Norwood J, Ledbetter A D, Doerfler D L, Hatch G E
National Health and Environmental Effects Research Laboratory, Office of Research and Development, MD-82, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA.
Toxicol Sci. 2001 May;61(1):144-53. doi: 10.1093/toxsci/61.1.144.
Inhaled urban particulate matter (PM) often contains metals that appear to contribute to its toxicity. These particles first make contact with a thin layer of epithelial lining fluid in the respiratory tract. Antioxidants present in this fluid and in cells might be important susceptibility factors in PM toxicity. We investigated the role of ascorbic acid (C) and glutathione (GSH) as determinants of susceptibility to inhaled residual oil fly ash (ROFA) in guinea pigs (male, Hartley). Guinea pigs were divided into four groups, +C+GSH, +C-GSH, -C+GSH, and -C-GSH, and exposed to clean air or ROFA (< 2.5 micron diameter, 19--25 mg/m(3) nose-only for 2.0 h). C and/or GSH were lowered by either feeding C-depleted diet (1 microg C/kg diet, 2 weeks) and/or by ip injection of a mixture of buthionine-S,R-sulfoximine (2.7 mmol/kg body weight) and diethylmaleate (1.2 mmol/kg, 2 h prior). Nasal lavage (NL) and bronchoalveolar lavage (BAL) fluid and cells were examined at 0 h and 24 h postexposure to ROFA. The C-deficient diet lowered C concentrations in BAL fluid and cells and in NL fluid by 90%, and the GSH-depletion regimen lowered both GSH and C in the BAL fluid and cells by 50%. ROFA deposition was calculated at time 0 from lung Ni levels to be 46 microg/g wet lung. In unexposed animals, the combined deficiency of C and GSH modified the cellular composition of cells recovered in lavage fluid, i.e., the increased number of eosinophils and macrophages in BAL fluid. ROFA inhalation increased lung injury in the -C-GSH group only (evidenced by increased BAL protein, LDH and neutrophils, and decreased BAL macrophages). ROFA exposure decreased C in BAL and NL at 0 h, and increased BAL C and GSH (2- to 4-fold above normal) at 24 h in nondepleted guinea pigs, but had no effect on C and GSH in depleted guinea pigs. Combined deficiency of C and GSH resulted in the highest macrophage and eosinophil counts of any group. GSH depletion was associated with increased BAL protein and LDH, increased numbers of BAL macrophages and eosinophils, and decreased rectal body temperatures. We conclude that combined deficiency of C and GSH increased susceptibility to inhaled ROFA; caused unusual BAL cellular changes; resulted in lower antioxidant concentrations in BAL than were observed with single deficiencies. Antioxidant deficiency may explain increased susceptibility to PM in elderly or diseased populations and may have important implications for extrapolating animal toxicity data to humans.
吸入的城市颗粒物（PM）通常含有一些金属，这些金属似乎会导致其毒性。这些颗粒首先与呼吸道中的一层薄薄的上皮衬液接触。该液体和细胞中存在的抗氧化剂可能是PM毒性的重要易感性因素。我们研究了抗坏血酸（C）和谷胱甘肽（GSH）作为豚鼠（雄性，哈特利）对吸入的残留油飞灰（ROFA）易感性决定因素的作用。将豚鼠分为四组，即+C+GSH、+C - GSH、 - C+GSH和 - C - GSH组，并使其暴露于清洁空气或ROFA（直径<2.5微米，仅经鼻19 - 25毫克/立方米，持续2.0小时）。通过喂食缺乏C的饮食（1微克C/千克饮食，持续2周）和/或腹腔注射丁硫氨酸 - S，R - 亚砜胺（2.7毫摩尔/千克体重）和马来酸二乙酯（1.2毫摩尔/千克，暴露前2小时）的混合物来降低C和/或GSH的水平。在暴露于ROFA后的0小时和24小时检查鼻灌洗（NL）液、支气管肺泡灌洗（BAL）液和细胞。缺乏C的饮食使BAL液、细胞和NL液中的C浓度降低了90%，而GSH耗竭方案使BAL液和细胞中的GSH和C均降低了50%。根据肺镍水平在0小时计算出ROFA沉积量为46微克/克湿肺。在未暴露的动物中，C和GSH的联合缺乏改变了灌洗液中回收细胞的细胞组成，即BAL液中嗜酸性粒细胞和巨噬细胞数量增加。仅 - C - GSH组吸入ROFA会增加肺损伤（表现为BAL蛋白、乳酸脱氢酶和中性粒细胞增加，BAL巨噬细胞减少）。在未耗竭的豚鼠中，ROFA暴露在0小时会降低BAL和NL中的C，并在24小时使BAL中的C和GSH增加（比正常水平高2至4倍），但对耗竭的豚鼠中的C和GSH没有影响。C和GSH的联合缺乏导致所有组中巨噬细胞和嗜酸性粒细胞计数最高。GSH耗竭与BAL蛋白和乳酸脱氢酶增加、BAL巨噬细胞和嗜酸性粒细胞数量增加以及直肠体温降低有关。我们得出结论，C和GSH的联合缺乏增加了对吸入ROFA的易感性；导致了不寻常的BAL细胞变化；导致BAL中的抗氧化剂浓度低于单一缺乏时观察到的浓度。抗氧化剂缺乏可能解释了老年人或患病群体对PM易感性增加的原因，并且可能对将动物毒性数据外推至人类具有重要意义。
