Estresse, imunidade, sistema antioxidante e metabolismo em peixes em condições simuladas comuns da criação
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Data
2020-11-26
Autores
Mello, Mariana Maluli Marinho de [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Muitas situações inerentes da piscicultura intensiva desencadeiam resposta de estresse nos animais, podendo causar perdas na produtividade. Manejos como a perseguição e o transporte e alterações na qualidade de água como baixos níveis de oxigênio dissolvido (OD) e mudanças na temperatura são exemplos de condições estressantes para os peixes. O conhecimento do impacto dessas condições na fisiologia dos peixes é importante para antever respostas e melhorar a saúde e bem-estar dos peixes, evitando, em consequência, perdas na produção. O uso de imunoestimulantes, como o β-glucano, na aquicultura, é uma alternativa para minimizar os efeitos negativos do estresse, incluindo prejuízos no sistema imune. Além disso, tanto as respostas metabólicas do estresse quanto as respostas do sistema imune são energeticamente caras e podem ter efeito no sistema de produção de energia e balanço redox intracelular. Neste contexto, esta tese é composta por três experimentos que objetivaram avaliar o efeito de situações estressantes na resposta de estresse, metabólica, imune e antioxidante de peixes imunoestimulados ou não com β-glucano. No primeiro experimento, juvenis de pacu, alimentados com β-glucano, foram submetidos à estresse crônico (perseguição) ou/e agudo (transporte), e inoculação com Aeromonas hydrophila inativada pelo calor. No segundo experimento, que originou dois capítulos desta tese, salmões foram mantidos por seis semanas em hipóxia (40% OD) e posteriormente foram inoculados com Aeromonas salmonicida inativada com formalina. No terceiro experimento, pacus foram alimentados com β-glucano e passaram por um desafio térmico, com queda severa na temperatura da água antes da inoculação com lipopolissacarídeo (LPS). Todos os estressores utilizados neste estudo desencadearam uma resposta de estresse nos peixes, prejudicando a resposta imune, antioxidante e metabólica. Enquanto os estressores agudos (transporte e estresse térmico) provocaram aumento na concentração plasmática de cortisol e/ou glicose, os estressores crônicos (perseguição e hipóxia) fadigaram a responsividade do eixo HPI. A imunoestimulação, seja por LPS ou por bactéria potencializou os efeitos negativos dos estressores, especialmente na resposta antioxidante. O β-glucano apresentou efeito protetor, diminuindo picos na concentração plasmática de cortisol e evitando a redução na atividade do sistema antioxidante.
Many inherent situations in intensive fish farming trigger stress response on 240 animals, which can cause productivity losses. Chase, transport and changes in 241 water quality, as low dissolved oxygen (DO) levels and alterations in water 242 temperature are examples of stressful conditions for fish. Understanding the impact 243 of stressful situations on fish physiology is important to predict responses and 244 improving fish health and well-being, preventing production losses. The use of 245 immunostimulants, as β-glucan, in aquaculture, is an alternative to minimize the 246 negative impacts of stress, including those in immune system. In addition, both 247 metabolic and immune system responses are of high energy cost, and can affect 248 the cellular system of energy production and the intracellular redox balance. In this 249 context, this thesis is composed of three experiments that aimed to evaluate the 250 effects of stressful situations on the stress, immune, metabolic and antioxidant 251 response of non-immunestimulated or glucan-immunestimulated fish. In the first 252 experiment, pacu juveniles fed with β-glucan were subjected to chronic (chase) 253 or/and acute (transport) stress and heat-killed Aeromonas hydrophila. In the second 254 experiment, present in two chapters of this thesis, salmon were kept in hypoxia (40% 255 DO) for six weeks before injection with formalin-killed Aeromonas salmonicida. In 256 the third experiment, pacu fed with β-glucan were thermal challenged, with severe 257 reduction in water temperature prior lipopolysaccharide (LPS) inoculation. All 258 stressors applied in this study triggered a stress response in fish, impairing the 259 immune, antioxidant and metabolic responses. While acute stressors (transport and 260 thermal challenge) increased plasma cortisol and/or glucose concentration, chronic 261 stressors (chase and hypoxia) reduced the responsiveness of HPI axis. 262 Immunostimulation, either by LPS or bacteria, potentiated the negative effects of 263 stressors, especially in the antioxidant response. The glucan showed a protective 264 effect, reducing peaks in plasma cortisol concentrations and avoiding a decrease in 265 antioxidant system activity.
Many inherent situations in intensive fish farming trigger stress response on 240 animals, which can cause productivity losses. Chase, transport and changes in 241 water quality, as low dissolved oxygen (DO) levels and alterations in water 242 temperature are examples of stressful conditions for fish. Understanding the impact 243 of stressful situations on fish physiology is important to predict responses and 244 improving fish health and well-being, preventing production losses. The use of 245 immunostimulants, as β-glucan, in aquaculture, is an alternative to minimize the 246 negative impacts of stress, including those in immune system. In addition, both 247 metabolic and immune system responses are of high energy cost, and can affect 248 the cellular system of energy production and the intracellular redox balance. In this 249 context, this thesis is composed of three experiments that aimed to evaluate the 250 effects of stressful situations on the stress, immune, metabolic and antioxidant 251 response of non-immunestimulated or glucan-immunestimulated fish. In the first 252 experiment, pacu juveniles fed with β-glucan were subjected to chronic (chase) 253 or/and acute (transport) stress and heat-killed Aeromonas hydrophila. In the second 254 experiment, present in two chapters of this thesis, salmon were kept in hypoxia (40% 255 DO) for six weeks before injection with formalin-killed Aeromonas salmonicida. In 256 the third experiment, pacu fed with β-glucan were thermal challenged, with severe 257 reduction in water temperature prior lipopolysaccharide (LPS) inoculation. All 258 stressors applied in this study triggered a stress response in fish, impairing the 259 immune, antioxidant and metabolic responses. While acute stressors (transport and 260 thermal challenge) increased plasma cortisol and/or glucose concentration, chronic 261 stressors (chase and hypoxia) reduced the responsiveness of HPI axis. 262 Immunostimulation, either by LPS or bacteria, potentiated the negative effects of 263 stressors, especially in the antioxidant response. The glucan showed a protective 264 effect, reducing peaks in plasma cortisol concentrations and avoiding a decrease in 265 antioxidant system activity.
Descrição
Palavras-chave
Estresse crônico, Estresse agudo, Pacu, Salmão, Inoculação