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.
ABSTRACT
Background Eicosapentaenoic acid(EPA)function as the critical lipid mediators involved in several biological events in human body and play important role in suppressing the genesis of vascular endothelial growth factor (VEGF),migration and proliferation of vascular endothelial cells.Many ocular diseases were proved to be associated with neovascularization.Objecfive The purpose of this study was to investigate the inhibitory effect of EPA on the proliferation of human umbilical vein endothelial cells (HUVEC) indueed by VEGF. Methods HUVEC strain was cultured and passaged,and difierent concentrations of EPA were added to the medium with and without VEGF.The cultured cells were identified by antiofactor Ⅷ polyclonal antibody.The suppressing role of different concentrations of EPA on the proliferation of VEGF-induced or-uninduced HUVEC was assessed by MTT method.The influence of difierent concentrations of EPA on the cellular cycle of VEGF-induced HUVEC was assayed using flow eytometry.The expression of Flk-1,a receptor of VEGF,in the HUVEC Was detected by immunohistochemistry. Results Cultured HUVEC showed the ftlsiform in shape and presented with the cobblestone-like arrangement with the positive response for Ⅷ factor-related antigen.Various concentrations of EPA showed obviously inhibitory effect on VEGF-induced or-unindueed HUVEC at a dose-dependent manner (F=23.072.P=0.000).The inhibitory ability of EPA on VEGF-induced HUVEC was stronger than VEGF-uninduced HUVEC(F=41.417,P=0.000).In 24,48 and 72 hours,the action of EPA on the proliferation of HUVEC was gradually enhanced with the prolong of time(F=1.495,P=0.236).Cell cycle analysis indicated that EPA arrested VEGF-induced HUVEC in G0/G1 phase.The ratio of HUVEC in G0/G1 phase in EPA group was(75.83±1.56)%,and that in control groups was(68.62±1.44)%,showing a significant difference between them(t=-5.88,P=0.00),and no apoptosis of HUVEC was found in both groups.Flk-1 was strongly expressed in the cellular nucleus and cytoplasm in control group.However,the positive expressing intensity of Flk-1 in the HUVEC weakened,and the positive cell number was evidently less in EPA group. Conclusion EPA can inhibit the proliferation of VEGF induced HUVEC through arresting the synthesis of DNA of HUVEC and downregulate the expression of Flk-1 in HUVEC.These results suggest that EPA might exert an antiangiogenic effect.