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" Mechanoregulation of Endoplasmic Reticulum Stress Mediates Inflammation in Arterial Endothelium "
Bailey, Keith Alan
Passerini, Anthony G.
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Latin Dissertation
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| Language of Document
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English
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| Record Number
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1052162
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| Doc. No
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TL51279
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| Main Entry
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Bailey, Keith Alan
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| Title & Author
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Mechanoregulation of Endoplasmic Reticulum Stress Mediates Inflammation in Arterial Endothelium\ Bailey, Keith AlanPasserini, Anthony G.
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| College
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University of California, Davis
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| Date
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2019
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| Degree
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Ph.D.
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| student score
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2019
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| Note
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105 p.
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| Abstract
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Atherosclerotic cardiovascular disease is the leading cause of death and disability globally. Atherosclerosis impacts arteries where disturbed blood flow renders the endothelium susceptible to inflammation. The frictional drag force of flowing blood gives rise to wall shear stress (SS) that is sensed by endothelial cells (EC) and regulates pathways that affect inflammation. Regions of disturbed flow are characterized by relatively low magnitudes and steep gradients in SS which prime EC for enhanced inflammation. At these sites, proinflammatory stimuli, such as cytokines circulated systemically after a high-fat meal, activate EC to upregulate VCAM-1 receptors that target monocyte recruitment and initiate inflammation. Recently, endoplasmic reticulum (ER) stress was identified as a signature of EC exposed to disturbed flow, and it has emerged as a possible regulator of the atherosusceptible phenotype. How gradients of shear forces are sensed by EC and transduced into biochemical signals to differentially affect ER stress-mediated inflammatory responses that underlie focal atherogenesis is not well understood. Therefore, the objectives of this work were two-fold: 1) to characterize the ER stress pathways responsible for SS modulation of cytokine-induced inflammation, and 2) to investigate the mechanosensor and downstream biochemical signaling pathways responsible for governing ER stress-mediated inflammation. Human aortic EC (HAEC) were activated with low-dose TNFα and exposed to a SS gradient within a vascular mimetic microfluidic flow channel. High-resolution immunofluorescence imaging was used to produce a detailed spatial map of inflammatory signaling as a function of SS that varied from anti- to pro-atherogenic along a continuous monolayer of HAEC. VCAM-1 peaked at atherosusceptible low SS (2 dynes/cm2) and decreased to below static levels at atheroprotective high SS, and this pattern of expression was dependent on the mechanosensor PECAM-1. Activation of the ER stress response proteins XBP1 and eIF2α also peaked at low SS, where VCAM-1 expression and monocyte recruitment rose to a maximum. Silencing of PECAM-1 or these ER stress effectors with shRNA downregulated the VCAM-1- specific transcription factor IRF-1 at low SS, which abrogated peak VCAM-1 expression and subsequent monocyte recruitment. PECAM-1-mediated mechanotransduction had a direct effect on the dynamics of p38 phosphorylation under cytokine stimulation that specifically enhanced ER stress-mediated VCAM-1 transcription. At relatively low levels of SS, HAEC responded with an increase in PI3K and a reduction in MKP-1 that elicited sustained levels of p38 activation. This, in turn, stabilized XBP1 and resulted in its increased translocation to the nucleus, where together with enhanced IRF-1 activity, it promoted maximal VCAM-1 expression. These data establish that low magnitude SS is a potent inducer of the ER stress response, which converges with finely-tuned p38 signaling to elicit maximal IRF-1-dependent VCAM-1 expression and monocyte adhesion to inflamed HAEC. In summary, this thesis reveals a mechanism by which SS regulates EC inflammation and highlights several targets for therapeutic intervention of atherosclerosis.
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| Descriptor
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Biomechanics
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Biomedical engineering
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| Added Entry
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Passerini, Anthony G.
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| Added Entry
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University of California, Davis
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