Oxidative stress upregulates Wnt signaling in human retinal microvascular endothelial cells through activation of disheveled.

Abnormal retinal neovascularization associated with various retinopathies can result in irreversible vision loss. Although the mechanisms involved in this occurrence is unclear, increasing evidence suggests that aberrant Wnt signaling participates in the pathogenesis of abnormal neovascularization. Because Wnt signaling upregulation can be induced by oxidative stress through the activation of disheveled (DVL), a key molecule in the Wnt signaling pathway, we investigated whether oxidative stress can activate Wnt signaling and induce angiogenic phenotypes in human retinal microvascular endothelial cells (HRMECs). We found that increased Wnt signaling activity, as well as enhanced angiogenic phenotypes, such as tube formation and cell migration, were detected in the hydrogen peroxide-treated HRMECs. Moreover, these effects were effectively suppressed by a small-molecule Wnt inhibitor targeting the PDZ domain of DVL. Therefore, we propose that targeting abnormal Wnt signaling at the DVL level with a small-molecule inhibitor may represent a novel approach in retinal neovascularization treatment and prevention.

Small-molecule inhibition of Wnt signaling abrogates dexamethasone-induced phenotype of primary human trabecular meshwork cells.

Trabecular meshwork (TM) cells are the governing regulators of the TM structure. When the functionality of these cells is impaired, the structure of the TM is perturbed which often results in increased ocular hypertension. High intraocular pressure is the most significant risk factor for steroid-induced glaucoma. Dexamethasone (Dex)-induced phenotype of TM cells is widely utilized as a model system to gain insight into mechanisms underlying damaged TM in glaucoma. In this study, to assess the possible role of abnormal Wnt signaling in steroid-induced glaucoma, we analyzed the effects of small-molecule Wnt signaling modulators on Dex-induced expression extracellular matrix proteins of primary human TM cells. While Dex-treated TM cells exhibited increased collagen and fibronectin expression, we found that Wnt signaling inhibitor 3235-0367 suppressed these Dex-induced effects. We therefore propose that Wnt signaling plays an important role in Dex-mediated impairment of TM cell functions. Moreover, the use of small-molecule Wnt signaling inhibitors to treat TM cells may provide an opportunity of restoring TM tissue in steroid-induced glaucoma.

Dexamethasone Modulates the Dynamics of Wnt Signaling in Human Trabecular Meshwork Cells.

Trabecular meshwork (TM) tissue is highly specialized, and its structural integrity is crucial for maintaining homeostatic intraocular pressure (IOP). The administration of glucocorticoids, such as dexamethasone (DEX), can perturb the TM structure and significantly increase IOP in susceptible individuals, resulting in ocular diseases such as steroid-induced glaucoma, a form of open-angle glaucoma. Although the exact mechanism involved in steroid-induced glaucoma remains elusive, increasing evidence suggests that DEX may act through various signaling cascades in TM cells. Despite uncertainty surrounding the specific process by which steroid-induced glaucoma occurs, there is growing evidence to indicate that DEX can impact multiple signaling pathways within TM cells. In this study, we examined the impact of DEX treatment on the Wnt signaling pathway in TM cells, given that Wnt signaling has been reported to play a crucial role in regulating extracellular matrix (ECM) levels in the TM. To further elucidate the role of Wnt signaling in the glaucomatous phenotype, we examined mRNA expression patterns between Wnt signaling markers AXIN2 and sFRP1 and DEX-mediated induction of myocilin (MYOC) mRNA and protein levels over 10 days in DEX-treated primary TM cells. We observed a sequential pattern of peak expression between AXIN2, sFRP1, and MYOC. Based on the study, we propose that sFRP1 upregulation could be a result of a negative feedback mechanism generated by stressed TM cells to suppress abnormal Wnt signaling activities.