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transient receptor potential melastatin 8 - Top 30 Publications

Effects of menthol and its interaction with nicotine-conditioned cue on nicotine-seeking behavior in rats.

Increasing clinical evidence suggests that menthol, a significant flavoring additive in tobacco products, may contribute to smoking and nicotine dependence. Relapse to smoking behavior presents a formidable challenge for the treatment of tobacco addiction. An unresolved issue is whether the mentholation of tobacco products precipitates relapse to tobacco use in abstinent smokers.

Novel selective, potent naphthyl TRPM8 antagonists identified through a combined ligand- and structure-based virtual screening approach.

Transient receptor potential melastatin 8 (TRPM8), a nonselective cation channel, is the predominant mammalian cold temperature thermosensor and it is activated by cold temperatures and cooling compounds, such as menthol and icilin. Because of its role in cold allodynia, cold hyperalgesia and painful syndromes TRPM8 antagonists are currently being pursued as potential therapeutic agents for the treatment of pain hypersensitivity. Recently TRPM8 has been found in subsets of bladder sensory nerve fibres, providing an opportunity to understand and treat chronic hypersensitivity. However, most of the known TRPM8 inhibitors lack selectivity, and only three selective compounds have reached clinical trials to date. Here, we applied two virtual screening strategies to find new, clinics suitable, TRPM8 inhibitors. This strategy enabled us to identify naphthyl derivatives as a novel class of potent and selective TRPM8 inhibitors. Further characterization of the pharmacologic properties of the most potent compound identified, compound 1, confirmed that it is a selective, competitive antagonist inhibitor of TRPM8. Compound 1 also proved itself active in a overreactive bladder model in vivo. Thus, the novel naphthyl derivative compound identified here could be optimized for clinical treatment of pain hypersensitivity in bladder disorders but also in different other pathologies.

Synthesis, high-throughput screening and pharmacological characterization of β-lactam derivatives as TRPM8 antagonists.

The mammalian transient receptor potential melastatin channel 8 (TRPM8), highly expressed in trigeminal and dorsal root ganglia, mediates the cooling sensation and plays an important role in the cold hypersensitivity characteristic of some types of neuropathic pain, as well as in cancer. Consequently, the identification of selective and potent ligands for TRPM8 is of great interest. Here, a series of compounds, having a β-lactam central scaffold, were prepared to explore the pharmacophore requirements for TRPM8 modulation. Structure-activity studies indicate that the minimal requirements for potent β-lactam-based TRPM8 blockers are hydrophobic groups (benzyl preferentially or (t) Bu) on R(1), R(2), R(3) and R(5) and a short N-alkyl chain (≤3 carbons). The best compounds in the focused library (41 and 45) showed IC50 values of 46 nM and 83 nM, respectively, in electrophysiology assays. These compounds selectively blocked all modalities of TRPM8 activation, i.e. menthol, voltage, and temperature. Molecular modelling studies using a homology model of TRPM8 identified two putative binding sites, involving networks of hydrophobic interactions, and suggesting a negative allosteric modulation through the stabilization of the closed state. Thus, these β-lactams provide a novel pharmacophore scaffold to evolve TRPM8 allosteric modulators to treat TRPM8 channel dysfunction.

Downregulations of TRPM8 expression and membrane trafficking in dorsal root ganglion mediate the attenuation of cold hyperalgesia in CCI rats induced by GFRα3 knockdown.

Cold hyperalgesia is an intractable sensory abnormality commonly seen in peripheral neuropathies. Although glial cell line-derived neurotrophic factor family receptor alpha3 (GFRα3) is required for the formation of pathological cold pain has been revealed, potential transduction mechanism is poorly elucidated. We have previously demonstrated the contribution of enhanced activity of transient receptor potential melastatin 8 (TRPM8) to cold hyperalgesia in neuropathic pain using a rat model of chronic constriction injury (CCI) to the sciatic nerve. Recently, the enhancement of TRPM8 activity is attributed to the increased TRPM8 plasma membrane trafficking. In addition, TRPM8 can be sensitized by the activation of GFRα3, leading to increased cold responses in vivo. The aim of this study was to investigate whether GFRα3 could influence cold hyperalgesia of CCI rats via modulating TRPM8 expression and plasma membrane trafficking in dorsal root ganglion (DRG).

3-Iodothyronamine, a Novel Endogenous Modulator of Transient Receptor Potential Melastatin 8?

The decarboxylated and deiodinated thyroid hormone (TH) derivative, 3-iodothyronamine (3-T1AM), is suggested to be involved in energy metabolism and thermoregulation. G protein-coupled receptors (GPCRs) are known as the main targets for 3-T1AM; however, transient receptor potential channels (TRPs) were also recently identified as new targets of 3-T1AM. This article reviews the current knowledge of a putative novel role of 3-T1AM in the modulation of TRPs. Specifically, the TRP melastatin 8 (TRPM8) was identified as a target of 3-T1AM in different cell types including neoplastic cells, whereby 3-T1AM significantly increased cytosolic Ca(2+) through TRPM8 activation. Similarly, the β-adrenergic receptor is involved in 3-T1AM-induced Ca(2+) influx. Therefore, it has been suggested that 3-T1AM-induced Ca(2+) mobilization might be due to β-adrenergic receptor/TRPM8 channel interaction, which adds to the complexity of GPCR regulation by TRPs. It has been revealed that TRPM8 activation leads to a decline in TRPV1 activity, which may be of therapeutic benefit in clinical circumstances such as treatment of TRPV1-mediated inflammatory hyperalgesia, colitis, and dry eye syndrome. This review also summarizes the inverse association between changes in TRPM8 and TRPV1 activity after 3-T1AM stimulation. This finding prompted further detailed investigations of the interplay between 3-T1AM and the GPCR/TRPM8 axis and indicated the probability of additional GPCR/TRP constellations that are modulated by this TH derivative.

N-glycosylation of the transient receptor potential melastatin 8 channel is altered in pancreatic cancer cells.

Transient receptor potential melastatin 8 (TRPM8), a membrane ion channel, is activated by thermal and chemical stimuli. In pancreatic ductal adenocarcinoma, TRPM8 is required for cell migration, proliferation, and senescence and is associated with tumor size and pancreatic ductal adenocarcinoma stages. Although the underlying mechanisms of these processes have yet to be described, this cation-permeable channel has been proposed as an oncological target. In this study, the glycosylation status of the TRPM8 channel was shown to affect cell proliferation, cell migration, and calcium uptake. TRPM8 expressed in the membrane of the Panc-1 pancreatic tumoral cell line is non-glycosylated, whereas human embryonic kidney cells transfected with human TRPM8 overexpress a glycosylated protein. Moreover, our data suggest that Ca(2+) uptake is modulated by the glycosylation status of the protein, thus affecting cell proliferation.

Activation of Transient Receptor Potential Melastatin Subtype 8 Attenuates Cold-Induced Hypertension Through Ameliorating Vascular Mitochondrial Dysfunction.

Environmental cold-induced hypertension is common, but how to treat cold-induced hypertension remains an obstacle. Transient receptor potential melastatin subtype 8 (TRPM8) is a mild cold-sensing nonselective cation channel that is activated by menthol. Little is known about the effect of TRPM8 activation by menthol on mitochondrial Ca(2+) homeostasis and the vascular function in cold-induced hypertension.

The identification of the TRPM8 channel on primary culture of human nasal epithelial cells and its response to cooling.

It has been proposed that the transient receptor potential (TRP) channel Melastatin 8 (TRPM8) is a cold-sensing TRP channel. However, its presence and its role in the nasal cavity have not yet been fully studied.

Identification of a Novel TRPM8 Agonist from Nutmeg: A Promising Cooling Compound.

The transient receptor potential melastatin 8 (TRPM8) ion channel is the primary receptor for innocuous cold stimuli (<28 °C) in humans. TRPM8 agonists such as l-(-)-menthol are widely used as flavors and additives to impart briskness, in addition to medicinal uses for inflammation and pain. Though various natural and synthetic agonists have been explored, only few natural compounds are known. We report herein the identification and characterization of the novel neolignan agonist erythro- and threo-Δ(8')-7-ethoxy-4-hydroxy-3,3',5'-trimethoxy-8-O-4'-neolignan (1) with an EC50 of 0.332 μM, which was isolated from a well-known spice, nutmeg (Myristica fragrans Houtt.). Structure activity relationships are also disclosed, showing that the 7-d-menthoxy derivative is the most potent agonist (EC50 = 11 nM). The combination of 1 and l-(-)-menthol has an additive effect, suggesting that neolignan compounds interact with TRPM8 at different sites from those of l-(-)-menthol.

Mechanisms of the analgesic effect of calcitonin on chronic pain by alteration of receptor or channel expression.

The polypeptide hormone calcitonin is well known clinically for its ability to relieve osteoporotic back pain and neuropathic pain such as spinal canal stenosis, diabetic neuropathy, chemotherapy-induced neuropathy, and complex regional pain syndrome. Because the analgesic effects of calcitonin have a broad range, the underlying mechanisms of pain relief by calcitonin are largely unknown. However, recent studies using several types of chronic pain models combined with various methods have been gradually clarifying the mechanism. Here, we review the mechanisms of the analgesic action of calcitonin on ovariectomy-induced osteoporotic and neuropathic pain. The analgesic action of calcitonin may be mediated by restoration of serotonin receptors that control selective glutamate release from C-afferent fibers in ovariectomized rats and by normalization of sodium channel expression in damaged peripheral nerves. Serotonin receptors are reduced or eliminated by the relatively rapid reduction in estrogen during the postmenopausal period, and damaged nerves exhibit hyperexcitability due to abnormal expression of Na(+) channel subtypes. In addition, in chemotherapy-induced peripheral neuropathy, inhibition of signals related to transient receptor potential ankyrin-1 and melastatin-8 is proposed to participate in the anti-allodynic action of calcitonin. Further, an unknown calcitonin-dependent signal appears to be present in peripheral nervous tissues and may be activated by nerve injury, resulting in regulation of the excitability of primary afferents by control of sodium channel transcription in dorsal root ganglion neurons. The calcitonin signal in normal conditions may be non-functional because no target is present, and ovariectomy or nerve injury may induce a target. Moreover, it has been reported that calcitonin reduces serotonin transporter but increases serotonin receptor expression in the thalamus in ovariectomized rats. These data suggest that calcitonin could alleviate lower back pain in patients with osteoporosis or neuropathic pain by the alteration in receptor or channel expression.

Roles of Transient Receptor Potential Ankyrin 1 in Oxaliplatin-Induced Peripheral Neuropathy.

Chemotherapy-induced peripheral neuropathy (CIPN), characterized by symptoms of paresthesia, dysesthesia, numbness, and pain, is a common adverse effect of several chemotherapeutic agents, including platinum-based agents, taxanes, and vinca alkaloids. However, no effective prevention or treatment strategies exist for CIPN because the mechanisms underpinning this neuropathy are poorly understood. Recent accumulating evidence suggests that some transient receptor potential (TRP) channels functioning as nociceptors in primary sensory neurons are responsible for CIPN. In this review, we focus on the specific roles of redox-sensitive TRP ankyrin 1 (TRPA1), which was first reported to be a cold nociceptor, in acute cold hypersensitivity induced by oxaliplatin, a platinum-based agent, because it induces a peculiar cold-triggered CIPN during or within hours after its infusion. Oxaliplatin-induced rapid-onset cold hypersensitivity is ameliorated by TRPA1 blockade or deficiency in mice. Consistent with this, oxaliplatin enhances the responsiveness of TRPA1 stimulation, but not of TRP melastatin 8 (TRPM8) and TRP vanilloid 1 (TRPV1), in mice and cultured mouse dorsal root ganglion neurons. These responses are mimicked by an oxaliplatin metabolite, oxalate. In human TRPA1 (hTRPA1)-expressing cells, oxaliplatin or oxalate causes TRPA1 sensitization to reactive oxygen species (ROS) by inhibiting prolyl hydroxylases (PHDs). Inhibition of PHD-mediated hydroxylation of a proline residue within the N-terminal ankyrin repeat of hTRPA1 endows TRPA1 with cold sensitivity by its sensing of cold-evoked ROS. This review discusses these findings and summarizes the evidence demonstrating that oxaliplatin-induced acute cold hypersensitivity is caused by TRPA1 sensitization to ROS via PHD inhibition, which enables TRPA1 to convert ROS signaling into cold sensitivity.

Cough and airway disease: The role of ion channels.

Cough is the most common reason for patients to visit a primary care physician, yet it remains an unmet medical need. It can be idiopathic in nature but can also be a troublesome symptom across chronic lung diseases such as asthma, COPD and idiopathic pulmonary fibrosis (IPF). Chronic cough affects up to 12% of the population and yet there are no safe and effective therapies. The cough reflex is regulated by vagal, sensory afferent nerves which innervate the airway. The Transient Receptor Potential (TRP) family of ion channels are expressed on sensory nerve terminals, and when activated can evoke cough. This review focuses on the role of 4 TRP channels; TRP Vannilloid 1 (TRPV1), TRP Ankyrin 1 (TRPA1), TRP Vannilloid 4 (TRPV4) and TRP Melastatin 8 (TRPM8) and the purinergic P2X3 receptor and their possible role in chronic cough. We conclude that these ion channels, given their expression profile and their role in the activation of sensory afferents and the cough reflex, may represent excellent therapeutic targets for the treatment of respiratory symptoms in chronic lung disease.

Lidocaine suppresses glioma cell proliferation by inhibiting TRPM7 channels.

Malignant glioma is the most common brain cancer with devastating prognosis. Recurrence of malignant glioma following surgery is very common with few preventive and therapeutic options. Novel targets and therapeutic agents are constantly sought for better outcome. Our previous study established that inhibition of transient receptor potential melastatin 7 (TRPM7) channels resulted in significant decrease of human glioma cell growth and proliferation. As local anesthetic lidocaine has been shown to inhibit TRPM7 currents, we hypothesize that lidocaine may suppress glioma cell proliferation through TRPM7 channel inhibition.

Inflammatory Effects of Menthol vs. Non-menthol Cigarette Smoke Extract on Human Lung Epithelial Cells: A Double-Hit on TRPM8 by Reactive Oxygen Species and Menthol.

Clinical studies suggest that smokers with chronic obstructive pulmonary disease who use menthol cigarettes may display more severe lung inflammation than those who smoke non-menthol cigarette. However, the mechanisms for this difference remain unclear. Menthol is a ligand of transient receptor potential melastatin-8 (TRPM8), a Ca(2+)-permeant channel sensitive to reactive oxygen species (ROS). We previously reported that exposure of human bronchial epithelial cells (HBECs) to non-menthol cigarette smoke extract (Non-M-CSE) triggers a cascade of inflammatory signaling leading to IL-8 induction. In this study, we used this in vitro model to compare the inflammatory effects of menthol cigarette smoke extract (M-CSE) and Non-M-CSE and delineate the mechanisms underlying the differences in their impacts. Compared with Non-M-CSE, M-CSE initially increased a similar level of extracellular ROS, suggesting the equivalent oxidant potency. However, M-CSE subsequently produced more remarkable elevations in intracellular Ca(2+), activation of the mitogen-activated protein kinases (MAPKs)/nuclear factor-κB (NF-κB) signaling, and IL-8 induction. The extracellular ROS responses to both CSE types were totally inhibited by N-acetyl-cysteine (NAC; a ROS scavenger). The intracellular Ca(2+) responses to both CSE types were also totally prevented by NAC, AMTB (a TRPM8 antagonist), or EGTA (an extracellular Ca(2+) chelator). The activation of the MAPK/NF-κB signaling and induction of IL-8 to both CSE types were suppressed to similar levels by NAC, AMTB, or EGTA. These results suggest that, in addition to ROS generated by both CSE types, the menthol in M-CSE may act as another stimulus to further activate TRPM8 and induce the observed responses. We also found that menthol combined with Non-M-CSE induced greater responses of intracellular Ca(2+) and IL-8 compared with Non-M-CSE alone. Moreover, we confirmed the essential role of TRPM8 in these responses to Non-M-CSE or M-CSE and the difference in these responses between the both CSE types using HBECs with TRPM8 knockdown and TRPM8 knockout, and using HEK293 cells transfected with hTRPM8. Thus, compared with exposure to Non-M-CSE, exposure to M-CSE induced greater TRPM8-mediated inflammatory responses in HBECs. These augmented effects may be due to a double-hit on lung epithelial TRPM8 by ROS generated from CSE and the menthol in M-CSE.

TRP channels in brown and white adipogenesis from human progenitors: new therapeutic targets and the caveats associated with the common antibiotic, streptomycin.

Transient receptor potential (TRP) channels are polymodal cell sensors responding to diverse stimuli and widely implicated in the developmental programs of numerous tissues. The evidence for an involvement of TRP family members in adipogenesis, however, is scant. We present the first comprehensive expression profile of all known 27 human TRP genes in mesenchymal progenitors cells during white or brown adipogenesis. Using positive trilineage differentiation as an exclusion criterion, TRP polycystic (P)3, and TPR melastatin (M)8 were found to be uniquely adipospecific. Knockdown of TRPP3 repressed the expression of the brown fat signature genes uncoupling protein (UCP)-1 and peroxisome proliferator-activated receptor γ coactivator (PGC)-1α as well as attenuated forskolin-stimulated uncoupled respiration. However, indices of generalized adipogenesis, such as lipid droplet morphology and fatty acid binding protein (FAPB)-4 expression, were not affected, indicating a principal mitochondrial role of TRPP3. Conversely, activating TRPM8 with menthol up-regulated UCP-1 expression and augmented uncoupled respiration predominantly in white adipocytes (browning), whereas streptomycin antagonized TRPM8-mediated calcium entry, downregulated UCP-1 expression, and mitigated uncoupled respiration; menthol was less capable of augmenting uncoupled respiration (thermogenesis) in brown adipocytes. TRPP3 and TRPM8 hence appear to be involved in the priming of mitochondria to perform uncoupled respiration downstream of adenylate cyclase. Our results also underscore the developmental caveats of using antibiotics in adipogenic studies.-Goralczyk, A., van Vijven, M., Koch, M., Badowski, C., Yassin, M. S., Toh, S.-A., Shabbir, A., Franco-Obregón, A., Raghunath, M. TRP channels in brown and white adipogenesis from human progenitors: new therapeutic targets and the caveats associated with the common antibiotic, streptomycin.

Vagus nerve is involved in the changes in body temperature induced by intragastric administration of 1,8-cineole via TRPM8 in mice.

Transient Receptor Potential Melastatin 8 (TRPM8) is a cold receptor activated by mild cold temperature (<28°C). TRPM8 expressed in cutaneous sensory nerves is involved in cold sensation and thermoregulation. TRPM8 mRNA is detected in various tissues, including the gastrointestinal mucosa, and in the vagal afferent nerve. The relationship between vagal afferent nerve-specific expression of TRPM8 and thermoregulation remains unclear. In this study, we aimed to investigate whether TRPM8 expression in the vagal afferent nerve is involved in autonomic thermoregulation. We found that intragastric administration of 1,8-cineole, a TRPM8 agonist, increased intrascapular brown adipose tissue and colonic temperatures, and M8-B-treatment (TRPM8 antagonist) inhibited these responses. Intravenous administration of 1,8-cineole also showed similar effects. In vagotomized mice, the responses induced by intragastric administration of 1,8-cineole were attenuated. These results suggest that TRPM8 expressed in tissues apart from cutaneous sensory nerves are involved in autonomic thermoregulation response.

Cutaneous Penetration-Enhancing Effect of Menthol: Calcium Involvement.

Menthol is a naturally occurring terpene used as a penetration enhancer in topical and transdermal formulations. Literature shows a growing interest in menthol's interactions with the transient receptor potential melastatin 8. A decrease in extracellular Ca(2+) due to the activation of the transient receptor potential melastatin 8 receptor produces inhibition of E-cadherin expression that is responsible for cell-cell adhesion. Because calcium is present in the entire epidermis, the purpose of this study is to evaluate whether the aforementioned properties of menthol are also related to its penetration-enhancing effects. We formulated 16 gels: (i) drug-alone (diphenhydramine or lidocaine), (ii) drug with menthol, (iii) drug, menthol, and calcium channel blocker (CCB; verapamil or diltiazem), and (iv) drug and CCB. In vitro studies showed no effect of the CCB on the release of the drugs either with or without menthol. In vivo experiments were performed for each drug/menthol/CCB combination gel by applying 4 formulations on a shaved rabbit's dorsum on the same day. Dermis concentration profiles were assessed with microdialysis. The gels containing menthol showed higher penetration of drugs than those without whereas the addition of the CCB consistently inhibited the penetration-enhancing effects of menthol. In summary, these findings strongly support the involvement of calcium in the penetration-enhancing effect of menthol.

TRPM7 channels mediate the functional changes in cardiac fibroblasts induced by angiotensin II.

Transient receptor potential melastatin 7 (TRPM7), a bifunctional channel protein owning both cation permeability and kinase activity, plays an important role in the pathophysiological process of many cell types, such as vascular smooth muscle cells, human glioma cells and mouse cortical astrocytes. However, whether TRPM7 channels play a key role in the functional change of cardiac fibroblasts (CFs) induced by angiotensin II (Ang II) remains unknown. Using Cell Counting Kit-8 (CCK-8) assay, immunofluorescence assay, western blot analysis, RT-qPCR, RNA interference (RNAi) and whole-cell patch-clamp techniques, the present study aimed to explore the role of TRPM7 channels in the proliferation, differentiation and collagen synthesis of CFs induced by Ang II. Our data showed that Ang II time-dependently increased TRPM7 expression and TRPM7 currents in the CFs. Downregulation of TRPM7 attenuated the TRPM7 current density, and inhibited the proliferation, differentiation and collagen synthesis of CFs induced by Ang II. Our results identified the TRPM7 channel as a pivotal member associated with the functional change of CFs induced by Ang II, and suggest that the TRPM7 channel may represent a promising therapeutic strategy for the treatment of fibrosis-related cardiac diseases.

Cutaneous TRPM8-expressing sensory afferents are a small population of neurons with unique firing properties.

It has been well documented that the transient receptor potential melastatin 8 (TRPM8) receptor is involved in environmental cold detection. The role that this receptor plays in nociception however, has been somewhat controversial since conflicting reports have shown different neurochemical identities and responsiveness of TRPM8 neurons. In order to functionally characterize cutaneous TRMP8 fibers, we used two ex vivo somatosensory recording preparations to functionally characterize TRPM8 neurons that innervate the hairy skin in mice genetically engineered to express GFP from the TRPM8 locus. We found several types of cold-sensitive neurons that innervate the hairy skin of the mouse but the TRPM8-expressing neurons were found to be of two specific populations that responded with rapid firing to cool temperatures. The first group was mechanically insensitive but the other did respond to high threshold mechanical deformation of the skin. None of these fibers were found to contain calcitonin gene-related peptide, transient receptor potential vanilloid type 1 or bind isolectin B4. These results taken together with other reports suggest that TRPM8 containing sensory neurons are environmental cooling detectors that may be nociceptive or non-nociceptive depending on the sensitivity of individual fibers to different combinations of stimulus modalities.

Development of TRPM8 Antagonists to Treat Chronic Pain and Migraine.

A review. Development of pharmaceutical antagonists of transient receptor potential melastatin 8 (TRPM8) have been pursued for the treatment of chronic pain and migraine. This review focuses on the current state of this progress.

TRPM8 in the negative regulation of TNFα expression during cold stress.

Transient Receptor Potential Melastatin-8 (TRPM8) reportedly plays a fundamental role in a variety of processes including cold sensation, thermoregulation, pain transduction and tumorigenesis. However, the role of TRPM8 in inflammation under cold conditions is not well known. Since cooling allows the convergence of primary injury and injury-induced inflammation, we hypothesized that the mechanism of the protective effects of cooling might be related to TRPM8. We therefore investigated the involvement of TRPM8 activation in the regulation of inflammatory cytokines. The results showed that TRPM8 expression in the mouse hypothalamus was upregulated when the ambient temperature decreased; simultaneously, tumor necrosis factor-alpha (TNFα) was downregulated. The inhibitory effect of TRPM8 on TNFα was mediated by nuclear factor kappa B (NFκB). Specifically, cold stress stimulated the expression of TRPM8, which promoted the interaction of TRPM8 and NFκB, thereby suppressing NFκB nuclear localization. This suppression consequently led to the inhibition of TNFα gene transcription. The present data suggest a possible theoretical foundation for the anti-inflammatory role of TRPM8 activation, providing an experimental basis that could contribute to the advancement of cooling therapy for trauma patients.

Toluene diisocyanate exposure induces airway inflammation of bronchial epithelial cells via the activation of transient receptor potential melastatin 8.

Toluene diisocyanate (TDI) is the most important cause of occupational asthma (OA), and various pathogenic mechanisms have been suggested. Of these mechanisms, neurogenic inflammation is an important inducer of airway inflammation. Transient receptor potential melastatin 8 (TRPM8) is a well-established cold-sensing cation channel that is expressed in both neuronal cells and bronchial epithelial cells. A recent genome-wide association study of TDI-exposed workers found a significant association between the phenotype of TDI-induced OA and the single-nucleotide polymorphism rs10803666, which has been mapped to the TRPM8 gene. We hypothesized that TRPM8 located in airway epithelial cells may be involved in the pathogenic mechanisms of TDI-induced OA and investigated its role. Bronchial epithelial cells were treated with TDI in a dose- and time-dependent manner. The expression levels of TRPM8 mRNA and protein were determined by quantitative real-time polymerase chain reaction and western blotting. TDI-induced morphological changes in the cells were evaluated by immunocytochemistry. Alterations in the transcripts of inflammatory cytokines were examined in accordance with TRPM8 activation by TDI. TRPM8 expression at both the mRNA and protein levels was enhanced by TDI in airway epithelial cells. TRPM8 activation by TDI led to significant increases in the mRNA of interleukin (IL)-4, IL-13, IL-25 and IL-33. The increased expression of the cytokine genes by TDI was partly attenuated after treatment with a TRPM8 antagonist. TDI exposure induces increased expression of TRPM8 mRNA in airway epithelial cells coupled with enhanced expression of inflammatory cytokines, suggesting a novel role of TRPM8 in the pathogenesis of TDI-induced OA.

Malignant infarction of the middle cerebral artery in a porcine model. A pilot study.

Interspecies variability and poor clinical translation from rodent studies indicate that large gyrencephalic animal stroke models are urgently needed. We present a proof-of-principle study describing an alternative animal model of malignant infarction of the middle cerebral artery (MCA) in the common pig and illustrate some of its potential applications. We report on metabolic patterns, ionic profile, brain partial pressure of oxygen (PtiO2), expression of sulfonylurea receptor 1 (SUR1), and the transient receptor potential melastatin 4 (TRPM4).

4-isopropylcyclohexanol has potential analgesic effects through the inhibition of anoctamin 1, TRPV1 and TRPA1 channel activities.

Interactions between calcium-activated chloride channel anoctamin 1 (ANO1) and transient receptor potential vanilloid 1 (TRPV1) enhance pain sensations in mice, suggesting that ANO1 inhibition could have analgesic effects. Here we show that menthol and the menthol analogue isopropylcyclohexane (iPr-CyH) inhibited ANO1 channels in mice. The iPr-CyH derivative 4-isopropylcyclohexanol (4-iPr-CyH-OH) inhibited mouse ANO1 currents more potently than iPr-CyH. Moreover, 4-iPr-CyH-OH inhibited the activities of TRPV1, TRP ankyrin 1 (TRPA1), TRP melastatin 8 (TRPM8) and TRPV4. Single-channel analysis revealed that 4-iPr-CyH-OH reduced TRPV1 and TRPA1 current open-times without affecting unitary amplitude or closed-time, suggesting that it affected gating rather than blocking the channel pore. The ability of 4-iPr-CyH-OH to inhibit action potential generation and reduce pain-related behaviors induced by capsaicin in mice suggests that 4-iPr-CyH-OH could have analgesic applications. Thus, 4-iPr-CyH-OH is a promising base chemical to develop novel analgesics that target ANO1 and TRP channels.

TRPM8 downregulation by angiotensin II in vascular smooth muscle cells is involved in hypertension.

Angiotensin II (Ang II)-induced injury of vascular smooth muscle cells (VSMCs) serves an important role in hypertension and other cardiovascular disorders. Transient receptor potential melastatin 8 (TRPM8) is a thermally‑regulated Ca2+‑permeable channel that is activated by reduced body temperature. Although several recent studies have revealed the regulatory effect of TRPM8 in vascular tone and hypertension, the precise role of TRPM8 in dysfunction of vascular smooth muscle cells (VSMCs) induced by Ang II remains elusive. In the present study, the possible function of TRPM8 in Ang II‑induced VSMCs malfunction in vivo and in vitro was investigated. In the aortae from rats that had undergone a two‑kidney one‑clip operation, which is a widely‑used renovascular hypertension model, the mRNA and protein levels of TRPM8 were reduced. In addition, exogenous Ang II treatment decreased TRPM8 mRNA and protein expression levels in primary cultures of rat VSMCs. TRPM8 activation by menthol, a pharmacological agonist, in VSMCs, significantly attenuated the Ang II‑induced increase in reactive oxygen species and H2O2 production. In addition, TRPM8 activation reduced the Ang II‑induced upregulation of NADPH oxidase (NOX) 1 and NOX4 in VSMCs. Furthermore, TRPM8 activation relieved the Ang II‑induced activation of ras homolog gene family, member A‑rho associated protein kinase 2 and janus kinase 2 signaling pathways in VSMCs. In conclusion, the results presented in the current study indicated that TRPM8 downregulation by Ang II in VSMCs may be involved in hypertension.

Shakuyakukanzoto attenuates oxaliplatin-induced cold dysesthesia by inhibiting the expression of transient receptor potential melastatin 8 in mice.

Oxaliplatin-induced peripheral neuropathy characterized especially as cold dysesthesia is a major dose-limiting side effect of the drug and is very difficult to control. In the present study, we examined whether the traditional herbal formulation Shakuyakukanzoto (SKT: Sháo Yào Gān Cǎo Tāng) could relieve oxaliplatin-induced cold dysesthesia in mice. The inhibitory mechanisms were also investigated. Repetitive administration of SKT (0.1-1.0 g/kg) starting from the day after oxaliplatin injection inhibited cold dysesthesia in a dose-dependent manner. Our previous report has shown that the mRNA expression of transient receptor potential melastatin 8 (TRPM8), characterized as a cold-sensing cation channel, is increased in the dorsal root ganglia of mice treated with oxaliplatin. In addition, TRPM8 antagonist TC-I 2014 (10 and 30 mg/kg) also attenuated cold dysesthesia in oxaliplatin-treated mice. Taken together, it is suggested that TRPM8 is involved in the cold dysesthesia induced by oxaliplatin. Repetitive administration of SKT inhibited the mRNA expression of TRPM8 induced by oxaliplatin in the dorsal root ganglia. These results suggested that prophylactic repetitive administration of SKT is effective in preventing the exacerbation of oxaliplatin-induced cold dysesthesia by inhibiting the mRNA expression of TRPM8 in the dorsal root ganglia.

Transient receptor potential melastatin (TRPM) 8 is expressed in freshly isolated native human odontoblasts.

Cold-sensitive ion channels, such as transient receptor potential melastatin (TRPM) 8 and transient receptor potential ankyrin (TRPA) 1, may play a crucial role in the nociceptive function of odontoblasts, whereas expression of these TRP channels in human native odontoblasts remains to be elucidated. This study aimed to analyze the expression of TRPM8 and TRPA1 in freshly isolated native human odontoblasts.

High-throughput proteome analysis reveals targeted TRPM8 degradation in prostate cancer.

The Ca2+-permeable ion channel TRPM8 is a hallmark of the prostate epithelium. We recently discovered that TRPM8 is an ionotropic testosterone receptor. This finding suggested that testosterone-induced TRPM8 activity regulates Ca2+ homeostasis in the prostate epithelium. Since androgens are significantly implicated in prostate cancer development, the role of the novel testosterone receptor TRPM8 in cancer was assessed in our study. Although TRPM8 mRNA levels increase at the early prostate cancer stages, we found that it is not proportionally translated into TRPM8 protein levels. High-throughput proteome analysis revealed that TRPM8 degradation is enhanced in human prostate cancer cells. This degradation is executed via a dual degradation mechanism with the involvement of both lysosomal and proteasomal proteolytic pathways. The evaluation of the TRPM8 expression pattern in prostate cancer patients further confirmed the incidence of TRPM8 removal from the plasma membrane and its internalization pattern coincided with the severity of the tumor. Together, our results indicate that enhanced TRPM8 hydrolysis in prostate cancer could present an adaptation mechanism, sustained via bypassing testosterone-induced rapid Ca2+ uptake through TRPM8, thus, diminishing the rates of apoptosis. In this light, recovery of TRPM8 may pose a novel therapeutic strategy for an anti-tumor defense mechanism.

Presynaptic facilitation by tetracaine of glutamatergic spontaneous excitatory transmission in the rat spinal substantia gelatinosa - Involvement of TRPA1 channels.

The amide-type local anesthetic (LA) lidocaine activates transient receptor potential (TRP) ankyrin-1 (TRPA1) channels to facilitate spontaneous l-glutamate release onto spinal substantia gelatinosa (SG) neurons, which play a crucial role in regulating nociceptive transmission. In contrast, the ester-type LA procaine reduces the spontaneous release of l-glutamate in SG neurons. In order to determine whether TRPA1 activation by LAs is specific to amide-types, we examined the actions of tetracaine, another ester-type LA, and other amide-type LAs on glutamatergic spontaneous excitatory transmission in SG neurons by focusing on TRP activation. Whole-cell patch-clamp recordings were performed on SG neurons of adult rat spinal cord slices at a holding potential of -70mV. Bath-applied tetracaine increased spontaneous excitatory postsynaptic current (sEPSC) frequency in a concentration-dependent manner. Tetracaine activity was resistant to the voltage-gated Na(+)-channel blocker tetrodotoxin, the TRP vanilloid-1 antagonist capsazepine, and the TRP melastatin-8 antagonist BCTC, but was inhibited by the non-selective TRP antagonist ruthenium red and the TRPA1 antagonist HC-030031. With respect to amide-type LAs, prilocaine had a tendency to increase sEPSC frequency, while ropivacaine and levobupivacaine reduced the frequency. In conclusion, tetracaine facilitated spontaneous l-glutamate release from nerve terminals by activating TRPA1 channels in the SG, resulting in an increase in the excitability of SG neurons. TRPA1 activation was not specific to amide-type or ester-type LAs. The facilitatory action of LAs may be involved in pain occurring after recovery from spinal anesthesia.

Synthesis and optimization of novel α-phenylglycinamides as selective TRPM8 antagonists.

Transient receptor potential melastatin 8 (TRPM8) is activated by innocuous cold and chemical substances, and antagonists of this channel have been considered to be effective for pain and urinary diseases. N-(3-aminopropyl)-2-{[(3-methylphenyl)methyl]oxy}-N-(2-thienylmethyl)benzamide hydrochloride (AMTB), a TRPM8 antagonist, was proposed to be effective for overactive bladder and painful bladder syndrome; however, there is a potential risk of low blood pressure. We report herein the synthesis and structure-activity relationships of novel phenylglycine derivatives that led to the identification of KPR-2579 (20l), a TRPM8 selective antagonist. KPR-2579 reduced the number of icilin-induced wet-dog shakes and rhythmic bladder contraction in rats, with no negative cardiovascular effects at the effective dose.