The effect of hepatocyte growth factor on secretory functions in human eosinophils

Hepatocyte growth factor (HGF), originally identified as a potent mitogen for mature hepatocytes, is now recognized as a humoral mediator in inflammatory and immune responses. Previous studies indicated that HGF negatively regulated allergic airway inflammation. In view of eosinophils playing a role in the pathogenesis of asthma, especially in airway remodeling as a rich source of pro-fibrogenic mediators, the effects of HGF on the different types of eosinophil secretory functions were examined in this study. We found that HGF significantly inhibited IL-5-induced secretion of TGF-β and VEGF from human eosinophils. The inhibitory effect is not associated with TGF-β transcription; rather, it is associated with ultrastructural granule emptying and loss of intracellular TGF-β contents, indicating HGF inhibits the process of piecemeal degranulation. The effect of HGF on extracellular trap cell death (ETosis) that mediates cytolytic degranulation was also investigated; however, immobilized IgG- or phorbol myristate acetate-induced ETosis was only minimally attenuated by HGF. These results reveal the effect of HGF on the distinct pathways of eosinophil secretory functions and also provide novel insights into the role of HGF in the pathogenesis of allergic inflammation.