Mitochondrial reactive oxygen species (mROS) that are overproduced by mitochondrial dysfunction are linked to pathological conditions including sensory abnormalities. Here, we explored whether mROS overproduction induces itch through transient receptor potential canonical 3 (TRPC3), which is sensitive to ROS. Intradermal injection of antimycin A (AA), a selective inhibitor of mitochondrial electron transport chain complex III for mROS overproduction, produced robust scratching behavior in naïve mice, which was suppressed by MitoTEMPO, a mitochondria-selective ROS scavenger, and Pyr10, a TRPC3-specific blocker, but not by blockers of TRPA1 or TRPV1. AA activated subsets of trigeminal ganglion neurons and also induced inward currents, which were blocked by MitoTEMPO and Pyr10. Besides, dry skin-induced chronic scratching was relieved by MitoTEMPO and Pyr10, and also by resveratrol, an antioxidant. Taken together, our results suggest that mROS elicit itch through TRPC3, which may underlie chronic itch, representing a potential therapeutic target for chronic itch.
Animals ; Antioxidants/pharmacology* ; Mice ; Mitochondria ; Pruritus/chemically induced* ; Reactive Oxygen Species/metabolism* ; TRPA1 Cation Channel

Our previous study found that some trigeminal ganglion (TG) nerve endings in the inner walls of rat anterior chambers were mechanosensitive, and transient receptor potential ankyrin 1 (TRPA1) was an essential mechanosensitive channel in the membrane. To address the effect of cannabinoids on the mechanosensitive TG nerve endings in the inner walls of anterior chambers of rat eye, we investigated the effect of the (R)-(+)-WIN55, 212-2 mesylate salt (WIN), a synthetic cannabinoid on their cell bodies in vitro. Rat TG neurons innervating the inner walls of the anterior chambers were labeled by 1,1'-dilinoleyl-3,3,3',3'-tetramethylindocarbocyanine, 4-chlorobenzenesulfona (FAST DiI). Whole cell patch clamp was performed to record the currents induced by drugs and mechanical stimulation. Mechanical stimulation was applied to the neurons by buffer ejection. WIN evoked inward currents via TRPA1 activation in FAST DiI-labeled TG neurons. WIN enhanced mechanosensitive currents via TRPA1 activation in FAST DiI-labeled TG neurons. Our results indicate that cannabinoids can enhance the mechanosensitivity of TG endings in the inner walls of anterior chambers of rat eye via TRPA1 activation.
Action Potentials ; drug effects ; Animals ; Anterior Chamber ; drug effects ; innervation ; Cannabinoids ; administration & dosage ; Eye ; drug effects ; innervation ; Neurons ; drug effects ; Patch-Clamp Techniques ; Rats ; Rats, Sprague-Dawley ; TRPA1 Cation Channel ; TRPC Cation Channels ; biosynthesis ; genetics ; Trigeminal Ganglion ; drug effects ; physiology

Transient receptor potential (TRP) A1, a member of TRP channel family, is activated by noxious cold. The aims of this study were to determine if TRPA1 contributed to cold-induced contractions in the isolated rat colon preparations and explore the potential mechanisms. The colon smooth muscle layers were surgically isolated from the male Wistar rats and changes in isotonic tension of longitudinal muscle under various treatments were recorded as colonic motilities. Cold stimuli were obtained by the reperfusion with Krebs-Henseleit solution at given temperature using Constant Flow Pump. The mRNA expressions of TRPA1, TRPV1 and TRPM8 in rat colon smooth muscle layer were examined by using reverse transcription-polymerase chain reaction (RT-PCR) techniques. The results showed that the contractions induced by cold stimuli (from 37 degrees C to 12 degrees C stepwise) were inversely proportional to the temperature with a maximum contraction at 17 degrees C in both proximal and distal colons (P<0.01). RT-PCR analysis revealed the expression of TRPA1, but not TRPM8 and TRPV1, in the rat proximal and distal colon smooth muscle layers. Cold-induced colonic contractions were specially inhibited by TRPA1 blocker, ruthenium red (30 μmol/L), in the proximal and distal colon (P<0.05). The cold-induced contractions of proximal (P<0.01, P<0.05) and distal colons (both P<0.001) were almost abolished or inhibited by the pretreatments of TRPA1 agonists, Allyl isothiocyanate (AITC, 300 μmol/L) and cinnamaldehyde (CA, 1 mmol/L). Extracellular calcium removal (EGTA, 1 mmol/L), PLC blocker (U73122, 10 μmol/L) and IP(3) receptor blocker (2-aminoethoxydiphenyl borate, 2-APB, 30 μmol/L) all decreased the contractions evoked by the cooling at 17 degrees C in the proximal and distal colon (P<0.001, P<0.05, P<0.001). Atropine (1 μmol/L) had no effects on these contractions. L-type Ca(2+) channels blocker nifedipine (1 μmol/L) and neurotoxin tetrodotoxin (TTX, 2 μmol/L) decreased the contractile response in the distal colon (P<0.01, P<0.05), but not in the proximal colon. In conclusion, TRPA1 contributes to cold-induced contractions of the rat colon smooth muscle, and the mechanism of TRPA1 activation involves PLC/IP(3)/Ca(2+) pathway. L-type Ca(2+) channel and neurogenic mechanism other than muscarinic receptor might be partially involved in cold-induced contraction of the distal colon, which probably resulted in higher contraction of distal colon compared with that of proximal colon.
Animals ; Calcium Channels, L-Type ; metabolism ; Cold Temperature ; Colon ; metabolism ; physiology ; In Vitro Techniques ; Male ; Muscle Contraction ; physiology ; Muscle, Smooth ; metabolism ; physiology ; Physical Stimulation ; RNA, Messenger ; genetics ; metabolism ; Rats ; Rats, Wistar ; TRPA1 Cation Channel ; TRPC Cation Channels ; genetics ; metabolism

Artemin is a neuronal survival and differentiation factor in the glial cell line-derived neurotrophic factor family. Its receptor GFRalpha3 is expressed by a subpopulation of nociceptor type sensory neurons in the dorsal root and trigeminal ganglia (DRG and TG). These neurons co-express the heat, capsaicin and proton-sensitive channel TRPV1 and the cold and chemical-sensitive channel TRPA1. To further investigate the effects of artemin on sensory neurons, we isolated transgenic mice (ARTN-OE mice) that overexpress artemin in keratinocytes of the skin and tongue. Enhanced levels of artemin led to a 20% increase in the total number of DRG neurons and increases in the level of mRNA encoding TRPV1 and TRPA1. Calcium imaging showed that isolated sensory neurons from ARTN-OE mice were hypersensitive to the TRPV1 agonist capsaicin and the TRPA1 agonist mustard oil. Behavioral testing of ARTN-OE mice also showed an increased sensitivity to heat, cold, capsaicin and mustard oil stimuli applied either to the skin or in the drinking water. Sensory neurons from wildtype mice also exhibited potentiated capsaicin responses following artemin addition to the media. In addition, injection of artemin into hindpaw skin produced transient thermal hyperalgesia. These findings indicate that artemin can modulate sensory function and that this regulation may occur through changes in channel gene expression. Because artemin mRNA expression is up-regulated in inflamed tissue and following nerve injury, it may have a significant role in cellular changes that underlie pain associated with pathological conditions. Manipulation of artemin expression may therefore offer a new pain treatment strategy.
Animals ; Hot Temperature ; Hyperalgesia ; metabolism ; Keratinocytes ; physiology ; Mice ; Mice, Transgenic ; Nerve Tissue Proteins ; genetics ; metabolism ; Nociceptors ; physiology ; Skin ; cytology ; TRPA1 Cation Channel ; TRPV Cation Channels ; metabolism ; Tongue ; cytology ; Transient Receptor Potential Channels ; metabolism

Cutaneous neurogenic inflammation (CNI) is inflammation that is induced (or enhanced) in the skin by the release of neuropeptides from sensory nerve endings. Clinical manifestations are mainly sensory and vascular disorders such as pruritus and erythema. Transient receptor potential vanilloid 1 and ankyrin 1 (TRPV1 and TRPA1, respectively) are non-selective cation channels known to specifically participate in pain and CNI. Both TRPV1 and TRPA1 are co-expressed in a large subset of sensory nerves, where they integrate numerous noxious stimuli. It is now clear that the expression of both channels also extends far beyond the sensory nerves in the skin, occuring also in keratinocytes, mast cells, dendritic cells, and endothelial cells. In these non-neuronal cells, TRPV1 and TRPA1 also act as nociceptive sensors and potentiate the inflammatory process. This review discusses the role of TRPV1 and TRPA1 in the modulation of inflammatory genes that leads to or maintains CNI in sensory neurons and non-neuronal skin cells. In addition, this review provides a summary of current research on the intracellular sensitization pathways of both TRP channels by other endogenous inflammatory mediators that promote the self-maintenance of CNI.
Animals ; Chronic Disease ; Dendritic Cells ; metabolism ; pathology ; Dermatitis ; metabolism ; pathology ; Gene Expression Regulation ; Humans ; Inflammation ; metabolism ; pathology ; Keratinocytes ; metabolism ; pathology ; Mast Cells ; metabolism ; pathology ; Sensory Receptor Cells ; metabolism ; pathology ; TRPA1 Cation Channel ; biosynthesis ; TRPV Cation Channels ; biosynthesis

Objective: To explore the expressions of transient receptor potential vanilloid 1 (TRPV1) and TRP ankyrin 1 (TRPA1) in the dorsal root ganglion (DRG) and their action mechanisms in the rat model of orchialgia. METHODS: The models of orchialgia were established in male SD rats by injection of 2% acetic acid into the testis. Then the number of spontaneous pain responses and withdrawal latency in the model rats were recorded by behavioral tests and the expressions of TRPV1 and TRPA1 in T13－L1 DRGs determined by RT-qPCR, Western blot and immunofluorescence staining. RESULTS: Compared with the normal control rats, the orchialgia models showed a significant increase in the number of spontaneous pain responses (0.13 ± 0.35 vs 22.63 ± 3.42, P<0.01) and a decrease in the withdrawal latency at 4 hours after injection (［12.75 ± 1.50］ vs ［4.85 ± 1.00］ s, P<0.05). The mRNA expressions of both TRPV1 and TRPA1 were observed in the membrane of the neurons in the DRG, the former increased by 1.77 times and the latter by 1.75 times that of the control (P<0.05). CONCLUSIONS The expressions of TRPV1 and TRPA1 were up-regulated in the DRG of the rat models of orchialgia, which may be involved in the allodynia and hyperalgesia of the rats.
Acetic Acid ; Animals ; Ganglia, Spinal ; metabolism ; Hyperalgesia ; chemically induced ; metabolism ; Male ; Membrane Glycoproteins ; Oxidoreductases ; Rats ; Rats, Sprague-Dawley ; TRPA1 Cation Channel ; metabolism ; TRPV Cation Channels ; metabolism ; Testicular Diseases ; chemically induced ; metabolism ; Up-Regulation

TRPA1 channels are non-selective cation channels that could be activated by plant-derived pungent products, including gingerol, a main active constituent of ginger. Ginger could improve the digestive function; however whether ginger improves the digestive function through activating TRPA1 receptor in gastrointestinal tract has not been investigated. In the present study, gingerol was used to stimulate cell lines (RIN14B or STC-1) while depletion of extracellular calcium. TRPA1 inhibitor (rethenium red) and TRPA1 gene silencing via TRPA1-specific siRNA were also used for mechanistic studies. The intracellular calcium and secretion of serotonin or cholecystokinin were measured by fura-2/AM and ELISA. Stimulation of those cells with gingerol increased intracellular calcium levels and the serotonin or cholecystokinin secretion. The gingerol-induced intracellular calcium increase and secretion (serotonin or cholecystokinin) release were completely blocked by ruthenium red, EGTA, and TRPA1-specific siRNA. In summary, our results suggested that gingerol derived from ginger might improve the digestive function through secretion releasing from endocrine cells of the gut by inducing TRPA1-mediated calcium influx.
Calcium ; metabolism ; Calcium Channels ; genetics ; metabolism ; Catechols ; pharmacology ; Cell Line ; Fatty Alcohols ; pharmacology ; Gastrointestinal Tract ; drug effects ; metabolism ; Ginger ; chemistry ; Humans ; Nerve Tissue Proteins ; genetics ; metabolism ; Plant Extracts ; pharmacology ; TRPA1 Cation Channel ; Transient Receptor Potential Channels ; genetics ; metabolism

OBJECTIVETo explore the molecular mechanism of pain associated with chronic prostatitis and chronic pelvic pain syndrome (CP/CPPS) in the rat model of prostatic inflammation.

METHODSThirty-six male SD rats were equally randomized to an experimental and a control group, the former injected with 50 μl of 3% λ-carrageenan into the ventral prostate to make the model of non-bacterial prostatic inflammation, while the latter with the same volume of sterile saline solution. At 1, 2 and 4 weeks after modeling, the prostate, L6-S1 dorsal root ganglion (DRG) and spinal cord were harvested for examination of the expressions of the nerve growth factor (NGF), transient receptor potential ankyrin 1 (TRPA1), and calcitonin-gene-related peptide (CGRP) by immunohistochemistry and Western blot.

RESULTSThe expressions of NGF, TRPA1 and CGRP in the prostatic tissue were all significantly increased in the experimental group as compared with the control (P <0.05), with a gradual decrease with the prolonging of time (P <0.05). In the L6-S1 DRG and spinal cord, the expressions of NGF, TRPA1 and CGRP exhibited no significant differences between the experimental and control groups at 1 week after modeling (P >0.05) and kept at high levels in the experimental group at 2 and 4 weeks, though not significantly different from those at 1 week (P >0.05). Statistically significant differences were observed in the expressions of the three proteins in the experimental rats among different time points (P <0.05), but not between the two groups at any time point (P >0.05).

CONCLUSIONThe molecular mechanism of CP/CPPS can be evaluated in the rat model of prostatic inflammation established by injecting λ-carrageenan into the prostate. TRPA1 may play an important role in connecting the upstream and down-stream pathways of CP/CPPS-associated pain.

Animals ; Calcitonin Gene-Related Peptide ; metabolism ; Carrageenan ; Chronic Disease ; Chronic Pain ; metabolism ; Ganglia, Spinal ; metabolism ; Humans ; Male ; Nerve Growth Factor ; metabolism ; Pelvic Pain ; metabolism ; Prostatitis ; chemically induced ; metabolism ; Rats ; Rats, Sprague-Dawley ; Spinal Cord ; metabolism ; TRPA1 Cation Channel ; TRPC Cation Channels ; metabolism

Injury or inflammation induces release of a range of inflammatory mediators. Bradykinin is one of the most important inflammatory mediators and plays a crucial role in mediating inflammatory pain. It is well known that multiple ion channels located in the nociceptors participate in pain sensation. Recent studies demonstrate an important role of bradykinin in regulating the function and expression of pain-related ion channels. This paper summarizes the recent advances in the understanding of the role of bradykinin in modulation of the channels and discusses future possibilities in the treatment of inflammatory pain.
Acid Sensing Ion Channels ; Animals ; Bradykinin ; pharmacology ; physiology ; Humans ; Inflammation ; complications ; Inflammation Mediators ; pharmacology ; physiology ; Ion Channels ; KCNQ Potassium Channels ; metabolism ; physiology ; Nerve Tissue Proteins ; metabolism ; Pain ; etiology ; metabolism ; physiopathology ; Receptors, AMPA ; metabolism ; Receptors, N-Methyl-D-Aspartate ; metabolism ; Receptors, Purinergic P2X3 ; metabolism ; Sodium Channels ; metabolism ; TRPA1 Cation Channel ; TRPV Cation Channels ; metabolism ; physiology ; Transient Receptor Potential Channels ; metabolism ; physiology