Role of Lipid Signaling by PTAFR in Tubular Epithelial Cells in AKI-to-CKD Transition

BACKGROUND: Acute kidney injury (AKI) represents a critical clinical complication with a high propensity of progression to chronic kidney disease (CKD), yet effective therapies remain limited. G protein-coupled receptors (GPCRs) mediate diverse pathophysiological processes and are promising therapeutic targets. Here, we investigated the role of platelet activating factor receptor (PTAFR), a lipophilic GPCR, in AKI-to-CKD transition. METHODS: A mouse model of ischemia-reperfusion injury (IRI) induced AKI was built by bilateral renal artery clamping. The phenotypic role of PTAFR in renal tubular cells(RTECs) after AKI was investigated in tubule-specific Ptafr deficiency mice. The functional and molecular mechanisms were determined by transcriptomic profiling, flow cytometry, co-immunoprecipitation, western blotting and immunofluorescence. Lipidomic analysis and biological experiments were employed to identify the endogenous ligand of PTAFR. The translational potential of PTAFR was evaluated by structure based high throughput virtual screening(HTVS) of a small-molecule inhibitor in vivo and in vitro assays. RESULTS: The expression of PTAFR was upregulated in RTECs after AKI in vivo and in vitro. Tubule-specific depletion of PTAFR alleviated IRI-induced RTEC injury and kidney fibrosis after AKI. Mechanistically, PTAFR promoted RTECs G2/M arrest via suppressing MDM2-mediated p53 ubiquitin degradation. Phosphatidylethanolamine (PE) (18:0/18:1) was identified as a novel PTAFR endogenous ligand inducing RTECs G2/M arrest. Urinary PE (18:0/18:1) was correlated with kidney dysfunction and was able to effectively distinguish AKI patients from healthy controls. HTVS identified WAY-639497, a small-molecule PTAFR antagonist, that was able to mitigate IRI-induced RTEC injury and kidney fibrosis after AKI. CONCLUSIONS: PTAFR promoted tubular epithelial cell G2/M arrest by inhibiting MDM2-mediated p53 ubiquitin degradation and further contributed AKI-to-CKD transition.