# C‐X‐C chemokine receptor type 4 promotes tubular cell senescence and renal fibrosis through β‐catenin‐inhibited fatty acid oxidation

## TL;DR

This study shows that CXCR4 contributes to kidney disease by causing cell aging and blocking fat metabolism, offering new insights into chronic kidney disease.

## Contribution

The study reveals a novel role of CXCR4 in promoting tubular cell senescence and renal fibrosis via β-catenin inhibition of fatty acid oxidation.

## Key findings

- CXCR4 is expressed in tubular epithelial cells and co-localizes with senescence markers.
- CXCR4 activates β-catenin and inhibits fatty acid oxidation, leading to lipid accumulation.
- Blocking β-catenin with ICG-001 reverses CXCR4's effects on fatty acid metabolism.

## Abstract

The prevalence of chronic kidney disease (CKD) is highly increasing. Renal fibrosis is a common pathological feature in various CKD. Previous studies showed tubular cell senescence is highly involved in the pathogenesis of renal fibrosis. However, the inducers of tubular senescence and the underlying mechanisms have not been fully investigated. C‐X‐C motif chemokine receptor 4 (CXCR4), a G‐protein‐coupled seven‐span transmembrane receptor, increases renal fibrosis and plays an important role in tubular cell injury. Whereas, whether CXCR4 could induce tubular cell senescence and the detailed mechanisms have not studied yet. In this study, we adopted adriamycin nephropathy and 5/6 nephrectomy models, and cultured tubular cell line. Overexpression or knockdown of CXCR4 was obtained by injection of related plasmids. We identified CXCR4 increased in injury tubular cells. CXCR4 was expressed predominantly in renal tubular epithelial cells and co‐localized with adipose differentiation‐related protein (ADRP) as well as the senescence‐related protein P16INK4A. Furthermore, we found overexpression of CXCR4 greatly induced the activation of β‐catenin, while knockdown of CXCR4 inhibited it. We also found that CXCR4 inhibited fatty acid oxidation and triggered lipid deposition in tubular cells. To inhibit β‐catenin by ICG‐001, an inhibitor of β‐catenin, could significantly block CXCR4‐suppressed fatty acid oxidation. Taken together, our results indicate that CXCR4 is a key mediator in tubular cell senescence and renal fibrosis. CXCR4 promotes tubular cell senescence and renal fibrosis by inducing β‐catenin and inhibiting fatty acid metabolism. Our findings provide a new theory for tubular cell injury in renal fibrosis.