Involvement of native TRPC3 proteins in ATP-dependent expression of VCAM-1 and monocyte adherence in coronary artery endothelial cells

Total flavone of flowers of Abelmoschus manihot (L.) Medic inhibits the expression of adhesion molecules in primary mesenteric arterial endothelial cells and ameliorates dextran sodium sulphate-induced ulcerative colitis in mice

BACKGROUND

Flowers of Abelmoschus manihot (L.) medic (AM) is a traditional Chinese medicine used to treat chronic nephritis, nephrotic syndrome, diabetic nephropathy, and colonic inflammation.

PURPOSE

This study aimed to explore the influence of the total flavone of AM flowers (TFA) on acute ulcerative colitis (UC) and the potential underlying mechanism.

METHODS

Efficacy of TFA (30, 60, 120 mg/kg) on UC was evaluated in a dextran sodium sulphate (DSS)-induced colonic inflammatory mouse model by analyzing disease activity index (DAI), histopathological score, colon length, and cytokine expression. Expression levels of critical adhesion molecules and nuclear factor kappa B (NF-κB) were examined by qRT-PCR, Western blotting, or immunofluorescence labeling. Myeloperoxidase activity was examined using ELISA. In vitro THP-1 adhesion assay was used to evaluate monocyte adhesion.

RESULTS

TFA significantly reduced DAI score, prevented colon shortening, and ameliorated histological injuries of colons in DSS-treated mice. TFA inhibited the expression of cytokines (IL-1β and TNF-α) and adhesion molecules (ICAM-1, VCAM-1, and MAdCAM-1) in colon tissues of DSS mice. In vitro studies on mesenteric arterial endothelial cells (MAECs) showed that TFA attenuated TNF-α-induced upregulation of ICAM-1, VCAM-1, and MAdCAM-1, as well as THP-1 cell adhesion to MAECs. TFA also suppressed the phosphorylation and nuclear translocation of NF-κB in MAECs.

CONCLUSION

TFA efficaciously ameliorates UC possibly by inhibiting monocyte adhesion through blocking TNF-α-induced NF-κB activation, which in turn suppresses the upregulation of adhesive molecules in colon endothelial cells. Inhibiting the expression of adhesion molecule in MAECs may represent a useful strategy for therapeutic development to treat UC, with TFA being a safe and efficacious therapeutic agent.

Six Decades of History of Hypertension Research at the University of Toledo: Highlighting Pioneering Contributions in Biochemistry, Genetics, and Host-Microbiota Interactions

PURPOSE OF REVIEW

The study aims to capture the history and lineage of hypertension researchers from the University of Toledo in Ohio and showcase their collective scientific contributions dating from their initial discoveries of the physiology of adrenal and renal systems and genetics regulating blood pressure (BP) to its more contemporary contributions including microbiota and metabolomic links to BP regulation.

RECENT FINDINGS

The University of Toledo College of Medicine and Life Sciences (UTCOMLS), previously known as the Medical College of Ohio, has contributed significantly to our understanding of the etiology of hypertension. Two of the scientists, Patrick Mulrow and John Rapp from UTCOMLS, have been recognized with the highest honor, the Excellence in Hypertension award from the American Heart Association for their pioneering work on the physiology and genetics of hypertension, respectively. More recently, Bina Joe has continued their legacy in the basic sciences by uncovering previously unknown novel links between microbiota and metabolites to the etiology of hypertension, work that has been recognized by the American Heart Association with multiple awards. On the clinical research front, Christopher Cooper and colleagues lead the CORAL trials and contributed importantly to the investigations on renal artery stenosis treatment paradigms. Hypertension research at this institution has not only provided these pioneering insights, but also grown careers of scientists as leaders in academia as University Presidents and Deans of Medical Schools. Through the last decade, the university has expanded its commitment to Hypertension research as evident through the development of the Center for Hypertension and Precision Medicine led by Bina Joe as its founding Director. Hypertension being the top risk factor for cardiovascular diseases, which is the leading cause of human mortality, is an important area of research in multiple international universities. The UTCOMLS is one such university which, for the last 6 decades, has made significant contributions to our current understanding of hypertension. This review is a synthesis of this rich history. Additionally, it also serves as a collection of audio archives by more recent faculty who are also prominent leaders in the field of hypertension research, including John Rapp, Bina Joe, and Christopher Cooper, which are cataloged at Interviews .

Role of mechanosensitive channels/receptors in atherosclerosis

Mechanical forces are critical physical cues that can affect numerous cellular processes regulating the development, tissue maintenance, and functionality of cells. The contribution of mechanical forces is especially crucial in the vascular system where it is required for embryogenesis and for maintenance of physiological function in vascular cells including aortic endothelial cells, resident macrophages, and smooth muscle cells. Emerging evidence has also identified a role of these mechanical cues in pathological conditions of the vascular system such as atherosclerosis and associated diseases like hypertension. Of the different mechanotransducers, mechanosensitive ion channels/receptors are gaining prominence due to their involvement in numerous physiological and pathological conditions. However, only a handful of potential mechanosensory ion channels/receptors have been shown to be involved in atherosclerosis, and their precise role in disease development and progression remains poorly understood. Here, we provide a comprehensive account of recent studies investigating the role of mechanosensitive ion channels/receptors in atherosclerosis. We discuss the different groups of mechanosensitive proteins and their specific roles in inflammation, endothelial dysfunction, macrophage foam cell formation, and lesion development, which are crucial for the development and progression of atherosclerosis. Results of the studies discussed here will help in developing an understanding of the current state of mechanobiology in vascular diseases, specifically in atherosclerosis, which may be important for the development of innovative and targeted therapeutics for this disease.

P2X4 deficiency reduces atherosclerosis and plaque inflammation in mice

Extracellular adenosine-5′-triphosphate (ATP) acts as an import signaling molecule mediating inflammation via purinergic P2 receptors. ATP binds to the purinergic receptor P2X₄ and promotes inflammation via increased expression of pro-inflammatory cytokines. Because of the central role of inflammation, we assumed a functional contribution of the ATP-P2X₄-axis in atherosclerosis. Expression of P2X₄ was increased in atherosclerotic aortic arches from low-density lipoprotein receptor-deficient mice being fed a high cholesterol diet as assessed by real-time polymerase chain reaction and immunohistochemistry. To investigate the functional role of P2X₄ in atherosclerosis, P2X₄-deficient mice were crossed with low-density lipoprotein receptor-deficient mice and fed high cholesterol diet. After 16 weeks, P2X₄-deficient mice developed smaller atherosclerotic lesions compared to P2X₄-competent mice. Furthermore, intravital microscopy showed reduced ATP-induced leukocyte rolling at the vessel wall in P2X₄-deficient mice. Mechanistically, we found a reduced RNA expression of CC chemokine ligand 2 (CCL-2), C-X-C motif chemokine-1 (CXCL-1), C-X-C motif chemokine-2 (CXCL-2), Interleukin-6 (IL-6) and tumor necrosis factor α (TNFα) as well as a decreased nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3)-inflammasome priming in atherosclerotic plaques from P2X₄-deficient mice. Moreover, bone marrow derived macrophages isolated from P2X₄-deficient mice revealed a reduced ATP-mediated release of CCL-2, CC chemokine ligand 5 (CCL-5), Interleukin-1β (IL-1β) and IL-6. Additionally, P2X₄-deficient mice shared a lower proportion of pro-inflammatory Ly6C^high monocytes and a higher proportion of anti-inflammatory Ly6C^low monocytes, and expressend less endothelial VCAM-1. Finally, increased P2X₄ expression in human atherosclerotic lesions from carotid endarterectomy was found, indicating the importance of potential implementations of this study’s findings for human atherosclerosis. Collectively, P2X₄ deficiency reduced experimental atherosclerosis, plaque inflammation and inflammasome priming, pointing to P2X₄ as a potential therapeutic target in the fight against atherosclerosis.

Function of the P2X7 receptor in hematopoiesis and leukemogenesis

Adenosine triphosphate (ATP) accumulates at tissue injury and inflammation sites. The P2X7 receptor is an ATP-gated ion channel known for its cytotoxic activity. However, P2X7 receptors also play important roles in the growth of cancer and the immune regulation. Functional P2X7 receptor is widely expressed in murine and human hematopoietic stem cells and their lineages, including monocytes, macrophages, mast cells, and B or T lymphocytes, and participates in various physiological and pathologic activities. Therefore, it is not surprising that the P2X7 receptor is important for the normal hematopoiesis and leukemogenesis. Here, we summarize the biological functions of P2X7 receptor during both normal hematopoiesis and leukemogenesis. In particular, we found that ATP levels are dramatically increased in the leukemic bone marrow niche and the fates of leukemia-initiating cells of acute myeloid leukemia are tightly controlled by P2X7 expression and ATP-P2X7-mediated signaling pathways. These findings strongly indicate that the P2X7 receptor may be considered a potential biomarker of hematological malignancies in bone marrow niches, and its antagonists may be useful for the leukemia treatment in addition to the traditional chemotherapy.

A Selective TRPC3 Inhibitor Pyr3 Attenuates Myocardial Ischemia/Reperfusion Injury in Mice

An emerging body of evidence indicates that transient receptor potential TRP channels act as important mediators for a wide variety of physiological functions and are potential targets for drug discovery. Our previous study has identified transient receptor potential channel 3 (TRPC3) and TRPC6 as cation channels through which most of the damaging calcium enters, aggravates pathological changes in vivo and increases ischemia/reperfusion (I/R) injury in mice. This study aimed to verify the effects of TRPC3 inhibitor Pyr3 on myocardial I/R injury in mice. C57BL/6J wild-type male mice (8 to 12 weeks old) were anesthetized with 3.3% chloral hydrate. A murine I (30 min)/R (24 h) injury model was established by temporary occlusion of the left anterior descending (LAD) coronary artery. Pyr3 was administered at concentrations of 0, 2.5, 5, or 10 mg/kg via the right jugular vein 5 min before reperfusion. We observed that the selective TRPC3 inhibitor, 10 mg/kg Pyr3, significantly decreased the infarct size of left ventricle, and reduced the myocardial cell apoptosis rate and inflammatory response in mice. In a conclusion, TRPC3 can function as a candidate target for I/R injury prevention, and Pyr3 may directly bind to TRPC3 channel protein, inhibit TRPC3 channel activity, and improve TRPC3-related myocardial I/R injury. Pyr3 may be used for clarification of TRPC3 functions and for treatments of TRPC3-mediated diseases.

Transient Receptor Potential Channels and Endothelial Cell Calcium Signaling

The vascular endothelium is a broadly distributed and highly specialized organ. The endothelium has a number of functions including the control of blood vessels diameter through the production and release of potent vasoactive substances or direct electrical communication with underlying smooth muscle cells, regulates the permeability of the vascular barrier, stimulates the formation of new blood vessels, and influences inflammatory and thrombotic processes. Endothelial cells that make up the endothelium express a variety of cell-surface receptors and ion channels on the plasma membrane that are capable of detecting circulating hormones, neurotransmitters, oxygen tension, and shear stress across the vascular wall. Changes in these stimuli activate signaling cascades that initiate an appropriate physiological response. Increases in the global intracellular Ca²⁺ concentration and localized Ca²⁺ signals that occur within specialized subcellular microdomains are fundamentally important components of many signaling pathways in the endothelium. The transient receptor potential (TRP) channels are a superfamily of cation-permeable ion channels that act as a primary means of increasing cytosolic Ca²⁺ in endothelial cells. Consequently, TRP channels are vitally important for the major functions of the endothelium. In this review, we provide an in-depth discussion of Ca²⁺ -permeable TRP channels in the endothelium and their role in vascular regulation. © 2019 American Physiological Society. Compr Physiol 9:1249-1277, 2019.

Atheroprone flow activates inflammation via endothelial ATP-dependent P2X7-p38 signalling

Objective

Atherosclerosis is a focal disease occurring at arterial sites of disturbed blood flow that generates low oscillating shear stress. Endothelial inflammatory signalling is enhanced at sites of disturbed flow via mechanisms that are incompletely understood. The influence of disturbed flow on endothelial adenosine triphosphate (ATP) receptors and downstream signalling was assessed.

Methods and results

Cultured human endothelial cells were exposed to atheroprotective (high uniform) or atheroprone (low oscillatory) shear stress for 72 h prior to assessment of ATP responses. Imaging of cells loaded with a calcium-sensitive fluorescent dye revealed that atheroprone flow enhanced extracellular calcium influx in response to 300 µM 2'(3')-O-(4-Benzoylbenzoyl) adenosine-5'-triphosphate. Pre-treatment with pharmacological inhibitors demonstrated that this process required purinergic P2X7 receptors. The mechanism involved altered expression of P2X7, which was induced by atheroprone flow conditions in cultured cells. Similarly, en face staining of the murine aorta revealed enriched P2X7 expression at an atheroprone site. Functional studies in cultured endothelial cells showed that atheroprone flow induced p38 phosphorylation and up-regulation of E-selectin and IL-8 secretion via a P2X7-dependent mechanism. Moreover, genetic deletion of P2X7 significantly reduced E-selectin at atheroprone regions of the murine aorta.

Conclusions

These findings reveal that P2X7 is regulated by shear forces leading to its accumulation at atheroprone sites that are exposed to disturbed patterns of blood flow. P2X7 promotes endothelial inflammation at atheroprone sites by transducing ATP signals into p38 activation. Thus P2X7 integrates vascular mechanical responses with purinergic signalling to promote endothelial dysfunction and may provide an attractive potential therapeutic target to prevent or reduce atherosclerosis.

TRPC3-mediated Ca2+ signals as a promising strategy to boost therapeutic angiogenesis in failing hearts: The role of autologous endothelial colony forming cells

Endothelial progenitor cells (EPCs) are a sub-population of bone marrow-derived mononuclear cells that are released in circulation to restore damaged endothelium during its physiological turnover or rescue blood perfusion after an ischemic insult. Additionally, they may be mobilized from perivascular niches located within larger arteries' wall in response to hypoxic conditions. For this reason, EPCs have been regarded as an effective tool to promote revascularization and functional recovery of ischemic hearts, but clinical application failed to exploit the full potential of patients-derived cells. Indeed, the frequency and biological activity of EPCs are compromised in aging individuals or in subjects suffering from severe cardiovascular risk factors. Rejuvenating the reparative phenotype of autologous EPCs through a gene transfer approach has, therefore, been put forward as an alternative approach to enhance their therapeutic potential in cardiovascular patients. An increase in intracellular Ca²⁺ concentration constitutes a pivotal signal for the activation of the so-called endothelial colony forming cells (ECFCs), the only known truly endothelial EPC subset. Studies from our group showed that the Ca²⁺ toolkit differs between peripheral blood- and umbilical cord blood (UCB)-derived ECFCs. In the present article, we first discuss how VEGF uses repetitive Ca²⁺ spikes to regulate angiogenesis in ECFCs and outline how VEGF-induced intracellular Ca²⁺ oscillations differ between the two ECFC subtypes. We then hypothesize about the possibility to rejuvenate the biological activity of autologous ECFCs by transfecting the cell with the Ca²⁺ -permeable channel Transient Receptor Potential Canonical 3, which selectively drives the Ca²⁺ response to VEGF in UCB-derived ECFCs.

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.

Impairment of Coronary Endothelial Function by Hypoxia-Reoxygenation Involves TRPC3 Inhibition-mediated KCa Channel Dysfunction: Implication in Ischemia-Reperfusion Injury

Despite increasing knowledge of the significance of calcium-activated potassium (K_Ca) and canonical transient receptor potential (TRPC) channels in endothelial physiology, no studies so far have investigated the link between these two distinct types of channels in the control of vascular tone in pathological conditions. We previously demonstrated that hypoxia-reoxygenation (H-R) inhibits endothelial K_Ca and TRPC3 channels in porcine coronary arteries (PCAs). The present study further investigated whether modulation of TRPC3 is involved in H-R-induced K_Ca channel inhibition and associated vasodilatory dysfunction using approaches of wire myography, whole-cell voltage-clamp, and coimmunoprecipitation. Pharmacological inhibition or siRNA silencing of TRPC3 significantly suppressed bradykinin-induced intermediate- and small-conductance K_Ca (IK_Ca and SK_Ca) currents in endothelial cells of PCAs (PCAECs). TRPC3 protein exists in physical association with neither IK_Ca nor SK_Ca. In H-R-exposed PCAECs, the response of IK_Ca and SK_Ca to bradykinin-stimulation and to TRPC3-inhibition was markedly weakened. Activation of TRPC3 channels restored H-R-suppressed K_Ca currents in association with an improved endothelium-derived hyperpolarizing factor (EDHF)-type vasorelaxation. We conclude that inhibition of TRPC3 channels contributes to H-R-induced suppression of K_Ca channel activity, which serves as a mechanism underlying coronary endothelial dysfunction in ischemia-reperfusion (I-R) injury and renders TRPC3 a potential target for endothelial protection in I-R conditions.

Protein Interactions at Endothelial Junctions and Signaling Mechanisms Regulating Endothelial Permeability

The monolayer of endothelial cells lining the vessel wall forms a semipermeable barrier (in all tissue except the relatively impermeable blood-brain and inner retinal barriers) that regulates tissue-fluid homeostasis, transport of nutrients, and migration of blood cells across the barrier. Permeability of the endothelial barrier is primarily regulated by a protein complex called adherens junctions. Adherens junctions are not static structures; they are continuously remodeled in response to mechanical and chemical cues in both physiological and pathological settings. Here, we discuss recent insights into the post-translational modifications of junctional proteins and signaling pathways regulating plasticity of adherens junctions and endothelial permeability. We also discuss in the context of what is already known and newly defined signaling pathways that mediate endothelial barrier leakiness (hyperpermeability) that are important in the pathogenesis of cardiovascular and lung diseases and vascular inflammation.

On the Roles of the Transient Receptor Potential Canonical 3 (TRPC3) Channel in Endothelium and Macrophages: Implications in Atherosclerosis

In the cardiovascular and hematopoietic systems the Transient Receptor Potential Canonical 3 (TRPC3) channel has a well-recognized role in a number of signaling mechanisms that impact the function of diverse cells and tissues in physiology and disease. The latter includes, but is not limited to, molecular and cellular mechanisms associated to the pathogenesis of cardiac hypertrophy, hypertension and endothelial dysfunction. Despite several of these functions being closely related to atherorelevant mechanisms, the potential roles of TRPC3 in atherosclerosis, the major cause of coronary artery disease, have remained largely unexplored. Over recent years, a series of studies from the authors' laboratory revealed novel functions of TRPC3 in mechanisms related to endothelial inflammation, monocyte adhesion to endothelium and survival and apoptosis of macrophages. The relevance of these new TRPC3 functions to atherogenesis has recently began to receive validation through studies in mouse models of atherosclerosis with conditional gain or loss of TRPC3 function. This chapter summarizes these novel findings and provides a discussion of their impact in the context of atherosclerosis, in an attempt to delineate a framework for further exploration of this terra incognita in the TRPC field.

"TRP inflammation" relationship in cardiovascular system

Despite considerable advances in the research and treatment, the precise relationship between inflammation and cardiovascular (CV) disease remains incompletely understood. Therefore, understanding the immunoinflammatory processes underlying the initiation, progression, and exacerbation of many cardiovascular diseases is of prime importance. The innate immune system has an ancient origin and is well conserved across species. Its activation occurs in response to pathogens or tissue injury. Recent studies suggest that altered ionic balance, and production of noxious gaseous mediators link to immune and inflammatory responses with altered ion channel expression and function. Among plausible candidates for this are transient receptor potential (TRP) channels that function as polymodal sensors and scaffolding proteins involved in many physiological and pathological processes. In this review, we will first focus on the relevance of TRP channel to both exogenous and endogenous factors related to innate immune response and transcription factors related to sustained inflammatory status. The emerging role of inflammasome to regulate innate immunity and its possible connection to TRP channels will also be discussed. Secondly, we will discuss about the linkage of TRP channels to inflammatory CV diseases, from a viewpoint of inflammation in a general sense which is not restricted to the innate immunity. These knowledge may serve to provide new insights into the pathogenesis of various inflammatory CV diseases and their novel therapeutic strategies.

Pannexin 1 channels regulate leukocyte emigration through the venous endothelium during acute inflammation

Inflammatory cell recruitment to local sites of tissue injury and/or infection is controlled by a plethora of signalling processes influencing cell-to-cell interactions between the vascular endothelial cells (ECs) in post-capillary venules and circulating leukocytes. Recently, ATP-sensitive P₂Y purinergic receptors have emerged as downstream regulators of EC activation in vascular inflammation. However, the mechanism(s) regulating cellular ATP release in this response remains elusive. Here we report that the ATP-release channel Pannexin1 (Panx1) opens downstream of EC activation by TNF-α. This process involves activation of type-1 TNF receptors, recruitment of Src family kinases (SFK) and SFK-dependent phosphorylation of Panx1. Using an inducible, EC-specific Panx1 knockout mouse line, we report a previously unidentified role for Panx1 channels in promoting leukocyte adhesion and emigration through the venous wall during acute systemic inflammation, placing Panx1 channels at the centre of cytokine crosstalk with purinergic signalling in the endothelium.

Endothelial cell activation by inflammation requires extracellular ATP release. Here the authors show that TNF-α induces Src-family kinase-dependent ATP release by Pannexin1 channels in endothelial cells, and that Pannexin1 is required for leukocyte adhesion and emigration into the inflamed tissue.

Pharmacological evidence for a role of the transient receptor potential canonical 3 (TRPC3) channel in endoplasmic reticulum stress-induced apoptosis of human coronary artery endothelial cells

Unresolved endoplasmic reticulum (ER) stress, with the subsequent persistent activation of the unfolded protein response (UPR) is a well-recognized mechanism of endothelial cell apoptosis with a major impact on the integrity of the endothelium during the course of cardiovascular diseases. As in other cell types, Ca(2+) influx into endothelial cells can promote ER stress and/or contribute to mechanisms associated with it. In previous work we showed that in human coronary artery endothelial cells (HCAECs) the Ca(2+)-permeable non-selective cation channel Transient Receptor Potential Canonical 3 (TRPC3) mediates constitutive Ca(2+) influx which is critical for operation of inflammatory signaling in these cells, through a mechanism that entails coupling of TRPC3 constitutive function to activation of Ca(2+)/calmodulin-dependent protein kinase II (CAMKII). TRPC3 has been linked to UPR signaling and apoptosis in cells other than endothelial, and CAMKII is a mediator of ER stress-induced apoptosis in various cell types, including endothelial cells. In the present work we used a pharmacological approach to examine whether in HCAECs TRPC3 and CAMKII also contribute to mechanisms of ER stress-induced apoptosis. The findings show for the first time that in HCAECs activation of the UPR and the subsequent ER stress-induced apoptosis exhibit a strong requirement for constitutive Ca(2+) influx and that TRPC3 contributes to this process. In addition, we obtained evidence indicating that, similar to its roles in non-endothelial cells, CAMKII participates in ER stress-induced apoptosis in HCAECs.

Increased size and cellularity of advanced atherosclerotic lesions in mice with endothelial overexpression of the human TRPC3 channel

In previous in vitro studies, we showed that Transient Receptor Potential Canonical 3 (TRPC3), a calcium-permeable, nonselective cation channel endowed with high constitutive function, is an obligatory component of the inflammatory signaling that controls expression of the vascular cell adhesion molecule-1 (VCAM-1) and monocyte adhesion to coronary artery endothelial cells. Also, TRPC3 expression in these cells was found to be up-regulated by proatherogenic factors, which enhanced inflammation and VCAM-1 expression. However, it remained to be determined whether these in vitro findings were of relevance to atherosclerotic lesion development in vivo. To answer this important question in the present work, we generated mice with endothelial-specific overexpression of human TRPC3 in an Apoe knockout background (TgEST3ApoeKO) and examined lesions in the aortic sinus following 10 and 16 wk on a high-fat diet. No significant differences were found in size or complexity of early stage lesions (10 wk). However, advanced plaques (16 wk) from TgEST3ApoeKO mice exhibited a significant increase in size and macrophage content compared with nontransgenic littermate controls. Remarkably, this change was correlated with increased VCAM-1 and phospho-IkBα immunoreactivity along the endothelial lining of lesions from transgenic animals compared with controls. These findings validate the in vivo relevance of previous in vitro findings and represent, to our knowledge, the first in vivo evidence for a proatherogenic role of endothelial TRPC3.

Protection of coronary endothelial function during cardiac surgery: potential of targeting endothelial ion channels in cardioprotection

Vascular endothelium plays a critical role in the control of blood flow by producing vasoactive factors to regulate vascular tone. Ion channels, in particular, K⁺ channels and Ca²⁺-permeable channels in endothelial cells, are essential to the production and function of endothelium-derived vasoactive factors. Impairment of coronary endothelial function occurs in open heart surgery that may result in reduction of coronary blood flow and thus in an inadequate myocardial perfusion. Hyperkalemic exposure and concurrent ischemia-reperfusion during cardioplegic intervention compromise NO and EDHF-mediated function and the impairment involves alterations of K⁺ channels, that is, K_ATP and K_Ca, and Ca²⁺-permeable TRP channels in endothelial cells. Pharmacological modulation of these channels during ischemia-reperfusion and hyperkalemic exposure show promising results on the preservation of NO and EDHF-mediated endothelial function, which suggests the potential of targeting endothelial K⁺ and TRP channels for myocardial protection during cardiac surgery.

The histone variant MacroH2A regulates Ca(2+) influx through TRPC3 and TRPC6 channels

The histone variant macroH2A replaces canonical H2A in the designated region of chromatin where its incorporation has the potential to establish a functionally distinct chromatin domain. The transient receptor potential canonical (TRPC) channels are a family of Ca²⁺-permeable cationic channels controlling changes in the cytosolic Ca²⁺ concentration. The proper regulation of Trpc gene expression requires chromatin remodeling, but little is known about the nature of these regulatory processes. Here, we show that macroH2A1 represses two Trpc family genes, Trpc3 and Trpc6, and attenuates Ca²⁺-dependent proliferative responses in bladder cancer cells. MacroH2A1 recruits histone deacetylase 1 (HDAC1) and HDAC2 to facilitate its persistent action, resulting in a compromise of histone acetylation across the Trpc3 and Trpc6 loci. Further, macroH2A1 depletion augments histone acetylation and Ca²⁺ influx, leading to increased cell growth and invasion. Our data provide new insights into TRPC3/TRPC6-mediated Ca²⁺ signaling and indicate a central role for macroH2A1 in regulating transcriptional competence of Trpc3 and Trpc6 genes.

Transient receptor potential canonical type 3 channels--their evolving role in hypertension and its related complications

: Recent studies indicate that transient receptor potential canonical type 3 (TRPC3) channels contribute to the regulation of blood pressure and vascular and renal function. Several studies show that TRPC3 dysfunction is associated with hypertension, atherosclerosis, cardiac hypertrophy, and cerebrovascular events. In this review, we summarize the role of TRPC3 channels in the cardiovascular system, and we focus on their pathophysiological role in hypertension and related target organ damages. We provide new insight into the involvement of TRPC3 channels in the development of hypertension and its related complications.

Canonical transient receptor potential 3 channel triggers vascular endothelial growth factor-induced intracellular Ca2+ oscillations in endothelial progenitor cells isolated from umbilical cord blood

Endothelial colony-forming cells (ECFCs) are the only endothelial progenitor cells (EPCs) that are capable of acquiring a mature endothelial phenotype. ECFCs are mainly mobilized from bone marrow to promote vascularization and represent a promising tool for cell-based therapy of severe ischemic diseases. Vascular endothelial growth factor (VEGF) stimulates the proliferation of peripheral blood-derived ECFCs (PB-ECFCs) through oscillations in intracellular Ca(2+) concentration ([Ca(2+)]i). VEGF-induced Ca(2+) spikes are driven by the interplay between inositol-1,4,5-trisphosphate (InsP3)-dependent Ca(2+) release and store-operated Ca(2+) entry (SOCE). The therapeutic potential of umbilical cord blood-derived ECFCs (UCB-ECFCs) has also been shown in recent studies. However, VEGF-induced proliferation of UCB-ECFCs is faster compared with their peripheral counterpart. Unlike PB-ECFCs, UCB-ECFCs express canonical transient receptor potential channel 3 (TRPC3) that mediates diacylglycerol-dependent Ca(2+) entry. The present study aimed at investigating whether the higher proliferative potential of UCB-ECFCs was associated to any difference in the molecular underpinnings of their Ca(2+) response to VEGF. We found that VEGF induces oscillations in [Ca(2+)]i that are patterned by the interaction between InsP3-dependent Ca(2+) release and SOCE. Unlike PB-ECFCs, VEGF-evoked Ca(2+) oscillations do not arise in the absence of extracellular Ca(2+) entry and after pharmacological (with Pyr3 and flufenamic acid) and genetic (by employing selective small interference RNA) suppression of TRPC3. VEGF-induced UCB-ECFC proliferation is abrogated on inhibition of the intracellular Ca(2+) spikes. Therefore, the Ca(2+) response to VEGF in UCB-ECFCs is shaped by a different Ca(2+) machinery as compared with PB-ECFCs, and TRPC3 stands out as a promising target in EPC-based treatment of ischemic pathologies.

Macrophage function in atherosclerosis: potential roles of TRP channels

Cation channels of the Transient Receptor Potential Canonical (TRPC) group, which belong to the larger TRP superfamily of channel proteins, are critical players in cardiovascular disease. Recent studies underscored a role of TRPC3 in macrophage survival and efferocytosis, two critical events in atherosclerosis lesion development. Also, other members of the TRP channel superfamily are found expressed in monocytes/macrophages, where they participate in processes that might be of significance to atherogenesis. These observations set a framework for future studies aimed at defining the ultimate functions not only of TRPC3, but probably other TRP channels, in macrophage biology. The purpose of this manuscript is to provide a timely revision of existing evidence on the role of members of the TRP channel superfamily, in particular TRPCs, in macrophages and discuss it in the context of the macrophage's function in atherogenesis.

Role of TRPC3 channel in human internal mammary artery

BACKGROUND AND AIMS

Intracellular calcium regulation in endothelial cells depends on transient receptor potential channels (TRPs). Canonical TRPs (TRPCs) are now recognized as the most important Ca(2+)-permeable cation channels in vascular endothelium and TRPC3 channel is reported to play a role in vasodilation in animal vessels. However, little is known about the role of TRPCs in human arteries. We therefore tested the hypothesis that TRPCs play a role in human arteries.

METHODS

Cumulative concentration-relaxation curves to acetylcholine (-11 to -4.5 log M) were established in the human internal mammary artery (IMA) rings (n = 42) taken from 28 patients undergoing coronary artery bypass grafting in precontraction induced by U46619 (-8 log M) in the absence or presence of SKF96365 (10 μmol/L) or Pyr3 (3 μmol/L). Protein expressions of TRPC3 were determined by Western blot and immunohistochemistry staining.

RESULTS

The maximal relaxation induced by acetylcholine was significantly attenuated by the nonspecific cation channels inhibitor, SKF96365 (48.2 ± 3.7 vs. 66.0 ± 0.9% in control, p <0.01) or the selective TRPC3 blocker, Pyr3 (58.4 ± 2.3% vs. 67.7 ± 1.1% in control, p <0.01). Protein expression of TRPC3 was detected in human IMA.

CONCLUSIONS

TRPC3 exists and plays a role in the acetylcholine-induced endothelium-dependent relaxation in the human IMA. This study suggests that TRPC3 may be a potential new target in endothelial protection in patients with endothelial dysfunction such as in patients with coronary artery disease in order to improve the long-term patency of the grafting vessels.

Update on vascular endothelial Ca2+ signalling: A tale of ion channels, pumps and transporters

A monolayer of endothelial cells (ECs) lines the lumen of blood vessels and forms a multifunctional transducing organ that mediates a plethora of cardiovascular processes. The activation of ECs from as state of quiescence is, therefore, regarded among the early events leading to the onset and progression of potentially lethal diseases, such as hypertension, myocardial infarction, brain stroke, and tumor. Intracellular Ca²⁺ signals have long been know to play a central role in the complex network of signaling pathways regulating the endothelial functions. Notably, recent work has outlined how any change in the pattern of expression of endothelial channels, transporters and pumps involved in the modulation of intracellular Ca²⁺ levels may dramatically affect whole body homeostasis. Vascular ECs may react to both mechanical and chemical stimuli by generating a variety of intracellular Ca²⁺ signals, ranging from brief, localized Ca²⁺ pulses to prolonged Ca²⁺ oscillations engulfing the whole cytoplasm. The well-defined spatiotemporal profile of the subcellular Ca²⁺ signals elicited in ECs by specific extracellular inputs depends on the interaction between Ca²⁺ releasing channels, which are located both on the plasma membrane and in a number of intracellular organelles, and Ca²⁺ removing systems. The present article aims to summarize both the past and recent literature in the field to provide a clear-cut picture of our current knowledge on the molecular nature and the role played by the components of the Ca²⁺ machinery in vascular ECs under both physiological and pathological conditions.

Monocyte-endothelial adhesion is modulated by Cx43-stimulated ATP release from monocytes

Adhesion of circulating monocytes to vascular endothelial cells is a crucial event in development of vascular inflammatory conditions, including atherosclerosis. We investigated the roles of connexin43 (Cx43) and ATP release on monocyte-endothelial adhesion. Cx43 function and expression were manipulated by connexin channel inhibitors, overexpression and siRNA. Connexin channel inhibitors rapidly decreased ATP release from U937 monocytes and increased adhesion to human umbilical vein endothelial cells (HUVEC). Monocyte ATP release correlated with Cx43 expression, not with Cx37 expression. Exogenous adenosine (ADO) or ATP decreased adhesion, and inhibition of ATP conversion to ADO increased adhesion. We infer that monocyte Cx43 channel activity causes ATP release, likely via Cx43-containing hemichannels, and that ATP decreases adhesion via conversion to ADO. Inhibition of HUVEC connexin channel activity did not affect ATP release or adhesion. In contrast, expression of Cx43 protein in U937 cells enhanced adhesion. Thus, Cx43 channel function and expression have opposite effects: Cx43 channel function in monocytes, but not in HUVEC, rapidly decreases adhesion via ATP release and conversion to ADO, whereas Cx43 expression itself enhances adhesion. These studies suggest that local regulation of monocyte Cx43 activity within the vasculature can dynamically modulate the monocyte-endothelial adhesion that is an initiating event in vascular inflammatory pathologies, with the baseline adhesion set by Cx43 expression levels. This balance of rapid and tonic influences may be crucial in development of vascular pathologies.

Canonical transient receptor potential channels in diabetes

Canonical transient receptor potential (TRPC) channel proteins have been identified as downstream molecules in a G protein-coupled receptor signaling pathway and are involved in a variety of cell functions due to their ability to regulate intracellular calcium signaling. TRPC channel physiology has been an increasingly interesting and relevant topic over the last decade, and the outcomes from various studies have advanced our understanding of TRPC function in the normal state. Recently, attention has turned to whether or not TRPC proteins are implicated in diseases. Emerging evidence suggests a significant contribution of several isoforms of TRPC proteins to cardiovascular as well as renal diseases. This review focuses on the implication of TRPC proteins as they pertain to diabetes. We summarize the recent findings by other investigators as well as ourselves and additionally discuss the important role of TRPC proteins in the development of various diabetic complications, such as diabetic nephropathy and diabetic vasculopathy. The underlying mechanisms which contribute to these complications are also outlined. Lastly, we elaborate on the role of TRPC proteins as a potential therapeutic target for treating diabetes-associated diseases.

Evidence for operation of nicotinic and muscarinic acetylcholine receptor-dependent survival pathways in human coronary artery endothelial cells

Nicotinic acetylcholine receptors (nAChRs) have recently emerged as critical players in modulation of endothelial function. In particular, studies on endothelial cells from different vascular beds have shown anti-apoptotic actions of nicotinic stimulation, but whether there is actually activation of survival signaling downstream nAChR function has not been explored. In the present work we used human coronary artery endothelial cells (HCAECs) and a pharmacological approach to examine the impact of cholinergic stimulation on survival signaling pathways. Our findings show that cholinergic receptors promote activation of three typical survival routes: the phosphatidyl-inositol-3-kinase (PI3K)/AKT axis, activated downstream muscarinic and nAChRs; the JAK2/STAT3 axis, activated downstream nAChR; and ERK1/2 MAP kinases, activated by both muscarinic acetylcholine receptor (mAChR) and nAChR. Based on their sensitivity to α-bungarotoxin, nicotinic regulation of JAK2/STAT3 and ERK1/2 occurs downstream α7-nAChRs. The present findings suggest that in HCAECs the two cholinergic receptors may act concertedly to induce an efficient survival response of coronary cells when exposed to pro-apoptotic stimuli.

Impairment of survival signaling and efferocytosis in TRPC3-deficient macrophages

We have recently shown that in macrophages proper operation of the survival pathways phosphatidylinositol-3-kinase (PI3K)/AKT and nuclear factor kappa B (NFkB) has an obligatory requirement for constitutive, non-regulated Ca(2+) influx. In the present work we examined if Transient Receptor Potential Canonical 3 (TRPC3), a member of the TRPC family of Ca(2+)-permeable cation channels, contributes to the constitutive Ca(2+) influx that supports macrophage survival. We used bone marrow-derived macrophages obtained from TRPC3(-/-) mice to determine the activation status of survival signaling pathways, apoptosis and their efferocytic properties. Treatment of TRPC3(+/+) macrophages with the pro-apoptotic cytokine TNFα induced time-dependent phosphorylation of IκBα, AKT and BAD, and this was drastically reduced in TRPC3(-/-) macrophages. Compared to TRPC3(+/+) cells TRPC3(-/-) macrophages exhibited reduced constitutive cation influx, increased apoptosis and impaired efferocytosis. The present findings suggest that macrophage TRPC3, presumably through its constitutive function, contributes to survival signaling and efferocytic properties.

Requirement for non-regulated, constitutive calcium influx in macrophage survival signaling

The phosphatidylinositol-3-kinase (PI3K)/AKT axis and the Nuclear Factor kappa B (NFκB) pathway play critical roles in macrophage survival. In cells other than macrophages proper operation of those two pathways requires Ca²(+) influx into the cell, but if that is the case in macrophages remains unexplored. In the present work we used THP-1-derived macrophages and a pharmacological approach to examine for the first time the role of constitutive, non-regulated Ca²(+) influx in PI3K/AKT and NFκB signaling. Blocking constitutive function of Ca²(+)-permeable channels with the organic channel blocker SKF96365 completely prevented phosphorylation of IκBα, AKT and its downstream target BAD in TNFα-treated macrophages. A similar effect was observed upon treating macrophages with the calmodulin (CAM) inhibitor W-7 or the calmodulin-dependent kinase II (CAMKII) inhibitor KN-62. In addition, pre-treating macrophages with SKF96365 significantly enhanced TNFα-induced apoptosis. Our findings suggest that in THP-1-derived macrophages survival signaling depends, to a significant extent, on constitutive Ca²(+) influx presumably through a mechanism that involves the CAM/CAMKII axis as a coupling component between constitutive Ca²(+) influx and activation of survival signaling.

A gain-of-function SNP in TRPC4 cation channel protects against myocardial infarction

AIMS

The TRPC4 non-selective cation channel is widely expressed in the endothelium, where it generates Ca(2+) signals that participate in the endothelium-mediated vasodilatory response. This study sought to identify single-nucleotide polymorphisms (SNPs) in the TRPC4 gene that are associated with myocardial infarction (MI).

METHODS AND RESULTS

Our candidate-gene association studies identified a missense SNP (TRPC4-I957V) associated with a reduced risk of MI in diabetic patients [odds ratio (OR) = 0.61; confidence interval (CI), 0.40-0.95, P= 0.02]. TRPC4 was also associated with MI in the Wellcome Trust Case-Control Consortium's genome-wide data: an intronic SNP (rs7319926) within the same linkage disequilibrium block as TRPC4-I957V showed an OR of 0.86 (CI, 0.81-0.94; P =10(-4)). Functional studies of the missense SNP were carried out in HEK293 and CHO cells expressing wild-type or mutant channels. Patch-clamp studies and measurement of intracellular [Ca(2+)] in response to muscarinic agonists and direct G-protein activation showed increased channel activity in TRPC4-I957V-transfected cells compared with TRPC4-WT. Site-directed mutagenesis and molecular modelling of TRPC4-I957V suggested that the gain of function was due to the presence of a less bulky Val-957. This permits a firmer interaction between the TRPC4 and the catalytic site of the tyrosine kinase that phosphorylates TRPC4 at Tyr-959 and facilitates channel insertion into the plasma membrane.

CONCLUSION

We provide evidence for the association of a TRPC4 SNP with MI in population-based genetic studies. The higher Ca(2+) signals generated by TRPC4-I957V may ultimately facilitate the generation of endothelium- and nitric oxide-dependent vasorelaxation, thereby explaining its protective effect at the vasculature.

The Constitutive Function of Native TRPC3 Channels Modulates Vascular Cell Adhesion Molecule-1 Expression in Coronary Endothelial Cells Through Nuclear Factor κB Signaling

Rationale : Upregulation of endothelial vascular cell adhesion molecule (VCAM)-1 and the subsequent increase in monocyte recruitment constitute critical events in atherogenesis. We have recently shown that in human coronary artery endothelial cells (HCAECs) regulated expression of VCAM-1 depends, to a significant extent, on expression and function of the Ca 2+ -permeable channel transient receptor potential canonical (TRPC)3, regardless of the ability of the stimulatory signal to induce regulated Ca 2+ influx, leading to the hypothesis that TRPC3 constitutive, rather than regulated function, contributes to the underlying signaling mechanism.

Objective : The present studies addressed this important question and gathered mechanistic insight on the signaling coupling constitutive TRPC3 function to VCAM-1 expression.

Methods and Results : In HCAECs, maneuvers that prevent Ca 2+ influx or knockdown of TRPC3 markedly reduced tumor necrosis factor (TNF)α-induced VCAM-1 and monocyte adhesion. TNFα also induced TRPC3 expression and TRPC3-mediated constitutive cation influx and currents. Stable (HEK293 cells) or transient (HCAECs) overexpression of TRPC3 enhanced TNFα-induced VCAM-1 compared to wild-type cells. IκBα phosphorylation/degradation was reduced by TRPC3 knockdown and increased by channel overexpression. Inhibition of calmodulin completely prevented nuclear factor κB activation, whereas blocking calmodulin-dependent kinases or NADPH oxidases rendered partial inhibition.

Conclusions : Our findings indicate that in HCAECs expression of VCAM-1 and monocyte adhesion depend, to a significant extent, on TRPC3 constitutive function through a signaling mechanism that requires constitutive TRPC3-mediated Ca 2+ influx for proper activation of nuclear factor κB, presumably through Ca 2+ -dependent activation of the calmodulin/calmodulin-dependent kinase axis.

Transient receptor potential channels and vascular function

TRP (transient receptor potential) channels play important roles in the regulation of normal and pathological cellular function. In the vasculature, TRP channels are present both in ECs (endothelial cells) and vascular SMCs (smooth muscle cells) and contribute to vasomotor control mechanisms in most vascular beds. Vascular TRP channels are activated by various stimuli, such as mechanical perturbation, receptor activation and dietary molecules. Some of the specific roles of these channels in normal and impaired vascular function have emerged in recent years and include participation in vascular signalling processes, such as neurotransmission, hormonal signalling, NO production, myogenic tone and autoregulation of blood flow, thermoregulation, responses to oxidative stress and cellular proliferative activity. Current research is aimed at understanding the interactions of TRP channels with other vascular proteins and signalling mechanisms. These studies should reveal new targets for pharmacological therapy of vascular diseases, such as hypertension, ischaemia and vasospasm, and vascular proliferative states.

Inhibition of TRPC1/TRPC3 by PKG contributes to NO-mediated vasorelaxation

Nitric oxide (NO) inhibits transient receptor potential channel 3 (TRPC3) channels via a PKG-dependent mechanism. We sought to determine 1) whether NO inhibition of TRPC3 occurs in freshly isolated smooth muscle cells (SMC); and 2) whether NO inhibition of TRPC3 channels contributes to NO-mediated vasorelaxation. We tested these hypotheses in freshly isolated rat carotid artery (CA) SMC using patch clamp and in intact CA by vessel myograph. We demonstrated TRPC3 expression in whole CA (mRNA and protein) that was localized to the smooth muscle layers. TRPC1 protein was also expressed and coimmunoprecipitated with TRPC3. Whole cell patch clamp demonstrated nonselective cation channel currents that were activated by UTP (60 microM) and completely inhibited by a TRPC channel inhibitor, La(3+) (100 microM). The UTP-stimulated current (I(UTP)) was also inhibited by intracellular application of anti-TRPC3 or anti-TRPC1 antibody, but not by anti-TRPC6 or anti-TRPC4 control antibodies. We next evaluated the NO signaling pathway on I(UTP). Exogenous NO [(Z)-1-{N-methyl-N-[6(N-methylammoniohexyl)amino]}diazen-1-ium-1,2-diolate (MAHMA NONOate)] or a cell-permeable cGMP analog (8-bromo-cGMP) significantly inhibited I(UTP). Preapplication of a PKG inhibitor (KT5823) reversed the inhibition of MAHMA NONOate or 8-bromo-cGMP, demonstrating the critical role of PKG in NO inhibition of TRPC1/TRPC3. Intact CA segments were contracted with UTP (100 microM) in the presence or absence of La(3+) (100 microM) and then evaluated for relaxation to an NO donor, sodium nitroprusside (1 nM to 1 microM). Relaxation to sodium nitroprusside was significantly reduced in the La(3+) treatment group. We conclude that freshly isolated SMC express TRPC1/TRPC3 channels and that these channels are inhibited by NO/cGMP/PKG. Furthermore, NO contributes to vasorelaxation by inhibition of La(3+)-sensitive channels consistent with TRPC1/TRPC3.