Abstract
Purpose: :
To characterize and investigate the mechanism of retinal inflammation that occurs in a murine model of EIU by measuring cytokine and chemokine production, adhesion molecules expression and inflammatory cell migration as a response to different parameters such as mouse strain, age, animal vendor, dose and time of LPS.
Methods: :
EIU was induced by intraperitoneal injection of LPS in 0.1ml PBS. Mice were euthanized at indicated time points. Eyes and retinas were collected and protein extracts were prepared for western blot, cytokine and chemokine analysis using a multiplex assay (Pierce). To determine retinal leukocyte infiltration, the opposite eye was fixed in 4% paraformaldehyde and retinas were dissected for whole mount immuno-staining of neutrophils (Gr-1) and macrophages (F4/80).
Results: :
Following LPS exposure, various inflammatory markers (IL-6, MCP-1, KC, IL-1b, VEFG) were up-regulated in the retina in a time and dose dependent manner. A time-dependent infiltration of inflammatory cells was also observed with the peak level at 24 hours. This retinal inflammation appeared more prominent in younger mice (6-7weeks old) than older mice (>11 weeks old). Further characterization revealed that the sensitivity of LPS stimulation in the retina was affected by mouse strains (C57BL/6 > Balb/c) and vendor source (C57BL/6 Taconic > Charles River Lab > Jackson). Moreover, mice carrying either TLR4 deletion or a defective LPS response allele Trl4lps-d were resistant to LPS-induced retinal inflammation. Lastly, blocking one of the signal transduction pathways downstream of TLR4, the TNFα pathway, by anti-TNFα antibody (Enbrel) i.p. partially inhibited the production of inflammatory mediators and retinal leukocyte accumulation.
Conclusions: :
Endotoxin induced uveitis is an useful model for studying inflammatory processes within the eye. Based on our study we found that age, mouse strain and vendor source had significant impacts on the ocular inflammatory response to LPS. TLR4 signaling is essential for LPS-induced retinal inflammation and can be ameliorated with anti-TNF therapy.
Keywords: uveitis-clinical/animal model • inflammation • retina