscular dystrophy where the in vivo biochemical abnormalities observed in the human can be better understood from investigations of the muscle and heart of the murine model for muscular dystrophy, the mdx mouse. In particular, the mdx mouse heart exhibits ECG (conduction) abnormalities similar to that in the human which we associate with the reduction of the neuronal nitric oxide synthase activity compared to controls. We have also demonstrated in the mouse model that the increased sensitivity of the heart to ischemia is associated with a decrease in the insulin-stimulated glucose transport. Imaging techniques involving NMR, visible light, and others will play an increasingly important role in linking genomics to functional "molecular physiology."
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PMID:Of mice and men: from early NMR studies of the heart to physiological genomics. 1060 10

The calpains form a growing family of structurally related intracellular multidomainal cysteine proteinases, which exhibit a catalytic domain distantly related to papain. In contrast to papain, however, their activity in most cases depends on calcium. The calpains are believed to play important roles in cytoskeletal remodeling processes, cell differentiation, apoptosis and signal transduction, but have also been implicated in muscular dystrophy, ischemia, traumatic brain injury, neurodegenerative diseases, rheumatoid arthritis and cataract formation. The best characterized calpains are the ubiquitously expressed mu- and m-calpains, consisting of a common 30 kDa small S-subunit (domains V and VI) and slightly differing 80 kDa large L-subunits (domains I to IV). We have recently determined the 2.3 A structure of recombinant full-length human m-calpain in the absence of calcium, which reveals that the catalytic domain and the two calmodulin-like domains, previously believed to represent the unique calcium switch, are not positioned adjacent to each other, but are separated by the beta-sandwich domain III, which distantly resembles C2 domains. Although the catalytic domain of apocalpain is strongly disrupted compared to papain (which explains its inactivity in the absence of calcium), the crystal structure reveals several sites where calcium could bind, thereby causing a subdomain fusion to form a papain-like catalytic center. All current evidence points to the cooperative interaction of several calcium binding sites. Sites identified include the three EF-hand binding sites in each calmodulin-like domain, the negatively charged segments arranged around the active-site cleft (provided by both catalytic subdomains), as well as an exposed acidic loop of domain III, whose charge compensation could allow the adjacent barrel-like subdomain IIb to move toward the helical subdomain IIa. The Gly-rich S-chain N-terminus and the calcium-loaded acidic loop could target the conventional calpains to cellular/nuclear membranes, thereby explaining their strongly reduced calcium requirement in vivo and in vitro in the presence of acidic phospholipids.
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PMID:Structural basis for possible calcium-induced activation mechanisms of calpains. 1151 28

Although the genetic and biochemical bases of many of the muscular dystrophies have been elucidated, the pathophysiological mechanisms leading to muscle cell death and degeneration remain elusive. Among the most well studied of the dystrophies are those due to defects in proteins that make up the dystrophin-glycoprotein complex (DGC). There has been much interest in the role of nitric oxide (NO(*)) in the pathogenesis of these diseases because the enzyme that synthesizes NO(*), nitric oxide synthase (NOS), is associated with the DGC. Recent studies of dystrophies related to DGC defects suggest that one mechanism of cellular injury is functional ischemia related to alterations in cellular NOS and disruption of a normal protective action of NO(*). This protective action is the prevention of local ischemia during contraction-induced increases in sympathetic vasoconstriction. However, the loss of this protection, alone, does not explain the subsequent muscle cell death and degeneration since mice lacking neuronal NOS (the predominant isoform expressed in muscle) do not develop a muscular dystrophy. Thus, there must be additional biochemical changes conferred upon the cells by these DGC defects, and these changes are discussed in terms of a proposed "two hit" hypothesis of the pathogenetic mechanisms that underlie the muscular dystrophies. According to this hypothesis, pathogenic defects in the DGC have at least two biochemical consequences: a reduction in NO(*)-mediated protection against ischemia, and an increase in cellular susceptibility to metabolic stress. Either one alone may be insufficient to lead to muscle cell death. However, in combination, the biochemical consequences are sufficient to cause muscle degeneration. The role of oxidative stress as a final common pathophysiologic pathway is discussed in terms of data showing that oxidative injury precedes pathologic changes and that muscle cells with defects in the DGC have an increased susceptibility to oxidant challenges. Accordingly, this "two hit" hypothesis may explain many of the complex spatial and temporal variations in disease expression that characterize the muscular dystrophies, such as grouped necrosis, a pre-necrotic phase of the disease, and selective muscle involvement.
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PMID:Role of nitric oxide in the pathogenesis of muscular dystrophies: a "two hit" hypothesis of the cause of muscle necrosis. 1174 61

Duchenne muscular dystrophy is caused by mutations in the gene encoding dystrophin, a 427 kd protein normally found at the cytoplasmic face of the sarcolemma. In normal muscle, dystrophin is associated with a multimolecular glycoprotein complex. Primary mutations in the genes encoding members of this glycoprotein complex are also associated with muscular dystrophy. The dystrophin-glycoprotein complex provides a physical linkage between the internal cytoskeleton of myofibers and the extracellular matrix, but the precise functions of the dystrophin-glycoprotein complex remain uncertain. In this review, five potential pathogenetic mechanisms implicated in the initiation of myofiber injury in dystrophin-glycoprotein complex deficiencies are discussed: (1) mechanical weakening of the sarcolemma, (2) inappropriate calcium influx, (3) aberrant cell signaling, (4) increased oxidative stress, and (5) recurrent muscle ischemia. Particular emphasis is placed on the multifunctional nature of the dystrophin-glycoprotein complex and the fact that the above mechanisms are in no way mutually exclusive and may interact with one another to a significant degree.
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PMID:Molecular pathophysiology of myofiber injury in deficiencies of the dystrophin-glycoprotein complex. 1240 21

Calpain was first discovered 30 years ago. Two major isoforms were subsequently isolated and purified. The presence of an endogenous protein inhibitor, calpastatin, was later discovered. Calpain activity is tightly regulated by Ca(2+). At physiological levels of Ca(2+), the role of calpain remains poorly understood, but is believed to be involved in mitosis and muscle cell differentiation. Calpain has also been implicated in various membrane fusion events through remodeling of the cytoskeletal network. Calpain activation has been shown to be increased during normal aging and in muscular dystrophy, cataract, arthritis and Alzheimer's disease, and in acute traumas such as traumatic brain injury (TBI), spinal cord injury and cerebral and cardiac ischemia. Early work on calpain inhibitors was limited to protein inhibitors and other nonselective enzyme inhibitors. Peptidyl aldehydes such as leupeptin and antipain are also among the earliest reported calpain inactivators. Irreversible inhibitors such as the E64 family have also been studied, and peptidyl halomethanes and diazomethanes have long been used as protease inhibitors. A variety of calpain inhibitors are under development. From a therapeutic perspective, calpain inhibitors may have several advantages over other more conventional targets such as ion channel blockers and glumate antagonists, since calpain proteolysis represents a later component of a pathway mediating cell death initiated by excitotoxicity and elevated Ca(2+) levels. Although the potential clinical utility of calpain inhibitors seems well established, a number of important considerations remain to be addressed. The role of other proteolytic cascades contributing to neuronal cell damage following TBI must also be considered.
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PMID:Potential contribution of proteases to neuronal damage. 1561 63

Cellular and tissue injury associated with reactive oxygen species (ROS) has been reported in many kinds of disorders. While the antioxidant enzymes play critical roles in inhibiting the ROS-mediated injury, glutathione peroxidase (GPx) is scavenging hydroperoxides including H(2)O(2). We previously reported that Shengmai-san (SMS), a traditional Chinese medicine, prevented ischemia/reperfusion injury of the brain and other organs in rats. To clarify the effect of SMS on intracellular responses of muscle cells against oxidative stress, C2C12 myoblasts were subjected to H(2)O(2) abuse. SMS pre-incubation prevented the decreasing cell viability after H(2)O(2) treatment. The accumulations of cellular protein carbonyl associated with apoptotic cell death were also inhibited by the SMS pre-incubation prior to oxidative damage induction. At the same time, enhanced activity, protein, and mRNA expression levels of GPx were observed in cells pre-incubated with SMS prior to H(2)O(2) abuse. Moreover, intracellular GSH was subsequently decreased after H(2)O(2) treatment. These findings suggest that SMS improved the antioxidant capacity against acute oxidative stress through the constitutive enhancement of GPx expression in C2C12 myoblasts. Because of its antioxidative property, SMS might be useful not only for the oxidative damage associated diseases but also for the transplantation of myoblasts into muscular dystrophy patients.
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PMID:Shengmai-san enhances antioxidant potential in C2C12 myoblasts through the induction of intracellular glutathione peroxidase. 1805 75


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