Mechanisms of Liver Injury. II. Mechanisms of neutrophil-induced liver cell injury during hepatic ischemia-reperfusion and other acute inflammatory conditions

GCDCA down-regulates gene expression by increasing Sp1 binding to the NOS-3 promoter in an oxidative stress dependent manner

During the course of cholestatic liver diseases, the toxic effect of bile acids accumulation has been related to the decreased expression of endothelial nitric oxide synthase (NOS-3) and cellular oxidative stress increase. In the present study, we have investigated the relationship between these two biological events. In the human hepatocarcinoma cell line HepG2, cytotoxic response to GCDCA was characterized by the reduced activity of the respiratory complexes II+III, the increased expression and activation of the transcription factor Sp1, and a higher binding capacity of this at positions -1386, -632 and -104 of the NOS-3 promoter (pNOS-3). This was associated with a decreased promoter activity and a consequent reduction of NOS-3 expression. The use of antioxidants in GCDCA-treated cells caused a lower activation of Sp1 and the recovery of the pNOS-3 activity and NOS-3 expression and activity. Similarly, the specific inhibition of Sp1 resulted in the improvement of NOS-3 expression. Both, antioxidant treatment and Sp1 inhibition were associated with the reduction of cell death-related parameters. Bile duct ligation in rats confirmed in vitro results concerning the activation of Sp1 and the reduction of NOS-3 expression. Our results provide direct evidence for the involvement of Sp1 in the regulation of NOS-3 expression during cholestasis. Thus, the identification of Sp1 as a potential negative regulator of NOS-3 expression represents a new mechanism by which the accumulation of bile acids causes a cytotoxic effect through the oxidative stress increase, and provides a new potential target in cholestatic liver diseases.

Aggravation of post-ischemic liver injury by overexpression of insulin-like growth factor binding protein 3

Insulin-like growth factor-1 (IGF-1) is known to inhibit reperfusion-induced apoptosis. IGF-binding protein-3 (IGFBP-3) is the major circulating carrier protein for IGF-1 and induces apoptosis. In this study, we determined if IGFBP-3 was important in the hepatic response to I/R. To deliver IGFBP-3, we used an adenovirus containing IGFBP-3 cDNA (AdIGFBP-3) or an IGFBP-3 mutant devoid of IGF binding affinity but retaining IGFBP-3 receptor binding ability (AdIGFBP-3(GGG)). Mice subjected to I/R injury showed typical patterns of hepatocellular damage. Protein levels of IGFBP-3 were increased after reperfusion and showed a positive correlation with the extent of liver injury. Prior injection with AdIGFBP-3 aggravated liver injury: serum aminotransferases, prothrombin time, proinflammatory cytokines, hepatocellular necrosis and apoptosis, and neutrophil infiltration were markedly increased compared to control mice. A decrease in antioxidant potential and an upregulation of NADPH oxidase might have caused these aggravating effects of IGFBP-3. Experiments using HepG2 cells and N-acetylcysteine-pretreated mice showed a discernible effect of IGFBP-3 on reactive oxygen species generation. Lastly, AdIGFBP-3 abolished the beneficial effects of ischemic preconditioning and hypothermia. Mice treated with AdIGFBP-3(GGG) exhibited effects similar to those of AdIGFBP-3, suggesting a ligand-independent effect of IGFBP-3. Our results suggest IGFBP-3 as an aggravating factor during hepatic I/R injury.

Cell-cycle arrest and acute kidney injury: the light and the dark sides

Acute kidney injury (AKI) is a common consequence of systemic illness or injury and it complicates several forms of major surgery. Two major difficulties have hampered progress in AKI research and clinical management. AKI is difficult to detect early and its pathogenesis is still poorly understood. We recently reported results from multi-center studies where two urinary markers of cell-cycle arrest, tissue inhibitor of metalloproteinases-2 (TIMP-2) and insulin-like growth factor-binding protein 7 (IGFBP7) were validated for development of AKI well ahead of clinical manifestations—azotemia and oliguria. Cell-cycle arrest is known to be involved in the pathogenesis of AKI and this ‘dark side’ may also involve progression to chronic kidney disease. However, cell-cycle arrest has a ‘light side’ as well, since this mechanism can protect cells from the disastrous consequences of entering cell division with damaged DNA or insufficient bioenergetic resources during injury or stress. Whether we can use the light side to help prevent AKI remains to be seen, but there is already evidence that cell-cycle arrest biomarkers are indicators of both sides of this complex physiology.

Fucoidan reduces inflammatory response in a rat model of hepatic ischemia-reperfusion injury

Ischemia-reperfusion (I/R) injury after a liver transplant is a major cause of severe complications that lead to graft dysfunction. Fucoidan, a complex of sulfated polysaccharides derived from marine brown algae, demonstrated antiapoptotic as well as potential anti-inflammatory properties in previous studies. Fucoidan has also shown protective effects on I/R-injured kidney and heart. However, whether fucoidan can attenuate hepatic I/R injury has not been examined. To clarify the role of fucoidan in hepatic I/R injury, Sprague-Dawley rats were subjected to sham operation or ischemia followed by reperfusion with treatment of saline or fucoidan (50, 100, or 200 mg·(kg body mass)(-1)·d(-1)). The fucoidan-treated group showed decreased levels of alanine aminotransferase and aspartate aminotransferase compared with the control group. Myeloperoxidase and malondialdehyde activities and mRNA levels of CD11b in the fucoidan-treated group were significantly decreased. Hepatocellular swelling/necrosis, sinusoidal/vascular congestion, and inflammatory cell infiltration were also attenuated in the fucoidan group. The expression of TNF-α, IL-6, IL-1β, CXCL-10, VCAM-1, and ICAM-1 were markedly decreased in the samples from the fucoidan-treated group. Fucoidan largely prevented activation of the inflammatory signaling pathway, compared with the control group. In summary, fucoidan can protect the liver from I/R injury through suppressing activation of the inflammatory signaling pathway, as well as the expression of inflammatory mediators, and inflammatory cell infiltration.

The Reg3α (HIP/PAP) Lectin Suppresses Extracellular Oxidative Stress in a Murine Model of Acute Liver Failure

BACKGROUND AND AIMS

Acute liver failure (ALF) is a rapidly progressive heterogeneous illness with high mortality rate and no widely accessible cure. A promising drug candidate according to previous preclinical studies is the Reg3α (or HIP/PAP) lectin, which alleviates ALF through its free-radical scavenging activity. Here we study the therapeutic targets of Reg3α in order to gain information on the nature of the oxidative stress associated with ALF.

METHODS

Primary hepatocytes stressed with the reactive oxygen species (ROS) inducers TNFα and H2O2 were incubated with a recombinant Reg3α protein. ALF was induced in C57BL/6J mice by an anti-CD95 antibody. Livers and primary hepatocytes were harvested for deoxycholate separation of cellular and extracellular fractions, immunostaining, immunoprecipitation and malondialdehyde assays. Fibrin deposition was studied by immunofluorescence in frozen liver explants from patients with ALF.

RESULTS

Fibrin deposition occurs during experimental and clinical acute liver injuries. Reg3α bound the resulting transient fibrin network, accumulated in the inflammatory extracellular matrix (ECM), greatly reduced extracellular ROS levels, and improved cell viability. Hepatocyte treatment with ligands of death receptors, e.g. TNFα and Fas, resulted in a twofold increase of malondialdehyde (MDA) level in the deoxycholate-insoluble fractions. Reg3α treatment maintained MDA at a level similar to control cells and thereby increased hepatocyte survival by 35%. No antioxidant effect of Reg3α was noted in the deoxycholate-soluble fractions. Preventing fibrin network formation with heparin suppressed the prosurvival effect of Reg3α.

CONCLUSIONS

Reg3α is an ECM-targeted ROS scavenger that binds the fibrin scaffold resulting from hepatocyte death during ALF. ECM alteration is an important pathogenic factor of ALF and a relevant target for pharmacotherapy.

Anti-inflammatory effect of rosmarinic acid and an extract of Rosmarinus officinalis in rat models of local and systemic inflammation

Rosmarinic acid is a polyphenolic compound and main constituent of Rosmarinus officinalis and has been shown to possess antioxidant and anti-inflammatory properties. We aimed to evaluate the anti-inflammatory properties of rosmarinic acid and of an extract of R. officinalis in local inflammation (carrageenin-induced paw oedema model in the rat), and further evaluate the protective effect of rosmarinic acid in rat models of systemic inflammation: liver ischaemia-reperfusion (I/R) and thermal injury models. In the local inflammation model, rosmarinic acid was administered at 10, 25 and 50 mg/kg (p.o.), and the extract was administered at 10 and 25 mg/kg (equivalent doses to rosmarinic acid groups) to male Wistar rats. Administration of rosmarinic acid and extract at the dose of 25 mg/kg reduced paw oedema at 6 hr by over 60%, exhibiting a dose-response effect, suggesting that rosmarinic was the main contributor to the anti-inflammatory effect. In the liver I/R model, rosmarinic acid was administered at 25 mg/kg (i.v.) 30 min. prior to the induction of ischaemia and led to the significant reduction in the serum concentration of transaminases (AST and ALT) and LDH. In the thermal injury model, rosmarinic acid was administered at 25 mg/kg (i.v.) 5 min. prior to the induction of injury and significantly reduced multi-organ dysfunction markers (liver, kidney, lung) by modulating NF-κB and metalloproteinase-9. For the first time, the anti-inflammatory potential of rosmarinic acid has been identified, as it causes a substantial reduction in inflammation, and we speculate that it might be useful in the pharmacological modulation of injuries associated to inflammation.

Protective effects of Hammada scoparia flavonoid-enriched fraction on liver injury induced by warm ischemia/reperfusion

CONTEXT

Hepatic ischemia/reperfusion injury (IRI) is a major cause of liver damage during liver surgery and transplantation. Plants have historically been used in treating liver damage, and Hammada scoparia (Pomel) (Chenopodiaceae) has been reported to possess a broad spectrum of pharmacological and therapeutic activities.

OBJECTIVE

In this study, a flavonoid-enriched fraction was used before the warm ischemia (WI) process as pharmacological preconditioning and in combination with technical postconditioning to evaluate their protective effects.

MATERIALS AND METHODS

The rats were divided into five groups: a sham group; a control group (Control-IR) that was submitted to 60 min WI; a Pharmacological Preconditioning group (PreC-IR) that received flavonoid-enriched fraction (200 mg/kg body weight); a Postconditioning group (PostC) and a PreC + PostC group.

RESULTS

The use of the flavonoid-enriched fraction was noted to significantly (p < 0.05) reduce liver injury, as evidenced by the decrease in liver transaminase activities (AST and ALT) and lactic dehydrogenase (LDH), alkaline phosphatase (ALP), and lipid peroxidation (TBARS), levels as well as the enhancement of antioxidant enzymes (catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx)) responses. The results also indicated that, compared with the separate application of pharmacological preconditioning and postconditioning, the combination of both treatments was more effective in reducing tissue oxidative stress levels through modulating SOD, GSH-PX, and CAT activities. Furthermore, the combined protocol further decreased the liver morphological score compared with solo treatment.

DISCUSSION AND CONCLUSION

Overall, the results indicate that the H. scoparia flavonoid-enriched fraction could be a promising candidate for future application as a pharmacological preconditioning agent against hepatic IRI.

NFκB1 is a suppressor of neutrophil-driven hepatocellular carcinoma

Hepatocellular carcinoma (HCC) develops on the background of chronic hepatitis. Leukocytes found within the HCC microenvironment are implicated as regulators of tumour growth. We show that diethylnitrosamine (DEN)-induced murine HCC is attenuated by antibody-mediated depletion of hepatic neutrophils, the latter stimulating hepatocellular ROS and telomere DNA damage. We additionally report a previously unappreciated tumour suppressor function for hepatocellular nfkb1 operating via p50:p50 dimers and the co-repressor HDAC1. These anti-inflammatory proteins combine to transcriptionally repress hepatic expression of a S100A8/9, CXCL1 and CXCL2 neutrophil chemokine network. Loss of nfkb1 promotes ageing-associated chronic liver disease (CLD), characterized by steatosis, neutrophillia, fibrosis, hepatocyte telomere damage and HCC. Nfkb1^S340A/S340Amice carrying a mutation designed to selectively disrupt p50:p50:HDAC1 complexes are more susceptible to HCC; by contrast, mice lacking S100A9 express reduced neutrophil chemokines and are protected from HCC. Inhibiting neutrophil accumulation in CLD or targeting their tumour-promoting activities may offer therapeutic opportunities in HCC.

The role of neutrophils in cancer development is not widely appreciated. Here, the authors show that NF-κB-deficient hepatocytes overproduce chemokines, leading to hepatocellular carcinoma due to excessive neutrophil recruitment, and that neutrophil depletion prevents liver cancer in these mice.

Clinical implication of perioperative inflammatory cytokine alteration

Cytokines are key modulators of inflammatory responses, and play an important role in the defense and repair mechanisms following trauma. After traumatic injury, an immuno-inflammatory response is initiated immediately, and cytokines rapidly appear and function as a regulator of immunity. In pathologic conditions, imbalanced cytokines may provide systemic inflammatory responses or immunosuppression. Expression of perioperative cytokines vary by different intensities of surgical trauma and types of anesthesia and anesthetic agents. Inflammatory cytokines play important roles in postoperative organ dysfunction including central nervous system, cardiovascular, lung, liver, and kidney injury. Inhibition of cytokines could protect against traumatic injury in some circumstances, therefore cytokine inhibitors or antagonists might have the potential for reducing postoperative tissue/organ dysfunction. Cytokines are also involved in wound healing and post-traumatic pain. Application of cytokines for the improvement of surgical wound healing has been reported. Anesthesia-related immune response adjustment might reduce perioperative morbidity because it reduces proinflammatory cytokine expression; however, the overall effects of anesthetics on postoperative immune-inflammatory responses needs to be further investigated.

Autophagy and liver ischemia-reperfusion injury

Liver ischemia-reperfusion (I-R) injury occurs during liver resection, liver transplantation, and hemorrhagic shock. The main mode of liver cell death after warm and/or cold liver I-R is necrosis, but other modes of cell death, as apoptosis and autophagy, are also involved. Autophagy is an intracellular self-digesting pathway responsible for removal of long-lived proteins, damaged organelles, and malformed proteins during biosynthesis by lysosomes. Autophagy is found in normal and diseased liver. Although depending on the type of ischemia, warm and/or cold, the dynamic process of liver I-R results mainly in adenosine triphosphate depletion and in production of reactive oxygen species (ROS), leads to both, a local ischemic insult and an acute inflammatory-mediated reperfusion injury, and results finally in cell death. This process can induce liver dysfunction and can increase patient morbidity and mortality after liver surgery and hemorrhagic shock. Whether autophagy protects from or promotes liver injury following warm and/or cold I-R remains to be elucidated. The present review aims to summarize the current knowledge in liver I-R injury focusing on both the beneficial and the detrimental effects of liver autophagy following warm and/or cold liver I-R.

Infiltrating neutrophils aggravate metabolic liver failure in fah-deficient mice

BACKGROUND & AIMS

Mice deficient in tyrosine catabolic enzyme fumarylacetoacetate hydrolase (fah(-/-) ) was a useful animal model for studying liver failure. Tyrosine metabolic toxicants accumulate in hepatocytes over time in fah(-/-) mice, leading to hepatocyte necrosis which we propose release many type of damage associated molecular patterns (DAMPs) and cause chronic inflammation. However, whether immune-mediated inflammations cause a second wave of liver damage in fah(-/-) mice have never been investigated.

METHODS

The progressive changes in body weight, survival rate and liver inflammation were examined after the protective drug (NTBC) withdrawal. Cell depletion and receptor blocking were used to define the key immune cells and molecules in liver injury.

RESULTS

After removing of NTBC, fah(-/-) mice lost their body weight gradually, and finally died when the body weight largely reduced (low to 70%), along with increased serum ALT and total bilirubin. Importantly, a large amount of liver-infiltrating neutrophils were observed. Neutrophils depletion reduced the liver failure, and resulted in a better survival of fah(-/-) mice after NTBC withdrawal. The liver tissues produce more CCR2 chemokine, with neutrophils expressing more CCR2. CCR2 inhibition reduced the number of liver-infiltrating neutrophils and increased the expression of repair cytokine IL-22, with a longer survival of fah(-/-) mice after NTBC withdrawal.

CONCLUSIONS

The excess infiltrating neutrophils exacerbate liver failure in fah(-/-) mice which can be attenuated by blocking CCR2.

Sterile inflammation in acute liver injury: myth or mystery?

Inflammation during liver injury normally serves as a mechanism for cleaning up debris and as a stimulant for regeneration. However, aberrant levels of inflammation can provoke further liver injury and inhibit regeneration through the release of damaging reactive oxygen species. Considerable effort has gone into understanding the mechanisms that control the switch between healthy and pathological inflammation. The identification of a receptor system that detects damage-associated molecular patterns and stimulates inflammation has led to the idea of sterile inflammation. This article will focus on the role of sterile inflammation during liver injury in three models where sterile inflammation has been presumed to mediate a portion of the injury mechanism and its potential relevance for the human pathophysiology.

Protective effect of the combinations of glycyrrhizic, ferulic and cinnamic acid pretreatment on myocardial ischemia-reperfusion injury in rats

The aim of this study was to find an effective drug cocktail pretreatment to protect myocardial tissue of the heart from ischemia-reperfusion (I/R) injury. The mechanisms underlying the effects of the drug cocktail were subsequently explored in order to expand the application of Dang-gui-si-ni-tang (DGSN), a Traditional Chinese Medicine. The active components of DGSN in the serum following oral administration were investigated using high-performance liquid chromatography. The activity of superoxide dismutase (SOD) and malondialdehyde (MDA) levels were then analyzed to show the effect of the active components in the treatment of myocardial I/R injury. An L16 (4⁴) orthogonal experiment was utilized to determine the most effective cocktail mix and the mechanism underlying the effect of this mix on myocardial I/R injury was investigated. It was observed that FCG, a mixture of glycyrrhizic (50 mg/kg), cinnamic (200 mg/kg) and ferulic (300 mg/kg) acid, was the optimal drug cocktail present in DGSN. This was absorbed into the blood following oral administration and was shown to decrease MDA levels and increase the activity of SOD. In conclusion, the findings suggest that FCG, a combination of active ingredients in the DGSN decoction, can be absorbed into the blood and protect the myocardium from I/R injury.

Tumor induced hepatic myeloid derived suppressor cells can cause moderate liver damage

Subcutaneous tumors induce the accumulation of myeloid derived suppressor cells (MDSC) not only in blood and spleens, but also in livers of these animals. Unexpectedly, we observed a moderate increase in serum transaminases in mice with EL4 subcutaneous tumors, which prompted us to study the relationship of hepatic MDSC accumulation and liver injury. MDSC were the predominant immune cell population expanding in livers of all subcutaneous tumor models investigated (RIL175, B16, EL4, CT26 and BNL), while liver injury was only observed in EL4 and B16 tumor-bearing mice. Elimination of hepatic MDSC in EL4 tumor-bearing mice using low dose 5-fluorouracil (5-FU) treatment reversed transaminase elevation and adoptive transfer of hepatic MDSC from B16 tumor-bearing mice caused transaminase elevation indicating a direct MDSC mediated effect. Surprisingly, hepatic MDSC from B16 tumor-bearing mice partially lost their damage-inducing potency when transferred into mice bearing non damage-inducing RIL175 tumors. Furthermore, MDSC expansion and MDSC-mediated liver injury further increased with growing tumor burden and was associated with different cytokines including GM-CSF, VEGF, interleukin-6, CCL2 and KC, depending on the tumor model used. In contrast to previous findings, which have implicated MDSC only in protection from T cell-mediated hepatitis, we show that tumor-induced hepatic MDSC themselves can cause moderate liver damage.

Some mechanisms of the protective effect of ischemic preconditioning on rat liver ischemia-reperfusion injury

Ischemia-reperfusion (I/R) injury is a multifactorial process that affects graft function after liver transplantation. An understanding of the mechanisms involved in I/R injury is essential for the design of therapeutic strategies to improve the outcome of liver transplantation. The generation of reactive oxygen species subsequent to reoxygenation inflicts tissue damage and initiates a cascade of deleterious cellular responses, leading to inflammation, cell death, and ultimate organ failure. Increasing experimental evidence has suggested that Kupffer cells and T-cells mediate activation of neutrophil inflammatory responses. Activated neutrophils infiltrate the injured liver in parallel with increased expression of adhesion molecules on endothelial cells. The heme oxygenase system is among the most critical of the cytoprotective mechanisms activated during cellular stress, exerting antioxidant and anti-inflammatory functions, modulating the cell cycle, and maintaining the microcirculation. Finally, the activation of toll-like receptors on Kupffer cells may play a fundamental role in exploring new therapeutic strategies based on the concept that hepatic I/R injury represents a case for host “innate” immunity. In the present study, there was a significant decrease in hepatic activity of glycogen in the I/R group as compared with corresponding values in the control group. On the other hand, there was a significant increase in the hepatic activity of glycogen in the I/R-IP (ischemic preconditioning) group as compared with corresponding values in the I/R group.

Dioscin attenuates hepatic ischemia-reperfusion injury in rats through inhibition of oxidative-nitrative stress, inflammation and apoptosis

BACKGROUND

Dioscin shows potent effects against liver damage in our previous studies; however, the action of it on hepatic ischemia-reperfusion (I/R) injury is still unknown. In the present article, the effects and possible mechanisms of dioscin against hepatic I/R injury were investigated.

METHODS

Seventy percent partial hepatic warm ischemia was induced in Wistar rats for 60 min followed by succedent reperfusion. In the prophylactic test, dioscin was administered intragastrically to the rats at doses of 20, 40, and 60 mg/kg once daily for seven consecutive days before I/R. In the therapeutic test, the rats received dioscin intragastrically at a dose of 60 mg/kg once 2 hr before I/R.

RESULTS

We found that dioscin significantly decreased serum alanine aminotransferase and aspartate aminotransferase activities, increased survival rate of rats, and improved I/R-induced hepatocyte abnormality. In addition, dioscin obviously increased the levels of SOD, CAT, GSH-Px, GSH, decreased the levels of MDA, TNOS, iNOS, NO, and prevented DNA fragmentation caused by I/R injury. Further research indicated that dioscin markedly decreased the gene expressions of interleukin-1β, interleukin-6, tumor necrosis factor-α, intercellular adhesion molecule-1, MIP-1α, MIP-2, Fas, FasL, decreased the protein expressions of NF-κB, AP-1, COX-2, HMGB-1, CYP2E1, Bak, caspase-3, p53, PARP, Caspase-9, decreased the levels of JNK, ERK and p38 MAPKs phosphorylation, and upregulated the levels of Bcl-2 and Bcl-x.

CONCLUSION

Our results suggest that dioscin has potent actions against hepatic I/R injury through suppression of inflammation, oxidative-nitrative stress, and apoptosis, which should be developed as a new drug to treat hepatic I/R injury in the future.

The mechanisms and physiological relevance of glycocalyx degradation in hepatic ischemia/reperfusion injury

SIGNIFICANCE

Hepatic ischemia/reperfusion (I/R) injury is an inevitable side effect of major liver surgery that can culminate in liver failure. The bulk of I/R-induced liver injury results from an overproduction of reactive oxygen and nitrogen species (ROS/RNS), which inflict both parenchymal and microcirculatory damage. A structure that is particularly prone to oxidative attack and modification is the glycocalyx (GCX), a meshwork of proteoglycans and glycosaminoglycans (GAGs) that covers the lumenal endothelial surface and safeguards microvascular homeostasis. ROS/RNS-mediated degradation of the GCX may exacerbate I/R injury by, for example, inducing vasoconstriction, facilitating leukocyte adherence, and directly activating innate immune cells.

RECENT ADVANCES

Preliminary experiments revealed that hepatic sinusoids contain a functional GCX that is damaged during murine hepatic I/R and major liver surgery in patients. There are three ROS that mediate GCX degradation: hydroxyl radicals, carbonate radical anions, and hypochlorous acid (HOCl). HOCl converts GAGs in the GCX to GAG chloramides that become site-specific targets for oxidizing and reducing species and are more efficiently fragmented than the parent molecules. In addition to ROS/RNS, the GAG-degrading enzyme heparanase acts at the endothelial surface to shed the GCX.

CRITICAL ISSUES

The GCX seems to be degraded during major liver surgery, but the underlying cause remains ill-defined.

FUTURE DIRECTIONS

The relative contribution of the different ROS and RNS intermediates to GCX degradation in vivo, the immunogenic potential of the shed GCX fragments, and the role of heparanase in liver I/R injury all warrant further investigation.

VEGFR1-positive macrophages facilitate liver repair and sinusoidal reconstruction after hepatic ischemia/reperfusion injury

Liver repair after acute liver injury is characterized by hepatocyte proliferation, removal of necrotic tissue, and restoration of hepatocellular and hepatic microvascular architecture. Macrophage recruitment is essential for liver tissue repair and recovery from injury; however, the underlying mechanisms are unclear. Signaling through vascular endothelial growth factor receptor 1 (VEGFR1) is suggested to play a role in macrophage migration and angiogenesis. The aim of the present study was to examine the role of VEGFR1 in liver repair and sinusoidal reconstruction after hepatic ischemia/reperfusion (I/R). VEGFR1 tyrosine kinase knockout mice (VEGFR1 TK-/- mice) and wild-type (WT) mice were subjected to hepatic warm I/R, and the processes of liver repair and sinusoidal reconstruction were examined. Compared with WT mice, VEGFR1 TK-/- mice exhibited delayed liver repair after hepatic I/R. VEGFR1-expressing macrophages recruited to the injured liver showed reduced expression of epidermal growth factor (EGF). VEGFR1 TK-/- mice also showed evidence of sustained sinusoidal functional and structural damage, and reduced expression of pro-angiogenic factors. Treatment of VEGFR1 TK-/- mice with EGF attenuated hepatoceullar and sinusoidal injury during hepatic I/R. VEGFR1 TK-/- bone marrow (BM) chimeric mice showed impaired liver repair and sinusoidal reconstruction, and reduced recruitment of VEGFR1-expressing macrophages to the injured liver. VEGFR1-macrophages recruited to the liver during hepatic I/R contribute to liver repair and sinusoidal reconstruction. VEGFR1 activation is a potential therapeutic strategy for promoting liver repair and sinusoidal restoration after acute liver injury.

Activation of NF-κB after chronic ethanol intake and haemorrhagic shock/resuscitation in mice

BACKGROUND AND PURPOSE

Chronic ethanol abuse and haemorrhagic shock are major causes of global mortality and, separately, induce profound hepato- and immune-toxic effects via activation of NF-κB. Here, we assessed the effects of chronic ethanol intake upon the pathophysiological derangements after haemorrhagic shock with subsequent resuscitation (H/R), with particular attention to the contribution of NF-κB.

EXPERIMENTAL APPROACH

Transgenic NF-κB(EGFP) mice, expressing the enhanced green fluorescent protein (EGFP) under the transcriptional control of NF-κB cis-elements were fed a Lieber-DeCarli diet containing ethanol (EtOH-diet) or an isocaloric control diet for 4 weeks and were then pairwise subjected to H/R. Liver tissues and peripheral blood were sampled at 2 or 24 h after H/R. Cytokines in blood and tissue and leukocyte activation (as CD11b expression) were measured, along with EGFP as a marker of NF-κB activation.

KEY RESULTS

The EtOH-diet increased mortality at 24 h after H/R and elevated liver injury, associated with an up-regulation of NF-κB-dependent genes and IL-6 release; it also increased production of NF-κB-driven intercellular adhesion molecule 1 (ICAM-1) and EGFP in liver tissue. At 2h after the H/R procedure in ethanol-fed mice we observed the highest proportion of NF-κB activated non-parenchymal cells and an NF-κB-dependent increase in polymorphonuclear leukocyte CD11b expression.

CONCLUSIONS AND IMPLICATIONS

The EtOH-diet exacerbated liver injury after H/R, accompanying an overwhelming hepatic and systemic immune response. Our findings contribute to evidence implicating NF-κB as a key player in the orchestration of the immune response in haemorrhagic shock patients with a history of chronic ethanol abuse.

Rosmarinic acid inhibits chemical hypoxia-induced cytotoxicity in primary cultured rat hepatocytes

We examine the effect of rosmarinic acid (RA) in chemical hypoxia-induced injury in rat hepatocytes. Cell viability was significantly decreased by cobalt chloride (CoCl2), a well-known hypoxia mimetic agent in a time- and dose- dependent manner. RA pretreatment before exposure to CoCl2 significantly attenuated the CoCl2-induced decrease of cell viability. Additionally, pretreatment with RA potentiated the decrease of Bcl-2 expression and attenuated the increase of Caspase-3 expression by CoCl2. CoCl2 treatment resulted in an increase of intracellular ROS generation, which is inhibited by RA or N-acetyl-cysteine (NAC, a ROS scavenger), and p38MAPK phosphorylation, which is also blocked by RA or NAC. CoCl2-induced increase of Bax/Bcl-2 ratio and Caspase-3 expression was attenuated by RA, NAC and SB203580 (p38MAPK inhibitor). CoCl2-induced decrease of cell viability was also attenuated by RA, NAC and SB203580 pretreatment. Additionally, RA inhibited CoCl2-induced COX-2 expression and prostaglandin E2 (PGE2) secretion. Similar to the effect of RA, both NAC and NS-398 (COX-2 inhibitor) blocked CoCl2-induced COX-2 expression and PGE2 secretion. NS-398 attenuated not only CoCl2-induced increase of Bax/Bcl-2 ratio and Caspase-3 expression, but decrease of cell viability. Taken together, RA protects primary cultured rat hepatocytes against CoCl2-induced cell injury through inhibition of ROS-activated p38MAPK and COX-2/PGE2 pathway.

Cellular and molecular mechanisms in the pathogenesis of liver fibrosis: An update

There have been considerable recent advances towards a better understanding of the complex cellular and molecular network underlying liver fibrogenesis. Recent data indicate that the termination of fibrogenic processes and the restoration of deficient fibrolytic pathways may allow the reversal of advanced fibrosis and even cirrhosis. Therefore, efforts have been made to better clarify the cellular and molecular mechanisms that are involved in liver fibrosis. Activation of hepatic stellate cells (HSCs) remains a central event in fibrosis, complemented by other sources of matrix-producing cells, including portal fibroblasts, fibrocytes and bone marrow-derived myofibroblasts. These cells converge in a complex interaction with neighboring cells to provoke scarring in response to persistent injury. Defining the interaction of different cell types, revealing the effects of cytokines on these cells and characterizing the regulatory mechanisms that control gene expression in activated HSCs will enable the discovery of new therapeutic targets. Moreover, the characterization of different pathways associated with different etiologies aid in the development of disease-specific therapies. This article outlines recent advances regarding the cellular and molecular mechanisms involved in liver fibrosis that may be translated into future therapies. The pathogenesis of liver fibrosis associated with alcoholic liver disease, non-alcoholic fatty liver disease and viral hepatitis are also discussed to emphasize the various mechanisms involved in liver fibrosis.

Helicobacter hepaticus induces an inflammatory response in primary human hepatocytes

Helicobacter hepaticus can lead to chronic hepatitis and hepatocellular carcinoma in certain strains of mice. Until now the pathogenic role of Helicobacter species on human liver tissue is still not clarified though Helicobacter species identification in human liver cancer was successful in case controlled studies. Therefore we established an in vitro model to investigate the interaction of primary human hepatocytes (PHH) with Helicobacter hepaticus. Successful co-culturing of PHH with Helicobacter hepaticus was confirmed by visualization of motile bacteria by two-photon-microscopy. Isolated human monocytes were stimulated with PHH conditioned media. Changes in mRNA expression of acute phase cytokines and proteins in PHH and stimulated monocytes were determined by Real-time PCR. Furthermore, cytokines and proteins were analyzed in PHH culture supernatants by ELISA. Co-cultivation with Helicobacter hepaticus induced mRNA expression of Interleukin-1 beta (IL-1β), Tumor necrosis factor-alpha, Interleukin-8 (IL-8) and Monocyte chemotactic protein-1 (MCP-1) in PHH (p<0.05) resulting in a corresponding increase of IL-8 and MCP-1 concentrations in PHH supernatants (p<0.05). IL-8 and IL-1β mRNA expression was induced in monocytes stimulated with Helicobacter hepaticus infected PHH conditioned media (p<0.05). An increase of Cyclooxygenase-2 mRNA expression was observed, with a concomitant increase of prostaglandin E2 concentration in PHH supernatants at 24 and 48 h (p<0.05). In contrast, at day 7 of co-culture, no persistent elevation of cytokine mRNA could be detected. High expression of intercellular adhesion molecule-1 on PHH cell membranes after co-culture was shown by two-photon-microscopy and confirmed by flow-cytomety. Finally, expression of Cytochrome P450 3A4 and albumin mRNA were downregulated, indicating an impairment of hepatocyte synthesis function by Helicobacter hepaticus presence. This is the first in vitro model demonstrating a pathogenic effect of a Helicobacter spp. on human liver cells, resulting in an inflammatory response with increased synthesis of inflammatory mediators and consecutive monocyte activation.

Characterization of microparticles after hepatic ischemia-reperfusion injury

BACKGROUND

Hepatic ischemia-reperfusion (I/R) is a well-studied model of liver injury and has demonstrated a biphasic injury followed by recovery and regeneration. Microparticles (MPs) are a developing field of study and these small membrane bound vesicles have been shown to have effector function in other physiologic and pathologic states. This study was designed to quantify the levels of MPs from various cell origins-platelets, neutrophils, and endolethial cells-following hepatic ischemia-reperfusion injury.

METHODS

A murine model was used with mice undergoing 90 minutes of partial hepatic ischemia followed by various times of reperfusion. Following reperfusion, plasma samples were taken and MPs of various cell origins were labeled and levels were measured using flow cytometry. Additionally, cell specific MPs were further assessed by Annexin V, which stains for the presence of phosphatidylserine, a cell surface marker linked to apoptosis. Statistical analysis was performed using one-way analysis of variance with subsequent Student-Newman-Keuls test with data presented as the mean and standard error of the mean.

RESULTS

MPs from varying sources show an increase in circulating levels following hepatic I/R injury. However, the timing of the appearance of different MP subtypes differs for each cell type. Platelet and neutrophil-derived MP levels demonstrated an acute elevation following injury whereas endothelial-derived MP levels demonstrated a delayed elevation.

CONCLUSION

This is the first study to characterize circulating levels of cell-specific MPs after hepatic I/R injury and suggests that MPs derived from platelets and neutrophils serve as markers of inflammatory injury and may be active participants in this process. In contrast, MPs derived from endothelial cells increase after the injury response during the reparative phase and may be important in angiogenesis that occurs in the regenerating liver.

The effect of octreotide on hepatic ischemia-reperfusion injury in a rabbit model

BACKGROUND

Hepatic ischemic-reperfusion injury (HIRI) is a major cause of morbidity and mortality following liver surgery. Octreotide (Oct) has been reported to improve hepatocellular energy metabolism in a rat HIRI model. This study was designed to evaluate whether Oct could protect the liver of rabbits against ischemic-reperfusion (I/R) injury.

METHODS

Twenty-four adult New Zealand rabbits were randomly divided into a sham operated group (Control), an ischemia/reperfusion group (I/R), and an ischemia/reperfusion + Oct pretreatment group (I/R + Oct). The hemodynamic (mean arterial pressure [MAP] and heart rate [HR]) changes, liver enzymes (alanine aminotransferase [ALT], aspartate aminotransferase [AST], and lactate dehydrogenase [LDH]) release, inflammatory cytokines (tumor necrosis factor [TNF]α and interleukin [IL]-1β) levels, and endotoxin (ETX) levels were measured during I/R.

RESULTS

Compared with the Control group, the MAP decreased and HR increased in I/R and I/R + Oct groups at ischemia 15 minutes (P < .05) but were less in the I/R + Oct group relative to the I/R group (P < .05). ALT, AST, LDH, IL-1β, and ETX levels were increased in the I/R and I/R + Oct groups at ischemia 30 minutes (P < .05), however, the increase was lower in the I/R + Oct group relative to the I/R group (P < .05). Bcl-2 expression in the I/R + Oct group was higher compared with other groups (P < .05) and Bax expression in the I/R group was reduced compared with other groups (P < .05). Hepatocellular damage in the I/R + Oct group appeared to be less than in the I/R group by microscopy.

CONCLUSIONS

Oct pretreatment attenuated hemodynamic changes and decreased liver enzyme changes induced by HIRI in a rabbit model. The protection mechanisms of Oct may be related to reduced ETX levels, down-regulation of the inflammatory cytokines TNFα and IL-1β, and inhibition of hepatocellular apoptosis, as well as the modulation of the mitochondrion-mediated Bcl-2/Bax apoptosis pathway. Based on our study it appears that Oct may be useful in decreasing liver injury after liver surgery and/or transplantation and may serve as a promising agent against HIRI.

NLRP3 regulates neutrophil functions and contributes to hepatic ischemia-reperfusion injury independently of inflammasomes

Inflammation plays a key role in the pathophysiology of hepatic ischemia-reperfusion (I/R) injury. However, the mechanism by which hepatic I/R induces inflammatory responses remains unclear. Recent evidence indicates that a sterile inflammatory response triggered by I/R is mediated through a multiple-protein complex called the inflammasome. Therefore, we investigated the role of the inflammasome in hepatic I/R injury and found that hepatic I/R stimuli upregulated the inflammasome-component molecule, nucleotide-binding oligomerization domain-like receptor (NLR) family pyrin domain-containing 3 (NLRP3), but not apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC). NLRP3(-/-) mice, but not ASC(-/-) and caspase-1(-/-) mice, had significantly less liver injury after hepatic I/R. NLRP3(-/-) mice showed reduced inflammatory responses, reactive oxygen species production, and apoptosis in I/R liver. Notably, infiltration of neutrophils, but not macrophages, was markedly inhibited in the I/R liver of NLRP3(-/-) mice. Bone marrow transplantation experiments showed that NLRP3 not only in bone marrow-derived cells, but also in non-bone marrow-derived cells contributed to liver injury after I/R. In vitro experiments revealed that keratinocyte-derived chemokine-induced activation of heterotrimeric G proteins was markedly diminished. Furthermore, NLRP3(-/-) neutrophils decreased keratinocyte-derived chemokine-induced concentrations of intracellular calcium elevation, Rac activation, and actin assembly formation, thereby resulting in impaired migration activity. Taken together, NLRP3 regulates chemokine-mediated functions and recruitment of neutrophils, and thereby contributes to hepatic I/R injury independently of inflammasomes. These findings identify a novel role of NLRP3 in the pathophysiology of hepatic I/R injury.

Sivelestat sodium hydrate inhibits neutrophil migration to the vessel wall and suppresses hepatic ischemia-reperfusion injury

BACKGROUND

Sivelestat sodium hydrate (sivelestat) is a specific neutrophil elastase inhibitor that is effective in treating acute lung injury associated with systemic inflammatory response syndrome. As such, it may be useful in treating hepatic ischemia-reperfusion injury (IRI), a condition in which neutrophils transmigrate into the interstitium, leading to release of neutrophil elastase from neutrophils and consequent damage to the affected tissue, particularly in cases of hepatic failure after liver transplantation or massive liver resection.

AIMS

The purpose of this study was to examine whether treatment with sivelestat inhibits neutrophil adhesion and migration to the vessel wall and suppresses hepatic IRI.

METHODS

Whether and, if so, the extent to which sivelestat suppresses the adhesion and migration of neutrophils and reduces liver damage in hepatic IRI was examined in a human umbilical vein endothelial cell (HUVEC) model and a rat hepatic IRI model.

RESULTS

In the HUVEC model, the extent of the adhesion and migration of neutrophils stimulated by platelet-activating factor were found to be dose-dependently inhibited by sivelestat treatment (p < 0.05). In the rat model, serum liver enzyme levels were significantly lower at 12 h after reperfusion, and the number of neutrophils that had migrated to extravascular sites was significantly less in the treatment group compared to the control group (p < 0.05).

CONCLUSION

Sivelestat inhibits the adhesion and migration of neutrophils to vascular endothelium in hepatic IRI, thereby suppressing liver injury.

Protective role of bortezomib in steatotic liver ischemia/reperfusion injury through abrogation of MMP activation and YKL-40 expression

Steatotic liver grafts tolerate ischemia-reperfusion (I/R) injury poorly, contributing to poor survival following transplantation. However the molecular mechanisms leading to I/R injury still remain to be defined. We have previously reported that the protective effect of bortezomib towards inhibiting cold induced I/R injury in obese rat liver transplant model is through NF-κB down modulation. In this report using an orthotopic liver transplant (OLT) model in Zucker rats (from obese, leptin deficient donor, to lean recipient) we defined the mechanisms of steatotic liver injury, and characterized the role of bortezomib in inhibiting MMP activation and YKL-40, both of which are involved in extracellular matrix deposition and fibrosis, the key pathological features of liver allograft failure. Obese donor rats were treated with bortezomib (i.v., 0.1mg/kg immediately prior to liver procurement) to assess the role of MMP and YKL-40 in steatotic liver I/R injury. I/R injury in steatotic livers resulted in significant increases in expression of YKL-40 (9 fold), and activation of MMP-2 (15 fold)/MMP-9 (12 fold). Bortezomib treatment reduced the expression of YKL-40 and MMP to basal levels. Bortezomib also inhibited the pro-fibrotic (VEGF, HGF, bFGF, TGF-β) and pro-inflammatory (IL-1β, TNF-α and IFN-γ) cytokines significantly in comparison to untreated animals with I/R injury. These results demonstrate that I/R injury in steatotic livers following transplantation are associated with MMP activation and YKL-40 upregulation resulting in pro-fibrotic and pro-inflammatory cytokine release. Administration of the proteosomal inhibitor, bortezomib, effectively attenuated the I/R injury by inhibiting MMP and YKL-40 expression and therefore support the clinical utility of this drug in donor management for preventing I/R injury and its sequelae.

Riboflavin (vitamin B-2) reduces hepatocellular injury following liver ischaemia and reperfusion in mice

Riboflavin has been shown to exhibit anti-inflammatory and antioxidant properties in the settings of experimental sepsis and ischaemia/reperfusion (I/R) injury. We investigated the effect of riboflavin on normothermic liver I/R injury. Mice were submitted to 60 min of ischaemia plus saline or riboflavin treatment (30 μmoles/kg BW) followed by 6 h of reperfusion. Hepatocellular injury was evaluated by aminotransferase levels, reduced glutathione (GSH) content and the histological damage score. Hepatic neutrophil accumulation was assessed using the naphthol method and by measuring myeloperoxidase activity. Hepatic oxidative/nitrosative stress was estimated by immunohistochemistry. Liver endothelial and inducible nitric oxide synthase (eNOS/iNOS) and nitric oxide (NO) amounts were assessed by immunoblotting and a chemiluminescence assay. Riboflavin significantly reduced serum and histological parameters of hepatocellular damage, neutrophil infiltration and oxidative/nitrosative stress. Furthermore, riboflavin infusion partially recovered hepatic GSH reserves and decreased the liver contents of eNOS/iNOS and NO. These data indicate that riboflavin exerts antioxidant and anti-inflammatory effects in the ischaemic liver, protecting hepatocytes against I/R injury. The mechanism of these effects appears to be related to the intrinsic antioxidant potential of riboflavin/dihydroriboflavin and to reduced hepatic expression of eNOS/iNOS and reduced NO levels, culminating in attenuation of oxidative/nitrosative stress and the acute inflammatory response.

Neutrophil activation during acetaminophen hepatotoxicity and repair in mice and humans

Following acetaminophen (APAP) overdose there is an inflammatory response triggered by the release of cellular contents from necrotic hepatocytes into the systemic circulation which initiates the recruitment of neutrophils into the liver. It has been demonstrated that neutrophils do not contribute to APAP-induced liver injury, but their role and the role of NADPH oxidase in injury resolution are controversial. C57BL/6 mice were subjected to APAP overdose and neutrophil activation status was determined during liver injury and liver regeneration. Additionally, human APAP overdose patients (ALT: >800 U/L) had serial blood draws during the injury and recovery phases for the determination of neutrophil activation. Neutrophils in the peripheral blood of mice showed an increasing activation status (CD11b expression and ROS priming) during and after the peak of injury but returned to baseline levels prior to complete injury resolution. Hepatic sequestered neutrophils showed an increased and sustained CD11b expression, but no ROS priming was observed. Confirming that NADPH oxidase is not critical to injury resolution, gp91(phox)⁻/⁻ mice following APAP overdose displayed no alteration in injury resolution. Peripheral blood from APAP overdose patients also showed increased neutrophil activation status after the peak of liver injury and remained elevated until discharge from the hospital. In mice and humans, markers of activation, like ROS priming, were increased and sustained well after active liver injury had subsided. The similar findings between surviving patients and mice indicate that neutrophil activation may be a critical event for host defense or injury resolution following APAP overdose, but not a contributing factor to APAP-induced injury.

Microbiota and nonalcoholic steatohepatitis

The recent rise in obesity-related diseases, such as nonalcoholic fatty liver disease and its strong association with microbiota, has elicited interest in the underlying mechanisms of these pathologies. Experimental models have highlighted several mechanisms connecting microbiota to the development of liver dysfunction in nonalcoholic steatohepatitis (NASH) such as increased energy harvesting from the diet, small intestine bacterial overgrowth, modulation of the intestinal barrier by glucagon-like peptide-2 secretions, activation of innate immunity through the lipopolysaccharide-CD14 axis caused by obesity-induced leptin, periodontitis, and sterile inflammation. The manipulation of microbiota through probiotics, prebiotics, antibiotics, and periodontitis treatment yields encouraging results for the treatment of obesity, diabetes, and NASH, but data in humans is scarce.

Chemokines in chronic liver allograft dysfunction pathogenesis and potential therapeutic targets

Despite advances in immunosuppressive drugs, long-term success of liver transplantation is still limited by the development of chronic liver allograft dysfunction. Although the exact pathogenesis of chronic liver allograft dysfunction remains to be established, there is strong evidence that chemokines are involved in organ damage induced by inflammatory and immune responses after liver surgery. Chemokines are a group of low-molecular-weight molecules whose function includes angiogenesis, haematopoiesis, mitogenesis, organ fibrogenesis, tumour growth and metastasis, and participating in the development of the immune system and in inflammatory and immune responses. The purpose of this review is to collect all the research that has been done so far concerning chemokines and the pathogenesis of chronic liver allograft dysfunction and helpfully, to pave the way for designing therapeutic strategies and pharmaceutical agents to ameliorate chronic allograft dysfunction after liver transplantation.

Nonsteroidal anti-inflammatory drug induces proinflammatory damage in gastric mucosa through NF-κB activation and neutrophil infiltration: anti-inflammatory role of heme oxygenase-1 against nonsteroidal anti-inflammatory drug

Nonsteroidal anti-inflammatory drug (NSAID)-induced mitochondrial oxidative stress (MOS) is an important prostaglandin (PG)-independent pathway of the induction of gastric mucosal injury. However, the molecular mechanism behind MOS-mediated gastric pathology is still obscure. In various pathological conditions of tissue injury oxidative stress is often linked with inflammation. Here we report that MOS induced by indomethacin (an NSAID) induces gastric mucosal inflammation leading to proinflammatory damage. Indomethacin, time dependently stimulated the expression of proinflammatory molecules such as intercellular adhesion molecule 1(ICAM-1), vascular cell adhesion molecule 1(VCAM-1), interleukin1β (IL-1β), and monocyte chemotactic protein-1 (MCP-1) in gastric mucosa in parallel with the increase of neutrophil infiltration and injury of gastric mucosa in rat. Western immunoblotting and confocal microscopic studies revealed that indomethacin induced nuclear translocation of nuclear factor kappa-B (NF-κB) in gastric mucosal cells, which resulted in proinflammatory signaling. The prevention of MOS by antioxidant tryptamine-gallic acid hybrid (SEGA) inhibited indomethacin-induced expression of ICAM-1, VCAM-1, IL-1β, and MCP-1. SEGA also prevented indomethacin-induced NF-κB activation and neutrophil infiltration as documented by chromatin immunoprecipitation studies and neutrophil migration assay, respectively. Heme oxygenase-1 (HO-1), a cytoprotective enzyme associated with tissue repair mechanisms is stimulated in response to oxidative stress. We have investigated the role of HO-1 against MOS and MOS-mediated inflammation in recovering from gastropathy. Indomethacin stimulated the expression of HO-1 and indomethacin-stimulated HO-1 expression was reduced by SEGA, an antioxidant, which could prevent MOS. Thus, the data suggested that the induction of HO-1 was a protective response against MOS developed by indomethacin. Moreover, the induction of HO-1 by cobalt protoporphyrin inhibited inflammation and chemical silencing of HO-1 by zinc protoporphyrin aggravated the inflammation by indomethacin. Thus, NSAID by promoting MOS-induced proinflammatory response damaged gastric mucosa and HO-1 protected NSAID-induced gastric mucosal damage by preventing NF-κB activation and proinflammatory activity.

Osteopontin is an initial mediator of inflammation and liver injury during obstructive cholestasis after bile duct ligation in mice

Osteopontin (OPN) is a chemotactic factor which can be cleaved to the pro-inflammatory form by matrix metalloproteinases (MMPs). To test the hypothesis that OPN can modulate inflammatory liver injury during cholestasis, wild-type (WT) C57BL/6 and OPN knockout (OPN-KO) mice underwent bile duct ligation (BDL). OPN-KO mice showed significant reduction in liver injury (plasma ALT and necrosis) and neutrophil recruitment compared with WT animals at 24h but not 72h after BDL. In WT mice, a 4-fold increase in hepatic MMP-3 mRNA and elevated MMP activities and cleaved OPN levels were observed in bile. WT mice subjected to BDL in the presence of the MMP inhibitor BB-94 showed reduced liver injury, less neutrophil extravasation and diminished levels of cleaved OPN in bile. Thus, during obstructive cholestasis, OPN released from biliary epithelial cells could be cleaved by MMPs in bile. When the biliary system leaks, cleaved OPN enters the parenchyma and attracts neutrophils. In the absence of OPN, other chemoattractants, e.g. chemokines, mediate a delayed inflammatory response and injury. Taken together, our data suggest that OPN is the pro-inflammatory mediator that initiates the early neutrophil-mediated injury phase during obstructive cholestasis in mice.

Oxysterols and redox signaling in the pathogenesis of non-alcoholic fatty liver disease

Oxysterols are oxidized species of cholesterol coming from exogenous (e.g. dietary) and endogenous (in vivo) sources. They play critical roles in normal physiologic functions such as regulation of cellular cholesterol homeostasis. Most of biological effects are mediated by interaction with nuclear receptor LXRα, highly expressed in the liver as well as in many other tissues. Such interaction participates in the regulation of whole-body cholesterol metabolism, by acting as "lipid sensors". Moreover, it seems that oxysterols are also suspected to play key roles in several pathologies, including cardiovascular and inflammatory disease, cancer, and neurodegeneration. Growing evidence suggests that oxysterols may contribute to liver injury in non-alcoholic fatty liver disease. The present review focuses on the current status of knowledge on oxysterols' biological role, with an emphasis on LXR signaling and oxysterols' physiopathological relevance in NAFLD, suggesting new pharmacological development that needs to be addressed in the near future.

Chronic plus binge ethanol feeding synergistically induces neutrophil infiltration and liver injury in mice: a critical role for E-selectin

Chronic plus binge ethanol feeding acts synergistically to induce liver injury in mice, but the mechanisms underlying this phenomenon remain unclear. Here, we show that chronic plus binge ethanol feeding synergistically up-regulated the hepatic expression of interleukin-1β and tumor necrosis factor alpha and induced neutrophil accumulation in the liver, compared with chronic or binge feeding alone. In vivo depletion of neutrophils through administration of an anti-Ly6G antibody markedly reduced chronic-binge ethanol feeding-induced liver injury. Real-time polymerase chain reaction analyses revealed that hepatic E-selectin expression was up-regulated 10-fold, whereas expression of other neutrophil infiltration-related adhesion molecules (e.g., P-selectin, intercellular adhesion molecule 1, and vascular cell adhesion molecule 1) was slightly up- or down-regulated in this chronic-binge model. The genetic deletion of E-selectin prevented chronic-binge ethanol-induced hepatic neutrophil infiltration as well as elevation of serum transaminases without affecting ethanol-induced steatosis. In addition, E-selectin-deficient mice showed reduced hepatic expression of several proinflammatory cytokines, chemokines, and adhesion molecules, compared to wild-type mice, after chronic-binge ethanol feeding. Finally, the expression of E-selectin was highly up-regulated in human alcoholic fatty livers, but not in alcoholic cirrhosis.

CONCLUSIONS

Chronic-binge ethanol feeding up-regulates expression of proinflammatory cytokines, followed by the induction of E-selectin. Elevated E-selectin plays an important role in hepatic neutrophil infiltration and injury induced by chronic-binge feeding in mice and may also contribute to the pathogenesis of early stages of human alcoholic liver disease.

Plasma biomarkers of liver injury and inflammation demonstrate a lack of apoptosis during obstructive cholestasis in mice

Cholestasis is a pathological common component of numerous liver diseases that results in hepatotoxicity, inflammation, and cirrhosis when untreated. While the predominant hypothesis in cholestatic liver injury remains hepatocyte apoptosis due to direct toxicity of hydrophobic bile acid exposure, recent work suggests that the injury occurs through inflammatory necrosis. In order to resolve this controversy, we used novel plasma biomarkers to assess the mechanisms of cell death during early cholestatic liver injury. C57Bl/6 mice underwent bile duct ligation (BDL) for 6-72 h, or sham operation. Another group of mice were given d-galactosamine and endotoxin as a positive control for apoptosis and inflammatory necrosis. Plasma levels of full length cytokeratin-18 (FL-K18), microRNA-122 (miR-122) and high mobility group box-1 protein (HMGB1) increased progressively after BDL with peak levels observed after 48 h. These results indicate extensive cell necrosis after BDL, which is supported by the time course of plasma alanine aminotransferase activities and histology. In contrast, plasma caspase-3 activity, cleaved caspase-3 protein and caspase-cleaved cytokeratin-18 fragments (cK18) were not elevated at any time during BDL suggesting the absence of apoptosis. In contrast, all plasma biomarkers of necrosis and apoptosis were elevated 6 h after Gal/End treatment. In addition, acetylated HMGB1, a marker for macrophage and monocyte activation, was increased as early as 12 h but mainly at 48-72 h. However, progressive neutrophil accumulation in the area of necrosis started at 6h after BDL. In conclusion, these data indicate that early cholestatic liver injury in mice is an inflammatory event, and occurs through necrosis with little evidence for apoptosis.

Protective Effects of Geniposide and Genipin against Hepatic Ischemia/Reperfusion Injury in Mice

Geniposide is an active product extracted from the gardenia fruit, and is one of the most widely used herbal preparations for liver disorders. This study examined the cytoprotective properties of geniposide and its metabolite, genipin, against hepatic ischemia/reperfusion (I/R) injury. C57BL/6 mice were subjected to 60 min of ischemia followed by 6 h of reperfusion. Geniposide (100 mg/kg) and genipin (50 mg/kg) were administered orally 30 min before ischemia. In the I/R mice, the levels of serum alanine aminotransferase and hepatic lipid peroxidation were elevated, whereas hepatic glutathione/glutathione disulfide ratio was decreased. These changes were attenuated by geniposide and genipin administration. On the other hand, increased hepatic heme oxygenase-1 protein expression was potentiated by geniposide and genipin administration. The increased levels of tBid, cytochrome c protein expression and caspase-3 activity were attenuated by geniposide and genipin. Increased apoptotic cells in the I/R mice were also significantly reduced by geniposide and genipin treatment. Our results suggest that geniposide and genipin offer significant hepatoprotection against I/R injury by reducing oxidative stress and apoptosis.

Recent advances in 2D and 3D in vitro systems using primary hepatocytes, alternative hepatocyte sources and non-parenchymal liver cells and their use in investigating mechanisms of hepatotoxicity, cell signaling and ADME

This review encompasses the most important advances in liver functions and hepatotoxicity and analyzes which mechanisms can be studied in vitro. In a complex architecture of nested, zonated lobules, the liver consists of approximately 80 % hepatocytes and 20 % non-parenchymal cells, the latter being involved in a secondary phase that may dramatically aggravate the initial damage. Hepatotoxicity, as well as hepatic metabolism, is controlled by a set of nuclear receptors (including PXR, CAR, HNF-4α, FXR, LXR, SHP, VDR and PPAR) and signaling pathways. When isolating liver cells, some pathways are activated, e.g., the RAS/MEK/ERK pathway, whereas others are silenced (e.g. HNF-4α), resulting in up- and downregulation of hundreds of genes. An understanding of these changes is crucial for a correct interpretation of in vitro data. The possibilities and limitations of the most useful liver in vitro systems are summarized, including three-dimensional culture techniques, co-cultures with non-parenchymal cells, hepatospheres, precision cut liver slices and the isolated perfused liver. Also discussed is how closely hepatoma, stem cell and iPS cell-derived hepatocyte-like-cells resemble real hepatocytes. Finally, a summary is given of the state of the art of liver in vitro and mathematical modeling systems that are currently used in the pharmaceutical industry with an emphasis on drug metabolism, prediction of clearance, drug interaction, transporter studies and hepatotoxicity. One key message is that despite our enthusiasm for in vitro systems, we must never lose sight of the in vivo situation. Although hepatocytes have been isolated for decades, the hunt for relevant alternative systems has only just begun.

Absence of a p53 allele delays nitrogen mustard-induced early apoptosis and inflammation of murine skin

Bifunctional alkylating agent sulfur mustard (SM) and its analog nitrogen mustard (NM) cause DNA damage leading to cell death, and potentially activating inflammation. Transcription factor p53 plays a critical role in DNA damage by regulating cell cycle progression and apoptosis. Earlier studies by our laboratory demonstrated phosphorylation of p53 at Ser15 and an increase in total p53 in epidermal cells both in vitro and in vivo following NM exposure. To elucidate the role of p53 in NM-induced skin toxicity, we employed SKH-1 hairless mice harboring wild type (WT) or heterozygous p53 (p53+/-). Exposure to NM (3.2mg) caused a more profound increase in epidermal thickness and apoptotic cell death in WT relative to p53+/- mice at 24h. However, by 72h after exposure, there was a comparable increase in NM-induced epidermal cell death in both WT and p53+/- mice. Myeloperoxidase activity data showed that neutrophil infiltration was strongly enhanced in NM-exposed WT mice at 24h persisting through 72h of exposure. Conversely, robust NM-induced neutrophil infiltration (comparable to WT mice) was seen only at 72h after exposure in p53+/- mice. Similarly, NM-exposure strongly induced macrophage and mast cell infiltration in WT, but not p53+/- mice. Together, these data indicate that early apoptosis and inflammation induced by NM in mouse skin are p53-dependent. Thus, targeting this pathway could be a novel strategy for developing countermeasures against vesicants-induced skin injury.

Atrial natriuretic peptide reduces hepatic ischemia-reperfusion injury in rabbits

PURPOSE

Atrial natriuretic peptide (ANP) has been known to be protective against hepatic ischemia/reperfusion injury. The purpose of this study was to verify the hypothesis that ANP conserves microvascular circulation and reduces ischemia-reperfusion injury in the in vivo rabbit model.

METHODS

With IRB approval, 30 male Japanese white rabbits under pentobarbital anesthesia were studied. These animals were randomly assigned to the following three groups (n = 10 each): control, ANP, and sham group. Animals in the ANP group received continuous infusion of ANP at 0.1 μg/kg/min throughout the study period. Animals in control and ANP groups underwent 90 min of partial hepatic ischemia by clamping the right hepatic artery and portal vein. Descending aortic blood flow (AoF) was monitored with a transit-time ultrasound flowmeter. Hepatic tissue microvascular blood flow (HTBF) at both right (ischemic) and left (nonischemic) lobe was intermittently evaluated with the hydrogen clearance method. After 180 min of reperfusion, hepatic injury was determined with serum AST and ALT. Galactose clearance of reperfused right lobe was also measured as an indicator of hepatic metabolic function. Histopathological change and the number of apoptotic hepatocytes were also evaluated.

RESULTS

Systemic hemodynamic data including mean arterial pressure, heart rate, and AoF did not differ among the three groups during the study period. ANP attenuated ischemia-induced right HTBF decrease. ANP also suppressed histopathological degeneration, apoptosis, and decline in galactose clearance after reperfusion.

CONCLUSIONS

ANP attenuated hepatic microvascular dysfunction and hepatocyte injury after reperfusion without significant hemodynamic change.

Matrix metalloproteinase-9 in the initial injury after hepatectomy in mice

AIM

To investigate the role of matrix metalloproteinase (MMP)-9 in the pathogenesis of postoperative liver failure (PLF) after extended hepatectomy (EH).

METHODS

An insufficient volume of the remnant liver (RL) results in higher morbidity and mortality, and a murine model with 80%-hepatectomy was used. All investigations were performed 6 h after EH. Mice were first divided into two groups based on the postoperative course (i.e., the PLF caused or did not), and MMP-9 expression was measured by Western blotting. The source of MMP-9 was then determined by immunohistological stainings. Tissue inhibitor of metalloproteinase (TIMP)-1 is the endogenous inhibitor of MMP-9, and MMP-9 behavior was assessed by the experiments in wild-type, MMP-9(-/-) and TIMP-1(-/-) mice by Western blotting and gelatin zymography. The behavior of neutrophils was also assessed by immunohistological stainings. An anti-MMP-9 monoclonal antibody and a broad-spectrum MMP inhibitor were used to examine the role of MMP-9.

RESULTS

Symptomatic mice showed more severe PLF (histopathological assessments: 2.97 ± 0.92 vs 0.11 ± 0.08, P < 0.05) and a higher expression of MMP-9 (71085 ± 18274 vs 192856 ± 22263, P < 0.01). Nonnative leukocytes appeared to be the main source of MMP-9, because MMP-9 expression corresponding with CD11b positive-cell was observed in the findings of immunohistological stainings. In the histopathological findings, the PLF was improved in MMP-9(-/-) mice (1.65% ± 0.23% vs 0.65% ± 0.19%, P < 0.01) and it was worse in TIMP-1(-/-) mice (1.65% ± 0.23% vs 1.78% ± 0.31%, P < 0.01). Moreover, neutrophil migration was disturbed in MMP-9(-/-) mice in the immunohistological stainings. Two methods of MMP-9 inhibition revealed reduced PLF, and neutrophil migration was strongly disturbed in MMP-9-blocked mice in the histopathological assessments (9.6 ± 1.9 vs 4.2 ± 1.2, P < 0.05, and 9.9 ± 1.5 vs 5.7 ± 1.1, P < 0.05).

CONCLUSION

MMP-9 is important for the process of PLF. The initial injury is associated with MMP-9 derived from neutrophils, and MMP-9 blockade reduces PLF. MMP-9 may be a potential target to prevent PLF after EH and to overcome an insufficient RL.