Mitogen-activated protein kinase inhibitor, PD98059, inhibits rat retinal pigment epithelial cell replication by cell cycle arrest

Purpose: To investigate the effect of PD98059, a mitogen-activated protein kinase (MAPK) inhibitor, on the replication of rat cultured retinal pigment epithelial (RPE) cells. Methods: Growth-phase rat RPE cells were exposed to various concentrations of PD98059 in serum-free F12 medium containing 0.1% dimethyl sulfoxide. Cell proliferation was assessed by cell counts using a hemocytometer. Cell viability was tested by CellTiter 96 AQueous Non-Radioactive Cell Proliferation Assay at 24 hours after PD98059 application. Hoechst 33552 and propidium iodide staining were used to assess nuclear morphology. Immunostaining with Ki67 antibody was used for cell cycle analysis because the staining patterns produced on cells are characteristic depending on their position within the cell cycle. Results: PD98059 inhibited cellular proliferation of cultured rat RPE cells in a dose-dependent manner but did not induce cell death. Twenty-four hours after the application of PD98059, cultured RPE cells were not immunopositive for Ki67, indicating that their cell cycle was arrested in the G0/G1 phase. Conclusion: These results demonstrated that MAPK inhibition arrested cell cycle progression of rat cultured RPE cells at the G0/G1 phase. The pharmacological induction of cell cycle arrest could be a new approach to inhibit cellular proliferation in such conditions as proliferative vitreoretinopathy.