CircRNA itchy E3 ubiquitin protein ligase improves mitochondrial dysfunction in sepsis-induced acute kidney injury by targeting microRNA-214-3p/ATP-binding cassette A1 axis

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/R-induced 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-1β, and TNF-α. 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-1β expression.

CONCLUSION

CircPICALM plays a critical role in H/R-induced neonatal AKI by sponging miR-204-5p and then activating the downstream IL-1β 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.

The roles of the ubiquitin-proteasome system in renal disease

The ubiquitin-proteasome system (UPS) is a major pathway of specific intracellular protein degradation through proteasome degradation of ubiquitin-labeled substrates. Numerous biological processes, including the cell cycle, transcription, translation, apoptosis, receptor activity, and intracellular signaling, are regulated by UPS. Alterations of the UPS, which render them more or less susceptible to degradation, are responsible for disorders of renal diseases. This review aims to summarize the mechanism of UPS in renal diseases. Besides, this review explores the relationship among UPS, autophagy, and deubiquitination in the development of renal disease. The specific molecular linkages among these systems and pathogenesis, on the other hand, are unknown and controversial. In addition, we briefly describe some anti-renal disease agents targeting UPS components. This review emphasizes UPS as a promising therapeutic modality for the treatment of kidney disease. Our work, though still basic and limited, could provide options to future potential therapeutic targets for renal diseases with a UPS underlying basis.

Potential therapeutic applications of circular RNA in acute kidney injury

Acute kidney injury (AKI) is a common clinical syndrome characterized by a rapid deterioration in renal function, manifested by a significant increase in creatinine and a sharp decrease in urine output. The incidence of morbidity and mortality associated with AKI is on the rise, with most patients progressing to chronic kidney disease or end-stage renal disease. Treatment options for patients with AKI remain limited. Circular RNA (circRNA) is a wide and diverse class of non-coding RNAs that are present in a variety of organisms and are involved in gene expression regulation. Studies have shown that circRNA acts as a competing RNA, is involved in disease occurrence and development, and has potential as a disease diagnostic and prognostic marker. CircRNA is involved in the regulation of important biological processes, including apoptosis, oxidative stress, and inflammation. This study reviews the current status and progress of circRNA research in the context of AKI.