Mechanisms of oxysterol-induced disease: insights from the biliary system

Oxysterols as Biomarkers of Aging and Disease

Oxysterols derive from either enzymatic or non-enzymatic oxidation of cholesterol. Even though they are produced as intermediates of bile acid synthesis pathway, they are recognised as bioactive compounds in cellular processes. Therefore, their absence or accumulation have been shown to be associated with disease phenotypes. This chapter discusses the contribution of oxysterol to ageing, age-related diseases such as neurodegeneration and various disorders such as cancer, cardiovascular disease, diabetes, metabolic and ocular disorders. It is clear that oxysterols play a significant role in development and progression of these diseases. As a result, oxysterols are being investigated as suitable markers for disease diagnosis purposes and some drug targets are in development targeting oxysterol pathways. However, further research will be needed to confirm the suitability of these potentials.

Curcumin analog WZ26 induces ROS and cell death via inhibition of STAT3 in cholangiocarcinoma

Cholangiocarcinoma (CCA) is an aggressive biliary epithelial tumor with limited therapeutic options and poor prognosis. Curcumin is a promising active natural compound with several anti-cancer properties, though its clinical uses remain hindered due to its poor bioavailability. We recently synthesized curcumin analogs with multifunctional pharmacological and bioactivities with enhanced bioavailability. Among these novel curcumin analogs, WZ26 is a representative molecule. However, the anti-tumor effect of WZ26 against CCA is unclear. In this study, we evaluated the anti-tumor effect of WZ26 in both CCA cells and CCA xenograft mouse model. The underlying molecular anti-cancer mechanism of WZ26 was also studied. Our results show that WZ26 significantly inhibited cell growth and induced mitochondrial apoptosis in CCA cell lines, leading to significant inhibition of tumor growth in xenograft tumor mouse model. Treatment of WZ26 increased reactive oxygen species (ROS) generation, subsequently decreased mitochondrial membrane potential and inhibited the phosphorylation of signal transducer and activator of transcription 3 (STAT3), thereby inducing G2/M cell cycle arrest and cell apoptosis. Pretreatment of N-acetyl cysteine (NAC), an antioxidant agent, could fully reverse the WZ26-induced ROS-mediated changes in CCA cells. Our findings provide experimental evidence that curcumin analog WZ26 could be a potential candidate against CCA via enhancing ROS induction and inhibition of STAT3 activation.

Oxidative Stress and Redox-Dependent Pathways in Cholangiocarcinoma

Cholangiocarcinoma (CCA) is a primary liver tumor that accounts for 2% of all cancer-related deaths worldwide yearly. It can arise from cholangiocytes of biliary tracts, peribiliary glands, and possibly from progenitor cells or even hepatocytes. CCA is characterized by high chemoresistance, aggressiveness, and poor prognosis. Potentially curative surgical therapy is restricted to a small number of patients with early-stage disease (up to 35%). Accumulating evidence indicates that CCA is an oxidative stress-driven carcinoma resulting from chronic inflammation. Oxidative stress, due to enhanced reactive oxygen species (ROS) production and/or decreased antioxidants, has been recently suggested as a key factor in cholangiocyte oncogenesis through gene expression alterations and molecular damage. However, due to different experimental models and conditions, contradictory results regarding oxidative stress in cholangiocarcinoma have been reported. The role of ROS and antioxidants in cancer is controversial due to their context-dependent ability to stimulate tumorigenesis and support cancer cell proliferation or promote cell death. On these bases, the present narrative review is focused on illustrating the role of oxidative stress in cholangiocarcinoma and the main ROS-driven intracellular pathways. Heterogeneous data about antioxidant effects on cancer development are also discussed.

Dietary cholesterol oxidation products: Perspectives linking food processing and storage with health implications

Dietary cholesterol oxidation products (COPs) are heterogeneous compounds formed during the processing and storage of cholesterol-rich foods, such as seafood, meat, eggs, and dairy products. With the increased intake of COPs-rich foods, the concern about health implications of dietary COPs is rising. Dietary COPs may exert deleterious effects on human health to induce several inflammatory diseases including atherosclerosis, neurodegenerative diseases, and inflammatory bowel diseases. Thus, knowledge regarding the effects of processing and storage conditions leading to formation of COPs is needed to reduce the levels of COPs in foods. Efficient methodologies to determine COPs in foods are also essential. More importantly, the biological roles of dietary COPs in human health and effects of phytochemicals on dietary COPs-induced diseases need to be established. This review summarizes the recent information on dietary COPs including their formation in foods during their processing and storage, analytical methods of determination of COPs, metabolic fate, implications for human health, and beneficial interventions by phytochemicals. The formation of COPs is largely dependent on the heating temperature, storage time, and food matrices. Alteration of food processing and storage conditions is one of the potent strategies to restrict hazardous dietary COPs from forming, including maintaining relatively low temperatures, shorter processing or storage time, and the appropriate addition of antioxidants. Once absorbed into the circulation, dietary COPs can contribute to the progression of several inflammatory diseases, where the absorbed dietary COPs may induce inflammation, apoptosis, and autophagy in cells in the target organs or tissues. Improved intake of phytochemicals may be an effective strategy to reduce the hazardous effects of dietary COPs.

Abnormal brain cholesterol homeostasis in Alzheimer's disease-a targeted metabolomic and transcriptomic study

The role of brain cholesterol metabolism in Alzheimer's disease (AD) remains unclear. Peripheral and brain cholesterol levels are largely independent due to the impermeability of the blood brain barrier (BBB), highlighting the importance of studying the role of brain cholesterol homeostasis in AD. We first tested whether metabolite markers of brain cholesterol biosynthesis and catabolism were altered in AD and associated with AD pathology using linear mixed-effects models in two brain autopsy samples from the Baltimore Longitudinal Study of Aging (BLSA) and the Religious Orders Study (ROS). We next tested whether genetic regulators of brain cholesterol biosynthesis and catabolism were altered in AD using the ANOVA test in publicly available brain tissue transcriptomic datasets. Finally, using regional brain transcriptomic data, we performed genome-scale metabolic network modeling to assess alterations in cholesterol biosynthesis and catabolism reactions in AD. We show that AD is associated with pervasive abnormalities in cholesterol biosynthesis and catabolism. Using transcriptomic data from Parkinson's disease (PD) brain tissue samples, we found that gene expression alterations identified in AD were not observed in PD, suggesting that these changes may be specific to AD. Our results suggest that reduced de novo cholesterol biosynthesis may occur in response to impaired enzymatic cholesterol catabolism and efflux to maintain brain cholesterol levels in AD. This is accompanied by the accumulation of nonenzymatically generated cytotoxic oxysterols. Our results set the stage for experimental studies to address whether abnormalities in cholesterol metabolism are plausible therapeutic targets in AD.

A Comprehensive Review on Oxysterols and Related Diseases

The present review aims to provide a complete and comprehensive summary of current literature relevant to oxysterols and related diseases. Oxidation of cholesterol leads to the formation of a large number of oxidized products, generally known as oxysterols. They are intermediates in the biosynthesis of bile acids, steroid hormones, and 1,25- dihydroxyvitamin D3. Although oxysterols are considered as metabolic intermediates, there is a growing body of evidence that many of them are bioactive, and their absence or excess may be part of the cause of a disease phenotype. These compounds derive from either enzymatic or non-enzymatic oxidation of cholesterol. This study provides comprehensive information about the structures, formation, and types of oxysterols even when involved in certain disease states, focusing on their effects on metabolism and linkages with these diseases. The role of specific oxysterols as mediators in various disorders, such as degenerative (age-related) and cancer-related disorders, has now become clearer. Oxysterol levels may be employed as suitable markers for the diagnosis of specific diseases or in predicting the incidence rate of diseases, such as diabetes mellitus, Alzheimer's disease, multiple sclerosis, osteoporosis, lung cancer, breast cancer, and infertility. However, further investigations may be required to confirm these mentioned possibilities.

Oxysterols of helminth parasites and pathogenesis of foodborne hepatic trematodiasis caused by Opisthorchis and Fasciola species

The foodborne trematodiases refer to a cluster of zoonotic neglected tropical diseases caused by trematodes, with transmission involving ingestion of contaminated plants, fishes, and crustaceans. Over 40 million people are infected with foodborne trematodes and 750 million are at risk of infection. From a public health point of view, important species include Clonorchis sinensis, Opisthorchis viverrini, Opisthorchis felineus, Fasciola hepatica, and Fasciola gigantica. Infection with C. sinensis and O. viverrini is classified as a group 1 biological carcinogen and a major risk factor for cholangiocarcinoma. The carcinogenic potential of the infection with O. felineus is less clear but recent biochemical and histopathological findings revealed that opisthorchiasis felinea also fits this pattern. By contrast, evidence of carcinogenic potential of infection with F. hepatica or F. gigantica, close phylogenetics relatives of Opisthorchis, is less certain. Oxysterols have been essentially described in animal model of opisthorchiasis and associated cholangiocarcinoma. Several oxysterol-like metabolites have been detected not only on developmental stages of O. viverrini and O. felineus but also on biofluids from experimentally infected hamsters as products of the activities of the liver flukes. These sterol derivatives are metabolized to active quinones that can modify host DNA. We have postulated that helminth parasite-associated sterols might induce tumor-like phenotypes in biliary epithelia, the cells of origin of liver fluke infection-associated cholangiocarcinoma, through the formation of DNA adducts, dysregulation of apoptosis, and other homeostatic pathways. Here we review, interpret, and discuss findings of oxysterol-like metabolites detected in liver flukes and their role in carcinogenesis, aiming to enhance understanding the pathogenesis of foodborne trematodiasis caused by Opisthorchis and Fasciola species. In future, further investigations will be necessary in order to comprehend relationship between liver flukes' oxysterols and their role in infection-associated diseases in humans.

7-Ketocholesterol in disease and aging

7-Ketocholesterol (7KC) is a toxic oxysterol that is associated with many diseases and disabilities of aging, as well as several orphan diseases. 7KC is the most common product of a reaction between cholesterol and oxygen radicals and is the most concentrated oxysterol found in the blood and arterial plaques of coronary artery disease patients as well as various other disease tissues and cell types. Unlike cholesterol, 7KC consistently shows cytotoxicity to cells and its physiological function in humans or other complex organisms is unknown. Oxysterols, particularly 7KC, have also been shown to diffuse through membranes where they affect receptor and enzymatic function. Here, we will explore the known and proposed mechanisms of pathologies that are associated with 7KC, as well speculate about the future of 7KC as a diagnostic and therapeutic target in medicine.

Cholest-4,6-Dien-3-One Promote Epithelial-To-Mesenchymal Transition (EMT) in Biliary Tree Stem/Progenitor Cell Cultures In Vitro

Human biliary tree stem/progenitor cells (hBTSCs), reside in peribiliary glands, are mainly stimulated by primary sclerosing cholangitis (PSC) and cholangiocarcinoma. In these pathologies, hBTSCs displayed epithelial-to-mesenchymal transition (EMT), senescence characteristics, and impaired differentiation. Here, we investigated the effects of cholest-4,6-dien-3-one, an oxysterol involved in cholangiopathies, on hBTSCs biology. hBTSCs were isolated from donor organs, cultured in self-renewal control conditions, differentiated in mature cholangiocytes by specifically tailored medium, or exposed for 10 days to concentration of cholest-4,6-dien-3-one (0.14 mM). Viability, proliferation, senescence, EMT genes expression, telomerase activity, interleukin 6 (IL6) secretion, differentiation capacity, and HDAC6 gene expression were analyzed. Although the effect of cholest-4,6-dien-3-one was not detected on hBTSCs viability, we found a significant increase in cell proliferation, senescence, and IL6 secretion. Interestingly, cholest-4.6-dien-3-one impaired differentiation in mature cholangiocytes and, simultaneously, induced the EMT markers, significantly reduced the telomerase activity, and induced HDAC6 gene expression. Moreover, cholest-4,6-dien-3-one enhanced bone morphogenic protein 4 (Bmp-4) and sonic hedgehog (Shh) pathways in hBTSCs. The same pathways activated by human recombinant proteins induced the expression of EMT markers in hBTSCs. In conclusion, we demonstrated that chronic exposition of cholest-4,6-dien-3-one induced cell proliferation, EMT markers, and senescence in hBTSC, and also impaired the differentiation in mature cholangiocytes.

Inhibition of Opisthorchis felineus glutathione-dependent prostaglandin synthase by resveratrol correlates with attenuation of cholangiocyte neoplasia in a hamster model of opisthorchiasis

Food-borne trematodiases represent major neglected parasitic diseases. Trematodes of the family Opisthorchiidae including Opisthorchis felineus, Opisthorchis viverrini and Clonorchis sinensis are ranked eight on the global list of the 24 most prevalent food-borne parasites. Chronic O. felineus infection symptoms include precancerous lesions with the potential for malignancy. In recent decades, liver flukes of the family Opisthorchiidae have been extensively scientifically explored, however despite this the molecular mechanisms of O. felineus pathogenicity and its carcinogenic potential have not been studied. Opisthorchis felineus glutathione-dependent prostaglandin synthase (GST σ) is the major component of the excretory-secretory product of this liver fluke. We hypothesised that the activity of this enzyme is involved in the infection pathogenesis, including the formation of precancerous lesions. To test this hypothesis and to gain insights into the mechanisms of precancerous lesion formation, we (i) investigated whether excretory parasitic GST σ retains its enzymatic activity, (ii) tested resveratrol (RSV) as a possible inhibitor of this enzyme, and (iii) assessed biliary neoplasia and oxidative DNA damage as well as the expression of neoplasia and fibrogenesis marker genes after prolonged administration of RSV in a hamster model. RSV was found to inhibit GST σ enzymatic activity in a dose-dependent manner (R = 0.85, P < 0.001; half-maximal effective dose (ED₅₀) = 48.6 μM). Prolonged administration of RSV significantly suppressed high-grade biliary neoplasia (P = 0.008), attenuated upregulation of hyperplasia and fibrogenesis-related genes (Tgfb, α-SMA and CK7), and decreased the elevated oxidative DNA damage. Taking into account that RSV can influence a wide range of pathways, further research is needed to confirm the role of GST σ in O. felineus pathogenicity. Nevertheless, the chemopreventive effect of RSV targeting biliary neoplasia formation might be useful for improving the outcomes in infected populations and represents a compelling rationale for RSV testing in combination chemotherapy of opisthorchiasis.

Localisation of oxysterols at the sub-cellular level and in biological fluids

Oxysterols are oxidized derivatives of cholesterol that are formed enzymatically or via reactive oxygen species or both. Cholesterol or oxysterols ingested as food are absorbed and packed into lipoproteins that are taken up by hepatic cells. Within hepatic cells, excess cholesterol is metabolised to form bile acids. The endoplasmic reticulum acts as the main organelle in the bile acid synthesis pathway. Metabolised sterols originating from this pathway are distributed within other organelles and in the cell membrane. The alterations to membrane oxysterol:sterol ratio affects the integrity of the cell membrane. The presence of oxysterols changes membrane fluidity and receptor orientation. It is well documented that hydroxylase enzymes located in mitochondria facilitate oxysterol production via an acidic pathway. More recently, the presence of oxysterols was also reported in lysosomes. Peroxisomal deficiencies favour intracellular oxysterols accumulation. Despite the low abundance of oxysterols compared to cholesterol, the biological actions of oxysterols are numerous and important. Oxysterol levels are implicated in the pathogenesis of multiple diseases ranging from chronic inflammatory diseases (atherosclerosis, Alzheimer's disease and bowel disease), cancer and numerous neurodegenerative diseases. In this article, we review the distribution of oxysterols in sub-cellular organelles and in biological fluids.

25-hydroxycholesterol impairs neuronal and muscular development in zebrafish

Oxysterols have essential effects on brain homeostasis and their levels are often altered in neurodegenerative and neuroinflammatory diseases. Several studies have demonstrated the cytotoxic effects of 25-HC on different cell lines, however, not much is known about its effects on neurons in vivo. In this study, we examined the effects of 25-HC exposure on the nervous system development in the zebrafish. We showed that survival rate of zebrafish embryos/larvae is significantly decreased at doses of 25-HC above 40 μM. 25-HC was found to affect the motility of zebrafish larvae, primary motor axon and muscle morphology. Furthermore, larvae treated with 25-HC showed a reduced neuronal network and number of HuC-positive cells in the brain. An increased cell death was also observed in both the brain and spinal cord of zebrafish treated with 25-HC. Interestingly, administration of 25-HC at later stages of development (24 and 48 h post fertilization) had no detrimental effects on motor axons. Altogether, our findings show that elevated levels of 25-HC may have important consequences on neuronal development and cell survival.

Microarray analysis of genes from animals treated with a traditional formulation ChandraprabhaVati reveals its therapeutic targets

Background

Traditional medicinal preparations have not received global acceptance, and their therapeutic benefits remain disputed due to lack of scientific evidence on their mechanism of action. Microarray analysis has emerged as a powerful technique that can aid in understanding the complex signaling networks activated by these formulations and thereby assess their beneficial as well as adverse effects.

Aim

The present work aims to investigate the differential influence of ChandraprabhaVati, Ayurvedic formulation used in the treatment of diabetes, anemia, urinary, respiratory, skin and liver disorders.

Materials and methods

The RNA from the liver of rats treated with different doses of ChandraprabhaVati for 28 days was isolated and studied for the genome-wide changes in the expression.

Results

The results revealed several molecular targets that could contribute to the therapeutic effects of ChandraprabhaVati. Several genes have been differentially expressed, among those miRNAs miR-434, miR877, and miRlet7e contribute to the anti-diabetic, anti-fibrotic and anti-inflammatory of CPV. The rejuvenative activity of CPV may be due to the MeOX1 and Upf3b genes. Up-regulation of Hbaa2 gene facilitates the anti-anemic effect. Interestingly gender-specific differential expressions of genes were also observed. Rab3d were found to be altered in female when compared to male animals.

Conclusion

Thus the microarray data for the CPV treated animals has revealed molecular targets that may be responsible for the various known therapeutic effects and also identified new beneficial effects of CPV.

Opisthorchis felineus infection provokes time-dependent accumulation of oxidative hepatobiliary lesions in the injured hamster liver

Opisthorchiasis caused by food-borne trematode Opisthorchis felineus is a substantial public health problem, with 17 million persons infected worldwide. This chronic disease is associated with hepatobiliary inflammation, cholangiocyte dysplasia, cholangiofibrosis, intraepithelial neoplasia, and even cholangiocarcinoma among chronically infected individuals. To provide first insights into the mechanism by which O. felineus infection causes precancerous liver lesions, we investigated the level of oxidative stress (lipid peroxidation byproducts and 8-hydroxy-2′-deoxyguanosine) as well as the time course profiles of chronic inflammation and fibrogenesis markers in the dynamics of opisthorchiasis from 1 month to 1.5 years postinfection in an experimental model based on golden hamsters Mesocricetus auratus. For the first time, we showed that O. felineus infection provokes time-dependent accumulation of oxidative hepatobiliary lesions in the injured liver of hamsters. In particular, over the course of infection, lipid peroxidation byproducts 4-hydroxynonenal and malondialdehyde were upregulated; these changes in general correlate with the dynamics of hepatic histopathological changes. We detected macrophages with various immunophenotypes and elevated levels of CD68, COX2, and CD163 in the O. felineus–infected animals. Meanwhile, there was direct time-dependent elevation of TNF-α (R = 0.79; p < 0.001) and CD163 protein levels (R = 0.58; p = 0.022). We also provide quantitative data about epithelial hyperplasia marker CK7 and a marker of myofibroblast activation (α smooth muscle actin). Our present data provide first insights into the histopathological mechanism by which O. felineus infection causes liver injuries. These findings support the inclusion of O. felineus in Group 1 of biological carcinogens.

25-hydroxycholesterol down-regulates oxysterol binding protein like 2 (OSBPL2) via the p53/SREBF2/NFYA signaling pathway

Oxysterol Binding Protein Like 2 (OSBPL2) is a lipid-binding protein implicated in various cellular processes. Previous studies have shown that depression of OSBPL2 significantly increases the level of cellular 25-hydroxycholesterol (25-OHC) which regulates the expression of lipid-metabolism-related genes. However, whether 25-OHC can regulate the expression of OSBPL2 remains unanswered. This study aimed to explore the molecular mechanism of 25-OHC regulating the expression of OSBPL2. Using dual-luciferase reporter assay, we found a decrease of nuclear transcription factor Y subunit alpha (NFYA) bound with OSBPL2 promoter when HeLa cells were treated with 25-OHC. Furthermore, transcriptome sequencing and RNA interference results revealed that the p53/sterol regulatory element binding transcription factor 2 (SREBF2) signaling pathway was involved in the NFYA-dependent transcription of OSBPL2 induced by 25-OHC. Based on these results, we concluded that pleomorphic adenoma gene 1 (PLAG1) and NFYA participated in the basal transcription of OSBPL2 and that 25-OHC decreased the transcription of OSBPL2 via the p53/SREBF2/NFYA signaling pathway. 25-OHC will accumulate over time in OSBPL2 knockdown cells. These results may provide a new insight into the deafness caused by OSBPL2 mutation.

Neoplastic Transformation of the Peribiliary Stem Cell Niche in Cholangiocarcinoma Arisen in Primary Sclerosing Cholangitis

Primary sclerosing cholangitis (PSC) is a chronic inflammatory cholangiopathy frequently complicated by cholangiocarcinoma (CCA). Massive proliferation of biliary tree stem/progenitor cells (BTSCs), expansion of peribiliary glands (PBGs), and dysplasia were observed in PSC. The aims of the present study were to evaluate the involvement of PBGs and BTSCs in CCA which emerged in PSC patients. Specimens from normal liver (n = 5), PSC (n = 20), and PSC-associated CCA (n = 20) were included. Samples were processed for histology, immunohistochemistry, and immunofluorescence. In vitro experiments were performed on human BTSCs, human mucinous primary CCA cell cultures, and human cholangiocyte cell lines (H69). Our results indicated that all CCAs emerging in PSC patients were mucin-producing tumors characterized by PBG involvement and a high expression of stem/progenitor cell markers. Ducts with neoplastic lesions showed higher inflammation, wall thickness, and PBG activation compared to nonneoplastic PSC-affected ducts. CCA showed higher microvascular density and higher expression of nuclear factor kappa B, interleukin-6, interleukin-8, transforming growth factor β, and vascular endothelial growth factor-1 compared to nonneoplastic ducts. CCA cells were characterized by a higher expression of epithelial-to-mesenchymal transition (EMT) traits and by the absence of primary cilia compared to bile ducts and PBG cells in controls and patients with PSC. Our in vitro study demonstrated that lipopolysaccharide and oxysterols (PSC-related stressors) induced the expression of EMT traits, the nuclear factor kappa B pathway, autophagy, and the loss of primary cilia in human BTSCs. Conclusion: CCA arising in patients with PSC is characterized by extensive PBG involvement and by activation of the BTSC niche in these patients, the presence of duct lesions at different stages suggests a progressive tumorigenesis.

What are the characteristics of vitamin D metabolism in opioid dependence? An exploratory longitudinal study in Australian primary care

OBJECTIVE

Compare vitamin D levels in opioid dependence and control population and adjust for relevant confounding effects. Nuclear hormone receptors (including the vitamin D receptor) have been shown to be key transducers and regulators of intracellular metabolism and comprise an important site of pathophysiological immune and metabolic dysregulation potentially contributing towards pro-ageing changes observed in opioid-dependent patients (ODPs).

DESIGN

Longitudinal prospective comparing ODPs with general medical controls (GMCs).

SETTING

Primary care.

PARTICIPANTS

Prospective review comparing 1168 ODP (72.5% men) and 415 GMC (51.6% men, p<0.0001). Mean ages were 33.92±0.31 (mean±SEM) and 41.22±1.32 years, respectively (p<0.0001). Opioid use in the ODP has been previously reported and shown to be typical.

INTERVENTIONS

Nil. Observational study only.

PRIMARY AND SECONDARY OUTCOMES

Serum vitamin D levels and relevant biochemical parameters.

RESULTS

Vitamin D levels were higher in the ODP (70.35±1.16 and 57.06±1.81 nmol/L, p<0.0001). The difference in ages between the two groups was handled in an age-matched case-control subanalysis and also by multiple regression. Sexes were analysed separately. The age:status (or age:time:status) was significant in case-control, cross-sectional and longitudinal analyses in both sexes (p<0.05). Modelled vitamin D was 62.71 vs 57.81 nmol/L in the two groups. Time-dependent mixed-effects models quadratic in age outperformed linear-only models (p=0.0377). ODP vitamin D was shown to vary with age and to correlate with alanine aminotransferase establishing it as a biomarker of age in this group. Hepatitis C seronegativity was significant in regression models (from p=0.0015).

CONCLUSION

Vitamin D was higher in ODP in both sexes in bivariate, cross-sectional, case-control and longitudinal analyses and was robust to the inclusion of metabolic and immune biomarkers. That Hepatitis C seronegativity was significant suggests opioid dependence has an effect beyond simply that of its associated hepatitides. This finding may relate to the accelerated ageing process previously described in opioid dependence.

Infection with Opisthorchis felineus induces intraepithelial neoplasia of the biliary tract in a rodent model

The liver fluke Opisthorchis felineus is a member of the triad of epidemiologically relevant species of the trematode family Opisthorchiidae, and the causative agent of opisthorchiasis felinea over an extensive range that spans regions of Eurasia. The International Agency for Research on Cancer classifies the infection with the liver flukes Opisthorchis viverrini and Clonorchis sinensis as group 1 agents and a major risk factor for cholangiocarcinoma. However, the carcinogenic potential of the infection with O. felineus is less clear. Here, we present findings that support the inclusion of O. felineus in the Group 1 list of biological carcinogens. Two discrete lines of evidence support the notion that infection with this liver fluke is carcinogenic. First, novel oxysterol-like metabolites detected by liquid chromatography-mass spectroscopy in the egg and adult developmental stages of O. felineus, and in bile, sera, and urine of liver fluke-infected hamsters exhibited marked similarity to oxysterol-like molecules known from O. viverrini. Numerous oxysterols and related DNA-adducts detected in the liver fluke eggs and in bile from infected hamsters suggested that infection-associated oxysterols induced chromosomal lesions in host cells. Second, histological analysis of liver sections from hamsters infected with O. felineus confirmed portal area enlargement, inflammation with severe periductal fibrosis and changes in the epithelium of the biliary tract characterized as biliary intraepithelial neoplasia, BilIN. The consonance of these biochemical and histopathological changes revealed that O. felineus infection in this rodent model induced precancerous lesions conducive to malignancy.

Cholangiocytes in the pathogenesis of primary sclerosing cholangitis and development of cholangiocarcinoma

Primary sclerosing cholangitis (PSC) is an idiopathic cholangiopathy strongly associated with inflammatory bowel disease (IBD) and characterized by cholestasis, chronic immune infiltration and progressive fibrosis of the intrahepatic and extrahepatic bile ducts. PSC confers a high risk of cholangiocarcinoma (CCA) with PSC-CCA representing the leading cause of PSC-associated mortality. PSC-CCA is derived from cholangiocytes and associated progenitor cells - a heterogeneous group of dynamic epithelial cells lining the biliary tree that modulate the composition and volume of bile production by the liver. Infection, inflammation and cholestasis can trigger cholangiocyte activation leading to an increased expression of adhesion and antigen-presenting molecules as well as the release of various inflammatory and fibrogenic mediators. As a result, activated cholangiocytes engage in a myriad of cellular processes, including hepatocellular proliferation, apoptosis, angiogenesis and fibrosis. Cholangiocytes can also regulate the recruitment of immune cells, mesenchymal cells, and endothelial cells that participate in tissue repair and destruction in settings of persistent inflammation. In PSC, the role of cholangiocytes and the mechanisms governing their transformation to PSC-CCA are unclear however localization of disease suggests that cholangiocytes are a key target and potential regulator of hepatobiliary immunity, fibrogenesis and tumorigenesis. Herein, we summarize mechanisms of cholangiocyte activation in PSC and highlight new insights into disease pathways that may contribute to the development of PSC-CCA. This article is part of a Special Issue entitled: Cholangiocytes in Health and Disease edited by Jesus Banales, Marco Marzioni, Nicholas LaRusso and Peter Jansen.

Cholangiocarcinoma

Biliary tract cancer accounts for <1% of all cancers and affects chiefly an elderly population, with predominance in men. We distinguish cholangiocarcinoma (intrahepatic, hilar and distal) and gallbladder cancer, with different pathogenesis and prognosis. The treatment is based on surgery (whenever possible), radiotherapy in selected cases, and chemotherapy. The standard cytotoxic treatment for advanced/metastatic disease is represented by the combination of gemcitabine and cisplatin, whereas fluoropyrimidines are generally administered in second line setting. At the present time, no biologic drug demonstrated a clear efficacy in this cancer, although the molecular characterisation could provide a promising basis for experimental treatments. A good supportive care and an early palliative care are warranted in most patients and should be delivered as a part of a global approach.

Why does infection with some helminths cause cancer?

Infections with Opisthorchis viverrini, Clonorchis sinensis and Schistosoma haematobium are classified as Group 1 biological carcinogens: definitive causes of cancer. These worms are metazoan eukaryotes, unlike the other Group 1 carcinogens including human papilloma virus, hepatitis C virus, and Helicobacter pylori. By contrast, infections with phylogenetic relatives of these helminths, also trematodes of the phylum Platyhelminthes and major human pathogens, are not carcinogenic. These inconsistencies prompt several questions, including how might these infections cause cancer? And why is infection with only a few helminth species carcinogenic? Here we present an interpretation of mechanisms contributing to the carcinogenicity of these helminth infections, including roles for catechol estrogen- and oxysterol-metabolites of parasite origin as initiators of carcinogenesis.

Primary Sclerosing Cholangitis as a Premalignant Biliary Tract Disease: Surveillance and Management

Primary sclerosing cholangitis (PSC) is a premalignant biliary tract disease that confers a significant risk for the development of cholangiocarcinoma (CCA). The chronic biliary tract inflammation of PSC promotes pro-oncogenic processes such as cellular proliferation, induction of DNA damage, alterations of the extracellular matrix, and cholestasis. The diagnosis of malignancy in PSC can be challenging because inflammation-related changes in PSC may produce dominant biliary tract strictures mimicking CCA. Biomarkers such as detection of methylated genes in biliary specimens represent noninvasive techniques that may discriminate malignant biliary ductal changes from PSC strictures. However, conventional cytology and advanced cytologic techniques such as fluorescence in situ hybridization for polysomy remain the practice standard for diagnosing CCA in PSC. Curative treatment options of malignancy arising in PSC are limited. For a subset of patients selected by using stringent criteria, liver transplantation after neoadjuvant chemoradiation is a potential curative therapy. However, most patients have advanced malignancy at the time of diagnosis. Advances directed at identifying high-risk patients, early cancer detection, and development of chemopreventive strategies will be essential to better manage the cancer risk in this premalignant disease. A better understanding of dysplasia definition and especially its natural history is also needed in this disease. Herein, we review recent developments in our understanding of the risk factors, pathogenic mechanisms of PSC associated with CCA, as well as advances in early detection and therapies.

Oxysterols: Influence on plasma membrane rafts microdomains and development of ocular diseases

Oxidation of cholesterol into oxysterols is a major way of elimination of cholesterol from the liver and extrahepatic tissues, including the brain and the retina. Oxysterols are involved in various cellular processes. Numerous links have been established between oxysterols and several disorders such as neurodegenerative pathologies, retinopathies and atherosclerosis. Different components of the lipid layer such as sphingolipids, sterols and proteins participate to membrane fluidity and forme lipid rafts microdomains. Few data are available on the links between lipids rafts and oxysterols. The purpose of this review is to suggest the potential role of lipid rafts microdomains in the development of retinopathies with special emphasis and opening perspectives of their interactions with oxysterols. Actually cholesterol oxidation mechanism may have deleterious effect on its ability to support rafts formation .This review suggest that the effect of oxysterols of lipid rafts would probably depend on the oxysterol molecule and cell type.

Effects of 5α-cholestan-3-one on the synaptic vesicle cycle at the mouse neuromuscular junction

We have investigated the effects of 5α-cholesten-3-one (5Ch3, 200 nM) on synaptic transmission in mouse diaphragm. 5Ch3 had no impact on the amplitude or frequency of miniature endplate currents (MEPCs, spontaneous secretion), but decreased the amplitude of EPCs (evoked secretion) triggered by single action potentials. Treatment with 5Ch3 increased the depression of EPC amplitude and slowed the unloading of the dye FM1-43 from synaptic vesicles (exocytosis rate) during high-frequency stimulation. The estimated recycling time of vesicles did not change, suggesting that the decline of synaptic efficiency was due to the reduction in the size of the population of vesicles involved in release. The effects of 5Ch3 on synaptic transmission may be related to changes in the phase properties of the membrane. We have found that 5Ch3 reduces the staining of synaptic regions with the B-subunit of cholera toxin (a marker of lipid rafts) and increases the fluorescence of 22-NBD-cholesterol, indicating a phase change within the membrane. Manipulations of membrane cholesterol (saturation or depletion) strongly reduced the influence of 5Ch3 on both FM1-43 dye unloading and staining with the B-subunit of cholera toxin. Thus, 5Ch3 reduces the number of vesicles which are actively recruited during synaptic transmission and alters membrane properties. These effects of 5Ch3 depend on membrane cholesterol.

Cholangiocarcinoma: molecular pathways and therapeutic opportunities

Cholangiocarcinoma (CCA) is an aggressive biliary tract malignancy with limited treatment options and low survival rates. Currently, there are no curative medical therapies for CCA. Recent advances have enhanced our understanding of the genetic basis of this disease, and elucidated therapeutically relevant targets. Therapeutic efforts in development are directed at several key pathways due to genetic aberrations including receptor tyrosine kinase pathways, mutant IDH enzymes, the PI3K-AKT-mTOR pathway, and chromatin remodeling networks. A highly desmoplastic, hypovascular stroma is characteristic of CCAs and recent work has highlighted the importance of targeting this pathway via stromal myofibroblast depletion. Future efforts should concentrate on combination therapies with action against the cancer cell and the surrounding tumor stroma. As the mutational landscape of CCA is being illuminated, molecular profiling of patient tumors will enable identification of specific mutations and the opportunity to offer directed, personalized treatment options.

Molecular pathogenesis of cholangiocarcinoma

It has become increasingly apparent of late that inflammation plays an integral role in a spectrum of malignancies including cholangiocarcinoma (CCA). Primary sclerosing cholangitis with chronic inflammation is the most common risk factor for CCA in the Western world. Recent work has highlighted that inflammatory pathways are essential in carcinogenesis and tissue invasion and migration. Inflammation advances carcinogenesis by induction of DNA damage, evasion of apoptosis, promotion of cell proliferation, and neoangiogenesis. CCA is characterized by the presence of a desmoplastic stroma consisting of cancer-associated fibroblasts, tumor-associated macrophages, and tumor-infiltrating lymphocytes. This rich inflammatory milieu is vital to the cancer ecosystem, and targeting its components represents an attractive therapeutic option.

Pathogenesis, diagnosis, and management of cholangiocarcinoma

Cholangiocarcinomas (CCAs) are hepatobiliary cancers with features of cholangiocyte differentiation; they can be classified anatomically as intrahepatic CCA (iCCA), perihilar CCA (pCCA), or distal CCA. These subtypes differ not only in their anatomic location, but in epidemiology, origin, etiology, pathogenesis, and treatment. The incidence and mortality of iCCA has been increasing over the past 3 decades, and only a low percentage of patients survive until 5 years after diagnosis. Geographic variations in the incidence of CCA are related to variations in risk factors. Changes in oncogene and inflammatory signaling pathways, as well as genetic and epigenetic alterations and chromosome aberrations, have been shown to contribute to the development of CCA. Furthermore, CCAs are surrounded by a dense stroma that contains many cancer-associated fibroblasts, which promotes their progression. We have gained a better understanding of the imaging characteristics of iCCAs and have developed advanced cytologic techniques to detect pCCAs. Patients with iCCAs usually are treated surgically, whereas liver transplantation after neoadjuvant chemoradiation is an option for a subset of patients with pCCAs. We review recent developments in our understanding of the epidemiology and pathogenesis of CCA, along with advances in classification, diagnosis, and treatment.