Improving the outcome of septic shock in children

Human IgG but not IgM antibodies can protect mice from the challenge with live O6 Escherichia coli

We evaluated the ability of human anti-lipopolysaccharide (LPS) O6 immunoglobulin G (IgG) and IgM antibodies to protect mice challenged with Escherichia coli serotype O6:K2ac. Purified whole IgG, commercial gammaglobulin, whole IgM-effluent, pool of normal human serum (NHS), agammaglobulinaemic serum (test groups) or phosphate-buffered saline (control group) was injected into adult male 18 h before a challenge with viable O6 E. coli. The mortality rate was assessed over a period of 72 h. To determine the opsonic and phagocytic activity of the antibody isotypes, we incubated peritoneal macrophages from the control and test groups collected at different times after challenge with the live bacteria with acridine orange for fluorescent analysis. Tumour necrosis factor (TNF)-alpha and interleukin (IL)-6 were quantified in serum of both the test and control groups. All mice that received commercial gammaglobulin or NHS survived. Purified whole IgG (containing 1.1 mg/l of anti-LPS O6 IgG antibodies) protected 87.5% of the animals tested in this experiment, while whole IgM-enriched effluent with 1.5 mg/l of anti-LPS O6 IgM antibodies protected only 12.5%. The agamma serum showed no protective capacity compared with PBS (serving as control). The minimal concentration of anti-LPS O6 IgG antibodies able to protect 50% of animals was 0.137 mg/l of purified whole IgG. Whole IgM-enriched effluent showed no protective capacity independently of the concentration tested (0.048-17.0 mg/l of anti-LPS O6 IgM antibodies). Fluorescent analysis of peritoneal macrophages from animals pretreated with purified whole IgG showed no bacteria at 8 h after the challenge. By contrast, whole IgM effluent showed an increasing number of live bacteria at the same time. Mice that had received whole IgM effluent (1.5 mg/l of anti-LPS O6 IgM antibodies) before the challenge with LPS O6 presented 20.5 microg/l of IL-6 and 1.5 microg/l of TNF-alpha. Serum from animals pretreated with purified IgG did not present any detectable pro-inflammatory cytokine. Our findings suggest that IgG but not IgM antibodies protect animals from a challenge with E. coli O6 serotype.

Tumor necrosis factor-alpha-induced caspase activation mediates endotoxin-related cardiac dysfunction

OBJECTIVE

Sepsis-induced cardiac dysfunction is a serious clinical syndrome characterized by hypotension, decreased systemic vascular resistance, and elevated cardiac index. Although cytokines such as tumor necrosis factor (TNF)-alpha have been shown to play a significant role early in this response, the downstream effects of TNF-alpha signaling on cardiac function, specifically its relationship to apoptosis, have not been fully elucidated.

DESIGN

Previous studies from our laboratory have identified endotoxin-induced apoptosis in cardiac cells in vitro. To further determine the role of lipopolysaccharide-induced apoptosis in vivo, mice were injected intraperitoneally with lipopolysaccharide (4 mg/kg), and cardiac apoptosis was detected and inhibited using a broad-spectrum caspase inhibitor.

SETTING

University research laboratory.

SUBJECTS

Adult male wild-type (B6:129PF1/J) and TNF receptor 1/receptor 2 (TNFR-1/2) knockout mice (B6;129S-Tnfrsf1aTnfrsf1b).

INTERVENTIONS

We sought to determine the dependence of cardiac apoptosis on TNF-alpha signaling and determine the physiologic role of caspase activation on lipopolysaccharide-induced cardiac dysfunction.

MEASUREMENTS AND MAIN RESULTS

Cardiac apoptosis was determined at baseline and at 2, 4, 8, and 24 hrs by detection of capase-3 and -8 activity, cytoplasmic levels of Bax/Bcl-2, cleaved caspase-3 immunohistochemistry, and terminal deoxynucleotidyl transferase UTP nick-end labeling (TUNEL) staining of histologic sections in wild-type and TNFR-1/2 knockout mice. To determine the role of caspase activation in lipopolysaccharide-induced cardiac dysfunction, a broad-spectrum caspase inhibitor Z-Val-Ala-Asp (ome)-FMK (sad) was given, and cardiac function was determined in isolated beating hearts (Langendorff preparation). Our experiments determined that caspase-3-dependent apoptosis was active in cardiac tissue by 2 hrs and that this activation was completely mediated by TNFR-1/2. The Bax/Bcl-2 ratios supported the finding and time course of apoptosis, whereas TUNEL staining of cardiac tissue sections identified sporadic apoptotic ventricular cells. The administration of zVAD significantly inhibited myocardial caspase-3 activity and preserved cardiac physiologic function (Langendorff preparation).

CONCLUSIONS

Endotoxin induces a TNF-alpha-dependent apoptotic cascade in the myocardium, which contributes to the development of cardiac dysfunction.

Procalcitonin, C-reactive protein, and endotoxin after bone marrow transplantation: identification of children at high risk of morbidity and mortality from sepsis

We prospectively evaluated the capacity of serum procalcitonin (PCT), compared with serum levels of C-reactive protein (CRP) and endotoxin, to identify children at high risk for mortality from sepsis after BMT. Of 47 pediatric bone marrow transplantation patients studied, 22 had an uneventful course post-transplant (Group 1), 17 survived at least one septic event (Group 2), and eight died from multiorgan failure (MOF) following septic shock (Group 3). Median concentrations of PCT over the course of the study were 1.3, 15.2, and 102.8 ng/ml, respectively, in each of the three groups (P<0.002 for each comparison). Median concentrations of CRP were 91, 213, and 260 mg/l, respectively (P<0.001 for Group 1 vs Group 2 and Group 3; P=NS for Group 2 vs Group 3). Median concentrations of endotoxin were 0.21, 0.30, and 0.93 U/l, respectively (P=NS for each comparison). Median concentrations of PCT, in contrast to serum CRP and endotoxin, correlated with the severity of sepsis (8.2 ng/ml in 'sepsis' and 22.3 ng/ml in 'severe sepsis', P=0.028) and provided useful prognostic information during septic episodes.