Ovalbumin-sensitized Guinea Pigs Research Articles

Prolonged allergen challenge in a guinea pig model of allergic rhinitis leads to nasal mucosa remodeling

The aim of this study was to use a guinea pig model of prolonged allergic-induced rhinitis to characterize the feature of nasal mucosa remodeling. Forty-eight male Hartley guinea pigs were randomly divided into six groups: allergen challenged groups (Group OVA(2w) , Group OVA(6w) and Group OVA(12w)) and control groups respectively (Group Sal(2w), Group Sal(6w) and Group Sal(12w)). Each group had 8 guinea pigs. To develop a guinea pig model of nasal mucosa remodeling, ovalbumin-sensitized guinea pigs were repeatedly challenged with allergen twice a week from two weeks to 12 weeks. Matched control groups were challenged with physiological saline. Nasal lavage was performed 24 hours after the last intranasal challenge. Then nasal mucosa were obtained. HE, AB-PAS, MT, and immunohistochemical staining against transforming growth factor-beta1 (TGF-beta1) were performed. Eosinophil cationic protein (ECP) and OVA-special IgE (OVA-sIgE) were detected by ELISA in nasal lavage fluid. (1) The levels of OVA-sIgE in nasal lavage fluid in Group OVA(6w) and Group OVA(12w) were significantly different from Group OVA(2w), while the levels of ECP had no significant difference among the experiment groups. The levels of OVA-sIgE and ECP in experiment groups were significantly different from control groups respectively (P < 0.01). (2) Grade 0 and Grade 1 of epithelial damage were significantly different in Group OVA(6w) and Group OVA(12w) when compared with from Group OVA(2w) (P < 0.01). At the same time, Grade 0 and Grade 1 of epithelial damage were statistically different in the experiment groups when compared with the respectively control groups (P < 0.05). (3) Goblet gland hyperplasia and collagen deposit within the extracellular matrix (ECM) were easily found in Group OVA(6w) and Group OVA(12w) compared with Group OVA(2w) (P < 0.01). The number of goblet gland and the ratio of collagen deposit were statistically more in Group OVA(6w) and Group OVA(12w) than in Group Sal(6w) and Group Sal(12w) (P < 0.05). That feature of the ratio of collagen deposit did not show in Group OVA(2w) versus Group Sal(2w). (4) Increased TGF-beta1 expressions were observed in Group OVA(6w) and Group OVA(12w) compared with Group OVA(2w) (P < 0.01). Those increasing expressions were also observed in experiment groups rather than in the respectively control groups (P < 0.01). Epithelial damage, goblet cells hyperplasia and collagen deposition in ECM were observed as the features of remodeling in this guinea pig model of allergic rhinitis under prolonged allergen challenge. Epithelial damage, excessive expression of related cytokines and enhancement activity of enzymes were observed in early time after challenge of allergen. The features of goblet cells hyperplasia and collagen deposition in ECM were observed at a later stage.

Non‐bronchodilating mechanisms of tiotropium prevent airway hyperreactivity in a guinea‐pig model of allergic asthma

Asthma is characterized by reversible bronchoconstriction and airway hyperreactivity. Although M(3) muscarinic receptors mediate bronchoconstriction, non-selective muscarinic receptor antagonists are not currently recommended for chronic control of asthma. We tested whether selective blockade of M(3) receptors, at the time of antigen challenge, blocks subsequent development of airway hyperreactivity in antigen-challenged guinea-pigs. Ovalbumin-sensitized guinea-pigs were pretreated with 1 µg·kg(-1) of a kinetically selective M(3) receptor antagonist, tiotropium, or 1 mg·kg(-1) of a non-selective muscarinic receptor antagonist, atropine, and challenged with inhaled ovalbumin. Animals were anaesthetized, paralyzed, ventilated and vagotomized 24 h later. We measured vagally mediated bronchoconstriction and i.v. ACh-induced bronchoconstriction. Electrical stimulation of both vagus nerves induced frequency-dependent bronchoconstriction in sensitized animals that was significantly increased after antigen challenge. Antigen-induced hyperreactivity was completely blocked by tiotropium pretreatment but only partially blocked by atropine pretreatment. Surprisingly, although tiotropium blocked bronchoconstriction induced by i.v. ACh, it did not inhibit vagally-induced bronchoconstriction in sensitized controls, suggesting that tiotropium does not block hyperreactivity by blocking receptors for vagally released ACh. Rather, tiotropium may have worked through an anti-inflammatory mechanism, since it inhibited eosinophil accumulation in the lungs and around nerves. These data confirm that testing M(3) receptor blockade with exogenous ACh does not predict vagal blockade. Our data also suggest that selective blockade of M(3) receptors may be effective in asthma via mechanisms that are separate from inhibition of bronchoconstriction.

Selective Inhibition of Phosphodiesterase 7 (PDE7) by BRL50481 in Healthy and Ovalbumin-Sensitized Guinea Pigs

Selective Inhibition of Phosphodiesterase 7 (PDE7) by BRL50481 in Healthy and Ovalbumin-Sensitized Guinea Pigs Phosphodiesterase (PDE) inhibitors may have significant clinical benefit in respiratory diseases associated with inflammation. The aim was to evaluate effects of selective PDE7 inhibitor (BRL50481) on citric acid induced cough, in vivo and in vitro airway smooth muscle reactivity in both healthy and ovalbumin sensitized guinea pigs, as well as its effectiveness in changes of blood cells count. Tested drugs were administered intraperitoneally to male guinea pigs once daily for 7 days either vehicle 10% DMSO (dimethyl sulfoxide) 3 ml/kg (as control) or BRL50481 1 mg/kg. Double chamber whole body plethysmograph was used for evaluation of citric acid (0.6 M) induced cough and specific airway resistance. Organ bath method was used for measurement of tracheal and lung tissue strips contractions evoked by cumulative doses (10-8 - 10-3 mol/L) of acetylcholine (ACH) and histamine (HIS). In healthy guinea pigs we did not observe significant effect of tested drug BRL50481 on in vitro contractions (similarly to in vivo conditions). The effect on cough was in healthy animals negligible. In ovalbumin-sensitized animals, more pronounced in vitro relaxing effect of BRL50481 in HIS induced contractions was observed with similar results in vivo and no significant change in number of cough efforts. Our results suggest that PDE7 inhibitors have stronger anti-inflammatory effect compared to its direct effect on smooth muscle and cough.

Dual effect of Taraxacum officinale leaves: Anticholinergic and inhibitory effect on inflammatory cells in ovalbumin-sensitized guinea-pigs

Bronchospasm is an important characteristic of allergen-induced airway inflammation.Taraxacum officinale herb is believed to have several therapeutic effects including anti-inflammatory properties. The anticholinergic effect of the T. officinale leaves extract (TOLE) was determined in ovalbumin (OA)-sensitized guinea-pig trachea. The test drugs (TOLE or prednisolone) were administered orally 1 h prior to aerosolized 2% ovalbumin challenge. Isolated ovalbumin-sensitized guinea-pig tracheal was challenged with acetylcholine and OA in the absence and presence of TOLE. The blood samples were collected and neutrophils, lymphocytes and monocytes (eosinophils, basophils and macrophages) counts assayed. Prednisolone (2.5 mg/kg body weight (BW) orally) was used as reference standard. TOLE application showed significant antagonistic effect on contraction of trachea to both acetylcholine (35.10 ± 0.04) and OA (18.6 ± 1.5). Also, the extract reduced monocytes (0.62 ± 0.23), lymphocytes (3.4 ± 0.59) and neutrophils (3.65 ± 0.20) counts in OA-sensitized guinea-pigs. Thus, TOLE possesses anticholinergic and reduces neutrophil, eosinophil and basophil counts in ovalbumin-sensitized guinea-pigs. Key words: Taraxacum officinale, inflammation, blood cell counts, anticholinergic.

The efficiency of polyphenolic compounds on allergen induced hyperreactivity of the airways

The results of some epidemiologic studies have suggested that the consumption of the food containing polyphenolic compounds might reduce the occurrence of asthma symptoms. The aim of our experiments was to evaluate the effect of the 21-day red-wine polyphenolic compounds (Provinol) administration on allergen (OVA) induced inflammation of the airways in experimental conditions. The allergic inflammation of the airways was induced in guinea pigs by 21-day ovalbumin sensitization. The tracheal smooth muscle reactivity was examined by in vitro method to bronchoconstricting mediator histamine (10 −8–10 −3 mol/L); the changes in airways resistance were examined by in vivo method by exposure to nebulized histamine (10 −6 mol/L). The histological investigation of the tracheal tissue and BALF levels of IL-4, IL-5 were used as parameters of the airway inflammation. A 21-day administration of Provinol caused a significant decrease of the specific airway resistance after the histamine nebulization and the decline in tracheal smooth muscle contraction amplitude to this bronchoconstrictor. Provinol minimized the degree of inflammation estimated on the basis of eosinophil calculation and levels of inflammatory cytokines IL-4 and IL5. In conclusion, the administration of Provinol leads to bronchodilating and anti-inflammatory effects in ovalbumin-sensitized guinea pigs, suggesting their possible use in the therapy of allergic inflammatory conditions of the airways.

Prostaglandin D2 induces contractions through activation of TP receptors in peripheral lung tissue from the guinea pig

Prostaglandin D(2) (PGD(2)), released through mast cell activation, is used as a non-invasive biomarker in patients with asthma. Since PGD(2) can elicit opposing effects on airway tone via activation of the PGD(2) receptors DP(1) and DP(2) as well as the thromboxane receptor TP, the aim of this study was to characterize the receptors that are activated by PGD(2) in the guinea pig lung parenchyma. PGD(2) and the thromboxane analog U46619 induced concentration-dependent contractions. U46619 was more potent and caused stronger effect than PGD(2). The specific TP receptor antagonist SQ-29548 and the combined TP and DP(2) receptor antagonist BAYu3405 concentration-dependently shifted the curves for both agonists to the right. The DP(1) receptor agonist BW245 induced a weak relaxation at high concentrations, whereas the DP(1) receptor antagonist BWA868C did not affect the PGD(2) induced contractions. The specific DP(2) receptor agonist 13,14-dihydro-15-keto-PGD(2) showed neither contractile nor relaxant effect in the parenchyma. Furthermore, studies in precision-cut lung slices specified that airways as well as pulmonary arteries and veins contracted to both PGD(2) and U46619. When the lung parenchyma from ovalbumin sensitized guinea pigs were exposed to ovalbumin, both thromboxane B(2) and PGD(2) were released. Ovalbumin also induced maximal contractions at similar level as PGD(2) in the parenchyma, which was partly reduced by SQ-29548. These data show that PGD(2) should be recognized as a TP receptor agonist in the peripheral lung inducing contraction on airways, arteries and veins. Therefore, a TP receptor antagonist can be useful in combination treatment of allergic responses in asthma.

Synergic bronchodilator effects of a phosphodiesterase 3 inhibitor olprinone with a volatile anaesthetic sevoflurane in ovalbumin-sensitised guinea pigs

Phosphodiesterase 3 (PDE3) inhibitors and sevoflurane are both known to have bronchodilator properties and the combination of these two agents may be synergistic. We tested this hypothesis in a model of airway hyperresponsiveness using ovalbumin-sensitised guinea pigs. Animals were randomised into five groups: control, sevoflurane, sevoflurane/theophylline, sevoflurane/milrinone and sevoflurane/olprinone. Total lung resistance (RL) and dynamic lung compliance (CL) were recorded and the dose-response curves for acetylcholine (Ach) of RL and CL were used to evaluate the bronchodilator effect. The dose-response curve for Ach of RL was elevated that for and CL was depressed significantly in the ovalbumin-sensitised animals compared to normal control guinea pigs. Among the five sensitised groups, RL was higher in the order of control > sevoflurane > sevoflurane/theophylline > sevoflurane/milrinone > sevoflurane/olprinone with increasing Ach concentration. Sevoflurane/olprinone treatment attenuated the bronchoconstriction induced by the highest dose of Ach with RL being significantly lower (0.318 ± 0.056 cmH2O ml(-1) s(-1)) than those observed in the control group (0.437 ± 0.061 cmH2O ml(-1) s(-1)), sevoflurane group (0.378 ± 0.052 cmH2O ml(-1) s(-1)) and in the sevoflurane/theophylline group (0.374 ± 0.073 cmH2O ml(-1) s(-1)). Combined use of PDE inhibitors with a volatile anaesthetic had a synergic bronchodilator effect in ovalbumin-sensitised guinea pigs. A greater bronchodilator effect can be obtained by using the selective PDE3 inhibitor olprinone with the volatile anaesthetic sevoflurane.

The relation between effects of adenosine, theophylline and enprofylline on the contractility of sensitized guinea-pig lung strips

Contractile responses of lung parenchymal strips from ovalbumin-sensitized guinea-pigs to cumulative addition of antigen were significantly potentiated by 10 min pretreatment with adenosine 10 microM. This potentiation was unaffected by the adenosine uptake inhibitor, dipyridamole, 2 microM. Cumulative addition of adenosine 0.1-100 microM to parenchymal strips without antigen produced variable responses, unrelated to sensitization, some contracting, some relaxing. Theophylline 100 microM caused relaxation of parenchymal strips and significantly inhibited the antigen-induced contraction with a parallel shift of the log concentration-response line. It also inhibited the adenosine-induced potentiation of contraction. Enprofylline 100 microM caused a greater relaxation of the tissue than theophylline. While it inhibited the adenosine-induced potentiation of the response, enprofylline, in contrast to theophylline, failed to inhibit the antigen-induced contraction of guinea-pig parenchyma. At these concentrations, theophylline and enprofylline each inhibited the antigen-induced release of SRSA (leukotrienes C4, D4 and E4), and of histamine, from sensitized guinea-pig lung fragments.

Potential immunomodulation effect of the extract of Nigella sativa on ovalbumin sensitized guinea pigs

Several different pharmacological effects have been described for Nigella sativa (Siah-Daneh), including an anti-inflammatory effect. In the present study, the effect of the extract of N. sativa on lung pathology and blood interleukin-4 (IL-4) and interferon-γ (IFN-γ) of sensitized guinea pigs was examined. Three groups (n=8 for each group) of guinea pigs sensitized to ovalbumin (OA) were given drinking water alone, and drinking water containing low and high concentrations of the plant extract, respectively. The animals of the control group (n=8) were treated with saline instead of OA and were given drinking water. The pathological changes of the lung, including infiltration of eosinophils and lymphocytes, local epithelial necrosis, the presence of oedema, thickening of the basement membrane, smooth muscle layer hypertrophy, mucosal secretion, and the presence of mucosal plug, and blood IL-4 and IFN-γ of sensitized guinea pigs were evaluated. The lungs of the sensitized group showed significant pathological changes (P<0.001). Blood IL-4 and IFN-γ were increased in sensitized animals compared to the controls (P<0.01 and P<0.001, respectively). Treatment of sensitized animals with the extract led to a significant decrease in pathological changes of the lung (P<0.01 to P<0.001), except for the oedema in the sensitized group treated with low concentration of the extract, but an increased IFN-γ. These results confirm a preventive effect of N. sativa extract on lung inflammation of sensitized guinea pigs.

Increased arginase activity contributes to airway remodelling in chronic allergic asthma

Airway remodelling, characterised by increased airway smooth muscle (ASM) mass, subepithelial fibrosis, goblet cell hyperplasia and mucus gland hypertrophy, is a feature of chronic asthma. Increased arginase activity could contribute to these features via increased formation of polyamines and l-proline downstream of the arginase product l-ornithine, and via reduced nitric oxide synthesis. Using the specific arginase inhibitor 2(S)-amino-6-boronohexanoic acid (ABH), we studied the role of arginase in airway remodelling using a guinea pig model of chronic asthma. Ovalbumin-sensitised guinea pigs were treated with ABH or PBS via inhalation before each of 12 weekly allergen or saline challenges, and indices of arginase activity, and airway remodelling, inflammation and responsiveness were studied 24 h after the final challenge. Pulmonary arginase activity of repeatedly allergen-challenged guinea pigs was increased. Allergen challenge also increased ASM mass and maximal contraction of denuded tracheal rings, which were prevented by ABH. ABH also attenuated allergen-induced pulmonary hydroxyproline (fibrosis) and putrescine, mucus gland hypertrophy, goblet cell hyperplasia, airway eosinophilia and interleukin-13, whereas an increased l-ornithine/l-citrulline ratio in the lung was normalised. Moreover, allergen-induced hyperresponsiveness of perfused tracheae was fully abrogated by ABH. These findings demonstrate that arginase is prominently involved in allergen-induced airway remodelling, inflammation and hyperresponsiveness in chronic asthma.

The effect of Nigella sativa extract on tracheal responsiveness and lung inflammation in ovalbumin-sensitized guinea pigs

OBJECTIVE:To examine the preventive effect of a hydro-ethanolic extract of Nigella sativa on the tracheal responsiveness and white blood cell count in the lung lavage fluid of sensitized guinea pigs.METHODS:Three groups of guinea pigs sensitized to intraperitoneally injected and inhaled ovalbumin were given drinking water alone (group S), drinking water containing a low concentration of N. sativa extract (group S+LNS) or drinking water containing a high concentration of N. sativa extract (group S+HNS). The tracheal responses of control animals (group C) and the three groups of sensitized guinea pigs (n = 7 for all groups) to methacholine were measured by the assessment of the tracheal smooth muscle response to increasing concentrations of methacholine, and the effective concentration causing 50% of the maximum response (EC50) was determined. Tracheal responses to 0.1% ovalbumin and white blood cell counts in the lung lavage fluid were also examined.RESULTS:The tracheal response of the group S guinea pigs to both methacholine and ovalbumin was significantly higher than the response of the controls (p<0.01 for both cases). The tracheal responses of the S+LNS and S+HNS groups to both methacholine and ovalbumin were significantly decreased compared to those of the S group (p<0.05 to p<0.01). The total white blood cell and eosinophil counts in the lung lavage fluid of group S were significantly higher than those of group C (p<0.01). The white blood cell counts in both treated groups showed significant improvements (p<0.01 for both cases).CONCLUSIONS:These results demonstrate the preventive effect of the N. sativa extract on the tracheal response and lung inflammation in sensitized guinea pigs.

The efficiency of polyphenolic compounds on allergen induced hyperreactivity of the airways

The results of some epidemiologic studies have suggested that the consumption of the food containing polyphenolic compounds might reduce the occurrence of asthma symptoms. The aim of our experiments was to evaluate the effect of the 21-day red-wine polyphenolic compounds (Provinol) administration on allergen (OVA) induced inflammation of the airways in experimental conditions. The allergic inflammation of the airways was induced in guinea pigs by 21-day ovalbumin sensitization. The tracheal smooth muscle reactivity was examined by in vitro method to bronchoconstricting mediator histamine (10 −8–10 −3 mol/L); the changes in airways resistance were examined by in vivo method by exposure to nebulized histamine (10 −6 mol/L). The histological investigation of the tracheal tissue and BALF levels of IL-4, IL-5 were used as parameters of the airway inflammation. A 21-day administration of Provinol caused a significant decrease of the specific airway resistance after the histamine nebulization and the decline in tracheal smooth muscle contraction amplitude to this bronchoconstrictor. Provinol minimized the degree of inflammation estimated on the basis of eosinophil calculation and levels of inflammatory cytokines IL-4 and IL5. In conclusion, the administration of Provinol leads to bronchodilating and anti-inflammatory effects in ovalbumin-sensitized guinea pigs, suggesting their possible use in the therapy of allergic inflammatory conditions of the airways.

Effect of thymoquinone on the lung pathology and cytokine levels of ovalbumin-sensitized guinea pigs

Different pharmacological effects from Nigella sativa have been demonstrated in guinea pig tracheal chains in previous studies. In the present study, the prophylactic effects of thymoquinone on lung pathology as well as blood IL-4 and IFN-γ levels in sensitized guinea pigs were examined. Three groups of guinea pigs sensitized to ovalbumin were given drinking water alone (group S) or drinking water containing low (LTQ) or high (HTQ) concentrations of thymoquinone (groups S+LTQ and S+HTQ). The lung pathology as well as blood IL-4 and IFN-γ levels of the sensitized and the control guinea pigs were evaluated in three sensitized and one control group (n=8, for all groups). The lungs of the S group showed significant pathological changes (p<0.001). Blood IL-4 and IFN-γ levels were increased in the sensitized animals compared to those of controls (p<0.01 and p<0.001, respectively). Treatment of the S animals with thymoquinone significantly improved their pathological changes to the lung and decreased their IL-4 levels (p<0.05 to p<0.001) but increased their IFN-γ levels (p<0.001). These results showed a preventive effect of thymoquinone on lung inflammation in sensitized guinea pigs.

Antiasthmatic action of dibenzylbutyrolactone lignans from fruits of Forsythia viridissima on asthmatic responses to ovalbumin challenge in conscious guinea‐pigs

It was reported previously that dibenzylbutyrolactone lignans from Forsythia viridissima fruits, which are traditional medicines for the treatment of inflammatory diseases, have antiinflammatory effects. In this study, the effects on the immediate-phase response (IAR) and late-phase response (LAR) following aerosolized-ovalbumin challenge in ovalbumin-sensitized guinea-pigs were evaluated by measuring the specific airway resistance (sRaw), recruitment of leukocytes and chemical mediators in the bronchoalveolar lavage fluids (BALF) as well as a histopathological survey. Arctiin and matairesinol at 12.5 mg/kg significantly (p < 0.05) decreased sRaw by 51.83% and 43.15% in IAR and by 47.41% and 35.43% in LAR, respectively, whereas arctigenin at 25 mg/kg was significantly active, compared with the controls. Furthermore, arctiin and arctigenin dose-dependently inhibited histamine, and the activities of phospholipase A₂ (PLA₂) and eosinophil peroxidase (EPO) in BALF, respectively, whereas matairesinol inhibited EPO and PLA₂ at 12.5 mg/kg and histamine at 50 mg/kg, in addition, they moderately improved the infiltration of eosinophils, compared with controls. Dexamethasone, cromolyn and salbutamol significantly inhibited sRaw in both IAR and LAR, and the recruitment of leukocytes and chemical mediators, whereas salbutamol did not alter chemical mediators, in BALF. These results indicate the three lignans have antiasthmatic effects which were less active than those of the reference drugs.

Leukotriene B4, administered via intracerebroventricular injection, attenuates the antigen-induced asthmatic response in sensitized guinea pigs

BackgroundDespite intensive studies focused on the pathophysiology of asthmatic inflammation, little is known about how cross-talk between neuroendocrine and immune systems regulates the inflammatory response during an asthmatic attack. We recently showed corresponding changes of cytokines and leukotriene B4 (LTB4) in brain and lung tissues of antigen-challenged asthmatic rats. Here, we investigated how LTB4 interacts with the neuroendocrine-immune system in regulating antigen-induced asthmatic responses in sensitized guinea pigs.MethodsOvalbumin-sensitized guinea pigs were challenged by inhalation of antigen. Vehicle, LTB4 or U75302 (a selective LTB4 BLT1 receptor inhibitor) was given via intracerebroventricular injection (i.c.v.) 30 min before challenge. Airway contraction response was evaluated using Penh values before and after antigen challenge. The inflammatory response in lung tissue was evaluated 24 h after challenge. The LTB4 content of lung and brain homogenate preparations was detected by reversed phase high-performance liquid chromatography (RP-HPLC). Plasma levels of adrenocorticotropic hormone (ACTH) and corticosterone (CORT) were measured using ELISA kits.ResultsAntigen challenge impaired pulmonary function and increased inflammatory cell infiltration in lung tissue. These responses could be significantly suppressed by LTB4, 30 ng i.c.v., in ovalbumin-sensitized guinea pigs. LTB4 content of lung and brain homogenates from antigen-challenged guinea pigs was significantly increased. In addition, administration of LTB4 via i.c.v. markedly increased CORT and ACTH level in plasma before antigen challenge, and there were further increases in CORT and ACTH levels in plasma after antigen challenge. U75302, 100 ng i.c.v., completely blocked the effects of LTB4. In addition, U75302, 100 ng via i.c.v. injection, markedly decreased LTB4 content in lung homogenates, but not in brain homogenates.ConclusionsIncreased LTB4 levels in brain during asthmatic attacks down-regulates airway contraction response and inflammation through the BLT1 receptor. Stimulation of the hypothalamic-pituitary-adrenal axis by LTB4 may result in an increase in systemic glucocorticoids which, in turn, would feed back to suppress the asthmatic response.

Effects of Flavin7 on allergen induced hyperreactivity of airways

Some studies have suggested that the polyphenolic compounds might reduce the occurrence of asthma symptoms. The aim of our experiments was to evaluate the effects of 21 days of the flavonoid Flavin7 administration on experimentally induced airway inflammation in ovalbumin-sensitized guinea pigs. We assessed tracheal smooth muscle reactivity by an in vitro muscle-strip method; changes in airway resistance by an in vivo plethysmographic method; histological picture of tracheal tissue; and the levels of interleukin 4 (IL-4), and interleukin 5 (IL-5) in bronchoalveolar lavage fluid (BALF). Histological investigation of tracheal tissue and the concentrations of the inflammatory cytokines IL-4 and IL-5 in BALF were used as indices of airway inflammation. Administration of Flavin7 caused a significant decrease of specific airway resistance after histamine nebulization and a decline in tracheal smooth muscle contraction amplitude in response to bronchoconstricting mediators. Flavin7 minimized the degree of inflammation estimated on the basis of eosinophil calculation and IL-4 and IL-5 concentrations. In conclusion, administration of Flavin7 showed bronchodilating and anti-inflammatory effects on allergen-induced airway inflammation.

Inhaled montelukast inhibits cysteinyl-leukotriene-induced bronchoconstriction in ovalbumin-sensitized guinea-pigs: The potential as a new asthma medication

Oral cysteinyl-leukotriene (LT) receptor antagonists such as montelukast are used for reducing airway inflammation and exacerbations. However, inhaled therapy using LT receptor antagonists has not been studied. In the present study, the effect of inhaled montelukast was investigated on airway hyperresponsiveness measured by cysteinyl-LT induced bronchoconstriction in an animal model of asthma. Bronchoconstriction responses were induced by inhaled LTC4 and LTD4 (0.2 µg/ml each) or three doses of intravenous LTC4 and LTD4 (0.3, 1, 3 µg/kg) in ovalbumin (OVA)-sensitized Hartley male guinea-pigs. The response was measured by the change in peak pressure of airway opening (Pao). The effect of montelukast was evaluated by the comparison of bronchoconstriction responses between the groups of animals pre-treated with 15-min inhalation of 10 mg/ml montelukast and saline. To evaluate the tissue injury which might be caused by montelukast inhalation, lung tissues were examined for the histology. The broncoconstriction responses induced by inhaled LTC4 and LTD4 were enhanced by OVA sensitization in the guinea-pigs. In sensitized animals, the significant increases in peak Pao were 18.5 ± 2.1 cmH 2O by LTC4 inhalation and 25.0 ± 1.6 cmH 2O by LTD4 inhalation on average. Prior treatment of inhaled montelukast potently suppressed the peak Pao increases induced by both inhaled and intravenous LTC4 and LTD4 (all P < 0.01 vs. saline control). Moreover, the suppression of inhaled montelukast against LTD4-induced bronchoconstriction was observed for at least up to 24 h. According to the histological examination, montelukast inhalation produced no injury to the lung tissue. Inhaled montelukast, a cysteinyl-LT receptor antagonist, was effective in inhibiting cysteinyl-LT-induced acute bronchoconstriction, and may have the potential for clinical use as a new asthma drug.

Etanercept prevents airway hyperresponsiveness by protecting neuronal M2 muscarinic receptors in antigen‐challenged guinea pigs

Increased tumour necrosis factor-alpha (TNF-alpha) is associated with airway hyperreactivity in antigen-challenged animals. In human asthmatics, TNF-alpha is increased and blocking it prevents airway hyperreactivity in some asthmatic patients. However, the mechanisms by which TNF-alpha mediates hyperreactivity are unknown. Airway hyperreactivity can be caused by dysfunction of neuronal M(2) muscarinic receptors that normally limit acetylcholine release from parasympathetic nerves. Here we test whether blocking TNF-alpha receptors with etanercept prevents M(2) receptor dysfunction and airway hyperreactivity in antigen-challenged guinea pigs. Ovalbumin-sensitized guinea pigs were challenged by inhalation of antigen. Some animals received etanercept (3 mg kg(-1) i.p.) 3 h before challenge. 24 h after challenge, airway hyperreactivity and M(2) receptor function were tested. Inflammatory cells in bronchoalveolar lavage, blood and lung were counted. TNF-alpha and its receptors were detected by real-time RT-PCR and immunocytochemistry in parasympathetic nerves from humans and guinea pigs and in human neuroblastoma cells. Antigen-challenged animals were hyperreactive to vagal stimulation and neuronal M(2) receptors were dysfunctional. Both M(2) receptor dysfunction and airway hyperreactivity were prevented by etanercept. Etanercept reduced eosinophils around airway nerves, and in blood, bronchoalveolar lavage and airway smooth muscle. Also, TNF-alpha decreased M(2) receptor mRNA in human and guinea pig parasympathetic neurons. Tumour necrosis factor-alpha may contribute to M(2) receptor dysfunction and airway hyperreactivity directly by decreasing receptor expression and indirectly by promoting recruitment of eosinophils, containing major basic protein, an M(2) antagonist. This suggests that etanercept may be beneficial in treatment of allergic asthma.

Activation of cannabinoid receptors prevents antigen‐induced asthma‐like reaction in guinea pigs

In this study we evaluated the effects of the CB1/CB2 cannabinoid receptor agonist CP55, 940 (CP) on antigen-induced asthma-like reaction in sensitized guinea pigs and we tested the ability of the specific CB2 receptor antagonist SR144528 (SR) and CB1 receptor antagonist AM251 (AM) to interfere with the effects of CP. Ovalbumin-sensitized guinea pigs placed in a respiratory chamber were challenged with the antigen given by aerosol. CP (0.4 mg/kg b.wt.) was given i.p. 3 hrs before ovalbumin challenge. Sixty minutes before CP administration, some animals were treated i.p. with either AM, or SR, or both (0.1 mg/kg b.wt.). Respiratory parameters were recorded and quantified. Lung tissue specimens were then taken for histopathological and morphometric analyses and for eosinophilic major basic protein immunohistochemistry. Moreover, myeloperoxidase activity, 8-hydroxy-2-deoxyguanosine, cyclic adenosine monophosphate (cAMP) and guanosine monophosphate (cGMP) levels, and CB1 and CB2 receptor protein expression by Western blotting were evaluated in lung tissue extracts. In the bronchoalveolar lavage fluid, the levels of prostaglandin D2 and tumour necrosis factor-α TNF-α were measured. Ovalbumin challenge caused marked abnormalities in the respiratory, morphological and biochemical parameters assayed. Treatment with CP significantly reduced these abnormalities. Pre-treatment with SR, AM or both reverted the protective effects of CP, indicating that both CB1 and CB2 receptors are involved in lung protection. The noted treatments did not change the expression of cannabinoid receptor proteins, as shown by Western blotting. These findings suggest that targeting cannabinoid receptors could be a novel preventative therapeutic strategy in asthmatic patients.

Beta-1 selective adrenergic antagonist landiolol and esmolol can be safely used in patients with airway hyperreactivity

This study was undertaken to clarify the effects of esmolol and landiolol, beta-1 selective adrenergic antagonists, on hyperreactive airways in both ovalbumin-sensitized guinea pigs and asthmatic patients. In the animal study, asthma was induced by ovalbumin. After control acetylcholine responses for total pulmonary resistance (Raw) and dynamic lung compliance (Cdyn) were obtained, the animals received propranolol, esmolol, or landiolol, and the same protocol was again performed. Sixty inpatients with coronary risk factors and asthma were enrolled in the human study. Under propofol anesthesia, the patients received saline, esmolol, or landiolol. To assess intubation-induced bronchoconstriction, the presence of wheezing was determined. The dose-response curves of Raw and Cdyn to acetylcholine were significantly elevated and declined in the ovalbumin-sensitized model compared with those in the control group. Neither esmolol nor landiolol had any effect on the acetylcholine-induced response curve in these sensitized animals. However, propranolol significantly enhanced Raw and reduced Cdyn in this model. Tracheal intubation increased the incidence of wheezing in asthmatic patients. However, there was no significant difference in the incidence of wheezing among these groups. The ultra-short-acting beta-1 selective adrenergic antagonists esmolol and landiolol can be safely used perioperatively in patients with airway hyperreactivity.