Misra B R, Misra H P
Department of Biomedical Sciences, College of Veterinary Medicine, Virginia Polytechnic Institute, Blacksburg 24061.
J Biol Chem. 1990 Sep 15;265(26):15371-4.
The neuropeptide vasoactive intestinal peptide (VIP), a highly basic 28-amino acid peptide, has a widespread distribution in the body. The functional specificity of this peptide not only includes its potent vasodilatory activity, but also its role in protecting lungs against acute injury, in preventing T-lymphocyte proliferation and in modulating immune function. We have investigated the possible antioxidant properties of VIP and found that VIP does not have significant O2-, OH., or H2O2 scavenging ability. However, VIP was found to inhibit, in a dose-dependent manner, the 1O2-dependent 2,2,6,6-tetramethylpiperidine N-oxyl (TEMPO) formation. 1O2 was produced in photosensitizing systems using rose bengal or methylene blue as sensitizers and was detected as TEMP-1O2 product (TEMPO) by electron paramagnetic resonance (EPR) spectroscopic techniques. The formation of TEMPO signal was strongly inhibited by known singlet quenchers, e.g. beta-carotene, histidine as well as azide, but not by catalase (20 micrograms/ml) which removes H2O2 and mannitol (6 mM) or ethanol (5.9 mM) which remove OH.. Superoxide dismutase (2.5 micrograms/ml) inhibited the photoreaction up to 20% by removing O2- and most probably by blocking the secondary charge transfer pathway of 1O2 formation. These results suggest that the formation of nitroxide radical by 1O2 attack on TEMP may be used as a simple and specific assay for 1O2, and VIP can serve as an effective 1O2 scavenger/quencher, thus it may modulate the oxidative tissue injury caused by this reactive species of oxygen.
神经肽血管活性肠肽（VIP）是一种由28个氨基酸组成的高度碱性肽，在体内广泛分布。这种肽的功能特异性不仅包括其强大的血管舒张活性，还包括其在保护肺部免受急性损伤、防止T淋巴细胞增殖和调节免疫功能方面的作用。我们研究了VIP可能具有的抗氧化特性，发现VIP没有显著的超氧阴离子（O2-）、羟自由基（OH·）或过氧化氢（H2O2）清除能力。然而，发现VIP以剂量依赖的方式抑制单线态氧（1O2）依赖的2,2,6,6-四甲基哌啶氮氧化物（TEMPO）的形成。1O2是在以孟加拉玫瑰红或亚甲蓝作为敏化剂的光敏体系中产生的，并通过电子顺磁共振（EPR）光谱技术检测为TEMP-1O2产物（TEMPO）。已知的单线态猝灭剂，如β-胡萝卜素、组氨酸以及叠氮化物，能强烈抑制TEMPO信号的形成，但过氧化氢酶（20微克/毫升）不能，过氧化氢酶可去除H2O2，甘露醇（6毫摩尔）或乙醇（5.9毫摩尔）可去除OH·。超氧化物歧化酶（2.5微克/毫升）通过去除O2-并很可能通过阻断1O2形成的二次电荷转移途径，将光反应抑制达20%。这些结果表明，1O2攻击TEMP形成氮氧化物自由基可作为一种简单而特异的1O2检测方法，且VIP可作为一种有效的1O2清除剂/猝灭剂，因此它可能调节由这种活性氧物种引起的氧化组织损伤。
