[Show abstract][Hide abstract] ABSTRACT: Background: Gastrointestinal disorders such as inflammatory bowel disease (IBD) are associated with pain symptoms also described in rodent models of IBD such as that induced by dextran sulfate sodium (DSS). Central sensitization has been proposed to contribute to the somatic pain symptoms in IBD and related rodent models. The transient receptor potential ankyrin 1 (TRPA1) channel expressed by a subpopulation of primary sensory neurons of the dorsal root ganglion (DRG) and trigeminal ganglion (TG) is a major transducer of nociceptive signals produced by inflammation and tissue injury and is involved in hypersensitivity conditions. There is indication that TRPA1 contributes to visceral pain-like behavior in DSS-evoked colitis. The present study was designed to investigate the role of TRPA1 channels in the colitis-evoked mechanical and thermal hypersensi-tivity at the somatic level. Methods: Colitis was induced in C57BL/6 male mice by adding 2 % DSS to the drinking water for 7 days. Following this treatment, on day 8, control and DSS-treated mice were tested for various parameters of colitis as well as mechanical sensitivity in the abdominal and facial skin and thermal sensitivity in the plantar skin. Pharmacological blockade of TRPA1 by the selective antagonist HC-030031 (100 mg/kg, i. p.) and genetic deletion of TRPA1 were used to investigate the role of TRPA1 in DSS-induced colitis. The pain sensitivity to mechanical stimuli was evaluated with von Frey hairs (facial and abdominal region) and to thermal stimuli with the hot-and cold-plate method (plantar skin). Colitis-associated parameters, such as body weight, disease activity score, colon length, colon weight and colonic myeloperoxidase (MPO) activity, were measured. The expression of mRNA of various TRP channels (TRPA1, TRPV1 and TRPV4) was quantified in isolated DRGs and TGs of control and DSS-treated mice. On day 8, control and DSS-treated mice were also tested for behavioural (freezing, locomotion, rearing) and molecular changes (c-Fos in spinal cord) in response to a chemical pain stimulus (intrarectal instillation of 2 % allylisothiocyanate; AITC) in the presence or absence of HC-030031 (100 mg/kg, i. p.). Results: Induction of colitis was confirmed by a decrease in body weight and colon length and an increase in colon weight, disease activity score and MPO activity. DSS increased the mechanical (abdominal and facial) and thermal (hot) sensitivity in mice. The TRPA1 antagonist reduced mechanical sensitivity of both the abdominal and facial region. DSS treatment caused an increase in TRPA1 mRNA expression in the DRG. Intrarectal AITC evoked freezing behaviour which was reduced in the presence of the TRPA1 antagonist. Discussion: Taken together, the current findings indicate that the TRPA1 channel participates in colitis-associated pain hypersensitivity at the somatic level. Acknowledgements: P. J. is a recipient of a Marietta Blau Fellowship , Federal Ministry
21st Scientific Symposium of the Austrian Pharmacological Society. Joint Meeting with the British Pharmacological Society and the Pharmacological Societies of Croatia, Serbia and Slovenia, Graz; 09/2015
[Show abstract][Hide abstract] ABSTRACT: Although still used by hundreds of millions of people worldwide, the mechanism of the analgesic action of the pyrazolone derivatives (PDs), dipyrone, propyphenazone and antipyrine, remains unknown. The transient receptor potential ankyrin 1 (TRPA1) channel, expressed by nociceptors, is emerging as a major pain transduction pathway. We hypothesized that PDs target the TRPA1 channel and by this mechanism produce their analgesic effect.
Calcium responses and currents were studied in cultured, TRPA1-expressing rodent dorsal root ganglion neurons and human cells. Acute nociception and mechanical hypersensitivity were investigated in naïve and genetically manipulated mice.
Pyrazolone and PDs selectively inhibit calcium responses and currents in TRPA1-expressing cells and acute nocifensor responses in mice evoked by reactive channel agonists (allyl isothiocyanate, acrolein and H2 O2 ). In line with recent results obtained with TRPA1 antagonists or TRPA1 gene deletion, the two most largely used PDs, dipyrone and propyphenazone, attenuate TRPA1-mediated nociception and mechanical allodynia in models of inflammatory and neuropathic pain (formalin, carrageenan, partial sciatic nerve ligation, and the chemotherapeutic drug, bortezomib). Notably, dipyrone and propyphenazone attenuate carrageenan-evoked mechanical allodynia, without affecting prostaglandin E2 levels. PD main metabolites do not target TRPA1 and do not affect TRPA1-dependent nociception and allodynia.
Evidence that in rodents the nociceptive/hyperalgesic effect produced by TRPA1 activation is blocked by PDs suggests that a similar pathway is attenuated by PDs in humans, and that TRPA1 antagonists could be novel analgesics, devoid of the hematologic liability of PDs.
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British Journal of Pharmacology 03/2015; 172(13). DOI:10.1111/bph.13129 · 4.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Use of aromatase inhibitors (AIs), exemestane, letrozole and anastrozole, for breast cancer therapy is associated with severe pain symptoms, the underlying mechanism of which is unknown. The electrophilic nature of AIs suggests that they may target the transient receptor potential ankyrin 1 (TRPA1) channel, a major pathway in pain transmission and neurogenic inflammation. AIs evoke TRPA1-mediated calcium response and current in rodent nociceptors and human cells expressing the recombinant channel. In mice, AIs produce acute nociception, which is exaggerated by pre-exposure to proalgesic stimuli, and, by releasing sensory neuropeptides, neurogenic inflammation in peripheral tissues. AIs also evoke mechanical allodynia and decreased grip strength, which do not undergo desensitization on prolonged AI administration. These effects are markedly attenuated by TRPA1 pharmacological blockade or in TRPA1-deficient mice. TRPA1 is a major mediator of the proinflammatory/proalgesic actions of AIs, thus suggesting TRPA1 antagonists for the treatment of pain symptoms associated with AI use.
[Show abstract][Hide abstract] ABSTRACT: Background & aims:
Patients with cholestatic disease have increased systemic concentrations of bile acids (BAs) and profound pruritus. The G-protein-coupled BA receptor 1 TGR5 (encoded by GPBAR1) is expressed by primary sensory neurons; its activation induces neuronal hyperexcitability and scratching by unknown mechanisms. We investigated whether the transient receptor potential ankyrin 1 (TRPA1) is involved in BA-evoked, TGR5-dependent pruritus in mice.
Co-expression of TGR5 and TRPA1 in cutaneous afferent neurons isolated from mice was analyzed by immunofluorescence, in situ hybridization, and single-cell polymerase chain reaction. TGR5-induced activation of TRPA1 was studied in in HEK293 cells, Xenopus laevis oocytes, and primary sensory neurons by measuring Ca(2+) signals. The contribution of TRPA1 to TGR5-induced release of pruritogenic neuropeptides, activation of spinal neurons, and scratching behavior were studied using TRPA1 antagonists or Trpa1(-/-) mice.
TGR5 and TRPA1 protein and messenger RNA were expressed by cutaneous afferent neurons. In HEK cells, oocytes, and neurons co-expressing TGR5 and TRPA1, BAs caused TGR5-dependent activation and sensitization of TRPA1 by mechanisms that required Gβγ, protein kinase C, and Ca(2+). Antagonists or deletion of TRPA1 prevented BA-stimulated release of the pruritogenic neuropeptides gastrin-releasing peptide and atrial natriuretic peptide B in the spinal cord. Disruption of Trpa1 in mice blocked BA-induced expression of Fos in spinal neurons and prevented BA-stimulated scratching. Spontaneous scratching was exacerbated in transgenic mice that overexpressed TRG5. Administration of a TRPA1 antagonist or the BA sequestrant colestipol, which lowered circulating levels of BAs, prevented exacerbated spontaneous scratching in TGR5 overexpressing mice.
BAs induce pruritus in mice by co-activation of TGR5 and TRPA1. Antagonists of TGR5 and TRPA1, or inhibitors of the signaling mechanism by which TGR5 activates TRPA1, might be developed for treatment of cholestatic pruritus.
[Show abstract][Hide abstract] ABSTRACT: Background and purpose:
Transient receptor potential vanilloid 1 (TRPV1) and TRP ankyrin 1 (TRPA1) are involved in many biological processes, including nociception and hyperalgesia. Whereas the involvement of TRPV1 in psychiatric disorders such as anxiety and depression has been reported, little is known regarding the role of TRPA1 in these conditions.
We investigated the role of TRPA1 in mice models of depression [forced swimming test (FST)] and anxiety [elevated plus maze (EPM) test].
Administration of the TRPA1 antagonist (HC030031, 30 nmol in 2 μL, i.c.v.) reduced immobility time in the FST. Similar results were obtained after oral administration of HC030031 (30-300 mg·kg(-1) ). The reduction in immobility time in FST induced by HC030031 (100 mg·kg(-1) ) was completely prevented by pretreatment with TRPA1 agonist, cinnamaldehyde (50 mg·kg(-1) , p.o.), which per se was inactive. In the EPM test, pretreatment with cinnamaldehyde (50 mg·kg(-1) , p.o.), which per se did not affect behaviour response, prevented the anxiolytic-like effect (increased open arm exploration) evoked by TRPA1 blockade (HC030031, 100 mg·kg(-1) , p.o.). Treatment with either cinnamaldehyde or HC030031 did not affect spontaneous ambulation. Furthermore, TRPA1-deficient mice showed anxiolytic- and antidepressant-like phenotypes in the FST and EPM test respectively.
Conclusion and implications:
The present findings indicate that genetic deletion or pharmacological blockade of TRPA1 produces inhibitory activity in mouse models of anxiety and depression. These results imply that TRPA1 exerts tonic control, promoting anxiety and depression, and that TRPA1 antagonism has potential as an innovative strategy for the treatment of anxiety and mood disorders.
British Journal of Pharmacology 05/2014; 171(18). DOI:10.1111/bph.12786 · 4.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Acute gout attacks produce severe joint pain and inflammation associated with monosodium urate (MSU) crystals leading to oxidative stress production. The transient potential receptor ankyrin 1 (TRPA1) is expressed by a subpopulation of peptidergic nociceptors and via its activation by endogenous reactive oxygen species, including hydrogen peroxide (H2O2), contributes to pain and neurogenic inflammation. The aim of the present study was to investigate the role of TRPA1 in hyperalgesia and inflammation in a model of acute gout attack in rodents. Inflammatory parameters and mechanical hyperalgesia were measured in male Wistar rats, wild-type (Trpa1(+/+)) or TRPA1-deficient (Trpa1(-/-)) male mice. Animals received intra-articular (i.a., ankle) injection of MSU. The role of TRPA1 was assessed by receptor antagonism, gene deletion or expression, sensory fiber defunctionalization, and calcitonin gene-related peptide (CGRP) release. We found that nociceptor defunctionalization, TRPA1 antagonist treatment (via i.a. or oral administration), and TRPA1 gene ablation abated hyperalgesia and inflammatory responses (edema, H2O2 generation, interleukin-1β release, and neutrophil infiltration) induced by i.a. MSU injection. In addition, we showed that MSU evoked generation of H2O2 in synovial tissue which stimulating TRPA1 producing CGRP release and plasma protein extravasation. The MSU-elicited responses were also reduced by the H2O2-detoxifying enzyme catalase and the reducing agent dithiothreitol. TRPA1 activation by MSU challenge-generated H2O2 mediates the entire inflammatory response in an acute gout attack rodent model, thus strengthening the role of the TRPA1 receptor and the H2O2 production as potential targets for treatment of acute gout attacks.
Free Radical Biology and Medicine 04/2014; 72. DOI:10.1016/j.freeradbiomed.2014.04.021 · 5.74 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The transient receptor potential ankyrin 1 (TRPA1), a member of the TRP superfamily of channels, is primarily localized to a subpopulation of primary sensory neurons of the trigeminal, vagal, and dorsal root ganglia. This subset of nociceptors produces and releases the neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP), which mediate neurogenic inflammatory responses. TRPA1 is activated by a number of exogenous compounds, including molecules of botanical origin, environmental irritants, and medicines. However, the most prominent feature of TRPA1 resides in its unique sensitivity for large series of reactive byproducts of oxidative and nitrative stress. Here, the role of TRPA1 in models of different types of pain, including inflammatory and neuropathic pain and migraine, is summarized. Specific attention is paid to TRPA1 as the main contributing mechanism to the transition of mechanical and cold hypersensitivity from an acute to a chronic condition and as the primary transducing pathway by which oxidative/nitrative stress produces acute nociception, allodynia, and hyperalgesia. A series of migraine triggers or medicines have been reported to modulate TRPA1 activity and the ensuing CGRP release. Thus, TRPA1 antagonists may be beneficial in the treatment of inflammatory and neuropathic pain and migraine.
Reviews of Physiology, Biochemistry and Pharmacology 03/2014; 176. DOI:10.1007/112_2014_18 · 6.27 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The discovery that a number of transient receptor potential (TRP) channels are expressed in a subpopulation of primary sensory neurons innervating the upper and lower airways as well as in nonneuronal cells in the airways and lungs has initiated a quest for the understanding of their role in the physiology and pathophysiology of the respiratory tract.
Various members of the TRP vanilloid subfamily (TRPV1, TRPV4) and the TRP ankyrin 1 (TRPA1), because of their localization in peptidergic sensory neurons, promote airway neurogenic inflammation. In particular, TRPA1, which is gated by oxidative and nitrative stress byproducts, has been found to mediate inflammatory responses produced by an unprecedented series of toxic and irritant agents produced by air pollution, contained in cigarette smoke, and produced by accidental events at the workplace. The observation that reactive molecules endogenously produced in the airways/lungs of asthma, work-related asthma, and chronic obstructive pulmonary disease target TRPA1 underscores the primary role of the TRPA1 channel in these conditions.
Identification of TRP channels, and especially TRPA1, as major targets of oxidative/nitrative stress and a variety of irritant environmental agents supports the hypothesis that neurogenic inflammation plays an important role in work-related inflammatory diseases and that antagonists for such channels may be novel therapeutic options for the treatment of these diseases.
Current Opinion in Allergy and Clinical Immunology 01/2014; 14(2). DOI:10.1097/ACI.0000000000000040 · 3.57 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The tachykinins, exemplified by substance P, are one of the most intensively studied neuropeptide families. They comprise a series of structurally related peptides that derive from alternate processing of three Tac genes and are expressed throughout the nervous and immune systems. Tachykinins interact with three neurokinin G protein-coupled receptors. The signaling, trafficking, and regulation of neurokinin receptors have also been topics of intense study. Tachykinins participate in important physiological processes in the nervous, immune, gastrointestinal, respiratory, urogenital, and dermal systems, including inflammation, nociception, smooth muscle contractility, epithelial secretion, and proliferation. They contribute to multiple diseases processes, including acute and chronic inflammation and pain, fibrosis, affective and addictive disorders, functional disorders of the intestine and urinary bladder, infection, and cancer. Neurokinin receptor antagonists are selective, potent, and show efficacy in models of disease. In clinical trials there is a singular success: neurokinin 1 receptor antagonists to treat nausea and vomiting. New information about the involvement of tachykinins in infection, fibrosis, and pruritus justifies further trials. A deeper understanding of disease mechanisms is required for the development of more predictive experimental models, and for the design and interpretation of clinical trials. Knowledge of neurokinin receptor structure, and the development of targeting strategies to disrupt disease-relevant subcellular signaling of neurokinin receptors, may refine the next generation of neurokinin receptor antagonists.
[Show abstract][Hide abstract] ABSTRACT: Migraine remains an elusive and poorly understood disease. The uncertainty is reflected by the current unsatisfactory acute and prophylactic migraine treatment. Genetic and pharmacological information points to certain transient receptor potential (TRP) in pain mechanisms. In particular, vanilloid 1 (TRPV1) and ankyrin 1 (TRPA1) seem to play a major role in different models of pain diseases. Recent findings have underscored the possibility that TRP channels expressed in the nerve terminals of peptidergic nociceptors contribute to the migraine mechanism. Among this channel subset, TRPA1, a sensor of oxidative, nitrative and electrophilic stress, is activated by an unprecedented series of irritant and pain provoking exogenous and endogenous agents, which by this neuronal pathway release the pro-migraine peptide, calcitonin gene-related peptide (CGRP). Some of the recently identified TRPA1 activators have long been known as migraine triggers. Furthermore, specific analgesic and antimigraine medicines have been shown to inhibit or desensitise the TRPA1 channel. Thus, TRPA1 is emerging as a major contributing pathway in migraine and as a novel target for the development of drugs for pain and migraine treatment.
British Journal of Pharmacology 11/2013; 171(10). DOI:10.1111/bph.12512 · 4.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To verify preliminary studies on patients with melanoma exposed to β-blockers that suggested a reduced risk of disease recurrence and death.
Data were obtained from all consecutive patients diagnosed as having melanoma between January 1, 1993, and December 31, 2009, at the Department of Dermatology of the University of Florence, Azienda Sanitaria di Firenze. Participants were excluded if at baseline they reported a previous diagnosis of cutaneous malignant melanoma or another malignant disease. We also excluded participants with evidence of visceral, lymph nodal, and in-transit metastasis at the time of the diagnosis.
Of 741 consecutive patients with melanoma, 79 (11%) were prescribed β-blockers (for hypertension in most cases) for 1 or more years (treated) and 662 (89%) were not (untreated). The multivariate Cox model indicated that the treated group had improved overall survival after a median follow-up of 4 years (P=.005). For each year of β-blocker use, the risk of death was reduced by 38%. The presence of hypertension, the use of antihypertensive agents for 1 or more years, or the use of other commonly used medicines were not associated with a better outcome for patients with melanoma.
The results confirm and strengthen previous findings that β-blocker use is associated with a reduced risk of melanoma recurrence and death. The results also indicate the strong need for a randomized clinical trial to conclusively assess whether β-blockers afford protection against melanoma recurrence and death.
Mayo Clinic Proceedings 11/2013; 88(11):1196-203. DOI:10.1016/j.mayocp.2013.09.001 · 6.26 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Objective
Gout is a common cause of inflammatory arthritis and is provoked by the accumulation of monosodium urate (MSU) crystals. However, the underlying mechanisms of the pain associated with acute attacks of gout are poorly understood. The aim of this study was to evaluate the role of transient receptor potential ankyrin 1 (TRPA-1) and TRPA-1 stimulants, such as H2O2, in a rodent model of MSU-induced inflammation. MethodsMSU or H2O2 was injected into the hind paws of rodents or applied in cultured sensory neurons, and the intracellular calcium response was measured in vitro. Inflammatory or nociceptive responses in vivo were evaluated using pharmacologic, genetic, or biochemical tools and methods. ResultsTRPA-1 antagonism, TRPA-1 gene deletion, or pretreatment of peptidergic TRP-expressing primary sensory neurons with capsaicin markedly decreased MSU-induced nociception and edema. In addition to these neurogenic effects, MSU increased H2O2 levels in the injected tissue, an effect that was abolished by the H2O2-detoxifying enzyme catalase. H2O2, but not MSU, directly stimulated sensory neurons through the activation of TRPA-1. The nociceptive responses evoked by MSU or H2O2 injection were attenuated by the reducing agent dithiothreitol. In addition, MSU injection increased the expression of TRPA-1 and TRP vanilloid channel 1 (TRPV-1) and also enhanced cellular infiltration and interleukin-1β levels, and these effects were blocked by TRPA-1 antagonism. Conclusion
Our results suggest that MSU injection increases tissue H2O2, thereby stimulating TRPA-1 on sensory nerve endings to produce inflammation and nociception. TRPV-1, by a previously unknown mechanism, also contributes to these responses.
[Show abstract][Hide abstract] ABSTRACT: Ever since their identification, interest in the role of transient receptor potential (TRP) channels in health and disease has steadily increased. Robust evidence has underlined the role of TRP channels expressed in a subset of primary sensory neurons of the trigeminal ganglion to promote, by neuronal excitation, nociceptive responses, allodynia and hyperalgesia. In particular, the TRP vanilloid 1 (TRPV1) and the TRP ankyrin 1 (TRPA1) are expressed in nociceptive neurons, which also express the sensory neuropeptides, tachykinins, and calcitonin gene-related peptide (CGRP), which mediate neurogenic inflammatory responses. Of interest, CGRP released from the trigeminovascular network of neurons is currently recognized as a main contributing mechanism of migraine attack. The ability of TRPA1 to sense and to be activated by an unprecedented series of exogenous and endogenous reactive molecules has now been extensively documented. Several of the TRPA1 activators are also known as triggers of migraine attack. Thus, TRP channels, and particularly TRPA1, may be proposed as novel pathways in migraine pathophysiology and as possible new targets for its treatment.
The Journal of Headache and Pain 08/2013; 14(1):71. DOI:10.1186/1129-2377-14-71 · 2.80 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: While feverfew has been used for centuries to treat pain and headaches and is recommended for migraine treatment, the mechanism for its protective action remains unknown. Migraine is triggered by calcitonin gene-related peptide (CGRP) release from trigeminal neurons. Peptidergic sensory neurons, express a series of transient receptor potential (TRP) channels, including the ankyrin 1 (TRPA1) channel. Recent findings have identified agents either inhaled from the environment or produced endogenously, which are known to trigger migraine or cluster headache attacks, as TRPA1 simulants. A major constituent of feverfew, parthenolide, may interact with TRPA1 nucleophilic sites, suggesting that feverfew antimigraine effect derives from its ability to target TRPA1. We found that parthenolide stimulates recombinant (transfected cells) or natively expressed (rat/mouse trigeminal neurons) TRPA1, where it, however, behaves as a partial agonist. Furthermore, in rodents, after initial stimulation, parthenolide desensitizes the TRPA1 channel, and renders peptidergic, TRPA1-expressing nerve terminals unresponsive to any stimulus. This effect of parthenolide abrogates nociceptive responses evoked by stimulation of peripheral trigeminal endings. TRPA1 targeting and neuronal desensitization by parthenolide inhibits CGRP release from trigeminal neurons and CGRP-mediated meningeal vasodilatation, evoked by either TRPA1 agonists or other unspecific stimuli. TRPA1 partial agonism, together with desensitization and nociceptor defunctionalization, ultimately resulting in inhibition of CGRP release within the trigeminovascular system, may contribute to the antimigraine effect of parthenolide.