Adhesion molecule expression in experimental myositis

Neutrophil extracellular traps are involved in the occurrence of interstitial lung disease in a murine experimental autoimmune myositis model

The excessive formation of neutrophil extracellular traps (NETs) has been demonstrated to be a pathogenic mechanism of idiopathic inflammatory myopathy (IIM)-associated interstitial lung disease (ILD). This study aimed to answer whether an experimental autoimmune myositis (EAM) model can be used to study IIM-ILD and whether NETs participate in the development of EAM-ILD. An EAM mouse model was established using skeletal muscle homogenate and pertussis toxin (PTX). The relationship between NETs and the ILD phenotype was determined via histopathological analysis. As NETs markers, serum cell-free DNA (cfDNA) and serum citrullinated histone 3 (Cit-H3)-DNA were tested. The healthy mouse was injected with PTX intraperitoneally to determine whether PTX intervention could induce NETs formation in vivo. Neutrophils isolated from the peripheral blood of healthy individuals were given different interventions to determine whether PTX and skeletal muscle homogenate can induce neutrophils to form NETs in vitro. EAM-ILD had three pathological phenotypes similar to IIM-ILD. Cit-H3, neutrophil myeloperoxidase, and neutrophil elastase were overexpressed in the lungs of EAM model mice. The serum cfDNA level and Cit-H3-DNA complex level were significantly increased in EAM model mice. Serum cfDNA levels were increased significantly in vivo intervention with PTX in mice. Both PTX and skeletal muscle homogenate-induced neutrophils to form NETs in vitro. EAM-ILD pathological phenotypes are similar to IIM-ILD, and NETs are involved in the development of ILD in a murine model of EAM. Thus, the EAM mouse model can be used as an ideal model targeting NETs to prevent and treat IIM-ILD.

STROBE: The correlation of Cyr61, CTGF, and VEGF with polymyositis/dermatomyositis

This study aims to explore the roles of cysteine-rich protein 61 (Cyr61/CCN1), connective tissue growth factor (CTGF/CCN2) and vascular endothelial growth factor (VEGF) in the vascular process of polymyositis (PM)/dermatomyositis (DM).Real-time quantitative polymerase chain reaction was used to determine the mRNA expression of Cyr61, CTGF, and VEGF in muscle tissues of initially treated PM/DM patients and controls. Enzyme-linked immunosorbent assay (ELISA) was used to determine the serum levels of Cyr61, CTGF, and VEGF of initially treated PM/DM patients before and after treatment. Data were statistically analyzed using statistical software SPSS 17.0.The mRNA expression levels of Cyr61, CTGF, and VEGF in muscle tissues were higher in the PM and DM groups than in the control group (P < .05). Differences in the mRNA expression levels of Cyr61, CTGF, and VEGF in muscle tissues between the PM and DM groups were not statistically significant (P > .05). Before treatment, the serum levels of Cyr61, CTGF, and VEGF were higher in the PM and DM groups than in the control group (P < .05). Furthermore, in the PM and DM groups, the expression levels of Cyr61, CTGF, and VEGF in serum at 6 months after treatment were lower than those before treatment (P < .05).Cyr61, CTGF, and VEGF are involved in the pathogenesis of PM/DM. These may be involved in the pathogenesis mainly by affecting the formation of blood vessels and promoting inflammatory response. This suggests that microvascular lesions play an important role in the immune pathogenesis of inflammatory myopathy PM/DM.

Skeletal muscle cells actively shape (auto)immune responses

Histopathological analyses of muscle specimens from myositis patients indicate that skeletal muscle cells play an active role in the interaction with immune cells. Research over the last few decades has shown that skeletal muscle cells exhibit immunobiological properties that perfectly define them as non-professional antigen presenting cells. They are able to present antigens via major histocompatibility complex molecules, exhibit costimulatory molecules and secrete soluble molecules that actively shape the immune response in an either pro- or anti-inflammatory manner. Skeletal muscle cells regulate both innate and adaptive immune responses and are essentially involved in the pathophysiological processes of idiopathic inflammatory myopathies. Understanding the role of skeletal muscle cells might help to identify new therapeutic targets for these devastating diseases. This review summarizes the immunobiological features of skeletal muscle cells, especially in the context of idiopathic inflammatory myopathies, and discusses shortcomings and limitations in skeletal muscle related research providing potential perspectives to overcome them in the future.

Effect of butylphthalide intervention on experimental autoimmune myositis in guinea pigs

Idiopathic inflammatory myopathies are a group of rare muscular diseases that are characterized by acute, subacute or chronic proximal and symmetric muscle weakness, muscle fiber necrosis and infiltration of inflammatory cells, particularly activated CD8⁺ cytotoxic T cells and phagocytes. 3-n-butylphthalide (NBP) protects mitochondria and reduces the inflammatory response in multiple disease models. In myositis, it has remained elusive whether NBP can protect muscle cells from muscle fiber injury. Experimental autoimmune myositis (EAM) was induced in a total of 40 guinea pigs by myosin immunization. After 4 weeks, low- or high-dose NBP solution was intraperitoneally injected. Saline solution was used as a negative control. After 10 days, the clinical manifestations were assessed by determining rodent grasping power, histopathological changes, Ca²⁺-adenosinetriphosphatase (ATPase) activity by an ATPase kit, and mRNA expression of interferon (IFN)-γ, retinoic acid receptor-related orphan nuclear receptor (ROR)γt and forkhead box (Fox) p3 in muscle tissue by reverse-transcription quantitative polymerase chain reaction analysis. It was demonstrated that NBP improved the myodynamia of guinea pigs with EAM and reduced the pathological inflammatory cell infiltration in a dose-dependent manner. NBP improved the Ca²⁺-ATPase activity of the muscle mitochondrial membrane and muscle plasma membrane in animals with EAM. It also reduced the mRNA expression of IFN-γ and RORγt, and significantly increased the mRNA expression of Foxp3 in muscle tissue. These results provided a basis for the consideration of NBP as a novel agent for the treatment of myositis and other muscular diseases associated with autoimmunity and inflammation.

Idiopathic inflammatory myopathies

The idiopathic inflammatory myopathies are a group of systemic autoimmune syndromes characterized by striated muscle inflammation. Here, we discuss the clinical features of this group of conditions and review the recent developments in the understanding of the pathogenesis and immunogenetics of the idiopathic inflammatory myopathies. The role of myositis-specific autoantibodies and their clinical significance and an overview of management are also provided.

Inhibition of CX3CL1 (fractalkine) improves experimental autoimmune myositis in SJL/J mice

Idiopathic inflammatory myopathy is a chronic inflammatory muscle disease characterized by mononuclear cell infiltration in the skeletal muscle. The infiltrated inflammatory cells express various cytokines and cytotoxic molecules. Chemokines are thought to contribute to the inflammatory cell migration into the muscle. We induced experimental autoimmune myositis (EAM) in SJL/J mice by immunization with rabbit myosin and CFA. In the affected muscles of EAM mice, CX3CL1 (fractalkine) was expressed on the infiltrated mononuclear cells and endothelial cells, and its corresponding receptor, CX3CR1, was expressed on the infiltrated CD4 and CD8 T cells and macrophages. Treatment of EAM mice with anti-CX3CL1 mAb significantly reduced the histopathological myositis score, the number of necrotic muscle fibers, and infiltration of CD4 and CD8 T cells and macrophages. Furthermore, treatment with anti-CX3CL1 mAb down-regulated the mRNA expression of TNF-alpha, IFN-gamma, and perforin in the muscles. Our results suggest that CX3CL1-CX3CR1 interaction plays an important role in inflammatory cell migration into the muscle tissue of EAM mice. The results also point to the potential therapeutic usefulness of CX3CL1 inhibition and/or blockade of CX3CL1-CX3CR1 interaction in idiopathic inflammatory myopathy.

Alterations in blood-brain barrier ICAM-1 expression and brain microglial activation after lambda-carrageenan-induced inflammatory pain

Previous studies showed that peripheral inflammatory pain increased blood-brain barrier (BBB) permeability and altered tight junction protein expression and the delivery of opioid analgesics to the brain. What remains unknown is which pathways and mediators during peripheral inflammation affect BBB function and structure. The current study investigated effects of lambda-carrageenan-induced inflammatory pain (CIP) on BBB expression of ICAM-1. We also examined the systemic contribution of a number of proinflammatory cytokines and microglial activation in the brain to elucidate pathways involved in BBB disruption during CIP. We investigated ICAM-1 RNA and protein expression levels in isolated rat brain microvessels after CIP using RT-PCR and Western blot analyses, screened inflammatory cytokines during the time course of inflammation, assessed white blood cell counts, and probed for BBB and central nervous system stimulation and leukocyte transmigration using immunohistochemistry and flow cytometry. Results showed an early increase in ICAM-1 RNA and protein expression after CIP with no change in circulating levels of several proinflammatory cytokines. Changes in ICAM-1 protein expression were noted at 48 h. Immunohistochemistry showed that the induction of ICAM-1 was region specific with increased expression noted in the thalamus and frontal and parietal cortices, which directly correlated with increased expression of activated microglia. The findings of the present study were that CIP induces increased ICAM-1 mRNA and protein expression at the BBB and that systemic proinflammatory mediators play no apparent role in the early response (1-6 h); however, brain region-specific increases in microglial activation suggest a potential for a central-mediated response.