A-type GABA receptor as a central target of TRPM8 agonist menthol.
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ABSTRACT:
SUBMITTER: Zhang XB
PROVIDER: S-EPMC2560999 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Menthol has historically been used topically to alleviate various pain conditions. At low concentrations, this non-selective TRPM8 agonist elicits a cooling sensation, however higher concentrations result in cold hyperalgesia in normal subjects and paradoxically analgesia in neuropathic patients. Through behavioural and electrophysiological means, we examined whether this back-translated into a pre-clinical rodent model. Menthol was applied topically to the hind paws of naive and spinal nerve-ligated (SNL) rats. In behavioural assays, menthol did not affect withdrawal thresholds to mechanical stimulation and 10% and 40% menthol rarely sensitised withdrawals to innocuous cooling in naïve rats. However, in SNL rats, 10% and 40% menthol alleviated cold hypersensitivity. This was partly corroborated by in vivo electrophysiological recordings of dorsal horn lamina V/VI neurones. As several studies have implicated TRPM8 in analgesia, we examined whether a novel systemically available TRPM8 agonist, M8-Ag, had more potent anti-hyperalgesic effects than menthol in neuropathic rats. In vitro, M8-Ag activates TRPM8, expressed in HEK293 cells, with an EC50 of 44.97 nM. In vivo, M8-Ag inhibited neuronal responses to innocuous and noxious cooling in SNL rats with no effect in sham-operated rats. This effect was modality selective; M8-Ag did not alter neuronal responses to mechanical, heat or brush stimulation. In addition, M8-Ag attenuated behavioural hypersensitivity to innocuous cooling but not mechanical stimulation. These data suggest that menthol induced hyperalgesia is not consistently replicable in the rat and that the analgesic properties are revealed by injury. Systemic TRPM8 agonists might be beneficial in neuropathy without affecting normal cold sensitivity.
| S-EPMC4220012 | biostudies-literature
Project description:1. TRPM8 (CMR1) is a Ca(2+)-permeable channel, which can be activated by low temperatures, menthol, eucalyptol and icilin. It belongs to the transient receptor potential (TRP) family, and therefore is related to vanilloid receptor type-1 (VR1, TRPV1). We tested whether substances which are structurally related to menthol, or which produce a cooling sensation, could activate TRPM8, and compared the responses of TRPM8 and VR1 to these ligands. 2. The effects of 70 odorants and menthol-related substances on recombinant mouse TRPM8 (mTRPM8), expressed in HEK293 cells, were examined using a FLIPR assay. In all, 10 substances (linalool, geraniol, hydroxycitronellal, WS-3, WS-23, FrescolatMGA, FrescolatML, PMD38, CoolactP and Cooling Agent 10) were found to be agonists. 3. The EC(50) values of the agonists defined their relative potencies: icilin (0.2+/-0.1 microM)>FrescolatML (3.3+/-1.5 microM) > WS-3 (3.7+/-1.7 microM) >(-)menthol (4.1+/-1.3 microM) >frescolatMAG (4.8+/-1.1 microM) > cooling agent 10 (6+/-2.2 microM) >(+)menthol (14.4+/-1.3 microM) > PMD38 (31+/-1.1 microM) > WS-23 (44+/-7.3 microM) > Coolact P (66+/-20 microM) > geraniol (5.9+/-1.6 mM) > linalool (6.7+/-2.0 mM) > eucalyptol (7.7+/-2.0 mM) > hydroxycitronellal (19.6+/-2.2 mM). 4. Known VR1 antagonists (BCTC, thio-BCTC and capsazepine) were also able to block the response of TRPM8 to menthol (IC(50): 0.8+/-1.0, 3.5+/-1.1 and 18+/-1.1 microM, respectively). 5. The Ca(2+) response of hVR1-transfected HEK293 cells to the endogenous VR1 agonist N-arachidonoyl-dopamine was potentiated by low pH. In contrast, menthol- and icilin-activated TRPM8 currents were suppressed by low pH. 6. In conclusion, in the present study, we identified 10 new agonists and three antagonists of TRPM8. We found that, in contrast to VR1, TRPM8 is inhibited rather than potentiated by protons.
| S-EPMC1574235 | biostudies-literature
Project description:Menthol is a naturally occurring monoterpene alcohol possessing remarkable biological properties including antipruritic, analgesic, antiseptic, anti-inflammatory and cooling effects. Here, we examined the menthol-evoked Ca2+ signals in breast and prostate cancer cell lines. The effect of menthol (50-500µM) was predicted to be mediated by the transient receptor potential ion channel melastatin subtype 8 (TRPM8). However, the intensity of menthol-evoked Ca2+ signals did not correlate with the expression levels of TRPM8 in breast and prostate cancer cells indicating a TRPM8-independent signaling pathway. Menthol-evoked Ca2+ signals were analyzed in detail in Du 145 prostate cancer cells, as well as in CRISPR/Cas9 TRPM8-knockout Du 145 cells. Menthol (500µM) induced Ca2+ oscillations in both cell lines, thus independent of TRPM8, which were however dependent on the production of inositol trisphosphate. Results based on pharmacological tools point to an involvement of the purinergic pathway in menthol-evoked Ca2+ responses. Finally, menthol (50-500µM) decreased cell viability and induced oxidative stress independently of the presence of TRPM8 channels, despite that temperature-evoked TRPM8-mediated inward currents were significantly decreased in TRPM8-knockout Du 145 cells compared to wild type Du 145 cells.
| S-EPMC5680524 | biostudies-literature
Project description:The stereoisomers of menthol elicit cooling sensation to various levels. Though the high-resolution three-dimensional structures of the menthol receptor, the transient receptor potential melastatin 8 (TRPM8) ion channels, have been revolved in different states, the menthol-bound state structure is not determined and how the stereoisomers of menthol interact with TRPM8 remains largely elusive. Taking advantage of the identical atom composition but distinct spatial orientation of chemical groups in menthol stereoisomers, we performed thermodynamic mutant cycle analysis (TMCA) with patch-clamp recordings to probe the interaction between these ligands and TRPM8. By comparing (-)-menthol with (+)-neoisomenthol or (+)-neomenthol, we observed that the isopropyl or hydroxyl group in menthol interacts with the S4 or S3 helix in TRPM8, respectively. These interactions were also corroborated in our molecular docking of the stereoisomers, though the predicted structural details in the interactions of these ligands with TRPM8 residues are different. Therefore, we suggest similar molecular mechanisms of TRPM8 activation by the stereoisomers of menthol, while the binding configuration of an individual stereoisomer is varied.
| S-EPMC9253294 | biostudies-literature
Project description:Transient receptor potential melastatin (TRPM) cation channels are polymodal sensors that are involved in a variety of physiological processes. Within the TRPM family, member 8 (TRPM8) is the primary cold and menthol sensor in humans. We determined the cryo-electron microscopy structure of the full-length TRPM8 from the collared flycatcher at an overall resolution of ~4.1 ångstroms. Our TRPM8 structure reveals a three-layered architecture. The amino-terminal domain with a fold distinct among known TRP structures, together with the carboxyl-terminal region, forms a large two-layered cytosolic ring that extensively interacts with the transmembrane channel layer. The structure suggests that the menthol-binding site is located within the voltage-sensor-like domain and thus provides a structural glimpse of the design principle of the molecular transducer for cold and menthol sensation.
| S-EPMC5810135 | biostudies-literature
Project description:The spatial and temporal distribution of receptors constitutes an important mechanism for controlling the magnitude of cellular responses. Several members of the transient receptor potential (TRP) ion channel family can regulate their function by modulating their expression at the plasma membrane (PM) through rapid vesicular translocation and fusion. The mechanisms underlying this regulation are not completely understood, and the contribution of vesicular trafficking to physiological function is unknown. TRPM8 receptors are expressed in mammalian peripheral sensory neurons and are essential for the detection of cold temperatures. Previously, we showed that TRPM8-containing vesicles are segregated into three main pools, immobile at the PM, simple diffusive and corralled-hopping. Here, we show that channel expression at the PM is modulated by TRPM8 agonists in F11 and HEK293T cells. Our results support a model in which the activation of TRPM8 channels, located at the PM, induces a short-lived recruitment of a TRPM8-containing vesicular pool to the cell surface causing a transitory increase in the number of functional channels, affecting intrinsic properties of cold receptor responses. We further demonstrate the requirement of intact vesicular trafficking to support sustained cold responses in the skin of mice.
| S-EPMC6605369 | biostudies-literature
Project description:Menthol in mints elicits coolness sensation by selectively activating TRPM8 channel. Although structures of TRPM8 were determined in the apo and liganded states, the menthol-bounded state is unresolved. To understand how menthol activates the channel, we docked menthol to the channel and systematically validated our menthol binding models with thermodynamic mutant cycle analysis. We observed that menthol uses its hydroxyl group as a hand to specifically grab with R842, and its isopropyl group as legs to stand on I846 and L843. By imaging with fluorescent unnatural amino acid, we found that menthol binding induces wide-spread conformational rearrangements within the transmembrane domains. By ? analysis based on single-channel recordings, we observed a temporal sequence of conformational changes in the S6 bundle crossing and the selectivity filter leading to channel activation. Therefore, our study suggested a 'grab and stand' mechanism of menthol binding and how menthol activates TRPM8 at the atomic level.
| S-EPMC7391767 | biostudies-literature
Project description:The transient receptor potential melastatin 8 (TRPM8) ion channel is the primary cold sensor in humans. TRPM8 is gated by physiologically relevant cold temperatures and chemical ligands that induce cold sensations, such as the analgesic compound menthol. Characterization of TRPM8 ligand-gated channel activation will lead to a better understanding of the fundamental mechanisms that underlie TRPM8 function. Here, the direct binding of menthol to the isolated hTRPM8 sensing domain (transmembrane helices S1-S4) is investigated. These data are compared with two mutant sensing domain proteins, Y745H (S2 helix) and R842H (S4 helix), which have been previously identified in full length TRPM8 to be menthol insensitive. The data presented herein show that menthol specifically binds to the wild type, Y745H, and R842H TRPM8 sensing domain proteins. These results are the first to show that menthol directly binds to the TRPM8 sensing domain and indicates that Y745 and R842 residues, previously identified in functional studies as crucial to menthol sensitivity, do not affect menthol binding but instead alter coupling between the sensing domain and the pore domain.
| S-EPMC4865251 | biostudies-literature
Project description:Beige adipocytes are a new type of recruitable brownish adipocytes, with highly mitochondrial membrane uncoupling protein 1 expression and thermogenesis. Beige adipocytes were found among white adipocytes, especially in subcutaneous white adipose tissue (sWAT). Therefore, beige adipocytes may be involved in the regulation of energy metabolism and fat deposition. Transient receptor potential melastatin 8 (TRPM8), a Ca2+-permeable non-selective cation channel, plays vital roles in the regulation of various cellular functions. It has been reported that TRPM8 activation enhanced the thermogenic function of brown adiposytes. However, the involvement of TRPM8 in the thermogenic function of WAT remains unexplored. Our data revealed that TRPM8 was expressed in mouse white adipocytes at mRNA, protein and functional levels. The mRNA expression of Trpm8 was significantly increased in the differentiated white adipocytes than pre-adipocytes. Moreover, activation of TRPM8 by menthol enhanced the expression of thermogenic genes in cultured white aidpocytes. And menthol-induced increases of the thermogenic genes in white adipocytes was inhibited by either KT5720 (a protein kinase A inhibitor) or BAPTA-AM. In addition, high fat diet (HFD)-induced obesity in mice was significantly recovered by co-treatment with menthol. Dietary menthol enhanced WAT "browning" and improved glucose metabolism in HFD-induced obesity mice as well. Therefore, we concluded that TRPM8 might be involved in WAT "browning" by increasing the expression levels of genes related to thermogenesis and energy metabolism. And dietary menthol could be a novel approach for combating human obesity and related metabolic diseases.
| S-EPMC5650405 | biostudies-other
Project description:BackgroundPhysical cooling of the eye surface relieves ocular discomfort, but translating this event to drug treatment of dry eye discomfort not been studied. Here, we synthesized a water-soluble TRPM8 receptor agonist called cryosim-3 (C3, 1-diisopropylphosphorylnonane) which selectively activates TRPM8 (linked to cooling) but not TRPV1 or TRPA1 (linked to nociception) and tested C3 in subjects with mild forms of dry eye disease.MethodsA set of 1-dialkylphosphoryalkanes were tested for activation of TRPM8, TRPV1 and TRPA1 receptors in transfected cells. The bioactivity profiles were compared by perioral, topical, and intravenous delivery to anesthetized rats. The selected lead candidate C3 or vehicle (water) was applied with a cotton gauze pad to upper eyelids of patients with dry eye disease (n = 30). Cooling sensation, tear film break-up time (TBUT), basal tear secretion, and corneal staining were evaluated. C3 was then applied four times daily for 2 weeks to patients using a pre-loaded single unit applicator containing 2 mg/mL of C3 in water (n = 20) or water only. TBUT, basal tear secretion, and corneal staining, and three questionnaires surveys of ocular discomfort (VAS scale, OSDI, and CVS symptoms) were analyzed before and at 1 and 2 weeks thereafter.ResultsC3 was a selective and potent TRPM8 agonist without TRPV1 or TRPA1 activity. In test animals, the absence of shaking behavior after C3 perioral administration made it the first choice for further study. C3 increased tear secretion in an animal model of dry eye disease and did not irritate when wiped on eyes of volunteers. C3 singly applied (2 mg/ml) produced significant cooling in <5 min, an effecting lasting 46 min with an increase in tear secretion for 60 min. C3 applied for 2 weeks also significantly increased basal tear secretion with questionnaire surveys of ocular discomfort indices clearly showing improvement of symptoms at 1 and 2 weeks. No complaints of irritation or pain were reported by any subject.ConclusionsC3 is a promising candidate for study of TRPM8 function on the eye surface and for relief of dry eye discomfort.Trial registrationISRCTN24802609 and ISRCTN13359367 . Registered 23 March 2015 and 2 September 2015.
| S-EPMC5485613 | biostudies-literature