The Inhibitory Effects of a Peripherally Restricted CB1 Receptor Antagonist on Myofibroblast Transdifferentiation of Human Retinal Pigment Epithelial Cells

Myofibroblasts derived from retinal pigment epithelial (RPE) cells play a key role in the pathogenesis of retinal fibrotic conditions such as proliferative vitreoretinopathy (PVR). Upon exposure to growth factors and cytokines such as TNF-α and TGF-β (TNT), RPE cells undergo epithelial-mesenchymal transition and subsequent transdifferentiation to contractile myofibroblasts. In this study, the effects of JD5037, a peripherally restricted CB1 antagonist, on myofibroblast transdifferentiation of primary cultures of human RPE cells were assessed. JD5037 significantly reduced TNT-induced, RPE cell-mediated collagen gel contraction, an indicator of myofibroblast function, in a concentration-dependent manner. Western blot analysis showed that JD5037 attenuated TNT-induced expression of α-SMA and fibronectin, two molecular markers of myofibroblasts. Furthermore, siRNA knockdown of CB1 cannabinoid receptor partially inhibited TNT-induced myofibroblast transdifferentation of human RPE cells and eliminated the inhibitory effects of JD5037 on myofibroblast transdifferentiation. These data demonstrate, for the first time, that peripherally restricted antagonists, such as JD5037, targeting the CB1 cannabinoid receptor have therapeutic potential for PVR and other retinal fibrotic conditions.