Characterizing factor XII thromboinflammatory functions in diabetes mellitus - venous thromboembolism (VTE) is a leading cause of cardiovascular death

Prior studies have shown that individuals with diabetes mellitus (DM) have a 5-fold higher risk of VTE than non-diabetic people. However, the mechanisms underlying the procoagulant state of DM, and their individual contribution to venous thrombosis, warrant further investigation. Despite therapeutic advances in recent years, all current anticoagulation therapies are associated with an increased risk of bleeding. Therefore, there is a critical need to identify therapeutic leads with an improved safety profile. We previously demonstrated that coagulation fxii contributes to the development of venous thrombosis (VT) through distinct zymogen and enzymatic (fxiia) functions. Neutrophils themselves express and secrete fxii which acts as a signaling messenger through its receptor urokinase plasminogen activator receptor (upar), to promote neutrophil trafficking at sites of venous stasis (zymogen activities). At these sites, neutrophils drive thromboinflammatory processes leading to amplification of thrombin generation, in part through plasma fxii activation on the surface of neutrophil extracellular traps [(nets), enzymatic fxii function]. DM is characterized by the accumulation of advanced glycation end-products (ages) which drive oxidative stress and inflammation. We recently showed that ages activate fxii into fxiia. Our preliminary data show that ages, simultaneously promote autocrine fxii release from neutrophils and upregulate the surface expression of upar. In a murine model of DM, neutrophils from wild type (WT) mice exhibit enhanced proinflammatory cytokine release and spontaneous net formation, which was abrogated in neutrophils of diabetic fxii-deficient (F12-/-) mice. Further, we found that fxii stimulation of neutrophils leads to increased expression of the receptor for ages (rage). These data support our central hypothesis that zymogen and enzymatic functions of fxii synergistically drive thromboinflammatory responses in DM, and accelerated age accumulation amplifies proinflammatory and prothrombotic fxii functions. In the current proposal, i will use site-directed fxii mutants and a microfluidic system to characterize the selective contribution of zymogen and enzymatic fxii functions on systemic hypercoagulability in DM (aim 1). To define the molecular mechanisms linking fxii to diabetic proinflammatory neutrophil phenotypes, i will investigate the effects of fxii deficiency on downstream age signaling networks (aim 2). The proposed studies will provide novel insights into the contribution of fxii and neutrophils to the pathophysiology of diabetes mellitus and illuminate key mechanisms coupling fxii functions to DM-associated thromboinflammatory responses. Since fxii is one of the few proteins that affect thrombosis without altering hemostasis, the proposed work should facilitate the translation of findings into new treatments for DM-associated thromboinflammatory responses with no risk of bleeding.