Objective To investigate the impact of Pseudomonas aeruginosa(PA) infection on the function of pulmonary vascular endothelial cells,and explore the mechanism of this bacterium in exacerbating lung inflammation in mice. Methods Two hours after human lung microvascular endothelial cell(HULEC-5a) were infected with the PA strain PAO1,the mRNA levels of autophagy-related gene 5(ATG5),6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3(PFKFB3),and calcium adhesion protein 5(CDH5) were determined by reverse transcription real-time fluorescent quantitative PCR(RT-qPCR).The protein levels of ATG5,PFKFB3,and vascular endothelial calcium adhesion protein(VE-cadherin) were detected by immunofluorescence.After the expression of ATG5 and PFKFB3 was respectively knocked down by small interfering RNA(siRNA),RT-qPCR was employed to measure the mRNA levels of ATG5,PFKFB3,and CDH5,and immunofluorescence to detect the protein levels of PFKFB3 and VE-cadherin.In addition,the lactate assay kit was used to determine the level of lactate in the cells.After mice were infected with PAO1,lung inflammation was assessed through histopathological section staining.Confocal microscopy was employed to capture and analyze fluorescence-labeled PFKFB3 and VE-cadherin in endothelial cells. Results Compared with the control group,the HULEC-5a cells infected with PAO1 showed up-regulated mRNA and protein levels of PFKFB3(all P<0.05),down-regulated mRNA level of CDH5(P=0.023),disrupted continuity and down-regulated protein level of VE-cadherin(P<0.001),and elevated lactate level(P=0.017).Compared with PAO1-infected HULEC-5a cells,knocking down PFKFB3 led to the up-regulated mRNA level of CDH5(P=0.043),lowered lactate level(P=0.047),and restored continuity of VE-cadherin;knocking down ATG5 led to up-regulated mRNA and protein levels of PFKFB3(P=0.013 and P=0.003),elevated lactate level(P=0.015),and down-regulated mRNA level of CDH5(P=0.020) and protein level of VE-cadherin(P=0.001).The HE staining results showed obvious red blood cell leakage,inflammatory cell infiltration,alveolar septal widening,and partial detachment of vascular endothelial cells in the alveoli of PA-infected mice.Immunofluorescence staining showed up-regulated expression of PFKFB3 and decreased fluorescence signal of VE-cadherin in endothelial cells of infected mice compared with normal mice. Conclusion PA may regulate the PFKFB3 pathway via AGT5 to disrupt the function of pulmonary vascular endothelial cells,thereby exacerbating the inflammation in the lungs of mice.
目的 探究铜绿假单胞菌(PA)感染对肺血管内皮细胞功能的影响,并探讨其加重小鼠肺部炎症反应的可能机制。方法 PAO1菌株感染人肺微血管内皮细胞HULEC-5a 2 h后,采用逆转录实时荧光定量PCR(RT-qPCR)检测自噬相关基因5(ATG5)、6-磷酸果糖-2-激酶/果糖-2,6-二磷酸酶3(PFKFB3)和钙黏蛋白5(CDH5)的mRNA表达,免疫荧光检测ATG5、PFKFB3和血管内皮钙黏蛋白(VE-cadherin)的蛋白表达。采用小干扰RNA(siRNA)分别敲减ATG5、PFKFB3后,RT-qPCR检测ATG5、PFKFB3和CDH5的mRNA表达,免疫荧光检测PFKFB3和VE-cadherin的蛋白表达,并采用乳酸测定试剂盒检测细胞内乳酸的水平。采用PAO1菌株感染小鼠后,肺组织切片病理染色观察小鼠肺部炎症,激光共聚焦显微镜观察并分析荧光标记的内皮细胞PFKFB3和VE-cadherin的表达量。结果 与对照组比较,PAO1感染HULEC-5a细胞后,PFKFB3 mRNA和蛋白表达均增加(P均<0.05),CDH5 mRNA表达减少(P=0.023),VE-cadherin蛋白表达减少(P<0.001),且连续性被破坏,乳酸含量升高(P=0.017)。与PAO1感染HULEC-5a细胞比较,PAO1感染敲减PFKFB3的HULEC-5a细胞后,CDH5 mRNA表达增加(P=0.043),VE-cadherin荧光连续性得到恢复,乳酸含量降低(P=0.047);PAO1感染敲减ATG5的HULEC-5a细胞后,PFKFB3 mRNA(P=0.013)和蛋白表达(P=0.003)均增加,CDH5 mRNA(P=0.020)和VE-cadherin蛋白表达(P=0.001)均减少,乳酸含量升高(P=0.015)。PAO1感染小鼠后,病理HE染色结果显示,肺泡内明显的红细胞渗漏,炎症细胞浸润,肺泡间隔增宽和部分血管内皮细胞脱落。免疫荧光染色结果显示,与正常小鼠比较,PAO1感染小鼠内皮细胞PFKFB3表达增加,VE-cadherin荧光减弱,且不连续。结论 PA可能通过AGT5调控PFKFB3通路,破坏肺血管内皮细胞功能,进而加重小鼠肺部炎症反应。.
Keywords:
6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3;