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

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.

Targeting platelet migration in the postischemic liver by blocking protease-activated receptor 4

BACKGROUND

Platelets play a critical role during hepatic ischemia/reperfusion (I/R). Antiplatelet strategies during liver transplantation are, however, limited because of bleeding complications. Thrombin is activated during reperfusion and regulates platelet and endothelial cell function via protease-activated receptor 4 (PAR-4). Interventions at the level of PAR-4, the main platelet receptor for thrombin, are assumed to attenuate the proinflammatory effects of thrombin without affecting blood coagulation. The aim of our study was to analyze the impact of PAR-4 blockade on platelet recruitment and microvascular injury during hepatic I/R.

METHODS

C57BL/6 mice undergoing hepatic I/R (90 min/60 min and 240 min) were treated either with a selective PAR-4 antagonist TcY-NH2 or vehicle. Sham-operated animals served as controls. Recruitment of freshly isolated and fluorescence-labeled platelets and CD4 T cells was analyzed using intravital video fluorescence microscopy. Parameters of tissue injury, regeneration, and blood coagulation were assessed in tissue/blood samples.

RESULTS

Results show that treatment with TcY-NH2 attenuated I/R-induced platelet and CD4 T-cell recruitment, improved sinusoidal perfusion failure, and reduced apoptotic and necrotic injury. The protective effect of PAR-4 blockade did not suppress hemostasis or liver regeneration.

CONCLUSION

Our in vivo data suggest PAR-4 as a potential target for future therapeutic strategies against platelet-mediated liver injury on transplantation.

Hepatitis C virus-related hepatocellular carcinoma: An insight into molecular mechanisms and therapeutic strategies

Hepatitis C virus (HCV) infects more than 170 million people worldwide, and thereby becomes a series global health challenge. Chronic infection with HCV is considered one of the major causes of end-stage liver disease including cirrhosis and hepatocellular carcinoma. Although the multiple functions of the HCV proteins and their impacts on the modulation of the intracellular signaling transduction processes, the drive of carcinogenesis during the infection with HCV, is thought to result from the interactions of viral proteins with host cell proteins. Thus, the induction of mutator phenotype, in liver, by the expression of HCV proteins provides a key mechanism for the development of HCV-associated hepatocellular carcinoma (HCC). HCC is considered one of the most common malignancies worldwide with increasing incidence during the past decades. In many countries, the trend of HCC is attributed to several liver diseases including HCV infection. However, the development of HCC is very complicated and results mainly from the imbalance between tumor suppressor genes and oncogenes, as well as from the alteration of cellular factors leading to a genomic instability. Besides the poor prognosis of HCC patients, this type of tumor is quite resistance to the available therapies. Thus, understanding the molecular mechanisms, which are implicated in the development of HCC during the course of HCV infection, may help to design a general therapeutic protocol for the treatment and/or the prevention of this malignancy. This review summarizes the current knowledge of the molecular mechanisms, which are involved in the development of HCV-associated HCC and the possible therapeutic strategies.

Expression of Anti-Apoptotic Protein, Bcl-2, in Liver Regeneration After a Partial Hepatectomy

BACKGROUND

Although Bcl-2 is well known to have anti-apoptotic activities in vitro and in vivo, the role of Bcl-2 relating to liver regeneration remains controversial. The aim of this study was to document the effect of Bcl-2 expression on liver regeneration in rats undergoing a partial hepatectomy.

MATERIAL AND METHODS

Adult male Wistar rats (n = 4/group) at 72 h before undergoing a 70% partial hepatectomy (PH) were administered 1 x 10(9) plaque-forming units of adenovirus vector encoding either human Bcl-2 (group 1) or LacZ (group 2) intravenously and were sacrificed at 0, 12 h, and at 1, 2, 3, 7, 14, and 21 days postoperatively. In group 3, normal saline was injected instead of adenovirus vector. Liver regeneration was monitored by measuring the restituted liver mass and proliferating cell nuclear antigen (PCNA) immunostaining. The incidence of apoptosis in the liver was analyzed by the immunohistochemical detection of single-stranded DNA at 14 and 21 days postoperatively.

RESULTS

The restituted liver mass showed significantly higher values in group 1 (26.1 +/- 7.2%) than in group 2 (14.7 +/- 6.8%) and 3 (13.6 +/- 5.0%) at 1 day after PH (P < 0.05). The PCNA labeling index was significantly higher in group 1 (47.2 +/- 9.9%) than in groups 2 (19.0 +/- 7.8%) and 3 (19.2 +/- 15.2%) at 1 day after a partial hepatectomy (P < 0.05). The hepatocyte growth factor (HGF) mRNA expression was significantly lower in group 1 than in group 2 at 12 h after PH (P < 0.05). The number of single-stranded DNA-positive cells decreased significantly more in group 1 (5.67 +/- 1.53 positive cells/10 fields per tissue) than those in group 2 (18.33 +/- 7.57 positive cells/10 fields per tissue) at 14 days after PH.

CONCLUSIONS

These results thus indicated that an overexpression of anti-apoptotic protein Bcl-2 does not necessarily have an anti-apoptotic effect on liver regeneration but appears to have a pro-proliferative effect in the early phase of liver regeneration.

Response of porcine hepatocytes in primary culture to plasma from severe viral hepatitis patients

AIM

To observe the effects of plasma from patients with severe viral hepatitis (SVHP) on the growth and metabolism of porcine hepatocytes and the clinical efficiency of bioartificial liver device.

METHODS

Hepatocytes were isolated from male porcines by collagenase perfusion. The synthesis of DNA and total protein, leakages of AST and LDH, changes in glutathione (GSH), catalase and morphology of porcine hepatocytes exposed to SVHP were investigated to indicate the effect of plasma from patients with severe hepatitis on the growth, injury, detoxification, and morphology of porcine hepatocytes.

RESULTS

The synthesis of DNA and protein was inhibited in the medium containing 100% SVHP compared to the controls. The leakages of LDH and AST increased in porcine hepatocytes following exposure to 100% SVHP for 5 h. The difference between 100% SVHP and 10% newborn calf serum (NCS) was significant in t-test (LDH: t = 24.552, P = 0.001; AST: t = 4.169, P = 0.014). After exposure to SVHP for 24 h, alterations in GSH status were significant (F = 2.746, P<0.05) between porcine hepatocytes in 100% SVHP and 10% NCS, but no alteration occurred in the culture medium after 48 h (F = 4.378, P<0.05). A similar profile was observed in catalase activity. Many round vacuoles were observed in porcine hepatocytes cultured in SVHP. The membranes of these cells became indistinct and almost all the cells died on d 5.

CONCLUSION

Plasma from patients with severe hepatitis inhibits the growth, injures membrane, disturbs GSH homeostasis and induces morphological changes of porcine hepatocytes. It is suggested that SVHP should be pretreated to reduce the toxin load and improve the performance of porcine hepatocytes in extracorporeal liver-support devices.

Adenoviral gene transfer of an NF-κB super-repressor increases collagen deposition in rodent cutaneous wound healing

BACKGROUND

The transcription factor nuclear factor-kappaB (NF-kappaB) plays an essential role in inflammation. To date, no studies have investigated the effect of inhibiting NF-kappaB-mediated inflammation on normal cutaneous wound healing. We tested this by locally administering an adenovirus recombinant that constitutively expresses a super-repressor isoform of inhibitory-kappaB (IkappaB) into rats undergoing a well-established model of dorsal wound healing.

METHODS

Seventy-two Sprague-Dawley rats underwent insertion of a sponge-pump construct into a dorsal subcutaneous pocket. One group of rats received pumps filled with the adenovirus expressing I-kappaB (rAd-Ikappab), a second group received pumps filled with adenovirus expressing green fluorescent protein (GFP) (rAd-gfp), and a third received pumps filled with normal saline (NS). Rats were killed in groups of 6 on days 1, 3, 5 and 7 postoperation. The wound fluid was analyzed for nitrite/nitrate (NOx) and tumor necrosis factor-alpha (TNF-alpha) concentrations. The wound fluid was assayed for hydroxyproline (OHP) content, an index of reparative collagen deposition.

RESULTS

Administration of rAd-Ikappab for 7 days resulted in higher collagen deposition (OHP) compared with the rAd-gfp and NS groups. NOx levels were significantly higher in the rAd-gfp group on day 1 and marginally so on day 5. TNF-alpha quantitation analysis found no significant difference among the 3 groups.

CONCLUSION

IkappaB expression through an adenoviral vector in the cutaneous wound may improve rodent healing, as shown by increased collagen deposition, through decreased inflammation. This mechanism appears to be TNF-alpha independent. Inhibition of NF-kappaB may reduce inflammation by reducing the local NOx concentrations.

Autocrine expression of hepatocyte growth factor and its cytoprotective effect on hepatocyte poisoning

AIM: To construct pEGFP-hepatocyte growth factor (HGF) expression vector, the to detect its expression in transfected human hepatocytes, and to investigate the influence of autocrine HGF expression on the proliferative potential and cytoprotective effects in human hepatocytes.

METHODS: Human HGF cDNA was ligated to the pEGFP vector. Recombinant plasmid was transfected into human hepatocyte line QZG with liposome. Expression of HGF protein was observed by fluorescence microscopy and immunohistochemistry. Hepatic cells were collected 24, 48, and 72 h after transfection to detect the number of [³H]-TdR uptake in DNA. DNA synthesis was observed by using PCNA stain immunohistochemistry. Acute liver cell damage was induced by carbon tetrachloride. Cytoprotective effect was observed by examining the survival rate of hepatocytes and leakage of intracellular alanine transaminase (ALT) and potassium ions.

RESULTS: HGF identification of pEGFP-HGF by enzyme digestion showed that HGF fragment was cloned into BamH I and Sal I sites of pEGFP-N3. Expression of GFP in transfected hepatocytes was observed with fluorescence microscopy. The [³H]-TdR uptake became 7 times as many as in the control group 96 h after transfection. After HGF transfection, the survival rate of hepatocytes poisoned by CCl₄ significantly increased (83% vs 61%, P < 0.05), and the leakage of intracellular alanine transaminase and potassium ions decreased (586 nkat/L vs 1089 nkat/L, P < 0.01; and 5.59 mmol/L vs 6.02 mmol/L, P < 0.01 respectively). Culture of transfected hepatic cells promoted the proliferation of other non-transfected cells.

CONCLUSION: Transfected HGF is expressed in hepatic cells and has the activity of promoting cell division and protecting hepatic cells against poisoning.