The role of glutathione and glutathione transferases in chemical carcinogenesis

Associations between exposure to phthalates and liver function among women undergoing assisted reproductive technology

Phthalates can induce hepatotoxicity in animal studies. We aimed to assess the associations of individual and mixture of urinary phthalate metabolites with serum liver function indicators among 764 women undergoing assisted reproductive technology (ART). In linear models, we observed inverse correlations between urinary mono-benzyl phthalate and serum total protein (TP) as well as globulin (β=-0.27 and -0.23, respectively, P<0.05). Additionally, negative associations were identified between mono-isobutyl phthalate and mono-butyl phthalate (MBP) and aspartate aminotransferase-to-alanine transaminase ratio (AST/ALT) (P<0.05). MBP and the sum of all phthalate metabolites (∑all.phth.m) were positively associated with bilirubin, with β ranging from 0.14 to 0.47. Most phthalate metabolites were also positively related to gamma-glutamyl transferase (GGT) (all P<0.05). In Bayesian kernel machine regression models, phthalate mixture was positively associated with bilirubin and GGT, whereas inversely associated with AST/ALT and TP. Our results suggest that phthalate exposure may impair liver function among women undergoing ART.

Smartphone-Based Janus Micromotors Strategy for Motion-Based Detection of Glutathione

Herein, we describe a Janus micromotor smartphone platform for the motion-based detection of glutathione. The system compromises a universal three-dimensional (3D)-printed platform to hold a commercial smartphone, which is equipped with an external magnification optical lens (20-400×) directly attached to the camera, an adjustable sample holder to accommodate a glass slide, and a light-emitting diode (LED) source. The presence of glutathione in peroxide-rich sample media results in the decrease in the speed of 20 μm graphene-wrapped/PtNPs Janus micromotors due to poisoning of the catalytic layer by a thiol bond formation. The speed can be correlated with the concentration of glutathione, achieving a limit of detection of 0.90 μM, with percent recoveries and excellent selectivity under the presence of interfering amino acids and proteins. Naked-eye visualization of the speed decrease allows for the design of a test strip for fast glutathione detection (30 s), avoiding previous amplification strategies or sample preparation steps. The concept can be extended to other micromotor approaches relying on fluorescence or colorimetric detection for future multiplexed schemes.

Superabsorbent polymers: A state-of-art review on their classification, synthesis, physicochemical properties, and applications

Superabsorbent polymers (SAP) and modified natural polymer hydrogels are widely and increasingly used in agriculture, health care textiles, effluent treatment, drug delivery, tissue engineering, civil concrete structure, etc. However, not many comprehensive reviews are available on this class of novel polymers. A review covering all the viable applications of SAP will be highly useful for researchers, industry persons, and medical, healthcare, and agricultural purposes. Hence, an attempt has been made to review SAPs with reference to their classifications, synthesis, modification by crosslinking, and physicochemical characterization such as morphology, swellability, thermal and mechanical properties, lifetime prediction, thermodynamics of swelling, absorption, release and transport kinetics, quantification of hydrophilic groups, etc. Besides, the possible methods of fine-tuning their structures for improving their absorption capacity, fast absorption kinetics, mechanical strength, controlled release features, etc. were also addressed to widen their uses. This review has also highlighted the biodegradability, commercial viability and market potential of SAPs, SAP composites, the feasibility of using biomass as raw materials for SAP production, etc. The challenges and future prospects of SAP, their safety, and environmental issues are also discussed.

The mercapturic acid pathway

The mercapturic acid pathway is a major route for the biotransformation of xenobiotic and endobiotic electrophilic compounds and their metabolites. Mercapturic acids (N-acetyl-l-cysteine S-conjugates) are formed by the sequential action of the glutathione transferases, γ-glutamyltransferases, dipeptidases, and cysteine S-conjugate N-acetyltransferase to yield glutathione S-conjugates, l-cysteinylglycine S-conjugates, l-cysteine S-conjugates, and mercapturic acids; these metabolites constitute a "mercapturomic" profile. Aminoacylases catalyze the hydrolysis of mercapturic acids to form cysteine S-conjugates. Several renal transport systems facilitate the urinary elimination of mercapturic acids; urinary mercapturic acids may serve as biomarkers for exposure to chemicals. Although mercapturic acid formation and elimination is a detoxication reaction, l-cysteine S-conjugates may undergo bioactivation by cysteine S-conjugate β-lyase. Moreover, some l-cysteine S-conjugates, particularly l-cysteinyl-leukotrienes, exert significant pathophysiological effects. Finally, some enzymes of the mercapturic acid pathway are described as the so-called "moonlighting proteins," catalytic proteins that exert multiple biochemical or biophysical functions apart from catalysis.

Sulfuric Odor Precursor S-Allyl-l-Cysteine Sulfoxide in Garlic Induces Detoxifying Enzymes and Prevents Hepatic Injury

S-Allyl-l-cysteine sulfoxide (ACSO) is a precursor of garlic-odor compounds like diallyl disulfide (DADS) and diallyl trisulfide (DATS) known as bioactive components. ACSO has suitable properties as a food material because it is water-soluble, odorless, tasteless and rich in bulbs of fresh garlic. The present study was conducted to examine the preventive effect of ACSO on hepatic injury induced by CCl₄ in rats. ACSO, its analogs and garlic-odor compounds were each orally administered via gavage for five consecutive days before inducing hepatic injury. Then, biomarkers for hepatic injury and antioxidative state were measured. Furthermore, we evaluated the absorption and metabolism of ACSO in the small intestine of rats and NF-E2-related factor 2 (Nrf2) nuclear translocation by ACSO using HepG2 cells. As a result, ACSO, DADS and DATS significantly suppressed the increases in biomarkers for hepatic injury such as the activities of aspartate transaminase (AST), alanine transaminase (ALT) and lactate dehydrogenase (LDH), and decreases in antioxidative potency such as glutathione (GSH) level and the activities of glutathione S-transferase (GST) and glutathione peroxidase (GPx). We also found ACSO was absorbed into the portal vein from the small intestine but partially metabolized to DADS probably in the small intestine. In in vitro study, ACSO induced Nrf2 nuclear translocation in HepG2 cells, which is recognized as an initial trigger to induce antioxidative and detoxifying enzymes. Taken together, orally administered ACSO probably reached the liver and induced antioxidative and detoxifying enzymes by Nrf2 nuclear translocation, resulting in prevention of hepatic injury. DADS produced by the metabolism of ACSO in the small intestine might also have contributed to the prevention of hepatic injury. These results suggest potential use of ACSO in functional foods that prevent hepatic injury and other diseases caused by reactive oxygen species (ROS).

Novel conjugates with dual suppression of glutathione S-transferases and tryptophan-2,3-dioxygenase activities for improving hepatocellular carcinoma therapy

Tryptophan-2,3-dioxygenase (TDO) is an immune checkpoint enzyme expressed in human tumors and involved in immune evasion and tumor tolerance. While glutathione S-transferases (GSTs) are pharmacological targets for several cancer. Here we demonstrated the utility of NBDHEX (GSTs inhibitor) and TDO inhibitor by the combinatorial linker design. Two novel conjugates with different linkers were prepared to reverse tumor immune suppression. The conjugates displayed significant antitumor activity against TDO and GSTs expression of HepG2 cancer cells. Further study indicated that compound 4 could induce higher apoptotic effect than its mother compounds via a mitochondrial-dependent pathway, simultaneously more effective to inhibit TDO and GSTs protein expression. Further study indicated that 4 could decrease the production of kynurenine and deactivate aryl hydrocarbon receptor (AHR), leading to CD3⁺T-cell activation and proliferation to involve in antitumor immune response.

Glutathione Regulated Inner Filter Effect of MnO2 Nanosheets on Boron Nitride Quantum Dots for Sensitive Assay

Glutathione (GSH) can help the body maintain the function of the normal immune system and its level change is associated with a variety of diseases. To achieve the ultrasensitive assay of GSH, a "switch on" nanosensor is designed on the basis of GSH regulating the inner filter effect (IFE) of MnO₂ nanosheets (MnO₂ NS) on boron nitride quantum dots (BNQDs). Here, the fluorescence of BNQDs is quenched efficiently in the presence of redoxable MnO₂ NS because of the superior light absorption capability; however, the introduction of GSH can trigger the decomposition of MnO₂ to Mn²⁺ and weaken the IFE, causing the partial fluorescence recovery. The recovered fluorescence is dependent on the concentration of GSH. Under the optimal conditions, this sensing platform shows the response to GSH in the range of 0.5-250 μM with the detection limit of 160 nM. On the basis of the GSH activated reduction of MnO₂ NS, the MnO₂ NS/BNQDs nanoprobes exhibit good selectivity to GSH. The practical application of the proposed system is demonstrated by detecting the GSH in human plasma samples with satisfying results.

Scientific Opinion on Flavouring Group Evaluation 200, Revision 1 (FGE.200 Rev.1): 74 α,β-unsaturated aliphatic aldehydes and precursors from chemical subgroup 1.1.1 of FGE.19

The Panel on Food Additives and Flavourings of the European Food Safety Authority was requested to evaluate the genotoxic potential of 74 flavouring substances from subgroup 1.1.1 of FGE.19 in the Flavouring Group Evaluation 200 Revision 1 (FGE.200 Rev1). In FGE.200, genotoxicity studies were provided for one representative substance, namely hex-2(trans)-enal [FL-no: 05.073], and for other two substances in the same subgroup, namely 2-dodecenal [FL-no: 05.037] and 2-nonenal [FL-no: 05.171]. The Panel concluded that the concern still remains with respect to genotoxicity for the substances of this subgroup and requested an in vivo Comet assay performed in duodenum and liver for hex-2(trans)-enal [FL-no: 05.073]. For the two other representative substances of subgroup 1.1.1 (nona-2(trans),6(cis)-dienal [FL-no: 05.058] and oct-2-enal [FL-no: 05.060]), the Panel requested a combined in vivo Comet assay and micronucleus assay. These data have been provided and are evaluated in the present opinion FGE.200 Rev1. Industry submitted genotoxicity studies on trans-2-octenal [FL-no: 05.190], instead of oct-2-enal [FL-no: 05.060]. Based on the available data, the Panel concluded that the concern for genotoxicity can be ruled out for hex-2(trans)-enal [FL-no: 05.073], trans-2-octenal [FL-no: 05.190] and nona-2(trans),6(cis)-dienal [FL-no: 05.058], therefore all the 74 substances [FL-no: 02.020, 02.049, 02.050, 02.090, 02.112, 02.137, 02.156, 02.192, 02.210, 02.231, 05.037, 05.058, 05.060, 05.070, 05.072, 05.073, 05.076, 05.078, 05.102, 05.109, 05.111, 05.114, 05.120, 05.144, 05.150, 05.171, 05.172, 05.179, 05.184, 05.189, 05.190, 05.191, 05.195, 06.025, 06.031, 06.072, 09.054, 09.097, 09.109, 09.119, 09.146, 09.233, 09.244, 09.247, 09.276, 09.277, 09.303, 09.312, 09.385, 09.394, 09.395, 09.396, 09.397, 09.398, 09.399, 09.400, 09.410, 09.411, 09.469, 09.482, 09.489, 09.492, 09.493, 09.498, 09.678, 09.701, 09.719, 09.741, 09.790, 09.841, 09.866, 09.947, 09.948, 13.004] can be evaluated through the Procedure for flavouring substances.

The multifaceted role of glutathione S-transferases in cancer

Glutathione S-transferases (GSTs) are phase II detoxifying enzymes involved in the maintenance of cell integrity, oxidative stress and protection against DNA damage by catalyzing the conjugation of glutathione to a wide variety of electrophilic substrates. Though enzymes of the glutathione synthesis and salvage pathways have been well characterized in the past, there is still a lack of comprehensive understanding of their independent and coordinate regulatory mechanisms in carcinogenesis. The present review discusses implication of GST in cancer development and progression, gene polymorphism, drug resistance, signaling and epigenetic regulation involving their role in cancer. It is anticipated that GST especially the GSTP1 class can be developed as a biomarker either used alone or in combination with other biomarkers for early cancer detection and/or diagnosis as well as for future targeted preventive and therapeutic interventions with dietary agents.

Modulation of xenobiotic metabolizing enzyme activities in rat liver by co-administration of morin, endosulfan, and 7,12-dimethylbenz[a]anthracene

Morin is a flavonoid which is present in many plants. Endosulfan and 7,12-dimethylbenz[a]anthracene (DMBA) are toxic chemicals that humans are exposed to in their daily lives. In this study, the protective role of morin was investigated in endosulfan and DMBA treated rats. Eight groups, each comprising seven 2.5-month-old adult male Wistar rats (weighing 170-255 g), were used. Endosulfan, morin, and DMBA were administered individually or in combinations, at 5 mg/kg body weight (bw) (three times/week), 25 mg/kg bw (three times/week), and 30 mg/kg bw (once/week for three weeks) via oral gavage, respectively. On day 54 of the administration period, the rats were killed. DMBA + endosulfan co-administration significantly increased CYP1A1-, CYP1A2-, CYP2E-, and GST-associated activities in the rats compared to the control. DMBA + endosulfan + morin significantly increased CYP1A1, CYP1A2, CYP3A, and GST associated activities in the rats relative to the control. Histopathological studies were performed to investigate protective effects of morin on liver damage. The results indicated that DMBA + endosulfan treatment induced liver damage, and morin reduced this damage. These findings suggest that CYP1A, CYP3A, and GST enzyme activities participate in the protective mechanism of morin against endosulfan and DMBA induced toxicity.

A review of the genotoxic, mutagenic, and carcinogenic potentials of several lower acrylates

Lower alkyl acrylate monomers include methyl-, ethyl-, n-butyl-, and 2-ethylhexyl acrylate. These acrylates are used in the manufacture of acrylic polymers and copolymers for plastics, food packaging, adhesives, and cosmetic formulations. Although there is limited potential for human environmental exposure, occupational exposure can occur via inhalation and dermal contact. Recently, new genotoxicity data have been generated, along with in silico and in vitro read-cross analyses, for these acrylates. The availability of high-throughput screening (HTS) data through the ToxCast™/Tox21 databases allows for consideration of computational toxicology and organization of these data according to the ten key characteristics of carcinogens. Therefore, we conducted a comprehensive review to evaluate the mechanistic, toxicokinetic, animal, and human data, including HTS data, for characterizing the potential carcinogenicity, mutagenicity, and genotoxicity of these acrylates. Toxicokinetic data demonstrate that these acrylates are metabolized rapidly by carboxylesterase hydrolysis and conjugation with glutathione. HTS data demonstrated an overall lack of bioactivity in cancer-related pathways. Overall, the genotoxicity and mutagenicity data support a cytotoxic, non-genotoxic mechanism for these acrylates. Cancer bioassay studies conducted by the oral, dermal, and inhalation routes in animal models with these acrylates did not show any increase in tumor incidence, with two exceptions. At high doses, and secondary to chronic site-of-contact irritation and corrosion, rodent forestomach tumors were induced by oral gavage dosing with ethyl acrylate, and skin tumors were observed following chronic dermal dosing with 2-ethylhexyl acrylate in C3H/HeJ inbred mice (a strain with deficiencies in wound healing), but not in the outbred NMRI strain. For both dermal and forestomach cancers, tumorigenesis is secondary to high doses and long-term tissue damage, shown to be reversible. With evidence that these chemicals are not genotoxic, and that they cause forestomach and dermal tumors through chronic irritation and regenerative proliferation mechanisms, these acrylates are unlikely to pose a human cancer hazard.

Modulatory role of GSTT1 and GSTM1 in Punjabi agricultural workers exposed to pesticides

Glutathione S-transferases are important detoxification enzymes involved in the metabolism of endogenous as well as exogenous compounds. Individuals differ in metabolic capacity due to inherited genetic variations. Due to the polymorphism exhibited by GSTT1 and GSTM1 that results in the complete loss of function, the present study was aimed towards the determination of the frequency distribution of GSTT1 and GSTM1 in agricultural workers in Punjab, India. The study aimed to investigate their contribution in susceptibility to increased disease risk. A total of 513 subjects were included in this study, out of which 250 were agriculture workers and 263 were non-exposed occupationally. GSTT1 and GSTM1 null-genotype distribution was analyzed through multiplex-PCR method. Complete gene deletion in either of the genes was strongly associated with an increased risk (OR = 1.8; 95% CI = 1.3-2.6; p < 0.0008) of DNA/cytogenetic damage, cancer, infertility, and many other serious health effects. Therefore, homozygous deletion in GSTT1 or GSTM1 could play a modulatory role in health of workers with long-term exposure to pesticides.

Effects of chronic alcohol consumption on DNA damage and immune regulation induced by the environmental pollutant dibenzo[a,l]pyrene in oral tissues of mice

Previously, we showed that oral application of the environmental pollutant dibenzo[a,l]pyrene (DB[a,l]P) induces oral tumors in mice. Thus, in the present investigation we examined the effect of alcohol on DB[a,l]P-induced DNA damage and immune regulation; we showed that alcohol (6.4% v/v in the diet, 35% of Calories) significantly enhanced the levels of (-)-anti-trans-DB[a,l]P-dA while decreased the levels of GSH in the mouse oral tissues. Analysis of RNA expression revealed that DB[a,l]P alone upregulates inflammatory genes while alcohol suppresses several markers of immune surveillance. Collectively, these results suggest that alcohol may enhance oral carcinogenesis induced by DB[a,l]P.

Influence of UV-A radiation on oxidative stress and antioxidant enzymes in Mythimna separata (Lepidoptera: Noctuidae)

Abiotic stress factors, including ultraviolet (UV) radiation, significantly affect insect life. UV-A radiation (320-400 nm) has been widely used for insect control since it increases the production of ROS and causes oxidative cell damage. In the present study, we evaluated the effects of UV-A irradiation on an important pest in China, the ear-cutting caterpillar, Mythimna separata (Lepidoptera: Noctuidae). We exposed 3-day-old M. separata adults to UV-A radiation for different periods of time (0, 30, 60, 90, and 120 min) and evaluated the resulting total antioxidant capacity and the activity of the antioxidant enzymes superoxide dismutase, catalase, peroxidase, and glutathione-S-transferase. The total antioxidant capacity significantly increased after exposure to UV-A radiation for 60 min but decreased after 90 and 120 min of exposure, compared with the control. The antioxidant activity of glutathione-S-transferase, superoxide dismutase, catalase, and peroxidase increased after 60-min exposure, and it was decreased at the longest exposure period 120 min. The longest exposure time period relatively activates the xenobiotic detoxifying enzymes like glutathione-S-transferase, superoxide dismutase, catalase, and peroxidase enzymes. The longest duration of UV-A radiation may cooperate with pesticide detoxification mechanism in insects, making them more susceptible to insecticides. Our results demonstrated that UV irradiation causes oxidative stress, affects the activity of antioxidant enzymes, and disturbs the physiology of M. separata adults.

Reduction Sensitive Lipid Conjugates of Tenofovir: Synthesis, Stability, and Antiviral Activity

The therapeutic value of numerous small molecules hinges on their ability to permeate the plasma membrane. This is particularly true for tenofovir (TFV), adefovir, and other antiviral nucleosides that demonstrate potent antiviral activity but poor bioavailability. Using TFV as a model substrate, we hybridized two disparate prodrug strategies to afford novel reduction-sensitive lipid conjugates of TFV that exhibit subnanomolar activity toward HIV-1 and are stable in human plasma for more than 24 h with a therapeutic index approaching 30000. These compounds significantly rival the clinically approved formulation of TFV and revitalize the potential of disulfide-bearing prodrugs which have seen limited in vitro and in vivo success since their debut over 20 years ago. We further demonstrate the utility of these conjugates as a tool to indirectly probe the enzymatic hydrolysis of phosphonomonoesters that may further advance the development of other prodrug strategies for nucleosides, peptides, and beyond.

PARTICIPATION OF Y89 AND Y97 IN THE CONJUGATING ACTIVITY OF Drosophila melanogaster GLUTATHIONE S-TRANSFERASE D3 (DmGSTD3)

Drosophila melanogaster glutathione S-transferase D3 (DmGSTD3) has a shorter amino acid sequence as compared to other GSTs known in the fruit flies. This is due to the 15 amino acid N-terminal truncation in which normally active amino acid residue is located. The work has made use of homology modeling to visualize the arrangement of amino acid side chains in the glutathione (GSH) substrate cavity. The identified amino acids were then replaced with amino acids without functional groups in the side chains and the mutants were analyzed kinetically. Homology modeling revealed that the side chains of Y89 and Y97 were shown facing toward the substrate cavity proposing their possible role in catalyzing the conjugation. Y97A and Y89A GSH gave large changes in Km (twofold increase), Vmax (fivefold reduction), and Kcat /Km values for GSH suggesting their significant role in the conjugation reaction. The replacement at either positions has not affected the affinity of the enzyme toward 1-chloro-2,4-dinitrobenzene as no significant change in values of Kmax was observed. The replacement, however, had significantly reduced the catalytic efficiency of both mutants with (Kcat /Km )(GSH) and (Kcat /Km )(CDNB) of eight- and twofold reduction. The recombinant DmGSTD3 has shown no activity toward 1,2-dichloro-4-nitrobenzene, 2,4-hexadienal, 2,4-heptadienal, p-nitrobenzyl chloride, ethacrynic acid, and sulfobromophthalein. Therefore, it was evident that DmGSTD3 has made use of distal amino acids Y97 and Y89 for GSH conjugation.

Halogenated hydrocarbon solvent-related cholangiocarcinoma risk: biliary excretion of glutathione conjugates of 1,2-dichloropropane evidenced by untargeted metabolomics analysis

Recently, the International Agency for Research on Cancer issued a warning about the carcinogenicity of 1,2-dichloropropane (1,2-DCP) to humans based on an epidemiological study suggesting a relationship between the incidence of cholangiocarcinoma and occupational exposure to halogenated hydrocarbon solvent comprised mostly of 1,2-DCP. Although this dihaloalkane has been used in various industrial fields, there has been no biological evidence explaining the cholangiocarcinoma latency, as well as little understanding of general cholangiocarcinoma risk. In the present study, we explored the biliary excretion of 1,2-DCP metabolites by an untargeted metabolomics approach and the related molecular mechanism with in vitro and in vivo experiments. We hypothesized that the biliary excretion of carcinogens derived from 1,2-DCP contribute to the increased cholangiocarcinoma risk. We found that 1,2-DCP was conjugated with glutathione in the liver, and that the glutathione-conjugated forms of 1,2-DCP, including a potential carcinogen that contains a chloride atom, were excreted into bile by the bile canalicular membrane transporter, ABCC2. These results may reflect a risk in the backfiring of biliary excretion as a connatural detoxification systems for xenobiotics. Our findings would contribute to uncover the latent mechanism by which the chronic exposure to 1,2-DCP increases cholangiocarcinoma risk and future understanding of cholangiocarcinoma biology.

Evaluation of oxidant-antioxidant status in tissue samples in oral cancer: A case control study

Background:

Imbalances between the oxidant-antioxidant status have been implicated in the pathogenesis of several diseases, including cancer. The aim of this study was to evaluate the extent of lipid peroxidation and antioxidants in the tissue samples of oral squamous cell carcinoma (OSCC) patients of different clinical stages in comparison with the healthy controls.

Materials and Methods:

A case-control study was designed with 20 new histopathologically proven oral carcinoma patients and an equal number of age, sex, and tobacco chewing habit matched healthy subjects. Their tissue samples were subjected to evaluation of lipid peroxidation product and antioxidant enzymes, namely, superoxide dismutase (SOD), catalase (CAT), reduced glutathione (GSH), and glutathione peroxidase (GPx) using spectrophotometric methods. The data are expressed as mean ± standard deviation. The statistical comparisons between the study groups were performed by independent Student's unpaired t-test and one-way analysis of variance. Post-hoc analysis was performed for within study group comparisons. Karl Pearson correlation was performed for the biochemical parameters within the group and between the groups. For statistically significant correlations, simple linear regression was performed using SPSS (α=0.05).

Results:

Significant reduction in lipid peroxidation (P < 0.001) SOD and CAT (P < 0.001) was observed in the tissue of OSCC patients as compared with the healthy controls. On the other hand, reduced GSH and GPx were significantly increased in tumor samples.

Conclusion:

Reduced lipid peroxidation and increased activity of reduced GSH and GPx provides the suitable environment for the local growth and invasion of the tumor and metastasis in the later stages. Among the antioxidant enzymes, GSH reductase appears to have a profound role in carcinogenesis and thus it can be considered as potential prognostic marker.

Non-Cytotoxic Quantum Dot-Chitosan Nanogel Biosensing Probe for Potential Cancer Targeting Agent

Quantum dot (Qdot) biosensors have consistently provided valuable information to researchers about cellular activity due to their unique fluorescent properties. Many of the most popularly used Qdots contain cadmium, posing the risk of toxicity that could negate their attractive optical properties. The design of a non-cytotoxic probe usually involves multiple components and a complex synthesis process. In this paper, the design and synthesis of a non-cytotoxic Qdot-chitosan nanogel composite using straight-forward cyanogen bromide (CNBr) coupling is reported. The probe was characterized by spectroscopy (UV-Vis, fluorescence), microscopy (Fluorescence, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Dynamic Light Scattering. This activatable (“OFF”/“ON”) probe contains a core–shell Qdot (CdS:Mn/ZnS) capped with dopamine, which acts as a fluorescence quencher and a model drug. Dopamine capped “OFF” Qdots can undergo ligand exchange with intercellular glutathione, which turns the Qdots “ON” to restore fluorescence. These Qdots were then coated with chitosan (natural biocompatible polymer) functionalized with folic acid (targeting motif) and Fluorescein Isothiocyanate (FITC; fluorescent dye). To demonstrate cancer cell targetability, the interaction of the probe with cells that express different folate receptor levels was analyzed, and the cytotoxicity of the probe was evaluated on these cells and was shown to be nontoxic even at concentrations as high as 100 mg/L.

The influence of the environment on the development of thyroid tumors: a new appraisal

Most epidemiological studies concerning differentiated thyroid cancers (DTC) indicate an increasing incidence over the last two decades. This increase might be partially explained by the better access to health services worldwide, but clinicopathological analyses do not fully support this hypothesis, indicating that there are carcinogenetic factors behind this noticeable increasing incidence. Although we have undoubtedly understood the biology and molecular pathways underlying thyroid carcinogenesis in a better way, we have made very little progresses in identifying a risk profile for DTC, and our knowledge of risk factors is very similar to what we knew 30-40 years ago. In addition to ionizing radiation exposure, the most documented and established risk factor for DTC, we also investigated the role of other factors, including eating habits, tobacco smoking, living in a volcanic area, xenobiotics, and viruses, which could be involved in thyroid carcinogenesis, thus, contributing to the increase in DTC incidence rates observed.

AMPK synergizes with the combined treatment of 1'-acetoxychavicol acetate and sodium butyrate to upregulate phase II detoxifying enzyme activities

SCOPE

Phase II enzymes play important roles in detoxifying xenobiotics. We previously reported that both 1'-acetoxychavicol acetate (ACA) and sodium butyrate individually increased phase II enzyme activities. Here, we determined the combined action of ACA and sodium butyrate on phase II enzyme activities in intestinal epithelial cells (IEC 6).

METHODS AND RESULTS

ACA and sodium butyrate synergistically increased phase II enzyme activities. Protein levels of intranuclear transcription factor NF-E2-related factor 2 (Nrf2) were increased by ACA or sodium butyrate treatment, but treatment with both did not produce a synergistic effect. Intranuclear p53 protein levels were increased by ACA but decreased by sodium butyrate alone or combined treatment with ACA and sodium butyrate. In contrast, p53 acetylation was promoted by sodium butyrate and the ACA and sodium butyrate combination. Inhibition of AMPK activity decreased phase II enzyme activities that were upregulated by treatment with ACA plus sodium butyrate or other phytochemicals, including kaempferol, quercetin, and epigallocatechin-3-gallate. Combined treatment with ACA and sodium butyrate increased phosphorylated AMPK levels.

CONCLUSION

These results suggest that ACA and sodium butyrate synergistically contribute to xenobiotics metabolism. The combined ACA and sodium butyrate treatment synergistically upregulated phase II enzyme activities through AMPK activation and p53 acetylation.

Evaluation of the effect of beetroot juice on DMBA-induced damage in liver and mammary gland of female Sprague-Dawley rats

Red beetroot contains a specific class of antioxidants collectively named betalains, which have been shown to have anticarcinogenic and anti-inflamatory potential. We investigated the effect of beetroot juice on the hepatic and mammary gland carcinogen metabolizing enzymes, DNA damage and liver injury, altered by 7,12-dimethylbenz[a]anthracene (DMBA). In the liver, pretreatment with beetroot juice significantly decreased levels and activities of the majority of tested biochemical parameters, elevated by DMBA. Feeding with beetroot juice decreased the activities of CYP1A1 and 1A2 and increased phase II enzymes. The activities of all enzymes tested were enhanced in the animals treated with DMBA alone and in combination with beetroot juice. The most significant changes in the level of the enzymes tested were observed for

NAD(P)H

quinone oxidoreductase-1. In mammary gland, beetroot juice induced the level of glutathione S-transferase pi, enzyme involved in active metabolites of DMBA detoxification. The final effects of beetroot juice are tissue specific and depend on the class of carcinogen.

BPDE-like DNA adduct level in oral tissue may act as a risk biomarker of oral cancer

OBJECTIVE

Most reports have shown that PAH-related DNA adducts are positively correlated with the smoking status of oral cancer patients. However, these reports did not focus on a specific carcinogen in cigarette smoke. The purpose of this study was to elucidate the role of the BPDE (7,8-dihydroxy-anti-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene)-DNA adduct in the development of oral cancer in Taiwanese patients.

DESIGN

We enrolled 158 oral cancer patients and 64 non-cancer controls to investigate whether there were differences in susceptibility to cigarette smoke exposure in the formation of DNA adducts between cancer patients and controls. Immunohistochemistry and ELISA (enzyme-linked immunosorbent assay) were used to evaluate BPDE-DNA adduct levels in this study.

RESULTS

Our data showed that the BPDE-DNA adduct levels were positively correlated with gender, smoking status, betel nut chewing and alcohol consumption. The difference in DNA adduct levels could be explained by genetic polymorphisms of glutathione S-transferase M1 (GSTM1), but not by cytochrome P-4501A1 (CYP1A1). Patients with high DNA adduct levels (≧34.03 adducts/10(8) nucleotides) had an approximately 9.936-fold risk of oral cancer compared with those with low DNA adduct levels (<34.03 adducts/10(8) nucleotides) (p<0.001).

CONCLUSIONS

We suggest that genetic background and carcinogen exposure may increase the risk of developing oral cancer.

The enhancement of phase 2 enzyme activities by sodium butyrate in normal intestinal epithelial cells is associated with Nrf2 and p53

Dietary fiber fermentation by the colonic bacterial flora produces short-chain fatty acids, acetate, propionate and butyrate. Among them, butyrate is considered to be the major energy substrate for colonocytes and, at least in rats, seems to protect against colonic carcinogenesis. In this study, we examined the effect and the mechanisms of short-chain fatty acids on the activity of phase 2 enzymes. Sodium butyrate increased phase 2 enzyme activities in normal rat small intestine epithelial cells, Glutathione S-transferase and NAD(P)H:quinone oxidoreductase (NQO) in a dose-dependent manner(;) however, other short-chain fatty acids did not increase them. The mechanism of the induction of phase 2 enzymes with sodium butyrate sodium butyrate, but not other short-chain fatty acids was related to the increase of NF-E2-related factor 2 (Nrf2) nuclear translocation and the decrease in the levels of nuclear fraction p53. Sodium butyrate also caused enhancement of Nrf2 mRNA levels and suppression of p53 mRNA levels. Sodium butyrate enhances the activities of phase 2 enzymes via an increase in the Nrf2 protein levels in the nucleus and a decrease in the mRNA and protein levels of p53.

Association of CYP1A1, GSTM1, and GSTT1 gene polymorphism with risk of oral submucous fibrosis in a section of North Indian population

Genetic alterations in the genes expressing drug metabolizing enzymes can make an individual susceptible to various cancers. This study detects the polymorphisms at CYP1A1, GSTM1, and GSTT1 genes in a section of North Indian population and determines the susceptibility to oral submucous fibrosis (OSF). In this case-control study one hundred and two OSF patients were genotyped to detect the GSTM1, GSTT1, CYP1A1 polymorphism. Two hundred healthy controls were also included. Genotypes were determined using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) approach. The frequency of GSTM1 and GSTT1 genotype was higher in OSF patients, as compared to controls. A trend risk analysis showed 7.6 fold increase in risk, when both the genes were absent. The frequency of CYP1A1 (m1) and CYP1A1 (m2) genotypes was higher in controls. No polymorphic alleles were detected in the m4 site. CYP1A1 (m1) wild genotype in the absence of GSTM1 null genotype, falls under the highest risk group (OR 3.74). Our findings suggest that CYP1A1 (m1) genotype and (m2) genotype singly acts as a protective factor but in the absence of GSTM1 and/or GSTT1 gene significantly alters risk towards OSF.

A functional trinucleotide repeat polymorphism in the 5'-untranslated region of the glutathione biosynthetic gene GCLC is associated with increased risk for lung and aerodigestive tract cancers

Glutathione (GSH), the major intracellular antioxidant, protects against cancer development by detoxifying carcinogens and free radicals and strengthening the immune system. Recently, a GAG-trinucleotide repeat polymorphism in the 5'-untranslated region of the gene for the rate-limiting enzyme for GSH biosynthesis, γ-glutamine cysteine ligase (GCL), was shown to be associated with lowered GCL activity and GSH levels in vitro and in vivo. We tested the hypothesis that this functional polymorphism in GCL is associated with the risk for lung and aerodigestive tract cancers. To this end, we conducted a case-control study that included 375 lung cancer cases, 200 aerodigestive tract cancer cases, and 537 controls. GAG repeat genotype (4, 7, 8, 9, and 10 repeat alleles) was determined by capillary electrophoresis of PCR products from the repeat region of the GCL catalytic subunit (GCLC). Odds ratios (OR) were calculated by logistic regression and adjusted for risk factors, including age, sex, body mass index, and smoking history. The GAG-7/7 genotype was associated with a 1.9-fold increased risk of lung cancer and 2.6-fold increased risk of aerodigestive tract cancer compared to the wild-type GAG-9/9 (P < 0.05). Similarly, the GAG-7 allele was associated with an increased risk of lung cancer (OR = 1.5, P = 0.01) and aerodigestive tract cancer (OR = 2.3, P < 0.001) compared to subjects without GAG-7 allele. These findings suggest that GSH synthesis affects the risk of lung and aerodigestive tract cancers, and further implicates a role for oxidative stress in the development of these cancers.

Impact of the location of CpG methylation within the GSTP1 gene on its specificity as a DNA marker for hepatocellular carcinoma

Hypermethylation of the glutathione S-transferase π 1 (GSTP1) gene promoter region has been reported to be a potential biomarker to distinguish hepatocellular carcinoma (HCC) from other liver diseases. However, reports regarding how specific a marker it is have ranged from 100% to 0%. We hypothesized that, to a large extent, the variation of specificity depends on the location of the CpG sites analyzed. To test this hypothesis, we compared the methylation status of the GSTP1 promoter region of the DNA isolated from HCC, cirrhosis, hepatitis, and normal liver tissues by bisulfite-PCR sequencing. We found that the 5' region of the position -48 nt from the transcription start site of the GSTP1 gene is selectively methylated in HCC, whereas the 3' region is methylated in all liver tissues examined, including normal liver and the HCC tissue. Interestingly, when DNA derived from fetal liver and 11 nonhepatic normal tissue was also examined by bisulfite-PCR sequencing, we found that methylation of the 3' region of the promoter appeared to be liver-specific. A methylation-specific PCR assay targeting the 5' region of the promoter was developed and used to quantify the methylated GSTP1 gene in various diseased liver tissues including HCC. When we used an assay targeting the 3' region, we found that the methylation of the 5'-end of the GSTP1 promoter was significantly more specific than that of the 3'-end (97.1% vs. 60%, p<0.0001 by Fisher's exact test) for distinguishing HCC (n = 120) from hepatitis (n = 35) and cirrhosis (n = 35). Encouragingly, 33.8% of the AFP-negative HCC contained the methylated GSTP1 gene. This study clearly demonstrates the importance of the location of CpG site methylation for HCC specificity and how liver-specific DNA methylation should be considered when an epigenetic DNA marker is studied for detection of HCC.

Encapsulated nanoepigallocatechin-3-gallate and elemental selenium nanoparticles as paradigms for nanochemoprevention

Chemoprevention that impedes one or more steps in carcinogenesis, via long-term administration of naturally occurring or synthetic compounds, is widely considered to be a crucial strategy for cancer control. Selenium (Se) has chemopreventive effects, but its application is limited due to a low therapeutic index as shown in numerous animal experiments. In contrast to Se, which was known for its toxicity prior to the discovery of its beneficial effects, the natural compound epigallocatechin-3-gallate (EGCG) was originally considered to be nontoxic. Due to its preventive effects on many types of cancer in various animal models, EGCG has been regarded as a prime example of a promising chemopreventive agent without major toxicity concerns. However, very recently, evidence has accumulated showing that efficacious doses of EGCG used in health promotion may not be far from its toxic dose level. Therefore, both Se and EGCG need to be modified by novel pharmaceutical technologies to attain enhanced efficacy and/or reduced toxicity. Nanotechnology may be one of these technologies. In support of this hypothesis, the characteristics of polylactic acid and polyethylene glycol-encapsulated nano-EGCG and elemental Se nanoparticles dispersed by bovine serum albumin are reviewed in this article. Encapsulation of EGCG to form nano-EGCG leads to its enhanced stability in plasma and remarkably superior chemopreventive effects, with more than tenfold dose advantages in inducing apoptosis and inhibition of both angiogenesis and tumor growth. Se at nanoparticle size (“Nano-Se”), compared with Se compounds commonly used in dietary supplements, has significantly lower toxicity, without compromising its ability to upregulate selenoenzymes at nutritional levels and induce phase II enzymes at supranutritional levels.

Reactive oxygen/nitrogen species and their functional correlations in neurodegenerative diseases

The continuous production and efflux of reactive oxygen/nitrogen species from endogenous and exogenous sources can damage biological molecules and initiate a cascade of events. Mitochondria are pivotal in controlling cell survival and death. Cumulative oxidative stress, disrupted mitochondrial respiration, and mitochondrial damage are related with various neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease, and others. Biochemical cascades of apoptosis are mediated in signaling molecules, including protein kinases and transcription factors. The expressions in the pro-apoptotic signal transduction networks may indeed promote cell death and degeneration in brain cells. The regulation of that protein phosphorylation by kinases and phosphatases is emerging as a prerequisite mechanism in the control of the apoptotic cell death program. In this review, we attempt to put forth the evidence for possible mechanistic explanations for involvement of free radicals in the pathogenesis of neurodegenerative diseases.

Age related changes in selenium and glutathione levels in different lobes of the rat prostate

Aging represents a major risk factor for prostate cancer; however, mechanisms responsible for this relationship remain unclear. Preclinical and some clinical investigations support the protective role of selenium against prostate cancer possibly through the reduction of oxidative stress. While increased levels of oxidative stress together with decreases in selenium and the major cellular antioxidant glutathione (GSH) are common in tissues of old animals, there is little data available on these parameters in the prostate. In the present study we have compared the levels of selenium, GSH and protein-bound GSH (GSSP) in blood and prostate tissues in young (4-month), mature (12-month), old (18 month), and very old (24 month) male F344 rats. Each prostate lobe (dorsolateral, DL; anterior, AL; ventral, VL) was analyzed separately based upon their differing potential for prostate cancer development. At all ages, selenium levels were lowest in DL<VL<AL. After 12 mo, an 85% reduction in selenium in the DL was observed (P<0.05), while levels in other lobes were unchanged. In animals of all ages, levels of GSH were lowest in the VL<DL=AL and no significant changes were observed in GSH levels by 18 mo. However, GSSP, a marker of oxidative stress, was increased 90% after 18 mo in the DL only (P<0.01). These findings of age-related changes in GSSP and selenium in the DL prostate are consistent with the sensitivity of this lobe to carcinogenesis and, thus, may be playing a mechanistic role.

An activatable multimodal/multifunctional nanoprobe for direct imaging of intracellular drug delivery

Multifunctional nanoparticles integrated with imaging modalities (such as magnetic resonance and optical) and therapeutic drugs are promising candidates for future cancer diagnostics and therapy. While targeted drug delivery and imaging of tumor cells have been the major focus in engineering nanoparticle probes, no extensive efforts have been made towards developing sensing probes that can confirm and monitor intracellular drug release events. Here, we present quantum dot (Qdot)-iron oxide (IO) based multimodal/multifunctional nanocomposite probe that is optically and magnetically imageable, targetable and capable of reporting on intracellular drug release events. Specifically, the probe consists of a superparamagnetic iron oxide nanoparticle core (IONP) decorated with satellite CdS:Mn/ZnS Qdots where the Qdots themselves are further functionalized with STAT3 inhibitor (an anti-cancer agent), vitamin folate (as targeting motif) and m-polyethylene glycol (mPEG, a hydrophilic dispersing agent). The Qdot luminescence is quenched in this nanocomposite probe ("OFF" state) due to combined electron/energy transfer mediated quenching processes involving IONP, folate and STAT3 agents. Upon intracellular uptake, the probe is exposed to the cytosolic glutathione (GSH) containing environment resulting in restoration of the Qdot luminescence ("ON" state), which reports on uptake and drug release. Probe functionality was validated using fluorescence and MR measurements as well as in vitro studies using cancer cells that overexpress folate receptors.

Binding of GSH conjugates to π-GST: a cross-docking approach

The high degree of flexibility characterizing the members of the GST protein family is supposed to be an evolution-resolved feature related to the detoxifying role of these enzymes. Many evidences suggest that overexpression of these enzymes may be implicated in the development of acquired resistance to antitumor agents. Among the most effective GST inhibitors, GSH conjugates have been found to be particularly promising because of their low toxicity. Here, we used a cross docking approach based on an ensemble of X-ray structures of GST bound complexes to model the effects of protein flexibility on the binding of GSH conjugates. We showed that our multitarget approach, allows to analyze the impact of protein flexibility and induced fit effects in GSH conjugate docking to GST. Moreover, the inclusion of conserved water molecules in the model allowed to include a further source of target variability and improve the performances in the docking of GSH conjugates through an enhanced description of the GSH moiety interactions. Therefore, a map of ligand-protein interactions reflecting the target variability included in the docking model was retraced and used to gain a thorough insight about the way GSH conjugates bind to GST.

Associations differ by sex for catechol-O-methyltransferase genotypes and bladder cancer risk in South Egypt

OBJECTIVES

To examine associations between urinary bladder cancer risk and polymorphisms of the gene encoding the catechol estrogen-metabolizing enzyme, catechol-O-methyltransferase (COMT), among Egyptian women and men.

MATERIALS AND METHODS

We used questionnaire and genotype data from a case-control study in Egypt. This analysis focused on South Egypt cases with confirmed urothelial (UC) or squamous cell (SCC) carcinoma of the bladder, and controls frequency-matched on sex, 5-year age-group, and residence governorate. Real-time PCR on blood specimen DNA was used to determine COMT genotypes encoding for Val/Val, Val/Met, and Met/Met, the enzyme forms associated with high, intermediate, or low activity, respectively.

RESULTS

The study sample, which included 255 women and 666 men, consisted of 394 cases with histologically confirmed UC (225) or SCC (n = 169), and 527 controls. The odds of having either type of bladder cancer were lower among men with genotypes encoding Val/Met or Met/Met than among those with the genotype encoding Val/Val, even after adjustment for other factors, such as smoking and schistosomiasis history [adjusted odds ratio (AOR): 0.64; 95% confidence interval (CI): 0.43, 0.96]; however, the association was statistically significant for SCC (AOR 0.57; 95% CI: 0.34, 0.96) but marginal for UC (AOR: 0.64; 95% CI: 0.39, 1.02). No significant associations were detected between bladder cancer risk and COMT genotypes among postmenopausal women.

CONCLUSIONS

These findings suggest that even after controlling for established risk factors, the involvement of COMT genotypes in bladder cancer risk differs among men compared with women in South Egypt.

Chokeberry (Aronia melanocarpa) juice modulates 7,12-dimethylbenz[a]anthracene induced hepatic but not mammary gland phase I and II enzymes in female rats

Chokeberry is a rich source of procyanidins known to have several types of biological activity including anticarcinogenic potential in experimental models. In this study we examined the effect of chokeberry juice on the hepatic and mammary gland carcinogen metabolizing enzyme expression altered by the polycyclic aromatic hydrocarbon, 7,12-dimethylbenz[a]anthracene (DMBA). Sprague-Dawley rats were gavaged with chokeberry juice (8 ml/kg b.w.) for 28 consecutive days. DMBA was administered i.p. on the 27th and the 28th days. Pretreatment with chokeberry juice reduced the activity of CYP1A1 and increased that of CYP2B involved in metabolic activation/detoxication of DMBA in rat liver, as well as expression and activity of phase II enzymes. Chokeberry juice had no effect on these parameters in the mammary gland and DMBA induced DNA damage in rat blood cells. These results together with our earlier observations indicate that metabolic alterations induced by chokeberry feeding are tissue specific and depend on the class of carcinogen.

Hesperidin, a flavanone glycoside, on lipid peroxidation and antioxidant status in experimental myocardial ischemic rats

Myocardial infarction continues to be a leading cause of mortality world-wide. Novel therapies are needed to treat the myocardial ischemia. This study was undertaken to evaluate the cardioprotective role of hesperidin on isoproterenol-induced myocardial ischemia in rats. Myocardial ischemia was induced by subcutaneous injection of isoproterenol hydrochloride (85 mg/kg body weight), for two consecutive days. Isoproterenol-administered rats showed elevated levels of cardiac markers (aspartate transaminase, alanine transaminase, lactate dehydrogenase, creatine kinase, creatine kinase-MB, cardiac troponins T and I) when compared with control and hesperidin treatment groups (100, 200 and 400 mg/kg body weight). The serum levels of cardiac markers were significantly reduced at the doses of 200 mg and 400 mg. All further experiments were carried out at the 200 mg dose. Lipid peroxidation markers (thiobarbituric acid reactive substances, lipid hydroperoxides and conjugated dienes) were elevated significantly in the plasma and heart whereas non-enzymic antioxidants (vitamin C, vitamin E and reduced glutathione) were decreased significantly. Activities of superoxide dismutase, catalase, glutathione peroxidase, glutathione-S-transferase and glutathione reductase declined significantly in the heart of ischemic rats. However, after hesperidin treatment, all the above parameters reverted to normal levels. This study demonstrated that the cardioprotective effect of hesperidin on ischemic rats could be due to its anti-lipid peroxidative and antioxidant properties.

Retinoic acid stimulation of VEGF secretion from human endometrial stromal cells is mediated by production of reactive oxygen species

It is widely accepted that vascular endothelial growth factor (VEGF) is involved in angiogenic functions that are necessary for successful embryonic implantation. We have shown that retinoic acid (RA), which is known to play a necessary role in early events in pregnancy, can combine with transcriptional activators of VEGF (e.g. TPA, TGF-β, IL-1β) to rapidly induce VEGF secretion from human endometrial stromal cells through a translational mechanism of action. We have now determined that this stimulation of VEGF by RA is mediated through an increased production of cellular reactive oxygen species (ROS). Results indicated that RA, but not TPA or TGF-β, directly increases ROS production in endometrial stromal cells and that the co-stimulating activity of RA on VEGF secretion can be mimicked by direct addition of H2O2. Importantly, co-treatment of RA with TPA or TGF-β further stimulated ROS production in a fashion that positively correlated with levels of VEGF secretion. The antioxidants N-acetylcysteine and glutathione monoethyl ester inhibited both RA + TPA and RA + TGF-β-stimulated secretion of VEGF, as well as RA-induced ROS production. Treatment of cells with RA resulted in a shift in the glutathione (GSH) redox potential to a more oxidative state, suggesting that the transduction pathway leading to increased VEGF secretion is at least partially mediated through the antioxidant capacity of GSH couples. The specificity of this action on GSH-sensitive signalling pathways is suggested by the determination that RA had no effect on the redox potential of thioredoxin. Together, these findings predict a redox-mediated mechanism for retinoid regulation of localized VEGF secretion in the human endometrium that may be necessary for the successful establishment of pregnancy.