急性肝衰竭犬模型肝细胞膜表面OATP1及MRP2蛋白表达与钆塞酸二钠增强MRI信号强度的相关性分析

Correlation of the protein expression of organic anion transport polypeptide 1 and multidrug resistance-associated protein 2 on the surface of hepatocyte membrane with signal intensity on Gd-EOB-DTPA-enhanced magnetic resonance imaging in dogs with acute liver failure

目的探讨钆塞酸二钠(Gd-EOB-DTPA)增强MRI信号强度与肝细胞膜表面有机阴离子转运多肽1(OATP1)及多药耐药相关蛋白2(MRP2)表达的相关性。方法选取健康成年雄性Beagle犬16只,随机分成对照组(n=8)和急性肝衰竭组(n=8)。急性肝衰竭组造模24 h后进行Gd-EOB-DTPA增强MRI扫描,测量肝实质不同信号区域信号强度及首过快速上升期中的增强斜率百分比,根据肝细胞期(注射Gd-EOB-DTPA 20 min时)的MRI图像选择高、中、低信号区域进行肝穿刺。对照组采用同样方法注射等剂量生理盐水后行Gd-EOB-DTPA增强MRI扫描,并在相应区域进行肝穿刺。将穿刺取得的肝组织用于Western Blot检测Gd-EOB-DTPA的摄取蛋白OATP1及排泄蛋白MRP2的表达情况。计量资料多组间比较采用单因素方差分析,进一步两两比较采用LSD-t检验,同一信号区不同组OATP1、MRP2蛋白表达的比较采用两个独立样本t检验。蛋白表达水平与信号强度的相关性采用Pearson分析。结果急性肝衰竭Beagle犬通过Gd-EOB-DTPA行MRI增强扫描在肝细胞期时图像呈现明显的高、中、低不同区域的信号差异,对应的SIbase值、SIst值、首过快速上升期中的增强斜率百分比对比差异有统计学意义(F值分别为70.70、55.12、19.82,P值均<0.001)。急性肝衰竭组不同MRI信号区域的肝组织中OATP1及MRP2的表达存在差异(F值分别为7.508、6.212,P值均<0.01),中、低不同信号区OATP1的表达与对照组相比呈逐渐下降的趋势(中、低信号区t值分别为3.301、3.641,P值均<0.05),并与肝细胞期信号减低的趋势相一致,以低信号区表达为著(高、低信号区对比t=3.436,中、低信号区对比t=2.378,P值均<0.05),差异具有统计学意义。急性肝衰竭组高、中、低不同信号区MRP2的表达与对照组相比均升高,且高、中、低信号区成逐渐升高的趋势,差异有统计学意义(t值分别为-7.236,-8.130、-9.614,P值均<0.05)。结论肝细胞膜表面OATP1、MRP2的表达水平与肝实质在Gd-EOB-DTPA增强肝细胞期的强化程度具有一定的关系,这为节段性评估肝细胞功能提供一定依据。

Objective To investigate the correlation of signal intensity on Gd-EOB-DTPA-enhanced magnetic resonance imaging(MRI)with the expression of organic anion transport polypeptide 1(OATP1)and multidrug resistance-associated protein 2(MRP2)on the surface of hepatocyte membrane.Methods A total of 16 healthy adult male beagle dogs were randomly divided into control group and acute liver failure group,with 8 dogs in each group.Gd-EOB-DTPA-enhanced MRI was performed for the dogs in the acute liver failure group at 24 hours after modeling to measure the signal intensity of different signal areas of liver parenchyma and the percentage of enhancement slope in the first-pass rapid rise period,and according to the MRI images of the hepatocyte phase(20 minutes after the injection of Gd-EOB-DTPA),the high-,medium-,and low-signal areas were selected for liver biopsy.Gd-EOB-DTPA-enhanced MRI was performed for the dogs in the control group after the injection of an equal volume of normal saline using the method,and liver biopsy was performed in the corresponding area.Western blot was used to measure the expression of the Gd-EOB-DTPA uptake protein OATP1 and its excretion protein MRP2 in liver tissue.An analysis of variance was used for comparison of continuous data between multiple groups,and the least significant difference t-test was used for further comparison between two groups;the independent samples t-test was used for comparison of the protein expression of OATP1 and MRP2 in the same signal area between groups.A Pearson correlation analysis was used to investigate the correlation between protein expression levels and signal intensity.Results The Gd-EOB-DTPA-enhanced MRI images of the beagle dogs with acute liver failure showed a significant difference in signal between the high-,medium-,and low-signal areas during hepatocyte phase,and there were also significant differences in the corresponding SIbase value,SIst value,and percentage of enhancement slope during the first-pass rapid rise period(F=70.70,55.12,and 19.82,all P<0.001).In the acute liver failure group,there were significant differences in the expression of OATP1 and MRP2 in liver tissue between different signal areas(F=7.508 and 6.212,both P<0.01),and compared with the control group,the acute liver failure group had a significant reduction in the expression of OATP1 in the medium-and low-signal areas(t=3.301 and 3.641,both P<0.05),which was consistent with the trend of signal reduction in hepatocyte phase;the reduction in the low-signal area was significantly greater than that in the high-signal area(t=3.436,P<0.05)and the medium-signal area(t=2.378,P<0.05).Compared with the control group,the acute liver failure group had a significant increase in the expression of MRP2 in the high-,medium-,and low-signal areas,with a tendency to increase from the high-signal area to the medium-signal area and low-signal area(t=-7.236,-8.130,and-9.614,all P<0.05).Conclusion The expression levels of OATP1 and MRP2 on the surface of hepatocyte membrane are correlated with the degree of enhancement of liver parenchyma in the hepatocyte phase of Gd-EOB-DTPA-enhanced MRI,which provides a certain basis for the segmental assessment of hepatocyte function.