Lipid Droplet-Associated Hydrolase Mobilizes Oxysterol Stores and Inhibits Atheroma Growth and Progression

Lipid droplets (LDs) of foam cells within atheroma contain abundant cholesterol, but also serve as reservoirs of central bioactive lipids. The mechanisms of storage and mobilization of many of these lipids remain obscure. LD-associated hydrolase (LDAH) localizes to LDs, has a lipase structure, and is abundant in atheroma. However, its lipid substrates and role in atherogenesis are unknown. Using knockout and transgenic mice we found that LDAH protects against atherosclerosis. Myeloid LDAH expression is sufficient to inhibit lesion progression and promote stable architectures, less necrotic, and richer in fibrillar collagen. Lipidomics coupled with RNA sequencing revealed that LDAH facilitates mobilization of esters of oxysterols that are liver X receptor agonists, leading to induction of cholesterol efflux transporters, reduced foam cell inflammation, and pro-fibrotic gene signatures. These studies identify LDAH as a novel player in neutral hydrolysis of esterified regulatory sterols that promotes atheroprotective and pro-stabilizing mechanisms beyond mass cholesterol removal. Overall design: To identify LDAH regulated differentially expressed genes in peritoneal macrophages loaded with oxidized LDL, RNAseq was performed in these cells for both LDAH KO and LDAH trangenic animals.