TRPV4 Channel Signaling in Macrophages Promotes Gastrointestinal Motility via Direct Effects on Smooth Muscle Cells.

Intestinal macrophages are critical for gastrointestinal (GI) homeostasis, but our understanding of their role in regulating intestinal motility is incomplete. Here, we report that CX3C chemokine receptor 1-expressing muscularis macrophages (MMs) were required to maintain normal GI motility. MMs expressed the transient receptor potential vanilloid 4 (TRPV4) channel, which senses thermal, mechanical, and chemical cues. Selective pharmacologic inhibition of TRPV4 or conditional deletion of TRPV4 from macrophages decreased intestinal motility and was sufficient to reverse the GI hypermotility that is associated with chemotherapy treatment. Mechanistically, stimulation of MMs via TRPV4 promoted the release of prostaglandin E2 and elicited colon contraction in a paracrine manner via prostaglandin E receptor signaling in intestinal smooth muscle cells without input from the enteric nervous system. Collectively, our data identify TRPV4-expressing MMs as an essential component required for maintaining normal GI motility and provide potential drug targets for GI motility disorders.

TRPV4 is a regulator of adipose oxidative metabolism, inflammation, and energy homeostasis.

PGC1α is a key transcriptional coregulator of oxidative metabolism and thermogenesis. Through a high-throughput chemical screen, we found that molecules antagonizing the TRPVs (transient receptor potential vanilloid), a family of ion channels, induced PGC1α expression in adipocytes. In particular, TRPV4 negatively regulated the expression of PGC1α, UCP1, and cellular respiration. Additionally, it potently controlled the expression of multiple proinflammatory genes involved in the development of insulin resistance. Mice with a null mutation for TRPV4 or wild-type mice treated with a TRPV4 antagonist showed elevated thermogenesis in adipose tissues and were protected from diet-induced obesity, adipose inflammation, and insulin resistance. This role of TRPV4 as a cell-autonomous mediator for both the thermogenic and proinflammatory programs in adipocytes could offer a target for treating obesity and related metabolic diseases.

The ion channel TRPV1 regulates the activation and proinflammatory properties of CD4⁺ T cells.

TRPV1 is a Ca(2+)-permeable channel studied mostly as a pain receptor in sensory neurons. However, its role in other cell types is poorly understood. Here we found that TRPV1 was functionally expressed in CD4(+) T cells, where it acted as a non-store-operated Ca(2+) channel and contributed to T cell antigen receptor (TCR)-induced Ca(2+) influx, TCR signaling and T cell activation. In models of T cell-mediated colitis, TRPV1 promoted colitogenic T cell responses and intestinal inflammation. Furthermore, genetic and pharmacological inhibition of TRPV1 in human CD4(+) T cells recapitulated the phenotype of mouse Trpv1(-/-) CD4(+) T cells. Our findings suggest that inhibition of TRPV1 could represent a new therapeutic strategy for restraining proinflammatory T cell responses.

Selective inhibition of overactive warmth-sensitive Ca2+-permeable TRPV3 channels by antispasmodic agent flopropione for alleviation of skin inflammation.

The temperature-sensitive Ca2+-permeable TRPV3 ion channel is robustly expressed in the skin keratinocytes, and its gain-of-function mutations are involved in the pathology of skin lesions. Here, we report the identification of an antispasmodic agent flopropione that alleviates skin inflammation by selective inhibition of TRPV3. In whole-cell patch clamp recordings, flopropione selectively inhibits macroscopic TRPV3 currents in a concentration-dependent manner with an IC50 value of 17.8 ± 3.5 µM. At the single-channel level, flopropione inhibits TRPV3 channel open probability without alteration of its unitary conductance. In an in vivo mouse model of skin inflammation induced by the skin sensitizer DNFB, flopropione also alleviates dorsal skin lesions and ear skin swelling. Further molecular docking combined with site-directed mutagenesis reveals that two residues E501 and I505 in the channel S2-helix are critical for flopropione-mediated inhibition of TRPV3. Taken together, our findings demonstrate that the spasmolytic drug flopropione as a selective inhibitor of TRPV3 channel not only provides a valuable tool molecule for understanding of TRPV3 channel pharmacology but also holds repurposing potential for therapy of skin disorders, such as dermatitis and pruritus.

Protective role of TRPV2 in synaptic plasticity through the ERK1/2-CREB-BDNF pathway in chronic unpredictable mild stress rats.

PURPOSE: Chronic stress is a significant risk factor for mood disorders such as depression, where synaptic plasticity plays a central role in pathogenesis. Transient Receptor Potential Vanilloid Type-2 (TRPV2) Ion Channels are implicated in hypothalamic-pituitary-adrenal axis disorders. Previous proteomic analysis indicated a reduction in TRPV2 levels in the chronic unpredictable mild stress (CUMS) rat model, yet its role in synaptic plasticity during depression remains to be elucidated. This study aims to investigate TRPV2's role in depression and its underlying mechanisms. METHODS: In vivo and in vitro experiments were conducted using the TRPV2-specific agonist probenecid and ERK1/2 inhibitors SCH772984. In vivo, rats underwent six weeks of CUMS before probenecid administration. Depressive-like behaviors were assessed through behavioral tests. ELISA kits measured 5-HT, DA, NE levels in rat hippocampal tissues. Hippocampal morphology was examined via Nissl staining. In vitro, rat hippocampal neuron cell lines were treated with ERK1/2 inhibitors SCH772984 and probenecid. Western blot, immunofluorescence, immunohistochemical staining, and RT-qPCR assessed TRPV2 expression, neurogenesis-related proteins, synaptic markers, and ERK1/2-CREB-BDNF signaling proteins. RESULTS: Decreased hippocampal TRPV2 levels were observed in CUMS rats. Probenecid treatment mitigated depressive-like behavior and enhanced hippocampal 5-HT, NE, and DA levels in CUMS rats. TRPV2 activation countered CUMS-induced synaptic plasticity inhibition. Probenecid activated the ERK1/2-CREB-BDNF pathway, suggesting TRPV2's involvement in this pathway via ERK1/2. CONCLUSION: These findings indicate that TRPV2 activation offers protective effects against depressive-like behaviors and enhances hippocampal synaptic plasticity in CUMS rats via the ERK1/2-CREB-BDNF pathway. TRPV2 emerges as a potential therapeutic target for depression.

Calcium-activated Potassium Channels as Amplifiers of TRPV4-mediated Pulmonary Edema Formation in Male Mice.

BACKGROUND: As a mechanosensitive cation channel and key regulator of vascular barrier function, endothelial transient receptor potential vanilloid type 4 (TRPV4) contributes critically to ventilator-induced lung injury and edema formation. Ca2+ influx via TRPV4 can activate Ca2+-activated potassium (KCa) channels, categorized into small (SK1-3), intermediate (IK1), and big (BK) KCa, which may in turn amplify Ca2+ influx by increasing the electrochemical Ca2+ gradient and thus promote lung injury. The authors therefore hypothesized that endothelial KCa channels may contribute to the progression of TRPV4-mediated ventilator-induced lung injury. METHODS: Male C57Bl/6J mice were ventilated for 2 h with low or high tidal volumes in the presence or absence of the nonselective KCa antagonists apamin and charybdotoxin or the selective IK1 antagonist TRAM34. Lung injury was similarly assessed in overventilated, endothelial-specific TRPV4-deficient mice or TRAM34-treated C57Bl/6J mice challenged with intratracheal acid installation. Changes in intracellular calcium Ca2+ concentration ([Ca2+]i) were monitored by real-time imaging in isolated-perfused lungs in response to airway pressure elevation or in human pulmonary microvascular endothelial cells in response to TRPV4 activation with or without inhibition of KCa channels. Analogously, changes in intracellular potassium concentration ([K+]i) and membrane potential were imaged in vitro. RESULTS: Endothelial TRPV4 deficiency or inhibition of KCa channels, and most prominently inhibition of IK1 by TRAM34, attenuated ventilator-induced lung injury as demonstrated by reduced lung edema, protein leak, and quantitative lung histology. All KCa antagonists reduced the [Ca2+]i response to mechanical stimulation or direct TRPV4 activation in isolated lungs. TRAM34 and charybdotoxin yet not apamin prevented TRPV4-induced potassium efflux and membrane hyperpolarization in human pulmonary microvascular endothelial cells. TRAM34 also attenuated the TRPV4 agonist-induced Ca2+ influx in vitro and reduced acid-induced lung injury in vivo. CONCLUSIONS: KCa channels, specifically IK1, act as amplifiers of TRPV4-mediated Ca2+ influx and establish a detrimental feedback that promotes barrier failure and drives the progression of ventilator-induced lung injury.

Discovery of N-(1,4-Benzoxazin-3-one) urea analogs as Mode-Selective TRPV1 antagonists.

A series of 1,4-benzoxazin-3-one analogs were investigated to discover mode-selective TRPV1 antagonists, since such antagonists are predicted to minimize target-based adverse effects. Using the high-affinity antagonist 2 as the lead structure, the structure activity relationship was studied by modifying the A-region through incorporation of a polar side chain on the benzoxazine and then by changing the C-region with a variety of substituted pyridine, pyrazole and thiazole moieties. The t-butyl pyrazole and thiazole C-region analogs provided high potency as well as mode-selectivity. Among them, antagonist 36 displayed potent and capsaicin-selective antagonism with IC50 = 2.31 nM for blocking capsaicin activation and only 47.5 % inhibition at 3 µM concentration toward proton activation, indicating that more than a 1000-fold higher concentration of 36 was required to inhibit proton activation than was required to inhibit capsaicin activation. The molecular modeling study of 36 with our homology model indicated that two π-π interactions with the Tyr511 and Phe591 residues by the A- and C-region and hydrogen bonding with the Thr550 residue by the B-region were critical for maintaining balanced and stable binding. Systemic optimization of antagonist 2, which has high-affinity but full antagonism for activators of all modes, led to the mode-selective antagonist 36 which represents a promising step in the development of clinical TRPV1 antagonists minimizing side effects such as hyperthermia and impaired heat sensation.

Discovery of first-in-class highly selective TRPV1 antagonists with dual analgesic and hypoglycemic effects.

Analgesia and blood sugar control are considered as two main unmet clinical needs for diabetes related neuropathic pain patients. Transient receptor potential vanilloid type-1 (TRPV1) channel is a highly validated target for pain perception, while no TRPV1 antagonists have been approved due to hyperthermia side effects. Herein, two series of new TRPV1 antagonists with flavonoid skeleton were designed by the structure-based drug design (SBDD) strategy. After comprehensive evaluation, compound CX-3 was identified as a promising TRPV1 antagonist. CX-3 exhibited equivalent TRPV1 antagonistic activity with classical TRPV1 antagonist BCTC in vitro, and exerted better analgesic activity in vivo than that of BCTC in the formalin induced inflammatory pain model without hyperthermia risk. Moreover, CX-3 exhibited robust glucose-lowering effects and showed high selectivity over other ion channels. Overall, these findings identified a first-in-class highly selective TRPV1 antagonist CX-3, which is a promising candidate to target the pathogenesis of diabetes related neuropathic pain.

A Diterpenoid of the Medicinal Plant Andrographis paniculata Targets Cutaneous TRPV3 Channel and Relieves Itch.

Transient receptor potential vanilloid subtype 3 (TRPV3) is an ion channel implicated in skin physiology and itch. TRPV3 inhibitors can present a novel strategy for combating debilitating itch conditions, and medicinal plants are a natural pool of such compounds. Here, we report the isolation of a TRPV3-inhibiting compound from Andrographis paniculata, a medicinal plant with anti-inflammatory properties whose bioactive components are poorly characterized in terms of molecular targets. Using 1H and 13C NMR and high-resolution mass spectrometry, the compound was identified as a labdane-type diterpenoid, 14-deoxy-11,12-didehydroandrographolide (ddA). The activity of the compound was evaluated by fluorescent calcium assay and manual whole-cell patch-clamp technique. ddA inhibited human TRPV3 in stably expressing CHO and HaCaT keratinocytes, acting selectively among other TRP channels implicated in itch and inflammation and not showing toxicity to HaCaT cells. Antipruritic effects of the compound were evaluated in scratching behavior models on ICR mice. ddA suppressed itch induced by the TRPV3 activator carvacrol. Additionally, ddA potently suppressed histamine-induced itch with efficacy comparable to loratadine, a clinically used antihistamine drug. These results suggest the potential of ddA as a possible safe and efficacious alternative for antipruritic therapy.

Exploration and structure-activity relationship research of benzenesulfonamide derivatives as potent TRPV4 inhibitors for treating acute lung injury.

RN-9893, a TRPV4 antagonist identified by Renovis Inc., showcased notable inhibition of TRPV4 channels. This research involved synthesizing and evaluating three series of RN-9893 analogues for their TRPV4 inhibitory efficacy. Notably, compounds 1b and 1f displayed a 2.9 to 4.5-fold increase in inhibitory potency against TRPV4 (IC50 = 0.71 ± 0.21 µM and 0.46 ± 0.08 µM, respectively) in vitro, in comparison to RN-9893 (IC50 = 2.07 ± 0.90 µM). Both compounds also significantly outperformed RN-9893 in TRPV4 current inhibition rates (87.6 % and 83.2 % at 10 µM, against RN-9893's 49.4 %). For the first time, these RN-9893 analogues were profiled in an in vivo mouse model, where intraperitoneal injections of 1b or 1f at 10 mg/kg notably mitigated symptoms of acute lung injury induced by lipopolysaccharide (LPS). These outcomes indicate that compounds 1b and 1f are promising candidates for acute lung injury treatment.

Withanicandrin Isolated from Datura Ferox Promotes Antinociception by Modulating the Asics and TRPS Channels and Anti-Inflammation in Adult Zebrafish.

This is the first study to analyze the anti-inflammatory and antinociceptive effect of withanicandrin, isolated from Datura Ferox leaves, and the possible mechanism of action involved in adult zebrafish (ZFa). To this end, the animals were treated intraperitoneally (i. p.) with withanicandrin (4; 20 and 40 mg/kg; 20 µL) and subjected to locomotor activity and acute toxicity. Nociception tests were also carried out with chemical agents, in addition to tests to evaluate inflammatory processes induced by κ-Carrageenan 1.5 % and a Molecular Docking study. As a result, withanicandrin reduced nociceptive behavior by capsaicin at a dose of 40 mg/kg and by acid saline at doses of 4 and 40 mg/kg, through neuromodulation of TRPV1 channels and ASICs, identified through blocking the antinociceptive effect of withanicandrin by the antagonists capsazepine and naloxone. Furthermore, withanicandrin caused an anti-inflammatory effect through the reduction of abdominal edema, absence of leukocyte infiltrate in the liver tissue and reduction of ROS in thel liver tissue and presented better affinity energy compared to control morphine (TRPV1) and ibuprofen (COX-1 and COX-2).

Three-Dimensional Quantitative Structure-Activity Relationship Study of Transient Receptor Potential Vanilloid 1 Channel Antagonists Reveals Potential for Drug Design Purposes.

Transient receptor potential vanilloid 1 (TRPV1) was reported to be a putative target for recovery from chronic pain, producing analgesic effects after its inhibition. A series of drug candidates were previously developed, without the ability to ameliorate the therapeutic outcome. Starting from previously designed compounds, derived from the hybridization of antagonist SB-705498 and partial agonist MDR-652, we performed a virtual screening on a pharmacophore model built by exploiting the Cryo-EM 3D structure of a nanomolar antagonist in complex with the human TRPV1 channel. The pharmacophore model was described by three pharmacophoric features, taking advantage of both the bioactive pose of the antagonist and the receptor exclusion spheres. The results of the screening were implemented inside a 3D-QSAR model, correlating with the negative decadic logarithm of the inhibition rate of the ligands. After the validation of the obtained 3D-QSAR model, we designed a new series of compounds by introducing key modifications on the original scaffold. Again, we determined the compounds' binding poses after alignment to the pharmacophoric model, and we predicted their inhibition rates with the validated 3D-QSAR model. The obtained values resulted in being even more promising than parent compounds, demonstrating that ongoing research still leaves much room for improvement.

Inhibition of Cutaneous TRPV3 Channels by Natural Caffeic Acid for the Alleviation of Skin Inflammation.

Natural caffeic acid (CA) and its analogues have been studied for their potential applications in the treatment of various inflammatory and infectious skin diseases. However, the molecular mechanism underlying the effects of the CA remains largely unknown. Here, we report that CA and its two analogues, caffeic acid phenethyl ester (CAPE) and caffeic acid methyl caffeate (CAMC), inhibit TRPV3 currents in their concentration- and structure-dependent manners with IC50 values ranging from 102 to 410 µM. At the single-channel level, CA reduces the channel open probability and open frequency without alteration of unitary conductance. CA selectively inhibits TRPV3 relative to other subtypes of thermo-TRPs, such as TRPA1, TRPV1, TRPV4, and TRPM8. Molecular docking combined with site-specific mutagenesis reveals that a residue T636 in the Pore-loop is critical for CA binding to TRPV3. Further in vivo evaluation shows that CA significantly reverses TRPV3-mediated skin inflammation induced by skin sensitizer carvacrol. Altogether, our findings demonstrate that CA exerts its anti-inflammatory effects by selectively inhibiting TRPV3 through binding to the pocket formed by the Pore-loop and the S6. CA may serve as a lead for further modification and identification of specific TRPV3 channel inhibitors.

Protein Kinase A Inhibitor Attenuates the Antinociceptive Effect of NMDA-Receptor Channel Antagonists in the Capsaicin Test in Mice.

Acute nociceptive pain in mice caused by subcutaneous (intraplantar) injection of TRPV1 ion channel agonist capsaicin (1.6 µg/mouse) and the effects of protein kinase A inhibitor H-89 (0.05 mg/mouse, intraplantar injection) and NMDA receptor channel antagonists MK-801 (7.5 and 15 µg/mouse, topical application) and hemantane (0.5 mg/mouse, topical application) on the pain were assessed. MK-801 and hemantane were found to reduce the duration of the pain response. H-89 did not significantly affect the pain in animals, but preliminary administration of this drug abolished the antinociceptive effect of MK-801 (7.5 µg/mouse) and weakens the effect of hemantane (0.5 mg/mouse).

Design, synthesis and functional validation of peptide inhibitors based on TRPV1 ion channel agonist RhTx. / é¶å‘çž¬æ—¶å—ä½“ç”µä½é¦™è‰é ¸äºšåž‹1离子通道的Nplus-RhTx多肽抑制剂理性设计及功能验证.

OBJECTIVES: To design and synthesize peptide inhibitors targeting transient receptor potential vanilloid 1 (TRPV1) ion channel, and to validate their function. METHODS: Based on previous studies on the relation of molecular structure and function of red head toxin (RhTx), a series of peptides were rationally designed and synthesized, with positive charged amino acids linked to the N terminus of RhTx. These Nplus-RhTx peptides were functionally validated by patch-clamp recordings in live cells. RESULTS: Among the 8 synthesized Nplus-RhTx peptides, four inhibited TRPV1 ion channel activated by capsaicin with IC50 of (188.3±4.7), (193.6±18.0), (282.8±11.9) and (299.5±6.4) µmol/L, respectively. CONCLUSIONS: It is feasible to develop TRPV1 peptide inhibitors by using rational design based on N terminal residues of RhTx.

Capsaicin inhibits intestinal Cl- secretion and promotes Na+ absorption by blocking TRPV4 channels in healthy and colitic mice.

Although capsaicin has been studied extensively as an activator of the transient receptor potential vanilloid cation channel subtype 1 (TRPV1) channels in sensory neurons, little is known about its TRPV1-independent actions in gastrointestinal health and disease. Here, we aimed to investigate the pharmacological actions of capsaicin as a food additive and medication on intestinal ion transporters in mouse models of ulcerative colitis (UC). The short-circuit current (Isc) of the intestine from WT, TRPV1-, and TRPV4-KO mice were measured in Ussing chambers, and Ca2+ imaging was performed on small intestinal epithelial cells. We also performed Western blots, immunohistochemistry, and immunofluorescence on intestinal epithelial cells and on intestinal tissues following UC induction with dextran sodium sulfate. We found that capsaicin did not affect basal intestinal Isc but significantly inhibited carbachol- and caffeine-induced intestinal Isc in WT mice. Capsaicin similarly inhibited the intestinal Isc in TRPV1 KO mice, but this inhibition was absent in TRPV4 KO mice. We also determined that Ca2+ influx via TRPV4 was required for cholinergic signaling-mediated intestinal anion secretion, which was inhibited by capsaicin. Moreover, the glucose-induced jejunal Iscvia Na+/glucose cotransporter was suppressed by TRPV4 activation, which could be relieved by capsaicin. Capsaicin also stimulated ouabain- and amiloride-sensitive colonic Isc. Finally, we found that dietary capsaicin ameliorated the UC phenotype, suppressed hyperaction of TRPV4 channels, and rescued the reduced ouabain- and amiloride-sensitive Isc. We therefore conclude that capsaicin inhibits intestinal Cl- secretion and promotes Na+ absorption predominantly by blocking TRPV4 channels to exert its beneficial anti-colitic action.

Simulated microgravity-induced oxidative stress and loss of osteogenic potential of osteoblasts can be prevented by protection of primary cilia.

Oxidative stress has been considered to be closely related to spaceflight-induced bone loss; however, mechanism is elusive and there are no effective countermeasures. Using cultured rat calvarial osteoblasts exposed to microgravity simulated by a random positioning machine, this study addressed the hypotheses that microgravity-induced shortening of primary cilia leads to oxidative stress and that primary cilium protection prevents oxidative stress and osteogenesis loss. Microgravity was found to induce oxidative stress (as represented by increased levels of reactive oxygen species (ROS) and malondialdehyde production, and decreased activities of antioxidant enzymes), which was perfectly replicated in osteoblasts growing in NG with abrogated primary cilia (created by transfection of an interfering RNA), suggesting the possibility that shortening of primary cilia leads to oxidative stress. Oxidative stress was accompanied by mitochondrial dysfunction (represented by increased mitochondrial ROS and decreased mitochondrial membrane potential) and intracellular Ca2+ overload, and the latter was found to be caused by increased activity of Ca2+ channel transient receptor potential vanilloid 4 (TRPV4), as also evidenced by TRPV4 agonist GSK1016790A-elicited Ca2+ influx. Supplementation of HC-067047, a specific antagonist of TRPV4, attenuated microgravity-induced mitochondrial dysfunction, oxidative stress, and osteogenesis loss. Although TRPV4 was found localized in primary cilia and expressed at low levels in NG, microgravity-induced shortening of primary cilia led to increased TRPV4 levels and Ca2+ influx. When primary cilia were protected by miR-129-3p overexpression or supplementation with a natural flavonoid moslosooflavone, microgravity-induced increased TRPV4 expression, mitochondrial dysfunction, oxidative stress, and osteogenesis loss were all prevented. Our data revealed a new mechanism that primary cilia function as a controller for TRPV4 expression. Microgravity-induced injury on primary cilia leads to increased expression and overactive channel of TRPV4, causing intracellular Ca2+ overload and oxidative stress, and primary cilium protection could be an effective countermeasure against microgravity-induced oxidative stress and loss of osteogenic potential of osteoblasts.

Functional validation of co-culture model of human keratinocytes and neuronal cell line for sensitive skin by using transient receptor potential channel vanilloid subfamily member 1 antagonist.

BACKGROUND: Sensitive skin is a subjective cutaneous hyper-reactivity that occurs in response to various innocuous stimuli. Keratinocytes have recently been shown to participate in sensory transduction by releasing many neuroactive molecules that bind to intra-epidermal free nerve endings and modulate nociception. In the literature, the characterization of these interactions has been based on the co-culture of keratinocyte and mammalian-origin neuronal cell lines. In this study, we established an in vitro model based on a co-culture of primary human keratinocytes and differentiated SH-SY5Y cells, a human neuronal cell line. METHODS: Human epidermal keratinocytes and SH-SY5Y cells were monocultured and co-cultured. Changes in calcium influx, substance P, inflammatory cytokines, and neuropeptides between the monoculture and co-culture groups treated with capsaicin only and capsaicin with transient receptor potential channel vanilloid subfamily member 1 (TRPV1) antagonist, trans-4-tert-butylcyclohexanol (TTBC), together. In addition, the difference in stinging sensation was evaluated by applying it to the volunteers. RESULTS: When SH-SY5Y cells were co-cultured with keratinocytes, they had no significant effect on axonal development. Substance P was also released after capsaicin treatment and reduced by TTBC under co-culture conditions. Moreover, the expression of inflammatory cytokines and neuropeptides was significantly increased in co-cultured keratinocytes compared to that under monoculture conditions. In addition, the stinging sensation was significantly induced after the application of capsaicin in vivo and was relieved after the application of the TRPV1 antagonist. CONCLUSION: We demonstrated that the novel co-culture model is functionally valid through capsaicin and TRPV1 antagonist. We also confirmed that TTBC could be used for the treatment of sensitive skin through a co-culture model and in vivo tests. This co-culture model of keratinocytes and SH-SY5Y cells may be useful in vitro alternatives for studying the close communication between keratinocytes and neuronal cells and for screening therapeutic drugs for sensitive skin.

Ca2+-permeable TRPV1 pain receptor knockout rescues memory deficits and reduces amyloid-ß and tau in a mouse model of Alzheimer's disease.

The transient receptor potential vanilloid 1 (TRPV1) protein is a pain receptor that elicits a hot sensation when an organism eats the capsaicin of red chili peppers. This calcium (Ca2+)-permeable cation channel is mostly expressed in the peripheral nervous system sensory neurons but also in the central nervous system (e.g. hippocampus and cortex). Preclinical studies found that TRPV1 mediates behaviors associated with anxiety and depression. Loss of TRPV1 functionality increases expression of genes related to synaptic plasticity and neurogenesis. Thus, we hypothesized that TRPV1 deficiency may modulate Alzheimer's disease (AD). We generated a triple-transgenic AD mouse model (3xTg-AD+/+) with wild-type (TRPV1+/+), hetero (TRPV1+/-) and knockout (TRPV1-/-) TRPV1 to investigate the role of TRPV1 in AD pathogenesis. We analyzed the animals' memory function, hippocampal Ca2+ levels and amyloid-ß (Aß) and tau pathologies when they were 12 months old. We found that compared with 3xTg-AD-/-/TRPV1+/+ mice, 3xTg-AD+/+/TRPV1+/+ mice had memory impairment and increased levels of hippocampal Ca2+, Aß and total and phosphorylated tau. However, 3xTg-AD+/+/TRPV1-/- mice had better memory function and lower levels of hippocampal Ca2+, Aß, tau and p-tau, compared with 3xTg-AD+/+/TRPV1+/+ mice. Examination of 3xTg-AD-derived primary neuronal cultures revealed that the intracellular Ca2+ chelator BAPTA/AM and the TRPV1 antagonist capsazepine decreased the production of Aß, tau and p-tau. Taken together, these results suggested that TRPV1 deficiency had anti-AD effects and promoted resilience to memory loss. These findings suggest that drugs or food components that modulate TRPV1 could be exploited as therapeutics to prevent or treat AD.

TRPV1 blockers as potential new treatments for psychiatric disorders.

The transient receptor potential vanilloid-1 channel (TRPV1) is responsible for decoding physical and chemical stimuli. TRPV1 is activated by capsaicin (a compound from chili peppers), heat (above 43°C) and acid environment, playing a major role in pain, inflammation and body temperature. Molecular and histological studies have suggested TRPV1 expression in specific brain regions, where it can be activated primarily by the endocannabinoid anandamide, fostering studies on its potential role in psychiatric disorders. TRPV1 blockers are effective in various animal models predictive of anxiolytic and antipanic activities, in addition to reducing conditioned fear. In models of antidepressant activity, these compounds reduce behavioral despair and promote active stress-coping behavior. TRPV1 blockers also reduce the effects of certain drugs of abuse and revert behavioral changes in animal models of neurodevelopmental disorders. The main limiting factor in developing TRPV1 blockers as therapeutic agents concerns their effects on body temperature, particularly hyperthermia. New compounds, which block specific states of the channel, could represent an alternative. Moreover, compounds blocking both TRPV1 and the anandamide-hydrolyzing enzyme, fatty acid amide hydrolase (FAAH), termed dual TRPV1/FAAH blockers, have been investigated with promising results. Overall, preclinical studies yield favorable results with TRPV1 blockers in animal models of psychiatric disorders.