Esser P, Tervooren D, Heimann K, Kociok N, Bartz-Schmidt K U, Walter P, Weller M
Department of Vitreoretinal Surgery, University Eye Clinic Koeln, Cologne, Germany.
Invest Ophthalmol Vis Sci. 1998 Jan;39(1):164-70.
Adjuvant intravitreal daunomycin is frequently used for the management of proliferative vitreoretinopathy (PVR). In this study the authors examined whether daunomycin could induce multidrug resistance (MDR), mediated by the mdr-1 gene product P-glycoprotein, in the cells responsible for reproliferation in vivo and in human retinal pigment epithelial (RPE) cells in vitro.
Expression of P-glycoprotein was examined by immunohistochemistry in surgically removed epiretinal membranes. The cellular source of P-glycoprotein was examined by colabeling for cytokeratin, glial fibrillary acidic protein, and the macrophage marker EBM-11. P-glycoprotein expression by cultured RPE cells was assessed by reverse transcription-polymerase chain reaction and immunoblot analysis. Daunomycin toxicity was quantified by crystal violet assay.
P-glycoprotein expression was detected in 10 of 10 patients pre-exposed to intravitreal daunomycin. In contrast, epiretinal membranes from only 2 of 13 patients never exposed to daunomycin showed faint P-glycoprotein expression. P-glycoprotein expression was strong within 8 months after daunomycin treatment and faded thereafter. Colocalization studies demonstrated predominant expression of P-glycoprotein by RPE cells. Pre-exposure of cultured human RPE cells to subtoxic concentrations of daunomycin induced resistance to daunomycin that was sensitive to the MDR inhibitor, verapamil. Induction of the MDR phenotype in RPE cells by daunomycin was associated with a minor increase in the mdr-1 mRNA level but a prominent increase in P-glycoprotein expression, thus suggesting a primarily translational mechanism of MDR development in human RPE cells.
Intravitreal daunomycin induced P-glycoprotein expression in PVR. Reproliferation in daunomycin-pretreated patients probably necessitates cotreatment with daunomycin and inhibitors of multidrug resistance such as verapamil or administration of antiproliferative drugs such as 5-fluorouracil, which act in a MDR-independent fashion.
辅助性玻璃体内注射柔红霉素常用于增殖性玻璃体视网膜病变（PVR）的治疗。在本研究中，作者检测了柔红霉素是否能在体内负责再增殖的细胞以及体外人视网膜色素上皮（RPE）细胞中诱导由多药耐药（MDR）基因产物P-糖蛋白介导的多药耐药。
通过免疫组织化学法检测手术切除的视网膜前膜中P-糖蛋白的表达。通过细胞角蛋白、胶质纤维酸性蛋白和巨噬细胞标志物EBM-11的共标记来检测P-糖蛋白的细胞来源。通过逆转录-聚合酶链反应和免疫印迹分析评估培养的RPE细胞中P-糖蛋白的表达。通过结晶紫测定法对柔红霉素毒性进行定量。
在10例预先接受玻璃体内柔红霉素治疗的患者中，有10例检测到P-糖蛋白表达。相比之下，在13例从未接受过柔红霉素治疗的患者中，只有2例的视网膜前膜显示出微弱的P-糖蛋白表达。柔红霉素治疗后8个月内P-糖蛋白表达强烈，此后逐渐减弱。共定位研究表明P-糖蛋白主要由RPE细胞表达。将培养的人RPE细胞预先暴露于亚毒性浓度的柔红霉素可诱导对柔红霉素的耐药性，这种耐药性对MDR抑制剂维拉帕米敏感。柔红霉素诱导RPE细胞产生MDR表型与mdr-1 mRNA水平略有增加但P-糖蛋白表达显著增加有关，因此提示人RPE细胞中MDR发展的主要是翻译机制。
玻璃体内注射柔红霉素可诱导PVR中P-糖蛋白的表达。对于预先接受柔红霉素治疗的患者，再增殖可能需要柔红霉素与多药耐药抑制剂（如维拉帕米）联合治疗，或给予5-氟尿嘧啶等抗增殖药物，这些药物以不依赖MDR的方式发挥作用。
