Current Issue August 2010, Vol. 126, No. 2

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  Fas ligand and matrix metalloproteinase 7: A dysfunctional relationship in asthma Airway inflammation and epithelial damage are hallmarks of chronic asthma. The molecule Fas ligand (FasL) is potentially involved in both processes; expression of membrane FasL on lung epithelial cells confers a protective "immune barrier" defense against damage caused by infiltrating immune cells, but FasL can be cleaved into a proinflammatory soluble attractant for neutrophils, an important effector cell in asthma. Wadsworth et al (p 366) demonstrate that the protease matrix metalloproteinase 7 (MMP-7) is potentially important in airway epithelial health and inflammation in patients with asthma through direct cleavage of membrane FasL off epithelial cells. The authors show that MMP-7 expression is altered in the airway epithelium of patients with severe asthma in vivo. As shown in the Figure, they demonstrate that treatment of airway epithelial cells in vitro with an "asthmalike" T_H2 cytokine mix causes MMP-7 (green) and FasL (red) to colocalize (yellow) at the cell membrane. This interaction leads to cleavage of the protective FasL from the epithelial cell membrane and release of the soluble proinflammatory form. The T_H2 cytokine environment in the airways of asthmatic patients might therefore trigger a persistent increase of epithelial cell MMP-7 activity with associated FasL cleavage. The authors show airway epithelial MMP-7 as a potential target in patients with severe asthma to reduce airway inflammation and epithelial remodeling events.
  
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