UC San Diego

Sepsis, a life-threatening organ dysfunction caused by a dysregulated host response to infection, poses a serious threat to human health. Many sepsis pathologies are tied to vascular dysregulation. The vascular glycocalyx (VGC), the collection of proteins and glycans exposed to vascular flow, is critical to vascular function and is dramatically remodeled in sepsis. Little is known about VGC composition in health or in sepsis. This dissertation consists of 6 chapters covering VGC remodeling during infection, detailed characterization of VGC composition using novel methodologies, and the impacts of specific alteration of the major VGC component heparan sulfate (HS) during sepsis. Chapter 1 is a summary of VGC composition, the VGC role in vascular function, VGC remodeling factors, and how VGC composition changes during infection. Chapter 2 describes a novel technique to characterize VGC protein composition and how it changes in sepsis. By using a perfusion technique to tag proteins exposed to vascular flow, VGC proteins from major organs were purified, identified, and quantified by novel proteomics methods. In healthy vasculatures, there are both shared and unique VGC components across organs. In Staphylococcus aureus sepsis, dramatic compositional changes occur in an organotypic fashion that reflect the inflammatory environment. Chapter 3 details studies that use genetic alteration of vascular HS (Ndst1f/fTie2Cre+) to stratify sepsis and tissue infection models across a diverse range of sepsis-causing bacterial agents. Ndst1f/fTie2Cre+ mice exhibit hypersensitivity only to S. aureus. Chapter 4 consists of studies showing endothelial HS mediates neutrophil infiltration and hepatic damage induced by S. aureus sepsis. Importantly, altering endothelial HS reduces neutrophil trafficking in both sterile and non-sterile hepatic inflammation, the first VGC component characterized to do so. Studies in Chapter 5 further characterize Ndst1f/fTie2Cre+ mouse hypersensitivity to S. aureus. Ndst1f/fTie2Cre+ mice exhibited a unique heart VGC during sepsis that lacked proteins characteristic of heart-protection, indicating S. aureus may induce improper cardiac vascular responses in Ndst1f/fTie2Cre+ mice. Hypersensitivity was dependent upon S. aureus alpha-toxin. Alpha-toxin bound to heparin, and heparan sulfate inhibited the activity of the alpha-toxin receptor Adam10. The studies of thesis uniquely examine the VGC in sepsis from the “omics” to the molecular level.