Alterações celulares e moleculares induzidas pelo choque térmico em espermatozoides bovinos
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Data
2017-02-24
Autores
Silva, Daniela Franco da [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
A função do espermatozoide pode ser comprometida por condições ambientais adversas. Estudos já demonstraram que a exposição in vivo e in vitro de espermatozoides bovinos a temperatura elevada induz a morte celular, reduz a motilidade espermática e o potencial fertilizante do espermatozoide. No entanto, as alterações celulares induzidas pelo choque térmico em espermatozoides bovinos ainda são controversas. Portanto, o objetivo deste estudo foi determinar o efeito do choque térmico em espermatozoides de touros holandeses na motilidade espermática, produção de espécies reativas de oxigênio (EROs), atividade mitocondrial, atividade de caspase, potencial de fertilização, cinética e desenvolvimento embrionário pré-implantacional. As amostras de sêmen foram descongeladas e submetidas ao gradiente de Percoll. Na amostra controle (sem incubação) os espermatozoides foram avaliados imediatamente após o gradiente de Percoll. Posteriormente, as amostras foram incubadas à 35 °C (Controle da temperatura testicular), 38,5 °C (temperatura corporal) e 41 °C (choque térmico) por 4 horas. O choque térmico de 41 °C reduziu a motilidade espermática após 2 h de incubação em comparação com 35 e 38,5 °C. A exposição de espermatozoides a diferentes temperaturas aumentou a produção de EROs, sendo este efeito mais acentuado no grupo 41°C em relação aos demais tratamentos. O aumento das EROs em espermatozoides submetidos ao choque térmico foi seguido da redução na atividade mitocondrial espermática e aumento na atividade de enzimas caspases. A exposição de espermatozoides ao choque térmico também reduziu o potencial fecundante do espermatozoide, alterou a cinética de desenvolvimento de embriões de 2-células, a cinética da clivagem embrionária e o desenvolvimento a blastocisto. Em conclusão, a exposição de espermatozoides de touros holandeses ao choque térmico desencadeou o estresse oxidativo, alterações celulares compatíveis com apoptose e comprometeu o desenvolvimento embrionário.
Sperm function can be compromised by adverse environmental conditions. It has been demonstrated that in vivo and in vitro exposure of bovine sperm to elevated temperature induces cell death, reduces sperm motility and fertilizing potential. However, the role of heat shock on sperm apoptosis still controversial. Therefore, the objective of this study was to determine the effect Holstein sperm heat shock on sperm motility, oxidative stress production, mitochondrial activity, caspase activity, fertilizing potential and subsequent preimplantation embryonic development. Frozen-thawed Holstein sperm were subjected to control (non-incubation: sperm were evaluated immediately after Percoll gradient) and incubation at 35°C (testicular temperature control), 38.5°C (body temperature) and 41°C (heat shock) for 4 hours. Heat shock reduced sperm motility after 3 and 4 h incubation at 41°C as compared to 35 and 38.5°C. Sperm mitochondrial activity was reduced by 38.5 and 41°C when compared to control. Heat shock also increased caspase activity after 41°C incubation for 4 hours as compared to 35°C and control. When sperm were incubated at different temperature for 4 h, there was a evidence enhance in ROS quantity induced by heat stress. Initial cleavages, evaluated as 2-cell embryo, were more expressive at 35 hpi when compared with other times of evaluation. Total cleavage was also more significant at 35 hpi.. The percentage of oocytes fertilized, cleaved and that reached the 2-cell and blastocyst stage was reduced by 41°C when compared to 35°C and control. There was no differences between 38.5 and 41°C for these variables. In conclusion, exposure of Holstein sperm to heat shock during 4 hours reduced sperm function as compared to sperm at testicular temperature.
Sperm function can be compromised by adverse environmental conditions. It has been demonstrated that in vivo and in vitro exposure of bovine sperm to elevated temperature induces cell death, reduces sperm motility and fertilizing potential. However, the role of heat shock on sperm apoptosis still controversial. Therefore, the objective of this study was to determine the effect Holstein sperm heat shock on sperm motility, oxidative stress production, mitochondrial activity, caspase activity, fertilizing potential and subsequent preimplantation embryonic development. Frozen-thawed Holstein sperm were subjected to control (non-incubation: sperm were evaluated immediately after Percoll gradient) and incubation at 35°C (testicular temperature control), 38.5°C (body temperature) and 41°C (heat shock) for 4 hours. Heat shock reduced sperm motility after 3 and 4 h incubation at 41°C as compared to 35 and 38.5°C. Sperm mitochondrial activity was reduced by 38.5 and 41°C when compared to control. Heat shock also increased caspase activity after 41°C incubation for 4 hours as compared to 35°C and control. When sperm were incubated at different temperature for 4 h, there was a evidence enhance in ROS quantity induced by heat stress. Initial cleavages, evaluated as 2-cell embryo, were more expressive at 35 hpi when compared with other times of evaluation. Total cleavage was also more significant at 35 hpi.. The percentage of oocytes fertilized, cleaved and that reached the 2-cell and blastocyst stage was reduced by 41°C when compared to 35°C and control. There was no differences between 38.5 and 41°C for these variables. In conclusion, exposure of Holstein sperm to heat shock during 4 hours reduced sperm function as compared to sperm at testicular temperature.
Descrição
Palavras-chave
Oxidative stress, Sperm motility, Mitochondrial and caspase activity