内毒素、网状内皮功能与肝脏损伤

内毒素系革兰氏阴性菌壁含脂多糖(LPS)的有毒成份,当肠道内有细菌死亡及生长活跃时,LPS大量产生。经常有小量的LPS被吸收,但被肝脏很快解毒。多年来很多学者研究这种正常解毒功能的丧失,有可能激起或加重肝损伤或引起全身性影响。本文综述了肝脏的网状内皮细胞、肠源性内毒素与肝脏损伤有关的一些实验与临床研究的证据。下图是要审议的一个假说:(a)门静脉血中有内毒素系正常的生理状态;(b)肝脏的血窦细胞,尤其是固定的巨噬细胞对内毒素的正常解毒极重要;(c)很多肝损伤开始时是肝血     

Kupffer细胞在内毒素诱导肝损伤发病机制中的作用

内毒素脂多糖(lipopolysaccharide,LPS)诱导的肝损伤参与了多种肝脏疾病发生发展的进程,肝脏巨噬细胞(即Kupffer细胞)在LPS诱导肝损伤的过程中发挥着重要作用.一方面,Kupffer细胞通过LPS4信号转导系统被激活而释放促炎因子,并在肝脏内其他细胞的相互作用下介导肝脏损害:另一方面,Kupffer细胞的活性又被LPS耐受和其他生理调控机制所抑制,避免Kupffer细胞活化而诱导肝脏损害.因此,Kupffer细胞同时受到激活和抑制性因素的共同作用并维持在相对平衡状态,一旦这种平衡机制被病理因素打破,就可能招致肝脏损伤;而Kupffer细胞活性的抑制性干预就成为保护内毒素诱导肝损伤的重要策略.     

库普弗细胞在内毒素血症致肝损伤中的作用

内毒素血症是导致肝损伤的一个重要因素。近年来研究证实,内毒素血症所致肝损伤与内毒素(LPS)引起库普弗细胞的过度活化密切相关,LPS导致库普弗细胞合成及分泌大量炎症介质和细胞因子,从而导致肝损伤。现就库普弗细胞在内毒素血症所致肝损伤中的作用作一综述。     

罗格列酮对脂多糖诱导的核因子-κB信号转导通路的影响

本研究通过对小鼠内毒素脂多糖(LPS)急性肝损伤动物模型应用过氧化物酶体增殖物激活受体(PPAR γ)的特异忡激动剂罗格列酮,探讨其对LPS诱发的急性肝损伤中肝脏核因子(NF)-κB信号转导通路方面的影响.     

肝窦内皮细胞在肝损伤中的功能研究进展

肝窦内皮细胞（liver sinusoidal endothelial cells, LSECs）位于肝血窦表面，是肝脏与血液接触的第一道防线，也是肝脏中含量最多的非实质细胞。在生理情况下，LSECs通过参与物质运输、代谢废物清除而诱导肝脏免疫耐受，从而维持肝脏稳态；在病理情况下，LSECs通过抗原递呈促进肝脏炎症反应。LSECs在维持肝再生和肝纤维化平衡中发挥了重要的调节作用。本文对LSECs功能、LSECs在肝损伤中的变化、调节LSECs功能相关的信号通路以及LSECs与肝内其他细胞的相互作用等四方面研究进展进行综述，从而进一步明确LSECs的功能及在肝损伤中的作用。     

肝血窦内皮细胞在肝再生和肝纤维化发生中的作用

肝血窦内皮细胞是肝脏非实质细胞的主要组成细胞,是覆盖于肝窦的薄层扁平状细胞,表面富含窗孔,是肝窦和窦状间隙之间溶质交换的开放通道。肝血窦内皮细胞的分泌功能尤其是Wnt信号通路在维持Axin2+源性肝细胞的自我更新、促进肝部分切除或肝损伤时肝再生中均发挥重要的保护作用。肝损伤时,肝血窦内皮细胞结构发生改变,表现为窗孔消失和内皮下基底膜的形成,即肝窦毛细血管化。肝窦毛细血管化既是肝纤维化发生的前奏,也会促进肝纤维化的进展。肝窦内皮细胞在不同生理或病理状态下可通过信号通路的转换实现肝再生和肝纤维化调控作用的转换。肝血窦内皮细胞参与肝再生和肝纤维化机制的深入认识有望为慢性肝病的防治提供新的治疗靶点。     

库普弗细胞SR表达变化与内毒素肝损伤的关系

目的 观察内毒素肝损伤过程中库普弗细胞（KC）清道夫受体（SR）表达的动态变化,进而探讨内毒素肝损伤的机理。方法 经尾静脉内注射不同剂量（1mg/kg、10mg/kg）大肠杆菌内毒素（LPS）,复制内毒素肝损伤模型,采用免疫组织化学方法观察小鼠肝脏SR表达变化;酶联免疫吸附法（ELISA）测定肝组织TNFFα、IL－6的水平,光镜观察肝组织学变化。结果 （1）内毒素肝损伤过程中,KC表面SR表达呈进行笥下调,且与内毒素呈明显的量效关系。（2）SR表达的平均光密度值（A值）与肝组织TNFα、IL－6及血清ALT、TBil呈显著的负相关。结论 内毒素肝损伤过程中,随着SR表达下调,KC对内毒素的清除作用下降,内毒素对KC的激活作用则相应增强。KC SR表达变化与肝损伤密切相关。     

TLR介导的Nrf2抗氧化通路在对乙酰氨基酚药物性肝损伤中的保护作用

目的研究内毒素(LPS)及Toll样受体(TLR)在对乙酰氨基酚(APAP)药物性肝损伤中的保护作用及其相关机制。方法雄性C57BL/6小鼠40只,分为4组,每组10只。空白对照组腹腔注射0.9%氯化钠溶液,LPS组腹腔注射LPS 10μg/kg,APAP组腹腔注射APAP 300 mg/kg,LPS+APAP组在APAP造模前16 h给予LPS 10μg/kg预处理。通过比较各组血清ALT和AST水平,并通过HE染色评价肝组织损伤程度,观察LPS对小鼠肝损伤的保护作用。测定相应时间点的肝脏组织丙二醛(MDA)、还原型谷胱甘肽(GSH)的变化以及肝组织DHE染色,评价小鼠氧化应激水平。应用Western印迹及RT-PCR检测肝脏Nrf2,Gclc及HO-1的表达水平。结果 LPS预处理可明显减轻APAP所致的肝脏氧化应激反应及肝损伤程度。LPS预处理组的小鼠血清ALT(518.3±142.3对4542±498.4 U/L)、AST(643.3±105.6对5432.1±569.2 U/L)水平及肝组织MDA(78.0±14.5对141.7±26.4 mmoL/mg)水平与模型组相比明显降低,而GSH(6.2±1.7对3.5±1.0μmol/g)水平明显升高(P0.05),肝组织病理损伤明显减轻。同时,LPS预处理可明显促进Nrf2及其下游抗氧化基因的表达。结论 LPS在小鼠APAP肝损伤中起到保护作用,作用机制与Nrf2抗氧化通路的激活相关,可能成为药物性肝损伤的新的治疗策略。     

TNF-α,IL-6及ICAM-1在急性肝损伤时肠源性内毒素血症中的作用

目的探讨肿瘤坏死因子（TNF）-α,白细胞介素（IL）-6及细胞间黏附分子（ICAM）-1在急性肝损伤肠源性内毒素血症中的作用机制。方法取Wistar大鼠20只随机分为2组,正常对照组（A组）及急性肝损伤造模组（B组）,每组各10只。测定大鼠血浆内毒素、谷丙转氨酶（ALT）及血浆TNF-α,IL-6水平,RT-PCR方法检测肝脏组织ICAM-1 mRNA的表达,取肝脏行病理学检测。结果与A组相比,B组血浆内毒素,ALT,TNF-α,IL-6水平明显升高（P〈0.01）,ICAM-1 mRNA的表达明显增加（P〈0.01）。肝脏病理检测结果显示,B组大鼠肝细胞呈弥漫性大片状坏死,肝窦结构被破坏,汇管区可见大量炎症细胞浸润。结论TNF-α,IL-6及ICAM-1在急性肝损伤肠源性内毒素血症中起着重要作用。     

内毒素在肝衰竭发生中的作用研究进展

<正>肝衰竭是指肝脏的合成和代谢功能发生严重障碍,在肝衰竭的发病过程中,肝细胞大量坏死、炎性细胞浸润以及肝脏缺血性损伤是其核心环节,当肝细胞坏死超出了肝脏的再生能力时,即会发生肝衰竭[1]。内毒素的主要成分脂多糖(lipopolysaccharide,LPS)存在于革兰氏阴性细菌细胞壁的外部结构中,动物实验证实各种实验性肝损伤多伴有内毒素血症(endotoxemia,ETM)[2]。有学者在肠源性内毒素血症(intestinal endotoxemia,     

Anemia and the liver. Hepatobiliary manifestations of anemia

Many types of hemolytic anemia may be associated with liver disease. Liver injury can be caused by the adherence of deformed or hemolyzed erythrocyses to hepatic vascular endothelium. Adhesion of large numbers of hemolyzed red blood cells to hepatic macrophages, or occlusion of hepatic sinusoids by fragmented red cells, can also result in injury of the liver. Thrombosis of the hepatic or portal vein is associated with some types of hemolytic anemia, and can cause severe liner injury. These are some examples of hepatic injury that can be caused by hemolytic anemias. This article discusses some aspects of liver disease that is associated with sickle cell anemia, paroxysmal nocturnal hemoglobinuria, glucose-6-phosphate dehydrogenase deficiency, hereditary spherocytosis, and HELLP syndrome.     

Overexpression of CYP3A aggravates endotoxin-induced liver injury in hypophysectomized female rats.

Aim: CYP3A2 is a male-specific isoform of cytochrome P450 enzyme which is expressed abundantly in male rats but not in intact female rats. Having previously reported that hepatic CYP3A2 promotes lipopolysaccharide (LPS)-induced liver injury in male rats, we further examined the impact of CYP3A on LPS-induced liver injury by comparing intact and hypophysectomized female rats. In hypophysectomized female rats, phenobarbital (PB), a cytochrome P450 inducer, markedly increased the hepatic content and activity of CYP3A1/2, but did not do so in intact rats. CYP2B1 increased to similar levels in PB-treated hypophysectomized and intact rats. Methods: Rats were administered 10 mg/kg LPS intravenously and some were given PB for three days before LPS injection. Liver injury was analyzed 8 h after LPS injection. Results: PB-LPS increased plasma alanine aminotransferase significantly more in hypophysectomized female rats than in intact female rats. Ketoconazole, a CYP3A inhibitor, inhibited the increase of liver injury. Hepatic 8-hydroxydeoxyguanosine in nuclei and 4-hydroxy-2-nonenal-modified proteins, measured to evaluate oxidative stress by LPS treatment, increased markedly more in PB-treated, hypophysectomized female rats, than in intact female rats. Conclusion: Overexpression of CYP3A aggravated LPS-induced liver injury in rats, apparently through the formation of reactive oxygen species.     

Cooperative IFN-gamma production of mouse liver B cells and natural killer cells stimulated with lipopolysaccharide

BACKGROUND/AIMS: Although mouse liver contains a large population of B cells, little is known about how hepatic B cells respond to bacterial lipopolysaccharide (LPS). METHODS: The cytokine and IgM productions of hepatic B cells were compared with those of splenic B cells. The effect of LPS-treated hepatic B cells on IFN-gamma production from co-cultured NK1.1+ cells was also examined by irradiation and transwell experiments. RESULTS: Hepatic B cells stimulated with LPS produced substantial amounts of IFN-gamma and IL-12 but a small amount of IgM, while splenic B cells did not produce any of these cytokines but produced a large amount of IgM. The hepatic B cells expressed surface markers similar to those on spleen B cells but expressed more C-X-C chemokine receptor 3 than spleen B cells. Notably, depletion of B220+ cells from liver MNCs (but not from spleen MNCs) greatly decreased LPS-induced IFN-gamma production. Furthermore, LPS-treated hepatic B cells stimulated liver NK1.1+ cells to produce a remarkable amount of IFN-gamma, not only through their soluble factors but also through direct cell-cell contact. CONCLUSIONS: Liver B cells may play an important role in the defense against gram-negative bacterial infections by inducing IFN-gamma production from liver NK cells.     

Differential effects of pyrrolidine dithiocarbamate on TNF-alpha-mediated liver injury in two different models of fulminant hepatitis

BACKGROUND/AIMS: Pyrrolidine dithiocarbamate (PDTC) is an inhibitor of nuclear factor kappa B (NF-kappaB) activation. The present study aimed to investigate the effects of PDTC on lipopolysaccharide (LPS)-induced liver injury in two different models of fulminant hepatitis. METHODS: Mice infected with Bacillus Calmette Guerin (BCG) were challenged with LPS (0.2 mg/kg) to induce the model of inflammatory liver injury. Mice were injected with D-galactosamine (GalN, 600 mg/kg) and LPS (20 microg/kg) to induce the model of apoptotic liver injury. In the treatment groups, mice were pre-treated with PDTC (100 mg/kg), initiated 24 h prior to LPS. RESULTS: PDTC pretreatment reduced the infiltration of inflammatory cells, inhibited NF-kappaB activation and the expression of tumor necrosis factor alpha (TNF-alpha), attenuated nitric oxide production, and alleviated hepatic glutathione depletion. Correspondingly, PDTC reduced serum alanine aminotransferase, improved hepatic necrosis, and prolonged the survival in the BCG/LPS model. Conversely, PDTC accelerated death and aggravated liver apoptosis in the GalN/LPS model, although it reduced nitric oxide production, attenuated glutathione depletion, and inhibited the expression of TNF-alpha in liver. CONCLUSIONS: PDTC protects mice against BCG/LPS-induced inflammatory liver injury through the repression of NF-kappaB-mediated TNF-alpha release, while it seems to be detrimental in GalN/LPS-induced apoptotic liver damage.     

Role of thromboxane derived from COX-1 and -2 in hepatic microcirculatory dysfunction during endotoxemia in mice

Although thromboxanes (TXs), whose synthesis is regulated by cyclooxygenase (COX), have been suggested to promote inflammation in the liver, little is known about the role of TXA(2) in leukocyte endothelial interaction during endotoxemia. The present study was conducted to investigate the role of TXA(2) as well as that of COX in lipopolysaccharide (LPS)-induced hepatic microcirculatory dysfunction in male C57Bl/6 mice. We observed during in vivo fluorescence microscopic study that LPS caused significant accumulation of leukocytes adhering to the hepatic microvessels and non-perfused sinusoids. Levels of serum alanine transaminase (ALT) and tumor necrosis factor alpha (TNF alpha) also increased. LPS raised the TXB(2) level in the perfusate from isolated perfused liver. A TXA(2) synthase inhibitor, OKY-046, and a TXA(2) receptor antagonist, S-1452, reduced LPS-induced hepatic microcirculatory dysfunction by inhibiting TNF alpha production. OKY-046 suppressed the expression of an intercellular adhesion molecule (ICAM)-1 in an LPS-treated liver. In thromboxane prostanoid receptor-knockout mice, hepatic responses to LPS were minimized in comparison with those in their wild-type counterparts. In addition, a selective COX-1 inhibitor, SC-560, a selective COX-2 inhibitor, NS-398, and indomethacin significantly attenuated hepatic responses to LPS including microcirculatory dysfunction and release of ALT and TNF alpha. The effects of the COX inhibitors on hepatic responses to LPS exhibited results similar to those obtained with TXA(2) synthase inhibitor, and TXA(2) receptor antagonist. In conclusion, these results suggest that TXA(2) is involved in LPS-induced hepatic microcirculatory dysfunction partly through the release of TNF alpha, and that TXA(2) derived from COX-1 and COX-2 could be responsible for the microcirculatory dysfunction during endotoxemia.     

Etoposide prevents apoptosis in mouse liver with D-galactosamine/lipopolysaccharide-induced fulminant hepatic failure resulting in reduction of lethality

D-Galactosamine (GalN)/lipopolysaccharide (LPS)-induced liver injury is an experimental model of fulminant hepatic failure in which tumor necrosis factor alpha (TNF-alpha) plays a pivotal role. We examined the effects of etoposide on GalN/LPS-induced fulminant hepatic failure. Mice were given an intraperitoneal dose of GalN (800 microg/g body weight)/LPS (100 ng/g body weight) with and without intraperitoneal etoposide (10 microg/g body weight) treatment. Liver injury was assessed biochemically and histologically. TNF-alpha levels in the serum, and apoptosis of hepatocytes and CPP32/caspase-3 in the liver, were determined. GalN/LPS treatment caused lethal liver injury in 87% of animals (13 of 15). The effect was associated with significant increases in TNF-alpha and alanine transaminase (ALT) levels in serum, the number of apoptotic hepatocytes, CPP32/caspase-3 activity, and TNF receptor 1 (TNFR1) mRNA expression in the liver. Etoposide (10 microg/g body weight) was given 3 times (at 50, 26, and 4 hours before GalN/LPS administration). Treatment of GalN/LPS-treated mice with etoposide reduced apoptosis of hepatocytes, resulting in reduction of lethality (13% [2 of 15]), while another topoisomerase II inhibitor, IRCF-193, showed no significant effect. The antilethal effect of etoposide was also confirmed in GalN/TNF-alpha-induced fulminant hepatic failure. Etoposide treatment reduced CPP32/caspase-3 activity in the liver, although it did not alter the serum TNF-alpha levels or hepatic TNFR1 mRNA expressions. In addition, etoposide treatment enhanced the mRNA and protein expression of Bcl-xL, an antiapoptotic molecule in the liver. The present findings suggest that etoposide prevents endotoxin-induced lethal liver injury by up-regulation of Bcl-xL, and that etoposide could be useful for the treatment of TNF-alpha-mediated liver diseases.     

Adiponectin protects LPS-induced liver injury through modulation of TNF-alpha in KK-Ay obese mice

Adiponectin, an adipocytokine, has been identified in adipose tissue, and its receptors are widely distributed in many tissues, including the liver. The present study was performed to clarify the role of adiponectin in lipopolysaccharide (LPS)-induced liver injury using KK-Ay obese mice. We analyzed the effects of adiponectin pretreatment on liver injury induced by D-galactosamine/LPS (GalN/LPS) in KK-Ay obese mice. GalN/LPS treatment induced significant increases in aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels in the blood, apoptotic and necrotic changes in hepatocytes, and/or showed a high degree of lethality. The GalN/LPS-induced liver injury was more pronounced in KK-Ay obese mice than in lean controls. Pretreatment with adiponectin ameliorated the GalN/LPS-induced elevation of serum AST and ALT levels and the apoptotic and necrotic changes in hepatocytes, resulting in a reduction in lethality. In addition, pretreatment with adiponectin attenuated the GalN/LPS-induced increases in serum and hepatic tumor necrosis factor alpha (TNF-alpha) levels and increased peroxisome proliferator-activated receptor (PPAR) alpha messenger RNA expression in the liver. Furthermore, abdominal macrophages from KK-Ay obese mice pretreated with adiponectin in vitro exhibited decreased LPS-induced TNF-alpha production compared with controls. Finally, adiponectin pretreatment also ameliorated TNF-alpha-induced liver injury. In conclusion, these findings suggest that adiponectin prevents LPS-induced hepatic injury by inhibiting the synthesis and/or release of TNF-alpha of KK-Ay obese mice.     

Hepatic sinusoidal obstruction after gemtuzumab ozogamicin (Mylotarg) therapy

Gemtuzumab ozogamicin (Mylotarg) targets leukemia cells expressing the CD33 receptor by means of a monoclonal antibody conjugated to a cytotoxic agent, calicheamicin. Treatment of acute myeloid leukemia (AML) with gemtuzumab ozogamicin may result in liver injury. We reviewed the course of 23 patients who were given gemtuzumab ozogamicin for AML that had relapsed after hematopoietic cell transplantation. Liver toxicity was assessed through physical examination, serum tests, histologic examination, and hepatic venous pressure measurements. Liver injury developed in 11 patients after gemtuzumab ozogamicin administration; it was manifested as weight gain, ascites, and jaundice in 7 patients. Seven patients died with persistent liver dysfunction and either multiorgan failure or sepsis at a median of 40 days after gemtuzumab ozogamicin infusion. Portal pressure measurements were elevated in 2 patients. Results of liver histologic examination in 5 patients showed sinusoidal injury with extensive sinusoidal fibrosis, centrilobular congestion, and hepatocyte necrosis. Six patients experienced AML remission that was sustained for at least 60 days after gemtuzumab ozogamicin infusion. In summary, hepatic sinusoidal liver injury developed after gemtuzumab ozogamicin infusion. Histology showed striking deposition of sinusoidal collagen, suggesting that gemtuzumab ozogamicin targets CD33(+) cells residing in hepatic sinusoids as the mechanism for its hepatic toxicity.     

Prophylactic effect of liposomal N-acetylcysteine against LPS-induced liver injuries

The aim of this study was to evaluate and compare the effectiveness of N-acetylcysteine (NAC) and liposomally-encapsulated NAC (L-NAC) in ameliorating the hepatotoxic effects of lipopolysaccharide (LPS). LPS, a major cell wall molecule of Gram-negative bacteria and the principal initiator of septic shock, causes liver injury in vivo that is dependent on neutrophils, platelets, and several inflammatory mediators, including tumour necrosis factor-alpha (TNF-alpha). Male Sprague-Dawley rats were pretreated intravenously with saline, plain liposomes (dipalmitoylphosphatidylcholine [DPPC]), NAC (25 mg/kg body weight), or L-NAC (25 mg/kg NAC body weight) and 4 h later were challenged intravenously with LPS (Escherichia coli O111:B4, 1.0 mg/kg body weight); animals were killed 20 h post-LPS challenge. Hepatic cell injury was evaluated by measuring the alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities in plasma. LPS-induced activation of the inflammatory response was evaluated by measuring the levels of myeloperoxidase activity and chloramine concentration in liver homogenates as well as TNF-alpha levels in plasma. The hepatic levels of lipid peroxidation products and non-protein thiols (NPSH) were used to assess the extent of involvement of oxidative stress mechanisms. In general, challenge of animals with LPS resulted in hepatic injuries, activation of the inflammatory response, decreases in NPSH levels and increases in the levels of lipid peroxidation products (malondialdehyde and 4-hydroxyalkenals). Pretreatment of animals with NAC or empty liposomes did not have any significant protective effect against LPS-induced hepatotoxicity. On the other hand, pretreatment of animals with an equivalent dose of L-NAC conferred protection against the liver injuries induced following LPS challenge. These data suggest that NAC when delivered as a liposomal formulation is a potentially more effective prophylactic pharmacological agent in alleviating LPS-induced liver injuries.     

Toll-like receptor 4 mediates inflammatory signaling by bacterial lipopolysaccharide in human hepatic stellate cells

Bacterial lipopolysaccharide (LPS) stimulates Kupffer cells and participates in the pathogenesis of alcohol-induced liver injury. However, it is unknown whether LPS directly affects hepatic stellate cells (HSCs), the main fibrogenic cell type in the injured liver. This study characterizes LPS-induced signal transduction and proinflammatory gene expression in activated human HSCs. Culture-activated HSCs and HSCs isolated from patients with hepatitis C virus-induced cirrhosis express LPS-associated signaling molecules, including CD14, toll-like receptor (TLR) 4, and MD2. Stimulation of culture-activated HSCs with LPS results in a rapid and marked activation of NF-kappaB, as assessed by in vitro kinase assays for IkappaB kinase (IKK), IkappaBalpha steady-state levels, p65 nuclear translocation, NF-kappaB-dependent luciferase reporter gene assays, and electrophoretic mobility shift assays. Lipid A induces NF-kappaB activation in a similar manner. Both LPS- and lipid A-induced NF-kappaB activation is blocked by preincubation with either anti-TLR4 blocking antibody (HTA125) or Polymyxin B. Lipid A induces NF-kappaB activation in HSCs from TLR4-sufficient (C3H/OuJ) mice but not from TLR4-deficient (C3H/HeJ) mice. LPS also activates c-Jun N-terminal kinase (JNK), as assessed by in vitro kinase assays. LPS up-regulates IL-8 and MCP-1 gene expression and secretion. LPS-induced IL-8 secretion is completely inhibited by the IkappaB super repressor (Ad5IkappaB) and partially inhibited by a specific JNK inhibitor, SP600125. LPS also up-regulates cell surface expression of ICAM-1 and VCAM-1. In conclusion, human activated HSCs utilize components of TLR4 signal transduction cascade to stimulate NF-kappaB and JNK and up-regulate chemokines and adhesion molecules. Thus, HSCs are a potential mediator of LPS-induced liver injury.