Cytokine gene expression in different strains of mice with endotoxin-induced uveitis (EIU)

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Abstract
The kinetics of various cytokines in the eye plays a critical role in endotoxin-induced uveitis (EIU). This study examined the cytokine kinetics and susceptibility of EIU in four mice strains. Four strains of TLR-4 or Toll-like receptor-4 (Lps, lipopolysaccharide-susceptible) gene-positive mice (C3H/HeN of H-2(k), C57/B6 of H-2(b), Balb/C of H-2(d), and 129/J of H-2(b)) were injected subcutaneously with either lipopolysaccharide (LPS) in phosphate-buffered saline (PBS) or PBS alone in two repeated experiments. Mice were sacrificed 1, 3, 6, 24 (1 d), 72 (3 d), 120 (5 d), or 168 (7 d) hours after LPS injection. Ocular histology and reverse transcriptase-polymerase chain reaction (RT-PCR) to detect ocular interleukin-1 alpha (IL-1 alpha), IL-6, tumor necrosis factor-alpha (TNF-alpha), and granulocyte-macrophage colony-stimulating factor (GM-CSF) mRNA were performed. Serum IL-1 alpha, IL-1 beta, IL-6, and TNF-alpha levels were measured using enzyme-linked immunosorbent assay (ELISA). No ocular inflammation was present in any mice within six hours after LPS injection. Only the C3H/HeN mice developed a biphasic ocular inflammatory response (1 d and 5 d), during which all proinflammatory cytokine messages were expressed. In the other three strains with minimal (129/J and Balb/C) to mild (C57/B6) EIU that peaked at 1 d, IL-6 mRNA was barely detectable in C57/B6 and Balb/C; GM-CSF mRNA was also present in C57/B6. Serum IL-1 alpha, IL-1 beta, IL-6, and TNF-alpha were high in all EIU mice within six hours after LPS injection. Control mice did not develop uveitis or measurable cytokine messages. In the most susceptible strain, C3H/HeN, EIU was biphasic and correlated to multiple proinflammatory cytokines released in the eye. The less susceptible mice strains exhibited a monophasic response to LPS that may result from no cytokine cascade.