Cigarette smoke impairs phagocytosis of apoptotic neutrophils by alveolar macrophages via inhibition of the histone deacetylase/Rac/CD9 pathways

Naotaka Noda, Koichiro Matsumoto, Satoru Fukuyama, Yukari Asai, Hiroko Kitajima, Nanae Seki, Yuko Matsunaga, Keiko Kan-O, Atsushi Moriwaki, Konosuke Morimoto, Hiromasa Inoue, Yoichi Nakanishi

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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.

Original languageEnglish
Article numberdxt033
Pages (from-to)643-650
Number of pages8
JournalInternational immunology
Volume25
Issue number11
DOIs
Publication statusPublished - Nov 2013

All Science Journal Classification (ASJC) codes

  • Immunology and Allergy
  • Immunology

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    Noda, N., Matsumoto, K., Fukuyama, S., Asai, Y., Kitajima, H., Seki, N., Matsunaga, Y., Kan-O, K., Moriwaki, A., Morimoto, K., Inoue, H., & Nakanishi, Y. (2013). Cigarette smoke impairs phagocytosis of apoptotic neutrophils by alveolar macrophages via inhibition of the histone deacetylase/Rac/CD9 pathways. International immunology, 25(11), 643-650. [dxt033]. https://doi.org/10.1093/intimm/dxt033