Airway hyperresponsiveness after endotoxin inhalation depends on leukocyte infiltration

We have investigated the relationship between acute airway hyperresponsiveness and polymorphonuclear cell (PMN) migration in airways following saline or endotoxin (ET) aerosol inhalation in 63 guinea pigs. In 20 of these animals, granulocytopenia was induced by prior treatment with hydroxyurea (HU). Airway responsiveness (AR) to inhaled methacholine, together with leukocyte counts in bronchoalveolar lavage fluid (BALF) and in tracheal epithelium, was also examined before and at 30 min, 1, 3 and 6 hr after saline or ET inhalation. In saline inhalation groups, AR and PMN counts in BALF and in tracheal epithelium did not differ from control animals at any time points. However, in ET inhalation groups AR increased significantly at 1 and 3 hr and returned to the pre-exposure level at 6 hr. This period of hyperresponsiveness was associated with an increment of PMN migration into tracheal epithelium. However, the increment of PMN counts in BALF was delayed to 3 and 6 hr after ET. In HU treated animals, AR and PMN counts in BALF and in tracheal epithelium did not change during 6 hr after ET inhalation. These results suggest that the hyperresponsiveness induced by ET inhalation either depends upon PMN migration into the tracheal epithelium.     

Effects of carbocysteine on antigen-induced increases in cough sensitivity and bronchial responsiveness in guinea pigs

Carbocysteine is a mucoactive drug and is being used for both acute and chronic infectious airway diseases. Although carbocysteine can repair the damage of epithelial cells caused by exposure to various agents, the effects of this agent on allergic airway diseases such as asthma and eosinophilic bronchitis with an isolated chronic cough, in both of which epithelial damage may be characteristic, is not clear. We investigated the effects of carbocysteine on antigen-induced cough hypersensitivity to inhaled capsaicin at 48 h and bronchial hyperresponsiveness to inhaled methacholine at 72 h after challenge with an aerosolized antigen in actively sensitized guinea pigs. After measuring bronchial responsiveness, we examined neutral endopeptidase (NEP) activity in the tracheal tissue. Carbocysteine (10, 30, or 100 mg/kg) was given intraperitoneally every 12 h for 3 days after antigen challenge. The number of coughs elicited by an aerosol of capsaicin (10(-4) M) was significantly (p < 0.01) decreased in carbocysteine groups (6.13 +/- 0.59 at 10 mg/kg, 4.88 +/- 0.67 at 30 mg/kg, and 4.50 +/- 0.33 at 100 mg/kg during 3 min measurement) compared with the control group (9.75 +/- 0.53). Furthermore, carbocysteine dose dependently repaired the antigen-induced decrease of NEP activity in the tracheal tissue, but it did not influence the bronchial hyperresponsiveness or bronchoalveolar lavage cell component. These findings suggest that carbocysteine promotes the repair of damaged epithelium by allergic reaction and may be useful in allergic airway diseases accompanied by isolated chronic coughing, especially eosinophilic bronchitis without asthma and tracheobronchitis with cough hypersensitivity.     

Role of cyclooxygenase isoforms and nitric-oxide synthase in the modulation of tracheal motor responsiveness in normal and antigen-sensitized Guinea pigs

The effects of selective cyclooxygenase (COX) isoform (COX-1, COX-2) inhibition, alone or in combination with nitric-oxide synthase (NOS) blockade, on in vitro tracheal muscle responsiveness to histamine were investigated in healthy and ovalbumin (OVA)-sensitized guinea pigs. Immunohistochemistry showed that COX-1 and COX-2 are constitutively present in normal guinea pig trachea, particularly in the epithelial layer, and that COX-2 expression is enhanced in OVA-sensitized animals both in epithelial and subepithelial tissues. In normal guinea pigs, SC-560 [5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-trifluoromethylpyrazole] (COX-1 inhibitor) or DFU [5,5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulphonyl)phenyl-2(5H)-furanone] (COX-2 inhibitor) significantly increased the contractile response to histamine, these effects being not additive. NOS inhibition by l-N(G)-nitro-arginine methyl ester (l-NAME) did not affect histamine-induced contraction but reversed the increase caused by COX-1 blockade while not modifying the enhancement associated with COX-2 inhibition. In guinea pigs subjected to OVA sensitization and challenge, COX-2, but not COX-1, inhibition enhanced the motor responses to histamine without any influence by l-NAME. In normal, but not in sensitized animals, the removal of epithelial layer from tracheal preparations abolished the enhancing action of DFU on histamine-mediated contraction. A COX-2-dependent release of prostacyclin (PGI(2)), but not prostaglandin E(2), was observed in tracheal tissues from normal and OVA-sensitized guinea pigs. In conclusion, both COX-1 and COX-2 are constitutive in guinea pig trachea, and COX-2 expression is enhanced by OVA sensitization; in normal animals, epithelial COX-2 exerts a PGI(2)-dependent inhibitory control on tracheal contractility, and this isoform is subjected to upstream regulation by epithelial COX-1 and NOS through a complex interplay; and following antigen sensitization, the inhibitory control on tracheal contractility is maintained by COX-2 induced at subepithelial cell sites.     

Role of lipoxygenase metabolites for the hyper-responsiveness to platelet-activating factor of lungs from actively sensitized guinea pigs

The contribution of lipoxygenase metabolites to active sensitization-induced lung hyper-responsiveness in the guinea pig was investigated. Active sensitization was performed by two injections of 10 micrograms of ovalbumin in 1 mg of AI(OH)3 at a 2-week interval. The i.a. administration of increasing doses (1, 100 and 1000 ng) of platelet-activating factor (PAF-acether) into isolated perfused lungs from actively sensitized guinea pigs was followed by an enhanced bronchoconstriction as compared to that observed in lungs from nonimmunized animals. PAF-acether stimulation of actively sensitized lungs was accompanied by histamine secretion and by an increased release of leukotriene (LT)-like material (as detected by bioassay using guinea pig tracheal strips superfused with the lung effluent and by a radioimmunoassay for LTC4). Maximal PAF-acether-induced lung responses were observed 7 days after the booster injection of the antigen and remained at a plateau for at least 4 months. Lung response to antigen challenge occurred in parallel with the increase of the level of circulating immunoglobulin G and with the development of hyper-responsiveness up to 7 days after the booster injection. Then, a progressive decrease in the antigen-induced bronchoconstriction and mediator release was observed. Lungs from animals in which the booster injection was omitted responded to PAF-acether in a similar fashion as lungs from nonimmunized guinea pigs, even though they underwent anaphylactic reaction upon antigen challenge. Enhanced bronchoconstriction, tracheal contraction, immunoreactive LTC4-like material release, but not histamine secretion were suppressed by BW 755C, a mixed cyclooxygenase and lipoxygenase inhibitor.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cigarette smoke induces bronchoconstrictor hyperresponsiveness to substance P and inactivates airway neutral endopeptidase in the guinea pig. Possible role of free radicals.

We examined the effects of acute exposure to cigarette smoke on the airway responses to substance P in anesthetized guinea pigs and on the activity of airway neutral endopeptidase (NEP). After exposure to air or to cigarette smoke we measured the change in total pulmonary resistance (RL) induced by increasing concentrations of aerosolized substance P in the absence or presence of the NEP inhibitor phosphoramidon. In the absence of phosphramidon the bronchoconstrictor responses to substance P were greater in cigarette smoke-exposed guinea pigs than in air-exposed animals. Phosphoramidon did not further potentiate the responses to substance P in smoke-exposed guinea pigs, whereas it did so in air-exposed animals. In the presence of phosphoramidon, bronchoconstrictor responses to substance P in animals exposed to air or to cigarette smoke were not different. Aerosols of SOD delivered before cigarette smoke exposures dramatically reduced smoke-induced hyperresponsiveness to substance P, whereas heat-inactivated SOD had no effect on smoke-induced hyper-responsiveness to substance P. Cigarette smoke solution inhibited NEP activity from tracheal homogenate in a concentration-dependent fashion, an inhibitory effect that was mostly due to the gas phase of the smoke, but not to nicotine. The mild chemical oxidant N-chlorosuccinimide mimicked the concentration-dependent inhibitory effect of smoke solution on airway NEP activity. We conclude that cigarette smoke causes enhanced airway responsiveness to substance P in vivo by inactivating airway NEP. We suggest that cigarette smoke-induced inhibition of airway NEP is due to effects of free radicals.     

Effect of ozone treatment on airway reactivity and epithelium-derived relaxing factor in guinea pigs

Ozone (O(3)) is toxic to respiratory epithelium and causes airway inflammation and hyperreactivity. To evaluate the role of the epithelium in the development of hyperreactivity, we examined in guinea pigs the effects of inhaled O(3) (3 ppm for 1 h; 0-24 h after exposure) on 1) reactivity to inhaled methacholine (MCh), 2) reactivity of the isolated, perfused trachea (IPT) to MCh, 3) epithelium-derived relaxing factor (EpDRF)-mediated relaxations of IPT induced by mucosal hyperosmolar solutions, 4) neurogenic contraction and relaxation responses, 5) transepithelial potential difference, and 6) microscopic analysis of nitrotyrosine immunofluorescence, substance P fiber density, and tracheal morphology. At 0 h, O(3) caused hyperreactivity to inhaled MCh and mucosally but not serosally applied MCh in IPT (only in the presence of the epithelium) and a decrease in transepithelial potential difference. Inhibition of EpDRF-induced relaxation responses occurred at 2 h. All of these changes returned to control by 12 to 18 h. O(3) had no effect on neurogenic responses. Nitrotyrosine immunofluorescence appeared in the trachea at 0 h in detached epithelial cell ghosts and in intrapulmonary airways by 6 h. Substance P fiber density was elevated in smooth muscle at 0 and 18 h but not in epithelium or lamina propria of intrapulmonary and extrapulmonary bronchi. Loss of cilia and mucosubstances in the mucosa occurred at 0 h; the epithelium became markedly attenuated over 12 to 24 h. A reversible increase in epithelial permeability and a decrease in EpDRF production may contribute to O(3)-induced hyperreactivity to MCh.     

THE RELATION BETWEEN ANTIANAPHYLAXIS AND ANTIBODY BALANCE : II. THE EFFECT OF SPECIFIC DESENSITIZATION UPON RESISTANCE TO INFECTION AND UPON ANTIBODY BALANCE

It has been shown that antianaphylaxis is not caused by a partial saturation of cellular or humoral antibodies by the following facts. 1. Guinea pigs passively sensitized with anti-horse or antipneumococcus serum and specifically desensitized do not manifest as great a reactivity upon resensitization with the same antiserum as upon the original sensitization. 2. Guinea pigs passively sensitized with anti-Friedländer Type B serum or antipneumococcus Type II serum and specifically desensitized do not attain the same degree of reactivity as normal animals when passively sensitized with anti-horse serum. 3. Guinea pigs passively sensitized with anti-Friedländer Type B serum and desensitized with the specific carbohydrate remain as resistant to infection with Friedlander''s bacillus Type B as undesensitized guinea pigs. Since in this case, at least, it is agreed that type-specific immunity and type-specific hypersensitiveness are due to the same type-specific antibody, a change in anaphylactic response should be accompanied by a change in immune response, provided this change depends on antibody balance. 4. A determination of the antibody content of the serum of sensitized as well as of desensitized guinea pigs by mouse protection tests indicates that a loss of reactivity in desensitized animals cannot be adequately accounted for on the basis of depletion of circulating antibody. These experiments suggest that hypersensitiveness and resistance are different manifestations of the same antigen-antibody reaction while antianaphylaxis is a state of refractoriness which is due neither to excess of circulating antibody nor to antibody depletion, but is the result of secondary changes the true nature of which is still not definitely established.     

Kinetics of Eotaxin Generation and Its Relationship to Eosinophil Accumulation in Allergic Airways Disease: Analysis in a Guinea Pig Model In Vivo

Challenge of the airways of sensitized guinea pigs with aerosolized ovalbumin resulted in an early phase of microvascular protein leakage and a delayed phase of eosinophil accumulation in the airway lumen, as measured using bronchoalveolar lavage (BAL). Immunoreactive eotaxin levels rose in airway tissue and BAL fluid to a peak at 6 h falling to low levels by 12 h. Eosinophil numbers in the tissue correlated with eotaxin levels until 6 h but eosinophils persisted until the last measurement time point at 24 h. In contrast, few eosinophils appeared in BAL over the first 12 h, major trafficking through the airway epithelium occurring at 12–24 h when eotaxin levels were low. Constitutive eotaxin was present in BAL fluid. Both constitutive and allergen-induced eosinophil chemoattractant activity in BAL fluid was neutralized by an antibody to eotaxin. Allergen-induced eotaxin appeared to be mainly in airway epithelium and macrophages, as detected by immunostaining. Allergen challenge of the lung resulted in a rapid release of bone marrow eosinophils into the blood. An antibody to IL-5 suppressed bone marrow eosinophil release and lung eosinophilia, without affecting lung eotaxin levels. Thus, IL-5 and eotaxin appear to cooperate in mediating a rapid transfer of eosinophils from the bone marrow to the lung in response to allergen challenge.     

THE BACTERIAL INDUCTION OF HOMOGRAFT SENSITIVITY : I. EFFECTS OF SENSITIZATION WITH GROUP A STREPTOCOCCI

Heat-killed Group A hemolytic streptococci can induce in guinea pigs a state of altered reactivity to skin homografts which is indistinguishable from that which results from sensitization with homologous tissues. Challenge of suitably prepared recipients with first-set skin homografts obtained from unrelated randomly selected donors elicits white graft reactions or accelerated rejection of such grafts. The gross and histologic appearance of these grafts is identical with that observed in similar reactions obtained in guinea pigs sensitized with homologous tissues. The ability of Group A hemolytic streptococci to induce homograft sensitivity in the guinea pig is a property shared by Types 4, 5, 6, 11, 12, 14, and 49 of Group A streptococci.     

Effect of removal of epithelium on antigen-induced smooth muscle contraction and mediator release from guinea pig isolated trachea

We examined the effect of removal of the epithelium on antigen-induced smooth muscle contraction and the release of mediators of inflammation from superfused, sensitized guinea-pig tracheal spirals in vitro. The epithelium was stripped from one-half of each trachea by mechanical means, and immunologic responses were evaluated by paired analysis. Removing the epithelium potentiated antigen-induced contraction, as reflected by a 5-fold leftward shift in the antigen dose-response curve, but the maximum response to antigen was not altered. This potentiation was not inhibited by pretreating the tissues with indomethacin (5 X 10(-6) M). At maximum concentrations of antigen removing the epithelium had no effect on the magnitude or kinetics of release of immunoreactive sulfidopeptide leukotrienes, prostaglandin (PG) D2, PGF2 alpha or thromboxane B2. Removing the epithelium did, however, significantly decrease the release of PGE and 6-keto-PGF1 alpha, a prostacyclin metabolite. Antigen-induced histamine release was enhanced by removing the epithelium; this effect varied inversely with antigen concentration. Selectively exposing either the luminal or serosal surface of an intact, superfused trachea to antigen resulted in the release of less than 5% of the total tissue histamine. Removing the epithelium from the intact trachea increased histamine release to approximately 25% following luminal but not serosal exposure to antigen. These studies demonstrate that the tracheal epithelium can act to inhibit antigen-induced airway contraction in vitro. This may in part reflect the role of the intact epithelium as a diffusion barrier which can limit the rate of influx of antigen molecules and thereby influence tissue mast cell activation.     

Bombesin-induced bronchoconstriction in the guinea pig: mode of action

Bombesin is a potent bronchoconstrictor in guinea pigs in vivo, but the mechanisms of its effect are not certain. In vivo increases in tracheal pressure induced by bombesin were measured as an index of airway caliber. Bombesin (0.3-10 micrograms/kg) produced a dose-related bronchoconstrictor response in vivo which was not inhibited by indomethacin (5 mg/kg), BW A4C (50 mg/kg, a lipoxygenase inhibitor), WEB 2086 (10 micrograms/kg, a platelet-activating factor antagonist) or mepyramine (10 mg/kg, a histamine H1-receptor antagonist). Capsaicin pretreatment (50 mg/kg), which depletes neuropeptides from sensory nerve endings, similarly failed to inhibit the action of bombesin. Propranolol (1 mg/kg) produced a small shift to the left and atropine (1 mg/kg) and the serotonin antagonist, methysergide (1 mg/kg), produced a small shift to the right in the bombesin dose-response curve. The bombesin receptor antagonist, BIM 26159 (50 micrograms/kg), transiently inhibited bombesin-induced bronchoconstriction. Isoproterenol (0.1-10 micrograms/kg) reversed the increase in tracheal pressure induced by bombesin, suggesting that contraction of airway smooth muscle was involved. Bombesin (10(-10)-3 x 10(-5) M) failed to produce contraction in trachea or main bronchi either denuded of epithelium or in tissues pretreated with phosphoramidon, captopril or indomethacin (all 10(-5) M) and was inactive in peripheral lung strip preparations. Thus, bombesin is a potent constrictor of guinea pig airways in vivo. The inability of bombesin to contract airway smooth muscle in vitro suggests that the bronchoconstrictor action of bombesin is largely due to the release of an unidentified spasmogenic substance.     

Parainfluenza 3 Infection Blocks the Ability of a Beta Adrenergic Receptor Agonist to Inhibit Antigen-induced Contraction of Guinea Pig Isolated Airway Smooth Muscle

Guinea pigs, actively sensitized to ovalbumin, were inoculated by nasal insufflation with parainfluenza 3 or virus growth medium 4 d before performing in vitro pharmacological studies on tracheal and bronchial smooth muscle. In each airway segment, cumulative dose-response effects of ovalbumin were obtained in the absence and presence of a maximally effective concentration of a beta adrenergic receptor agonist, sulfonterol. Sulfonterol shifted the dose-response curve to the right and reduced the maximum smooth muscle contractile response to ovalbumin. Virus infection did not alter the dose-response effects of ovalbumin. However, the magnitude of the inhibitory effects of sulfonterol was smaller in segments taken from animals inoculated with virus. Blockade by virus infection of the inhibitory effect of sulfonterol was reversed when the concentrations of beta agonist were increased. Sulfonterol did not alter the dose-response effects of histamine at any of the concentrations that markedly antagonized the effects of ovalbumin. Virus infection did not alter the sensitivities to sulfonterol or papaverine in producing relaxation in either airway segment. The magnitude of relaxation produced by papaverine was significantly larger in bronchial rings taken from animals infected with virus for 4 d, but there was no alteration by virus of the dose-response effects of histamine or carbachol. In experiments measuring antigen-induced release of slow reacting substance of anaphylaxis and histamine from minced lung, virus infection did not alter the sensitivity or the maximum effects of ovalbumin. Also, the ability of sulfonterol to inhibit the release of slow reacting substance of anaphylaxis and histamine was not affected by virus infection.These results demonstrate that infection of guinea pigs with respiratory virus results in a selective blockade of the beta adrenergic-mediated inhibition of antigen-induced contraction of airway smooth muscle. The guinea pig may serve as a useful model in physiological studies of virus-induced asthma.     

Pretreatment with antibody to eosinophil major basic protein prevents hyperresponsiveness by protecting neuronal M2 muscarinic receptors in antigen-challenged guinea pigs.

In antigen-challenged guinea pigs there is recruitment of eosinophils into the lungs and to airway nerves, decreased function of inhibitory M2 muscarinic autoreceptors on parasympathetic nerves in the lungs, and airway hyperresponsiveness. A rabbit antibody to guinea pig eosinophil major basic protein was used to determine whether M2 muscarinic receptor dysfunction, and the subsequent hyperresponsiveness, are due to antagonism of the M2 receptor by eosinophil major basic protein. Guinea pigs were sensitized, challenged with ovalbumin and hyperresponsiveness, and M2 receptor function tested 24 h later with the muscarinic agonist pilocarpine. Antigen-challenged guinea pigs were hyperresponsive to electrical stimulation of the vagus nerves compared with controls. Likewise, loss of M2 receptor function was demonstrated since the agonist pilocarpine inhibited vagally-induced bronchoconstriction in control but not challenged animals. Pretreatment with rabbit antibody to guinea pig eosinophil major basic protein prevented hyperresponsiveness, and protected M2 receptor function in the antigen-challenged animals without inhibiting eosinophil accumulation in the lungs or around the nerves. Thus, hyperresponsiveness is a result of inhibition of neuronal M2 muscarinic receptor function by eosinophil major basic protein in antigen-challenged guinea pigs.     

Exogenous irritant-induced airway hyperreactivity and inhibition of soluble guanylyl cyclase

The majority of nitric oxide (NO) effects in the respiratory system are caused by stimulation of soluble guanylyl cyclase (sGC) with subsequent increase of cyclic guanosine monophosphate (cGMP) production. The importance of this mechanism of NO action in airway hyperreactivity (AHR) pathogenesis is unknown. Therefore, the aim of our experiment was to examine the changes of airway reactivity enhanced by toluene vapor exposure in the presence or inhibition of sGC activity in guinea pigs. Animals were treated with a nonspecific sGC inhibitor, methylene blue, in a dose of 50 or 100 mg/kg body weight, administered by intraperitoneal injection 30 min before or after exposure to toluene vapors. The toluene exposure lasted 2 hr in each of 3 consecutive days under in vivo conditions. Thereafter, the tracheal and lung tissue smooth muscle response to cumulative doses of mediators (histamine or acetylcholine) was recorded under in vitro conditions. The exposure to toluene vapors significantly increased the airway reactivity to both mediators in comparison with the healthy animal group. The administration of methylene blue decreased the amplitude of airway smooth muscle contraction in toluene-induced hyperreactivity. The decreases were dependent on the inhibitor doses, on a regimen of administration (before or after toluene inhalation), the level of the respiratory system (trachea, lung), and the bronchoconstrictor mediators. Our results suggest that the interaction between NO and sGC may be important for airway reactivity changes, but other mechanisms of NO action are important in AHR pathogenesis, too.     

Peripheral type benzodiazepine receptor and airway smooth muscle relaxation

It has been postulated that a benzodiazepine receptor with a micromolar affinity may be associated with Ca++ channels in peripheral organs. We examined the actions of Ro5-4684 (parachlorodiazepam) and midazolam on guinea pig tracheal smooth muscle contraction. Binding studies using [3H]Ro5-4684 indicate the presence of a "peripheral" type binding site with a Kd of approximately 4 nM and maximum binding of 1 pmol/mg of protein. Midazolam did not displace radioligand. In tension studies no activity was seen for Ro5-4684 or midazolam at concentrations below 1 microM. Higher concentrations relaxed the airway smooth muscle under basal tone, the effect was augmented significantly by epithelium removal. Similar results were obtained in tissues precontracted with methacholine or KCl. Midazolam (1 or 100 microM) significantly (P less than .05) attenuated the response to Ca++ in K+-depolarized tracheal strips, the effect was greater at low Ca++ concentrations. The compounds appear to function as Ca++ antagonists in airway smooth muscle but ar not typical as shown by their ability to reduce basal tone in airway smooth muscle.     

Influence of electrical field stimulation on antigen-induced contraction and mediator release in the guinea pig isolated superfused trachea and bronchus

These studies examined the ability of electrical field stimulation (EFS) to influence antigen-induced responses in the guinea pig isolated trachea and main-stem bronchi. Airways isolated from guinea pigs actively sensitized to ovalbumin were superfused and stimulated transmurally with square pulses of 1 msec duration at a frequency of 16 pulses per sec. In the trachea, EFS caused an atropine-sensitive contraction followed by a maintained relaxation. The relaxation consisted of adrenergic and nonadrenergic components. In the bronchus, EFS caused a maintained contraction. This contraction was due to a combination of cholinergic (atropine-sensitive) and noncholinergic (capsaicin-sensitive) mechanisms. Histamine could not be detected in superfusate samples during electrical stimulation alone of either the trachea or bronchus. EFS significantly inhibited ovalbumin-induced tracheal contractions by about 30% without altering ovalbumin-induced histamine or immunoreactive peptido-leukotriene release from the tissues. EFS had a similar inhibitory effect on the contraction induced by application of exogenous histamine (10(-5) M). The electrical stimulus-induced inhibition of the antigen-induced contraction was abolished by tetrodotoxin and propranolol and reduced by a combination of atropine, propranolol and phentolamine. Norepinephrine (5 x 10(-6) M) inhibited ovalbumin-induced histamine release by about 30% without altering the contraction. Carbamylcholine had no effect on ovalbumin-induced histamine release. In the guinea pig bronchus, EFS stimulation had no effect on either histamine release or contraction induced by ovalbumin. These results demonstrate that in the guinea pig trachea nerve stimulation can significantly antagonize antigen-induced contractions and suggest that this is due to a functional antagonism by adrenergic and nonadrenergic relaxant neurotransmitters at the level of the airway smooth muscle.(ABSTRACT TRUNCATED AT 250 WORDS)     

Antibody to VLA-4, but not to L-selectin, protects neuronal M2 muscarinic receptors in antigen-challenged guinea pig airways.

Antigen challenge of sensitized guinea pigs decreases the function of inhibitory M2 muscarinic autoreceptors on parasympathetic nerves in the lung, potentiating vagally induced bronchoconstriction. Loss of M2 receptor function is associated with the accumulation of eosinophils around airway nerves. To determine whether recruitment of eosinophils via expression of VLA-4 and L-selectin is critical for loss of M2 receptor function, guinea pigs were pretreated with monoclonal antibodies to VLA-4 (HP1/2) or L-selectin (LAM1-116). Guinea pigs were sensitized and challenged with ovalbumin, and M2 receptor function was tested. In controls, blockade of neuronal M2 muscarinic receptors by gallamine potentiated vagally induced bronchoconstriction, while in challenged animals this effect was markedly reduced, confirming M2 receptor dysfunction. Pretreatment with HP1/2, but not with LAM1-116, protected M2 receptor function in the antigen-challenged animals. HP1/2 also inhibited the development of hyperresponsiveness, and selectively inhibited accumulation of eosinophils in the lungs as measured by lavage and histology. Thus, inhibition of eosinophil influx into the lungs protects the function of M2 muscarinic receptors, and in so doing, prevents hyperresponsiveness in antigen-challenged guinea pigs.     

STUDIES ON DELAYED HYPERSENSITIVITY : I. INFERENCES ON THE COMPARATIVE BINDING AFFINITIES OF ANTIBODIES MEDIATING DELAYED AND IMMEDIATE HYPERSENSITIVITY REACTIONS IN THE GUINEA PIG

Experiments carried out with several well defined antigenic systems (hapten conjugates of poly-L-lysine and guinea pig serum albumin) in guinea pigs demonstrated that: 1. Arthus reactions also manifest carrier specificity, although to a smaller extent than do delayed hypersensitivity reactions. 2. Desensitization by injection of minute doses of antigen results in moderate specific desensitization of delayed hypersensitivity without desensitization of Arthus reactivity to the same antigenic determinant. 3. Insoluble antigen-antibody complexes prepared from high affinity guinea pig antibodies can elicit specific delayed skin reactions in sensitized guinea pigs. 4. Homologous conjugates of structurally similar haptens show considerably less cross-reactivity in delayed reactions than in immediate hypersensitivity reactions to the same antigenic determinant. These experimental results are interpreted as indicating that delayed hypersensitivity reactions in the guinea pig are mediated by "antibodies" of comparatively high binding affinities. High binding affinities are achieved for these antibodies more likely by closer structural adaptation between antigen and antibody than by a larger area of specific contact.     

Experimental hypersensitivity pneumonitis: transfer with cultured cells

The importance of antibody and sensitized cells in hypersensitivity pneumonitis (HP) is unknown. In an attempt to create a model suitable for investigation of the mechanisms of HP, we transferred cells and serum from sensitized (Micropolyspora faeni in Freund's adjuvant) strain 2 guinea pigs to naive animals. Cells (peritoneal exudate, lymph node, or spleen) were cultured for 72 hours with either concanavalin A (Con A, 1 microgram/ml) or a soluble extract of M. faeni (10 micrograms/ml). We then injected the cells intravenously (IV) into naive guinea pigs, skin tested with purified protein derivative (PPD), challenged the animals intratracheally (IT) with M. faeni 48 hours after the cell transfer, and killed them 4 days (IT) with M. faeni 48 hours after the cell transfer, and killed them 4 days after IT challenge. We also transferred noncultured cells and antibody-containing serum from sensitized animals. Randomly selected microscopic fields of the lung (150 per animal) were judged to be normal or abnormal. All guinea pigs were maintained in high-efficiency particulate accumulator-filtered air. Compared with control animals that received media IV, there was a substantial increase (P less than 0.01) in the extent of pulmonary abnormalities in the animals receiving lymph node cells or spleen cells cultured with M. faeni, and peritoneal exudate cells cultured with Con A. Findings in recipients of peritoneal exudate cells cultured with M. faeni, or lymph node cells or spleen cells cultured with Con A did not differ from those in the control group. In contrast to cultured cells, noncultured cells and antibody-containing serum did not transfer susceptibility. PPD skin reactivity was present only in recipients of noncultured cells and not in recipients of serum or cultured cells. We conclude that experimental HP can be transferred with cultured cells from sensitized animals and that HP appears to be a cell-mediated process.     

An examination of the influence of the epithelium on contractile responses to peptidoleukotrienes and blockade by ICI 204,219 in isolated guinea pig trachea and human intralobar airways

The influence of the epithelium on antagonism by ICI 204,219 of contractile responses to peptide leukotriene (LT) agonists was examined in guinea pig tracheal and human bronchial rings. The -log molar KB values for ICI 204,219 were found to be independent of the epithelium in both tissues. Even though uninfluenced by the epithelium, the -log molar KB values for ICI 204,219 were about 10-fold smaller in human airways than in guinea pig trachea. Removal of the epithelium from guinea pig trachea resulted in small leftward shifts of the concentration-response curves to LTC4 and LTD4 and rightward shifts of the concentration-response curves to LTE4 when examined in the presence of indomethacin. The potentiation of LTC4 and LTD4 by epithelium removal was not seen in the presence of inhibitors of the transformation of LTC4 to LTD4 and LTD4 to LTE4. The influence of the epithelium on responses to LTE4 remained in the presence of these metabolic inhibitors. The lipoxygenase inhibitors nordihydroguaiaretic acid, B755C, Rev 5901 and AA861 antagonized responses to LTE4 in the presence, but not in the absence of epithelium. In human airways, epithelium removal resulted in a small leftward shift of the concentration-response curve to LTD4 whereas responses to LTC4 and LTE4 were unaltered. This effect was not observed in the presence of indomethacin, relating it to reduced release of cyclooxygenase products. These data suggest that contractile responses of guinea pig trachea to LTE4 are modulated by LTE4-induced release of 5-lipoxygenase product(s) only when the epithelium is present.(ABSTRACT TRUNCATED AT 250 WORDS)