Gender-Dependent Mechanisms of Alpha-Tocopherol Protection from Benzo[a]pyrene Exposure in Rats

Polycyclic aromatic hydrocarbons (PAHs), including benzo[a]pyrene (BP), are environmental pollutants linked to increased disease susceptibilities. Alpha-Tocopherol (aT) supplementation decreases BP-DNA adducts in smokers, particularly women; but the mechanism is unknown. To test the hypothesis that aT protection from BP exposure is gender-dependent, male and female rats received 7 daily subcutaneous (SQ) injections of aT (100 mg aT/ kg body wt) or vehicle, followed by a single ip injection of BP (20 mg/kg, spiked with 3H-BP) on day 9. Urine and bile were collected pre- and post-BP. Plasma and tissues were collected 5 or 24 hr post-BP. aT supplementation increased aT levels in females greater than males. Compared to vehicle, aT supplementation increased total urinary and biliary excretion of BP and/or BP metabolites more than 2.5-fold in females, but decreased total BP and/or BP metabolite excretion in males (p<0.05). SQ aT prevented BP-induced increases in urine 8-isoprostanes (males) and decreased tissue malondialdehyde levels in a tissue- and gender-dependent manner. These data are the first to suggest that aT protection from BP exposure is gender-dependent and occurs by both antioxidant and non-antioxidant mechanisms. Further elucidation of the mechanism(s) of aT protection against PAHs may lead to the development of novel protective strategies for occupational PAH exposures.Thesis poster fair presentation.Keywords: Xenobiotic, Polycyclic aromatic hydrocarbon, Benzo[a]pyrene, Alph-tocopherol, Vitamin E, Gende

Altered expression of thioredoxin reductase-1 in dysplastic bile ducts and cholangiocarcinoma in a hamster model

Thioredoxin reductase 1 (TrxR) is a homodimeric selenoenzyme catalyzing thioredoxin (Trx) in an NADPH-dependent manner. With regard to carcinogenesis, these redox proteins have been implicated in cell proliferation, transformation and anti-apoptosis. In the present study, using a hamster cholangiocarcinoma (ChC) model, we evaluated the immunohistochemical expression pattern of TrxR in precancerous lesions and ChCs as well as in normal bile ducts. The goal of this study was to determine the potential role and importance of TrxR in cholangiocarcinogenesis. For the ChC model, we obtained liver tissue specimens with dysplastic bile ducts prior to the development of ChC 8 weeks after initiation of the experiment and ChC samples at 27 weeks. The immunohistochemical analysis showed diffuse cytoplasmic overexpression of TrxR in the dysplastic bile duct epithelial cells as well as in cholangiocarcinoma; this was comparable to the negative or weakly positive in normal and type 1 hyperplastic bile ducts. However, TrxR appeared to be considerably down-regulated in the ChCs when compared to the higher expression observed in the dysplastic bile ducts. Therefore, these results suggest that TrxR overexpression followed by down-regulation might be an important event in cholangiocarcinogenesis, especially at early stages including the cellular transformation of candidate bile ducts. Further studies are however required to determine whether TrxR may be a potential target molecule for chemoprevention against cholangiocarcinogenesis. In addition, the molecular mechanism as well as the importance of the loss of TrxR in the development of cholangiocarcinoma, following dysplastic transformation of bile duct cells, also remains to be clarified

Discovery of anti-cancer activity for benzo[1,2,4]triazin-7-ones : very strong correlation to pleurotin and thioredoxin reductase inhibition

The thioredoxin (Trx)-thioredoxin reductase (TrxR) system plays a key role in maintaining the cellular redox balance with Trx being over-expressed in a number of cancers. Inhibition of TrxR is an important strategy for anti-cancer drug discovery. The natural product pleurotin is a well-known irreversible inhibitor of TrxR. The cytotoxicity data for benzo[1,2,4]triazin-7-ones showed very strong correlation (Pearson correlation coefficients ~0.8) to pleurotin using National Cancer Institute COMPARE analysis. A new 3-CF3 substituted benzo[1,2,4]triazin-7-one gave submicromolar inhibition of TrxR, although the parent compound 1,3-diphenylbenzo[1,2,4]triazin-7-one was more cytotoxic against cancer cell lines. Benzo[1,2,4]triazin-7-ones exhibited different types of reversible inhibition of TrxR, and cyclic voltammetry showed characteristic quasi-reversible redox processes. Cell viability studies indicated strong dependence of cytotoxicity on substitution at the 6-position of the 1,3-diphenylbenzo[1,2,4]triazin-7-one ring.F.A. thanks the Irish Research Council (IRC) for a Government of Ireland Postgraduate Scholarship for Martin Sweeney and College of Science, National University of Ireland Galway (NUI Galway) for a postgraduate scholarship for Robert Coyle. We thank the National Cancer Institute (USA), Development Therapeutic Program for providing us with a small quantity of pleurotin. P.A.K. thanks the Cyprus Research Promotion Foundation [Grants: NEAYPODOMH/NEKYP/0308/02 and YGEIA/BIOS/0308(BIE)/13], the University of Cyprus (Medium Sized Grant), and the following organizations in Cyprus for generous donations of chemicals and glassware: the State General Laboratory, the Agricultural Research Institute, the Ministry of Agriculture, Medochemie Ltd and Biotronics Ltd. Furthermore, P.A.K. thanks the A. G. Leventis Foundation for helping to establish the NMR facility in the University of Cyprus.2018-05-3

Role of Glutathione Redox State in Oxygen Sensing by Carotid Body Chemoreceptor Cells

Producción CientíficaThis article first presents some basic structural traits of the carotid body (CB) arterial chemoreceptors to understand the relationship between the arterial blood PO2 and the activation of chemoreceptor cells, which are the O2 sensing structures of the CB. Some considerations in relation to the intensity of CB blood flow and O2 consumption of the organ would allow us to define the threshold for the detection of the hypoxic stimulus, which would lead us to the cardinal theme of the article, namely whether at the PO2 levels detected by the CB there alterations in the genesis of re-active oxygen species (ROS). An alteration in the rate of ROS productionwould impinge on the glutathione system [reduced glutathione (GSH) and oxidized glutathione (GSSG)], causing modifications in the GSH/GSSG ratio that are detected by direct measurement; the GSH/GSSG system rep-resents the quantitatively most important mechanism to dispose ROS and to maintain the overall redox status or redox environment in mammalian cells.1 The relationship between GSH/GSSG and oxygen chemoreception is approached from two different points of view. We will measure GSH/GSSG levels and calculate the redox environment of the cells and correl-ation with the activity of chemoreceptor cells in normoxia and in hypoxia. We will also present data on pharmacological manipulation of the redox environment of the cells, as assessed by GSH/GSSG quotients, and pos-sible correlations with the level of activity of chemoreceptor cells. The possible mechanisms of coupling between ROS and the GSH/GSSG system to the cellular effector machineries have been reviewed.2,

Interactions between genes involved in the antioxidant defence system and breast cancer risk

The aim of the study is to examine the association between multilocus genotypes across 10 genes encoding proteins in the antioxidant defence system and breast cancer. The 10 genes are SOD1, SOD2, GPX1, GPX4, GSR, CAT, TXN, TXN2, TXNRD1 and TXNRD2. In all, 2271 cases and 2280 controls were used to examine gene–gene interactions between 52 single nucleotide polymorphisms (SNPs) that are hypothesised to tag all common variants in the 10 genes. The statistical analysis is based on three methods: unconditional logistic regression, multifactor dimensionality reduction and hierarchical cluster analysis. We examined all two- and three-way combinations with unconditional logistic regression and multifactor dimensionality reduction, and used a global approach with all SNPs in the hierarchical cluster analysis. Single-locus studies of an association of genetic variants in the antioxidant defence genes and breast cancer have been contradictory and inconclusive. It is the first time, to our knowledge, the association between multilocus genotypes across genes coding for antioxidant defence enzymes and breast cancer is investigated. We found no evidence of an association with breast cancer with our multilocus approach. The search for two-way interactions gave experiment-wise significance levels of P=0.24 (TXN [t2715c] and TXNRD2 [g23524a]) and P=0.58 (GSR [c39396t] and TXNRD2 [a442g]), for the unconditional logistic regression and multifactor dimensionality reduction, respectively. The experiment-wise significance levels for the three-way interactions were P=0.94 (GPX4 [t2572c], TXN [t2715c] and TXNRD2 [g23524a]) and P=0.29 (GSR [c39396t], TXN [t2715c] and TXNRD2 [a442g]) for the unconditional logistic regression and multifactor dimensionality reduction, respectively. In the hierarchical cluster analysis neither the average across four rounds with replacement of missing values at random (P=0.12) nor a fifth round with more balanced proportion of missing values between cases and controls (P=0.17) was significant

Sulforaphane Potentiates RNA Damage Induced by Different Xenobiotics

Background: The isothiocyanate sulforaphane (SFN) possesses interesting anticancer activities. However, recent studies reported that SFN promotes the formation of reactive oxygen species (ROS) as well as DNA breakage. Methodology/Principal Findings: We investigated whether SFN is able to damage RNA, whose loss of integrity was demonstrated in different chronic diseases. Considering the ability of SFN to protect from genotoxicity, we also examined whether SFN is able to protect from RNA damage induced by different chemicals (doxorubicin, spermine, S-nitroso-Nacetylpenicillamine, H2O2). We observed that SFN was devoid of either RNA damaging and RNA protective activity in human leukemic cells. It was able to potentiate the RNA damage by doxorubicin and spermine. In the first case, the effect was attributable to its ability of modulating the bioreductive activation of doxorubicin. For spermine, the effects were mainly due to its modulation of ROS levels produced by spermine metabolism. As to the cytotoxic relevance of the RNA damage, we found that the treatment of cells with a mixture of spermine or doxorubicin plus SFN increased their proapoptotic potential. Thus it is conceivable that the presence of RNA damage might concur to the overall toxic response induced by a chemical agent in targeted cells. Conclusions/Significance: Since RNA is emerging as a potential target for anticancer drugs, its ability to enhance spermineand doxorubicin-induced RNA damage and cytotoxicity could represent an additional mechanism for the potentiatin