Increased transient receptor potential canonical type 3 channels in vasculature from hypertensive rats

Role of transient receptor potential channels in the regulation of vascular tone

Vascular tone is a major element in the control of hemodynamics. Transient receptor potential (TRP) channels conducting monovalent and/or divalent cations (e.g. Na+ and Ca2+) are expressed in the vasculature. Accumulating evidence suggests that TRP channels participate in regulating vascular tone by regulating intracellular Ca2+ signaling in both vascular smooth muscle cells (VSMCs) and endothelial cells (ECs). Aberrant expression/function of TRP channels in the vasculature is associated with vascular dysfunction in systemic/pulmonary hypertension and metabolic syndromes. This review intends to summarize our current knowledge of TRP-mediated regulation of vascular tone in both physiological and pathophysiological conditions and to discuss potential therapeutic approaches to tackle abnormal vascular tone due to TRP dysfunction.

Pathophysiological significance and modulation of the transient receptor potential canonical 3 ion channel

Transient receptor potential canonical 3 (TRPC3) protein belongs to the TRP family of nonselective cation channels. Its activation occurs by signaling through a G protein-coupled receptor (GPCR) and a phospholipase C-dependent (PLC) pathway. Perturbations in the expression of TRPC3 are associated with a plethora of pathophysiological conditions responsible for disorders of the cardiovascular, immune, and central nervous systems. The recently solved cryo-EM structure of TRPC3 provides detailed inputs about the underlying mechanistic aspects of the channel, which in turn enables more efficient ways of designing small-molecule modulators. Pharmacologically targeting TRPC3 in animal models has demonstrated great efficacy in treating diseases including cancers, neurological disorders, and cardiovascular diseases. Despite extensive scientific evidence supporting some strong correlations between the expression and activity of TRPC3 and various pathophysiological conditions, therapeutic strategies based on its pharmacological modulations have not led to clinical trials. The development of small-molecule TRPC3 modulators with high safety, sufficient brain penetration, and acceptable drug-like profiles remains in progress. Determining the pathological mechanisms for TRPC3 involvement in human diseases and understanding the requirements for a drug-like TRPC3 modulator will be valuable in advancing small-molecule therapeutics to future clinical trials. In this review, we provide an overview of the origin and activation mechanism of TRPC3 channels, diseases associated with irregularities in their expression, and new development in small-molecule modulators as potential therapeutic interventions for treating TRPC3 channelopathies.

Milestone Papers on Signal Transduction Mechanisms of Hypertension and Its Complications

To celebrate 100 years of American Heart Association-supported cardiovascular disease research, this review article highlights milestone papers that have significantly contributed to the current understanding of the signaling mechanisms driving hypertension and associated cardiovascular disorders. This article also includes a few of the future research directions arising from these critical findings. To accomplish this important mission, 4 principal investigators gathered their efforts to cover distinct yet intricately related areas of signaling mechanisms pertaining to the pathogenesis of hypertension. The renin-angiotensin system, canonical and novel contractile and vasodilatory pathways in the resistance vasculature, vascular smooth muscle regulation by membrane channels, and noncanonical regulation of blood pressure and vascular function will be described and discussed as major subjects.

Endothelial IK and SK channel activation decreases pulmonary arterial pressure and vascular remodeling in pulmonary hypertension

Endothelial cells (ECs) from small pulmonary arteries (PAs) release nitric oxide (NO) and prostacyclin, which lower pulmonary arterial pressure (PAP). In pulmonary hypertension (PH), the levels of endothelium-derived NO and prostacyclin are reduced, contributing to elevated PAP. Small-and intermediate-conductance Ca²⁺-activated K⁺ channels (IK and SK)-additional crucial endothelial mediators of vasodilation-are also present in small PAs, but their function has not been investigated in PH. We hypothesized that endothelial IK and SK channels can be targeted to lower PAP in PH. Whole-cell patch-clamp experiments showed functional IK and SK channels in ECs, but not smooth muscle cells, from small PAs. Using a SU5416 plus chronic hypoxia (Su + CH) mouse model of PH, we found that currents through EC IK and SK channels were unchanged compared with those from normal mice. Moreover, IK/SK channel-mediated dilation of small PAs was preserved in Su + CH mice. Consistent with previous reports, endothelial NO levels and NO-mediated dilation were reduced in small PAs from Su + CH mice. Notably, acute treatment with IK/SK channel activators decreased PAP in Su + CH mice but not in normal mice. Further, chronic activation of IK/SK channels decreased PA remodeling and right ventricular hypertrophy, which are pathological hallmarks of PH, in Su + CH mice. Collectively, our data provide the first evidence that, unlike endothelial NO release, IK/SK channel activity is not altered in PH. Our results also demonstrate proof of principle that IK/SK channel activation can be used as a strategy for lowering PAP in PH.

Vascular smooth muscle ion channels in essential hypertension

Hypertension is a highly prevalent chronic disease and the major risk factor for cardiovascular diseases, the leading cause of death worldwide. Hypertension is characterized by an increased vascular tone determined by the contractile state of vascular smooth muscle cells that depends on intracellular calcium levels. The interplay of ion channels determine VSMCs membrane potential and thus intracellular calcium that controls the degree of contraction, vascular tone and blood pressure. Changes in ion channels expression and function have been linked to hypertension, but the mechanisms and molecular entities involved are not completely clear. Furthermore, the literature shows discrepancies regarding the contribution of different ion channels to hypertension probably due to differences both in the vascular preparation and in the model of hypertension employed. Animal models are essential to study this multifactorial disease but it is also critical to know their characteristics to interpret properly the results obtained. In this review we summarize previous studies, using the hypertensive mouse (BPH) and its normotensive control (BPN), focused on the identified changes in the expression and function of different families of ion channels. We will focus on L-type voltage-dependent Ca2+ channels (Cav1.2), canonical transient receptor potential channels and four different classes of K+ channels: voltage-activated (Kv), large conductance Ca2+-activated (BK), inward rectifiers (Kir) and ATP-sensitive (KATP) K+ channels. We will describe the role of these channels in hypertension and we will discuss the importance of integrating individual changes in a global context to understand the complex interplay of ion channels in hypertension.

Sodium-Glucose Cotransporter 2 Inhibitor Canagliflozin Antagonizes Salt-Sensitive Hypertension Through Modifying Transient Receptor Potential Channels 3 Mediated Vascular Calcium Handling

Background Salt-sensitive hypertension is highly prevalent and associated with cardiorenal damage. Large clinical trials have demonstrated that SGLT2 (sodium-glucose cotransporter 2) inhibitors exert hypotensive effect and cardiorenal protective benefits in patients with hypertension with and without diabetes. However, the underlying mechanism remains elusive. Methods and Results Dahl salt-sensitive rats and salt-insensitive controls were fed with 8% high-salt diet and some of them were treated with canagliflozin. The blood pressure, urinary sodium excretion, and vascular function were detected. Transient receptor potential channel 3 (TRPC3) knockout mice were used to explain the mechanism. Canagliflozin treatment significantly reduced high-salt-induced hypertension and this effect was not totally dependent on urinary sodium excretion in salt-sensitive hypertensive rats. Assay of vascular function and proteomics showed that canagliflozin significantly inhibited vascular cytoplasmic calcium increase and vasoconstriction in response to high-salt diet. High salt intake increased vascular expression of TRPC3 in salt-sensitive rats, which could be alleviated by canagliflozin treatment. Overexpression of TRPC3 mimicked salt-induced vascular cytosolic calcium increase in vitro and knockout of TRPC3 erased the antihypertensive effect of canagliflozin. Mechanistically, high-salt-induced activation of NCX1 (sodium-calcium exchanger 1) reverse mode increased cytoplasmic calcium level and vasoconstriction, which required TRPC3, and this process could be blocked by canagliflozin. Conclusions We define a previously unrecognized role of TRPC3/NCX1 mediated vascular calcium dysfunction in the development of high-salt-induced hypertension, which can be improved by canagliflozin treatment. This pathway is potentially a novel therapeutic target to antagonize salt-sensitive hypertension.

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.

Endothelin-1 potentiates TRPV1-mediated vasoconstriction of human adipose arterioles in a protein kinase C-dependent manner

BACKGROUND AND PURPOSE

The TRPV cation channels have emerged as important regulators of vascular tone. TRPV1 channels and endothelin-1 are independently associated with the pathophysiology of coronary vasospasm, but the relationship between their vasomotor functions remains unclear. We characterized the vasomotor function of TRPV1 channels in human arterioles and investigated regulation of their vasomotor function by endothelin-1.

EXPERIMENTAL APPROACH

Human arterioles (mainly from adipose tissue) were threaded on two metal wires, equilibrated in a physiological buffer at 37°C and exposed to increasing concentrations of capsaicin, with or without SB366791 (TRPV1-selective inhibitor) or GF109203X (PKC-selective inhibitor). Some arterioles were pre-constricted with endothelin-1 or phenylephrine or high potassium buffer. TRPV1 mRNA and protein expression in human arteries were also assessed.

KEY RESULTS

TRPV1 transcripts and proteins were detected in human resistance arteries. Capsaicin (1 μM) induced concentration-dependent constriction of endothelium-intact and endothelium-denuded human adipose arterioles (HAA), which was significantly inhibited by SB366791. Pre-constriction of HAA with endothelin-1, but not high potassium buffer or phenylephrine, significantly potentiated capsaicin (0.1 μM)-induced constriction. GF109203X significantly inhibited potentiation of capsaicin-induced constriction by endothelin-1.

CONCLUSION AND IMPLICATIONS

TRPV1 channels are expressed in the human vasculature and affect vascular tone of human arterioles on activation. Their vasomotor function is modulated by endothelin-1, mediated in part by PKC. These findings reveal a novel interplay between endothelin-1 signalling and TRPV1 channels in human VSMC, adding to our understanding of the ion channel mechanisms that regulate human arteriolar tone and may also contribute to the pathophysiology of coronary vasospasm.

Revisiting the mechanism of hypoxic pulmonary vasoconstriction using isolated perfused/ventilated mouse lung

Hypoxic Pulmonary Vasoconstriction (HPV) is an important physiological mechanism of the lungs that matches perfusion to ventilation thus maximizing O2 saturation of the venous blood within the lungs. This study emphasizes on principal pathways in the initiation and modulation of hypoxic pulmonary vasoconstriction with a primary focus on the role of Ca2+ signaling and Ca2+ influx pathways in hypoxic pulmonary vasoconstriction. We used an ex vivo model, isolated perfused/ventilated mouse lung to evaluate hypoxic pulmonary vasoconstriction. Alveolar hypoxia (utilizing a mini ventilator) rapidly and reversibly increased pulmonary arterial pressure due to hypoxic pulmonary vasoconstriction in the isolated perfused/ventilated lung. By applying specific inhibitors for different membrane receptors and ion channels through intrapulmonary perfusion solution in isolated lung, we were able to define the targeted receptors and channels that regulate hypoxic pulmonary vasoconstriction. We show that extracellular Ca2+ or Ca2+ influx through various Ca2+-permeable channels in the plasma membrane is required for hypoxic pulmonary vasoconstriction. Removal of extracellular Ca2+ abolished hypoxic pulmonary vasoconstriction, while blockade of L-type voltage-dependent Ca2+ channels (with nifedipine), non-selective cation channels (with 30 µM SKF-96365), and TRPC6/TRPV1 channels (with 1 µM SAR-7334 and 30 µM capsazepine, respectively) significantly and reversibly inhibited hypoxic pulmonary vasoconstriction. Furthermore, blockers of Ca2+-sensing receptors (by 30 µM NPS2143, an allosteric Ca2+-sensing receptors inhibitor) and Notch (by 30 µM DAPT, a γ-secretase inhibitor) also attenuated hypoxic pulmonary vasoconstriction. These data indicate that Ca2+ influx in pulmonary arterial smooth muscle cells through voltage-dependent, receptor-operated, and store-operated Ca2+ entry pathways all contribute to initiation of hypoxic pulmonary vasoconstriction. The extracellular Ca2+-mediated activation of Ca2+-sensing receptors and the cell-cell interaction via Notch ligands and receptors contribute to the regulation of hypoxic pulmonary vasoconstriction.

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.

[Correlation between transient receptor potential canonical channel with heart and kidney injure of rat model of obstructive sleep apnea hypopnea syndrome]

OBJECTIVE

To investigate the expression of transient receptor potential canonical channels (TRPCs) in the heart and kidney of rat model of obstructive sleep apnea hypopnea syndrome (OSAHS).

METHODS

Eighteen male SD rats were randomly assigned to intermittent hypoxia (IH) group (n=9 ) and control group (n=9). In IH group, rats were placed in a chamber and exposed to intermittent hypoxia for 8h (10AM-6PM) daily. The expression of TRPC-related mRNA and protein in the heart and kidney tissue were detected by qRT-PCR and Western blotting, respectively.

RESULTS

The mRNA expressions of TRPC3/TRPC4/TRPC5 in heart tissues of IH group were increased significantly compared with the control group (all P>0.05); while there were no significant differences in the mRNA expressions of TRPC1/TRPC3/TRPC4/TRPC5/TRPC6/TRPC7 in kidney tissue between two groups (all P<0.05). The mRNA expressions of TRPC4, TRPC5 and TRPC6 in kidney tissues of IH group were lower than that in heart tissues (all P<0.05). The mRNA expression of TRPC7 in kidney tissues of control group was significantly higher than that in heart tissues (P<0.05). The expression of TRPC5 protein in heart tissues of IH group was significantly higher than that in the control group (P<0.05); while there was no significant differences in the expression of TRPC5/TRPC6/TRPC7 protein in kidney tissue between two groups (all P>0.05).

CONCLUSIONS

The IH rat model shows that TRPC5 channel is likely to be involved in the OSAHS induced pathophysiological changes in the myocardium and may become a target to prevent OSAHS related cardiac damage.

PIP2: A critical regulator of vascular ion channels hiding in plain sight

The phosphoinositide, phosphatidylinositol 4,5-bisphosphate (PIP₂), has long been established as a major contributor to intracellular signaling, primarily by virtue of its role as a substrate for phospholipase C (PLC). Signaling by G_q-protein-coupled receptors triggers PLC-mediated hydrolysis of PIP₂ into inositol 1,4,5-trisphosphate and diacylglycerol, which are well known to modulate vascular ion channel activity. Often overlooked, however, is the role PIP₂ itself plays in this regulation. Although numerous reports have demonstrated that PIP₂ is critical for ion channel regulation, how it impacts vascular function has received scant attention. In this review, we focus on PIP₂ as a regulator of ion channels in smooth muscle cells and endothelial cells-the two major classes of vascular cells. We further address the concerted effects of such regulation on vascular function and blood flow control. We close with a consideration of current knowledge regarding disruption of PIP₂ regulation of vascular ion channels in disease.

TRPC and TRPV Channels' Role in Vascular Remodeling and Disease

Transient receptor potentials (TRPs) are non-selective cation channels that are widely expressed in vascular beds. They contribute to the Ca²⁺ influx evoked by a wide spectrum of chemical and physical stimuli, both in endothelial and vascular smooth muscle cells. Within the superfamily of TRP channels, different isoforms of TRPC (canonical) and TRPV (vanilloid) have emerged as important regulators of vascular tone and blood flow pressure. Additionally, several lines of evidence derived from animal models, and even from human subjects, highlighted the role of TRPC and TRPV in vascular remodeling and disease. Dysregulation in the function and/or expression of TRPC and TRPV isoforms likely regulates vascular smooth muscle cells switching from a contractile to a synthetic phenotype. This process contributes to the development and progression of vascular disorders, such as systemic and pulmonary arterial hypertension, atherosclerosis and restenosis. In this review, we provide an overview of the current knowledge on the implication of TRPC and TRPV in the physiological and pathological processes of some frequent vascular diseases.

High-salt intake increases TRPC3 expression and enhances TRPC3-mediated calcium influx and systolic blood pressure in hypertensive patients

Enhanced transient receptor potential canonical subtype 3 (TRPC3) expression and TRPC3-mediated calcium influx in monocytes from hypertensive rats and patients are associated with increased blood pressure. Daily salt intake is closely related to hypertension, but the relationship between TRPC3 expression and salt intake has not yet been evaluated in hypertensive patients. Using reverse transcription-polymerase chain reaction, we studied the expression of TRPC3 and TRPC3-related store-operated calcium entry (SOCE) in peripheral blood mononuclear cells (PBMCs) from hypertensive and normotensive control subjects. Measurement of SOCE was performed using the fluorescent dye Fura-2 AM. Participants were divided into a low-salt group (<9 g) and a high-salt group (≥9 g) based on 24-h urinary sodium excretion. Increased TRPC3 mRNA expression levels and SOCE were observed in THP-1 cells after high-NaCl treatment. However, administration of the TRPC3-specific inhibitor Pyr3 significantly decreased the effect. Furthermore, the TRPC3 mRNA expression levels in PBMCs from high-salt intake patients with essential hypertension were significantly higher than those in low-salt intake patients compared with those in normotensive control subjects. We also observed significantly increased TRPC3-mediated SOCE in PBMCs from hypertensive subjects (but not from normotensive control subjects), with calcium concentration correlating with salt intake. More importantly, TRPC3 mRNA levels showed a significant correlation with salt intake and systolic blood pressure in patients with essential hypertension. This study demonstrated, for the first time, that increased TRPC3 mRNA levels are associated with elevated salt intake and systolic blood pressure in hypertensive patients.

Upregulation of Transient Receptor Potential Canonical Type 3 Channel via AT1R/TGF-β1/Smad2/3 Induces Atrial Fibrosis in Aging and Spontaneously Hypertensive Rats

Fibroblast proliferation and migration are central in atrial fibrillation (AF) promoting structure remodeling, which is strongly associated with aging and hypertension. Transient receptor potential canonical-3 channel (TRPC3) is a key mediator of cardiac fibrosis and the pathogenesis of AF. Here, we have observed the increased TRPC3 expression that induced atrial fibrosis which possibly is either mediated by the aging process or related to hypertensive progression. In this study, we measured the pathological structure remodeling by H&E staining, Masson staining, and transmission electron microscope (TEM). The protein expression levels of fibrotic biomarkers and TRPC3 were measured by Western blotting with atrial tissues from normotensive Wistar Kyoto rats (WKY 4m-o (4 months old)), old WKY (WKY 24m-o (24 months old)), spontaneously hypertensive rat (SHR 4m-o (4 months old)), and old SHR (SHR 24m-o (24 months old)). To illuminate the molecular mechanism of TRPC3 in atrial fibrosis of aging rats and SHR, we detected the inhibited role of TRPC3 selective blocker ethyl-1-(4-(2,3,3-trichloroacrylamide) phenyl)-5-(trifluoromethyl)-1H-pyrazole-4-carboxylate,pyrazole-3 (Pyr3) on angiotensin II (Ang II) induced fibrosis in neonatal rat atrial fibroblasts. The pathological examination showed that the extracellular matrix (ECM) and collagen fibrils were markedly increased in atrial tissues from aged and hypertensive rats. The protein expressions of fibrotic biomarkers (collagen I, collagen III, and transforming growth factor-β1 (TGF-β1)) were significantly upregulated in atrial tissues from the WKY 24m-o group, SHR 4m-o group, and SHR 24m-o group compared with the WKY 4m-o group. Meanwhile, the expression level of TRPC3 was significantly upregulated in WKY 24m-o and SHR 4m-o atrial tissues compared to WKY 4m-o rats. In isolated and cultured neonatal rat atrial fibroblasts, Ang II induced the atrial fibroblast migration and proliferation and upregulated the expression levels of TRPC3 and fibrotic biomarkers. TRPC3 selected blocker Pyr3 attenuated the migration and proliferation in neonatal rat atrial fibroblasts. Furthermore, Pyr3 significantly alleviated Ang II-induced upregulation of TRPC3, collagen I, collagen III, and TGF-β1 through the molecular mechanism of the TGF-β/Smad2/3 signaling pathway. Similarly, knocking down TRPC3 using short hairpin RNA (shTRPC3) also attenuated Ang II-induced upregulation of TGF-β1. Pyr3 preconditioning decreased Ang II-induced intracellular Ca²⁺ transient amplitude elevation. Furthermore, AT1 receptor was involved in Ang II-induced TRPC3 upregulation. Hence, upregulation of TRPC3 in aging and hypertension is involved in an atrial fibrosis process. Inhibition of TRPC3 contributes to reverse Ang II-induced fibrosis. TRPC3 may be a potential therapeutic target for preventing fibrosis in aging and hypertension.

TRPC3 deficiency attenuates high salt-induced cardiac hypertrophy by alleviating cardiac mitochondrial dysfunction

Long-term high salt intake leads to cardiac hypertrophy, but the mechanism remains elusive. Transient receptor potential channel, canonical 3(TRPC3), located in mitochondria, regulates mitochondrial calcium and reactive oxygen species(ROS) production. Herein, we investigated whether TRPC3 participates in high salt-induced cardiac hypertrophy by impairing cardiac mitochondrial function. High salt treatment increased the expression of mitochondrial TRPC3 in cardiomyocytes, accompanied by enhanced mitochondrial calcium uptake and elevated ROS production. Inhibition of TRPC3 significantly reduced high salt-induced ROS generation, promoted ATP production by stimulating oxidative phosphorylation, and increased enzyme activity in mitochondria in cardiomyocytes. Additionally, TRPC3 deficiency inhibited high salt-induced cardiac hypertrophy in vivo. A long-term high salt diet increased cardiac mitochondrial TRPC3 expression, elevated expression of cardiac hypertrophic markers atrial natriuretic peptide (ANP),brain natriuretic peptide (BNP) and β-myosin heavy chain (β-MHC) and decreased ATP production and mitochondrial complex I and II enzyme activity in a TRPC3-dependent manner. TRPC3 deficiency antagonises high salt diet-mediated cardiac hypertrophy by ameliorating TRPC3-mediated cardiac mitochondrial dysfunction. TRPC3 may therefore represent a novel target for preventing high salt-induced cardiac damage.

Calcium signals that determine vascular resistance

Small arteries in the body control vascular resistance, and therefore, blood pressure and blood flow. Endothelial and smooth muscle cells in the arterial walls respond to various stimuli by altering the vascular resistance on a moment to moment basis. Smooth muscle cells can directly influence arterial diameter by contracting or relaxing, whereas endothelial cells that line the inner walls of the arteries modulate the contractile state of surrounding smooth muscle cells. Cytosolic calcium is a key driver of endothelial and smooth muscle cell functions. Cytosolic calcium can be increased either by calcium release from intracellular stores through IP3 or ryanodine receptors, or the influx of extracellular calcium through ion channels at the cell membrane. Depending on the cell type, spatial localization, source of a calcium signal, and the calcium-sensitive target activated, a particular calcium signal can dilate or constrict the arteries. Calcium signals in the vasculature can be classified into several types based on their source, kinetics, and spatial and temporal properties. The calcium signaling mechanisms in smooth muscle and endothelial cells have been extensively studied in the native or freshly isolated cells, therefore, this review is limited to the discussions of studies in native or freshly isolated cells. This article is categorized under: Biological Mechanisms > Cell Signaling Laboratory Methods and Technologies > Imaging Models of Systems Properties and Processes > Mechanistic Models.

Increased caveolin-1 expression enhances the receptor-operated Ca2+ entry in the aorta of two-kidney, one-clip hypertensive rats

NEW FINDINGS

What is the central question of this study? The aim was to examine and compare the contributions of caveolin-1 to the contractile responses mediated by L-type voltage-dependent calcium channels, store-operated Ca²⁺ channels and receptor-operated Ca²⁺ channels in two different types of arteries from two-kidney, one-clip hypertensive rats. What is the main finding and its importance? We demonstrated that the density of caveolae and caveolin-1 expression were significantly upregulated in the aorta of two-kidney, one-clip hypertensive rats, but not in the third-order branches of mesenteric arteries. We highlight that caveolin-1 plays an important role in aortic constriction by enhancing receptor-operated Ca²⁺ entry in the hypertensive rat model.

ABSTRACT

Calcium and its multiple regulatory mechanisms are crucial for the development of hypertension. Among these regulatory mechanisms, store-operated Ca²⁺ entry (SOCE) and receptor-operated Ca²⁺ entry (ROCE) mediate agonist-induced calcium influx, contributing to vascular contraction. The SOCE and ROCE are regulated by a variety of mechanisms involving caveolin-1 (Cav1), which has been found to be strongly associated with hypertension in gene polymorphism. In the present study, we investigated the role of Cav1 during the enhanced activity of calcium channels in hypertensive arteries. We demonstrated that the expression level of Cav1 was significantly increased in the aorta of two-kidney, one-clip (2K1C) hypertensive rats. The disruption of caveolae by methyl-β-cyclodextrin did not cause a marked difference in agonist-induced vasoconstriction in the third-order branches of the mesenteric arteries but strongly suppressed the aortic contractile response to endothelin-1 in the 2K1C group, which was not found in the control group. The increase in Cav1 by introduction of Cav1 scaffolding domain enhancing peptide promoted the 1-oleoyl-2-acetyl-glycerol-induced ROCE in hypertensive aortic smooth muscle cells but did not enhance the cyclopiazonic acid-induced SOCE. In the resistance arteries, similar changes were not observed, and no statistical changes of Cav1 expression were evident in the third-order branches of the mesenteric arteries. Our results indicate that increased Cav1 expression might promote the altered [Ca²⁺ ]_i -induced aortic vasoreactivity by enhancing ROCE and be involved in the pathogenesis of hypertension.

The effects of transient receptor potential channel (TRPC) on airway smooth muscle cell isolated from asthma model mice

This study aimed to validate whether transient receptor potential channel1 (TRPC1) and TRPC3 participate in the regulation the proliferation of airway smooth muscle cells (ASMCs) through modulating calcium ion (Ca²⁺ ) influx in vitro. Chronic model of murine asthma was induced and ASMCs isolated from asthmatic mice were used in this whole study. TRPC1 and TRPC3 were upregulated in asthmatic mouse ASMCs and selected for further investigation. Ca²⁺ concentration and the cell viability of asthmatic mouse ASMCs were significantly higher than that from non- asthma mice, however, TRPC channels blocker SKF96365 alleviated these effects. Furthermore, TRPC1 or TRPC3 overexpression markedly increased Ca²⁺ concentration and significantly induced the viability of ASMCs; whereas TRPC1 or TRPC3 knockdown exerted the completely conversed effects. Moreover, knockdown of TRPC1 and TRPC3 also exerted different effects on the protein expression of growth-related proteins p-p38, p-JNK, cleaved caspase-3 and Bcl-2, as well as on cell cycle. Finally, we found Ca²⁺ chelator EGTA or BAPTA-AM significantly diminished the effects of si-TRPC1 and si-TRPC3 on the cell viability, cell cycle, and the protein expression of p-p38, p-JNK, cleaved caspase-3, and Bcl-2 in asthmatic mouse ASMCs. Our findings demonstrated that the effects of TRPC1 and TRPC3 on the cell viability and cell cycle of ASMCs were, at least partially, through regulating Ca²⁺ influx.

Cyclic Stretch Alters Vascular Reactivity of Mouse Aortic Segments

Large, elastic arteries buffer the pressure wave originating in the left ventricle and are constantly exposed to higher amplitudes of cyclic stretch (10%) than muscular arteries (2%). As a crucial factor for endothelial and smooth muscle cell function, cyclic stretch has, however, never been studied in ex vivo aortic segments of mice. To investigate the effects of cyclic stretch on vaso-reactivity of mouse aortic segments, we used the Rodent Oscillatory Tension Set-up to study Arterial Compliance (ROTSAC). The aortic segments were clamped at frequencies of 6–600 bpm between two variable preloads, thereby mimicking dilation as upon left ventricular systole and recoiling as during diastole. The preloads corresponding to different transmural pressures were chosen to correspond to a low, normal or high amplitude of cyclic stretch. At different time intervals, cyclic stretch was interrupted, the segments were afterloaded and isometric contractions by α₁-adrenergic stimulation with 2 μM phenylephrine in the absence and presence of 300 μM L-NAME (eNOS inhibitor) and/or 35 μM diltiazem (blocker of voltage-gated Ca²⁺ channels) were measured. As compared with static or cyclic stretch at low amplitude (<10 mN) or low frequency (0.1 Hz), cyclic stretch at physiological amplitude (>10 mN) and frequency (1–10 Hz) caused better ex vivo conservation of basal NO release with time after mounting. The relaxation of PE-precontracted segments by addition of ACh to stimulate NO release was unaffected by cyclic stretch. In the absence of basal NO release (hence, presence of L-NAME), physiological in comparison with aberrant cyclic stretch decreased the baseline tension, attenuated the phasic contraction by phenylephrine in the absence of extracellular Ca²⁺ and shifted the smaller tonic contraction more from a voltage-gated Ca²⁺ channel-mediated to a non-selective cation channel-mediated. Data highlight the need of sufficient mechanical activation of endothelial and vascular smooth muscle cells to maintain basal NO release and low intracellular Ca²⁺ in the smooth muscle cells in large arteries. Both phenomena may play a vital role in maintaining the high compliance of large arteries.

TRPC Channels and Stroke

TRPC channels play important roles in neuronal death/survival in ischemic stroke, vasospasm in hemorrhagic stroke, thrombin-induced astrocyte pathological changes, and also in the initiation of stroke by affecting blood pressure and atherogenesis. TRPCs' unique channel characters and downstream pathways make them possible new targets for stroke therapy. TRPC proteins have different functions in different cell types. Considering TRPCs' extensive distribution in various tissues and cell types, drugs targeting them could induce more complicated effects. More specific agonists/antagonists and antibodies are required for future study of TRPCs as potential targets for stroke therapy.

Canonical Transient Receptor Potential Channels and Their Link with Cardio/Cerebro-Vascular Diseases

The canonical transient receptor potential channels (TRPCs) constitute a series of nonselective cation channels with variable degrees of Ca²⁺ selectivity. TRPCs consist of seven mammalian members, TRPC1, TRPC2, TRPC3, TRPC4, TRPC5, TRPC6, and TRPC7, which are further divided into four subtypes, TRPC1, TRPC2, TRPC4/5, and TRPC3/6/7. These channels take charge of various essential cell functions such as contraction, relaxation, proliferation, and dysfunction. This review, organized into seven main sections, will provide an overview of current knowledge about the underlying pathogenesis of TRPCs in cardio/cerebrovascular diseases, including hypertension, pulmonary arterial hypertension, cardiac hypertrophy, atherosclerosis, arrhythmia, and cerebrovascular ischemia reperfusion injury. Collectively, TRPCs could become a group of drug targets with important physiological functions for the therapy of human cardio/cerebro-vascular diseases.

Enhanced Mitochondrial Transient Receptor Potential Channel, Canonical Type 3-Mediated Calcium Handling in the Vasculature From Hypertensive Rats

BACKGROUND

Mitochondrial Ca2+ homeostasis is fundamental to the regulation of mitochondrial reactive oxygen species (ROS) generation and adenosine triphosphate production. Recently, transient receptor potential channel, canonical type 3 (TRPC3), has been shown to localize to the mitochondria and to play a role in maintaining mitochondrial calcium homeostasis. Inhibition of TRPC3 attenuates vascular calcium influx in spontaneously hypertensive rats (SHRs). However, it remains elusive whether mitochondrial TRPC3 participates in hypertension by increasing mitochondrial calcium handling and ROS production.

METHODS AND RESULTS

In this study we demonstrated increased TRPC3 expression in purified mitochondria in the vasculature from SHRs, which facilitates enhanced mitochondrial calcium uptake and ROS generation compared with Wistar-Kyoto rats. Furthermore, inhibition of TRPC3 by its specific inhibitor, Pyr3, significantly decreased the vascular mitochondrial ROS production and H2O2 synthesis and increased adenosine triphosphate content. Administration of telmisartan can improve these abnormalities. This beneficial effect was associated with improvement of the mitochondrial respiratory function through recovering the activity of pyruvate dehydrogenase in the vasculature of SHRs. In vivo, chronic administration of telmisartan suppressed TRPC3-mediated excessive mitochondrial ROS generation and vasoconstriction in the vasculature of SHRs. More importantly, TRPC3 knockout mice exhibited significantly ameliorated hypertension through reduction of angiotensin II-induced mitochondrial ROS generation.

CONCLUSIONS

Together, we give experimental evidence for a potential mechanism by which enhanced TRPC3 activity at the cytoplasmic and mitochondrial levels contributes to redox signaling and calcium dysregulation in the vasculature from SHRs. Angiotensin II or telmisartan can regulate [Ca2+]mito, ROS production, and mitochondrial energy metabolism through targeting TRPC3.

Physiological and pathophysiological role of transient receptor potential canonical channels in cardiac myocytes

Transient receptor potential canonical (TRPC) channels constitute a family of seven Ca²⁺ permeable ion channels, named TRPC1 to 7. These channels are abundantly expressed in the mammalian heart, yet mechanisms underlying activation of TRPC channels and their precise role in cardiac physiology remain poorly understood. In this review, we perused original literature regarding TRPC channels in cardiomyocytes. We first reviewed studies on TRPC channel assembly and sub-cellular localization across multiple species and cell types. Our review indicates that TRPC localization in cardiac cells is still a topic of controversy. We then examined common molecular biology tools used to infer on location and physiological roles of TRPC channels in the heart. We subsequently reviewed pharmacological tools used to modulate TRPC activity in both cardiac and non-cardiac cells. Suggested physiological roles in the heart include modulation of heart rate and sensing of mechanical strain. We examined studies on the contribution of TRPC to cardiac pathophysiology, mainly hypertrophic signaling. Several TRPC channels, particularly TRPC1, 3 and 6 were proposed to play a crucial role in hypertrophic signaling. Finally, we discussed gaps in our understanding of the location and physiological role of TRPC channels in cardiomyocytes. Closing these gaps will be crucial to gain a full understanding of the role of TRPC channels in cardiac pathophysiology and to further explore these channels as targets for treatments for cardiac diseases, in particular, hypertrophy.

Muscling in on TRP channels in vascular smooth muscle cells and cardiomyocytes

The human TRP protein family comprises a family of 27 cation channels with diverse permeation and gating properties. The common theme is that they are very important regulators of intracellular Ca²⁺ signaling in diverse cell types, either by providing a Ca²⁺ influx pathway, or by depolarising the membrane potential, which on one hand triggers the activation of voltage-gated Ca²⁺ channels, and on the other limits the driving force for Ca²⁺ entry. Here we focus on the role of these TRP channels in vascular smooth muscle and cardiac striated muscle. We give an overview of highlights from the recent literature, and highlight the important and diverse roles of TRP channels in the pathophysiology of the cardiovascular system. The discovery of the superfamily of Transient Receptor Potential (TRP) channels has significantly enhanced our knowledge of multiple signal transduction mechanisms in cardiac muscle and vascular smooth muscle cells (VSMC). In recent years, multiple studies have provided evidence for the involvement of these channels, not only in the regulation of contraction, but also in cell proliferation and remodeling in pathological conditions. The mammalian family of TRP cation channels is composed by 28 genes which can be divided into 6 subfamilies groups based on sequence similarity: TRPC (Canonical), TRPM (Melastatin), TRPML (Mucolipins), TRPV (Vanilloid), TRPP (Policystin) and TRPA (Ankyrin-rich protein). Functional TRP channels are believed to form four-unit complexes in the plasma, each of them expressed with six transmembrane domain and intracellular N and C termini. Here we review the current knowledge on the expression of TRP channels in both muscle types, and discuss their functional properties and role in physiological and pathophysiological processes.

Smooth Muscle Ion Channels and Regulation of Vascular Tone in Resistance Arteries and Arterioles

Vascular tone of resistance arteries and arterioles determines peripheral vascular resistance, contributing to the regulation of blood pressure and blood flow to, and within the body's tissues and organs. Ion channels in the plasma membrane and endoplasmic reticulum of vascular smooth muscle cells (SMCs) in these blood vessels importantly contribute to the regulation of intracellular Ca2+ concentration, the primary determinant of SMC contractile activity and vascular tone. Ion channels provide the main source of activator Ca2+ that determines vascular tone, and strongly contribute to setting and regulating membrane potential, which, in turn, regulates the open-state-probability of voltage gated Ca2+ channels (VGCCs), the primary source of Ca2+ in resistance artery and arteriolar SMCs. Ion channel function is also modulated by vasoconstrictors and vasodilators, contributing to all aspects of the regulation of vascular tone. This review will focus on the physiology of VGCCs, voltage-gated K+ (KV) channels, large-conductance Ca2+-activated K+ (BKCa) channels, strong-inward-rectifier K+ (KIR) channels, ATP-sensitive K+ (KATP) channels, ryanodine receptors (RyRs), inositol 1,4,5-trisphosphate receptors (IP3Rs), and a variety of transient receptor potential (TRP) channels that contribute to pressure-induced myogenic tone in resistance arteries and arterioles, the modulation of the function of these ion channels by vasoconstrictors and vasodilators, their role in the functional regulation of tissue blood flow and their dysfunction in diseases such as hypertension, obesity, and diabetes. © 2017 American Physiological Society. Compr Physiol 7:485-581, 2017.

Renoprotection: focus on TRPV1, TRPV4, TRPC6 and TRPM2

Members of the transient receptor potential (TRP) cation channel receptor family have unique sites of regulatory function in the kidney which enables them to promote regional vasodilatation and controlled Ca²⁺ influx into podocytes and tubular cells. Activated TRP vanilloid 1 receptor channels (TRPV1) have been found to elicit renoprotection in rodent models of acute kidney injury following ischaemia/reperfusion. Transient receptor potential cation channel, subfamily C, member 6 (TRPC6) in podocytes is involved in chronic proteinuric kidney disease, particularly in focal segmental glomerulosclerosis (FSGS). TRP vanilloid 4 receptor channels (TRPV4) are highly expressed in the kidney, where they induce Ca²⁺ influx into endothelial and tubular cells. TRP melastatin (TRPM2) non-selective cation channels are expressed in the cytoplasm and intracellular organelles, where their inhibition ameliorates ischaemic renal pathology. Although some of their basic properties have been recently identified, the renovascular role of TRPV1, TRPV4, TRPC6 and TRPM2 channels in disease states such as obesity, hypertension and diabetes is largely unknown. In this review, we discuss recent evidence for TRPV1, TRPV4, TRPC6 and TRPM2 serving as potential targets for acute and chronic renoprotection in chronic vascular and metabolic disease.

Differences in TRPC3 and TRPC6 channels assembly in mesenteric vascular smooth muscle cells in essential hypertension

KEY POINTS

Canonical transient receptor potential (TRPC)3 and TRPC6 channels of vascular smooth muscle cells (VSMCs) mediate stretch- or agonist-induced cationic fluxes, contributing to membrane potential and vascular tone. Native TRPC3/C6 channels can form homo- or heterotetrameric complexes, which can hinder individual TRPC channel properties. The possibility that the differences in their association pattern may change their contribution to vascular tone in hypertension is unexplored. Functional characterization of heterologously expressed channels showed that TRPC6-containing complexes exhibited Pyr3/Pyr10-sensitive currents, whereas TRPC3-mediated currents were blocked by anti-TRPC3 antibodies. VSMCs from hypertensive (blood pressure high; BPH) mice have larger cationic basal currents insensitive to Pyr10 and sensitive to anti-TRPC3 antibodies. Consistently, myography studies showed a larger Pyr3/10-induced vasodilatation in BPN (blood pressure normal) mesenteric arteries. We conclude that the increased TRPC3 channel expression in BPH VSMCs leads to changes in TRPC3/C6 heteromultimeric assembly, with a higher TRPC3 channel contribution favouring depolarization of hypertensive VSMCs.

ABSTRACT

Increased vascular tone in essential hypertension involves a sustained rise in total peripheral resistance. A model has been proposed in which the combination of membrane depolarization and higher L-type Ca²⁺ channel activity generates augmented Ca²⁺ influx into vascular smooth muscle cells (VSMCs), contraction and vasoconstriction. The search for culprit ion channels responsible for membrane depolarization has provided several candidates, including members of the canonical transient receptor potential (TRPC) family. TRPC3 and TRPC6 are diacylglycerol-activated, non-selective cationic channels contributing to stretch- or agonist-induced depolarization. Conflicting information exists regarding changes in TRPC3/TRPC6 functional expression in hypertension. However, although TRPC3-TRPC6 channels can heteromultimerize, the possibility that differences in their association pattern may change their functional contribution to vascular tone is largely unexplored. We probe this hypothesis using a model of essential hypertension (BPH mice; blood pressure high) and its normotensive control (BPN mice; blood pressure normal). First, non-selective cationic currents through homo- and heterotetramers recorded from transfected Chinese hamster ovary cells indicated that TRPC currents were sensitive to the selective antagonist Pyr10 only when TRPC6 was present, whereas intracellular anti-TRPC3 antibody selectively blocked TRPC3-mediated currents. In mesenteric VSMCs, basal and agonist-induced currents were more sensitive to Pyr3 and Pyr10 in BPN cells. Consistently, myography studies showed a larger Pyr3/10-induced vasodilatation in BPN mesenteric arteries. mRNA and protein expression data supported changes in TRPC3 and TRPC6 proportions and assembly, with a higher TRPC3 channel contribution in BPH VSMCs that could favour cell depolarization. These differences in functional and pharmacological properties of TRPC3 and TRPC6 channels, depending on their assembly, could represent novel therapeutical opportunities.

The role of transient receptor potential channels in hypertension and metabolic vascular damage

NEW FINDINGS

What is the topic of this review? Transient receptor potential (TRP) channels are highly implicated in the pathogenesis of hypertension and the regulation of metabolism. What advances does it highlight? Dysfunction of TRP channels leads to hypertension and metabolic disorders. Elucidating the role of TRP channels in hypertension and metabolic vascular damage would facilitate the design of novel target therapeutics for these intractable diseases. Intracellular Ca²⁺ homeostasis is critical for vascular function and the regulation of metabolism. Metabolic disorders are major risk factors for hypertension. A family of transient receptor potential (TRP) channels plays an important role in the regulation of cellular calcium signalling and cardiometabolic function. Emerging evidence indicates that TRP channels are highly implicated in the pathogenesis of hypertension and metabolic disorders. Dysfunction of TRP channels leads to hypertension and metabolic dysfunction. Activation of certain subtypes of TRP channels could attenuate metabolic vascular damage and alleviate hypertension. Therefore, elucidating the role of TRP channels in the physiological state and in cardiometabolic diseases will facilitate the design of novel targeted therapeutics for these intractable diseases.

The mitochondrial calcium uniporter is involved in mitochondrial calcium cycle dysfunction: Underlying mechanism of hypertension associated with mitochondrial tRNA(Ile) A4263G mutation

Recent studies have shown that the mitochondrial DNA mutations are involved in the pathogenesis of hypertension. Our previous study identified mitochondrial tRNA(Ile) A4263G mutation in a large Chinese Han family with maternally-inherited hypertension. This mutation may contribute to mitochondrial Ca(2+) cycling dysfuntion, but the mechanism is unclear. Lymphoblastoid cell lines were derived from hypertensive and normotensive individuals, either with or without tRNA(Ile) A4263G mutation. The mitochondrial calcium ([Ca(2+)]m) in cells from hypertensive subjects with the tRNA(Ile) A4263G mutation, was lower than in cells from normotension or hypertension without mutation, or normotension with mutation (P<0.05). Meanwhile, cytosolic calcium ([Ca(2+)]c) in hypertensive with mutation cells was higher than another three groups. After exposure to caffeine, which could increase the [Ca(2+)]c by activating ryanodine receptor on endoplasmic reticulum, [Ca(2+)]c/[Ca(2+)]m increased higher than in hypertensive with mutation cells from another three groups. Moreover, MCU expression was decreased in hypertensive with mutation cells compared with in another three groups (P<0.05). [Ca(2+)]c increased and [Ca(2+)]m decreased after treatment with Ru360 (an inhibitor of MCU) or an siRNA against MCU. In this study we found decreased MCU expression in hypertensive with mutation cells contributed to dysregulated Ca(2+) uptake into the mitochondria, and cytoplasmic Ca(2+) overload. This abnormality might be involved in the underlying mechanisms of maternally inherited hypertension in subjects carrying the mitochondrial tRNA(Ile) A4263G mutation.

Angiotensin II type 1 receptor antagonists in animal models of vascular, cardiac, metabolic and renal disease

We have reviewed the effects of angiotensin II type 1 receptor antagonists (ARBs) in various animal models of hypertension, atherosclerosis, cardiac function, hypertrophy and fibrosis, glucose and lipid metabolism, and renal function and morphology. Those of azilsartan and telmisartan have been included comprehensively whereas those of other ARBs have been included systematically but without intention of completeness. ARBs as a class lower blood pressure in established hypertension and prevent hypertension development in all applicable animal models except those with a markedly suppressed renin-angiotensin system; blood pressure lowering even persists for a considerable time after discontinuation of treatment. This translates into a reduced mortality, particularly in models exhibiting marked hypertension. The retrieved data on vascular, cardiac and renal function and morphology as well as on glucose and lipid metabolism are discussed to address three main questions: 1. Can ARB effects on blood vessels, heart, kidney and metabolic function be explained by blood pressure lowering alone or are they additionally directly related to blockade of the renin-angiotensin system? 2. Are they shared by other inhibitors of the renin-angiotensin system, e.g. angiotensin converting enzyme inhibitors? 3. Are some effects specific for one or more compounds within the ARB class? Taken together these data profile ARBs as a drug class with unique properties that have beneficial effects far beyond those on blood pressure reduction and, in some cases distinct from those of angiotensin converting enzyme inhibitors. The clinical relevance of angiotensin receptor-independent effects of some ARBs remains to be determined.

Dietary Capsaicin Protects Cardiometabolic Organs from Dysfunction

Chili peppers have a long history of use for flavoring, coloring, and preserving food, as well as for medical purposes. The increased use of chili peppers in food is very popular worldwide. Capsaicin is the major pungent bioactivator in chili peppers. The beneficial effects of capsaicin on cardiovascular function and metabolic regulation have been validated in experimental and population studies. The receptor for capsaicin is called the transient receptor potential vanilloid subtype 1 (TRPV1). TRPV1 is ubiquitously distributed in the brain, sensory nerves, dorsal root ganglia, bladder, gut, and blood vessels. Activation of TRPV1 leads to increased intracellular calcium signaling and, subsequently, various physiological effects. TRPV1 is well known for its prominent roles in inflammation, oxidation stress, and pain sensation. Recently, TRPV1 was found to play critical roles in cardiovascular function and metabolic homeostasis. Experimental studies demonstrated that activation of TRPV1 by capsaicin could ameliorate obesity, diabetes, and hypertension. Additionally, TRPV1 activation preserved the function of cardiometabolic organs. Furthermore, population studies also confirmed the beneficial effects of capsaicin on human health. The habitual consumption of spicy foods was inversely associated with both total and certain causes of specific mortality after adjustment for other known or potential risk factors. The enjoyment of spicy flavors in food was associated with a lower prevalence of obesity, type 2 diabetes, and cardiovascular diseases. These results suggest that capsaicin and TRPV1 may be potential targets for the management of cardiometabolic vascular diseases and their related target organs dysfunction.

Excitation-Contraction Coupling and Excitation-Transcription Coupling in Blood Vessels: Their Possible Interactions in Hypertensive Vascular Remodeling

Vascular smooth muscle cells (VSMC) display considerable phenotype plasticity which can be studied in vivo on vascular remodeling which occurs during acute or chronic vascular injury. In differentiated cells, which represent contractile phenotype, there are characteristic rapid transient changes of intracellular Ca2+ concentration ([Ca2+]i), while the resting cytosolic [Ca2+]i concentration is low. It is mainly caused by two components of the Ca2+ signaling pathways: Ca2+ entry via L-type voltage-dependent Ca2+ channels and dynamic involvement of intracellular stores. Proliferative VSMC phenotype is characterized by long-lasting [Ca2+]i oscillations accompanied by sustained elevation of basal [Ca2+]i. During the switch from contractile to proliferative phenotype there is a general transition from voltage-dependent Ca2+ entry to voltage-independent Ca2+ entry into the cell. These changes are due to the altered gene expression which is dependent on specific transcription factors activated by various stimuli. It is an open question whether abnormal VSMC phenotype reported in rats with genetic hypertension (such as spontaneously hypertensive rats) might be partially caused by a shift from contractile to proliferative VSMC phenotype.

Taurine Supplementation Lowers Blood Pressure and Improves Vascular Function in Prehypertension: Randomized, Double-Blind, Placebo-Controlled Study

Taurine, the most abundant, semiessential, sulfur-containing amino acid, is well known to lower blood pressure (BP) in hypertensive animal models. However, no rigorous clinical trial has validated whether this beneficial effect of taurine occurs in human hypertension or prehypertension, a key stage in the development of hypertension. In this randomized, double-blind, placebo-controlled study, we assessed the effects of taurine intervention on BP and vascular function in prehypertension. We randomly assigned 120 eligible prehypertensive individuals to receive either taurine supplementation (1.6 g per day) or a placebo for 12 weeks. Taurine supplementation significantly decreased the clinic and 24-hour ambulatory BPs, especially in those with high-normal BP. Mean clinic systolic BP reduction for taurine/placebo was 7.2/2.6 mm Hg, and diastolic BP was 4.7/1.3 mm Hg. Mean ambulatory systolic BP reduction for taurine/placebo was 3.8/0.3 mm Hg, and diastolic BP was 3.5/0.6 mm Hg. In addition, taurine supplementation significantly improved endothelium-dependent and endothelium-independent vasodilation and increased plasma H2S and taurine concentrations. Furthermore, changes in BP were negatively correlated with both the plasma H2S and taurine levels in taurine-treated prehypertensive individuals. To further elucidate the hypotensive mechanism, experimental studies were performed both in vivo and in vitro. The results showed that taurine treatment upregulated the expression of hydrogen sulfide-synthesizing enzymes and reduced agonist-induced vascular reactivity through the inhibition of transient receptor potential channel subtype 3-mediated calcium influx in human and mouse mesenteric arteries. In conclusion, the antihypertensive effect of chronic taurine supplementation shows promise in the treatment of prehypertension through improvement of vascular function.

Reduction of blood pressure by store-operated calcium channel blockers

The voltage-operated Ca(2+) channels (VOCC), which allow Ca(2+) influx from the extracellular space, are inhibited by anti-hypertensive agents such as verapamil and nifedipine. The Ca(2+) entering from outside into the cell triggers Ca(2+) release from the sarcoplasmic reticulum (SR) stores. To refill the depleted Ca(2+) stores in the SR, another type of Ca(2+) channels in the cell membrane, known as store-operated Ca(2+) channels (SOCC), are activated. These SOCCs are verapamil and nifedipine resistant, but are SKF 96465 (SK) and gadolinium (Gd(3+) ) sensitive. Both SK and Gd(3+) have been shown to reduce [Ca(2+) ]i in the smooth muscle, but their effects on blood pressure have not been reported. Our results demonstrated that both SK and Gd(3+) produced a dose-dependent reduction in blood pressure in rat. The combination of SK and verapamil produced an additive action in lowering the blood pressure. Furthermore, SK, but not Gd(3+) suppressed proliferation of vascular smooth muscle cells in the absence or presence of lysophosphatidic acid (LPA). SK decreased the elevation of [Ca(2+) ]i induced by LPA, endothelin-1 (ET-1) and angiotensin II (Ang II), but did not affect the norepinephrine (NE)-evoked increase in [Ca(2+) ]i . On the other hand, Gd(3+) inhibited the LPA and Ang II induced change in [Ca(2+) ]i , but had no effect on the ET-1 and NE induced increase in [Ca(2+) ]i . The combination of verapamil and SK abolished the LPA- or adenosine-5'-triphosphate (ATP)-induced [Ca(2+) ]i augmentation. These results suggest that SOCC inhibitors, like VOCC blocker, may serve as promising drugs for the treatment of hypertension.

The role of rare variants in systolic blood pressure: analysis of ExomeChip data in HyperGEN African Americans

Cardiovascular diseases are among the most significant health problems in the United States today, with their major risk factor, hypertension, disproportionately affecting African Americans (AAs). Although GWAS have identified dozens of common variants associated with blood pressure (BP) and hypertension in European Americans, these variants collectively explain <2.5% of BP variance, and most of the genetic variants remain yet to be identified. Here, we report the results from rare-variant analysis of systolic BP using 94,595 rare and low-frequency variants (minor allele frequency, MAF, <5%) from the Illumina exome array genotyped in 2,045 HyperGEN AAs. In addition to single-variant analysis, 4 gene-level association tests were used for analysis: burden and family-based SKAT tests using MAF cutoffs of 1 and 5%. The gene-based methods often provided lower p values than the single-variant approach. Some consistency was observed across these 4 gene-based analysis options. While neither the gene-based analyses nor the single-variant analysis produced genome-wide significant results, the top signals, which had supporting evidence from multiple gene-based methods, were of borderline significance. Though additional molecular validations are required, 6 of the 16 most promising genes are biologically plausible with physiological connections to BP regulation.

Broad-range TRP channel inhibitors (2-APB, flufenamic acid, SKF-96365) affect differently contraction of resistance and conduit femoral arteries of rat

Transient receptor potential (TRP) channels are proposed to contribute to membrane depolarization and Ca2+ influx into vascular smooth muscle (VSM) cells. Our aim was to study the effects of widely used broad-range TRP channel inhibitors--2-aminoethoxydiphenyl borate (2-APB), flufenamic acid (FFA) and SKF-96365--on the contraction of freshly isolated small and large arteries. Endothelium-denuded resistance (≈250 µm) and conduit (≈1000 µm) femoral arteries were isolated from adult Wistar rats and mounted in wire myograph. The effects of the above mentioned TRP channel inhibitors and voltage-dependent calcium channel inhibitor nifedipine were studied on arterial contractions induced by phenylephrine, U-46619 or K+. Phenylephrine-induced contractions were also studied in the absence of extracellular Na+. mRNA expression of particular canonical and melastatin TRP channel subunits in femoral vascular bed was determined. TRP channel inhibitors attenuated K+-induced contraction less than nifedipine. Phenylephrine-induced contraction was more influenced by 2-APB in resistance arteries, while FFA completely prevented U-46619-induced contraction in both sizes of arteries. The absence of extracellular Na+ prevented the inhibitory effects of 2-APB, but not those of FFA. The observed effects of broad-range TRP channel inhibitors, which were dependent on the size of the artery, confirmed the involvement of TRP channels in agonist-induced contractions. The inhibitory effects of 2-APB (but not those of FFA or SKF-96365) were dependent on the presence of extracellular Na+.

Transient receptor potential channels in the vasculature

The mammalian genome encodes 28 distinct members of the transient receptor potential (TRP) superfamily of cation channels, which exhibit varying degrees of selectivity for different ionic species. Multiple TRP channels are present in all cells and are involved in diverse aspects of cellular function, including sensory perception and signal transduction. Notably, TRP channels are involved in regulating vascular function and pathophysiology, the focus of this review. TRP channels in vascular smooth muscle cells participate in regulating contractility and proliferation, whereas endothelial TRP channel activity is an important contributor to endothelium-dependent vasodilation, vascular wall permeability, and angiogenesis. TRP channels are also present in perivascular sensory neurons and astrocytic endfeet proximal to cerebral arterioles, where they participate in the regulation of vascular tone. Almost all of these functions are mediated by changes in global intracellular Ca(2+) levels or subcellular Ca(2+) signaling events. In addition to directly mediating Ca(2+) entry, TRP channels influence intracellular Ca(2+) dynamics through membrane depolarization associated with the influx of cations or through receptor- or store-operated mechanisms. Dysregulation of TRP channels is associated with vascular-related pathologies, including hypertension, neointimal injury, ischemia-reperfusion injury, pulmonary edema, and neurogenic inflammation. In this review, we briefly consider general aspects of TRP channel biology and provide an in-depth discussion of the functions of TRP channels in vascular smooth muscle cells, endothelial cells, and perivascular cells under normal and pathophysiological conditions.

Increased TRPP2 expression in vascular smooth muscle cells from high-salt intake hypertensive rats: The crucial role in vascular dysfunction

SCOPE

High-salt intake is a major risk factor in the development of hypertension. The underlying mechanism of high sodium on the cardiovascular system has received extensive attention. TRPP2 (Polycystin-2) is a Ca(2+) permeable nonselective cation channel that mediates Ca(2+) mobilization to control vascular smooth muscle cells (VSMCs) contraction. Here, we investigated TRPP2 expression change in VSMCs from high-salt intake hypertensive rats and role of TRPP2 in the development of high-salt diet-induced hypertension.

METHODS AND RESULTS

After 4 ws of dietary treatment, systolic blood pressure was significantly elevated in high-salt intake rats (132 ± 3 mmHg) compared with regular diet control rats (104 ± 2 mmHg). Results from vessel tension and diameter measurements show that high-salt intake potentiated phenylephrine-induced contraction in denuded mesenteric artery and thoracic aorta. Immunoblot and immunofluorescence data indicate that TRPP2 expression in VSMCs from mesenteric artery and thoracic aorta was significantly increased in high-salt intake-induced hypertensive rats. However, agonist-induced contractions in denuded mesenteric artery and thoracic aorta were markedly decreased if TRPP2 was knocked down by specific shRNA.

CONCLUSION

Our data demonstrate that high-salt intake increased TRPP2 expression in VSMCs, which in turn potentiated blood vessel response to contractors; this may participate in the development of hypertension.

Phospholipase Cγ1 connects the cell membrane pathway to the nuclear receptor pathway in insect steroid hormone signaling

In addition to the classical nuclear receptor pathway, there is a nongenomic pathway in the cell membrane that regulates gene expression in animal steroid hormone signaling; however, this mechanism is unclear. Here, we report that the insect steroid hormone 20-hydroxyecdysone (20E) regulates calcium influx via phospholipase Cγ1 (PLCG1) to modulate the protein kinase C phosphorylation of the transcription factor ultraspiracle (USP1) in the lepidopteran insect Helicoverpa armigera. The PLCG1 mRNA levels are increased during the molting and metamorphic stages. The depletion of PLCG1 by RNA interference can block 20E-enhanced pupation, cause larvae death and pupation defects, and repress 20E-induced gene expression. 20E may induce the tyrosine phosphorylation of PLCG1 at the cytosolic tyrosine kinase (Src) homology 2 domains and then determine the migration of PLCG1 toward the plasma membrane. The G-protein-coupled receptor (GPCR) inhibitor suramin, Src family kinase inhibitor PP2, and the depletions of ecdysone-responsible GPCR (ErGPCR) and Gαq restrain the 20E-induced tyrosine phosphorylation of PLCG1. PLCG1 participates in the 20E-induced Ca(2+) influx. The inhibition of GPCR, PLC, inositol 1,4,5-trisphosphate receptor, and calcium channels represses the 20E-induced Ca(2+) influx. Through calcium signaling, PLCG1 mediates the transcriptional activation driven by the ecdysone-response element. Through PLCG1 and calcium signaling, 20E regulates PKC phosphorylation of USP1 at Ser-21 to determine its ecdysone-response element binding activity. These results suggest that 20E activates PLCG1 via the ErGPCR and Src family kinases to regulate Ca(2+) influx and PKC phosphorylation of USP1 to subsequently modulate gene transcription for metamorphosis.

Activation of cold-sensing transient receptor potential melastatin subtype 8 antagonizes vasoconstriction and hypertension through attenuating RhoA/Rho kinase pathway

Environmental cold is a nonmodifiable hypertension risk factor. Transient receptor potential melastatin subtype 8 (TRPM8) is a cold-sensing cation channel that can be activated by menthol, a compound with a naturally cold sensation in mint. Little is known about the effect of TRPM8 activation on vascular function and blood pressure. Here, we report that TRPM8 is abundantly expressed in the vasculature. TRPM8 activation by menthol attenuated vasoconstriction via RhoA/Rho kinase pathway inhibition in wild-type mice, but the effect was absent in TRPM8(-/-) mice. Chronic dietary menthol blunted mesenteric arterial constriction and lowered blood pressure in genetic hypertensive rats via inhibition of RhoA/Rho kinase expression and activity in the vivo study. TRPM8 effect was associated with inhibition of intracellular calcium release from the sarcoplasmic reticulum, RhoA/Rho kinase activity, and sustained arterial contraction in the vitro study. Importantly, 8-week chronic menthol capsule treatment moderately lowered systolic blood pressure and diastolic blood pressure in prehypertensive individuals compared with the placebo group. Furthermore, chronic menthol capsule administration also improved flow-mediated dilatation in prehypertensive individuals, but not in the placebo group. In conclusion, our study demonstrates that TRPM8 activation by menthol benefits vascular function and blood pressure by inhibiting calcium signaling-mediated RhoA/Rho kinase activation in the vasculature. These findings add to the evidence that long-term dietary menthol treatment had favorable effects on hypertension treatment.