Emodin suppresses alkali burn-induced corneal inflammation and neovascularization by the vascular endothelial growth factor receptor 2 signaling pathway

OBJECTIVE

To investigate the effects of emodin on alkali burn-induced corneal inflammation and neovascularization.

METHODS

The ability of emodin to target vascular endothelial growth factor receptor 2 (VEGFR2) was predicted by molecular docking. The effects of emodin on the invasion, migration, and proliferation of human umbilical vein endothelial cells (HUVEC) were determined by cell counting kit-8, Transwell, and tube formation assays. Analysis of apoptosis was performed by flow cytometry. CD31 levels were examined by immunofluorescence. The abundance and phosphorylation state of VEGFR2, protein kinase B (Akt), signal transducer and activator of transcription 3 (STAT3), and P38 were examined by immunoblot analysis. Corneal alkali burn was performed on 40 mice. Animals were divided randomly into two groups, and the alkali-burned eyes were then treated with drops of either 10 μM emodin or phosphate buffered saline (PBS) four times a day. Slit-lamp microscopy was used to evaluate inflammation and corneal neovascularization (CNV) in all eyes on Days 0, 7, 10, and 14. The mice were killed humanely 14 d after the alkali burn, and their corneas were removed and preserved at －80 ℃ until histological study or protein extraction.

RESULTS

Molecular docking confirmed that emodin was able to target VEGFR2. The findings revealed that emodin decreased the invasion, migration, angiogenesis, and proliferation of HUVEC in a dose-dependent manner. In mice, emodin suppressed corneal inflammatory cell infiltration and inhibited the development of corneal neovascularization induced by alkali burn. Compared to those of the PBS-treated group, lower VEGFR2 expression and CD31 levels were found in the emodin-treated group. Emodin dramatically decreased the expression of VEGFR2, p-VEGFR2, p-Akt, p-STAT3, and p-P38 in VEGF-treated HUVEC.

CONCLUSION

This study provides a new avenue for evaluating the molecular mechanisms underlying corneal inflammation and neovascularization. Emodin might be a promising new therapeutic option for corneal alkali burns.

Knockdown of EGFR inhibits growth and invasion of gastric cancer cells

The epidermal growth factor receptor (EGFR) is an oncogenic trans-membranous receptor, which is overexpressed in multiple human cancers. However, the role of EGFR in gastric cancer (GC) is still elusive. In this study, we aimed to investigate the expression and molecular mechanisms of EGFR in GC cells. Forty cases of GC and the corresponding adjacent non-cancerous tissues (ANCT) were collected, and the expression of EGFR was assessed using immunohistochemistry in biopsy samples. Furthermore, EGFR signaling was blocked by constructed recombinant small hairpin RNA lentiviral vector (Lv-shRAGE) used to transfect into human GC SGC-7901 cells. The expression of AKT, proliferating cell nuclear antigen (PCNA) and matrix metallopeptidase-9 (MMP-9) was detected by real-time PCR and western blotting assays. Cell proliferative activities and invasive capability were, respectively, determined by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) and Transwell assays. Cell apoptosis and cycle distribution were analyzed by flow cytometry. EGFR was found highly expressed in cancer tissues compared with the ANCT and correlated with lymph node metastases. Knockdown of EGFR reduced cell proliferation and invasion of GC with decreased expression of AKT, PCNA and MMP-9 and induced cell apoptosis and cycle arrest. Upregulation of EGFR expression is associated with lymph node metastases of GC, and blockade of EGFR signaling suppresses growth and invasion of GC cells through AKT pathway, suggesting that EGFR may represent a potential therapeutic target for this aggressive malignancy.