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Nitric oxide and muscle repair : multiple actions converging on therapeutic efficacy
No full textMuscular dystrophies comprise an heterogeneous group of diseases characterised by primary wasting of skeletal muscle, in the most severe forms leading to progressive paralysis and death. Current therapies for these conditions are extremely limited and based on corticosteroids that bear significant side effects. Several studies have proposed possible alternative strategies, ranging from cell and gene therapy to more classical pharmacological approaches. Nitric oxide is a gaseous messenger involved in many mechanisms responsible for preserving muscle function and stimulating muscle repair. We herein review the most recent pre-clinical and clinical findings that open new prospective for the development of nitric oxide as a therapeutic tool for muscular dystrophies
Fat deposition and accumulation in the damaged and inflamed skeletal muscle : cellular and molecular players
No full textThe skeletal muscle has the capacity to repair damage by the activation and differentiation of fiber sub-laminar satellite cells. Regeneration impairment due to reduced satellite cells number and/or functional capacity leads to fiber substitution with ectopic tissues including fat and fibrous tissue and to the loss of muscle functions. Muscle mesenchymal cells that in physiological conditions sustain or directly contribute to regeneration differentiate in adipocytes in patients with persistent damage and inflammation of the skeletal muscle. These cells comprise the fibro-adipogenic precursors, the PW1-expressing cells and some interstitial cells associated with vessels (pericytes, mesoangioblasts and myoendothelial cells). Resident fibroblasts that are responsible for collagen deposition and extracellular matrix remodeling during regeneration yield fibrotic tissue and can differentiate into adipose cells. Some authors have also proposed that satellite cells themselves could transdifferentiate into adipocytes, although recent results by lineage tracing techniques seem to put this theory to discussion. This review summarizes findings about muscle resident mesenchymal cell differentiation in adipocytes and recapitulates the molecular mediators involved in intramuscular adipose tissue deposition
Cell death : tipping the balance of autoimmunity and tissue repair.
No full textInflammation is a key homeostatic process elicited by microbial components and by tissue damage. Increasing evidence indicates that the outcomes either tissue repair or persistent inflammatory damage and degeneration tightly depend on the pattern of cell death in situ and on infiltrating leukocytes and antigen presenting cells. Defects in the initiation andexecution steps of programmed cell death such as in the clearance of cell debris are indeed often associated to inflammation defective repair and autoinummity. Here we report recent developments on the control of apoptosis induction and execution discussing how cell death may be exploited for therapeutic purposes and the links between cell death persisting inflammation and stem cell recruitment and activation in experimental models of complex human diseases such as muscular dystrophy and cancer
Requirement of Inducible Nitric Oxide Synthase for Skeletal Muscle Regeneration after Acute Damage
Full text linkAdult skeletal muscle regeneration results from activation, proliferation, and fusion of muscle stem cells, such as myogenic precursor cells. Macrophages are consistently present in regenerating skeletal muscles and participate into the repair process. The signals involved in the cross-talk between various macrophage populations and myogenic precursor cells have been only partially identified. In this study, we show a key role of inducible NO synthase (iNOS), expressed by classically activated macrophages in the healing of skeletal muscle. We found that, after sterile injury, iNOS expression is required for effective regeneration of the tissue, as myogenic precursor cells in the muscle of injured iNOS(-/-) mice fail to proliferate and differentiate. We also found that iNOS modulates inflammatory cell recruitment: damaged muscles of iNOS(-/-) animals express significantly higher levels of chemokines such as MIP2, MCP1, MIP-1 alpha, and MCP1, and display more infiltrating neutrophils after injury and a persistence of macrophages at later time points. Finally, we found that iNOS expression in the injured muscle is restricted to infiltrating macrophages. To our knowledge, these data thus provide the first evidence that iNOS expression by infiltrating macrophages contributes to muscle regeneration, revealing a novel mechanism of inflammation-dependent muscle healing
Nitric oxide boosts chemoimmunotherapy via inhibition of acid sphingomyelinase in a mouse model of melanoma
No full textCisplatin is one of the most effective anticancer drugs, but its severe toxic effects, including depletion of immune-competent cells, limit its efficacy. We combined the systemic treatment with cisplatin with intratumor delivery of dendritic cells (DC) previously treated ex vivo with a pulse of nitric oxide (NO) released by the NO donors (z)-1-[2-(2-aminoethyl)-N-(2- ammonioethyl)amino]-diazen-1-ium-1,2-diolate or isosorbide dinitrate. We found that this chemoimmunotherapy, tested in the B16 mouse model of melanoma, was significantly more efficacious than cisplatin alone, leading to tumor regression and animal survival at low doses of cisplatin that alone had no effect. Tumor cure was not observed when combining cisplatin with DCs not exposed to NO donors, indicating the key role of the pretreatment with NO. We investigated the mechanisms responsible for the synergic effect of NO-treated DCs and cisplatin and found that NO-treated DCs were protected both in vitro and in vivo from cisplatin-induced cytotoxicity. Cisplatin triggered DC apoptosis through increased expression and activation of acid sphingomyelinase; pretreatment of DCs with NO donors prevented such activation and inhibited activation of the downstream proapoptotic events, including generation of ceramide, activation of caspases 3 and 9, and mitochondrial depolarization. The effects of NO were mediated through generation of its physiologic messenger, cyclic GMP. We conclude that NO and NO gener ating drugs represent promising tools to increase the efficacy of chemoimmunotherapies in vivo, promoting the survival and increasing the function of injected cells by targeting a key pathway in cisplatin-induced cytotoxicity
In vivo PET monitoring of an experimental model of peritoneal carcinogenesis
No full textIntroduction: Peritoneal carcinogenesis is present in 80% of ovarian carcinoma patients at the time of diagnosis and occurs also in gastric, colon, bladder and pancreas cancer patients[1]. It is characterized by neoplastic masses and an inflammatory infiltrate in which tumour associated-macrophages are present. These cells release a vast number of factors that promote tumourigenesis, remodelling of extracellular matrix and neo-angiogenesis[2]. Pre-clinical studies of peritoneal carcinogenesis have been hampered by the inaccessibility of the peritoneal cavity. In this work we evaluated the feasibility of PET imaging to monitor non invasively the extent of peritoneal carcinogenesis in living animals[3] and consequentially the role of macrophages in the peritoneal carcinosis evaluating an active therapy on Immune System.
Methods: We established a murine model of peritoneal carcinogenesis by injecting i.p. in syngeneic hosts murine adenocarcinoma cell line (TS/A). Animals were treated with clodronate encapsulated in liposomes or empty liposomes as control to deplete macrophages. For animal-PET studies, mice were injected i.v. with 116.74±7.39 mCi of [18F]FDG. PET acquisition started at 60 minutes after tracer injection and lasted for 30 minutes (6 frames of 5 minutes). For the images quantification, tumour regions of interest (ROIs) were automatically generated by thresholding 3D PET studies using ImageJ software. To investigate regional differences in tumour uptake and dispersion in the same individual through time and in comparison with animals of different groups, an automatic analysis was performed in MATLAB 7 software. Briefly, each PET acquisition was masked with the respective 3D ROIs previously generated and tumour average (± SD) uptake values, minimal, maximal values, number of pixel involved in the region were calculated. After death, peritoneal liquid was analyzed by FACS (F4/80 and CD11) in order to characterize the tumour infiltration and to assess the efficiency of the depletion.
Results: PET-[18F]FDG revealed the onset and the progression of masses in the abdominal cavity. Moreover the intensity of the radioactive signal correlated with the size of lesions. Animals treated with clodronate developed less neoplastic masses whereas animals no treated showed an higher PET signal due also to inflammation. By quantifying the 3D images obtained by PET by masking tumor regions we verified that information gathered through PET scans were in keeping with the net weight of tumor lesions for the clodronate treated group. We obtained an efficiently depletion of peritoneal macrophages.
Conclusions: Our results indicated PET imaging represents an accurate PET in vivo preclinical technique to visualize and monitor peritoneal carcinosis. Preliminary results suggest that clodronate might exert a positive effect on peritoneal lesions producing a significant regression of neoplastic lesions or associated inflammatory process
Synergism of nitric oxide and maturation signals on human dendritic cells occurs through a cyclic GMP-dependent pathway
Full text linkNitric oxide (NO), generated by phagocytes at inflammation sites, contributes to regulate immune responses through autocrine and paracrine actions on bystander cells. Among the latter are dendritic cells (DCs). Little is known about regulation of DC function by NO, especially in the human system. We exposed human monocyte-derived DCs to the NO donor (z)-1-[2-(2-aminoethyl)-N-(2-ammonioethyl)amino] diazen-1-ium-1,2 diolate (DETA-NO) during their maturation process induced by treatment with tumor necrosis factor alpha or lipopolysaccharide or by CD40 activation. We report here that after exposure to DETA-NO, DCs exhibit a significantly increased ability to activate T lymphocytes stimulated by mycobacterial antigens, Staphylococcus aureus Cowen strain B, allo-antigens, or cross-linking of the CD3-T cell receptor complex. This effect persists after removal of DETA-NO, depends on the generation of cyclic guanosine 5'-monophosphate, and is a result of enhanced release by DCs of soluble factors, in particular interleukin (IL)-12. This modulation of DC function is a result of a synergism between NO and the various maturation stimuli, as neither enhanced T cell activation nor IL-12 release was observed after DC exposure to DETA-NO only. These results provide the first evidence that NO acts as a cosignaling molecule regulating human DC response to maturation stimuli
The tissue pentraxin PTX3 limits C1q-mediated complement activation and phagocytosis of apoptotic cells by dendritic cells
No full textPentraxins (PTX) and complement belong to the humoral arm of the innate immune system and have essential functions in immune defense to microbes and in scavenging cellular debris. The prototypic long PTX, PTX3, and the first component of the classical complement pathway, C1q, are innate opsonins involved in the disposal of dying cells by phagocytes. Whether the interaction between various innate opsonins impacts on their function is not fully understood. We show here that characterized Toll-like receptor (TLR) ligands elicit the production of C1q and PTX3 by immature dendritic cells (DC). Moreover, these molecules bind to dying cells with similar kinetics, although they recognize different domains on the cell membranes. PTX3 binds in the fluid phase to C1q, decreasing C1q deposition and subsequent complement activation on apoptotic cells. C1q increases the phagocytosis of apoptotic cells by DC and the release of interleukin-12 in the presence of TLR4 ligands and apoptotic cells; PTX3 inhibits both events. Moreover, PTX3 inhibited the cross-presentation of the MELAN-A/melanoma antigen-reactive T cell 1 (MART-1) tumor antigen expressed by dying cells, even in the presence of C1q. These results suggest that interaction of C1q and PTX3 influences the clearance of apoptotic cells by DC. The coordinated induction by primary, proinflammatory signals of C1q and PTX3 and their reciprocal regulation during inflammation influences the clearance of apoptotic cells by antigen-presenting cells and possibly plays a role in immune homeostasis
Transplanted mesoangioblasts require macrophage IL-10 for survival in a mouse model of muscle injury
Full text linkThe aim of this study was to verify whether macrophages influence the fate of transplanted mesoangioblasts - vessel-associated myogenic precursors - in a model of sterile toxin-induced skeletal muscle injury. We have observed that in the absence of macrophages, transplanted mesoangioblasts do not yield novel fibers. Macrophages retrieved from skeletal muscles at various times after injury display features that resemble those of immunoregulatory macrophages. Indeed, they secrete IL-10 and express CD206 and CD163 membrane receptors and high amounts of arginase I. We have reconstituted the muscle-associated macrophage population by injecting polarized macrophages before mesoangioblast injection: alternatively activated, immunoregulatory macrophages only support mesoangioblast survival and function. This action depends on the secretion of IL-10 in the tissue. Our results reveal an unanticipated role for tissue macrophages in mesoangioblast function. Consequently, the treatment of muscle disorders with mesoangioblasts should take into consideration coexisting inflammatory pathways, whose activation may prove crucial for its success. Copyright © 2012 by The American Association of Immunologists, Inc
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