目的 研究68Ga-citrate对软组织感染正电子发射计算机断层(PET-CT)显像分子机制相关基因Tfrc、Trf、和Ttf对感染应答的基因表达变化,探讨小鼠多药及毒性外排转运子1(multidrug and toxin extrusion1,mMATE1)在小鼠软组织感染的68Ga-citrate PET-CT显像中可能的作用.方法 用金黄色葡萄球菌感染小鼠形成脓肿,取不同时间点的脓肿组织,用荧光定量PCR(real-time PCR)鉴定Tfrc、Trf、Ttf基因和mMATE1基因Slc47a1的相对表达量.用68Ga标记柠檬酸(citrate),阻断实验使用PET-CT技术研究mMATE1转运子在小鼠软组织感染68Ga-citrate显像中的相关性.结果 real-time PCR显示转铁蛋白TF基因Trf和乳铁蛋白TLF基因Ttf在4d时间点表达量最高,mMATE1转运子基因Slc47a1的表达类型与转铁蛋白受体TFRC基因Tfrc类似,在1h左右达到峰值,随后逐渐降低,而Na+偶联的柠檬酸转运子NaCT的基因SLC13A5表达量在所有时间点未有明显变化.Trf、Ttf、Slc47a1和Tfrc基因表达最高值与0h时间点的表达量相比均有显著差异(57.21±11.62和7.53±1.74,t = 35.38;43.03±6.8和6.26±1.32,t = 12.05;28.79±2.16和8.21±1.23,t = 8.22;1 091.36±30.76和290.84±10.62,t = 52.08;P<0.01),且Slc47a1基因表达最高值显著高于SLC13A5基因同时间点的基因表达量(28.79±2.16和1.67±0.51,t = 79.81,P<0.01).PET-CT显示68Ga-citrate或68GaCl3尾静脉注射不同处理对小鼠左后腿相应部位68Ga聚集有显著影响(F = 13.77,P<0.01),其中炎症小鼠感染部位有明显68Ga聚集(SUVmax = 3.87±0.32),而对照未感染部位未见明显68Ga聚集(SUVmax = 0.31±0.13),差异有统计学意义(t检验,P<0.01),mMATE1阻断的感染小鼠感染部位对68Ga的摄取明显减少(SUVmax = 1.62±1.03),与未阻断感染小鼠比较差异有统计学意义(t检验,P<0.05).结论 从分子水平上证实Tfrc、Trf和Ttf在感染处高表达,多药及毒素外排转运子mMATE1 可能参与金黄色葡萄球菌诱导小鼠软组织感染的68Ga-citrate PET-CT显像.
Objective To investigate the changes in the gene expression of Tfrc、Trf、and Ttf related to the molecular mechanism of 68Ga-citrate PET-CT imaging of soft tissue infections and explore the possible role of mMATE1 transporter in the 68Ga-citrate PET-CT imaging of soft tissue infections in mice.Methods Mice were infected with Staphylococcus aureus to develop abscesses,and the rela-tive expression levels of Tfrc、Trf、Ttf and Slc47a1 genes were determined by real-time PCR at different time points.68Ga-citrate was used for PET-CT imaging,and the blocking experiment was performed to investigate the correlation between mMATE1 transporter and 68Ga-citrate PET-CT imaging of mouse infections.Results Real-time PCR demonstrated that the expression of genes for transferrin Trf and lactoferrin Ttf peaked at the time point of 4 days,and the expression pattern of transferrin receptor TFRC gene Tfrc was similar with that of Slc47a1,peaking at 1h time point and gradually decreasing with time.However,the gene expression of Na+ coupled citrate transporter NaCT almost kept unchanged at all time points.There were significant differences between the peak value of gene expression for genes Trf、Ttf、Slc47a1 and Tfrc and those at 0 time points(57.21±11.62 and 7.53±1.74,t = 35.38;43.03±6.8 and 6.26±1.32,t = 12.05;28.79±2.16和8.21±1.23,t = 8.22;1 091.36±30.76 and 290.84±10.62,t = 52.08;P<0.01).The highest value of Slc47a1 gene expression was significantly higher than that of SLC13A5 at the same time point(28.79±2.16 and 1.67±0.51,t = 79.81,P<0.01).PET-CT displayed that different treatments had significant influence on the 68Ga localization at the infected left hind legs af-ter 68Ga-citrate or 68GaCl3 injection intravenously(F = 13.77,P<0.01).68Ga-citrate apparently localized at infected sites(SUVmax = 3.87±0.32)while the imaging agent rarely localized at sterile sits(SUVmax = 0.31±0.13)and there was a significant difference be-tween both(t test,P<0.01).For the case of mMATE1 blocked,the localization of imaging agent at the infected site after blocking was obviously reduced(SUVmax = 1.62±1.03)and there was a significant difference comparing with the unblocked infected sites(t test,P<0.05).Conclusion Tfrc,Trf and Ttf genes were highly expressed at the infected sites associated with 68Ga-citrate PET-CT imaging of soft tissue infections in mice caused by Staphylococcus aureus.The mMATE1 transporter may be involved in the 68Ga-citrate PET-CT imaging of soft tissue infections.