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Enhanced alveolar monocytic phagocyte (macrophage) proliferation in tobacco and marijuana smokers
R G Barbers1, M J Evans, H Gong
1Department of Medicine, University of California-Los Angeles School of Medicine.
Abstract:
We tested the hypothesis that enhanced cell division accounted for the augmented numbers of monocytic phagocytes with characteristics attributed to alveolar macrophages (AM) found in the lungs of habitual tobacco (T) and marijuana (M) smokers. The monocytic phagocytes, that is, alveolar macrophages, were obtained by bronchoalveolar lavage (BAL) from 12 nonsmoking subjects; 10 subjects who smoked T only (TS); 13 subjects who smoked M only (MS); and 6 smokers of both T and M (MTS). The replication of these cells was determined by measuring the incorporation of [3H]thymidine into the DNA of dividing cells and visually counting 2,000 cells on autoradiographically prepared cytocentrifuge cell preparations. This study demonstrated that the number of [3H]thymidine-labeled monocytic phagocytes with characteristics of alveolar macrophages from either TS or MS have a higher proliferative index compared to cells (macrophages) from nonsmokers, p less than 0.05 by one-way ANOVA. The total number of BAL macrophages that are in mitosis in TS (17.90 +/- 4.50 labeled AM x 10(3)/ml) or MTS (10.50 +/- 4.20 labeled AM x 10(3)/ml) are 18- and 10-fold greater, respectively, than the number obtained from nonsmokers (1.01 +/- 0.18 labeled AM x 10(3)/ml). Interestingly, the number of [3H]thymidine-labeled macrophages from MS (2.90 +/- 0.66 labeled AM x 10(3)/ml) are also greater than the number obtained from nonsmokers, although this is not statistically significant. The stimulus augmenting alveolar macrophage replication is as yet unknown but may likely be found in the T or M smoke.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Tobacco and marijuana smoking increase the proliferation of lung macrophages. This study found higher cell division rates in macrophages from smokers compared to non-smokers, suggesting smoking stimulates these immune cells.
Area of Science:
- Pulmonary immunology
- Cell biology
- Toxicology
Background:
- Alveolar macrophages (AM) are key immune cells in the lungs.
- Habitual smoking of tobacco (T) and marijuana (M) is associated with increased numbers of lung phagocytes.
- Enhanced cell division is hypothesized to contribute to increased AM populations in smokers.
Purpose of the Study:
- To test the hypothesis that increased cell division (replication) accounts for the higher numbers of alveolar macrophages (AM) in smokers.
- To compare the proliferative activity of AM from non-smokers, tobacco-only smokers (TS), marijuana-only smokers (MS), and dual tobacco/marijuana smokers (MTS).
Main Methods:
- Alveolar macrophages (AM) were collected via bronchoalveolar lavage (BAL) from 4 groups: non-smokers, TS, MS, and MTS.
- Cell replication was quantified by measuring [3H]thymidine incorporation into cellular DNA.
- Cell proliferation was also assessed by visually counting mitotic cells in autoradiographically prepared samples.
Main Results:
- Smokers of tobacco (TS) and dual smokers (MTS) showed a significantly higher proliferative index of AM compared to non-smokers (p < 0.05).
- The number of mitotic AM in TS and MTS was 18-fold and 10-fold greater, respectively, than in non-smokers.
- While AM from marijuana-only smokers (MS) also showed increased proliferation, this finding was not statistically significant compared to non-smokers.
Conclusions:
- Enhanced cell division contributes to the increased number of alveolar macrophages observed in tobacco smokers.
- The specific component(s) in tobacco or marijuana smoke responsible for stimulating AM replication remain to be identified.
- These findings highlight the impact of smoking on lung immune cell dynamics and proliferation.