Plasma levels and hepatic mRNA expression of transforming growth factor-beta1 in patients with fulminant hepatic failure

Review of the potential value of serum interleukin levels as prognostic biomarkers of liver failure

Liver failure (LF) is prevalent in China and is characterized by complex pathogenesis, challenging clinical management, poor prognosis, and rising incidence and mortality rates. The immune status is an important factor affecting LF prognosis. Interleukins (Ils) are a type of cytokine that act and interact with multiple cells, including immune cells. These signaling molecules play important roles in intercellular information transmission, including the regulation of immune cells; mediation of the activation, proliferation, and differentiation of T and B cells; and orchestration of the inflammatory response. To date, many studies have explored the correlation between IL expression and liver disease prognosis, but few studies have evaluated Ils as the prognostic biomarkers of LF. This article reviews the potential use of Ils as the prognostic biomarkers of LF. Particularly, it evaluates the predictive values of IL-21, IL-22, and IL-31, the three often overlooked yet promising prognostic biomarkers, in predicting susceptibility to LF. Harnessing biomarkers for early prognostic insights can facilitate tailored treatment strategies and enhance patient survival. Thus, this article focuses on the identification of IL-21, IL-22, and IL-33 as biomarkers in preclinical and clinical studies on LF and reviews their role as biomarkers in the pathogenesis and diagnosis of LF.

An orally deliverable ornithine-based self-assembling polymer nanomedicine ameliorates hyperammonemia in acetaminophen-induced acute liver injury

l-Ornithine (Orn) is a core amino acid responsible for ammonia detoxification in the body via the hepatic urea cycle. Clinical studies in Orn therapy have focused on interventions for hyperammonemia-associated diseases, such as hepatic encephalopathy (HE), a life-threatening neurological symptom affecting more than 80% of patients with liver cirrhosis. However, its low molecular weight (LMW) causes Orn to diffuse nonspecifically and be rapidly eliminated from the body after oral administration, resulting in unfavorable therapeutic efficacy. Hence, Orn is constantly supplied by intravenous infusion in many clinical settings; however, this treatment inevitably decreases patient compliance and limits its application in long-term management. To improve the performance of Orn, we designed self-assembling polyOrn-based nanoparticles for oral administration through ring-opening polymerization of Orn-N-carboxy anhydride initiated with amino-ended poly(ethylene glycol), followed by acylation of free amino groups in the main chain of the polyOrn segment. The obtained amphiphilic block copolymers, poly(ethylene glycol)-block-polyOrn(acyl) (PEG-block-POrn(acyl)), enabled the formation of stable nanoparticles (NanoOrn(acyl)) in aqueous media. We employed the isobutyryl (iBu) group for acyl derivatization in this study (NanoOrn(iBu)). In the healthy mice, daily oral administration of NanoOrn(iBu) for one week did not induce any abnormalities. In the mice exhibiting acetaminophen (APAP)-induced acute liver injury, oral pretreatment with NanoOrn(iBu) effectively reduced systemic ammonia and transaminases levels compared to the LMW Orn and untreated groups. The results suggest that the application of NanoOrn(iBu) is of significant clinical value with the feasibility of oral delivery and improvement in APAP-induced hepatic pathogenesis. STATEMENT OF SIGNIFICANCE: Liver injury is often accompanied by hyperammonemia, a life-threatening condition characterized by elevated blood ammonia levels. Current clinical treatments for reducing ammonia typically entail the invasive approach of intravenous infusion, involving the administration of l-ornithine (Orn) or a combination of Orn and L-aspartate. This method is employed due to the poor pharmacokinetics associated with these compounds. In our pursuit of enhancing therapy, we have developed an orally administrable nanomedicine based on Orn-based self-assembling nanoparticle (NanoOrn(iBu)), which provides sustained Orn supply to the injured liver. Oral administration of NanoOrn(iBu) to healthy mice did not cause any toxic effects. In a mouse model of acetaminophen-induced acute liver injury, oral administration of NanoOrn(iBu) surpassed Orn in reducing systemic ammonia levels and liver damage, thereby establishing NanoOrn(iBu) as a safe and effective therapeutic option.

Serum Interleukins as Potential Prognostic Biomarkers in HBV-Related Acute-on-Chronic Liver Failure

Hepatitis B virus-related acute-on-chronic liver failure (HBV-ACLF) is relatively common in China and has complex pathogenesis, difficult clinical treatment, and poor prognosis. Immune status is an important factor affecting ACLF prognosis. Interleukins are a family of secreted lymphocyte factors that interact with a host of cell types including immune cells. These signaling molecules play important roles in transmitting information; regulating immune cells; mediating the activation, proliferation, and differentiation of T and B cells; and modulating inflammatory responses. Many studies have investigated the correlation between interleukin expression and the prognosis of HBV-ACLF. This review focuses on the potential use of interleukins as prognostic biomarkers in HBV-ACLF. References were mainly identified through PubMed and CNKI search, including relevant studies published until December 2021. We have summarized reports of several promising diagnostic interleukin biomarkers that predict susceptibility to HBV-ACLF. The use of biomarkers to understand early prognosis can help devise different therapeutic measures and improve patient survival. Ongoing research on prognostic biomarkers of HBV-ACLF is promising, and future preclinical and clinical studies are warranted.

Hepatic TGFβr1 Deficiency Attenuates Lipopolysaccharide/D-Galactosamine-Induced Acute Liver Failure Through Inhibiting GSK3β-Nrf2-Mediated Hepatocyte Apoptosis and Ferroptosis

BACKGROUND & AIMS

Acute liver failure (ALF) is a condition with high mortality and morbidity, characterized by glutathione depletion, oxidative stress, and mitochondrial dysfunction. Ferroptosis may be involved in ALF. Indeed, emerging studies have shown that ferroptosis plays a significant role in ALF. However, the mechanism of ferroptosis in hepatocytes during ALF remains unknown.

METHODS

Hepatic-specific transforming growth factor β receptor 1 knockout (TGFβr1^Δhep-CKO) mice and nuclear factor erythroid 2-related factor 2 knockout (Nrf2^-/-) mice were generated and subjected to ALF. Electron microscopy was used to detect mitochondrial and other cell substructure changes during ALF.

RESULTS

In this study, we noticed that lipopolysaccharide (LPS)/D-galactosamine (D-GalN) induced caspases-mediated apoptosis as current research reported, we also found lipid peroxidation, reactive oxygen species accumulation, and glutathione, co-enzyme Q10 system inhibition mediated ferroptosis during LPS/D-GalN-induced ALF. Rescue studies have shown that ferrostatin-1 (Fer-1) and deferoxamine mesylate (DFOM), the inhibitor of ferroptosis, could alleviate LPS/D-GalN-induced ALF. In addition, we noticed that TGFβ1 was increased during ALF, while ALF was relieved in TGFβr1^Δhep-CKO mice. We also noticed that liver TGFβr1 deficiency alleviated LPS/D-GalN-induced apoptosis and ferroptosis by affecting the phosphorylation of glycogen synthase kinase 3β and Nrf2, a key antioxidant factor, by up-regulating the levels of glutathione peroxidase 4 (GPX4), glutamine antiporter xCT (XCT), dihydroorotate dehydrogenase (DHODH), and ferroptosis suppressor protein 1 (FSP1), and down-regulating transferrin receptor (TFR), prostaglandin-endoperoxide synthase (Ptgs2), chaC glutathione specific gamma-glutamylcyclotransferase 1 (CHAC1), and cytochrome P450 reductase (POR) expression. The further supplemental experiment showed that ferroptosis was aggravated significantly in Nrf2^-/- mice compared with its wild-type controls and reversed by ferrostatin-1.

CONCLUSIONS

This study shows that TGFβr1 plays a critical role in mediating LPS/D-GalN-induced ALF by promoting apoptosis and ferroptosis.

Lupeol ameliorates LPS/D-GalN induced acute hepatic damage by suppressing inflammation and oxidative stress through TGFβ1-Nrf2 signal pathway

Acute hepatic damage is a severe condition characterized by inflammation and oxidative stress, which is a serious threat to people's life and health. But there are few effective treatments for acute liver injury. Therefore, safe and effective therapeutic approaches for preventing acute liver damage are urgently needed. Lupeol is a natural compound, which has significant antioxidant and anti-inflammatory properties in liver disease. However, the protective mechanism of lupeol against acute liver injury remains unclear. Here, zebrafish and mutant mice were utilized to investigate the protective effects of lupeol against lipopolysaccharide (LPS)/ D-galactosamine(D-GalN) -induced liver injury and the underlying mechanisms. We found that pretreatment with lupeol attenuated the LPS/D-GalN-induced liver injury by decreasing the infiltration of inflammatory cells and reducing pro-inflammatory cytokines. We also demonstrated that lupeol could protect injured liver from oxidative stress by downregulating the expression of TGFβ1 and upregulating Nrf2. Notably, our experimental results provided the support that lupeol effectively protected against LPS/D-GalN-induced acute liver injury via suppression of inflammation response and oxidative stress, which were largely dependent on the upregulation of the Nrf2 pathway via downregulating TGFβ1.

IL-35: A Novel Immunomodulator in Hepatitis B Virus-Related Liver Diseases

Chronic hepatitis B virus (HBV) infection is a risk factor for liver cirrhosis (LC) and hepatocellular carcinoma (HCC), however, little is known about the mechanisms involved in the progression of HBV-related diseases. It has been well acknowledged that host immune response was closely related to the clinical outcomes of patients with HBV infection. As the factors closely related to the immunomodulatory process, cytokines are crucial in the cell-cell communication and the host responses to HBV infection. Recently, a newly discovered cytokine, designated as interleukin-35 (IL-35), has been proved to be essential for the progression of chronic HBV infection, the development of cirrhosis, the transformation of cirrhosis to HCC, and the metastasis of HCC. Specifically, it showed various biological activities such as inhibiting the HBV-specific cytotoxic T lymphocyte (CTL) proliferation and cytotoxicity, deactivating the immature effector T-cells (Teffs), as well as delaying the proliferation of dendritic cells. It regulated the immune responses by acting as a “brake” on the activation of Teffs, which subsequently played important roles in the pathogenesis of various inflammatory diseases and malignancies. In this review, we focused on the most recent data on the relationship between IL-35 and chronic HBV infection, LC and HCC.

The TGFβ1 Receptor Antagonist GW788388 Reduces JNK Activation and Protects Against Acetaminophen Hepatotoxicity in Mice

Acute liver failure is a serious consequence of acetaminophen (APAP)-induced hepatotoxic liver injury with high rates of morbidity and mortality. Transforming growth factor beta 1 (TGFβ1) is elevated during liver injury and influences hepatocyte senescence during APAP-induced hepatotoxicity. This study investigated TGFβ1 signaling in the context of inflammation, necrotic cell death, and oxidative stress during APAP-induced liver injury. Male C57Bl/6 mice were injected with 600 mg/kg APAP to generate liver injury in the presence or absence of the TGFβ receptor 1 inhibitor, GW788388, 1 h prior to APAP administration. Acetaminophen-induced liver injury was characterized using histological and biochemical measures. Transforming growth factor beta 1 expression and signal transduction were assessed using immunohistochemistry, Western blotting and ELISA assays. Hepatic necrosis, liver injury, cell proliferation, hepatic inflammation, and oxidative stress were assessed in all mice. Acetaminophen administration significantly induced necrosis and elevated serum transaminases compared with control mice. Transforming growth factor beta 1 staining was observed in and around areas of necrosis with phosphorylation of SMAD3 observed in hepatocytes neighboring necrotic areas in APAP-treated mice. Pretreatment with GW788388 prior to APAP administration in mice reduced hepatocyte cell death and stimulated regeneration. Phosphorylation of SMAD3 was reduced in APAP mice pretreated with GW788388 and this correlated with reduced hepatic cytokine production and oxidative stress. These results support that TGFβ1 signaling plays a significant role in APAP-induced liver injury by influencing necrotic cell death, inflammation, oxidative stress, and hepatocyte regeneration. In conclusion, targeting TGFβ1 or downstream signaling may be a possible therapeutic target for the management of APAP-induced liver injury.

Thrombospondin-1 Exacerbates Acute Liver Failure and Hepatic Encephalopathy Pathology in Mice by Activating Transforming Growth Factor β1

Severe hepatic insults can lead to acute liver failure and hepatic encephalopathy (HE). Transforming growth factor β1 (TGFβ1) has been shown to contribute to HE during acute liver failure; however, TGFβ1 must be activated to bind its receptor and generate downstream effects. One protein that can activate TGFβ1 is thrombospondin-1 (TSP-1). Therefore, the aim of this study was to assess TSP-1 during acute liver failure and HE pathogenesis. C57Bl/6 or TSP-1 knockout (TSP-1-/-) mice were injected with azoxymethane (AOM) to induce acute liver failure and HE. Liver damage, neurologic decline, and molecular analyses of TSP-1 and TGFβ1 signaling were performed. AOM-treated mice had increased TSP-1 and TGFβ1 mRNA and protein expression in the liver. TSP-1-/- mice administered AOM had reduced liver injury as assessed by histology and serum transaminase levels compared with C57Bl/6 AOM-treated mice. TSP-1-/- mice treated with AOM had reduced TGFβ1 signaling that was associated with less hepatic cell death as assessed by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling staining and cleaved caspase 3 expression. TSP-1-/- AOM-treated mice had a reduced rate of neurologic decline, less cerebral edema, and a decrease in microglia activation in comparison with C57Bl/6 mice treated with AOM. Taken together, TSP-1 is an activator of TGFβ1 signaling during AOM-induced acute liver failure and contributes to both liver pathology and HE progression.

Elevated circulating TGFβ1 during acute liver failure activates TGFβR2 on cortical neurons and exacerbates neuroinflammation and hepatic encephalopathy in mice

BACKGROUND

Acute liver failure resulting from drug-induced liver injury can lead to the development of neurological complications called hepatic encephalopathy (HE). Hepatic transforming growth factor beta 1 (TGFβ1) is upregulated due to liver failure in mice and inhibiting circulating TGFβ reduced HE progression. However, the specific contributions of TGFβ1 on brain cell populations and neuroinflammation during HE are not known. Therefore, the aim of this study was to characterize hepatic and brain TGFβ1 signaling during acute liver failure and its contribution to HE progression using a combination of pharmacological and genetic approaches.

METHODS

C57Bl/6 or neuron-specific transforming growth factor beta receptor 2 (TGFβR2) null mice (TGFβR2^ΔNeu) were treated with azoxymethane (AOM) to induce acute liver failure and HE. The activity of circulating TGFβ1 was inhibited in C57Bl/6 mice via injection of a neutralizing antibody against TGFβ1 (anti-TGFβ1) prior to AOM injection. In all mouse treatment groups, liver damage, neuroinflammation, and neurological deficits were assessed. Inflammatory signaling between neurons and microglia were investigated in in vitro studies through the use of pharmacological inhibitors of TGFβ1 signaling in HT-22 and EOC-20 cells.

RESULTS

TGFβ1 was expressed and upregulated in the liver following AOM injection. Pharmacological inhibition of TGFβ1 after AOM injection attenuated neurological decline, microglia activation, and neuroinflammation with no significant changes in liver damage. TGFβR2^ΔNeu mice administered AOM showed no effect on liver pathology but significantly reduced neurological decline compared to control mice. Microglia activation and neuroinflammation were attenuated in mice with pharmacological inhibition of TGFβ1 or in TGFβR2^ΔNeu mice. TGFβ1 increased chemokine ligand 2 (CCL2) and decreased C-X3-C motif ligand 1 (CX3CL1) expression in HT-22 cells and reduced interleukin-1 beta (IL-1ß) expression, tumor necrosis factor alpha (TNFα) expression, and phagocytosis activity in EOC-20 cells.

CONCLUSION

Increased circulating TGFβ1 following acute liver failure results in activation of neuronal TGFβR2 signaling, driving neuroinflammation and neurological decline during AOM-induced HE.

Mechanistic Modelling of Drug-Induced Liver Injury: Investigating the Role of Innate Immune Responses

Drug-induced liver injury (DILI) remains an adverse event of significant concern for drug development and marketed drugs, and the field would benefit from better tools to identify liver liabilities early in development and/or to mitigate potential DILI risk in otherwise promising drugs. DILIsym software takes a quantitative systems toxicology approach to represent DILI in pre-clinical species and in humans for the mechanistic investigation of liver toxicity. In addition to multiple intrinsic mechanisms of hepatocyte toxicity (ie, oxidative stress, bile acid accumulation, mitochondrial dysfunction), DILIsym includes the interaction between hepatocytes and cells of the innate immune response in the amplification of liver injury and in liver regeneration. The representation of innate immune responses, detailed here, consolidates much of the available data on the innate immune response in DILI within a single framework and affords the opportunity to systematically investigate the contribution of the innate response to DILI.

Toxicant-Induced Hepatic Injury

The sudden failure of a previously healthy and functioning liver is a dramatic and devastating event. Acute liver failure is the common final pathway of a multitude of conditions and insults, all of which result in massive hepatic necrosis or loss of normal hepatic function. The ensuing multiorgan system failure frequently has a fatal outcome, with mortality rates in most series ranging from approximately 55% to 95% [1]. Acute liver failure (ALF, previously often referred to as fulminant hepatic failure (FHF)) knows no age boundaries, with many cases occurring in those younger than 30 years. Short of excellent intensive care unit (ICU) support and liver transplantation in selected cases, few viable treatment options are available. Over the past few decades, however, survival has been improved by anticipation, recognition, and early treatment of associated complications, as well as the application of prognostic criteria for early identification of patients requiring liver transplantation (along with improvement in the techniques and science of transplantation itself). The etiology of ALF varies from country to country and the incidence change over time. Paracetamol (acetaminophen) has now replaced viral hepatitis as the leading cause of ALF [2]. In a study from London including 310 patients with ALF in the period 1994–2004, 42% of the cases were caused by paracetamol [3], whereas this was only the cause in 2% of 267 patients in Spain from 1992 to 2000 [4]. However, less than 10% of all liver transplants are performed in patients with ALF [5, 6].

TGF-β1 gene - 509C > T promoter polymorphism modulates TGF-β1 levels in hepatitis E patients

Elevated levels of transforming growth factor-β1 (TGF-β1) and its positive correlation with Foxp3 expression in hepatitis E patients have indicated involvement of TGF-β1 in hepatitis E pathogenesis. The current study determined polymorphisms in TGF-β1 gene, plasma TGF-β1 levels and T effector (Teff) cell proliferation and explored their association in a case control study. Polymorphisms in three selected sites (- 509C > T, + 869T > C and + 915G > C) of TGF-β1 gene by PCR & restriction fragment length polymorphism methods, plasma TGF-β1 quantitation by ELISA and Teff (CD4 + CD25 -) cell proliferation by CFSE method were carried out in 277 hepatitis E patients (HE) with self-limiting infection and 233 ethnically matched healthy controls (HCs) from western India. Frequency of CT genotype of - 509C > T site was significantly higher in hepatitis E patients compared to healthy controls (p = 0.017; OR 1.53, 95% CI 1.07-2.17). Plasma TGF-β1 levels were significantly higher in HE compared to HCs. TGF-β1 level of patient group having CT genotype of - 509C > T site was significantly higher compared to those having CC or TT genotypes. Teff cell proliferation was negatively correlated with plasma TGF-β1 levels in HE patients (r = - 0.568; p = 0.014). Influence of TGF-β1 promoter (- 509C > T) polymorphism on plasma TGF-β1 levels and inverse correlation of Teff cell proliferation with plasma TGF-β1 levels in self-limiting hepatitis E patients suggest key role of TGF-β1 in augmentation of reported T regulatory cell mediated pathogenesis in hepatitis E.

The Transforming Growth Factor β1/Interleukin-31 Pathway Is Upregulated in Patients with Hepatitis B Virus-Related Acute-on-Chronic Liver Failure and Is Associated with Disease Severity and Survival

The transforming growth factor β1/interleukin-31 (TGF-β1/IL-31) pathway plays an important role in the process of cell injury and inflammation. The purpose of this work was to explore the role of the TGF-β1/IL-31 pathway in the cytopathic process of hepatitis B virus (HBV)-related acute-on-chronic liver failure (ACLF). The quantitative serum levels of TGF-β1, IL-9, IL-10, IL-17, IL-22, IL-23, IL-31, IL-33, and IL-35 were analyzed among chronic hepatitis B (CHB) patients (n = 17), ACLF patients (n = 18), and normal control (NC) subjects (n = 18). Disease severity in patients with ACLF was assessed using the model for end-stage liver disease (MELD) and Child-Pugh scores. Serum TGF-β1 levels were strongly positively correlated with IL-31 in all subjects, and both of them were positively correlated with IL-17, IL-22, and IL-33. In CHB and ACLF patients, serum levels of TGF-β1 and IL-31 were both increased significantly compared with those in NC subjects and positively correlated with total bilirubin (TBil) and alpha-fetoprotein (AFP) levels. ACLF patients showed the highest levels of TGF-β1 and IL-31, which were positively correlated with Child-Pugh scores. Furthermore, the recovery from the liver injury in CHB was accompanied by decreased TGF-β1 and IL-31 levels. More importantly, serum levels of TGF-β1 and IL-31 were markedly upregulated in ACLF nonsurvivors, and IL-31 displayed the highest sensitivity and specificity (85.7% and 100.0%, respectively) in predicting nonsurvival of ACLF patients. Increasing activity of the TGF-β1/IL-31 pathway is well correlated with the extent of liver injury, disease severity, and nonsurvival of ACLF patients, while reducing activity is detected along the recovery from liver injury in CHB, suggesting its potential role in the pathogenesis of liver injury during chronic HBV infection.

Elevated TGF-β1/IL-31 Pathway Is Associated with the Disease Severity of Hepatitis B Virus-Related Liver Cirrhosis

The proinflammatory cytokines transforming growth factor beta 1 (TGF-β1) and interleukin (IL)-31 have been implicated in tissue injury. However, whether TGF-β1/IL-31 are stimulated and elevated in response to liver injury that leads to fibrogenesis in hepatitis B virus-related liver cirrhosis (HBV-LC) remains unclear. To investigate the association between TGF-β1/IL-31 and stages of chronic HBV infection, serum TGF-β1, IL-9, IL-10,IL-17, IL-22, IL-23, IL-31, IL-33, and IL-35 were determined among patients with chronic hepatitis B (CHB; n=19), HBV-LC (n=20), and a normal control population (NC; n=18). Disease severity in patients with HBV-LC was assessed using model for end-stage liver disease (MELD) scores. Serum TGF-β1 and IL-31 levels were strongly positively linked in all subjects, and both correlated positively with IL-22, IL-33, and IL-17. TGF-β1 and IL-31 levels in the blood were both significantly higher in CHB and HBV-LC patients than in NC subjects. Elevated serum TGF-β1 and IL-31 levels were positively associated with albumin, alpha-fetoprotein, creatinine, white blood cell count, and platelet levels. Serum TGF-β1 and IL-31 were markedly higher in HBV-LC patients who did not have esophageal varices, and IL-31 had the highest sensitivity and specificity (90.9% and 66.7%, respectively) for indicating the absence of this complication. In summary, TGF-β1 and IL-31 were linked to progression from CHB to LC, and correlated well with the severity of HBV-LC. These findings suggest possible roles of the TGF-β1/IL-31 pathway in the pathogenesis of liver fibrosis during chronic HBV infection.

An overview of animal models for investigating the pathogenesis and therapeutic strategies in acute hepatic failure

Acute hepatic failure (AHF) is a severe liver injury accompanied by hepatic encephalopathy which causes multiorgan failure with an extremely high mortality rate, even if intensive care is provided. Management of severe AHF continues to be one of the most challenging problems in clinical medicine. Liver transplantation has been shown to be the most effective therapy, but the procedure is limited by shortage of donor organs. Although a number of clinical trials testing different liver assist devices are under way, these systems alone have no significant effect on patient survival and are only regarded as a useful approach to bridge patients with AHF to liver transplantation. As a result, reproducible experimental animal models resembling the clinical conditions are still needed. The three main approaches used to create an animal model for AHF are: surgical procedures, toxic liver injury and infective procedures. Most common models are based on surgical techniques (total/partial hepatectomy, complete/transient devascularization) or the use of hepatotoxic drugs (acetaminophen, galactosamine, thioacetamide, and others), and very few satisfactory viral models are available. We have recently developed a viral model of AHF by means of the inoculation of rabbits with the virus of rabbit hemorrhagic disease. This model displays biochemical and histological characteristics, and clinical features that resemble those in human AHF. In the present article an overview is given of the most widely used animal models of AHF, and their main advantages and disadvantages are reviewed.

Pleiotrophin inhibits transforming growth factor beta1-induced apoptosis in hepatoma cell lines

Pleiotrophin (PTN) is a hepatocyte growth factor and considered to play roles in liver fibrogenesis and hepatocarcinogenesis. In this study we examined the mechanism of the action of PTN in these pathological processes. First, we confirmed that hepatic stellate cells (HSCs) and Kupffer cells, and also later hepatocytes in hyperplastic nodules increased PTN mRNA expressions during carbon tetrachloride-induced liver fibrosis. Then, the relationship between PTN and transforming growth factor beta1 (TGFbeta1), a known potent pro-fibrogenetic cytokine, in carcinogenesis was investigated using hepatoma cell lines. Huh-7 human hepatoma cells weakly expressed PTN, but HepG2 human hepatoma cells and FaO rat hepatoma cells did not. Recombinant (r) TGFbeta1 induced the cultured Huh-7 cells to undergo apoptosis, which was inhibited by rPTN. Huh-7 cells became resistant to TGFbeta1-, but not mitomycin C-induced apoptosis when transfected with PTN gene, indicating the specificity of the PTN anti-apoptotic activity. Poly ADP ribose polymerase, procaspase-8 and procaspase-3 were not cleaved in the TGFbeta1-reluctant cells. The TGFbeta1-induced caspase-3 activation was also suppressed in Huh-7 and FaO cells both transduced with PTN gene-bearing adenoviruses. In summary, PTN was expressed in HSCs, Kupffer cells, and hepatocytes in fibrotic liver. We propose that PTN specifically antagonizes the TGFbeta1 activity during liver fibrosis.

Pathogenic molecular mechanisms in an animal model of fulminant hepatic failure: rabbit hemorrhagic viral disease

In this study we sought to determine whether molecular mechanisms involved in the pathogenesis of fulminant hepatic failure are present in rabbits experimentally infected with rabbit hemorrhagic disease virus (RHDV). The activities of aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase, as well as bilirubin concentration, were found to be significantly increased 36 hours after infection. Infected animals also demonstrated significant decreases in factor VII activity, in the Fischer index, and in the deterioration of prothrombin time. The concentration of reduced glutathione was significantly decreased 36 hours after infection, and we noted a marked increase in the ratio of oxidized to reduced glutathione. Infected animals showed progressive decreases in liver activity of the antioxidant enzyme superoxide dismutase. Expression of hepatocyte growth factor and c-met was found to be progressively reduced from 24 hours after infection, during which time we detected no modification in messenger RNA (mRNA) levels of transforming growth factor (TGF)-alpha. TFG-beta 1 was overexpressed 24 and 36 hours after infection, and 36 hours after infection we detected a significant increase in TNF-alpha mRNA levels. Experimental RHDV infection also induced marked activation of nuclear factor-kappaB and a significant increase in inducible nitric oxide synthase mRNA levels from 24 hours after infection. Data obtained from this animal model support its usefulness in the investigation of potential novel therapeutical modalities aimed at neutralizing reactive oxygen species and hepatocyte growth inhibitors or enhancing hepatocyte responsiveness to mitogens.

Coexpression of hepatocyte growth factor/scatter factor (HGF/SF) and its receptor cMET predict recurrence of meningiomas

Hepatocyte growth factor/scatter factor (HGF/SF) and its receptor, the cMET tyrosine kinase participate in cancer invasion, angiogenesis and metastasis in a wide variety of neoplastic cells. Meningioma is a bening tumour, however, it has a high rate of recurrence after surgery; the most important factor to predict relapse is the extent of surgical resection, several other potentially predictive factors have been studied with poor results. We examined by immunohistochemistry the expression of HGF/SF and its cMET receptor in a group of patients with benign meningioma with or without recurrence (n = 17 and n = 25, respectively), after a minimal follow-up of least 6 years. Expression and coexpression of HGF/SF and cMET were compared with cell proliferation index, vascular density and clinical outcome. Coexpression of HGF/SF and cMET in meningiomas had a significant association with cell proliferation index and with recurrence (P < 0.037). Determination of HGF and cMET coexpression in meningiomas could be used as a predictor of recurrence.

Up-regulation of hepatocyte growth factor caused by an over-expression of transforming growth factor beta, in the rat model of fulminant hepatic failure

BACKGROUND

The role of transforming growth factor beta (TGF-beta), a potent regulator of cellular growth, was investigated in the rat model of fulminant hepatic failure (FHF).

MATERIALS AND METHODS

The rat FHF model was created by a combination of a 68% partial hepatectomy (PH) and 7% of necrosis (each n = 25 in Groups 1, 2 and 3). Adenovirus mediated gene transfer of mature human TGF-beta1 gene was performed by the systemic injection of AxCAhTGFb1 (1 x 10(9) pfu) in Group 1, 3 days before FHF. In control Groups 2 and 3, recombinant lacZ adenovirus (AxCAlacZ, Group 2) and normal saline (1 ml, Group 3) were used, instead of AxCAhTGFb1.

RESULTS

An excessive expression of TGF-beta1 in Group 1 resulted in an inhibition of hepatocyte proliferation (24-48 h after FHF) and gaining of liver weight (24-48 h), increased expression of HGF in liver tissue (24 h), and decreased expression of TGF-alpha (24 h), compared to those in control Groups 2 and 3. Serum IL-6 levels were also elevated by a TGF-beta1 over-expression at 24 hrs after FHF in Group 1.

CONCLUSIONS

The forced expression of TGF-beta1 in the FHF liver yields both a secondary increase of HGF production and a suppression of liver regeneration, which might explain the mechanism of increased serum HGF observed in a clinical FHF. TGF-beta1 is thus thought to have an important role in inhibiting liver regeneration after FHF.

Spectrum of molecular changes during hepatocarcinogenesis induced by DEN and other chemicals in Fisher 344 male rats [Mechanisms of Ageing and Development 123 (2002) 1665-1680]

Unlike other tissues such as breast, colon and renal cell carcinoma, it is not an easy task to single out any representative oncogene or tumor suppressor genes in the development of hepatocellular carcinoma (HCC), which play a pivotal role. To investigate putatively altered main pathways in HCC, F344 male rats were treated with a single injection of N-nitrosodiethylamine (DEN), followed by either twice/week injections of nodularin for 10 weeks or thioacetamide (TAA) in drinking water for 39 weeks. p53 expression was dramatic in both hepatocytes and mesenchymal cells after a single injection of DEN, however, PCR-SSCP assay could not detect any p53 mutation during the development of hepatocellular adenoma (HCA). The data indicate that wtp53 response was mostly for removal of damaged cells during the initiation of carcinogenesis. When treated with DEN-TAA, induction of gankyrin expression during hepatic fibrosis preceded the loss of pRB protein, accompanied with significant expressions of G1phase cyclins and CDKs. Moreover, p16(INK4A) exon 1 was hypermethylated during the development of poorly differentiated HCCs. These changes would result in complete inactivation of the pRB regulatory pathway during hepatocarcinogenesis. Induction of TGF-beta1 expression with loss of its receptor expression occurred rapidly in the altered hepatocytes by DEN-nodularin treatment.

CONCLUSION

Therefore, escape from TGF-beta1 induced apoptosis and severe degradation of pRB protein during the early stage of carcinogenesis can perform a symphony to proliferate and to transform the altered hepatocytes to tumor cells. Inactivation of p16(INK4A) and p53 genes at the later stage of carcinogenesis would endow HCC with malignancy, which is highly resistant to any therapeutic trials.

Transforming growth factor beta in hepatitis C virus infection: in vivo and in vitro findings

BACKGROUND

Hepatitis C virus (HCV) is a leading cause of chronic liver disease (CLD) worldwide. The chronicity is a result of viral persistence and the ability of the virus to escape from the immune mechanisms of the host. Transforming growth factor (TGF)-beta is a cytokine thought to be responsible for viral persistence and liver fibrogenesis.

METHODS

The present study examined the levels of TGF-beta messenger (m)RNA by reverse transcription polymerase chain reaction (RT-PCR) in 35 liver biopsies and HCV-transfected HepG2 cells.

RESULTS

Transforming growth factor-beta mRNA was detected in nine liver biopsies from patients with chronic HCV infection, but was not detected in patients with non-HCV-related CLD or controls. On quantitation by semiquantitative PCR, TGF-beta mRNA levels ranged from 10-4.75 to 10-12.8 amol (10-7.46 +/- 3.771) in liver biopsies of HCV-related CLD. No significant difference in TGF-beta receptor levels was observed by RT-PCR in HCV- or non-HCV-related CLD by immunohistochemistry. To correlate these findings with in vitro experiments, levels of TGF-beta mRNA and its receptors were determined by RT-PCR in HepG2 cells transfected with HCV and hepatitis B virus (HBV) constructs, using mock-transfected cells as control. The TGF-beta protein levels were quantitated in these cell supernatants by enzyme immunoassay. The TGF-beta mRNA and protein levels were two logs and approximately 30 times higher in HCV-transfected HepG2 cells than in HBV- and mock-transfected cells, respectively. The TGF-beta receptors in HepG2 cells were also downregulated in HCV-transfected cells as compared with mock-transfected cells.

CONCLUSION

These observations suggest upregulation of TGF-beta in HCV infection and a probable role for TGF-beta in the pathogenesis of HCV-related CLD.

Rabbit hemorrhagic viral disease: characterization of a new animal model of fulminant liver failure

In this study we sought to characterize a novel model of fulminant liver failure (FLF) by means of experimental infection of rabbits with the rabbit hemorrhagic disease virus (RHDV). Thirty-seven 9-week-old rabbits were injected intramuscularly with 2 x 10(4) hemagglutination units of an RHDV isolate. Eighty-five percent of rabbits died 36 to 54 hours after infection. From 36 hours after infection we noted marked increases in transaminases, lactate dehydrogenase, and total bilirubin. The rabbits exhibited hypoglycemia and coagulation abnormalities, with a significant decrease in factor V, factor VII, and prothrombin. Plasma aromatic amino acids and taurine showed progressive increases, and the Fischer index was significantly reduced. Expression of hepatocyte growth factor messenger RNA was inhibited from 36 hours after infection. Prostration and side recumbency were present at later stages, and neurologic symptoms rapidly progressed to coma. Onset of brain death was associated with a significant increase in intracranial pressure and blood ammonia. RHDV infection reproduces clinical, biochemical, and histologic features of the FLF syndrome and satisfies criteria for a suitable animal model. Rabbit hemorrhagic viral disease could provide a useful tool for the study of FLF and the evaluation of new liver-support technologies in human subjects.

Activin A and follistatin in acute liver failure

BACKGROUND

Liver regeneration may be impaired in acute liver failure due to either inhibition of the proliferative response or ongoing liver cell death. Activin A, a member of the TGFbeta superfamily, inhibits hepatocyte DNA synthesis and induces apoptosis.

METHODS

Levels of activin A and its binding protein follistatin in the serum of 23 patients with acute liver failure were determined by enzyme-linked immunosorbent assay.

RESULTS

Serum activin A was significantly increased in acute liver failure patients (median 2.15 ng/ml, range 0.28-6.87 ng/ml) compared to normal controls (median 0.25 ng/ml, range 0.19-0.53 ng/ml; = 10; 0.001). However, this was not linked to the final disease outcome. Higher levels of activin A were found in the serum of patients with acute liver failure due to paracetamol overdose (median 2.87 ng/ml, range 0.72-6.87 ng/ml; = 17) than in patients with acute liver failure due to non-A to E hepatitis (median 1.10 ng/ml, range 0.28-2.70 ng/ml; = 6; 0.05). Serum follistatin was also increased in acute liver failure patients (median 2.84 ng/ml, range 0.57-13.24 ng/ml) compared to normal controls (median 0.68 ng/ml, range 0.32-3.70 ng/ml; 0.01).

CONCLUSION

Serum activin A is increased in acute liver failure and could be a factor in the inhibition of liver regeneration.

Spectrum of molecular changes during hepatocarcinogenesis induced by DEN and other chemicals in Fischer 344 male rats

Unlike other tissues such as breast, colon and renal cell carcinoma, it is not an easy task to single out any representative oncogene or tumor suppressor genes in the development of hepatocellular carcinoma (HCC), which play a pivotal role. To investigate putatively altered main pathways in HCC, F344 male rats were treated with a single injection of N-nitrosodiethylamine (DEN), followed by either twice/week injections of nodularin for 10 weeks or thioacetamide (TAA) in drinking water for 39 weeks. p53 expression was dramatic in both hepatocytes and mesenchymal cells after a single injection of DEN, however, PCR-SSCP assay could not detect any p53 mutation during the development of hepatocellular adenoma. The data indicate that wtp53 response was mostly for removal of damaged cells during the initiation of carcinogenesis. When treated with DEN-TAA, induction of gankyrin expression during hepatic fibrosis preceded the loss of pRB protein, accompanied with significant expressions of G1 phase cyclins and CDKs. Moreover, p16(INK4A) exon 1 was hypermethylated during the development of poorly differentiated HCCs. These changes would result in complete inactivation of the pRB regulatory pathway during hepatocarcinogenesis. Induction of TGF-beta1 expression with loss of its receptor expression occurred rapidly in the altered hepatocytes by DEN-nodularin treatment.

CONCLUSION

Therefore, escape from TGF-beta1 induced apoptosis and severe degradation of pRB protein during the early stage of carcinogenesis can perform a symphony to proliferate and to transform the altered hepatocytes to tumor cells. Inactivation of p16(INK4A) and p53 genes at the later stage of carcinogenesis would endow HCC with malignancy, which is highly resistant to any therapeutic trials.

Hepatocyte growth factor is associated with poor prognosis of malignant gliomas and is a predictor for recurrence of meningioma

BACKGROUND

Hepatocyte growth factor (HGF) is a cytokine that participates in multiple cell functions; it promotes proliferation, motility, and morphogenesis of epithelial cells. Some malignant tumors, such as breast carcinoma, bronchogenic carcinoma, and multiple myeloma, overexpress it and its receptor. Hepatocyte growth factor is also present in normal astrocytes; therefore, it is important to investigate whether HGF participates in the pathophysiology of malignant gliomas and other brain tumors. Intratumoral concentration of HGF in human intracranial neoplasms was measured and correlated with prognosis, tumor recurrence, vasogenic edema, cell proliferation index, and vascular density.

METHODS

Hepatocyte growth factor concentration was measured in 62 intracranial tumors, including 16 anaplasic astrocytomas (AA), 16 glioblastoma multiformes (GM), 11 meningiomas, 9 hypophyseal adenomas, 7 oligodendrogliomas, and 3 cordomas, and in 4 samples of nonneoplastic brain tissue. The following parameters were correlated with HGF values: survival and tumor recurrence, cell proliferation index and vascular density as determined by immunohistopathologic analysis, and peritumoral edema as seen by magnetic resonance imaging.

RESULTS

Hepatocyte growth factor concentration (pg/mL) was significantly higher in malignant gliomas (AA and GM) than in adenomas, oligodendrogliomas, and nonneoplastic brain tissue, but it was similar to that of meningiomas. Mean survival of patients with AA was 16.5 +/- 3.6 months and for patients with GM 12.3 +/- 1.3 months. Hepatocyte growth factor concentration was higher in GM than in AA (15,844 +/- 2504 vs. 7499 +/- 1703, P = 0.0375) and was correlated with the cell proliferation index and with poor prognosis. Likewise, mean tumoral concentration of HGF was higher in meningiomas that relapsed than in those without recurrence (22,887 +/- 6489 vs. 2090 +/- 497, P = 0.008).

CONCLUSIONS

Intratumoral concentration of HGF in gliomas is associated with malignancy and poor prognosis. High HGF is also found in meningiomas and is related with long term recurrence. The current findings suggest that the routine measurement of HGF may be used as a predictive factor for planning therapeutic strategies in both malignant gliomas and meningiomas. The potential use of HGF inhibitors or antagonists for therapy of these tumors should be explored.

Immediate early genes and p21 regulation in liver of rats with acute hepatic failure

It has been observed that liver regeneration in acute hepatic failure (AHF) is suppressed [Eguchi et al. Hepatology 1996;24(6):1452-9]. The molecular mechanism regulating this inhibition is not known. We previously reported that in AHF rats, hepatocyte proliferation was significantly impaired with elevation in serum IL-6, TGF-beta1, and HGF [Kamohara et al. Biochem Biophys Res Commun 2000;273(1):129-35]. Following either 70% partial hepatectomy (PH) or liver injury, quiescent mature hepatocytes are "primed" to re-enter the cell cycle. The process of "priming" appears to be triggered by extracellular cytokines (IL-6 and TNF-alpha) and is characterized by expression of immediate early genes. Under the stimulation of growth factors such as HGF, "primed" hepatocytes exit the G1 phase of the cell cycle. G1-associated cyclins and their inhibitors play a pivotal role in G1/S cell cycle transition. Here, we demonstrate that immediate early gene (i.e. c-myc, c-fos) expression and AP-1 activity are preserved in AHF rat livers despite absence of hepatocyte proliferation. In contrast, p21 mRNA and protein are both over-expressed in AHF livers compared to livers from rats undergoing PH; this elevation leads to inhibition in Cdk2 activity, resulting in G1 cell cycle arrest and inhibition of regeneration.

Acute liver failure: established and putative hepatitis viruses and therapeutic implications

Any virus that can cause an acute hepatitis will, on occasion, give rise to acute liver failure. Such infections can be separated into those due to the primary hepatitis viral infections A to E and those where hepatitis occurs as part of a systemic viral infection, as with infection with, for instance, Epstein-Barr virus, cytomegalovirus, Varicella zoster virus, adenovirus and Herpes simplex virus. In general, the frequency with which the different hepatitis viruses are responsible for acute liver failure is related to their underlying prevalence in particular countries. An apparent exception is the striking geographical variation in the reported prevalence of acute liver failure due to hepatitis C virus infection, with a much higher proportion of cases generally attributed to this agent in Japan and Taiwan than in Western countries. Recent work has focused on the possible importance of mutant hepatitis B viral strains, co- and super-infection with known hepatitis viruses and certain newly described agents that may account for otherwise unexplained cases of acute liver failure. Despite an improved understanding of the pathogenesis of complicating cerebral oedema and advances in general supportive care, it is likely that the most severely affected patients with acute liver failure due to viral causes will survive only with liver transplantation, at least until approaches for promoting adequate liver regeneration are successfully developed and implemented.

Current status of liver support systems

The search for a support system for liver failure has been intensified. Methods currently being tested include those based on artificial support, on biological approaches (including extracorporeal liver perfusion and transplanted hepatocytes) as well as hybrid devices that combine artificial aspects with biological systems. Each of these three areas is undergoing fast technological and conceptual development. Controlled clinical trials are also under way.

Macrophage-derived transforming growth factor-beta1 induces hepatocellular injury via apoptosis in rat severe acute pancreatitis

BACKGROUND

The mechanism of acute pancreatitis-induced hepatocellular injury is unclear. We have observed hepatocyte apoptosis in rat acute necrotizing pancreatitis. These studies were designed to determine the mediator(s) responsible for hepatocyte apoptosis and to clarify the significance of macrophages as its source.

METHODS

A rat sodium deoxycholate-induced pancreatitis model was used. Immunohistochemical studies for apoptosis-inducing mediators on hepatocytes were examined in the liver and on the peritoneal macrophages. The levels of transforming growth factor-beta1 (TGF-beta1) were also evaluated quantitatively with an enzyme-linked immunosorbent assay. Induction of apoptosis on the hepatocytes was evaluated by in situ nick-end labeling and tissue DNA fragmentation enzyme-linked immunosorbent assay. Finally, the effects of TGF-beta1 neutralization and macrophage depletion were examined.

RESULTS

In the liver and the peritoneal macrophages, strong expression of TGF-beta1 was detected early in the course of pancreatitis. In sodium deoxycholate-induced pancreatitis, the levels of TGF-beta1 were also elevated in the plasma (9.2 +/- 0.8 ng/mL), in the pancreatitis-associated ascitic fluid (11.5 +/- 0.6 ng/mL), and in the liver homogenate (2.8 +/- 0.3 ng/g of liver tissue). Moreover, the amount of fragmented DNA of the liver with pancreatitis was 290% +/- 20% of that with a sham operation and serum alanine aminotransferase levels elevated to 248.2 +/- 67.0 IU/L. TGF-beta1 neutralization partly blocked the positive labeling on the nuclei of the hepatocytes, the elevation of the amounts of fragmented DNA (205% +/- 10% of sham operation), and the serum alanine aminotransferase level (144.2 +/- 14.9 IU/L). On the other hand, the macrophage depletion caused a marked decrease in the TGF-beta1 protein level in the plasma (4.8 +/- 1.2 ng/mL) or in the pancreatitis-associated ascitic fluid (8.0 +/- 1.0 ng/mL). Moreover, the macrophage depletion completely inhibited the elevation of the TGF-beta1 protein level in the liver homogenate (1.5 +/- 0.4 ng/g of liver tissue), and thereafter decreased the amounts of the positive labeling on the nuclei of the hepatocytes and decreased the amount of fragmented DNA (120% +/- 18% of sham operation) and the serum alanine aminotransferase elevation (119.2 +/- 24.2 IU/L).

CONCLUSIONS

In a model of sodium deoxycholate-induced pancreatitis, macrophages are responsible for pancreatitis-induced hepatocellular injury by means of apoptosis, and macrophage-derived TGF-beta1 is one of the major factors inducing the hepatocyte apoptosis.

Acute liver failure: targeted artificial and hepatocyte-based support of liver regeneration and reversal of multiorgan failure

Acute liver failure (ALF) still represents a major therapeutic challenge for hepatologists due to its high mortality rate as a result of multiorgan failure. Although emergency orthotopic liver transplantation represents a major advance in the management of selected patients, it is not applicable to all candidates due to limited organ availability. Therefore, new therapeutic options should be developed to bridge selected patients to transplantation or to treat patients not candidates for liver transplantation. Although new techniques for cell culture and perfusion have resulted in a number of promising devices for the provision of temporary liver support in acute liver failure, their clinical efficacy is as yet uncertain. Controlled trials on a multi-centre basis in well-defined patient groups and with standardised outcome measures, including the extent to which treatment influences cell damage and regeneration and prevents or reverses multiorgan failure, will be essential to properly evaluate the clinical value of current and evolving artificial and bioartificial devices. The same considerations must also apply to the assessment of therapeutic efficacy of hepatocyte transplantation. A better understanding of mechanisms responsible for the development of liver cell death, along with cellular and molecular mechanisms allowing surviving cells to proliferate in a hostile environment, will be required if a more targeted therapeutic approach to decreasing hepatocellular injury and enhancing liver regeneration is to be achieved. Whether extracorporeal devices or the transplantation of primary hepatocytes, stem cells or cells genetically engineered to over-express key metabolic functions, a proliferative phenotype and/or cytoprotective pathways will be best suited to meeting these demanding challenges remains to be determined.

Fulminant hepatic failure

In recent years, considerable progress has been made in developing specific and supportive medical measures that have improved prognosis in FHF. Although new techniques for cell culture and perfusion have also resulted in a number of promising devices for the provision of temporary liver support, their clinical efficacy is as yet uncertain. Controlled multicenter trials in well-defined patient groups and with standardized outcome measures will be essential to evaluate the clinical value of these devices properly. The same considerations must also apply in assessing the efficacy of hepatocyte transplantation in FHF. A better understanding of mechanisms responsible for liver cell death and multiorgan failure, and the development of strategies to enhance liver regeneration may, in the future, allow a more targeted approach to therapy.

Acute liver failure

Severe hepatitis A infection is an infrequent but well-recognized cause of acute liver failure that can now be effectively prevented with vaccination against hepatitis A virus. Bromfenac and troglitazone hepatotoxicity as well as various herbal remedies are some of the newly identified causes of acute liver failure. The recently identified transfusion-transmitted virus has been implicated in some cases of idiopathic acute liver failure whereas hepatitis G virus does not appear to be a causative agent. Recognizing, monitoring, and treating patients with life-threatening cerebral edema remain critically important but difficult aspects of the clinical care of acute liver failure. Hypothermia and N-acetylcysteine are promising experimental approaches to cerebral edema but emergency liver transplantation is the only proven means of improving patient survival. Although recent changes in organ allocation may reduce waiting time to transplantation, more reliable and validated markers of liver regeneration and prognosis are needed to triage patients. The potential application and limitations of novel technologies including bioartificial liver devices and auxiliary liver transplantation continue to evolve from pioneering work in animal models and human subjects.

TGF-beta1 in liver fibrosis: an inducible transgenic mouse model to study liver fibrogenesis

Transforming growth factor-beta1 (TGF-beta1) is a powerful stimulus for collagen formation in vitro. To determine the in vivo effects of TGF-beta1 on liver fibrogenesis, we generated transgenic mice overexpressing a fusion gene [C-reactive protein (CRP)/TGF-beta1] consisting of the cDNA coding for an activated form of TGF-beta1 under the control of the regulatory elements of the inducible human CRP gene promoter. Two transgenic lines were generated with liver-specific overexpression of mature TGF-beta1. After induction of the acute phase response (15 h) with lipopolysaccharide (100 microgram ip), plasma TGF-beta1 levels reached >600 ng/ml in transgenic animals, which is >100 times above normal plasma levels. Basal plasma levels of uninduced transgenic animals were about two to five times above normal. As a consequence of hepatic TGF-beta1 expression, we could demonstrate marked transient upregulation of procollagen I and procollagen III mRNA in the liver 15 h after the peak of TGF-beta1 expression. Liver histology after repeated induction of transgene expression showed an activation of hepatic stellate cells in both transgenic lines. The fibrotic process was characterized by perisinusoidal deposition of collagen in a linear pattern. This transgenic mouse model gives in vivo evidence for the important role of TGF-beta1 in stellate cell activation and liver fibrogenesis. Due to the ability to control the level of TGF-beta1 expression, this model allows the study of the regulation and kinetics of collagen synthesis and fibrolysis as well as the degree of reversibility of liver fibrosis. The CRP/TGF-beta1 transgenic mouse model may finally serve as a model for the testing of antifibrogenic agents.