Lack of association between VAP-1/SSAO activity and corneal neovascularization in a rabbit model

Abstract

The aim of this study is to determine the efficacy of a potent and specific vascular adhesive protein-1/semicarbazide-sensitive amine oxidase (VAP-1/SSAO) inhibitor, LJP 1207, as a potential antiangiogenic and anti-inflammatory agent in the therapy of corneal neovascularization. Corneal neovascularization was induced with intrastromal suturing in rabbits (n = 20). Topical treatment with VAP-1/SSAO inhibitor LJP 1207 (n = 5, 4 times a day), bevacizumab (n = 5, daily), their combination (n = 5) and vehicle only (n = 5, 4 times a day) were applied postoperatively for 2 weeks. The development and extent of corneal neovascularization were evaluated by digital image analysis. At the end of the observation period, the level of corneal and serum VAP-1/SSAO activity was measured fluorometrically and radiochemically. The corneal VAP-1/SSAO activity was significantly elevated in the suture-challenged vehicle-treated group (3,075 ± 1,009 pmol/mg/h) as compared to unoperated controls (464.2 ± 135 pmol/mg/h, p < 0.001). Treatment with LJP 1207 resulted in slower early phase neovascularization compared to vehicle-treated animals (not significant). At days 7-14, there was no significant difference in the extent of corneal neovascularization between inhibitor- and vehicle-treated corneas, even though inhibitor treatment caused a normalization of corneal VAP-1/SSAO activity (885 ± 452 pmol/mg/h). Our results demonstrate that the significant elevation of VAP-1/SSAO activity due to corneal injury can be prevented with VAP-1/SSAO inhibitor LJP 1207 treatment. However, normalization of VAP-1/SSAO activity in this model does not prevent the development of corneal neovascularization.

Fig. 1

Representative photographs of differently treated n = 5 groups (a–d VAP-1/SSAO inhibitor LJP 1207 treatment, e–h LJP 1207 in combination with bevacizumab treatment, i–l bevacizumab treatment, m–p vehicle treatment) of rabbits at days 3, 7, 10 and 14 (a, e, i, m day 3; b, f, j, n day 7; c, g, k, o day 10; d, h, l, p day 14), after placement of intrastromal corneal sutures

Fig. 2

Neovascularized corneal area in the proportion of the entire corneal surface (n = 5 in each group, data are mean ± SD, *p <0.05, **p <0.001)

Fig. 3

SSAO activity in corneal tissue of suture-challenged animals receiving different types of treatments for 14 days (LJP 1207, LJP 1207 combined with bevacizumab, bevacizumab, vehicle) and healthy control animals (n = 5 in each group, data are mean ± SD, *p <0.05, **p <0.005)

Fig. 4

Serum SSAO activity in suture-challenged animals receiving different types of treatments for 14 days (LJP 1207, LJP 1207 combined with bevacizumab, bevacizumab, vehicle) and healthy control animals (n = 5 in each group, data are mean ± SD, *p <0.05)