PURPOSE. Human cationic antimicrobial protein 18 (hCAP18, 18 kDa) was originally identified in leukocytes on the basis of its antimicrobial activity. The peptide composed of the 27 C-terminal amino acids of hCAP18 (hCAP18 log-135) binds lipopolysaccharide (LPS). The purpose of the present study was to investigate the effects of hCAP18 peptide on endotoxin-induced uveitis (EIU) in rats. METHODS. EIU was induced by footpad injection of LPS. Each rat was injected intravenously with 1, 10, or 100 μg hCAP18 peptide in 0.1 mL of PBS immediately after LPS injection in male Lewis rats. At 24 hours after LPS injection, enzyme-linked immunosorbent assay was performed to evaluate concentrations of protein, nitric oxide (NO), tumor necrosis factor (TNF)-α, prostaglandin (PG)-E2, interleukin (IL)-6, monocyte chemoattractant protein (MCP)-1 and macrophage inflammatory protein (MIP)-2 in aqueous humor. Also, EIU was evaluated by counting inflammatory cells in aqueous humor. RESULTS. hCAP18 peptide at 10 and 100 μg significantly suppressed an LPS-induced increase in the number of inflammatory cells and the levels of protein, NO, TNF-α, PGE2, MCP-1, and MIP-2. The anti-inflammatory effect of 10 μg hCAP18 peptide was as strong as that of 100 μg hCAP18 peptide. Treatment with 1 μg hCAP18 peptide did not suppress EIU, compared with the LPS group. CONCLUSIONS. The present results indicate that hCAP18 peptide suppresses development of EIU. A possible mechanism for the ocular anti-inflammatory effect of hCAP18 peptide is that it suppresses onset of LPS-triggered inflammatory reactions by binding directly to LPS.
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