[Cardiovascular effects of beta1 and beta3-adrenergic receptor autoantibodies in Lewis rat]. / Effets cardiovasculaires des auto-anticorps anti-récepteurs béta1 et béta3-adrénergiques chez le rat Lewis.

PURPOSE: To analyze vascular reactivity changes in response to immunization protocols with antigens corresponding to the second extracellular loop of -ß3 and -ß1 and 3 adrenergic receptors (AR). METHODS: Lewis rats were immunized for 3months with peptidic sequences corresponding to the second extracellular loop of ß3-AR or ß1 and 3-AR. Specific ß3-AR antibodies were characterized by Elisa and purified using "Proteus Protein G" kit. Their functionality were tested in rabbit isolated ventricular cardiomyocytes. Aortic and mesenteric artery rings isolated from control or immunized rats were mounted in organ baths and precontracted with phenylephrine. Then, relaxant curves were established. RESULTS: SR58611A (10nM), a preferential ß3-AR agonist and purified ß3-AR antibodies (25µg/mL) induced a decrease of cell shortening (-39.56±4.4% [n=11] and -18.45±3.9% [n=10] respectively) in isolated cardiomyocytes. This decrease was significantly inhibited when the cardiomyocytes were pre-incubated with the L-748337 (1µM), a selective ß3-AR antagonist (P<0.05). In contrast with what was observed in rats immunized against the ß1-AR, vasorelaxations induced by acetylcholine and SR58611A in both aorta and mesenteric arteries were unaltered in rats immunized against the ß3-AR and ß1 and 3-AR. CONCLUSION: These results show, for the first time, that ß3-AR antibodies induced a ß3-AR agonist-like activity. They would not have a vascular pathogenic action but would offset the endothelial dysfunction caused by ß1-AR antibodies.

Antibodies against the second extracellular loop of ß1-adrenergic receptors induce endothelial dysfunction in conductance and resistance arteries of the Wistar rat.

Autoantibodies against ß1-adrenoceptors (ß1-ARs) have been detected in the serum of patients with various cardiac diseases; however, the pathological impact of these autoantibodies (ß1-AABs) has only been evaluated in cardiac tissue. The purpose of the present study was to evaluate whether ß1-AABs have deleterious effects on vascular reactivity in rats. An enzyme-linked immunosorbent assay was used to detect ß1-AABs in sera from immunized rats over a period of 1-3 months using the peptidic sequence of the second extracellular loop of human ß1-AR. Functional studies were performed in thoracic aortic (TA) and small mesenteric artery (SMA) rings from immunized rats. Following pre-contraction with phenylephrine (0.3 µM and 3 µM for the TA and SMA respectively), cumulative concentration-response curves (CCRCs) to various ß-AR agonists (isoproterenol, dobutamine, salbutamol, SR 58611A), acetylcholine, A23187, and sodium nitroprusside (SNP) were then plotted. The relaxations induced by dobutamine, SR 58611A, and acetylcholine were significantly impaired, but salbutamol-induced relaxations were not affected, in both vessels from immunized rats. A significant impairment of isoproterenol-induced relaxation was only observed in SMA. CCRCs to SNP were not modified in either of the vessels. A23187-induced relaxation was impaired in immunized rats. Following pretreatment with L-arginine, vasorelaxation to acetylcholine and SR 58611A was restored in immunized rats. This study demonstrates that immunization against the second extracellular loop of ß1-ARs has a deleterious impact on vasorelaxations in the TA and SMA of rats, involving alterations in endothelium-dependent NO signaling pathways.

[Antibodies against the second extracellular loop of beta1-adrenergic receptor induce aortic endothelial dysfunction in Wistar rat]. / Les anticorps dirigés contre la deuxième boucle extracellulaire des récepteurs adrénergiques ß(1) induisent une dysfonction endothéliale dans l'aorte de rat Wistar.

PURPOSE: To evaluate the effect of active immunization with a peptide corresponding to the second extracellular loop of the human beta1-adrenoceptors (ß(1)-AR) on the reactivity of Wistar rat isolated aorta. METHODS: Nine-week-old Wistar rats were actively immunized for 3months with a peptide corresponding to the second extracellular loop of the human ß(1)-AR. Specific immunoglobulins G (IgG) were characterized by Elisa and the bicinchonic acid protein assay and their functionality were tested in isolated ventricular cardiomyocytes (IVC) from control rats. Aortic rings isolated from control or immunized rats were mounted in organ baths. Then, contractile curves to phenylephrine (1nM to 300µM) and relaxant curves to acetylcholine (1nM to 100µM) and isoprenaline (1nM to 30µM) were established. RESULTS: Cell shortening increased dose-dependently in rat IVC superfused with IgG containing ß(1)-AR antibodies (10 or 25µg/mL). Isoprenaline-induced positive inotropy was strongly reduced in IgG containing ß(1)-AR antibodies preincubated (3h) IVC. Phenylephrine-and acetylcholine-induced aortic responses were greatly inhibited in immunized rats compared to control ones. However, active immunization did not influence the isoprenaline-mediated relaxation. CONCLUSIONS: The present work confirms that ß(1)-AR antibodies directed against the second extracellular loop of ß(1)-AR induce a positive inotropic effect in adult rat IVC. Moreover, we demonstrated, for the first time, that 3-month immunization with ß(1)-AR peptide was associated with altered aortic endothelial function without change in the ß-AR-mediated vasorelaxation.