Defining Endotheliopathy in Murine Polytrauma Models

Syndecan-1 as the Effect or Effector of the Endothelial Inflammatory Response?

INTRODUCTION

Syndecan-1 is a heparan sulfate proteoglycan found in the glycocalyx of vascular endothelial cells. Serum levels of syndecan-1 have repeatedly been demonstrated to increase following traumatic injury and shock, but it is unclear whether syndecan-1 plays an active role in the inflammatory response or is simply a biomarker of a state of hypoperfusion. The aim of this study was to identify the role of syndecan-1 role in the inflammatory process in the absence of trauma.

METHODS

Male mice were randomized into five groups (n = 3). Four groups received increasing concentrations of syndecan-1 (1, 10, 100, and 1000pg/mL per blood volume) and a fifth group was given normal saline as a control via intravenous injection. These concentrations were selected based on previous syndecan-1 enzyme-linked immunosorbent assay data acquired following induced hemorrhagic shock in mice resulting in serum levels of 10-6000 pg/mL. Mice from each group were sacrificed at 1-, 4-, and 24-h time points for serum biomarker evaluation. A multiplex enzyme-linked immunosorbent assay was performed to analyze proinflammatory cytokines and chemokines including interleukin (IL)-1a, IL-1b, IL-2, IL-3, IL-4, IL-6, IL-10, IL-12, IL-17, monocyte chemoattractant protein-1, TNF-α, macrophage inflammatory protein-1α, granulocyte-macrophage colony-stimulating factor, and normal T cell expressed and presumably secreted levels. Whole blood was analyzed via rotational thromboelastometry in a separate group of mice dosed with syndecan-1 at 1000 pg/mL and compared to sham mice at 1 h.

RESULTS

Tumor necrosis factor-α was significantly elevated in the 1000 pg/mL group compared to sham animals. There were no significant changes in IL-1a, IL-1b, IL-2, IL-3, IL-4, IL-6, IL-10, IL-12, monocyte chemoattractant protein--1, macrophage inflammatory protein-1α, granulocyte-macrophage colony-stimulating factor, or normal T cell expressed and presumably secretedat 1, 4, and 24 h for any group when compared to mice receiving saline alone. No significant differences were noted in coagulability between the 1000 pg/mL syndecan-1 group and shams at 1 h CONCLUSIONS: Inflammatory cytokine concentrations did not change with increasing dosage of syndecan-1 within mice at any timepoint, except for an acute change in tumor necrosis factor-α which was transient. Based on our results, syndecan-1 appears to be a biomarker for inflammation rather than an active participant in eliciting an inflammatory response. Further research will focus on the role of syndecan-1 following hemorrhagic shock.

THE NEUROENDOTHELIAL AXIS IN TRAUMATIC BRAIN INJURY: MECHANISMS OF MULTIORGAN DYSFUNCTION, NOVEL THERAPIES, AND FUTURE DIRECTIONS

ABSTRACT

Severe traumatic brain injury (TBI) often initiates a systemic inflammatory response syndrome, which can potentially culminate into multiorgan dysfunction. A central player in this cascade is endotheliopathy, caused by perturbations in homeostatic mechanisms governed by endothelial cells due to injury-induced coagulopathy, heightened sympathoadrenal response, complement activation, and proinflammatory cytokine release. Unique to TBI is the potential disruption of the blood-brain barrier, which may expose neuronal antigens to the peripheral immune system and permit neuroinflammatory mediators to enter systemic circulation, propagating endotheliopathy systemically. This review aims to provide comprehensive insights into the "neuroendothelial axis" underlying endothelial dysfunction after TBI, identify potential diagnostic and prognostic biomarkers, and explore therapeutic strategies targeting these interactions, with the ultimate goal of improving patient outcomes after severe TBI.

Experimental Models of Traumatic Injuries: Do They Capture the Coagulopathy and Underlying Endotheliopathy Induced by Human Trauma?

Trauma-induced coagulopathy (TIC) is a major cause of morbidity and mortality in patients with traumatic injury. It describes the spectrum of coagulation abnormalities that occur because of the trauma itself and the body's response to the trauma. These coagulation abnormalities range from hypocoagulability and hyperfibrinolysis, resulting in potentially fatal bleeding, in the early stages of trauma to hypercoagulability, leading to widespread clot formation, in the later stages. Pathological changes in the vascular endothelium and its regulation of haemostasis, a phenomenon known as the endotheliopathy of trauma (EoT), are thought to underlie TIC. Our understanding of EoT and its contribution to TIC remains in its infancy largely due to the scarcity of experimental research. This review discusses the mechanisms employed by the vascular endothelium to regulate haemostasis and their dysregulation following traumatic injury before providing an overview of the available experimental in vitro and in vivo models of trauma and their applicability for the study of the EoT and its contribution to TIC.