The crosstalk between macrophages and cancer cells potentiates pancreatic cancer cachexia

With limited treatment options, cachexia remains a major challenge for patients with cancer. Characterizing the interplay between tumor cells and the immune microenvironment may help identify potential therapeutic targets for cancer cachexia. Herein, we investigate the critical role of macrophages in potentiating pancreatic cancer induced muscle wasting via promoting TWEAK (TNF-like weak inducer of apoptosis) secretion from the tumor. Specifically, depletion of macrophages reverses muscle degradation induced by tumor cells. Macrophages induce non-autonomous secretion of TWEAK through CCL5/TRAF6/NF-κB pathway. TWEAK promotes muscle atrophy by activating MuRF1 initiated muscle remodeling. Notably, tumor cells recruit and reprogram macrophages via the CCL2/CCR2 axis and disrupting the interplay between macrophages and tumor cells attenuates muscle wasting. Collectively, this study identifies a feedforward loop between pancreatic cancer cells and macrophages, underlying the non-autonomous activation of TWEAK secretion from tumor cells thereby providing promising therapeutic targets for pancreatic cancer cachexia.

Soluble Factors Associated with Denervation-induced Skeletal Muscle Atrophy

Skeletal muscle tissue has the critical function of mechanical support protecting the body. In addition, its functions are strongly influenced by the balanced synthesis and degradation processes of structural and regulatory proteins. The inhibition of protein synthesis and/or the activation of catabolism generally determines a pathological state or condition called muscle atrophy, a reduction in muscle mass that results in partial or total loss of function. It has been established that many pathophysiological conditions can cause a decrease in muscle mass. Skeletal muscle innervation involves stable and functional neural interactions with muscles via neuromuscular junctions and is essential for maintaining normal muscle structure and function. Loss of motor innervation induces rapid skeletal muscle fiber degeneration with activation of atrophy-related signaling and subsequent disassembly of sarcomeres, altering normal muscle function. After denervation, an inflammation stage is characterized by the increased expression of pro-inflammatory cytokines that determine muscle atrophy. In this review, we highlighted the impact of some soluble factors on the development of muscle atrophy by denervation.

Fn14 promotes myoblast fusion during regenerative myogenesis

Skeletal muscle regeneration involves coordinated activation of an array of signaling pathways. Fibroblast growth factor-inducible 14 (Fn14) is a bona fide receptor for the TWEAK cytokine. Levels of Fn14 are increased in the skeletal muscle of mice after injury. However, the cell-autonomous role of Fn14 in muscle regeneration remains unknown. Here, we demonstrate that global deletion of the Fn14 receptor in mice attenuates muscle regeneration. Conditional ablation of Fn14 in myoblasts but not in differentiated myofibers of mice inhibits skeletal muscle regeneration. Fn14 promotes myoblast fusion without affecting the levels of myogenic regulatory factors in the regenerating muscle. Fn14 deletion in myoblasts hastens initial differentiation but impairs their fusion. The overexpression of Fn14 in myoblasts results in the formation of myotubes having an increased diameter after induction of differentiation. Ablation of Fn14 also reduces the levels of various components of canonical Wnt and calcium signaling both in vitro and in vivo. Forced activation of Wnt signaling rescues fusion defects in Fn14-deficient myoblast cultures. Collectively, our results demonstrate that Fn14-mediated signaling positively regulates myoblast fusion and skeletal muscle regeneration.

Targeted ablation of Fn14 receptor improves exercise capacity and inhibits neurogenic muscle atrophy

Skeletal muscle atrophy is a prevalent complication in multiple chronic diseases and disuse conditions. Fibroblast growth factor-inducible 14 (Fn14) is a member of the TNF receptor superfamily and a bona fide receptor of the TWEAK cytokine. Accumulating evidence suggests that Fn14 levels are increased in catabolic conditions as well as during exercise. However, the role of Fn14 in the regulation of skeletal muscle mass and function remains poorly understood. In this study, through the generation of novel skeletal muscle-specific Fn14-knockout mice, we have investigated the muscle role of Fn14 in the regulation of exercise capacity and denervation-induced muscle atrophy. Our results demonstrate that there was no difference in skeletal muscle mass between control and muscle-specific Fn14-knockout mice. Nevertheless, the deletion of Fn14 in skeletal muscle significantly improved exercise capacity and resistance to fatigue. This effect of Fn14 deletion is associated with an increased proportion of oxidative myofibers and higher capillaries number per myofiber in skeletal muscle. Furthermore, our results demonstrate that targeted deletion of Fn14 inhibits denervation-induced muscle atrophy in adult mice. Deletion of Fn14 reduced the expression of components of the ubiquitin-proteasome system and non-canonical NF-kappa B signaling in denervated skeletal muscle, as well as increased the phosphorylation of Akt kinase and FoxO3a transcription factor. Collectively, our results demonstrate that targeted inhibition of Fn14 improves exercise tolerance and inhibits denervation-induced muscle atrophy in adult mice.

Dysregulation of Tweak and Fn14 in skeletal muscle of spinal muscular atrophy mice

BACKGROUND

Spinal muscular atrophy (SMA) is a childhood neuromuscular disorder caused by depletion of the survival motor neuron (SMN) protein. SMA is characterized by the selective death of spinal cord motor neurons, leading to progressive muscle wasting. Loss of skeletal muscle in SMA is a combination of denervation-induced muscle atrophy and intrinsic muscle pathologies. Elucidation of the pathways involved is essential to identify the key molecules that contribute to and sustain muscle pathology. The tumor necrosis factor-like weak inducer of apoptosis (TWEAK)/TNF receptor superfamily member fibroblast growth factor-inducible 14 (Fn14) pathway has been shown to play a critical role in the regulation of denervation-induced muscle atrophy as well as muscle proliferation, differentiation, and metabolism in adults. However, it is not clear whether this pathway would be important in highly dynamic and developing muscle.

METHODS

We thus investigated the potential role of the TWEAK/Fn14 pathway in SMA muscle pathology, using the severe Taiwanese Smn^-/-; SMN2 and the less severe Smn^2B/- SMA mice, which undergo a progressive neuromuscular decline in the first three post-natal weeks. We also used experimental models of denervation and muscle injury in pre-weaned wild-type (WT) animals and siRNA-mediated knockdown in C2C12 muscle cells to conduct additional mechanistic investigations.

RESULTS

Here, we report significantly dysregulated expression of Tweak, Fn14, and previously proposed downstream effectors during disease progression in skeletal muscle of the two SMA mouse models. In addition, siRNA-mediated Smn knockdown in C2C12 myoblasts suggests a genetic interaction between Smn and the TWEAK/Fn14 pathway. Further analyses of SMA, Tweak^-/-, and Fn14^-/- mice revealed dysregulated myopathy, myogenesis, and glucose metabolism pathways as a common skeletal muscle feature, providing further evidence in support of a relationship between the TWEAK/Fn14 pathway and Smn. Finally, administration of the TWEAK/Fn14 agonist Fc-TWEAK improved disease phenotypes in the two SMA mouse models.

CONCLUSIONS

Our study provides mechanistic insights into potential molecular players that contribute to muscle pathology in SMA and into likely differential responses of the TWEAK/Fn14 pathway in developing muscle.

TNF-like weak inducer of apoptosis / nuclear factor κB axis feedback loop promotes spinal cord injury by inducing astrocyte activation

Non-canonical signaling pathways have been proved to act as potent sites of astrocytes osmotic expanding or proliferation, which promotes the regeneration of axons in areas with non-neural spinal cord injury (SCI). However, the relevant signal pathway that induces autophagic cell death in astrocytes and its function relative to the TNF-like weak inducer of apoptosis/nuclear factor κB (TWEAK/NF-κB) axis remains elusive. The SCI model was established by vertically striking the spinal cord according to Allen’s model. Astrocytes and neuronal cells were prepared from spinal cells extracted from spinal cord tissues of SCI or normal C57BL/6 newborn mice. After co-culturing astrocytes and neurons, cell viability and autophagy were determined by CCK-8, transmission electron microscopy (TEM), and western blot. The expression of TWEAK, NF-κB and inflammatory cytokines was confirmed by qRT-PCR, western blot, Immunofluorescence and ELISA assay. Chromatin immunoprecipitation (CHIP) was used to evaluate the interaction between TWEAK and NF-κB. Our results demonstrated that knockdown of TWEAK and NF-κB inhibited secretion of high levels of TNF-α/IL-1β, partially counteracted by adding Rap. TWEAK/NF-κB was the positive correlation feedback loop regulating the proliferation and autophagy of astrocytes involved in SCI. Moreover, restraining the excess growth of astrocytes was beneficial to the growth of neurons. Collectively, our findings illustrated that the TWEAK/NF-κB pathway might act as a positive modulator of SCI by inducing astrocyte activation, shedding new insights for SCI treatment.

Comprehensive expression analysis with cell-type-specific transcriptome in ALS-linked mutant SOD1 mice: Revisiting the active role of glial cells in disease

Non-cell autonomous mechanisms are involved in the pathogenesis of amyotrophic lateral sclerosis (ALS), an adult neurodegenerative disease characterized by selective motor neuron loss. While the emerging role of glial cells in ALS has been noted, the detailed cell-type-specific role of glial cells has not been clarified. Here, we examined mRNA expression changes using microarrays of the spinal cords of three distinct lines of mutant superoxide dismutase (SOD) 1 transgenic mice, an established ALS model. Our analysis used a transcriptome database of component cell types in the central nervous system (CNS), as well as SOD1 ^G93A cell-type transcriptomes. More than half of the differentially expressed genes (DEGs) were highly expressed in microglia, and enrichment analysis of DEGs revealed that immunological reactions were profoundly involved and some transcription factors were upregulated. Our analysis focused on DEGs that are highly expressed in each cell type, as well as chemokines, caspases, and heat shock proteins. Disease-associated microglial genes were upregulated, while homeostatic microglial genes were not, and galectin-3 (Mac2), a known activated microglial marker, was predicted to be ectopically expressed in astrocytes in mutant SOD1 mice. In mutant SOD1 mice, we developed a prediction model for the pathophysiology of different cell types related to TREM2, apolipoprotein E, and lipoproteins. Our analysis offers a viable resource to understand not only the molecular pathologies of each CNS constituent cell type, but also the cellular crosstalk between different cell types under both physiological and pathological conditions in model mice for various neurodegenerative diseases.

Immune Response in Neurological Pathology: Emerging Role of Central and Peripheral Immune Crosstalk

Neuroinflammation is a key component of neurological disorders and is an important therapeutic target; however, immunotherapies have been largely unsuccessful. In cases where these therapies have succeeded, particularly multiple sclerosis, they have primarily focused on one aspect of the disease and leave room for improvement. More recently, the impact of the peripheral immune system is being recognized, since it has become evident that the central nervous system is not immune-privileged, as once thought. In this review, we highlight key interactions between central and peripheral immune cells in neurological disorders. While traditional approaches have examined these systems separately, the immune responses and processes in neurological disorders consist of substantial crosstalk between cells of the central and peripheral immune systems. Here, we provide an overview of major immune effector cells and the role of the blood-brain barrier in regard to neurological disorders and provide examples of this crosstalk in various disorders, including stroke and traumatic brain injury, multiple sclerosis, neurodegenerative diseases, and brain cancer. Finally, we propose targeting central-peripheral immune interactions as a potential improved therapeutic strategy to overcome failures in clinical translation.

Peripheral and Central Nervous System Immune Response Crosstalk in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by muscle weakness due to the degeneration of the upper and lower motor neurons. Neuroinflammation is known as a prominent pathological feature of ALS. Although neuroinflammation cannot trigger ALS, activated central nervous system (CNS) microglia and astrocytes, proinflammatory periphery monocytes/macrophages and T lymphocytes, and infiltrated monocytes/macrophages and T lymphocytes, as well as the immunoreactive molecules they release, are closely related to disease progression. The crosstalk between the peripheral and CNS immune components mentioned above significantly correlates with survival in patients with ALS. This review provides an update on the role of this crosstalk between the CNS and peripheral immune responses in ALS. Additionally, we discuss changes in the composition of gut microbiota because these can directly or indirectly influence this crosstalk. These recent advances may well provide innovative ways for targeting the molecules associated with this crosstalk and breaking the current treatment impasse in ALS.

Cellular and molecular features of neurogenic skeletal muscle atrophy

Neurogenic atrophy refers to the loss of muscle mass and function that results directly from injury or disease of the peripheral nervous system. Individuals with neurogenic atrophy may experience reduced functional status and quality of life and, in some circumstances, reduced survival. Distinct pathological findings on muscle histology can aid in diagnosis of a neurogenic cause for muscle dysfunction, and provide indicators for the chronicity of denervation. Denervation induces pleiotypic responses in skeletal muscle, and the molecular mechanisms underlying neurogenic muscle atrophy appear to share common features with other causes of muscle atrophy, including activation of FOXO transcription factors and corresponding induction of ubiquitin-proteasomal and lysosomal degradation. In this review, we provide an overview of histologic features of neurogenic atrophy and a summary of current understanding of underlying mechanisms.

TWEAK/Fn14 axis in respiratory diseases

Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) is a well known multifunctional cytokine extensively distributed in cell types and tissues. Accumulating evidence has shown that TWEAK binding to the receptor factor-inducible 14 (Fn14) participates in diverse pathologic processes including cell proliferation and death, angiogenesis, carcinogenesis and inflammation. Interestingly, alterations of intracellular signaling cascades are correlated to the development of respiratory disease. Recently, a several lines of evidence suggests that TWEAK in lung tissues are closely associated with these signaling pathways. In this review, we explore if TWEAK could provide a novel therapeutic strategy for managing respiratory disease in general and pulmonary arterial hypertension (PAH), obstructive sleep apnea syndrome (OSAS), asthma, idiopathic pulmonary fibrosis (IPF), chronic obstructive pulmonary disease (COPD) and non-small cell lung cancer (NSCLC), specifically.

Tnfrsf12a-Mediated Atherosclerosis Signaling and Inflammatory Response as a Common Protection Mechanism of Shuxuening Injection Against Both Myocardial and Cerebral Ischemia-Reperfusion Injuries

Shuxuening injection (SXNI) is a widely prescribed herbal medicine of Ginkgo biloba extract (EGB) for cerebral and cardiovascular diseases in China. However, its curative effects on ischemic stroke and heart diseases and the underlying mechanisms remain unknown. Taking an integrated approach of RNA-seq and network pharmacology analysis, we compared transcriptome profiles of brain and heart ischemia reperfusion injury in C57BL/6J mice to identify common and differential target genes by SXNI. Models for myocardial ischemia reperfusion injury (MIRI) by ligating left anterior descending coronary artery (LAD) for 30 min ischemia and 24 h reperfusion and cerebral ischemia reperfusion injury (CIRI) by middle cerebral artery occlusion (MCAO) for 90 min ischemia and 24 h reperfusion were employed to identify the common mechanisms of SXNI on both cerebral and myocardial ischemia reperfusion. In the CIRI model, ischemic infarct volume was markedly decreased after pre-treatment with SXNI at 0.5, 2.5, and 12.5 mL/kg. In the MIRI model, pre-treatment with SXNI at 2.5 and 12.5 mL/kg improved cardiac function and coronary blood flow and decreased myocardial infarction area. Besides, SXNI at 2.5 mL/kg also markedly reduced the levels of LDH, AST, CK-MB, and CK in serum. RNA-seq analysis identified 329 differentially expressed genes (DEGs) in brain and 94 DEGs in heart after SXNI treatment in CIRI or MIRI models, respectively. Core analysis by Ingenuity Pathway Analysis (IPA) revealed that atherosclerosis signaling and inflammatory response were top-ranked in the target profiles for both CIRI and MIRI after pre-treatment with SXNI. Specifically, Tnfrsf12a was recognized as an important common target, and was regulated by SXNI in CIRI and MIRI. In conclusion, our study showed that SXNI effectively protects brain and heart from I/R injuries via a common Tnfrsf12a-mediated pathway involving atherosclerosis signaling and inflammatory response. It provides a novel knowledge of active ingredients of Ginkgo biloba on cardio-cerebral vascular diseases in future clinical application.

Muscle microRNA signatures as biomarkers of disease progression in amyotrophic lateral sclerosis

ALS is a fatal neurodegenerative disorder of motor neurons leading to progressive atrophy and weakness of muscles. Some of the earliest pathophysiological changes occur at the level of skeletal muscle and the neuromuscular junction. We previously identified distinct mRNA patterns, including members of the Smad and TGF-β family, that emerge in muscle tissue at the earliest (pre-clinical) stages. These patterns track disease progression in the mutant SOD1 mouse and are present in human ALS muscle. Because miRNAs play a direct regulatory role in mRNA expression, we hypothesized in this study that there would be distinct miRNA patterns in ALS muscle appearing in early stages that could track disease progression. We performed next-generation miRNA sequencing on muscle samples from G93A SOD1 mice at early (pre-clinical) and late (symptomatic) stages, and identified distinct miRNA patterns at both stages with some overlap. An Ingenuity Pathway Analysis predicted effects on a number of pathways relevant to ALS including TGF-β signaling, axon guidance signaling, and mitochondrial function. A subset of miRNAs was validated in the G93A SOD1 mouse at four stages of disease, and several appeared to track disease progression, including miR-206. We assessed these miRNAs in a large cohort of human ALS and disease control samples and found that some had similar changes but were not specific for ALS. Surprisingly, miR-206 levels did not change overall compared to normal controls, but did correlate with changes in strength of the muscle biopsied. In summary, we identified distinct miRNA patterns in ALS muscle that reflected disease stage which could potentially be used as biomarkers of disease activity.

Pathogenic commonalities between spinal muscular atrophy and amyotrophic lateral sclerosis: Converging roads to therapeutic development

Spinal muscular atrophy (SMA) and amyotrophic lateral sclerosis (ALS) are the two most common motoneuron disorders, which share typical pathological hallmarks while remaining genetically distinct. Indeed, SMA is caused by deletions or mutations in the survival motor neuron 1 (SMN1) gene whilst ALS, albeit being mostly sporadic, can also be caused by mutations within genes, including superoxide dismutase 1 (SOD1), Fused in Sarcoma (FUS), TAR DNA-binding protein 43 (TDP-43) and chromosome 9 open reading frame 72 (C9ORF72). However, it has come to light that these two diseases may be more interlinked than previously thought. Indeed, it has recently been found that FUS directly interacts with an Smn-containing complex, mutant SOD1 perturbs Smn localization, Smn depletion aggravates disease progression of ALS mice, overexpression of SMN in ALS mice significantly improves their phenotype and lifespan, and duplications of SMN1 have been linked to sporadic ALS. Beyond genetic interactions, accumulating evidence further suggests that both diseases share common pathological identities such as intrinsic muscle defects, neuroinflammation, immune organ dysfunction, metabolic perturbations, defects in neuron excitability and selective motoneuron vulnerability. Identifying common molecular effectors that mediate shared pathologies in SMA and ALS would allow for the development of therapeutic strategies and targeted gene therapies that could potentially alleviate symptoms and be equally beneficial in both disorders. In the present review, we will examine our current knowledge of pathogenic commonalities between SMA and ALS, and discuss how furthering this understanding can lead to the establishment of novel therapeutic approaches with wide-reaching impact on multiple motoneuron diseases.

Regulation of Neuroinflammation: What Role for the Tumor Necrosis Factor-Like Weak Inducer of Apoptosis/Fn14 Pathway?

Observed in many central nervous system diseases, neuroinflammation (NI) proceeds from peripheral immune cell infiltration into the parenchyma, from cytokine secretion and from oxidative stress. Astrocytes and microglia also get activated and proliferate. NI manifestations and consequences depend on its context and on the acute or chronic aspect of the disease. The tumor necrosis factor-like weak inducer of apoptosis (TWEAK)/Fn14 pathway has been involved in chronic human inflammatory pathologies such as neurodegenerative, autoimmune, or malignant diseases. New data now describe its regulatory effects in tissues or fluids from patients with neurological diseases. In this mini-review, we aim to highlight the role of TWEAK/Fn14 in modulating NI in multiple sclerosis, neuropsychiatric systemic lupus erythematosus, stroke, or glioma. TWEAK/Fn14 can modulate NI by activating canonical and non-canonical nuclear factor-κB pathways but also by stimulating mitogen-activated protein kinase signaling. These downstream activations are associated with (i) inflammatory cytokine, chemokine and adhesion molecule expression or release, involved in NI propagation, (ii) matrix-metalloproteinase 9 secretion, implicated in blood–brain barrier disruption and tissue remodeling, (iii) astrogliosis and microgliosis, and (iv) migration of tumor cells in glioma. In addition, we report several animal and human studies pointing to TWEAK as an attractive therapeutic target.

MicroRNA Dysregulation in Aging and Pathologies of the Skeletal Muscle

Skeletal muscle is one of the biggest organs of the body with important mechanistic and metabolic functions. Muscle homeostasis is controlled by environmental, genetic, and epigenetic factors. Indeed, MiRNAs, small noncoding RNAs robust regulators of gene expression, have and have been shown to regulate muscle homeostasis on several levels: through controlling myogenesis, muscle growth (hypertrophy) and atrophy, as well as interactions of muscle with other tissues. Given the large number of MiRNA target genes and the important role of MiRNAs in most physiological processes and various diseases, MiRNAs may have an enormous potential as therapeutic targets against numerous disorders, including pathologies of muscle. The purpose of this review is to present the current knowledge of the role of MiRNAs in skeletal muscle homeostasis and pathologies and the potential of MiRNAs as therapeutics for skeletal muscle wasting, with particular focus on the age- and disease-related loss of muscle mass and function.

Wildtype motoneurons, ALS-Linked SOD1 mutation and glutamate profoundly modify astrocyte metabolism and lactate shuttling

The selective degeneration of motoneuron that typifies amyotrophic lateral sclerosis (ALS) implicates non-cell-autonomous effects of astrocytes. However, mechanisms underlying astrocyte-mediated neurotoxicity remain largely unknown. According to the determinant role of astrocyte metabolism in supporting neuronal function, we propose to explore the metabolic status of astrocytes exposed to ALS-associated conditions. We found a significant metabolic dysregulation including purine, pyrimidine, lysine, and glycerophospholipid metabolism pathways in astrocytes expressing an ALS-causing mutated superoxide dismutase-1 (SOD1) when co-cultured with motoneurons. SOD1 astrocytes exposed to glutamate revealed a significant modification of the astrocyte metabolic fingerprint. More importantly, we observed that SOD1 mutation and glutamate impact the cellular shuttling of lactate between astrocytes and motoneurons with a decreased in extra- and intra-cellular lactate levels in astrocytes. Based on the emergent strategy of metabolomics, this work provides novel insight for understanding metabolic dysfunction of astrocytes in ALS conditions and opens the perspective of therapeutics targets through focusing on these metabolic pathways. GLIA 2017 GLIA 2017;65:592-605.

The Role of Skeletal Muscle in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal adult‐onset disease primarily characterized by upper and lower motor neuron degeneration, muscle wasting and paralysis. It is increasingly accepted that the pathological process leading to ALS is the result of multiple disease mechanisms that operate within motor neurons and other cell types both inside and outside the central nervous system. The implication of skeletal muscle has been the subject of a number of studies conducted on patients and related animal models. In this review, we describe the features of ALS muscle pathology and discuss on the contribution of muscle to the pathological process. We also give an overview of the therapeutic strategies proposed to alleviate muscle pathology or to deliver curative agents to motor neurons. ALS muscle mainly suffers from oxidative stress, mitochondrial dysfunction and bioenergetic disturbances. However, the way by which the disease affects different types of myofibers depends on their contractile and metabolic features. Although the implication of muscle in nourishing the degenerative process is still debated, there is compelling evidence suggesting that it may play a critical role. Detailed understanding of the muscle pathology in ALS could, therefore, lead to the identification of new therapeutic targets.

Panel of Oxidative Stress and Inflammatory Biomarkers in ALS: A Pilot Study

Background: Pathophysiological mechanisms that contribute to neurodegeneration in Amyotrophic Lateral Sclerosis (ALS) include oxidative stress and inflammation. We conducted a preliminary study to explore these mechanisms, to discuss their link in ALS, and to determine the feasibility of incorporating this combined analysis into current biomarkers research. Methods: We enrolled 10 ALS patients and 10 controls. We measured the activities of glutathione peroxidase, glutathione reductase, superoxyde dismutase (SOD), and the levels of serum total antioxidant status (TAS), malondialdehyde (MDA), 8-hydroxy-2’-deoxyguanosine (8-OHdG), and glutathione status (e.g. glutathione disulfide, GSSG/reduced glutathione, GSH). We analysed the concentrations of homocysteine, several cytokines, vitamins and metals by standard methods used in routine practice. Results: There was a significant decrease in TAS levels (p=0.027) and increase in 8-OHdG (p=0.014) and MDA (p=0.011) levels in ALS patients. We also observed a significantly higher GSSG/GSH ratio (p=0.022), and IL-6 (p=0.0079) and IL-8 (p=0.009) concentrations in ALS patients. Correlations were found between biological and clinical markers (homosysteine vs. clinical status at diagnosis, p=0.02) and between some biological markers such as IL-6 vs. GSSG/GSH (p=0.045) or SOD activity (p=0.017). Conclusion: We confirmed the systemic alteration of both the redox and the inflammation status in ALS patients, and we observed a link with some clinical parameters. These promising results encourage us to pursue this study with collection of combined oxidative stress and inflammatory markers.

Cytokine Signaling in Skeletal Muscle Wasting

Skeletal muscle wasting occurs in a variety of diseases including diabetes, cancer, Crohn's disease, chronic obstructive pulmonary disease (COPD), disuse, and denervation. Tumor necrosis factor α (TNF-α) is involved in mediating the wasting effect. To date, a causal relationship between TNF-α signaling and muscle wasting has been established in animal models. However, results from clinical trials are conflicting. This is partly due to the fact that other factors such as TNF-like weak inducer of apoptosis (TWEAK) and interleukin 6 (IL-6) are also involved in skeletal muscle wasting. Because muscle wasting is often associated with physical inactivity and reduced food intake, therapeutic interventions will be most effective when multiple approaches are used in conjunction with nutritional support and exercise.

TWEAK Regulates Muscle Functions in a Mouse Model of RNA Toxicity

Myotonic dystrophy type 1 (DM1), the most common form of muscular dystrophy in adults, is caused by toxic RNAs produced from the mutant DM protein kinase (DMPK) gene. DM1 is characterized by progressive muscle wasting and weakness. Therapeutic strategies have mainly focused on targeting the toxic RNA. Previously, we found that fibroblast growth factor-inducible 14 (Fn14), the receptor for TWEAK, is induced in skeletal muscles and hearts of mouse models of RNA toxicity and that blocking TWEAK/Fn14 signaling improves muscle function and histology. Here, we studied the effect of Tweak deficiency in a RNA toxicity mouse model. The genetic deletion of Tweak in these mice significantly reduced muscle damage and improved muscle function. In contrast, administration of TWEAK in the RNA toxicity mice impaired functional outcomes and worsened muscle histopathology. These studies show that signaling via TWEAK is deleterious to muscle in RNA toxicity and support the demonstrated utility of anti-TWEAK therapeutics.

PGC-1α Silencing Compounds the Perturbation of Mitochondrial Function Caused by Mutant SOD1 in Skeletal Muscle of ALS Mouse Model

Amyotrophic lateral sclerosis (ALS) is a lethal neurodegenerative disease causing death of motor neurons. This study investigated the roles of energy metabolism in the pathogenesis of ALS in the SOD1(G93A) transgenic mouse model. Control and SOD1(G93A) mice were administered with shcontrol or shPGC-1α in combination with PBS or thiazolidinedione (TZD) for 8 weeks. Gene expression was analyzed by quantitative real-time PCR and Western blot. ROS and fibrosis were assessed with a colorimetric kit and Sirius staining, respectively. Inflammatory cytokines were measured using ELISA kits. The levels of tissue ROS and serum inflammatory cytokines were significantly higher in SOD1(G93A) mice compared to control mice, and knocking down peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) drastically increased cytokine levels in both control and SOD1(G93A) mice. Muscle fibrosis was much severer in SOD1(G93A) mice, and worsened by silencing PGC-1α and attenuated by TZD. The expression levels of PGC-1α, SOD1, UCP2, and cytochrome C were substantially reduced by shPGC-1α and increased by TZD in muscle of both control and SOD1(G93A) mice, whereas the level of NF-κB was significantly elevated in SOD1(G93A) mice, which was further increased by PGC-1α silencing. These data indicated that disruption of energy homeostasis would exacerbate the pathological changes caused by SOD1 mutations to promote the pathogenesis of ALS.