Allopregnant IgG binds and modulates the activity of uterine beta adrenoceptors

Ratones hembra Balb/c fueron apareados con machos C3H para obtener de las hembras una IgG de preñez alogeneica. Esta IgG activa los receptores ß adrenérgicos presentes en el útero de hembras C3H. En este trabajo se muestra que la IgG obtenida de hembras en alopreñez al interactuar con el receptor ß adrenérgico uterino de hembras C3H produce una inhibición de la motilidad espontánea uterina e incrementa los niveles intracelulares de AMPc. Ambos efectos son bloqueados por el antagonista ß adrenérgico propranolol. Por otra parte la IgG de preñez alogeneica interfiere la unión del radioligando ß específico 3H dihidroalprenolol comportándose como un inhibidor no competitivo. Los datos indican que esta IgG sería capaz de modular la actividad funcional de los receptores ß adrenérgicos uterinos (AU)

Allopregnant IgG binds and modulates the activity of uterine beta adrenoceptors.

Female Balb/c mice were mated to C3H male mice, to obtain an allopregnant IgG. This allopregnant IgG con activate beta-adrenoceptors of C3H uterus. Here we show that allopregnant IgG interacts with beta-adrenoceptors in uterus of C3H mice and produces a decrease of the spontaneous motility and an increase of the intracellular cAMP concentration. Both effects are blocked by propranolol, a beta-adrenergic antagonist. Allopregnant IgG interferes with the binding of a specific beta adrenergic radioligand 3H-dihydroalprenolol behaving as a non competitive inhibitor. All these data indicate that allopregnant IgG could modulate the activity of uterine beta-adrenoceptors.

Interacción de anticuerpos con receptores cardiacos para neurotransmisores / Interaction of antibodies with cardiac receptors for neurotransmitters

En este trabajo se demuestra que los anticuerpos dirigidos contra los receptores a neurotransmisores cardíacos son capaces de alterar la fisiología, farmacología y bioquímica del órgano adrenérgicos cardíacos y modular la actividad cardíaca. Estos anticuerpos simulan la actividad de un agonista beta adrenérgico parcial, puesto que incrementan la contractilidad cardíaca, pero disminuyen la reactividad del agonista beta adrenérgico exógeno. La IgG chagásica inhibe la unión del radioligando específico de los receptores beta adrenérgicos en membranas cardíacas purificadas. De la interacción del anticuerpo con los receptores beta adrenérgicos, se producen señales intracelulares que se traducen por un incremento en la actividad de adenilatociclasa, una estimulación de la Ca++-ATPasa e inhibición de la Na+ + K+-ATPAsa. La disminución de estas enzimas involucra modificaciones del equilibrio termodinámico celular, que llevan a alteraciones morfológicas y funcionales del tejido, lo que permite atribuir al anticuerpo un probable rol patogénico en la miocardiopatía chagásica. Otros anticuerpos dirigidos contra antígenos carditis autoinmune, también son capaces de unirse al receptor beta adrenérgico cardíaco acoplado a la adenilatociclasa y alterar así la función del órgano blanco. La detección de anticuerpos dirigidos contra receptores a neurotransmisores podría servir de marcador biológico durante las etapas tempranas del desarrollo de enfermedades autoinmunes (AU)

Interacción de anticuerpos con receptores cardíacos para neurotransmisores. / [Interaction of antibodies with cardiac neurotransmitter receptors]

This paper demonstrates that antibodies against neurotransmitter receptors of the cardiac membrane are able to alter the physiology, pharmacology and biochemistry of the target organ. Sera from chagasic patients contain an antibody which binds to beta adrenoceptors of myocardium and modulates their activity. Chagasic IgG simulates a partial beta agonist by increasing contractility and diminishing reactivity to exogenous norepinephrine. Moreover, chagasic IgG inhibits the binding of the specific radioligand to purified cardiac membranes. The interaction of chagasic IgG with beta-adrenoceptors triggers signal transduction resulting in the stimulation of adenylate cyclase with an increased production of cAMP. Stimulation of Ca(++)-ATPase and inhibition of Na+ + K(+)-ATPase are also observed. These enzyme dysfunctions induce modifications of cellular thermodynamic equilibrium that trigger both morphological and functional alterations of the myocardium. Other immune sera can also trigger pharmacologic effects on isolated atria. Immune IgG directed against specific alloantigens and IgG from mice with autoimmune myocarditis are able to recognize the beta adrenergic receptor-coupled adenylate cyclase system and alter the function of target organs. The detection of antibodies against neurotransmitter receptors could be a useful marker during the early stages of development of autoimmune diseases.

Participation of autonomic nervous system in the pathogenesis of Chagas disease.

Evidences accumulated over the last decade give adequate proof for the existence of circulating antibodies in Chagas disease which binds to beta adrenergic and muscarinic cholinergic receptor of lymphocytes and myocardium. The interaction of the antibodies with lymphocytes and cardiac neurotransmitter receptors behaving as an agonist, triggers in the cells intracellular signal transductions that alter the physiological behaviour of this cells. These events converted the cells in pathologically active cells. Thus, antibodies activating beta adrenergic receptors of T helper (Th) lymphocytes increase cAMP and releases PGE2 by T suppressor/cytotoxic (Ts/c) cell, inducing in this way, immunosuppression by simultaneous inhibition of Th and stimulation of Ts/c cell function. All these antibodies actions were mimetized by parasites membranes. On the other hand, the interaction of antibodies against heart beta adrenergic and cholinergic receptors trigger physiologic, morphologic, enzymatic and molecular alterations, that leading to cardiac damage. The analysis of the prevalence and distribution of these antibodies shows a strong association with seropositive asymptomatic patients with autonomic dysfunction in comparison with those asymptomatic without alteration of the heart autonomic disorders; pointing to that the presence of these antibodies may partially explain the cardiomyoneuropathy of Chagas disease, in which the sympathetic and parasympathetic systems are affected. The deposit of autoantibodies on the myocardial neurotransmitter receptors, behaving like an agonist, could induced desensitization and/or down regulation of the receptors. This in turn, could led to a progressive blockade of myocardium neurotransmitter receptors, with sympathetic and parasympathetic dennervation, a phenomenon that has been described in the course of Chagas cardioneuropathy.

Opposite effects of interleukin-2 (IL-2) and interferon gamma (IFN gamma) on rat atria contractility.

We have recently shown that interleukin 2 (IL-2) can increase the contractile strength or rat atrial muscle through the activation of phospholipases and protein kinase C. The results of this study confirm that the reaction of IL-2 with rat atria involves protein kinase C and not the Ca(++)-calmodulin dependent kinases. Phorbol 12-myristate 13-acetate (PMA), a tumor promoter that activates protein kinase C directly (bypassing the phosphoinositide turnover step), has effects that are similar to those of IL-2 on atrial contractility. Furthermore, preincubation of the tissue with PMA prevents the IL-2 effect, suggesting that the kinases activated by the tumor promoter and IL-2 share a common substrate. This effect of IL-2 on atrial contractility opposes the cholinomimetic inhibitory action of IFN gamma. Thus, preincubation of cardiac tissue with IL-2 or PMA eliminates the effects of IFN gamma and viceversa. Apparently, the inhibitory action of IL-2 on IFN gamma involves an impaired response or atria to cholinergic activation, as IL-2 shifts to the right the dose response curve of the tissue to the cholinergic muscarinic agonist carbachol. Protein kinase C is also necessary for the occurrence of the IL-2-IFN gamma interference. The results of this study suggest that, during an inflammatory reaction in the heart, the balance of the two lymphokines can determine changes in the response of the tissue to autonomous nervous system agonists or to the cytokines that mimic the effects of these neurotransmitters.

Experimental autoimmune myocarditis: a suitable model to study neuroimmune crosstalk.

This review regards the main functional characteristics of hearts subjected to an autoimmune response, focusing especially on the role of T lymphocytes and autoantibodies in the development of cardiac dysfunction. Evidence of a strong association in the onset and time-course of immune response and cardiac dysfunction is presented and the results are viewed comparatively with myocarditis models induced by heart, parasite or virus inoculation. Cardiac damage is evaluated regarding various aspects, namely histologic, immunologic, biochemical, pharmacologic, physiologic. Finally, the model, for its characteristics of resulting from an autoimmune response against the heart with functional consequences, has proved its usefulness to study neuroimmune interaction, mainly the immune to nervous direction, as autoantibodies and T cell-derived factors have a role in cardiac failure.

Myocardial mitogenic effect of erythropoietin through the activation of Na+-K+-ATPase activity

La eritropoyetina ha sido descripta clásicamente como el principal factor de crecimiento que promueve la proliferación y diferenciación de las células de la progenic eritroidea. En este trabajo hemos observado una acción modulatoria, dosis dependiente, de la eritropoyetina humana recombinante (rHuEpo) sobre la proliferación de un cultivo primario de miocardiocitos de rata. La rHuEpo en bajas concentraciones (0,1-1U/ml) estimula el crecimiento celular, pero en altas concentraciones (3-10 U/ml) lo inhibe. La acción mitogénica de la hormona tiene correlación con la actividade de Na+-K+-ATPasa microsomal cardíaca de modo tal que concentraciones de rHuEpo que incrementan el crecimiento celular estimulan la actividad de paranitrofenilfosfatasa (pNPfasa) mientras que concentraciones que inhiben la actividad enzimática bloquean la acción mitogénica de la hormona. Más aún, ouabaina 10**-5M, concentración que inhibe la actividade de Na+-ATPasa, impide la acción estimulatoria que ejerce la rHuEpo sobre la proliferación celular. A su vez, la rHuEpo mientras estimula la actividad de Na+-K+-ATPasa microsomal cardíaca, es capaz de modificar la acción contráctil de la ouabaina sobre aurículas aisladas de ratas neonatas de modo tal que 1 U/ml de EpoHur produjo un incremento de la acción no-tóxica del glicósido cardíaco, atenuando y retrasando el comienzo del efecto tóxico de la ouabaina. Estos resultados muestran que la rHuEpo presenta un efecto no hematopoyético sobre el miocardio, asociado con la actividad de Na+-K+-ATPasa cardíaca, que regula el crecimiento de miocardiocitos en eultivo y la acción biológica de los glicósidos cardíacos sobre la aurícula aislada de rata neonata (AU)

Functional pharmacological and morphological characteristics of two regions of rat uterine horns.

A histological, physiological and pharmacological study of two regions of the isolated uterine muscle of the rat., i.e., the myometrial one (a zone close to the mesometrial insertion) and the linea uteri (the antimesometrial zone) was performed. From the histological point of view the linea uteri (LU) is characterized by the presence of small bundles of longitudinal smooth muscle fibers (20 to 50), closely packed and clearly surrounded by a connective tissue, whereas in the myometrial zone (M) the smooth muscle fibers are less closely packed and the connective tissue is surrounding a greater number of them. The spontaneous oxytocin or electrically-induced initial tension developed by the LU or the M, was similar. Also the stability with time did not differ between both regions. Atropine depressed consistently the isometric developed tension of M strips, either spontaneously active or driven by oxytocin or electrical stimulation, but had no action on the mechanical activity of preparations from the LU. A pretreatment with hemicholinium also inhibited the spontaneous as well the oxytocin-induced motility of M strips, without affecting those of LU. Pharmacologic evidences suggest that acetylcholine may play a [quot ]facilitating[quot ] role in M strips for the conduction of coordinate contractions. This does not appear to be the case in the LU, which has the required characteristics to be recognized as a conductive like tissue.

Myocardial mitogenic effect of erythropoietin through the activation of Na(+)-K(+)-ATPase activity.

Erythropoietin is considered unique among the hematopoietic growth factor with a specific action on the differentiation and proliferation of erythroid progenitor cells. We have observed a dose-dependent modulatory action of human recombinant erythropoietin (rHuEpo) stimulated the rate of cell growth but at higher ones (3-10 U/ml) inhibited it. The mitogenic action of the hormone is correlated with cardiac membrane Na(+)-K(+)-ATPase activity since concentrations of rHuEpo that increased cell growth stimulated paranitrophenilphosphatase (pNPPase) activity, while those concentrations that inhibit the enzyme markedly bloqued its mitogenic action. Moreover, ouabain (10(-5) M), concentration that inhibits Na(+)-K(+)-ATPase activity, blunted the stimulatory action of rHuEpo on cell proliferation. We also demonstrated that rHuEpo while activated the cardiac membrane Na(+)-K(+)-ATPase was able to alter the contractile action of ouabain on isolated neonatal rat atria. Indeed rHuEpo (1 U/ml) enhanced the non toxic action of the cardiac glycoside attenuating and delaying the onset of the toxic effect of the drug. These results show that rHuEpo has a non hematopoietic cardiac effect, associated with the cardiac Na(+)-K(+)-ATPase activity, that regulates the myocytes growth and the biological action of cardiac glycosides on isolated rat myocardium.

Functional pharmacological and morphological characteristics of two regions of rat uterine horns

A histological, physiological and pharmacological study of two regions of the isolated uterine muscle of the rat., i.e., the myometrial one (a zone close to the mesometrial insertion) and the linea uteri (the antimesometrial zone) was performed. From the histological point of view the linea uteri (LU) is characterized by the presence of small bundles of longitudinal smooth muscle fibers (20 to 50), closely packed and clearly surrounded by a connective tissue, whereas in the myometrial zone (M) the smooth muscle fibers are less closely packed and the connective tissue is surrounding a greater number of them. The spontaneous oxytocin or electrically-induced initial tension developed by the LU or the M, was similar. Also the stability with time did not differ between both regions. Atropine depressed consistently the isometric developed tension of M strips, either spontaneously active or driven by oxytocin or electrical stimulation, but had no action on the mechanical activity of preparations from the LU. A pretreatment with hemicholinium also inhibited the spontaneous as well the oxytocin-induced motility of M strips, without affecting those of LU. Pharmacologic evidences suggest that acetylcholine may play a [quot ]facilitating[quot ] role in M strips for the conduction of coordinate contractions. This does not appear to be the case in the LU, which has the required characteristics to be recognized as a conductive like tissue.

Efecto de linfocitos activados sobre la contractilidad cardiaca / The effect of activated lymphocytes on cardiac contractility

En esta serie de estudios se analizó la interacción del miocardio auricular aislado con linfocitos humanos normales estimulados con fitohemaglutinina o con los productos solubles liberados al sobrenadante. Los resultados indican que los linfocitos activados, de fenotipo CD4, inducen efectos inotrópicos positivos sobre la aurícula aislada de rata. Esta acción está vinculada a etapas de la estimulación linfocitaria que preceden la división blástica. El efecto estimulante de los linfocitos activados sería mediado por factores solubles liberados al sobrenadante. Entre ellos, la interleuquina-2 (IL-2) tendría fundamental importancia, ya que es posible disminuir la actividad biológica con anticuerpo monoclonal anti-IL-2 o por pre-incubación de las aurículas con anticuerpo monoclonal contra el receptor de IL-2 (anti-Tac): A concentraciones altas (10 unidades/ml), la IL-2 actúa por sí misma, pero en dosis menores requiere cofactores sinérgicos como el ácido araquidónico (AA) o el ionóforo de Ca A23187. Mediante estudios realizados con inhibidores, se demuestra que la IL-2 dispara la activación del ciclo de los fosfoinosítidos en el corazón a través de la fosfolipasa C. Luego, la proteína que los infiltrados linfocitarios presentes en cardiomiopatías inflamatorias podrían provocar cambios similares en la contractilidad. Por otra parte, hay que tener en cuenta que estos trastornos pueden ocurrir en el tratamiento masivo con IL-2 (AU)

Antibodies against beta adrenoceptors in mothers of children with congenital heart block

En este trabajo se empleó un modelo experimental "in vitro" en el cual se midió la frecuencia de las contracciones, la producción de AMPc y la la unión de ligandos específicos al receptor ß adrenérgicos en las aurículas de ratas neonatales y adultas; a fin de, determinar si anticuerpos con actividad ß adrenérgica interactuaban con receptores ß adrenérgicos cardíacos y alteraban su compartimiento fisiológico. Los sueros y la fracción IgG de madres de infantes con bloqueo cardíaco neonatal congénito incrementaron la frecuencia de las contracciones y la producciín de AMPc en el miocardio auricular neonato. Este efecto fue inhibido por propranolol, puntalizando una participación ß adrenérgica. La IgG también compitió con el radiologando específico por los receptores ß adrenérgicos (3H-CGP) en las membranas purificadas de miocardio neonatal. Ni los efectos biológicos ni los ensayos de unión específica fueron modificados cuando se usó miocardio de rata adulta. La reactividad contra adrenoreceptores cardíacos por parte de anticuerpos provenientes de madres de niños con bloqueo neonatal congénito, podría ser otro factor sérico que debería considerarse en la patofisiología del desarrollo del bloqueo neonatal congénito (AU)

Efecto de linfocitos activados sobre la contractilidad cardíaca. / [The effect of activated lymphocytes on cardiac contractility]

Activated lymphocytes may have potent biologic effects outside the frame of the immune system. In these studies we analyzed the interaction of activated normal human lymphocytes and/or soluble products of lymphocyte activation on the contractile activity of isolated rat atria. The results indicate that phytohemagglutinin activated lymphocytes of the CD4 phenotype exert a positive inotropic effect on spontaneously beating atria. This effect is linked to steps of lymphocyte activation that precede cell division. Soluble factors released to the supernatant of stimulated lymphocytes can substitute for the intact cells. Interleukin-2 (IL-2) appears to be an important component of the active supernatants, as their activity can be reduced by monoclonal anti-IL-2 or by preincubation of the heart tissue with monoclonal anti-IL-2 receptor (anti-Tac). Highly purified IL-2 was active at 10 units/ml. In order to induce a positive inotropic effect at lower doses of natural or recombinant IL-2 (2-3 units/ml), synergic factors were required (2 x 10(-6) M arachidonic acid, AA, or Ca ionophore A 23187). Indirect evidence indicates that IL-2 exerts its biologic effect by turning on the phosphoinositide cycle and activating protein kinase C in the heart tissue target. It is postulated that similar mechanisms may be activated in inflammatory myocardiopathies or during the treatment of cancer with massive doses of IL-2.

Antibodies against beta adrenoceptors in mothers of children with congenital heart block.

To determine whether antibodies against beta adrenergic activity interact with neonatal cardiac cell receptors and alter their physiological behaviour. An [quot ]in vitro[quot ] experimental model measuring the frequency of contraction, the production of cAMP and binding assay on neonatal and adult rat atria was employed. Sera and IgG fraction from mothers of infants with congenital heart block (CHB) interact with neonatal rat atria increasing the frequency of contraction and cAMP production. These effects were abolished by propranolol, pointing to a beta adrenergic participation. IgG also competed with 3H-CGP to beta adrenergic receptors on neonatal cardiac membranes. Neither the contractile nor the cAMP effects or binding assay were obtained using adult instead of neonatal rat atria. Reactivity against cardiac neurotransmitter receptors may be another serum factor(s) to be considered in the pathophysiology of the development of CHB.