Proinflammatory cytokines in a mouse model of central retinal artery occlusion

PURPOSE To analyze cytokines in the retina and serum in an experimental model of central retinal artery occlusion (CRAO) in mice. METHODS CRAO was induced by laser activation of intravenously injected rose bengal, a photosensitive dye, in 60 C57Bl/6 mice. mRNA and protein levels of macrophage inhibitory protein-2 (MIP-2), interleukin-6 (IL-6), and tumor necrosis factor- alpha (TNF-alpha) were analyzed using real-time polymerase chain reaction, and western blot, respectively. Cytokine levels in serum were measured by ELISA. Analysis was performed at various time intervals from CRAO induction. RESULTS In the retina, MIP-2 and IL-6 mRNA expression decreased 3 h after induction of CRAO and increased thereafter, peaking at 12-24 h. By 7 days, levels were again mostly undetectable. TNF-alpha mRNA expression increased at 3 h and decreased to control levels at 7 days. At the protein level, all cytokines were present at 3 h, following similar patterns to their respective gene expression thereafter. In serum, MIP-2 and TNF-alpha levels peaked early, and decreased to control levels at 12 h, with a second late rise of TNF-alpha. IL-6 levels increased between 3 and 12 h and decreased at 24 h. CONCLUSIONS Temporal variations in cytokines were observed following the induction of CRAO, both at the retinal mRNA expression and protein levels. These temporal changes, and the variable effects of the cytokines at the different time intervals, should be taken into account during the formulation of therapeutic strategies.