Response of neuroendocrine cells and splenic macrophages to tumor development in the colon

Introduction. High cancer incidence requires finding new ways for comprehensive studying car-cinogenesis. Therefore, it is crucial to understand immune organ cell response and cell interaction in tumor development. The aim of the research was to study Synaptophysin+-, CD68+-cells, and biogenic amines in rat spleens during tumor development in the colon during dysplasia stages and adenocarcinoma formation. Materials and methods. Spleen histological slides of 110 mature male rats were studied 1 and 4 months after 1,2-dimethylhydrazine carcinogen administration using immunohistochemical, morphometric, and luminescent histochemical methods. Results. We found imbalanced production of biogenic amines (serotonin, histamine, and catecholamines) in the spleen and, therefore, a decrease in the cellular activity of the germinal centers of the lymphoid nodules. We also observed activation of periarteriolar lymphoid sheath (PALS) and red pulp in rats with precancerous colon lesions (1 month after carcinogen administration). At the same time, there was an increase in the number of CD68+ macrophages and Synaptophysin+ cells in the red pulp. In animals with adenocarcinoma (4 months after carcinogen introduction), the level of catecholamines in the luminescent granular cells of the PALS and the functional activity of these cells increased significantly. Simultaneously, the number of macrophages decreased in all the studied spleen compartments. Amid the decreased level of all biogenic amines in the red pulp, the quantity of Synaptophysin+ cells grew even more. Conclusion. The cells of all spleen compartments react to colon carcinogenesis, with reactivity of PALS cells and the red pulp being the most pronounced. The population of spleen macrophages undergoes rapid changes: their number increases in the red pulp in animals with precancerous lesions, while it decreases in all the splenic structures of rats with adenocarcinoma. Synaptophysin+ neuroendocrine cells of the red pulp play an important role in the reaction of the spleen to tumor development, and the number of these cells rises over time. Biogenic amines participate in the interaction of spleen cells with each other and with tumor-associated cells. Keywords: spleen, biogenic amines, neuroendocrine cells, synaptophysin, carcinogenesis