Participation of hepatic α/β-adrenoceptors and AT1 receptors in glucose release and portal hypertensive response induced by adrenaline or angiotensin II

It has been previously demonstrated that the hemodynamic effect induced by angiotensin II (AII) in the liver was completely abolished by losartan while glucose release was partially affected by losartan. Angiotensin II type 1 (AT1) and adrenergic (∝1- and β-) receptors (AR) belong to the G-proteins superfamily, which signaling promote glycogen breakdown and glucose release. Interactive relationship between AR and AT1-R was shown after blockade of these receptors with specific antagonists. The isolated perfused rat liver was used to study hemodynamic and metabolic responses induced by AII and adrenaline (Adr) in the presence of AT1 (losartan) and ∝1-AR and β-AR antagonists (prazosin and propranolol). All antagonists diminished the hemodynamic response induced by Adr. Losartan abolished hemodynamic response induced by AII, and AR antagonists had no effect when used alone. When combined, the antagonists caused a decrease in the hemodynamic response. The metabolic response induced by Adr was mainly mediated by ∝1-AR. A significant decrease in the hemodynamic response induced by Adr caused by losartan confirmed the participation of AT1-R. The metabolic response induced by AII was impaired by propranolol, indicating the participation of β-AR. When both ARs were blocked, the hemodynamic and metabolic responses were impaired in a cumulative effect. These results suggested that both ARs might be responsible for AII effects. This possible cross-talk between β-AR and AT1-R signaling in the hepatocytes has yet to be investigated and should be considered in the design of specific drugs.

Avaliação dos eixos ECA / ANG II / AT1 e ECA-2 / ANG (1-7) / MAS em fibroblastos de gengiva e ligamento periodontal humanos estimulados por IL-1ß e sua contribuição na produção e regulação de citocinas e quimiocinas / Evaluation ACE /ANG II /AT1 and ACE-2 /ANG (1-7) /MAS axis in gingival and periodontal ligament human fibroblasts stimulated with IL-1ß and its contribution in the production of cytokines and chemokines

O Sistema renina-angiotensina (SRA) tem sido relatado como um importante modulador de processos inflamatórios e imunológicos, incluindo a doença periodontal (DP). Estudos sugerem neste sistema um eixo alternativo (ECA-2 /ANG(1-7) /MAS) que atuaria como um contra-regulador de efeitos mediados pelo clássico eixo (ECA /ANGII /AT1). Sabe-se que bactérias periodontopatogênicas, como a Porphyromonas gingivalis (Pg), possuem componentes bioativos de membrana (ex. lipopolissacarídeos-LPS) capazes de induzir uma forte resposta imune no hospedeiro devido à liberação de citocinas nas células, entre elas Interleucina (IL)- 1ß. Neste contexto, fibroblastos são as células mais abundantes nos tecidos periodontais e possuem em sua superfície celular receptores necessários para o reconhecimento da invasão bacteriana, ativando cascatas intracelulares, que levam à produção de citocinas. O objetivo deste estudo foi verificar se os eixos ECA/ ANGII/ AT1 e ECA-2/ ANG(1-7)/ MAS contribuem para a produção e/ ou regulação de citocinas inflamatórias (CI) por fibroblastos de gengiva humana (HGF) e ligamento periodontal humano (HPLF) estimulados por IL-1ß. Após o pré-tratamento com Losartan e Ang (1-7) ou silenciamento mediado por RNA de interferência (RNAi) de AT1, HGF e HPLF foram estimulados por IL-1ß por 3 horas (RNAm) ou 24 horas (proteína). Expressão de RNAm para AT1, MAS, ECA, ECA-2, IL-1ß, TNF-α, IL-6, IL-8, IL-10, TGF-ß, CXCL12, RANK-L e OPG foram avaliados por RT-qPCR e das proteínas IL-6, IL-8, ECA e ECA-2 por ELISA. Foi realizado também Western Blot para detecção de AT1 e ECA nos extratos celulares e dosagem de nitrito no sobrenadante das culturas. Ambos os subtipos de fibroblastos mostraram aumento da expressão de RNAm para AT1, IL-1ß, IL-6, IL-8, TNF-α e OPG, quando estimulados por IL-1ß. No entanto, apenas em HPLF foi observado aumento para MAS, ECA e TGF-ß. Losartan e Ang (1-7) não modularam o transcrito, a secreção de CI e nem a produção de nitrito no sobrenadante das culturas, tanto em HGF como em HPLF. O silenciamento do receptor AT1 reduziu a secreção de IL-6 e IL-8 induzida por IL-1ß em cultura de HGF e HPLF e aumentou a expressão gênica de OPG somente em HGF. Estes resultados sugerem que o silenciamento de AT1, mas não o bloqueio farmacológico deste receptor pelo antagonista Losartan, em HGF e HPLF, pode controlar a produção de IL-6 e IL-8, que por sua vez contribuem para a patogênese periodontal.(AU)

The renin-angiotensin system (RAS) has been reported as an important modulator of inflammatory and immune responses, including periodontal disease (PD). Studies suggest an alternative axis as part of this system (ACE-2 / ANG (1-7) / MAS) that would act as counter-regulatory to the classical axis (ECA / ANGII / AT1). It is known that periodontal bacteria such as Porphyromonas gingivalis (Pg) have bioactive components in their membrane (such as lipopolysaccharide-LPS) capable of inducing a strong immune response in the host due to the release of cytokines in cells, including interleukin (IL) - 1ß. In this regard, fibroblasts are the most abundant cells in periodontal tissues and receptors needed for the recognition of bacterial invasion by activating intracellular cascades that lead to cytokine production. The aim of this study was to determine whether the axes ACE / ANGII / AT1 and ACE-2 / ANG (1-7) / MAS contribute to the production and / or regulation of inflammatory cytokines (IC) by fibroblasts of human gingiva (HGF) and human periodontal ligament (HPLF) stimulated IL-1ß. After pre-treatment with Losartan, Ang (1-7) or silencing mediated by RNA interference (RNAi) of AT1, HGF and HPLF were stimulated by IL-1ß for 3 hours (RNAm) or 24 hours (protein). Expression mRNA for AT1, MAS, ACE, ACE-2, IL-1ß, TNF-α, IL-6, IL-8, IL-10, TGF-ß, CXCL12, RANK-L and OPG was assessed by RT- qPCR and proteins IL-6, IL-8, ACE and ACE-2 by ELISA. Western Blot for the detection of AT1 and ECA and dosage of nitrite was also performed. Experiments stimulated by IL-1ß showed a positive control for gene expression AT1, IL-1ß, IL-6, IL-8, TNF-α and OPG in HGF and HPLF and MAS, ACE and TGF-ß only HPLF. Losartan and Ang (1-7) did not modulate the transcription and secretion of IC and no nitrite production in the culture supernatant of HGF and HPLF. The silencing AT1 reduced IL-6 secretion and IL-8 induced by IL- ß in cultured HGF and HPLF and increased OPG gene expression only HGF. These results suggest that silencing AT1, but not pharmacological blockade of this receptor by Losartan in HPLF and HGF, can control the production of IL-6 and IL-8, which in turn contribute to the pathogenesis of periodontal disease.(AU)

Acciones de endotelina 1 y angiotensina II en embarazos complicados con preeclampsia / Endothelin 1 and angiotensin II in preeeclampsia

Introduction. It is generally thought that development of hypertension in preeclampsia (PE) is due to generalized endothelial dysfunction and/or results from an imbalance in the production and/or action of vasoactive factors, resulting in higher citosolic Ca2+ concentration which in turn leads to vasoconstriction and decreased blood pressure perfusion in organs, including the fetoplacental unit. Among vasoactive factors involved in blood pressure regulation, endothelin 1 (ET-1) and angiotensin II (Ang II) regulate citosolic Ca2+ concentrations and therefore are considered in this review. PE is associated with higher circulating and placental ET-1 levels, observation that explains, at least in part, vasoconstriction and oxidative stress. Higher and lower Ang II sensitivity seen in PE and normal pregnancy, respectively, could not be explained by changes in renin-angiotensin system components, including Ang II receptors (ATI). During normal pregnancy, ATI receptors are found as monomers and are inactivated by reactive oxygen species (ROS) leading to lower Ang II sensitivity. In contrast, PE is associated with increased ATl/bradicinin receptors (B2) heterodimers which are resistant to inactivation by ROS, maintaining increased ATI-receptor stimulated signaling in PE. In adittion, AT-1 agonistic antibodies (AT1-AA) obtained from PE women increases intracellular Ca2+, NADPH oxidase components and ROS, effects not observed with normal pregnancy AT1-AA. Conclusion. High ET-1 levels, the presence of AT1/B2 receptor heterodimers and increased AT1-AA are involved, at least in part, in the hypertensive and oxidative stress states in PE.

Introducción. Se reconoce que el desarrollo de la hipertensión en la preeclampsia (PE) resulta del daño endotelial generalizado y/o de la falta de equilibrio en la producción y/o acción de agentes vasoactivos, lo que conlleva al incremento en la concentración citosólica de Ca2+ que resulta en vasoconstricción y disminución de la perfusión sanguínea en los órganos, incluyendo la unidad fetoplacentaria. Dentro de los factores vaso-activos que regulan la presión arterial, en la presente revisión se consideró a la endotelina 1 (ET-1) y a la angiotensina II (Ang II), factores que regulan la concentración citosólica de Ca2+. En comparación con el embarazo normal, la PE se asocia con mayor concentración en suero y placenta de ET-1, lo que explica en parte la vasoconstricción y el estado de estrés oxidativo. La respuesta exagerada en la PE y el estado de refractariedad en el embarazo normal a la Ang II no pueden explicarse por componentes del sistema renina-angiotensina, incluyendo a los receptores de Ang II (ATI). Durante el embarazo normal los receptores AT-1 se encuentran en forma de monómeros y son inactivados por las especies reactivas de oxígeno (ROS), lo que se asocia con menor respuesta a Ang II. En cambio, la respuesta exagerada a la Ang II durante la PE puede deberse a la heterodimerizacion de los receptores ATI con los de bradicinina (B2), estado que les confiere resistencia a la inactivación por las especies reactivas de oxígeno (ROS), lo que explica el incremento en la concentración del Ca2+ intracelular. Además, los anticuerpos agonistas del receptor ATI (AT1-AA) de mujeres PE aumenta la concentración de Ca2+ intracelular, de la NADPH oxidasa y de ROS, efectos que no se presentan al utilizar AT1-AA de embarazadas normotensas. Conclusión. Las altas concentraciones de ET-1, la presencia de receptores ATI en forma de heterodimeros ATI/ B2 y el aumento en los AT1-AA explican en parte, el estado de hipertensión y de estrés oxidativo de la PE.