ABSTRACT
BACKGROUND: The role of myeloid-derived suppressor cells (MDSCs) in patients with severe tuberculosis who suffer from uncontrolled pulmonary inflammation caused by hypervirulent mycobacterial infection remains unclear. METHODS: This issue was addressed using C57BL/6 mice infected with highly virulent Mycobacterium bovis strain MP287/03. RESULTS: CD11b+GR1int population increased in the bone marrow, blood and lungs during advanced disease. Pulmonary CD11b+GR1int (Ly6GintLy6Cint) cells showed granularity similar to neutrophils and expressed immature myeloid cell markers. These immature neutrophils harbored intracellular bacilli and were preferentially located in the alveoli. T-cell suppression occurred concomitantly with CD11b+GR1int cell accumulation in the lungs. Furthermore, lung and bone marrow GR1+ cells suppressed both T-cell proliferation and interferon γ production in vitro. Anti-GR1 therapy given when MDSCs infiltrated the lungs prevented expansion and fusion of primary pulmonary lesions and the development of intragranulomatous caseous necrosis, along with increased mouse survival and partial recovery of T-cell function. Lung bacterial load was reduced by anti-GR1 treatment, but mycobacteria released from the depleted cells proliferated extracellularly in the alveoli, forming cords and clumps. CONCLUSIONS: Granulocytic MDSCs massively infiltrate the lungs during infection with hypervirulent mycobacteria, promoting bacterial growth and the development of inflammatory and necrotic lesions, and are promising targets for host-directed therapies.
Subject(s)
Granulocytes , Lung/metabolism , Mycobacterium bovis , Myeloid-Derived Suppressor Cells , Tuberculosis , Animals , Antigens, Ly , Bone Marrow , CD11b Antigen , Cell Proliferation , Disease Models, Animal , Granulocytes/immunology , Immunomodulation , Lung/pathology , Mice , Mice, Inbred C57BL , Mycobacterium bovis/pathogenicity , Myeloid Cells , Myeloid-Derived Suppressor Cells/immunology , Myeloid-Derived Suppressor Cells/pathology , Neutrophils , Tuberculosis/pathologyABSTRACT
An excessive consumption of a high-fat diet (HFD) results in becoming overweight or obese, which triggers a chronic inflammatory condition that is associated with a high white blood cell count. Because of the potential for yerba maté (Ilex paraguariensis) (YM) to impact obesity, this study aimed to investigate the effects of YM consumption on the hematological response and on the production of interleukin (IL)-1α, IL-6, tumor necrosis factor (TNF)-α, and IL-10 by bone marrow cells from Wistar rats fed a HFD. Male Wistar rats were fed a control (CON) or HFD diet for twelve weeks. At the end of this period, the rats received YM (1 g/kg/day body weight) for 4 weeks. After euthanasia, hemograms and myelograms were evaluated, while the bone marrow cells were cultured in the presence or absence of lipopolysaccharide (LPS) to evaluate the production of IL-1α, IL-6, TNF-α, and IL-10. The consumption of YM reduced the body weight, the body adiposity, and the cholesterol levels in HFD-fed rats. Bone marrow cells from the HFD group produced more IL-1α, IL-6, and TNF-α, and less IL-10, when compared to cells from the control group, and YM consumption reduced the IL-1α, IL-6, and TNF-α production by the cells. However, cells from the HFD rats that were stimulated with LPS increased their IL-1α, IL-6, and TNF-α production, but YM consumption did not change this result. In summary, the consumption of YM affects the production of IL-1α, IL-6, and TNF-α by bone marrow cells, promotes weight loss, decreases the number of white blood cells, and significantly improves serum cholesterol level in HFD-fed rats. However, the bone marrow cells from the HFD+YM-fed rats challenged with LPS did not show improvement in the inflammatory response compared to the cells from animals fed only a HFD that were also challenged with LPS.
