Lanthanum chloride causes blood–brain barrier disruption through intracellular calcium-mediated RhoA/Rho kinase signaling and myosin light chain kinase

Rare earth elements (REEs) have caused bioaccumulation and adverse health effects attributed to extensive application. The penetrability of REEs across the blood–brain barrier (BBB) contributes to their neurotoxicity process, but potential mechanisms affecting BBB integrity are still obscure. The present study was designed to investigate the effects of lanthanum on BBB adheren junctions and the actin cytoskeleton in vitro using bEnd.3 cells. After lanthanum chloride (LaCl₃, 0.125, 0.25 and 0.5 mM) treatment, cytotoxicity against bEnd.3 cells was observed accompanied by increased intracellular Ca²⁺. Higher paracellular permeability presented as decreased TEER (transendothelial electrical resistance) and increased HRP (horse radish peroxidase) permeation, and simultaneously reduced VE-cadherin expression and F-actin stress fiber formation caused by LaCl₃ were reversed by inhibition of ROCK (Rho-kinase) and MLCK (myosin light chain kinase) using inhibitor Y27632 (10 μM) and ML-7 (10 μM). Moreover, chelating overloaded intracellular Ca²⁺ by BAPTA-AM (25 μM) remarkably abrogated RhoA/ROCK and MLCK activation and downstream phosphorylation of MYPT1 (myosin phosphatase target subunit 1) and MLC2 (myosin light chain 2), therefore alleviating LaCl₃-induced BBB disruption and dysfunction. In conclusion, this study indicated that lanthanum caused endothelial barrier hyperpermeability accompanied by loss of VE-cadherin and rearrangement of the actin cytoskeleton though intracellular Ca²⁺-mediated RhoA/ROCK and MLCK pathways.