Sepsis is life-threatening organ dysfunction produced by a dysregulated host response to infection in which neutrophils release neutrophil extracellular traps (NETs). NETs consist of DNA, histones, and antimicrobial peptides which kill pathogens. However, DNA and histones also exert damage by activating the intrinsic pathway of coagulation and inducing endothelial cell death, respectively. AADH, a 15kDa non-anticoagulant unfractionated heparin (UFH), prevents histone-mediated cytotoxicity in vitro and improves survival in septic mice. We explored the effectiveness of Vasoflux, a 5.5kDa low-molecular-weight-heparin as an anti-sepsis treatment as compared to enoxaparin and UFH. Vasoflux has reduced anticoagulant functions and hence reduces the risk of bleeding as compared to enoxaparin or UFH. We showed that UFH, enoxaparin, or Vasoflux at concentrations of up to 13.3uM, 40uM, or 40uM, neutralize histone-mediated cytotoxicity. These results suggest that these glycosaminoglycans (GAGs) are able to neutralize histone-mediated cytotoxicity independent of the AT-binding pentasaccharide. To quantitate the binding affinity between GAGs and histones, surface plasmon resonance was conducted. UFH is a more potent inhibitor of histone-mediated cytotoxicity compared to Vasoflux as UFH has a 10-fold greater binding affinity to histones compared to Vasoflux. To translate our in vitro findings to in vivo, Vasoflux, enoxaparin, and UFH were administered in a murine model of sepsis. Vasoflux at 8mg/kg - 50mg/kg reduced survival and exhibited damage in the lung, liver, and kidney in septic mice compared to 10 mg/kg of UFH or 8mg/kg of enoxaparin. This may be due to Vasoflux and UFH disrupting the DNA-histone complex, thereby releasing free procoagulant DNA. This is evident by our gel electrophoresis experiments, where addition of 1uM Vasoflux or 3.3uM UFH to DNA-histone complexes lead to histone dissociation from DNA. UFH bound to histones may be able to inhibit DNA-mediated thrombin generation, as it retains its anticoagulant properties, demonstrated by UFH-histone complexes attenuating DNA and TF-mediated thrombin generation. In contrast, Vasoflux may not neutralize the procoagulant DNA leading to a hypercoagulable state in the mice. Our study may have important clinical implications as there is an ongoing trial, HALO, which will administer intravenous UFH to patients suspected to have septic shock to reduce mortality. Based on our results, future clinical trials should consider the antithrombin-dependent anticoagulant activity of UFH being used as a sepsis treatment. / Thesis / Master of Science (MSc) / Sepsis is a life threatening condition caused by the body’s extreme response to microbial infection of the blood, whereby neutrophils release traps composed of cell-free DNA (cfDNA), histones, and antimicrobial proteins. In addition to fighting off infections, these traps also exert harmful effects like triggering clotting and killing host cells. Currently, no specific anti-septic drugs exist. Studies have shown that DNase1 (a recombinant protein that digests double stranded cfDNA) or a modified form of heparin (neutralizes histones) improves survival in septic mice. Our goal was to explore the protective effects of Vasoflux, (a non-anticoagulant heparin) and DNase1 in a mouse model of sepsis. We hypothesize that the combined therapy of DNase1 and Vasoflux will improve survival. We found that Vasoflux has minimal blood thinning activity and can prevent histones from killing cells. However, Vasoflux administered into septic mice worsened organ damage and decreased survival. We hypothesize that this damage may be due to Vasoflux’s ability to displace histones from histone-DNA complexes, thereby releasing free DNA, which promotes excessive blood clotting in sepsis.