[Effects of mTOR-Cdc42 signaling pathway on phagocytosis of alveolar macrophages in chronic obstructive pulmonary disease mice].

Abstract

Objective: To investigate effects of mammalian target of rapamycin (mTOR)- cell division cycle 42 (Cdc42) signaling pathway on phagocytosis of alveolar macrophages (AMs) in chronic obstructive pulmonary disease (COPD) mice. Methods: Forty mice were randomly divided into control group and model group. Each group contained 20 mice. COPD model group were established by cigarette smoking exposure. AMs were isolated from lung tissue by discontinuous density gradient centrifugation. AMs from control group were divided into health control group and rapamycin control group while AMs from model group were divided into COPD group and rapamycin COPD group. The AMs from rapamycin control group and rapamycin COPD group were incubated with a final concentration of 10 nmol/L rapamycin for 24 hours. Mean fluorescence intensity (MFI) and the positive percent of alveolar macrophage engulfed flurescein isothiocyanate-labeled Escherichina coli (FITC-E.coli) AM (AM%) were detected by flow cytometry. Real time PCR (RT-PCR) and Western blot were applied to detect mRNA and protein. The activity of Cdc42 was detected by G-LISA Small GTPase Activation Assays (G-LISA) Cdc42 Kit. The cytoskeleton structure of AM was observed by laser scanning confocal microscopy. Results: MFI and AM% in COPD group were decreased than those in health control group[4 060±590 vs 9 190±988 and (28.65±1.26)% vs (67.50±4.56)%]; Compared with COPD group, MFI and AM% in rapamycin COPD group[4 856±762, (38.31±1.71)%]were increased (all P<0.05). The expression of mRNA, protein and activity of mTOR in COPD group were increased than those in health control group[(2.62±0.46, 1.30±0.52, 1.46±0.43) vs (1.00±0.00, 0.48±0.27, 0.58±0.26)]; compared with COPD group, the expression of mRNA, protein and activity of mTOR in rapamycin COPD group (1.40±0.36, 0.90±0.66, 0.92±0.28) were decreased (all P<0.05). The Cdc42 mRNA, protein and activity in COPD group were higher than those in health control group[(2.56±0.50, 1.61±0.37, 0.46±0.09) vs (1.00±0.00, 0.67±0.22, 0.30±0.07)](all P<0.01); compared with COPD group, the expression of mRNA, protein and activity of Cdc42 in rapamycin COPD group (1.38±0.34, 0.91±0.48, 0.36±0.06) were decreased (all P<0.01). Filopodia protruding can not be seen in the cytoskeleton of AMs from health control group and rapamycin control group; some filopodia protruding can be seen in AM from COPD group; some long filopodia protruding can be seen in AM from rapamycin COPD group. Negative correlations were existed between the mRNA, protein and activity of mTOR, Cdc42 and MFI in all group. Conclusions: mTOR-Cdc42 signaling pathway is activated and related to phagocytosis deficiency of AM in COPD. It can be inferred that the pathway is involved in the pathogenesis of COPD.