Endothelial NMDA receptor involvement in retinal neurovascular damage following prenatal alcohol exposure in mouse model

Prenatal alcohol exposure (PAE) induces neurodevelopmental damage leading to fetal alcohol spectrum disorders (FASD) by altering both brain and ocular development. Recent data showed that PAE impairs brain cortical and retinal vasculature leading to defective positioning of interneurons. In the retina, PAE disturbs vascular development and the association of calretinin neurons with vessels. The NMDA receptor (NMDAR) is a major target of alcohol in the brain, and both ligand binding to NMDARs and the expression of NMDAR subunits are altered in FASD. Given that NMDAR is also expressed in endothelial cells and that glutamate stimulation of endothelial NMDAR (eNMDAR) regulates cortical interneuron positioning along blood vessels, we hypothesize that eNMDAR is critical for retinal vascular development and mediates PAE-induced defects. Using an in vivo model of FASD and transgenic mice lacking, specifically in endothelial cells, the GluN1 subunit of the NMDAR, this study aimed to characterize the neurovascular phenotype of the developing retina. The results show that eNMDAR knockout delays the formation of the superficial vascular plexus and prevents the alterations in vascular organization and neuronal density induced by PAE, particularly cells positioned closer to the retinal vasculature, namely ganglion, amacrine, and horizontal cells. Moreover, eNMDAR deletion led to an increased number of calretinin-positive interneurons in contact with perforating vessels and prevents the decrease induced by PAE. Together, these findings demonstrate that eNMDARs are essential for normal retinal neurovascular development and mediate, at least in part, the detrimental effects of ethanol exposure in FASD. Significance statementUsing a murine model of Fetal Alcohol Spectrum Disorder (FASD) and transgenic mice lacking the GluN1 subunit of the NMDA receptor specifically in endothelial cells (eNMDAR), this study demonstrates that eNMDAR plays a critical role in mediating prenatal alcohol exposure (PAE)-induced neurovascular abnormalities in the retina. Loss of eNMDAR alters the progression of the superficial vascular plexus and prevents the vascular impairments typically observed following PAE. In addition, eNMDAR deletion protects against PAE-induced neuronal damage, particularly affecting retinal ganglion cells, calbindin-positive, and calretinin-positive interneurons. Notably, this study identifies, for the first time, a role for endothelial NMDAR in regulating neurovascular interactions between retinal vessels and calretinin-positive neurons, highlighting this receptor as a key molecular mediator of ethanol-induced retinal damage.