Immunomodulators targeting MARCO expression improve resistance to postinfluenza bacterial pneumonia

M Wu, JG Gibbons, GM DeLoid… - … of Physiology-Lung …, 2017 - journals.physiology.org
M Wu, JG Gibbons, GM DeLoid, AS Bedugnis, RK Thimmulappa, S Biswal, L Kobzik
American Journal of Physiology-Lung Cellular and Molecular …, 2017journals.physiology.org
Downregulation of the alveolar macrophage (AM) receptor with collagenous structure
(MARCO) leads to susceptibility to postinfluenza bacterial pneumonia, a major cause of
morbidity and mortality. We sought to determine whether immunomodulation of MARCO
could improve host defense and resistance to secondary bacterial pneumonia. RNAseq
analysis identified a striking increase in MARCO expression between days 9 and 11 after
influenza infection and indicated important roles for Akt and Nrf2 in MARCO recovery. In …
Downregulation of the alveolar macrophage (AM) receptor with collagenous structure (MARCO) leads to susceptibility to postinfluenza bacterial pneumonia, a major cause of morbidity and mortality. We sought to determine whether immunomodulation of MARCO could improve host defense and resistance to secondary bacterial pneumonia. RNAseq analysis identified a striking increase in MARCO expression between days 9 and 11 after influenza infection and indicated important roles for Akt and Nrf2 in MARCO recovery. In vitro, primary human AM-like monocyte-derived macrophages (AM-MDMs) and THP-1 macrophages were treated with IFNγ to model influenza effects. Activators of Nrf2 (sulforaphane) or Akt (SC79) caused increased MARCO expression and a MARCO-dependent improvement in phagocytosis in IFNγ-treated cells and improved survival in mice with postinfluenza pneumococcal pneumonia. Transcription factor analysis also indicated a role for transcription factor E-box (TFEB) in MARCO recovery. Overexpression of TFEB in THP-1 cells led to marked increases in MARCO. The ability of Akt activation to increase MARCO expression in IFNγ-treated AM-MDMs was abrogated in TFEB-knockdown cells, indicating Akt increases MARCO expression through TFEB. Increasing MARCO expression by targeting Nrf2 signaling or the Akt-TFEB-MARCO pathway are promising strategies to improve bacterial clearance and survival in postinfluenza bacterial pneumonia.
American Physiological Society