Myeloid atg5 deletion impairs n-3 PUFA-mediated atheroprotection

Abstract

Background and aims: Dietary long-chain (≥ 20 carbons) n-3 polyunsaturated fatty acids (PUFAs) reduce atherosclerosis and enhance macrophage autophagy activation. How macrophage autophagy impacts atherosclerotic progression, particularly when comparing dietary n-3 PUFA supplementation vs. saturated fat feeding, is unknown. Methods:We generated myeloid-specific autophagy-deficient and control mice in the Ldlr −/− background by transplanting bone marrow from myeloid-specific autophagy-related (atg) 5 knockout mice and wild type controls into irradiated Ldlr −/− recipients. After 7 weeks for recovery from radiation, mice were fed an atherogenic diet containing 0.2% cholesterol and 20% calories as palm oil (PO diet), or 10% calories as PO plus 10% calories as fish oil (FO diet) for 16 weeks.Results: Compared to PO, FO significantly reduced plasma cholesterol, triglyceride, hepatic neutral lipid, and aortic caspase-1 cleavage, but increased aortic efferocytosis, leading to attenuated atherosclerosis in Ldlr −/− mice receiving wild type bone marrow. Myeloid atg5 deletion had little impact on plasma lipid concentrations and hepatic neutral lipid content, regardless of diet. Myeloid atg5 deletion increased aortic caspase-1 cleavage, decreased aortic efferocytosis and worsened atherosclerosis only in the FO-fed Ldlr −/− mice.

Oxidative Stress Triggers Defective Autophagy in Endothelial Cells: Role in Atherothrombosis Development

“…Finally, the authors demonstrated that the endothelial knockdown of Atg5 or the pharmacological inhibition of autophagy resulted in a similar in vivo alteration of hemostasis [ 95 ] Accordingly, Atg7 deletion is associated with a reduction in arterial thrombosis in a murine model of atherothrombosis [ 96 ]. Moreover, Atg5 interaction is necessary to promote n-3 polyunsaturated fatty acid (n3 PUFA)-induced atheroprotection [ 97 ]. Recently, autophagy has been proven to be an important tool in the differentiation of stem cells into endothelial lineage by promoting angiogenesis through the release of proangiogenic factors in a paracrine manner [ 98 ].…”

Effect of Lipids and Lipoproteins on Hematopoietic Cell Metabolism and Commitment in Atherosclerosis

“…Elevated availability of saturated FAs in the HSCs dampens the activity of autophagy related 5 (Atg5), a key protein involved in the extension of the phagophoric membrane in autophagic vesicles, and this results into reduced cellular mitochondrial cellular mass of hematopoietic cells committed to become lymphocytes, in favor of a preferential expansion of the myeloid compartment. Also, Atg5 repression in myeloid lineage aggravates atherosclerosis and negatively impact on the inflammatory composition of atherosclerotic lesions in mice fed on diet enriched in polyunsaturated fats (PUFAs) [ 52 ], lipid dietary sources that favors the activity of macrophage autophagy [ 53 ]. Accordingly, myeloid skewing of hematopoietic cells appears proportional to the quantity of white adipose tissue volume in the mid-shaft of the bones [ 54 , 55 ].…”

Hematopoietic-SLC37A2 deficiency accelerates atherosclerosis in LDL receptor-deficient mice

“…Total RNA in the liver, adipose tissue, peritoneal macrophages, or BMDMs was extracted using Trizol (Invitrogen). cDNA preparation and real-time PCR were conducted as described previously (25,61).…”

“…BMT: BMT was performed as described before (61). Briefly, male Ldlr -/recipient mice at 7 wks of age received a sublethal dose of radiation (900 rads) 4 h prior to bone marrow injection.…”

“…Liver lipids were extracted with chloroform: methanol (2:1), and the extract was used for enzymatic assays (cholesterol, Wako; TG, Roche). Data were normalized to wet liver weight (61). Macrophage cholesterol was extracted from BMDMs using isopropyl alcohol.…”