The protective role of Hepatopoietin Cn on liver injury induced by carbon tetrachloride in rats*

Background: Hepatopoietin Cn (HPPCn) is a member of the leucine‐rich acidic nuclear protein family (LANP), and studies of partially hepatectomized (PH) mice show that levels of HPPCn mRNA increase following liver injury. Furthermore, the recombinant human protein (rhHPPCn) was shown to stimulate hepatic DNA synthesis and activate signaling pathways involved in hepatocyte proliferation in vitro and in vivo. Aim: The aim of the study was to evaluate the protective effect of rhHPPCn on liver injury and fibrosis induced by carbon tetrachloride (CCl4) injection. Methods: Wistar rats weighing 200 g were given a single and repeated intraperitoneal injections of CCl4. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activity in rat serum were measured using biochemical assay. Hepatic hydroxyproline (Hyp) level was determined in the hydrolysates of liver samples. Immunostaining and Masson's trichrome staining were conducted to evaluate hepatocyte proliferation and fibrosis. Results: The results showed that exogenous rhHPPCn could alleviate hepatocyte necrosis and protect the liver from the development of fibrotic lesions by proliferation stimulation. Additionally, HPPCn could reduce ALT/AST levels in rat serum following single and repeated CCl4 injection. Conclusion: It was suggested that HPPCn could protect hepatocytes from injury induced by CCl4 as a proliferation stimulator.     

Selective elimination of hepatic natural killer T cells with concanavalin A improves liver regeneration in mice.

BACKGROUND: Although concanavalin A (Con A) as a T cell stimulant can cause natural killer T (NKT) cell-mediated liver injury in mice and a nonhepatotoxic dose of Con A can trigger innate immune cells including NKT cells to prevent tumor metastasis in the liver, little is known about the role of Con A-primed NKT cells in liver repair. In this study, we aimed to investigate the effect of pretreatment with a nontoxic dose of Con A on subsequent liver regeneration in mice. METHODS: A nontoxic dose of Con A was injected intravenously 24 h before partial hepatectomy (PHx), which was used as a model of liver regeneration. Ratios of remnant liver mass to body weight, bromodeoxyuridine (BrdU) incorporation and proliferating cell nuclear antigen (PCNA) labeling were used to assess liver regeneration. RESULTS: Hepatic mononuclear cells were isolated and analyzed by flow cytometry. After PHx, the ratios of liver weight to body weight, PCNA-positive hepatocytes and BrdU-positive hepatocytes in Con A-pretreated mice were significantly higher than that of phosphate-buffered saline-treated mice, indicating that Con A pretreatment can accelerate liver regeneration. Flow cytometric analysis showed that NKT cells were significantly activated and selectively eliminated after the Con A administration. Moreover, NKT cells expressed more apoptosis-related molecules, Fas and Annexin V. CONCLUSIONS: Taken together, Con A accelerates liver regeneration in mice by eliminating hepatic NKT cells via activation-induced cell death.     

Isolation and functional identification of a novel human hepatic growth factor: hepatopoietin Cn

Hepatic stimulating substance (HSS) was first isolated from weanling rat liver in 1975 and found to stimulate hepatic DNA synthesis both in vitro and in vivo. Since then, mammalian and human HSS have been investigated for their potential to treat hepatic diseases. However, the essential nature in composition and structure of HSS remain puzzling because HSS has not been completely purified. Heating, ethanol precipitation, and ion-exchange chromatographies had been carried out to isolate the protein with specific stimulating activity from newborn calf liver, and [(3)H]thymidine deoxyribose (TdR)/bromodeoxyuridine (BrdU) incorporation and carboxyfluorescein diacetate succinimidyl ester (CFSE)-based proliferation assay to determine the bioactivity in vitro and in vivo. We report the purification of a novel 30-kDa protein from a crude extract of calf liver HSS. This protein is a member of the leucine-rich acidic nuclear protein family (LANP) and has been named hepatopoietin Cn (HPPCn). Studies of partially hepatectomized (PH) mice show that levels of HPPCn messenger RNA (mRNA) increase after liver injury. Furthermore, the recombinant human protein (rhHPPCn) was shown to stimulate hepatic DNA synthesis and activate signaling pathways involved in hepatocyte proliferation in vitro and in vivo. CONCLUSION: HPPCn is a novel hepatic growth factor that plays a role in liver regeneration.     

Altered hepatic triglyceride content after partial hepatectomy without impaired liver regeneration in multiple murine genetic models

Liver regeneration is impaired following partial hepatectomy (PH) in mice with genetic obesity and hepatic steatosis and also in wild-type mice fed a high-fat diet. These findings contrast with other data showing that liver regeneration is impaired in mice in which hepatic lipid accumulation is suppressed by either pharmacologic leptin administration or by disrupted glucocorticoid signaling. These latter findings suggest that hepatic steatosis may actually be required for normal liver regeneration. We have reexamined this relationship using several murine models of altered hepatic lipid metabolism. Liver fatty acid (FA) binding protein knockout mice manifested reduced hepatic triglyceride (TG) content compared to controls, with no effect on liver regeneration or hepatocyte proliferation. Examination of early adipogenic messenger RNAs revealed comparable induction in liver from both genotypes despite reduced hepatic steatosis. Following PH, hepatic TG was reduced in intestine-specific microsomal TG transfer protein deleter mice, which fail to absorb dietary fat, increased in peroxisome proliferator activated receptor alpha knockout mice, which exhibit defective FA oxidation, and unchanged (from wild-type mice) in liver-specific FA synthase knockout mice in which endogenous hepatic FA synthesis is impaired. Hepatic TG increased in the regenerating liver in all models, even in animals in which lipid accumulation is genetically constrained. However, in no model -- and over a >90-fold range of hepatic TG content -- was liver regeneration significantly impaired following PH. CONCLUSION: Although hepatic TG content is widely variable and increases during liver regeneration, alterations in neither exogenous or endogenous lipid metabolic pathways, demonstrated to promote or diminish hepatic steatosis, influence hepatocyte proliferation.     

Dietary factors alter hepatic innate immune system in mice with nonalcoholic fatty liver disease

Dietary factors promote obesity and obesity-related disorders, such as fatty liver disease. Natural killer T (NKT) cells are components of the innate immune system that regulate proinflammatory (Th-1) and anti-inflammatory (Th-2) immune responses. Previously, we noted that NKT cells are selectively reduced in the fatty livers of obese, leptin-deficient ob/ob mice and demonstrated that this promotes proinflammatory polarization of hepatic cytokine production, exacerbating lipopolysaccharide (LPS) liver injury in these animals. In the current study, we show that hepatic NKT cells are also depleted by diets that induce obesity and fatty livers in wild-type mice, promoting Th-1 polarization of hepatic cytokine production and sensitization to LPS liver injury despite persistent leptin. Adult male C57BL6 mice fed diets containing high amounts of either fat or sucrose, or combined high-fat, high-sucrose, develop increased hepatic NKT cell apoptosis and reduced liver NKT cells. The hepatic lymphocytes are more Th-1 polarized with increased intracellular interferon gamma and tumor necrosis factor alpha. Mice fed high-fat diets also exhibit more liver injury, reflected by 2-fold greater serum alanine aminotransferase (ALT) than control animals after receiving LPS. In conclusion, when otherwise normal mice are fed with high-fat or sucrose diet, they become obese, develop fatty livers, and acquire hepatic innate immune system abnormalities, including increased NKT cell apoptosis. The latter reduces liver NKT cell populations and promotes excessive hepatic production of Th-1 cytokines that promote hepatic inflammation. These diet-induced alterations in the hepatic innate immune system may contribute to obesity-related liver disease.     

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.     

Inhibition of concanavalin A-induced hepatic injury of mice by bacterial lipopolysaccharide via the induction of IL-6 and the subsequent reduction of IL-4: the cytokine milieu of concanavalin A hepatitis.

BACKGROUND/AIMS: Liver natural killer 1.1 antigen (NK1)+ T cells and IL-4 play a crucial role in concanavalin-A (Con-A)-induced hepatic injury in mice, and a T helper (Th) 2 immune response was thus suggested to be involved. This study was designed to examine the effect of bacterial lipopolysaccharide (LPS), a strong inducer of a Th 1 immune response, on Con-A hepatic injury and also to clarify further the cytokine milieu of Con-A hepatitis. Methods: LPS were injected into mice before Con-A injection to evaluate the effect on hepatic injury. The effect of the pretreatment with various T1 and Th2 cytokines or anti-cytokine antibodies on Con-A hepatitis was also examined. Results: LPS in quantities > or = 500 ng/mouse, when injected 24 h before Con-A injection, abrogated the Con-A-induced elevation of transaminases, hepatocyte destruction and serum IL-4 elevation. This LPS inhibitory effect was blocked when the mice were injected with either anti-IL-6 antibody before LPS injection or IL-4 before Con-A injection. IL-6, but neither IL-10 nor IL-12 pretreatment suppressed Con-A-induced IL-4 production and hepatitis. NK1+ T cells produced IL-4 while both NK1+ T cells and NK1- T cells produced IFN-gamma. Not only anti-IL-4 antibody but also the anti-IFN-gamma antibody pretreatment inhibited Con-A hepatitis. However, although the anti-IL4 antibody suppressed IL-4 alone, the anti-IFN-gamma Ab unexpectedly inhibited both IFN-gamma and IL-4 elevation, while IL-4 injection evoked a moderate Con-A hepatitis even in the anti-IFN-gamma antibody-treated mice. Furthermore, the IL-4 mutant mice did not develop Con-A hepatitis. CONCLUSION: LPS inhibited Con-A hepatitis by inducing IL-6 and thereby inhibited IL-4 synthesis from NK1+ T cells. Although both IL-4 and IFN-gamma were required for the full induction of Con-A hepatic injury, exogenous IL-4 evoked a moderate Con-A hepatitis, even in the absence of IFN-gamma.     

Prevention of hepatic fibrosis in nonobese diabetic mice: a critical role for interferon-gamma.

BACKGROUND/AIMS: Nonobese diabetic (NOD) mice, a model of type I diabetes mellitus, harbor certain unique defects in their immune system. The aim of this study was to investigate how NOD mice show hepatic injury and subsequent fibrogenic responses. METHODS: Hepatic fibrosis was induced by intraperitoneal injections of dimethylnitrosamine (DMN), and assessed biochemically and histologically. Expressions of cytokine messenger RNA (mRNA) in the liver were determined. RESULTS: In a model of liver cirrhosis induced by dimethylnitrosamine (DMN), we found that NOD mice had lower levels of hepatic fibrosis and better survival than control ICR mice. The resistance to DMN-induced lethality in NOD mice was independent of apoptosis and necrosis of hepatocytes, but apparently due to the prevention of hepatic fibrosis. We also found increased inductions of interferon-gamma (IFN-gamma) mRNA in the liver of NOD mice and of intracellular IFN-gamma from intrahepatic T cells following DMN administration. Treatment with neutralizing anti-IFN-gamma-antibody cancelled the inhibition of hepatic fibrosis in NOD mice. CONCLUSIONS: These results suggest that IFN-gamma is effective for inhibiting hepatic fibrosis and that genetic host factors may be important in determining differential responses to injury.     

Activated natural killer T cells induce liver injury by Fas and tumor necrosis factor-alpha during alcohol consumption

BACKGROUND & AIMS: Chronic alcohol abuse induces liver injury and increases the severity of viral hepatitis, but the precise mechanisms responsible are not well understood. In particular, little is known about the role of natural killer T cells in alcohol-induced liver injury. Natural killer T cells are mediators of important regulator and effector functions making use of Fas and tumor necrosis factor (TNF)-alpha in apoptosis induction. This report analyzes the role of natural killer T cells, Fas, and TNF-alpha in a model of chronic alcohol consumption. METHODS: Mice fed alcohol by intragastric tube were assayed for serum alanine aminotransferase values, liver histology, and liver mononuclear cells before and after activation of natural killer T cells by ligand alpha-galactosylceramide. RESULTS: In alcohol-consuming animals, liver natural killer T cells increase, and further activation by alpha-galactosylceramide causes lethal liver injury. This is explained by alcohol-induced hepatocyte sensitization to cell-mediated lysis, which develops concomitant to increased cytolytic activity of natural killer T cells. Natural killer T cell-mediated apoptosis proceeds by the Fas pathway, and Fas is essential for alcohol-associated liver injury. TNF-alpha plays an additional role as a defect in TNF receptor-1 inhibits alcohol-associated liver injury. Alcohol-fed natural killer T cell-deficient Jalpha281(-/-) mice express a delay in alcohol-induced liver injury. CONCLUSIONS: Alcohol consumption induces an increase of natural killer T cells in the liver and a high sensitivity of hepatocytes to cell-mediated lysis. Stimulation of natural killer T cells during alcohol consumption induces serious liver injury by a mechanism that involves concomitant signals by Fas and tumor necrosis factor receptor-1 on alcohol-stressed hepatocytes.     

Loss of hepatic B cells following lipopolysaccharide injection and polymicrobial sepsis

Background and Aim:  B cells possess pleiotropic functions and are important for both humoral as well as cellular immune responses. However, there is little information about how hepatic B cells respond to lipopolysaccharide (LPS) and/or sepsis.
Methods:  We evaluated the changes in the number of hepatic and splenic B cells, and the expression of immunoglobulins after injecting pathogens, such as LPS, flagellin and CpG oligonucleotides in mice. In addition, we examined the role of natural killer (NK) cells in these changes using mutant bg/bg mice with genetically impaired NK cell functions.
Results:  Significant temporal loss of hepatic B cells, but not splenic B cells, was seen following LPS treatment. We have shown that bacterial components other than LPS were also responsible for such decline in hepatic B cells. However, loss of hepatic B cells was not seen following LPS treatment in bg/bg mice. In addition, loss of hepatic B cells and systemic immunoglobulin G2a production after LPS treatment was at least in part mediated by interleukin-12, γ-interferon and tumor necrosis factor-α, all of which substantially enhanced the NK cell activity.
Conclusion:  Hepatic B cells play an essential role during sepsis by synergistically interacting with NK cells. However, whether decline of hepatic B cells after LPS treatment and/or polymicrobial sepsis is simply a phenomenon or has a substantial clinical importance is yet to be determined.     

TRAIL mediates liver injury by the innate immune system in the bile duct-ligated mouse

The contribution of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), a death ligand expressed by cells of the innate immune system, to cholestatic liver injury has not been explored. Our aim was to ascertain if TRAIL contributes to liver injury in the bile duct-ligated (BDL) mouse. C57/BL6 wild-type (wt), TRAIL heterozygote (TRAIL(+/-)), and TRAIL knockout (TRAIL(-/-)) mice were used for these studies. Liver injury and fibrosis were examined 7 and 14 days after BDL, respectively. Hepatic TRAIL messenger RNA (mRNA) was 6-fold greater in BDL animals versus sham-operated wt animals (P < 0.01). The increased hepatic TRAIL expression was accompanied by an increase in liver accumulation of natural killer 1.1 (NK 1.1)-positive NK and natural killer T (NKT) cells, the predominant cell types expressing TRAIL. Depletion of NK 1.1-positive cells reduced hepatic TRAIL mRNA expression and serum alanine aminotransferase (ALT) values. Consistent with a role for NK/NKT cells in this model of liver injury, stress ligands necessary for their recognition of target cells were also up-regulated in hepatocytes following BDL. Compared to sham-operated wt mice, BDL mice displayed a 13-fold increase in terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) and an 11-fold increase in caspase 3/7-positive hepatocytes (P < 0.01). The number of TUNEL and caspase 3/7-positive cells was reduced by >80% in BDL TRAIL knockout animals (P < 0.05). Likewise, liver histology, number of bile infarcts, serum ALT values, hepatic fibrosis, and animal survival were also improved in BDL TRAIL(-/-) animals as compared to wt animals. Conclusion: These observations support a pivotal role for TRAIL in cholestatic liver injury mediated by NK 1.1-positive NK/NKT cells.     

Requirement for interleukin-12 in the pathogenesis of warm hepatic ischemia/reperfusion injury in mice

Hepatic ischemia and reperfusion causes neutrophil-dependent liver injury. Although the mechanisms of ischemia/reperfusion-induced liver neutrophil recruitment are somewhat understood, less is known regarding the early events that initiate the inflammatory injury. Using a murine model of partial hepatic ischemia and reperfusion, we evaluated the role of endogenous interleukin (IL)-12 in this inflammatory response. Hepatic ischemia for 90 minutes and reperfusion for up to 4 hours resulted in hepatocyte expression of IL-12. By 8 hours of reperfusion there were large increases in serum levels of interferon-gamma (IFNgamma) and tumor necrosis factor-alpha (TNFalpha). In addition, hepatic ischemia/reperfusion caused significant increases in liver neutrophil recruitment, hepatocellular injury, and liver edema, as defined by liver myeloperoxidase content, serum alanine aminotransferase, and liver wet to dry weight ratios, respectively. In mice treated with neutralizing antibody to IL-12 and in mice deficient in the IL-12 p40 gene, ischemia/reperfusion-induced increases in IFNgamma and TNFalpha were greatly diminished. These conditions also caused significant reductions in liver myeloperoxidase content and attenuated the parameters of liver injury. The data suggest that IL-12 is required for the full induction of injury after hepatic ischemia and reperfusion.     

Impaired liver regeneration and increased oval cell numbers following T cell-mediated hepatitis

The regeneration of liver tissue following transplantation is often complicated by inflammation and tissue damage induced by a number of factors, including ischemia and reperfusion injury and immune reactions to the donor tissue. The purpose of the current study is to characterize the effects of T cell-mediated hepatitis induced by concanavalin A (ConA) on the regenerative response in vivo. Liver regeneration following a partial (70%) hepatectomy (pHx) was associated with elevations in serum enzymes and the induction of key cell cycle proteins (cyclin D, cyclin E, and Stat3) and hepatocyte proliferation. The induction of T cell-mediated hepatitis 4 days before pHx increased serum enzymes 48 hours after pHx, reduced early cyclin D expression and Stat3 activation, and suppressed hepatocyte proliferation. This inhibition of proliferation was also associated with increased expression of p21, the activation of Smad2, the induction of transforming growth factor beta and interferon gamma expression, and reduced hepatic interleukin 6 production. Moreover, the ConA pretreatment increased the numbers of separate oval cell-like CD117(+) cells and hematopoietic-like Sca-1(+) cell populations 48 hours following pHx. The depletion of natural killer (NK) cells, an important component of the innate immune response, did not affect liver injury or ConA-induced impairment of hepatocyte proliferation but did increase the numbers of both CD117-positive and Sca-1-positive cell populations. Finally, splenocytes isolated from ConA-pretreated mice exerted cytotoxicity toward autologous bone marrow cells in an NK cell-dependent manner. CONCLUSION: T cell-mediated hepatitis alters early cytokine responses, reduces hepatocellular regeneration, and induces NK cell-sensitive oval cell and hematopoietic-like cell expansion following pHx.     

Significance of morphological alteration by portal vein branch ligation in endotoxin-induced liver injury after partial hepatectomy.

BACKGROUND: Regenerating liver after partial hepatectomy (PH) is susceptible to endotoxin. This study was conducted to investigate how morphological alteration by preoperative portal vein branch ligation (PVL) affects endotoxin-induced liver injury after PH. METHODS: Male Sprague-Dawley rats were divided into a PVL group undergoing left PVL and into a non-PVL group receiving a sham operation. Seven days later, animals in both groups were subjected to PH (the left lateral, median and caudate lobes). Lipopolysaccharide (LPS) was intravenously administered to both groups 2 days after PH. RESULTS: A significant increase in hepatocyte and sinusoidal endothelial cell proliferation assessed by Ki-67 immunostaining reached a peak at day 2 and 3 after PVL, respectively, in accordance with the changes in plasma interleukin-6 concentrations after PVL. The proliferation response of these cells after PH was observed in both groups, showing a significantly weaker response in the PVL group. The sinusoidal width after PH was significantly reduced in the non-PVL group when compared with that in the PVL group. LPS administration induced a marked elevation of plasma tumour necrosis factor-alpha levels in the non-PVL group compared with the PVL group. PVL before PH significantly attenuated endotoxin-induced functional and structural liver damage with greater hepatic polymorphonuclear leucocyte infiltration and microcirculatory derangement, resulting in an improvement in the 7-day survival rate. CONCLUSIONS: Morphological alteration by PVL is of great advantage in preventing the development of endotoxin-induced liver injury in the regeneration process after PH.     

Characterization and enrichment of hepatic progenitor cells in adult rat liver

AIM: To detect the markers of oval cells in adult rat liver and to enrich them for further analysis of characterization in vitro. METHODS: Rat model for hepatic oval cell proliferation was established with 2-acetylaminofluorene and two third partial hepatectomy (2-AAF/PH). Paraffin embedded rat liver sections from model (11 d after hepatectomy) and control groups were stained with HE and OV6, cytokeratin19 (CK19), albumin, alpha fetoprotein (AFP), connexin43, and c-kit antibodies by immunohistochemistry. Oval cell proliferation was measured with BrdU incorporation test. C-kit positive oval cells were enriched by using magnetic activated cell sorting (MACS).The sorted oval cells were cultured in a low density to observe colony formation and to examine their characterization in vitro by immunocytochemistry and RT-PCR. RESULTS: A 2-AAF/PH model was successfully established to activate the oval cell compartment in rat liver. BrdU incorporation test of oval cell was positive. The hepatic oval cells coexpressed oval cell specific marker OV6, hepatocyte-marker albumin and cholangiocyte-marker CK19. They also expressed AFP and connexin 43. C-kit, one hematopoietic stem cell receptor, was expressed in hepatic oval cells at high levels. By using c-kit antibody in conjunction with MACS, we developed a rapid oval cell isolation protocol. The sorted cells formed colony when cultured in vitro. Cells in the colony expressed albumin or CK19 or coexpressed both and BrdU incorporation test was positive. RT-PCR on colony showed expression of albumin and CK19 gene. CONCLUSION: Hepatic oval cells in the 2-AAF/PH model had the properties of hepatic stem/progenitor cells. Using MACS, we established a method to isolate oval cells. The sorted hepatic oval cells can form colony in vitro which expresses different combinations of phenotypic markers and genes from both hepatocytes and cholangiocyte lineage.     

Exogenous melatonin protects small‐for‐size liver grafts by promoting monocyte infiltration and releases interleukin‐6

Defective regeneration of small‐for‐size (SFS ) liver remnants and partial grafts remains a key limiting factor in the application of liver surgery and transplantation. Exogenous melatonin (MLT ) has protective effects on hepatic ischemia‐reperfusion injury (IRI ), but its influence on graft regeneration is unknown. The aim of the study is to investigate the role of MLT in IRI and graft regeneration in settings of partial liver transplantation. We established three mouse models to study hepatic IRI and regeneration associated with partial liver transplantation: (I) IR +PH group: 60 minutes liver ischemia (IR ) plus 2/3 hepatectomy (PH ); (II ) IR +exPH group: 60 minutes liver IR plus extended hepatectomy (exPH ) associated with the SFS syndrome; (III ) SFS ‐LT group: Arterialized 30% SFS liver transplant. Each group was divided into MLT or vehicle‐treated subgroups. Hepatic injury, inflammatory signatures, liver regeneration, and animal survival rates were assessed. MLT reduced liver injury, enhanced liver regeneration, and promoted interleukin (IL ) 6, IL 10, and tumor necrosis factor‐α release by infiltrating, inflammatory Ly6C+ F4/80+ monocytes in the IR +PH group. MLT ‐induced IL 6 significantly improved hepatic microcirculation and survival in the IR +exPH model. In the SFS ‐LT group, MLT promoted graft regeneration and increased recipient survival along with increased IL 6/GP 130‐STAT 3 signaling. In IL 6 ^?/? mice, MLT failed to promote liver recovery, which could be restored through recombinant IL 6. In the IR +exPH and SFS ‐LT groups, inhibition of the IL 6 co‐receptor GP 130 through SC 144 abolished the beneficial effects of MLT . MLT ameliorates SFS liver graft IRI and restores regeneration through monocyte‐released IL 6 and downstream IL 6/GP 130‐STAT 3 signaling.     

Activation of mouse natural killer T cells accelerates liver regeneration after partial hepatectomy

BACKGROUND & AIMS: Activation of natural killer T cells with the synthetic ligand alpha-galactosylceramide (alpha-GalCer) induced hepatotoxicity through the tumor necrosis factor (TNF) and Fas-ligand-mediated pathway in aged mice. The aim of this study was to elucidate how alpha-GalCer-activated natural killer T cells function in hepatocyte proliferation and liver regeneration in partially hepatectomized (PHx) mice. METHODS: Mice were injected with alpha-GalCer at 36 hours after 70% PHx. Hepatocyte mitosis was evaluated by either mitotic figures or proliferating cell nuclear antigen staining. The role of TNF and Fas-ligand in hepatocyte mitosis also was assessed. RESULTS: In PHx mice injected with alpha-GalCer, hepatocyte mitosis was greatly enhanced at 44 hours after surgery and the increase was more obvious in aged mice than in young mice. The expression of both TNF receptor 1 and Fas-ligand in liver natural killer T cells tended to increase after alpha-GalCer injection in PHx mice. Treatment of mice with anti-NK1.1 Ab 3 days before and just after hepatectomy greatly inhibited the effect of alpha-GalCer on hepatocyte mitosis and liver regeneration. Furthermore, pretreatment of PHx mice with either anti-TNF Ab or anti-FasL Ab 1 hour before alpha-GalCer injection mostly abrogated the increase in hepatocyte proliferation. alpha-GalCer injection did not accelerate hepatocyte proliferation in Fas-mutated lpr mice after PHx. CD1d-/- mice without alpha-GalCer injection showed decreased hepatocyte mitosis after PHx. CONCLUSIONS: Activated natural killer T cells help hepatocyte proliferation and liver regeneration after PHx via the TNF and Fas/Fas-ligand-mediated pathway.