Aging changes the mechanism that underlies JAK2 modulation of neutrophil function

Janus kinase 2 (JAK2) has been linked to various neutrophil functions, but the intracellular mechanisms underlying its modulation are unknown. Neutrophils are essential cells for host defense. Neutrophil effector functions include migration, neutrophil extracellular trap production (NETosis), reactive oxygen species (ROS) production, and degranulation. The goal of this study was to elucidate the signaling mechanism through which JAK2 modulates neutrophil function and the effect of aging on this pathway. We hypothesized that JAK2-mediated modulation changes the molecular mechanisms associated with neutrophil function in an age-dependent manner. Neutrophils from young (3 mo) and aged (≥22 mo) male and female C57BL/6J mice were isolated, treated with a JAK2 inhibitor (AZD1480) or a pan-JAK inhibitor (baricitinib), and stimulated with PMA. Functional assays were conducted to assess migration, degranulation, NETosis, and metabolism. Mass spectrometry and Luminex assays provided proteomic and cytokine profiles. Our data showed that JAK2 promotes migration via membrane composition and actin remodeling, with age-dependent shifts in chemokine secretion. JAK2 primes ROS production by altering NADPH oxidase components, which contributes to NET production. JAK2 influences degranulation through actin remodeling. While aged neutrophils display impaired ROS-granule release, both young and aged neutrophils have distinct JAK-dependent release of granule contents. Metabolically, JAK2 enhances pentose phosphate pathway activity in young neutrophils and decreases glycogen breakdown in aged cells. These findings reveal mechanisms by which JAK2 modulates neutrophil function and suggest that organismal age plays a role in this modulation.