Dantrolene improves in vitro structural changes induced by serum from Trypanosoma cruzi-infected mice

Essential roles of the dystrophin-glycoprotein complex in different cardiac pathologies

The dystrophin-glycoprotein complex (DGC), situated at the sarcolemma dynamically remodels during cardiac disease. This review examines DGC remodeling as a common denominator in diseases affecting heart function and health. Dystrophin and the DGC serve as broad cytoskeletal integrators that are critical for maintaining stability of muscle membranes. The presence of pathogenic variants in genes encoding proteins of the DGC can cause absence of the protein and/or alterations in other complex members leading to muscular dystrophies. Targeted studies have allowed the individual functions of affected proteins to be defined. The DGC has demonstrated its dynamic function, remodeling under a number of conditions that stress the heart. Beyond genetic causes, pathogenic processes also impinge on the DGC, causing alterations in the abundance of dystrophin and associated proteins during cardiac insult such as ischemia-reperfusion injury, mechanical unloading, and myocarditis. When considering new therapeutic strategies, it is important to assess DGC remodeling as a common factor in various heart diseases. The DGC connects the internal F-actin-based cytoskeleton to laminin-211 of the extracellular space, playing an important role in the transmission of mechanical force to the extracellular matrix. The essential functions of dystrophin and the DGC have been long recognized. DGC based therapeutic approaches have been primarily focused on muscular dystrophies, however it may be a beneficial target in a number of disorders that affect the heart. This review provides an account of what we now know, and discusses how this knowledge can benefit persistent health conditions in the clinic.

Early dystrophin loss is coincident with the transition of compensated cardiac hypertrophy to heart failure

Hypertension causes cardiac hypertrophy, one of the most important risk factors for heart failure (HF). Despite the importance of cardiac hypertrophy as a risk factor for the development of HF, not all hypertrophied hearts will ultimately fail. Alterations of cytoskeletal and sarcolemma-associated proteins are considered markers cardiac remodeling during HF. Dystrophin provides mechanical stability to the plasma membrane through its interactions with the actin cytoskeleton and, indirectly, to extracellular matrix proteins. This study was undertaken to evaluate dystrophin and calpain-1 in the transition from compensated cardiac hypertrophy to HF. Wistar rats were subjected to abdominal aorta constriction and killed at 30, 60 and 90 days post surgery (dps). Cardiac function and blood pressure were evaluated. The hearts were collected and Western blotting and immunofluorescence performed for dystrophin, calpain-1, alpha-fodrin and calpastatin. Statistical analyses were performed and considered significant when p<0.05. After 90 dps, 70% of the animals showed hypertrophic hearts (HH) and 30% hypertrophic+dilated hearts (HD). Systolic and diastolic functions were preserved at 30 and 60 dps, however, decreased in the HD group. Blood pressure, cardiomyocyte diameter and collagen content were increased at all time points. Dystrophin expression was lightly increased at 30 and 60 dps and HH group. HD group showed decreased expression of dystrophin and calpastatin and increased expression of calpain-1 and alpha-fodrin fragments. The first signals of dystrophin reduction were observed as early as 60 dps. In conclusion, some hearts present a distinct molecular pattern at an early stage of the disease; this pattern could provide an opportunity to identify these failure-prone hearts during the development of the cardiac disease. We showed that decreased expression of dystrophin and increased expression of calpains are coincident and could work as possible therapeutic targets to prevent heart failure as a consequence of cardiac hypertrophy.

Interference with Ca2+-Dependent Proteolysis Does Not Alter the Course of Muscle Wasting in Experimental Cancer Cachexia

Protein hypercatabolism significantly contributes to the onset and progression of muscle wasting in cancer cachexia. In this regard, a major role is played by the ATP-ubiquitin-proteasome-dependent pathway and by autophagy. However, little is known about the relevance of the Ca²⁺-dependent proteolytic system. Since previous results suggested that this pathway is activated in the skeletal muscle of tumor hosts, the present study was aimed to investigate whether inhibition of Ca²⁺-dependent proteases (calpains) may improve cancer-induced muscle wasting. Two experimental models of cancer cachexia were used, namely the AH-130 Yoshida hepatoma and the C26 colon carcinoma. The Ca²⁺-dependent proteolytic system was inhibited by treating the animals with dantrolene or by overexpressing in the muscle calpastatin, the physiologic inhibitor of Ca²⁺-dependent proteases. The results confirm that calpain-1 is overexpressed and calpastatin is reduced in the muscle of rats implanted with the AH-130 hepatoma, and show for the first time that the Ca²⁺-dependent proteolytic system is overactivated also in the C26-bearing mice. Yet, administration of dantrolene, an inhibitor of the Ca²⁺-dependent proteases, did not modify tumor-induced body weight loss and muscle wasting in the AH-130 hosts. Dantrolene was also unable to reduce the enhancement of protein degradation rates occurring in rats bearing the AH-130 hepatoma. Similarly, overexpression of calpastatin in the tibialis muscle of the C26 hosts did not improve muscle wasting at all. These observations suggest that inhibiting a single proteolytic system is not a good strategy to contrast cancer-induced muscle wasting. In this regard, a more general and integrated approach aimed at targeting the catabolic stimuli rather than the proteolytic activity of a single pathway would likely be the most appropriate therapeutic intervention.