Increased store-operated and 1-oleoyl-2-acetyl-sn-glycerol-induced calcium influx in monocytes is mediated by transient receptor potential canonical channels in human essential hypertension

Enhanced TRPC3 transcription through AT1R/PKA/CREB signaling contributes to mitochondrial dysfunction in renal tubular epithelial cells in D-galactose-induced accelerated aging mice

Aging-associated renal dysfunction promotes the pathogenesis of chronic kidney disease. Mitochondrial dysfunction in renal tubular epithelial cells is a hallmark of senescence and leads to accelerated progression of renal disorders. Dysregulated calcium profiles in mitochondria contribute to aging-associated disorders, but the detailed mechanism of this process is not clear. In this study, modulation of the sirtuin 1/angiotensin II type 1 receptor (Sirt1/AT1R) pathway partially attenuated renal glomerular sclerosis, tubular atrophy, and interstitial fibrosis in D-galactose (D-gal)-induced accelerated aging mice. Moreover, modulation of the Sirt1/AT1R pathway improved mitochondrial dysfunction induced by D-gal treatment. Transient receptor potential channel, subtype C, member 3 (TRPC3) upregulation mediated dysregulated cellular and mitochondrial calcium homeostasis during aging. Furthermore, knockdown or knockout (KO) of Trpc3 in mice ameliorated D-gal-induced mitochondrial reactive oxygen species production, membrane potential deterioration, and energy metabolism disorder. Mechanistically, activation of the AT1R/PKA pathway promoted CREB phosphorylation and nucleation of CRE2 binding to the Trpc3 promoter (-1659 to -1648 bp) to enhance transcription. Trpc3 KO significantly improved the renal disorder and cell senescence in D-gal-induced mice. Taken together, these results indicate that TRPC3 upregulation mediates age-related renal disorder and is associated with mitochondrial calcium overload and dysfunction. TRPC3 is a promising therapeutic target for aging-associated renal disorders.

The mechanisms of exercise improving cardiovascular function by stimulating Piezo1 and TRP ion channels: a systemic review

Mechanosensitive ion channels are widely distributed in the heart, lung, bladder and other tissues, and plays an important role in exercise-induced cardiovascular function promotion. By reviewing the PubMed databases, the results were summarized using the terms "Exercise/Sport", "Piezo1", "Transient receptor potential (TRP)" and "Cardiovascular" as the keywords, 124-related papers screened were sorted and reviewed. The results showed that: (1) Piezo1 and TRP channels play an important role in regulating blood pressure and the development of cardiovascular diseases such as atherosclerosis, myocardial infarction, and cardiac fibrosis; (2) Exercise promotes cardiac health, inhibits the development of pathological heart to heart failure, regulating the changes in the characterization of Piezo1 and TRP channels; (3) Piezo1 activates downstream signaling pathways with very broad pathways, such as AKT/eNOS, NF-κB, p38MAPK and HIPPO-YAP signaling pathways. Piezo1 and Irisin regulate nuclear localization of YAP and are hypothesized to act synergistically to regulate tissue mechanical properties of the cardiovascular system and (4) The cardioprotective effects of exercise through the TRP family are mostly accomplished through Ca2+ and involve many signaling pathways. TRP channels exert their important cardioprotective effects by reducing the TRPC3-Nox2 complex and mediating Irisin-induced Ca2+ influx through TRPV4. It is proposed that exercise stimulates the mechanosensitive cation channel Piezo1 and TRP channels, which exerts cardioprotective effects. The activation of Piezo1 and TRP channels and their downstream targets to exert cardioprotective function by exercise may provide a theoretical basis for the prevention of cardiovascular diseases and the rehabilitation of clinical patients.

Urinary polycyclic aromatic hydrocarbon metabolites were associated with hypertension in US adults: data from NHANES 2009-2016

Polycyclic aromatic hydrocarbons (PAHs) are widely existing organic pollutants in the environment, and their persistence in the environment makes us have to pay continuous attention to their health effects. However, since the American Heart Association updated its definition of hypertension in 2017, few studies have explored the relationship. This study aimed to investigate the relationship between PAH exposure and hypertension after the updated definition of hypertension and explore whether body mass index (BMI) moderates this relationship. A total of 6332 adult participants from the 2009-2016 National Health and Nutrition Examination Survey (NHANES) were examined. Multiple logistic regression and restricted cubic splines were used to analyze the association between urinary polycyclic aromatic hydrocarbon metabolites and hypertension, and the dose-response relationship. Weighted quantile sum (WQS) regression was applied to blood pressure to reveal multiple exposure effects and the relative weights of each PAH. The prevalence of hypertension in the study population was 48.52%. There was a positive dose-response relationship between high exposure to 1-hydroxynaphthalene, 2&3-hydroxyphenanthrene, and the risk of hypertension. Naphthalene metabolites accounted for the most significant proportion of systolic blood pressure, and phenanthrene metabolites accounted for the most significant proportion of diastolic blood pressure. Obese individuals with high PAH exposure were at greater risk for hypertension than individuals with low PAH exposure and normal BMI. Higher prevalence rate and stronger association of metabolites with outcomes were obtained in the general population of the USA under the new guideline. High levels of exposure to PAHs were positively associated with the risk of hypertension, and these effects were modified by BMI.

New Insights on the Role of TRP Channels in Calcium Signalling and Immunomodulation: Review of Pathways and Implications for Clinical Practice

Calcium is the most abundant mineral in the human body and is central to many physiological processes, including immune system activation and maintenance. Studies continue to reveal the intricacies of calcium signalling within the immune system. Perhaps the most well-understood mechanism of calcium influx into cells is store-operated calcium entry (SOCE), which occurs via calcium release-activated channels (CRACs). SOCE is central to the activation of immune system cells; however, more recent studies have demonstrated the crucial role of other calcium channels, including transient receptor potential (TRP) channels. In this review, we describe the expression and function of TRP channels within the immune system and outline associations with murine models of disease and human conditions. Therefore, highlighting the importance of TRP channels in disease and reviewing potential. The TRP channel family is significant, and its members have a continually growing number of cellular processes. Within the immune system, TRP channels are involved in a diverse range of functions including T and B cell receptor signalling and activation, antigen presentation by dendritic cells, neutrophil and macrophage bactericidal activity, and mast cell degranulation. Not surprisingly, these channels have been linked to many pathological conditions such as inflammatory bowel disease, chronic fatigue syndrome and myalgic encephalomyelitis, atherosclerosis, hypertension and atopy.

Dysregulation of Neuronal Calcium Signaling via Store-Operated Channels in Huntington's Disease

Huntington's disease (HD) is a progressive neurodegenerative disorder that is characterized by motor, cognitive, and psychiatric problems. It is caused by a polyglutamine expansion in the huntingtin protein that leads to striatal degeneration via the transcriptional dysregulation of several genes, including genes that are involved in the calcium (Ca²⁺) signalosome. Recent research has shown that one of the major Ca²⁺ signaling pathways, store-operated Ca²⁺ entry (SOCE), is significantly elevated in HD. SOCE refers to Ca²⁺ flow into cells in response to the depletion of endoplasmic reticulum Ca²⁺ stores. The dysregulation of Ca²⁺ homeostasis is postulated to be a cause of HD progression because the SOCE pathway is indirectly and abnormally activated by mutant huntingtin (HTT) in γ-aminobutyric acid (GABA)ergic medium spiny neurons (MSNs) from the striatum in HD models before the first symptoms of the disease appear. The present review summarizes recent studies that revealed a relationship between HD pathology and elevations of SOCE in different models of HD, including YAC128 mice (a transgenic model of HD), cellular HD models, and induced pluripotent stem cell (iPSC)-based GABAergic medium spiny neurons (MSNs) that are obtained from adult HD patient fibroblasts. SOCE in MSNs was shown to be mediated by currents through at least two different channel groups, Ca²⁺ release-activated Ca²⁺ current (I_CRAC) and store-operated Ca²⁺ current (I_SOC), which are composed of stromal interaction molecule (STIM) proteins and Orai or transient receptor potential channel (TRPC) channels. Their role under physiological and pathological conditions in HD are discussed. The role of Huntingtin-associated protein 1 isoform A in elevations of SOCE in HD MSNs and potential compounds that may stabilize elevations of SOCE in HD are also summarized. Evidence is presented that shows that the dysregulation of molecular components of SOCE or pathways upstream of SOCE in HD MSN neurons is a hallmark of HD, and these changes could lead to HD pathology, making them potential therapeutic targets.

Codonopsis lanceolata Contributes to Ca2+ Homeostasis by Mediating SOCE and PLC/IP3 Pathways in Vascular Endothelial and Smooth Muscle Cells

Codonopsis lanceolata has been widely used as an anti-inflammatory and anti-lipogenic agent in traditional medicine. Recently, C. lanceolata was reported to prevent hypertension by improving vascular function. This study evaluated the effects of C. lanceolata and its major component lancemaside A on cytosolic calcium concentration in vascular endothelial cells and vascular smooth muscle cells. Cytosolic calcium concentration was measured using fura-2 AM fluorescence. C. lanceolata or lancemaside A increased the cytosolic calcium concentration by releasing Ca²⁺ from the endoplasmic reticulum and sarcoplasmic reticulum and by Ca²⁺ entry into endothelial cells and vascular smooth muscle cells from extracellular sources. The C. lanceolata- and lancemaside A-induced cytosolic calcium concentration increases were significantly inhibited by lanthanum, an inhibitor of non-selective cation channels, in both endothelial cells and vascular smooth muscle cells. Moreover, C. lanceolata and lancemaside A significantly inhibited store-operated Ca²⁺ entry under pathological extracellular Ca²⁺ levels. In Ca²⁺-free extracellular fluid, increases in the cytosolic calcium concentration induced by C. lanceolata or lancemaside A were significantly inhibited by U73122, an inhibitor of phospholipase C, and 2-APB, an inositol 1,4,5-trisphosphate receptor antagonist. In addition, dantrolene treatment, which inhibits Ca²⁺ release through ryanodine receptor channels, also inhibited C. lanceolata- or lancemaside A-induced increases in the cytosolic calcium concentration through the phospholipase C/inositol 1,4,5-trisphosphate pathway. These results suggest that C. lanceolata and lancemaside A increase the cytosolic calcium concentration through the non-selective cation channels and phospholipase C/inositol 1,4,5-trisphosphate pathways under physiological conditions and inhibit store-operated Ca²⁺ entry under pathological conditions in endothelial cells and vascular smooth muscle cells. C. lanceolata or lancemaside A can protect endothelial cells and vascular smooth muscle cells by maintaining cytosolic calcium concentration homeostasis, suggesting possible applications for these materials in diets for preventing vascular damage.

Combustion Particle-Induced Changes in Calcium Homeostasis: A Contributing Factor to Vascular Disease?

Air pollution is the leading environmental risk factor for disease and premature death in the world. This is mainly due to exposure to urban air particle matter (PM), in particular, fine and ultrafine combustion-derived particles (CDP) from traffic-related air pollution. PM and CDP, including particles from diesel exhaust (DEP), and cigarette smoke have been linked to various cardiovascular diseases (CVDs) including atherosclerosis, but the underlying cellular mechanisms remain unclear. Moreover, CDP typically consist of carbon cores with a complex mixture of organic chemicals such as polycyclic aromatic hydrocarbons (PAHs) adhered. The relative contribution of the carbon core and adhered soluble components to cardiovascular effects of CDP is still a matter of discussion. In the present review, we summarize evidence showing that CDP affects intracellular calcium regulation, and argue that CDP-induced impairment of normal calcium control may be a critical cellular event through which CDP exposure contributes to development or exacerbation of cardiovascular disease. Furthermore, we highlight in vitro research suggesting that adhered organic chemicals such as PAHs may be key drivers of these responses. CDP, extractable organic material from CDP (CDP-EOM), and PAHs may increase intracellular calcium levels by interacting with calcium channels like transient receptor potential (TRP) channels, and receptors such as G protein-coupled receptors (GPCR; e.g., beta-adrenergic receptors [βAR] and protease-activated receptor 2 [PAR-2]) and the aryl hydrocarbon receptor (AhR). Clarifying a possible role of calcium signaling and mechanisms involved may increase our understanding of how air pollution contributes to CVD.

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.

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.

Mitochondrial TRPC3 promotes cell proliferation by regulating the mitochondrial calcium and metabolism in renal polycystin-2 knockdown cells

PURPOSE

Previous studies indicate that autosomal dominant polycystic kidney disease (ADPKD) cells exhibited dysregulated calcium homeostasis and enhanced cell proliferation. TRPC3 has been shown to function in the modulation of calcium and sodium entry, but whether TRPC3 plays a role in cellular abnormalities of ADPKD cells has not been defined.

METHODS

Human conditionally immortalized proximal tubular epithelial cells and mouse IMCD3 cells were used with polycystin-2 (PC2, TRPP2) knockdown. Cell proliferation assay was used to detect the cell proliferations upon different treatments. QRT-PCR and western blotting were used to measure the expression profiles of TRPP2 and other proteins. High-resolution respirometry, enzymic activities and ROS levels were detected to reflect the mitochondrial functions. Calcium and sodium uptakes were measured using Fura2-AM and SBFI dyes.

RESULTS

We showed that PC2 knockdown promoted cell proliferation, ROS productions and ERK phosphorylation, compared with negative control. Meanwhile, we demonstrated that receptor-operated calcium entry (ROCE) exhibited less reductions compared with store-operated calcium entry (SOCE) upon PC2 knockdown. Inhibition of ROCE and SOCE by specific inhibitors partially reversed the enhanced cell proliferation, ROS productions and ERK phosphorylation induced by PC2 knockdown. Moreover, TRPC3 upregulation was observed upon PC2 knockdown, which acted as both SOC and ROC, promoting cation entry, cell proliferation and ERK phosphorylation. Furthermore, we showed that mitochondrial located TRPC3 was upregulated and modulating mitochondrial calcium uptake, thus promoting the ROS productions in the presence of PC2 knockdown.

CONCLUSIONS

We demonstrated that TRPC3 upregulation upon PC2 knockdown aggravated the mitochondrial abnormalities and cell proliferation by modulating mitochondrial calcium uptake. Targeting TRPC3 might be a promising target for ADPKD treatment.

Emerging Roles of Diacylglycerol-Sensitive TRPC4/5 Channels

Transient receptor potential classical or canonical 4 (TRPC4) and TRPC5 channels are members of the classical or canonical transient receptor potential (TRPC) channel family of non-selective cation channels. TRPC4 and TRPC5 channels are widely accepted as receptor-operated cation channels that are activated in a phospholipase C-dependent manner, following the G_q/11 protein-coupled receptor activation. However, their precise activation mechanism has remained largely elusive for a long time, as the TRPC4 and TRPC5 channels were considered as being insensitive to the second messenger diacylglycerol (DAG) in contrast to the other TRPC channels. Recent findings indicate that the C-terminal interactions with the scaffolding proteins Na⁺/H⁺ exchanger regulatory factor 1 and 2 (NHERF1 and NHERF2) dynamically regulate the DAG sensitivity of the TRPC4 and TRPC5 channels. Interestingly, the C-terminal NHERF binding suppresses, while the dissociation of NHERF enables, the DAG sensitivity of the TRPC4 and TRPC5 channels. This leads to the assumption that all of the TRPC channels are DAG sensitive. The identification of the regulatory function of the NHERF proteins in the TRPC4/5-NHERF protein complex offers a new starting point to get deeper insights into the molecular basis of TRPC channel activation. Future studies will have to unravel the physiological and pathophysiological functions of this multi-protein channel complex.

Lipophilic Chemicals from Diesel Exhaust Particles Trigger Calcium Response in Human Endothelial Cells via Aryl Hydrocarbon Receptor Non-Genomic Signalling

Exposure to diesel exhaust particles (DEPs) affects endothelial function and may contribute to the development of atherosclerosis and vasomotor dysfunction. As intracellular calcium concentration [Ca2+]i is considered important in myoendothelial signalling, we explored the effects of extractable organic matter from DEPs (DEP-EOM) on [Ca2+]i and membrane microstructure in endothelial cells. DEP-EOM of increasing polarity was obtained by pressurized sequential extraction of DEPs with n-hexane (n-Hex-EOM), dichloromethane (DCM-EOM), methanol, and water. Chemical analysis revealed that the majority of organic matter was extracted by the n-Hex- and DCM-EOM, with polycyclic aromatic hydrocarbons primarily occurring in n-Hex-EOM. The concentration of calcium was measured in human microvascular endothelial cells (HMEC-1) using micro-spectrofluorometry. The lipophilic n-Hex-EOM and DCM-EOM, but not the more polar methanol- and water-soluble extracts, induced rapid [Ca2+]i increases in HMEC-1. n-Hex-EOM triggered [Ca2+]i increase from intracellular stores, followed by extracellular calcium influx consistent with store operated calcium entry (SOCE). By contrast, the less lipophilic DCM-EOM triggered [Ca2+]i increase via extracellular influx alone, resembling receptor operated calcium entry (ROCE). Both extracts increased [Ca2+]i via aryl hydrocarbon receptor (AhR) non-genomic signalling, verified by pharmacological inhibition and RNA-interference. Moreover, DCM-EOM appeared to induce an AhR-dependent reduction in the global plasma membrane order, as visualized by confocal fluorescence microscopy. DCM-EOM-triggered [Ca2+]i increase and membrane alterations were attenuated by the membrane stabilizing lipid cholesterol. In conclusion, lipophilic constituents of DEPs extracted by n-hexane and DCM seem to induce rapid AhR-dependent [Ca2+]i increase in HMEC-1 endothelial cells, possibly involving both ROCE and SOCE-mediated mechanisms. The semi-lipophilic fraction extracted by DCM also caused an AhR-dependent reduction in global membrane order, which appeared to be connected to the [Ca2+]i increase.

On the Role of Store-Operated Calcium Entry in Acute and Chronic Neurodegenerative Diseases

In both excitable and non-excitable cells, calcium (Ca²⁺) signals are maintained by a highly integrated process involving store-operated Ca²⁺ entry (SOCE), namely the opening of plasma membrane (PM) Ca²⁺ channels following the release of Ca²⁺ from intracellular stores. Upon depletion of Ca²⁺ store, the stromal interaction molecule (STIM) senses Ca²⁺ level reduction and migrates from endoplasmic reticulum (ER)-like sites to the PM where it activates the channel proteins Orai and/or the transient receptor potential channels (TRPC) prompting Ca²⁺ refilling. Accumulating evidence suggests that SOCE dysregulation may trigger perturbation of intracellular Ca²⁺ signaling in neurons, glia or hematopoietic cells, thus participating to the pathogenesis of diverse neurodegenerative diseases. Under acute conditions, such as ischemic stroke, neuronal SOCE can either re-establish Ca²⁺ homeostasis or mediate Ca²⁺ overload, thus providing a non-excitotoxic mechanism of ischemic neuronal death. The dualistic role of SOCE in brain ischemia is further underscored by the evidence that it also participates to endothelial restoration and to the stabilization of intravascular thrombi. In Parkinson's disease (PD) models, loss of SOCE triggers ER stress and dysfunction/degeneration of dopaminergic neurons. Disruption of neuronal SOCE also underlies Alzheimer's disease (AD) pathogenesis, since both in genetic mouse models and in human sporadic AD brain samples, reduced SOCE contributes to synaptic loss and cognitive decline. Unlike the AD setting, in the striatum from Huntington's disease (HD) transgenic mice, an increased STIM2 expression causes elevated synaptic SOCE that was suggested to underlie synaptic loss in medium spiny neurons. Thus, pharmacological inhibition of SOCE is beneficial to synapse maintenance in HD models, whereas the same approach may be anticipated to be detrimental to cortical and hippocampal pyramidal neurons. On the other hand, up-regulation of SOCE may be beneficial during AD. These intriguing findings highlight the importance of further mechanistic studies to dissect the molecular pathways, and their corresponding targets, involved in synaptic dysfunction and neuronal loss during aging and neurodegenerative diseases.

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.

Summary of ISN Forefronts Symposium 2015: ‘Immunomodulation of Cardio-Renal Function’

The International Society of Nephrology Forefronts Symposium Immunomodulation of Cardio-Renal Function took place October 22 to 25, 2015, in Shenzhen, China. The program covered basic and clinical aspects of cardio-renal pathophysiology and immunity. Leading scientists from different and related disciplines of clinical and basic research described and reviewed recent discoveries, and discussed emerging topics under the headings “Immunity and Renal Pathophysiology”; “Autoimmunity and the Inflammasome”; “Immunity and the Gut Microbiome”; “Immuno-Metabolism”; “Immunogenetics, Transcriptomics and Epigenetics; “Immunity and Hypertension”; and “Immunity, Fibrosis, and Kidney Disease.”

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.

Mitochondrial respiratory dysfunctions of blood mononuclear cells link with cardiac disturbance in patients with early-stage heart failure

Patients with cardiometabolic risk factors and asymptomatic cardiac hypertrophy are hallmarks of early-stage heart failure (HF). We hypothesized that mitochondrial respiratory dysfunctions of peripheral blood mononuclear cells (PBMCs) may be associated with inflammation and oxidative stress in early-stage HF patients complicated with cardiometabolic risk factors. Totally 49 subjects were enrolled with 25 early-stage HF patients (stages A and B) having cardiac hypertrophy and dysfunction and 24 healthy controls. It showed that excessive inflammation and reduced antioxidant capacity were closely associated with cardiac abnormalities in early-stage HF patients. Furthermore, the values of mitochondrial respiratory functional parameters R, CIOXPHOS, CIIOXPHOS, CI+IIOXPHOS, CI+IIETS and CIIETS were significantly lowered in early-stage HF patients. Interestingly, these respiratory parameters were correlated with inflammation and antioxidant capacity in participants. Finally, cardiometabolic risk factors such as salt intake and blood pressure were related to the mitochondrial respiratory dysfunctions, which were further validated by in vitro experiments. Our study indicated that cardiometabolic risk factor-mediated mitochondrial respiratory dysfunctions of PBMCs link with the cellular inflammation / oxidative stress and cardiac disturbance in early-stage HF.

A methylation-based regulatory network for microRNA 320a in chemoresistant breast cancer

We previously demonstrated that the overexpression of transient receptor potential channel C5 (TRPC5) and nuclear factor of activated T-cells isoform c3 (NFATC3) are essential for cancer chemoresistance, but how TRPC5 and NFATC3 are regulated was still unclear. In this study, microRNA 320a (miR-320a) was found to be down-regulated in chemoresistant cancer cells. MiR-320a directly targeted TRPC5 and NFATC3, and down-regulation of miR-320a triggered TRPC5 and NFATC3 overexpression. In chemoresistant cells, down-regulation of miR-320a was associated with regulation by methylation, which implicated promoter methylation of the miR-320a coding sequence. Furthermore, the transcription factor v-ets erythroblastosis virus E26 oncogene homolog 1 (ETS-1), which inhibited miR-320a expression, was activated in chemoresistant cancer cells; such activation was associated with hypomethylation of the ETS-1 promoter. Lastly, the down-regulation of miR-320a and high expression of TRPC5, NFATC3, and ETS-1 were verified in clinically chemoresistant samples. Low expression of MiR-320a was also found to be a significant unfavorable predictor for clinic outcome. In conclusion, miR-320a is a mediator of chemoresistance by targeting TRPC5 and NFATC3. Expression of miR-320a is regulated by methylation of its promoter and that of ETS-1.

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.

Contribution and regulation of TRPC channels in store-operated Ca2+ entry

Store-operated calcium entry (SOCE) is activated in response to depletion of the endoplasmic reticulum-Ca(2+) stores following stimulation of plasma membrane receptors that couple to PIP2 hydrolysis and IP3 generation. Search for the molecular components of SOCE channels led to the identification of mammalian transient receptor potential canonical (TRPC) family of calcium-permeable channels (TRPC1-TRPC7), which are all activated in response to stimuli that result in PIP2 hydrolysis. While several TRPCs, including TRPC1, TRPC3, and TRPC4, have been implicated in SOCE, the data are most consistent for TRPC1. Extensive studies in cell lines and knockout mouse models have established the contribution of TRPC1 to SOCE. Furthermore, there is a critical functional interaction between TRPC1 and the key components of SOCE, STIM1, and Orai1, which determines the activation of TRPC1. Orai1-mediated Ca(2+) entry is required for recruitment of TRPC1 and its insertion into surface membranes while STIM1 gates the channel. Notably, TRPC1 and Orai1 generate distinct patterns of Ca(2+) signals in cells that are decoded for the regulation of specific cellular functions. Thus, SOCE appears to be a complex process that depends on temporal and spatial coordination of several distinct steps mediated by proteins in different cellular compartments. Emerging data suggest that, in many cell types, the net Ca(2+) entry measured in response to store depletion is the result of the coordinated regulation of different calcium-permeable ion channels. Orai1 and STIM1 are central players in this process, and by mediating recruitment or activation of other Ca(2+) channels, Orai1-CRAC function can elicit rapid changes in global and local [Ca(2+)]i signals in cells. It is most likely that the type of channels and the [Ca(2+)]i signature that are generated by this process reflect the physiological function of the cell that is regulated by Ca(2+).

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.

Integration of transient receptor potential canonical channels with lipids

Transient receptor potential canonical (TRPC) channels are the canonical (C) subset of the TRP proteins, which are widely expressed in mammalian cells. They are thought to be primarily involved in determining calcium and sodium entry and have wide-ranging functions that include regulation of cell proliferation, motility and contraction. The channels are modulated by a multiplicity of factors, putatively existing as integrators in the plasma membrane. This review considers the sensitivities of TRPC channels to lipids that include diacylglycerols, phosphatidylinositol bisphosphate, lysophospholipids, oxidized phospholipids, arachidonic acid and its metabolites, sphingosine-1-phosphate, cholesterol and some steroidal derivatives and other lipid factors such as gangliosides. Promiscuous and selective lipid sensing have been detected. There appear to be close working relationships with lipids of the phospholipase C and A₂ enzyme systems, which may enable integration with receptor signalling and membrane stretch. There are differences in the properties of each TRPC channel that are further complicated by TRPC heteromultimerization. The lipids modulate activity of the channels or insertion in the plasma membrane. Lipid microenvironments and intermediate sensing proteins have been described that include caveolae, G protein signalling, SEC14-like and spectrin-type domains 1 (SESTD1) and podocin. The data suggest that lipid sensing is an important aspect of TRPC channel biology enabling integration with other signalling systems.

Properties and therapeutic potential of transient receptor potential channels with putative roles in adversity: focus on TRPC5, TRPM2 and TRPA1

Mammals contain 28 genes encoding Transient Receptor Potential (TRP) proteins. The proteins assemble into cationic channels, often with calcium permeability. Important roles in physiology and disease have emerged and so there is interest in whether the channels might be suitable therapeutic drug targets. Here we review selected members of three subfamilies of mammalian TRP channel (TRPC5, TRPM2 and TRPA1) that show relevance to sensing of adversity by cells and biological systems. Summarized are the cellular and tissue distributions, general properties, endogenous modulators, protein partners, cellular and tissue functions, therapeutic potential, and pharmacology. TRPC5 is stimulated by receptor agonists and other factors that include lipids and metal ions; it heteromultimerises with other TRPC proteins and is involved in cell movement and anxiety control. TRPM2 is activated by hydrogen peroxide; it is implicated in stress-related inflammatory, vascular and neurodegenerative conditions. TRPA1 is stimulated by a wide range of irritants including mustard oil and nicotine but also, controversially, noxious cold and mechanical pressure; it is implicated in pain and inflammatory responses, including in the airways. The channels have in common that they show polymodal stimulation, have activities that are enhanced by redox factors, are permeable to calcium, and are facilitated by elevations of intracellular calcium. Developing inhibitors of the channels could lead to new agents for a variety of conditions: for example, suppressing unwanted tissue remodeling, inflammation, pain and anxiety, and addressing problems relating to asthma and stroke.

Erythropoietin Increases Expression and Function of Transient Receptor Potential Canonical 5 Channels

Hypertension is a common complication in hemodialysis patients during erythropoietin (EPO) treatment. The underlying mechanisms of EPO-induced hypertension still remain to be determined. Increased transient receptor potential canonical (TRPC) channels have been associated with hypertension. Now, TRPC gene expression was investigated using quantitative real-time RT-PCR and immunoblotting in cultured human endothelial cells and in monocytes from hemodialysis patients. EPO dose-dependently increased TRPC5 mRNA in endothelial cells. EPO increased TRPC5 mRNA stability, that is, EPO prolonged the half-life period for TRPC5 mRNA from 16 hours (control) to 24 hours ( P <0.05). The poly(A) tail length was measured by rapid amplification of cDNA ends-poly(A) test. Increased TRPC5 mRNA stability was attributed to longer 3′ poly(A) tail lengths after EPO administration. EPO also significantly increased TRPC5 channel protein abundance by 70% ( P <0.05). Whole-cell patch clamp showed that angiotensin II–induced, TRPC5-mediated currents were dramatically increased in endothelial cells treated with EPO. Fluorescent dye techniques confirmed that increased calcium influx after EPO treatment was abolished after TRPC5 knockdown ( P <0.05). EPO also significantly increased intracellular reactive oxygen species production. Knockdown of TRPC5 alleviated EPO-induced reactive oxygen species generation in endothelial cells ( P <0.05). In vivo, EPO-treated hemodialysis patients showed significantly increased amounts of TRPC5 mRNA in monocytes compared with EPO-free hemodialysis patients (6.0±2.4 [n=12] versus 1.0±0.5 [n=9]; P <0.01). Patients undergoing EPO treatment also showed significantly elevated systolic blood pressure (160±7 versus 139±6 mm Hg; P <0.05). Our findings suggest that upregulated functional TRPC5 gene may be one cause of EPO-induced hypertension in patients with chronic kidney disease.

TRP channels and their implications in metabolic diseases

The transient receptor potential (TRP) channel superfamily is composed of 28 nonselective cation channels that are ubiquitously expressed in many cell types and have considerable functional diversity. Although changes in TRP channel expression and function have been reported in cardiovascular disease and renal disorders, the pathogenic roles of TRP channels in metabolic diseases have not been systemically reviewed. In this review, we summarised the distribution of TRP channels in several metabolic tissues and discussed their roles in mediating and regulating various physiological and pathophysiological metabolic processes and diseases including diabetes, obesity, dyslipidaemia, metabolic syndrome, atherosclerosis, metabolic bone diseases and electrolyte disturbances. This review provides new insight into the involvement of TRP channels in the pathogenesis of metabolic disorders and implicates these channels as potential therapeutic targets for the management of metabolic diseases.

Transient receptor potential canonical type 3 channels and blood pressure in humans

OBJECTIVE

There is evidence that transient receptor potential canonical type 3 (TRPC3) cation channels are involved in the regulation of blood pressure, but this has not been studied using human renal tissue. We tested the hypothesis that the expression of TRPC3 in human renal tissue is associated with blood pressure in patients.

MATERIAL AND METHODS

TRPC3 was detected in cultured human endothelial cells and in vascular endothelium cells from human renal tissue by immunoblotting, immunohistochemistry, and quantitative real-time reverse transcriptase-PCR. The changes of TRPC3 and vascular endothelial growth factor receptor type 2 expression in cultured human endothelial cells were measured after administration of vascular endothelial growth factor isoform 121.

RESULTS

In cultured human endothelial cells, vascular endothelial growth factor isoform 121 significantly reduced TRPC3 expression by 57% and vascular endothelial growth factor receptor type 2 by 70%. This reduction was partly blocked by phosphatidylinositol 3-kinase inhibitors, wortmannin, or LY294002. Downregulation of TRPC3 channel expression was associated with reduced calcium influx. The changes of calcium influx could be abolished by the inhibitor of TRPC channels, 2-aminoethoxydiphenylborane, pointing to their functional importance. TRPC3 expression was significantly higher in patients with SBP more than 140 mmHg compared with patients with SBP of 140 mmHg or less (0.00181 +/- 0.00059 versus 0.00037 +/- 0.00012 arbitrary units; P < 0.01).

CONCLUSION

The data support the hypothesis that TRPC3 expression in human renal tissue including vascular endothelium is associated with blood pressure regulation in humans.

Flow cytometric calcium flux assay: evaluation of cytoplasmic calcium kinetics in whole blood leukocytes

In leukocytes, as in many other cell types, cytoplasmic calcium ([Ca(2+)](i)) changes play a key role in a series of pathways leading to activation. Here we describe a flow cytometric method allowing the simultaneous kinetic analysis of changes in [Ca(2+)](i) in the three types of leukocytes, i.e. monocytes, granulocytes and lymphocytes. Heparinised whole blood was diluted in phosphate buffered saline with Ca(2+) and 1 mM sodium pyruvate and incubated with the Ca(2+) indicator fluo3-acetoxymethyl ester. Leukocytes were identified by labelling with the phycoerythrin-conjugated antibody against CD45, the leukocyte common antigen. Resuspension of the cells in PBS with or without Ca(2+) allowed us to detect the origin of Ca(2+) changes. During flow cytometric analysis only CD45-positive cells were counted and monocytes, granulocytes and lymphocytes were evaluated separately. Baseline fluorescence of the fluo3-Ca(2+)-complex was determined and changes in [Ca(2+)](i) after stimulation with the calcium ionophore A23187 or the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (fMLP) were recorded over a time period of 150 s. Stimulation with A23187 resulted in a rise in [Ca(2+)](i) in all three leukocyte subpopulations. This rise was sustained in the presence of extracellular Ca(2+) (Ca(2+)(ex)) but had a transient character in the absence of Ca(2+)(ex). For fMLP, [Ca(2+)](i) changes occurred only in monocytes and granulocytes and were transient irrespective of the presence or absence of Ca(2+)(ex). In conclusion, the present method is a simple, fast and easy tool to analyse in vitro [Ca(2+)](i) changes over time in leukocytes under physiologically relevant conditions, without the need for their isolation or the lysis of erythrocytes. The whole blood approach allows a continuous interaction between the different leukocyte subpopulations and other blood components and a minimum of preparative manipulations avoids artefactual activation of the cells. A distinction can be made between Ca(2+) release from the intracellular stores and the entry of Ca(2+) from outside the cell. The approach allows to evaluate the effect of various agonists on [Ca(2+)](i) changes in leukocytes, with physiological, patho-physiological or therapeutic purposes.

Synergistic activation of vascular TRPC6 channel by receptor and mechanical stimulation via phospholipase C/diacylglycerol and phospholipase A2/omega-hydroxylase/20-HETE pathways

TRPC6 is a non-voltage-gated Ca(2+) entry/depolarization channel associated with vascular tone regulation and remodeling. Expressed TRPC6 channel responds to both neurohormonal and mechanical stimuli, the mechanism for which remains controversial. In this study, we examined the possible interactions of receptor and mechanical stimulations in activating this channel using the patch clamp technique. In HEK293 cells expressing TRPC6, application of mechanical stimuli (hypotonicity, shear, 2,4,6-trinitrophenol) caused, albeit not effective by themselves, a prominent potentiation of cationic currents (I(TRPC6)) induced by a muscarinic receptor agonist carbachol. This effect was insensitive to a tarantula toxin GsMTx-4 (5 mumol/L). A similar extent of mechanical potentiation was observed after activation of I(TRPC6) by GTPgammaS or a diacylglycerol analog 1-oleoyl-2-acetyl-sn-glycerol (OAG). Single TRPC6 channel activity evoked by carbachol was also enhanced by a negative pressure added in the patch pipette. Mechanical potentiation of carbachol- or OAG-induced I(TRPC6) was abolished by small interfering RNA knockdown of cytosolic phospholipase A(2) or pharmacological inhibition of omega-hydroxylation of arachidonic acid into 20-HETE (20-hydroxyeicosatetraenoic acid). Conversely, direct application of 20-HETE enhanced both OAG-induced macroscopic and single channel TRPC6 currents. Essentially the same results were obtained for TRPC6-like cation channel in A7r5 myocytes, where its activation by noradrenaline or Arg8 vasopressin was greatly enhanced by mechanical stimuli via 20-HETE production. Furthermore, myogenic response of pressurized mesenteric artery was significantly enhanced by weak receptor stimulation dependently on 20-HETE production. These results collectively suggest that simultaneous operation of receptor and mechanical stimulations may synergistically amplify transmembrane Ca(2+) mobilization through TRPC6 activation, thereby enhancing the vascular tone via phospholipase C/diacylglycerol and phospholipase A(2)/omega-hydroxylase/20-HETE pathways.

TRPC channel lipid specificity and mechanisms of lipid regulation

TRPC channels are a subset of the transient receptor potential (TRP) proteins widely expressed in mammalian cells. They are thought to be primarily involved in determining calcium or sodium entry and have broad-ranging functions that include regulation of cell proliferation, motility and contraction. The channels do not respond to a single stimulator but rather are activated or modulated by a multiplicity of factors, potentially existing as integrators at the plasma membrane. This review considers the sensitivity of TRPCs to lipid factors, with focus on sensitivities to diacylglycerols, lysophospholipids, arachidonic acid and its metabolites, sphingosine-1-phosphate (S1P), cholesterol and derivatives, and other lipid factors such as gangliosides. Promiscuous and selective lipid-sensing are apparent. In many cases the lipids stimulate channel function or increase insertion of channels in the membrane. Both direct and indirect (receptor-dependent) lipid effects are evident. Although information is limited, the lipid profiles are consistent with TRPCs having close working relationships with phospholipase C and A2 enzymes. We need much more information about lipid-sensing by TRPCs if we are to fully appreciate its significance, but the available data suggest that lipid-sensing is a key, but not exclusive, aspect of TRPC biology.

Increased TRPC3 expression in vascular endothelium of patients with malignant hypertension

An increased expression of transient receptor potential canonical type 3 (TRPC3) cation channels has been proposed as one of the factors contributing to the pathogenesis of hypertension. To test that hypothesis we compared the expression of TRPC3 and TRPC6 as an endogenous control in human vascular endothelium of preglomerular arterioles in kidney biopsies from six patients with malignant hypertension and from four patients with diarrhea-associated hemolytic-uremic syndrome. Patients with malignant hypertension showed significantly higher systolic blood pressure and more prominent expression of TRPC3 in vascular endothelium of preglomerular arterioles compared to patients with hemolytic-uremic syndrome. The expression of TRPC6 was not different between the two groups. The study supports the hypothesis that the increased expression of TRPC3 is associated with malignant hypertension in humans.

TRPC3 activation by erythropoietin is modulated by TRPC6

Regulation of intracellular calcium ([Ca(2+)](i)) by erythropoietin (Epo) is an essential part of signaling pathways controlling proliferation and differentiation of erythroid progenitors, but regulatory mechanisms are largely unknown. TRPC3 and the homologous TRPC6 are two members of the transient receptor potential channel (TRPC) superfamily that are expressed on normal human erythroid precursors. Here we show that TRPC3 expression increases but TRPC6 decreases during erythroid differentiation. This is associated with a significantly greater increase in [Ca(2+)](i) in response to Epo stimulation, suggesting that the ratio of TRPC3/TRPC6 is physiologically important. In HEK 293T cells heterologously expressing TRPC and erythropoietin receptor (Epo-R), Epo stimulated an increase in [Ca(2+)](i) through TRPC3 but not TRPC6. Replacement of the C terminus of TRPC3 with the TRPC6 C terminus (TRPC3-C6C) resulted in loss of activation by Epo. In contrast, substitution of the C terminus of TRPC6 with that of TRPC3 (TRPC6-C3C) resulted in an increase in [Ca(2+)](i) in response to Epo. Substitution of the N termini had no effect. Domains in the TRPC3 C terminus between amino acids 671 and 746 are critical for the response to Epo. Epo-R and phospholipase Cgamma associated with TRPC3, and these interactions were significantly reduced with TRPC6 and TRPC3-C6C chimeras. TRPC3 and TRPC6 form heterotetramers. Coexpression of TRPC6 or C3/C6 chimeras with TRPC3 and Epo-R inhibited the Epo-stimulated increase in [Ca(2+)](i). In a heterologous expression system, Epo stimulation increased cell surface expression of TRPC3, which was inhibited by TRPC6. However, in primary erythroblasts, an increase in TRPC3 cell surface expression was not observed in erythroblasts in which Epo stimulated an increase in [Ca(2+)](i), demonstrating that increased membrane insertion of TRPC3 is not required. These data demonstrate that TRPC6 regulates TRPC3 activation by Epo. Endogenously, regulation of TRPC3 by TRPC6 may primarily be through modulation of signaling mechanisms, including reduced interaction of TRPC6 with phospholipase Cgamma and Epo-R.

Physiology and pathophysiology of canonical transient receptor potential channels

The existence of a mammalian family of TRPC ion channels, direct homologues of TRP, the visual transduction channel of flies, was discovered during 1995-1996 as a consequence of research into the mechanism by which the stimulation of the receptor-Gq-phospholipase Cbeta signaling pathway leads to sustained increases in intracellular calcium. Mammalian TRPs, TRPCs, turned out to be nonselective, calcium-permeable cation channels, which cause both a collapse of the cell's membrane potential and entry of calcium. The family comprises 7 members and is widely expressed. Many cells and tissues express between 3 and 4 of the 7 TRPCs. Despite their recent discovery, a wealth of information has accumulated, showing that TRPCs have widespread roles in almost all cells studied, including cells from excitable and nonexcitable tissues, such as the nervous and cardiovascular systems, the kidney and the liver, and cells from endothelia, epithelia, and the bone marrow compartment. Disruption of TRPC function is at the root of some familial diseases. More often, TRPCs are contributing risk factors in complex diseases. The present article reviews what has been uncovered about physiological roles of mammalian TRPC channels since the time of their discovery. This analysis reveals TRPCs as major and unsuspected gates of Ca(2+) entry that contribute, depending on context, to activation of transcription factors, apoptosis, vascular contractility, platelet activation, and cardiac hypertrophy, as well as to normal and abnormal cell proliferation. TRPCs emerge as targets for a thus far nonexistent field of pharmacological intervention that may ameliorate complex diseases.

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

We tested the hypothesis that transient receptor potential canonical type 3 (TRPC3) channels are increased in vascular smooth muscle cells and aortic tissue from spontaneously hypertensive rats (SHR) compared with normotensive Wistar Kyoto rats. Expression of TRPC3 was analyzed by immunohistochemistry and Western blotting. TRPC3 gene knockdown was performed by specific small interfering RNA and TRPC3 overexpression using the pAdEasy-1 system. Cytosolic calcium was measured using fluorescence spectrophotometry and vasoconstriction of aortic rings using a force transducer. In SHR, the expression of TRPC3 channel protein was significantly higher in aortic rings (1.48+/-0.05 versus 1.00+/-0.06; each n=6; P<0.01) and vascular smooth muscle cells (1.28+/-0.08 versus 1.00+/-0.03; each n=6; P<0.05) compared with Wistar Kyoto rats. Knockdown of TRPC3 gene expression by specific small interfering RNA significantly reduced the angiotensin II-induced calcium influx by 30+/-3% (n=6; P<0.01), whereas TRPC3 overexpression significantly increased it by 55+/-3% (n=6; P<0.01). The angiotensin II-induced calcium increase was significantly enhanced in vascular smooth muscle cells from SHR compared with Wistar Kyoto rats, even in the presence of the calcium channel blocker amlodipine. Angiotensin II significantly elevated the TRPC3 channel protein expression in vascular smooth muscle cells from SHR from 1.28+/-0.08 to 1.61+/-0.08 (each n=6; P<0.01). Angiotensin II-induced TRPC3 expression was prevented by telmisartan. Administration of telmisartan to SHR for 4 weeks significantly reduced blood pressure, angiotensin II-induced vasoconstriction, and TRPC3 channel protein expression in aortic tissue. TRPC3 expression was not significantly reduced after reduction of blood pressure in SHR using amlodipine. In conclusion, we give experimental evidence that increased TRPC3 channel protein expression in the vasculature is important for elevated blood pressure.

High Glucose Enhances Transient Receptor Potential Channel Canonical Type 6–Dependent Calcium Influx in Human Platelets via Phosphatidylinositol 3-Kinase–Dependent Pathway

Background— Transient receptor potential canonical type 6 (TRPC6) channels mediating 1-oleoyl-2-acetyl-sn-glycerol (OAG)–induced calcium entry have been identified on human platelets. In the present study we tested the hypothesis that hyperglycemia increases the expression of TRPC6 channels.

Methods and Results— Platelets from healthy control subjects and patients with type 2 diabetes mellitus were incubated with glucose and calcium influx was measured using the fluorescent dye technique. TRPC channel protein expression was investigated using immunofluorescence and fluorescence microscopy of single platelets. Administration of 25 mmol/L glucose significantly enhanced the OAG-induced calcium influx, which was attenuated by inhibitors of the phosphatidylinositol 3-kinase, wortmannin or LY294002. The glucose-enhanced and OAG-induced calcium influx was concentration- and time-dependent. Glucose significantly increased the TRPC6 protein expression in platelets to 131±12% (n=33; P <0.05), whereas the expression of TRPC1, TRPC3, TRPC4, or TRPC5 were unchanged. The glucose-induced TRPC6 expression was significantly attenuated in the presence of wortmannin or LY294002. Platelets from patients with type 2 diabetes mellitus showed increased TRPC6 expression compared to nondiabetic individuals ( P <0.05).

Conclusion— The study indicates that high glucose increases TRPC6 channel protein expression on the platelet surface which is mediated by a phosphatidylinositol 3-kinase–dependent pathway.

Association of transient receptor potential canonical type 3 (TRPC3) channel transcripts with proinflammatory cytokines

We investigated whether expression of non-selective cation channels of the transient receptor potential canonical (TRPC) channel family are associated with proinflammatory cytokines in monocytes. Using quantitative RT-PCR we studied the expression of TRPC3, interleukin-1beta (IL-1beta), and tumor necrosis factor-alpha (TNF-alpha) in monocytes from 15 patients with essential hypertension and 16 age- and sex-matched normotensive control subjects. We observed an approximately 8-fold increase of TRPC3 transcripts in monocytes from patients with essential hypertension compared to normotensive control subjects (p<0.05). We found an approximately 3-fold increase of IL-1beta, and an approximately 9-fold increase of TNF-alpha in patients with essential hypertension compared to normotensive control subjects (each p<0.05). We observed a significant correlation between TRPC3 transcripts with systolic blood pressure, expression of IL-1beta, and TNF-alpha. Using quantitative RT-PCR we observed an association of TRPC3 transcripts and proinflammatory cytokines in monocytes.