Mesenteric artery smooth muscle cells from hypertensive rats have increased microtubule acetylation.

The dynamic nature of the microtubule network is dependent in part by post-translational modifications (PTMs) - particularly through acetylation, which stabilizes the microtubule network. Whether PTMs of the microtubule network in vascular smooth muscle cells (VSMCs) contribute to the pathophysiology of hypertension is unknown. The aim of this study was to determine the acetylated state of the microtubule network in the mesenteric arteries of spontaneously hypertensive rats (SHR).

Microtubule-Mediated Regulation of βAR Translation and Function in Failing Hearts.

Background: βAR (beta-1 adrenergic receptor) and βAR (beta-2 adrenergic receptor)-mediated cyclic adenosine monophosphate signaling has distinct effects on cardiac function and heart failure progression. However, the mechanism regulating spatial localization and functional compartmentation of cardiac β-ARs remains elusive. Emerging evidence suggests that microtubule-dependent trafficking of mRNP (messenger ribonucleoprotein) and localized protein translation modulates protein compartmentation in cardiomyocytes.

Functional LTCC-βAR Complex Needs Caveolin-3 and Is Disrupted in Heart Failure.

Background: Beta-2 adrenergic receptors (βARs) but not beta-2 adrenergic receptors (βARs) form a functional complex with L-type Ca channels (LTCCs) on the cardiomyocyte membrane. However, how microdomain localization in the plasma membrane affects the function of these complexes is unknown. We aim to study the coupling between LTCC and β adrenergic receptors in different cardiomyocyte microdomains, the distinct involvement of PKA and CAMKII (Ca/calmodulin-dependent protein kinase II) and explore how this functional complex is disrupted in heart failure.

GPER limits adverse changes to Ca signalling and arrhythmogenic activity in ovariectomised guinea pig cardiomyocytes.

The increased risk of post-menopausal women developing abnormalities of heart function emphasises the requirement to understand the effect of declining oestrogen levels on cardiac electrophysiology and structure, and investigate possible therapeutic targets, namely the G protein-coupled oestrogen receptor 1 (GPER). Female guinea pigs underwent sham or ovariectomy (OVx) surgeries. Cardiomyocytes were isolated 150-days post-operatively.

Nerve growth factor transfer from cardiomyocytes to innervating sympathetic neurons activates TrkA receptors at the neuro-cardiac junction.

Sympathetic neurons densely innervate the myocardium with non-random topology and establish structured contacts (i.e. neuro-cardiac junctions, NCJ) with cardiomyocytes, allowing synaptic intercellular communication.

Local hyperactivation of L-type Ca channels increases spontaneous Ca release activity and cellular hypertrophy in right ventricular myocytes from heart failure rats.

Right ventricle (RV) dysfunction is an independent predictor of patient survival in heart failure (HF). However, the mechanisms of RV progression towards failing are not well understood. We studied cellular mechanisms of RV remodelling in a rat model of left ventricle myocardial infarction (MI)-caused HF.

Nanoscale Study of Calcium Handling Remodeling in Right Ventricular Cardiomyocytes Following Pulmonary Hypertension.

Pulmonary hypertension is a complex disorder characterized by pulmonary vascular remodeling and right ventricular hypertrophy, leading to right heart failure. The mechanisms underlying this process are not well understood. We hypothesize that the structural remodeling occurring in the cardiomyocytes of the right ventricle affects the cytosolic Ca handling leading to arrhythmias.

Interaction of the Joining Region in Junctophilin-2 With the L-Type Ca Channel Is Pivotal for Cardiac Dyad Assembly and Intracellular Ca Dynamics.

Rationale: Ca-induced Ca release (CICR) in normal hearts requires close approximation of L-type calcium channels (LTCCs) within the transverse tubules (T-tubules) and RyR (ryanodine receptors) within the junctional sarcoplasmic reticulum. CICR is disrupted in cardiac hypertrophy and heart failure, which is associated with loss of T-tubules and disruption of cardiac dyads. In these conditions, LTCCs are redistributed from the T-tubules to disrupt CICR.

Mediastinal Lymphadenopathy, Class-Switched Auto-Antibodies and Myocardial Immune-Complexes During Heart Failure in Rodents and Humans.

Mediastinal lymphadenopathy and auto-antibodies are clinical phenomena during ischemic heart failure pointing to an autoimmune response against the heart. T and B cells have been convincingly demonstrated to be activated after myocardial infarction, a prerequisite for the generation of mature auto-antibodies. Yet, little is known about the immunoglobulin isotype repertoire thus pathological potential of anti-heart auto-antibodies during heart failure.

Short-term angiotensin II treatment regulates cardiac nanomechanics via microtubule modifications.

Mechanical properties of single myocytes contribute to the whole heart performance, but the measurement of mechanics in living cells at high resolution with minimal force interaction remains challenging. Angiotensin II (AngII) is a peptide hormone that regulates a number of physiological functions, including heart performance. It has also been shown to contribute to cell mechanics by inducing cell stiffening.

Nanoscale regulation of L-type calcium channels differentiates between ischemic and dilated cardiomyopathies.

Background: Subcellular localization and function of L-type calcium channels (LTCCs) play an important role in regulating contraction of cardiomyocytes. Understanding how this is affected by the disruption of transverse tubules during heart failure could lead to new insights into the disease.

Methods: Cardiomyocytes were isolated from healthy donor hearts, as well as from patients with cardiomyopathies and with left ventricular assist devices.

Junctophilin-2 tethers T-tubules and recruits functional L-type calcium channels to lipid rafts in adult cardiomyocytes.

Aim: In cardiomyocytes, transverse tubules (T-tubules) associate with the sarcoplasmic reticulum (SR), forming junctional membrane complexes (JMCs) where L-type calcium channels (LTCCs) are juxtaposed to Ryanodine receptors (RyR). Junctophilin-2 (JPH2) supports the assembly of JMCs by tethering T-tubules to the SR membrane. T-tubule remodelling in cardiac diseases is associated with downregulation of JPH2 expression suggesting that JPH2 plays a crucial role in T-tubule stability.

Microtubules regulate cardiomyocyte transversal Young's modulus.

The field of cardiomyocyte mechanobiology is gaining significant attention, due to accumulating evidence concerning the significant role of cellular mechanical effects on the integrated function of the heart. To date, the protein titin has been demonstrated as a major contributor to the cardiomyocytes Young's modulus (YM). The microtubular network represents another potential regulator of cardiac mechanics.

Ankyrin-G mediates targeting of both Na and K channels to the rat cardiac intercalated disc.

We investigated targeting mechanisms of Na and K channels to the intercalated disk (ICD) of cardiomyocytes. Patch clamp and surface biotinylation data show reciprocal downregulation of each other's surface density. Mutagenesis of the Kir6.

Cardiomyocyte-myofibroblast contact dynamism is modulated by connexin-43.

Healthy cardiomyocytes are electrically coupled at the intercalated discs by gap junctions. In infarcted hearts, adverse gap-junctional remodeling occurs in the border zone, where cardiomyocytes are chemically and electrically influenced by myofibroblasts. The physical movement of these contacts remains unquantified.

Partial Mechanical Unloading of the Heart Disrupts L-Type Calcium Channel and Beta-Adrenoceptor Signaling Microdomains.

We investigated the effect of partial mechanical unloading (PMU) of the heart on the physiology of calcium and beta-adrenoceptor-cAMP (βAR-cAMP) microdomains. Previous studies have investigated PMU using a model of heterotopic-heart and lung transplantation (HTHAL). These studies have demonstrated that PMU disrupts the structure of cardiomyocytes and calcium handling.

The adhesion function of the sodium channel beta subunit (β1) contributes to cardiac action potential propagation.

Computational modeling indicates that cardiac conduction may involve ephaptic coupling - intercellular communication involving electrochemical signaling across narrow extracellular clefts between cardiomyocytes. We hypothesized that β1(SCN1B) -mediated adhesion scaffolds -activating Na1.5 (SCN5A) channels within narrow (<30 nm) perinexal clefts adjacent to gap junctions (GJs), facilitating ephaptic coupling.

Role of low-voltage-activated calcium current and extracellular calcium in controlling the firing pattern of developing CA1 pyramidal neurons.

The firing pattern of individual neurons is an important element for information processing and storing. During the first weeks of development, there is a transitional period during which CA1 pyramidal neurons display burst-spiking behavior in contrast to the adult regular-firing pattern. Spike after-depolarizations (ADPs) constitute a major factor underlying burst-spiking behavior.

Microdomain-Specific Modulation of L-Type Calcium Channels Leads to Triggered Ventricular Arrhythmia in Heart Failure.

Rationale: Disruption in subcellular targeting of Ca(2+) signaling complexes secondary to changes in cardiac myocyte structure may contribute to the pathophysiology of a variety of cardiac diseases, including heart failure (HF) and certain arrhythmias.

Objective: To explore microdomain-targeted remodeling of ventricular L-type Ca(2+) channels (LTCCs) in HF.

Methods And Results: Super-resolution scanning patch-clamp, confocal and fluorescence microscopy were used to explore the distribution of single LTCCs in different membrane microdomains of nonfailing and failing human and rat ventricular myocytes.

Angular Approach Scanning Ion Conductance Microscopy.

Scanning ion conductance microscopy (SICM) is a super-resolution live imaging technique that uses a glass nanopipette as an imaging probe to produce three-dimensional (3D) images of cell surface. SICM can be used to analyze cell morphology at nanoscale, follow membrane dynamics, precisely position an imaging nanopipette close to a structure of interest, and use it to obtain ion channel recordings or locally apply stimuli or drugs. Practical implementations of these SICM advantages, however, are often complicated due to the limitations of currently available SICM systems that inherited their design from other scanning probe microscopes in which the scan assembly is placed right above the specimen.

Microtubule-Dependent Mitochondria Alignment Regulates Calcium Release in Response to Nanomechanical Stimulus in Heart Myocytes.

Arrhythmogenesis during heart failure is a major clinical problem. Regional electrical gradients produce arrhythmias, and cellular ionic transmembrane gradients are its originators. We investigated whether the nanoscale mechanosensitive properties of cardiomyocytes from failing hearts have a bearing upon the initiation of abnormal electrical activity.

Direct Evidence for Microdomain-Specific Localization and Remodeling of Functional L-Type Calcium Channels in Rat and Human Atrial Myocytes.

Background: Distinct subpopulations of L-type calcium channels (LTCCs) with different functional properties exist in cardiomyocytes. Disruption of cellular structure may affect LTCC in a microdomain-specific manner and contribute to the pathophysiology of cardiac diseases, especially in cells lacking organized transverse tubules (T-tubules) such as atrial myocytes (AMs).

Methods And Results: Isolated rat and human AMs were characterized by scanning ion conductance, confocal, and electron microscopy.

Side-specific mechanical properties of valve endothelial cells.

Aortic valve endothelial cells (ECs) function in vastly different levels of shear stress. The biomechanical characteristics of cells on each side of valve have not been investigated. We assessed the morphology and mechanical properties of cultured or native valve ECs on intact porcine aortic valve cusps using a scanning ion conductance microscope (SICM).