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(Arteriosclerosis, Thrombosis, and Vascular Biology. 2009;29:1937.)
© 2009 American Heart Association, Inc.

Cell Biology/Signaling

Inhibition of Long-Chain Acyl Coenzyme A Synthetases During Fatty Acid Loading Induces Lipotoxicity in Macrophages

Viswanathan Saraswathi; Alyssa H. Hasty

From the Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, Tenn.

Correspondence to Alyssa H. Hasty, Vanderbilt University Medical Center, 702 Light Hall, Nashville, TN 37232-0615. E-mail alyssa.hasty{at}vanderbilt.edu

Objectives— Obesity is often associated with hypertriglyceridemia and elevated free fatty acids (FFAs), which are independent risk factors for cardiovascular disease and diabetes. Although impairment of cholesterol homeostasis is known to induce toxicity in macrophages, the consequence of altered fatty acid homeostasis is not clear.

Methods and Results— Long-chain acyl CoA synthetases (ACSLs) play a critical role in fatty acid homeostasis by channeling fatty acids to diverse metabolic pools. We treated mouse peritoneal macrophages (MPMs) with VLDL or FFAs in the presence of triacsin C, an inhibitor of the 3 ACSL isoforms present in macrophages. Treatment of macrophages with VLDL and triacsin C resulted in reduced TG accumulation but increased intracellular FFA levels, which induced lipotoxicity characterized by apoptosis. Treatment of MPMs with the saturated fatty acid stearic acid in the presence of triacsin C increased intracellular stearic acid and induced apoptosis. Stromal vascular cells collected from high-fat diet–fed mice displayed foam cell morphology and exhibited increased mRNA levels of macrophage markers and ACSL1. Importantly, all of these changes were associated with increased FFA level in AT.

Conclusions— Inhibition of ACSLs during fatty acid loading results in apoptosis via accumulation of FFAs. Our data have implications in understanding the consequences of dysregulated fatty acid metabolism in macrophages.

Inhibition of macrophage ACSLs during fatty acid loading increased intracellular FFAs and induced apoptosis. Adipose tissue from obese mice had increased FFA levels, and SVCs displayed foam cell morphology and exhibited increased expression of macrophage markers and ACSL1. ACSLs play an important role in regulating fatty acid homeostasis in macrophages.

Key Words: VLDL • foam cells • free fatty acids • triacsin C • long chain acyl CoA synthetases • stearic acid • apoptosis