Antiangiogenic effects of catalpol on rat corneal neovascularization

To investigate the effects of catalpol on corneal neovascularization (CNV) and associated inflammation, eye drops (5 mM catalpol or PBS) were administered four times daily to alkali-burn rat models of CNV and inflammation. Clinical evaluations of CNV and the degree of inflammation were performed on days 0, 4, 7, 10 and 14 under slit lamp microscopy. Eyes were collected on day 14 and prepared for hematoxylin and eosin, and immunofluorescence staining; corneal cell apoptosis was investigated via terminal deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) staining. Protein expression levels of angiogenic and proinflammatory factors, including vascular endothelial growth factor (VEGF), pigment epithelium-derived factor (PEDF), tumor necrosis factor-α (TNF-α) and necrosis factor-κB (NF-κB) were determined by western blotting. The effects of catalpol on cell proliferation were investigated in vitro using human umbilical vein endothelial cells (HUVECs) and a Cell Counting kit-8 (CCK-8); alterations in migration and tube formation were investigated via HUVEC wound closure and tube formation assays. HUVEC viability and proliferative ability were inhibited in a dose-dependent manner; catalpol also decreased HUVEC cell migration and tube forming ability. Within alkali-burn rat models, decreased inflammation and CNV was associated with catalpol administration; as demonstrated with TUNEL, corneal cell apoptosis was decreased in response to catalpol. Western blot analysis revealed reduced protein expression levels of VEGF and TNF-α; however, PEDF and phosphorylated-NF-κB p65 were increased due to catalpol administration. The present study demonstrated the inhibitory effects exerted by catalpol on CNV and inflammation within alkali-burned rat models. Topical application of catalpol in vivo was associated with reduced CNV and inflammation; therefore, catalpol may be considered an anti-inflammatory agent for the clinical treatment of CNV.