To examine whether free fatty acid receptor 4 (FFAR4) activation can protect against choroidal neovascularization (CNV), which is a common cause of blindness, and to elucidate the mechanism underlying the inhibition, we used the mouse model of laser-induced CNV to mimic angiogenic aspects of age-related macular degeneration (AMD). Laser-induced CNV was compared between groups treated with an FFAR4 agonist or vehicle, and between FFAR4 wild-type (Ffar4+/+) and knock out (Ffar4-/-) mice on a C57BL/6J/6N background. The ex vivo choroid-sprouting assay, including primary retinal pigment epithelium (RPE) and choroid, without retina was used to investigate whether FFAR4 affects choroidal angiogenesis. Western blotting for pNF-ĸB/NF-ĸB and qRT-PCR for Il-6, Il-1β, Tnf-α, Vegf, and Nf-ĸb were used to examine the influence of FFAR4 on inflammation, known to influence CNV. RPE isolated from Ffar4+/+ and Ffar4-/- mice were used to assess RPE contribution to inflammation. The FFAR4 agonist suppressed laser-induced CNV in C57BL/6J mice, and CNV increased in Ffar4-/- compared to Ffar4+/+ mice. We showed that the FFAR4 agonist acted through the FFAR4 receptor. The FFAR4 agonist suppressed mRNA expression of inflammation markers (Il-6, Il-1β) via the NF-ĸB pathway in the retina, choroid, RPE complex. The FFAR4 agonist suppressed neovascularization in the choroid-sprouting ex vivo assay and FFAR4 deficiency exacerbated sprouting. Inflammation markers were increased in primary RPE cells of Ffar4-/- mice compared with Ffar4+/+ RPE. In this mouse model, the FFAR4 agonist suppressed CNV, suggesting FFAR4 to be a new molecular target to reduce pathological angiogenesis in CNV.
Keywords: Age-related macular degeneration (AMD); Free fatty acid receptor 4 (FFAR4); IL-6; Laser-induced choroidal neovascularization (CNV); NF-ĸb.