sEH promotes macrophage phagocytosis and lung clearance of Streptococcus pneumoniae
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
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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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 5

Impaired proinflammatory cytokine responses to S. pneumoniae in Ephx2–/– macrophages in vitro.

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Impaired proinflammatory cytokine responses to S. pneumoniae in Ephx2–/–...
Peritoneal macrophages from WT and Ephx2–/– mice were stimulated with S. pneumoniae (1 × 106 CFU) for 4 hours. Macrophages were then assayed to measure the levels of Il1b, Il6, and Tnfa (A) and Pglyrp1, Tlr2, or Tlr4 (B) by real-time quantitative RT-PCR. Data represent the mean ± SEM. n = 6 per group. (C) Confocal microscopy of TLR2 in lung macrophages from WT and Ephx2–/– mice after S. pneumoniae infection in vivo. Scale bars: 10 μm. Original magnification, ×40 (insets were digitally enlarged by 2.6-fold). (D) Tnfa, Pglyrp1, and Tlr2 transcript levels, as measured by real-time quantitative RT-PCR, in WT macrophages treated or not with 10 μg/mL PGN in the presence or absence of 1 μM 11,12-EET, 1 μM 14,15-EET, or 10 μM 14,15-EEZE. n = 5 per group. *P < 0.05, by Student’s t test (A and B) or ordinary 1-way ANOVA, followed by Tukey’s post hoc multiple-comparison test (D).