The Synergistic and Neuroprotective Effects of Alcohol–Antioxidant Treatment on Blood–Brain Barrier Endothelial Cells

• Published in: Alcoholism, clinical and experimental research clinical and experimental research, 2020-10, Vol.44 (10), p.1997-2007
• Main Authors: Fisher, David, Thomas, Kelly Angelique, Abdul‐Rasool, Sahar
• Format: Article
• Language: English
• Subjects: Alcohol; Alcohol use; Antioxidants; Aspalathin; Blood; Blood-brain barrier; Brain Barrier; Brain Endothelial Cells; Cell number; Cell proliferation; Cell viability; Claudin‐5; Electrical resistivity; Endothelial cells; Ethanol; Fermented food; Membrane permeability; Neuroprotection; Oxidative stress; Permeability; Tight junctions; Toxicity; Transcription
• ISSN: 0145-6008; 1530-0277
• DOI: 10.1111/acer.14433

Background Alcohol (EtOH) is reported to adversely affect one of the most crucial roles of the blood–brain barrier (BBB), the regulation of its permeability, thereby compromising the stability of the homeostatic environment of the brain. The central component of the BBB, endothelial cells (ECs), regulates BBB transcellular transport, while their paracellular pathways are made virtually impermeable by molecular structures called tight junctions (TJs). These TJs are composed of proteins, such as claudin‐5, a protein involved in the regulation of paracellular permeability and of key interest in this study. Methods and Results The working hypothesis of this study postulated that the high levels of antioxidants (AOs) in the fermented Aspalathus linearis (Rooibos; Rf) tincture may protect the ECs of the BBB against oxidative stress induced by EtOH exposure. Cells were exposed for 24 hours to selected concentrations of EtOH (25 and 100 mM), Rf (containing an antioxidant equivalence of 1.9 nM Aspalathin), and cotreatments of EtOH and Rf. Cell viability, live cell number, and toxicity were analyzed using the trypan blue exclusion assay. RT‐qPCR was implemented to quantify claudin‐5 transcription. In addition, permeability (Transepithelial Electrical Resistance) of bEnd5 monolayers was measured. The experimental timeline for the above‐mentioned parameters was 24 and 48 hours. Conclusions Our study showed that simultaneous exposure of Rf and EtOH was able to negate the effects of EtOH on cell viability and cell proliferation, but was not able to reverse or reduce the effects of EtOH on claudin‐5 transcription and paracellular permeability. Furthermore, a novel finding in this study suggests that very low concentrations of AOs in tinctures such as Rooibos tea could profoundly alter the redox status of brain ECs. The capillary endothelial cells (BECs) are key components of the Blood‐brain barrier (BBB), responsible for the homeostatic regulation of the brain. Alcohol easily permeates into the brain, escaping the regulatory controls of the BBB, but through the generation of alcohol‐induced oxidative stress (OS), compromises the BECs functionality. Hereby, alcohol compromises the intercellular‐proteins which increases the BBB permeability and severely impedes angiogenesis (>35%). Co‐treatment with antioxidants completely reversed the alcohol‐induced effects on angiogenesis, but not on BBB permeability.