Abstract:
A nanotecnologia vem se desenvolvendo de forma exponencial, porém estudos sobre os possíveis efeitos induzidos pelos nanomateriais ainda são escassos, principalmente em organismos aquáticos. A família dos grafenos é considerada como os materiais mais resistente do mundo e devido a isso estão sendo utilizadas nas mais diferenciadas aplicações incluindo tecnológicas e biomédicas. Com o aumento da utilização destes nanomateriais surge também o aumento do risco de contaminação do ambiente aquático e dos organismos. Além disso, ainda não existem dados sobre a interação deste nanomaterial com outros contaminantes como é o caso do arsênio, que é conhecido por induzir estresse oxidativo e modular o sistema de defesa antioxidante, além de ser bioacumulado e metabolizado pelos organismos aquáticos. Portanto, o presente trabalho buscou avaliar em diferentes níveis (químicos, bioquímicos, moleculares e histológicos) se a co-exposição ao óxido de grafeno pode alterar parâmetros bioquímicos vinculados a indução de estresse oxidativo e a modulação do sistema de defesa antioxidante, bem como as capacidades de acumulação e metabolização do arsênio em diferente tecidos do camarão branco Litopenaeus vannamei. A metodologia desenvolvida avaliou desde a acumulação e a especiação do conteúdo de compostos arsênicos nos diferentes tecidos analisados, bem como a atividade total da glutationa-S-transferase e sua isoforma ômega, responsável pela metabolização do arsênio. Foram determinadas a concentração de espécies reativas de oxigênio, os níveis de peroxidação lipídica, a capacidade antioxidante total contra radicais peroxil e os níveis de glutationa reduzida, um poderoso antioxidante endógeno. Por fim, análises histológicas com o intuito de verificar anomalias estruturais e/ou celulares também foram efetuadas.
The research about potential toxic effects of carbon nanomaterials has been attracted much interest on the scientific community, but still little is known about their toxic effects in aquatic organisms under co-expositions with other contaminants as metals on environment for example. In the present study, a wide investigation around chemical, biochemical, histological and molecular responses to arsenic (As) contamination in co-exposition with grapene oxide (GO) was made, measuring the accumulation and chemical speciation of arsenic, followed by the determination of activity of total glutathione-S-transferase (GST), glutathione-S-transferase omega (GST-) activity and gene expression, key enzyme in As detoxification, the levels of reduced glutathione (GSH), concentration of reactive oxygen species (ROS), levels of lipid peroxidation products and determination of total antioxidant capacity against peroxyl radicals (ACAP) to answer whether this nanomaterial is able to change the pattern of accumulation and metabolism of As in different tissues of white shrimp Litopenaeus vannamei (Crustacea, Decapoda). A remarkable accumulation of As was detected in gut under co-exposition, indicating that GO facilitates the entry of As into this tissue, but speciation reveal that the co-exposition in hepatopancreaspancreas and muscle accumulated predominantly dimethylarsenic (DMA), a moderately toxic As compound. GST- gene expression was not altered by treatments while its activity was significantly increased in all tested tissues. Besides ROS concentrations were not influenced by As exposure in gills, the co-expositions was responsible for a marked increase in ROS levels in this tissue, indicating that the co-exposition can induce a state of oxidative stress. Although the intracellular content of GSH was not influenced by the co-exposition, the activity of total GST was positively modulated in gills and muscle. Finally, ACAP was observed only in muscle under co-exposure and notwithstanding the levels of lipid peroxidation were increased only in gills and gut, histological analysis shown that co-exposition between As and GO lead to several deleterious effects in all tested tissues. The findings of this study demonstrated that co-exposition between As and GO can modulate the typical answers to As contamination in different tissues of L. vannamei.
