Salinomycin inhibits proliferative vitreoretinopathy formation in a mouse model.

Proliferative vitreoretinopathy (PVR) is a progressive disease that develops in a subset of patients who undergo surgery for retinal detachment repair, and results in significant vision loss. PVR is characterized by the migration of retinal pigment epithelial (RPE) cells into the vitreous cavity, where they undergo epithelial-to-mesenchymal transition and form contractile membranes within the vitreous and along the retina, resulting in recurrent retinal detachments. Currently, surgical intervention is the only treatment for PVR and there are no pharmacological agents that effectively inhibit or prevent PVR formation. Here, we show that a single intravitreal injection of the polyether ionophore salinomycin (SNC) effectively inhibits the formation of PVR in a mouse model with no evidence of retinal toxicity. After 4 weeks, fundus photography and optical coherence tomography (OCT) demonstrated development of mean PVR grade of 3.5 (SD: 1.3) in mouse eyes injected with RPE cells/DMSO (vehicle), compared to mean PVR grade of 1.6 (SD: 1.3) in eyes injected with RPE cells/SNC (p = 0.001). Additionally, immunohistochemistry analysis showed RPE cells/SNC treatment reduced both fibrotic (αSMA, FN1, Vim) and inflammatory (GFAP, CD3, CD20) markers compared to control RPE cells/DMSO treatment. Finally, qPCR analysis confirmed that Tgfß, Tnfα, Mcp1 (inflammatory/cytokine markers), and Fn1, Col1a1 and Acta2 (fibrotic markers) were significantly attenuated in the RPE cells/SNC group compared to RPE/DMSO control. These results suggest that SNC is a potential pharmacologic agent for the prevention of PVR in humans and warrants further investigation.

The polyether ionophore salinomycin targets multiple cellular pathways to block proliferative vitreoretinopathy pathology.

Proliferative vitreoretinopathy (PVR) is characterized by membranes that form in the vitreous cavity and on both surfaces of the retina, which results in the formation of tractional membranes that can cause retinal detachment and intrinsic fibrosis of the retina, leading to retina foreshortening. Currently, there are no pharmacologic therapies that are effective in inhibiting or preventing PVR formation. One of the key aspects of PVR pathogenesis is retinal pigment epithelial (RPE) cell epithelial mesenchymal transition (EMT). Here we show that the polyether ionophore compound salinomycin (SNC) effectively inhibits TGFß-induced EMT of RPE cells. SNC blocks the activation of TGFß-induced downstream targets alpha smooth muscle actin (αSMA) and collagen 1 (Col1A1). Additionally, SNC inhibits TGFß-induced RPE cell migration and contraction. We show that SNC functions to inhibit RPE EMT by targeting both the pTAK1/p38 and Smad2 signaling pathways upon TGFß stimulation. Additionally, SNC is able to inhibit αSMA and Col1A1 expression in RPE cells that have already undergone TGFß-induced EMT. Together, these results suggest that SNC could be an effective therapeutic compound in both the prevention and treatment of PVR.