Hasala Hannele, Giembycz Mark A, Janka-Junttila Mirkka, Moilanen Eeva, Kankaanranta Hannu
The Immunopharmacology Research Group, Medical School/B, University of Tampere, FIN-33014 Tampere, Finland.
Pulm Pharmacol Ther. 2008;21(1):222-33. doi: 10.1016/j.pupt.2007.03.002. Epub 2007 Mar 28.
Eosinophils are essential inflammatory cells in the pathogenesis of asthma and atopic conditions. Histamine, released from mast cells and basophils in response to allergen exposure, is a critical mediator in the allergic response. Histamine exerts its effects via four unequivocally characterized histamine receptors, H(1-4). Several functions of eosinophils have previously been shown to be stimulated by histamine. However, its effects on eosinophil apoptosis are unknown. The aim of the present study was to resolve the effects of histamine on constitutive apoptosis of human eosinophils and on the survival-enhancing action of interleukin (IL)-5. Additional experiments were conducted to elucidate the histamine receptor(s) involved in any response seen and the associated signal transduction cascade. Human isolated peripheral blood eosinophils were cultured in the absence or presence of histamine, IL-5 and receptor antagonists/agonists or mediator inhibitors/analogues. Apoptosis was assessed by measuring the relative DNA content of propidium iodide (PI)-stained cells and the effects were confirmed by morphological analysis with bright field microscopy. Caspase activities were assessed by using commercial Caspase-Glo 3/7, 8 and 9 luminescence assays. Histamine (10-100 microM) partially reversed IL-5-induced human eosinophil survival by enhancing apoptosis as assessed by measuring the relative DNA content of PI-stained cells. This effect was not mediated through any of the known histamine receptors or through non-specific activation of 5-hydroxytryptamine receptors or alpha-adrenoceptors. Moreover, the reversal of IL-5-inhibited eosinophil apoptosis by histamine seemed not to utilize the conventional intracellular second-messenger pathways including cyclic AMP, protein kinase A or phospholipase C. Inhibition of caspase 6 and caspases 1, 10 or 12 reversed the effects of histamine but also inhibited apoptosis in general. In conclusion, the data presented herein indicate that histamine induces human eosinophil apoptosis in the presence of a survival-prolonging cytokine by a mechanism that does not apparently involve the activation of any of the currently known histamine receptor subtypes. The possibility exists that another, as yet unidentified, histamine receptor may exist in human eosinophils that regulates survival, although the participation of histamine receptor-independent mechanisms cannot be excluded.
嗜酸性粒细胞是哮喘和特应性疾病发病机制中的重要炎症细胞。肥大细胞和嗜碱性粒细胞在接触变应原后释放的组胺是过敏反应中的关键介质。组胺通过四种明确表征的组胺受体H(1 - 4)发挥作用。此前已证明组胺可刺激嗜酸性粒细胞的多种功能。然而，其对嗜酸性粒细胞凋亡的影响尚不清楚。本研究的目的是确定组胺对人嗜酸性粒细胞组成性凋亡以及对白细胞介素（IL）-5增强存活作用的影响。进行了额外的实验以阐明参与任何观察到的反应的组胺受体以及相关的信号转导级联反应。将人分离的外周血嗜酸性粒细胞在不存在或存在组胺、IL-5以及受体拮抗剂/激动剂或介质抑制剂/类似物的情况下进行培养。通过测量碘化丙啶（PI）染色细胞的相对DNA含量评估凋亡，并通过明场显微镜形态分析证实结果。使用商业Caspase-Glo 3/7、8和9发光测定法评估半胱天冬酶活性。通过测量PI染色细胞的相对DNA含量评估，组胺（10 - 100 microM）通过增强凋亡部分逆转了IL-5诱导的人嗜酸性粒细胞存活。这种作用不是通过任何已知的组胺受体介导，也不是通过5-羟色胺受体或α-肾上腺素能受体的非特异性激活介导。此外，组胺对IL-5抑制的嗜酸性粒细胞凋亡的逆转似乎未利用包括环磷酸腺苷、蛋白激酶A或磷脂酶C在内的传统细胞内第二信使途径。抑制半胱天冬酶6以及半胱天冬酶1、10或12可逆转组胺的作用，但通常也会抑制凋亡。总之，本文提供的数据表明，组胺在存在延长存活的细胞因子的情况下通过一种显然不涉及激活任何当前已知组胺受体亚型的机制诱导人嗜酸性粒细胞凋亡。尽管不能排除组胺受体非依赖性机制的参与，但人嗜酸性粒细胞中可能存在另一种尚未鉴定的组胺受体调节细胞存活。
