Wright D T, Adler K B, Akley N J, Dailey L A, Friedman M
Department of Toxicology, North Carolina State University, Raleigh 27695.
Toxicol Appl Pharmacol. 1994 Jul;127(1):27-36. doi: 10.1006/taap.1994.1135.
Inhalation of ozone (O3) has been associated with development of inflammation in the respiratory airways and a variety of alterations in pulmonary function. Epithelial cells lining the airways are the first cells with which inhaled O3 comes into contact and thus represent a potential major target of acute O3 toxicity. In addition, upon appropriate stimulation or injury, these cells are capable of releasing a spectrum of secondary mediators that could relate to the pathogenesis of O3-associated lesions. We exposed organotypically cultured guinea pig primary tracheal epithelial (GPTE) cells in an air/liquid interface to photochemically generated O3 in vitro and monitored effects of O3 exposure on activation of phospholipases A2 (PLA2), C (PLC), and D (PLD), as well as release of the humoral mediator, platelet activating factor (PAF). PLA2 acts on ether-linked phosphatidylcholine, which upon further metabolism forms PAF;PLC acts on inositol phospholipids to produce inositol phosphates and diacylglycerol; and PLD generates phosphatidic acid. GPTE cell cultures exposed to O3 (0.05-1.0 ppm) for 1 hr displayed an elevated total release of PAF (apical+basolateral). Maximal stimulation in both apical and total release of PAF occurred at 1.0 ppm O3 (405 +/- 47 and 282 +/- 23% of air control values, respectively, n = 7). The 1.0 ppm O3-induced increased PAF release was significantly inhibitable by the PLA2 inhibitor mepacrine (1 mM), suggesting a connection between PAF release and PLA2 activation. O3 exposure activated PLC in GPTE cells in a concentration- (0.1-1.0 ppm) and time-dependent (10-60 min) manner to produce a significant accumulation of inositol-1,4,5-triphosphate, with maximal accumulation at 1.0 ppm O3 for 1 hr (417 +/- 121% of air control, n = 6). PAF receptor antagonists Ro 24-4736 (1 microM) and Ro 41-5036 (1 microM) did not affect O3-stimulated inositol phosphate accumulation. PLD also was activated in GPTE cells exposed to 1.0 ppm O3 for 1 hr (169 +/- 80% of air control, n = 5). These results suggest that GPTE cells respond to O3 exposure in vitro by increasing production and/or release of PAF via a mechanism that may involve activation of PLA2, PLC, and PLD. Epithelial-derived mediators, such as PAF, may play a role in the pathogenesis of lesions associated with inhalation of O3.
吸入臭氧（O₃）与呼吸道炎症的发展以及肺功能的多种改变有关。呼吸道内衬的上皮细胞是吸入的O₃首先接触的细胞，因此是急性O₃毒性的潜在主要靶点。此外，在适当的刺激或损伤后，这些细胞能够释放一系列可能与O₃相关病变发病机制有关的二级介质。我们在气液界面将器官型培养的豚鼠原代气管上皮（GPTE）细胞体外暴露于光化学产生的O₃中，并监测O₃暴露对磷脂酶A₂（PLA₂）、C（PLC）和D（PLD）激活的影响，以及体液介质血小板活化因子（PAF）的释放。PLA₂作用于醚键连接的磷脂酰胆碱，后者进一步代谢形成PAF；PLC作用于肌醇磷脂产生肌醇磷酸和二酰甘油；PLD产生磷脂酸。暴露于O₃（0.05 - 1.0 ppm）1小时的GPTE细胞培养物显示PAF的总释放量（顶端 + 基底外侧）升高。PAF顶端释放和总释放的最大刺激在1.0 ppm O₃时出现（分别为空气对照值的405 ± 47%和282 ± 23%，n = 7）。1.0 ppm O₃诱导的PAF释放增加可被PLA₂抑制剂米帕林（1 mM）显著抑制，表明PAF释放与PLA₂激活之间存在联系。O₃暴露以浓度（0.1 - 1.0 ppm）和时间依赖性（10 - 60分钟）的方式激活GPTE细胞中的PLC，以产生肌醇-1,4,5-三磷酸的显著积累，在1.0 ppm O₃暴露1小时时积累最大（为空气对照的417 ± 121%，n = 6）。PAF受体拮抗剂Ro 24 - 4736（1 μM）和Ro 41 - 5036（1 μM）不影响O₃刺激的肌醇磷酸积累。暴露于1.0 ppm O₃ 1小时的GPTE细胞中的PLD也被激活（为空气对照的169 ± 80%，n = 5）。这些结果表明，GPTE细胞在体外对O₃暴露的反应是通过可能涉及PLA₂、PLC和PLD激活的机制增加PAF的产生和/或释放。上皮来源的介质，如PAF，可能在与吸入O₃相关的病变发病机制中起作用。
