0bjective   To investigate the role of CX3CL1/CX3CR1 in light-induced photoreceptor degeneration and the relationship between photoreceptor apoptosis and retinal microglial activation.

Methods  The Transwell co-culture system was used. A murine photoreceptor cell line (661W cells) plated in in 6-well plates was
exposed to intense blue light for 6 hours while retinal microglia were cultured on porous Transwell membrane inserts at the same time. The 661W cell viability was assessed by terminal dUTP transferase nick end labeling (TUNEL) and microglial activation was assessed morphologically by microscopy Antibodies were used to label CX3CL1/CX3CR1 and retinal microglia at different time points . Reverse transcription polymerase chain reaction was used to examine mRNA levels of several chemokines and noxious factors in the MGCM-treated photoreceptor cells and the PRCM-treated microgial. Western blotting was used
to analyze NF-êB p65 subunit, phosphorylated MAPKs p38, p44/42 (Erk1/2), and c-Jun N-terminal kinase (JNK).

Results  Our results showed the expression of CX3CL1 increased in the outer nuclear layer of the retina and OX42-positive microglia also occurred in the same place.CX3CR1 was expressed major in the microglial. Expression of CX3CL1/CX3CR1 mRNA and