RSDR, a Novel Potential Biomarker, Protects Against AKI by Interacting with hnRNPK to Regulate DHODH-Mediated Ferroptosis

Rationale: This study elucidated the protective role of the novel lncRNA RSDR in acute kidney injury (AKI) and its underlying mechanism while investigating its potential as a diagnostic biomarker for AKI.Methods: RSDR was identified through RNA sequencing in two AKI mouse models induced by cisplatin and ischemia-reperfusion injury. To delineate its regulatory mechanisms, RNA immunoprecipitation (RIP), pull-down assays, mass spectrometry (MS), and Chromatin Isolation by RNA Purification sequencing (ChIRP-seq) were employed to examine interactions between RSDR and hnRNPK. Transgenic mouse models, including RSDR knock-in mice and hnRNPK renal tubular epithelial cell-specific knockout mice, were utilized to assess the in vivo effects of RSDR and hnRNPK in AKI. In vitro experiments involved generating cell lines overexpressing RSDR and DHODH, as well as hnRNPK knockout cell lines, to evaluate the impact on renal tubular epithelial cell function. Adenoviral vectors were utilized for in vivo overexpression of RSDR and DHODH. Urine samples from patients with AKI and healthy controls were analyzed to determine the potential of urine RSDR as a diagnostic biomarker.Results: RNA sequencing of AKI mouse models identified RSDR as a critical regulator of renal injury. MS, RIP, and pull-down assays confirmed a direct interaction between RSDR and hnRNPK, while RNA-seq and ChIRP-seq revealed that this interaction facilitates the recruitment of hnRNPK to the DHODH promoter, thereby enhancing its transcription through epigenetic modulation. In vitro, RSDR overexpression elevated DHODH expression and mitigated ferroptosis in renal tubular epithelial cells, whereas knockdown of hnRNPK or RSDR suppressed DHODH expression and exacerbated ferroptosis. In vivo, RSDR overexpression conferred protection against renal injury in AKI mouse models, while hnRNPK knockout intensified renal damage, an effect reversed by DHODH overexpression. Clinical analysis demonstrated significantly reduced urine RSDR levels in patients with AKI compared to healthy controls. Receiver operating characteristic (ROC) curve analysis indicated that urine RSDR exhibited high sensitivity and specificity as a potential diagnostic biomarker for AKI.Conclusion: RSDR protects renal function in AKI by interacting with hnRNPK to epigenetically upregulate DHODH transcription, thereby inhibiting ferroptosis in renal tubular epithelial cells. Additionally, reduced urine RSDR levels may serve as a promising early diagnostic biomarker for AKI.