Use of novel therapeutic agents for the treatment of serious infection

Digest

Dr Hiram C. Polk Jr has this month summarized the best of the October to December 1993 issues of The American Journal of Surgery, of which he is Editor. Professor John Farndon's reciprocal digest appears in the March issue of the American journal.

Immunomodulation of Bu-Zhong-Yi-Qi-Tang on in vitro granulocyte colony-stimulating-factor and tumor necrosis factor-alpha production by peripheral blood mononuclear cells

Bu-Zhong-Yi-Qi-Tang (BZYQT) is a Chinese medicine, and has been used for the treatment of hepatocellular carcinoma (HCC) patients. At present, we still do not fully understand the effects of BZYQT on the cellular physiology. Present in vitro study demonstrated that BZYQT is capable of increasing granulocyte colony-stimulating-factor (G-CSF) and tumor necrosis factor-alpha (TNF-alpha) production by peripheral blood mononuclear cells (PBMC) in healthy volunteers and patients with HCC. The productions of G-CSF and TNF-alpha by PBMC of volunteers were significantly stimulated by more than 125 microg/ml of BZYQT. G-CSF levels stimulated by PBMC of healthy volunteers were higher than in PBMC of the HCC patients when more than 625 microg/ml of BZYQT was administrated. The reason may be due to the impaired immunologic reactivity of mononuclear cells in HCC patients. However, the production levels of TNF-alpha in HCC patients can be stimulated to levels as high as those in healthy volunteers. When adding high concentration (3.125 mg/ml) of BZYQT to the cultured PBMC, the increments of G-CSF and TNF-alpha production decreased although there were no obvious changes in the number of metabolic active PBMC changed. TNF-alpha andG-CSF are known to play important roles in the biological defensive mechanism. These findings show that BZYQT is a unique formula for the stimulation of PBMC to produce G-CSF and TNF-alpha. Administration of BZYQT may be beneficial for patients with HCC to modulate these cytokines.

Role of platelet-activating factor antagonism in posthemorrhage septic shock in pigs

OBJECTIVES

To study the role of platelet-activating factor (PAF) antagonism in posthemorrhage septic shock in pigs.

DESIGN

Experimental study.

MATERIALS AND METHODS

Twelve anesthetized pigs were bled, kept with a mean arterial pressure of 30 mm Hg for 30 minutes, and then resuscitated with 50 mL/kg of isotonic saline. A continuous infusion of Escherichia coli endotoxin 36 micrograms/kg/hour was given intravenously for 3.5 hours starting 30 minutes after resuscitation. The animals were divided into two groups of six each. One group received I mg/kg of BB-882 (a potent specific PAF receptor antagonist) as a bolus during resuscitation, followed by a continuous infusion of BB-882 1 mg/kg/hour. The other group received vehicle alone.

MEASUREMENTS AND MAIN RESULTS

The measured variables were blood temperature, heart rate, intravascular pressures, cardiac output, systemic and pulmonary vascular resistance, lung-thorax compliance, blood gases, hemoglobin oxygen saturation, packed cell volume and blood sugar and serum lactic acid concentrations. The group treated with BB-882 had significantly higher intracardiac pressures and cardiac output, and had less increase in systemic vascular resistance. The BB-882 group had significantly less lactic acidemia than the control group (p < 0.05, analysis of variance appropriate for repeated measurement design). BB-882 had no effect on endotoxin-induced hypoxia or reduced lung-thorax compliance.

CONCLUSIONS

PAF antagonism reduced the increase in systemic vascular resistance, improved cardiac output, and reduced lactic acidemia in posthemorrhage septic shock in pigs, but it did not improve hypoxia or reduced lung-thorax compliance.

Experimental gut-derived endotoxaemia and bacteraemia are reduced by systemic administration of monoclonal anti-LPS antibodies

This study aimed to investigate the effects and mechanisms of action of systemic administration of monoclonal antibodies, anti-endotoxin (HA-1A), in an animal model of gut-origin sepsis. In the first experiment, Balb/c mice were transfused with allogeneic blood (C3H/HeJ mice). Five days post-transfusion the animals were gavaged with 1 x 10(9) Escherichia coli and randomized into three groups (n = 22 each) to receive a sham burn (SB group) or a 20 per cent TBSA thermal injury, immediately followed by the systemic administration of monoclonal antibodies (3 mg/kg) (HA-1A group) or aliquots of sterile saline (Control group). The animal survival rate was observed for 10 days postburn. In the second experiment transfusion and burn injury were reproduced but the mice (n = 8/group) were gavaged with 10(9) E.coli labelled with 111indium oxine. Four hours after the burn the mesenteric lymph nodes, liver, lungs and blood were harvested to determine plasma endotoxin levels and the magnitude of translocation of labelled bacteria measured by the residual radioactivity in the organs. Circulating endotoxin levels were determined by limulus assay. The mortality rate of the HA-1A group (9 per cent) was similar to the SB group (0 per cent) and significantly lower than the control group (59 per cent) (P < 0.05). Both plasma endotoxin levels and degree of bacterial translocation in all extraintestinal tissues were significantly lower (by approximately 50 per cent) in the HA-1A group than in the control group (P < 0.05). Systemic administration of HA-1A exerts a beneficial effect by reducing the circulating levels of endotoxin and by increasing the gut barrier function to translocating microorganisms.

Cellular functions during activation and damage by pathogens: immunogold studies of the interaction of bacterial endotoxins with target cells

Bacterial endotoxins (lipopolysaccharides or LPS) are active components of Gram-negative bacteria that act on numerous cellular functions through the processes of cell activation and damage. The molecular mechanisms involved in the "endotoxic phenomenon" are not defined yet, although extensive studies have been carried out. Immunogold and electron microscopy (EM) have contributed to identify the primary target cells of endotoxins and the subcellular systems that receive the direct action of these bacterial agents. Here, we review our studies on immunogold detection of endotoxins in cellular and subcellular systems. The analysis of the interaction between endotoxins and cells was focussed on the following aspects: (1) morphological characteristics of the LPS aqueous suspensions used in experimental work; (2) binding of endotoxins to the plasma membrane of type II pneumocytes and alveolar macrophages (two of their cellular targets), and influence of the state of aggregation of the LPS; (3) movement and distribution of endotoxins inside the cell, from the plasma membrane to the nucleoplasm; and (4) interaction of LPS with microtubules and its effects on the integrity of the microtubular network. These approaches provide information at the molecular level as well as data for the establishment of physiological models of endotoxicity.

Endogenously opsonized particles divert prostanoid action from lethal to protective in models of experimental endotoxemia

We report that, in rats, the lethal consequences of high-dose endotoxin challenge are exacerbated by the intravascular administration of prostaglandin E1 but attenuated by the intravascular administration of endocytosable particles. This protection is mediated by opsonins. Nonopsonizable particles were unable to provide protection unless first pseudoopsonized with antibody directed against the CR3 (CD11b/CD18) phagocyte receptor. We show that endogenously opsonized particles can act in concert with prostaglandin E1 (putatively by elevation of neutrophil intracellular cAMP and the resultant downregulation of CR3) to completely rescue animals from the lethal late-stage sequelae of experimental endotoxemia. These data illustrate that the interaction of particles with cellular receptors can transform the overall systemic response to prostaglandin E1 from pro- to antiinflammatory. This suggests a role for multiple receptor engagement events in defining the systemic prostaglandin response and offers a rationale for developing new therapeutic modalities in the treatment of sepsis and other inflammatory diseases.