Abstract
Purpose: :
Interleukin–23 (IL–23) is a novel antigen–presenting cell–derived cytokine that belongs to the family of IL–12–related molecules. IL–23 consists of p19 and p40 subunits and it specifically induces the production of IL–17, IL–6, and TNF–α. Thus, IL–23 is strongly implicated in inflammation. Although most downstream cytokines of IL–23 are well documented in uveitis, the role of IL–23 in ocular inflammation remains to be defined. In this study, we examined whether the expression of IL–23 is up–regulated in the endotoxin–induced uveitis model.
Methods: :
Uveitis was induced by intravitreal injection of 250 ng lipopolysaccharide (LPS) from Escherichia coli 055:B5 in 2 µl phosphate–buffered saline (PBS) or PBS alone as a control. At 24 hours after LPS injection, mice were sacrificed and the eyes were harvested. The eyes were either dissected for RNA isolation or homogenized with PBS containing 1% Triton X–100 with proteinase inhibitor.
Results: :
Semi–quantitative RT–PCR revealed a strong up–regulation of IL–23p19 mRNA in uveal samples from the mice after intravital LPS challenge, whereas expression of an independent housekeeping gene (GAPDH) was not affected. Moreover, at 24 hours after the endotoxin treatment, IL–23 in the ocular homogenates was measured by ELISA specifically recognizing the IL–23p40 subunit. Compared to control mice receiving vehicle alone, endotoxin treatment induced IL–23 protein expression by approximately 70–fold. Finally, in vitro incubation of LPS–treated ocular homogenates with splenocytes significantly induced IL–17 production.
Conclusions: :
These results implicate IL–23 in endotoxin–induced uveitis and suggest that IL–23 is biologically active in clinical uveitis. IL–23 is a potential target of therapeutic intervention for uveitis.
Keywords: cytokines/chemokines • inflammation • uveitis-clinical/animal model