Role of TRP channels in the cardiovascular system

TRPM6 in murine kidneys-of targets and antibodies

Magnesium is the fourth most abundant cation in the human organism. As a key-player in many enzymatic reactions, magnesium homeostasis disbalance can cause severe disorders. In the early 2000s, the transient receptor potential melastatin channel 6 (TRPM6) was identified as a critical protein in renal Mg2+-reabsorption in the distal convoluted tubule (DCT). As the key-interface responsible for salt/water adaptation to environmental changes, the kidney is a highly dynamic system. Therefore, renal TRPM6 expression and Mg2+-reabsorption might not be restricted to the DCT, as previously indicated. To address this, protein targeting is mandatory since genomic detection is insufficient to conclude on functional expression. For this purpose, we used a polyclonal TRPM6 antibody from an established manufacturer and detected immunostaining in murine proximal and distal tubules. As a matter of fact, the specificity of most commercially available TRPM6 antibodies is insufficiently validated which relies on the lack of constitutive trpm6 knockouts. Therefore, conditional trpm6 knockout mice were used for control experiments. Similar signals were observed in the knockout tissue when compared to wildtype using the TRPM6 antibody. Overlaps with TRPM7 epitopes or other peptides are conceivable. Thus, TRPM6 immunohistochemistry and immunofluorescence results are difficult to interpret, and the spectrum of renal TRPM6 expression is not yet elucidated.

Influence of the 'painless' TRP channel on temperature-dependent escape and humidity-related pupation in Bactrocera dorsalis larvae

BACKGROUND

Temperature and humidity are critical environmental factors that shape insect growth, development and survival. The larval stage is particularly vulnerable, making the ability to detect and respond to adverse environmental conditions vital for avoiding harm. The oriental fruit fly, Bactrocera dorsalis, is a major global pest inflicting damage on >150 fruit crops. However, the behavioral responses of nonmodel insect larvae to temperature and humidity remain poorly characterized.

RESULTS

We found that temperature and humidity significantly influence key larval behaviors. To uncover the molecular mechanisms driving these behaviors, we identified B. dorsalis painless (Bdorpainless) homologs and confirmed their expression during larval behavioral stages. Genetic disruption of Bdorpainless notably impaired the larvae's temperature-escape response. Although humidity sensing remained unaffected in Bdorpainless-mutant larvae, their pupation rate was significantly reduced.

CONCLUSIONS

Our findings provide new insights into the role of environmental factors in B. dorsalis behavior and highlight Bdorpainless as a potential molecular target for pest control. For example, RNA-based biopesticides targeting Bdorpainless could impair larvae's environmental adaptability, offering a novel pest management approach. © 2025 Society of Chemical Industry.

Sex differences in the vasoactive effect of transient receptor potential channels: TRPM3 as a new therapeutic target for (neuro)vascular disorders

BACKGROUND AND PURPOSE

Sex-dependent vascular effects of transient receptor potential (TRP) channels and sex dimorphism in migraine are not yet fully characterized. We investigated the differential vasoactive effects of TRP ankyrin 1 (TRPA1), TRP melastatin 3 (TRPM3) and TRP vanilloid 1 (TRPV1) channels, their pharmacological mechanism(s), and localization and expression in human isolated blood vessels.

EXPERIMENTAL APPROACH

Agonist responses to cinnamaldehyde (TRPA1), pregnenolone sulfate (PregS, TRPM3) or capsaicin (TRPV1) were analysed using wire myography in segments of human coronary (HCAs) and middle meningeal (HMMAs) arteries from men and women. The mechanisms involved in these responses were investigated using the antagonists/blockers/inhibitors: HC-030031 (TRPA1), isosakuranetin (TRPM3), capsazepine (TRPV1), olcegepant (calcitonin gene-related peptide [CGRP] receptor), L-NAME (nitric oxide synthase [NOS]), indomethacin (cyclooxygenase [COX]), TRAM-34 + apamin (K+ channels) or MK-801 (N-methyl-d-aspartate [NMDA] receptor). Fluorescence microscopy, quantitative polymerase chain reaction (qPCR), and western blotting were performed to investigate their location and expression, respectively.

KEY RESULTS

In HCAs and HMMAs, (i) capsaicin-induced relaxation remained unchanged after the above-mentioned antagonists/blockers/inhibitors and (ii) cinnamaldehyde-induced relaxation was blocked by olcegepant. PregS-induced maximal relaxation was significantly enhanced in isolated arteries from females compared with males and was inhibited after isosakuranetin, MK-801 or L-NAME. TRPM3 mRNA and protein expression, along with NMDA protein levels, were higher in arteries from females than males.

CONCLUSION AND IMPLICATIONS

Modulation of vascular tone in HCAs and HMMAs by activation of TRPM3 is sex-dependent, likely involving NMDA receptors. This represents a new therapeutic direction, targeting sex dimorphism in migraine and its related cardiovascular events.

Role of ferroptosis in atrial fibrillation: a review

Cardiovascular disease remains the leading cause of mortality, with atrial fibrillation emerging as one of the most common conditions encountered in clinical practice. However, its underlying mechanisms remain poorly understood, prompting ongoing research. Ferroptosis, a recently discovered form of regulated cell death characterized by lipid peroxidation and disrupted cellular redox balance leading to cell death due to iron overload, has attracted significant attention. Since its identification, ferroptosis has been extensively studied in various contexts, including cancer, stroke, myocardial ischemia/reperfusion injury, and heart failure. Growing evidence suggests that ferroptosis may also play a critical role in the onset and progression of atrial fibrillation, though research in this area is still limited. This article provides a concise overview of the potential mechanisms by which ferroptosis may contribute to the pathogenesis of atrial fibrillation.

TRPM8 and TRPA1 ideal targets for treating cold-induced pain

TRP channels are essential for detecting variations in external temperature and are ubiquitously expressed in both the peripheral and central nervous systems as integral channel proteins. They primarily mediate a range of sensory responses, including thermal sensations, nociception, mechanosensation, vision, and gustation, thus playing a critical role in regulating various physiological functions. In colder climates, individuals often experience pain associated with low temperatures, leading to significant discomfort. Within the TRP channel family, TRPM8 and TRPA1 ion channels serve as the primary sensors for cold temperature fluctuations and are integral to both cold nociception and neuropathic pain pathways. Recent advancements in the biosynthesis of inhibitors targeting TRPM8 and TRPA1 have prompted the need for a comprehensive review of their structural characteristics, biological activities, biosynthetic pathways, and chemical synthesis. This paper aims to delineate the distinct roles of TRPM8 and TRPA1 in pain perception, elucidate their respective protein structures, and compile various combinations of TRPM8 and TRPA1 antagonists and agonists. The discussion encompasses their chemical structures, structure-activity relationships (SARs), biological activities, selectivity, and therapeutic potential, with a particular focus on the conformational relationships between antagonists and the channels. This review seeks to provide in-depth insights into pharmacological strategies for managing pain associated with TRPM8 and TRPA1 activation and will pave the way for future investigations into pharmacotherapeutic approaches for alleviating cold-induced pain.

Deficiency of endothelial TRPV4 cation channels ameliorates experimental abdominal aortic aneurysm

BACKGROUND

Abdominal aortic aneurysm (AAA), albeit usually asymptomatic, is highly lethal if ruptured. The 28-member transient receptor potential (TRP) ion channel superfamily, most of which are present in the aortic cells, is understudied in AAA. We aim to identify single TRP channel that could represent a novel therapeutic target, and dissect dysfunctional ionic signaling that drives AAA.

METHODS

AAA was developed in mice by perfusing porcine pancreatic elastase into the infrarenal abdominal aorta. AAA was assessed by measurement of external diameter with a digital caliper, or internal diameter with ultrasonography. Aortic pathohistology was evaluated via histological and immunohistochemical staining. The TRP channel family was analyzed in the GSE17901 dataset. TRPC6, TRPC1/4/5 and TRPC3 channels were blocked in aneurysmal mice by BI749327, Pico145 and Pyr3, respectively. Endothelial cell-selective Trpv4 knockout mice were generated and leveraged for AAA analysis. TRPV4 channel was activated indirectly by TPPU or directly opened by GSK1016790A.

RESULTS

RNA-seq data mining revealed altered expression profiles of Trpc3/Trpc6, Trpv4. Pharmacological block of TRPC6, TRPC1/4/5 or TRPC3 did not influence AAA, whereas selective deletion of endothelial TRPV4 protected against AAA in endothelial cell-selective Trpv4 knockout mice. Indirect activation of TRPV4 by TPPU exacerbated AAA, but TRPV4-mediated nitric oxide signaling contributed minimally to AAA. TRPV4 activation promoted endothelial cell apoptosis in a Ca2+-dependent manner, a relevant mechanism underlying AAA.

CONCLUSIONS

Our data underscore the pathogenic importance of Ca2+ perturbation in AAA and illuminate that endothelial TRPV4 cation channel could be harnessed for AAA treatment.

Transient Receptor Potential Canonical Channels in Cardiovascular Pathology and Their Modulators

ABSTRACT

Ion channels play a crucial role in various aspects of cardiac function, such as regulating rhythm and contractility. As a result, they serve as key targets for therapeutic interventions in cardiovascular diseases. Cell function is substantially influenced by the concentration of free cytosolic calcium (Ca 2+ ) and the voltage across the plasma membrane. These characteristics are known to be regulated by Ca 2+ -permeable nonselective cationic channels, although our knowledge of these channels is still inadequate. The transient receptor potential (TRP) superfamily comprises of many nonselective cation channels with diverse Ca 2+ permeability. Canonical or classical TRP (TRPC) channels are a subgroup of the TRP superfamily that are expressed ubiquitously in mammalian cells. TRPC channels are multidimensional signaling protein complexes that play essential roles in a variety of physiological and pathological processes in humans, including cancer, neurological disorders, cardiovascular diseases, and others. The objective of this article was to focus on the role that TRPC channels play in the cardiovascular system. The role of TRPC channels will be deeply discussed in cardiovascular pathology. Together, a critical element in developing novel treatments that target TRPC channels is comprehending the molecular mechanisms and regulatory pathways of TRPC channels in related cardiovascular diseases and conditions.

Site-specific genetic and functional signatures of aortic endothelial cells at aneurysm predilection sites in healthy and AngII ApoE-/- mice

Aortic aneurysm is characterized by a pathological dilation at specific predilection sites of the vessel and potentially results in life-threatening vascular rupture. Herein, we established a modified "Häutchen method" for the local isolation of endothelial cells (ECs) from mouse aorta to analyze their spatial heterogeneity and potential role in site-specific disease development. When we compared ECs from aneurysm predilection sites of healthy mice with adjacent control segments we found regulation of genes related to extracellular matrix remodeling, angiogenesis and inflammation, all pathways playing a critical role in aneurysm development. We also detected enhanced cortical stiffness of the endothelium at these sites. Gene expression of ECs from aneurysms of the AngII ApoE-/- model when compared to sham animals mimicked expression patterns from predilection sites of healthy animals. Thus, this work highlights a striking genetic and functional regional heterogeneity in aortic ECs of healthy mice, which defines the location of aortic aneurysm formation in disease.

A Mechanism for the Treatment of Cardiovascular and Renal Disease: TRPV1 and TRPA1

ABSTRACT

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality globally. CVD and kidney disease are closely related, with kidney injury increasing CVD mortality. The pathogenesis of cardiovascular and renal diseases involves complex and diverse interactions between multiple extracellular and intracellular signaling molecules, among which transient receptor potential vanilloid 1 (TRPV1)/transient receptor potential ankyrin 1 (TRPA1) channels have received increasing attention. TRPV1 belongs to the vanilloid receptor subtype family of transient receptor potential ion channels, and TRPA1 belongs to the transient receptor potential channel superfamily. TRPV1/TRPA1 are jointly involved in the management of cardiovascular and renal diseases and play important roles in regulating vascular tension, promoting angiogenesis, antifibrosis, anti-inflammation, and antioxidation. The mechanism of TRPV1/TRPA1 is mainly related to regulation of intracellular calcium influx and release of nitric oxide and calcitonin gene-related peptide. Therefore, this study takes the TRPV1/TRPA1 channel as the research object, analyzes and summarizes the process and mechanism of TRPV1/TRPA1 affecting cardiovascular and renal diseases, and lays a foundation for the treatment of cardiorenal diseases.

Bidirectional regulation mechanism of TRPM2 channel: role in oxidative stress, inflammation and ischemia-reperfusion injury

Transient receptor potential melastatin 2 (TRPM2) is a non-selective cation channel that exhibits Ca2+ permeability. The TRPM2 channel is expressed in various tissues and cells and can be activated by multiple factors, including endogenous ligands, Ca2+, reactive oxygen species (ROS) and temperature. This article reviews the multiple roles of the TRPM2 channel in physiological and pathological processes, particularly on oxidative stress, inflammation and ischemia-reperfusion (I/R) injury. In oxidative stress, the excessive influx of Ca2+ caused by the activation of the TRPM2 channel may exacerbate cellular damage. However, under specific conditions, activating the TRPM2 channel can have a protective effect on cells. In inflammation, the activation of the TRPM2 channel may not only promote inflammatory response but also inhibit inflammation by regulating ROS production and bactericidal ability of macrophages and neutrophils. In I/R, the activation of the TRPM2 channel may worsen I/R injury to various organs, including the brain, heart, kidney and liver. However, activating the TRPM2 channel may protect the myocardium from I/R injury by regulating calcium influx and phosphorylating proline-rich tyrosine kinase 2 (Pyk2). A thorough investigation of the bidirectional role and regulatory mechanism of the TRPM2 channel in these physiological and pathological processes will aid in identifying new targets and strategies for treatment of related diseases.

Exploring the mechanisms underlying effects of bisphenol a on cardiovascular disease by network toxicology and molecular docking

Background

Globally, cardiovascular disease (CVD) has emerged as a leading cause of mortality. Bisphenol A (BPA), recognized as one of the most prevalent and widely distributed endocrine-disrupting chemicals (EDCs), has been consistently linked to the progression of CVD. This research centers on unraveling the molecular mechanisms responsible for the toxic effects of BPA exposure on CVD. Key targets and pathways involved in action of BPA on CVD were investigated by network toxicology. Binding abilities of BPA to core targets were evaluated by molecular docking.

Methods and results

Based on information retrieved from ChEMBL, DrugBank, and OMIM databases, a total of 27 potential targets were found to be associated with the influence of BPA on CVD. Furthermore, the STRING and Cytoscape software were employed to identify three central genes-ESR1, PPARG, and PTGS2-and to construct both the protein-protein interaction network and an interaction diagram of potential targets. Gene ontology (GO) and KEGG (Kyoto Encyclopedia of Genes and Genomes, KEGG) pathway enrichment analyses via WebGestalt revealed key biological processes (BP), cellular components (CC), molecular functions (MF), and pathways, such as the calcium signaling pathway, inflammatory mediator regulation of TRP channels, gap junction, adrenergic signaling in cardiomyocytes, cGMP-PKG signaling pathway, and cAMP signaling pathway, predominantly involved in BPA-induced CVD toxicity. By using molecular docking investigations, it proved that BPA binds to ESR1, PPARG, and PTGS2 steadily and strongly.

Conclusion

This study not only establishes a theoretical framework for understanding the molecular toxicity mechanism of BPA in cardiovascular disease (CVD) but also introduces an innovative network toxicology approach to methodically investigate the influence of environmental contaminants on CVD. This methodology sets the stage for drug discovery efforts targeting CVD linked to exposure to endocrine-disrupting chemicals (EDCs).

High-content method for mechanosignaling studies using IsoStretcher technology and quantitative Ca2+ imaging applied to Piezo1 in cardiac HL-1 cells

The importance of mechanosensory transduction pathways in cellular signalling has prominently come to focus in the last decade with the discovery of the Piezo ion channel family. Mechanosignaling involving Piezo1 ion channels in the function of the heart and cardiovascular system has only recently been identified to have implications for cardiovascular physiology and pathophysiology, in particular for heart failure (i.e., hypertrophy or dilative cardiomyopathy). These results have emphasized the need for higher throughput methods to study single-cell cardiovascular mechanobiology with the aim of identifying new targets for therapeutic interventions and stimulating the development of new pharmacological agents. Here, we present a novel method to assess mechanosignaling in adherent cardiac cells (murine HL-1 cell line) using a combination of isotropic cell stretch application and simultaneous Ca2+ fluorescence readout with quantitative analysis. The procedure implements our IsoStretcher technology in conjunction with a single-cell- and population-based analysis of Ca2+ signalling by means of automated image registration, cell segmentation and analysis, followed by automated classification of single-cell responses. The method is particularly valuable for assessing the heterogeneity of populations with distinct cellular responses to mechanical stimulation and provides more user-independent unbiased drug response classifications.

Cardiac arrhythmogenesis: roles of ion channels and their functional modification

Cardiac arrhythmias cause significant morbidity and mortality and pose a major public health problem. They arise from disruptions in the normally orderly propagation of cardiac electrophysiological activation and recovery through successive cardiomyocytes in the heart. They reflect abnormalities in automaticity, initiation, conduction, or recovery in cardiomyocyte excitation. The latter properties are dependent on surface membrane electrophysiological mechanisms underlying the cardiac action potential. Their disruption results from spatial or temporal instabilities and heterogeneities in the generation and propagation of cellular excitation. These arise from abnormal function in their underlying surface membrane, ion channels, and transporters, as well as the interactions between them. The latter, in turn, form common regulatory targets for the hierarchical network of diverse signaling mechanisms reviewed here. In addition to direct molecular-level pharmacological or physiological actions on these surface membrane biomolecules, accessory, adhesion, signal transduction, and cytoskeletal anchoring proteins modify both their properties and localization. At the cellular level of excitation-contraction coupling processes, Ca2+ homeostatic and phosphorylation processes affect channel activity and membrane excitability directly or through intermediate signaling. Systems-level autonomic cellular signaling exerts both acute channel and longer-term actions on channel expression. Further upstream intermediaries from metabolic changes modulate the channels both themselves and through modifying Ca2+ homeostasis. Finally, longer-term organ-level inflammatory and structural changes, such as fibrotic and hypertrophic remodeling, similarly can influence all these physiological processes with potential pro-arrhythmic consequences. These normal physiological processes may target either individual or groups of ionic channel species and alter with particular pathological conditions. They are also potentially alterable by direct pharmacological action, or effects on longer-term targets modifying protein or cofactor structure, expression, or localization. Their participating specific biomolecules, often clarified in experimental genetically modified models, thus constitute potential therapeutic targets. The insights clarified by the physiological and pharmacological framework outlined here provide a basis for a recent modernized drug classification. Together, they offer a translational framework for current drug understanding. This would facilitate future mechanistically directed therapeutic advances, for which a number of examples are considered here. The latter are potentially useful for treating cardiac, in particular arrhythmic, disease.

High fat diet-induced downregulation of TRPV2 mediates hepatic steatosis via p21 signalling

The global prevalence and incidence of non-alcoholic fatty liver disease (NAFLD) are exhibiting an increasing trend. NAFLD is characterized by a significant accumulation of lipids, though its underlying mechanism is still unknown. Here we report that high-fat diet (HFD) feeding induced hepatic steatosis in mice, which was accompanied by a reduction in the expression and function of hepatic TRPV2. Moreover, conditional knockout of TRPV2 in hepatocytes exacerbated HFD-induced hepatic steatosis. In an in vitro model of NAFLD, TRPV2 regulated lipid accumulation in HepG2 cells, and TRPV2 activation inhibited the expression of the cellular senescence markers p21 and p16, all of which were mediated by AMPK phosphorylation. Finally, we found that administration of probenecid, a TRPV2 agonist, impaired HFD-induced hepatic steatosis and suppressed HFD-induced elevation in p21 and p16. Collectively, our findings imply that hepatic TRPV2 protects against the accumulation of lipids by modulating p21 signalling.

Targeting TRP channels: recent advances in structure, ligand binding, and molecular mechanisms

Transient receptor potential (TRP) channels are a large and diverse family of transmembrane ion channels that are widely expressed, have important physiological roles, and are associated with many human diseases. These proteins are actively pursued as promising drug targets, benefitting greatly from advances in structural and mechanistic studies of TRP channels. At the same time, the complex, polymodal activation and regulation of TRP channels have presented formidable challenges. In this short review, we summarize recent progresses toward understanding the structural basis of TRP channel function, as well as potential ligand binding sites that could be targeted for therapeutics. A particular focus is on the current understanding of the molecular mechanisms of TRP channel activation and regulation, where many fundamental questions remain unanswered. We believe that a deeper understanding of the functional mechanisms of TRP channels will be critical and likely transformative toward developing successful therapeutic strategies targeting these exciting proteins. This endeavor will require concerted efforts from computation, structural biology, medicinal chemistry, electrophysiology, pharmacology, drug safety and clinical studies.

Evidence for the involvement of TRPV2 channels in the modulation of vascular tone in the mouse aorta

AIMS

Transient receptor potential vanilloid 2 (TRPV2) channels are expressed in both smooth muscle and endothelial cells and participate in vascular mechanotransduction and sensing of high temperatures and lipids. Nevertheless, the impact of TRPV2 channel activation by agonists on the coordinated and cell-type specific modulation of vasoreactivity is unknown.

MAIN METHODS

Aorta from 2- to 4-months-old male Oncins France 1 mice was dissected and mounted in tissue baths for isometric tension measurements. TRPV2 channel expression was assessed by immunofluorescence and western blot in mice aortas and in cultured A7r5 rat aortic smooth muscle cells.

KEY FINDINGS

TRPV2 channels were expressed in all three mouse aorta layers. Activation of TRPV2 channels with probenecid evoked endothelium-dependent relaxations through a mechanism that involved activation of smooth muscle Kir and Kv channels. In addition, TRPV2 channel inhibition with tranilast increased endothelium-independent relaxations to probenecid and this effect was abrogated by the KATP channel blocker glibenclamide, revealing that smooth muscle TRPV2 channels induce negative feedback on probenecid relaxations mediated via KATP channel inhibition. Exposure to the NO donor sodium nitroprusside increased TRPV2 channel translocation to the plasma membrane in cultured smooth muscle cells and enhanced negative feedback on probenecid relaxations.

SIGNIFICANCE

In conclusion, we present the first evidence that TRPV2 channels may modulate vascular tone through a balance of opposed inputs from the endothelium and the smooth muscle leading to net vasodilation. The fact that TRPV2 channel-induced activity can be amplified by NO emphasizes the pathophysiological relevance of these findings.

ROS-Activated TRPM2 Channel: Calcium Homeostasis in Cardiovascular/renal System and Speculation in Cardiorenal Syndrome

The transient receptor potential melastatin 2 (TRPM2) channel is a nonselective calcium channel that is sensitive to oxidative stress (OS), and is widely expressed in multiple organs, such as the heart, kidney, and brain, which is inextricably related to calcium dyshomeostasis and downstream pathological events. Due to the increasing global burden of kidney or cardiovascular diseases (CVDs), safe and efficient drugs specific to novel targets are imperatively needed. Notably, investigation of the possibility to regard the TRPM2 channel as a new therapeutic target in ROS-related CVDs or renal diseases is urgently required because the roles of the TRPM2 channel in heart or kidney diseases have not received enough attention and thus have not been fully elaborated. Therefore, we aimed to review the involvement of the TRPM2 channel in cardiovascular disorders related to kidney or typical renal diseases and attempted to speculate about TRPM2-mediated mechanisms of cardiorenal syndrome (CRS) to provide representative perspectives for future research about novel and effective therapeutic strategies.

Impact of aging on vascular ion channels: perspectives and knowledge gaps across major organ systems

Individuals aged ≥65 yr will comprise ∼20% of the global population by 2030. Cardiovascular disease remains the leading cause of death in the world with age-related endothelial "dysfunction" as a key risk factor. As an organ in and of itself, vascular endothelium courses throughout the mammalian body to coordinate blood flow to all other organs and tissues (e.g., brain, heart, lung, skeletal muscle, gut, kidney, skin) in accord with metabolic demand. In turn, emerging evidence demonstrates that vascular aging and its comorbidities (e.g., neurodegeneration, diabetes, hypertension, kidney disease, heart failure, and cancer) are "channelopathies" in large part. With an emphasis on distinct functional traits and common arrangements across major organs systems, the present literature review encompasses regulation of vascular ion channels that underlie blood flow control throughout the body. The regulation of myoendothelial coupling and local versus conducted signaling are discussed with new perspectives for aging and the development of chronic diseases. Although equipped with an awareness of knowledge gaps in the vascular aging field, a section has been included to encompass general feasibility, role of biological sex, and additional conceptual and experimental considerations (e.g., cell regression and proliferation, gene profile analyses). The ultimate goal is for the reader to see and understand major points of deterioration in vascular function while gaining the ability to think of potential mechanistic and therapeutic strategies to sustain organ perfusion and whole body health with aging.

The Dysfunction of Ca2+ Channels in Hereditary and Chronic Human Heart Diseases and Experimental Animal Models

Chronic heart diseases, such as coronary heart disease, heart failure, secondary arterial hypertension, and dilated and hypertrophic cardiomyopathies, are widespread and have a fairly high incidence of mortality and disability. Most of these diseases are characterized by cardiac arrhythmias, conduction, and contractility disorders. Additionally, interruption of the electrical activity of the heart, the appearance of extensive ectopic foci, and heart failure are all symptoms of a number of severe hereditary diseases. The molecular mechanisms leading to the development of heart diseases are associated with impaired permeability and excitability of cell membranes and are mainly caused by the dysfunction of cardiac Ca2+ channels. Over the past 50 years, more than 100 varieties of ion channels have been found in the cardiovascular cells. The relationship between the activity of these channels and cardiac pathology, as well as the general cellular biological function, has been intensively studied on several cell types and experimental animal models in vivo and in situ. In this review, I discuss the origin of genetic Ca2+ channelopathies of L- and T-type voltage-gated calcium channels in humans and the role of the non-genetic dysfunctions of Ca2+ channels of various types: L-, R-, and T-type voltage-gated calcium channels, RyR2, including Ca2+ permeable nonselective cation hyperpolarization-activated cyclic nucleotide-gated (HCN), and transient receptor potential (TRP) channels, in the development of cardiac pathology in humans, as well as various aspects of promising experimental studies of the dysfunctions of these channels performed on animal models or in vitro.

Discovery of novel TRPV1 modulators through machine learning-based molecular docking and molecular similarity searching

The transient receptor potential vanilloid 1 (TRPV1) channel belongs to the transient receptor potential channel superfamily and participates in many physiological processes. TRPV1 modulators (both agonists and antagonists) can effectively inhibit pain caused by various factors and have curative effects in various diseases, such as itch, cancer, and cardiovascular diseases. Therefore, the development of TRPV1 channel modulators is of great importance. In this study, the structure-based virtual screening and ligand-based virtual screening methods were used to screen compound databases respectively. In the structure-based virtual screening route, a full-length human TRPV1 protein was first constructed, three molecular docking methods with different precisions were performed based on the hTRPV1 structure, and a machine learning-based rescoring model by the XGBoost algorithm was constructed to enrich active compounds. In the ligand-based virtual screening route, the ROCS program was used for 3D shape similarity searching and the EON program was used for electrostatic similarity searching. Final 77 compounds were selected from two routes for in vitro assays. The results showed that 8 of them were identified as active compounds, including three hits with IC50 values close to capsazepine. In addition, one hit is a partial agonist with both agonistic and antagonistic activity. The mechanisms of some active compounds were investigated by molecular dynamics simulation, which explained their agonism or antagonism.

TRP (transient receptor potential) ion channel family: structures, biological functions and therapeutic interventions for diseases

Transient receptor potential (TRP) channels are sensors for a variety of cellular and environmental signals. Mammals express a total of 28 different TRP channel proteins, which can be divided into seven subfamilies based on amino acid sequence homology: TRPA (Ankyrin), TRPC (Canonical), TRPM (Melastatin), TRPML (Mucolipin), TRPN (NO-mechano-potential, NOMP), TRPP (Polycystin), TRPV (Vanilloid). They are a class of ion channels found in numerous tissues and cell types and are permeable to a wide range of cations such as Ca²⁺, Mg²⁺, Na⁺, K⁺, and others. TRP channels are responsible for various sensory responses including heat, cold, pain, stress, vision and taste and can be activated by a number of stimuli. Their predominantly location on the cell surface, their interaction with numerous physiological signaling pathways, and the unique crystal structure of TRP channels make TRPs attractive drug targets and implicate them in the treatment of a wide range of diseases. Here, we review the history of TRP channel discovery, summarize the structures and functions of the TRP ion channel family, and highlight the current understanding of the role of TRP channels in the pathogenesis of human disease. Most importantly, we describe TRP channel-related drug discovery, therapeutic interventions for diseases and the limitations of targeting TRP channels in potential clinical applications.

Electrical Remodeling in Right Ventricular Failure Due to Pulmonary Hypertension: Unraveling Novel Therapeutic Targets

Arrhythmias in the setting of right-ventricular (RV) remodeling contribute to majority of deaths in patients with pulmonary hypertension. However, the underlying mechanism of electrical remodeling remains elusive, especially ventricular arrhythmias. Here, we analyzed the RV transcriptome of pulmonary arterial hypertension (PAH) patients with compensated RV or decompensated RV and identified 8 and 45 differentially expressed genes known to be involved in regulating the electrophysiological properties of excitation and contraction of cardiac myocytes, respectively. Transcripts encoding voltage-gated Ca2+ and Na+ channels were notably decreased in PAH patients with decompensated RV, along with significant dysregulation of KV and Kir channels. We further showed similarity of the RV channelome signature with two well-known animal models of PAH, monocrotaline (MCT)- and Sugen-hypoxia (SuHx)-treated rats. We identified 15 common transcripts among MCT, SuHx, and PAH patients with decompensated RV failure. In addition, data-driven drug repurposing using the channelome signature of PAH patients with decompensated RV failure predicted drug candidates that may reverse the altered gene expression. Comparative analysis provided further insight into clinical relevance and potential preclinical therapeutic studies targeting mechanisms involved in arrhythmogenesis.

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.

TRPC1 channels underlie stretch-modulated sarcoplasmic reticulum calcium leak in cardiomyocytes

Transient receptor potential canonical 1 (TRPC1) channels are Ca2+-permeable ion channels expressed in cardiomyocytes. An involvement of TRPC1 channels in cardiac diseases is widely established. However, the physiological role of TRPC1 channels and the mechanisms through which they contribute to disease development are still under investigation. Our prior work suggested that TRPC1 forms Ca2+ leak channels located in the sarcoplasmic reticulum (SR) membrane. Prior studies suggested that TRPC1 channels in the cell membrane are mechanosensitive, but this was not yet investigated in cardiomyocytes or for SR localized TRPC1 channels. We applied adenoviral transfection to overexpress or suppress TRPC1 expression in neonatal rat ventricular myocytes (NRVMs). Transfections were evaluated with RT-qPCR, western blot, and fluorescent imaging. Single-molecule localization microscopy revealed high colocalization of exogenously expressed TRPC1 and the sarco/endoplasmic reticulum Ca2+ ATPase (SERCA2). To test our hypothesis that TRPC1 channels contribute to mechanosensitive Ca2+ SR leak, we directly measured SR Ca2+ concentration ([Ca2+]SR) using adenoviral transfection with a novel ratiometric genetically encoded SR-targeting Ca2+ sensor. We performed fluorescence imaging to quantitatively assess [Ca2+]SR and leak through TRPC1 channels of NRVMs cultured on stretchable silicone membranes. [Ca2+]SR was increased in cells with suppressed TRPC1 expression vs. control and Transient receptor potential canonical 1-overexpressing cells. We also detected a significant reduction in [Ca2+]SR in cells with Transient receptor potential canonical 1 overexpression when 10% uniaxial stretch was applied. These findings indicate that TRPC1 channels underlie the mechanosensitive modulation of [Ca2+]SR. Our findings are critical for understanding the physiological role of TRPC1 channels and support the development of pharmacological therapies for cardiac diseases.

Predictive value of TRPV2 expression from peripheral blood mononuclear cells on the early recurrence of atrial fibrillation after radiofrequency catheter ablation

BACKGROUND

Recent study has shown that the transient receptor potential vanilloid 2 (TRPV2) channel was exclusively upregulated in patients with atrial fibrillation (AF), and that this overexpression might be detrimental for occurrence and maintenance of AF. We aimed to characterize the expression levels of TRPV2 mRNA in peripheral blood mononuclear cells (PBMCs) with/without early recurrence of atrial fibrillation (ERAF) after radiofrequency catheter ablation (RFCA), and to find a reliable predictor for ERAF.

METHODS

65 patients of AF, who underwent RFCA successfully, then divided into two groups according to ERAF during following 3 months. PBMCs were isolated from whole blood by Ficoll gradient centrifugation before and after RFCA. Gene set enrichment analysis was performed to evaluate TRPV channels expression levels and Kyoto Encyclopedia of Genes and Genomes (KEGG) mapping was used for pathway enrichment analysis.

RESULTS

There was no significant difference in the TRPV2 mRNA expression level between the two groups before RFCA, while without ERAF group of TRPV2 expression was markedly reduced compared to ERAF group after RFCA. Moreover, the number of TRPV2 expression was confirmed as an independent predictor for the first time through receiver operating characteristic and Kaplan-Meier survival curve analysis. It should be pointed out that the above results were only used to predict ERAF, and have no predictive significance for late recurrence of atrial fibrillation according to the current data. Additionally, ERAF was inversely correlated with P wave dispersion. KEGG mapping further clustered 41 pathways, revealing that ''cyclic guanosine monophosphate-protein kinase G signaling pathway'' was significantly enriched.

CONCLUSIONS

We firstly assume that downregulated expression of peripheral TRPV2 appear in patients without ERAF after RFCA. TRPV2 may thus represent a novel predictor of early phase after successful radiofrequency ablation.

Transient Receptor Potential (TRP) Channels in Tumor Vascularization

Tumor diseases are unfortunately quick spreading, even though numerous studies are under way to improve early diagnosis and targeted treatments that take into account both the different characteristics associated with the various tumor types and the conditions of individual patients. In recent years, studies have focused on the role of ion channels in tumor development, as these proteins are involved in several cellular processes relevant to neoplastic transformation. Among all ion channels, many studies have focused on the superfamily of Transient Receptor Potential (TRP) channels, which are non-selective cation channels mediating extracellular Ca²⁺ influx. In this review, we examined the role of different endothelial TRP channel isoforms in tumor vessel formation, a process that is essential in tumor growth and metastasis.

Mining of Potential Biomarkers and Pathway in Valvular Atrial Fibrillation (VAF) via Systematic Screening of Gene Coexpression Network

Purpose. We apply the bioinformatics method to excavate the potential genes and therapeutic targets associated with valvular atrial fibrillation (VAF). Methods. The downloaded gene expression files from the gene expression omnibus (GEO) included patients with primary severe mitral regurgitation complicated with sinus or atrial fibrillation rhythm. Subsequently, the differential gene expression in left and right atrium was analyzed by R software. Additionally, weighted correlation network analysis (WGCNA), principal component analysis (PCA), and linear model for microarray data (LIMMA) algorithm were used to determine hub genes. Then, Metascape database, DAVID database, and STRING database were used to annotate and visualize the gene ontology (GO) analysis, KEGG pathway enrichment analysis, and PPI network analysis of differentially expressed genes (DEGs). Finally, the TFs and miRNAs were predicted by using online tools, such as PASTAA and miRDB. Results. 20,484 differentially expressed genes related to atrial fibrillation were obtained through the analysis of left and right atrial tissue samples of GSE115574 gene chip, and 1,009 were with statistical significance, including 45 upregulated genes and 964 downregulated genes. And the hub genes implicated in AF of NPC2, ODC1, SNAP29, LAPTM5, ST8SIA5, and FCGR3B were screened. Finally, the main regulators of targeted candidate biomarkers and microRNAs, EIF5A2, HIF1A, ZIC2, ELF1, and STAT2, were found in this study. Conclusion. These hub genes, NPC2, ODC1, SNAP29, LAPTM5, ST8SIA5, and FCGR3B, are important for the development of VAF, and their enrichment pathways and TFs elucidate the involved molecular mechanisms and assist in the validation of drug targets.

A TRPV1 common missense variant affected the prognosis of ischemic cardiomyopathy

The purpose was to identify the Transient receptor potential (TRP) superfamily gene variants associate with the prognosis of ischemic cardiomyopathy (ICM). A whole-exome sequencing study involving 252 ICM and 252 healthy controls participants enrolled from March 2003 to November 2017. Optimal sequence kernel association test and Cox regression dominant was conducted to identify the cause genes of TRP with ICM and association of common SNPs with prognosis of ICM. Rs224534 was verified in the replication population. Besides, the expression of TRPV1 was detectable in human failed heart ventricular tissues. The TRPs was not associated with the risk of ICM (P > .05). Rs224534 was significantly associated with the prognosis of ICM (Hazard ratio, 2.27, 95%CI: 1.31-3.94; P = 3.7 × 10-3), in the replication cohort, (hazard ratio 1.47, 95%CI: 1.04-2.07; P = 2.9 × 10-2), and in combined cohort hazard ratio 1.62 (95%CI: 1.21-2.18; P = 1.1 × 10-3). The common SNP of TRPV1 (rs224534) is associated with the prognosis of ICM, and homozygote rs224534-AA showed an unfavorable prognosis of ICM in the dominant model tested. Genotyping the variant may benefit to further progress judgment of ICM.

Function of Transient Receptor Potential-Like Channel in Insect Egg Laying

The transient receptor potential-like channel (TRPL) is a member of the transient receptor potential (TRP) channel family involved in regulating many fundamental senses, such as vision, pain, taste, and touch, in both invertebrates and vertebrates. Yet, the function of TRPL in other important biological processes remains unclear. We discover that TRPL regulates egg laying in two insect species, the brown planthopper, Nilaparvata lugens, and the fruit fly, Drosophila melanogaster. In both insects, trpl is expressed in the female reproductive organ. Loss of trpl leads to significantly defects in egg laying. In addition, TRPL is functionally interchangeable between the brown planthoppers and flies in egg laying. Altogether, our work uncovers a novel role played by TRPL in regulating egg laying and indicates TRPL as a potential pesticide target in brown planthoppers.

Evidence of retinal arteriolar narrowing in patients with autosomal-dominant polycystic kidney disease

Introduction

The aim of this study was to examine retinal vessels in autosomal dominant polycystic kidney disease (ADPKD) patients with normal kidney function and without diabetes mellitus.

Materials and Methods

We enrolled 39 adult individuals with ADPKD and 45 gender- and age-matched individuals as controls. A full ophthalmologic examination, including retinal vessel caliber and reactions to flicker stimulation analysis and grading of hypertensive retinopathy according to the Keith-Wagener classification, was performed.

Results

Multivariable analysis of ADPKD patients and controls, adjusted for age, gender, estimated glomerular filtration rate (e-GFR) and the presence of hypertension, revealed that ADPKD was an independent factor associated with lower arteriovenous ratio (AVR) values (by 0.069 on average, β = −0.50, p < 0.0001). The severity of hypertensive retinopathy according to the Keith-Wagener classification appeared to be more advanced in the ADPKD group than in the controls, despite the lack of vascular abnormalities, such as retinal hemorrhages, exudates, cotton wool spots or papilledema, as well as microaneurysms, which are very characteristic signs of ADPKD in other vascular beds.

Conclusions

Lower AVR values could be a specific pathophysiological ocular manifestation of systemic vasculopathy in the course of ADPKD.

Magnolol and honokiol target TRPC4 to regulate extracellular calcium influx and relax intestinal smooth muscle

ETHNOPHARMACOLOGICAL RELEVANCE

Magnolia officinalis Cortex (M. officinalis) is a classical traditional Chinese medicine (TCM) widely used to treat digestive system diseases. It effectively regulates gastrointestinal motility to improve abdominal pain, abdominal distension and other symptoms. Magnolol (MAG) and honokiol (HON) are the main pharmacodynamic components responsible for the gastrointestinal activity of M. officinalis.

AIM OF THE STUDY

The transient receptor potential (TRP) family is highly expressed in the gastrointestinal tract and participates in the regulation of gastrointestinal motility, visceral hypersensitivity, visceral secretion and other physiological activities. In this study, the calcium-lowering mechanisms of MAG and HON contributing to the smooth muscle relaxation associated with TRP are discussed.

MATERIALS AND METHODS

The relaxation smooth muscle effects of MAG and HON were tested by the isolated intestine tone tests. A synthetic MAG probe (MAG-P) was used to target fishing for their possible target. The distribution of MAG on the smooth muscle was identified by a molecular tracer based on chemical biology. Ca²⁺ imaging and dual-luciferase reporter assays were used to determine the effects on the target proteins. Finally, the calcium-mediating effects of MAG and HON on smooth muscle cells and TRPC4-knockdown cells were compared to verify the potential mechanism.

RESULTS

After confirming the smooth muscle relaxation in the small intestine induced by MAG and HON, the relaxation effect was identified mainly due to the downregulation of intracellular calcium by controlling external calcium influx. Although MAG and HON inhibited both TRPV4 and TRPC4 channels to reduce calcium levels, the inhibitory effect on TRPC4 channels is an important mechanism of their smooth muscle relaxation effect, since TRPC4 is widely expressed in the small intestinal smooth muscle cells.

CONCLUSIONS

The inhibition of MAG and HON on TRPC4 channels contributes to the relaxation of intestinal smooth muscle.

Targeting Lipid—Ion Channel Interactions in Cardiovascular Disease

General lipid-lowering strategies exhibit clinical benefit, however, adverse effects and low adherence of relevant pharmacotherapies warrants the investigation into distinct avenues for preventing dyslipidemia-induced cardiovascular disease. Ion channels play an important role in the maintenance of vascular tone, the impairment of which is a critical precursor to disease progression. Recent evidence suggests that the dysregulation of ion channel function in dyslipidemia is one of many contributors to the advancement of cardiovascular disease thus bringing to light a novel yet putative therapeutic avenue for preventing the progression of disease mechanisms. Increasing evidence suggests that lipid regulation of ion channels often occurs through direct binding of the lipid with the ion channel thereby creating a potential therapeutic target wherein preventing specific lipid-ion channel interactions, perhaps in combination with established lipid lowering therapies, may restore ion channel function and the proper control of vascular tone. Here we first detail specific examples of lipid-ion channel interactions that promote vascular dysfunction and highlight the benefits of preventing such interactions. We next discuss the putative therapeutic avenues, such as peptides, monoclonal antibodies, and aspects of nanomedicine that may be utilized to prevent pathological lipid-ion channel interactions. Finally, we discuss the experimental challenges with identifying lipid-ion channel interactions as well as the likely pitfalls with developing the aforementioned putative strategies.

Protein detection and localization of the non-selective cation channel TRPC6 in the human heart

Due to longer lifespans in societies in industrialized countries, cardiovascular diseases are becoming increasingly important for medical research. It has already been shown that the cell membrane-bound, non-selective TRPC6 ion channel is important in the pathogenesis of heart diseases. Among other things, it is permeable to calcium ion, which plays a critical role in cardiac contraction and relaxation. The TRPC6 ion channel is a promising therapeutic target in the treatment of cardiovascular diseases. A deeper understanding of the physiological and pathophysiological role as well as the localization of TRPC6 in human cardiac tissue is the basis for new drug development. Although the TRPC6 channel has been detected in animal studies, at the mRNA level in humans, and sparse TRPC6 protein has been detected in humans, there are no systematic studies of TRPC6 protein detection in the human heart. For the first time, TRPC6 ion channel protein was detected histologically in human heart tissue from body donors in different structures, localizations, and histological layers - particularly in cardiomyocytes and intramuscular arterioles - by immunohistochemistry, just as TRPC6 expression has already been shown in animal models of the heart by other research groups. In the sense of the translational concept, this indicates a possible transferability of research results from animal models to humans.

Evidence of retinal arteriolar narrowing in patients with autosomal-dominant polycystic kidney disease

Introduction

The aim of this study was to examine retinal vessels in autosomal dominant polycystic kidney disease (ADPKD) patients with normal kidney function and without diabetes mellitus.

Materials and Methods

We enrolled 39 adult individuals with ADPKD and 45 gender- and age-matched individuals as controls. A full ophthalmologic examination, including retinal vessel caliber and reactions to flicker stimulation analysis and grading of hypertensive retinopathy according to the Keith-Wagener classification, was performed.

Results

Multivariable analysis of ADPKD patients and controls, adjusted for age, gender, estimated glomerular filtration rate (e-GFR) and the presence of hypertension, revealed that ADPKD was an independent factor associated with lower arteriovenous ratio (AVR) values (by 0.069 on average, β = −0.50, p < 0.0001). The severity of hypertensive retinopathy according to the Keith-Wagener classification appeared to be more advanced in the ADPKD group than in the controls, despite the lack of vascular abnormalities, such as retinal hemorrhages, exudates, cotton wool spots or papilledema, as well as microaneurysms, which are very characteristic signs of ADPKD in other vascular beds.

Conclusions

Lower AVR values could be a specific pathophysiological ocular manifestation of systemic vasculopathy in the course of ADPKD.

Unraveling the Cardiac Effects Induced by Carvacrol in Spontaneously Hypertensive Rats: Involvement of Transient Receptor Potential Melastatin Subfamily 4 and 7 Channels

ABSTRACT

Accumulating evidence indicates that transient receptor potential (TRP) channels are involved in the pathophysiological process in the heart, and monoterpenes, such as carvacrol, are able to modulate these channels activity. In this article, our purpose was to evaluate the direct cardiac effect of carvacrol on the contractility of cardiomyocytes and isolated right atria from spontaneously hypertensive and Wistar Kyoto rats. In this way, in vitro experiments were used to evaluate the ventricular cardiomyocytes contractility and the Ca2+ transient measuring, in addition to heart rhythm in the right atria. The role of TRPM channels in carvacrol-mediated cardiac activities was also investigated. The results demonstrated that carvacrol induced a significant reduction in ventricular cell contractility, without changes in transient Ca2+. In addition, carvacrol promoted a significant negative chronotropic response in spontaneously hypertensive and Wistar Kyoto rats' atria. Selective blockage of TRPM channels suggests the involvement of TRP melastatin subfamily 2 (TRPM2), TRPM4, and TRPM7 in the carvacrol-mediated cardiac effects. In silico studies were conducted to further investigate the putative role of TRPM4 in carvacrol-mediated cardiac action. FTMap underscores a conserved pocket in both TRPM4 and TRPM7, revealing a potential carvacrol binding site, and morphological similarity analysis demonstrated that carvacrol shares a more than 85% similarity to 9-phenanthrol. Taken together, these results suggest that carvacrol has direct cardiac actions, leading to reduced cellular contractility and inducing a negative chronotropic effect, which may be related to TRPM7 and TRPM4 modulation.

Pharmacology of TRPC Channels and Its Potential in Cardiovascular and Metabolic Medicine

Transient receptor potential canonical (TRPC) proteins assemble to form homo- or heterotetrameric, nonselective cation channels permeable to K⁺, Na⁺, and Ca²⁺. TRPC channels are thought to act as complex integrators of physical and chemical environmental stimuli. Although the understanding of essential physiological roles of TRPC channels is incomplete, their implication in various pathological mechanisms and conditions of the nervous system, kidneys, and cardiovascular system in combination with the lack of major adverse effects of TRPC knockout or TRPC channel inhibition is driving the search of TRPC channel modulators as potential therapeutics. Here, we review the most promising small-molecule TRPC channel modulators, the understanding of their mode of action, and their potential in the study and treatment of cardiovascular and metabolic disease.

Arrhythmogenic Remodeling in the Failing Heart

Chronic heart failure is a clinical syndrome with multiple etiologies, associated with significant morbidity and mortality. Cardiac arrhythmias, including ventricular tachyarrhythmias and atrial fibrillation, are common in heart failure. A number of cardiac diseases including heart failure alter the expression and regulation of ion channels and transporters leading to arrhythmogenic electrical remodeling. Myocardial hypertrophy, fibrosis and scar formation are key elements of arrhythmogenic structural remodeling in heart failure. In this article, the mechanisms responsible for increased arrhythmia susceptibility as well as the underlying changes in ion channel, transporter expression and function as well as alterations in calcium handling in heart failure are discussed. Understanding the mechanisms of arrhythmogenic remodeling is key to improving arrhythmia management and the prevention of sudden cardiac death in patients with heart failure.

Calcineurin in the heart: New horizons for an old friend

Calcineurin, also known as PP2B or PPP3, is a member of the PPP family of protein phosphatases that also includes PP1 and PP2A. Together these three phosphatases carryout the majority of dephosphorylation events in the heart. Calcineurin is distinct in that it is activated by the binding of calcium/calmodulin (Ca2+/CaM) and therefore acts as a node for integrating Ca2+ signals with changes in phosphorylation, two fundamental intracellular signaling cascades. In the heart, calcineurin is primarily thought of in the context of pathological cardiac remodeling, acting through the Nuclear Factor of Activated T-cell (NFAT) family of transcription factors. However, calcineurin activity is also essential for normal heart development and homeostasis in the adult heart. Furthermore, it is clear that NFAT-driven changes in transcription are not the only relevant processes initiated by calcineurin in the setting of pathological remodeling. There is a growing appreciation for the diversity of calcineurin substrates that can impact cardiac function as well as the diversity of mechanisms for targeting calcineurin to specific sub-cellular domains in cardiomyocytes and other cardiac cell types. Here, we will review the basics of calcineurin structure, regulation, and function in the context of cardiac biology. Particular attention will be given to: the development of improved tools to identify and validate new calcineurin substrates; recent studies identifying new calcineurin isoforms with unique properties and targeting mechanisms; and the role of calcineurin in cardiac development and regeneration.

Distinct Morphological and Behavioural Alterations in ENU-Induced Heterozygous Trpc7K810Stop Mutant Mice

Trpc7 (transient receptor potential cation channel, subfamily C, member 7; 862 amino acids) knockout mice are described showing no clear phenotypic alterations, therefore, the functional relevance of the gene remains unclear. A complementary approach for the functional analysis of a given gene is the examination of individuals harbouring a mutant allele of the gene. In the phenotype-driven Munich ENU mouse mutagenesis project, a high number of phenotypic parameters was used for establishing novel mouse models on the genetic background of C3H inbred mice. The phenotypically dominant mutant line SMA002 was established and further examined. Analysis of the causative mutation as well as the phenotypic characterization of the mutant line were carried out. The causative mutation was detected in the gene Trpc7 which leads to the production of a truncated protein due to the novel stop codon at amino acid position 810 thereby affecting the highly conserved cytoplasmic C terminus of the protein. Trpc7 heterozygous mutant mice of both sexes were viable and fertile, but showed distinct morphological and behavioural alterations which is in contrast to the published phenotype of Trpc7 knockout mice. Thus, the Trpc7^K810Stop mutation leads to a dominant negative effect of the mutant protein.

Investigation of Hemodynamic Receptors of the Internal Carotid Artery Segments

Objectives

Internal carotid artery (ICA), the main artery of the brain, passes through the cavernous sinus (CS) which forms one of these venous pools. During this transition, while there is arterial blood in the lumen of ICA, its outer surface is in contact with venous blood from the brain. Herein, we aimed to detect the receptor differences of ICA in this highly specialized anatomical region of the skull base.

Methods

We performed the study on 10 human cadavers and searched CGRPR, TRP12, ASIC3 and ACTHR receptors via immunostaining using laser scanning confocal microscopy.

Results

We determined TRP12 receptor positive in the tunica media and tunica adventitia layers of the cavernous segment of ICA. We did not detect similar positivity in the cervical part of the ICA. In the receptor scan we made in terms of CGRPR, while we detected positivity in the tunica media layer of the cavernous segment, we found positivity in the tunica intima layer of the cervicalis segment of the ICA. We did not detect any positivity for ASIC3 and ACTHR receptors in both parts of the ICA.

Conclusions

As a result, we observed various differences in receptors between ICA segments. While the outer surface of the ICA in the cervical region did not show any receptor positivity, we detected TRP12 receptor positivity along the tissue contour of vessel in the CS. We assume that it may provide a new perspective on pathologies of the CS/ICA and preservation of brain hemodynamics for clinicians.

TRP Channels as Sensors of Aldehyde and Oxidative Stress

The transient receptor potential (TRP) cation channel superfamily comprises more than 50 channels that play crucial roles in physiological processes. TRP channels are responsive to several exogenous and endogenous biomolecules, with aldehydes emerging as a TRP channel trigger contributing to a cellular cascade that can lead to disease pathophysiology. The body is not only exposed to exogenous aldehydes via tobacco products or alcoholic beverages, but also to endogenous aldehydes triggered by lipid peroxidation. In response to lipid peroxidation from inflammation or organ injury, polyunsaturated fatty acids undergo lipid peroxidation to aldehydes, such as 4-hydroxynonenal. Reactive aldehydes activate TRP channels via aldehyde-induced protein adducts, leading to the release of pro-inflammatory mediators driving the pathophysiology caused by cellular injury, including inflammatory pain and organ reperfusion injury. Recent studies have outlined how aldehyde dehydrogenase 2 protects against aldehyde toxicity through the clearance of toxic aldehydes, indicating that targeting the endogenous aldehyde metabolism may represent a novel treatment strategy. An addition approach can involve targeting specific TRP channel regions to limit the triggering of a cellular cascade induced by aldehydes. In this review, we provide a comprehensive summary of aldehydes, TRP channels, and their interactions, as well as their role in pathological conditions and the different therapeutical treatment options.

Normalization of wall shear stress as a physiological mechanism for regulating maternal uterine artery expansive remodeling during pregnancy

Outward remodeling of the maternal uterine circulation during pregnancy is essential for normal uteroplacental perfusion and pregnancy outcome. The physiological mechanism by which this process is regulated is unknown; we hypothesized that it involved the normalization of wall shear stress (WSS). Pregnant Sprague-Dawley rats underwent unilateral ligation of the main uterine artery and vein at the cervical end of the uterus on gestational day 10, thus restricting inflow/outflow of blood into that uterine horn to a single point at the ovarian end; the contralateral sham-operated side provided an internal control. This procedure alters uterine hemodynamics by increasing WSS, since the entire uterine horn is supplied by one rather than two vessels. Arterial diameter and blood flow velocity values were measured by intravital ultrasonographic pulse-wave Doppler on gestational day 20 and used to calculate WSS. Although both ovarian artery lumen diameter and blood velocity increased, WSS was similar in both horns. These data support the concept that increased WSS secondary to hemochorial placentation is the primary physiological stimulus for uterine vascular remodeling and that its normalization may be the primary mechanism that regulates the extent of arterial circumferential growth required to maintain placental perfusion. We further hypothesize that shallow spiral artery invasion, such as occurs in preeclampsia, limits the increase in upstream shear stress and results in attenuated remodeling and placental under-perfusion.

Electrophysiological Effects of the Transient Receptor Potential Melastatin 4 Channel Inhibitor (4-Chloro-2-(2-chlorophenoxy)acetamido) Benzoic Acid (CBA) in Canine Left Ventricular Cardiomyocytes

Transient receptor potential melastatin 4 (TRPM4) plays an important role in many tissues, including pacemaker and conductive tissues of the heart, but much less is known about its electrophysiological role in ventricular myocytes. Our earlier results showed the lack of selectivity of 9-phenanthrol, so CBA ((4-chloro-2-(2-chlorophenoxy)acetamido) benzoic acid) was chosen as a new, potentially selective inhibitor. Goal: Our aim was to elucidate the effect and selectivity of CBA in canine left ventricular cardiomyocytes and to study the expression of TRPM4 in the canine heart. Experiments were carried out in enzymatically isolated canine left ventricular cardiomyocytes. Ionic currents were recorded with an action potential (AP) voltage-clamp technique in whole-cell configuration at 37 °C. An amount of 10 mM BAPTA was used in the pipette solution to exclude the potential activation of TRPM4 channels. AP was recorded with conventional sharp microelectrodes. CBA was used in 10 µM concentrations. Expression of TRPM4 protein in the heart was studied by Western blot. TRPM4 protein was expressed in the wall of all four chambers of the canine heart as well as in samples prepared from isolated left ventricular cells. CBA induced an approximately 9% reduction in AP duration measured at 75% and 90% of repolarization and decreased the short-term variability of APD₉₀. Moreover, AP amplitude was increased and the maximal rates of phase 0 and 1 were reduced by the drug. In AP clamp measurements, CBA-sensitive current contained a short, early outward and mainly a long, inward current. Transient outward potassium current (I_to) and late sodium current (I_Na,L) were reduced by approximately 20% and 47%, respectively, in the presence of CBA, while L-type calcium and inward rectifier potassium currents were not affected. These effects of CBA were largely reversible upon washout. Based on our results, the CBA induced reduction of phase-1 slope and the slight increase of AP amplitude could have been due to the inhibition of I_to. The tendency for AP shortening can be explained by the inhibition of inward currents seen in AP-clamp recordings during the plateau phase. This inward current reduced by CBA is possibly I_Na,L, therefore, CBA is not entirely selective for TRPM4 channels. As a consequence, similarly to 9-phenanthrol, it cannot be used to test the contribution of TRPM4 channels to cardiac electrophysiology in ventricular cells, or at least caution must be applied.

Cross-Talk between Mechanosensitive Ion Channels and Calcium Regulatory Proteins in Cardiovascular Health and Disease

Mechanosensitive ion channels are widely expressed in the cardiovascular system. They translate mechanical forces including shear stress and stretch into biological signals. The most prominent biological signal through which the cardiovascular physiological activity is initiated or maintained are intracellular calcium ions (Ca²⁺). Growing evidence show that the Ca²⁺ entry mediated by mechanosensitive ion channels is also precisely regulated by a variety of key proteins which are distributed in the cell membrane or endoplasmic reticulum. Recent studies have revealed that mechanosensitive ion channels can even physically interact with Ca²⁺ regulatory proteins and these interactions have wide implications for physiology and pathophysiology. Therefore, this paper reviews the cross-talk between mechanosensitive ion channels and some key Ca²⁺ regulatory proteins in the maintenance of calcium homeostasis and its relevance to cardiovascular health and disease.

Proline hydroxylase domain-containing enzymes regulate calcium levels in cardiomyocytes by TRPA1 ion channel

The proline hydroxylase domain-containing enzymes (PHDs) acts as cellular oxygen sensors, inducing a series of responses to hypoxia, especially during the regulation of metabolism and energy homeostasis. The increase of Ca²⁺ in cardiomyocytes, induced by the opening of PHD signaling pathway, is the key initiation signal necessary for the PHD-mediated regulation of the energy metabolism pathway, but the underlying molecular mechanism remains incompletely understood. This study used PHD inhibitors (PHIs) and PHD2-specific RNA interference (PHD2shRNA) to inhibit PHD signals in cardiomyocytes to explore whether transient receptor potential ankyrin 1 (TRPA1) is involved in the regulation of calcium ion influx in the PHD activation pathway associated with to AMP-activated protein kinase (AMPK). The Fluo-3AM probe was used to measure changes in free intracellular calcium ion concentrations, and western blot analysis was used to detect the levels of phosphorylated (P)-AMPK, TRPA1, and P-Ca²⁺/calmodulin-dependent protein kinase Ⅱ (CaMKⅡ) levels. The PHI-mediated inhibition of PHD resulted in an increase in free Ca²⁺ fluorescence in cardiomyocytes, which activated AMPK, TRPA1, and CaMKⅡ. The TRPA1 inhibitor HC030031, the CaMKII inhibitor KN93, and a ryanodine inhibitor (Ryanodine) were all able to inhibit the PHI-induced increase in intracellular Ca²⁺ and AMPK activation. Both PHIs and PHD2shRNA were able to effectively activate CaMKII and TRPA1. However, an inositol 1,4,5-triphosphate receptor (IP3R) inhibitor and the protein kinase A (PKA) inhibitor H89 did not significantly inhibit the PHI-induced increase in intracellular Ca²⁺ and AMPK activation. These results indicated that PHD might activate the CaMKⅡ pathway through the TRPA1 ion channel, inducing the release of calcium from the sarcoplasmic reticulum through ryanodine receptor 2 (RyR2), activating AMPK to initiate the protective effects of hypoxia in cardiomyocytes.

A comprehensive analysis of gene expression changes in a high replicate and open-source dataset of differentiating hiPSC-derived cardiomyocytes

We performed a comprehensive analysis of the transcriptional changes occurring during human induced pluripotent stem cell (hiPSC) differentiation to cardiomyocytes. Using single cell RNA-seq, we sequenced > 20,000 single cells from 55 independent samples representing two differentiation protocols and multiple hiPSC lines. Samples included experimental replicates ranging from undifferentiated hiPSCs to mixed populations of cells at D90 post-differentiation. Differentiated cell populations clustered by time point, with differential expression analysis revealing markers of cardiomyocyte differentiation and maturation changing from D12 to D90. We next performed a complementary cluster-independent sparse regression analysis to identify and rank genes that best assigned cells to differentiation time points. The two highest ranked genes between D12 and D24 (MYH7 and MYH6) resulted in an accuracy of 0.84, and the three highest ranked genes between D24 and D90 (A2M, H19, IGF2) resulted in an accuracy of 0.94, revealing that low dimensional gene features can identify differentiation or maturation stages in differentiating cardiomyocytes. Expression levels of select genes were validated using RNA FISH. Finally, we interrogated differences in cardiac gene expression resulting from two differentiation protocols, experimental replicates, and three hiPSC lines in the WTC-11 background to identify sources of variation across these experimental variables.

The relevant targets of anti-oxidative stress: a review

Previous studies have found that oxidative stress is the negative reaction of the imbalance between oxidation and antioxidation caused by free radicals, and it is the fuse of aging and many diseases. Scavenging the accumulation of free radicals in the body and inhibiting the production of free radicals are effective ways to reduce the occurrence of oxidative stress. In recent years, studies have found that oxidative stress has other effects on the body, such as anti-tumour. In this paper, the targets related to anti-oxidative stress were introduced, and they were divided into nuclear transcription factors, enzymes, solute carrier family 7, member 11 (SLC7A11) genes and iron death, ion channels, molecular chaperones, small molecules according to their different functions. In addition, we introduce the research status of agonists/inhibitors related to these targets, so as to provide some reference for the follow-up research and clinical application of anti-oxidative stress drugs.

TRP channels in health and disease at a glance

The transient receptor potential (TRP) channel superfamily consists of a large group of non-selective cation channels that serve as cellular sensors for a wide spectrum of physical and environmental stimuli. The 28 mammalian TRPs, categorized into six subfamilies, including TRPC (canonical), TRPV (vanilloid), TRPM (melastatin), TRPA (ankyrin), TRPML (mucolipin) and TRPP (polycystin), are widely expressed in different cells and tissues. TRPs exhibit a variety of unique features that not only distinguish them from other superfamilies of ion channels, but also confer diverse physiological functions. Located at the plasma membrane or in the membranes of intracellular organelles, TRPs are the cellular safeguards that sense various cell stresses and environmental stimuli and translate this information into responses at the organismal level. Loss- or gain-of-function mutations of TRPs cause inherited diseases and pathologies in different physiological systems, whereas up- or down-regulation of TRPs is associated with acquired human disorders. In this Cell Science at a Glance article and the accompanying poster, we briefly summarize the history of the discovery of TRPs, their unique features, recent advances in the understanding of TRP activation mechanisms, the structural basis of TRP Ca2+ selectivity and ligand binding, as well as potential roles in mammalian physiology and pathology.

Calcium and Heart Failure: How Did We Get Here and Where Are We Going?

The occurrence and prevalence of heart failure remain high in the United States as well as globally. One person dies every 30 s from heart disease. Recognizing the importance of heart failure, clinicians and scientists have sought better therapeutic strategies and even cures for end-stage heart failure. This exploration has resulted in many failed clinical trials testing novel classes of pharmaceutical drugs and even gene therapy. As a result, along the way, there have been paradigm shifts toward and away from differing therapeutic approaches. The continued prevalence of death from heart failure, however, clearly demonstrates that the heart is not simply a pump and instead forces us to consider the complexity of simplicity in the pathophysiology of heart failure and reinforces the need to discover new therapeutic approaches.

The P2X7 Receptor Is Involved in Diabetic Neuropathic Pain Hypersensitivity Mediated by TRPV1 in the Rat Dorsal Root Ganglion

The purinergic 2X₇ (P2X₇) receptor expressed in satellite glial cells (SGCs) is involved in the inflammatory response, and transient receptor potential vanilloid 1 (TRPV1) participates in the process of neurogenic inflammation, such as that in diabetic neuropathic pain (DNP) and peripheral neuralgia. The main purpose of this study was to explore the role of the P2X₇ receptor in DNP hypersensitivity mediated by TRPV1 in the rat and its possible mechanism. A rat model of type 2 diabetes mellitus-related neuropathic pain (NPP) named the DNP rat model was established in this study. The mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) of DNP rats were increased after intrathecal injection of the P2X₇ receptor antagonist A438079, and the mRNA and protein levels of TRPV1 in the dorsal root ganglion (DRG) were decreased in DNP rats treated with A438079 compared to untreated DNP rats; in addition, A438079 also decreased the phosphorylation of p38 and extracellular signal-regulated kinase 1/2 (ERK1/2) in the DNP group. Based on these results, the P2X₇ receptor might be involved in DNP mediated by TRPV1.