Kamat J P, Devasagayam T P
Radiation Biology and Biochemistry Division, Bhabha Atomic Research Centre, Bombay, India.
Chem Biol Interact. 1996 Jan 5;99(1-3):1-16. doi: 10.1016/0009-2797(95)03653-9.
Methylene blue plus visible light, in the presence of oxygen, induced lipid peroxidation in rat liver microsomes, as assessed by the formation of thiobarbituric acid reactive substances (TBARS), lipid hydroperoxides and the loss of membrane-bound enzymes. Peroxidation was enhanced by deuteration of the buffer and inhibited by scavengers of singlet oxygen (1O2) and superoxide (O2.-). The damage induced seemed to be mainly due to Type II involving 1O2 and to a lesser extent Type I reactions with O2.- and hydroxyl radical (.OH) as intermediates. Nicotinamide or vitamin B3, an endogenous metabolite occurring at high concentrations in tissues, had a relatively high rate constant of 1.8 x 108 M-1 s-1 with 102 and had a significant inhibitory effect on lipid peroxidation induced by photosensitization. This effect was both time- and concentration-dependent, high inhibition being associated with millimolar concentrations. Chemically related endogenous compounds like tryptophan and isonicotinic acid also had significant inhibitory properties. Similar protective effects were observed with natural antioxidants such as beta-carotene, canthaxanthin, lipoic acid, glutathione, alpha-tocopherol and to a lesser extent ascorbic acid. Nicotinamide was a more effective antioxidant than ascorbic acid. It also showed a similar inhibitory effect against NADPH-ADP-FE3(+)-induced lipid peroxidation. Our results suggest that nicotinamide had significant ability to protect against photosensitization-induced cytotoxicity and cell damage and that it may do so by its ability to react with 102 and other reactive oxygen species.
在有氧存在的情况下，亚甲蓝加可见光可诱导大鼠肝微粒体中的脂质过氧化，这可通过硫代巴比妥酸反应性物质（TBARS）、脂质氢过氧化物的形成以及膜结合酶的损失来评估。缓冲液的氘化增强了过氧化作用，而单线态氧（1O2）和超氧阴离子（O2.-）的清除剂则抑制了过氧化作用。所诱导的损伤似乎主要归因于涉及1O2的II型反应，以及程度较小的以O2.-和羟基自由基（·OH）为中间体的I型反应。烟酰胺或维生素B3是组织中高浓度存在的内源性代谢物，它与1O2的反应速率常数相对较高，为1.8×108 M-1 s-1，并且对光致敏诱导的脂质过氧化具有显著的抑制作用。这种作用具有时间和浓度依赖性，高抑制作用与毫摩尔浓度相关。化学相关的内源性化合物如色氨酸和异烟酸也具有显著的抑制特性。天然抗氧化剂如β-胡萝卜素、角黄素、硫辛酸、谷胱甘肽、α-生育酚以及程度较小的抗坏血酸也观察到了类似的保护作用。烟酰胺是比抗坏血酸更有效的抗氧化剂。它对NADPH-ADP-Fe3(+)-诱导的脂质过氧化也表现出类似的抑制作用。我们的结果表明，烟酰胺具有显著的能力来保护免受光致敏诱导的细胞毒性和细胞损伤，并且它可能通过与1O2和其他活性氧物种反应的能力来做到这一点。
