[The effect of fine particles on the phagocytosis of alveolar macrophages potentially by Arp2/3 complex in a mouse model of chronic obstructive pulmonary disease].

Abstract

Objective: To investigate the mechanism of fine particulate matter (PM2.5) on the phagocytosis of alveolar macrophages (AM) in mice with chronic obstructive pulmonary disease (COPD) through actin-related protein (Arp) 2/3 complex. Methods: Forty mice were divided into healthy control(A) group, healthy PM2.5 (B) group, COPD(C) group, and COPD PM2.5(D) group according to the random number table method. A mouse model of COPD was established by cigarette smoke exposure method. PM2.5 (662 μg/m(3)) model was established by continuously inhalation for 90 days in healthy PM2.5 group and COPD PM2.5 group. Flow cytometry was used to detect the ability of AM to phagocytose fluorescein isothiocyanate-labeled E.coli (FITC-E.coli), expressed as mean fluorescence intensity (MFI) and percentage of phagocytic positive cells (phagocytosis percentage); Western blotting was used to detect AM Arp2 and F-actin content, and laser confocal microscopy for AM Arp2 and F-actin and phagocytic FITC-E.coli average optical density and colocalization of Arp2 and F-actin, while scanning electron microscopy was used to observes the morphology of AM after phagocytizing FITC-E.coli. Results: AM phagocytosis: MFI and phagocytosis percentage in the COPD group [4 656±251, (31.9±1.7)%] were lower than the healthy control group [8 657±247, (65.7±1.9)%] (both P<0.01); and healthy PM2.5 group and COPD PM2.5 group [7 653±228, (47.9±1.6)% and 3 660±237, (19.2±1.2)%] were lower than the respective control groups (all P<0.01), and the decrease in the COPD group was more pronounced. AM Arp2, F-actin content: the COPD group (0.51±0.02, 0.46±0.03) were lower than the healthy control group (0.81±0.04, 0.71±0.04, both P<0.01); the healthy PM2.5 group and the COPD PM2.5 group [(0.64±0.03, 0.56±0.04) and (0.29±0.02, 0.26±0.02)] were lower than the respective control groups (all P<0.01), and the decrease in COPD group was more significant. Arp2, F-actin, and phagocytic FITC-E.coli mean optical density values: the COPD group (33.0±2.3, 62.0±0.7, 41.0±0.4) were lower than the healthy control group (141.0±4.2, 145.0±2.9, 189.0±2.6, both P<0.01); the healthy PM2.5 group and the COPD PM2.5 group (127.0±2.8, 124.0±0.7, 154.0±0.9, and 24.0±2.4, 37.0±0.4, 29.0±0.8) were lower than the respective control groups (all P<0.01), and the decrease in the COPD group was more significant. Colocalization of AM Arp2 and F-actin: Montessori colocalization coefficient (MOC) (0.38±0.03) in the COPD group was lower than the healthy control group (0.88±0.03, P<0.01); healthy PM2.5 group and COPD PM2.5 group [(0.58±0.03) and (0.14±0.02)] were lower than the respective control groups (both P<0.01), and the decrease in COPD group was more significant. Morphology of AM phagocytosis of FITC-E.coli: AM in the healthy control group was obviously deformed, and the surface of the cell membrane was slightly wrinkled and high, and the free edge of the micro-pleated fold had a long and dense filamentous pseudopodia extension. The changes of morphology of AM in the COPD group was not obvious, the micro-wrinkles on the surface of the cell membrane were rare, and the filopodia poorly extended or even absent. The AM form of the healthy PM2.5 group changed slightly, mostly irregular circular or elliptical. The micro-wrinkles on the surface of the cell membrane were less and flat, and the filopodia protrudes short and less; the AM form of the COPD PM2.5 group was stiff, and the micro-wrinkles on the surface of the cell membrane were few and flat, no obvious filopodia or protrusions. Correlation analysis: After basal state and PM2.5 intervention, AM Arp2, F-actin content and MOC values of Arp2 and F-actin were positively correlated with MFI. Conclusions: The phagocytic function of AM in COPD mice was low, which was related to the abnormal rearrangement of cytoskeleton involved in Arp2/3 complex and F-actin. It was speculated that PM2.5 might inhibit Arp2/3 complex and F-actin. The cytoskeletal rearrangement of proteins was involved in the aggravation of AM phagocytosis in mice with COPD.