The role of apoptosis versus oncotic necrosis in liver injury: facts or faith?

In Vitro Liver Toxicity Testing of Chemicals: A Pragmatic Approach

The liver is among the most frequently targeted organs by noxious chemicals of diverse nature. Liver toxicity testing using laboratory animals not only raises serious ethical questions, but is also rather poorly predictive of human safety towards chemicals. Increasing attention is, therefore, being paid to the development of non-animal and human-based testing schemes, which rely to a great extent on in vitro methodology. The present paper proposes a rationalized tiered in vitro testing strategy to detect liver toxicity triggered by chemicals, in which the first tier is focused on assessing general cytotoxicity, while the second tier is aimed at identifying liver-specific toxicity as such. A state-of-the-art overview is provided of the most commonly used in vitro assays that can be used in both tiers. Advantages and disadvantages of each assay as well as overall practical considerations are discussed.

Exogenous Ghrelin Could Not Ameliorate 3,4-methylenedioxymethamphetamine-induced Acute Liver Injury in The Rat: Involved Mechanisms

MDMA (3,4-methylenedioxymethamphetamine, ecstasy) is often abused by youth as a recreational drug. MDMA abuse is a growing problem in different parts of the world. An important adverse consequence of the drug consumption is hepatotoxicity of different intensities. However, the underlying mechanism of this toxicity has not been completely understood. Ghrelin is a gut hormone with growth hormone stimulatory effect. It expresses in liver, albeit at a much lower level than in stomach, and exerts a hepatoprotective effect. In this study, we investigated hepatotoxicity effect of MDMA alone and its combination with ghrelin as a hepatoprotective agent. MDMA and MDMA+ ghrelin could transiently increase serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) followed by tissue necrosis. However, they could significantly decrease liver tumor necrosis factor-a (TNF-±) in both treatment groups. Unexpectedly, in MDMA treated rats, Bax, Bcl-xl, Bcl-2, Fas, Fas ligand (Fas-L), caspase 8, cytochrome c, caspase 3 gene expression, and DNA fragmentation were nearly unchanged. In addition, apoptosis in MDMA+ ghrelin group was significantly reduced when compared with MDMA treated animals. In all, MDMA could transiently increase serum transaminases and induce tissue necrosis and liver toxicity. Ghrelin, however, could not stop liver enzyme rise and MDMA hepatotoxicity. MDMA hepatotoxicity seems to be mediated via tissue necrosis than apoptotic and inflammatory pathways. Conceivably, ghrelin as an anti-inflammatory and anti-apoptotic agent may not protect hepatocytes against MDMA liver toxicity.

Induction of hepatic portal fibrosis, mitochondria damage, and extracellular vesicle formation in Sprague-Dawley rats exposed to copper, manganese, and mercury, alone and in combination

Increased anthropogenic activity and subsequent environmental exposure to heavy metals induce the production of reactive oxygen species (ROS), which increases oxidative stress and the risk of associated diseases. The aim of this study, in a subacute model of toxicity, was to investigate the effects of copper (Cu), manganese (Mn), and mercury (Hg) alone and in combination on the liver tissue of male Sprague-Dawley rats, exposed orally to 100 times the World Health Organization's acceptable water limits of each metal. General histological alterations as well as ultrastructural changes were investigated using light microscopy and transmission electron microscopy (TEM) respectively. Exposure to Cu, Mn, and Hg, alone and in combinations, caused hydropic swelling of the hepatocytes, dilation of the sinusoids, formation of binucleated hepatocytes with an increased inflammatory cell accumulation at the portal triad. Increased collagen deposition with associated fibrosis was also observed. Evaluation of hepatocyte ultrastructure revealed mitochondrial membrane damage and inner membrane swelling especially for hepatocytes exposed to Mn. Extracellular vesicle (EV) formation was observed in the liver tissue of all exposed rats. Furthermore, increased damage observed for metal combinations was possibly due to synergism. In conclusion, Cu, Mn, and Hg alone and as part of a mixture cause cellular damage, inflammation, and fibrosis increasing the risk of associated diseases.

Serp-2, a virus-derived apoptosis and inflammasome inhibitor, attenuates liver ischemia-reperfusion injury in mice

BACKGROUND

Ischemia-reperfusion injury (IRI) is an antigen-independent, innate immune response to arterial occlusion and ischemia with subsequent paradoxical exacerbation after reperfusion. IRI remains a critical problem after vessel occlusion and infarction or during harvest and surgery in transplants. After transplant, liver IRI (LIRI) contributes to increased acute and chronic rejection and graft loss. Tissue loss during LIRI has been attributed to local macrophage activation and invasion with excessive inflammation together with hepatocyte apoptosis and necrosis. Inflammatory and apoptotic signaling are key targets for reducing post-ischemic liver injury.Myxomavirus is a rabbit-specific leporipoxvirus that encodes a suite of immune suppressing proteins, often with extensive function in other mammalian species. Serp-2 is a cross-class serine protease inhibitor (serpin) which inhibits the inflammasome effector protease caspase-1 as well as the apoptotic proteases granzyme B and caspases 8 and 10. In prior work, Serp-2 reduced inflammatory cell invasion after angioplasty injury and after aortic transplantation in rodents. In this report, we explore the potential for therapeutic treatment with Serp-2 in a mouse model of LIRI.

METHODS

Wildtype (C57BL/6 J) mice were subjected to warm, partial (70%) hepatic ischemia for 90 min followed by treatment with saline or Serp-2 or M-T7, 100 ng/g/day given by intraperitoneal injection on alternate days for 5 days. M-T7 is a Myxomavirus-derived inhibitor of chemokine-GAG interactions and was used in this study for comparative analysis of an unrelated viral protein with an alternative immunomodulating mechanism of action. Survival, serum ALT levels and histopathology were assessed 24 h and 10 days post-LIRI.

RESULTS

Serp-2 treatment significantly improved survival to 85.7% percent versus saline-treated wildtype mice (p = 0.0135), while M-T7 treatment did not significantly improve survival (p = 0.2584). Liver viability was preserved by Serp-2 treatment with a significant reduction in serum ALT levels (p = 0.0343) and infarct scar thickness (p = 0.0016), but with no significant improvement with M-T7 treatment. Suzuki scoring by pathologists blinded with respect to treatment group indicated that Serp-2 significantly reduced hepatocyte necrosis (p = 0.0057) and improved overall pathology score (p = 0.0046) compared to saline. Immunohistochemistry revealed that Serp-2 treatment reduced macrophage infiltration into the infarcted liver tissue (p = 0.0197).

CONCLUSIONS

Treatment with Serp-2, a virus-derived inflammasome and apoptotic pathway inhibitor, improves survival after liver ischemia-reperfusion injury in mouse models. Treatment with a cross-class immune modulator provides a promising new approach designed to reduce ischemia-reperfusion injury, improving survival and reducing chronic transplant damage.

In vitro testing of basal cytotoxicity: Establishment of an adverse outcome pathway from chemical insult to cell death

In this paper, an in vitro basal cytotoxicity testing strategy is described for new chemical entities that lack any pre-existing information on potential toxicity. Special attention is paid to the selection of the cellular system, cytotoxicity assay and exposure conditions. This approach is based on a newly proposed generic adverse outcome pathway from chemical insult to cell death that consists of 3 steps, including initial cell injury, mitochondrial dysfunction and cell demise. The suggested strategy to consider in vitro basal cytotoxicity as a first step in evaluating the toxicity of new chemical entities can be placed in a tiered strategy that could be continued by evaluating more specific types of toxicity.

N-acetylcysteine reduces the renal oxidative stress and apoptosis induced by hemorrhagic shock

BACKGROUND

Renal ischemia/reperfusion injury induced by hemorrhagic shock (HS) and subsequent fluid resuscitation is a common cause of acute renal failure. The objective of this study was to evaluate the effect of combining N-acetylcysteine (NAC) with fluid resuscitation on renal injury in rats that underwent HS.

MATERIALS AND METHODS

Two groups of male Wistar rats were induced to controlled HS at 35 mm Hg mean arterial pressure for 60 min. After this period, the HS and fluid resuscitation (HS/R) group was resuscitated with lactate containing 50% of the blood that was withdrawn. The HS/R + NAC group was resuscitated with Ringer's lactate combined with 150 mg/kg of NAC and blood. The sham group animals were catheterized but were not subjected to shock. All animals were kept under anesthesia and euthanized after 120 min of fluid resuscitation or observation.

RESULTS

Animals treated with NAC presented attenuation of histologic lesions, reduced oxidative stress, and apoptosis markers when compared with animals from the HS/R group. The serum creatinine was similar in all the groups.

CONCLUSIONS

NAC is a promising drug for combining with fluid resuscitation to attenuate the kidney injury associated with HS.

Metformin prevents ischemia reperfusion-induced oxidative stress in the fatty liver by attenuation of reactive oxygen species formation

Nonalcoholic fatty liver disease is associated with chronic oxidative stress. In our study, we explored the antioxidant effect of antidiabetic metformin on chronic [high-fat diet (HFD)-induced] and acute oxidative stress induced by short-term warm partial ischemia-reperfusion (I/R) or on a combination of both in the liver. Wistar rats were fed a standard diet (SD) or HFD for 10 wk, half of them being administered metformin (150 mg·kg body wt(-1)·day(-1)). Metformin treatment prevented acute stress-induced necroinflammatory reaction, reduced alanine aminotransferase and aspartate aminotransferase serum activity, and diminished lipoperoxidation. The effect was more pronounced in the HFD than in the SD group. The metformin-treated groups exhibited less severe mitochondrial damage (markers: cytochrome c release, citrate synthase activity, mtDNA copy number, mitochondrial respiration) and apoptosis (caspase 9 and caspase 3 activation). Metformin-treated HFD-fed rats subjected to I/R exhibited increased antioxidant enzyme activity as well as attenuated mitochondrial respiratory capacity and ATP resynthesis. The exposure to I/R significantly increased NADH- and succinate-related reactive oxygen species (ROS) mitochondrial production in vitro. The effect of I/R was significantly alleviated by previous metformin treatment. Metformin downregulated the I/R-induced expression of proinflammatory (TNF-α, TLR4, IL-1β, Ccr2) and infiltrating monocyte (Ly6c) and macrophage (CD11b) markers. Our data indicate that metformin reduces mitochondrial performance but concomitantly protects the liver from I/R-induced injury. We propose that the beneficial effect of metformin action is based on a combination of three contributory mechanisms: increased antioxidant enzyme activity, lower mitochondrial ROS production, and reduction of postischemic inflammation.

Hepatitis B Virus X Protein Sensitizes TRAIL-Induced Hepatocyte Apoptosis by Inhibiting the E3 Ubiquitin Ligase A20

Hepatitis B virus (HBV) infection causes hepatocyte death and liver damage, which may eventually lead to cirrhosis and liver cancer. Hepatitis B virus X protein (HBx) is a key antigen that is critically involved in HBV-associated liver diseases. However, the molecular basis for its pathogenesis, particularly in liver damage, has not been well defined. Herein, we report that HBx was able to enhance the susceptibility of hepatocytes to TNF-related apoptosis-inducing ligand (TRAIL)-induced apoptosis. Increased sensitivity to TRAIL was associated with HBx-induced upregulation of miR-125a, which, in turn, suppressed the expression of its putative target gene, A20 E3 ligase. Importantly, we demonstrate that the defective expression of A20 impaired the K63-linked polyubiquitination of caspase-8, which reciprocally enhanced the activation of caspase-8, the recruitment of Fas-associated death domain (FADD), and the formation of death-inducing signaling complex (DISC), thereby promoting HBx-mediated apoptotic signaling. Accordingly, antagonizing miR-125a or ectopically expressing A20 in hepatocytes abolished the pro-apoptotic effect of HBx. Conversely, the overexpression of miR-125a or knockdown of A20 mimicked HBx to enhance TRAIL susceptibility in hepatocytes. Thus, we establish, for the first time, a miR-125a/A20-initiated and caspase-8-targeted mechanism by which HBx modulates apoptotic signaling and increases hepatic susceptibility to the damaging agent, which might provide novel insight into HBV-related liver pathology.

Anti-apoptotic therapeutic approaches in liver diseases: do they really make sense?

A variety of data suggesting apoptotic cell death as a key feature of liver injury stimulated researchers to investigate the therapeutic potential of anti-apoptotic strategies in experimental models. However, the overestimated role of apoptotic cell death in liver injury has tempered the clinical translation of the protection afforded by anti-apoptotic regimes in experimental models. Thus, the hope for apoptosis modulation as potential treatment strategy for injured liver in humans could not be confirmed. Herein, we evaluated the degree of apoptosis in different hepatic stress models which are relevant for the human pathophysiology. Using morphological criteria of apoptosis, caspase-3 activation as well as TUNEL assay in combination with a positive control of apoptosis in liver injury, we quantified apoptotic cell death discriminating between parenchymal and non-parenchymal cells and confirmed these results by cleaved caspase-3 and PARP-1 protein expression. Discussing our findings and relating them to the existing literature on the potential role of apoptotic cell death, we strongly recommend reconsidering anti-apoptotic strategies to ameliorate liver injury efficiently.

Primary hepatocytes and their cultures in liver apoptosis research

Apoptosis not only plays a key role in physiological demise of defunct hepatocytes, but is also associated with a plethora of acute and chronic liver diseases as well as with hepatotoxicity. The present paper focuses on the modelling of this mode of programmed cell death in primary hepatocyte cultures. Particular attention is paid to the activation of spontaneous apoptosis during the isolation of hepatocytes from the liver, its progressive manifestation upon the subsequent establishment of cell cultures and simultaneously to strategies to counteract this deleterious process. In addition, currently applied approaches to experimentally induce controlled apoptosis in this in vitro setting for mechanistic research purposes and thereby its detection using relevant biomarkers are reviewed.

Expression of TRAIL in liver tissue from patients with different outcomes of HBV infection

OBJECTIVES

Hepatitis B virus (HBV) infection triggers the production of TRAIL, suggesting that TRAIL may play a role in liver injury after HBV infection. However, it remains unclear whether TRAIL expression in liver tissue correlates with the extent of liver injury caused by HBV infection. The aim of this article was to investigate the correlation of TRAIL expression and disease severity.

METHODS

Liver biopsy specimens were collected from 71 patients with different outcomes of HBV infection, including 25 cases of chronic hepatitis B (CHB), 18 cases of severe hepatitis B (SHB), and 28 cases of liver cirrhosis (LC). Besides, specimens from 33 healthy individuals without detectable liver diseases were used as negative control (NC). The expression of TRAIL was measured by immunohistochemistry.

RESULTS

Expression of TRAIL in the HBV-infected patients was higher than that in the NC (P<0.001). Among the patients, TRAIL expression in the ones with CHB was significantly higher than that in NC (P<0.001). However, there was no statistically significant difference between patients with SHB and NC or between the ones with LC and NC (P=0.067 and P=0.178, respectively). Moreover, TRAIL expression in patients with CHB was higher than that in patients with SHB or LC (P<0.001 for both), whereas no statistically significant difference was observed between patients with SHB and the ones with LC (P=0.511).

CONCLUSION

TRAIL is involved in the inflammatory and immunoregulatory response after HBV infection. However, there was no significant correlation between expression of TRAIL and the extent of liver injury.

Effect of N-acetylcysteine on pulmonary cell death in a controlled hemorrhagic shock model in rats

PURPOSE

To evaluate the effect of N-acetylcysteine (NAC) combined with fluid resuscitation on pulmonary cell death in rats induced with controlled hemorrhagic shock (HS).

METHODS

Two arteries (MAP calculation and exsanguination) and one vein (treatments) were catheterized in 22 anesthetized rats. Two groups of male albino rats were induced with controlled HS at 35mmHg MAP for 60 min. After this period, the RL group was resuscitated with Ringer's lactate and the RL+NAC group was resuscitated with Ringer's lactate combined with 150mg/Kg NAC. The control group animals were cannulated only. The animals were euthanized after 120 min of fluid resuscitation. Lung tissue samples were collected to evaluate the following: histopathology, TUNEL and imunohistochemical expression of caspase 3.

RESULTS

RL showed a greater number of cells stained by TUNEL than RL + NAC, but there was no change in caspase 3 expression in any group.

CONCLUSION

N-acetylcysteine associate to fluid resuscitation, after hemorrhagic shock, decreased cell death attenuating lung injury.

Bone marrow cell transplantation is associated with fibrogenic cells apoptosis during hepatic regeneration in cholestatic rats

Liver fibrosis is accompanied by hepatocyte death and proliferation of α-SMA+ fibrogenic cells (activated hepatic stellate cells and myofibroblasts), which synthesize extracellular matrix components that contribute to disorganization of the hepatic parenchyma and loss of liver function. Therefore, apoptosis of these fibrogenic cells is important to hepatic regeneration. This study aimed to analyze the effect of cell therapy using bone marrow mononuclear cell (BMMNC) transplantation on α-SMA expression and on apoptosis of hepatic cells during liver fibrosis induced by bile duct ligation (BDL). Livers were collected from normal rats, fibrotic rats after 14 and 21 days of BDL, and rats that received BMMNC at 14 days of BDL and were analyzed after 7 days. Apoptosis in fibrogenic cells was analyzed by immunoperoxidase, confocal microscopy, and Western blotting, and liver regeneration was assessed by proliferating cell nuclear antigen staining. Results showed that caspase-3 and proliferating cell nuclear antigen expression were significantly increased in the BMMNC-treated group. Additionally, confocal microscopy analysis showed cells coexpressing α-SMA and caspase-3 in these animals, suggesting fibrogenic cell death. These results suggest a novel role for BMMNC in liver regeneration during fibrotic disease by stimulating fibrogenic cells apoptosis and hepatocyte proliferation, probably through secretion of specific cytokines that modulate the hepatic microenvironment toward an antifibrogenic balance.

Characterization of spontaneous cell death in monolayer cultures of primary hepatocytes

Monolayer cultures of primary hepatocytes, isolated from freshly removed livers, represent widely used in vitro tools in the area of liver physiology and pathology, pharmacology and toxicology. However, a major shortcoming of these systems is that they cope with dedifferentiation, which is accompanied by spontaneous cell death. The goal of the present study was to elucidate the mechanisms that drive the process of self-generated cell demise in primary hepatocyte cultures. For this purpose, isolated rat hepatocytes were cultivated under conventional conditions, and the occurrence of apoptosis and necrosis was monitored during 4 days by performing a set of acknowledged cell death assays. These included examination of cell morphology by light microscopy, quantification of apoptotic and necrotic cell populations by Hoechst 33342 and propidium iodide in situ staining, assessment of apoptotic and necrotic activities by measuring caspase 3-like activity and extracellular leakage of lactate dehydrogenase, and studying the expression of apoptosis regulators through immunoblot analysis. In essence, two cell death peaks were observed, namely shortly after cell seeding and in the final stages of the cultivation period, both involving apoptotic and necrotic actions. The outcome of this study not only sheds new light onto the molecular processes that underlie spontaneous cell death in primary hepatocyte cultures, but also opens perspectives for the establishment of strategies to increase cell survival in these popular in vitro systems.

Reactive oxygen species mediate human hepatocyte injury during hypoxia/reoxygenation

Increasing evidence shows that reactive oxygen species (ROS) may be critical mediators of liver damage during the relative hypoxia of ischemia/reperfusion injury (IRI) associated with transplant surgery or of the tissue microenvironment created as a result of chronic hepatic inflammation or infection. Much work has been focused on Kupffer cells or liver resident macrophages with respect to the generation of ROS during IRI. However, little is known about the contribution of endogenous hepatocyte ROS production or its potential impact on the parenchymal cell death associated with IRI and chronic hepatic inflammation. For the first time, we show that human hepatocytes isolated from nondiseased liver tissue and human hepatocytes isolated from diseased liver tissue exhibit marked differences in ROS production in response to hypoxia/reoxygenation (H-R). Furthermore, several different antioxidants are able to abrogate hepatocyte ROS-induced cell death during hypoxia and H-R. These data provide clear evidence that endogenous ROS production by mitochondria and nicotinamide adenine dinucleotide phosphate oxidase drives human hepatocyte apoptosis and necrosis during hypoxia and H-R and may therefore play an important role in any hepatic diseases characterized by a relatively hypoxic liver microenvironment. In conclusion, these data strongly suggest that hepatocytes and hepatocyte-derived ROS are active participants driving hepatic inflammation. These novel findings highlight important functional/metabolic differences between hepatocytes isolated from normal donor livers, hepatocytes isolated from normal resected tissue obtained during surgery for malignant neoplasms, and hepatocytes isolated from livers with end-stage disease. Furthermore, the targeting of hepatocyte ROS generation with antioxidants may offer therapeutic potential for the adjunctive treatment of IRI and chronic inflammatory liver diseases.

E-cadherin protects primary hepatocyte spheroids from cell death by a caspase-independent mechanism

Cultivation of primary hepatocytes as spheroids creates an efficient three-dimensional model system for hepatic studies in vitro and as a cell source for a spheroid reservoir bioartificial liver. The mechanism of spheroid formation is poorly understood, as is an explanation for why normal, anchorage-dependent hepatocytes remain viable and do not undergo detachment-induced apoptosis, known as anoikis, when placed in suspension spheroid culture. The purpose of this study was to investigate the role of E-cadherin, a calcium-dependent cell adhesion molecule, in the formation and maintenance of hepatocyte spheroids. Hepatocyte spheroids were formed by a novel rocker technique and cultured in suspension for up to 24 h. The dependence of spheroid formation on E-cadherin and calcium was established using an E-cadherin blocking antibody and a calcium chelator. We found that inhibiting E-cadherin prevented cell-cell attachment and spheroid formation, and, surprisingly, E-cadherin inhibition led to hepatocyte death through a caspase-independent mechanism. In conclusion, E-cadherin is required for hepatocyte spheroid formation and may be responsible for protecting hepatocytes from a novel form of caspase-independent cell death.

Diabetes and apoptosis: liver

The liver is a central regulator of glucose homeostasis and stores or releases glucose according to metabolic demands. In insulin resistant states or diabetes the dysregulation of hepatic glucose release contributes significantly to the pathophysiology of these conditions. Acute or chronic liver disease can aggravate insulin resistance and the physiological effects of insulin on hepatocytes are disturbed. Insulin resistance has also been recognized as an independent risk factor for the development of liver injury. In the healthy liver tissue homeostasis is achieved through cell turnover by apoptosis and dysregulation of the physiological process resulting in too much or too little cell death can have potentially devastating effects on liver tissue. The delineation of the signaling pathways that mediate apoptosis changed the paradigms of understanding of many liver diseases. These signaling events include cell surface based receptor-ligand systems and intracellular signaling pathways that are regulated through kinases on multiple levels. The dissection of these signaling pathways has shown that the regulators of apoptosis signaling events in hepatocytes can also modulate insulin signaling pathways and that mediators of insulin resistance in turn influence liver cell apoptosis. This review will summarize the potential crosstalk between apoptosis and insulin resistance signaling events and discuss the involved mediators.

Knockout of myeloid cell leukemia-1 induces liver damage and increases apoptosis susceptibility of murine hepatocytes

Myeloid cell leukemia-1 (Mcl-1) is an antiapoptotic member of the Bcl-2 protein family. It interacts with proapoptotic Bcl-2 family members, thereby inhibiting mitochondrial activation and induction of apoptosis. Mcl-1 is essential for embryonal development and the maintenance of B cells, T cells, and hematopoietic stem cells. We have recently shown that induction of Mcl-1 by growth factors rescues primary human hepatocytes from CD95-mediated apoptosis. This prompted us to further analyze the relevance of Mcl-1 for hepatocellular homeostasis. Therefore, we generated a hepatocyte-specific Mcl-1 knockout mouse (Mcl-1(flox/flox)-AlbCre). Deletion of Mcl-1 in hepatocytes results in liver cell damage caused by spontaneous induction of apoptosis. Livers of Mcl-1(flox/flox)-AlbCre mice are smaller compared to control littermates, due to higher apoptosis rates. As a compensatory mechanism, proliferation of hepatocytes is enhanced in the absence of Mcl-1. Importantly, hepatic pericellular fibrosis occurs in Mcl-1 negative livers in response to chronic liver damage. Furthermore, Mcl-1(flox/flox)-AlbCre mice are more susceptible to hepatocellular damage induced by agonistic anti-CD95 antibodies or concanavalin A.

CONCLUSION

The present study provides in vivo evidence that Mcl-1 is a crucial antiapoptotic factor for the liver, contributing to hepatocellular homeostasis and protecting hepatocytes from apoptosis induction.

Naringenin-loaded nanoparticles improve the physicochemical properties and the hepatoprotective effects of naringenin in orally-administered rats with CCl(4)-induced acute liver failure

PURPOSE

A novel naringenin-loaded nanoparticles system (NARN) was developed to resolve the restricted bioavailability of naringenin (NAR) and to enhance its hepatoprotective effects in vivo on oral administration.

MATERIALS AND METHODS

Physicochemical characterizations of NARN included assessment of particle size and morphology, powder X-ray diffraction, fourier transform infrared spectroscopy, and dissolution study. In addition, to evaluate its bioactivities and its oral treatment potential against liver injuries, we compared the hepatoprotective, antioxidant, and antiapoptotic effects of NARN and NAR on carbon tetrachloride (CCl(4))-induced hepatotoxicity in rats.

RESULTS

NARN had a significantly higher release rate than NAR and improved its solubility. NARN also exhibited more liver-protective effects compared to NAR with considerable reduction in liver function index and lipid peroxidation, in conjunction to a substantial increase in the levels of the antioxidant enzymes (P < 0.05). Moreover, NARN was able to significantly inhibit the activation of caspase-3, -8, and -9 signaling, whereas NAR only markedly inhibited caspase-3 and -9 (P < 0.05).

CONCLUSION

NARN effectively improved the release of NAR which resulted in more hepatoprotective effects mediated by its antioxidant and antiapoptotic properties. These observations also suggest that nanoformulation can improve the free drug's bioactivity on oral administration.

Peripheral blood serum markers for apoptosis and liver fibrosis: are they trustworthy indicators of liver realness?

BACKGROUND/AIMS

No reliable serum markers for liver inflammation, apoptosis and fibrosis have been established yet, although a large number have been evaluated. Moreover, it is not clear if a molecule detected and quantified in peripheral vein blood is a really trustworthy marker of the liver condition. To answer to this question, we had the opportunity to study paired serum samples drawn simultaneously during haemodynamic study from the right hepatic vein and from a peripheral vein from patients with hepatitis C virus related cirrhosis.

METHODS

The serum levels of transforming growth factor beta-1, tumour necrosis factor-alpha, hyaluronic acid, soluble (s)human leukocyte class I antigens, soluble FAS ligand, and stumour necrosis factor related ligand were assessed in a consecutive series of 15 patients with hepatitis C virus related cirrhosis.

RESULTS

No statistically significant differences were found between hepatic vein and peripheral vein levels for the cytokines, substance or soluble molecules evaluated, excepted for shuman leukocyte class I antigens. Instead a strong correlation between hepatic vein and peripheral vein levels was present for: hepatic vein, shuman leukocyte class I antigens, tumour necrosis factor-alpha, soluble FAS ligand and stumour necrosis factor related ligand, but not for transforming growth factor beta-1.

CONCLUSIONS

Our results show that peripheral vein measurements seem to reflect the liver compartment in a large majority of cases, but not for all molecules and probably for any liver diseases. Further studies on this line are warranted in particular for new molecules.

Early growth response-1 contributes to galactosamine/lipopolysaccharide-induced acute liver injury in mice

Early growth response (Egr)-1 is a transcription factor that regulates genes involved in inflammation, innate and adaptive immunity, coagulation, and wound healing; however, little is known about the role of Egr-1 in acute liver injury. We tested the hypothesis that Egr-1 is involved in acute liver injury induced by galactosamine/lipopolysaccharide (GalN/LPS). GalN/LPS exposure biphasically increased hepatic egr-1 mRNA accumulation at 1 h and again at 4-5.5 h after treatment in wild-type mice. Within 4-5.5 h after GalN/LPS exposure, wild-type mice exhibited histological evidence of hepatocyte injury, cell death, and extensive areas of hemorrhage, as well as increased plasma alanine aminotransferase activities. In contrast, these parameters were largely attenuated in egr-1(-/-) mice. The initial expression of tumor necrosis factor-alpha, macrophage inflammatory protein-2, monocyte chemoattractant protein-1, and intercellular adhesion molecule-1 mRNA or protein was equivalent between genotypes at 1 h after GalN/LPS administration. However, at subsequent time points, hepatic expression of these genes was decreased in egr-1(-/-) compared with wild-type mice. In addition, neutrophil extravasation from hepatic sinusoids into the liver parenchyma was decreased in egr-1(-/-) compared with wild-type mice 4 h after GalN/LPS. Whereas caspase-3 activation and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling-positive nuclei were detected in wild-type mice at 4 and 5.5 h after GalN/LPS administration, respectively, these markers of apoptosis were delayed in egr-1(-/-) mice. Delayed development of apoptosis was associated with an extension of survival by 1 h in egr-1(-/-) compared with wild-type mice. These data demonstrate that Egr-1 plays an important role in acceleration of hepatic inflammation, apoptosis, and subsequent mortality in GalN/LPS-induced acute liver injury.

Importance of peroxisome proliferator-activated receptor-gamma in hepatic ischemia/reperfusion injury in mice

BACKGROUND/AIMS

Peroxisome proliferator-activated receptor-gamma (PPARgamma) is a transcriptional factor belonging to the nuclear receptor superfamily. Recent studies have suggested that PPARgamma regulates inflammatory responses and PPARgamma specific agonists have beneficial effects on several disease conditions in the various organs. However, the precise role of PPARgamma in acute liver injury remains unknown.

METHODS

We investigated the pathophysiological role of PPARgamma and the effect of the selective PPARgamma agonist, pioglitazone, on the hepatic ischemia/reperfusion (I/R) injury.

RESULTS

PPARgamma expression in the liver was upregulated after reperfusion following ischemia. Pioglitazone treatment significantly inhibited hepatic I/R injury as determined by serological and histological analyses. The protective effect was associated with downregulation of the local expression of several potent proinflammatory cytokines, chemokines and adhesion molecules after reperfusion. The neutrophil accumulation was also inhibited by the treatment. Furthermore, the treatment inhibited the induction of apoptosis on hepatocytes. Finally, pioglitazone significantly improved the mouse survival in a lethal model of hepatic I/R injury.

CONCLUSIONS

PPARgamma plays an inhibitory role in hepatic I/R injury and the stimulation by selective agonist has a significant beneficial effect. Thus, PPARgamma may be a new therapeutic target for the protection of the liver against acute injury.

Hepatobiliary pathology

PURPOSE OF REVIEW

Recent papers on disorders of the liver and biliary tract which clarify their pathogenesis and attendant morphologic changes are highlighted.

RECENT FINDINGS

The concept of 'bystander hepatitis' was cited in studies showing hepatic infiltration of CD8-positive T cells in the setting of extrahepatic infections such as influenza virus and severe acute respiratory syndrome. Diabetic liver lesions include glycogenic hepatopathy (in which poor diabetic control leads to swollen, glycogen-filled hepatocytes without fat, steatohepatitis or fibrosis) and diabetic hepatosclerosis in which there is diffuse perisinusoidal fibrosis (type IV collagen) without zonal predilection. Ground-glass hepatocellular inclusions (positive with periodic acid-Schiff stain for glycogen) were reported in three separate series of patients who were hepatitis B virus-negative, often transplant recipients, immunosuppressed and on multiple medications. A Banff consensus paper expertly compared and contrasted the histologic features which characterize the various causes of late liver allograft dysfunction.

SUMMARY

Informative papers emerged this past year concerning collateral damage to the liver in extrahepatic infections, diabetic lesions and causes of liver dysfunction after transplantation, among other topics.