Human Hepatic HepG2 Research Articles

Cytotoxicity of pyrrolizidine alkaloid in human hepatic parenchymal and sinusoidal endothelial cells: Firm evidence for the reactive metabolites mediated pyrrolizidine alkaloid-induced hepatotoxicity

Pyrrolizidine alkaloids (PAs) widely distribute in plants and can cause hepatic sinusoidal obstruction syndrome (HSOS), which typically presents as a primary sinusoidal endothelial cell damage. It is well-recognized that after ingestion, PAs undergo hepatic cytochromes P450 (CYPs)-mediated metabolic activation to generate dehydropyrrolizidine alkaloids (DHPAs), which are hydrolyzed to dehydroretronecine (DHR). DHPAs and DHR are reactive metabolites having same core pyrrole moiety, and can bind proteins to form pyrrole-protein adducts, which are believed as the primary cause for PA-induced HSOS. However, to date, the direct evidences supporting the toxicity of DHPAs and DHR in the liver, in particular in the sinusoidal endothelial cells, are lacking. Using human hepatic sinusoidal endothelial cells (HSEC) and HepG2 (representing hepatic parenchymal cells), cells that lack CYPs activity, this study determined the direct cytotoxicity of dehydromonocrotaline, a representative DHPA, and DHR, but no cytotoxicity of the intact PA (monocrotaline) in both cell lines, confirming that reactive metabolites mediate PA intoxication. Comparing with HepG2, HSEC had significantly lower basal glutathione (GSH) level, and was significantly more susceptible to the reactive metabolites with severer GSH depletion and pyrrole-protein adducts formation. The toxic potency of two reactive metabolites was also compared. DHPA was more reactive than DHR, leading to severer toxicity. In conclusion, our results unambiguously provided the first direct evidence for the critical role of DHPA and DHR in the reactive metabolites-mediated PA-induced hepatotoxicity, which occurs predominantly in HSEC due to severe GSH depletion and the significant formation of pyrrole-protein adducts in HSEC.

ヒト肝細胞分化およびCYP3A4誘導性をモニター可能なCYP3A4G/7R HepaRGおよびHepG2細胞の特性解析

ヒト肝細胞分化およびCYP3A4誘導性をモニター可能なCYP3A4G/7R HepaRGおよびHepG2細胞の特性解析

Hesperidin from Citrus seed induces human hepatocellular carcinoma HepG2 cell apoptosis via both mitochondrial and death receptor pathways.

Citrus seeds are full of phenolic compounds, such as flavonoids. The aims of this study were to identify the types of flavonoids in Citrus seed extracts, the cytotoxic effect, mode of cell death, and signaling pathway in human hepatic cancer HepG2 cells. The flavonoids contain anticancer, free radical scavenging, and antioxidant activities. Neohesperidin, hesperidin, and naringin, active flavanone glycosides, were identified in Citrus seed extract. The cytotoxic effect of three compounds was in a dose-dependent manner, and IC50 levels were determined. The sensitivity of human HepG2 cells was as follows: hesperidin > naringin > neohesperidin > naringenin. Hesperidin induced HepG2 cells to undergo apoptosis in a dose-dependent manner as evidenced by the externalization of phosphatidylserine and determined by annexin V-fluorescein isothiocyanate and propidium iodide staining using flow cytometry. Hesperidin did not induce the generation of reactive oxygen species, which was determined by using 2′,7′-dichlorohydrofluorescein diacetate and flow cytometry method. The number of hesperidin-treated HepG2 cells with the loss of mitochondrial transmembrane potential increased concentration dependently, using 3,3′-dihexyloxacarbocyanine iodide employing flow cytometry. Caspase-9, -8, and -3 activities were activated and increased in hesperidin-treated HepG2 cells. Bcl-xL protein was downregulated whereas Bax, Bak, and tBid protein levels were upregulated after treatment with hesperidin in a dose-dependent manner. In conclusion, the bioflavanone from Citrus seeds, hesperidin, induced human HepG2 cell apoptosis via mitochondrial pathway and death receptor pathway. Citrus seed flavonoids are beneficial and can be developed as anticancer drug or food supplement, which still needs further in vivo investigation in animals and human beings.

Metabolism and antiproliferative effects of sulforaphane and broccoli sprouts in human intestinal (Caco-2) and hepatic (HepG2) cells

The purpose of this work was to study the absorption and metabolism of sulforaphane (SFN) from broccoli sprouts, their major glucosinolate glucoraphanin and its hydrolysis product SFN. This was done by monitoring SFN's main metabolites, i.e. SFN, SFN-glutathione and SFN-cysteine, in two different cell models of absorption and metabolism (Caco-2 colorectal carcinoma cells and HepG2 hep- atocellular carcinoma cells), during 3, 6, and 24 h of treatment, using a selective UHPLC-QqQ-MS/MS procedure. Concentrations ranging 0.5-90 nmol/l were found within the cells and released in the medium, depending on the type of analyte under study. Cells were capable of conjugative metabolism, since the SFN mercapturic derivatives could be identified in the cell medium. The antiproliferative activity of broccoli sprouts, glucoraphanin and sul- foraphane was compared in Caco-2 and HT-29 human colorectal carcinoma cells, and HepG2 hepatocellular carcinoma cells, establishing the minimal concentration of a given compound to achieve half inhibition of the maximal cell growth (IC50) for broccoli sprouts extract and sulforaphane. However, glucoraphanin did not show an antiproliferative effect in the cells under study.

Oligonol suppresses lipid accumulation and improves insulin resistance in a palmitate-induced in HepG2 hepatocytes as a cellular steatosis model.

BackgroundOligonol is a low molecular weight form of polyphenol polymers derived from lychee fruits. Several studies suggest that Oligonol has an anti-obesity effect. Since obesity is tightly associated with insulin resistance, we investigated a possible remission effect of Oligonol on lipid accumulation and insulin resistance in human hepatic HepG2 cells.MethodsHepG2 cells were treated with palmitate for 24 h to induce cellular hepatic steatosis and insulin resistance. The cells were then treated with Oligonol at subtoxic concentrations and examined for lipid metabolism, cytokine production, and insulin signaling using quantitative RT-PCR and western blot analysis.ResultsOligonol treatment reversed the palmitate-induced intracellular lipid accumulation, down regulated the expression of lipogenic genes, and up-regulated genes for fatty acid degradation. Oligonol restored insulin sensitivity, as was determined by the phosphorylation states of IRS-1. Oligonol also inhibited STAT3-SOCS3 signaling and increased AMPK phosphorylation in HepG2 cells.ConclusionOligonol treatment improved palmitate-induced cellular steatosis and insulin resistance in HepG2 cells with concomitant reduction of inflammatory cytokines and decrease in STAT3-SOCS3 and AMPK-mTOR pathways. Oligonol may have beneficial effects in lipid metabolism and insulin resistance in the liver.

A novel compound 4010B-30 upregulates apolipoprotein A-I gene expression through activation of PPARγ in HepG2 cells

ObjectiveApolipoprotein (Apo) A-I is the major lipoprotein content of HDL and upregulating endogenous ApoA-I expression has been proposed as a desirable approach to raise the functional HDL. In this study we investigated the effect of a novel small molecule 4010B-30 on transcriptional regulation of ApoA-I gene in HepG2 cells, and the influence on the level of ApoA-I expression and function. Then the mechanisms by which 4010B-30 regulated ApoA-I expression was further explored. Methods and resultsIn human hepatic HepG2 cells, 4010B-30 increased the mRNA level and the protein production of ApoA-I both in cell lysates and media. The 4010B-30-induced ApoA-I containing particles increased cholesterol efflux from RAW264.7 macrophages. 4010B-30 also upregulated ABCA1 expression confirmed by transcriptional activity assay and Western blot analysis in both HepG2 and RAW264.7 cells. Promoter luciferase assay was used to identify the 4010B-30-responsive region which is mapped to the proximal −277bp region of the ApoA-I promoter. Further study indicated that the regulation of 4010B-30 on ApoA-I transcription or protein expression in HepG2 cells was abrogated with the suppression of PPARγ by its small interfering RNA or a specific inhibitor, GW9662. ConclusionsThese findings suggest that the novel small molecular upregulator 4010B-30 increases ApoA-I gene expression, thereby enhances its function of promoting cholesterol efflux, as well as ABCA1 expression in vitro, and activation of PPARγ is required for 4010B-30 to induce hepatic ApoA-I production.

Expression of ST3Gal, ST6Gal, ST6GalNAc and ST8Sia in human hepatic carcinoma cell lines, HepG-2 and SMMC-7721 and normal hepatic cell line, L-02.

We measured ST3Gal, ST6Gal, ST6GalNAc and ST8Sia expression in human hepatic carcinoma cell lines, HepG-2 and SMMC-7721 and normal hepatic cell line, L-02 to reveal the relationship between hepatic carcinoma cell lines sialyltransferases expression and cell membrane sialic acid sugar chains. Membrane sialic acid sugar chains in L-02, HepG-2 and SMMC-7721 cell lines were measured with lectin microarrays to find expression profiles. Expression of 20 sialyltransferases was measured with DNA microarray. qRT-PCR and Western blot were used to verify DNA microarrays data. Siaα 2-3Galβ1-3[Siaα2-6GalNAc]α-R and Siaα 2-6Gal/GalNAc sugar chains in hepatic carcinoma cell lines, HepG-2 and SMMC-7721 were upregulated, and 7differentially expressed sialyltransferases were captured. ST3Gal-IV and ST6Gal I were overexpressed and ST3Gal-I, ST3Gal-V, ST3Gal-VI, ST6GalNAcII and ST6GalNAcVI were downregulated in HepG-2 and SMMC-7721 cell Lines, compared with control cell line. ST6GalNAc-IV and ST8sia expressions were not detected. Other sialyltransferases were not different among cell lines. Results from qRT-PCR and Western blot were consistent with DNA microarray. Overexpression of ST3Gal-IV and ST6Gal I in HepG-2 and SMMC-7721 cell lines may correlate with upregulation of Siaα 2-3Galβ1-3[Siaα2-6GalNAc]α-R and Siaα 2-6Gal/GalNAc sugar chains on cell membranes.

Effect of wilfortrine on human hepatic cancer HepG2 cell proliferation potential in vitro.

Liver cancers are characterized by high morbidity and mortality owing to few effective drugs for its treatment. Wilfortrine has several pharmacological effects, including an inhibitory effect on liver cancer cell proliferation. However, whether wilfortrine can induce liver cancer cell apoptosis has not been elucidated. We investigated the role of wilfortrine on liver cancer cell HepG2 apoptosis and analyzed its possible mechanisms to provide a theoretical basis for clinical analysis of liver cancer pathogenesis. The liver cancer cell line HepG2 was treated with 40 mM wilfortrine for 48 h. Flow cytometry was applied to detect HepG2 cell apoptosis and cell cycle changes. Western blot was used to analyze Bcl-2 and Bax expression. The HepG2 cell apoptosis rate increased significantly after treatment with wilfortrine, especially the early apoptosis rate (P < 0.05). However, wilfortrine did not change the cell cycle of HepG2 cells. After wilfortrine treatment, Bcl- 2 expression decreased significantly (P < 0.05); on the contrary, Bax expression increased noticeably compared with the control group (P < 0.05). Wilfortrine can induce liver cancer cell HepG2 apoptosis, but with no effect on the cell cycle, mainly by promoting Bax expression and inhibiting anti-apoptotic protein Bcl-2 expression.

Microencapsulation of Fucoxanthin by Water-in-Oil-in-Water (W/O/W) Double Emulsion Solvent Evaporation Method: A Review

Fucoxanthin is a major xanthophyll present in brown seaweeds such as Sargassum binderi, S. duplicatum, Turbinaria turbinata, Padina australis, Undaria pinnatifida and Hijkia fusiformis. This carotenoid has a unique structure including oxygenic functional group such as, two hydroxy, keto, epoxy (5,6-monoepoxide), and an allenic bond. Fucoxanthin has some anticancer activities such as, exhibits inhibitory property on colon cancer cells and human hepatic carcinoma HepG2 cell line. This xanthophyll also induces apoptosis of human leukemia cancer HL-60 cells, human prostate cancer PC-3 cell, human lung cancer H1299 cell line etc. Unfortunately, the poor solubility of this carotenoid in water hinders it to be a drug candidate. Fucoxanthin is also a pigment that is sensitive to temperature and light. One of the possible ways to circumvent the problem with light and temperature is by microencapsulating it. Microencapsulation (ME) in biodegradable polymers, e.g. poly(D,L-lactic-co-glycolic acid) (PLGA) is a promising approach to protect any potential drug from rapid degradation. Solvent evaporation method is the most popular technique of preparing PLGA microsphere (MS) and this technique has been extensively studied in recent years for the preparation of MS. In the water-in-oil-in-water (w/o/w) double emulsion solvent evaporation method, stability of the primary emulsion (PE) is a critical factor. When the PE is unstable, encapsulation efficiency (EE) is low. Stability of PE can be enhanced by including emulsifying agent or stabilizers such as polyvinyl alcohol (PVA). The presence of a stabilizer/ emulsifier plays a significant role in influencing particle size (PS), external morphology of microsphere and colloidal stability.

Leucine alters hepatic glucose/lipid homeostasis via the myostatin-AMP-activated protein kinase pathway - potential implications for nonalcoholic fatty liver disease.

BackgroundElevated plasma levels of the branched-chain amino acid (BCAA) leucine are associated with obesity and insulin resistance (IR), and thus the propensity for type 2 diabetes mellitus development. However, other clinical studies suggest the contradictory view that leucine may in fact offer a degree of protection against metabolic syndrome. Aiming to resolve this apparent paradox, we assessed the effect of leucine supplementation on the metabolism of human hepatic HepG2 cells.ResultsWe demonstrate that pathophysiological leucine appears to be antagonistic to insulin, promotes glucose uptake (and not glycogen synthesis), but results in hepatic cell triglyceride (TG) accumulation. Further, we provide evidence that myostatin (MSTN) regulation of AMP-activated protein kinase (AMPK) is a key pathway in the metabolic effects elicited by excess leucine. Finally, we report associated changes in miRNA expression (some species previously linked to metabolic disease etiology), suggesting that epigenetic processes may contribute to these effects.ConclusionsCollectively, our observations suggest leucine may be both ‘friend’ and ‘foe’ in the context of metabolic syndrome, promoting glucose sequestration and driving lipid accumulation in liver cells. These observations provide insight into the clinical consequences of excess plasma leucine, particularly for hyperglycemia, IR and nonalcoholic fatty liver disease (NAFLD).

In vitro experimental study of novel porphyrin-typed photosensitizer photodynamically treating hepatic carcinoma

Objective To study the photodynamic therapy (PDT) mediated by a novel porphyrin-typed photosensitizer on human hepatic carcinoma HepG2 cell and the mechanisms.Methods Experiments were derided into four groups:control group,PDT group,photosensitizer group and photosensitizer+PDT group.The photostability of novel photosensitizer upon repetitive illumination was evaluated by bleaching method,and cell survival rate was determined by MTT assay.Cellular uptake of novel photosensitizer was measured with luminescence spectrometer,and cellular localization ofphotosensitizer was observed by laser scanning confocal microscopy (LSCM).Furthermore,apoptotic cell was detected with Hoechst 333342 staining.Results Novel photosensitizer was stable after repetitive light irradiation,and PDT or photosensitizer alone showed no dark cytotoxicity toward HepG2 cell (P＞0.05),but intense killing was observed in photosensitizer+PDT group (P＜0.05).The IC50 is 1.21 μmol/L.Cellular uptake of novel photosensitizer was concentration-dependent and the highest uptake is at concentration of 12.5 μmol/L.Novel photosensitizer localizes in lysosomes of HepG2 cell,and the death mode of HepG2 cell was mainly apoptosis.Conclusions Novel photosensitizer exerts profound cytotoxic effects on HepG2 cell mainly through the initiation of secondary cell apoptosis by lysosome destruction. Key words: Novel photosensitizer; HepG2 cell; Photosensitizer uptake; Subcellular localization; Apoptosis

Preparation and characterization of glycyrrhetinic acid-modified poly(ethylene glycol)-poly(β-benzyl-l-asparate) nanoparticles as liver-targeted delivery system

An effective liver-targeted delivery system was successfully developed by designing ligand-mediated nanoparticles composed of glycyrrhetinic acid (GA)-conjugated block copolymers (glycyrrhetinic acid-modified poly(ethylene glycol)-poly(β-benzyl-l-asparate, GA-PEG-PBLA) synthesized via ring-opening polymerization of the β-benzyl-l-asparate N-carboxyanhydride (BLA-NCA) monomer initiated by GA-modified polyethylene glycol (PEG). Chemical structures of the synthesized polymers were confirmed by 1H nuclear magnetic resonance (1H NMR) and Fourier transform infrared assay (FTIR) and molecular weight determined by gel permeation chromatography (GPC). The copolymers were processed into nanoparticles for delivery of paclitaxel (PTX). In this work, the PTX-loaded nanoparticles were prepared by the emulsion-solvent evaporation method, and the physicochemical properties and cytotoxicity were investigated. The particle sizes of nanoparticles determined by dynamic light scattering measurements were around 70 nm. Transmission electron microscopy showed that the nanoparticles were spherical in shape. The results of in vitro release tests showed that the release profiles of PTX-loaded nanoparticles had a sustained drug release pattern, and PTX release from nanoparticles at pH 5.8 was much faster than that at pH 7.4. The drug release profiles were also fitted for mathematical models to analyze the release mechanism, and the Korsmeyer-Peppas model was found to be the best fit model, indicating a combined effect of diffusion and erosion mechanisms for drug release. The cytotoxicity based on 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay against human hepatic carcinoma HepG2 cells indicated that the GA-PEG-PBLA nanoparticles had low cytotoxicity and good biocompatibility. These results indicated that the GA-PEG-PBLA nanoparticles could be a novel candidate for liver-targeted delivery of poorly water-soluble anticancer drugs.

Anticancer activity and DNA-binding investigations of the Cu(II) and Ni(II) complexes with coumarin derivative.

Two new copper(II) (2) and nickel(II) (3) complexes with a new coumarin derivative have been synthesized and structurally characterized. The DNA-binding activities of the two complexes have been investigated by spectrometric titrations, ethidium bromide displacement experiments, CD (circular dichroism) spectral analysis, and viscosity measurements. The results indicate that the two complexes, especially the complex 2, can strongly bind to calf-thymus DNA (CT--DNA). The intrinsic binding constants Kb of the complexes with CT-DNA are 2.99 × 10(5) and 0.61 × 10(5) for 2 and 3, respectively. Comparative cytotoxic activities of the two complexes are also determined by MTT assay. The results show that the drugs designed here have significant cytotoxic activity against the human hepatic (HepG2), human promyelocytic leukemia (HL60), and human prostate (PC3) cell lines. Cell apoptosis was detected by Annexin V/PI flow cytometry, and the results show that the two copper complexes can induce apoptosis of the three human tumor cells. In conclusions, the two complexes show considerable cytotoxic activity against the three human cancer and induce apoptosis of the threes.

Dual-color fluorescence imaging to monitor CYP3A4 and CYP3A7 expression in human hepatic carcinoma HepG2 and HepaRG cells.

Human adult hepatocytes expressing CYP3A4, a major cytochrome P450 enzyme, are required for cell-based assays to evaluate the potential risk of drug-drug interactions caused by transcriptional induction of P450 enzymes in early-phase drug discovery and development. However, CYP3A7 is preferentially expressed in premature hepatoblasts and major hepatic carcinoma cell lines. The human hepatocellular carcinoma cell line HepaRG possesses a high self-renewal capacity and can differentiate into hepatic cells similar to human adult hepatocytes in vitro. Transgenic HepaRG cells, in which the expression of fluorescent reporters is regulated by 35 kb regulatory elements of CYP3A4, have a distinct advantage over human hepatocytes isolated by collagenase perfusion, which are unstable in culture. Thus, we created transgenic HepaRG and HepG2 cells by replacing the protein-coding regions of human CYP3A4 and CYP3A7 with enhanced green fluorescent protein (EGFP) and DsRed reporters, respectively, in a bacterial artificial chromosome vector that included whole regulatory elements. The intensity of DsRed fluorescence was initially high during the proliferation of transgenic HepaRG cells. However, most EGFP-positive cells were derived from those in which DsRed fluorescence was extinguished. Comparative analyses in these transgenic clones showed that changes in the total fluorescence intensity of EGFP reflected fold changes in the mRNA level of endogenous CYP3A4. Moreover, CYP3A4 induction was monitored by the increase in EGFP fluorescence. Thus, this assay provides a real-time evaluation system for quality assurance of hepatic differentiation into CYP3A4-expressing cells, unfavourable CYP3A4 induction, and fluorescence-activated cell sorting-mediated enrichment of CYP3A4-expressing hepatocytes based on the total fluorescence intensities of fluorescent reporters, without the need for many time-consuming steps.

Bile acids reduce endocytosis of high-density lipoprotein (HDL) in HepG2 cells.

High-density lipoprotein (HDL) transports lipids to hepatic cells and the majority of HDL-associated cholesterol is destined for biliary excretion. Cholesterol is excreted into the bile directly or after conversion to bile acids, which are also present in the plasma as they are effectively reabsorbed through the enterohepatic cycle. Here, we provide evidence that bile acids affect HDL endocytosis. Using fluorescent and radiolabeled HDL, we show that HDL endocytosis was reduced in the presence of high concentrations of taurocholate, a natural non-cell-permeable bile acid, in human hepatic HepG2 and HuH7 cells. In contrast, selective cholesteryl-ester (CE) uptake was increased. Taurocholate exerted these effects extracellularly and independently of HDL modification, cell membrane perturbation or blocking of endocytic trafficking. Instead, this reduction of endocytosis and increase in selective uptake was dependent on SR-BI. In addition, cell-permeable bile acids reduced HDL endocytosis by farnesoid X receptor (FXR) activation: chenodeoxycholate and the non-steroidal FXR agonist GW4064 reduced HDL endocytosis, whereas selective CE uptake was unaltered. Reduced HDL endocytosis by FXR activation was independent of SR-BI and was likely mediated by impaired expression of the scavenger receptor cluster of differentiation 36 (CD36). Taken together we have shown that bile acids reduce HDL endocytosis by transcriptional and non-transcriptional mechanisms. Further, we suggest that HDL endocytosis and selective lipid uptake are not necessarily tightly linked to each other.

A pH-sensitive micelle for codelivery of siRNA and doxorubicin to hepatoma cells

Aiming to effectively codeliver chemotherapeutic drugs (DOX) and siRNA (BCL-2 siRNA) into tumor cells, well-defined triblock copolymers composed of hydrophilic and hydrophobic blocks were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. The poly(ethylene glycol) (PEG) macroRAFT agent and two pH-sensitive monomers (2-(diethylamino)ethyl methacrylate, DEA and 2-(dimethylamino)ethyl methacrylate, DMA) were used for synthesizing the copolymers consisting of pH-sensitive PDEA, PDMA and PEG blocks. At pH 10, the copolymer in aqueous solution self-assembled into a micelle with hydrophobic core consisting of PDEA and PDMA for doxorubicin (DOX) encapsulation, owing to the deprotonation of the side tertiary amino groups. At neutral pH, the hydrophobic core became porous and positively charged to allow siRNA complexation due to PDMA solubilization (the pKa of PDMA is around 8.0). Inside the acidic lysosomal compartments, PDEA was protonated and thus became hydrophilic to result in rapid release of DOX. Moreover, existence of two pH-sensitive blocks PDMA and PDEA endowed the copolymer with proton buffering effect that facilitated lysosomal escape of nanocomplex and siRNA release inside cells. Our results showed that the two codelivered therapeutic agents acted synergistically on the human hepatic carcinoma HepG2 cells to induce apoptosis in a highly effective manner.

Role and mechanism of the alkylglycerone phosphate synthase in suppressing the invasion potential of human glioma and hepatic carcinoma cells in vitro.

Ether lipids have been implicated in the exacerbation of human tumors. Accumulating evidence suggests that the alkylglycerone phosphate synthase (AGPS) is involved in the suppression of some types of tumor. However, the role and molecular mechanism of AGPS in the invasion of human glioma and hepatic carcinoma remain unclear. In the present study, using AGPS-knockdown human glioma U87 and hepatic carcinoma HepG2 cell lines, we explored the role of AGPS, as well as its molecular mechanism, in invasion in vitro. It was demonstrated that silencing AGPS expression resulted in a decreased expression of cellular lipids such as LPA, LPAe and PGE2, adhesion, invasion potential and arrested cell cycle in tumor cells. The expression of invasion-related genes such as MMP-2/9, E-cadherin and CD44 showed marked changes in AGPS‑knockdown cells. In addition, we found that AGPS regulated the activity of the MAPK pathway, as well as the transcriptional activity of Twist, AP-1, and Snail. The results demonstrated that AGPS negatively regulated the invasion potential of glioma and hepatic carcinoma cells by modulating the expression of relevant genes and activity of the MAPK pathway. Therefore, AGPS may be a potential glioma and hepatic carcinoma therapeutic target.

Endoplasmic reticulum stress impairs cholesterol efflux and synthesis in hepatic cells

Metabolic disorders such as type 2 diabetes cause hepatic endoplasmic reticulum (ER) stress, which affects neutral lipid metabolism. However, the role of ER stress in cholesterol metabolism is incompletely understood. Here, we show that induction of acute ER stress in human hepatic HepG2 cells reduced ABCA1 expression and caused ABCA1 redistribution to tubular perinuclear compartments. Consequently, cholesterol efflux to apoA-I, a key step in nascent HDL formation, was diminished by 80%. Besides ABCA1, endogenous apoA-I expression was reduced upon ER stress induction, which contributed to reduced cholesterol efflux. Liver X receptor, a key regulator of ABCA1 in peripheral cells, was not involved in this process. Despite reduced cholesterol efflux, cellular cholesterol levels remained unchanged during ER stress. This was due to impaired de novo cholesterol synthesis by reduction of HMG-CoA reductase activity by 70%, although sterol response element-binding protein-2 activity was induced. In mice, ER stress induction led to a marked reduction of hepatic ABCA1 expression. However, HDL cholesterol levels were unaltered, presumably because of scavenger receptor class B, type I downregulation under ER stress. Taken together, our data suggest that ER stress in metabolic disorders reduces HDL biogenesis due to impaired hepatic ABCA1 function.

Effects of artificial sweeteners on the AhR- and GR-dependent CYP1A1 expression in primary human hepatocytes and human cancer cells

Food constituents may cause a phenomenon of food–drug interactions. In the current study, we examined the effects of artificial sweeteners (aspartame, acesulfame, cyclamate, saccharin) on the aryl hydrocarbon receptor (AhR) and glucocorticoid receptor (GR)–dependent expression of CYP1A1 in human hepatocytes, hepatic HepG2 and intestinal LS174T cancer cell lines. Sweeteners were tested in concentrations up to those occurring in non-alcoholic beverages. Basal and ligand-inducible AhR- and GR-dependent reporter gene activation in stably transfected HepG2 and HeLa cells, respectively, were not affected by either of the sweeteners tested after 24h of incubation. The expression of CYP1A1 mRNA and protein in primary cultures of human hepatocytes and in LS174T and HepG2 cells was not induced by any of the tested sweeteners. Overall, aspartame, acesulfame, saccharin and cyclamate had no effects on CYP1A1 expression and transcriptional activities of AhR and GR. These data imply the safety of artificial sweeteners in terms of interference with AhR, GR and CYP1A1.

Fatty acid composition and biological activities of Isochrysis galbana T-ISO, Tetraselmis sp. and Scenedesmus sp.: possible application in the pharmaceutical and functional food industries

Organic and water extracts of Isochrysis galbana T-ISO (=Tisochrysis lutea), Tetraselmis sp. and Scenedesmus sp. were evaluated for their antioxidant activity, acetylcholinesterase (AChE) inhibition, cytotoxicity against tumour cell lines, and fatty acids and total phenolic content (TPC). I. galbana T-ISO had the highest TPC (3.18 mg GAE g−1) and radical scavenging activity, with an IC50 value of 1.9 mg mL−1 on the acetone extract. The extracts exhibited a higher ability to chelate Fe2+ than Cu2+, and the maximum Fe2+ chelating capacity was observed in the hexane extract of Scenedesmus sp. (IC50=0.73 mg mL−1) and Scenedesmus sp. (IC50 = 0.73 mg mL−1). The highest ability to inhibit AChE was observed in the water and ether extracts of Scenedesmus sp., with IC50 values of 0.11 and 0.15 mg mL−1, respectively, and in the water extract of I. galbana (IC50 = 0.16 mg mL−1). The acetone extract of I. galbana T-ISO significantly reduced the viability of human hepatic carcinoma HepG2 cells (IC50 = 81.3 μg mL−1) as compared to the non-tumour murine stromal S17 cell line, and displayed a selectivity index of 3.1 at the highest concentration tested (125 μg mL−1). All species presented a highly unsaturated fatty acids profile. Results suggest that these microalgae, particularly I. galbana T-ISO, could be a source of biomolecules for the pharmaceutical industry and the production of functional food ingredients and can be considered as an advantageous alternative to several currently produced microalgae.