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Cui, Xizhong, Mahtab Moayeri, Yan Li, Xuemei Li, Michael Haley, Yvonne Fitz, Rosaly Correa-Araujo, Steven M. Banks, Stephen H. Leppla, and Peter Q. Eichacker. Lethality during continuous anthrax lethal toxin infusion is associated with circulatory shock but not inflammatory cytokine or nitric oxide release in rats. Am J Physiol Regul Integr Comp Physiol 286:R699-R709, 2004. First published January 8, 2004; 10.1152/ajpregu.00593.2003.--Although circulatory shock related to lethal toxin (LeTx) may play a primary role in lethality due to Bacillus anthracis infection, its mechanisms are unclear. We investigated whether LeTx-induced shock is associated with inflammatory cytokine and nitric oxide (NO) release. Sprague-Dawley rats with central venous and arterial catheters received 24-h infusions of LeTx (lethal factor 100 [micro]g/kg; protective antigen 200 [micro]g/kg) that produced death beginning at 9 h and a 7-day mortality rate of 53%. By 9 h, mean arterial blood pressure, heart rate, pH, and base excess were decreased and lactate and hemoglobin levels were increased in LeTx nonsurvivors compared with LeTx survivors and controls (diluent only) (P [less than or equal to] 0.05 for each comparing the 3 groups). Despite these changes, arterial oxygen and circulating leukocytes and platelets were not decreased and TNF-[alpha], IL- 1 [beta], IL-6, and IL- 10 levels were not increased comparing either LeTx nonsurvivors or survivors to controls. Nitrate/nitrite levels and tissue histology also did not differ comparing LeTx animals and controls. In additional experiments, although 24-h infusions of LeTx and Esherichia coli LPS produced similar mortality rates (54 and 56%, respectively) and times to death (13.2 [+ or -] 0.8 vs. 11.0 [+ or -] 1.7 h, respectively) compared with controls, only LPS reduced circulating leukocytes, platelets, and IL-2 levels and increased TNF-[alpha], IL-1[alpha] and -1 [beta], IL-6, IL-10, interferon-[gamma], granulocyte macrophage-colony stimulating factor, RANTES, migratory inhibitory protein-1[alpha], -2, and -3, and monocyte chemotactic protein-l, as well as nitrate/nitrite levels (all P [less than or equal to] 0.05 for the effects of LPS). Thus, in contrast to LPS, excessive inflammatory cytokine and NO release does not appear to contribute to the circulatory shock and lethality occurring with LeTx in this rat model. Although therapies to modulate these host mediators may be applicable for shock caused by LPS or other bacterial toxins, they may not with LeTx. Bacillus anthracis; sepsis; pathogenesis; model

Although lethal toxin (LT) and edema toxin (ET) contribute to lethality during Bacillus anthracis infection, whether they increase vascular permeability and the extravascular fluid accumulation characterizing this infection is unclear. We employed an isolated perfused Sprague-Dawley rat lung model to investigate LT and ET effects on pulmonary vascular permeability. Lungs (n ≥ 6 per experimental group) were isolated, ventilated, suspended from a force transducer, and perfused. Lung weight and pulmonary artery (Ppa) and left atrial pressures were measured over 4 h, after which pulmonary capillary filtration coefficients (Kf.c) and lung wet-to-dry weight ratios (W/D) were determined. When compared with controls, LT increased Ppa over 4 h and Kf.c and W/D at 4 h (P < 0.0001). ET decreased Ppa in a significant trend (P = 0.09) but did not significantly alter Kf.c or W/D (P ≥ 0.29). Edema toxin actually blocked LT increases in Ppa but not LT increases in Kf.c and W/D. When Ppa was maintained at control levels, LT still increased Kf.c and W/D (P ≤ 0.004). Increasing the dose of each toxin five times significantly increased and a toxin-directed monoclonal antibody decreased the effects of each toxin (P ≤ 0.05). Two rho-kinase inhibitors (GSK269962 and Y27632) decreased LT increases in P pa (P ≤ 0.02) but actually increased Kf.c and W/D in LT and control lungs (P ≤ 0.05). A vascular endothelial growth factor receptor inhibitor (ZM323881) had no significant effect (P ≥ 0.63) with LT. Thus, LT but not ET can increase pulmonary vascular permeability independent of increased Ppa and could contribute to pulmonary fluid accumulation during anthrax infection. However, pulmonary vascular dilation with ET could disrupt protective hypoxic vasoconstriction. NEW & NOTEWORTHY The most important findings from the present study are that Bacillus anthracis lethal toxin increases pulmonary artery pressure and pulmonary permeability independently in the isolated rat lung, whereas edema toxin decreases the former and does not increase permeability. Each effect could be a basis for organ dysfunction in patients with this lethal infection. These findings further support the need for adjunctive therapies that limit the effects of both toxins during infection. [ABSTRACT FROM AUTHOR]

We investigated whether decreases in circulating polymorphonuclear neutrophils (PMN) during lethal Escherichia coli (E. coli) sepsis in canines are related to insufficient host granulocyte colony-stimulating factor (G-CSF). Two-year-old purpose-bred beagles had intraperitoneal E. coli-infected or -noninfected fibrin clots surgically placed. By 10 to 12 h following clot, both infected survivors and nonsurvivors had marked increases (P = 0.001) in serum G-CSF levels (mean peak G-CSF ng/ml [+ or -] SE, 1,931 [+ or -] 364 and 2,779 [+ or -] 681, respectively) compared with noninfected controls (134 [+ or -] 79), which decreased at 24 to 48 h. Despite increases in G-CSF, infected clot placement caused delayed (P = 0.06) increases in PMN (mean [+ or -] SE change from baseline in cells x [10.sup.3]/[mm.sup.3] at 24 and 48 h) in survivors (+3.9 [+ or -] 3.9 and +13.8 [+ or -] 3.6) compared with noninfected controls (+13.1 [+ or -] 2.8 and +9.1 [+ or -] 2.5). Furthermore, infected nonsurvivors had decreases in PMN (-1.4 [+ or -] 1.0 and -1.1 [+ or -] 2.3, P = 0.006 compared with the other groups). We next investigated whether administration of G-CSF immediately after clot placement and continued for 96 h to produce more rapid and prolonged high levels of G-CSF after infection would alter PMN levels. Although G-CSF caused large increases in PMN compared with control protein from 2 to 48 h following clot in noninfected controls, it caused much smaller increases in infected survivors and decreases in infected nonsurvivors (P = 0.03 for the ordered effect of G-CSF comparing the three groups). Thus insufficient host G-CSF is unlikely the cause of decreased circulating PMN in this canine model of sepsis. Other factors associated with sepsis either alone or in combination with G-CSF itself may reduce increases or cause decreases in circulating PMN. granulocyte colony-stimulating factor; infection

We showed previously that Bacillus anthracis edema toxin (ET), comprised of protective antigen (PA) and edema factor (EF), inhibits phenylephrine (PE)-induced contraction in rat aortic rings and these effects are diminished in endothelial-denuded rings. Therefore, employing rat aortic ring and in vivo models, we tested the hypothesis that nitric oxide (NO) contributes to ET's arterial effects. Compared with rings challenged with PA alone, ET (PA + EF) reduced PE-stimulated maximal contractile force (MCF) and increased the PE concentration producing 50% MCF (EC50) (P < 0.0001). Compared with placebo, L-nitro-arginine methyl-ester (L-NAME), an NO synthase (NOS) inhibitor, reduced ET's effects on MCF and EC50 in patterns that approached or were significant (P = 0.06 and 0.03, respectively). In animals challenged with 24-h ET infusions, L-NAME (0.5 or 1.0 mg·kg-1·h-1) coadministration increased survival to 17 of 28 animals (60.7%) compared with 4 of 27 (14.8%) given placebo (P = 0.01). Animals receiving L-NAME but no ET all survived. Compared with PBS challenge, ET increased NO levels at 24 h and L-NAME decreased these increases (P < 0.0001). ET infusion decreased mean arterial blood pressure (MAP) in placebo and L-NAME-treated animals (P < 0.0001) but L-NAME reduced decreases in MAP with ET from 9 to 24 h (P = 0.03 for the time interaction). S-methyl-Lthiocitrulline, a selective neuronal NOS inhibitor, had effects in rings and, at a high dose in vivo models, comparable to L-NAME, whereas N'-[3-(aminomethyl)benzyl]-acetimidamide, a selective inducible NOS inhibitor, did not. NO production contributes to ET's arterial relaxant, hypotensive, and lethal effects in the rat. [ABSTRACT FROM AUTHOR]