O3-induced airway hyperresponsiveness to noncholinergic system and other stimuli.

The effect of O3 exposure (3 ppm, 1 h) on the in vivo and in vitro airway responsiveness, as well as the changes in cell contents in bronchoalveolar lavage (BAL) fluid, were evaluated 16-18 h after O3 exposure in sensitized and nonsensitized male guinea pigs. The sensitization procedure was performed through repeated inhalation of ovalbumin for 3 wk. Increase in pulmonary insufflation pressure produced by the excitatory nonadrenergic noncholinergic (eNANC) system, histamine, and antigen were assessed in in vivo conditions, whereas airway responsiveness to histamine and substance P was evaluated in in vitro conditions by use of tracheal chains with or without epithelium and lung parenchymal strips. We found that O3 exposure 1) increased the neutrophil content in BAL fluids in both sensitized and nonsensitized guinea pigs, 2) caused hyperresponsiveness to eNANC stimulation in nonsensitized guinea pigs (although combination of sensitization and O3 exposure paradoxically abolished the hyperresponsiveness to eNANC stimulation), 3) increased the in vivo bronchoconstrictor responses to histamine and antigen, 4) caused hyperresponsiveness to substance P in nonsensitized tracheae with or without epithelium and in sensitized tracheae with epithelium, 5) did not modify the responsiveness to histamine in tracheae with or without epithelium (and in addition, epithelium removal caused hyperresponsiveness to histamine even in those tracheae exposed to O3), and 6) produced hyperresponsiveness to histamine in lung parenchymal strips either from sensitized or nonsensitized guinea pigs.     

Chronic tobacco smoke exposure increases airway sensitivity to capsaicin in awake guinea pigs.

Tobacco smoke (TS) exposure induces airway hyperreactivity, particularly in sensitive individuals with asthma. However, the mechanism of this airway hyperreactivity is not well understood. To investigate the relative susceptibility of atopic and nonatopic individuals to TS-induced airway hyperreactivity, we exposed ovalbumin (OA)-sensitized and nonsensitized guinea pigs to TS exposure (5 mg/l air, 30-min exposure, 7 days/wk for 120-156 days). Two similar groups exposed to compressed air served as controls. Airway reactivity was assessed as an increase in enhanced pause (Penh) units using a plethysmograph that allowed free movement of the animals. After 90 days of exposure, airway reactivity increased in OA-TS guinea pigs challenged with capsaicin, bradykinin, and neurokinin A fragment 4--10 aerosols. In addition, substance P content increased in lung perfusate of OA-TS guinea pigs in response to acute TS challenge compared with that of the other groups. Airway hyperirritability was not enhanced by phosphoramidon but was attenuated by a cocktail of neurokinin antagonists, nor was airway hyperreactivity observed after either methacholine or histamine challenge in OA-TS guinea pigs. Chronic TS exposure enhanced neither airway reactivity to histamine or methacholine nor contractility of isolated tracheal rings. In conclusion, chronic TS exposure increased airway reactivity to capsaicin and bradykinin aerosol challenge, and OA-TS guinea pigs were most susceptible to airway dysfunction as the result of exposure to TS compared with the other groups. Increased airway reactivity to capsaicin suggests a mechanism involving neurogenic inflammation, such as increased activation of lung C fibers.     

Epithelium modulates the reactivity of ovalbumin-sensitized guinea-pig airway smooth muscle

Mechanical removal of the airway epithelium alters the in vitro reactivity of airway smooth muscle. The modulation of reactivity may involve the release of inhibitory and excitatory factors from epithelial cells. Guinea pigs sensitized with ovalbumin have been used as an animal model of airway hyperreactivity. We evaluated the influence of the epithelium on the reactivity of in vitro tracheal smooth muscle from control and ovalbumin-sensitized guinea pigs, and the extent to which the presence of the epithelium affects the contractile response to in vitro challenge with ovalbumin. In both control and ovalbumin-sensitized tissues, epithelium removal increased the sensitivity of the preparations to histamine, methacholine and isoproterenol to a similar extent, i.e., 2- to 2.5-fold. Epithelium removal resulted in an 8.1-fold increase in sensitivity to ovalbumin in sensitized tissues. The epithelium appears not only to modulate the reactivity of the tissues to bronchoactive agents, but it also influences the magnitude of the contractile response following antigen challenge.     

The effect of a novel leukotriene C4/D4 antagonist, BAY-x-7195, on experimental allergic reaction

The effects of a novel leukotriene (LT) C₄/D₄ antagonist, BAY-x-7195 on experimental allergic reactions in airway and skin were compared to that of ONO-1078. BAY-x-7195 showed an antagonistic action to LTD₄-induced bronchoconstriction in vitro and in vivo. In in vitro experiments, BAY-x-7195 inhibited LTD₄-induced contraction of isolated guinea pig tracheal muscle (pA2=8.03). BAY-x-7195 at doses of 3 – 30 mg/kg clearly inhibited LTD₄-induced increases in respiratory resistance (Rrs) in guinea pigs. In contrast, BAY-x-7195 inhibited significantly U-46619-induced increases in Rrs at a dose of 30 mg/kg in guinea pigs. BAY-x-7195 at doses of 3 — 30 mg/kg inhibited the aerosolized antigen-induced biphasic increase in Rrs in guinea pigs. Moreover BAY-x-7195 inhibited repeated aeroantigen-induced airway hyperreactivity in guinea pigs. In mice, aeroantigen-induced airway inflammation were clearly inhibited by BAY-x-7195. These results show the efficacy of BAY-x-7195 against the antigen-induced increase in airway resistance and antigen-induced airway hyperreactivity in guinea pigs and mice, probably due to anti-LTD₄ antagonistic action and the inhibition of antigen-induced airway inflammation.     

OKY-046 inhibits anaphylactic bronchoconstriction and reduces histamine level in bronchoalveolar lavage fluid in sensitized guinea pigs.

We investigated the effects of OKY-046, a potent and selective thromboxane A2 (TxA2) synthetase inhibitor, on anaphylactic bronchoconstriction and release of chemical mediators into airway lumen in sensitized guinea pigs in vivo. OKY-046 dose-dependently inhibited antigen-induced anaphylactic bronchoconstriction with or without mepyramine, a histamine H1 antagonist. In the presence of mepyramine, OKY-046 (300 mg/kg, p.o.) elicited significant reductions in histamine (1 min) and TxB2 increases (1-15 min) in bronchoalveolar lavage (BAL) fluid but significantly increased the plasma level of 6-keto-PGF1 alpha, a stable PGI2 metabolite, after antigen challenge. On the contrary, indomethacin only significantly reduced increases in TxB2 levels. These results suggest that the antiasthmatic effect of OKY-046 is probably due to inhibition of TxA2 synthesis and suppression of histamine release via a PGI2 shunting mechanism.     

The effect of ONO-3708, a novel TxA2 receptor antagonist, on U-46619-induced contraction of guinea pig and human tracheal strips in vitro and on bronchoconstriction in guinea pigs in vivo.

The effect of (9, 11), (11, 12)-didedoxa-9 alpha, 11-alpha-dimethylmethano-11,12-methano-13,14-dihydro-13-aza-14-oxo -15-cyclo-pentyl-16, 17, 18, 19, 20-pentanor-15-epi-TxA2 (ONO-3708) on 9,11-methanoepoxy-prostaglandin H2 (U-46619)-induced contraction of airway smooth muscle in the guinea pigs and human in vitro and bronchoconstriction in guinea pigs in vivo was investigated. In in vitro experiments, ONO-3708 inhibited the U-46619-induced contraction of isolated guinea pig and human tracheal smooth muscle in a dose related fashion (guinea pig; pA2=7.78, human; pA2 = 7.43). The contractions of guinea pig tracheal muscle caused by histamine and leukotriene D4 (LTD4) were not inhibited by ONO-3708. In in vivo experiments, intravenous injection of ONO-3708 at doses between 1 and 20 mg/kg inhibited the U-46619-induced increase of airway insufflation pressure as measured by Konzett-R?ssler method. In addition, ONO-3708 inhibited the U-46619-induced increase in airway reactivity to acetylcholine. These data suggest that ONO-3708 has possible therapeutic utility for asthma in which TxA2 participates.     

Effect of a novel leukotoriene synthesis inhibitor, BAY x1005, on the antigen- and LPS-induced airway hyperresponsiveness in guinea pigs

Due to the inhibition of 5-lipoxygenase-activating protein (FLAP), BAY x1005 is a new selective inhibitor of leukotriene synthesis. The effects of BAY x1005 on the antigen- and bacterial lipopolysaccharide (LPS)-induced airway hyperresponsiveness in guinea pigs were investigated. Six times provocation of aeroantigen caused biphasic increases in airway resistance which peaked at 1 hr (immediate phase reaction) and 4 hrs (late phase reaction). It also caused airway hyperreactivity to acetylcholine. BAY x1005 at doses of 10mg/kg and 30mg/kg significantly inhibited antigen-induced increase in respiratory resistance (Rrs) at 1 and 4 hrs after the last antigen challenge. Simultaneously, BAY x1005 inhibited the antigen-induced airway hyperresponsiveness at doses of 10 and 30mglkg and airway eosinophilia (bronchoalveolar lavage study) at a dose of 30 mg/kg. In addition, BAY x1005 at a dose of 30mg/kg inhibited bacterial LPS-induced airway hyperreactivity to acetylcholine. In this model, BAY x1005 did not affect the increase of the number of leukocytes in bronchoalveolar lavage fluid.These results suggest that BAY x1005 is a potent anti-asthmatic agent with an inhibitory action to airway hyperreactivity.     

Bronchial mucosal permeability.

The tracheobronchial epithelium has well-developed tight junctions which on a morphologic basis should be markedly resistant to penetration by protein molecules. Despite this, antigen inhalation in monkeys allergic to Ascaris suum results in the rapid onset of pulmonary physiologic changes. Recent studies in man and animals have shown that a substantial number of mast cells exist in the bronchial lumen and epithelium. We suggest that antigen-antibody interaction initially occurs on these superficial mast cells leading to mediator release and the stimulation of airway irritant receptors. Antigen challenge also results in increased epithelial permeability to protein in the Ascaris-allergic monkey, and from studies on guinea pigs we suggest that this is due to alterations in the tight junctions. Antigen challenge in the monkey also produces increased permeability to labeled histamine and hyperresponsiveness to low concentrations of histamine. We suggest that the apparent airway hyperreactivity to inhaled histamine seen after inhalation of ozone, and NO2, or after upper respiratory infections could be due to damage to epithelial tight junctions. The resultant increase in mucosal permeability would result in an increased amount of histamine reaching airway smooth muscle for a given inhaled concentration.     

Development of an animal model of late asthmatic response in guinea pigs and effects of anti-asthmatic drugs.

We developed an animal model of late asthmatic response (LAR) in guinea pigs and examined the effects of anti-asthmatic drugs and peptide leukotriene antagonist, MCI-826, on this model. Bronchial challenge of DNP-As (Dinitrophenylated-Ascaris suum extract)-sensitized guinea pigs induced a biphasic increase in pulmonary resistance (RL) with the maximal increase being observed immediately (IAR, immediate asthmatic response) and 3 to 5 hr after antigen inhalation (LAR). Twelve of 22 guinea pigs showed both IAR and LAR. The average increases in RL for all 22 guinea pigs at IAR and LAR, were 168 +/- 13 and 207 +/- 16 (% of baseline value), respectively. Bronchoalveolar lavage (BAL) fluid of guinea pigs that received antigen, revealed increases in the numbers of eosinophils (7.3-fold compared to animals receiving saline) and neutrophils (5.3-fold compared to animals receiving saline) 4 hr after antigen inhalation. When DSCG (disodium cromoglycate) was administered (10 mg/kg, i.v.) before antigen challenge, DSCG significantly inhibited IAR (p less than 0.05) and slightly inhibited LAR (p less than 0.2). Theophylline (30 mg/kg, p.o.) administered before antigen, slightly inhibited both IAR and LAR (p less than 0.2). Salbutamol (3 mg/kg, i.p.) administered before antigen, significantly inhibited IAR (p less than 0.05), but did not affect LAR. These results were correlated with clinical trials. Moreover, peptide leukotriene antagonist, MCI-826, (E)-2,2-Diethyl-3'-[2-[2-(4- isopropyl)thiazolyl] ethenyl]succinanilic acid (0.1 mg/kg, p.o.) administered 1 hr before antigen challenge, significantly inhibited both IAR and LAR (p less than 0.05). MCI-826 (0.1 mg/kg, p.o.) administered 1.5 hr after antigen inhalation, also inhibited LAR (p less than 0.05). Analysis of BAL fluid revealed that DSCG and MCI-826 significantly inhibited the increase in eosinophils (p less than 0.05). These data suggest that leukotriene plays an important role in the development of the pathogenesis of LAR, and that our model is an useful experimental model for investigating the mechanisms of LAR and examining the effects of several anti-asthmatic drugs on LAR.     

The inhaled Rho kinase inhibitor Y-27632 protects against allergen-induced acute bronchoconstriction, airway hyperresponsiveness, and inflammation

Recently, we have shown that allergen-induced airway hyperresponsiveness (AHR) after the early (EAR) and late (LAR) asthmatic reaction in guinea pigs could be reversed acutely by inhalation of the Rho kinase inhibitor Y-27632. The present study addresses the effects of pretreatment with inhaled Y-27632 on the severity of the allergen-induced EAR and LAR, the development of AHR after these reactions, and airway inflammation. Using permanently instrumented and unrestrained ovalbumin (OA)-sensitized guinea pigs, single OA challenge-induced EAR and LAR, expressed as area under the lung function (pleural pressure, P(pl)) time-response curve, were measured, and histamine PC(100) (provocation concentration causing a 100% increase of P(pl)) values were assessed 24 h before, and at 6 and 24 h after, the OA challenge (after the EAR and LAR, respectively). Thirty minutes before and 8 h after OA challenge, saline or Y-27632 (5 mM) was nebulized. After the last PC(100) value, bronchoalveolar lavage (BAL) was performed, and the inflammatory cell profile was determined. It was demonstrated that inhalation of Y-27632 before allergen challenge markedly reduced the immediate allergen-induced peak rise in P(pl), without significantly reducing the overall EAR and LAR. Also, pretreatment with Y-27632 considerably protected against the development of AHR after the EAR and fully prevented AHR after the LAR. These effects could not be explained by a direct effect of Y-27632 on the histamine responsiveness, because of the short duration of the acute bronchoprotection of Y-27632 (<90 min). In addition, Y-27632 reduced the number of total inflammatory cells, eosinophils, macrophages, and neutrophils recovered from the BAL. Altogether, inhaled Y-27632 protects against acute allergen-induced bronchoconstriction, development of AHR after the EAR and LAR, and airway inflammation in an established guinea pig model of allergic asthma.     

U-60, 257 inhibits O3-induced bronchial hyperreactivity in the guinea pig

We studied the effects on ozone-induced airway hyperreactivity of U-60, 257, a pyrroloprostacyclin shown to inhibit leukotriene C/D biosynthesis in vitro. A group of 5 guinea pigs were pretreated with U-60, 257 (5 mg/kg IV), and studied before and 30 min after a 15 min exposure to 3.0 ppm ozone. These animals were compared to a similarly exposed group that was untreated (n=10). Reactivity was determined by measuring specific airway resistance (SRaw) upon intravenous acetylcholine infusion in unanesthetized, spontaneously breathing animals. Prior to ozone exposure, we found that U-60, 257 treatment did not affect either SRaw or muscarinic reactivity. After exposure to 3.0 ppm, all untreated guinea pigs showed substantial muscarinic hyperreactivity. In contrast, no significant change in SRaw or muscarinic reactivity occurred after ozone in any animal pretreated with U-60, 257. We conclude that ozone-induced bronchial hyperreactivity in the guinea pig rapidly develops after a brief, high level exposure. This effect may be mediated, in part, by leukotrienes generated upon ozone exposure.     

Atropine pretreatment enhances airway hyperreactivity in antigen-challenged guinea pigs through an eosinophil-dependent mechanism

Airway hyperreactivity in antigen-challenged animals is mediated by eosinophil major basic protein (MBP) that blocks inhibitory M(2) muscarinic receptors on parasympathetic nerves, increasing acetylcholine release onto M(3) muscarinic receptors on airway smooth muscle. Acutely, anticholinergics block hyperreactivity in antigen-challenged animals and reverse asthma exacerbations in the human, but are less effective in chronic asthma. We tested whether atropine, given before antigen challenge, affected hyperreactivity, M(2) receptor function, eosinophil accumulation, and activation. Sensitized guinea pigs received atropine (1 mg/kg ip) 1 h before challenge and 6 h later. Twenty-four hours after challenge, animals were anesthetized, vagotomized, paralyzed, and ventilated. Airway reactivity to electrical stimulation of the vagi and to intravenous acetylcholine was not altered by atropine pretreatment in nonsensitized animals, indicating that atropine was no longer blocking postjunctional muscarinic receptors. Antigen challenge induced airway hyperreactivity to vagal stimulation that was significantly potentiated by atropine pretreatment. Bronchoconstriction induced by acetylcholine was not changed by antigen challenge or by atropine pretreatment. M(2) receptor function was lost in challenged animals but protected by atropine pretreatment. Eosinophils in bronchoalveolar lavage and within airway tissues were significantly increased by challenge but significantly reduced by atropine pretreatment. However, extracellular MBP in challenged airways was significantly increased by atropine pretreatment, which may account for reduced eosinophils. Depleting eosinophils with antibody to IL-5 before challenge prevented hyperreactivity and significantly reduced MBP in airways of atropine-pretreated animals. Thus atropine pretreatment potentiated airway hyperreactivity by increasing eosinophil activation and degranulation. These data suggest that anticholinergics enhance eosinophil interactions with airway nerves.     

Prevention of antigen-induced bronchial hyperreactivity and airway inflammation in sensitized guinea-pigs by tacrolimus

We examined the effect of the immunosuppressive agent, tacrolimus (FK506), on antigen-induced bronchial hyperreactivity to acetylcholine and leukocyte infiltration into the airways of ovalbumin-challenged guinea-pigs. Subcutaneous injection of 0.5 mg/kg of FK506, 1 h before and 5 h after intra-nasal antigen challenge prevented bronchial hyperreactivity to aerosolized acetylcholine, eosinophilia in bronchoalveolar lavage (BAL) fluid and bronchial tissue and the invasion of the bronchial wall by CD4+ T-lymphocytes. FK506 also suppressed ovalbumin-induced increase in the number of leukocytes adhering to the pulmonary vascular endothelium and expressing alpha4-integrins. Inhibition by FK506 of antigen-induced bronchial hyperreactivity in sensitized guinea-pigs may thus relate to its ability to prevent the emergence of important inflammatory components of airway inflammation, such as eosinophil accumulation, as well as CD4+ T-lymphocyte infiltration into the bronchial tissue.     

U-60,257 inhibits O3-induced bronchial hyperreactivity in the guinea pig

We studied the effects on ozone-induced airway hyperreactivity of U-60,257, a pyrroloprostacyclin shown to inhibit leukotriene C/D biosynthesis in vitro. A group of 5 guinea pigs were pretreated with U-60,257 (5 mg/kg IV), and studied before and 30 min after a 15 min exposure to 3.0 ppm ozone. These animals were compared to a similarly exposed group that was untreated (n = 10). Reactivity was determined by measuring specific airway resistance (SRaw) upon intravenous acetylcholine infusion in unanesthetized, spontaneously breathing animals. Prior to ozone exposure, we found that U-60,257 treatment did not affect either SRaw or muscarinic reactivity. After exposure to 3.0 ppm, all untreated guinea pigs showed substantial muscarinic hyperreactivity. In contrast, no significant change in SRaw or muscarinic reactivity occurred after ozone in any animal pretreated with U-60,257. We conclude that ozone-induced bronchial hyperreactivity in the guinea pig rapidly develops after a brief, high level exposure. This effect may be mediated, in part, by leukotrienes generated upon ozone exposure.     

Effect of a novel 5-lipoxygenase inhibitor, E6080 on bronchospasm, airway cellular infiltration and leukotriene production in guinea pigs.

6-Hydroxy-2-(4-sulfamoylbenzylamino)-4,5,7-trimethylbenzothiazo le hydrochloride (E6080), an orally active and selective 5-lipoxygenase inhibitor, dose-dependently inhibited the bronchospasm induced by antigen (ovalbumin) inhalation in sensitized conscious guinea pigs. The inhibitory effect of E6080 was more potent than that of a typical 5-lipoxygenase inhibitor, AA861, but less than that of a leukotriene (LT) antagonist, LY171883. When airway infiltration of neutrophils and eosinophils was measured in bronchoalveolar lavage fluid (BALF) at 6 h after antigen inhalation by passively sensitized guinea pigs, the inhibitory effect of E6080 on neutrophil infiltration was more marked than that on eosinophil infiltration. The inhibitory effect of E6080 on bronchoalveolar cellular infiltration and bronchoepithelial damage was confirmed by examination of photomicrographs of the lung. In addition to the above pharmacological effects, E6080 inhibited the increase in BALF levels of both i-LTC4 and i-LTB4. These results suggest that E6080 may prove to be effective for the treatment of asthma, in which large amounts of leukotrienes (LTs) are elaborated.     

Change of Cu,Zn-superoxide dismutase activity of guinea pig lung in experimental asthma

Correlation between the level of reactive oxygen species (ROS) generated by airway inflammatory cells and superoxide dismutase (SOD) activity of pulmonary tissue during an asthma attach was investigated in a guinea pig model of allergic asthma. In addition, the influence of SOD inhibition by diethyldithiocarbamate (DDC, Cu-chelating agent) on the airway was investigated in terms of pulmonary function during an asthma attach. Relative to controls, the capacity of bronchoalveolar lavage fluid (BAL) cells to release ROS was significantly increased in guinea pigs sensitized with ovalbumin (OA) as the antigen, and significantly increased in guinea pigs with an asthma attack provoked by the inhalation of OA. SOD activity was increased significantly in the antigen-sensitized group. The asthma provocation group showed a tendency for increase in total SOD activity, compared with the sensitization group, whose increase was dependent on the increase in copper, zinc-SOD (Cu, Zn-SOD) activity. Pretreatment with DDC increased the severity and duration of the asthma attack. These results were indicated that Cu, Zn-SOD was closely involved in the asthma process, particularly in the scavenging of oxygen radicals secreted from BAL cells.     

Airway hyperresponsiveness to bronchoconstrictor challenge after wood smoke exposure in guinea pigs.

Prior airway exposure to wood smoke induces an increase in airway responsiveness to subsequent smoke inhalation in guinea pigs (Life Sci. 63: 1513, 1998; 66: 971, 2000). To further characterize this airway hyperreactivity, we investigated and compared the airway responsiveness to bronchoconstrictor challenge before and 30 min after sham air exposure or wood smoke exposure in anesthetized and artificially ventilated guinea pigs. Various doses of substance P (0.8-6.4 microg/kg), capsaicin (0.2-3.2 microg/kg), prostaglandin F2alpha (30-3000 microg/kg), histamine (1-8 microg/kg), or acetylcholine (5-20 microg/kg) were intravenously injected at 2-min intervals in successively increasing doses to obtain the dose required to provoke a 200% increase in baseline total lung resistance (ED200). Wood smoke exposure significantly lowered the ED200 of substance P, capsaicin, and prostaglandin F2alpha whereas sham air exposure failed to do so. Furthermore, wood smoke exposure did not significantly alter the ED200 of histamine or acetylcholine. Pretreatment with phosphoramidon (2 mg/kg), an inhibitor of the neutral endopeptidase (the major degradation enzyme of substance P), before smoke exposure did not significantly affect the smoke-induced reduction in ED200 of substance P. Sectioning both cervical vagi before smoke exposure did not significantly alter the smoke-induced reduction in ED200 of capsaicin or prostaglandin F2alpha. These results suggest that airway exposure to wood smoke acutely produces airway hyperresponsiveness to substance P, capsaicin, and prostaglandin F2alpha, but not to histamine or acetylcholine. Since the combination of phosphoramidon and wood smoke exposure did not result in an additive potentiation of smoke-induced airway hyperresponsiveness to substance P, it is suggested that an inhibition of the degradation enzyme of substance P may contribute to this increase in airway reactivity. Furthermore, vagally-mediated bronchoconstriction does not play a vital role in enhanced airway responsiveness to capsaicin or prostaglandin F2alpha.     

Change of Cu,Zn-superoxide Dismutase Activity of Guinea Pig Lung in Experimental Asthma

Correlation between the level of reactive oxygen species (ROS) generated by airway inflammatory cells and superoxide dismutase (SOD) activity of pulmonary tissue during an asthma attach was investigated in a guinea pig model of allergic asthma. In addition, the influence of SOD inhibition by diethyldithiocarbamate (DDC, Cu-chelating agent) on the airway was investigated in terms of pulmonary function during an asthma attach. Relative to controls, the capacity of bronchoalveolar lavage fluid (BAL) cells to release ROS was significantly increased in guinea pigs sensitized with ovalbumin (OA) as the antigen, and significantly increased in guinea pigs with an asthma attack provoked by the inhalation of OA. SOD activity was increased significantly in the antigen-sensitized group. The asthma provocation group showed a tendency for increase in total SOD activity, compared with the sensitization group, whose increase was dependent on the increase in copper, zinc-SOD (Cu, Zn-SOD) activity. Pretreatment with DDC increased the severity and duration of the asthma attack. These results were indicated that Cu, Zn-SOD was closely involved in the asthma process, particularly in the scavenging of oxygen radicals secreted from BAL cells.     

Glutamate receptors and the airways hyperreactivity

It is proposed the link between the hyperactivity of NMDA receptors and airway hyperresponsiveness. We investigated the effect of agents modulating the activity of NMDA receptors in the ovalbumin-induced airway hyperreactivity in guinea pigs. The airways hyperreactivity was influenced by the agonist (NMDA) and selective antagonist - competitive (AP-5) and non-competitive (MK-801) of NMDA receptors. Airway responsiveness to histamine or acetylcholine was evaluated in in vitro conditions. NMDA administration caused the increase of tracheal smooth muscle response in ovalbumin-induced hyperreactivity to acetylcholine. MK 801 as well as AP-5 provoked the decrease of reactivity mainly to acetylcholine in tracheal smooth muscle, while the former, non-competitive antagonist was more effective. We recorded more pronounced response in tracheal than in lung tissue smooth muscle with more considerable response to acetylcholine than to histamine. The results of experiments show the modification of airway smooth muscles responses by agents modulating the activity of NMDA receptors. They confirm the possibility of NMDA receptors participation in experimental airway hyperreactivity. The results enlarge information regarding the link of the inflammatory diseases and glutamatergic system.     

Responsiveness, inflammation, and effects of deep breaths on obstruction in mild asthma

Using cellular and biochemical characteristics of bronchoalveolar lavage (BAL) liquid as an index of inflammation, we examined the relationships between change of airway caliber after a deep inhalation (DI), degree of base-line airway hyperresponsiveness, and peripheral airway inflammation in a group of 16 atopic asymptomatic mild asthmatics and 6 normal subjects. Compared with normal subjects, asthmatics demonstrated 1) significantly higher BAL concentrations of histamine, total protein, the sulfidopeptide leukotrienes (SRS-A), and leukotiene B4; 2) a decrease in specific airway conductance (sGaw) with a DI at base line vs. an increase in normal subjects (before vs. after percent change in sGaw, -10 vs. 12, P less than 0.05); and 3) no significant difference in BAL total cell count or leukocyte differential. Significant correlations were demonstrated between 1) percent of BAL eosinophils vs. degree of airway hyperresponsiveness; 2) base-line level of airway obstruction vs. degree of hyperresponsiveness; 3) effects of a DI vs. BAL concentrations of eosinophils, total protein, and histamine; 4) base-line forced expired volume in 1 s vs. BAL concentrations of total protein and histamine; and 5) BAL concentrations of the various mediators with each other. These data support the notion that 1) the response to a DI in mild, stable asthmatics represents a physiological indicator of peripheral obstruction because of inflammation and 2) this inflammation is associated with increases in several known mediators of airway inflammation and hyperreactivity.