Efeitos fisiológicos em nototenídeos antárticos submetidos ao estresse térmico de curto e longo prazo

Orientadora: Profa. Dra. Lucélia DonattiTese (doutorado) - Universidade Federal do Paraná, Setor de Ciências Biológicas, Programa de Pós-Graduação em Biologia Celular e Molecular. Defesa : Curitiba, 02/03/2018Inclui referênciasResumo: Peixes antárticos são altamente estenotérmicos apresentando adaptações fisiológicas que permitem a sobrevivência nas águas frias e estáveis (-1,8 a +3ºC) do oceano Antártico. A temperatura é um fator abiótico que afeta os organismos ectotérmicos devido a sua influência nas reações enzimáticas e na estabilidade das macromoléculas. Por isso, ao considerar as tendências de aquecimento na região da Península Antártica questionamentos são levantados a respeito da flexibilidade e dos mecanismos fisiológicos desencadeados para a restauração da homeostase em organismos antárticos submetidos ao estresse térmico. Dessa forma, esta tese teve como objetivo verificar os efeitos fisiológicos do estresse térmico (8ºC), de longo (90 dias) e curto (2 a 144 horas) prazo, em nototenídeos antárticos presentes na Baía do Almirantado, Ilha Rei George, Península Antártica. Ao analisar os efeitos do estresse térmico de longo prazo em N. rossii, constata-se que, apesar de não haver a alteração do fator de condição, há indícios de aumento da demanda energética na temperatura de 8ºC. Entre as alterações, observou-se a hiperglicemia, a redução do índice hepatossomático, a mobilização do estoque lipídico nos tecidos hepático e muscular, o aumento da atividade da citrato sintase no fígado, o aumento do potencial gliconeogênico no fígado, rim, brânquia, coração e músculo, bem como aumento do potencial anaeróbico em todos os tecidos (excetuando-se as brânquias). A não modulação ou ainda a redução dos níveis de atividade da superóxido dismutase (SOD), catalase (CAT) e glutationa-S-tranferase (GST) indicam que os níveis presentes são suficientes para condição de 8ºC e 90 dias. Nos experimentos de curto prazo, observou-se que no tecido renal de N. rossii, os níveis de atividade das enzimas glicolíticas e da via do ácido cítrico foram modulados nas primeiras 12h em 8ºC. Enquanto, N. coriiceps apresentou valores semelhantes aos do controle a partir de 6h de experimento. Acredita-se que a manutenção do metabolismo de carboidratos no rim de N. coriiceps ocorreu devido ao consumo das reservas de glicogênio renais. Em N. rossii, a redução dos níveis de atividade da CAT, GST, glutationa peroxidase (GPx) e glutationa redutase (GR) nas primeiras horas de estresse térmico possivelmente contribuíram para o aumento da LPO em 72h. Já em N. coriiceps, não se observaram danos lipídicos nem proteicos. Através das análises plasmáticas constatou-se o aumento do cortisol em N. coriiceps expostas ao aumento térmico, o que desencadeou respostas secundárias a fim de subsidiar o aumento da demanda energética. Como a hiperglicemia em 6, 12 e 72h, a redução dos níveis de proteína total em 6 e 144h e de triglicerídeos em 144h. Ainda em N. coriiceps, observou-se o aumento da atividade da SOD e da CAT plasmáticas. Em N. rossii, não se verificou o efeito clássico de resposta primária ao estresse, contudo a hiperglicemia transiente nos tempos de 6 e 12h possivelmente ocorreu pelo efeito das catecolaminas. Diante dos resultados obtidos nesta tese verificamos que as respostas observadas são tempo-, tecido- e espécie-dependentes. Sendo N. coriiceps um potencial bioindicador da Baía do Almirantado, por ser mais sensível fisiologicamente ao estresse térmico do que N. rossii. Palavras-chave: Peixes antárticos. Notothenidae. Temperatura. Aquecimento. Metabolismo. Biomarcadores.Abstract: Antarctic fish are highly estenothermic exhibiting physiological adaptations that allow survival in the cold and stable waters (-1.8 to + 3ºC) of the Antarctic Ocean. Temperature is an abiotic factor that affects ectothermal organisms due to its influence on the enzymatic reactions and the stability of the macromolecules. Therefore, when considering warming trends in the region of the Antarctic Peninsula, questions are raised regarding the flexibility and physiological mechanisms triggered for the restoration of homeostasis in Antarctic organisms subjected to thermal stress. The objective of this thesis was to verify the physiological effects of thermal stress (8ºC), in short (2 to 144 hours) and long (90 days) term, in Antarctic nototeniids present in Almirantado Bay, King George Island, Antarctic Peninsula. Among the effects of longterm thermal stress on N. rossii, it was observe that, although there is no change in the condition factor, there is evidence of an increase in energy demand at 8ºC. Which are demonstrated by hyperglycemia, hepatosomatic index reduction, mobilization of lipid stores in the hepatic and muscular tissues, increased activity of citrate synthase in the liver, increased gluconeogenic potential in the liver, kidney, gill, heart and muscle, as well as increased anaerobic potential in all tissues (except gills). Unchanged or reduced activity levels of superoxide dismutase (SOD), catalase (CAT) and glutathione-s-transferase (GST) indicate that the levels present are possibly sufficient at 8ºC and 90 days. In the short-term experiments, it was observed that in the renal tissue of N. rossii, the activity levels of the glycolytic enzymes and the citric acid pathway were modulated in the first 12 hours at 8ºC. While N. coriiceps presented values similar to those of the control from 6h of experiment. It is believed that the maintenance of carbohydrate metabolism in the N. coriiceps kidney occurred due to the consumption of renal glycogen stores. Reduction of CAT, GST, glutathione peroxidase (GPx) and glutathione redutase (GR) activity levels in the first hours of thermal stress possibly contributed to an increase in LPO in 72h-group of N. rossii. In N. coriiceps, no lipid or protein damage was observed. Plasma analyzes revealed cortisol increase in N. coriiceps exposed to thermal increase, which triggered secondary responses in order to subsidized the increase in energy demand. As hyperglycemia at 6, 12 and 72h, reduction of total protein levels in 6 and 144h and of triglycerides in 144h. In N. coriiceps, increased activity of plasma SOD and CAT was observed. In N. rossii, the classic effect of the primary response to stress was not found, however, transient hyperglycemia at 6 and 12h was possibly due to the release of catecholamines. In view of the results obtained in this thesis we verified that the observed responses are time-, tissue- and species-dependent. N. coriiceps is a potential bioindicator of Admiralty Bay for being more physiologically sensitive to thermal stress than N. rossii. Keywords: Antarctic fish. Notothenidae. Temperature. Warming. Metabolism. Biomarkers

LPS modulates the expression of iron-related immune genes in two Antarctic notothenoids

The non-specific immunity can induce iron deprivation as a defense mechanism against potential bacterial pathogens, but little information is available as to its role in Antarctic fish. In this study the response of iron metabolism related genes was evaluated in liver and head kidney of the Antarctic notothenoids Notothenia coriiceps and Notothenia rossii 7 days after lipopolysaccharide (LPS) injection. Average plasma Fe2+ concentration was unaffected by treatment in any of the species. The gene expression response to LPS varied between tissues and species, being stronger in N. coriiceps and more prominent in the head kidney than liver. The reaction to LPS was marked by increased individual variability in most genes analyzed, even when the change in expression was not statistically significant, suggesting different individual sensitivity and coping responses in these wild fish. We found that iron related genes had an attenuated and homogenous response to LPS but there was no detectable relationship between plasma Fe2+ and gene expression. However, overall in both tissues and species LPS exposure set a multilevel response that concur to promote intracellular accumulation of iron, an indication that Antarctic Notothenoids use innate nutritional immunity as a resistance mechanism against pathogens.FCT-NSFC/0002/2016; CCMAR/Multi/04326/2013; PTDC/BIAANM/3484/2014info:eu-repo/semantics/publishedVersio

Effect of long-term thermal challenge on the Antarctic notothenioid Notothenia rossii

The thermal stability of the Antarctic Ocean raises questions concerning the metabolic plasticity of Antarctic notothenioids to changes in the environmental temperature. In this study, Notothenia rossii survived 90 days at 8 degrees C, and their condition factor level was maintained. However, their hepatosomatic (0.29x) index decreased, indicating a decrease in nutrient storage as a result of changes in the energy demands to support survival. At 8 degrees C, the plasma calcium, magnesium, cholesterol, and triglyceride concentrations decreased, whereas the glucose (1.91x) and albumin (1.26x) concentrations increased. The main energy substrate of the fish changed from lipids to glucose due to a marked increase in lactate dehydrogenase activity, as demonstrated by an increase in anaerobic metabolism. Moreover, malate dehydrogenase activity increased in all tissues, suggesting that fish acclimated at 8 degrees C exhibit enhanced gluconeogenesis. The aerobic demand increased only in the liver due to an increase (2.23x) in citrate synthase activity. Decreases in the activities of superoxide dismutase, catalase, and glutathione-Stransferase to levels that are most likely sufficient at 8 degrees C were observed, establishing a new physiological activity range for antioxidant defense. Our findings indicate that N. rossii has some compensatory mechanisms that enabled its long-term survival at 8 degrees C.CAPESCAPESCNPqNational Council for Scientific and Technological Development (CNPq)FAPERJ through projects PNPD (CAPES) [2443/2011]EBA (MCTI/CNPq) [52.0125/2008-8]INCT-APA (CNPq)National Council for Scientific and Technological Development (CNPq) [574018/2008-5, FAPERJ E-26/170.023/2008]EBA (CNPq)National Council for Scientific and Technological Development (CNPq) [305562/2009-6, 305969/2012-9