C‐X‐C motif chemokine receptor 4 aggravates renal fibrosis through activating JAK/STAT/GSK3β/β‐catenin pathway

Chronic kidney disease (CKD) has a high prevalence worldwide. Renal fibrosis is the common pathological feature in various types of CKD. However, the underlying mechanisms are not determined. Here, we adopted different CKD mouse models and cultured human proximal tubular cell line (HKC‐8) to examine the expression of C‐X‐C motif chemokine receptor 4 (CXCR4) and β‐catenin signalling, as well as their relationship in renal fibrosis. In CKD mice and humans with a variety of nephropathies, CXCR4 was dramatically up‐regulated in tubules, with a concomitant activation of β‐catenin. CXCR4 expression level was positively correlated with the expression of β‐catenin target MMP‐7. AMD3100, a CXCR4 receptor blocker, and gene knockdown of CXCR4 significantly inhibited the activation of JAK/STAT and β‐catenin signalling, protected against tubular injury and renal fibrosis. CXCR4‐induced renal fibrosis was inhibited by treatment with ICG‐001, an inhibitor of β‐catenin signalling. In HKC‐8 cells, overexpression of CXCR4 induced activation of β‐catenin and deteriorated cell injury. These effects were inhibited by ICG‐001. Stromal cell–derived factor (SDF)‐1α, the ligand of CXCR4, stimulated the activation of JAK2/STAT3 and JAK3/STAT6 signalling in HKC‐8 cells. Overexpression of STAT3 or STAT6 decreased the abundance of GSK3β mRNA. Silencing of STAT3 or STAT6 significantly blocked SDF‐1α‐induced activation of β‐catenin and fibrotic lesions. These results uncover a novel mechanistic linkage between CXCR4 and β‐catenin activation in renal fibrosis in association with JAK/STAT/GSK3β pathway. Our studies also suggest that targeted inhibition of CXCR4 may provide better therapeutic effects on renal fibrosis by inhibiting multiple downstream signalling cascades.