TRPV1

Atopic dermatitis (AD) and psoriasis (Pso) are two common inflammatory skin diseases which are symptomatically characterized by pruritus to variable degrees. Whereas AD is nearly always associated with pruritus, only 50%-70% of patients with Pso suffer from itching. Within the last decade, the development of biologic agents targeting specific cytokines or cytokine receptors has led to tremendous progress in suppressing inflammation (and thus improving quality of life) in these two diseases. While suppressing inflammation would generally reduce pruritus in these inflammatory diseases, pruritus is still recalcitrant for treatment in some patients due to relative lack of therapeutics that specifically inhibit pruritus signaling. There is abundant evidence that certain cytokines and neuropeptides-ion channels signaling mediate pruritus that is independent of inflammation in AD and psoriasis. Of note, Janus kinase (JAK) and nerve growth factor (NGF)-tropomyosin receptor kinase A (TrkA)-transient receptor potential vanilloid 1 (TRPV1) signaling partially regulates pruritus in AD and psoriasis. JAK kinases inhibitors decrease the extent of itch in patients with AD and Pso. In clinical trials, topical inhibitors of TrkA and TRPV1 have been reported to reduce pruritus in patients with Pso and AD, respectively. In this article, we review recent literature knowledge regarding the mechanisms underlying pruritus in AD and Pso, providing hypotheses for why pruritus may be more common in AD than in Pso. In light of the different mechanisms underlying these two diseases, the current and developing therapeutics, either in human clinical trials or animal studies, for targeting pruritus are also discussed.

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 signaling, indicating that TRPV1 may be a putative target for pain modulation in this chronic pain condition.

Protein-protein interactions (PPIs) have emerged as important targets for pharmaceutical intervention because of their essential role in numerous physiological and pathological processes, but screening efforts using small-molecules have led to very low hit rates. Linear peptides could represent a quick and effective approach to discover initial PPI hits, particularly if they have inherent ability to adopt specific peptide secondary structures. Here, we address this hypothesis through a linear helical peptide library, composed of four sublibraries, which was designed by theoretical predictions of helicity (Agadir software). The 13-mer peptides of this collection fixes either a combination of three aromatic or two aromatic and one aliphatic residues on one face of the helix (Ac-SSEEX(5)ARNX(9)AAX(12)N-NH2), since these are structural features quite common at PPIs interfaces. The 81 designed peptides were conveniently synthesized by parallel solid-phase methodologies, and the tendency of some representative library components to adopt the intended secondary structure was corroborated through CD and NMR experiments. As proof of concept in the search for PPI modulators, the usefulness of this library was verified on the widely studied p53-MDM2 interaction and on the communication between VEGF and its receptor Flt-1, two PPIs for which a hydrophobic α-helix is essential for the interaction. We have demonstrated here that, in both cases, selected peptides from the library, containing the right hydrophobic sequence of the hot-spot in one of the protein partners, are able to interact with the complementary protein. Moreover, we have discover some new, quite potent inhibitors of the VEGF-Flt-1 interaction, just by replacing one of the aromatic residues of the initial F(5)Y(9)Y(12) peptide by W, in agreement with previous results on related antiangiogenic peptides. Finally, the HTS evaluation of the full collection on thermoTRPs has led to a few antagonists of TRPV1 and TRPA1 channels, which open new avenues on the way to innovative modulators of these channels.

Econazole is an anti-mycotic agent widely used for the treatment of cutaneous fungal infections, and for the therapy of vaginal candidiasis. Topical application of this azole is generally safe, although some patients have complained of mild burning sensation/cutaneous irritation and itching, especially when administered intravaginally. The underlying mechanisms responsible of these adverse effects are poorly understood, though they suggest excitation of cutaneous nociceptor terminals. We report that exposure of primary cultures of rat nociceptors to econazole augments neuronal excitability. This effect appears mediated by increments in the intracellular Ca2+ by stimulating Ca2+ entry and release from the endoplasmic reticulum. Ca2+ entry was not due to activation of thermo transient receptor potential (TRP) channels, suggesting a different ion channel targeted by the azole. Noteworthy, econazole-evoked responses were potentiated by a pro-inflammatory agent, which resulted in an increase in neuronal excitability. Econazole-elicited action potential firing was significantly abolished by the inflammatory cytokine inhibiting drug benzydamine via blockade of voltage-gated Na+ (Nav) channels. Collectively, our results indicate that the burning sensation of econazole is due at least in part to modulation of nociceptor excitability, and such sensation is increased in the presence of pro-inflammatory stimuli and blocked by benzydamine. These findings imply that a combination of the azole with benzydamine has the potential to reduce significantly the unpleasant symptoms related to infection and to the adverse effects of topical econazole formulations.

Abstract
Background

Surgeons, Native Americans and Eclectics have all sworn to the multiple healing properties including anthelmintic, analgesic, and anti-cancer effects that Dicentra Formosa possess. However, none of the above provided any scientifically proven data to conclude the healing properties of Dicentra Formosa as fact.
Purpose

Here, I’ve examined the analgesic effect of Dicentra Formosa in two pain models and also identified the molecular target for the analgesic effect of Dicentra.

Experimental approach

In the chronic pain model of carrageenan-induced inflammation and sciatic nerve ligation, I observed that the threshold for thermal and mechanical nociception was increased in Dicentra-treated mice compared to the vehicle-treated group. As TRP channels, especially TRPV1 and TRPA1 are known to play a crucial role in the hypersensitivity to thermal and mechanical stimuli, we proceeded to test the analgesic effect of Dicentra Formosa on TRPV1, TRPA1 channel activities; followed by Calcium imaging and Patch Clamp recordings.
Key Results

Calcium imaging and Patch Clamp recordings revealed Dicentra Formosa to have an antagonistic effect on the TRPA1 channel comparable to the known TRPA1 antagonist, HC-030031. However, Dicentra Formosa showed no inhibitory effect on the TRPV1 channel.
Conclusions & Implications

Therefore Dicentra Formosa shows a substantial analgesic effect in inflamed and neuropathic pain, which is presumably mediated by the inhibition of TRPA1 channel. These findings are the first scientific report for analgesic effect of Dicentra Formosa, which provides potential therapeutic promise of Dicentra Formosa for pain relief.

The vasopressin (AVP) and oxytocin (OXT) magnocellular neurons in the hypothalamic supraoptic (SON) and paraventricular nuclei (PVN) display reversible structural plasticity of neurons and glial cells under different conditions of neuropeptide secretion. In the present study, we investigated the expression of two immunoglobulin superfamily (IgSF) proteins, Kilon and OBCAM, in the magnocellular neurons by using monoclonal antibodies. Anti-Kilon antibody reacted specifically with the bacterially expressed recombinant Kilon but not with the recombinant OBCAM, and similarly anti-OBCAM antibody specifically recognized the recombinant OBCAM. Western blotting analysis revealed the specific expression of Kilon and OBCAM in the SON homogenates. Although Kilon and OBCAM of the SON homogenates were present as the insoluble form, most Kilon was present in the Triton-insoluble fraction, and OBCAM was localized mainly in the Triton-soluble fraction. Immunocytochemistry revealed Kilon and OBCAM immunoreactivity in the magnocellular neurons of the SON and PVN of the rat hypothalamus compared with outside of the SON and PVN in the hypothal-amus. The double-labeling study with confocal microscopy further demonstrated that Kilon immunoreactivity was observed mainly in the dendrites of AVP-secreting neurons and also occasionally OXT-secreting neurons. However, OBCAM immunoreactivity was exclusively seen in the dendrites of AVP-secreting magnocellular neurons. Chronic physiological stimulation by 2% NaCl had no effect on the expression levels of either IgLON protein in the SON. Our study thus demonstrated specific expression of Kilon and OBCAM in the hypothalamic magnocellular neurons, particularly in dendrites, suggesting that they confer on magno-cellular neurons the ability to rearrange dendritic connectivity.

It has been shown previously that rats treated as neonates with capsaicin exhibited hyperactivity in a novel environment and had brain changes, including reduced brain weight, reduced hippocampal area, reduced cortical thickness and increased neuronal density in several cortical areas. These brain changes resembled those found in subjects with schizophrenia. This mini review discusses recent findings on the effects of capsaicin on hippocampal neurons and the role of TRPV1 channels in the central nervous system, which provide a possible explanation for the effects of capsaicin on the developing rat brain. Future studies on the role of TRPV1 channels in the brain hold great promise for further understanding of neuropsychiatric disorders.

Paracetamol also known as acetaminophen, is a widely used analgesic and antipyretic agent. We report the synthesis and biological evaluation of adamantyl analogues of paracetamol with important analgesic properties. The mechanism of nociception of compound 6a/b, an analog of paracetamol, is not exerted through direct interaction with cannabinoid receptors, nor by inhibiting COX. It behaves as an interesting selective TRPA1 channel antagonist, which may be responsible for its analgesic properties, whereas it has no effect on the TRPM8 nor TRPV1 channels. The possibility of replacing a phenyl ring by an adamantyl ring opens new avenues in other fields of medicinal chemistry.

Transient receptor potential vanilloid 1 (TRPV1) mediates a novel form of presynaptic long-term depression (LTD) in hippocampal interneurons. To date, while TRPV1 is currently being heavily studied in the PNS for its anti-nociceptive and anti-inflammatory properties, much less is known regarding TRPV1 signaling and function in the CNS, including the mechanism mediating hippocampal interneuron LTD. Here we performed whole-cell voltage clamp electrophysiology experiments on CA1 hippocampal interneurons from Sprague-Dawley male rats to identify this signaling mechanism. Because calcineurin is linked to multiple synaptic plasticity types, we investigated whether TRPV1 activates presynaptic calcineurin, which in turn induces LTD. To do so we employed calcineurin inhibitors cyclosporin A or FK-506. To determine the location of the calcineurin involved we either bath applied calcineurin antagonists, blocking calcineurin activity ubiquitously in the slice, presynaptically and postsynaptically, or applied antagonists to the internal solution to block calcineurin postsynaptically. Both calcineurin antagonists applied to the bath blocked TRPV1-dependent LTD, indicating calcineurin involvement in LTD. Because calcineurin antagonist applied to the internal solution did not block TRPV1-LTD it suggests presynaptic calcineurin is required for LTD. Finally, because high frequency stimulus used to induce LTD could potentially activate receptors besides TRPV1, we confirmed that bath, but not intracellularly applied cyclosporin A, also blocked TRPV1 agonist-induced depression of CA1 interneurons. In conclusion, these data illustrate that presynaptic calcineurin activity is required for both TRPV1-induced LTD and TRPV1 agonist-induced depression. This finding is the first to demonstrate the TRPV1-induced signaling mechanism in CA1 hippocampus.