Apoptosis in chronic viral hepatitis parallels histological activity: an immunohistochemical investigation using anti-activated caspase-3 and M30 cytodeath antibody

Serum keratin-18 detects hepatic inflammation and predicts progression in compensated alcohol-associated liver disease

Alcohol-associated liver fibrosis accumulates over decades, driven by hepatic inflammation and cell death. We investigated the diagnostic accuracy of keratin-18 degradation, measured using serum M30 and M65 levels, and the ActiTest for hepatic inflammatory activity in patients with compensated alcohol-associated liver disease (ALD). Furthermore, we evaluated the prognostic accuracy of markers for liver-related events and all-cause mortality. All findings were compared with routine liver function tests: Aspartate aminotransferase (AST), alanine aminotransferase (ALT), and gamma-glutamyltransferase. Our prospective, biopsy-controlled, single-center study included 265 patients with ongoing or prior excessive alcohol intake, representing the full spectrum of compensated ALD. We defined hepatic inflammatory activity as a combined score of lobular inflammation and ballooning. For severe hepatic inflammatory activity (n = 40), we found excellent diagnostic accuracy for M30 (area under the receiver operating characteristics curve [AUROC] = 0.90), M65 (AUROC = 0.86), and AST (AUROC = 0.86). Elevated M30 (M30 > 240 U/L) had the highest positive predictive value (PPV) and specificity, significantly higher than M65, ActiTest and ALT, but not AST (M30: sensitivity = 83%, specificity = 82%, positive predictive value = 45%, negative predictive value = 95%). Patients were followed up for 1445 patient-years. All markers, except for ALT, significantly predicted liver-related events and all-cause mortality. After adjusting for advanced fibrosis, drinking behavior and body mass index, M30 and M65 remained significant predictors of liver-related events, whereas M30 and AST were significant predictors of all-cause mortality. Conclusion: M30 and AST accurately detect severe hepatic inflammatory activity in patients with compensated ALD. M30 was the only significant predictor of both liver-related events and all-cause mortality after adjusting for advanced fibrosis, body mass index, and drinking behavior at inclusion.

Hepatocyte and immune cell crosstalk in non-alcoholic fatty liver disease

Introduction: Nonalcoholic fatty liver disease (NAFLD) is the most widespread chronic liver disease in the world. It can evolve into nonalcoholic steatohepatitis (NASH) where inflammation and hepatocyte ballooning are key participants in the determination of this steatotic state.Areas covered: To provide a systematic overview and current understanding of the role of inflammation in NAFLD and its progression to NASH, the function of the cells involved, and the activation pathways of the innate immunity and cell death; resulting in inflammation and chronic liver disease. A PubMed search was made with relevant articles together with relevant references were included for the writing of this review.Expert opinion: Innate and adaptive immunity are the key players in the NAFLD progression; some of the markers presented during NAFLD are also known to be immunity biomarkers. All cells involved in NAFLD and NASH are known to have immunoregulatory properties and their imbalance will completely change the cytokine profile and form a pro-inflammatory microenvironment. It is necessary to fully answer the question of what initiators and metabolic imbalances are particularly important, considering sterile inflammation as the architect of the disease. Due to the shortage of elucidation of NASH progression, we discuss in this review, how inflammation is a key part of this development and we presume the targets should lead to inflammation and oxidative stress treatment.

Niclosamide-loaded polymeric micelles ameliorate hepatocellular carcinoma in vivo through targeting Wnt and Notch pathways

AIM

Niclosamide (NIC) is an anthelmintic agent repurposed as a potent anticancer agent. However, its use is hindered by its poor solubility. We investigated the underlying mechanisms of NIC anticancer activity employing a novel oral NIC pluronic-based nanoformulation and tested its effect in thioacetamide-induced hepatocellular carcinoma (HCC) in rats. We evaluated its antitumor effect through regulating Wnt/β-catenin and Notch signaling pathways and apoptosis.

MAIN METHODS

Niclosamide-loaded pluronic nanoparticles (NIC-NPs) were optimally developed and characterized with sustained release properties up to 7 days. Sixteen weeks after HCC induction, NIC (70 mg/kg) and an equivalent dose of NIC-NPs were administered orally for 3 consecutive weeks. Hepatocyte integrity was assessed by measuring serum levels of aminotransferases, ALP, GGT, bilirubin, albumin and total protein. HCC development was detected by measuring AFP expression. Necroinflammation and fibrosis were scored by histopathological examination. Wnt/β-catenin and Notch signaling were evaluated by measuring hepatic mRNA levels of Wnt3A, Lrp5 and Lrp6 Co-receptors, Dvl-2, Notch1 and Hes1 and β-catenin protein levels. Apoptosis was assessed by measuring mRNA and protein levels of cyclin D1 and caspase-3.

KEY FINDING

The novel NIC-NPs restored liver integrity, reduced AFP levels and showed improved anticancer and proapoptotic activities compared to drug alone. The inhibitory effect of NIC on Wnt/β-catenin and Notch signaling pathways was potentiated by the NIC-NPs formulation.

SIGNIFICANCE

We conclude that NIC acts by inhibiting Wnt/β-catenin and Notch signaling and inducing apoptosis in HCC. Developing pluronic-based nanoformulations may be a promising approach to improve NIC solubility and offer the possibility of controlled release.

Antioxidant and anti-inflammatory activities of berberine attenuate hepatic fibrosis induced by thioacetamide injection in rats

Berberine (BBR) is an isoquinoline alkaloid extracted from the roots, rhizomes and stems of coptis. Liver fibrosis is a worldwide health problem with no established therapy until now. The aim of our study is to investigate the efficacy of BBR on hepatic fibrosis induced in rats and to uncover other mechanisms. Rats were injected with thioacetamide (TAA) (200 mg/kg, i.p) twice per week for 6 weeks to induce fibrosis. Treated groups were gavaged with BBR (50 mg/kg/day, p.o) simultaneously with TAA injection. Hepatic antioxidant enzymes (catalase, SOD, GPx) were assessed in hepatic homogenate. Their activities were attenuated by TAA injection and elevated by BBR administration. Additionally, serum IL-6 and mRNA levels of IL-1β, IL-6, IL-10 and IFN-γ were evaluated as inflammatory markers. Our results showed that BBR suppressed the inflammation induced by TAA injection. Tissue expression of α-SMA (marker of activated HSCs), TGF-β1 and fibronectin were measured by immunohistochemistry as well as mRNA expressions of TGF-β1 and fibronectin were quantified as fibrotic markers. The collagen deposition in hepatic tissues was assessed by Masson's trichome staining. BBR significantly alleviated TGF-β1 production, decreased collagen and fibronectin deposition and consequently attenuated hepatic fibrogenesis. Akt pathway controls cell survival, proliferation, migration and adhesion. The relative phosphorylation of Akt was determined in hepatic homogenates that was increased with TAA injection and decreased by BBR treatment. Inhibition of Akt pathway has been linked to the intrinsic pathway of apoptosis. Caspase-3, caspase-9, Bcl-2 and Bax were quantified as apoptotic markers using qPCR and also caspase-3 by immunohistochemistry. BBR-treated rats showed an increase in the expression of apoptotic markers. Moreover, BBR-treated rats showed restoration of normal liver lobular architecture as shown by H&E staining. In conclusion, BBR is a potential therapeutic candidate for liver fibrosis owing to its antioxidant and anti-inflammatory activities.

Naringin attenuates thioacetamide-induced liver fibrosis in rats through modulation of the PI3K/Akt pathway

AIMS

Naringin (NR) is a flavanone glycoside extracted from grapefruits and citrus fruits. The aim of this study is to investigate the antifibrotic efficacy of NR in thioacetamide (TAA)-induced hepatic fibrosis in rats through evaluating NR effect on the PI3K/Akt pathway.

MAIN METHODS

Hepatic fibrosis was induced in rats by intraperitoneal injection of TAA (200mg/kg) twice per week for 6weeks. Simultaneously, NR (40mg/kg/day, p.o.) was given along with TAA injection. The ratio of P-Akt/Akt was assessed in hepatic homogenate as well as antioxidant enzymes (catalase, superoxide dismutase (SOD), glutathione peroxidase (GPx)) and lipid peroxidation marker, malondialdehyde (MDA). Serum level of interleukin (IL)-6 were measured using ELISA. Hepatic tissues were examined histopathologically using hematoxylin and eosin (H&E) and Masson trichome staining. Tissue expression of alpha smooth muscle actin (α-SMA), transforming growth factor β1 (TGF-β1), caspase-3 and fibronectin were scored immunohistochemically. Finally, the mRNA level of cytokine genes (IL-1β, IL-6, IL-10, interferon gamma (IFN-γ)), caspase-3, TGF-β1 and fibronectin were quantified using qPCR.

KEY FINDINGS

NR significantly suppressed Akt phosphorylation associated with increased number of caspase-3 positive cells especially in the fibrotic areas. Liver tissues of treated rats showed restoration of normal liver histology and decrease in collagen and fibronectin deposition. Furthermore, NR treatment ameliorated oxidative stress and inflammatory cytokine production.

SIGNIFICANCE

NR alleviated experimental liver fibrosis through inhibition of PI3K/Akt pathway beside its anti-inflammatory and antioxidant effects. Therefore, NR is a promising therapeutic candidate for hepatic fibrosis.

Serum profiles of M30, M65 and interleukin-17 compared with C-reactive protein in patients with mild and severe acute pancreatitis

BACKGROUND

Several studies state that a test of severity early in the course of acute pancreatitis is still needed. In this prospective study, an assay of the biomarkers M30 and M65 as well as of interleukin 17 (IL-17) is investigated.

METHODS

One hundred and fifty patients and 70 controls were evaluated. The prognostic value of M30, M65 and their ratio M30/M65 is assessed by ELISA. The same method is used for the study of IL-17.

RESULTS

At 24 h after symptom onset, the concentrations of M30 and M65 as well as their ratio, differed significantly in severe compared to mild disease (P = 0.016). C-reactive protein (CRP) was significantly higher (P < 0.001) in severe pancreatitis on the same day. The sensitivity of M65 to show severe acute pancreatitis at 24 h was 100% for values above the cut-off point of 428.15 U/l. The sensitivity of CRP was 100% as well. Concerning IL-17, its concentrations were higher in patients than in the control group (P < 0.001) in the first 24 h.

CONCLUSIONS

Plasma concentrations of M65 and the M30/M65 ratio can be useful in predicting the severity of acute pancreatitis as early as 24 h after the onset of symptoms. The rates of IL-17 early in the course of acute pancreatitis are indicative of the disease.

Distinctive intrahepatic characteristics of paediatric and adult pathogenesis of chronic hepatitis C infection

Mechanisms leading to liver damage in chronic hepatitis C (CHC) are being discussed, but both the immune system and the virus are involved. The aim of this study was to evaluate intrahepatic viral infection, apoptosis and portal and periportal/interface infiltrate in paediatric and adult patients to elucidate the pathogenesis of chronic hepatitis C. HCV-infected, activated caspase-3(+) and TUNEL(+) hepatocytes, as well as total, CD4(+), CD8(+), Foxp3(+) and CD20(+) lymphocytes infiltrating portal and periportal/interface tracts were evaluated in 27 paediatric and 32 adult liver samples by immunohistochemistry or immunofluorescence. The number of infected hepatocytes was higher in paediatric than in adult samples (p 0.0078). In children, they correlated with apoptotic hepatocytes (activated caspase-3(+) r = 0.74, p < 0.0001; TUNEL(+) r = 0.606, p 0.0017). Also, infected (p = 0.026) and apoptotic hepatocytes (p = 0.03) were associated with the severity of fibrosis. In adults, activated caspase-3(+) cell count was increased in severe hepatitis (p = 0.009). Total, CD4(+), CD8(+) and Foxp3(+) lymphocyte count was higher in adult samples (p < 0.05). Paediatric CD8(+) cells correlated with infected (r = 0.495, p 0.04) and TUNEL(+) hepatocytes (r = 0.474, p = 0.047), while adult ones correlated with activated caspase-3(+) hepatocytes (r = 0.387, p 0.04). In adults, CD8(+) was associated with hepatitis severity (p < 0.0001) and correlated with inflammatory activity (CD8(+) r = 0.639, p 0.0003). HCV, apoptosis and immune response proved to be involved in CHC pathogenesis of both paediatric and adult patients. However, liver injury in paediatric CHC would be largely associated with a viral cytopathic effect mediated by apoptosis, while in adults it would be mainly associated with an exacerbated immune response.

Serum cytochrome c and m30-neoepitope of cytokeratin-18 in chronic hepatitis C

BACKGROUND & AIMS

Cytochrome c (CYC) and M30-neoepitope of cytokeratin-18 (M30-CK18) are involved at different levels in apoptotic pathways. We aimed to evaluate an association between serum CYC, M30-CK18 and disease activity as well response to therapy in chronic hepatitis C (CHC).

METHODS

Seventy CHC patients were enrolled in this study. Forty five of them completed pegylated interferon plus ribavirin therapy. Histopathological evaluation of hepatic inflammatory activity and fibrosis, as well as blood liver function tests, was performed. Serum concentrations of M30-CK18 and CYC were measured by ELISA.

RESULTS

Median serum concentration of M30-CK18 was higher in CHC patients [283 U/L] vs. control [113 U/L] (P = 0.0003) and was associated with inflammatory activity and liver fibrosis (P < 0.001). Serum M30-CK18 positively correlated with serum activity of ALT and GGT. CYC was not detected in sera of control group, whereas in CHC, 41.43% patients had detectable CYC in serum samples [0.60 ng/ml]. Detectable baseline serum CYC had been negatively associated with sustained virological response (SVR). In patients with detectable CYC, SVR rate was 20% vs. 60% in patients with undetectable CYC (P = 0.007).

CONCLUSIONS

Elevated serum M30-CK18, as an indicator of enhanced apoptosis of hepatocytes, parallels active hepatic inflammation and fibrosis but also biochemical activity in CHC; thus, it may serve as a comprehensive non-invasive marker of disease activity. On the other hand, detection of serum CYC at baseline may be negatively associated with treatment response to pegylated interferon plus ribavirin in CHC.

Expression of apoptosis- and vitamin D pathway-related genes in hepatocellular carcinoma

BACKGROUND/AIMS

Hepatocellular carcinoma (HCC) is the sixth most common malignancy worldwide and therapeutic options are scarce. As they might represent future targets for cancer therapy, the expression of apoptosis-related genes in HCC is of particular interest. In this pilot study, we further examined apoptosis-related genes in human HCC and also focused on vitamin D signaling as this might be a regulator of HCC cell apoptosis.

METHODS

We employed tumor tissue and serum samples from 62 HCC patients as well as 62 healthy controls for these studies. Tissue and serum specimens were analyzed by quantitative RT-PCR, immunohistochemistry and ELISA.

RESULTS

In HCC patients the apoptosis marker M30 was found to be elevated and several pro-apoptotic (TRAIL, FasL and FasR) as well as anti-apoptotic genes (Mcl-1 and Bcl-2) were simultaneously upregulated in tumor tissue and especially tumor-surrounding tissue as compared to healthy control livers. Moreover, vitamin D serum levels were decreased in HCC patients whereas vitamin D receptor mRNA expression was increased in tumor tissue and tumor-surrounding tissue as compared to healthy livers.

CONCLUSIONS

In human HCC, M30 serum levels are elevated indicating an increased cell turnover. Modulation of the vitamin D pathway might be a supportive, pro-apoptotic HCC therapy.

Diagnosis and treatment of hepatocellular carcinoma: A new beginning

In endemic areas for hepatitis B virus (HBV) infection, hepatocellular carcinoma (HCC) is one of the leading causes of cancer death, posing a serious threat to human health. Because of the high incidence and high mortality rate of HCC in the world, it has become a global health problem. Hepatitis B vaccination is an important means of preventing HBV infection, which can indirectly reduce the occurrence of HCC. Currently, although alpha-fetoprotein (AFP) and liver ultrasonography are still important for early diagnosis of HCC, they have some limitations. The emergence of new tumor markers and imaging technology will help improve the accuracy of early diagnosis of HCC. Molecularly targeted drugs are a hotspot of oncologic research in recent years, and multidisciplinary treatment gives us new hope for defeating HCC.

Microwave ablation of the liver: a description of lesion evolution over time and an investigation of the heat sink effect

AIM

Microwave ablation has been successfully used to treat unresectable liver tumours for many years. However, despite its widespread use, there seems to be a relative paucity of experimental data regarding lesion evolution and the effects of any surrounding vasculature on ablation morphology. The aim of this study was to investigate the principal pathological changes in the liver following microwave ablation, in particular the heat sink effect. In addition we carefully reviewed the available literature to provide an overview of all relevant pathological studies.

METHODS

Microwave ablation was carried out on male rats at various distances from the hilum. Histological (H&E) and immunocytochemical (caspase 3) analyses of the lesion were performed at various time points; 0, 4, 24, 48  hours, 2 weeks and 1 month. A literature review was carried out using Medline, Embase and the Cochrane database to identify all relevant histological studies.

RESULTS

The lesion underwent complete coagulative necrosis and was extremely regular at the ablation edge with no evidence of any influence from surrounding blood vessels at all time points. H&E and caspase 3 results were consistent and microwave caused little collateral damage outside the intended ablation zone.

CONCLUSION

This study suggests that microwave ablation is extremely concise and is minimally affected by the heat sink effect. Comparative investigations with other treatment modalities are required.

Reliability of caspase activity as a biomarker of hepatic apoptosis in nonalcoholic fatty liver disease

A letter in response to: Yilmaz Y, Kurt R, Kalayci C. Apoptosis in nonalcoholic steatohepatitis with normal aminotransferase values: zooming in on cytokeratin 18 fragments. Biomarkers Med. 4(5), 743–745 (2010).

Bioengineering functional copolymers. XV. Synthesis of organoboron amide-ester branched derivatives of oligo(maleic anhydride) and their interaction with HeLa and L929 fibroblast cells

Novel bioengineering functional organoboron oligomers were synthesized by (i) amidolysis of oligo(maleic anhydride) (OMA) with 2-aminoethyldiphenylborinate (2-AEPB), (ii) esterification of organoboron oligomer (OMA-B) with α-hydroxy-ω-methoxypoly(ethylene oxide) (PEO) as a compatibilizer and (iii) conjugation of organoboron PEO branches (OMA-B-PEO) with folic acid as a taggering agent. Structure and composition of the synthesized oligomers were characterized by FTIR-ART and 1H (13C) NMR spectroscopy, chemical and physical analysis methods. Interaction of functional oligomers and oligomer···FA complex (OMA-B-PEO-F) with HeLa and L929 fibroblast cells were investigated by using different biochemical methods such as cytotoxicity, statistical, apoptotic and necrotic cell indexes, double staining and caspase-3 immunostaining, light and fluorescence inverted microscope analyses. It was found that citotoxisity and apoptotic/necrotic effects of oligomers significantly depend on the structure and composition of studied oligomers, and increase the following raw: OMA << OMA-B < OMA-B-PEO < OMA-B-PEO-F. A folic acid complex (MA-PEG-B-F) at 400 μg ml–1 (2.36 μmol ml–1) concentration as a therapeutic drug exhibits minimal toxcisity toward the fibroblast cells, but influential for HeLa cells.

Soluble cytokeratin 18 biomarkers may provide information on the type of cell death during early ischemia and reperfusion periods of liver transplantation

Hepatocellular damage takes place as a result of ischemia and reperfusion during liver transplantation (LT). To discriminate the type of cell death and quantitate its severity may provide new insights into the mechanisms of hepatocellular damage. Therefore, we investigated the type of cell death by ELISA-based assays in patient sera. Apoptosis was specifically assessed by measuring a novel soluble biomarker, the caspase-cleaved cytokeratin 18, while total cell death (apoptosis and necrosis) by cytokeratin 18 released from dead (necrotic and apoptotic) cells. Twenty-seven live (LDLT) and 14 deceased (DDLT) donor liver transplantations were analyzed before the operation, at the anhepatic stage, first, sixth and 24th hour after the reperfusion. Both apoptosis and total cell death have successfully been demonstrated although they have not been confirmed by the liver biopsy that is impossible to perform in this setting. Apoptosis was not induced in LDLT. Total cell death (primarily necrosis) only transiently appeared the first hour after the reperfusion in LDLT, while it sharply increased the first hour after the reperfusion and maintained its level in DDLT. Soluble cytokeratin 18 biomarkers seem to be useful to discriminate and quantitate the type of cell death during early ischemia and reperfusion periods of LT.

Total and caspase-cleaved cytokeratin 18 in chronic cholecystitis: a prospective study

BACKGROUND

Cell death mode has been studied in cancer, autoimmune, and neurodegenerative diseases. In this study, apoptosis and necrosis are investigated for the first time in patients with chronic calculous cholecystitis.

METHODS AND MATERIALS

Thirty five (35) patients (27 women and 8 men, aged 55.65 +/- 13.48 years) with symptomatic chronic calculous cholecystitis underwent laparoscopic cholecystectomy. The early specific apoptotic tendency (caspase-cleaved cytokeratin 18) was studied in these patients with M30 Apoptosense ELISA and the total cytokerarin 18 (both derived from apoptosis and necrosis) with M65 ELISA. The ratio M30/M65 (caspase-cleaved to total cytokeratin 18) was also computed. According to the histopathological examination, the patients were divided in two groups: group A included patients with chronic inactive cholecystitis (n = 10), and group B those with chronic active cholecystitis (n = 25).

RESULTS

The concentrations of caspase-cleaved cytokerarin 18 (CK18), and especially those of total CK18, were higher in bile samples than in serum samples. In group B, there were significant differences between serum and bile samples regarding both caspase-cleaved CK18 and total CK18. Cells staining positive for caspase-cleaved CK18 were present in the epithelial cells of the mucosa of the gallbladder.

CONCLUSION

CK18 is expressed in the gallbladder epithelial cells. The concentrations of both caspase-cleaved CK18 and total CK18 were higher in bile samples than in serum samples. The levels of total CK18, as well as caspase-cleaved CK18, do not seem to differ between active and inactive chronic cholecystitis.

Caspase-cleaved cytokeratin 18 and 20 S proteasome in liver degeneration

Apoptosis of epithelial hepatocytes plays a pivotal role in acute as well as in chronic liver diseases. The cleavage of cytokeratin-18 (CK-18) by caspases is an early event in the apoptotic process. We therefore sought to investigate serum levels of CK-18 and 20S proteasome in patients with liver cirrhosis, primary graft dysfunction (PDF), and acute liver failure (ALF), and in healthy volunteers. Enzyme-linked immunosorbent assay (ELISA) was utilized to measure the concentration of M30, a fragment of CK-18 cleaved at Asp396 (M30 neoantigen), and the concentration of 20S proteasome. Serum levels of the CK-18 neoepitope M30 were significantly increased in ALF, primary graft dysfunction, and liver cirrhosis vs. healthy controls (1,993.6+/-124.7 U/L, 2,238.1+/-235.9 U/L, and 673.6+/-86.5 U/L vs. 66.8+/-29.1 U/L, respectively, P<0.001). Similar results were detected with the evaluation of 20S proteasome (124,014.5+/-13,235.6 ng/mL, 76,993.2+/-15,720.1 ng/mL, and 2,395.9+/-1,098.2 ng/mL vs. 1,074.5+/-259.4 ng/mL, respectively; P<0.001). Detection of CK-18 neoepitope M30 and 20S proteasome may represent a novel marker of tracing apoptotic epithelium, respectively mirroring degenerative liver processes in affected patient population.

Effects of JC virus infection on anti-apoptotic protein survivin in progressive multifocal leukoencephalopathy

Progressive multifocal leukoencephalopathy (PML) is a fatal demyelinating disease of the central nervous system resulting from the productive infection of oligodendrocytes by the opportunistic polyomavirus JC virus (JCV). Apoptosis is a host defense mechanism to dispose of damaged cells; however, certain viruses have the ability to deregulate apoptotic pathways to complete their life cycles. One such pathway involves survivin, a member of the inhibitor of apoptosis family, which is abundantly expressed during development in proliferating tissues but should be absent in normal, terminally differentiated cells. Immunohistochemistry performed in 20 cases of PML revealed the presence of survivin in JCV-infected oligodendrocytes and bizarre astrocytes within demyelinated plaques. Survivin up-regulation was also found in oligodendroglial and astrocytic cultures infected with JCV. Cell cycle analysis and DNA laddering demonstrated a significantly lower number of cells undergoing apoptosis on JCV infection compared with noninfected cultures; small interfering RNA inhibition of survivin resulted in a dramatic increase in apoptotic cells in JCV-infected cultures. This is the first report describing the activation of survivin by JCV infection in vitro and in PML clinical cases. These observations provide new insights into the anti-apoptotic mechanisms used by JCV to complete its lytic cycle and may suggest new therapeutic targets for PML.

Interleukin-4 induces human hepatocyte apoptosis through a Fas-independent pathway

IL-4 is overexpressed in liver grafts during severe recurrent hepatitis C and rejection. Hepatocyte apoptosis is involved in both these phenomena. We therefore examined the proapoptotic effect of IL-4 on HepG2 cells and human hepatocytes in vitro, together with the underlying mechanisms. We first measured IL-4 receptor expression, STAT6 activation by IL-4, and STAT6 inhibition by an anti-IL-4 antibody or by STAT6 siRNA transfection. We then focused on the pathways involved in IL-4-mediated apoptosis and the role of STAT6 activation in apoptosis initiation. The IL-4 receptor was expressed on both cell types, and STAT6 was activated by IL-4. Both anti-IL-4 and STAT-6 siRNA inhibited this activation. IL-4 induced apoptosis of both HepG2 cells (P=0.008 vs. untreated control) and human hepatocytes (P<0.001 vs. untreated control). IL-4 reduced the mitochondrial membrane potential, activated Bid and Bax, and augmented caspase 3, 8, and 9 activity. STAT6 blockade inhibited IL-4-induced apoptosis. Expression of Fas and Fas ligand was unaffected when HepG2 cells and hepatocytes were cultured with IL-4, and Fas/FasL pathway blockade failed to inhibit IL-4-induced apoptosis. These results show that IL-4 induces apoptosis of human hepatocytes through IL-4 receptor binding, STAT6 activation, decreased mitochondrial membrane potential, and increased caspase activation, independently of the Fas pathway. IL-4 might thus contribute to the progression of severe liver graft damage.

L’apoptose hépatique

Apoptosis or programmed cell death occurs in the liver as in other organs. In the normal state it is not a frequent mode of hepatic cell destruction. Morphological and biochemical characteristics of liver cell apoptosis do not differ from what is observed in other cells. The Fas receptor pathway, a frequent hepatic apoptotic pathway among various others, involves intra-cellular signals amplified by mitochondria. Although hepatic apoptosis may occur by following several others pathways, Fas, which is abundantly expressed in the plasma membrane of hepatocytes, is very often involved in hepatocyte demise during B or C viral hepatitis irrespective of their clinical form, alcoholic hepatitis, cholestasis due to accumulation of hepatic biliary salts, or certain types of drug-induced hepatitis. Fas is also probably responsible for the death of biliary cells in primary biliary cirrhosis. In contrast one of the causes of resistance to apoptosis of hepatic cancerous cells could be related to an alteration of the Fas receptor. This is why much experimental work is presently performed to achieve inhibition of the Fas receptor either at the mRNA level or at the level of Fas-inductible proteolytic enzymes called caspases. One perspective is a specific treatment of apoptosis as an adjuvant treatment of liver diseases.

Employment of liver tissue slice analysis to assay hepatotoxicity linked to replicative and nonreplicative adenoviral agents

Whereas virotherapy has emerged as a novel and promising approach for neoplastic diseases, appropriate model systems have hampered preclinical evaluation of candidate conditionally replicative adenovirus agents (CRAds) with respect to liver toxicity. This is due to the inability of human viral agents to cross species. We have recently shown the human liver tissue slice model to be a facile means to validate adenoviral replication. On this basis, we sought to determine whether our ex vivo liver tissue slice model could be used to assess CRAd-mediated liver toxicity. We analyzed and compared the toxicity of a conditionally replicative adenovirus (AdDelta24) to that of a replication incompetent adenovirus (Adnull [E1-]) in mouse and human liver tissue slices. To accomplish this, we examined the hepatic apoptosis expression profile by DNA microarray analyses, and compared these results to extracellular release of aminotransferase enzymes, along with direct evidence of apoptosis by caspase-3 immunhistochemical staining and TUNEL assays. Human and mouse liver tissue slices demonstrated a marked increase in extracellular release of aminotransferase enzymes on infection with AdDelta24 compared to Adnull. AdDelta24-mediated liver toxicity was further demonstrated by apoptosis induction, as detected by caspase-3 immunohistochemical staining, TUNEL assay and microarray analysis. In conclusion, concordance of CRAd-mediated apoptosis in both the human and the mouse liver tissue slice models was demonstrated, despite the limited replication ability of CRAds in mouse liver slices. The results of this study, defining the CRAd-mediated apoptosis gene expression profiles in human and mouse liver, may lay a foundation for preclinical liver toxicity analysis of CRAd agents.