Efeitos do inseticida acefato em modelos simples de membranas lipídicas baseados em filmes de Langmuir e GUVs: interações em nível molecular e alterações morfológicas
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Data
2021-01-21
Autores
Morato, Luis Fernando do Carmo
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Universidade Estadual Paulista (Unesp)
Resumo
O acefato é um dos agrotóxicos mais utilizados em lavouras brasileiras e possui o maior índice de uso irregular registrado pela Anvisa. Proveniente da família dos organofosforados, este inseticida foi escolhido por nós para ser investigado neste trabalho pelo potencial de riscos à saúde humana, principalmente ao sistema neurológico. A fim de se estudar os efeitos do acefato em membranas plasmáticas, sistemas miméticos destas estruturas baseados em monocamadas (filmes de Langmuir) e bicamadas (vesículas unilamelares gigantes – GUVs, e grandes - LUVs) lipídicas foram utilizados. Focamos nos fosfolipídios DPPC, que possui duas caudas de hidrocarboneto saturadas e uma cabeça zwiteriônica, e POPC, que difere do DPPC no comprimento de uma das cadeias e por uma instauração na cadeia alifática, porém mimetiza a fase fluida da membrana plasmática. Outros quatro lipídios que possuem dupla cauda saturada e compartilham grupos químicos referentes à cabeça polar dos fosfolipídios foram utilizados: DODAB (grupo amônia quaternária); DHP (grupo fosfato); DPTAP (grupo glicerol e grupo colina); e DPPA (grupo glicerol e grupo fosfato). Nos estudos de filmes de Langmuir apenas os lipídios DODAB e DPTAP tiveram suas isotermas π-A deslocadas e a morfologia alterada. Espectros de PM-IRRAS permitiram atribuir tais efeitos a afinidade dos grupos positivos da cabeça dos lipídios DPPC, DODAB e DPTAP com o acefato. Enquanto que em GUVs de DPPC, POPC, DODAB e DPTAP não foram observadas alterações morfológicas significativas na presença do acefato, LUVs de DPPC, DODAB e DPTAP indicaram que apenas aquelas formadas a partir de lipídios catiônicos apresentaram aumento no diâmetro e diminuição do potencial zeta quando na presença do pesticida. Experimentos realizados com monocamadas e bicamadas de POPC não evidenciaram nenhum efeito do acefato nestas estruturas. Porém, dada a afinidade do acefato por estruturas positivas, os resultados sugerem que processos biológicos governados por espécies que apresentem tais estruturas, se na presença do acefato, podem perder sua função pela ação do pesticida via interação eletrostática.
Acephate is one the agrochemicals most used in Brazilian crops and the first used in irregular ways registered by Anvisa. Being of organophosphorus family, this insecticide was chosen by its potential risk to the human health, mainly in the neurological system. In order to study the effects of acephate in cell membranes, mimetic systems of these structures based on lipid monolayers (Langmuir films) and bilayers (Giant Unilamellar Vesicles – GUVs and Large Unilamellar Vesicles - LUVs) were evaluated. We focused on the phospholipids DPPC, which has two saturated hydrocarbon chains and a zwitterionic head, and POPC, which differs from DPPC by an unsaturation and length in one of the aliphatic chain, but mimetics the fluid phase of cell membrane. Another four lipids which have saturated chain and shares chemical groups relative to the polar head of the phospholipids were used: DODAB (quaternary ammonium group); DHP (phosphate group); DPTAP (glycerol and choline group); and DPPA (glycerol and phosphate group). In Langmuir films experiments, only DODAB and DPTAP showed interaction with acephate, once its π-A isotherms shifted to smaller molecular areas and its morphology had alterations. PM-IRRAS spectra reveals that these effects are due the affinity between the positive head groups of DPPC, DODAB and DPTAP with acephate. Despite DPPC, POPC, DODAB and DPTAP GUVs morphology did not change in presence of acephate, DPPC, DODAB and DPTAP LUVs indicated that only cationic ones were affected in presence of the pesticide, once its size increase and the zeta potential diminish. Monolayers and bilayers of POPC does not reveal any interaction with the insecticide. However, due the affinity of acephate by positive structures, the results suggests that biological process governed by species which present those structures, if in presence of acephate, can loss its function by the action of the pesticide by electrostatic interaction.
Acephate is one the agrochemicals most used in Brazilian crops and the first used in irregular ways registered by Anvisa. Being of organophosphorus family, this insecticide was chosen by its potential risk to the human health, mainly in the neurological system. In order to study the effects of acephate in cell membranes, mimetic systems of these structures based on lipid monolayers (Langmuir films) and bilayers (Giant Unilamellar Vesicles – GUVs and Large Unilamellar Vesicles - LUVs) were evaluated. We focused on the phospholipids DPPC, which has two saturated hydrocarbon chains and a zwitterionic head, and POPC, which differs from DPPC by an unsaturation and length in one of the aliphatic chain, but mimetics the fluid phase of cell membrane. Another four lipids which have saturated chain and shares chemical groups relative to the polar head of the phospholipids were used: DODAB (quaternary ammonium group); DHP (phosphate group); DPTAP (glycerol and choline group); and DPPA (glycerol and phosphate group). In Langmuir films experiments, only DODAB and DPTAP showed interaction with acephate, once its π-A isotherms shifted to smaller molecular areas and its morphology had alterations. PM-IRRAS spectra reveals that these effects are due the affinity between the positive head groups of DPPC, DODAB and DPTAP with acephate. Despite DPPC, POPC, DODAB and DPTAP GUVs morphology did not change in presence of acephate, DPPC, DODAB and DPTAP LUVs indicated that only cationic ones were affected in presence of the pesticide, once its size increase and the zeta potential diminish. Monolayers and bilayers of POPC does not reveal any interaction with the insecticide. However, due the affinity of acephate by positive structures, the results suggests that biological process governed by species which present those structures, if in presence of acephate, can loss its function by the action of the pesticide by electrostatic interaction.
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Palavras-chave
Acefato, Filmes de Langmuir, PM-IRRAS, BAM, GUVs, LUVs, Acephate, Langmuir films