Neuromuscular electrical stimulation prevents skeletal muscle dysfunction in adjuvant-induced arthritis rat

Probiotics Attenuate Myopathic Changes in Aging Rats via Activation of the Myogenic Stellate Cells

Aging represents a complex biological process associated with decline in skeletal muscle functions. Aging impairs satellite cells that serve as muscle progenitor cells. Probiotic supplementation may have many beneficial effects via various mechanisms. We examined the possible effects of probiotics in stimulating the proliferation of myogenic stellate cells in aging rats. Twenty-four male albino Sprague-Dawley rats were classified equally into four groups: adult control, old control, adult + probiotics, and old + probiotics. Probiotics (Lactobacillus LB) were administered gavage at a dose of 1 ml (1 × 109 CFU/ml/day) for 4 weeks. A significant increase in the relative gastrocnemius weight ratio and improvement of contractile parameters was detected in the old + probiotics group (0.6 ± 0.01) compared to the old control group (0.47 ± 0.01; P < 0.001). Probiotics significantly upregulated the activities of GSH, while NO and MDA were markedly decreased compared to control groups (P ≤ 0.001). Also, probiotics increased the mRNA and protein expressions of myogenin and CD34 (P < 0.05) as determined by real-time PCR and immunohistochemistry. Moreover, the old + probiotics group showed apparent restoration of the connective tissue spaces, reflecting the all-beneficial effects of probiotics. Our findings indicated that probiotics attenuated myopathic changes in aging rats probably through activation of the myogenic stellate cells. Probiotics improved the muscle weight, function, antioxidant activity, and myogenic transcription factors of the skeletal muscle.

Sarcopenia in Autoimmune and Rheumatic Diseases: A Comprehensive Review

Sarcopenia refers to a decrease in skeletal muscle mass and function. Because sarcopenia affects mortality, and causes significant disability, the clinical importance of sarcopenia is emerging. At first, sarcopenia was recognized as an age-related disease but, recently, it has been reported to be prevalent also in younger patients with autoimmune diseases. Specifically, the association of sarcopenia and autoimmune diseases such as rheumatoid arthritis has been studied in detail. Although the pathogenesis of sarcopenia in autoimmune diseases has not been elucidated, chronic inflammation is believed to contribute to sarcopenia, and moreover the pathogenesis seems to be different depending on the respective underlying disease. The definition of sarcopenia differs among studies, which limits direct comparisons. Therefore, in this review, we cover various definitions of sarcopenia used in previous studies and highlight the prevalence of sarcopenia in diverse autoimmune diseases including rheumatoid arthritis, spondyloarthritis, systemic sclerosis, inflammatory bowel disease, and autoimmune diabetes. In addition, we cover the pathogenesis and treatment of sarcopenia in autoimmune and rheumatic diseases. This review provides a comprehensive understanding of sarcopenia in various autoimmune diseases and highlights the need for a consistent definition of sarcopenia.

Eccentric training enhances the αB-crystallin binding to the myofibrils and prevents skeletal muscle weakness in adjuvant-induced arthritis rat

Patients with rheumatoid arthritis (RA) frequently suffer from muscle weakness. We examined whether eccentric training prevents skeletal muscle weakness in adjuvant-induced arthritis (AIA) rat, a widely used animal model for RA. AIA was induced in the knees of Wistar rats by injection of complete Freund’s adjuvant. To induce eccentric contractions (ECCs), neuromuscular electrical stimulation (45 V) was applied to the plantar flexor muscles simultaneously with forced dorsiflexion of the ankle joint (0–40°) and was given every 6 s. ECC exercise was applied every other day for a total of 11 sessions and consisted of 4 sets of 5 contractions. There was a significant reduction in in vitro maximum Ca2+-activated force in skinned fibers in gastrocnemius muscle from AIA rats. These changes were associated with reduced expression levels of contractile proteins (i.e., myosin and actin), increased levels of inflammation redox stress-related biomarkers (i.e., TNF-α, malondialdehyde-protein adducts, NADPH oxidase 2, and neuronal nitric oxide synthase), and autolyzed active calpain-1 in AIA muscles. ECC training markedly enhanced the steady-state levels of αB-crystallin, a small heat shock protein, and its binding to the myofibrils and prevented the AIA-induced myofibrillar dysfunction, reduction in contractile proteins, and inflammation-oxidative stress insults. Our findings demonstrate that ECC training preserves myofibrillar function without muscle damage in AIA rats, which is at least partially attributable to the protective effect of αB-crystallin on the myofibrils against oxidative stress-mediated protein degeneration. Thus ECC training can be a safe and effective intervention, counteracting the loss of muscle strength in RA patients.

NEW & NOTEWORTHY Eccentric contractions (ECCs) are regarded as an effective way to increase muscle strength. No studies, however, assess safety and effectiveness of ECC training on muscle weakness associated with rheumatoid arthritis. Here, we used adjuvant-induced arthritis (AIA) rats to demonstrate that ECC training prevents intrinsic contractile dysfunction without muscle damage in AIA rats, which may be attributed to the protective effect of αB-crystallin on the myofibrils against inflammation-oxidative stress insults.

Electrical Stimulation Prevents Preferential Skeletal Muscle Myosin Loss in Steroid-Denervation Rats

Severe muscle weakness concomitant with preferential depletion of myosin has been observed in several pathological conditions. Here, we used the steroid-denervation (S-D) rat model, which shows dramatic decrease in myosin content and force production, to test whether electrical stimulation (ES) treatment can prevent these deleterious changes. S-D was induced by cutting the sciatic nerve and subsequent daily injection of dexamethasone for 7 days. For ES treatment, plantarflexor muscles were electrically stimulated to produce four sets of five isometric contractions each day. Plantarflexor in situ isometric torque, muscle weight, skinned muscle fiber force, and protein and mRNA expression were measured after the intervention period. ES treatment partly prevented the S-D-induced decreases in plantarflexor in situ isometric torque and muscle weight. ES treatment fully prevented S-D-induced decreases in skinned fiber force and ratio of myosin heavy chain (MyHC) to actin, as well as increases in the reactive oxygen/nitrogen species-generating enzymes NADPH oxidase (NOX) 2 and 4, phosphorylation of p38 MAPK, mRNA expression of the muscle-specific ubiquitin ligases muscle ring finger-1 (MuRF-1) and atrogin-1, and autolyzed active calpain-1. Thus, ES treatment is an effective way to prevent muscle impairments associated with loss of myosin.

Pharmacological characterization of crotamine effects on mice hind limb paralysis employing both ex vivo and in vivo assays: Insights into the involvement of voltage-gated ion channels in the crotamine action on skeletal muscles

The high medical importance of Crotalus snakes is unquestionable, as this genus is the second in frequency of ophidian accidents in many countries, including Brazil. With a relative less complex composition compared to other genera venoms, as those from the Bothrops genus, the Crotalus genus venom from South America is composed basically by the neurotoxin crotoxin (a phospholipase A2), the thrombin-like gyroxin (a serinoprotease), a very potent aggregating protein convulxin, and a myotoxic polypeptide named crotamine. Interestingly not all Crotalus snakes express crotamine, which was first described in early 50s due to its ability to immobilize animal hind limbs, contributing therefore to the physical immobilization of preys and representing an important advantage for the envenoming efficacy, and consequently, for the feeding and survival of these snakes in nature. Representing about 10–25% of the dry weight of the crude venom of crotamine-positive rattlesnakes, the polypeptide crotamine is also suggested to be of importance for antivenom therapy, although the contribution of this toxin to the main symptoms of envenoming process remains far unknown until now. Herein, we concomitantly performed in vitro and in vivo assays to show for the first time the dose-dependent response of crotamine-triggered hind limbs paralysis syndrome, up to now believed to be observable only at high (sub-lethal) concentrations of crotamine. In addition, ex vivo assay performed with isolated skeletal muscles allowed us to suggest here that compounds active on voltage-sensitive sodium and/or potassium ion channels could both affect the positive inotropic effect elicited by crotamine in isolated diaphragm, besides also affecting the hind limbs paralysis syndrome imposed by crotamine in vivo. By identifying the potential molecular targets of this toxin, our data may contribute to open new roads for translational studies aiming to improve the snakebite envenoming treatment in human. Interestingly, we also demonstrate that the intraplantal or intraperitoneal (ip) injections of crotamine in mice do not promote pain. Therefore, this work may also suggest the profitable utility of non-toxic analogs of crotamine as a potential tool for targeting voltage-gated ion channels in skeletal muscles, aiming its potential use in the therapy of neuromuscular dysfunctions and envenoming therapy.

Representing more than 10% of the dry weight of the crude venom of crotamine-positive rattlesnakes, crotamine may act as toxin mainly by imposing the physical immobilization of preys. Its presence was described to be important for antivenom therapy, although the knowledge on the effective contribution of crotamine to the main symptoms of envenoming process remains elusive and limited. Herein, we show for the first time the dose-dependent response for the hind limbs paralysis syndrome promoted by crotamine. We also report herein that compounds active on voltage-sensitive sodium and/or potassium ion channels can affect the positive inotropic effect elicited by crotamine in vitro in isolated diaphragm and also in the hind limbs paralysis syndrome triggered by crotamine in vivo. This potential targeting of voltage-sensitive sodium and/or potassium ion channels suggested here for crotamine may contribute to open new roads for translational studies aiming to improve the snakebite envenoming treatment in human. More importantly, nociceptive threshold evaluation demonstrated that crotamine does not trigger pain, and therefore, we also suggest crotamine as a potential tool for targeting voltage-gated ion channels present in skeletal muscles, with potential to be used as a lead compound to develop drugs for neuromuscular dysfunctions therapy.

Effects of contraction mode and stimulation frequency on electrical stimulation-induced skeletal muscle hypertrophy

We compared the skeletal muscle hypertrophy resulting from isometric (Iso) or eccentric (Ecc) electrical stimulation (ES) training with different stimulation frequencies. Male Wistar rats were assigned to the Iso and Ecc groups. These were divided into three further subgroups that were stimulated at 10 Hz (Iso-10 and Ecc-10), 30 Hz (Iso-30 and Ecc-30), or 100 Hz (Iso-100 and Ecc-100). In experiment 1, the left plantarflexor muscles were stimulated every other day for 3 wk. In experiment 2, mammalian target of rapamycin complex 1 (mTORC1) signaling was investigated 6 h after one bout of ES. The contralateral right muscle served as a control (non-ES). Ecc contractions comprised forced dorsiflexion combined with ES. The peak torque and torque-time integral during ES were higher in the Ecc group than that in the Iso group in all stimulation frequencies examined. The gastrocnemius muscle weight normalized to body weight in ES side was increased compared with the non-ES side by 6, 7, and 17% in the Ecc-30, Iso-100, and Ecc-100 groups, respectively, with a greater gain in Ecc-100 than the Ecc-30 and Iso-100 groups. The p70S6K (Thr389) phosphorylation level was higher in the Ecc-30 and -100 than in the Iso-30 and -100 groups, respectively. The peak torque and torque-time integral were highly correlated with the magnitude of increase in muscle mass and the phosphorylation of p70S6K. These data suggest that ES-induced muscle hypertrophy and mTORC1 activity are determined by loading intensity and volume during muscle contraction independent of the contraction mode.

NEW & NOTEWORTHY Eccentric contraction and high-frequency stimulation (HFS) are regarded as an effective way to increase muscle mass by electrical stimulation (ES) training. However, little is known about whether muscle hypertrophy is affected by contraction mode and stimulation frequency in ES training. Here, we provide the evidence that muscle hypertrophy and mammalian target of rapamycin complex 1 activity are determined by mechanical loading during contraction but not on the contraction mode itself, with a greater gain at HFS.