miR-21 protects against lipopolysaccharide-stimulated acute kidney injury and apoptosis by targeting CDK6

BACKGROUND: Septic acute kidney injury (AKI) causes a sharp deterioration of renal function, and it is a major reason for mortality in intensive care units. Although miR-21 has been proven to be dysregulated in patients with sepsis, the evidence is scarce concerning its role in mediating cellular apoptosis in AKI. METHODS: Mice were injected intraperitoneally with 10 mg/kg of lipopolysaccharide (LPS) to establish septic AKI model, miR-21 mimic and inhibitor were used to manipulate the expression of miR-21, the creatinine levels were detected by a creatinine assay kit, the renal cell proliferation and apoptosis were detected by MTT assay, flow cytometry assay and acridine orange/ethidium bromide (AO/EB) fluorescence staining, the renal function was evaluated by renal histology and tubular injury score, western blot analysis was used to detect the target protein levels. Several bioinformatics tools were performed to show the downstream target of miR-21, and further confirmed by luciferase reporter assay and caspase-3 activity assay. RESULTS: miR-21 silencing was able to promote renal function and decrease LPS-stimulated renal cell apoptosis in vitro and in vivo, and it could decrease the Bax/Bcl-2 ratio and caspase-3 activity. On the contrary, miR-21 overexpression had the opposite effects. Cyclin-dependent kinase 6 (CDK6) was confirmed as a target gene of miR-21 and was associated with renal cell apoptosis. Moreover, miR-21 was also found to be up-regulated in septic AKI. CONCLUSIONS: Current evidences suggest that miR-21 has a potential application in treating septic AKI.