Investigação da dessensibilização e internalização de adrenoceptores α1A nativos e recombinantes
Carregando...
Data
2008
Autores
Akinaga, Juliana [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
Os α1-ARs são membros da superfamília de receptores acoplados à proteína G (GPCR), podendo ser divididos em três diferentes subtipos (α1A-, α1B- e α1D-ARs), sendo todos semelhantemente ativados pela noradrenalina e adrenalina. Os agonistas seletivos de α1-ARs podem ser classificados em duas classes químicas, as feniletilaminas e as imidazolinas e são utilizados, por exemplo, para tratamento de hipotensão e também como descongestionantes nasais. O presente estudo investigou a capacidade dos agonistas de α1-ARs induzirem taquifilaxia nas contrações do ducto deferente de rato e internalização de α1A-ARs conjugados com proteína fluorescente verde (GFP) expressos em células HEK293. Os resultados mostram que dentre todos os agonistas testados da classe das feniletilaminas (noradrenalina, metoxamina e fenilefrina) e imidazolinas (A61603, nafazolina e oximetazolina) apenas a oximetazolina foi capaz de induzir taquifilaxia em curvas concentração-resposta consecutivas próprias e também em curvas concentraçãoresposta de noradrenalina feitas em preparações de ducto deferente de rato. A taquifilaxia induzida pela oximetazolina é dependente da ativação de α1A-ARs, uma vez que a incubação concomitante da oximetazolina com o antagonista seletivo de α1-ARs, o prazosin, inibiu a taquifilaxia. Estudos feitos com microscopia confocal utilizando α1A-ARs conjugados com GFP mostram que a oximetazolina é capaz de induzir um aumento da fluorescência intracelular já nos primeiros 5 minutos de incubação enquanto que a noradrenalina não é capaz de induzir aumento do mesmo parâmetro mesmo após 30 minutos de incubação. Esse aumento da fluorescência intracelular é um indicativo do processo de internalização dos α1A-ARs conjugados com GFP induzido pela oximetazolina mas não pela noradrenalina e pode estar relacionado com a taquifilaxia observada nos experimentos...
The α1-ARs are G-protein coupled receptors (GPCR) composed by three subtypes (α1A-, α1B- e α1D-ARs), similarly activated by epinephrine an norepinephrine. The selective agonists of α1-ARs can be classified into two different chemical classes, the phenylethylamines and imidazolines, which are used for treatment of hypertension and as nasal decongestants. The present study investigated the ability of some α1-ARs agonists to induce tachyphylaxis in the contractions of rat vas deferens and internalization of the α1A-ARs tagget with green fluorescent protein (GFP) expressed in HEK293 cells. It was observed in the rat vas deferens that, among all agonists tested (the phenylethylamines norepinephrine, metoxamine, phenylephrine and imidazolines A61603, naphazoline and oxymetazoline), only oxymetazoline can induce tachyphylaxis in consecutive concentration-response curves and also in concentration-response curves to norepinephrine. The tachyphylaxis induced by oxymetazoline is dependent on α1-ARs activation, since it was inhibited in presence of prazosin, a α1-ARs selective antagonist. Confocal microscopy studies of HEK 293 cells expressing α1A-ARs tagget with GFP show that oxymetazoline can induce prompt and time-dependent increase in intracellular fluorescence already after 5 minutes of incubation, whereas norepinheprine was unable to increase intracellular fluorescence even after 30 minutes of incubation. This increase in intracellular fluorescence indicates that oxymetazoline, but not norepinephrine, induces internalization of the α1A-ARs tagget with the GFP. The internalization of α1A-ARs tagget with the GFP induced by oxymetazoline may be related to the tachyphylaxis observed in funtional experiments. However, other studies are necessary to understand the mechanisms of tachyphylaxis and internalization induced by oxymetazoline in the present study.
The α1-ARs are G-protein coupled receptors (GPCR) composed by three subtypes (α1A-, α1B- e α1D-ARs), similarly activated by epinephrine an norepinephrine. The selective agonists of α1-ARs can be classified into two different chemical classes, the phenylethylamines and imidazolines, which are used for treatment of hypertension and as nasal decongestants. The present study investigated the ability of some α1-ARs agonists to induce tachyphylaxis in the contractions of rat vas deferens and internalization of the α1A-ARs tagget with green fluorescent protein (GFP) expressed in HEK293 cells. It was observed in the rat vas deferens that, among all agonists tested (the phenylethylamines norepinephrine, metoxamine, phenylephrine and imidazolines A61603, naphazoline and oxymetazoline), only oxymetazoline can induce tachyphylaxis in consecutive concentration-response curves and also in concentration-response curves to norepinephrine. The tachyphylaxis induced by oxymetazoline is dependent on α1-ARs activation, since it was inhibited in presence of prazosin, a α1-ARs selective antagonist. Confocal microscopy studies of HEK 293 cells expressing α1A-ARs tagget with GFP show that oxymetazoline can induce prompt and time-dependent increase in intracellular fluorescence already after 5 minutes of incubation, whereas norepinheprine was unable to increase intracellular fluorescence even after 30 minutes of incubation. This increase in intracellular fluorescence indicates that oxymetazoline, but not norepinephrine, induces internalization of the α1A-ARs tagget with the GFP. The internalization of α1A-ARs tagget with the GFP induced by oxymetazoline may be related to the tachyphylaxis observed in funtional experiments. However, other studies are necessary to understand the mechanisms of tachyphylaxis and internalization induced by oxymetazoline in the present study.
Descrição
Palavras-chave
Obesidade mórbida, Resistência à insulina, Disturbios menstruais
Como citar
AKINAGA, Juliana. Investigação da dessensibilização e internalização de adrenoceptores α1A nativos e recombinantes. 2008. 47 f. Dissertação (mestrado) - Universidade Estadual Paulista, Instituto de Biociências de Botucatu, 2008.