Transient Receptor Potential Cation Research Articles

Oxygen physiology: sensors and ion channels.

Ever since Pfluger, it has been always a major issue of physiology to identify the core principles underlying our body’s ability to sense and adapt to the changes in the availability of ambient molecular oxygen (O2) [3, 5]. The milestone discovery of an O2 sensor was first achieved at the organ level by Heymans, who demonstrated that inspired hypoxia triggers increased breathing through the stimulation of the carotid bodies (CBs) [2]. With regard to the cellular and molecular mechanisms underlying the acute hypoxia-sensing in the CBs, it is generally accepted that hypoxia inhibits K+ channels to depolarize the chemoreceptor glomus cells, leading to the activation of voltage-dependent Ca2+ channels and consequent release of neurotransmitters that relays information to regulate the respiration [10]. Another milestone is the discovery of a soluble factor erythropoietin (Epo) that is essential for the chronic phases of O2 adaptation. At the end of nineteenth century, it was recognized by Viault that exposure to high altitude hypoxia elicits a robust burst of erythropoiesis in humans [1]. Almost a half century later, Epo was demonstrated to mediate hypoxia-induced erythropoiesis. While the initial characterizations of the expression of Epo suggested its production in the fetal liver and adult kidney, it was only recently that the localization of the renal Epo-producing (REP) cell was found to be in the peritubular interstitial space located in the deep renal outer medulla region [4]. In addition, hypoxia-inducible factor (HIF) [6] is recognized as the transcription factor central to chronic cellular responses to hypoxia including erythropoiesis via Epo production. Thus, CBs, Epo, and HIF provide solid bases for understanding the body’s ability to sense and adapt to the ambient O2. Even after the above discoveries of the core principles, the physiology of O2 sensing and adaptation never loses its glory. This is highlighted by recent findings concerning the diversity and ubiquity of O2-sensing mechanisms. For example, in addition to multiple K+ channel subtypes and mediators previously reported responsible for hypoxia sensing, transient receptor potential (TRP) cation channels have emerged as O2–regulated ion channels critical for O2 sensing in non-CB chemoreceptors and tissues [7, 11]. Importantly, HIF, which binds to the hypoxia-responsive element present in the 3′ enhancer region of the Epo gene [6], is expressed widely throughout the body and is intriguingly found in lower organisms that produce neither Epo nor red blood cells. In addition to erythropoiesis, chronic hypoxia induces the expression of numerous genes whose products facilitate non-oxidative synthesis of ATP and multiply the number of vessels supplying the hypoxic area of tissues [8] through the action of HIFs. These lines of evidence suggest the ubiquitous presence of O2-sensing cells and organs in the animal body. In this context, it is interesting to note that two HIF isoforms HIF1 and HIF2 play distinctive roles in the regulation of hypoxic responses of CBs by differentially promoting cellular redox status [12]. Moreover, the physiological importance of hypoxia has been demonstrated in maintaining the hematopoietic stem cell niche for cell cycle quiescence through the action of HIF in the bone marrow [9]. In this special issue, reviews of these recent developments are included together with several important original research articles, which indeed enrich our knowledge in O2 physiology. We believe that there is a great prospect that O2 physiology will further enhance its current status as a major issue in physiology. A future direction of O2 physiology is systems physiology, in which regulation of O2 sensing and adaptation through interplays among different chemoreceptors and molecules are studied. Another possible direction is to understand O2 sensing and adaptation in the context of redox biology, where alterations in redox homeostasis (via reactive chemical species and antioxidant systems) in response to changes in the O2 availability are integrated with other types of stress such as metabolic perturbation, heat, and proinflammatory mediators. Adding these future developments to O2 physiology should lead us to understand our body’s ability as a total system to adapt to changes in ambient O2 availability.

Intracellular postsynaptic cannabinoid receptors link thyrotropin-releasing hormone receptors to TRPC-like channels in thalamic paraventricular nucleus neurons

In rat thalamic paraventricular nucleus of thalamus (PVT) neurons, activation of thyrotropin-releasing hormone (TRH) receptors enhances excitability via concurrent decrease in G protein-coupled inwardly-rectifying potassium (GIRK)-like and activation of transient receptor potential cation (TRPC)4/5-like cationic conductances. An exploration of intracellular signaling pathways revealed the TRH-induced current to be insensitive to phosphatidylinositol-specific phospholipase C (PI-PLC) inhibitors, but reduced by D609, an inhibitor of phosphatidylcholine-specific PLC (PC-PLC). A corresponding change in the I–V relationship implied suppression of the cationic component of the TRH-induced current. Diacylglycerol (DAG) is a product of the hydrolysis of PC. Studies focused on the isolated cationic component of the TRH-induced response revealed a reduction by RHC80267, an inhibitor of DAG lipase, the enzyme involved in the hydrolysis of DAG to the endocannabinoid 2-arachidonoylglycerol (2-AG). Further investigation revealed enhancement of the cationic component in the presence of either JZL184 or WWL70, inhibitors of enzymes involved in the hydrolysis of 2-AG. A decrease in the TRH-induced response was noted in the presence of rimonabant or SR144528, membrane permeable CB1 and CB2 receptor antagonists, respectively. A decrease in the TRH-induced current by intracellular, but not by bath application of the membrane impermeable peptide hemopressin, selective for CB1 receptors, suggests a postsynaptic intracellular localization of these receptors. The TRH-induced current was increased in the presence of arachidonyl-2′-chloroethylamide (ACEA) or JWH133, CB1 and CB2 receptor agonists, respectively. The PI3-kinase inhibitor LY294002, known to inhibit TRPC translocation, decreased the response to TRH. In addition, a TRH-induced enhancement of the low-threshold spike was prevented by both rimonabant, and SR144528. TRH had no influence on excitatory or inhibitory miniature postsynaptic currents, suggesting presynaptic CB receptors are not involved in this situation. Collectively, the data imply that activation of TRH receptors in these midline thalamic neurons engages novel signaling pathways that include postsynaptic intracellular CB1 and CB2 receptors in the activation of TRPC4/5-like channels.

Increased TRPC5 glutathionylation contributes to striatal neuron loss in Huntington's disease.

Aberrant glutathione or Ca(2+) homeostasis due to oxidative stress is associated with the pathogenesis of neurodegenerative disorders. The Ca(2+)-permeable transient receptor potential cation (TRPC) channel is predominantly expressed in the brain, which is sensitive to oxidative stress. However, the role of the TRPC channel in neurodegeneration is not known. Here, we report a mechanism of TRPC5 activation by oxidants and the effect of glutathionylated TRPC5 on striatal neurons in Huntington's disease. Intracellular oxidized glutathione leads to TRPC5 activation via TRPC5 S-glutathionylation at Cys176/Cys178 residues. The oxidized glutathione-activated TRPC5-like current results in a sustained increase in cytosolic Ca(2+), activated calmodulin-dependent protein kinase and the calpain-caspase pathway, ultimately inducing striatal neuronal cell death. We observed an abnormal glutathione pool indicative of an oxidized state in the striatum of Huntington's disease transgenic (YAC128) mice. Increased levels of endogenous TRPC5 S-glutathionylation were observed in the striatum in both transgenic mice and patients with Huntington's disease. Both knockdown and inhibition of TRPC5 significantly attenuated oxidation-induced striatal neuronal cell death. Moreover, a TRPC5 blocker improved rearing behaviour in Huntington's disease transgenic mice and motor behavioural symptoms in littermate control mice by increasing striatal neuron survival. Notably, low levels of TRPC1 increased the formation of TRPC5 homotetramer, a highly Ca(2+)-permeable channel, and stimulated Ca(2+)-dependent apoptosis in Huntington's disease cells (STHdh(Q111/111)). Taken together, these novel findings indicate that increased TRPC5 S-glutathionylation by oxidative stress and decreased TRPC1 expression contribute to neuronal damage in the striatum and may underlie neurodegeneration in Huntington's disease.

Localization and Role of Transient Receptor Potential Cation Channels in Rabbit Ventricular Myocytes

Several members of the transient receptor potential cation (TRPC) channel family are stretch activated. They are thought to play a critical role in mechano-electrical coupling in cardiac myocytes and in cardiac hypertrophic remodeling. However, studies on their subcellular localization in cardiomyocytes are conflicting, and their functions in cardiac myocytes are barely understood. In this study, we investigated the spatial distribution of TRPC channels in isolated ventricular myocytes from adult rabbit using immunolabeling and three-dimensional confocal microscopy. Colocalization of TRPC with (i) sarcolemma labeled with wheat germ agglutinin (WGA), (ii) sarcoplasmic reticulum (SR) labeled for SR calcium ATPase (SERCA2), and (iii) cytoskeletal proteins including sarcomeric α-actinin, desmin, vinculin and β-tubulin, was assessed by a quantitative approach. Furthermore, we measured stretch-activated current with whole-cell voltage clamping. Our results from confocal imaging revealed a transverse striated distribution of TRPC1 and TRPC6 channels. We found colocalization of TRPC1 and TRPC6 with sarcomeric α-actinin, SERCA2A and desmin, but not with WGA, vinculin and β-tubulin. Additionally, no stretch-activated current was detected when stretching isolated cardiomyocytes to approximately 10% of their resting length. Taken together, our data indicate that TRPC1 and TRPC6 are not located in the sarcolemma, but in the membrane of the SR adjacent to the Z-disks in rabbit ventricular myocytes. We suggest that a potential role of TRPC1 and TRPC6 channels is in stretch-dependent calcium leak from the SR and/or counter current balancing calcium release from the SR through ryanodine receptors.

Pdx-1 Activates Islet α- and β-Cell Proliferation via a Mechanism Regulated by Transient Receptor Potential Cation Channels 3 and 6 and Extracellular Signal-Regulated Kinases 1 and 2

The homeodomain transcription factor Pdx-1 has important roles in pancreatic development and β-cell function and survival. In the present study, we demonstrate that adenovirus-mediated overexpression of Pdx-1 in rat or human islets also stimulates cell replication. Moreover, cooverexpression of Pdx-1 with another homeodomain transcription factor, Nkx6.1, has an additive effect on proliferation compared to either factor alone, implying discrete activating mechanisms. Consistent with this, Nkx6.1 stimulates mainly β-cell proliferation, whereas Pdx-1 stimulates both α- and β-cell proliferation. Furthermore, cyclins D1/D2 are upregulated by Pdx-1 but not by Nkx6.1, and inhibition of cdk4 blocks Pdx-1-stimulated but not Nkx6.1-stimulated islet cell proliferation. Genes regulated by Pdx-1 but not Nkx6.1 were identified by microarray analysis. Two members of the transient receptor potential cation (TRPC) channel family, TRPC3 and TRPC6, are upregulated by Pdx-1 overexpression, and small interfering RNA (siRNA)-mediated knockdown of TRPC3/6 or TRPC6 alone inhibits Pdx-1-induced but not Nkx6.1-induced islet cell proliferation. Pdx-1 also stimulates extracellular signal-regulated kinase 1 and 2 (ERK1/2) phosphorylation, an effect partially blocked by knockdown of TRPC3/6, and blockade of ERK1/2 activation with a MEK1/2 inhibitor partially impairs Pdx-1-stimulated proliferation. These studies define a pathway by which overexpression of Pdx-1 activates islet cell proliferation that is distinct from and additive to a pathway activated by Nkx6.1.

A functional interaction between TRPC/NCKX induced by DAG plays a role in determining calcium influx independently from PKC activation

Ca2+influx might occur through K+-dependent Na+/Ca2+ exchanger operating in reverse mode (rNCKX). In a cellular model different from platelets, an interaction between canonical transient receptor potential cation (TRPC) channels and NCX has been found. The aim of this study was to verify whether the TRPC/NCKX interaction operates in human platelets. Our results showed that the diacylglycerol (DAG) analogue, 1-oleoyl-2-acetyl-sn-glycerol (OAG) induced rNCKX-mediated Ca2+ influx through TRPC-mediated Na+ influx. DAG-induced activation of TRPC/NCKX occurs independently of protein kinase C (PKC) activation, as PKC inhibitor did not modify OAG-mediated Ca2+ influx. Moreover, as both rNCKX and TRPC inhibitors reduced OAG-induced platelet aggregation which, conversely, was increased by flufenamic acid, known to develop TRPC activity, it could be suggested that the TRPC/NCKX interaction has a role in OAG-dependent platelet aggregation.

Novel pyrazole compounds for pharmacological discrimination between receptor-operated and store-operated Ca(2+) entry pathways.

Background and purposePyrazole derivatives have recently been suggested as selective blockers of transient receptor potential cation (TRPC) channels but their ability to distinguish between the TRPC and Orai pore complexes is ill-defined. This study was designed to characterize a series of pyrazole derivatives in terms of TRPC/Orai selectivity and to delineate consequences of selective suppression of these pathways for mast cell activation.Experimental approachPyrazoles were generated by microwave-assisted synthesis and tested for effects on Ca2+ entry by Fura-2 imaging and membrane currents by patch-clamp recording. Experiments were performed in HEK293 cells overexpressing TRPC3 and in RBL-2H3 mast cells, which express classical store-operated Ca2+ entry mediated by Orai channels. The consequences of inhibitory effects on Ca2+ signalling in RBL-2H3 cells were investigated at the level of both degranulation and nuclear factor of activated T-cells activation.Key ResultsPyr3, a previously suggested selective inhibitor of TRPC3, inhibited Orai1- and TRPC3-mediated Ca2+ entry and currents as well as mast cell activation with similar potency. By contrast, Pyr6 exhibited a 37-fold higher potency to inhibit Orai1-mediated Ca2+ entry as compared with TRPC3-mediated Ca2+ entry and potently suppressed mast cell activation. The novel pyrazole Pyr10 displayed substantial selectivity for TRPC3-mediated responses (18-fold) and the selective block of TRPC3 channels by Pyr10 barely affected mast cell activation.Conclusions and ImplicationsThe pyrazole derivatives Pyr6 and Pyr10 are able to distinguish between TRPC and Orai-mediated Ca2+ entry and may serve as useful tools for the analysis of cellular functions of the underlying Ca2+ channels.

Abeta‐polyacrolein is neurotoxic in an amyloid‐independent manner

A previous study indicated that amyloid beta peptide (ABP) exhibits surfactant properties, suggesting that the toxicity of ABP in Alzheimer disease (AD) is attributed to the peptide's effect on the organization of water molecules. We previously proposed that ABP‐polyacrolein, which is derived from ABP‐induced polymerization of acrolein, may contribute to the neurotoxicity in AD. In this study, we examined the effect of ABP‐polyacrolein on gene expression in differentiated SH‐SY5Y cells using a PCR array composed of probes for 84 genes that are involved in neurotoxicity. We compared the results against the effects of ABP alone. We observed that ABP alone decreased the expression of eight different genes (criterion: greater than 2‐fold change). However, the downregulation of three of these genes (epiregulin, tryptophan hydroxylase‐1, and transient receptor potential cation channel‐M4) were appreciably attenuated by ABP‐polyacrolein presumably due to ABP‐polyacrolein's abrogation of ABP's surfactant‐like injury to the cell. Furthermore, we observed a unique downregulation of three genes with ABP‐polyacrolein (hephaestin, notch 4, and transient receptor potential cation channel‐M1). This suggests a novel mechanism of neurotoxicity not seen with ABP alone and likely due to the extensive polymeric arrangement of ABP‐polyacrolein, which is quite dissimilar from the typical amyloid structure.

Decreased Expression of Transient Receptor Potential Channels in Cerebral Vascular Tissue from Patients After Hypertensive Intracerebral Hemorrhage

Recent data indicate that transient receptor potential (TRP) cation channels play an important role in hypertension. Now, we tested the hypothesis that TRP expression is altered in human cerebral vascular tissue in patients who had experienced hypertensive intracerebral hemorrhage. TRPC1, TRPC3, TRPC5, TRPC6, TRPM4, TRPM6, and TRPM7 channels were detected in cerebral vascular tissue by quantitative real-time RT-PCR. Control cerebral vascular tissue was obtained from normotensive patients who underwent neurosurgical operation because of brain tumor. To examine a possible relation between the expression of TRP expression and hypoxic conditions caused by the intracerebral bleeding, we examined the expression of hypoxia inducible factor 1a (HIF1a). Transcripts of TRPC3, TRPC5, TRPM6, and HIF1a were significantly reduced in cerebral vascular tissue from patients after hypertensive intracerebral hemorrhage compared to controls. TRPC3 mRNA correlated well with the expression of HIF1a mRNA (r2 = 0.59; p = 0.01). TRPC3 expression is associated with hypertension and hypoxic conditions in human cerebral vascular tissue.

Assessment of Mucosal Movement in the Gastroesophageal Junction High-Pressure Zone During Swallowing Using Simultaneous Endoluminal Ultrasound and Manometry

BACKGROUND & AIM: Allyl isothiocyanate, the pungent ingredient of wasabi and mustard oil, is known to activate transient receptor potential (TRP) cation channels TRPA1. TRPA1 was recently shown to be functionally expressed in the gastrointestinal tract, whose ion channel presents in a subpopulation of primary sensory neurons that coexpressed with TRPV1. Previously, we also reported (1) that TRPV1-expressing sensory nerve fivers abundantly exist around blood vessels in the submucosa in the rat stomach, suggesting that TRPV1 plays an important role in control of local blood flow (Scand J. Gastroenterol. 39, 303-312, 2004), and (2) that allyl isothiocyanate facilitates to increase gastric mucosal blood flow (GMBF) in the rat stomach (Gastroenterology 138 (Suppl.1) S-721, 2010). However, the mechanism for the increased GMBF in response to allyl isothiocyanate remains unknown. In the present studies, we examined the effect of a TRPA1 activator allyl isothiocyanate on GMBF in the ex-vivo stomach of normal and sensory deafferented rats. METHODS: Male SD rats (160-200 g) were used after 18 hr-fasting. GMBFwasmeasured in the ex-vivo stomach of urethane-anesthetized rats by using the laser Doppler flowmeter. Allyl isothiocyanate (0.3310 mM) or a TRPV1 channel activator capsaicin (3.3 mM) was topically applied for 10 min to the rat stomach, and changes in GMBF were monitored. Either a TRPA1 channel blocker HC-030031 (14.1 mM) or a TRPV1 channel blocker BCTC (0.8 mM) was co-applied with allyl isothiocyanate (10 mM) for 10 min to the stomach. RESULTS: Mucosal application of allyl isothiocyanate increased GMBF in a concentration-dependentmanner.When themucosa was exposed to allyl isothiocyanate (10 mM) repeatedly, this response showed a marked desensitization. The increased GMBF response caused by allyl isothiocyanate was entirely blocked by co-application with HC-030031, but not BCTC. Interestingly, the increased GMBF in response to allyl isothiocyanate was significantly attenuated, but not completely disappear, by chemical deafferentation following systemic capsaicin injections (total dose: 100 mg/kg), although the increased GMBF in response to capsaicin was completely abolished by chemical deafferentation. The increased GMBF response to capsaicin was also significantly decreased in allyl isothiocyanate-desensitized preparation of the ex-vivo stomach. CONCLUSION: These results suggested that allyl isothiocyanate increases GMBF through activation of TRPA1, but not TRPV1. It is assumed that the increased GMBF in response to allyl isothiocyanate is mediated by TRPA1 located on both TRPV1-expresseing and TRPV1 nonexpressing sensory nerves.

The Facultative Role of Lipid Rafts and Membrane Microdomains in Controlling the Assembly of the Store-Operated Channel Complex

Calcium influx is an important factor in a wide variety of cellular functions. The signal initiating calcium influx may originate from the activation of G-protein coupled receptors, or arise from inside the cell, via maneuvers that can lead to depletion of intracellular calcium storage compartments. While the role of members from the Transient Receptor Potential Cation (TRPC) family of channels as receptor-operated channels (ROC) is well established and supported by abundant studies, the role of this family of channels as store-operated channels (SOC) has been the focus of a heated controversy over the last few years. In the present study, we have explored the modulation of STIM1 on human TRPC1 channel. We have found that the association of STIM1 to TRPC1 favors the insertion of this channel into lipid rafts, where TRPC1 functions as a SOC in association to Orai channels forming a complex we have named SOCIC (store-operated calcium influx complex). In the absence of STIM1, TRPC1 associates to other members from the TRPC family of channels to form ROCs. A novel imaging method implemented for the present study based on multicolor LightGuide Total Internal Reflection Fluorescence Microscopy (LG-TIRFM), illustrates the relevance of the dynamic association between STIM1 and TRPC1 for the activation of SOC and the lipid raft localization of the STIM1-TRPC1-Orai complex. This study provides new evidence about the dual activity of TRPC1 (forming ROC or SOC) and the partners needed to determine TRPC1 functional fate. It highlights also the role of plasma membrane microdomains (lipid rafts) and ER-PM junctions in modulating TRPC1 channel function. Using LG-TIRFM, we identified new partners of the SOCIC, and studied the dynamics of SOCIC assembly and disassembly in real time.

Association Study of TRPC4 as a Candidate Gene for Generalized Epilepsy with Photosensitivity

Photoparoxysmal response (PPR) is characterized by abnormal visual sensitivity of the brain to photic stimulation. Frequently associated with idiopathic generalized epilepsies (IGEs), it might be an endophenotype for cortical excitability. Transient receptor potential cation (TRPC) channels are involved in the generation of epileptiform discharges, and TRPC4 constitutes the main TRPC channel in the central nervous system. The present study investigated an association of PPR with sequence variations of the TRPC4 gene. Thirty-five single nucleotide polymorphisms (SNP) within TRPC4 were genotyped in 273 PPR probands and 599 population controls. Association analyses were performed for the broad PPR endophenotype (PPR types I-IV; n = 273), a narrow model of affectedness (PPR types III and IV; n = 214) and PPR associated with IGE (PPR/IGE; n = 106) for each SNP and for corresponding haplotypes. Association was found between the intron 5 SNP rs10507456 and PPR/IGE both for single markers (P = 0.005) and haplotype level (P = 0.01). Three additional SNPs (rs1535775, rs10161932 and rs7338118) within the same haplotype block were associated with PPR/IGE at P < 0.05 (uncorrected) as well as two more markers (rs10507457, rs7329459) located in intron 3. Again, the corresponding haplotype also showed association with PPR/IGE. Results were not significant following correction for multiple comparisons by permutation analysis for single markers and Bonferroni-Holm for haplotypes. No association was found between variants in TRPC4 and other phenotypes. Our results showed a trend toward association of TRPC4 variants and PPR/IGE. Further studies including larger samples of photosensitive probands are required to clarify the relevance of TRPC4 for PPR and IGE.

Transient receptor potential (TRP) cation channels

Transient receptor potential (TRP) cation channels

STIMulating store-operated Ca2+ entry

Calcium influx through plasma membrane store-operated Ca(2+) (SOC) channels is triggered when the endoplasmic reticulum (ER) Ca(2+) store is depleted - a homeostatic Ca(2+) signalling mechanism that remained enigmatic for more than two decades. RNA-interference (RNAi) screening and molecular and cellular physiological analysis recently identified STIM1 as the mechanistic 'missing link' between the ER and the plasma membrane. STIM proteins sense the depletion of Ca(2+) from the ER, oligomerize, translocate to junctions adjacent to the plasma membrane, organize Orai or TRPC (transient receptor potential cation) channels into clusters and open these channels to bring about SOC entry.

Camphoric acid stimulates osteoblast differentiation and induces glutamate receptor expression

We found that camphoric acid significantly stimulated the differentiation of mouse osteoblastic MC3T3-E1 subclone 4 cells, as indicated by the induction of markers of osteoblastic differentiation. To elucidate the mechanism of action of camphoric acid in osteoblast differentiation, we evaluated the induction of transient receptor potential (TRP) cation channel family members and glutamate signaling molecules. TRPM7 and TRPV1 were highly expressed, but their expression was unaffected by camphoric acid. Camphoric acid is structurally similar to glutamate receptor ligands and significantly induced the expression of NMDAR1, GluR3/4, and mGluR8. However, camphoric acid exhibited weak regulatory activity toward glutamate receptors in a radioligand binding assay. Camphoric acid also significantly induced the activation of NF-kappaB and AP-1. Together, these data suggest that the stimulatory effect of camphoric acid on osteoblast differentiation was the result of its ability to induce mRNA expression of glutamate signaling molecules and to activate transcription factors.

The HERACLES Cardiovascular Network

In 2002, a group of researchers in the fields of cell electrophysiology, cardiology, population genetics, epidemiology, proteomics, molecular biology, bioinformatics and statistics decided to take up the challenge of investigating the mechanisms and genetics of arterial hypertension (AH). Mechanisms related to ion channel regulation of arterial smooth muscle function were identified. The HERACLES (Hipertensión Esencial: Red de Análisis de Canales iónicos de la musculatura Lisa arterial y su Explotación terapéutica Sistemática) network was honored with a distinguished mention in the 2005 evaluation, and was strengthened by the incorporation of new research groups in 2007. The work of the HERACLES network is characterized as much by the transfer of knowledge "from bedside to bench" as by its converse: "from bench to bedside". The current objectives of the HERACLES network are: a) to study the Ca2+-dependent K+ channels, the transient receptor potential (TRP) cation channels, and the Ca2+-dependent Cl- channels that are involved in vascular physiology; b) to study protein expression maps in plasma and cardiovascular tissue and their significance for drug treatment; c) to study the effect of flavonoids on ion transport and responses to oxidative stress, and d) to identify biomarkers of risk, prognosis, and treatment responses in extreme AH phenotypes. Our project includes a number of lines of research coordinated within cross-sectional programs based on centralized facilities, which are used by them. The HERACLES network has published more than 60 articles (available from: http://www.redheracles.net), funding has been received for more than 90 projects in competitive submissions to Spanish and six international bodies, and there is a DNA Biobank.

Capsaicin-Induced Increase of Intestinal Cefazolin Absorption in Rats

The effect of capsaicin on intestinal cefazolin absorption was examined by means of an in situ closed loop method in rats to clarify whether the vanilloid receptor (TRPV1) is involved in drug absorption driven by passive diffusion. In control experiments with 1 mg/mL cefazolin, the amount of cefazolin absorbed from the closed loop was 15.3+/-1.5 microg/cm in the rat jejunum. The absorption amount was increased to 22.8+/-0.9 and 23.4+/-2.4 microg/cm when capsaicin was applied with cefazolin at concentrations of 10 and 400 microM, respectively. The enhancing effect of capsaicin on cefazolin absorption was suppressed when ruthenium red, a non-selective inhibitor of transient receptor potential (TRP) cation channels, was intravenously infused into the rat during the experiment. Cefazolin accumulation in the intestinal tissue was not altered in the presence of capsaicin. Collectively, the mechanism accounting for the capsaicin-induced increase in the intestinal cefazolin absorption is probably that capsaicin associating with TRPV1 increases the intrinsic permeability of cefazolin in intestine.