Characterization of Lymphoid Cells in the Lungs of Mice Following Oral Administration of 4NQO

Abstract

IntroductionChronic inflammation is a risk factor in development and progression of lung cancer. The carcinogen 4‐nitroquinoline‐1‐oxide (4NQO) induces oral cancer in mice and mimics the effects of tobacco use. Here we investigated whether oral administration of 4NQO could cause injury and inflammatory changes in the lung. We also examined the possible effect of sex and a high or low in saturated fat diet on lung inflammation as manifested by the presence of lymphoid cells. The number and pattern of distribution of T lymphocytes, macrophages, and neutrophils were evaluated in lung tissues. We hypothesized that treatment with 4NQO would induce inflammation and cancer in lungs, and that sex and dietary fat content would affect 4NQO‐induced lung pathology.Materials and methodsMale and female C57Bl/6 mice (n=36 each gender, 5 weeks old), were divided into low fat (10kcal% fat; LF) and high fat (60 kcal% fat; HF) diet groups. After one week mice in the experimental groups began a treatment with 50μg/mL of 4NQO in 1.25% propylene glycol (PG) in water (4NQO group). Mice in control groups were provided with water or PG in water. After 17 weeks of treatment all mice were given water alone for 6 weeks prior to euthanasia. Lung tissues were harvested, fixed in formalin, and processed for histological evaluation. Lung tissue sections were stained with antibodies against CD3 to detect T lymphocytes, CD68 to detect macrophages, and Ly6‐g to detect neutrophils. Positively‐stained cells were counted in 4 randomly chosen areas at 10× magnification using ImageJ software. Analysis was done using GraphPad Prism 7.0. All animal work was in compliance with the regulations of IACUC at Midwestern University, Downers Grove, IL.ResultsLymphoid cells were present in the control lung tissue, however, 4NQO treatment resulted in a significant increase in all three cell populations (T lymphocytes 194 vs. 283, macrophages 136 vs. 195, and neutrophils 102 vs. 266 cells/per mm2, p<0.002). Neutrophils and macrophages were primarily located in lung parenchyma, while T cells were located both in parenchyma and lymphoid nodules. In 4NQO mice the number of neutrophils and macrophages, but not T cells, was significantly higher (p<0.001) in males than in females (354 vs. 179, 250 vs. 138, and 177 vs. 288 cells/per mm2, respectively). HF diet resulted in significantly more neutrophils in the 4NQO male lungs (324 vs. 100 cells/mm2, p<0.001), but had no effect on the number of macrophages and T cells.ConclusionOral administration of 4NQO induced lung inflammation as manifested by a significant increase in the presence of lymphoid cells. The inflammatory responses in the lungs may be affected by dietary fat and sex. This mouse model of oral cancer that was developed to mimic the effects of smoking may be extended to serve as a model to study the effects of tobacco and diet on the lungs.Support or Funding InformationThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.