Albumin Nanoparticle Endocytosing Subset of Neutrophils for Precision Therapeutic Targeting of Inflammatory Tissue Injury

Abstract

The complex involvement of neutrophils in inflammatory diseases makes them intriguing but challenging targets for therapeutic intervention. Here, we tested the hypothesis that varying endocytosis capacities would delineate functionally distinct neutrophil subpopulations that could be specifically targeted for therapeutic purposes. By using uniformly sized (∼120 nm in diameter) albumin nanoparticles (ANP) to characterize mouse neutrophils in vivo , we found two subsets of neutrophils, one that readily endocytosed ANP (ANP high neutrophils) and another that failed to endocytose ANP (ANP low population). These ANP high and ANP low subsets existed side by side simultaneously in bone marrow, peripheral blood, spleen, and lungs, both under basal conditions and after inflammatory challenge. Human peripheral blood neutrophils showed a similar duality. ANP high and ANP low neutrophils had distinct cell surface marker expression and transcriptomic profiles, both in naive mice and in mice after endotoxemic challenge. ANP high and ANP low neutrophils were functionally distinct in their capacities to kill bacteria and to produce inflammatory mediators. ANP high neutrophils produced inordinate amounts of reactive oxygen species and inflammatory chemokines and cytokines. Targeting this subset with ANP loaded with the drug piceatannol, a spleen tyrosine kinase (Syk) inhibitor, mitigated the effects of polymicrobial sepsis by reducing tissue inflammation while fully preserving neutrophilic host-defense function.

Neutrophils are gatekeepers of mucosal immunity

“…The endocytosis capacity of neutrophils has recently been suggested as a factor for neutrophil heterogeneity. Two subsets of neutrophils have been characterized in murine lungs, bone marrow, peripheral blood, and spleen both under steady state and after inflammatory challenge based on endocytosis capacity 112 . These two subsets were characterized by their capability to endocytose albumin nanoparticles (ANP), one that readily endocytosed ANP (ANP high neutrophils) and another that failed to endocytose ANP (ANP low neutrophils).…”

Pink1-mediated mitophagy in the endothelium releases proteins encoded by mitochondrial DNA and activates neutrophil responses

“…Given the strong protective effect of endothelial Pink1 deletion in inflammatory injury, and the limited effect on endothelial barrier function, we hypothesized that endothelial Pink1 induces inflammatory injury by acting on the recruitment of immune cells such as neutrophils which are key mediators of lung injury and death in endotoxemia-induced inflammatory lung injury (Hayashi, Means et al 2003, Nathan 2006, Bachmaier, Stuart et al 2022). Neutrophils are recruited into the lung 2-24 hours following systemic delivery of LPS where they are early drivers of inflammation induced tissue injury (Matute-Bello, Frevert et al 2008, Zemans and Matthay 2017).…”

Regulation of cGAS Activity and Downstream Signaling

“…Neutrophils and tissue-resident macrophages propagate inflammatory responses by releasing various inflammatory cytokines and chemoattractants. However, these cells also seem to have a resolving role in ALI [ 106 ]. Upon sensing pathogens macrophages orchestrate the inflammatory signaling by releasing inflammatory cytokines leading to the influx of activated neutrophils [ 107 ].…”