RESUMEN
The use of chemical insecticides continues to play a major role in the control of disease vector populations, which is leading to the global dissemination of insecticide resistance. A greater capacity to detoxify insecticides, due to an increase in the expression or activity of three major enzyme families, also known as metabolic resistance, is one major resistance mechanisms. The esterase family of enzymes hydrolyse ester bonds, which are present in a wide range of insecticides; therefore, these enzymes may be involved in resistance to the main chemicals employed in control programs. Historically, insecticide resistance has driven research on insect esterases and schemes for their classification. Currently, several different nomenclatures are used to describe the esterases of distinct species and a universal standard classification does not exist. The esterase gene family appears to be rapidly evolving and each insect species has a unique complement of detoxification genes with only a few orthologues across species. The examples listed in this review cover different aspects of their biochemical nature. However, they do not appear to contribute to reliably distinguish among the different resistance mechanisms. Presently, the phylogenetic criterion appears to be the best one for esterase classification. Joint genomic, biochemical and microarray studies will help unravel the classification of this complex gene family.
Asunto(s)
Esterasas/clasificación , Inactivación Metabólica/genética , Resistencia a los Insecticidas/genética , Animales , Esterasas/química , Esterasas/genética , FilogeniaRESUMEN
The use of chemical insecticides continues to play a major role in the control of disease vector populations, which is leading to the global dissemination of insecticide resistance. A greater capacity to detoxify insecticides, due to an increase in the expression or activity of three major enzyme families, also known as metabolic resistance, is one major resistance mechanisms. The esterase family of enzymes hydrolyse ester bonds, which are present in a wide range of insecticides; therefore, these enzymes may be involved in resistance to the main chemicals employed in control programs. Historically, insecticide resistance has driven research on insect esterases and schemes for their classification. Currently, several different nomenclatures are used to describe the esterases of distinct species and a universal standard classification does not exist. The esterase gene family appears to be rapidly evolving and each insect species has a unique complement of detoxification genes with only a few orthologues across species. The examples listed in this review cover different aspects of their biochemical nature. However, they do not appear to contribute to reliably distinguish among the different resistance mechanisms. Presently, the phylogenetic criterion appears to be the best one for esterase classification. Joint genomic, biochemical and microarray studies will help unravel the classification of this complex gene family.
Asunto(s)
Animales , Esterasas/clasificación , Resistencia a los Insecticidas/genética , Inactivación Metabólica/genética , Esterasas/química , Esterasas/genética , FilogeniaRESUMEN
In Brazil, Aedes aegypti resistance to temephos, used since 1967, was detected in several municipalities in 2000. Organophosphates were substituted by pyrethroids against adults and, in some localities, by Bti against larvae. However, high temephos resistance ratios were still detected between 2001 and 2004. Field-simulated assays confirmed a low temephos residual effect. Acethylcholinesterase and Mixed Function Oxidase profiles were not altered. In contrast, higher Esterase activity, studied with three substrates, was found in all examined populations collected in 2001. From 2001 to 2004, a slight reduction in alpha-Esterase (EST) and beta-EST activity together with a gradual increase of p-nitrophenyl acetate (PNPA)-EST was noted. Gluthathione-S-transferase alteration was encountered only in the northeast region in 2001, spreading the entire country thereafter. In general, except for alpha-EST and beta-EST, only one enzyme class was altered in each mosquito specimen. Data are discussed in the context of historic application of insecticides in Brazil.
Asunto(s)
Aedes/efectos de los fármacos , Resistencia a los Insecticidas/fisiología , Insecticidas/farmacología , Animales , Brasil , Larva , Factores de TiempoRESUMEN
The susceptibility of Aedes aegypti (L.) larvae from several Brazilian populations to the juvenile hormone analog methoprene and the organophosphate insecticide temephos were investigated. Populations from Natal (northeastern region), Macapá (northern region), and Jardim América, Rio de Janeiro (southeastern region) are temephos-resistant (RR90 = 24.4, 13.3, and 15.8, respectively), whereas populations from Presidente Prudente (southeastern region) and Porto Velho (northern region) exhibit only an incipient temephos-altered susceptibility status (RR90 = 1.8 and 2.6, respectively). Biochemical assays revealed alterations of the enzymes implicated in metabolic resistance, glutathione S-transferase, mixed function oxidases and esterases, among these populations. Dose-response assays showed at most a low resistance to methoprene of all populations tested, irrespective of their temephos resistance level. However, sequential exposure of Macapá and Natal populations to temephos and methoprene indicated a potential cross-resistance when larvae are exposed to both insecticides. Nevertheless, susceptibility of the Brazilian Ae. aegypti populations to methoprene alone suggests this insect growth regulator could substitute for temephos in the control of the dengue vector in the country.