ABSTRACT
Background: Transient receptor potential (TRP) channels have been found to have significant implications in neuronal outgrowth, survival, inflammatory neurogenic pain, and various epileptogenic processes. Moreover, there is a growing body of evidence indicating that transient receptor potential (TRP) channels have a significant impact on epilepsy and its drug-resistant subtypes. Objective: We postulated that EGb 761 would modulate TRPA1 channels, thereby exhibiting anti-inflammatory and neuroprotective effects in a neuroblastoma cell line. Our rationale was to investigate the impact of EGb 761 in a controlled model of pentylenetetrazole-induced generalized epilepsy. Methodology: We evaluated the neuroprotective, antioxidant and anti-apoptotic effects of EGb 761 both before and after the pentylenetetrazole application in a neuroblastoma cell line. Specifically, we focused on the effects of EGB 761 on the activity of Transient receptor potential (TRP) channels. Results: EGb 761 applications both before and after the pentylenetetrazole incubation period reduced Ca release and restored apoptosis, ROS changes, mitochondrial depolarization and caspase levels, suggesting a prominent prophylactic and therapeutic effect of EGb 761 in the pentylenetetrazole-induced epileptogenesis process. Conclusion: Our basic mechanistic framework for elucidating the pathophysiological significance of fundamental ion mechanisms in a pentylenetetrazole treated neuroblastoma cell line provided compelling evidence for the favorable efficacy and safety profile of Egb 761 in human-relevant in vitro model of epilepsy. To the best of our knowledge, this is the first study to investigate the combined effects of EGb 761 and pentylenetetrazole on TRP channels and measure their activation level in a relevant model of human epileptic diseases.
ABSTRACT
Dietary fibers have been shown to increase the intestinal absorption of calcium (Ca2+) and magnesium (Mg2+). However, the mechanisms that explain the enhanced electrolyte absorption remain unknown. Therefore, this study aims to investigate the short-term and long-term effects of 5% (w/w) sodium butyrate (Na-butyrate), an important end-metabolite of bacterial fermentation of dietary fibers, on Ca2+ and Mg2+ homeostasis in mice. Serum Ca2+ levels were only significantly increased in mice treated with Na-butyrate for 1 day. This was associated with a twofold increase in the mRNA expression levels of Trpv6 in the proximal and distal colon. Contrary, Na-butyrate did not affect serum Mg2+ concentrations at either of the intervention periods. However, we observed a reduction in urinary Mg2+ excretion, although not significantly, after 1 day of treatment. A significant reduction of 2.5-fold in urinary Mg2+ excretion was observed after 14 days of treatment. Indeed, 14-day Na-butyrate supplementation increased colonic Trpm7 expression by 1.2-fold compared to control mice. In conclusion, short-term Na-butyrate supplementation increases serum Ca2+ levels in mice. This was associated with increased mRNA expression levels of Trpv6 in the colon, suggesting that Na-butyrate regulates the expression of genes involved in active intestinal Ca2+ absorption.
Subject(s)
Sodium, Dietary , TRPM Cation Channels , Animals , Butyric Acid/pharmacology , Calcium/metabolism , Calcium Channels/genetics , Calcium Channels/metabolism , Colon , Dietary Fiber/metabolism , Dietary Fiber/pharmacology , Mice , RNA, Messenger/genetics , RNA, Messenger/metabolism , Sodium/metabolism , Sodium Chloride, Dietary/metabolism , Sodium, Dietary/metabolism , Sodium, Dietary/pharmacology , TRPM Cation Channels/metabolism , TRPV Cation Channels/genetics , TRPV Cation Channels/metabolismABSTRACT
Overcoming refractory epilepsy's resistance to the combination of antiepileptic drugs (AED), mitigating side effects, and preventing sudden unexpected death in epilepsy are critical goals for therapy of this disorder. Current therapeutic strategies are based primarily on neurocentric mechanisms, overlooking the participation of astrocytes and microglia in the pathophysiology of epilepsy. This review is focused on a set of non-selective membrane channels (permeable to ions and small molecules), including channels and ionotropic receptors of neurons, astrocytes, and microglia, such as: the hemichannels formed by Cx43 and Panx1; the purinergic P2X7 receptors; the transient receptor potential vanilloid (TRPV1 and TRPV4) channels; calcium homeostasis modulators (CALHMs); transient receptor potential canonical (TRPC) channels; transient receptor potential melastatin (TRPM) channels; voltage-dependent anion channels (VDACs) and volume-regulated anion channels (VRACs), which all have in common being activated by epileptic activity and the capacity to exacerbate seizure intensity. Specifically, we highlight evidence for the activation of these channels/receptors during epilepsy including neuroinflammation and oxidative stress, discuss signaling pathways and feedback mechanisms, and propose the functions of each of them in acute and chronic epilepsy. Studying the role of these non-selective membrane channels in epilepsy and identifying appropriate blockers for one or more of them could provide complementary therapies to better alleviate the disease.
Subject(s)
Epilepsy , Transient Receptor Potential Channels , Connexins/metabolism , Epilepsy/drug therapy , Epilepsy/metabolism , Humans , Microglia/metabolism , Nerve Tissue Proteins/metabolism , Neurons/metabolism , Seizures/metabolism , Transient Receptor Potential Channels/metabolismABSTRACT
Bronchial asthma, a chronic inflammatory airway disease, belongs to the category of wheezing disease in the system of traditional Chinese medicine (TCM). The wheezing symptom of this disease is mainly caused by the imbalance of lung Qi. According to the theory of five flavor compatibility, the Chinese medicinal materials with five different flavors (pungent, bitter, sour, sweet, and salty) can be combined to produce new functions. The pungent medicinal materials have dispersing effect and the bitter medicinal materials have discharging effect, which are important components in the theory of five flavor compatibility. Pungent herbs and bitter herbs can relieve the adverse lung Qi, occupying an important position in the current medication for the treatment of asthma. However, there is still a lack of in-depth analysis of the TCM theory and mechanism of the compatibility of pungent herbs and bitter herbs in the treatment of asthma. The molecular mechanisms of action of pungent herbs and bitter herbs are closely related to transient receptor potential (TRP) channels and bitter taste receptors (TAS2Rs), respectively. Ca2+ signaling has been recognized in the process of asthma and is involved in the development of multiple symptoms of asthma. The TRP channels and TAS2Rs located on the cell membrane have been proved to directly regulate the intracellular Ca2+ signal and play a role in the treatment of asthma. Therefore, the dispersing effect of pungent herbs and the discharging effect of bitter herbs may be realized through the Ca2+ signaling pathway mediated by TRPs/TAS2Rs. We summarized the theoretical understanding and modern studies of pungent herbs dispersing lung Qi and bitter herbs discharging lung Qi, aiming to explain the internal relationship and mechanism of the compatibility of pungent herbs and bitter herbs in the treatment of asthma from the perspective of TCM theory and modern medicine. The compatibility of pungent herbs and bitter herbs based on the theory of five flavor compatibility for the treatment of asthma has a solid theoretical basis of TCM, and its mechanism can be verified by modern research. Therefore, it may be a main research direction in the treatment of asthma by Chinese medicinal herbs in the future.
ABSTRACT
With the recent interest in medical marijuana, research into cannabinoids is regaining wider attention. Cannabinoids are collectively a group of active compounds that can be produced by animals (endocannabinoids), plants (phytocannabinoids), or synthetically. By acting on a number of different receptors like cannabinoids receptors and transient receptor potential ion channel family, cannabinoids are known to modulate cutaneous inflammation, pain, and itch. Rosacea is a highly prevalent disease and can be associated with a significant degree of morbidity associated with its symptom. Transient receptor potential ion channels are known to be triggered in rosacea and may underlie a portion of rosacea's pathophysiology. This article aims to detail the transient receptor potential channel pathways in rosacea and the known effects of cannabinoids on these pathways and further discussing the potential role of cannabinoids in treating rosacea.
Subject(s)
Cannabinoids , Rosacea , Animals , Cannabinoids/pharmacology , Cannabinoids/therapeutic use , Endocannabinoids , Humans , Pain , Rosacea/drug therapyABSTRACT
TRPV3, a representative of the vanilloid subfamily of TRP channels, is predominantly expressed in skin keratinocytes and has been implicated in cutaneous sensation and associated with numerous skin pathologies and cancers. TRPV3 is inhibited by the natural coumarin derivative osthole, an active ingredient of Cnidium monnieri, which has been used in traditional Chinese medicine for the treatment of a variety of human diseases. However, the structural basis of channel inhibition by osthole has remained elusive. Here we present cryo-EM structures of TRPV3 in complex with osthole, revealing two types of osthole binding sites in the transmembrane region of TRPV3 that coincide with the binding sites of agonist 2-APB. Osthole binding converts the channel pore into a previously unidentified conformation with a widely open selectivity filter and closed intracellular gate. Our structures provide insight into competitive inhibition of TRPV3 by osthole and can serve as a template for the design of osthole chemistry-inspired drugs targeting TRPV3-associated diseases.
Subject(s)
Coumarins , TRPV Cation Channels , Coumarins/metabolism , Coumarins/pharmacology , Humans , Keratinocytes/metabolism , Skin/metabolism , TRPV Cation Channels/metabolismABSTRACT
Affinin is mainly recognized by its antinociceptive effect. Recently, our research group demonstrated that this compound produces vasodilation via activation of the gasotransmitters signaling pathways. However, the molecular targets of affinin were not identified. Considering the structural similarity of this alkamide with anandamide, we hypothesized that affinin-induced vasodilation could involve participation of TRP channels and cannabinoid receptors. In this work, by using the isolated rat aorta assay, we assessed involvement of TRP channels, the cannabinoid system, and the HNO-CGRP-TRPA1 pathway on the mechanism of action of affinin. Additionally, we measured NO and H2S levels elicited by affinin on rat aorta homogenates and carried out computer simulations of molecular interactions between affinin and the TRPA1 and TRPV1 channels and the CB1 receptor. Our results indicated that affinin induces an increase in aortic NO and H2S levels. We found evidence that the vasodilator effect induced by affinin involves activation of TRPA1 and TRPV1 channels and the CB1 and eCB receptors. In silico analyses showed that affinin is able to bind with high affinity to these molecular targets. Moreover, we also proved that affinin-induced vasodilation is partly mediated via activation of the HNO-TRPA1-CGRP pathway. Based on these results we propose a novel mechanism of action to explain the vasodilatory effect of affinin, which could be developed as an alternative drug to treat cardiovascular diseases.
Subject(s)
Polyunsaturated Alkamides/pharmacology , Receptors, Cannabinoid/metabolism , TRPV Cation Channels/metabolism , Vasodilation/drug effects , Animals , Aorta/drug effects , Hydrogen Sulfide , In Vitro Techniques , Male , Molecular Docking Simulation , Nitric Oxide , Rats , Rats, WistarABSTRACT
OBJECTIVES: Neuropathic pain (NP) is a chronic inflammation of the sciatic nerve, associated with complex pathophysiological events like neuronal ectopic discharge with changes in neurotransmitters, growth factors, receptors/ion channels including N-methyl-d-aspartate receptors, Transient receptor cation channels, Voltage-gated calcium channels. All these events eventually lead to inflammation and apoptosis of the sciatic nerve in NP. Icariin (ICA), a natural flavonoid is well known for its anti-inflammatory potential. Hence, the present study is designed to evaluate its anti-inflammatory potential against neuropathic pain using in silico and in vivo studies. METHODS: In silico studies were conducted using targets of N-methyl-D-aspartate receptor subtype-2B (NR2B), The capsaicin receptor transient receptor cation channel subfamily-V member-1 (TRPV1), N-type voltage-gated calcium (CaV2.2) channels. In in vivo studies, after partial sciatic nerve ligation surgery to animals, received their respective treatment for 21 days, further TNF-α, IL-6, Bax (proapoptotic) and Bcl-2 (antiapoptotic) expressions were estimated. KEY FINDINGS: ICA decreased the expressions of TNF-α, IL-6, Bax and increased expression of Bcl-2. In silico studies revealed a good energy binding score towards NR2B, TRPV1 receptors and CaV2.2 ion Channel. CONCLUSIONS: ICA could be a promising agent in alleviating neuropathic pain by inhibiting NR2B, TRPV1 receptors and Cav2.2 channels, which induces anti-apoptotic potential and inhibits inflammation.
Subject(s)
Calcium Channels, N-Type/metabolism , Flavonoids/pharmacology , Neuralgia , Receptors, N-Methyl-D-Aspartate/metabolism , TRPV Cation Channels/metabolism , Animals , Anti-Inflammatory Agents/pharmacology , Apoptosis Regulatory Proteins/analysis , Disease Models, Animal , Drugs, Chinese Herbal/pharmacology , Neuralgia/drug therapy , Neuralgia/metabolism , Rats , Sciatic Nerve/drug effects , Sciatic Nerve/pathologyABSTRACT
Transient receptor potential (TRP) channels are critical receptors in the transduction of nociceptive stimuli. The microenvironment of diverse types of cancer releases substances, including growth factors, neurotransmitters, and inflammatory mediators, which modulate the activity of TRPs through the regulation of intracellular signaling pathways. The modulation of TRP channels is associated with the peripheral sensitization observed in patients with cancer, which results in mild noxious sensory stimuli being perceived as hyperalgesia and allodynia. Secondary metabolites derived from plant extracts can induce the activation, blocking, and desensitization of TRP channels. Thus, these compounds could act as potential therapeutic agents, as their antinociceptive properties could be beneficial in relieving cancer-derived pain. In this review, we will summarize the role of TRPV1 and TRPA1 in pain associated with cancer and discuss molecules that have been reported to modulate these channels, focusing particularly on the mechanisms of channel activation associated with molecules released in the tumor microenvironment.
Subject(s)
Cancer Pain , Neoplasm Proteins , Neoplasms , Signal Transduction , TRPA1 Cation Channel , TRPV Cation Channels , Animals , Cancer Pain/drug therapy , Cancer Pain/genetics , Cancer Pain/metabolism , Humans , Hyperalgesia/drug therapy , Hyperalgesia/genetics , Hyperalgesia/metabolism , Neoplasm Proteins/genetics , Neoplasm Proteins/metabolism , Neoplasms/drug therapy , Neoplasms/genetics , Neoplasms/metabolism , TRPA1 Cation Channel/genetics , TRPA1 Cation Channel/metabolism , TRPV Cation Channels/genetics , TRPV Cation Channels/metabolismABSTRACT
Pain is a complex physiological process that includes many components. Growing evidence supports the idea that oxidative stress and Ca2+ signaling pathways participate in pain detection by neurons. The main source of endogenous reactive oxygen species (ROS) is mitochondrial dysfunction induced by membrane depolarization, which is in turn caused by Ca2+ influx into the cytosol of neurons. ROS are controlled by antioxidants, including selenium. Selenium plays an important role in the nervous system, including the brain, where it acts as a cofactor for glutathione peroxidase and is incorporated into selenoproteins involved in antioxidant defenses. It has neuroprotective effects through modulation of excessive ROS production, inflammation, and Ca2+ overload in several diseases, including inflammatory pain, hypersensitivity, allodynia, diabetic neuropathic pain, and nociceptive pain. Ca2+ entry across membranes is mediated by different channels, including transient receptor potential (TRP) channels, some of which (e.g., TRPA1, TRPM2, TRPV1, and TRPV4) can be activated by oxidative stress and have a role in the induction of peripheral pain. The results of recent studies indicate the modulator roles of selenium in peripheral pain through inhibition of TRP channels in the dorsal root ganglia of experimental animals. This review summarizes the protective role of selenium in TRP channel regulation, Ca2+ signaling, apoptosis, and mitochondrial oxidative stress in peripheral pain induction.
Subject(s)
Nervous System Diseases/physiopathology , Selenium/physiology , Animals , Calcium Signaling , Humans , Neuralgia/physiopathology , Transient Receptor Potential Channels/metabolismABSTRACT
The Transient Receptor Potential (TRP) protein superfamily is a group of cation channels expressed in various cell types and involved in respiratory diseases such as cystic fibrosis (CF), the genetic disease caused by CF Transmembrane conductance Regulator (CFTR) mutations. In human airway epithelial cells, there is growing evidence for a functional link between CFTR and TRP channels. TRP channels contribute to transmitting extracellular signals into the cells and, in an indirect manner, to CFTR activity via a Ca2+ rise signaling. Indeed, mutated CFTR-epithelial cells are characterized by an increased Ca2+ influx and, on the opposite, by a decreased of magnesium influx, both being mediated by TRP channels. This increasing cellular Ca2+ triggers the activation of calcium-activated chloride channels (CaCC) or CFTR itself, via adenylyl cyclase, PKA and tyrosine kinases activation, but also leads to an exaltation of the inflammatory response. Another shortcoming in mutated CFTR-epithelial cells is a [Mg2+]i decrease, associated with impaired TRPM7 functioning. This deregulation has to be taken into consideration in CF physiopathology, as Mg2+ is required for ATP hydrolysis and CFTR activity. The modulation of druggable TRP channels could supplement CF therapy either an anti-inflammatory drug or for CFTR potentiation, according to the balance between exacerbation and respite phases. The present paper focus on TRPA1, TRPC6, TRPM7, TRPV2, TRPV4, TRPV6 and ORAI 1, the proteins identified, for now, as dysfunctional channels, in CF cells.
Subject(s)
Cystic Fibrosis/metabolism , Inflammation/metabolism , Transient Receptor Potential Channels/metabolism , Animals , Anti-Inflammatory Agents/therapeutic use , Calcium Signaling , Cystic Fibrosis/drug therapy , Cystic Fibrosis/genetics , Cystic Fibrosis Transmembrane Conductance Regulator/genetics , Humans , Inflammation/drug therapy , Inflammation/genetics , Magnesium/metabolism , Mutation/geneticsABSTRACT
BACKGROUND: Oral ulcerative mucositis causes severe pain during eating and speaking, resulting in poor quality of life for patients with cancer undergoing chemoradiotherapy. Recently, some basic and clinical studies demonstrated that hangeshashinto, a traditional Japanese herbal medicine, alleviated oral ulcerative mucositis-induced pain. Here, we review a recently revealed pain mechanism underlying oral ulcerative mucositis in a preclinical rat model and the pharmacological analgesic effect of hangeshashinto. HIGHLIGHT: In a rat model of experimentally induced oral ulcerative mucositis, the mucosal surface of the ulcerative region is damaged, which increases oral bacterial loading in the mucosa and prostanoid production. Chemotherapeutic drugs exaggerate the pathological condition and cause severe pain. The pain-related TRP channels, TRPV1, TRPA1, and/or TRPV4, mediate spontaneous and mechanical pain in oral ulcerative mucositis models. Swab application of hangeshashinto had a prolonged localized analgesic effect on oral ulcerative mucositis, even in a chemotherapy-treated oral ulcer model. Two ingredients of hangeshashinto, gingerol and shogaol, strongly inhibit voltage-activated sodium channels (though they have agonistic effects on TRPV1 and TRPA1), which confers hyposensitivity to the oral mucosa. Their analgesic effects on oral ulcerative mucositis are accompanied by accelerated delivery of drugs (other saponin-containing herbal extracts) into the ulcerative region. CONCLUSION: Elucidation of the pain mechanism of oral ulcerative mucositis and analgesic mechanism of hangeshashinto will allow identification of novel therapeutic approaches against oral ulcerative mucositis-induced pain in patients. The traditional Japanese herbal medicine hangeshashinto is a reliable drug with supporting scientific evidence.
Subject(s)
Drugs, Chinese Herbal , Mucositis , Animals , Herbal Medicine , Humans , Pain , Quality of Life , Rats , TRPV Cation ChannelsABSTRACT
Human brown adipose tissue (BAT) has attracted clinical interest not only because it dissipates energy but also for its potential capacity to counteract obesity and related metabolic disorders (e.g., insulin resistance and dyslipidemia). Cold exposure is the most powerful stimulus for activating and recruiting BAT, and this stimulatory effect is mediated by the transient receptor potential (TRP) channels. BAT can also be activated by other receptors such as the G-protein-coupled bile acid receptor 1 (GPBAR1) or ß-adrenergic receptors. Interestingly, these receptors also interact with several dietary components; in particular, capsinoids and tea catechins appear to mimic the effects of cold through a TRP-BAT axis, and they consequently seem to decrease body fat and improve metabolic blood parameters. This systematic review critically addresses the evidence behind the available human studies analyzing the effect of several dietary components (e.g., capsinoids, tea catechins, and ephedrine) on BAT activity. Even though the results of these studies are consistent with the outcomes of preclinical models, the lack of robust study designs makes it impossible to confirm the BAT-activation capacity of the specified dietary components. Further investigation into the effects of dietary components on BAT is warranted to clarify to what extent these components could serve as a powerful strategy to treat obesity and related metabolic disorders.
Subject(s)
Adipose Tissue, Brown/drug effects , Capsaicin/pharmacology , Catechin/pharmacology , Ephedrine/pharmacology , Phytochemicals/pharmacology , Humans , Receptors, Adrenergic, beta/metabolism , Receptors, G-Protein-Coupled/metabolism , Tea/chemistry , Transient Receptor Potential Channels/metabolismABSTRACT
BACKGROUND: Millions of people worldwide are suffering from Alzheimer's disease (AD), and there are only symptomatic treatments available for this disease. Thus, there is a great need to identify drugs capable of arresting or reversing AD. Constituents of the spice turmeric, in particular, curcuminoids, seem to be very promising, as evident from in vitro experiments and tests using animal models of AD. However, most of the clinical trials did not reveal any beneficial effects of curcuminoids in the treatment of AD. These controversies, including conflicting results of clinical trials, are thought to be related to bioavailability of curcuminoids, which is low unless it is enhanced by developing a special formulation. However, there is growing evidence suggesting that other reasons may be of even greater importance, but these avenues are less explored. OBJECTIVE: Review relevant literature, and analyze potential reasons for the controversial results. METHODOLOGY: Recent in vitro and preclinical studies; clinical trials (without a limiting period) were searched in PubMed and Google Scholar. RESULTS: While recent in vitro and preclinical studies confirm the therapeutic potential of curcuminoids in the treatment of AD and cognitive dysfunctions, results of corresponding clinical trials remain rather controversial. CONCLUSION: The controversial results obtained in the clinical trials may be in part due to particularities of the curcuminoid formulations other than bioavailability. Namely, it seems likely that the various formulations differ in terms of their minor turmeric constituent(s). We hypothesize that these distinctions may be of key importance for efficacy of the particular formulation in clinical trials. A testable approach addressing this hypothesis is suggested.
Subject(s)
Alzheimer Disease/drug therapy , Curcumin/therapeutic use , Acid Sensing Ion Channels/chemistry , Acid Sensing Ion Channels/metabolism , Alzheimer Disease/metabolism , Alzheimer Disease/pathology , Amyloid beta-Peptides/antagonists & inhibitors , Amyloid beta-Peptides/metabolism , Animals , Cholinesterases/chemistry , Cholinesterases/metabolism , Clinical Trials as Topic , Curcumin/metabolism , Humans , Insulin/metabolism , Transient Receptor Potential Channels/antagonists & inhibitors , Transient Receptor Potential Channels/metabolismABSTRACT
Objective To screen out the key chemical constituents and target protein of essential oil of Desmodium styracifolium for its anti-inflammatory effect. Methods Steam distillation method was used to extract the volatile oils from D. styraci folium, and its chemical constituents were identified by GC-MS, and the relative content of chemical constituents was determined by peak area normalization. The small molecule ligand library was established based on Traditional Chinese Medicine Systems Pharmacology (TCMSP). Reverse target prediction was conducted online using Swiss Target Prediction, the anti-inflammatory pathways were screened by KOBAX 3.0, conducting energy match between the key small molecular and the target protein in the TRP channels by molecular docking (SYBYL2.1). Construction of chemical constituents-targets network model was based on Cytoscape 3.5.1. Results A total of 48 chromatographic peaks were detected from D. styracifolium volatile oils, and 33 kinds of compound structure were determined by searching in mass spectral database and document retrieval, which account for 90.1% of total volatile oils. There were 17 key chemical constituents, and 88 target proteins were selected. TRP channels included 11 potential targets. Through molecular docking, we found that the phytol, hentriacontane, farnesyl acetone, and squalene were the key anti-inflammatory chemical constituents of D. styraci folium volatile oils. TPRV1 (transient receptor potential cation channel, subfamily V, member 1), PRKCB (protein kinase C, beta), and PRKCD (protein kinase C, delta) (degree > 10) are the key anti-inflammatory target protein. Conclusion We preliminarily select the key anti-inflammatory target and active constituents of D. styraci folium volatile oils from this study, and this research provides the theoretical basis for the development and application of its products.
ABSTRACT
In mammals, the main molecular entity involved in innocuous cold transduction is TRPM8. This polymodal ion channel is activated by cold, cooling compounds such as menthol and voltage. Despite its relevance, the molecular determinants involved in its activation by cold remain elusive. In this study we explored the use of TRPM8 orthologs with different cold responses as a strategy to identify new molecular determinants related with their thermosensitivity. We focused on mouse TRPM8 (mTRPM8) and chicken TRPM8 (cTRPM8), which present complementary thermosensitive and chemosensitive phenotypes. Although mTRPM8 displays larger responses to cold than cTRPM8 does, the avian ortholog shows a higher sensitivity to menthol compared with the mouse channel, in both HEK293 cells and primary somatosensory neurons. We took advantage of these differences to build multiple functional chimeras between these orthologs, to identify the regions that account for these discrepancies. Using a combination of calcium imaging and patch clamping, we identified a region encompassing positions 526-556 in the N terminus, whose replacement by the cTRPM8 homolog sequence potentiated its response to agonists. More importantly, we found that the characteristic cold response of these orthologs is due to nonconserved residues located within the pore loop, suggesting that TRPM8 has evolved by increasing the magnitude of its cold response through changes in this region. Our results reveal that these structural domains are critically involved in cold sensitivity and functional modulation of TRPM8, and support the idea that the pore domain is a key molecular determinant in temperature responses of this thermo-transient receptor potential (TRP) channel.
Subject(s)
Avian Proteins/metabolism , Calcium/metabolism , Cold Temperature , Ion Channel Gating/physiology , TRPM Cation Channels/metabolism , Amino Acid Sequence , Animals , Avian Proteins/genetics , Chickens , HEK293 Cells , Humans , Ion Channel Gating/drug effects , Menthol/pharmacology , Mice , Mutagenesis, Site-Directed , Mutation , Protein Domains , Sequence Homology , TRPM Cation Channels/geneticsABSTRACT
Currently, neuropathic pain is an underestimated socioeconomic health problem affecting millions of people worldwide, which incidence may increase in the next years due to chronification of several diseases, such as cancer and diabetes. Growing evidence links neuropathic pain present in several disorders [i.e., spinal cord injury (SCI), cancer, diabetes and alcoholism] to central sensitization, as a global result of mitochondrial dysfunction induced by oxidative and nitrosative stress. Additionally, inflammatory signals and the overload in intracellular calcium ion could be also implicated in this complex network that has not yet been elucidated. Recently, calcium channels namely transient receptor potential (TRP) superfamily, including members of the subfamilies A (TRAP1), M (TRPM2 and 7), and V (TRPV1 and 4), have demonstrated to play a role in the nociception mediated by sensory neurons. Therefore, as neuropathic pain could be a consequence of the imbalance between reactive oxygen species and endogen antioxidants, antioxidant supplementation may be a treatment option. This kind of therapy would exert its beneficial action through antioxidant and immunoregulatory functions, optimizing mitochondrial function and even increasing the biogenesis of this vital organelle; on balance, antioxidant supplementation would improve the patient's quality of life. This review seeks to deepen on current knowledge about neuropathic pain, summarizing clinical conditions and probable causes, the relationship existing between oxidative stress, mitochondrial dysfunction and TRP channels activation, and scientific evidence related to antioxidant supplementation.
ABSTRACT
Suramin is a trypan blue analogon originally developed to treat protozoan infections, which was found to have diverse antitumor effects. One of the most severe side effects in clinical trials was the development of a peripheral sensory-motor polyneuropathy. In this study, we aimed to investigate suramin-induced neuropathy with a focus on calcium (Ca2+) homeostasis as a potential pathomechanism. Adult C57Bl/6 mice treated with a single injection of 250 mg/kg bodyweight suramin developed locomotor and sensory deficits, which were confirmed by electrophysiological measurements showing a predominantly sensory axonal-demyelinating polyneuropathy. In a next step, we used cultured dorsal root ganglia neurons (DRGN) as an in vitro cell model to further investigate underlying pathomechanisms. Cell viability of DRGN was significantly decreased after 24-hour suramin treatment with a calculated IC50 of 283 µM. We detected a suramin-induced Ca2+ influx into DRGN from the extracellular space, which could be reduced with the voltage-gated calcium channel (VGCC) inhibitor nimodipine. Co-incubation of suramin and nimodipine partially improved cell viability of DRGN after suramin exposure. In summary, we describe suramin-induced neurotoxic effects on DRGN as well as potentially neuroprotective agents targeting intracellular Ca2+ dyshomeostasis.
Subject(s)
Neuroprotection/drug effects , Neuroprotective Agents/pharmacology , Neurotoxins/adverse effects , Suramin/adverse effects , Animals , Calcium/metabolism , Calcium Channels/metabolism , Cell Survival/drug effects , Disease Models, Animal , Dose-Response Relationship, Drug , Drug Evaluation, Preclinical , Ganglia, Spinal/cytology , Mice , Models, Animal , Neurons/drug effects , Neurons/metabolism , Polyneuropathies/drug therapy , Polyneuropathies/etiology , Polyneuropathies/physiopathologyABSTRACT
KEY POINTS: Endothelial cell function in resistance arteries integrates Ca2+ signalling with hyperpolarization to promote relaxation of smooth muscle cells and increase tissue blood flow. Whether complementary signalling occurs in lymphatic endothelium is unknown. Intracellular calcium and membrane potential were evaluated in endothelial cell tubes freshly isolated from mouse collecting lymphatic vessels of the popliteal fossa. Resting membrane potential measured using intracellular microelectrodes averaged â¼-70 mV. Stimulation of lymphatic endothelium by acetylcholine or a TRPV4 channel agonist increased intracellular Ca2+ with robust depolarization. Findings from Trpv4-/- mice and with computational modelling suggest that the initial mobilization of intracellular Ca2+ leads to influx of Ca2+ and Na+ through TRPV4 channels to evoke depolarization. Lymphatic endothelial cells lack the Ca2+ -activated K+ channels present in arterial endothelium to generate endothelium-derived hyperpolarization. Absence of this signalling pathway with effective depolarization may promote rapid conduction of contraction along lymphatic muscle during lymph propulsion. ABSTRACT: Subsequent to a rise in intracellular Ca2+ ([Ca2+ ]i ), hyperpolarization of the endothelium coordinates vascular smooth muscle relaxation along resistance arteries during blood flow control. In the lymphatic vasculature, collecting vessels generate rapid contractions coordinated along lymphangions to propel lymph, but the underlying signalling pathways are unknown. We tested the hypothesis that lymphatic endothelial cells (LECs) exhibit Ca2+ and electrical signalling properties that facilitate lymph propulsion. To study electrical and intracellular Ca2+ signalling dynamics in lymphatic endothelium, we excised collecting lymphatic vessels from the popliteal fossa of mice and removed their muscle cells to isolate intact LEC tubes (LECTs). Intracellular recording revealed a resting membrane potential of â¼-70 mV. Acetylcholine (ACh) increased [Ca2+ ]i with a time course similar to that observed in endothelium of resistance arteries (i.e. rapid initial peak with a sustained 'plateau'). In striking contrast to the endothelium-derived hyperpolarization (EDH) characteristic of arteries, LECs depolarized (>15 mV) to either ACh or TRPV4 channel activation. This depolarization was facilitated by the absence of Ca2+ -activated K+ (KCa ) channels as confirmed with PCR, persisted in the absence of extracellular Ca2+ , was abolished by LaCl3 and was attenuated â¼70% in LECTs from Trpv4-/- mice. Computational modelling of ion fluxes in LECs indicated that omitting K+ channels supports our experimental results. These findings reveal novel signalling events in LECs, which are devoid of the KCa activity abundant in arterial endothelium. Absence of EDH with effective depolarization of LECs may promote the rapid conduction of contraction waves along lymphatic muscle during lymph propulsion.
Subject(s)
Calcium Signaling , Endothelium, Vascular/metabolism , Lymphatic Vessels/metabolism , Membrane Potentials , Acetylcholine/pharmacology , Animals , Endothelium, Vascular/drug effects , Endothelium, Vascular/physiology , Leucine/analogs & derivatives , Leucine/pharmacology , Lymphatic Vessels/drug effects , Lymphatic Vessels/physiology , Male , Mice , Mice, Inbred C57BL , Sulfonamides/pharmacology , TRPV Cation Channels/agonists , TRPV Cation Channels/metabolismABSTRACT
A series of 33 curcumin analogues was synthesized and tested on TRPA1, TRPM8, and TRPV1 channels. Twenty of them acted as good modulators of TRPA1 channels. None was able to significantly activate TRPM8 channels, while curcumin itself and six curcuminoids belonging to the 1,3-dicarbonyl and acyclic series behaved as 'true' antagonists with IC50 values<5µM. Only few curcuminoids were able to modulate TRPV1 channels with EC50 and IC50 values ranging from 3.4 and 6.0µM.