The inflammatory regulation of TRPA1 expression in human A549 lung epithelial cells

Airway and cardiovascular remodeling in chronic obstructive pulmonary disease (COPD) as a target for transient receptor potential ankyrin 1 (TRPA1) channel modulators

Chronic obstructive pulmonary disease (COPD) is characterized by chronic inflammation, which leads to airway remodeling (AR). AR refers to various structural changes occurring in the airway wall, resulting in thickening, and narrowing of the airways. Apart from airways, and lung tissue, pulmonary vasculature also undergoes remodeling. Thus, the pressure in vascular bed is increased, leading to pulmonary hypertension and further right and left ventricle hypertrophy, as well as myocardial fibrosis. Currently, there is lack of effective treatment directly targeting airway and cardiovascular remodeling in the course of COPD. Due to a lot of research showing involvement of transient receptor potential ankyrin 1 (TRPA1) in respiratory disorders, it seems reasonable to consider this ion channel as a molecular target in treatment of remodeling consequences of COPD. The aim of this review is to summarize current knowledge of its role in this case and to identify areas requiring further research. Moreover, we provide few patented structures intended to treat chronic respiratory diseases, which may be worth investigating in the context of airway remodeling.

The TRPA1 cation channel is upregulated by cigarette smoke in mouse and human macrophages modulating lung inflammation

Cigarette smoke (CS) is a well-known source of several inflammatory, cytotoxic and genotoxic compounds that cause chronic lung diseases. The transient receptor potential ankyrin 1 (TRPA1), a smoking-responsive, non-selective cation channel, is expressed by both capsaicin-sensitive peptidergic sensory nerves and non-neuronal cells of the lung, but there are few and controversial data on its expression and function on macrophages. Here, we investigated TRPA1 mRNA and protein expression in mouse and human lung tissues and human 3D spheroids, with a particular focus on its expression and potential regulatory effects on pro- and anti-inflammatory macrophage functions in response to CS. TRPA1 was stably expressed in both human and mouse alveolar macrophages, being upregulated after CS exposure and its functional activity was demonstrated in mouse macrophage culture. Moreover, besides CS, the TRPA1 genotype itself affected the expression of M1- (Il-1β, Il-23) and M2-type (Il-10, Tgfβ) macrophage cytokines. Furthermore, CS extract increased TRPA1 mRNA in human lung spheroids showing more prominent expression in macrophage-containing 3D aggregates, while CS extract influenced an elevated TGFβ expression specifically in macrophage-containing spheroids. These results suggest the fine-tuning role of TRPA1 activation in CS-induced airway inflammation, particularly in macrophages, but further studies are needed to draw precise conclusions.

Role of TRP Channels in Cancer-Induced Bone Pain

The burden of cancer is growing in almost every country. Bone metastases significantly affect the prognosis and lead to an increase in mortality and morbidity. The management of cancer-induced bone pain (CIBP) still shows various unmet needs. Opioid use is burdened by a number of possible side effects. Moreover, recent progresses in cancer treatment significantly increased the life expectancy of cancer patients, even those with metastatic disease. In this narrative review, we reported the main findings regarding TRP channel function in cancer pain models. TRP cation channels play a key role in different functions of cancer cells, including the regulation of their potential for metastasization, and are the main channels involved in the pathways of pain perception, through peripheral and central effects. Genetic deletion decreased pain sensitivity following tumour cell inoculation. Preclinical data suggest a potential role for modulators of some TRP channels, such as TRPV1, TRPA1, TRPM7 and TRPM8. Clinical results are still scarce; however, the physiological role in modulating bone remodelling and the involvement of TRP channels in preclinical models of bone cancer pain have garnered interest as areas of research in the last few years, as innovative analgesic strategies that may overcome the long-term side effects of opioids.

TRPA1 nanovesicle-conjugated receptonics for rapid biocide screening

Although biocides are important materials in modern society and help protect human health and the environment, increasing exposure to combined biocides can cause severe side effects in the human body, such as lung fibrosis. In this study, we developed a receptonics system to screen for biocides in combined household chemical products based on biocides. The system contains transient receptor potential ankyrin 1 (TRPA1) nanovesicles (NVs) to sense biocides based on pain receptors and a side-gated field-effect transistor (SGFET) using a single-layer graphene (SLG) micropattern channel. The binding affinities between the TRPA1 receptor and the various biocides were estimated by performing biosimulation and using a calcium ion (Ca2+) assay, and the sensitivity of the system was compared with that of TRPA1 NV receptonics systems. Based on the results of the TRPA1 NV receptonics system, the antagonistic and potentiation effects of combined biocides and household chemical products depended on the concentration. Finally, the TRPA1 NV receptonics system was applied to screen for biocides in real products, and its performance was successful. Based on these results, the TRPA1 NV receptonics system can be utilized to perform risk evaluations and identify biocides in a simple and rapid manner.

Label-free optical detection of calcium ion influx in cell-derived nanovesicles using a conical Au/PDMS biosensor

Ion channels, which are key to physiological regulation and drug discovery, control ion flux across membranes, and their dysregulation leads to various diseases. Ca2+ monitoring is crucial for cellular signaling when performing Ca-based assays in ion channel research; these assays are widely utilized in both academic and pharmaceutical contexts for drug screening and pharmacological profiling. However, existing detection methods are limited by slow detection speeds, low throughput, complex processes, and low analyte viability. In this study, we developed a label-free optical biosensing method using a conical Au/polydimethylsiloxane platform tailored to detect Ca2+ influx in A549-originated nanovesicles facilitated by the transient receptor potential ankyrin 1 (TRPA1) channel. Nanovesicles expressing cellular signaling components mimic TRPA1 signal transduction in cell membranes and improve analyte viability. The conical Au/polydimethylsiloxane sensor converted Ca2+ influx events induced by specific agonist exposure into noticeable changes in relative transmittance under visible light. The optical transmittance change accompanying Ca2+ influx resulted in an enhanced sensing response, high accuracy and reliability, and rapid detection (∼5 s) without immobilization or ligand treatments. In the underlying sensing mechanism, morphological variations in nanovesicles, which depend on Ca2+ influx, induce a considerable light scattering change at an interface between the nanovesicle and Au, revealed by optical simulation. This study provides a foundation for developing biosensors based on light-matter interactions. These sensors are simple and cost-effective with superior performance and diverse functionality.

A comprehensive analysis of TRP-related gene signature, and immune infiltration in patients with colorectal cancer

BACKGROUND

Transient receptor potential (TRP) channels are involved in the development and progression of tumors. However, their role in colorectal cancer (CRC) remains unclear, and this study aims to investigate the role of TRP-related genes in CRC.

METHODS

Data was obtained from The Cancer Genome Atlas (TCGA) database, and analyses were conducted on the GSE14333 and GSE38832 datasets to assess the prognosis and mark TRP-related genes (TRGs). Subsequently, clustering analysis and immune infiltration analysis were performed to explore the relevant TRGs. In vitro validation of key TRGs' gene and protein expression was conducted using human colon cancer cells.

RESULTS

Compared to normal tissues, 8 TRGs were significantly upregulated in CRC, while 11 were downregulated. TRPA1 was identified as a protective prognostic factor, whereas TRPM5 (HR = 1.349), TRPV4 (HR = 1.289), and TRPV3 (HR = 1.442) were identified as prognostic risk factors. Receiver operating characteristic (ROC) curves and Kaplan-Meier (KM) analyses yielded similar results. Additionally, lower expression of TRPA1 and higher expression of TRPV4 and TRPM5 were negatively correlated with patient prognosis, and experimental validation confirmed the underexpression of TRPA1 and overexpression of TRPV4 and TRPM5 in CRC cell lines.

CONCLUSION

This study identifies a TRP channel-related prognosis in CRC, providing a novel approach to stratifying CRC prognosis.

Dual role of transient receptor potential ankyrin 1 in respiratory and gastrointestinal physiology: From molecular mechanisms to therapeutic targets

The transient receptor potential ankyrin 1 (TRPA1) channel plays a pivotal role in the respiratory and gastrointestinal tracts. Within the respiratory system, TRPA1 exhibits diverse distribution patterns across key cell types, including epithelial cells, sensory nerves, and immune cells. Its activation serves as a frontline sensor for inhaled irritants, triggering immediate protective responses, and influencing airway integrity. Furthermore, TRPA1 has been implicated in airway tissue injury, inflammation, and the transition of fibroblasts, thereby posing challenges in conditions, such as severe asthma and fibrosis. In sensory nerves, TRPA1 contributes to nociception, the cough reflex, and bronchoconstriction, highlighting its role in both immediate defense mechanisms and long-term respiratory reflex arcs. In immune cells, TRPA1 may modulate the release of pro-inflammatory mediators, shaping the overall inflammatory landscape. In the gastrointestinal tract, the dynamic expression of TRPA1 in enteric neurons, epithelial cells, and immune cells underscores its multifaceted involvement. It plays a crucial role in gut motility, visceral pain perception, and mucosal defense mechanisms. Dysregulation of TRPA1 in both tracts is associated with various disorders such as asthma, Chronic Obstructive Pulmonary Disease, Irritable Bowel Syndrome, and Inflammatory Bowel Disease. This review emphasizes the potential of TRPA1 as a therapeutic target and discusses the efficacy of TRPA1 antagonists in preclinical studies and their promise for addressing respiratory and gastrointestinal conditions. Understanding the intricate interactions and cross-talk of TRPA1 across different cell types provides insight into its versatile role in maintaining homeostasis in vital physiological systems, offering a foundation for targeted therapeutic interventions.

A novel transient receptor potential C3/C6 selective activator induces the cellular uptake of antisense oligonucleotides

Antisense oligonucleotide (ASO) therapy is a novel therapeutic approach in which ASO specifically binds target mRNA, resulting in mRNA degradation; however, cellular uptake of ASOs remains critically low, warranting improvement. Transient receptor potential canonical (TRPC) channels regulate Ca2+ influx and are activated upon stimulation by phospholipase C-generated diacylglycerol. Herein, we report that a novel TRPC3/C6/C7 activator, L687, can induce cellular ASO uptake. L687-induced ASO uptake was enhanced in a dose- and incubation-time-dependent manner. L687 enhanced the knockdown activity of various ASOs both in vitro and in vivo. Notably, suppression of TRPC3/C6 by specific siRNAs reduced ASO uptake in A549 cells. Application of BAPTA-AM, a Ca2+ chelator, and SKF96365, a TRPC3/C6 inhibitor, suppressed Ca2+ influx via TRPC3/C6, resulting in reduced ASO uptake, thereby suggesting that Ca2+ influx via TRPC3/C6 is critical for L687-mediated increased ASO uptake. L687 also induced dextran uptake, indicating that L687 increased endocytosis. Adding ASO to L687 resulted in endosome accumulation; however, the endosomal membrane disruptor UNC7938 facilitated endosomal escape and enhanced knockdown activity. We discovered a new function for TRPC activators regarding ASO trafficking in target cells. Our findings provide an opportunity to formulate an innovative drug delivery system for the therapeutic development of ASO.

Transient Receptor Potential Ankyrin 1 Ion Channel Is Expressed in Osteosarcoma and Its Activation Reduces Viability

Osteosarcoma is a highly malignant, painful cancer with poor treatment opportunities and a bad prognosis. Transient receptor potential ankyrin 1 (TRPA1) and vanilloid 1 (TRPV1) receptors are non-selective cation channels that have been of great interest in cancer, as their expression is increased in some malignancies. In our study we aim to characterize the expression and functionality of the TRPA1 and TRPV1 channels in human and mouse osteosarcoma tissues and in a mouse cell line. TRPA1/Trpa1 and TRPV1/Trpv1 mRNA expressions were demonstrated by PCR gel electrophoresis and RNAscope in situ hybridization. The function of these channels was confirmed by their radioactive 45Ca2+ uptake in response to the TRPA1 agonist, Allyl-isothiocyanate (AITC), and TRPV1 agonist, capsaicin, in K7M2 cells. An ATP-based K2M7 cell viability luminescence assay was used to determine cell viability after AITC or capsaicin treatments. Both TRPA1/Trpa1 and TRPV1/Trpv1 were expressed similarly in human and mouse osteosarcoma tissues, while Trpa1 transcripts were more abundantly present in K7M2 cells. TRPA1 activation with 200 µM AITC induced a significant 45Ca2+ influx into K7M2 cells, and the antagonist attenuated this effect. In accordance with the lower Trpv1 expression, capsaicin induced a moderate 45Ca2+ uptake, which did not reach the level of statistical significance. Both AITC and capsaicin significantly reduced K7M2 cell viability, demonstrating EC50 values of 22 µM and 74 µM. The viability-decreasing effect of AITC was significantly but only partially antagonized by HC-030031, but the action of capsaicin was not affected by the TRPV1 antagonist capsazepine. We provide here the first data on the functional expression of the TRPA1 and TRPV1 ion channels in osteosarcoma, suggesting novel diagnostic and/or therapeutic perspectives.

Research Progress on TRPA1 in Diseases

For a long time, the physiological activity of TRP ion channels and the response to various stimuli have been the focus of attention, and the physiological functions mediated by ion channels have subtle links with the occurrence of various diseases. Our group has been engaged in the study of ion channels. In recent years, the report rate of TRPA1, the only member of the TRPA subfamily in the newly described TRP channel, has been very high. TRPA1 channels are not only abundantly expressed in peptidergic nociceptors but are also found in many nonneuronal cell types and tissues, and through the regulation of Ca2+ influx, various neuropeptides and signaling pathways are involved in the regulation of nerves, respiration, circulation, and various diseases and inflammation throughout the body. In this review, we mainly summarize the effects of TRPA1 on various systems in the body, which not only allows us to have a more systematic and comprehensive understanding of TRPA1 but also facilitates more in-depth research on it in the future.

Potentiating TRPA1 by Sea Anemone Peptide Ms 9a-1 Reduces Pain and Inflammation in a Model of Osteoarthritis

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.

Transient Receptor Potential Ankyrin 1 (TRPA1) Channel Mediates Acrolein Cytotoxicity in Human Lung Cancer Cells

Transient receptor potential ankyrin 1 (TRPA1) is a nonselective ion channel implicated in thermosensation and inflammatory pain. It has been reported that expression of the TRPA1 channel is induced by cigarette smoke extract. Acrolein found in cigarette smoke is highly toxic and known as an agonist of the TRPA1 channel. However, the role of TRPA1 in the cytotoxicity of acrolein remains unclear. Here, we investigated whether the TRPA1 channel is involved in the cytotoxicity of acrolein in human lung cancer A549 cells. The IC₅₀ of acrolein in A549 cells was 25 μM, and acrolein toxicity increased in a concentration- and time-dependent manner. When the effect of acrolein on TRPA1 expression was examined, the expression of TRPA1 in A549 cells was increased by treatment with 50 μM acrolein for 24 h or 500 μM acrolein for 30 min. AP-1, a transcription factor, was activated in the cells treated with 50 μM acrolein for 24 h, while induction of NF-κB and HIF-1α was observed in the cells treated with 500 μM acrolein for 30 min. These results suggest that acrolein induces TRPA1 expression by activating these transcription factors. Overexpression of TRPA1 in A549 cells increased acrolein sensitivity and the level of protein-conjugated acrolein (PC-Acro), while knockdown of TRPA1 in A549 cells or treatment with a TRPA1 antagonist caused tolerance to acrolein. These findings suggest that acrolein induces the TRPA1 channel and that an increase in TRPA1 expression promotes the cytotoxicity of acrolein.

The regulation of TRPA1 expression and function by Th1 and Th2-type inflammation in human A549 lung epithelial cells

BACKGROUND

Transient Receptor Potential Ankyrin 1 (TRPA1) is a cation channel that mediates pain, itch, cough, and neurogenic inflammation in response to pungent compounds such as acrolein in cigarette smoke. TRPA1 is also activated by endogenous factors and promotes inflammation in asthma models. We have recently shown that TRPA1 is upregulated by inflammatory cytokines in A549 human lung epithelial cells. Here, we explored the effects of Th1 and Th2-type inflammation on TRPA1.

METHODS AND RESULTS

TRPA1 expression and function was studied in A549 human lung epithelial cells. To induce inflammation, the cells were exposed to a combination of cytokines TNF-α and IL-1β; and to model Th1 or Th2-type responses, IFN-γ or IL-4/IL-13 was added, respectively. TRPA1 expression (measured by RT-PCR and Western blot) and function (assessed by Fluo-3AM intracellular calcium measurement) was enhanced under the influence of TNF-α + IL-1β. IFN-γ further enhanced TRPA1 expression and function, whereas IL-4 and IL-13 suppressed them. The effects of IFN-γ and IL-4 on TRPA1 expression were reversed by the Janus kinase (JAK) inhibitors baricitinib and tofacitinib, and those of IL-4 also by the STAT6 inhibitor AS1517499. The glucocorticoid dexamethasone downregulated TRPA1 expression, whereas the PDE4 inhibitor rolipram had no effect. Under all conditions, TRPA1 blockade was found to reduce the production of LCN2 and CXCL6.

CONCLUSIONS

TRPA1 expression and function in lung epithelial cells was upregulated under inflammatory conditions. IFN-γ further increased TRPA1 expression while IL-4 and IL-13 suppressed that in a JAK-STAT6 dependent manner which is novel. TRPA1 also modulated the expression of genes relevant to innate immunity and lung disease. We propose that the paradigm of Th1 and Th2 inflammation is a major determinant of TRPA1 expression and function, which should be considered when targeting TRPA1 for pharmacotherapy in inflammatory (lung) disease.

Intraganglionic reactive oxygen species mediate inflammatory pain and hyperalgesia through TRPA1 in the rat

Reactive oxygen species (ROS) are generated in nociceptive pathways in response to inflammation and injury. ROS are accumulated within the sensory ganglia following peripheral inflammation, but the functional role of intraganlionic ROS in inflammatory pain is not clearly understood. The aims of this study were to investigate whether peripheral inflammation leads to prolonged ROS accumulation within the trigeminal ganglia (TG), whether intraganglionic ROS mediate pain hypersensitivity via activation of TRPA1, and whether TRPA1 expression is upregulated in TG during inflammatory conditions by ROS. We demonstrated that peripheral inflammation causes excess ROS production within TG during the period when inflammatory mechanical hyperalgesia is most prominent. Additionally, scavenging intraganglionic ROS attenuated inflammatory mechanical hyperalgesia and a pharmacological blockade of TRPA1 localized within TG also mitigated inflammatory mechanical hyperalgesia. Interestingly, exogenous administration of ROS into TG elicited mechanical hyperalgesia and spontaneous pain-like responses via TRPA1, and intraganglionic ROS induced TRPA1 upregulation in TG. These results collectively suggest that ROS accumulation in TG during peripheral inflammation contributes to pain and hyperalgesia in a TRPA1 dependent manner, and that ROS further exacerbate pathological pain responses by upregulating TRPA1 expression. Therefore, any conditions that exacerbate ROS accumulation within somatic sensory ganglia can aggravate pain responses and treatments reducing ganglionic ROS may help alleviate inflammatory pain.

Transient Receptor Potential Ankyrin 1 (TRPA1) Methylation and Chronic Pain: A Systematic Review

BACKGROUND AND OBJECTIVE

Chronic pain represents a major global health issue in terms of psycho-physiological, therapeutic, and economic burden, not limited to adults but also to the pediatric age. Despite its great impact, its molecular mechanisms have still not been completely unraveled. Focusing on the impact of epigenetics in the pain complex trait, we assessed the association between chronic pain and the methylation pattern of TRPA1, a key gene related to pain sensitivity.

METHODS

We conducted a systematic review retrieving articles from three different databases. After deduplication, 431 items were subjected to manual screening, and then 61 articles were selected and screened again. Of these, only six were maintained for meta-analysis and analyzed using specific R packages.

RESULTS

Six articles were divided into two groups (group 1: comparison of mean methylation levels between healthy subjects and patients with chronic pain; group 2: correlation between mean methylation levels and pain sensation). A non-significant mean difference was obtained from the analysis of group 1 with a value of 3.97 (95% C.I. -7.79; 15.73). Analysis of group 2 showed a high level of variability between studies (correlation = 0.35, 95% C.I. -0.12; 0.82) due to their heterogeneity (I2 = 97%, p < 0.01).

CONCLUSIONS

Despite the high variability observed in the different studies analyzed, our results suggest that hypermethylation and increased pain sensitivity could be connected, possibly due to the variation of TRPA1 expression.

Mechanisms and Consequences of Variable TRPA1 Expression by Airway Epithelial Cells: Effects of TRPV1 Genotype and Environmental Agonists on Cellular Responses to Pollutants in Vitro and Asthma

BACKGROUND

Transient receptor potential ankyrin-1 [transient receptor potential cation channel subfamily A member 1 (TRPA1)] and vanilloid-1 [transient receptor potential cation channel subfamily V member 1 (TRPV1)] detect inhaled irritants, including air pollutants and have roles in the development and exacerbation of asthma.

OBJECTIVES

This study tested the hypothesis that increased expression of TRPA1, stemming from expression of the loss-of-function TRPV1 (I585V; rs8065080) polymorphic variant by airway epithelial cells may explain prior observations of worse asthma symptom control among children with the TRPV1 I585I/V genotype, by virtue of sensitizing epithelial cells to particulate materials and other TRPA1 agonists.

METHODS

TRP agonists, antagonists, small interfering RNA (siRNA), a nuclear factor kappa light chain enhancer of activated B cells (NF-κB) pathway inhibitor, and kinase activators and inhibitors were used to modulate TRPA1 and TRPV1 expression and function. Treatment of genotyped airway epithelial cells with particulate materials and analysis of asthma control data were used to assess consequences of TRPV1 genotype and variable TRPA1 expression on cellular responses in vitro and asthma symptom control among children as a function of voluntarily reported tobacco smoke exposure.

RESULTS

A relationship between higher TRPA1 expression and function and lower TRPV1 expression and function was revealed. Findings of this study pointed to a mechanism whereby NF-κB promoted TRPA1 expression, whereas NF-κB-regulated nucleotide-binding oligomerization domain, leucine rich repeat and pyrin domain containing 2 (NLRP2) limited expression. Roles for protein kinase C and p38 mitogen activated protein kinase were also demonstrated. Finally, the TRPV1 I585I/V genotype was associated with increased TRPA1 expression by primary airway epithelial cells and amplified responses to selected air pollution particles in vitro. However, the TRPV1 I585I/V genotype was not associated with worse asthma symptom control among children exposed to tobacco smoke, whereas other TRPA1 and TRPV1 variants were.

DISCUSSION

This study provides insights on how airway epithelial cells regulate TRPA1 expression, how TRPV1 genetics can affect TRPA1 expression, and that TRPA1 and TRPV1 polymorphisms differentially affect asthma symptom control. https://doi.org/10.1289/EHP11076.

TRPA1 Role in Inflammatory Disorders: What Is Known So Far?

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.