The Experts below are selected from a list of 20643 Experts worldwide ranked by ideXlab platform
Arpad Szallasi - One of the best experts on this subject based on the ideXlab platform.
-
Vanilloid (capsaicin) receptors in health and disease.
American journal of clinical pathology, 2002Co-Authors: Arpad SzallasiAbstract:The cloned Vanilloid (capsaicin) receptor subtype 1 (VR1) integrates multiple noxious stimuli on peripheral terminals of primary sensory neurons. The initial excitation of these neurons is followed by a lasting refractory state, traditionally termed desensitization, that has clear therapeutic potential. Capsaicin is used to relieve neuropathic pain, uremic pruritus, and bladder overactivity. The ultrapotent Vanilloid resiniferatoxin, now in phase 2 clinical trials, has improved tolerability. A less recognized human exposure to high capsaicin concentrations may occur by pepper sprays used in law enforcement. Evidence is mounting that VR1 expression is not restricted to sensory neurons. From the olfactory bulb to the cerebellum, VR1-expressing neurons are present in a number of brain nuclei, where they might be activated by anandamide. VR1 presence also was demonstrated in nonneuronal tissues. These discoveries place VR1 in a much broader perspective than pain perception and enhance the potential for unforeseen side effects, especially following prolonged Vanilloid therapy. The expression of VR1 is plastic and down-regulated during Vanilloid therapy, which might have a pivotal role in desensitization. Good evidence suggests altered VR1 expression in various disease states. This recognition not only may provide novel insights into pathogenesis but also may prove useful in diagnosis.
-
After a decade of intravesical Vanilloid therapy: still more questions than answers
The Lancet. Neurology, 2002Co-Authors: Arpad Szallasi, Clare J. FowlerAbstract:Vanilloid sensitivity is a functional signature of a subset of unmyelinated fibres innervating the urinary bladder. The role that these nerves have in the physiological control of storage and voiding is unclear. However, after the bladder has been disconnected by spinal injury from the pontine micturition centre, Vanilloid-sensitive fibres assume a central role in the reflex emptying of the bladder that occurs at low volumes. Intravesical Vanilloid (capsaicin or resiniferatoxin) administration is beneficial in this disorder by "desensitising" these nerves. Resiniferatoxin is superior to capsaicin in terms of its tolerability profile. Investigators are moving rapidly to identify the mechanisms by which desensitisation to Vanilloids occurs. Vanilloids induce lasting, but fully reversible, changes in gene expression, including downregulation of the Vanilloid receptor subtype 1. It is hoped that application of gene chip technologies will address the global profile of Vanilloid-induced changes in gene expression and their relative contribution to desensitisation. Drugs that target signalling mechanisms that bring about these changes in gene expression have obvious therapeutic potential.
-
Vanilloid Receptor Ligands
Drugs & Aging, 2001Co-Authors: Arpad SzallasiAbstract:Neurons possessing C-fibers transmit nociceptive information into the central nervous system and participate in various reflex responses. These neurons carry receptors that bind capsaicin, recently identified as the Vanilloid VR1 receptor. Excitation of these cells by capsaicin is followed by a lasting refractory state, termed desensitisation, in which the neurons fail to respond to a variety of noxious stimuli. Desensitisation to capsaicin has a clear therapeutic potential in relieving neuropathic pain and ameliorating urinary bladder overactivity, just to cite 2 important examples. Vanilloids may also be beneficial in the treatment of benign prostate hyperplasia (BPH). Since the majority of elderly patients have neuropathic pain co-existent with urinary incontinence and/or BPH, a drug that ameliorates pain and improves urinary symptoms at the same time promises to be of great clinical value in geriatric medicine. In fact, capsaicin has already been shown to have a role in the treatment of conditions that can arise in the elderly, including herpes zoster-related neuropathic pain, diabetic neuropathy, postmastectomy pain, uraemic itching associated with renal failure, and urinary incontinence. The potent VR1 agonist resiniferatoxin, now in phase II clinical trials, appears to be superior to capsaicin in terms of its tolerability profile. Recent discoveries enhance the therapeutic potential of Vanilloids. The recognition that VR1 also functions as a principal receptor for protons and eicosanoids implies that VR1 antagonists may be of value in the treatment of inflammatory hyperalgesia and pain. Animal experimentation has already lent support to this assumption. The discovery of VR1-expressing cells in the brain as well as in non-neural tissues such as the kidney and urothelium places VR1 in a much broader perspective than peripheral pain perception, and is hoped to identify further, yet unsuspected, indications for Vanilloid therapy. The realisation that VR1 and cannabinoid CB_1 receptors have overlapping ligand recognition properties may also have far-reaching implications for Vanilloid therapy. In fact, arvanil, a combined agonist of VR1 and CB_1 receptors, has already proved to be a powerful analgesic drug in the mouse. From academic molecular biology laboratories to industrial drug discovery centres to the clinics, there is a steady flow of new data, forcing us to constantly revise the ways we are thinking about Vanilloid receptor ligands and their hopes and realities for the future. This review covers the most promising current trends in Vanilloid research with special emphasis on geriatric medicine.
-
Vanilloid receptor ligands: hopes and realities for the future.
Drugs & aging, 2001Co-Authors: Arpad SzallasiAbstract:Neurons possessing C-fibers transmit nociceptive information into the central nervous system and participate in various reflex responses. These neurons carry receptors that bind capsaicin, recently identified as the Vanilloid VR1 receptor. Excitation of these cells by capsaicin is followed by a lasting refractory state, termed desensitisation, in which the neurons fail to respond to a variety of noxious stimuli. Desensitisation to capsaicin has a clear therapeutic potential in relieving neuropathic pain and ameliorating urinary bladder overactivity, just to cite 2 important examples. Vanilloids may also be beneficial in the treatment of benign prostate hyperplasia (BPH). Since the majority of elderly patients have neuropathic pain co-existent with urinary incontinence and/or BPH, a drug that ameliorates pain and improves urinary symptoms at the same time promises to be of great clinical value in geriatric medicine. In fact, capsaicin has already been shown to have a role in the treatment of conditions that can arise in the elderly, including herpes zoster-related neuropathic pain, diabetic neuropathy, postmastectomy pain, uraemic itching associated with renal failure, and urinary incontinence. The potent VR1 agonist resiniferatoxin, now in phase II clinical trials, appears to be superior to capsaicin in terms of its tolerability profile. Recent discoveries enhance the therapeutic potential of Vanilloids. The recognition that VR1 also functions as a principal receptor for protons and eicosanoids implies that VR1 antagonists may be of value in the treatment of inflammatory hyperalgesia and pain. Animal experimentation has already lent support to this assumption. The discovery of VR1-expressing cells in the brain as well as in non-neural tissues such as the kidney and urothelium places VR1 in a much broader perspective than peripheral pain perception, and is hoped to identify further, yet unsuspected, indications for Vanilloid therapy. The realisation that VR1 and cannabinoid CB1 receptors have overlapping ligand recognition properties may also have far-reaching implications for Vanilloid therapy. In fact, arvanil, a combined agonist of VR1 and CB1 receptors, has already proved to be a powerful analgesic drug in the mouse. From academic molecular biology laboratories to industrial drug discovery centres to the clinics, there is a steady flow of new data, forcing us to constantly revise the ways we are thinking about Vanilloid receptor ligands and their hopes and realities for the future. This review covers the most promising current trends in Vanilloid research with special emphasis on geriatric medicine.
-
distribution of mrna for Vanilloid receptor subtype 1 vr1 and vr1 like immunoreactivity in the central nervous system of the rat and human
Proceedings of the National Academy of Sciences of the United States of America, 2000Co-Authors: Eva Mezey, Peter M. Blumberg, James E. Krause, Zsuzsanna Toth, Daniel N Cortright, Michelle K Arzubi, Robert Elde, Athena Guo, Arpad SzallasiAbstract:The cloned Vanilloid receptor VR1 has attracted recent attention as a molecular integrator of painful stimuli on primary sensory neurons. The existence of Vanilloid-sensitive neurons in the brain is, however, controversial. In this study, we have used an antibody and a complementary RNA probe to explore the distribution of neurons that express VR1 in rat and in certain areas of human brain. In the rat, we observed VR1-expressing neurons throughout the whole neuroaxis, including all cortical areas (in layers 3 and 5), several members of the limbic system (e.g., hippocampus, central amygdala, and both medial and lateral habenula), striatum, hypothalamus, centromedian and paraventricular thalamic nuclei, substantia nigra, reticular formation, locus coeruleus, cerebellum, and inferior olive. VR1-immunopositive cells also were found in the third and fifth layers of human parietal cortex. Reverse transcription–PCR performed with rat VR1-specific primers verified the expression of VR1 mRNA in cortex, hippocampus, and hypothalamus. In the central nervous system, neonatal capsaicin treatment depleted VR1 mRNA from the spinal nucleus of the trigeminal nerve, but not from other areas such as the inferior olive. The finding that VR1 is expressed not only in primary sensory neurons but also in several brain nuclei is of great importance in that it places VRs in a much broader perspective than pain perception. VRs in the brain (and putative endogenous Vanilloids) may be involved in the control of emotions, learning, and satiety, just to name a few exciting possibilities.
Peter M. Blumberg - One of the best experts on this subject based on the ideXlab platform.
-
Novel Radiolabeled Vanilloid with Enhanced Specificity for Human Transient Receptor Potential Vanilloid 1 (TRPV1)
Journal of medicinal chemistry, 2017Co-Authors: Larry V. Pearce, Peter M. Blumberg, Jihyae Ann, Aeran Jung, Shivaji A. Thorat, Brienna K. A. Herold, Amelework D. Habtemichael, Jeewoo LeeAbstract:Transient receptor potential Vanilloid 1 (TRPV1) has emerged as a promising therapeutic target. While radiolabeled resiniferatoxin (RTX) has provided a powerful tool for characterization of Vanilloid binding to TRPV1, TRPV1 shows 20-fold weaker binding to the human TRPV1 than to the rodent TRPV1. We now describe a tritium radiolabeled synthetic Vanilloid antagonist, 1-((2-(4-(methyl-[3H])piperidin-1-yl-4-[3H])-6-(trifluoromethyl)pyridin-3-yl)methyl)-3-(3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazin-8-yl)urea ([3H]MPOU), that embodies improved absolute affinity for human TRPV1 and improved synthetic accessibility.
-
Engineering Vanilloid-sensitivity into the rat TRPV2 channel.
eLife, 2016Co-Authors: Feng Zhang, Larry V. Pearce, Peter M. Blumberg, Andres Jara-oseguera, Sonya M. Hanson, Dmitriy Krepkiy, Chanhyung Bae, Simon Newstead, Kenton J. SwartzAbstract:The TRPV1 channel is a detector of noxious stimuli, including heat, acidosis, Vanilloid compounds and lipids. The gating mechanisms of the related TRPV2 channel are poorly understood because selective high affinity ligands are not available, and the threshold for heat activation is extremely high (>50°C). Cryo-EM structures of TRPV1 and TRPV2 reveal that they adopt similar structures, and identify a putative Vanilloid binding pocket near the internal side of TRPV1. Here we use biochemical and electrophysiological approaches to investigate the resiniferatoxin(RTx) binding site in TRPV1 and to explore the functional relationships between TRPV1 and TRPV2. Collectively, our results support the interaction of Vanilloids with the proposed RTx binding pocket, and demonstrate an allosteric influence of a tarantula toxin on Vanilloid binding. Moreover, we show that sensitivity to RTx can be engineered into TRPV2, demonstrating that the gating and permeation properties of this channel are similar to TRPV1.
-
Resiniferatoxin-Amide and Analogues as Ligands for Protein Kinase C and Vanilloid Receptors and Determination of Their Biological Activities as Vanilloids
Journal of neurochemistry, 2002Co-Authors: Geza Acs, Nancy E. Lewin, Jeewoo Lee, Victor E. Marquez, Shaomeng Wang, George W. A. Milne, Peter M. BlumbergAbstract:The naturally occurring diterpene resiniferatoxin (RTX) is an ultrapotent analogue of capsaicin. Acting on polymodal afferent neurons, RTX induces a generally similar pattern of responses as does capsaicin. However, the two compounds, as well as other Vanilloid derivatives, display different relative potencies for different responses. In the present study, we examined the Vanilloid-like activities of two new derivatives, the amide analogue of RTX and phorbol 12,13-dibenzoate 20-homovanillylamide. Structurally, RTX-amide resembles capsaicin more closely than does RTX, and after cleavage of the amide bond the resulting amine would be predicted to not bind to protein kinase C in contrast to resiniferonol 9,13,14-orthophenylacetate, the parent diterpene of RTX. In contrast to our expectations the binding potency of the RTX-amide for the Vanilloid receptor present in rat spinal cord was 450-fold lower than that of RTX (Ki values for the RTX-amide and RTX were 10.4 +/- 0.7 nM and 23.1 +/- 3.2 pM, respectively). In the case of phorbol 12,13-dibenzoate 20-homovanillylamide, there was a further loss of affinity for the Vanilloid receptor compared with RTX; nonetheless, the Ki (8.56 +/- 0.61 microM) was comparable with that of capsaicin (5.31 +/- 0.37 microM). Computer fitting of the binding data yielded Hill coefficient values of 2.25 +/- 0.03, 2.33 +/- 0.03, and 1.84 +/- 0.05 for RTX, RTX-amide, and phorbol 12,13-dibenzoate 20-homovanillylamide, respectively, indicating that both new compounds induced apparent positive cooperativity among Vanilloid binding sites.(ABSTRACT TRUNCATED AT 250 WORDS)
-
analysis of the native quaternary structure of Vanilloid receptor 1
Journal of Biological Chemistry, 2001Co-Authors: Noemi Kedei, Tamás Szabó, Zoltan Olah, Michael J Iadarola, Jack Lile, James J S Treanor, Peter M. BlumbergAbstract:Vanilloid receptor subtype 1 (VR1) is a ligand-gated channel that can be activated by capsaicin and other Vanilloids as well as by protons and heat. In the present study, we have analyzed the oligomeric state of VR1. Co-immunoprecipitation of differently tagged VR1 molecules indicated that VR1 can form oligomers. Using two different heterologous VR1 expression systems as well as endogenous VR1 expressed in dorsal root ganglion cells, we analyzed oligomer formation using perfluoro-octanoic acid polyacrylamide gel electrophoresis. Results were confirmed both with chemical cross-linking agents as well as through endogenous cross-linking mediated by transglutaminase. Our results clearly show that VR1 forms multimers in each of the expression systems with a homotetramer as a predominant form. The oligomeric structure of VR1 may contribute to the complexity of VR1 pharmacology. Finally, differences in glycosylation between the systems were observed, indicating the need for caution in the use of the heterologous expression systems for analysis of VR1 properties.
-
ligand induced dynamic membrane changes and cell deletion conferred by Vanilloid receptor 1
Journal of Biological Chemistry, 2001Co-Authors: Zoltan Olah, Peter M. Blumberg, Tamás Szabó, Laszlo Karai, Chris Hough, Douglas R Fields, Robert M Caudle, Michael J IadarolaAbstract:The real time dynamics of Vanilloid-induced cytotoxicity and the specific deletion of nociceptive neurons expressing the wild-type Vanilloid receptor (VR1) were investigated. VR1 was C-terminally tagged with either the 27-kDa enhanced green fluorescent protein (eGFP) or a 12-amino acid epsilon-epitope. Upon exposure to resiniferatoxin, VR1eGFP- or VR1epsilon-expressing cells exhibited pharmacological responses similar to those of cells expressing the untagged VR1. Within seconds of Vanilloid exposure, the intracellular free calcium ([Ca(2+)](i)) was elevated in cells expressing VR1. A functional pool of VR1 also was localized to the endoplasmic reticulum that, in the absence of extracellular calcium, also was capable of releasing calcium upon agonist treatment. Confocal imaging disclosed that resiniferatoxin treatment induced vesiculation of the mitochondria and the endoplasmic reticulum ( approximately 1 min), nuclear membrane disruption (5-10 min), and cell lysis (1-2 h). Nociceptive primary sensory neurons endogenously express VR1, and resiniferatoxin treatment induced a sudden increase in [Ca(2+)](i) and mitochondrial disruption which was cell-selective, as glia and non-VR1-expressing neurons were unaffected. Early hallmarks of cytotoxicity were followed by specific deletion of VR1-expressing cells. These data demonstrate that Vanilloids disrupt vital organelles within the cell body and, if administered to sensory ganglia, may be employed to rapidly and selectively delete nociceptive neurons.
A Szallasi - One of the best experts on this subject based on the ideXlab platform.
-
Vanilloid receptor loss is independent of the messenger plasticity that follows systemic resiniferatoxin administration.
Brain research, 1996Co-Authors: T Farkas-szallasi, P M Blumberg, G J Bennett, T Hökfelt, J M Lundberg, A SzallasiAbstract:Resiniferatoxin (RTX) depletes Vanilloid (capsaicin) receptors from lumbar dorsal root ganglia (DRG) of the rat. In addition, RTX causes changes in neuropeptide and nitric oxide synthase expression in lumbar DRG neurons, similar to those described following axotomy; this latter phenomenon is referred to as messenger plasticity. These findings suggested that Vanilloid receptor loss may be part of the plasticity that follows RTX treatment. Here we show that Vanilloid receptor expression, as detected by [3H]RTX autoradiography, is not changed in lumbar DRGs of axotomized rats, nor is it altered in a rat model (chronic constriction injury) of neuropathic pain. Thus, the in vivo expression of Vanilloid receptors detected by specific [3H]RTX binding does not require the presence of intraaxonally transported trophic factors such as nerve growth factor. We conclude that messenger plasticity and Vanilloid receptor loss are mediated by distinct mechanisms.
-
Vanilloid receptors: new insights enhance potential as a therapeutic target.
Pain, 1996Co-Authors: A Szallasi, P M BlumbergAbstract:Compounds related to capsaicin and its ultrapotent analog, resiniferatoxin (RTX), collectively referred to as Vanilloids, interact at a specific membrane recognition site (Vanilloid receptor), expressed almost exclusively by primary sensory neurons involved in nociception and neurogenic inflammation. Desensitization to Vanilloids is a promising therapeutic approach to mitigate neuropathic pain and pathological conditions (e.g. vasomotor rhinitis) in which neuropeptides released from primary sensory neurons play a major role. Capsaicin-containing preparations are already commercially available for these purposes. The use of capsaicin, however, is severely limited by its irritancy, and the synthesis of novel Vanilloids with an improved pungency/desensitization ratio is an on-going objective. This review highlights the emerging evidence that the Vanilloid receptor is not a single receptor but a family of receptors, and that these receptors recognize not simply RTX and capsaicin structural analogs but are broader in their ligand-binding selectivity. We further focus on ligand-induced messenger plasticity, a recently discovered mechanism underlying the analgesic actions of Vanilloids. Lastly, we give a brief overview of the current clinical uses of Vanilloids and their future therapeutic potential. The possibility is raised that Vanilloid receptor subtype-specific drugs may be synthesized, devoid of the undesirable side-effects of capsaicin.
-
Vanilloid (capsaicin) receptors in the rat: distribution in the brain, regional differences in the spinal cord, axonal transport to the periphery, and depletion by systemic Vanilloid treatment.
Brain research, 1995Co-Authors: A Szallasi, P M Blumberg, T Farkas-szallasi, T Hökfelt, S Nilsson, J M LundbergAbstract:Vanilloid (capsaicin) receptors were visualized by [3H]resiniferatoxin (RTX) autoradiography in the brain of newborn as well as adult (both control and colchicine-treated) rats. Specific labelling was seen in the brain stem only, in the nucleus of the solitary tract extending into the area postrema and the spinal sensory nucleus of the trigeminal nerve. Also, a strong signal was seen in the dorsal horn, dorsal root, trigeminal and nodose ganglia. Membranes obtained from the cervical, thoracic, and lumbar segments of the spinal cord showed similar affinities for RTX and likewise for capsaicin and capsazepine; maximal receptor density was similar in the cervical and thoracic segments (approximately 70 fmol/mg protein) but was twice as high in the lumbar segment. 24 h after ligation of the vagal or the sciatic nerves, a strong accumulation of specific RTX binding sites was observed mainly proximal to the ligature, implying intraaxonal receptor transport from the nodose and dorsal root ganglia, respectively, to the periphery. Systemic (s.c.) Vanilloid treatment depleted specific [3H]RTX binding sites from the brain stem, the sensory (dorsal root as well as trigeminal) ganglia, and the spinal cord. RTX was approximately 200-fold more potent than capsaicin for eliminating Vanilloid receptors from the spinal cord. The present results suggest a discrete expression of Vanilloid receptors in the brain stem (sensory nuclei); although intrinsic Vanilloid receptor-expressing neurons are though to exist in the rat brain, they remain undetected by the present [3H]RTX autoradiography methodology.
-
Identification of alpha-1-acid glycoprotein (orosomucoid) as a major Vanilloid binding protein in serum.
The Journal of pharmacology and experimental therapeutics, 1992Co-Authors: A Szallasi, N E Lewin, Peter M. BlumbergAbstract:We have used the Vanilloid (capsaicin) receptor assay to search for modulators of binding activity. We report here that both capsaicin and its ultrapotent analog, resiniferatoxin (RTX), bind to the plasma protein alpha-1-acid glycoprotein (AGP) with high affinity (10.5 and 0.3 microM, respectively). AGP seems to be the dominant Vanilloid (capsaicin/RTX) binding protein in serum. [3H] RTX binding to AGP is inhibited by chlorpromazine and by Trisbutoxyethylphosphate, indicating that Vanilloids compete for a well-characterized drug binding domain on the AGP molecule. The 35-fold difference in the affinity of AGP for RTX and capsaicin may result in differences in the pharmacodynamics and pharmacokinetics of these two compounds; the contribution of AGP binding to the unique spectra of action of RTX or to the marked species differences in Vanilloid actions, however, remains to be determined. An important practical application of AGP is its inclusion in the [3H]RTX binding assay utilizing sensory ganglion membranes to reduce nonspecific binding by up to 5-fold.
Jeewoo Lee - One of the best experts on this subject based on the ideXlab platform.
-
Novel Radiolabeled Vanilloid with Enhanced Specificity for Human Transient Receptor Potential Vanilloid 1 (TRPV1)
Journal of medicinal chemistry, 2017Co-Authors: Larry V. Pearce, Peter M. Blumberg, Jihyae Ann, Aeran Jung, Shivaji A. Thorat, Brienna K. A. Herold, Amelework D. Habtemichael, Jeewoo LeeAbstract:Transient receptor potential Vanilloid 1 (TRPV1) has emerged as a promising therapeutic target. While radiolabeled resiniferatoxin (RTX) has provided a powerful tool for characterization of Vanilloid binding to TRPV1, TRPV1 shows 20-fold weaker binding to the human TRPV1 than to the rodent TRPV1. We now describe a tritium radiolabeled synthetic Vanilloid antagonist, 1-((2-(4-(methyl-[3H])piperidin-1-yl-4-[3H])-6-(trifluoromethyl)pyridin-3-yl)methyl)-3-(3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazin-8-yl)urea ([3H]MPOU), that embodies improved absolute affinity for human TRPV1 and improved synthetic accessibility.
-
n 4 substituted benzyl n tert butylbenzyl thioureas as Vanilloid receptor ligands investigation on the role of methanesulfonamido group in antagonistic activity
Bioorganic & Medicinal Chemistry Letters, 2004Co-Authors: Hyeunggeun Park, Hawon Cho, Young-ger Suh, Ji-yeon Choi, Seahoon Choi, Mikyung Park, Jihye Lee, Jiyoun Lee, Sanguk Kang, Jeewoo LeeAbstract:A series of N-4-substituted-benzyl-N′-tert-butylbenzyl thioureas were prepared for the study of their agonistic/antagonistic activities to the Vanilloid receptor in rat DRG neurons. Their structure–activity relationship reveals that not only the two oxygens and amide hydrogen of sulfonamido group, but also the optimal size of methyl in methanesulfonamido group play an integral role for the antagonistic activity on Vanilloid receptor.
-
Novel non-Vanilloid VR1 antagonist of high analgesic effects and its structural requirement for VR1 antagonistic effects
Bioorganic & medicinal chemistry letters, 2003Co-Authors: Young-ger Suh, Yong-sil Lee, Kyung-hoon Min, Ok-hui Park, Ho-sun Seung, Hee-doo Kim, Hyoung-geun Park, Ji-yeon Choi, Jeewoo Lee, Sangwook KangAbstract:A novel non-Vanilloid VR1 antagonist consisting of a new Vanilloid equivalent exhibits excellent analgesic effects as well as highly potent antagonistic activities in both capsaicin single channel and calcium uptake assays. In addition, the structural requirement for the Vanilloid equivalent of the potent VR1 antagonist has also been elucidated.
-
Resiniferatoxin-Amide and Analogues as Ligands for Protein Kinase C and Vanilloid Receptors and Determination of Their Biological Activities as Vanilloids
Journal of neurochemistry, 2002Co-Authors: Geza Acs, Nancy E. Lewin, Jeewoo Lee, Victor E. Marquez, Shaomeng Wang, George W. A. Milne, Peter M. BlumbergAbstract:The naturally occurring diterpene resiniferatoxin (RTX) is an ultrapotent analogue of capsaicin. Acting on polymodal afferent neurons, RTX induces a generally similar pattern of responses as does capsaicin. However, the two compounds, as well as other Vanilloid derivatives, display different relative potencies for different responses. In the present study, we examined the Vanilloid-like activities of two new derivatives, the amide analogue of RTX and phorbol 12,13-dibenzoate 20-homovanillylamide. Structurally, RTX-amide resembles capsaicin more closely than does RTX, and after cleavage of the amide bond the resulting amine would be predicted to not bind to protein kinase C in contrast to resiniferonol 9,13,14-orthophenylacetate, the parent diterpene of RTX. In contrast to our expectations the binding potency of the RTX-amide for the Vanilloid receptor present in rat spinal cord was 450-fold lower than that of RTX (Ki values for the RTX-amide and RTX were 10.4 +/- 0.7 nM and 23.1 +/- 3.2 pM, respectively). In the case of phorbol 12,13-dibenzoate 20-homovanillylamide, there was a further loss of affinity for the Vanilloid receptor compared with RTX; nonetheless, the Ki (8.56 +/- 0.61 microM) was comparable with that of capsaicin (5.31 +/- 0.37 microM). Computer fitting of the binding data yielded Hill coefficient values of 2.25 +/- 0.03, 2.33 +/- 0.03, and 1.84 +/- 0.05 for RTX, RTX-amide, and phorbol 12,13-dibenzoate 20-homovanillylamide, respectively, indicating that both new compounds induced apparent positive cooperativity among Vanilloid binding sites.(ABSTRACT TRUNCATED AT 250 WORDS)
Stefano Manzini - One of the best experts on this subject based on the ideXlab platform.
-
Vanilloid receptors in the urinary bladder: regional distribution, localization on sensory nerves, and species-related differences.
Naunyn-Schmiedeberg's archives of pharmacology, 1993Co-Authors: Arpad Szallasi, Peter M. Blumberg, Bruno Conte, Cristina Goso, Stefano ManziniAbstract:Using selective surgical ablations we have investigated the localization of Vanilloid receptors (specific [3H]resiniferatoxin binding sites) on terminals of the pelvic, hypogastric, and pudendal nerves in the rat urinary bladder. Pelvic and hypogastric nerve resections resulted in 90%6 and 25% loss of specific [3H]resiniferatoxin (RTX) binding sites, respectively, whilst pudendic nerve resection had no measurable effect on the binding. In control animals, the density of Vanilloid receptors was 1.7-fold higher in the neck than in the dome of the urinary bladder; the Bmax values were 57±8 and 34±7 fmol/mg protein, respectively. The binding characteristics of the Vanilloid receptor were similar in the urinary bladder of the rat and mouse: Kd values were 87±15 and 61±11 pM, Bmax values were 37±2 and 60±10 fmol/mg protein, respectively. In contrast to the findings for the rat and mouse, in the urinary bladder of the guinea pig and the hamster the low level of specific [3H]RTX binding prevented the detailed characterization of Vanilloid receptors. Nonetheless, at a fixed (60 pM) concentration of [3H]RTX, specific binding both in the guinea pig and hamster urinary bladder was approximately 20% of that in the rat urinary bladder. In the urinary bladder of newborn rats, as in adults, a single class of specific [3H]RTX binding sites was found which bound RTX with an affinity of 110±20 pM and with a maximal binding capacity of 30±5 fmol/mg protein. We conclude that, in accord with the physiological findings, the majority of Vanilloid receptors are located on terminals of the pelvic nerve in the rat urinary bladder with higher receptor density in the bladder neck as compared to the bladder dome. Whereas the comparably high density of Vanilloid receptors in the rat and mouse urinary bladder and the low receptor density in the hamster are mirrored by the in vivo Vanilloid-sensitivity of these species, the low level of Vanilloid receptors in the urinary bladder of the guinea pig contrasts to the marked sensitivity of this species to capsaicin. We conclude that the level of Vanilloid receptors is an important but not exclusive determinant of Vanilloid-sensitivity.
-
Characterization of a peripheral Vanilloid (capsaicin) receptor in the urinary bladder of the rat
Life sciences, 1993Co-Authors: Arpad Szallasi, Peter M. Blumberg, Bruno Conte, Cristina Goso, Stefano ManziniAbstract:Abstract Specific binding of [ 3 H]resiniferatoxin (RTX) is thought to represent the Vanilloid (capsaicin) receptor. In the present study, we have used this binding assay to identify for the first time a Vanilloid receptor in the periphery and to compare it to central Vanilloid receptors presents in dorsal root ganglia (DRG) as well as in spinal cord of the rat. Rat urinary bladder membranes bound [ 3 H]RTX with a K d of 30 ± 4 pM and B max of 65 ± 14 fol/mg protein; the corresponding values were 19 ± 3 pM and 104 ± 14 fmol/mg protein in DRG, and 16 ± 3 pM and 50 ± 9 fmol/mg protein in spinal cord. Capsaicin inhibited [ 3 H]RTX binding to membranes from urinary bladder, spinal cord, and DRG with similar potency (K i values were 0.5 ± 0.1 μ M, 0.3 ± 0.1, and 0.6 ± 0.1 μ M, respectively). Interestingly, [ 3 H]RTX bound to urinary bladder in a non-cooperative fashion in contrast with the apparent positive cooperativity of [ 3 H]RTX binding in both DRG and spinal cord (cooperativity index = 1.8 and 1.7, respectively). This finding suggests heterogeneity in the properties of the Vanilloid receptors in the rat.
