Antimycin A-induced defenestration in rat hepatic sinusoidal endothelial cells

Liver sinusoidal endothelial cells (LSECs) possess fenestrae arranged in sieve plates. Hepatic endothelial fenestrae are open pores approximately 100 to 200 nm in diameter. Alterations in their number or diameter by hormones, xenobiotics, and diseases have important implications for hepatic microcirculation and function. Numerous reports of hepatotoxin-induced defenestration suggest that the cytoskeleton and the energy status of hepatic endothelial cells play a key role in the regulation of fenestrae. Therefore, we investigated the effect of antimycin A, an inhibitor of mitochondrial energy production, on the number of fenestrae in cultured LSECs using high-resolution microscopy and immunocytochemistry. Prolonged incubation (greater than 30 min) with antimycin A resulted in defenestrated cells and coincided with the appearance of F-actin dots, whereas the distribution of G-actin remained unchanged. Adenosine triphosphate (ATP) was depleted dramatically to less than 5% within 30 minutes within the LSECs. After treatment with antimycin A, unusual elevated fenestrated complexes were apparent, organized as a meshwork of anastomosing fenestrae at the center of and above the sieve plates. The position and appearance of these novel structures and their association with defenestration suggest that they are implicated in the process of defenestration. In conclusion, the results of experiments with antimycin A suggest that ATP is needed to maintain fenestrae and the underlying fenestrae-associated cytoskeleton rings that maintain fenestrae patency. Antimycin A-induced defenestration of LSECs is associated with the development of a structure in the sieve plate that appears to be intrinsically involved in defenestration.     

Toxic injury to hepatic sinusoids: sinusoidal obstruction syndrome (veno-occlusive disease)

The term veno-occlusive disease of the liver refers to a form of toxic liver injury characterized clinically by the development of hepatomegaly, ascites, and jaundice, and histologically by diffuse damage in the centrilobular zone of the liver. The cardinal histologic features of this injury are marked sinusoidal fibrosis, necrosis of pericentral hepatocytes, and narrowing and eventual fibrosis of central veins. Recent studies suggest that the primary site of the toxic injury is sinusoidal endothelial cells, followed by a series of biologic processes that lead to circulatory compromise of centrilobular hepatocytes, fibrosis, and obstruction of liver blood flow. Thus we propose a more appropriate name for this form of liver injury--sinusoidal obstruction syndrome. This review encompasses historical perspectives, clinical manifestations of sinusoidal obstruction syndrome in the setting of hematopoietic cell transplantation, histologic features of centrilobular injury, and a discussion of the pathophysiology of sinusoidal injury, based on both animal and clinical investigations.     

肝窦内皮细胞与肝窦毛细血管化研究进展

肝窦内皮细胞具有开放的、没有横膈膜的窗孔,内皮下没有基底膜。这种结构有利于调控肝细胞与肝窦血液的物质交换。肝窦内皮细胞能分泌内皮素-1和一氧化氮,并通过窗孔的变化,对肝脏微循环进行调节,同时可分泌大量的形成基底膜的成分,在肝窦毛细血管化的过程中起主导作用。肝窦内皮细胞表型标志发生变化,Ⅷ因子相关抗原、CD44等表达增强,也是肝窦毛细血管化的重要标志。笔者对肝窦内皮细胞的结构及其在肝窦毛细血管化中的功能和表型变化进行综述。     

Characterization of a reproducible rat model of hepatic veno-occlusive disease.

Lack of a reproducible animal model has hampered progress in understanding hepatic veno-occlusive disease (HVOD). This article characterizes a reproducible model of HVOD. Rats gavaged with monocrotaline, 160 mg/kg, were killed between days 1 and 10. Sections were evaluated by light microscopy with a standardized scoring system, by immunoperoxidase staining with ED-1 (monocytes, macrophages) and ED-2 (Kupffer cells) antibodies, and by transmission (TEM) and scanning electron microscopy (SEM). On days 1 and 2, the earliest manifestations were progressive injury to the sinusoidal wall with loss of sinusoidal lining cells, sinusoidal hemorrhage, and mild damage to central vein (CV) endothelium. On days 3 through 5 ("early HVOD"), there was centrilobular coagulative necrosis, severe injury to sinusoids, severe sinusoidal hemorrhage, and severe CV endothelial damage; inflammation with ED-1-positive cells was most marked on these days. Days 6 and 7 ("late HVOD") were characterized by subendothelial and advential fibrosis of CVs, damage of the CV endothelium with subendothelial hemorrhage, and some restoration of the sinusoidal wall. Between days 8 and 10, sections showed interindividual variation ranging from mild, residual fibrosis to severe, late HVOD. From days 1 through 10, ED-2-positive cells were decreased in number, and the number of ED-1-positive cells was increased. Sinusoidal damage is the earliest change in HVOD. Coagulative necrosis follows sinusoidal injury and resolves with improvement in sinusoidal endothelial cell (SEC) morphology. Moderate-to-severe CV fibrosis occurs after reappearance of sinusoidal lining cells and resolution of hepatocyte necrosis. The inflammatory response within the lobule and CVs is a result of recruitment of monocytes, whereas Kupffer cells are decreased in number.     

Glycine prevents apoptosis of rat sinusoidal endothelial cells caused by deprivation of vascular endothelial growth factor

Apoptosis of sinusoidal endothelial cells (SECs) is one of the initial events in the development of ischemia-reperfusion injury of the liver. Glycine has been shown to diminish ischemia-reperfusion injury in the liver and improve graft survival in the rat liver transplantation model. Here, we investigated the effect of glycine on apoptosis of primary cultured rat SECs induced by vascular endothelial growth factor (VEGF) deprivation. Isolated rat SECs were cultured in EBM-2 medium supplemented with 10% fetal bovine serum (FBS) and growth factors including 20 ng/mL VEGF for 3 days. SECs at 3 days of culture showed spindle-like shapes; however, cells started shrinking and detaching from dishes by VEGF deprivation. Apoptosis was detected by terminal deoxynucleotidyl transferase (TdT)-mediated d-uridine triphosphate (dUTP)-biotin nick end labeling (TUNEL) staining in these conditions. Control SECs contained only a few percent of TUNEL-positive cells; however, they started increasing 4 hours after VEGF deprivation, and the percentage of TUNEL-positive cells reached about 50% at 8 hours and almost 100% at 16 hours after VEGF deprivation. Interestingly, this increase in TUNEL-positive cells after VEGF deprivation was prevented significantly when glycine (1-10 mmol/L) was added to the medium, the levels being around 60% of VEGF deprivation without glycine. Furthermore, strychnine (1 micromol/L), a glycine receptor antagonist, inhibited this effect of glycine, suggesting the possible involvement of the glycine receptor/chloride channel in the mechanism. Moreover, Bcl-2 protein levels in SECs were decreased 8 hours after VEGF deprivation, which was prevented almost completely by glycine. It is concluded that glycine prevents apoptosis of primary cultured SECs under VEGF deprivation.     

N-acetylcysteine for hepatic veno-occlusive disease after allogeneic stem cell transplantation

Three patients developed veno-occlusive disease of the liver (VOD) after allogeneic stem cell transplantation. On the day after diagnosis, N-acetylcysteine (NAC) was given, initially in loading doses and thereafter 50-150 mg/kg/day for 12 to 31 days. The maximum bilirubin levels were 137, 58 and 138 mmol/l in the three patients, respectively. After the introduction of NAC, bilirubin, aspartate aminotransferase, sIL-2 receptor and IL-8 decreased. All three patients achieved normal bilirubin levels and prothrombin times. To conclude, NAC may be useful for treatment of VOD.     

肝小静脉闭塞病研究进展

肝小静脉闭塞病(HVOD)缺乏特异治疗,重症患者常因多脏器功能衰竭而死亡,通过危险因素的分析有效避免其发生或在发病早期及时识别以早期干预至关重要。近年来对HVOD的诊断和防治取得了一定进展,此文对此作一综述。     

造血干细胞移植后肝静脉闭塞病的临床观察

目的 探讨造血干细胞移植（HSCT）后肝静脉闭塞病（HVOD）的临床特征、相关危险因素.方法 用回顾性分析方法对145例HSCT患者移植后HVOD的发病情况进行临床分析.结果 145例患者中,发生HVOD 8例,发生率为5.5%.对HVOD的相关危险因素分析发现,HSCT患者移植前乙型肝炎表面抗原（HbsAg）阳性或HBV-DNA阳性患者HVOD发生率显著增高,是HVOD发生的高危因素（P＜0.01）;PGE1脂质微球（Lipo-PGE1）预防HVOD的效果显著优于PGE1组（P＜0.05）,原因可能与本组病例PGE1预防剂量相对不足有关.结论 HVOD是HSCT常见并发症之一,移植前患者感染乙型肝炎病毒是其发生的高危因素;Lipo-PGE1对HVOD具有较好的预防效果.     

Acute alcohol administration to mice induces hepatic sinusoidal endothelial cell dysfunction

Ethanol administration to mice (4.4 g kg⁻¹ body wt., i.p.) induced a marked increase (125%) in plasma hyaluronan (HA) concentration associated with a significant decrease (46%) in HA uptake by the isolated, perfused liver. Similar changes were obtained after i.v. administration ofEscherichia coli lipopolysaccaharide (1 mg kg⁻¹ body wt.), a strong activator of Kupffer cells. Since: (a) hepatic HA uptake is predominantly a function of the sinusoidal endothelial cells, reflecting their functional state, and (b) liver is a major site of HA clearance from the blood, we conclude that alcohol alters sinusoidal endothelial cell functions, including HA endocytosis. Changes in Kupffer cell functional state may be a primary event underlying the effects of both ethanol and LPS on sinusoidal endothelial cells.     

Advanced glycation end products impair the scavenger function of rat hepatic sinusoidal endothelial cells

AIMS/HYPOTHESIS: We have previously reported that advanced glycation end products are eliminated from the circulation mainly by scavenger receptor-mediated uptake in hepatic sinusoidal endothelial cells. Our experiments showed that the degradation of AGE-modified protein after endocytosis in hepatic sinusoidal endothelial cells occurs slowly compared with that of other scavenger receptor ligands. The aim of this study was to investigate further the mechanism whereby AGE-modified protein affects the important scavenger function of hepatic sinusoidal endothelial cells. METHODS: Primary cultures of hepatic sinusoidal endothelial cells were pre-incubated with unlabelled ligand, unbound ligand was washed off, and the endocytic capacity was measured by addition of radiolabelled ligand, and immune electron microscopy. RESULTS: Pre-incubation with unlabelled AGE-modified bovine serum albumin reduced subsequent endocytosis of radiolabelled scavenger receptor ligands AGE-modified bovine serum albumin, formaldehyde-treated serum albumin, oxidized low density lipoprotein and acetylated low density lipoprotein by 50, 56, 32 and 20%, respectively. Non-scavenger receptor-mediated endocytosis was not affected by pre-exposure to AGE-modified protein. Pre-incubation with a number of non-AGE-ligands did not affect subsequent endocytosis via any of the major endocytosis receptors in hepatic sinusoidal endothelial cells. Incubation in fresh medium for 6 h after pre-exposure to AGE-modified protein almost completely restored normal scavenger receptor-mediated endocytic activity. Quantitative immune electron microscopy showed that the amount of a newly described scavenger receptor for AGE-modified protein is reduced after pre-incubation with AGE-modified protein. Subcellular fractionation showed that pre-incubation with AGE-modified protein delays intracellular transport of scavenger receptor ligands. CONCLUSION/INTERPRETATION: Endocytosis of AGE-modified protein leads to loss of scavenger receptors and delayed intracellular transport in hepatic sinusoidal endothelial cells.     

Prevention and treatment of hepatic veno-occlusive disease

Hematopoietic stem cell transplantation is currently the main cause of hepatic veno-occlusive disease, which is the early complication of this procedure with the highest short-term morbidity and mortality.Given that mortality from severe hepatic veno-occlusive disease can be nearly 100%, the search for measures to prevent of treat this complication is essential.Several risk factors for this complication have been identified and the triggering event that leads to sinusoidal obstruction has been shown to be sinusoidal endothelial cell injury.The present review analyzes measures to avoid or modify the casual risk factors for this complication, as well as the pharmacological agents that can prevent or modify the initial endothelial dysfunction or the resulting sinusoidal occlusion.     

Role of oxidative stress in hypoxia-reoxygenation injury to cultured rat hepatic sinusoidal endothelial cells

To characterize the role of oxidative stress in cultured rat sinusoidal endothelial cells, we studied the production of superoxide after reoxygenation, the relationship of reduced glutathione (GSH) levels to cell injury, and the protective efficacy of antioxidants. Hypoxia (pO(2) 1-2 mm Hg) was achieved by culturing cells under 95% N(2)5% CO(2) for 4 hours. Reoxygenation was then reestablished, and viability was determined at 24 hours by trypan blue exclusion; putative protective agents were added at the time of reoxygenation (4 hours). As previously reported, reoxygenation after 4 hours hypoxia accentuated sinusoidal cell death fourfold compared with hypoxic or normoxic controls (P <.0001). Superoxide was not produced on reoxygenation, and superoxide dismutase provided no protection against reoxygenation injury. Cellular levels of GSH fell to 37 +/- 4% of normoxic controls (P <.0001) following reoxygenation. These changes were essentially abrogated by Trolox (Aldrich Chemical Co., Milwaukee, WI) and dimethyl sulfoxide, both of which also completely protected against reoxygenation injury. When cellular GSH levels were lowered by addition of diethylmaleate (which conjugates GSH), this reduced the viability of endothelial cells cultured under normoxic conditions and greatly augmented reoxygenation injury. Conversely, addition of exogenous GSH partially protected endothelial cells against hypoxia-reoxygenation injury. Desferrioxamine also protected against reoxygenation injury, but catalase was only partly protective. It is concluded that sinusoidal endothelial cells undergo significant intracellular oxidative stress following reoxygenation, and their viability is critically dependent on GSH levels. Reactive oxygen species are likely mediators of oxidative stress in hepatic sinusoidal endothelial cells.     

土三七水煎剂所致肝小静脉闭塞病大鼠模型的建立

目的通过观察不同浓度土三七水煎剂所致的大鼠肝脏病理学变化,建立一种模拟临床患者服药所致肝小静脉闭塞病（HVOD）的动物模型。方法土三七2100g水煎制成浓度为1．5g/ml土三七生药煎剂,SD大鼠76只随机分为A、B、C、D四组,A、B、C组每组20只,分别以土三七水煎剂高（15g·kg^-1·d^-1）、中（7．5g·kg^-1·d^-1）、低（3．75g·kg^-1·d^-1）浓度灌胃,D组16只以温开水灌胃作为对照,各组大鼠雌、雄各半。每日测量大鼠体重并记录异常表现,灌胃1周和2周后各组大鼠分别处死各半,肝脏标本行病理检查,HE及Masson染色,光镜下参照Deleve评分标准判定病变及严重程度。结果土三七高、中、低浓度组分别有83．3％（15／18）、75．0％（15／20）、40．0％（5／20）出现了肝小静脉闭塞病病理表现;相同剂量下雌性较雄性更易发病,雌、雄鼠造模成功率分别为79．3％（23／29）和41．3％（12／29）（P=0．003）。结论土三七水煎剂灌胃可以成功建立HVOD大鼠模型,剂量和大鼠性别与造模成功率直接相关。