Premium
Blood‐Brain Barrier Dysfunction and Microvascular Hyperpermeability Following Mild Traumatic Brain Injury
Author(s) -
Tharakan Binu,
Alluri Himakarnika,
Shaji Chinchusha Anasooya,
WigginsDohlvik Katie,
Beeram Madhava R,
Davis Matthew L
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.1204.8
Subject(s) - evans blue , blood–brain barrier , traumatic brain injury , extravasation , tight junction , in vivo , pharmacology , medicine , vascular permeability , chemistry , microbiology and biotechnology , pathology , biology , central nervous system , psychiatry
Microvascular hyperpermeability, the excessive leakage of fluid and proteins from intravascular space to the interstitium is the leading cause of tissue vasogenic edema in a variety of pathologies. Brain edema, elevated intracranial pressure and reduced cerebral perfusion pressure occurring in traumatic brain injury (TBI) are attributed heavily to the hyperpermeability of the blood‐brain barrier (BBB). Recent studies indicate that ATP sensitive purinergic receptors (P2X 7 R) play a major role in promoting brain edema following traumatic brain injury. In the BBB, zonula occludens‐1 (ZO‐1) is an important TJ associated protein that binds to the transmembrane tight junction proteins (TJPs) and actin cytoskeleton intracellularly and plays a key role in maintaining its barrier functions. Our objective was to evaluate the relative difference in BBB permeability following mild and moderate TBI and to determine if P2X 7 R inhibition will protect the BBB against mild TBI using in vitro and in vivo approaches. For in vitro studies, rat brain microvascular endothelial cell (RBMEC) monolayers transfected with P2X 7 R siRNA were exposed to BzATP, a potent analogue of ATP followed by monolayer permeability assay using FITC‐dextran. The potential change in ZO‐1 protein and gene expression were studied using western blotting and RT‐PCR analysis respectively. For in vivo studies, mild and moderate TBI was induced in mice using a controlled cortical impactor and BBB integrity/permeability was studied utilizing Evans blue extravasation studied fluorometrically. To test if pharmacological inhibition of P2X 7 R will protect the BBB, mice pretreated with KN62 (P2X 7 R inhibitor) were subjected to mild TBI followed by Evans Blue assay. RBMEC monolayers exposed to BzATP (10μM; 4 hours) following P2X 7 R knockdown showed a decrease in permeability compared BzATP group or BzATP + control siRNA group significantly ( p <0.05). The cells treated with BzATP (10μM; 4 hours) showed a decrease in ZO‐1 protein expression but the gene expression was unaltered. Mild and moderate TBI induced a significant increase in Evans blue extravasation indicating BBB hyperpermeability compared to sham control group ( p <0.05). TBI group pretreated with KN62 (10 μg/gram body weight) showed a decrease in Evans blue extravasation vs. TBI group (p<0.05) suggesting BBB protection following traumatic brain injury. These results suggest that ATP‐sensitive P2X 7 R plays a significant role in promoting BBB hyperpermeability and pharmacological inhibition of this pathway is protective against TBI‐induced BBB dysfunction.