Inhibitory effects of eicosapentaenoic acid on expression of nuclear factor-kB and cytokine in rat corneal neovascularization / 中华实验眼科杂志

ABSTRACT

Background Corneal neovascularization (CNV) is an important cause of visual impairment and graft rejection after allograft corneal transplantation in inflammatory corneal diseases. The mechanisms and therapy relating to CNV are intensely investigated at all times. Objective This study was to evaluate the effect of eicosapentaenoic acid (EPA) on CNV induced by alkali cauterization and its mechanism. Methods The animal models of corneal neovasculation were induced in the right eyes in 72 Sprayue-Dawley rats by putting a piece of 3 mmfilter paper with 1 mol/L NaOH at the center of the cornea for 30 seconds. The rats were then divided randomly into the 0.02 mg EPA treatment group (24 rats) ,0.03 mg EPA treatment group (24 rats) ,model group (24 rats) and normal group (6 rats). EPA of 0.04 ml with doses of 0.02 mg or 0. 03 mg or saline solution of 0. 04 ml was injected subconjunctivally in model rats and immediately after cauterization. The presence of CNV and corneal edema were observed daily by slit lamp biomicroscope. 1,4,7 and 14 days after operation, corneal histopathological examination was performed by hematoxylin and eosin staining. The vascular endothelial cells were stained with CD34 by immunohistochemistry,and the expression of IL-1α,IL-6 mRNA and the nuclear factor-κBp65 ( NF-κBp65 ) proteins was measured by reverse transcription polymerase chain reaction (RT-PCR) and Western blot analysis. The use of animals complied with the Regulations for the Administration of Affair Concerning Experimental Animals by Hebei Province( version 1998 ). Results Under the slit lamp, CNV grew slowly from days 2-4 with obvious corneal edema and defect of epithelium. Larger CNV area and less edema were seen from days 7-10. Maximal vessel growth was observed 14 days after injury with thinner vessels in the model group. Histological examination showed that part of the corneal epithelium was damaged;serious corneal edema, more inflammatory cells and a lot of CNV in the stroma were presented in the model group. However, repairing of the corneal epithelium without CNV ,light corneal edema and less inflammatory cells were found in both the 0. 02 mg EPA and 0. 03 mg EPA treatment groups 7 days after alkali cauterization. The relative area of CNV in the 0. 02 mg EPA treatment group was ( 15.80±6.43 )% and ( 11.06±2. 14)% ,and that in the 0. 03 mg EPA treatment group was (16. 10±7.41 )% and (11.06±2. 51 )%, showing significant reduction in comparison with the model group [ (84. 74±7.77)% and (89.63±7.50) % ] 7 days and 14 days after operation ( P＜0. 05 ). Stronger expression of CD34 in the vascular endothelial cells of the cornea stroma was observed in the model group and an absence of CD34 was observed in the EPA-treated groups on the 7th day. RT-PCR revealed that the expression of IL-1α mRNA and IL-6 mRNA was lower in the EPA treatment groups than the model group ( P＜0. 05 ), and Western blot analysis showed that the expression of NF-κB/p65 in the corneas in the EPA treatment groups was significantly lower than that in the model group on the 4th day after operation (P＜0.05).Conclusion Topical application of EPA suppresses CNV induced by alkali burn possibly by inhibiting the expression of NF-κB,IL-1α and IL-6.