Elevated plasma levels of hyaluronic acid indicate endothelial cell dysfunction in the initial stages of alcoholic liver disease in the rat

The evolving role of liver sinusoidal endothelial cells in liver health and disease

LSECs are a unique population of endothelial cells within the liver and are recognized as key regulators of liver homeostasis. LSECs also play a key role in liver disease, as dysregulation of their quiescent phenotype promotes pathological processes within the liver including inflammation, microvascular thrombosis, fibrosis, and portal hypertension. Recent technical advances in single-cell analysis have characterized distinct subpopulations of the LSECs themselves with a high resolution and defined their gene expression profile and phenotype, broadening our understanding of their mechanistic role in liver biology. This article will review 4 broad advances in our understanding of LSEC biology in general: (1) LSEC heterogeneity, (2) LSEC aging and senescence, (3) LSEC role in liver regeneration, and (4) LSEC role in liver inflammation and will then review the role of LSECs in various liver pathologies including fibrosis, DILI, alcohol-associated liver disease, NASH, viral hepatitis, liver transplant rejection, and ischemia reperfusion injury. The review will conclude with a discussion of gaps in knowledge and areas for future research.

Portal Hypertension in Alcohol-Associated Hepatitis

Purpose of Review

This review article will examine portal hypertension in alcoholic hepatitis (AH) from both a basic mechanistic and a clinical perspective.

Recent Findings

Alcoholic hepatitis is a major public health problem in the USA, accounting for over 300,000 hospital admissions in a recent year of data (Jinjuvadia et al. J Clin Gastroenterol. 60;49:506–511). Portal hypertension is a key consequence of AH and a driver of liver-related morbidity and mortality. Alcohol may directly mediate portal hypertension via multiple possible mechanisms, including increased portal inflow, increased intrahepatic vasoconstriction, inflammation, and changes in the liver vasculature such as perisinusoidal fibrosis and phlebosclerosis.

Summary

Portal hypertension is a key consequence of AH and a critical area for future research.

Complement complex 1 subunit q-mediated hepatic stellate cell activation with connective tissue growth factor elevation is a prognostic factor for survival in rat and human chronic liver diseases

Complement complex 1 subunit q (C1q) has multiple functions, including cell migration, in addition to its traditional complement-activating effect. Research shows C1q is a ligand for frizzled receptors (FZDs). FZD-induced yes-associated protein (YAP)/transcriptional co-activator with PDZ-binding motif (TAZ) alternate Wnt signaling activation induces connective tissue growth factor (CTGF) production and hepatic stellate cell (HSC) activation. However, no study exists in which C1q directly induces CTGF in HSCs. Here, we investigated the role of C1q in HSC activation. Human HSCs (LX2) were incubated with C1q to assess HSC activation. C1q and fibrotic markers were assessed using immunohistochemistry, immunoblotting, and quantitative reverse-transcription polymerase chain reaction in cirrhotic rats administered CCl₄ for 21 weeks. Serum C1q, liver function, and fibrosis score were measured in 91 patients with chronic liver disease. The correlations between serum C1q and liver function, fibrosis score, and survival prognosis were examined. C1q-activated LX2s showed morphologic changes, up-regulation of CTGF, tissue inhibitors of metalloproteinases (TIMP-1), and alternate Wnt signal genes FZD2, TAZ, and cysteine-rich angiogenic inducer 61 (Cyr61). Cirrhotic rat liver C1q expression correlated with the Azan-positive area and expression of CTGF, TIMP-1, hyaluronan synthase (HAS)1, HAS3, and CD44. Expression of C1q protein and C1q, CTGF, and TIMP-1 genes were higher in deceased cirrhotic rat livers compared to surviving rats. Human serum C1q levels increased in liver cirrhosis compared to chronic hepatitis and correlated with liver fibrosis and functional markers. Ten patients suffered liver-related death over a 66-month observation period. The C1q cut-off value (11 mg/dl) showed patients with serum values < 11 mg/dl had longer rates of survival compared to C1q ≥ 11 mg/dl. Conclusion: C1q-mediated HSC activation in liver fibrosis is associated with CTGF elevation. Additionally, serum C1q may be diagnostic for survival in human chronic liver diseases.

Defining Endotheliopathy in Murine Polytrauma Models

INTRODUCTION

"Endotheliopathy of trauma" is recognized as endothelial dysfunction following traumatic injury leading to poor patient outcomes. Acute post-traumatic disruptions in endothelial cell function have been associated with profound physiologic, hemodynamic, and coagulation derangements. The goal of this study was to define the generation and extent of endotheliopathy in murine polytrauma models by evaluating the post-traumatic release of serum biomarkers of ongoing cellular injury.

METHODS

Mice were randomized to undergo moderately severe concussive TBI by weight drop, 60-min hemorrhagic shock to MAP 25 mmHg with subsequent resuscitation with Lactated Ringer's, submandibular bleed (SMB), and/or midline laparotomy with rectus muscle crush. Mice were sacrificed at 1, 4, or 24 h for serum biomarker evaluation.

RESULTS

Serum biomarkers revealed differential timing of elevation and injury-dependent release.At 24 h, soluble thrombomodulin was significantly elevated in combined TBI + shock + lap crush compared to untouched, and shock alone. Syndecan-1 levels were significantly elevated after shock 1 to 24 h compared to untouched cohorts with a significant elevation in TBI + shock + lap crush 24 h after injury compared to shock alone. UCHL-1 was significantly elevated in shock mice at 1 to 24 h post-injury compared to untouched mice. UCHL-1 was also significantly elevated in the TBI + shock cohort 24 h after injury compared to shock alone. Hyaluronic acid release at 4 h was significantly elevated in shock alone compared to the untouched cohort with further elevations in TBI + shock + lap crush and TBI + shock compared to shock alone at 24 h. Hyaluronic acid was also increased in lap crush and laparotomy only cohort compared to untouched mice 24 h after injury.

CONCLUSIONS

A murine model of polytrauma including TBI, hemorrhagic shock, and laparotomy abdominal crush is a reliable method for evaluation of endotheliopathy secondary to trauma as indicated by differential changes in serum biomarkers.

Alcohol-induced Hsp90 acetylation is a novel driver of liver sinusoidal endothelial dysfunction and alcohol-related liver disease

BACKGROUND & AIMS

Liver sinusoidal endothelial cell (LSEC) dysfunction has been reported in alcohol-related liver disease, yet it is not known whether LSECs metabolize alcohol. Thus, we investigated this, as well as the mechanisms of alcohol-induced LSEC dysfunction and a potential therapeutic approach for alcohol-induced liver injury.

METHODS

Primary human, rat and mouse LSECs were used. Histone deacetylase 6 (HDAC6) was overexpressed specifically in liver ECs via adeno-associated virus (AAV)-mediated gene delivery to decrease heat shock protein 90 (Hsp90) acetylation in ethanol-fed mice.

RESULTS

LSECs expressed CYP2E1 and alcohol dehydrogenase 1 (ADH1) and metabolized alcohol. Ethanol induced CYP2E1 in LSECs, but not ADH1. Alcohol metabolism by CYP2E1 increased Hsp90 acetylation and decreased its interaction with endothelial nitric oxide synthase (eNOS) leading to a decrease in nitric oxide (NO) production. A non-acetylation mutant of Hsp90 increased its interaction with eNOS and NO production, whereas a hyperacetylation mutant decreased NO production. These results indicate that Hsp90 acetylation is responsible for decreases in its interaction with eNOS and eNOS-derived NO production. AAV8-driven HDAC6 overexpression specifically in liver ECs deacetylated Hsp90, restored Hsp90's interaction with eNOS and ameliorated alcohol-induced liver injury in mice.

CONCLUSION

Restoring LSEC function is important for ameliorating alcohol-induced liver injury. To this end, blocking acetylation of Hsp90 specifically in LSECs via AAV-mediated gene delivery has the potential to be a new therapeutic strategy.

LAY SUMMARY

Alcohol metabolism in liver sinusoidal endothelial cells (LSECs) and the mechanism of alcohol-induced LSEC dysfunction are largely unknown. Herein, we demonstrate that LSECs can metabolize alcohol. We also uncover a mechanism by which alcohol induces LSEC dysfunction and liver injury, and we identify a potential therapeutic strategy to prevent this.

Tissue-specific Fixation Methods Are Required for Optimal In Situ Visualization of Hyaluronan in the Ovary, Kidney, and Liver

Hyaluronan (HA) is a ubiquitous component of the extracellular matrix. The spatial-temporal localization of HA can be visualized in situ using biotinylated HA binding proteins (HABPs). This assay is sensitive to fixation conditions, and there are currently no best practices for HA detection. Thus, the goal of this study was to optimize fixation conditions for visualizing HA in the ovary, kidney, and liver through analysis of six commonly used fixatives for HA detection: Bouin's Solution, Carnoy's Solution, Ethanol-Formalin-Glacial Acetic Acid (EFG), Histochoice, Modified Davidson's Solution, and 10% Neutral Buffered Formalin. Organs were harvested from CB6F1 mice and fixed with one of the identified fixatives. Fixed organs were sectioned, and the HABP assay was performed on sections in parallel. Hematoxylin and eosin staining was also performed to visualize tissue architecture. HABP signal localization and intensity varied between fixatives. EFG and Carnoy's Solution best preserved the HA signal intensity in the ovary and liver, showing HA localization in various sub-organ structures. In the kidney, only Modified Davidson's Solution was less than optimal. Our findings demonstrate that fixation can alter the ability to detect HA in tissue macro- and microstructures, as well as localization in a tissue-specific manner, in situ.

Differential effects of hyaluronan synthase 3 deficiency after acute vs chronic liver injury in mice

Background

Hyaluronan (HA) is a ubiquitous extracellular matrix (ECM) glycosaminoglycan synthesized by three different enzymes, hyaluronan synthase (HAS)1, 2, and 3. HA synthesis mediated by HAS3 promotes inflammation and is pathogenic in animal models of human lung and intestinal disease. Liver fibrosis is a common endpoint to chronic liver injury and inflammation for which there is no cure. Although plasma HA is a commonly used biomarker for liver disease, if and how HA contributes to disease pathogenesis remains unclear. Here, we tested the hypothesis that HA synthesized by HAS3 enhances inflammation and fibrosis. To test this hypothesis, we exposed wild-type or Has3−/− mice to carbon tetrachloride (CCl₄) once (acute) or ten (chronic) times.

Results

HAS3-deficient mice exhibited increased hepatic injury and inflammatory chemokine production 48 h after acute CCl₄; this was associated with a threefold reduction in plasma HA levels and alterations in the proportions of specific molecular weight HA polymer pools. Hepatic accumulation of fibrosis-associated transcripts was also greater in livers from HAS3-deficient mice compared to controls after acute CCl₄ exposure. Surprisingly, fibrosis was not different between genotypes. Hepatic matrix metalloproteinase (MMP)13 mRNA and MMP13 activity was greater in livers from Has3-null mice after chronic CCl₄; this was prevented by a MMP13-specific inhibitor. Collectively, these data suggest that Has3, or more likely HA produced by HAS3, limits hepatic inflammation after acute injury and attenuates MMP13-mediated matrix metabolism after chronic injury.

Conclusions

These data suggest that HA should be investigated further as a novel therapeutic target for acute and chronic liver disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s13069-016-0041-5) contains supplementary material, which is available to authorized users.

15-deoxy-delta 12,14-prostaglandin J2 prevents inflammatory response and endothelial cell damage in rats with acute obstructive cholangitis

Acute obstructive cholangitis is a common disease with a high mortality rate. Ligands for peroxisome proliferator-activated receptor-gamma (PPARgamma), such as 15-deoxy-Delta(12,14)-prostaglandin J(2) (15D-PGJ(2)), have been proposed as a new class of anti-inflammatory compounds. This study investigated the effect of 15D-PGJ(2) treatment on lipopolysaccharide (LPS)-induced acute obstructive cholangitis. The rats were randomly assigned to five groups: sham operation (Sham; simple laparotomy), sham operation with intraperitoneal saline infusion (Sham+Saline), sham operation with intraperitoneal LPS infusion (Sham+LPS), bile duct ligation (BDL) with saline infusion into the bile duct (BDL+Saline), and BDL with LPS infusion into the bile duct (BDL+LPS). Biochemical assays of blood samples, histology of the liver, portal venous pressure, hyaluronic acid clearance, and expression of inflammation-associated genes in the liver were evaluated. Furthermore, the Sham+LPS and the BDL+LPS group were divided into two groups (with and without 15D-PGJ(2) treatment), and their survival rates were compared. Biochemical assays of blood samples, portal venous pressure, hyaluronic acid clearance, and expression of inflammation-associated genes in the liver were all significantly higher in the BDL+LPS group compared with those in the BDL+Saline group, indicating the presence of increased liver damage in the first group. However, preoperative administration of 15D-PGJ(2) significantly improved these outcomes. Furthermore, the survival rate after establishment of cholangitis was significantly improved by the administration of 15D-PGJ(2) in the BDL+LPS group. These results clearly demonstrate that 15D-PGJ(2) inhibits the inflammatory response and endothelial cell damage seen in acute obstructive cholangitis and could contribute to improve the outcome of this pathology.

Anti-inflammatory and anti-apoptotic roles of endothelial cell STAT3 in alcoholic liver injury

BACKGROUND

It is generally believed that the hepatoprotective effect of interleukin-6 (IL-6) is mediated via activation of signal transducer and activator of transcription 3 (STAT3) in hepatocytes. IL-6-deficient mice are more susceptible to alcohol-induced hepatocyte apoptosis and steatosis and elevation of serum alanine transaminase (ALT); however, whereas hepatocyte-specific STAT3 knockout mice are more susceptible to alcohol-induced hepatic steatosis, they have similar hepatocyte apoptosis and serum ALT after alcohol feeding compared with wild-type mice. This suggests that the hepatoprotective effect of IL-6 in alcoholic liver injury may be mediated via activation of STAT3-independent signals in hepatocytes, activation of STAT3 in nonparenchymal cells, or both. We have previously shown that IL-6 also activates STAT3 in sinusoidal endothelial cells (SECs). Thus, the purpose of this study was to investigate whether STAT3 in endothelial cells also plays a protective role in alcoholic liver injury.

METHODS

Wild-type and endothelial cell-specific STAT3 knockout (STAT3(E-/-)) mice were pair-fed and fed ethanol containing diet for 4 weeks. Liver injury and inflammation were determined.

RESULTS

Feeding mice with ethanol-containing diet for 4 weeks induced greater hepatic injury (elevation of serum ALT) and liver weight in STAT3(E-/-) mice than wild-type control groups. In addition, ethanol-fed STAT3(E-/-) mice displayed greater hepatic inflammation and substantially elevated serum and hepatic levels of IL-6 and TNF-alpha compared with wild-type mice. Furthermore, ethanol-fed STAT3(E-/-) mice displayed a greater abundance of apoptotic SECs and higher levels of serum hyaluronic acid than wild-type controls.

CONCLUSIONS

These data suggest that endothelial cell STAT3 plays important dual functions of attenuating hepatic inflammation and SEC death during alcoholic liver injury.

Decreased Activity of Plasma ADAMTS13 May Contribute to the Development of Liver Disturbance and Multiorgan Failure in Patients with Alcoholic Hepatitis

BACKGROUND

The pathogenesis of alcoholic hepatitis (AH) remains unclear and the prognosis of severe alcoholic hepatitis (SAH) is very poor. Deficiency of von Willebrand factor (VWF)-cleaving protease (VWF-CP/ADAMTS13) results in an increase of the plasma unusually large VWF multimer and leads to platelet clumping, which causes microcirculatory disturbance and finally multiorgan failure. The aim of this study was to explore the potential role of ADAMTS13 on the development of liver disturbance and multiorgan failure in AH.

METHODS

The activity of plasma ADAMTS13 and its clinical correlation were determined in 14 patients with AH, 4 with SAH (Maddrey score, mean 62), and 10 with alcoholic liver cirrhosis (LC).

RESULTS

The activity of the plasma ADAMTS13 significantly decreased in patients with AH (mean 59%, p < 0.001), SAH (17%, p < 0.001) and LC (76%, p < 0.02) as compared with the healthy subjects (102%, n = 60). The activity was markedly lower in SAH than in AH (p < 0.02) and LC (p < 0.02). In three nonsurvivors with SAH who had multiorgan failure, it was extremely low (4.5%, 5.0%, and 16.0%, respectively), but in a survivor with SAH it remained mild decrease (44%). In AH, the protease activity increased at the recovery stage (42% --> 75%, p < 0.05). In the univariate analysis, the activity correlated with 10 clinical variables including functional liver capacity, inflammation signs, renal function, and platelet count in patients with AH and SAH. Among these, multivariate analysis showed that serum total bilirubin and C-reactive protein independently correlated with the protease activity.

CONCLUSION

The activity of plasma ADAMTS13 markedly decreased in SAH in addition to AH. The activity was closely related to hyperbilirubinemia and inflammation signs, and was extremely low in nonsurvivors with SAH and multiorgan failure. The marked decrease of plasma ADAMTS13 may, in part, contribute to not only the progression of liver disturbance in AH, but also the development of multiorgan failure in SAH through microcirculatory disturbance.

Glial fibrillary acidic protein as an early marker of hepatic stellate cell activation in chronic and posttransplant recurrent hepatitis C

Activated alpha-smooth muscle actin (alpha-SMA)-positive hepatic stellate cells (HSCs) are pericytes responsible for fibrosis in chronic liver injury. The glial fibrillary acidic protein (GFAP), commonly expressed by astrocytes in the central nervous system, is expressed in vivo in the liver in a subpopulation of quiescent stellate cells. In the rat, increased GFAP expression in the acute response to injury and down-regulation in the chronic response have been observed, whereas reports concerning GFAP expression in human liver are still conflicting. We investigated the utility of GFAP compared to alpha-SMA as an immunohistochemical marker of early activated HSCs in chronic and posttransplant recurrent hepatitis C and correlated GFAP expression with vascular remodeling and fibrosis progression. With immunohistochemistry and a semiquantitative scoring system, the expression of GFAP and alpha-SMA in HSCs and the microvessel density were analyzed in biopsies from normal livers obtained from cadaveric donors [donor liver (DL); n = 21] and from livers from posttransplant hepatitis C virus recurrent hepatitis (HCV-PTR) patients (n = 19), hepatitis C virus chronic hepatitis (HCV-CH) patients, (n = 12), and hepatitis C virus cirrhosis (HCV-C) patients (n = 16). The percentage of alpha-SMA-positive HSCs was significantly higher in the HCV-PTR, HCV-CH, and HCV-C groups compared to the DL group (P < 0.01). The percentage of GFAP-positive HSCs was significantly higher in the HCV-PTR group compared to the DL, HCV-C (P < 0.01), and HCV-CH (P < 0.05) groups and in the HCV-CH group compared to the DL group (P < 0.01), inversely correlating with the extent of fibrosis and microvessel density (P < 0.01). In the HCV-PTR group, the percentage of GFAP-positive HSCs correlated with fibrosis progression (P < 0.01). In conclusion, GFAP could represent a useful marker of early activation of HSCs in HCV-CH and seems to predict fibrosis progression in HCV-PTR.

Suprahepatic vena cava manipulative bleeding alleviates hepatic ischemia-reperfusion injury in rats

BACKGROUND

Little is known about time course and peak level of reactive oxygen species in suprahepatic vena cava after liver ischemia-reperfusion.

OBJECTIVE

To determine time course and peak level of reactive oxygen species in suprahepatic vena cava after liver ischemia-reperfusion. To focus on the effects of suprahepatic vena cava manipulative bleeding on the hepatic ischemia-reperfusion injury in rat model.

METHODS

In experiment Part I, blood was taken from suprahepatic vena cava and infrahepatic vena cava for malondialdehyde detection at different time points after reperfusion. Furthermore, we treated the experimental rats in Part II by suprahepatic vena cava manipulative bleeding or infrahepatic vena cava manipulative bleeding at 10 min after reperfusion.

RESULTS

In experiment Part I, malondialdehyde concentration in suprahepatic vena cava elevated obviously with time and peaked at 10 min after reperfusion. The numbers of accumulated polymorphonuclear neutrophils was significantly increased in ischemia-reperfusion group from 10 min after reperfusion, compared with sham-operated group. In Part II, 2% of body weight suprahepatic vena cava manipulative bleeding with blood transfusion at 10 min after reperfusion significantly decreased circulating malondialdehyde, tumour necrosis factor-alpha, endothelin-1, hyaluronic acid, alanine aminotransferase, aspartate aminotransferase levels and polymorphonuclear neutrophil infiltrations in the liver. The 7-day survival rate of this group was 68.75% (11/16) which was significantly higher than other groups.

CONCLUSIONS

We provided the first evidence that 2% of body weight suprahepatic vena cava manipulative bleeding with blood transfusion at 10 min after reperfusion significantly prevented liver ischemia-reperfusion injury.

Successive observation of laminin and hyaluronic acid on the formation of non-alcoholic fatty liver fibrosis in rabbits

AIM: To observe the changes of laminin (LN) and hyaluronic acid (HA) on the formation of non-alcoholic fatty liver fibrosis in rabbits.

METHODS: Firstly, the rabbit models of fatty liver and liver fibrosis were set up by hypercholesteremia. Liver tissues were collected and the histopathological changes were observed using transmission endoscopy and staining methods. Immunohistochemistry was used to detect LN expression and radioimmunoassy was used the measure serum HA concentration. Successive observation was used to outline the dynamic changes of basement membrane of hepatic sinusoid during the formation of non-alcoholic fatty liver fibrosis in rabbits.

RESULTS: Sinusoidal capillarization was characterized by defenestration of sinusoidal endothelial cells (SEC) and formation of basement membrane. Along with the formation of liver fibrosis, the positive expression (area percentage) of LN on sinusoidal wall and the concentration (mg/L) of serum HA increased gradually, and both of them reached the peak at 8 wk; there were significant differences in contrast with those in the normal group (LN: 25.2 ± 1.0 vs 5.1 ± 0.7, P < 0.01; serum HA: 1422.18 ± 20.9 vs 1189.3 ± 13.1, P < 0.01). After stopping high-sterone feeding, the positive expression of LN and concentration of HA decreased gradually.

CONCLUSION: The changes of serum HA concentration are in accordance with the defenestration of hepatic sinusoid and LN changes. LN and HA may be used as cardinal markers for hepatic sinusoidal capillarization and liver fibrosis.

Non-invasive markers to predict the liver fibrosis in non-alcoholic fatty liver disease

BACKGROUND/AIM

The aim of this study was to find a non-invasive marker, which could predict liver fibrosis without the need of liver biopsy in non-alcoholic steatohepatitis (NASH).

PATIENTS/METHODS

Fifty patients were included. All patients had one or more conditions that characterize the metabolic syndrome and histological proven NASH. Hyaluronic acid (HA), leptin (LT) and laminin (LN) were determined from serum withdrawn at the day of biopsy.

RESULTS

Patients were divided into two groups according to the histological findings. The first group consisted of 23 patients with NASH and fibrosis and the second group had 27 patients with NASH, ballooned cells, without fibrosis. Subjects with NASH and fibrosis had statistically significantly higher HA and LN than those with NASH without fibrosis, P<0.001, respectively. In contrast, there was no statistically significant difference between the levels of serum LT in the two groups. The stage of liver fibrosis in the 23 patients of group 1 was related only to the values of hyaluronic acid (P<0.001) and not to the ones of LT and LN.

CONCLUSION

Measurement of hyaluronic acid could be a predictive factor of the presence and stage of liver fibrosis in NASH. LN could be used to diagnose liver fibrosis but has no value in staging.

Hyaluronic acid and aspartate aminotransferase levels normalized by liver function can reflect sinusoidal impairment in chronic liver disease

BACKGROUND/AIM

To evaluate the relationship between hyaluronic acid/aminopyrine breath test (HA/ABT) ratio and fibrosis score in chronic hepatitis, and between HA/ABT and clinical staging (child-turcotte-pugh'score, CTP; and model for end stage liver disease, MELD) in cirrhosis, as well as to evaluate the aspartate aminotransferase (AST)/ABT in relation to the HA/ABT.

METHODS

We studied 48 patients with histologically proven chronic hepatitis C (CHC) and 35 patients with compensated cirrhosis (CIR).

RESULTS

HA/ABT and AST/ABT showed a more significant correlation with the fibrosis score than HA or ABT or AST alone in the 48 CHC patients: r=0.568 (P<0.0001), r=0.610 (P<0.0001), r=0.450 (P=0.0021), r=-0.449 (P=0.0021), and r=0.472(P=0.0012), respectively. Progressive liver damage (fibrosis 1-2 vs fibrosis 3-6 vs cirrhosis) was significantly (P<0.05) reflected by both HA/ABT (mean+/-SEM: 4.0+/-0.9 vs 18.1+/-4.2 vs 149.9+/-33.1) and AST/ABT (6.3+/-1.8 vs 12.7+/-1.6 vs 42.1+/-14.6). A strong relationship was found between HA/ABT and AST/ABT (r=0.755 P<0.0001). In cirrhotic patients, the most significant relationship was observed between HA/ABT and CTP r=0.483 and P=0.0049, and MELD r=0.523 and P=0.0023.

CONCLUSION

Considering that HA levels in chronic hepatitis depend on the progressive impairment of sinusoidal endothelial cells (SEC), related to progressive fibrosis, HA/ABT ratio would seem to be the most specific reflection of progressive impairment of the SEC. AST/ABT could be used as a possible surrogate of HA in identifying SEC impairment in chronic hepatitis.

Serum hyaluronan and hyaluronidase: very early markers of toxic liver injury

BACKGROUND

Dimethylnitrosamine (DMN), a potent hepatotoxin, administered to rats, provides a convenient model for toxic liver injury. Indicators of early liver injury are important clinically, for surveillance, for screening new drugs that are potentially hepatotoxic and for identifying drugs that protect against liver injury. Both cirrhosis and wound healing culminate in deposition of fibrous connective tissue and scarring. Increased hyaluronan (HA) occurs in the earliest stage of wound healing. Hyaluronidase, the enzyme that degrades hyaluronan, is also elevated whenever rapid turnover of hyaluronan occurs. We test the hypothesis that elevated levels of circulating hyaluronan and hyaluronidase could provide indicators of very early liver damage.

METHODS

Dimethylnitrosamine was administered to adult male albino rats by intraperitoneal injections for 7 consecutive days.

RESULTS

Increased serum hyaluronan levels observed on day 2 reached a maximum on day 4. Hyaluronidase was elevated on the first day and reached a maximum on day 2 that was 30-times control levels. Hyaluronan-specific staining in liver sections was maximal on day 7, occurring predominantly in portal triads and in sinusoidal spaces. Individual hepatocytes were slightly enlarged and contained intracellular hyaluronan, which was not evident in control sections. Though circulating hyaluronan levels had decreased after day 4, continued hyaluronan staining persisted in liver sections through day 21. Conventional indicators of liver injury, such as serum aminotransferase enzymes, did not reach a peak until day 7. Conventional gross and histopathological changes, including severe centrilobular congestion and hemorrhagic necrosis, were observed only after day 7. Both hyaluronan and hyaluronidase are indicators of very early liver damage in the dimethylnitrosamine-treated rat, occurring well before conventional indicators appear, or before overt histopathologic changes of liver damage can be seen. However, levels are increased only transiently, indicating that serial assays are necessary.

CONCLUSIONS

Measures of circulating hyaluronidase activity may be used to assess liver damage.

Expression of hyaluronic acid in N-nitrosodimethylamine induced hepatic fibrosis in rats

Hyaluronic acid (HA) plays prominent role in the pathogenesis of liver fibrosis. The mechanism of increased serum and liver HA during hepatic fibrosis was studied in rats. Liver injury was induced by intraperitoneal injections of N-nitrosodimethylamine (NDMA) for 7 consecutive days. A group of animals were sacrificed on everyday during injection and also on days 14 and 21 after the start of NDMA administration. The alpha-smooth muscle actin (alpha-SMA) was stained as a marker for activated stellate cells. Liver HA was studied by histochemical methods and serum HA was monitored by HA binding protein assay. CD44 was stained immunohistochemically. After the start of NDMA administration, necrosis was initiated on day 3 and massive necrosis was observed on days 5 and 7. Fibrosis was developed on day 14 and early cirrhosis was present on day 21. Staining of alpha-SMA demonstrated activated stellate cells from day 3 onwards. Serum HA peaked on day 7 and reduced afterwards. Serial liver sections stained for HA revealed excessive accumulation of HA during NDMA administration. On days 14 and 21, alpha-SMA and HA staining was remarkable in fibrotic and cirrhotic areas. CD44 staining was negative except during necrosis. It is concluded that the early elevation of serum HA is due to the increased synthesis and simultaneous release from the necrotic liver. In latter stages the increase of both serum and liver HA is contributed by the increased synthesis by the activated stellate cells and reduced clearance by the impaired sinusoidal endothelial cells.

Influence factors of serum fibrosis markers in liver fibrosis

AIM: To analyze the factors which influence the serum levels of hyaluronic acid (HA), type III pro-collagen (PCIII), laminin (LN) and type IV collagen (C-IV) in liver fibrosis.

METHODS: The serum specimens from 141 chronic hepatitis patients were assayed for fibrosis indexes including HA, PCIII, LN and C-IV with radioimmunoassay (RIA) and liver function indexes by an automatic biochemistry analyzer. The patients were then divided into consistent group and inconsistent group. The patients'clinical manifestations were recorded, routine blood pictures were done by a blood counter and analyzer (AC-900). Liver biopsy specimens were examined path-morphologically. The inner diameters of portal vein, splenic vein and thickness of spleen were all measured by ultrasonography.

RESULTS: Sixteen patients (14.16%) had serum fibrosis indexes inconsistent with histological stage of their hepatic fibrosis. Their serum fibrosis indexes did not correlate with the stage of hepatic fibrosis (P > 0.05), but were positively correlated with the grade of inflammation (χ² = 12.07, P < 0.05). At the same time, serum albumin (ALB) and the ratio of albumin and globulin (A/G) were significantly increased (t = 3.06, P < 0.01), (t = 3.70, P < 0.01). Serum levels of glutamic-pyruvic transaminase (ALT), glutamic-oxaloacetic transaminase (AST), γ-glutamyl transferase (GGT) and globulin (GLB) were all significantly decreased (t = 2.45, P < 0.05), (t = 2.33, P < 0.05), (t = 2.08, P < 0.05), (t = 3.03, P < 0.01). Weary degree also decreased more obviously (χ² = 7.52, P < 0.05), but other clinical manifestations, routine blood indexes, serum levels of alkaline phosphatase (AKP), total bilirubin (TBIL), total protein (TP), width of main portal vein, width of splenic vein and thickness of spleen had no significant change (P > 0.05).

CONCLUSION: Serum fibrosis indexes can be influenced by the grade of inflammation, some liver function indexes and clinical manifestations. Comprehensive analysis is necessary for its proper interpretation.

Assessment of prognosis in alcoholic liver disease: can serum hyaluronate replace liver biopsy?

1. Only 15-20% of chronic alcohol misusers ever develop cirrhosis. 2. Currently it is not possible to predict clinically who will develop progressive fibrotic alcoholic liver disease. 3. Liver biopsy is currently the gold standard diagnostic test in alcoholic liver disease, but it has associated morbidity and mortality. 4. Serum hyaluronic acid is a simple non-invasive test that may be able to give an estimate of the severity of fibrosis in alcoholic liver disease. The full clinical assessment of alcoholic liver disease includes liver biopsy, since accurate clinical prediction of the severity of liver damage is extremely difficult in all except very advanced cases. Unfortunately, liver biopsy has an associated complication rate and is contraindicated in, or unacceptable to, some patients. A reliable non-invasive test of the severity of fibrotic disease would be clinically useful at initial clinical assessment in some patients with alcoholic liver disease. Such a test would be more useful in subsequent monitoring of disease progression, and in particular may diminish the need for follow-up liver biopsy. Serum hyaluronic acid has been put forward as such a non-invasive test. Based on current evidence, serum hyaluronic acid may well be a useful adjunctive test in the assessment of certain categories of alcoholic liver disease patients, but at present it is unlikely to displace liver biopsy as the investigation of choice in alcoholic liver disease.

Von Willebrand factor in plasma and in liver tissue after partial hepatectomy in the rat

BACKGROUND/AIMS

Von Willebrand factor (vWf) is found in high levels in plasma of patients with acute and chronic liver disease. The role of vWf in liver injury and repair is unknown. We studied the effect of liver mass and remodeling on plasma and tissue vWf after partial hepatectomy.

METHODS

Rats were sacrificed postoperatively at intervals ranging from 60 min to 5 days, and vWf plasma levels were measured by enzyme-linked immunosorbent assay, using rabbit anti-human vWf, and by immunoperoxidase on cryosections, using rabbit anti-vWf/factor VIII. Northern blot hybridization was prepared with a complementary DNA specific to human vWf.

RESULTS

vWf plasma levels increased early after sham operation and after 70% partial hepatectomy. The highest levels were reached at 24 h, remaining high for 5 days. Immunostaining showed intense staining of sinusoidal lining cells 4 h after partial hepatectomy, remaining so for 5 days. Non-significant changes in overall liver messenger RNA expression of vWf were seen over 5 days in sham operation and partial hepatectomy.

CONCLUSIONS

After partial hepatectomy, plasma vWf is increased, probably due to both acute-phase reaction and decreased degradation. An increase in sinusoidal vWf immunostaining may suggest a role for this factor in tissue remodeling.

Changes in serum hyaluronic acid levels and expression of CD44 and CD44 mRNA in hepatic sinusoidal endothelial cells after major hepatectomy in cirrhotic rats

Serum hyaluronic acid (HA) is widely distributed in connective tissues, and the majority of circulating HA is degraded by hepatic sinusoidal endothelial cells (SECs) via a receptor recycling pathway. Our previous clinical study revealed that monitoring serum HA levels after hepatectomy is useful in predicting the development of liver failure. In the present study, to determine the mechanism of the high HA levels after hepatectomy, especially in patients with liver cirrhosis, expression of the major HA receptor, CD44, and its mRNA was investigated in SECs isolated from rats with thioacetamide-induced liver cirrhosis subjected to 70% hepatectomy (group I) and from rats with a normal liver that were subjected to 70% hepatectomy (group II). The 48-hour postoperative survival rate in group I (13.3%) was significantly lower than in group II (100%). In group II, the expression of CD44 mRNA had increased significantly at 6 hours after hepatectomy, and this was followed by progressive increases in expression of CD44, indicating activation of SEC function. The increased serum HA levels after hepatectomy in group II became normal as CD44 expression increased. By contrast, the expression of CD44 and CD44 mRNA in group I was markedly attenuated after hepatectomy. The very low CD44 expression was followed by a significant and sustained increase in serum HA levels, indicating functional failure of the SECs. These results suggest that the significantly impaired functional reserve of SECs in liver cirrhosis is associated with increased mortality after 70% hepatectomy.

The expression levels of plasma membrane transporters in the cholestatic liver of patients undergoing biliary drainage and their association with the impairment of biliary secretory function

OBJECTIVES

Percutaneous transhepatic biliary drainage (PTBD) has been believed to reduce hyperbilirubinemia in patients with obstructive cholestasis and to lessen liver injury through bile acid retention. The efficacy may be closely related to the capability of cholestatic liver to produce and secrete bile, which in turn depends on the expressions and functional activities of plasma membrane transporters in the liver. The aim of the present study was to determine the expression levels of these transporters in the cholestatic liver of patients undergoing PTBD.

METHODS

A total of 24 patients who had experienced obstructive cholestasis and had undergone preoperative PTBD were included in the study. Liver biopsy specimens were analyzed to determine the expression levels of the multidrug resistance-associated proteins (MRP) MRP2 and MRP3 and the canalicular bile salt export pump BSEP in the liver.

RESULTS

The messenger RNA (mRNA) levels of MRP2, the canalicular bilirubin conjugate export pump, and bile salt export pump (BSEP) were unchanged in liver specimens from the 14 patients well drained by PTBD but were reduced in specimens from the 10 patients poorly drained, compared to the levels of control subjects. Immunostainings of MRP2 and BSEP outlined the canalicular membrane domain but seemed fuzzy to varying degrees in specimens obtained from cholestatic liver, especially in specimens from liver that had been poorly drained, in contrast to the linear and intense localization in the liver of control subjects, correlating with the impaired bilirubin conjugate and bile acid secretion. The mRNA of MRP3, functioning as an inducible export pump for bilirubin conjugate and bile acid, was expressed not only in the cholestatic liver but also in the liver of control subjects, and the mRNA level was increased in specimens from both the cholestatic liver that had been well drained and from the liver that had been poorly drained. Immunostaining of MRP3 was observed in the epithelia of intrahepatic bile ducts in the liver of both control subjects and cholestatic patients, and in the epithelia of proliferated bile ductules and the hepatocytes surrounding the portal tracts in the cholestatic liver.

CONCLUSIONS

From the results of the present study, it is concluded that 1) the mRNA and immunohistochemical expression levels of MRP2 and BSEP may be altered in the cholestatic liver of patients undergoing PTBD; 2) both the decreased mRNA levels and the diminished canalicular membrane localization may be associated with the impairment of bile formation and secretion, i.e., the efficacy of PTBD; and 3) upregulated MRP3 in the cholangiocytes and hepatocytes may play a significant role in bile acid transport in the cholestatic hepatobiliary system.

The rat liver Na(+)/bile acid cotransporter. Importance of the cytoplasmic tail to function and plasma membrane targeting

To understand the potential functions of the cytoplasmic tail of Na(+)/taurocholate cotransporter (Ntcp) and to determine the basolateral sorting mechanisms for this transporter, green fluorescent protein-fused wild type and mutant rat Ntcps were constructed and the transport properties and cellular localization were assessed in transfected COS 7 and Madin-Darby canine kidney (MDCK) cells. Truncation of the 56-amino acid cytoplasmic tail demonstrates that the cytoplasmic tail of rat Ntcp is involved membrane delivery of this protein in nonpolarized and polarized cells and removal of the tail does not affect the bile acid transport function of Ntcp. Using site-directed mutagenesis, two tyrosine residues, Tyr-321 and Tyr-307, in the cytoplasmic tail of Ntcp have been identified as important for the basolateral sorting of rat Ntcp in transfected MDCK cells. Tyr-321 appears to be the major basolateral-sorting determinant, and Tyr-307 acts as a supporting determinant to ensure delivery of the transporter to the basolateral surface, especially at high levels of protein expression. When the two Tyr-based basolateral sorting motifs have been removed, the N-linked carbohydrate groups direct the tyrosine to alanine mutants to the apical surface of transfected MDCK cells. The major basolateral sorting determinant Tyr-321 is within a novel beta-turn unfavorable tetrapeptide Y(321)KAA, which has not been found in any naturally occurring basolateral sorting motifs. Two-dimensional NMR spectroscopy of a 24-mer peptide corresponding to the sequence from Tyr-307 to Thr-330 on the cytoplasmic tail of Ntcp confirms that both the Tyr-321 and Tyr-307 regions do not adopt any turn structure. Since the major motif YKAA contains a beta-turn unfavorable structure, the Ntcp basolateral sorting may not be related to the clathrin-adaptor complex pathway, as is the case for many basolateral proteins.

Pulmonary vascular sclerosis in an albino rat with leukemia

The animal investigated was a two years old male control Sprague-Dawley rat which died spontaneously during a carcinogenicity study. Post-mortem examination disclosed hepatic and splenic enlargement. At microscopical examination, massive leucaemic infiltration was observed in many tissues/organs, including bone marrow, spleen, liver and renal blood vessels. A very unusual finding was observed in the lung, consisting of scattered micronodules which replaced most of the lung parenchyma. They contained collagen, displaying a somewhat circular distribution at the periphery of the lesions, fibrin, leukemic cells and fibroblasts. Immunostaining for desmin revealed the presence of smooth muscle fibers within the nodules, while staining for elastic fibers showed clearly that the internal and external elastic membranes were identifiable within the nodules. The diagnosis of pulmonary vascular sclerosis was made on the basis of microscopical and immunohistochemical findings.

Hepatocyte-supported serum-free culture of rat liver sinusoidal endothelial cells

BACKGROUND/AIMS

A major problem in rat liver endothelial cell culture is the rapid loss of cells after 48 h. This study aimed to develop a protocol that allowed easy maintenance and proliferation of sinusoidal endothelial cells in serum-free culture for 5-6 days.

METHODS

Cells isolated from adult rat liver by collagenase digestion were purified by centrifugal elutriation and cultured on glutaraldehyde-crosslinked collagen.

RESULTS

At high plating densities cells could be maintained serum-free for 6 days in the presence of hydrocortisone and basic fibroblast growth factor; at lower plating densities medium had to be supplemented with additional growth-promoting factors. Conditioned medium of adult rat hepatocytes proved to be the most effective growth stimulus; it increased thymidine incorporation, DNA content and cell number per dish with a half-maximal effect at 20% (v/v). Cell proliferation was also observed with either vascular endothelial growth factor, phorbol ester or conditioned media from FAO or HEPG2 liver cell lines provided the cultures were additionally supplemented with 1% newborn calf serum. Vascular endothelial growth factor was detected in all conditioned media. In the absence of hepatocyte-conditioned medium, 1% serum helped to maintain cultures; it itself exerted a low proliferative effect. Higher serum concentrations (>5%), however, led to cell loss after 48 h. The numerous sieve plates of 6-h-old cells progressively disappeared during culture and were replaced by randomly distributed pores, which later grouped together at cell-cell borders. More than 90% of the cells endocytosed acetylated low-density lipoprotein.

CONCLUSIONS

The study shows that cultured hepatocytes secrete growth-promoting substances that stimulate in vitro endothelial cell proliferation in the absence of serum; this effect could be mimicked by the combined addition of vascular endothelial growth factor and 1% serum. The new media formulations should facilitate future research on liver endothelial cells in mono- or coculture.

Effects of exogenous superoxide anion and nitric oxide on the scavenging function and electron microscopic appearance of the sinusoidal endothelium in the isolated, perfused rat liver

BACKGROUND/AIMS

Functional and morphological alterations of the hepatic sinusoidal endothelial cell occur in several models of experimental liver injury and in clinical settings. The causes of these alterations are multiple. The aim of this study was to test the hypothesis that the early functional impairment and morphological alterations of the sinusoidal endothelial cell and hepatic sinusoid associated with liver injury are mediated by free radical species, such as superoxide anion and nitric oxide.

METHODS

Isolated rat livers were perfused by recirculation with hemoglobin-free, Krebs-Henseleit bicarbonate buffer and presented with a source of superoxide anion (xanthine oxidase+hypoxanthine) or nitric oxide (S-nitroso-N-acetyl penicillamine). Hyaluronan uptake (an index of sinusoidal endothelial cell scavenging function), thiobarbituric acid-reactive substances content of the tissue (a marker of lipid peroxidation), reduced and oxidized glutathione (a marker of the thiol system oxidation/reduction state), lactate dehydrogenase and alanine aminotransferase activities (markers of cytolysis), as well as scanning and transmission electron microscopic appearance of the sinusoid were evaluated.

RESULTS

At the high concentrations used, both free radical generating systems suppressed hyaluronan uptake, increased malondialdehyde content of the tissue, enhanced the release of both liver enzymes, decreased the total glutathione content of the liver, and altered the ratio of reduced/oxidized glutathione. Both free radical species induced dose-dependent morphological alterations of the sinusoid, consisting of the appearance of large gaps replacing the sieve-plated fenestration.

CONCLUSIONS

The free radical species-induced functional impairment and morphological alterations of the liver sinusoid, presented in this study, closely resemble the early in vivo changes associated with liver injury under a variety of conditions, such as preservation and reperfusion, or administration of hepatotoxicants such as D-galactosamine, Gram-negative bacterial lipopolysaccharides, acetaminophen, alcohol and others. Therefore, we suggest that early liver sinusoid injury, observed under these conditions, can be attributed to the action of free radicals, such as superoxide anion and nitric oxide.

Physiology and pathophysiology of apoptosis in epithelial cells of the liver, pancreas, and intestine

Cell death of gastrointestinal epithelial cells occurs by a process referred to as apoptosis. In this review, we succinctly define apoptosis and summarize the role of apoptosis in the physiology and pathophysiology of epithelial cells in the liver, pancreas, and small and large intestine. The physiological mediators regulating apoptosis in gastrointestinal epithelial cells, when known, are discussed. Selected pathophysiological consequences of excessive apoptosis and inhibition of apoptosis are used to illustrate the significance of apoptosis in disease processes. These examples demonstrate that excessive apoptosis may result in epithelial cell atrophy, injury, and dysfunction, whereas inhibition of apoptosis results in hyperplasia and promotes malignant transformation. The specific cellular mechanisms responsible for dysregulation of epithelial cell apoptosis during pathophysiological disturbances are emphasized. Potential future areas of physiological research regarding apoptosis in gastrointestinal epithelia are highlighted when appropriate.