RESUMO
Alamandine (ALA) exerts protective effects similar to angiotensin (Ang) (1-7) through Mas-related G protein-coupled receptor type D receptor (MrgDR) activation, distinct from Mas receptor (MasR). ALA induces anti-inflammatory effects in mice but its impact in human macrophages remains unclear. We aimed to investigate the anti-inflammatory effects of ALA in human macrophages. Interleukin (IL)-6 and IL-1ß were measured by ELISA in human THP-1 macrophages and human monocyte-derived macrophages exposed to lipopolysaccharide (LPS). Consequences of MasR-MrgDR heteromerization were investigated in transfected HEK293T cells. ALA decreased IL-6 and IL-1ß secretion in LPS-activated THP-1 macrophages. The ALA-induced decrease in IL-6 but not in IL-1ß was prevented by MasR blockade and MasR downregulation, suggesting MasR-MrgDR interaction. In human monocyte-derived M1 macrophages, ALA decreased IL-1ß secretion independently of MasR. MasR-MrgDR interaction was confirmed in THP-1 macrophages, human monocyte-derived macrophages, and transfected HEK293T cells. MasR and MrgDR formed a constitutive heteromer that was not influenced by ALA. ALA promoted Akt and ERK1/2 activation only in cells expressing MasR-MrgDR heteromers, and this effect was prevented by MasR blockade. While Ang-(1-7) reduced cellular proliferation in MasR -but not MrgDR- expressing cells, ALA antiproliferative effect was elicited in cells expressing MasR-MrgDR heteromers. ALA also induced an antiproliferative response in THP-1 cells and this effect was abolished by MasR blockade, reinforcing MasR-MrgDR interaction. MasR-MrgDR heteromerization is crucial for ALA-induced anti-inflammatory and antiproliferative responses in human macrophages. This study broaden our knowledge of the protective axis of the RAS, thus enabling novel therapeutic approaches in inflammatory-associated diseases.
RESUMO
The renin angiotensin system (RAS) plays a major role in blood pressure regulation and electrolyte homeostasis and is mainly composed by two axes mediating opposite effects. The pressor axis, constituted by angiotensin (Ang) II and the Ang II type 1 receptor (AT1R), exerts vasoconstrictor, proliferative, hypertensive, oxidative and pro-inflammatory actions, while the depressor/protective axis, represented by Ang-(1-7), its Mas receptor (MasR) and the Ang II type 2 receptor (AT2R), opposes the actions elicited by the pressor arm. The MasR belongs to the G protein-coupled receptor (GPCR) family. To avoid receptor overstimulation, GPCRs undergo internalization and trafficking into the cell after being stimulated. Then, the receptor may induce other signaling cascades or it may even interact with other receptors, generating distinct biological responses. Thus, control of a GPCR regarding space and time affects the specificity of the signals transduced by the receptor and the ultimate cellular response. The present chapter is focused on the signaling and trafficking pathways of MasR under physiological conditions and its participation in the pathogenesis of numerous brain diseases.
Assuntos
Endocitose , Proto-Oncogene Mas , Sistema Renina-Angiotensina , Humanos , Angiotensina II/metabolismo , Angiotensina II/farmacologia , Pressão Sanguínea/fisiologia , Proto-Oncogene Mas/metabolismo , Receptores Acoplados a Proteínas G/metabolismo , Sistema Renina-Angiotensina/fisiologiaRESUMO
A close relationship between angiotensin II (ANG II) and the renal dopaminergic system (RDS) has been reported. Our aim was to study whether renal dopamine and ANG II can interact to modify renal sodium handling and then to elucidate the related mechanism. Anesthetized male Sprague-Dawley rats were used in experiments. ANG II, exogenous dopamine, and decynium-22 (or D-22, an isocyanine that specifically blocks electrogenic organic cation transporters, OCTs), were infused in vivo for 120 min. We analyzed renal and hemodynamic parameters, renal Na+, K+-ATPase levels, OCT activity, and urinary dopamine concentrations. We also evaluated the expression of D1 receptor, electroneutral organic cation transporters (OCTNs), and OCTs. ANG II decreased renal excretion of sodium in the presence of exogenous dopamine, increased Na+, K+-ATPase activity, and decreased the urinary dopamine concentration. D-22 treatment exacerbated the ANG II-mediated decrease in renal excretion of sodium and dopamine urine excretion but did not modify ANG II stimulation of Na+, K+-ATPase activity. The infusion of ANG II did not affect the expression of D1 receptor, OCTs, or OCTNs. However, the activity of OCTs was diminished by the presence of ANG II. Although ANG II did not alter the expression of D1 receptor, OCTs, and OCTNs in renal tissues, it modified the activity of OCTs and thereby decreased the urinary dopamine concentration, showing a novel mechanism by which ANG II decreases dopamine transport and its availability in the tubular lumen to stimulate D1 receptor. This study demonstrates a relationship between ANG II and dopamine, where both agents counteract their effects on sodium excretion.
Assuntos
Angiotensina II , Cátions , Rim , Adenosina Trifosfatases/metabolismo , Angiotensina II/farmacologia , Animais , Cátions/metabolismo , Dopamina/metabolismo , Rim/efeitos dos fármacos , Masculino , Ratos , Ratos Sprague-Dawley , Sódio/metabolismoRESUMO
G-protein-coupled receptors (GPCRs) are targets for around one third of currently approved and clinical prescribed drugs and represent the largest and most structurally diverse family of transmembrane signaling proteins, with almost 1000 members identified in the human genome. Upon agonist stimulation, GPCRs are internalized and trafficked inside the cell: they may be targeted to different organelles, recycled back to the plasma membrane or be degraded. Once inside the cell, the receptors may initiate other signaling pathways leading to different biological responses. GPCRs' biological function may also be influenced by interaction with other receptors. Thus, the ultimate cellular response may depend not only on the activation of the receptor from the cell membrane, but also from receptor trafficking and/or the interaction with other receptors. This review is focused on angiotensin receptors and how their biological function is influenced by trafficking and interaction with others receptors.
RESUMO
The aim of this study was to demonstrate the effects of atrial natriuretic peptide (ANP) on organic cation transporters (OCTs) expression and activity, and its consequences on dopamine urinary levels, Na+, K+-ATPase activity and renal function. Male Sprague Dawley rats were infused with isotonic saline solution during 120 minutes and randomized in nine different groups: control, pargyline plus tolcapone (P+T), ANP, dopamine (DA), D-22, DA+D-22, ANP+D-22, ANP+DA and ANP+DA+D-22. Renal functional parameters were determined and urinary dopamine concentration was quantified by HPLC. Expression of OCTs and D1-receptor in membrane preparations from renal cortex tissues were determined by western blot and Na+, K+-ATPase activity was determined using in vitro enzyme assay. 3H-DA renal uptake was determined in vitro. Compared to P+T group, ANP and dopamine infusion increased diuresis, urinary sodium and dopamine excretion significantly. These effects were more pronounced in ANP+DA group and reversed by OCTs blockade by D-22, demonstrating that OCTs are implied in ANP stimulated-DA uptake and transport in renal tissues. The activity of Na+, K+-ATPase exhibited a similar fashion when it was measured in the same experimental groups. Although OCTs and D1-receptor protein expression were not modified by ANP, OCTs-dependent-dopamine tubular uptake was increased by ANP through activation of NPR-A receptor and protein kinase G as signaling pathway. This effect was reflected by an increase in urinary dopamine excretion, natriuresis, diuresis and decreased Na+, K+-ATPase activity. OCTs represent a novel target that links the activity of ANP and dopamine together in a common mechanism to enhance their natriuretic and diuretic effects.