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Impairment of phagocytic functions of alveolar macrophages by hydrogen peroxide
R S Oosting1, L van Bree, J F van Iwaarden
1Department of Inhalation Toxicology, National Institute of Public Health and Environmental Protection, Bilthoven, The Netherlands.
Abstract:
Hydrogen peroxide (H2O2) inhibited phagocytosis and superoxide anion production by rat alveolar macrophages. The inhibition was irreversible and concentration and exposure time dependent. The potential relationship between H2O2-induced biochemical perturbations and impaired alveolar macrophage phagocytic functions was investigated. Alveolar macrophage viability and Fc receptor binding capacity were not affected by H2O2. There was probably no correlation between a H2O2-induced rise in cytosolic [Ca2+] ([Ca2+]i) and the impairment of phagocytosis by alveolar macrophages, as was suggested by the following findings. First, the H2O2-induced rise in [Ca2+]i could be inhibited by chelation of extracellular Ca2+, whereas the H2O2-induced impairment of phagocytosis could not. Second, the H2O2-induced rise in [Ca2+]i was reversible, whereas the impairment of phagocytosis was not. And finally, a rise in [Ca2+]i by incubation of alveolar macrophages with the calcium ionophore A23187 did not affect phagocytosis. Various experiments suggested that ATP depletion may play an important role in the H2O2 toxicity for alveolar macrophages. Comparable concentrations of H2O2 caused an irreversible decrease both in cellular ATP and in phagocytosis and superoxide production by alveolar macrophages. In addition, time course of ATP depletion and induction of impaired alveolar macrophage function were similar. In view of the fact that the strong oxidant H2O2 may react with a large variety of biological substances, possible other toxic lesions may not be excluded as underlying mechanism for H2O2-induced inhibition of phagocytic functions of alveolar macrophages.
Insights
Hydrogen peroxide irreversibly inhibits rat alveolar macrophage phagocytosis and superoxide production. ATP depletion, not calcium levels, is likely responsible for this impaired function.
Area of Science:
- Immunology
- Cell Biology
- Toxicology
Background:
- Alveolar macrophages are crucial for lung immunity.
- Hydrogen peroxide (H2O2) is a reactive oxygen species produced during inflammation.
- Understanding H2O2's effects on macrophage function is vital for respiratory health.
Purpose of the Study:
- To investigate the biochemical mechanisms underlying H2O2-induced inhibition of rat alveolar macrophage phagocytosis.
- To determine if changes in cytosolic calcium or ATP levels correlate with impaired phagocytic function.
Main Methods:
- Exposure of rat alveolar macrophages to varying concentrations and durations of H2O2.
- Assays for phagocytosis, superoxide anion production, cell viability, Fc receptor binding, cytosolic calcium ([Ca2+]i), and cellular ATP levels.
- Experiments using calcium ionophore A23187 and extracellular calcium chelation.
Main Results:
- H2O2 caused irreversible inhibition of phagocytosis and superoxide production, dependent on concentration and exposure time.
- H2O2 did not affect macrophage viability or Fc receptor binding.
- H2O2-induced cytosolic calcium ([Ca2+]i) increase was reversible and not correlated with phagocytosis impairment.
- H2O2 caused a concentration- and time-dependent irreversible decrease in cellular ATP, mirroring the impairment of phagocytosis and superoxide production.
Conclusions:
- ATP depletion is a likely mechanism for H2O2-induced toxicity in alveolar macrophages.
- H2O2 impairs phagocytosis and superoxide production independently of changes in cytosolic calcium levels.
- Further research may explore other H2O2-induced biochemical lesions affecting macrophage phagocytic functions.