title: Cigarette smoke impairs phagocytosis of apoptotic neutrophils by alveolar macrophages via inhibition of the histone deacetylase/Rac/CD9 pathways.
abstract: Efferocytosis, which is the homeostatic phagocytosis of apoptotic cells, prevents the release of toxic intracellular contents and subsequent tissue damage. Impairment of efferocytosis was reported in alveolar macrophages (AMs) of patients with chronic obstructive pulmonary disease (COPD), a common disease caused by smoking. In COPD, histone deacetylase (HDAC) activity is reduced in AMs. We investigated whether the reduction of HDAC activity is associated with the impairment of efferocytosis. Murine AMs were collected by bronchoalveolar lavage and their ability to efferocytose apoptotic human polymorphonuclear leukocytes was assessed. Pre-treatment of AMs with cigarette smoke extract (CSE) or trichostatin A (TSA), an HDAC inhibitor, suppressed efferocytosis and CSE reduced HDAC activity. TSA inhibited the activity of Rac, a key mediator of efferocytosis. These TSA-induced impairments were restored by treatment of AMs with aminophylline, a potent activator of HDAC. To further elucidate the underlying mechanism, we explored a role of CD9 in TSA-induced impairment of efferocytosis. CD9 is a transmembrane protein of the tetraspanin family that facilitates the uptake of several pathogens and other material. TSA profoundly down-regulated the expression of CD9 on AMs. The expression of CD9 was partly down-regulated by the Rac inhibitor. Pretreatment with an anti-CD9 mAb or CD9 small interfering RNA inhibited efferocytosis, which was attributable to the reduced binding of AMs to apoptotic cells. These results suggest that smoking impairs efferocytosis via inhibition of HDAC/Rac/CD9 pathways. Aminophylline/theophylline is effective in restoring the impairment of efferocytosis and might have benefit for the treatment of patients with COPD.
authors.affiliation: Research Institute for Diseases of the Chest, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
authors.forename: Naotaka
authors.initials: N
authors.lastname: Noda
authors.forename: Koichiro
authors.initials: K
authors.lastname: Matsumoto
authors.forename: Satoru
authors.initials: S
authors.lastname: Fukuyama
authors.forename: Yukari
authors.initials: Y
authors.lastname: Asai
authors.forename: Hiroko
authors.initials: H
authors.lastname: Kitajima
authors.forename: Nanae
authors.initials: N
authors.lastname: Seki
authors.forename: Yuko
authors.initials: Y
authors.lastname: Matsunaga
authors.forename: Keiko
authors.initials: K
authors.lastname: Kan-O
authors.forename: Atsushi
authors.initials: A
authors.lastname: Moriwaki
authors.forename: Konosuke
authors.initials: K
authors.lastname: Morimoto
authors.forename: Hiromasa
authors.initials: H
authors.lastname: Inoue
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Nakanishi
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000276:immunology*; D064368:Healthy Volunteers; D006655:Histone Deacetylases / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D016676:Macrophages, Alveolar / Q000201:enzymology / Q000276:immunology / Q000473:pathology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009504:Neutrophils / Q000166:cytology* / Q000201:enzymology / Q000276:immunology; D010587:Phagocytosis / Q000276:immunology*; D012907:Smoking / Q000009:adverse effects* / Q000276:immunology; D060245:Tetraspanin 29 / Q000037:antagonists & inhibitors* / Q000276:immunology / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000037:antagonists & inhibitors* / Q000276:immunology / Q000378:metabolism
chemical_list: C554869:CD9 protein, human; C554870:Cd9 protein, mouse; D060245:Tetraspanin 29; D006655:Histone Deacetylases; D020744:rac GTP-Binding Proteins
keywords: aminophylline; chronic obstructive pulmonary disease; efferocytosis; tethering