Sodium nitrate decreases agrin-induced acetylcholine receptor clustering

Ionic medicine: Exploiting metallic ions to stimulate skeletal muscle tissue regeneration

The regeneration of healthy and functional skeletal muscle at sites of injuries and defects remains a challenge. Mimicking the natural environment surrounding skeletal muscle cells and the application of electrical and mechanical stimuli are approaches being investigated to promote muscle tissue regeneration. Likewise, chemical stimulation with therapeutic (biologically active) ions is an emerging attractive alternative in the tissue engineering and regenerative medicine fields, specifically to trigger myoblast proliferation, myogenic differentiation, myofiber formation, and ultimately to promote new muscle tissue growth. The present review covers the specialized literature focusing on the biochemical stimulation of muscle tissue repair by applying inorganic ions (bioinorganics). Extracting information from the literature, different ions and their potential influence as chemical cues on skeletal muscle regeneration are discussed. It is revealed that different ions and their varied doses have an individual effect at different stages of muscle cellular development. The dose-dependent effects of ions, as well as applications of ions alone and in combination with biomaterials, are also summarized. Some ions, such as boron, silicon, magnesium, selenium and zinc, are reported to exhibit a beneficial effect on skeletal muscle cells in carefully controlled doses, while the effects of other ions such as iron and copper appear to be contradictory. In addition, calcium is an essential regulatory ion for the differentiation of myoblasts. On the other hand, some ions such as phosphate have been shown to inhibit muscle cell behavior. This review thus provides a complete overview of the application of ionic stimulation for skeletal muscle tissue engineering applications, highlighting the importance of inorganic ions as an attractive alternative to the application of small molecules and growth factors to stimulate muscle tissue repair. STATEMENT OF SIGNIFICANCE: Ionic medicine (IM) is emerging as a promising and attractive approach in the field of tissue engineering, including muscle tissue regeneration. IM is based on the delivery of biologically active ions to injury sites, acting as stimulants for the repair process. This method offers a potentially simpler and more affordable alternative to conventional biomolecule-based regulators such as growth factors. Different biologically active ions, depending on their specific doping concentrations, can have varying effects on cellular development, which could be either beneficial or inhibitory. This literature review covers the field of IM in muscle regeneration with focus on the impact of various ions on skeletal muscle regeneration. The paper is thus a critical summary for guiding future research in ionic-related regenerative medicine, highlighting the potential and challenges of this approach for muscle regeneration.

Sodium nitrate co-supplementation does not exacerbate low dose metronomic doxorubicin-induced cachexia in healthy mice

The purpose of this study was to determine whether (1) sodium nitrate (SN) treatment progressed or alleviated doxorubicin (DOX)-induced cachexia and muscle wasting; and (2) if a more-clinically relevant low-dose metronomic (LDM) DOX treatment regimen compared to the high dosage bolus commonly used in animal research, was sufficient to induce cachexia in mice. Six-week old male Balb/C mice (n = 16) were treated with three intraperitoneal injections of either vehicle (0.9% NaCl; VEH) or DOX (4 mg/kg) over one week. To test the hypothesis that sodium nitrate treatment could protect against DOX-induced symptomology, a group of mice (n = 8) were treated with 1 mM NaNO₃ in drinking water during DOX (4 mg/kg) treatment (DOX + SN). Body composition indices were assessed using echoMRI scanning, whilst physical and metabolic activity were assessed via indirect calorimetry, before and after the treatment regimen. Skeletal and cardiac muscles were excised to investigate histological and molecular parameters. LDM DOX treatment induced cachexia with significant impacts on both body and lean mass, and fatigue/malaise (i.e. it reduced voluntary wheel running and energy expenditure) that was associated with oxidative/nitrostative stress sufficient to induce the molecular cytotoxic stress regulator, nuclear factor erythroid-2-related factor 2 (NRF-2). SN co-treatment afforded no therapeutic potential, nor did it promote the wasting of lean tissue. Our data re-affirm a cardioprotective effect for SN against DOX-induced collagen deposition. In our mouse model, SN protected against LDM DOX-induced cardiac fibrosis but had no effect on cachexia at the conclusion of the regimen.

Agrin-LRP4-MuSK signaling as a therapeutic target for myasthenia gravis and other neuromuscular disorders

INTRODUCTION

Signal transduction at the neuromuscular junction (NMJ) is compromised in a diverse array of diseases including myasthenia gravis, Lambert-Eaton myasthenic syndrome, Isaacs' syndrome, congenital myasthenic syndromes, Fukuyama-type congenital muscular dystrophy, amyotrophic lateral sclerosis, and sarcopenia. Except for sarcopenia, all are orphan diseases. In addition, the NMJ signal transduction is impaired by tetanus, botulinum, curare, α-bungarotoxin, conotoxins, organophosphate, sarin, VX, and soman to name a few. Areas covered: This review covers the agrin-LRP4-MuSK signaling pathway, which drives clustering of acetylcholine receptors (AChRs) and ensures efficient signal transduction at the NMJ. We also address diseases caused by autoantibodies against the NMJ molecules and by germline mutations in genes encoding the NMJ molecules. Expert opinion: Representative small compounds to treat the defective NMJ signal transduction are cholinesterase inhibitors, which exert their effects by increasing the amount of acetylcholine at the synaptic space. Another possible therapeutic strategy to enhance the NMJ signal transduction is to increase the number of AChRs, but no currently available drug has this functionality.

Dietary Genistein Influences Number of Acetylcholine Receptors in Female Diabetic Jejunum

BACKGROUND

Intestinal dysfunction in the ob/ob mouse model of diabetes mimics that seen clinically.

METHODS

We determined the effects of a 4-week genistein diet (600 mg genistein/kg food) on intestinal function (contractility, morphology, AChR, and motility) in female ob/ob and lean mice.

RESULTS

Contractility of the jejunum in response to incrementally increasing concentrations of KCl was comparable in ob/ob females and lean controls regardless of a genistein-diet. There were no changes in the wall thickness measured. We assessed the number of clusters of AChR in the jejunum wall; AChR were decreased by 48% in ob/ob mice versus leans, and the genistein diet reversed this. In utilizing a video-imaging system to evaluate gastrointestinal motility, we determined that the distance between consecutive contractile events was significantly increased by 1.87-fold in ob/ob mice versus leans, and the genistein diet was without effect.

CONCLUSIONS

These data suggest that slowed intestinal transit in the diabetic ob/ob mouse may be due in part to decreased AChR and decreased contraction events occurring per unit time. A genistein diet rescues the number of AChR to levels of leans yet did not change the number of contractile events. Feeding ob/ob mice a genistein-rich diet has potential therapeutic benefits towards improving the debilitating diabetes-related gastrointestinal dysfunction.