Laboratory of Ion Channel Research

Leuven, Belgium

Laboratory of Ion Channel Research

Leuven, Belgium
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Dutta K.,National Brain Research Center | Ghosh D.,National Brain Research Center | Ghosh D.,Laboratory of Ion Channel Research | Nazmi A.,National Brain Research Center | And 2 more authors.
PLoS ONE | Year: 2010

Background: Benzo[a]pyrene (B[a]P) belongs to a class of polycyclic aromatic hydrocarbons that serve as micropollutants in the environment. B[a]P has been reported as a probable carcinogen in humans. Exposure to B[a]P can take place by ingestion of contaminated (especially grilled, roasted or smoked) food or water, or inhalation of polluted air. There are reports available that also suggests neurotoxicity as a result of B[a]P exposure, but the exact mechanism of action is unknown. Methodology/Principal Findings: Using neuroblastoma cell line and primary cortical neuron culture, we demonstrated that B[a]P has no direct neurotoxic effect. We utilized both in vivo and in vitro systems to demonstrate that B[a]P causes microglial activation. Using microglial cell line and primary microglial culture, we showed for the first time that B[a]P administration results in elevation of reactive oxygen species within the microglia thereby causing depression of antioxidant protein levels; enhanced expression of inducible nitric oxide synthase, that results in increased production of NO from the cells. Synthesis and secretion of proinflammatory cytokines were also elevated within the microglia, possibly via the p38MAP kinase pathway. All these factors contributed to bystander death of neurons, in vitro. When administered to animals, B[a]P was found to cause microglial activation and astrogliosis in the brain with subsequent increase in proinflammatory cytokine levels. Conclusions/Significance: Contrary to earlier published reports we found that B[a]P has no direct neurotoxic activity. However, it kills neurons in a bystander mechanism by activating the immune cells of the brain viz the microglia. For the first time, we have provided conclusive evidence regarding the mechanism by which the micropollutant B[a]P may actually cause damage to the central nervous system. In today's perspective, where rising pollution levels globally are a matter of grave concern, our study throws light on other health hazards that such pollutants may exert. © 2010 Dutta et al.

Kang D.,Rosalind Franklin University of Medicine and Science | Kang D.,Gyeongsang National University | Wang J.,Rosalind Franklin University of Medicine and Science | Hogan J.O.,Rosalind Franklin University of Medicine and Science | And 4 more authors.
Journal of Physiology | Year: 2014

The current model of O2 sensing by carotid body chemoreceptor (glomus) cells is that hypoxia inhibits the outward K+ current and causes cell depolarization, Ca2+ influx via voltage-dependent Ca2+ channels and a rise in intracellular [Ca2+] ([Ca2+]i). Here we show that hypoxia (<5% O2), in addition to inhibiting the two-pore domain K+ channels TASK-1/3 (TASK), indirectly activates an ~20 pS channel in isolated glomus cells. The 20 pS channel was permeable to K+, Na+ and Cs+ but not to Cl- or Ca2+. The 20 pS channel was not sensitive to voltage. Inhibition of TASK by external acid, depolarization of glomus cells with high external KCl (20 mm) or opening of the Ca2+ channel with FPL64176 activated the 20 pS channel when 1 mm Ca2+ was present in the external solution. Ca2+ (10 μm) applied to the cytosolic side of inside-out patches activated the 20 pS channel. The threshold [Ca2+]i for activation of the 20 pS channel in cell-attached patches was ~200 nm. The reversal potential of the 20 pS channel was estimated to be -28 mV. Our results reveal a sequential mechanism in which hypoxia (<5% O2) first inhibits the K+ conductance and then activates a Na+-permeable, non-selective cation channel via depolarization-induced rise in [Ca2+]i. Our results suggest that inhibition of K+ efflux and stimulation of Na+ influx both contribute to the depolarization of glomus cells during moderate to severe hypoxia. © 2014 The Physiological Society.

Kunzelmann K.,University of Regensburg | Nilius B.,Laboratory of Ion Channel Research | Owsianik G.,Laboratory of Ion Channel Research | Schreiber R.,University of Regensburg | And 5 more authors.
Pflugers Archiv European Journal of Physiology | Year: 2014

Anoctamin 6 (Ano6; TMEM16F gene) is a ubiquitous protein; the expression of which is defective in patients with Scott syndrome, an inherited bleeding disorder based on defective scrambling of plasma membrane phospholipids. For Ano6, quite diverse functions have been described: (1) it can form an outwardly rectifying, Ca2+-dependent and a volume-regulated Cl- channel; (2) it was claimed to be a Ca2+-regulated nonselective cation channel permeable for Ca2+; (3) it was shown to be essential for Ca2+-mediated scrambling of membrane phospholipids; and (4) it can regulate cell blebbing and microparticle shedding. Deficiency of Ano6 in blood cells from Scott patients or Ano6 null mice appears to affect all of these cell responses. Furthermore, Ano6 deficiency in mice impairs the mineralization of osteoblasts, resulting in reduced skeletal development. These diverse results have been obtained under different experimental conditions, which may explain some of the contradictions. This review therefore aims to summarize the currently available information on the diverse roles of Ano6 and tries to clear up some of the existing controversies. © 2013 Springer-Verlag Berlin Heidelberg.

Mathar I.,Saarland University | Vennekens R.,Laboratory of Ion Channel Research | Meissner M.,Saarland University | Kees F.,University of Regensburg | And 11 more authors.
Journal of Clinical Investigation | Year: 2010

Hypertension is an underlying risk factor for cardiovascular disease. Despite this, its pathogenesis remains unknown in most cases. Recently, the transient receptor potential (TRP) channel family was associated with the development of several cardiovascular diseases linked to hypertension. The melastatin TRP channels TRPM4 and TRPM5 have distinct properties within the TRP channel family: they form nonselective cation channels activated by intracellular calcium ions. Here we report the identification of TRPM4 proteins in endothelial cells, heart, kidney, and chromaffin cells from the adrenal gland, suggesting that they have a role in the cardiovascular system. Consistent with this hypothesis, Trpm4 gene deletion in mice altered long-term regulation of blood pressure toward hypertensive levels. No changes in locomotor activity, renin-angiotensin system function, electrolyte and fluid balance, vascular contractility, and cardiac contractility under basal conditions were observed. By contrast, inhibition of ganglionic transmission with either hexamethonium or prazosin abolished the difference in blood pressure between Trpm4-/- and wild-type mice. Strikingly, plasma epinephrine concentration as well as urinary excretion of catecholamine metabolites were substantially elevated in Trpm4-/- mice. In freshly isolated chromaffin cells, lack of TRPM4 was shown to cause markedly more acetylcholineinduced exocytotic release events, while neither cytosolic calcium concentration, size, nor density of vesicles were different. We therefore conclude that TRPM4 proteins limit catecholamine release from chromaffin cells and that this contributes to increased sympathetic tone and hypertension.

Marshall-Gradisnik S.,Griffith University | Smith P.,Griffith University | Nilius B.,Laboratory of Ion Channel Research | Staines D.R.,Griffith University
Immunology and Immunogenetics Insights | Year: 2015

OBJECTIVE:Chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) is a disorder characterized by debilitating fatigue accompanied by pain and impairments in memory, cognition, and concentration. Acetylcholine (ACh) has a plethora of roles in neuronal and neuromuscular transmission. There are two types of ACh receptors, muscarinic and nicotinic, comprising 17 different subunits of the nicotinic ACh receptor (nAChR) and five different subtypes of the muscarinic receptor (mAChR) that have been identified in humans. The purpose of this study was to determine the role of ACh receptor (nAChRs and mAChRs) single nucleotide polymorphisms (SNPs) in CFS/ME patients. METHODS:One-hundred and fifteen CFS/ME patients (age = 48.68 ± 1.06 years) and 90 nonfatigued controls (age = 46.48 ± 1.22 years) participated in this study, where CFS/ME patients were defined according to the 1994 Center for Disease Prevention and Control (CDC) criteria. A total of 464 SNPs for nine mammalian ACh receptor genes (M1, M2, M3, M4, M5, alpha 2, 5, 7, and10) were examined via the Agena Biosciences iPLEX Gold assay. Statistical analysis was performed using the PLINK analysis software. RESULTS:Seventeen SNPs were significantly associated with CFS/ME patients compared with the controls. Nine of these SNPs were associated with mAChRM3(rs4463655; P = 0.00281, rs589962; P = 0.00348, rs1072320; P = 0.00371, rs7543259; P = 0.00513, rs6661621; P = 0.00536 rs7520974; P = 0.0167, rs726169; P = 0.02349, rsrs6669810; P = 0.02361, rsrs6429157; P = 0.0375), while the remainder were associated with nAChR alpha 10 (rs2672211; P = 0.0107, rs2672214; P = 0.0108, rs2741868; P = 0.01185, rs2741870; P = 0.01281, rs2741862; P = 0.03043), alpha 5(rs951266; P = 0.01153; rs7180002, P = 0.03682), and alpha 2(rs2565048; P = 0.01403). CONCLUSION:The data from this pilot study suggest an association between ACh receptors, predominantly M3 and CFS. ACh receptor SNPs may contribute to the pathomechanism of CFS/ME. © the authors, publisher and licensee libertas academica limited.

Marshall-Gradisnik S.M.,Griffith University | Smith P.,Griffith University | Brenu E.W.,Griffith University | Nilius B.,Laboratory of Ion Channel Research | And 2 more authors.
Immunology and Immunogenetics Insights | Year: 2015

BACKGROUND: The transient receptor potential (TRP) superfamily in humans comprises 27 cation channels with permeability to monovalent and diva-lent cations. These channels are widely expressed within humans on cells and tissues and have significant sensory and regulatory roles on most physiological functions. Chronic fatigue syndrome (CFS) is an unexplained disorder with multiple physiological impairments. OBJECTIVES: The purpose of this study was to determine the role of TRPs in CFS. METHODS: The study comprised 115 CFS patients (age = 48.68 ± 1.06 years) and 90 nonfatigued controls (age = 46.48 ± 1.22 years). CFS patients were defined according to the 1994 Center for Disease Prevention and Control criteria for CFS. A total of 240 single nucleotide polymorphisms (SNPs) for 21 mammalian TRP ion channel genes (TRPA1, TRPC1, TRPC2, TRPC3, TRPC4, TRPC6, TRPC7, TRPM1, TRPM2, TRPM3, TRPM4, TRPM5, TRPM6, TRPM7, TRPM8, TRPV1, TRPV2, TRPV3, TRPV4, TRPV5, and TRPV6) were examined via the Agena Biosciences iPLEX Gold assay. Statis-tical analysis was performed using the PLINK analysis software. RESULTS: Thirteen SNPs were significantly associated with CFS patients compared with the controls. Nine of these SNPs were associated with TRPM3 (rs12682832; P ≤ 0.003, rs11142508; P ˂ 0.004, rs1160742; P ˂ 0.08, rs4454352; P ≤ 0.013, rs1328153; P ≤ 0.013, rs3763619; P ≤ 0.014, rs7865858; P ≤ 0.021, rs1504401; P ≤ 0041, rs10115622; P ≤ 0.050), while the remainder were associated with TRPA1 (rs2383844; P ≤ 0.040, rs4738202; P ≤ 0.018) and TRPC4 (rs6650469; P ≤ 0.016, rs655207; P ≤ 0.018). CONCLUSION: The data from this pilot study suggest an association between TRP ion channels, predominantly TRPM3 and CFS. This and other TRPs identified may contribute to the etiology and pathomechanism of CFS. © the authors, publisher and licensee Libertas Academica Limited.

Meseguer V.,University Miguel Hernández | Alpizar Y.A.,Laboratory of Ion Channel Research | Luis E.,University Miguel Hernández | Tajada S.,University of Valladolid | And 18 more authors.
Nature Communications | Year: 2014

Gram-negative bacterial infections are accompanied by inflammation and somatic or visceral pain. These symptoms are generally attributed to sensitization of nociceptors by inflammatory mediators released by immune cells. Nociceptor sensitization during inflammation occurs through activation of the Toll-like receptor 4 (TLR4) signalling pathway by lipopolysaccharide (LPS), a toxic by-product of bacterial lysis. Here we show that LPS exerts fast, membrane delimited, excitatory actions via TRPA1, a transient receptor potential cation channel that is critical for transducing environmental irritant stimuli into nociceptor activity. Moreover, we find that pain and acute vascular reactions, including neurogenic inflammation (CGRP release) caused by LPS are primarily dependent on TRPA1 channel activation in nociceptive sensory neurons, and develop independently of TLR4 activation. The identification of TRPA1 as a molecular determinant of direct LPS effects on nociceptors offers new insights into the pathogenesis of pain and neurovascular responses during bacterial infections and opens novel avenues for their treatment. © 2014 Macmillan Publishers Limited. All rights reserved.

Nilius B.,Laboratory of Ion Channel Research | Owsianik G.,Laboratory of Ion Channel Research
Genome Biology | Year: 2011

The transient receptor potential (TRP) multigene superfamily encodes integral membrane proteins that function as ion channels. Members of this family are conserved in yeast, invertebrates and vertebrates. The TRP family is subdivided into seven subfamilies: TRPC (canonical), TRPV (vanilloid), TRPM (melastatin), TRPP (polycystin), TRPML (mucolipin), TRPA (ankyrin) and TRPN (NOMPC-like); the latter is found only in invertebrates and fish. TRP ion channels are widely expressed in many different tissues and cell types, where they are involved in diverse physiological processes, such as sensation of different stimuli or ion homeostasis. Most TRPs are non-selective cation channels, only few are highly Ca 2+selective, some are even permeable for highly hydrated Mg 2+ions. This channel family shows a variety of gating mechanisms, with modes of activation ranging from ligand binding, voltage and changes in temperature to covalent modifications of nucleophilic residues. Activated TRP channels cause depolarization of the cellular membrane, which in turn activates voltage-dependent ion channels, resulting in a change of intracellular Ca 2+concentration; they serve as gatekeeper for transcellular transport of several cations (such as Ca 2+and Mg 2+), and are required for the function of intracellular organelles (such as endosomes and lysosomes). Because of their function as intracellular Ca 2+release channels, they have an important regulatory role in cellular organelles. Mutations in several TRP genes have been implicated in diverse pathological states, including neurodegenerative disorders, skeletal dysplasia, kidney disorders and pain, and ongoing research may help find new therapies for treatments of related diseases. © 2011 BioMed Central Ltd.

Gees M.,Laboratory of Ion Channel Research | Alpizar,Laboratory of Ion Channel Research | Luyten T.,Catholic University of Leuven | Parys J.B.,Catholic University of Leuven | And 4 more authors.
Chemical Senses | Year: 2014

Transient receptor potential cation channel subfamily M member 5 (TRPM5) is a Ca2+-activated nonselective cation channel involved in the transduction of sweet, bitter, and umami tastes. We previously showed that TRPM5 is a locus for the modulation of taste perception by temperature changes, and by quinine and quinidine, 2 bitter compounds that suppress gustatory responses. Here, we determined whether other bitter compounds known to modulate taste perception also affect TRPM5. We found that nicotine inhibits TRPM5 currents with an effective inhibitory concentration of ~1.3 mM at -50 mV. This effect may contribute to the inhibitory effect of nicotine on gustatory responses in therapeutic and experimental settings, where nicotine is often employed at millimolar concentrations. In addition, it implies the existence of a TRPM5-independent pathway for the detection of nicotine bitterness. Nicotine seems to act from the extracellular side of the channel, reducing the maximal whole-cell conductance and inducing an acceleration of channel closure that leads to a negative shift of the activation curve. TRPM5 currents were unaffected by nicotine's metabolite cotinine, the intensive sweetener saccharin or by the bitter xanthines caffeine, theobromine, and theophylline. We also tested the effects of bitter compounds on another essential element of the sweet taste transduction pathway, the type 3 IP3 receptor (IP3R3). We found that IP3R3-mediated Ca2+ flux is slightly enhanced by nicotine, not affected by saccharin, modestly inhibited by caffeine, theobromine, and theophylline, and strongly inhibited by quinine. Our results demonstrate that bitter compounds have differential effects on key elements of the sweet taste transduction pathway, suggesting for heterogeneous mechanisms of bitter-sweet taste interactions. © The Author 2014. Published by Oxford University Press.

Meseguer V.M.,University Miguel Hernández | Denlinger B.L.,University Miguel Hernández | Talavera K.,University Miguel Hernández | Talavera K.,Laboratory of Ion Channel Research
Current Pharmaceutical Biotechnology | Year: 2011

Transient Receptor Potential channels are exquisite molecular transducers of multiple physical and chemical stimuli, hence the raising interest to study their relevance to Sensory Biology. Here we discuss a number of aspects of the biophysical and pharmacological properties of TRP channels, which we consider essential for a clear understanding of their sensory function in vivo. By examining concrete examples extracted from recent literature we illustrate that TRP channel research is a field in motion, and that many established dogmas on biophysical properties, drug specificity and physiological role are continuously reshaped, and sometimes even dismantled. © 2011 Bentham Science Publishers Ltd.

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