Efeitos da artrite induzida por adjuvante (AIA) sobre as respostas da aorta à angiotensina II em ratos submetidos ou não à castração cirúrgica
Carregando...
Data
2018-03-02
Autores
Tozzato, Gabriela Palma Zochio
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
A expectativa de vida diminui com artrite reumatoide (AR) devido ao aumento da mortalidade por doenças cardiovasculares. Isto se deve, possivelmente, à disfunção endotelial resultante da intensa atividade inflamatória relacionada à AR. Evidências tem apontado para um possível envolvimento do sistema renina-angiotensina (SRA) nos danos cardiovasculares inerentes à AR. Acredita-se que a participação do SRA agrave o comprometimento endotelial decorrente de inflamações sistêmicas através da ativação do receptor de angiotensina II tipo 1 (AT1) pela angiotensina II (Ang II). Por outro lado, a literatura também reporta a influência dos hormônios andrógenos, principalmente da testosterona, nas ações da Ang II sobre os tecidos vasculares. Assim, o objetivo do presente estudo é investigar os efeitos da artrite induzida por adjuvante (AIA) sobre o equilíbrio redox, a função endotelial e as respostas da aorta de ratos à Ang II, bem como, verificar se esses efeitos podem ser influenciados pela redução dos níveis circulantes de testosterona. Para isto, ratos Wistar machos adultos foram submetidos à falsa-castração e falsa-imunização (Controles), castração seguida de falsa-imunização (ORX), falsa-castração seguida de imunização (ORX) e castração seguida de imunização (ORX+AIA). Ao final do experimento, segmentos de aorta torácica foram desafiadas em cubas de órgãos isolados com acetilcolina (ACh), Ang II, KCl e nitroprussiato de sódio e, das curvas concentração resposta obtidas, calculou-se o pEC50 e efeito máximo (Emax). Determinou-se também a expressão proteica dos receptores de Ang II AT1 e AT2 em aortas, assim como a capacidade antioxidante do plasma (FRAP), o consumo de peróxido por Xylenol Orange (FOX), o nitrito/nitrato por Griess e ácido úrico no plasma. Os resultados mostraram que tanto a AIA quanto a ORX não alteraram o perfil das curvas concentração-respostas para ACh na ausência ou presença do L-NAME (10-4M), Apocinina (10-4M) ou Tiron (10-4M). AIA ou ORX também não alteraram as respostas à Ang II na ausência ou presença de Indometacina (10-5M), KCl 60 mm/L, 1400W (10-6M) Tiron (10-4M) ou PD123,319 (10-6M). Contudo, na presença do L-NAME (10-4M), observou-se um aumento do Emax da Ang II nos animais Controle e ORX em comparação aos animais submetidos à AIA. Este aumento de Emax, por sua vez, desapareceu quando esse desafio foi feito em cubas contendo solução nutritiva despolarizante (KCl 60 mm/L) ou quando o BQ123 (10-6M) ou BQ788 (10-6M) foram acrescidos na incubação, junto com o L-NAME (10-4M). Observou-se também um aumento do Emax da Ang II nos animais ORX, em comparação aos animais AIA e ORX+AIA, quando o desafio foi realizado na presença da Apocinina (10-4M). Além disso, AIA e/ou ORX diminuíram a expressão proteica dos receptores AT1, sem modificar os receptores AT2. Valores de FRAP, nitrito/nitrato e ácido úrico não apresentaram maiores alterações entre os grupos estudados, mas os valores de FOX diminuíram no grupo AIA. Esses dados sugerem que a AIA ou a ORX não modificam substancialmente o balanço redox sistêmico, a função endotelial, bem como as respostas da aorta à Ang II, se todos os mecanismos moduladores endoteliais estiverem presentes. Todavia, a AIA parece mobilizar mecanismos endoteliais para atuar no lugar do NO, sempre que a síntese deste é inibida. Possivelmente, tais mecanismos são ativados via receptores ETA e ETB e envolvem tanto prostanoides vasodilatadores quanto mecanismos indutores de hiperpolarização das células da musculatura lisa vascular presentes na aorta. A testosterona, por sua vez, não parece ter um papel determinante para a mobilização desses mecanismos locais que cooperam com o NO.
Life expectancy of patients with rheumatoid arthritis (RA) is lower due to increased mortality in consequence of cardiovascular diseases. Presumably, this occurs due to endothelial dysfunction resulting from severe inflammatory activity related to RA. Evidence has demonstrated a possible involvement of the renin-angiotensin system (RAS) in the cardiovascular injury inherent to RA. The RAS involvement is considered to worsen the endothelial impairment due to systemic inflammation through angiotensin II type 1 receptor (AT1) activation of Ang II. (Ang II). Additionally, previous studies also observed that androgen hormones, mainly the testosterone, modulate the Ang II actions in cardiovascular tissues. Thus, the aim of the present study is to investigate the effects of adjuvant-induced arthritis (AIA) on systemic redox balance, endothelial function and rat aorta responses to Ang II, as well as, whether these effects may be influenced by the reduction of circulating levels of testosterone. For this, adult male Wistar rats were submitted to false-castration and false-immunization (Controls), castration followed by false-immunization (ORX), false-castration followed by immunization (ORX) and castration followed by immunization (ORX + AIA) . At the end of the experiment, thoracic aorta segments were challenged in isolated organ bath with acetylcholine (ACh), Ang II, KCl and sodium nitroprusside and, from the concentrantion-response curves obtained were calculated pEC50 and maximal effect (Emax). The protein expression of Ang II type 1 and 2 receptor (AT1 and AT2, respectively) were also determined, as well as, plasma antioxidant capacity (FRAP), peroxide consumption by Xylenol Orange (FOX), nitrite/nitrate by Griess and uric acid in plasma. The results showed that both AIA and ORX did not change the concentration-response curves profile for ACh in the absence or presence of L-NAME (10-4M), Apocynin (10-4M) or Tiron (10-4M). AIA or ORX also did not change Ang II responses in the absence or presence of Indomethacin (10-5M), KCl 60mm/L, 1400W (10-6M) Tiron (10-4M) or PD123,319 (10-6M). However, in the presence of L-NAME (10-4M), was observed an increase of the Ang II Emax in Control and ORX animals in comparison to the animals submitted to AIA. This increase in Emax, in turn, disappeared when this challenge was realized in organ bath containing depolarizing nutrient solution (KCl 60 mm/L) or when BQ123 (10-6M) or BQ788 (10-6M) were added in the incubation together with L-NAME (10-4M). It was also observed an increase of the Ang II Emax in the ORX animals compared to the AIA and ORX+AIA animals, when the challenge was performed in the presence of Apocynin (10-4M). In addition, AIA and/or ORX decreased the protein expression of AT1 receptors without modifying AT2 receptors. The values of FRAP, nitrite/nitrate and uric acid did not show differences between the studied groups, but FOX values decreased in the AIA group. These data suggest that AIA or ORX does not substantially modify systemic redox balance, endothelial function, as well as aortic and Ang II responses, if all endothelial modulatory mechanisms are present. However, AIA seems to mobilize endothelial mechanisms to act as NO backup, whenever the synthesis of this gas is inhibited. Possibly, such mechanisms are activated via ETA and ETB receptors and involve both vasodilatory prostanoids and mechanisms that induce hyperpolarization of vascular smooth muscle cells present in the aorta. Testosterone, on the other hand, does not seem to play a decisive role in the mobilization of these local mechanisms that cooperate with NO.
Life expectancy of patients with rheumatoid arthritis (RA) is lower due to increased mortality in consequence of cardiovascular diseases. Presumably, this occurs due to endothelial dysfunction resulting from severe inflammatory activity related to RA. Evidence has demonstrated a possible involvement of the renin-angiotensin system (RAS) in the cardiovascular injury inherent to RA. The RAS involvement is considered to worsen the endothelial impairment due to systemic inflammation through angiotensin II type 1 receptor (AT1) activation of Ang II. (Ang II). Additionally, previous studies also observed that androgen hormones, mainly the testosterone, modulate the Ang II actions in cardiovascular tissues. Thus, the aim of the present study is to investigate the effects of adjuvant-induced arthritis (AIA) on systemic redox balance, endothelial function and rat aorta responses to Ang II, as well as, whether these effects may be influenced by the reduction of circulating levels of testosterone. For this, adult male Wistar rats were submitted to false-castration and false-immunization (Controls), castration followed by false-immunization (ORX), false-castration followed by immunization (ORX) and castration followed by immunization (ORX + AIA) . At the end of the experiment, thoracic aorta segments were challenged in isolated organ bath with acetylcholine (ACh), Ang II, KCl and sodium nitroprusside and, from the concentrantion-response curves obtained were calculated pEC50 and maximal effect (Emax). The protein expression of Ang II type 1 and 2 receptor (AT1 and AT2, respectively) were also determined, as well as, plasma antioxidant capacity (FRAP), peroxide consumption by Xylenol Orange (FOX), nitrite/nitrate by Griess and uric acid in plasma. The results showed that both AIA and ORX did not change the concentration-response curves profile for ACh in the absence or presence of L-NAME (10-4M), Apocynin (10-4M) or Tiron (10-4M). AIA or ORX also did not change Ang II responses in the absence or presence of Indomethacin (10-5M), KCl 60mm/L, 1400W (10-6M) Tiron (10-4M) or PD123,319 (10-6M). However, in the presence of L-NAME (10-4M), was observed an increase of the Ang II Emax in Control and ORX animals in comparison to the animals submitted to AIA. This increase in Emax, in turn, disappeared when this challenge was realized in organ bath containing depolarizing nutrient solution (KCl 60 mm/L) or when BQ123 (10-6M) or BQ788 (10-6M) were added in the incubation together with L-NAME (10-4M). It was also observed an increase of the Ang II Emax in the ORX animals compared to the AIA and ORX+AIA animals, when the challenge was performed in the presence of Apocynin (10-4M). In addition, AIA and/or ORX decreased the protein expression of AT1 receptors without modifying AT2 receptors. The values of FRAP, nitrite/nitrate and uric acid did not show differences between the studied groups, but FOX values decreased in the AIA group. These data suggest that AIA or ORX does not substantially modify systemic redox balance, endothelial function, as well as aortic and Ang II responses, if all endothelial modulatory mechanisms are present. However, AIA seems to mobilize endothelial mechanisms to act as NO backup, whenever the synthesis of this gas is inhibited. Possibly, such mechanisms are activated via ETA and ETB receptors and involve both vasodilatory prostanoids and mechanisms that induce hyperpolarization of vascular smooth muscle cells present in the aorta. Testosterone, on the other hand, does not seem to play a decisive role in the mobilization of these local mechanisms that cooperate with NO.
Descrição
Palavras-chave
Angiotensina II, Artrite experimental, EDHF, Endotelina-1, Eicosanoides, Testosterona, Angiotensin II, Experimental arthritis, Endothelin-1, Eicosanoids, Testosterone