Osteopontin induces airway smooth muscle cells proliferation and migration by modulating FAK/Src/YAP axis

BACKGROUND: Osteopontin (OPN), a multifunctional bioactive protein, has been shown to be elevated in the serum and bronchoalveolar lavage fluid (BALF) of. individuals with asthma and modulate the airway smooth muscle cells (ASMCs) proliferation and migration, yet its underlying molecular mechanisms are not completely understood. The aim of the present study is to address this issue. METHODS: Primary rat ASMCs were cultured to verify the effects of OPN and focal adhesion kinase (FAK)/Src/yes-associated protein (YAP) axis on cell proliferation and migration. Cell proliferation was assessed by BrdU incorporation assay. Cell migration was assessed by Transwell assay. Immunofluorescence and immunoblotting analysis confirmed that OPN activated FAK/Src/YAP axis. Moreover, we established an ovalbumin (OVA)-induced asthma rat model to verify whether OPN/FAK/Src/YAP cascade axis was involved in airway remodeling and asthma progression. RESULTS: OPN induced YAP dephosphorylation and nuclear localization via the αVβ3 integrin mediated activation of FAK/Src pathway, and this in turn increased thrombospondin 1 (THBS1) expression leading to ASMCs proliferation and migration. Intriguingly, THBS1 further activated FAK/Src to form a positive feedback loop. Pre-treatment of cells with anti-αvβ3 neutralizing antibody, FAK inhibitor PF573228 or Src inhibitor Dasatinib blocked OPN-induced alterations of YAP, THBS1 and functions of ASMCs. In addition, OPN promotes airway remodeling in asthma by activating FAK/Src/YAP axis. CONCLUSIONS: Our study indicates that OPN stimulates ASMCs proliferation and migration by binding to αVβ3 and activating FAK/Src/YAP axis, suggesting that targeting this pathway might have potential value in the management of airway remodeling of asthma.