Repeated aeroallergen challenge induces lung dysfunction but not bronchial hyperresponsiveness in conscious guinea pigs.

Adult male Hartley-strain guinea pigs were sensitized by 10 min exposure to aerosolized 1% ovalbumin (OA; 10 mg/ml in normal saline containing 4% heat-killed B. pertussis vaccine and 0.02% antifoam B emulsion). One week after sensitization, animals were placed in an exposure chamber and challenged (nebulized OA 0.5%) until each animal showed labored breathing. Maximal exposure time was 10 min. Diphenhydramine (20 mg/kg, i.p.) was given 1 h before each OA challenge to protect the animals from bronchospasmic death. Antigen challenge was repeated twice a week for 2 weeks. The specific airway resistance (sR(aw)) changes in response to increasing concentrations of aerosolized acetylcholine (Ach) were determined. The data obtained in this study demonstrated that repeated antigen challenge produced a significant bronchial tone i.e. an increase in sR(aw) and a decline in specific airway conductance (sG(aw)) and failed to induce bronchial hyperreactivity to aerosolized acetylcholine (Ach) in conscious guinea pigs.     

Decrease in ovalbumin-induced pulmonary allergic response by benzaldehyde but not acetaldehyde exposure in a Guinea pig model

The pulmonary effects of two environmentally relevant aldehydes were investigated in nonsensitized or ovalbumin (OA)-sensitized guineapigs (GPs). Four-week-old male Hartley GPs, weighing about 400 g, were intraperitoneally injected with 1 ml of an NaCl solution containing 100 microg OA and 100 mg Al(OH)(3). They were then exposed to either acetaldehyde (200 ppb) or benzaldehyde (500 ppb) for 4 wk (6 h/d, 5 d/wk). At the end of exposure, GPs were challenged with an OA aerosol (0.1% in NaCl) and pulmonary functions were measured. The day after, guinea pigs were anesthetized and several endpoints related to inflammatory and allergic responses were assessed in blood, whole-lung histology, and bronchoalveolar lavage (BAL). Sensitized nonexposed GPs showed bronchial hyperresponsiveness to OA and an increased number of eosinophils in blood and BAL, together with a rise in total protein and leukotrienes (LTB(4) and LTC(4)/D(4)/E(4)) in BAL. In nonsensitized GPs, exposure to acetaldehyde or benzaldehyde did not induce any change in the tested parameters, with the exception of irritation of the respiratory tract as detected by histology and an increased number of alveolar macrophages in animals exposed to acetaldehyde. In sensitized GPs, exposure to acetaldehyde induced a moderate irritation of the respiratory tract but no change in biological parameters linked to the inflammatory and allergic responses. In contrast, exposure to benzaldehyde induced a decrease both in OA-induced bronchoconstriction and in eosinophil and neutrophil numbers in BAL, an increase in the bronchodilatator mediator prostaglandin E(2) (PGE(2)), and a decrease in the bronchoconstrictor mediators LTC(4)/D(4)/E(4). Further investigations are needed to determine if the attenuated response observed in sensitized GPs exposed to benzaldehyde is due to an alteration of the mechanism of sensitization or to a more direct effect on various mechanisms of the allergic response.     

Intratracheal sensitization/challenge-induced biphasic asthmatic response and airway hyperresponsiveness in guinea pigs

In most experimental model of asthma using guinea pigs, the animals are made to inhale an aerosolized antigen which passes through the nasal cavity. In the present study, we attempted to create an animal model of asthma showing a biphasic asthmatic response and airway hyperresponsiveness, in which the allergic responses are restricted to the lung. Guinea pigs were sensitized by the intratracheal instillation of ovalbumin (OVA)+Al(OH)? once a day for 7 d, and then intratracheally challenged with OVA 12 d after the last sensitization. The change in specific airway resistance (sRaw) and airway responsiveness to histamine were measured. Pranlukast (100 mg/kg), theophylline (50 mg/kg), and dexamethasone (10 mg/kg) were orally administered 18 and 2 h before the antigen challenge. The challenge caused a marked biphasic elevation of sRaw with peaks at 5 min and 4 h. At 24 h, airway hyperresponsiveness to histamine was observed. Pranlukast, theophylline, and dexamethasone suppressed the late asthmatic response and airway hyperresponsiveness. The early asthmatic response was inhibited by theophylline and dexamethasone. In conclusion, the intratracheal sensitization and challenge caused a biphasic asthmatic response and airway hyperresponsiveness in guinea pigs. This model may be useful for the evaluation of anti-asthma drugs.     

Participation of chemical mediators in the development of experimental allergic conjunctivitis in rats

In the present study, we investigated the participation of chemical mediators in the development of experimental allergic conjunctivitis in rats. Cetirizine (a histamine H1 receptor antagonist), ramatroban (a thromboxane A2 (TXA2) receptor antagonist) and zafirlukast (a cysteinyl leukotrienes (cys-LTs) receptor antagonist) were orally administered from day 14 to day 42 during repeated topical antigen challenge. An increase in reactivity to antigen- and histamine-induced eye scratching behavior was observed by topical sensitization in sensitized rats. Although increased reactivity to antigen was not influenced by cetirizine, ramatoroban and zafirlukast, increased reactivity to histamine was significantly inhibited by ramatroban. The development of conjunctival edema was also observed for topical sensitization. Cetirizine caused no inhibition of the development of conjunctival edema, but ramatroban and zafirlukast inhibited the development of conjunctival edema. In addition, the number of eosinophils in the conjunctiva was increased by topical sensitization. Cetirizine had no significant effect on the increase in the number of eosinophils. However, ramatroban and zafirlukast were effective in inhibiting an increase in the number of eosinophils induced by topical sensitization. These results indicate that TXA2 is involved in increased histamine reactivity, and TXA2 and cys-LTs are associated with not only the conjunctival edema but also eosinophil infiltration during the development of experimental allergic conjunctivitis in rats.     

Activation of hamster mast cells for IgE-mediated histamine release

The conditions for active sensitization of hamster peritoneal and pleural mast cells and IgE-induced histamine release as well as cell desensitization were defined. Immunization of hamsters with ovalbumin (5 micrograms) in Al/OH/3 gel (5 mg) with several boosters resulted in sensitization of peritoneal and pleural mast cells; in the presence of extracellular Ca++, pH of medium 7.2 and at 37 degrees C these cells released up to 70% of histamine on the challenge with specific antigen. Partial release was observed when the cells were challenged with antigen in the absence of extracellular calcium. The rate of release is high during the first seconds of activation and is complete at 1 min. 30 min preincubation of peritoneal and pleural mast cells in calcium-free conditions (in the presence of 4 mM EDTA) resulted in complete desensitization of cells to subsequent action of antigen in optimal conditions. The present experiments demonstrate, that hamster peritoneal and pleural mast cells can be a useful model system for in vitro studies of the mechanisms of IgE-induced cell activation.     

Dose-dependent allergic responses to an extract of Penicillium chrysogenum in BALB/c mice

Indoor mold has been associated with the development of allergic asthma. Penicillium chrysogenum, a common indoor mold, is known to have several allergens and can induce allergic responses in a mouse model of allergic penicilliosis. Our hypothesis is that soluble components of P. chrysogenum (PCE) can dose-dependently induce responses typical of allergic asthma in BALB/c mice. Mice were exposed to 10, 20, 50, or 70 microg of PCE by involuntary aspiration four times over a 4-week period. Serum and bronchoalveolar lavage fluid (BALF) were collected before (day 0), and at days 1 and 3 following the final exposure. PCE-exposed mice demonstrated dose-dependent increases in: BALF total cell numbers including eosinophil, serum and BALF total IgE levels, BALF IL-5 levels, and increased severity of histopathologic lesions. A single exposure to the highest dose of PCE resulted in edema and cellular damage but not immune responses. Four exposures to Metarhizium anisopliae crude antigen (10 microg, positive control) resulted in equivalent or greater allergic asthma-like responses than those demonstrated by multiple exposures to 50 or 70 microg of PCE. Multiple exposures to 70 microg of PCE showed increased allergen-triggered immediate respiratory responses as well as non-specific airway hyperresponsiveness to methacholine as assessed by barometric whole-body plethysmography. Taken together, repeated pulmonary challenge with P. chrysogenum extract induced dose-dependent allergic asthma-like responses in mice.     

A new model of allergic rhinitis in rats by topical sensitization and evaluation of H(1)-receptor antagonists

An animal model of chronic allergic rhinitis was developed by repeated local booster sensitization into the nasal cavity in sensitized rats. The severity of allergic rhinitis was assessed by determining the extent of two markers of nasal allergic symptoms (sneezing and nasal rubbing) after antigen challenge. The number of incidents of sneezing and nasal rubbing was markedly increased during intranasal instillation of antigen in sensitized rats. The PCA titers were also markedly elevated by intranasal sensitization. Some histamine H(1)-receptor antagonists such as chlorpheniramine, ketotifen, astemizole and epinastine inhibited the increase in antigen-induced nasal symptoms in a dose-related manner. Nasal rubbing was more potently inhibited by H(1)-receptor antagonists than sneezing.In conclusion, we developed a chronic allergic rhinitis model showing nasal symptoms in rats, and this model may be useful for evaluating the effects of drugs on allergic rhinitis.     

Microinjection of CART peptide 55-102 into the nucleus accumbens blocks both the expression of behavioral sensitization and ERK phosphorylation by cocaine

The role of the biologically active CART 55-102 peptide in the nucleus accumbens (NAcc) in the expression of cocaine-induced behavioral sensitization was investigated. Rats were divided into four groups: one for saline and the other three for cocaine pre-exposures (15 mg/kg, i.p., once daily for 7 days). After 3 weeks of withdrawal, rats were microinjected into the NAcc either saline or CART 55-102 (1.0, or 2.5 microg/0.5 microl/side) followed by cocaine challenge (10 mg/kg, i.p.). Microinjection into the NAcc of CART 55-102 peptide dose-dependently blocked the expression of locomotor sensitization produced by repeated cocaine pre-exposures. Next, we further examined the effect of CART 55-102 microinjection on extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation levels in the NAcc. Additional four groups of rats were all cocaine pre-exposed and, after 3 weeks of withdrawal, they were either saline or cocaine challenged systemically following microinjection into the NAcc of either saline, CART 55-102 (2.5 microg/0.5 microl/side), or the equivalent mole amount of inactive CART 1-27 peptide. The increase of ERK1/2 phosphorylation levels in the NAcc by cocaine was completely blocked by CART 55-102 microinjection in this site, while it remains unaffected by inactive CART 1-27 peptide. These results suggest that CART 55-102 peptide in the NAcc may play a compensatory inhibitory role in the expression of behavioral sensitization by cocaine and these effects may be mediated by its inhibition of ERK1/2 phosphorylation in this site.     

Allergen-triggered airway hyperresponsiveness and lung pathology in mice sensitized with the biopesticide Metarhizium anisopliae

Metarhizium anisopliae is an entomopathogenic fungus recently licensed for indoor control of cockroaches, a major source of allergens. While M. anisopliae has been shown to be non-infectious and non-toxic to mammals there has been only limited research on potential allergenicity. Using a mouse model, we previously demonstrated allergic immune and inflammatory responses to this agent. The present study was designed to determine whether these responses were associated with changes in pulmonary responses, lung pathology, and the cytokine profile in bronchoalveolar lavage fluid (BALF). Soluble factors from fungal components were combined in equal protein amounts to form M. anisopliae crude antigen (MACA). BALB/C mice were intratracheally (i.t.) challenged with 10 microg MACA 14 days post intraperitoneal sensitization with 25 microg fungal antigen in aluminum hydroxide adjuvant. Physiological and cellular changes were examined. The mice were tested for airway hyperresponsiveness before (No Chal) and after (1, 3, and 8 days post challenge (DPIT)) MACA IT challenge. Subsequently, serum, BALF and the lungs were harvested. All treatment groups concurrently demonstrated significant non-specific pulmonary inflammation (neutrophil influx) and increased pulmonary sensitivity to methacholine (Mch) at 1 DPIT MACA challenge. Where as both adjuvant treated and na?ve mice airway responses had returned to near normal levels by 3 DPIT, mice which were previously sensitized with MACA were still hyperresponsive to Mch challenge at 3 and 8 DPIT. This hyperresponsiveness correlates with eosinophil and lymphocyte influx, which is maximal at 3 DPIT and still elevated at 8 DPIT. Interleukin (IL) 5 was elevated for all treatment groups at 1 DPIT but only the MACA sensitized mice maintained elevated levels for both 3 and 8 DPIT. Furthermore, MACA sensitized mice had a more extensive inflammatory histopathology at all examined time points with peribronchial and perivascular infiltrates, like those associated with allergic responsiveness, peaking at 3 DPIT. These pulmonary pathologic changes appeared to be consistent with elevated levels of serum and BALF total IgE, BALF IL-4, eosinophils, and lymphocytes following MACA IT challenge in MACA sensitized mice. There were no significant differences among the three treatment groups with regard to BALF interferon (IFN) gamma. The cytokines profiled indicate a Th2-type response, which is reflected in the cellular influx and total IgE induction. These data further indicate that immune inflammatory responses, observed in mice following MACA sensitization and challenge, are associated with physiologic changes and histopathology characteristic of allergic disease.     

DECREASE IN OVALBUMIN-INDUCED PULMONARY ALLERGIC RESPONSE BY BENZALDEHYDE BUT NOT ACETALDEHYDE EXPOSURE IN A GUINEA PIG MODEL

The pulmonary effects of two environmentally relevant aldehydes were investigated in nonsensitized or ovalbumin (OA)-sensitized guineapigs (GPs). Four-week-old male Hartley GPs, weighing about 400 g, were intraperitoneally injected with 1 ml of an NaCl solution containing 100 µ g OA and 100 mg Al(OH) 3 . They were then exposed to either acetaldehyde (200 ppb) or benzaldehyde (500 ppb) for 4 wk (6 h/d, 5 d/wk). At the end of exposure, GPs were challenged with an OA aerosol (0.1% in NaCl) and pulmonary functions were measured. The day after, guinea pigs were anesthetized and several endpoints related to inflammatory and allergic responses were assessed in blood, whole-lung histology, and bronchoalveolar lavage (BAL). Sensitized nonexposed GPs showed bronchial hyperresponsiveness to OA and an increased number of eosinophils in blood and BAL, together with a rise in total protein and leukotrienes (LTB 4 and LTC 4 /D 4 /E 4 ) in BAL. In nonsensitized GPs, exposure to acetaldehyde or benzaldehyde did not induce any change in the tested parameters, with the exception of irritation of the respiratory tract as detected by histology and an increased number of alveolar macrophages in animals exposed to acetaldehyde. In sensitized GPs, exposure to acetaldehyde induced a moderate irritation of the respiratory tract but no change in biological parameters linked to the inflammatory and allergic responses. In contrast, exposure to benzaldehyde induced a decrease both in OA-induced bronchoconstriction and in eosinophil and neutrophil numbers in BAL, an increase in the bronchodilatator mediator prostaglandin E 2 (PGE 2 ), and a decrease in the bronchoconstrictor mediators LTC 4 /D 4 /E 4 . Further investigations are needed to determine if the attenuated response observed in sensitized GPs exposed to benzaldehyde is due to an alteration of the mechanism of sensitization or to a more direct effect on various mechanisms of the allergic response.     

Behavioural sensitization after repeated exposure to Δ9-tetrahydrocannabinol and cross-sensitization with morphine

RATIONALE: Repeated exposure to several drugs of abuse has been reported to induce behavioural sensitization. So far no evidence has been provided that such a phenomenon also applies to cannabinoids. OBJECTIVES: In this study we investigated if repeated exposure to Delta(9)-tetrahydrocannabinol (Delta(9)-THC) induces behavioural sensitization. In addition we tested the possibility of cross-sensitization between Delta(9)-THC and morphine. METHODS: Male Sprague-Dawley rats were administered for 3 days, twice daily, with increasing doses of Delta(9)-tetrahydrocannabinol (2, 4 and 8 mg/kg i.p.) or increasing doses of morphine (10, 20 and 40 mg/kg s.c.) or vehicle. After a washout of 14 days the animals were challenged with Delta(9)-THC (75 and 150 microg/kg i.v.), with a synthetic cannabinoid agonist WIN55212-2 (75 and 150 microg/kg i.v.) or with morphine (0.5 mg/kg i.v.), through a catheter inserted into the left femoral vein 24 h before, and the behaviour recorded. RESULTS: Rats previously administered with Delta(9)-THC showed a greater behavioural activation compared to controls in response to challenge with Delta(9)-THC (150 microg/kg i.v.) and to challenge with morphine (0.5 mg/kg i.v.). Similar to that observed after repeated opiates, this behavioural sensitization was characterized by stereotyped activity. Animals administered with a schedule of morphine that induces behavioural sensitization to morphine also showed a behavioural sensitization to challenge with cannabinoids (Delta(9)-HC and WIN55212-2, 75 and 150 microg/kg i.v.). The effect of the challenge with Delta(9)-THC was prevented by the administration of the CB1 antagonist SR141716A (1 mg/kg i.p.), 40 min beforehand. CONCLUSIONS: The results of the present study demonstrate that repeated exposure to Delta(9)-THC induces behavioural sensitization not only to cannabinoids but also to opiates. This cross-sensitization was symmetrical since rats behaviourally sensitized to morphine were also sensitized to cannabinoids. These observations further support the evidence of an interaction between the opioid and the cannabinoid system and might provide a neurobiological basis for a relationship between cannabis use and opiate abuse.     

Delayed type allergic itch-associated response induced by toluene-2,4-diisocyanate in hairless mice

To develop an allergic dermatitis model showing persistent scratching in mice, toluene-2,4-diisocyanate (TDI) was repeatedly painted onto the skin of hairless HR-1 mice, and induction of itch-associated scratching behavior was observed. When HR-1 mice were epicutaneously sensitized with 1% TDI and then challenged by repeated painting the cervicodorsal skin with 0.1% TDI once every 10 days until the 10th challenge, delayed type scratching responses peaked at 1 - 2 days after challenge. TDI at 0.1% hardly induced scratching in non-sensitized HR-1 mice. The delayed scratching response was influenced by neither an H(1) nor 5-HT(1/2) receptor antagonist. On the other hand, intradermal injection of histamine and serotonin induced frequent scratching in HR-1 mice. In conclusion, repeated application of TDI can induce delayed type allergic scratching. Although HR-1 mice are high responders to both histamine and serotonin, induction of the delayed response depends on neither of these chemical mediators. This delayed response may be useful in analyzing the mechanisms of allergic pruritis.     

Comparison of respiratory responses to Metarhizium anisopliae extract using two different sensitization protocols

Metarhizium anisopliae, an entomopathogenic fungus, is a prototypic microbial pesticide licensed for indoor control of cockroaches, a major source of allergens. We have previously demonstrated allergy and asthma-like responses in BALB/c mice intraperitoneally (IP) sensitized in the presence of adjuvant and intratracheally (IT) challenged with the soluble factors from M. anisopliae crude antigen (MACA) (Ward et al., 1998, 2000). This protocol has been used frequently to establish animal models of allergenicity. However, the sensitization protocol is artificial and not representative of an environmental exposure. Concern has been raised that this protocol might produce allergic responses that would not occur under normal environmental exposure conditions. The objective of this study was to compare responses in mice to MACA by two exposure protocols: (1) exclusive respiratory exposures without adjuvant (representative of environmental exposures) and (2) intraperitoneal sensitization in the presence of adjuvant followed by IT challenge (the traditional approach). The intratracheal protocol consisted of four IT exposures of 10 microg MACA in 50 microl HBSS each over a 4-week period. A vehicle control group of mice was exposed IT to HBSS. The intraperitoneal protocol consisted of IP sensitization with 25 microg MACA in 0.2 ml of 1.3% alhydrogel (aluminum hydroxide) followed 14 days later with an IT challenge (10 microg MACA/50 microl HBSS). Airway reactivity responsiveness to methacholine was assessed, serum and bronchoalveolar lavage fluid (BALF) samples were obtained, and the lungs were fixed for histopathology at 1, 3, and 8 days following the last MACA IT challenge. Both groups exhibited immune and pulmonary responses typical of allergic asthma. In general, local responses in the lung, including inflammatory responses (eosinophils, lymphocytes, and macrophages), BALF IgE, and functional responses to methacholine were greater in the IT sensitized group compared to the IP sensitized group, whereas the systemic IgE response was greater in the IP sensitized group. The BALF IL-5 cytokine levels were elevated before and throughout the eosinophil influx. IL-4 was detected in the BALF of IP sensitized, but not IT sensitized mice. Histopathologic changes in the two groups were similar in nature but more severe in the IT mice. The results suggest that the IP sensitization protocol does not induce the level of respiratory responsiveness that results from sensitization by a physiologically relevant route of exposure. Thus total serum IgE levels, which were greater following IP sensitization, may not be the best indicator of allergen potency, at least with respect to respiratory responses.     

Involvement of cyclooxygenase-2 in allergic nasal inflammation in rats

This study was undertaken to investigate the involvement of cyclooxygenase-2 (COX-2) in allergic nasal inflammation in actively sensitized rats. An allergic rhinitis model was developed by the repeated topical application of antigen into the nasal cavities in the sensitized rats. The severity of allergic rhinitis was studied by measuring the nasal behavior, as well as electroencephalogram (EEG) activity by antigen challenge. The electrodes were implanted chronically into the bilateral olfactory bulb of the rats and the EEG was measured monopolarly with an electroencephalograph (EEG, Nohon Kohden, Japan). The intranasal application of antigen caused the increase of nasal allergic signs as well as an EEG spike in a dose-dependent fashion, and at a dose of 50 microg/site, it showed a significant effect. The responses induced by the antigen were evaluated with certain drugs, etodolac (a selective COX-2 inhibitor), indomethacin (a non-selective COX inhibitor), ramatroban (a thromboxane A2 receptor antagonist) and zafirlukast (a cys-leukotriene receptor antagonist). Etodolac showed the inhibition of nasal behavior and EEG spike in a dose-related fashion, and at doses of 3 and 10 mg/kg, it showed a significant effect. Moreover, ramatroban also caused the dose-related inhibition of nasal behavior and EEG spike induced by antigen. On the other hand, both indomethacin and zafirlukast had no effects on the responses induced by antigen, even at a higher dose. Therefore, it can be concluded that cyclooxygenase-2 actively participates in the allergic nasal inflammation in actively sensitized rats.     

Effects of 5-HT1B receptor ligands microinjected into the ventral tegmental area on the locomotor and sensitizating effects of cocaine in rats.

The present study was aimed at finding out whether 5-HT(1B) receptors located in the ventral tegmental area (VTA) played a role in the locomotor hyperactivity induced by a single dose of cocaine and in the sensitization evoked by repeated exposure to the psychostimulant in rats. Male Wistar rats, implanted bilaterally with cannulae in the VTA, were microinjected with GR 55562 (an antagonist of 5-HT(1B) receptors) or CP 93129 (an agonist of 5-HT(1B) receptors). GR 55562 (0.3-3 microg/side) did not affect locomotor hyperactivity response to a single dose of cocaine (10 mg/kg). CP 93129 in a dose of 1 microg/side (but not lower), which stimulated basal locomotor activity, enhanced the cocaine-induced locomotor hyperactivity. The rats that were treated repeatedly (for 5 days) with cocaine (10 mg/kg) and then challenged with cocaine (10 mg/kg) after 5-day withdrawal period (day 10 of the experiment) showed significantly higher locomotor hyperactivity compared to the effect observed in saline-pretreated and cocaine-challenged rats. GR 55562 (a dose of 3 microg/side, but not lower), administered for 5 days into the VTA just prior to daily cocaine, attenuated cocaine sensitization. When injected for 5 days into the VTA, CP 93129 (0.03-0.1 microg/side) enhanced the development of cocaine sensitization. The enhancing effect of CP 93129 (0.1 microg/side) was blocked by GR 55562 (1 microg/side). To examine the effects of GR 55562 and CP 93129 on the expression of cocaine sensitization, the 5-HT(1B) receptor ligands were given acutely before the challenge dose of cocaine administered on day 10. No change in cocaine sensitization was observed after intra-VTA microinjections of GR 55562 (0.3-3 microg/side) or CP 93129 (0.1-1 microg/side). Our findings suggest that 5-HT(1B) receptors located in the VTA play a permissive role in the development of cocaine sensitization, but are not involved in the locomotor hyperactivity induced by a single dose of cocaine or in the expression of the sensitization to the psychostimulant.     

A chronic model for evaluating the itching associated with allergic conjunctivitis in rats

The present study was performed to develop a new model for evaluating itching associated with allergic conjunctivitis in rats. Repeated topical application of antigen caused an increase in eye scratching behavior in sensitized animals, and a significant difference was observed from days 21 to 42. Almost the same findings were observed in allergic symptoms, hyperemia and edema. Instillation of histamine also resulted in an increase in eye scratching behavior. The sensitivity to histamine in eye scratching behavior was increased by topical antigen application for 42 days after sensitization. In addition, the number of conjunctival eosinophils was significantly increased by repeated topical antigen application from days 21 to 42 in sensitized rats. Some anti-allergic drugs such as olopatadine (H1 antagonist), cetiridine (H1 antagonist) and ramatroban (thromboxane A2 (TXA2) antagonist) caused an inhibition of eye scratching behavior induced by topical sensitization in a dose-related manner. However, zafirlukast (cys-LT antagonist) caused no significant inhibition even at a dose of 30 mg/kg. The findings in present model of itching in allergic conjunctivitis were mainly through histamine H1-activity, and thromboxane A2 receptors were also involved in the response.     

BI-L-239, a 5-lipoxygenase inhibitor, blocks inhaled antigen-induced airway hyperresponsiveness in conscious guinea pigs.

Male Hartley guinea pigs were actively sensitized to ovalbumin (OA). Respiratory system resistance (Rrs) was measured by forced oscillations superimposed on tidal breathing. Airway responsiveness (inhaled methacholine PC100) was determined three days prior and three days after (day 10) three alternate day inhalations of OA. Airway cell composition was assessed on day 10 by lung lavage. Three groups (n = 5-6) were studied: A) vehicle challenged, B) OA challenged/placebo treated, C) OA challenged/BI-L-239 (2,6-dimethyl-4-[2-(4-fluorophenyl)ethenyl]phenol) treated (10 x 0.75 mg/actuation, 10 minutes prior to each OA challenge). Animals were treated with pyrilamine and indomethacin (10 mg/kg i.p.) 30 minutes prior to each OA challenge. OA induced acute increases in Rrs of 143 +/- 29%, 238 +/- 73% and 102 +/- 43% in placebo and 86 +/- 34%, 45 +/- 35% (p, 0.05 vs. placebo) and 102 +/- 31% in BI-L-239 treated. OA induced a significant (p less than 0.05) increase in airway leukocytes in placebo (487 +/- 36 to 1615 +/- 421 x 10(3)/ml) but not BI-L-239 treated (to 881 +/- 155 x 10(3)/ml) and decrease in methacholine PC100 in placebo (1.487 +/- 0.49 to 0.39 +/- 0.18 mg/ml) but not BI-L-239 treated (0.99 +/- 34 to 1.04 +/- 0.39 mg/ml). We conclude that BI-L-239 attenuates the airway constriction, inflammation and hyperresponsiveness induced by repeated antigen inhalations in conscious guinea pigs.     

Effect of protease-activated receptor-2 deficiency on allergic dermatitis in the mouse ear

To investigate the involvement of protease-activated receptor-2 (PAR-2) in allergic dermatitis, we generated PAR-2-deficient (PAR-2(-/-)) mice. Ear thickness, contact hypersensitivity (CH) induced by topical application of picryl chloride (PC) or oxazolone (Ox) after sensitization, and vascular permeability after ear passive cutaneous anaphylaxis (PCA) were compared between wild-type (WT) and PAR-2(-/-) mice. Ear thickness was almost the same in untreated WT and PAR-2(-/-) mice. Topical application of PC or Ox thickened the ears at 6, 24 and 48 h after challenge with a peak at 24 h in WT mice. In PAR-2(-/-) mice, the ear swelling induced by both PC and Ox was suppressed at every time point, and significant inhibition was found at 24 h in PC-induced CH and at 24 and 48 h in Ox-induced CH. Histopathological observation of the ears at 24 h after challenge revealed that PC- or Ox-induced ear edema and infiltration of inflammatory cells in WT mice were greatly attenuated in PAR-2(-/-) mice. The vascular permeability in the ears after PCA was not different between WT and PAR-2(-/-) mice. These results strongly suggest that PAR-2 plays a crucial role in type IV allergic dermatitis but not in type I allergic dermatitis.     

大鼠过敏性气道炎症中VCAM—1表达、嗜酸细胞浸润和药理调节

目的:探讨过敏性气道炎症大鼠肺内VCAM-1表达和嗜酸细胞浸润,以及速激肽NK-1受体拮抗剂SR140333和地塞米松的可能调节方式.方法:致敏大鼠以1％卵白蛋白气雾吸入攻击后24小时,测定VCAM-1在不同组别大鼠肺内的表达和支气管周围嗜酸细胞浸润.抗原攻击前3天,每天2次腹腔注射SR140333(0.01,0.10mg/kg)或地塞米松(0.50mg/kg).结果:与未致敏大鼠相比VCAM-1在致敏大鼠肺内表达增加(P<0.05),预先用地塞米松处理可抑制其增加(P<0.05),SR140333无此作用(P>0.05).此外,抗原攻击致敏大鼠促使支气管周围嗜酸细胞浸润,但不能进一步增加VCAM-1的表达(P>0.05).SR140333抑制嗜酸细胞浸润(P<0.05),但不影响VCAM-1表达(P>0.05);地塞米松则抑制这两种反应(P<0.05).结论:VCAM-1表达在抗原致敏后增加,地塞米松和SR140333抑制大鼠过敏性气道炎症的机制可能不同.     

Suppression of allergic immune responses to house dust mite (HDM) in rats exposed to 2,3,7,8-TCDD.

Exposure to various xenobiotics, including oxidant gases, diesel exhaust, and certain pesticides, has been reported to exacerbate pulmonary allergic hypersensitivity responses. Increased lymphocyte proliferative responses to parasite antigens or increased antibody responses to sheep erythrocyte have also been reported in rats exposed to TCDD before infection or immunization. As a result, these studies were conducted to test the hypothesis that TCDD exposure exacerbates the allergic response to house dust mite antigen. Brown Norway rats were injected, ip, with 0, 1, 10, or 30 microg TCDD/kg 7 days before intratracheal (it) sensitization to semipurified house dust mite allergen (HDM). Fourteen days later, rats were challenged with HDM and immediate bronchospasm was measured. At this time point, plus 2 and 7 days later, inflammatory cells in bronchoalveolar lavage fluid (BALF), HDM-specific IgE levels in serum, and HDM-driven cell proliferation in bronchial lymph nodes and spleen were evaluated. TCDD exposure decreased both immediate bronchoconstriction and specific IgE synthesis after the HDM challenge; 7 days later, HDM-specific IgE responses remained suppressed. Total serum IgE levels were similar in all groups. HDM challenge alone significantly increased cellular and biochemical indicators of lung injury, both of which were suppressed by TCDD exposure. The proliferative response of lymph node cells, but not of spleen cells, to HDM was also suppressed at the highest TCDD dose, although the splenic response to Concanavalin A was elevated. It appears that early events in the response to HDM are affected by TCDD exposure, since message for IL5 was dramatically reduced 2 days after sensitization, but not after challenge. We therefore conclude that TCDD exposure suppressed, rather than enhanced the development of allergic immune responses and the expression of immune-mediated lung disease.