Role of Known Transient Receptor Potential Vanilloid Channels in Modulating Cardiac Mechanobiology

Effects of SGLT2 inhibitors on ion channels in heart failure: focus on the endothelium

Heart failure (HF) is a life-threatening cardiovascular disease associated with high mortality, diminished quality of life, and a significant economic burden on both patients and society. The pathogenesis of HF is closely related to the endothelium, where endothelial ion channels play an important role in regulating intracellular Ca2+ signals. These ion channels are essential to maintain vascular function, including endothelium-dependent vascular tone, inflammation response, and oxidative stress. Sodium-glucose cotransporter 2 inhibitors (SGLT2i) have shown promising cardiovascular benefits in HF patients, reducing mortality risk and hospitalization in several large clinical trials. Clinical and preclinical studies indicate that the cardioprotective effects of SGLT2i in HF are mediated by endothelial nitric oxide (NO) pathways, as well as by reducing inflammation and reactive oxygen species in cardiac endothelial cells. Additionally, SGLT2i may confer endothelial protection by lowering intracellular Ca2+ level through the inhibition of sodium-hydrogen exchanger 1 (NHE1) and sodium-calcium exchanger (NCX) in endothelial cells. In this review, we discuss present knowledge regarding the expression and role of Ca2+-related ion channels in endothelial cells in HF, focusing on the effects of SGLT2i on endothelial NHE1, NCX as well as on vascular tone.

Unlocking the power of empagliflozin: Rescuing inflammation in hyperglycaemia-exposed human cardiomyocytes through comprehensive multi-level analysis

AIMS

Hyperglycaemic conditions increase cardiac stress, a common phenomenon associated with inflammation, aging, and metabolic imbalance. Sodium-glucose cotransporter 2 inhibitors, a class of anti-diabetic drugs, showed to improve cardiovascular functions although their mechanism of action has not yet been fully established. This study investigated the effects of empagliflozin on cardiomyocytes following high glucose exposure, specifically focusing on inflammatory and metabolic responses.

METHODS AND RESULTS

A three-part strategy was formulated: (i) a meta-analysis of selected randomized clinical trials was carried out to assess the anti-inflammatory effects of empagliflozin in diabetic patients; (ii) the impact of empagliflozin on human cardiomyocyte AC16 cells exposed to normal (5 mM) and high (33 mM) glucose concentrations for 2 and 7 days was explored by evaluating gene expression and protein levels of pivotal markers associated with cardiac inflammation, stress, endoplasmic reticulum damage, and calcium modulation; (iii) in silico data from bioinformatic analyses were exploited to construct an interaction map delineating the potential mechanism of action of empagliflozin on cardiac tissue. Empagliflozin reversed high-glucose mediated alterations at the transcriptional level, decreasing inflammatory, metabolic, and aging signatures. Specifically, in vitro experiments on human cardiomyocytes, meta-analyses of clinical data on inflammatory biomarkers from diabetic peripheral blood samples, and sequencing of pathological human heart tissues, all support that empagliflozin exerts anti-inflammatory effects both systemically and directly in cardiac tissue, on cardiomyocytes.

CONCLUSION

Our study provides insights based on robust mechanistic data for optimizing heart failure management and highlights the intricate interplay between diabetes, inflammation, aging, and cardiovascular health.

Spinal Afferent Innervation From Left Dorsal Root Ganglia in the Flat-Mounts of Whole Atria of Rats: Anterograde Tracing

The spinal afferent innervation of the heart helps to regulate cardiac functions by sending sensory information through the dorsal root ganglia (DRG) to the brain. However, the distribution and morphology of spinal afferents in the heart are not well characterized due to tracer selections, the surgical access to upper thoracic DRGs, and the thickness of the heart tissues. In this study, we injected tracer dextran biotin (DB) into the left DRGs (C8-T3) of male Sprague-Dawley rats (3-5 months). After 16 days, flat-mounts of the whole left and right atria were prepared and diaminobenzidine stained. Then, the DB-labeled axons in the tissues were imaged, traced, and digitized using the Neurolucida system. Our results showed that the DB-labeled axons from left DRGs entered the left precaval vein and projected to the left and right atria, with predominant projection in the left atrial wall. DB-labeled varicose axons were observed in different layers, mostly in the epicardium and myocardium, but much less in the endocardium. In those layers, these spinal afferent axons branched out into simple to complex terminal arborizations, forming close appositions with cardiac muscles, intrinsic cardiac ganglia, blood vessels, and fat tissue. This work, for the first time, characterized cardiac spinal afferent distribution of the rat atria using anterograde tracing, which will provide the foundation for future studies of topographical cardiac spinal afferent innervation and remodeling in heart disease models.

The Pathogenic Mechanisms of and Novel Therapies for Lamin A/C-Related Dilated Cardiomyopathy Based on Patient-Specific Pluripotent Stem Cell Platforms and Animal Models

Variants (pathogenic) of the LMNA gene are a common cause of familial dilated cardiomyopathy (DCM), which is characterised by early-onset atrioventricular (AV) block, atrial fibrillation and ventricular tachyarrhythmias (VTs), and progressive heart failure. The unstable internal nuclear lamina observed in LMNA-related DCM is a consequence of the disassembly of lamins A and C. This suggests that LMNA variants produce truncated or alternative forms of protein that alter the nuclear structure and the signalling pathway related to cardiac muscle diseases. To date, the pathogenic mechanisms and phenotypes of LMNA-related DCM have been studied using different platforms, such as patient-specific induced pluripotent stem-cell-derived cardiomyocytes (iPSC-CMs) and transgenic mice. In this review, point variants in the LMNA gene that cause autosomal dominantly inherited forms of LMNA-related DCM are summarised. In addition, potential therapeutic targets based on preclinical studies of LMNA variants using transgenic mice and human iPSC-CMs are discussed. They include mitochondria deficiency, variants in nuclear deformation, chromatin remodelling, altered platelet-derived growth factor and ERK1/2-related pathways, and abnormal calcium handling.

Therapeutic potential of cannabidiol (CBD) in the treatment of cardiovascular diseases

INTRODUCTION

Cannabidiol (CBD) is the primary non-psychoactive chemical derived from Cannabis Sativa, and its growing popularity is due to its potential therapeutic properties while avoiding the psychotropic effects of other phytocannabinoids, such as tetrahydrocannabinol (THC). Numerous pre-clinical studies in cellular and animal models and human clinical trials have demonstrated a positive impact of CBD on physiological and pathological processes. Recently, the FDA approved its use for the treatment of seizures, and clinical trials to test the efficacy of CBD in myocarditis and pericarditis are ongoing.

AREAS COVERED

We herein reviewed the current literature on the reported effects of CBD in the cardiovascular system, highlighting the physiological effects and the outcomes of using CBD as a therapeutic tool in pathological conditions to address this significant global health concern.

EXPERT OPINION

The comprehensive examination of the literature emphasizes the potential of CBD as a therapeutic option for treating cardiovascular diseases through its anti-inflammatory, vasodilatory, anti-fibrotic, and antioxidant properties in different conditions such as diabetic cardiomyopathy, myocarditis, doxorubicin-induced cardiotoxicity, and ischemia-reperfusion injury.

TRPV2 inhibitor tranilast prevents atrial fibrillation in rat models of pulmonary hypertension

Atrial fibrillation (AF) is common in pulmonary hypertension (PH), whereas the mechanisms and treatments remain to be explored. TRPV2 regulates the structure and function of the cardiovascular system; however, little attention has been given to its role in AF. This study was to determine whether TRPV2 was involved in PH-induced AF and the effects of TRPV2 inhibitor tranilast on AF in rat models of PH. Monocrotaline (MCT) and SU5416/hypoxia (SuHx)-induced PH models were performed to detect atrial electrophysiological parameters. Daily tranilast (a TRPV2 inhibitor) or saline was given starting 1 day before PH establishment. PH increased the susceptibility to AF, with TRPV2 up-regulated in the right atria. Compared to PH rats, tranilast reduced AF inducibility and the prolongations of ERP and APD; mitigated cardiopulmonary remodeling and the increases in P-wave duration and P-R interval; partially reversed the down-regulation of ion channels such as Cav1.2, Nav1.5, Kv4.3, Kv4.2, Kv1.5, Kir2.1, Kir3.1, Kir3.4 as well as connexin (Cx) 40 and Cx43; improved right atrial (RA) fibrosis, enlargement, and myocardial hypertrophy; decreased the accumulation of inflammatory cells; down-regulated inflammatory indicators such as TNF-α, IL-1β, CXCL1, and CXCL2; and inhibited the activation of the PI3K-AKT-NF-κB signaling pathway. Our results reveal that TRPV2 participates in PH-induced AF, and TRPV2 inhibitor tranilast prevents PH-induced RA remodeling. TRPV2 might be a promising target for PH-induced AF.

Pathophysiological Roles of the TRPV4 Channel in the Heart

The transient receptor potential vanilloid 4 (TRPV4) channel is a non-selective cation channel that is mostly permeable to calcium (Ca²⁺), which participates in intracellular Ca²⁺ handling in cardiac cells. It is widely expressed through the body and is activated by a large spectrum of physicochemical stimuli, conferring it a role in a variety of sensorial and physiological functions. Within the cardiovascular system, TRPV4 expression is reported in cardiomyocytes, endothelial cells (ECs) and smooth muscle cells (SMCs), where it modulates mitochondrial activity, Ca²⁺ homeostasis, cardiomyocytes electrical activity and contractility, cardiac embryonic development and fibroblast proliferation, as well as vascular permeability, dilatation and constriction. On the other hand, TRPV4 channels participate in several cardiac pathological processes such as the development of cardiac fibrosis, hypertrophy, ischemia-reperfusion injuries, heart failure, myocardial infarction and arrhythmia. In this manuscript, we provide an overview of TRPV4 channel implications in cardiac physiology and discuss the potential of the TRPV4 channel as a therapeutic target against cardiovascular diseases.

Progress on role of ion channels of cardiac fibroblasts in fibrosis

Cardiac fibrosis is defined as excessive deposition of extracellular matrix (ECM) in pathological conditions. Cardiac fibroblasts (CFs) activated by injury or inflammation differentiate into myofibroblasts (MFs) with secretory and contractile functions. In the fibrotic heart, MFs produce ECM which is composed mainly of collagen and is initially involved in maintaining tissue integrity. However, persistent fibrosis disrupts the coordination of excitatory contractile coupling, leading to systolic and diastolic dysfunction, and ultimately heart failure. Numerous studies have demonstrated that both voltage- and non-voltage-gated ion channels alter intracellular ion levels and cellular activity, contributing to myofibroblast proliferation, contraction, and secretory function. However, an effective treatment strategy for myocardial fibrosis has not been established. Therefore, this review describes the progress made in research related to transient receptor potential (TRP) channels, Piezo1, Ca²⁺ release-activated Ca²⁺ (CRAC) channels, voltage-gated Ca²⁺ channels (VGCCs), sodium channels, and potassium channels in myocardial fibroblasts with the aim of providing new ideas for treating myocardial fibrosis.

Capsaicin Inhibits Multiple Voltage-Gated Ion Channels in Rabbit Ventricular Cardiomyocytes in TRPV1-Independent Manner

Capsaicin is a naturally occurring alkaloid derived from chili pepper which is responsible for its hot, pungent taste. It exerts multiple pharmacological actions, including pain-relieving, anti-cancer, anti-inflammatory, anti-obesity, and antioxidant effects. Previous studies have shown that capsaicin significantly affects the contractility and automaticity of the heart and alters cardiovascular functions. In this study, the effects of capsaicin were investigated on voltage-gated ion currents in rabbit ventricular myocytes. Capsaicin inhibited rapidly activated (I_Kr) and slowly activated (I_Ks) K⁺ currents and transient outward (I_to) K⁺ current with IC₅₀ values of 3.4 µM,14.7 µM, and 9.6 µM, respectively. In addition, capsaicin, at higher concentrations, suppressed voltage-gated Na⁺ and Ca²⁺ currents and inward rectifier I_K1 current with IC₅₀ values of 42.7 µM, 34.9 µM, and 38.8 µM, respectively. Capsaicin inhibitions of I_Na, I_L-Ca, I_Kr, I_Ks, I_to, and I_K1 were not reversed in the presence of capsazepine (3 µM), a TRPV1 antagonist. The inhibitory effects of capsaicin on these currents developed gradually, reaching steady-state levels within 3 to 6 min, and the recoveries were usually incomplete during washout. In concentration-inhibition curves, apparent Hill coefficients higher than unity suggested multiple interaction sites of capsaicin on these channels. Collectively, these findings indicate that capsaicin affects cardiac electrophysiology by acting on a diverse range of ion channels and suggest that caution should be exercised when capsaicin is administered to carriers of cardiac channelopathies or to individuals with arrhythmia-prone conditions, such as ischemic heart diseases.