[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]

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.

[Effects of PI3Kδ-RhoA pathway on phagocytosis defect of alveolar macrophages in a mouse model of chronic obstructive pulmonary disease]

Objective: To investigate effects of Phosphoinositide3-Kinases (PI3Kδ)-Ras homolog gene family member A(RhoA) pathway on phagocytosis deficiency of alveolar macrophages (AMs) in a mouse model of chronic obstructive pulmonary disease (COPD). Methods: Twenty mice were exposed to cigarette smoking to establish the COPD model, with 20 mice as the control group. AMs were isolated from lung tissue by discontinuous density gradient centrifugation and then divided into a healthy control group, a COPD group, a healthy IC87114 group and a COPD IC87114 group. The culture of IC87114 group was mixed with a final concentration of 1 nmol/L IC87114 for 24 hours. Mean fluorescence intensity (MFI) and the positive percent of AMs engulfing flurescein isothiocyanate-labeled Escherichina coli (FITC-E.coli) (AM%) were detected by flow cytometry. Real-Time PCR(RT-PCR)and Western blot were applied to detect mRNA and protein. G-LISA RhoA Kit was used to detect the activity of RhoA, and laser scanning confocal microscopy was used to observe the cytoskeleton structure of AMs. Results: Phagocytosis of AM: MFI and AM %in the COPD group [(4 512±517), (32.2±4.6)%] were decreased than those in the healthy control group [(9 857±1 042), (68.0±4.0)%, all P<0.01]. Compared with the COPD group, MFI and AM% in the COPD IC87114 group [(6 894±472), (50.6±2.1)%] were increased (all P<0.01). The expressions of mRNA and protein of PI3Kδ in the COPD group (3.14±0.54, 0.84±0.08) were increased than those in the healthy control group (1.00±0.00, 0.57±0.07) (all P<0.01). Compared with the COPD group, the expressions of mRNA and protein of PI3Kδ in the COPD IC87114 group (1.52±0.28, 0.66±0.13) were decreased (all P<0.01). The RhoA mRNA, protein and activity in the COPD group (0.70±0.07, 0.41±0.10, 0.70±0.06) were decreased compared to those in the healthy control group (1.00±0.00, 0.56±0.09, 1.19±0.09) (all P<0.01). Compared with the COPD group, the expression of mRNA, protein and activity of RhoA in the COPD IC87114 group(0.91±0.08, 0.48±0.06, 0.86±0.06) were increased (P<0.01, P<0.05). Cytoskeleton of AM: The pseudopods of the healthy control group and the healthy IC87114 group extended well, and the ability of phagocytosing FITC-E.coli was intact, but there were some defects in the COPD group. Compared with the COPD group, the COPD IC87114 group was better, both in phagocytosing and extending of pseudopods. Negative correlations existed between the mRNA, protein of PI3Kδ with mRNA, protein and activity of RhoA. Negative correlations also existed between the mRNA, protein of PI3Kδ with MFI, but positive correlations between RhoA and MFI were observed in all groups. Conclusion: The phagocytosis of AMs in COPD mice was defective, with abnormal rearrangement of the cytoskeleton. PI3Kδ negatively regulated RhoA, while PI3Kδ over activation resulted in decreasing activity of RhoA and then induced abnormal cytoskeleton rearrangement in AMs, which led to phagocytosis deficiency.IC87114 inhibited PI3Kδ activation, improved the activity of RhoA and partly recovered phagocytosis of AMs.