Erythropoiesis Suppression Is Associated with Anthrax Lethal Toxin-Mediated Pathogenic Progression

Abstract

Anthrax is a disease caused by the bacterium Bacillus anthracis, which results in high mortality in animals and humans. Although some of the mechanisms are already known such as asphyxia, extensive knowledge of molecular pathogenesis of this disease is deficient and remains to be further investigated. Lethal toxin (LT) is a major virulence factor of B. anthracis and a specific inhibitor/protease of mitogen-activated protein kinase kinases (MAPKKs). Anthrax LT causes lethality and induces certain anthrax-like symptoms, such as anemia and hypoxia, in experimental mice. Mitogen-activated protein kinases (MAPKs) are the downstream pathways of MAPKKs, and are important for erythropoiesis. This prompted us to hypothesize that anemia and hypoxia may in part be exacerbated by erythropoietic dysfunction. As revealed by colony-forming cell assays in this study, LT challenges significantly reduced mouse erythroid progenitor cells. In addition, in a proteolytic activity-dependent manner, LT suppressed cell survival and differentiation of cord blood CD34+-derived erythroblasts in vitro. Suppression of cell numbers and the percentage of erythroblasts in the bone marrow were detected in LT-challenged C57BL/6J mice. In contrast, erythropoiesis was provoked through treatments of erythropoietin, significantly ameliorating the anemia and reducing the mortality of LT-treated mice. These data suggested that suppressed erythropoiesis is part of the pathophysiology of LT-mediated intoxication. Because specific treatments to overcome LT-mediated pathogenesis are still lacking, these efforts may help the development of effective treatments against anthrax.

Erythrocytic Mobilization Enhanced by the Granulocyte Colony-Stimulating Factor Is Associated with Reduced Anthrax-Lethal-Toxin-Induced Mortality in Mice

“…Our previous report revealed that LT suppressed erythropoiesis in bone marrow [15]. Following similar approaches [15], [25], we used surface expression of CD71 and TER-119 to verify the maturation status of various bone marrow erythroblasts under the G-CSF treatments with or without anthrax LT challenges.…”

“…Our previous report revealed that LT suppressed erythropoiesis in bone marrow [15]. Following similar approaches [15], [25], we used surface expression of CD71 and TER-119 to verify the maturation status of various bone marrow erythroblasts under the G-CSF treatments with or without anthrax LT challenges. Although we found that G-CSF treatment rescued LT-induced erythrocytopenia (please see the following section), G-CSF pre-treatments could not overcome LT-mediated suppression on the cell numbers of both total erythroblast and individual subpopulations of erythroblast (R1 to R4 populations) (Figure 2C and 2D).…”

Acquired coagulant factor VIII deficiency induced byBacillus anthracislethal toxin in mice

“…4,5,14,16,52,55,56 For cell and animal studies, high-performance liquid chromatography (HPLC)-purified LF and PA were reconstituted as LT in a ratio of 1:5, which resembles the ratio of PA and LF in the culture supernatants of B. anthracis. The LPS contamination was monitored using a Limulus Amoebocyte Lysate QCL -1000 kit (Lonza, Walkersville, MD, USA).…”

Endothelial Cell Sensitization by Death Receptor Fractions of an Anti–Dengue Nonstructural Protein 1 Antibody Induced Plasma Leakage, Coagulopathy, and Mortality in Mice

“…The Abs used for ELISA (detecting soluble thrombomodulin) and flow cytometry (detecting endothelial surface TRAIL-R expression) analyses were anti-thrombomodulin Ig (Santa Cruz Biotechnology) and anti-TRAIL-R (1-4) Ig (R&D Systems), respectively. The endothelial cells were challenged with (+DENV) (multiplicity of infection [MOI] of 0.2, subcytotoxic) or without DENV (2DENV) in combination with or without preimmune Ig, anti-NS1 Ig, anti-NS1-DR4 Ig treatments (20 mg/ml, subcytotoxic; 24 and 48 h), and then the surface expression levels of TRAIL-Rs were analyzed by flow cytometry (FACSCalibur; BD Biosciences, San Jose, CA) (29)(30)(31). Fluorescence-labeled isotype-matched control Igs were used to determine the background staining levels in the flow cytometry analyses.…”