Ye Bin, Zheng Yu-Qiang, Wu Wei-Hua, Zhang Jing
Department of Parasitology, Chongqing University of Medical Sciences, Chongqing 400016, China.
Chin Med J (Engl). 2004 Nov;117(11):1704-8.
Although there are several drugs and drug combinations for the treatment of Pneumocystis carinii (P. carinii) pneumonia, all drugs have the toxicity as well as low efficacy. Iron chelators have been proposed as a source of new drugs for combating these infections. We hypothesized that iron chelators would suppress the growth of P. carinii by deprivation of the nutritional iron required for growth. In this study, a short-term axenic culture system of P. carinii was established. Daphnetin (7,8-dihydroxycoumarin), a known iron chelator, was demonstrated to exhibit in vitro activity against P. carinii in this system.
P. carinii organisms were obtained from the lungs of immunosuppressed rats. The culture system consisted of Iscove Dulbecco Eagle's Minimum Essential Medium (IMDM), supplemented with S-adenosyl-L-methionine, N-acetylglucosamine, putrescine, L-cysteine, L-glutamine, 2-mercaptoethanol, and fetal bovine serum, and was maintained at 37 degrees C, in 5% CO(2), 95% O(2), at the optimal pH of 8.0. The culture system was used to assess the effect of daphnetin on the proliferation of P. carinii organisms. The ultrastructures of the treated organisms were observed by transmission electron microscopy.
The number of cysts and trophozoites increased 8- to 9-fold and 11- to 12-fold, respectively, after 10 days of culture. Daphnetin was found to suppress the growth of P. carinii in a dose-dependent manner at concentrations between 1 micromol/L and 20 micromol/L. The inhibitory activity was suppressed by the chelation of daphnetin with ferrous sulfate in a 2:1 molar ratio, but it was not suppressed by mixing the culture medium with magnesium sulfate. Reduction of P. carinii numbers after treatment with daphnetin correlated with morphological changes in the organisms, as determined by transmission electron microscopy.
Daphnetin can suppress the growth of P. carinii in vitro. The efficacy of daphnetin in suppressing the the growth of P. carinii in vitro is related to its ability to chelate iron.
尽管有多种药物及药物组合可用于治疗卡氏肺孢子虫肺炎，但所有药物都有毒性且疗效欠佳。铁螯合剂已被提议作为对抗这些感染的新药来源。我们推测铁螯合剂会通过剥夺卡氏肺孢子虫生长所需的营养性铁来抑制其生长。在本研究中，建立了卡氏肺孢子虫的短期无细胞培养系统。在该系统中，已知的铁螯合剂瑞香素（7,8 - 二羟基香豆素）被证明对卡氏肺孢子虫具有体外活性。
从免疫抑制大鼠的肺中获取卡氏肺孢子虫生物体。培养系统由伊思柯夫改良杜氏伊格尔最低限度基础培养基（IMDM）组成，添加了S - 腺苷 - L - 甲硫氨酸、N - 乙酰葡糖胺、腐胺、L - 半胱氨酸、L - 谷氨酰胺、2 - 巯基乙醇和胎牛血清，并在37℃、5%二氧化碳、95%氧气、最适pH值为8.0的条件下维持。该培养系统用于评估瑞香素对卡氏肺孢子虫生物体增殖的影响。通过透射电子显微镜观察经处理生物体的超微结构。
培养10天后，包囊和滋养体数量分别增加了8至9倍和11至12倍。发现瑞香素在1微摩尔/升至20微摩尔/升的浓度范围内以剂量依赖方式抑制卡氏肺孢子虫的生长。瑞香素与硫酸亚铁以2:1摩尔比螯合后，其抑制活性受到抑制，但将培养基与硫酸镁混合并未抑制该活性。经瑞香素处理后卡氏肺孢子虫数量的减少与透射电子显微镜所确定的生物体形态变化相关。
瑞香素可在体外抑制卡氏肺孢子虫的生长。瑞香素在体外抑制卡氏肺孢子虫生长的疗效与其螯合铁的能力有关。
