IL-12 induced STAT4 activation plays a role in pro-inflammatory neutrophil functions

Abstract

Abstract Signal transducer and activator of transcription 4 (STAT4) becomes activated via Jak/Tyk kinases in response to IL-12 and other cytokines, leading to expression of genes involved in pro-inflammatory pathways. STAT4 has been well characterized in T lymphocytes and NK cells, yet less is known of its potential role in neutrophils. Neutrophils have recently been shown to play a contributing role in atherogenesis. Our published data demonstrate that global deficiency of STAT4 results in decreased atherogenesis in atherosclerotic ApoE−/− mice. However, the cell specific role of STAT4 in atherosclerosis is unknown. Western blot analysis revealed STAT4 expression and IL-12 induced phospho-STAT4 in isolated neutrophils with no distinguishable difference between blood and bone marrow neutrophils. IL-12 dependent activation of wild-type (WT) neutrophils induced an increase in reactive oxygen species (ROS) production when compared to non-stimulated WT neutrophils in both blood and bone marrow. Similarly, IL-12 stimulated WT neutrophils showed an increase in neutrophil extracellular trap (NET) elastase activity versus unstimulated controls. IL-12 stimulated neutrophils from Stat4−/− mice displayed no changes in NET elastase activity when compared to non-stimulated STAT4 deficient neutrophils suggesting STAT4-dependent NETosis. Furthermore, IL-12 stimulated Stat4−/− neutrophils showed decreases in both ROS production and NET elastase activity when compared to IL-12 stimulated WT neutrophils. Our data suggest a novel pro-inflammatory, IL-12 dependent role of STAT4 in neutrophils. Inhibition of these processes by targeting the IL-12/STAT4 pathway may serve as a possible therapeutic approach to treating atherosclerosis.