Disodium cromoglycate protects dystrophin-deficient muscle fibers from leakiness

Neuropeptide Initiated Mast Cell Activation by Transcutaneous Electrical Acupoint Stimulation of Acupoint LI4 in Rats

Transcutaneous electrical acupoint stimulation (TEAS) has been consistently used clinically for its ease of operation, non-invasiveness and painlessness, in contrast to the characteristics of inserted needles. However, the mechanism remains unknown. The aim of this study was to investigate the local response of TEAS at Hegu acupoint (LI4). Immunohistochemistry was used to measure the expression of tryptase-positive mast cells, neuropeptides of the calcitonin gene-related peptide (CGRP) and substance P (SP) in LI4. Mast cells were also labelled with serotonin (5-HT), neurokinin-1 receptor (NK-1R) and toluidine blue. The results showed that cutaneous CGRP and SP immune-positive (CGRP-IP or SP-IP) nerve fibres in LI4 were more highly expressed. There were high degrees of mast cell aggregation and degranulation with release of 5-HT near the CGRP-IP or SP-IP nerve fibres and blood vessels after TEAS. The degranulation of mast cells (MCs) was accompanied by expression of NK-1R after TEAS. Either mast cell membrane stabilizer (Disodium cromoglycate) or NK-1R antagonist (RP 67580) diminished the accumulation and degranulation of MCs induced by TEAS. Taken together, the findings demonstrated that TEAS induced sensory nerve fibres to express CGRP and SP, which then bound to the NK-1R on MCs, after which MCs degranulated and released 5-HT, resulting in TEAS-initiated acupuncture-like signals.

Laser de baixa intensidade favorece a regeneração muscular em modelo experimental desnutrido e recuperado

RESUMO A terapia por laser de baixa intensidade (Low-Level Laser Therapy - LLLT) é utilizada com frequência nas lesões musculares, mas precisa ser investigada em modelo de desnutrição. O objetivo desse estudo foi analisar os efeitos da LLLT na regeneração muscular de ratos submetidos à desnutrição e recuperação proteica. Foram utilizados 40 ratos Wistar, recém-desmamados, divididos em grupo controle (C), que consumiu ração normoproteica (14% caseína), e grupo desnutrido (D), que consumiu ração hipoproteica (6% caseína) por 45 dias e ração normoproteica até o final do experimento. Posteriormente, o músculo tibial anterior direito foi criolesado e tratado com LLLT (AsGaAl 830nm, 30mW, 20J/cm²), três vezes por semana, por 7 e 21 dias. Houve redução da área de inflamação/regeneração no grupo C21 comparado ao D21 (p<0,05), sendo mais evidente com a LLLT (C21L e D21L). O conteúdo de TNF-α foi reduzido após 21 dias da lesão. A área de densidade de tecido conjuntivo (ADTC) foi menor nos grupos C21 e C21L comparados aos respectivos grupos desnutridos (p<0,05). A LLLT reduziu a ADTC no grupo D21L quando comparado do D21 (p<0,05), porém o conteúdo de TGF-β1 não foi influenciado. A área de secção transversa (AST) da fibra muscular aumentou nos grupos 21 dias. A m-TOR apresentou maior conteúdo no grupo C21L quando comparado ao D21L (p<0,05). Concluiu-se que a LLLT favoreceu a regeneração muscular na fase tardia no modelo experimental de desnutrição pós-natal e posterior recuperação proteica.

Selective modulation through the glucocorticoid receptor ameliorates muscle pathology in mdx mice

The over-expression of NF-κB signalling in both muscle and immune cells contribute to the pathology in dystrophic muscle. The anti-inflammatory properties of glucocorticoids, mediated predominantly through monomeric glucocorticoid receptor inhibition of transcription factors such as NF-κB (transrepression), are postulated to be an important mechanism for their beneficial effects in Duchenne muscular dystrophy. Chronic glucocorticoid therapy is associated with adverse effects on metabolism, growth, bone mineral density and the maintenance of muscle mass. These detrimental effects result from direct glucocorticoid receptor homodimer interactions with glucocorticoid response elements of the relevant genes. Compound A, a non-steroidal selective glucocorticoid receptor modulator, is capable of transrepression without transactivation. We confirm the in vitro NF-κB inhibitory activity of compound A in H-2K(b) -tsA58 mdx myoblasts and myotubes, and demonstrate improvements in disease phenotype of dystrophin deficient mdx mice. Compound A treatment in mdx mice from 18 days of post-natal age to 8 weeks of age increased the absolute and normalized forelimb and hindlimb grip strength, attenuated cathepsin-B enzyme activity (a surrogate marker for inflammation) in forelimb and hindlimb muscles, decreased serum creatine kinase levels and reduced IL-6, CCL2, IFNγ, TNF and IL-12p70 cytokine levels in gastrocnemius (GA) muscles. Compared with compound A, treatment with prednisolone, a classical glucocorticoid, in both wild-type and mdx mice was associated with reduced body weight, reduced GA, tibialis anterior and extensor digitorum longus muscle mass and shorter tibial lengths. Prednisolone increased osteopontin (Spp1) gene expression and osteopontin protein levels in the GA muscles of mdx mice and had less favourable effects on the expression of Foxo1, Foxo3, Fbxo32, Trim63, Mstn and Igf1 in GA muscles, as well as hepatic Igf1 in wild-type mice. In conclusion, selective glucocorticoid receptor modulation by compound A represents a potential therapeutic strategy to improve dystrophic pathology.

VBP15, a novel anti-inflammatory and membrane-stabilizer, improves muscular dystrophy without side effects

Absence of dystrophin makes skeletal muscle more susceptible to injury, resulting in breaches of the plasma membrane and chronic inflammation in Duchenne muscular dystrophy (DMD). Current management by glucocorticoids has unclear molecular benefits and harsh side effects. It is uncertain whether therapies that avoid hormonal stunting of growth and development, and/or immunosuppression, would be more or less beneficial. Here, we discover an oral drug with mechanisms that provide efficacy through anti-inflammatory signaling and membrane-stabilizing pathways, independent of hormonal or immunosuppressive effects. We find VBP15 protects and promotes efficient repair of skeletal muscle cells upon laser injury, in opposition to prednisolone. Potent inhibition of NF-κB is mediated through protein interactions of the glucocorticoid receptor, however VBP15 shows significantly reduced hormonal receptor transcriptional activity. The translation of these drug mechanisms into DMD model mice improves muscle strength, live-imaging and pathology through both preventive and post-onset intervention regimens. These data demonstrate successful improvement of dystrophy independent of hormonal, growth, or immunosuppressive effects, indicating VBP15 merits clinical investigation for DMD and would benefit other chronic inflammatory diseases.

Doxycycline ameliorates the dystrophic phenotype of skeletal and cardiac muscles in mdx mice

INTRODUCTION

We examined whether doxycycline, an antibiotic member of the tetracycline family, improves the histopathology and muscle function in mdx mice, the experimental model of DMD.

METHODS

Doxycycline was administered for 36 days (starting on postnatal day 0) and for 9 months (starting at 8 months of age) in drinking water. Histopathological, biochemical (creatine kinase), and functional (forelimb muscle grip strength) parameters were evaluated in limb, diaphragm, and cardiac muscle.

RESULTS

Doxycycline significantly minimized the dystrophic phenotype of skeletal and cardiac muscles and improved forelimb muscle strength. The drug protected muscle fibers against myonecrosis and reduced inflammation. Furthermore, it slowed the progression of myocardial fibrosis.

CONCLUSIONS

This study provides evidence that doxycycline may be a potential therapeutic agent for DMD.

Evidence questioning cromolyn's effectiveness and selectivity as a 'mast cell stabilizer' in mice

Cromolyn, widely characterized as a 'mast cell stabilizer', has been used in mice to investigate the biological roles of mast cells in vivo. However, it is not clear to what extent cromolyn can either limit the function of mouse mast cells or influence biological processes in mice independently of effects on mast cells. We confirmed that cromolyn (at 10 mg/kg in vivo or 10-100 μM in vitro) can inhibit IgE-dependent mast cell activation in rats in vivo (measuring Evans blue extravasation in passive cutaneous anaphylaxis (PCA) and increases in plasma histamine in passive systemic anaphylaxis (PSA)) and in vitro (measuring peritoneal mast cell (PMC) β-hexosaminidase release and prostaglandin D(2) synthesis). However, under the conditions tested, cromolyn did not inhibit those mast cell-dependent responses in mice. In mice, cromolyn also failed to inhibit the ear swelling or leukocyte infiltration at sites of PCA. Nor did cromolyn inhibit IgE-independent degranulation of mouse PMCs induced by various stimulators in vitro. At 100 mg/kg, a concentration 10 times higher than that which inhibited PSA in rats, cromolyn significantly inhibited the increases in plasma concentrations of mouse mast cell protease-1 (but not of histamine) during PSA, but had no effect on the reduction in body temperature in this setting. Moreover, this concentration of cromolyn (100 mg/kg) also inhibited LPS-induced TNF production in genetically mast cell-deficient C57BL/6-Kit(W-sh/W-sh) mice in vivo. These results question cromolyn's effectiveness and selectivity as an inhibitor of mast cell activation and mediator release in the mouse.

Eicosapentaenoic acid decreases TNF-α and protects dystrophic muscles of mdx mice from degeneration

In dystrophin-deficient fibers of mdx mice and in Duchenne muscular dystrophy, inflammation and increased production of tumor necrosis factor alpha (TNF-α) contribute to myonecrosis. We examined the effects of eicosapentaenoic acid (EPA) on dystrophic muscle degeneration. Mdx mice (14 days old) received EPA for 16 days. The sternomastoid, diaphragm and biceps brachii muscles were removed. Control mdx mice received vehicle. EPA decreased creatine kinase and myonecrosis and reduced the levels of TNF-α. These results suggest that EPA plays a protective role in dystrophic muscle degeneration, possibly by reducing TNF-α, and support further investigations of EPA as a potential therapy for dystrophinopathies.

Fiber type composition of the sternomastoid and diaphragm muscles of dystrophin-deficient mdx mice

The muscle fiber phenotype is mainly determined by motoneuron innervation and changes in neuromuscular interaction alter the muscle fiber type. In dystrophin-deficient mdx mice, changes in the molecular assembly of the neuromuscular junction and in nerve terminal sprouting occur in the sternomastoid (STN) muscle during early stages of the disease. In this study, we were interested to see whether early changes in neuromuscular assembly are correlated with alterations in fiber type in dystrophic STN at 2 months of age. A predominance of hybrid fast myofibers (about 52% type IIDB) was observed in control (C57Bl/10) STN. In mdx muscle, the lack of dystrophin did not change this profile (about 54% hybrid type IIDB). Pure fast type IID fibers predominated in normal and dystrophic diaphragm (DIA; about 39% in control and 30% in mdx muscle) and a population of slow Type I fibers was also present (about 10% in control and 13% in mdx muscle). In conclusion, early changes in neuromuscular assembly do not affect the fiber type composition of dystrophic STN. In contrast to the pure fast fibers of the more affected DIA, the hybrid phenotype of the STN may permit dynamic adaptations during progression of the disease.

Effects of mast cell modulation on early host response to implanted synthetic meshes

INTRODUCTION

Mast cells (MCs) and their products (e.g., histamine, serotonin, heparin, prostaglandins, cytokines, etc.) play key roles in controlling local inflammation, wound healing, and foreign body reactions in vivo. Investigation of the role of MCs in mediating local tissue responses to synthetic hernia meshes has been very limited to date. We aimed to determine the effects of MCs/MC products in mice undergoing synthetic mesh implantation.

MATERIALS AND METHODS

Circular samples (5 mm) of heavyweight microporous polypropylene (Trelex), midweight microporous polypropylene (ProLite), lightweight macroporous polypropylene with poliglecaprone (Ultrapro), and 3-dimensional macroporous polyester (Parietex) meshes were implanted subcutaneously in C57BL/6 J mice with and without cromolyn (MC stabilizer/suppressant) treatment (50 mg/kg, daily IP). Two weeks post-implantation, all meshes were explanted and evaluated histologically using H&E and trichrome stains.

RESULTS

Chronic inflammation was focused around individual mesh fibers; inter-fiber inflammation and fibrosis diminished as mesh porosity increased. MC accumulation was seen at the periphery of inflammatory reactions, and in association with mesh-induced fibrosis and neovascularization. Cromolyn treatment resulted in significantly decreased fibrotic responses to all four meshes and reduced inflammation induced by Trelex, ProLite, and Parietex meshes but not Ultrapro.

CONCLUSION

We demonstrated that MCs play important roles in mesh-induced host tissue reactions. Blocking MC degranulation decreased early inflammation and fibrosis induced by most synthetic meshes in this study. Further evaluation and understanding of the role of MCs in mesh-induced tissue reactions will provide new therapeutic approaches to enhance the biocompatibility of surgical meshes and ultimately improve clinical outcomes in patients undergoing hernia repair with synthetic biomaterials.

Preclinical drug trials in the mdx mouse: assessment of reliable and sensitive outcome measures

The availability of animal models for Duchenne muscular dystrophy has led to extensive preclinical research on potential therapeutics. Few studies have focused on reliability and sensitivity of endpoints for mdx mouse drug trials. Therefore, we sought to compare a wide variety of reported and novel endpoint measures in exercised mdx and normal control mice at 10, 20, and 40 weeks of age. Statistical analysis as well as power calculations for expected effect sizes in mdx preclinical drug trials across different ages showed that body weight, normalized grip strength, horizontal activity, rest time, cardiac function measurements, blood pressure, total central/peripheral nuclei per fiber, and serum creatine kinase are the most effective measurements for detecting drug-induced changes. These data provide an experimental basis upon which standardization of preclinical drug testing can be developed. Muscle Nerve, 2008.

The effect of asthma therapeutics on signalling and transcriptional regulation of airway smooth muscle function

SCOPE OF THE REVIEW

Our knowledge of the multifunctional nature of airway smooth muscle (ASM) has expanded rapidly in the last decade, but the underlying molecular mechanisms and how current therapies for obstructive airway diseases, such as asthma and chronic obstructive pulmonary disease (COPD), affect these are still being elucidated. Our current knowledge has built on the pharmacology of human ASM contraction and relaxation established prior to that and which is reviewed in detail elsewhere in this issue. The advent of methods to isolate and culture ASM cells, especially human ASM cells, has made it possible to study how they may contribute to airway remodelling through their synthetic, proliferative, and migratory capacities. Now the underlying molecular mechanisms of ASM growth factor secretion, extracellular matrix (ECM) production, proliferation and migration, as well as contraction and relaxation, are being determined. A complex network of signalling pathways leading to gene transcription in ASM cells permits this functional plasticity in healthy and diseased airways. This review is an overview of the effects of current therapies, and some of those in development, on key signalling pathways and transcription factors involved in these ASM functions.