目的:探讨沉默信息调节因子6(silent information regulator 6,SIRT6)对四氯化碳(carbon tetrachlo-ride,CCl4)诱导的小鼠肝纤维化作用和机制,以及肝星状细胞在SIRT6沉默后其下游通路的表达变化.方法:将30只雄性C57BL/6J小鼠随机分为正常对照组(n=6)和模型组(造模2、4、8、12周,n=24),采用腹腔注射CCl4制备肝纤维化小鼠模型,每周2次,持续12周.检测各组小鼠血清丙氨酸氨基转移酶(alanine aminotransferase,ALT)、天门冬氨酸氨基转移酶(aspartate aminotransferase,AST)含量评估肝损伤;HE、Masson染色观察小鼠肝脏病理学改变;免疫组织化学染色检测小鼠肝脏α-平滑肌肌动蛋白(α-smooth muscle actin,α-SMA)的表达;Western blot检测肝脏α-SMA、SIRT6、第9位赖氨酸乙酰化的组蛋白H3(acetyl histone H3 at Lys9,H3K9ac)、第56位赖氨酸乙酰化的组蛋白H3(acetyl histone H3 at Lys56,H3K56ac)、白细胞介素1β(interleukin-1β,IL-1β)和IL-18蛋白的表达.将大鼠肝星状细胞(hepatic stellate cells-T6,HSC-T6)进行SIRT6基因沉默,分为NC siRNA组和SIRT6 siRNA组.Western blot检测SIRT6、H3K9ac和H3K56ac蛋白的表达.结果:与正常对照组比较,模型组小鼠血清中ALT和AST含量均显著升高(P<0.05);HE染色和Masson结果显示,模型组肝脏病理变化逐渐加重,胶原纤维沉积逐渐增多;免疫组织化学染色与Western blot均显示,在8和12周模型组中肝脏α-SMA表达显著增加(P<0.05);Western blot检测结果显示,CCl4造模后各组小鼠肝脏中SIRT6蛋白表达均低于正常对照组(P<0.05),并随肝纤维化的加重逐渐降低;同时模型组小鼠肝脏H3K9ac、H3K56ac、IL-1β和IL-18表达水平在8、12周时明显升高(P<0.05);SIRT6沉默后,与NC siRNA组比较,SIRT6 siRNA组中的H3K9ac和H3K56ac显著增加(P<0.05).结论:SIRT6缺乏通过H3K9ac和H3K56ac的异常增多使得IL-1β和IL-18的表达升高,加剧炎症反应而促进肝纤维化进程,提示SIRT6的表达异常参与了肝纤维化进程的发展.
Role of SIRT6 in progression of liver fibrosis and its mechanism
AIM:This study aims to investigate the effects and mechanisms of silent information regulator 6(SIRT6)on carbon tetrachloride(CCl4)-induced liver fibrosis in mice,as well as the expression changes in the down-stream pathways of hepatic stellate cells after SIRT6 silencing.METHODS:Thirty male C57BL/6J mice were randomly divided into a normal control group(n=6)and a model group(modeling at 2,4,8,12 weeks,n=24).A liver fibrosis model in mice was prepared by intraperitoneal injection of CCl4 twice a week for 12 weeks.Serum alanine aminotransfer-ase(ALT)and aspartate aminotransferase(AST)levels were measured to assess liver injury.Hematoxylin-eosin(HE)and Masson staining were used to observe the pathological changes in mouse liver tissues.Immunohistochemical staining was conducted to detect the expression of α-smooth muscle actin(α-SMA)in the liver,Western blot analysis was used to measure the expression of liver α-SMA,SIRT6,acetyl histone H3 at Lys9(H3K9ac),acetyl histone H3 at Lys56(H3K56ac),interleukin-1β(IL-1β),and IL-18 proteins.Hepatic stellate cells-T6(HSC-T6)underwent SIRT6 gene si-lencing,divided into NC siRNA group and SIRT6 siRNA group,with Western blot performed to detect the expression of SIRT6,H3K9ac,and H3K56ac proteins.RESULTS:Compared with the normal control group,the serum ALT and AST levels in the model group were significantly increased(P<0.05);HE and Masson staining results showed that the patho-logical changes in the liver of the model group worsened over time,with an increase in collagen fiber deposition.Both im-munohistochemistry and Western blot showed that the expression of liver α-SMA significantly increased at 8 and 12 weeks in the model group(P<0.05).Western blot results showed that the expression of SIRT6 protein in the liver of all model group mice was lower than that in the normal control group(P<0.05),and decreased gradually with the progression of liv-er fibrosis;also,the expression levels of H3K9ac,H3K56ac,IL-1β,and IL-18 in the liver of the model group mice were significantly elevated at 8 and 12 weeks(P<0.05);after SIRT6 silencing,compared with the NC siRNA group,the levels of H3K9ac and H3K56ac in the SIRT6 siRNA group significantly increased(P<0.05).CONCLUSION:The deficiency of SIRT6,by abnormally increasing H3K9ac and H3K56ac,raises the expression of IL-1β and IL-18,intensifying the in-flammatory response and promoting the progression of liver fibrosis,indicating that the aberrant expression of SIRT6 is in-volved in the development of liver fibrosis.
liver fibrosiscarbon tetrachloridehepatic stellate cellssilent information regulator 6inflam-matory factors
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