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Intracellular free zinc ([Zn 2+ ] i ) is mobilized in neuronal and non-neuronal cells under physiological and/or pathophysiological conditions; therefore, [Zn 2+ ] i is a component of cellular signal transduction in biological systems. Although several transporters and ion channels that carry Zn 2+ have been identified, proteins that are involved in Zn 2+ supply into cells and their expression are poorly understood, particularly under inflammatory conditions. Here, we show that the expression of Zn 2+ transporters ZIP8 and ZIP14 is increased via the activation of hypoxia-induced factor 1α (HIF-1α) in inflammation, leading to [Zn 2+ ] i accumulation, which intrinsically activates transient receptor potential ankyrin 1 (TRPA1) channel and elevates basal [Zn 2+ ] i . In human fibroblast-like synoviocytes (FLSs), treatment with inflammatory mediators, such as tumor necrosis factor-α (TNF-α) and interleukin-1α (IL-1α), evoked TRPA1-dependent intrinsic Ca 2+ oscillations. Assays with fluorescent Zn 2+ indicators revealed that the basal [Zn 2+ ] i concentration was significantly higher in TRPA1-expressing HEK cells and inflammatory FLSs. Moreover, TRPA1 activation induced an elevation of [Zn 2+ ] i level in the presence of 1 μM Zn 2+ in inflammatory FLSs. Among the 17 out of 24 known Zn 2+ transporters, FLSs that were treated with TNF-α and IL-1α exhibited a higher expression of ZIP8 and ZIP14 . Their expression levels were augmented by transfection with an active component of nuclear factor-κB P65 and HIF-1α expression vectors, and they could be abolished by pretreatment with the HIF-1α inhibitor echinomycin (Echi). The functional expression of ZIP8 and ZIP14 in HEK cells significantly increased the basal [Zn 2+ ] i level. Taken together, Zn 2+ carrier proteins, TRPA1, ZIP8, and ZIP14, induced under HIF-1α mediated inflammation can synergistically change [Zn 2+ ] i in inflammatory FLSs.

This study was conducted to investigate whether a transient receptor potential ankyrin 1 (TRPA1) antagonist (HC-030031) can reduce airway inflammation and hyperresponsiveness in a murine allergic rhinitis (AR) model. BALB/c mice were sensitized and challenged by ovalbumin (OVA) to induce AR. HC-030031 or vehicle was administrated to mice via intraperitoneal injection prior to OVA challenges. Nose-scratching events, histopathologic alterations of the airways, and bronchial hyperresponsiveness (BHR) were assessed. Differential cells and proinflammatory cytokines in the nasal lavage (NAL) and bronchoalveolar lavage (BAL) fluid were measured. Expressions of TRPA1 in nasal mucosa were examined by immunohistochemistry. TRPA1-expressing vagal neurons were labeled by immunofluorescent staining. HC-030031-treated AR mice had markedly reduced type-2 inflammation in nasal mucosa and ameliorated-nose-scratching events than AR mice received vehicle. HC-030031 treatment also dramatically reduced leucocyte numbers and IL-8 level in the BAL fluid, inhibited lower airway remodeling and fibrosis, and nearly abolished BHR. HC-0300031 treatment significantly inhibited the upregulated number of TRPA1 expressing nasal epithelial cells and TRPA1 expressing sensory neurons, leading to downregulation of SP in both upper and lower airways. Targeting TRPA1 may represent a promising strategy for treating AR and AR-related asthma., (© 2021 Federation of American Societies for Experimental Biology.)

Background: Classically activated macrophages contribute to the development of renal ischemia-reperfusion injury (IRI). This study aimed to investigate the role of transient receptor potential ankyrin 1 (Trpa1), a regulator of macrophage activation, in IRI-induced acute kidney injury (AKI) by using the Trpa1 gene knockout (Trpa1-/-) mouse model., Methods: Male 8-week-old Trpa1-/- mice and wild-type (WT) littermates were subjected to renal ischemia for 35 minutes by clamping bilateral renal pedicles under isoflurane anesthesia, and blood and tissue samples were collected 24 hours after reperfusion and analyzed with histological and molecular measurements., Results: Following IRI, Trpa1-/- mice developed more deteriorated biochemical and morphological signs of AKI when comparing with WT mice. More classically activated M1 macrophages were found in the kidneys of Trpa1-/- mice comparing with WT mice after IRI, while the counts of alternatively activated M2 macrophages in the kidney were similar between the 2 strains after IRI. Furthermore, significantly higher expression levels of proinflammatory markers including interleukin-1 beta and tumor necrosis factor alpha were detected in the kidney of Trpa1-/- mice compared with WT mice after IRI. The levels of TRPA1 protein in the kidney of WT mice were also decreased after IRI., Conclusions: Our results show that ablation of Trpa1 exacerbates infiltration of classically activated macrophages, renal inflammation, and renal injury in mice after IRI. These findings suggest that activation of TRPA1 may protect against IRI-induced AKI via regulation of macrophage-mediated inflammatory pathway., (© American Journal of Hypertension, Ltd 2020. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Aims: The aim of this study was to investigate the role of TRPA1 in the pathogenesis of AD., Main Methods: The experimental atopic dermatitis (AD)-like skin lesions were established using 2,4-dinitrochlorobenzene (DNCB). Mice were divided into three groups: TRPA1 -/- and WT groups were treated with DNCB dissolved in a 3:1 mixture of acetone and olive oil; the negative control group was treated with 3:1 mixture of acetone and olive oil without DNCB. The treatment lasted for 21 days, after which the animals were sacrificed and their blood, ears and dorsal skin tissue samples were collected for analysis., Key Findings: Lower dermatitis score, ear thickness, pruritus score, and epidermal hyperplasia were observed in mice in TRPA1 -/- mice compared to the WT group. Besides, lower dermal mast cell infiltration, proinflammatory cytokines, Th2 cytokines and the infiltration of macrophages were observed in the TRPA1 -/- mice compared to the WT group. Furthermore, we demonstrated that TRPA1 antagonist HC-030031 could alleviate AD-like symptoms and reduce the degree of epidermal hyperplasia in mice., Significance: TRPA1 has a crucial role during the AD pathogenesis in mice, thus may be used as a potential new target for treating patients with chronic skin inflammatory disease., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Transient receptor potential ankyrin 1 (TRPA1), a membrane protein ion channel, is known to mediate itch and pain in skin. The function of TRPA1, however, in psoriasiform dermatitis (PsD) is uncertain. Herein, we found that expression of TRPA1 is highly up-regulated in human psoriatic lesional skin. To study the role of TRPA1 in PsD, we assessed Psoriasis Severity Index (PSI) scores, transepidermal water loss (TEWL), skin thickness and pathology, and examined dermal inflammatory infiltrates, Th17-related genes and itch-related genes in c57BL/6 as wild-type (WT) and TRPA1 gene knockout (KO) mice following daily application of topical IMQ cream for 5 days. Compared with WT mice, clinical scores, skin thickness change and TEWL scores were similar on day 3, but were significantly decreased on day 5 in IMQ-treated TRPA1 KO mice (vs WT mice), suggesting reduced inflammation and skin barrier defects. Additionally, the relative area of epidermal Munro's microabscesses and mRNA levels of neutrophil inducible chemokines (S100A8, S100A9 and CXCL1) were decreased in the treated skin of TRPA1 KO mice, suggesting that neutrophil recruitment was impaired in the KO mice. Furthermore, mast cells, CD31 + blood vascular cells, CD45 + leukocytes and CD3 + T cells were all reduced in the treated skin of TRPA1 KO mice. Lastly, mRNA expression levels of IL-1β, IL-6, IL-23, IL-17A, IL-17F and IL-22 were decreased in TRPA1 KO mice. In summary, these results suggest a key role for TRPA1 in psoriasiform inflammation and raising its potential as a target for therapeutic intervention., (© 2019 The Authors. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine.)

The dietary constituent, resveratrol, was recently identified as a transient receptor potential ankyrin 1 (TRPA1) antagonist, voltage-dependent sodium ion (Na + ) channel, and cyclooxygenase-2 (COX-2) inhibitor. The aim of the present study was to investigate whether pretreatment with resveratrol attenuates acute inflammation-induced sensitization of nociceptive processing in rat spinal trigeminal nucleus caudalis (SpVc) and upper cervical (C1) dorsal horn neurons, via c-fos immunoreactivity. Mustard oil (MO), a TRPA1 channel agonist, was injected into the whisker pads of rats to induce inflammation. Pretreatment with resveratrol significantly decreased the mean thickness of inflammation-induced edema in whisker pads compared with those of untreated, inflamed rats. Ipsilateral of both the superficial and deep laminae of SpVc and C1 dorsal horn, there were significantly more c-fos-immunoreactive SpVc/C1 neurons in inflamed rats compared with naïve rats, and resveratrol pretreatment significantly decreased that number relative to untreated, inflamed rats. These results suggest that systemic administration of resveratrol attenuates acute inflammation-induced augmented nociceptive processing of trigeminal SpVc and C1 neurons. These findings support resveratrol as a potential therapeutic agent for use in alternative, complementary medicine to attenuate, or even prevent, acute trigeminal inflammatory pain., (© 2017 Eur J Oral Sci.)

Candida albicans can enter skeletal tissue through a skin wound in an immunocompromised host or by contamination during orthopedic surgery. Such Candida osteomyelitis is accompanied by severe pain and bone destruction. It is established that nociceptor innervation occurs in skin and bone, but the mechanisms of nociceptive modulation in fungal inflammation remain unclear. In this study, we show that C. albicans stimulates Nav1.8-positive nociceptors via the β-glucan receptor Dectin-1 to induce calcitonin gene-related peptide (CGRP). This induction of CGRP is independent of Bcl-10 or Malt-1 but dependent on transient receptor potential cation channel subfamily V member 1 (TRPV1)/transient receptor potential cation channel subfamily A member 1 (TRPA1) ion channels. Hindpaw β-glucan injection after Nav1.8-positive nociceptor ablation or in TRPV1/TRPA1 deficiency showed dramatically increased osteoinflammation accompanied by impaired CGRP production. Strikingly, CGRP suppressed β-glucan-induced inflammation and osteoclast multinucleation via direct suppression of nuclear factor-κB (NF-κB) p65 by the transcriptional repressor Jdp2 and inhibition of actin polymerization, respectively. These findings clearly suggest a role for Dectin-1-mediated sensocrine pathways in the resolution of fungal osteoinflammation., (Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.)

The transient receptor potential ankyrin 1 (TRPA1) channel has been implicated in pathophysiological processes that include asthma, cough, and inflammatory pain. Agonists of TRPA1 such as mustard oil and its key component allyl isothiocyanate (AITC) cause pain and neurogenic inflammation in humans and rodents, and TRPA1 antagonists have been reported to be effective in rodent models of pain. In our pursuit of TRPA1 antagonists as potential therapeutics, we generated AMG0902, a potent (IC 90 of 300 nM against rat TRPA1), selective, brain penetrant (brain to plasma ratio of 0.2), and orally bioavailable small molecule TRPA1 antagonist. AMG0902 reduced mechanically evoked C-fiber action potential firing in a skin-nerve preparation from mice previously injected with complete Freund's adjuvant, supporting the role of TRPA1 in inflammatory mechanosensation. In vivo target coverage of TRPA1 by AMG0902 was demonstrated by the prevention of AITC-induced flinching/licking in rats. However, oral administration of AMG0902 to rats resulted in little to no efficacy in models of inflammatory, mechanically evoked hypersensitivity; and no efficacy was observed in a neuropathic pain model. Unbound plasma concentrations achieved in pain models were about 4-fold higher than the IC 90 concentration in the AITC target coverage model, suggesting that either greater target coverage is required for efficacy in the pain models studied or TRPA1 may not contribute significantly to the underlying mechanisms., (© The Author(s) 2016.)

Objectives: Intra-articularly injected monosodium iodoacetate (MIA) induces joint pathology mimicking osteoarthritis (OA) and it is a widely used experimental model of OA. MIA induces acute inflammation, cartilage degradation and joint pain. Transient Receptor Potential Ankyrin 1 (TRPA1) is an ion channel known to mediate nociception and neurogenic inflammation. Here, we tested the hypothesis that TRPA1 would be involved in the development of MIA-induced acute inflammation, cartilage changes and joint pain., Methods: The effects of pharmacological blockade (by TCS 5861528) and genetic depletion of TRPA1 were studied in MIA-induced acute paw inflammation. Cartilage changes (histological scoring) and joint pain (weight-bearing test) in MIA-induced experimental OA were compared between wild type and TRPA1 deficient mice. The effects of MIA were also studied in primary human OA chondrocytes and in mouse cartilage., Results: MIA evoked acute inflammation, degenerative cartilage changes and joint pain in wild type mice. Interestingly, these responses were attenuated in TRPA1 deficient animals. MIA-induced paw inflammation was associated with increased tissue levels of substance P; and the inflammatory edema was reduced by pretreatment with catalase, with the TRPA1 antagonist TCS 5861528 and with the neurokinin 1 receptor antagonist L703,606. In chondrocytes, MIA enhanced interleukin-1 induced cyclooxygenase-2 (COX-2) expression, an effect that was blunted by pharmacological inhibition and genetic depletion of TRPA1., Conclusions: TRPA1 was found to mediate acute inflammation and the development of degenerative cartilage changes and joint pain in MIA-induced experimental OA in the mouse. The results reveal TRPA1 as a potential mediator and drug target in OA., (Copyright © 2015. Published by Elsevier Ltd.)

Hydrogen sulfide (H2 S), a toxic volcanic gas, functions as a gaseous physiological and pathophysiological molecule. Recently we have shown that H2 S elicits acute pain through the activation of transient receptor potential ankyrin 1 (TRPA1), which is expressed mainly in primary nociceptive neurons. We also demonstrated enhancement of H2 S-induced TRPA1 activation and pain under inflammatory acidic conditions, but the underlying mechanism has not been elucidated. Here, we attempted to clarify this mechanism by using endogenously TRPA1-expressing RIN-14B, a rat pancreatic islet cell line. For this purpose, the intracellular Ca(2+) concentration ([Ca(2+) ]i )], reactive oxygen species (ROS), and intracellular pH (pHi ) were measured with fluorescent imaging techniques. The intracellular H2 S concentration was assayed by the methylene blue method. To clarify the cellular function of H2 S, 5-hydroxytryptamine (5-HT) secretion was analyzed. In RIN-14B, the increase of [Ca(2+) ]i and the release of 5-HT induced by NaHS, an H2 S donor, were enhanced under inflammatory acidic conditions. Transition of H2 S into cells was enhanced at pH 6.8. H2 S failed to increase the intracellular ROS level and only slightly decreased pHi . These results suggest that H2 S directly activates TRPA1 and that its increment of diffusion into cells may be involved in the potentiation of TRPA1 activation under external acidic conditions. Thus, our study supports the pathophysiological functions of H2 S in inflammatory pain., (Copyright © 2013 Wiley Periodicals, Inc.)

This article in Frontiers in Pain Research explores the role of intraganglionic reactive oxygen species (ROS) in inflammatory pain and hyperalgesia in rats. The study suggests that ROS accumulation in the trigeminal ganglia contributes to hyperalgesia through the TRPA1 receptor. The researchers also discuss potential therapeutic approaches to reduce ROS accumulation or downregulate TRPA1 expression. The document further delves into the intraganglionic mechanisms involved in pain modulation, such as neuropeptide release, ion channel regulation, immune cell interaction, glial cell activation, synaptic plasticity, and modulation of sensory neuron excitability. The understanding of these mechanisms is crucial for developing targeted treatments for chronic pain conditions. The document acknowledges the financial support received for the research and declares no conflicts of interest. [Extracted from the article]

Background and Purpose: Pulpitis is associated with tooth hypersensitivity and results in pulpal damage. Thermosensitive transient receptor potential (TRP) ion channels expressed in the dental pulp may be key transducers of inflammation and nociception. We aimed at investigating the expression and role of thermo‐TRPs in primary human dental pulp cells (hDPCs) in normal and inflammatory conditions. Experimental Approach: Inflammatory conditions were induced in hDPC cultures by applying polyinosinic:polycytidylic acid (poly(I:C)). Gene expression and pro‐inflammatory cytokine release were measured by RT‐qPCR and ELISA. Functions of TRPA1 channels were investigated by monitoring changes in intracellular Ca2+ concentration. Mitochondrial superoxide production was measured using a fluorescent substrate. Cellular viability was assessed by measuring the activity of mitochondrial dehydrogenases and cytoplasmic esterases. TRPA1 activity was modified by agonists, antagonists, and gene silencing. Key Results: Transcripts of TRPV1, TRPV2, TRPV4, TRPC5, and TRPA1 were highly expressed in control hDPCs, whereas TRPV3, TRPM2, and TRPM3 expressions were much lower, and TRPM8 was not detected. Poly(I:C) markedly up‐regulated TRPA1 but not other thermo‐TRPs. TRPA1 agonist‐induced Ca2+ signals were highly potentiated in inflammatory conditions. Poly(I:C)‐treated cells displayed increased Ca2+ responses to H2O2, which was abolished by TRPA1 antagonists. Inflammatory conditions induced oxidative stress, stimulated mitochondrial superoxide production, resulted in mitochondrial damage, and decreased cellular viability of hDPCs. This inflammatory cellular damage was partly prevented by the co‐application of TRPA1 antagonist or TRPA1 silencing. Conclusion and Implications: Pharmacological blockade of TRPA1 channels may be a promising therapeutic approach to alleviate pulpitis and inflammation‐associated pulpal damage. [ABSTRACT FROM AUTHOR]

Kaifang Yao,1,* Zhihan Chen,1,* Yanwei Li,1 Baomin Dou,1 Zhifang Xu,1– 3 Yajing Ma,1 Simin Du,1 Jiangshan Wang,1 Jiangjiang Fu,1 Qi Liu,1 Zezhi Fan,1 Yangyang Liu,1– 3 Xiaowei Lin,1– 3 Yuan Xu,1– 3 Yuxin Fang,1– 3 Shenjun Wang,1– 3 Yi Guo1,3,4 1Research Center of Experimental Acupuncture Science, Tianjin University of Traditional Chinese Medicine, Tianjin City, People’s Republic of China; 2School of Acupuncture & Moxibustion and Tuina, Tianjin University of Traditional Chinese Medicine, Tianjin City, People’s Republic of China; 3National Clinical Research Center for Chinese Medicine Acupuncture and Moxibustion, Tianjin City, People’s Republic of China; 4School of Chinese Medicine, Tianjin University of Traditional Chinese Medicine, Tianjin City, People’s Republic of China*These authors contributed equally to this workCorrespondence: Yi Guo; Shenjun Wang, School of Acupuncture & Moxibustion and Tuina, Tianjin University of Traditional Chinese Medicine, No. 10 Poyang Lake Road, Tuanbo New Town, Jinghai District, Tianjin, 301617, People’s Republic of China, Tel +86 22-5959-6290, Email guoyi_168@163.com; shenjunwang@163.comPurpose: Acupuncture (ACU) has been demonstrated to alleviate inflammatory pain. Mechanoreceptors are present in acupuncture points. When acupuncture exerts mechanical force, these ion channels open and convert the mechanical signals into biochemical signals. TRPA1 (T ransient receptor potential ankyrin 1) is capable of sensing various physical and chemical stimuli and serves as a sensor for inflammation and pain. This protein is expressed in immune cells and contributes to local defense mechanisms during early tissue damage and inflammation. In this study, we investigated the role of TRPA1 in acupuncture analgesia.Patients and Methods: We injected complete Freund’s adjuvant (CFA) into the mouse plantars to establish a hyperalgesia model. Immunohistochemistry and immunofluorescence analyses were performed to determine the effect of acupuncture on the TRPA1 expression in the Zusanli (ST36). We used TRPA1−/− mouse and pharmacological methods to antagonize TRPA1 to observe the effect on acupuncture analgesia. On this basis, collagenase was used to destroy collagen fibers at ST36 to observe the effect on TRPA1.Results: We found that the ACU group vs the CFA group, the number of TRPA1-positive mast cells, macrophages, and fibroblasts at the ST36 increased significantly. In CFA- inflammatory pain models, the TRPA1−/− ACU vs TRPA1+/+ ACU groups, the paw withdrawal latency (PWL) and paw withdrawal threshold (PWT) downregulated significantly. In the ACU + high-, ACU + medium-, ACU + low-dose HC-030031 vs ACU groups, the PWL and PWT were downregulated, and in carrageenan-induced inflammatory pain models were consistent with these results. We further found the ACU + collagenase vs ACU groups, the numbers of TRPA1-positive mast cells, macrophages, and fibroblasts at the ST36 were downregulated.Conclusion: These findings together imply that TRPA1 plays a significant role in the analgesic effects produced via acupuncture at the ST36. This provides new evidence for acupuncture treatment of painful diseases.Keywords: acupuncture, TRPA1, ST36, inflammation, immune, analgesia

Progressive articular surface degradation during arthritis causes ongoing pain and hyperalgesia that lead to the development of functional disability. TRPA1 channel significantly contributes to the activation of sensory neurons that initiate neurogenic inflammation and mediates pain signal transduction to the central nervous system. Peptide Ms 9a-1 from the sea anemone Metridium senile is a positive allosteric modulator of TRPA1 and shows significant anti-inflammatory and analgesic activity in different models of pain. We used a model of monosodium iodoacetate (MIA)-induced osteoarthritis to evaluate the anti-inflammatory properties of Ms 9a-1 in comparison with APHC3 (a polypeptide modulator of TRPV1 channel) and non-steroidal anti-inflammatory drugs (NSAIDs) such as meloxicam and ibuprofen. Administration of Ms 9a-1 (0.1 mg/kg, subcutaneously) significantly reversed joint swelling, disability, thermal and mechanical hypersensitivity, and grip strength impairment. The effect of Ms 9a-1 was equal to or better than that of reference drugs. Post-treatment histological analysis revealed that long-term administration of Ms9a-1 could reduce inflammatory changes in joints and prevent the progression of cartilage and bone destruction at the same level as meloxicam. Peptide Ms 9a-1 showed significant analgesic and anti-inflammatory effects in the model of MIA-induced OA, and therefore positive allosteric modulators could be considered for the alleviation of OA symptoms. [ABSTRACT FROM AUTHOR]

Background and purpose: Addition of preservatives ensures microbial stability, especially in multidose containers of parenterally administered pharmaceuticals. These compounds can cause side effects, and particularly at the site of application, might elicit or facilitate pain. TRPA1 is a cation channel expressed in peripheral neurons which contributes to pain and inflammation and is sensitive to many irritants. The most commonly used preservatives, in particular with a focus on parenteral formulations, were investigated for their potential to activate TRPA1. Experimental approach: Sixteen preservatives were screened for mediating calcium influx in human TRPA1-transfected HEK293t cells. Untransfected cells served as control, results were further validated in mouse sensory neurons. In addition, proinflammatory mediators serotonin, histamine and prostaglandin E2 were co-administered to probe a potential sensitisation of preservativeinduced TRPA1 activation. Key results: Butylparaben, propylparaben, ethylparaben, bronopol, methylparaben, phenylethyl alcohol and phenol induced a TRPA1-dependent calcium influx in transfected HEK293t cells at concentrations used for preservation. Other preservatives increased calcium within the used concentration ranges, but to a similar degree in untransfected controls. Serotonin, histamine, and prostaglandin enhanced TRPA1 activation of phenylethyl alcohol, bronopol, ethylparaben, propylparaben and butylparaben. Conclusion and implications: Systematic screening of common preservatives applied for parenterally administered drugs resulted in identifying several preservatives with substantial TRPA1 channel activation. This activation was enhanced by the addition of proinflammatory meditators. This allows selecting a preservative without TRPA1 activation, particularly in case of pharmaceuticals that could act proinflammatory. [ABSTRACT FROM AUTHOR]

Introduction: Stilbenoid compounds have been described to have antiinflammatory properties in animal models in vivo, and have been shown to inhibit Ca2+-influx through the transient receptor potential ankyrin 1 (TrpA1). Methods: To study how stilbenoid compounds affect inflammatory signaling in vivo, we have utilized the fruit fly, Drosophila melanogaster, as a model system. To induce intestinal inflammation in the fly, we have fed flies with the intestinal irritant dextran sodium sulphate (DSS). Results: We found that DSS induces severe changes in the bacteriome of the Drosophila intestine, and that this dysbiosis causes activation of the NF-kB transcription factor Relish. We have taken advantage of the DSS-model to study the anti-inflammatory properties of the stilbenoid compounds pinosylvin (PS) and pinosylvin monomethyl ether (PSMME). With the help of in vivo approaches, we have identified PS and PSMME to be transient receptor ankyrin 1 (TrpA1)-dependent antagonists of NF-κB-mediated intestinal immune responses in Drosophila. We have also computationally predicted the putative antagonist binding sites of these compounds at Drosophila TrpA1. Discussion: Taken together, we show that the stilbenoids PS and PSMME have anti-inflammatory properties in vivo in the intestine and can be used to alleviate chemically induced intestinal inflammation in Drosophila. [ABSTRACT FROM AUTHOR]

Background and purpose: Addition of preservatives ensures microbial stability, especially in multidose containers of parenterally administered pharmaceuticals. These compounds can cause side effects, and particularly at the site of application, might elicit or facilitate pain. TRPA1 is a cation channel expressed in peripheral neurons which contributes to pain and inflammation and is sensitive to many irritants. The most commonly used preservatives, in particular with a focus on parenteral formulations, were investigated for their potential to activate TRPA1.Experimental approach: Sixteen preservatives were screened for mediating calcium influx in human TRPA1-transfected HEK293t cells. Untransfected cells served as control, results were further validated in mouse sensory neurons. In addition, proinflammatory mediators serotonin, histamine and prostaglandin E2 were co-administered to probe a potential sensitisation of preservative-induced TRPA1 activation.Key results: Butylparaben, propylparaben, ethylparaben, bronopol, methylparaben, phenylethyl alcohol and phenol induced a TRPA1-dependent calcium influx in transfected HEK293t cells at concentrations used for preservation. Other preservatives increased calcium within the used concentration ranges, but to a similar degree in untransfected controls. Serotonin, histamine, and prostaglandin enhanced TRPA1 activation of phenylethyl alcohol, bronopol, ethylparaben, propylparaben and butylparaben.Conclusion and implications: Systematic screening of common preservatives applied for parenterally administered drugs resulted in identifying several preservatives with substantial TRPA1 channel activation. This activation was enhanced by the addition of proinflammatory meditators. This allows selecting a preservative without TRPA1 activation, particularly in case of pharmaceuticals that could act proinflammatory.

Background: Transient receptor potential ankyrin 1 (TRPA1) channels are known to be actively involved in various pathophysiological conditions, including neuronal inflammation, neuropathic pain, and various immunological responses. Heat shock protein 90 (Hsp90), a cytoplasmic molecular chaperone, is well-reported for various cellular and physiological processes. Hsp90 inhibition by various molecules has garnered importance for its therapeutic significance in the downregulation of inflammation and are proposed as anti-cancer drugs. However, the possible role of TRPA1 in the Hsp90-associated modulation of immune responses remains scanty. Results: Here, we have investigated the role of TRPA1 in regulating the anti-inflammatory effect of Hsp90 inhibition via 17-(allylamino)-17-demethoxygeldanamycin (17-AAG) in lipopolysaccharide (LPS) or phorbol 12-myristate 13-acetate (PMA) stimulation in RAW 264.7, a mouse macrophage cell lines and PMA differentiated THP-1, a human monocytic cell line similar to macrophages. Activation of TRPA1 with Allyl isothiocyanate (AITC) is observed to execute an anti-inflammatory role via augmenting Hsp90 inhibition-mediated anti-inflammatory responses towards LPS or PMA stimulation in macrophages, whereas inhibition of TRPA1 by 1,2,3,6-Tetrahydro-1,3-dimethyl-N-[4-(1-methylethyl)phenyl]-2,6-dioxo-7 H-purine-7-acetamide,2-(1,3-Dimethyl-2,6-dioxo-1,2,3,6-tetrahydro-7 H-purin-7-yl)-N-(4-isopropylphenyl)acetamide (HC-030031) downregulates these developments. LPS or PMA-induced macrophage activation was found to be regulated by TRPA1. The same was confirmed by studying the levels of activation markers (major histocompatibility complex II (MHCII), cluster of differentiation (CD) 80 (CD80), and CD86, pro-inflammatory cytokines (tumor necrosis factor (TNF) and interleukin 6 (IL-6)), NO (nitric oxide) production, differential expression of mitogen-activated protein kinase (MAPK) signaling pathways (p-p38 MAPK, phospho-extracellular signal-regulated kinase 1/2 (p-ERK 1/2), and phosphor-stress-activated protein kinase/c-Jun N-terminal kinase (p-SAPK/JNK)), and induction of apoptosis. Additionally, TRPA1 has been found to be an important contributor to intracellular calcium levels toward Hsp90 inhibition in LPS or PMA-stimulated macrophages. Conclusion: This study indicates a significant role of TRPA1 in Hsp90 inhibition-mediated anti-inflammatory developments in LPS or PMA-stimulated macrophages. Activation of TRPA1 and inhibition of Hsp90 has synergistic roles towards regulating inflammatory responses associated with macrophages. The role of TRPA1 in Hsp90 inhibition-mediated modulation of macrophage responses may provide insights towards designing future novel therapeutic approaches to regulate various inflammatory responses. [ABSTRACT FROM AUTHOR]

Abstract Background Systemic sclerosis is a rheumatoid disease best known for its fibrotic skin manifestations called scleroderma. Alternatively activated (M2-type) macrophages are normally involved in the resolution of inflammation and wound healing but also in fibrosing diseases such as scleroderma. TRPA1 is a non-selective cation channel, activation of which causes pain and neurogenic inflammation. In the present study, we investigated the role of TRPA1 in bleomycin-induced skin fibrosis mimicking scleroderma. Methods Wild type and TRPA1-deficient mice were challenged with intradermal bleomycin injections to induce a scleroderma-mimicking disease. Macrophages were investigated in vitro to evaluate the underlying mechanisms. Results Bleomycin induced dermal thickening and collagen accumulation in wild type mice and that was significantly attenuated in TRPA1-deficient animals. Accordingly, the expression of collagens 1A1, 1A2, and 3A1 as well as pro-fibrotic factors TGF-beta, CTGF, fibronectin-1 and YKL-40, and M2 macrophage markers Arg1 and MRC1 were lower in TRPA1-deficient than wild type mice. Furthermore, bleomycin was discovered to significantly enhance M2-marker expression particularly in the presence of IL-4 in wild type macrophages in vitro, but not in macrophages harvested from TRPA1-deficient mice. IL-4-induced PPARγ-expression in macrophages was increased by bleomycin, providing a possible mechanism behind the phenomenon. Conclusions In conclusion, the results indicate that interfering TRPA1 attenuates fibrotic and inflammatory responses in bleomycin-induced scleroderma. Therefore, TRPA1-blocking treatment could potentially alleviate M2 macrophage driven diseases like systemic sclerosis and scleroderma.

The detection of environmental temperatures is critical for survival, yet inappropriate responses to thermal stimuli can have a negative impact on overall health. The physiological effect of cold is distinct among somatosensory modalities in that it is soothing and analgesic, but also agonizing in the context of tissue damage. Inflammatory mediators produced during injury activate nociceptors to release neuropeptides, such as calcitonin gene-related peptide (CGRP) and substance P, inducing neurogenic inflammation, which further exasperates pain. Many inflammatory mediators induce sensitization to heat and mechanical stimuli but, conversely, inhibit cold responsiveness, and the identity of molecules inducing cold pain peripherally is enigmatic, as are the cellular and molecular mechanisms altering cold sensitivity. Here, we asked whether inflammatory mediators that induce neurogenic inflammation via the nociceptive ion channels TRPV1 (vanilloid subfamily of transient receptor potential channel) and TRPA1 (transient receptor potential ankyrin 1) lead to cold pain in mice. Specifically, we tested cold sensitivity in mice after intraplantar injection of lysophosphatidic acid or 4-hydroxy-2-nonenal, finding that each induces cold pain that is dependent on the cold-gated channel transient receptor potential melastatin 8 (TRPM8). Inhibition of CGRP, substance P, or toll-like receptor 4 (TLR4) signaling attenuates this phenotype, and each neuropeptide produces TRPM8-dependent cold pain directly. Further, the inhibition of CGRP or TLR4 signaling alleviates cold allodynia differentially by sex. Last, cold pain induced by both inflammatory mediators and neuropeptides requires TRPM8, as well as the neurotrophin artemin and its receptor GDNF receptor a3 (GFRa3). These results are consistent with artemin-induced cold allodynia requiring TRPM8, demonstrating that neurogenic inflammation alters cold sensitivity via localized artemin release that induces cold pain via GFRa3 and TRPM8. [ABSTRACT FROM AUTHOR]

Osteoarthritis (OA) is a chronic joint disease with increasing prevalence. Chondrocytes (CHs) are highly differentiated end-stage cells with a secretory phenotype that keeps the extracellular matrix (ECM) balanced and the cartilage environment stable. Osteoarthritis dedifferentiation causes cartilage matrix breakdown, accounting for one of the key pathogenesis of osteoarthritis. Recently, the activation of transient receptor potential ankyrin 1 (TRPA1) was claimed to be a risk factor in osteoarthritis by causing inflammation and extracellular matrix degradation. However, the underlying mechanism is still unknown. Due to its mechanosensitive property, we speculated that the role of TRPA1 activation during osteoarthritis is matrix stiffness-dependent. In this study, we cultured the chondrocytes from patients with osteoarthritis on stiff vs. soft substrates, treated them with allyl isothiocyanate (AITC), a transient receptor potential ankyrin 1 agonist, and compared the chondrogenic phenotype, containing cell shape, F-actin cytoskeleton, vinculin, synthesized collagen profiles and their transcriptional regulatory factor, and inflammation-related interleukins. The data suggest that allyl isothiocyanate treatment activates transient receptor potential ankyrin 1 and results in both positive and harmful effects on chondrocytes. In addition, a softer matrix could help enhance the positive effects and alleviate the harmful ones. Thus, the effect of allyl isothiocyanate on chondrocytes is conditionally controllable, which could be associated with transient receptor potential ankyrin 1 activation, and is a promising strategy for osteoarthritis treatment.

Arthroplasty is an orthopedic surgical procedure that replaces a dysfunctional joint by an orthopedic prosthesis, thereby restoring joint function. Upon the use of the joint prosthesis, a wearing process begins, which releases components such as titanium dioxide (TiO2) that trigger an immune response in the periprosthetic tissue, leading to arthritis, arthroplasty failure, and the need for revision. Flavonoids belong to a class of natural polyphenolic compounds that possess antioxidant and anti-inflammatory activities. Hesperidin methyl chalcone's (HMC) analgesic, anti-inflammatory, and antioxidant effects have been investigated in some models, but its activity against the arthritis caused by prosthesis-wearing molecules, such as TiO2, has not been investigated. Mice were treated with HMC (100 mg/kg, intraperitoneally (i.p.)) 24 h after intra-articular injection of 3 mg/joint of TiO2, which was used to induce chronic arthritis. HMC inhibited mechanical hyperalgesia, thermal hyperalgesia, joint edema, leukocyte recruitment, and oxidative stress in the knee joint (alterations in gp91phox, GSH, superoxide anion, and lipid peroxidation) and in recruited leukocytes (total reactive oxygen species and GSH); reduced patellar proteoglycan degradation; and decreased pro-inflammatory cytokine production. HMC also reduced the activation of nociceptor-sensory TRPV1+ and TRPA1+ neurons. These effects occurred without renal, hepatic, or gastric damage. Thus, HMC reduces arthritis triggered by TiO2, a component released upon wearing of prosthesis. [ABSTRACT FROM AUTHOR]

Pain is often debilitating, and current treatments are neither universally efficacious nor without risks. Transient receptor potential (TRP) ion channels offer alternative targets for pain relief, but little is known about the regulation or identities of endogenous TRP ligands that affect inflammation and pain. Here, transcriptomic and targeted lipidomic analysis of damaged tissue from the mouse spinal nerve ligation (SNL)-induced chronic pain model revealed a time-dependent increase in Cyp1b1 mRNA and a concurrent accumulation of 8,9-epoxyeicosatrienoic acid (EET) and 19,20-EpDPA post injury. Production of 8,9-EET and 19,20-EpDPA by human/mouse CYP1B1 was confirmed in vitro, and 8,9-EET and 19,20-EpDPA selectively and dose-dependently sensitized and activated TRPA1 in overexpressing HEK-293 cells and Trpa1 -expressing/AITC-responsive cultured mouse peptidergic dorsal root ganglia (DRG) neurons. TRPA1 activation by 8,9-EET and 19,20-EpDPA was attenuated by the antagonist A967079, and mouse TRPA1 was more responsive to 8,9-EET and 19,20-EpDPA than human TRPA1. This latter effect mapped to residues Y933, G939, and S921 of TRPA1. Intra-plantar injection of 19,20-EpDPA induced acute mechanical, but not thermal hypersensitivity in mice, which was also blocked by A967079. Similarly, Cyp1b1 -knockout mice displayed a reduced chronic pain phenotype following SNL injury. These data suggest that manipulation of the CYP1B1–oxylipin–TRPA1 axis might have therapeutic benefit. Targeting CYP1B1–Oxylipin–TRPA1 network may represent a novel treatment option for preventing chronic pain in patients. [Display omitted] [ABSTRACT FROM AUTHOR]

Progressive articular surface degradation during arthritis causes ongoing pain and hyperalgesia that lead to the development of functional disability. TRPA1 channel significantly contributes to the activation of sensory neurons that initiate neurogenic inflammation and mediates pain signal transduction to the central nervous system. Peptide Ms 9a-1 from the sea anemone Metridium senile is a positive allosteric modulator of TRPA1 and shows significant anti-inflammatory and analgesic activity in different models of pain. We used a model of monosodium iodoacetate (MIA)-induced osteoarthritis to evaluate the anti-inflammatory properties of Ms 9a-1 in comparison with APHC3 (a polypeptide modulator of TRPV1 channel) and non-steroidal anti-inflammatory drugs (NSAIDs) such as meloxicam and ibuprofen. Administration of Ms 9a-1 (0.1 mg/kg, subcutaneously) significantly reversed joint swelling, disability, thermal and mechanical hypersensitivity, and grip strength impairment. The effect of Ms 9a-1 was equal to or better than that of reference drugs. Post-treatment histological analysis revealed that long-term administration of Ms9a-1 could reduce inflammatory changes in joints and prevent the progression of cartilage and bone destruction at the same level as meloxicam. Peptide Ms 9a-1 showed significant analgesic and anti-inflammatory effects in the model of MIA-induced OA, and therefore positive allosteric modulators could be considered for the alleviation of OA symptoms.

The transient receptor potential (TRP) protein superfamily is a special group of cation channels expressed in different cell types and signaling pathways. In this review, we focus on TRPA1 (transient receptor potential ankyrin 1), an ion channel in this family that exists in the cell membrane and shows a different function from other TRP channels. TRPA1 usually has a special activation effect that can induce cation ions, especially calcium ions, to flow into activated cells. In this paper, we review the role of TRPA1 in fibroblasts. To clarify the relationship between fibroblasts and TRPA1, we have also paid special attention to the interactions between TRPA1 and inflammatory factors leading to fibroblast activation. TRPA1 has different functions in the fibrosis process in different organs, and there have also been interesting discussions of the mechanism of TRPA1 in fibroblasts. Therefore, this review aims to describe the function of TRP channels in controlling fibrosis through fibroblasts in different organ inflammatory and immune-mediated diseases. We attempt to prove that TRPA1 is a target for fibrosis. In fact, some clinical trials have already proven that TRPA1 is a potential adjuvant therapy for treating fibrosis. [ABSTRACT FROM AUTHOR]

The TRPA1 channel is involved in a variety of physiological processes and its activation leads to pain perception and the development of inflammation. Peptide Ms 9a-1 from sea anemone Metridium senile is a positive modulator of TRPA1 and causes significant analgesic and anti-inflammatory effects by desensitization of TRPA1-expressing sensory neurons. For structural and functional analysis of Ms 9a-1, we produced four peptides—Ms 9a-1 without C-terminal domain (abbreviated as N-Ms), short C-terminal domain Ms 9a-1 alone (C-Ms), and two homologous peptides (Ms 9a-2 and Ms 9a-3). All tested peptides possessed a reduced potentiating effect on TRPA1 compared to Ms 9a-1 in vitro. None of the peptides reproduced analgesic and anti-inflammatory properties of Ms 9a-1 in vivo. Peptides N-Ms and C-Ms were able to reduce pain induced by AITC (selective TRPA1 agonist) but did not decrease AITC-induced paw edema development. Fragments of Ms 9a-1 did not effectively reverse CFA-induced thermal hyperalgesia and paw edema. Ms 9a-2 and Ms 9a-3 possessed significant effects and anti-inflammatory properties in some doses, but their unexpected efficacy and bell-shape dose–responses support the hypothesis of other targets involved in their effects in vivo. Therefore, activity comparison of Ms 9a-1 fragments and homologues peptides revealed structural determinants important for TRPA1 modulation, as well as analgesic and anti-inflammatory properties of Ms9a-1. [ABSTRACT FROM AUTHOR]

Introduction: Transient receptor potential ankyrin 1 (TRPA1) is a protein expressed in many living organisms. During the study of TRPA1, its unique biological role as a universal and polymodal sensor of various altering agents was found. The aim of this study is to search and generalize information about structural features and molecular determinants, mechanisms of activation, action and modulation of TRPA1 as a universal pain and inflammation sensor, as well as the nature of activators and antagonists of this target and their therapeutic potential. Materials and methods: This article presents an overview of the results of scientific research of TRPA1, its modulators, as well as an overview of their pharmacological potential over the period from the discovery of these channels to the present, with an emphasis on the last decade. Results and discussion: The main collected data on expression, structural features and molecular determinants, mechanisms of activation and action of TRPA1 indicate its role as a universal and labile element of the primary response of the body to adverse exogenous and endogenous factors. Regardless of the nature of the stimulus, hyperstimulation of TRPA1 channels can lead to such phenomena as pain, inflammation, itching, edema and other manifestations of alteration, and therefore TRPA1 blockade can be used in the treatment of various diseases accompanied by these pathological conditions. Currently, TRPA1 antagonists are being actively searched for and studied, as evidenced by a high patent activity over the past 14 years; however, the molecular mechanisms of action and pharmacological properties of TRPA1 blockers remain understudied. Conclusion: Acquire of new information about TRPA1 will help in the development of its modulators, which can become promising analgesics, anti-inflammatory drugs, bronchodilators, and agents for the treatment of cardiovascular diseases of new generations. [ABSTRACT FROM AUTHOR]

The transient receptor potential ankyrin 1 (TRPA1), a member of the TRP superfamily of channels, is primarily localized in a subpopulation of primary sensory neurons of the trigeminal, vagal, and dorsal root ganglia, where its activation mediates neurogenic inflammatory responses. TRPA1 expression in resident tissue cells, inflammatory, and immune cells, through the indirect modulation of a large series of intracellular pathways, orchestrates a range of cellular processes, such as cytokine production, cell differentiation, and cytotoxicity. Therefore, the TRPA1 pathway has been proposed as a protective mechanism to detect and respond to harmful agents in various pathological conditions, including several inflammatory diseases. Specific attention has been paid to TRPA1 contribution to the transition of inflammation and immune responses from an early defensive response to a chronic pathological condition. In this view, TRPA1 antagonists may be regarded as beneficial tools for the treatment of inflammatory conditions. [ABSTRACT FROM AUTHOR]

Activation of pancreatic stellate cells attenuates intracellular Ca SP 2+ sp signals due to downregulation of TRPA1 and protects against cell death induced by alcohol metabolites. Keywords: TRPA1; Ca 2+ signaling; pancreatic stellate cells; pancreatic fibrosis; alcoholic pancreatitis EN TRPA1 Ca 2+ signaling pancreatic stellate cells pancreatic fibrosis alcoholic pancreatitis 1 3 3 10/21/22 20220901 NES 220901 The TRP channel TRPA1, also known as the transient receptor potential ankyrin 1 channel or the Wasabi receptor, is regarded as an important mediator of the inflammatory actions of environmental irritants.[1],[2] Although the channel has been primarily studied in nerves, it is present in many different tissues.[1] It is a relatively nonselective cation channel with a significant permeability for Ca SP 2+ sp and opening of the channel will therefore mediate Ca SP 2+ sp influx.[1] It has been shown that TRPA1 can be activated by a number of noxious chemical agents as well as by the inflammatory peptide bradykinin (BK).[3] BK has for a long time been implicated in the inflammatory disease acute pancreatitis[4] and since TRPA1 is expressed widely in the gastro-intestinal tract[1], it would be of interest to investigate the possible role of this channel in the pathophysiology of pancreatitis. These Ca SP 2+ sp signals cause both acinar and stellate cell necrosis.[5] When most of the stellate cells are dead, chronic pancreatitis cannot develop because only these cells are capable of producing the fibrotic microenvironment. [Extracted from the article]

Apoptosis, overload Ca2+ entry and oxidative stress are induced in neurons by hypoxia. Drug-resistant cancer cells are killed by hypoxic conditions. α-Lipoic acid (ALA) has antioxidant and pro-oxidant functions. The TRPA1 channel is activated by oxidative stress and pro-oxidant ALA may have a regulator role in the TRPA1 activity in the human glioblastoma (DBTRG) cells. The aim of this study was to evaluate if a combination therapy of ALA with a hypoxia can alter the effect of this hypoxia through TRPA1 activation in the DBTRG cells.The DBTRG cells were divided into four treatment groups as control, ALA (50 μM), and hypoxia and hypoxia + ALA. Hypoxia in the cells was induced by CoCl2 (200 μM).Apoptosis, Annexin V, mitochondrial membrane depolarization (JC-1), reactive oxygen species (ROS) production, IL-1β, IL-18, caspase 3 and 9 values were increased through activation of TRPA1 (cinnamaldehyde) in the cells by the hypoxia induction, although cell viability, reduced glutathione and glutathione peroxidase values were decreased by the treatments. The values were modulated in the cells by TRPA1 blocker (AP18) and ALA treatments. Involvements of TRPA1 activity on values in the cells were also confirmed by patch-clamp and laser confocal microscopy analyses.In conclusion, apoptotic, inflammatory and oxidant effects of hypoxia were increased by activation of TRPA1, but its action on the values was decreased by the ALA treatment. ALA treatment could be used as an effective strategy in the treatment of hypoxia-induced oxidative stress, apoptosis and inflammation in the neurons.

The TRPA1 channel is involved in a variety of physiological processes and its activation leads to pain perception and the development of inflammation. Peptide Ms 9a-1 from sea anemone Metridium senile is a positive modulator of TRPA1 and causes significant analgesic and anti-inflammatory effects by desensitization of TRPA1-expressing sensory neurons. For structural and functional analysis of Ms 9a-1, we produced four peptides—Ms 9a-1 without C-terminal domain (abbreviated as N-Ms), short C-terminal domain Ms 9a-1 alone (C-Ms), and two homologous peptides (Ms 9a-2 and Ms 9a-3). All tested peptides possessed a reduced potentiating effect on TRPA1 compared to Ms 9a-1 in vitro. None of the peptides reproduced analgesic and anti-inflammatory properties of Ms 9a-1 in vivo. Peptides N-Ms and C-Ms were able to reduce pain induced by AITC (selective TRPA1 agonist) but did not decrease AITC-induced paw edema development. Fragments of Ms 9a-1 did not effectively reverse CFA-induced thermal hyperalgesia and paw edema. Ms 9a-2 and Ms 9a-3 possessed significant effects and anti-inflammatory properties in some doses, but their unexpected efficacy and bell-shape dose–responses support the hypothesis of other targets involved in their effects in vivo. Therefore, activity comparison of Ms 9a-1 fragments and homologues peptides revealed structural determinants important for TRPA1 modulation, as well as analgesic and anti-inflammatory properties of Ms9a-1.

TRPA1 is a calcium permeable non-selective cation channel, its expression is up-regulated in atherosclerosis plaque, yet its function in macrophages activation is unknown. We sought to establish the role of TRPA1 in inflammatory macrophages activation. TRPA1 −/− ApoE −/− mice and C57BL/6 J control were treated with a high-fat diet (HFD) and the TRPA1 agonist cinnamaldehyde (CIN). Third-order branches of superior aorta of patients and mice were collected. Oil Red O staining and hematoxylin and eosin staining were performed to measure atherosclerotic lesions. The RNA-seq was performed to identify TRPA1 function in atherosclerosis. The expression of bone marrow-derived macrophages (BMDMs) markers was tested by Western blot. In addition, the levels of inflammatory factors were checked by ELISA. Chromatin immunoprecipitation (ChIP)-PCR and luciferase reporter gene assays were used to explore if TRPA1 could regulate histone modifications. TRPA1 −/− ApoE −/− mice showed a significant increase in atherosclerosis plaques compared to ApoE −/− mice after HFD treatment. Conversely, activation of TRPA1 by CIN sharply reduced atherosclerosis progression. Atherosclerosis was associated with a significant change in macrophage polarization toward the M1 proinflammatory phenotype. We found that inhibition of TRPA1 remarkably stimulated M1 marker genes expression, while repressed M2 marker genes expression. The interaction between TRPA1 and Ezh2, a subunit of polycomb repressive complex 2, suppressed the proteasome-dependent degradation of Ezh2. Thus, TRPA1 epigenetically regulated H3K27 trimethylation level in macrophages. Our results demonstrate that TRPA1, up-regulated in atherosclerosis plaque, could regulate the macrophages toward an inflammatory phenotype, thereby modulating atherosclerosis progression. Activation of TRPA1 might serve as an atherosclerosis therapeutic target. Image 1 • TRPA1 activation reduced atherosclerosis progression by suppressing macrophage polarization toward the M1 proinflammatory phenotype. • The interaction between TRPA1 and Ezh2 suppressed the proteasome-dependent degradation of Ezh2, which regulated H3K27 trimethylation level in macrophages epigenetically. • TRPA1 might play an important role in the pathogenesis of atherosclerosis. • Targeting the action of TRPA1 in polarizes macrophages presents a potential therapeutic intervention for atherosclerosis. [ABSTRACT FROM AUTHOR]

Intracellular free zinc ([Zn2+]i) is mobilized in neuronal and non-neuronal cells under physiological and/or pathophysiological conditions; therefore, [Zn2+]i is a component of cellular signal transduction in biological systems. Although several transporters and ion channels that carry Zn2+ have been identified, proteins that are involved in Zn2+ supply into cells and their expression are poorly understood, particularly under inflammatory conditions. Here, we show that the expression of Zn2+ transporters ZIP8 and ZIP14 is increased via the activation of hypoxia-induced factor 1α (HIF-1α) in inflammation, leading to [Zn2+]i accumulation, which intrinsically activates transient receptor potential ankyrin 1 (TRPA1) channel and elevates basal [Zn2+]i. In human fibroblast-like synoviocytes (FLSs), treatment with inflammatory mediators, such as tumor necrosis factor-α (TNF-α) and interleukin-1α (IL-1α), evoked TRPA1-dependent intrinsic Ca2+ oscillations. Assays with fluorescent Zn2+ indicators revealed that the basal [Zn2+]i concentration was significantly higher in TRPA1-expressing HEK cells and inflammatory FLSs. Moreover, TRPA1 activation induced an elevation of [Zn2+]i level in the presence of 1 μM Zn2+ in inflammatory FLSs. Among the 17 out of 24 known Zn2+ transporters, FLSs that were treated with TNF-α and IL-1α exhibited a higher expression of ZIP8 and ZIP14. Their expression levels were augmented by transfection with an active component of nuclear factor-κB P65 and HIF-1α expression vectors, and they could be abolished by pretreatment with the HIF-1α inhibitor echinomycin (Echi). The functional expression of ZIP8 and ZIP14 in HEK cells significantly increased the basal [Zn2+]i level. Taken together, Zn2+ carrier proteins, TRPA1, ZIP8, and ZIP14, induced under HIF-1α mediated inflammation can synergistically change [Zn2+]i in inflammatory FLSs.

TRPA1 (transient receptor potential ankyrin 1), the lone member of the mammalian ankyrin TRP subfamily, is a Ca2+-permeable, non-selective cation channel. TRPA1 channels are localized to the plasma membranes of various cells types, including sensory neurons and vascular endothelial cells. The channel is endogenously activated by byproducts of reactive oxygen species, such as 4-hydroxy-2-noneal, as well as aromatic, dietary molecules including allyl isothiocyanate, a derivative of mustard oil. Several studies have implicated TRPA1 as a regulator of vascular tone that acts through distinct mechanisms. First, TRPA1 on adventitial sensory nerve fibers mediates neurogenic vasodilation by stimulating the release of the vasodilator, calcitonin gene-related peptide. Second, TRPA1 is expressed in the endothelium of the cerebral vasculature, but not in other vascular beds, and its activation results in localized Ca2+ signals that drive endothelium-dependent vasodilation. Finally, TRPA1 is functionally present on brain capillary endothelial cells, where its activation orchestrates a unique biphasic propagation mechanism that dilates upstream arterioles. This response is vital for neurovascular coupling and functional hyperemia in the brain. This review provides a brief overview of the biophysical and pharmacological properties of TRPA1 and discusses the importance of the channel in vascular control and pathophysiology.

TRPA1, a nonselective cation channel, is expressed in sensory afferent that innervates peripheral targets. Neuronal TRPA1 can promote tissue repair, remove harmful stimuli and induce protective responses via the release of neuropeptides after the activation of the channel by chemical, exogenous, or endogenous irritants in the injured tissue. However, chronic inflammation after repeated noxious stimuli may result in the development of several diseases. In addition to sensory neurons, TRPA1, activated by inflammatory agents from some non-neuronal cells in the injured area or disease, might promote or protect disease progression. Therefore, TRPA1 works as a molecular sentinel of tissue damage or as an inflammation gatekeeper. Most kidney damage cases are associated with inflammation. In this review, we summarised the role of TRPA1 in neurogenic or non-neurogenic inflammation and in kidney disease, especially the non-neuronal TRPA1. In in vivo animal studies, TRPA1 prevented sepsis-induced or Ang-II-induced and ischemia-reperfusion renal injury by maintaining mitochondrial haemostasis or via the downregulation of macrophage-mediated inflammation, respectively. Renal tubular epithelial TRPA1 acts as an oxidative stress sensor to mediate hypoxia–reoxygenation injury in vitro and ischaemia–reperfusion-induced kidney injury in vivo through MAPKs/NF-kB signalling. Acute kidney injury (AKI) patients with high renal tubular TRPA1 expression had low complete renal function recovery. In renal disease, TPRA1 plays different roles in different cell types accordingly. These findings depict the important role of TRPA1 and warrant further investigation.

Although lutein is known to inhibit chronic inflammation, its effect on acute inflammation‐induced nociceptive processing in the trigeminal system remains to be determined. The aim of the present study was to investigate whether pretreatment with lutein attenuates acute inflammation‐induced sensitization of nociceptive processing in rat spinal trigeminal nucleus caudalis (SpVc) and upper cervical (C1) dorsal horn neurons, via c‐Fos immunoreactivity. Mustard oil, a transient receptor potential ankyrin‐1 channel agonist, was injected into the whisker pads to induce inflammation. Pretreatment of rats with lutein resulted in significant decreases in the inflammation‐induced mean times of face grooming and the thickness of inflammation‐induced edema in whisker pads relative to those features in inflamed rats (i.e., rats with no lutein pretreatment). In both the ipsilateral superficial and deep laminae of the SpVc and C1 dorsal horn, there were significantly larger numbers of c‐Fos‐positive neurons in inflamed rats than in naïve rats, and lutein pretreatment significantly decreased that number relative to inflamed rats. These results suggest that systemic administration of lutein attenuates acute inflammation‐induced nocifensive behavior and augmented nociceptive processing of SpVc and C1 neurons that send stimulus localization and intensity information to higher pain centers. These findings support lutein as a potential therapeutic agent for use as an alternative, complementary medicine to attenuate, or even prevent, acute inflammatory pain. [ABSTRACT FROM AUTHOR]

Background: Transient receptor potential ankyrin 1 (TRPA1) is an ion channel known to mediate nociception and neurogenic inflammation, and to be activated by reactive oxygen and nitrogen species (ROS and RNS) produced at the sites of inflammation. Because neurogenic inflammation as well as the release of ROS and RNS are typical features of early stages of allergic responses, we hypothesized that TRPA1 may be involved in triggering and/or amplifying allergic inflammation. Objective: This study aims at exploring the role of TRPA1 ion channel in acute ovalbumin-induced allergic inflammation in applicable murine models. Methods: The effects of pharmacological blockade and genetic deletion of TRPA1 in ovalbumin-induced allergic conjunctivitis and acute paw inflammation were studied in mice sensitized to ovalbumin. Results: Ovalbumin-induced allergic conjunctivitis was milder in TRPA1-deficient mice and alleviated in wild-type mice treated with the TRPA1 antagonist TCS 5861528. Subcutaneous challenge with ovalbumin caused a significant paw edema and interleukin (IL)-4 production in sensitized mice; these responses were attenuated in animals treated with the TRPA1 antagonist and in TRPA1-deficient mice. Interestingly, blockade of the major secondary effector of TRPA1, substance P, also resulted in attenuated ovalbumin-induced paw edema and IL-4 production. However, the splenocytes' responses to ovalbumin were similar in cells from wild-type and TRPA1-deficient mice sensitized to ovalbumin. Conclusion: These results introduce a novel concept that TRPA1 mediates early events in allergic inflammation, but does not seem to affect allergic sensitization, and could therefore be a novel drug target to treat conditions associated with allergic inflammation. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Ibuprofen is a widely used non-steroidal anti-inflammatory drug (NSAID) that exerts analgesic and anti-inflammatory actions. The transient receptor potential ankyrin 1 (TRPA1) channel, expressed primarily in nociceptors, mediates the action of proalgesic and inflammatory agents. Ibuprofen metabolism yields the reactive compound, ibuprofen-acyl glucuronide, which, like other TRPA1 ligands, covalently interacts with macromolecules. To explore whether ibuprofen-acyl glucuronide contributes to the ibuprofen analgesic and anti-inflammatory actions by targeting TRPA1, we used in vitro tools (TRPA1-expressing human and rodent cells) and in vivo mouse models of inflammatory pain. Ibuprofen-acyl glucuronide, but not ibuprofen, inhibited calcium responses evoked by reactive TRPA1 agonists, including allyl isothiocyanate (AITC), in cells expressing the recombinant and native human channel and in cultured rat primary sensory neurons. Responses by the non-reactive agonist, menthol, in a mutant human TRPA1 lacking key cysteine-lysine residues, were not affected. In addition, molecular modeling studies evaluating the covalent interaction of ibuprofen-acyl glucuronide with TRPA1 suggested the key cysteine residue C621 as a probable alkylation site for the ligand. Local administration of ibuprofen-acyl glucuronide, but not ibuprofen, in the mouse hind paw attenuated nociception by AITC and other TRPA1 agonists and the early nociceptive response (phase I) to formalin. Systemic ibuprofen-acyl glucuronide and ibuprofen, but not indomethacin, reduced phase I of the formalin response. Carrageenan-evoked allodynia in mice was reduced by local ibuprofen-acyl glucuronide, but not by ibuprofen, whereas both drugs attenuated PGE 2 levels. Ibuprofen-acyl glucuronide, but not ibuprofen, inhibited the release of IL-8 evoked by AITC from cultured bronchial epithelial cells. The reactive ibuprofen metabolite selectively antagonizes TRPA1, suggesting that this novel action of ibuprofen-acyl glucuronide might contribute to the analgesic and anti-inflammatory activities of the parent drug. [ABSTRACT FROM AUTHOR]

Graphical abstract Modulator role of α-Lipoic acid (ALA) through inhibition of TRPA1 on hypoxia-induced mitochondrial reactive oxygen species (ROS), cytokine and apoptosis productions in DBTRG cell line. Hypoxia induced the TRPA1 activation resulting in the overload Ca2+ entry, apoptosis, cytokine production and mitochondrial oxidative stress. However, ALA and TRPV1 antagonist (AP18) protected the DBTRG cells from hypoxia-induced injury via maintaining the intracellular Ca2+ hemostasis and via inhibiting apoptosis pathways, as well as down-regulating mitochondrial oxidative stress pathway. ALA induced TRPA1 blocker effect through upregulation thiol redox system members [glutathione (GSH) and glutathione peroxidase (GSH-Px)] and down-regulation of mitochondrial ROS and extracellular productions. Highlights • Calcium ion influx plays important role in hypoxia. • Apoptosis, inflammation and TRPA1 activation levels increased in the DBTRG cells. • The TRPA1 are inhibited in the neurons by α-Lipoic acid. Abstract Apoptosis, overload Ca2+ entry and oxidative stress are induced in neurons by hypoxia. Drug-resistant cancer cells are killed by hypoxic conditions. α-Lipoic acid (ALA) has antioxidant and pro-oxidant functions. The TRPA1 channel is activated by oxidative stress and pro-oxidant ALA may have a regulator role in the TRPA1 activity in the human glioblastoma (DBTRG) cells. The aim of this study was to evaluate if a combination therapy of ALA with a hypoxia can alter the effect of this hypoxia through TRPA1 activation in the DBTRG cells. The DBTRG cells were divided into four treatment groups as control, ALA (50 μM), and hypoxia and hypoxia + ALA. Hypoxia in the cells was induced by CoCl 2 (200 μM). Apoptosis, Annexin V, mitochondrial membrane depolarization (JC-1), reactive oxygen species (ROS) production, IL-1β, IL-18, caspase 3 and 9 values were increased through activation of TRPA1 (cinnamaldehyde) in the cells by the hypoxia induction, although cell viability, reduced glutathione and glutathione peroxidase values were decreased by the treatments. The values were modulated in the cells by TRPA1 blocker (AP18) and ALA treatments. Involvements of TRPA1 activity on values in the cells were also confirmed by patch-clamp and laser confocal microscopy analyses. In conclusion, apoptotic, inflammatory and oxidant effects of hypoxia were increased by activation of TRPA1, but its action on the values was decreased by the ALA treatment. ALA treatment could be used as an effective strategy in the treatment of hypoxia-induced oxidative stress, apoptosis and inflammation in the neurons. [ABSTRACT FROM AUTHOR]

TRPA1 is a cation channel located on the plasma membrane of many types of human and animal cells, including skin sensory neurons and epithelial cells of the intestine, lungs, urinary bladder, etc. TRPA1 is the major chemosensor that also responds to thermal and mechanical stimuli. Substances that activate TRPA1, e.g., allyl isothiocyanates (pungent components of mustard, horseradish, and wasabi), cinnamaldehyde from cinnamon, organosulfur compounds from garlic and onion, tear gas, acrolein and crotonaldehyde from cigarette smoke, etc., cause burning, mechanical and thermal hypersensitivity, cough, eye irritation, sneezing, mucus secretion, and neurogenic inflammation. An increased activity of TRPA1 leads to the emergence of chronic pruritus and allergic dermatitis and is associated with episodic pain syndrome, a hereditary disease characterized by episodes of debilitating pain triggered by stress. TRPA1 is now considered as one of the targets for developing new anti-inflammatory and analgesic drugs. This review summarizes information on the structure, function, and physiological role of this channel, as well as describes known TRPA1 ligands and their significance as therapeutic agents in the treatment of inflammation-associated pain. [ABSTRACT FROM AUTHOR]

Background/Aims: Bortezomib (BTZ) is largely used as a chemotherapeutic agent for the treatment of multiple myeloma. However, one of the significant limiting complications of BTZ is painful peripheral neuropathy during BTZ therapy. The purpose of this study was to examine the underlying mechanisms leading to neuropathic pain induced by BTZ. Methods: ELISA and western blot analysis were used to examine the levels of tumor necrosis factor alpha (TNF-α) and its receptor, transient receptor potential ankyrin 1 (TRPA1) and intracellular p38-MAPK and JNK signal in the lumbar dorsal root ganglion. Behavioral test was performed to determine mechanical pain and cold sensitivity in a rat model. Results: Systemic injection of BTZ significantly increased mechanical pain and cold sensitivity as compared with control animals (P< 0.05 vs. control rats). Our data also showed that protein expression of TRPA1 was upregulated in the dorsal root ganglion of BTZ rats and blocking TRPA1 attenuated mechanical pain and cold sensitivity in control rats and BTZ rats (P< 0.05 vs. vehicle control). Notably, the inhibitory effect of blocking TRPA1 on mechanical pain and cold sensitivity was smaller in BTZ rats than that in control rats. In addition, a blockade of TNF-α attenuated intracellular p38-MAPK and JNK signal in the dorsal root ganglion. This also decreased TRPA1 expression and alleviated mechanical hyperalgesia and cold hypersensitivity in BTZ rats. Conclusion: We revealed specific signaling pathways leading to neuropathic pain induced by chemotherapeutic BTZ. The data also suggest that blocking TRPA1 and tumor necrosis factor alpha is beneficial to alleviate neuropathic pain during BTZ intervention. [ABSTRACT FROM AUTHOR]

Oxidative stress and inflammation play important roles in the pathophysiology of acute kidney injury (AKI). Transient receptor potential ankyrin 1 (TRPA1) is a Ca2+-permeable ion channel that is sensitive to reactive oxygen species (ROS). The role of TRPA1 in AKI remains unclear. In this study, we used human and animal studies to assess the role of renal TRPA1 in AKI and to explore the regulatory mechanism of renal TRPA1 in inflammation via in vitro experiments. TRPA1 expression increased in the renal tubular epithelia of patients with AKI. The severity of tubular injury correlated well with tubular TRPA1 or 8-hydroxy-2′-deoxyguanosine expression. In an animal model, renal ischemia-reperfusion injury (IR) increased tubular TRPA1 expression in wild-type (WT) mice. Trpa1−/− mice displayed less IR-induced tubular injury, oxidative stress, inflammation, and dysfunction in kidneys compared with WT mice. In the in vitro model, TRPA1 expression increased in renal tubular cells under hypoxia-reoxygenation injury (H/R) conditions. We demonstrated that H/R evoked a ROS-dependent TRPA1 activation, which elevated intracellular Ca2+ level, increased NADPH oxidase activity, activated MAPK/NF-κB signaling, and increased IL-8. Renal tubular TRPA1 may serve as an oxidative stress sensor and a crucial regulator in the activation of signaling pathways and promote the subsequent transcriptional regulation of IL-8. These actions might be evident in mice with IR or patients with AKI.

Transient receptor potential ankyrin 1 (TRPA1) is a membrane-bound ion channel found in neurons, where it mediates nociception and neurogenic inflammation. Recently, we have discovered that TRPA1 is also expressed in human osteoarthritic (OA) chondrocytes and downregulated by the anti-inflammatory drugs aurothiomalate and dexamethasone. We have also shown TRPA1 to mediate inflammation, pain, and cartilage degeneration in experimental osteoarthritis. In this study, we investigated the role of TRPA1 in joint inflammation, focusing on the pro-inflammatory cytokine interleukin-6 (IL-6). We utilized cartilage/chondrocytes from wild-type (WT) and TRPA1 knockout (KO) mice, along with primary chondrocytes from OA patients. The results show that TRPA1 regulates the synthesis of the OA-driving inflammatory cytokine IL-6 in chondrocytes. IL-6 was highly expressed in WT chondrocytes, and its expression, along with the expression of IL-6 family cytokines leukemia inhibitory factor (LIF) and IL-11, were significantly downregulated by TRPA1 deficiency. Furthermore, treatment with the TRPA1 antagonist significantly downregulated the expression of IL-6 in chondrocytes from WT mice and OA patients. The results suggest that TRPA1 is involved in the upregulation of IL-6 production in chondrocytes. These findings together with previous results on the expression and functions of TRPA1 in cellular and animal models point to the role of TRPA1 as a potential mediator and novel drug target in osteoarthritis.

To investigate whether transient receptor potential ankyrin 1 (TRPA1) and transient receptor potential melastatin 8 (TRPM8) have a function in responding to environmental stimuli in human odontoblast-like cells (hOLCs). Additionally, to explore whether activation of TRPA1 and TRPM8 in hOLCs participates in the regulation of the inflammatory process. Changes in gene and protein expression levels of TRPA1 and TRPM8 in cultured hOLCs following lipopolysaccharide (LPS) stimulation, which mimics inflammation, were examined using quantitative reverse transcription-polymerase chain reaction and western blot analysis. Furthermore, we compared the expression profiles of 80 cytokines between LPS- and vehicle-treated hOLCs and investigated how the production of highly increased cytokines in LPS-treated hOLCs was affected by the pharmacological inhibition of TRPA1 and TRPM8. The expression of TRPA1 and TRPM8 in hOLCs was observed and their mRNAs and proteins were upregulated in hOLCs after LPS treatment. Moreover, cytokine antibody assays revealed that monocyte chemoattractant protein-1 (MCP-1, CCL2), growth-regulated protein α (GROα, CXCL1), interleukin-6 (IL-6), and IL-8 (CXCL8) were significantly upregulated by LPS. The pharmacological inhibition of TRPA1 (HC-030031) during LPS treatment attenuated the expression of CCL2, CXCL1, and IL-8, whereas the pharmacological inhibition of TRPM8 (PF05105679) suppressed the expression of CCL2, CXCL1, and IL-8 as well as IL-6. These results indicate that hOLCs express TRPA1 and TRPM8, which are upregulated during inflammation. In addition to being sensors of potentially harmful stimuli, TRPA1 and TRPM8 in hOLCs play important roles in regulating inflammatory responses. • Upregulation of TRPA1 and TRPM8 in hOLCs by LPS. • Upregulation of CCL2, CXCL1, IL-6, and IL-8 in LPS-treated hOLCs. • hOLCs expressing TRPA1 and TRPM8 are involved in regulating inflammatory responses. [ABSTRACT FROM AUTHOR]

Acute gastritis is often untreatable by acid secretion-inhibiting drugs. Understanding the protective mechanisms including the role of Transient Receptor Potential Ankyrin1 (TRPA1) and Vanilloid1 (TRPV1) channels localized on capsaicin-sensitive afferents and non-neuronal structures might identify novel therapeutic approaches. Therefore, we characterized a translational gastritis model using iodoacetamide (IAA) and investigated TRPA1/V1 expressions. Wistar rats and CD1, C57Bl/6J mice were exposed to IAA-containing (0.05, 0.1, 0.2, 0.3, 0.5%) drinking water for 7 or 14 days. Body weight and water consumption were recorded daily. Macroscopic lesions were scored, qualitative histopathologic investigation was performed, TRPA1/V1 immunopositivity and mRNA expressions were measured. IAA induced a concentration-dependent weight loss and reduced water intake in both species. Hyperemia, submucosal edema, inflammatory infiltration and hemorrhagic erosions developed after 7 days, while ulcers after 14 days in rats. Trpa1 mRNA/protein expressions were upregulated at both timepoints. Meanwhile, TRPV1 immunopositivity was upregulated in the gastric corpus after 0.05% IAA ingestion, but downregulated after 0.2%, whereas Trpv1 mRNA did not change. Interestingly, no macroscopic/microscopic changes were observed in mice. These are the first data for the concentration- and duration-dependent changes in the IAA-induced gastritis in rats accompanied by TRPA1 upregulation, therefore, its therapeutic potential in gastritis should further be investigated.

The TRPA1 and TRPV1 receptors are important pharmaceutical targets for antipruritic and analgesic therapy. Obtaining further knowledge on their roles and interrelationship in humans is therefore crucial. Preclinical results are contradictory concerning coexpression and functional interdependency of TRPV1 and TRPA1, but no human evidence exists. This human experimental study investigated whether functional responses from the subpopulation of TRPA1 nociceptors could be evoked after defunctionalization of TRPV1 nociceptors by cutaneous application of high-concentration capsaicin. Two quadratic areas on each forearm were randomized to pretreatment with an 8% topical capsaicin patch or vehicle for 24 hours. Subsequently, areas were provoked by transdermal 1% topical capsaicin (TRPV1 agonist) or 10% topical allyl isothiocyanate ("AITC," a TRPA1 agonist), delivered by 12 mm Finn chambers. Evoked pain intensities were recorded during pretreatments and chemical provocations. Quantitative sensory tests were performed before and after provocations to assess changes of heat pain sensitivity. Imaging of vasomotor responses was used to assess neurogenic inflammation after the chemical provocations. In the capsaicin-pretreated areas, both the subsequent 1% capsaicin- and 10% AITC-provoked pain was inhibited by 92.9 ± 2.5% and 86.9 ± 5.0% (both: P < 0.001), respectively. The capsaicin-ablated skin areas showed significant heat hypoalgesia at baseline (P < 0.001) as well as heat antihyperalgesia, and inhibition of neurogenic inflammation evoked by both 1% capsaicin and 10% AITC provocations (both: P < 0.001). Ablation of cutaneous capsaicin-sensitive afferents caused consistent and equal inhibition of both TRPV1- and TRPA1-provoked responses assessed psychophysically and by imaging of vasomotor responses. This study suggests that TRPA1 nociceptive responses in human skin strongly depend on intact capsaicin-sensitive, TRPV1 fibers. [ABSTRACT FROM AUTHOR]

Injury, inflammation and nerve damage initiate a wide variety of cellular and molecular processes that culminate in hyperexcitation of sensory nerves, which underlies chronic inflammatory and neuropathic pain. Using behavioral readouts of pain hypersensitivity induced by Angiotensin II (Ang II) injection into mouse hindpaws, our study shows that activation of the type 2 Ang II receptor (AT2R) and the cell damage-sensing ion channel TRPA1 are required for peripheral mechanical pain sensitization induced by Ang II in male and female mice. However, we show that AT2R is not expressed in mouse and human dorsal root ganglia (DRG) sensory neurons. Instead, expression/activation of AT2R on peripheral/skin macrophages (MΦs) constitutes a critical trigger of mouse and human DRG sensory neuron excitation. Ang II-induced peripheral mechanical pain hypersensitivity can be attenuated by chemogenetic depletion of peripheral MΦs. Furthermore, AT2R activation in MΦs triggers production of reactive oxygen/nitrogen species, which trans-activate TRPA1 on mouse and human DRG sensory neurons, via cysteine-modification of the channel. Our study thus identifies a translatable immune cell-to-sensory neuron signaling crosstalk underlying peripheral nociceptor sensitization. This form of cell-to-cell signaling represents a critical peripheral mechanism for chronic pain, and thus identifies multiple druggable analgesic targets. [ABSTRACT FROM AUTHOR]

Transient receptor potential ankyrin 1 (TRPA1), a cold receptor in sensory neurons activated by a variety of stimuli, is implicated in nociception and mechanotransduction. To help understand the vesicular glutamate transporter (VGLUT)-mediated glutamate signaling in TRPA1-immunopositive (+) neurons, we examined the expression of VGLUT1 and VGLUT2 in the TRPA1+ neurons in the male rat trigeminal ganglion (n = 19) under normal conditions and following experimental inflammation in the vibrissal pad by light microscopic immunohistochemistry (n = 11), western blot (n = 8), and quantitative analysis. One half (50.8%, 250/492) of the TRPA1+ neurons expressed VGLUT2, and a small fraction (8.3%, 57/683) also expressed VGLUT1. The majority of the VGLUT2-expressing TRPA1+ (VGLUT2+/TRPA1+) neurons coexpressed the markers of peptidergic and non-peptidergic neurons, CGRP, IB4, and TRPV1 but not the markers of neurons with myelinated fibers, NF200 and parvalbumin. In contrast, most VGLUT1+/TRPA1+ neurons coexpressed NF200 and parvalbumin but rarely expressed CGRP, IB4, or TRPV1. Following experimental inflammation, the fraction of VGLUT2+ (experimental vs. control: 34.7% vs. 22.3%), TRPA1+ (39.3% vs. 25.3%), and VGLUT2+/TRPA1+ (60.7% vs. 49.7%) neurons and the protein levels for TRPA1 and VGLUT2 increased significantly, compared to control, whereas the fraction of VGLUT1+ and VGLUT1+/TRPA1+ neurons and the protein level for VGLUT1 remained unchanged. These findings suggest that both VGLUT1 and VGLUT2 are involved in the glutamate signaling in TRPA1+ neurons under normal conditions in the male rats, and raise a possibility that VGLUT2 may play a role in the TRPA1-induced hypersensitivity following inflammation. [ABSTRACT FROM AUTHOR]