清道夫受体A基因敲除对小鼠肝脏代谢及胆囊结石形成的影响

Liver metabolism and cholesterol gallstone formation in SRA knockout mice with lithogenic diet

目的探讨清道夫受体A(scavenger receptor class A,SRA)基因敲除对小鼠肝脏代谢及胆囊结石形成的影响。方法 SRAKO小鼠以及C57BL/6野生型小鼠分别给予成石饲料(lithogenic diet,LD)和普通饲料(Chow)喂养8周后,观察胆囊成石情况,并采集肝脏和胆囊组织。采用免疫荧光染色法测定小鼠肝脏巨噬细胞标记F4/80的表达,Western印迹法测定小鼠肝脏SRA表达,QT-PCR法检测肝脏脂质代谢相关基因及炎症因子的表达,胆固醇试剂盒测定胆囊和肝脏组织胆固醇含量。结果 LD喂养8周后,SRAKO小鼠和C57BL/6野生型小鼠成石率均为100%,而普通饲料喂养均不成石;LD喂养的小鼠肝脏脂质沉积增加,炎性细胞和巨噬细胞浸润增加;LD喂养的C57BL/6野生型小鼠肝脏SRA蛋白表达较普通饲料增高,胆固醇代谢相关基因ABCG5、ABCG8和炎症因子IL-1、TNF-α表达增加(P<0.05)。LD喂养的SRAKO组小鼠胆固醇代谢基因ABCG8、胆汁酸磷脂基因ABCB4和炎症因子TNF-α表达均增加(P<0.05);LD喂养的小鼠胆囊组织中胆固醇酯和游离胆固醇含量均较普通饲料增加(P<0.05)。结论敲除SRA基因不改变小鼠胆囊结石形成率,高胆固醇可能更易导致胆囊结石的形成。

Objective To investigate the role of scavenger receptor class A（SRA） gene in liver metabolism and cholesterol gallstone formation in mice with lithogenic diet.Methods Male SRA knockout （SRAKO） mice and male C57BL/6 mice were fed with lithogenic diet （containing 1.25% cholesterol and 0.5% cholic acid） or chow diet for 8 weeks.At the end of experiments animals were sacrificed, liver and gallbladder samples were collected.Macrophages in liver tissue were detected with immunofluorescence staining using F4/80 as marker;the protein level of SRA was determined by Western blot;the expression of genes involved in lipid metabolism and inflammation in liver tissue were detected by quantitative QT-PCR;free cholesterol and cholesteryl ester in liver tissue were assayed with enzymatic kits.Results Gallstone formed in all wild-type C57BL/6 and SRAKO mice, but none in the control group.Apparent lipid deposition and the infiltration of inflammation cells were observed in mice fed with LD diet.Hepatic SRA protein was increased in mice fed with LD diet.The mRNA expression of hepatic ABCG5, ABCG8 and IL-1, TNF-α were significantly elevated in C57BL/6 mice fed with LD diet compared to the control group （ P 〈0.05）.In SRAKO mice fed with LD diet, the expression of hepatic ABCG8, ABCB4 and TNF-α mRNA were significantly higher than the control group （ P 〈0.05）.Free cholesterol and cholesteryl ester significantly elevated in gallbladder of both wild-type C57BL/6 and SRAKO mice fed with LD diet compared to control group （ P 〈0.05）.Conclusion The results showed that knockout of SRA gene could not prevent the formation of gallstone.High cholesterol may play a more critical role in the pathogenesis of gallstone formation.