Characterization of complex formation between lipopolysaccharide and lysozyme

The binding of lysozyme (LZM) to bacterial lipopolysaccharide (LPS) inhibited the biological activities of LPS as well as the enzymic activity of LZM. The mode of binding has been characterized by using dansylated LZM and enzyme inhibition. The binding of LPS to LZM significantly increased the fluorescence intensity (Fl-intensity) of the danyl group and was found to be time-dependent; the complex was produced gradually and became stabilized within 20 min at 37 degrees, 10 min at 50 degrees, and 1 min at 70 degrees. The maximum level of binding was also dependent on the reaction temperature, and more complex was formed at higher temperatures. Complexation was strongly dependent on the salt concentration and was not observed at greater than 0.5M NaCl. From collected evidence of the Fl-intensities of various dansyl derivatives and amphiphiles, it is concluded that LZM interacts with LPS by multiple binding-modes, the first being strongly related to the enzyme inhibition, the second being close to the Fl-intensity, and the third being dependent on the inhibition of immunopharmacological activities. For the amphiphiles used in this study, sodium dodecyl sulfate (SDS), 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS), 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxy-propanesulfonate (CHAPSO), decansulfonic acid, and cardiolipin have binding modes similar to that of LPS.     

Down-regulation of macrophage lysozyme by lipopolysaccharide and interferon

Lipopolysaccharide (LPS) treatment of resident mouse peritoneal macrophages (M phi) was found to suppress intracellular as well as secreted lysozyme (LZM). Interferon (IFN) had a similar effect. LZM was identified by the capacity of cell lysates or medium to lyse Micrococcus lysodeikticus, and by the presence of a 14.5 Kd protein band which co-migrated with human LZM in SDS-PAGE and which reacted positively in Western blots with antiserum to human LZM. The size of the 14.5 Kd band decreased sequentially with increasing concentrations of LPS to which the cells were exposed. Although the LPS influence on LZM levels was dose-dependent, the intracellular LZM pool responded more readily than secreted LZM. Maximal intracellular LZM suppression of 80% was obtained with 10 micrograms LPS, whereas secreted LZM was reduced by only 66%. An IFN concentration of 100 U reduced secreted LZM by 24%, whereas 10,000 U of IFN decreased the amount of LZM secreted by 71%. Thioglycolate-elicited M phi had 75% less intracellular LZM than untreated resident M phi. Moreover, thioglycolate-elicited M phi were hyporesponsive to the suppressive effects of LPS added in vitro. Because both LPS and IFN have been shown to stimulate numerous M phi functions, the data are of interest because they support the concept, based on other studies, that agents which are capable of enhancing some M phi activities may concomitantly down-regulate other functions.     

Characteristics of lipopolysaccharide interaction with human peripheral-blood monocytes.

The interaction between radioiodinated lipopolysaccharide from Escherichia coli 0111:B4 (125I-LPS) and human peripheral-blood monocytes was studied. The association of 125I-LPS with monocytes at 37 degrees C appeared to depend on binding to the cell membrane with subsequent internalization of the molecule, and was not saturable with time (up to 2 h) or 125I-LPS concentration (up to 10 micrograms/ml). There was no apparent difference in the behaviour of unlabelled LPS and 125I-LPS with respect to monocyte association. 125I-LPS association with monocytes was inhibited by LPS and O-polysaccharide from E. coli 0111:B4 and Salmonella typhi 0901, but not by lipid A or polymyxin B. We propose that the mechanism of human monocyte stimulation by LPS involves polysaccharide-dependent binding to the cell membrane followed by internalization of the LPS molecule. We were unable to demonstrate a specific LPS receptor such as that found on murine B-lymphocytes.     

Influence of CD14 on ligand interactions between lipopolysaccharide and its receptor complex

The interaction of LPS (endotoxin) with the CD14-TLR4 receptor complex modulates the host innate immune response. Several studies using partial structures of LPS have suggested that TLR4 determines the ligand specificity of this complex, and that CD14 indiscriminately serves to deliver the ligand to TLR4. This conclusion has been made despite observations that the response of TLR4(+/+),CD14(-/-) macrophages to LPS is very weak. To determine whether CD14 itself plays a role in specific ligand recognition, the influences of various partial structures of LPS on induction of the proinflammatory cytokine, TNF, by CD14(+/+) and CD14(-/-) macrophages were compared. These studies show that the ligand specificities of CD14(+/+) and CD14(-/-) macrophages are very different. When CD14 is present, the receptor complex shows exquisite specificity for smooth LPS, the major form expressed by Gram-negative bacteria; however, as increasing amounts of carbohydrate are removed from smooth LPS, the sensitivity of CD14(+/+) macrophages decreases as much as 500-fold. In contrast, CD14(-/-) macrophages are unable to distinguish between smooth LPS and its various partial structures. Furthermore, CD14(-/-) macrophages are 150,000-fold less sensitive than CD14(+/+) macrophages to smooth LPS. A similar ability to distinguish the differing LPS structures of various bacteria such as Bacteroides fragilis and Salmonella abortus are observed for CD14(+/+), but not CD14(-/-), macrophages. Thus, CD14(+/+), but not CD14(-/-), macrophages are highly sensitive to stimulation by natural forms of LPS and show the ability to distinguish between various LPS ligands, consistent with CD14 being a highly specific receptor.     

Lipopolysaccharide interactions with lysozyme differentially affect lipopolysaccharide immunostimulatory activity

The effect of complex formation between lysozyme and lipopolysaccharide (LPS) on the immunostimulatory activities of LPS have been investigated in vitro. Three prototype immunostimulatory activities were examined: B-lymphocyte proliferation, B-lymphocyte differentiation and macrophage production of lymphocyte-activating factor activity. Different effects of lysozyme were noted, depending upon the structure of the LPS, even though previous studies have established that all LPS preparations readily bind lysozyme. Both Re-LPS- and lipid-A-dependent immunostimulatory activities were readily inhibited by lysozyme in a dose-dependent fashion. In contrast, S-LPS and Ra-LPS were unaffected in their immunostimulatory activities by lysozyme. These differences were not the result of quantitative differences in LPS binding of lysozyme, or effects of lysozyme on overall binding of LPS to target cells. These data suggest that the factors which dictate the initial interactions between LPS and lymphoreticular cells may not be identical for all LPS preparations and/or purified lipid A.     

Induction of a novel mechanism of accelerated bacterial clearance by lipopolysaccharide in CD14-deficient and Toll-like receptor 4-deficient mice

Despite the lack of a proinflammatory response to LPS, CD14-deficient mice clear Gram-negative bacteria (Escherichia coli 0111) at least 10 times more efficiently than normal mice. In this study, we show that this is due to an early and intense recruitment of neutrophils following the injection of Gram-negative bacteria or LPS in CD14-deficient mice; in contrast, neutrophil infiltration is delayed by 24 h in normal mice. Similar results of early LPS-induced PMN infiltration and enhanced clearance of E. coli were seen in Toll-like receptor (TLR) 4-deficient mice. Furthermore, the lipid A moiety of LPS induced early neutrophil infiltration not only in CD14-deficient and TLR-4-deficient mice, but also in normal mice. In conclusion, the lipid A component of LPS stimulates a unique and critical pathway of innate immune responses that is independent of CD14 and TLR4 and results in early neutrophil infiltration and enhanced bacterial clearance.     

Development and characterization of synthetic glucopyranosyl lipid adjuvant system as a vaccine adjuvant

Innate immune responses to vaccine adjuvants based on lipopolysaccharide (LPS), a component of gram-negative bacterial cell walls, are driven by Toll-like receptor (TLR) 4 and adaptor proteins including MyD88 and TRIF, leading to the production of inflammatory cytokines, type I interferons, and chemokines. We report here on the characterization of a synthetic hexaacylated lipid A derivative, denoted as glucopyranosyl lipid adjuvant (GLA). We assessed the effects of GLA on murine and human dendritic cells (DC) by combining microarray, mRNA and protein multiplex assays and flow cytometry analyses. We demonstrate that GLA has multifunctional immunomodulatory activity similar to naturally-derived monophosphory lipid A (MPL) on murine DC, including the production of inflammatory cytokines, chemokines, DC maturation and antigen-presenting functions. In contrast, hexaacylated GLA was overall more potent on a molar basis than heterogeneous MPL when tested on human DC and peripheral blood mononuclear cells (PBMC). When administered in vivo, GLA enhanced the immunogenicity of co-administered recombinant antigens, producing strong cell-mediated immunity and a qualitative T(H)1 response. We conclude that the GLA adjuvant stimulates and directs innate and adaptive immune responses by inducing DC maturation and the concomitant release of pro-inflammatory cytokines and chemokines associated with immune cell trafficking, activities which have important implications for the development of future vaccine adjuvants.     

Lipopolysaccharide interaction with lysozyme. Binding of lipopolysaccharide to lysozyme and inhibition of lysozyme enzymatic activity

Experiments have been carried out to characterize the binding of lysozyme (LZM) to bacteriol lipopolysaccharide (LPS). The formation of LPS.LZM complexes can be readily demonstrated using either physical-chemical separation techniques or a radiolabeled photoaffinity LPS probe. The binding affinity of LZM for LPS has been estimated to be approximately 10(8) liters/mol. Binding of LPS results in loss of LZM enzymatic activity by a noncompetitive inhibition, as assessed by either particulate or soluble substrates. This interaction of LPS with LZM is dictated primarily by hydrophobic interactions and appears to be a general property of both constituents. Binding can be demonstrated with LZM of both human and avian sources, as well as with LPS isolated from a variety of Gram-negative organisms. The addition of LPS to biologically relevant fluids containing LZM results in dose-dependent inhibition of LZM enzymatic activity suggesting that such interactions may have relevance in Gram-negative infections. Finally LZM has been shown to reduce the endotoxic activity of LPS as assessed by gelation of Limulus amoebocyte lysates.     

Genome-wide expression profiling and mutagenesis studies reveal that lipopolysaccharide responsiveness appears to be absolutely dependent on TLR4 and MD-2 expression and is dependent upon intermolecular ionic interactions

Lipid A (a hexaacylated 1,4' bisphosphate) is a potent immune stimulant for TLR4/MD-2. Upon lipid A ligation, the TLR4/MD-2 complex dimerizes and initiates signal transduction. Historically, studies also suggested the existence of TLR4/MD-2-independent LPS signaling. In this article, we define the role of TLR4 and MD-2 in LPS signaling by using genome-wide expression profiling in TLR4- and MD-2-deficient macrophages after stimulation with peptidoglycan-free LPS and synthetic Escherichia coli lipid A. Of the 1396 genes significantly induced or repressed by any one of the treatments in the wild-type macrophages, none was present in the TLR4- or MD-2-deficient macrophages, confirming that the TLR4/MD-2 complex is the only receptor for endotoxin and that both are required for responses to LPS. Using a molecular genetics approach, we investigated the mechanism of TLR4/MD-2 activation by combining the known crystal structure of TLR4/MD-2 with computer modeling. According to our murine TLR4/MD-2-activation model, the two phosphates on lipid A were predicted to interact extensively with the two positively charged patches on mouse TLR4. When either positive patch was abolished by mutagenesis into Ala, the responses to LPS and lipid A were nearly abrogated. However, the MyD88-dependent and -independent pathways were impaired to the same extent, indicating that the adjuvant activity of monophosphorylated lipid A most likely arises from its decreased potential to induce an active receptor complex and not more downstream signaling events. Hence, we concluded that ionic interactions between lipid A and TLR4 are essential for optimal LPS receptor activation.     

Lactoferrin-lipopolysaccharide interactions. Effect on lactoferrin binding to monocyte/macrophage-differentiated HL-60 cells.

Lactoferrin (LF) has been implicated in a number of functions including the negative regulation of myelopoiesis in vitro and in vivo, an effect mediated by suppression of cytokine release from monocytes/macrophages. This suppression is abrogated by bacterial LPS. In the present study, HL-60 cells were induced to differentiate to monocytes/macrophages by 12-O-tetradecanoyl phorbol-13-acetate, and LF-binding assays were performed. After differentiation, HL-60 cells showed a twofold increase of LF-binding sites with no difference in the specificity or affinity of LF between pre- and post-differentiated cells. CD11a, CD11b, and CD11c Ag, which have been associated with specific binding sites for LPS on monocytes/macrophages, were also increased three- to fourfold after differentiation. With the use of this system, the effect of LPS on LF binding was studied. At 37 degrees C, LPS enhanced LF binding on HL-60 cells, especially after differentiation. Conversely, at 4 degrees C, LPS inhibited LF binding. There was little effect of temperature on LF binding in the absence of LPS. In the presence of polymyxin B sulfate, the enhanced LF binding by LPS was abrogated. Also, pretreatment with mAbCD11 and/or mAb5D3, which are associated with or directed against candidate LPS receptors, reduced LF binding. Cross-linking studies using an iodinated, photoactivatable LPS derivative ([125I]ASD-LPS) demonstrated directly the specific binding of LPS to LF. These data indicate a dichotomous nature of LF binding on monocyte/macrophage-differentiated HL-60 cells--one being mediated by specific LF receptors whereas the other is apparently mainly via LPS receptors after formation of an LF-LPS complex. These interactions, for which a model is proposed, help to explain the mechanism behind LPS abrogation of the myelopoietic suppressive effects of LF, and a situation that probably occurs during bacterial infection.     

Effects of bacterial lipopolysaccharide on the hydrolysis of phosphatidylinositol-4,5-bisphosphate in murine peritoneal macrophages

LPS and lipid A initiated enhanced hydrolysis of PIP2 in macrophages. When murine peritoneal macrophages were labeled with [2-3H]myoinositol and stimulated with either LPS or lipid A, a rapid (within 10 sec) rise in Ins(1,4,5)P3 was observed. The breakdown pattern of Ins(1,4,5)P3 was complex; this included breakdown of Ins(1,4,5)P3 and formation of Ins(1,3,4,5)P4 (approximately 10 to 30 sec), and ultimately formation of Ins(1,3,4)P3 (approximately 60 sec). Within 10 sec after treatment, LPS caused an average increase of about fourfold to fivefold in Ins(1,4,5)P3, which declined over 5 min. When the total isomers of InsP3 were measured, levels rose about twofold in response to LPS or to lipid A and remained elevated for as long as 5 min. Lipid A, in the concentration range of 0.1 to 10 micrograms/ml, induced elevated intracellular levels of Ca2+ as quantified by fluorescence with Quin 2 or with Fura 2. When single, adherent Fura 2-loaded macrophages were treated with lipid A, basal levels of calcium rose over 10 sec from approximately 55 nM to almost 600 nM. LPS, paradoxically, did not cause such substantial increases in intracellular calcium (i.e., increases of approximately 26 nM) when judged by Fura 2 fluorescence. LPS treatment led to enhanced phosphorylation of a characteristic set of proteins, similar to those induced by stimulating protein kinase C (PKC) with phorbol myristate acetate as previously reported. The enhanced phosphorylation of pp28, pp33, and pp67 in macrophages was evident by 15 min and optimal by 30 min. Taken together, these observations indicate that LPS and lipid A cause increased breakdown of phosphatidylinositol 4,5-bisphosphate, which led to enhanced intracellular levels of calcium and also to enhanced protein phosphorylation, presumably mediated by PKC. The data thus suggest that one major intracellular signal transduction mechanism, initiated by LPS and lipid A in macrophages, is the rapid breakdown of PIP2.     

Effects of the antimicrobial peptide BMAP-27 in a mouse model of obstructive jaundice stimulated by lipopolysaccharide

An experimental study was designed to investigate the efficacy of BMAP-27, a compound of the cathelicidin family, in neutralizing Escherichia coli 0111:B4 lipopolysaccharide (LPS) in bile duct-ligated mice. Main outcome measures were: endotoxin and TNF-alpha concentrations in plasma, evidence of bacterial translocation in blood and peritoneum, and lethality. Adult male BALB/c mice were injected intraperitoneally with 2 mg/kg E. coli 0111:B4 LPS 1 week after sham operation or bile duct ligation (BDL). Six groups were studied: sham with placebo, sham with 120 mg/kg tazobactam-piperacillin (TZP), sham with 1 mg/kg BMAP-27, BDL with placebo, BDL with 120 mg/kg TZP, and BDL with 1mg/kg BMAP-27. After LPS, TNF-alpha plasma levels were significantly higher in BDL mice compared to sham-operated animals. BMAP-27 achieved a significant reduction of plasma endotoxin and TNF-alpha concentration when compared with placebo- and TZP-treated groups. On the other hand, both TZP and BMAP-27 significantly reduced the bacterial growth compared with saline treatment. Finally, LPS induced 60% and 55% lethality in BDL placebo- and TZP-treated treated mice and no lethality in sham-operated mice, while only BMAP-27 significantly reduced the lethality to 10%. In light of its dual antimicrobial and anti-endotoxin properties, BMAP-27 could be an interesting compound to inhibit bacterial translocation and endotoxin release in obstructive jaundice.     

High concentrations of bacterial lipopolysaccharide, but not microbial infection-induced inflammation, activate macrophage C3 receptors for phagocytosis

Macrophage C3 receptors are normally immobilized in the plane of the cells' plasma membrane and are unable to promote phagocytosis even though they promote avid particle binding. We have previously identified a lymphokine that activates macrophage C3 receptors for phagocytosis both in vitro and in vivo, and others have found that certain types of nonimmunologically mediated inflammation are also able to activate mononuclear phagocyte C3 receptors. These findings raised the possibility that macrophage C3 receptor activation is a universal consequence of inflammation. We sought in the present experiments to determine whether or not inflammation induced by microbial infection in a nonimmune host resulted in activation of macrophage C3 receptors. We injected mice i.p. with either viable microorganisms, microbe-containing immune complexes, or bacterial LPS. Macrophages were harvested by peritoneal lavage 4 days later; nearly all lavage fluids grew the microorganism with which the mouse had been injected, indicating that an infection had been established. Monolayers of macrophages were established and their interaction with sheep E coated with C3 (EIgMC) was determined. All macrophages bound EIgMC, but only macrophages from mice injected with either very high concentrations of LPS or microbe-containing immune complexes ingested them. C3 receptors of macrophages that ingested EIgMC were mobile; others were not. Thus, inflammation induced by microbial infection does not commonly, if at all, activate macrophage C3 receptors; microbe-containing immune complexes and high concentrations of LPS do. The mechanism of receptor activation in each case is C3 receptor mobilization, which is probably mediated by a lymphokine.     

5-Lipoxygenase Activating Protein (FLAP) Dependent Leukotriene Biosynthesis Inhibition (MK591) Attenuates Lipid A Endotoxin-Induced Inflammation

The Lipid A moiety of endotoxin potently activates TLR-4 dependent host innate immune responses. We demonstrate that Lipid-A mediated leukotriene biosynthesis regulates pathogen-associated molecular patterns (PAMP)-dependent macrophage activation. Stimulation of murine macrophages (RAW264.7) with E. coli 0111:B4 endotoxin (LPS) or Kdo2-lipid A (Lipid A) induced inflammation and Lipid A was sufficient to induce TLR-4 mediated macrophage inflammation and rapid ERK activation. The contribution of leukotriene biosynthesis was evaluated with a 5-lipoxygenase activating protein (FLAP) inhibitor, MK591. MK591 pre-treatment not only enhanced but also sustained ERK activation for up to 4 hours after LPS and Lipid A stimulation while inhibiting cell proliferation and enhancing cellular apoptosis. Leukotriene biosynthesis inhibition attenuated inflammation induced by either whole LPS or the Lipid A fraction. These responses were regulated by inhibition of the key biosynthesis enzymes for the proinflammatory eicosanoids, 5-lipoxygenase (5-LO), and cyclooxygenase-2 (COX-2) quantified by immunoblotting. Inhibition of leukotriene biosynthesis differentially regulated TLR-2 and TLR-4 cell surface expression assessed by flow cytometry, suggesting a close mechanistic association between TLR expression and 5-LO associated eicosanoid activity in activated macrophages. Furthermore, MK591 pre-treatment enhanced ERK activation and inhibited cell proliferation after LPS or Lipid A stimulation. These effects were regulated in part by increased apoptosis and modulation of cell surface TLR expression. Together, these data clarify the mechanistic association between 5-lipoxygenase activating protein-mediated leukotriene biosynthesis and 5-LO dependent eicosanoid metabolites in mediating the TLR-dependent inflammatory response after endotoxin exposure typical of bacterial sepsis.     

Saturated fatty acids, but not unsaturated fatty acids, induce the expression of cyclooxygenase-2 mediated through Toll-like receptor 4

Results from our previous studies demonstrated that activation of Toll-like receptor 4 (Tlr4), the lipopolysaccharide (LPS) receptor, is sufficient to induce nuclear factor kappaB activation and expression of inducible cyclooxygenase (COX-2) in macrophages. Saturated fatty acids (SFAs) acylated in lipid A moiety of LPS are essential for biological activities of LPS. Thus, we determined whether these fatty acids modulate LPS-induced signaling pathways and COX-2 expression in monocyte/macrophage cells (RAW 264.7). Results show that SFAs, but not unsaturated fatty acids (UFAs), induce nuclear factor kappaB activation and expression of COX-2 and other inflammatory markers. This induction is inhibited by a dominant-negative Tlr4. UFAs inhibit COX-2 expression induced by SFAs, constitutively active Tlr4, or LPS. However, UFAs fail to inhibit COX-2 expression induced by activation of signaling components downstream of Tlr4. Together, these results suggest that both SFA-induced COX-2 expression and its inhibition by UFAs are mediated through a common signaling pathway derived from Tlr4. These results represent a novel mechanism by which fatty acids modulate signaling pathways and target gene expression. Furthermore, these results suggest a possibility that propensity of monocyte/macrophage activation is modulated through Tlr4 by different types of free fatty acids, which in turn can be altered by kinds of dietary fat consumed.     

A role for human Sp alpha as a pattern recognition receptor

Human Sp alpha is a soluble protein belonging to group B of the scavenger receptor cysteine-rich (SRCR) superfamily for which little functional information is available. It is expressed by macrophages present in lymphoid tissues (spleen, lymph node, thymus, and bone marrow), and it binds to myelomonocytic and lymphoid cells, which suggests that it may play an important role in the regulation of the innate and adaptive immune systems. In the present study we show that recombinant human Sp alpha (rSp alpha) binds to the surface of several gram-positive and gram-negative bacterial strains. Competition studies indicated that such binding is mediated by the recognition of lipoteichoic acid (LTA) and lipopolysaccharide (LPS), respectively, through nonoverlapping sites on the Sp alpha molecule. The most conserved part of LPS (2-keto-3-deoxyoctulosonic acid and lipid A) was shown to be involved in the recognition by Sp alpha. Bacterial binding studies using the SRCR domain 1 of Sp alpha showed that this domain retains both the LPS and LTA binding activities, indicating that both bacterial interacting sites are retained in a single SRCR domain. Furthermore, rSp alpha induced aggregation of gram-positive and gram-negative bacteria strains. On the other hand, rSp alpha inhibited tumor necrosis factor-alpha secretion by human monocytes stimulated with LPS or LTA. Binding of Sp alpha to conserved components of bacterial surfaces and modulation of the monocyte response indicate that this molecule is an active constituent of the innate immune response of the host.     

Chitohexaose Activates Macrophages by Alternate Pathway through TLR4 and Blocks Endotoxemia

Sepsis is a consequence of systemic bacterial infections leading to hyper activation of immune cells by bacterial products resulting in enhanced release of mediators of inflammation. Endotoxin (LPS) is a major component of the outer membrane of Gram negative bacteria and a critical factor in pathogenesis of sepsis. Development of antagonists that inhibit the storm of inflammatory molecules by blocking Toll like receptors (TLR) has been the main stay of research efforts. We report here that a filarial glycoprotein binds to murine macrophages and human monocytes through TLR4 and activates them through alternate pathway and in the process inhibits LPS mediated classical activation which leads to inflammation associated with endotoxemia. The active component of the nematode glycoprotein mediating alternate activation of macrophages was found to be a carbohydrate residue, Chitohexaose. Murine macrophages and human monocytes up regulated Arginase-1 and released high levels of IL-10 when incubated with chitohexaose. Macrophages of C3H/HeJ mice (non-responsive to LPS) failed to get activated by chitohexaose suggesting that a functional TLR4 is critical for alternate activation of macrophages also. Chitohexaose inhibited LPS induced production of inflammatory molecules TNF-α, IL-1β and IL-6 by macropahges in vitro and in vivo in mice. Intraperitoneal injection of chitohexaose completely protected mice against endotoxemia when challenged with a lethal dose of LPS. Furthermore, Chitohexaose was found to reverse LPS induced endotoxemia in mice even 6/24/48 hrs after its onset. Monocytes of subjects with active filarial infection displayed characteristic alternate activation markers and were refractory to LPS mediated inflammatory activation suggesting an interesting possibility of subjects with filarial infections being less prone to develop of endotoxemia. These observations that innate activation of alternate pathway of macrophages by chtx through TLR4 has offered novel opportunities to cell biologists to study two mutually exclusive activation pathways of macrophages being mediated through a single receptor.     

Detoxification of lipopolysaccharide (LPS) by egg white lysozyme

Abstract 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 physiochemical 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.