Ascorbate recycling in human neutrophils: induction by bacteria

Area of Science:

• Immunology
• Cell Biology
• Biochemistry

Background:

• Ascorbate (vitamin C) recycling is a crucial cellular process involving extracellular oxidation, transport as dehydroascorbic acid, and intracellular reduction.
• Understanding the regulation of ascorbate recycling, particularly in response to pathogens, is vital for comprehending immune responses and cellular defense mechanisms.

Purpose of the Study:

• To investigate the induction of ascorbate recycling in human neutrophils by pathogenic microorganisms.
• To determine if microorganisms themselves exhibit ascorbate recycling capabilities.
• To explore the potential of ascorbate recycling as a eukaryotic defense mechanism.

Main Methods:

• Human neutrophils were exposed to Gram-positive bacteria, Gram-negative bacteria, and Candida albicans.
• Intracellular ascorbate accumulation was measured to quantify ascorbate recycling.
• Dehydroascorbic acid reduction by microorganism lysates was assessed.

Main Results:

• Pathogenic bacteria and Candida albicans induced significant ascorbate recycling in human neutrophils, increasing intracellular ascorbate up to 30-fold.
• Recycling occurred rapidly (within 20 min) at physiological ascorbate concentrations and was dependent on extracellular oxidation.
• Ascorbate recycling was not observed in bacteria or C. albicans, with limited dehydroascorbic acid uptake and intracellular reduction.

Conclusions:

• Human neutrophils possess a robust ascorbate recycling system induced by microbial pathogens, suggesting a eukaryotic defense against oxidants.
• Microorganisms lack the capacity for ascorbate recycling, highlighting a potential difference in cellular defense strategies.
• The findings suggest potential clinical implications for ascorbate recycling in host-pathogen interactions and immune defense.