Transient Receptor Potential Melastatin 8 mRNA Research Articles

Abstract 5577: TRPM8 mediated Ca2+ signaling as a therapeutic target in prostate cancer

Abstract Prostate cancer (PC) is a prevalent and deadly malignancy, necessitating the development of innovative therapeutic strategies. Transient receptor potential melastatin 8 (TRPM8), an ion channel highly expressed in prostate epithelium, has emerged as a potential target. Our preliminary studies demonstrate that TRPM8 plays a crucial role in PC progression. We observed an initial increase in TRPM8 mRNA expression during early-stage PC, followed by a decline in advanced and androgen-independent prostate cancer (AIPC) stages. Additionally, TRPM8 knockout mice exhibited elevated serum testosterone levels, heightened androgen receptor (AR) activity, and increased cell cycle, invasion, and adhesion-related effects. In xenograft models, TRPM8 demonstrated potent antitumor properties in both AR+ and AR- contexts. Our research suggests that TRPM8 activation on the plasma membrane promotes calcium influx and induces apoptosis in PC cells. Conversely, TRPM8 internalization correlates with PC pathogenesis. By exploring the effects of TRPM8 on PTEN-mediated cellular signaling, we aim to uncover novel insights into the molecular mechanisms underlying TRPM8's role in PC. This abstract underscores the potential of targeting TRPM8-mediated Ca2+ signaling as a promising therapeutic approach to combat PC progression, offering hope for improved patient outcomes. Citation Format: Swapna Asuthkar, Kiran Velpula, Vander Don Griend. TRPM8 mediated Ca2+ signaling as a therapeutic target in prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5577.

Effect of TRPM8 on pain symptom and neuronal proliferation in mice with interstitial cystitis/bladder pain syndrome

Objective: To explore the effects between transient receptor potential melastatin 8 (TRPM8) on pain symptom and neuronal proliferation in mice with interstitial cystitis/bladder pain syndrome (IC/BPS). Methods: Female wild-type C57BL/6 mice (8-10 weeks old) were divided into control group, IC/BPS model group, and IC/BPS model+menthol group (6 mice each) by random number table method; TRPM8 knockout mice were randomly divided into TRPM8 knockout group and TRPM8 knockout model group (6 mice each). The IC/BPS model group, the IC/BPS model+menthol group, and the TRPM8 knockout model group were injected subcutaneously with residues 65-84 of murine uroplakin 3A (UPK3A65-84). The IC/BPS model+menthol group continued to be injected with menthol. After successful modeling, the differences in pain thresholds between the groups were assessed by mechanosensitivity. The bladder wall was injected with a cell membrane red fluorescent probe (Dil), and the dorsal root ganglion (DRG) tissues were collected 10 days later. The differences in the protein and mRNA levels of TRPM8 and GAP43 in the groups were detected by Western blotting and quantitative real-time polymerase chain reaction (qRT-PCR), respectively. Immunofluorescence was used to detect the distribution of TRPM8 expression with GAP43 or Dil in DRG tissues. The relationship between TRPM8 and pain symptom and its role in neuronal proliferation in IC/BPS mice were analyzed. Results: The models were all constructed successfully. Compared with the control group, the pain thresholds of mice in the IC/BPS model group and IC/BPS model+menthol group were reduced [(8.50±1.22), (5.50±1.05) vs (11.67±2.16), respectively, all P<0.001]. Compared with the control group, the expression of TRPM8 mRNA was elevated in the IC/BPS model group and IC/BPS model+menthol group, while TRPM8 was not expressed in the TRPM8 knockout group [(3.16±0.05), (6.46±0.21), and 0 vs (1.00±0.06), respectively, all P<0.001]. The expression of TRPM8 protein and mRNA in each group had the same trend (P<0.001). Compared with the control group, the expression of GAP43 mRNA in the DRG of the IC/BPS model group and the IC/BPS model+menthol group was increased, whereas the expression of GAP43 mRNA in the TRPM8 knockout model group was decreased (all P<0.001). The trend of GAP43 protein expression was the same as that of mRNA expression (P<0.001). Immunofluorescence results showed an increase in the number of GAP43-positive neurons in the DRG of the IC/BPS model group and the IC/BPS model+menthol group, and a decrease in the TRPM8 knockout group compared with the control group (all P<0.001). Compared with the control group, the number of Dil-positive neurons in the DRG of the IC/BPS model group and the IC/BPS model+menthol group was increased, while the TRPM8 knockout group was decreased (all P<0.001). Conclusion: TRPM8 can exacerbate pain symptom in IC/BPS mice, and the mechanism may be related to the induction of sensory nerve proliferation at the DRG level.

DNA Sensor-Based Strategy to Visualize the TRPM7 mRNA-Mg2+ Signaling Pathway in Cancer Cells.

Technological advances and methodological innovations in cell signaling pathway analysis will facilitate progress in understanding biological processes, intervening in diseases, and screening drugs. In this work, an elaborate strategy for visualizing and monitoring the transient receptor potential melastatin 7 (TRPM7)-Mg2+ signaling pathway in living cells was constructed through the logical analysis of upstream mRNA and downstream molecules by two individual DNA sensors. The DNA sensors are constructed by modifying the dye-labeled DNA sequences on the surface of gold nanoparticles. By hybridizing with upstream mRNA, Cy5-modified DNA sensor 1 can detect and silence it simultaneously, outputting a red fluorescence signal. When the upstream mRNA is silenced, the concentration of downstream molecules of Mg2+ will be affected and down-regulated. The FAM-modified DNA sensor 2 detects this change and emits a green fluorescence as a signal. Therefore, the dynamic information on TRPM7 mRNA and the Mg2+-mediated signaling pathway can be successfully obtained by fluorescence imaging methods. Furthermore, the TRPM7 mRNA-Mg2+ signaling pathway also affects cell activity and migratory function through cell scratching and other experiments. More importantly, the proposed sensor also shows potential for screening signaling pathway inhibitors. Our work provides a simple and general strategy for the visualization of signaling pathways, which helps to understand the changes in the physiological activities of cancer cells and the causes of carcinogenesis and is crucial for cancer diagnosis and prognosis.

Expression of TRPM8 in sheep reproductive tissues and brain areas important for the expression of reproductive behavior

The Transient Receptor Potential Melastatin 8 (TRPM8) channel is a temperature-sensitive, calcium permeable ion channel and purported testosterone receptor. To determine how the hormone environment influences the expression of TRPM8 in gonadal tissue and areas of the brain important for reproduction, tissue from western white-faced cross-bred ewes, rams, and gonadectomized males (wethers; n = 6 per group) approximately 6 mo of age were collected. TRPM8 mRNA expression was greater (P = 0.01) in prostate of rams than wethers. Testes had greater (P = 0.004) expression of TRPM8 mRNA than the ovary. Differences in protein expression was similar with the testes having greater (P = 0.007) TRPM8 protein than the ovary. Protein expression did not differ (P = 0.6) in the prostate due to presence (ram) or absence (wether) of the testes. In the brain, TRPM8 varied in the amygdala with rams tending (P = 0.07) to express more mRNA which was reflected in greater (P = 0.04) number of neurons staining positive for TRPM8 in the central amygdala. Differences among ewes and wethers were not detected. This pattern was not observed (P ≥ 0.16) in the hypothalamus or olfactory bulb. To determine if TRPM8 was associated with the expression of ram sexual behavior, brains from rams categorized as high (n = 4) or low (n = 3) sexual activity were collected and blocked. Presence of TRPM8 channels was verified in the amygdala and hypothalamus of rams but was absent in the ventral tegmental area. Numbers of neurons staining positive for TRPM8 did not differ by expression of sexual behavior (P ≥ 0.2) in any area quantified. While expression of TRPM8 is more robust in tissues from intact males, expression of the channel does not appear to be important in the expression of sexual behavior.

Abstract 5277: Activation of TRPM8 channel suppresses prostate cancer growth and progression

Abstract Prostate cancer (PC) is one of the most prevalent male malignancies and a leading cause of cancer-related deaths in men. While androgen-deprivation therapy is successful in the early stages of PC, tumor cells eventually become resistant to its effects. With a median survival of 18 months, the shift to androgen-independent prostate cancer (AIPC) has a poor prognosis. Mechanisms causing this change have yet to be explained, however mounting evidence implicates the loss of transient receptor potential melastatin 8 (TRPM8) as a significant contributor. The prostate epithelium normally expresses the ionotropic receptor TRPM8. Our team has recently shown that testosterone-induced activation of TRPM8 enhances Ca2+ absorption and causes apoptosis. This prompted us to propose that increased TRPM8 activity on the plasma membrane is cytotoxic to PC cells and that TRPM8 internalization is a crucial step in the pathogenesis of PC. We examined the amounts of TRPM8 mRNA in benign tumor and metastatic PC patient datasets. TRPM8 mRNA is initially elevated in the early stages of PC but is increasingly lost during the progression to AIPC. In addition, male and female TRPM8−/− mice exhibited increased serum testosterone levels, heightened AR activity, and activation of cell cycle, invasion, and adhesion-related effectors. In both AR+ and AR− xenograft models, our research reveals that TRPM8 possesses potent antitumor properties. Given this, investigating the in vivo role of TRPM8 in PC has the potential to significantly enhance patient outcomes by preventing progression to the androgen-independent state. Citation Format: Swapna Asuthkar. Activation of TRPM8 channel suppresses prostate cancer growth and progression. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5277.

Abstract 5670: TRPM8 ion channel role in prostate cancer: Actions as a rapid testosterone signaling receptor

Abstract The transient receptor potential melastatin 8 (TRPM8) is well-known for its role in cold sensation in somatosensory neurons. TRPM8 was first identified as a prostate epithelial cell-specific gene, however, its role was unclear due to the absence of its endogenous agonist. We are the first to discover the novel role of TRPM8 as a rapid testosterone receptor. The TRPM8 mRNA is highly expressed in prostate cancer (PC) and is lost during the transition to androgen-independent prostate cancer (AIPC). Although emerging studies have shed light regarding androgen regulation of TRPM8 mRNA expression, we found that the addition of androgen receptor (AR) on the lipid bilayers inhibited testosterone-TRPM8 induced Ca2+ uptake. Additionally, our IHC revealed increased internalization of the TRPM8 protein in high-grade PC and that TRPM8 protein was targeted for proteasomal degradation in PC. We observed that inhibition of AR and UBA1 promoted the stabilization of TRPM8 on the plasma membrane, triggering Ca2+-induced cytotoxicity and apoptosis in both androgen dependent and androgen independent PC cells. Furthermore, in line with previous studies, we showed that testosterone-induced TRPM8 activation on the planar lipid bilayers also required phosphatidylinositol 4,5-bisphosphate (PIP2). Loss of PTEN is associated with tumor recurrence and the transition to AIPC. Thus, PTEN loss mediated PIP2 deficiency may be an important mechanism of TRPM8 desensitization in PC. Therefore, we propose that the rescue of TRPM8 activity on the plasma membrane combined with AR targeting may be an effective therapy for PC. Citation Format: Kiran Velpula, Katherine Shishido, Susovon Bayen, Swapna Asuthkar. TRPM8 ion channel role in prostate cancer: Actions as a rapid testosterone signaling receptor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5670.

A putative anti-inflammatory role for TRPM8 in irritable bowel syndrome-An exploratory study.

Chronic and recurring pain is a characteristic symptom in irritable bowel syndrome (IBS). Altered signaling between immune cells and sensory neurons within the gut may promote generation of pain symptoms. As transient receptor potential melastatin 8 (TRPM8) agonists, such as L-menthol in peppermint oil, have shown to attenuate IBS pain symptoms, we began investigating potential molecular mechanisms. Colonic biopsy tissues were collected from patients with IBS and controls, in two separate cohorts. Immunohistochemistry was performed to identify TRPM8 localization. Quantitative PCR was performed to measure mucosal mRNA levels of TRPM8. In addition, functional experiments with the TRPM8 agonist icilin were performed ex vivo to examine cytokine release from biopsies. Daily diaries were collected to ascertain pain symptoms. In biopsy tissue from IBS patients, we showed that TRPM8 immunoreactivity is colocalized with immune cells predominantly of the dendritic cell lineage, in close approximation to nerve endings, and TRPM8 protein and mRNA expression was increased in IBS patients compared to controls (p<0.001). TRPM8 mRNA expression showed a significant positive association with abdominal pain scores (p=0.015). Treatment of IBS patient biopsies with icilin reduced release of inflammatory cytokines IL-1β, IL-6, and TNF-α (p<0.05). These data indicate TRPM8 may have important anti-inflammatory properties and by this virtue can impact neuro-immune disease mechanisms in IBS.

Transient Receptor Potential Melastatin 2 Enhances Vascular Reactivity During Development of Atherosclerosis in Mice.

To investigate the function of transient receptor potential melastatin 2 (TRPM2) in vascular reactivity induced by 5-hydroxytryptamine (5-HT) in the aorta during development of atherosclerosis in mice. Forty mice were randomly divided into 4 groups: C57BL/6J on normal diet (C57 + ND), C57BL/6J on high-fat diet (C57 + HFD), apolipoprotein E gene knockout mice (ApoE-/-) on ND (ApoE-/- + ND), and ApoE-/- on HFD (ApoE-/- + HFD). They were fed with a ND or HFD for 16 weeks. Aortic TRPM2 expression and isometric contractions were analyzed. In the ApoE-/- + HFD group, body weight, blood glucose, and blood lipid concentrations were increased, and aortic plaques were developed. Compared with the other 3 groups, aortic TRPM2 mRNA and protein levels were significantly increased in the ApoE-/- + HFD group (P < 0.01). Aortic reactivity to 5-HT was enhanced in ApoE-/- + HFD mice with lower EC50 values. The enhanced reactivity to 5-HT was significantly inhibited by TRPM2 inhibitors, N-p-amylcinnamoyl anthranilic acid (1 µmol/l) and 2-aminoethyl diphenylborinate (10 µmol/l). Aortic TRPM2 expression is upregulated in ApoE knockout mice fed with a HFD. Upregulation of TRPM2 enhances 5-HT vascular reactivity during development of atherosclerosis.

PSII-23 Aflatoxin B1 influences expression of TRPM8 in SKOV, ovarian epithelial cancer cells

Abstract Aflatoxins are mold products of Aspergillus flavus. They are common food contaminants that affect dietary staples. Aflatoxins are most prevalent in emerging countries and negatively impact the health and reproduction of several animals. Aflatoxin B1 (AFB1) affects fertility in many species by decreasing the number of gametes. The mechanism for aflatoxin’s effect on gamete production has not been fully elucidated. In aflatoxin treated rats, steroidogenesis is affected by the competitive binding of aflatoxin to the StAR protein. The transient receptor potential melastatin 8 (TRPM8) is a nonselective cation channel highly expressed in male reproductive tracts, and sheep ovaries. TRPM8 binds testosterone and is responsive to steroids. The objective of these experiments is to determine if AFB1 influenced the expression of TRPM8 channels in an ovarian cell line. Human epithelial ovarian cells, SKOV, were seeded into chamber slides and treated in triplicate with media containing ethanol, 5µg/ml AFB1, 10µg/ml AFB1, or 20µg/ml AFB1 for 24 hours. The cells were stained for TRPM8 using immunocytochemistry and in a replicate experiment, analyzed for mRNA using Real Time RT-PCR protocols. Images were captured at 200x magnification and analyzed. Mean gray scale intensity was used to determine staining intensity as a reflection of TRPM8 expression. SKOV cells treated with AFB1 had increased staining (P ≤ 0.001) compared to ethanol treated cells. Relative TRPM8 mRNA did not differ with AFB1 treatments (P = 0.2). Inconsistency between mRNA and protein expression may be due to the timing of mRNA synthesis and translation of the protein. Based on these results, expression of TRPM8 in SKOV cells increased in response to AFB1. Although it is not certain if this effect is restricted to these transformed cells, the possibility remains that changes in TRPM8 expression may contribute to the negative reproductive consequences of AFB1 exposure in humans and livestock species.

Neuroprotective Effect of 2-Aminoethoxydiphenyl Borate (2-APB) in Amyloid β-Induced Memory Dysfunction: A Mechanistic Study.

β-Amyloid (Aβ) peptide is a characteristic feature of Alzheimer's disease (AD) and accumulation of Aβ is associated with loss of synaptic plasticity and neuronal cell death. Aggregation of Aβ initiates numerous molecular signalling pathways leading to oxidative stress, mitochondrial dysfunction as well as an imbalance of calcium ion influx homeostasis. Recently, it has been shown that transient receptor potential melastatin 2 (TRPM2), a non-selective calcium-permeable cation channel has been postulated to play a vital role in the neuronal death, indicating the potential of TRPM2 inhibition in CNS disease. In this study, neuroprotective potential of 2-aminoethoxydiphenyl borate (2-APB), a broad-spectrum calcium channels blocker was investigated in Aβ-induced memory deficits in rats. In addition, effect of 2-APB on TRPM2 channels gene and protein expressions and also on calcium and memory related proteins was investigated in the hippocampus. Intracerebroventricular (I.C.V.) administration of Aβ (Aβ25-35, 10μg) markedly induced cognitive impairment and upregulation of mRNA and protein expression of TRPM2 in the hippocampus. In addition, AChE activity was also increased in the cortex of the Aβ administered animals. Three-week treatment with 2-APB led to the down-regulation of TRPM2 mRNA and protein expression in the hippocampus and also improved the cognitive functions which was evident from the behavioral parameters. Moreover, 2-APB treatment also increased the calcium and memory associated proteins namely p-CaMKII, p-GSK-3β, p-CREB and PSD-95 in the hippocampus and reduced the mRNA level of calcium buffering proteins and calcineurin A (PPP3CA) in the hippocampus. Furthermore, 2-APB treatment significantly reduced the AChE activity in the cortex. Thus, our findings suggest the neuroprotective effect of 2-APB in Aβ-induced cognitive impairment.

TRPM8: A Therapeutic Target for Neuroinflammatory Symptoms Induced by Severe Dry Eye Disease.

Dry eye disease (DED) is commonly associated with ocular surface inflammation and pain. In this study, we evaluated the effectiveness of repeated instillations of transient receptor potential melastatin 8 (TRPM8) ion channel antagonist M8-B on a mouse model of severe DED induced by the excision of extra-orbital lacrimal and Harderian glands. M8-B was topically administered twice a day from day 7 until day 21 after surgery. Cold and mechanical corneal sensitivities and spontaneous ocular pain were monitored at day 21. Ongoing and cold-evoked ciliary nerve activities were next evaluated by electrophysiological multi-unit extracellular recording. Corneal inflammation and expression of genes related to neuropathic pain and inflammation were assessed in the trigeminal ganglion. We found that DED mice developed a cold allodynia consistent with higher TRPM8 mRNA expression in the trigeminal ganglion (TG). Chronic M8-B instillations markedly reversed both the corneal mechanical allodynia and spontaneous ocular pain commonly associated with persistent DED. M8-B instillations also diminished the sustained spontaneous and cold-evoked ciliary nerve activities observed in DED mice as well as inflammation in the cornea and TG. Overall, our study provides new insight into the effectiveness of TRPM8 blockade for alleviating corneal pain syndrome associated with severe DED, opening a new avenue for ocular pain management.

Increased Transient Receptor Potential Melastatin 8 Expression in the Development of Bladder Pain in Patients With Interstitial Cystitis/Bladder Pain Syndrome

ObjectiveTo explore the role of transient receptor potential melastatin 8 (TRPM8) in the occurrence and development of bladder pain in interstitial cystitis/bladder pain syndrome (IC/BPS) patients. The differences in the content and location distribution of TRPM8 in bladder were compared between IC/BPS and control group. MethodsAll enrolled patients answered questionnaire such as O'leary-Sant symptom index, visual analog scale (VAS), quality of life (QOL), and pelvic pain and urinary urgency frequency (PUF) score, then bladder specimens were collected. Analyses such as qRT-PCR, western blot, and immunofluorescence were performed to determine the changes in TRPM8 content and expression in neurons and sensory nerves between the IC/BPS and control group, and the relationships between TRPM8 and various clinical scores were also analyzed. ResultsThere were significant differences in the O'leary-Sant score, PUF score, VAS, and QOL score between IC/BPS and the control group (P < .05). Compared with the control group, the expression levels of TRPM8 mRNA and protein were significantly increased in the IC/BPS bladder tissues (P < .01). Immunofluorescence examination also revealed that (1) the number of neurons and sensory nerves displayed a significant upward trend in the bladder tissue of IC/BPS patients (2) the expression levels of TRPM8 on neurons and sensory nerves also increased significantly in IC/BPS group. ConclusionIn IC/BPS patients, TRPM8 content increased significantly and mainly expressed on increased neurons and sensory nerves in bladder tissue. These results may indicate a mechanism by which bladder pain is more easily to spread in IC/BPS patients, and may also indicate an important mechanism for pain sensitization in such patients.

TRPM8 Inhibition Regulates the Proliferation, Migration and ROS Metabolism of Bladder Cancer Cells.

IntroductionBased on accumulating evidence, transient receptor potential (TRP) ion channels may play important roles in the occurrence and the progression of cancer. TRP melastatin 8 (TRPM8), a member of the TRP family, functions as a Ca2+-permeable channel and regulates various physiological and pathological processes. However, the effects of TRPM8 on bladder cancer (BCa) and its underlying mechanisms have not been elucidated.MethodsBCa tissues and matched noncancerous tissues were collected to examine the expression of the TRPM8 mRNA and protein using qRT-PCR, Western blotting and immunofluorescence staining. Meanwhile, the effect of knockdown or inhibition of the activity of the TRPM8 protein on the proliferation, migration and ROS metabolism of bladder cancer cells was detected using the MTT assay, clonogenic survival assay, Transwell chamber migration assay, and reactive oxygen species (ROS) detection, respectively. Furthermore, a mouse model transplanted with BCa cells was established to assess tumor growth after TRPM8 expression was inhibited in vivo.ResultsCompared with the noncancerous tissues, the levels of TRPM8 in BCa tissues were significantly increased. Knockdown or inhibition of the activity of the TRPM8 protein in BCa cells reduced cell proliferation and migration. Moreover, the production of ROS was increased in cells treated with siTRPM8, which was accompanied by increased levels of Catalase, HO-1 and SOD2. Furthermore, a mouse model transplanted with the stable TRPM8-deficient T24 cell line was established, demonstrating that knockdown of TRPM8 delayed tumor growth in vivo.DiscussionTRPM8 might play an essential for BCa tumor progression and metastasis by interfering with BCa cell proliferation, motility, ROS metabolism and migration.

Modulation of the excitability of stellate neurons in the ventral cochlear nucleus of mice by TRPM2 channels

Oxidative stress-induced Ca2+ permeable transient receptor potential melastatin 2 (TRPM2) channels are expressed at high levels in the brain, appear to link neuronal excitability to cellular metabolism, and are involved in the pathogenesis of neurodegenerative disorders. We aimed to study the electrophysiological properties of TRPM2 channels in stellate cells of the mouse ventral cochlear nucleus (VCN) using molecular, immunohistochemical and electrophysiological approaches.In the present study, the real time PCR analysis revealed the presence of the TRPM2 mRNA in the mouse VCN tissue. Cell bodies of stellate cells were moderately labeled with TRPM2 antibodies using immunohistochemical staining.Stellate cells were sensitive to intracellular ADP-ribose (ADPR), a TRPM2 agonist. Upon the application of ADPR, the resting membrane potential of the stellate cells was significantly depolarized, shifting from −61.2 ± 0.9 mV to −57.0 ± 0.8 mV (P < 0.001; n = 21), and the firing rate significantly increased (P < 0.001, n = 6). When the pipette solution contained ADPR (300 μM) and the TRPM2 antagonists flufenamic acid (FFA) (100 μM), N-(p-amylcinnamoyl) anthranilic acid (ACA) (50 μM) and 8-bromo-cADP-Ribose (8-Br-cADPR) (50 μM), the membrane potential shifted in a hyperpolarizing direction. ADPR did not significantly change the resting membrane potential and action potential firing rate of stellate cells from TRPM2−/− mice.In conclusion, the results obtained using these molecular, immunohistochemical and electrophysiological approaches reveal the expression of functional TRPM2 channels in stellate neurons of the mouse VCN. TRPM2 might exert a significant modulatory effect on setting the level of resting excitability.

Pharmacological Inhibition of Transient Receptor Potential Melastatin 2 (TRPM2) Channels Attenuates Diabetes-induced Cognitive Deficits in Rats: A Mechanistic Study.

Diabetes is a chronic metabolic disorder affecting the central nervous system. A growing body of evidence has depicted that high glucose level leads to the activation of the transient receptor potential melastatin 2 (TRPM2) channels. However, there are no studies targeting TRPM2 channels in diabetes-induced cognitive decline using a pharmacological approach. The present study intended to investigate the effects of 2-aminoethoxydiphenyl borate (2-APB), a TRPM2 inhibitor, in diabetes-induced cognitive impairment. Streptozotocin (STZ, 50 mg/kg, i.p.) was used to induce diabetes in rats. Animals were randomly divided into the treatment group, model group and age-matched control and pre se group. 2-APB treatment was given for three weeks to the animals. After 10 days of behavioural treatment, parameters were performed. Animals were sacrificed at 10th week of diabetic induction and the hippocampus and cortex were isolated. After that, protein and mRNA expression study was performed in the hippocampus. Acetylcholinesterase (AchE) activity was done in the cortex. Our study showed the 10th week diabetic animals developed cognitive impairment, which was evident from the behavioural parameters. Diabetic animals depicted an increase in the TRPM2 mRNA and protein expression in the hippocampus as well as increased AchE activity in the cortex. However, memory associated proteins were down-regulated, namely Ca2+/calmodulin-dependent protein kinase II (CaMKII-Thr286), glycogen synthase kinase 3 beta (GSK-3β-Ser9), cAMP response element-binding protein (CREB-Ser133), and postsynaptic density protein 95 (PSD-95). Gene expression of parvalbumin, calsequestrin and brain-derived neurotrophic factor (BDNF) were down-regulated while mRNA level of calcineurin A/ protein phosphatase 3 catalytic subunit alpha (PPP3CA) was upregulated in the hippocampus of diabetic animals. A three-week treatment with 2-APB significantly ameliorated the alteration in behavioural cognitive parameters in diabetic rats. Moreover, 2-APB also down-regulated the expression of TRPM2 mRNA and protein in the hippocampus as well as AchE activity in the cortex of diabetic animals as compared to diabetic animals. Moreover, the 2-APB treatment also upregulated the CaMKII (Thr-286), GSK-3β (Ser9), CREB (Ser133), and PSD-95 expression and mRNA levels of parvalbumin, calsequestrin, and BDNF while mRNA level of calcineurin A was down-regulated in the hippocampus of diabetic animals. This study confirms the ameliorative effect of TRPM2 channel inhibitor in the diabetes- induced cognitive deficits. Inhibition of TRPM2 channels reduced the calcium associated downstream signaling and showed a neuroprotective effect of TRPM2 channels in diabetesinduced cognitive impairment.

Neuroprotective effects of 2‐aminoethoxydiphenyl borate (2‐APB) in β‐amyloid‐induced memory dysfunction is mediated through inhibition of transient receptor potential melastatin 2 (TRPM2) channels

β‐amyloid (Aβ) peptide is a hallmark of Alzheimer’s disease (AD) and associated with a progressive decline of cognition, a characteristic feature of AD. Aggregation of Aβ initiates the dysregulation of calcium ion homeostasis. Recently, it has been shown that transient receptor potential melastatin 2 (TRPM2), a Ca2+‐permeable non‐selective cation channel plays a crucial role in the Aβ‐induced neuronal cell death. However, the therapeutic potential of 2‐aminoethoxydiphenyl borate (2‐APB), a TRPM2 inhibitor has not been investigated in the Aβ‐induced cognitive deficits in rats yet. In the present study, I.C.V. administration of Aβ (Aβ25‐35, 10 μg) markedly induced cognitive impairment which shown in cognitive behavioral parameters. Moreover, mRNA and protein expression of TRPM2 were upregulated in the hippocampus of Aβ‐treated animals. AchE activity was also increased in the cortex of Aβ‐treated animals. Three‐week treatment with 2‐APB led to the down‐regulation of TRPM2 mRNA and protein expression in the hippocampus and also improved the cognitive functions. Moreover, the 2‐APB treatment also increased the calcium and memory associated proteins namely p‐CaMKII, p‐GSK3β, p‐CREB and PSD‐95 in the hippocampus and reduced the mRNA level of calcium buffering protein and calcineurin A (PPP3CA) in the hippocampus. Furthermore, 2‐APB significantly reduced the AchE activity in the cortex. Thus, our findings suggest that 2‐APB depicted potential neuroprotective effect against Aβ‐induced cognitive impairment.Support or Funding InformationNational Institute of Pharmaceutical Education and Research and National Agri‐Food Biotechnology Institute

Transient Receptor Potential Melastatin 8 (TRPM8)-Based Mechanisms Underlie Both the Cold Temperature-Induced Inflammatory Reactions and the Synergistic Effect of Cigarette Smoke in Human Bronchial Epithelial (16HBE) Cells.

Transient receptor potential melastatin 8 (TRPM8) is a major receptor of cold environment. Recently, we found that cigarette smoke extract (CSE) upregulated TRPM8 mRNA and protein expression in bronchial tissues that made them more sensitive to cold stimuli. In our present study, we found that cold temperature (18°C)-induced activation of TRPM8 in 16HBE (human bronchial epithelial) cells facilitated Ca2+ influx and subsequently led to the increased expression of interleukin (IL)-6, IL-8, and tumor necrosis factor (TNF)-α via the upregulation of p-extracellular signal-regulated kinase (ERK) and the activation of NF-κB. In addition, 16HBE cells that co-stimulated with 18°C and CSE were used to explore the synergistic effect of CSE on cold temperature-induced inflammatory cytokine production as well as the possible involved signaling pathway. RT-PCR and western blot analysis revealed that CSE upregulated TRPM8 mRNA and protein level in 16HBE cells. Ca2+ imaging, western blot, and luciferase assay showed more robust increase in intracellular Ca2+ and promoted phosphorylated ERK, P38, and NF-κB activity, respectively, in 16HBE cells co-stimulated with CSE and cold temperature, and such alteration was attenuated by TRPM8 short hairpin RNA (shRNA) transfection and BCTC pretreatment. Furthermore, enhanced levels of IL-6, IL-8, and TNF-α showed by enzyme-linked immunosorbent assay (ELISA) were reduced by specific inhibitors of ERK and NF-κB. Collectively, our results suggest that mitogen-activated protein kinase (MAPK)/NF-κB signaling is involved in TRPM8-mediated cold temperature-induced inflammatory cytokine expression. In addition, CSE synergistically amplifies cold temperature-induced inflammatory factors release via upregulating TRPM8 expression and enhancing MAPK/NF-κB signaling pathway.

Riluzole prevents oxaliplatin-induced cold allodynia via inhibition of overexpression of transient receptor potential melastatin 8 in rats

Oxaliplatin causes acute cold hypersensitivity in most patients. We previously reported oxalate derived from oxaliplatin induced cold allodynia via overexpression of transient receptor potential melastatin 8 (TRPM8) in the dorsal root ganglion (DRG) in rats. In this study, we examined the effect of riluzole on oxaliplatin-induced cold allodynia. In cultured DRG neurons, riluzole suppressed oxalate-induced increase of the number of menthol (TRPM8 agonist)-sensitive cells. Moreover, riluzole prevented cold allodynia and increase in levels of TRPM8 mRNA in oxaliplatin-treated rats. These results suggest that riluzole prevents oxaliplatin-induced cold allodynia via inhibition of TRPM8 overexpression in the DRG.

Expression of TRPM8 in human reactive lymphoid tissues and mature B-cell neoplasms.

Transient receptor potential melastatin 8 (TRPM8) is a member of the transient receptor potential superfamily of Ca2+ channels. The aim of the present study was to clarify TRPM8 expression in reactive lymphoid tissues and mature B-cell neoplasms. Reactive and neoplastic lymphoid tissues were used to evaluate TRPM8 expression by immunohistochemistry and reverse transcription-polymerase chain reaction (RT-PCR). TRPM8+ cells were frequently detected in the follicular light zone and marginal zone of reactive lymphoid tissues. Double immunostaining revealed that TRPM8+ cells co-expressed cluster of differentiation (CD) 38, CD79a, CD138, interferon regulatory factor 4/melanoma associated antigen (mutated) 1, B cell CLL/lymphoma 6 and transmembrane activator and CAML interactor. TRPM8+ neoplastic cells were frequently detected in plasma cell myeloma. The positive band of TRPM8 mRNA was confirmed by RT-PCR in cases of myeloma. The present study is, to the best of our knowledge, the first to demonstrate the expression of TRPM8 in reactive lymphoid tissues and mature B-cell neoplasms, revealing that TRPM8 is frequently expressed in pre-plasmablasts, plasmablasts, plasma cells and mature B-cell lymphomas that are likely to differentiate into plasma cells.

Exosomes Secreted by Adipose-Derived Stem Cells Contribute to Angiogenesis of Brain Microvascular Endothelial Cells Following Oxygen-Glucose Deprivation In Vitro Through MicroRNA-181b/TRPM7 Axis.

Adipose-derived stem cells (ADSCs) have been demonstrated to promote cerebral vascular remodeling processes after stroke. However, the exact molecular mechanism by which ADSCs exert protective roles in ischemic stroke is still poorly understood. In this study, we identified the role of exosomal microRNA-181b-5p (181b-Exos) in regulating post-stroke angiogenesis. The results of migration assay and capillary network formation assay showed that exosomes secreted by ADSCs (ADSCs-Exos) promoted the mobility and angiogenesis of brain microvascular endothelial cells (BMECs) after oxygen-glucose deprivation (OGD). Quantitative real-time polymerase chain reaction (qRT-PCR) showed that microRNA-212-5p (miR-212-5p) and miR-181b-5p were upregulated in BMECs subjected to the brain extract of the middle cerebral artery occlusion rats. The migration distance and tube length were increased in BMECs cultured with 181b-Exos. Furthermore, we identified that transient receptor potential melastatin 7 (TRPM7) was a direct target of miR-181b-5p. TRPM7 mRNA and protein levels were declined in BMECs cultured with 181b-Exos, but not in BMECs cultured with 212-Exos. Overexpression of TRPM7 reversed the effects of 181b-Exos on migration and tube formation of BMECs. In addition, 181b-Exos upregulated the protein expression of hypoxia-inducible factor 1α and vascular endothelial cell growth factor, and downregulated the protein expression of tissue inhibitor of metalloproteinase 3. The regulatory effect of 181b-Exos was attenuated by overexpressing TRPM7. Altogether, ADSCs-Exos promote the angiogenesis of BMECs after OGD via miR-181b-5p/TRPM7 axis, suggesting that ADSCs-Exos may represent a novel therapeutic approach for stroke recovery.