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[The mechanism of corneal ring formation caused by bacterial endotoxin]
1Department of Bacteriology, School of Medicine, Iwate Medical University, Morioka, Japan.
Abstract:
Corneal ring can be produced experimentally by injection of endotoxin into the rabbit cornea. To clarify this phenomenon, the effects of inhibitors of arachidonic acid metabolite were studied on the formation of the corneal ring. Phospholipase A2 inhibitor (dexamethasone) and lipoxygenase inhibitor (TEI-3308) blocked the accumulation of polymorphonuclear leukocytes (PMNs) in the endotoxin-injected cornea, while cyclooxygenase inhibitor (indomethacin) enhanced PMN accumulation. This result suggests that products of the lipoxygenase reaction of arachidonic acid are related to the formation of the corneal ring induced by endotoxin. The existence of endotoxin in active form for a long period was also demonstrated immunohistochemically.
Insights
Experimental endotoxin injection in rabbit corneas forms a corneal ring. Inhibiting lipoxygenase, but not cyclooxygenase, blocked polymorphonuclear leukocyte accumulation, suggesting lipoxygenase products are key to ring formation.
Area of Science:
- Ophthalmology
- Inflammation Research
- Biochemistry
Background:
- Corneal ring formation is an experimental phenomenon induced by endotoxin.
- The precise mechanisms underlying endotoxin-induced corneal ring formation require further elucidation.
Purpose of the Study:
- To investigate the role of arachidonic acid metabolites in endotoxin-induced corneal ring formation.
- To determine the effects of specific enzyme inhibitors on inflammatory cell infiltration in the cornea.
Main Methods:
- Experimental induction of corneal ring formation using endotoxin in rabbit corneas.
- Administration of phospholipase A2 inhibitor (dexamethasone), lipoxygenase inhibitor (TEI-3308), and cyclooxygenase inhibitor (indomethacin).
- Assessment of polymorphonuclear leukocyte (PMN) accumulation via immunohistochemistry.
Main Results:
- Dexamethasone and TEI-3308 inhibited PMN accumulation in endotoxin-injected corneas.
- Indomethacin treatment enhanced PMN accumulation.
- Immunohistochemistry confirmed the prolonged presence of active endotoxin.
Conclusions:
- Products of the lipoxygenase pathway of arachidonic acid metabolism are implicated in corneal ring formation.
- The balance between lipoxygenase and cyclooxygenase pathways influences inflammatory responses in the cornea.
- Endotoxin remains biologically active for an extended duration following injection.