Ogmundsdóttir H M, Zoëga G M, Gissurarson S R, Ingólfsdóttir K
Molecular and Cell Biology Research Laboratory, Icelandic Cancer Society, Reykjavík.
J Pharm Pharmacol. 1998 Jan;50(1):107-15. doi: 10.1111/j.2042-7158.1998.tb03312.x.
Several lichen species have been used traditionally as medicinal plants. It has previously been shown that two low-molecular-weight lichen metabolites, lobaric acid isolated from Stereocaulon alpinum Laur. and protolichesterinic acid isolated from Cetraria islandica L. (Ach.), have in-vitro inhibitory effects on arachidonate 5-lipoxygenase. We have studied the effects of these compounds on cultured cells from man, including three malignant cell-lines (T-47D and ZR-75-1 from breast carcinomas and K-562 from erythro-leukaemia), as well as normal skin fibroblasts and peripheral blood lymphocytes. Both test substances caused a significant reduction in DNA synthesis, as measured by thymidine uptake, in all three malignant cell-lines; the dose inducing 50% of maximum inhibition (ED50) was between 1.1 and 24.6 microg mL(-1) for protolichesterinic acid and between 14.5 and 44.7 microg mL(-1) for lobaric acid. The breast-cancer cell-lines were more sensitive than K-562. The proliferative response of mitogen-stimulated lymphocytes was inhibited with a mean ED50 of 8.4 microg mL(-1) and 24.5 microg mL(-1) for protolichesterinic acid and lobaric acid, respectively. These concentrations are of the same order of magnitude as the IC50 values in the 5-lipoxygenase assay. Significant cell death (assessed by the MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-( 4-sulfophenyl)-2H-tetrazolium) assay and trypan blue exclusion) occurred in the three malignant cell-lines at protolichesterinic acid and lobaric acid concentrations above 20 and 30 microg mL(-1), respectively. In K-562 morphological changes consistent with apoptosis were detected. Up to 38% cell death was observed at 20 microg mL(-1) for protolichesterinic acid and 15 microg mL(-1) for lobaric acid in mitogen-stimulated lymphocytes but unstimulated lymphocytes were clearly less sensitive. In contrast, the DNA synthesis, proliferation and survival of normal skin fibroblasts were not affected at doses up to 20 microg mL(-1) for protolichesterinic acid and 30 microg mL(-1) for lobaric acid. We conclude that the anti-proliferative and cytotoxic effects observed might be related to the 5-lipoxygenase inhibitory activity of protolichesterinic acid and lobaric acid. These results open up the opportunity for future studies of these lichen metabolites with regard to their anti-tumour and anti-inflammatory properties.
几种地衣物种传统上一直被用作药用植物。此前已经表明，两种低分子量地衣代谢产物，即从高山石蕊（Stereocaulon alpinum Laur.）中分离出的洛巴酸和从冰岛衣（Cetraria islandica L. (Ach.)）中分离出的原地衣硬脂酸，对花生四烯酸5-脂氧合酶具有体外抑制作用。我们研究了这些化合物对人培养细胞的影响，包括三种恶性细胞系（来自乳腺癌的T-47D和ZR-75-1以及来自红白血病的K-562），以及正常皮肤成纤维细胞和外周血淋巴细胞。两种受试物质均导致所有三种恶性细胞系中通过胸苷摄取测量的DNA合成显著减少；原地衣硬脂酸诱导最大抑制50%（ED50）的剂量在1.1至24.6微克/毫升之间，洛巴酸的剂量在14.5至44.7微克/毫升之间。乳腺癌细胞系比K-562更敏感。原地衣硬脂酸和洛巴酸对丝裂原刺激的淋巴细胞增殖反应的抑制作用的平均ED50分别为8.4微克/毫升和24.5微克/毫升。这些浓度与5-脂氧合酶测定中的IC50值处于同一数量级。当原地衣硬脂酸和洛巴酸浓度分别高于20微克/毫升和30微克/毫升时，三种恶性细胞系中出现了显著的细胞死亡（通过MTS（3-(4,5-二甲基噻唑-2-基)-5-(3-羧甲氧基苯基)-2-(4-磺基苯基)-2H-四唑）测定和台盼蓝排斥法评估）。在K-562中检测到与凋亡一致的形态学变化。在丝裂原刺激的淋巴细胞中，原地衣硬脂酸在20微克/毫升时观察到高达38%的细胞死亡，洛巴酸在15微克/毫升时观察到高达38%的细胞死亡，但未刺激的淋巴细胞明显不太敏感。相比之下，对于原地衣硬脂酸剂量高达20微克/毫升和洛巴酸剂量高达30微克/毫升时，正常皮肤成纤维细胞的DNA合成、增殖和存活未受影响。我们得出结论，观察到的抗增殖和细胞毒性作用可能与原地衣硬脂酸和洛巴酸的5-脂氧合酶抑制活性有关。这些结果为未来研究这些地衣代谢产物的抗肿瘤和抗炎特性提供了机会。
