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Abstract(s)
Apesar de representar apenas 2% da massa corporal do ser humano, o cérebro é considerado um órgão altamente evoluído e com elevados consumos metabólicos. Deste modo, este contém uma rede especializada, a unidade neurovascular, que é responsável pela manutenção dos níveis de perfusão adequados para existir uma correta homeostasia cerebral. Dentro desta rede, podemos destacar as células musculares lisas (SMC) que são os componentes celulares maioritários que constituem as artérias e são responsáveis pela alteração do diâmetro das mesmas, recorrendo a mecanismos de contração e relaxamento, permitindo assim a regulação do fluxo sanguíneo em função das necessidades energéticas e metabólicas do cérebro. No entanto, quando ocorrem alterações fisiológicas, como por exemplo, após uma situação de isquemia, devido à tentativa de adaptação, pode haver modificação da sinalização entre as células astrocitárias, endoteliais e SMC, que pode levar tanto à vasodilatação como à vasoconstrição. Por este motivo, o objetivo fulcral deste trabalho é analisar o efeito do G-1, um agonista do recetor 1 de estrogénio acoplado à proteína G (GPER), com propriedades vasoativas na regulação da função vascular. Para tal, recorreu-se ao isolamento das artérias cerebrais médias (MCA) de ratos Wistar que foram explantadas em placas de culturas previamente revestidas com colagénio. A partir dessas artérias cerebrais foi possível obter-se culturas puras de SMC. Estas células foram expostas ao composto G-1 em diferentes concentrações e também a meios condicionados por co-culturas de neurónios e astrócitos, previamente submetidos a privação de oxigénio e glucose (OGD), de modo a simular a situação de isquemia e posteriormente incubados com diferentes concentrações de G-1. Utilizando a técnica de Planar Cell Surface Area (PCSA) foi possível analisar a resposta das SMC ao agente contráctil, noroadrenalina (NA), ao agente relaxante, nitroprussiato de sódio (SNP) e ao G-1 diretamente.
A utilização direta do G-1, nas SMC da MCA, parecia ser um bom componente terapêutico. No entanto, quando incubamos as SMC, durante um período de 24 horas a capacidade vasodilatadora do G-1 começou a reduzir. Ainda, no momento em que verificámos o efeito nestas células, quando incubadas com co-culturas neuro-gliais de astrócitos e neurónios com G-1, após OGD, verificámos que as SMC obtiveram um comportamento contraditório, passando a expressar uma resposta vasoconstritora. Nesta perspetiva, o agonista do GPER, aparenta não induzir neuroproteção após um evento isquémico, uma vez que leva à contração das SMC. Assim, devem ser feitos mais estudos para avaliar os efeitos neurovasculares do G-1.
The brain is considered a highly evolved organ with high metabolic consumption, even though it represents only 2% of the human body mass. Therefore, it contains a specialised network, the neurovascular unit, which is responsible for maintaining adequate perfusion levels for correct cerebral homeostasis. Within this network, we can highlight smooth muscle cells (SMC), which are the main cellular components that constitute the arteries. These cells are responsible for controlling blood vessel’ diameter, using contraction and relaxation mechanisms, thus regulating the blood flow according to the brain's energy and metabolic needs. However, when physiological alterations occur, such as after a situation of ischaemic, there may be a modification in the signalling mechanisms between the astrocytic, endothelial cells and SMC, which may lead to both vasodilation and vasoconstriction. For this reason, the main objective of this work is to analyse the effect of G-1, an GPER agonist with vasoactive properties, on the regulation of vascular function. For this purpose, we used isolated medium cerebral arteries (MCA) from Wistar rats which were explanted in culture plates, previously coated with collagen. From these cerebral arteries it was possible to obtain pure cultures of SMC. Then, these cells were exposed to different concentrations of G-1 and also to medium conditioned by co-cultures of neurons and astrocytes, previously submitted to oxygen and glucose deprivation (OGD) - to simulate the situation of ischemia - and later incubated with different concentrations of G-1. Using the Planar Cell Surface Area (PCSA) technique it was possible to analyse the SMC response to the contractile agent, noroadrenaline (NA), to the relaxing agent, sodium nitroprusside (SNP) and to G-1 directly. The administration of G-1, in the SMC of MCA, appeared to be a good therapeutic drug. However, when SMC were incubated, over 24 hours, the vasodilator capacity of G-1 started to reduce. Also, when these cells were incubated with neuro-glial co-cultures of astrocytes and neurons with G-1, after OGD, we found that SMCs obtained a contradictory behaviour, starting to express a vasoconstrictor response. For this reason, the GPER agonist does not induced neuroprotection after an ischaemic event. Thus, further studies should be done to evaluate the neurovascular effects of G-1.
The brain is considered a highly evolved organ with high metabolic consumption, even though it represents only 2% of the human body mass. Therefore, it contains a specialised network, the neurovascular unit, which is responsible for maintaining adequate perfusion levels for correct cerebral homeostasis. Within this network, we can highlight smooth muscle cells (SMC), which are the main cellular components that constitute the arteries. These cells are responsible for controlling blood vessel’ diameter, using contraction and relaxation mechanisms, thus regulating the blood flow according to the brain's energy and metabolic needs. However, when physiological alterations occur, such as after a situation of ischaemic, there may be a modification in the signalling mechanisms between the astrocytic, endothelial cells and SMC, which may lead to both vasodilation and vasoconstriction. For this reason, the main objective of this work is to analyse the effect of G-1, an GPER agonist with vasoactive properties, on the regulation of vascular function. For this purpose, we used isolated medium cerebral arteries (MCA) from Wistar rats which were explanted in culture plates, previously coated with collagen. From these cerebral arteries it was possible to obtain pure cultures of SMC. Then, these cells were exposed to different concentrations of G-1 and also to medium conditioned by co-cultures of neurons and astrocytes, previously submitted to oxygen and glucose deprivation (OGD) - to simulate the situation of ischemia - and later incubated with different concentrations of G-1. Using the Planar Cell Surface Area (PCSA) technique it was possible to analyse the SMC response to the contractile agent, noroadrenaline (NA), to the relaxing agent, sodium nitroprusside (SNP) and to G-1 directly. The administration of G-1, in the SMC of MCA, appeared to be a good therapeutic drug. However, when SMC were incubated, over 24 hours, the vasodilator capacity of G-1 started to reduce. Also, when these cells were incubated with neuro-glial co-cultures of astrocytes and neurons with G-1, after OGD, we found that SMCs obtained a contradictory behaviour, starting to express a vasoconstrictor response. For this reason, the GPER agonist does not induced neuroprotection after an ischaemic event. Thus, further studies should be done to evaluate the neurovascular effects of G-1.
Description
Keywords
Artéria Cerebral Média Células do Músculo Liso Contratibilidade G-1 Isquemia Privação de Oxigénio e Glucose Unidade Neurovascular