Abstract
Purpose: :
Platelet-activating factor (PAF) is a strong bioactive inflammatory mediator that inhibits corneal wound healing. The action of PAF is blocked by the novel PAF receptor antagonist LAU-0901 (ARVO 2011). Lipoxin A4 (LXA4), a lipid mediator derived from arachidonic acid by the action of a 15-lipoxigenase, is involved in inflammation resolution and tissue repair. The purpose of this study was to evaluate the action of LXA4 on an in vivo mouse model of corneal epithelial and stromal injury sustained by PAF.
Methods: :
Male 5-7-week-old C57BL/6 mice were used. The corneal epithelium and anterior stroma (about 25%) from one eye was removed up to the limbal border using an Algerbrush II with a 0.5 mm burr under a surgical microscope. The mice were treated topically with 10µg/ml PAF (5µl) once a day, LXA4 (1µg) 3 times/day or both together. Mice were euthanized at 1, 2, and 7 days after injury, and corneas were excised and processed for histopathology (H&E staining). ELISA, enzymatic activity for myeloperoxidase (MPO) , or immunofluorescence staining with antibodies for metalloproteinase-9 (MMP-9), interlukin-1α ( IL-1α), keratinocyte-derived chemokine (KC/CXCL1), α-smooth muscle actin (α-SMA), neutrophils and MPO were performed.
Results: :
Topical treatment with LXA4 suppressed the effect of PAF on wound healing. At day 1, the injury area was reduced up to 80% compared to PAF alone, and at day 2 by up to 95%. By day 7, the healing was complete. The strong stromal cell infiltration and neutrophil recruitment induced by PAF was decrease with LXA4 treatment. The activity and expression of MPO were also decreased. LXA4 blocked PAF- induced MMP-9 and cytokines IL-1α and KC expression.
Conclusions: :
PAF is a strong inflammatory mediator and a potent activator of MMP-9 that delays cornea wound healing. The potent counteracting action of LXA4 in arresting the sustained inflammatory response of PAF suggests the potential use of this lipoxin as a therapeutic tool in treating corneal injuries that compromise the stroma.
Keywords: wound healing • inflammation • lipids