# Oxytocin supports the barrier integrity of brain endothelial cells via oxytocin receptors

## TL;DR

Oxytocin helps maintain the integrity of brain endothelial cells, especially under low-oxygen conditions, by acting through oxytocin receptors.

## Contribution

This study reveals that oxytocin enhances brain endothelial barrier function via oxytocin receptors, particularly under hypoxia.

## Key findings

- bEnd.3 cells express oxytocin and V1a receptors.
- Oxytocin increases claudin-5 expression and localization at the cell surface.
- Oxytocin preserves endothelial barrier integrity under hypoxic conditions.

## Abstract

Oxytocin plays an emerging role in vascular regulation and neuroprotection, but its effect on brain endothelial cells and blood–brain barrier functionality is not fully defined. To assess oxytocin and vasopressin receptor expression in brain endothelial cells and to evaluate the impact of oxytocin on endothelial barrier integrity under physiological (normoxic) and low‐oxygen (hypoxic) conditions we used bEnd.3 brain endothelial cells. Receptor expression was evaluated by real‐time PCR and RNAscope. Oxytocin treatment was applied under normoxic and hypoxic conditions and Transendothelial Electrical Resistance and tight junction proteins expression (claudin‐5, zonula occludens‐1) were analyzed. Our results indicate that 1) bEnd.3 cells express oxytocin and V1a receptors. 2) Activation of the oxytocin receptor enhanced brain endothelial barrier integrity by increasing claudin‐5 expression and its localization at the cell surface, without affecting zonula occludens‐1.3) Under hypoxic conditions, oxytocin preserved Transendothelial Electrical Resistance and claudin‐5 expression at the cell membrane, thereby preventing endothelial barrier impairment. Our findings demonstrate that oxytocin receptor signaling enhances and preserves brain endothelial barrier function, underscoring the relevance of oxytocin in neurovascular regulation and its therapeutic potential in blood–brain barrier dysfunction.