Abstract
Purpose :
In quest of identifying novel therapeutic candidates for Age-related Macular Degeneration (AMD), this study tested the hypothesis that Citicoline, a naturally occurring nootropic, will protect against apoptotic cell death in transmitochondrial AMD RPE cybrid cells (an in vitro AMD model). Citicoline maintains neuronal membrane integrity and its endogenous production from choline is an intermediate step in the synthesis of cell membrane phospholipids.
Methods :
Purified Citicoline was exogenously added to transmitochondrial AMD RPE cybrid cells which had identical nuclei derived from mitochondria-deficient ARPE-19 cells, but differed in mitochondrial (mt) DNA content derived from clinically characterized AMD patients. The ability of Citicoline to attenuate apoptosis was examined via: 1) Analysis of untreated and Citicoline-treated AMD cybrid cells stained with Caspase-3/7 (quantifies cells undergoing caspase-3/7-mediated apoptosis) and NucLight red (stains live-cell nuclei) reagents in an IncuCyte live-cell imaging system; 2) Flow Cytometry analysis of untreated and Citicoline-treated AMD cybrid cells stained with apoptotic and dead cell markers namely AnnexinV and Propidium Iodide (PI) respectively.
Results :
Addition of Citicoline led to a 55.99 % decrease in Overlap object count (i.e., Caspase-3/7 Green+NucLight Red staining)/ NucLight Red object count in AMD cybrid cells: Untreated- 1±0.078 a.u. and Citicoline-treated- 0.440±0.125 a.u.(p=0.03,n=4) at 48 h. At 72 h, a 47.54 % drop in Overlap object count was observed in Citicoline-treated AMD cybrid cells (0.52±0.11 a.u.) compared to their untreated counterparts (1±0.082 a.u.) (p=0.03, n=4). Furthermore, Flow cytometry analyses revealed a 21.67 % decrease in AnnexinV/PI double positives’ fluorescence intensity in Citicoline-treated AMD cybrid cells (0.783±0.06 a.u.) compared to their untreated counterparts (1±0.059 a.u.)(p=0.04, n=6).
Conclusions :
In conclusion, this data support our hypothesis as Citicoline conferred significant protection against apoptotic cell death that was in-part mediated by damaged mtDNA from AMD patients in transmitochondrial AMD cybrid cells. Although further studies with Citicoline/ AMD cybrid cells are underway, these results present novel findings that identify Citicoline to be a potential protector which attenuates apoptotic cell death in AMD. Citicoline usage offers the advantage of easy access as it is available as an over-the-counter dietary supplement in the U.S.
This is a 2020 ARVO Annual Meeting abstract.