Δ9-tetrahydrocannabinol induces blood-brain barrier disruption: Involving the activation of CB1R and oxidative stress

Abstract

Cannabis abuse has increased with the continuous relaxation of cannabis policies. However, the mechanism by which Δ⁹-tetrahydrocannabinol (THC) negatively affects the central nervous system, especially the blood-brain barrier (BBB), remains unclear. THC exposure models were established in vivo and in vitro. The BBB properties were examined using Western blotting (WB), immunofluorescence staining (IF), transendothelial electrical resistance (TEER), and flux of sodium fluorescein (SF). The oxidative stress regulators were examined using IF and assay kits. The activation of cannabinoid receptor 1 (CB1R) was examined using WB and IF. The THC exposure caused barrier integrity damage and endothelial dysfunction in murine and hCMEC/D₃ cells, conclude albumin leakage, increased SF permeability and reduced TEER value. The expression of tight junction proteins, including claudin 5, occludin, and junctional adhesion molecules, was decreased. Additionally, key oxidative stress regulators, including reactive oxygen species, hydrogen peroxide, malonaldehyde levels, and antioxidant enzyme activities, including catalase, glutathione peroxidase, glutathione S-transferase, and superoxide dismutase, and heme oxygenase 1, were increased. Activation of CB1R has been detected in brain microvascular endothelial cells in vivo and in vitro. Furthermore, inhibition of oxidative stress and CB1R could mitigate the aforementioned conditions and BBB damage after THC exposure. The effect of THC on murine and human brain microvascular endothelial cells revealed that THC-induced BBB damage was partly mediated by CB1R activation, triggering the oxidative stress response. This study provides new theoretical insights into the mechanisms of THC-induced BBB damage and offers novel scientific evidence for the potential neurotoxicity and adverse reactions induced by THC.