Aggregation-Enhanced Energy Transfer for Mitochondria-Targeted ATP Ratiometric Imaging in Living Cells.

Förster resonance energy transfer (FRET) from fluorescent nanoparticles to fluorescent dyes is an attractive approach for bioanalysis in living cells. However, the luminescence of the nanoparticle donor/acceptor has not been effectively used to produce highly efficient FRET because the distance between the energy donor and energy acceptor is often larger than the effective FRET radius (about 10 nm) and the uncontrolled rotational and translational diffusion of luminophores. Here, we develop an aggregation-enhanced energy transfer strategy that can overcome the impedance for effective energy transfer. The functional nanoprobes, named TPP-CDs-FITC, are carbon dots (CDs) functionalized with triphenylphosphine (TPP) and ∼117 fluorescein 5-isothiocyanate (FITC) on the surface. In dispersed solution, the 3.8 nm TPP-CDs-FITC show weak FRET efficiency (15.4%). After TPP-instructed mitochondrial targeting, enhanced FRET efficiency (53.2%) is induced due to the aggregation of TPP-CDs-FITC selectively triggered by adenosine triphosphate (ATP) in the mitochondria. The enhanced FRET efficiency can be attributed to the joint effect of the augment of numbers of FITC acceptors within 10 nm from dispersed 117 to aggregated 5499 and the restricted rotational and translational motions of TPP-CDs donors and FITC acceptors. Ultimately, we successfully observe the fluctuations of ATP levels in the mitochondria using the aggregation-enhanced energy transfer strategy of the TPP-CDs-FITC nanodevice.

The electrophilic character of quinones is essential for the suppression of Bach1.

The activation of nuclear factor erythroid 2-related factor 2 (Nrf2) is the most important cellular defense mechanisms against oxidative attack. BTB and CNC homology-1 (Bach1), like Kelch-like ECH-associated protein 1 (Keap1), is one of a negative regulator of Nrf2 that control antioxidant response elements (ARE)-dependent gene expressions. In the current study, we found that quinones show greater capacity than hydroquinones in nuclear Bach1 export, as well as ubiquitin-dependent Bach1 degradation in our experimental time frame. Consistently, quinones are easier than hydroquinones in Nrf2 activation and ARE-driven antioxidant protein expressions. Considering the redox cycling potential of quinone-hydroquinone couple, we investigated the effect of transit metal oxidation on the regulation of Nrf2 activity. As shown, Fe3+ enhanced hydroquinone-induced Nrf2 activation and ARE-driven gene expressions, suggesting quinones rather than hydroquinone activate Nrf2 through Bach1 arylation. Taking together, our investigation illustrated that the electrophilic character of quinones ensure their conjugation with Bach1, which is important for the downregulation of Bach1 and the upregulation of Nrf2 signaling.

Tetrachlorobenzoquinone induces Nrf2 activation via rapid Bach1 nuclear export/ubiquitination and JNK-P62 signaling.

Our previous studies demonstrated that tetrachlorobenzoquinone (TCBQ), an active metabolite of pentachlorophenol, has effects on the generation of reactive oxygen species (ROS) and oxidative stress in vitro and in vivo. Nuclear factor erythroid-derived 2-like 2 (Nrf2) is a cellular sensor of electrophilic or oxidative stress that regulates the expression of antioxidant enzymes and defensive proteins. We have illustrated that TCBQ activates Nrf2 signaling by promoting the formation of the Kelch-like ECH-associated protein 1 (Keap1) cross-linking dimer and the formation of an ubiquitination switch from Nrf2 to Keap1. The activation of Nrf2 by TCBQ may serve as an adaptive response to a TCBQ-induced oxidative insult. BTB and CNC homolog 1 (Bach1) compete with Nrf2, leading to the negative regulation of the antioxidant response element (ARE). In this report, we propose that TCBQ induces the dynamic inactivation of Bach1. We observed a rapid nuclear efflux of Bach1 and an accumulation of Nrf2 in nuclei upon TCBQ treatment that precedes the binding of Nrf2 with ARE. We found that the nuclear export of Bach1 is dependent on its chromosomal region maintenance 1 (Crm1) interaction and tyrosine phosphorylation. Although TCBQ induces the ubiquitination of Bach1, TCBQ also increases the mRNA and protein levels of Bach1, returning Bach1 to normal levels. Moreover, we found that TCBQ-induced activation of Nrf2 involves c-Jun N-terminal kinase (JNK)-P62 signaling.

Quinones Derived from Polychlorinated Biphenyls Induce ROS-Dependent Autophagy by Evoking an Autophagic Flux and Inhibition of mTOR/p70S6k.

Autophagy is a "self-eating" destructive process that eliminates damaged organelles to maintain cellular homeostasis. Polychlorinated biphenyls (PCBs) are one of the most infamous industrial pollutants, which are ubiquitous in nature. In the present study, we found that an active, quinone-type PCB metabolite (PCB29-pQ) treatment causes an autophagic response through mTOR/p70S6k inhibition in HepG2 and MDA-MB-231 cells. Furthermore, our data suggested that PCB29-pQ enhances autophagosome formation through autophagic vacuole (AV) biogenesis, which evokes autophagic flux and induces AV-lysosome colocalization. The inhibition of autophagy enhanced PCB29-pQ-caused cytotoxicity, suggesting that autophagy serves as pro-survival machinery that plays a protective role in the early stage of PCB29-pQ-induced insult. However, higher concentration of PCB29-pQ exposure (>5 µM) caused autophagic cell death, which implied a shift from "pro-survival" to "pro-death" upon autophagic signaling. N-Acetylcysteine suppressed PCB29-pQ-induced autophagy and cytotoxicity, suggesting that ROS plays an important role in the regulation of PCB29-pQ-induced autophagy. Because autophagy shows significant implications in various human diseases and conditions, our current study provides a new mechanism for PCB-associated toxicity.

Tetrachlorobenzoquinone Stimulates NLRP3 Inflammasome-Mediated Post-Translational Activation and Secretion of IL-1ß in the HUVEC Endothelial Cell Line.

Our previous studies suggested that tetrachlorobenzoquinone (TCBQ) elicits pro-inflammatory activities; however, the mechanism of its toxicity toward vascular endothelial cell has not been characterized. Although TCBQ has been shown to stimulate interleukin-1 beta (IL-1ß) expression, it is unknown whether TCBQ regulates post-translational IL-1ß activation. Using human umbilical vein endothelial cells, we discovered that TCBQ not only promotes the expression of NOD-like receptor family, pyrin domain-containing protein 3 (NLRP3) components [composed of NLRP3, adaptor molecule apoptosis-associated speck like protein containing a caspase activation and recruitment domain (ASC), and pro-caspase 1] but also participates in priming the NLRP3 inflammasome. Activation of the NLRP3 inflammasome results in the maturation and release of IL-1ß. Further experiments showed that K(+) efflux, reactive oxygen species (ROS) production, and mitochondrial DNA damage may be involved in NLRP3 inflammasome activation mediated by TCBQ. Moreover, TCBQ downregulates the ubiquitination of NLRP3, further facilitating the activation of the NLRP3 inflammasome. These results suggest that the NLRP3/IL-1ß signaling pathway plays an important role in TCBQ-induced endothelial cell pro-inflammatory responses, which may point to potential therapeutic approaches against TCBQ-mediated toxicity.

Tetrachlorobenzoquinone exhibits neurotoxicity by inducing inflammatory responses through ROS-mediated IKK/IκB/NF-κB signaling.

Tetrachlorobenzoquinone (TCBQ) is a joint metabolite of persistent organic pollutants (POPs), hexachlorobenzene (HCB) and pentachlorophenol (PCP). Previous studies have been reported that TCBQ contributes to acute hepatic damage due to its pro-oxidative nature. In the current study, TCBQ showed the highest capacity on the cytotoxicity, ROS formation and inflammatory cytokines release among four compounds, i.e., HCB, PCP, tetrachlorohydroquinone (TCHQ, reduced form of TCBQ) and TCBQ, in PC 12 cells. Further mechanistic study illustrated TCBQ activates nuclear factor-kappa B (NF-κB) signaling. The activation of NF-κB was identified by measuring the protein expressions of inhibitor of nuclear factor kappa-B kinase (IKK) α/ß, p-IKKα/ß, an inhibitor of NF-κB (IκB) α, p-IκBα, NF-κB (p65) and p-p65. The translocation of NF-κB was assessed by Western blotting of p65 in nuclear/cytosolic fractions, electrophoretic mobility shift assay (EMSA) and luciferase reporter gene assay. In addition, TCBQ significantly induced protein and mRNA expressions of inflammatory cytokines and mediators, such as interleukin-1 beta (IL-1ß), IL-6, tumor necrosis factor-alpha (TNF-α), inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) and the production of nitric oxide (NO) and prostaglandin E2 (PGE2). Pyrrolidine dithiocarbamate (PDTC), a specific NF-κB inhibitor inhibited these effects efficiently, further suggested TCBQ-induced inflammatory responses involve NF-κB signaling. Moreover, antioxidants, i.e., N-acetyl-l-cysteine (NAC), Vitamin E and curcumin, ameliorated TCBQ-induced ROS generation as well as the activation of NF-κB, which implied that ROS serve as the upstream molecule of NF-κB signaling. In summary, TCBQ exhibits a neurotoxic effect by inducing oxidative stress-mediated inflammatory responses via the activation of IKK/IκB/NF-κB pathway in PC12 cells.

Polychlorinated Biphenyl Quinone Metabolite Promotes p53-Dependent DNA Damage Checkpoint Activation, S-Phase Cycle Arrest and Extrinsic Apoptosis in Human Liver Hepatocellular Carcinoma HepG2 Cells.

Polychlorinated biphenyls (PCBs) are a group of persistent organic pollutants. The toxic behavior and mechanism of PCBs individuals and congeners have been extensively investigated. However, there is only limited information on their metabolites. Our previous studies have shown that a synthetic PCB metabolite, PCB29-pQ, causes oxidative damage with the evidence of cytotoxicity, genotoxicity, and mitochondrial-derived intrinsic apoptosis. Here, we investigate the effects of PCB29-pQ on DNA damage checkpoint activation, cell cycle arrest, and death receptor-related extrinsic apoptosis in human liver hepatocellular carcinoma HepG2 cells. Our results illustrate that PCB29-pQ increases the S-phase cell population by down-regulating cyclins A/D1/E, cyclin-dependent kinases (CDK 2/4/6), and cell division cycle 25A (CDC25A) and up-regulating p21/p27 protein expressions. PCB29-pQ also induces apoptosis via the up-regulation of Fas/FasL and the activation of caspase 8/3. Moreover, p53 plays a pivotal role in PCB29-pQ-induced cell cycle arrest and apoptosis via the activation of ATM/Chk2 and ATR/Chk1 checkpoints. Cell cycle arrest and apoptotic cell death were attenuated by the pretreatment with antioxidant N-acetyl-cysteine (NAC). Taken together, these results demonstrate that PCB29-pQ induces oxidative stress and promotes p53-dependent DNA damage checkpoint activation, S-phase cycle arrest, and extrinsic apoptosis in HepG2 cells.

Neohesperidin dihydrochalcone down-regulates MyD88-dependent and -independent signaling by inhibiting endotoxin-induced trafficking of TLR4 to lipid rafts.

Fulminant hepatic failure (FHF) is a lethal clinical syndrome characterized by the activation of macrophages and the increased production of inflammatory mediators. The purpose of this study was to investigate the effects of neohesperidin dihydrochalcone (NHDC), a widely-used low caloric artificial sweetener against FHF. An FHF experimental model was established in mice by intraperitoneal injection of D-galactosamine (d-GalN) (400mg/kg)/lipopolysaccharides (LPS) (10 µg/kg). Mice were orally administered NHDC for 6 continuous days and at 1h before d-GalN/LPS administration. RAW264.7 macrophages were used as an in vitro model. Cells were pre-treated with NHDC for 1h before stimulation with LPS (10 µg/ml) for 6h. d-GalN/LPS markedly increased the serum transaminase activities and levels of oxidative and inflammatory markers, which were significantly attenuated by NHDC. Mechanistic analysis indicated that NHDC inhibited LPS-induced myeloid differentiation factor 88 (MyD88) and TIR-containing adapter molecule (TRIF)-dependent signaling. Transient transfection of TLR4 or MyD88 siRNA inhibited the downstream inflammatory signaling. This effect could also be achieved by the pretreatment with NHDC. The fluorescence microscopy and flow cytometry results suggested that NHDC potently inhibited the binding of LPS to TLR4 in RAW264.7 macrophages. In addition, the inhibitory effect of NHDC on LPS-induced translocation of TLR4 into lipid raft domains played an important role in the amelioration of production of downstream pro-inflammatory molecules. Furthermore, the activation of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) by NHDC inhibited TLR4 signaling. In conclusion, our results suggest that NHDC attenuates d-GalN/LPS-induced FHF by inhibiting the TLR4-mediated inflammatory pathway, demonstrating a new application of NHDC as a hepatoprotective agent.

Artificial sweetener neohesperidin dihydrochalcone showed antioxidative, anti-inflammatory and anti-apoptosis effects against paraquat-induced liver injury in mice.

The present study evaluated the protective effect of artificial sweetener neohesperidin dihydrochalcone (NHDC) against paraquat (PQ)-induced acute liver injury in mice. A single dose of PQ (75mg/kg body weight, i.p.) induced acute liver toxicity with the evidences of increased liver damage biomarkers, aspartate transaminase (AST) and alanine transaminase (ALT) activities in serum. Consistently, PQ decreased the antioxidant capacity by reducing glutathione peroxidase (GP-X), glutathione-S-transferase (GST) and catalase (CAT) activities, glutathione (GSH) level and total antioxidant capacity (T-AOC), as well as increasing reactive oxygen species (ROS) and thiobarbituric acid reactive substances (TBARS) levels. Histopathological examination revealed that PQ induced numerous changes in the liver tissues. Immunochemical staining assay indicated the upregulation of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) expressions. However, NHDC ameliorates PQ-induced hepatic toxicity in mice by reversing these parameters. Additionally, NHDC significantly inhibited PQ-induced nuclear factor-kappa B (NF-κB) expression and mitochondrial-driven apoptotic signaling. TUNEL assay confirmed that PQ-induced apoptosis was relieved by NHDC. In conclusion, these findings suggested that NHDC showed potent antioxidant, anti-inflammatory and anti-apoptotic effects against PQ-induced acute liver damage.

Tetrachlorobenzoquinone triggers the cleavage of Bid and promotes the cross-talk of extrinsic and intrinsic apoptotic signalings in pheochromocytoma (PC) 12 cells.

Although there are few studies suggested PCP exposure induced developmental and behavioral disorders, however, the occurrence of neurotoxicity and PCP has not been firmly established. Tetrachlorobenzoquinone (TCBQ) is a reactive metabolite of environmental pollutant pentachlorophenol (PCP). To the best of our knowledge, there has no information regarding to the neurological toxic effect of TCBQ available. Here, we demonstrated that TCBQ induces cytotoxicity in pheochromocytoma PC12 cell line, and the mode-of-action analysis indicated the involvement of apoptotic signalings, such as the activation of caspase family proteins, the increased expressions of Fas and Fas-associated death domain (FADD), the loss of mitochondrial membrane potential (MMP), the release of cytochrome c (Cyt c) and the cleavage of the caspase substrates poly(ADP-ribose) polymerase (PARP). BI-6C9, a specific BH3-interacting domain death agonist (Bid) inhibitor, repressed TCBQ-induced Bid truncation, along with the activation of caspase 3 and the release of Cyt c, suggested the cross-talk of extrinsic and intrinsic apoptotic signalings. Furthermore, the inhibition of caspase 8 impaired TCBQ-induced the activation of caspase 3, as well as the release of Cyt c and the cleavage of Bid, suggesting caspase 8 acting as the upstream molecule of Bid, and TCBQ-induced apoptosis is initiated via caspase 8, leads to the activation of caspase 9/3 through Bid-mediated amplification loop. Finally, the pretreatment of antioxidant NAC ameliorated Fas, FADD and caspase 8/3 expressions, which illustrated that TCBQ-induced apoptotic signaling is ROS dependent. Taken together, these results indicated that the cleavage of Bid may play an important role in TCBQ-induced neurotoxicity which promotes the cross-talk of extrinsic and intrinsic apoptotic signalings in PC12 cells.

Neohesperidin Dihydrochalcone versus CCl4-Induced Hepatic Injury through Different Mechanisms: The Implication of Free Radical Scavenging and Nrf2 Activation.

Neohesperidin dihydrochalcone (NHDC), a sweetener derived from citrus, belongs to the family of bycyclic flavonoids dihydrochalcones. NHDC has been reported to act against CCl4-induced hepatic injury, but its mechanism is still unclear. We first discovered that NHDC showed a strong ability to scavenge free radicals. In addition, NHDC induces the phase II antioxidant enzymes heme oxygenase 1 (HO-1) and NAD(P)H/quinone oxidoreductase 1 (NQO1) through the activation of the nuclear factor (erythroid-derived 2)-like 2 (Nrf2)/antioxidant response element (ARE) signaling. Further assays demonstrated that NHDC induces accumulation of Nrf2 in the nucleus and augmented Nrf2-ARE binding activity. Moreover, NHDC inhibits the ubiquitination of Nrf2 and suggests the modification of Kelch-like ECH-associated protein 1 (Keap1) and the disruption of the Keap1/Nrf2 complex. c-Jun N-terminal kinase (JNK) and p38 but not extracellular signal-regulated protein kinase (ERK) phosphorylations were up-regulated by NHDC treatment. Taken together, NHDC showed its protective antioxidant effect against CCl4-induced oxidative damage via the direct free radical scavenging and indirect Nrf2/ARE signaling pathway.

Polychlorinated biphenyl quinone induces endoplasmic reticulum stress, unfolded protein response, and calcium release.

Organisms are able to respond to environmental insult to maintain cellular homeostasis, which include the activation of a wide range of cellular adaptive responses with tightly controlled mechanisms. The endoplasmic reticulum (ER) is an organelle responsible for protein folding and calcium storage. ER stress leads to the accumulation of unfolded proteins in the ER lumen. To be against or respond to this effect, cells have a comprehensive signaling system, called unfolded protein response (UPR), to restore homeostasis and normal ER function or activate the cell death program. Therefore, it is critical to understand how environmental insult regulates the ingredients of ER stress and UPR signalings. Previously, we have demonstrated that polychlorinated biphenyl (PCB) quinone caused oxidative stress, cytotoxicity, genotoxicity, and apoptosis in HepG2 cells. Here, we investigated the role of a PCB quinone, PCB29-pQ on ER stress, UPR, and calcium release. PCB29-pQ markedly increased the hallmark genes of ER stress, namely, glucose-regulated protein 78 (GRP78), GRP94, and C/EBP homologous protein (CHOP) on both protein and mRNA levels in HepG2 cells. We also confirmed PCB29-pQ induced ER morphological defects by using transmission electron microscopy. Moreover, PCB29-pQ induced intracellular calcium accumulation and calpain activity, which were significantly inhibited by the pretreatment of BAPTA-AM (Ca(2+) chelator). These results were correlated with the outcome that PCB29-pQ induces ER stress-related apoptosis through caspase family gene 12, while salubrinal and Z-ATAD-FMK (a specific inhibitor of caspase 12) partially ameliorated this effect, respectively. N-Acetyl-l-cysteine (NAC) scavenged ROS formation and consequently alleviated PCB29-pQ-induced expression of ER stress-related genes. In conclusion, our result demonstrated for the first time that PCB quinone leads to ROS-dependent induction of ER stress, and UPR and calcium release in HepG2 cells, and the evaluation of the perturbations of ER stress, UPR, and calcium signaling provide further information on the mechanisms of PCB-induced toxicity.

Polychlorinated biphenyl quinone induces oxidative DNA damage and repair responses: The activations of NHEJ, BER and NER via ATM-p53 signaling axis.

Our previous studies demonstrated that polychlorinated biphenyl (PCB) quinone induced oxidative DNA damage in HepG2 cells. To promote genomic integrity, DNA damage response (DDR) coordinates cell-cycle transitions, DNA repair and apoptosis. PCB quinone-induced cell cycle arrest and apoptosis have been documented, however, whether PCB quinone insult induce DNA repair signaling is still unknown. In this study, we identified the activation of DDR and corresponding signaling events in HepG2 cells upon the exposure to a synthetic PCB quinone, PCB29-pQ. Our data illustrated that PCB29-pQ induces the phosphorylation of p53, which was mediated by ataxia telangiectasia mutated (ATM) protein kinase. The observed phosphorylated histone H2AX (γ-H2AX) foci and the elevation of 8-hydroxy-2'-deoxyguanosine (8-OHdG) indicated that DDR was stimulated by PCB29-pQ treatment. Additionally, we found PCB29-pQ activates non-homologous end joining (NHEJ), base excision repair (BER) and nucleotide excision repair (NER) signalings. However, these repair pathways are not error-free processes and aberrant repair of DNA damage may cause the potential risk of carcinogenesis and mutagenesis.

Tetrachlorobenzoquinone activates Nrf2 signaling by Keap1 cross-linking and ubiquitin translocation but not Keap1-Cullin3 complex dissociation.

Tetrachlorobenzoquinone (TCBQ), a metabolite of industrial herbicide pentachlorophenol, showed hepatotoxicity and genotoxicity through reactive oxygen species (ROS) mechanism in vivo and in vitro models. Nuclear factor erythroid-derived 2-like 2 (Nrf2) is a cellular sensor of oxidative or electrophilic stress, which controls the expression of detoxifying enzymes and antioxidant proteins. Using the human hepatoma HepG2 cell line as an in vitro model, we demonstrated a significant induction of Nrf2 but not its negative regulator Kelch-like ECH-associated protein 1 (Keap1), following exposure to TCBQ. Also, our results clearly demonstrated the translocation of cytosolic Nrf2 into the nucleus. After translocation, Nrf2 subsequently binds to the antioxidant response element (ARE), up-regulated heme oxygenase-1 (HO-1), and NADH quinone oxidoreductase subunit 1 (NQO1), which may be considered as an antioxidative response to TCBQ-intoxication. The luciferase reporter assay confirmed the formation of the Nrf2-ARE complex. Furthermore, mechanism studies proposed that TCBQ promoted the formation of the Keap1 cross-linking dimer, a ubiquitination switch from Nrf2 to Keap1 but not the dissociation of the Keap1-Cullin3 (Cul3) complex.

Bazhen decoction protects against acetaminophen induced acute liver injury by inhibiting oxidative stress, inflammation and apoptosis in mice.

Bazhen decoction is a widely used traditional Chinese medicinal decoction, but the scientific validation of its therapeutic potential is lacking. The objective of this study was to investigate corresponding anti-oxidative, anti-inflammatory and anti-apoptosis activities of Bazhen decoction, using acetaminophen-treated mice as a model system. A total of 48 mice were divided into four groups. Group I, negative control, treated with vehicle only. Group II, fed with 500 mg/kg/day Bazhen decoction for 10 continuous days. Group III, received a single dose of 900 mg/kg acetaminophen. Group IV, fed with 500 mg/kg/day Bazhen decoction for 10 continuous days and a single dose of 900 mg/kg acetaminophen 30 min before last Bazhen decoction administration. Bazhen decoction administration significantly decrease acetaminophen-induced serum ALT, AST, ALP, LDH, TNF-α, IL-1ß, ROS, TBARS and protein carbonyl group levels, as well as GSH depletion and loss of MMP. Bazhen decoction restore SOD, CAT, GR and GPx activities and depress the expression of pro-inflammatory factors, such as iNOS, COX-2, TNF-α, NF-κB, IL-1ß and IL-6, respectively. Moreover, Bazhen decoction down-regulate acetaminophen-induced Bax/Bcl-2 ratio, caspase 3, caspase 8 and caspase 9. These results suggest the anti-oxidative, anti-inflammatory and anti-apoptosis properties of Bazhen decoction towards acetaminophen-induced liver injury in mice.

Tetrachloro-p-benzoquinone induces hepatic oxidative damage and inflammatory response, but not apoptosis in mouse: the prevention of curcumin.

This study investigated the protective effects of curcumin on tetrachloro-p-benzoquinone (TCBQ)-induced hepatotoxicity in mice. TCBQ-treatment causes significant liver injury (the elevation of serum AST and ALT activities, histopathological changes in liver section including centrilobular necrosis and inflammatory cells), oxidative stress (the elevation of TBAR level and the inhibition of SOD and catalase activities) and inflammation (up-regulation of iNOS, COX-2, IL-1ß, IL-6, TNF-α and NF-κB). However, these changes were alleviated upon pretreatment with curcumin. Interestingly, TCBQ has no effect on caspase family genes or B-cell lymphoma 2 (Bcl-2)/Bcl-2 associated X (Bax) protein expressions, which implied that TCBQ-induced hepatotoxicity is independent of apoptosis. Moreover, curcumin was shown to induce phase II detoxifying/antioxidant enzymes HO-1 and NQO1 through the activation of nuclear factor erythroid-derived 2-like 2 (Nrf2). In summary, the protective mechanisms of curcumin against TCBQ-induced hepatoxicity may be related to the attenuation of oxidative stress, along with the inhibition of inflammatory response via the activation of Nrf2 signaling.

Role of α-lipoic acid in LPS/d-GalN induced fulminant hepatic failure in mice: studies on oxidative stress, inflammation and apoptosis.

This study investigated the protective effect of α-lipoic acid (LA) on lipopolysaccharide (LPS)/d-galactosamine (d-GalN)-induced fulminant hepatic failure in mice. First, we found that LA markedly reduced LPS/d-GalN-induced increases in serum ALT and AST activities, which were supplemented with histopathological examination, suggested that LA has a protective effect on this model of hepatic damage. Livers challenged with LPS/d-GalN exhibited extensive areas of vacuolization with the disappearance of nuclei and the loss of hepatic architecture. On the contrary, these pathological alterations were ameliorated by LA treatment. Next, we found that ROS and TBARS levels were increased in LPS/d-GalN treated liver homogenates, which were attenuated by LA administration. Consistently, decreases in hepatic CAT and GPx activities were observed in LPS/d-GalN group and were significantly restored by LA administration. Moreover, pretreatment with LA markedly reduced LPS/d-GalN-induced iNOS, COX-2, TNF-α, NF-κB, IL-1ß and IL-6 expressions. Furthermore, our data showed that TUNEL-positive cells increased in LPS/d-GalN-treated mice liver which was counteracted by LA administration. LPS/d-GalN induced apoptosis of hepatocytes, as estimated by caspase 3, caspase 8 and caspase 9 activations. Also, the increasing of Bax and the decreasing of Bcl-2 expressions also supported LPS/d-GalN induced apoptosis. Interestingly, LA marked relieved these apoptotic features. Taking together, our results indicated that LA plays an important role on LPS/d-GalN-induced fulminant hepatic failure through its antioxidant, anti-inflammatory and anti-apoptotic activities.

Hepatotoxicity and genotoxicity of patulin in mice, and its modulation by green tea polyphenols administration.

Patulin (PAT) is a mycotoxin produced by certain species of Penicillium, Aspergillus, and Byssochlamys. Previous studies demonstrated its cytotoxic, genotoxic, and mutagenic effects in different cell lines. However, there is little information available concerning its toxic behavior in vivo. In the present study, we investigated PAT-induced hepatotoxicity and genotoxicity in mice. We also investigated the antioxidant and anti-genotoxicity efficiency of green tea polyphenols (GTP) against PAT-induced toxicity. We found that PAT-treatment induced serum alanine transaminase (ALT) and aspartate transaminase (AST) activities significantly. PAT-induced lipid peroxidation was confirmed with the elevation of thiobarbituric acid-reactive substances (TBARS). Moreover, the increasing of reactive oxygen species (ROS) and decreasing of GSH level implied its oxidative damage mechanism. In bone marrow cell, PAT was found to induce micronucleus and chromosomal aberration formation. In addition, our result suggested that GTP administration has dose-dependent antioxidative and antigenotoxic effect in against PAT-induced hepatotoxicity and genotoxicity.

Selenium supplementation shows protective effects against patulin-induced brain damage in mice via increases in GSH-related enzyme activity and expression.

AIMS: This study was designed to investigate the protective effects of selenium supplementation on patulin-induced neurotoxicity. MAIN METHODS: Mice were subjected to patulin for 8 weeks. Sodium selenite (Na2SeO3) and selenium-methionine (Se-Met) were supplemented with the diet, and we investigated the effects of selenium on patulin-induced neurotoxicity. The animals were randomly divided into 4 groups containing 6-8 mice each. The first group was used as a control, and only physiological saline (0.9%) was injected. The second group was treated with patulin (1mg/kg) intraperitoneally. The third group was treated with patulin (1mg/kg) along with a dietary supplementation of Na2SeO3 (0.2mg Se/kg of diet). The fourth group was treated with patulin (1mg/kg) plus Se-Met (0.2mg Se/kg of diet). KEY FINDINGS: Patulin treatment increased oxidative damage in the brain, as evidenced by a decrease in non-protein thiol and total thiol groups, along with significant increases in GSSG, reactive oxygen species, thiobarbituric acid reactive substances and protein carbonyl levels. Moreover, the activities of glutathione peroxidase (GPx) and glutathione reductase were inhibited with patulin treatment. Selenium supplementation significantly ameliorated these biological parameter changes. In addition, selenium treatments significantly increased the mRNA levels of GPx-1, GPx-4 and thioredoxin reductase. SIGNIFICANCE: Our data show that selenium supplementation increases the activity and expression of glutathione-related enzymes and offers significant protection against brain damage induced by patulin.

Polychlorinated biphenyl quinone-induced genotoxicity, oxidative DNA damage and γ-H2AX formation in HepG2 cells.

Our previous study has demonstrated that PCB quinone is cytotoxic in HepG2 cells (Toxicology in Vitro 26 (2012) 841-848). However, it is not clear whether PCB quinone is also carcinogenic (or mutagenic). In the current study, we investigated the genotoxicity of PCB quinone (2,3,5-trichloro-6-phenyl-[1,4]benzoquinone, PCB29-pQ) in HepG2 cells using single cell gel electrophoresis (SCGE) assay and micronucleus (MN) assay. We found PCB29-pQ exposure significantly increased olive tail moment (OTM) and micronuclei (MN) frequencies in HepG2 cells. These data suggested that PCB29-pQ caused DNA strand breaks and chromosome breaks. We further investigated whether the genotoxicity of PCB29-pQ is associated with the generation of reactive oxygen species (ROS). Using enzyme-linked immunosorbent assay for 8-hydroxydeoxyguanosine (8-OHdG) detection, we demonstrated that the level of oxidative DNA damage was significantly evaluated with PCB29-pQ exposure concentration and time dependently. Moreover, γ-H2AX appeared after the treatment of PCB29-pQ in HepG2 cells, may indicate double strand breaks (DSBs). In addition, the pretreatment of ROS scavengers inhibited the genotoxicity of PCB29-pQ significantly. In conclusion, our data suggested that PCB29-pQ causes genotoxic effects in HepG2 cells, probably via ROS-induced oxidative DNA damage.