Muscle atrophy induced by SOD1G93A expression does not involve the activation of caspase in the absence of denervation

BACKGROUND: The most remarkable feature of skeletal muscle is the capacity to adapt its morphological, biochemical and molecular properties in response to several factors. Nonetheless, under pathological conditions, skeletal muscle loses its adaptability, leading to atrophy or wasting. Several signals might function as physiopathological triggers of muscle atrophy. However, the specific mechanisms underlying the atrophic phenotype under different pathological conditions remain to be fully elucidated. In this paper, we address the involvement of caspases in the induction of muscle atrophy in experimental models of amyotrophic lateral sclerosis (ALS) expressing the mutant SOD1G93A transgene either locally or ubiquitously. RESULTS: We demonstrate that SOD1G93A-mediated muscle atrophy is independent from caspase activity. In particular, the expression of SOD1G93A promotes a reduction of the phosphatidylinositol 3-kinase/Akt pathway associated with activation of forkhead box O3. In contrast, the activation of caspases occurs later and is causally linked to motor neuron degeneration, which is associated with exacerbation of the atrophic phenotype and a shift in fiber-type composition. CONCLUSION: This study suggests that muscle atrophy induced by the toxic effect of SOD1G93A is independent from the activation of apoptotic markers and that caspase-mediated apoptosis is a process activated upon muscle denervation

Postmitotic Expression of SOD1G93A Gene Affects the Identity of Myogenic Cells and Inhibits Myoblasts Differentiation

To determine the role of mutant SOD1 gene (SOD1G93A) on muscle cell differentiation, we derived C2C12 muscle cell lines carrying a stably transfected SOD1G93A gene under the control of a myosin light chain (MLC) promoter-enhancer cassette. Expression of MLC/SOD1G93A in C2C12 cells resulted in dramatic inhibition of myoblast differentiation. Transfected SOD1G93A gene expression in postmitotic skeletal myocytes downregulated the expression of relevant markers of committed and differentiated myoblasts such as MyoD, Myogenin, MRF4, and the muscle specific miRNA expression. The inhibitory effects of SOD1G93A gene on myogenic program perturbed Akt/p70 and MAPK signaling pathways which promote differentiation cascade. Of note, the inhibition of the myogenic program, by transfected SOD1G93A gene expression, impinged also the identity of myogenic cells. Expression of MLC/SOD1G93A in C2C12 myogenic cells promoted a fibro-adipogenic progenitors (FAPs) phenotype, upregulating HDAC4 protein and preventing the myogenic commitment complex BAF60C-SWI/SNF. We thus identified potential molecular mediators of the inhibitory effects of SOD1G93A on myogenic program and disclosed potential signaling, activated by SOD1G93A, that affect the identity of the myogenic cell population

Efficacy of hemostatic powders as monotherapy or rescue therapy in gastrointestinal bleeding related to neoplastic or non-neoplastic lesions

Background Hemostatic powder (HP) in gastrointestinal bleeding (GIB) is mainly used as rescue therapy after failure of conventional hemostatic procedures (CHP). Aim To define the best field of application and the efficacy of HP as first choice monotherapy or rescue therapy. Methods We compared the efficacy of HP monotherapy, HP rescue therapy, and CHP in the management of active GIB due to neoplastic and non-neoplastic lesions. Results A total of 108 patients, 43 treated with HP as either first choice or rescue therapy and 65 with CHP, were included in the study. The most frequent sources of bleeding were peptic ulcer and malignancy. Immediate hemostasis rates were: HP monotherapy = 100% in peptic ulcer and 100% in malignancy; HP rescue therapy = 93.2% in peptic ulcer and 85.7% in malignancy; CHP = 77.9% in peptic ulcer and 41.7 in malignancy. Definitive hemostasis rates were: HP monotherapy = 50% in peptic ulcer and 45.5% in malignancy; HP rescue therapy = 73.3% in peptic ulcer and 85.7% in malignancy; CHP = 69.1% in peptic ulcer and 33.3% in malignancy. No difference was found in terms of additional intervention between the three groups. Conclusions HP is highly effective as monotherapy and rescue therapy in GIB. GIB related to malignancy may be the best field of application of HP, but confirmatory studies are necessary

Skeletal muscle is a primary target of SOD1G93A-mediated toxicity

The antioxidant enzyme superoxide dismutase 1 (SOD1) is a critical player of the antioxidative defense whose activity is altered in several chronic diseases, including amyotrophic lateral sclerosis. However, how oxidative insult affects muscle homeostasis remains unclear. This study addresses the role of oxidative stress on muscle homeostasis and function by the generation of a transgenic mouse model expressing a mutant SOD1 gene (SOD1(G93A)) selectively in skeletal muscle. Transgenic mice developed progressive muscle atrophy, associated with a significant reduction in muscle strength, alterations in the contractile apparatus, and mitochondrial dysfunction. The analysis of molecular pathways associated with muscle atrophy revealed that accumulation of oxidative stress served as signaling molecules to initiate autophagy, one of the major intracellular degradation mechanisms. These data demonstrate that skeletal muscle is a primary target of SOD1(G93A) -mediated toxicity and disclose the molecular mechanism whereby oxidative stress triggers muscle atrophy

Localized accumulation of oxidative stress causes muscle atrophy through activation of an autophagic pathway.

A crucial system severely affected in different chronic diseases is the antioxidative defense, leading to accumulation of reactive oxygen species (ROS). The discovery that deletion in the antioxidant genes shortens significantly the mouse life span, and that mutation in the major antioxidant enzyme SOD1 is associated with neurodegenerative diseases, has placed oxidative stress as a central mechanism in the pathogenesis of many pathological conditions. However, how such an oxidative insult plays a role in the disease-related decrease of muscle performance and mass remains largely unknown. We recently demonstrated that autophagy plays a dominant role in the promotion of muscle atrophy associated with local alteration in the activity of the antioxidant enzyme SOD1. In particular, transcription of autophagy-related genes, such as those encoding LC3, Cathepsin-L and Bnip3, is activated in response to localized accumulation of oxidative stress and is mediated by FoxO3. In addition, our study documents how the T-tubule might be the potential donor of membrane that forms sequestering autophagic vesicles. Here we discuss the sequence of events leading to muscle atrophy

Local expression of mIgf-1 modulates ubiquitin, caspase and CDK5 expression in skeletal muscle of an ALS mouse model

OBJECTIVE: The functional connection between muscle and nerve is often altered in several neuromuscular diseases, including amyotrophic lateral sclerosis (ALS). Knowledge about the molecular and cellular mechanisms involved in the restorative reactions is important to our understanding of the processes involved in neuromuscular maintenance. We previously reported that muscle-restricted expression of a localized Igf-1 isoform maintained muscle integrity, stabilized neuromuscular junctions, reduced inflammation in the spinal cord and enhanced motor neuronal survival in SOD(G93A) mice, delaying the onset and progression of the disease. In this study, we analysed potential molecular pathways that are modulated by mIgf-1 to counteract muscle wasting and to preserve motor neurons activity. METHODS: We performed molecular and morphologic analysis to address the specific proposed questions. RESULTS AND DISCUSSION: Ubiquitin expression and caspase activity resulted markedly increased in SOD(G93A) muscle but maintained at very low levels in the SOD(G93A) x MLC/mIgf-1 (SOD(G93A)/mIgf-1) transgenic muscle. In addition, CDK5 expression, a serine-threonine protein kinase that has been implicated in a number of physiologic processes in nerve and muscle cells, was reduced in SOD(G93A) muscle but increased in SOD(G93A)/mIgf-1 muscle. Notably, while the toxic p25 protein accumulated in SOD(G93A) muscle, no accumulation was evident in the SOD(G93A)/mIgf-1 muscle. The maintenance of muscle phenotype was also associated with maintenance of a normal peripheral nerve, and a greater number of myelinated axons. CONCLUSION: These observations offer novel insights into the role of mIgf-1 in the attenuation of muscle wasting in the mouse model of ALS disease