TRPC5-eNOS Axis Negatively Regulates ATP-Induced Cardiomyocyte Hypertrophy

At the heart of inflammation: Unravelling cardiac resident macrophage biology

Cardiovascular disease remains one of the leading causes of death globally. Recent advancements in sequencing technologies have led to the identification of a unique population of macrophages within the heart, termed cardiac resident macrophages (CRMs), which exhibit self-renewal capabilities and play crucial roles in regulating cardiac homeostasis, inflammation, as well as injury and repair processes. This literature review aims to elucidate the origin and phenotypic characteristics of CRMs, comprehensively outline their contributions to cardiac homeostasis and further summarize their functional roles and molecular mechanisms implicated in the onset and progression of cardiovascular diseases. These insights are poised to pave the way for novel therapeutic strategies centred on targeted interventions based on the distinctive properties of resident macrophages.

Supersulfide catabolism participates in maladaptive remodeling of cardiac cells

The atrophic myocardium resulting from mechanical unloading and nutritional deprivation is considered crucial as maladaptive remodeling directly associated with heart failure, as well as interstitial fibrosis. Conversely, myocardial hypertrophy resulting from hemodynamic loading is perceived as compensatory stress adaptation. We previously reported the abundant presence of highly redox-active polysulfide molecules, termed supersulfide, with two or more sulfur atoms catenated in normal hearts, and the supersulfide catabolism in pathologic hearts after myocardial infarction correlated with worsened prognosis of heart failure. However, the impact of supersulfide on myocardial remodeling remains unclear. Here, we investigated the involvement of supersulfide metabolism in cardiomyocyte remodeling, using a model of adenosine 5'-triphosphate (ATP) receptor-stimulated atrophy and endothelin-1 receptor-stimulated hypertrophy in neonatal rat cardiomyocytes. Results revealed contrasting changes in intracellular supersulfide and its catabolite, hydrogen sulfide (H2S), between cardiomyocyte atrophy and hypertrophy. Stimulation of cardiomyocytes with ATP decreased supersulfide activity, while H2S accumulation itself did not affect cardiomyocyte atrophy. This supersulfide catabolism was also involved in myofibroblast formation of neonatal rat cardiac fibroblasts. Thus, unraveling supersulfide metabolism during myocardial remodeling may lead to the development of novel therapeutic strategies to improve heart failure.

Transient Receptor Potential Canonical 5 (TRPC5): Regulation of Heart Rate and Protection against Pathological Cardiac Hypertrophy

TRPC5 is a non-selective cation channel that is expressed in cardiomyocytes, but there is a lack of knowledge of its (patho)physiological role in vivo. Here, we examine the role of TRPC5 on cardiac function under basal conditions and during cardiac hypertrophy. Cardiovascular parameters were assessed in wild-type (WT) and global TRPC5 knockout (KO) mice. Despite no difference in blood pressure or activity, heart rate was significantly reduced in TRPC5 KO mice. Echocardiography imaging revealed an increase in stroke volume, but cardiac contractility was unaffected. The reduced heart rate persisted in isolated TRPC5 KO hearts, suggesting changes in basal cardiac pacing. Heart rate was further investigated by evaluating the reflex change following drug-induced pressure changes. The reflex bradycardic response following phenylephrine was greater in TRPC5 KO mice but the tachycardic response to SNP was unchanged, indicating an enhancement in the parasympathetic control of the heart rate. Moreover, the reduction in heart rate to carbachol was greater in isolated TRPC5 KO hearts. To evaluate the role of TRPC5 in cardiac pathology, mice were subjected to abdominal aortic banding (AAB). An exaggerated cardiac hypertrophy response to AAB was observed in TRPC5 KO mice, with an increased expression of hypertrophy markers, fibrosis, reactive oxygen species, and angiogenesis. This study provides novel evidence for a direct effect of TRPC5 on cardiac function. We propose that (1) TRPC5 is required for maintaining heart rate by regulating basal cardiac pacing and in response to pressure lowering, and (2) TRPC5 protects against pathological cardiac hypertrophy.

The Pleiotropic Role of Extracellular ATP in Myocardial Remodelling

Myocardial remodelling is a molecular, cellular, and interstitial adaptation of the heart in response to altered environmental demands. The heart undergoes reversible physiological remodelling in response to changes in mechanical loading or irreversible pathological remodelling induced by neurohumoral factors and chronic stress, leading to heart failure. Adenosine triphosphate (ATP) is one of the potent mediators in cardiovascular signalling that act on the ligand-gated (P2X) and G-protein-coupled (P2Y) purinoceptors via the autocrine or paracrine manners. These activations mediate numerous intracellular communications by modulating the production of other messengers, including calcium, growth factors, cytokines, and nitric oxide. ATP is known to play a pleiotropic role in cardiovascular pathophysiology, making it a reliable biomarker for cardiac protection. This review outlines the sources of ATP released under physiological and pathological stress and its cell-specific mechanism of action. We further highlight a series of cardiovascular cell-to-cell communications of extracellular ATP signalling cascades in cardiac remodelling, which can be seen in hypertension, ischemia/reperfusion injury, fibrosis, hypertrophy, and atrophy. Finally, we summarize current pharmacological intervention using the ATP network as a target for cardiac protection. A better understanding of ATP communication in myocardial remodelling could be worthwhile for future drug development and repurposing and the management of cardiovascular diseases.

Sex differences and related estrogenic effects in heart failure with preserved ejection fraction

Heart failure with preserved ejection fraction (HFpEF) is an essential subtype of heart failure accounting for 40% of the total. However, the related pathological mechanism and drug therapy research have been stagnant for a long time. The direct cause of this dilemma is the heterogeneity of HFpEF. And some researchers believe that there is no common pathway to reach the origin of HFpEF; others argue that there is an unidentified unified pathophysiological process hidden beneath the ice surface. Aside from the debate, a series of clinical studies have shown that hypertension and obesity play a fundamental role in the pathogenesis of HFpEF. These results imply that there may be two parallel pathological processes interweaved in one disease, manifested as multiple coexistent pathological phenomena, like a shadow. Meanwhile, the prevalence of HFpEF in women is higher than in men in any given age group, especially prominent in elderly patients. These pathological processes and epidemiological data reflect gender differences, reminding us to shift our attention to estrogen. This article will review the parallel pathogenesis of HFpEF, and also introduce sex differences and the potential effect of estrogen in this condition below.

Therapeutic potential of traditional Chinese medicine in atherosclerosis: A review

Atherosclerosis is the onset of endothelial cell damage and is characterized by abnormal accumulation of fibrinogen and lipid in large and middle arteries. Recent researches indicate that traditional Chinese medicine including Notoginseng Radix et Rhizoma, Astragali Radix, Salviae Miltiorrhizae Radix et Rhizoma, Ginseng Radix et Rhizoma, Fructus Crataegi, Glycyrrhizae Radix et Rhizoma, Polygoni Multiflori Radix, Fructus Lycii, and Coptidis Rhizoma have therapeutic effects on atherosclerosis. Furthermore, the pharmacological roles of these kinds of traditional Chinese medicine in atherosclerosis refer to endothelial function influences, cell proliferation and migration, platelet aggregation, thrombus formation, oxidative stress, inflammation, angiogenesis, apoptosis, autophagy, lipid metabolism, and the gut microbiome. Traditional Chinese medicine may serve as potential and effective anti-atherosclerosis drugs. However, a critical study has shown that Notoginseng Radix et Rhizoma may also have toxic effects including pustules, fever, and elevate circulating neutrophil count. Further high-quality studies are still required to determine the clinical safety and efficacy of traditional Chinese medicine and its active ingredients.

An Overview of the TRP-Oxidative Stress Axis in Metabolic Syndrome: Insights for Novel Therapeutic Approaches

Metabolic syndrome (MS) is a complex pathology characterized by visceral adiposity, insulin resistance, arterial hypertension, and dyslipidaemia. It has become a global epidemic associated with increased consumption of high-calorie, low-fibre food and sedentary habits. Some of its underlying mechanisms have been identified, with hypoadiponectinemia, inflammation and oxidative stress as important factors for MS establishment and progression. Alterations in adipokine levels may favour glucotoxicity and lipotoxicity which, in turn, contribute to inflammation and cellular stress responses within the adipose, pancreatic and liver tissues, in addition to hepatic steatosis. The multiple mechanisms of MS make its clinical management difficult, involving both non-pharmacological and pharmacological interventions. Transient receptor potential (TRP) channels are non-selective calcium channels involved in a plethora of physiological events, including energy balance, inflammation and oxidative stress. Evidence from animal models of disease has contributed to identify their specific contributions to MS and may help to tailor clinical trials for the disease. In this context, the oxidative stress sensors TRPV1, TRPA1 and TRPC5, play major roles in regulating inflammatory responses, thermogenesis and energy expenditure. Here, the interplay between these TRP channels and oxidative stress in MS is discussed in the light of novel therapies to treat this syndrome.

Role of store-operated Ca2+ entry in cardiovascular disease

Store-operated channels (SOCs) are highly selective Ca2+ channels that mediate Ca2+ influx in non-excitable and excitable (i.e., skeletal and cardiac muscle) cells. These channels are triggered by Ca2+ depletion of the endoplasmic reticulum and sarcoplasmic reticulum, independently of inositol 1,4,5-trisphosphate (InsP3), which is involved in cell growth, differentiation, and gene transcription. When the Ca2+ store is depleted, stromal interaction molecule1 (STIM1) as Ca2+ sensor redistributes into discrete puncta near the plasma membrane and activates the protein Ca2+ release activated Ca2+ channel protein 1 (Orai1). Accumulating evidence suggests that SOC is associated with several physiological roles in endothelial dysfunction and vascular smooth muscle proliferation that contribute to the progression of cardiovascular disease. This review mainly elaborates on the contribution of SOC in the vasculature (endothelial cells and vascular smooth muscle cells). We will further retrospect the literature implicating a critical role for these proteins in cardiovascular disease.

Rutaecarpine Ameliorates Pressure Overload Cardiac Hypertrophy by Suppression of Calcineurin and Angiotensin II

Cardiac hypertrophy is a major pathological process to result in heart failure and sudden death. Rutaecarpine, a pentacyclic indolopyridoquinazolinone alkaloid extracted from Evodia rutaecarpa with multiple pharmacological activities, yet the underlying protective effects and the mechanisms on cardiac hypertrophy remain unclear. This study aimed to evaluate the potential effects of rutaecarpine on pressure overload cardiac hypertrophy. Cardiac hypertrophy in rat was developed by abdominal aortic constriction (AAC) for 4 weeks, which was improved by rutaecarpine supplementation (20 or 40 mg/kg/day, i.g.) for another 4 weeks. The level of angiotensin II was increased; the mRNA expression and the activity of calcineurin in the left ventricular tissue were augmented following cardiac hypertrophy. Rutaecarpine administration decreased angiotensin II content and reduced calcineurin expression and activity. Noteworthily, in angiotensin II-induced cardiomyocytes, rutaecarpine ameliorated the hypertrophic effects in a dose-dependent manner and downregulated the increased mRNA expression and activity of calcineurin. In conclusion, rutaecarpine can improve cardiac hypertrophy in pressure overload rats, which may be related to the inhibition of angiotensin II-calcineurin signal pathway.

Estrogen-Mediated Gaseous Signaling Molecules in Cardiovascular Disease

Gender difference is well recognized as a key risk factor for cardiovascular disease (CVD). Estrogen, the primary female sex hormone, improves cardiovascular functions through receptor (ERα, ERβ, or G protein-coupled estrogen receptor)-initiated genomic or non-genomic mechanisms. Gaseous signaling molecules, including nitric oxide (NO), hydrogen sulfide (H₂S), and carbon monoxide (CO), are important regulators of cardiovascular function. Recent studies have demonstrated that estrogen regulates the production of these signaling molecules in cardiovascular cells to exert its cardiovascular protective effects. We discuss current understanding of gaseous signaling molecules in cardiovascular disease (CVD), the underlying mechanisms through which estrogen exerts cardiovascular protective effects by regulating these molecules, and how these findings can be translated to improve the health of postmenopausal women.

Targeting Ca2 + Handling Proteins for the Treatment of Heart Failure and Arrhythmias

Diseases of the heart, such as heart failure and cardiac arrhythmias, are a growing socio-economic burden. Calcium (Ca²⁺) dysregulation is key hallmark of the failing myocardium and has long been touted as a potential therapeutic target in the treatment of a variety of cardiovascular diseases (CVD). In the heart, Ca²⁺ is essential for maintaining normal cardiac function through the generation of the cardiac action potential and its involvement in excitation contraction coupling. As such, the proteins which regulate Ca²⁺ cycling and signaling play a vital role in maintaining Ca²⁺ homeostasis. Changes to the expression levels and function of Ca²⁺-channels, pumps and associated intracellular handling proteins contribute to altered Ca²⁺ homeostasis in CVD. The remodeling of Ca²⁺-handling proteins therefore results in impaired Ca²⁺ cycling, Ca²⁺ leak from the sarcoplasmic reticulum and reduced Ca²⁺ clearance, all of which contributes to increased intracellular Ca²⁺. Currently, approved treatments for targeting Ca²⁺ handling dysfunction in CVD are focused on Ca²⁺ channel blockers. However, whilst Ca²⁺ channel blockers have been successful in the treatment of some arrhythmic disorders, they are not universally prescribed to heart failure patients owing to their ability to depress cardiac function. Despite the progress in CVD treatments, there remains a clear need for novel therapeutic approaches which are able to reverse pathophysiology associated with heart failure and arrhythmias. Given that heart failure and cardiac arrhythmias are closely associated with altered Ca²⁺ homeostasis, this review will address the molecular changes to proteins associated with both Ca²⁺-handling and -signaling; their potential as novel therapeutic targets will be discussed in the context of pre-clinical and, where available, clinical data.

Transient Receptor Potential Canonical (TRPC) Channels: Then and Now

Twenty-five years ago, the first mammalian Transient Receptor Potential Canonical (TRPC) channel was cloned, opening the vast horizon of the TRPC field. Today, we know that there are seven TRPC channels (TRPC1-7). TRPCs exhibit the highest protein sequence similarity to the Drosophila melanogaster TRP channels. Similar to Drosophila TRPs, TRPCs are localized to the plasma membrane and are activated in a G-protein-coupled receptor-phospholipase C-dependent manner. TRPCs may also be stimulated in a store-operated manner, via receptor tyrosine kinases, or by lysophospholipids, hypoosmotic solutions, and mechanical stimuli. Activated TRPCs allow the influx of Ca2+ and monovalent alkali cations into the cytosol of cells, leading to cell depolarization and rising intracellular Ca2+ concentration. TRPCs are involved in the continually growing number of cell functions. Furthermore, mutations in the TRPC6 gene are associated with hereditary diseases, such as focal segmental glomerulosclerosis. The most important recent breakthrough in TRPC research was the solving of cryo-EM structures of TRPC3, TRPC4, TRPC5, and TRPC6. These structural data shed light on the molecular mechanisms underlying TRPCs' functional properties and propelled the development of new modulators of the channels. This review provides a historical overview of the major advances in the TRPC field focusing on the role of gene knockouts and pharmacological tools.

Modulation of P2Y6R expression exacerbates pressure overload-induced cardiac remodeling in mice

Cardiac tissue remodeling caused by hemodynamic overload is a major clinical outcome of heart failure. Uridine-responsive purinergic P2Y₆ receptor (P2Y₆R) contributes to the progression of cardiovascular remodeling in rodents, but it is not known whether inhibition of P2Y₆R prevents or promotes heart failure. We demonstrate that inhibition of P2Y₆R promotes pressure overload-induced sudden death and heart failure in mice. In neonatal cardiomyocytes, knockdown of P2Y₆R significantly attenuated hypertrophic growth and cell death caused by hypotonic stimulation, indicating the involvement of P2Y₆R in mechanical stress-induced myocardial dysfunction. Unexpectedly, compared with wild-type mice, deletion of P2Y₆R promoted pressure overload-induced sudden death, as well as cardiac remodeling and dysfunction. Mice with cardiomyocyte-specific overexpression of P2Y₆R also exhibited cardiac dysfunction and severe fibrosis. In contrast, P2Y₆R deletion had little impact on oxidative stress-mediated cardiac dysfunction induced by doxorubicin treatment. These findings provide overwhelming evidence that systemic inhibition of P2Y₆R exacerbates pressure overload-induced heart failure in mice, although P2Y₆R in cardiomyocytes contributes to the progression of cardiac fibrosis.

Evidence of a Role for the TRPC Subfamily in Mediating Oxidative Stress in Parkinson's Disease

Parkinson's disease (PD) represents one of the most common multifactorial neurodegenerative disorders affecting the elderly population. It is associated with the aggregation of α-synuclein protein and the loss of dopaminergic neurons in the substantia nigra pars compacta of the brain. The disease is mainly represented by motor symptoms, such as resting tremors, postural instability, rigidity, and bradykinesia, that develop slowly over time. Parkinson's disease can also manifest as disturbances in non-motor functions. Although the pathology of PD has not yet been fully understood, it has been suggested that the disruption of the cellular redox status may contribute to cellular oxidative stress and, thus, to cell death. The generation of reactive oxygen species and reactive nitrogen intermediates, as well as the dysfunction of dopamine metabolism, play important roles in the degeneration of dopaminergic neurons. In this context, the transient receptor potential channel canonical (TRPC) sub-family plays an important role in neuronal degeneration. Additionally, PD gene products, including DJ-1, SNCA, UCH-L1, PINK-1, and Parkin, also interfere with mitochondrial function leading to reactive oxygen species production and dopaminergic neuronal vulnerability to oxidative stress. Herein, we discuss the interplay between these various biochemical and molecular events that ultimately lead to dopaminergic signaling disruption, highlighting the recently identified roles of TRPC in PD.

TRPC Channels in Cardiac Plasticity

The heart flexibly changes its structure in response to changing environments and oxygen/nutrition demands of the body. Increased and decreased mechanical loading induces hypertrophy and atrophy of cardiomyocytes, respectively. In physiological conditions, these structural changes of the heart are reversible. However, chronic stresses such as hypertension or cancer cachexia cause irreversible remodeling of the heart, leading to heart failure. Accumulating evidence indicates that calcium dyshomeostasis and aberrant reactive oxygen species production cause pathological heart remodeling. Canonical transient receptor potential (TRPC) is a nonselective cation channel subfamily whose multimodal activation or modulation of channel activity play important roles in a plethora of cellular physiology. Roles of TRPC channels in cardiac physiology have been reported in pathological cardiac remodeling. In this review, we summarize recent findings regarding the importance of TRPC channels in flexible cardiac remodeling (i.e., cardiac plasticity) in response to environmental stresses and discuss questions that should be addressed in the near future.

TRPC Channels: Dysregulation and Ca2+ Mishandling in Ischemic Heart Disease

Transient receptor potential canonical (TRPC) channels are ubiquitously expressed in excitable and non-excitable cardiac cells where they sense and respond to a wide variety of physical and chemical stimuli. As other TRP channels, TRPC channels may form homo or heterotetrameric ion channels, and they can associate with other membrane receptors and ion channels to regulate intracellular calcium concentration. Dysfunctions of TRPC channels are involved in many types of cardiovascular diseases. Significant increase in the expression of different TRPC isoforms was observed in different animal models of heart infarcts and in vitro experimental models of ischemia and reperfusion. TRPC channel-mediated increase of the intracellular Ca²⁺ concentration seems to be required for the activation of the signaling pathway that plays minor roles in the healthy heart, but they are more relevant for cardiac responses to ischemia, such as the activation of different factors of transcription and cardiac hypertrophy, fibrosis, and angiogenesis. In this review, we highlight the current knowledge regarding TRPC implication in different cellular processes related to ischemia and reperfusion and to heart infarction.

Effect of SKF‑96365 on cardiomyocyte hypertrophy induced by angiotensin II

Angiotensin II (Ang II) is an important bioactive peptide in the renin-angiotensin system, and it can contribute to cell proliferation and cardiac hypertrophy. Dysfunctions in transient receptor potential canonical (TRPC) channels are involved in many types of cardiovascular diseases. The aim of the present study was to investigate the role of the TRPC channel inhibitor SKF-96365 in cardiomyocyte hypertrophy induced by Ang II and the potential mechanisms of SKF-96365. H9c2 cells were treated with different concentrations of Ang II. The expression levels of cardiomyocyte hypertrophy markers and TRPC channel-related proteins were also determined. The morphology and surface area of the H9c2 cells, the expression of hypertrophic markers and TRPC channel-related proteins and the [³H] leucine incorporation rate were detected in the Ang II-treated H9c2 cells following treatment with the TRPC channel inhibitor SKF-96365. The intracellular Ca²⁺ concentration was tested by flow cytometry. The present results suggested that the surface area of H9c2 cells treated with Ang II was significantly increased compared with untreated H9c2 cells. The fluorescence intensity of α-actinin, the expression of hypertrophic markers and TRPC-related proteins, the [³H] leucine incorporation rate and the intracellular Ca²⁺ concentration were all markedly increased in the Ang II-treated H9c2 cells but decreased following SKF-96365 treatment. The present results suggested that Ang II induced cardiomyocyte hypertrophy in H9c2 cells and that the TRPC pathway may be involved in this process. Therefore, SKF-96365 can inhibit cardiomyocyte hypertrophy induced by Ang II by suppressing the TRPC pathway. The present results indicated that TRPC may be a therapeutic target for the development of novel drugs to treat cardiac hypertrophy.

TRPC3-Nox2 axis mediates nutritional deficiency-induced cardiomyocyte atrophy

Myocardial atrophy, characterized by the decreases in size and contractility of cardiomyocytes, is caused by severe malnutrition and/or mechanical unloading. Extracellular adenosine 5′-triphosphate (ATP), known as a danger signal, is recognized to negatively regulate cell volume. However, it is obscure whether extracellular ATP contributes to cardiomyocyte atrophy. Here, we report that ATP induces atrophy of neonatal rat cardiomyocytes (NRCMs) without cell death through P2Y₂ receptors. ATP led to overproduction of reactive oxygen species (ROS) through increased amount of NADPH oxidase (Nox) 2 proteins, due to increased physical interaction between Nox2 and canonical transient receptor potential 3 (TRPC3). This ATP-mediated formation of TRPC3-Nox2 complex was also pathophysiologically involved in nutritional deficiency-induced NRCM atrophy. Strikingly, knockdown of either TRPC3 or Nox2 suppressed nutritional deficiency-induced ATP release, as well as ROS production and NRCM atrophy. Taken together, we propose that TRPC3-Nox2 axis, activated by extracellular ATP, is the key component that mediates nutritional deficiency-induced cardiomyocyte atrophy.

Neuronal NO synthase mediates plenylephrine induced cardiomyocyte hypertrophy through facilitation of NFAT-dependent transcriptional activity

Neuronal nitric oxide synthase (NOS1) has been consistently shown to be the predominant isoform of NOS and/or NOS-derived NO that may be involved in the myocardial remodeling including cardiac hypertrophy. However, the direct functional contribution of NOS1 in this process remains to be elucidated. Therefore, in the present study, we attempted to use silent RNA and adenovirus mediated silencing or overexpression to investigate the role of NOS1 and the associated molecular signaling mechanisms during OKphenylephrine (PE)-induced cardiac hypertrophy growth in neonatal rat ventricular cardiomyocytes (NRVMs). We found that the expression of NOS1 was enhanced in PE-induced hypertrophic cardiomyocytes. Moreover, LVNIO treatment, a selective NOS1 inhibitor, significantly decreased PE-induced NRVMs hypertrophy and [3H]-leucine incorporation. We demonstrated that NOS1 gene silencing attenuated both the increased size and the transcriptional activity of the hypertrophic marker atrial natriuretic factor (ANF) induced by PE stimulation. Further investigation suggested that deficiency of NOS1-induced diminished NRVMS hypertrophy resulted in decreased calcineurin protein expression and activity (assessed by measuring the transcriptional activity of NFAT) and, an increased activity of the anti-hypertrophic pathway, GSK-3β (estimated by its augmented phosphorylated level). In contrast, exposing the NOS1 overexpressed NRVMs to PE-treatment further increased the hypertrophic growth, ANF transcriptional activity and calcineurin activity. Together, the results of the present study suggest that NOS1 is directly involved in controlling the development of cardiomyocyte hypertrophy.

TRPC-mediated Ca2+ signaling and control of cellular functions

Canonical members of the TRP superfamily of ion channels have long been recognized as key elements of Ca²⁺ handling in a plethora of cell types. The emerging role of TRPC channels in human physiopathology has generated considerable interest in their pharmacological targeting, which requires detailed understanding of their molecular function. Although consent has been reached that receptor-phospholipase C (PLC) pathways and generation of lipid mediators constitute the prominent upstream signaling process that governs channel activity, multimodal sensing features of TRPC complexes have been demonstrated repeatedly. Downstream signaling by TRPC channels is similarly complex and involves the generation of local and global cellular Ca²⁺ rises, which are well-defined in space and time to govern specific cellular functions. These TRPC-mediated Ca²⁺ signals rely in part on Ca²⁺ permeation through the channels, but are essentially complemented by secondary mechanisms such as Ca²⁺ mobilization from storage sites and Na⁺/Ca²⁺ exchange, which involve coordinated interaction with signaling partners. Consequently, the control of cell functions by TRPC molecules is critically determined by dynamic assembly and subcellular targeting of the TRPC complexes. The very recent availability of high-resolution structure information on TRPC channel complexes has paved the way towards a comprehensive understanding of signal transduction by TRPC channels. Here, we summarize current concepts of cation permeation in TRPC complexes, TRPC-mediated shaping of cellular Ca²⁺ signals and the associated control of specific cell functions.

TRP Channels: Current Perspectives in the Adverse Cardiac Remodeling

Calcium is an important second messenger required not only for the excitation-contraction coupling of the heart but also critical for the activation of cell signaling pathways involved in the adverse cardiac remodeling and consequently for the heart failure. Sustained neurohumoral activation, pressure-overload, or myocardial injury can cause pathologic hypertrophic growth of the heart followed by interstitial fibrosis. The consequent heart’s structural and molecular adaptation might elevate the risk of developing heart failure and malignant arrhythmia. Compelling evidences have demonstrated that Ca²⁺ entry through TRP channels might play pivotal roles in cardiac function and pathology. TRP proteins are classified into six subfamilies: TRPC (canonical), TRPV (vanilloid), TRPM (melastatin), TRPA (ankyrin), TRPML (mucolipin), and TRPP (polycystin), which are activated by numerous physical and/or chemical stimuli. TRP channels participate to the handling of the intracellular Ca²⁺ concentration in cardiac myocytes and are mediators of different cardiovascular alterations. This review provides an overview of the current knowledge of TRP proteins implication in the pathologic process of some frequent cardiac diseases associated with the adverse cardiac remodeling such as cardiac hypertrophy, fibrosis, and conduction alteration.

TRPC channels in exercise-mimetic therapy

Physical exercise yields beneficial effects on all types of muscle cells, which are essential for the maintenance of cardiovascular homeostasis and good blood circulation. Daily moderate exercise increases systemic antioxidative capacity, which can lead to the prevention of the onset and progression of oxidative stress-related diseases. Therefore, exercise is now widely accepted as one of the best therapeutic strategies for the treatment of ischemic (hypoxic) diseases. Canonical transient receptor potential (TRPC) proteins are non-selective cation channels activated by mechanical stress and/or stimulation of phospholipase C-coupled surface receptors. TRPC channels, especially diacylglycerol-activated TRPC channels (TRPC3 and TRPC6; TRPC3/6), play a key role in the development of cardiovascular remodeling. We have recently found that physical interaction between TRPC3 and NADPH oxidase (Nox) 2 under hypoxic stress promotes Nox2-dependent reactive oxygen species (ROS) production and mediates rodent cardiac plasticity, and inhibition of the TRPC3-Nox2 protein complex results in enhancement of myocardial compliance and flexibility similar to that observed in exercise-treated hearts. In this review, we describe current understanding of the roles of TRPC channels in striated muscle (patho)physiology and propose that targeting TRPC-based protein complexes could be a new strategy to imitate exercise therapy.