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.

No abstract

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.