Uromodulin alleviates fibrosis in acute kidney injury to chronic kidney disease transition by reducing EGFR.

BACKGROUND: Uromodulin has been speculated as a protective factor for acute kidney injury (AKI) and chronic kidney disease (CKD), possibly based on the uromodulin-mediated cross-talk between thick ascending limbs and proximal tubules. Here, we explored the roles of uromodulin in the AKI-CKD transition. METHODS: Wild-type SD rats and UMOD-/- rats were subjected to the AKI-CKD transition models. Cisplatin-stimulated HK-2 cells were treated with or without uromodulin. The renal injury and cell damage were evaluated. RESULTS: UMOD-/- rats observed no spontaneous kidney injury and fibrosis. In two rat models of AKI-CKD transition, induced by repeated cisplatin nephrotoxicity and ischemia-reperfusion injury, UMOD deficiency exacerbated the kidney insufficiency and fibrosis along with the over-activation of EGFR signaling. In the kidneys treated with cisplatin repeatedly, immunofluorescence showed the translocation of uromodulin and its proximity to EGFR and coimmunoprecipitation experiments also verified their interaction. Molecular docking and microscale thermophoresis demonstrated a significant binding capacity of EGFR with uromodulin and its EGF-like domains. Supplying uromodulin to cisplatin-stimulated HK-2 cells decreased the fibrotic process and the EGFR abundance, associated with the elevated EGFR ubiquitylation. Recombinant EGF-like domains of uromodulin showed a similar binding capacity and EGFR suppression effect with uromodulin. Uromodulin-induced EGFR endocytosis was impaired by the EGFR kinase inhibitor or monoclonal antibody. CONCLUSIONS: Collectively, we discovered uromodulin may alleviate the progression of AKI-CKD transition via the EGFR suppression.