Induction of lysosomal dilatation, arrested autophagy, and cell death by chloroquine in cultured ARPE-19 cells.

Investigative Ophthalmology & Visual Science

PubMedID: 20574031

Yoon YH, Cho KS, Hwang JJ, Lee SJ, Choi JA, Koh JY. Induction of lysosomal dilatation, arrested autophagy, and cell death by chloroquine in cultured ARPE-19 cells. Invest Ophthalmol Vis Sci. 2010;51(11):6030-7.
PURPOSE
To characterize and investigate the mechanism of chloroquine (CQ) retinotoxicity in human retinal pigment epithelium-derived ARPE-19 cells.

METHODS
Cultured ARPE-19 cells were exposed to 10 to 250 ┬ÁM CQ, and cell death was quantified using a lactate dehydrogenase release assay. Autophagy was studied in ARPE-19 cells transfected with GFP-LC3. Lysosomes in living cells were stained and observed by live-cell confocal microscopy.

RESULTS
After exposure to CQ, ARPE-19 cells developed cytosolic vacuoles within 1 hour and underwent cell lysis within 24 hours. The levels of LC3-II, beclin-1 and, p62, as well as the number GFP-LC3- and RPF-LC3-positive autophagic vacuoles (AVs), increased after CQ treatment, indicating that autophagy was activated. However, lysosomal staining revealed that almost all AVs were separate from lysosomes; thus, fusion between AVs and lysosomes was completely blocked. In addition, the levels of ubiquitinated proteins and GFP-mHttp aggregates in ARPE-19 cells were increased by CQ, providing further evidence that autophagic degradation was inhibited.

CONCLUSIONS
CQ induces vacuole formation and cell death in ARPE-19 cells. Initially, vacuoles developed from enlarged lysosomes, followed by the activation of upstream steps in the autophagy pathway and the formation of LC3-positive AVs. Because CQ blocked the fusion of AVs with lysosomes, autophagic protein degradation was inhibited, indicating that CQ-induced retinotoxicity may be caused by the accumulation of potentially toxic ubiquitinated proteins.