Li X Y, Gilmour P S, Donaldson K, MacNee W
Department of Medicine, Royal Infirmary, Edinburgh, UK.
Thorax. 1996 Dec;51(12):1216-22. doi: 10.1136/thx.51.12.1216.
Epidemiological evidence has implicated fine particulate air pollution, particularly particles less than 10 microns in diameter (PM10), in the development of exacerbations of asthma and chronic obstructive pulmonary disease (COPD) although the mechanism is unknown. The hypothesis that PM10 particles induce oxidant stress, causing inflammation and injury to airway epithelium, was tested.
The effects of intratracheal instillation of PM10 was assessed in rat lungs (three per group). Inflammatory cell influx was measured by bronchoalveolar lavage (BAL) and air space epithelial permeability was assessed as the total protein in BAL fluid in vivo. The oxidant properties of PM10 particles were determined by their ability to cause damage to plasmid DNA and by changes in reduced (GSH) and oxidised (GSSG) glutathione. The effects of PM10 particles were compared in some experiments with those of fine (CB) and ultrafine (ufCB) carbon black particles.
Six hours after intratracheal instillation of PM10 there was an influx of neutrophils (up to 15% of total cells in BAL fluid) into the alveolar space, increased epithelial permeability, the mean (SE) total protein in the BAL fluid increasing from 0.39 (0.01) to 0.62 (0.01) mg/ml, and increased lactate dehydrogenase (LDH) concentrations in the BAL fluid. An even greater inflammatory response was seen following intratracheal instillation of ufCB but not following CB instillation. PM10 particles had free radical activity in vivo, as shown by a decrease in GSH levels in the BAL fluid from 0.36 (0.05) to 0.25 (0.01) nmol/ml following instillation. The free radical activity of PM10 was confirmed in vitro by its ability to deplete supercoiled plasmid DNA, an effect which could be reversed by mannitol, a specific hydroxyl radical scavenger. BAL fluid leucocytes from rats treated with PM10 produced greater amounts of nitric oxide (NO), measured as nitrite (control 3.07 (0.33), treated 4.45 (0.23) microM/1 x 10(6) cells), and tumour necrosis factor alpha (control 21.0 (3.1), treated 179.2 (29.4) units/l x 10(6) cells) in culture than those obtained from control animals. Since the PM10 preparation was contaminated with small amounts of filter fibres due to the extraction process, the effects of instillation of filter fibres alone was assessed. These studies showed that filter fibres did not account for the proinflammatory and injurious effects of the PM10 suspension.
These findings provide evidence that PM10 has free radical activity and causes lung inflammation and epithelial injury. These data support the proposed hypothesis for the mechanism by which particulate air pollution causes adverse effects in patients with airways diseases.
流行病学证据表明，细颗粒物空气污染，尤其是直径小于10微米的颗粒物（PM10），与哮喘和慢性阻塞性肺疾病（COPD）急性加重的发生有关，但其机制尚不清楚。本研究对PM10颗粒诱发氧化应激，导致气道上皮炎症和损伤这一假说进行了验证。
通过气管内滴注PM10评估其对大鼠肺脏的影响（每组3只）。通过支气管肺泡灌洗（BAL）检测炎症细胞流入情况，并在体内将BAL液中的总蛋白作为气腔上皮通透性的评估指标。通过PM10颗粒对质粒DNA的损伤能力以及还原型（GSH）和氧化型（GSSG）谷胱甘肽的变化来确定其氧化特性。在一些实验中，将PM10颗粒的作用与细炭黑颗粒（CB）和超细炭黑颗粒（ufCB）进行了比较。
气管内滴注PM10后6小时，中性粒细胞流入肺泡腔（占BAL液中细胞总数的15%），上皮通透性增加，BAL液中总蛋白平均（SE）含量从0.39（0.01）mg/ml增至0.62（0.01）mg/ml，BAL液中乳酸脱氢酶（LDH）浓度升高。气管内滴注ufCB后炎症反应更明显，但滴注CB后未出现这种情况。PM10颗粒在体内具有自由基活性，滴注后BAL液中GSH水平从0.36（0.05）nmol/ml降至0.25（0.01）nmol/ml即表明了这一点。PM10的自由基活性在体外也得到证实，它能够使超螺旋质粒DNA减少，甘露醇（一种特异性羟基自由基清除剂）可逆转这一作用。与对照组动物相比，用PM10处理的大鼠BAL液白细胞在培养过程中产生更多的一氧化氮（NO）（以亚硝酸盐计，对照组为3.07（0.33），处理组为4.45（0.23）μM/1×$10^6$细胞）和肿瘤坏死因子α（对照组为21.0（3.1），处理组为179.2（29.4）单位/1×$10^6$细胞）。由于提取过程导致PM10制剂被少量滤过纤维污染，因此评估了单独滴注滤过纤维的影响。这些研究表明，滤过纤维不能解释PM10悬浮液的促炎和损伤作用。
这些发现提供了证据，证明PM10具有自由基活性，并可导致肺部炎症和上皮损伤。这些数据支持了关于颗粒物空气污染对气道疾病患者产生不利影响机制的假说。
