Nonionotropic Action of Endothelial NMDA Receptors on Blood–Brain Barrier Permeability via Rho/ROCK-Mediated Phosphorylation of Myosin

Abstract

Increase in blood-brain barrier (BBB) permeability is a crucial step in neuroinflammatory processes. We previously showed that N Methyl D Aspartate Receptor (NMDARs), expressed on cerebral endothelial cells forming the BBB, regulate immune cell infiltration across this barrier in the mouse. Here, we describe the mechanism responsible for the action of NMDARs on BBB permeabilization. We report that mouse CNS endothelial NMDARs display the regulatory GluN3A subunit. This composition confers to NMDARs' unconventional properties: these receptors do not induce Ca 2ϩ influx but rather show nonionotropic properties. In inflammatory conditions, costimulation of human brain endothelial cells by NMDA agonists (NMDA or glycine) and the serine protease tissue plasminogen activator, previously shown to potentiate NMDAR activity, induces metabotropic signaling via the Rho/ROCK pathway. This pathway leads to an increase in permeability via phosphorylation of myosin light chain and subsequent shrinkage of human brain endothelial cells. Together, these data draw a link between NMDARs and the cytoskeleton in brain endothelial cells that regulates BBB permeability in inflammatory conditions.

Brain endothelial cell tissue-nonspecific alkaline phosphatase (TNAP) activity promotes maintenance of barrier integrityviathe ROCK pathway

“…levamisole, induced the retraction of endothelial cells [33]. Endothelial cell retraction and detachment are prototypical indicators of cytoskeletal reorganization and have been shown to accompany BBB dysfunction and increase cellular permeability [46,47]. We observed that treatment of BMECs with TNF-α and IFN-γ combined with inhibition of TNAP enzymatic activity disrupted the actin cytoskeleton.…”

“…ROCK protein expression has been shown to play a role in regulating cytoskeletal proteins such as vimentin and actin by initiating F-actin contraction/retraction and cellular detachment [37,35,46]. Upstream of ROCK is the RhoA protein, one of many proteins that drives the activation of ROCK, and the Rho-ROCK pathway has been shown to play an important role in endothelial cell function Based on our cytoskeletal findings, we addressed whether the Rho/ROCK pathway was implicated in TNAP signaling.…”

Brain Barriers and brain fluids research in 2020 and the fluids and barriers of the CNS thematic series on advances in in vitro modeling of the blood–brain barrier and neurovascular unit

“…In mouse experimental autoimmune encephalomyelitis (a model of multiple sclerosis), gene inactivation of cortactin reduced neuroinflammation and a lack of cortactin ameliorated leukocyte migration across the brain endothelium in vivo and in vitro. Mehra et al [6] also reported that activation of N-Methyl-d-Aspartate Receptors (NMDARs) in brain endothelial cells upregulates immune cell infiltration into brain by phosphorylating myosin light chain and subsequent cell shrinkage. Interestingly, endothelial and neuronal NMDARs differ in structure, function and pharmacology.…”

Minocycline improves the recovery of nerve function and alleviates blood-brain barrier damage by inhibiting endoplasmic reticulum in traumatic brain injury mice model

“…Previously, it was shown that post-TBI inflammatory responses are initiated by peripheral immune mediators that enter the CNS through the porous BBB. 7 Therefore, in trauma, inhibiting the expression of related immune mediators and repairing the integrity of the BBB can stabilize the brain microenvironment, reduce the pathological response, and improve the long-term disease prognosis. Accumulation of the misfolded proteins in the endoplasmic reticulum (ER), causing dysfunction of ER, is known as ER stress.…”