Inhibition of bronchial hyperresponsiveness to histamine induced by intravenous administration of leukotriene C4 by novel thromboxane A2 receptor antagonists ONO-NT-126 and ONO-8809 in guinea-pigs

We studied the effect of intravenous administration of leukotriene (LT) C4 on bronchial responsiveness to histamine and airway wall thickening in guinea-pigs. Guinea-pigs were killed and the lungs were fixed in formalin. Slides from paraffin-embedded sections of the lungs were stained and the airways that were cut in transverse sections were measured by tracing enlarged images using a digitizer. Moreover, airway resistance (Raw) was determined by a pulmonary mechanics analyser and we calculated two indices, an index of airway wall thickening and the one of airway hyperresponsiveness to histamine, from changes of baseline-Raw and peak-Raw following intravenous administration of histamine before and after the intravenous administration of LTC4. Intravenous administration of 3 microg/kg LTC4 for 1 hr induced an increase of the relative thickness of the airway wall in peripheral bronchi by the histological examination. In analysis of airway function, intravenous administration of 3 microg/kg LTC4 for 1 hr induced airway hyperresponsiveness to histamine with airway wall thickening. Thromboxane A2 receptor antagonists ONO-NT-126 and ONO-8809 inhibited the LTC4-induced airway hyperresponsiveness to histamine in a dose-dependent manner, but not the airway wall thickening induced by LTC4, suggesting that the effect of LTC4 on bronchial hyperresponsiveness is likely to be mediated through TXA2.     

Inhibition by a novel peptide leukotriene receptor antagonist ONO-1078 of airway wall thickening and airway hyperresponsiveness to histamine induced by leukotriene C4 or leukotriene D4 in guinea-pigs

We studied the effect of intravenous administration of leukotriene (LT) C₄ or LTD., on airway responsiveness to histamine and airway wall thickening in guinea-pigs. Guinea-pigs were killed and the lungs were fixed in formalin. Slides from paraffin-embedded section of the lungs were stained and the airways that were cut in transverse section were measured by tracing enlarged images using a digitizer, Moreover, airway resistance (Raw) was determined by a pulmonary mechanics analyser and we calculated two indices, an index of airway wall thickening and the one of airway hyperresponsiveness to histamine, from changes of baseline-Raw and peak-Raw following intravenous administration of histamine before and after the intravenous administration of LTC₄ or LTD₄. The infusion of LTC₄ or LTD₄ induced an increase of the relative thickness of the airway wall in peripheral bronchi demonstrable by the histological examination. In analysis of airway function, intravenous administration of LTC₄ or LTD₄ induced airway hyperresponsiveness to histamine with airway wall thickening. The LTC₄ and LTD₄ receptor antagonist ONO-1078 inhibited these effects of LTC₄ and LTD₄, suggesting LTC₄ and LTD₄ may induce airway wall thickening and airway hyperresponsiveness through LTC₄ and LTD₄ receptors in the airways.     

Bronchial hyperresponsiveness and airway neutrophil accumulation induced by interleukin-8 and the effect of the thromboxane A2 antagonist S-1452 in guinea-pigs

Interleukin-8 (IL-8) has been shown to be a chemotactic factor for neutrophils, T-lymphocytes and eosinophils, but it is unknown whether the IL-8-induced inflammatory cell accumulation into the airways can cause the bronchial hyperresponsiveness (BHR) characteristic of asthma. IL-8 at a dose of 0.5 or 5μg/kg was administered intranasally to guinea-pigs twice a week for 3 weeks. One day after the last administration, animals were anesthetized and artificially ventilated through tracheal cannula and lateral pressure at the cannula (Pao) was measured as an overall index of airway responses to increasing concentrations of inhaled histamine (25, 50, 100, and 200 μg/ml). The IL-8 treatment significantly enhanced bronchial responsiveness to histamine in a dose-dependent manner (ANOVA P < 0.01). The provocative concentration of histamine causing a 100% increase in Pao (PC100) at a dose of 0.5 and 5μg/kg of IL-8 was 68.1 (Gsem 1.12) and 35.6 (Gsem 1.25) μg/ml, respectively. The latter was significantly (P < 0.01) lower than that in control animals treated with PBS (93.3 [Gsem , 1.14] μg/ml)- The IL-8 treatment also induced a significant influx of neutrophils, but not eosinophils, in bronchoalveolar lavage (BAL) fluid (18.3 ± 8.8 and 30.6 ± 8.3% in animals treated with 0.5 and 5 μg/kg, respectively, of IL-8 vs 3.6 ± 0.7% in phosphate buffered saline-(PBS)-treated animals). Furthermore, we examined the effect of the thromboxane receptor antagonist S-1452 (0.01 or 0.1 mg/kg, i.p. 24 and 1 h before anesthesia) on this IL-8 induced BHR. S-1452 significantly inhibited the BHR dose-dependently (ANOVA P < 0.001). PC100 was 94.0 (Gsem 1.19), 137.4 (Gsem 1.17) and 43.0 (Gsem 1.24) μg/ml with S-1452 at doses of 0.01 and 0.1mg/ml and saline, respectively. We conclude that IL-8 causes BHR and airway neutrophil inflammation, and that thromboxane A₂ is important in the development of BHR induced by IL-8.     

Comparative vascular effects of histamine, prostaglandin (PG) D2 and its metabolite 9α, 11β-PGF2 in human skin

In this double-blind study we have investigated the vascular effects of prostaglandin, (PG) D₂, in normal skin and compared these effects with histamine and the initial PGD₂ metabolite 9α, 11β-PGF₂. In eight healthy subjects the vascular response to intradermal injections of histamine, PGD₂, a combination of histamine and PGD₂, and 9α, 11β-PGF₂, was assessed by measurement of the weal and flare area. Histamine caused dose-related increases in weal area ( P <0.01). The weal response due to PGD₂ was greater than saline control only at a dose of 71.0 and 710 nmol ( P <0.05). Because of the small size of the weal produced by PGD₂ when compared with histamine, it was not possible to determine their relative potencies. Histamine and PGD₂ caused dose-related increases in flare area ( P <0.05), and when compared at a response level of 10 cm² and 15 cm², histamine was 45 and 251 ( P <0.01) times more potent than PGD₂ in molar terms. Weal and flare responses due to 9α, 11β-PGF₂ were similar to those observed with the equimolar concentration of PGD₂. The weal and flare responses when PGD₂ and histamine when combined were not significantly different from that predicted by a purely additive effect. We conclude that histamine is likely to be an important mediator contributing towards increased vascular permeability and vasodilatation following immunological activation of skin mast cells in vivo , while PGD₂ and its metabolite 9α, 11β-PGF₂ play only a minor role.     

PGF2α challenge test in asthma and chronic bronchitis

PGF_2SaL challenge tests were performed in twenty-three patients with bronchial asthma and six patients with chronic bronchitis; two patients with allergic rhinitis and four healthy volunteers also participated in the trial. FEV¹ measurements were used in assessing the reactions. PGE_2α challenge proved safe and practical in clinical use. A wide scattering in PGF_2α reactivity was seen, but sensitivity to PGF_2α did not correlate to several clinical criteria. Comparison with an ordinary histamine challenge revealed that the sensitivity of the patients to PGF_2α and histamine was not uniform.     

Cyclic AMP-dependent Cl− secretion induced by thromboxane A2 in isolated human colon

Increased release of thromboxane A₂ (TXA₂) has been shown to be involved in inflammatory bowel diseases. In the present study, we have investigated the effect of a stable TXA₂ analogue (STA₂) on the electrical parameters in isolated human colonic mucosa. In the human mucosa set between Ussing chambers, STA₂ stimulated Cl⁻ secretion in a concentration-dependent manner with an EC₅₀ of 0.06 μ m . The STA₂-induced Cl⁻ secretion was significantly inhibited by ONO-3708 (10 μ m ), a specific TXA₂ receptor antagonist. The effect of STA₂ (0.3 μ m ) was independent of the colonic segment from which the tissue was obtained, from caecum to rectum. Chromanol 293B, an inhibitor of the cAMP-dependent KvLQT1 channel, attenuated the STA₂-induced Cl⁻ secretion in the human colonic mucosa (IC₅₀ value 1.18 μ m ). We found that KvLQT1 mRNA and protein were expressed in all the tested segments of the human colon. The STA₂-induced Cl⁻ secretion was significantly inhibited by 8-bromo-2'-monobutyryladenosine-3',5'-cyclic monophosphorothioate (50 μ m ), a membrane-permeant cAMP antagonist. STA₂ (0.3 μ m ) significantly increased the intracellular cAMP levels and the short-circuit current via TXA₂ receptor in a human colonic cell line. These results suggest that the TXA₂-induced Cl⁻ secretion in the colon is mediated via the cAMP pathway in addition to the Ca²⁺–calmodulin pathway which was previously reported.     

Thymic differentiation of TCRαβ+ CD8αα+ IELs

Summary:  Intraepithelial lymphocytes (IELs) contain several subsets, but the origin of the T-cell receptor (TCR)αβ⁺ CD8αα⁺ IELs has been particularly controversial. Here we provide a synthesis, based on recent work, that attempts to unify the divergent views. The intestine has a primordial function in lymphopoiesis, and precursors with the potential to differentiate into T cells are found both in the epithelium and underlying lamina propria. Moreover, the thymus has been reported to export cells to the intestine that are not fully differentiated. TCRαβ⁺ CD8αα⁺ IELs can differentiate in the intestine from each of these sources, but in normal euthymic mice, the thymus appears to be the major source for TCRαβ⁺ CD8αα⁺ IELs. This unique IEL subset is a self-reactive population that requires exposure to self-agonists for selection in the thymus, similar to other regulatory T-cell populations. IELs transition through a double-positive (DP) intermediate in the thymus, but they originate from a subset of the DP cells that can be identified by its expression of CD8αα homodimers. The agonist-selected cells in the thymus are TCRβ⁺ but CD4 and CD8 double negative. The evidence suggests that reacquired expression of CD8αα and downregulation of CD5 occur after thymus export, perhaps in the intestine under the influence of interleukin-15. As a result of agonist exposure, a new gene expression program is activated. Therefore, the increased understanding of the developmental origin of TCRαβ⁺ CD8αα⁺ IELs may help us to understand how they participate in immune regulation and protection in the intestine.     

Increased expression of collagen receptors: α1β1 and α2β1 integrins on blood eosinophils in bronchial asthma

BACKGROUND: Eosinophils are one of the major effector cells in bronchial asthma. Their infiltration of airways correlates with the asthma severity. Recruitment and activation of eosinophils are partially mediated by integrins alpha4beta1 and alpha4beta7. Collagens type I and IV constitute important components of extracellular matrix and vascular basement membrane, respectively. Therefore, collagen-binding integrins (alpha1beta1 and alpha2beta1) may also play a role in eosinophil lung infiltration. OBJECTIVE: To evaluate the possible presence of alpha1beta1 and alpha2beta1 integrins on peripheral blood eosinophils from asthmatic subjects. METHODS: Collagen receptors were studied on eosinophils separated by immunomagnetic CD16-negative method from healthy donors (n=13) and patients with moderate persistent atopic bronchial asthma (n=15). Surface receptor identification was performed by flow cytometry and cell adhesion assay. RESULTS: Eosinophils isolated from the patients showed increased expression of both alpha1beta1 and alpha2beta1 integrins as compared with healthy controls. Moreover, adhesive function of eosinophils to collagen type IV was inhibited by snake venom disintegrins: viperistatin and obtustatin. These disintegrins contain KTS active motif and are specific inhibitors of alpha1beta1 integrin. CONCLUSION: We demonstrated for the first time that collagen receptors: alpha1beta1 and alpha2beta1 integrins are overexpressed on the surface of peripheral blood eosinophils of asthmatic subjects. Further studies may reveal potential application of KTS-disintegrins or their structural analogs for therapy of bronchial asthma.     

Immunostaining for α1-antichymotrypsin and α1-antitrypsin in gliomas

Antisera to α₁-antichymotrypsin, α₁-antitrypsin and lysozyme were reacted with 20 cases of glioblastoma multiforme, seven anaplastic astrocytomas, eight astrocytomas, six oligodendrogliomas, four ependymomas and the cerebral cortex from six normal autopsy brains. In addition, two pleomorphic xantho-astrocytomas and two heavily lipidized malignant gliomas were similarly examined. All astrocytic lesions were confirmed with anti-GFAP antisera. Thirty astrocytic tumours (77%), four oligodendrogliomas (67%) and three ependymomas (75%) reacted positively with anti-α₁-antichymotrypsin; 25 astrocytic tumours (64%), three oligodendrogliomas (50%) and three ependymomas (75%) showed positive staining for α₁-antitrypsin. The pattern of staining with either of these two markers did not correlate with tumour grading. None of the gliomas examined stained positively with anti-lysozyme. Non-neoplastic glial elements did not react with any of the three antisera. The results of this study suggest that staining for α₁-antichymotrypsin and α₁-antitrypsin is of little value in the differential diagnosis of neuroepithelial or mesenchymal lesions in the brain.     

CNS effects of histamine H1 antagonists

An accurate evaluation of the functions of the human brain during the administration of drugs is one of the most complex tasks in medical science. In the case of H₁ antihistamines, there are many biases that can explain why the interpretation of pharmacological data and those from clinical studies can be very difficult. First of all, the allergic disease itself may modify central nervous system (CNS) functioning and effective medical treatment may accordingly influence the self-reported CNS sensations of patients. Moreover, the carefully selected populations that are enrolled both in pharmacological and clinical studies do not reflect the profile of patients who are trreated with such drugs on an everyday basis. Finally, studies of performance impairment and those relying on self-reported sensations may give different and indeed conflicting results.It may be concluded that the various pronouncements on the CNS properties of H₁ antihistamines must be treated with some caution.     

Specific contribution of human T-type calcium channel isotypes (α1G, α1H and α1I) to neuronal excitability

The glutamine transporter SN1 has recently been identified as one of the major glutamine transporters in hepatocytes and brain astrocytes. It appears to be the molecular correlate of system N amino acid transport. Two different transport mechanisms have been proposed for this transporter. These are an electroneutral mechanism, in which glutamine uptake is coupled to an exchange of 1Na⁺ and 1H⁺, or an electrogenic mechanism coupled to the exchange of 2Na⁺ against 1H⁺. This study was performed to solve these discrepancies and to investigate the reversibility of the transporter. When SN1 was expressed in Xenopus laevis oocytes, glutamine uptake was accompanied by a cotransport of 2–3 Na⁺ ions as determined by ²²Na⁺ fluxes. However, at the same time a rapid release of intracellular Na⁺ was observed indicating an active exchange of Na⁺ ions. The driving force of the proton electrochemical gradient was equivalent to that of the sodium electrochemical gradient. Acidification of the extracellular medium caused the transporter to run in reverse and to release glutamine. Determination of accumulation ratios at different driving forces were in agreement with an electroneutral 1Na⁺-glutamine cotransport-1H⁺ antiport. Inward currents that were observed during glutamine uptake were much smaller than expected for a stoichiometric cotransport of charges. A slippage mode in the transporter mechanism and pH-regulated endogenous oocyte cation channels are likely to contribute to the observed currents.     

Heterozygous α-antichymotrypsin and PiZ (α1-antitrypsin deficiency

In a case-control study we compared the prevalence of heterozygous deficiency of two closely related anti-neutrophil protease inhibitors, alpha 1-antitrypsin and alpha 1-antichymotrypsin, in 172 consecutive children with asthma. In a cohort study the clinical spectrum and severity were compared. On the basis of family studies 5/172 (2.9%) were classified as heterozygotes for alpha 1-antichymotrypsin deficiency, a high prevalence compared with that of an unselected adult population (prevalence ratio 4.5 (1.7-11.9), P less than 0.005). This finding suggests that the carrier state of this rare allele (prevalence 0.64%) may predispose to asthma in children. Among these heterozygous patients the prevalence of positive RAST tests for foodstuffs was significantly increased (prevalence ratio 4.8 (1.7-13.2), P less than 0.005) and 2/5 manifested food allergy with Quincke oedema. Either the PiMZ or SZ phenotype of alpha 1-antitrypsin deficiency was found in 12 (7.0%) of the 172 patients, a prevalence similar to that of a normal population (prevalence ratio 1.3 (0.67-2.6), P = 0.44). However, the asthma was more severe among the Z allele carriers, judged by the number of hospital admissions, compared with the non-Z asthmatic children (mean 2.92 vs. 1.72, P less than 0.05). The results indicate that heterozygous deficiency of protease inhibitors directed against neutrophil proteases may affect the severity and clinical spectrum of childhood asthma, and to some degree be predisposing.     

Role of Ca2+ mobilization and Ca2+ sensitization in 8-iso-PGF2α-induced contraction in airway smooth muscle

Background Isoprostanes are prostaglandin (PG)-like compounds synthesized by oxidative stress, not by cyclooxygenase, and increase in bronchoalveolar lavage fluid of patients with asthma. The airway inflammation implicated in this disease may be amplified by oxidants. Although isoprostanes are useful biomarkers for oxidative stress, the action of these agents on airways has not been fully elucidated. Objective This study was designed to determine the intracellular mechanisms underlying the effects of oxidative stress on airway smooth muscle, focused on Ca²⁺ signalling pathways involved in the effect of 8-iso-PGF_2α. Methods Using simultaneous recording of isometric tension and F₃₄₀/F₃₈₀ (an indicator of intracellular concentrations of Ca²⁺, [Ca²⁺]_i), we examined the correlation between tension and [Ca²⁺]_i in response to 8-iso-PGF_2α in the fura-2 loaded tracheal smooth muscle. Results Augmented tension and F₃₄₀/F₃₈₀ by 8-iso-PGF_2α were attenuated by ICI-192605, an antagonist of thromboxane A₂ receptors (TP receptors). Moreover, D609, an antagonist of phosphatidylcholine-specific phospholipase C, markedly reduced both the tension and F₃₄₀/F₃₈₀ induced by 8-iso-PGF_2α, whereas U73122, an antagonist of phosphatidylinositol-specific phospholipase C, modestly inhibited them by 8-iso-PGF_2α. SKF96365, a non-selective antagonist of Ca²⁺ channels, markedly reduced both tension and F₃₄₀/F₃₈₀ by 8-iso-PGF_2α. However, diltiazem and verapamil, voltage-dependent Ca²⁺ channel inhibitors, modestly attenuated tension although their reduction of F₃₄₀/F₃₈₀ was not different from that by SKF96365. Y-27632, an inhibitor of Rho-kinase, significantly attenuated contraction induced by 8-iso-PGF_2α without reducing F₃₄₀/F₃₈₀, whereas GF109203X and Go6983, protein kinase C inhibitors, did not markedly antagonize them although reducing F₃₄₀/F₃₈₀ with a potency similar to Y-27632. Conclusion 8-iso-PGF_2α causes airway smooth muscle contraction via activation of TP receptors. Ca²⁺ mobilization by SKF96365- and D609-sensitive Ca²⁺ influx and Ca²⁺ sensitization by Rho-kinase contribute to the intracellular mechanisms underlying the action of 8-iso-PGF_2α. Rho-kinase may be a therapeutic target for the physiologic abnormalities induced by oxidative stress in airways.     

Inhibitory effect of inhaled procaterol on anaphylactic bronchoconstriction and thromboxane A2 production in guinea-pigs

This study was designed to examine whether an inhaled beta 2-agonist, procaterol, inhibits thromboxane A2 (TXA2) production induced by antigen challenge in passively sensitized guinea-pigs in vivo. Antigen-induced bronchoconstriction was markedly inhibited by pre-treatment with procaterol. Inhaled procaterol significantly reduced in a dose-dependent manner the increment in TXB2 concentration in bronchoalveolar lavage fluid obtained 5 min after antigen challenge. Aerosol administration of procaterol significantly inhibited bronchoconstriction induced by inhaled histamine. These results suggest that inhalation of procaterol has an inhibitory effect on antigen-induced TXA2 production as well as a protective effect against bronchoconstriction induced by bronchoactive agents.