Exposure Of HepG2 Cells Research Articles

New insights into mechanism of ellagic acid alleviating arsenic-induced oxidative stress through MAPK/keap1-Nrf2 signaling pathway response, molecular docking and metabolomics analysis in HepG2 cells

The increase of oxidative stress level is one of the vital mechanisms of liver toxicity induced by arsenic (As). Ellagic acid (EA) is widely known due to its excellent antioxidation. Nevertheless, whether EA could alleviate As-induced oxidative stress and the underlying mechanisms remain unknown. Herein, As (2 and 4 μM) and EA (25 and 50 μM) were selected for alone and combined exposure of HepG2 cells to investigate the effects of EA on As-induced oxidative stress. Results indicated that EA could alleviate the oxidative stress caused by As via decreasing intracellular ROS level and MDA content, as well as improving SOD, CAT and GSH-PX activities. qRT-PCR showed that EA might enhance the expression levels of antioxidant enzymes NQO1, CAT and GPX1 by activating MAPK (JNK, p38 and ERK)/keap1-Nrf2 signaling pathway. EA was found to promote dissociation from keap1 and nuclear translocation of Nrf2 by competing with Nrf2 at ARG-380 and ARG-415 sites on keap1 to exert antioxidation using molecular docking. Moreover, metabolomics revealed that EA might maintain the redox balance of HepG2 cells by modulating or reversing disorders of carbon, amino acid, lipid and other metabolisms caused by As. This study provides diversified new insights for the removal of liver toxicity of As and the application of EA.

Extracellularly secreted cysteine derived from cystine regulates oxidative and electrophilic stress in HepG2 cells

While cysteine (CysSH) is known to be exported into the extracellular space, its biological significance is not well understood. The present study examined the movement of extracellular CysSH using stable isotope-labeled cystine (CysSSCys), which is transported into cells and reduced to CysSH. Exposure of HepG2 cells to 100 µM stable isotope-labeled CysSSCys resulted in 70 µM labeled CysSH in cell medium 1 h after CysSSCys exposure. When the cell medium was collected and incubated with either hydrogen peroxide (H2O2) or atmospheric electrophiles, such as 1,2-naphthoquinone, 1,4-naphthoquinone and 1,4-benzoquinone, CysSH in the cell medium was almost completely consumed. In contrast, extracellular levels of CysSH were unaltered during exposure of HepG2 cells to H2O2 for up to 2 h, suggesting redox cycling of CysSSCys/CysSH in the cell system. Experiments with and without changing cell medium containing CysSH from HepG2 cells revealed that oxidative and electrophilic modifications of cellular proteins, caused by exposure to H2O2 and 1,2-naphthoquinone, were significantly repressed by CysSH in the medium. We also examined participation of enzymes and/or antioxidants in intracellular reduction of CysSSCys to CysSH. These results provide new findings that extracellular CysSH derived from CysSSCys plays a role in the regulation of oxidative and electrophilic stress.

Peripheral amyloid-β clearance mediates cognitive impairment in non-alcoholic fatty liver disease

BackgroundNon-alcoholic fatty liver disease (NAFLD) is a prevalent risk factor for cognitive impairment. Cerebral amyloid-β (Aβ) accumulation, as an important pathology of cognitive impairment, can be caused by impaired Aβ clearance in the periphery. The liver is the primary organ for peripheral Aβ clearance, but the role of peripheral Aβ clearance in NAFLD-induced cognitive impairment remains unclear. MethodsWe examined correlations between NAFLD severity, Aβ accumulation, and cognitive performance in female Sprague-Dawley rats. The impact of NAFLD on hepatic Aβ clearance and the involvement of low-density lipoprotein receptor-related protein 1 (LRP-1) were assessed in rat livers and cultured hepatocytes. Additionally, a case-control study, including 549 NAFLD cases and 549 controls (782 males, 316 females), investigated the interaction between NAFLD and LRP-1 rs1799986 polymorphism on plasma Aβ levels. FindingsThe severity of hepatic steatosis and dysfunction closely correlated with plasma and cerebral Aβ accumulations and cognitive deficits in rats. The rats with NAFLD manifested diminished levels of LRP-1 and Aβ in liver tissue, with these reductions inversely proportional to plasma and cerebral Aβ concentrations and cognitive performance. In vitro, exposure of HepG2 cells to palmitic acid inhibited LRP-1 expression and Aβ uptake, which was subsequently reversed by a peroxisome proliferator-activated receptor α (PPARα) agonist. The case-control study revealed NAFLD to be associated with an increment of 8.24% and 10.51% in plasma Aβ40 and Aβ42 levels, respectively (both P <0.0001). Moreover, the positive associations between NAFLD and plasma Aβ40 and Aβ42 levels were modified by the LRP-1 rs1799986 polymorphism (P for interaction = 0.0017 and 0.0015, respectively). InterpretationLRP-1 mediates the adverse effect of NAFLD on peripheral Aβ clearance, thereby contributing to cerebral Aβ accumulation and cognitive impairment in NAFLD. FundingMajor International (Regional) Joint Research Project, National Key Research and Development Program of China, National Natural Science Foundation of China, and the Angel Nutrition Research Fund.

Legacy perfluoro-alkyl substances impair LDL-cholesterol uptake independently from PCSK9-function

Perfluoro-alkyl substances (PFAS) are pollutants, whose exposure was associated with altered levels of low-density lipoproteins (LDL) in humans. Here we investigated this clinical outcome in two groups of young male adults residing in areas of respectively low and high environmental exposure to perfluoro-octanoic-acid (PFOA). From the Regional Authority data on pollution areas, 38 not-exposed and 59 exposed age-matched participants were evaluated for serum levels of total cholesterol (Total-Chol), LDL-Chol, high-density lipoprotein cholesterol (HDL-Chol), triglycerides (Tgl) and chromatography quantified PFOA. Human hepato-carcinoma cell line HepG2 was exposed to PFOA or perfluoro-octane-sulfonate (PFOS), as legacy PFAAs, and C6O4 as new generation compound. Fluorimetry was used to evaluate the cell-uptake of labelled-LDL. Proprotein Convertase Subtilisin/Kexin 9 (PCSK9)-mediated LDL-receptor (LDL-R) degradation and sub-cellular localization of LDL-R were evaluated by western blot analysis. Serum levels of PFOA, were positively and significantly correlated with Total-Chol (ρ = 0.312, P = 0.002), LDL-Chol (ρ = 0.333, P = 0.001) and Tgl (ρ = 0.375, P < 0.001). Participants with high serum LDL-Chol and Tgl levels, according to the cardiovascular risk, were more prevalent in exposed compared to not-exposed subjects (respectively: 23.7% vs 5.3%, P = 0.023 and 18,6% vs 0%, P = 0.006). Exposure of HepG2 cells to PFOA or C6O4 100 ng/mL was associated with a significantly lower LDL uptake than controls but no major impact of any PFAAs on PCSK9-mediated LDL-R degradation was observed. Compared to controls, exposure to PFAS showed an unbalanced LDL-R partition between membrane and cytoplasm. Endocytosis inducer sphingosine restored LDL-R partition only in samples exposed to C6O4. These data suggest a novel endocytosis-based mechanism of altered lipid trafficking associated with the exposure to legacy PFAS.

Development of multi-drug resistance to anticancer drugs in HepG2 cells due to MRP2 upregulation on exposure to menthol.

Menthol exerts relaxing, antibacterial, and anti-inflammatory activities, and is marketed as a functional food and therapeutic drug. In the present study, the effects of menthol on the expression of multidrug resistance associated protein 2 (MRP2) and its association with the cytotoxicity of epirubicin (EPI) and cisplatin (CIS) were examined using HepG2 cells. The expression levels of target genes were examined by real-time PCR. The intracellular concentration of incorporated EPI was measured by high-performance liquid chromatography. Cell viability was evaluated by MTT analysis. The expression of MRP2 mRNA was increased by exposing HepG2 cells to menthol for 24 hr. Consistent with a previous report suggesting an inverse correlation between MRP2 and Akt behavior, increased expression of MRP2 was also observed on suppression of the Akt function. Intracellular accumulation of EPI was significantly decreased by exposure of HepG2 cells to menthol, and a significant decrease in the intracellular concentration of EPI remaining was observed in HepG2 cells exposed to menthol. The decreased intracellular accumulation of EPI was significantly suppressed by treatment with MK-571, but not verapamil. Both EPI and CIS exerted cytocidal effects on HepG2 cells, but the decrease in cell viability was significantly attenuated by 24-hr menthol pre-exposure. These results demonstrate that menthol causes hepatocellular carcinoma to acquire resistance to anticancer drugs such as EPI and CIS by MRP2 induction.

Glycan node profiling of soluble and membrane glycoproteins in whole cell lysates

Glycan node analysis (GNA) is a molecularly bottom-up glycomics technique based on the relative quantification of glycan linkage-specific monosaccharide units (“glycan nodes”). It was originally applied to blood plasma/serum, where it detected and predicted progression, reoccurrence, and survival in different types of cancer. Here, we have adapted this technology to previously inaccessible membrane glycoproteins from cultured cells. The approach is facilitated by methanol/chloroform precipitation of cell lysates and a “liquid phase permethylation” (LPP) procedure. LPP gave better signal-to-noise, yield and precision for most of the glycan nodes from membrane glycoproteins/glycolipids than the conventional solid phase permethylation approach. This GNA approach in cell lysates revealed that specific glycan features such as antennary fucosylation, N-glycan branching, and α2,6-sialylation were elevated in hepatocellular carcinoma (HepG2) cells relative to leukemia cells (THP-1 and K562) and normal donor PBMCs. Additional nodes commonly associated with glycolipids were elevated in the leukemia cells relative to HepG2 cells and PBMCs. Exposure of HepG2 cells to a fucosyltransferase inhibitor resulted in a significant reduction in the relative abundance of 3,4-substituted GlcNAc, which represents antennary fucosylation—providing further proof-of-concept that downregulation of glycosyltransferase activity is detected by shifts in glycan node expression—now detectable in membrane glycoproteins.

Altered Gene Expression of Cytochrome P450 and ABC Transporter in Human Hepatocellular Carcinoma HepG2 Cells Exposed to Bardoxolone Methyl.

Bardoxolone methyl (BX) is expected to be an innovate therapeutic agent for chronic kidney disease (CKD). The aim of the present study was to examine whether the expression of subtypes of cytochrome P450 (CYP) and ABC transporters was altered in human hepatocellular carcinoma HepG2 cells by exposure to BX. The expression of mRNAs for CYP1A2, CYP2E1, P-glycoprotein, multidrug resistance-associated protein 1-3, and breast cancer resistance protein was significantly increased by exposure of HepG2 cells to BX, while the expression of CYP3A4 mRNA was significantly decreased under the same conditions. BX had no significant effect on the expression of mRNAs for CYP2C9 and CYP2C19 in HepG2 cells. In conclusion, this study demonstrated that the gene expression of several CYPs and ABC transporters in HepG2 cells was altered when exposed to BX, suggesting the need to pay careful attention to drug-drug interactions in patients receiving BX for CKD treatment.

Exogenous hydrogen sulfide alleviates hepatic endoplasmic reticulum stress via SIRT1/FoxO1/PCSK9 pathway in NAFLD.

High-fat-induced endoplasmic reticulum (ER) stress has been the main reason for the occurrence and development of nonalcoholic fatty liver disease (NAFLD). Hydrogen sulfide (H2 S) produces a marked effect on regulating lipid metabolism and antioxidation, whose effects on ER stress of NAFLD are still unclear. Here, we studied the influence of exogenous H2 S on NAFLD and its potential mechanism. In vivo, NAFLD model was induced by high-fat diet (HFD) for 12 weeks, followed by intraperitoneal injection of exogenous H2 S intervention for 4 weeks. HepG2 cells exposure to lipid mixture (LM) were used as vitro model to explore the potential mechanism. We found exogenous H2 S significantly inhibited the hepatic ER stress and improved the liver fat deposition of HFD-fed mice. These similar results were also observed in HepG2 cells dealt with LM after exogenous H2 S treatment. Further mechanism studies showed exogenous H2 S strengthened the combination of FoxO1 with the PCSK9 promoter gene through SIRT1-mediated deacetylation, thereby inhibiting the PCSK9 expression to relieve the hepatic ER stress. However, SIRT1 knockout eliminated the effects of exogenous H2 S on FoxO1 deacetylation, PCSK9 inhibition, and remission of hepatic ER stress and steatosis. In conclusion, exogenous H2 S improved NAFLD by inhibiting hepatic ER stress through SIRT1/FoxO1/PCSK9 pathway. Exogenous H2 S and ER stress may be potential drug and target for the treatment of NAFLD, respectively.

Cytotoxic Efficacy of Indigo and Yellow 2G with Vitamin C on the HepG2 Cell Line

We aimed to examine the effect of indigo and yellow 2G (Y2G) dyes, that are also commonly used as food additive and colorant, individually and combination with vitamin C on HepG2 human liver carcinoma cell line proliferation in vitro. MTT assay was applied to investigate the effect of dyes individually combined with vitamin C on HepG2 cells by treatment with different concentrations of these dyes for varying exposure times and performed. Regarding the exposure of HepG2 cells to indigo and Y2G dyes for 24, 48 and 72 h, 50 and 500 µg/ml (p=0.001 and p=0.003 respectively) of indigo at 24 h and 500 µg/ml (p=0.012) at 72 h; it showed that 5 µg/ml of Y2G for 24 h (p=0.004) and 1 µg/ml for 48 and 72 h (p=0.000, p=0.001) had the highest cytotoxic effect. Also, the results indicated that, especially the combinations of “indigo + vitamin C“ significantly increased cytotoxic effects on the HepG2 cell line (p=0.003). The obtained findings provide an exciting insight into the cytotoxic effects of indigo on HepG2 cells, and how they might work together to combat HCC's aggression.

Anti-Cancer Effects of Queen Bee Acid (10-Hydroxy-2-Decenoic Acid) and Its Cellular Mechanisms against Human Hepatoma Cells

Hepatocellular carcinoma (HCC) is the most common form of liver cancer that occurs in hepatocytes. Although many chemical drugs, e.g., cisplatin, methotrexate, taxis, and doxorubicin are used to treat HCC, there have been numerous reports related to the side effects of these drugs (e.g., emerging drug resistance, bone marrow failure, and gastrointestinal disorders). These issues led scientists to search for the novel anti-cancer drugs, mainly in natural products with greater efficiency and less toxicity. The current survey was intended to assess the anti-cancer effects of queen bee acid (10-Hydroxy-2-Decenoic Acid, 10-HDA) and its cellular mechanisms against the human hepatoma cell line HepG2. The MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay was used to evaluate the effect of 10-HDA on the viability of HepG2 cells. The initial and late apoptosis in the HepG2 cells treated with 10-HDA were assessed by the Annexin-V (AV) assay. The level of the gene and protein expression of some apoptosis genes (e.g., caspase-3, Bcl-2-associated X protein (BAX), and B-cell lymphoma protein 2 (Bcl-2)), Poly (ADP-ribose) polymerases (PARP), and miRNA-34a (miR-34a), were measured by real-time PCR and Western blot. The obtained findings revealed that HepG2 cell viability was markedly reduced (p < 0.01) following exposure to 10-HDA in a dose-dependent matter. The calculated half maximal cytotoxic concentration (CC50) value of 10-HDA was 59.6 µg/mL for HepG2 cells, while this value for normal THLE-3 cells was 106.4 µg/mL. We found that 10-HDA markedly elevated (p < 0.01) the percentage of necrotic and apoptotic cells from 0.94 to 9.7 and 27.6%, respectively. The real-time PCR results showed that the expression levels of the caspase-3, Bax, and miR-34a genes were significantly (p < 0.001) elevated. Contrary to these results, a significant (p < 0.01) reduction in the expression level of the Bcl2 gene was observed. The levels of protein expression of Caspase-3, PARP, and Bax were markedly elevated following exposure of HepG2 cells to 10-HDA at ¼ CC50, ½ CC50, and CC50. The level of protein expression of Bcl-2 was markedly reduced following exposure of HepG2 cells to 10-HDA at ¼ CC50, ½ CC50, and CC50 (p < 0.01). The current results confirmed the potent in vitro cytotoxic effects of 10-HDA on HepG2 cells with no significant cytotoxic effects on normal cells. Although its mechanisms of action have not been fully studied, the induction of apoptosis via different pathways was determined as one of the principle mechanisms of action of 10-HDA against HepG2 cells. Nevertheless, additional surveys must be performed to clearly understand the mechanisms of action and safety of this fatty acid.

Activation of the Keap1/Nrf2 Pathway as an Adaptive Response to an Electrophilic Metabolite of Morphine.

Morphinone (MO) is an electrophilic metabolite of morphine that covalently binds to protein thiols via its α,β-unsaturated carbonyl group, resulting in toxicity in vitro and in vivo. Our previous studies identified a variety of redox signaling pathways that are activated during electrophilic stress. Here, we examined in vitro activation of a signaling pathway involving Kelch-like ECH-associated protein 1 (Keap1) and nuclear factor erythroid 2-related factor 2 (Nrf2) in response to MO. Exposure of HepG2 cells to MO caused covalent modification of Keap1 thiols (evaluated using biotin-PEAC5-maleimide labeling) and nuclear translocation of Nrf2, thereby up-regulating downstream genes encoding ATP binding cassette subfamily C member 2, solute carrier family 7 member 11, glutamate-cysteine ligase catalytic subunit, glutamate-cysteine ligase modifier subunit, glutathione S-transferase alpha 1, and heme oxygenase 1. However, dihydromorphinone, a metabolite of morphine lacking the reactive C7-C8 double bond, had little effect on Nrf2 activation. These results suggest that covalent modification is crucial in the Keap1/Nrf2 pathway activation and that this pathway is a redox signaling-associated adaptive response to MO metabolism.

Effect of pentavalent inorganic arsenic salt on erythropoietin production and autophagy induction

Arsenic is abundant in the environment and takes the form of trivalent and pentavalent arsenic compounds. Arsenite has been reported to both promote and suppress erythropoietin (EPO) production and autophagy induction. EPO production is involved in hematopoiesis, and autophagy induction is involved in cytoprotection, both of which are thought to be cellular responses to arsenic stress. While there are reports that show the effects of EPO on autophagy induction, the relationship between EPO production and autophagy induction is unclear. Therefore, this study analyzed the effect of the pentavalent inorganic arsenic salt arsenate on EPO production in vitro and in vivo and EPO-induced autophagy in HepG2 cells. Exposure of HepG2 cells to low-concentration arsenate was observed to increase EPO production and induced autophagy. Moreover, a ROS scavenger suppressed the arsenate-induced increase in autophagy and EPO mRNA levels. Both EPO production and autophagy induction contributed to protection from arsenate-induced cytotoxic stress. HepG2 cells expressed the EPO receptor and production of EPO by HepG2 cells acted in an autoregulatory manner to suppress autophagy induction. In vivo administration of low-concentration arsenate to rats increased EPO mRNA levels in the liver and kidney. These results suggested that low-concentration arsenate promotes EPO production and autophagy induction in HepG2 cells, and the resultant EPO production contributes to cytoprotection of cultured cells via EPO receptor activation.

Syringic acid induces cancer cell death in the presence of Cu (II) ions via pro-oxidant activity

Objective: To investigate the effects of syringic acid on HEK 293 and HepG2 cells in the absence and presence of exogenous Cu (II) and Fe (II) ions. Methods: The antiproliferative effects of syringic acid on HEK 293 and HepG2 cells in the absence and presence of exogenous Cu (II) and Fe (II) ions were examined by MTT assay. Additionally, colony-forming, reactive oxidative species (ROS) generation, apoptosis induction, autophagy, mitochondrial membrane potential, and mitochondrial mass were investigated. Results: At 24 and 72 h, no significant differences were observed in the viability of HepG2 cells between the control and syringic acid + Fe (II) groups. However, exposure of HepG2 cells to syringic acid + Cu (II) for 72 h reduced the cell viability significantly. Furthermore, ROS formation, induction of apoptosis, and autophagic vacuoles were significantly increased in HepG2 cells without marked changes in mitochondrial membrane potential and mitochondrial mass. Moreover, syringic acid + Cu (II) reduced the plating efficiency and surviving fraction significantly. Conclusions: The combination of syringic acid with Cu (II) was toxic to cancer cells and showed pro-oxidant activity. In addition, this combination induced autophagy in cancer cells with less cytotoxic effects on normal cells, which is a potential candidate for the development of novel therapeutics towards cancer.

Potential obesogenic effects of TBBPA and its alternatives TBBPS and TCBPA revealed by metabolic perturbations in human hepatoma cells

To date, increasing numbers of studies have shown the obesogenic effects of tetrabromobisphenol A (TBBPA). Tetrabromobisphenol S (TBBPS) and tetrachlorobisphenol A (TCBPA) are two common alternatives to TBBPA, and their environmental distributions are frequently reported. However, their toxicity and the associated potential health risks are poorly documented. Herein, we performed untargeted metabolomics to study the metabolic perturbations in HepG2 cells exposed to TBBPA and its alternatives. Consequently, no loss of cellular viability was observed in HepG2 cells exposed to 0.1 μmol/L and 1 μmol/L TBBPA, TBBPS and TCBPA. However, multivariate analysis and metabolic profiles revealed significant perturbations in glycerophospholipid and fatty acyl levels in HepG2 cells exposure to TBBPS and TCBPA. The evident increases in the glucose 1-phosphate and fructose 6-phosphate levels in HepG2 cells were proposed to be induced by the promotion of PGM1/PGM2 and GPI gene expression and the suppression of UPG2 and GFPT1/GFPT2 gene expression. Our results suggest that TBBPS and TCBPA are more likely to disrupt liver metabolic homeostasis and potentially drive liver dysfunction than TBBPA. Our study is significant for the re-evaluation of the health risks associated with TBBPA and its alternatives TBBPS and TCBPA.

Effect of combined exposure to environmental aliphatic electrophiles from plants on Keap1/Nrf2 activation and cytotoxicity in HepG2 cells: A model of an electrophile exposome

Electrophiles, ubiquitously found in the environment, modify thiol groups of sensor proteins, leading to activation of redox signaling pathways such as the Kelch-like ECH-associated protein 1 (Keap1)/nuclear factor E2 related factor 2 (Nrf2) pathway. Nrf2 activation by exposure to single electrophiles has been established. However, the effect of exposure to a combination of electrophiles on Nrf2 activation has not been well evaluated. The current study examined whether combined exposure to electrophiles enhances the modification of thiol groups and Keap1/Nrf2 activation in HepG2 cells. Six electrophiles [1,2-naphthoquinone (1,2-NQ), 1,4-NQ, 1,4-benzoquinone, (E)-2-hexenal (hexenal), (E)-2-decenal, and (E)-2-butenal] were tested for S-modification of albumin in vitro and for cytotoxicity to HepG2 cells. Interestingly, a mixture of the electrophiles enhanced S-modification of albumin and cytotoxicity compared with exposure to each electrophile separately. Herein, we focused on 1,2-NQ, 1,4-NQ, and hexenal to clarify the combined effect of electrophiles on Keap1/Nrf2 activation in HepG2 cells. A concentration addition model revealed that 1,2-NQ and/or 1,4-NQ additively enhanced hexenal-mediated S-modification of GSH in vitro, whereas the cytotoxicity of hexenal was synergistically increased by simultaneous exposure of HepG2 cells to the NQs. Furthermore, an NQ cocktail (2.5 μM each) that does not activate Nrf2 enhanced hexenal-mediated Nrf2 activation. These results suggest that combined exposure to electrophiles at low concentrations induces stronger activation of redox signaling compared with exposure to each electrophile alone and worsens their cytotoxicity.

Utilizing systems biology to reveal cellular responses to peroxisome proliferator-activated receptor γ ligand exposure

Peroxisome proliferator-activated receptor γ (PPARγ) is a nuclear receptor that, upon activation by ligands, heterodimerizes with retinoid X receptor (RXR), binds to PPAR response elements (PPREs), and activates transcription of downstream genes. As PPARγ plays a central role in adipogenesis, fatty acid storage, and glucose metabolism, PPARγ-specific pharmaceuticals (e.g., thiazolidinediones) have been developed to treat Type II diabetes and obesity within human populations. However, to our knowledge, no prior studies have concurrently assessed the effects of PPARγ ligand exposure on genome-wide PPARγ binding as well as effects on the transcriptome and lipidome within human cells at biologically active, non-cytotoxic concentrations. In addition to quantifying concentration-dependent effects of ciglitazone (a reference PPARγ agonist) and GW 9662 (a reference PPARγ antagonist) on human hepatocarcinoma (HepG2) cell viability, PPARγ abundance in situ, and neutral lipids, HepG2 cells were exposed to either vehicle (0.1% DMSO), ciglitazone, or GW 9662 for up to 24 h, and then harvested for 1) chromatin immunoprecipitation-sequencing (ChIP-seq) to identify PPARγ-bound regions across the entire genome, 2) mRNA-sequencing (mRNA-seq) to identify potential impacts on the transcriptome, and 3) lipidomics to identify potential alterations in lipid profiles. Following exposure to ciglitazone and GW 9662, we found that PPARγ levels were not significantly different after 2–8 h of exposure. While ciglitazone and GW 9662 resulted in a concentration-dependent increase in neutral lipids, the magnitude and localization of PPARγ-bound regions across the genome (as identified by ChIP-seq) did not vary by treatment. However, mRNA-seq and lipidomics revealed that exposure of HepG2 cells to ciglitazone and GW 9662 resulted in significant, treatment-specific effects on the transcriptome and lipidome. Overall, our findings suggest that exposure of human cells to PPARγ ligands at biologically active, non-cytotoxic concentrations results in toxicity that may be driven by a combination of both PPARγ-dependent and PPARγ-independent mechanisms.

Design, molecular docking, in vitro, and in vivo studies of new quinazolin-4(3H)-ones as VEGFR-2 inhibitors with potential activity against hepatocellular carcinoma

A series of new VEGFR-2 inhibitors were designed, synthesized and evaluated for their anti-proliferative activities against hepatocellular carcinoma (HepG-2 cell line). Compound 29b (IC50 = 4.33 ± 0.2 µg/ml) was found to be the most potent derivative as it has showed to be more active than doxorubicin (IC50 = 4.50 ± 0.2 µg/ml) and 78% of sorafenib activity (IC50 = 3.40 ± 0.25 µg/ml). The inhibitory profiles against VEGFR-2 were also assessed for the most promising candidates (16b, 20c, 22b, 24a, 24b, 28c, 28e, 29a, 29b and 29c). Compounds 29b, 29c and 29a exhibited potent inhibitory activities towards VEGFR-2 at IC50 values of 3.1 ± 0.04, 3.4 ± 0.05 and 3.7 ± 0.06 µM, respectively, comparing sorafenib (IC50 = 2.4 ± 0.05 µM). Furthermorer, compound 29b induced apoptosis and arrested the cell cycle growth at G2/M phase. Additionally, in vivo antitumor experiments revealed that compounds 29b and 29c have significant tumor growth inhibition. The test of immuno-histochemical expression of activated caspase-3 revealed that there is a time-dependent increase in cleaved caspase-3 protein expression upon exposure of HepG-2 cells to compound 29b. Moreover, the fibroblastic proliferative index test revealed that compound 29b could attenuate liver fibrosis. Docking studies also supported the results concluded from the biological screening via prediction of the possible binding interactions of the target compounds with VEGFR-2 active sites using the crystal structure of VEGFR-2 downloaded from the Protein Data Bank, (PDB ID: 2OH4) using Discovery Studio 2.5 software. Further structural optimization of the most active candidates may serve as a useful strategy for getting new lead compounds in search for powerful and selective antineoplastic agents.

Functional analysis of a species-specific inhibitor selective for human Na+-coupled citrate transporter (NaCT/SLC13A5/mINDY).

The Na+-coupled citrate transporter (NaCT/SLC13A5/mINDY) in the liver delivers citrate from the blood into hepatocytes. As citrate is a key metabolite and regulator of multiple biochemical pathways, deletion of Slc13a5 in mice protects against diet-induced obesity, diabetes, and metabolic syndrome. Silencing the transporter suppresses hepatocellular carcinoma. Therefore, selective blockers of NaCT hold the potential to treat various diseases. Here we report on the characteristics of one such inhibitor, BI01383298. It is known that BI01383298 is a high-affinity inhibitor selective for human NaCT with no effect on mouse NaCT. Here we show that this compound is an irreversible and non-competitive inhibitor of human NaCT, thus describing the first irreversible inhibitor for this transporter. The mouse NaCT is not affected by this compound. The inhibition of human NaCT by BI01383298 is evident for the constitutively expressed transporter in HepG2 cells and for the ectopically expressed human NaCT in HEK293 cells. The IC50 is ∼100 nM, representing the highest potency among the NaCT inhibitors known to date. Exposure of HepG2 cells to this inhibitor results in decreased cell proliferation. We performed molecular modeling of the 3D-structures of human and mouse NaCTs using the crystal structure of a humanized variant of VcINDY as the template, and docking studies to identify the amino acid residues involved in the binding of citrate and BI01383298. These studies provide insight into the probable bases for the differential effects of the inhibitor on human NaCT versus mouse NaCT as well as for the marked species-specific difference in citrate affinity.

A strategy for repression of arsenic toxicity through nuclear factor E2 related factor 2 activation mediated by the (E)-2-alkenals in Coriandrum sativum L. leaf extract

Activation of the Kelch-like ECH-associated protein 1 (Keap1)/nuclear factor E2 related factor 2 (Nrf2) system plays a role in repression of xenobiotic toxicity. The Coriandrum sativum L. leaf extract (CSLE) contains various aliphatic electrophiles such as (E)-2-decenal and (E)-2-dodecenal. In the present study, we examined the activation of Nrf2 coupled to chemical modification of Keap1 mediated by (E)-2-alkenals in CSLE, and the protective role of CSLE and (E)-2-alkenals against inorganic arsenite (iAsIII) cytotoxicity. Ultra-performance liquid chromatography-elevated collision energy mass spectrometry analysis revealed that (E)-2-decenal modified recombinant Keap1 at Cys241, Cys249, Cys257 and His274. Exposure of HepG2 cells to CSLE, (E)-2-decenal, or (E)-2-dodecenal upregulated Nrf2-related downstream signaling such as expression of phase-II xenobiotic-metabolizing enzymes and phase-III transporters involved in cytoprotection against iAsIII. Pretreatment with CSLE or (E)-2-butenal, a prototype of (E)-2-alkenal, prior to iAsIII exposure suppressed accumulation of iAsIII significantly and reduced iAsIII-induced cytotoxicity in cells. Oral administration of CSLE to C57BL/6 mice upregulated downstream proteins of Nrf2 and reduced accumulation of arsenic in liver tissue. The present study indicates that CSLE containing (E)-2-alkenals activates Nrf2, leading to a reduction in arsenic accumulation in vivo.

Cyanidin-3-glucoside prevents hydrogen peroxide (H2O2)-induced oxidative damage in HepG2 cells.

The aim of this study is to evaluate the cytoprotection and potential molecular mechanisms of cyanidin-3-glucoside (C3G) on hydrogen peroxide (H2O2)-induced oxidative damage in HepG2 cells. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was carried out to examine the viability of HepG2 cells exposure to H2O2 or C3G. Meanwhile, the antioxidant properties of C3G were measured by determining the activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT) and the malondialdehyde (MDA) levels. Flow cytometry was employed to determine HepG2 cells apoptosis, and HepG2 cells were stained with Hoechst 33342 to observe cell morphology. 2',7'-dichlorofluorescin diacetate (DCFH-DA) was used to evaluate the production of intracellular reactive oxygen species (ROS). Finally, the expression of apoptosis-related protein was monitored through western blot analysis. HepG2 cells induced with H2O2 presented a remarkable decrease in cell viability that was suppressed when HepG2 cells were interfered with C3G (2.5-10μM). C3G interference memorably and dose-dependently inhibited H2O2-induced intracellular ROS and MDA overproduction, while C3G treatment markedly increased H2O2-induced the activities of intracellular SOD, GSH-Px and CAT. Eventually, the relative proteins expression levels of p53, cleaved caspase-9/3, cytochrome c, Fas-L, Fas, FADD and caspase-8 were substantially up-regulated in H2O2-triggered HepG2 cells, and Bax/Bcl-2 ratio and the relative proteinexpression levels of PARP were dramatically down-regulated. However, the expression levels of these relative proteins were reversed in C3G-interfered HepG2 cells. C3G could protect HepG2 cells from oxidative damage, and the effects that were mediated by the mitochondrial apoptotic pathways and the external pathways.