Particulate matter air pollution disrupts endothelial cell barrier via calpain-mediated tight junction protein degradation

Part Fibre Toxicol. 2012 Aug 29:9:35. doi: 10.1186/1743-8977-9-35.

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.

Objectives: 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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Acetylcysteine / pharmacology
  • Air Pollutants / toxicity*
  • Calcium / metabolism
  • Calpain / metabolism*
  • Cells, Cultured
  • Electric Impedance
  • Endothelium, Vascular / drug effects*
  • Endothelium, Vascular / metabolism
  • Free Radical Scavengers / pharmacology
  • Humans
  • Lung / cytology
  • Oxidative Stress / drug effects
  • Particulate Matter / toxicity*
  • Permeability
  • Reactive Oxygen Species / metabolism
  • TRPM Cation Channels / metabolism*
  • Zonula Occludens-1 Protein / metabolism*

Substances

  • Air Pollutants
  • Free Radical Scavengers
  • Particulate Matter
  • Reactive Oxygen Species
  • TJP1 protein, human
  • TRPM Cation Channels
  • TRPM2 protein, human
  • Zonula Occludens-1 Protein
  • Calpain
  • CAPN2 protein, human
  • Calcium
  • Acetylcysteine