Increased hepatotoxicity of tumor necrosis factor-related apoptosis-inducing ligand in diseased human liver

Polyethylenimine (PEI) in gene therapy: Current status and clinical applications

Polyethlyenimine (PEI) was introduced 1995 as a cationic polymer for nucleic acid delivery. PEI and its derivatives are extensively used in basic research and as reference formulations in the field of polymer-based gene delivery. Despite its widespread use, the number of clinical applications to date is limited. Thus, this review aims to consolidate the past applications of PEI in DNA delivery, elucidate the obstacles that hinder its transition to clinical use, and highlight potential prospects for novel iterations of PEI derivatives. The present review article is divided into three sections. The first section examines the mechanism of action employed by PEI, examining fundamental aspects of cellular delivery including uptake mechanisms, release from endosomes, and transport into the cell nucleus, along with potential strategies for enhancing these delivery phases. Moreover, an in-depth analysis is conducted concerning the mechanism underlying cellular toxicity, accompanied with approaches to overcome this major challenge. The second part is devoted to the in vivo performance of PEI and its application in various therapeutic indications. While systemic administration has proven to be challenging, alternative localized delivery routes hold promise, such as treatment of solid tumors, application as a vaccine, or serving as a therapeutic agent for pulmonary delivery. In the last section, the outcome of completed and ongoing clinical trials is summarized. Finally, an expert opinion is provided on the potential of PEI and its future applications. PEI-based formulations for nucleic acid delivery have a promising potential, it will be an important task for the years to come to introduce innovations that address PEI-associated shortcomings by introducing well-designed PEI formulations in combination with an appropriate route of administration.

Investigation of oxidative damage, antioxidant balance, DNA repair genes, and apoptosis due to radiofrequency-induced adaptive response in mice

This study aims to determine whether exposure to non-ionizing radiofrequency fields could induce an adaptive response (AR) in adult mice and to reveal potential molecular mechanisms triggered by RF-induced AR. The study was performed on 24 adult male Swiss-Albino mice. The average mass of the mice was 37 g. Four groups of adult mice, each consisting of 6, were formed. The radiofrequency group (R) and the adaptive response group (RB) were exposed to 900 MHz of global system for mobile communications (GSM) signal at 0.339 W/kg (1 g average specific absorption rate) 4 h/day for 7 days, while the control group (C) and the bleomycin group (B) were not exposed. 20 minutes after the last radiofrequency field (RF) exposure, the mice in the B and RB groups were injected intraperitoneal (ip) bleomycin (BLM), 37.5 mg/kg. All the animals were sacrificed 30 minutes after the BLM injection. Oxidative damage and antioxidant mechanism were subsequently investigated in the blood samples. Changes in the expression of the genes involved in DNA repair were detected in the liver tissue. TUNEL method was used to determine the apoptosis developed by DNA fragmentation in the liver tissue. The RB group, which produced an adaptive response, was compared with the control group. According to the results, the increase of reactive oxygen species (ROS) in the RB group may have played an important role in triggering the adaptive response and producing the required minimum stress level. Furthermore, tumor suppressor 53(p53), oxo guanine DNA glycosylase (OGG-1) levels responsible for DNA repair mechanism genes expression were increased in conjunction with the increase in ROS. The change in the poly (ADP-ribose) polymerase 1 (PARP-1) and glutathione peroxidase 1 (GPx-1) gene expression were not statistically significant. The antioxidant enzyme levels of superoxide dismutase (SOD), catalase (CAT), and total antioxidant capacity (TAC) were decreased in the group with adaptive response. According to the data obtained from terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) analysis, apoptosis was decreased in the RB group due to the decrease in cell death, which might have resulted from an increase in gene expression responsible for DNA repair mechanisms. The results of our study show that exposure to RF radiation may create a protective reaction against the bleomycin. The minimal oxidative stress due to the RF exposure leads to an adaptive response in the genes that play a role in the DNA repair mechanism and enzymes, enabling the survival of the cell.

TRAIL & EGFR affibody dual-display on a protein nanoparticle synergistically suppresses tumor growth

The TNF-related apoptosis-inducing ligand (TRAIL) is a promising anticancer drug candidate because it selectively binds to the proapoptotic death receptors, which are frequently overexpressed in a wide range of cancer cells, subsequently inducing strong apoptosis in these cells. However, the therapeutic benefit of TRAIL has not been clearly proven, mainly because of its poor pharmacokinetic characteristics and frequent resistance to its application caused by the activation of a survival signal via the EGF/epidermal growth factor receptor (EGFR) signaling pathway. Here, a lumazine synthase protein cage nanoparticle isolated from Aquifex aeolicus (AaLS) was used as a multiple ligand-displaying nanoplatform to display polyvalently both TRAIL and EGFR binding affibody molecules (EGFRAfb) via a SpyTag/SpyCatcher protein-ligation system, to form AaLS/TRAIL/EGFRAfb. The dual-ligand-displaying AaLS/TRAIL/EGFRAfb exhibited a dramatically enhanced cytotoxicity on TRAIL-resistant and EGFR-overexpressing A431 cancer cells in vitro, effectively disrupting the EGF-mediated EGFR survival signaling pathway by blocking EGF/EGFR binding as well as strongly activating both the extrinsic and intrinsic apoptotic pathways synergistically. The AaLS/TRAIL/EGFRAfb selectively targeted A431 cancer cells in vitro and actively reached the tumor sites in vivo. The A431 tumor-bearing mice treated with AaLS/TRAIL/EGFRAfb exhibited a significant suppression of the tumor growth without any significant side effects. Collectively, these findings showed that the AaLS/TRAIL/EGFRAfb could be used as an effective protein-based therapeutic for treating EGFR-positive cancers, which are difficult to manage using mono-therapeutic approaches.

Loss of SNORA73 reprograms cellular metabolism and protects against steatohepatitis

Dyslipidemia and resulting lipotoxicity are pathologic signatures of metabolic syndrome and type 2 diabetes. Excess lipid causes cell dysfunction and induces cell death through pleiotropic mechanisms that link to oxidative stress. However, pathways that regulate the response to metabolic stress are not well understood. Herein, we show that disruption of the box H/ACA SNORA73 small nucleolar RNAs encoded within the small nucleolar RNA hosting gene 3 (Snhg3) causes resistance to lipid-induced cell death and general oxidative stress in cultured cells. This protection from metabolic stress is associated with broad reprogramming of oxidative metabolism that is dependent on the mammalian target of rapamycin signaling axis. Furthermore, we show that knockdown of SNORA73 in vivo protects against hepatic steatosis and lipid-induced oxidative stress and inflammation. Our findings demonstrate a role for SNORA73 in the regulation of metabolism and lipotoxicity.

BH3-only protein expression determines hepatocellular carcinoma response to sorafenib-based treatment

Hepatocellular carcinoma (HCC) represents a global health challenge with limited therapeutic options. Anti-angiogenic immune checkpoint inhibitor-based combination therapy has been introduced for progressed HCC, but improves survival only in a subset of HCC patients. Tyrosine-kinase inhibitors (TKI) such as sorafenib represent an alternative treatment option but have only modest efficacy. Using different HCC cell lines and HCC tissues from various patients reflecting HCC heterogeneity, we investigated whether the sorafenib response could be enhanced by combination with pro-apoptotic agents, such as TNF-related apoptosis-inducing ligand (TRAIL) or the BH3-mimetic ABT-737, which target the death receptor and mitochondrial pathway of apoptosis, respectively. We found that both agents could enhance sorafenib-induced cell death which was, however, dependent on specific BH3-only proteins. TRAIL augmented sorafenib-induced cell death only in NOXA-expressing HCC cells, whereas ABT-737 enhanced the sorafenib response also in NOXA-deficient cells. ABT-737, however, failed to augment sorafenib cytotoxicity in the absence of BIM, even when NOXA was strongly expressed. In the presence of NOXA, BIM-deficient HCC cells could be in turn strongly sensitized for cell death induction by the combination of sorafenib with TRAIL. Accordingly, HCC tissues sensitive to apoptosis induction by sorafenib and TRAIL revealed enhanced NOXA expression compared to HCC tissues resistant to this treatment combination. Thus, our results suggest that BH3-only protein expression determines the treatment response of HCC to different sorafenib-based drug combinations. Individual profiling of BH3-only protein expression might therefore assist patient stratification to certain TKI-based HCC therapies.

Increased Serum Levels of Activated Caspases in Murine and Human Biliary Atresia

In biliary atresia (BA), apoptosis is part of the pathomechanism, which results in progressive liver fibrosis. There is increasing evidence suggesting that apoptotic liver injury can be non-invasively detected by measuring the caspase activity in the serum. The purpose of this study was to investigate whether serological detection of caspase activation mirrors apoptotic liver injury in the infective murine BA-model and represents a suitable biomarker for BA in humans. Analysis showed increased caspase-3 activity and apoptosis in the livers of cholestatic BALB/c mice, which correlated significantly with caspase activation in the serum. We then investigated caspase activation and apoptosis in liver tissues and sera from 26 BA patients, 23 age-matched healthy and 11 cholestatic newborns, due to other hepatopathies. Compared to healthy individuals, increased caspase activation in the liver samples of BA patients was present. Moreover, caspase-3 activity was significantly higher in sera from BA infants compared to patients with other cholestatic diseases (sensitivity 85%, specificity 91%). In conclusion, caspase activation and hepatocyte apoptosis play an important role in experimental and human BA. We demonstrated that serological detection of caspase activation represents a reliable non-invasive biomarker for monitoring disease activity in neonatal cholestatic liver diseases including BA.

A dietary ketone ester mitigates histological outcomes of NAFLD and markers of fibrosis in high-fat diet fed mice

Nutritional ketosis as a therapeutic tool has been extended to the treatment of metabolic diseases, including obesity, type 2 diabetes, and nonalcoholic fatty liver disease (NAFLD). The purpose of this study was to determine whether dietary administration of the ketone ester (KE) R,S-1,3-butanediol diacetoacetate (BD-AcAc2) attenuates markers of hepatic stellate cell (HSC) activation and hepatic fibrosis in the context of high-fat diet (HFD)-induced obesity. Six-week-old male C57BL/6J mice were placed on a 10-wk ad libitum HFD (45% fat, 32% carbohydrates, 23% proteins). Mice were then randomized to one of three groups (n = 10 per group) for an additional 12 wk: 1) control (CON), continuous HFD; 2) pair-fed (PF) to KE, and 3) KE (HFD + 30% energy from BD-AcAc2, KE). KE feeding significantly reduced histological steatosis, inflammation, and total NAFLD activity score versus CON, beyond improvements observed for calorie restriction alone (PF). Dietary KE supplementation also reduced the protein content and gene expression of profibrotic markers (α-SMA, COL1A1, PDGF-β, MMP9) versus CON (P < 0.05), beyond reductions observed for PF versus CON. Furthermore, KE feeding increased hepatic markers of anti-inflammatory M2 macrophages (CD163) and also reduced proinflammatory markers [tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) and cellular communication network factor 1 (CCN1)] versus CON and PF (P ≤ 0.05), in the absence of changes in markers of total hepatic macrophage content (F4/80 and CD68; P > 0.05). These data highlight that the dietary ketone ester BD-AcAc2 ameliorates histological NAFLD and inflammation and reduces profibrotic and proinflammatory markers. Future studies to further explore potential mechanisms are warranted.NEW & NOTEWORTHY To our knowledge, this is the first study focusing on hepatic outcomes in response to dietary ketone ester feeding in male mice with HFD-induced NAFLD. Novel findings include that dietary ketone ester feeding ameliorates NAFLD outcomes via reductions in histological steatosis and inflammation. These improvements were beyond those observed for caloric restriction alone. Furthermore, dietary ketone ester feeding was associated with greater reductions in markers of hepatic fibrogenesis and inflammation compared with control and calorie-restricted mice.

Processes exacerbating apoptosis in non-alcoholic steatohepatitis

Non-alcoholic fatty liver disease (NAFLD) is a significant public health concern, owing to its high prevalence, progressive nature and lack of effective medical therapies. NAFLD is a complex and multifactorial disease involving the progressive and concerted action of factors that contribute to the development of liver inflammation and eventually fibrosis. Here, we summarize fundamental molecular mechanisms underlying the pathogenesis of non-alcoholic steatohepatitis (NASH), how they are interrelated and possible translation to clinical applications. We focus on processes triggering and exacerbating apoptotic signalling in the liver of NAFLD patients and their metabolic and pathological implications. Indeed, liver injury and inflammation are cardinal histopathological features of NASH, a duo in which derailment of apoptosis is of paramount importance. In turn, the liver houses a very high number of mitochondria, crucial metabolic unifiers of both extrinsic and intrinsic signals that converge in apoptosis activation. The role of lifestyle options is also dissected, highlighting the management of modifiable risk factors, such as obesity and harmful alcohol consumption, influencing apoptosis signalling in the liver and ultimately NAFLD progression. Integrating NAFLD-associated pathologic mechanisms in the cell death context could provide clues for a more profound understating of the disease and pave the way for novel rational therapies.

Shaping of Innate Immune Response by Fatty Acid Metabolite Palmitate

Innate immune cells monitor invading pathogens and pose the first-line inflammatory response to coordinate with adaptive immunity for infection removal. Innate immunity also plays pivotal roles in injury-induced tissue remodeling and the maintenance of tissue homeostasis in physiological and pathological conditions. Lipid metabolites are emerging as the key players in the regulation of innate immune responses, and recent work has highlighted the importance of the lipid metabolite palmitate as an essential component in this regulation. Palmitate modulates innate immunity not only by regulating the activation of pattern recognition receptors in local innate immune cells, but also via coordinating immunological activity in inflammatory tissues. Moreover, protein palmitoylation controls various cellular physiological processes. Herein, we review the updated evidence that palmitate catabolism contributes to innate immune cell-mediated inflammatory processes that result in immunometabolic disorders.

Cell death in drug-induced liver injury

Drug-induced liver injury (DILI) is an important cause of liver toxicity which can have varying clinical presentations, the most severe of which being acute liver failure. Hepatocyte death as a cause of drug toxicity is a feature of DILI. There are multiple cell death subroutines; some, like apoptosis, necroptosis, autophagy, and necrosis have been extensively studied, while others such as pyroptosis and ferroptosis have been more recently described. The mode of cell death in DILI depends on the culprit drug, as it largely dictates the mechanism and extent of injury. The main cell death subroutines in DILI are apoptosis and necrosis, with mitochondrial involvement being pivotal for the execution of both. A few drugs such as acetaminophen (APAP) can cause direct, dose-dependent toxicity, while the majority of drugs cause idiosyncratic DILI (IDILI). IDILI is an unpredictable form of liver injury that is not dose dependent, occurs in individuals with a genetic predisposition, and presents with variable latency. APAP-induced programmed necrosis has been extensively studied. However, the mechanisms and pathogenesis of cell death from drugs causing IDILI are harder to elucidate due to the complex and multifactorial nature of the disease. Cell death in IDILI is likely death receptor-mediated apoptosis and the result of an activated innate and adaptive immune system, compounded by other host factors such as genetics, gender, age, and capacity for immune tolerance. This chapter will review the different modes of cell death, namely apoptosis, necrosis, necroptosis, autophagy, pyroptosis, and ferroptosis and their pertinence to DILI.

Molecular pathways of nonalcoholic fatty liver disease development and progression

Nonalcoholic fatty liver disease (NAFLD) is a main hepatic manifestation of metabolic syndrome. It represents a wide spectrum of histopathological abnormalities ranging from simple steatosis to nonalcoholic steatohepatitis (NASH) with or without fibrosis and, eventually, cirrhosis and hepatocellular carcinoma. While hepatic simple steatosis seems to be a rather benign manifestation of hepatic triglyceride accumulation, the buildup of highly toxic free fatty acids associated with insulin resistance-induced massive free fatty acid mobilization from adipose tissue and the increased de novo hepatic fatty acid synthesis from glucose acts as the "first hit" for NAFLD development. NAFLD progression seems to involve the occurrence of "parallel, multiple-hit" injuries, such as oxidative stress-induced mitochondrial dysfunction, endoplasmic reticulum stress, endotoxin-induced, TLR4-dependent release of inflammatory cytokines, and iron overload, among many others. These deleterious factors are responsible for the triggering of a number of signaling cascades leading to inflammation, cell death, and fibrosis, the hallmarks of NASH. This review is aimed at integrating the overwhelming progress made in the characterization of the physiopathological mechanisms of NAFLD at a molecular level, to better understand the factor influencing the initiation and progression of the disease.

Review article: drug-induced liver injury in the context of nonalcoholic fatty liver disease - a physiopathological and clinical integrated view

BACKGROUND

Nonalcoholic fatty disease (NAFLD) is the most common liver disease, since it is strongly associated with obesity and metabolic syndrome pandemics. NAFLD may affect drug disposal and has common pathophysiological mechanisms with drug-induced liver injury (DILI); this may predispose to hepatoxicity induced by certain drugs that share these pathophysiological mechanisms. In addition, drugs may trigger fatty liver and inflammation per se by mimicking NAFLD pathophysiological mechanisms.

AIMS

To provide a comprehensive update on (a) potential mechanisms whereby certain drugs can be more hepatotoxic in NAFLD patients, (b) the steatogenic effects of drugs, and (c) the mechanism involved in drug-induced steatohepatitis (DISH).

METHODS

A language- and date-unrestricted Medline literature search was conducted to identify pertinent basic and clinical studies on the topic.

RESULTS

Drugs can induce macrovesicular steatosis by mimicking NAFLD pathogenic factors, including insulin resistance and imbalance between fat gain and loss. Other forms of hepatic fat accumulation exist, such as microvesicular steatosis and phospholipidosis, and are mostly associated with acute mitochondrial dysfunction and defective lipophagy, respectively. Drug-induced mitochondrial dysfunction is also commonly involved in DISH. Patients with pre-existing NAFLD may be at higher risk of DILI induced by certain drugs, and polypharmacy in obese individuals to treat their comorbidities may be a contributing factor.

CONCLUSIONS

The relationship between DILI and NAFLD may be reciprocal: drugs can cause NAFLD by acting as steatogenic factors, and pre-existing NAFLD could be a predisposing condition for certain drugs to cause DILI. Polypharmacy associated with obesity might potentiate the association between this condition and DILI.

A Placebo-Controlled, Multicenter, Double-Blind, Phase 2 Randomized Trial of the Pan-Caspase Inhibitor Emricasan in Patients with Acutely Decompensated Cirrhosis

BACKGROUND

Cirrhosis and acute-on-chronic liver failure (ACLF) are associated with systemic inflammation, and caspase-mediated hepatocyte cell death. Emricasan is a novel, pan-caspase inhibitor. Aims of this study were to assess the pharmacokinetics, pharmacodynamics, safety and clinical outcomes of emricasan in acute decompensation (AD) of cirrhosis.

METHODS

This was a phase 2, multicentre, double-blind, randomized trial. The primary objective was to evaluate the pharmacokinetics, pharmacodynamics and safety of emricasan in patients with cirrhosis presenting with AD and organ failure. AD was defined as an acute decompensating event ≤6 weeks' duration. Patients were randomized proportionately to emricasan 5 mg bid, emricasan 25 mg bid, emricasan 50 mg bid or placebo. Treatment was continued to 28 days, or voluntary discontinuation.

RESULTS

Twenty-three subjects were randomized, of whom 21 were dosed (placebo n = 4; 5 mg n = 5; 25 mg n = 7; 50 mg n = 5). Pharmacokinetic data showed 5 mg dose was associated with low plasma levels (<50 ng/ml), and 25 mg and 50 mg doses showed comparable pharmacokinetic profiles. Therefore, for analysis of secondary endpoints, placebo and 5 mg groups were merged into a 'placebo/low-dose' group, and 25 mg and 50 mg groups were merged into a 'high-dose' group. Five deaths occurred amongst the 21 patients, all due to progression of liver disease (2 in placebo/low-dose, 3 in high-dose). No statistically significant changes from baseline MELD score or CLIF-C ACLF score were noted between placebo/low-dose and high-dose groups at day 7 (MELD -1 vs -1, CLIF-C ACLF 0.7 vs 0.8). An initial reduction in cleaved keratin M30 fragment was noted between placebo/low-dose and high-dose groups (percent relative change: day 2: -11.6 vs -42.6, P = 0.017, day 4: -3.5 vs -38.9 P = 0.017) although this did not persist to day 7 (-3.1 vs -20.8, P = 0.342).

CONCLUSION

This study demonstrates that emricasan is safe and well tolerated in advanced liver disease. However, this study fails to provide proof-of-concept support for caspase inhibition as a treatment strategy for ACLF.

TRIAL REGISTRATION

EudraCT 2012-004245-33.

Designed trimer-mimetic TNF superfamily ligands on self-assembling nanocages

Presentation of an endogenous bioactive ligand in its native form is a key factor in controlling and determining its bioactivity, stability, and therapeutic efficacy. In this study, we developed a novel strategy for presenting trimeric ligands on nanocages by designing, optimizing and testing based on the rational design, high-resolution structural analysis and agonistic activity assays in vitro and in vivo. We successfully designed a nanocage that presents the TNF superfamily member, TRAIL (TNF-related apoptosis-inducing ligand) in its native-like trimeric structure. The native structure of TRAIL complexes was mimicked on the resulting trimeric TRAIL-presenting nanocages (TTPNs) by inserting sufficient spacing, determined from three-dimensional structural models, to provide optimal access to the corresponding receptors. The efficacy of TTPNs as an anti-tumor agent was confirmed in preclinical studies, which revealed up to 330-fold increased affinity, 62.5-fold enhanced apoptotic activity, and improved pharmacokinetic characteristics and stability compared with the monomeric form of TRAIL (mTRAIL). In this latter context, TTPNs exhibited greater than 90% stability over 1 mo, whereas ∼50% of mTRAIL aggregated within 2 d. Consistent with their enhanced stability and ultra-high affinity for the TRAIL receptor, TTPNs effectively induced apoptosis of tumor cells in vivo, leading to effective inhibition of tumor growth. Although TRAIL was used here as a proof-of-concept, all members of the TNF superfamily share the TNF homology domain (THD) and have similar distances between ecto-domain C-termini. Thus, other TNF superfamily ligands could be genetically substituted for the TRAIL ligand on the surface of this biomimetic delivery platform.

Ethanol sensitizes hepatocytes for TGF-β-triggered apoptosis

Alcohol abuse is a global health problem causing a substantial fraction of chronic liver diseases. Abundant TGF-β—a potent pro-fibrogenic cytokine—leads to disease progression. Our aim was to elucidate the crosstalk of TGF-β and alcohol on hepatocytes. Primary murine hepatocytes were challenged with ethanol and TGF-β and cell fate was determined. Fluidigm RNA analyses revealed transcriptional effects that regulate survival and apoptosis. Mechanistic insights were derived from enzyme/pathway inhibition experiments and modulation of oxidative stress levels. To substantiate findings, animal model specimens and human liver tissue cultures were investigated. Results: On its own, ethanol had no effect on hepatocyte apoptosis, whereas TGF-β increased cell death. Combined treatment led to massive hepatocyte apoptosis, which could also be recapitulated in human HCC liver tissue treated ex vivo. Alcohol boosted the TGF-β pro-apoptotic gene signature. The underlying mechanism of pathway crosstalk involves SMAD and non-SMAD/AKT signaling. Blunting CYP2E1 and ADH activities did not prevent this effect, implying that it was not a consequence of alcohol metabolism. In line with this, the ethanol metabolite acetaldehyde did not mimic the effect and glutathione supplementation did not prevent the super-induction of cell death. In contrast, blocking GSK-3β activity, a downstream mediator of AKT signaling, rescued the strong apoptotic response triggered by ethanol and TGF-β. This study provides novel information on the crosstalk between ethanol and TGF-β. We give evidence that ethanol directly leads to a boost of TGF-β’s pro-apoptotic function in hepatocytes, which may have implications for patients with chronic alcoholic liver disease.

MicroRNA-145 Increases the Apoptosis of Activated Hepatic Stellate Cells Induced by TRAIL through NF-κB Signaling Pathway

During the liver fibrosis recovery stage tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) can effectively induce apoptosis of activated hepatic stellate cells (HSCs). Normal hepatic stellate cells are resistant to TRAIL cytotoxicity. Therefore, enhancing the sensitivity of TRAIL-induced apoptosis of HSCs may be useful to treat hepatic fibrogenesis. Here, we demonstrated that miR-145 and TRAIL were down-regulated in both liver fibrosis tissue samples and transforming growth factor-β1 induced HSCs, concomitant with increased the expression of ZEB2. In addition, we found that mimics-mediated over-expression of miR-145 led to resistance to the ZEB2 expression and up-regulation of the TRAIL-induced apoptosis after treatment of LX-2 cells with TRAIL. Furthermore, ZEB2-siRNA transfected LX-2 cells showed the increased sensitivity to TRAIL-induced apoptosis. Whereas, opposite results were obtained in miR-145-inhibitor group or ZEB2 plasmid group. Moreover, miR-145 regulated ZEB2 gene expression by specifically interacting with the 3′-UTR of ZEB2 mRNA to inhibit the expression of ZEB2. Further studies showed that the over-expression of ZEB2 could inhibit TRAIL-induced apoptosis via inhibiting nuclear factor-κB (NF-κB) signaling pathway in LX-2 cells. Collectively, our data suggest that up-regulation of miR-145 can down-regulate ZEB2 expression, consequently promoting TRAIL-induced apoptosis in LX-2 cells through NF-κB signaling pathway, which facilitates the resolution of liver fibrosis.

Interaction and Mutual Activation of Different Innate Immune Cells Is Necessary to Kill and Clear Hepatitis C Virus-Infected Cells

Innate immune cells can sense hepatitis C virus (HCV)-infected cells and respond with anti-viral actions including secretion of interferons (IFNs). In previous studies, the response of individual innate immune cells against HCV was analyzed in detail. We hypothesized that interaction of multiple innate immune cells increases the magnitude of the immune response and eventually leads to clearance of HCV-infected cells. To investigate this, we co-cultured Huh-7 HCV subgenomic replicon (SGR) cells with peripheral blood mononuclear cells (PBMCs). We confirm secretion of IFNα by plasmacytoid dendritic cells (pDCs) and IFNγ by natural killer (NK) cells in the co-culture setup. Moreover, we observed that also monocytes contribute to the anti-viral response. Flow cytometry and ImageStream analysis demonstrated that monocytes take up material from HCV SGR cells in co-culture with PBMCs. Preceding the uptake, PBMCs caused apoptosis of HCV SGR cells by tumor necrosis factor-related apoptosis inducing ligand (TRAIL) expression on NK cells. We observed that only the interplay of monocytes, pDCs, and NK cells resulted in efficient clearance of HCV SGR cells, while these cell populations alone did not kill HCV SGR cells. Despite similar TRAIL receptor expression on Huh-7 control cells and HCV SGR cells, HCV activated PBMCs specifically killed HCV SGR cells and did not target Huh-7 control cells. Finally, we showed that HCV replicating cells per se are sensitive toward TRAIL-induced apoptosis. Our results highlight the importance of the interplay of different innate immune cells to initiate an efficient, rapid, and specific response against HCV-infected cells.

Apoptosis in the aging liver

Various changes in the liver during aging can reduce hepatic function and promote liver injury. Aging is associated with high morbidity and a poor prognosis in patients with various liver diseases, including nonalcoholic fatty liver disease, hepatitis C and liver cancer, as well as with surgeries such as partial hepatectomy and liver transplantation. In addition, apoptosis increases with liver aging. Because apoptosis is involved in regeneration, fibrosis and cancer prevention during liver aging, and restoration of the appropriate level of apoptosis can alleviate the adverse effects of liver aging, it is important to understand the mechanisms underlying this process. Herein, we elaborate on the causes of apoptosis during liver aging, with a focus on oxidative stress, genomic instability, lipotoxicity, endoplasmic reticulum stress, dysregulation of nutrient sensing, and liver stem/progenitor cell activity.

TRAIL Deletion Prevents Liver, but Not Adipose Tissue, Inflammation during Murine Diet-Induced Obesity

Tumor necrosis factor‐related apoptosis‐inducing ligand (TRAIL) and its cognate receptor(s) are up‐regulated in human and murine nonalcoholic steatohepatitis (NASH); however, the consequence of this enhanced expression on NASH pathogenesis remains unclear. TRAIL may either accentuate liver injury by promoting hepatic steatosis and inflammation or it may mitigate the disease process by improving systemic insulin resistance and averting hepatic fibrosis. Herein, we investigated the role of TRAIL in an obesity‐induced murine model of NASH. C57BL/6 wild‐type mice and Trail^–/– mice were placed on a 20‐week standard chow or a high‐fat, high‐fructose, and high‐cholesterol (FFC) diet, which induces obesity, insulin resistance, and NASH. Metabolic phenotype, liver injury, inflammation and fibrosis, and adipose tissue homeostasis were examined. FFC diet‐fed Trail^–/– mice displayed no difference in weight gain and metabolic profile when compared to wild‐type mice on the same diet. All FFC‐fed mice developed significant hepatic steatosis, which was attenuated in Trail^–/– mice. TRAIL deficiency also significantly decreased FFC diet‐induced liver injury as manifested by reduced serum alanine aminotransferase values, hepatic terminal deoxynucleotidyl transferase‐mediated deoxyuridine triphosphate nick‐end labeling‐positive cells, and macrophage‐associated inflammation. FFC diet‐associated hepatic stellate cell activation and hepatic collagen deposition were also abrogated in Trail^–/– mice. In contrast to the liver, TRAIL deletion did not improve FFC diet‐induced adipose tissue injury and inflammation and actually aggravated insulin resistance. Conclusion: NASH pathogenesis may be dissociated from other features of the metabolic syndrome, and liver‐targeted inhibition of TRAIL signaling may be salutary. (Hepatology Communications 2017;1:648–662)

Serum cell death biomarker mirrors liver cancer regression after transarterial chemoembolisation

BACKGROUND

Hepatocellular carcinoma (HCC) represents an increasing health problem with limited therapeutic options. In patients with intermediate disease stage, transarterial chemoembolisation (TACE) is widely applied. Treatment response is routinely assessed by imaging techniques according to the international response evaluation criteria in solid tumours (RECIST), which consider tumour regression or additionally tumour necrosis (modified RECIST). Evaluation of treatment response, however, by these methods is time- and cost-intensive and usually performed at earliest several months following TACE.

AIM

To investigate the suitability of novel non-invasive cell death biomarkers for an earlier prediction of TACE response.

METHODS

We analysed activation of pro-apoptotic caspases and the proteolytic cleavage of the caspase substrate CK-18 in liver tissues and sera from HCC patients by immunohistochemistry, a luminometric substrate assay and ELISA.

RESULTS

Both caspase activity and caspase-cleaved CK-18 fragments were elevated in HCC patients compared to healthy controls. CK-18 serum levels significantly increased during the first 3 days and peaked at day two following TACE. Interestingly, we found significant differences in CK-18 levels between patients with and without tumour regression. Detection of CK-18 fragments revealed a promising performance for the early prediction of TACE response with an area under the curve value of 0.76.

CONCLUSIONS

Caspase-cleaved CK-18 levels mirror liver cancer regression and allow an earlier prediction of TACE response. The concordance with mRECIST suggests that the detection of CK-18 levels immediately after TACE might be used as a short-term decision guide to continue or change HCC therapy.

Lipotoxic lethal and sublethal stress signaling in hepatocytes: relevance to NASH pathogenesis

The accumulation of lipids is a histologic and biochemical hallmark of obesity-associated nonalcoholic fatty liver disease (NAFLD). A subset of NALFD patients develops progressive liver disease, termed nonalcoholic steatohepatitis, which is characterized by hepatocellular apoptosis and innate immune system-mediated inflammation. These responses are orchestrated by signaling pathways that can be activated by lipids, directly or indirectly. In this review, we discuss palmitate- and lysophosphatidylcholine (LPC)-induced upregulation of p53-upregulated modulator of apoptosis and cell-surface expression of the death receptor TNF-related apoptosis-inducing ligand receptor 2. Next, we review the activation of stress-induced kinases, mixed lineage kinase 3, and c-Jun N-terminal kinase, and the activation of endoplasmic reticulum stress response and its downstream proapoptotic effector, CAAT/enhancer binding homologous protein, by palmitate and LPC. Moreover, the activation of these stress signaling pathways is linked to the release of proinflammatory, proangiogenic, and profibrotic extracellular vesicles by stressed hepatocytes. This review discusses the signaling pathways induced by lethal and sublethal lipid overload that contribute to the pathogenesis of NAFLD.

Spatial Control of Gene Expression by Nanocarriers Using Heparin Masking and Ultrasound-Targeted Microbubble Destruction

We developed a method to spatially control gene expression following nonviral delivery of DNA. This method includes surface-modifying DNA nanocarriers with heparin to inhibit passive gene transfer in both the target and the off-target tissues and using ultrasound-targeted microbubble destruction (UTMD) to selectively activate heparin-inhibited gene transfer at the target site. We observed that the engraftment of heparin onto the surface of cationic liposomes reduced off-target gene expression in the liver, a major site of nanoplex accumulation, by more than 700-fold compared to the nonheparinized PEGylated liposomes. We further observed that tumor-directed UTMD increased gene transfer with heparin-modified nanoplexes by more than 10-fold. This method augmented tumor-to-liver selectivity of gene expression by 4000-fold compared to controls. We conclude that heparinization of DNA nanocarriers in conjunction with localized activation of gene transfer by UTMD may enable greater spatial control over genetic therapy.

Systemically administered AAV9-sTRAIL combats invasive glioblastoma in a patient-derived orthotopic xenograft model

Adeno-associated virus (AAV) vectors expressing tumoricidal genes injected directly into brain tumors have shown some promise, however, invasive tumor cells are relatively unaffected. Systemic injection of AAV9 vectors provides widespread delivery to the brain and potentially the tumor/microenvironment. Here we assessed AAV9 for potential glioblastoma therapy using two different promoters driving the expression of the secreted anti-cancer agent sTRAIL as a transgene model; the ubiquitously active chicken β-actin (CBA) promoter and the neuron-specific enolase (NSE) promoter to restrict expression in brain. Intravenous injection of AAV9 vectors encoding a bioluminescent reporter showed similar distribution patterns, although the NSE promoter yielded 100-fold lower expression in the abdomen (liver), with the brain-to-liver expression ratio remaining the same. The main cell types targeted by the CBA promoter were astrocytes, neurons and endothelial cells, while expression by NSE promoter mostly occurred in neurons. Intravenous administration of either AAV9-CBA-sTRAIL or AAV9-NSE-sTRAIL vectors to mice bearing intracranial patient-derived glioblastoma xenografts led to a slower tumor growth and significantly increased survival, with the CBA promoter having higher efficacy. To our knowledge, this is the first report showing the potential of systemic injection of AAV9 vector encoding a therapeutic gene for the treatment of brain tumors.

Targeting cell death signalling in cancer: minimising 'Collateral damage'

Targeting apoptosis for the treatment of cancer has become an increasingly attractive strategy, with agents in development to trigger extrinsic apoptosis via TRAIL signalling, or to prevent the anti-apoptotic activity of BCL-2 proteins or inhibitor of apoptosis (IAP) proteins. Although the evasion of apoptosis is one of the hallmarks of cancer, many cancers have intact apoptotic signalling pathways, which if unblocked could efficiently kill cancerous cells. However, it is becoming increasing clear that without a detailed understanding of both apoptotic and non-apoptotic signalling, and the key proteins that regulate these pathways, there can be dose-limiting toxicity and adverse effects associated with their modulation. Here we review the main apoptotic pathways directly targeted for anti-cancer therapy and the unforeseen consequences of their modulation. Furthermore, we highlight the importance of an in-depth mechanistic understanding of both the apoptotic and non-apoptotic functions of those proteins under investigation as anti-cancer drug targets and outline some novel approaches to sensitise cancer cells to apoptosis, thereby improving the efficacy of existing therapies when used in combination with novel targeted agents.

Cytokines elevated in patients with HBV-related acute-on-chronic liver failure promote NK cell mediated cytotoxicity through TRAIL

BACKGROUND AND AIMS

The role of NK cells on inducing liver injury in patients with HBV-related acute-on-chronic liver failure (HBV-ACLF) is not well understood. The aim of this study was to determine the cytotoxicity of tumor necrosis factor-related apoptosis inducing ligand (TRAIL)-expressed NK cells from HBV-ACLF patients and facilitate a better understanding of the immune pathogenesis of HBV-ACLF.

METHODS

Peripheral blood samples were obtained from HBV-ACLF patients, mild chronic hepatitis B (CHB) patients and healthy controls (HC). Circulating NK cells phenotype was determined using flow cytometry. Serum cytokine concentrations were ascertained using the CBA Inflammation kit. Cell apoptosis was analyzed using the FITC-annexin V Apoptosis Detection Kit.

RESULTS

Peripheral NK cells from HBV-ACLF expressed higher levels of TRAIL than those from CHB and HC. Expression of TRAIL on NK cells was correlated positively with serum IL-6 and IL-8 concentrations in HBV-ACLF patients, which is further confirmed by cytokines stimulation in vitro. NK cells caused a significant increase of apoptotic hepatocytes, and further increased the frequency of apoptosis in IL-6 and IL8-stimulated hepatocytes; the apoptosis was then inhibited partially by an anti-TRAIL monoclonal antibody.

CONCLUSION

These results suggested that inflammation cytokines elevated in patients with HBV-ACLF may promote NK cell mediated cytotoxicity through TRAIL pathway.

Bok is a genuine multi-BH-domain protein that triggers apoptosis in the absence of Bax and Bak

The pro-apoptotic multidomain Bcl-2 proteins Bax and Bak (also known as BAK1) are considered the gatekeepers of the intrinsic pathway of apoptosis by triggering the mitochondrial release of cytochrome c The role of the third Bax- and Bak-homologous multidomain protein Bok, however, is still unresolved. As cells doubly deficient for Bax and Bak are largely resistant to various apoptotic stimuli, it has been proposed that Bok is either dispensable for apoptosis or that its role is dependent on Bax and Bak. Here, we demonstrate, in several cell systems, that Bok efficiently induces cytochrome c release and apoptosis even in the complete absence of both Bak and Bax. Moreover, modulation of endogenous Bok levels affects the apoptosis response. By RNA interference and targeted deletion of the Bok gene, we demonstrate that Bok can significantly influence the apoptotic response to chemotherapeutic drugs in ovarian carcinoma cells. Hence, our results not only establish Bok as a Bak- and Bax-independent apoptosis inducer, but also suggest a potential impact of Bok expression in ovarian cancer therapy.

Smad2 increases the apoptosis of activated human hepatic stellate cells induced by TRAIL

The activation of hepatic stellate cells (HSCs) plays a critical role in the development of liver fibrosis. The induction of apoptosis in activated HSCs during the recovery phase of hepatic fibrosis represents a potential anti-fibrotic therapy. We have previously shown that Smad2 protects against hepatic fibrogenesis; however, the role of Smad2 in the regulation of activated HSC apoptosis remains unknown. We hypothesized that Smad2 regulates the apoptosis of activated HSCs, leading to the resolution of liver fibrosis. To test this hypothesis, the livers of rats were harvested at 0 and 4 weeks after hepatic fibrosis was established by CCl4 injection. Furthermore, TGF-β1-activated HSCs were treated with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) following the silencing or overexpression of Smad2. Both the phosphorylation of Smad2 and TRAIL were detected in fibrotic liver tissues. The results of TUNEL and α-SMA double-staining showed an increase in the apoptosis of activated HSCs during the spontaneous recovery phase. The knockdown of Smad2 reduced TRAIL-induced apoptosis in TGF-β1-activated human LX-2 cells and resulted in an increased expression of α-SMA and collagen I (Col. I). In contrast, the overexpression of Smad2 increased TRAIL-induced HSC apoptosis and reduced the expression of α-SMA and Col. I. The mechanisms underlying these findings were associated with the Smad2-mediated down-regulation of X-linked inhibitor of apoptosis protein (XIAP), resulting in enhanced caspase-3 activity and apoptosis. In conclusion, Smad2 enhances TRAIL-induced apoptosis in activated HSCs, which facilitates the resolution of hepatic fibrosis.

Engineering Stem Cells for Biomedical Applications

Stem cells are characterized by a number of useful properties, including their ability to migrate, differentiate, and secrete a variety of therapeutic molecules such as immunomodulatory factors. As such, numerous pre-clinical and clinical studies have utilized stem cell-based therapies and demonstrated their tremendous potential for the treatment of various human diseases and disorders. Recently, efforts have focused on engineering stem cells in order to further enhance their innate abilities as well as to confer them with new functionalities, which can then be used in various biomedical applications. These engineered stem cells can take on a number of forms. For instance, engineered stem cells encompass the genetic modification of stem cells as well as the use of stem cells for gene delivery, nanoparticle loading and delivery, and even small molecule drug delivery. The present Review gives an in-depth account of the current status of engineered stem cells, including potential cell sources, the most common methods used to engineer stem cells, and the utilization of engineered stem cells in various biomedical applications, with a particular focus on tissue regeneration, the treatment of immunodeficiency diseases, and cancer.

Agonists of the TRAIL Death Receptor DR5 Sensitize Intestinal Stem Cells to Chemotherapy-Induced Cell Death and Trigger Gastrointestinal Toxicity

The combination of TRAIL death receptor agonists and radiochemotherapy to treat advanced cancers continues to be investigated in clinical trials. We previously showed that normal cells with a functional DNA damage response (DDR) upregulate the expression of death-inducing receptor DR5/TRAILR2/TNFRSF10B in a p53-dependent manner that sensitizes them to treatment with DR5 agonists. However, it is unclear if targeting DR5 selectively sensitizes cancer cells to agonist treatment following exposure to DNA-damaging chemotherapy, and to what extent normal tissues are targeted. Here, we show that the combined administration of the DR5 agonistic monoclonal antibody (mAb) and chemotherapy to wild-type mice triggered synergistic gastrointestinal toxicities (GIT) that were associated with the death of Lgr5(+) crypt base columnar stem cells in a p53- and DR5-dependent manner. Furthermore, we confirmed that normal human epithelial cells treated with the human DR5-agonistic mAb and chemotherapeutic agents were also greatly sensitized to cell death. Interestingly, our data also indicated that genetic or pharmacologic targeting of Chk2 may counteract GIT without negatively affecting the antitumor responses of combined DR5 agonist/chemotherapy treatment, further linking the DDR to TRAIL death receptor signaling in normal cells. In conclusion, the combination of DR5-targeting agonistic mAbs with DNA damaging chemotherapy may pose a risk of developing toxicity-induced conditions, and the effects of mAb-based strategies on the dose-limiting toxicity of chemotherapy must be considered when establishing new combination therapies.

Stem cell-based gene therapy activated using magnetic hyperthermia to enhance the treatment of cancer

Stem cell-based gene therapies, wherein stem cells are genetically engineered to express therapeutic molecules, have shown tremendous potential for cancer applications owing to their innate ability to home to tumors. However, traditional stem cell-based gene therapies are hampered by our current inability to control when the therapeutic genes are actually turned on, thereby resulting in detrimental side effects. Here, we report the novel application of magnetic core-shell nanoparticles for the dual purpose of delivering and activating a heat-inducible gene vector that encodes TNF-related apoptosis-inducing ligand (TRAIL) in adipose-derived mesenchymal stem cells (AD-MSCs). By combining the tumor tropism of the AD-MSCs with the spatiotemporal MCNP-based delivery and activation of TRAIL expression, this platform provides an attractive means with which to enhance our control over the activation of stem cell-based gene therapies. In particular, we found that these engineered AD-MSCs retained their innate ability to proliferate, differentiate, and, most importantly, home to tumors, making them ideal cellular carriers. Moreover, exposure of the engineered AD-MSCS to mild magnetic hyperthermia resulted in the selective expression of TRAIL from the engineered AD-MSCs and, as a result, induced significant ovarian cancer cell death in vitro and in vivo.

Interferon-Mediated Cytokine Induction Determines Sustained Virus Control in Chronic Hepatitis C Virus Infection

Hepatitis C virus (HCV) infection is a major cause of chronic liver disease and associated complications such as liver cirrhosis and hepatocellular carcinoma. Interferons (IFNs) are crucial for HCV clearance and a sustained virological response (SVR), but a significant proportion of patients do not respond to IFNα. The underlying mechanisms of an insufficient IFN response remain largely unknown. In this study, we found that patients responding to IFNα with viral clearance had significantly higher serum levels of TNF-related apoptosis inducing ligand (TRAIL), compared with patients who failed to control HCV. In addition, upon direct IFNα exposure, peripheral blood mononuclear cells (PBMCs) from patients with SVR upregulated TRAIL, as well as IFN-γ and the chemokines CXCL9 and CXCL10, much more strongly than cells from patients with antiviral treatment failure. As a possible mechanism of the stronger IFNα-induced cytokine response, we identified higher levels of expression and phosphorylation of the transcription factor STAT1 in PBMCs from patients with SVR. Increased TRAIL expression additionally involved the NF-κB and JNK signaling pathways. Thus, SVR in chronic HCV infection is associated with a strong IFNα-induced cytokine response, which might allow for the early prediction of treatment efficacy in HCV infection.

Targeted drug delivery to circulating tumor cells via platelet membrane-functionalized particles

Circulating tumor cells (CTCs) are responsible for metastases in distant organs via hematogenous dissemination. Fundamental studies in the past decade have suggested that neutralization of CTCs in circulation could represent an effective strategy to prevent metastasis. Current paradigms of targeted drug delivery into a solid tumor largely fall into two main categories: unique cancer markers (e.g. overexpression of surface receptors) and tumor-specific microenvironment (e.g. low pH, hypoxia, etc.). While relying on a surface receptor to target CTCs can be greatly challenged by cancer heterogeneity, targeting of tumor microenvironments has the advantage of recognizing a broader spectrum of cancer cells regardless of genetic differences or tumor types. The blood circulation, however, where CTCs transit through, lacks the same tumor microenvironment as that found in a solid tumor. In this study, a unique "microenvironment" was confirmed upon introduction of cancer cells of different types into circulation where activated platelets and fibrin were physically associated with blood-borne cancer cells. Inspired by this observation, synthetic silica particles were functionalized with activated platelet membrane along with surface conjugation of tumor-specific apoptosis-inducing ligand cytokine, TRAIL. Biomimetic synthetic particles incorporated into CTC-associated micro-thrombi in lung vasculature and dramatically decreased lung metastases in a mouse breast cancer metastasis model. Our results demonstrate a "Trojan Horse" strategy of neutralizing CTCs to attenuate metastasis.

The pan-caspase inhibitor Emricasan (IDN-6556) decreases liver injury and fibrosis in a murine model of non-alcoholic steatohepatitis

BACKGROUND & AIMS

Hepatocyte apoptosis, the hallmark of non-alcoholic steatohepatitis (NASH) contributes to liver injury and fibrosis. Although, both the intrinsic and extrinsic apoptotic pathways are involved in the pathogenesis of NASH, the final common step of apoptosis is executed by a family of cysteine-proteases termed caspases. Thus, our aim was to ascertain if administration of Emricasan, a pan-caspase inhibitor, ameliorates liver injury and fibrosis in a murine model of NASH.

METHODS

C57/BL6J-mice were fed regular chow or high fat diet (HFD) for 20 weeks. All mice were treated with vehicle or Emricasan.

RESULTS

Mice fed a HFD diet demonstrate a five-fold increase in hepatocyte apoptosis by the TUNEL assay and a 1.5-fold and 1.3-fold increase in caspase-3 and-8 activities respectively; this increase in apoptosis was substantially attenuated in mice fed a HFD treated with Emricasan (HFD-Em). Likewise, liver injury and inflammation were reduced in mice fed HFD-Em as compare to HFD by measuring serum aspartate aminotransferase and alanine aminotransferase levels, NAS histological score and IL 1-β, TNF-α, monocyte chemoattractant protein (MCP-1) and C-X-C chemokine ligand-2 (CXCL2) quantitative reverse-transcription polymerase chain reaction (qPCR). These differences could not be attributed to differences in hepatic steatosis as liver triglycerides content were similar in both HFD groups. Hepatic fibrosis was reduced by Emricasan in HFD animals by decreasing αSMA (a marker for hepatic stellate cell activation), fibrosis score, Sirius red staining, hydroxyproline liver content and profibrogenic cytokines by qPCR.

CONCLUSION

In conclusion, these data demonstrate that in a murine model of NASH, liver injury and fibrosis are suppressed by inhibiting hepatocytes apoptosis and suggests that Emricasan may be an attractive antifibrotic therapy in NASH.

Free fatty acids shift insulin-induced hepatocyte proliferation towards CD95-dependent apoptosis

Insulin is known to induce hepatocyte swelling, which triggers via integrins and c-Src kinase an activation of the epidermal growth factor receptor (EGFR) and subsequent cell proliferation (1). Free fatty acids (FFAs) are known to induce lipoapoptosis in liver cells in a c-Jun-NH2-terminal kinase (JNK)-dependent, but death receptor-independent way (2). As non-alcoholic steatohepatitis (NASH) is associated with hyperinsulinemia and increased FFA-blood levels, the interplay between insulin and FFA was studied with regard to hepatocyte proliferation and apoptosis in isolated rat and mouse hepatocytes. Saturated long chain FFAs induced apoptosis and JNK activation in primary rat hepatocytes, but did not activate the CD95 (Fas, APO-1) system, whereas insulin triggered EGFR activation and hepatocyte proliferation. Coadministration of insulin and FFAs, however, abolished hepatocyte proliferation and triggered CD95-dependent apoptosis due to a JNK-dependent association of the activated EGFR with CD95, subsequent CD95 tyrosine phosphorylation and formation of the death-inducing signaling complex (DISC). JNK inhibition restored the proliferative insulin effect in presence of FFAs and prevented EGFR/CD95 association, CD95 tyrosine phosphorylation and DISC formation. Likewise, in presence of FFAs insulin increased apoptosis in hepatocytes from wild type but not from Alb-Cre-FAS(fl/fl) mice, which lack functional CD95. It is concluded that FFAs can shift insulin-induced hepatocyte proliferation toward hepatocyte apoptosis by triggering a JNK signal, which allows activated EGFR to associate with CD95 and to trigger CD95-dependent apoptosis. Such phenomena may contribute to the pathogenesis of NASH.

Death Receptor-Mediated Cell Death and Proinflammatory Signaling in Nonalcoholic Steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is becoming public health problem worldwide. A subset of patients develop an inflammatory disease, nonalcoholic steatohepatitis (NASH), characterized by steatosis, hepatocellular death, macrophage and neutrophil accumulation and varying stages of fibrosis. Hepatocyte cell death triggers the cellular inflammatory response and, therefore, reducing cell death may be salutary in the steatohepatitis disease process. Recently, a better understanding of hepatocyte apoptosis in NASH has been obtained and new information regarding other cell death modes, such as necroptosis and pyroptosis, has been reported. Hepatocyte lipotoxicity is often triggered by death receptors. In addition to causing apoptosis, death receptors have been shown to mediate proinflammatory signaling, suggesting that apoptosis in this context is not an immunologically silent process. Here we review recent developments in our understanding of hepatocyte cell death by death receptors and its mechanistic link to inflammation in NASH. We emphasize how proapoptotic signaling by death receptors may induce the release of proinflammatory extracellular vesicles, thereby recruiting and activating macrophages and promoting the steatohepatitis process. Potential therapeutic strategies are discussed based on this evolving information.

TRAIL enhances apoptosis of human hepatocellular carcinoma cells sensitized by hepatitis C virus infection: therapeutic implications

Hepatitis C virus (HCV) infection causes chronic liver diseases leading to hepatocellular carcinoma (HCC) and liver failure. We have previously shown that HCV sensitizes hepatocytes to mitochondrial apoptosis via the TRAIL death receptors DR4 and DR5. Although TRAIL and its receptors are selective targets for cancer therapy, their potential against HCC with chronic HCV infection has not been explored yet. Here we show that HCV induces DR4/DR5-dependent activation of caspase-8 leading to elevation of apoptotic signaling in infected cells and also present TRAIL effect in HCV-induced apoptotic signaling. HCV induced proteolytic cleavage of caspase-9 by stimulating DR4 and DR5, resulting in subsequent cleavage of caspase-3. Further, HCV-induced proteolytic cleavage in caspase-8, caspase-9, and caspase-3 was enhanced in the presence of recombinant TRAIL. HCV-induced cleavage in caspase-9 and increase in caspase-3/7 activity was completely suppressed by silencing of either DR4 or DR5. Perturbing DR4/DR5-caspase-8 signaling complex by silencing DR4 and DR5 or by chemical inhibitor specific to caspase-8 led to decrease of HCV-induced cleavage of poly(ADP-ribose) polymerase (PARP), a substrate for caspase-3 during apoptosis, indicating the functional role of caspase-8 in HCV-induced apoptotic signaling network. Furthermore, TRAIL enhanced PARP cleavage in apoptotic response induced by HCV infection, indicating the effect of TRAIL for the induction of selective apoptosis of HCC cells infected with HCV. Given the importance of apoptosis in HCC development, our data suggest that HCV-induced DR4 and DR5 may be considered as an attractive target for TRAIL therapy against HCC with chronic HCV infection.

Evolving concepts in the pathogenesis of NASH: beyond steatosis and inflammation

Non-alcoholic steatohepatitis (NASH) is characterised by hepatic steatosis and inflammation and, in some patients, progressive fibrosis leading to cirrhosis. An understanding of the pathogenesis of NASH is still evolving but current evidence suggests multiple metabolic factors critically disrupt homeostasis and induce an inflammatory cascade and ensuing fibrosis. The mechanisms underlying these changes and the complex inter-cellular interactions that mediate fibrogenesis are yet to be fully elucidated. Lipotoxicity, in the setting of excess free fatty acids, obesity, and insulin resistance, appears to be the central driver of cellular injury via oxidative stress. Hepatocyte apoptosis and/or senescence contribute to activation of the inflammasome via a variety of intra- and inter-cellular signalling mechanisms leading to fibrosis. Current evidence suggests that periportal components, including the ductular reaction and expansion of the hepatic progenitor cell compartment, may be involved and that the Th17 response may mediate disease progression. This review aims to provide an overview of the pathogenesis of NASH and summarises the evidence pertaining to key mechanisms implicated in the transition from steatosis and inflammation to fibrosis. Currently there are limited treatments for NASH although an increasing understanding of its pathogenesis will likely improve the development and use of interventions in the future.

Models of hepatotoxicity and the underlying cellular, biochemical and immunological mechanism(s): a critical discussion

Liver is a primary organ involved in biotransformation of food and drugs. Hepatic diseases are a major worldwide problem. Hepatic disorders are mainly caused by toxic chemicals (alcohol), xenobiotics (carbon tetrachloride, chlorinated hydrocarbons and gases CO₂ and O₂) anticancer (azathioprine, doxorubicin, cisplatin), immunosuppressant (cyclosporine), analgesic anti-inflammatory (paracetamol, thioacetamide), anti-tubercular (isoniazid, rifampicin) drugs, biologicals (Bacillus-Calmette-Guerin vaccine), radiations (gamma radiations), heavy metals (cadmium, arsenic), mycotoxin (aflatoxin), galactosamine, lipopolysaccharides, etc. Various risk factors for hepatic injury include concomitant hepatic diseases, age, gender, alcoholism, nutrition and genetic polymorphisms of cytochrome P450 enzymes have also been emphasized. The present review enumerates various in vivo animal models and in vitro methods of hepatic injury using diverse toxicants, their probable metabolic pathways, and numerous biochemical changes viz. serum biomarkers enzymes, liver function, oxidative stress associated events like free radicals formation, lipid peroxidation, enzyme antioxidants and participation of cytokines (tumour necrosis factor-α, transforming growth factor-β, tumour necrosis factor-related apoptosis inducing ligand), and other biomolecules (Fas and C-jun N-terminal kinase) are also discussed. The underlying cellular, molecular, immunological, and biochemical mechanism(s) of action responsible for liver damage (toxicity) are also been discussed. This review should be immensely useful for researchers especially for phytochemists, pharmacologists and toxicologists working on hepatotoxicity, hepatotoxic chemicals and drugs, hepatoprotective agents and drug research organizations involved especially in phytopharmaceuticals and other natural products.

Chemoprevention of nonalcoholic fatty liver disease by dietary natural compounds

Nonalcoholic fatty liver disease (NAFLD) refers to a wide spectrum of liver disease that is not from excess alcohol consumption, but is often associated with obesity, type 2 diabetes, and metabolic syndrome. NAFLD pathogenesis is complicated and involves oxidative stress, lipotoxicity, mitochondrial damage, insulin resistance, inflammation, and excessive dietary fat intake, which increase hepatic lipid influx and de novo lipogenesis and impair insulin signaling, thus promoting hepatic triglyceride accumulation and ultimately NAFLD. Overproduction of proinflammatory adipokines from adipose tissue also affects hepatic metabolic function. Current NAFLD therapies are limited; thus, much attention has been focused on identification of potential dietary substances from fruits, vegetables, and edible plants to provide a new strategy for NAFLD treatment. Dietary natural compounds, such as carotenoids, omega-3-PUFAs, flavonoids, isothiocyanates, terpenoids, curcumin, and resveratrol, act through a variety of mechanisms to prevent and improve NAFLD. Here, we summarize and briefly discuss the currently known targets and signaling pathways as well as the role of dietary natural compounds that interfere with NAFLD pathogenesis.

Increased plasma levels of CK-18 as potential cell death biomarker in patients with HELLP syndrome

HELLP (hemolysis, elevated liver enzymes, low platelets) syndrome represents a life-threatening pregnancy disorder with high fetal and maternal mortality, but its underlying molecular mechanisms remain unknown. Although apoptosis has been implicated in HELLP syndrome, its pathogenic role remains largely unclear. In the present study, we investigated whether the detection of apoptosis by novel plasma biomarkers is of diagnostic value in HELLP patients. For this purpose, we analyzed two biomarkers that specifically detect apoptosis or overall cell death of epithelial cells, such as hepatocytes or placental trophoblasts, through the release of caspase-cleaved or total (caspase-cleaved and uncleaved) cytokeratin-18 (CK-18) in plasma of HELLP patients compared with pregnant as well as non-pregnant healthy women. In addition, caspase activation and cell death were determined in placental tissues of HELLP patients and individuals with normal pregnancy. In contrast to pregnant or non-pregnant healthy controls, we observed significantly increased levels of both caspase-cleaved and total CK-18 in plasma of HELLP patients. Following delivery, CK-18 levels rapidly decreased in HELLP patients. Caspase activation and cell death were also elevated in placental tissues from HELLP patients compared with healthy pregnant women. These data demonstrate not only that apoptosis is increased in HELLP syndrome, but also that caspase-cleaved or total CK-18 are promising plasma biomarkers to identify patients with HELLP syndrome. Thus, further studies are warranted to evaluate the utility of these biomarkers for monitoring disease activity in HELLP syndrome.

Systemic tumor-specific gene delivery

The objective of a systemically administered cancer gene therapy is to achieve gene expression that is isolated to the tumor tissue. Unfortunately, viral systems have strong affinity for the liver, and delivery from non-viral cationic systems often results in high expression in the lungs. Non-specific delivery to these organs must be overcome if tumors are to be aggressively treated with genes such as IL-12 which activates a tumor immune response, and TNF-alpha which can induce tumor cell apoptosis. Techniques which have led to specific expression in tumor tissue include receptor targeting through ligand conjugation, utilization of tumor specific promoters and viral mutation in order to take advantage of proteins overexpressed in tumor cells. This review analyzes these techniques applied to liposomal, PEI, dendrimer, stem cell and viral gene delivery systems in order to determine the techniques that are most effective in achieving tumor specific gene expression after systemic administration.

Membrane expression of the death ligand trail receptors DR4 and DR5 in the normal endometrium, endometrial atypical hyperplasia and endometrioid endometrial cancer

To assess membrane expression of DR4 and DR5 in the normal endometrium (NE), endometrial atypical hyperplasia (EAH) and endometrioid endometrial cancer (EEC), the study examined 101 patients: 20 NE, 14 EAH and 67 EEC. The expression of DR4 and DR5 was examined and presented as the total score (TS). DR4 expression was seen in 18 NE, 11 EAH and 10 EEC. DR5 expression was seen in 20 NE, 13 EAH and 21 EEC. A strong correlation between type of endometrial tissue and TS of both receptors was identified. In EEC TS of DR4 and DR5 was not related to grading, staging or survival. Malignant transformation in the endometrium is related to reduction of membrane DR4 and DR5 expression. The level of membrane staining of the receptors in EEC is not dependent on grading and staging, and is not sufficient to predict survival in EEC patients.