Myeloid cell–specific serine palmitoyltransferase subunit 2 haploinsufficiency reduces murine atherosclerosis
Mahua Chakraborty, … , Guoqing Cao, Xian-Cheng Jiang
Mahua Chakraborty, … , Guoqing Cao, Xian-Cheng Jiang
Published March 15, 2013
Citation Information: J Clin Invest. 2013;123(4):1784-1797. https://doi.org/10.1172/JCI60415.
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Myeloid cell–specific serine palmitoyltransferase subunit 2 haploinsufficiency reduces murine atherosclerosis

Abstract

Serine palmitoyltransferase (SPT) is the first and rate-limiting enzyme of the de novo biosynthetic pathway of sphingomyelin (SM). Both SPT and SM have been implicated in the pathogenesis of atherosclerosis, the development of which is driven by macrophages; however, the role of SPT in macrophage-mediated atherogenesis is unknown. To address this issue, we have analyzed macrophage inflammatory responses and reverse cholesterol transport, 2 key mediators of atherogenesis, in SPT subunit 2–haploinsufficient (Sptlc2+/–) macrophages. We found that Sptlc2+/– macrophages have significantly lower SM levels in plasma membrane and lipid rafts. This reduction not only impaired inflammatory responses triggered by TLR4 and its downstream NF-κB and MAPK pathways, but also enhanced reverse cholesterol transport mediated by ABC transporters. LDL receptor–deficient (Ldlr–/–) mice transplanted with Sptlc2+/– bone marrow cells exhibited significantly fewer atherosclerotic lesions after high-fat and high-cholesterol diet feeding. Additionally, Ldlr–/– mice with myeloid cell–specific Sptlc2 haploinsufficiency exhibited significantly less atherosclerosis than controls. These findings suggest that SPT could be a novel therapeutic target in atherosclerosis.

Authors

Mahua Chakraborty, Caixia Lou, Chongmin Huan, Ming-Shang Kuo, Tae-Sik Park, Guoqing Cao, Xian-Cheng Jiang

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Figure 7

Sptlc2 haploinsufficiency increases macrophage cholesterol efflux, ex vivo and in vivo.

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Sptlc2 haploinsufficiency increases macrophage cholesterol efflux, ex v...
(A) Macrophage ABCA1, ABCG1, and SR-B1 Western blot and quantitation after treatment with 50 μg/ml acetylated-LDL for 16 hours. (B) Macrophage surface expression of ABCA1, ABCG1, and SR-B1 after treatment with 50 μg/ml acetylated-LDL for 16 hours, as measured by flow cytometry. (C and D) In vitro cholesterol efflux mediated by apoA-I (C) and HDL (D) in WT and Sptlc2+/– macrophages. (E and F) Sptlc2+/– or WT bone marrow–derived macrophages were loaded with cholesterol by incubation with acetylated-LDL and [3H]-cholesterol. Labeled macrophages were injected i.p. into C57BL/6 acceptor mice. (E) Plasma samples were collected at 6, 24, and 48 hours, and (F) feces were collected at 24 and 48 hours; all were analyzed for tracer counts using liquid scintillation counter. Data are representative of 3 independent experiments (n = 3 per group). For in vivo studies, n = 7. *P < 0.01.