Ion channel mRNA distribution and expression in the sinoatrial node and right atrium of dogs and monkeys.
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SUBMITTER: Sano T
PROVIDER: S-EPMC8280307 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Spontaneous diastolic depolarization in the sinoatrial (SA) node enables it to serve as pacemaker of the heart. The variable cell morphology within the SA node predicts that ion channel expression would be heterogeneous and different from that in the atrium. To evaluate ion channel heterogeneity within the SA node, we used fluorescent in situ hybridization to examine ion channel expression in the ferret SA node region and atrial appendage. SA nodal cells were distinguished from surrounding cardiac myocytes by expression of the slow (SA node) and cardiac (surrounding tissue) forms of troponin I. Nerve cells in the sections were identified by detection of GAP-43 and cytoskeletal middle neurofilament. Transcript expression was characterized for the 4 hyperpolarization-activated cation channels, 6 voltage-gated Na(+) channels, 3 voltage-gated Ca(2+) channels, 24 voltage-gated K(+) channel ?-subunits, and 3 ancillary subunits. To ensure that transcript expression was representative of protein expression, immunofluorescence was used to verify localization patterns of voltage-dependent K(+) channels. Colocalizations were performed to observe any preferential patterns. Some overlapping and nonoverlapping binding patterns were observed. Measurement of different cation channel transcripts showed heterogeneous expression with many different patterns of expression, attesting to the complexity of electrical activity in the SA node. This study provides insight into the possible role ion channel heterogeneity plays in SA node pacemaker activity.
| S-EPMC2957791 | biostudies-literature
Project description:Numerous studies implicate the sinoatrial node (SAN) as a participant in atrial arrhythmias, including atrial flutter (AFL) and atrial fibrillation (AF). However, the direct role of the SAN has never been described.The SAN was optically mapped in coronary perfused preparations from normal canine hearts (n=17). Optical action potentials were recorded during spontaneous rhythm, overdrive atrial pacing, and AF/AFL induced by acetylcholine (ACh; 0.3 to 3 micromol/L) and/or isoproterenol (Iso; 0.2 to 1 micromol/L). An optical action potential multiple component algorithm and dominant frequency analysis were used to reconstruct SAN activation and to identify specialized sinoatrial conduction pathways. Both ACh and Iso facilitated pacing-induced AF/AFL by shortening atrial repolarization. The entire SAN structure created a substrate for macroreentry with 9.6+/-1.7 Hz (69 episodes in all preparations). Atrial excitation waves could enter the SAN through the sinoatrial conduction pathways and overdrive suppress the node. The sinoatrial conduction pathways acted as a filter for atrial waves by slowing conduction and creating entrance block. ACh/Iso modulated filtering properties of the sinoatrial conduction pathways by increasing/decreasing the degree of the entrance block, respectively. Thus, the SAN could beat independently from AF/AFL reentrant activity during ACh (49+/-39%) and ACh/Iso (62+/-25%) (P=0.38). Without ACh, the AF/AFL waves captured the SAN and overdrive suppressed it. Spontaneous SAN activity could terminate or convert AFL to AF during cholinergic withdrawal.The specialized structure of the SAN can be a substrate for AF/AFL. Cholinergic stimulation not only can slow sinus rhythm and facilitate AF/AFL but also protects the intrinsic SAN function from the fast AF/AFL rhythm.
| S-EPMC3001400 | biostudies-literature
Project description:BackgroundTwo-pore K(+) channels have emerged as potential targets to selectively regulate cardiac cell membrane excitability; however, lack of specific inhibitors and relevant animal models has impeded the effort to understand the role of 2-pore K(+) channels in the heart and their potential as a therapeutic target. The objective of this study was to determine the role of mechanosensitive 2-pore K(+) channel family member TREK-1 in control of cardiac excitability.Methods and resultsCardiac-specific TREK-1-deficient mice (αMHC-Kcnk(f/f)) were generated and found to have a prevalent sinoatrial phenotype characterized by bradycardia with frequent episodes of sinus pause following stress. Action potential measurements from isolated αMHC-Kcnk2(f/f) sinoatrial node cells demonstrated decreased background K(+) current and abnormal sinoatrial cell membrane excitability. To identify novel pathways for regulating TREK-1 activity and sinoatrial node excitability, mice expressing a truncated allele of the TREK-1-associated cytoskeletal protein βIV-spectrin (qv(4J) mice) were analyzed and found to display defects in cell electrophysiology as well as loss of normal TREK-1 membrane localization. Finally, the βIV-spectrin/TREK-1 complex was found to be downregulated in the right atrium from a canine model of sinoatrial node dysfunction and in human cardiac disease.ConclusionsThese findings identify a TREK-1-dependent pathway essential for normal sinoatrial node cell excitability that serves as a potential target for selectively regulating sinoatrial node cell function.
| S-EPMC4859279 | biostudies-literature
Project description:BackgroundThe hyperpolarization-activated current, If, plays an important role in sinoatrial node (SAN) pacemaking. Surprisingly, the distribution of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels in human SAN has only been investigated at the mRNA level. Our aim was to define the expression pattern of HCN proteins in human SAN and different atrial regions.Methods and resultsEntire SAN complexes were isolated from failing (n=5) and nonfailing (n=9) human hearts cardioplegically arrested in the operating room. Three-dimensional intramural SAN structure was identified as the fibrotic compact region around the SAN artery with Connexin 43-negative pacemaker cardiomyocytes visualized in Masson's trichrome and immunostained cryosections. SAN protein was precisely isolated from the adjacent frozen SAN tissue blocks using a 16G biopsy needle. The purity of the SAN protein was confirmed by Connexin 43 immunoblot. All 3 HCN isoform proteins were detected in SAN. HCN1 was predominantly distributed in the human SAN with a 125.1±40.2 (n=12) expression ratio of SAN to right atrium. HCN2 and HCN4 expression levels were higher in SAN than in atria, with SAN to right atrium ratios of 6.1±0.9 and 4.6±0.6 (n=12), respectively.ConclusionsThis is the first study to conduct precise 3D molecular mapping of the human SAN by isolating pure pacemaker SAN tissue. All 3 cardiac HCN isoforms had higher expression in the SAN than in the atria. HCN1 was almost exclusively expressed in SAN, emphasizing its utility as a new specific molecular marker of the human SAN and as a potential target of specific treatments intended to modify sinus rhythm.
| S-EPMC4618238 | biostudies-literature
Project description:The aim of the study was to develop a three-dimensional (3D) anatomically-detailed model of the rabbit right atrium containing the sinoatrial and atrioventricular nodes to study the electrophysiology of the nodes. A model was generated based on 3D images of a rabbit heart (atria and part of ventricles), obtained using high-resolution magnetic resonance imaging. Segmentation was carried out semi-manually. A 3D right atrium array model (∼3.16 million elements), including eighteen objects, was constructed. For description of cellular electrophysiology, the Rogers-modified FitzHugh-Nagumo model was further modified to allow control of the major characteristics of the action potential with relatively low computational resource requirements. Model parameters were chosen to simulate the action potentials in the sinoatrial node, atrial muscle, inferior nodal extension and penetrating bundle. The block zone was simulated as passive tissue. The sinoatrial node, crista terminalis, main branch and roof bundle were considered as anisotropic. We have simulated normal and abnormal electrophysiology of the two nodes. In accordance with experimental findings: (i) during sinus rhythm, conduction occurs down the interatrial septum and into the atrioventricular node via the fast pathway (conduction down the crista terminalis and into the atrioventricular node via the slow pathway is slower); (ii) during atrial fibrillation, the sinoatrial node is protected from overdrive by its long refractory period; and (iii) during atrial fibrillation, the atrioventricular node reduces the frequency of action potentials reaching the ventricles. The model is able to simulate ventricular echo beats. In summary, a 3D anatomical model of the right atrium containing the cardiac conduction system is able to simulate a wide range of classical nodal behaviours.
| S-EPMC4224508 | biostudies-literature
Project description:Heart failure (HF) is frequently accompanied with the sinoatrial node (SAN) dysfunction, which causes tachy-brady arrhythmias and increased mortality. MicroRNA (miR) alterations are associated with HF progression. However, the transcriptome of HF human SAN, and its role in HF-associated remodeling of ion channels, transporters, and receptors responsible for SAN automaticity and conduction impairments is unknown. We conducted comprehensive high-throughput transcriptomic analysis of pure human SAN primary pacemaker tissue and neighboring right atrial tissue from human transplanted HF hearts (n = 10) and non-failing (nHF) donor hearts (n = 9), using next-generation sequencing. Overall, 47 miRs and 832 mRNAs related to multiple signaling pathways, including cardiac diseases, tachy-brady arrhythmias and fibrosis, were significantly altered in HF SAN. Of the altered miRs, 27 are predicted to regulate mRNAs of major ion channels and neurotransmitter receptors which are involved in SAN automaticity (e.g. HCN1, HCN4, SLC8A1) and intranodal conduction (e.g. SCN5A, SCN8A) or both (e.g. KCNJ3, KCNJ5). Luciferase reporter assays were used to validate interactions of miRs with predicted mRNA targets. In conclusion, our study provides a profile of altered miRs in HF human SAN, and a novel transcriptome blueprint to identify molecular targets for SAN dysfunction and arrhythmia treatments in HF.
| S-EPMC8481550 | biostudies-literature
Project description:BackgroundIt is known that autonomic nerve activity controls the sinus rate. However, the coupling between local nerve activity and electrical activation at the sinoatrial node (SAN) remains unclear. We hypothesized that we would be able to record nerve activity at the SAN to investigate if right stellate ganglion (RSG) activation can increase the local intrinsic nerve activity, accelerate sinus rate, and change the earliest activation sites.MethodsHigh-density mapping of the epicardial surface of the right atrium including the SAN was performed in 6 dogs during stimulation of the RSG and after RSG stellectomy. A radio transmitter was implanted into 3 additional dogs to record RSG and local nerve activity at the SAN.ResultsHeart rate accelerated from 108±4 bpm at baseline to 125±7 bpm after RSG stimulation (P=0.001), and to 132±7 bpm after apamin injection (P<0.001). Both electrical RSG stimulation and apamin injection induced local nerve activity at the SAN with the average amplitudes of 3.60±0.72 and 3.86±0.56 μV, respectively. RSG stellectomy eliminated the local nerve activity and decreased the heart rate. In ambulatory dogs, local nerve activity at the SAN had a significantly higher average Pearson correlation to heart rate (0.72±0.02, P=0.001) than RSG nerve activity to HR (0.45±0.04, P=0.001).ConclusionsLocal intrinsic nerve activity can be recorded at the SAN. Short bursts of these local nerve activities are present before each atrial activation during heart rate acceleration induced by stimulation of the RSG.
| S-EPMC7887084 | biostudies-literature
Project description:RNA Sequencing of Mouse Sinoatrial Node Reveals an Upstream Regulatory Role for Islet-1 in Cardiac Pacemaker Cells Rationale: Treatment of sinus node disease with regenerative or cell-based therapies will require a detailed understanding of gene regulatory networks in cardiac pacemaker cells (PCs). Objective: To characterize the transcriptome of PCs using RNA sequencing, and to identify transcriptional networks responsible for PC gene expression. Methods and Results: We used laser capture micro-dissection (LCM) on a sinus node reporter mouse line to isolate RNA from PCs for RNA sequencing (RNA-Seq). Differential expression and network analysis identified novel SAN-enriched genes, and predicted that the transcription factor Islet-1 (Isl1) is active in developing pacemaker cells. RNA-Seq on SAN tissue lacking Isl1 established that Isl1 is an important transcriptional regulator within the developing SAN. Conclusions: (1) The PC transcriptome diverges sharply from other cardiomyocytes; (2) Isl1 is a positive transcriptional regulator of the PC gene expression program. There are 25 RNA-Sequencing Samples
2015-02-06 | E-GEOD-65658 | biostudies-arrayexpress
Project description:Despite a century of extensive study on the human sinoatrial node (SAN), the structure-to-function features of specialized SAN conduction pathways (SACP) are still unknown and debated. We report a new method for direct analysis of the SAN microstructure in optically-mapped human hearts with and without clinical history of SAN dysfunction.Two explanted donor human hearts were coronary-perfused and optically-mapped. Structural analyses of histological sections parallel to epicardium (?13-21 ?m intervals) were integrated with optical maps to create 3D computational reconstructions of the SAN complex. High-resolution fiber fields were obtained using 3D Eigen-analysis of the structure tensor, and used to analyze SACP microstructure with a fiber-tracking approach.Optical mapping revealed normal SAN activation of the atria through a lateral SACP proximal to the crista terminalis in Heart #1 but persistent SAN exit block in diseased Heart #2. 3D structural analysis displayed a functionally-observed SAN border composed of fibrosis, fat, and/or discontinuous fibers between SAN and atria, which was only crossed by several branching myofiber tracts in SACP regions. Computational 3D fiber-tracking revealed that myofiber tracts of SACPs created continuous connections between SAN #1 and atria, but in SAN #2, SACP region myofiber tracts were discontinuous due to fibrosis and fat.We developed a new integrative functional, structural and computational approach that allowed for the resolution of the specialized 3D microstructure of human SACPs for the first time. Application of this integrated approach will shed new light on the role of the specialized SAN microanatomy in maintaining sinus rhythm.
| S-EPMC4808362 | biostudies-literature
Project description:The spontaneous activity of the sinoatrial node initiates the heartbeat. Sino-atrial node dysfunction (SND) and sick sinoatrial (sick sinus) syndrome are caused by the heart's inability to generate a normal sinoatrial node action potential. In clinical practice, SND is generally considered an age-related pathology, secondary to degenerative fibrosis of the heart pacemaker tissue. However, other forms of SND exist, including idiopathic primary SND, which is genetic, and forms that are secondary to cardiovascular or systemic disease. The incidence of SND in the general population is expected to increase over the next half century, boosting the need to implant electronic pacemakers. During the last two decades, our knowledge of sino-atrial node physiology and of the pathophysiological mechanisms underlying SND has advanced considerably. This review summarizes the current knowledge about SND mechanisms and discusses the possibility of introducing new pharmacologic therapies for treating SND.
| S-EPMC7790915 | biostudies-literature