Vitamin C: A Novel Regulator of Neutrophil Extracellular Trap Formation

Abstract

Introduction: Neutrophil extracellular trap (NET) formation was recently identified as a novel mechanism to kill pathogens. However, excessive NET formation in sepsis can injure host tissues. We have recently shown that parenteral vitamin C (VitC) is protective in sepsis. Whether VitC alters NETosis is unknown. Methods: We used Gulo^−/− mice as they lack the ability to synthesize VitC. Sepsis was induced by intraperitoneal infusion of a fecal stem solution (abdominal peritonitis, FIP). Some VitC deficient Gulo^−/− mice received an infusion of ascorbic acid (AscA, 200 mg/kg) 30 min after induction of FIP. NETosis was assessed histologically and by quantification for circulating free DNA (cf-DNA) in serum. Autophagy, histone citrullination, endoplasmic reticulum (ER) stress, NFκB activation and apoptosis were investigated in peritoneal PMNs. Results: Sepsis produced significant NETs in the lungs of VitC deficient Gulo^−/− mice and increased circulating cf-DNA. This was attenuated in the VitC sufficient Gulo^−/− mice and in VitC deficient Gulo^−/− mice infused with AscA. Polymorphonuclear neutrophils (PMNs) from VitC deficient Gulo^−/− mice demonstrated increased activation of ER stress, autophagy, histone citrullination, and NFκB activation, while apoptosis was inhibited. VitC also significantly attenuated PMA induced NETosis in PMNs from healthy human volunteers.