Background. G9a, a well-known methyltransferase, plays a vital role in biological processes. However, its role in corneal neovascularization (CoNV) remains unclear. Methods. In vitro and in vivo models were assessed in hypoxia-stimulated angiogenesis and in a mouse model of alkali burn-induced CoNV. Human umbilical vein endothelial cells (HUVECs) were cultured under hypoxic conditions and different reoxygenation times to identify the molecular mechanisms involved in this process. Results. In this study, we found that G9a was positively related to corneal alkali burn-induced injury. Inhibition of G9a with BIX 01294 (BIX) alleviated corneal injury, including oxidative stress and neovascularization in vivo. Similarly, inhibition of G9a with either BIX or small interfering RNA (siRNA) exerted an inhibitory effect on hypoxia/reoxygenation (H/R)-induced oxidative stress and angiogenesis in HUVECs. Moreover, our study revealed that ablation of reactive oxygen species (ROS) with N-acetyl-cysteine suppressed angiogenesis in HUVECs exposed to H/R stimulation. Furthermore, NADPH oxidase 4 (Nox4), which was positively associated with ROS production and angiogenesis, was elevated during H/R. This effect could be reversed through suppression of the transcription activity of G9a with BIX or siRNA. In addition, the Nrf2/HO-1 pathway, upstream of Nox4, was activated in both BIX-treated mice and G9a-inhibited HUVECs. Collectively, our results demonstrated that inhibition of G9a-alleviated corneal angiogenesis by inhibiting Nox4-dependent ROS production through the Nrf2/HO-1 signaling pathway. These findings indicate that G9a may be a valuable therapeutic target for CoNV.
Involvement of NADPH oxidases in alkali burn-induced corneal injury
