sEH promotes macrophage phagocytosis and lung clearance of Streptococcus pneumoniae
Hong Li, … , Shepherd H. Schurman, Darryl C. Zeldin
Hong Li, … , Shepherd H. Schurman, Darryl C. Zeldin
Published September 30, 2021
Citation Information: J Clin Invest. 2021;131(22):e129679. https://doi.org/10.1172/JCI129679.
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Research Article Cell biology Infectious disease

sEH promotes macrophage phagocytosis and lung clearance of Streptococcus pneumoniae

Abstract

Epoxyeicosatrienoic acids (EETs) have potent antiinflammatory properties. Hydrolysis of EETs by soluble epoxide hydrolase/ epoxide hydrolase 2 (sEH/EPHX2) to less active diols attenuates their antiinflammatory effects. Macrophage activation is critical to many inflammatory responses; however, the role of EETs and sEH in regulating macrophage function remains unknown. Lung bacterial clearance of Streptococcus pneumoniae was impaired in Ephx2-deficient (Ephx2–/–) mice and in mice treated with an sEH inhibitor. The EET receptor antagonist EEZE restored lung clearance of S. pneumoniae in Ephx2–/– mice. Ephx2–/– mice had normal lung Il1b, Il6, and Tnfa expression levels and macrophage recruitment to the lungs during S. pneumoniae infection; however, Ephx2 disruption attenuated proinflammatory cytokine induction, Tlr2 and Pgylrp1 receptor upregulation, and Ras-related C3 botulinum toxin substrates 1 and 2 (Rac1/2) and cell division control protein 42 homolog (Cdc42) activation in PGN-stimulated macrophages. Consistent with these observations, Ephx2–/– macrophages displayed reduced phagocytosis of S. pneumoniae in vivo and in vitro. Heterologous overexpression of TLR2 and peptidoglycan recognition protein 1 (PGLYRP1) in Ephx2–/– macrophages restored macrophage activation and phagocytosis. Human macrophage function was similarly regulated by EETs. Together, these results demonstrate that EETs reduced macrophage activation and phagocytosis of S. pneumoniae through the downregulation of TLR2 and PGLYRP1 expression. Defining the role of EETs and sEH in macrophage function may lead to the development of new therapeutic approaches for bacterial diseases.

Authors

Hong Li, J. Alyce Bradbury, Matthew L. Edin, Joan P. Graves, Artiom Gruzdev, Jennifer Cheng, Samantha L. Hoopes, Laura M. DeGraff, Michael B. Fessler, Stavros Garantziotis, Shepherd H. Schurman, Darryl C. Zeldin

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Figure 6

Impaired signaling in Ephx2–/– macrophages after PGN treatment or infection with S. pneumoniae.

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Impaired signaling in Ephx2–/– macrophages after PGN treatment or infect...
(A and B) Immunoblot analysis of phosphorylated (p-) and total ERK, p38 MAPK, and IkBα in WT and Ephx2–/– macrophages stimulated with 10 μg/mL PGN for 0–60 minutes. (C) Immunoblot analysis of phosphorylated and total ERK in WT and Ephx2–/– macrophages infected with 1 × 106 CFU S. pneumoniae for 0–60 minutes. (D) Immunoblot analysis of phosphorylated and total ERK and p38 MAPK in WT and Ephx2–/– macrophages treated with 1 μg/mL LPS. (E) GTPase family proteins such as Cdc42 and Rac1 are inactive when bound to GDP and active when bound to GTP. Regulation of this molecular switch occurs through a GDP-GTP cycle that is controlled by the opposing activities of guanine nucleotide exchange factors (GEFs), which catalyze the exchange of GDP for GTP, and GTPase-activating proteins (GAPs), which increase the rate of GTP hydrolysis to GDP. GTPases interact with various effector proteins to influence their activity and/or localization, which ultimately affects macrophage phagocytosis. (F) GTP-Cdc42 and GTP-Rac1 levels were analyzed by immunoblotting in WT and Ephx2–/– macrophages stimulated with 10 μg/mL PGN for 0–60 minutes. For all immunoblots, data are representative of at least 3 independent experiments, and β-actin was used as a loading control.