ABSTRACT
BACKGROUND: Atherosclerosis is a chronic disease affecting artery wall and a major contributor to cardiovascular diseases. Large necrotic cores increase risk of plaque rupture leading to thrombus formation. Necrotic cores are rich in debris from dead macrophages. Programmed necrosis (necroptosis) contributes to necrotic core formation. HDL (high-density lipoprotein) exerts direct atheroprotective effects on different cells within atherosclerotic plaques. Some of these depend on the SR-B1 (scavenger receptor class B type I) and the adapter protein PDZK1 (postsynaptic density protein/Drosophila disc-large protein/Zonula occludens protein containing 1). However, a role for HDL in protecting against necroptosis and necrotic core formation in atherosclerosis is not completely understood. METHODS: Low-density lipoprotein receptor-deficient mice engineered to express different amounts of ApoA1 (apolipoprotein A1), or to lack PDZK1 were fed a high fat diet for 10 weeks. Atherosclerotic plaque areas, necrotic cores, and key necroptosis mediators, RIPK3 (receptor interacting protein kinase 3), and MLKL (mixed lineage kinase domain-like protein) were characterized. Cultured macrophages were treated with HDL to determine its effects, as well as the roles of SR-B1, PDZK1, and the PI3K (phosphoinositide 3-kinase) signaling pathway on necroptotic cell death. RESULTS: Genetic overexpression reduced, and ApoA1 knockout increased necrotic core formation and RIPK3 and MLKL within atherosclerotic plaques. Macrophages were protected against necroptosis by HDL and this protection required SR-B1, PDZK1, and PI3K/Akt pathway. PDZK1 knockout increased atherosclerosis in LDLRKO mice, increasing necrotic cores and phospho-MLKL; both of which were reversed by restoring PDZK1 in BM-derived cells. CONCLUSIONS: Our findings demonstrate that HDL in vitro and ApoA1, in vivo, protect against necroptosis in macrophages and necrotic core formation in atherosclerosis, suggesting a pathway that could be a target for the treatment of atherosclerosis.
Subject(s)
Atherosclerosis , Plaque, Atherosclerotic , Animals , Mice , Plaque, Atherosclerotic/metabolism , Lipoproteins, HDL/metabolism , Phosphatidylinositol 3-Kinases/metabolism , Apolipoprotein A-I/genetics , Apolipoprotein A-I/metabolism , Necroptosis , Necrosis/metabolism , Macrophages/metabolism , Atherosclerosis/genetics , Atherosclerosis/prevention & control , Atherosclerosis/metabolism , Mice, Knockout , Mice, Inbred C57BLABSTRACT
Doxorubicin, an agent used to treat a variety of cancers, is cardiotoxic by triggering cardiomyocyte apoptosis. We previously showed that treating cultured cardiomyocytes with human high-density lipoprotein in vitro or transgenic overexpression of human apolipoprotein A1, its main structural protein, protects against doxorubicin-induced cardiomyocyte apoptosis in a manner dependent on the scavenger receptor class B type I [Durham KK, Chathely KM, Mak KC, Momen A, Thomas CT, Zhao YY, MacDonald ME, Curtis JM, Husain M, Trigatti BL. HDL protects against doxorubicin-induced cardiotoxicity in a scavenger receptor class B type 1-, phosphatidylinositol 3-kinase-, and Akt-dependent manner. Am J Physiol Heart Circ Physiol 314: H31-H44, 2018]. This was due to high-density lipoprotein-induced activation of Akt signaling in cardiomyocytes. We now demonstrate that mice lacking the scavenger receptor class B, type I exhibit increased sensitivity to doxorubicin-induced cardiomyocyte apoptosis in vivo. Cardiomyocytes expressing scavenger receptor class B, type I are protected from doxorubicin-induced apoptosis by preincubation with high-density lipoprotein isolated from wild-type mice, whereas high-density lipoprotein from scavenger receptor class B, type 1 knockout mice is less effective. Cardiomyocytes from scavenger receptor class B, type I knockout mice, however, are not protected by high-density lipoprotein in vitro, and hearts from knockout mice are more sensitive to doxorubicin in vivo. Pharmacological administration of purified apolipoprotein A1 dramatically protected wild-type mice from doxorubicin-induced cardiotoxicity and left ventricular dysfunction, whereas this protection was lost in scavenger receptor class B, type I-deficient mice. This demonstrates, at least in mice, that high-density lipoprotein therapy can confer protection against doxorubicin-induced cardiomyocyte apoptosis in a manner mediated by the scavenger receptor class B, type I. NEW & NOTEWORTHY We show that scavenger receptor class B, type I (SR-B1) mediates HDL-dependent protection against doxorubicin-induced cardiomyocyte apoptosis and that this is a property of SR-B1 in cardiomyocytes in vitro and in hearts in vivo. We also demonstrate that pharmacological treatment with apolipoprotein A1, the major HDL structural protein, protects mice against doxorubicin-induced cardiomyocyte apoptosis and left ventricular dysfunction in an SR-B1-dependent manner. This suggests that HDL-targeted pharmacological therapy may hold promise for protecting against the deleterious, cardiotoxic side effects of this commonly used chemotherapeutic drug.
Subject(s)
Apolipoprotein A-I/pharmacology , Apoptosis/drug effects , Cardiomyopathies/prevention & control , Doxorubicin , Myocytes, Cardiac/drug effects , Scavenger Receptors, Class B/metabolism , Ventricular Dysfunction, Left/prevention & control , Ventricular Function, Left/drug effects , Animals , Cardiomyopathies/chemically induced , Cardiomyopathies/metabolism , Cardiomyopathies/pathology , Cytoprotection , Disease Models, Animal , Male , Mice, Inbred C57BL , Mice, Knockout , Myocytes, Cardiac/metabolism , Myocytes, Cardiac/pathology , Scavenger Receptors, Class B/deficiency , Scavenger Receptors, Class B/genetics , Signal Transduction , Ventricular Dysfunction, Left/chemically induced , Ventricular Dysfunction, Left/metabolism , Ventricular Dysfunction, Left/physiopathologyABSTRACT
Diabetes is a risk factor for development of atherosclerotic cardiovascular disease. Animal model studies in mice revealed that hyperglycemia increases development of atherosclerosis in the aorta as well as myocardial fibrosis in surgical models of coronary artery ligation; however, the impact of hyperglycemia on coronary artery atherosclerosis and subsequent heart disease is less clear. To investigate the effect of hyperglycemia on atherosclerosis and coronary heart disease, we used a mouse model of diet-induced coronary artery atherosclerosis and myocardial infarction, the high fat/high cholesterol (HFC) diet fed SR-B1 knockout (KO)/apoE-hypomorphic (HypoE) mouse. Hyperglycemia was induced in these mice by streptozotocin (STZ) treatment. This increased HFC diet-dependent atherosclerosis development (p = 0.02) and necrotic core formation (p = 0.0008) in atherosclerotic plaques in the aortic sinus but did not increase the extent of atherosclerosis in coronary arteries. However, it did increase the extent of platelet accumulation in atherosclerotic coronary arteries (p = 0.017). This was accompanied by increased myocardial fibrosis (p = 0.005) and reduced survival (p = 0.01) compared to control-treated, normoglycemic mice. These results demonstrate that STZ-treatment exerted differential effects on the level of atherosclerosis in the aortic sinus and coronary arteries. These results also suggest that SR-B1-KO/HypoE mice may be a useful non-surgical model of diabetic cardiomyopathy in the context of coronary artery atherothrombosis.
