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Intravitreal daunomycin induces multidrug resistance in proliferative vitreoretinopathy
P Esser1, D Tervooren, K Heimann
1Department of Vitreoretinal Surgery, University Eye Clinic Koeln, Cologne, Germany.
Purpose:
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.
Methods:
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.
Results:
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.
Conclusions:
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.
Insights
Intravitreal daunomycin can induce multidrug resistance (MDR) in proliferative vitreoretinopathy (PVR) by increasing P-glycoprotein expression in retinal pigment epithelial cells. This suggests combination therapy with MDR inhibitors or alternative antiproliferative drugs for better treatment outcomes.
Area of Science:
- Ophthalmology
- Cell Biology
- Pharmacology
Background:
- Intravitreal daunomycin is a common treatment for proliferative vitreoretinopathy (PVR).
- The potential for daunomycin to induce multidrug resistance (MDR) via P-glycoprotein has not been fully elucidated in PVR.
- Retinal pigment epithelial (RPE) cells are implicated in PVR reproliferation.
Purpose of the Study:
- To investigate if intravitreal daunomycin induces MDR in PVR.
- To determine if daunomycin upregulates P-glycoprotein expression in RPE cells.
- To explore the mechanism of MDR development in RPE cells.
Main Methods:
- Immunohistochemistry to detect P-glycoprotein in epiretinal membranes from PVR patients.
- Colabeling to identify cellular sources of P-glycoprotein.
- Reverse transcription-polymerase chain reaction and immunoblot analysis of cultured RPE cells.
- Crystal violet assay to quantify daunomycin toxicity.
Main Results:
- P-glycoprotein expression was significantly higher in PVR patients pre-exposed to daunomycin compared to those never exposed.
- Daunomycin treatment of cultured RPE cells induced resistance to daunomycin, reversible with verapamil.
- MDR induction in RPE cells was primarily mediated by increased P-glycoprotein expression, suggesting a translational mechanism.
Conclusions:
- Intravitreal daunomycin induces P-glycoprotein expression, contributing to MDR in PVR.
- Reproliferation in daunomycin-treated PVR patients may require combination therapy with MDR inhibitors (e.g., verapamil) or MDR-independent antiproliferative drugs (e.g., 5-fluorouracil).
- Understanding MDR mechanisms is crucial for optimizing PVR management.