Neutrophils Isolated from Septic Patients Exhibit Elevated Uptake of Vitamin C and Normal Intracellular Concentrations despite a Low Vitamin C Milieu.
Level 4 - case-series / case-control
Case-control observational study with ex vivo cellular assays
PubMed 34679743 · doi:10.3390/antiox10101607
What was done
Ascorbate (vitamin C) concentrations were measured in plasma, isolated neutrophils, and erythrocytes from 18 critically ill patients with sepsis and 20 healthy volunteers using HPLC. Plasma myeloperoxidase concentrations were measured by ELISA. Ex vivo uptake of ascorbate and dehydroascorbic acid by isolated neutrophils was also evaluated.
What was found
Plasma ascorbate was significantly lower in septic patients compared to healthy controls (14 vs. 88 µmol/L, p < 0.001). Despite this deficit, neutrophil intracellular ascorbate content was comparable between septic patients and healthy controls (0.33 vs. 0.35 nmol/10^6 cells, p > 0.05), with septic neutrophils showing elevated ex vivo ascorbate uptake. Erythrocyte ascorbate was significantly lower in septic patients than controls (30 vs. 69 µmol/L, p = 0.002), though 2.2-fold higher than patient plasma (p = 0.008). Plasma myeloperoxidase was markedly elevated in sepsis (194 vs. 14 mg/mL, p < 0.0001).
Why it matters
This study demonstrates that circulating neutrophils preserve intracellular vitamin C levels during sepsis despite severe systemic plasma hypovitaminosis C, likely through compensatory uptake mechanisms.
Limits
Small sample size (18 septic patients, 20 healthy volunteers). Non-fasting blood samples were used. Clinical characteristics, sepsis severity, confounders, and patient outcomes were not reported in the abstract. Exact molecular mechanisms driving increased uptake were not definitively established.
Cited by
- supports Neutrophils and leukocytes maintain intracellular vitamin C concentrations 50 to 100 times higher than plasma concentrations.