Timolol Maleate, a β Blocker Eye Drop, Improved Edema in a Retinal Vein Occlusion Model

Purpose: To investigate the therapeutic effects of eye drops, namely, timolol maleate, a β-adrenergic receptor antagonist, and latanoprost, a prostaglandin F2α analog, on retinal edema in a murine retinal vein occlusion (RVO) model.

Methods: An RVO model was established using laser-induced RVO in mice, which were administered timolol maleate and latanoprost eye drops several times after venous occlusion. Subsequently, the thickness of the inner nuclear layer (INL) and the expression levels of such genes as and , which are stress markers of the endoplasmic reticulum, were examined. Primary human cultured retinal microvascular endothelial cells (HRMECs) were treated with timolol under hypoxic conditions, after which the gene expression pattern was investigated. Importantly, an integrated stress response inhibitor (ISRIB) was used in the RVO model, he known , which suppresses the expression of in retinal edema.

Results: Increased INL thickness was suppressed by timolol eye drops, as were the expressions of and , in the RVO model. However, latanoprost eye drops did not induce any change in INL thickness. In HRMECs, hypoxic stress and serum deprivation increased the and expressions; in response, treatment with timolol suppressed the expression. Furthermore, the ISRIB decreased the expression pattern and edema formation, which are associated with RVO.

Conclusions: These results indicate that timolol eye drops may be a potential option for RVO treatment.