CircTMCO3 alleviates sepsis-induced acute kidney injury via regulating miR-218-5p/ZEB2 axis.

Background: Growing evidence has found the critical role of circular RNAs (circRNAs) in sepsis-induced acute kidney injury (S-AKI). CircTMCO3 has been found to be involved in tumor microenvironment changes of ovarian cancer. This study aimed to explore whether circTMCO3 functions in S-AKI, and if so, to elucidate the molecular mechanism.

Methods: CircTMCO3 expression was analyzed in lipopolysaccharide (LPS)-induced HK-2 cells and in the kidney tissues of mice treated with cecal ligation and puncture (CLP), respectively. Furthermore, the effects of circTMCO3 on S-AKI and the related mechanisms were evaluated in both models through gain- and/or loss-of-function strategies.

Results: CircTMCO3 expression was suppressed in both S-AKI models. Upregulation of circTMCO3 mitigated LPS-induced apoptosis, oxidative stress and inflammation in HK-2 cells. In contrast, circTMCO3 downregulation exacerbated LPS-induced injuries in HK-2 cells. Intravenous injection of circTMCO3 lentivirus to increase circTMCO3 expression improved renal function and attenuated kidney injury in S-AKI mice, as evidenced by the decrease in serum creatinine and blood urea nitrogen concentrations, amelioration of tubular pathological injury, reduction of renal cell apoptosis, and mitigation of oxidative stress and proinflammatory cytokines (TNF-α, IL-1β, and IL-6). Moreover, circTMCO3 directly targeted miR-218-5p, and the mimic of which abolished the protective effect of circTMCO3 in cell models. ZEB2 was identified to be a target of miR-218-5p; its downregulation not only reversed the impacts of miR-218-5p inhibitor on S-AKI, but also mitigated the effects mediated by circTMCO3 upregulation in vitro.

Conclusions: CircTMCO3 protects against S-AKI by regulating miR-218-5p/ZEB2 axis, thereby mediating anti-apoptotic, antioxidant and anti-inflammatory activities. This indicates that increasing circTMCO3 expression might be a future therapeutic method for S-AKI.