Gilmour P S, Brown D M, Lindsay T G, Beswick P H, MacNee W, Donaldson K
Department of Biological Sciences and Advanced Materials Centre, Napier University, Edinburgh, Scotland.
Occup Environ Med. 1996 Dec;53(12):817-22. doi: 10.1136/oem.53.12.817.
Environmental particles < 10 microns average aerodynamic diameter (PM10) are associated with mortality, exacerbation of airways diseases, and decrement in lung function. It is hypothesised that PM10 particles, along with other pathogenic particles, generate free radicals at their surface in reactions involving iron, and that this is a factor in the pathogenicity of PM10 particles. Identification of free radical activity in PM10 and examination of the content and role of iron in this process was undertaken.
Free radical activity was detected with a supercoiled plasmid, phi X174 RF1 DNA, and measured as scission of the supercoiled DNA (mediated by free radicals) by scanning laser densitometry. The role of the hydroxyl radical was confirmed by the use of the specific scavenger mannitol, and the role of iron investigated with the iron chelator desferrioxamine-B (DSF-B). Iron released from PM10 particles at pH 7.2 and pH 4.6 (to mimic conditions on the lung surface and in macrophage phagolysosomes, respectively) was assessed spectrophotometrically with the Fe++ chelator ferrozine and the Fe+ + + chelator DSF-B.
PM10 particles showed significant free radical activity by their ability to degrade supercoiled DNA. A substantial part of this activity was due to the generation of hydroxyl radicals, as shown by partial protection with mannitol. Similarly, DSF-B also conferred protection against the damage caused to plasmid DNA indicating the role of iron in generation of hydroxyl radicals. Negligible Fe++ was released at either pH 7.2 or pH 4.6 by contrast with Fe+ + +, which was released in substantial quantities at both pHs, although twice as much was released at pH 4.6.
PM10 particles generate the hydroxyl radical, a highly deleterious free radical, in aqueous solution. This occurs by an iron dependent process and hydroxyl radicals could play a part in the pathogenicity of PM10 particles. Iron release was greatest at the pH of the lysosome (pH 4.6) indicating that iron may be mobilised inside macrophages after phagocytosis, leading to oxidative stress in the macrophages.
平均空气动力学直径小于10微米的环境颗粒物（PM10）与死亡率、气道疾病加重以及肺功能下降有关。据推测，PM10颗粒与其他致病颗粒一起，在涉及铁的反应中在其表面产生自由基，而这是PM10颗粒致病性的一个因素。对PM10中的自由基活性进行了鉴定，并对该过程中铁的含量和作用进行了研究。
用超螺旋质粒phi X174 RF1 DNA检测自由基活性，并通过扫描激光密度测定法将超螺旋DNA的断裂（由自由基介导）作为自由基活性的衡量指标。通过使用特异性清除剂甘露醇证实了羟基自由基的作用，并使用铁螯合剂去铁胺-B（DSF-B）研究了铁的作用。用Fe++螯合剂亚铁嗪和Fe+++螯合剂DSF-B通过分光光度法评估在pH 7.2和pH 4.6（分别模拟肺表面和巨噬细胞吞噬溶酶体中的条件）下从PM10颗粒中释放的铁。
PM10颗粒通过其降解超螺旋DNA的能力表现出显著的自由基活性。如甘露醇的部分保护所示，这种活性的很大一部分是由于羟基自由基的产生。同样，DSF-B也对质粒DNA所受的损伤起到保护作用，表明铁在羟基自由基的产生中起作用。与Fe+++相比，在pH 7.2或pH 4.6时释放的Fe++可忽略不计，Fe+++在两个pH值下都大量释放，尽管在pH 4.6时释放量是前者的两倍。
PM10颗粒在水溶液中产生羟基自由基，这是一种高度有害的自由基。这是通过铁依赖性过程发生的，羟基自由基可能在PM10颗粒的致病性中起作用。在溶酶体的pH值（pH 4.6）下铁释放量最大，表明铁可能在吞噬作用后在巨噬细胞内被动员，导致巨噬细胞内的氧化应激。
