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 1

Characterization of bone marrow–derived Sptlc2+/– macrophages.

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Characterization of bone marrow–derived Sptlc2+/– macrophages. Bone ma...
Bone marrow–derived macrophages were isolated from WT and Sptlc2+/– mice. (A and B) Sptlc2+/– macrophages exhibited reduced expression of SPTLC2 and SPTLC1 subunits, as measured by Western blot from whole cell lysates with densitometric quantification. (C) Total RNA was extracted using TRIzol method, and Sptlc1, Sptlc2, and Sptlc3 mRNA were measured by real-time PCR using specific primers. (D) SPT activity in Sptlc2+/– macrophages with densitometric quantification. SPT activity in bone marrow–derived macrophage homogenate was measured using [14C]-serine and palmitoyl-CoA as substrates. The product, [14C]-keto-dihydrosphingosine (KDS), was separated from the reaction mix by thin layer chromatography, and the plate was scanned using Phosphorimager. (E) Intracellular SM content in macrophages was measured by LC/MS/MS. Data are representative of 3 independent experiments (n = 4 per group). *P < 0.05.