Expression of NO‐synthase in cells of foreign‐body and BCG‐induced granulomata in mice: influence of L‐NAME on the evolution of the lesion

Abstract

The microbicidal activity of macrophages in an inflammatory milieu has been related to the production of a large number of cytokins and intermediary metabolites of oxygen and nitrogen among them, nitric oxide (NO). Considering that granulomatous inflammation is predominantly composed of macrophages and epithelioid cells, we decided to investigate the participation of NO in this peculiar type of inflammation. Two models were used: glass cover slip implantation into the subcutaneous tissue of mice and, the inoculation of live bacillus Calmette-Guérin (BCG) into the footpad of the animals. Using a histochemical method for the detection of NO synthase and of the concentration of citrulin metabolized by cells obtained from cover slips implanted on different time intervals or BCG-activated peritoneal cells, it was possible to demonstrate that epithelioid cells do not produce NO. Cells from granuloma induced by BCG inoculation express NO synthase, with different degrees of reactivity with a higher intensity in the cytoplasm of cells located in the edge of the lesions. The expression of NO synthase in the cytoplasm of these cells decreases with the age of the lesions. It could also be demonstrated that in mice treated with l-name, an inhibitor of NO metabolism, the lesions induced by BCG lost the granulomatous architecture, were necrotic, and had a significant increase in the bacillary load of the lesion. These data allow us to conclude that NO production by macrophages is a determining factor in the organization of the granulomatous lesion and that it also controls the bacterial load in BCG-induced lesions in mice.

Lethal Mycobacterium Bovis Bacillus Calmette Guérin Infection in Nitric Oxide Synthase 2-Deficient Mice: Cell-Mediated Immunity Requires Nitric Oxide Synthase 2

“…Although the requirement of NO for the control of M. tuberculosis infection has been demonstrated, the roles of NOS2, NO, and RNI in cellular immunity against M. bovis BCG and granuloma formation have not been investigated. Differential susceptibility of mouse strain to BCG infection has been correlated to distinct activation of NOS2 and NO production by macrophages (Barrera et al, 1994;Yoshida et al, 1995) and an inhibitor role of NO in granuloma organization has been reported (Kreuger et al, 1998).…”

Recombinant interleukin-4-treated macrophages, epithelioid cell surrogates, harbor and arrest Mycobacterium avium multiplication in vitro

“…We have previously shown that rIL-4 induces morphological and functional modifications on macrophages that overlap features of ECs found in granulomas [14], such as the presence of interdigitations that maintain a close contact between the cells, downregulation of Fcg receptor-mediated phagocytosis [15] and reduction in NO release [16]. Additionally, increased expression of MHC class II molecules has been found on rIL-4-treated macrophages when compared with untreated cells.…”

Analysis of Nitric Oxide Synthase and Nitrotyrosine Expression in Human Pulmonary Tuberculosis

“…These studies, together with in vitro investigations showing that human macrophages can kill M. tuberculosis via NO (8), suggest that NO may, directly or indirectly, serve an antimycobacterial role in human TB. Although the precise role of NO in TB has not been clearly defined, NO has been found to be essential in granuloma formation of infectious (11)(12)(13)(14)(15)(16) and noninfectious (17) animal models. However, morphologic characterization of NO and NOS isoforms in granulomatous lesions of human pulmonary TB has not been previously reported.…”