title: Ca2+ entry via alpha1G and TRPV4 channels differentially regulates surface expression of P-selectin and barrier integrity in pulmonary capillary endothelium.
abstract: Pulmonary vascular endothelial cells express a variety of ion channels that mediate Ca(2+) influx in response to diverse environmental stimuli. However, it is not clear whether Ca(2+) influx from discrete ion channels is functionally coupled to specific outcomes. Thus we conducted a systematic study in mouse lung to address whether the alpha(1G) T-type Ca(2+) channel and the transient receptor potential channel TRPV4 have discrete functional roles in pulmonary capillary endothelium. We used real-time fluorescence imaging for endothelial cytosolic Ca(2+), immunohistochemistry to probe for surface expression of P-selectin, and the filtration coefficient to specifically measure lung endothelial permeability. We demonstrate that membrane depolarization via exposure of pulmonary vascular endothelium to a high-K(+) perfusate induces Ca(2+) entry into alveolar septal endothelial cells and exclusively leads to the surface expression of P-selectin. In contrast, Ca(2+) entry in septal endothelium evoked by the selective TRPV4 activator 4alpha-phorbol-12,13-didecanoate (4alpha-PDD) specifically increases lung endothelial permeability without effect on P-selectin expression. Pharmacological blockade or knockout of alpha(1G) abolishes depolarization-induced Ca(2+) entry and surface expression of P-selectin but does not prevent 4alpha-PDD-activated Ca(2+) entry and the resultant increase in permeability. Conversely, blockade or knockout of TRPV4 specifically abolishes 4alpha-PDD-activated Ca(2+) entry and the increase in permeability, while not impacting depolarization-induced Ca(2+) entry and surface expression of P-selectin. We conclude that in alveolar septal capillaries Ca(2+) entry through alpha(1G) and TRPV4 channels differentially and specifically regulates the transition of endothelial procoagulant phenotype and barrier integrity, respectively.
authors.affiliation: Center for Lung Biology and Dept. of Pharmacology, Univ. of South Alabama College of Medicine, Mobile, AL 36688-0002, USA.
authors.forename: Songwei
authors.initials: S
authors.lastname: Wu
authors.forename: Ming-Yuan
authors.initials: MY
authors.lastname: Jian
authors.forename: Yan-Chun
authors.initials: YC
authors.lastname: Xu
authors.forename: Chun
authors.initials: C
authors.lastname: Zhou
authors.forename: Abu-Bakr
authors.initials: AB
authors.lastname: Al-Mehdi
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Liedtke
authors.forename: Hee-Sup
authors.initials: HS
authors.lastname: Shin
authors.forename: Mary I
authors.initials: MI
authors.lastname: Townsley
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020747:Calcium Channels, T-Type / Q000378:metabolism*; D020013:Calcium Signaling; D002273:Carcinogens / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007124:Immunoenzyme Techniques; D051379:Mice; D018345:Mice, Knockout; D019007:P-Selectin / Q000378:metabolism*; D010703:Phorbol Esters / Q000494:pharmacology; D011651:Pulmonary Artery / Q000378:metabolism; D050916:TRPV Cation Channels / Q000378:metabolism*
chemical_list: C498197:Cacna1g protein, mouse; D020747:Calcium Channels, T-Type; D002273:Carcinogens; D019007:P-Selectin; D010703:Phorbol Esters; D050916:TRPV Cation Channels; C486576:Trpv4 protein, mouse; C008876:phorbol-12,13-didecanoate; D002118:Calcium