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The effects of organophosphate exposure on Seratonergic system
Abstracts / Toxicology Letters 189S (2009) S57–S273
Z05 The effects of organophosphate exposure on Seratonergic system Shadia Ramadan 1,2,∗ , Chris Morris 2 , John Harris 2 1
Faculty of Veterinary Medicine, Pharmacology and Toxicology, Tripoli, Libyan Arab Jamahiriya, 2 Newcastle University, Toxicology, Newcastle, United Kingdom Organophosphates (OPs) are amongst the most commonly used pesticides, both in agriculture and in the domestic setting. Whilst high level exposure to these compounds has long been associated with systemic toxicity due to acetylcholinesterase inhibition, environmental exposure to low levels of OPs has been suggested to be linked to an increased risk of psychiatric morbidity such as depression, anxiety and suicidal thoughts. Depression and other mood disorders have been associated with alterations in brain monoamine levels. This study aims to investigate whether subtoxic exposure to the OP diazinon could contribute to alterations of the monoamine-ergic systems, which would correlate with the psychiatric and cognitive dysfunctions observed in exposed individuals. Following exposure of rats to the OP diazinon, blood and brain cholinesterase activity was monitored based on a modified Ellman’s assay. Serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and creatine kinase (CK) were assessed to identify whether given doses of diazinon induced systemic toxicity. Serotonin (5-HT) and 5-hydroxyindol acetic acid (5-HIAA) were estimated using High Performance Liquid Chromatography (HPLC). 5-HT turnover was also measured as metabolite ratio. The results showed there was little or no effects on blood or brain cholinesterase activity, and no systemic toxicity. Exposure however induced significant alterations in brain monoamines. Cortical levels of 5-HT and 5-HIAA showed significant reductions. Hippocampal 5HT levels were also significantly decrease and hippocampal 5-HT turnover was also significantly elevated. There was no significant recovery in 5-HT, 5-HIAA and turnover 5 days after cessation of diazinon administration. These results suggest that low level exposure to diazinon in the absence of cholinesterase inhibition can lead to alterations of brain monoamines, which may be associated with psychiatric and cognitive problems in exposed individuals. doi:10.1016/j.toxlet.2009.06.540
S209
treatment against organophosphate intoxication (Bajgar, 2004). The pretreatment is based on competitive inhibition of AChE prior to organophosphate (OP) poisoning. Consequently, the OP cannot influence the inhibited AChE and is degraded by other esterases. Although various competitive inhibitors are used globally, pyridostigmine still remains the most broaden. Its side effects including gastrointestinal effects (nausea, intestinal obstruction), increased bronchial secretion, cardiac arrhythmia or cholinergic crisis are well described. Moreover, some bisquaternary competitive inhibitors (e.g. SAD-128) were used to decrease lethal effects of OP poisoning in vivo. The further studies dealing with SAD-128 showed its increased ability to interact with brain muscarinic acetylcholine receptors as allosteric inhibitors (Kloog, 1985). On the other hand, pyridostigmine bromide, neostigmine bromide or ambenonium dichloride are used for early Myasthenia gravis treatment (Garcia-Carrasco et al., 2007). Their peripheral effect allows sufficient quantity of acetylcholine available for decreasing amount of AChE receptors. However, the side effect remains the same. The small molecules derived from quaternized pyridine, quinoline and isoquinoline were designed as AChE inhibitors. Their ability to inhibit AChE or BChE was determined in vitro using IC50 . The IC50 data were compared within each group of compounds with emphasis on selectivity AChE versus BChE. The overall study will be presented. Acknowledgement: The work was supported by Grant Agency of Czech Republic No. 203/09/P130.
References Bajgar, 2004. J. Adv. Clin. Chem. 38, 151. Kloog, Y., 1985. Mol. Pharmacol. 27, 418. Garcia-Carrasco, M., et al., 2007. Autoimmun. Rev. 6, 373.
夽 Selected for Oral Presentation. doi:10.1016/j.toxlet.2009.06.541
Z07 Retrospective evaluation of Acute Reference Doses (ARfD) for 夽 pesticides in the European Union Tomas Moeller ∗ , Bernd Stein, Roland Solecki Federal Institute for Risk Assessment, 62, Berlin, Germany
Z06 Small quaternary AChE inhibitors—Implication for pretreat夽 ment of OP poisoning or MG treatment Kamil Musilek 1,2,∗ , Marketa Komloova 3 , Ondrej Holas 3 , Miroslav Pohanka 4 , Veronika Opletalova 3 , Martin Dolezal 3 , Kamil Kuca 4 1
Faculty of Military Health Sciences, University of Defence, Department of Toxicology, Hradec Kralove, Czech Republic, 2 Faculty of Science, University of Jan Evangelista Purkyne, Department of Chemistry, Usti nad Labem, Czech Republic, 3 Faculty of Pharmacy in Hradec Kralove, Charles University in Prague, Department of Pharmaceutical Chemistry and Drug Control, Hradec Kralove, Czech Republic, 4 Faculty of Military Health Sciences, University of Defence, Centre of Advanced Studies, Hradec Kralove, Czech Republic Small quaternary acetylcholinesterase (AChE) inhibitors are used (e.g. pyridostigmine bromide) or scoped (e.g. SAD-128) for pre-
A WHO-analysis of ARfD values in 2002 indicated large differences between regulatory bodies. In the mean time the regulatory authorities made more comprehensive experiences with the ARfD derivation. In 2007 OECD decided to develop a new guidance for the ARfD derivation and for the design of a single exposure study if additional data are needed as basis for the ARfD. Therefore, it was necessary to perform a new retrospective analysis in order to identify the toxicological studies on which the ARfD values are based up till now and to estimate how often additional single exposure tests may be needed. The current retrospective analysis was based on data of active pesticide substances which have been included in Annex I of EU directive 91/414/EEC and which have been published by the European Food Safety Authority (EFSA). In result of this analysis it was shown that so far only in few cases (4%) single exposure ARfD-studies have been used for the derivation of the ARfD. These special acute studies do not belong to the basic requirements and agreed guidance does not exist. Therefore,
Z05 The effects of organophosphate exposure on Seratonergic system Shadia Ramadan 1,2,∗ , Chris Morris 2 , John Harris 2 1
Faculty of Veterinary Medicine, Pharmacology and Toxicology, Tripoli, Libyan Arab Jamahiriya, 2 Newcastle University, Toxicology, Newcastle, United Kingdom Organophosphates (OPs) are amongst the most commonly used pesticides, both in agriculture and in the domestic setting. Whilst high level exposure to these compounds has long been associated with systemic toxicity due to acetylcholinesterase inhibition, environmental exposure to low levels of OPs has been suggested to be linked to an increased risk of psychiatric morbidity such as depression, anxiety and suicidal thoughts. Depression and other mood disorders have been associated with alterations in brain monoamine levels. This study aims to investigate whether subtoxic exposure to the OP diazinon could contribute to alterations of the monoamine-ergic systems, which would correlate with the psychiatric and cognitive dysfunctions observed in exposed individuals. Following exposure of rats to the OP diazinon, blood and brain cholinesterase activity was monitored based on a modified Ellman’s assay. Serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and creatine kinase (CK) were assessed to identify whether given doses of diazinon induced systemic toxicity. Serotonin (5-HT) and 5-hydroxyindol acetic acid (5-HIAA) were estimated using High Performance Liquid Chromatography (HPLC). 5-HT turnover was also measured as metabolite ratio. The results showed there was little or no effects on blood or brain cholinesterase activity, and no systemic toxicity. Exposure however induced significant alterations in brain monoamines. Cortical levels of 5-HT and 5-HIAA showed significant reductions. Hippocampal 5HT levels were also significantly decrease and hippocampal 5-HT turnover was also significantly elevated. There was no significant recovery in 5-HT, 5-HIAA and turnover 5 days after cessation of diazinon administration. These results suggest that low level exposure to diazinon in the absence of cholinesterase inhibition can lead to alterations of brain monoamines, which may be associated with psychiatric and cognitive problems in exposed individuals. doi:10.1016/j.toxlet.2009.06.540
S209
treatment against organophosphate intoxication (Bajgar, 2004). The pretreatment is based on competitive inhibition of AChE prior to organophosphate (OP) poisoning. Consequently, the OP cannot influence the inhibited AChE and is degraded by other esterases. Although various competitive inhibitors are used globally, pyridostigmine still remains the most broaden. Its side effects including gastrointestinal effects (nausea, intestinal obstruction), increased bronchial secretion, cardiac arrhythmia or cholinergic crisis are well described. Moreover, some bisquaternary competitive inhibitors (e.g. SAD-128) were used to decrease lethal effects of OP poisoning in vivo. The further studies dealing with SAD-128 showed its increased ability to interact with brain muscarinic acetylcholine receptors as allosteric inhibitors (Kloog, 1985). On the other hand, pyridostigmine bromide, neostigmine bromide or ambenonium dichloride are used for early Myasthenia gravis treatment (Garcia-Carrasco et al., 2007). Their peripheral effect allows sufficient quantity of acetylcholine available for decreasing amount of AChE receptors. However, the side effect remains the same. The small molecules derived from quaternized pyridine, quinoline and isoquinoline were designed as AChE inhibitors. Their ability to inhibit AChE or BChE was determined in vitro using IC50 . The IC50 data were compared within each group of compounds with emphasis on selectivity AChE versus BChE. The overall study will be presented. Acknowledgement: The work was supported by Grant Agency of Czech Republic No. 203/09/P130.
References Bajgar, 2004. J. Adv. Clin. Chem. 38, 151. Kloog, Y., 1985. Mol. Pharmacol. 27, 418. Garcia-Carrasco, M., et al., 2007. Autoimmun. Rev. 6, 373.
夽 Selected for Oral Presentation. doi:10.1016/j.toxlet.2009.06.541
Z07 Retrospective evaluation of Acute Reference Doses (ARfD) for 夽 pesticides in the European Union Tomas Moeller ∗ , Bernd Stein, Roland Solecki Federal Institute for Risk Assessment, 62, Berlin, Germany
Z06 Small quaternary AChE inhibitors—Implication for pretreat夽 ment of OP poisoning or MG treatment Kamil Musilek 1,2,∗ , Marketa Komloova 3 , Ondrej Holas 3 , Miroslav Pohanka 4 , Veronika Opletalova 3 , Martin Dolezal 3 , Kamil Kuca 4 1
Faculty of Military Health Sciences, University of Defence, Department of Toxicology, Hradec Kralove, Czech Republic, 2 Faculty of Science, University of Jan Evangelista Purkyne, Department of Chemistry, Usti nad Labem, Czech Republic, 3 Faculty of Pharmacy in Hradec Kralove, Charles University in Prague, Department of Pharmaceutical Chemistry and Drug Control, Hradec Kralove, Czech Republic, 4 Faculty of Military Health Sciences, University of Defence, Centre of Advanced Studies, Hradec Kralove, Czech Republic Small quaternary acetylcholinesterase (AChE) inhibitors are used (e.g. pyridostigmine bromide) or scoped (e.g. SAD-128) for pre-
A WHO-analysis of ARfD values in 2002 indicated large differences between regulatory bodies. In the mean time the regulatory authorities made more comprehensive experiences with the ARfD derivation. In 2007 OECD decided to develop a new guidance for the ARfD derivation and for the design of a single exposure study if additional data are needed as basis for the ARfD. Therefore, it was necessary to perform a new retrospective analysis in order to identify the toxicological studies on which the ARfD values are based up till now and to estimate how often additional single exposure tests may be needed. The current retrospective analysis was based on data of active pesticide substances which have been included in Annex I of EU directive 91/414/EEC and which have been published by the European Food Safety Authority (EFSA). In result of this analysis it was shown that so far only in few cases (4%) single exposure ARfD-studies have been used for the derivation of the ARfD. These special acute studies do not belong to the basic requirements and agreed guidance does not exist. Therefore,