Exogenous arachidonic acid mediates permeability of human brain microvessel endothelial cells through prostaglandin E₂ activation of EP₃ and EP₄ receptors

Abstract

The blood-brain barrier, formed by microvessel endothelial cells, is the restrictive barrier between the brain parenchyma and the circulating blood. Arachidonic acid (ARA; 5,8,11,14-cis-eicosatetraenoic acid) is a conditionally essential polyunsaturated fatty acid [20:4(n À 6)] and is a major constituent of brain lipids. The current study examined the transport processes for ARA in confluent monolayers of human brain microvascular endothelial cells (HBMEC). Addition of radioactive ARA to the apical compartment of HBMEC cultured on Transwell â inserts resulted in rapid incorporation of radioactivity into the basolateral medium. Knock down of fatty acid transport proteins did not alter ARA passage into the basolateral medium as a result of the rapid generation of prostaglandin E 2 (PGE 2 ), an eicosanoid known to facilitate opening of the blood-brain barrier. Permeability following ARA or PGE 2 exposure was confirmed by an increased movement of fluorescein-labeled dextran from apical to basolateral medium. ARA-mediated permeability was attenuated by specific cyclooxygenase-2 inhibitors. EP 3 and EP 4 receptor antagonists attenuated the ARA-mediated permeability of HBMEC. The results indicate that ARA increases permeability of HBMEC monolayers likely via increased production of PGE 2 which acts upon EP 3 and EP 4 receptors to mediate permeability. These observations may explain the rapid influx of ARA into the brain previously observed upon plasma infusion with ARA. Keywords: arachidonic acid, blood-brain barrier, endothelial cells, fatty acid. Abbreviations used: ARA, arachidonic acid; BBB, blood-brain barrier; CNS, central nervous system; cPGES, cytosolic prostaglandin E 2 synthase; EP 1-4 , prostaglandin E 2 receptors 1-4; HBMEC, human brain microvascular endothelial cells; mPGES, microsomal prostaglandin E 2 synthase MRP4multi-drug resistance protein 4; PGE 2 , prostaglandin E 2 ; PGT, prostaglandin transporter.

Generation of Bioactive Oxylipins from Exogenously Added Arachidonic, Eicosapentaenoic and Docosahexaenoic Acid in Primary Human Brain Microvessel Endothelial Cells

“…In brain endothelial cells, exposure to both bacterial endotoxin as well as inflammatory cytokines results in the production and release of PGE 2 [8,9,25]. Within the brain microvasculature, PGE 2 promotes increased permeability and reduced BBB integrity [7,8]. The effects of increased PGE 2 within the brain are associated with a number of pathologies, including pyretic response to bacterial infection [26], HIV-and Alzheimer's disease-related microglial response and cognitive deficits [27,28], neurotoxicity in stroke and traumatic brain injury [29].…”

“…Such bioactive lipids may play a role in autoregulation of the cerebral microvasculature under both physiological and pathophysiological conditions. For example, we recently demonstrated that incubation of confluent monolayers of human brain microvessel endothelial cells with arachidonic acid (ARA) resulted in the generation of the oxylipin prostaglandin (PG) E 2 , which plays a role in regulating brain microvessel permeability [7][8][9]. However, there are potentially many other such oxylipins with biological activity that have yet to be identified in the brain endothelium.…”

Neurovascular contributions to migraine: Moving beyond vasodilation

“…Therefore, in order to restore metabolic balance, cortical neurons including interneurons and astroglia are thought to release of a variety of neurotransmitters including NO, carbon monoxide, adenosine, hydrogen ions, potassium ions, and lipoxygenase products known to alter cerebral vascular tone (Cauli et al, 2004; Vaucher et al, 2000; Zonta et al, 2003; Filosa et al, 2006; Koehler et al, 2006; Busija et al, 2008). Independent of vascular tone, these signaling molecules also directly affect endothelial cell signaling pathways (De Caterina et al, 1995; Jozkowicz et al, 2003; Erlinge and Burnstock, 2008; Dalvi et al, 2015; Mark et al, 2001). Moreover, the close association between cerebral blood vessels and neurons (Hawkins and Davis, 2005) facilitates 2-way communication between cortical neurons and endothelial cells comprising the blood vessels.…”

Blood–brain barrier and brain fatty acid uptake: Role of arachidonic acid and PGE2

“…With this background, I will highlight the significant advances in the field that are found in a new publication from the Hatch group at the University of Manitoba (Dalvi et al . ). In this work, they demonstrate using human microvascular endothelial cell cultures, a model of the human BBB, that a physiologically relevant concentration of ARA induces an increase in permeability in this BBB model.…”