Predições in silico sobre a toxicidade das microcistinas e caracterização de cianobactérias e cianotoxinas em pontos de atividade recreacional do Reservatório Billings SP
Data
2023-06-24
Autores
Silva, Cristiane Gonçalves da 
Orientadores
Niero, Cristina Viana
Tipo
Tese de doutorado
Título da Revista
ISSN da Revista
Título de Volume
Resumo
Cianobactérias são microrganismos que podem produzir toxinas tais como microcistinas (MC) e saxitoxinas (STX). Atualmente, são reconhecidas 279 variantes de microcistina que provocam, principalmente, danos hepáticos em animais e humanos. As saxitoxinas possuem 57 congêneres e apresentam toxicidade neurológica. Os efeitos tóxicos das variantes das cianotoxinas em seres humanos ainda não foram completamente esclarecidos. Assim, os principais objetivos desse trabalho foram: i. verificar se programas ADMET (absorção, distribuição, metabolismo, excreção e toxicidade) podem contribuir com predições in silico sobre a toxicidade das microcistinas; ii. avaliar a correlação entre biovolumes de cianobactérias e pluviometria e tempo de retenção do reservatório; iii. quantificar as toxinas em amostras de água provenientes de pontos de atividade recreacional humana no reservatório Billings; e iv. realizar a detecção de genes envolvidos na síntese de cianotoxinas. Os resultados indicaram que os programas Admet Predictor®, AdmetSar 2.0, SwissADME e T.E.S.T podem ser utilizados para obter predições sobre microcistinas. Admet Predictor® apresentou maior número de modelos com domínio de aplicabilidade adequados, inclusive sobre MC-HarHar, uma variante rara encontrada neste reservatório. As predições sobre microcistinas em ratos e humanos mostraram diferenças de toxicidade das variantes. Todas as microcistinas preditas foram consideradas cancerígenas e a sensibilidade respiratória categorizou-as em 2 grupos (sensibilizadoras e não sensibilizadoras) em ratos. Em humanos, duas variantes de microcistina (MC-LR e -RR) induziram fosfolipidose, sendo que MC-LR apresentou maior absorção intestinal e biodisponibilidade. Houve correlação entre biovolume de cianobactérias e pluviometria mensal. Em períodos de estiagem, as baixas pluviometrias e o alto tempo de retenção se comparado com o período chuvoso favoreceram a formação de florações dos táxons Woronichinia, Planktothrix e Dolichospermum. Nos períodos chuvosos, houve redução do tempo de retenção, aumento da pluviometria e de espécies de cianobactérias encontradas. Microcistina foi encontrada nos pontos onde os genes mcyB e mcyE estavam presentes. Entretanto, as concentrações de microcistinas totais foram abaixo dos limites indicados pela Organização Mundial da Saúde para realização de atividades recreacionais. Apesar da amplificação dos genes sxtS e sxtA, saxitoxina não foi detectada nas amostras analisadas.
Cyanobacteria are microorganisms that can produce toxins such as microcystins (MC) and saxitoxins (SXT). Currently, 279 microcystin variants are recognized, mainly causing liver damage in animals and humans. Saxitoxins have 57 congeners and exhibit neurological toxicity. The toxic effects of cyanotoxin variants in humans have not yet been fully clarified. Thus, the main objectives of this work were: i. to verify if ADMET (absorption, distribution, metabolism, excretion and toxicity) programs can contribute with in silico predictions about microcystin toxicity; ii. to evaluate the correlation between cyanobacterial biovolumes and pluviometry and reservoir retention time; iii. to quantify toxins in water samples from points of human recreational activity in the Billings Reservoir by ELISA; iv. to detect genes involved in the synthesis of cyanotoxins by PCR. Results indicated that the programs Admet Predictor®, AdmetSar 2.0, SwissADME and T.E.S.T can be used to obtain predictions about microcystins. Admet Predictor® had most models with adequate applicability domain, including on MC-HarHar, a rare variant found in this reservoir. Predictions about microcystins in rats and humans showed differences in variant toxicity. All predicted microcystins were considered carcinogenic and respiratory sensitivity categorized them into 2 groups (sensitizers and non-sensitizers) in rats. In humans, two microcystin variants (MC-LR and -RR) induced phospholipidosis, and MC-LR showed greater intestinal absorption and bioavailability. There was a correlation between cyanobacterial biovolume and monthly pluviometry. During periods of drought, low rainfall and high retention time favored the formation of blooms of Woronichinia, Planktothrix and Dolichospermum taxa. During rainy periods, there was a reduction in retention time, an increase in pluviometry and in the number of cyanobacterial species found. Microcystin was found at the spots where mcyB and mcyE genes were present. However, concentrations of total microcystins were below the limits indicated by the World Health Organization for carrying out recreational activities. Despite amplification of sxtS and sxtA genes, saxitoxin was not detected in the analyzed samples.
Cyanobacteria are microorganisms that can produce toxins such as microcystins (MC) and saxitoxins (SXT). Currently, 279 microcystin variants are recognized, mainly causing liver damage in animals and humans. Saxitoxins have 57 congeners and exhibit neurological toxicity. The toxic effects of cyanotoxin variants in humans have not yet been fully clarified. Thus, the main objectives of this work were: i. to verify if ADMET (absorption, distribution, metabolism, excretion and toxicity) programs can contribute with in silico predictions about microcystin toxicity; ii. to evaluate the correlation between cyanobacterial biovolumes and pluviometry and reservoir retention time; iii. to quantify toxins in water samples from points of human recreational activity in the Billings Reservoir by ELISA; iv. to detect genes involved in the synthesis of cyanotoxins by PCR. Results indicated that the programs Admet Predictor®, AdmetSar 2.0, SwissADME and T.E.S.T can be used to obtain predictions about microcystins. Admet Predictor® had most models with adequate applicability domain, including on MC-HarHar, a rare variant found in this reservoir. Predictions about microcystins in rats and humans showed differences in variant toxicity. All predicted microcystins were considered carcinogenic and respiratory sensitivity categorized them into 2 groups (sensitizers and non-sensitizers) in rats. In humans, two microcystin variants (MC-LR and -RR) induced phospholipidosis, and MC-LR showed greater intestinal absorption and bioavailability. There was a correlation between cyanobacterial biovolume and monthly pluviometry. During periods of drought, low rainfall and high retention time favored the formation of blooms of Woronichinia, Planktothrix and Dolichospermum taxa. During rainy periods, there was a reduction in retention time, an increase in pluviometry and in the number of cyanobacterial species found. Microcystin was found at the spots where mcyB and mcyE genes were present. However, concentrations of total microcystins were below the limits indicated by the World Health Organization for carrying out recreational activities. Despite amplification of sxtS and sxtA genes, saxitoxin was not detected in the analyzed samples.