2-3-4-tri-o-acetylarabinopyranosyl-isothiocyanate and Disease-Models--Animal

Despite the development of effective therapies, a substantial proportion of asthmatics continue to have uncontrolled symptoms, airflow limitation, and exacerbations. Transient receptor potential cation channel member A1 (TRPA1) agonists are elevated in human asthmatic airways, and in rodents, TRPA1 is involved in the induction of airway inflammation and hyperreactivity. Here, the discovery and early clinical development of GDC-0334, a highly potent, selective, and orally bioavailable TRPA1 antagonist, is described. GDC-0334 inhibited TRPA1 function on airway smooth muscle and sensory neurons, decreasing edema, dermal blood flow (DBF), cough, and allergic airway inflammation in several preclinical species. In a healthy volunteer Phase 1 study, treatment with GDC-0334 reduced TRPA1 agonist-induced DBF, pain, and itch, demonstrating GDC-0334 target engagement in humans. These data provide therapeutic rationale for evaluating TRPA1 inhibition as a clinical therapy for asthma.

Topics: Adolescent; Adult; Animals; Asthma; Cohort Studies; Disease Models, Animal; Dogs; Double-Blind Method; Female; Guinea Pigs; Healthy Volunteers; Humans; Isothiocyanates; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Middle Aged; Neurogenic Inflammation; Pain; Pruritus; Pyridines; Pyrimidines; Rats; Rats, Sprague-Dawley; Treatment Outcome; TRPA1 Cation Channel; Young Adult

Hydrogen sulfide (H(2)S), formed by multiple enzymes, including cystathionine-γ-lyase (CSE), targets Ca(v)3.2 T-type Ca(2+) channels (T channels) and transient receptor potential ankyrin-1 (TRPA1), facilitating somatic pain. Pancreatitis-related pain also appears to involve activation of T channels by H(2)S formed by the upregulated CSE. Therefore, this study investigates the roles of the Ca(v)3.2 isoform and/or TRPA1 in pancreatic nociception in the absence and presence of pancreatitis. In anesthetized mice, AP18, a TRPA1 inhibitor, abolished the Fos expression in the spinal dorsal horn caused by injection of a TRPA1 agonist into the pancreatic duct. As did mibefradil, a T-channel inhibitor, in our previous report, AP18 prevented the Fos expression following ductal NaHS, an H(2)S donor. In the mice with cerulein-induced acute pancreatitis, the referred hyperalgesia was suppressed by NNC 55-0396 (NNC), a selective T-channel inhibitor; zinc chloride; or ascorbic acid, known to inhibit Ca(v)3.2 selectively among three T-channel isoforms; and knockdown of Ca(v)3.2. In contrast, AP18 and knockdown of TRPA1 had no significant effect on the cerulein-induced referred hyperalgesia, although they significantly potentiated the antihyperalgesic effect of NNC at a subeffective dose. TRPA1 but not Ca(v)3.2 in the dorsal root ganglia was downregulated at a protein level in mice with cerulein-induced pancreatitis. The data indicate that TRPA1 and Ca(v)3.2 mediate the exogenous H(2)S-induced pancreatic nociception in naïve mice and suggest that, in the mice with pancreatitis, Ca(v)3.2 targeted by H(2)S primarily participates in the pancreatic pain, whereas TRPA1 is downregulated and plays a secondary role in pancreatic nociceptive signaling.

Topics: Analysis of Variance; Animals; Benzimidazoles; Calcium Channel Blockers; Calcium Channels, T-Type; Ceruletide; Cyclopropanes; Disease Models, Animal; Hydrogen Sulfide; Hyperalgesia; Isothiocyanates; Male; Mice; Naphthalenes; Oligodeoxyribonucleotides, Antisense; Pancreatitis; Posterior Horn Cells; Proto-Oncogene Proteins c-fos; Transient Receptor Potential Channels; TRPA1 Cation Channel; Visceral Pain

There is little evidence to support the down-regulation of coughing from the nose. The cough response to citric acid (CA) was studied in anesthetized and conscious guinea pigs after nasal pretreatment with saline, 1% DMSO, allylisothiocyanate (TRPA1 agonist) and allylisothiocyanate +AP-18 (TRPA1 antagonist). Cough was induced by adding citric acid (CA) to the tracheal perfusion in anaesthetized animals, or by inhaling 0.4M CA in conscious animals. The cough response was counted from the dose response curves, airflow traces and cough sound analysis. In conscious animals, nasal allylisothiocyanate induced reproducible, dose dependent nasal symptoms and a significant drop in respiratory rate. Cough induced by CA was suppressed after nasal allylisothiocyanate (p<0.05), and this effect was prevented by AP-18 (1mM). In anaesthetized animals, nasal allylisothiocyanate induced a significant drop in respiratory rate. Cough induced subsequently by CA was suppressed when compared to baseline and vehicle responses (p<0.05). The reasons for the suppression of CA induced cough by TRPA1 agonist applied to the nose are not clear and remain to be elucidated.

Topics: Administration, Intranasal; Anesthesia; Animals; Anticoagulants; Antitussive Agents; Citric Acid; Consciousness; Cough; Disease Models, Animal; Dose-Response Relationship, Drug; Guinea Pigs; Isothiocyanates; Male; Respiration

Despite the increasing interest in TRPA1 channel as a pain target, its role in cold sensation and body temperature regulation is not clear; the efficacy and particularly side effects resulting from channel blockade remain poorly understood. Here we use a potent, selective, and bioavailable antagonist to address these issues. A-967079 potently blocks human (IC(50): 51 nmol/L, electrophysiology, 67 nmol/L, Ca(2+) assay) and rat TRPA1 (IC(50): 101 nmol/L, electrophysiology, 289 nmol/L, Ca(2+) assay). It is >1000-fold selective over other TRP channels, and is >150-fold selective over 75 other ion channels, enzymes, and G-protein-coupled receptors. Oral dosing of A-967079 produces robust drug exposure in rodents, and exhibits analgesic efficacy in allyl isothiocyanate-induced nocifensive response and osteoarthritic pain in rats (ED(50): 23.2 mg/kg, p.o.). A-967079 attenuates cold allodynia produced by nerve injury but does not alter noxious cold sensation in naive animals, suggesting distinct roles of TRPA1 in physiological and pathological states. Unlike TRPV1 antagonists, A-967079 does not alter body temperature. It also does not produce locomotor or cardiovascular side effects. Collectively, these data provide novel insights into TRPA1 function and suggest that the selective TRPA1 blockade may present a viable strategy for alleviating pain without untoward side effects.

Topics: Animals; Blood Pressure; Body Temperature; Body Temperature Regulation; Calcitonin Gene-Related Peptide; Calcium; Calcium Channels; Cells, Cultured; Cold Temperature; Disease Models, Animal; Drug Interactions; Ganglia, Spinal; Heart Rate; Humans; Hyperalgesia; Inhibitory Concentration 50; Isothiocyanates; Magnetic Resonance Imaging; Male; Mice; Nerve Tissue Proteins; Neurons; Oximes; Pain; Pain Measurement; Rats; Rats, Sprague-Dawley; Reaction Time; Sensation; Sensory Thresholds; Transient Receptor Potential Channels; Tritium; TRPA1 Cation Channel; TRPV Cation Channels

Chronic itch is symptomatic of many skin conditions and systemic diseases. Little is known about pathophysiological alterations in itch-signaling neural pathways associated with chronic itch. We used a mouse model of hindpaw chronic dry skin itch to investigate properties of presumptive itch-signaling neurons. Neurons in the lumbar superficial dorsal horn ipsilateral to hindpaw dry skin treatment exhibited a high level of spontaneous activity that was inhibited by scratching the plantar surface. Most spontaneously active units exhibited further increases in firing rate following intradermal injection of an agonist of the protease-activated receptor PAR-2, or histamine. The large majority of pruritogen-responsive units also responded to capsaicin and allyl isothiocyanate. For neurons ipsilateral to dry skin treatment, responses elicited by the PAR-2 agonist, but not histamine or mechanical stimuli, were significantly larger compared with neurons ipsilateral to vehicle (water) treatment or neurons recorded in naïve (untreated) mice. The spontaneous activity may signal ongoing itch, while enhanced PAR-2 agonist-evoked responses may underlie hyperknesis (enhanced itch), both of which are symptomatic of many chronic itch conditions. The enhancement of neuronal responses evoked by the PAR-2 agonist, but not by histamine or mechanical stimuli, implies that the dry skin condition selectively sensitized PAR-2 agonist-sensitive primary afferent pruriceptors.

Topics: Acetone; Action Potentials; Analysis of Variance; Animals; Antipruritics; Capsaicin; Disease Models, Animal; Drug Synergism; Functional Laterality; Histamine; Isothiocyanates; Mice; Models, Biological; Oligopeptides; Physical Stimulation; Posterior Horn Cells; Pruritus; Receptors, Proteinase-Activated; Serotonin; Solvents; Spinal Cord; Water

We have revealed that local stimulation of sensory neurons is involved in the adjuvant effect of dibutyl phthalate (DBP) in a fluorescein isothiocyanate-induced mouse contact hypersensitivity model. Transient receptor potential (TRP) A1 and TRPV1 seemed to be candidate DBP targets. Here we directly demonstrated that DBP activates a subset of neurons in mouse dorsal root ganglia responsive to TRPA1 and TRPV1 agonists. TRPA1 and TRPV1 activation was further demonstrated using cultured cells expressing TRP channels. Among structurally different phthalate esters, there is a positive relationship between the activation of TRPA1- or TRPV1-expressing cells and the adjuvant effect.

Topics: Animals; Calcium; Capsaicin; CHO Cells; Cricetinae; Cricetulus; Dermatitis, Contact; Dibutyl Phthalate; Disease Models, Animal; Dose-Response Relationship, Drug; Edema; Female; Fluorescein-5-isothiocyanate; Fluorescent Dyes; Ganglia, Spinal; Gene Expression; Isothiocyanates; Mice; Mice, Inbred BALB C; Plasticizers; Rats; Sensory Receptor Cells; Transfection; Transient Receptor Potential Channels; TRPA1 Cation Channel; TRPV Cation Channels