ABSTRACT
Objective:To investigate the repair effect of amphiregulin (Areg) on injured lung tissue in mice with acute respiratory distress syndrome (ARDS) and its underlying mechanism.Methods:The ARDS mouse model was made by tracheal infusion of lipopolysaccharide (LPS), and bronchoalveolar lavage fluid (BALF) was extracted for 7 consecutive days. Adult male C57BL/6 mice were randomly (random number) divided into 5 groups ( n=4 per group): (1) Control group; (2) Areg group: mice were treated intraperitoneally (i.p.) with recombinant Areg; (3) LPS+PBS group; (4) LPS+Areg group; and (5) LPS+Anti-Areg group; mice were instilled with LPS, then were injected i.p. with PBS, Areg or Areg neutralization antibody (Anti-Areg) 30 min later. Lung tissue and BALF were extracted at day 1, 3, 5 and 7 after ARDS. HE staining was used to evaluate the pathological changes of lung tissues. The total protein content in BALF was detected by BCA method, and the concentrations of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), IL-1β and immunoglobulin M (IgM) were determined by ELISA method. The phosphorylated levels of epidermal growth factor receptor (EGFR) and expressions of proliferating cell nuclear antigen (PCNA) and surface proteins-C (SP-C) were tested by Western blot. The immunofluorescence was used to detect the co-expression of PCNA and SP-C in lung tissues. One-way analysis of variance was used to compare the mean values of normally distributed measurement data between groups. Comparisons between groups were performed using the least significant difference t-test. Results:Compared with that at before modeling [(51.05±2.47) pg/mL], Areg concentrations were increased significantly at day 1 [(71.97±6.51) pg/mL; P<0.01] and day 3 [(147.58±7.56) pg/mL, P<0.01] in the BALF after ARDS. At day 1 after ARDS, there were significant interstitial edema, neutrophil infiltration and alveolar collapse in the LPS+PBS group and LPS+Areg group. Compared with the LPS+PBS group at day 3, 5 and 7, the pathological changes of lung tissues were notably improved in the LPS+Areg group, while were more serious in the LPS+Anti-Areg group. Compared with the control group, the LPS+PBS group had higher levels of neutrophil number, total protein, IgM, TNF-α, IL-1β, and IL-6. However, Areg treatment significantly reduced the levels of these indicators. Moreover, the expressions of PCNA (1.34±0.10), SP-C (1.48±0.10) and p-EGFR (0.92±0.032) in the LPS+Areg group were significantly up-regulated compared with those in the LPS+PBS group (0.88±0.03, 1.06±0.15, and 0.68±0.03, all P<0.01). And compared with the LPS+PBS group, PCNA and SP-C double positive cells were significantly increased in the LPS+Areg group, but decreased in the LPS+Anti-Areg group. Conclusions:Areg enhances the proliferation of alveolar typeⅡ epithelial cells by activating EGFR pathway, therefore promotes the repair of lung tissues during ARDS development.