Effect of steroids on Acanthamoeba cysts and trophozoites.
Effect of steroids on Acanthamoeba cysts and trophozoites.
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DOI：
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发表时间：
2001-11
影响因子：
4.4
通讯作者：
K. McClellan;K. Howard;J. Niederkorn;H. Alizadeh
中科院分区：
文献类型：
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作者：
K. McClellan;K. Howard;J. Niederkorn;H. Alizadeh
局部类固醇常用于控制角膜炎症和葡萄膜炎，或在手术后使用，以防止角膜移植排斥反应。本研究旨在探讨类固醇激素对卡氏阿米巴致病性的影响。方法应用地塞米松磷酸盐对弓形虫滋养体和包囊脱囊、增殖和包囊形成的影响。在体外检测Castellanii。类固醇处理的阿米巴细胞溶解能力进行了定量的分光光度测定，纤溶酶原激活剂测定的纤维蛋白溶解试验。在中国仓鼠阿米巴角膜炎模型中，研究了类固醇治疗对角膜感染的影响。结果：与未处理的对照培养物相比，用地塞米松处理阿米巴包囊诱导滋养体数量增加4- 10倍。用地塞米松处理滋养体时，观察到滋养体增殖加速。然而，地塞米松治疗没有影响包囊的阿米巴滋养体。地塞米松处理的滋养体或包囊与未处理的微生物相比，对角膜上皮细胞产生显著的细胞病变效应。从地塞米松处理或未处理的生物体收集的上清液未能溶解角膜上皮细胞。用地塞米松处理有机体对阿米巴滋养体产生纤溶酶原激活物没有影响。地塞米松肌肉注射对角膜炎的发生率、严重程度和慢性化有深远的影响。地塞米松处理的仓鼠的角膜炎在所有时间点都比未处理的动物显著更严重（P < 0.05）。结论：这些发现表明，暴露于地塞米松的阿米巴滋养体和包囊增加了生物体的致病性。结果强调，如果局部类固醇用于阿米巴角膜炎的管理，保持足够的阿米巴治疗的重要性。
PURPOSE Topical steroids are frequently used to control corneal inflammation and uveitis or is administered after surgery, to prevent corneal graft rejection. This study was undertaken to determine whether steroids could affect the pathogenicity of Acanthamoeba castellanii. METHODS The effect of dexamethasone phosphate on excystment, proliferation, and encystment of trophozoites and cysts of A. castellanii was examined in vitro. Cytolysis capacity of steroid-treated Acanthamoeba was quantified by a spectrophotometric assay, and plasminogen activators were measured by a fibrinolysis assay. The influence of steroid treatment on corneal infection in a Chinese hamster model of Acanthamoeba keratitis was examined in vivo. RESULTS Treatment of Acanthamoeba cysts with dexamethasone induced 4- to 10-fold increases in the number of trophozoites compared with untreated control cultures. Acceleration of trophozoite proliferation was observed when trophozoites were treated with dexamethasone. However, dexamethasone treatment did not affect encystment of Acanthamoeba trophozoites. Dexamethasone-treated trophozoites or cysts induced a significant cytopathic effect on corneal epithelial cells compared with untreated organisms. Supernatants collected from either dexamethasone-treated or untreated organisms failed to lyse corneal epithelial cells. Treatment of organisms with dexamethasone had no effect on production of plasminogen activators by Acanthamoeba trophozoites. Intramuscular injection of dexamethasone had a profound effect on the incidence, severity, and chronicity of keratitis. Keratitis in dexamethasone-treated hamsters was significantly more severe at all time points than in untreated animals (P < 0.05). CONCLUSIONS These findings indicate that exposure of Acanthamoeba trophozoites and cysts to dexamethasone increases the pathogenicity of the organisms. The results emphasize the importance of maintaining adequate amebicidal therapy if a topical steroid is used in the management of Acanthamoeba keratitis.