Characterization of METRNβ as a novel biomarker of Coronavirus disease 2019 severity and prognosis

Meteorin-β: A Novel Biomarker and Therapeutic Target on Its Way to the Regulation of Human Diseases

The novel secreted protein Meteorin-β (Metrnβ) is a homologous protein of the neurotrophic regulator Meteorin, which is widely expressed in the skin, mucous membranes, and white adipose tissue upon stimulation by a variety of inflammatory mediators, including cytokines and chemokines, while, at the same time Metrnβ may also regulate the expression of these cytokines and chemokines. As a small secreted protein with low tissue specificity, Metrnβ plays vital roles in energy metabolism, insulin sensitivity regulation, neurodevelopment, white fat browning, and inflammatory response. Specifically, Metrnβ may act as an adipokine, myokine, neurotrophic factor, and cytokine, thereby being involved in the pathological and physiological processes of various human diseases, including metabolic, autoimmune and infectious/allergic diseases, and certain types of tumors. This review aims to systematically introduce the current research progress on Metrnβ, including its expression and distribution profiles, biological functions, and immunomodulatory roles in the process of human diseases. Additionally, we also discuss its potential as a biomarker, as well as a therapeutic/preventive agent for human diseases.

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.