[Hepatitis B virus X protein promotes podocyte pyroptosis in hepatitis B virus-associated glomerulonephritis by down-regulating microRNA -223 targeting NLRP3 inflammasome]

Abstract

Objective: To investigate the potential function and related mechanism of microRNA-223 (miRNA-223) in the podocyte pyroptosis of hepatitis B virus (HBV)-associated glomerulonephritis induced by HBV X protein (HBx). Methods: HBx-overexpressing lentivirus was transfected into human renal podocytes to mimic the pathogenesis of HBV-GN. Real-time fluorescence quantitative PCR and Western blotting experiments were used to detect the mRNA and protein expression of pyroptosis-related proteins [nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3), apoptosis-associated speck-like protein containing a CARD (ASC) and caspase-1], and inflammatory factors (interleukin-1β and interleukin-18), respectively.TUNEL staining and flow cytometry were used to detect the number of pyroptosis cells. Immunofluorescence staining was used to detect the expression of podocytes biomarkers desmin and nephrin; Hoechst 33342 staining was used to observe the morphological and quantitative changes of podocyte nuclei. Enzyme-linked immunosorbent assay was used to measure caspase-1 activity. The dual luciferase reporter gene assay was used to verify the downstream target of miRNA-223. Podocytes were divided into the following nine groups: control group (no special treatment), empty plasmid group (transfected with empty plasmid), HBx overexpression group (transfected with HBx overexpression lentivirus), HBx overexpression+miRNA-223 mimic group (transfected with HBx overexpression lentivirus and miRNA-223 mimic), HBx overexpression+miRNA-223 inhibitor group (transfected with HBx overexpression lentivirus and miRNA-223 inhibitor), HBx overexpression+miRNA-223 mimic+NLRP3 group (transfected with HBx overexpression lentivirus, miRNA-223 mimic and NLRP3 overexpression plasmid), HBx overexpression+miRNA-223 mimic+ NLRP3 siRNA group (transfected with HBx overexpression lentivirus, miRNA-223 mimic and NLRP3 siRNA), HBx overexpression+miRNA-223 inhibitor+NLRP3 group (transfected with HBx overexpression lentivirus, miRNA-223 inhibitor and NLRP3 overexpression plasmid), HBx overexpression+miRNA-223 inhibitor+NLRP3 siRNA group (transfected with HBx overexpression lentivirus, miRNA-223 inhibitor and NLRP3 siRNA). Results: miRNA-223 was down-regulated in HBx overexpression group compared with the control group (P < 0.05). TUNEL and immunofluorescence staining showed that NLRP3 knockdown attenuated podocyte injury and pyroptosis induced by HBx overexpression (P < 0.05). Dual luciferase reporter gene assay demonstrated that NLRP3 was one of the downstream targets of miRNA-223. Rescue experiments revealed that NLRP3 overexpression weakened the protective effect of miRNA-223 in podocyte injury (P < 0.05). The addition of miRNA-223 mimic and NLRP3 siRNA decreased the expression of NLRP3 inflammasome and cytokines, and reduced the number of pyroptosis cells induced by HBx overexpression (all P < 0.05); The addition of miRNA-223 inhibitor and NLRP3 overexpression plasmid significantly increased the expression of NLRP3 inflammasome and cytokines, caspase-1 activity, and the number of pyroptosis cells (all P < 0.05). Conclusion: HBx may promote podocyte pyroptosis of HBV-GN via downregulating miRNA-223 targeting NLRP3 inflammasome, suggesting that miRNA-223 is expected to be a potential target for the treatment of HBV-GN.