MECHANISMS OF TRANSITION METAL-INDUCED CARCINOGENESIS

过渡金属致癌机制

• 批准号: 6289067
• 负责人: Lucy M Anderson
• 金额: --
• 依托单位: DIVISION OF BASIC SCIENCES - NCI
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6289067
• 关键词: DNA damage; DNA repair; chemical carcinogenesis; chemical related neoplasm /cancer; deoxyguanosine; free radical oxygen; heavy metals; histones; kidney; laboratory rat; liver; metal complex; metalloenzyme; molecular oncology; nickel; oxidation; oxidative stress

Certain transition metals, including nickel, chromium, cadmium, and copper, are carcinogenic to humans and/or animals. Their effects include cancer in the progeny of fathers exposed to welding fumes and other metal dusts. However, mechanisms of the carcinogenic activity of these metals remain obscure. In recent years, we have been testing a hypothesis that one such mechanism would involve metal-mediated oxidative damage to DNA and nuclear proteins. In 1998/99 we continued mechanistic studies of that hypothesis. Our investigations on transition metals interactions with protamine HP2 were directed towards binding of Zn(II) and Ni(II) to its model peptides HP2 1-15, HP2 1-25, HP2 26-40, HP2 37-47, HP2 43-57, and the effects of this binding on association of the peptides with a 20-mer double stranded oligonucleotide. Zn(II) was found to bind to all these peptides and increase their association with the oligonucleotide, although with different strength. Zn(II) binding sites differed from those for Ni(II).Using synthetic model peptides, we continued to investigate Ni(II) interactions with the core histones. The formation of a strong complex at pH 7 and above with the TESHHK motif in the C-terminal tail of histone H2A and hydrolysis of this motif by Ni(II) were confirmed in longer peptides, acetyl-TESHHKAKGK, and a 34-mer peptide (H2A 1-34) modeling the entire tail. The primary complexes lack significant oxidation-mediating activity towards DNA. However, a secondary complex formed between Ni(II) and the SHHKAKGK product of hydrolysis of the primary complexes is redox-active and is capable of enhancing oxidative damage by hydrogen peroxide to plasmid DNA (single strand breaks and base oxidation). Also, this complex is degraded by hydrogen peroxide, especially at its histidine and serine residues. Since the physiological roles of the histone tail include locking interactions with other histones and DNA, the observed truncation of this tail by Ni(II) may affect gene expression. The redox activity of the cut-off product may enhance promutagenic damage to DNA.Another investigation focused on 8-oxo-dGTPases, a class of enzymes preventing incorporation of promutagenic 8-oxo-dGTP into DNA. Our former experiments revealed strong inhibition by Cd(II) and weak inhibition by Ni(II) of the isolated mammalian enzyme. Using our newly developed in vivo assay for 8-oxo-dGTPase we confirmed the inhibition of its activity by Cd(II) in the testes of rats exposed to Cd(II), but not Ni(II). The inhibition was accompanied by a significant increase of the promutagenic 8-oxo-dG lesion in testicular DNA. The epigenetic toxicity of Ni(II) was studied in cultured CHO cells. Ni(II) caused cell cycle arrest at G2/M phase and apoptosis. It did not, however, affect the expression of p53 protein. Using the differential display technique, we found that the exposure of cells to Ni(II) resulted in up-regulation of the H ferritin and hSNF2H genes, and down-regulation of the vimentin gene. All the results indicate that Ni(II) and, perhaps, other carcinogenic metals can act through both genetic and epigenetic mechanisms involving oxidative damage and other chemical mechanisms. In addition, our research provides an experimental basis for collaborative studies on oxidative damage by other carcinogenic insults (see projects ZO1 BC 05301 and ZO1 BC 05302). - 8-oxo-dG, Chemical carcinogenesis, dGTPase, DNA damage, DNA repair, Histones, Metal carcinogenesis, Nickel, Nuclear proteins, Protamines,

某些过渡金属，包括镍，铬，镉和铜，对人类和/或动物具有致癌性。它们的影响包括暴露于焊接烟雾和其他金属尘的父亲的后代中的癌症。但是，这些金属的致癌活性机制仍然晦涩难懂。近年来，我们一直在检验一个假设，即这样一种机制将涉及金属介导的对DNA和核蛋白的氧化损伤。在1998/99年，我们继续对该假设进行机械研究。我们对过渡金属与精蛋白HP2相互作用的研究针对Zn（II）和Ni（II）与其模型肽HP2 1-15，HP2 1-25，HP2 1-25，HP2 26-40，HP2 37-47，HP2 37-47，HP2 43-57，以及这种结合对与peptide pypepides的结合的影响。发现锌（II）与所有这些肽结合，并增加与寡核苷酸的缔合，尽管强度不同。 Zn（ii）结合位点与Ni的结合位点不同（II）。通过合成模型肽，我们继续研究Ni（II）与核心组蛋白的相互作用。 Ni（II）在组蛋白H2a的C末端尾部的pH 7及以上形成了pH 7及以上的强络合物，并在较长的肽，乙酰基 - teshhkakgk和34-mer肽（H2A 1-34）中证实了Ni（II）对该基序的水解。初级复合物缺乏对DNA的显着氧化介导活性。然而，在Ni（II）和主要配合物水解的Shhkakgk产物之间形成的二级复合物是氧化还原活性的，能够增强过氧化氢对质粒DNA的氧化损伤（单链断裂和碱基氧化）。同样，该复合物被过氧化氢降解，尤其是在其组氨酸和丝氨酸残基上。由于组蛋白尾巴的生理作用包括与其他组蛋白和DNA的锁定相互作用，因此Ni（II）对此尾巴的截断可能会影响基因表达。截止产物的氧化还原活性可能会增强对DNA的正当损害。另一个研究集中在8-oxo-dgtpase上，这是一类酶，可防止将正当的8-oxo-DGTP掺入DNA中。我们以前的实验表明，CD（II）强烈抑制和Ni（II）对分离的哺乳动物酶的抑制作用。使用我们新开发的体内测定对8-oxo-DGTPase，我们证实了CD（II）在暴露于CD（II）的大鼠睾丸中对其活性的抑制作用，而不是Ni（II）。抑制作用伴随着睾丸DNA中的前期8-oxo-DG病变的显着增加。在培养的CHO细胞中研究了Ni（II）的表观遗传毒性。 Ni（II）在G2/M期和凋亡中引起细胞周期停滞。但是，它不影响p53蛋白的表达。使用差分显示技术，我们发现细胞对Ni（II）的暴露导致H铁蛋白和HSNF2H基因的上调，以及Vimentin基因的下调。所有结果表明，Ni（II）以及其他致癌金属可以通过涉及氧化损伤和其他化学机制的遗传和表观遗传机制作用。此外，我们的研究为其他致癌性损伤提供了有关氧化损害的协作研究的实验基础（请参阅项目ZO1 BC 05301和ZO1 BC 05302）。 -8-oxo-DG，化学癌变，DGTPase，DNA损伤，DNA修复，组蛋白，金属癌变，镍，核蛋白质，精神病