Sphingosine‐1‐phosphate protects against brain microvascular endothelial junctional protein disorganization and barrier dysfunction caused by alcohol

Abstract

Objective: Sphingosine-1-phosphate (S1P) has known endothelial barrier protective properties, but whether this extends to the blood-brain barrier (BBB) is unclear. We hypothesized that alcohol-induced disruption of brain microvascular endothelial barrier function and junctional protein organization can be ameliorated by S1P treatment. Methods: Cultured primary human brain microvascular endothelial cell (HBMEC) monolayers were used to characterize endothelial-specific mechanisms of BBB regulation. Transendothelial electrical resistance (TER) and apparent permeability coefficients for albumin, dextran-4 kDa, and sodium fluorescein were used as indices of barrier function. Junctional localization of Claudin-5, VE-cadherin and β-catenin were determined by immunofluorescence confocal microscopy. S1P was applied following treatment with alcohol. Results: Alcohol significantly impaired HBMEC TER. Application of S1P after alcohol treatment resulted in a hastened recovery to the baseline HBMEC TER. Alcohol-treated HBMEC had a significantly higher mean permeability than control that was reversed by S1P. Alcohol caused formation of gaps between cells. Treatment with S1P (after alcohol) increased junctional localization of VE-Cadherin, Claudin-5 and β-catenin. Conclusions: Alcohol impairs the barrier function and junctional organization of HBMEC monolayers. S1P enhanced barrier function and restored junctions in the presence of alcohol, and thus may be useful for restoring BBB function during alcohol intoxication.

Blood-Brain Barrier Dysfunction Amplifies the Development of Neuroinflammation: Understanding of Cellular Events in Brain Microvascular Endothelial Cells for Prevention and Treatment of BBB Dysfunction

“…The direct effect of S1P on cultured BMECs remains controversial. Some research groups have reported barrier enhancement following treatment with S1P ( van Doorn et al, 2012 ; Alves et al, 2019 ), while other research groups found that S1P decreased barrier properties in BMECs ( Wiltshire et al, 2016 ; Nakagawa and Aruga, 2020 ). Given that S1P has different effects on endothelial barrier function depending on the S1PRs involved ( Camm et al, 2014 ), the differences between these conflicting findings may be caused by altered expression of S1PRs in different cell types and culture conditions.…”

Sigma‐1 receptor activation‐induced glycolytic ATP production and endothelial barrier enhancement

“…TER served as an indicator of barrier function of endothelial cell monolayers. TER was determined using an electrical cell‐substrate impedance sensor (ECIS) (Applied Biophysics) as previously described 24,27 . This method allows for real‐time detection of small, momentary changes in barrier function relating to nanometer‐scale changes in junctional structures 37 .…”

“…Endothelial cells have a critical role in controlling blood‐tissue gas and solute exchange 19 . The barrier function of the endothelium depends on the integrity of endothelial structure, which can be actively altered by the responses of endothelial cells to various inflammatory mediators, growth factors, and physical forces 20‐25 . Endothelial junctional proteins and cytoskeleton dynamics have a well‐characterized role in endothelial health 23,26,27 .…”

The Microvascular-Lymphatic Interface and Tissue Homeostasis: Critical Questions That Challenge Current Understanding

“…However, more direct approaches could also be more effective. Several investigators have shown with both in vitro and animal models that the bioactive lipid sphingosine-1-phosphate (S1P) can reduce microvascular permeability in a variety of models of inflammation [62][63][64][65][66]. S1P and drugs that activate S1P receptor-1 have been shown to reduce microvascular leakage following experimental trauma in rodents [38,40,67].…”

“…Would decreasing permeability of the capillaries and venules reduce or alleviate lymphedema? This remains a significant question considering that specific therapeutics that reduce microvascular permeability by directly targeting blood endothelial cells, such as S1P [38, 40, 64] or sigma receptor agonists [128], remain in an experimental stage. Also, from a therapeutic perspective, there is concern that common agonists/drugs typically affect both vascular and lymphatic endothelia.…”