Experimental elimination of tumor necrosis factor in low-dose endotoxin models has variable effects on survival

Escherichia coli Braun Lipoprotein (BLP) exhibits endotoxemia - like pathology in Swiss albino mice

The endotoxin lipopolysaccharide (LPS) promotes sepsis, but bacterial peptides also promote inflammation leading to sepsis. We found, intraperitoneal administration of live or heat inactivated E. coli JE5505 lacking the abundant outer membrane protein, Braun lipoprotein (BLP), was less toxic than E. coli DH5α possessing BLP in Swiss albino mice. Injection of BLP free of LPS purified from E. coli DH5α induced massive infiltration of leukocytes in lungs and liver. BLP activated human polymorphonuclear cells (PMNs) ex vivo to adhere to denatured collagen in serum and polymyxin B independent fashion, a property distinct from LPS. Both LPS and BLP stimulated the synthesis of platelet activating factor (PAF), a potent lipid mediator, in human PMNs. In mouse macrophage cell line, RAW264.7, while both BLP and LPS similarly upregulated TNF-α and IL-1β mRNA; BLP was more potent in inducing cyclooxygenase-2 (COX-2) mRNA and protein expression. Peritoneal macrophages from TLR2^−/− mice significantly reduced the production of TNF-α in response to BLP in contrast to macrophages from wild type mice. We conclude, BLP acting through TLR2, is a potent inducer of inflammation with a response profile both common and distinct from LPS. Hence, BLP mediated pathway may also be considered as an effective target against sepsis.

Carnitine and septic shock: a review

Most studies have reported reduced carnitine levels in the tissues of patients with sepsis, probably due to increased urinary excretion. Because of the increased utilization of fatty acids and ketone bodies as sources of energy in sepsis, the carnitine deficiency can further impair the fuel metabolism and contribute to the unregulated lipid metabolism in these patients.

Recently, experimental and clinical studies have shown that carnitine and its congeners are able to: (a) downmodulate the spontaneous and endotoxin (LPS)-triggered overproduction of tumor necrosis factor (TNF)-alpha; (b) ameliorate the lipid metabolism; and (c) reduce the severity of illness, accelerate recovery, and, in some cases, improve survival in experimental septic shock.

Many questions concerning the ultimate molecular mechanism of action of these compounds in endotoxaemia are still unanswered. Yet, these compounds may be helpful in patients with sepsis, when associated with conventional therapy, in that they can effectively reduce TNF-alpha levels and ameliorate the host's metabolic processes.

Recombinant human interleukin-11 prevents hypotension in LPS-treated anesthetized rabbits

Recombinant human interleukin-11 (rhlL-11) was evaluated in a New Zealand White rabbit model of endotoxemia. Animals received Escherichia coli LPS (150 μg/kg i.v.) via a femoral venous catheter. 30 min later, animals were treated with rhlL-11 (100 μg/kg i.v., n = 7), or rhlL-11 formulation buffer (n = 6). Arterial pressures were monitored for 6 h following rhlL-11. Approximately 5 h after LPS treatment, mean arterial pressure in vehicle-treated control animals was 46.7 mmHg, or 55% of group mean baseline, while that of rhlL-11-treated animals was 74.8 mmHg, or 94% of group mean baseline (P < 0.0005). Histologic evaluation of ileum, cecum and colon from rhlL-11-treated rabbits showed decreased hemorrhage, edema, and mucosal damage (P < 0.02), compared to the vehicle-treated controls. Intravenous LPS evokes hypotension mediated by the induction of inducible nitric oxide synthase (iNOS) and subsequent production of NO. Maintenance of blood pressure by rhIL-11 in LPS-treated rabbits in addition to the concurrent significant decrease in NO levels compared to vehicle-treated animals ( P < 0.04) suggests that rhlL-11 interferes with the production of NO by iNOS and or the physiologic effects of NO on vascular smooth muscle.

In vivo neutralization of tumor necrosis factor attenuates the generalized Shwartzman reaction in the rabbit

A role for tumor necrosis factor (TNF) and TNF-induced tissue factor (TF) expression has been postulated in endotoxin (LPS)-induced diffuse intravascular coagulation (DIC). We studied the protective efficacy of goat polyclonal gammaglobulin (lgG) against recombinant human (rh)-TNF in the generalized Shwartzman reaction (GSR) in rabbits, a model of DIC. Administration of anti-rhTNF 2 h before the first, preparative, LPS injection afforded 95% neutralization of TNF released during the GSR. Compared to saline-pretreated controls, a modest attenuation of fibrin deposition in kidney, lung, liver and spleen was observed 4 h after the second provocative LPS injection. Except for the lung, fibrin deposition in the anti-rhTNF group was not attenuated compared to the non-immune goat IgG (ni-lgG)-pretreated group. Both ni-lgG and anti-rhTNF prevented LPS-induced TF expression by mononuclear cells, but not by isolated glomeruli. Other mediators than TNF and TF are involved as well in glomerular injury and fibrin deposition after LPS.

The effect of female sexual hormones on the intestinal and serum cytokine response after traumatic brain injury: different roles for estrogen receptor subtypes

The purpose of this study was to evaluate the effect of female sexual hormones on intestinal and serum cytokines following traumatic brain injury (TBI). Adult female rats were ovariectomized and distributed among the following 9 groups: (i) sham trauma, (ii) TBI (Marmarou's method), (iii) vehicle (dimethylsulfoxide) treated, (iv) estrogen (E2) treated, (v) progesterone (P) treated, (vi) treated with E2+P, (vii) propylpyrazole triol (PPT) treated, (viii) diarylpropionitrile (DPN) treated, and (ix) control. PPT and DPN are estrogen receptor αand β agonists, respectively. Serum and intestinal levels of interleukin (IL)-1β were increased by TBI (P < 0.001). The level of intestinal IL-1β was increased in the group treated with E2 (P < 0.001). There was a reduction in serum IL-1β (P < 0.01) and an increase in intestinal IL-1β level (P < 0.001) in the PPT-treated group compared with the vehicle-treated group. TBI reduced serum IL-6 (P < 0.01) and increased intestinal IL-6 (P < 0.001). Serum IL-6 was increased in the group treated with E2 (P < 0.001), P (P < 0.001), E2+P (P < 0.01), and DPN (P < 0.001) after TBI; however, intestinal IL-6 was higher in the E2-treated group compared with the vehicle-treated group (P < 0.01). Intestinal tumor necrosis factor α (TNF-α) was increased by TBI (P < 0.001). Progesterone decreased serum TNF-α (P < 0.01). Intestinal TNF-α in the E2 (P < 0.01), E2+P (P < 0.001), and PPT (P < 0.001) treatment groups was less than in the vehicle-treated group. In conclusion, estrogen influences the intestinal levels of proinflammatory cytokines, in particular TNF-α, mediated through estrogen receptor α.

LPS-induced serum TNF production and lethality in mice: effect of L-carnitine and some acyl-derivatives

The effect of L-carnitine and some of its acyl derivatives on serum TNF production and lethality in a murine experimental endotoxin shock model was investigated. In some instances, serum IL-6 production was also evaluated. In this experimental model, C57BL/6 mice received 30 mg/kg LPS (E. cell 055:B5) injected intraperitoneally, while L-carnitine and its derivatives were administered according to different schedules. Serum levels of TNF and IL-6 were evaluated 1 h following LPS injection. The treated animals were also monitored daily for differences in body temperature, feeding, and survival for 10 days after LPS injection. Although some derivatives were able to significantly affect TNF production, the marked decrease in serum TNF levels of LPS-treated mice was not paralleled by a substantial increase in survival.

Autoantibody-mediated angiotensin receptor activation contributes to preeclampsia through tumor necrosis factor-alpha signaling

Preeclampsia is a prevalent life-threatening hypertensive disorder of pregnancy for which the pathophysiology remains largely undefined. Recently, a circulating maternal autoantibody, the angiotensin II type I (AT(1)) receptor agonistic autoantibody (AA), has emerged as a contributor to disease features. Increased circulating maternal tumor necrosis factor alpha (TNF-alpha) is also associated with the disease; however, it is unknown whether this factor directly contributes to preeclamptic symptoms. Here we report that this autoantibody increases the proinflammatory cytokine TNF-alpha in the circulation of AT(1)-AA-injected pregnant mice but not in nonpregnant mice. Coinjection of AT(1)-AA with a TNF-alpha neutralizing antibody reduced cytokine availability in AT(1)-AA-injected pregnant mice. Moreover, TNF-alpha blockade in AT(1)-AA-injected pregnant mice significantly attenuated the key features of preeclampsia. Autoantibody-induced hypertension was reduced from 131+/-4 to 110+/-4 mm Hg, and proteinuria was reduced from 212+/-25 to 155+/-23 microg of albumin per milligram of creatinine (both P<0.05). Injection of AT(1)-AA increased the serum levels of circulating soluble fms-like tyrosine kinase 1 and soluble endoglin (34.1+/-5.1, 2.4+/-0.3 ng/mL, respectively) and coinjection with the TNF-alpha blocker significantly reduced their levels (21.7+/-3.4 and 1.2+/-0.4 ng/mL, respectively). Renal damage and placental abnormalities were also decreased by TNF-alpha blockade. Lastly, the elevated circulating TNF-alpha in preeclamptic patients is significantly correlated with the AT(1)-AA bioactivity in our patient cohort. Similarly, the autoantibody, through AT(1) receptor-mediated TNF-alpha induction, contributed to increased soluble fms-like tyrosine kinase 1, soluble endoglin secretion, and increased apoptosis in cultured human villous explants. Overall, AT(1)-AA is a novel candidate that induces TNF-alpha, a cytokine that may play an important pathogenic role in preeclampsia.

NEUTRALIZATION OF TUMOR NECROSIS FACTOR IN PRECLINICAL MODELS OF SEPSIS

Tumor necrosis factor (TNFalpha), a cardinal early mediator of the innate host inflammatory response, has been an attractive target for therapeutic intervention in human sepsis. However, pooled data from 12 completed randomized controlled trials show only a very modest impact on mortality in a highly heterogeneous population of patients. To gain insight into the preclinical in vivo biology of TNFalpha that might aid in better identifying appropriate patient populations for therapeutic intervention, we undertook a systematic review of published reports of preclinical studies assessing the consequences of neutralization of TNFalpha in models of acute infection or inflammation. We identified 143 reports incorporating 484 unique experimental comparisons in seven different animal species. The effects of neutralization of TNFalpha in these were quite variable. Neutralization of TNFalpha was beneficial in endotoxemia, or after systemic challenge with gram-negative organisms, Staphylococcus aureus, or Group B streptococci. On the other hand, neutralization was detrimental in infections caused by Streptococcus pneumoniae, Candida spp., or intracellular pathogens such as Listeria and Mycobacterium tuberculosis, and in models of pneumonia. Treatment was more efficacious when delivered before infectious challenge, and the therapeutic signal increased as the baseline mortality in the placebo group increased. Evidence of neutralization of TNFalpha bioactivity, and of attenuation of inflammation, was typically accompanied by evidence of impairment of antimicrobial defenses. Multiple specific and nonspecific therapeutic strategies were identified. We conclude that the beneficial effects of TNF in systemic inflammation occur at the cost of impaired antimicrobial defenses, and that a better understanding of the consequences of neutralization of TNFalpha in vivo could aid in better defining optimal patient populations for therapeutic intervention.

Cutting edge: an endogenous pathway to systemic inflammatory response syndrome (SIRS)-like reactions through Toll-like receptor 4

Systemic inflammatory response syndrome (SIRS) is typically associated with trauma, surgery, or acute pancreatitis. SIRS resembles sepsis, triggered by exogenous macromolecules such as LPS acting on Toll-like receptors. What triggers SIRS in the absence of infection, however, is unknown. In this study, we report that a SIRS-like response can be induced in mice by administration of soluble heparan sulfate, a glycosaminoglycan associated with nucleated cells and extracellular matrices, and by elastase, which cleaves and releases heparan sulfate proteoglycans. The ability of heparan sulfate and elastase to induce SIRS depends on functional Toll-like receptor 4, because mutant mice lacking that receptor or its function do not respond. These results provide a molecular explanation for the initiation of SIRS.

Differential effects between marimastat, a TNF-alpha converting enzyme inhibitor, and anti-TNF-alpha antibody on murine models for sepsis and arthritis

We investigated the effects of marimastat, an inhibitor of TNF-alpha converting enzyme and matrix metalloproteinases, and anti-TNF-alpha antibodies on a murine model for sepsis, and on arthritis in human TNF-alpha transgenic mice. Marimastat (25-200 mg/kg) inhibited lipopolysaccharide (LPS)-induced soluble TNF-alpha production in mice in a dose-dependent manner. At an oral dose of 200 mg/kg, marimastat almost completely inhibited LPS-induced soluble TNF-alpha production, but only slightly delayed LPS lethality. On the other hand, anti-TNF-alpha antibodies completely abolished LPS-induced morbidity. In addition, anti-TNF-alpha antibodies, but not marimastat (200 mg/kg/day), inhibited the development of arthritis in human TNF-alpha transgenic mice. These results suggest that cell surface TNF-alpha may be important in the pathogenesis of murine models for sepsis and arthritis.

Tumor necrosis factor is involved in chlorpyrifos--induced changes in core temperature in the female rat

Chlorpyrifos (CHP), an OP-based pesticide, induces hypothermia in the rat followed by a fever that persists for several days. The cytokine, tumor necrosis factor-alpha (TNF), is induced by lipopolysaccharide (LPS) and released during fever and has both pyrogenic and cryogenic (i.e. antipyretic) properties. Administering antibodies to TNF (anti-TNF) is known to disrupt fever from infection. Thus, the purpose of this study was to examine whether anti-TNF also disrupts CHP-induced changes in body temperature of the female Long-Evans rat. A positive effect would suggest a role of TNF in the etiology of OP toxicity. In study one, rats were given either saline or anti-TNF (50,000 units, i.p.). Three hours later, animals were given corn oil (CO) or 25 mg/kg CHP by oral gavage in the morning. In study two, rats were given anti-TNF followed by CO or 10 mg/kg CHP in the afternoon. Core temperature and motor activity were monitored continuously by telemetry. In study one, anti-TNF (50,000 units) had no effect on the hypothermic response to 25 mg/kg CHP. However, anti-TNF treated animals maintained higher fevers 3 days (48-96 h post-injection) after CHP treatment. In study two, anti-TNF attenuated the hypothermic response induced by 10 mg/kg CHP but had no effect on the magnitude of the delayed fever. Overall, 25 mg/kg CHP elicited a longer period of hypothermia and delayed fever compared to 10 mg/kg CHP. Anti-TNF pretreatment attenuated the hypothermic response at the lower CHP dose and exacerbated the fever at the higher CHP dose. Anti-TNF also attenuated the hypothermic effect of high doses of LPS and exacerbated LPS-induced fever. These data indicate that endogenously produced TNF is involved in the etiology of CHP mediated hypothermia and fever.

Early neuronal expression of tumor necrosis factor-alpha after experimental brain injury contributes to neurological impairment

Tumor necrosis factor-alpha (TNF alpha) is a pleiotropic cytokine involved in inflammatory cascades associated with CNS injury. To examine the role of TNF alpha in the acute pathophysiology of traumatic brain injury (TBI), we studied its expression, localization and modulation in a clinically relevant rat model of non-penetrating head trauma. TNF alpha levels increased significantly in the injured cortex at 1 and 4, but not at 12, 24 or 72 h after severe lateral fluid-percussion trauma (2.6-2.7 atm). TNF alpha was not elevated after mild injury. At 1 and 4 h after severe TBI, marked increases of TNF alpha were localized immunocytochemically to neurons of the injured cerebral cortex. A small population of astrocytes, ventricular cells and microvessels, also showed positive TNF alpha staining, but this expression was not injury-dependent. Macrophages that were present in a hemorrhagic zone along the external capsule, corpus callosum and alveus hippocampus at 4 h after TBI did not express TNF alpha. Intracerebroventricular administration of a selective TNF alpha antagonist--soluble TNF alpha receptor fusion protein (sTNFR:Fc) (37.5 microg)--at 15 min before and 1 h after TBI, improved performance in a series of standardized motor tasks after injury. In contrast, intravenous administration of sTNFR:Fc (0.2, 1 or 5 mg/kg) at 15 min after trauma did not improve motor outcome. Collectively, this evidence suggests that enhanced early neuronal expression of TNF alpha after TBI contributes to subsequent neurological dysfunction.

Tumor necrosis factor alpha receptor I is important for survival from Streptococcus pneumoniae infections

Tumor necrosis factor alpha (TNF-alpha) is important in resistance to various microorganisms and provides signals to the target cells through two different receptors, TNF-alpha receptor I (TNFRI) (p55 receptor) and TNFRII (p75 receptor). To delineate the significance of the two different signaling pathways in resisting infections with extracellular bacteria, we examined the resistance of mice to Streptococcus pneumoniae (serotype 6B). TNF-alpha needs to be present early in infections, since one injection of wild-type mice with anti-TNF-alpha leads to an increased susceptibility of these mice to S. pneumoniae. TNF-alpha signaling through the p55 receptor (but not the p75 receptor) is crucial in resisting S. pneumoniae infections, because intraperitoneal injection of 100 CFU/mouse killed p55-deficient mice by day 2 of infection, whereas 1,000,000 CFU/mouse was needed to kill half of the control mice. p55-deficient mice do not show evidence of a deficient acute-phase response. All three types of mice (p55 deficient, p75 deficient, and normal) showed comparable rises in the levels of two acute-phase proteins (serum amyloid P and C3) at 24, 48, and 72 h after the experimental infections, and all of the mice showed comparable influxes of neutrophils to the site of infection. Finally, it was demonstrated that p55-deficient mice can be protected from the lethal effects of S. pneumoniae infection by injection of antibodies specific for S. pneumoniae polysaccharide capsule.

Enhanced Epidermal Langerhans Cell Migration in IL-10 Knockout Mice

The migration of epidermal Langerhans cells (LC) to lymph nodes (LN) is critical in the initiation of contact hypersensitivity (CHS) responses. Studies suggest that contact allergen-induced epidermal proinflammatory cytokines, including IL-1 and TNF-α, play important roles in promoting LC migration. Contact allergens also induce epidermal anti-inflammatory cytokines such as IL-10. Since IL-10 down-regulates proinflammatory cytokine production and inhibits CHS, we hypothesized that IL-10 might inhibit LC migration. To test this hypothesis, IL-10 knockout (KO) mice were epicutaneously sensitized with the hapten, FITC, and 24 h later hapten-bearing cells in the draining LN were examined. The number of hapten-bearing cells in the LN was significantly greater in IL-10 KO mice than in wild-type mice. The mutant mice also had an exaggerated CHS to FITC. Pretreatment with anti-TNF-α Ab or IL-1R antagonist significantly reduced the number of hapten-bearing cells in the LN, suggesting that IL-10 modulation of LC migration involves IL-1 and TNF-α. Moreover, IL-10 KO mice demonstrated a greater increase in TNF-α, IL-1α, and IL-1β mRNAs in the allergen-exposed epidermis, and keratinocytes derived from the mutant mice were able to produce higher amounts of TNF-α and IL-1α protein. These data suggest that IL-10 plays an inhibitory role in LC migration and that this effect may occur via the down-regulation of TNF-α and IL-1 production.

Mechanisms involved in the pathogenesis of sepsis are not necessarily reflected by in vitro cell activation studies

It is thought that lipopolysaccharide (LPS) from gram-negative bacteria contributes significantly to the pathogenesis of septic shock. In vitro studies to address the mechanisms involved in this process have often investigated human monocytes or mouse macrophages, since these cells produce many of the mediators found in septic patients. Targeting of these mediators, especially tumor necrosis factor alpha (TNF-alpha), has been pursued as a means of reducing mortality in sepsis. Two experimental approaches were designed to test the assumption that in vitro studies with macrophages accurately predict in vivo mechanisms of LPS pathogenesis. In the first approach, advantage was taken of the fact that on consecutive days after injection of thioglycolate into mice, increased numbers of macrophages could be harvested from the peritoneum. These cells manifested markedly enhanced levels of in vitro TNF-alpha, interleukin 6 (IL-6), and nitric oxide production in response to LPS. In D-galactosamine-sensitized mice, however, thioglycolate treatment significantly decreased mortality due to LPS, as well as levels of circulating TNF-alpha and IL-6. Anti-TNF-alpha treatment confirmed this cytokine's role in the observed lethality. In a second experimental approach, we compared the mouse macrophage-stimulating potencies of different LPS preparations with their lethalities to mice. In these studies, the in vitro macrophage-stimulating profiles presented by rough-LPS and smooth-LPS preparations were the reverse of their relative lethal potencies in vivo. In conclusion, peritoneal macrophages appear not to be the major cells responsible for the overall host response during endotoxic shock. These findings underscore the importance of verifying the correlation of in vivo systems with in vitro systems when attributing specific functions to a cell type.

Lipopolysaccharide-induced cytokine cascade and lethality in LT alpha/TNF alpha-deficient mice

BACKGROUND

Tumor necrosis factor alpha (TNF-alpha) is often considered the main proinflammatory cytokine induced by lipopolysaccharide (LPS) and consequently the critical mediator of the lethality associated with septic shock.

MATERIALS AND METHODS

We used mice carrying a deletion of both the lymphotoxin alpha (LT-alpha) and TNF-alpha genes to assess the role of TNF in the cytokine cascade and lethality induced by LPS.

RESULTS

Initial production of IL-1 alpha, IL-1 beta, IL-6, and IL-10 is comparable in wild-type and mutant mice. However, at later times, expression of IL-1 alpha, IL-1 beta, and IL-10 is prolonged, whereas that of IL-6 decreases in mutant mice. Expression of IFN-gamma is almost completely abrogated in mutants, which is in agreement with a more significant alteration of the late phase of the cytokine cascade. We measured similar LD50 (600 micrograms) for the intravenous injection of LPS in mice of the three genotypes (+/+, +/-, -/-), demonstrating that the absence of TNF does not confer long-term protection from lethality. However, death occurred much more slowly in mutant mice, who were protected more efficiently from death by CNI 1493, an inhibitor of proinflammatory cytokine production, than were wild-type mice.

DISCUSSION

Thus, while TNF-alpha is not required for the induction of these cytokines by LPS, it modulates the kinetics of their expression. The lethality studies simultaneously confirm a role for TNF as a mediator of early lethality and establish that, in the absence of these cytokines, other mediators take over, resulting in the absence of long-term protection from LPS toxicity.

Inhibition of tumor necrosis factor-alpha action within the CNS markedly reduces the plasma adrenocorticotropin response to peripheral local inflammation in rats

The present study tested the hypothesis that the cytokine tumor necrosis factor-alpha (TNF-alpha) is an important CNS mediator of the hypothalamo-pituitary-adrenal (HPA) axis response to local inflammation in the rat. Recombinant murine TNF-alpha administered directly into the cerebroventricles of normal rats produced a dose-dependent increase in plasma adrenocorticotropin (ACTH) concentration. Local inflammation induced by the intramuscular injection of turpentine (50 microl/100 gm body weight) also produced an increase in plasma ACTH, peaking at 160-200 pg/ml at 7.5 hr after injection (compared with 10-30 pg/ml in controls). Intracerebroventricular pretreatment with either 5 microl of anti-TNF-alpha antiserum or 1-50 microg of soluble TNF receptor construct (rhTNFR:Fc) reduced the peak of the ACTH response to local inflammation by 62-72%. In contrast, intravenous treatment with the same doses of anti-TNF-alpha or rhTNFR:Fc had no significant effect on the ACTH response to local inflammation. Although these data indicated an action of TNF-alpha specifically within the brain, no increase in brain TNF-alpha protein (measured by bioassay) or mRNA (assessed using either in situ hybridization histochemical or semi-quantitative RT-PCR procedures) was demonstrable during the onset or peak of HPA activation produced by local inflammation. Furthermore, increased passage of TNF-alpha from blood to brain seems unlikely, because inflammation did not affect plasma TNF-alpha biological activity. Collectively these data demonstrate that TNF-alpha action within the brain is critical to the elaboration of the HPA axis response to local inflammation in the rat, but they indicate that increases in cerebral TNF-alpha synthesis are not a necessary accompaniment.

Inhibition of tumor necrosis factor-alpha action within the CNS markedly reduces the plasma adrenocorticotropin response to peripheral local inflammation in rats

The present study tested the hypothesis that the cytokine tumor necrosis factor-alpha (TNF-alpha) is an important CNS mediator of the hypothalamo-pituitary-adrenal (HPA) axis response to local inflammation in the rat. Recombinant murine TNF-alpha administered directly into the cerebroventricles of normal rats produced a dose-dependent increase in plasma adrenocorticotropin (ACTH) concentration. Local inflammation induced by the intramuscular injection of turpentine (50 microl/100 gm body weight) also produced an increase in plasma ACTH, peaking at 160-200 pg/ml at 7.5 hr after injection (compared with 10-30 pg/ml in controls). Intracerebroventricular pretreatment with either 5 microl of anti-TNF-alpha antiserum or 1-50 microg of soluble TNF receptor construct (rhTNFR:Fc) reduced the peak of the ACTH response to local inflammation by 62-72%. In contrast, intravenous treatment with the same doses of anti-TNF-alpha or rhTNFR:Fc had no significant effect on the ACTH response to local inflammation. Although these data indicated an action of TNF-alpha specifically within the brain, no increase in brain TNF-alpha protein (measured by bioassay) or mRNA (assessed using either in situ hybridization histochemical or semi-quantitative RT-PCR procedures) was demonstrable during the onset or peak of HPA activation produced by local inflammation. Furthermore, increased passage of TNF-alpha from blood to brain seems unlikely, because inflammation did not affect plasma TNF-alpha biological activity. Collectively these data demonstrate that TNF-alpha action within the brain is critical to the elaboration of the HPA axis response to local inflammation in the rat, but they indicate that increases in cerebral TNF-alpha synthesis are not a necessary accompaniment.

Acute lethal toxicity following passive immunization for treatment of murine cryptococcosis

Passive immunization with monoclonal antibodies (MAbs) specific for the major capsular polysaccharide of Cryptococcus neoformans alters the course of murine cryptococcosis. During studies of passive immunization for treatment of murine cryptococcosis, we noted the occurrence of an acute, lethal toxicity. Toxicity was characterized by scratching, lethargy, respiratory distress, collapse, and death within 20 to 60 min after injection of antibody. The toxic effect was observed only in mice with a cryptococcal infection and was reduced or absent in the early and late stages of disease. The clinical course and histopathology were consistent with those for shock. There was considerable variation between mouse strains in susceptibility to toxicity. Swiss Webster mice from the Charles River colony were most susceptible, followed by C3H/He, BALB/c, and C57BL/6 mice. DBA/2 mice and Swiss Webster mice from the Simonsen colony were resistant. Acute toxicity was mimicked by injection of preformed complexes of MAb and purified polysaccharide. The toxic effect was also produced by injection of MAbs into mice that were preloaded with polysaccharide. The toxic effect was not blocked by treatment of mice with chloropheniramine or anti-tumor necrosis factor alpha antibodies or by depletion of complement components via pretreatment with cobra venom factor. Toxicity was reduced by treatment of mice with high doses of epinephrine, dexamethasone, or chlorpromazine. Finally, the toxic effect was completely blocked by treatment of mice with the platelet-activating factor antagonist WEB 2170 BS or by pretreatment of mice with the liposome-encapsulated drug dichloromethylene diphosphonate, a procedure which depletes macrophages from the spleen and liver.

Role of tumor necrosis factor alpha in pathogenesis of pneumococcal pneumonia in mice

The production and role of tumor necrosis factor alpha (TNF-alpha) in pneumococcal pneumonia were investigated in a mouse pneumonia model. When approximately 10(6) CFU of Streptococcus pneumoniae TUM19 were used to inoculate CBA/J mice intranasally, TNF-alpha levels in the lungs and serum began to increase from 1 and 3 days after infection, respectively, concomitantly with the increase in bacterial counts in the lungs. Anti-TNF-alpha antibody accelerated bacterial proliferation in the blood and the death of the mice. Although serum levels of immunoglobulin G antibody against the infecting bacteria were not affected by the anti-TNF-alpha antibody treatment, neutrophil counts in the blood were decreased by the treatment. These results suggest that TNF-alpha produced in the course of pneumococcal pneumonia prevents bacteremia by increasing the number of neutrophils in the blood.

Strategies for blocking the systemic effects of cytokines in the sepsis syndrome

OBJECTIVES

To review and evaluate animal and human data regarding strategies to intervene in the pathogenesis of the sepsis syndrome by specifically blocking the action of single cytokines.

DATA SOURCES

The English language medical literature was reviewed, including reports of human clinical trials, animal experiments, and in vitro studies elucidating cellular and molecular interactions.

STUDY SELECTION

Emphasis was placed on controlled experimental studies that elucidated the effectiveness of antibodies, soluble receptors, and receptor antagonists in intervening in the pathogenesis of the sepsis reaction.

DATA EXTRACTION

This review focuses on data that directly involve the induction and regulation of protein mediators of sepsis, especially tumor necrosis factor-alpha, interleukin-1 beta, interleukin-6, and interleukin-8.

DATA SYNTHESIS

Information concerning the potential of cytokine blockers in modulating the sepsis reaction is presented in a logical, clinically oriented fashion. The purpose is to emphasize the potential role of these agents by focusing on the actual existing data.

CONCLUSIONS

The pathophysiology of the sepsis reaction appears to involve the sequential release of cytokines. Interventions designed to specifically block the biological effects of single cytokines appear to have a role in the management of sepsis syndrome, but well-designed, prospective, randomized, placebo-controlled clinical trials in well-defined clinical populations are necessary to define this role. These trials require the cooperation of clinical and basic scientists.

Anti-gamma interferon and anti-interleukin-6 antibodies affect staphylococcal enterotoxin B-induced weight loss, hypoglycemia, and cytokine release in D-galactosamine-sensitized and unsensitized mice

Administration of staphylococcal enterotoxin B (SEB) to BALB/c mice was found to induce a cytokine release syndrome hallmarked by weight loss and hypoglycemia. A neutralizing monoclonal antibody against gamma interferon (IFN-gamma) given before SEB counteracted weight loss and prevented hypoglycemia. This protective effect of anti-IFN-gamma antibody was associated with decreased IFN-gamma levels in serum; tumor necrosis factor (TNF) and interleukin-6 (IL-6) levels remained unchanged. A monoclonal anti-IL-6 antibody, known for its ability to cause accumulation of biologically active IL-6 in the circulation, did not modify SEB-induced body weight loss or hypoglycemia. Levels of TNF, IFN-gamma, and IL-6 in serum were all more elevated in anti-IL-6-treated mice than in corresponding SEB-challenged control mice. In D-galactosamine-sensitized mice, SEB-induced weight loss but not hypoglycemia was more severe, resulting mostly in death within 24 h. Higher levels of biologically active TNF and IFN-gamma in serum were noted in these mice than in mice receiving SEB only. In D-galactosamine-sensitized mice, anti-IFN-gamma antibody did prevent hypoglycemia but failed to reduce the severity of the syndrome. Again, TNF levels in anti-IFN-gamma-treated mice remained unchanged. Pretreatment with anti-IL-6 antibody temporarily attenuated SEB-induced hypoglycemia in sensitized mice. Thus, at 6 h post-SEB injection, anti-IL-6-treated mice were less hypoglycemic than corresponding controls. However, at 24 h, hypoglycemia was significantly aggravated. Concomitantly, IL-6 levels were dramatically increased. Neither anti-IFN-gamma nor anti-IL-6 antibody treatment modulated mortality levels in D-galactosamine-sensitized mice. The data obtained with anti-IFN-gamma antibody clearly indicate that endogenous IFN-gamma is instrumental in bringing about hypoglycemia and body weight loss in mice exposed to SEB but also that hypoglycemia is not a crucial determinant of mortality in D-galactosamine-sensitized mice. The data obtained with anti-IL-6 antibody indicate that endogenous IL-6 is involved in regulating the levels of TNF and IFN-gamma in serum.

Detoxification of lipopolysaccharide (LPS) by egg white lysozyme

Recent studies carried out by our group suggest that lysozyme binds to bacterial lipopolysaccharide with a high affinity to produce a complex, and inhibits various biological activities of lipopolysaccharide. Although the basic structure of lipopolysaccharide is independent of the species and strains of Gram-negative bacteria, many structural factors such as O-antigenic polysaccharide, lipid A, substituted groups, and associated molecules, affect the biological activities of lipopolysaccharide. In this study, we prepared lysozyme/lipopolysaccharide complexes using various structures of lipopolysaccharide and compared the activity and physicochemical properties. Native and dansylated lysozyme were found to bind to all tested lipopolysaccharides. The mitogenic activity and TNF production by all tested lipopolysaccharides were significantly reduced by complex formation in vitro. Administration of the complex prepared by various lipopolysaccharides produced significantly less quantities of TNF in the septic shock model. These results suggested that binding of lysozyme to lipopolysaccharide is important for the host both in pathophysiological responses to lipopolysaccharides and in the modification of lipopolysaccharide biological activity.

Immunological priming attenuates the in vivo pathophysiological response to lipopolysaccharide. Comparison of cytokine production, tissue injury, and lethality in complete Freund's adjuvant-primed mice and in unprimed mice

Previous reports have indicated that immunological priming of animals will result in increased cytokine production and enhanced susceptibility to the toxicity of cytokines. We primed mice with complete Freund's adjuvant and challenged 2 weeks later with 1 mg/mouse of lipopolysaccharide. Primed mice produced less tumor necrosis factor than naive mice (35 +/- 8 vs 108 +/- 20 ng/ml) and also less interleukin-6 (182 +/- 37 vs 6.39 +/- 155 ng/ml). Leukopenia developed only in the naive mice. Although neutropenia and lymphocytosis developed in both groups, the alterations manifested themselves more quickly in primed mice. Primed mice had substantially greater pulmonary neutrophil sequestration determined both enzymatically and histologically but no lung damage. However, primed mice had significantly less small bowel damage than naive mice. Mortality was substantially reduced in primed mice compared with unprimed mice. These results demonstrate that immunological priming in vivo decreases cytokine production in response to lipopolysaccharide challenge, decreases organ injury, and reduces mortality.

Cytokine appearance and effects of anti-tumor necrosis factor alpha antibodies in a neonatal rat model of group B streptococcal infection

Cytokines are suspected of playing an important role in the pathophysiology of septic shock. This study was undertaken to determine whether tumor necrosis factor alpha (TNF-alpha) induces the production of other cytokines and mediates mortality in a neonatal rat model of sepsis caused by group B streptococci (GBS). We have measured TNF-alpha, interleukin-1 alpha (IL-1 alpha), interleukin-6 (IL-6), and gamma interferon (IFN-gamma) levels in neonatal rats infected with different strains (H738, 259, and 90) and doses (1 50% lethal dose [LD50] and 5 90% lethal doses [LD90]) of type III GBS. TNF-alpha and IL-6 were detected by the L929 cytotoxicity and the B9 proliferation assays, respectively, in serial plasma samples. IL-1 alpha and IFN-gamma were measured in spleen homogenates by enzyme-linked immunosorbent assay kits by using antibodies raised against the corresponding mouse cytokines. Plasma TNF-alpha levels significantly rose above baseline values within 12 h after intraperitoneal challenge with 5 LD90 of GBS strain H738, corresponding to 3 x 10(3) CFU. A mean peak TNF-alpha concentration of 232 +/- 124 U/ml was reached at 20 h. Peak IL-1 alpha and IL-6 levels of 766 +/- 404 U/g and 1,033 +/- 520 U/ml, respectively, were reached at 24 h after bacterial challenge. Maximal spleen concentrations of IFN-gamma (449 +/- 283 U/g) were measured at 36 h. Concentrations of TNF-alpha, but not other cytokines, remained significantly elevated at 72 h, a time when mortality approached 100%. Significant correlations were found between concentrations of each of the cytokines tested and the logs of CFU concentrations in the blood. In order to ascertain whether TNF-alpha influenced the production of other cytokines, rat pups received two injections of anti-murine TNF-alpha or normal rabbit serum at 2 h before and at 26 h after challenge with live GBS. Plasma TNF-alpha bioactivity was undetectable in anti-TNF-alpha-treated animals, while IL-6 and IFN-gamma, but not IL-1 alpha, levels were significantly reduced, compared with normal serum controls. Rat pups pretreated with anti-TNF-alpha serum and infected with 1 and 5 LD90 of strains H738 and 259 showed enhanced early (48 to 72 h) survival. However, by 96 h this protection was no longer apparent.

High serum levels of TNF-alpha after its administration for isolation perfusion of the limb

In a phase II study, 18 patients with locally spreading melanoma or sarcoma of lower limb were treated by isolation perfusion (ILP) with hyperthermia and local infusion of high dose of recombinant human tumor necrosis factor alpha (rHuTNF-alpha) (4 mg). Bioactive TNF-alpha and interleukin 6 (IL-6) serum levels were measured serially. In the limb, TNF-alpha rapidly reached a plateau at 2 mu/ml, while IL-6 appeared later and progressively increased until the end of ILP. In the systemic circulation TNF-alpha rose up to a median concentration of 31 ng/ml after 1 hour, then decreased and became negligible after 6 hours. IL-6 peaked only after 5 hours after start of ILP (median: 36.7 ng/ml). In patients with substantial leakage towards systemic circulation, both cytokines peaked higher and earlier as compared with patients with minimal leakage. No correlation was found between cytokine levels and severity of side effects which in all cases were reversible. We conclude that high dose TNF-alpha infusion in ILP results in extremely high levels of bioactive TNF-alpha in the systemic circulation without irreversible side effect, and provokes a delayed blood release of large amounts of IL-6; there was a correlation between leakage from the limb during procedure and the magnitude of systemic cytokines levels.

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)

Protective effects of a leukotriene inhibitor and a leukotriene antagonist on endotoxin-induced mortality in carrageenan-pretreated mice

The leukotrienes and tumor necrosis factor (TNF) play an important role in the pathophysiology of septic shock, in which hypotension, leukopenia, thrombocytopenia, and hemoconcentration are observed. This study was performed to examine the effects of a 5-lipoxygenase inhibitor (AA-861), a selective leukotriene receptor antagonist (ONO-1078), and a cyclooxygenase inhibitor (indomethacin) on endotoxin-induced mortality and TNF production in mice. Mice were injected intraperitoneally with carrageenan (5 mg per mouse), which we previously reported as an effective priming agent for lipopolysaccharide (LPS)-induced TNF production and mortality (M. Ogata, S. Yoshida, M. Kamochi, A. Shigematsu, and Y. Mizuguchi, Infect. Immun. 59:679-683, 1991). The indicated doses of AA-861, ONO-1078, indomethacin, or controls were administrated subcutaneously 30 min before LPS (50 micrograms per mouse) provocation. The mortality of mice was significantly decreased by pretreatment with AA-861 (P less than 0.001) or ONO-1078 (P less than 0.01) but not by pretreatment with indomethacin. The 50% lethal dose of LPS in the mice treated with dimethyl sulfoxide or ethanol was 32 or 33 micrograms, respectively, and it increased to 83 micrograms with AA-861 or 59 micrograms with ONO-1078, respectively. Neither AA-861 nor ONO-1078 suppressed LPS-induced TNF production in sera. Treatment with AA-861 significantly decreased the leukopenia and thrombocytopenia, and ONO-1078 significantly decreased the hemoconcentration and thrombocytopenia. The role of endogenous TNF was also examined in the carrageenan-pretreated mice. Treatment with 2 x 10(5) U of rabbit anti TNF-alpha antibody intravenously 2 h before LPS challenge significantly suppressed the LPS-induced TNF activity and decreased the mortality. Therefore, both leukotrienes and TNF play important roles in endotoxin-induced shock and mortality.