Neutrophil extracellular traps exacerbate microglia/macrophages-mediated neuroinflammation via cGAS in mice with traumatic brain injury

Abstract Intense neuroinflammatory response with widespread microglia/macrophage activation and leucocyte infiltration occurring during the acute phase of traumatic brain injury (TBI) is an important mediator of secondary neurological injury. Neutrophils, as the most abundant leukocytes in peripheral circulation and the first-line transmigrated immune cells at the contused parenchyma following TBI, are suggested to worsen TBI outcomes and exacerbate TBI-related neuroinflammation, via unclear mechanisms. We hypothesized that neutrophil extracellular trap (NET) formation as a key mechanistic regulator, exacerbate microglia/macrophage-mediated neuroinflammation and acute neurological deficits after TBI. In this study, we observed massive NET formation in contused brain tissue of TBI patients and elevated plasma NET biomarkers correlated with upregulated cGAS-STING pathway. Overexpression of peptidylarginine deiminase 4 (PAD4) induces an increase in the NET formation that is accompanied by upregulation of the cGAS-STING pathway and exacerbation of microglia/macrophages-mediated neuroinflammation and neurological injury. Additionally, degradation of NETs-associated DNA by DNase 1 and inhibition of NET formation by pharmacological inhibition of PAD effectively inhibit cGAS-STING pathway activation and ameliorate microglia/macrophages-mediated neuroinflammatory responses. Collectively, our data highlight that targeting NETs is a promising therapeutic strategy for TBI treatment.