Propionic acid stimulates superoxide generation in human neutrophils

Area of Science:

• Immunology
• Microbiology
• Cellular Biology

Background:

• Short-chain carboxylic acids (SCCAs) are bacterial byproducts found at infection sites.
• Propionic acid (a SCCA) was previously shown to increase intracellular calcium ([Ca2+]i) in human neutrophils.
• The effect of propionic acid on neutrophil superoxide generation remains unclear.

Purpose of the Study:

• To investigate the impact of propionic acid on superoxide generation in human neutrophils.
• To compare the effects of propionic acid with formylmethionyl-leucyl-phenylalanine (fMLP) on neutrophil activation.

Main Methods:

• Human neutrophils were stimulated with propionic acid and fMLP.
• Measurements included inositol 1,4,5-trisphosphate (IP3) formation and intracellular calcium ([Ca2+]i) levels.
• Superoxide generation was assessed, along with responses to Ca2+ ionophore A23187 and thapsigargin.

Main Results:

• Propionic acid (10 mm) induced IP3 formation and a transient [Ca2+]i increase, but not superoxide generation.
• fMLP (1 µm) stimulated IP3, Ca2+ mobilization, and superoxide generation.
• Propionic acid's Ca2+ mobilization was weaker and shorter-lasting than fMLP's.
• Propionic acid enhanced superoxide generation induced by A23187 and thapsigargin.

Conclusions:

• Propionic acid induces weaker Ca2+ mobilization in neutrophils compared to fMLP.
• Propionic acid alone does not trigger significant superoxide generation.
• Propionic acid can potentiate superoxide generation in the presence of Ca2+ influx activators.