Dkk1 is accumulated in the lung during acute pulmonary inflammation. (A-C) Two-hit LPS and MV model. (A) The mRNA expression of Wnt antagonists (sFRP1 and Dkk1-4) in the whole-lung tissues of LM-challenged and control mice was determined by real-time PCR and plotted as the fold change over control animals with 18S rRNA as a reference gene. (B) The protein levels of Dkk1 in the whole-lung tissues of control and LM-challenged animals were measured by western blotting using β-actin as a loading control. The density of the bands was quantified by ImageJ and normalized to β-actin. The result was expressed as a ratio to control animals. (C) The Dkk1 concentrations in the BAL and plasma of LM-challenged mice were measured by ELISA. (D-G) Influenza viral pneumonia model. (D) The mRNA level of Dkk1 in the whole-lung tissues of H1N1 influenza virus PR/8-infected mice for 0 to 7 days was analyzed by real-time PCR and normalized to the control mice with 18S rRNA as a reference gene. (E) The Dkk1 concentrations in the BAL and plasma of H1N1 influenza virus PR/8-infected mice were measured by ELISA. (F) Immunostaining of Dkk1 in the lungs of control, LM-challenged, and H1N1 influenza virus PR/8-infected (7 dpi) mice. Scale bar = 75 µm. (G) The protein levels of T1α (AEC I marker), CD141 (endothelial cell marker), IgM (epithelial-endothelial barrier damage marker), and Dkk1 in the BALs of H1N1 influenza virus PR/8-infected mice (day 0 to day 7) were determined by western blotting. Data are expressed as the mean ± SEM (n = 3-8 animals) and statistical significance is determined by the Student t test. *P < .05 vs control.