Enhanced degradation of pesticide dichlorophen by laccase

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Enhanced degradation of pesticide dichlorophen by laccase immobilized on nanoporous materials: a cytotoxic and molecular simulation investigation Abraham Vidal, Patricia Concepción García-Suárez, Evarista Arellano-García, Oscar Edel Contreras, and Sergio Aguila Bioconjugate Chem., Just Accepted Manuscript • DOI: 10.1021/acs.bioconjchem.7b00739 • Publication Date (Web): 16 Jan 2018 Downloaded from http://pubs.acs.org on January 19, 2018

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Bioconjugate Chemistry is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

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Bioconjugate Chemistry

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Enhanced degradation of pesticide dichlorophen by laccase immobilized on

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nanoporous materials: a cytotoxic and molecular simulation investigation

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Abraham Vidal-Limon† ; Patricia Concepción García Suárez†‡ ; Evarista ArellanoGarcía‡; Oscar E. Contreras†; Sergio A. Aguila† *

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†Centro de Nanociencias y Nanotecnologia, Universidad Nacional Autonoma de

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Mexico, km. 107 Carretera Tijuana-Ensenada, Pedregal Playitas, PO. 22860 Ensenada,

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Baja California, Mexico.

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‡Universidad Autonoma de Baja California, km. 105 Carretera Tijuana-Ensenada,

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Pedregal Playitas, PO. 22860. Ensenada, Baja California, Mexico.

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[email protected]

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[email protected]

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[email protected]

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[email protected]

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[email protected] *

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Highlights •

dichlorophen.

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A reduction on apoptotic, cytotoxic and genotoxic effects were found after treatment of dichlorophen with laccase-MSU-F.

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A hybrid nanomaterial (laccase-MSU-F) readily oxidizes organochlorine pesticide



Theoretical affinity of oxidized sub-products of dichlorophen was reduced on human steroid hormone nuclear receptors after laccase-MSU-F treatment.

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Abstract

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Use of pesticides is usually related to over-production of crops in order to overcome

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worldwide demand of food and alimentary safety. Nevertheless, pesticides are

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environmental persistent molecules, such as the organochlorine pesticides, which are

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often found in undesired places. In this work, we show that a hybrid nanomaterial

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(laccase – MSU-F) readily oxidizes the pesticide dichlorophen, reducing its acute

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genotoxicity and apoptotic effects. In order to predict chronic alterations related to

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endocrine disruption, we compared the calculated affinity of dichlorophen oxidized sub-

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products to steroid hormone nuclear receptors (NRs), using molecular simulation

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methods. We found a reduction in theoretical affinity of sub-products of oxidized

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dichlorophen for the ligand-binding pocket of NRs (~5 Kcal/mol) likewise of changes in

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binding modes that suggest a reduction in binding events (RMSD values < 10 Å).

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Keywords: Dichlorophen; laccase; molecular dynamics; MSU-F; Nanomaterials.

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Abbreviations

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CP, chlorophen.

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DCP, dichlorophen.

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DDT, dichlorodiphenyltrichloroethane..

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FEB, free energy of binding.

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oxDCP, laccase-oxidized dichlorophen.

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MD, molecular dynamics.

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MSU-F, mesoporous synthetic silica foam.

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NR, steroid hormone nuclear receptors.

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RMSD, root mean square deviation.

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Bioconjugate Chemistry

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Introduction

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Worldwide use of pesticides has drastically risen during the last 60 years, with a 15-20-

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fold increase related to agricultural and public health control areas

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pesticides are known to be persistent compounds, which often appear in undesired

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places (groundwater, agricultural soils or accumulated in trophic networks) 3. Exposure

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to organochlorines, among many others pesticides, has toxic effects on human health

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(Food and Environment Protection Act, 1985), from intense acute responses such as

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eye or skin irritation, and allergic sensitization

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disruption of endocrine hormone physiology or reproductive abnormalities

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1,2

. However,

to chronic immune suppression, 7–10

. At

11–13

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cellular scale, diverse injuries have been reported after pesticide exposure

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nuclear abnormalities, induction of pro-apoptotic signaling, high mutagenic rates and

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overall decrease of cellular proliferation. Thus, the effects of organochlorine pesticides

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have turned into a worldwide environmental and public health issue, with records of ~ 1

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x 106 annual intoxications and 2 x 104 annual deaths (WHO, 2014). Besides, a strong

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correlation between usage of pesticides and cancer has been found for at least 3.7 x

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104 cases annually 14,15. In the particular case of Mexico, an annual average of 3.5 x 105

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Tons of pesticides are administered to the registered 3.5 x 107 Ha agricultural areas

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(INEGI, 2014), leaving a very extensive and environmentally impacted landscape.

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Moreover, nearly 350 reports of intoxications due to acute exposure to pesticides are

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reported each year 16,17.

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Dichlorophen(2,2′-methylenebis(4-chlorophenol), DCP) is an environmentally persistent

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organochlorine pesticide, with fungicide, vermicide and bactericide activities

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its persistency, dichlorophen is commonly found on soils and effluents (~ 10-145 ng/L)

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19,20

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demonstrated that after acute exposure of rats to sub-lethal doses of dichlorophen,

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cellular abnormalities appeared such as chromosomal aberrations and loss of genetic

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material in bone marrow cells and erythrocytes. Chronic effects can be traced to a

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disruption of endocrine hormone physiology, since several studies suggest that

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organochlorine pesticides can act as antagonists of human nuclear receptors 21,22

, where it interacts preferably with lipidic cellular regions

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, i.e.

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. Due to

. Lone et al.

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Among the most efficient approaches, physicochemical strategies have been developed

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to tackle the persistence of organochlorine pesticides in the environment, with the aim

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of ameliorating their well-documented detrimental effects. Xiao et al. reported a mixed

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approach of UV irradiation and ozonation (UV/O3) to degrade chlorophen (CP) in

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aqueous media, enhancing in one order of magnitude the oxidation rate of CP and

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DCP. In this approach, the mechanism of degradation was mediated by HO—, which was

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produced after photodecomposition of H2O2 (the latter was produced after UV irradiation

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