We demonstrate a novel dual strategy against inflammation and pain through body-wide desensitization of nociceptors via TRPA1. Attenuation of experimental colitis by capsazepine (CPZ) has long been attributed to its antagonistic action on TRPV1 and associated inhibition of neurogenic inflammation. In contrast, we found that CPZ exerts its anti-inflammatory effects via profound desensitization of TRPA1. Micromolar CPZ induced calcium influx in isolated dorsal root ganglion (DRG) neurons from wild-type (WT) but not TRPA1-deficient mice. CPZ-induced calcium transients in human TRPA1-expressing HEK293t cells were blocked by the selective TRPA1 antagonists HC 030031 and A967079 and involved three cysteine residues in the N-terminal domain. Intriguingly, both colonic enemas and drinking water with CPZ led to profound systemic hypoalgesia in WT and TRPV1−/− but not TRPA1−/− mice. These findings may guide the development of a novel class of disease-modifying drugs with anti-inflammatory and anti-nociceptive effects.

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Camphor is known to potentiate both heat and cold sensations. Although the sensitization to heat could be explained by the activation of heat-sensitive transient receptor potential (TRP) channels TRPV1 and TRPV3, the camphor-induced sensitization to cooling remains unexplained. In this study, we present evidence for the activation of the cold- and menthol-sensitive channel transient receptor potential melastatin 8 (TRPM8) by camphor. Calcium transients evoked by camphor in HEK293 cells expressing human and rat TRPM8 are inhibited by the TRPM8 antagonists 4-(3-chloro-2-pyridinyl)-N-[4-(1,1-dimethylethyl)phenyl]-1-piperazinecarboxamide and 2-aminoethyl diphenylborinate. Camphor also sensitized the cold-induced calcium transients and evoked desensitizing outward-rectifying currents in TRPM8-expressing HEK293 cells. In the presence of ruthenium red (a blocker of TRPV1, TRPV3, and TRPA1), the camphor sensitivity of cultured rat dorsal root ganglion neurons was highest in a subpopulation of cold- and icilin-sensitive neurons, strongly suggesting that camphor activates native TRPM8. Camphor has a dual action on TRPM8: it not only activates the channel but also inhibits its response to menthol. The icilin-insensitive chicken TRPM8 was also camphor insensitive. However, camphor was able to activate an icilin-insensitive human TRPM8 mutant channel. The activation and sensitization to cold of mammalian TRPM8 are likely to be responsible for the psychophysical enhancement of innocuous cold and "stinging/burning" cold sensations by camphor.

The transient receptor potential ankyrin type 1 (TRPA1) channel belongs to the TRP superfamily of ion channels. TRPA1 is a membrane protein with multiple functions able to respond to noxious stimuli, reactive oxygen species, inflammatory cytokines or pungent substances, and it participates in pain signalling, taste, inflammation and various steps of the tumorigenic process. To date, no reports have addressed the expression and function of TRPA1 in pancreatic ductal adenocarcinoma (PDAC) cells. This work reports the endogenous expression of TRPA1 channels in human pancreatic adenocarcinoma cell lines and provides insights into the function of the TRPA1 protein in the Panc-1 cell line. This study reports that cell lines isolated from PDAC patients had different levels of TRPA1 expression. The channel activity in Panc-1 cells, as assessed with electrophysiological (whole-cell patch clamp) and microfluorimetry methods, showed that non-selective cationic currents were activated by allyl isothiocyanate (AITC) in Panc-1 cells and inhibited by the selective TRPA1 antagonist A-967079. The current elicited by the specific agonist was associated with a robust increase in intracellular Ca2+. Furthermore, siRNA-induced downregulation of TRPA1 enhanced cell migration in the wound healing assay, indicating a possible role of ion channels independent from pore function. Finally, TRPA1 activation changed the cell cycle progression. Taken together, these results support the idea of channel-dependent and independent role for TRPA1 in tumoral processes.

The transient receptor potential melastatin type 8 (TRPM8) receptor channel is expressed in primary afferent neurons where it is the main transducer of innocuous cold temperatures and also in a variety of tumors, where it is involved in progression and metastasis. Modulation of this channel by intracellular signaling pathways has therefore important clinical implications. We investigated the modulation of recombinant and natively expressed TRPM8 by the Src kinase, which is known to be involved in cancer pathophysiology and inflammation. Human TRPM8 expressed in HEK293T cells is constitutively tyrosine phosphorylated by Src which is expressed either heterologously or endogenously. Src action on TRPM8 potentiates its activity, as treatment with PP2, a selective Src kinase inhibitor, reduces both TRPM8 tyrosine phosphorylation and cold‐induced channel activation. RNA interference directed against the Src kinase diminished the extent of PP2‐induced functional downregulation of TRPM8, confirming that PP2 acts mainly through Src inhibition. Finally, the effect of PP2 on TRPM8 cold activation was reproduced in cultured rat dorsal root ganglion neurons, and this action was antagonized by the protein tyrosine phosphatase inhibitor pervanadate, confirming that TRPM8 activity is sensitive to the cellular balance between tyrosine kinases and phosphatases. This positive modulation of TRPM8 by Src kinase may be relevant for inflammatory pain and cancer signaling.

Psoralen is a naturally occurring furanocoumarin, found in the seeds of Psoralea corylifolia, and also in figs, celery, parsley and citrus fruits, which has been used to treat a number of skin conditions since the antiquity (Pathak & Fitzpatrick, 1992). In modern medicine, psoralen-derived compounds, such as 8-methoxypsoralen (8-MOP) and 5-methoxypsoralen (5-MOP), are used in combination with UVA light (320-400 nm) exposure (PUVA therapy) to treat severe psoriasis, eczema, vitiligo, cutaneous T-cell lymphoma, mycosis fungoides and other conditions (Lapolla, Yentzer,

Loss-of-function mutations in the enzyme 7-dehydrocholesterol reductase are responsible for the Smith-Lemli-Opitz syndrome, in which 7-dehydrocholesterol (7-DHC) levels are markedly increased in the plasma and tissues of patients. This increase in 7-DHC is probably associated with the painful and itchy photosensitivity reported by the majority of patients with Smith-Lemli-Opitz syndrome. To identify the molecular targets involved in the activation and photosensitization of primary afferents by 7-DHC, we focused on TRPA1 and TRPV1, two ion channels expressed in nociceptive nerve endings and previously shown to respond to ultraviolet and visible light under pathophysiological circumstances. Recombinant human TRPA1 is activated and photosensitized in the presence of 7-DHC. Prolonged preexposure to 7-DHC causes more pronounced photosensitization, and while TRPV1 contributes less to the acute effect, it too becomes highly photosensitive upon preincubation with 7-DHC for 1 to 15 hours. Dorsal root ganglion neurons in primary culture display acute sensitivity to 7-DHC in the dark and also light-evoked responses in the presence of 7-DHC, which are exclusively dependent on TRPA1 and TRPV1. Similarly, prolonged exposure of mouse dorsal root ganglion neurons to 7-DHC renders these cells photosensitive in a largely TRPA1- and TRPV1-dependent manner. Single-fiber recordings in mouse skin-nerve preparations demonstrate violet light-evoked activation and a sensitization to 7-DHC exposure. Vice versa, 7-DHC pretreatment of the isolated trachea leads to a TRPA1- and TRPV1-dependent increase of the light-induced calcitonin gene-related peptide release. Taken together, our results implicate TRPA1 and TRPV1 channels as potential pharmacological targets to address the 7-DHC-induced hypersensitivity to light in patients.

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