Involvement of cyclooxygenase–2 in rat models of anterior ocular inflammation.

Abstract

Abstract: : Purpose:To determine which isoform of cyclooxygenase (COX), constitutive COX–1 or inducible COX–2, is involved in two rat models of anterior ocular inflammation. Methods:To induce conjunctivitis, carrageenan or bacterial lipopolysaccharide (LPS) was injected into rat conjunctivae. Vascular permeability in inflamed conjunctivae was measured by uptake of systemic Evans blue dye. Changes in mRNA or protein for COX–1 and COX–2 in conjunctivae were detected by RT–PCR or by immunoblotting, respectively. To elucidate involvement of COX–2 in conjunctivitis, COX–2 inhibitor was topically administrated. Results:The dye content of conjunctivae was significantly increased 4 hours after injection of carrageenan or LPS. In the carrageenan–injected model, mRNA for COX–2 was significantly increased by 2 hours and gradually increased until 24 hours. In the LPS–injected model, mRNA for COX–2 was significantly increased 1 hour after injection, peaked at 2 hours, and decreased at 4 hours. COX–1 mRNA did not show major changes until 24 hours after injection of carrageenan or LPS. COX–2 protein increased 4 hours (carrageenan) or 2 hours (LPS) after injection. Topical administration of COX–2 inhibitor lowered dye–leakage into conjunctiva 4 hours after injection of carrageenan or LPS. Conclusions:These results suggested that the mechanism for anterior ocular inflammation may due to up–regulation of COX–2.

Keywords: conjunctivitis • inflammation • enzymes/enzyme inhibitors