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Influence of various antibiotics on superoxide generation by normal human neutrophils
Abstract:
Among the several killing mechanisms displayed by human neutrophils, the oxidative system is the most efficient. We have studied the influence of various antibiotics on the generation of superoxide by isolated human polymorphonuclear leukocytes (PMNL) stimulated by phorbol-myristate acetate. Among the antibiotics tested, only coumermycin significantly inhibited superoxide generation; this effect was dose-related, it depended on extracellular calcium concentration and was potentiated by sub-inhibitory concentrations of calcium channel-blocking agents. Coumermycin inhibited the influx of calcium produced by the ionophore A23187 as well as directed chemotaxis in agar and the intracellular killing of a highly susceptible strain of S. aureus. These inhibitory effects required at least 15 min of preincubation of the PMNL. Coumermycin, at clinically achievable serum concentrations, significantly impaired several PMNL functions. The mechanism could be a specific or a non-specific interaction with calcium-channels.
Insights
Coumermycin antibiotic significantly inhibits superoxide generation in human neutrophils, impacting calcium influx and bacterial killing. This effect is dose-dependent and requires preincubation, suggesting a role in immune cell function.
Area of Science:
- Immunology
- Pharmacology
- Cell Biology
Background:
- Human neutrophils utilize an oxidative system, primarily superoxide generation, as a key mechanism for pathogen killing.
- Understanding how pharmacological agents influence neutrophil oxidative function is crucial for assessing their impact on host defense.
Purpose of the Study:
- To investigate the effects of various antibiotics on superoxide generation by human polymorphonuclear leukocytes (PMNL).
- To elucidate the mechanism by which coumermycin affects PMNL function, particularly calcium influx and oxidative activity.
Main Methods:
- Isolated human PMNL were stimulated with phorbol-myristate acetate to assess superoxide generation.
- The influence of coumermycin and other antibiotics was evaluated, along with dose-dependency and calcium concentration effects.
- Calcium influx, chemotaxis, and intracellular killing of S. aureus were measured following coumermycin preincubation.
Main Results:
- Coumermycin was the only antibiotic tested that significantly inhibited PMNL superoxide generation in a dose-related manner.
- This inhibition was dependent on extracellular calcium and potentiated by calcium channel blockers.
- Coumermycin also inhibited calcium influx, chemotaxis, and intracellular bacterial killing, requiring a 15-minute preincubation period.
Conclusions:
- Coumermycin, at clinically relevant concentrations, impairs critical human neutrophil functions, including superoxide generation and pathogen killing.
- The observed effects suggest coumermycin may interact with calcium channels, thereby modulating PMNL oxidative and antimicrobial activities.
- Further research is warranted to confirm the precise mechanism of coumermycin's interaction with calcium-dependent neutrophil functions.