Showing papers on "TRPV published in 2017"

TRP Channel Classification.

Abstract: The transient receptor potential (TRP) ion channels are named after the discovery of the photo-transducted channels in Drosophila. TRPs, activated by various extracellular and intracellular stimuli, play a plethora of physiological and pathological roles. There are seven families of TRPs including TRPC (canonical), TRPV (vanilloid), TRPM (melastatin), TRPA (ankyrin), TRPP (polycystin), TRPML (mucolipin), and TRPN (Drosophila NOMPC) in mammals. In yeast, the eighth TRP family was recently identified and named as TRPY. We here briefly summarize the classification and function of TRP cation channel superfamily.

Temperature-activated ion channels in neural crest cells confer maternal fever-associated birth defects.

Abstract: Birth defects of the heart and face are common, and most have no known genetic cause, suggesting a role for environmental factors. Maternal fever during the first trimester is an environmental risk factor linked to these defects. Neural crest cells are precursor populations essential to the development of both at-risk tissues. We report that two heat-activated transient receptor potential (TRP) ion channels, TRPV1 and TRPV4, were present in neural crest cells during critical windows of heart and face development. TRPV1 antagonists protected against the development of hyperthermia-induced defects in chick embryos. Treatment with chemical agonists of TRPV1 or TRPV4 replicated hyperthermia-induced birth defects in chick and zebrafish embryos. To test whether transient TRPV channel permeability in neural crest cells was sufficient to induce these defects, we engineered iron-binding modifications to TRPV1 and TRPV4 that enabled remote and noninvasive activation of these channels in specific cellular locations and at specific developmental times in chick embryos with radio-frequency electromagnetic fields. Transient stimulation of radio frequency-controlled TRP channels in neural crest cells replicated fever-associated defects in developing chick embryos. Our data provide a previously undescribed mechanism for congenital defects, whereby hyperthermia activates ion channels that negatively affect fetal development.

Versatile Roles of Intracellularly Located TRPV1 Channel.

Abstract: The ubiquitous expression in many organs throughout the body and the ability to respond to a wide variety of physical and chemical stimuli have brought transient receptor potential (TRP) channels to the vanguards of our sensory systems. TRP vanilloid-1 (TRPV1) is the founding member of the TRPV subfamily. TRPV1 can be activated by noxious heat, protons, and vanilloids. Previous studies have shown that TRPV1 is located on the plasma membrane, serving to non-selectively permeate calcium ion from the extracellular region to the cytoplasm. Interestingly, increasing evidence suggests that TRPV1 is also located intracellularly in various cell types such as neurons, myocytes, and numerous cancer cells. By immunocytochemistry and/or fractionation followed by Western blotting, TRPV1 was found to express on the endoplasmic reticulum/sarcoplasmic reticulum and the mitochondria. By using various pharmacological and molecular tools, intracellular TRPV1 was also found to functionally express to control calcium level both inside the organelles and in the cytoplasm. Recent studies have shown that intracellularly located TRPV1 serves versatile functions in various physiological and pathological conditions (e.g., exercise endurance and hypertrophy). In this review, we not only have summarized the well-characterized roles of TRPV1, but also have highlighted the increasing importance of intracellular TRPV1-mediated pathways. Lastly, we have pointed out future research direction for answering several important questions that have remained unanswered. Vigorous investigation of the emerging roles of intracellular TRPV1 can allow a better understanding of how TRPV1 controls the cellular calcium homeostasis and its role in various physiological and pathophysiological conditions. J. Cell. Physiol. 232: 1957-1965, 2017. © 2016 Wiley Periodicals, Inc.

TRP Channels and Pain

Abstract: Pain is one of the primary responses developed by our body to protect us from harm. However, there are numerous pathological conditions, such as diabetes, viral infections, nerve damage, and inflammation that produce persistent pain. Chronic pain has no apparent useful purpose and is, in most cases, refractory to current pharmacological treatments.Following the onset of a painful peripheral stimulus, nociceptive neurons are activated to initiate a cascade of action potentials that propagate along the axons of the primary afferent fibers (C and Aδ fibers) to the nerve terminals found in laminae I and II of the dorsal horn in the spinal cord (Figure 8.1a). These nerve terminals release neurotransmitters such as glutamate, substance P, and calcitonin gene-related peptide (CGRP) to activate postsynaptic receptors located in spinothalamic tract neurons (Boadas-Vaello et al., 2016). The projections that reach the thalamus function in pain perception (Figure 8.1b). A variety of receptors and ion channels propagate and process pain signals.Nociceptive neurons send signals from the periphery, through the afferent fibers, to the visceral, trigeminal, and somatic regions, and also connect the spinal cord to the brain, thus serving as mediators in painful stimulus transmission between the central and peripheral nervous systems (CNS and PNS) (Figure 8.1a). These neurons express a wide variety of receptors and ion channels that are distributed along the fibers and the somas. These are the molecules that detect noxious stimuli, transforming them into electrical signals and directing them to the CNS (Dubin and Patapoutian, 2010). The most important ion channel family that detects and transmits noxious stimuli is the transient receptor potential (TRP) channel family. This family contains proteins that are conserved nonselective calcium-permeable channels (Julius, 2013). In general, TRP channels act as molecular sensors of multiple stimuli, ranging from changes in pH, chemical agents, temperature, and osmolarity. The TRP family of ion channels is composed of 28 members divided into six subfamilies, classified as canonical (TRPC), vanilloid (TRPV), ankyrin (TRPA), melastatin (TRPM), polycystin (TRPP), and mucolipin (TRPML) (Wu et al., 2010).The TRP channel structure varies considerably; however, there are certain shared domains that allow them to be grouped into the six subfamilies mentioned above. TRP channels consist of four subunits, each containing six transmembrane segments (S1–S6). A hydrophilic loop between the S5 and S6 forms the ion-conducting pore. The amino acids located before the pore confer channel selectivity. These channels are nonselective for cations but have preference for calcium (Owsianik et al., 2006b).The most highly variable regions within the TRP channel sequences are the carboxyl and amino terminal ends. The ankyrin repeat is located at the amino terminus of the TRPC, TRPA, and TRPV subfamilies. The TRP box, which is a conserved six amino acid sequence found in the TRPC, TRPM, TRPA, and TRPV subfamilies, is located at the carboxyl end, and several studies have shown that the TRP box is important for channel gating (Valente et al., 2008). In addition to the ankyrin repeat and TRP box domains, TRP family members contain other domains, including the EF-hand, PDZ, or NUDIX domains. These domains are distributed among various TRP family members (Owsianik et al., 2006a). Because of their diversity in domain structures, TRP channels are able to respond to a wide variety of stimuli and form complexes with multiple proteins involved in different cellular processes. The ability to respond to different stimuli has positioned the TRP channels as the primary channels responsible for nociception in physiological and pathophysiological conditions such as chronic pain. In this chapter, we summarize the most relevant findings related to the TRPA, TRPM, and TRPV subfamilies in nociception and their importance in pain development and maintenance.

TRP Channels in the Brain: What Are They There For?

Abstract: Transient receptor potential (TRP) family proteins form tetrameric nonselective cation channels. Upon activation, TRP channels depolarize the membrane potential, which can lead to activation or inactivation of voltage-gated ion channels, and regulate Ca2+ signaling, which controls diverse cellular functions (Wu et al., 2010; Nilius and Szallasi, 2014). It is well known that some members of the TRP canonical (TRPC), TRP melastatin (TRPM), and TRP vanilloid (TRPV) subfamilies of TRP channels are highly expressed and play important roles in the brain (Vennekens et al., 2012; Nilius and Szallasi, 2014). They regulate diverse neuronal and glial functions including developmental and homeostatic functions of the brain. Recent studies show that dysregulation of the TRP channel functions is involved in various pathological events of neurological and psychiatric disorders. Here, we review the current insights of the physiological roles of the TRPC, TRPM, and TRPV channels, mainly TRPC3/TRPC6/TRPC7, TRPM2, and TRPV1 in neurons and glia, and their pathophysiological roles in neurological and psychiatric disorders.

Insect TRP channels as targets for insecticides and repellents

Abstract: This review provides a brief overview of ion channels, then focuses on TRP channels, describing the properties and functions of the seven TRP channel classes found in insects. Finally, recent work showing that a heteromeric channel composed of Nanchung and Inactive vanilloid TRP (TRPV) channel subunits is the target of the selective feeding blockers pymetrozine and pyrifluquinazon is described. The possible utility of other TRP channels as targets of insecticides and repellents is also considered.

Enhancement of immune cytokines and splenic CD4+ T cells by electroacupuncture at ST36 acupoint of SD rats.

Abstract: Electroacupuncture at the ST36 acupoint can enhance the body’s immune function. However, the mechanism for this enhancement has not been fully described. Our study was designed to investigate the effect of electroacupuncture on the immune function of Sprague-Dawley (SD) rats. The rats were randomly divided into three groups: a control group, a non-acupoint group (abdominal muscle acupuntured) and a ST36 acupoint group. Our results showed that successive electroacupuncture at the ST36 acupoint for 3 d significantly enhanced the interferon-γ (IFN-γ) level in the serum of SD rats. The results also showed that the serum and extracts from spleen cells of the ST36 acupoint group contained higher levels of interleukin (IL)-2 and IL-17 compared to those of the other two groups. Immunohistochemical analysis showed that electroacupuncture applied to the ST36 acupoint enhanced the expression level of CD4 in spleen cells. Furthermore, it was observed that CD4 co-localized with transient receptor potential vanilloid (TRPV) channels at the membrane of splenic CD4+ T cells and the expression level of CD4 was related to TRPV channels in the electroacupuncture treatment. These observations indicated that electroacupuncture stimulation at the ST36 acupoint enhanced the level of immune cytokines and splenic CD4+ T cells through TRPV channels in this system.

TRPV4 heats up ANO1-dependent exocrine gland fluid secretion.

Abstract: Several ion channels and transporters regulate fluid secretion in salivary and lacrimal glands. In salivary glands, the major anion channel involved in fluid secretion is the calcium-activated chloride channel anoctamin 1 (ANO1). Several members of the transient receptor potential (TRP) channel superfamily regulate ANO1 activity. Here, we report a functional interaction between thermosensitive TRP vanilloid (TRPV)4 and ANO1 in acinar cells isolated from mouse salivary and lacrimal glands. TRPV4 activation induced chloride currents and shrinkage of acinar cells by increasing intracellular calcium concentrations. The chloride currents evoked by a TRPV4-specific activator (GSK1016790A) were identified as ANO1-mediated currents. Moreover, TRPV4 activation by an inositol 1,4,5-trisphosphate (IP3)-dependent mechanism was found to contribute to the muscarinic pathway of fluid secretion. Muscarinic stimulation of saliva and tear secretion was down-regulated in both TRPV4-deficient mice and in acinar cells treated with a TRPV4-specific antagonist (HC-067047). Furthermore, the temperature dependence of muscarinic salivation was shown to depend mainly on TRPV4. Our results suggest that TRPV4 interacts with IP3 receptors and ANO1 to regulate the muscarinic pathway that mediates salivation and lacrimation.-Derouiche, S., Takayama, Y., Murakami, M., Tominaga, M. TRPV4 heats up ANO1-dependent exocrine gland fluid secretion.

Neurovascular microcirculatory vasodilation mediated by C-fibers and Transient receptor potential vanilloid-type-1 channels (TRPV 1) is impaired in type 1 diabetes

Abstract: Microvascular dysfunction may have an early onset in type 1 diabetes (T1D) and can precede major complications. Our objectives were to assess the endothelial-dependent (acetylcholine, ACh; and post-occlusive hyperemia, PORH), non-endothelial-dependent (sodium nitroprusside, SNP) and neurovascular-dependent (local heating, LH and current induced vasodilation, CIV) microcirculatory vasodilation in T1D patients compared with matched control subjects using a laser speckle contrast imager. Seventeen T1D patients - matched with 17 subjects according to age, gender, Body-Mass-Index, and smoking status - underwent macro- and microvascular investigations. The LH early peak assessed the transient receptor potential vanilloid type 1 channels (TRPV1) mediated vasodilation, whereas the plateau assessed the Nitirc-Oxyde (NO) and endothelium-derived hyperpolarizing factor (EDHF) pathways. PORH explored sensory nerves and (EDHF), while CIV assessed sensory nerves (C-fibers) and prostaglandin-mediated vasodilation. Using neurological investigations, we observed that C-fiber and A-delta fiber functions in T1D patients were similar to control subjects. PORH, CIV, LH peak and plateau vasodilations were significantly decreased in T1D patients compared to controls, whereas there was no difference between the two groups for ACh and SNP vasodilations. Neurovascular microcirculatory vasodilations (C-fibers and TRPV 1-mediated vasodilations) are impaired in TD1 patients whereas no abnormalities were found using clinical neurological investigations. Clinicaltrials: No. NCT02538120.

Analysis of TRPV channel activation by stimulation of FCεRI and MRGPR receptors in mouse peritoneal mast cells

Abstract: The activation of mast cells (MC) is part of the innate and adaptive immune responses and depends on Ca2+ entry across the plasma membrane, leading to the release of preformed inflammatory mediators by degranulation or by de novo synthesis. The calcium conducting channels of the TRPV family, known by their thermo and osmotic sensitivity, have been proposed to be involved in the MC activation in murine, rat, and human mast cell models. So far, immortalized mast cell lines and nonspecific TRPV blockers have been employed to characterize the role of TRPV channels in MC. The aim of this work was to elucidate the physiological role of TRPV channels by using primary peritoneal mast cells (PMCs), a model of connective tissue type mast cells. Our RT-PCR and NanoString analysis identified the expression of TRPV1, TRPV2, and TRPV4 channels in PMCs. For determination of the functional role of the expressed TRPV channels we performed measurements of intracellular free Ca2+ concentrations and beta-hexosaminidase release in PMCs obtained from wild type and mice deficient for corresponding TRPV1, TRPV2 and TRPV4 in response to various receptor-mediated and physical stimuli. Furthermore, substances known as activators of corresponding TRPV-channels were also tested using these assays. Our results demonstrate that TRPV1, TRPV2, and TRPV4 do not participate in activation pathways triggered by activation of the high-affinity receptors for IgE (FceRI), Mrgprb2 receptor, or Endothelin-1 receptor nor by heat or osmotic stimulation in mouse PMCs.

Interactions of the Mechanosensitive Channels with Extracellular Matrix, Integrins, and Cytoskeletal Network in Osmosensation.

Abstract: Life is maintained in a sea water-like internal environment. The homeostasis of this environment is dependent on osmosensory system translation of hydromineral information into osmotic regulatory machinery at system, tissue, and cell levels. In the osmosensation, hydromineral information can be converted into cellular reactions through osmoreceptors, which changes thirst and drinking, secretion of antidiuretic vasopressin (VP), reabsorption of water and salt in the kidneys at systemic level as well as cellular metabolic activity and survival status at tissue level. The key feature of osmosensation is the activation of mechanoreceptors or mechanosensors, particularly transient receptor potential vallinoid (TRPV) and canonical (TRPC) family channels, which increases cytosolic Ca2+ levels and activation of osmosensory cells including VP neurons and triggers a series of secondary reactions. TRPV channels are sensitive to both hyperosmotic and hyposmotic stimuli while TRPC channels are more sensitive to hyposmotic challenge in neurons. The activation of TRP channels relies on changes in cell volume, membrane stretch, and cytoskeletal reorganization as well as hydration status of extracellular matrix, activity of integrins; different families of TRP channels could be activated differently in response to hyperosmotic and hyposmotic stimuli in different spatiotemporal orders, leading to differential reactions of osmosensory cells. Together, they constitute the osmosensory machinery. The activation of this osmoreceptor complex is also associated with the activity of other osmolarity-regulating organelles, such as water channel protein aquaporins, Na-K-2Cl cotransporters, volume-sensitive anion channels, sodium pump and purinergic receptors in addition to intercellular interactions, typically the astrocytic neuronal interaction. In this paper, we review our current understandings of the composition of osmoreceptors and the processes of osmosensation.

Stretch-activated TRPV2 channels: Role in mediating cardiopathies

Abstract: Transient receptor potential vanilloid type 2, TRPV2, is a calcium-permeable cation channel belonging to the TRPV channel family. Although this channel has been first characterized as a noxious heat sensor, its mechanosensor property recently gained importance in various physiological functions. TRPV2 has been described as a stretch-mediated channel and a regulator of calcium homeostasis in several cell types and has been shown to be involved in the stretch-dependent responses in cardiomyocytes. Hence, several studies in the last years support the idea that TRPV2 play a key role in the function and structure of the heart, being involved in the cardiac compensatory mechanisms in response to pathologic or exercise-induced stress. We present here an overview of the current literature and concepts of TRPV2 channels involvement (i) in the mechanical coupling mechanisms in heart and (ii) in the mechanisms that lead to cardiomyopathies. All these studies lead us to think that TRPV2 may also be an important cardiac drug target based on its major physiological roles in heart.

Expression and distribution of three transient receptor potential vanilloid(TRPV) channel proteins in human odontoblast-like cells

Abstract: Odontoblasts have been suggested to contribute to nociceptive sensation in the tooth via expression of the transient receptor potential (TRP) channels. The TRP channels as a family of nonselective cation permeable channels play an important role in sensory transduction of human. In this study, we examined the expression of transient receptor potential vanilloid-1 (TRPV1), transient receptor potential vanilloid-2 (TRPV2) and transient receptor potential vanilloid-3 (TRPV3) channels in native human odontoblasts (HODs) and long-term cultured human dental pulp cells with odontoblast phenotyoe (LHOPs) obtained from healthy wisdom teeth with the use of immunohistochemistry (IHC), immunofluorescence (IF), quantitative real-time polymerase chain reaction (qRT-PCR),western blotting (WB) and immunoelectron microscopy (IEM) assay. LHOPs samples were made into ultrathin sections, mounted on nickel grids, floated of three TRPV antibodies conjugated with 10 nm colloidal gold particles and observed under IEM at 60,000 magnifications. The relative intracellular distributions of these three channels were analyzed quantitatively on IEM images using a robust sampling, stereological estimation and statistical evaluation method. The results of IHC and IF convinced that TRPV1, TRPV2 and TRPV3 channels were expressed in native HODs and (LHOPs). The result of qRT-PCR and WB confirmed that the gene and protein expression of TRPV1, TRPV2, and TRPV3 channels and TRPV1 mRNA are more abundantly expressed than TRPV2 and TRPV3 in HODs (P < 0.05). Quantitative analysis of IEM images showed that the relative intracellular distributions of these three channels are similar, and TRPV1, TRPV2 and TRPV3 proteins were preferential labeled in human odontoblast processes, mitochondria, and endoplasmic reticulum. Thus, HODs could play an important role in mediating pulp thermo-sensation due to the expression of these three TRPV channels. The difference of relative intracellular distributions of three channels suggests that special structures such as processes may have an important role to sensing of the outer stimuli first.

Regulation of chondrocyte functions by transient receptor potential cation channel V6 in osteoarthritis.

Abstract: Transient receptor potential vanilloid (TRPV) channels function to maintain the dynamic balance of calcium signaling and calcium metabolism in bones. The goal of this study was to determine the potential role of TRPV6 in regulation of chondrocytes. The level of TRPV6 expression was analyzed by western blot in articular cartilage derived from the knee joints of osteoarthritis (OA) rat models and OA patients. Bone structure and osteoarthritic changes in the knee joints of TRPV6 knockout mice were examined using micro-computed and histological analysis at the age of 6 and 12 months old. Furthermore, to investigate the effects of TRPV6 on chondrocyte extracellular matrix secretion, the release of matrix degrading enzymes, cell proliferation, and apoptosis, we decreased and increased TRPV6 expression in chondrocytes with lentiviral constructs encoding shRNA targeting TRPV6 and encoding TRPV6, respectively. The results showed that the level of TRPV6 expression in an OA rat model was markedly down-regulated. TRPV6 knockout mice showed severe osteoarthritis changes, including cartilage fibrillation, eburnation, and loss of proteoglycans. In addition, deficiency of TRPV6 clearly affected chondrocyte function, such as extracellular matrix secretion, the release of matrix degrading enzymes, cell proliferation, and apoptosis. Taken together, our results implicated that TRPV6 channel, as a chondro-protective factor, was involved in the pathogenesis of OA.

Exploring the Role of TRPV and CGRP in Adenosine Preconditioning and Remote Hind Limb Preconditioning-Induced Cardioprotection in Rats.

Abstract: The cardioprotective effects of remote hind limb preconditioning (RIPC) are well known, but mechanisms by which protection occurs still remain to be explored. Therefore, the present study was designed to investigate the role of TRPV and CGRP in adenosine and remote preconditioning-induced cardioprotection, using sumatriptan, a CGRP release inhibitor and ruthenium red, a TRPV inhibitor, in rats. For remote preconditioning, a pressure cuff was tied around the hind limb of the rat and was inflated with air up to 150 mmHg to produce ischemia in the hind limb and during reperfusion pressure was released. Four cycles of ischemia and reperfusion, each consisting of 5 min of inflation and 5 min of deflation of pressure cuff were used to produce remote limb preconditioning. An ex vivo Langendorff's isolated rat heart model was used to induce ischemia reperfusion injury by 30 min of global ischemia followed by 120 min of reperfusion. RIPC demonstrated a significant decrease in ischemia reperfusion-induced significant myocardial injury in terms of increase in LDH, CK, infarct size and decrease in LVDP, +dp/dtmax and -dp/dtmin. Moreover, pharmacological preconditioning with adenosine produced cardioprotective effects in a similar manner to RIPC. Pretreatment with sumatriptan, a CGRP release blocker, abolished RIPC and adenosine preconditioning-induced cardioprotective effects. Administration of ruthenium red, a TRPV inhibitor, also abolished adenosine preconditioning-induced cardioprotection. It may be proposed that the cardioprotective effects of adenosine and remote preconditioning are possibly mediated through activation of a TRPV channels and consequent, release of CGRP.

TRP Channels : What Do They Look Like?

Abstract: The first transient receptor potential (TRP) ion channel was identified as a Drosophila locus that gave rise to a phenotype in which the photoreceptor light response decayed to baseline during prolonged illumination (Cosens and Manning, 1969; Minke et al., 1975). The identification of the TRP fly in 1969 and the molecular identification of the trp gene in 1975 set the stage for the subsequent explosion of discoveries that continue even today.The mid-1990s through the early 2000s were a particularly productive time for identification of many new TRP subfamilies and subfamily members. This is apparent from the rapid increase in the number of publications on TRP channels listed in PubMed (Figure 1.1); once many new TRP channels were identified, work on understanding their physiology progressed rapidly. Six subfamilies of TRP channels have now been identified in mammals, with an additional subfamily found in invertebrates and nonmammalian vertebrate animals (Figure 1.1, right panel). Because of diverse nomenclature for any given TRP channel, only the characters used to describe each column in Figure 1.1 were used as search terms. Although this approach clearly underestimates the work on all TRP channels, it likely underestimates those TRP channels with primarily clinical publications more than others.TRP channels are members of the voltage-gated superfamily of ion channels that includes the voltage gated K+, Na+, and Ca2+ channels as well as related cyclic nucleotide-gated channels. They form as tetramers of identical subunits (Figure 1.2), although heterotetramers of TRP channel subunits have been reported (reviewed in Cheng et al., 2010). Like other members of the voltage-gated superfamily, each subunit includes six membrane-spanning helices with a reentrant pore loop between the fifth and six transmembrane helices, and intracellular amino- and carboxy-terminali. The first four transmembrane segments (Figure 1.2, blue) form the voltage-sensing or voltage-sensing-like domain. The remaining two transmembrane segments, along with the reentrant pore loop (Figure 1.2, yellow), form the ion-conducting pore of the channel.Although some TRP channels (e.g., TRPM8) show voltage-dependent activation (Voets et al., 2007); others show little or no voltage-dependent gating (e.g., TRPV1) (Liu et al., 2009). This variability in function is likely due to variability in the amino acid sequence in the fourth transmembrane helix, which for voltage-gated channels includes a number of positively charged residues and for voltage-independent channels does not (Figure 1.3). It is worth noting that the macroscopic current-voltage relationship of TRPV1 shows significant outward rectification. However, this is due almost exclusively to rectification in the unitary conductance (Liu et al., 2009).A hallmark of many TRP channels is the TRP domain following the sixth transmembrane helix (Figures 1.2 (purple) and 1.4). This can be recognized based on primary sequence in TRPC, TRPM, and TRPV channels. Although it was not obvious from the primary sequence of TRPA1 channels that they included a TRP domain, structural homology in this region was revealed by the recent cryoEM structures of TRPV1 (Liao et al., 2013) and TRPA1 (Paulsen et al., 2015) and is shown in Figure 1.2. The TRP domain consists of an alpha helical segment parallel and in close proximity to the plasma membrane. Although a definitive function for the TRP domain has not been established, it is positioned well to interact with both the membrane and the amino-terminal region.Three TRP subfamilies, TRPC, TRPV, and TRPA, have amino-terminal ankyrin repeat domains of varying lengths (Figures 1.2 and 1.5). TRPA1's domain is the longest, although we do not yet know how many ankyrin repeats may be present in TRPA1 channels—only that it is a large number. The function of these domains is not fully understood, but in some channels this structural element appears to influence gating. For example, in TRPV1 the ankyrin repeats contain a reactive cysteine that promotes channel opening (Salazar et al., 2008), and the region has been proposed to be a functionally important binding site for ATP (Lishko et al., 2007) and calmodulin (Rosenbaum et al., 2004).The TRP channel superfamily can be subdivided into seven separate subfamilies: TRPA, TRPC, TRPM, TRPML, TRPN, TRPP, and TRPV. The individual subunits of all seven subfamilies’ members are thought to contain six transmembrane segments that assemble as tetramers to form functional TRP channels (Figure 1.2). However, the tissue distribution, function, and even in which species each subfamily can be found vary wildly (Figure 1.6), representing the myriad roles that TRP channels play in neurobiology.

Immunolocalization of cannabinoid receptor type 1 and CB2 cannabinoid receptors, and transient receptor potential vanilloid channels in pterygium

Abstract: Cannabinoids, as multi‑target mediators, activate cannabinoid receptors and transient receptor potential vanilloid (TRPV) channels. There is evidence to support a functional interaction of cannabinoid receptors and TRPV channels when they are coexpressed. Human conjunctiva demonstrates widespread cannabinoid receptor type 1 (CB1), CB2 and TRPV channel localization. The aim of the present study was to investigate the expression profile for cannabinoid receptors (CB1 and CB2) and TRPV channels in pterygium, an ocular surface lesion originating from the conjunctiva. Semi‑serial paraffin‑embedded sections from primary and recurrent pterygium samples were immunohistochemically examined with the use of specific antibodies. All of the epithelial layers in 94, 78, 96, 73 and 80% of pterygia cases, exhibited CB1, CB2, TRPV1, TRPV2 and TRPV3 cytoplasmic immunoreactivity, respectively. The epithelium of all pterygia cases (100%) showed strong, mainly nuclear, TRPV4 immunolocalization. In the pterygium stroma, scattered cells demonstrated intense CB2 immunoreactivity, whereas vascular endothelial cells were immunopositive for the cannabinoid receptors and all TRPV channels. Quantitative analyses of the immunohistochemical findings in epithelial cells demonstrated a significantly higher expression level in conjunctiva compared with primary pterygia (P=0.04) for CB1, but not for CB2 (P>0.05). Additionally, CB1 and CB2 were significantly highly expressed in primary pterygia (P=0.01), compared with recurrent pterygia. Furthermore, CB1 expression levels were significantly correlated with CB2 expression levels in primary pterygia (P=0.005), but not in recurrent pterygia (P>0.05). No significant difference was detected for all TRPV channel expression levels between pterygium (primary or recurrent) and conjunctival tissues (P>0.05). A significant correlation between the TRPV1 and TRPV3 expression levels (P<0.001) was detected independently of pterygium recurrence. Finally, TRPV channel expression was identified to be significantly higher than the expression level of cannabinoid receptors in the pterygium samples (P<0.001). The differentiated expression of cannabinoid receptors in combination with the presence of TRPV channels, in primary and recurrent pterygia, imply a potential role of these cannabinoid targets in the underlying mechanisms of pterygium.

Human podocytes express functional thermosensitive TRPV channels.

Abstract: BACKGROUND AND PURPOSE Heat sensitive transient receptor potential vanilloid (TRPV) channels are expressed in various epithelial tissues regulating, among else, barrier functions. Their expression is well established in the distal nephron; however, we have no data about their presence in podocytes. Since podocytes are indispensable in the formation of the glomerular filtration barrier, we investigated the presence and function of Ca2+-permeable TRPV1-4 channels in human podocyte cultures. EXPERIMENTAL APPROACH The expression of TRPV1-4 was investigated at protein (immunocytochemistry, western blot) and mRNA (Q-PCR) level in a conditionally immortalized human podocyte cell line. The channel functionality was assessed by measuring intracellular Ca2+ concentration using fluo-4 Ca2+-indicator dye and patch clamp electrophysiology upon applying various activators and inhibitors. KEY RESULTS Thermosensitive TRP channels were expressed in podocytes. The TRPV1 specific agonists capsaicin and resiniferatoxin did not induce any alteration in the intracellular Ca2+ concentration. Cannabidiol, an activator of TRPV2 and TRPV4 induced moderate Ca2+-influxes which were inhibited by both tranilast and HC067047, blockers of TRPV2 and TRPV4, respectively. The TRPV4-specific agonists GSK1016790A and 4α-Phorbol 12,13-didecanoate resulted robust Ca2+-signals which were abolished in the presence of HC067047. Non-specific agonists of TRPV3 induced marked Ca2+ transients. However, TRPV3 blockers, ruthenium red and isopentenyl diphosphate only partially inhibited the responses and TRPV3 silencing was ineffective suggesting remarkable off-target effects of the compounds. CONCLUSION AND IMPLICATIONS Our results indicate the functional presence of TRPV4 and other thermosensitive TRPV channels in human podocytes and raise the possibility of their involvement in the regulation of glomerular filtration barrier.

A Critical Role for TRP Channels in the Skin

Abstract: The transient receptor potential (TRP) channels were first described in Drosophila, in which photoreceptors carrying trp gene mutations exhibited a transient voltage response to continuous light stimulation (Minke, 1977; Montell et al., 1985). Mammalian TRP channels have six subfamilies including TRPC, TRPV, TRPM, TRPA, TRPML, and TRPP (Clapham, 2003), with about 28 mammalian subfamily members, most of which have splicing variants. All TRP channels have six transmembrane domains with the N- and C-terminal regions located inside the cell and are assembled as tetramers to form nonselective cation-permeable pores (Liao et al., 2014). TRP channels are expressed in a wide variety of tissues, and they are commonly embedded either in the membrane surface or cytosolic organelles, such as endosomes and lysosomes. Activation of TRP channels generally promotes excitability of excitable cells and Ca2+ influx in many forms of cellular processes in both excitable and nonexcitable cells.The skin is divided into three layers: (1) The epidermis, the outermost layer of skin, provides a waterproof barrier and creates the skin tone. Although the most abundant cells of the epidermis are keratinocytes, there are also nonepithelial immune cells present in the epidermis, such as Langerhans cells and dendritic epidermal T cells (DETCs). (2) The dermis, directly under the epidermis, contains tough connective tissue, hair follicles (HFs), and sweat glands. The dermis also hosts different subtypes of T cells that recirculate through skin-draining lymph nodes and are involved in normal immunity as well as inflammatory skin diseases such as psoriasis (Bos et al., 1987; Streilein, 1983). In addition to T cells, the dermis is enriched with tissue macrophages and dendritic cells that originate from the yolk sac and self-renew within the skin under inflammatory conditions (Jenkins, 2011). Together with cutaneous innate immune cells, the circulating monocytes traffic through the skin to survey the environment and transport antigens to the draining lymph nodes (Jakubzick et al., 2013). (3) The deeper subcutaneous tissue (hypodermis) is made of fat and connective tissue.In the skin, TRP channels are not only expressed in sensory nerve endings but also in many nonneuronal cell populations including keratinocytes and skin-resident immune cells (Figure 6.1). Various TRP channels participate in the formation and maintenance of skin barrier, HF growth, and cutaneous immunological and inflammatory processes, thereby maintaining skin homeostasis as well as contributing to many types of skin disorders (Figure 6.2). More importantly, several skin-expressing TRP channels act as the first-order sensors of temperature, mechanical, and chemical stimuli and mediate our senses of temperature, touch, itch, and pain under both physiological and pathological conditions.

Effect of Nanodiamond and Nanoplatinum Liquid, DPV576, on Human Primary Keratinocytes.

Abstract: Nanofabrics are now being used in a wide range of products that come into direct contact with skin, including carpet, clothing, and medical fabrics. In the current study, we examined the effect of a dispersed aqueous mixture of nanodiamond (ND) and nanoplatinum (NP) (DPV576) on human primary keratinocytes with respect to transient receptor potential vanilloid (TRPV) channel expression, secretion of cytokines and production of nerve growth factor (NGF). Keratinocytes were treated with DPV576 at concentrations of 1:10 and 1:100 dilutions for 24 hours in vitro, and their activation of was determined by production of cytokines TNF-α, IL-1β, and prostaglandin (PGE2), and by production of NGF. Inhibitor experiments were carried out by incubating keratinocytes with the TRPV4-selective antagonist HC-067047. TRPV receptor expression (TRPV1, TRPV3 and TRPV4) on keratinocytes as well as changes in Ca2+ potential were examined by flow cytometry. DPV576 treatment of keratinocytes resulted in the following effects: (1) stimulation of keratinocytes as indicated by the significant secretion of cytokines IL-1β, TNF-α, and PGE2, an effect noted only at higher concentration (1:10); (2) significant decrease in the expression of TRPV4 on keratinocytes with a spike in the calcium flux, but no change in the expression of TRPV1 and TRPV3; (3) induction of cytokine secretion independent of TRPV4, as the addition of TRPV4 inhibitor had no significant effect on the cytokine production from keratinocytes; (4) induction of NGF secretion by keratinocytes. These results demonstrate that DPV576 activates keratinocytes via multiple signaling pathways which may reduce stress associated with inflammation, pain, and circadian rhythms. ND/NP-coated fabrics that target the modulation of local inflammation, pain, and circadian rhythms could potentially be of benefit to humans.

Fertility and TRP Channels

Abstract: Author(s): Bjorkgren, I; Lishko, PV | Abstract: Since their discovery in late 1970, transient receptor potential (TRP) channels have been implicated in a variety of cellular and physiological functions (Minke, 2010). The superfamily of TRP channels consists of nearly 30 members that are organized into seven major subgroups based on their specic function and sequence similarities (Owsianik et al., 2006; Ramsey et al., 2006). With the exception of TRPN channels that are only found in invertebrates and sh, mammalian genomes contain representatives of all six subfamilies: (1) TRPV (vanilloid); (2) TRPC (canonical); (3) TRPM (melastatin); (4) TRPA (ankyrin); (5) TRPML (mucolipin); and (6) TRPP (polycystin). TRP channels play crucial regulatory roles in many physiological processes, including those associated with reproductive tissues. As calcium-permeable cation channels that respond to a variety of signals (Clapham et al., 2003; Wu et al., 2010), TRP channels exert their role as sensory detectors in both male and female gametes, and play regulatory functions in germ cell development and maturation. Recent evidence obtained from Caenorhabditis elegans studies point to the importance of these proteins during fertilization where certain sperm TRP channels could migrate from a spermatozoon into an egg to ensure successful fertilization and embryo development. In this chapter we discuss how TRP channels can regulate both female and male fertility in different species and their specic roles.