Endotoxin stimulates in vivo expression of inflammatory cytokines tumor necrosis factor alpha, interleukin-1beta, -6, and high-mobility-group protein-1 in skeletal muscle

Unilateral hindlimb ischaemia-induced systemic inflammation is associated with non-ischaemic skeletal muscle inflammation

Skeletal muscle atrophy and dysfunction commonly accompany cardiovascular diseases such as peripheral arterial disease and may be partially attributable to systemic inflammation. We sought to determine whether acute systemic inflammation in a model of hindlimb ischaemia (HLI) could affect skeletal muscle macrophage infiltration, fibre size, or capillarization, independent of the ischaemia. Eight-week-old C57BL/6 male mice underwent either Sham or HLI surgery, and were killed 1, 3, or 7 days post-surgery. Circulating inflammatory cytokine concentrations were measured, as well as immune cell infiltration and morphology of skeletal muscle from both limbs of HLI and Sham mice. In HLI compared with Sham mice at day 1, plasma interleukin-1β levels were 216% higher (0.48 ± 0.10 vs. 0.15 ± 0.01 pg/μL, P = 0.005) and decreased by day 3. This was followed by increased macrophage presence in muscle from both ischaemic and non-ischaemic limbs of HLI mice by day 7 (7.3- and 2.3-fold greater than Sham, respectively, P < 0.0001). In HLI mice, muscle from the ischaemic limb had 21% lower fibre cross-sectional area than the non-ischaemic limb (724 ± 28 vs. 916 ± 46 μm2, P = 0.01), but the non-ischaemic limb of HLI mice was no different from Sham. This shows that HLI induces acute systemic inflammation accompanied by immune infiltration in both ischaemic and remote skeletal muscle; however, this did not induce skeletal muscle atrophy in remote muscle within the 7-day time course of this study. This effect of local skeletal muscle ischaemia on the inflammatory status of remote skeletal muscle may signal a priming of muscle for subsequent atrophy over a longer time course. HIGHLIGHTS: What is the central question of this study? Does hindlimb ischaemia-induced inflammation cause acute immune, inflammatory and morphological alterations in remote non-ischaemic skeletal muscle? What is the main finding and its importance? Hindlimb ischaemia induced systemic inflammation with subsequent neutrophil and macrophage infiltration in both ischaemic and non-ischaemic skeletal muscle; however, morphological changes did not occur in non-ischaemic muscle within 7 days. These immune alterations may have functional implications that take longer than 7 days to manifest, and subsequent or prolonged systemic inflammation and immune infiltration of muscle could lead to morphological changes and functional decline.

Frontiers in sarcopenia: Advancements in diagnostics, molecular mechanisms, and therapeutic strategies

The onset of sarcopenia is intimately linked with aging, posing significant implications not only for individual patient quality of life but also for the broader societal healthcare framework. Early and accurate identification of sarcopenia and a comprehensive understanding of its mechanistic underpinnings and therapeutic targets paramount to addressing this condition effectively. This review endeavors to present a cohesive overview of recent advancements in sarcopenia research and diagnosis. We initially delve into the contemporary diagnostic criteria, specifically referencing the European Working Group on Sarcopenia in Older People (EWGSOP) 2 and Asian Working Group on Sarcopenia (AWGS) 2019 benchmarks. Additionally, we elucidate comprehensive assessment techniques for muscle strength, quantity, and physical performance, highlighting tools such as grip strength, chair stand test, dual-energy X-ray Absorptiometry (DEXA), bioelectrical impedance analysis (BIA), gait speed, and short physical performance battery (SPPB), while also discussing their inherent advantages and limitations. Such diagnostic advancements pave the way for early identification and unequivocal diagnosis of sarcopenia. Proceeding further, we provide a deep-dive into sarcopenia's pathogenesis, offering a thorough examination of associated signaling pathways like the Myostatin, AMP-activated protein kinase (AMPK), insulin/IGF-1 Signaling (IIS), and the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathways. Each pathway's role in sarcopenia mediation is detailed, underscoring potential therapeutic target avenues. From a mechanistic perspective, the review also underscores the pivotal role of mitochondrial dysfunction in sarcopenia, emphasizing elements such as mitochondrial oxidative overload, mitochondrial biogenesis, and mitophagy, and highlighting their therapeutic significance. At last, we capture recent strides made in sarcopenia treatment, ranging from nutritional and exercise interventions to potential pharmacological and supplementation strategies. In sum, this review meticulously synthesizes the latest scientific developments in sarcopenia, aiming to enhance diagnostic precision in clinical practice and provide comprehensive insights into refined mechanistic targets and innovative therapeutic interventions, ultimately contributing to optimized patient care and advancements in the field.

Ursolic acid alleviates cancer cachexia by inhibiting STAT3 signaling pathways in C2C12 myotube and CT26 tumor-bearing mouse model

Cancer cachexia, a multi-organ disorder resulting from tumor and immune system interactions, prominently features muscle wasting and affects the survival of patients with cancer. Ursolic acid (UA) is known for its antioxidant, anti-inflammatory, and anticancer properties. However, its impact on cancer cachexia remains unexplored. This study aimed to assess the efficacy of UA in addressing muscle atrophy and organ dysfunction in cancer cachexia and reveal the mechanisms involved. UA dose-dependently ameliorated C2C12 myotube atrophy. Mechanistically, it inhibited the expression of muscle-specific RING finger containing protein 1 (MURF1) and the phosphorylation of signal transducer and activator of transcription 3 (STAT3), and upregulated the mRNA or protein levels of myogenic differentiation antigen and myogenin in cultured C2C12 myotubes treated with conditioned medium. In vivo, UA protected CT26 tumor-bearing mice against loss of body weight, as well as increased skeletal muscle and epididymal fat without affecting tumor growth. Additionally, UA increased food intake in CT26 tumor-bearing mice. The mRNA expression of tumor necrosis-α and interleukin 6 was significantly downregulated in the intestine, gastrocnemius, and heart tissues following 38 d UA administration. UA treatment reversed the levels of myocardial function indicators, including creatine kinase, creatine kinase-MB, lactate dehydrogenase, car-dial troponin T, and glutathione. Finally, UA treatment significantly inhibited the expression of MURF1, the phosphorylation of nuclear factor kappa-B p65, and STAT3 in the gastrocnemius muscle and heart tissues of cachexic mice. Our findings suggest that UA is a promising natural compound for developing dietary supplements for cancer cachexia therapy owing to its anti-catabolic effects.

Nanoparticles and Their Applications in Lipid Signaling

This chapter provides an overview of the diverse range of applications associated with nanoparticles. The application of nanoparticles in the medical field has garnered considerable attention due to their unique properties and versatile compositions. They have shown promise in the treatment of cancer, fungal and viral infections, and pain management. These systems provide numerous benefits, such as increased drug stability, improved bioavailability, and targeted delivery to specific tissues or cells. The objective of this chapter is to provide a brief analysis of the differences between nanoparticles and lipid particles, focusing particularly on the importance of nanoparticle size and composition in their interactions with lipids. Additionally, the applications of nanoparticles in lipid signaling will be discussed, considering the vital roles lipids play in cellular signaling pathways. Nanoparticles have shown immense potential in the regulation and control of medical pathways. In this case, we will focus on the manufacture of liposomes, a type of nanoparticle composed of lipids. The reason behind the extensive investigation into liposomes as drug delivery vehicles is their remarkable biocompatibility and adaptability. This section will provide insights into the methods and techniques employed for liposome formulation.

The immunomodulatory effect of minocycline on gene expression of inflammation related cytokines in lipopolysaccharide-treated human peripheral blood mononuclear cells

To evaluate the immunomodulatory effect of minocycline, the present study was carried out on the gene expression of toll-like receptor type-4 (TLR4) and some pro-inflammatory (IL-1β, IL-6) and anti-inflammatory cytokines (IL-10) associated with lipopolysaccharide (LPS) -induced inflammation in human peripheral blood mononuclear cells (PBMCs). The PBMCs were collected and then 5.4 × 106 PBMCs/mL were used in eight groups as follows: control group (only media), LPS group (only LPS), methylprednisolone (Pred) group (LPS plus Pred), meloxicam (Melo) group (LPS plus Melo), three minocycline groups [M1, M5 and M25] (LPS plus 1, 5, and 25 µg/mL minocycline, respectively) and minocycline control (MC) group (5 µg/mL minocycline). After incubation for 24 h, the PBMCs were subjected to quantitative PCR assays. Gene expression levels of TLR4 were not changed in any groups. The IL-1β levels were increased in the LPS group but the increases were much more intense in the other groups except Pred group. Compared with control group, IL-6 levels increased significantly in Melo, M1 and M25 groups. Significant increases of IL-10 levels were also observed in Melo, M25 and MC groups. It can be concluded that minocycline had dual pro- and anti-inflammatory activities with potential clinical immunomodulatory effects.

Anti-Inflammatory and Therapeutic Effects of a Novel Small-Molecule Inhibitor of Inflammation in a Male C57BL/6J Mouse Model of Obesity-Induced NAFLD/MAFLD

Purpose

Non-alcoholic fatty liver disease (NAFLD), recently renamed metabolic (dysfunction) associated fatty liver disease (MAFLD), is the most common chronic liver disease in the United States. Presently, there is an intense and ongoing effort to identify and develop novel therapeutics for this disease. In this study, we explored the anti-inflammatory activity of a new compound, termed IOI-214, and its therapeutic potential to ameliorate NAFLD/MAFLD in male C57BL/6J mice fed a high fat (HF) diet.

Methods

Murine macrophages and hepatocytes in culture were treated with lipopolysaccharide (LPS) ± IOI-214 or DMSO (vehicle), and RT-qPCR analyses of inflammatory cytokine gene expression were used to assess IOI-214's anti-inflammatory properties in vitro. Male C57BL/6J mice were also placed on a HF diet and treated once daily with IOI-214 or DMSO for 16 weeks. Tissues were collected and analyzed to determine the effects of IOI-214 on HF diet-induced NAFL D/MAFLD. Measurements such as weight, blood glucose, serum cholesterol, liver/serum triglyceride, insulin, and glucose tolerance tests, ELISAs, metabolomics, Western blots, histology, gut microbiome, and serum LPS binding protein analyses were conducted.

Results

IOI-214 inhibited LPS-induced inflammation in macrophages and hepatocytes in culture and abrogated HF diet-induced mesenteric fat accumulation, hepatic inflammation and steatosis/hepatocellular ballooning, as well as fasting hyperglycemia without affecting insulin resistance or fasting insulin, cholesterol or TG levels despite overall obesity in vivo in male C57BL/6J mice. IOI-214 also decreased systemic inflammation in vivo and improved gut microbiota dysbiosis and leaky gut.

Conclusion

Combined, these data indicate that IOI-214 works at multiple levels in parallel to inhibit the inflammation that drives HF diet-induced NAFLD/MAFLD, suggesting that it may have therapeutic potential for NAFLD/MAFLD.

Altered Osteogenic Differentiation in Mesenchymal Stem Cells Isolated from Compact Bone of Chicken Treated with Varying Doses of Lipopolysaccharides

Persistent inflammation biologically alters signaling molecules and ultimately affects osteogenic differentiation, including in modern-day broilers with unique physiology. Lipopolysaccharides (LPS) are Gram-negative bacterial components that activate cells via transmembrane receptor activation and other molecules. Previous studies have shown several pathways associated with osteogenic inductive ability, but the pathway has yet to be deciphered, and data related to its dose-dependent effect are limited. Primary mesenchymal stem cells (MSCs) were isolated from the bones of day-old broiler chickens, and the current study focused on the dose-dependent variation (3.125 micrograms/mL to 50 micrograms/mL) in osteogenic differentiation and the associated biomarkers in primary MSCs. The doses in this study were determined using a cell viability (MTT) assay. The study revealed that osteogenic differentiation varied with dose, and the cells exposed to higher doses of LPS were viable but lacked differentiating ability. However, this effect became transient with lower doses, and this phenotypic character was observed with differential staining methods like Alizarin Red, Von Kossa, and alkaline phosphatase. The data from this study revealed that LPS at varying doses had a varying effect on osteogenic differentiation via several pathways acting simultaneously during bone development.

Soleus muscle contains a higher concentration of lipid metabolites than extensor digitorum longus in rats with lipopolysaccharide-induced acute muscle atrophy

BACKGROUND & AIMS

Muscle atrophy is one of the most important and frequent problems for critically ill patients. The purpose of this study was to evaluate the effect of lipid mediators on acute muscle atrophy. Skeletal muscle fiber-specific analysis of lipid mediators in endotoxemic rats was therefore performed.

METHODS

Male Wistar rats were intraperitoneally injected with lipopolysaccharide (LPS). Slow-twitch soleus muscle and fast-twitch extensor digitorum longus (EDL) muscle were harvested 0, 6, and 24 h after LPS injection. Lipid mediators were profiled using liquid chromatography-tandem mass spectrometry, and free fatty acid (FFA) concentrations were measured using gas chromatography-mass spectrometry. Muscles were weighed and their cross-sectional areas were evaluated. Expression levels of mRNAs encoding inflammatory cytokines, autophagy-related transcription factors, and members of the ubiquitin-proteasome system were measured using real-time PCR.

RESULTS

Before LPS injection, the concentrations of all FFAs, including arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid, and all measured lipid mediators were higher in soleus muscle than in EDL muscle, especially those of pro-inflammatory prostaglandin E2 (PGE2) and leukotriene B4. LPS injection, increased PGE2 and D2 and decreased FFAs in soleus muscle but did not change in EDL muscle. The concentrations of specialized pro-resolving mediators E-series hydroxy-eicosapentaenoic acid and D-series hydroxy-docosahexaenoic acid were higher in soleus muscle. Muscle cross-sectional area decreased and the expression level of atrogin-1 was upregulated in EDL muscle, but both were unchanged in soleus muscle. After LPS injection, a discrepancy involving an increased PGE2 concentration and decreased muscle atrophy was identified in this acute muscle atrophy model of critical illness.

CONCLUSION

Concentrations of FFAs and lipid mediators were higher in soleus muscle than in EDL muscle, and LPS injection rapidly increased concentrations of pro-inflammatory lipid mediators. However, muscle atrophy with upregulation of autophagy-related transcription factors was observed in EDL muscle but not in soleus muscle.

Experimental study of dexamethasone-loaded hollow hydroxyapatite microspheres applied to direct pulp capping of rat molars

Background

Dexamethasone (DEX) exerts anti-inflammatory and osteogenic effects. Hydroxyapatite is commonly used in bone repair due to its osteoconductivity, osseointegration, and osteogenesis induction. Hollow hydroxyapatite (HHAM) is often used as a drug carrier.

Objective

This study aimed to investigate the histological responses of exposed dental pulp when dexamethasone-loaded nanohydroxyapatite microspheres (DHHAM) were used as a direct capping agent.

Methods

Cavities were created in the left maxillary first molar of Wistar rats and filled with Dycal, HHAM, and DHHAM. No drug was administered to the control group. The rats were sacrificed at 1, 2, and 4 weeks after the procedure. The molars were extracted for fixation, demineralization, dehydration, embedding, and sectioning. H&E staining was performed to detect the formation of reparative dentin. H&E and CD45 immunohistochemical staining were performed to detect pulp inflammation. Immunohistochemical staining was performed to assess the expressions of dentin matrix protein 1 (DMP-1), interleukin (IL)-6, tumor necrosis factor (TNF)-α, and IL-1β.

Results

The results of H&E and CD45 immunohistochemical staining showed that the degree of inflammation in the DHHAM group was less than that in the Control and HHAM groups at 1, 2, and 4 weeks after capping of the rat molar teeth (p<0.01). The H&E staining showed that the percentage of reparative dentin formed in the DHHAM group was higher than that in the Control, HHAM (p<0.001), and Dycal groups (p<0.01) at 1 and 2 weeks, and was significantly higher than that in the Control group (p<0.001) and the HHAM group (p<0.01) at 4 weeks. The immunohistochemical staining showed a lower range and intensity of expression of IL-1β, IL-6, and TNF-α and high expression levels of DMP-1 in the DHHAM group at 1, 2, and 4 weeks after pulp capping relative to the Control group.

Conclusions

DHHAM significantly inhibited the progression of inflammation and promoted reparative dentin formation.

Mechanism of immune attack in the progression of obesity-related type 2 diabetes

Obesity and overweight are widespread issues in adults, children, and adolescents globally, and have caused a noticeable rise in obesity-related complications such as type 2 diabetes mellitus (T2DM). Chronic low-grade inflammation is an important promotor of the pathogenesis of obesity-related T2DM. This proinflammatory activation occurs in multiple organs and tissues. Immune cell-mediated systemic attack is considered to contribute strongly to impaired insulin secretion, insulin resistance, and other metabolic disorders. This review focused on highlighting recent advances and underlying mechanisms of immune cell infiltration and inflammatory responses in the gut, islet, and insulin-targeting organs (adipose tissue, liver, skeletal muscle) in obesity-related T2DM. There is current evidence that both the innate and adaptive immune systems contribute to the development of obesity and T2DM.

The anti-inflammatory effects of minocycline on lipopolysaccharide-induced paw oedema in rats: a histopathological and molecular study

Minocycline is a semi-synthetic antimicrobial agent with claimed anti-inflammatory properties reported from different experimental models. This study was aimed to evaluate the anti-inflammatory effects of minocycline, compared to the actions of two common anti-inflammatory agents, on lipopolysaccharide (LPS)-induced paw oedema through some clinical, histopathological, haematological and molecular analyses. Forty-eight rats were divided into eight groups (n = 6). In control group (Ctrl), each animal was injected with normal saline into its sub-plantar region of hind paw. In groups 2-7, hind paw oedema was induced by injection of LPS. One hour before injections, groups 1 (Ctrl) and 2 (LPS) were treated orally with distilled water, 3 and 4 with methylprednisolone (Pred) and meloxicam (Melo) and 5-7 with minocycline in doses of 50, 150 and 450 mg/kg (M50, M150 and M450, respectively). The 8th group (MC) was given minocycline (150 mg/kg) orally and normal saline was injected into sub-plantar region. Paw swelling and body temperature were assessed at 0, 2, 4, 6 and 24 h post-injections. At 24 h, samples of blood and liver, kidney, spleen and hind paw tissues were taken for haematological and histopathological examinations. Some samples of the paw were also obtained for molecular analysis of some inflammatory-related cytokines at mRNA level. Paw swelling and body temperature increased in all LPS-injected groups 2 h post-injection. In LPS group, they remained significantly increased up to 24 h; however, these parameters decreased to normal in Pred, Melo and all minocycline groups. The histological findings showed mild-to-moderate signs of inflammation in tissue samples of groups 2-6, but not in group M450. Additionally, gene expression of pro-inflammatory cytokines (IL-1β and IL-6) increased significantly in LPS group compared to other groups. In conclusion, this study supports the role of minocycline as an anti-inflammatory agent with effects comparable to those of meloxicam and methylprednisolone.

IMPORTANCE OF THE INNATE IMMUNE RESPONSE IN SKELETAL MUSCLE TO SEPSIS-INDUCED ALTERATIONS IN PROTEIN BALANCE

ABSTRACT

There is growing appreciation that skeletal muscle is a fully functional component of the body's innate immune system with the potential to actively participate in the host response to invading bacteria as opposed to being a passive target. In this regard, skeletal muscle in general and myocytes specifically possess an afferent limb that recognizes a wide variety of host pathogens via their interaction with multiple classes of cell membrane-bound and intracellular receptors, including toll-like receptors, cytokine receptors, NOD-like receptors, and the NLRP inflammasome. The efferent limb of the innate immune system in muscle is equally robust and with an increased synthesis and secretion of a variety of myocyte-derived cytokines (i.e., myokines), including TNF-α, IL-1, IL-6, and NO as well as multiple chemokines in response to appropriate stimulation. Herein, the current narrative review focuses primarily on the immune response of myocytes per se as opposed to other cell types within whole muscle. Moreover, because there are important differences, this review focuses specifically on systemic infection and inflammation as opposed to the response of muscle to direct injury and various types of muscular dystrophies. To date, however, there are few definitive muscle-specific studies that are necessary to directly address the relative importance of muscle-derived immune activation as a contributor to either the systemic immune response or the local immune microenvironment within muscle during sepsis and the resultant downstream metabolic disturbances.

Moringa isothiocyanate-1 inhibits LPS-induced inflammation in mouse myoblasts and skeletal muscle

This study aims to investigate the anti-inflammatory effects of moringa isothiocyanate-1 (MIC-1) extracted from seeds of Moringa oleifera Lam. in lipopolysaccharide (LPS)-induced inflammation models. MIC-1 decreased nitric oxide production and reduced the expression of pro-inflammatory markers (TNF-α, Ifn-α, IL-1β, IL-6) in C2C12 myoblasts. The daily oral treatment of MIC-1 (80 mg/kg) for three days significantly reduced the expression of pro-inflammatory markers in gastrocnemius muscle tissue of LPS-treated C57BL/6 male mice. Transcriptomic analysis provided further insights into the inhibitory effects of MIC-1 on the LPS-induced inflammation, which suggested that MIC-1 affects inflammation and immunity-related genes in myoblasts and skeletal muscle tissue. MIC-1 inhibited the nuclear accumulation of the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) in the LPS-treated myoblasts. Our data support the hypothesis that the MIC-1's effects in the muscle cells are mediated through the inhibition of the NF-κB translocation in the nucleus, which, in turn, results in immunomodulating and anti-inflammatory responses at the gene expression levels.

Metastatic or xenograft colorectal cancer models induce divergent anabolic deficits and expression of pro-inflammatory effectors of muscle wasting in a tumor-type-dependent manner

We investigated the impact of tumor burden on muscle wasting in metastatic (m) and xenograft (x) models of colorectal cancer (CRC). Male Nod SCID γ and CD2F1 mice were injected subcutaneously or intrasplenically with HCT116 or C26 tumor cells, respectively. CRC tumors resulted in significant muscle wasting regardless of tumor type or model, although muscle loss was exacerbated in mHCT116 hosts. The mHCT116 model decreased ribosomal (r)RNA content and rDNA transcription, whereas the mC26 model showed no loss of rRNA and the upregulation of rDNA transcription. The xHCT116 model reduced mTOR, RPS6, and 4E-BP1 phosphorylation, whereas the mHCT116 model had a similar effect on RPS6 and 4E-BP1 without altering mTOR phosphorylation. The C26 models caused a reduction in 4E-BP1 phosphorylation independent of mTOR. Muscle interleukin (IL)-6 mRNA was elevated in all models except xHCT116, and the NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) mRNA was induced only in the mC26 model. IL-1β mRNA increased in all groups with greater expression in metastatic relative to the xenograft model regardless of tumor types. Our findings indicate that HCT116 tumor burden results in more drastic muscle wasting and anabolic deficits, whereas C26 tumor burden causes similar muscle wasting but exhibits a divergent proinflammatory phenotype. These results highlight potentially important divergence in the pathogenesis of muscle wasting among preclinical models of CRC and demonstrate that tumor burden plays a role in determining anabolic deficits and the expression of proinflammatory effectors of muscle wasting in a tumor-type-dependent manner.NEW & NOTEWORTHY We provide evidence demonstrating that colorectal tumor burden plays a role in determining anabolic deficits and the expression of proinflammatory effectors of muscle wasting in a tumor-type-dependent manner.

Chromatin-Associated Molecular Patterns (CAMPs) in sepsis

Several molecular patterns have been identified that recognize pattern recognition receptors. Pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) are commonly used terminologies to classify molecules originating from pathogen and endogenous molecules, respectively, to heighten the immune response in sepsis. Herein, we focus on a subgroup of endogenous molecules that may be detected as foreign and similarly trigger immune signaling pathways. These chromatin-associated molecules, i.e., chromatin containing nuclear DNA and histones, extracellular RNA, mitochondrial DNA, telomeric repeat-containing RNA, DNA- or RNA-binding proteins, and extracellular traps, may be newly classified as chromatin-associated molecular patterns (CAMPs). Herein, we review the release of CAMPs from cells, their mechanism of action and downstream immune signaling pathways, and targeted therapeutic approaches to mitigate inflammation and tissue injury in inflammation and sepsis.

Inducible MicroRNA-132 Inhibits the Production of Inflammatory Cytokines by Targeting TRAF6, TAK1, and TAB1 in Teleost Fish

The innate immune response is the first line of defense against pathogen infection. Eradication of pathogen infection requires appropriate immune and inflammatory responses, but excessive inflammation may cause inflammatory and autoimmune diseases. MicroRNAs (miRNAs) are a group of small noncoding RNAs, and accumulating evidence has shown that in mammals, they can act as negative regulators that participate in the regulation of inflammation and immune responses. However, the miRNA-mediated immune regulation networks in the inflammatory responses of lower vertebrates are largely unknown. In this study, we report an miRNA, miR-132, identified from miiuy croaker, that acts as a negative regulator in the host's bacterium-induced inflammatory response. We found that miR-132 expression was dramatically increased upon infection by the Gram-negative bacterium Vibrio harveyi and lipopolysaccharide (LPS). Inducible miR-132 inhibits the production of inflammatory cytokines by targeting tumor necrosis factor receptor-associated factor 6 (TRAF6), transforming growth factor-activated protein kinase 1 (TAK1), and TAK1 binding protein 1 (TAB1), thus avoiding an excessive inflammatory response. Furthermore, we demonstrate that miR-132 modulates the inflammatory response through a TRAF6-, TAK1-, and TAB1-mediated NF-κB signaling pathway. These results collectively reveal that miR-132 plays a negative regulatory role in the host antibacterial immune response, which will help to gain insight into the intricate network of host resistance to pathogen infection in lower vertebrates.

Lipopolysaccharide-Induced Cytokine Secretion from In Vitro Mouse Slow and Fast Limb Muscle

ABSTRACT

Skeletal muscles play important roles in innate immunity. However, in vitro, their sensitivity to LPS is low. In other tissues, LPS sensing is facilitated by the presence of plasma, LPS binding protein (LBP), or soluble CD14 (sCD14). This study addressed whether these are critical for LPS sensitivity in skeletal muscle and whether LPS responsiveness is different between slow versus fast muscle. Soleus (SOL) or extensor digitorum longus (EDL) muscles from adult male C57bl/6 mice were mounted in 1 mL oxygenated baths containing: buffer only; buffer+1% mouse plasma; buffer+1 μg/mL LBP; or buffer+1% plasma from sCD14-/- mice. In each condition, muscles were exposed to LPS from 0 μg/mL to 1.0 μg/mL. Bath samples were collected at 0, 1, and 2 h, and analyzed using cytokine multiplex arrays. In both SOL and EDL the predominant responding cytokines/chemokines were KC(CXCL1), IL-6, and MCP-1(CCL2) and their average responses were amplified by ∼10-fold in the presence of 1% plasma. Overall, SOL and EDL exhibited similar secretory responses in the presence of 1% plasma, with a lower limit of sensitivity to LPS of 0.01 μg/mL. LBP supplementation did not augment secretion; however, 1% plasma from CD14-/- mice suppressed cytokine/chemokine secretion from EDL muscle. In conclusion, intact slow and fast mouse muscles have similar cytokine/chemokine responses to LPS but depend on the presence of low levels of plasma constituents. Though sCD14 plays some role in EDL muscle, neither sCD14 nor LBP can fully account for the strong effects of plasma on LPS sensitivity.

Exercise mitigates the Toll of muscle atrophy: A narrative review of the effects of exercise on Toll-like receptor-4 in leukocytes and skeletal muscle

Conditions characterized by muscle wasting such as cachexia and sarcopenia are devastating at the individual level, and they place a profound burden on public health. Evidence suggests that inflammation is likely a mechanistic contributor to the pathogenesis of these conditions. One specific molecule, lipopolysaccharide, has gained attention due to its role in initiating inflammation. Toll-like receptor-4 is the primary receptor for lipopolysaccharide and has been shown to be implicit in the downstream proinflammatory response associated with lipopolysaccharide. Importantly, Toll-like receptor-4 is expressed on various cell types throughout the human body such as leukocytes and skeletal muscle fibers and may have site-specific effects that contribute to muscle wasting conditions based on the location in which activation occurs. Accordingly, reducing proinflammatory signaling at these locations may be an effective strategy at mitigating muscle wasting. Regular exercise training is believed to elicit anti-inflammatory adaptations, but the mechanisms by which this occurs are yet to be fully understood. Understanding the mechanisms by which Toll-like receptor-4 activation contributes to muscle wasting and how exercise affects this, may allow for the development of a non-pharmacological therapeutic intervention. Therefore, in this review, we summarize the current understanding of the lipopolysaccharide/Toll-like receptor-4 axis in leukocytes and skeletal muscle fibers on the pathogenesis of muscle wasting conditions and we critically examine the current evidence regarding the effects of exercise on this axis.

[Preventive and Ameliorating Effects of Food Factors on Obesity-related Diseases by Regulating Inflammation]

Japan is currently a super-aging society, and lifestyle-related diseases that increase in incidence with age and the related rise in national medical expenses are major social problems. Preventive medicine and self-medication are becoming more important. Recently, various in vitro and in vivo studies have shown that food-derived natural compounds may contribute to the prevention and treatment of obesity-related diseases, such as diabetes mellitus. This report reviews our previous studies on the usefulness of the citrus flavonoid naringenin for obesity-related diseases. We showed that naringenin exerts an anti-diabetic effect by regulating inflammation pathways involving adipocytes and adipose tissue, and also showed an interaction between naringenin and anti-diabetic drugs. Because natural compounds are generally inexpensive and safe, they have the advantage of being easily applied to clinical applications. However, more detailed studies, such as clinical trials in humans, are required. Further research and scientific evidence will be required for the proper use of food factors in disease prevention and treatment.

Out of Control: The Role of the Ubiquitin Proteasome System in Skeletal Muscle during Inflammation

The majority of critically ill intensive care unit (ICU) patients with severe sepsis develop ICU-acquired weakness (ICUAW) characterized by loss of muscle mass, reduction in myofiber size and decreased muscle strength leading to persisting physical impairment. This phenotype results from a dysregulated protein homeostasis with increased protein degradation and decreased protein synthesis, eventually causing a decrease in muscle structural proteins. The ubiquitin proteasome system (UPS) is the predominant protein-degrading system in muscle that is activated during diverse muscle atrophy conditions, e.g., inflammation. The specificity of UPS-mediated protein degradation is assured by E3 ubiquitin ligases, such as atrogin-1 and MuRF1, which target structural and contractile proteins, proteins involved in energy metabolism and transcription factors for UPS-dependent degradation. Although the regulation of activity and function of E3 ubiquitin ligases in inflammation-induced muscle atrophy is well perceived, the contribution of the proteasome to muscle atrophy during inflammation is still elusive. During inflammation, a shift from standard- to immunoproteasome was described; however, to which extent this contributes to muscle wasting and whether this changes targeting of specific muscular proteins is not well described. This review summarizes the function of the main proinflammatory cytokines and acute phase response proteins and their signaling pathways in inflammation-induced muscle atrophy with a focus on UPS-mediated protein degradation in muscle during sepsis. The regulation and target-specificity of the main E3 ubiquitin ligases in muscle atrophy and their mode of action on myofibrillar proteins will be reported. The function of the standard- and immunoproteasome in inflammation-induced muscle atrophy will be described and the effects of proteasome-inhibitors as treatment strategies will be discussed.

Does the Interaction between Local and Systemic Inflammation Provide a Link from Psychology and Lifestyle to Tissue Health in Musculoskeletal Conditions?

Musculoskeletal conditions are known to involve biological, psychological, social and, often, lifestyle elements. However, these domains are generally considered in isolation from each other. This siloed approach is unlikely to be adequate to understand the complexity of these conditions and likely explains a major component of the disappointing effects of treatment. This paper presents a hypothesis that aims to provide a foundation to understand the interaction and integration between these domains. We propose a hypothesis that provides a plausible link between psychology and lifestyle factors with tissue level effects (such as connective tissue dysregulation/accumulation) in musculoskeletal conditions that is founded on understanding the molecular basis for interaction between systemic and local inflammation. The hypothesis provides plausible and testable links between mind and body, for which empirical evidence can be found for many aspects. We present this hypothesis from the perspective of connective tissue biology and pathology (fibrosis), the role of inflammation locally (tissue level), and how this inflammation is shaped by systemic inflammation through bidirectional pathways, and various psychological and lifestyle factors via their influence on systemic inflammation. This hypothesis provides a foundation for new consideration of the development and refinement of personalized multidimensional treatments for individuals with musculoskeletal conditions.

The impact of hindlimb disuse on sepsis-induced myopathy in mice

Sepsis induces a myopathy characterized by loss of muscle mass and weakness. Septic patients undergo prolonged periods of limb muscle disuse due to bed rest. The contribution of limb muscle disuse to the myopathy phenotype remains poorly described. To characterize sepsis-induced myopathy with hindlimb disuse, we combined the classic sepsis model via cecal ligation and puncture (CLP) with the disuse model of hindlimb suspension (HLS) in mice. Male C57bl/6j mice underwent CLP or SHAM surgeries. Four days after surgeries, mice underwent HLS or normal ambulation (NA) for 7 days. Soleus (SOL) and extensor digitorum longus (EDL) were dissected for in vitro muscle mechanics, morphological, and histological assessments. In SOL muscles, both CLP+NA and SHAM+HLS conditions elicited ~20% reduction in specific force (p < 0.05). When combined, CLP+HLS elicited ~35% decrease in specific force (p < 0.05). Loss of maximal specific force (~8%) was evident in EDL muscles only in CLP+HLS mice (p < 0.05). CLP+HLS reduced muscle fiber cross-sectional area (CSA) and mass in SOL (p < 0.05). In EDL muscles, CLP+HLS decreased absolute mass to a smaller extent (p < 0.05) with no changes in CSA. Immunohistochemistry revealed substantial myeloid cell infiltration (CD68+) in SOL, but not in EDL muscles, of CLP+HLS mice (p < 0.05). Combining CLP with HLS is a feasible model to study sepsis-induced myopathy in mice. Hindlimb disuse combined with sepsis induced muscle dysfunction and immune cell infiltration in a muscle dependent manner. These findings highlight the importance of rehabilitative interventions in septic hosts to prevent muscle disuse and help attenuate the myopathy.

NLRP3 Inflammasome: Potential Role in Obesity Related Low-Grade Inflammation and Insulin Resistance in Skeletal Muscle

Among multiple mechanisms, low-grade inflammation is critical for the development of insulin resistance as a feature of type 2 diabetes. The nucleotide-binding oligomerization domain-like receptor family (NOD-like) pyrin domain containing 3 (NLRP3) inflammasome has been linked to the development of insulin resistance in various tissues; however, its role in the development of insulin resistance in the skeletal muscle has not been explored in depth. Currently, there is limited evidence that supports the pathological role of NLRP3 inflammasome activation in glucose handling in the skeletal muscle of obese individuals. Here, we have centered our focus on insulin signaling in skeletal muscle, which is the main site of postprandial glucose disposal in humans. We discuss the current evidence showing that the NLRP3 inflammasome disturbs glucose homeostasis. We also review how NLRP3-associated interleukin and its gasdermin D-mediated efflux could affect insulin-dependent intracellular pathways. Finally, we address pharmacological NLRP3 inhibitors that may have a therapeutical use in obesity-related metabolic alterations.

Curcumin Ameliorated Oxidative Stress and Inflammation-Related Muscle Disorders in C2C12 Myoblast Cells

The purpose of the current study was to investigate antioxidant and anti-inflammatory effects of spray dry powder containing 40% curcumin (CM-SD) in C2C12 myoblast cells. CM-SD increased DPPH radical scavenging activity in a dose-dependent manner, and up to 30 μg/mL of CM-SD did not express cytotoxicity in C2C12 cells. Exposure to hydrogen peroxide (H2O2) drastically decreased the viability of C2C12 cells, but pre-treatment of CM-SD significantly increased the cell viability (p < 0.01). CM-SD significantly transactivated the nuclear factor erythroid-2-related factor 2 (Nrf2)-dependent luciferase activity in a dose-dependent manner and enhanced the levels of heme oxygenase (HO)-1, glutamate cysteine ligase catalytic subunit (GCLC), and NAD(P)H-dependent quinone oxidoreductase (NQO)-1. CM-SD also significantly reduced reactive oxygen species (ROS) production and lipid peroxidation and restored glutathione (GSH) depletion in H2O2-treated C2C12 cells. Moreover, CM-SD significantly reduced lipopolysaccharides (LPS)-mediated interleukin (IL)-6 production in the conditioned medium. Results from the current study suggest that CM-SD could be a useful candidate against oxidative stress and inflammation-related muscle disorders.

Necroptosis Underlies Hepatic Damage in a Piglet Model of Lipopolysaccharide-Induced Sepsis

Background

Necroptosis is a newly recognized form of programmed cell death with characteristics of both necrosis and apoptosis. The role of necroptosis in hepatic damage during sepsis is poorly understood. In this study, we investigated the occurrence of necroptosis in hepatic damage, and its contribution to hepatic damage in a piglet model of lipopolysaccharide (LPS)-induced sepsis.

Methods

Two animal experiments were conducted. In trial 1, piglets were challenged with LPS and sacrificed at different time points after LPS challenge. In trial 2, piglets were pretreated with necrostatin-1, a specific inhibitor of necroptosis, prior to LPS challenge. Alterations in the hepatic structure and function, pro-inflammatory cytokine expression, and the necroptosis signaling pathway were investigated. Typical ultrastructural characteristics of cell necrosis was observed in the liver of LPS-challenged piglets.

Results

Expressions of critical components of necroptosis including kinases (RIP1, RIP3, and MLKL), mitochondrial proteins (PGAM5 and DRP1), and an intracellular damage-associated molecular pattern (HMGB1) were increased in the liver in a time-dependent manner, followed by hepatic inflammation, morphological damage, and dysfunction as manifested by elevated hepatic expression of IL-1β, IL-6 and TNF-α as well as increased serum AST and AKP activities and the AST/ALT ratio. Pretreatment with necrostatin-1 significantly reduced the expression of RIP1, RIP3 and MLKL as well as PGAM5, DRP1 and HMGB1, which subsequently led to obvious attenuation of hepatic inflammation and damage.

Conclusions

Our study demonstrates that necroptosis occurs in the liver during sepsis and contributes to septic hepatic injury.

Necroptosis is active and contributes to intestinal injury in a piglet model with lipopolysaccharide challenge

Necroptosis, a newly discovered form of programmed cell death that combines the features of apoptosis and necrosis, is important in various physiological and pathological disorders. However, the role of necroptosis on intestinal injury during sepsis has been rarely evaluated. This study aimed to investigate the presence of necroptosis in intestinal injury, and its contribution to intestinal injury in a piglet model challenged with Escherichia coli lipopolysaccharide (LPS). Firstly, a typical cell necrotic phenomenon was observed in jejunum of LPS-challenged pigs by transmission electron microscope. Protein expression of necroptosis signals including receptor-interacting protein kinase (RIP) 1, RIP3, and phosphorylated mixed-lineage kinase domain-like protein (MLKL), mitochondrial proteins including phosphoglycerate mutase family member 5 (PGAM5) and dynamin-related protein 1 (DRP1), and cytoplasmic high-mobility group box 1 (HMGB1) were time-independently increased in jejunum of LPS-challenged piglets, which was accompanied by the impairment of jejunal morphology, and digestive and barrier function indicated by lower activities of jejunal disaccharidases and protein expression of jejunal tight junction proteins claudin-1 and occludin. Pro-inflammatory cytokines including tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6 were also dynamically induced in serum and jejunum of piglets after LPS challenge. Moreover, pretreatment with necrostatin-1 (Nec-1), an specific inhibitor of necroptosis, inhibited necroptosis indicated by decreased necrotic ultrastructural changes and decreased protein expression of RIP1, RIP3, and phosphorylated MLKL as well as PGAM5, DRP1, and cytoplasmic HMGB1. Nec-1 pretreatment reduced jejunal morphological injury, and improved digestive and barrier function. Nec-1 pretreatment also decreased the levels of serum and jejunal pro-inflammatory cytokines and the numbers of jejunal macrophages and monocytes. These findings indicate for the first time that necroptosis is present and contributes to LPS-induced intestinal injury. Nec-1 may have a preventive effect on intestinal injury during sepsis.

Docosahexaenoic and eicosapentaenoic fatty acids differentially regulate glucose and fatty acid metabolism in L6 rat skeletal muscle cells

The objective of this study was to investigate whether the n-3 polyunsaturated fatty acids (PUFAs) docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) can directly regulate glucose and fat metabolism in skeletal muscle besides exerting anti-inflammatory effects. To accomplish this, L6 skeletal muscle cells were treated with 50 µM of either DHA or EPA for 1, 3, and 5 days. Here, we report that basal and insulin-stimulated rates of glucose uptake, glycogen synthesis, protein kinase B (AKT), and glycogen synthase kinase 3 (GSK3) phosphorylation were not affected by DHA or EPA. However, glucose and palmitate oxidation were consistently elevated by DHA treatment, whereas EPA only increased this variable transiently. Similarly, only DHA caused significant and sustained increases in AMP-activated protein kinase (AMPK) phosphorylation and protein levels of carnitine-palmitoyl transferase-1b (CPT1b) and peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α) in skeletal muscle cells. DHA also caused a larger anti-inflammatory effect than EPA in these cells. In conclusion, besides exerting anti-inflammatory effects, DHA and EPA directly regulated glucose and fat metabolism in skeletal muscle cells, although DHA was more effective in doing so than EPA. Thus, by directly enhancing glucose and fat oxidation, DHA may increase glucose disposal and reduce intramyocellular lipid accumulation.

Cellular dynamics of myogenic cell migration: molecular mechanisms and implications for skeletal muscle cell therapies

Directional cell migration is a critical process underlying morphogenesis and post-natal tissue regeneration. During embryonic myogenesis, migration of skeletal myogenic progenitors is essential to generate the anlagen of limbs, diaphragm and tongue, whereas in post-natal skeletal muscles, migration of muscle satellite (stem) cells towards regions of injury is necessary for repair and regeneration of muscle fibres. Additionally, safe and efficient migration of transplanted cells is critical in cell therapies, both allogeneic and autologous. Although various myogenic cell types have been administered intramuscularly or intravascularly, functional restoration has not been achieved yet in patients with degenerative diseases affecting multiple large muscles. One of the key reasons for this negative outcome is the limited migration of donor cells, which hinders the overall cell engraftment potential. Here, we review mechanisms of myogenic stem/progenitor cell migration during skeletal muscle development and post-natal regeneration. Furthermore, strategies utilised to improve migratory capacity of myogenic cells are examined in order to identify potential treatments that may be applied to future transplantation protocols.

Chronic Resistance Exercise Improves Functioning and Reduces Toll-Like Receptor Signaling in Elderly Patients With Postoperative Deconditioning

OBJECTIVE

Elderly patients continue to experience low levels of mobility during and following postoperative hospitalization that lead to persistent physical decline. Therefore, here we compared chronic resistance (CR) exercise against chronic aerobic (CA) exercise in ameliorating postoperative functioning and reducing proinflammatory muscular Toll-like receptor (TLR)-associated signaling in elderly postoperative patients.

METHODS

We conducted a prospective, randomized trial comparing the effects of 3 exercise programs (CR, CA, and CR + CA) in 66 elderly patients recovering from recent hip, femur, or pelvic fracture repair surgery. The primary outcomes were changes in anatomic/physical performance parameters (ie, maximal oxygen intake, endurance, quadriceps cross-sectional area, and maximum knee-extensor force). The secondary outcomes were changes in TLR/nuclear factor kappa beta signaling pathway marker expression.

RESULTS

Three of the 4 anatomic/physical performance parameters significantly improved for the CR and CR + CA cohorts. Muscular expression of myeloid differentiation primary response gene 88, transforming growth factor beta-activated kinase 1 (TLR signaling pathway markers), p50, p65, tumor necrosis factor α, and interleukin 6 (nuclear factor kappa beta signaling pathway markers) all showed significant reductions after CR and CR + CA. Serum expression of 2 key TLR4 ligands, heat shock protein 70 and serum amyloid A, also showed significant reductions after CR and CR + CA.

CONCLUSIONS

Three months of CR or CR + CA improves maximal oxygen consumption, quadriceps cross-sectional area, and maximum knee-extensor force while lowering muscular proinflammatory signaling markers in elderly adults with postoperative deconditioning.

Effects of Astaxanthin on Inflammation and Insulin Resistance in a Mouse Model of Gestational Diabetes Mellitus

Gestational diabetes mellitus (GDM) is a condition in which a hormone made by the placenta prevents the body from using insulin effectively. It is important to find an effective treatment. A mouse model of GDM was used to testify the effects of astaxanthin on glucose tolerance and insulin sensitivity. Production of inflammatory cytokines, reactive oxygen species (ROS), and glucose transporter type 4 (GLUT4) translocation and insulin-related signaling were measured in the presence of astaxanthin both in vivo and in vitro. It was found that astaxanthin improved insulin sensitivity, glucose tolerance, and litter size of offspring and reduced birth weight of offspring and inflammation in GDM mouse. Moreover, astaxanthin increased GLUT4 translocating to membrane without altering its secretion/expression and glucose uptake and consumption in C2C12 skeletal muscle cells. Furthermore, ROS generation and insulin-related signaling inhibited by tumor necrosis factor α was restored by astaxanthin. It is concluded that astaxanthin has the potential to attenuate GDM symptoms by regulating inflammation and insulin resistance in skeletal muscle of pregnant mice. Our findings suggest that astaxanthin could be a promising and effective molecule to treat GDM.

Muscle protein turnover and low-protein diets in patients with chronic kidney disease

Adaptation to a low-protein diet (LPD) involves a reduction in the rate of amino acid (AA) flux and oxidation, leading to more efficient use of dietary AA and reduced ureagenesis. Of note, the concept of 'adaptation' to low-protein intakes has been separated from the concept of 'accommodation', the latter term implying a decrease in protein synthesis, with development of wasting, when dietary protein intake becomes inadequate, i.e. beyond the limits of the adaptive mechanisms. Acidosis, insulin resistance and inflammation are recognized mechanisms that can increase protein degradation and can impair the ability to activate an adaptive response when an LPD is prescribed in a chronic kidney disease (CKD) patient. Current evidence shows that, in the short term, clinically stable patients with CKD Stages 3-5 can efficiently adapt their muscle protein turnover to an LPD containing 0.55-0.6 g protein/kg or a supplemented very-low-protein diet (VLPD) by decreasing muscle protein degradation and increasing the efficiency of muscle protein turnover. Recent long-term randomized clinical trials on supplemented VLPDs in patients with CKD have shown a very good safety profile, suggesting that observations shown by short-term studies on muscle protein turnover can be extrapolated to the long-term period.

PPARβ/δ Agonism Upregulates Forkhead Box A2 to Reduce Inflammation in C2C12 Myoblasts and in Skeletal Muscle

Daily activities expose muscles to innumerable impacts, causing accumulated tissue damage and inflammation that impairs muscle recovery and function, yet the mechanism modulating the inflammatory response in muscles remains unclear. Our study suggests that Forkhead box A2 (FoxA2), a pioneer transcription factor, has a predominant role in the inflammatory response during skeletal muscle injury. FoxA2 expression in skeletal muscle is upregulated by fatty acids and peroxisome proliferator-activated receptors (PPARs) but is refractory to insulin and glucocorticoids. Using PPARβ/δ agonist GW501516 upregulates FoxA2, which in turn, attenuates the production of proinflammatory cytokines and reduces the infiltration of CD45+ immune cells in two mouse models of muscle inflammation, systemic LPS and intramuscular injection of carrageenan, which mimic localized exercise-induced inflammation. This reduced local inflammatory response limits tissue damage and restores muscle tetanic contraction. In line with these results, a deficiency in either PPARβ/δ or FoxA2 diminishes the action of the PPARβ/δ agonist GW501516 to suppress an aggravated inflammatory response. Our study suggests that FoxA2 in skeletal muscle helps maintain homeostasis, acting as a gatekeeper to maintain key inflammation parameters at the desired level upon injury. Therefore, it is conceivable that certain myositis disorders or other forms of painful musculoskeletal diseases may benefit from approaches that increase FoxA2 activity in skeletal muscle.

TAK-242, a specific inhibitor of Toll-like receptor 4 signalling, prevents endotoxemia-induced skeletal muscle wasting in mice

Circulating lipopolysaccharide (LPS) concentrations are often elevated in patients with sepsis or various endogenous diseases related to bacterial translocation from the gut. Systemic inflammatory responses induced by endotoxemia induce severe involuntary loss of skeletal muscle, termed muscle wasting, which adversely affects the survival and functional outcomes of these patients. Currently, no drugs are available for the treatment of endotoxemia-induced skeletal muscle wasting. Here, we tested the effects of TAK-242, a Toll-like receptor 4 (TLR4)-specific signalling inhibitor, on myotube atrophy in vitro and muscle wasting in vivo induced by endotoxin. LPS treatment of murine C2C12 myotubes induced an inflammatory response (increased nuclear factor-κB activity and interleukin-6 and tumour necrosis factor-α expression) and activated the ubiquitin-proteasome and autophagy proteolytic pathways (increased atrogin-1/MAFbx, MuRF1, and LC-II expression), resulting in myotube atrophy. In mice, LPS injection increased the same inflammatory and proteolytic pathways in skeletal muscle and induced atrophy, resulting in reduced grip strength. Notably, pretreatment of cells or mice with TAK-242 reduced or reversed all the detrimental effects of LPS in vitro and in vivo. Collectively, our results indicate that pharmacological inhibition of TLR4 signalling may be a novel therapeutic intervention for endotoxemia-induced muscle wasting.

Paeonia lactiflora root extract suppresses cancer cachexia by down-regulating muscular NF-κB signalling and muscle-specific E3 ubiquitin ligases in cancer-bearing mice

ETHNOPHARMACOLOGICAL RELEVANCE

The dried root of Paeonia lactiflora Pall. (Radix Paeoniae) has been traditionally used to treat various inflammatory diseases in many Asian countries.

AIM OF THE STUDY

Cancer cachexia is a catabolic syndrome driven by inflammation and characterised by a loss of skeletal muscle. This study aimed to assess the effects of an ethanolic extract of Radix Paeoniae (RP) on cancer cachexia and elucidate its mechanism of action.

MATERIAL AND METHODS

The anti-cachexic effect and mechanism of RP were examined in mouse models of cancer cachexia established in C57BL/6 mice by subcutaneously injecting Lewis lung carcinoma or MC38 colon carcinoma cells. Skeletal muscle tissues were analysed by RNAseq, real-time quantitative reverse transcription PCR, western blotting, and immunofluorescence microscopy. Megestrol acetate, which is recommended for the treatment of cachexia in cancer patients, was used as the comparator treatment in this study.

RESULTS

In lung and colon cancer-bearing mice, RP significantly restored food intake and muscle mass, along with muscle function measured by grip strength and treadmill running time. In the skeletal muscle tissue of the cancer-bearing mice, RP suppressed NF-κB signalling and reduced inflammatory cytokines, including TNF-α, IL-6, and IL-1β; it also down-regulated the muscle-specific E3 ubiquitin ligases MuRF1 and MAFbx.

CONCLUSION

RP restored skeletal muscle function and mass in cancer-bearing mice by down-regulating the muscular NF-κB signalling pathway and muscle-specific E3 ubiquitin ligases. Our study indicates that RP is a potential candidate for development as a therapeutic agent against cancer cachexia.

Purinergic signaling in hepatic disease

Extracellular purines (ATP and adenosine) are ubiquitous intercellular messengers. During tissular damage, they function as damage-associated molecular patterns (DAMPs). In this context, purines announce tissue alterations to initiate a reparative response that involve the formation of the inflammasome complex and the recruitment of specialized cells of the immune system. The present review focuses on the role of the purinergic system in liver damage, mainly during the onset and development of fibrosis. After hepatocellular injury, extracellular ATP promotes a signaling cascade that ameliorates tissue alterations to restore the hepatic function. However, if cellular damage becomes chronic, ATP orchestrates an aberrant reparative process that results in severe liver diseases such as fibrosis and cirrhosis. ATP and adenosine, their receptors, and extracellular ectonucleotidases are mediators of unique processes that will be reviewed in detail.

The Inducible microRNA-21 Negatively Modulates the Inflammatory Response in Teleost Fish via Targeting IRAK4

Eradication of bacterial infection requires timely and appropriate immune and inflammatory responses, but excessive induction of inflammatory cytokines can cause acute or chronic inflammatory disorders. Thus, various layers of negative regulators and mechanisms are needed to ensure maintenance of the homeostasis for the immune system. miRNAs are a family of small non-coding RNAs that emerged as significant and versatile regulators involved in regulation of immune responses. Recently, the molecular mechanisms of miRNA in host-pathogen interaction networks have been extensively studied in mammals, whereas the underlying regulatory mechanisms in fish are still poorly understood. In this study, we identify miR-21 as a negative regulator of the teleost inflammatory response. We found that lipopolysaccharide and Vibrio anguillarum significantly upregulated the expression of fish miR-21. Upregulated miR-21 suppresses LPS-induced inflammatory cytokine expression by targeting IL-1 receptor-associated kinase 4 (IRAK4), thereby avoiding excessive inflammatory responses. Furthermore, we demonstrated that miR-21 regulates inflammatory responses through NF-κB signaling pathways. The collective findings indicate that miR-21 plays a regulatory role in host-pathogen interactions through IRAK4-mediated NF-κB signaling pathway.

Muscle characteristics in chicks challenged with Salmonella Enteritidis and the effect of preventive application of the probiotic Enterococcus faecium

The present study was conducted to assess the effects of the probiotic Enterococcus faecium AL41 (EF) and of the enteric pathogen Salmonella Enteritidis PT4 (SE) on the development of posthatch pectoralis major muscle (PM) of broiler chicks. The four experimental groups were control (CON), EF, SE, and EF+SE (EFSE). EF and SE were given per os from days 1 to 7 and at day 4 posthatch, respectively. Muscle samples from 6 chicks per group were taken at day 8 (D8) and day 11 (D11) to evaluate PM myofiber growth, capillarization, DNA, RNA, and protein content, as well as enzyme activities (isocitrate dehydrogenase, lactate dehydrogenase, creatine kinase). PM growth rate was 7.45 ± 2.7 g/d in non-SE groups (CON, EF) and 5.10 ± 1.82 g/d in SE-infected groups (P < 0.02). Compared with group CON, application of bacteria (groups EF and SE) reduced the fiber cross-sectional area (246 and 262 vs. 347 ± 19 μm2) and the number of myonuclei per fiber (0.66 and 0.64 vs. 0.79 ± 0.03). At D11, hypertrophic myofiber growth normalized in the EF group, but negative effects persisted in SE and EFSE birds contributing to lower daily PM gain. In addition, SE infection strongly disturbed PM capillarization. Negative effects on capillary cross-sectional area and on the area (%) covered by capillaries persisted until D11 in the SE group, whereas pre-feeding of EF restored capillarization in the EFSE group to control levels. We conclude that supplementation of the probiotic bacteria EF AL41 had positive effects on PM capillarization and, thus, on delivery of O2, supply of nutrients, and removal of metabolites. Supplementation of probiotic bacteria might therefore reduce energetic stress and improve muscle health and meat quality during SE infection.

Imoxin attenuates LPS-induced inflammation and MuRF1 expression in mouse skeletal muscle

The double-stranded RNA-dependent protein kinase (PKR) contributes to inflammatory cytokine expression and disease pathogenesis in many conditions. Limited data are available on the efficacy of the PKR inhibitor imoxin to prevent lipopolysaccharide (LPS)-induced inflammation in skeletal muscle in vivo. The aim of this study was to evaluate the effect of imoxin, a PKR inhibitor, on inflammatory and atrophy signaling in skeletal muscle in response to an acute inflammatory insult with LPS. Six-week old C57BL/6J mice received vehicle (saline) or 0.5 mg/kg imoxin 24 and 2 h prior to induction of inflammation via 1 mg/kg LPS. Gastrocnemius muscles were collected 24 h post-LPS and mRNA and protein expression were assessed. LPS lead to a loss of body weight, which was similar in Imoxin+LPS. There were no differences in muscle weight among groups. LPS increased gastrocnemius mRNA expression of TNF-α and IL-1β, and protein levels of NLRP3, all of which were attenuated by imoxin. Similarly, IL-6 mRNA and IL-1β protein were suppressed in Imoxin+LPS compared to LPS alone. LPS increased mRNA of the atrogenes, MuRF1 and MAFbx, and imoxin attenuated the LPS-induced increase in MuRF1 mRNA, and lowered MuRF1 protein. Imoxin+LPS increased p-Akt compared to saline or LPS, whereas p-mTOR was unaltered. FoxO1 was upregulated and p-FoxO1/FoxO1 reduced by LPS, both of which were prevented by imoxin. Both LPS and Imoxin+LPS had diminished p-FoxO3/FoxO3 compared to control. These results demonstrate the potential anti-inflammatory and anti-atrophy effects of imoxin on skeletal muscle in vivo.

The crux of positive controls - Pro-inflammatory responses in lung cell models

Positive controls are an important feature in experimental studies as they show the responsiveness of the model under investigation. An often applied reagent for a pro-inflammatory stimulus is the endotoxin lipopolysaccharide (LPS), which has been shown to induce a cytokine release by various cell cultures. The effect of LPS in monocultures of 16HBE14o-, a bronchial cell line, and of A549, an alveolar cell line, were compared in submerged and air-liquid interface cultures, as well as in co-cultures of the two epithelial cells with monocyte-derived macrophages and dendritic cells. The protein and mRNA levels of the two most relevant pro-inflammatory mediators, Tumor necrosis factor alpha (TNF) and Interleukin 8 (CXCL8), were measured after 4 h and 24 h exposure. 16HBE14o- cells alone as well as in co-cultures are non-responsive to an LPS stimulus, but an already increased basal expression of both pro-inflammatory mediators after prolonged time in culture was observed. In contrary, A549 in monocultures showed increased CXCL8 production at the gene and protein level after LPS exposure, while TNF-levels were below detection limit. In A549 co-cultured with immune cells both mediators were upregulated. This study shows the importance of a careful evaluation of the culture system used, including the application of positive controls. In addition, the use of co-cultures with immune cells more adequately reflects the inflammatory response upon exposure to toxicants.

Curcumin ameliorates palmitate-induced inflammation in skeletal muscle cells by regulating JNK/NF-kB pathway and ROS production

Curcumin, a natural polyphenol compound, has the beneficial effects on several diseases such as metabolic syndrome, cancer, and diabetes. The anti-inflammatory property of curcumin has been demonstrated in different cells; however, its role in prevention of palmitate-induced inflammation in skeletal muscle C2C12 cells is not known. In this study, we examined the effect of curcumin on the inflammatory responses stimulated by palmitate in C2C2 cells. The results showed that palmitate upregulated the mRNA expression and protein release of IL-6 and TNF-α cytokines in C2C12 cells, while pretreatment with curcumin was able to attenuate the effect of palmitate on inflammatory cytokines. The anti-inflammatory effect of curcumin was associated with the repression of phosphorylation of IKKα-IKKβ, and JNK. Palmitate also caused an increase in reactive oxygen species (ROS) level that curcumin abrogated it. Collectively, these findings suggest that curcumin may represent a promising therapy for prevention of inflammation in skeletal muscle cells.

Porcine Reproductive and Respiratory Syndrome virus reduces feed efficiency, digestibility, and lean tissue accretion in grow-finish pigs

Porcine reproductive and respiratory syndrome (PRRS) virus is a major swine virus that causes reproductive impairment in sows, as well as respiratory disease, reduction in growth rates, and mortalities in all ages of pigs. The objective of this study was to quantify the impact PRRS has on grower-finisher pig feed efficiency and tissue accretion rates. Thirty PRRS naïve, littermate pairs of maternal line Choice Genetics gilts (33.6 ± 0.58 kg BW) were selected and pairs split across 2 barns consisting of 5 pens (n = 6 pigs/pen per barn). Pigs in both barns were fed corn-soybean-DDGS diets ad libitum. All pigs in one barn were inoculated (CHAL) via an i.m. injection of a live PRRS strain isolated from the region (0 d post inoculation, dpi), while pigs in the other barn were given a saline control injection (CONT). Pig performance (ADG, ADFI, G:F) was assessed from 35 kg BW until each group reached market BW (128 kg). Additionally, longitudinal apparent total tract digestibility (ATTD) and body composition was assessed using Dual-energy X-ray absorptiometry (DXA) post inoculation (dpi) to estimate lean, protein, fat and bone accretion rates. Serological data from CHAL pigs showed that PRRS titers peaked 7 dpi and these pigs seroconverted by 35 dpi. According to both genomic and protein PRRS titers, CONT pigs were naïve to CHAL throughout the study. The PRRS infection reduced (P < 0.001) ATTD of dry matter, energy and nitrogen by 3 to 5% at 21 dpi and the reduction in ATTD persisted after 65 dpi. Compared to the CONT, CHAL pigs had decreased ADG (0.89 vs. 0.80 kg/d, P < 0.001), ADFI (2.05 vs. 1.93 kg/d, P < 0.001), and G:F (0.44 vs. 0.41 kg/d, P < 0.001) over the entire test period. The CHAL pigs also had attenuated DXA predicted whole body accretion of lean (547 vs. 633 g/d, P = 0.001), protein (109 vs. 126 g/d, P = 0.001) and fat (169 vs. 205 g/d, P = 0.001) compared to their CONT counterparts from dpi 0 to 80. Based on carcass data at slaughter (and consistent with the DXA data), CHAL pigs had leaner carcasses and reduced yields. These data clearly demonstrate that PRRS infection reduces digestibility, feed efficiency and protein accretion rates in grower-finisher pigs.

Tumor induces muscle wasting in mice through releasing extracellular Hsp70 and Hsp90

Cachexia, characterized by muscle wasting, is a major contributor to cancer-related mortality. However, the key cachexins that mediate cancer-induced muscle wasting remain elusive. Here, we show that tumor-released extracellular Hsp70 and Hsp90 are responsible for tumor’s capacity to induce muscle wasting. We detected high-level constitutive release of Hsp70 and Hsp90 associated with extracellular vesicles (EVs) from diverse cachexia-inducing tumor cells, resulting in elevated serum levels in mice. Neutralizing extracellular Hsp70/90 or silencing Hsp70/90 expression in tumor cells abrogates tumor-induced muscle catabolism and wasting in cultured myotubes and in mice. Conversely, administration of recombinant Hsp70 and Hsp90 recapitulates the catabolic effects of tumor. In addition, tumor-released Hsp70/90-expressing EVs are necessary and sufficient for tumor-induced muscle wasting. Further, Hsp70 and Hsp90 induce muscle catabolism by activating TLR4, and are responsible for elevation of circulating cytokines. These findings identify tumor-released circulating Hsp70 and Hsp90 as key cachexins causing muscle wasting in mice.

Cachexia affects many cancer patients causing weight loss and increasing mortality. Here, the authors identify extracellular Hsp70 and Hsp90, either in soluble form or secreted as part of exosomes from tumor cells, to be responsible for tumor induction of cachexia.

Lipopolysaccharide inhibits myogenic differentiation of C2C12 myoblasts through the Toll-like receptor 4-nuclear factor-κB signaling pathway and myoblast-derived tumor necrosis factor-α

Background

Circulating lipopolysaccharide (LPS) concentrations are often elevated in patients with sepsis or with various endogenous diseases that are associated with metabolic endotoxemia. Involuntary loss of skeletal muscle, termed muscle wasting, is commonly observed in these conditions, suggesting that circulating LPS might play an essential role in its development. Although impairment of muscle regeneration is an important determinant of skeletal muscle wasting, it is unclear whether LPS affects this process and, if so, by what mechanism. Here, we used the C2C12 myoblast cell line to investigate the effects of LPS on myogenesis.

Methods

C2C12 myoblasts were grown to 80% confluence and induced to differentiate in the absence or presence of LPS (0.1 or 1 μg/mL); TAK-242 (1 μM), a specific inhibitor of Toll-like receptor 4 (TLR4) signaling; and a tumor necrosis factor (TNF)-α neutralizing antibody (5 μg/mL). Expression of a skeletal muscle differentiation marker (myosin heavy chain II), two essential myogenic regulatory factors (myogenin and MyoD), and a muscle negative regulatory factor (myostatin) was analyzed by western blotting. Nuclear factor-κB (NF-κB) DNA-binding activity was measured using an enzyme-linked immunosorbent assay.

Results

LPS dose-dependently and significantly decreased the formation of multinucleated myotubes and the expression of myosin heavy chain II, myogenin, and MyoD, and increased NF-κB DNA-binding activity and myostatin expression. The inhibitory effect of LPS on myogenic differentiation was reversible, suggesting that it was not caused by nonspecific toxicity. Both TAK-242 and anti-TNF-α reduced the LPS-induced increase in NF-κB DNA-binding activity, downregulation of myogenic regulatory factors, and upregulation of myostatin, thereby partially rescuing the impairment of myogenesis.

Conclusions

Our data suggest that LPS inhibits myogenic differentiation via a TLR4–NF-κB-dependent pathway and an autocrine/paracrine TNF-α-induced pathway. These pathways may be involved in the development of muscle wasting caused by sepsis or metabolic endotoxemia.

MicroRNA-148 as a negative regulator of the common TLR adaptor mediates inflammatory response in teleost fish

MicroRNAs are small endogenous noncoding RNAs implicating in the regulation of diverse biological processes, including proliferation, differentiation, cancer, apoptosis, and viral infections. MicroRNAs regulate gene expression by either mRNA degradation or inhibition of protein translation. Although microRNAs have emerged as important controller involved in regulation of inflammatory response, the microRNA-mediated regulatory mechanism remains less clear in teleost. Here, we report that miR-148 targets MyD88 and down-regulates its expression by inhibition protein translation rather than degradation mRNA in miiuy croaker. Additionally, we found that miR-148 was significantly upregulated in miiuy croaker after treated with Vibro harveyi, as well as LPS. Overexpression of miR-148 inhibited LPS-induced inflammatory cytokines production, such as IL-6 and IL-1β, which then avoid excessive inflammation response. miR-148 has also been identified to suppress NF-κB pathway through targeting and repressing MyD88 expression. Taken together, our findings indicate that miR-148 participates in bacteria-induced inflammatory response and act as a negative regulator for MyD88-mediated NF-κB signaling, which may clarify the mechanism of microRNAs for avoiding excessive inflammation in teleost fish.

Muscle-specific deletion of SOCS3 does not reduce the anabolic response to leucine in a mouse model of acute inflammation

Excessive inflammation reduces skeletal muscle protein synthesis leading to wasting and weakness. The janus kinase/signal transducers and activators of transcription-3 (JAK/STAT3) pathway is important for the regulation of inflammatory signaling. As such, suppressor of cytokine signaling-3 (SOCS3), the negative regulator of JAK/STAT signaling, is thought to be important in the control of muscle homeostasis. We hypothesized that muscle-specific deletion of SOCS3 would impair the anabolic response to leucine during an inflammatory insult. Twelve week old (n=8 per group) SOCS3 muscle-specific knockout mice (SOCS3-MKO) and littermate controls (WT) were injected with lipopolysaccharide (LPS, 1mg/kg) or saline and were studied during fasted conditions or after receiving 0.5g/kg leucine 3h after the injection of LPS. Markers of inflammation, anabolic signaling, and protein synthesis were measured 4h after LPS injection. LPS injection robustly increased mRNA expression of inflammatory molecules (Socs3, Socs1, Il-6, Ccl2, Tnfα and Cd68). In muscles from SOCS3-MKO mice, the Socs3 mRNA response to LPS was significantly blunted (∼6-fold) while STAT3 Tyr705 phosphorylation was exacerbated (18-fold). Leucine administration increased protein synthesis in both WT (∼1.6-fold) and SOCS3-MKO mice (∼1.5-fold) compared to basal levels. LPS administration blunted this effect, but there were no differences between WT and SOCS3-MKO mice. Muscle-specific SOCS3 deletion did not alter the response of AKT, mTOR, S6 or 4EBP1 under any treatment conditions. Therefore, SOCS3 does not appear to mediate the early inflammatory or leucine-induced changes in protein synthesis in skeletal muscle.

Toll-like receptor 4 mediates Lewis lung carcinoma-induced muscle wasting via coordinate activation of protein degradation pathways

Cancer-induced cachexia, characterized by muscle wasting, is a lethal metabolic syndrome with undefined etiology. Current consensus is that multiple factors contribute to cancer-induced muscle wasting, and therefore therapy requires combinational strategies. Here, we show that Toll-like receptor 4 (TLR4) mediates cancer-induced muscle wasting by directly activating muscle catabolism as well as stimulating an innate immune response in mice bearing Lewis lung carcinoma (LLC), and targeting TLR4 alone effectively abrogate muscle wasting. Utilizing specific siRNAs we observed that LLC cell-conditioned medium (LCM)-treated C2C12 myotubes underwent a rapid catabolic response in a TLR4-dependent manner, including activation of the p38 MAPK−C/EBPβ signaling pathway as well as the ubiquitin-proteasome and autophagy-lysosome pathways, resulting in myotube atrophy. Utilizing a reporter cell-line it was confirmed that LCM activated TLR4. These results suggest that LLC-released cachexins directly activate muscle catabolism via activating TLR4 on muscle cells independent of immune responses. Critically, LLC tumor-bearing TLR4^−/− mice were spared from muscle wasting due to a blockade in muscle catabolic pathways. Further, tumor-induced elevation of circulating TNFα and interleukin-6 (IL-6) was abolished in TLR4^−/− mice. These data suggest that TLR4 is a central mediator and therapeutic target of cancer-induced muscle wasting.

MicroRNA-3570 Modulates the NF-κB Pathway in Teleost Fish by Targeting MyD88

The inflammatory response, a protective process to clear detrimental stimuli, constitutes the defense against infectious pathogens. However, excessive inflammation disrupts immune homeostasis, which may induce autoimmune and inflammatory diseases. In this study, we report that microRNA (miR)-3570 plays a negative role in the bacteria-induced inflammatory response of miiuy croaker. Upregulation of miR-3570 by Vibrio anguillarum and LPS inhibits LPS-induced inflammatory cytokine production, thus avoiding an excessive inflammation response. Evidence showed that miR-3570 targets MyD88 and posttranscriptionally downregulates its expression. Overexpression of miR-3570 in macrophages suppresses the expression of MyD88, as well as its downstream signaling of IL-1R-associated kinases 1 and 4 and TNFR-associated factor 6. These results suggest that miR-3570 plays a regulatory in the bacteria-induced inflammatory response through the MyD88-mediated NF-κB signaling pathway by targeting MyD88.