New insights in cardiovascular regulation under physiological and pathophysiological condition

Abstract

The present study was grouped into five Projects investigating the cardiovascular regulation under physiological - Project 1 - and physiopathological - heart failure (HF) - condition, i.e. Project 2, 3, 4A e 4B.Project 1 aims to characterize the presence of substance P in the axons of the aortic depressor nerve (ADN) and nodose ganglion. To accomplish this, it will be used immunohistochemical staining, Western Blotting and expression of mRNA by means of Real Time-PCR. The technique for staining substance P from unmyelinated fibers will use transverse and longitudinal sections. The presence of choline acetil transferase (ChAT) will also be investigated, using phrenic nerves as controls.Because it was demonstrated in HF following myocardial infarction (MI) an attenuation of the baroreflex, Project 2 will examine the hemodynamic responses - arterial pressure (AP) and heart rate (HR) - to electrical stimulation of the ADN in conscious HF rats, in order to identify which segment - afferences, central nervous system, efferences (sympathetic and parasympathetic) - of the baroreflex arch is deranged. Moreover, conscious HF rats will be submitted to pharmacological blockade with atropine, atenolol and prazosin to evaluate the role played by autonomic efferences (sympathetic and parasympathetic) in the regulation of AP and HR.Stem cell therapy has shown promising results after MI in both, patients and experimental animals, especially those using mesenchymal stem cells (MSC), which has shown potential pro-angiogenic, anti-fibrotic and immunomodulatory effect. However, studies have shown differentiation of MSC into adrenergic nerves in the heart, which might have deleterious outcome, especially in MI. Therefore, Project 3 aims to examine the effect of MSC on cardiac sympathovagal balance in HF rats following MI. The size of MI will be assessed by single photon emission computed tomography (SPECT), while the cardiac function will be assessed by isotopic cardiac ventriculography.The examination of HF after MI proposed in the current study involves also a new methodological approach, i.e. genetically modified mice: knockout for the gene of serino-protease elastase-2 (ELA2) and knockdown for the gene of vesicular acetylcholine transporter (VAChT KDHOM).Recent studies have demonstrated the presence of alternative pathways for angiotensin converting enzyme (ACE) to yield angiotensin II (Ang II) in tissues of several species including humans. One of these pathways is the ELA-2, which is widely distributed in several rodent organs. To evaluate the importance of ELA-2, it was developed a mouse with total deletion (knockout) of this enzyme. Therefore, the aim of Subproject 4A is to characterize the hemodynamic parameters (AP and HR), autonomic balance and cardiovascular and renal structures of mice with total deletion (knockout) of ELA-2 before and after the development of HF induced by MI.A knockdown homozygous mouse for the gene of vesicular acetylcholine transporter (VAChT KDHOM) has been developed. This model is particularly suitable for the investigation of parasympathetic function under pathological condition such as HF. Therefore, the Subproject 4B will evaluate in VAChT KDHOM mice, after MI, the effects of the attenuation of the cholinergic function on the hemodynamic parameters (AP and HR) and the sympathovagal balance upon cardiovascular regulation, by means of telemetry. In addition, it will be also examined the cardiovascular responses of these genetically modified mice during the development of HF. (AU)