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Endotoxin is a component of gram-negative bacteria that causes hematologic and immunologic changes through its induction of cytokines. Interleukin-1 receptor antagonist (IL-1Ra) is a naturally occurring inhibitor of IL-1 that competes with IL-1 for occupancy of cell-surface receptors but possesses no agonist activity. We investigated the ability of human recombinant IL-1Ra to block the effects of low-dose endotoxin. Fourteen healthy male volunteers between 18 and 30 years old were injected intravenously with 3 ng/kg Escherichia coli endotoxin. Concurrent with the injections, nine volunteers received a 3-hour continuous intravenous infusion of IL-1Ra. The other five subjects were given a 3-hour infusion of saline. Volunteers injected with endotoxin experienced a threefold increase in circulating neutrophils over baseline. This neutrophilia was significantly reduced by 48% in subjects administered endotoxin plus IL-1Ra (P = .0253). Ex vivo mitogen-induced peripheral blood mononuclear cell proliferation decreased by greater than 60% at 3 and 6 hours after endotoxin injection (P = .0053). This endotoxin-induced reduction in mitogen response was reversed in subjects coinjected with IL-1Ra (P = .0253). Endotoxin-induced symptoms, fever, and tachycardia were unaffected by IL-1Ra. IL-1 appears to be an important mediator in endotoxemia because some of its hematologic and immunomodulatory effects can be blocked by IL-1Ra.

When administered parenterally, endotoxin stimulates the synthesis of IL-1, TNF-alpha, and IL-6. However, this initial injection induces tolerance; a second injection of endotoxin results in lower levels of circulating cytokines. In our study, five healthy male volunteers between the ages of 18 and 30 were injected with Escherichia coli endotoxin. Four subjects received only saline. Immediately before the injection and 3, 6, and 24 h afterward, PBMC were isolated and stimulated in vitro with endotoxin, IL-1, or toxic shock syndrome toxin-1. Inasmuch as CD14+ monocytes are the primary source of the cytokines induced by these stimuli, results are expressed as cytokine production per 10(6) CD14+ cells. Six h after endotoxin injection, endotoxin-stimulated CD14+ cells synthesized 66% less IL-1 beta (p < 0.01), 47% less TNF-alpha (p < 0.001), 56% less IL-6 (p < 0.01), and 49% less IL-8 (p < 0.01) than cells obtained before the injection. This suppression was not specific for endotoxin; IL-1 beta-induced IL-1 alpha and TNF-alpha were reduced by 84% (p = 0.01) and 68% (p < 0.001), respectively. A decrease in cytokine synthesis was also observed using toxic shock syndrome toxin-1 as a stimulus: 57% for IL-1 beta (p = 0.06), 70% for TNF-alpha (p < 0.01), 56% for IL-6 (p < 0.05), and 71% for IL-8 (p = 0.001). When data were expressed as cytokine production per 10(6) PBMC, cells isolated 3 h after endotoxin injection synthesized significantly less stimulus-induced IL-1, TNF-alpha, IL-6, and IL-8 than did PBMC from saline-injected controls. We conclude that endotoxin tolerance is due, in part, to changes in the stimulus-induced cytokine response of circulating CD14+ cells.

The tumor necrosis factor (TNF) soluble receptor derived from the cell surface p55 TNF receptor (TNFsRp55) is a naturally occurring substance generated during infection and inflammation. TNFsRp55 inhibits biologic effects of TNF. An RIA was developed to quantitate TNFsRp55 in human blood. Recovery of TNFsRp55 from blood anticoagulated with EDTA was optimal compared with recovery from serum or heparinized plasma. TNF did not interfere with the assay. With the RIA based on radiolabeled nonglycosylated Escherichia coli-derived recombinant TNFsRp55, a mean concentration of 198 +/- 15 pg/mL was found in 14 volunteers. When glycosylated CHO cell-derived TNFsRp55 was used, the mean level was 1656 +/- 95 pg/mL. Infusion of endotoxin into volunteers induced TNFsRp55, which peaked at 517 +/- 99 pg/mL for the E. coli-based RIA and 7300 +/- 1810 pg/mL for the CHO cell-based RIA. These findings demonstrate that blood collected in EDTA is optimal for measuring circulating TNFsRp55 and that this soluble receptor is present in health but elevated during endotoxemia.

We have previously shown that chlorpromazine (CPZ) inhibits tumour necrosis factor (TNF) production and protects against endotoxic shock in mice. In this paper we investigated the effect of pretreatment with CPZ, 4 mg/kg i.p. 30 min before, compared with dexamethasone (DEX; 3 mg/ kg) on the induction of other endotoxin (lipopolysaccharide; LPS)-induced cytokines in the serum of mice, i.e. interleukin-lα (IL-lα), IL-6 and IL-b, and TNF. We also studied the effect of CPZ on serum and spleen-associated TNF. Both DEX and CPZ inhibited TNF production, whereas induction of IL-b and IL-6 was inhibited by DEX but not by CPZ. DEX did not affect IL-l0, while CPZ potentiated its induction. CPZ also inhibited spleen-associated TNF induction in LPS- treated mice, suggesting an effect on the synthesis of TNF. CPZ inhibited TNF induction by Gram-positive bacteria (heat-killed Staphylococcus epidermidis) and by anti-CD3 monoclonal antibodies. Intraperitoneal administration of CPZ also inhibited the induction of brain-associated TNF induced by intra-cerebroventricular injection of LPS. Therefore, CPZ is a more specific inhibitor of TNF production than DEX; in particular, CPZ increased the induction of 1L-l0, which is a `protective' cytokine known to inhibit LPS toxicity and TNF production. CPZ inhibited TNF production in vivo, irrespective of the TNF stimulus used to induce TNF. Finally, CPZ did not induce the `rebound' effect of DEX that, when given 24 hr before LPS, potentiates TNF production, but it did inhibit TNF production after 24 hr. [ABSTRACT FROM AUTHOR]