Chiba Yoshihiko, Saitoh Nobuyuki, Matsuo Kensuke, Misawa Miwa
Department of Pharmacology, School of Pharmacy, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan.
Int Arch Allergy Immunol. 2002 Apr;127(4):285-93. doi: 10.1159/000057745.
Nasal hyperresponsiveness is a common feature of allergic rhinitis, but the underlying mechanisms have yet to be elucidated. The effects of repeated antigen inhalation on the characteristics of histamine H(1) receptors and expression levels of heterotrimeric guanosine 5'-triphosphate-binding proteins in nasal mucosa were investigated to understand the mechanisms of the pathogenesis of nasal hyperresponsiveness in allergic rhinitis.
Male Hartley guinea pigs were sensitized by the inhalation of dinitrophenylated ovalbumin antigen (10 mg of protein/ml) and repeatedly challenged by inhaling aerosolized dinitrophenylated ovalbumin antigen for 3 weeks. Twenty-four hours after the last antigen inhalation, in vivo nasal responsiveness to histamine was measured. [(3)H]Mepyramine binding assays and immunoblotting for alpha subunits of the G(q) protein were also performed using membrane preparations of isolated nasal mucosae.
The histamine-induced increase in intranasal pressure was significantly augmented after repeated antigen challenge, indicating that nasal hyperresponsiveness was achieved. In saturation binding studies, no significant change was observed in the density and antagonist affinity of H(1) receptors in the hyperresponsive animals. On the other hand, the affinity of histamine for high-affinity agonist binding sites in the hyperresponsive group, measured by histamine competition binding studies, was much greater than that in control animals, and these results were affected by guanosine 5'-O-(3-thiotriphosphate) in both groups. Moreover, Galpha(q) levels in nasal mucosal homogenates were significantly increased after repeated antigen challenge.
Elevated G protein levels in nasal mucosa might induce an increased binding affinity of histamine to its receptors, resulting in an augmented nasal response to histamine, that is, nasal hyperresponsiveness, in guinea pigs.
鼻高反应性是变应性鼻炎的一个常见特征，但其潜在机制尚未阐明。为了解变应性鼻炎鼻高反应性的发病机制，研究了反复吸入抗原对鼻黏膜中组胺H(1)受体特性及异三聚体鸟苷5'-三磷酸结合蛋白表达水平的影响。
雄性Hartley豚鼠通过吸入二硝基苯基化卵清蛋白抗原（10mg蛋白/ml）致敏，并通过吸入雾化的二硝基苯基化卵清蛋白抗原反复激发3周。在最后一次吸入抗原24小时后，测量体内鼻对组胺的反应性。还使用分离的鼻黏膜膜制剂进行了[(3)H]美吡拉敏结合试验和G(q)蛋白α亚基的免疫印迹分析。
反复抗原激发后，组胺诱导的鼻内压升高显著增强，表明实现了鼻高反应性。在饱和结合研究中，高反应性动物中H(1)受体的密度和拮抗剂亲和力未观察到显著变化。另一方面，通过组胺竞争结合研究测量，高反应性组中组胺对高亲和力激动剂结合位点的亲和力远大于对照动物，并且两组的这些结果均受鸟苷5'-O-(3-硫代三磷酸)影响。此外，反复抗原激发后鼻黏膜匀浆中的Gα(q)水平显著升高。
鼻黏膜中G蛋白水平升高可能导致组胺与其受体的结合亲和力增加，从而导致豚鼠对组胺的鼻反应增强，即鼻高反应性。
