Effect of actin-related protein 2-3 complex on phagocytosis defect of alveolar macrophages in a mouse model of chronic obstructive pulmonary disease

Abstract

Objective: To investigate the role of actin-related protein 2-3 complex (Arp2/3) complex on phagocytosis of alveolar macrophages (AMs) in a mouse model of chronic obstructive pulmonary (COPD). Methods: Forty mice were randomly divided into healthy control group, healthy Arp2/3 complex inhibitor (CK666) group, COPD group and COPD CK666 group with 10 mice in each group. COPD group and COPD CK666 group were established by cigarette smoke exposure, and the control group had no smoke exposure. After 90 days of molding, AMs were isolated from lung tissue of mice in each group. Mean fluorescence intensity (MFI) and the positive percent of AMs engulfing fluorescein isothiocyanate-labeled Escherchina coli (FITC-E.coli) (AM%) were detected by flow cytometry. Western blot was applied to detect protein. Laser scanning confocal microscopy was used to measure the mean optical density of Arp2, F-actin and engulfed FITC-E. coli and quantify the colocalization of Arp2 and F-actin by a Manders' overlap coefficient. Scanning electron microscopy was used to observe the ultrastructure of AM phagocytizing FITC-E.coli. Results: Phagocytosis of AM: MFI and AM% in the COPD group were significantly decreased than those in the healthy control group[(4 702±243), (8 684±234) and (32.21±1.66)%, (65.88±1.77)%, all P<0.01]. MFI and AM% in the COPD CK666 group [(3 597±307), (22.09±1.89)%] and in the healthy CK666 group [(7 446±236), (50.09±1.64)%] were decreased compared to those in their respective control groups (all P<0.01). The expressions of protein of Arp2 and F-actin in the COPD group were significantly decreased than those in the healthy control group (0.508±0.025, 0.813±0.040 and 0.462±0.029, 0.720±0.039) (all P<0.01). The F-actin in the COPD CK666 group (0.265±0.014) and in the healthy CK666 group (0.637±0.032) were significantly decreased compared to those in their respective control groups (all P<0.01). The mean optical density of Arp2, F-actin and FITC-E.coli in the COPD group were significantly decreased compared to those in the healthy group (34.43±0.56, 142.83±1.90 and 61.59±0.70, 145.93±3.05 and 41.49±0.33, 189.17±2.60) (all P<0.01); the mean optical density of F-actin, FITC-E. coli in the COPD CK666 group (37.73±1.04, 28.84±2.95) and in the healthy CK666 group (137.07±1.35, 157.46±1.00) were significantly decreased compared to those in their respective control groups (all P<0.01). The Manders' overlap coefficient of Arp2 and phalloidin' coefficient in the COPD group (0.395±0.014) were significantly decreased than the healthy control group (0.395±0.014 and 0.880±0.002, P<0.01). The Manders' overlap coefficient of Arp2 and phalloidin' coefficient in the COPD CK666 group (0.297±0.006) and in the healthy CK666 group (0.737±0.031) were significantly decreased compared to those in their respective control groups (all P<0.01). Shape of AM: Long filopodia protruding and plentiful dorsal ruffle can be seen in AM from the healthy control group; AM pseudopods extension and dorsal ruffle reduced in the health CK666 group; there were pseudopods and dorsal ruffle defects in the COPD group and the COPD CK666 group. Positive correlations existed between the proteins of Arp2, F-actin with MFI. Positive correlations also existed between the Manders' overlap coefficient of Arp2 and phalloidin' coefficient with MFI. Conclusion: Decreased activity of Arp2/3 complex leads to low phagocytosis of AM in COPD mice, and AM in COPD mice is more sensitive to Arp2/3 complex inhibitor.