Carine Smith

The Inflammatory Response to Skeletal Muscle Injury

Injury of skeletal muscle, and especially mechanically induced damage such as contusion injury, frequently occurs in contact sports, as well as in accidental contact sports, such as hockey and squash. The large variations with regard to injury severity and affected muscle group, as well as nonspecificity of reported symptoms, complicate research aimed at finding suitable treatments. Therefore, in order to increase the chances of finding a successful treatment, it is important to understand the underlying mechanisms inherent to this type of skeletal muscle injury and the cellular processes involved in muscle healing following a contusion injury.Arguably the most important of these processes is inflammation since it is a consistent and lasting response. The inflammatory response is dependent on two factors, namely the extent of actual physical damage and the degree of muscle vascularization at the time of injury. However, long-term antiinflammatory treatment is not necessarily effective in promoting healing, as indicated by various studies on NSAID treatment. Because of the factors named earlier, human studies on the inflammatory response to contusion injury are limited, but several experimental animal models have been designed to study muscle damage and regeneration.The early recovery phase is characterized by the overlapping processes of inflammation and occurrence of secondary damage. Although neutrophil infiltration has been named as a contributor to the latter, no clear evidence exists to support this claim. Macrophages, although forming part of the inflammatory response, have been shown to have a role in recovery, rather than in exacerbating secondary damage. Several probable roles for this cell type in the second phase of recovery, involving resolution processes, have been identified and include the following: (i) phagocytosis to remove cellular debris; (ii) switching from a pro- to anti-inflammatory phenotype in regenerating muscle; (iii) preventing muscle cells from undergoing apoptosis; (iv) releasing factors to promote muscle precursor cell activation and growth; and (v) secretion of cytokines and growth factors to facilitate vascular and muscle fibre repair. These many different roles suggest that a single treatment with one specific target cell population (e.g. neutrophils, macrophages or satellite cells) may not be equally effective in all phases of the post-injury response.To find the optimal targeted, but time-course-dependent, treatments requires substantial further investigations. However, the techniques currently used to induce mechanical injury vary considerably in terms of invasiveness, tools used to induce injury, muscle group selected for injury and contractile status of the muscle, all of which have an influence on the immune and/or cytokine responses. This makes interpretation of the complex responses more difficult. After our review of the literature, we propose that a standardized non-invasive contusion injury is the ideal model for investigations into the immune responses to mechanical skeletal muscle injury. Despite its suitability as a model, the currently available literature with respect to the inflammatory response to injury using contusion models is largely inadequate.Therefore, it may be premature to investigate highly targeted therapies, which may ultimately prove more effective in decreasing athlete recovery time than current therapies that are either not phase-specific, or not administered in a phase-specific fashion.

Evaluation of a Nisin-Eluting Nanofiber Scaffold To Treat Staphylococcus aureus-Induced Skin Infections in Mice

ABSTRACT Staphylococcus aureus is a virulent pathogen and a major causative agent of superficial and invasive skin and soft tissue infections (SSSTIs). Antibiotic resistance in S. aureus, among other bacterial pathogens, has rapidly increased, and this is placing an enormous burden on the health care sector and has serious implications for infected individuals, especially immunocompromised patients. Alternative treatments thus need to be explored to continue to successfully treat infections caused by S. aureus, including antibiotic-resistant strains of S. aureus. In this study, an antimicrobial nanofiber wound dressing was generated by electrospinning nisin (Nisaplin) into poly(ethylene oxide) and poly(d,l-lactide) (50:50) blend nanofibers. Active nisin diffused from the nanofiber wound dressings for at least 4 days in vitro, as shown by consecutive transfers onto plates seeded with strains of methicillin-resistant S. aureus (MRSA). The nisin-containing nanofiber wound dressings significantly reduced S. aureus Xen 36 bioluminescence in vivo and viable cell numbers in a murine excisional skin infection model. The bacterial burden of wounds treated with nisin-containing nanofiber wound dressings was 4.3 × 102 CFU/wound, whereas wounds treated with control nanofiber wound dressings had 2.2 × 107 CFU/wound on the last day of the trial (day 7). Furthermore, the wound dressings stimulated wound closure of excisional wounds, and no adverse effects were observed by histological analysis. Nisin-containing nanofiber wound dressings have the potential to treat S. aureus skin infections and to potentially accelerate wound healing of excisional wounds.

The effect of Sutherlandia frutescens on steroidogenesis: confirming indigenous wisdom.

Sutherlandia frutescens (Cancer bush), a Southern African indigenous plant, is traditionally used to treat stress related maladies linked to the endocrine system. Extracts of the shrub were used to investigate the claimed stress‐relieving properties of the shrub. Dysregulation of the stress response is associated with elevated glucocorticoid levels. A model of chronic intermittent immobilization stress was investigated in 40 adult male Wistar rats to determine the effect of Sutherlandia. Immobilization stress resulted in increased corticosterone levels in the control group while rats receiving Sutherlandia extract showed significantly decreased corticosterone levels (P < 0.005). Since the biosynthesis of glucocorticoids in the adrenals is catalyzed by the cytochrome P450‐dependent enzymes, the influence of Sutherlandia extracts on adrenal steroidogenesis was determined in ovine adrenocortical microsomes and mitochondria, using spectral binding and enzyme conversion assays. Water extracts showed inhibition of substrate binding to cytochrome P450 21‐hydroxylase (CYP21) by 38% and cytochrome P450 11β‐hydroxylase (CYP11B1) by 60%. The conversion of progesterone and pregnenolone was inhibited by 34% and 30%, respectively. Subsequent extractions with chloroform and methanol showed inhibition of substrate binding and conversion with hydrophobic compounds exhibiting a greater inhibitory effect on deoxycorticosterone binding to CYP11B1 (30%) and on progesterone binding to CYP21 (50%). The inhibition of binding of pregnenolone to CYP17 by the chloroform extract was 62%, with negligible inhibition by the methanol extract. The chloroform extract showed a greater inhibitory effect than the methanol extract on progesterone and pregnenolone metabolism (20%–50%).

Accelerated skeletal muscle recovery after in vivo polyphenol administration.

Acute skeletal muscle damage results in fiber disruption, oxidative stress and inflammation. We investigated cell-specific contributions to the regeneration process after contusion-induced damage (rat gastrocnemius muscle) with or without chronic grape seed-derived proanthocyanidolic oligomer (PCO) administration. In this placebo-controlled study, male Wistar rats were subjected to PCO administration for 2 weeks, after which they were subjected to a standardised contusion injury. Supplementation was continued after injury. Immune and satellite cell responses were assessed, as well as oxygen radical absorption capacity and muscle regeneration. PCO administration resulted in a rapid satellite cell response with an earlier peak in activation (Pax7⁺, CD56⁺, at 4 h post-contusion) vs. placebo groups (PLA) (P<.001: CD56⁺ on Day 5 and Pax7⁺ on Day 7). Specific immune-cell responses in PLA followed expected time courses (neutrophil elevation on Day 1; sustained macrophage elevation from Days 3 to 5). PCO dramatically decreased neutrophil elevation to nonsignificant, while macrophage responses were normal in extent, but significantly earlier (peak between Days 1 and 3) and completely resolved by Day 5. Anti-inflammatory cytokine, IL-10, increased significantly only in PCO (Day 3). Muscle fiber regeneration (MHC(f) content and central nuclei) started earlier and was complete by Day 14 in PCO, but not in PLA. Thus, responses by three crucial cell types involved in muscle recovery were affected by in vivo administration of a specific purified polyphenol in magnitude (neutrophil), time course (macrophages), or time course and activation state (satellite cell), explaining faster effective regeneration in the presence of proanthocyanidolic oligomers.

Endocrine and immune effects of dexamethasone in unilateral total knee replacement

The effect of acute pre-surgery dexamethasone treatment on the inflammatory immune and endocrine responses to orthopaedic surgery was investigated. Whole blood samples were obtained before and 5 days after surgery for immune analysis, and serum was obtained before and 6 h, 3 days and 5 days after surgery for endocrine assessment. Dexamethasone did not affect the post-surgery granulocyte response, but inhibited the increase in monocyte count (an average increase of 38.5% was seen in the control group). Peak C-reactive protein concentration (3 days after surgery) was 51.4% lower in the dexamethasone group than in the control group. Dexamethasone had a major effect on cortisol concentrations and the cortisol:testosterone and cortisol: dehydroepiandrosterone ratios, but no effect on anabolic hormone concentrations. In conclusion, acute pre-surgery dexamethasone treatment may have beneficial effects in the post-surgery period, by limiting the extent of systemic inflammation and the cortisol response.

Ageing-Associated Oxidative Stress and Inflammation Are Alleviated by Products from Grapes

Advanced age is associated with increased incidence of a variety of chronic disease states which share oxidative stress and inflammation as causative role players. Furthermore, data point to a role for both cumulative oxidative stress and low grade inflammation in the normal ageing process, independently of disease. Therefore, arguably the best route with which to address premature ageing, as well as age-associated diseases such as diabetes, cardiovascular disease, and dementia, is preventative medicine aimed at modulation of these two responses, which are intricately interlinked. In this review, we provide a detailed account of the literature on the communication of these systems in the context of ageing, but with inclusion of relevant data obtained in other models. In doing so, we attempted to more clearly elucidate or identify the most probable cellular or molecular targets for preventative intervention. In addition, given the absence of a clear pharmaceutical solution in this context, together with the ever-increasing consumer bias for natural medicine, we provide an overview of the literature on grape (Vitis vinifera) derived products, for which beneficial effects are consistently reported in the context of both oxidative stress and inflammation.

Postcontusion polyphenol treatment alters inflammation and muscle regeneration.

PURPOSE Given the major role that oxidants play in cellular damage, and the recent focus on antioxidants as treatment for muscle injuries, the aim of this study was to examine the effect of short-term postinjury grape seed-derived polyphenol supplementation on muscle inflammation and repair processes after contusion injury. METHODS Experimental injury of the right gastrocnemius muscle was achieved by drop-mass method (200 g from a height of 50 cm), after which rats were gavaged with either 0.9% saline (placebo-PLA) or 20 mg·kg⁻¹·d⁻¹ of proanthocyanidolic oligomer (PCO) from 2 h after contusion injury, for up to 14 d after injury. Blood samples and injured muscle were collected at 4 h and at days 1, 3, 5, 7, and 14 after injury. RESULTS Compared to an uninjured control group, PCO supplementation resulted in an earlier peak in number of activated satellite cells in contusion-injured muscle tissue (4 h for PCO vs day 3 for PLA, n = 4 per time point per group) and fetal myosin heavy chain expression (day 5 for PCO, P < 0.01 with no change in PLA, n = 3 per time point per group), indicative of quicker muscle regeneration. PCO supplementation limited neutrophil infiltration and facilitated earlier macrophage infiltration into the injured area (n = 4 per group). PCO also resulted in an earlier return toward control levels of muscle proinflammatory cytokines on day 3 (P < 0.01 for interleukin 6 and P < 0 05 for tumor necrosis factor α, both n = 3 per group). CONCLUSIONS Data show that short-term postinjury PCO supplementation was able to quicken muscle regeneration by facilitating earlier recruitment of activated satellite cells and to modulate the immune system in favor of an anti-inflammatory status.

Daily brief restraint stress alters signaling pathways and induces atrophy and apoptosis in rat skeletal muscle

Skeletal muscle protein loss, known as atrophy, occurs during inactivity, disease, and aging. Atrophy may be the result of increased catabolic factors, e.g. glucocorticoids, or reduced influence of anabolic factors, e.g. insulin. The purpose of this study was to investigate atrophy, signaling mechanisms, and apoptosis in a rat model of restraint stress in 40 adult male Wistar rats. Due to the anxiolytic effects of Sutherlandia frutescens, we also determined if any of the molecular events in gastrocnemius muscle would be affected by daily treatment with S. frutescens. Rats were randomly assigned to four experimental groups: control placebo (CP); control Sutherlandia (CS) treatment; Restraint Placebo (RP) and Restraint Sutherlandia (RS) treatment. Restraint resulted in a significant increase in myostatin which was significantly reduced with Sutherlandia treatment. In addition, MyoD expression was significantly attenuated in RP and this effect was also counteracted by Sutherlandia treatment. Restraint also resulted in a significant attenuation of the PI3-Kinase/Akt signaling pathway and increased apoptosis which was reversed with Sutherlandia treatment. This study demonstrates for the first time that psychological stress elevates markers of muscle atrophy and apoptosis, whilst a herbal remedy, Sutherlandia, inhibits apoptosis, and signaling pathways associated with muscle atrophy.

Contusion Injury with Chronic In vivo Polyphenol Supplementation: Leukocyte Responses

INTRODUCTION In vivo, daily proanthocyanidolic oligomer (PCO) supplementation before and after experimental skeletal muscle contusion injury has been shown to result in a blunted neutrophil response in tissue, quicker macrophage infiltration into muscle, and faster recovery due to a left shift in time course of inflammation. The current study investigated effects of PCO on circulatory neutrophils and macrophage subpopulations as well as in vitro neutrophil migration. METHODS Primary cultured neutrophils obtained from control animals were incubated in media with 20% conditioned plasma. To obtain conditioned media, male Wistar rats were supplemented with PCO (20 mg·kg(-1)d(-1)) or placebo (PLA) for 2 wk before a mass-drop contusion injury. Conditioned plasma was prepared from blood collected at different time points after injury (12 h, 1 d, 3 d, and 5 d). Macrophage subpopulation distribution, inflammatory cytokine, and myeloperoxidase levels were assessed for all time points. RESULTS On day 1 postinjury, circulating neutrophil numbers were significantly lower in PLA than PCO, suggesting that extravasation from the blood was reduced by PCO. Concurrently, neutrophil migration in vitro was blunted in the presence of conditioned plasma from PCO supplemented rats compared with PLA supplemented rats. Plasma M1 and M2c macrophage numbers differed over time and between groups. M1 macrophage numbers peaked on day 3 with PCO supplementation, followed by a rise in M2c macrophages on day 5, when M1 macrophages numbers were still high in PLA. CONCLUSIONS We conclude that PCO supplementation limits neutrophil migration capacity in vitro despite a chemotactic gradient. Furthermore, the earlier appearance of type M2 macrophages suggests a switch to an anti-inflammatory phenotype after injury even in circulation.

Interplay of the Inflammatory and Stress Systems in a Hepatic Cell Line: Interactions between Glucocorticoid Receptor Agonists and Interleukin-6

The liver plays an important role in inflammation and stress by producing the acute phase proteins (APPs) required for resolution of inflammation as well as by delivering systemic glucose, through gluconeogenesis, required to fuel the stress response. Disruption of the interplay between interleukin 6 (IL-6) and glucocorticoids (GCs), the peripheral mediators of inflammation and stress, respectively, may lead to side-effects associated with the pharmacological use of GCs. The current study investigated the interplay between IL-6 and GCs in a hepatoma cell line (BWTG3) at protein (protein activity assays, Western blotting, and ELISA) and mRNA (qPCR) levels. Specifically, the action of dexamethasone (Dex), a known antiinflammatory drug and glucocorticoid receptor (GR) agonist, is compared to that of Compound A (CpdA), a selective glucocorticoid receptor agonist (SEGRA). CpdA, like IL-6, but unlike Dex, increases GR binding and decreases the metabolic enzymes, tyrosine aminotransferase, phosphoenolpyruvate carboxykinase, and gamma glutamyltransferase, at protein or mRNA level. Like Dex, both CpdA and IL-6 increase the positive APPs, serum amyloid A and C-reactive protein, and decrease the negative APP, corticosteroid binding globulin. The study shows that the GC, Dex, and IL-6 generally have divergent effects on the GR and metabolic enzymes, while their functions are convergent on the APPs. In contrast to Dex, CpdA has effects convergent to that of IL-6 on the GR, metabolic enzymes, and APPs. Thus these findings suggest that CpdA, like Dex, modulates APPs, leading to effective control of inflammation, while, in contrast to Dex, it is less likely to lead to GC-induced side-effects.