Decreased NADPH oxidase expression and antioxidant activity in cachectic skeletal muscle

Soil-dwelling grub larvae of Protaetia brevitarsis biodegrade polystyrene: Responses of gut microbiome and host metabolism

Plastic pollution poses a significant threat to terrestrial ecosystems, yet the potential for soil fauna to contribute to plastic biodegradation remains largely unexplored. In this study, we reveal that soil-dwelling grubs, Protaetia brevitarsis larvae, can effectively biodegrade polystyrene (PS) plastics. Over a period of 4 weeks, these grubs achieved a remarkable 61.5 % reduction in PS foam mass. This biodegradation was confirmed by the depolymerization of ingested PS, formation of oxidative functional groups, noticeable chemical modifications, and an increase of δ13C of residual PS in frass. Additionally, antibiotic treatment to suppress gut microbes led to variations in the biodegradation process. PS ingestion induced a significant shift in the gut microbiome, promoting the growth of degradation-related bacteria such as Promicromonosporaceae, Bacillaceae, and Paenibacillaceae. Furthermore, the digestion of plastic triggered extensive metabolomic reprogramming of grubs' intestines, enhancing redox capabilities and facilitating PS biodegradation. These results indicate that responsive adaptation of both the gut microbiome and the host's intestinal metabolism contributes to PS degradation. Collectively, these findings demonstrate P. brevitarsis larvae's capability to alleviate soil plastic pollution, and highlight the potential of researching soil fauna further for sustainable plastic waste management solutions.

Preventing loss of sirt1 lowers mitochondrial oxidative stress and preserves C2C12 myotube diameter in an in vitro model of cancer cachexia

Cancer cachexia is a multifactorial syndrome associated with advanced cancer that contributes to mortality. Cachexia is characterized by loss of body weight and muscle atrophy. Increased skeletal muscle mitochondrial reactive oxygen species (ROS) is a contributing factor to loss of muscle mass in cachectic patients. Mice inoculated with Lewis lung carcinoma (LLC) cells lose weight, muscle mass, and have lower muscle sirtuin-1 (sirt1) expression. Nicotinic acid (NA) is a precursor to nicotinamide dinucleotide (NAD+) which is exhausted in cachectic muscle and is a direct activator of sirt1. Mice lost body and muscle weight and exhibited reduced skeletal muscle sirt1 expression after inoculation with LLC cells. C2C12 myotubes treated with LLC-conditioned media (LCM) had lower myotube diameter. We treated C2C12 myotubes with LCM for 24 h with or without NA for 24 h. C2C12 myotubes treated with NA maintained myotube diameter, sirt1 expression, and had lower mitochondrial superoxide. We then used a sirt1-specific small molecule activator SRT1720 to increase sirt1 activity. C2C12 myotubes treated with SRT1720 maintained myotube diameter, prevented loss of sirt1 expression, and attenuated mitochondrial superoxide production. Our data provides evidence that NA may be beneficial in combating cancer cachexia by maintaining sirt1 expression and decreasing mitochondrial superoxide production.

Nanomedicine-mediated recovery of antioxidant glutathione peroxidase activity after oxidative-stress cellular damage: Insights for neurological long COVID

Nanomedicine for treating post-viral infectious disease syndrome is at an emerging stage. Despite promising results from preclinical studies on conventional antioxidants, their clinical translation as a therapy for treating post-COVID conditions remains challenging. The limitations are due to their low bioavailability, instability, limited transport to the target tissues, and short half-life, requiring frequent and high doses. Activating the immune system during coronavirus (SARS-CoV-2) infection can lead to increased production of reactive oxygen species (ROS), depleted antioxidant reserve, and finally, oxidative stress and neuroinflammation. To tackle this problem, we developed an antioxidant nanotherapy based on lipid (vesicular and cubosomal types) nanoparticles (LNPs) co-encapsulating ginkgolide B and quercetin. The antioxidant-loaded nanocarriers were prepared by a self-assembly method via hydration of a lyophilized mixed thin lipid film. We evaluated the LNPs in a new in vitro model for studying neuronal dysfunction caused by oxidative stress in coronavirus infection. We examined the key downstream signaling pathways that are triggered in response to potassium persulfate (KPS) causing oxidative stress-mediated neurotoxicity. Treatment of neuronally-derived cells (SH-SY5Y) with KPS (50 mM) for 30 min markedly increased mitochondrial dysfunction while depleting the levels of both glutathione peroxidase (GSH-Px) and tyrosine hydroxylase (TH). This led to the sequential activation of apoptotic and necrotic cell death processes, which corroborates with the crucial implication of the two proteins (GSH-Px and TH) in the long-COVID syndrome. Nanomedicine-mediated treatment with ginkgolide B-loaded cubosomes and vesicular LNPs showed minimal cytotoxicity and completely attenuated the KPS-induced cell death process, decreasing apoptosis from 32.6% (KPS) to 19.0% (MO-GB), 12.8% (MO-GB-Quer), 14.8% (DMPC-PEG-GB), and 23.6% (DMPC-PEG-GB-Quer) via free radical scavenging and replenished GSH-Px levels. These findings indicated that GB-LNPs-based nanomedicines may protect against KPS-induced apoptosis by regulating intracellular redox homeostasis.

Cancer Cachexia and breast cancer stem cell signalling - A crosstalk of signalling molecules

Cancer Cachexia is a condition characterized by the involuntary loss of lean body mass, a negative protein and energy balance, and systemic inflammation. This syndrome profoundly impacts the patient's quality of life and is linked to poor chemotherapy response and reduced survival. Despite multiple mechanisms being implicated in its development, and various cytokines believed to contribute to the persistent catabolic state, cachexia is still not fully recognized and is often left untreated. Cachexia is caused by altered metabolic adaptation and lack of anticactic therapy due to systemic cytokines promoting and fuelling cancer growth. The exact molecular mechanisms and clinical endpoints remain poorly defined. It has an occurrence rate of 30%-80%, accounting for 20% of total cancer mortality. Tumor cells remodel the microenvironment suitable for their proliferation, wherein they communicate with fibroblast cells to modulate their expression and induce tumor progressive cytokines. Several studies have reported its strong correlation with systemic cytokines that initiate and aggravate the condition. Plenty of studies show the prominent role of cancer-induced cachexia in pancreatic cancer, colon cancer, and lung cancer. However, limited data are available for breast cancer-induced cachexia, highlighting the need for studying it. Breast cancer stem cells (BCSCs) are a prominently explored area in breast cancer research. They are characterized by CD44+/CD24-/ALDH+ expression and are a focus of cancer research. They are a source of renewal and differentiation within the tumor environment and are responsible for progression, and chemotherapeutic resistance. The tumor microenvironment and its cytokines are responsible for maintaining and inducing their differentiation. Cytokines significantly impact BCSC development and self-renewal, stimulating or inhibiting proliferation depending on cytokine and environment. Pro-inflammatory mediators like IL-6, TNF-α, and IL-8 increase proliferation, promoting tumor growth. Experimental models and clinical studies have shown a direct relationship between cytokines and BCSC proliferation. Several of them seem to be interconnected as they initiate signalling down different pathways but converge at BCSC increase and tumor proliferation. This review highlights the common pathways between cachexia and BCSC signalling, to identify potential therapeutic targets that can aid both conditions.

Skeletal muscle analysis of cancer patients reveals a potential role for carnosine in muscle wasting

BACKGROUND

Muscle wasting during cancer cachexia is mediated by protein degradation via autophagy and ubiquitin-linked proteolysis. These processes are sensitive to changes in intracellular pH ([pH]i ) and reactive oxygen species, which in skeletal muscle are partly regulated by histidyl dipeptides, such as carnosine. These dipeptides, synthesized by the enzyme carnosine synthase (CARNS), remove lipid peroxidation-derived aldehydes, and buffer [pH]i . Nevertheless, their role in muscle wasting has not been studied.

METHODS

Histidyl dipeptides in the rectus abdominis (RA) muscle and red blood cells (RBCs) of male and female controls (n = 37), weight stable (WS: n = 35), and weight losing (WL; n = 30) upper gastrointestinal cancer (UGIC) patients, were profiled by LC-MS/MS. Expression of enzymes and amino acid transporters, involved in carnosine homeostasis, was measured by Western blotting and RT-PCR. Skeletal muscle myotubes were treated with Lewis lung carcinoma conditioned medium (LLC CM), and β-alanine to study the effects of enhancing carnosine production on muscle wasting.

RESULTS

Carnosine was the predominant dipeptide present in the RA muscle. In controls, carnosine levels were higher in men (7.87 ± 1.98 nmol/mg tissue) compared with women (4.73 ± 1.26 nmol/mg tissue; P = 0.002). In men, carnosine was significantly reduced in both the WS (5.92 ± 2.04 nmol/mg tissue, P = 0.009) and WL (6.15 ± 1.90 nmol/mg tissue; P = 0.030) UGIC patients, compared with controls. In women, carnosine was decreased in the WL UGIC (3.42 ± 1.33 nmol/mg tissue; P = 0.050), compared with WS UGIC patients (4.58 ± 1.57 nmol/mg tissue), and controls (P = 0.025). Carnosine was significantly reduced in the combined WL UGIC patients (5.12 ± 2.15 nmol/mg tissue) compared with controls (6.21 ± 2.24 nmol/mg tissue; P = 0.045). Carnosine was also significantly reduced in the RBCs of WL UGIC patients (0.32 ± 0.24 pmol/mg protein), compared with controls (0.49 ± 0.31 pmol/mg protein, P = 0.037) and WS UGIC patients (0.51 ± 0.40 pmol/mg protein, P = 0.042). Depletion of carnosine diminished the aldehyde-removing ability in the muscle of WL UGIC patients. Carnosine levels were positively associated with decreases in skeletal muscle index in the WL UGIC patients. CARNS expression was decreased in the muscle of WL UGIC patients and myotubes treated with LLC-CM. Treatment with β-alanine, a carnosine precursor, enhanced endogenous carnosine production and decreased ubiquitin-linked protein degradation in LLC-CM treated myotubes.

CONCLUSIONS

Depletion of carnosine could contribute to muscle wasting in cancer patients by lowering the aldehyde quenching abilities. Synthesis of carnosine by CARNS in myotubes is particularly affected by tumour derived factors and could contribute to carnosine depletion in WL UGIC patients. Increasing carnosine in skeletal muscle may be an effective therapeutic intervention to prevent muscle wasting in cancer patients.

The culprits of superoxide dismutase inactivation under size-dependent stress of ultrafine carbon black: Superoxide anion, genotoxicity and protein corona

As a critical component of atmospheric ultrafine particulates, ultrafine carbon black (UFCB) brings great exposure risk to organisms. At present, the action pathway and activity regulation mechanism of UFCB on functional proteins in vivo are not clear, and the size-dependent effects of UFCB during this process need to be elucidated. Superoxide dismutase (SOD), one of the most applied biomarkers to assess the environmental impact of pollutants, plays crucial roles in resistance to oxidative stress. Here, based on the inactivation of SOD (84.79 %, 86.81 % and 91.70 %) in primary mouse hepatocytes exposed to UFCB (13 nm, 50 nm and 95 nm), oxidative stress, genotoxicity and protein molecular studies were employed to elucidate the inactivation mechanisms. Results showed that inhibition of UFCB-mediated superoxide anion (O₂^-) contributed to a decrease in SOD activity. Furthermore, the significant increase in 8-hydroxy-2-deoxyguanosine content and the comet tail formation indicated the occurrence of DNA damage, supporting that concomitant aberrant transcriptional and protein translational under gene regulation should be responsible for SOD inactivation. At the molecular level, the constricted backbone, reduced content of α-helix and fluorescence sensitization all demonstrated that the attachment-type binding of SOD on UFCB to form the 'protein corona' disrupted protein structure. Enzyme activity assays indicated that SOD backbone tightening and helix decay resulted in decreased activity, which should be another reason for intracellular SOD inactivation. More importantly, the particle sizes of UFCB exert powerful influences on SOD inactivation mechanisms. Smaller UFCB (13 nm) induced more severe O₂^- inhibition and DNA damage, while UFCB_50nm with the best dispersity bound more SOD and induced stronger molecular toxicity, which are their different strengths in stressing SOD inactivation in hepatocytes. Our findings provide novel insights for exploring functional proteins activity and underscore a potentially size-dependent risk of nanoparticles.

N-acetyloxfenicine strongly induces mitohormesis in mice as well as in insects

Mitohormesis defines the increase in fitness induced by adaptive responses to mild mitochondrial stress. Here, we show that N-acetyloxfenicine (NAO) exerted higher thermotolerance than an endogenous mitohormesis inducer, N-acetyltyrosine (NAT). This activity was not observed in armyworm larvae injected with oxfenicine, suggesting the importance of N-acetylation. NAO-induced hormetic effect was triggered by transient perturbation of mitochondria, which causes a small increase in ROS production and leads to retrograde responses including enhanced expression of antioxidant enzyme genes via activation of FoxO transcription factors. Furthermore, pretreatment with NAO significantly repressed stress-induced peroxidation of lipids in mice and growth of colorectal cancer HCT116 cells that had been transplanted into nude mice. Taken together, NAO is a potent mitohormesis inducer that is similar to NAT in terms of structure and functions.

Metabolic Remodeling in Skeletal Muscle Atrophy as a Therapeutic Target

Skeletal muscle is a highly responsive tissue, able to remodel its size and metabolism in response to external demand. Muscle fibers can vary from fast glycolytic to slow oxidative, and their frequency in a specific muscle is tightly regulated by fiber maturation, innervation, or external causes. Atrophic conditions, including aging, amyotrophic lateral sclerosis, and cancer-induced cachexia, differ in the causative factors and molecular signaling leading to muscle wasting; nevertheless, all of these conditions are characterized by metabolic remodeling, which contributes to the pathological progression of muscle atrophy. Here, we discuss how changes in muscle metabolism can be used as a therapeutic target and review the evidence in support of nutritional interventions and/or physical exercise as tools for counteracting muscle wasting in atrophic conditions.

The Role of Autophagy Modulated by Exercise in Cancer Cachexia

Cancer cachexia is a syndrome experienced by many patients with cancer. Exercise can act as an autophagy modulator, and thus holds the potential to be used to treat cancer cachexia. Autophagy imbalance plays an important role in cancer cachexia, and is correlated to skeletal and cardiac muscle atrophy and energy-wasting in the liver. The molecular mechanism of autophagy modulation in different types of exercise has not yet been clearly defined. This review aims to elaborate on the role of exercise in modulating autophagy in cancer cachexia. We evaluated nine studies in the literature and found a potential correlation between the type of exercise and autophagy modulation. Combined exercise or aerobic exercise alone seems more beneficial than resistance exercise alone in cancer cachexia. Looking ahead, determining the physiological role of autophagy modulated by exercise will support the development of a new medical approach for treating cancer cachexia. In addition, the harmonization of the exercise type, intensity, and duration might play a key role in optimizing the autophagy levels to preserve muscle function and regulate energy utilization in the liver.

Aerobic Exercise Ameliorates Cancer Cachexia-Induced Muscle Wasting through Adiponectin Signaling

Cachexia is a multifactorial syndrome characterized by muscle loss that cannot be reversed by conventional nutritional support. To uncover the molecular basis underlying the onset of cancer cachectic muscle wasting and establish an effective intervention against muscle loss, we used a cancer cachectic mouse model and examined the effects of aerobic exercise. Aerobic exercise successfully suppressed muscle atrophy and activated adiponectin signaling. Next, a cellular model for cancer cachectic muscle atrophy using C2C12 myotubes was prepared by treating myotubes with a conditioned medium from a culture of colon-26 cancer cells. Treatment of the atrophic myotubes with recombinant adiponectin was protective against the thinning of cells through the increased production of p-mTOR and suppression of LC3-II. Altogether, these findings suggest that the activation of adiponectin signaling could be part of the molecular mechanisms by which aerobic exercise ameliorates cancer cachexia-induced muscle wasting.

Reversible Treatment of Pressure Overload-Induced Left Ventricular Hypertrophy through Drd5 Nucleic Acid Delivery Mediated by Functional Polyaminoglycoside

Left ventricular hypertrophy and fibrosis are major risk factors for heart failure, which require timely and effective treatment. Genetic therapy has been shown to ameliorate hypertrophic cardiac damage. In this study, it is found that in mice, the dopamine D5 receptor (D5R) expression in the left ventricle (LV) progressively decreases with worsening of transverse aortic constriction-induced left ventricular hypertrophy. Then, a reversible treatment of left ventricular hypertrophy with Drd5 nucleic acids delivered by tobramycin-based hyperbranched polyaminoglycoside (SS-HPT) is studied. The heart-specific increase in D5R expression by SS-HPT/Drd5 plasmid in the early stage of left ventricular hypertrophy attenuates cardiac hypertrophy and fibrosis by preventing oxidative and endoplasmic reticulum (ER) stress and ameliorating autophagic dysregulation. By contrast, SS-HPT/Drd5 siRNA promotes the progression of left ventricular hypertrophy and accelerates the deterioration of myocardial function into heart failure. The reduction in cardiac D5R expression and dysregulated autophagy are observed in patients with hypertrophic cardiomyopathy and heart failure. The data show a cardiac-specific beneficial effect of SS-HPT/Drd5 plasmid on myocardial remodeling and dysfunction, which may provide an effective therapy of patients with left ventricular hypertrophy and heart failure.

Cancer cachexia in a mouse model of oxidative stress

BACKGROUND

Cancer is associated with muscle atrophy (cancer cachexia) that is linked to up to 40% of cancer-related deaths. Oxidative stress is a critical player in the induction and progression of age-related loss of muscle mass and weakness (sarcopenia); however, the role of oxidative stress in cancer cachexia has not been defined. The purpose of this study was to examine if elevated oxidative stress exacerbates cancer cachexia.

METHODS

Cu/Zn superoxide dismutase knockout (Sod1KO) mice were used as an established mouse model of elevated oxidative stress. Cancer cachexia was induced by injection of one million Lewis lung carcinoma (LLC) cells or phosphate-buffered saline (saline) into the hind flank of female wild-type mice or Sod1KO mice at approximately 4 months of age. The tumour developed for 3 weeks. Muscle mass, contractile function, neuromuscular junction (NMJ) fragmentation, metabolic proteins, mitochondrial function, and motor neuron function were measured in wild-type and Sod1KO saline and tumour-bearing mice. Data were analysed by two-way ANOVA with Tukey-Kramer post hoc test when significant F ratios were determined and α was set at 0.05. Unless otherwise noted, results in abstract are mean ±SEM.

RESULTS

Muscle mass and cross-sectional area were significantly reduced, in tumour-bearing mice. Metabolic enzymes were dysregulated in Sod1KO mice and cancer exacerbated this phenotype. NMJ fragmentation was exacerbated in tumour-bearing Sod1KO mice. Myofibrillar protein degradation increased in tumour-bearing wild-type mice (wild-type saline, 0.00847 ± 0.00205; wildtype LLC, 0.0211 ± 0.00184) and tumour-bearing Sod1KO mice (Sod1KO saline, 0.0180 ± 0.00118; Sod1KO LLC, 0.0490 ± 0.00132). Muscle mitochondrial oxygen consumption was reduced in tumour-bearing mice compared with saline-injected wild-type mice. Mitochondrial protein degradation increased in tumour-bearing wild-type mice (wild-type saline, 0.0204 ± 0.00159; wild-type LLC, 0.167 ± 0.00157) and tumour-bearing Sod1KO mice (Sod1KO saline, 0.0231 ± 0.00108; Sod1 KO LLC, 0.0645 ± 0.000631). Sciatic nerve conduction velocity was decreased in tumour-bearing wild-type mice (wild-type saline, 38.2 ± 0.861; wild-type LLC, 28.8 ± 0.772). Three out of eleven of the tumour-bearing Sod1KO mice did not survive the 3-week period following tumour implantation.

CONCLUSIONS

Oxidative stress does not exacerbate cancer-induced muscle loss; however, cancer cachexia may accelerate NMJ disruption.

Cell autonomous requirement of neurofibromin (Nf1) for postnatal muscle hypertrophic growth and metabolic homeostasis

BACKGROUND

Neurofibromatosis type 1 (NF1) is a multi-organ disease caused by mutations in neurofibromin 1 (NF1). Amongst other features, NF1 patients frequently show reduced muscle mass and strength, impairing patients' mobility and increasing the risk of fall. The role of Nf1 in muscle and the cause for the NF1-associated myopathy are mostly unknown.

METHODS

To dissect the function of Nf1 in muscle, we created muscle-specific knockout mouse models for NF1, inactivating Nf1 in the prenatal myogenic lineage either under the Lbx1 promoter or under the Myf5 promoter. Mice were analysed during prenatal and postnatal myogenesis and muscle growth.

RESULTS

Nf1^Lbx1 and Nf1^Myf5 animals showed only mild defects in prenatal myogenesis. Nf1^Lbx1 animals were perinatally lethal, while Nf1^Myf5 animals survived only up to approximately 25 weeks. A comprehensive phenotypic characterization of Nf1^Myf5 animals showed decreased postnatal growth, reduced muscle size, and fast fibre atrophy. Proteome and transcriptome analyses of muscle tissue indicated decreased protein synthesis and increased proteasomal degradation, and decreased glycolytic and increased oxidative activity in muscle tissue. High-resolution respirometry confirmed enhanced oxidative metabolism in Nf1^Myf5 muscles, which was concomitant to a fibre type shift from type 2B to type 2A and type 1. Moreover, Nf1^Myf5 muscles showed hallmarks of decreased activation of mTORC1 and increased expression of atrogenes. Remarkably, loss of Nf1 promoted a robust activation of AMPK with a gene expression profile indicative of increased fatty acid catabolism. Additionally, we observed a strong induction of genes encoding catabolic cytokines in muscle Nf1^Myf5 animals, in line with a drastic reduction of white, but not brown adipose tissue.

CONCLUSIONS

Our results demonstrate a cell autonomous role for Nf1 in myogenic cells during postnatal muscle growth required for metabolic and proteostatic homeostasis. Furthermore, Nf1 deficiency in muscle drives cross-tissue communication and mobilization of lipid reserves.

Nutraceuticals and Exercise against Muscle Wasting during Cancer Cachexia

Cancer cachexia (CC) is a debilitating multifactorial syndrome, involving progressive deterioration and functional impairment of skeletal muscles. It affects about 80% of patients with advanced cancer and causes premature death. No causal therapy is available against CC. In the last few decades, our understanding of the mechanisms contributing to muscle wasting during cancer has markedly increased. Both inflammation and oxidative stress (OS) alter anabolic and catabolic signaling pathways mostly culminating with muscle depletion. Several preclinical studies have emphasized the beneficial roles of several classes of nutraceuticals and modes of physical exercise, but their efficacy in CC patients remains scant. The route of nutraceutical administration is critical to increase its bioavailability and achieve the desired anti-cachexia effects. Accumulating evidence suggests that a single therapy may not be enough, and a bimodal intervention (nutraceuticals plus exercise) may be a more effective treatment for CC. This review focuses on the current state of the field on the role of inflammation and OS in the pathogenesis of muscle atrophy during CC, and how nutraceuticals and physical activity may act synergistically to limit muscle wasting and dysfunction.

Pharmacological targeting of mitochondrial function and reactive oxygen species production prevents colon 26 cancer-induced cardiorespiratory muscle weakness

Cancer cachexia is a syndrome characterized by profound cardiac and diaphragm muscle wasting, which increase the risk of morbidity in cancer patients due to failure of the cardiorespiratory system. In this regard, muscle relies greatly on mitochondria to meet energy requirements for contraction and mitochondrial dysfunction can result in muscle weakness and fatigue. In addition, mitochondria are a major source of reactive oxygen species (ROS) production, which can stimulate increased rates of muscle protein degradation. Therefore, it has been suggested that mitochondrial dysfunction may be an underlying factor that contributes to the pathology of cancer cachexia. To determine if pharmacologically targeting mitochondrial dysfunction via treatment with the mitochondria-targeting peptide SS-31 would prevent cardiorespiratory muscle dysfunction, colon 26 (C26) adenocarcinoma tumor-bearing mice were administered either saline or SS-31 daily (3 mg/kg/day) following inoculation. C26 mice treated with saline demonstrated greater ROS production and mitochondrial uncoupling compared to C26 mice receiving SS-31 in both the heart and diaphragm muscle. In addition, saline-treated C26 mice exhibited a decline in left ventricular function which was significantly rescued in C26 mice treated with SS-31. In the diaphragm, muscle fiber cross-sectional area of C26 mice treated with saline was significantly reduced and force production was impaired compared to C26, SS-31-treated animals. Finally, ventilatory deficits were also attenuated in C26 mice treated with SS-31, compared to saline treatment. These data demonstrate that C26 tumors promote severe cardiac and respiratory myopathy, and that prevention of mitochondrial dysfunction is sufficient to preclude cancer cachexia-induced cardiorespiratory dysfunction.

The Redox Balance: A Target for Interventions Against Muscle Wasting in Cancer Cachexia?

Significance: The management of cancer patients is frequently complicated by the occurrence of a complex syndrome known as cachexia. It is mainly characterized by muscle wasting, a condition that associates with enhanced protein breakdown and with negative energy balance. While the mechanisms underlying cachexia have been only partially elucidated, understanding the pathogenesis of muscle wasting in cancer hosts is mandatory to design new targeted therapeutic strategies. Indeed, most of cancer patients will experience cachexia during the course of their disease, and about 25% of cancer-related deaths are due to this syndrome, rather than to the tumor itself. Recent Advances: Compelling evidence suggests that an altered redox homeostasis likely contributes to cancer-induced muscle protein depletion, directly or indirectly activating the intracellular degradative pathways. In addition, oxidative stress impinges on both mitochondrial number and function; the other way round, altered mitochondria lead to enhanced redox imbalance, creating a vicious loop that eventually results in negative energy metabolism. Critical Issues: The present review focuses on the possibility that pharmacological and nonpharmacological strategies able to restore a physiologic redox balance could be useful components of treatment schedules aimed at counteracting cancer-induced muscle wasting. Future Directions: Exercise and the use of exercise mimetic drugs represent the most promising approaches capable of reinforcing the muscle antioxidant defenses of cancer patients. The results from ongoing and new clinical trials are needed to validate the preclinical studies and provide effective therapies for cancer cachexia. Antioxid. Redox Signal. 33, 542-558.

Bioenergetic defects in muscle fibers of RYR1 mutant knock-in mice associated with malignant hyperthermia

Mutations in the skeletal muscle ryanodine receptor gene (RYR1) can cause susceptibility to malignant hyperthermia (MH), a potentially lethal genetic condition triggered by volatile anesthetics. MH is associated with hypermetabolism, which has directed research interest into oxidative phosphorylation and muscle bioenergetics. The most common cause of MH in the United Kingdom is the c.7300G>A RYR1 variant, which is present in ∼16% of MH families. Our study focuses on the MH susceptible G2435R-RYR1 knock-in mouse model, which is the murine equivalent of the human c.7300G>A genotype. Using a combination of transcriptomics, protein expression, and functional analysis, we investigated adult muscle fiber bioenergetics in this mouse model. RNA-Seq data showed reduced expression of genes associated with mitochondria and fatty acid oxidation in RYR1 mutants when compared with WT controls. Mitochondrial function was assessed by measuring oxygen consumption rates in permeabilized muscle fibers. Comparisons between WT and homozygous G2435R-RYR1 mitochondria showed a significant increase in complex I-facilitated oxidative phosphorylation in mutant muscle. Furthermore, we observed a gene-dose-specific increase in reactive oxygen species production in G2435R-RYR1 muscle fibers. Collectively, these findings provide evidence of metabolic defects in G2435R-RYR1 knock-in mouse muscle under basal conditions. Differences in metabolic profile could be the result of differential gene expression in metabolic pathways, in conjunction with mitochondrial damage accumulated from chronic exposure to increased oxidative stress.

Mitochondrial Metabolism in Cancer Cachexia: Novel Drug Target

BACKGROUND

Cancer cachexia is a metabolic syndrome prevalent in the majority of the advanced cancers and is associated with complications such as anorexia, early satiety, weakness, anaemia, and edema, thereby reducing performance and impairing quality of life. Skeletal muscle wasting is a characteristic feature of cancer-cachexia and mitochondria is responsible for regulating total protein turnover in skeletal muscle tissue.

METHODS

We carried out exhaustive search for cancer cachexia and role of mitochondria in the same in various databases. All the relevant articles were gathered and the pertinent information was extracted out and compiled which was further structured into different sub-sections.

RESULTS

Various findings on the mitochondrial alterations in connection to its disturbed normal physiology in various models of cancer-cachexia have been recently reported, suggesting a significant role of the organelle in the pathogenesis of the complications involved in the disorder. It has also been reported that reduced mitochondrial oxidative capacity is due to reduced mitochondrial biogenesis as well as altered balance between fusion and fission protein activities. Moreover, autophagy in mitochondria (termed as mitophagy) is reported to play an important role in cancer cachexia.

CONCLUSION

The present review aims to put forth the changes occurring in mitochondria and hence explore possible targets which can be exploited in cancer-induced cachexia for treatment of such a debilitating condition.

The Emerging Roles of Nicotinamide Adenine Dinucleotide Phosphate Oxidase 2 in Skeletal Muscle Redox Signaling and Metabolism

Significance: Skeletal muscle is a crucial tissue to whole-body locomotion and metabolic health. Reactive oxygen species (ROS) have emerged as intracellular messengers participating in both physiological and pathological adaptations in skeletal muscle. A complex interplay between ROS-producing enzymes and antioxidant networks exists in different subcellular compartments of mature skeletal muscle. Recent evidence suggests that nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOXs) are a major source of contraction- and insulin-stimulated oxidants production, but they may paradoxically also contribute to muscle insulin resistance and atrophy. Recent Advances: Pharmacological and molecular biological tools, including redox-sensitive probes and transgenic mouse models, have generated novel insights into compartmentalized redox signaling and suggested that NOX2 contributes to redox control of skeletal muscle metabolism. Critical Issues: Major outstanding questions in skeletal muscle include where NOX2 activation occurs under different conditions in health and disease, how NOX2 activation is regulated, how superoxide/hydrogen peroxide generated by NOX2 reaches the cytosol, what the signaling mediators are downstream of NOX2, and the role of NOX2 for different physiological and pathophysiological processes. Future Directions: Future research should utilize and expand the current redox-signaling toolbox to clarify the NOX2-dependent mechanisms in skeletal muscle and determine whether the proposed functions of NOX2 in cells and animal models are conserved into humans.

Arterial stiffness induced by carotid calcification leads to cerebral gliosis mediated by oxidative stress

BACKGROUND

Arterial stiffness is a risk factor for cognitive decline and dementia. However, its precise effects on the brain remain unexplored. Using a mouse model of carotid stiffness, we investigated its effect on glial activation and oxidative stress.

METHODS

Arterial stiffness was induced by the application of calcium chloride to the adventitial region of the right carotid. Superoxide anion production, NADPH activity and levels, as well as glial activation were examined with immunohistochemical and biochemical approaches, 2-week postcalcification. Antioxidant treatment was done with Tempol (1 mmol/l) administered in the drinking water during 2 weeks.

RESULTS

The current study revealed that arterial stiffness increases the levels of the microglial markers ionized calcium-binding adapter molecule 1 and cluster of differentiation 68 in hippocampus, and of the astrocyte marker, s100 calcium binding protein β in hippocampus and frontal cortex. The cerebral inflammatory effects of arterial stiffness were specific to the brain and not due to systemic inflammation. Treatment with Tempol prevented the increase in superoxide anion in mice with carotid stiffness and attenuated the activation of microglia and astrocytes in the hippocampus. To determine whether the increased oxidative stress derives from NADPH oxidase, superoxide anion production was assessed by incubating brain tissue in the presence of gp91ds-tat, a selective NADPH oxidase 2 inhibitor. This peptide inhibited superoxide anion production to a greater extent in the brains of mice with carotid calcification compared with controls.

CONCLUSION

Carotid calcification leads to cerebral gliosis mediated by oxidative stress. Correcting arterial stiffness could offer a novel paradigm to protect the brain in populations where stiffness is prominent.

Moderate Exercise Improves Experimental Cancer Cachexia by Modulating the Redox Homeostasis

Cachexia is a debilitating syndrome that complicates the management of cancer patients. Muscle wasting, one of the main features of cachexia, is associated with hyper-activation of protein degradative pathways and altered mitochondrial function that could both result from impaired redox homeostasis. This study aimed to investigate the contribution of oxidative stress to cancer-induced cachexia in the presence or in the absence of moderate exercise training. Mice bearing the colon C26 carcinoma, either sedentary or exercised, were used. The former showed muscle wasting and redox imbalance, with the activation of an antioxidant response and with upregulation of markers of proteasome-dependent protein degradation and autophagy. Moderate exercise was able to relieve muscle wasting and prevented the loss of muscle strength; such a pattern was associated with reduced levels of Reactive Oxygen Species (ROS), carbonylated proteins and markers of autophagy and with improved antioxidant capacity. The muscle of sedentary tumor hosts also showed increased levels of molecular markers of mitophagy and reduced mitochondrial mass. Conversely, exercise in the C26 hosts led to increased mitochondrial mass. In conclusion, moderate exercise could be an effective non-pharmacological approach to prevent muscle wasting in cancer patients, decreasing muscle protein catabolism and oxidative stress and preserving mitochondria.

The Skeletal Muscle as an Active Player Against Cancer Cachexia

The management of cancer patients is frequently complicated by the occurrence of cachexia. This is a complex syndrome that markedly impacts on quality of life as well as on tolerance and response to anticancer treatments. Loss of body weight, wasting of both adipose tissue and skeletal muscle and reduced survival rates are among the main features of cachexia. Skeletal muscle wasting has been shown to depend, mainly at least, on the induction of protein degradation rates above physiological levels. Such hypercatabolic pattern is driven by overactivation of different intracellular proteolytic systems, among which those dependent on ubiquitin-proteasome and autophagy. Selective rather than bulk degradation of altered proteins and organelles was also proposed to occur. Within the picture described above, the muscle is frequently considered a sort of by-stander tissue where external stimuli, directly or indirectly, can poise protein metabolism toward a catabolic setting. By contrast, several observations suggest that the muscle reacts to the wasting drive imposed by cancer growth by activating different compensatory strategies that include anabolic capacity, the activation of autophagy and myogenesis. Even if muscle response is eventually ill-fated, its occurrence supports the idea that in the presence of appropriate treatments the development of cancer-induced wasting might not be an ineluctable event in tumor hosts.

Mitochondrial dynamics in cancer-induced cachexia

Cancer-induced cachexia has a negative impact on quality of life and adversely affects therapeutic outcomes and survival rates. It is characterized by, often severe, loss of muscle, with or without loss of fat mass. Insight in the pathophysiology of this complex metabolic syndrome and direct treatment options are still limited, which creates a research demand. Results from recent studies point towards a significant involvement of muscle mitochondrial networks. However, data are scattered and a comprehensive overview is lacking. This paper aims to fill existing knowledge gaps by integrating published data sets on muscle protein or gene expression from cancer-induced cachexia animal models. To this end, a database was compiled from 94 research papers, comprising 11 different rodent models. This was combined with four genome-wide transcriptome datasets of cancer-induced cachexia rodent models. Analysis showed that the expression of genes involved in mitochondrial fusion, fission, ATP production and mitochondrial density is decreased, while that of genes involved ROS detoxification and mitophagy is increased. Our results underline the relevance of including post-translational modifications of key proteins involved in mitochondrial functioning in future studies on cancer-induced cachexia.

Over-expression of a cardiac-specific human dopamine D5 receptor mutation in mice causes a dilated cardiomyopathy through ROS over-generation by NADPH oxidase activation and Nrf2 degradation

Dilated cardiomyopathy (DCM) is a severe disorder caused by medications or genetic mutations. D₅ dopamine receptor (D5R) gene knockout (D5^-/-) mice have cardiac hypertrophy and high blood pressure. To investigate the role and mechanism by which the D5R regulates cardiac function, we generated cardiac-specific human D5R F173L(hD5^F173L-TG) and cardiac-specific human D5R wild-type (hD5^WT-TG) transgenic mice, and H9c2 cells stably expressing hD5^F173L and hD5^WT. We found that cardiac-specific hD5^F173L-TG mice, relative to hD5^WT-TG mice, presented with DCM and increased cardiac expression of cardiac injury markers, NADPH oxidase activity, Nrf2 degradation, and activated ERK1/2/JNK pathway. H9c2-hD5^F173L cells also had an increase in NADPH oxidase activity, Nrf2 degradation, and phospho-JNK (p-JNK) expression. A Nrf2 inhibitor also increased p-JNK expression in H9c2-hD5^F173L cells but not in H9c2-hD5^WT cells. We suggest that the D5R may play an important role in the preservation of normal heart function by inhibiting the production of reactive oxygen species, via inhibition of NADPH oxidase, Nrf2 degradation, and ERK1/2/JNK pathways.

Role of Oxidative Stress as Key Regulator of Muscle Wasting during Cachexia

Skeletal muscle atrophy is a pathological condition mainly characterized by a loss of muscular mass and the contractile capacity of the skeletal muscle as a consequence of muscular weakness and decreased force generation. Cachexia is defined as a pathological condition secondary to illness characterized by the progressive loss of muscle mass with or without loss of fat mass and with concomitant diminution of muscle strength. The molecular mechanisms involved in cachexia include oxidative stress, protein synthesis/degradation imbalance, autophagy deregulation, increased myonuclear apoptosis, and mitochondrial dysfunction. Oxidative stress is one of the most common mechanisms of cachexia caused by different factors. It results in increased ROS levels, increased oxidation-dependent protein modification, and decreased antioxidant system functions. In this review, we will describe the importance of oxidative stress in skeletal muscles, its sources, and how it can regulate protein synthesis/degradation imbalance, autophagy deregulation, increased myonuclear apoptosis, and mitochondrial dysfunction involved in cachexia.

Mitochondrial degeneration precedes the development of muscle atrophy in progression of cancer cachexia in tumour-bearing mice

BACKGROUND

Cancer cachexia is largely irreversible, at least via nutritional means, and responsible for 20-40% of cancer-related deaths. Therefore, preventive measures are of primary importance; however, little is known about muscle perturbations prior to onset of cachexia. Cancer cachexia is associated with mitochondrial degeneration; yet, it remains to be determined if mitochondrial degeneration precedes muscle wasting in cancer cachexia. Therefore, our purpose was to determine if mitochondrial degeneration precedes cancer-induced muscle wasting in tumour-bearing mice.

METHODS

First, weight-stable (MinStable) and cachectic (MinCC) ApcMin/+ mice were compared with C57Bl6/J controls for mRNA contents of mitochondrial quality regulators in quadriceps muscle. Next, Lewis lung carcinoma (LLC) cells or PBS (control) were injected into the hind flank of C57Bl6/J mice at 8 week age, and tumour allowed to develop for 1, 2, 3, or 4 weeks to examine time course of cachectic development. Succinate dehydrogenase stain was used to measure oxidative phenotype in tibialis anterior muscle. Mitochondrial quality and function were assessed using the reporter MitoTimer by transfection to flexor digitorum brevis and mitochondrial function/ROS emission in permeabilized adult myofibres from plantaris. RT-qPCR and immunoblot measured the expression of mitochondrial quality control and antioxidant proteins. Data were analysed by one-way ANOVA with Student-Newman-Kuels post hoc test.

RESULTS

MinStable mice displayed ~50% lower Pgc-1α, Pparα, and Mfn2 compared with C57Bl6/J controls, whereas MinCC exhibited 10-fold greater Bnip3 content compared with C57Bl6/J controls. In LLC, cachectic muscle loss was evident only at 4 weeks post-tumour implantation. Oxidative capacity and mitochondrial content decreased by ~40% 4 weeks post-tumour implantation. Mitochondrial function decreased by ~25% by 3 weeks after tumour implantation. Mitochondrial degeneration was evident by 2 week LLC compared with PBS control, indicated by MitoTimer red/green ratio and number of pure red puncta. Mitochondrial ROS production was elevated by ~50 to ~100% when compared with PBS at 1-3 weeks post-tumour implantation. Mitochondrial quality control was dysregulated throughout the progression of cancer cachexia in tumour-bearing mice. In contrast, antioxidant proteins were not altered in cachectic muscle wasting.

CONCLUSIONS

Functional mitochondrial degeneration is evident in LLC tumour-bearing mice prior to muscle atrophy. Contents of mitochondrial quality regulators across ApcMin/+ and LLC mice suggest impaired mitochondrial quality control as a commonality among pre-clinical models of cancer cachexia. Our data provide novel evidence for impaired mitochondrial health prior to cachectic muscle loss and provide a potential therapeutic target to prevent cancer cachexia.

Redox Control of Skeletal Muscle Regeneration

Skeletal muscle shows high plasticity in response to external demand. Moreover, adult skeletal muscle is capable of complete regeneration after injury, due to the properties of muscle stem cells (MuSCs), the satellite cells, which follow a tightly regulated myogenic program to generate both new myofibers and new MuSCs for further needs. Although reactive oxygen species (ROS) and reactive nitrogen species (RNS) have long been associated with skeletal muscle physiology, their implication in the cell and molecular processes at work during muscle regeneration is more recent. This review focuses on redox regulation during skeletal muscle regeneration. An overview of the basics of ROS/RNS and antioxidant chemistry and biology occurring in skeletal muscle is first provided. Then, the comprehensive knowledge on redox regulation of MuSCs and their surrounding cell partners (macrophages, endothelial cells) during skeletal muscle regeneration is presented in normal muscle and in specific physiological (exercise-induced muscle damage, aging) and pathological (muscular dystrophies) contexts. Recent advances in the comprehension of these processes has led to the development of therapeutic assays using antioxidant supplementation, which result in inconsistent efficiency, underlying the need for new tools that are aimed at precisely deciphering and targeting ROS networks. This review should provide an overall insight of the redox regulation of skeletal muscle regeneration while highlighting the limits of the use of nonspecific antioxidants to improve muscle function. Antioxid. Redox Signal. 27, 276-310.

Reactive Oxygen Species/Nitric Oxide Mediated Inter-Organ Communication in Skeletal Muscle Wasting Diseases

SIGNIFICANCE

Cachexia is defined as a complex metabolic syndrome that is associated with underlying illness and a loss of muscle with or without loss of fat mass. This disease is associated with a high incidence with chronic diseases such as heart failure, cancer, chronic obstructive pulmonary disease (COPD), and acquired immunodeficiency syndrome (AIDS), among others. Since there is currently no effective treatment available, cachectic patients have a poor prognosis. Elucidation of the underlying mechanisms is, therefore, an important medical task. Recent Advances: There is accumulating evidence that the diseased organs such as heart, lung, kidney, or cancer tissue secrete soluble factors, including Angiotensin II, myostatin (growth differentiation factor 8 [GDF8]), GDF11, tumor growth factor beta (TGFβ), which act on skeletal muscle. There, they induce a set of genes called atrogenes, which, among others, induce the ubiquitin-proteasome system, leading to protein degradation. Moreover, elevated reactive oxygen species (ROS) levels due to modulation of NADPH oxidases (Nox) and mitochondrial function contribute to disease progression, which is characterized by loss of muscle mass, exercise resistance, and frailty.

CRITICAL ISSUES

Although substantial progress was achieved to elucidate the pathophysiology of cachexia, effectice therapeutic strategies are urgently needed.

FUTURE DIRECTIONS

With the identification of key components of the aberrant inter-organ communication leading to cachexia, studies in mice and men to inhibit ROS formation, induction of anti-oxidative superoxide dismutases, and upregulation of muscular nitric oxide (NO) formation either by pharmacological tools or by exercise are promising approaches to reduce the extent of skeletal muscle wasting. Antioxid. Redox Signal. 26, 700-717.

The Janus-Faced Role of Antioxidants in Cancer Cachexia: New Insights on the Established Concepts

Chronic inflammation and excessive loss of skeletal muscle usually occur during cancer cachexia, leading to functional impairment and delaying the cure of cancer. The release of cytokines by tumor promotes the formation of reactive oxygen species (ROS), which in turn regulate catabolic pathways involved in muscle atrophy. ROS also exert a dual role within tumor itself, as they can either promote proliferation and vascularization or induce senescence and apoptosis. Accordingly, previous studies that used antioxidants to modulate these ROS-dependent mechanisms, in cancer and cancer cachexia, have obtained contradictory results, hence the need to gather the main findings of these studies and draw global conclusions in order to stimulate more oriented research in this field. Based on the literature reviewed in this paper, it appears that antioxidant supplementation is (1) beneficial in cancer cachectic patients with antioxidant deficiencies, (2) most likely harmful in cancer patients with adequate antioxidant status (i.e., lung, gastrointestinal, head and neck, and esophageal), and (3) not recommended when undergoing radiotherapy. At the moment, measuring the blood levels of antioxidants may help to identify patients with systemic deficiencies. This approach is simple to realize but could not be a gold standard method for cachexia, as it does not necessarily reflect the redox state in other organs, like muscle.

Epigenetic Regulatory Effect of Exercise on Glutathione Peroxidase 1 Expression in the Skeletal Muscle of Severely Dyslipidemic Mice

Exercise is an effective approach for primary and secondary prevention of cardiovascular diseases (CVD) and loss of muscular mass and function. Its benefits are widely documented but incompletely characterized. It has been reported that exercise can induce changes in the expression of antioxidant enzymes including Sod2, Trx1, Prdx3 and Gpx1 and limits the rise in oxidative stress commonly associated with CVD. These enzymes can be subjected to epigenetic regulation, such as DNA methylation, in response to environmental cues. The aim of our study was to determine whether in the early stages of atherogenesis, in young severely dyslipidemic mice lacking LDL receptors and overexpressing human ApoB100 (LDLR-/-; hApoB+/+), exercise regulates differentially the expression of antioxidant enzymes by DNA methylation in the skeletal muscles that consume high levels of oxygen and thus generate high levels of reactive oxygen species. Expression of Sod2, Txr1, Prdx3 and Gpx1 was altered by 3 months of exercise and/or severe dyslipidemia in 6-mo dyslipidemic mice. Of these genes, only Gpx1 exhibited changes in DNA methylation associated with dyslipidemia and exercise: we observed both increased DNA methylation with dyslipidemia and a transient decrease in DNA methylation with exercise. These epigenetic alterations are found in the second exon of the Gpx1 gene and occur alongside with inverse changes in mRNA expression. Inhibition of expression by methylation of this specific locus was confirmed in vitro. In conclusion, Gpx1 expression in the mouse skeletal muscle can be altered by both exercise and dyslipidemia through changes in DNA methylation, leading to a fine regulation of free radical metabolism.

Transforming growth factor type beta (TGF-β) requires reactive oxygen species to induce skeletal muscle atrophy

Transforming growth factor beta 1 (TGF-β1) is a classical modulator of skeletal muscle and regulates several processes, such as myogenesis, regeneration, and muscle function in skeletal muscle diseases. Skeletal muscle atrophy, characterised by the loss of muscle strength and mass, is one of the pathological conditions regulated by TGF-β. Atrophy also results in increased myosin heavy chain (MHC) degradation and the expression of two muscle-specific E3 ubiquitin ligases, atrogin-1 and MuRF-1. Reactive oxygen species (ROS) are modulators of muscle wasting, and NAD(P)H oxidase (NOX) is one of the main sources of ROS. While it was recently found that TGF-β1 induces atrophy in skeletal muscle, the underlying mechanism is not fully understood. In this study, the role of NOX-derived ROS in skeletal muscle atrophy induced by TGF-β was assessed. TGF-β1 induced an atrophic effect in C2C12 myotubes, as evidenced by decreased myotube diameter and MHC levels, together with increased MuRF-1 levels. Concomitantly, TGF-β increased NOX-induced ROS contents. Interestingly, NOX inhibition through apocynin and the antioxidant treatment with N-acetyl cysteine (NAC) decreased increased ROS levels in myotubes. Additionally, both apocynin and NAC completely prevented the decreased MHC, decreased myotube diameter, and increased MuRF-1 induced by TGF-β. Injection of TGF-β1 into the tibialis anterior muscle induced atrophy, as observed by decreased fibre diameter and MHC levels, together with increased MuRF-1 levels. Likewise, TGF-β increased the ROS contents in the smaller fibres of skeletal muscle. Additionally, the administration of NAC to mice prevented all atrophic effects and the increase in ROS induced by TGF-β in the tibialis anterior. This is the first study to report that TGF-β has an atrophic effect dependent on NOX-induced ROS in skeletal muscle.

Systemic Inflammation in Cachexia - Is Tumor Cytokine Expression Profile the Culprit?

Cachexia affects about 80% of gastrointestinal cancer patients. This multifactorial syndrome resulting in involuntary and continuous weight loss is accompanied by systemic inflammation and immune cell infiltration in various tissues. Understanding the interactions among tumor, immune cells, and peripheral tissues could help attenuating systemic inflammation. Therefore, we investigated inflammation in the subcutaneous adipose tissue and in the tumor, in weight stable and cachectic cancer patients with same diagnosis, in order to establish correlations between tumor microenvironment and secretory pattern with adipose tissue and systemic inflammation. Infiltrating monocyte phenotypes of subcutaneous and tumor vascular-stromal fraction were identified by flow cytometry. Gene and protein expression of inflammatory and chemotactic factors was measured with qRT-PCR and Multiplex Magpix(®) system, respectively. Subcutaneous vascular-stromal fraction exhibited no differences in regard to macrophage subtypes, while in the tumor, the percentage of M2 macrophages was decreased in the cachectic patients, in comparison to weight-stable counterparts. CCL3, CCL4, and IL-1β expression was higher in the adipose tissue and tumor tissue in the cachectic group. In both tissues, chemotactic factors were positively correlated with IL-1β. Furthermore, positive correlations were found for the content of chemoattractants and cytokines in the tumor and adipose tissue. The results strongly suggest that the crosstalk between the tumor and peripheral tissues is more pronounced in cachectic patients, compared to weight-stable patients with the same tumor diagnosis.

Inhibition of UVB-induced skin damage by exopolymers from Aureobasidium pullulans SM-2001 in hairless mice

Because antioxidants from natural sources may be an effective approach to the treatment and prevention of UV radiation-induced skin damage, the effects of purified exopolymers from Aureobasidium pullulans SM-2001 ('E-AP-SM2001') were evaluated in UVB-induced hairless mice. E-AP-SM2001 consists of 1.7% β-1,3/1,6-glucan, fibrous polysaccharides and other organic materials, such as amino acids, and mono- and di-unsaturated fatty acids (linoleic and linolenic acids) and shows anti-osteoporotic and immunomodulatory effects, through antioxidant and anti-inflammatory mechanisms. Hairless mice were treated topically with vehicle, E-AP-SM2001 stock and two and four times diluted solutions once per day for 15 weeks against UVB irradiation (three times per week at 0.18 J/cm(2) ). The following parameters were evaluated in skin samples: myeloperoxidase (MPO) activity, cytokine levels [interleukin (IL)-1β and IL-10], endogenous antioxidant content (glutathione, GSH), malondialdehyde (MDA) levels, superoxide anion production; matrix metalloproteases (MMP-1, -9 and -13), GSH reductase and Nox2 (gp91phox) mRNA levels, and immunoreactivity for nitrotyrosine (NT), 4-hydroxynonenal (HNE), caspase-3, and cleaved poly(ADP-ribose) polymerase (PARP). Photoageing was induced by UVB irradiation through ROS-mediated inflammation, which was related to the depletion of endogenous antioxidants, activation of MMPs and keratinocyte apoptosis. Topical treatment with all three doses of E-AP-SM2001 and 5 nm myricetin attenuated the UV-induced depletion of GSH, activation of MMPs, production of IL-1β, the decrease in IL-10 and keratinocyte apoptosis. In this study, E-AP-SM2001 showed potent inhibitory effects against UVB-induced skin photoageing. Thus, E-AP-SM2001 may be useful as a functional ingredient in cosmetics, especially as a protective agent against UVB-induced skin photoageing.

Disruption of pro-oxidant and antioxidant systems with elevated expression of the ubiquitin proteosome system in the cachectic heart muscle of nude mice

BACKGROUND

Current research into the mechanisms of organ atrophy associated with cancer cachexia have centred on the loss of skeletal muscle, as it is one of the most profound physical changes of the disease. However, many patients with cancer cachexia also experience significant atrophy of the heart. The mechanisms causing cardiac tissue wastage in cancer cachexia are largely unknown. However, it is believed to involve a number of molecular interactions between the tumour and host. Increased levels of oxidative stress have been found in cancer cachectic skeletal muscle and has been linked to the activation of the ubiquitin proteosome system (UPS). The aim of the current study was to examine the role of oxidative stress and the UPS in the hearts of mice with cancer cachexia.

METHODS

Oxidative damage to DNA (8-OH-2dG), mRNA levels of the ROS-producing enzymes NADPH oxidase (NOX), and xanthine oxidase (XDH), the antioxidant enzyme superoxide dismutase (SOD) and key components of the UPS was measured in the heart of mice with cancer cachexia. Protein expression levels of NOX enzyme subunits and SOD enzyme activity was also measured in the same heart samples.

RESULTS

8-OH-2dG levels were 1.5-fold higher in the heart of mice with cancer cachexia, and this was associated with a 1.7-fold lower level of NOX2 mRNA and twofold higher XDH mRNA in the same hearts. Cancer cachexia was also associated with a 1.5-fold lower level of SOD activity in the heart. Accompanying these pro- and antioxidant differences was a significantly higher level of mRNA for the key UPS elements MURF-1 (4.3=fold) and MAFbx (3.8-fold) in the hearts of mice with cancer cachexia.

CONCLUSIONS

The current study demonstrated that cardiac atrophy of cachectic mice is associated with oxidative damage to DNA in the myocardium. The higher levels of XDH mRNA in cachectic hearts suggest that xanthine oxidase may have an important role to play in producing oxidative stress. It appears that the combination of higher XDH expression and lower SOD enzyme activity are key contributors to oxidative stress and cardiac tissue damage in cancer-induced cardiac atrophy. Oxidative stress in the myocardium as with skeletal muscle may also induce increased expression of the E3 ligases MURF-1 and MAFbx as seen in this study.

Urotensin II inhibits skeletal muscle glucose transport signaling pathways via the NADPH oxidase pathway

Our previous studies have demonstrated that the urotensin (UII) and its receptor are up-regulated in the skeletal muscle of mice with type II diabetes mellitus (T2DM), but the significance of UII in skeletal muscle insulin resistance remains unknown. The purpose of this study was to investigate the effect of UII on NADPH oxidase and glucose transport signaling pathways in the skeletal muscle of mice with T2DM and in C2C12 mouse myotube cells. KK/upj-AY/J mice (KK) mice were divided into the following groups: KK group, with saline treatment for 2 weeks; KK+ urantide group, with daily 30 µg/kg body weight injections over the same time period of urantide, a potent urotensin II antagonist peptide; Non-diabetic C57BL/6J mice were used as normal controls. After urantide treatment, mice were subjected to an intraperitoneal glucose tolerance test, in addition to measurements of the levels of ROS, NADPH oxidase and the phosphorylated AKT, PKC and ERK. C2C12 cells were incubated with serum-free DMEM for 24 hours before conducting the experiments, and then administrated with 100 nM UII for 2 hours or 24 hours. Urantide treatment improved glucose tolerance, decreased the translocation of the NADPH subunits p40-phox and p47-phox, and increased levels of the phosphorylated PKC, AKT and ERK. In contrast, UII treatment increased ROS production and p47-phox and p67-phox translocation, and decreased the phosphorylated AKT, ERK1/2 and p38MAPK; Apocynin abrogated this effect. In conclusion, UII increased ROS production by NADPH oxidase, leading to the inhibition of signaling pathways involving glucose transport, such as AKT/PKC/ERK. Our data imply a role for UII at the molecular level in glucose homeostasis, and possibly in skeletal muscle insulin resistance in T2DM.

Redefining the major contributors to superoxide production in contracting skeletal muscle. The role of NAD(P)H oxidases

The production of reactive oxygen and nitrogen species (RONS) by skeletal muscle is important as it (i) underlies oxidative damage in many degenerative muscle pathologies and (ii) plays multiple regulatory roles by fulfilling important cellular functions. Superoxide and nitric oxide (NO) are the primary radical species produced by skeletal muscle and studies in the early 1980s demonstrated that their generation is augmented during contractile activity. Over the past 30 years considerable research has been undertaken to identify the major sites that contribute to the increased rate of RONS generation in response to contractions. It is widely accepted that NO is regulated by the nitric oxide synthases, however the sites that modulate changes in superoxide during exercise remain unclear. Despite the initial indications that the mitochondrial electron transport chain was the predominant source of superoxide during activity, with the development of analytical methods a number of alternative potential sites have been identified including the NAD(P)H oxidases, xanthine oxidase, cyclooxygenases, and lipoxygenases linked to the activity of the phospholipase A2 enzymes. In the present review we outline the subcellular sites that modulate intracellular changes in superoxide in skeletal muscle and based on the available experimental evidence in the literature we conclude that the NAD(P)H oxidases are likely to be the major superoxide generating sources in contracting skeletal muscle.

Cancer cachexia: impact, mechanisms and emerging treatments

Many forms of cancer present with a complex metabolic profile characterised by loss of lean body mass known as cancer cachexia. The physical impact of cachexia contributes to decreased patient quality of life, treatment success and survival due to gross alterations in protein metabolism, increased oxidative stress and systemic inflammation. The psychological impact also contributes to decreased quality of life for both patients and their families. Combination therapies that target multiple pathways, such as eicosapentaenoic acid administered in combination with exercise, appetite stimulants, antioxidants or anti-inflammatories, have potential in the treatment of this complex syndrome and require further development.

Highlights of mechanistic and therapeutic cachexia and sarcopenia research 2010 to 2012 and their relevance for cardiology

Sarcopenia and cachexia are significant medical problems with a high disease-related burden in cardiovascular illness. Muscle wasting and weight loss are very frequent particularly in chronic heart failure and they relate to poor prognosis. Although clinically largely underestimated, the fields of cachexia and sarcopenia are of great relevance to cardiologists. In cachexia and sarcopenia a significant number of research publications related to basic science questions of muscle wasting and lipolysis were published between 2010 and 2012. Recently, the two processes of muscle wasting and lipolysis were found to be closely linked. Treatment research in pre-clinical models involves studies on a number of different therapeutic entities, including ghrelin, selective androgen receptor modulators (SARMs), as well as drugs targeting myostatin or melanocortin-4. In the human setting, studies using enobosarm (a SARM) and anamorelin (ghrelin) are in phase III. The last 3 years have seen significant efforts to define the field using consensus statements. In the future, these definitions should also be considered for guidelines and treatment trials in cardiovascular medicine. The current review aims to summarize important information and development in the fields of muscle wasting, sarcopenia and cachexia, focusing on findings in cardiovascular research, in order for cardiologists to have a better understanding of the progress in this still insufficiently known field.

Marine polyunsaturated fatty acids and cancer therapy

Polyunsaturated fatty acids (PUFAs) derived from marine sources, including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are widely consumed as supplements within the community. However, the use of marine PUFAs in a therapeutic context is also increasing in patients receiving treatment for a range of cancer types. On balance, the literature suggests that marine PUFAs have potential as an effective adjuvant to chemotherapy treatment, may have direct anticancer effects, and may help ameliorate some of the secondary complications associated with cancer. Although a range of doses have been trialled, it would appear that supplementation of fish oil (>3 g per day) or EPA/DHA (>1 g EPA and >0.8 g DHA per day) is associated with positive clinical outcomes. However, further research is still required to determine the mechanisms via which marine PUFAs are mediating their effects. This review summarises our current understanding of marine PUFAs and cancer therapy.

Eicosapentaenoic acid and oxypurinol in the treatment of muscle wasting in a mouse model of cancer cachexia

Cancer cachexia is a wasting condition, driven by systemic inflammation and oxidative stress. This study investigated eicosapentaenoic acid (EPA) in combination with oxypurinol as a treatment in a mouse model of cancer cachexia. Mice with cancer cachexia were randomized into 4 treatment groups (EPA (0.4 g/kg/day), oxypurinol (1 mmol/L ad-lib), combination, or control), and euthanized after 29 days. Analysis of oxidative damage to DNA, mRNA analysis of pro-oxidant, antioxidant and proteolytic pathway components, along with enzyme activity of pro- and antioxidants were completed on gastrocnemius muscle. The control group displayed earlier onset of tumor compared to EPA and oxypurinol groups (P<0.001). The EPA group maintained body weight for an extended duration (20 days) compared to the oxypurinol (5 days) and combination (8 days) groups (P<0.05). EPA (18.2±3.2 pg/ml) and combination (18.4±3.7 pg/ml) groups had significantly higher 8-OH-dG levels than the control group (12.9±1.4 pg/ml, P≤0.05) indicating increased oxidative damage to DNA. mRNA levels of GPx1, MURF1 and MAFbx were higher following EPA treatment compared to control (P≤0.05). Whereas oxypurinol was associated with higher GPx1, MnSOD, CAT, XDH, MURF1, MAFbx and UbB mRNA compared to control (P≤0.05). Activity of total SOD was higher in the oxypurinol group (32.2±1.5 U/ml) compared to control (27.0±1.3 U/ml, P<0.01), GPx activity was lower in the EPA group (8.76±2.0 U/ml) compared to control (14.0±1.9 U/ml, P<0.05), and catalase activity was lower in the combination group (14.4±2.8 U/ml) compared to control (20.9±2.0 U/ml, P<0.01). There was no change in XO activity. The increased rate of weight decline in mice treated with oxypurinol indicates that XO may play a protective role during the progression of cancer cachexia, and its inhibition is detrimental to outcomes. In combination with EPA, there was little significant improvement from control, indicating oxypurinol is unlikely to be a viable treatment compound in cancer cachexia.