Effects of combination therapy with montelukast and carbocysteine in allergen-induced airway hyperresponsiveness and airway inflammation

Background and purpose:

Montelukast and S-carbocysteine have been used in asthmatic patients as an anti-inflammatory or mucolytic agent respectively. S-carbocysteine also exhibits anti-inflammatory properties.

Experimental approach:

Ovalbumin (OVA) sensitized BALB/c mice were challenged with OVA for 3 days followed by single OVA re-challenge (secondary challenge) 2 weeks later. Forty-eight hours after secondary challenge, mice were assessed for airway hyperresponsiveness (AHR) and cell composition in bronchoalveolar lavage (BAL) fluid. Suboptimal doses of 10 mg·kg⁻¹ of S-carbocysteine by intraperitoneal injection (ip), 20 mg·kg⁻¹ of montelukast by gavage, the combination of S-carbocysteine and montelukast or 3 mg·kg⁻¹ of dexamethasone as a control were administered from 1 day before the secondary challenge to the last experimental day. Isolated lung cells were cultured with OVA and montelukast to determine the effects on cytokine production.

Key results:

Treatment with S-carbocysteine or montelukast reduced both AHR and the numbers of eosinophils in BAL fluid. Neutralizing IFN-γ abolished the effects of S-carbocysteine on these airway responses. Combination of the two drugs showed further decreases in both AHR and eosinophils in the BAL fluid. Goblet cell metaplasia and Th2-type cytokines, interleukin (IL)-4, IL-5 and IL-13, in BAL fluid were decreased with montelukast treatment. Conversely, S-carbocysteine increased Th1-type cytokines, IFN-γ and IL-12 in BAL fluid.

Conclusions and inplications:

The combination of two agents, montelukast and S-carbocysteine, demonstrated additive effects on AHR and airway inflammation in a secondary allergen model most likely through independent mechanisms of action.     

孟鲁司特对哮喘豚鼠气道嗜酸粒细胞炎症的抑制作用

目的　研究白三烯受体拮抗剂孟鲁司特 (mon telukast,MK )对哮喘豚鼠气道嗜酸性粒细胞 (Eosinophil,Eos)炎症的影响 ,探讨孟鲁司特拮抗哮喘气道炎症的可能机制。方法　以卵白蛋白致敏豚鼠制备哮喘模型。用密度梯度分离法分离并计数支气管肺泡灌洗液 (BALF)中不同密度的嗜酸性粒细胞 ;采用TUNEL技术原位检测嗜酸性粒细胞凋亡 ;通过ELISA法检测BALF中IL 5的含量 ;采用荧光酶标记法在PharmaciaUnicap 10 0System中测定BALF中嗜酸性粒细胞阳离子蛋白 (ECP)的水平。结果　孟鲁司特能降低哮喘豚鼠BALF中Eos的数量 ;在孟鲁司特治疗组 ,嗜酸性粒细胞凋亡指数明显升高 ,BALF中IL 5和ECP的含量降低 ,与模型组比较差异均有显著性。结论　降低气道IL 5和ECP的水平 ,促进嗜酸性粒细胞凋亡 ,减少嗜酸性粒细胞浸润 ,可能是白三烯受体拮抗剂孟鲁司特拮抗哮喘气道炎症的一个重要机制。     

Anti-inflammatory effect of thymoquinone in a mouse model of allergic lung inflammation

Thymoquinone (TQ), the main active constituent of the volatile oil extracted from Nigella sativa's seeds, has been reported to have an anti-inflammatory and immune stimulatory effect on bronchial asthma and inflammation. However, little is known about the factors and mechanisms underlying these effects. In the present study, we examined the effect of TQ on airway inflammation in a mouse model of allergic asthma. Intraperitoneal injection of TQ before airway challenge of ovalbumin (OVA)-sensitized mice resulted in a marked decrease in lung eosinophilia and the elevated Th2 cytokines observed after airway challenge with OVA antigen; both in vivo, in the bronchoalveolar lavage (BAL) fluid and in vitro, following stimulation of lung cells with OVA. TQ also decreased the elevated serum levels of OVA-specific IgE and IgG1. Histological examination of lung tissue demonstrated that TQ significantly inhibited allergen-induced lung eosinophilic inflammation and mucus-producing goblet cells. While TQ showed a significant effect in inhibiting IL-4, IL-5 and IL-13 and some effect in inducing IFN-gamma production in the BAL fluid, it did show a slight effect on in vitro production of IL-4 by cultured lung cells stimulated with OVA antigen. These data suggest that TQ attenuates allergic airway inflammation by inhibiting Th2 cytokines and eosinophil infiltration into the airways; thus demonstrating its potential anti-inflammatory role during the allergic response in the lung.     

Long-term methylglyoxal intake aggravates murine Th2-mediated airway eosinophil infiltration

Asthma outcomes is aggravated in obese patients. Excess of methylglyoxal (MGO) in obese/diabetic patients has been associated with diverse detrimental effects on cell function. This study aimed to evaluate the effects of long-term oral intake of MGO on ovalbumin-induced eosinophil inflammation. Male C57/Bl6 mice received 0.5% MGO in the drinking water for 12 weeks. Mice were sensitized and challenged with ovalbumin (OVA), and at 48 h thereafter, bronchoalveolar lavage (BAL) fluid and lungs were collected for cell counting, morphological analysis, and ELISA, mRNA expressions and DHE assays. In MGO-treated mice, OVA challenge significantly increased the peribronchiolar infiltrations of inflammatory cells and eosinophils compared with control group. Higher levels of IL-4, IL-5, and eotaxin in BAL fluid were also detected in MGO compared with control group. In addition, lung tissue of MGO-treated mice displayed significant increases in mRNA expressions of NF-κB and iNOS whereas COX-2 expression remained unchanged. The high TNF-α mRNA expression observed in lungs of OVA-challenged control mice was not further increased by MGO treatment. In MGO group, OVA-challenge increased significantly the NOX-2 and NOX-4 mRNA expressions, without affecting the NOX-1 expression. Levels of reactive-oxygen species (ROS) were significantly higher in lungs of MGO-treated mice, and no further increase by OVA-challenge was observed. In conclusion, 12-week intake of MGO exacerbates Th2-mediated airway eosinophil infiltration by activation of NF-kB/iNOS-dependent signaling pathway and positive regulation of NOX-2 and NOX-4 in the lung tissues. Scavengers of MGO could be an option to prevent obesity-related asthma.     

A review of montelukast in the treatment of asthma and allergic rhinitis

Montelukast sodium (Singulair, Merck) is a selective and orally-active leukotriene-receptor antagonist (LTRA) that inhibits the cysteinyl leukotriene 1 (CysLT1) receptor. Montelukast is an effective and well-tolerated preventative treatment for asthma and allergic rhinitis in adults and children. The upper and lower airway show similar inflammatory responses to allergen challenge. Leukotrienes are inflammatory mediators that are known as the slow-reacting substance of anaphylaxis produced by a number of cell types including mast cells, eosinophils, basophils, macrophages and monocytes. Synthesis of these mediators results from the cleavage of arachidonic acid in cell membranes and they exert their biological effects by binding and activating specific receptors. This occurs in a series of events that lead to contraction of the human airway smooth muscle, chemotaxis and increased vascular permeability. These effects have led to their important role in the diseases of asthma and allergic rhinitis. As these agents lead to the production of symptoms in patients that are asthmatic or allergic, the use of LTRAs, particularly montelukast, may seem appropriate. Clinical trials have shown that montelukast is effective and safe in the treatment of patients with asthma, allergic rhinitis or both diseases.     

Comparative study to elucidate the mechanism underlying the difference in airway hyperresponsiveness between two mouse strains

The mechanism underlying airway hyperresponsiveness (AHR), a characteristic feature of asthma, remains obscure. We attempted to elucidate the mechanism responsible for the different degrees of AHR in two mouse strains, BALB/c and C57BL/6, following exposure to an anaphylactic trigger. When ovalbumin (OVA)-sensitized mice were challenged daily with OVA for up to three consecutive days, the BALB/c mice showed a higher degree of airway responsiveness to methacholine than did C57BL/6. Following the OVA challenge, eosinophils and macrophages in bronchoalveolar lavage fluid (BALF) from BALB/c increased significantly in number compared to those from C57BL/6. BALB/c mice also exhibited a higher serum IgE level than that of C57BL/6 after OVA challenge. The enhanced AHR and eosinophilic infiltration in BALF were significantly reduced by pretreatment with a selective cysteinyl-leukotriene type 1 receptor (cysLT(1)R) antagonist, montelukast. In the in vitro study, cysLT production was significantly lower in the dissected lung tissue from BALB/c than in tissue from C57BL/6 when both groups were stimulated with saline. The lungs from BALB/c generated significantly larger amounts of cysLTs on incubation with OVA rather than with saline, while the lungs from C57BL/6 did not show any significant increase in cysLTs with antigen stimulation. Significant upregulation of cysLT(1)R and cysLT(2)R mRNA expression was induced by OVA challenge in the lungs of BALB/c, but not in those of C57BL/6. It is suggested that, after an anaphylactic reaction, the degree of AHR is dependent on the genetic background and that cysLTs play an important role in the mechanism involved.     

Continued inhalation of lidocaine suppresses antigen-induced airway hyperreactivity and airway inflammation in ovalbumin-sensitized guinea pigs

It is unclear whether inhaled lidocaine is effective against airway hyperreactivity and inflammation in asthma. The aim of this study was to investigate the effects of inhaled lidocaine on airway hyperreactivity and inflammation. Airway reactivity to inhaled histamine, cellular composition of bronchoalveolar lavage (BAL) fluid, plasma substance P (SP), and isolated lung tissue were evaluated in ovalbumin (OVA)-sensitized guinea pigs 7 days after OVA challenge. The effects of inhaled lidocaine on this model were also evaluated. Treatment with lidocaine was administered in two fashions: as single inhalation or inhalation bid for 7 consecutive days, for comparison with a saline-inhaled control group. Airway hyperreactivity to histamine, increase in number of total cells and increased proportion of eosinophils in BAL fluid, and marked eosinophil infiltration in airway walls were noted even 7 days after OVA challenge in the control group. Plasma SP level was also significantly increased. Although treatment with single lidocaine inhalation did not affect airway hyperreactivity, continued inhalation (bid for 7 days) attenuated airway hyperreactivity. Continued, but not single, inhalation of lidocaine also suppressed infiltration of eosinophils in BAL fluid and in airway walls. In addition, plasma SP levels were significantly reduced by continued but not by single inhalation. It appears possible that lidocaine when inhaled suppresses eosinophilic inflammation of the airway and SP-induced neurogenic inflammation, leading to alleviation of airway hyperreactivity.     

Effects of montelukast, a cysteinyl-leukotriene type 1 receptor antagonist, on the pathogenesis of bleomycin-induced pulmonary fibrosis in mice

Cysteinyl-leukotrienes are potent mediators involved in various inflammatory diseases and lung disorders such as asthma. However, their precise role in the pathogenesis of pulmonary fibrosis is unknown. In the present study, we investigated the effect of montelukast, a cysteinyl-leukotriene type 1 receptor antagonist, on bleomycin-induced pulmonary fibrosis in mice. Montelukast (10 mg/kg/day) was orally administered to the bleomycin-induced pulmonary fibrosis mice for 3 days before and 14 days after intratracheal instillation of bleomycin. We evaluated the effects of montelukast on the development of pulmonary fibrosis in these mice and investigated the expression of various cytokines and two cysteinyl-leukotriene receptors. Treatment with montelukast significantly attenuated the increased fibrotic area and hydroxyproline content in the fibrotic lungs of bleomycin-instilled mice. Montelukast treatment also decreased mRNA levels of IL-6, IL-10, IL-13, and TGF-β1, all of which were elevated in fibrotic lungs. In fibrotic lungs, TNF-α and IL-1β mRNA levels were increased and IFN-γ mRNA levels were decreased, but montelukast did not affect these mRNA levels. Furthermore, cysteinyl-leukotriene type 1 receptor mRNA levels were increased, whereas cysteinyl-leukotriene type 2 receptor mRNA levels were decreased in fibrotic lungs. Montelukast treatment induced the recovery of cysteinyl-leukotriene type 2 receptor mRNA levels to normal control levels but did not change cysteinyl-leukotriene type 1 receptor mRNA levels. These results suggest that montelukast exhibits its beneficial effects by inhibiting the overexpression of IL-6, IL-10, IL-13, and TGF-β1 and by modulating the homeostatic balance between the cysteinyl-leukotriene type 1 and type 2 receptors.     

A review of montelukast in the treatment of asthma and allergic rhinitis

Montelukast sodium (Singulair^®, Merck) is a selective and orally-active leukotriene-receptor antagonist (LTRA) that inhibits the cysteinyl leukotriene 1 (CysLT1) receptor. Montelukast is an effective and well-tolerated preventative treatment for asthma and allergic rhinitis in adults and children. The upper and lower airway show similar inflammatory responses to allergen challenge. Leukotrienes are inflammatory mediators that are known as the slow-reacting substance of anaphylaxis produced by a number of cell types including mast cells, eosinophils, basophils, macrophages and monocytes. Synthesis of these mediators results from the cleavage of arachidonic acid in cell membranes and they exert their biological effects by binding and activating specific receptors. This occurs in a series of events that lead to contraction of the human airway smooth muscle, chemotaxis and increased vascular permeability. These effects have led to their important role in the diseases of asthma and allergic rhinitis. As these agents lead to the production of symptoms in patients that are asthmatic or allergic, the use of LTRAs, particularly montelukast, may seem appropriate. Clinical trials have shown that montelukast is effective and safe in the treatment of patients with asthma, allergic rhinitis or both diseases.     

Histamine decreases myogenic tone in rat cerebral arteries by H2-receptor-mediated KV channel activation, independent of endothelium and cyclic AMP

Adenosine produces bronchoconstriction in allergic rabbits, primates, and humans by activating adenosine A(1) receptors. Previously, it is reported that a high dose of L-97-1, a water-soluble, small molecule adenosine A(1) receptor antagonist, blocks early and late allergic responses, and bronchial hyper-responsiveness to histamine in a hyper-responsive rabbit model of allergic asthma. Effects of a lower dose of L-97-1 are compared to montelukast, a cysteinyl leukotriene-1 receptor antagonist on early allergic response, late allergic response, bronchial hyper-responsiveness, and inflammatory cells in bronchoalveolar lavage (BAL) fluid following house dust mite administration. Rabbits received intraperitoneal injections of house dust mite extract within 24 h of birth followed by booster house dust mite injections. Hyper-responsive rabbits received aerosolized house dust mite (2500 allergen units), 1 h after intragastric administration of L-97-1 (1 mg/kg) or montelukast (0.15 mg/kg) and lung dynamic compliance was measured for 6 h. Lung dynamic compliance was significantly higher following L-97-1 at all time points and with montelukast at 60-300 min following house dust mite (P<0.05). L-97-1 blocks both early and late allergic responses. Montelukast blocks only the late allergic response. Both L-97-1 and montelukast significantly blocked bronchial hyper-responsiveness at 24 h (P<0.05). Both L-97-1 and montelukast significantly reduced BAL eosinophils at 6 h and neutrophils at 6 and 24 h (P<0.05). L-97-1 significantly reduced BAL lymphocytes at 6 and 24 h (P<0.05). Montelukast significantly reduced BAL macrophages at 6 and 24 h (P<0.05). By blocking both bronchoconstriction and airway inflammation, L-97-1 may be an effective oral anti-asthma treatment.     

Enhancement of the pulmonary allergic granulocyte recruitment in rats exposed to DMTI-II, a Kunitz-type inhibitor isolated from Dimorphandra mollis seeds

DMTI-II (23-kDa trypsin inhibitor purified from Dimorphandra mollis seeds) promotes acute inflammation accompanied by an early infiltration of eosinophils, a critical cell type involved in allergic diseases. We have evaluated here the capacity of DMTI-II to enhance the allergic pulmonary inflammation, looking over time to the leukocyte trafficking from bone marrow to peripheral blood, and their recruitment into the allergic airways. Male Wistar rats were sensitized and challenged with ovalbumin (OVA). At 2 to 16h prior to OVA challenge, animals were exposed to DMTI-II (10μg). Bronchoalveolar lavage fluid (BAL), circulating blood and bone marrow were examined at 24h post-OVA challenge. Challenge with OVA significantly increased the influx of total inflammatory cells, neutrophils and eosinophils in BAL and lung tissue. Pre-exposure to DMTI-II potentiated total inflammatory cell and neutrophil recruitment (p<0.05). Neutropoiesis and neutrophilia accompanied pulmonary cell influx. Pre-exposure to DMTI-II also significantly increased eosinophil recruitment to BAL, an effect starting at 4h, remaining markedly elevated at 16h (p<0.05). Eosinopoiesis and eosinophilia (seen within 2 to 4h) were also observed. Exposure to DMTI-II alone increased the IL-4 levels, and further increased the IL-4 levels in OVA-challenged rats. The levels of IgE, LTB(4) and eotaxin in OVA-challenged rats were greater compared with non-sensitized rats, but DMTI-II exposure failed to further enhance such levels. In summary, our study shows that DMTI-II itself presents granulocytopoietic activity, and enhances allergen-induced neutrophil and eosinophil mobilization from bone marrow to lung tissues that is accompanied by enhanced IL-4 production.     

Effects of hardwood smoke exposure on allergic airway inflammation in mice

Hardwood smoke (HWS) from wood burning stoves and fireplaces can be a significant contributor to the composition of ambient air pollution. We hypothesize that the inhalation of HWS by ovalbumin (OVA)-sensitized mice with preexisting lung inflammation leads to the exacerbation of allergic airway responses. Two different models were employed to characterize the effects of inhaled wood smoke on allergic airway inflammation. In both models, male BALB/c mice were sensitized by injection with OVA and alum. In one model, mice were challenged by inhalation with OVA 1 day prior to exposure to HWS (30, 100, 300, or 1000 microg particulate matter [PM]/m(3)) for 6 h/day on 3 consecutive days. In the other model, mice were exposed by inhalation to OVA, rested for 11 days, were exposed to HWS for 3 consecutive days, and then were exposed to OVA immediately after the final HWS exposure. Bronchoalveolar lavage (BAL), and blood collection were performed approximately 18 h after the last HWS or OVA exposure. HWS exposure after the final allergen challenge (first model) led to a significant increase in BAL eosinophils only at the 300 microg/m(3) level. In contrast, changes in BAL cells did not reach statistical significance in the second model. There were no HWS-induced changes in BAL interleukin (IL)-2, IL-4, IL-13, and interferon (IFN)gamma levels in either model following OVA challenge. These results suggest that acute HWS exposure can minimally exacerbate some indices of allergic airway inflammation when a final OVA challenge precedes HWS exposure, but does not alter Th1/Th2 cytokine levels.     

当归对阴虚哮喘BALB/c小鼠Th2优势免疫应答的影响

目的 探讨当归对阴虚哮喘BALB/c小鼠Th2细胞优势免疫应答的影响。方法 采用注射卵清白蛋白(ovalbumin,OVA)致敏、吸入OVA激发的方法来复制BALB/c小鼠哮喘模型,实验后期给予甲状腺素以复制阴虚哮喘模型,通过观测哮喘行为学、血清及支气管肺泡灌洗液(broncho-alveolar lavage fluid,BALF)中IL-4、IL-13的水平、BALF及肺组织中炎性细胞的含量、肺组织中GATA-3蛋白表达水平,探讨当归的平喘作用及对Th2细胞优势免疫应答的影响。结果 当归可明显减少阴虚哮喘小鼠哮喘发作的次数及其发作时的症状,改善肺组织病理学而减少肺组织及BALF中炎性细胞的数量,降低血清及BALF中IL-4、IL-13的水平,抑制肺组织中GATA-3蛋白的表达(P<0.05或0.01);同时,当归与地塞米松配伍后对嗜酸粒细胞、IL-4及GATA-3的抑制作用具有一定的协同作用(P<0.05或0.01)。结论 当归具有平喘作用,抑制细胞因子IL-4、IL-13及转录因子GATA-3的表达而缓解Th2优势免疫应答可能是其作用机制之一。     

CCR3 monoclonal antibody inhibits airway eosinophilic inflammation and mucus overproduction in a mouse model of asthma

AIM: To explore the effect of a rat anti-mouse CC-chemokine receptor-3 (CCR3) monoclonal antibody (CCR3 mAb) on airway eosinophilia and mucus overproduction in asthmatic mice. METHODS: An asthma model was sensitized and challenged by ovalbumin (OVA) in male C57BL/6 mice. Asthmatic mice were given dual administration (intraperitoneal injection and aerosol inhalation) of CCR3 mAb or nonspecific rat IgG (ns-IgG). The number of total and differential inflammatory cells in the bronchial alveolar lavage fluid (BALF) was counted. Eosinophils number, the goblet cell percentage (GCP) and airway mucus index (AMI) were measured in the lung tissues. Interleukin (IL)-5 levels in the BALF were examined. The expression of MUC5AC and the epidermal growth factor receptor (EGFR) mRNA in the lung tissues was detected by semi-quantitative RT-PCR. The results were compared among the groups. RESULTS: CCR3 mAb significantly suppressed the increased eosinophils in the BALF and lung tissues in OVA-challenged mice compared with ns-IgG-treated mice. IL-5 levels in the BALF in CCR3 mAb and ns-IgG administration mice exhibited no obvious changes relative to OVA-challenged asthmatic mice. CCR3 mAb reduced the increased GCP and AMI after OVA challenge and decreased the enhanced expression of MUC5AC and EGFR mRNA in lung tissues in asthmatic animals. CONCLUSION: CCR3 mAb can significantly inhibit airway eosinophilia and mucus overproduction in asthmatic mice. Blockage of CCR3 may represent a new strategy to asthma therapy.     

孟鲁司特对哮喘豚鼠气道嗜酸性粒细胞凋亡及Fas mRNA表达的影响

目的研究白三烯受体拮抗剂孟鲁司特(montelukast,MK)对哮喘豚鼠气道嗜酸性粒细胞(eosinophil,Eos)凋亡和Fas mRNA表达的影响。方法以卵白蛋白致敏豚鼠制备哮喘模型。用密度梯度离心法分离并计数支气管肺泡灌洗液(BALF)中的嗜酸性粒细胞；采用TUNEL技术原位检测嗜酸性粒细胞凋亡；通过逆转录-多聚酶链反应(RT-PCR)技术检测嗜酸性粒细胞Fas mRNA的表达。结果孟鲁司特能显著降低哮喘豚鼠BALF中Eos的数量；在孟鲁司特治疗组，嗜酸性粒细胞凋亡指数明显升高，Fas mRNA的表达显著增强，与模型组比较均有显著性差异。结论嗜酸性粒细胞凋亡与Fas mRNA表达增加高度相关；增强气道嗜酸性粒细胞Fas mRNA的表达，促进其凋亡，可能是孟鲁司特拮抗哮喘气道炎症的一个重要机制。     

Airway inflammation and adjuvant effect after repeated airborne exposures to di-(2-ethylhexyl)phthalate and ovalbumin in BALB/c mice

BACKGROUND: Epidemiological studies have suggested an association between exposure to phthalate plasticizers, including di-(2-ethylhexyl)phthalate (DEHP), and increased prevalence of asthma, rhinitis or wheezing. Furthermore, studies in mice have demonstrated an adjuvant effect from DEHP after parenteral administration with the model allergen ovalbumin (OVA). OBJECTIVE: Exposures to DEHP were investigated for adjuvant effects and airway inflammation in a mouse inhalation model. METHODS: BALB/cJ mice were exposed to aerosols of 0.022-13 mg/m(3) DEHP and 0.14 mg/m(3) OVA 5 days/week for 2 weeks and thereafter weekly for 12 weeks. Mice exposed to OVA alone or OVA+Al(OH)(3) served as control groups. Finally, all groups were exposed to a nebulized 1% OVA solution on three consecutive days. Serum, bronchoalveolar lavage (BAL) fluid, and draining lymph nodes were collected 24h later. RESULTS: In the OVA+Al(OH)(3) group, significantly increased levels of OVA-specific IgE and IgG1 in serum as well as of eosinophils in BAL fluid were observed. DEHP affected OVA-specific IgG1 production in a concentration-dependent manner, whereas little effect was seen on IgE and IgG2a. Dose-dependent increases in inflammatory cells were observed in BAL fluids, leading to significantly higher lymphocyte, neutrophil and eosinophil numbers in the OVA+13 mg/m(3) DEHP group. Ex vivo cytokine secretion by cultures of draining lymph nodes suggested that DEHP has a mixed Th1/Th2 cytokine profile. CONCLUSION: Airborne DEHP is able to increase serum IgG1 and lung inflammatory cell levels, but only at very high concentrations. Realistic DEHP levels do not have an adjuvant effect or induce allergic lung inflammation in the present mouse model.     

Role of adenosine in airway inflammation in an allergic mouse model of asthma

In the present study, we examined dynamic changes in cellular profile of bronchoalveolar lavage (BAL) fluid after adenosine challenge in ragweed sensitized and challenged mice. Mice systemically sensitized and airway challenged with ragweed showed marked airway inflammation manifesting increased eosinophils, lymphocytes, neutrophils and activated macrophages in BAL. Adenosine challenge further enhanced influx of inflammatory cells into BAL, notably neutrophils from 1 to 72 h and eosinophils from 1 to 48 h time-points (p<0.05), which sharply rose at 6-h time-point following adenosine challenge. Greater infiltration of lymphocytes into BAL was observed at 1 and 72 h and macrophages from 6 to 72 h (p<0.05) after adenosine challenge. Accordingly, markers of eosinophils, neutrophils and mast cells were analyzed at 6-h time-point after adenosine challenge. Adenosine challenge significantly increased the levels of eosinophil peroxidase, neutrophil myeloperoxidase and beta-hexosaminidase in BAL. There were more significant effects of adenosine challenge on the degranulation of mast cells in the lung than that in blood. The chemoattractant, eotaxin, was detected in BAL, which increased after adenosine challenge. Theophylline, a non-specific adenosine receptor antagonist, prevented adenosine-enhanced infiltration of inflammatory cells and their respective markers. Our findings suggest that adenosine plays an important role in airway inflammation in an allergic mouse model.     

Obesity enhances eosinophilic inflammation in a murine model of allergic asthma

Background and purpose:

Obesity is associated with deterioration in asthma outcomes. Although airways eosinophil accumulation is characteristic of lung allergic diseases, little is known about the influence of obesity on the allergic eosinophil trafficking from bone marrow to lung tissues, and recruitment to airways lumen. Here, we have assessed the effects of diet-induced obesity on allergic eosinophilic inflammation in mice, examining eosinophil trafficking from bone marrow to airways, and production of T_H1/T_H2 cytokines.

Experimental approach:

C57BL/6 mice fed for 10 weeks with standard chow or high-fat diet were sensitized and challenged with ovalbumin. At 24–96 h post-ovalbumin challenge, bronchoalveolar lavage (BAL) fluid, lung tissue and bone marrow were examined.

Key results:

The high-fat-fed mice exhibited increased body weight and epididymal fat, glucose intolerance and alterations in lipid profile compared with the lean mice. Obesity markedly elevated serum leptin and lowered adiponectin levels. Ovalbumin challenge in obese mice promoted a markedly higher eosinophil accumulation in bone marrow and connective tissue surrounding the bronchial and bronchiolar segments. Eosinophil number in BAL fluid of obese mice was lower at 24 and 48 h. Levels of interleukin (IL)-5, eotaxin, tumour necrosis factor-α and IL-10 in BAL fluid of obese mice were significantly higher than in lean mice.

Conclusions and implications:

Diet-induced obesity enhanced eosinophil trafficking from bone marrow to lung tissues, and delayed their transit through the airway epithelium into the airway lumen. Consequently, eosinophils remain longer in lung peribronchiolar segments due to overproduction of T_H1/T_H2 cytokines and chemokines.     

Pharmacological profile and clinical effects of montelukast sodium (Singulair chewable tablet), an antiasthmatic agent

Montelukast (Singulair) is an antiasthmatic agent that has the chemical structure of a quinoline. Montelukast has a high affinity for the CysLT1 receptor and a potency that is not influenced by human serum protein. Montelukast antagonizes contractions of guinea-pig trachea induced by LTD4 in a competitive manner. Intravenous montelukast inhibited bronchoconstriction induced by LTD4 in guinea pigs. Oral montelukast inhibited increased airway resistance induced by antigen in squirrel monkeys. Montelukast also inhibited both inflammatory and immunologic responses induced by either LTD4 or antigen in guinea pigs and rats. Plasma concentrations of montelukast after oral administration of 10 mg in humans were shown to be over the effective level for at least 24 h. These lines of evidence support the effectiveness of a regimen of 10 mg/day for asthmatic symptoms in humans. In a number of clinical experiments, montelukast not only improved asthmatic symptoms and respiratory indices, but also inhibited airway inflammation and exercise-induced bronchoconstriction. These effects persisted during extended treatment. Montelukast produced an additive effect to basic therapy with an inhaled steroid. There were no differences in the incidence and magnitude of adverse effects between montelukast and placebo groups in clinical experiments. Montelukast is expected to serve as a first line of asthmatic therapy because of its consistent efficacy and good safety profile and it is associated with good compliance in patients because of its simple regimen of one 10 mg tablet/day.     

Impact of emerging pollutants on pulmonary inflammation in asthmatic rats: ethanol vapors and agglomerated TiO2 nanoparticles

Context: Titanium dioxide nanoparticles (nano-TiO₂) and ethanol vapors are air contaminants with increasing importance. The presence of a pathological pulmonary condition, such as asthma, may increase lung susceptibility to such contaminants.

Objective: This study aimed to investigate if exposure to inhaled ethanol vapors or nano-TiO₂ can modulate the rat pulmonary inflammatory response resulting from an allergic asthmatic reaction.

Materials and methods: Brown Norway rats were sensitized (sc) and challenged (15?min inhalation, 14 days later) with chicken egg ovalbumin (OVA). Leukocytes were counted in bronchoalveolar lavages (BAL) performed at 6, 24, 36, 48 and 72?h following the challenge and either after ethanol exposures (3000 ppm, 6?h/day, daily) or at 48?h (peak inflammation) for nano-TiO₂ exposures (9.35?mg/m³ aerosol for 6 and 42?h after the OVA challenge). For the nano-TiO₂ exposures, plasma and BAL cytokines were measured and lung histological analyzes were performed.

Results: Exposure to ethanol did not significantly affect BAL leukocytes after OVA challenge. Exposure to nano-TiO₂ significantly decreased BAL leukocytes compared to OVA-challenged controls. Plasma and BAL IL-4, IL-6, and INF-γ levels were also decreased in the nano-TiO₂ group.

Discussion: While ethanol vapors do not modify the pulmonary inflammation in rats during an asthmatic response, a surprising protective effect for agglomerated nano-TiO₂ was observed. A putative mechanistic basis involving a decrease in the Th2 response caused by OVA is proposed.

Conclusion: Allergic pulmonary inflammation is not up-regulated by inhalation of the pollutants ethanol and nano-TiO₂. On the contrary, nano-TiO₂ decreases lung inflammation in asthmatic rats.