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Transient Receptor Potential (transient + receptor_potential)
Terms modified by Transient Receptor Potential Selected AbstractsTRP channels as therapeutic targets: hot property, or time to cool down?NEUROGASTROENTEROLOGY & MOTILITY, Issue 8 2006G. A. Hicks Abstract,Transient receptor potential (TRP) channels are involved in a wide range of processes ranging from osmoregulation, thermal, chemical and sensory signalling, and potentially in the pathophysiology associated with several diseases. Patents for TRPV1 antagonists alone span diseases ranging across chronic pain, neuropathies, headache, bladder disorders, irritable bowel syndrome (IBS), gastro-oesophageal reflux disease (GORD), and cough amongst others. Most research is currently focused around those TRP channels involved in sensory processes, with the neurogastroenterology and motility field playing a major role, for example, through recent discoveries of differential roles for TRPV receptor subtypes in chemosensitivity and mechanosensitivity of visceral afferents. At this time, however, the understanding of the role of even TRPV1, let alone most of the other TRP channels in disease pathophysiology is only just beginning, and although enthusiasm around the therapeutic potential for modulators of these channels is understandable, based largely upon the experience of the effects of natural ligands, such as capsaicin, the sheer size and complexity of the TRP family as a whole must serve as a warning against expecting too much too soon from drug discovery efforts. [source] Gene Transfer of TRPC6DN (Dominant Negative) Restores Erectile Function in Diabetic RatsTHE JOURNAL OF SEXUAL MEDICINE, Issue 3 2010Jae Hun Jung MD ABSTRACT Introduction., Transient receptor potential (TRP) channels play an important role in modulating intracellular Ca2+ ([Ca2+]i) levels. Aim., We examined the hypothesis that overexpression of TRPC6DN (dominant negative) may contribute to decreased [Ca2+]i levels in corporal smooth muscle (CSM). We also investigated whether gene transfer of TRPC6DN could restore erectile function in diabetic rats. Methods., For the in vitro study, the KCa, KATP, and TRPC6DN channel genes were transferred using cDNA, into cultured human CSM cells and human embryonic kidney cells. For the in vivo study, young adult rats were divided into three groups: normal controls; diabetic controls transfected with vector only; and a diabetic group transfected with pcDNA of the TRPC6DN gene. Main Outcome Measures., After gene transfer, the effects of reducing [Ca2+]i levels were assessed by Fura-2-based imaging analysis. The intracavernosal pressure (ICP) response to cavernosal nerve stimulation was assessed after intracorporal injection of TRPC6DN pcDNA. The transgene expression of the TRPC6DN was examined by reverse transcription polymerase chain reaction (RT-PCR) in rats transfected with TRPC6DN pcDNA. Results., Gene transfer of ion channels effectively reduced [Ca2+]i. Among these channels, transfer of the TRPC6DN gene resulted in the greatest reduction of [Ca2+]i in human CSM. The mean (±standard error of the mean) ratio of ICP to mean arterial pressure (BP) in the gene-transfer rats was 79.4 ± 2.4% (N = 8). This was significantly higher than that in control rats (55.6 ± 3.7% [N = 8]), and similar to that in the young control rats (83 ± 2.2% [N = 12]). The RT-PCR showed expression of TRPC6DN genes in the transfected rats. Conclusion., Gene transfer of TRPC6DN not only reduced [Ca2+]i in human CSM but also restored erectile function in diabetic rats. These results suggest that pcDNA transfer of TRPC6DN may represent a promising new form of therapy for the treatment of male erectile dysfunction in the future. Jung JH, Kim BJ, Chae MR, Kam SC, Jeon J-H, So I, Chung KH, and Lee SW. Gene transfer of TRPC6DN (dominant negative) restores erectile function in diabetic rats. J Sex Med 2010;7:1126,1138. [source] 4,-PDD induces Ca2+ influx in human corneal epithelial cells by activating TRPV4 channelsACTA OPHTHALMOLOGICA, Issue 2007S MERGLER Purpose: Transient receptor potential (TRP) isoform expression is evident in human corneal epithelial cells (HCEC-SV40). However, their role in maintaining corneal epithelial homeostasis is not fully understood. We probed for gene and protein expression as well as functional activity of the vanilloid subtype, TRPV4, in immortalized HCEC-SV40 since they elicit Ca2+ dependent regulatory volume decrease (RVD) responses during exposure to a hypotonic challenge. Methods: RT-PCR and Western blotting analyses identified TRPV4 gene and protein expression. Functional activity was assessed based on determining whether the TRPV4 selective agonist, 4,-PDD, induced transients increases in intracellular Ca2+ concentration. Results: Single cell fluorescence imaging results showed that 4,-PDD (3 ,M) increased intracellular Ca2+ concentration. The fura2 fluorescence ratio (f340/f380) was 0.39 ± 0.03578 in the resting state (n = 5). After application of 4,-PDD it increased to 0.904 ± 0.14363 (n = 5; p = 5.72077×10-5). This increase was abolished by the TRP channel blocker ruthenium red or by Ca2+-free Ringer's medium. Conclusions: In conclusion, there is functional TRPV4 expression in HCEC-SV40. TRPV4 expression may provide an osmosensor role to induce RVD behavior during exposure to a hypotonic challenge since this response is mediated through intracellular Ca2+ transients. Supported in part DFG Pl 150/14-1 and NIH, EY04795. CR: none [source] The calcium-conducting ion channel transient receptor potential canonical 6 is involved in macrophage inflammatory protein-2-induced migration of mouse neutrophils,ACTA PHYSIOLOGICA, Issue 1 2009N. Damann Abstract Aim:, The role of the calcium-conducting ion channel transient receptor potential canonical 6 (TRPC6) in macrophage inflammatory protein-2 (MIP-2) induced migration of mouse neutrophils was investigated. Methods:, Neutrophil granulocytes isolated from murine bone marrow of wild-type (TRPC6+/+) and TRPC6 knockout (TRPC6,/,) mice were tested for the presence of TRPC6 channel expression using quantitative real-time polymerase chain reactions and immunocytochemistry. The effect of different stimuli (e.g. MIP-2, 1-oleoyl-2-acetyl-sn-glycerol, formyl-methionyl-leucyl-phenylalanin) on migration of isolated neutrophils was tested by two-dimensional (2D) migration assays, phalloidin staining and intracellular calcium imaging. Results:, We found that neutrophil granulocytes express TRPC6 channels. MIP-2 induced fast cell migration of isolated neutrophils in a 2D cell-tracking system. Strikingly, MIP-2 was less potent in neutrophils derived from TRPC6,/, mice. These cells showed less phalloidin-coupled fluorescence and the pattern of cytosolic calcium transients was altered. Conclusions:, We describe in this paper for the first time a role for transient receptor potential (TRP) channels in migration of native lymphocytes as a new paradigm for the universal functional role of TRPs. Our data give strong evidence that TRPC6 operates downstream to CXC-type Gq -protein-coupled chemokine receptors upon stimulation with MIP-2 and is crucial for the arrangement of filamentous actin in migrating neutrophils. This is a novel cell function of TRP channel beyond their well-recognized role as universal cell sensors. [source] Mechanisms of metabotropic glutamate receptor-mediated synaptic signalling in cerebellar Purkinje cellsACTA PHYSIOLOGICA, Issue 1 2009J. Hartmann Abstract The metabotropic glutamate receptors type 1 (mGluR1s) are required for a normal function of the mammalian cerebellum. These G-protein-coupled receptors are abundantly expressed in the principle cerebellar cells, namely the Purkinje neurones. Under physiological conditions, mGluR1s are activated during repetitive activity of both afferent glutamatergic synaptic inputs provided by the climbing and parallel fibres respectively. Unlike the common ionotropic glutamate receptors that underlie rapid synaptic excitation, mGluR1s produce a complex post-synaptic response consisting of a Ca2+ -release signal from intracellular stores and a slow excitatory post-synaptic potential. While it is well established that the mGluR1-dependent Ca2+ -release signal from intracellular stores involves the activation of inositol-trisphosphate receptors, the mechanisms underlying the slow synaptic excitation remained unclear. Here we will review recent evidence indicating an essential role of C-type transient receptor potential (TRPC) cation channels, especially that of the subunit TRPC3, for the generation of the mGluR1-dependent synaptic current. For the signalling pathways underlying both, Ca2+ -release from intracellular stores and the slow synaptic potential, we present current knowledge about the activators, downstream effectors and possible roles for mGluR1-dependent signalling in Purkinje neurones. [source] Effect of capsaicin on Ca2+ fluxes in Madin-Darby canine renal tubular cellsDRUG DEVELOPMENT RESEARCH, Issue 2 2010Jeng-Hsien Yeh Abstract The effect of capsaicin, a transient receptor potential vanniloid-1 (TRPV1) receptor agonist, on cytosolic free Ca2+ concentrations ([Ca2+]i) in Madin Darby canine kidney (MDCK) cells is unclear. This study explored whether capsaicin changed basal [Ca2+]i levels in suspended MDCK cells by using fura-2 as a Ca2+ -sensitive fluorescent dye. Capsaicin at concentrations between 10,100,µM increased [Ca2+]i in a concentration-dependent manner. The Ca2+ signal was reduced by 80% by removing extracellular Ca2+. Capsacin induced Mn2+ influx, leading to quench of fura-2 fluorescence suggesting Ca2+ influx. This Ca2+ influx was inhibited by phospholipase A2 inhibitor aristolochic acid and the non-selective Ca2+ entry blocker La3+, but not by store-operated Ca2+ channel blockers nifedipine, econazole, and SK&F96365, and protein kinase C/A modulators. In Ca2+ -free medium, pretreatment with the endoplasmic reticulum Ca2+ pump inhibitor thapsigargin abolished capsaicin-induced Ca2+ release. Conversely, pretreatment with capsaicin partly reduced thapsigargin-induced [Ca2+]i rise. Inhibition of phospholipase C with U73122 did not alter capsaicin-induced [Ca2+]i rise. The TRPV1 receptor antagonist capsazepine also induced significant Ca2+ entry and Ca2+ release. Collectively, in MDCK cells, capsaicin induced [Ca2+]i rises by causing phospholipase C-independent Ca2+ release from the endoplasmic reticulum and Ca2+ influx via phospholipase A2-regulated, La3+ -sensitive Ca2+ channels in a manner dissociated from stimulation of TRPV1 receptors. Drug Dev Res, 2009. © 2009 Wiley-Liss, Inc. [source] Transient receptor potential A1 mediates acetaldehyde-evoked pain sensationEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 9 2007Sangsu Bang Abstract Six transient receptor potential (TRP) ion channels expressed in the sensory afferents play an important role as body thermosensors and also as peripheral pain detectors. It is known that a number of natural compounds specifically activate those sensory neuronal TRP channels, and a well-known example is cinnamaldehyde for TRPA1. Here we show that human and mouse TRPA1 are activated by acetaldehyde, an intermediate substance of ethanol metabolism, in the HEK293T cell heterologous expression system and in cultured mouse trigeminal neurons. Acetaldehyde failed to activate other temperature-sensitive TRP channels expressed in sensory neurons. TRPA1 antagonists camphor and gadolinium, and a general TRP blocker ruthenium red inhibited TRPA1 activation by acetaldehyde. Camphor, gadolinium and ruthenium red also suppressed the acute nociceptive behaviors induced by the intradermal administration of acetaldehyde into the mouse footpads. Intradermal co-application of prostaglandin E2 and acetaldehyde greatly potentiated the acetaldehyde-induced nociceptive responses, and this effect was reversed by treatment with the TRPA1 antagonist camphor. These results suggest that acetaldehyde causes nociception via TRPA1 activation. Our data may also help elucidate the mechanisms underlying acetaldehyde-related pathological symptoms such as hangover pain. [source] Urinary pheromones promote ERK/Akt phosphorylation, regeneration and survival of vomeronasal (V2R) neuronsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2006Jing Xia Abstract The G protein-coupled pheromone receptor neurons (V1R and V2R) of the vomeronasal organ (VNO) are continually replaced throughout the lifetime of the mouse. Moreover, active signalling of V2Rs via the transient receptor potential 2(TRPC2) channel is necessary for regeneration of receptors, as the TRPC2 null mutant mouse showed a 75% reduction of V2Rs by the age of two months. Here we describe V2R mediated signalling in a neuronal line established from vomeronasal stem cells taken from postnatal female mice. Cells were immunoreactive for G,o and V2R, whereas V1R and G,i immunoreactivity could not be detected. Biological ligands (dilute urine and its protein fractions) were found to increase proliferation and survival of these neurons. Dilute mouse urine but not artificial urine also induced ERK, Akt and CREB signalling in a dose dependent way. The volatile fraction of male mouse urine alone was without effect while the fraction containing peptides (> 5 kDa) also stimulated ERK and Akt phosphorylation. The ERK, Akt and CREB phosphorylation response was sensitive to pertussis toxin, confirming the involvement of V2R linked G,o. Dilute mouse urine or its high molecular weight protein fraction increased survival and proliferation of these neurons. Hence, urinary pheromones, which signal important social information via mature neurons, also promote survival and proliferation of their regenerating precursors. These data show that regenerating V2Rs respond to urine and the urinary peptides by activation of the Ras-ERK and PI3-Akt pathways, which appear to be important for vomeronasal neural survival and proliferation. [source] Ca2+ entry through TRPC1 channels contributes to intracellular Ca2+ dynamics and consequent glutamate release from rat astrocytesGLIA, Issue 8 2008Erik B. Malarkey Abstract Astrocytes can respond to a variety of stimuli by elevating their cytoplasmic Ca2+ concentration and can in turn release glutamate to signal adjacent neurons. The majority of this Ca2+ is derived from internal stores while a portion also comes from outside of the cell. Astrocytes use Ca2+ entry through store-operated Ca2+ channels to refill their internal stores. Therefore, we investigated what role this store-operated Ca2+ entry plays in astrocytic Ca2+ responses and subsequent glutamate release. Astrocytes express canonical transient receptor potential (TRPC) channels that have been implicated in mediating store-operated Ca2+ entry. Here, we show that astrocytes in culture and freshly isolated astrocytes from visual cortex express TRPC1, TRPC4, and TRPC5. Indirect immunocytochemistry reveals that these proteins are present throughout the cell; the predominant expression of functionally tested TRPC1, however, is on the plasma membrane. Labeling in freshly isolated astrocytes reveals changes in TRPC expression throughout development. Using an antibody against TRPC1 we were able to block the function of TRPC1 channels and determine their involvement in mechanically and agonist-evoked Ca2+ entry in cultured astrocytes. Blocking TRPC1 was also found to reduce mechanically induced Ca2+ -dependent glutamate release. These data indicate that Ca2+ entry through TRPC1 channels contributes to Ca2+ signaling in astrocytes and the consequent glutamate release from these cells. © 2008 Wiley-Liss, Inc. [source] Calcium Channel TRPV6 Is Involved in Murine Maternal,Fetal Calcium Transport,,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 8 2008Yoshiro Suzuki Abstract Maternal,fetal calcium (Ca2+) transport is crucial for fetal Ca2+ homeostasis and bone mineralization. In this study, the physiological significance of the transient receptor potential, vanilloid 6 (TRPV6) Ca2+ channel in maternal,fetal Ca2+ transport was investigated using Trpv6 knockout mice. The Ca2+ concentration in fetal blood and amniotic fluid was significantly lower in Trpv6 knockout fetuses than in wildtypes. The transport activity of radioactive Ca2+ (45Ca) from mother to fetuses was 40% lower in Trpv6 knockout fetuses than in wildtypes. The ash weight was also lower in Trpv6 knockout fetuses compared with wildtype fetuses. TRPV6 mRNA and protein were mainly localized in intraplacental yolk sac and the visceral layer of extraplacental yolk sac, which are thought to be the places for maternal,fetal Ca2+ transport in mice. These expression sites were co-localized with calbindin D9K in the yolk sac. In wildtype mice, placental TRPV6 mRNA increased 14-fold during the last 4 days of gestation, which coincides with fetal bone mineralization. These results provide the first in vivo evidence that TRPV6 is involved in maternal,fetal Ca2+ transport. We propose that TRPV6 functions as a Ca2+ entry pathway, which is critical for fetal Ca2+ homeostasis. [source] Differentiation dependent expression of TRPA1 and TRPM8 channels in IMR-32 human neuroblastoma cellsJOURNAL OF CELLULAR PHYSIOLOGY, Issue 1 2009Lauri M. Louhivuori TRPA1 and TRPM8 are transient receptor potential (TRP) channels involved in sensory perception. TRPA1 is a non-selective calcium permeable channel activated by irritants and proalgesic agents. TRPM8 reacts to chemical cooling agents such as menthol. The human neuroblastoma cell line IMR-32 undergoes a remarkable differentiation in response to treatment with 5-bromo-2-deoxyuridine. The cells acquire a neuronal morphology with increased expression of N-type voltage gated calcium channels and neurotransmitters. Here we show using RT-PCR, that mRNA for TRPA1 and TRPM8 are strongly upregulated in differentiating IMR-32 cells. Using whole cell patch clamp recordings, we demonstrate that activators of these channels, wasabi, allyl-isothiocyanate (AITC) and menthol activate membrane currents in differentiated cells. Calcium imaging experiments demonstrated that AITC mediated elevation of intracellular calcium levels were attenuated by ruthenium red, spermine, and HC-030031 as well as by siRNA directed against the channel. This indicates that the detected mRNA level correlate with the presence of functional channels of both types in the membrane of differentiated cells. Although the differentiated IMR-32 cells responded to cooling many of the cells showing this response did not respond to TRPA1/TRPM8 channel activators (60% and 90% for AITC and menthol respectively). Conversely many of the cells responding to these activators did not respond to cooling (30%). This suggests that these channels have also other functions than cold perception in these cells. Furthermore, our results suggest that IMR-32 cells have sensory characteristics and can be used to study native TRPA1 and TRPM8 channel function as well as developmental expression. J. Cell. Physiol. 221: 67,74, 2009. © 2009 Wiley-Liss, Inc [source] Ethanol inhibits cold-menthol receptor TRPM8 by modulating its interaction with membrane phosphatidylinositol 4,5-bisphosphateJOURNAL OF NEUROCHEMISTRY, Issue 1 2007Jan Benedikt Abstract Ethanol has opposite effects on two members of the transient receptor potential (TRP) family of ion channels: it inhibits the cold-menthol receptor TRPM8, whereas it potentiates the activity of the heat- and capsaicin-gated vanilloid receptor TRPV1. Both thermosensitive cation channels are critically regulated by the membrane lipid, phosphatidylinositol 4,5-bisphosphate (PIP2). The effects of this phospholipid on TRPM8 and TRPV1 are also functionally opposite: PIP2 is necessary for the activation of TRPM8 but it constitutively inhibits TRPV1. This parallel led us to investigate the possible role of PIP2 in the ethanol-induced modulation of rat TRPM8, heterologously expressed in HEK293T cells. In this study, we characterize the effects of ethanol (0.1,10%) on whole-cell currents produced by menthol and by low temperature (< 17°C). We show that the inclusion of PIP2 in the intracellular solution results in a strong reduction in the ethanol-induced inhibition of menthol-evoked responses. Conversely, intracellular dialysis with anti-PIP2 antibody or with the PIP2 scavenger, poly l -lysine, enhanced the ethanol-induced inhibition of TRPM8. A 20 min pre-incubation with wortmannin caused a modest decrease in inhibition produced by 1% ethanol, indicating that the ethanol-induced inhibition is not mediated by lipid kinases. These findings suggest that ethanol inhibits TRPM8 by weakening the PIP2,TRPM8 channel interaction; a similar mechanism may contribute to the ethanol-mediated modulation of some other PIP2 -sensitive TRP channels. [source] TRPV1-mediated itch in seasonal allergic rhinitisALLERGY, Issue 5 2009L. Alenmyr Background:, Patients with allergic rhinitis may be abnormally sensitive to stimulation of the ion channel transient receptor potential vanilloid-1 (TRPV1). Aim of the study:, To examine effects of various TRP ion channel activators on sensory symptoms in allergic rhinitis prior to and during seasonal allergen exposure. Methods:, Nasal challenges were carried out with the TRPV1-activators capsaicin, anandamide and olvanil. Moreover, challenges were performed with mustard oil (allylisothiocyanate) and cinnamaldehyde as well as menthol, activators of TRPA1 and TRPM8, respectively. Nasal symptoms were monitored after each challenge and compared with symptoms reported following corresponding sham challenges. Symptoms recorded after challenge prior to pollen season were also compared with challenge-induced symptoms during pollen season. Results:, The TRPV1, TRPA1 and TRPM8-activators produced sensory symptoms dominated by pain and smart. During seasonal allergen exposure, but not prior to season, TRPV1-activators also induced itch. Furthermore, the seasonal challenge to the TRPV1-activator olvanil was associated with rhinorrhoea. Conclusion:, Patients with allergic rhinitis feature an increased itch response to TRPV1 stimulation at seasonal allergen exposure. We suggest that this reflects part of the hyperresponsiveness that characterizes on-going allergic rhinitis. Intervention with the TRPV1-signalling pathway may offer potential treatments of this condition. [source] TRPV1 in colitis: is it a good or a bad receptor?NEUROGASTROENTEROLOGY & MOTILITY, Issue 8 2007a viewpoint Abstract, The role of the transient receptor potential vanilloid-1 (TRPV1) receptor has been repeatedly investigated in animal models of inflammation. The present issue of Neurogastroenterology and Motility includes another report on this issue and not unexpectedly, many questions on the precise role of TRPV1 receptors in inflammation remain unanswered. This Editorial Viewpoint discusses the present knowledge on TRPV1 receptor involvement in intestinal inflammation and discusses the question whether the TRPV1 has to be regarded as the good or the bad receptor in this context. Since TRPV1 activation turns out being a valuable approach, translation of this knowledge to human disease is highly recommended. [source] Mechanisms of stretch-induced muscle damage in normal and dystrophic muscle: role of ionic changesTHE JOURNAL OF PHYSIOLOGY, Issue 3 2005D. G. Allen Muscle damage, characterized by prolonged weakness and delayed onset of stiffness and soreness, is common following contractions in which the muscles are stretched. Stretch-induced damage of this sort is more pronounced in the muscular dystrophies and the profound muscle damage observed in these conditions may involve similar pathways. It has been known for many years that damaged muscles accumulate calcium and that elevating calcium in normal muscles simulates many aspects of muscle damage. The changes in intracellular calcium, sodium and pH following stretched contractions are reviewed and the various pathways which have been proposed to allow ion entry are discussed. One possibility is that TRPC1 (transient receptor potential, canonical), a protein which seems to form both a stretch-activated channel and a store-operated channel, is the main source of Ca2+ entry. The mechanisms by which the changes in intracellular ions contribute to reduced force production, to increased protein breakdown and to increased membrane permeability are considered. A hypothetical scheme for muscle damage which incorporates these ideas is presented. [source] Multiple regulation by calcium of murine homologues of transient receptor potential proteins TRPC6 and TRPC7 expressed in HEK293 cellsTHE JOURNAL OF PHYSIOLOGY, Issue 2 2004Juan Shi We investigated, by using the patch clamp technique, Ca2+ -mediated regulation of heterologously expressed TRPC6 and TRPC7 proteins in HEK293 cells, two closely related homologues of the transient receptor potential (TRP) family and molecular candidates for native receptor-operated Ca2+ entry channels. With nystatin-perforated recording, the magnitude and time courses of activation and inactivation of carbachol (CCh; 100 ,m)-activated TRPC6 currents (ITRPC6) were enhanced and accelerated, respectively, by extracellular Ca2+ (Ca2o+) whether it was continuously present or applied after receptor stimulation. In contrast, Ca2o+ solely inhibited TRPC7 currents (ITRPC7). Vigorous buffering of intracellular Ca2+ (Ca2i+) under conventional whole-cell clamp abolished the slow potentiating (i.e. accelerated activation) and inactivating effects of Ca2o+, disclosing fast potentiation (EC50: ,0.4 mm) and inhibition (IC50: ,4 mm) of ITRPC6 and fast inhibition (IC50: ,0.4 mm) of ITRPC7. This inhibition of ITRPC6 and ITRPC7 seems to be associated with voltage-dependent reductions of unitary conductance and open probability at the single channel level, whereas the potentiation of ITRPC6 showed little voltage dependence and was mimicked by Sr2+ but not Ba2+. The activation process of ITRPC6 or its acceleration by Ca2o+ probably involves phosphorylation by calmodulin (CaM)-dependent kinase II (CaMKII), as pretreatment with calmidazolium (3 ,m), coexpression of Ca2+ -insesentive mutant CaM, and intracellular perfusion of the non-hydrolysable ATP analogue AMP-PNP and a CaMKII-specific inhibitory peptide all effectively prevented channel activation. However, this was not observed for TRPC7. Instead, single CCh-activated TRPC7 channel activity was concentration-dependently suppressed by nanomolar Ca2i+ via CaM and conversely enhanced by IP3. In addition, the inactivation time course of ITRPC6 was significantly retarded by pharmacological inhibition of protein kinase C (PKC). These results collectively suggest that TRPC6 and 7 channels are multiply regulated by Ca2+ from both sides of the membrane through differential Ca2+,CaM-dependent and -independent mechanisms. [source] TRPM1: The endpoint of the mGluR6 signal transduction cascade in retinal ON-bipolar cellsBIOESSAYS, Issue 7 2010Catherine W. Morgans Abstract For almost 30 years the ion channel that initiates the ON visual pathway in vertebrate vision has remained elusive. Recent findings now indicate that the pathway, which begins with unbinding of glutamate from the metabotropic glutamate receptor 6 (mGluR6), ends with the opening of the transient receptor potential (TRP)M1 cation channel. As a component of the mGluR6 signal transduction pathway, mutations in TRPM1 would be expected to cause congenital stationary night blindness (CSNB), and several such mutations have already been identified in CSNB families. Furthermore, expression of TRPM1 in both the retina and skin raises the possibility that a genetic link exists between certain types of visual and skin disorders. [source] Activation of the transient receptor potential vanilloid-1 (TRPV1) channel opens the gate for pain reliefBRITISH JOURNAL OF PHARMACOLOGY, Issue 8 2008G Jancsó Pharmacological modulation of the transient receptor potential vanilloid-1 (TRPV1) receptor function offers a promising means of producing pain relief at the level of the primary sensory neuron. In this issue of the BJP, the pharmacological approaches and the available experimental data that focus on the TRPV1 receptor to achieve therapeutically useful alleviation of pain and inflammation are reviewed. The potentials to inactivate TRPV1 receptor function by site- and modality-specific TRPV1 antagonists, uncompetitive TRPV1 blockers and drugs interfering with TRPV1 sensitization, are evaluated. A crucial issue of producing pain relief at the level of the nocisensor remains whether it can be achieved solely through inactivation of the TRPV1 receptor or TRPV1 agonist-induced defunctionalization of the whole primary afferent neuron is required. The accumulated evidence indicates that both pharmacological modulation of the intracellular trafficking of the TRPV1 receptor and defunctionalization of the nocisensors by TRPV1 agonists are promising novel approaches to tame the TRPV1 receptor. British Journal of Pharmacology (2008) 155, 1139,1141; doi:fn1; published online 10 November 2008 [source] In vivo effects of CB2 receptor-selective cannabinoids on the vasculature of normal and arthritic rat knee jointsBRITISH JOURNAL OF PHARMACOLOGY, Issue 2 2008J J McDougall Background and purpose: Cannabinoids (CBs) are known to be vasoactive and to regulate tissue inflammation. The present study examined the in vivo vasomotor effects of the CB2 receptor agonists JWH015 and JWH133 in rat knee joints. The effect of acute and chronic joint inflammation on CB2 receptor-mediated responses was also tested. Experimental approach: Blood flow was assessed in rat knee joints by laser Doppler imaging both before and following topical administration of CB2 receptor agonists. Vasoactivity was measured in normal, acute kaolin/carrageenan inflamed and Freund's complete adjuvant chronically inflamed knees. Key results: In normal animals, JWH015 and JWH133 caused a concentration-dependent increase in synovial blood flow which in the case of JWH133 was blocked by the selective CB2 receptor antagonist AM630 as well as the transient receptor potential vanilloid-1 (TRPV1) antagonist SB366791. The vasodilator effect of JWH133 was significantly attenuated in both acute and chronically inflamed knees. Given alone, AM630 had no effect on joint blood flow. Conclusion and implications: In normal joints, the cannabinomimetic JWH133 causes hyperaemia via a CB2 and TRPV1 receptor mechanism. During acute and chronic inflammation, however, this vasodilatatory response is significantly attenuated. British Journal of Pharmacology (2008) 153, 358,366; doi:10.1038/sj.bjp.0707565; published online 5 November 2007 [source] New potent and selective inhibitors of anandamide reuptake with antispastic activity in a mouse model of multiple sclerosisBRITISH JOURNAL OF PHARMACOLOGY, Issue 1 2006Alessia Ligresti We previously reported that the compound O-2093 is a selective inhibitor of the reuptake of the endocannabinoid anandamide (AEA). We have now re-examined the activity of O-2093 in vivo and synthesized four structural analogs (O-2247, O-2248, O-3246, and O-3262), whose activity was assessed in: (a) binding assays carried out with membranes from cells overexpressing the human CB1 and CB2 receptors; (b) assays of transient receptor potential of the vanilloid type-1 (TRPV1) channel functional activity (measurement of [Ca2+]i); (c) [14C]AEA cellular uptake and hydrolysis assays in rat basophilic leukaemia (RBL-2H3) cells; (d) the mouse ,tetrad' tests (analgesia on a hot plate, immobility on a ,ring', rectal hypothermia and hypolocomotion in an open field); and (e) the limb spasticity test in chronic relapsing experimental allergic encephalomyelitis (CREAE) mice, a model of multiple sclerosis (MS). O-2093, either synthesized by us or commercially available, was inactive in the ,tetrad' up to a 20 mg kg,1 dose (i.v.). Like O-2093, the other four compounds exhibited low affinity in CB1 (Ki from 1.3 to >10 ,M) and CB2 binding assays (1.3 Inhibition of TRPM2 function by PARP inhibitors protects cells from oxidative stress-induced deathBRITISH JOURNAL OF PHARMACOLOGY, Issue 5 2004Barbara A Miller TRPM2 is a member of the transient receptor potential (TRP) protein superfamily of calcium-permeable, voltage-independent ion channels expressed in nonexcitable cells. Activation of TRPM2 by oxidative stress results in calcium influx and susceptibility to cell death, whereas inhibition of TRPM2 function enhances cell survival. In the present edition of this journal, Fonfria et al. demonstrate a role for poly(ADP ribose) polymerase (PARP) as a mediator between oxidative stress and TRPM2 activation. They present evidence that inhibition of either PARP or TRPM2 protects cells from plasma membrane damage and cell death. The therapeutic implications of this important observation are discussed. British Journal of Pharmacology (2004) 143, 515,516. doi:10.1038/sj.bjp.0705923 [source] 3133: Planar patch-clamping in human corneal endothelial cells: a new tool for clinical application?ACTA OPHTHALMOLOGICA, Issue 2010S MERGLER Purpose Identification of apoptotic or damaged human corneal endothelial cells (HCECs) is limited to morphological evaluation such as phase contrast microscopy and vital staining. The molecular mechanisms of corneal endothelial cell loss are not fully understood. Special investigations in cellular signalling and ion channel research are necessary to elucidate the mechanisms of corneal cell loss. In this context, it is known that this cell loss is often caused by apoptosis in oxidative stress. Methods Automated planar patch-clamp has become common in drug development and safety programs because it enables efficient and systematic testing of compounds against ion channels during voltage-clamp. A particularly successful automated approach is based on planar patch-clamp chips and this is the basis for the technology used here. Routine intracellular or extracellular perfusion opens possibilities for studying the regulation and pharmacology of ion channels. Previously, these studies were available only to highly skilled and dedicated experimenters. Results Notable, definite ion channel activities could be demonstrated by conventional as well as by planar patch-clamp in HCECs for the first time. In particular, temperature-sensing transient receptor potential (TRP)-like non-selective cation channel currents as well as capsaicin-sensitive ion channel currents could be detected. The expression of TRPV1-3 ion channels in HCEC could also be confirmed by RT-PCR, Western blot analysis and fluorescence cell imaging. Conclusion The administration of this novel measuring technology opens new perspectives in the investigation of the physiology of HCEC. The findings may have direct clinical implication (eye banking procedures, keratoplasty). [source] Involvement of nonselective cation channels in the depolarisation initiating vasomotionCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 5-6 2010Stephanie E Wölfle Summary 1. Coordinated oscillations in diameter occur spontaneously in cerebral vessels and depend on the opening of voltage dependent calcium channels. However, the mechanism that induces the initial depolarisation has remained elusive. We investigated the involvement of canonical transient receptor potential (TRPC) channels, which encode nonselective cation channels passing Na+ and Ca2+ currents, by measuring changes in diameter, intracellular Ca2+ and membrane potential in branches of juvenile rat basilar arteries. 2. Removal of extracellular Ca2+ abolished vasomotion and relaxed arteries, but paradoxically produced depolarisation. 3. Decrease in temperature to 24°C or inhibition of phospholipase C (PLC) abolished vasomotion, hyperpolarised and relaxed arteries and decreased intracellular Ca2+. 4. Reduction in the driving force for Na+ through decrease in extracellular Na+ produced similar effects and prevented the depolarisation elicited by removal of extracellular Ca2+. 5. Nonselective TRP channel blockers, SKF96365 and gadolinium, mimicked the effects of inhibition of the PLC pathway. 6. Depolarisation of vessels in which TRP channels were blocked with SKF96365 reinstated vascular tone and vasomotion. 7. Quantitative polymerase chain reaction revealed TRPC1 as the predominantly expressed TRPC subtype. 8. Incubation with a function blocking TRPC1 antibody delayed the onset of vasomotion. 9. We conclude that nonselective cation channels contribute to vasoconstriction and vasomotion of cerebral vessels by providing an Na+ -induced depolarisation that activates voltage dependent calcium channels. Our antibody data suggest the involvement of TRPC1 channels that might provide a target for treatment of therapy-refractory vasospasm. [source]
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