Focal liver necrosis appears early after partial hepatectomy and is dependent on T cells and antigen delivery from the gut

Paeoniflorin protects hepatocytes from APAP-induced damage through launching autophagy via the MAPK/mTOR signaling pathway

BACKGROUND

Drug-induced liver injury (DILI) is gradually becoming a common global problem that causes acute liver failure, especially in acute hepatic damage caused by acetaminophen (APAP). Paeoniflorin (PF) has a wide range of therapeutic effects to alleviate a variety of hepatic diseases. However, the relationship between them is still poorly investigated in current studies.

PURPOSE

This work aimed to explore the protective effects of PF on APAP-induced hepatic damage and researched the potential molecular mechanisms.

METHODS

C57BL/6J male mice were injected with APAP to establish DILI model and were given PF for five consecutive days for treatment. Aiming to clarify the pharmacological effects, the molecular mechanisms of PF in APAP-induced DILI was elucidated by high-throughput and other techniques.

RESULTS

The results demonstrated that serum levels of ALP, γ-GT, AST, TBIL, and ALT were decreased in APAP mice by the preventive effects of PF. Moreover, PF notably alleviated hepatic tissue inflammation and edema. Meanwhile, the results of TUNEL staining and related apoptotic factors coincided with the results of transcriptomics, suggesting that PF inhibited hepatocyte apoptosis by regulated MAPK signaling. Besides, PF also acted on reactive oxygen species (ROS) to regulate the oxidative stress for recovery the damaged mitochondria. More importantly, transmission electron microscopy showed the generation of autophagosomes after PF treatment, and PF was also downregulated mTOR and upregulated the expression of autophagy markers such as ATG5, ATG7, and BECN1 at the mRNA level and LC3, p62, ATG5, and ATG7 at the protein level, implying that the process by which PF exerted its effects was accompanied by the occurrence of autophagy. In addition, combinined with molecular dynamics simulations and western blotting of MAPK, the results suggested p38 as a direct target for PF on APAP. Specifically, PF-activated autophagy through the downregulation of MAPK/mTOR signaling, which in turn reduced APAP injury.

CONCLUSIONS

Paeoniflorin mitigated liver injury by activating autophagy to suppress oxidative stress and apoptosis via the MAPK/mTOR signaling pathway. Taken together, our findings elucidate the role and mechanism of paeoniflorin in DILI, which is expected to provide a new therapeutic strategy for the development of paeoniflorin.

Gelatin scaffold ameliorates proliferation & stem cell differentiation into the hepatic like cell and support liver regeneration in partial-hepatectomized mice model

Stem cell-based tissue engineering is an emerging tool for developing functional tissues of choice. To understand pluripotency and hepatic differentiation of mouse embryonic stem cells (mESCs) on a three-dimensional (3D) scaffold, we established an efficient approach for generating hepatocyte-like cells (HLCs) from hepatoblast cells. We developed porous and biodegradable scaffold, which was stimulated with exogenous growth factors and investigated stemness and differentiation capacity of mESCs into HLCs on the scaffoldin-vitro. In animal studies, we had cultured mESCs-derived hepatoblast-like cells on the scaffold and then, transplanted them into the partially hepatectomized C57BL/6 male mice model to evaluate the effect of gelatin scaffold on hepatic regeneration. The 3D culture system allowed maintenance of stemness properties in mESCs. The step-wise induction of mESCs with differentiation factors leads to the formation of HLCs and expressed liver-specific genes, including albumin, hepatocyte nucleic factor 4 alpha, and cytokeratin 18. In addition, cells also expressed Ki67, indicating cells are proliferating. The secretome showed expression of albumin, urea, creatinine, alanine transaminase, and aspartate aminotransferase. However, the volume of the excised liver which aids regeneration has not been studied. Our results indicate that hepatoblast cells on the scaffold implanted in PH mouse indicates that these cells efficiently differentiate into HLCs and cholangiocytes, forming hepatic lobules with central and portal veins, and bile duct-like structures with neovascularization. The gelatin scaffold provides an efficient microenvironment for liver differentiation and regeneration bothin-vitroandin-vivo. These hepatoblasts cells would be a valuable source for 3D liver tissue engineering/transplantation in liver diseases.

Serine proteases mediate leukocyte recruitment and hepatic microvascular injury in the acute phase following extended hepatectomy

OBJECTIVE

Post-hepatectomy liver failure (PHLF) is the main limitation of extended liver resection. The molecular mechanism and the role of leukocytes in the development of PHLF remain to be unveiled. We aimed to address the impact of serine proteases (SPs) on the acute phase after liver resection by intravitally analyzing leukocyte recruitment and changes in hemodynamics and microcirculation of the liver.

METHODS

C57BL/6 mice undergoing 60% partial hepatectomy were treated with aprotinin (broad-spectrum SP inhibitor), tranexamic acid (plasmin inhibitor), or vehicle. Sham-operated animals served as controls. In vivo fluorescence microscopy was used to quantify leukocyte-endothelial interactions immediately after, as well as 120 min after partial hepatectomy in postsinusoidal venules, along with measurement of sinusoidal perfusion rate and postsinusoidal shear rate. Recruitment of leukocytes, neutrophils, T cells, and parameters of liver injury were assessed in tissue/blood samples.

RESULTS

Leukocyte recruitment, sinusoidal perfusion failure rate, and shear rate were significantly increased in mice after 60% partial hepatectomy compared to sham-operated animals. The inhibition of SPs or plasmin significantly attenuated leukocyte recruitment and improved the perfusion rate in the remnant liver. ICAM-1 expression and neutrophil recruitment significantly increased after 60% partial hepatectomy and were strongly reduced by plasmin inhibition.

CONCLUSIONS

Endothelial activation and leukocyte recruitment in the liver in response to the increment of sinusoidal shear rate were hallmarks in the acute phase after liver resection. SPs mediated leukocyte recruitment and contributed to the impairment of sinusoidal perfusion in an ICAM-1-dependent manner in the acute phase after liver resection.

Paeoniflorin Protects against Acetaminophen-Induced Liver Injury in Mice via JNK Signaling Pathway

BACKGROUND

Drug-induced liver injury (DILI), represented by acetaminophen (APAP), is a common cause of acute liver failure in clinics. Paeoniflorin (PF) has been proven to demonstrate a significant hepatoprotective effect. However, it is still unclear whether it can be a potential agent against hepatotoxicity induced by APAP. This study aimed to explore the preventive and therapeutic effects and mechanisms of PF on APAP-induced liver injury.

METHODS

Different doses of PF (50, 100, and 200 mg/kg) were given to C57BL/6 male mice for five consecutive days. After 12 h of APAP (250 mg/kg i.p.) treatment, blood and liver tissues were collected and isolated for detection.

RESULTS

The results showed that the therapeutic effects of PF on APAP mice were presented in the downregulation of the content of serum indices and significantly improved hepatic tissue edema and inflammatory infiltration. Meanwhile, PF reduces the level of the mitochondrial metabolic enzyme. Ulteriorly, it was found that PF has a downregulating effect on the apoptotic reaction and could inhibit the protein expression of CYP2E1/JNK signaling, which in turn reduces the damage of APAP.

CONCLUSION

Our findings showed that PF acted as a protective agent against APAP-induced hepatotoxicity by inhibiting JNK-related signals, suggesting a novel insight into treating APAP-induced liver injury.

Hepatoprotective Effects of Glycyrrhetinic Acid on Lithocholic Acid-Induced Cholestatic Liver Injury Through Choleretic and Anti-Inflammatory Mechanisms

Cholestasis is a clinical syndrome triggered by the accumulation and aggregation of bile acids by subsequent inflammatory responses. The present study investigated the protective effect of glycyrrhetinic acid (GA) on the cholestatic liver injury induced by lithocholic acid (LCA) from both anti-inflammatory and choleretic mechanistic standpoints. Male C57BL/6 mice were treated with LCA twice daily for 4 days to induce intrahepatic cholestasis. GA (50 mg/kg) and pregnenolone 16α-carbonitrile (PCN, 45 mg/kg) were intraperitoneally injected 3 days before and throughout the administration of LCA, respectively. Plasma biochemical indexes were determined by assay kits, and hepatic bile acids were quantified by LC-MS/MS. Hematoxylin and eosin staining of liver sections was performed for pathological examination. Protein expression of the TLRs/NF-κB pathway and the mRNA levels of inflammatory cytokines and chemokines were examined by Western blotting and PCR, respectively. Finally, the hepatic expression of pregnane X receptor (PXR) and farnesoid X receptor (FXR) and their target genes encoding metabolic enzymes and transporters was evaluated. GA significantly reversed liver necrosis and decreased plasma ALT and ALP activity. Plasma total bile acids, total bilirubin, and hepatic bile acids were also remarkably preserved. More importantly, the recruitment of inflammatory cells to hepatic sinusoids was alleviated. Additionally, the protein expression of TLR2, TLR4, and p-NF-κBp65 and the mRNA expression of CCL2, CXCL2, IL-1β, IL-6, and TNF-α were significantly decreased. Moreover, GA significantly increased the expression of hepatic FXR and its target genes, including BSEP, MRP3, and MRP4. In conclusion, GA protects against LCA-induced cholestatic liver injury by inhibiting the TLR2/NF-κB pathway and upregulating hepatic FXR expression.

Spleen: Reparative Regeneration and Influence on Liver

This review considers experimental findings on splenic repair, obtained in two types of small animal (mouse, rat, and rabbit) models: splenic resections and autologous transplantations of splenic tissue. Resection experiments indicate that the spleen is able to regenerate, though not necessarily to the initial volume. The recovery lasts one month and preserves the architecture, albeit with an increase in the relative volume of lymphoid follicles. The renovated tissues, however, exhibit skewed functional profiles; notably, the decreased production of antibodies and the low cytotoxic activity of T cells, consistent with the decline of T-dependent zones and prolonged reduction in T cell numbers. Species-specific differences are evident as well, with the post-repair organ mass deficiency most pronounced in rabbit models. Autotransplantations of splenic material are of particular clinical interest, as the procedure can possibly mitigate the development of post-splenectomy syndrome. Under these conditions, regeneration lasts 1-2 months, depending on the species. The transplants effectively destroy senescent erythrocytes, assist in microbial clearance, and produce antibodies, thus averting sepsis and bacterial pneumonia. Meanwhile, cellular sources of splenic recovery in such models remain obscure, as well as the time required for T and B cell number reconstitution.

Different effects of ursodeoxycholic acid on intrahepatic cholestasis in acute and recovery stages induced by alpha-naphthylisothiocyanate in mice

The aim of this study was to determine the effect of ursodeoxycholic acid (UDCA) on the alpha-naphthylisothiocyanate (ANIT)-induced acute and recovery stage of cholestasis model mice. In the acute stage of model mice, pretreatment with UDCA (25, 50, and 100 mg·kg^-1, ig) for 12 days prior to ANIT administration (50 mg·kg^-1, ig) resulted in the dramatic increase in serum biochemistry, with aggrevation of bile infarcts and hepatocyte necrosis. The elevation of beta-muricholic acid (β-MCA), cholic acid (CA), and taurocholic acid (TCA) in serum and liver, and reduction of these bile acids (BAs) in bile was observed. In contrast, in the recovery stage of model mice, treatment with UDCA (25, 50, and 100 mg·kg^-1, ig) for 7 days after ANIT administration (50 mg·kg^-1, ig) resulted in the significant decrease in levels of serum alanine aminotransferase (ALT) and total bile acid (TBA). Liver injury was attenuated, and the levels of TBA, CA, TCA, and β-MCA in the liver were significantly decreased. Additionally, UDCA can upregulate expression of BSEP, but it cannot upregulate expression of AE2. UDCA, which induced BSEP to increase bile acid-dependent bile flow, aggravated cholestasis and liver injury when the bile duct was obstructed in the acute stage of injury in model mice. In contrast, UDCA alleviated cholestasis and liver injury induced by ANIT when the obstruction was improved in the recovery stage.

Large-Scale Quantitative Proteomics Identifies the Ubiquitin Ligase Nedd4-1 as an Essential Regulator of Liver Regeneration

The liver is the only organ in mammals that fully regenerates even after major injury. To identify orchestrators of this regenerative response, we performed quantitative large-scale proteomics analysis of cytoplasmic and nuclear fractions from normal versus regenerating mouse liver. Proteins of the ubiquitin-proteasome pathway were rapidly upregulated after two-third hepatectomy, with the ubiquitin ligase Nedd4-1 being a top hit. In vivo knockdown of Nedd4-1 in hepatocytes through nanoparticle-mediated delivery of small interfering RNA caused severe liver damage and inhibition of cell proliferation after hepatectomy, resulting in liver failure. Mechanistically, we demonstrate that Nedd4-1 is required for efficient internalization of major growth factor receptors involved in liver regeneration and their downstream mitogenic signaling. These results highlight the power of large-scale proteomics to identify key players in liver regeneration and the importance of posttranslational regulation of growth factor signaling in this process. Finally, they identify an essential function of Nedd4-1 in tissue repair.

Impact of NKT Cells and LFA-1 on Liver Regeneration under Subseptic Conditions

Background

Activation of the immune system in terms of subseptic conditions during liver regeneration is of paramount clinical importance. However, little is known about molecular mechanisms and their mediators that control hepatocyte proliferation. We sought to determine the functional role of immune cells, especially NKT cells, in response to partial hepatectomy (PH), and to uncover the impact of the integrin lymphocyte function-associated antigen-1 (LFA-1) on liver regeneration in a subseptic setting.

Methods

Wild-type (WT) and LFA-1^-/- mice underwent a 2/3 PH and low-dose lipopolysaccharid (LPS) application. Hepatocyte proliferation, immune cell infiltration, and cytokine profile in the liver parenchyma were determined.

Results

Low-dose LPS application after PH results in a significant delay of liver regeneration between 48h and 72h, which is associated with a reduced number of CD3⁺ cells within the regenerating liver. In absence of LFA-1, an impaired regenerative capacity was observed under low-dose LPS application. Analysis of different leukocyte subpopulations showed less CD3⁺NK1.1⁺ NKT cells in the liver parenchyma of LFA-1^-/- mice after PH and LPS application compared to WT controls, while CD3^-NK1.1⁺ NK cells markedly increased. Concordantly with this observation, lower levels of NKT cell related cytokines IL-12 and IL-23 were expressed in the regenerating liver of LFA-1^-/- mice, while the expression of NK cell-associated CCL5 and IL-10 was increased compared to WT mice.

Conclusion

A subseptic situation negatively alters hepatocyte proliferation. Within this scenario, we suggest an important impact of NKT cells and postulate a critical function for LFA-1 during processes of liver regeneration.

Alisol B 23-acetate protects against ANIT-induced hepatotoxity and cholestasis, due to FXR-mediated regulation of transporters and enzymes involved in bile acid homeostasis

Intrahepatic cholestasis is a clinical syndrome with systemic and intrahepatic accumulation of excessive toxic bile acids that ultimately cause hepatobiliary injury. Appropriate regulation of bile acids in hepatocytes is critically important for protection against liver injury. In the present study, we characterized the protective effect of alisol B 23-acetate (AB23A), a natural triterpenoid, on alpha-naphthylisothiocyanate (ANIT)-induced liver injury and intrahepatic cholestasis in mice and further elucidated the mechanisms in vivo and in vitro. AB23A treatment dose-dependently protected against liver injury induced by ANIT through reducing hepatic uptake and increasing efflux of bile acid via down-regulation of hepatic uptake transporters (Ntcp) and up-regulation of efflux transporter (Bsep, Mrp2 and Mdr2) expression. Furthermore, AB23A reduced bile acid synthesis through repressing Cyp7a1 and Cyp8b1, increased bile acid conjugation through inducing Bal, Baat and bile acid metabolism through an induction in gene expression of Sult2a1. We further demonstrate the involvement of farnesoid X receptor (FXR) in the hepatoprotective effect of AB23A. The changes in transporters and enzymes, as well as ameliorative liver histology in AB23A-treated mice were abrogated by FXR antagonist guggulsterone in vivo. In vitro evidences also directly demonstrated the effect of AB23A on FXR activation in a dose-dependent manner using luciferase reporter assay in HepG2 cells. In conclusion, AB23A produces protective effect against ANIT-induced hepatotoxity and cholestasis, due to FXR-mediated regulation of transporters and enzymes.

Matrix metalloproteinase-10 expression is induced during hepatic injury and plays a fundamental role in liver tissue repair

BACKGROUND & AIMS

Upon tissue injury, the liver mounts a potent reparative and regenerative response. A role for proteases, including serine and matrix metalloproteinases (MMPs), in this process is increasingly recognized. We have evaluated the expression and function of MMP10 (stromelysin-2) in liver wound healing and regeneration.

METHODS

The hepatic expression of MMP10 was examined in two murine models: liver regeneration after two-thirds partial hepatectomy (PH) and bile duct ligation (BDL). MMP10 was detected in liver tissues by qPCR, western blotting and immunohistochemistry. The effect of growth factors and toll-like receptor 4 (TLR4) agonists on MMP10 expression was studied in cultured parenchymal and biliary epithelial cells and macrophages respectively. The role of MMP10 was evaluated by comparing the response of Mmp10+/+ and Mmp10-/- mice to PH and BDL. The intrahepatic turnover of the extracellular matrix proteins fibrin (ogen) and fibronectin was examined.

RESULTS

MMP10 mRNA was readily induced after PH and BDL. MMP10 protein was detected in hepatocytes, cholangiocytes and macrophages. In cultured liver epithelial cells, MMP10 expression was additively induced by transforming growth factor-β and epidermal growth factor receptor ligands. TLR4 ligands also stimulated MMP10 expression in macrophages. Lack of MMP10 resulted in increased liver injury upon PH and BDL. Resolution of necrotic areas was impaired, and Mmp10-/- mice showed increased fibrogenesis and defective turnover of fibrin (ogen) and fibronectin.

CONCLUSIONS

MMP10 expression is induced during mouse liver injury and participates in the hepatic wound healing response. The profibrinolytic activity of MMP10 may be essential in this novel hepatoprotective role.

Reduced liver cell death using an alginate scaffold bandage: a novel approach for liver reconstruction after extended partial hepatectomy

Extended partial hepatectomy may be needed in cases of large hepatic mass, and can lead to fulminant hepatic failure. Macroporous alginate scaffold is a biocompatible matrix which promotes the growth, differentiation and long-term hepatocellular function of primary hepatocytes in vitro. Our aim was to explore the ability of implanted macroporous alginate scaffolds to protect liver remnants from acute hepatic failure after extended partial hepatectomy. An 87% partial hepatectomy (PH) was performed on C57BL/6 mice to compare non-treated mice to mice in which alginate or collagen scaffolds were implanted after PH. Mice were scarified 3, 6, 24 and 48 h and 6 days following scaffold implantation and the extent of liver injury and repair was examined. Alginate scaffolds significantly increased animal survival to 60% vs. 10% in non-treated and collagen-treated mice (log rank=0.001). Mice with implanted alginate scaffolds manifested normal and prolonged aspartate aminotransferases and alanine aminotransferases serum levels as compared with the 2- to 20-fold increase in control groups (P<0.0001) accompanied with improved liver histology. Sustained normal serum albumin levels were observed in alginate-scaffold-treated mice 48 h after hepatectomy. Incorporation of BrdU-positive cells was 30% higher in the alginate-scaffold-treated group, compared with non-treated mice. Serum IL-6 levels were significantly decreased 3h post PH. Biotin-alginate scaffolds were quickly well integrated within the liver tissue. Collectively, implanted alginate scaffolds support liver remnants after extended partial hepatectomy, thus eliminating liver injury and leading to enhanced animal survival after extended partial hepatectomy.

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.

Effect of specific activation of γ-aminobutyric acid receptor in vivo on oxidative stress-induced damage after extended hepatectomy

AIM

  γ-Aminobutyric acid (GABA) is a multifunctional molecule with various physiological effects throughout the body. The regulation of GABA receptor (GABAR) plays a key role in reducing the damage mediated by oxidative stress (OS). Extended hepatectomy causes fatal OS-induced injury in the liver remnant. We aimed to investigate the effect of a GABAR agonist in extended hepatectomy.

METHODS

  Saline or a GABAR agonist (43.56 nmol/g bodyweight of muscimol) was administrated intravenously at 4 h preoperatively. C57BL/6 mice were divided into three groups: laparotomy only, 90% hepatectomy with saline and 90% hepatectomy with a GABAR agonist. Liver samples were obtained at 6 h after surgery.

RESULTS

  Survival curves were prolonged by the GABAR agonist. Histopathological findings and biochemical profiles showed that the GABAR agonist reduced liver damage. Immunohistological assessment demonstrated that the GABAR agonist prevented apoptotic induction. As shown by 4-hydroxynonenal, which reflects OS-induced damage, 90% hepatectomy caused OS and the GABAR agonist reduced OS. We measured ataxia-telangiectasia mutated kinase (ATM), H2AX, Akt and free radical scavenging enzymes because they may be affected by GABAR regulation, and found that Akt was greatly decreased after 90% hepatectomy, but it recovered with the GABAR agonist.

CONCLUSION

  GABAR is activated by a specific agonist in the liver in vivo. This activation reduces OS-mediated damage after extended hepatectomy in vivo, and the mechanism via an Akt-dependent pathway may be a key.

Simple and reproducible hepatectomy in the mouse using the clip technique

AIM: To investigate the reliability of massive hepatectomy models by using clip techniques.

METHODS: We analyzed anatomical findings in 100 mice following massive hepatectomy induced by liver reduction > 70%. The impact of various factors in the different models was also analyzed, including learning curves, operative time, survival curves, and histopathological findings.

RESULTS: According to anatomical results, models with 75%, 80%, and 90% hepatectomy produced massive hepatectomy. Learning curves and operative times were most optimal with the clip technique. Each hepatectomy performed using the clip technique produced a reasonable survival curve, and there were no differences in histopathological findings between the suture and clip techniques.

CONCLUSION: Massive hepatectomy by the clip technique is simple and can provide reliable and relevant data.

Matrix metalloproteinase-9 contributes to parenchymal hemorrhage and necrosis in the remnant liver after extended hepatectomy in mice

AIM: To investigate the effect of matrix metalloproteinase-9 (MMP-9) on the remnant liver after massive hepatectomy in the mouse.

METHODS: Age-matched, C57BL/6 wild-type (WT), MMP-9(-/-), and tissue inhibitors of metalloproteinases (TIMP)-1(-/-) mice were used. The mice received 80%-partial hepatectomy (PH). Samples were obtained at 6 h after 80%-PH, and we used histology, immunohistochemical staining, western blotting analysis and zymography to investigate the effect of PH on MMP-9. The role of MMP-9 after PH was investigated using a monoclonal antibody and MMP inhibitor.

RESULTS: We examined the remnant liver 6 h after 80%-PH and found that MMP-9 deficiency attenuated the formation of hemorrhage and necrosis. There were significantly fewer and smaller hemorrhagic and necrotic lesions in MMP-9(-/-) remnant livers compared with WT and TIMP-1(-/-) livers (P < 0.01), with no difference between WT and TIMP-1(-/-) mice. Serum alanine aminotransaminase levels were significantly lower in MMP-9(-/-) mice compared with those in TIMP-1(-/-) mice (WT: 476 ± 83 IU/L, MMP-9(-/-): 392 ± 30 IU/L, TIMP-1(-/-): 673 ± 73 IU/L, P < 0.01). Western blotting and gelatin zymography demonstrated a lack of MMP-9 expression and activity in MMP-9(-/-) mice, which was in contrast to WT and TIMP-1(-/-) mice. No change in MMP-2 expression was observed in any of the study groups. Similar to MMP-9(-/-) mice, when WT mice were treated with MMP-9 monoclonal antibody or the synthetic inhibitor GM6001, hemorrhagic and necrotic lesions were significantly smaller and fewer than in control mice (P < 0.05). These results suggest that MMP-9 plays an important role in the development of parenchymal hemorrhage and necrosis in the small remnant liver.

CONCLUSION: Successful MMP-9 inhibition attenuates the formation of hemorrhage and necrosis and might be a potential therapy to ameliorate liver injury after massive hepatectomy.

Acute liver failure: mechanisms of immune-mediated liver injury

Acute liver failure (ALF) is a syndrome of diverse aetiology, including hepatic encephalopathy, renal, cardiac and pulmonary failures, which result in a rapid loss of hepatic function. The mechanisms of liver injury contributing to ALF can be summarized into two categories: direct damage and immune-mediated liver injury. This review summarizes current concepts of immune-mediated liver injury from both clinical studies and animal models. We highlight immune responses of ALF from the liver injury perspective, which combines a variety of molecular and cellular mechanisms, particularly, the contribution of cytokines and the innate immune system. Hepatic and circulating inflammatory cytokines play a significant role in the pathophysiology of ALF including hepatocyte necrosis, extrahepatic complications and hepatocyte regeneration. Overproduction of cytokines, if unchecked, is hazardous to the host and may cause severe outcomes. Measuring pro-inflammatory cytokines in ALF may be of value for predictors of outcome. Innate and adaptive immune systems both involved in ALF contribute to immune-mediated liver injury. The innate immune response is activated much more rapidly compared with adaptive immunity, particularly in acute liver injury where the host has little time to trigger an effective adaptive immune response. From this point of view, the innate immune system may make a more profound contribution than the adaptive immune system. Furthermore, immune responses crosstalk with other physiological or pathophysiological factors, for example, coagulation factors which in turn determine the outcome of ALF and these are discussed.