Inhibition of allergic airways inflammation and airway hyperresponsiveness in mice by dexamethasone: role of eosinophils,IL-5, eotaxin,and IL-13

BACKGROUND: Glucocorticoids inhibit allergen-induced airway eosinophilia and airway hyperresponsiveness (AHR). Whether glucocorticoids mediate their effects on AHR by inhibiting eotaxin and IL-5, 2 of the principal mediators of eosinophilia, or through IL-13, an important mediator of AHR, has not been established. OBJECTIVE: We sought to investigate the effects of glucocorticoids on airway eosinophilia and the expression of IL-5, eotaxin, and IL-13 in relation to the induction of AHR in a murine model of allergic asthma. METHODS: Dexamethasone (4 mg/kg) and mAbs against eotaxin (80 micro g/kg) and IL-5 (100 micro g/kg) singly and in combination were administered to immunized mice before antigen challenge. Airway responsiveness to methacholine was measured in anesthetized and mechanically ventilated animals. Eotaxin, IL-5, and IL-13 in bronchoalveolar lavage fluid (BALF), lung homogenates, or both were measured by means of ELISA. RESULTS: A single antigen challenge induced AHR that lasted at least 10 days. Eotaxin protein and mRNA levels increased in lung tissue but not in BALF after challenge. IL-5 protein and mRNA levels increased both in BALF and in lung tissue. Dexamethasone reduced airway eosinophilia, AHR, and protein and mRNA for eotaxin and IL-5. Anti-murine eotaxin and anti-IL-5 antibodies alone and in combination reduced the ovalbumin-induced airway eosinophilia significantly but failed to inhibit AHR. Both dexa-methasone and anti-IL-5/anti-eotaxin inhibited the increases in lung IL-13 levels after ovalbumin challenge to a similar extent. CONCLUSION: These findings suggest that the inhibition of AHR by the glucocorticoid dexamethasone does not appear to be explained by effects on eosinophilia, eotaxin, IL-5, or IL-13.     

Use of short-acting beta2-agonists during pregnancy and the risk of pregnancy-induced hypertension

BACKGROUND: The effect of inhaled short-acting beta(2)-agonists (SABAs) on pregnancy outcome, especially hypertensive complications, is not well documented. After the finding of a possible protective association of inhaled SABAs with pregnancy-induced hypertension (PIH) in a previous study, we decided to further investigate their effect on this condition. OBJECTIVE: We sought to determine the effect of inhaled SABA use during pregnancy on the risk of PIH (gestational hypertension, preeclampsia, or eclampsia) in asthmatic women. METHODS: Three of Quebec's administrative databases were linked to constitute a cohort of asthmatic women who had at least 1 delivery between 1990 and 2000. A nested case-control study was performed using up to 10 control subjects matched to each case patient for the year of conception and gestational age. Statistical analyses considered 22 confounders. RESULTS: The cohort was composed of 3505 asthmatic women who had a total of 4593 pregnancies. Three hundred two patients with PIH and 3013 control subjects were identified. Compared with nonuse, inhaled SABA use during pregnancy was significantly associated with a reduced risk of PIH (adjusted rate ratios: >0-3 doses/week, 0.62 (95% CI, 0.44-0.87); > 3-10 doses/week, 0.51 (95% CI, 0.34-0.79); and >10 doses/week, 0.48 (95% CI, 0.30-0.75)). CONCLUSIONS: To our knowledge, this is the first study reporting that inhaled SABA use during pregnancy is associated with a reduced risk of PIH. Potential explanations include pharmacologic and physiological effects or residual confounding. CLINICAL IMPLICATIONS: These results increase the evidence about the safety of inhaled SABAs in this population, although they should not undervalue the importance of maintaining good control of asthma symptoms.     

Role of cysteinyl leukotrienes in CD4(+) T cell-driven late allergic airway responses

Cysteinyl leukotrienes (cys LTs) play an important role in late responses to allergen challenge of actively sensitized rats. The aim of this study was to determine whether T cell-dependent late airway responses (LARs) also are mediated by cys LTs. To do this we tested the effects of the selective and potent LTD(4) antagonist pranlukast on airway responses to ovalbumin (OVA) challenge of naive recipients of CD4(+) T cells isolated from the cervical lymph nodes of OVA-sensitized donor rats. CD4(+) T cells (5 million) were purified by immunomagnetic separation and administered i.p. 2 days before OVA challenge. The pulmonary resistance was measured for 8 h after challenge and bronchoalveolar lavage (BAL) was performed for analysis of leukocytes and major basic protein-positive cells. The LAR, determined as the area under the curve of pulmonary resistance against time from 3 to 8 h after challenge, was 8.9 +/- 1.79 cm H(2)O/ml/s x min after OVA compared with 2.8 +/- 0.50 cm H(2)O/ml/s x min (P <.01) after OVA and pranlukast treatment. The total cell count in BAL was not significantly greater in the OVA challenged group (3.55 +/- 0.41 x 10(6) cells) compared with the OVA- and pranlukast-treated group (2.65 +/- 0.45 x 10(6) cells). However, lymphocytes and eosinophils were reduced in numbers by pranlukast. Interleukin-5 mRNA-positive cells were diminished by 50% in pranlukast-treated animals. In conclusion, pranlukast inhibits LAR, BAL eosinophilia, and Interleukin-5 expression in rats with adoptively transferred LAR, indicating an important role for cys LTs in these T cell-driven responses.     

Guinea pig kurloff (NK-like) cells mediate TNF-dependent cytotoxic activity: Analogy with NC effector cells

Kurloff cells are mononuclear cells possessing a large cytoplasmic inclusion body specific to the guinea pig. In this report, we present strong evidence that Kurloff cells can mediate NC activity against tumor cells in addition to their previously reported NK activity. Using an 18 h⁵¹Cr-release assay we have shown that Kurloff cells were highly effective in killing the TNF-sensitive WEHI 164 target cell line. Lower but significant cytotoxic activity was also observed after only 4 h. However, our results suggest a different mechanism of lysis in the 4 h and 18 h assay. Lysis of WEHI 164 target cells by Kurloff cells in the 4 h assay could be strongly increased in the presence of TPA alone or in combination with ionomycin whereas ionomycin alone was uneffective. In contrast, stimulation of Kurloff cells for 18 h with ionomycin alone or in combination with TPA could induce the release of TNF-like factor(s) as observed by the TNF bioassay using L-929 TNF-sensitive target cells. Release of TNF-like factor(s) could also be induced by stimulation with WEHI 164 target cells. Supernatants of Kurloff cells stimulated for 18 h with TPA + ionomycin were also highly cytotoxic against WEHI 164 target cells, but not against the TNF-resistant P815 target cell line. Pretreatment of these supernatants with antimurine TNF antibodies could almost completely inhibit their cytotoxic activity against WEHI 164 target cells. In contrast, supernatants of Kurloff cells stimulated for only 4 h did not show any TNF-like activity against the L-929 target cell line and were not cytotoxic against WEHI 164 target cells even after 18 h. Taken together, these results suggest that Kurloff cells can mediate NC activity against tumor cells in addition to their previously reported NK activity. By using multiple lytic pathways, these cells may play a crucial role in anti-tumor surveillance and defenses.Supported by grants from the National Cancer Institute and the Medical Research Council of Canada.Recipient of a studentship from the F.C.A.R.     

Kinetics of eosinophilia and eosinophil activation in the development of non-allergic bronchial hyperresponsiveness in guinea pigs injected with Sephadex beads

Eosinophils are believed to play a crucial role in the pathogenesis of airway hyperresponsiveness (AHR). In the present study, the involvement of blood and pulmonary eosinophilia as well as the eosinophil activation in the onset of non-allergic AHR caused by the injection of G-50 Sephadex beads in guinea pigs was investigated. Reactivity of the isolated lower bronchus to histamine was measured ex vivo in a bioassay system. The increase of reactivity of the isolated lower bronchus of Sephadex-injected animals to histamine was observed as early as 3 h after the Sephadex injection and was maximal between 6–24 h. Sephadex-induced blood eosinophilia was characterized by two successive increases of blood eosinophil counts peaking at 3 and 12 h respectively. The recruitment of inflammatory cells into the lungs, as measured in bronchoalveolar lavage fluid (BALF) have shown that the neutrophils were initially increased at 3 h whereas the number of eosinophils increased only 6 h after the bead injection; both cell populations were maximal 24 h later. Eosinophil peroxidase (EPO) activity was used as a marker for the apparent number of eosinophils in airways and the degree of activation of eosinophils recovered in BALF. Results have shown that EPO activity in the lower bronchus of Sephadex-injected animals increased at 6 h, decreased at 12 h and was maximal 24 h later. The EPO activity recovered in BALF was maximal between 6 to 24 h after the bead injection in guinea pigs. Correlation between the number of eosinophils and the EPO activity in BALF suggests that BALF eosinophils have been activated and have degranulated in airways. Correlation studies also indicated that both Sephadex-induced blood eosinophilia and eosinophil activation were associated to the development of AHR. In contrast, the increase of EPO activity in the lower bronchus and BALF eosinophilia were not correlated to the development of AHR in our model. In conclusion, our results suggest that Sephadex-induced non-allergic AHR in guinea pigs could be related, at least in part, to blood eosinophilia and eosinophil activation. Whether blood, airway and BALF eosinophilia as well as eosinophil activation are relevant factors to determine the potential role of eosinophils in the pathogenesis of AHR is discussed.     

Involvement of the cysteinyl-leukotrienes in allergen-induced airway eosinophilia and hyperresponsiveness in the mouse

The leukotriene modifiers are a novel generation of therapeutic agents in the treatment of allergic asthma. However, the mechanisms by which the cysteinyl (cys) leukotrienes (LTs) participate in allergen-induced airway eosinophilia and airway hyperresponsiveness (AHR) are still unclear. In the present study, we have investigated the role of cys-LTs in ovalbumin (OVA)-induced airway responses in a murine model of asthma. Montelukast (3 or 10 mg/kg), a selective cys-LT1 receptor antagonist, reduced airway eosinophilia and AHR after OVA challenge. The levels of interleukin (IL)-5 and eotaxin in the bronchoalveolar lavage fluid (BALF) from montelukast-treated (3 mg/kg) mice were unaffected, although a decrease in IL-5 was observed with a dose of 10 mg/kg. LTD4 (50 ng) instilled intranasally to immunized mice augmented macrophages in the BALF, but in conjunction with OVA challenge it caused BALF eosinophilia and neutrophilia when given before challenge and BALF neutrophilia but not eosinophilia when given 2 h after challenge. However, there were no increases of IL-5 or eotaxin in BALF following LTD4 treatment. Repeated instillations of LTD4 to immunized mice, mimicking allergen challenge, did not induce AHR but in conjunction with OVA challenge LTD4 enhanced AHR. These results indicate that allergen-induced eosinophilia and AHR are in part mediated by the cys-LT1 receptor, and that, although LTD4 alone has no effect on airway eosinophilia, in conjunction with antigenic stimulation it potentiates the degree of airway inflammation and AHR.     

Characterization of airway inflammation after repeated exposures to occupational agents

BACKGROUND: Little is known about the comparative kinetics of eosinophil recruitment after exposure to low- and high-molecular-weight sensitizers in subjects with occupational asthma (OA). OBJECTIVES: The aims of the study were to investigate the kinetics of changes in inflammatory mediators associated with eosinophil infiltration (IL-5 and eotaxin) and to examine the nature of the airway inflammation induced in response to different types of occupational agents. METHODS: We investigated 15 subjects with OA caused by high- and low-molecular-weight agents. The subjects were exposed to increasing doses of the relevant occupational agent over 3 to 4 days until a 20% fall in FEV(1) occurred. Methacholine challenge and sputum induction were performed at the end of each day of exposure. Sputum samples were assessed for differential cell counts, including eosinophils, IL-5, and eotaxin messenger RNA. RESULTS: There was an increase in sputum eosinophils, eotaxin, and IL-5 on the day preceding the occurrence of asthmatic reaction, although there was no change in functional parameters (FEV(1) and PC(20)). Increase in sputum eosinophils was more prominent in subjects exposed to low-molecular-weight agents than to high-molecular-weight agents. CONCLUSION: Changes in eosinophils, IL-5, and eotaxin precede functional changes after exposure to occupational agents in subjects with OA. Eosinophil inflammation is a feature of exposure to both high- and low-molecular-weight agents. Induced sputum may be a useful tool in the early diagnosis of OA.