Cholesterol 25-hydroxylase promotes efferocytosis and resolution of lung inflammation
Jennifer H. Madenspacher, … , Mark M. Wurfel, Michael B. Fessler
Jennifer H. Madenspacher, … , Mark M. Wurfel, Michael B. Fessler
Published April 28, 2020
Citation Information: JCI Insight. 2020;5(11):e137189. https://doi.org/10.1172/jci.insight.137189.
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Research Article Inflammation Pulmonology

Cholesterol 25-hydroxylase promotes efferocytosis and resolution of lung inflammation

Abstract

Alveolar macrophages (AM) play a central role in initiation and resolution of lung inflammation, but the integration of these opposing core functions is poorly understood. AM expression of cholesterol 25-hydroxylase (CH25H), the primary biosynthetic enzyme for 25-hydroxycholesterol (25HC), far exceeds the expression of macrophages in other tissues, but no role for CH25H has been defined in lung biology. As 25HC is an agonist for the antiinflammatory nuclear receptor, liver X receptor (LXR), we speculated that CH25H might regulate inflammatory homeostasis in the lung. Here, we show that, of natural oxysterols or sterols, 25HC is induced in the inflamed lung of mice and humans. Ch25h–/– mice fail to induce 25HC and LXR target genes in the lung after LPS inhalation and exhibit delayed resolution of airway neutrophilia, which can be rescued by systemic treatment with either 25HC or synthetic LXR agonists. LXR-null mice also display delayed resolution, suggesting that native oxysterols promote resolution. During resolution, Ch25h is induced in macrophages upon their encounter with apoptotic cells and is required for LXR-dependent prevention of AM lipid overload, induction of Mertk, efferocytic resolution of airway neutrophilia, and induction of TGF-β. CH25H/25HC/LXR is, thus, an inducible metabolic axis that programs AMs for efferocytic resolution of inflammation.

Authors

Jennifer H. Madenspacher, Eric D. Morrell, Kymberly M. Gowdy, Jeffrey G. McDonald, Bonne M. Thompson, Ginger Muse, Jennifer Martinez, Seddon Thomas, Carmen Mikacenic, Jerry A. Nick, Edward Abraham, Stavros Garantziotis, Renee D. Stapleton, Julie M. Meacham, Mary Jane Thomassen, William J. Janssen, Donald N. Cook, Mark M. Wurfel, Michael B. Fessler

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Figure 6

Apoptotic cells induce Ch25h-dependent Mertk in efferocytic macrophages.

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Apoptotic cells induce Ch25h-dependent Mertk in efferocytic macrophages....
(A) WT peritoneal exudate macrophages (PEMs) were cocultured for 16 hours with live or apoptotic Jurkat T cells, after which Ch25h mRNA was quantified by qPCR (fold change [FC], n = 4/condition). (B) Ifnar+/+ and Ifnar–/– PEMs were treated and analyzed as in A (n = 3/condition). (C) WT PEMs (n = 4/condition) were treated with 400 ng/mL Gas6 protein for the indicated times and then analyzed by qPCR for Ch25h mRNA. (D and E) Ch25h+/+ and Ch25h–/– PEMs were treated as in B and then analyzed by qPCR for the indicated targets (n = 5–8/condition). (F) Ch25h+/+ and Ch25h–/– PEMs were treated with phosphatidylserine (PS) or phosphatidylcholine (PC [control]) liposomes (400 μg/mL, 4 hours) and then analyzed by qPCR for the indicated targets (n = 3/condition). (G) RNA purified from AMs isolated by negative selection from patients (n = 30) enrolled within 48 hours after ARDS onset in the omega-3 fatty acids trial (50) was analyzed by microarray. A Pearson’s test was used to generate a correlation coefficient between normalized log2 CH25H and MERTK probe intensities. (H) Ch25h+/+ and Ch25h–/– PEMs were treated as in D and then analyzed by qPCR for Tgfb1 mRNA (n = 4–6/condition). (I) Mice of the indicated genotypes were exposed to 3 mg/mL LPS aerosol and BALF TGF-β analyzed by ELISA (n = 3–4/condition). (J) PEMs freshly harvested from Ch25h+/+ and Ch25h–/– mice were analyzed by qPCR for Tgfb1 mRNA (n = 3/genotype). Data are mean ± SEM and are representative of 2–4 independent experiments. *P < 0.05; **P < 0.01; ψP = 0.059 by unpaired t test other than for G.