Gender-specific effects of calcitonin gene-related peptide and substance P on coronary blood flow in an experimental model

Distribution and morphology of CGRP-IR axons in flat-mounts of whole male and female mouse atria

Due to a lack of anatomical studies utilizing female specimens, it is unclear how the nociceptive innervation of the mouse heart compares between sexes. To address this, flat-mount preparations of the left and right atria of male and female mice were immunohistochemically labeled for calcitonin gene-related peptide (CGRP, a common marker for nociceptive nerves), imaged, and digitally traced in high quality. The results show that 1) A network of CGRP-IR axons densely innervated the right and left atria. Large nerve bundle entry points and regional concentration of CGRP-IR axons were similar in both sexes. 2) The detailed distribution of CGRP-IR bundles and axons were digitized and mapped using Arivis (Zeiss) Vision4D software. The general distribution patterns in male and female mice were comparable to one another. 3) The density of CGRP-IR axons in the sinoatrial (SA) node region (Male: 0.0258 μm/μm2 ± 0.003; Female: 0.0347 μm/μm2 ± 0.006) and atrioventricular (AV) node region (Male: 0.0138 μm/μm2 ± 0.001; Female: 0.0228 μm/μm2 ± 0.005) were not found to be significantly different. 4) The distance between adjacent varicosities in the auricle (Male: 4.049 μm ± 0.3; Female: 4.241 μm ± 0.34), SA node region (Male: 2.812 μm ± 0.21; Female: 3.352 μm ± 0.29), and AV node region (Male: 2.999 μm ± 0.3; Female: 3.526 μm ± 0.26) were not significantly different between sexes. 5) Likewise, maximum varicosity diameters in the auricle (Male: 0.5356 μm ± 0.04; Female: 0.5274 μm ± 0.03), SA node region (Male: 0.4714 μm ± 0.02; Female: 0.5634 μm ± 0.04), and AV node region (Male: 0.5103 μm ± 0.02; Female: 0.5103 μm ± 0.03) between male and female specimens were similar. Our data shows the comparable nature of the CGRP-IR axons in mouse atria in both sexes. Moreover, this is the first time we employed flat-mount preparations of whole atria to analyze the distribution of CGRP-IR axons in male and female mice.

Changes Caused by Low Doses of Bisphenol A (BPA) in the Neuro-Chemistry of Nerves Located in the Porcine Heart

Simple Summary

Bisphenol A (BPA) is a substance commonly used in the plastics industry, which is a part of many everyday items. It may leach from plastics and penetrate food, water, soil and air. It is known that BPA negatively affects living organisms. It impairs the functions of the intestine, neurons, reproductive organs, endocrine glands and immune cells. Previous studies have also reported that BPA negatively influences the cardiovascular system, leading to heart arrhythmia, intensification of atherosclerosis, blood hypertension and increased risk of a heart attack. However, many aspects of the influence of BPA on the heart are still poorly understood. One of these aspects is the BPA impact on heart innervation. Therefore, this article aimed to investigate the influence of low doses of BPA on the number of nerves containing selected active substances taking part in neuronal stimuli conduction located in the porcine heart apex. The results indicate that even relatively low doses of BPA are not neutral to the cardiovascular system, because they affect the neurochemical characterization of nerves in the heart. These changes may underlie the negative effects of BPA on the heart.

Abstract

Bisphenol A (BPA) contained in plastics used in the production of various everyday objects may leach from these items and contaminate food, water and air. As an endocrine disruptor, BPA negatively affects many internal organs and systems. Exposure to BPA also contributes to heart and cardiovascular system dysfunction, but many aspects connected with this activity remain unknown. Therefore, this study aimed to investigate the impact of BPA in a dose of 0.05 mg/kg body weight/day (in many countries such a dose is regarded as a tolerable daily intake–TDI dose of BPA–completely safe for living organisms) on the neurochemical characterization of nerves located in the heart wall using the immunofluorescence technique. The obtained results indicate that BPA (even in such a relatively low dose) increases the number of nerves immunoreactive to neuropeptide Y, substance P and tyrosine hydroxylase (used here as a marker of sympathetic innervation). However, BPA did not change the number of nerves immunoreactive to vesicular acetylcholine transporter (used here as a marker of cholinergic structures). These observations suggest that changes in the heart innervation may be at the root of BPA-induced circulatory disturbances, as well as arrhythmogenic and/or proinflammatory effects of this endocrine disruptor. Moreover, changes in the neurochemical characterization of nerves in the heart wall may be the first sign of exposure to BPA.

Substance P Inhibits the Collagen Synthesis of Rat Myocardial Fibroblasts Induced by Ang II

BACKGROUND The aim of this study was to explore the regulating effects of Substance P (SP) on the collagen synthesis of rat myocardial fibroblasts (CFBs) induced by angiotensin II (Ang II) and its potential mechanism. MATERIAL AND METHODS The CFBs of a neonatal SD rat were separately cultured and divided into the control group, Ang II treatment group, and treatment groups with different concentrations of SP, Ang II +; each group was given corresponding treatment respectively. RESULTS Ang II successfully induced the collagen synthesis of CFBs. Compared with the control group, the phosphorylation levels of TGF-β, erk, and smad2/3 were higher (p<0.05). Different concentrations of SP had an effect on Ang II-induced CFBs, reduced the collagen synthesis of CFBs, and increased the expressions of SP receptors, accompanied by lowering TGF-β protein, erk protein phosphorylation level, and smad2/3 protein phosphorylation level (p<0.05). Moreover, the higher the concentrations of SP, the more obvious of an effect it exerted. Treating the Ang II + SP group with aprepitant reduced the inhibiting effects of SP on collagen synthesis. The expression changes of collagen I and collagen III detected by immunocytochemistry were exactly in accordance with the results of qPCR and Western blotting. CONCLUSIONS SP can inhibit collagen synthesis of CFBs after Ang II inducing which may adjust the downstream signaling pathways associated protein including TGF-β, erk and smad2/3. SP can block the progress of myocardial fibrosis and is dose dependent, which is expected to be a promising target for the treatment of myocardial fibrosis.

Distribution and morphology of calcitonin gene-related peptide and substance P immunoreactive axons in the whole-mount atria of mice

The murine model has been used to investigate the role of cardiac sensory axons in various disease states. However, the distribution and morphological structures of cardiac nociceptive axons in normal murine tissues have not yet been well characterized. In this study, whole-mount atria from FVB mice were processed with calcitonin gene-related peptide (CGRP) and substance P (SP) primary antibodies followed by secondary antibodies, and then examined using confocal microscopy. We found: 1) Large CGRP-IR axon bundles entered the atria with the major veins, and these large bundles bifurcated into small bundles and single axons that formed terminal end-nets and free endings in the epicardium. Varicose CGRP-IR axons had close contacts with muscle fibers, and some CGRP-IR axons formed varicosities around principle neurons (PNs) within intrinsic cardiac ganglia (ICGs). 2) SP-IR axons also were found in the same regions of the atria, attached to veins, and within cardiac ganglia. Similar to CGRP-IR axons, these SP-IR axons formed terminal end-nets and free endings in the atrial epicardium and myocardium. Within ICGs, SP-IR axons formed varicose endings around PNs. However, SP-IR nerve fibers were less abundant than CGRP-IR fibers in the atria. 3) None of the PNs were CGRP-IR or SP-IR. 4) CGRP-IR and SP-IR often colocalized in terminal varicosities around PNs. Collectively, our data document the distribution pattern and morphology of CGRP-IR and SP-IR axons and terminals in different regions of the atria. This knowledge provides useful information for CGRP-IR and SP-IR axons that can be referred to in future studies of pathological remodeling.