Search

Bone marrow-derived mesenchymal stromal cell- (BM-MSC-) based therapy is a promising option for regenerative medicine. An important role in the control of the processes influencing the BM-MSC therapeutic efficacy, namely, extracellular matrix remodelling and proliferation and secretion ability, is played by matrix metalloproteinase- (MMP-) 2. Therefore, the identification of paracrine/autocrine regulators of MMP-2 function may be of great relevance for improving BM-MSC therapeutic potential. We recently reported that BM-MSCs release the bioactive lipid sphingosine 1-phosphate (S1P) and, here, we demonstrated an impairment of MMP-2 expression/release when the S1P receptor subtype S1PR1 is blocked. Notably, active S1PR1/MMP-2 signalling is required for F-actin structure assembly (lamellipodia, microspikes, and stress fibers) and, in turn, cell proliferation. Moreover, in experimental conditions resembling the damaged/regenerating tissue microenvironment (hypoxia), S1P/S1PR1 system is also required for HIF-1α expression and vinculin reduction. Our findings demonstrate for the first time the trophic role of S1P/S1PR1 signalling in maintaining BM-MSCs’ ability to modulate MMP-2 function, necessary for cytoskeleton reorganization and cell proliferation in both normoxia and hypoxia. Altogether, these data provide new perspectives for considering S1P/S1PR1 signalling a pharmacological target to preserve BM-MSC properties and to potentiate their beneficial potential in tissue repair. [ABSTRACT FROM AUTHOR]

Sphingosine 1-phosphate (S1P) is a bioactive lipid that is characterized by a peculiar mechanism of action. In fact, S1P, which is produced inside the cell, can act as an intracellular mediator, whereas after its export outside the cell, it can act as ligand of specific G-protein coupled receptors, which were initially named endothelial differentiation gene (Edg) and eventually renamed sphingosine 1-phosphate receptors (S1PRs). Among the five S1PR subtypes, S1PR1, S1PR2 and S1PR3 isoforms show broad tissue gene expression, while S1PR4 is primarily expressed in immune system cells, and S1PR5 is expressed in the central nervous system. There is accumulating evidence for the important role of S1P as a mediator of many processes, such as angiogenesis, carcinogenesis and immunity, and, ultimately, fibrosis. After a tissue injury, the imbalance between the production of extracellular matrix (ECM) and its degradation, which occurs due to chronic inflammatory conditions, leads to an accumulation of ECM and, consequential, organ dysfunction. In these pathological conditions, many factors have been described to act as pro- and anti-fibrotic agents, including S1P. This bioactive lipid exhibits both pro- and anti-fibrotic effects, depending on its site of action. In this review, after a brief description of sphingolipid metabolism and signaling, we emphasize the involvement of the S1P/S1PR axis and the downstream signaling pathways in the development of fibrosis. The current knowledge of the therapeutic potential of S1PR subtype modulators in the treatment of the cardiac functions and fibrinogenesis are also examined. [ABSTRACT FROM AUTHOR]

Bone-marrow-derived mesenchymal stromal cells (MSCs) have the potential to significantly contribute to skeletal muscle healing through the secretion of paracrine factors that support proliferation and enhance participation of the endogenous muscle stem cells in the process of repair/regeneration. However, MSC-derived trophic molecules have been poorly characterized. The aim of this study was to investigate paracrine signaling effects of MSCs on skeletal myoblasts. It was found, using a biochemical and morphological approach that sphingosine 1-phosphate (S1P), a natural bioactive lipid exerting a broad range of muscle cell responses, is secreted by MSCs and represents an important factor by which these cells exert their stimulatory effects on C2C12 myoblast and satellite cell proliferation. Indeed, exposure to conditioned medium obtained from MSCs cultured in the presence of the selective sphingosine kinase inhibitor (iSK), blocked increased cell proliferation caused by the conditioned medium from untreated MSCs, and the addition of exogenous S1P in the conditioned medium from MSCs pre-treated with iSK further increased myoblast proliferation. Finally, we also demonstrated that the myoblast response to MSC-secreted vascular endothelial growth factor (VEGF) involves the release of S1P from C2C12 cells. Our data may have important implications in the optimization of cell-based strategies to promote skeletal muscle regeneration. [ABSTRACT FROM AUTHOR]

Simple Summary: Skeletal muscle (SkM) represents the largest "organ" in the human body as it constitutes at least 40% of the body mass. SkM mass wasting is a serious conditions since pathological tissue degeneration significantly worsens the prognosis of the associated disease and significantly reduces the quality and life expectancy with an incidence of 10–50% in patients suffering of cancer, chronic infection and inflammation. Therefore, it is urgent to investigate the molecular basis of SkM mass wasting and identify potential therapeutic targets. Apart from cytokines and chemokines, also sphingolipid mediators, particularly sphingosine-1-phosphate and ceramide 1-phosphate (C1P), contribute to cancer and inflammation, however, the contribution of  ceramide kinase (CerK), and its product ceramide 1-phosphate (C1P), to SkM mass wasting in these conditions is missing. The present study was developed using mice bearing the C26, or Lewis lung carcinoma (LLC) tumors, well characterized models of cancer-associated SkM atrophy, and in murine and human myotubes treated with conditioned media obtained from C26 or LLC-cells or with the corticosteroid dexamethasone. The results obtained reveal that CerK protein expression and the Ceramide/C1P axis are markedly impaired in all experimental models, demonstrating that the CerK/C1P axis plays a crucial role as molecular regulator of SkM mass associated to cancer or corticosteroids. Apart from cytokines and chemokines, sphingolipid mediators, particularly sphingosine-1-phosphate (S1P) and ceramide 1-phosphate (C1P), contribute to cancer and inflammation. Cancer, as well as other inflammatory conditions, are associated with skeletal muscle (SkM) atrophy, which is characterized by the unbalance between protein synthesis and degradation. Although the signaling pathways involved in SkM mass wasting are multiple, the regulatory role of simple sphingolipids is limited. Here, we report the impairment of ceramide kinase (CerK), the enzyme responsible for the phosphorylation of ceramide to C1P, associated with the accomplishment of atrophic phenotype in various experimental models of SkM atrophy: in vivo animal model bearing the C26 adenocarcinoma or Lewis lung carcinoma tumors, in human and murine SkM cells treated with the conditioned medium obtained from cancer cells or with the glucocorticoid dexamethasone. Notably, we demonstrate in all the three experimental approaches a drastic decrease of CerK expression. Gene silencing of CerK promotes the up-regulation of atrogin-1/MAFbx expression, which was also observed after cell treatment with C8-ceramide, a biologically active ceramide analogue. Conversely, C1P treatment significantly reduced the corticosteroid's effects. Altogether, these findings provide evidence that CerK, acting as a molecular modulator, may be a new possible target for SkM mass regulation associated with cancer or corticosteroids. [ABSTRACT FROM AUTHOR]

Bone-marrow-derived mesenchymal stromal cells (BM-MSCs)–based therapy represents a promising option in the field of regenerative medicine. Their therapeutic potential is mainly dependent on paracrine secretion, proliferation and ECM remodeling abilities whose modulation involves Matrix Metalloproteinase (MMP)-2 functionality. Thus, the identification of paracrine/autocrine factors regulating MMP-2 expression/ activity may be of great biological relevance for potentiating BM-MSC theraputic efficacy. Our research group has demonstrated that BM-MSCs release the bioactive lipid sphingosine-1-phosphate (S1P). Here we demonstrated : i) the requirement for BMMSC of S1P production to synthesize functional gelatinases; ii) an impairment of gelatinolytic activity and MMP-2 expression/release when the S1P receptor subtype 1 (S1PR1) is blocked. Notably, in these experimental conditions BM-MSCs did not exhibit the formation of plasmamembrane-associated F-actin structures (lamellipodia, filopodia, microspikes) and, in turn, showed a reduction of the proliferation rate. Moreover, S1P1-mediated signaling is required for HIF-1alpha expression and MMP-2 expression/activity, reduction of vinculin expression and stress fiber formation and proliferation in hypoxia, an experimental condition mimicking the injured/regenerating tissue microenvironment. In conclusion, our findings, demonstrating the trophic role exerted by the autocrine S1P/S1PR1 signaling in maintaining BM-MSC ability to modulate MMP-2 function, required for ECM remodeling, cytoskeleton assembly and cell proliferation may provide perspectives for considering S1P/S1PR1 as a pharmacological target to preserve BM-MSCs properties and improve their efficacy in tissue repair. [ABSTRACT FROM AUTHOR]

Plants contain a wide range of non-nutritive phytochemicals, many of which have protective or preventive properties for human diseases. The aim of the present work has been to investigate the nutraceutical properties of sweet chestnut flour extracts obtained from fruits collected from 7 geographic areas of Tuscany (Italy), and their ability in modulating skeletal muscle atrophy. We found that the cultivars from different geographic areas are characterized by the composition and quantity of various nutrients and specific bioactive components, such as tocopherols, polyphenols and sphingolipids. The nutraceutical properties of chestnut sweet flours have been evaluated in C2C12 myotubes induced to atrophy by serum deprivation or dexamethasone. We found that the pretreatment with both total extracts of tocopherols and sphingolipids is able to counterbalance cell atrophy, reducing the decrease in myotube size and myonuclei number, and attenuating protein degradation and the increase in expression of MAFbx/atrogin-1 (a muscle-specific atrophy marker). By contrast, polyphenol extracts were not able to prevent atrophy. Since we also found that γ-tocopherol is the major form of tocopherol in sweet flour and its content differs depending on the procedure of sweet flour preparation, the mechanisms by which γ-tocopherol as well as sphingolipids affect skeletal muscle cell atrophy have been also investigated. This is the first evidence that chestnut sweet flour is a natural source of specific bioactive components with a relevant role in the prevention of cell degeneration and maintenance of skeletal muscle mass, opening important implications in designing appropriate nutritional therapeutic approaches to skeletal muscle atrophy.