Li L, Clark K, Lau B H
Department of Microbiology and Molecular Genetics, School of Medicine, Loma Linda University, California 92350, USA.
Biotechnol Ther. 1994;5(1-2):87-97.
The glutathione redox cycle plays an important role in antioxidant and detoxification mechanisms. We recently reported that a calf thymic peptide (TP) protected vascular endothelial cells from oxidant injury induced by hydrogen peroxide. Using electrophoresis and amino acid sequencing analysis, we have now shown that TP consists of two peptides. The fast-moving peptide has 9 amino acid residues at the NH2 terminal and accounts for 92% of total quantity, while the other peptide has 18 amino acid residues at the NH2 terminal and amounts to 8%. The present study investigated the effect of TP on glutathione redox cycle. Confluent monolayers of bovine pulmonary artery endothelial cells (PAEC) were incubated with TP (12.5-100 micrograms/mL) for 24-48 h. TP caused a dose-dependent increase in glutathione (GSH) level and glutathione disulfide reductase activity but no significant change in GSH peroxidase activity. Exposure of PAEC to an organic oxidant t-butyl hydroperoxide (tBHP) resulted in decreased GSH level, increased lipid peroxidation, and elevated leakage of intracellular lactate dehydrogenase. Preincubation of PAEC with TP prevented these changes induced by tBHP. The data suggest that the antioxidant effect of TP may be due, at least in part, to its modulation of the GSH redox cycle in vascular endothelial cells. TP may thus be considered a new antioxidant with novel activities in addition to being an immune regulator.
谷胱甘肽氧化还原循环在抗氧化和解毒机制中发挥着重要作用。我们最近报道，一种小牛胸腺肽（TP）可保护血管内皮细胞免受过氧化氢诱导的氧化损伤。通过电泳和氨基酸测序分析，我们现已表明TP由两种肽组成。快速移动的肽在NH2末端有9个氨基酸残基，占总量的92%，而另一种肽在NH2末端有18个氨基酸残基，占8%。本研究调查了TP对谷胱甘肽氧化还原循环的影响。将汇合的牛肺动脉内皮细胞（PAEC）单层与TP（12.5 - 100微克/毫升）孵育24 - 48小时。TP导致谷胱甘肽（GSH）水平和谷胱甘肽二硫化物还原酶活性呈剂量依赖性增加，但GSH过氧化物酶活性无显著变化。将PAEC暴露于有机氧化剂叔丁基过氧化氢（tBHP）会导致GSH水平降低、脂质过氧化增加以及细胞内乳酸脱氢酶泄漏增加。用TP对PAEC进行预孵育可防止tBHP诱导的这些变化。数据表明，TP的抗氧化作用可能至少部分归因于其对血管内皮细胞中GSH氧化还原循环的调节。因此，TP除了作为免疫调节剂外，还可被视为一种具有新活性的新型抗氧化剂。
