The active metabolite of leflunomide, A77 1726, protects rat hepatocytes against bile acid-induced apoptosis

BACKGROUND/AIMS: Leflunomide is used in the treatment of autoimmune diseases as an anti-inflammatory agent. Leflunomide and its active metabolite A77 1726 modulate mitogen-activated protein kinases (MAPK), Src kinases, the phosphoinositide-3 kinase (PI3K)/Akt-pathway and nuclear factor (NF)-kappaB activation. Both cell protective and cytotoxic effects of leflunomide have been described. Since leflunomide affects pathways involved in hepatocyte cell survival, we examined the effects of A77 1726 on hepatocyte cell death. METHODS: Primary rat hepatocytes were exposed to the bile acid glycochenodeoxycholic acid (GCDCA), the superoxide anion donor menadione, or tumor necrosis factor (TNF) alpha in combination with actinomycin D. Activation of MAP-kinases was determined by Western blot analysis. Apoptosis and necrosis were analyzed by acridine orange staining and caspase activity and Sytox Green staining, respectively. RESULTS: A77 1726 dose-dependently reduces GCDCA-induced apoptosis and necrosis, but not menadione- or TNFalpha/ActD-induced apoptosis. The hepatoprotective effect of A77 1726 does not involve ERK1/2, p38 or PI3K/Akt activation. A77 1726 does not inhibit NF-kappaB activation in hepatocytes. CONCLUSIONS: Since A77 1726 inhibits bile acid-induced apoptosis and does not sensitize hepatocytes to TNFalpha, our results suggest that A77 1726 could be considered for the treatment of chronic liver diseases accompanied by elevated bile acid levels and inflammation.     

Role of mitogen-activated protein kinases in tauroursodeoxycholic acid-induced bile formation in cholestatic rat liver.

Aim: Ursodeoxycholic acid exerts anticholestatic effects in various cholestatic disorders and experimental models of cholestasis. Its taurine conjugate (TUDCA) stimulates bile salt secretion in isolated perfused rat livers (IPRL) under physiological, non-cholestatic conditions, in part by mitogen-activated protein kinase (MAPK)-dependent mechanisms. The role of MAPK in the anticholestatic effect of TUDCA, however, is unclear. Therefore, we studied the role of MAPK in the anticholestatic effect of TUDCA in IPRL and isolated rat hepatocytes (IRH) in taurolithocholic acid (TLCA)-induced cholestasis. Methods: Bile flow, biliary levels of 2,4-dinitrophenyl-S-glutathione (GS-DNP) as a marker of hepatobiliary organic anion secretion and activity of lactate dehydrogenase (LDH) in hepatovenous effluate as a marker of hepatocellular damage in IPRL perfused with TUDCA and/or TLCA were determined in the presence or absence of MAPK inhibitors. In addition, phosphorylation of Erk 1/2 and p38(MAPK) induced by TUDCA and/or TLCA was studied by Western immunoblot in IPRL and IRH. Results: TUDCA-induced bile flow was impaired by the Erk 1/2 inhibitor PD98059 in normal livers (-28%), but not in livers made cholestatic by TLCA. GS-DNP secretion was unaffected by PD98059 under both conditions. TUDCA-induced bile formation and organic anion secretion both in the presence and absence of TLCA were unaffected by the p38(MAPK) inhibitor SB202190. Erk 1/2 phosphorylation in liver tissue was unchanged after bile salt exposure for 70 min, but was transiently enhanced by TUDCA in IRH. Conclusion: MAPK do not mediate the anticholestatic effects of TUDCA in TLCA-induced cholestasis.     

胆汁酸在胆汁淤积性肝损伤发病中的作用研究进展

胆汁酸由肝脏产生,是胆汁的主要成分之一。在胆汁分泌受阻时,血清和肝脏胆汁酸浓度上升,进而导致肝损害。尽管过去对于胆汁酸导致肝损害有过很多研究,但是其导致肝损害的分子机制目前仍存在争议。在本文中,我们总结了胆汁酸导致肝损伤发病机制的最新研究进展。在病理条件下,胆汁酸诱导肝细胞损害是通过处于应激条件下的肝细胞诱导炎症反应而发生的。本文主要聚焦胆汁酸如何诱导炎症因子的产生从而进一步诱导相关免疫细胞的聚集,以及基于对这些病理基础的认识,他们探讨了可能对胆汁淤积性肝损害有潜在治疗的新方法。     

Phosphoinositide 3-kinase, but not mitogen-activated protein kinase, pathway is involved in hepatocyte growth factor-mediated protection against bile acid-induced apoptosis in cultured rat hepatocytes

We have previously shown that cAMP protects against hydrophobic bile acid-induced apoptosis in cultured rat hepatocytes through pathways dependent on activation of phosphoinositide 3-kinase and inhibition of mitogen activated protein kinase. Hepatocyte growth factor protects epithelial cells against apoptosis and activates both of these kinases in hepatocytes. We studied the effect of hepatocyte growth factor on glycochenodeoxycholate-induced apoptosis to determine whether hepatocyte growth factor protects hepatocytes against bile acid-induced apoptosis and whether the protective effect is mediated via phosphoinositide 3-kinase and/or mitogen-activated protein kinase pathways. Two-hour exposure of cultured rat hepatocytes to glycochenodeoxycholate resulted in apoptosis in 12.5 +/- 0.49% of the cells. Pretreatment with hepatocyte growth factor (50 ng/mL) decreased apoptosis by 50% to 70%. Hepatocyte growth factor cytoprotection was prevented by pretreatment with the phosphoinositide 3-kinase inhibitors, wortmannin (50 nmol/L) or Ly 294002 (40 micromol/L). Hepatocyte growth factor activated phosphoinositide 3-kinase dependent protein kinase B and mitogen-activated protein kinase. Pretreatment of hepatocytes with a mitogen-activated protein kinase inhibitor, U0126 (40 micromol/L) or an inhibitor of pp70(s6) kinase, rapamycin (100 nmol/L), had no effect on the growth factor's anti-apopotic effect. Treatment with hepatocyte growth factor resulted in mitogen-activated protein kinase-dependent phosphorylation of BAD on serine(112). In summary, hepatocyte growth factor protection against bile acid-induced apoptosis occurs via a phosphoinositide 3-kinase pathway and is not dependent on the mitogen-activated protein kinase pathway, phosphorylation of BAD on serine(112), or activation of p70(S6) kinase.     

Urinary trypsin inhibitor attenuates hepatic ischemia-reperfusion injury by reducing nuclear factor-kappa B activation

BACKGROUND:Urinary trypsin inhibitor(UTI)inhibits the inflammatory response and protects against ischemia- reperfusion(I/R)injury.The inflammatory response is mediated by nuclear factor-kappa B(NF-κB)and its related target genes and products such as vascular endothelial cell adhesion molecule and CXC chemokines.We aimed to assess the roles of those mediators in a UTI-treated mouse model of hepatic I/R injury. METHODS:Treatment group 1(UTI given 5 minutes prior to liver ischemia),treatment group 2(UTI given ...     

一氧化氮对急性肺损伤发病过程中核因子-κB活化的调节作用

目的:探讨一氧化氮(NO)在急性重症胰腺炎急性肺损伤大鼠发病中的作用及肺泡巨噬细胞核因子-κB(NF-κB)活化的关系．方法:健康雄性SD大鼠随机分为:假手术组、模型组、硝普钠(SNP)组、左旋精氨酸组、氨基胍组,每组6只．经胰管逆行注入去氧胆酸钠复制大鼠急性重症胰腺炎急性肺损伤模型．采用凝胶电泳迁移率方法检测肺泡巨噬细胞中NF-κB活性,RT-PCR分析iNOS mRNA 的表达,同时亦检测NO、TNF-α、iNOS的水平和肺组织病理学的改变．结果:模型组中NF-κB活性、iNOS mRNA表达及TNF-α、NO、iNOS的含量均显著高于假手术组(P=0．02)．肺组织病理学显示严重损害．NO的供体硝普钠及iNOS选择性抑制剂氨基胍可降低NF-κB活性(213．47±12．34, 222．98±17．69 vs 327．13±13．46,P<0．05),下调iNOS mRNA表达(SNP:2．35±0．34 vs 3．1 ±0．38,P<0．05)以及TNF-α(0．38±0．034, 0．45±0．043 μg/L vs 0．76±0．045 μg/L)、 NO(168．2±0．78,146．4±0．59 mmol/L vs 229．3 ±0．98 mmol/L)的水平,减轻肺组织病理学损伤．而左旋精氨酸组则无明显调节作用．离体实验结果与体内试验一致．结论:外源性NO可抑制NF-κB活化,降低 iNOS mRNA的表达,进而减少NO、TNF-α的释放．同样,经iNOS选择性抑制剂抑制内源性 NO的产生,也可控制机体的过度炎症反应．     

Cyclin kinase inhibitor p21 potentiates bile acid-induced apoptosis in hepatocytes that is dependent on p53

Prolonged activation of the mitogen-activated protein kinase (MAPK) pathway enhances expression of the cyclin kinase inhibitor p21 that can promote growth arrest and cell survival in response to cytotoxic insults. Bile acids can also cause prolonged MAPK activation that is cytoprotective against bile acid-induced cell death. Here, we examined the impact of bile acid-induced MAPK signaling and p21 expression on the survival of primary mouse hepatocytes. Deoxycholic acid (DCA) caused prolonged activation of the MAPK pathway that weakly enhanced p21 protein expression. When DCA-induced MAPK activation was blocked using MEK1/2 inhibitors, both hepatocyte viability and expression of p21 were reduced. Surprisingly, constitutive overexpression of p21 in p21+/+ hepatocytes enhanced DCA-induced cell killing. In agreement with these findings, treatment of p21-/- hepatocytes with DCA and MEK1/2 inhibitors also caused less apoptosis than observed in wild-type p21+/+ cells. Expression of p21 in p21-/- hepatocytes did not modify basal levels of apoptosis but restored the apoptotic response of p21-/- cells to those of p21+/+ cells overexpressing p21. These findings suggest that basal expression of p21 plays a facilitating, proapoptotic role in DCA-induced apoptosis. Overexpression of p21 enhanced p53 protein levels. In agreement with a role for p53 in the enhanced apoptotic response, overexpression of p21 did not potentiate apoptosis in p53-/- hepatocytes but, instead, attenuated the death response in these cells. In conclusion, our data suggest that overexpression of p21 can promote apoptosis, leading to elevated sensitivity to proapoptotic stimuli.     

Genistein prevents nuclear factor-kappa B activation and acute lung injury induced by lipopolysaccharide.

Protein tyrosine kinase (PTK) inhibitors have been proposed to reduce lung injury and lethal toxicity. The mechanisms responsible for the effects of PTK inhibitors remain obscure. The purpose of the present study was to examine whether genistein, a specific inhibitor of PTK, inhibits nuclear factor-kappa B (NF-kappaB) activation during acute lung injury induced by lipopolysaccharide (LPS) and, if so, to enumerate the effects of inhibition of NF-kappaB activation on LPS-induced proinflammatory gene products, such as cytokine-inducible neutrophil chemoattractant (CINC) and matrix metalloproteinase-9 (MMP-9), as well as neutrophil influx into the lungs. Intratracheal treatment of rats with LPS (6 mg/kg) resulted in increases in total protein and lactate dehydrogenase activity in bronchoalveolar lavage fluid and activated DNA-binding activity of NF-kappaB in alveolar macrophages and lung tissue. A 2-h pretreatment with genistein (50 mg/kg, intraperitoneally) inhibited the LPS-induced changes in lung injury parameters and the induction of NF-kappaB activation. Furthermore, these inhibitory effects of genistein correlated with a depression of LPS-induced protein tyrosine phosphorylation (approximately molecular masses of 46, 48, and 54 kD) and phosphorylation of Jun N-terminal kinase (JNK) in lung tissue. Genistein also substantially reduced the LPS-induced CINC production and MMP-9 activity and suppressed neutrophil recruitment. These results suggest that genistein attenuates LPS-induced acute lung responses through inhibition of NF-kappaB activation. In addition, NF-kappaB activation appears to be an important mechanism mediating LPS-induced CINC production and MMP-9 activity and resulting neutrophil recruitment associated with acute lung inflammation and injury.     

Bilirubin inhibits bile acid induced apoptosis in rat hepatocytes

BACKGROUND AND AIMS: Hydrophobic bile acids contribute to hepatocellular injury in cholestasis and rapidly induce apoptosis in vitro; however, unlike Fas agonists, cholestasis does not cause extensive hepatocyte apoptosis. As antioxidants provide protection against bile acid induced liver injury, our premise was that bilirubin, a free radical scavenger with increased plasma levels in the presence of liver disease, could protect hepatocytes against bile acid induced apoptosis. METHODS: Freshly isolated rat hepatocytes were incubated for four hours with 100 micromol/l glycochenodeoxycholate (GCDC) alone or with increasing concentrations of unconjugated (UCB) or conjugated (CB) bilirubin. RESULTS: Both UCB and CB inhibited GCDC induced apoptosis in a dose dependent fashion and suppressed the generation of reactive oxygen species by hepatocytes. CONCLUSIONS: The antiapoptotic effect of bilirubin associated with its antioxidant properties indicates that hyperbilirubinaemia may have a protective role in liver disease.     

抑制转录因子核因子保护大鼠心肌缺血的研究

目的 :探讨转录因子核因子 (NF κB)在大鼠心肌缺血损伤过程中的作用机制及抑制NF κB激活对缺血心肌的保护作用。方法 :4 0只SD大鼠随机分为对照组、异丙肾上腺素 (Iso)组、Iso加吡咯烷二硫代氨基甲酸酯 (PDTC) 5 0、10 0、15 0mg/kg组 ,每组 8只。Iso造成心肌缺血模型 ,腹腔注射PDTC抑制NF κB的激活 ,测定血清中肿瘤坏死因子 α(TNF α)、血管细胞粘附分子 1(VCAM 1)、超氧化物歧化酶 (SOD)、丙二醛 (MDA)、乳酸脱氢酶 (LDH)及心肌匀浆中SOD、MDA的水平 ,免疫组化观察心肌NF κB的激活程度。结果 :腹腔注射Iso引起典型心肌缺血损伤的组织学改变 ,NF κB在缺血组织的血管壁及浸润的炎性细胞中大量激活 ,血清中LDH、TNF α、VCAM Ⅰ、MDA的含量及心肌匀浆中MDA的水平均显著高于对照组 (P <0 .0 1) ,血清及心肌匀浆中SOD活力均显著低于正常 (P <0 .0 1)。而用PDTC抑制NF κB ,上述改变可呈剂量依赖性地减轻 ,其中PDTC 15 0mg/kg剂量组可显著减轻Iso造成的心肌缺血损伤 ,只有极少量的NF κB被激活 ,血清及心肌匀浆各指标与对照组比较差异无显著性意义 (P >0 .0 5 )。结论 :NF κB在心肌缺血过程中被大量激活 ,产生相应细胞因子、粘附分子等递质 ,造成心肌损伤 ,抑制NF κB激活 ,能起到显著的保护作用     

Endogenous interferon gamma protects against cholestatic liver injury in mice

Cholestatic patients suffer from high perioperative morbidity and mortality, but the pathophysiology is still unknown. Interferon gamma (IFN-gamma) may play a role during cholestasis. Therefore, bile duct ligation (BDL) was induced in IFN-gamma alpha-chain receptor-deficient (IFN-gammaR(1)-/-) and wild-type (IFN-gammaR(1)+/+) mice. BDL elicited increased IFN-gamma messenger RNA and protein levels in the liver. One week after BDL, IFN-gammaR(1)+/+ mice showed less severe jaundice and liver injury than IFN-gammaR(1)-/- mice, as reflected by lower bilirubin and liver enzyme levels. In accordance, livers of IFN-gammaR(1)+/+ mice displayed smaller areas of necrosis by two-thirds than IFN-gammaR(1)-/- mice on histopathologic examination (P <.05), whereas mitotic activity and proliferating cell nuclear antigen (PCNA) labeling index was more than twice as high in IFN-gammaR(1)+/+ mice (P <.05). Livers of IFN-gammaR(1)+/+ mice displayed higher rates of apoptosis as indicated by DNA fragmentation rate, the number of apoptotic bodies, and poly ADP-ribose polymerase (PARP) immunostaining. BDL was not associated with lethality in IFN-gammaR(1)+/+ mice; IFN-gammaR(1)-/- mice, however, died from 10 days onward and survival after 2 weeks was 62% (10 of 16). In conclusion, these data suggest that IFN-gamma protects against liver injury during extrahepatic cholestasis by stimulation of apoptosis and subsequent proliferation of hepatocytes, leading to elegant removal of damaged hepatocytes, thus preventing necrosis and concomitant inflammatory responses.     

核因子-κB在硫代乙酰胺所致急性肝损伤中的作用及机制研究

目的 探讨核因子-κB(NF-κB)在硫代乙酰胺(TAA)所致急性肝损伤中的作用及机制.方法 雄性Wistar大鼠78只分为正常组18只,TAA造模组30只及脯氨酸二硫代氨基甲酸酯(PDTC)预处理组30只.PDTC预处理组于建立急性肝损伤模型前1 h腹腔内注射PDTC 100 mg/kg.然后,三组大鼠分别于6、24、48 h处死,TAA造模组及PDTC预处理组每时间点各取10只大鼠,正常组每时间点各取6只大鼠.测定大鼠血浆内毒素、肿瘤坏死因子-α(TNF-α)、白细胞介素-6(IL-6)水平,RT-PCR方法检测肝脏组织细胞间粘附因子-1(ICAM-1)mRNA表达,取肝脏行病理学及免疫组化检测NF-κB活性.结果 ①TAA造模组造模后6、24和48 h NF-κB细胞阳性率分别为(87.11±8.23)%、(78.55±6.82)%和(74.27±6.26)%,与正常组相比差异均有统计学意义[(4.64±1.82)%、(4.55±1.67)%和(4.91±2.12)%,P值均＜0.01].PDTC预处理组各时间点NF-κB细胞阳性率分别为(31.88±4.14)%、(27.58±3.44)%和(26.67±3.88)%,与TAA造模组相比阳性率明显降低(P值均＜0.01).②TAA造模组各时间点血浆内毒素和TNF-α水平含量明显较正常组升高(P值均＜0.01),而PDTC预处理组则较TAA造模组降低(P值均＜0.01),但较正常组有所增高(P值均＜0.01).③TAA造模组各时间点IL-6水平较正常组显著升高(P值均＜0.01).PDTC预处理组各时间点IL-6水平较TAA造模组明显降低(P值分别＜0.05和0.01);24和48 h较正常组增加(P值均＜0.01).④TAA造模组各时间点ICAM-lmRNA表达较正常组显著升高(P值均＜0.01).PDTC预处理组各时间点ICAM-lmRNA表达较TAA造模组明显降低(P值均＜0.01).但较正常组增高(P值均＜0.01).⑤TAA造模组各时间段可见肝组织坏死,PDTC预处理组各时间段肝组织病理改变较TAA造模组同时间点明显减轻.结论 NF-κB在TAA所致急性肝损伤中通过促进TNF-α、IL-6及ICAM-1的表达而发挥作用,加重肝损伤.     

肝细胞核因子-κB异常激活与肝细胞癌变

核因子-κB（nuclear factor-κB，NF-κB）是具有和某些基因上启动子区固定核苷酸序列结合而启动该基因转录的蛋白质。NF-κB是具有多向性调节作用的核转录因子，可调控多种基因（免疫、炎症反应、病毒和原癌基因）的转录表达。激活的NF-κB参与癌症的启动、发生及发展过程，在炎症性相关的肝癌（HCC）发生发展中呈高表达，在肝细胞炎症与癌变间起桥梁作用，其中包括肝脏免疫炎症反应相关基因、肝炎病毒相关基因和原癌基因的转录表达。在肝癌组织中异常激活，可抑制细胞凋亡，促进肝细胞存活，与肝癌的发生发展密切相关。