TRPM8 Channels Research Articles

CTNI-79. ASSESSING SYSTEMIC AND LOCAL LEVELS OF LIDOCAINE DURING SURGERY FOR GLIOBLASTOMA

Abstract The objective of this study is to assess the pharmacokinetics of lidocaine penetration into tumor tissue during glioblastoma surgery. In-vitro studies of glioblastoma have demonstrated co-culture with lidocaine inhibits glioblastoma proliferation via inhibition of TRPM7 channels. TRPM7 is a transmembrane ion channel that modulates proliferation and migration in several human cancers. Scalp block with lidocaine during glioblastoma surgery has been associated with improved survival in human studies. Twelve patients were enrolled in this study. The study group received an intravenous bolus dose of 1.5 mg/kg IBW of lidocaine at induction of anesthesia followed by 2 mg/kg IBW/hr infusion of lidocaine. Craniotomy was performed in the standard fashion. A total of 3 fresh tumor specimens were collected hourly from each patient after confirmation of glioblastoma diagnosis by frozen section. Plasma samples were simultaneously collected for analysis. Lidocaine concentration was measured using mass spectroscopy. The maximum concentration of lidocaine (Cmax), time from bolus to maximum concentration (Tmax), and area under curve from 0-3 hours (AUC) were calculated for each patient. Patients were followed for survival and adverse events. The median tumor specimen Cmax, Tmax, and AUC values were 333 ng/dL (range 226-555), 179 min (range 126-211), and 20665 ng*min/dL (range 8003-55,426), respectively. Peak lidocaine concentration was reached in 6 of 12 cases. Median Cmax and Tmax for plasma samples were 1195 ng/dL (range 951-1475) and 191 min (range 156-211), respectively. Median overall survival was 308 days (range 74-413). Two grade 3 adverse events occurred which were deemed to be unlikely to be related to the study intervention. In conclusion, lidocaine infiltrates tumor tissue when administered intravenously during glioblastoma surgery. Concentrations do not reach levels previously demonstrated to inhibit tumor growth in in vitro studies (roughly 2*108 ng/dL lidocaine). Alternative mechanisms may explain previously observed improved outcomes with lidocaine administration in human studies.

TRPM8 channels, cold and headache: data of experimental and clinical studies

Abstract – Different types of headaches, including migraine, may have a causal relationship with cold exposure, and this relationship can be either positive or negative, i.e. cold can both provoke and alleviate cephalalgia. Various representatives of the transient receptor potential ion channel superfamily, in particular TRPM8, act as molecular thermoreceptors that provide signal transduction in the response to low temperatures. These channels, which are known to mediate the normal cold sensation and play a role in both cold-induced pain and cryoanalgesia, are often considered as a promising target for the development of principally new anti-migraine drugs. This review summarizes recently obtained data on the TRPM8 structure and function, and their role in the pathogenesis of migraine, as well as discusses the intriguingly inconsistent results of studying TRPM8 agonists and antagonists in experimental headache models and clinical trials. Analyzing data from various studies allows to conclude that TRPM8 activation can be both pro- and antinociceptive; this correlates with the reported dual effect of cold exposure on the induction and resolution of headaches, leaving open the question on the vector of the TRPM8 pharmacological modulation required to produce anticephalgic effect.

Conservation of the cooling agent binding pocket within the TRPM subfamily.

Transient receptor potential (TRP) channels are a large and diverse family of tetrameric cation-selective channels that are activated by many different types of stimuli, including noxious heat or cold, organic ligands such as vanilloids or cooling agents, or intracellular Ca2+. Structures available for all subtypes of TRP channels reveal that the transmembrane domains are closely related despite their unique sensitivity to activating stimuli. Here, we use computational and electrophysiological approaches to explore the conservation of the cooling agent binding pocket identified within the S1-S4 domain of the Melastatin subfamily member TRPM8, the mammalian sensor of noxious cold, with other TRPM channel subtypes. We find that a subset of TRPM channels, including TRPM2, TRPM4, and TRPM5, contain pockets very similar to the cooling agent binding pocket in TRPM8. We then show how the cooling agent icilin modulates activation of mouse TRPM4 to intracellular Ca2+, enhancing the sensitivity of the channel to Ca2+ and diminishing outward-rectification to promote opening at negative voltages. Mutations known to promote or diminish activation of TRPM8 by cooling agents similarly alter activation of TRPM4 by icilin, suggesting that icilin binds to the cooling agent binding pocket to promote opening of the channel. These findings demonstrate that TRPM4 and TRPM8 channels share related ligand binding pockets that are allosterically coupled to opening of the pore.

Expression Profiling Identified TRPM7 and HER2 as Potential Targets for the Combined Treatment of Cancer Cells.

TRPM7 is a divalent cation-permeable channel that is highly active in cancer cells. The pharmacological inhibitors of TRPM7 have been shown to suppress the proliferation of tumor cells, highlighting TRPM7 as a new anticancer drug target. However, the potential benefit of combining TRPM7 inhibitors with conventional anticancer therapies remains unexplored. Here, we used genome-wide transcriptome profiling of human leukemia HAP1 cells to examine cellular responses caused by the application of NS8593, the potent inhibitor of the TRPM7 channel, in comparison with two independent knockout mutations in the TRPM7 gene introduced by the CRISPR/Cas9 approach. This analysis revealed that TRPM7 regulates the expression levels of several transcripts, including HER2 (ERBB2). Consequently, we examined the TRPM7/HER2 axis in several non-hematopoietic cells to show that TRPM7 affects the expression of HER2 protein in a Zn2+-dependent fashion. Moreover, we found that co-administration of pharmacological inhibitors of HER2 and TRPM7 elicited a synergistic antiproliferative effect on HER2-overexpressing SKBR3 cells but not on HER2-deficient MDA-MB-231 breast cancer cells. Hence, our study proposes a new combinatorial strategy for treating HER2-positive breast cancer cells.

Genetics of Exertional Heat Illness: Revealing New Associations and Expanding Heterogeneity

Environmental heat stress represents a pervasive threat to warfighters, athletes, and occupational workers, impacting performance and increasing the risk of injury. Exertional heat illness (EHI) is a spectrum of clinical disorders of increasing severity. While frequently predictable, EHI can occur unexpectedly and may be followed by long-term comorbidities, including cardiovascular dysfunction and exercise intolerance. The objective of this study was to assess genetic factors contributing to EHI. Whole-exome sequencing was performed in a cohort of 53 cases diagnosed with EHI. Rare variants in prioritized gene sets were analyzed and classified per published guidelines. Clinically significant pathogenic and potentially pathogenic variants were identified in 30.2% of the study cohort. Variants were found in 14 genes, including the previously known RYR1 and ACADVL genes and 12 other genes (CAPN3, MYH7, PFKM, RYR2, TRPM4, and genes for mitochondrial disorders) reported here for the first time in EHI. Supporting structural and functional studies of the TRPM4 p.Arg905Trp variant show that it impairs the thermal sensitivity of the TRPM4 channel, revealing a potentially new molecular mechanism contributing to EHI susceptibility. Our study demonstrates associations between EHI and genes implicated in muscle disorders, cardiomyopathies, thermoregulation, and oxidative phosphorylation deficiencies. These results expand the genetic heterogeneity of EHI and shed light on its molecular pathogenesis.

Effects of vitamin E on calcium signaling and oxidative injury in neutrophils of patients with ischemia/reperfusion (surgical arthroscopy) under sevoflurane anesthesia

Sevoflurane is an anesthetic, and it acts on oxidative activity by activating Ca2+ influx. In human neutrophils, oxidative stress activates the voltage-gated calcium channels (VGCC) and the TRPM2 channel; on the other hand, these channels are inhibited by 2-aminoethoxydiphenyl borate (2-APB) and verapamil plus diltiazem (V+D), respectively. Under sevoflurane anesthesia, surgical arthroscopy poses a significant risk to oxidative stress and Ca2+ influx-induced neutrophil infiltration and injury of patients. However, vitamin E may inhibit lipid peroxidation (LP) by upregulating reduced glutathione (GSH) and glutathione peroxidase (GSH-Px) but downregulating TRPM2 and VGCC in the neutrophils of surgical arthroscopy patients. This topic was examined in the current study. We enrolled 20 patients in the current study, separating them into two primary groups: patients and patients plus vitamin E. Ten patients were divided into two groups: preoperative (N1) and postoperative (N2), both of which were not given vitamin E therapy. The remaining ten patients were given 300 IU of vitamin E two hours prior to their surgical arthroscopy (E1), and their blood was again drawn following the procedure (E2). Prior to fMLP stimulation, the isolated neutrophils from each of the four groups were cultured with 10 uM V+D and 100 uM 2-APB. In the neutrophils, there was an increase in intracellular free Ca2+ ([Ca2+]i) concentration and LP levels due to the downregulation of GSH and GSH-Px; however, following vitamin E treatment, GSH concertation and GSH-Px activity increased in the E2 group. While 2-APB and V+D treatment reduced the concentration of [Ca2+]i in the neutrophils, vitamin E administration had no effect on this measurement. In summary, vitamin E treatment mitigated the GSH and GSH-Px alterations induced by I/R damage, while TRPM2 and VGCC inhibition reduced the [Ca2+]i rise induced by I/R injury. One potential treatment approach for I/R-induced oxidative neutrophil damage is the suppression of TRPM2 and VGCC.

Immunohistochemical examination of immunoreactivity of transient receptor potential melastatin 2, glutathione peroxidase 4 and spexin in lichen planus.

In this study, we aimed to investigate the potential contributions to the disease by examining the immunoreactivities of SPX in LP-affected skin tissue using immunohistochemical methods, in light of its recent prominence as a molecule related to diabetes mellitus, along with apoptosis and ferroptosis mediated by GPX4 and TRPM2 channels facilitating oxidative stress-induced cell death. This research explored the immunohistochemical expressions of TRPM2, GPX4, and SPX in Lichen Planus (LP) patients compared to healthy individuals. Forty skin samples were collected, split equally between LP patients and healthy controls, excluding those with other conditions. Samples underwent immunohistochemical staining for TRPM2, SPX, and GPX4, using secondary antibodies and chromogens AEC or DAB. Histoscores were calculated based on staining diffusiveness and severity. Statistical analyses were performed with SPSS 22.0, using t-tests and ANOVA, with significance set at p < 0.05. There were no demographic differences between groups (p > 0.05). LP patients showed significantly lower TRPM2 and GPX4 histoscores and higher SPX histoscores compared to controls (TRPM2 and GPX4: p < 0.001, SPX: p < 0.001). Gender and age did not affect histoscores significantly. Findings suggest TRPM2, GPX4, and SPX play roles in LP pathogenesis, indicating a need for further molecular studies to clarify their involvement. This contributes to understanding LP beyond the traditional apoptosis perspective.

Humulus lupulus L.: Evaluation of Phytochemical Profile and Activation of Bitter Taste Receptors to Regulate Appetite and Satiety in Intestinal Secretin Tumor Cell Line (STC-1 Cells).

Inflorescences of the female hop plant (Humulus lupulus L.) contain biologically active compounds, most of which have a bitter taste. Given the rising global obesity rates, there is much increasing interest in bitter taste receptors (TAS2Rs). Intestinal TAS2Rs can have beneficial effects on obesity when activated by bitter agonists. This study aims to investigate the mechanism of action of a hydroalcoholic hop extract in promoting hormone secretion that reduces the sense of hunger at the intestinal level through the interaction with TAS2Rs. The results demonstrate that the hop extract is a rich source of bitter compounds (mainly α-, β-acids) that stimulate the secretion of anorexigenic peptides (glucagon-like peptide 1 [GLP-1], cholecystokinin [CCK]) in a calcium-dependent manner while reducing levels of hunger-related hormones like ghrelin. This effect is mediated through interaction with TAS2Rs, particularly Tas2r138 and Tas2r120, and through the activation of downstream signaling cascades. Knockdown of these receptors using siRNA transfection and inhibition of Trpm5, Plcβ-2, and other calcium channels significantly reduces the hop-induced calcium response as well as GLP-1 and CCK secretion. This study provides a potential application of H. lupulus extract for the formulation of food supplements with satiating activity capable of preventing or combating obesity.

6494 GLP-1/GIP/Glucagon Triagonist Improves Glycemic Control via Gαq Signaling Pathway and TRPM5 Activation

Abstract Disclosure: N. Khajavi: None. P.C. Schreier: None. P. Beyerle: None. P.S. Reinach: None. A. Breit: None. I. Boekhoff: None. T.D. Müller: Grant Recipient; Self; Novo Nordisk. Speaker; Self; Novo Nordisk. Stock Owner; Self; Novo Nordisk. T. Gudermann: None. Cutting-edge research on obesity and diabetes strives to pioneer innovative drug combinations targeting various dysfunctional metabolic regulatory pathways. The single-molecule triagonist has been developed to directly interact with the glucagon-like peptide-1 receptor (GLP-1R), glucose-dependent insulinotropic polypeptide receptor (GIPR), and the glucagon receptor (GcgR). It provides a breakthrough in the treatment of obesity and type 2 diabetes because of greater efficacy compared to conventional single-agonist therapy. While the triagonist is already undergoing phase two clinical trials, the downstream mechanism requires further study. Previously, we showed that triagonist elicits transient rises in intracellular Ca2+ concentration that augment glucose-induced rises in insulin secretion in murine (MIN6) and human (1.1B4) pancreatic β cell lines. Although Gαs signaling is known as the main mediator of both GLP-1 and GIP signaling, our research indicates that the superior effect of the triagonist on insulin secretion is not solely dependent on the activation of the classical Gαs pathway and the exchange factor activated by cAMP (EPAC) signaling. Instead, we report that the triagonist enhances glucose-induced rises in insulin secretion via Gαq signaling and its downstream effector, the TRPM5 channel. This involvement is evident, as blocking Gαq signaling with a specific blocker, YM254890, reduced triagonist-induced rises in insulin secretion in mouse pancreatic islets. Similarly, blocking TRPM5 with the TPPO blocker attenuated triagonist-induced increases in insulin secretion and Ca2+ signaling in mouse pancreatic islets. Strikingly, both blockers had no remarkable impact on GLP-1- and GIP-induced rises in insulin secretion. Our in vivo analysis demonstrates that the triagonist improves glucose tolerance in diet-induced obese wild-type mice, but this effect was absent in TRPM5 knockout mice. Notably, the triagonist augments glucose-induced insulin secretion in isolated islets of wild-type mice more than treatment with GLP1 and GIP mono-agonists. Furthermore, this enhanced response is absent in TRPM5 knockout islets. Recent studies propose that persistent membrane depolarization of β cells leads to a switch from Gαs to Gαq signaling, which is a major amplifying pathway of insulin secretion under diabetic conditions. Our study shows that the enhancing effect of the triagonist, acting as a biased agonist, on insulin secretion is dependent on TRPM5 activation through the Gαq signaling pathway. Presentation: 6/2/2024

Implications of TRPM3 and TRPM8 for sensory neuron sensitisation.

Sensory neurons serve to receive and transmit a wide range of information about the conditions of the world around us as well as the external and internal state of our body. Sensitisation of these nerve cells, i.e.becoming more sensitive to stimuli or the emergence or intensification of spontaneous activity, for example in the context of inflammation or nerve injury, can lead to chronic diseases such as neuropathic pain. For many of these disorders there are only very limited treatment options and in order to find and establish new therapeutic approaches, research into the exact causes of sensitisation with the elucidation ofthe underlying mechanisms and the identification of themolecular components is therefore essential. These components include plasma membrane receptors and ion channels that are involved in signal reception and transmission. Members of the transient receptor potential (TRP) channel family are also expressed in sensory neurons and some of them play a crucial role in temperature perception. This review article focuses on the heat-sensitive TRPM3 andthe cold-sensitive TRPM8 (and TRPA1) channels and their importance in sensitisation of dorsal root ganglion sensory neurons is discussed based on studies related to inflammation and injury- as well as chemotherapy-induced neuropathy.

Endosomal fusion of pH-dependent enveloped viruses requires ion channel TRPM7

The majority of viruses classified as pandemic threats are enveloped viruses which enter the cell through receptor-mediated endocytosis and take advantage of endosomal acidification to activate their fusion machinery. Here we report that the endosomal fusion of low pH-requiring viruses is highly dependent on TRPM7, a widely expressed TRP channel that is located on the plasma membrane and in intracellular vesicles. Using several viral infection systems expressing the envelope glycoproteins of various viruses, we find that loss of TRPM7 protects cells from infection by Lassa, LCMV, Ebola, Influenza, MERS, SARS-CoV-1, and SARS-CoV-2. TRPM7 ion channel activity is intrinsically necessary to acidify virus-laden endosomes but is expendable for several other endosomal acidification pathways. We propose a model wherein TRPM7 ion channel activity provides a countercurrent of cations from endosomal lumen to cytosol necessary to sustain the pumping of protons into these virus-laden endosomes. This study demonstrates the possibility of developing a broad-spectrum, TRPM7-targeting antiviral drug to subvert the endosomal fusion of low pH-dependent enveloped viruses.

A Dataset for Constructing the Network Pharmacology of Overactive Bladder and Its Application to Reveal the Potential Therapeutic Targets of Rhynchophylline

Objectives: Network pharmacology is essential for understanding the multi-target and multi-pathway therapeutic mechanisms of traditional Chinese medicine. This study aims to evaluate the influence of database quality on target identification and to explore the therapeutic potential of rhynchophylline (Rhy) in treating overactive bladder (OAB). Methods: An OAB dataset was constructed through extensive literature screening. Using this dataset, we applied network pharmacology to predict potential targets for Rhy, which is known for its therapeutic effects but lacks a well-defined target profile. Predicted targets were validated through in vitro experiments, including DARTS and CETSA. Results: Our analysis identified Rhy as a potential modulator of the M3 receptor and TRPM8 channel in the treatment of OAB. Validation experiments confirmed the interaction between Rhy and these targets. Additionally, the GeneCards database predicted other targets that are not directly linked to OAB, corroborated by the literature. Conclusions: We established a more accurate and comprehensive dataset of OAB targets, enhancing the reliability of target identification for drug treatments. This study underscores the importance of database quality in network pharmacology and contributes to the potential therapeutic strategies for OAB.

Navigating the Controversies: Role of TRPM Channels in Pain States.

Chronic pain is a debilitating condition that affects up to 1.5 billion people worldwide and bears a tremendous socioeconomic burden. The success of pain medicine relies on our understanding of the type of pain experienced by patients and the mechanisms that give rise to it. Ion channels are among the key targets for pharmacological intervention in chronic pain conditions. Therefore, it is important to understand how changes in channel properties, trafficking, and molecular interactions contribute to pain sensation. In this review, we discuss studies that have demonstrated the involvement of transient receptor potential M2, M3, and M8 channels in pain generation and transduction, as well as the controversies surrounding these findings.

Erucic acid increases the potency of cisplatin-induced colorectal cancer cell death and oxidative stress by upregulating the TRPM2 channel.

Erucic acid (ErA) is a source of omega-9 monounsaturated fatty acids. ErA exhibited antitumor effects by causing apoptosis and oxidative stress in tumor cells, with the exception of the HT-29 human colorectal cancer cell line. The apoptotic and Ca2+ signaling pathways in tumor cells are triggered when mitochondrial Ca2+ and Zn2+ accumulation produce reactive free oxygen species (ROS), which in turn activate TRPM2. ErA-induced ROS and TRPM2 stimulation may augment the anticancer action of cisplatin (CSP). We aimed to study the effects of ErA and CSP incubations on ROS, apoptosis, and cell death in the HT-29 cells by activating TRPM2. The cells were divided into five groups: control, ErA (200 µM for 48 h), CSP (25 µM for 24 h), and ErA + CSP + TRPM2 antagonists (200 µM carvacrol and 25 µM N-(p-amylcinnamoyl)anthranilic acid for 24 h). The TRPM2 antagonists reduced ErA plus CSP-induced increases in H2O2-induced intracellular free Ca2+ concentration ([Ca2+]c) and adenosine diphosphate-ribose-caused TRPM2 currents. ErA and CSP were found to cause apoptosis and cell death by raising the intracellular free Zn2+ concentration (Zn2+]c), caspase-3, -8, and -9, mitochondrial membrane dysfunction, and ROS, while lowering reduced glutathione, cell viability, and cell number. The oxidative, apoptotic, and tumor cell death effects of CSP in the cells were enhanced by the increase of ErA-mediated [Ca2+]c and Zn2+]c entering mitochondria through the activation of TRPM2. In conclusion, we observed that the combination of ErA and CSP was synergistic via TRPM2 activation for the treatment of HT-29 tumor cells.

The neurotrophic factor artemin and its receptor GFRα3 mediate migraine-like pain via the ion channel TRPM8.

Migraine has a strong genetic foundation, including both monogenic and polygenic types. The former are rare, with most migraine considered polygenic, supported by genome-wide association studies (GWAS) identifying numerous genetic variants associated with migraine risk. Surprisingly, some of the most common mutations are associated with TRPM8, a non-selective cation channel that is the primary sensor of cold temperatures in primary afferent neurons of the somatosensory system. However, it is unlikely that the temperature sensitivity of TRPM8 underlies its role in migraine pathogenesis. To define the basis of the channel's involvement, we reasoned that cellular processes that increase cold sensitivity in the skin, such as the neurotrophic factor artemin, via its receptor GFRα3, also mediate TRPM8-associated migraine-like pain in the meninges. To investigate the role of artemin and GFRα3 in preclinical rodent migraine models, we infused nitroglycerin acutely and chronically, and measured changes in periorbital and hind paw mechanical sensitivity in male and female mice lacking GFRα3, after neutralization of free artemin with specific monoclonal antibodies, or by systemic treatment with a TRPM8-specific antagonist. Further, in wildtypes and mice lacking either GFRα3 or TRPM8, we tested the effects of supradural infusions of a mix of inflammatory mediators, artemin, and a TRPM8-specific agonist on migraine-related pain in mice. We find that mechanical allodynia induced by systemic nitroglycerin, or supradural infusion of inflammatory mediators, involves GFRα3. In addition, neutralization of circulating artemin reduces the nitroglycerin phenotype, demonstrating the importance of this neurotrophic pathway. Further, we show TRPM8 expression in the meninges and that direct supradural infusion of either a TRPM8-specific agonist or artemin itself produces mechanical allodynia, the latter dependent on TRPM8 and ameliorated by concurrent treatment with sumatriptan. These results indicate that neuroinflammatory events in the meninges can produce migraine-like pain in mice via artemin and GFRα3, likely acting upstream of TRPM8, providing a novel pathway that may contribute to migraine pathogenesis.

Protective effects of menthol against olanzapine-induced metabolic alterations in female mice

AimMetabolic comorbidities such as obesity type 2 diabetes, insulin resistance, glucose intolerance, dyslipidemia are the major contributors for lower life expectancy and reduced patient compliance during antipsychotic therapy in patients with severe mental illnesses such as schizophrenia, bipolar disorder, and depression. TRPM8 activation by menthol is also reported to alleviate high fat diet-induced obesity in mice. Additionally, this TRPM8 activation leads to increase in gene expression of thermogenic genes in white adipocytes and dietary menthol was found to increase browning of WAT along with improved glucose utilization. Therefore, we aimed to evaluate the plausible role of TRPM8 channels in olanzapine-induced metabolic alterations in female balb/c mice. Methods6 weeks olanzapine (6 mg kg−1, per oral) model was used in female balb/c mice. Pharmacological manipulation of TRPM8 channel was done using menthol and N-(3-aminopropyl)-2-[(3-methylphenyl)methoxy]-N-(2-thienylmethyl)-benzamide (AMTB), the agonist and antagonist respectively. Key resultsMenthol co-treatment for six weeks prevented olanzapine-induced metabolic alterations such as weight gain, increased food intake, decreased energy expenditure, adiposity, liver lipid accumulation, systemic inflammation and insulin resistance. Although no significant change in TRPM8 mRNA expression was found in the hypothalamus, however, some of the protective effects of menthol were absent in presence of AMTB indicating possible involvement of TRPM8 channels. ConclusionOur results suggest possible therapeutic implications of menthol in the management of antipsychotic-induced weight gain and other metabolic alterations.

The ion channel TRPM8 is a direct target of the immunosuppressant rapamycin in primary sensory neurons.

The mechanistic target of rapamycin (mTOR) signalling pathway is a key regulator of cell growth and metabolism. Its deregulation is implicated in several diseases. The macrolide rapamycin, a specific inhibitor of mTOR, has immunosuppressive, anti-inflammatory and antiproliferative properties. Recently, we identified tacrolimus, another macrolide immunosuppressant, as a novel activator of TRPM8 ion channels, involved in cold temperature sensing, thermoregulation, tearing and cold pain. We hypothesized that rapamycin may also have agonist activity on TRPM8 channels. Using calcium imaging and electrophysiology in transfected HEK293 cells and wildtype or Trpm8 KO mouse DRG neurons, we characterized rapamycin's effects on TRPM8 channels. We also examined the effects of rapamycin on tearing in mice. Micromolar concentrations of rapamycin activated rat and mouse TRPM8 channels directly and potentiated cold-evoked responses, effects also observed in human TRPM8 channels. In cultured mouse DRG neurons, rapamycin increased intracellular calcium levels almost exclusively in cold-sensitive neurons. Responses were markedly decreased in Trpm8 KO mice or by TRPM8 channel antagonists. Cutaneous cold thermoreceptor endings were also activated by rapamycin. Topical application of rapamycin to the eye surface evokes tearing in mice by a TRPM8-dependent mechanism. These results identify TRPM8 cationic channels in sensory neurons as novel molecular targets of the immunosuppressant rapamycin. These findings may help explain some of its therapeutic effects after topical application to the skin and the eye surface. Moreover, rapamycin could be used as an experimental tool in the clinic to explore cold thermoreceptors.

The role of oxidative stress, apoptosis and altered TRPM2 channel activation in doxorubicin-induced liver injury; the protective effect of selenium

Aim: Doxorubicin (DOXR) is frequently used alone or as combination therapy in the treatment of various types of cancer. Although dose-dependent side effects are known, its effects on liver health are not fully known. This study aimed to investigate the role of the transient receptor potential melastatin-2 (TRPM2) channel in DOXR-treated rats using the TRPM-2 channel blocker N-(p-amylcinamoyl) anthranilic acid (ACA) and to investigate the protective effects of selenium (Se). Methods: Rats were allocated into six groups, each containing ten rats: control, DMSO, DOXR, DOXR + Se, DOXR + ACA, and DOXR + ACA + Se. Serum levels of AST, ALT, LDH, triglycerides, and total cholesterol were measured. Additionally, liver tissues were subjected to immunohistochemical tests for TRPM2 channel, 8-OHdG, and caspase-3 (Casp-3) expressions and also histopathological evaluation. Results: Serum AST, ALT, LDH, triglyceride and total cholesterol levels, as well as liver 8-OHdG, TRPM2 channel and Casp-3 expressions in the DOXR group were significantly higher than in the DOXR + Se, DOXR + ACA and DOXR + ACA + Se groups (p &amp;lt; 0.05). However, these parameters were significantly reduced in the Se and ACA-treated groups compared to the DOXR group (p &amp;lt; 0.05). Conclusions: The results suggest that simultaneous administration of Se or ACA with DOXR may provide an effective therapeutic approach to combat DOXR-induced hepatotoxicity.

Discovery of selective Orai channel blockers bearing an indazole or a pyrazole scaffold

The calcium release activated calcium (CRAC) channel is highly expressed in T lymphocytes and plays a critical role in regulating T cell proliferation and functions including activation of the transcription factor nuclear factor of activated T cells (NFAT), cytokine production and cytotoxicity. The CRAC channel consists of the Orai pore subunit and STIM (stromal interacting molecule) endoplasmic reticulum calcium sensor. Loss of CRAC channel mediated calcium signaling has been identified as an underlying cause of severe combined immunodeficiency (SCID), leading to drastically weakened immunity against infections. Gain-of-function mutations in Orai and STIM have been associated with tubular aggregated myopathy (TAM), a skeletal muscle disease. While a number of small molecules have shown activity in inhibiting the CRAC signaling pathway, the usefulness of those tool compounds is limited by their off-target activity against TRPM4 and TRPM7 ion channels, high lipophilicity, and a lack of understanding of their mechanism of action. We report structure-activity relationship (SAR) studies that resulted in the characterization of compound 4k [1-(cyclopropylmethyl)-N-(3-fluoropyridin-4-yl)-1H-indazole-3-carboxamie] as a fast onset, reversible, and selective CRAC channel blocker. 4k fully blocked the CRAC current (IC50: 4.9 μM) and the nuclear translocation of NFAT at 30 and 10 μM, respectively, without affecting the electrophysiological function of TRPM4 and TRPM7 channels. Computational modeling appears to support its direction binding to Orai proteins that form the transmembrane CRACchannel.

Conservation of the cooling agent binding pocket within the TRPM subfamily.

Transient Receptor Potential (TRP) channels are a large and diverse family of tetrameric cation selective channels that are activated by many different types of stimuli, including noxious heat or cold, organic ligands such as vanilloids or cooling agents, or intracellular Ca 2+ . Structures available for all subtypes of TRP channels reveal that the transmembrane domains are closely related despite their unique sensitivity to activating stimuli. Here we use computational and electrophysiological approaches to explore the conservation of the cooling agent binding pocket identified within the S1-S4 domain of the Melastatin subfamily member TRPM8, the mammalian sensor of noxious cold, with other TRPM channel subtypes. We find that a subset of TRPM channels, including TRPM2, TRPM4 and TRPM5, contain pockets very similar to the cooling agent binding pocket in TRPM8. We then show how the cooling agent icilin modulates activation of TRPM4 to intracellular Ca 2+ , enhancing the sensitivity of the channel to Ca 2+ and diminishing outward-rectification to promote opening at negative voltages. Mutations known to promote or diminish activation of TRPM8 by cooling agents similarly alter activation of TRPM4 by icilin, suggesting that icilin binds to the cooling agent binding pocket to promote opening of the channel. These findings demonstrate that TRPM4 and TRPM8 channels share related ligand binding pockets that are allosterically coupled to opening of the pore.