title: Particulate matter air pollution disrupts endothelial cell barrier via calpain-mediated tight junction protein degradation.
abstract: BACKGROUND
  Exposure to particulate matter (PM) is a significant risk factor for increased cardiopulmonary morbidity and mortality. The mechanism of PM-mediated pathophysiology remains unknown. However, PM is proinflammatory to the endothelium and increases vascular permeability in vitro and in vivo via ROS generation.
  
  
  OBJECTIVE
  We explored the role of tight junction proteins as targets for PM-induced loss of lung endothelial cell (EC) barrier integrity and enhanced cardiopulmonary dysfunction.
  
  
  METHODS
  Changes in human lung EC monolayer permeability were assessed by Transendothelial Electrical Resistance (TER) in response to PM challenge (collected from Ft. McHenry Tunnel, Baltimore, MD, particle size >0.1 μm). Biochemical assessment of ROS generation and Ca2+ mobilization were also measured.
  
  
  RESULTS
  PM exposure induced tight junction protein Zona occludens-1 (ZO-1) relocation from the cell periphery, which was accompanied by significant reductions in ZO-1 protein levels but not in adherens junction proteins (VE-cadherin and β-catenin). N-acetyl-cysteine (NAC, 5 mM) reduced PM-induced ROS generation in ECs, which further prevented TER decreases and atteneuated ZO-1 degradation. PM also mediated intracellular calcium mobilization via the transient receptor potential cation channel M2 (TRPM2), in a ROS-dependent manner with subsequent activation of the Ca2+-dependent protease calpain. PM-activated calpain is responsible for ZO-1 degradation and EC barrier disruption. Overexpression of ZO-1 attenuated PM-induced endothelial barrier disruption and vascular hyperpermeability in vivo and in vitro.
  
  
  CONCLUSIONS
  These results demonstrate that PM induces marked increases in vascular permeability via ROS-mediated calcium leakage via activated TRPM2, and via ZO-1 degradation by activated calpain. These findings support a novel mechanism for PM-induced lung damage and adverse cardiovascular outcomes.
authors.affiliation: Institute for Personalized Respiratory Medicine, Section of Pulmonary, Critical Care, Sleep and Allergy, Department of Medicine, University of Illinois at Chicago, Chicago, IL, USA.
authors.forename: Ting
authors.initials: T
authors.lastname: Wang
authors.forename: Lichun
authors.initials: L
authors.lastname: Wang
authors.forename: Liliana
authors.initials: L
authors.lastname: Moreno-Vinasco
authors.forename: Gabriel D
authors.initials: GD
authors.lastname: Lang
authors.forename: Jessica H
authors.initials: JH
authors.lastname: Siegler
authors.forename: Biji
authors.initials: B
authors.lastname: Mathew
authors.forename: Peter V
authors.initials: PV
authors.lastname: Usatyuk
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Samet
authors.forename: Alison S
authors.initials: AS
authors.lastname: Geyh
authors.forename: Patrick N
authors.initials: PN
authors.lastname: Breysse
authors.forename: Viswanathan
authors.initials: V
authors.lastname: Natarajan
authors.forename: Joe G N
authors.initials: JG
authors.lastname: Garcia
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D000393:Air Pollutants / Q000633:toxicity*; D002118:Calcium / Q000378:metabolism; D002154:Calpain / Q000378:metabolism*; D002478:Cells, Cultured; D017097:Electric Impedance; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000378:metabolism; D016166:Free Radical Scavengers / Q000494:pharmacology; D006801:Humans; D008168:Lung / Q000166:cytology; D018384:Oxidative Stress / Q000187:drug effects; D052638:Particulate Matter / Q000633:toxicity*; D010539:Permeability; D017382:Reactive Oxygen Species / Q000378:metabolism; D050053:TRPM Cation Channels / Q000378:metabolism*; D062826:Zonula Occludens-1 Protein / Q000378:metabolism*
chemical_list: D000393:Air Pollutants; D016166:Free Radical Scavengers; D052638:Particulate Matter; D017382:Reactive Oxygen Species; C569042:TJP1 protein, human; D050053:TRPM Cation Channels; C121934:TRPM2 protein, human; D062826:Zonula Occludens-1 Protein; D002154:Calpain; C569870:CAPN2 protein, human; D002118:Calcium; D000111:Acetylcysteine