MICROVASCULAR ENDOTHELIAL ACTIVATION/DYSFUNCTION AND DYSREGULATION OF THE ANGIOPOIETIN-TIE2 SYSTEM IN THE PATHOGENESIS OF LIFE-THREATENING INFECTIONS.

Microvascular endothelial activation/dysfunction has emerged as an important mechanistic pathophysiological process in the development of morbidity and mortality in life-threatening infections. The angiopoietin-Tie2 system plays an integral role in the regulation of microvascular endothelial integrity. Angiopoietin-1 (Ang-1), produced by platelets and pericytes, is the cognate agonistic ligand for Tie2, promoting endothelial quiescence and inhibiting microvascular leak. Angiopoietin-2 (Ang-2), released from activated endothelial cells in Weibel-Palade bodies, competes with Ang-1 for binding to Tie-2, thereby promoting endothelial activation/dysfunction and microvascular leak. In healthy homeostasis, levels of Ang-1 far exceed Ang-2 in circulating serum/plasma. In diseases associated with systemic inflammation, Ang-1 falls and Ang-2 rises (i.e., Ang-1/2 dysregulation). Our research has shown that Ang-1/2 dysregulation is a prominent feature in a number of life-threatening infections and critical illnesses, including sepsis, cerebral malaria, COVID-19, streptococcal toxic shock syndrome (STSS), hemolytic-uremic syndrome (HUS), dengue, and CAR T-cell-associated neurotoxicity. Further work has implicated Ang-1/2 dysregulation in the development of end-organ injury, including acute lung injury/ARDS, acute kidney injury (AKI), and blood-brain-barrier (BBB) breakdown. Current studies are focused in three areas: (a) translation of Ang-1 and -2 as clinically informative prognostic and "theranostic" biomarkers in critically ill individuals; (b) incorporation of Ang-1/2 assays in a point of care device for clinical triage decision making; and (c) development of an engineered Ang-1 super agonist nanoparticle as a novel pathogen-agnostic therapeutic to prevent and/or mitigate end-organ dysfunction in individuals with life-threatening infections and critical illnesses associated with systemic inflammation.