Transient Vanilloid Receptor Research Articles

Novel Topical Treatments for Itch.

The experience of itch often poses a burden on patient quality of life and has the capacity to inflict significant suffering. Topical therapies are a mainstay of treatment for many cutaneous and systemic diseases and afford patients the opportunity to manage their conditions without many of the systemic side effects of non-topical therapies. We review a multitude of new topical medications targeting the skin, immune system, and neural receptors. The list includes Janus kinase inhibitors, tyrosine kinase inhibitors, phosphodiesterase inhibitors, transient receptor vanilloid inhibitors, topical cannabinoids, and topical acetaminophen. Many of the topical therapies reviewed show promising data in phase2-3 clinical trials, but further research is needed to compare therapies head-to-head and test their efficacy on a broader range of conditions.

Permeant cations modulate pore dynamics and gating of TRPV1 ion channels.

The transient receptor vanilloid 1 (TRPV1) is a non-selective ion channel, which is activated by several chemical ligands and heat. We have previously shown that activation of TRPV1 by different ligands results in single-channel openings with different conductance, suggesting that the selectivity filter is highly dynamic. TRPV1 is weakly voltage dependent; here, we sought to explore whether the permeation of different monovalent ions could influence the voltage dependence of this ion channel. By using single-channel recordings, we show that TRPV1 channels undergo rapid transitions to closed states that are directly connected to the open state, which may result from structural fluctuations of their selectivity filter. Moreover, we demonstrate that the rates of these transitions are influenced by the permeant ion, suggesting that ion permeation regulates the voltage dependence of these channels. Our data could be the basis for more detailed MD simulations exploring the permeation mechanism and how the occupancy of different ions alters the three-dimensional structure of the pore of TRPV1 channels.

The periodontal ligament, temperature-sensitive ion channels TRPV1-4, and the mechanosensitive ion channels Piezo1 and 2: A Nobel connection.

Teeth are subject to a variety of mechanical forces and vectors. The periodontal ligament (PDL), fibrous tissue that connects the cementum of the tooth to the bony socket, plays a decisive role in transmitting force to alveolar bone via Sharpey fibers, transforming and converting these forces into biological signals. This interaction effects significant osteoblastic and osteoclastic responses via autocrine proliferative and paracrine responses. Recent discoveries of receptors for temperature and touch by the Nobel laureates David Julius and Ardem Patapoutian, respectively have a profound impact on orthodontics. Transient receptor vanilloid channel 1 (TRPV1), initially described as a receptor for temperature, has been proposed to participate in the sensing of force. TRPV4, another ion channel receptor, perceives tensile forces as well as thermal and chemical stimuli. Piezo1 and 2, the classic receptors for touch, in addition to the aforementioned receptors, have similarly been described on PDL-derived cells. In this text, we review the role of the temperature-sensitive ion channels and mechanosensitive ion channels on their biological function and influence in orthodontic treatment.

Immunomodulatory effect from ethanol extract and ethyl acetate fraction of Curcuma heyneana Valeton and Zijp: Transient receptor vanilloid protein approach

This study aims to discover the immunomodulatory potential of the ethanol extract (EE) and the ethyl acetate fraction (EAF) of Curcuma heyneana Valeton and Zijp (Indonesian name: temu giring) rhizome using mice models. The affinity of the curcuminoid (curcumin, dimethoxy-, and bisdemethoxy-) through the Transient Receptor Potential Vanilloid 1 (TRPV1) was determined using Mollegro molecular docking in silico. The curcuminoid concentration of the EE and EAF of C. heyneana rhizome were determined using thin-layer chromatography densitometry. In vivo studies in mice models were conducted using the carbon clearance method to determine the phagocytosis index, and the number of leukocytes in the blood and spleen. Forty mice were divided into eight groups, including negative control (given 1% CMC-Na), positive control (given Stimuno Forte® suspension at a dose of 6.5 mg/kg BW), three groups given the EAF of C. heyneana rhizome extract at a dose of 125 mg/kg BW, 250 mg/kg BW, and 500 mg/kg BW, respectively, and three groups were given EE of temu giring rhizome extract with doses of 125 mg/kg BW, 250 mg/kg BW, and 500 mg/kg BW, respectively. E.E. and E.A.F. of C. heyneana (temu giring) rhizome extract contained dimethoxy curcumin (0.176 ± 0.01 and 4.53 ± 0.02 %b/b) greater than another curcuminoid, bisdemetoxy curcumin and curcumin. EE at 125 mg/kg BW and EAF dose at 500 mg/kg B W. of temu giring rhizome have immunostimulant activity with a phagocytosis index value of >1 compared to the negative control (p < 0.05). Additionally, both increase the number of lymphocytes, monocytes, and neutrophil cells in peripheral blood and spleen compared to the negative control (p < 0.05). Their activity was seen as similar to the positive control. Therefore, the EE of C. heyneana rhizome has immunostimulant activity, and the EAF of C. heyneana rhizome has immunosuppressant activity at 125 mg/kg BW and immunostimulant at a higher dose. The activity of temu giring as an immunomodulator was associataed with its affinity to TRPV1.

Coxsackievirus B3 infects and disrupts human induced-pluripotent stem cell derived brain-like endothelial cells.

Coxsackievirus B3 (CVB3) is a significant human pathogen that is commonly found worldwide. CVB3 among other enteroviruses, are the leading causes of aseptic meningo-encephalitis which can be fatal especially in young children. How the virus gains access to the brain is poorly-understood, and the host-virus interactions that occur at the blood-brain barrier (BBB) is even less-characterized. The BBB is a highly specialized biological barrier consisting primarily of brain endothelial cells which possess unique barrier properties and facilitate the passage of nutrients into the brain while restricting access to toxins and pathogens including viruses. To determine the effects of CVB3 infection on the BBB, we utilized a model of human induced-pluripotent stem cell-derived brain-like endothelial cells (iBECs) to ascertain if CVB3 infection may alter barrier cell function and overall survival. In this study, we determined that these iBECs indeed are susceptible to CVB3 infection and release high titers of extracellular virus. We also determined that infected iBECs maintain high transendothelial electrical resistance (TEER) during early infection despite possessing high viral load. TEER progressively declines at later stages of infection. Interestingly, despite the high viral burden and TEER disruptions at later timepoints, infected iBEC monolayers remain intact, indicating a low degree of late-stage virally-mediated cell death, which may contribute to prolonged viral shedding. We had previously reported that CVB3 infections rely on the activation of transient receptor vanilloid potential 1 (TRPV1) and found that inhibiting TRPV1 activity with SB-366791 significantly limited CVB3 infection of HeLa cervical cancer cells. Similarly in this study, we observed that treating iBECs with SB-366791 significantly reduced CVB3 infection, which suggests that not only can this drug potentially limit viral entry into the brain, but also demonstrates that this infection model could be a valuable platform for testing antiviral treatments of neurotropic viruses. In all, our findings elucidate the unique effects of CVB3 infection on the BBB and shed light on potential mechanisms by which the virus can initiate infections in the brain.

Transient Receptor Vanilloid Subtype 4-Mediated Ca2+ Influx Promotes Glomerular Endothelial Inflammation in Sepsis-Associated Acute Kidney Injury

Sepsis-associated acute kidney injury (S-AKI) is a frequent complication in patients who are critically ill, which is often initiated by glomerular endothelial cell dysfunction. Although transient receptor vanilloid subtype 4 (TRPV4) ion channels are known to be permeable to Ca2+ and are widely expressed in the kidneys, the role of TRPV4 on glomerular endothelial inflammation in sepsis remains elusive. In the present study, we found that TRPV4 expression in mouse glomerular endothelial cells (MGECs) increased after lipopolysaccharide (LPS) stimulation or cecal ligation and puncture challenge, which increased intracellular Ca2+ in MGECs. Furthermore, the inhibition or knockdown of TRPV4 suppressed LPS-induced phosphorylation and translocation of inflammatory transcription factors NF-κB and IRF-3 in MGECs. Clamping intracellular Ca2+ mimicked LPS-induced responses observed in the absence of TRPV4. In vivo experiments showed that the pharmacologic blockade or knockdown of TRPV4 reduced glomerular endothelial inflammatory responses, increased survival rate, and improved renal function in cecal ligation and puncture-induced sepsis without altering renal cortical blood perfusion. Taken together, our results suggest that TRPV4 promotes glomerular endothelial inflammation in S-AKI and that its inhibition or knockdown alleviates glomerular endothelial inflammation by reducing Ca2+ overload and NF-κB/IRF-3 activation. These findings provide insights that may aid in the development of novel pharmacologic strategies for the treatment of S-AKI.

Endothelial Ion Channels and Cell-Cell Communication in the Microcirculation

Endothelial cells in resistance arteries, arterioles, and capillaries express a diverse array of ion channels that contribute to Cell-Cell communication in the microcirculation. Endothelial cells are tightly electrically coupled to their neighboring endothelial cells by gap junctions allowing ion channel-induced changes in membrane potential to be conducted for considerable distances along the endothelial cell tube that lines arterioles and forms capillaries. In addition, endothelial cells may be electrically coupled to overlying smooth muscle cells in arterioles and to pericytes in capillaries via heterocellular gap junctions allowing electrical signals generated by endothelial cell ion channels to be transmitted to overlying mural cells to affect smooth muscle or pericyte contractile activity. Arteriolar endothelial cells express inositol 1,4,5 trisphosphate receptors (IP3Rs) and transient receptor vanilloid family member 4 (TRPV4) channels that contribute to agonist-induced endothelial Ca2+ signals. These Ca2+ signals then activate intermediate and small conductance Ca2+-activated K+ (IKCa and SKCa) channels causing vasodilator-induced endothelial hyperpolarization. This hyperpolarization can be conducted along the endothelium via homocellular gap junctions and transmitted to overlying smooth muscle cells through heterocellular gap junctions to control the activity of voltage-gated Ca2+ channels and smooth muscle or pericyte contraction. The IKCa- and SKCa-induced hyperpolarization may be amplified by activation of inward rectifier K+ (KIR) channels. Endothelial cell IP3R- and TRPV4-mediated Ca2+ signals also control the production of endothelial cell vasodilator autacoids, such as NO, PGI2, and epoxides of arachidonic acid contributing to control of overlying vascular smooth muscle contractile activity. Cerebral capillary endothelial cells lack IKCa and SKCa but express KIR channels, IP3R, TRPV4, and other Ca2+ permeable channels allowing capillary-to-arteriole signaling via hyperpolarization and Ca2+. This allows parenchymal cell signals to be detected in capillaries and signaled to upstream arterioles to control blood flow to capillaries by active parenchymal cells. Thus, endothelial cell ion channels importantly participate in several forms of Cell-Cell communication in the microcirculation that contribute to microcirculatory function and homeostasis.

TRPV4 Regulates Soman-Induced Status Epilepticus and Secondary Brain Injury via NMDA Receptor and NLRP3 Inflammasome.

Nerve agents are used in civil wars and terrorist attacks, posing a threat to public safety. Acute exposure to nerve agents such as soman (GD) causes serious brain damage, leading to death due to intense seizures induced by acetylcholinesterase inhibition and neuronal injury resulting from increased excitatory amino-acid levels and neuroinflammation. However, data on the anticonvulsant and neuroprotective efficacies of currently-used countermeasures are limited. Here, we evaluated the potential effects of transient receptor vanilloid 4 (TRPV4) in the treatment of soman-induced status epilepticus (SE) and secondary brain injury. We demonstrated that TRPV4 expression was markedly up-regulated in rat hippocampus after soman-induced seizures. Administration of the TRPV4 antagonist GSK2193874 prior to soman exposure significantly decreased the mortality rate in rats and reduced SE intensity. TRPV4-knockout mice also showed lower incidence of seizures and higher survival rates than wild-type mice following soman exposure. Further in vivo and in vitro experiments demonstrated that blocking TRPV4 prevented NMDA receptor-mediated glutamate excitotoxicity. The protein levels of the NLRP3 inflammasome complex and its downstream cytokines IL-1β and IL-18 increased in soman-exposed rat hippocampus. However, TRPV4 inhibition or deletion markedly reversed the activation of the NLRP3 inflammasome pathway. In conclusion, our study suggests that the blockade of TRPV4 protects against soman exposure and reduces brain injury following SE by decreasing NMDA receptor-mediated excitotoxicity and NLRP3-mediated neuroinflammation. To our knowledge, this is the first study regarding the "dual-switch" function of TRPV4 in the treatment of soman intoxication.

A Luminescence-Based Human TRPV1 Assay System for Quantifying Pungency in Spicy Foods.

The quantitation of pungency is difficult to achieve using sensory tests because of persistence, accumulation, and desensitization to the perception of pungency. Transient receptor vanilloid 1 (TRPV1), which is a chemosensory receptor, plays a pivotal role in the perception of many pungent compounds, suggesting that the activity of this receptor might be useful as an index for pungency evaluation. Although Ca2+-sensitive fluorescence dyes are commonly used for measuring human TRPV1 (hTRPV1) activity, their application is limited, as foods often contain fluorescent substances that interfere with the fluorescent signals. This study aims to design a new pungency evaluation system using hTRPV1. Instead of employing a fluorescent probe as the Ca2+ indicator, this assay system uses the luminescent protein aequorin. The luminescence assay successfully evaluated the hTRPV1 activity in foods without purification, even for those containing fluorescent substances. The hTRPV1 activity in food samples correlated strongly with the pungency intensity obtained by the human sensory test. This luminescence-based hTRPV1 assay system will be a powerful tool for objectively quantifying the pungency of spicy foods in both laboratory and industrial settings.

TRPV1 Channel: A Noxious Signal Transducer That Affects Mitochondrial Function

The Transient Receptor Vanilloid 1 (TRPV1) or capsaicin receptor is a nonselective cation channel, which is abundantly expressed in nociceptors. This channel is an important transducer of several noxious stimuli, having a pivotal role in pain development. Several TRPV1 studies have focused on understanding its structure and function, as well as on the identification of compounds that regulate its activity. The intracellular roles of these channels have also been explored, highlighting TRPV1′s actions in the homeostasis of Ca2+ in organelles such as the mitochondria. These studies have evidenced how the activation of TRPV1 affects mitochondrial functions and how this organelle can regulate TRPV1-mediated nociception. The close relationship between this channel and mitochondria has been determined in neuronal and non-neuronal cells, demonstrating that TRPV1 activation strongly impacts on cell physiology. This review focuses on describing experimental evidence showing that TRPV1 influences mitochondrial function.

TRPV1 Responses in the Cerebellum Lobules V, VIa and VII Using Electroacupuncture Treatment for Inflammatory Hyperalgesia in Murine Model.

Inflammatory pain sensation is an important symptom which protects the body against additional tissue damage and promotes healing. Discovering long-term and effective treatments for pain remains crucial in providing efficient healthcare. Electroacupuncture (EA) is a successful therapy used for pain relief. We aimed to investigate effects and mechanisms of Complete Freund’s Adjuvant (CFA)-inducing inflammatory pain in the cerebellum, and the inhibition of this inflammatory hyperalgesia using EA at Zusanli acupoint (ST36). The results display a significant increase in mechanical and thermal sensitivities in the CFA and CFA + SHAM groups, which was significantly reduced in the CFA+EA and CFA + KO groups. This evidence was substantiated in the protein levels observed using immunoblotting, and presented with significant escalations after CFA inducing inflammatory hyperalgesia in CFA and CFA + SHAM groups. Then, they were significantly attenuated by EA in the CFA + EA group. Furthermore, the CFA + transient receptor vanilloid member 1 (TRPV1)−/− group indicated similar significant decreases of protein expression. Additionally, a concomitant overexpression in lobule VIa was also observed in immunofluorescence. These consequences suggest that CFA-induced inflammatory pain provokes modifications in cerebellum lobules V, VIa and VII, which can subsequently be regulated by EA treatment at the ST36 through its action on TRPV1 and related molecular pathways.

Evidence for acupoint catgut embedding treatment and TRPV1 gene deletion increasing weight control in murine model

Obesity is a global health problem affecting the general population. Acupoint catgut embedding (ACE) is an alternative treatment that involves the implantation of absorbable catgut suture at acupoints. The transient receptor vanilloid member 1 (TRPV1) is a calcium ion channel that responds to several chemical ligands and is identified in numerous locations throughout the body. The aim of the present study was to examine the effect of ACE treatment on obesity and its associated complications through various neural mechanisms in a murine model. A C57/BL6 wild type (WT) and TRPV1-/- (KO) mouse model was utilized to exclude any psychological factors associated with obesity. The WT-HFD-ACE and WT-HFD-SHAM groups received weekly ACE or placebo treatments at the bilateral ST36 acupoint. The mice were fed with a normal mice chow diet (ND) or a high-fat food diet (HFD; 45 kcal%), and their body weights were recorded once a week. After 8 weeks, the subjects were sacrificed and changes in the levels of a number of biomarkers were investigated using ELISA, immunoblotting and immunofluorescence. The results indicated a significant decrease in body weight variation for the WT-HFD-ACE group compared with the WT-HFD and WT-HFD-SHAM groups, using the WT-ND group as the body weight baseline. By contrast, KO mice fed with ND or HFD demonstrated notable body weight maintenance throughout the experimental period. Similar patterns were observed in adipose tissue mass, glucose, leptin and insulin plasma levels, and protein molecule density of TRPV1 and its associated molecules in the hypothalamus and nucleus tractus solitarii. In contrast, in the prefrontal cortex, significant decreases in the concentrations of MAPK pathway proteins in the WT-HFD and WT-HFD-SHAM groups were observed. The levels of these proteins were significantly increased in the WT-HFD-ACE and KO-HFD groups. These results suggested that TRPV1 and its associated pathways may be involved in body weight maintenance, and may be controlled through ACE treatment or genetic manipulation.

Extracellular Vesicles From Pathological Microenvironment Induce Endothelial Cell Transformation and Abnormal Angiogenesis via Modulation of TRPV4 Channels.

The soluble and mechanical microenvironment surrounding endothelial cells influences and instructs them to form new blood vessels. The cells in the pathological tumor microenvironment release extracellular vesicles (EVs) for paracrine signaling. EVs have been shown to induce angiogenesis by communicating with endothelial cells, but the underlying molecular mechanisms are not well known. We have recently shown that the mechanosensitive ion channel transient receptor vanilloid 4 (TRPV4) expression and activity is significantly reduced in tumor endothelial cells (TEC), and that activation of TRPV4 normalized the tumor vasculature and improved cancer therapy. However, whether and how the tumor microenvironment downregulates TRPV4 and transforms the normal endothelial cell phenotype remains unknown. To explore this, we exposed normal human endothelial cells (hNEC) to human lung tumor cell conditioned media (TCM) and measured phenotypic changes and angiogenesis. We found that treatment with TCM transformed hNEC to a TEC-like phenotype (hTEC) as evidenced by increased expression of tumor endothelial cell marker 8 (TEM8) and exhibition of abnormal angiogenesis on 2D-Matrigels compared to normal hNEC. Mechanistically, expression and activity of TRPV4 was decreased in hTEC. Further, when pre-treated with exosome inhibitor GW4869, TCM failed to induce hNEC transformation to hTEC. Finally, addition of purified EVs from TCM induced transformation of hNEC to hTEC as evidenced by abnormal angiogenesis in vitro. Taken together, our results suggest that the pathological (tumor) microenvironment transforms normal endothelial cells into a tumor endothelial cell-like phenotype through EVs via the downregulation of TRPV4.

The selective TRPV4 channel antagonist HC-067047 attenuates mechanical allodynia in diabetic mice

Painful diabetic neuropathy (PDN) is a serious symptom that compromises quality of life and remains without effective pharmacological treatment. The transient receptor vanilloid 4 (TRPV4) is a cation-permeable channel implicated in sensory transduction and pain signalling. Therefore, drugs that act on TRPV4 may have therapeutic applications to treat PDN. In the present work, we assessed the effect of the selective TRPV4 channel antagonist HC-067047 on painful neuropathy associated with streptozotocin (STZ)-induced diabetes in mice. STZ-treated animals presented both mechanical and cold allodynia at 6 weeks after diabetes induction. Notably, HC-067047 (1 mg/kg, s.c.) given daily between 2 and 6 weeks after diabetes induction significantly prevented the development of mechanical allodynia. Additionally, both single and repeated treatments with HC-067047 (10 mg/kg, s.c.) significantly reverted established mechanical allodynia induced by STZ. However, HC-067047 was not capable of affecting either thermal cold allodynia or hyperglycemia. Similarly, HC-067047 treatments showed no effect on body weight, temperature, locomotor activity or motor coordination of control mice. Immunohistochemistry assay showed that TRPV4 expression was not different in sciatic nerve, dorsal root ganglia (DRG) or hind paw plantar skin from diabetic and non-diabetic mice, suggesting that HC-067047 acts on constitutive receptors to inhibit mechanical allodynia. Taken together, the data generated in the present study show the potential relevance of using TRPV4 antagonists to treat painful neuropathy associated with diabetes.

Tumor microenvironment regulates endothelial cell transformation via modulation of TRPV4 channels

Abnormal angiogenesis and hyper‐permeable vessels characterize the tumor vasculature. Together, these attributes contribute to atypical growth rate and metastasis of tumor cells. We have recently shown that the mechanosensitive ion channel, transient receptor vanilloid 4 (TRPV4) expression and activity is significantly reduced in tumor endothelial cells (TEC), and that activation of TRPV4 normalized tumor vasculature and improved cancer therapy. However, whether and how the tumor microenvironment downregulates TRPV4 and transforms normal endothelial cell phenotype remains unknown. To explore this, we repeatedly exposed normal human endothelial cells (NhEC) to human lung adenocarcinoma (tumor) cell conditioned media and measured phenotypic changes, angiogenesis, and functional expression of TRPV4. We found that treatment with cancer cell conditioned media changed NhEC to a tumor endothelial‐like phenotype (ThEC) as evidenced by; increased expression of tumor endothelial cell marker 8 (TEM8) and exhibition of abnormal angiogenesis on 2D‐Matrigels compared to normal NhEC. Mechanistically, we observed that expression and activity of TRPV4 was reduced in ThEC. Finally, we found that treatment with a Rho kinase inhibitor, Y‐27632 normalized abnormal tube formation exhibited by ThEC. Taken together, our results suggest that the tumor microenvironment transforms normal endothelial cells into tumor endothelial cell‐like phenotype through the downregulation of TRPV4.Support or Funding InformationNIH (1RO1HL119705), NIH (1R15CA202847‐01), and start‐up funds from NEOMED (CKT).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Osteoporotic Pain is Associated with Increased Transient Receptor Vanilloid 4 Expression in the Dorsal Root Ganglia of Ovariectomized Osteoporotic Rats: A Pilot Basic Study.

Introduction Osteoporosis can produce a persistent state of pain known as osteoporotic pain. One proposed mechanism of this pathology is increased calcitonin gene-related peptide (CGRP; a marker related to inflammatory pain) expression in the dorsal root ganglia (DRG) innervating osteoporotic vertebrae. Alternatively, a previous study revealed that axial loading caused osteoporotic pain in a rodent model of coccygeal vertebrae compression. Because this compression model is associated with trauma, additional mechanistic studies of osteoporotic pain in the absence of trauma are required. The current study aimedto evaluate the expression and relative distribution of transient receptor potential vanilloid 4 (TRPV4), a pain-related mechanoreceptor, in ovariectomized (OVX) osteoporotic rats. Methods CGRP-immunoreactive (-ir) and TRPV4-ir DRG neurons innervating the L3 vertebrae of Sprague-Dawley rats were labeled with a neurotracer, FluoroGold. Intravertebral pH was also measured during the neurotracer procedure. TRPV4-ir/CGRP-ir FluoroGold-positive DRG neurons were quantified in sham control and OVX rats (n = 10, ea). The threshold for statistical significance was set at P < 0.05. Results There was no statistical difference in the number of FluoroGold-positive DRG neurons between groups; however, there were significantly more CGRP-ir/TRPV4-ir FluoroGold-positive DRG neurons in the OVX group compared with the sham control group (P < 0.05) as well as the significantly increased molecular production of each peptide. Intravertebral pH was also lower in the OVX group compared with the sham control group (P < 0.05). Conclusion Sensory neurons innervating osteoporotic vertebrae exhibited increased expression of co-localized CGRP and TRPV4 in OVX osteoporotic rats. Additionally, intravertebral pH was low in the vicinity osteoporotic vertebrae. Considering that TRPV4 is a mechanosensitive nociceptor that is activated in acidic environments, its upregulation may be associated with the pathology of osteoporotic pain derived from microinflammation involved in osteoporosis.

17.4 POSSIBLE MECHANISMS INVOLVED IN THE ANTIPSYCHOTIC EFFECTS OF CANNABIDIOL (CBD)

BackgroundLaboratory rodents and human studies have demonstrated that cannabidiol (CBD) presents antipsychotic effects. Several mechanisms of action have been associated to CBD effects. Most of the studies that have investigated these mechanisms have been performed in vitro and their relevance for the in vivo effects of this drug is still uncertain.MethodsIn spite of its low affinity for CB1 receptor (CB1R), CBD is capable of antagonizing CB1R agonists at reasonable low concentrations. CBD can also inhibit anandamide uptake and metabolism, enhancing endocannabinoid tonus. It is also possible to attribute the antipsychotic action of CBD to an antagonism of CB1R. This suggestion was reinforced by the observation that patients in the initial prodromal states of psychosis and patients with schizophrenia had higher levels of anandamide in CSF than health controls. Moreover, there would be a decrease in glutamatergic inputs from this area to the prefrontal cortex, impairing locomotor activity and working memory and endocannabinoids could regulate this system. CBD could facilitate endocannabinoids “on demand” synthesis in post-synaptic neurons, acting pre-synaptic terminals and negatively regulating the release of neurotransmitters, particularly GABA and glutamate.ResultsAlso, an increase in anandamide levels induced by CBD could attenuate GABA release from ventral pallidum neurons, restoring the normal function of this system in psychotic patients. CBD can also increase adult neurogenesis in mice and that this effect has been shown to be dependent on the CB1 receptors. In addition to the mechanisms discussed above, CBD can produce several other effects that could also be involved to be responsible for its antipsychotic properties, including interaction with 5HT1A and TRPV1 receptors and anti-inflammatory/neuroprotective effects. CBD can act as a serotonin 1A receptor (5HT1A) agonist, although the role of 5-HT1A-mediated neurotransmission in schizophrenia is unclear, aripiprazole, an atypical antipsychotic, acts as a partial agonist at this receptor, an effect that could, together with its actions on D2 and 5-HT2A receptors, contribute to therapeutic effects of this drug. CBD can also activate Transient Receptor Vanilloid-1 (TRPV1) receptors that are expressed in several brain areas related to psychosis such as the prefrontal cortex, amygdala and hippocampus. Since CBD is also a potent anti-inflammatory, antioxidant and neuroprotective compound, it is possible that these effects are involved in its antipsychotic action.DiscussionSince CBD is also a potent anti-inflammatory, antioxidant and neuroprotective compound, it is possible that these effects are involved in its antipsychotic action.

TRPV4 channels contribute to calcium transients in astrocytes and neurons during peri-infarct depolarizations in a stroke model.

Stroke is one of the leading causes of death and long-term disability. In the penumbra, that is, the area surrounding the infarct core, peri-infarct depolarizations (PIDs) are accompanied by strong intracellular calcium elevations in astrocytes and neurons, thereby negatively affecting infarct size and clinical outcome. The dynamics of PIDs and the cellular pathways that are involved during PID formation and progression remain incompletely understood. We have previously shown that inositol triphosphate-gated calcium release from internal stores is a major component of PID-related astroglial calcium signals, but whether external calcium influx through membrane-localized channels also contributes to PIDs has remained unclear. In this study, we investigated the role of two astroglial membrane channels, transient receptor vanilloid 4 (TRPV4) channel and aquaporin-4 (AQP4). We combined in vivo multiphoton microscopy, electrophysiology as well as laser speckle contrast imaging with the middle cerebral artery occlusion stroke model. Using knockout mice and pharmacological inhibitors, we found that TRPV4 channels contribute to calcium influx into astrocytes and neurons and subsequent extracellular glutamate accumulation during PIDs. AQP4 neither influenced PID-related calcium signals nor PID-related edema of astrocyte somata. Both channels did not alter the dynamics, frequency and cerebrovascular response of PIDs in the penumbra. These data indicate that TRPV4 channels may represent a potential target to ameliorate the PID-induced calcium overload of astrocytes and neurons during acute stroke.

TRPV1 gene polymorphisms in patients with diabetes compared with healthy individuals

Type 1 diabetes is an autoimmune disease that is caused by pancreatic islet inflammation. Various studies on non-obese diabetic mice have shown associations between transient receptor vanilloid type-1 (TRPV1) gene polymorphism in pancreatic sensory neurons and the incidence of insulitis and insulin resistance. Inhibition of these neurons improves insulitis and prevents the onset of autoimmune diabetes. The aim of this study was to investigate the genetic variation of TRPV1 gene in type 1 diabetic patients and healthy controls. The genotypes of three single nucleotide polymorphisms (SNPs) of the TRPV1 gene (rs222749, rs222447, and rs224534) were investigated in 50 patients with type 1 diabetes and 50 healthy controls using PCR-restriction fragment length polymorphism analysis and DNA sequencing. Then, the frequencies of TRPV1 gene variants were compared between patient and control groups. The results showed that there was no significant difference in allele frequency of the three TRPV1 gene SNPs between patients with type 1 diabetes and healthy controls. Likewise, distribution of genotypes did not significantly differ between patients and controls. In this study, no significant association was found between TRPV1 gene polymorphisms and the presence of type 1 diabetes.

Endovanilloid control of pain modulation by the rostroventromedial medulla in an animal model of diabetic neuropathy

The involvement of transient receptor vanilloid type-1 (TRPV1) channels in pain modulation by the brain remains understudied. The rostroventromedial medulla (RVM) plays a key role in conveying to the spinal cord pain modulatory influences triggered in higher brain centres, with co-existence of inhibitory (antinociceptive) and facilitatory (pronociceptive) effects. In spite of some reports of TRPV1 expression in the RVM, it remains unknown if endovanilloid signalling plays a direct role in local pain modulation. Here we used a model of diabetic neuropathy, the streptozotocin (STZ)-diabetic rat, to study the role of endovanilloid signalling in RVM-mediated pain modulation during chronic pain. Four weeks after diabetes induction, the levels of TRPV1 mRNA and fatty acid amide hydrolase (FAAH), a crucial enzyme for endovanilloid catabolism, in the RVM of STZ-diabetic rats were higher than control. The RVM of STZ-diabetic rats presented decreased levels of several TRPV1 endogenous ligands, namely anandamide (AEA), palmitoylethanolamide (PEA) and oleoylethanolamide (OEA). Administration of capsaicin (a TRPV1 agonist) into the RVM decreased nociceptive behavioural responses in the inflammatory phase of the formalin test (phase 2). These findings suggest that diabetic neuropathy induces plastic changes of RVM endovanilloid signalling, indicating that TRPV1 may be a putative target for pain modulation in this chronic pain condition.