Possible involvement of gap junctions in the barrier function of tight junctions of brain and lung endothelial cells.
Gap-junction plaques are often observed with tight-junction strands of vascular endothelial cells but the molecular interaction and functional relationships between these two junctions remain obscure. We herein show that gap-junction proteins connexin40 (Cx40) and Cx43 are colocalized and coprecipitated with tight-junction molecules occludin, claudin-5, and ZO-1 in porcine blood-brain barrier (BBB) endothelial cells. Gap junction blockers 18beta-glycyrrhetinic acid (18beta-GA) and oleamide (OA) did not influence expression of Cx40, Cx43, occludin, claudin-5, junctional adhesion molecule (JAM)-A, JAM-B, JAM-C, or ZO-1, or their subcellular localization in the porcine BBB endothelial cells. In contrast, these gap-junction blocking agents inhibited the barrier function of tight junctions in cells, determined by measurement of transendothelial electrical resistance and paracellular flux of mannitol and inulin. 18beta-GA also significantly reduced the barrier property in rat lung endothelial (RLE) cells expressing doxycycline-induced claudin-1, but did not change the interaction between Cx43 and either claudin-1 or ZO-1, nor their expression levels or subcellular distribution. These findings suggest that Cx40- and/or Cx43-based gap junctions might be required to maintain the endothelial barrier function without altering the expression and localization of the tight-junction components analyzed.
Nagasawa
Kunihiko
K
Department of Pathology, Sapporo Medical University School of Medicine, Sapporo, Japan.
Chiba
Hideki
H
Fujita
Hiroki
H
Kojima
Takashi
T
Saito
Tsuyoshi
T
Endo
Toshiaki
T
Sawada
Norimasa
N
D000818:Animals; D001812:Blood-Brain Barrier / Q000187:drug effects / Q000502:physiology*; D001921:Brain / Q000166:cytology* / Q000502:physiology; D002460:Cell Line; D002478:Cells, Cultured; D018031:Connexin 43 / Q000032:analysis / Q000235:genetics / Q000502:physiology; D017630:Connexins / Q000032:analysis / Q000235:genetics / Q000502:physiology; D017097:Electric Impedance; D004730:Endothelium, Vascular / Q000737:chemistry / Q000166:cytology* / Q000502:physiology; D017629:Gap Junctions / Q000737:chemistry / Q000187:drug effects / Q000502:physiology*; D005786:Gene Expression Regulation / Q000187:drug effects; D006034:Glycyrrhetinic Acid / Q000494:pharmacology; D015151:Immunoblotting; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D008168:Lung / Q000166:cytology* / Q000502:physiology; D008565:Membrane Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology; D062793:Occludin; D009829:Oleic Acids / Q000494:pharmacology; D010750:Phosphoproteins / Q000032:analysis / Q000235:genetics / Q000502:physiology; D051381:Rats; D015398:Signal Transduction / Q000502:physiology; D013552:Swine; D013556:Swine, Miniature; D019108:Tight Junctions / Q000737:chemistry / Q000502:physiology*; D062826:Zonula Occludens-1 Protein; D000097003:Gap Junction alpha-5 Protein
D018031:Connexin 43; D017630:Connexins; D006034:Glycyrrhetinic Acid; D008565:Membrane Proteins; D062793:Occludin; D009829:Oleic Acids; D010750:Phosphoproteins; D062826:Zonula Occludens-1 Protein; D000097003:Gap Junction alpha-5 Protein; C568987:Ocln protein, rat; C569044:Tjp1 protein, rat; C029407:oleylamide