Expression of Transthyretin during bovine myogenic satellite cell differentiation

Neuroprotective effects of an in vitro BBB permeable phenoxythiophene sulfonamide small molecule in glutamate-induced oxidative injury

Reactive oxygen species (ROS) play a central role in oxidative stress-associated neuronal cell death during ischemia. Further investigation into the inhibition of excessive ROS generation post-stroke is urgently required for the treatment of ischemic stroke. In the present study, the neuroprotective properties of the blood-brain barrier (BBB) penetrant B355227 were investigated. B355227 is a chemical analogue of B355252, and the role of the phenoxythiophene sulfonamide compound B355227 was further investigated in a glutamate-induced oxidative injury model. An in vitro model of the BBB was established in the immortalized mouse brain capillary endothelial cell line, bEnd.3. Formation of barrier in Transwell inserts was confirmed using EVOM resistance meter and Caffeine, Imatinib and Axitinib were used to validate the efficacy of the model. The validated BBB assay in combination with high performance liquid chromatography were used to analyse and verify the permeability of B355227 through the barrier. The integrity of the cell junctions after the BBB assays were confirmed using immunofluorescence to visualize the expression of the barrier junction protein zonula occludens-1. Cell survival was measured with Resazurin, a redox indicator dye, in HT22, a hippocampal neuronal cell treated with 5 mM glutamate or co-treated with the B355227 recovered from the BBB permeability experiment. Changes in glutathione levels were detected using a glutathione detection kit, while analyses of ROS, calcium (Ca2+), and mitochondrial membrane potential (MMP) were accomplished with the fluorescent dyes 2',7'-dichlorofluorescein diacetate, Fura-2 AM and MitoTracker Red dyes, respectively. Immunoblotting was also performed to detect the expression and activation of Erk1/2, p-38, JNK, Bax and Bcl-2. The results of the present study demonstrated that B355227 crossed the BBB in vitro and protected HT22 from oxidative injury induced by glutamate exposure. Treatment of cells with B355227 blocked the glutamate-dependent depletion of intracellular glutathione and significantly reduced ROS production. Increased Ca2+ influx and subsequent collapse of the MMP was attenuated by B355227. Furthermore, the results of the present study demonstrated that B355227 protected against oxidative stress via the MAPK pathway, by increasing the activation of Erk1/2, JNK and P38, and restoring anti-apoptotic Bcl-2. Collectively, the results of the present study indicate that B355227 has potent antioxidant and neuroprotective attributes in glutamate-induced neuronal cell death. Further investigation into the role of B355227 in the modulation of glutamate-dependent oxidative stress is required.

Low-Frequency Electrical Stimulation Promotes Satellite Cell Activities to Facilitate Muscle Regeneration at an Early Phase in a Rat Model of Muscle Strain

The capability of regeneration for skeletal muscle after injury depends on the differentiation and proliferation ability of the resident stem cells called satellite cells. It has been reported that electrical stimulation was widely used in clinical conditions to facilitate muscle regeneration after injury, but the characterization of satellite cell responses to the context of low-frequency electrical stimulation in early-phase muscle strain conditions has not been fully clarified. In this study, we aim to investigate the effects of low-frequency electrical stimulation (frequency: 20 Hz; duration: 30 minutes, twice daily) on satellite cell activities in a rat model for the early phase of muscle strain. Firstly, we adopted our previously developed rat model to mimic the early phase of muscle strain in human. After then, we examined the effects of low-frequency electrical stimulation on histopathological changes of the muscle fiber by hematoxylin and eosin (H&E) staining. Finally, we investigated the effects of low-frequency electrical stimulation on satellite cell proliferation and differentiation by quantification of the expression level of the specific proteins using western blot analyses. The muscle strain in biceps femoris muscles of rats can be induced by high-speed rotation from knee flexion 50° to full knee extension at 960°·s⁻¹ angular velocity during its tetany by activating the sciatic nerve, as evidenced by a widening of the interstitial space between fibers, and more edema or necrosis fibers were detected in the model rats without treatment than in control rats. After treatment with low-frequency electrical stimulation (frequency: 20 Hz; duration: 30 minutes, twice daily), the acute strained biceps femoris muscles of rats showed obvious improvement of histomorphology as indicated by more mature muscle fibers with well-ordered formation with clear boundaries. Consistently, the expression levels of the MyoD and myogenin were marked higher than those in the rats in the animal model group, indicating increased satellite cell proliferating and differentiating activities by low-frequency electrical stimulation. This study shows that low-frequency electrical stimulation provides an effective stimulus to upregulate the protein expression of MyoD/myogenin and accelerate the restoration of structure during the early phase of muscle strain. This may have significance for clinical practice. Optimization of low-frequency electrical stimulation parameters may enhance the therapeutic outcome in patients.

Transthyretin: A Transporter Protein Essential for Proliferation of Myoblast in the Myogenic Program

Irregularities in the cellular uptake of thyroid hormones significantly affect muscle development and regeneration. Herein, we report indispensable role of transthyretin (TTR) in maintaining cellular thyroxine level. TTR was found to enhance recruitment of muscle satellite cells to the site of injury, thereby regulating muscle regeneration. Fluorescence-activated cell sorting (FACS) and immunofluorescence analysis of TTR_wt (TTR wild type) and TTR_kd (TTR knock-down) cells revealed that TTR controlled cell cycle progression by affecting the expression of Cyclin A2. Deiodinase 2 (D2) mediated increases in triiodothyronine levels were found to regulate the expression of myogenic marker, myogenin (MYOG). Moreover, use of a coumarin derivative (CD) revealed a significant reduction in cellular thyroxine, thereby indicating that TTR play a role in the transport of thyroxine. Taken together, these findings suggest that TTR mediated transport of thyroxine represents a survival mechanism necessary for the myogenic program. The results of this study will be highly useful to the strategic development of novel therapeutics to combat muscular dystrophies.

Meeting the meat: delineating the molecular machinery of muscle development

Muscle, studied mostly with respect to meat production, represents one of the largest protein reservoirs of the body. As gene expression profiling holds credibility to deal with the increasing demand of food from animal sources, excessive loss due to myopathies and other muscular dystrophies was found detrimental as it aggravates diseases that result in increased morbidity and mortality. Holding key point towards improving the developmental program of muscle in meat producing animals, elucidating the underlying mechanisms of the associated pathways in livestock animals is believed to open up new avenues towards enhancing the lean tissue deposition. To this end, identification of vital candidate genes having no known function in myogenesis, is believed to increase the current understanding of the physiological processes going on in the skeletal muscle tissue. Taking consequences of gene expression changes into account, knowledge of the pathways associated with their activation and as such up-regulation seems critical for the overall muscle homeostasis. Having important implications on livestock production, a thorough understanding of postnatal muscle development seems a timely step to fulfil the growing need of ever increasing populations of the world.