Abstract: Objective To observe the changes of miR-21 induced by lipopolysaccharide (LPS) in the inflammatory reaction of human renal cortical proximal tubular epithelial cells (HK-2 cells), and to explore the role of miR-21 by transfecting miR-21 mimics (miR-21 mimics). Methods 11 K-2 cells were cultured and we induced its inflammatory response by LPS. HK-2 cells were cultured, then transfected with miR-21 mimics or JNC, and and we induced its inflammatory response by LPS. The cells were collected, and real-time fluorescence quantitative polymerase chain reaction (RT-qPCR) was used to detect miR-21 and IL-6 mRNA, and Western blotting was used to detect IL-6 protein. Results 1) Compared with the control group, the mRNA and protein expression of IL-6 increased at each time point in the LPS-stimulated Hk-2 cells (P < 0.05), and the miR-21 expression decreased (P < 0.05). (2) Compared with the cells transfected with NC mimics, the expression of miR-21 increased in HK-2 cells after transfection with miR-21 mimics for 24 h (P< 0.05). After transfection with miR-21 mimics for 24 h and 10 ug/mL LPS stimulation for 8 h, the expression of IL-6 mRNA decreased in HK-2 eells as compared with that of HK-2 cells undergoing NC mimics transfection and LPS stimulation (P < 0.05). (3) After transfection with miR-21 mimics for 24 h and LPS treatment for 12 h, the expression of miR-21 increased in HK-2 cells as compared with that of HK-2 cells undergoing NC mimics transfection and LPS stimulation (P <0.05); after transfection with miR-21 mimics for 24 h and LPS treatment for 24 h, IL-6 protein expression decreased in HK-2 cells as compared with that of HK-2 cells undergoing NC mimics transfection and LPS stimulation of 24 h {P < 0.05). Conclusion LPS can induce inflammatory response in HK-2 cells, IL-6 expression increases, and miR-21 expression decreases. Transfection with miR-21 mimics can attenuate LPS-induced inflammatory response in 11K-2 cells. [ABSTRACT FROM AUTHOR]