Astragaloside IV Inhibits Galactose-Deficient IgA1 Secretion via miR-98-5p in Pediatric IgA Nephropathy.

Caiqiong Liu,Xiqiang Dang,Ying Liu,Qingnan He,Shiqiu Xiong,Fangrong Peng,Mingyi Zhao,Xiaoyan Li,Lanjun Shuai

doi:10.3389/fphar.2021.658236

Abstract

Purpose: The factor associated with IgA nephropathy (IgAN) is an abnormality of IgA known as galactose-deficient IgA1 (Gd-IgA1). The purpose of this study was to determine the molecular role played by miRNAs in the formation of Gd-IgA1 in IgAN and investigate the regulatory role of Astragaloside IV (AS-IV) in miRNAs. Patients and methods: Bioinformatics analysis, along with functional and mechanistic experiments, were used to investigate the relationship and function of miRNA, β-1, 3-galactosyltransferase (C1GALT1), Gd-IgA1, and AS-IV. Analyses involved a series of tools, including quantitative real-time polymerase chain reaction (qRT-qPCR), Western blot, enzyme-linked immunosorbent assay (ELISA), Vicia Villosa lectin-binding assay (VVA), Cell counting kit-8 assay (CCK-8), and the dual-luciferase reporter assay. Results: miRNA screening and validation showed that miR-98-5p was significantly upregulated in the peripheral blood mononuclear cells (PBMCs) of pediatric patients with IgAN compared with patients diagnosed with mesangial proliferative glomerulonephritis (MsPGN) and immunoglobulin A vasculitis nephritis (IgAV-N), and healthy controls (p < 0.05). Experiments with the dual-luciferase reporter confirmed that miR-98-5p might target C1GALT1. The overexpression of miR-98-5p in DAKIKI cells decreased both the mRNA and protein levels of C1GALT1 and increased the levels of Gd-IgA1 levels; these effects were reversed by co-transfection with the C1GALT1 plasmid, and vice versa. In addition, AS-IV downregulated the levels of Gd-IgA1 level in DAKIKI cells by inhibiting miR-98-5p. Conclusions: Our results revealed that AS-IV could inhibit Gd-IgA1 secretion via miR-98-5p. Increased levels of miR-98-5p in pediatric IgAN patients might affect the glycosylation of IgA1 by targeting C1GALT1. In addition, our analyses suggest that the pathogenesis of IgAN may differ from that of IgAV-N. Collectively, these results provide significant insight into the pathogenesis of IgAN and identify a potential therapeutic target.

Highlights

IgA nephropathy (IgAN) is the most prevalent form of primary glomerulonephritis and predominantly affects children and young adults
These results suggest that C1GALT1 was significantly downregulated in IgAN and immunoglobulin A vasculitis nephritis (IgAV-N), but more significantly in IgAN; galactose-deficient IgA1 (Gd-IgA1) was significantly upregulated in IgAN and IgAV-N, but more significantly in IgAN
We found that the levels of Gd-IgA1 increased in the plasma, and that the mRNA and protein levels of C1GALT1 decreased in the PBMCs of patients with IgAN

Summary

Introduction

IgA nephropathy (IgAN) is the most prevalent form of primary glomerulonephritis and predominantly affects children and young adults. The mainstream pathogenesis of IgAN is described by the multi-hit hypothesis which involves four major steps: the overproduction of galactose-deficient IgA1 (Gd-IgA1) and autoantibodies against Gd-IgA1, the formation of circulating immune complexes (CICs) which are subsequently deposited in the glomeruli, and the activation of mesangial cells, resulting in renal injury (Suzuki et al, 2011). These data indicate that Gd-IgA1 plays a crucial role in the pathogenesis of IgAN. We know very little about the molecular mechanisms underlying these processes

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