Expression of integrin subunits αv and β3 in acute lung inflammation
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Integrin subunits αv and β3 form a dimer, αvβ3, which is expressed on normal neutrophils and endothelium. We investigated the expression of integrin subunits αv and β3 in acute lung inflammation in Sprague-Dawley rats (n=5 each) following intratracheal challenge with Escherichia coli or Streptococcus pneumoniae, which induce neutrophil recruitment through different mechanisms. Control rats (n=5) were given endotoxin-free saline. Both bacterial challenges induced similar levels of recruitment of neutrophils in lungs. Western blots showed lower expression of integrin subunits αv and β3 in lungs challenged with E. coli compared to those given S. pneumoniae. Immunohistochemistry and immunogold electron microscopy localized both integrin subunits in neutrophils and endothelium in the control and treated rat lungs. Quantitative immunohistochemistry showed that E. coli-challenged rat lungs contained a lower percentage of neutrophils expressing integrin subunits αv and β3 compared to those challenged with S. pneumoniae (P<0.05). We conclude that E. coli infection decreased the percentage of neutrophils expressing integrin subunits αv and β3 compared to S. pneumoniae infection. These data lay the foundation for further characterization of these integrin subunits in neutrophil migration specifically in S. pneumoniae infection that utilizes molecules other than β2 integrins for neutrophil recruitment.
KeywordsIntegrin αv Integrin β3 Lung Neutrophils Inflammation
This work was supported through grants from Natural Sciences and Engineering Research Council of Canada and Saskatchewan Health Research Foundation to Dr. Singh. Dr. Janardhan is supported through a University of Saskatchewan Graduate Merit Scholarship. We thank Ms Sarah Caldwell for help with immunogold electron microscopy.
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