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化学品的生产与使用改善了人类生活质量,但与此同时引发的环境问题和健康危害也不容忽视[1],化学物质可以通过多种途径排放到大气和水体中,母体化合物在环境中发生各种反应,可能会产生毒性更强的污染物[2]. 目前的毒性评价研究更多关注母体化学物质的毒性效应,需进一步研究其在环境中转化产物的毒性和健康效应[3].
吡啶类化合物广泛应用于燃料、农药和医药等生产中[4],被大量排放到环境中,在大气、水和土壤介质中广泛存在. 吡啶是一种高水溶性的含氮芳香族有机化合物,环境中的吡啶类污染物可通过化学和生物方式降解为羟基吡啶[5-6]. 研究表明,许多吡啶化合物具有较强的生物活性,容易诱导急性、亚急性和遗传毒性效应[7]. 遗传毒性特别重要,它与致突变性、致癌性以及癌症有关,氧化应激和DNA损伤修复是遗传毒性中的两条通路,由环境中化学物质引起细胞氧化应激或DNA损伤均可能导致可遗传的性状改变,如细胞突变,可进一步引发癌症[8],有研究表明羟基吡啶可对细胞造成氧化应激,进一步诱导遗传毒性[9]. 突变型和致癌性的生态健康问题越来越凸显,因此需要具有高效率和低成本的遗传毒性筛查评估方法. 大肠杆菌是一种被充分研究的模式生物,基于大肠杆菌的高通量基因毒性评估已经成为DNA损伤修复和氧化应激的重要手段,在环境污染物的暴露下,大肠杆菌中的基因会编码蛋白质进行相关修复,并生成绿色荧光蛋白. 该方法可以检测和量化DNA损伤修复以及氧化应激通路中蛋白质的分子水平变化,涵盖了29种基因标志物,可以对环境污染物进行快速、定量的毒性评估[10-11]. 有机污染物在环境中的降解产物可能表现出比原始污染物更大的毒性效应[12]. 目前,对于吡啶类化合物在光降解过程的中间产物的毒性效应了解甚少,是否会产生毒性更强的转化产物尚未可知,因此运用基于遗传毒性的评价方法评估化学物质的损伤效应能为保护人体健康提供一定的参考价值.
太阳中的紫外线根据波长可以分为UVA(315—400 nm),UVB(280—315 nm)和UVC(200—290 nm),UVC大部分被平流层中的臭氧吸收,到达地面的主要为UVA和UVB[13],2-py、3-py、4-py和2,6-dm-3-py在大气环境中广泛存在,可以在紫外线的作用下发生变化,4种吡啶类化合物对紫外线的吸收峰值距离365 nm和312 nm较近,对这两种波长的紫外线吸收效果较好. 本文利用天然发光菌(费氏弧菌)和重组发光大肠杆菌,研究4种吡啶类化合物经365 nm和312 nm紫外线照射后急性毒性、遗传毒性和氧化应激毒性变化规律.
紫外线照射对羟基吡啶毒性效应的影响
Study on mechanism of toxicity of pyridine compounds under ultraviolet irradiation
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摘要: 吡啶类化合物广泛存在于各种环境介质中,本文以羟基吡啶(2-羟基吡啶(2-py)、3-羟基吡啶(3-py)、4-羟基吡啶(4-py)和2,6-二甲基-3-羟基吡啶(2,6-dm-3-py))为研究对象,利用费氏弧菌和基因重组大肠杆菌,评估4种羟基吡啶经紫外线照射后急性毒性、遗传毒性和氧化应激效应变化规律. 结果表明,2-py、3-py和2,6-dm-3-py经365 nm和312 nm紫外线照射后,毒性随照射时间延长而增强,其急性毒性相较于未照射前,分别增强了24.7%—99.4%和84.0%—99.9%(照射8 h后). 而4-py 经两种波长的紫外线照射后毒性变化不同,经365 nm紫外线照射后,急性毒性降低;但经312 nm紫外线照射8 h后,急性毒性增强77.7%,说明4-py经两种波长紫外线照射后生成了不同的降解产物. 遗传毒性测试结果表明,4种羟基吡啶及其降解产物对DNA损伤和修复过程具有浓度依赖性,在20—100 mg·L−1C浓度下,细胞SOS响应和氧化还原应激相关基因表达显著,但在6.4 —10 mg·L−1C 浓度范围内,毒性相关基因表达变化不大,说明4种羟基吡啶及其降解产物在20—100 mg·L−1 C内可引起DNA损伤和氧化应激效应.Abstract: Pyridine compounds are widely found in various environments. In order to understand the toxic effects in the environment and reveal the influence of ultraviolet (UV) light on their toxicity, the toxicities of 4 pyridine compounds (2-hydroxypyridine (2-py), 3-hydroxypyridine (3-py), 4-hydroxypyridine (4-py) and 2,6-dimethyl-3-hydroxypyridine (2,6-dm-3-py) and their degradation products after UV irradiation were evaluated by both Vibrio fischeri luminescence inhibition assay and genotoxicity assay using recombinant Escherichia coli, respectively. The results showed that the acute toxicities of 2-py, 3-py and 2, 6-dm-3-py increased by 24.7%—99.4% and 84.0%—99.9% after 365 nm and 312 nm UV irradiation for 8 h, respectively. The acute toxicity of 4-py was unchanged after irradiated by 365 nm UV for 8 h, on the contrary, increased by 77.7% after irradiation at 312 nm for 8 h. The DNA damage and repair process induced by the four pyridine compounds and their degradation products was concentration-depended. At the concentration of 20—100 mg·L−1C, the SOS response and Redox stress-related genes were significantly expressed, but at the concentration of 6.4 mg·L−1 to 10 mg·L−1C, the expression of toxicity-related genes showed little change, indicating that the four pyridine compounds and their degradation products at 20—100 mg·L−1C could cause DNA damage and oxidative stress.
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图 2 4种羟基吡啶(a: 4-py, b: 3-py, c: 2-py, d: 2,6-dm-3-py,未经辐照、经365 nm和312 nm紫外线辐照2 h)对重组菌遗传毒性及氧化应激毒性通路相关基因表达谱的影响
Figure 2. Effects of 4 kinds of pyridine compounds (a: 4-py, b: 3-py, c: 2-py, d: 2,6-dm-3-py, unirradiated, irradiated for 2 h with 365 and 312 nm) on the expression of genes involved in genotoxicity and oxidative stress pathways in recombinant bacteria.
图 3 羟基吡啶化合物(a-d: DNA应激相关基因TELI值,其中a: 4-py, b: 3-py, c: 2-py, d: 2,6-dm-3-py,e-f: 氧化应激相关基因TELI值,其中e: 4-py, f: 3-py, g: 2-py, h: 2,6-dm-3-py,未经辐照、经365 nm和312 nm紫外线照射1h、2 h)基于TELI值的剂量响应曲线
Figure 3. Dose response curves(The TELI value of the blank control group during DNA stress was 19, and that of the blank control group during oxidative stress was 10) based on TELI values for 4 kinds of pyridine compounds
表 1 四种羟基吡啶样品
Table 1. Four hydroxypyridine samples
中文名称
Chinese name英文名称
English name简称
Abbreviation分子式
Molecular formulaCAS 4-羟基吡啶 4-pyridone 4-py C5H5NO 626-64-2 3-羟基吡啶 3-pyridone 3-py C5H5NO 109-00-2 2-羟基吡啶 2-pyridone 2-py C5H5NO 142-08-5 2,6-二甲基-3-羟基吡啶 2,6-Dimethyl-3-pyridone 2,6-dm-3-py C7H9NO 1122-43-6 表 2 所选重组大肠杆菌重组基因及其功能
Table 2. Endpoints and functions of genes selected by genotoxicity tests
基因通路
Gene pathways基因
Genes功能
FunctionsDNA应激
DNA stressuvrA 识别细胞内的损伤 recX 调控基因 dinG 超家族II解旋酶之一 ybfE DNA损伤耐受 sbmC 调节基因 ftsK 编码ATP酶 recN 维持染色体结构 yebG 受到lexA基因的调控 sulA 为受损DNA修复提供时间 polB 参与碱基切除修复 uvrD 超家族I DNA解旋酶 lexA 调控DNA修复和突变 DNA应激
DNA stressrecA 调控DNA修复和突变 umuD 参与基因突变 ssb 参与定向错配修复 ada 参与DNA烷基化修复基因转录 mutT 参与碱基切除修复 dinB 编码DNA聚合酶 nfo 参与碱基切除修复 氧化还原应激
Redox stresssoxS 活性氧传感器,编码抗氧化酶 soxR 活性氧传感器,编码抗氧化酶 oxyR 活性氧传感器,保护细胞 inaA 编码蛋白酶 dps 非特异性DNA结合蛋白 ahpF 调节烷基氢过氧化物还原酶 katG 消除过氧化氢 sodA 调控超氧化物歧化酶 ahpC 调节烷基氢过氧化物还原酶 katE 消除过氧化氢 -
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