Molecular and Translational Studies in Hematologic Disorders

This application for an NHLBI R35 Outstanding Investigator Award is to continue R35-funded studies on mech- anism of disease in von Willebrand Disease (VWD) and sickle cell disease (SCD). Both diseases involve von Willebrand factor (VWF). In VWD, VWF has a starring role; in SCD, it is one of many actors involved in a very complex pathophysiology. In types 2A and 2B VWD, caused by dysfunctional VWF that results in loss of the largest and hemostatically most active multimers, excessive ADAMTS13-mediated cleavage occurs and the number of small, cleaved VWF fragments is high. In the proposed studies, we will investigate the impact of these fragments on hemostasis, as we have evidence that the small fragments have functions not found in large multimers, one fragment interfering with hemostasis by blocking platelet binding and VWF self-association, and the other competitively inhibiting ADAMTS13. In our SCD studies, we have substantial evidence that oxidation- induced changes to lipids in the sickle erythrocyte membrane and plasma lipoproteins play major roles in the pathophysiology of vasoocclusion. Oxidation converts the sickle erythrocyte to an agonist capable of activating platelets, leukocytes, and endothelial cells, probably by generating bioactive oxidized lipids such as platelet- activating factor and lysophospholipids. Oxidation of usually protective plasma high-density lipoprotein makes it proinflammatory. In this application, we propose to use a wide variety of in vitro and in vivo approaches to address these questions. For the VWD studies, we will study normal blood and patient blood, recombinant pro- teins, and use AI-assisted structure and docking. Experimentally, we will use a variety of microfluidic techniques and observe the in vivo effects of VWF cleavage fragments using intravital microscopy. For the SCD studies, we will continue to refine mass spectrometry techniques to identify candidate oxidized phospholipids in erythro- cytes and lipoproteins and study the lipidomes of a variety of patients to understand the extent of variability. Finally, we will evaluate candidate lipids for their ability to induce vasoocclusion and test interventions to re- duce the negative impact of in vivo oxidation. We expect these studies to increase our understanding of the mechanisms of disease in the two disorders, to provide new biomarkers to study the diseases, and to improve the treatment in afflicted patients, both by increasing understanding and by providing new therapeutic leads.