To evaluate the neuroprotective effects of betaxolol (betaxolol hydrochloride) under hypoxic conditions using retinal ganglion cells (RGC-5) and determine whether heme oxygenase-1 (HO-1) expression exerts cytoprotective effects.

In this study, cultured RGC-5 cells were incubated with different concentrations of betaxolol hydrochloride (0.1 µM, 1 µM or 5 µM) and with 10 µM zinc protoporphyrin (ZnPP), in a hypoxia incubator (1% O₂, 5% CO₂, 94% N₂) for 48 hours and the cell viability of each group was determined. Additionally, cell viability was measured after RGC-5 cells were incubated with 5 µM of brinzolamide (Azopt®), brimonidine tartrate (Alphagan®) or travoprost (Travatan®). RGC-5 cells were divided into three groups and incubated under three different conditions, normoxia group (20% O₂, 5% CO₂), hypoxia group (1% O₂, 5% CO₂) and the group with 5 µM of Betoptic S® treated under hypoxic conditions (hypoxia, Betoptic S®). After incubation for 4, 8, 12 and 24 hours, HO-1 expression was analyzed using Western blotting.

Cell viability significantly increased in RGC-5 cells treated with Betoptic S® compared with other antiglaucoma agents. Increased levels of HO-1 expression indicate its relevance in cell viability. Furthermore, increased RGC-5 cell viability by Betoptic S® was significantly reduced in the HO-1 inhibitor ZnPP-treated group.

We reaffirmed the known cytoprotective effects of Betoptic S® and the results suggests that HO-1 expression exerts cytoprotective effects against hypoxia.