# Exploring the Relationship Between 91 Inflammatory Cytokines and IgA Nephropathy Using a Two-Sample Mendelian Randomization Study and the Gene Expression Omnibus Database

## TL;DR

This study investigates how 91 inflammatory cytokines might cause IgA nephropathy using genetic data and finds three cytokines linked to increased disease risk.

## Contribution

The study identifies TGF-alpha, LIF, and CCL19 as potential causal factors in IgA nephropathy through Mendelian randomization and gene expression data.

## Key findings

- TGF-alpha, LIF, and CCL19 are linked to increased IgAN risk.
- CCL19 is significantly upregulated in IgAN patient renal tissues.
- No causal link was found from IgAN to the cytokines.

## Abstract

Objectives: Previous research has demonstrated associations between various inflammatory cytokines and IgA nephropathy (IgAN). However, the causal relationships between them remain unclear. The purpose of this study is to extensively analyze the causal links between 91 circulating cytokines and IgAN.

Methods: This study commenced with a two-sample bidirectional Mendelian randomization analysis. Genetic variations associated with 91 circulating inflammatory cytokines were extracted from genome-wide association study (GWAS) data involving individuals of European ancestry (n = 14824). In the corresponding GWAS dataset, the genetic variations for IgAN were obtained from a Finnish cohort of European ancestry, consisting of a case group (n = 653) and a control group (n = 411528). The findings from the Mendelian randomization analysis were subsequently subjected to preliminary validation using the GSE116626 dataset from the GEO database.

Results: Our MR analysis indicates that transforming growth factor-alpha (TGF-alpha), leukemia inhibitory factor (LIF), and C–C motif chemokine 19 (CCL19) are linked to an increased risk of IgAN. There were no causal connections found when IgAN was used as an exposure and the 91 circulating inflammatory cytokines as outcomes. In addition, the GSE116626 dataset from the GEO database revealed significant upregulation of CCL19 in renal tissues from patients diagnosed with IgAN.

Conclusions: This study shows a causal link between inflammatory cytokines and IgAN, suggesting that TGF-alpha, LIF, and CCL19 may act as upstream mediators in the pathogenic pathways of IgAN. The critical role of CCL19 in the pathogenesis of IgAN was further validated using data from the GEO database. However, whether these cytokines can be used to predict or ameliorate the progression of IgAN requires further investigation.