Familial hypercholesterolemia (FH) is an autosomal dominant disorder, most commonly due to mutations in the LDLR gene, characterized by severely elevated levels of LDL-C and increased risk of premature atherosclerotic cardiovascular disease (ASCVD). Although lowering LDL-C is the undisputed primary goal of therapy, there is mounting evidence that HDL function is impaired in FH. A major hypothesis of this project is that dysfunctional HDL contributes to the residual inflammatory risk of cardiovascular events in FH patients. Reactive dicarbonyls including MDA, IsoLG, and ONE are highly reactive species that rapidly adduct to apoAI and HDL phospholipids impairing HDL function. We have discovered that ApoAI and HDL are modified by MDA and IsoLG in FH and that HDL function is dramatically impaired in terms of cholesterol efflux capacity, as well as anti-inflammatory and antioxidant functions. Furthermore, we have recently discovered that two small molecule dicarbonyl scavengers, 2-HOBA and PPM, improve HDL function, reduce LDL oxidation, and dramatically reduce atherosclerosis in Ldlr-/- deficient mice, a model of FH, in the absence of significant changes in plasma lipid levels. In addition, the lesions were characterized by a dramatic reduction in necrosis, which was associated with increased macrophage survival and efferocytosis. The lesions had features of stable atherosclerotic plaques, suggesting the hypothesis that dicarbonyl scavengers promote lesion remodeling, inflammatory resolution and plaque stabilization. Therefore, in Specific Aim 1, we will examine the hypothesis that dicarbonyl scavengers are capable of remodeling pre-existing atherosclerotic lesions in Ldlr-/- mice. We will examine the hypothesis that improved HDL function promotes inflammatory resolution as characterized by increased macrophage efferocytosis and increased Tregs, contributing to the antiatherogenic mechanisms of dicarbonyl scavengers. In addition, we will test the hypothesis that the atheroprotective effects of dicarbonyl scavenging are in large part due to preservation of HDL functions by performing atherosclerosis studies in HDL deficient Ldlr-/-ApoAI-/- vs. Ldlr-/- mice.
In Aim1 c, we will examine the hypothesis that macrophage scavenger receptors, CD36 and SR-BI, play critical roles in mediating the impact of reactive dicarbonyls on atherosclerosis. These mechanistic studies of the impact of dicarbonyl scavengers on atherosclerosis will set the stage for a clinical translational study in humans. Recent Phase I studies with 2-HOBA have demonstrated its safety in humans. Therefore, in Specific Aim 2, we will test the hypothesis that 2-HOBA will reduce modification of HDL and improve HDL function in humans with heterozygous FH and in subjects with coronary artery disease without FH. The impact of 2-HOBA on HDL small RNAs will be examined. Finally, we will test the hypothesis that ?-Me-2-HOBA will have improved pharmacokinetic attributes and better ability to reduce atherosclerosis in Ldlr-/- mice compared to 2-HOBA, as a first step toward developing ?-Me-2-HOBA as a second-generation scavenger that has an improved pharmacokinetic profile with the goal of improving HDL function and reducing ASCVD in humans.
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