P2Y12 antagonist attenuates eosinophilic inflammation and airway hyperresponsiveness in a mouse model of asthma

Cysteinyl Leukotrienes in Allergic Inflammation

The cysteinyl leukotrienes (CysLTs), LTC4, LTD4, and LTE4, are potent lipid mediators derived from arachidonic acid through the 5-lipoxygenase pathway. These mediators produce both inflammation and bronchoconstriction through three distinct G protein-coupled receptors (GPCRs)-CysLT1, CysLT2, and OXGR1 (also known as CysLT3 or GPR99). While CysLT-mediated functions in the effector phase of allergic inflammation and asthma have been established for some time, recent work has demonstrated novel roles for these mediators and their receptors in the induction and amplification of type 2 inflammation. Additionally, in vitro studies and murine models have uncovered diverse regulatory mechanisms that restrain or amplify CysLT receptor activation and CysLT receptor function. This review provides an overview of CysLT biosynthesis and its regulation, the molecular and functional pharmacology of CysLT receptors, and an overview of the established and emerging roles of CysLTs in asthma, aspirin-exacerbated respiratory disease, and type 2 inflammation.

The role of the P2X7 receptor in inactivated SARS-CoV-2-induced lung injury

Purinergic signaling plays a role in the pathophysiology of different viral infections. Recently, we showed that COVID-19 increases extracellular ATP levels, which may amplify the pro-inflammatory signals in the disease. The P2X7 receptor can be a protagonist in the pro-inflammatory responses. Herein, we investigated the role of the P2X7 receptor in the lung immune response triggered by inoculation of inactivated SARS-CoV-2 (iSARS-CoV-2) in K18-Human ACE2 transgenic mice. Pharmacological inhibition of the P2X7 receptor was performed with intraperitoneal administration of 50 mg/kg of Brilliant Blue G (BBG) one day before viral inoculation. Animals were divided into four groups: a control group (MOCK), a group inoculated with the inactivated virus iSARS-CoV-2, a BBG-treated control group (MOCK + BBG), and a BBG-treated inoculated group (iSARS-CoV-2 + BBG). Virus inoculation was intratracheal with 50 µl of mock or 2 × 106 Plaque Forming Units (PFU) of iSARS-CoV-2. After three days, blood and lungs were collected. We found a significant increase in ATP and LDH in serum and mRNA levels of P2X7 and P2Y12 receptors, CD39, IL-1β, and TNF-α in the lung of the iSARS-CoV-2 group when compared with the control group. BBG treatment attenuated these increases. Lung histological analyses showed severe lung damage in the iSARS-CoV-2 group, which was reduced by the BBG treatment. Immunohistochemical staining confirmed the increased presence of P2X7, P2Y12, and CD39 proteins in the iSARS-CoV-2 vs. the MOCK group. Thus, P2X7 receptor inhibition decreases iSARS-CoV-2-induced lung inflammation, indicating that this receptor might contribute to SARS-CoV-2 pathology.

Mediation of the JNC/ILC2 pathway in DBP-exacerbated allergic asthma: A molecular toxicological study on neuroimmune positive feedback mechanism

BACKGROUND

Dibutyl phthalate (DBP), a commonly used plasticizer, has been found to be strongly linked to a consistently high prevalence of allergic diseases, particularly allergic asthma. Previous animal experiments have demonstrated that exposure to DBP can worsen asthma by triggering the production of calcitonin gene-related peptide (CGRP), a neuropeptide in the lung tissue. However, the precise neuroimmune mechanism and pathophysiology of DBP-exacerbated allergic asthma with the assistance of CGRP remain unclear.

OBJECTIVE

The present study was to investigate the potential pathophysiological mechanism in DBP-exacerbated asthma from the perspective of neural-immune interactions.

METHODS AND RESULTS

C57BL/6 mice were orally exposed to different concentrations (0.4, 4, 40 mg/kg) of DBP for 28 days. They were then sensitized with OVA and nebulized with OVA for 7 consecutive excitations. To investigate whether DBP exacerbates allergic asthma in OVA induced mice, we analyzed airway hyperresponsiveness and lung histopathology. To investigate the activation of JNC and TRPV1 neurons and the release of CGRP by JNC cells, we measured the levels of TRPV1 channels, calcium inward flow, and downstream neuropeptide CGRP. Results showed that TRPV1 expression, inward calcium flux, and CGRP levels were significantly elevated in the lung tissues of the 40DBP + OVA group, suggesting the release of CGRP by JNC cells. To counteract the detrimental effects of DBP mediated by CGRP, we employed olcegepant (also known as BIBN-4096), a CGRP receptor specific antagonist. Results revealed that 40DBP + OVA + olcegepant led to notable decreases in TRPV1, calcium inward flow, and CGRP expression in lung tissues compare with 40DBP + OVA, further supporting the efficacy of olcegepant. Additionally, we also conducted ILC2 flow sorting and observed that neuropeptide CGRP-activated ILC2 cells have a crucial role as key effector cells in DBP-induced neuroimmune positive feedback regulation. Finally, we examined the protein expression of CGRP, GATA3 and P-GATA3, and found that significant upregulations of CGRP and P-GATA3 in the 40DBP + OVA group, suggest that GATA3 acted as a key regulator of CGRP-activated ILC2.

CONCLUSION

The aforementioned studies indicate that exposure to DBP can exacerbate allergic asthma, leading to airway inflammation. This exacerbation occurs through the activation of TRPV1 in JNC, resulting in the release of CGRP. The excessive release of CGRP further promotes the release of Th2 cytokines by inducing the activation of ILC2 through GATA phosphorylation. Consequently, this process contributes to the development of airway inflammation and allergic asthma. The increased production of Th2 cytokines also triggers the production of IgE, which interacts with FcεRI on JNC neurons, thereby mediating neuro-immune positive feedback regulation.

G protein-coupled P2Y12 receptor is involved in the progression of neuropathic pain

The pathological mechanism of neuropathic pain is complex, which seriously affects the physical and mental health of patients, and its treatment is also difficult. The role of G protein-coupled P2Y12 receptor in pain has been widely recognized and affirmed. After nerve injury, stimulated cells can release large amounts of nucleotides into the extracellular matrix, act on P2Y12 receptor. Activated P2Y12 receptor activates intracellular signal transduction and is involved in the development of pain. P2Y12 receptor activation can sensitize primary sensory neurons and receive sensory information. By transmitting the integrated information through the dorsal root of the spinal cord to the secondary neurons of the posterior horn of the spinal cord. The integrated information is then transmitted to the higher center through the ascending conduction tract to produce pain. Moreover, activation of P2Y12 receptor can mediate immune cells to release pro-inflammatory factors, increase damage to nerve cells, and aggravate pain. While inhibits the activation of P2Y12 receptor can effectively relieve pain. Therefore, in this article, we described P2Y12 receptor antagonists and their pharmacological properties. In addition, we explored the potential link between P2Y12 receptor and the nervous system, discussed the intrinsic link of P2Y12 receptor and neuropathic pain and as a potential pharmacological target for pain suppression.

The Signaling Pathway of the ADP Receptor P2Y12 in the Immune System: Recent Discoveries and New Challenges

P2Y12 is a G-protein-coupled receptor that is activated upon ADP binding. Considering its well-established role in platelet activation, blocking P2Y12 has been used as a therapeutic strategy for antiplatelet aggregation in cardiovascular disease patients. However, receptor studies have shown that P2Y12 is functionally expressed not only in platelets and the microglia but also in other cells of the immune system, such as in monocytes, dendritic cells, and T lymphocytes. As a result, studies were carried out investigating whether therapies targeting P2Y12 could also ameliorate inflammatory conditions, such as sepsis, rheumatoid arthritis, neuroinflammation, cancer, COVID-19, atherosclerosis, and diabetes-associated inflammation in animal models and human subjects. This review reports what is known about the expression of P2Y12 in the cells of the immune system and the effect of P2Y12 activation and/or inhibition in inflammatory conditions. Lastly, we will discuss the major problems and challenges in studying this receptor and provide insights on how they can be overcome.

The Function and Regulation of Platelet P2Y12 Receptor

In addition to the key role in hemostasis and thrombosis, platelets have also been wildly acknowledged as immune regulatory cells and involving in the pathogenesis of inflammation-related diseases. Since purine receptor P2Y12 plays a crucial role in platelet activation, P2Y12 antagonists such as clopidogrel, prasugrel, and ticagrelor have been widely used in cardiovascular diseases worldwide in recent decades due to their potent antiplatelet and antithrombotic effects. Meanwhile, the role of P2Y12 in inflammatory diseases has also been extensively studied. Relatively, there are few studies on the regulation of P2Y12. This review first summarizes the various roles of P2Y12 in the process of platelet activation, as well as downstream effects and signaling pathways; then introduces the effects of P2Y12 in inflammatory diseases such as sepsis, atherosclerosis, cancer, autoimmune diseases, and asthma; and finally reviews the current researches on P2Y12 regulation.

Leukotrienes vs. Montelukast—Activity, Metabolism, and Toxicity Hints for Repurposing

Increasing environmental distress is associated with a growing asthma incidence; no treatments are available but montelukast (MTK)—an antagonist of the cysteinyl leukotrienes receptor 1—is widely used in the management of symptoms among adults and children. Recently, new molecular targets have been identified and MTK has been proposed for repurposing in other therapeutic applications, with several ongoing clinical trials. The proposed applications include neuroinflammation control, which could be explored in some neurodegenerative disorders, such as Alzheimer’s and Parkinson’s diseases (AD and PD). However, this drug has been associated with an increasing number of reported neuropsychiatric adverse drug reactions (ADRs). Besides, and despite being on the market since 1998, MTK metabolism is still poorly understood and the mechanisms underlying neuropsychiatric ADRs remain unknown. We review the role of MTK as a modulator of leukotriene pathways and systematize the current knowledge about MTK metabolism. Known toxic effects of MTK are discussed, and repurposing applications are presented comprehensively, with a focus on AD and PD.

Emerging Roles of Platelets in Allergic Asthma

Allergic asthma is a complex chronic inflammatory disease of the airways, driven by Th2 immune responses and characterized by eosinophilic pulmonary inflammation, airway hyperresponsiveness, excessive mucus production, and airway remodeling. Overwhelming evidence from studies in animal models and allergic asthmatic patients suggests that platelets are aberrantly activated and recruited to the lungs. It has been established that platelets can interact with other immune cells and secrete various biochemical mediators to promote allergic sensitization and airway inflammatory response, and platelet deficiency may alleviate the pathological features and symptoms of allergic asthma. However, the comprehensive roles of platelets in allergic asthma have not been fully clarified, leaving attempts to treat allergic asthma with antiplatelet agents questionable. In this review, we summarize the role of platelet activation and pulmonary accumulation in allergic asthma; emphasis is placed on the different interactions between platelets with crucial immune cell types and the contribution of platelet-derived mediators in this context. Furthermore, clinical antiplatelet approaches to treat allergic asthma are discussed. This review provides a clearer understanding of the roles of platelets in the pathogenesis of allergic asthma and could be informative in the development of novel strategies for the treatment of allergic asthma.

Candida albicans elicits protective allergic responses via platelet mediated T helper 2 and T helper 17 cell polarization

Fungal airway infection (airway mycosis) is an important cause of allergic airway diseases such as asthma, but the mechanisms by which fungi trigger asthmatic reactions are poorly understood. Here, we leverage wild-type and mutant Candida albicans to determine how this common fungus elicits characteristic Th2 and Th17 cell-dependent allergic airway disease in mice. We demonstrate that rather than proteinases that are essential virulence factors for molds, C. albicans instead promoted allergic airway disease through the peptide toxin candidalysin. Candidalysin activated platelets through the Von Willebrand factor (VWF) receptor GP1bα to release the Wnt antagonist Dickkopf-1 (Dkk-1) to drive Th2 and Th17 cell responses that correlated with reduced lung fungal burdens. Platelets simultaneously precluded lethal pulmonary hemorrhage resulting from fungal lung invasion. Thus, in addition to hemostasis, platelets promoted protection against C. albicans airway mycosis through an antifungal pathway involving candidalysin, GP1bα, and Dkk-1 that promotes Th2 and Th17 responses.

Platelets, Not an Insignificant Player in Development of Allergic Asthma

Allergic asthma is a chronic and heterogeneous pulmonary disease in which platelets can be activated in an IgE-mediated pathway and migrate to the airways via CCR3-dependent mechanism. Activated platelets secrete IL-33, Dkk-1, and 5-HT or overexpress CD40L on the cell surfaces to induce Type 2 immune response or interact with TSLP-stimulated myeloid DCs through the RANK-RANKL-dependent manner to tune the sensitization stage of allergic asthma. Additionally, platelets can mediate leukocyte infiltration into the lungs through P-selectin-mediated interaction with PSGL-1 and upregulate integrin expression in activated leukocytes. Platelets release myl9/12 protein to recruit CD4⁺CD69⁺ T cells to the inflammatory sites. Bronchoactive mediators, enzymes, and ROS released by platelets also contribute to the pathogenesis of allergic asthma. GM-CSF from platelets inhibits the eosinophil apoptosis, thus enhancing the chronic inflammatory response and tissue damage. Functional alterations in the mitochondria of platelets in allergic asthmatic lungs further confirm the role of platelets in the inflammation response. Given the extensive roles of platelets in allergic asthma, antiplatelet drugs have been tested in some allergic asthma patients. Therefore, elucidating the role of platelets in the pathogenesis of allergic asthma will provide us with new insights and lead to novel approaches in the treatment of this disease.

The blocking effect of the glycoprotein IIb/IIIa receptor in the mouse model of asthma

BACKGROUND

It is apparent that the interaction between platelets and eosinophils plays a critical role in the activation of allergic inflammation. We investigated whether blocking of the glycoprotein (GP) IIb/IIIa receptor can attenuate allergic inflammation and airway hyperresponsiveness through inhibition of platelet-eosinophil aggregation (PEA) in asthma.

METHODS

BALB/c mice were sensitized by intraperitoneal injection of ovalbumin (OVA) on days 0 and 14, followed by 3 nebulized OVA challenges on days 28-30. On each challenge day, 5 mg/kg tirofiban was administered intraperitoneally 30 min before the challenge. Mice were assessed for airway hyperresponsiveness (AHR), airway inflammation, and the degree of PEA. Finally, the activation levels of platelets and eosinophils were evaluated.

RESULTS

Tirofiban treatment decreased AHR and eosinophilic inflammation in Bronchoalveolar Lavage (BAL) fluid. This treatment also reduced the levels of interleukin (IL)-4, IL-5, and IL-13 in BAL fluid and airway inflammatory cell infiltration in histological evaluation. Interestingly, the blocking of the GP IIb/IIIa receptor more reduced PEA in both blood and lung tissue of tirofiban-treated mice than in those of the positive control mice, and both eosinophilic and platelet activations were attenuated in tirofiban-treated mice.

CONCLUSIONS

The blocking of GP IIb/IIIa receptor with tirofiban can attenuate AHR and airway inflammation through the inhibition of PEA and activation.

Novel pharmacological therapies for the treatment of bronchial asthma

Asthma has long been recognised as a chronic inflammatory disease of the airways, often in response to inhaled allergens prompting inappropriate activation of the immune response. involving a range of cells including mast cells, Th2 lymphocytes and eosinophils and a wide range of inflammatory mediators. First-line therapy for treatment of persistent asthma involves the use of inhaled corticosteroids (ICS) in combination with inhaled β2-agonists enabling both the control of the underlying airways inflammation and a reduction of airway hyperresponsiveness. However, many patients remain symptomatic despite high-dose therapy. There is therefore a continued unmet clinical need to develop specifically new anti-inflammatory therapies for patients with asthma, either as an add-on therapy to ICS or as replacement monotherapies. The success of fixed dose combination inhalers containing both a bronchodilator and an anti-inflammatory drug has also led to the development of "bifunctional" drugs which are molecules specifically designed to have two distinct pharmacological actions based on distinct pharmacophores. In this review we will discuss these different pharmacological approaches under development for the treatment of bronchial asthma and the available pre-clinical and clinical data.

Administration of vitamin E attenuates airway inflammation through restoration of Nrf2 in a mouse model of asthma

Accumulating evidence reveals that ROS is one of the key mediators that contribute to the development of asthma. Studies on antioxidants have shown to have beneficial effects on asthma management. However, we still do not know the precise mechanism, and the effects depend on age. This study was conducted to assess the levels of ROS and the effect of antioxidants in younger and older mice using an eosinophilic asthma model. We analyzed airway hyperresponsiveness (AHR), cytokines in bronchoalveolar lavage fluid (BALF), inflammatory cell counts, and the expression levels of NFκB, Nrf2, EPx, and EDN in the lung tissue, as well as the level of ROS in the lung tissue and BALF. The degree of eosinophilia and the levels of IL-5, ROS, and NFκB were significantly increased, whereas the endogenous levels of vitamin E and Nrf2 were decreased in the lung and BALF in the older mice compared to younger mice. The administration of vitamin E attenuated AHR, airway inflammation, and the level of IL-13 and ROS and enhanced the Nrf2 level in the older mice compared to the younger mice. Taken together, vitamin E treatment may have the therapeutic potential through restoration of the Nrf2 level, especially in elderly asthma.

Purinergic Receptors in the Airways: Potential Therapeutic Targets for Asthma?

Extracellular ATP functions as a signaling messenger through its actions on purinergic receptors, and is known to be involved in numerous physiological and pathophysiological processes throughout the body, including in the lungs and airways. Consequently, purinergic receptors are considered to be promising therapeutic targets for many respiratory diseases, including asthma. This review explores how online bioinformatics resources combined with recently generated datasets can be utilized to investigate purinergic receptor gene expression in tissues and cell types of interest in respiratory disease to identify potential therapeutic targets, which can then be investigated further. These approaches show that different purinergic receptors are expressed at different levels in lung tissue, and that purinergic receptors tend to be expressed at higher levels in immune cells and at more moderate levels in airway structural cells. Notably, P2RX1, P2RX4, P2RX7, P2RY1, P2RY11, and P2RY14 were revealed as the most highly expressed purinergic receptors in lung tissue, therefore suggesting that these receptors have good potential as therapeutic targets for asthma and other respiratory diseases.

The Leukotriene Receptor Antagonist Montelukast as a Potential COVID-19 Therapeutic

The emergence and global impact of COVID-19 has focused the scientific and medical community on the pivotal influential role of respiratory viruses as causes of severe pneumonia, on the understanding of the underlying pathomechanisms, and on potential treatment for COVID-19. The latter concentrates on four different strategies: (i) antiviral treatments to limit the entry of the virus into the cell and its propagation, (ii) anti-inflammatory treatment to reduce the impact of COVID-19 associated inflammation and cytokine storm, (iii) treatment using cardiovascular medication to reduce COVID-19 associated thrombosis and vascular damage, and (iv) treatment to reduce the COVID-19 associated lung injury. Ideally, effective COVID-19 treatment should target as many of these mechanisms as possible arguing for the search of common denominators as potential drug targets. Leukotrienes and their receptors qualify as such targets: they are lipid mediators of inflammation and tissue damage and well-established targets in respiratory diseases like asthma. Besides their role in inflammation, they are involved in various other aspects of lung pathologies like vascular damage, thrombosis, and fibrotic response, in brain and retinal damages, and in cardiovascular disease. In consequence, leukotriene receptor antagonists might be potential candidates for COVID-19 therapeutics. This review summarizes the current knowledge on the potential involvement of leukotrienes in COVID-19, and the rational for the use of the leukotriene receptor antagonist montelukast as a COVID-19 therapeutic.

LncRNA-AK149641 associated with airway inflammation in an OVA-induced asthma mouse model

Asthma is defined as a heterogeneous disease, usually characterized by chronic airway inflammation. Long noncoding RNAs (lncRNAs) play important roles in various biological processes. To know more about the relationships between lncRNAs and asthma, gene microarray analysis was performed to screen differentially expressed lncRNAs between the lung tissue of ovalbumin (OVA) mice and control mice. Further studies showed that downregulating differentially expressed lncRNA-AK149641 by adeno-associated virus 6 (AAV6) in OVA mice inhibited airway inflammation, with improved airway compliance and resistance, diminished infiltration of inflammatory cells, as well as less secretions of mucus, tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6). Moreover, the activity of nuclear factor-kappa B (NF-κB) in the lung tissue was reduced after downregulating lncRNA-AK149641. In conclusion, we proposed that downregulation of lncRNA-AK149641 attenuated the airway inflammatory response in an OVA-induced asthma mouse model, probably in association with modulation of the NF-κB signaling pathway.

Clopidogrel combats neuroinflammation and enhances learning behavior and memory in a rat model of Alzheimer's disease

BACKGROUND AND AIM

Alzheimer's disease (AD) is a progressive neurodegenerative disease. Multiple molecular mechanisms have been employed in its pathogenesis such as Amyloid β (Aβ) formation, tau protein hyperphosphorylation, reduced acetylcholine (ACh) level, and neuroinflammation. This study aimed to assess the possible neuroprotective effect of clopidogrel in AD model induced by aluminum chloride (AlCl₃) in rats.

METHODS

Sixty adult male Sprague-Dawley rats were divided into four different groups: Control, AlCl₃, AlCl₃ + donepezil, and AlCl₃ + Clopidogrel. AlCl₃ and the drugs were given orally once/day for 42 days. The spatial learning and memory and recognition memory were evaluated using Morris Water Maze (MWM) and Novel Object Recognition (NOR) tests, respectively. After euthanasia, hippocampal acetylcholinesterase (AChE) activity, tumor necrosis factor-alpha (TNF-α), and interleukin-1β (IL-1β) levels were biochemically assessed. Moreover, amyloid precursor protein (APP) mRNA gene expression was analyzed in the hippocampi of all rats. Histopathology for amyloid plaques was done.

RESULTS

Clopidogrel co-treatment significantly ameliorated the cognitive deficits induced by AlCl₃ in rats. Besides, clopidogrel significantly reduced AChE activity, TNF-α and IL-1β concentrations, and APP mRNA gene expression in the hippocampi of rats compared to AlCl₃ rats. The decrease of hippocampal TNF-α and IL-1β concentrations by clopidogrel was significant compared to donepezil co-treated rats. Clopidogrel co-treatment lessened amyloid plaque deposition in the hippocampal tissues of rats compared to AlCl₃ rats.

CONCLUSION

These findings demonstrate that clopidogrel could alleviate learning and memory deficit induced by AlCl₃ in rats and significantly reduced AChE activity. The neuroprotective outcome of clopidogrel might be assigned to its anti-inflammatory effect.

P2Y12 Receptor Antagonist Clopidogrel Attenuates Lung Inflammation Triggered by Silica Particles

Silicosis is an occupational lung disease caused by inhalation of silica particles. It is characterized by intense lung inflammation, with progressive and irreversible fibrosis, leading to impaired lung function. Purinergic signaling modulates silica-induced lung inflammation and fibrosis through P2X7 receptor. In the present study, we investigate the role of P2Y12, the G-protein-coupled subfamily prototype of P2 receptor class in silicosis. To that end, BALB/c mice received an intratracheal injection of PBS or silica particles (20 mg), without or with P2Y12 receptor blockade by clopidogrel (20 mg/kg body weight by gavage every 48 h) - groups CTRL, SIL, and SIL + Clopi, respectively. After 14 days, lung mechanics were determined by the end-inflation occlusion method. Lung histology was analyzed, and lung parenchyma production of nitric oxide and cytokines (IL-1β, IL-6, TNF-α, and TGF-β) were determined. Silica injection reduced animal survival and increased all lung mechanical parameters in relation to CTRL, followed by diffuse lung parenchyma inflammation, increased neutrophil infiltration, collagen deposition and increased pro-inflammatory and pro-fibrogenic cytokine secretion, as well as increased nitrite production. Clopidogrel treatment prevented silica-induced changes in lung function, and significantly reduced lung inflammation, fibrosis, as well as cytokine and nitrite production. These data suggest that inhibition of P2Y12 signaling improves silica-induced lung inflammation, preventing lung functional changes and mortality. Our results corroborate previous observations of silica-induced lung changes and expand the understanding of purinergic signaling in this process.

P2Y12 Inhibition beyond Thrombosis: Effects on Inflammation

The P2Y₁₂ receptor is a key player in platelet activation and a major target for antithrombotic drugs. The beneficial effects of P2Y₁₂ receptor antagonists might, however, not be restricted to the primary and secondary prevention of arterial thrombosis. Indeed, it has been established that platelet activation also has an essential role in inflammation. Additionally, nonplatelet P2Y₁₂ receptors present in immune cells and vascular smooth muscle cells might be effective players in the inflammatory response. This review will investigate the biological and clinical impact of P2Y₁₂ receptor inhibition beyond its platelet-driven antithrombotic effects, focusing on its anti-inflammatory role. We will discuss the potential molecular and cellular mechanisms of P2Y₁₂-mediated inflammation, including cytokine release, platelet–leukocyte interactions and neutrophil extracellular trap formation. Then we will summarize the current evidence on the beneficial effects of P2Y₁₂ antagonists during various clinical inflammatory diseases, especially during sepsis, acute lung injury, asthma, atherosclerosis, and cancer.

Cardioprotective properties of the platelet P2Y12 receptor inhibitor prasugrel on cardiac ischemia/reperfusion injury

OBJECTIVE

The effects of prasugrel, a third-generation thienopyridine, on myocardial infarction, and ischemia-induced ventricular arrhythmias was evaluated in open-chest anesthetized rats. The role of protein kinase C and phosphoinositide 3-kinase pathways in these effects was also examined.

METHODS

The effect of P2Y₁₂ receptor inhibition by prasugrel (3-10 mg/kg, po) on infarct size after 30-min coronary artery occlusion and 120-min reperfusion or on arrhythmias after 7-min coronary occlusion and 7-min reperfusion was evaluated.

RESULTS

In the control group, 31.25 ± 3.01% of the risk zone infarcted. At both prasugrel doses, infarct size was significantly smaller than that in the control group: 5.03 ± 0.81% for 3 mg/kg (p < 0.0001), and 8.78 ± 2.04% for 10 mg/kg (p < 0.0001). The protein kinase C antagonist chelerythrine abolished the anti-infarct effect of prasugrel at 24.77 ± 1.73% as did the phosphoinositide 3-kinase antagonist wortmannin abolished the anti-infarct effect of prasugrel at 27.45 ± 2.74%. Ten mg/kg prasugrel reduced the duration of VT (p = 0.0152 vs control), and wortmannin, but not chelerythrine, reversed the effect of prasugrel on arrhythmias (p = 0.0295).

CONCLUSION

The selective P2Y₁₂ inhibitor prasugrel provides effective protection against myocardial infarction and ischemia-induced ventricular arrhythmias in rats. As in ischemic postconditioning, protein kinase C and phosphoinositide 3-kinase signaling pathways play a role in this protection.

Targeting cell signaling in allergic asthma

Asthma is chronic inflammation of the airways characterized by airway hyper-responsiveness, wheezing, cough, and dyspnea. Asthma affects >350 million people worldwide. The Th2 immune response is a major contributor to the pathophysiology of asthma. Targeted therapy modulating cell signaling pathways can be a powerful strategy to design new drugs to treat asthma. The potential molecular pathways that can be targeted include IL-4-IL-13-JAK-STAT-MAP kinases, adiponectin-iNOS-NF-κB, PGD2-CRTH2, IFNs-RIG, Wnt/β-catenin-FAM13A, FOXC1-miR-PI3K/AKT, JNK-Gal-7, Nrf2-ROS, Foxp3-RORγt, CysLTR, AMP, Fas-FasL, PTHrP/PPARγ, PAI-1, FcɛRI-LAT-SLP-76, Tim-3-Gal-9, TLRs-MyD88, PAR2, and Keap1/Nrf2/ARE. Therapeutic drugs can be designed to target one or more of these pathways to treat asthma.

ADP secreted by dying melanoma cells mediates chemotaxis and chemokine secretion of macrophages via the purinergic receptor P2Y12

Melanoma immunotherapy is still not satisfactory due to immunosuppressive cell populations within the tumor stroma. Targeting tumor-associated macrophages (TAM) can help to restore an anti-tumor immunity. Previously, we could show that classical TAM markers expressed in vivo need a 7 day M-CSF/dexamethasone/IL-4 (MDI) stimulation for their induction in peripheral blood monocytes (pBM) in vitro. To identify possible novel therapeutic targets on TAM, gene expression analysis of MDI-treated pBM was performed. This identified up-regulation of the purinergic G-protein coupled receptor P2Y12, the therapeutic target of the clinically approved anti-thrombotic drugs cangrelor, clopidogrel, ticagrelor, and prasugrel. We generated a peptide antibody and validated its specificity using transgenic P2Y12+ U937 cells. With the help of this antibody, P2Y12 expression was confirmed on CD68+ CD163+ TAM of melanoma in situ. Functional analysis revealed that treatment of transgenic P2Y12+ U937 cells with the receptor agonist 2-MeSADP induced ERK1/2 and Akt phosphorylation and increased the secretion of the chemokines CXCL2, CXCL7, and CXCL8. These effects could be abolished with the P2Y12 antagonist PSB0739 or with Akt and ERK inhibitors. In addition, P2Y12+ macrophages migrated towards the ADP-rich culture medium of puromycin-treated dying B16F1 melanoma cells. Cangrelor treatment blocked migration. Taken together, our results indicate that P2Y12 is an important chemotaxis receptor, which triggers migration of macrophages towards nucleotide-rich, necrotic tumor areas, and modulates the inflammatory environment upon ADP binding.

Asthma pharmacotherapy: an update on leukotriene treatments

Introduction: Asthma is a chronic inflammatory disease of the airways with a large heterogeneity of clinical phenotypes. There has been increasing interest regarding the role of cysteinyl leukotriene (LT) and leukotriene receptor antagonists (LTRA) in asthma treatment.Areas covered: This review summarized the data (published in PubMed during 1984-2019) regarding LTRA treatment in asthma and LTs-related airway inflammation mechanisms. Involvement of LTs C₄/D₄/E₄ has been demonstrated in the several aspects of airway inflammation and remodeling. Novel pathways related to LTE₄, the most potent mediator, and its respective receptors have recently been studied. Antagonists against cysteinyl leukotriene receptor (CysLTR) type 1, including montelukast, pranlukast and zafirlukast, have been widely prescribed in clinical practices; however, some clinical trials have shown insignificant responses to LTRAs in adult asthmatics, while some phenotypes of adult asthma showed more favorable responses to LTRAs including aspirin-exacerbated respiratory disease, elderly asthma, asthma associated with smoking, obesity and allergic rhinitis.Expert opinion: Further investigations are needed to understand the role of LTs in airway inflammation and remodeling of the asthmatic airways. There is a lack of biomarkers to predict responsiveness to LTRA, especially in adult asthmatics. Besides CysLTR1 antagonists, targets aiming other LT pathways should be considered.

Pharmacological strategies for targeting platelet activation in asthma

The activation of platelets during host defence and inflammatory disorders has become increasingly documented. Clinical studies of patients with asthma reveal heightened platelet activation and accumulation into lung tissue. Accompanying studies in animal models of allergic lung inflammation, using protocols of experimentally induced thrombocytopenia proclaim an important role for platelets during the leukocyte recruitment cascade, tissue integrity, and lung function. The functions of platelets during these inflammatory events are clearly distinct to platelet functions during haemostasis and clot formation, and have led to the concept that a dichotomy (or polytomy, depending on what else platelets do) in platelet activation exists. The platelet, therefore, presents us with novel opportunities for modulating these inflammatory responses. This review discusses the rationale and effectiveness of current anti-platelet drugs in their use to supress inflammation with regard to asthma, and the need to consider novel possibilities for pharmacological modulation of platelet function associated with inflammation that are pharmacologically distinct to current anti-platelet therapies.

Autocrine stimulation of P2Y1 receptors is part of the purinergic signaling mechanism that regulates T cell activation

Previous studies have shown that T cell receptor (TCR) and CD28 coreceptor stimulation involves rapid ATP release, autocrine purinergic feedback via P2X receptors, and mitochondrial ATP synthesis that promote T cell activation. Here, we show that ADP formation and autocrine stimulation of P2Y1 receptors are also involved in these purinergic signaling mechanisms. Primary human CD4 T cells and the human Jurkat CD4 T cell line express P2Y1 receptors. The expression of this receptor increases following T cell stimulation. Inhibition of P2Y1 receptors impairs the activation of mitochondria, as assessed by mitochondrial Ca²⁺ uptake, and reduces cytosolic Ca²⁺ signaling in response to TCR/CD28 stimulation. We found that the addition of exogenous ADP or overexpression of P2Y1 receptors significantly increased IL-2 mRNA transcription in response to TCR/CD28 stimulation. Conversely, antagonists or silencing of P2Y1 receptors reduced IL-2 mRNA transcription and attenuated T cell functions. We conclude that P2Y1 and P2X receptors have non-redundant, synergistic functions in the regulation of T cell activation. P2Y1 receptors may represent potential therapeutic targets to modulate T cell function in inflammation and host defense.

The synergistic effects of clopidogrel with montelukast may be beneficial for asthma treatment

Platelets modulate asthma pathogenesis by forming the platelet‐eosinophil aggregation (PEA), which facilitates the activation of eosinophils. Platelets exhibit the purinergic receptor (P2Y12R), which responds to cysteinyl leukotriene E4 (LTE₄). We have suggested that the combination of an antiplatelet drug (clopidogrel, [Clo]) and montelukast (Mon) would synergistically suppress asthma. BALB/c mice were intraperitoneally sensitized with ovalbumin (OVA) on days 0 and 14 and subsequently challenged on days 28‐30 and 42‐44. Mice were administered with Clo (10 mg/kg), Mon (10 mg/kg) or both drugs (Clo/Mon) orally 30 minutes before the OVA (1%) challenge on days 42‐44. Mice were assayed for airway hyper‐responsiveness (AHR) to methacholine and airway inflammation. Clopidogrel and montelukast attenuated the increased AHR; the combined treatment was more effective than a single treatment for total and eosinophil counts (all P < 0.05). Levels of interleukin (IL)‐4, IL‐5, IL‐13, platelet factor 4, eosinophil peroxidase and LTE₄ increased in the bronchoalveolar lavage fluid of asthmatic mice, but these levels decreased in mice treated with Clo/Mon (all P < 0.05). Goblet cell hyperplasia decreased in response to Clo/Mon. Mouse platelets and eosinophils were isolated and co‐cultured for an in vitro assay with 10 µmol/L adenosine diphosphate (ADP), LTE₄ (200 nmol/L), Mon (1 µmol/L), Clo (1 µmol/L) and Clo/Mon (1 µmol/L). Flow cytometry revealed that the increased formation of the PEA (%) was fully mediated by ADP and partly mediated by LTE₄. Clo/Mon reduced ADP‐induced PEA formation and P‐selectin expression (P < 0.05). In conclusion, Clo/Mon synergistically relieved asthma by inhibiting ADP‐mediated PEA formation.

Characterization of cysteinyl leukotriene-related receptors and their interactions in a mouse model of asthma

Identification of the characterization of cysteinyl leukotrienes receptor (CysLTRs) could facilitate our understanding of these receptors' role in asthma. We aimed to investigate the localization and interactions of CysLTRs using a mouse model of asthma. BALB/c mice were administered ovalbumin (OVA) to induce allergic asthma. Some mice were administered the antagonists of CysLTR1, CysLTR2, and purinergic receptor P2Y12 (P2Y12R) (montelukast, HAMI 3379 and clopidogrel, respectively). The expression levels of CysLTR1, CysLTR2, and P2Y12R on lung tissues and inflammatory cells were evaluated by western blot, flow cytometry, and immunochemistry. CysLTR1 and P2Y12R were significantly up-regulated in lung tissues (P < 0.05 for each) from mouse after being sensitized and challenged with OVA (OVA/OVA). The ratio of CysLTR1: CysLTR2: P2Y12R in lungs of negative control (NC) mice was shifted from 1:0.43:0.35 to 1:0.65:1.34 in OVA/OVA mice. Montelukast significantly diminished the up-regulation of CysLTR1, CysLTR2, and P2Y12R (P < 0.05 for each), while the effects of HAMI 3379 and clopidogrel were predominant on the expression of CysLTR2 and P2Y12R, respectively. Montelukast predominantly diminished the cell count, while clopidogrel potently inhibited the release of interleukin (IL)-4, IL-5, and IL-13. Our study demonstrated the interactions between CysLTRs, thereby highlighting the potential synergistic effects of CysLTR antagonists in asthma treatment.

Clopidogrel reduces lipopolysaccharide-induced inflammation and neutrophil-platelet aggregates in an experimental endotoxemic model

Platelet activation contributes to organs failure in inflammation and plays an important role in endotoxemia. Clopidogrel inhibits platelet aggregation and activation. However, the role of clopidogrel in modulating inflammatory progression of endotoxemia remains largely unexplored. Therefore, we investigated the role of clopidogrel on the activation of platelet and leukocytes in lipopolysaccharide (LPS)-induced inflammation in mice. Animals were treated with clopidogrel or vehicle before LPS induction. The expression of neutrophil-platelet aggregates and platelet activation and tissue factor was determined. Immunofluorescence was used to analyze platelet-leukocyte interactions and tissue factor (TF) expression on leukocytes. Clopidogrel pretreatment markedly decreased lung damage, inhibited platelet-neutrophil aggregates and TF expression. In addition, clopidogrel reduced thrombocytopenia and affected the number of circulating white blood cell in endotoxemia mice. Moreover, clopidogrel also reduced platelet shedding of CD40L and CD62P in endotoxemic mice. Taken together, clopidogrel played an important role through reducing platelet activation and inflammatory process in endotoxemia.

Urinary Leukotriene E4 as a Biomarker of Exposure, Susceptibility, and Risk in Asthma: An Update

Measurement of urinary leukotriene E₄ (uLTE₄) is a sensitive and noninvasive method of assaying total body cysteinyl leukotriene (CysLT) production and changes in CysLT production. Recent studies have reported on novel LTE4 receptor interactions and genetic polymorphisms causing CysLT variability. The applications of uLTE₄ as a biomarker continue to expand, including evaluation of environmental exposures, asthma severity risk, aspirin sensitivity, predicting atopy in preschool age children, obstructive sleep apnea, and predicting susceptibility to leukotriene receptor antagonists.

Structure, Pharmacology and Roles in Physiology of the P2Y12 Receptor

P2Y receptors are G-protein-coupled receptors (GPCRs) for extracellular nucleotides. The platelet ADP-receptor which has been denominated P2Y₁₂ receptor is an important target in pharmacotherapy. The receptor couples to G_αi2 mediating an inhibition of cyclic AMP accumulation and additional downstream events including the activation of phosphatidylinositol-3-kinase and Rap1b proteins. The nucleoside analogue ticagrelor and active metabolites of the thienopyridine compounds ticlopidine, clopidogrel and prasugrel block P2Y₁₂ receptors and, thereby, inhibit ADP-induced platelet aggregation. These drugs are used for the prevention and therapy of cardiovascular events such as acute coronary syndromes or stroke. The recently published three-dimensional crystal structures of the human P2Y₁₂ receptor in complex with agonists and antagonists will facilitate the development of novel therapeutic agents with reduced adverse effects. P2Y₁₂ receptors are also expressed on vascular smooth muscle cells and may be involved in the pathophysiology of atherogenesis. P2Y₁₂ receptors on microglial cells operate as sensors for adenine nucleotides released during brain injury. A recent study indicated the involvement of microglial P2Y₁₂ receptors in the activity-dependent neuronal plasticity. Interestingly, there is evidence for changes in P2Y₁₂ receptor expression in CNS pathologies including Alzheimer's diseases and multiple sclerosis. P2Y₁₂ receptors may also be involved in systemic immune modulating responses and the susceptibility to develop bronchial asthma.

Leukotriene receptors as potential therapeutic targets

Leukotrienes, a class of arachidonic acid-derived bioactive molecules, are known as mediators of allergic and inflammatory reactions and considered to be important drug targets. Although an inhibitor of leukotriene biosynthesis and antagonists of the cysteinyl leukotriene receptor are clinically used for bronchial asthma and allergic rhinitis, these medications were developed before the molecular identification of leukotriene receptors. Numerous studies using cloned leukotriene receptors and genetically engineered mice have unveiled new pathophysiological roles for leukotrienes. This Review covers the recent findings on leukotriene receptors to revisit them as new drug targets.

Platelet Munc13-4 regulates hemostasis, thrombosis and airway inflammation

Platelet degranulation is crucial for hemostasis and may participate in inflammation. Exocytosis in platelets is mediated by SNARE proteins and should be controlled by Munc13 proteins. We found that platelets express Munc13-2 and -4. We assessed platelet granule exocytosis in Munc13-2 and -4 global and conditional knockout (KO) mice, and observed that deletion of Munc13-4 ablates dense granule release and indirectly impairs alpha granule exocytosis. We found no exocytic role for Munc13-2 in platelets, not even in the absence of Munc13-4. In vitro, Munc13-4-deficient platelets exhibited defective aggregation at low doses of collagen. In a flow chamber assay, we observed that Munc13-4 acted as a rate-limiting factor in the formation of thrombi. In vivo, we observed a dose-dependency between Munc13-4 expression in platelets and both venous bleeding time and time to arterial thrombosis. Finally, in a model of allergic airway inflammation, we found that platelet-specific Munc13-4 KO mice had a reduction in airway hyper-responsiveness and eosinophilic inflammation. Taken together, our results indicate that Munc13-4-dependent platelet dense granule release plays essential roles in hemostasis, thrombosis and allergic inflammation.