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Metabolic enhancement and increase of alveolar macrophages induced by ozone
1Basic Medical Sciences Division, National Institute for Environmental Studies, Ibaraki, Japan.
Abstract:
Male Wistar rats were exposed to 0.2 ppm ozone (O3) for 14 days and at intervals alveolar macrophages were collected by bronchoalveolar lavage to examine the effects of O3. The specific activities of glucose-6-phosphate dehydrogenase and glutathione peroxidase of alveolar macrophages increased to 1.6-fold (on the 3rd day) and 1.5-fold (on the 5th day), respectively, those of the control values. Similarly, the specific activities of pyruvate kinase, lactate dehydrogenase, and hexokinase also increased to 1.6-fold, 1.4-fold, and 1.2-fold, respectively, those of the control values on the 3rd day. The activities of all enzymes tested were maintained at significantly higher levels until the 14th day. Furthermore, the incorporation of [14C]thymidine into alveolar macrophages increased twice the control values on the 1st and 3rd days and was almost completely inhibited by the addition of 1.23 x 10(-4) M aphidicolin, a competitive inhibitor of DNA polymerase alpha. The number of alveolar macrophages collected from exposed animals also increased to 1.5-fold that of the control value on the 3rd day and was maintained at significantly higher level until the 14th day. It was noted that alveolar macrophages of small size preferentially increased between the 5th and 14th days. These results show that exposures to 0.2 ppm O3 induced a metabolic enhancement of the peroxidative metabolism, glycolysis, and DNA synthesis in alveolar macrophages and increased the macrophages of small size.
Insights
Ozone exposure (0.2 ppm) in rats significantly boosted alveolar macrophage metabolism, increasing enzymes for peroxidative metabolism and glycolysis. This ozone exposure also enhanced DNA synthesis and the number of small alveolar macrophages.
Area of Science:
- Environmental Toxicology
- Cellular Biology
- Pulmonary Medicine
Background:
- Ozone (O3) is a major air pollutant with known respiratory effects.
- Alveolar macrophages are critical immune cells in the lungs, responding to environmental insults.
Purpose of the Study:
- To investigate the effects of sub-chronic ozone exposure on rat alveolar macrophage metabolism and proliferation.
- To analyze changes in key enzymes involved in cellular energy production and DNA synthesis.
Main Methods:
- Male Wistar rats were exposed to 0.2 ppm ozone for 14 days.
- Alveolar macrophages were collected via bronchoalveolar lavage at various intervals.
- Enzyme activities (glucose-6-phosphate dehydrogenase, glutathione peroxidase, pyruvate kinase, lactate dehydrogenase, hexokinase) and [14C]thymidine incorporation were measured.
- Cell size and number were quantified.
Main Results:
- Ozone exposure significantly increased the specific activities of key metabolic enzymes, including those for peroxidative metabolism and glycolysis.
- DNA synthesis in alveolar macrophages doubled, indicating enhanced proliferation, and was inhibited by aphidicolin.
- The total number of alveolar macrophages increased, with a notable rise in smaller-sized cells.
Conclusions:
- Sub-chronic ozone exposure at 0.2 ppm induces significant metabolic enhancement in alveolar macrophages.
- Ozone exposure stimulates DNA synthesis and proliferation of alveolar macrophages.
- The observed increase in smaller alveolar macrophages suggests a response involving cell division or recruitment.