Heme oxygenase-1 overexpression increases liver injury after bile duct ligation in rats

AIM： To investigate the effects of heme oxygenase-1 （HO-1） against oxidant-induced injury caused by bile duct ligation （BDL）.METHODS： Either cobalt protoporphyrin （CoPP）, a HO-1 inducer, or saline were injected intraperitoneally in male SD-rats. Three days later, BDL or sham-operations were performed. Rats were sacrificed 3 wk after BDL and livers were harvested for histology. Fibrosis was evaluated by sirius red staining and image analysis. Alpha-smooth muscular actin, which indicates activation of stellate cells, was detected by immunohistochemical staining, and q/tokine and collagen- Iα （Col- I α） mRNA expression was detected using RNase protection assays.RESULTS： Serum alanine transaminase increased 8-fold above normal levels one day after BDL. Surprisingly, enzyme release was not reduced in rats receiving CoPP. Liver fibrosis was evaluated 3 wk after BDL and the sirius red-positive area was found to be increased to about 7.8%. However, in CoPP pretreated rats sirius redpositive areas were increased to about 11.7% after BDL. Collagen-1 α and TGF-β mRNA increased significantly by BDL. Again, this effect was increased by HO-1 overexpression.CONCLUSION： Hepatic fibrosis due to BDL is not reduced by the HO-1 inducer CoPP. In contrast, HO-1 overexpression increases liver injury in rats under conditions of experimental chronic cholestasis.

Dietary glycine blunts liver injury after bile duct ligation in rats

AIM： To investigate the effects of （dietary） glycine against oxidant-induced injury caused by bile duct ligation （BDL）.METHODS： Either a diet containing 5% glycine or a standard diet was fed to male Sprague-Dawley （SD） rats. Three days later, BDL or sham-operation was performed. Rats were sacrificed 1 to 3 d after BDL. The influence of deoxycholic acid （DCA） in the presence or absence of glycine on liver cells was determined by measurement of calcium and chloride influx in cultivated Kupffer cells and lactate dehydrogenase （LDH） activity was determined in the supernatant of cultivated hepatocytes.RESULTS： Serum alanine transaminase levels increased to about 600 U/L 1 d alter BDL. However, enzyme release was blunted by about two third in rats receiving glycine. Release of the alkaline phosphatase and aspartate aminotransferase was also blocked significantly in the group fed glycine. Focal necrosis was observed 2 d after BDL. Glycine partially blocked the histopathological changes. Incubation of Kupffer cells with DCA led to increased intracellular calcium that could be blocked by incubation with glycine. However, systemic blockage of Kupffer cells with gadolinium chloride had no effects on transaminase release. Incubation of isolated hepatocytes with DCA led to a significant release of LDH after 4 h. This release was largely blocked when incubation with glycine was performed.CONCLUSION： These data indicate that glycine significantly decreased liver injury, most likely by a direct effect on hepatocytes. Kupffer cells do not appear to play an important role in the pathological changes caused by cholestasis.

脂质过氧化在再灌流性肝损伤中的作用

采用低流率-再灌流模型研究脂质过氧化在再灌流性肝损伤中的作用,肝脏经过90min低速率灌流未见明显损伤,当灌流速率恢复到正常后中心静脉周围区(PC区)细胞发生迅速不可逆损害,并伴有丙二醛生成率大幅度上升,低速率灌流期间,灌流液中黄嘌呤与次黄嘌吟浓度由原来的1.5和3.6μmol·L^(-1)逐步升高至5.5和11.5μmol·L^(-1),自由基清除剂儿茶酸能使再灌流期丙二醛生成率由295 nm01·g^(-1)·h^(-1)下降至109 nmol·g^(-1)·h^(-1),并使LDH释放率减少约50％,PC区细胞死亡率减少89％,再灌流初期用氮饱和灌流液冲洗3 min,使再灌流所致的LDH释放下降约50％,PC区细胞死亡率减少84％,别嘌吟醇(2～6mmol·L^(-1))对防止再灌流性肝损伤表现出明显的剂量效应关系。 与预计结果相反低浓度别嘌呤醇(0.5～1mmol·^(-1))能增加再灌流性肝损伤,400μmol·L^(-1)黄嘌呤则使再灌流性肝损伤明显减轻,其代谢产物尿酸对降低再灌流时丙二醛生成率以及细胞损害均表现出明显的剂量反应关系。

油酸盐对苯并[A]芘酚葡萄糖醛酸化抑制的作用机理

利用肝脏灌流模型及肝脏微粒体对油酸影响羟基苯并[a]芘葡萄糖醛酸化的机理进行了研究,结果表明,低剂量的油酰辅酶A可非竞争性地抑制大鼠肝微粒体UDP-葡萄醛酰转移酶的活性,使3-羟基苯并芘葡萄糖醛酰化作用受抑制,牛血清白蛋白与Triton X-100可促进油酰辅酶A对转移酶的抑制作用。 600 μmol·L^(-1)的油酸灌流肝脏,可使肝脏中UDPGA,UDPG及ATP分别下降44％,49％及44％,因此高剂量的油酸亦可通过改变辅因子供应而抑制羟基苯并芘的葡萄糖醛酸化过程。 250μmol·L^(-1)的油酸灌流缺乏β-葡萄糖醛酸酶的C_3H/He小鼠肝脏,可使流出液中游离羟基苯并芘增加136％,而与葡萄糖醛酸结合的羟基苯并芘减少了32％,同时肝脏中与葡萄糖醛酸结合的羟基苯并芘减少64％,以油酸灌流具有高β-葡萄糖醛酸酶的DBA/2小鼠肝脏可见同样改变,在肝脏微粒体的实验中亦未见油酰辅酶A对苯并芘-0-葡萄糖醛酸的水解作用有何影响,据此,油酸对羟基苯并芘葡萄醛酸化状态的影响与β-葡萄糖醛酸酶无关。