CircPICALM promotes neonatal acute kidney injury triggered by hypoxia/ reoxygenation via sponging microRNA-204-5p

Background: Circular RNAs (circRNAs) have been documented to regulate neonatal acute kidney injury (AKI). Based on previous RNA-sequence findings, circPICALM exhibited significantly disparate expression between AKI newborns and Controls. This study aimed to provide further insights into the regulatory mechanism of circPICALM in neonatal AKI. Methods: C57BL/6 mice born 7 days were divided into Control group and hypoxia groups (11%O2 and 8%O2 groups). Human tubule epithelial cells (HK-2) were stimulated with hypoxia/reoxygenation (H/R) to establish an AKI cell model. Through overexpression and knockdown techniques, the regulatory role of circPICALM in H/Rinduced kidney injury was explored. Inflammatory cytokines, cell apoptosis, and oxidative stress were also detected to confirm the regulatory function of circPICALM in neonatal AKI. Results: RT-qPCR confirmed that circPICALM was highly expressed in the serum of AKI newborns, neonatal I/R mice and H/R-treated HK-2 cells. Functionally, circPICALM exacerbated H/R-induced HK-2 cell injury by aggravating apoptosis and mitochondrial oxidative stress, increasing the expression of inflammatory factors, including IL-6, IL-1 beta, and TNF-alpha. Conversely, inhibition of circPICALM alleviated H/R injury in the HK-2 cell line. The interaction between circPICALM and miR-204-5p was validated through RNA immunoprecipitation and luciferase assay. Finally, circPICALM functioned as a molecular sponge of miR-204-5p and promoted the upregulation of downstream IL-1 beta expression. Conclusion: CircPICALM plays a critical role in H/R-induced neonatal AKI by sponging miR-204-5p and then activating the downstream IL-1 beta signaling axis. The inhibition of circPICALM and subsequent suppression of pro- inflammatory factors could serve as a promising biomarker and therapeutic target for early intervention in neonatal AKI.