Fillion L, Collins A, Southon S
Rowett Research Institute, Bucksburn, Aberdeen, UK.
Acta Biochim Pol. 1998;45(1):183-90.
Epidemiological studies have revealed a strong correlation between high intake of fruit and vegetables and low incidence of certain cancers. Micronutrients present in these foods are thought to decrease free radical attack on DNA and hence protect against mutations that cause cancer, but the fine details of the causal mechanism have still to be elucidated. Whether dietary factors can modulate DNA repair--a crucial element in the avoidance of carcinogenesis--is an intriguing question that has not yet been satisfactorily answered. In order to investigate the effects of beta-carotene on oxidative damage and its repair, volunteers were given a single 45 mg dose and lymphocytes taken before and after the supplement were treated in vitro with H2O2. DNA strand breaks and oxidised pyrimidines were measured at intervals, to monitor the removal of oxidative DNA damage. We found inter-individual variations in response. In cases where the baseline plasma beta-carotene concentration was high, or where supplementation increased the plasma concentration, recovery from oxidative damage (i.e. removal of both oxidised pyrimidines and strand breaks) was relatively rapid. However, what seems to be an enhancement of repair might in fact represent an amelioration of the continuing oxidative stress encountered by the lymphocytes under in vitro culture conditions. We found that culture in a 5% oxygen atmosphere enhanced recovery of lymphocytes from H2O2 damage.
流行病学研究表明，大量摄入水果和蔬菜与某些癌症的低发病率之间存在密切关联。这些食物中含有的微量营养素被认为可以减少自由基对DNA的攻击，从而预防导致癌症的突变，但因果机制的具体细节仍有待阐明。饮食因素是否能够调节DNA修复（这是避免致癌作用的关键因素）是一个尚未得到圆满解答的有趣问题。为了研究β-胡萝卜素对氧化损伤及其修复的影响，给志愿者单次服用45毫克剂量的β-胡萝卜素，并在补充前后采集淋巴细胞，然后在体外用过氧化氢进行处理。定期测量DNA链断裂和氧化嘧啶，以监测氧化DNA损伤的清除情况。我们发现个体之间的反应存在差异。在基线血浆β-胡萝卜素浓度较高或补充后血浆浓度升高的情况下，氧化损伤的恢复（即氧化嘧啶和链断裂的清除）相对较快。然而，看似修复增强的情况实际上可能代表着淋巴细胞在体外培养条件下所遭遇的持续氧化应激得到了改善。我们发现，在5%氧气氛围中培养可增强淋巴细胞从过氧化氢损伤中的恢复能力。
