Building a better NET: Neutrophil extracellular trap targeted therapeutics in the treatment of infectious and inflammatory disorders

ABSTRACT

Infectious and inflammatory stimuli induce the release of neutrophil extracellular traps (NETs), webs of cell-free (cf) DNA complexed with histones and antimicrobial proteins, that capture and kill pathogens. Despite their protective role in the initial stages of sepsis, excessive NET release accompanied by NET degradation, leads to the release of NET degradation products (NDPs), including cfDNA, histones, and myeloperoxidase that injure the microvasculature. Murine studies have shown that clearance or neutralization of NDPs improves outcomes, demonstrating that NETs have a causal link to disease and are not merely biomarkers. Recently, elevated NDPs have been associated with disease severity in sepsis and coronavirus disease 2019, raising further interest in targeting NETs. Many propose eliminating NETs, either by preventing their release, or by degrading them. However, NET inhibition may impede the innate immune response and is difficult to achieve in rapid-onset conditions such as sepsis. On the other hand, approaches that accelerate NET degradation have met with mixed results in murine studies, raising the concern that this strategy may liberate NET-captured pathogens while increasing circulating levels of harmful NDPs. Alternative NET-directed strategies include therapies that neutralize, sequester, or remove NDPs from the circulation. Others propose modifying released NETs to decrease their capacity to induce collateral tissue damage while enhancing their ability to capture microorganisms. Synthetic NETs have also been designed to combat antibiotic-resistant organisms. Although it is still in its infancy, the field of NET-targeted therapeutics is advancing rapidly and may soon find application in the treatment of sepsis and other inflammatory disorders.