Neutrophil Defensins Enhance Lung Epithelial Wound Closure and Mucin Gene ExpressionIn Vitro


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Abstract

Human airways are frequently exposed to potentially harmful agents that cause tissue injury. Upon such injury, a repair process is initiated that comprises cell migration, proliferation, and differentiation. We have previously shown that human neutrophil defensins (human neutrophil peptides 1–3 [HNP1–3]) induce airway epithelial cell proliferation. Because of the role of cell proliferation in epithelial wound repair, we investigated the effect of HNP1–3 on airway epithelial wound closure and mucin gene expression in vitro. Using NCI-H292 airway epithelial cell cultures, we demonstrated that HNP1–3 cause a dose- and time-dependent increase of wound closure as well as increased cell migration. Furthermore, HNP1–3 caused a biphasic activation of the mitogen-activated protein kinase extracellular-regulated kinase 1 and 2 (ERK1/2). Both the effects of HNP1–3 on wound closure and ERK1/2 activation were blocked by specific inhibitors of the mitogen-activated protein kinase kinase MEK, whereas inhibitors of epidermal growth factor receptor tyrosine kinase, phosphatidylinositol 3-kinase, and Src did block defensin-enhanced wound closure but not ERK1/2 activation. Finally, HNP1–3 increased mRNA encoding the mucins MUC5B and MUC5AC, suggesting a role for defensins in mucous cell differentiation. These results indicate that neutrophil defensins increase epithelial wound repair in vitro, which involves migration and proliferation, and mucin production. Neutrophil defensin-enhanced wound repair appears to require epidermal growth factor receptor activation and downstream signaling pathways.

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