Effect of NIR light on the permeability of the blood-brain barriers in in vitro models

The blood-brain barrier (BBB) is a dynamic barrier between the blood microcirculation system and the brain parenchyma, which plays an important role in the pathogenesis of a variety of neurological diseases. Meanwhile, a non-invasive therapeutic approach of photobiomodulation (PBM) has emerged as a promising treatment for neurological disorders through irradiation with near infrared (NIR) light. However, despite multiple encouraging results reported for PBM in vitro and in vivo, the mechanisms of its therapeutic effect on brain, especially on the BBB, remain barely known. Herein, the effect of NIR light irradiation on the in vitro BBB models was studied. 808 nm laser irradiation at the doses of 10 and 30 J/cm² was found to significantly increase the permeability of this BBB model. The results showed that NIR light affected mitochondria of cells in the in vitro BBB models, leading to an increase in the mitochondrial activity, reactive oxygen species (ROS) level and Ca²⁺ influx. The activity of matrix metalloproteinases and the expression of the tight junction proteins in the endothelial cells were found to be inhibited by the NIR light, resulting in an increase in the BBB permeability. This study suggested a new strategy for drug transport across the BBB in development of treatments for brain disorders.