Ascorbic acid attenuates activation and cytokine production in sepsis-like monocytes

AbstractSepsis manifests due to the host’s dysregulated immune response to an infection. High dose ascorbic acid (AA) has emerged as a potential treatment of sepsis, yet little is known regarding how ascorbic acid influences the immune system in sepsis, such as monocytes. The objective of this study is to investigate the effects of high dose AA on monocyte polarization and cytokine production in vitro.Monocytes were isolated from healthy donors (n=6) and polarized in vitro for 48hrs using lipopolysaccharide (LPS) and lipoteichoic acid (LTA). Polarization was confirmed by surface marker expression using flow cytometry. In parallel, monocytes from septic patients (n=3) were analyzed for polarization markers as a comparison to the in vitro polarization. The effect of AA on monocyte polarization was evaluated. Finally, monocytes were analyzed for cytokine production of TNF and IL-8 by intracellular staining.Both LPS and LTA induced polarization in healthy monocytes in vitro, with increased expression of both pro- (CD40 and PDL1, p<0.05) and anti-inflammatory (CD16 and CD163, p<0.05) polarization markers. This pattern resembled that of monocytes from septic patients. Treatment with AA significantly inhibited surface expression of CD16 and CD163 (p<0.05) in a dose dependent manner. Finally, AA attenuated LPS or LTA-induced cytokine production of IL-8 and TNF (both p<0.05) in a dose-dependent manner.Thus, AA attenuates cytokine production and upregulation of anti-, but not pro-inflammatory related markers in LPS or LTA polarized monocytes. This study provides important insight into the effects of high dose AA on monocytes, and potential implications in sepsis.Summary sentenceAscorbic acid inhibits production of IL-8, TNF, and upregulation of the polarization markers CD16 and CD163 in LPS or LTA polarized monocytes in vitro.