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.
Muscle regeneration following injury is characterized by myonecrosis accompanied by local inflammation, activation of satellite cells, and repair of injured fibers. The resolution of the inflammatory response is necessary to proceed toward muscle repair, since persistence of inflammation often renders the damaged muscle incapable of sustaining efficient muscle regeneration. Here, we show that local expression of a muscle-restricted insulin-like growth factor (IGF)-1 (mIGF-1) transgene accelerates the regenerative process of injured skeletal muscle, modulating the inflammatory response, and limiting fibrosis. At the molecular level, mIGF-1 expression significantly down-regulated proinflammatory cytokines, such as tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta, and modulated the expression of CC chemokines involved in the recruitment of monocytes/macrophages. Analysis of the underlying molecular mechanisms revealed that mIGF-1 expression modulated key players of inflammatory response, such as macrophage migration inhibitory factor (MIF), high mobility group protein-1 (HMGB1), and transcription NF-kappaB. The rapid restoration of injured mIGF-1 transgenic muscle was also associated with connective tissue remodeling and a rapid recovery of functional properties. By modulating the inflammatory response and reducing fibrosis, supplemental mIGF-1 creates a qualitatively different environment for sustaining more efficient muscle regeneration and repair.
Reelin is an extracellular matrix protein that plays a pivotal role in development of the central nervous system. Reelin is also expressed in the adult brain, notably in the cerebral cortex, where it might play a role in synaptic plasticity. The mechanism of action of reelin at the molecular level has been the subject of several hypotheses. Here we show that reelin is a serine protease and that proteolytic activity is relevant to its function, since (i) Reelin expression in HEK 293T cells impairs their ability to adhere to fibronectin-coated surfaces, and adhesion to fibronectin is restored by micromolar concentrations of diisopropyl phosphorofluoridate, a serine hydrolase inhibitor; (ii) purified Reelin binds FPPeg-biotin, a trap probe which irreversibly binds to serine residues located in active catalytic sites of serine hydrolases; (iii) purified Reelin rapidly degrades fibronectin and laminin, while collagen IV is degraded at a much slower rate; fibronectin degradation is inhibited by inhibitors of serine proteases, and by monoclonal antibody CR-50, an antibody known to block the function of Reelin both in vitro and in vivo. The proteolytic activity of Reelin on adhesion molecules of the extracellular matrix and/or receptors on neurons may explain how Reelin regulates neuronal migration and synaptic plasticity.Reelin (1, 2) is an extracellular matrix protein that plays a pivotal role in neuronal migration during development of laminar structures of the mammalian brain including the cerebral cortex, hippocampus, cerebellum, and several brainstem nuclei, as shown by spontaneous Reelin null mutations (i.e. the reeler mouse) (3, 4). In the developing cerebral cortex, Reelin is secreted by Cajal-Retzius cells, located in the marginal zone. Reelin must be secreted into the extracellular matrix to exert its biological effect (5).In the reeler mouse, migrating neurons fail to pass through earlier-generated neurons, possibly because they are unable to penetrate the subplate, or because they maintain extensive contacts with the radial glial fibers (6). Several hypotheses have been suggested regarding the function of Reelin: (i) Reelin may act as an attractant molecule for migrating neurons; (ii) it may act as a repulsive molecule; or (iii) Reelin may interrupt the association between migrating neurons and radial glia (7,8), thus allowing migrating neurons to switch from a "gliophilic" to a "neurophilic" state (9). Furthermore, Reelin has been recently shown to be expressed in several adult neuronal cells, including glutamatergic cerebellar granule neurons and specific GABAergic interneurons of the cerebral cortex and hippocampus (10), and in the adult mammalian blood, liver, pituitary pars intermedia, and adrenal chromaffin cells (11,12). The cellular function of Reelin in the adult organism is unknown. Evidence is accumulating for involvement of Reelin in human diseases such as autosomal recessive lissencephaly (13), schizophrenia (14), and autistic disorder (15).The mouse Reelin sequence (1) encompasses 3461 amino a...
Acidic tumor microenvironment and Wnt/β-catenin pathway activation have been recognized as two crucial events associated with the initiation and progression of cancer. The aim of this study was to clarify the molecular mechanisms underlying the anti-proliferative effects of atrial natriuretic peptide (ANP) as well as to investigate the relationship between the cellular pH and the Wnt/β-catenin signaling in cancer cells.To pursue our aims, we conducted investigations in DHD/K12/Trb rat colon adenocarcinoma cells. Intracellular pH was measured by Confocal Laser Scanning Microscopy (CLSM) using the lysosensor Green DND-189 probe. Expression of crucial molecules in the Wnt/β-catenin signaling pathway was analyzed by CLSM, western blot, and real time PCR. Measurements of activation (phosphorylation state) of Akt, ERK1/2, and p38MAPKinase were performed by Reverse-Phase Protein Microarray Analysis (RPMA).We showed that ANP triggered a NHE-1-mediated increase of the intracellular acidity, inhibiting the Wnt/β-catenin signaling simultaneously. Moreover, we observed that the Wnt1a, a Wnt signaling activator, affected the intracellular pH in an opposite fashion. Results from the comparative analysis of ANP and EIPA (a NHE-1 specific inhibitor) showed that these two molecules affect both the intracellular acidification and the Wnt/β-catenin signaling cascade. Specifically, ANP acts on the upstream of the cascade, through a Frizzled-mediated activation, while EIPA does on the downstream.We show for the first time that the Akt activity might be a relevant molecular event linking the NHE-1-regulated intracellular pH and the Wnt/β-catenin signaling. This provides evidence for a cross-talk between the intracellular alkalinization and the Wnt signaling in tumor cells.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.