Abstract
Purpose:
Age-related macular degeneration (AMD) represents the leading cause of vision loss in the elderly. There is a large body of evidence that oxidative stress is a primary contributing factor to AMD. The cumulative oxidative injury induces retinal pigment epithelium (RPE) membrane microparticles production, RPE cell death and cellular senescence. The RPE blebs are implicated in the formation of sub-retinal deposit. Nonetheless, the pathophysiological roles of RPE microparticles (RMPs) remain largely unexplored. This study was designed to investigate whether RMPs participate in the retinal cells dysfunction, more specifically to investigate how RPE cells response to the oxidative stress-induced RMPs.
Methods:
RMPs and fluorescent DiI-labelled RMPs were isolated from cultured ARPE-19 cells under oxidative stress using methods involving multiple centrifugation steps. DiI-labelled RMPs were used in RPE uptake experiment. RMPs-treated RPE cells were subjected to WST-1, cellular senescent, apoptotic assay and FACS cell cycle analysis respectively. The antibody against CD36 was used in uptake experiment to determine the involvement of scavenger receptor CD36.
Results:
Our study revealed that uptake of RMPs by RPE cells is time-dependent, and this process is partially dependent on CD36 evidenced by an approximately 50% decrease of RMPs uptake caused by CD36 antibody treatment. In addition, RMPs significantly reduced RPE cell viability in a dose-dependent manner. RMPs in a concentration of 5% µg/ml significantly induced RPE cell-cycle arrest at G0/G1 phase. RMPs-treated cells exhibited a 19% increase in G0/G1 phase, with associated increases of the senescence-associated β-galactosidase activity. RMPs in higher concentrations (≥20µg/ml) induced cell death.
Conclusions:
We demonstrated for the first time that RPE cells uptake microparticles derived from RPE cells under oxidative stress. RMPs uptake is a receptor-mediated process, and consequently induce RPE cell senescence and cell death. These findings strongly suggest that RMPs function as mediators to exacerbate the oxidative damages to RPE cells, and indicate a pathological role of RMPs in AMD.
Keywords: 412 age-related macular degeneration •
695 retinal degenerations: cell biology •
645 phagocytosis and killing