RESUMO
Even though technologies involving nano/microparticles have great potential, it is crucial to determine possible toxicity of these technological products before extensive use. Fullerenes C60 are nanomaterials with unique physicochemical and biological properties that are important for the development of many technological applications. The aim of this study was to evaluate the consequences of nonphotoexcited fullerene C60 exposure in brain acetylcholinesterase expression and activity, antioxidant responses, and oxidative damage using adult zebrafish as an animal model. None of the doses tested (7.5, 15, and 30 mg/kg) altered AChE activity, antioxidant responses, and oxidative damage when zebrafish were exposed to nonphotoexcited C60 nano/microparticles during 6 and 12 hours. However, adult zebrafish exposed to the 30 mg/kg dose for 24 hours have shown enhanced AChE activity and augmented lipid peroxidation (TBARS assays) in brain. In addition, the up-regulation of brain AChE activity was neither related to the transcriptional control (RT-qPCR analysis) nor to the direct action of nonphotoexcited C60 nano/microparticles on the protein (in vitro results) but probably involved a posttranscriptional or posttranslational modulation of this enzymatic activity. Taken together these findings provided further evidence of toxic effects on brain after C60 exposure.
Assuntos
Acetilcolinesterase/metabolismo , Encéfalo/enzimologia , Fulerenos/farmacologia , Peroxidação de Lipídeos/efeitos dos fármacos , Nanopartículas/química , Peritônio/metabolismo , Peixe-Zebra/metabolismo , Envelhecimento/metabolismo , Animais , Antioxidantes/metabolismo , Encéfalo/efeitos dos fármacos , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Tamanho da Partícula , Peritônio/efeitos dos fármacos , SuspensõesRESUMO
Endosulfan is a broad spectrum organochlorine pesticide that is still widely in use in many developing countries. Following application, endosulfan can get to watercourses through surface runoff from agricultural fields and disturb the non-target aquatic animals including freshwater fish species. Given that the activity of the enzyme acetylcholinesterase (AChE) is one of the most recurrently used biomarkers of exposure to pesticides and there are controversial results concerning the effects of endosulfan exposure and AChE activity in fish, the aim of the present study was to evaluate the effects of endosulfan in brain AChE activity and its gene expression pattern using adult zebrafish (Danio rerio) as an animal model. Moreover, we have analyzed the effects of endosulfan exposure in different parameters of zebrafish swimming activity and in long-term memory formation. After 96 h of exposition, fish in the 2.4 µg endosulfan/L group presented a significant decrease in AChE activity (9.44 ± 1.038 µmol SCh h(-1) mg protein(-1); p=0.0205) when compared to the control group (15.87 ± 1.768 µmol SCh h(-1) mg protein(-1); p=0.0205) which corresponds to approximately 40%. The down-regulation of brain AChE activity is not directly related with the transcriptional control as demonstrated by the RT-qPCR analysis. Our results reinforce AChE activity inhibition as a pathway of endosulfan-induced toxicity in brain of fish species. In addition, exposure to 2.4 µg endosulfan/L during 96 h impaired all exploratory parameters evaluated: decreased line crossings (≈21%, 273.7 ± 28.12 number of line crossings compared to the control group 344.6 ± 21.30, p=0.0483), traveled distance (≈20%, 23.44 ± 2.127 m compared to the control group 29.39 ± 1.585, p=0.0281), mean speed (≈25%, 0.03 ± 0.003 m/s compared to the control group 0.04 ± 0.002, p=0.0275) and body turn angle (≈21%, 69,940 ± 4871 absolute turn angle compared to the control group 88,010 ± 4560, p=0.0114). These results suggest that endosulfan exposure significantly impairs animals' exploratory performance, and potentially compromises their ecological and interspecific interaction. Our results also showed that the same endosulfan exposure did not compromise animals' performance in the inhibitory avoidance apparatus. These findings provide further evidence of the deleterious effects of endosulfan exposure in the nervous system.