Alisan Kahraman

JNK1-dependent PUMA expression contributes to hepatocyte lipoapoptosis

Free fatty acids (FFA) induce hepatocyte lipoapoptosis by a c-Jun N-terminal kinase (JNK)-dependent mechanism. However, the cellular processes by which JNK engages the core apoptotic machinery during lipotoxicity, especially activation of BH3-only proteins, remain incompletely understood. Thus, our aim was to determine whether JNK mediates induction of BH3-only proteins during hepatocyte lipoapoptosis. The saturated FFA palmitate, but not the monounsaturated FFA oleate, induces an increase in PUMA mRNA and protein levels. Palmitate induction of PUMA was JNK1-dependent in primary murine hepatocytes. Palmitate-mediated PUMA expression was inhibited by a dominant negative c-Jun, and direct binding of a phosphorylated c-Jun containing the activator protein 1 complex to the PUMA promoter was identified by electrophoretic mobility shift assay and a chromatin immunoprecipitation assay. Short hairpin RNA-targeted knockdown of PUMA attenuated Bax activation, caspase 3/7 activity, and cell death. Similarly, the genetic deficiency of Puma rendered murine hepatocytes resistant to lipoapoptosis. PUMA expression was also increased in liver biopsy specimens from patients with non-alcoholic steatohepatitis as compared with patients with simple steatosis or controls. Collectively, the data implicate JNK1-dependent PUMA expression as a mechanism contributing to hepatocyte lipoapoptosis.

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

The contribution of tumor necrosis factor–related apoptosis‐inducing ligand (TRAIL), a death ligand expressed by cells of the innate immune system, to cholestatic liver injury has not been explored. Our aim was to ascertain if TRAIL contributes to liver injury in the bile duct–ligated (BDL) mouse. C57/BL6 wild‐type (wt), TRAIL heterozygote (TRAIL+/−), and TRAIL knockout (TRAIL−/−) mice were used for these studies. Liver injury and fibrosis were examined 7 and 14 days after BDL, respectively. Hepatic TRAIL messenger RNA (mRNA) was 6‐fold greater in BDL animals versus sham‐operated wt animals (P < 0.01). The increased hepatic TRAIL expression was accompanied by an increase in liver accumulation of natural killer 1.1 (NK 1.1)–positive NK and natural killer T (NKT) cells, the predominant cell types expressing TRAIL. Depletion of NK 1.1–positive cells reduced hepatic TRAIL mRNA expression and serum alanine aminotransferase (ALT) values. Consistent with a role for NK/NKT cells in this model of liver injury, stress ligands necessary for their recognition of target cells were also up‐regulated in hepatocytes following BDL. Compared to sham‐operated wt mice, BDL mice displayed a 13‐fold increase in terminal deoxynucleotidyl transferase–mediated dUTP nick‐end labeling (TUNEL) and an 11‐fold increase in caspase 3/7–positive hepatocytes (P < 0.01). The number of TUNEL and caspase 3/7–positive cells was reduced by >80% in BDL TRAIL knockout animals (P < 0.05). Likewise, liver histology, number of bile infarcts, serum ALT values, hepatic fibrosis, and animal survival were also improved in BDL TRAIL−/− animals as compared to wt animals. Conclusion: These observations support a pivotal role for TRAIL in cholestatic liver injury mediated by NK 1.1–positive NK/NKT cells. (HEPATOLOGY 2008.)

Major histocompatibility complex class I–related chains A and B (MIC A/B): A novel role in nonalcoholic steatohepatitis

Stress‐induced soluble major histocompatibility complex class I–related chains A/B (MIC A/B) are increased in chronic liver diseases and hepatocellular malignancy. We investigated the impact of these molecules on liver injury, apoptosis, and fibrosis in nonalcoholic steatohepatitis (NASH). Blood and liver tissue were obtained from 40 patients with NASH undergoing bariatric surgery for obesity. The control group consisted of 10 healthy individuals. We also investigated 10 patients with nonalcoholic fatty liver (NAFL). Polymerase chain reaction was used to measure messenger RNA (mRNA) transcripts of MIC A/B, natural killer cell receptor G2D (NKG2D), CD95/Fas, and tumor necrosis factor–related apoptosis‐inducing ligand (TRAIL)–death receptor 5 (DR5). Apoptosis was quantified by way of terminal deoxynucleotidyl transferase‐mediated dUTP nick‐end labeling (TUNEL) (intrahepatic) and M30/M65 (systemic). Liver injury was assessed histopathologically and serologically (alanine aminotransferase/aspartate aminotransferase). Fibrosis was identified by Sirius red staining, quantitative morphometry, and α‐smooth muscle actin and collagen 1α transcripts. Compared with controls, patients with NASH revealed significant increases in (1) NKG2D mRNA (13.1‐fold) and MIC A/B mRNA (3.6‐fold and 15.8‐fold, respectively); (2) TRAIL–DR5 and CD95/Fas mRNA (2.7‐fold and 3.6‐fold, respectively); (3) TUNEL‐positive hepatocytes (4.0‐fold); and (4) M30 and M65 levels (4.6‐fold and 3.4‐fold, respectively). We found relevant correlations between MIC protein expression rates and NAS and fibrosis stages. In contrast, NKG2D and MIC A/B transcripts were attenuated in patients with NAFL compared with NASH. Histopathologically, NASH patients revealed increased NAS scores, an accumulation of natural killer cells, and 2.7‐fold increased hepatic fibrosis by quantitative morphometry. Conclusion: Our findings suggest an important role for MIC A/B in liver injury. Therapeutic intervention aimed at reducing MIC A/B levels may beneficially affect the progression of NASH. (HEPATOLOGY 2009.)

DEATH RECEPTOR 5 INTERNALIZATION IS REQUIRED FOR LYSOSOMAL PERMEABILIZATION BY TRAIL IN MALIGNANT LIVER CELL LINES

BACKGROUND & AIMSnTumor necrosis factor-related apoptosis-inducing ligand (TRAIL) cytotoxicity in hepatocellular carcinoma cells is mediated by lysosomal permeabilization. Our aims were to determine which TRAIL receptor, death receptor (DR) 4 or DR5, mediates lysosomal permeabilization and assess whether receptor endocytosis followed by trafficking to lysosomes contributes in this process.nnnMETHODSnTRAIL ligand internalization in Huh-7 cells was examined by confocal microscopy using Flag-tagged TRAIL, whereas DR4- and DR5-enhanced green fluorescent protein internalization was assessed by total internal reflection microscopy. Clathrin-dependent endocytosis was inhibited by expressing dominant negative dynamin.nnnRESULTSnAlthough Huh-7 cells express both TRAIL receptors, short hairpin RNA silencing of DR5 but not DR4 attenuated TRAIL-mediated lysosomal permeabilization and apoptosis. The TRAIL/DR5 complex underwent rapid cellular internalization upon ligand stimulation, whereas the TRAIL/DR4 complex was not efficiently internalized. DR5-enhanced green fluorescent protein internalization was dependent on a dileucine-based internalization motif. Endocytosis of the TRAIL/DR5 complex was dynamin dependent and was required for rapid lysosomal permeabilization and apoptosis in multiple malignant hepatocellular and cholangiocarcinoma cell lines. Upon TRAIL treatment, DR5 colocalized with lysosomes after internalization. Inhibition of DR5 trafficking to lysosomes by Rab7 small interfering RNA also reduced TRAIL-mediated lysosomal disruption and apoptosis.nnnCONCLUSIONSnTRAIL-mediated endocytosis of DR5 with trafficking to lysosomes contributes to lysosomal protease release into the cytosol and efficient apoptosis in malignant liver cell lines.

Matrix metalloproteinase inhibitor, CTS-1027, attenuates liver injury and fibrosis in the bile duct-ligated mouse.

Aim:u2002 Excessive matrix metalloproteinase (MMP) activity has been implicated in the pathogenesis of acute and chronic liver injury. CTS‐1027 is an MMP inhibitor, which has previously been studied in humans as an anti‐arthritic agent. Thus, our aim was to assess if CTS‐1027 is hepato‐protective and anti‐fibrogenic during cholestatic liver injury.

Overexpression of Mcl-1 attenuates liver injury and fibrosis in the bile duct-ligated mouse

Hepatocyte apoptosis contributes to liver injury and fibrosis after cholestatic injury. Our aim was to ascertain if the anti-apoptotic protein Mcl-1 alters liver injury or fibrosis in the bile duct–ligated mouse. Markers of apoptosis and fibrosis were compared in wild-type and transgenic mice expressing human Mcl-1 after bile duct ligation. Compared to hMcl-1 transgenic animals, ligated wild-type mice displayed a significant increase in TUNEL-positive cells and in caspase 3/7-positive hepatocytes. Consistent with apoptotic injury, the pro-apoptotic protein Bak underwent a conformational change to an activated form upon cholestatic injury, a change mitigated by hMcl-1 overexpression. Likewise, liver histology, number of bile infarcts, serum ALT values, markers of hepatic fibrosis, and animal survival were improved in bile duct–ligated mice transgenic for hMcl-1 as compared to wild-type mice. In conclusion, increased Mcl-1 expression plays a role in hepatoprotection upon cholestatic liver injury.

Diagnostic Dilemma in a Patient with Jaundice: How to Differentiate between Autoimmune Pancreatitis, Primary Sclerosing Cholangitis and Pancreas Carcinoma

A 68-year-old male patient was referred to our institution in May 2011 for a suspected tumor in the pancreatic head with consecutive jaundice. Using magnetic resonance imaging, further differentiation between chronic inflammation and a malignant process was not possible with certainty. Apart from cholestasis, laboratory studies showed increased values for CA 19-9 to 532 U/ml (normal <37 U/ml) and hypergammaglobulinemia (immunoglobulin G, IgG) of 19.3% (normal 8.0–15.8%) with an elevation of the IgG4 subtype to 2,350 mg/l (normal 52–1,250 mg/l). Endoscopic retrograde cholangiopancreatography revealed a prominent stenosis of the distal ductus hepaticus communis caused by pancreatic head swelling and also a bihilar stenosis of the main hepatic bile ducts. Cytology demonstrated inflammatory cells without evidence of malignancy. Under suspicion of autoimmune pancreatitis with IgG4-associated cholangitis, immunosuppressive therapy with steroids and azathioprine was started. Follow-up endoscopic retrograde cholangiopancreatography after 3 months displayed regressive development of the diverse stenoses. Jaundice had disappeared and blood values had returned to normal ranges. Moreover, no tumor of the pancreatic head was present in the magnetic resonance control images. Due to clinical and radiological similarities but a consecutive completely different prognosis and therapy, it is of fundamental importance to differentiate between pancreatic cancer and autoimmune pancreatitis. Especially, determination of serum IgG4 levels and associated bile duct lesions induced by inflammation should clarify the diagnosis of autoimmune pancreatitis and legitimate immunosuppressive therapy.

Potential triggering factors of acute liver failure as a first manifestation of autoimmune hepatitis-a single center experience of 52 adult patients

AIM To investigate potential triggering factors leading to acute liver failure (ALF) as the initial presentation of autoimmune hepatitis (AIH). METHODS A total of 565 patients treated at our Department between 2005 and 2017 for histologically-proven AIH were retrospectively analyzed. However, 52 patients (9.2%) fulfilled the criteria for ALF defined by the “American Association for the Study of the Liver (AASLD)”. According to this definition, patients with “acute-on-chronic” or “acute-on-cirrhosis” liver failure were excluded. Following parameters with focus on potential triggering factors were evaluated: Patients’ demographics, causation of liver failure, laboratory data (liver enzymes, MELD-score, autoimmune markers, virus serology), liver histology, immunosuppressive regime, and finally, outcome of our patients. RESULTS The majority of patients with ALF were female (84.6%) and mean age was 43.6 ± 14.9 years. Interestingly, none of the patients with ALF was positive for anti-liver kidney microsomal antibody (LKM). We could identify potential triggering factors in 26/52 (50.0%) of previously healthy patients presenting ALF as their first manifestation of AIH. These were drug-induced ALF (57.7%), virus-induced ALF (30.8%), and preceding surgery in general anesthesia (11.5%), respectively. Unfortunately, 6 out of 52 patients (11.5%) did not survive ALF and 3 patients (5.7%) underwent liver transplantation (LT). Comparing data of survivors and patients with non-recovery following treatment, MELD-score (P < 0.001), age (P < 0.05), creatinine (P < 0.01), and finally, ALT-values (P < 0.05) reached statistical significance. CONCLUSION Drugs, viral infections, and previous surgery may trigger ALF as the initial presentation of AIH. Advanced age and high MELD-score were associated with lethal outcome.

Liver Maximum Capacity: A Novel Test to Accurately Diagnose Different Stages of Liver Fibrosis

Aim: To assess the diagnostic accuracy of liver maximum capacity (LiMAx®) test compared to transient elastography (TE) and serum biomarkers for the noninvasive detection of different stages of liver fibrosis and cirrhosis. Patients and Methods: We retrospectively correlated LiMAx®, TE, aspartate aminotransferase (AST) to alanine aminotransferase (ALT) ratio (AAR), AST-to-platelet ratio index (APRI), and fibrosis-4 (FIB-4) score with histological specimens in 102 patients with chronic liver disease (CLD) who underwent liver biopsy (either percutaneously or via mini-laparoscopy) at the University Clinic of Essen between 10/2016 and 12/2017. Results: Median LiMAx® values showed a tendency to decrease in accordance with increasing histological degree of fibrosis based on the Desmet scoring system (F0: 446.5 [381.0–592.5] µg/h/kg, F1: 405.0 [343.0–547.0] µg/h/kg, F2: 337.0 [250.0–394.0] µg/h/kg, F3: 281.0 [262.0–364.0] µg/h/kg, and F4: 181.5 [130.0–256.5] µg/h/kg. Furthermore, LiMAx® was superior to TE, FIB-4, AAR, and APRI in detecting different stages of fibrosis, while Spearman’s rank correlation test showed a statistically significant association of –0.68, 0.62, 0.61, 0.46, and 0.42, respectively. However, the combination of TE and LiMAx® had the highest diagnostic accuracy in detecting liver cirrhosis (sensitivity 88.9%, specificity 84.6%, Youden index 0.735). Conclusion: Enzymatic liver function measured by LiMAx® showed strong correlation with histology in patients with CLD irrespective of its underlying etiology and was superior to TE and serum biomarkers, possibly making it useful as a novel and noninvasive tool for the determination of hepatic disease severity.