IL-1ß Inhibition Partially Negates the Beneficial Effects of Diet-Induced Atherosclerosis Regression in Mice.

BACKGROUND: Thromboembolic events secondary to rupture or erosion of advanced atherosclerotic lesions is the global leading cause of death. The most common and effective means to reduce these major adverse cardiovascular events, including myocardial infarction and stroke, is aggressive lipid lowering via a combination of drugs and dietary modifications. However, we know little regarding the effects of reducing dietary lipids on the composition and stability of advanced atherosclerotic lesions, the mechanisms that regulate these processes, and what therapeutic approaches might augment the benefits of lipid lowering. METHODS: Smooth muscle cell lineage-tracing Apoe-/- mice were fed a high-cholesterol Western diet for 18 weeks and then a zero-cholesterol standard laboratory diet for 12 weeks before treating them with an IL (interleukin)-1ß or control antibody for 8 weeks. We assessed lesion size and remodeling indices, as well as the cellular composition of aortic and brachiocephalic artery lesions, indices of plaque stability, overall plaque burden, and phenotypic transitions of smooth muscle cell and other lesion cells by smooth muscle cell lineage tracing combined with single-cell RNA sequencing, cytometry by time-of-flight, and immunostaining plus high-resolution confocal microscopic z-stack analysis. RESULTS: Lipid lowering by switching Apoe-/- mice from a Western diet to a standard laboratory diet reduced LDL cholesterol levels by 70% and resulted in multiple beneficial effects including reduced overall aortic plaque burden, as well as reduced intraplaque hemorrhage and necrotic core area. However, contrary to expectations, IL-1ß antibody treatment after diet-induced reductions in lipids resulted in multiple detrimental changes including increased plaque burden and brachiocephalic artery lesion size, as well as increasedintraplaque hemorrhage, necrotic core area, and senescence as compared with IgG control antibody-treated mice. Furthermore, IL-1ß antibody treatment upregulated neutrophil degranulation pathways but downregulated smooth muscle cell extracellular matrix pathways likely important for the protective fibrous cap. CONCLUSIONS: Taken together, IL-1ß appears to be required for the maintenance of standard laboratory diet-induced reductions in plaque burden and increases in multiple indices of plaque stability.

IL-1ß inhibition partially negates the beneficial effects of diet-induced lipid lowering.

Background: Thromboembolic events secondary to rupture or erosion of advanced atherosclerotic lesions are the leading cause of death in the world. The most common and effective means to reduce these major adverse cardiovascular events (MACE), including myocardial infarction (MI) and stroke, is aggressive lipid lowering via a combination of drugs and dietary modifications. However, little is known regarding the effects of reducing dietary lipids on the composition and stability of advanced atherosclerotic lesions, the mechanisms that regulate these processes, and what therapeutic approaches might augment the benefits of lipid lowering. Methods: Smooth muscle cell (SMC)-lineage tracing Apoe-/- mice were fed a Western diet (WD) for 18 weeks and then switched to a low-fat chow diet for 12 weeks. We assessed lesion size and remodeling indices, as well as the cellular composition of aortic and brachiocephalic artery (BCA) lesions, indices of plaque stability, overall plaque burden, and phenotypic transitions of SMC, and other lesion cells by SMC-lineage tracing combined with scRNA-seq, CyTOF, and immunostaining plus high resolution confocal microscopic z-stack analysis. In addition, to determine if treatment with a potent inhibitor of inflammation could augment the benefits of chow diet-induced reductions in LDL-cholesterol, SMC-lineage tracing Apoe-/- mice were fed a WD for 18 weeks and then chow diet for 12 weeks prior to treating them with an IL-1ß or control antibody (Ab) for 8-weeks. Results: Lipid-lowering by switching Apoe-/- mice from a WD to a chow diet reduced LDL-cholesterol levels by 70% and resulted in multiple beneficial effects including reduced overall aortic plaque burden as well as reduced intraplaque hemorrhage and necrotic core area. However, contrary to expectations, IL-1ß Ab treatment resulted in multiple detrimental changes including increased plaque burden, BCA lesion size, as well as increased cholesterol crystal accumulation, intra-plaque hemorrhage, necrotic core area, and senescence as compared to IgG control Ab treated mice. Furthermore, IL-1ß Ab treatment upregulated neutrophil degranulation pathways but down-regulated SMC extracellular matrix pathways likely important for the protective fibrous cap. Conclusions: Taken together, IL-1ß appears to be required for chow diet-induced reductions in plaque burden and increases in multiple indices of plaque stability.

PDK4 Deficiency Induces Intrinsic Apoptosis in Response to Starvation in Fibroblasts from Doberman Pinschers with Dilated Cardiomyopathy.

The Doberman pinscher (DP) canine breed displays a high incidence of idiopathic, nonischemic dilated cardiomyopathy (DCM) with increased mortality. A common mutation in DPs is a splice site deletion in the pyruvate dehydrogenase kinase 4 (PDK4) gene that shows a positive correlation with DCM development. PDK4, a vital mitochondrial protein, controls the switch between glycolysis and oxidative phosphorylation based upon nutrient availability. It is likely, although unproven, that DPs with the PDK4 mutation are unable to switch to oxidative phosphorylation during periods of low nutrient availability, and thus are highly susceptible to mitochondrial-mediated apoptosis. This study investigated cell viability, mitochondrial stress, and activation of the intrinsic (mitochondrial mediated) apoptotic pathway in dermal fibroblasts from DPs that were healthy (PDK4wt/wt), heterozygous (PDK4wt/del), and homozygous (PDK4del/del) for the PDK4 mutation under conditions of high (unstarved) and low (starved) nutrient availability in vitro. As hypothesized, PDK4wt/del and PDK4del/del cells showed evidence of mitochondrial stress and activation of the intrinsic apoptotic pathway following starvation, while the PDK4wt/wt cells remained healthy and viable under these conditions. Adeno-associated virus (AAV) PDK4-mediated gene replacement experiments confirmed cause-effect relationships between PDK4 deficiency and apoptosis activation. The restoration of function observed following administration of AAV-PDK4 provides strong support for the translation of this gene therapy approach into the clinical realm for PDK4-affected Dobermans.