Vascular endothelial growth factor antagonism restores epithelial barrier dysfunction via affecting zonula occludens...

Epithelial barrier dysfunction is important in the pathogenesis of asthma and allergic responses, and is therefore a therapeutic target. The aim of the present study was to investigate the effects of dexamethasone, a classic therapeutic agent, an anti-tumor necrosis factor agent (etanercept), which is used to treat difficult cases of asthma, and an anti-vascular endothelial growth factor (VEGF) agent (bevacizumab), which is an angiogenesis inhibitor, on zonula occludens (ZO) proteins in an experimental asthma model. The experimental model of asthma was developed using intraperitoneal (IP) and inhaled administration of ovalbumin in 38 BALB/c mice, which were divided into four groups. The control group (n=6) did not receive any treatment, while the four remaining groups (n=8 per group) received an IP injection of saline, etanercept, bevacizumab or dexamethasone, respectively. Occludin, claudin and junctional adhesion molecule (JAM) were immunohistochemically stained in the left middle lobe samples using an indirect avidin-peroxidase method, after which the staining was semiquantified with H-scores. Statistically significant differences were observed in the occludin, claudin and JAM H-scores among the four groups (P<0.001). In the untreated asthma, etanercept, bevacizumab and dexamethasone groups, the median H-scores for occludin were 93, 177, 280 and 198, respectively, while the H-scores for claudin were 82, 193.5, 274 and 202.5, respectively, and the median H-scores for JAM were 130, 210, 288 and 210, respectively. Pairwise comparisons revealed that all three ZO protein H-scores were significantly lower in the saline group when compared with each treatment group. However, the H-scores of the ZO proteins were not significantly different between the etanercept and dexamethasone groups. Furthermore, the bevacizumab group exhibited higher H-scores for all the proteins compared with the dexamethasone group. Therefore, antagonism of VEGF with bevacizumab restores the epithelial barrier to a greater extent when compared with dexamethasone treatment. This result may be promising for the development of novel therapeutic agents.