Involvement of cyclooxygenase-2 in rat models of conjunctivitis

Curr Eye Res. 2004 Jul;29(1):27-34. doi: 10.1080/02713680490513164.

Abstract

Purpose: Using two animal models to determine which isoform of cyclooxygenase (COX), constitutive COX-1 or inducible COX-2, is involved in the progression of anterior ocular inflammation.

Methods: Lambda-carrageenan (500 mg/eye) or bacterial lipopolysaccharide (LPS; 3 mg/eye) was injected into rat conjunctiva to induce conjunctivitis. Vascular permeability in inflamed conjunctiva was measured by uptake of systemic Evans blue. Changes in mRNA for COX-1 and COX-2 in conjunctiva were detected by RT-PCR. Changes in COX-2 protein were detected by immunoblotting after immunoprecipitation. To assess involvement of COX-2 in carrageenan and LPS-induced conjunctivitis, NS-398 (a selective COX-2 inhibitor) or indomethacin (non-selective COX inhibitor) was topically administrated at 15 and 30 minutes before inflammatory stimulator-injection.

Results: In the carrageenan-injected model, the dye content of conjunctiva (12.4 +/- 2.8 mg/eye) was significantly increased 4 hours after injection compared to saline-injected control rats (3.7 +/-1.1 mg/eye). mRNA for COX-2 was significantly increased by 2 hours and gradually increased until 24 hours; COX-1 mRNA did not show major changes until 24 hours after injection. COX-2 protein was markedly elevated 4 hours after injection of carrageenan. COX-2 protein levels were well correlated with increased mRNA levels. In the LPS-injected model, the dye content of conjunctiva (5.8 +/- 1.2 mg/eye) was significantly increased 4 hours after injection compared to saline-injected control rats (3.1 +/- 0.6 mg/eye). Expression of COX-2 mRNA was increased 1 hour after injection, peaked at 2 hours, and decreased at 4 hours. mRNA for COX-1 did not change by 24 hours. COX- 2 protein increased 2 hours after injection of LPS. COX-2 protein levels were well correlated with increased mRNA. Topical administration of 1% NS-398 exhibited strong inhibition of dye-leakage into conjunctiva 4 hours after injection of carrageenan or LPS, since 59% or 83% of dye-uptake were inhibited, respectively. 1% of indomethacin eye drops showed only a minimal effect.

Conclusions: These results suggest that the mechanism for anterior ocular inflammation may be due to up-regulation of COX-2.

MeSH terms

  • Animals
  • Capillary Permeability
  • Carrageenan
  • Conjunctivitis / chemically induced
  • Conjunctivitis / enzymology*
  • Cyclooxygenase 1
  • Cyclooxygenase 2
  • Cyclooxygenase 2 Inhibitors
  • Cyclooxygenase Inhibitors / pharmacology
  • Disease Models, Animal*
  • Evans Blue / metabolism
  • Gene Expression Regulation, Enzymologic*
  • Immunoblotting
  • Immunoprecipitation
  • Isoenzymes / genetics*
  • Isoenzymes / metabolism
  • Lipopolysaccharides
  • Male
  • Membrane Proteins
  • Nitrobenzenes / pharmacology
  • Prostaglandin-Endoperoxide Synthases / genetics*
  • Prostaglandin-Endoperoxide Synthases / metabolism
  • RNA, Messenger / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Rats, Wistar
  • Reverse Transcriptase Polymerase Chain Reaction
  • Sulfonamides / pharmacology
  • Up-Regulation

Substances

  • Cyclooxygenase 2 Inhibitors
  • Cyclooxygenase Inhibitors
  • Isoenzymes
  • Lipopolysaccharides
  • Membrane Proteins
  • Nitrobenzenes
  • RNA, Messenger
  • Sulfonamides
  • N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide
  • Evans Blue
  • Carrageenan
  • Cyclooxygenase 1
  • Cyclooxygenase 2
  • Prostaglandin-Endoperoxide Synthases
  • Ptgs1 protein, rat