Silencing circular ANRIL protects HK-2 cells from lipopolysaccharide-induced inflammatory injury through up-regulating microRNA-9

Circular antisense non-coding RNA in the INK4 locus (cANRIL) participated in inflammation of endothelial cells. However, whether cANRIL is associated with inflammatory injury of HK-2 cells, thereby affecting chronic kidney disease has not been investigated. We tested the hypothesis that cANRIL participated in inflammatory response in vitro. HK-2 cells were stimulated by lipopolysaccharides (LPS). RT-qPCR was executed for cANRIL expression assessment. After transfection, cell viability, apoptosis, inflammatory cytokines and ROS generation were appraised to evaluate the impact of silencing cANRIL on LPS-induced inflammatory injury. The regulatory relationship between cANRIL and microRNA-9 (miR-9) was verified. In addition, whether miR-9 affected LPS-induced inflammatory injury was measured after miR-9 inhibitor transfection. Western blot was utilized to detect NF-κB and JNK/p38 pathway-related proteins. The results showed that LPS promoted cANRIL expression and cell injuries in HK-2 cells. Furthermore, silencing cANRIL alleviated inflammatory injuries by promoting viability, suppressing apoptosis, inflammatory cytokines and ROS generation in HK-2 cells. In addition, miR-9 expression was accelerated by silencing cANRIL. Meanwhile, miR-9 down-regulation invalidated the effect of silencing cANRIL on inflammation and NF-κB and JNK/p38 pathways. The study clarified that silencing cANRIL hindered NF-κB and JNK/p38 pathways by positively regulating miR-9, thereby protecting HK-2 cells from LPS-induced injury.