The cooperative effects of TNF-alpha and IFN-gamma are determining factors in the ability of IL-10 to protect mice from lethal endotoxemia

Early Activation of iNKT Cells Increased Survival Time of BALB/c Mice in a Murine Model of Melioidosis

Melioidosis is an infectious disease caused by Burkholderia pseudomallei. High interferon gamma (IFN-γ) levels in naive mice were reported to mediate protection against B. pseudomallei infection. Invariant natural killer T (iNKT) cells can produce and secrete several cytokines, including IFN-γ. When iNKT cell-knockout (KO) BALB/c mice were infected with B. pseudomallei, their survival time was significantly shorter than wild-type mice. Naive BALB/c mice pretreated intraperitoneally with α-galactosylceramide (α-GalCer), an iNKT cell activator, 24 h before infection demonstrated 62.5% survival at the early stage, with prolonged survival time compared to nonpretreated infected control mice (14 ± 1 days versus 6 ± 1 days, respectively). At 4 h after injection with α-GalCer, treated mice showed significantly higher levels of serum IFN-γ, interleukin-4 (IL-4), IL-10, and IL-12 than control mice. Interestingly, the IFN-γ levels in the α-GalCer-pretreated group were decreased at 4, 24, and 48 h after infection, while they were highly increased in the control group. At 24 h postinfection in the α-GalCer group, bacterial loads were significantly lower in blood (no growth and 1,780.00 ± 51.21, P < 0.0001), spleens (no growth and 34,300 ± 1,106.04, P < 0.0001), and livers (1,550 ± 68.72 and 13,400 ± 1,066.67, P < 0.0001) than in the control group, but not in the lungs (15,300 ± 761.10 and 1,320 ± 41.63, P < 0.0001), and almost all were negative at 48 h postinfection. This study for the first time shows that early activation of iNKT cells by α-GalCer helps clearance of B. pseudomallei and prolongs mouse survival.

Cruzipain Sulfotopes-Specific Antibodies Generate Cardiac Tissue Abnormalities and Favor Trypanosoma cruzi Infection in the BALB/c Mice Model of Experimental Chagas Disease

Trypanosoma cruzi cruzipain (Cz) bears a C-terminal domain (C-T) that contains sulfated epitopes “sulfotopes” (GlcNAc6S) on its unique N-glycosylation site. The effects of in vivo exposure to GlcNAc6S on heart tissue ultrastructure, immune responses, and along the outcome of infection by T. cruzi, were evaluated in a murine experimental model, BALB/c, using three independent strategies. First, mice were pre-exposed to C-T by immunization. C-T-immunized mice (C-T_IM) showed IgG2a/IgG1 <1, induced the production of cytokines from Th2, Th17, and Th1 profiles with respect to those of dC-T_IM, which only induced IL-10 respect to the control mice. Surprisingly, after sublethal challenge, both C-T_IM and dC-T_IM showed significantly higher parasitemia and mortality than the control group. Second, mice exposed to BSA-GlcNAc6S as immunogen (BSA-GlcNAc6S_IM) showed: severe ultrastructural cardiac alterations while BSA-GlcNAc_IM conserved the regular tissue architecture with slight myofibril changes; a strong highly specific humoral-immune-response reproducing the IgG-isotype-profile obtained with C-T_IM; and a significant memory-T-cell-response demonstrating sulfotope-immunodominance with respect to BSA-GlcNAc_IM. After sublethal challenge, BSA-GlcNAc6S_IM showed exacerbated parasitemias, despite elevated IFN-γ levels were registered. In both cases, the abrogation of ultrastructural alterations when using desulfated immunogens supported the direct involvement of sulfotopes and/or indirect effect through their specific antibodies, in the induction of tissue damage. Finally, a third strategy using a passive transference of sulfotope-specific antibodies (IgG-GlcNAc6S) showed the detrimental activity of IgG-GlcNAc6S on mice cardiac tissue, and mice treated with IgG-GlcNAc6S after a sublethal dose of T. cruzi, surprisingly reached higher parasitemias than control groups. These findings confirmed the indirect role of the sulfotopes, via their IgG-GlcNAc6S, both in the immunopathogenicity as well as favoring T. cruzi infection.

New Insights into the Immune Molecular Regulation of the Pathogenesis of Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome is an inflammatory disease characterized by dysfunction of pulmonary epithelial and capillary endothelial cells, infiltration of alveolar macrophages and neutrophils, cell apoptosis, necroptosis, NETosis, and fibrosis. Inflammatory responses have key effects on every phase of acute respiratory distress syndrome. The severe inflammatory cascades impaired the regulation of vascular endothelial barrier and vascular permeability. Therefore, understanding the relationship between the molecular regulation of immune cells and the pulmonary microenvironment is critical for disease management. This article reviews the current clinical and basic research on the pathogenesis of acute respiratory distress syndrome, including information on the microenvironment, vascular endothelial barrier and immune mechanisms, to offer a strong foundation for developing therapeutic interventions.

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.

Interaction of Streptococcus agalactiae and Cellular Innate Immunity in Colonization and Disease

Streptococcus agalactiae (Group B streptococcus, GBS) is highly adapted to humans, where it is a normal constituent of the intestinal and vaginal flora. Yet, GBS has highly invasive potential and causes excessive inflammation, sepsis, and death at the beginning of life, in the elderly and in diabetic patients. Thus, GBS is a model pathobiont that thrives in the healthy host, but has not lost its potential virulence during coevolution with mankind. It remains incompletely understood how the innate immune system contains GBS in the natural niches, the intestinal and genital tracts, and which molecular events underlie breakdown of mucocutaneous resistance. Newborn infants between days 7 and 90 of life are at risk of a particularly striking sepsis manifestation (late-onset disease), where the transition from colonization to invasion and dissemination, and thus from health to severe sepsis is typically fulminant and not predictable. The great majority of late-onset sepsis cases are caused by one clone, GBS ST17, which expresses HvgA as a signature virulence factor and adhesin. In mice, HvgA promotes the crossing of both the mucosal and the blood–brain barrier. Expression levels of HvgA and other GBS virulence factors, such as pili and toxins, are regulated by the upstream two-component control system CovR/S. This in turn is modulated by acidic epithelial pH, high glucose levels, and during the passage through the mouse intestine. After invasion, GBS has the ability to subvert innate immunity by mechanisms like glycerinaldehyde-3-phosphate-dehydrogenase-dependent induction of IL-10 and β-protein binding to the inhibitory phagocyte receptors sialic acid binding immunoglobulin-like lectin 5 and 14. On the host side, sensing of GBS nucleic acids and lipopeptides by both Toll-like receptors and the inflammasome appears to be critical for host resistance against GBS. Yet, comprehensive models on the interplay between GBS and human immune cells at the colonizing site are just emerging.

Aging predisposes to acute inflammatory induced pathology after tumor immunotherapy

Aging strongly promotes inflammation responses, which may predispose individuals after cancer therapies to lethal system toxicities and pathology that can be partially prevented by TNF blockade.

Cancer commonly occurs in the elderly and immunotherapy (IT) is being increasingly applied to this population. However, the majority of preclinical mouse tumor models assessing potential efficacy and toxicities of therapeutics use young mice. We assessed the impact of age on responses to systemic immune stimulation. In contrast to young mice, systemic cancer IT regimens or LPS given to aged mice resulted in rapid and lethal toxicities affecting multiple organs correlating with heightened proinflammatory cytokines systemically and within the parenchymal tissues. This inflammatory response and increased morbidity with age was independent of T cells or NK cells. However, prior in vivo depletion of macrophages in aged mice resulted in lesser cytokine levels, increased survival, and decreased liver histopathology. Furthermore, macrophages from aged mice and normal human elderly volunteers displayed heightened TNF and IL-6 production upon in vitro stimulation. Treatment of both TNF knockout mice and in vivo TNF blockade in aged mice resulted in significant increases in survival and lessened pathology. Importantly, TNF blockade in tumor-bearing, aged mice receiving IT displayed significant anti-tumor effects. These data demonstrate the critical role of macrophages in the age-associated hyper-inflammatory cytokine responses to systemic immunostimulation and underscore the importance of performing preclinical assessments in aged mice.

Maternal immunization with actinomycetales immunomodulators reduces parasitemias in offspring challenged with Trypanosoma cruzi

This article describes the first use of heat-killed, borate-buffered preparations of aerobic actinomycetales to immunize pregnant animals in order to determine the effect on their pregnancy and fertility and the survival coefficients of their offspring. Pregnant rats received three injections of Gordonia bronchialis, Rhodococcus coprophylus or physiological saline and a proportion of their offspring were challenged with live Trypanosoma cruzi at the time of weaning. Levels of parasitemia and, in some animals, of the cytokines IFN-γ and IL-10 were measured. The progress of pregnancy, fertility and survival of offspring were unaffected by the maternal immunizations. The offspring of rats immunized with G. bronchialis displayed significantly reduced parasitemias, with increased levels of IFN-γ and reduced levels of IL-10, 4 days after challenge. The offspring of rats immunized with R. coprophylus displayed greater parasitemias than did those of the control group. These unexpected results are discussed and their causation considered.

Regulatory effects of hydrogen sulfide on IL-6, IL-8 and IL-10 levels in the plasma and pulmonary tissue of rats with acute lung injury

We examined the possible role of hydrogen sulfide (H2S) in the pathogenesis of oleic acid (OA)-induced acute lung injury (ALI) and its regulatory effects on the inflammatory response. Compared to control rats, the OA-treated rats had decreased partial pressure of oxygen in the arterial blood (PaO2) levels, an increased pulmonary wet/dry weight (W/D) ratio, increased index of quantitative assessment (IQA) score and increased frequency of polymorphonuclear (PMN) cells in the lung 2, 4 or 6 h after OA injection (0.1 ml/kg, intravenous injection). In addition, significantly increased IL-6, IL-8 and IL-10 levels together with decreased H2S levels were observed in the plasma and lung tissue of OA-treated rats compared to controls. Administration of the H2S donor sodium hydrosulfide (NaHS, 56 micromol/L, intraperitoneal injection) into OA-treated rats increased the PaO2 level, reduced the lung W/D ratio and infiltration of PMN cells, and alleviated the degree of ALI (measured by the IQA score). In addition, NaHS decreased IL-6 and IL-8 levels but increased IL-10 levels in the plasma and lung tissues, suggesting that H2S may regulate the inflammatory response during ALI via regulation of IL-6, IL-8 and IL-10. Thus, the down-regulation of endogenous H2S production might be involved in the pathogenesis of OA-induced ALI in rats.

Pathophysiology of pulmonary complications of acute pancreatitis

Acute pancreatitis in its severe form is complicated by multiple organ system dysfunction, most importantly by pulmonary complications which include hypoxia, acute respiratory distress syndrome, atelectasis, and pleural effusion. The pathogenesis of some of the above complications is attributed to the production of noxious cytokines. Clinically significant is the early onset of pleural effusion, which heralds a poor outcome of acute pancreatitis. The role of circulating trypsin, phospholipase A2, platelet activating factor, release of free fatty acids, chemoattractants such as tumor necrosis factor (TNF)-alpha, interleukin (IL)-1, IL-6, IL-8, fMet-leu-phe (a bacterial wall product), nitric oxide, substance P, and macrophage inhibitor factor is currently studied. The hope is that future management of acute pancreatitis with a better understanding of the pathogenesis of lung injury will be directed against the production of noxious cytokines.

Morphine withdrawal sensitizes mice to lipopolysaccharide: Elevated TNF-α and nitric oxide with decreased IL-12

Mice made dependent on morphine using slow-release morphine pellets for 96 h were withdrawn by removal of pellets, followed by a sublethal dose of LPS 24 h later. These animals exhibited 100% lethality. Animals withdrawn from placebo pellets receiving LPS all survived, as did morphine-withdrawn mice receiving saline. Morphine-withdrawn LPS-treated animals had elevated serum TNF-alpha and nitric oxide levels, and depressed IL-12 levels compared to controls. Anti-TNF-alpha antibody given prior to LPS challenge afforded significant protection to morphine-withdrawn animals. These studies show that morphine withdrawal sensitizes to LPS lethality via increased production of TNF-alpha.

n-3 fatty acids, inflammation, and immunity--relevance to postsurgical and critically ill patients

Excessive or inappropriate inflammation and immunosuppression are components of the response to surgery, trauma, injury, and infection in some individuals and these can lead, progressively, to sepsis and septic shock. The hyperinflammation is characterized by the production of inflammatory cytokines, arachidonic acid-derived eicosanoids, and other inflammatory mediators, while the immunosuppression is characterized by impairment of antigen presentation and of T helper cell type-1 responses. Long-chain n-3 FA from fish oil decrease the production of inflammatory cytokines and eicosanoids. They act both directly (by replacing arachidonic acid as an eicosanoid substrate and by inhibiting arachidonic acid metabolism) and indirectly (by altering the expression of inflammatory genes through effects on transcription factor activation). Thus, long-chain n-3 FA are potentially useful anti-inflammatory agents and may be of benefit in patients at risk of developing sepsis. As such, an emerging application of n-3 FA is in surgical or critically ill patients where they may be added to parenteral or enteral formulas. Parenteral or enteral nutrition including n-3 FA appears to preserve immune function better than standard formulas and appears to partly prevent some aspects of the inflammatory response. Studies to date are suggestive of clinical benefits from these approaches, especially in postsurgical patients.

A role for histamine in cytokine modulation by the adenosine A(3) receptor agonist, 2-Cl-IB-MECA

The effects of adenosine receptor agonists on cytokine production in vivo were investigated in mouse models of endotoxemia. Selective adenosine A(3) (2-chloro-N(6)-(3-iodobenzyl) adenosine-5'-N-methyluronamide) (2-Cl-IB-MECA) and A(2A) (2-p-(2-carboxyethyl) phenethylamino-5'-N-ethylcarboxamido adenosine hydrochloride) (CGS 21860) receptor agonists were found to modulate endotoxin-induced cytokine responses in mice sensitized to D-galactosamine or primed with Corynebacterium parvum. The adenosine receptor agonists had similar effects in these models of endotoxemia, suppressing the production of tumor necrosis factor alpha (TNF-alpha) and interleukin-12 while enhancing that of interleukin-10. However, 2-Cl-IB-MECA also caused a dramatic increase in circulating histamine levels shortly after its injection into mice. The cytokine modulatory activities of 2-Cl-IB-MECA were mimicked by the mast cell depleting compound 48/80 and both drugs only produced such effects at doses that caused an elevation in circulating histamine levels. Furthermore, the capacity of 2-Cl-IB-MECA to modulate cytokine responses was greatly diminished when the drug was administered to mast cell deficient (WBB6F-W/W(V)) mice. Together, these results strongly suggest a role for histamine in cytokine modulation by 2-Cl-IB-MECA. Cimetidine, a histamine H(2) receptor antagonist, did not reverse cytokine modulation by 2-Cl-IB-MECA and pyrilamine, a histamine H(1) receptor antagonist, prevented the increase in serum histamine that was induced by 2-Cl-IB-MECA. This effect of pyrilamine and other histamine H(1) receptor antagonists confounded attempts to determine a role for the histamine H(1) receptor in cytokine modulation by 2-Cl-IB-MECA. However, under some experimental conditions, pyrilamine appeared to antagonize the modulatory effects of the adenosine A(3) receptor agonist on cytokine responses. The apparent antagonism of pyrilamine was unrelated to its suppressive effects on histamine release and appeared to reflect activity at the level of the histamine H(1) receptor.

Antiinflammatory effect of retrovirally transfected interleukin-10 on monosodium urate monohydrate crystal-induced acute inflammation in murine air pouches

OBJECTIVE

To investigate the role of interleukin-10 (IL-10) in the inflammatory response, the antiinflammatory effect of retrovirally transfected IL-10 was evaluated both in vitro and in vivo.

METHODS

A recombinant retrovirus containing the murine IL-10 gene was constructed using the pLXSN vector and was designated as LXSN-IL-10. Murine IL-10 was introduced into embryonic C57BL/6J fibroblast cells using LXSN-IL-10 to create C57-IL-10 cells. The effect of IL-10 in the culture supernatant of these cells was then evaluated by determining changes in the production of tumor necrosis factor alpha (TNFalpha), macrophage inflammatory protein 1alpha (MIP-1alpha), and MIP-1beta by macrophages. The antiinflammatory effect of C57-IL-10 cells was also investigated using an in vivo model of monosodium urate monohydrate (MSU) crystal-induced acute inflammation.

RESULTS

The IL-10 gene transcript and its product were detected by reverse transcriptase-polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. The level of IL-10 in the culture supernatant of C57-IL-10 cells was estimated to be 50 ng/ml. The culture supernatant of these cells exerted the biologic activity of IL-10, showing inhibition of TNFalpha, MIP-1alpha, and MIP-1beta production by macrophages. Injection of C57-IL-10 cells into murine air pouches significantly inhibited MSU crystal-induced cellular infiltration (P < 0.01) and production of the mouse CXC chemokine KC (P < 0.05). These findings were consistent with the results obtained by the injection of recombinant human IL-10 into air pouches.

CONCLUSION

In this murine air pouch model of MSU crystal-induced inflammation, IL-10 seemed to inhibit the recruitment of neutrophils at least partly by suppressing KC production. These findings seem to suggest that IL-10 gene therapy may be useful for inflammatory diseases.

Differential susceptibility to acute Trypanosoma cruzi infection in BALB/c and C57BL/6 mice is not associated with a distinct parasite load but cytokine abnormalities

Inoculation of Trypanosoma cruzi, Tulahuén strain, into C57BL/6 and BALB/c mice led to an acute infection characterized by marked parasitaemia, myocardial inflammation and thymocyte depletion. While C57BL/6 mice showed a progressive and lethal disease, BALB/c mice partly recovered. To characterize these murine models more effectively, we studied the parasite burden, serum levels of major infection outcome-related cytokines, the in vitro features of T. cruzi infection in peritoneal macrophages and the immunophenotype of thymic cells. The greater disease severity of T. cruzi-infected C57BL/6 mice was not linked to an increased parasite load, as parasitaemia, myocardial parasite nests and amastigote counts in peritoneal macrophages were not different from those in BALB/c mice. Cortical thymocyte loss was accompanied by the presence of apoptotic bodies and fragmented nuclear DNA, whereas fluorocytometric analysis at 17 days postinfection (p.i.) revealed a more pronounced loss of CD4+ CD8+ cells in C57BL/6 mice. This group displayed higher levels of TNF-alpha on days 14 and 21 p.i., in the presence of lower IL-1beta and IL-10 concentrations by days 14 and 21, and days 7 and 14 p.i., respectively. Day-21 evaluation showed higher concentrations of nitrate and TNF-alpha soluble receptors in C57BL/6 mice with no differences in IFN-gamma levels, with respect to the BALB/c group. Increased morbidity of C57BL/6 T. cruzi-infected mice does not seem to result from an aggravated infection but from an unbalanced relationship between pro- and anti-inflammatory mediators.

Intestinal permeability is reduced and IL-10 levels are increased in septic IL-6 knockout mice

Sepsis is associated with increased intestinal permeability, but mediators and mechanisms are not fully understood. We examined the role of interleukin (IL)-6 and IL-10 in sepsis-induced increase in intestinal permeability. Intestinal permeability was measured in IL-6 knockout (IL-6 -/-) and wild-type (IL-6 +/+) mice 16 h after induction of sepsis by cecal ligation and puncture or sham operation. In other experiments, mice or intestinal segments incubated in Ussing chambers were treated with IL-6 or IL-10. Intestinal permeability was assessed by determining the transmucosal transport of the 4.4-kDa marker fluorescein isothiocyanate conjugated dextran and the 40-kDa horseradish peroxidase. Intestinal permeability for both markers was increased in septic IL-6 +/+ mice but not in septic IL-6 -/- mice. Treatment of nonseptic mice or of intestinal segments in Ussing chambers with IL-6 did not influence intestinal permeability. Plasma IL-10 levels were increased in septic IL-6 -/- mice, and treatment of septic mice with IL-10 resulted in reduced intestinal permeability. Increased intestinal permeability during sepsis may be regulated by an interaction between IL-6 and IL-10. Treatment with IL-10 may prevent the increase in mucosal permeability during sepsis.

Modulation of cytokine responses in Corynebacterium parvum-primed endotoxemic mice by centrally administered cannabinoid ligands

The cannabinoid receptor agonists [(-)-11-hydoxy-Delta(8)tetrahydrocannabinol-dimethylheptyl] (HU-210) and [(R)-(+)-[2,3-dihydro-5-methyl-3-[(4-morpholinyl)methyl[pyrrolo[1,2,3-de]1,4-benzoxazin-6-yl](1-naphthalenyl) methanone] (WIN 55212-2) were previously shown to downregulate inflammatory cytokines (tumor necrosis factor alpha and interleukin-12) and to upregulate antiinflammatory interleukin-10 when administered intraperitoneally (i.p.) to mice before an endotoxin challenge. Cytokine modulation coincided with the onset of behavioral changes that are associated with cannabinoid agonist activated central cannabinoid CB(1) receptors. Both effects were antagonized by [N-(piperdin-1-yl)-5-(4-chloropheny)-1-(2,4-dichloropheny)-4-methyl-1H-pyrazole-3-carboxamide hydrochloride] (SR141716A) a selective cannabinoid CB(1) receptor antagonist. In the present study, we have investigated further the apparent role of central CB(1) cannabinoid receptors in cytokine modulation by HU-210 and WIN 55212-2. When administered intracerebroventricularly (i.c.v.), the drugs modulated cytokine responses at doses that were threefold to fourfold lower than those found effective by the i.p. route. SR141716A blocked cytokine modulation when coadministered centrally with the agonists, while a selective cannabinoid CB(2) receptor antagonist, (N-[(1S)-endo-1,3,3-trimethylbicyclo[2.2.1]heptan-2-yl]5-(4-choro-3 methylphenyl)-1-(4-methylbenzyl)pyrazole-3-carboxamide) (SR144528) had no effect. Surprisingly, SR144528 was found to modulate cytokines itself when injected i.c.v.

Immune response to autologous and heterologous Helicobacter pylori antigens in humans

Infection of humans with Helicobacter pylori results in the development of chronic gastritis and plays an important role in gastric ulcer pathogenesis. Despite the infiltration of the mucosa with specific immunocompetent cells and production of specific antibodies, the infection usually persists for life. This study was performed to investigate if immunologic mechanisms exist which could contribute to the inability of the host to terminate the infection. Therefore, we compared the in vitro immunoreactivity of peripheral blood mononuclear cells (PBMC) from H. pylori-infected patients after stimulation with sonicated H. pylori bacteria from the stomach of the patient (autologous bacterial strain) with stimulation by bacteria from other patients (heterologous bacteria). We measured cell proliferation, expression of T cell activation markers CD25, HLA-DR, and CD71, as well as production ofinterleukin-10 (IL-10), an inhibitory cytokine. We found that the proliferative response of PBMC was significantly lower after autologous than after heterologous stimulation. Furthermore, secretion of IL-10 in the culture supernatants was significantly higher when PBMC were incubated with autologous than with heterologous H. pylori antigens. No significant differences between autologous or heterologous stimulation were observed in the increased expression of T cell activation markers. These data indicate that systemic immunologic response to H. pylori are strain-dependent. For further studies of the immune responses towards H. pylori, the use of an autologous stimulatory system seems necessary.

Gamma interferon prevents the inhibitory effects of oxidative stress on host responses to Escherichia coli infection

Oxidative stress occurs in animals challenged with bacterial endotoxin and can affect the expression of important host inflammatory genes. However, much less is known about the effects of oxidative stress on responses to gram-negative bacteria. The current study compared the effects of redox imbalance on hepatic responses of mice to Escherichia coli bacteria versus purified endotoxic lipopolysaccharide (LPS). Oxidative stress induced by glutathione depletion virtually eliminated hepatic tumor necrosis factor alpha responses to both E. coli and LPS. Inducible NO synthase (iNOS) and intercellular adhesion molecule-1 (ICAM-1) expression was also markedly inhibited by glutathione depletion in LPS-challenged mice, but was unaffected in E. coli-infected animals. Three findings suggested that gamma interferon (IFN-gamma) production explained the differences between LPS and bacterial challenge. Glutathione depletion completely inhibited the IFN-gamma response to LPS, but only partially inhibited IFN-gamma production in infected mice. Exogenous IFN-gamma restored iNOS and ICAM-1 responses to LPS in stressed mice. Conversely, IFN-gamma-deficient, glutathione-depleted mice showed a marked decrease in iNOS and ICAM-1 expression when challenged with E. coli. These findings indicate that both the nature of the microbial challenge and the production of IFN-gamma can be important in determining the effects of redox imbalance during gram-negative bacterial infections.

Cytokine gene expression in innately susceptible BALB/c mice and relatively resistant C57BL/6 mice during infection with virulent Burkholderia pseudomallei

Production of cytokines including gamma interferon (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha) is an important early-stage host response following infection with intracellular pathogens. Development of immunity to these pathogens is determined to a large extent by the timing and relative level of expression of the cytokines. Numerous studies have shown that early cytokine responses involving interleukin-12 (IL-12) and IFN-gamma are important for resistance to intracellular pathogens, whereas responses involving IL-4 and IL-10 increase host susceptibility. These often-indistinct early cytokine responses influence the differentiation of naïve CD4(+) T helper cells, which later develop into what have commonly been termed Th1- and Th2-type cells. The characterization of CD4(+) T-helper-cell responses as Th1 or Th2 type is based largely on the cytokine profiles during the specific phase and has been used in recent years to account for the innate resistance and susceptibility of different inbred strains of mice to several intracellular pathogens. Studies investigating cytokine production in terms of CD4(+) T-helper-cell polarization in Burkholderia pseudomallei infection have not been undertaken. In this study, we used semiquantitative reverse transcription-PCR to assess induction of cytokine mRNA in liver and spleen of B. pseudomallei-susceptible BALB/c and relatively resistant C57BL/6 mice following infection with virulent B. pseudomallei. The levels of mRNA for IFN-gamma, TNF-alpha, IL-1beta, IL-6, IL-10, and IL-12 increased in both BALB/c and C57BL/6 mice 24 to 36 h after infection. A comparison of BALB/c and C57BL/6 responses revealed the relative levels of expression of mRNA for several of these cytokines, including IFN-gamma, were greater in BALB/c mice, suggesting a role for endotoxic shock and cytokine-mediated immunopathology in the development of acute melioidosis. Early induction of mRNA for the cytokines classically associated with development of Th1- and Th2-type responses was absent or minimal, and induction levels in both strains of mice were similar. During the specific phase, cytokine mRNA profiles occurred as a combination of Th1- and Th2-type patterns. Collectively, these results demonstrate that cytokine mRNA responses in BALB/c and C57BL/6 mice following infection with virulent B. pseudomallei do not develop as polarized Th1- or Th2-type profiles. Considering the role of TNF-alpha and IFN-gamma in the processes of endotoxic shock, these results also indicate that selected cytokines, while important for resistance to B. pseudomallei infection, are also potential contributors to immunopathology and the development of acute fulminating disease.

Inflammatory mediators in acute pancreatitis

Inflammatory mediators play a key role in acute pancreatitis and the resultant multiple organ dysfunction syndrome, which is the primary cause of death in this condition. Recent studies have confirmed the critical role played by inflammatory mediators such as TNF-alpha, IL-1beta, IL-6, IL-8, PAF, IL-10, C5a, ICAM-1, and substance P. The systemic effects of acute pancreatitis have many similarities to those of other conditions such as septicaemia, severe burns, and trauma. The delay between the onset of inflammation in the pancreas and the development of the systemic response makes acute pancreatitis an ideal experimental and clinical model with which to study the role of inflammatory mediators and to test novel therapies. Elucidation of the key mediators involved in the pathogenesis of acute pancreatitis will facilitate the development of clinically effective anti-inflammatory therapy.

Inflammatory mediators in acute pancreatitis

Inflammatory mediators play a key role in acute pancreatitis and the resultant multiple organ dysfunction syndrome, which is the primary cause of death in this condition. Recent studies have confirmed the critical role played by inflammatory mediators such as TNF-alpha, IL-1beta, IL-6, IL-8, PAF, IL-10, C5a, ICAM-1, and substance P. The systemic effects of acute pancreatitis have many similarities to those of other conditions such as septicaemia, severe burns, and trauma. The delay between the onset of inflammation in the pancreas and the development of the systemic response makes acute pancreatitis an ideal experimental and clinical model with which to study the role of inflammatory mediators and to test novel therapies. Elucidation of the key mediators involved in the pathogenesis of acute pancreatitis will facilitate the development of clinically effective anti-inflammatory therapy.

Multiple Roles for IL-12 in a Model of Acute Septic Peritonitis

The present study addressed the role of IL-12 in a murine model of septic peritonitis, induced by cecal ligation and puncture (CLP). Although CLP surgery induced IL-12 production at 6 and 24 h after surgery, IL-12 immunoneutralization was clearly deleterious in this model: 54% of CLP mice receiving preimmune serum survived, whereas mice administered IL-12 antisera prior to CLP experienced a 25% survival rate. IL-12 immunoneutralization not only led to increased mortality, but also appeared to promote a shift away from IL-12 and IFN-γ, in favor of IL-10. This cytokine shift corresponded to changes in bacterial load, as CLP mice receiving IL-12 antiserum yielded more CFUs from the peritoneal cavity at 24 h after CLP. To address the role of bacterial infection in IL-12 antiserum-induced mortality following CLP, antibiotics were administered for 4 days after surgery. Despite regular antibiotic administration, IL-12 immunoneutralization still reduced survival in CLP mice. Furthermore, histology of the ceca revealed that mice administered IL-12 antisera failed to show typical organization of the damaged cecum wall. Accordingly, Gram staining revealed bacteria within peritoneal fluids from these mice, while peritoneal fluids from CLP mice that received preimmune serum and antibiotics were free of bacteria. Altogether, these data suggested multiple important roles for IL-12 in the evolution of murine septic peritonitis.

Dietary lipids modify the cytokine response to bacterial lipopolysaccharide in mice

To investigate the effect of dietary lipids with different fatty acid compositions upon the in vivo cytokine response to bacterial lipopolysaccharide (LPS), mice were fed for 5 weeks on a low-fat diet or on one of four high-fat diets that contained 20%, by weight, of coconut oil (CO), olive oil (OO), safflower oil (SO) or fish oil (FO). The mice were injected intraperitoneally with a non-lethal dose of Escherichia coli LPS (100 micrograms/20 g body weight) and killed 90 or 180 min later. Plasma tumour necrosis factor-alpha (TNF-alpha), interleukin (IL)-1alpha, IL-6 and IL-10 concentrations were measured by enzyme-linked immunosorbent assay (ELISA). Plasma TNF-alpha and IL-10 concentrations were higher 90 min postinjection than after 180 min, whereas plasma IL-1beta and IL-6 concentrations were higher 180 min postinjection than after 90 min. Peak plasma TNF-alpha, IL-1beta and IL-6 concentrations were lower in the CO- and FO-fed mice than in those fed the SO diet. Peak plasma IL-10 concentrations were higher in CO-fed mice than in those fed some of the other diets. These observations suggest that, relative to the n-6 polyunsaturated fatty acid-rich SO diet, CO and FO diminish production of proinflammatory cytokines in vivo. This indicates that these fatty acids might be useful therapies in acute and chronic inflammatory diseases. The enhanced production of IL-10 following CO feeding appears to be an additional antiinflammatory effect of this oil, which could give added benefit in various clinical conditions.

Endogenous mouse interleukin-10 is up-regulated by exogenously administered recombinant human interleukin-10, but does not contribute to the efficacy of the human protein in mouse models of endotoxemia

In murine models of experimental endotoxemia, inflammatory cytokines as well as antiinflammatory interleukin-10 (IL-10) appear in the circulation after the injection of lipopolysaccharide (LPS). There is considerable experimental evidence to suggest that the major function of endogenously produced IL-10 is to down-regulate inflammatory cytokine production. Indeed, the protective effects of exogenously administered IL-10 against murine endotoxin lethality have been shown to correlate with its ability to inhibit the LPS-induced production of tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma). While mouse IL-10 (mIL-10) has been used in the majority of studies in murine endotoxemia, we have found the human homolog to be equally effective in suppressing inflammatory cytokine production and in protecting mice from endotoxin lethality. However, we have recently observed that the LPS-induced endogenous IL-10 response is enhanced when mice are treated with recombinant human IL-10 (rhuIL-10). The upregulation of endogenous IL-10 by exogenously administered rhuIL-10 is particularly evident in mice that are primed with Corynebacterium partum (Proprionibacterium acnes). In the present study, we have examined the potential contributions of the increased circulating levels of mouse IL-10 to the inhibitory effects seen with rhuIL-10 on inflammatory cytokine production and endotoxin lethality. We show that pretreatment with a neutralizing anti-mouse IL-10 monoclonal antibody (mAb) has no effect on the ability of rhuIL-10 to suppress an LPS-induced inflammatory cytokine response in these mice. In contrast, the suppressive effects of the human protein on inflammatory cytokine responses are blocked completely by pretreating the animals with an anti-huIL-10 mAb. These data show that despite the up-regulated endogenous IL-10 response, it is the exogenously administered rhuIL-10 that is directly responsible for the suppressed inflammatory cytokine responses that are observed when the human protein is given to endotoxemic mice.

An antipyretic role for interleukin-10 in LPS fever in mice

Interleukin (IL)-10 inhibits the synthesis of proinflammatory cytokines implicated in fever, including IL-1beta, IL-6, and tumor necrosis factor (TNF)-alpha. We hypothesized that IL-10 functions as an antipyretic in the regulation of fevers to lipopolysaccharide (LPS) and turpentine. Body temperature was measured by biotelemetry. Swiss Webster (SW) mice treated with recombinant murine IL-10 were resistant to fever induced by a low dose of LPS (100 microgram/kg ip) and to the hypothermic and febrile effects of a high (septiclike) dose of LPS (2.5 mg/kg ip). IL-10 knockout mice developed an exacerbated and prolonged fever in response to a low dose of LPS (50 microgram/kg ip) compared with their wild-type counterparts. At 4 h after injection of the low dose of LPS, plasma levels of IL-6, but not TNF-alpha, were significantly elevated in the IL-10 knockout mice compared with their wild-type controls (ANOVA, P < 0.05). After injection of the same high dose of LPS injected into SW mice, wild-type mice developed a fever at 24 h whereas IL-10 knockout mice immediately developed a profound hypothermia that lasted through 41 h (ANOVA, P < 0.05). Body weight and food intake were more significantly depressed in response to the high dose of LPS in the knockout mice compared with their wild-type controls. Only 30% of the IL-10 knockout mice survived compared with 100% of the wild-type mice (Fisher's exact test, P < 0.05). Fever in response to the injection of turpentine (100 microliter/mouse sc) did not differ between wild-type and IL-10 knockout mice. These data support the hypotheses that 1) IL-10 functions as an endogenous antipyretic following exposure to LPS, 2) a putative mechanism of the early antipyretic action of IL-10 is through the inhibition of plasma levels of IL-6, 3) IL-10 has a protective role in the lethal effects of exposure to high levels of LPS, and 4) endogenous IL-10 does not have a role in fever induced by turpentine.

Involvement of intrasinusoidal hemostasis in the development of concanavalin A-induced hepatic injury in mice

Concanavalin A (Con A) stimulation induces T-cell activation-associated hepatic injury. This study is designed to show the involvement of microcirculatory disturbance in the pathogenesis. Con A administration led to prominent intrasinusoidal hemostasis, which consisted of erythrocyte agglutination, lymphocyte/neutrophil sticking to endothelial cells, and platelet aggregation and degranulation, resulting in a marked decrease in the intrahepatic blood flow and elevation of portal perfusion pressure. After hemostasis, confluent hepatic necrosis occurred within the congested area of liver parenchyma. Reduction in the extent of hemostasis by the treatment with heparin (thrombin inhibitor) or cyproheptadine (serotonin inhibitor) decreased hepatic injury. Pretreatment with either anti-tumor necrosis factor alfa (TNF-alpha) or anti-interferon gamma (IFN-gamma) monoclonal antibody (MAb) moderately decreased hemostasis and hepatic injury, whereas combined use of two MAbs almost perfectly protected mice from these disorders. Complete obliteration of hemostasis and hepatic injury was also accomplished by the pretreatment with FK506 which suppressed TNF-alpha and IFN-gamma production. Intrasinusoidal accumulation of leukocytes and platelets was, however, not blocked by FK506, indicating that Con A activities other than the stimulation of cytokine production are responsible for this event. The administration of anti-CD3 MAb, a T-cell stimulant without agglutination activities, which elevated plasma cytokine levels in a comparable degree without inducing prominent leukocyte infiltration, did not induce hepatic congestion and injury. These findings indicate that the agglutination activities of Con A and T-cell activation mediated TNF-alpha/IFN-gamma production are both required for the induction of intrasinusoidal hemostasis, which is indispensable for the development of hepatic injury.

Role of gamma interferon in the pathogenesis of bacteremic pneumococcal pneumonia

Gamma interferon (IFN-gamma) concentrations in blood, but not in lungs, rose significantly at 24 to 48 h after murine pulmonary infection with virulent pneumococci. In contrast, infection with avirulent pneumococcal strains produced minimal rises in serum IFN-gamma concentrations. Compared with that of immunocompetent mice, mortality was appreciably increased after pulmonary infection of IFN-gamma gene knockout mice, suggesting a protective role for IFN-gamma in host response to pneumococcal disease.

MCP-1 protects mice in lethal endotoxemia

The overzealous production of proinflammatory cytokines in sepsis can result in shock, multiorgan dysfunction, and even death. In this study, we assessed the role of monocyte chemoattractant protein-1 (MCP-1) as a mediator of sepsis in endotoxin-challenged mice. Intraperitoneal administration of LPS to CD-1 mice induced a substantial time-dependent increase in MCP-1 in plasma, lung, and liver. The passive immunization of mice with rabbit antimurine MCP-1 antiserum 2 h before endotoxin administration resulted in a striking increase in LPS-induced mortality from 10% in control animals to 65% in anti-MCP-1-treated animals. Importantly, the administration of anti-MCP-1 antibodies to endotoxin-challenged mice resulted in increases in peak TNF-alpha and IL-12 levels, and also in a trend toward decreased serum levels of IL-10. Conversely, the administration of recombinant murine MCP-1 intraperitoneally significantly protected mice from endotoxin-induced lethality, and resulted in an increase in IL-10 levels, a decrease in IL-12 levels, and a trend toward decreased levels of TNF. In conclusion, our findings indicate that MCP-1 is a protective cytokine expressed in murine endotoxemia, and does so by shifting the balance in favor of antiinflammatory cytokine expression in endotoxin-challenged animals.

Preventive effect of cyclosporin A on experimentally induced acute liver injury in rats

We examined the effect of cyclosporin A (CsA) on the pathogenesis of acute experimental liver injury in rats induced by injection of heat-killed Propionibacterium acnes (P. acnes) and subsequent injection of lipopolysaccharide (LPS). Pretreatment with CsA significantly reduced serum alanine aminotransferase (ALT), serum tumor necrosis factor-alpha (TNF-alpha) production, without changing the TNF-alpha mRNA level in the liver, and plasma interferon-gamma (IFN-gamma), following LPS injection in this model. Twenty-four-hour mortality was also markedly improved, from 100% in the P. acnes plus LPS group to 0% in the CsA-pretreated group. Although direct addition of CsA to isolated hepatic macrophages from P. acnes-pretreated rats did not prevent the production of TNF-alpha and active oxygen species, isolated hepatic macrophages from P. acnes plus CsA-pretreated rats significantly reduced their production in response to the addition of LPS. These results suggest that CsA protects against P. acnes plus LPS-induced acute liver injury, not by direct inhibition of hepatic macrophage activation, but by indirect prevention of hepatic macrophage activation, presumably related to the reduction in plasma IFN-gamma levels.

Suppression of tumor necrosis factor-alpha production by interleukin-10 is enhanced by cAMP-elevating agents

The pro-inflammatory peptide tumor necrosis factor-alpha (TNF) stimulates production of the anti-inflammatory cytokine-interleukin-10 by monocytes which in turn inhibits the synthesis of TNF. This inhibitory effect of interleukin-10 may contribute to the balance of pro- and anti-inflammatory cytokines in several diseases, e.g., chronic inflammatory bowel disease. In the present study we addressed the question whether interleukin-10 in combination with other TNF-suppressing agents leads to enhanced suppression of TNF synthesis. We investigated the inhibitory potency of interleukin-10 in combination with rolipram, a specific type IV phosphodiesterase inhibitor, or with cicaprost, a stable prostacyclin analogue in lipopolysaccharide-stimulated human peripheral blood mononuclear cells. Peripheral blood mononuclear cells were stimulated with 10 ng/ml lipopolysaccharide in the absence or presence of interleukin-10 or one of the cAMP-elevating agents. First, we confirmed the TNF-suppressing effect of interleukin-10, rolipram and cicaprost alone and determined the IC50 for these substances. Second, for the combination of interleukin-10 with one of the cAMP-elevating substances we were able to demonstrate enhanced TNF inhibition. Of these, the combination of interleukin-10 and rolipram revealed an additive effect. The maximal TNF synthesis of 5.5 +/- 1.1 ng/ml after lipopolysaccharide stimulation alone was inhibited by 0.1 ng/ml interleukin-10 to 2.7 +/- 0.6 ng/ml TNF and by 100 nM rolipram to 3.1 +/- 0.6 ng/ml TNF. Both substances combined suppressed TNF synthesis to 1.5 +/- 0.3 ng/ml. After stimulation with Staphylococcus epidermidis we could demonstrate a more pronounced inhibition of TNF synthesis by interleukin-10 compared to rolipram which was more effective after stimulation with lipopolysaccharide. Finally, the additive inhibitory effect of interleukin-10 and rolipram could be confirmed on the level of TNF mRNA. The results obtained in the present investigation could form a prerequisite to study the combination of interleukin-10 and cAMP-elevating agents in in vivo models of acute or chronic inflammatory diseases.

Interleukin-10 protects neonatal mice from lethal group B streptococcal infection

We investigated the role of interleukin-10 (IL-10) in a neonatal mouse model of lethal group B streptococci (GBS) sepsis. Plasma IL-10 levels significantly increased at 24 and 48 h after GBS inoculation. Neutralization of IL-10 with specific antibodies had no effect on lethality. Administration of recombinant IL-10 at 20 or 4 h before challenge, but not at later times, resulted in decreased tumor necrosis factor alpha levels and improved survival. IL-10 could be potentially useful for the treatment of GBS sepsis.

Association of interleukin-10 with rejection-sparing effect in septic kidney transplant recipients

Certain cytokines, particularly gamma-interferon (IFN) and interleukin (IL)-2 associated with TH1 cell function, have been shown to play a role in allograft rejection. One paradigm for long-term allograft acceptance involves TH2 cytokine predominance (IL-4 and IL-10). We describe two renal allograft recipients for whom immunosuppression was discontinued due to serious sepsis and who maintained stable renal function over 2-6 months without immunosuppression. During this time, there were higher levels of both IFN-gamma and IL-10 in the peripheral blood than in stable control kidney transplant recipients on immunosuppression. In one of the patients, levels of IL-10 fell, while those of IFN-gamma remained persistently elevated. This was associated with biopsy-proven rejection. Although peripheral blood cytokine levels may not reflect intragraft events, these data are consistent with an allograft protective role for IL-10 offsetting that of IFN-gamma in both patients off immunosuppression.

Staphylococcal enterotoxin B and tumor-necrosis factor-alpha-induced relapses of experimental allergic encephalomyelitis: protection by transforming growth factor-beta and interleukin-10

A study was made of the ability of the superantigen staphylococcal enterotoxin B (SEB) to induce relapses of experimental allergic encephalomyelitis (EAE) in SJL mice that had partially or completely recovered from acute EAE. We find that a single injection of 0.05 mg SEB i.v. induces mild relapses in 50% of such mice. In addition, tumor necrosis factor (TNF)-alpha (0.2 micrograms, i.p.) also induces EAE relapses in 43% of SJL mice when injected 1-2 months after recovery. SEB does not induce a second relapse if reinjected when V beta 17a+T cells are still partially deleted. In these mice, however, TNF-alpha is equally effective in inducing relapses as in mice that did not receive SEB previously. We showed earlier that transforming growth factor (TGF)-beta and TNF-alpha have antagonistic effects on experimental autoimmune diseases; e.g., in spontaneously relapsing EAE, TGF-beta and anti-TNF were protective, while anti-TGF-beta caused disease exacerbation. Interleukin (IL)-10 is also known to counteract certain TNF effects. We now find that both human IL-10 and TGF-beta 2 lower the incidence of EAE relapses when given simultaneously with SEB or TNF-alpha. The protective effect of TGF-beta is significant only against relapses induced by SEB (reduced to 9%), and that of IL-10 only against relapses induced by TNF (reduced to 0%) with the treatment regimens employed. Neutralizing anti-TGF-beta does not increase the incidence of SEB-induced EAE relapses. In contrast, anti-IL-10 increases both the incidence and the severity of such relapses. We conclude that TNF production is probably important in causing EAE relapses, but that other aspects of the SEB-induced reactivation of myelin-specific T cells also contribute. Furthermore, endogenous IL-10 rather than TGF-beta production appears to limit the susceptibility to induction of EAE relapses in this model.

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.