Modulation of endotoxin lethality in mice by hydrazine sulfate

Uridine protection against D-galactosamine-sensitized LPS lethality in mice is complete

These studies show that uridine supplementation can quantitatively prevent D-galactosamine sensitization to lethal endotoxin shock. This observation serves to discount the possibility that mechanisms which do not involve uridine nucleotide depletion may contribute even marginally to the basic biochemical mechanism of D-galactosamine sensitization.

Review: D-Galactosamine lethality model: scope and limitations

D-Galactosamine (D-galN) is well established as sensitizing mice and other animals to the lethal effects of TNF, specifically, and by several orders of magnitude. Protection by anti-TNF neutralizing antibody is complete, as is (metabolically-based) protection by uridine. Sensitization occurs regardless of the origin of the released TNF, whether it is released from macrophages and/or T-cells. The same is true for the challenging agent which leads to the release of TNF, whether it is endotoxin, a superantigen, lipoprotein, bacterial DNA, or bacteria, either killed or proliferating. Most studies have utilized endotoxin as the challenging agent, and more than 70 agents have been reported to confer protection against LPS and/or TNF challenge in the model. The model has provided new insight regarding modes of protection, including from dexamethasone, which protects against challenge from LPS but not from challenge by TNF. The D-galN lethality model has also been used to test for synergistic behavior between different bacterial components, and to test for lethality when only small amounts of the challenging agent are available (lipid A chemistry).

Lipopolyamines: novel antiendotoxin compounds that reduce mortality in experimental sepsis caused by gram-negative bacteria

The interactions of lipopolyamines, a class of structurally unique compounds currently being used as transfection (lipofection) agents, with lipopolysaccharide (LPS) have been characterized. Our studies have demonstrated that 1,3-di-oleoyloxy-2-(6-carboxyspermyl)-propylamide), available commercially as DOSPER, binds to purified LPS with an affinity of about 1/10 that of polymyxin B. This essentially nontoxic compound inhibits, in a dose-dependent manner, LPS-induced activation of the Limulus clotting cascade and the production of tumor necrosis factor alpha (TNF-alpha) interleukin-6 (IL-6), and nitric oxide from LPS-stimulated J774.A1 cells, a murine macrophage-like cell line. Cytokine inhibition is paralleled by decreased steady-state levels of TNF-alpha and IL-6 mRNA and inhibits the nuclear translocation of nuclear factor kappa B. These findings suggest that the lipopolyamine compound sequesters LPS, thereby blocking downstream cellular activation events that lead to the production of proinflammatory mediators. Administration of DOSPER to D-galactosamine-sensitized mice challenged either with LPS or with Escherichia coli organisms provided significant protection against lethality both with and without antibiotic chemotherapy. Partial protection is evident in LPS-challenged mice treated with DOSPER as late as 2 to 4 h following the endotoxin challenge. A greater degree of protection is observed in E. coli-challenged animals receiving ceftazidime than in those receiving imipenem, which is probably attributable to the higher levels of LPS released in vivo by the former antibiotic. Potent antiendotoxic activity, low toxicity, and ease of synthesis render the lipopolyamines candidate endotoxin-sequestering agents of potential significant therapeutic value.

Pro-inflammatory cytokines in a ruminant model: pathophysiological, pharmacological, and therapeutic aspects

Infection evokes complex changes which are thought to be caused by production and release of pro-inflammatory cytokines such as tumour necrosis factor (TNF-alpha), interferons (INFs), and interleukins (ILs). They regulate local inflammatory reactions, but may also gain access to the circulation and induce systemic effects collectively known as the Acute Phase Response. To improve our understanding of the pathophysiology of pro-inflammatory cytokines in ruminants, studies have been performed with TNF-alpha, IL1-alpha/beta, and IFN-alpha/ gamma as well as with cytokine-inducers in dwarf goats. In relation to therapy, the following aspects may be of interest: a) Cytokine therapy given before or just after microbial challenge induces in vivo antimicrobial activity. Moreover, cytokines potentiate in vivo the antimicrobial activity of antibiotics, b) Cytokines may act as biological response modifiers for enhancing specific immunity to vaccines, and c) Cytokines may affect drug absorption, disposition, and metabolite formation in disease states. Although studies of the actions of corticosteroids, nonsteroidal anti-inflammatory and antipyretic agents, antibodies to endotoxin, TNF-alpha, or IL-1, synthetic E. coli lipid A precursors, hydrazine, isoniazid, chloroquine, polymyxin B, bicyclic imidazoles, hydroxamates, and tyrosine kinase inhibitors in endotoxaemic animals have shed further light on inflammatory processes, clinical studies in this field are urgently required to evaluate their beneficial effect.

Murine tissues exposed to cytotoxic drugs display altered patterns of Candida albicans adhesion

An ex vivo adhesion assay was used to examine the binding of Candida albicans yeast cells to tissues from mice treated with cytotoxic drugs such as lipopolysaccharide and the clinically used anticancer drugs doxorubicin, cisplatin, and vincristine. No major differences were observed in binding of the fungal cells to liver and kidney tissues from treated or untreated animals. All drug-treated spleens displayed altered patterns of C. albicans adhesion compared with the control group, with yeast cells bound not only to the marginal zone but also to the white and red pulp. Immunostaining for macrophages, which are proposed as the site of normal adhesion, showed no apparent differences between the control and the experimental spleens that could account for the change in adhesion patterns. Scanning electron microscopy images suggested that yeast binding to the white pulp of treated tissue is mediated through fibers, perhaps extracellular matrix components exposed as result of the cytotoxic treatment. Exposure of new attachment sites for C. albicans in treated tissues may facilitate initiation of infection.

Is the pharmacological treatment of cancer cachexia possible?

Cancer cachexia is highly prevalent in patients with advanced cancer. Its main clinical manifestation is profound anorexia. Progestational drugs have shown meaningful effects on appetite, food intake, and nutritional status in patients with advanced cancer and AIDS, and could be useful in managing anorexia. Corticosteroids also seem to produce increased appetite, but these effects are short-lived. Cyproheptadine, hydrazine sulfate, and cannabinoids also are being studied in the management of cancer-induced anorexia, but their role has not yet been clearly established. Future research should evaluate how the different drugs affect specific symptoms associated with cachexia.

Endogenous and exogenous glucocorticoids have different roles in modulating endotoxin lethality in D-galactosamine-sensitized mice

Endotoxin sensitivity and dexamethasone protection have been assessed in mice that were adrenalectomized and also treated with D-galactosamine at the time of endotoxin challenge. Our data establish that adrenalectomy did not detectably alter the magnitude of the increased sensitivity induced by D-galactosamine alone. Furthermore, protection provided by acute exogenous glucocorticoid treatment was still demonstrable in these mice and was not influenced by chronic experimentally induced glucocorticoid deficiency. Our data confirm that the adrenalectomized mouse model of endotoxin lethality is characterized by increased sensitivity to endotoxin and establish that the magnitude of this sensitizing effect is more than 100-fold. We also show for the first time that adrenalectomy causes an appreciable kinetic shift in the endotoxic crisis and that dexamethasone, given at the time of endotoxin challenge, will significantly reverse the increased sensitivity to lethality. Our results indicate that the protective effects of corticosteroids may involve important chronic as well as acute responses. In particular, we conclude that endogenous glucocorticoid need not always increase host resistance to endotoxin, nor does such a circumstance eliminate the possibility for exogenous glucocorticoid-mediated protective effects.

Identification of tumor necrosis factor as a transcriptional regulator of the phosphoenolpyruvate carboxykinase gene following endotoxin treatment of mice

The decreased synthesis of hepatic phosphoenolpyruvate carboxykinase (PEPCK), the rate-limiting enzyme of gluconeogenesis, that occurs during endotoxemia was shown previously in rats to occur at the transcriptional level. In the current study, the exogenous administration of human recombinant tumor necrosis factor (TNF), a proximal mediator of endotoxic shock, reduced the PEPCK transcription rate, mRNAPEPCK levels, and PEPCK enzyme activity in a time- and dose-dependent manner in CD-1 mice. Comparable amounts of circulating TNF were measured in mice 2 h after injection of human recombinant TNF (10(5) U) or a 50% lethal dose of Escherichia coli endotoxin (20 mg/kg). Direct action of TNF to decrease the PEPCK transcription rate was confirmed in vitro with H-4-II-E Reuber hepatoma cells, in which a dose-dependent inhibition of PEPCK transcription was observed with 1 to 100 U of TNF per ml. A role for TNF-elicited changes in PEPCK gene expression during endotoxemia was confirmed by the protective effect of rabbit polyclonal antibodies to recombinant murine TNF. C57BL/6 mice passively immunized with anti-TNF 4 h prior to endotoxin challenge exhibited normal PEPCK enzyme activity. Neutralization of circulating TNF with anti-TNF failed, however, to prevent the hypoglycemia commonly observed during endotoxemia, suggesting the participation of other mediators. Anti-TNF treatment reduced circulating interleukins 1 and 6 at 3 and 6 h after endotoxin treatment, respectively. These results suggest that during endotoxemia, the development of hypoglycemia is multifaceted and that several cytokines are most likely involved. The findings from the Reuber hepatoma cell model afford an opportunity in future work to map putative cytokine response elements in the PEPCK promoter responsible for perturbed hormonal regulation of the gene during endotoxemia.

In vivo effects of the antiglucocorticoid RU 486 on glucocorticoid and cytokine responses to Escherichia coli endotoxin

The endogenous adrenocortical response to sepsis is critical for host survival. The in vivo interactions among the endogenous glucocorticoid response, the induction of cytokines, and host survival during endotoxemia were explored in this study by use of the glucocorticoid receptor antagonist RU 486. Male Lewis rats underwent sterile insertion of a right jugular venous catheter. After a 72-h recovery period, animals received a 50% lethal dose of Escherichia coli endotoxin (2.5 mg/kg) via the catheter after pretreatment for 30 min prior to lipopolysaccharide (LPS) treatment with (i) vehicle alone intravenously (i.v.) (-corticosterone [-Cort]/-RU 486/+LPS) (n = 10), (ii) the antiglucocorticoid RU 486 (10 mg/kg) i.v. (-Cort/+RU 486/+LPS) (n = 11), or (iii) RU 486 (10 mg/kg) i.v. in animals that had undergone subcutaneous implantation of a corticosterone pellet at the time of catheter insertion (+Cort/+RU 486/+LPS) (n = 10). Except in animals receiving corticosterone pretreatment, baseline plasma corticosterone levels were low in all groups. Plasma corticosterone levels increased significantly (P less than 0.001) above the baseline following LPS administration. Animals in the -Cort/+RU 486/+LPS-treated group exhibited significantly increased mortality (P less than 0.001), with only 9% of the animals surviving at 72 h, as well as significantly increased plasma interleukin-6 levels, compared with animals receiving the vehicle alone (-Cort/-RU 486/+LPS), which showed 50% mortality. Pretreatment with corticosterone and RU 486 (+Cort/+RU 486/+LPS) significantly (P less than 0.001) reversed the mortality observed with RU 486 pretreatment alone (-Cort/+RU 486/+LPS), with 70% of the animals surviving at 72 h, and significantly attenuated the peak plasma tumor necrosis factor and interleukin-6 responses to LPS, compared with those in the animals treated with vehicle alone. These data demonstrate that the blockade of glucocorticoid binding by RU 486 increases LPS-induced mortality. The reversal of this effect by the induction of hypercorticosteronemia prior to RU 486 and LPS exposure (+Cort/+RU 486/+LPS) improves survival and is further associated with significant attenuation of cytokine production. Therefore, these data suggest that the protective effect of the endogenous glucocorticoid response to acute endotoxemia may result from the down-regulation of a potentially lethal cytokine response.

Hydrazine sulfate protection against endotoxin lethality: analysis of effects on expression of hepatic cytokine genes and an acute-phase gene

Hydrazine sulfate (HS) pretreatment protects mice against the lethal effects of bacterial endotoxin lipopolysaccharide (LPS) through mechanisms yet to be established. The liver was examined as a model organ to determine HS effects on (a) LPS activation of leukocyte (Kupffer cell) interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha) genes and (b) subsequent cytokine-mediated induction of the acute-phase response as measured by hepatic metallothionein (MT) gene expression. The utility of this model was documented by in situ hybridization which showed that acute induction by LPS of the IL-1 beta gene occurred in cells found in liver sinusoids, consistent with Kupffer cells, whereas induction of the MT gene occurred in hepatocytes. The cell specific expression of these genes was further verified by Northern blot hybridization to LPS-treated liver RNA which showed that the LPS-mediated increase in hepatic cytokine mRNA levels, unlike that of MT, was not prevented by D-galactosamine (D-GalN) treatment. Northern blot hybridization established that HS pretreatment did not block the acute induction of hepatic cytokine mRNAs (IL-1 beta and TNF-alpha) by LPS nor did it induce these cytokine mRNAs in the absence of LPS. Northern blot hybridization further established that HS did not prevent LPS-mediated activation of hepatocyte MT gene expression. Thus, HS does not prevent LPS from activating liver leukocytes. These results also suggest that HS pretreatment neither prevents the general release of cytokines from LPS activated leukocytes nor the general induction of acute-phase protein gene expression in hepatocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Virulence of Wolinella recta in a murine abscess model

The virulence of Wolinella recta isolates was studied in an experimental animal model by using monoinfection of BALB/c mice. Infection with clinical isolates of W. recta 576 and W. recta 234 induced dry, flat, depressed gangrenous necrotic skin lesions, whereas W. recta ATCC 33238 failed to induce a similar lesion. Histological examination of the skin lesion 72 h postinfection revealed coagulation necrosis of the epidermis, subcutis and cutaneous truncus muscle, with marked exudation of serum proteins and neutrophils. Virulence-modulating agents such as dexamethasone, galactosamine, hydrazine sulfate, and dextran microcarrier beads were used in conjunction with W. recta infection. Dexamethasone, hydrazine sulfate, and dextran beads enhanced the infectivity and pathogenicity of W. recta for lesion formation and tissue destruction compared with what was found in untreated control mice. Galactosamine sensitization enhanced the virulence potential of W. recta to such an extent that a lethal outcome was observed. Laboratory passage of clinical isolates demonstrated a decreased virulence in high-passage strains, which correlated with the minimal virulence observed in the extensively passaged W. recta ATCC 33238. Serum immunoglobulin G (IgG) and IgM responses were detected in the serum of infected animals, and cross-reacting antibody indicated variation in the antigenic makeup of various W. recta strains. Enhanced IgG antibody responses were observed following the secondary challenge. Mice with acquired antibody response to initial infection remained susceptible to lesion formation with subsequent challenge, but the size of the lesion was significantly reduced, indicating partial protection. Serum IgG and IgM antibody levels were significantly increased by active immunization when compared with levels in mice which had recovered from infection. The immunization significantly decreased the lesion size; however, even these high levels of antibody failed to abrogate the lesion induction.

Isoniazid protects mice against endotoxin lethality without influencing tumor necrosis factor synthesis and release

Treatment of NMRI mice with isoniazid (INH; 25 mg/kg) intraperitoneally induced significant protection when it was injected before or after a lethal intravenous challenge with endotoxin. The INH preparation used was not contaminated with endotoxin. Tumor necrosis factor (TNF) was not elevated in sera from NMRI mice 2 h after the injection of INH. INH did not influence TNF synthesis or release determined in human monocytes in vitro. Therefore, it is concluded that the protective effect of INH against lethal endotoxin is not due to a suppressive effect of INH on TNF production.

Roles of interleukin-1 and tumor necrosis factor in lipopolysaccharide-induced hypoglycemia

In this study, hypoglycemia induced by injection of lipopolysaccharide (LPS) or the recombinant cytokine interleukin-1 alpha or tumor necrosis factor alpha (administered alone or in combination) was compared. LPS-induced hypoglycemia was reversed significantly by recombinant interleukin-1 receptor antagonist.

Hydrazine sulfate protects D-galactosamine-sensitized mice against endotoxin and tumor necrosis factor/cachectin lethality: evidence of a role for the pituitary

In previously published studies, we had demonstrated that hydrazine sulfate pretreatment protected mice against the lethal effects of endotoxin and that this protection was accompanied by a sustained increase in hepatic phosphoenolpyruvate carboxykinase activity (Silverstein, R., C.A. Christoffersen, and D.C. Morrison. 1989. Infect. Immun. 57:2072). The same hydrazine sulfate pretreatment has now been found to protect mice against endotoxin in the D-galactosamine model with an increase in the endotoxin LD50 of approximately four orders of magnitude. Elimination of the pretreatment period, or administration of an additional dose of D-galactosamine at the time of hydrazine sulfate pretreatment, renders the mice refractory to the protection. Given the sensitivity of phosphoenolpyruvate carboxykinase regulation to several hormones, we investigated the possibility that protection may have been hormone mediated. In addition to determining the effect of hydrazine sulfate on the plasma levels of phosphoenolpyruvate carboxykinase regulating hormones, we have investigated the effects of hydrazine sulfate on endotoxin lethality in mice whose capacity to respond hormonally to external stimuli has been compromised by hypophysectomy. Our results show a significant enhancement in circulating levels of plasma corticosterone 30 min after hydrazine sulfate injection. Moreover, hypophysectomy results in a marked increase in sensitivity of mice to endotoxin challenge as well as an abrogation of the protection against endotoxin lethality mediated by hydrazine sulfate. Although hydrazine sulfate protection distinguishes between sensitivity brought on, individually, by D-galactosamine and by hypophysectomy, mice sensitized by both hypophysectomy and D-galactosamine are not protected against endotoxin lethality by hydrazine sulfate. We conclude that hydrazine sulfate protection against endotoxin lethality is endocrine dependent, with the available evidence implicating a pituitary/adrenal axis, with glucocorticoid involvement. In as much as D-galactosamine is known to act directly in the liver in disrupting protein synthesis, it is proposed that events in the liver are critical to the hydrazine sulfate-mediated protection against endotoxin and are possibly the target of the endocrine involvement. Hydrazine sulfate pretreatment also protects D-galactosamine-sensitized mice against the lethal effects of injected tumor necrosis factor/cachectin.