Adrenergic mechanisms of myocardium contractility regulation in genetic model of Alzheimer’s disease

Abstract

Aim. Study is aimed to investigate contractility impairments and receptor mechanisms of adrenergic regulation of myocardium inotropic function in Alzheimer’s disease model on transgenic mice.Methods. Experiments were performed on isolated preparations of atria and ventricles myocardium of mice. Transgenic mice of B6C3-Tg(APP695)85Dbo Tg(PSENI)85Dbo genotype were used as animal model of Alzheimer’s disease. Contractile responses of myocardium were registered by conventional myographic technique in isometric conditions. To evaluate the expression of adrenergic receptors, immunofluorescence staining of myocardium with specific antibodies was performed.Results. Transgenic mice showed not only a decreased effect of norepinephrine on myocardium inotropic function but also the inversion of the effect of norepinephrine - the use of 10-5-10-4 M of norepinephrine decreased myocardium inotropic function. Immunofluorescent staining showed decrease of expression of β1- and especially β2-adrenergic receptors ventricular myocardium of transgenic mice comparing to wild type mice. Adrenergic deregulation was registered in ventricles, but not in atria. The features of adrenergic regulatory mechanisms of myocardial contractility in transgenic APP/PS1 mice aged 8-10 months are specific, although somewhat similar to wild type mice aged 8-10 months, and are evidently due to Alzheimer’s disease. The inversion of norepinephrine inotropic effect (from positive to negative) may be explained by switching the intracellular cascade pathway of β2-adrenergic receptors effects to another type of G-protein.Conclusion. The results indicate that peripheral adrenergic mechanisms of myocardial contractility regulation are impaired in studied transgenic mice model of Alzheimer’s disease. Obtained data widen our understanding of Alzheimer’s disease pathogenesis, as well as our conception of relations between cardiovascular diseases and neurodegeneration.