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 7

TLR2 and PGLYRP1 overexpression rescue downstream signaling and phagocytosis defects in Ephx2–/– macrophages.

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TLR2 and PGLYRP1 overexpression rescue downstream signaling and phagocyt...
(A) Immunoblot analysis of total and phosphorylated p38 MAPK and ERK in PGN-stimulated WT macrophages, Ephx2–/– macrophages, and Ephx2–/– macrophages overexpressing either TLR2 or PGLYRP1. n = 5 per group. β-Actin was used as a loading control. (B) Phagocytosis of FITC-labeled S. pneumoniae by WT macrophages, Ephx2–/– macrophages and Ephx2–/– macrophages overexpressing either TLR2 or PGLYRP1 as measured by flow cytometry. Each square represents an individual mouse: white squares, WT; black squares, Ephx2–/–). n = 5 per group. *P < 0.05, by ordinary 2-way ANOVA, followed by Tukey’s post hoc multiple-comparison test (B).