Abstract
Purpose: :
To determine the effect of aging on retinal inflammation that occurs in a murine model of EIU by measuring cytokine and chemokine production, adhesion molecule expression and inflammatory cell migration as a response to LPS.
Methods: :
Seven week, 6 month, and 1 year old C57Bl/6 mice were purchased from Taconic. EIU was induced by intraperitoneal injection of 50 ug LPS in 0.1ml PBS. Mice were euthanized 24 hours after LPS injection. Plasma, eyes and retinas were collected and protein extracts were prepared for cytokine and chemokine analysis using a multiplex assay (Pierce). To determine retinal leukocyte infiltration, the contralateral eye was fixed in 4% paraformaldehyde and retinas were dissected for whole mount immuno-staining of neutrophils (Gr-1) and macrophages (F4/80). Fluorescent images of five regions on each retina were captured using the Axiocam MR3 camera on an Axio.ImageM1 microscope. The number of neutrophils and macrophages was quantified with Axiovision software.
Results: :
Following LPS exposure, neutrophil and macrophage recruitment to the retina are statistically reduced in 6 month and 1 year old mice as compared to 7 week-old (>80% neutrophil and approximately 50% macrophage). Despite these dramatic changes in cell recruitment, differences in cytokine and chemokine levels in response to LPS are varied. Some inflammatory markers were gradually increased with age such as ICAM-1 and IL-6, in the absence of LPS treatment. Others showed a decrease in response to LPS with age such as MCP-1/JE and IP-10 in ocular tissue.
Conclusions: :
Endotoxin induced uveitis is a useful model for studying the effect of age on inflammatory processes within the eye. We demonstrated that neutrophil and macrophage recruitment to the retinal surface after LPS exposure were markedly reduced. These reductions might result from the declining response to LPS in certain chemokines as well as the increased basal levels in others in aged animals.
Keywords: uveitis-clinical/animal model • inflammation • retina