The role of DCLK1 in thrombin-induced IL-8/CXCL8 expression in human lung epithelial cells

Airway neutrophilia has been linked to the severity of asthma and lack of response to corticosteroids. Thrombin, a multifunctional serine protease that participates in the pathogenesis of asthma, can enhance the secretion of IL-8/CXCL8 as a powerful chemoattractant for neutrophils. DCLK1 (doublecortin-like kinase 1) has been identified as a marker of stem cell in a variety of cancer types. The purpose of this research was to investigate the role of DCLK1 in thrombin-induced IL-8/CXCL8 expression in human lung epithelial cells. We confirmed in this study that the expression of DCLK1 thrombin, and IL-8/CXCL8 (MIP-2) were upregulated in bronchial tissues patients with severe asthma and ovalbumin (OVA)-challenged mice in immunohistochemistry and immunofluorescence staining. In addition, our in vitro study in human epithelial cell lines, BEAS-2B and A549, showed that siRNA against DCLK1 or DCLK1 inhibitor (LRKK2-IN-1) diminished the release of IL-8/CXCL8 triggered by thrombin, indicating that DCLK1 engages in IL-8/CXCL8 production enhanced by thrombin in lung epithelial cells. Thrombin also activated RhoA and YAP through DCLK1 in A549 cells. U0126 (ERK inhibitor) suppressed thrombin-stimulated the activation of DCLK1, RhoA, and YAP, showing that ERK was the upstream of DCLK1/RhoA/YAP pathway. Moreover, siRNA against DCLK1 inhibited thrombin-stimulated YAP and p65 complex and their binding to κB promoter region of IL-8/CXCL8. All of these results demonstrate the role of DCLK1 in mediating thrombin-induced IL-8/CXCL8 expression in human lung epithelial cells. Thrombin induces IL-8/CXCL8 expression through DCLK1-dependent RhoA and YAP pathway. Hence, our results provided new insight into the function of DCLK1 in the induction of IL-8/CXCL8 production by thrombin in human lung epithelial cells. Thrombin-stimulated IL-8/CXCL8 production in asthmatic lungs may require DCLK1, suggesting a new therapeutic approach for severe asthma.