Measurement of oxidative stress markers in rat tissues and blood after long term administration of a mixture of pesticides and food preservatives of low doses explosure

Long-term exposure of humans to xenobiotics increases the risk of the onset of various diseases. Numerous studies have investigated the effects of long-term low-dose exposure regimen to individual xenobiotics on the redox profile of various organisms. However, the approach of the present study according to which the effects of long-term low-dose exposure regimen to mixtures of xenobiotics on redox profile need to be examined is pioneering. This study approached the so-called real-life risk simulation . Thus, the aim of the study was to evaluate the effect of a mixture of xenobiotics that was administered long-term in doses much lower than NOAEL on rats. For this purpose, 40 rats were exposed for 18 months to a mixture of 13 chemicals (carbaryl, dimethoate, glyphosate, methomyl, methyl parathion, triadimefon, aspartame, sodium benzoate, calcium disodium ethylene diamine tetra-acetate, ethylparaben, butylparaben, bisphenol A, and acacia gum) in 3 dose levels (low, medium high). At 6, 12 and 18 months, several redox biomarkers were measured in blood, while at 18 months both in blood and the rat tissues. According to the results, the exposure for 6 and 12 months to all 3 doses and for 18 months to low and medium dose induced useful physiological adaptations enhancing the antioxidant arsenal of the animals. In contrast, exposure to the high dose of the mixture for 18 months caused a significant disruption in the redox equilibrium of blood and tissues inducing oxidative stress. The adoption of similar approaches will strongly contribute to the assessment of anthropogenic and environmental risks in our modern world and will drive regulatory authorities and organizations to the re-evaluation of safety assessment testing and establishing future safety norms both for hazard and risk assessment.Η μακροχρόνια έκθεση του ανθρώπου σε ξενοβιοτικές ουσίες επιφέρει αυξημένο κίνδυνο εμφάνισης διαφόρων νόσων. Πολλές έρευνες έχουν πραγματοποιηθεί για τη μελέτη της επίδρασης της μακροχρόνιας έκθεσης μεμονωμένων χημικών ουσιών σε χαμηλές δόσεις στην οξειδοαναγωγική κατάσταση διαφόρων οργανισμών. Η ιδέα της χορήγησης ενός μείγματος χημικών ουσιώνσε δόσεις μικρότερες του NOAEL (No observed adverse effect level) που παρουσιάζεται στην πειραματική αυτή μελέτη είναι πρωτοποριακή. Με τη μελέτη αυτή προσεγγίστηκε η προσομοίωση κινδύνου σε ρεαλιστικά σενάρια (real-life risk simulation). Σκοπός της παρούσας διατριβής ήταν να αξιολογηθεί η επίδραση που έχει ένα μείγμα ξενοβιοτικών ουσιών που χορηγήθηκε για μεγάλο χρονικό διάστημα σε συγκεντρώσεις χαμηλότερες από το NOAEL, στο οξειδοαναγωγικό προφίλ επιμύων. Για το σκοπό αυτό χρησιμοποιήθηκαν 40 επίμυες στους οποίους χορηγήθηκε για 18 μήνες, μείγμα 13 χημικών ουσιών (καρβαρύλιο, διμεθοϊκό, γλυφοσικό, μεθομυλεστέρας, μεθυλοπαραθείον, τριαδιμεθόνη, ασπαρτάμη, βενζοϊκό νάτριο, τετραοξικό δινάτριο αιθυλενοδιαμίνης (EDTA), αιθυλοπαραβένιο, βουτυλοπαραβένιο, διφαινόλη Α και αραβικό κόμμι) σε 3 δόσεις (μικρή, μεσαία, μεγάλη).Στους 6, 12 και 18 μήνες πραγματοποιήθηκε μέτρηση βιοδεικτών οξειδοαναγωγής στο αίμα ενώ στους 18 μήνες και στους ιστούς των ζώων. Σύμφωνα με τα αποτελέσματα των βιοδεικτών του αίματος στους 6 και 12 μήνες η έκθεση στη μικρή συγκέντρωση του μείγματος και στους 18 μήνες στη μικρή και στη μεσαία συγκέντρωση προκάλεσε φυσιολογικές προσαρμογές, ενισχύοντας τον αντιοξειδωτικό μηχανισμό. Αντίθετα, η έκθεση στο μείγμα στη μεγαλύτερη δόση στους 18 μήνες προκάλεσε σημαντική διαταραχή στην οξειδοαναγωγική ισορροπία του αίματος και των ιστών, επομένως οξειδωτικό στρες. Η εργασία αυτή καταδεικνύει ότι η χρόνια χορήγηση ξενοβιοτικών που εκτίθεται ο άνθρωπος στην καθημερινότητά του, ακόμα και σε πολύ μικρές συγκεντρώσεις προκαλεί οξειδωτικό στρες. Επομένως, με βάση τα δεδομένα αυτής αλλά και άλλων παρόμοιων μελετών προκύπτει ότι ίσως θα πρέπει να επανεξεταστούν οι διαδικασίες κατά τις οποίες ορίζονται οι επιβλαβείς και οι ακίνδυνες δόσεις διαφόρων ξενοβιοτικών για τον άνθρωπο

A mixture of routinely encountered xenobiotics induces both redox adaptations and perturbations in blood and tissues of rats after a long-term low-dose exposure regimen: The time and dose issue

Exposure of humans to xenobiotic mixtures is a continuous state during their everyday routine. However, the majority of toxicological studies assess the in vivo effects of individual substances rather than mixtures. Therefore, our main objective was to evaluate the impact of the 12- and 18-month exposure of rats to a mixture containing 13 pesticides, food, and life-style additives in three dosage levels (i.e. 0.0025 × NOAEL, 0.01 × NOAEL, and 0.05 × NOAEL), on redox biomarkers in blood and tissues. Our results indicate that the exposure to the mixture induces physiological adaptations by enhancing the blood antioxidant mechanism (i.e., increased glutathione, catalase and total antioxidant capacity and decreased protein carbonyls and TBARS) at 12 months of exposure. On the contrary, exposure to the 0.05 × NOAEL dose for 18 months induces significant perturbations in blood and tissue redox profile (i.e., increased carbonyls and TBARS). This study simulates a scenario of real-life risk exposure to mixtures of xenobiotics through a long-term low-dose administration regimen in rats. The results obtained could support, at least in part, the necessity of introducing testing of combined stimuli at reference doses and long term for the evaluation of the risk from exposure to chemicals. © 2019 Elsevier B.V

Six months exposure to a real life mixture of 13 chemicals' below individual NOAELs induced non monotonic sex-dependent biochemical and redox status changes in rats

This study assessed the potential adverse health effects of long-term low-dose exposure to chemical mixtures simulating complex real-life human exposures. Four groups of Sprague Dawley rats were administered mixtures containing carbaryl, dimethoate, glyphosate, methomyl, methyl parathion, triadimefon, aspartame, sodium benzoate, calcium disodium ethylene diamine tetra-acetate, ethylparaben, butylparaben, bisphenol A, and acacia gum at doses of 0, 0.25, 1 or 5 times the respective Toxicological Reference Values (TRV): acceptable daily intake (ADI) or tolerable daily intake (TDI) in a 24 weeks toxicity study. Body weight gain, feed and water consumption were evaluated weekly. At 24 weeks blood was collected and biochemistry parameters and redox status markers were assessed. Adverse effects were observed on body weight gain and in hepatotoxic parameters such as the total bilirubin, alanine aminotransferase (ALT) and alkaline phosphatase (ALP), especially in low dose and affecting mainly male rats. The low dose group showed increased catalase activity both in females and males, whereas the high dose group exhibited decreased protein carbonyl and total antioxidant capacity (TAC) levels in both sex groups. Non-monotonic effects and adaptive responses on liver function tests and redox status, leading to non-linear dose-responses curves, are probably produced by modulation of different mechanisms. © 2018 Elsevier Lt

PCR assays for the identification of rare recombination types from VP1 to 3D genomic region of vaccine derived poliovirus strains

Poliomyelitis has been effectively controlled by the use of inactivated poliovirus vaccine (IPV) or trivalent live attenuated oral poliovirus vaccine (OPV). Since 1964, the use of OPV in mass vaccinations has resulted in drastic reductions of the number of poliomyelitis cases caused by wild-type polioviruses. However, the characterization of OPV derivatives with increased neurovirulence, constituted a real problem with respect to OPV safety. Mutations at attenuating sites of the genome and recombination events between Sabin strains of the trivalent OPV vaccine have been correlated with the loss of the attenuated phenotype of OPV strains and the acquisition of traits characteristic of wild polioviruses. In consequence, early detection and characterization of recombinant evolved derivatives of vaccine strains is highly important. In this report, ten PCR assays are described which allow for the identification of rare recombination events located in VP1, 2A, 2C, 3A, 3C and 3D genomic regions and predominant recombination events located in 2C and 3D genomic regions of OPV derivatives. These assays could be readily implemented in diagnostics laboratories lacking sequencing facilities as a first approach for the early detection and characterization of recombinant OPV derivatives. (c) 2013 Elsevier Ltd. All rights reserved