Abstract Tu0046: Cholesterol-mTOR Nexus: Dissecting the Impact of Hypercholesterolemia in Lysosomal Dysfunction

Introduction: Atherosclerosis is the primary cause of death globally. During atherosclerosis, cholesterol in arterial walls triggers inflammation, recruiting monocytes and macrophages. These cells show impaired autophagy, creating a hyperinflammatory, proatherogenic state unaddressed by current cholesterol-lowering therapies.

Hypothesis: We hypothesized that blood low-density lipoprotein cholesterol (LDL-c) correlates with circulating monocyte mammalian target of rapamycin complex 1 (mTORC1) activity, which impairs autophagy and promotes atherogenesis in macrophages.

Methods: Mouse Models: Peritoneal macrophages (pMACs) were treated with LDL-c to evaluate mTORC1 activity, autophagy, and apoptosis. ApoE-null mice (n=10) were fed a Western diet for 10 days followed by a Chow diet for 10 days. Plasma cholesterol and circulating monocyte mTORC1 activity were analyzed using FACS and western blot for phosphorylated S6 (pS6).

Human Studies: Human monocyte-derived macrophages (HMDMs) were treated with LDL-c to assess mTORC1 activation and autophagy. In the clinical study, hypercholesterolemic patients (LDL>160 mg/dL, n=10) and healthy controls (LDL<130 mg/dL, n=10) were enrolled. Blood samples will be collected at baseline to isolate monocytes and measure cholesterol levels. After 12 weeks of lipid-lowering therapy (e.g., statins), hypercholesterolemic patients will provide a second sample for analysis of monocyte mTORC1 activity.

Results: Mouse Studies: LDL activated mTORC1 in pMACs in a time- and dose-dependent manner, suppressing autophagy and promoting apoptosis. ApoE-null mice on a Western diet showed a ~4-fold increase in plasma cholesterol and ~10-fold increase in monocyte mTORC1 activity. Switching to a Chow diet from Day 4 sharply reduced cholesterol levels and mTORC1 signaling in monocytes.

Human Studies: LDL treatment activated mTORC1 in HMDMs, suppressing autophagy and promoting apoptosis. Preliminary data indicate elevated monocyte mTORC1 activation in hypercholesterolemic patients compared to controls. The study is ongoing, with post-treatment data collection underway to assess the effects of lipid-lowering therapy on mTORC1 activity and related markers.

Conclusions: Cholesterol-driven mTORC1 activation impairs autophagy and lysosomal function, promoting cellular apoptosis and plaque formation in atherosclerosis. These findings highlight the cholesterol-mTORC1-autophagy axis as a potential therapeutic target to mitigate cardiovascular disease progression.