Effects of proprotein convertase subtilisin/kexin type 9 on oxidative inflammation and cell pyroptosis in HK-2 cells during renal ischemia-reperfusion injury and the mechanisms
Objective To investigate the role and mechanisms of proprotein convertase subtilisin/kexin type 9(PCSK9)in oxidative inflammation and cell pyroptosis in HK-2 cells during renal ischemia-reperfusion injury(IRI).Methods A hypoxia-reoxygenation model was established using HK-2 cells(American Type Culture Collection).HK-2 cells were randomly divided into hypoxia reoxygenation group,control group,PCSK9 silenced group and PCSK9 silenced control group.Quantitative real-time polymerase chain reaction(qRT-PCR)was employed to detect PCSK9 expression at different time points of reoxygen-ation injury.Commercial assay kits were used to assess the impact of PCSK9 transfection on superoxide dis-mutase(SOD)and malondialdehyde(MDA)levels in HK-2 cells.Enzyme-linked immunosorbent assay(ELISA)kits were utilized to measure the effects of PCSK9 transfection on the inflammatory factors[inter-leukin(IL)-1 β and IL-18]in HK-2 cells.Western blotting experiments were conducted to evaluate the in-fluence of PCSK9 transfection on the expression levels of pyroptosis-related proteins NLR family,pyrin do-main containing 3(NLRP3)and cysteinyl aspartate-specific protease(Caspase)-1 in HK-2 cells.The paired sample t test was used for comparison between groups and one-way analysis of variance for multiple group comparisons.Results The results of qRT-PCR showed that the mRNA expression levels of PCSK9 in control group and hypoxia reoxygenation group(0,2,4,6,8 h)(1.00±0.18,3.24±0.31,3.61±0.36,3.79±0.39,4.26±0.43,4.08±0.39)were higher than those in the control group of non-hypoxic HK-2 cells(1.00±0.18,1.02±0.11,1.01±0.15,1.00±0.12,1.05±0.11,0.99±0.12).Com-pared to the control group of non-hypoxic HK-2 cells,PCSK9 expression significantly increased with pro-longed reoxygenation injury,peaking at 6 h(F=34.47,P<0.05).SOD and MDA assays revealed that SOD levels in the hypoxia-reoxygenation group were lower than those in the control group[(5.23±0.46)U/mgvs.(13.18±1.02)U/mg,t=12.306,P<0.05],and MDA levels were higher than those in the control group[(3.53±0.27)nmol/mg vs.(1.66±0.18)nmol/mg,t=-9.981,P<0.05].In the PCSK9 silencing group,SOD levels were higher than those in the control group[(10.12±0.98)U/mg vs.(5.19±0.50)U/mg,t=-7.762,P<0.05],and MDA levels were lower than those in the control group[(2.09±0.18)nmol/mg vs.(3.54±0.29)nmol/mg,t=7.358,P<0.05].ELISA results indi-cated that IL-1β and IL-18 levels in the hypoxia-reoxygenation group were higher than those in the control group[IL-1β:(35.12±3.21)pg/ml vs.(15.64±1.88)pg/ml,t=-9.070,P<0.05;IL-18:(98.76±9.71)pg/ml vs.(52.17±5.09)pg/ml,t=-7.361,P<0.05].In the PCSK9 silencing group,IL-1β and IL-18 levels were lower than those in the control group[IL-1 β:(22.31±1.98)pg/ml vs.(35.24±3.46)pg/ml,t=5.618,P<0.05;IL-18:(71.36±6.98)pg/ml vs.(99.23±9.78)pg/ml,t=4.018,P<0.05].Western blotting results revealed that NLRP3 and Caspase-1 expres-sion levels in the hypoxia-reoxygenation group were higher than those in the control group(NLRP3:0.57±0.05 vs.0.27±0.02,t=-9.649,P<0.05;Caspase-1:0.47±0.04 vs.0.20±0.03,t=-9.353,P<0.05),whereas in the PCSK9 silencing group,these levels were lower than those in the control group(NLRP3:0.31±0.03 vs.0.55±0.05,t=7.129,P<0.05;Caspase-1:0.25±0.02 vs.0.48±0.04,t=8.908,P<0.05).Conclusion PCSK9 is highly expressed in HK-2 cells and may contribute to renal IRI by enhancing oxidative inflammation and promoting cell pyroptosis.
Renal ischemia-reperfusion injuryProprotein convertase subtilisin/kexin type 9InflammationCell pyroptosis