Poliaminas beta-adrenoceptores

Pharmacological Reports
2010, 62, 696–706 ISSN 1734-1140

Copyright © 2010 by Institute of Pharmacology Polish Academy of Sciences

Functional effects of polyamines via activation of human b1- and b2-adrenoceptors stably expressed in CHO cells
Clara Meana1*, Javier Bordallo1,3*, Carmen Bordallo2,3, Lorena Suárez3, Begoña Cantabrana1,3, Manuel Sánchez1,3


Farmacología, Departamento deMedicina, Universidad de Oviedo, Julián Clavería 6, Oviedo 33006, Spain
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Departamento de Bioquímica y Biología Molecular and Instituto Universitario de Oncología del Principado de Asturias, Edificio Santiago Gascón, Campus El Cristo, Universidad de Oviedo, 33006 Oviedo, Spain Correspondence: Manuel Sánchez, e-mail: sanchezf@uniovi.es

Abstract: Polyamines mediate acute metabolic effects andcardiac hypertrophy associated with b-adrenoceptor stimulation. They may also modulate b-adrenoceptors, causing functional responses in rat atria and tracheal smooth muscle. The aim of this study was to determine whether polyamines interact with human b1- and b2-adrenoceptors and the functional consequences of such an interaction. Chinese hamster ovary (CHO) cells stably transfected with human b1-and b2-adrenoceptors were used to evaluate the effect of polyamines binding to b-adrenoceptors, cAMP production and morphological changes, which were pharmacologically validated by investigating the effects of the b-adrenoceptor agonists, isoproterenol and salbutamol. Polyamines interacted with human b1- and b2-adrenoceptors, as shown by the displacement of [125I]iodocyanopindolol in the bindingassay. Putrescine showed higher affinity to b1- than b2-adrenoceptors. Spermidine and spermine produced partial displacement (approximately 50%) and, at the highest concentration, the effect was reversed. Putrescine and spermine acutely increased cAMP and, in a serum-free medium, induced a stellate-like form in cells, which was inhibited by propranolol, a b-blocker. A 10 to 15 h incubation withputrescine produced a spindle-like form and spatial organization via b-adrenoceptor activation, evidenced by the antagonizing effect by propranolol and lack of effect in wild-type CHO cells. Additionally, it decreased cell proliferation independently of b-adrenoceptor activation. Spermine caused cell death via fetal bovine serum-dependent and -independent mechanisms. The results suggest thatputrescine may act as a non-selective and low affinity agonist of human b1- and b2-adrenoceptors, eliciting morphological changes. These findings may be of importance in physiology and in diseases involving b-adrenoceptor functionality. Key words: polyamines, putrescine, spermine, b-adrenoceptors, cAMP, Chinese hamster ovary (CHO)

Introduction

The polyamines, putrescine, spermidine and spermine,belong to a family of low-molecular-weight or* C. Meana and J. Bordallo contributed equally to this work

ganic polycations that are involved in several physiological [34] and pathological conditions [19, 21, 25]. These effects are due to the interactions of polyamines with DNA, RNA and a variety of cytoplasmic ligands and membrane proteins.

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Pharmacological Reports, 2010, 62, 696–706Cellular effects of polyamines via human b-adrenoceptors
Clara Meana et al.

In the heart, intracellular polyamines are mediators of acute effects caused by isoproterenol, such as the increase of Ca2+ flux [9, 15], which may increase contractile responses by increasing myofilament Ca2+ sensitivity [27, 41]. The polyamine putrescine elicited cardiotonic effects associated with an increase ofcAMP [2]. The inhibition of ornithine decarboxylase activity, the initial rate-limiting enzyme in the biosynthesis of polyamines, by a-difluoromethylornithine [24] antagonized these effects [2], which suggested that cytoplasmic polyamines may have a role in the contractile properties of cardiac muscle [2, 11]. In addition, polyamines are involved in cardiac hypertrophy and myocardial damage...