Bradykinin sensitizes the cough reflex via a B2 receptor dependent activation of TRPV1 and TRPA1 channels through metabolites of cyclooxygenase and 12-lipoxygenase

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.

Evaluation of Urtica dioica Phytochemicals against Therapeutic Targets of Allergic Rhinitis Using Computational Studies

Allergic rhinitis (AR) is a prevalent inflammatory condition affecting millions globally, with current treatments often associated with significant side effects. To seek safer and more effective alternatives, natural sources like Urtica dioica (UD) are being explored. However, UD's mechanism of action remains unknown. Therefore, to elucidate it, we conducted an in silico evaluation of UD phytochemicals' effects on known therapeutic targets of allergic rhinitis: histamine receptor 1 (HR1), neurokinin 1 receptor (NK1R), cysteinyl leukotriene receptor 1 (CLR1), chemoattractant receptor-homologous molecule expressed on type 2 helper T cells (CRTH2), and bradykinin receptor type 2 (BK2R). The docking analysis identified amentoflavone, alpha-tocotrienol, neoxanthin, and isorhamnetin 3-O-rutinoside as possessing a high affinity for all the receptors. Subsequently, molecular dynamics (MD) simulations were used to analyze the key interactions; the free energy of binding was calculated through Generalized Born and Surface Area Solvation (MMGBSA), and the conformational changes were evaluated. Alpha-tocotrienol exhibited a high affinity while also inducing positive conformational changes across all targets. Amentoflavone primarily affected CRTH2, neoxanthin targeted NK1R, CRTH2, and BK2R, and isorhamnetin-3-O-rutinoside acted on NK1R. These findings suggest UD's potential to treat AR symptoms by inhibiting these targets. Notably, alpha-tocotrienol emerges as a promising multi-target inhibitor. Further in vivo and in vitro studies are needed for validation.

Lavender (Lavandula angustifolia) syrup as an adjunct to standard care in patients with mild to moderate COVID-19: An open-label, randomized, controlled clinical trial

Objective

ongoing COVID-19 pandemic has been associated with clinical signs characterized by fever, fatigue and cough. Our study aimed to assess the efficacy of a Persian medicine formulation, lavender syrup, as an add-on to standard care in patients with mild to moderate COVID-19.

Materials and Methods

In this clinical trial which was conducted in Gorgan (Iran), 84 male and female COVID-19 outpatients were randomly allocated to either lavender syrup receiving 9 ml/twice/day for 21 days with standard conventional care or control groups. The primary objectives were to assess the improvement of clinical symptoms, while the secondary objectives were treatment satisfaction and anxiety levels which were evaluated once a week for 3 weeks.

Results

Out of 84 participants, 81 were analyzed (41 in the add-on group). The comparison between groups for cough severity and anosmia showed a higher reduction in the lavender group. The effect size was 0.6 for cough relief. Other symptoms and the Hamilton total score decreased in both groups with no statistically significant differences between the groups. The lavender group showed greater patients' satisfaction score.

Conclusion

Adjunctive therapy with lavender syrup could reduce cough and improve the quality of life in patients with COVID-19 patients.

Transient receptor potential ankyrin 1 (TRPA1) modulators: Recent update and future perspective

The transient receptor potential ankyrin 1 (TRPA1) channel is a non-selective cation channel that senses irritant chemicals. Its activation is closely associated with pain, inflammation, and pruritus. TRPA1 antagonists are promising treatments for these diseases, and there has been a recent upsurge in their application to new areas such as cancer, asthma, and Alzheimer's disease. However, due to the generally disappointing performance of TRPA1 antagonists in clinical studies, scientists must pursue the development of antagonists with higher selectivity, metabolic stability, and solubility. Moreover, TRPA1 agonists provide a deeper understanding of activation mechanisms and aid in antagonist screening. Therefore, we summarize the TRPA1 antagonists and agonists developed in recent years, with a particular focus on structure-activity relationships (SARs) and pharmacological activity. In this perspective, we endeavor to keep abreast of cutting-edge ideas and provide inspiration for the development of more effective TRPA1-modulating drugs.

Modification of the TRP Channel TRPA1 as a Relevant Factor in Migraine-Related Intracranial Hypersensitivity

Recently, the transient receptor potential ankyrin 1 (TRPA1) has gained more attention in migraine-related research. The involvement of the TRPA1 receptor in migraine headaches is proposed by the fact that TRPA1 may be a target of some migraine-triggering factors. Although it is doubtful that activation of TRPA1 alone is sufficient to induce pain, behavioral studies have demonstrated that TRPA1 is involved in injury- and inflammation-induced hypersensitivity. Here, we review the functional relevance of TRPA1 in headaches and its therapeutic potential, mainly focusing on its role in the development of hypersensitivity, referring to its altered expression in pathological conditions, and its functional interaction with other TRP channels.

Infectious and Inflammatory Pathways to Cough

Coughing is a dynamic physiological process resulting from input of vagal sensory neurons innervating the airways and perceived airway irritation. Although cough serves to protect and clear the airways, it can also be exploited by respiratory pathogens to facilitate disease transmission. Microbial components or infection-induced inflammatory mediators can directly interact with sensory nerve receptors to induce a cough response. Analysis of cough-generated aerosols and transmission studies have further demonstrated how infectious disease is spread through coughing. This review summarizes the neurophysiology of cough, cough induction by respiratory pathogens and inflammation, and cough-mediated disease transmission.

Effect of nano-curcumin on various diseases: A comprehensive review of clinical trials

The antioxidant, anti-inflammatory, and antibacterial properties of curcumin have made it a valuable herbal product for improving various disorders, such as COVID-19, cancer, depression, anxiety, osteoarthritis, migraine, and diabetes. Recent research has demonstrated that encapsulating curcumin in nanoparticles might improve its therapeutic effects and bioavailability. To our knowledge, the efficacy of nano-curcumin on different aspects of health and disease has not been summarized in a study. Therefore, this review aimed to evaluate nano-curcumin's efficacy in various diseases based on the findings of clinical trials. In order to review publications focusing on nanocurcumin's impact on various diseases, four databases were searched, including PubMed, Scopus, Web of Science, and Google Scholar. This review highlights the potential benefits of nano-curcumin in improving a wide range of human diseases including COVID-19, neurological disorders, chronic disease, oral diseases, osteoarthritis, metabolic syndrome, and other diseases, especially as an adjunct to standard therapy and a healthy lifestyle.

Combined biological effects and lung proteomics analysis in mice reveal different toxic impacts of electronic cigarette aerosol and combustible cigarette smoke on the respiratory system

Combustible cigarettes produce many toxic substances that have been linked to diseases, such as lung cancer and chronic obstructive pulmonary disease. For those smokers unable or unwilling to quit, electronic cigarettes (e-cigarettes) could be used as an alternative to cigarettes. However, the effects and mechanisms of e-cigarette aerosol (ECA) on respiratory function have not been fully elucidated, and in vivo studies of its safety are limited compared to cigarette smoke (CS). In this article, we chose nicotine levels as dosing references and C57BL/6 mice for a 10-week subchronic inhalation toxicity study. A comprehensive set of toxicological endpoints was used to study the effect of exposure. Both CS (6 mg/kg) and ECA (6 or 12 mg/kg) inhalation had decreased the animal’s lung function and increased levels of inflammation markers, along with pathological changes in the airways and lungs, with ECA displaying a relatively small effect at the same dose. Proteomic analysis of lung tissue showed greater overall protein changes by CS than that of ECA, with more severe inflammatory network perturbations. Compared with ECA, KEGG analysis of CS revealed upregulation of more inflammatory and virus-related pathways. Protein–protein interactions (PPI) showed that both ECA and CS significantly changed ribosome and complement system-related proteins in mouse lung tissue. The results support that e-cigarette aerosol is less harmful to the respiratory system than cigarette smoke at the same dose using this animal model, thus providing additional evidence for the relative safety of e-cigarettes.

Transient receptor potential Ankyrin 1: structure, function and ligands

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.

Multifactorial pathways in burn injury-induced chronic pain: novel targets and their pharmacological modulation

Burn injuries are among the highly prevalent medical conditions worldwide that occur mainly in children, military veterans and victims of fire accidents. It is one of the leading causes of temporary as well as permanent disabilities in patients. Burn injuries are accompanied by pain that persists even after recovery from tissue damage which puts immense pressure on the healthcare system. The pathophysiology of burn pain is poorly understood due to its complex nature and lack of considerable preclinical and clinical shreds of evidence, that creates a substantial barrier to the development of new analgesics. Burns damage the skin layers supplied with nociceptors such as NAV1.7, TRPV1, and TRPA1. Burn injury-mediated co-localization and simultaneous activation of TRPA1 and TRPV1 in nociceptive primary afferent C-fibers which contributes to the development and maintenance of chronic pain. Burn injuries are accompanied by central sensitization, a key feature of pain pathophysiology mainly driven by a series of cascades involving aberrations in the glutamatergic system, microglial activation, release of neuropeptides, cytokines, and chemokines. Activation of p38 mitogen-activated protein kinase, altered endogenous opioid signaling, and distorted genomic expression are other pathophysiological factors responsible for the development and maintenance of burn pain. Here we discuss comprehensive literature on molecular mechanisms of burn pain and potential targets that could be translated into near future therapeutics.

The Effectiveness of Wogonin on Treating Cough Mice With Mycoplasma Pneumoniae Infection

Background: Cough is the main symptom of mycoplasma pneumoniae (MP) infection. Cough potential protein transient receptor potential A1 (TRPA1) plays an important role in cough reflex. The purpose of this study was to clarify the mechanism of wogonin, the effective component of Qinbai Qingfei concentrated pellet (Qinbai), in the treatment of cough after MP infection.

Methods: The Biacore™ system was used to detect whether there was specific binding between Qinbai and cough potential protein TRPA1. Biacore™ fishing technology and UPLC-Q-TOF-MS technology were used during fishing combined active components and identification and analysis of recovered samples. The expression levels of TRPA1, substance P (SP), calcitonin gene-related peptide (CGRP), cough-related proteins, and mRNA in the lung tissues from each group were detected by immunohistochemistry, Western blot, and real-time PCR.

Results: Biacore™ results showed that Qinbai had strong specific binding to TRPA1 protein with a binding value of 99.0 resonance unit (RU). The samples obtained from angling were identified and analyzed by UPLC-Q-TOF-MS as wogonin. The results of immunohistochemistry, Western blot, and real-time PCR showed that compared with the model group, the wogonin group had lower expressions of mRNA, TRPA1, SP, and CGRP in the lung tissue of cough mice with MP infection (p < 0.01 or p < 0.05), and the effects were superior to those of azithromycin and pentoxyverine control groups.

Conclusion: Wogonin can treat cough after MP infection by affecting the expressions of cough-related proteins, such as TRPA1, SP, and CGRP. This study provided a theoretical foundation for the clinical research of Qinbai.

Immunouniverse of SARS-CoV-2

SARS-CoV-2 virus has become a global health problem that has caused millions of deaths worldwide. The infection can present with multiple clinical features ranging from asymptomatic or mildly symptomatic patients to patients with severe or critical illness that can even lead to death. Although the immune system plays an important role in pathogen control, SARS-CoV-2 can drive dysregulation of this response and trigger severe immunopathology. Exploring the mechanisms of the immune response involved in host defense against SARS-CoV-2 allows us to understand its immunopathogenesis and possibly detect features that can be used as potential therapies to eliminate the virus. The main objective of this review on SARS-CoV-2 is to highlight the interaction between the virus and the immune response. We explore the function and action of the immune system, the expression of molecules at the site of infection that cause hyperinflammation and hypercoagulation disorders, the factors leading to the development of pneumonia and subsequent severe acute respiratory distress syndrome which is the leading cause of death in patients with COVID-19.

Effects of Preserving the Pulmonary Vagus Nerve Branches on Cough After Pneumonectomy During Video-Assisted Thoracic Surgery

Background

Cough is one of the most common complications of early-stage non-small cell lung cancer (NSCLC) after video-assisted thoracoscopic surgery (VATS). The vagus nerve plays an important role in pulmonary inflammation and the cough reflex. In this study, we attempted to reduce the incidence of postoperative chronic cough and other complications by preserving the pulmonary vagus nerve branches.

Patients and Methods

This study was a randomized controlled double-blinded trial of subjects and observers. A total of 158 NSCLC patients were enrolled. We randomly assigned 79 patients to Group A (pulmonary branch of vagus nerve preservation group) and 79 cases to Group B (conventional surgical treatment group). In the final analysis, 72 patients from Group A and 69 patients from Group B were included. The main outcome measure of the study was the occurrence of CAP or other postoperative complications within five weeks. This trial was registered with ClinicalTrials.gov (number NCT03921828).

Results

There was no significant difference in preoperative general clinical data between the two groups. No death during the perioperative period occurred in either of the two groups. There was no significant difference between the two groups in operation time, intraoperative bleeding, number of lymph nodes sent for examination, number of cases transferred to ICU after operation, postoperative catheterization time, or postoperative hospital stay (P>0.05). There was no significant difference in other pulmonary and cardiovascular complications between the two groups, including pulmonary infection (2.78% vs. 8.70%, P = 0.129), atelectasis (1.39% vs. 0%, P = 0.326), pleural effusion (2.78% vs. 1.45%, P = 0.585), persistent pulmonary leakage (2.78% vs. 2.90%, P = 0.965), arrhythmia (2.78% vs. 1.45%, P = 0.585), and heart failure (0% vs. 1.45%, P = 0.305). The incidence of CAP in Group A was significantly lower than that in Group B (13.89% vs. 30.43%, P = 0.018). The LCQ-MC scores in Group A were significantly higher than those in Group B at two and five weeks after operation (P<0.05). Univariate and multivariate analysis showed that the risk factors for postoperative CAP were surgical side (right lung), surgical lung lobe (upper lobe), preservation of pulmonary branch of the vagus nerve during operation, and duration of anesthesia.

Conclusions

Preserving the pulmonary vagus nerve branches during VATS in patients with stage IA1-2 NSCLC can reduce the incidence of postoperative CAP.

The Mechanism of Pertussis Cough Revealed by the Mouse-Coughing Model

Pertussis, also known as whooping cough, is a contagious respiratory disease caused by the Gram-negative bacterium Bordetella pertussis. This disease is characterized by severe and uncontrollable coughing, which imposes a significant burden on patients. However, its etiological agent and the mechanism are totally unknown because of a lack of versatile animal models that reproduce the cough. Here, we present a mouse model that reproduces coughing after intranasal inoculation with the bacterium or its components and demonstrate that lipooligosaccharide (LOS), pertussis toxin (PTx), and Vag8 of the bacterium cooperatively function to cause coughing. Bradykinin induced by LOS sensitized a transient receptor potential ion channel, TRPV1, which acts as a sensor to evoke the cough reflex. Vag8 further increased bradykinin levels by inhibiting the C1 esterase inhibitor, the major downregulator of the contact system, which generates bradykinin. PTx inhibits intrinsic negative regulation systems for TRPV1 through the inactivation of G_i GTPases. Our findings provide a basis to answer long-standing questions on the pathophysiology of pertussis cough.

Prostaglandin E2 sensitizes the cough reflex centrally via EP3 receptor-dependent activation of NaV 1.8 channels

Background

Cough hypersensitivity is a major characteristic feature associated with several types of cough, including chronic cough, but its underlying mechanisms remain to be fully understood. Inflammatory mediators, such as prostaglandin E₂ (PGE₂), have been implicated in both peripheral induction and sensitization of the cough reflex. In this study, using a conscious guinea pig model of cough, we investigated whether PGE₂ can sensitize the cough reflex via central actions and, if so, via which mechanisms.

Methods

All drugs were administered by intracerebroventricular (i.c.v.) route and whole-body plethysmograph set-up was used for both induction, using aerosolized citric acid (0.2 M), and recording of cough. Immunohistochemistry was performed to confirm the expression of NaV 1.8 channels in the nucleus tractus solitarius (nTS).

Results

We show that both PGE₂ and the non-selective EP1/EP3 agonist, sulprostone, dose-dependently enhanced the citric acid-induced cough (P ≤ 0.001, P ≤ 0.01, respectively). Pretreatment with the EP1 antagonist, ONO-8130, did not affect the sulprostone-induced cough sensitization, whilst the EP3 antagonist, L-798,106, dose-dependently inhibited this effect (P ≤ 0.05). Furthermore, treatment with either the EP2 agonist, butaprost or the EP4 agonist, L-902,688, had no effect on cough sensitization. Additionally, pretreatment with either the TRPV1 antagonist, JNJ-17203212 or the TRPA1 antagonist, HC-030031, alone or in combination, nor with the NaV 1.1, 1.2, 1.3, 1.4, 1.6 and 1.7 channel blocker, tetrodotoxin, had any effect on the cough. In contrast, pretreatment with the NaV 1.8 antagonist, A-803467, dose-dependently inhibited this effect (P ≤ 0.05). Furthermore, NaV 1.8 channels were shown to be expressed in the nTS.

Conclusion

Collectively, our findings show that PGE₂ sensitizes the cough reflex centrally via EP3 receptor-dependent activation of NaV 1.8 but independently of TRPV1,TRPA1 and TTX-sensitive sodium channel activation. These results indicate that PGE₂ plays an important role in central sensitization of the cough reflex and suggest that central EP3 receptors and/or NaVv 1.8 channels may represent novel antitussive molecular targets.

Graphical Abstract

Which ones, when and why should renin-angiotensin system inhibitors work against COVID-19?

The article describes the possible pathophysiological origin of COVID-19 and the crucial role of renin-angiotensin system (RAS), providing several “converging” evidence in support of this hypothesis. SARS-CoV-2 has been shown to initially upregulate ACE2 systemic activity (early phase), which can subsequently induce compensatory responses leading to upregulation of both arms of the RAS (late phase) and consequently to critical, advanced and untreatable stages of COVID-19 disease. The main and initial actors of the process are ACE2 and ADAM17 zinc-metalloproteases, which, initially triggered by SARS-CoV-2 spike proteins, work together in increasing circulating Ang 1–7 and Ang 1–9 peptides and downstream (Mas and Angiotensin type 2 receptors) pathways with anti-inflammatory, hypotensive and antithrombotic activities. During the late phase of severe COVID-19, compensatory secretion of renin and ACE enzymes are subsequently upregulated, leading to inflammation, hypertension and thrombosis, which further sustain ACE2 and ADAM17 upregulation. Based on this hypothesis, COVID-19-phase-specific inhibition of different RAS enzymes is proposed as a pharmacological strategy against COVID-19 and vaccine-induced adverse effects. The aim is to prevent the establishment of positive feedback-loops, which can sustain hyperactivity of both arms of the RAS independently of viral trigger and, in some cases, may lead to Long-COVID syndrome.

Oral nano-curcumin formulation efficacy in the management of mild to moderate outpatient COVID-19: A randomized triple-blind placebo-controlled clinical trial

BACKGROUND

Curcumin, a natural polyphenolic compound, is proposed as a potential treatment option for patients with coronavirus disease by inhibiting the entry of virus to the cell, encapsulation of the virus and viral protease, as well as modulating various cellular signaling pathways. In this study, the efficacy and safety of nanocurcumin oral formulation has been evaluated in patients with mild-moderate Coronavirus disease 2019 (COVID-19) in outpatient setting.

METHODS

In this triple-blind randomized placebo-controlled clinical trial, sixty mild to moderate COVID-19 patients in outpatient setting who fulfilled the inclusion criteria were randomly allocated to treatment (n = 30) group to receive oral nanocurcumin formulation (Sinacurcumin soft gel which contains 40 mg curcuminoids as nanomicelles), two soft gels twice a day after food for 2 weeks or placebo (n = 30) group. Patients' symptoms and laboratory data were assessed at baseline and during follow-up period and compared between two groups.

RESULTS

All symptoms except sore throat resolved faster in the treatment group and the difference was significant for chills, cough and smell and taste disturbances. The CRP serum level was lower in the treatment group at the end of two weeks and the lymphocyte count was significantly higher in treatment group. No significant adverse reaction reported in the treatment group.

CONCLUSION

Oral nanoformulation of curcumin can significantly improve recovery time in patients with mild to moderate COVID-19 in outpatient setting. Further studies with larger sample size are recommended.

Epigenetics and sarcoidosis

Epigenetic modifications are emerging as important regulatory mechanisms of gene expression in lung disease, given that they are influenced by environmental exposures and genetic variants, and that they regulate immune and fibrotic processes. In this review, we introduce these concepts with a focus on the study of DNA methylation and histone modifications and discuss how they have been applied to lung disease, and how they can be applied to sarcoidosis. This information has implications for other exposure and immunologically mediated lung diseases, such as chronic beryllium disease, hypersensitivity pneumonitis, and asbestosis.

Indomethacin: Can It Counteract Bradykinin Effects in COVID-19 Patients?

COVID-19 represents the biggest health challenge. Although the mortality rate of COVID-19 is low, the high numbers of infected people and those with post-COVID-19 symptoms represent a real problem for the health system. A high number of patients with COVID-19 or people recovered from COVID-19 suffer from a dry cough and/or myalgia. Interestingly, an imbalance in bradykinin was observed in COVID-19 patients, which might be due to the accumulation of bradykinin as a result of a reduction in the degradation of bradykinin. This finding inspired the idea of possible similitude between the dry cough that is induced by angiotensin-converting enzyme inhibitors and the COVID-19-induced dry cough. Both of these types of cough are mediated, at least partially, by bradykinin. They both manifested as a persistent dry cough that is not responded to traditional dry cough remedies. However, several drugs were previously investigated for the treatment of angiotensin-converting enzyme inhibitor–induced dry cough. Here, we hypothesized that such treatment might be useful in COVID-19-induced dry cough and other bradykinin-related symptoms such as generalized pain and myalgia. In this article, evidence was presented to support the use of indomethacin as a potential treatment of COVID-19-induced dry cough. The choice of indomethacin was based on its ability to suppress the cyclooxygenase enzyme while also lowering the level of the inflammatory mediator bradykinin. Furthermore, indomethacin has been shown to be effective in treating angiotensin-converting enzyme inhibitor–induced dry cough. Moreover, indomethacin is a long-established, low-cost, effective, and readily available medication.

The role of TRPA1 and TRPV4 channels in bronchoconstriction and plasma extravasation in airways of rats treated with captopril

Angiotensin-converting enzyme inhibitors (ACEis) may cause adverse airway events, such as cough and angioedema, due to a reduction in bradykinin breakdown and consequent activation of bradykinin type 2 receptor (B₂ receptor). Recent studies have shown that bradykinin can also sensitize pro-inflammatory receptors such as the transient receptor potential ankyrin 1 (TRPA1) and vanilloid 4 (TRPV4), which are implicated in several inflammatory airway diseases. Based on these considerations, the aim of this study was to understand the role of TRPA1 and TRPV4 channels in the bronchoconstrictive response and plasma extravasation in the trachea of rats pretreated with captopril. Using methods to detect alterations in airway resistance and plasma extravasation, we found that intravenous (i.v.) administration of bradykinin (0.03-0.3 μmol/kg, B₂ receptor agonist), allyl isothiocyanate (100-1000 μmol/kg, TRPA1 agonist) or GSK1016790A (0.01-0.1 μmol/kg, TRPV4 agonist), but not des-arg⁹-bradykinin (DABK; 100-300 μmol/kg, B₁ receptor agonist), induced bronchoconstriction in anaesthetized rats. In doses that did not cause significant bronchoconstriction, bradykinin (0.03 μmol/kg) or allyl isothiocyanate (100 μmol/kg), but not GSK1016790A (0.01 μmol/kg) or DABK (300 μmol/kg) induced an increased bronchoconstrictive response in rats pretreated with captopril (2.5 mg/kg, i.v.). On the other hand, in rats pretreated with captopril (5 mg/kg, i.v.), an increased bronchoconstrictive response to GSK1016790A (0.01 μmol/kg) was observed. The bronchoconstrictive response induced by bradykinin in captopril-pretreated rats was inhibited by intratracheal treatment (i.t.) with HC030031 (300 μg/50 μl; 36 ± 9%) or HC067047 (300 μg/50 μl; 35.1 ± 16%), for TRPA1 and TRPV4 antagonists, respectively. However, the co-administration of both antagonists did not increase this inhibition. The bronchoconstriction induced by allyl isothiocyanate in captopril-pretreated rats (2.5 mg/kg) was inhibited (58.3 ± 8%) by the B₂ receptor antagonist HOE140 (10 nmol/50 μl, i.t.). Similarly, the bronchoconstriction induced by GSK1016790A in captopril-pretreated rats (5 mg/kg) was also inhibited (84.2 ± 4%) by HOE140 (10 nmol/50 μl, i.t.). Furthermore, the plasma extravasation induced by captopril on the trachea of rats was inhibited by pretreatment with HC030031 (47.2 ± 8%) or HC067047 (38.9 ± 8%). Collectively, these findings support the hypothesis that TRPA1 and TRPV4, via a B₂ receptor activation-dependent pathway, are involved in the plasma extravasation and bronchoconstriction induced by captopril, making them possible pharmacological targets to prevent or remediate ACEi-induced adverse respiratory reactions.

The Enigma of Prodromes in Hereditary Angioedema (HAE)

A prodrome is a premonitory set of signs and symptoms indicating the onset of a disease. Prodromes are frequently reported by hereditary angioedema (HAE) patients, antedating attacks by a few hours or even longer. In some studies, high incidence of prodromes was reported by patients, with considerable number being able to predict oncoming attacks. Regrettably, prodromes have never received a consensual definition and have not been properly investigated in a systematic fashion. Therefore, their nature remains elusive and their contribution to the diagnosis and treatment of disorders is uncertain. The term "prodrome," as used in various pathologies, denotes different meanings, timing, and duration, so it may not be equally suitable for all clinical situations. Perception of a prodrome is unique for each individual patient depending on self-experience. As modern drugs delegate the administration decision to the patients, early detection of a developing attack may help mitigate its severity and allow deployment of appropriate therapy. New diagnostic instruments were recently developed that can assist in defining the attributes of prodromes and their association with attacks. We will review the prodrome phenomenon as exhibited in certain clinical situations, with an emphasis on prodromes of HAE.

ACE inhibitor induced visceral angioedema: an elusive diagnosis

ACE inhibitors are widely used and well-tolerated drugs. Angioedema is a well-known adverse effect, which involves the viscera rarely. This is a case of a 44-year-old African-American man with newly diagnosed hypertension, who presented with lower abdominal pain and diarrhoea. Based on the clinical picture and radiographic findings, lisinopril-induced intestinal angioedema was diagnosed. He recovered with supportive treatment, and the lisinopril was permanently discontinued. The mechanism of angioedema is thought to be the inhibition of ACE-mediated degradation of bradykinin, which is a peptide responsible for vasodilation and increased vascular permeability. While the external angioedema is unmistakable, intestinal angioedema has a relatively non-specific presentation and chronology, often leading to missed diagnosis and unnecessary interventions. Most common symptoms are abdominal pain and diarrhoea. Characteristic radiographic findings include ‘doughnut sign’ and ‘stacked coin’ appearance. Treatment is supportive. ACE inhibitors should be discontinued to prevent a recurrence.

Emerging Mechanisms of Pulmonary Vasoconstriction in SARS-CoV-2-Induced Acute Respiratory Distress Syndrome (ARDS) and Potential Therapeutic Targets

The 1918 influenza killed approximately 50 million people in a few short years, and now, the world is facing another pandemic. In December 2019, a novel coronavirus named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused an international outbreak of a respiratory illness termed coronavirus disease 2019 (COVID-19) and rapidly spread to cause the worst pandemic since 1918. Recent clinical reports highlight an atypical presentation of acute respiratory distress syndrome (ARDS) in COVID-19 patients characterized by severe hypoxemia, an imbalance of the renin-angiotensin system, an increase in thrombogenic processes, and a cytokine release storm. These processes not only exacerbate lung injury but can also promote pulmonary vascular remodeling and vasoconstriction, which are hallmarks of pulmonary hypertension (PH). PH is a complication of ARDS that has received little attention; thus, we hypothesize that PH in COVID-19-induced ARDS represents an important target for disease amelioration. The mechanisms that can promote PH following SARS-CoV-2 infection are described. In this review article, we outline emerging mechanisms of pulmonary vascular dysfunction and outline potential treatment options that have been clinically tested.

Curcumin (a constituent of turmeric): New treatment option against COVID-19

In late December 2019, the outbreak of respiratory illness emerged in Wuhan, China, and spreads worldwide. World Health Organization (WHO) named this disease severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused by a new member of beta coronaviruses. Several medications are prescribed to patients, and some clinical trials are underway. Scientists are trying to find a specific drug against this virus. In this review, we summarize the pathogenesis, clinical features, and current treatments of coronavirus disease 2019 (COVID-19). Then, we describe the possible therapeutic effects of curcumin and its molecular mechanism against coronavirus-19. Curcumin, as an active constituent of Curcuma longa (turmeric), has been studied in several experimental and clinical trial studies. Curcumin has some useful clinical effects such as antiviral, antinociceptive, anti-inflammatory, antipyretic, and antifatigue effects that could be effective to manage the symptoms of the infected patient with COVID-19. It has several molecular mechanisms including antioxidant, antiapoptotic, and antifibrotic properties with inhibitory effects on Toll-like receptors, NF-κB, inflammatory cytokines and chemokines, and bradykinin. Scientific evidence suggests that curcumin could have a potential role to treat COVID-19. Thus, the use of curcumin in the clinical trial, as a new treatment option, should be considered.

Establishment of a mouse model with all four clinical features of eosinophilic bronchitis

Eosinophilic bronchitis (EB) is a clinical disease characterized by chronic cough, airway eosinophil infiltration, and responsive to steroid therapy but with the absence of airway hyperreactivity (AHR). This study established an EB mouse model with all the above features. First, 42 mice were divided into 7 groups to investigate the optimal time interval between cough and AHR detections. Afterward, 28 mice were divided into the asthma, EB, normal saline (NS), and dexamethasone (DXM) groups. Mice were challenged using nasal drops of 200 µg ovalbumin (OVA), 10 µg OVA, NS, or intraperitoneal injections of 5 mg/kg of DXM one hour prior to 10 µg OVA challenge. Airway reactivity was measured 6 h after cough was observed. The frequency of coughs in the asthma and EB groups increased significantly compared to mice in the NS group. After DXM administration, frequency of coughs was significantly decreased compared to mice in the asthma and EB groups. Lung resistance in the asthma group was significantly higher compared to mice in the NS, EB, and DXM groups. Obvious airway eosinophilic inflammation in BALF and lung tissues were observed in the asthma and EB groups, while DXM administration could attenuate airway inflammatory infiltration. In summary, we developed a mouse EB model with all four clinical features of EB by the administration of 10 µg OVA nasal drops.

Complex Regulatory Role of the TRPA1 Receptor in Acute and Chronic Airway Inflammation Mouse Models

The Transient Receptor Potential Ankyrin 1 (TRPA1) cation channel expressed on capsaicin-sensitive afferents, immune and endothelial cells is activated by inflammatory mediators and exogenous irritants, e.g., endotoxins, nicotine, crotonaldehyde and acrolein. We investigated its involvement in acute and chronic pulmonary inflammation using Trpa1 gene-deleted (Trpa1^-/-) mice. Acute pneumonitis was evoked by intranasal Escherichia coli endotoxin (lipopolysaccharide: LPS) administration, chronic bronchitis by daily cigarette smoke exposure (CSE) for 4 months. Frequency, peak inspiratory/expiratory flows, minute ventilation determined by unrestrained whole-body plethysmography were significantly greater, while tidal volume, inspiratory/expiratory/relaxation times were smaller in Trpa1^-/- mice. LPS-induced bronchial hyperreactivity, myeloperoxidase activity, frequency-decrease were significantly greater in Trpa1^-/- mice. CSE significantly decreased tidal volume, minute ventilation, peak inspiratory/expiratory flows in wildtypes, but not in Trpa1^-/- mice. CSE remarkably increased the mean linear intercept (histopathology), as an emphysema indicator after 2 months in wildtypes, but only after 4 months in Trpa1^-/- mice. Semiquantitative histopathological scores were not different between strains in either models. TRPA1 has a complex role in basal airway function regulation and inflammatory mechanisms. It protects against LPS-induced acute pneumonitis and hyperresponsiveness, but is required for CSE-evoked emphysema and respiratory deterioration. Further research is needed to determine TRPA1 as a potential pharmacological target in the lung.

Hypersensitivity of Airway Reflexes Induced by Hydrogen Sulfide: Role of TRPA1 Receptors

The activation of capsaicin-sensitive lung vagal (CSLV) afferents can elicit airway reflexes. Hypersensitivity of these afferents is known to contribute to the airway hypersensitivity during airway inflammation. Hydrogen sulfide (H₂S) has been suggested as a potential therapeutic agent for airway hypersensitivity diseases, such as asthma, because of its relaxing effect on airway smooth muscle and anti-inflammatory effect. However, it is still unknown whether H₂S affects airway reflexes. Our previous study demonstrated that exogenous application of H₂S sensitized CSLV afferents and enhanced Ca²⁺ transients in CSLV neurons. The present study aimed to determine whether the H₂S-induced sensitization leads to functional changes in airway reflexes and elevates the electrical excitability of the CSLV neurons. Our results showed that, first and foremost, in anesthetized, spontaneously breathing rats, the inhalation of aerosolized sodium hydrosulfide (NaHS, a donor of H₂S; 5 mg/mL, 3 min) caused an enhancement in apneic response evoked by several stimulants of the CSLV afferents. This enhancement effect was found 5 min after NaHS inhalation and returned to control 30 min later. However, NaHS no longer enhanced the apneic response after perineural capsaicin treatment on both cervical vagi that blocked the conduction of CSLV fibers. Furthermore, the enhancing effect of NaHS on apneic response was totally abolished by pretreatment with intravenous HC-030031 (a TRPA1 antagonist; 8 mg/kg), whereas the potentiating effect was not affected by the pretreatment with the vehicle of HC-030031. We also found that intracerebroventricular infusion pretreated with HC-030031 failed to alter the potentiating effect of NaHS on the apneic response. Besides, the cough reflex elicited by capsaicin aerosol was enhanced by inhalation of NaHS in conscious guinea pigs. Nevertheless, this effect was entirely eliminated by pretreatment with HC-030031, not by its vehicle. Last but not least, voltage-clamp electrophysiological analysis of isolated rat CSLV neurons showed a similar pattern of potentiating effects of NaHS on capsaicin-induced inward current, and the involvement of TRPA1 receptors was also distinctly shown. In conclusion, these results suggest that H₂S non-specifically enhances the airway reflex responses, at least in part, through action on the TRPA1 receptors expressed on the CSLV afferents. Therefore, H₂S should be used with caution when applying for therapeutic purposes in airway hypersensitivity diseases.

A hypothesized role for dysregulated bradykinin signaling in COVID-19 respiratory complications

As of April 20, 2020, over time, the COVID-19 pandemic has resulted in 157 970 deaths out of 2 319 066 confirmed cases, at a Case Fatality Rate of ~6.8%. With the pandemic rapidly spreading, and health delivery systems being overwhelmed, it is imperative that safe and effective pharmacotherapeutic strategies are rapidly explored to improve survival. In this paper, we use established and emerging evidence to propose a testable hypothesis that, a vicious positive feedback loop of des-Arg(9)-bradykinin- and bradykinin-mediated inflammation → injury → inflammation, likely precipitates life threatening respiratory complications in COVID-19. Through our hypothesis, we make the prediction that the FDA-approved molecule, icatibant, might be able to interrupt this feedback loop and, thereby, improve the clinical outcomes. This hypothesis could lead to basic, translational, and clinical studies aimed at reducing COVID-19 morbidity and mortality.

Mammalian Transient Receptor Potential TRPA1 Channels: From Structure to Disease

The transient receptor potential ankyrin (TRPA) channels are Ca²⁺-permeable nonselective cation channels remarkably conserved through the animal kingdom. Mammals have only one member, TRPA1, which is widely expressed in sensory neurons and in non-neuronal cells (such as epithelial cells and hair cells). TRPA1 owes its name to the presence of 14 ankyrin repeats located in the NH₂ terminus of the channel, an unusual structural feature that may be relevant to its interactions with intracellular components. TRPA1 is primarily involved in the detection of an extremely wide variety of exogenous stimuli that may produce cellular damage. This includes a plethora of electrophilic compounds that interact with nucleophilic amino acid residues in the channel and many other chemically unrelated compounds whose only common feature seems to be their ability to partition in the plasma membrane. TRPA1 has been reported to be activated by cold, heat, and mechanical stimuli, and its function is modulated by multiple factors, including Ca²⁺, trace metals, pH, and reactive oxygen, nitrogen, and carbonyl species. TRPA1 is involved in acute and chronic pain as well as inflammation, plays key roles in the pathophysiology of nearly all organ systems, and is an attractive target for the treatment of related diseases. Here we review the current knowledge about the mammalian TRPA1 channel, linking its unique structure, widely tuned sensory properties, and complex regulation to its roles in multiple pathophysiological conditions.

Role of TRP channels in Gq-coupled protease-activated receptor 1-mediated activation of mouse nodose pulmonary C-fibers

We evaluated the mechanisms underlying protease-activated receptor 1 (PAR1)-mediated activation of nodose C-fibers in mouse lungs. The PAR1-induced action potential discharge at the terminals was strongly inhibited in phospholipase C-β3 (PLCβ3)-deficient animals. At the level of the cell soma, PAR1 activation led to an increase in cytosolic calcium that was largely inhibited by transient receptor potential (TRP) A1 antagonism. Patch-clamp recordings, however, revealed that neither TRPA1 nor TRPV1 or any other ruthenium red-sensitive ion channels are required for the PAR1-mediated inward current or membrane depolarization in isolated nodose neurons. Consistent with these findings, PAR1-mediated action potential discharge in mouse lung nodose C-fiber terminals was unaltered in Trpa1/Trpv1 double-knockout animals and Trpc3/Trpc6 double-knockout animals. The activation of the C-fibers was also not inhibited by ruthenium red at concentrations that blocked TRPV1- and TRPA1-dependent responses. The biophysical data show that PAR1/G_q-mediated activation of nodose C-fibers may involve multiple ion channels downstream from PLCβ3 activation. TRPA1 is an ion channel that participates in PAR1/G_q-mediated elevation in intracellular calcium. There is little evidence, however, that TRPA1, TRPV1, TRPC3, TRPC6, or other ruthenium red-sensitive TRP channels are required for PAR1/G_q-PLCβ3-mediated membrane depolarization and action potential discharge in bronchopulmonary nodose C-fibers in the mouse.

Transient receptor potential ankyrin 1 (TRPA1)-mediated toxicity: friend or foe?

Transient receptor potential (TRP) channels have been widely studied during the last decade. New studies uncover new features and potential applications for these channels. TRPA1 has a huge distribution all over the human body and has been reported to be involved in different physiological and pathological conditions including cold, pain, and damage sensation. Considering its role, many studies have been devoted to evaluating the role of this channel in the initiation and progression of different toxicities. Accordingly, we reviewed the most recent studies and divided the role of TRPA1 in toxicology into the following sections: neurotoxicity, cardiotoxicity, dermatotoxicity, and pulmonary toxicity. Acetaminophen, heavy metals, tear gases, various chemotherapeutic agents, acrolein, wood smoke particulate materials, particulate air pollution materials, diesel exhaust particles, cigarette smoke extracts, air born irritants, sulfur mustard, and plasticizers are selected compounds and materials with toxic effects that are, at least in part, mediated by TRPA1. Considering the high safety of TRPA1 antagonists and their efficacy to resolve selected toxic or adverse drug reactions, the future of these drugs looks promising.