GSK3β Inhibitors Inhibit TGFβ Signaling in the Human Trabecular Meshwork

Abstract

Purpose: Primary open-angle glaucoma (POAG) is a leading cause of blindness, and its primary risk factor is elevated intraocular pressure (IOP) due to pathologic changes in the trabecular meshwork (TM). We previously showed that there is a cross-inhibition between TGFβ and Wnt signaling pathways in the TM. In this study, we determined if activation of the Wnt signaling pathway using small-molecule Wnt activators can inhibit TGFβ2-induced TM changes and ocular hypertension (OHT).

Methods: Primary human TM (pHTM) cells and transduced SBE-GTM3 cells were treated with or without Wnt and/or TGFβ signaling activators and used for luciferase assays; for the extraction of whole-cell lysate, conditioned medium, cytosolic proteins, and nuclear proteins for Western immunoblotting (WB); or for immunofluorescent staining. Human donor eyes were perfusion cultured to study the effect of Wnt activators on IOP.

Results: We found that the small-molecule Wnt activators (GSK3β inhibitors) (BIO, SB216763, and CHIR99021) activated canonical Wnt signaling in pHTM cells without toxicity at tested concentrations. This activation inhibited TGFβ signaling as well as TGFβ2-induced extracellular matrix deposition and formation of cross-linked actin networks in pHTM cells or SBE-GTM3 cells. We also observed nuclear translocation of both Smad4 and β-catenin in pHTM cells, which suggested that the cross-inhibition between the TGFβ and Wnt signaling pathways may occur in the nucleus. Using our ex vivo model, we found that CHIR99021 inhibited TGFβ2-induced OHT in perfusion-cultured human eyes.

Conclusions: Our results showed that small-molecule Wnt activators have the potential for treating TGFβ signaling-induced OHT in patients with POAG.