Kobayashi Hatasu, Oikawa Shinji, Hirakawa Kazutaka, Kawanishi Shosuke
Department of Environmental and Molecular Medicine, Mie University School of Medicine, Edobashi 2-174, Tsu, Mie 514-8507, Japan.
Mutat Res. 2004 Mar 14;558(1-2):111-20. doi: 10.1016/j.mrgentox.2003.11.002.
Propyl gallate (PG), widely used as an antioxidant in foods, is carcinogenic to mice and rats. PG increased the amount of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), a characteristic oxidative DNA lesion, in human leukemia cell line HL-60, but not in HP100, which is hydrogen peroxide (H2O2)-resistant cell line derived from HL-60. Although PG induced no or little damage to 32P-5'-end-labeled DNA fragments obtained from genes that are relevant to human cancer, DNA damage was observed with treatment of esterase. HPLC analysis of the products generated from PG incubated with esterase revealed that PG converted into gallic acid (GA). GA induced DNA damage in a dose-dependent manner in the presence of Fe(III)EDTA or Cu(II). In the presence of Fe(III) complex such as Fe(III)EDTA or Fe(III)ADP, GA caused DNA damage at every nucleotide. Fe(III) complex-mediated DNA damage by GA was inhibited by free hydroxy radical (*OH) scavengers, catalase and an iron chelating agent. These results suggested that the Fe(III) complex-mediated DNA damage caused by GA is mainly due to *OH generated via the Fenton reaction. In the presence of Cu(II), DNA damage induced by GA occurred at thymine and cytosine. Although *OH scavengers did not prevent the DNA damage, methional inhibited the DNA damage. Cu(II)-mediated DNA damage was inhibited by catalase and a Cu(I) chelator. These results indicated that reactive oxygen species formed by the interaction of Cu(I) and H2O2 participates in the DNA damage. GA increased 8-oxodG content in calf thymus DNA in the presence of Cu(II), Fe(III)EDTA or Fe(III)ADP. This study suggested that metal-mediated DNA damage caused by GA plays an important role in the carcinogenicity of PG.
棓丙酯（PG）在食品中广泛用作抗氧化剂，对小鼠和大鼠具有致癌性。PG增加了人白血病细胞系HL-60中8-氧代-7,8-二氢-2'-脱氧鸟苷（8-氧代dG）的含量，8-氧代dG是一种典型的氧化性DNA损伤，但在HP100中未增加，HP100是源自HL-60的抗过氧化氢（H2O2）细胞系。尽管PG对从与人类癌症相关的基因获得的32P-5'-末端标记的DNA片段没有或几乎没有造成损伤，但用酯酶处理时观察到了DNA损伤。对PG与酯酶孵育产生的产物进行高效液相色谱分析表明，PG转化为没食子酸（GA）。在Fe（III）EDTA或Cu（II）存在下，GA以剂量依赖性方式诱导DNA损伤。在Fe（III）络合物如Fe（III）EDTA或Fe（III）ADP存在下，GA在每个核苷酸处都导致DNA损伤。GA介导的Fe（III）络合物对DNA的损伤被游离羟基自由基（OH）清除剂、过氧化氢酶和铁螯合剂抑制。这些结果表明，GA引起的Fe（III）络合物介导的DNA损伤主要是由于通过芬顿反应产生的OH。在Cu（II）存在下，GA诱导的DNA损伤发生在胸腺嘧啶和胞嘧啶处。尽管*OH清除剂不能阻止DNA损伤，但甲硫醛抑制了DNA损伤。Cu（II）介导的DNA损伤被过氧化氢酶和Cu（I）螯合剂抑制。这些结果表明，Cu（I）与H2O2相互作用形成的活性氧参与了DNA损伤。在Cu（II）、Fe（III）EDTA或Fe（III）ADP存在下，GA增加了小牛胸腺DNA中8-氧代dG的含量。这项研究表明，GA引起的金属介导的DNA损伤在PG的致癌性中起重要作用。
