Lipopolysaccharide: neutralization by polymyxin B shuts down the signaling pathway of nuclear factor kappaB in peripheral blood mononuclear cells, even during activation

Mucosal IL-10 and TGF-beta play crucial roles in preventing LPS-driven, IFN-gamma-mediated epithelial damage in human colon explants

IL-10 is an immunomodulatory cytokine that plays an obligate role in preventing spontaneous enterocolitis in mice. However, little is known about IL-10 function in the human intestinal mucosa. We showed here that IL-10 was constitutively expressed and secreted by the human normal colonic mucosa, including epithelial cells. Depletion of IL-10 in mucosal explants induced both downregulation of the IL-10-inducible, immunosuppressive gene BCL3 and upregulation of IFN-gamma, TNF-alpha, and IL-17. Interestingly, TGF-beta blockade also strongly induced IFN-gamma production. In addition, the high levels of IFN-gamma produced upon IL-10 depletion were responsible for surface epithelium damage and crypt loss, mainly by apoptosis. Polymyxin B, used as a scavenger of endogenous LPS, abolished both IFN-gamma production and epithelial barrier disruption. Finally, adding a commensal bacteria strain to mucosa explant cultures depleted of both IL-10 and LPS reproduced the ability of endogenous LPS to induce IFN-gamma secretion. These findings demonstrate that IL-10 ablation leads to an endogenous IFN-gamma-mediated inflammatory response via LPS from commensal bacteria in the human colonic mucosa. We also found that both IL-10 and TGF-beta play crucial roles in maintaining human colonic mucosa homeostasis.

Toll-like receptor 4 mediates induction of the Bcl10-NFkappaB-interleukin-8 inflammatory pathway by carrageenan in human intestinal epithelial cells

The sulfated polysaccharide carrageenan (CGN) induces activation of NFkappaB and interleukin 8 (IL-8) in human colonic epithelial cells through a pathway of innate immunity mediated by Bcl10 (B-cell CLL/lymphoma 10). In this report, we identify Toll-like receptor 4 (TLR4), a member of the family of innate immune receptors, as the surface membrane receptor for CGN in human colonic epithelial cells. Experiments with fluorescence-tagged CGN demonstrated a marked reduction in binding of CGN to human intestinal epithelial cells and to RAW 264.7 mouse macrophages, following exposure to TLR4 blocking antibody (HTA-125). Binding of CGN to 10ScNCr/23 mouse macrophages, which are deficient in the genetic locus for TLR4, was absent. Additional experiments with TLR4 blocking antibody and TLR4 small interfering RNAs showed 80% reductions in CGN-induced increases in Bcl10 and IL-8. Transfection with dominant-negative MyD88 plasmid demonstrated MyD88 dependence of the CGN-TLR4-triggered increases in Bcl10 and IL-8. Therefore, these results indicate that CGN-induced inflammation in human colonocytes proceeds through a pathway of innate immunity, perhaps related to the unusual alpha-1,3-galactosidic linkage characteristic of CGN, and suggest how dietary CGN intake may contribute to human intestinal inflammation. Because CGN is a commonly used food additive in the Western diet, clarification of its effects and mechanisms of action are vital to issues of food safety.

Endotoxin downregulates peroxisome proliferator-activated receptor-gamma via the increase in TNF-alpha release

The nuclear receptor peroxisome proliferator-activated receptor-gamma (PPAR-gamma) is anti-inflammatory in a cell-based system and in animal models of endotoxemia. We have shown that PPAR-gamma gene expression is downregulated in macrophages after lipopolysaccharide (LPS) stimulation. However, it remains unknown whether hepatic PPAR-gamma is altered in sepsis and, if so, whether LPS directly downregulates PPAR-gamma. To study this, rats were subjected to sepsis by cecal ligation and puncture (CLP). Hepatic tissues were harvested at 5, 10, and 20 h after CLP. PPAR-gamma gene expression and protein levels were determined by RT-PCR and Western blot analysis, respectively. The results showed that PPAR-gamma gene expression decreased at 10 and 20 h and that its proteins levels were reduced at 20 h after CLP. PPAR-gamma levels were also decreased in animals that were administered LPS. To determine the direct effects of LPS on PPAR-gamma downregulation, LPS binding agent polymyxin B (PMB) was administered intramuscularly after CLP. The administration of PMB significantly reduced plasma levels of endotoxin, but it did not prevent the downregulation of PPAR-gamma expression. We found that circulating levels of TNF-alpha still remained significantly elevated in PMB-treated septic animals. We, therefore, hypothesize that the decrease of PPAR-gamma expression is TNF-alpha dependent. To investigate this, Kupffer cells (KCs) were isolated from normal rats and stimulated with LPS or TNF-alpha. TNF-alpha significantly attenuated PPAR-gamma gene expression in KCs. Although LPS decreased PPAR-gamma in KCs, the downregulatory effect of LPS was blocked by the addition of TNF-alpha-neutralizing antibodies. Furthermore, the administration of TNF-alpha-neutralizing antibodies to animals before the onset of sepsis prevented the downregulation of PPAR-gamma in sepsis. We, therefore, conclude that LPS downregulates PPAR-gamma expression during sepsis via an increase in TNF-alpha release.

Endotoxin removal with a polymyxin B-immobilized hemoperfusion cartridge improves cardiopulmonary function after cardiopulmonary bypass

BACKGROUND

Cardiac surgery using cardiopulmonary bypass (CPB) is performed widely, given the progress in cardioprotective methods. However, endotoxemia caused by CPB leads to systemic inflammatory response syndrome and deterioration of organ function. We evaluated the effectiveness of endotoxin removal with a polymyxin B-immobilized hemoperfusion cartridge (PMX) in CPB.

MATERIALS AND METHODS

Pigs weighing about 25 kg were divided into control (n = 5) and PMX (n = 5) groups. Normothermic CPB was performed in the control group, while endotoxin was removed with PMX under normothermic CPB in the PMX group. Endotoxin removal was performed from the start to end of CPB. The end-systolic pressure-volume ratio (E(max)), left ventricular pressure (LVP), maximum and minimum rates of increase in LVP (+/-LVdp/dt), and cardiac output (CO) were measured 2 h after CPB, and the recovery rates of the parameters were compared between the two groups. A histopathological study was also conducted.

RESULTS

The recovery rates of E(max), CO, and LVP were significantly better (P < 0.05) in the PMX group than in the control group. The PaO(2) 2 h after CPB was significantly higher (P < 0.05) in the PMX group than in the control group. The interleukin (IL)-8 level 2 h after CPB was significantly lower (P < 0.05) in the PMX group. Histopathologically, the heart and pulmonary tissues were better preserved in the PMX group.

CONCLUSION

The PMX treatment reduced the inflammatory reaction caused by CPB, and cardiac and pulmonary functions after normothermic CPB were well preserved.

Yulda-Hanso-Tang attenuates the endotoxin-induced inflammatory cytokine production in peripheral blood mononuclear cells

Yulda-Hanso-Tang (YHT) has been used as a formula for the cerebral infarction (CI) patients. This study investigated the anti-inflammatory effects and possible mechanism of YHT on lipopolysaccharide (LPS)-stimulated peripheral blood mononuclear cells. The amount of interleukin-1beta, IL-4, IL-6, IL-8, and tumor necrosis factor-alpha was increased in the LPS-treated cells. But, increased cytokine was inhibited by YHT except IL-8. The study showed that YHT inhibited the IL-1beta mRNA expression. YHT also inhibited LPS-induced activation of NF-kappaB and degradation of IkappaBalpha. These results suggest that YHT is an inhibitor of NF-kappaB, which might explain its beneficial effect in the treatment of inflammatory diseases.

Homologous high-throughput expression and purification of highly conserved E coli proteins

Background

Genetic factors and a dysregulated immune response towards commensal bacteria contribute to the pathogenesis of Inflammatory Bowel Disease (IBD). Animal models demonstrated that the normal intestinal flora is crucial for the development of intestinal inflammation. However, due to the complexity of the intestinal flora, it has been difficult to design experiments for detection of proinflammatory bacterial antigen(s) involved in the pathogenesis of the disease. Several studies indicated a potential association of E. coli with IBD. In addition, T cell clones of IBD patients were shown to cross react towards antigens from different enteric bacterial species and thus likely responded to conserved bacterial antigens. We therefore chose highly conserved E. coli proteins as candidate antigens for abnormal T cell responses in IBD and used high-throughput techniques for cloning, expression and purification under native conditions of a set of 271 conserved E. coli proteins for downstream immunologic studies.

Results

As a standardized procedure, genes were PCR amplified and cloned into the expression vector pQTEV2 in order to express proteins N-terminally fused to a seven-histidine-tag. Initial small-scale expression and purification under native conditions by metal chelate affinity chromatography indicated that the vast majority of target proteins were purified in high yields. Targets that revealed low yields after purification probably due to weak solubility were shuttled into Gateway (Invitrogen) destination vectors in order to enhance solubility by N-terminal fusion of maltose binding protein (MBP), N-utilizing substance A (NusA), or glutathione S-transferase (GST) to the target protein. In addition, recombinant proteins were treated with polymyxin B coated magnetic beads in order to remove lipopolysaccharide (LPS). Thus, 73% of the targeted proteins could be expressed and purified in large-scale to give soluble proteins in the range of 500 μg.

Conclusion

Here, we report a cost-efficient procedure to produce around 200 soluble recombinant E. coli proteins in large-scale, including removal of LPS by polymyxin B coated beads for subsequent use of the proteins in downstream immunological studies.

Endotoxin apheresis for sepsis

The principle use of apheresis in the treatment of sepsis may be summarized as the removal of toxic substances and the restoration of normal organs function. It is ideal to control the early phases of inflammatory cascade when treating sepsis by removing microbial components, such as endotoxin or peptidoglycan. This review discusses endotoxin apheresis with particular emphasis on treatment using polymyxin B immobilized fiber columns (Toraymyxin) which are used widely in Japan for endotoxin removal therapy in patients with septic shock. Lixelle and CTR which have recently been shown to remove circulating bacterial components are also included in this review.

Lipopolysaccharide (Endotoxin)-host defense antibacterial peptides interactions: role in bacterial resistance and prevention of sepsis

Lipopolysaccharide (LPS) is the major molecular component of the outer membrane of Gram-negative bacteria and serves as a physical barrier providing the bacteria protection from its surroundings. LPS is also recognized by the immune system as a marker for the detection of bacterial pathogen invasion, responsible for the development of inflammatory response, and in extreme cases to endotoxic shock. Because of these functions, the interaction of LPS with LPS binding molecules attracts great attention. One example of such molecules are antimicrobial peptides (AMPs). These are large repertoire of gene-encoded peptides produced by living organisms of all types, which serve as part of the innate immunity protecting them from pathogen invasion. AMPs are known to interact with LPS with high affinities. The biophysical properties of AMPs and their mode of interaction with LPS determine their biological function, susceptibility of bacteria to them, as well as the ability of LPS to activate the immune system. This review will discuss recent studies on the molecular mechanisms underlying these interactions, their effects on the resistance of the bacteria to AMPs, as well as their potential to neutralize LPS-induced endotoxic shock.

Endotoxin-neutralizing activity of polymyxin B in blood after IV administration in horses

OBJECTIVES

To measure serum polymyxin B concentration after single and repeated IV infusions in horses.

ANIMALS

5 healthy horses.

PROCEDURES

In study 1, 1 mg (6,000 U) of polymyxin B/kg was given IV and blood samples were collected for 24 hours. In study 2, 1 mg of polymyxin B/kg was given IV every 8 hours for 5 treatments and blood samples were collected until 24 hours after the last dose. Polymyxin B concentration was measured as the ability to suppress nitrite production by murine macrophages stimulated with lipopolysaccharide and interferon-alpha. Urine was collected prior to the first drug infusion and 24 hours after the fifth drug infusion for determination of urinary gamma-glutamyl transferase (GGT)-to-creatinine ratios.

RESULTS

In study 1, mean +/- SEM maximal serum polymyxin B concentration was 2.93 +/- 0.38 microg/mL. Polymyxin B was undetectable 18 hours after infusion. In study 2, maximal polymyxin B concentrations after the first and fifth doses were 2.98 +/- 0.81 microg/mL and 1.91 +/- 0.50 microg/mL, respectively. Mean trough concentration for all doses was 0.22 +/- 0.01 microg/mL. A significant effect of repeated administration on peak and trough serum concentration was not detected. Urine GGT-to-creatinine ratios were not affected by polymyxin B administration.

CONCLUSIONS AND CLINICAL RELEVANCE

Polymyxin B given as multiple infusions to healthy horses by use of this protocol did not accumulate in the vascular compartment and appeared safe. Results support repeated IV use of 1 mg of polymyxin B/kg at 8-hour intervals as treatment for endotoxemia.

The place of early haemoperfusion with polymyxin B fibre column in the treatment of sepsis

Direct haemoperfusion with polymyxin B-immobilized fibre (PMX-F) is a promising treatment for Gram-negative sepsis in critically ill patients. Indeed, it has been used routinely in Japan for a decade. Recent evidence presented in this journal suggests that PMX-F can have a positive impact on outcome in patients with sepsis, although other reports in the literature have presented confusing or even conflicting results. This commentary considers whether the available evidence allows us to establish an appropriate role for PMX-F treatment in sepsis and what further work is needed.

Direct Effects of Polymyxin B on Human Dendritic Cells Maturation

Polymyxin B is a lipopolysaccharide binding antibiotic used to inactivate potential lipopolysaccharide contaminations when evaluating the activity of different agents on innate immune cells. We report that polymyxin B is able to induce directly in monocyte-derived human dendritic cells (DCs) several functional and molecular modifications characteristic of DCs undergoing a maturation process. DCs incubated with polymyxin B up-regulate the expression of HLA class I and II, the co-stimulatory CD86 molecule, and show an increase in the fraction of adherent cells at short time, which persist at 48 h of incubation. Adhesion to the plate was required for the polymyxin B-induced DCs maturation. A transient activation of IkappaB-alpha/NF-kappaB and ERK1/2 pathways at short time and a further ERK1/2 activation at long term were also detected. Neither up-regulation of the maturation marker CD83 nor activation of p38 nor induction of cytokines secretion was observed in DCs treated with polymyxin B. We demonstrated that inhibition of IkappaB-alpha/NF-kappaB pathway abolishes polymyxin B effects. ERK1/2 inhibition instead allowed DCs treated with polymyxin B to progress in their maturation process as revealed by the increased up-regulation of the CD83 co-stimulatory molecules, the activation of p38, and the reduced adhesion to culture plates at 48 h of incubation. Our results indicate that polymyxin B induces a partial maturation of human DCs through increased adhesion to a substrate and activation of the IkappaB-alpha/NF-kappaB pathway. The increased ERK1/2 activation observed, even though correlating with the initial phases of the maturation process, actually inhibits the occurrence of full maturation.

Polysaccharides extracted from the leaves of Plantago palmata Hook.f. induce nitric oxide and tumor necrosis factor-α production by interferon-γ-activated macrophages

Ethnopharmacological data from eastern African traditional uses of Plantago palmata leaves suggest that some therapeutical activities could be dependent on their content in polysaccharides (PS). To further investigate immunomodulatory properties of these PS, they were extracted in water from leaves by maceration either at (i) 50 degrees C without filtration (PS50); (ii) 50 degrees C and filtration (PS50F); (iii) 100 degrees C, without filtration (PS100); or 100 degrees C and filtration (PS100F). The extract PS50 was further fractionated by high performance liquid chromatography (gel permeation chromatography) in three fractions namely F1, F2, and F3. The immunomodulatory properties of these four crude extracts and PS50 fractions were investigated by the measurement of nitric oxide (NO), tumor necrosis factor-alpha (TNF-alpha), and interleukin-10 (IL-10) production using interferon gamma-(IFN-gamma)-activated macrophages and non-activated macrophages as control. Non-activated J774 cell line macrophages, treated with any of the PS extracts, did produce neither NO, nor TNF-alpha, nor IL-10. In contrast, IFN-gamma-activated J774 macrophages synergized with PS50, but not with the three other crude extracts, to produce both NO and TNF-alpha, but not IL-10. Immunomodulatory effects due to traces of lipopolysaccharides (LPS) in PS extracts and fractions were ruled out by the use of macrophages from C3H/Hej mice known to be very low responders to LPS and similar results were obtained. In addition, F2 fraction from PS50 was particularly active in enhancing NO and TNF-alpha (but not IL-10) production by IFN-gamma-activated C3H/Hej macrophages. These results suggest that PS from P. palmata leaves possess immunomodulatory properties by stimulating NO and TNF-alpha production by activated macrophages.

Modulation of human leukocyte antigen-DR on monocytes and CD16 on granulocytes in patients with septic shock using hemoperfusion with polymyxin B-immobilized fiber

BACKGROUND

Hemoperfusion with PMX-F (polymyxin B covalently immobilized on fibers) has been reported to be safe and effective for patients with septic shock. However, the molecular mechanism of this usefulness is not yet clear. The purpose of this study was to evaluate whether the expression of CD14, human leukocyte antigen (HLA)-DR on monocytes, and the expression of CD16, CD11b/CD18 on neutrophils, are altered in septic patients according to the severity, and whether PMX-F treatment affects the clinical parameters and the expression of leukocyte surface antigen expression.

PATIENTS AND METHODS

Thirty-four patients who were taken to the National Defense Medical College hospital at emergency, and who had an identified focus of infections, were enrolled in this study. The patients were divided into three groups: non-systemic inflammatory response syndrome [SIRS]) group, sepsis group, and septic shock group. Peripheral blood samples were collected at the time of admission to our hospital. The CD14, HLA-DR expression on monocytes and the CD11b/CD18, CD16 expression on granulocytes were evaluated using flowcytometry, and the serum interleukin (IL)-6 and IL-10 levels were measured using enzyme-linked immunosorbent assay. Treatment with a PMX-F column was performed in 10 patients with septic shock.

RESULTS

The HLA-DR expression on monocytes and the CD16 intensity on granulocytes in patients with septic shock were significantly lower than those in patients with sepsis. The serum IL-6 and 10 levels in patients with septic shock were significantly higher than those in patients with sepsis. The mean systolic blood pressure in patients with septic shock was significantly increased after the PMX-F treatment; furthermore, the HLA-DR expression on monocytes and the CD16 intensity on granulocytes were significantly increased after the PMX-F treatment. The serum IL-10 levels were significantly decreased after the PMX-F treatment.

CONCLUSIONS

We showed that the surface antigens, HLA-DR on monocytes and CD16 on granulocytes, are extremely decreased in patients with septic shock, and that PMX-F treatment is effective for beneficially increasing the surface antigen expression on leukocytes. This therapy might be a new strategy for helping patients recover from immunoparalysis in septic conditions.

Regulation of IFN Regulatory Factor-7 and IFN-α Production by Enveloped Virus and Lipopolysaccharide in Human Plasmacytoid Dendritic Cells

Human plasmacytoid dendritic cells (PDC) are a major source of IFN-alpha upon exposure to enveloped viruses and TLR-7 and TLR-9 ligands. Although IFN regulatory factor-7 (IRF-7) is known to play an essential role in virus-activated transcription of IFN-alpha genes, the molecular mechanisms of IFN-alpha production in human PDC remain poorly understood. We and others have recently reported high constitutive levels of IRF-7 expression in PDC as compared with other PBMC. In this study, we demonstrate that both LPS and HSV up-regulate the expression of IRF-7 in PDC, and that this enhancement of IRF-7 is dependent on NF-kappa B activation. The NF-kappa B inhibitors MG132 and pyrrolidinedithiocarbamate efficiently inhibited the induction of IRF-7 by HSV or LPS, and also down-regulated the constitutive expression of IRF-7 in PDC and blocked the HSV-induced production of IFN-alpha. In addition, we found that nuclear translocation of IRF-7 occurred rapidly in response to HSV stimulation, but not in response to LPS, which is consistent with the stimulation of IFN-alpha production by virus and not by LPS. Although LPS by itself was not able to induce IFN-alpha production, it led to rapid up-regulation of TLR-4 on PDC and increased the magnitude and accelerated the kinetics of HSV-induced IFN-alpha production in PDC, providing a mechanism that might be operative in a scenario of mixed infection. In contrast to the current concept of IFN-alpha regulation established in cell lines, this study strongly supports the immediate availability of high constitutive levels of IRF-7 expression in PDC, and suggests an activation required for IRF-7 that contributes to IFN-alpha production in virus-stimulated PDC.