Valverde M, Trejo C, Rojas E
Departamento de Genética y Toxicología Ambiental, Instituto de Investigaciones Biomédicas and Instituto de Fisiología Celular, UNAM Ciudad Universitaria, CP 04510, México D.F., Mexico.
Mutagenesis. 2001 May;16(3):265-70. doi: 10.1093/mutage/16.3.265.
Even though the toxic effects of lead and cadmium compounds have been studied over many years, inconsistent results have been obtained about their mutagenic, clastogenic and carcinogenic properties. However, these metals are considered to be potential human carcinogens. The mechanism of metal-induced carcinogenesis is still unknown, but one possible pathway may involve the interaction of metals with DNA, either directly or indirectly. In this work we explore the capacity of lead, cadmium or a mixture of both metals to interact with acellular DNA, by employing a variant of the comet assay. Our results, using low non-cytotoxic metal concentrations (0.01, 0.1 and 1.0 microM) with the standard protocol for the acellular assay, showed an induction of DNA damage in cells of all organs studied; however, basal DNA damage was different in each organ. To confirm that we were working with pure DNA, proteinase K was added to the lysis solution. With this enriched-lysis solution we found a negative response in the induction of DNA damage in cells derived from the liver, kidney and lung of CD-1 male mice. To support the results obtained by the enriched-acellular assay, we studied the capacity of lead and cadmium (0.1 microM) to induce breaks in pooled genomic DNA in cells of the same organs, with negative results. Consistent with these findings, these metals do not induce DNA breaks in the plasmid pUSE amp+. On the whole, we did not detect direct induction of DNA strand breaks by lead acetate, cadmium chloride or a mixture of both metals, all at low non-cytotoxic concentrations. However, we found an induction of lipid peroxidation and an increase in free radical levels in the different organs of CD-1 male mice after inhalation of lead acetate (0.0068 microg/cc) or cadmium chloride (0.08 microg/cc) for 1 h, suggesting the induction of genotoxicity and carcinogenicity by indirect interactions, such as oxidative stress.
尽管铅和镉化合物的毒性作用已研究多年，但关于它们的致突变性、染色体断裂性和致癌性，研究结果并不一致。然而，这些金属被认为是潜在的人类致癌物。金属诱导致癌的机制尚不清楚，但一种可能的途径可能涉及金属与DNA直接或间接的相互作用。在这项工作中，我们采用彗星试验的一种变体，探索铅、镉或这两种金属的混合物与无细胞DNA相互作用的能力。我们使用低非细胞毒性金属浓度（0.01、0.1和1.0微摩尔）并按照无细胞试验的标准方案进行实验，结果显示在所研究的所有器官的细胞中均诱导了DNA损伤；然而，每个器官的基础DNA损伤情况不同。为了确认我们处理的是纯DNA，在裂解液中加入了蛋白酶K。使用这种富集裂解液，我们发现CD - 1雄性小鼠肝脏、肾脏和肺细胞的DNA损伤诱导呈阴性反应。为了支持富集无细胞试验获得的结果，我们研究了铅和镉（0.1微摩尔）诱导相同器官细胞中汇集的基因组DNA断裂的能力，结果为阴性。与这些发现一致，这些金属不会诱导质粒pUSE amp +中的DNA断裂。总体而言，我们未检测到低非细胞毒性浓度的醋酸铅、氯化镉或这两种金属的混合物直接诱导DNA链断裂。然而，我们发现吸入醋酸铅（0.0068微克/立方厘米）或氯化镉（0.08微克/立方厘米）1小时后，CD - 1雄性小鼠不同器官中的脂质过氧化作用增强，自由基水平升高，这表明通过氧化应激等间接相互作用诱导了遗传毒性和致癌性。
