Meteorin-like protein overexpression ameliorates fulminant hepatitis in mice by inhibiting chemokine-dependent immune cell infiltration

Meteorin-like protein/METRNL/Interleukin-41 ameliorates atopic dermatitis-like inflammation

BACKGROUND

Meteorin-like protein (METRNL)/Interleukin-41 (IL-41) is a novel immune-secreted cytokine/myokine involved in several inflammatory diseases. However, how METRNL exerts its regulatory properties on skin inflammation remains elusive. This study aims to elucidate the functionality and regulatory mechanism of METRNL in atopic dermatitis (AD).

METHODS

METRNL levels were determined in skin and serum samples from patients with AD and subsequently verified in the vitamin D3 analogue MC903-induced AD-like mice model. The cellular target of METRNL activity was identified by multiplex immunostaining, single-cell RNA-seq and RNA-seq.

RESULTS

METRNL was significantly upregulated in lesions and serum of patients with dermatitis compared to healthy controls (p <.05). Following repeated MC903 exposure, AD model mice displayed elevated levels of METRNL in both ears and serum. Administration of recombinant murine METRNL protein (rmMETRNL) ameliorated allergic skin inflammation and hallmarks of AD in mice, whereas blocking of METRNL signaling led to the opposite. METRNL enhanced β-Catenin activation, limited the expression of Th2-related molecules that attract the accumulation of Arginase-1 (Arg1)hi macrophages, dendritic cells, and activated mast cells.

CONCLUSIONS

METRNL can bind to KIT receptor and subsequently alleviate the allergic inflammation of AD by inhibiting the expansion of immune cells, and downregulating inflammatory gene expression by regulating the level of active WNT pathway molecule β-Catenin.

Metrnl/C-KIT Axis Attenuates Early Brain Injury Following Subarachnoid Hemorrhage by Inhibiting Neuronal Ferroptosis

BACKGROUND AND PURPOSE

Ferroptosis is a distinct form of cell death characterized by iron-dependent lipid peroxidation and plays a crucial role in the early brain injury (EBI) following subarachnoid hemorrhage (SAH). As a newly discovered endogenous ligand for the C-KIT receptor tyrosine kinase, meteorin-like protein (Metrnl) exerts regulatory functions in oxidative stress and protects against various diseases. However, the specific role of the Metrnl/C-KIT axis in neuronal ferroptosis during EBI following SAH remains to be elucidated.

METHODS

Sprague Dawley rats were used to establish the SAH model through endovascular perforation. r-Metrnl was administered intranasally 1 h after SAH. Metrnl shRNA, C-KIT inhibitor ISCK03, AMPK inhibitor dorsomorphin, and Nrf2 inhibitor ML385 were administered intracerebroventricularly or intraperitoneally before r-Metrnl treatment to explore the underlying mechanisms. Neurobehavioral assessments, immunofluorescence, western blot, ELISA, Fluoro-Jade C staining, transmission electron microscopy, and Nissl staining were conducted to evaluate the effects. Additionally, primary neuron culture with hemoglobin (Hb) stimulation was used for in vitro studies.

RESULTS

Phosphorylated C-KIT and endogenous Metrnl levels were upregulated after SAH. Knockdown of Metrnl aggravated neurobehavioral deficits and neuronal ferroptosis, whereas r-Metrnl treatment showed a protective effect. Mechanistically, r-Metrnl significantly increased the protein levels of SLC7A11, GPX4, FTH, FSP1, and GSH, whereas it decreased the levels of ACSL4, 4HNE, and MDA in the ipsilateral hemisphere 24 h after SAH. Also, r-Metrnl reduced mitochondrial shrinkage, increased mitochondrial crista, and decreased membrane density. However, the beneficial effects of r-Metrnl were partially reversed by ISCK03, dorsomorphin, or ML385 treatment both in vivo and in vitro.

CONCLUSIONS

Our study demonstrated that r-Metrnl reduced neuronal ferroptosis and improved neurological outcomes after SAH by modulating the C-KIT/AMPK/Nrf2 signaling pathway.

Metrnl and Cardiomyopathies: From Molecular Mechanisms to Therapeutic Insights

Cardiomyopathies, a diverse group of diseases affecting the heart muscle, continue to pose significant clinical challenges due to their complex aetiologies and limited treatment options targeting underlying genetic and molecular dysregulations. Emerging evidence indicates that Metrnl, a myokine, adipokine and cardiokine, plays a significant role in the pathogenesis of various cardiomyopathies. Therefore, the objective of this review is to examine the role and mechanism of Metrnl in various cardiomyopathies, with the expectation of providing new insights for the treatment of these diseases.

The role of novel adipokines in hepatocellular carcinoma progression: a mini review

Hepatocellular carcinoma (HCC), which originates from hepatocytes, accounts for the majority of primary liver cancers. Globally, HCC ranks among the most common cancers and is a leading cause of cancer-related deaths. Obesity, a growing health issue worldwide, is increasingly recognized as a critical risk factor for HCC, influenced by both epidemiological and clinical factors. Adipokines, secreted by adipocytes, have been shown to play pivotal roles in the tumor microenvironment, affecting cancer progression, metastasis, and resistance to therapies through various signaling mechanisms. Despite inconsistencies in certain findings, a substantial body of research supports the significant role of adipokines in HCC development. This review focuses on exploring newly identified adipokines and their mechanisms in HCC, with the goal of uncovering potential therapeutic targets for improved management and treatment strategies.

Metrnl as a secreted protein: Discovery and cardiovascular research

Secreted proteins have gained more and more attentions, since they can become therapeutic targets, drugs and biomarkers for prevention, diagnosis and treatment of disease and aging. In 2014, Metrnl (also named Meteorin-like, Cometin, Subfatin, Interleukin-39, Interleukin-41, Meteorin-β, and Metrn-β/Metrnβ), as a novel secreted protein released from a certain tissue, was reported by us and others. During the past decade, the number of articles on Metrnl has continued to increase. Different sources of Metrnl have been described with different functions, including Metrnl as an adipokine for insulin sensitization, a cardiokine against cardiac hypertrophy and dysfunction, an endothelium-derived factor against endothelial dysfunction and atherosclerosis, etc. Especially, we show that endothelial Metrnl is a major source for circulating Metrnl levels. Meanwhile, lots of clinical studies have investigated the relationship between blood Metrnl levels and metabolic, inflammatory and cardiovascular diseases. Metrnl appears a protective factor and a promising therapeutic target and/or drug against these diseases, given the relatively consistent conclusion from the preclinical studies. In addition to graphically demonstrating the role of Metrnl in various organs and diseases, this review will mainly describe the discovery of Metrnl, summarize the role of Metrnl in cardiovascular system that is a recently major progress in Metrnl research, and highlight several perspectives for future basic and translational research. Also, we suggest using one name Metrnl instead of other multiple names for the same protein.

Metrnl: a promising biomarker and therapeutic target for cardiovascular and metabolic diseases

Modern human society is burdened with the pandemic of cardiovascular and metabolic diseases. Metrnl is a widely distributed secreted protein in the body, involved in regulating glucose and lipid metabolism and maintaining cardiovascular system homeostasis. In this review, we present the predictive and therapeutic roles of Metrnl in various cardiovascular and metabolic diseases, including atherosclerosis, ischemic heart disease, cardiac remodeling, heart failure, hypertension, chemotherapy-induced myocardial injury, diabetes mellitus, and obesity.

Chronic vascular pathogenesis results in the reduced serum Metrnl levels in ischemic stroke patients

Metrnl is a secreted protein involved in neurite outgrowth, insulin sensitivity, immunoinflammatory responses, blood lipids and endothelial protection. In this study, we investigated the role of Metrnl in ischemic stroke. Fifty-eight ischemic stroke patients (28 inpatient patients within 2 weeks of onset and 30 emergency patients within 24 h of onset) and 20 healthy controls were enrolled. Serum Metrnl was measured by enzyme-linked immunosorbent assay. We showed that serum Metrnl levels were significantly reduced in both inpatient and emergency patient groups compared with the controls. Different pathological causes for ischemic stroke such as large artery atherosclerosis and small artery occlusion exhibited similar reduced serum Metrnl levels. Transient ischemic attack caused by large artery atherosclerosis without brain infarction also had lower serum Metrnl levels. Metrnl was correlated with some metabolic, inflammatory and clotting parameters. Reduced serum Metrnl was associated with the severity of intracranial arterial stenosis and the presence of ischemic stroke. In order to elucidate the mechanisms underlying the reduced serum Metrnl levels, we established animal models of ischemic stroke in normal mice, atherosclerotic apolipoprotein E-knockout mice and Metrnl-knockout mice by middle cerebral artery occlusion (MCAO) using intraluminal filament or electrocoagulation. We demonstrated that serum Metrnl levels were significantly lower in atherosclerosis mice than normal mice, whereas acute ischemic stroke injury in normal mice and atherosclerosis mice did not alter serum Metrnl levels. Metrnl knockout did not affect acute ischemic stroke injury and death. We conclude that reduced serum Metrnl levels are attributed to the chronic vascular pathogenesis before the onset of ischemic stroke. Metrnl is a potential target for prevention of ischemic stroke.

Serum Metrnl is Decreased in Metabolic Dysfunction-Associated Fatty Liver Disease: A Case-Control Study

Context

Metrnl is a novel adipokine mainly produced by white adipose tissue, which plays important roles in insulin sensitization, and energy homeostasis. However, information about the function of Metrnl in Metabolic dysfunction-associated fatty liver disease (MAFLD) remains unclear.

Methods

This is a control study, which enrolled 176 adults with MAFLD and 176 normal controls. They were matched in body mass index (BMI), age, and sex. Serum Metrnl was determined by ELISA. Other biochemical data were also collected.

Results

Compared to the controls, circulating Metrnl was prominently decreased in the MAFLD adults (P<0.001). Next, binary logistic regression model indicated that sex, waist circumference (WC), triglyceride, γ-gamma glutamyl transferase(γ-GGT), and Metrnl was independently associated with MAFLD. Further, as Metrnl levels elevated across its tertiles, the rate of MAFLD decreased (67.52, 66.95, and 15.38%; P value for trend<0.001). Data from multivariate logistic regression models evidenced that compared with the lowest tertile of Metrnl, the odds ratio of MAFLD was 0.023(95% CI 0.006-0.086, P<0.001) for the highest tertile after adjusting for potential confounders. Besides, area under ROC curve of Metrnl for diagnosis MAFLD was 0.755(95% CI 0.705-0.805). Metrnl was positively correlated with diastolic blood pressure, WC, BMI, systolic blood pressure, γ-GGT, and Creatinine in MAFLD. Finally, we found systolic blood pressure and Creatinine were independently related to serum Metrnl in MAFLD.

Conclusion

Serum Metrnl is reduced in adult with MAFLD. The results suggest that Metrnl may be a protective factor associated with the pathogenesis of MAFLD.

Interleukin-41 as a biomarker of the anti-inflammatory response associated with hyperuricemia

BACKGROUND

Interleukin (IL)-41 is a recently discovered secreted protein that is expressed in a variety of tissues, and it is associated with several immune and metabolic diseases. However, IL-41 has not been studied in hyperuricemia (HUA).

METHODS

Forty-four HUA patients and 44 healthy controls (HCs) were included in this study, and we collected theirgeneral and biochemical parameters, including white blood cell, neutrophil, lymphocyte, and platelet counts, mean platelet volume, platelet distribution width, serum creatinine, blood urea nitrogen, fasting blood glucose, total triglyceride, total cholesterol, high-density lipoprotein, low-density lipoprotein, total protein, albumin, alkaline phosphatase, gamma-glutamyltransferase, and hemoglobin concentration. The level of serum IL-41 was determined using an enzyme-linked immunosorbent assay. Multivariate logistic regression analysis was exploited to identify the independent risk factors associated with HUA, and the clinical diagnostic value of IL-41 was analyzed by applying the receiver operating characteristic (ROC) curve. We assessed the association between IL-41 and clinical parameters with Spearman's rank correlation.

RESULTS

Circulating IL-41 levels were significantly higher in HUA patients than in the HCs group (460.3 pg/mL vs. 261.3 pg/mL, respectively; P < 0.001). The area under the ROC curve (AUC) for IL-41 in HUA patients was 0.7443 (with a cut-off value of 311.055 pg/mL, a sensitivity of 68.18 %, and a specificity of 72.73 %), while the AUC for IL-41 combined with the platelet count was 0.8109. Correlation analysis revealed that the circulating IL-41 level was positively correlated with age in HCs and HUA patients.

CONCLUSIONS

We herein demonstrated that serum IL-41 was elevated in HUA patients and that it may constitute a novel biomarker of anti-inflammatory response related to HUA.

N-Acetylcysteine may exert hepatoprotective effect by regulating Meteorin-Like levels in Adriamycin-induced liver injury

Adriamycin (ADR) is an important chemotherapeutic drug, but it has serious side effects such as hepatotoxicity. This study aimed to evaluate whether N-acetylcysteine (NAC) has hepatoprotective effects against ADR-induced hepatotoxicity in rats. In addition, it was aimed to determine how Meteorin-Like (MtrnL), which has pleiotropic effects on immunology, inflammation, and metabolism, is affected by ADR and/or NAC applications in liver tissue. 28 rats were randomly assigned to one of four equal groups in the study: control (no treatment), NAC (150 mg/kg/day of NAC intraperitoneally (i.p), ADR (15 mg/kg only on the first day of the experiment), and ADR + NAC (ADR 15 mg/kg on the first day of the experiment + 150 mg/kg/day NAC i.p). After 15 days, liver enzyme levels in serum, oxidant/antioxidant parameters in liver tissue, histopathological changes, caspase 3 (Casp3) and heat shock protein 70 (HSP-70) immunoreactivities, and MtrnL levels were examined. Histopathological changes, liver enzyme levels, as well as HSP-70, and Casp3 immunoreactivities increased due to ADR application. Additionally, MtrnL levels in liver tissue were significantly increased as a result of ADR application. However, it was detected that the NAC application significantly regulated the ADR-induced changes. Furthermore, it was determined that NAC administration regulated the changes in ADR-induced oxidative stress parameters. We propose that NAC may exert a hepatoprotective effect by regulating ADR-induced altered oxidative stress parameters, MtrnL levels, Casp3, and HSP-70 immunoreactivities in the liver.

Elevation of Metrnβ and Its Association with Disease Activity in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is an auto-immune disease, the pathogenesis of which remains to be fully addressed. Metrnβ is a novel cytokine involved in the pathogenesis of inflammatory disease, but its regulatory roles in SLE are unclear. We aimed to comprehensively investigate the clinical value of Metrnβ in SLE. A massive elevation of circulating Metrnβ levels was observed in SLE, and patients with an active phase displayed higher Metrnβ concentrations than those with inactive phases. Additionally, we found that Metrnβ expression was positively correlated with clinical indicators of SLE. Longitudinal cytokine and chemokine profiles revealed a disturbed immune response in SLE, with high activity profiles displayed severe pathogenic inflammation, and a positive correlation of the serum Metrnβ with CXCL9, IL10, IL18 and IL1RA was observed as well. Moreover, Metrnβ expressions exhibited an inverse correlation with Treg and B10. Of note, a significant decrease of ILC2 was found in SLE, and there was a negative correlation of Metrnβ with ILC2 as well. Further ROC analysis showed that the area under the curve (AUC) for Metrnβ was 0.8250 (95% CI: 0.7379-0.9121), with a cutoff value of 1131 pg/mL to effectively distinguish SLE patients from healthy controls. Our study herein demonstrated for the first time that Metrnβ values were increased and were immunologically correlated with SLE activity, which could be utilized as an alternative biomarker for the early identification and predicting of the immuno-response of SLE.