Attenuation of cellular toxicity by calpain inhibitor induced by bacterial endotoxin: a mechanistic study using muscle precursor cells as a model system

Lipopolysaccharide Promotes the Proliferation and Differentiation of Goose Embryonic Myoblasts by Promoting Cytokine Expression and Appropriate Apoptosis Processes

Lipopolysaccharide (LPS) can trigger a series of immune reactions, leading to the occurrence of disease and a decrease in the growth performance of geese. However, the mechanisms of LPS in geese muscle development have not been reported. This study aimed to investigate the effects and mechanisms of LPS on proliferation and differentiation of goose embryonic myoblasts. Embelin and belnacasan combined with LPS were used to explore these effects. Our results demonstrated that LPS significantly induced inflammatory cytokine production in both proliferation and differentiation stages. LPS and embelin treatment significantly improved the proliferation ability (p < 0.05), while LPS reduced the differentiation ability of goose embryonic myoblasts. By adding embelin, the differentiation ability of myoblasts was enhanced, while by adding belnacasan, LPS treatment led to a lower differentiation ability. Combined with the correlation of the expression levels of myogenic, cell cycle, and inflammatory-related genes and proteins, it is speculated that one of the reason for the decrease of differentiation ability of goose embryo myoblasts induced by LPS is the increase of the expression levels of pro-inflammatory factors. Moreover, LPS, embelin and belnacasan, and LPS treatments could significantly increase the apoptosis rate of goose embryonic myoblasts. Taken together, these findings suggest that LPS promotes the proliferation and differentiation of goose embryonic myoblasts by promoting cytokine expression and appropriate apoptosis processes. These findings lay a foundation for the study of the mechanisms of LPS in goose muscle development.

l-Arginine Alleviates LPS-Induced Oxidative Stress and Apoptosis via Activating SIRT1-AKT-Nrf2 and SIRT1-FOXO3a Signaling Pathways in C2C12 Myotube Cells

l-arginine (l-Arg) has been reported to possess a wide range of functions, including anti-inflammatory, anti-oxidative, and anti-apoptosis. However, the role of l-Arg in LPS-induced muscle injury and its potential protective mechanism has not been well elucidated. This study aimed to investigate the effects of l-Arg on the LPS-induced oxidative stress and apoptosis in differentiated C2C12 myotube cells. Our results demonstrated that myotube cells treated with 0.2 mg/mL LPS significantly decreased cell viability. l-Arg treatment significantly suppressed LPS induced ROS accumulation and cell apoptosis. Furthermore, l-Arg improved antioxidant-related enzymes’ activities; increased antioxidant ability via Akt-Nrf2 signaling pathway; maintained the mitochondrial membrane potential (MMP); and enhanced FOXO3a expression, leading to a decrease in the mitochondrial-associated apoptotic proteins. In addition, l-Arg exposure dramatically increased the mRNA and protein expressions of SIRT1. The cytoprotective effect of l-Arg was restricted by the SIRT1 inhibitor EX527, which led to an increase in ROS level, apoptosis rate, and decreased cell MMP. The results also demonstrated that EX527 treatment significantly eliminated the effect of l-Arg on LPS-induced oxidative damage and mitochondria-mediated cell apoptosis. Our findings revealed that l-Arg could be used as a potential nutraceutical in reducing muscle injury via regulating SIRT1-Akt-Nrf2 and SIRT1-FOXO3a-mitochondria apoptosis signaling pathways.

Changes in activity of µ- and m-calpains and signs of neuroinflammation in the hippocampus and striatum of rats after single intraperitoneal injection of subseptic dose of endotoxin

Some mechanisms of neuronal degeneration in endotoxinemia are already well described, but need to be detailed. In this study, we tested the effect of a single intraperitoneal injection of a LPS sub-septic dose (1 mg/kg of animal weight) on calpain activity in the striatum and hippocampus. We showed, that in the hippocampus the day after LPS administration an increase in production of IL-1β and TNF-α mRNA, followed by elevated mRNA expression and activity of µ- and m-calpains without signs of microglia activation is observed. In striatal cells, the day after LPS injection an increase in expression of IL-1β, TNF-α, IBA-1, m-calpain and calpastatin mRNA is revealed, which only intensifies over time. The elicited changes are accompanied by a decrease in motor behavior, which can be considered as a sign of sickness behavior. In the hippocampus, 180 days after LPS administration expression of TNF-α, content and activity of µ-calpain are increased. In the striatum, elevation in expression of TNF-α, IBA-1, µ- and m-calpain mRNA, with hyperactivation of only m-calpain, is observed. Significantly reduced motor activity can be a consequence of LPS-induced neuronal death. A long-lasting endotoxin activates microglia that damage neurons via proinflammation cytokines and calpain hyperactivation. The endotoxin hypothesis of neurodegeneration is unproven, but if correct, then neurodegeneration may be reduced by decreasing endotoxin-induced neuroinflammation and m-calpain hyperactivation. Therefore, the drugs, that decrease endotoxin-induced neuroinflammation and differently inhibit µ- or m-calpain, can be used to prevent or reduce the severity of neurodegeneration.

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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.

Influence of Capsaicin on Inflammatory Cytokines Induced by Lipopolysaccharide in Myoblast Cells Under In vitro Environment

BACKGROUND

ellular damage initiated by reactive oxygen species (ROS) is the main cause of numerous severe diseases and therefore for this reason, the natural antioxidants have note worthy significance in human health. Capsaicin possesses noteworthy analgesic and anti-inflammatory properties. It also possesses healing effects for treatment of arthritis, diabetic neuropathy, gastric lesions, and cardiac excitability that is why it is incorporated in creams and gels.

OBJECTIVE

The present study was carried out to estimate the in vitro antioxidant and ROS scavenging activities of capsaicin against muscle precursor cells. Till date, no investigation has been carried out to study the effect of capsaicin on myoblasts.

MATERIALS AND METHODS

Herein, the cytotoxicity was induced by endotoxin lipopolysaccharide (LPS) to analyze the effect of capsaicin on LPS induced inflammation and apoptosis on muscle cells. To find out the toxicity of endotoxin, myoblasts were exposed to different concentrations of LPS, viability and morphology was checkedby the means of CCK-8 test and microscopy, respectively. Apoptotic cell death was examined by fluorescence staining. Additionally, LPS-induced apoptosis was determined by mRNAexpression of calpain, caspase-3 and tumor necrosisfactor alpha (TNF-α), and were quantified by qRT-PCR.

RESULTS

The outcome of the presentstudy demonstrated that LPS stimulation generatestoxicity in dose-dependent manner. Pre-treatmentof myoblasts with capsaicin can considerably alleviate LPS-induced inflammation.

CONCLUSION

In conclusion, this study indicates that dietetic supplementation of capsicum may help to alleviate/reduce the inflammatory effects and is therefore potent source of natural antioxidant agent which can be utilized to control muscle related diseases, such as myotube atrophy.

SUMMARY

In the present study cytotoxicity was induced by LPS to analyze the effect of capsaicin on LPS induced inflammation and apoptosis on muscle cells.The results of this investigation demonstrated that LPS stimulation generates toxicity in dose dependent manner. Pre-treatment of myoblasts with capsaicin can considerably reduce LPS induced inflammation.It has been concluded on the basis of results that the dietetic supplementation of capsicum may help to minimize inflammatory effects and are potent sources of natural antioxidants which can be utilized to control muscle related diseases such as atrophy. Abbreviation used: AMP: Adenosine monophosphate, AO/EB: Acridine orange / Ethidium bromide, ATL: T-cell leukemi, CAP: Capsaicin, CCK-8: Cell counting Kit-8, CLSM: Laser Scanning Microscopy, DCF-DA: 2', 7'-dichlorofluorescein diacetate, DMEM: Dulbecco's modified Eagle's medium, DPPH: α, α-diphenyl-β-picrylhydrazyl, FBS: Fetal bovine serum, KA: Kainic acid, LPS: Lipopolysaccharide, MDA: Malondialdehyde, NF-κB: Nuclear factor kgene binding, PBS: Phosphate buffer saline, pNA: p-nitroanilide, RNW: RNase free water, ROS: Reactive oxygen species, TNF-α: Tumor necrosis factor alpha, TRPV1: Transient receptor potential vanilloid 1.