P121: Morphological and functional changes in the population of alveolar macrophages of mice with induced carcinogenesis in the lung

Abstract

Background Alveolar macrophages (AM) are pulmonary residents of the bone marrow-derived mononuclear phagocyte system that play a critical role in several diverse lung functions and in lung host defense. The role of AM in lung cancer is multifaceted. AM secretion of proinflammatory cytokines has been found to enhance antitumor functions, cytostasis and cytotoxicity. AM have also demonstrated to have protumor functions resulting in tumor progression. Materials and methods 24-week-old male A/f mice were kept in plastic cages under standard laboratory conditions and received food and water ad libitum. Animals were randomly assigned to the following experimental groups: I – control, II – radiation only, III – sulphur dioxide only, IV – sulphur dioxide + radiation. Animals were subjected to total irradiation at dose 1.0 Gy (dose density of 16.6 cGy/min, using a 60Co gamma equipment). After irradiation mice were inhaled air with sulphur dioxide (20 mg/m 3 for 1 h) in separate exposure chamber. At the 20th week of experiment the 20 mice per each group were subjected to autopsy. Excised lungs were fixed in neutral buffered 10% formalin. To obtain an index of tumor incidence, the percentage of tumor – bearing mice per total number of mice in each group was calculated. Tumor multiplicity was defined as the average number of tumors per mice, obtained by dividing the total number of tumors by the total number of mice per group, including non-tumor bearing animals. Bronchoalveolar lavage (BAL) of lungs was performed on 6 mice (animals were anesthetized by an ip injection of sodium thiopental) from each study group at the 1, 7, 15 and 30 days after irradiation and SO2 inhalation. Total cells of BAL were counted using hemocytometer chamber and an optical microscope with a 400× zoom. BAL differential cell (macrophages, lymphocytes, eosinophiles and neutrophils) counts were performed on slides (Romanowsky stain). Phagocytic activity of AM was counted on slides. AM morphometric study was done by measuring the area of each cell (square of cell) and the area of nuclear of each cell (square of nuclear) with use of the original image analyzer computer system. Results Results of the combined effects of radiation and inhalation of sulfur dioxide showed the growth of tumor quantity in the lung: the frequency of adenomas/mouse was more than 42% higher than that of control group. Synergism coefficient was 1.1 in this case. Irradiation at a dose of 1.0 Gy modifies the reaction of free cells of lung on the action of sulfur dioxide, which is manifested in the change of the number of cells in the BAL fluid, the phagocytic activity of the AM, as well as of the changes the morphometric parameters of their cells. Conclusion Thus, if the amount of radiation exposure of BAL cells was significantly reduced by the 1st and 7th days, and after inhalation of sulfur dioxide – tended to increase, then the combined action on the 7th day it was almost half the theoretical (hypothetical) the sum of the separate effects of the studied factors. Exposure to sulfur dioxide significantly slowed the activation of cell count. It was found, that after combined action of the investigated factors the morphological characteristics of macrophages (reducing the square of cells and their nuclei) have changed (7th and 15th day). The absorption activity of phagocytes was significantly reduced (7 day).