Muscle cells could serve as antigen-presenting cells, and participate in the activation of immune response. Immunological characteristics of muscle cells, and their capacities to equip themselves with immunorelevant molecules, remain to be elucidated. In this study, we investigated the immunological properties of myoblasts and differentiated myotubes in vitro and in vivo, under the IFN-γ induced inflammatory condition. We found that the fused C C myotubes are more sensitive to inflammatory stimulation, and significantly upregulated the expression levels of MHC-I/II and TLR3/7 molecules, than that of proliferated myoblasts. As well, some co-stimulatory/-inhibitory molecules, including CD40, CD86, ICAM-I, ICOS-L, and PD-L1, were prominently upregulated in IFN-γ induced myotubes. Notably, we detected the protein levels of ASC, NLRP3, and Caspase-1 increased in stimulated myotubes, and IL-1β in cell culture supernatant, implying the activation of NLRP3 inflammasomes in IFN-γ treated myotubes. The pro-inflammatory cytokines and chemokines mRNA levels in IFN-γ induced C C myotubes and myoblasts, involving IL-1, IL-6, and MCP-1, increased markedly. T cell activation test further verified IFN-γ induced C C myotubes prompt to the proliferation of the splenic CD4 and CD8 T cells. In Cardiotoxin-damaged tibialis anterior (TA) muscle, some regenerated myofibers expressed both MHC class I and class II molecules under IFN-γ enhanced inflammatory condition. Thus, our work demonstrates that muscle cells are active participants of local immune reactions. Anat Rec, 301:1551-1563, 2018. © 2018 Wiley Periodicals, Inc.

◥Epigenetic changes are one underlying cause for cancer development and often due to dysregulation of enzymes modifying DNA or histones. Most Jumonji C domain-containing (JMJD) proteins are histone lysine demethylases (KDM) and therefore epigenetic regulators. One JMJD subfamily consists of JMJD1A/KDM3A, JMJD1B/KDM3B, and JMJD1C/KDM3C that are roughly 50% identical at the amino acid level. All three JMJD1 proteins are capable of removing dimethyl and monomethyl marks from lysine 9 on histone H3 and might also demethylate histone H4 on arginine 3 and nonhistone proteins. Analysis of knockout mice revealed critical roles for JMJD1 proteins in fertility, obesity, metabolic syndrome, and heart disease. Importantly, a plethora of studies demonstrated that especially JMJD1A and JMJD1C are overexpressed in various tumors, stimulate cancer cell proliferation and invasion, and facilitate efficient tumor growth. However, JMJD1A may also inhibit the formation of germ cell tumors. Likewise, JMJD1B appears to be a tumor suppressor in acute myeloid leukemia, but a tumor promoter in other cancers. Notably, by reducing methylation levels on histone H3 lysine 9, JMJD1 proteins can profoundly alter the transcriptome and thereby affect tumorigenesis, including through upregulating oncogenes such as CCND1, JUN, and MYC. This epigenetic activity of JMJD1 proteins is sensitive to heavy metals, oncometabolites, oxygen, and reactive oxygen species, whose levels are frequently altered within cancer cells. In conclusion, inhibition of JMJD1 enzymatic activity through small molecules is predicted to be beneficial in many different cancers, but not in the few malignancies where JMJD1 proteins apparently exert tumor-suppressive functions.

The objective of this study is to investigate the role of Calmodulin-dependent protein kinase IV (CaMKIV) in Cardiotoxin (CTX)-induced mice muscle inflammation. CTX injection i.m. was performed to induce B6 mice acute tibialis anterior (TA) muscle injury. The mice were then injected i.p. with the recombinant CaMKIV protein or its antagonist KN-93. Immunoblotting was used to assess Calmodulin (CaM) and CaMKIV levels. Immunofluorescence was used to detect intramuscular infiltration or major histocompatibility complex (MHC)-I expression in damaged muscle. The extent of infiltration was evaluated by fluorescent intensity analysis. Cytokines/chemokines levels were determined by qPCR. CaMKIV gene knockdown in C2C12 cells was performed in order to evaluate the effects of CaMKIV on immuno-behavior of muscle cells. CTX administration induced a strong up-regulation of CaM and p-CaMKIV levels in infiltrated mononuclear cells and regenerated myofibers. In vivo adding of the recombinant CaMKIV protein enhanced intramuscular infiltration of monocytes/macrophages in damaged muscle and increased the number of proinflammatory Ly-6CF4/80 macrophage cells. CaMKIV protein treatment induced a striking up-regulation of mRNA levels of IL-1, IL-6, MCP-1, and MCP-3 in CD45 cells sorted from damaged muscle; increased the infiltration of CD8 T cells; and induced the up-regulation of MHC-I in partial regenerated myofibers, which was rarely observed in muscle damage alone. Additionally, CaMKIV protein treatment diminished the regulatory T cells (Tregs) number and led to the damaged TA muscle repair delay. In vitro CaMKIV gene knockdown reversed IFN-γ-induced up-regulation of MHC-I/II and TLR3 in the differentiated C2C12 myotubes. CaMKIV can act as an immunostimulation molecule and enhances the acute muscle inflammatory responses.

Synthetic peptide-based polyurethanes (PUs), introduced as bioactive agents and possessing impressive properties, have emerged as attractive functional biomaterials for tissue regeneration.

Key points There is a close relationship between skeletal muscle physiology and Ca2+/calmodulin (CaM) signalling. Despite the effects of Ca2+/CaM signalling on immune and inflammatory responses having been extensively explored, few studies have investigated the role of CaM pathway activation on the post‐injury muscle inflammatory response. In this study, we investigated the role of CaM‐dependent signalling in muscle inflammation in cardiotoxin induced myoinjuries in mice. The Ca2+/calmodulin‐dependent protein kinase II (CaMII), Ca2+/calmodulin‐dependent protein kinase IV (CaMKIV), and nuclear factor of activated T cells (NFAT) pathways are likely to be simultaneously activated in muscle cells and in infiltrating lymphocytes and to regulate the immune behaviours of myofibres in an inflammatory environment, and these pathways ultimately affect the outcome of muscle inflammation. Abstract Calcium/calmodulin (Ca2+/CaM) signalling is essential for immune and inflammatory responses in tissues. However, it is unclear if Ca2+/CaM signalling interferes with muscle inflammation. Here we investigated the roles of CaM‐dependent signalling in muscle inflammation in mice that had acute myoinjuries in the tibialis anterior muscle induced by intramuscular cardiotoxin (CTX) injections and received intraperitoneal injections of either the CaM inhibitor calmidazolium chloride (CCL) or CaM agonist calcium‐like peptide 1 (CALP1). Multiple inflammatory parameters, including muscle autoantigens and toll‐like receptors, mononuclear cell infiltration, cytokines and chemokines associated with peripheral muscle inflammation, were examined after the injury and treatment. CALP1 treatment enhanced intramuscular infiltration of monocytes/macrophages into the damaged tibialis anterior muscle and up‐regulated mRNA and protein levels of muscle autoantigens (Mi‐2, HARS and Ku70) and Toll‐like receptor 3 (TLR3), and mRNA levels of tumor necrosis factor α (TNF‐α), interleukin‐6 (IL‐6), Monocyte chemoattractant protein‐1 (MCP1), Monocyte chemoattractant protein‐3 (MCP3) and Macrophage inflammatory protein‐1(MIP‐1α) in damaged muscle. In contrast, CCL treatment decreased the intramuscular cell infiltration and mRNA levels of the inflammatory mediators. After CALP1 treatment, a substantial up‐regulation in Ca2+/calmodulin‐dependent protein kinase II (CaMKII), Ca2+/calmodulin‐dependent protein kinase IV (CaMKIV) and nuclear factor of activated T cells (NFAT) activity was detected in CD45+ cells isolated from the damaged muscle. More pro‐inflammatory F4/80+Ly‐6C+ cells were detected in CD45‐gated cells after CALP1 treatment than in those after CCL treatment or no treatment. Consistently, in interferon‐γ‐stimulated cultured myoblasts and myotubes, CALP1 treatment up‐regulated the activities of CaMKII, CaMKIV and NFAT, and levels of class I/II major histocompatibility complexes (MHC‐I/II) and TLR3. Our findings demonstrated that CaM‐dependent signalling pathways mediate the injury‐induced acute muscle inflammatory response.

Skeletal muscle repair and systemic inflammation/immune responses are linked to endoplasmic reticulum stress (ER stress) pathways in myopathic muscle, and muscle cells play an active role in muscular immune reactions by exhibiting immunological characteristics under persistent proinflammation stimuli. Whether ER stress affects the intrinsic immunological capacities of myocytes in the inflammatory milieu, as it does to immune cells, and which arms of the unfolded protein response (UPR) mainly participate in these processes remain mostly unknown. We investigated this issue and showed that inflammatory stimuli can induce the activation of the protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK) and inositol-requiring enzyme 1α (IRE1α) arms of the UPR in myocytes both in vivo and in vitro. UPR stressor administration reversed the increased IFN-γ-induced expression of the MHC-II molecule H2-Ea, the MHC-I molecule H-2Kb, toll-like receptor 3 (TLR3) and some proinflammatory myokines in differentiated primary myotubes in vitro. However, further IRE1α inhibition thoroughly corrected the trend in the UPR stressor-triggered suppression of immunobiological molecules. In IFN-γ-treated myotubes, dramatic p38 MAPK activation was observed under IRE1α inhibitory conditions, and the pharmacological inhibition of p38 reversed the immune molecule upregulation induced by IRE1α inhibition. In parallel, our coculturing system verified that the ovalbumin (OVA) antigen presentation ability of inflamed myotubes to OT-I T cells was enhanced by IRE1α inhibition, but was attenuated by further p38 inhibition. Thus, the present findings demonstrated that p38 MAPK contributes greatly to IRE1α arm-dependent immunobiological suppression in myocytes under inflammatory stress conditions.

TGF-β is considered to be an important immuno regulatory cytokine. However, it remains unknown whether and how the muscle fiber specific-TGF-β signaling is directly involved in intramuscular inflammatory regulation by affecting T cells. Here, we addressed these in a mouse tibialis anterior muscle Cardiotoxin injection-induced injury repair model in MCK-Cre control or transgenic mice with TGF-β receptor II (TGF-βr2) being specifically deleted in muscle cells (SM TGF-βr2-/-). In control mice, TGF-β2 and TGF-βr2 were found significantly up-regulated in muscle after the acute injury. In mutant mice, deficiency of TGF-β signaling in muscle cells caused more serious muscle inflammation, with the increased infiltration of macrophages and CD4+ T cells at the degeneration stage (D4) and the early stage of regeneration (D7) after myoinjury. Notably, the loss of TGF-β signaling in myofibers dramatically affected on CD4+ T cell function and delayed T cells withdrawal at the later stage of muscle regeneration (D10 and D15), marked by the elevated Th17, but the impaired Tregs response. Furthermore, in vivo and in vitro, the intrinsic TGF-β signaling affected on immune behaviors of muscle cells, and directed CD4+ T cells differentiation by impairing IL-6 production and release. It suggests that local muscle inflammation can be inhibited potentially by directly activating the TGF-β signaling pathway in muscle cells to suppress Th17, but induce Tregs responses. Thus, according to the results of this study, we found a new idea for the control of local acute inflammation in skeletal muscle.

In this work, we used the injectable PNIPAM hydrogel as a new bio-driver to induce chronic skeletal muscle inflammation response.