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 5

Ch25h-null macrophages display cholesterol dysregulation and defective efferocytosis.

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Ch25h-null macrophages display cholesterol dysregulation and defective ...
(A) Chimeric mice generated by bone marrow transfer from Ch25h+/+ (WT) or Ch25h–/– (KO) donors to irradiated WT or KO recipients (shown as donor → recipient) were exposed to inhaled LPS, and bronchoalveolar lavage (BAL) PMNs were quantified 48 hours later (n = 5/genotype/time point). (B) Alveolar macrophages (AMs) from Ch25h+/+ and Ch25h–/– mice collected 48 hours after LPS inhalation were stained with Oil Red O (left) and stain-positive (foam) cells quantified (right) (n = 8/genotype). Arrow indicates a stain-positive cell. (C) A similar analysis as shown in B was conducted on peritoneal exudate macrophages (PEMs) harvested 72 hours after i.p. thioglycollate (n = 4/genotype). (D) PEMs freshly harvested from Ch25h+/+ and Ch25h–/– mice (n = 3–9/genotype) were analyzed by qPCR for the targets shown (fold change, FC). (E) WT PEMs were treated with 25HC or T0901317 in the presence or absence of LXR antagonist GSK2033 and then analyzed by qPCR for normalized Mertk mRNA. (F) WT mice were treated i.p. with 25HC or vehicle (Veh.), and then lung tissue was analyzed by qPCR for Mertk (n = 8–10/condition). (G) Ch25h+/+ and Ch25h–/– mice (n = 6/genotype) were instilled i.t. with apoptotic WT thymocytes 48 hours after LPS inhalation. AMs that had internalized thymocytes (efferocytic AMs) were manually quantified 90 minutes later. (H) Apoptotic (FLIVO+) PMNs were quantified in BALF of Ch25h+/+ and Ch25h–/– mice (n = 5/genotype) 48 hours after LPS inhalation. (I) Internalization of bacterial bioparticles by Ch25h+/+ and Ch25h–/– PEMs was quantified at 37°C and 0°C (control). Data are mean ± SEM and are representative of 3–6 independent experiments. ΨP = 0.06; *P < 0.05; **P < 0.01; ***P < 0.001 by unpaired t test.