Targeting the tight junction protein, zonula occludens-1, with the connexin43 mimetic peptide, αCT1, reduces VEGF-dependent RPE pathophysiology

A critical target tissue in age-related macular degeneration (AMD) is the retinal pigment epithelium (RPE), which forms the outer blood-retina barrier (BRB). RPE-barrier dysfunction might result from attenuation/disruption of intercellular tight junctions. Zonula occludens-1 (ZO-1) is a major structural protein of intercellular junctions. A connexin43-based peptide mimetic, alpha CT1, was developed to competitively block interactions at the PDZ2 domain of ZO-1, thereby inhibiting ligands that selectively bind to this domain. We hypothesized that targeting ZO-1 signaling using alpha CT1 would maintain BRB integrity and reduce RPE pathophysiology by stabilizing gap- and/or tight-junctions. RPE-cell barrier dysfunction was generated in mice using laser photocoagulation triggering choroidal neovascularization (CNV) or bright light exposure leading to morphological damage. alpha CT1 was delivered via eye drops. alpha CT1 treatment reduced CNV development and fluid leakage as determined by optical coherence tomography, and damage was correlated with disruption in cellular integrity of surrounding RPE cells. Light damage significantly disrupted RPE cell morphology as determined by ZO-1 and occludin staining and tiling pattern analysis, which was prevented by alpha CT1 pre-treatment. In vitro experiments using RPE and MDCK monolayers indicated that alpha CT1 stabilizes tight junctions, independent of its effects on Cx43. Taken together, stabilization of intercellular junctions by alpha CT1 was effective in ameliorating RPE dysfunction in models of AMD-like pathology.