Abstract TP300: Apolipoprotein-E Deficiency and High Fat Diet Alter Immunomodulatory Cellular and Molecular Determinants Promoting Atherosclerosis, a Stroke Risk Factor

Abstract

Background: Most ischemic strokes are caused by atherosclerosis. Atherosclerotic plaque formation is modulated by genetic and environmental interactions. Apolipoprotein E (ApoE) regulates lipid metabolism, and its deficiency is associated with dyslipidemia and atherosclerosis. ApoE is abundantly expressed in glial cells and neurons of the brain, affecting the blood brain barrier and cognitive function. Poor dietary habits promote the onset of atherosclerosis. In this study, we examined the effects of ApoE deficiency and high fat diet (HFD) on plaque formation and immunomodulatory cellular and molecular mechanisms in mice models. Methods: Wild type and ApoE knockout (KO) mice were fed with normal or HFD. Carotid plaques were examined using hematoxylin and eosin staining. Targeted proteomic profiling identified the circulating inflammatory proteins. Pathway specific transcriptomic profiles were identified using PCR arrays and real-time PCR. Immunohistochemistry assays were done in brain sections using a neuronal marker (NeuN), an astrocyte marker (GFAP) and a microglia marker (Iba1). The expression of Pentraxin-3 (PTX3), lipocalin2, and PAI-1 were examined using immunohistochemistry. Images were acquired and analyzed using a Keyence fluorescence microscope and NIH ImageJ. Results: ApoE deficiency and HFD enhanced atherosclerotic plaque formation as a function of age in association with a significant increase in circulating pro-inflammatory cytokines in blood/plasma, including M-CSF, C-reactive protein, and PTX3. The number of microglial cells and astrocytes was increased with altered morphology in ApoE KO and aged animals’ brain cortex and dentate gyrus. Whereas neuronal cell number was decreased in the brains of ApoE deficient and aged mice. The mRNA levels of SELE, PAI-1, lipocalin2, and PTX3 were upregulated in ApoE deficient and WT animals fed with HFD. Higher levels of PTX3 were also observed in atherosclerotic plaques. Conclusion: ApoE deficiency and HFD may play a key role in altering immunomodulatory cellular responses and initiating pro-inflammatory molecular signaling. These events may promote atherosclerotic plaque formation, a risk factor for ischemic stroke and worsen brain damage.