Mast Cells in Aspirin-Exacerbated Respiratory Disease.

PURPOSE OF REVIEW: Aspirin-exacerbated respiratory disease (AERD) is a syndrome of high type 2 inflammation and is known to critically involve mast cell activation. The mast cell is an important cell in the baseline inflammatory processes in the upper and lower airway by maintaining and amplifying type 2 inflammation. But it also is prominent in the hypersensitivity reaction to COX-1 inhibition which defines this condition. RECENT FINDINGS: Recent work highlights the mast cell as a focal point in AERD pathogenesis. Using AERD as a specific model of both high type 2 asthma and chronic sinusitis, the role of mast cell activity can be better understood in other aspects of airway inflammation. Further dissecting out the mechanism of COX-1-mediated mast cell activation in AERD will be an important next phase in our understanding of NSAID-induced hypersensitivity as well as AERD pathophysiology.

Potential of Anti-Leukotriene Drugs as New Therapeutic Agents for Inhibiting Cholangiocarcinoma Progression.

Cholangiocarcinoma (CCA) is a cancer with a poor prognosis due to difficulties in diagnosis and limited treatment options, highlighting the urgent need for new targeted therapies. In a clinical setting, we found that leukotriene levels in bile were higher than in serum. Immunohistochemical analysis of surgically resected samples also revealed that CysLT receptor 1 (CysLTR1) was more highly expressed in CCA than in normal bile duct tissue, prompting us to investigate leukotriene as a potential therapeutic target in CCA. In vitro studies using CCA cell lines expressing CysLTR1 showed that leukotriene D4, a major ligand of CysLTR1, promoted cell proliferation, with increased phosphorylation of AKT and extracellular signal-regulated kinase 1/2 (ERK1/2). Additionally, treatment with two clinically available anti-allergic drugs-zileuton, an inhibitor of CysLT formation, and montelukast, a CysLTR1 inhibitor-had inhibitory effects on cell proliferation and migratory capacity, accompanied by the reduced phosphorylation of AKT and ERK1/2. Furthermore, the simultaneous administration of both drugs synergistically enhanced the inhibitory effect on cell proliferation. Our study suggests that use of these drugs may represent a novel approach to treat CCA through drug repositioning.

Can montelukast sodium be an alternative treatment in the treatment of interstitial cystitis?

Background: The leukotriene D4 receptors have been detected in human bladder detrusor myocytes, and they can play the role of interstitial cystitis etiology. Aim: Our study aims to explain the role of mast cells histologically and immunohistochemically in the pathogenesis and the effectiveness of montelukast that leukotriene D4 receptor antagonist in the treatment of interstitial cystitis. Subjects and Methods: Twenty-four Wistar albino adult female rats were used. Group 1 (n = 8): control (sham) group, Group 2 (n = 8): interstitial cystitis group, and Group 3 (n = 8): treatment group. Groups 2 and 3 rats were administered 75 mg/kg cyclophosphamide four times every three days intraperitoneally. The rats in the treatment group were started on montelukast sodium as 10 mg/kg, 1 × 1/day per orally after the last administration of cyclophosphamide and were given for 14 days. Mast cells in the bladder tissues were examined histologically, and the presence of IL-6, 8, VEGF, and TNF alpha was examined immunohistochemically. Results: Thin transitional epithelium, loose connective tissue, weak smooth muscle bundles, and signs of chronic inflammation were observed in the interstitial cystitis group. Regenerated transitional epithelium, intact basement membrane, compact lamina propia, thick smooth muscle bundles, and rare inflammatory cells were observed after the treatment with the montelukast. Mast cells were decreased in bladder tissue after treatment. IL-6, IL-8, VEGF, and TNF alpha levels were significantly decreased after treatment. Conclusions: We found that inflammatory mediators were significantly reduced after treatment with montelukast in the interstitial cystitis group. Montelukast can be used as an effective drug in the treatment of interstitial cystitis.

Leukotriene receptor antagonists enhance HCC treatment efficacy by inhibiting ADAMs and suppressing MICA shedding.

In our previous genome-wide association study, we demonstrated the association between MHC class I-related chain A (MICA) and hepatocellular carcinoma (HCC) development in patients with chronic hepatitis C. Increasing membrane-bound MICA (mMICA) in cancer cells by reducing MICA sheddases facilitates natural killer (NK) cell-mediated cytotoxicity. Our recent study clarified that A disintegrin and metalloproteases (ADAM), including ADAM9, are MICA sheddases in HCC, and that the suppression of ADAMs increases mMICA, demonstrating the rationality of mMICA-NK targeted therapy. Furthermore, we showed that regorafenib suppresses ADAM9 transcriptionally and translationally. A library of FDA-approved drugs was screened for more efficient inhibitors of ADAM9. Flow cytometry evaluation of the expression of mMICA after treatment with various candidate drugs identified leukotriene receptor antagonists as potential ADAM9 inhibitors. Furthermore, leukotriene receptor antagonists alone or in combination with regorafenib upregulated mMICA, which was in turn downregulated by leukotriene C4 and D4 via ADAM9 function. Our study demonstrates that leukotriene receptor antagonists could be developed as novel drugs for immunological control and suppression of ADAM9 in HCC. Further, leukotriene receptor antagonists should be explored as combination therapy partners with conventional multi-kinase inhibitors for developing therapeutic strategies with enhanced efficacies for HCC management and treatment.

Understanding the pathophysiological changes via untargeted metabolomics in COVID-19 patients.

Coronavirus disease 2019 (COVID-19) is an infectious respiratory disease caused by a new strain of the coronavirus. There is limited data on the pathogenesis and the cellular responses of COVID-19. In this study, we aimed to determine the variation of metabolites between healthy control and COVID-19 via the untargeted metabolomics method. Serum samples were obtained from 44 COVID-19 patients and 41 healthy controls. Untargeted metabolomics analyses were performed by the LC/Q-TOF/MS (liquid chromatography quadrupole time-of-flight mass spectrometry) method. Data acquisition, classification, and identification were achieved by the METLIN database and XCMS. Significant differences were determined between patients and healthy controls in terms of purine, glutamine, leukotriene D4 (LTD4), and glutathione metabolisms. Downregulations were determined in R-S lactoglutathione and glutamine. Upregulations were detected in hypoxanthine, inosine, and LTD4. Identified metabolites indicate roles for purine, glutamine, LTD4, and glutathione metabolisms in the pathogenesis of the COVID-19. The use of selective leukotriene D4 receptor antagonists, targeting purinergic signaling as a therapeutic approach and glutamine supplementation may decrease the severity and mortality of COVID-19.

Cysteinyl leukotriene D4 (LTD4) promotes airway epithelial cell inflammation and remodelling.

OBJECTIVE: Cysteinyl leukotrienes (CysLTs), a group of inflammatory lipid mediators, are found elevated in obese-asthmatic patients. Leukotriene D4 (LTD4), a representative CysLT, is implicated in promoting lung inflammation and remodelling in allergic asthma, but its role in non-allergic asthma, especially in obese-asthmatic patients, is not known. Here, using primary human small airway epithelial cells (SAECs) we have investigated the mechanism of LTD4-induced inflammation and remodelling and assessed high proneness of obese mice to develop asthma upon challenge with allergen ovalbumin (OVA). METHODS: Primary human small airway epithelial cells (SAECs) were stimulated with different concentrations of LTD4 for different time intervals and various inflammatory markers were measured through cytokine array, membrane-based ELISA and Western blotting. An air-liquid interface (ALI) model of SAECs was used to study the effects of LTD4-induced remodelling in SAECs using Western blotting, H&E staining and PAS staining. Further, OVA-based murine model was used to examine the propensity of high-fat diet (HFD)-fed obese mice to develop asthma symptoms by studying the infiltration of inflammatory cells (assessed by bronchioalveolar lavage (BAL) cytology) and airway remodelling (assessed by histopathology) upon allergen exposure. RESULTS: The human primary small airway epithelial cells (SAECs) treated with LTD4 showed significant alterations in the levels of inflammatory markers such as GM-CSF, TNF-α, IL-1ß, EGF and eotaxin in dose- and time-dependent manner. Further, LTD4 enhanced the activation of inflammasomes as evidenced by increased levels of NALP3, cleaved caspase-1 and IL-1ß. LTD4 also enhanced inflammation by increasing the expression of COX-2 in SAECs. The airway remodelling markers Vimentin and Muc5AC were found elevated in ALI culture of SAECs when stimulated with LTD4, as it also increased TGF-ß levels and activation of Smad2/3 phosphorylation in SAECs. Last, sensitization and challenge of HFD-fed obese mice with OVA showed increased infiltration of inflammatory cells in BAL and enhanced levels of remodeling phenotypes like loss of cilia, mucus cell metaplasia and collagen deposition in mice lung tissues. CONCLUSION: The results suggest that LTD4 could induce inflammatory response in human airway epithelial cell by activating NALP3 inflammasome. LTD4 could further promote airway epithelial cells' remodelling through TGF-ß/smad2/3-mediated pathway. Our in vivo results suggested that obesity predisposed the OVA challenged mice to develop lung inflammation and remodelling akin to asthma-like phenotypes during obesity.

Anti-Allergic Drug Suppressed Pancreatic Carcinogenesis via Down-Regulation of Cellular Proliferation.

Pancreatic cancer is a fatal disease, and thus its chemoprevention is an important issue. Based on the recent report that patients with allergic diseases have a low risk for pancreatic cancer, we examined the potential chemopreventive effect of anti-allergic agents using a hamster pancreatic carcinogenesis model. Among the three anti-allergic drugs administered, montelukast showed a tendency to suppress the incidence of pancreatic cancer. Further animal study revealed a significantly decreased incidence of pancreatic cancer in the high-dose montelukast group compared with controls. The development of the pancreatic intraepithelial neoplasia lesions was also significantly suppressed. The Ki-67 labeling index was significantly lower in pancreatic carcinomas in the high-dose montelukast group than in controls. In vitro experiments revealed that montelukast suppressed proliferation of pancreatic cancer cells in a dose-dependent manner with decreased expression of phospho-ERK1/2. Montelukast induced G1 phase arrest. Conversely, leukotriene D4 (LTD4), an agonist of CYSLTR1, increased cellular proliferation of pancreatic cancer cells with an accumulation of phospho-ERK1/2. In our cohort, pancreatic ductal adenocarcinoma patients with high CYSLTR1 expression showed a significantly unfavorable clinical outcome compared with those with low expression. Our results indicate that montelukast exerts a chemopreventive effect on pancreatic cancer via the LTD4-CYSLTR1 axis and has potential for treatment of pancreatic carcinogenesis.

Lipid mediator Leukotriene D4-induces airway epithelial cells proliferation through EGFR/ERK1/2 pathway.

BACKGROUND: Cysteinyl leukotrienes (CysLTs), the potent lipid inflammatory mediators, are elevated in many pathological conditions and implicated in various inflammatory diseases including asthma, however their role in airway epithelial cells modulation is not clearly understood. We have investigated the effects of a CysLT, Leukotriene D4 (LTD4) on human airway epithelial cells, and assessed its role and mode of action in these cells. METHODOLOGY: Human small airway epithelial cells (SAECs) and A549 cells were incubated with different concentrations of LTD4 for different time intervals. Subsequently trypan blue dye exclusion assay, MTT assay, Western blotting, RT-PCR and immunofluorescence experiments were performed to examine the effects of LTD4 on proliferation and related molecular changes in the airway epithelial cells. RESULTS: The treatment of human airway epithelial cells with LTD4 resulted in a significant increase in cell proliferation and modulation in the expression of receptors, CysLT1R and CysLT2R in SAECs as well as A549 cells. In both types of cells, LTD4 increased the expression levels of PCNA and c-myc, and trans-activated EGF receptor and increased the activation of ERK1/2. When treated along with epidermal growth factor (EGF), LTD4 showed a marginal additive effect in ERK1/2 and EGFR phosphorylation compared to LTD4 alone in both types of airway epithelial cells. CONCLUSION: In conclusion, these results suggest that sustained presence of lipid inflammatory mediator LTD4 could induce human airway epithelial cell proliferation through ERK1/2 phosphorylation, either directly via CysLT1 receptor or by transactivating EGFR.

Leukotriene D4 and prostaglandin E2 signals synergize and potentiate vascular inflammation in a mast cell-dependent manner through cysteinyl leukotriene receptor 1 and E-prostanoid receptor 3.

BACKGROUND: Although arachidonic acid metabolites, cysteinyl leukotrienes (cys-LTs; leukotriene [LT] C4, LTD4, and LTE4), and prostaglandin (PG) E2 are generated at the site of inflammation, it is not known whether crosstalk exists between these 2 classes of inflammatory mediators. OBJECTIVE: We sought to determine the role of LTD4-PGE2 crosstalk in inducing vascular inflammation in vivo, identify effector cells, and ascertain specific receptors and pathways involved in vitro. METHODS: Vascular (ear) inflammation was assessed by injecting agonists into mouse ears, followed by measuring ear thickness and histology, calcium influx with Fura-2, phosphorylation and expression of signaling molecules by means of immunoblotting, PGD2 and macrophage inflammatory protein 1ß generation by using ELISA, and expression of transcripts by using RT-PCR. Candidate receptors and signaling molecules were identified by using antagonists and inhibitors and confirmed by using small interfering RNA. RESULTS: LTD4 plus PGE2 potentiated vascular permeability and edema, gearing the system toward proinflammation in wild-type mice but not in Kit(W-sh) mice. Furthermore, LTD4 plus PGE2, through cysteinyl leukotriene receptor 1 (CysLT1R) and E-prostanoid receptor (EP) 3, enhanced extracellular signal-regulated kinase (Erk) and c-fos phosphorylation, inflammatory gene expression, macrophage inflammatory protein 1ß secretion, COX-2 upregulation, and PGD2 generation in mast cells. Additionally, we uncovered that this synergism is mediated through Gi, protein kinase G, and Erk signaling. LTD4 plus PGE2-potentiated effects are partially sensitive to CysLT1R or EP3 antagonists but completely abolished by simultaneous treatment both in vitro and in vivo. CONCLUSIONS: Our results unravel a unique LTD4-PGE2 interaction affecting mast cells through CysLT1R and EP3 involving Gi, protein kinase G, and Erk and contributing to vascular inflammation in vivo. Furthermore, current results also suggest an advantage of targeting both CysLT1R and EP3 in attenuating inflammation.

Montelukast potentiates the anticonvulsant effect of phenobarbital in mice: an isobolographic analysis.

Although leukotrienes have been implicated in seizures, no study has systematically investigated whether the blockade of CysLT1 receptors synergistically increases the anticonvulsant action of classic antiepileptics. In this study, behavioral and electroencephalographic methods, as well as isobolographic analysis, are used to show that the CysLT1 inverse agonist montelukast synergistically increases the anticonvulsant action of phenobarbital against pentylenetetrazole-induced seizures. Moreover, it is shown that LTD4 reverses the effect of montelukast. The experimentally derived ED50mix value for a fixed-ratio combination (1:1 proportion) of montelukast plus phenobarbital was 0.06±0.02 µmol, whereas the additively calculated ED50add value was 0.49±0.03 µmol. The calculated interaction index was 0.12, indicating a synergistic interaction. The association of montelukast significantly decreased the antiseizure ED50 for phenobarbital (0.74 and 0.04 µmol in the absence and presence of montelukast, respectively) and, consequently, phenobarbital-induced sedation at equieffective doses. The demonstration of a strong synergism between montelukast and phenobarbital is particularly relevant because both drugs are already used in the clinics, foreseeing an immediate translational application for epileptic patients who have drug-resistant seizures.

Protein kinase C-mediated phosphorylation of RKIP regulates inhibition of Na-alanine cotransport by leukotriene D(4) in intestinal epithelial cells.

Leukotriene D4 (LTD4) is an important immune inflammatory mediator that is known to be elevated in the mucosa of chronically inflamed intestine and alter nutrient absorption. LTD4 inhibits Na-alanine cotransport in intestinal epithelial cells by decreasing the affinity of the cotransporter ASCT1. LTD4 is known to increase intracellular Ca(++) and cAMP concentrations. However, the intracellular signaling mechanism of LTD4-mediated ASCT1 inhibition is unknown. In the present study, pretreatment with calcium chelator BAPTA-AM or inhibition of Ca(++)-dependent protein kinase C (PKC), specifically PKCα, resulted in the reversal of LTD4-mediated inhibition of ASCT1, revealing the involvement of the Ca(++)-activated PKC pathway. PKCα is known to phosphorylate Raf kinase inhibitor protein (RKIP), thus activating its downstream signaling pathway. Immunoblotting with anti-RKIP-Ser(153) antibody showed an increase in phosphorylation levels of RKIP in LTD4-treated cells. Downregulation of endogenous RKIP showed no decrease in ASCT1 activity by LTD4, thus confirming its involvement in ASCT1 regulation. Phosphorylation of RKIP by PKC is known to activate different signaling pathways, and in this study it was found to activate cAMP-activated protein kinase A (PKA) pathway. Although protein abundance of ASCT1 was not altered in any of the experimental conditions, there was an increase in the levels of phosphothreonine in ASCT1 protein, thus showing that phosphorylation changes were responsible for the altered affinity of ASCT1 by LTD4. In conclusion, LTD4 inhibits ASCT1 through PKC-mediated phosphorylation of RKIP, leading to the subsequent activation of PKA pathway, possibly through ß2-andrenergic receptor activation.

Rosuvastatin inhibits human airway smooth muscle cells mitogenic response to eicosanoid contractile agents.

BACKGROUND: The concept of permanent narrowing of the airways resulting from chronic inflammation and fibrosis is called remodeling and is a common feature of asthma and chronic obstructive pulmonary disease (COPD). The eicosanoid contractile agents thromboxane A(2) (TxA(2)) and cysteinyl-leukotriene D(4) (LTD(4)) are among the recognized mitogens for human airway smooth muscle (ASM) cells. Statins are known to possess anti-inflammatory and immunomodulatory properties that are independent on their cholesterol-lowering effects and may result in clinical lung benefits. Rosuvastatin is the last agent of the lipid-lowering drugs to be introduced and experimental evidence indicates that it possess favorable pleiotropic effects in the cardiovascular and nervous systems. Yet, no data is available in the literature regarding its effects on human airway remodeling. The present study was aimed at examining the effect of rosuvastatin and the involvement of prenylated proteins in the response of human ASM cells to serum, epidermal growth factor (EGF) and eicosanoid contractile mitogens that activate TxA(2) prostanoid and LTD(4) receptors. METHODS: Cell growth was assessed by nuclear incorporation of [(3)H]thymidine in human ASM cells serum-starved and then stimulated for 48 h in MEM plus 0.1% BSA containing mitogens in the absence and presence of modulators of the mevalonate and prenylation pathways. RESULTS: We found that rosuvastatin dose-dependently inhibited serum-, EGF-, the TxA(2) stable analog U46619-, and LTD(4)-induced human ASM cells growth. All these effects were prevented by pretreatment with mevalonate. Addition of the prenylation substrates farnesol and geranylgeraniol reversed the effect of rosuvastatin on EGF and U46619, respectively. Interestingly, only mevalonate showed restoration of cell growth following rosuvastatin treatment in LTD(4) and LTD(4) plus EGF treated cells, suggesting a possible involvement of both farnesylated and geranylgeranylated proteins in the cysteinyl-LT-induced cell growth. CONCLUSIONS: The hydrophilic statin rosuvastatin exerts direct effects on human ASM cells mitogenic response in vitro by inhibiting prenylation of signaling proteins, likely small G proteins. These findings are consistent with previous observed involvement of small GTPase signaling in EGF- and U46619-induced human airway proliferation and corroborate the recent interest in the potential clinical benefits of statins in asthma/COPD.

Differential cardiotoxicity in response to chronic doxorubicin treatment in male spontaneous hypertension-heart failure (SHHF), spontaneously hypertensive (SHR), and Wistar Kyoto (WKY) rats.

Life threatening complications from chemotherapy occur frequently in cancer survivors, however little is known about genetic risk factors. We treated male normotensive rats (WKY) and strains with hypertension (SHR) and hypertension with cardiomyopathy (SHHF) with 8 weekly doses of doxorubicin (DOX) followed by 12weeks of observation to test the hypothesis that genetic cardiovascular disease would worsen delayed cardiotoxicity. Compared with WKY, SHR demonstrated weight loss, decreased systolic blood pressure, increased kidney weights, greater cardiac and renal histopathologic lesions and greater mortality. SHHF showed growth restriction, increased kidney weights and renal histopathology but no effect on systolic blood pressure or mortality. SHHF had less severe cardiac lesions than SHR. We evaluated cardiac soluble epoxide hydrolase (sEH) content and arachidonic acid metabolites after acute DOX exposure as potential mediators of genetic risk. Before DOX, SHHF and SHR had significantly greater cardiac sEH and decreased epoxyeicosatrienoic acid (EET) (4 of 4 isomers in SHHF and 2 of 4 isomers in SHR) than WKY. After DOX, sEH was unchanged in all strains, but SHHF and SHR rats increased EETs to a level similar to WKY. Leukotriene D4 increased after treatment in SHR. Genetic predisposition to heart failure superimposed on genetic hypertension failed to generate greater toxicity compared with hypertension alone. The relative resistance of DOX-treated SHHF males to the cardiotoxic effects of DOX in the delayed phase despite progression of genetic disease was unexpected and a key finding. Strain differences in arachidonic acid metabolism may contribute to variation in response to DOX toxicity.

Leukotriene receptor antagonist reduces inflammation and alveolar bone loss in a rat model of experimental periodontitis.

BACKGROUND: Leukotrienes (LTs) participate in the process of tissue damage in periodontal disease by leukocyte chemotaxis and osteoclastic activation. The activation of Cysteinyl-LT receptor is associated with increased expression of proinflammatory molecules and osteoclastogenesis. However, its implications on periodontal disease progression have not been studied. The present study evaluated the effect of the cysteinyl-LT receptor antagonist (montelukast [MT]) on ligature-induced experimental periodontitis (EP) in rats. METHODS: Adult male Wistar rats were subjected to bilateral ligature-induced periodontitis and orally treated with MT (at doses of 10 or 30 mg/kg/d, MT10, and MT30, respectively). Sham animals had the ligatures immediately removed and received placebo treatment. Sets of animals were euthanized 7, 14, or 21 days after ligature placement and the mandibles were removed for macroscopic evaluation of alveolar bone loss (ABL). In addition, histological analysis of periodontal tissues, myeloperoxidase (MPO) activity of gingival tissues, and periodontal tissue expression of collagen type I, RUNX2, RANK, RANKL, OPG, BLT1, Cys-LTR1, LTA4H, and LTC4S were also analyzed. RESULTS: MT significantly reduced ABL at 14 (MT10 and MT30) and 21 days (MT10) (P < 0.05), gingival MPO at 7 (MT10) and 14 days (MT30) (P < 0.05), LTA4H, BLT1 and LTC4S gene expression on day 14 day (MT30, P < 0.05) and increased RUNX2 expression on day 14 (MT30, P < 0.05). CONCLUSION: Systemic therapy with MT decreases periodontal inflammation and ABL in ligature-induced periodontitis in rats.

Montelukast and Coronavirus Disease 2019: A Scoping Review.

Coronavirus disease 2019 (COVID-19) is an emerging worldwide issue, that has affected a large number of people around the world. So far, many studies have aimed to develop a therapeutic approach against COVID-19. Montelukast (MK) is a safe asthma controller drug, which is considered as a potential antiviral drug for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This review has a systematic approach to investigate the reports on the use of MK as a part of treatment or a prophylactic agent in COVID-19. The search was conducted in PubMed, Web of Science, and Scopus databases and yielded 35 studies containing the influence of MK on SARS-CoV-2. Ultimately, MK appears to be worth being used as an adjuvant therapeutic and prophylactic drug against SARS-CoV-2. Nevertheless, more clinical trials are required to accurately investigate its effectiveness.

[Leukotriene D4 bronchial provocation test for detection of airway hyper-responsiveness in children].

OBJECTIVE: To explore the value of leukotriene D4 (LTD4) bronchial provocation test (BPT) in detection of airway hyper-responsiveness (AHR) in children. METHODS: A total of 151 children aged 6 to 14 years, including 86 in remission of asthma and 65 with acute bronchitis, who were followed up in our respiratory clinic between November, 2017 and August, 2018. The children were randomly divided into LTD4 group (78 cases) and methacholine (MCH) group (73 cases). In LTD4 group, the 78 children underwent LTD4-BPT, including 46 with asthma and 32 children having re-examination for previous episodes of acute bronchitis; in MCH group, the 73 children underwent MCH-BPT, including 40 with asthma and 33 with acute bronchitis. MCH-BPT was also performed in the asthmatic children in the LTD4 group who had negative responses to LTD4 after an elution period. The major adverse reactions of the children to the two BPT were recorded. The diagnostic values of the two BPT were evaluated using receiver-operating characteristic (ROC) curve. RESULTS: There was no significant difference in the results of basic lung function tests between LTD4 group and MCH group (P>0.05). The positive rate of BPT in asthmatic children in the LTD4 group was significantly lower than that in the MCH group (26.1% vs 72.5%; P < 0.05). The positive rate of BPT in children with previous acute bronchitis in the LTD4 group was lower than that in the MCH group (3.1% vs 15.2%). The positive rate of MCH-BPT in asthmatic children had negative BPT results in LTD4 group was 58.8%, and their asthma was mostly mild. The sensitivity was lower in LTD4 group than in MCH group (0.2609 vs 0.725), but the specificity was slightly higher in LTD4 group (0.9688 vs 0.8485).The area under ROC curvein LTD4 group was lower than that in MCH group (0.635 vs 0.787). In children with asthma in the LTD4 group, the main adverse reactions in BPT included cough (34.8%), shortness of breath (19.6%), chest tightness (15.2%), and wheezing (10.9%). The incidence of these adverse reactions was significantly lower in LTD4 group than in MCH group (P < 0.05). Serious adverse reactions occurred in neither of the two groups. CONCLUSIONS: LTD4-BPT had high safety in clinical application of children and was similar to the specificity of MCH-BPT. However, it had low sensitivity, low diagnostic value, and limited application value in children's AHR detection.

Leukotriene D4 role in allergic asthma pathogenesis from cellular and therapeutic perspectives.

Asthma is a chronic inflammatory and allergic disease that is mainly characterized by reversible airway obstruction and bronchial hyperresponsiveness. The incidence of asthma is increasing with more than 350 million people worldwide are affected. Up to now, there is no therapeutic option for asthma and most of the prescribed drugs aim to ameliorate the symptoms of the disease especially during the acute exacerbations after trigger exposure. Asthma is a heterogonous disease that involves interactions between inflammatory mediators and cellular components within the disease microenvironment including inflammatory and structural cells. Cysteinyl leukotrienes (cys-LTs) are inflammatory lipid mediators that have potent roles in asthma pathogenesis. CysLTs consisting of LTC4, LTD4, and LTE4 are mainly secreted by leukocytes and act through three main G-protein coupled receptors (CysLT1R, CysLT2R, and CysLT3R). LTD4 is the most potent bronchoconstrictor which gives it the priority to be discussed in detail in this review. LTD4 binds with high affinity to CysLT1R and many studies showed that using CysLT1R antagonists such as montelukast has a beneficial effect for asthmatics especially in corticosteroid refractory cases. Since asthma is a heterogeneous inflammatory disease of many cell types involved in the disease pathogenies and LTD4 has a special role in inflammation and bronchoconstriction, this review highlights the role of LTD4 on each cellular component in asthma and the benefits of using CysLT1R antagonists in ameliorating LTD4-induced effects.

Leukotriene D4 induces cellular senescence in osteoblasts.

Aging is associated with the development of osteoporosis, in which cellular senescence in osteoblasts plays a key role. Leukotriene D4 (LTD4), an important cysteinyl leukotriene (cysLT), is a powerful pro-inflammatory mediator formed from arachidonic acid. However, little information regarding the effects of LTD4 on the pathogenesis of osteoporosis has been reported before. In the present study, we defined the physiological roles of LTD4 in cellular senescence in osteoblasts. Our results indicate that LTD4 treatment decreased the expression of SIRT1 in a dose-dependent manner in MC3T3-E1 osteoblastic cells. Additionally, LTD4 significantly increased the expression of p53, p21 and plasminogen activator inhibitor-1 (PAI-1). LTD4 was also found to elevate the activity of ß-galactosidase (SA-ß-Gal) but to prevent BrdU incorporation. Our results indicate that cysteinyl leukotriene receptor 1 (cysLT1R) could be detected in MC3T3-E1 osteoblastic cells at both the mRNA and protein levels. However, cysLT2R was not expressed in these cells. Interestingly, we found that knockdown of cysLT1R or use of the selective cysLT1R antagonist montelukast abolished the LTD4-induced reduction in SIRT1 and increase in p53, p21, and PAI-1. Notably, knockdown of cysLT1R by transfection with cysLT1R siRNA or treatment with montelukast attenuated the LTD4-induced increase in SA-ß-Gal activity. Our study shows for the first time that LTD4 has a significant impact on cellular senescence in osteoblasts.

Effects of leukotriene D4 and histamine nasal challenge on airway responsiveness and inflammation in persistent allergic rhinitis patients.

BACKGROUND: Both histamine and leukotrienes are implicated in the pathogenesis of allergic rhinitis (AR), although the pattern and severity of the nasal response to these two potent inflammatory mediators may differ, which has not been adequately studied in patients with persistent AR. OBJECTIVE: We sought to compare the differential effects of nasal challenge with leukotriene D4 (LTD4 ) and histamine on the airway response and inflammation in patients with AR. METHODS: An open-label, crossover study was performed in 25 persistent AR patients (AR group) and 16 healthy subjects (control group). Participants randomly underwent histamine and LTD4 nasal provocation within a two-week interval. Nasal symptoms according to a visual analogue scale (VAS), fractional exhaled nitric oxide (FENO), nasal lavage, induced sputum, and spirometry were evaluated before and after nasal challenge. RESULTS: Nasal airway resistance (NAR) increased significantly after both LTD4 and histamine nasal challenge in AR patients (P < .05). The potency of LTD4 was 142-fold higher than that of histamine in increasing NAR (P < .001). The nasal symptom score induced by histamine challenge was significantly higher than that triggered by LTD4 (3.42 ± 0.83 vs. 1.16 ± 0.94, P < .05) in the AR group. LTD4 and histamine nasal challenge led to a significant increase in neutrophils in the nasal lavage and induced sputum (P < .05) in AR patients. There were no significant differences in the changes of eosinophils before and after LTD4 and histamine nasal challenges in nasal lavage and induced sputum. No significant changes in NAR, the induced symptom score, or inflammatory cells in the nasal lavage and sputum were found in the control group. CONCLUSIONS: LTD4 and histamine nasal challenge caused different patterns and severities of nasal symptoms, which correlated with symptoms (TSS) that affect patient's daily life. LTD4 was far more potent than histamine at increasing the NAR, while histamine nasal challenge induced more sneezing and nasal discharge. These results may guide the prescription of anti-histamine or anti-leukotriene agents for treating different AR phenotypes.