Atorvastatin Promotes Phagocytosis and Attenuates Pro-Inflammatory Response in Human Retinal Pigment Epithelial Cells

Abstract

Purpose : RPE dysfunction plays an essential role in the pathogenesis of age-related macular degeneration (AMD), a leading cause of irreversible blindness in the elderly of developed countries. High dose atorvastatin was reported to result in visual improvement in a subset of high-risk subgroup of AMD patients in our previous pilot Phase1/2 clinical study. However, its effect on RPE cells has not been fully elucidated. The purpose of this study is to explore the effect of high dose atorvastatin on phagocytic function of ARPE-19 cells as well as the secretion of interleukins IL-6 and IL-8 triggered by pathologic stimuli relevant to AMD.

Methods : ARPE-19 cells were incubated with polystyrene microspheres along with different doses of atorvastatin. The percentage of phagocytic ARPE-19 cells and the mean fluorescence intensity (MIF) of engulfed particles were measured after 6 hours by flow cytometry. Furthermore, the effect of atorvastatin on cell membrane fluidity was assessed by Fluorescence Recovery After Photo-bleaching (FRAP) measurements. ARPE-19 cells were then pretreated by atorvastatin and then challenged with cholesterol crystals for 6 hours, or oxidized low-density lipoproteins (ox-LDL) for 18 hours. The phagocytic function was determined using the same method as above. Subsequently, the cells were treated with different doses of atorvastatin for 16 hours after being primed with IL-1α, and then incubated with cholesterol crystals or ox-LDL. Τhe levels of IL-6 and IL-8 were evaluated using western blot or ELISA after 6 hours incubation.

Results : Atorvastatin treatment promoted phagocytic function of ARPE-19 cells by increasing the percentage of phagocytic cells and the MIF of engulfed particles compared to the control group in a dose-dependent manner (p<0.05). Interestingly, atorvastatin also increased the ARPE-19 cell membrane fluidity compared to the control (p<0.05). In addition, pre-treatment with atorvastatin abrogated the decreased percentage of phagocytic cells and the MIF, as well as the IL-6 and IL-8 secretion induced by cholesterol crystals and ox-LDL (p<0.05).

Conclusions : Our study shows that hydrophobic statins, at high dose enhance and preserve the phagocytic function of RPE in cell culture while also exhibiting anti-inflammatory properties. More investigation is needed on the role of statins in conditions such as AMD.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.