The injury-induced myokine insulin-like 6 is protective in experimental autoimmune myositis

The diverse influences of relaxin-like peptide family on tumor progression: Potential opportunities and emerging challenges

Relaxin-like peptide family exhibit differential expression patterns in various types of cancers and play a role in cancer development. This family participates in tumorigenic processes encompassing proliferation, migration, invasion, tumor microenvironment, immune microenvironment, and anti-cancer resistance, ultimately influencing patient prognosis. In this review, we explore the mechanisms underlying the interaction between the RLN-like peptide family and tumors and provide an overview of therapeutic approaches utilizing this interaction.

Single-cell transcriptomic analysis reveals rich pituitary-Immune interactions under systemic inflammation

The pituitary represents an essential hub in the hypothalamus-pituitary-adrenal (HPA) axis. Pituitary hormone-producing cells (HPCs) release several hormones to regulate fundamental bodily functions under normal and stressful conditions. It is well established that the pituitary endocrine gland modulates the immune system by releasing adrenocorticotropic hormone (ACTH) in response to neuronal activation in the hypothalamus. However, it remains unclear how systemic inflammation regulates the transcriptomic profiles of pituitary HPCs. Here, we performed single-cell RNA-sequencing (scRNA-seq) of the mouse pituitary and revealed that upon inflammation, all major pituitary HPCs respond robustly in a cell type-specific manner, with corticotropes displaying the strongest reaction. Systemic inflammation also led to the production and release of noncanonical bioactive molecules, including Nptx2 by corticotropes, to modulate immune homeostasis. Meanwhile, HPCs up-regulated the gene expression of chemokines that facilitated the communication between the HPCs and immune cells. Together, our study reveals extensive interactions between the pituitary and immune system, suggesting multifaceted roles of the pituitary in mediating the effects of inflammation on many aspects of body physiology.

Myocardial Infarction-Induced INSL6 Decrease Contributes to Breast Cancer Progression

Myocardial infarction (MI) induces early-stage breast cancer progression and increases breast cancer patients' mortality and morbidity. Insulin-like peptide 6 (INSL6) overexpression can impede cardiotoxin-induced injury through myofiber regeneration, playing a significant role in MI progression. To investigate the diverse significance of INSL6 in a variety of malignant tumors, we explored INSL6 through MI GEO dataset and multiple omics data integrative analysis, such as gene expression level, enriched pathway analysis, protein-protein interaction (PPI) analysis, and immune subtypes as well as diagnostic value and prognostic value in pancancer. INSL6 expression was downregulated in the MI group, and overall survival analysis demonstrated that INSL6 could be the prognostic biomarkers in the overall survival of breast cancer (BRCA). INSL6 expression differs significantly not only in most cancers but also in different molecular and immune subtypes of cancers. INSL6 might be a potential diagnostic and prognostic biomarker of cancers due to the high accuracy in diagnostic and prognostic value. Furthermore, we focused on BRCA and further investigated INSL6 from the perspective of the correlations with clinical characteristics, prognosis in different clinical subgroups, coexpression genes, and differentially expressed genes (DEGs) and PPI analysis. Overall survival and disease-specific survival analysis of subgroups in BRCA demonstrated that lower INSL6 expression had a worse prognosis. Therefore, INSL6 aberrant expression is associated with the progression and immune cell infiltration of the tumor, especially in KIRP and BRCA. Therefore, INSL6 may serve as a potential prognostic biomarker and the crosstalk between MI and tumor progression.

Major histocompatibility complex I-induced endoplasmic reticulum stress mediates the secretion of pro-inflammatory muscle-derived cytokines

Major histocompatibility complex (MHC) I is an important component of intracellular antigen presentation. However, improper expression of MHC I upon the cell surface has been associated with several autoimmune diseases. Myositis is a rare acquired autoimmune disease which targets skeletal muscle, and MHC I overexpression on the surface of muscle fibres and immune cell infiltration are clinical hallmarks. MHC I overexpression may have an important pathogenic role, mediated by the activation of the endoplasmic reticulum (ER) stress response. Given the evidence that muscle is a diverse source of cytokines, we aimed to investigate whether MHC I overexpression can modify the profile of muscle-derived cytokines and what role the ER stress pathway may play. Using C2C12 myoblasts we overexpressed MHC I with a H-2k^b vector in the presence or absence of salubrinal an ER stress pathway modifying compound. MHC I overexpression induced ER stress pathway activation and elevated cytokine gene expression. MHC I overexpression caused significant release of cytokines and chemokines, which was attenuated in the presence of salubrinal. Conditioned media from MHC I overexpressing cells induced in vitro T-cell chemotaxis, atrophy of healthy myotubes and modified mitochondrial function, features which were attenuated in the presence of salubrinal. Collectively, these data suggest that MHC I overexpression can induce pro-inflammatory cytokine/chemokine release from C2C12 myoblasts, a process which appears to be mediated in-part by the ER stress pathway.

Role of Myokines in Myositis Pathogenesis and Their Potential to be New Therapeutic Targets in Idiopathic Inflammatory Myopathies

Idiopathic inflammatory myopathies (IIM) represent a heterogeneous group of autoimmune diseases whose treatment is often a challenge. Many patients, even after immunosuppressive therapy, do not respond to treatment, so new alternatives have been sought for this. Therefore, other signaling pathways that could contribute to the pathogenesis of myositis have been investigated, such as the expression of myokines in skeletal muscle in response to the inflammatory process. In this review, we will refer to these muscle cytokines that are overexpressed or downregulated in skeletal muscle in patients with various forms of IIM, thus being able to contribute to the maintenance of the autoimmune process. Some muscle cytokines, through their antagonistic action, may be a helpful contributor to the disease modulation, and thus, they could represent personalized treatment targets. Here, we consider the main myokines involved in the pathogenesis of myositis, expressing our view on the possibility of using them as potential therapeutic targets: interleukins IL-6, IL-15, and IL-18; chemokines CXCL10, CCL2, CCL3, CCL4, CCL5, and CCL20; myostatin; follistatin; decorin; osteonectin; and insulin-like 6. An interesting topic regarding the complex connection between myokines and noninflammatory pathways implied in IIM has also been briefly described, because it is an important scientific approach to the pathogenesis of IIM and can be a therapeutic alternative to be considered, especially for the patients who do not respond to immunosuppressive treatment.

Comparison of rapamycin and methylprednisolone for treating inflammatory muscle disease in a murine model of experimental autoimmune myositis

Idiopathic inflammatory myopathies (IIMs) are a group of autoimmune inflammatory muscle diseases. Rapamycin has been shown to ameliorate inflammation and improve muscle function in a mouse model of experimental autoimmune myositis (EAM). In the present study, the therapeutic effect of rapamycin was compared with methylprednisolone (MP) on EAM. Mice were injected with myosin for 10 days to induce EAM and were subsequently treated with rapamycin (1.5 mg/kg), MP (40 mg/kg) or placebo (DMSO) for 14 days. The rapamycin-treated group exhibited significantly decreased severe inflammation and improved muscle strength compared with the MP-treated group. The plasma transforming growth factor-β (TGF-β) concentration in the rapamycin-treated group was significantly higher compared with the placebo group. However, both treatment groups exhibited significantly lower plasma interleukin-10 levels compared with the placebo group. Moreover, splenic regulatory T cell frequency in both the rapamycin- and MP-treated animals was significantly lower than that in the animals of the placebo group. Rapamycin showed better immune suppressive effects than MP in this model of EAM, and these effects were likely to be mediated by the TGF-β signaling pathway.

Relaxin Family Member Insulin-Like Peptide 6 Ameliorates Cardiac Fibrosis and Prevents Cardiac Remodeling in Murine Heart Failure Models

BACKGROUND

The insulin/insulin-like growth factor/relaxin family represents a group of structurally related but functionally diverse proteins. The family member relaxin-2 has been evaluated in clinical trials for its efficacy in the treatment of acute heart failure. In this study, we assessed the role of insulin-like peptide 6 (INSL6), another member of this protein family, in murine heart failure models using genetic loss-of-function and protein delivery methods.

METHODS AND RESULTS

Insl6-deficient and wild-type (C57BL/6N) mice were administered angiotensin II or isoproterenol via continuous infusion with an osmotic pump or via intraperitoneal injection once a day, respectively, for 2 weeks. In both models, Insl6-knockout mice exhibited greater cardiac systolic dysfunction and left ventricular dilatation. Cardiac dysfunction in the Insl6-knockout mice was associated with more extensive cardiac fibrosis and greater expression of fibrosis-associated genes. The continuous infusion of chemically synthesized INSL6 significantly attenuated left ventricular systolic dysfunction and cardiac fibrosis induced by isoproterenol infusion. Gene expression profiling suggests liver X receptor/retinoid X receptor signaling is activated in the isoproterenol-challenged hearts treated with INSL6 protein.

CONCLUSIONS

Endogenous Insl6 protein inhibits cardiac systolic dysfunction and cardiac fibrosis in angiotensin II- and isoproterenol-induced cardiac stress models. The administration of recombinant INSL6 protein could have utility for the treatment of heart failure and cardiac fibrosis.

In vivo generation of a mature and functional artificial skeletal muscle

Extensive loss of skeletal muscle tissue results in mutilations and severe loss of function. In vitro-generated artificial muscles undergo necrosis when transplanted in vivo before host angiogenesis may provide oxygen for fibre survival. Here, we report a novel strategy based upon the use of mouse or human mesoangioblasts encapsulated inside PEG-fibrinogen hydrogel. Once engineered to express placental-derived growth factor, mesoangioblasts attract host vessels and nerves, contributing to in vivo survival and maturation of newly formed myofibres. When the graft was implanted underneath the skin on the surface of the tibialis anterior, mature and aligned myofibres formed within several weeks as a complete and functional extra muscle. Moreover, replacing the ablated tibialis anterior with PEG-fibrinogen-embedded mesoangioblasts also resulted in an artificial muscle very similar to a normal tibialis anterior. This strategy opens the possibility for patient-specific muscle creation for a large number of pathological conditions involving muscle tissue wasting.

Development of an improved animal model of experimental autoimmune myositis

Multiple animal models of experimental autoimmune myositis (EAM) have been developed. However, these models vary greatly in the severity of disease and reproducibility. The goal of this study was to test whether vaccination twice with increased dose of rat myosin and pertussis toxin (PT) could induce EAM with severer disease in mice. BALB/c mice were injected with 1 mg rat myosin in 50% complete Freund's adjuvant (CFA) weekly for four times and one time of PT (EAM) or twice with 1.5 mg myosin in CFA and PT (M-EAM). In comparison with that in the CFA and PT injected controls, vaccination with rat myosin and injection PT significantly reduced the muscle strength and EMG duration, elevated serum creatine kinase levels, promoted inflammatory infiltration in the muscle tissues, leading to pathological changes in the muscle tissues, demonstrating to induce EAM. Interestingly, we found that vaccination twice with the high dose of myosin and PT prevented EAM-related gain in body weights and caused significantly less muscle strength in mice. More importantly, all of the mice receiving high dose of myosin and PT survived while 3 out of 16 mice with four times of low dose of myosin died. Finally, vaccination with high dose of myosin promoted CD4(+) and CD8(+) T cell infiltration in the muscle tissues and up-regulated MHC-I expression in the muscle tissues of mice. Hence, the new model of EAM is a time-saving, efficient and easily replicable tool for studying autoimmune myositis.