Repurposing Griseofulvin as a Non‐Toxic Angiogenesis Inhibitor

Abstract

BackgroundOcular neovascularization causes vision loss in major blinding diseases such as proliferative diabetic retinopathy, retinopathy of prematurity, and neovascular age‐related macular degeneration. Over 30% of patients are refractive to current therapies, hence developing small molecules targeting ocular neovascularization is critical. We previously identified the heme biosynthesis enzyme ferrochelatase (FECH) as an angiogenesis mediator. FECH is upregulated in human and mouse eyes undergoing neovascularization, and knockdown or mutation abolished angiogenesis in vitro and in vivo. FECH inhibition is therefore a promising therapeutic approach for blocking neovascularization. The FDA‐approved anti‐fungal drug, griseofulvin, inhibits FECH as an off‐target effect and blocks choroidal neovascularization ex‐vivo and in mice. Here, we investigated the anti‐angiogenic effect of griseofulvin in the mouse oxygen‐induced retinopathy (OIR) model of retinal neovascularization, and explored its ocular toxicity.MethodsIn the OIR model, newborn mice are exposed to 75% oxygen at postnatal day 7 (P7) for 5 days, causing retinal vascular regression. At P12, upon return to normoxia, the retina becomes ischemic, forming pre‐retinal neovascularization. Temporal expression of FECH was analyzed at various ages in mouse OIR retinas. Griseofulvin was intravitreally injected in OIR mice at P12 and retinal neovascularization assessed at P17 using Isolectin B4 staining. Tip cell filopodia and retinal sprouting were assessed by murine retinal ex‐vivo assays. For toxicity studies, adult mice were intravitreally injected with griseofulvin and retinal damage analyzed after 7 and 14 days. Structural and morphological analyses were performed using optical coherence tomography (OCT) and histology. Vascular leakage was assessed by fluorescein angiography (FA). Functional analysis of the retina was performed using electroretinogram (ERG). Apoptosis and immune cell activation were assessed by immunohistochemistry.ResultsTemporal FECH upregulation was observed in mouse OIR retinas. Griseofulvin inhibited retinal neovascularization in OIR and also decreased the avascular area in the OIR retina. Further, griseofulvin inhibited retinal tip cell filopodia and retinal sprouting ex‐vivo. OCT and FA revealed that retinal structure was maintained and no vascular leakage was found in griseofulvin injected eyes. ERG showed that retinal function was normal in griseofulvin treated mice, and histology showed normal retinal stratification in griseofulvin treated eyes. Immunostaining revealed no aberrant cell death, microglia activation or gliosis in griseofulvin treated eyes, suggesting no cellular toxicity or stress.ConclusionsGriseofulvin inhibits retinal neovascularization and also promotes revascularization, suggesting a dual effect on vascular repair. Griseofulvin lacks ocular toxicity. Together, these findings suggest that griseofulvin could be repurposed to treat neovascularization in ocular diseases.Support or Funding InformationNIH/NEI R01EY025641, Research to Prevent Blindness, Inc.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.