Studies about the cooperative signaling between p75^NTR and Trk receptors in the modulation of choroidal neovascularization.

Abstract

Purpose : Neovascular age-related macular degeneration (AMD) commonly causes vision loss from aberrant angiogenesis, termed choroidal neovascularization (CNV). To unravel the mechanisms underlying CNV, we focused on the p75 neurotrophin receptor (p75^NTR), a transmembrane protein known to mediate neuronal survival and death, and also vascular changes. P75^NTR can couple to different co-receptors to transduce intracellular signals. Our previous results showed that p75^NTR increases 7 days post-laser in retinal glia (GS+ or GFAP+) and RPE (retinal pigment epithelium)-choroid infiltrate (F4/80+) cells of mice with CNV. The deletion of the receptor reduced CNV area and prevented photoreceptor dysfunction. It has been reported that p75^NTR can potentiate Trk signalling in some scenarios. Thus, we aim to determine if p75^NTR modulates Trk activation to modify neovessel formation in a mouse model of laser-induced CNV.

Methods : 2- months old mice were anesthetized and their pupils were dilated; then, 4 injuries were performed in the retina using a photocoagulation laser with a 532nm wavelength slit lamp. 7 days after laser the mice were sacrificed. Samples include RPE-Choroid flatmounts, retina cryosections for immunostaining, and retinal and RPE-Choroid extracts processed separately for Western blot. WT (n=15) and p75^NTR KO (n=21) mice were included in the experimental design and animals without CNV (n=10) were used as control.

Results : We estimated Trk activation through the activation of its downstream signaling molecule ERK. We detected decreased expression of phosphor-ERK in retina from CNV mice respect to control (p=0,014) and similar phospho-ERK levels in RPE-choroid 7 days post laser (p=0,227) by Western Blot. Immunostaining did not show localization of pan-Trk nor phospho-ERK in retinal glia. Similarly, no overlapping was detected between pan-Trk and RPE-Choroid infiltrate assessed in RPE-Choroid flatmounts. Consistently, p75^NTRKO mice showed equal phospho-ERK levels 7 days after laser in retina (p=0,322) and RPE-Choroid (p=0,353).

Conclusions : In sum, our results suggest that the formation of vascular tufts that are produced during the CNV is not mediated by the cooperative signalling between p75^NTR and Trk receptors.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.