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Rat surfactant apoprotein A (SP-A) exhibits antioxidant effects on alveolar macrophages
1First Department of Internal Medicine, Tokyo Women's Medical College, Japan.
Abstract:
The effects of surfactant apoprotein A (SP-A) on the superoxide production of rat alveolar macrophages (AM) were studied. Superoxide production was measured by the ferricytochrome c reduction method. When AM were incubated with SP-A only during the measurement of superoxide production, superoxide production was not influenced by SP-A. However, when AM were preincubated with SP-A at a concentration of 1, 2, and 10 micrograms/ml, superoxide production by AM was significantly inhibited (P < 0.05, P < 0.01, P < 0.01, respectively). The superoxide production of AM stimulated by PMA was significantly inhibited by SP-A at a concentration of 1 microgram/ml (P < 0.01), and superoxide production stimulated by zymosan was also inhibited by SP-A at a concentration of 10 micrograms/ml (P < 0.05). Suppression of superoxide production of unstimulated and PMA-stimulated AM was significantly inhibited by anti-SP-A antibody. Superoxide generation by the xanthine and xanthine oxidase system was not affected by the presence of SP-A. Our results suggest that superoxide production of AM can be inhibited by SP-A and that this inhibitory effect on AM is due to a specific effect of SP-A. From these results, it is speculated that SP-A may have a protective role for oxidant injury by AM in the lung.
Insights
Surfactant apoprotein A (SP-A) inhibits superoxide production in rat alveolar macrophages (AM). This suggests SP-A may protect the lungs from oxidant injury.
Area of Science:
- Pulmonary immunology
- Cellular biology
- Biochemistry
Background:
- Alveolar macrophages (AM) play a crucial role in lung defense.
- Superoxide production by AM is a key component of the inflammatory response.
- Surfactant apoprotein A (SP-A) is a major protein component of pulmonary surfactant.
Purpose of the Study:
- To investigate the effect of SP-A on superoxide production by rat AM.
- To determine if SP-A modulates AM's response to stimuli.
- To explore the potential protective role of SP-A in lung injury.
Main Methods:
- Superoxide production measured using the ferricytochrome c reduction method.
- AM were preincubated with varying concentrations of SP-A.
- Stimulation of AM with phorbol myristate acetate (PMA) and zymosan.
- Effect of anti-SP-A antibody on SP-A mediated inhibition.
Main Results:
- SP-A significantly inhibited superoxide production in unstimulated and stimulated AM.
- Inhibition was dose-dependent and specific to SP-A.
- Anti-SP-A antibody reversed the inhibitory effect.
- SP-A did not affect superoxide generation in a cell-free xanthine/xanthine oxidase system.
Conclusions:
- SP-A exerts a specific inhibitory effect on superoxide production by AM.
- SP-A may play a protective role against oxidant-induced lung injury.
- These findings highlight a novel immunomodulatory function of SP-A in the lung.