COBRE Pilot Project for Hainsworth Shin: Center of Research in Obesity and Cardiovascular Disease

This application is for pilot funding from the COCVD/BBDOC/CCTS to generate critical evidence that substantiates a novel link between obesity-related hypercholesterolemia (HC) and impaired regulation of neutrophil adhesivity by hemodynamic shear stress. We believe this pathogenic mechanism is one of the earliest triggers of microvascular dysregulation upstream of lethal arterial vasculopathy due to HC. In addition to providing a basis for developing novel diagnostic and therapeutic strategies, the results from the proposed studies will also provide key preliminary data for a future R01 proposal resubmission to the National Institutes of Health (NIH), National Heart Lung and Blood Institute (NHLBI). Recently, we identified a link between the cholesterol-related fluidity of the cell membrane of the neutrophils and the anti-inflammatory role of hemodynamic shear stresses in regulating their activity level. We also showed that gradual blood cholesterol elevations, during the onset and progression of HC, impair neutrophil shear sensitivity. Notably, HC is associated with dysregulated tissue blood flow typified by a chronically inflamed blood state that promotes neutrophil adhesion in the microcirculation and, in doing so, impairs microvascular flow regulation. But, the mitigating event that links blood cholesterol elevations and microvascular pathogenesis due to neutrophil adhesion is still unclear. Previously, we showed that shear stress stimulates neutrophils to release lysosomal cathepsin B (catB) to cleave CD11b integrin adhesion molecules off their cell surface. Based on the key role of C11b integrins in cell adhesion during acute inflammatory processes, our data indicate that shear-induced CD11b shedding likely serves to prevent or reverse spontaneous neutrophil binding to other cells, e.g., platelets and endothelial cells (EC), during non-pathogenic (non-inflamed) conditions. Also, the impairment of this putative control mechanism likely drives the pathogenesis of microvascular dysfunction due to HC. Fundamentally, the goal of the proposed study is to determine whether there is a link between HC, an impaired regulation of neutrophil adhesivity by shear stress, and tissue blood flow dysregulation due to chronic neutrophil activation in the microcirculation. Specifically, we propose to test the hypothesis that HC compromises this shearsensitive control mechanism, leading to dysregulated neutrophil adhesion in the microcirculation and microvascular dysfunction. To address this, we will [Aim 1] determine whether extracellular cholesterol elevations compromise the catB-related shear stress control of CD11b expression on neutrophils, thereby increasing their firm adhesion to ECs and [Aim 2] determine whether HC impairs microvascular function by its effect on the CD11b cleavage-related response of neutrophils to shear stress. We will use cell biomechanics and cell biology tools along with in vivo, non-invasive, spectroscopic analyses of tissue blood flow to reveal insight into the link between shear sensitive regulation of neutrophils and microvascular flow regulation at the tissue level. Notably, microvascular dysfunction is considered to forecast lethal remodeling of the large arteries that typifies HC. We thus expect the results of the proposed study to provide a basis for designing novel prognostic and therapeutic strategies to directly treat the early downstream pathobiology of HC.