Cytokine-induced sequential migration of neutrophils through endothelium and epithelium

Immunostimulatory effects of cell wall-based nanoparticles in boiled radix water extracts involves TLR4

A number of immunostimulant effects of herbal medicines have been reported; however, the underlying mechanisms of their immunostimulatory effects have not been elucidated in detail. Our previous study showed that sugar-based nanoparticles derived from cell walls acted as the immunostimulatory component of boiled Glycyrrhizae radix water extracts. Therefore, the aim of the present study was to clarify the molecular mechanisms by which these cell wall-based nanoparticles functioned as immunostimulants. Mouse macrophage RAW-blue cells were stimulated by these nanoparticles and several immunological effects were investigated. When phosphorylation of nuclear factor-κB (NF)-κB p65 subunit was increased, the expression of the inflammatory cytokines interleukin-6 and tumor necrosis factor-α were induced via NF-κB. On the other hand, Toll-like receptor 4 recognizes cell wall components of bacteria and fungi. In the present study, it was also shown that these cell wall-based nanoparticles serve an immunostimulatory role as ligands of Toll-like receptor 4 by RNA interference experiments. The results of the present study suggested that the signaling pathway of nanoparticles obtained from boiled Glycyrrhizae radix water extracts, at least partially involved TLR4 and downstream signaling from this receptor, resulting in the immunostimulatory effects of these nanoparticles in RAW-blue cells.

Developing accurate models of the human airways

Objectives

Particle delivery to the airways is an attractive prospect for many potential therapeutics, including vaccines. Developing strategies for inhalation of particles provides a targeted, controlled and non-invasive delivery route but, as with all novel therapeutics, in vitro and in vivo testing are needed prior to clinical use. Whilst advanced vaccine testing demands the use of animal models to address safety issues, the production of robust in vitro cellular models would take account of the ethical framework known as the 3Rs (Replacement, Reduction and Refinement of animal use), by permitting initial screening of potential candidates prior to animal use. There is thus a need for relevant, realistic in vitro models of the human airways.

Key findings

Our laboratory has designed and characterised a multi-cellular model of human airways that takes account of the conditions in the airways and recapitulates many salient features, including the epithelial barrier and mucus secretion.

Summary

Our human pulmonary models recreate many of the obstacles to successful pulmonary delivery of particles and therefore represent a valid test platform for screening compounds and delivery systems.

Alveolocapillary model system to study alveolar re-epithelialization

In the present study an in vitro bilayer model system of the pulmonary alveolocapillary barrier was established to investigate the role of the microvascular endothelium on re-epithelialization. The model system, confluent monolayer cultures on opposing sides of a porous membrane, consisted of a human microvascular endothelial cell line (HPMEC-ST1.6R) and an alveolar type II like cell line (A549), stably expressing EGFP and mCherry, respectively. These fluorescent proteins allowed the real time assessment of the integrity of the monolayers and the automated analysis of the wound healing process after a scratch injury. The HPMECs significantly attenuated the speed of re-epithelialization, which was associated with the proximity to the A549 layer. Examination of cross-sectional transmission electron micrographs of the model system revealed protrusions through the membrane pores and close contact between the A549 cells and the HPMECs. Immunohistochemical analysis showed that these close contacts consisted of heterocellular gap-, tight- and adherens-junctions. Additional analysis, using a fluorescent probe to assess gap-junctional communication, revealed that the HPMECs and A549 cells were able to exchange the fluorophore, which could be abrogated by disrupting the gap junctions using connexin mimetic peptides. These data suggest that the pulmonary microvascular endothelium may impact the re-epithelialization process.

TNF regulates sialyl-Lewisx and 6-sulfo-sialyl-Lewisx expression in human lung through up-regulation of ST3GAL4 transcript isoform BX

Bronchial mucins from severely infected patients suffering from lung diseases such as chronic bronchitis or cystic fibrosis exhibit increased amounts of sialyl-Lewis(x) (NeuAcα2-3Galβ1-4[Fucα1-3]GlcNAc-R, sLe(x)) glycan structures. In cystic fibrosis, sLe(x) and its sulfated form 6-sulfo-sialyl-Lewis(x) (NeuAcα2-3Galβ1-4[Fucα1-3](HO(3)S-6)GlcNAc-R, 6-sulfo-sLe(x)) serve as receptors for Pseudomonas aeruginosa and are involved in the chronicity of airway infection. However, little is known about the molecular mechanisms regulating the changes in glycosylation and sulfation of mucins in airways. Herein, we show that the pro-inflammatory cytokine TNF increases the expression of α2,3-sialyltransferase gene ST3GAL4, both in human bronchial mucosa and in A549 lung carcinoma cells. The role of sialyltransferase ST3Gal IV in sLe(x) biosynthesis was confirmed by siRNA silencing of ST3GAL4 gene. BX is the major transcript isoform expressed in healthy bronchial mucosa and in A549 cells, and is up-regulated by TNF in both models. Bioinformatics analysis and luciferase assays have confirmed that the 2 kb genomic sequence surrounding BX exon contains a promoter region regulated by TNF-related transcription factors. These results support further work aiming at the development of anti-inflammatory strategy to reduce chronic airway infection in diseases such as cystic fibrosis.

Wallerian degeneration and peripheral nerve conditions for both axonal regeneration and neuropathic pain induction

Wallerian degeneration is a cascade of stereotypical events in reaction to injury of nerve fibres. These events consist of cellular and molecular alterations, including macrophage invasion, activation of Schwann cells, as well as neurotrophin and cytokine upregulation. This review focuses on cellular and molecular changes distal to various types of peripheral nerve injury which simultaneously contribute to axonal regeneration and neuropathic pain induction. In addition to the stereotypical events of Wallerian degeneration, various types of nerve damage provide different conditions for both axonal regeneration and neuropathic pain induction. Wallerian degeneration of injured peripheral nerve is associated with an inflammatory response including rapid upregulation of the immune signal molecules like cytokines, chemokines and transcription factors with both beneficial and detrimental effects on nerve regeneration or neuropathic pain induction. A better understanding of the molecular interactions between the immune system and peripheral nerve injury would open the possibility for targeting these inflammatory mediators in therapeutic interventions. Understanding the pleiotropic effects of cytokines/chemokines, however, requires investigating their highly specific pathways and precise points of action.

Lonchocarpus sericeus lectin decreases leukocyte migration and mechanical hypernociception by inhibiting cytokine and chemokines production

In this study, we tested the potential use of a lectin from Lonchocarpus sericeus seeds (LSL), to control neutrophil migration and inflammatory hypernociception (decrease of nociceptive threshold). Pretreatment of the animals intravenously (15 min before) with LSL inhibited neutrophil migration to the peritoneal cavity in a dose-dependent fashion confirmed by an inhibition of rolling and adhesion of leukocytes by intravital microscopy. We also tested the ability of the pretreatment with LSL to inhibit neutrophil migration on immunised mice, and it was observed that a strong inhibition of neutrophil migration induced by ovoalbumin in immunized mice. Another set of experiments showed that pretreatment of the animals with LSL, inhibited the mechanical hypernociception in mice induced by the i.pl. injection of OVA in immunized mice and of carrageenan in naïve mice, but not that induced by prostaglandin E(2) (PGE(2)) or formalin. This anti-nociceptive effect correlated with an effective blockade of neutrophil influx, as assessed by the hind paw tissue myeloperoxidase levels. In addition, we measured cytokines (TNF-alpha and IL-1beta) and chemokines (MIP-1alpha [CCL3] and KC [CXCL1]) from the peritoneal exudates and i.pl. tissue. Animals treated with LSL showed inhibition of cytokines and chemokines release in a dose-dependent manner. In conclusion, we demonstrated that the inhibitory effects of LSL on neutrophil migration and mechanical inflammatory hypernocicepetion are associated with the inhibition of the production of cytokines and chemokines.

Modulation of endotoxin-induced neutrophil transendothelial migration by alveolar epithelium in a defined bilayer model

Within the alveolus, epithelial cells, due to their close association with endothelial cells, can potentially influence endothelial cell responsiveness during inflammation and their interaction with leukocytes. To investigate this, three lung epithelial cell lines (A549, Calu-3, or NCI-H441) were grown with endothelium on opposing surfaces of Transwell filters and the formation and stability of bilayers was rigorously evaluated. All epithelial lines disrupted endothelial monolayer formation on filters with 3- or 5-microm pores by breaching the filter, and this occurred regardless of seeding density, matrix composition, or duration of culture. Endothelial disruption was not detectable by electrical resistance or permeability measurements but required cell-specific staining with immunofluorescence and microscopy. Distinct bilayers formed only on filters with 0.4-microm pores and only with A549 cells and human umbilical vein endothelial cells. Endotoxin (lipopolysaccharide [LPS]) stimulation of bilayers (4 hours) enhanced neutrophil transendothelial migration, but this was significantly decreased compared with the response of endothelium grown alone, irrespective of whether LPS exposure was via the epithelial or endothelial side of the bilayer. Down-modulation required epithelial-endothelial approximation and was not seen when these cells were separated by 0.5 to 1 mm. This study defines optimal conditions required for generation of intact bilayers of lung epithelial cells with endothelium for the study of leukocyte-transendothelial migration. Furthermore, it was demonstrated that lung epithelial cells can modulate endothelial cell responsiveness to an environmental inflammatory stimulus such as LPS and thus may have an important role in minimizing excessive and deleterious neutrophilic inflammation in the lung alveolus.

Regulation of polymorphonuclear leukocyte apoptosis: role of lung endothelium-epithelium bilayer transmigration

Delayed polymorphonuclear leukocyte (PMN) apoptosis exacerbates acute lung injury. To reach the alveolar spaces, PMNs must migrate across both pulmonary endothelial and epithelial cell layers. We hypothesized that transmigration across the endothelium-epithelium bilayer suppresses PMN apoptosis and sought to elucidate the underlying mechanisms. PMNs freshly isolated from normal volunteers were allowed to migrate across polycarbonate membranes alone or membranes coated with a bilayer of human lung endothelial and epithelial cells. After migration toward different chemoattractants (IL-8, formyl-Met-Leu-Phe, or leukotriene B(4)), PMN apoptosis and caspase activities were assessed by annexin V, histology, and enzymatic assays, respectively. Messenger RNA and specific protein expression in three receptor ligand-mediated, apoptosis-inducing pathways (Fas, TNF-alpha, and TNF-related apoptosis-inducing ligand) were further examined by gene array, RT-PCR, flow cytometry, and Western blot analyses. The data demonstrated that transbilayer migration suppressed PMN apoptosis, and this effect was not chemoattractant type specific. Kinetic analyses further showed that the delay of apoptosis was sustained to at least 18 h. Transbilayer migration caused significant decreases in caspase (-3, -8, and -9) activities. The changes in apoptosis-related gene expression support the survival role of transbilayer migration. Furthermore, the reduced apoptosis was correlated with downregulation of Fas ligand and TNF receptor 1 expression. Our data reveal that migration across a lung endothelium-epithelium bilayer suppresses PMN apoptosis. The decreased activity and/or expression of proapoptotic proteins may provide possible targets for the regulation of inappropriate delay in PMN apoptosis during lung inflammation and injury.

Modulation of plasma levels of soluble adhesion molecules and nitric oxide in healthy volunteers by exposure to swine dust

Short-time exposure to swine dust causes an intense airways inflammation and symptoms of systemic inflammation in healthy volunteers. Here, we sought to study whether this response involved signs of endothelial cell activation. Peripheral blood cell counts and plasma levels of sE-selectin, sP-selectin, sICAM-1, interleukin-8, nitrite and nitrate were measured in blood samples from 17 healthy subjects before and after a 3-hr exposure to swine dust in a swine confinement building. Dust exposure induced a 3-fold increase of blood neutrophil p = 0.0009) and 1.5-fold increase of monocyte counts (p = 0.0047). IL-8 was detected in 15 individuals after exposure (p = 0.001). Endothelial cell markers such as sICAM and nitrate increased by 10 and 34% resp. (p = 0.011 and 0.017), whereas sE-selectin remained unchanged and sP-selectin was reduced by 15% (p = 0.031). Thus, short time exposure to swine dust induced a systemic inflammatory response with evidence of endothelial and inflammatory cell activation.

Migratory responses of polymorphonuclear leukocytes to kinin peptides

The present study examines the influence of kinins on the migratory capacity of human polymorphonuclear leukocytes under in vitro conditions using the Boyden chamber technique. By means of checkerboard analysis the migration of neutrophils induced by bradykinin could be characterized as true chemotaxis. The stimulation of human neutrophils with bradykinin, with the nonpeptide B(2) receptor agonist FR190997 as well as with des-Arg(9)-bradykinin and des-Arg(10)-kallidin results in a concentration-dependent migration. Pretreatment of the neutrophils with the B(2) receptor antagonist HOE-140 (icatibant) inhibited the bradykinin-induced migration but not that induced by B(1) receptor agonists, whereas the B(1 )receptor antagonist des-Arg(10)HOE-140 abolished the migration elicited by des-Arg(9)-bradykinin or des-Arg(10)-kallidin but not that evoked by bradykinin. Pretreatment of the neutrophils with the leukotriene B(4) (LTB(4)) antagonist ZK158252 inhibited the LTB(4)-induced chemotaxis as well as the chemotaxis produced by bradykinin and des-Arg(10)-kallidin. An involvement of interleukin-1beta and of the chemokine IL-8 in the bradykinin-induced migration in vitro could be excluded during the migration time of the neutrophils. In conclusion, the present study provides pharmacological evidence showing that B(1) and B(2) kinin receptors are involved in the migration of human neutrophils in vitro, that LTB(4) participates in the downstream pathway and that the B(1) kinin receptor seems to be expressed already under physiological conditions.

Inhibition of leukocyte rolling by nitric oxide during sepsis leads to reduced migration of active microbicidal neutrophils

We developed two models of sepsis with different degrees of severity, sublethal and lethal sepsis, induced by cecal ligation and puncture. Lethal sepsis induced by cecal ligation and puncture (L-CLP) resulted in failure of neutrophil migration to the infection site and high mortality. Treatment of septic animals with aminoguanidine (AG), a nitric oxide (NO) synthase inhibitor, precluded the failure of neutrophil migration and protected the animals from death. However, cytokine-induced NO synthase (iNOS)-deficient (iNOS(-/-)) mice subjected to L-CLP did not present neutrophil migration failure, but 100% lethality occurred. iNOS(-/-) mice subjected to sublethal sepsis induced by cecal ligation and puncture (SL-CLP) also suffered high mortality despite the occurrence of neutrophil migration. This apparent paradox could be explained by the lack of microbicidal activity in neutrophils of iNOS(-/-) mice present at the infection site due to their inability to produce NO. Notably, SL- and L-CLP iNOS(-/-) mice showed high bacterial numbers in exudates. The inhibition of neutrophil migration by NO is due to inhibition of a neutrophil/endothelium adhesion mechanism, since a reduction in leukocyte rolling, adhesion, and emigration was observed in L-CLP wild-type mice. These responses were prevented by AG treatment and were not observed in the iNOS(-/-) L-CLP group. There was no significant change in L-selectin expression in neutrophils from L-CLP mice. Thus, it seems that the decrease in leukocyte rolling is due to a defect in the expression of adhesion molecules on endothelial surfaces mediated by iNOS-derived NO. In conclusion, the results indicate that despite the importance of NO in neutrophil microbicidal activity, its generation in severe sepsis reduces neutrophil migration by inhibiting leukocyte rolling and their firm adhesion to the endothelium, in effect impairing the migration of leukocytes and consequently their fundamental role in host cell defense mechanisms.

Tumor necrosis factor-alpha-stimulated polymorphonuclear leukocytes suppress migration and bactericidal activity of polymorphonuclear leukocytes in a paracrine manner

OBJECTIVE

Polymorphonuclear leukocytes (PMN) and tumor necrosis factor-alpha (TNF-alpha) play prominent roles in acute respiratory distress syndrome, ischemia-reperfusion injury, trauma, and sepsis. Whereas direct effects of TNF-alpha on PMN function and viability are well documented, little data are available addressing the ability of PMN to communicate with each other in response to cytokine stimulation. Therefore, the aim of this study was to determine whether TNF-alpha can modulate PMN function by inducing PMN to secrete products upon stimulation, which would affect other PMN in vitro in a manner independent of cell contact.

METHODS

PMN were purified daily from blood obtained from a pool of 22 healthy volunteers. Conditioned media (CM-TNF) was prepared by incubating PMN in Hanks' balanced salt solution plus TNF-alpha for 1-4 hrs. Freshly isolated PMN were resuspended in CM-TNF and analyzed for 1) phagocytosis of opsonized Escherichia coli, 2) oxidative metabolism as measured as an index of DCF-DA activation, and 3) migration to chemoattractants through Transwell inserts.

RESULTS

CM-TNF decreased PMN phagocytotic activity by 8% to 15% and completely suppressed oxidative metabolism but did not modulate the expression of receptors associated with these functions. CM-TNF suppressed the migration of PMN to two biologically relevant agents, N-formyl-methionyl-leucyl-phenylalanine and leukotriene B4, by approximately 65%, but had no effect on PMN migration to interleukin-8. This suppression was observed for migration across plastic filters as well as extracellular matrix proteins.

CONCLUSION

Our data demonstrate that PMN stimulated with TNF-alpha suppress the immunologic function and migration of other PMN independent of cell-cell contact and suggest that TNF-alpha may participate in a negative feedback loop by inducing a PMN-derived factor that counteracts its activity.

Tumor necrosis factor alpha increases the expression of glycosyltransferases and sulfotransferases responsible for the biosynthesis of sialylated and/or sulfated Lewis x epitopes in the human bronchial mucosa

There is increasing evidence that inflammation may affect glycosylation and sulfation of various glycoproteins. The present study reports the effect of tumor necrosis factor alpha (TNF-alpha), a proinflammatory cytokine, on the glycosyl- and sulfotransferases of the human bronchial mucosa responsible for the biosynthesis of Lewis x epitope and of its sialylated and/or sulfated derivatives, which are expressed in human bronchial mucins. Fragments of macroscopically normal human bronchial mucosa were exposed to TNF-alpha at a concentration of 20 ng/ml. TNF-alpha was shown to increase alpha1,3-fucosyltransferase activity as well as expression of the two alpha1,3-fucosyltransferase genes expressed in the human airway, FUT3 and FUT4. It had no influence on alpha1,2-fucosyltransferase activity or FUT2 expression. It also increased alpha2,3-sialyltransferase activity and the expression of ST3Gal-III and, more importantly, ST3Gal-IV and both N-acetylglucosamine 6-O-sulfotransferase and galactose 3-O-sulfotransferase. These results are consistent with the observation of oversialylation and increased expression sialyl-Lewis x epitopes on human airway mucins secreted by patients with severe lung infection such as those with cystic fibrosis, whose airways are colonized by Pseudomonas aeruginosa. However, other cytokines may also be involved in this process.

Hyporesponsiveness of donor cells to lipopolysaccharide stimulation reduces the severity of experimental idiopathic pneumonia syndrome: potential role for a gut-lung axis of inflammation

Idiopathic pneumonia syndrome (IPS) is a major complication of allogeneic bone marrow transplantation (BMT). We have shown that experimental IPS is associated with increased levels of LPS and TNF-alpha in the bronchoalveolar lavage (BAL) fluid. We hypothesized that the deleterious effects of these inflammatory mediators in the lung may be linked to gut injury that develops after BMT. To test this hypothesis, we used mouse strains that differ in their sensitivity to LPS as donors in an experimental BMT model. Lethally irradiated C3FeB6F(1) hosts received BMT from either LPS-sensitive or LPS-resistant donors. Five weeks after BMT, LPS-resistant BMT recipients had significantly less lung injury compared with recipients of LPS-sensitive BMT. This effect was associated with reductions in TNF-alpha secretion (both in vitro and in vivo), BAL fluid LPS levels, and intestinal injury. The relationship between TNF-alpha, gut toxicity, and lung injury was examined further by direct cytokine blockade in vivo; systemic neutralization of TNF-alpha resulted in a significant reduction in gut histopathology, BAL fluid LPS levels, and pulmonary dysfunction compared with control-treated animals. We conclude that donor resistance to endotoxin reduces IPS in this model by decreasing the translocation of LPS across the intestinal border and systemic and pulmonary TNF-alpha production. These data demonstrate a potential etiologic link between gut and lung damage after BMT and suggest that methods that reduce inflammatory responses to LPS, and specifically, those that protect the integrity of the gut mucosa, may be effective in reducing IPS after BMT.

Effect of intramammary infusion of tumour necrosis factor-alpha on milk protein composition and induction of acute-phase protein in the lactating cow

The present study was designed to evaluate the effects of tumour necrosis factor-alpha (TNF-alpha) on lactating bovine mammary functions such as milk protein secretion and the integrity of the milk-blood barrier. The effect on the induction of the systemic inflammatory response was also examined using concentrations of serum haptoglobin (Hp), a major inflammatory acute-phase protein, as an index. One hundred micrograms per mammary gland of recombinant bovine (rBo) TNF-alpha or placebo saline was individually infused into a rear mammary gland of each of four lactating cows, and milk and blood samples were collected before and 4, 8, 24, 32, 48, 96 and 168 h after infusion. In the rBoTNF-alpha-infused gland, increases of somatic cell counts were observed at 4-48 h. Although concentrations of total milk protein were not changed, compositions of milk proteins varied following rBoTNF-alpha infusion. Concentrations of caseins, alpha-lactalbumin and beta-lactoglobulin were significantly decreased at 4 and 8 h. Lactoferrin concentrations were significantly increased at 4 h. Significant infiltrations of serum albumin, immunoglobulin G1 (IgG1) and IgG2 were observed at 4 and 8 h. Elevations of the serum concentration of Hp were detected at 8-32 h, but were very small in comparison with those reported in inflammatory diseases. Changes in rectal temperature and white blood cell counts were not significant. These results show that single rBoTNF-alpha infusion into the lactating mammary gland suppresses the lactogenic function of the gland and influences the function of the milk-blood barrier, with little effect on the generalized inflammatory response.

Tumor necrosis factor-alpha neutralization reduces lung injury after experimental allogeneic bone marrow transplantation

BACKGROUND

Idiopathic pneumonia syndrome (IPS) is a frequent and potentially fatal complication of bone marrow transplantation (BMT). We have previously shown that experimental IPS is associated with increased levels of lipopolysaccaride (LPS) and tumor necrosis factor-alpha (TNFalpha) in the bronchoalveolar lavage (BAL) fluid, and that administration of LPS to animals with extensive graft versus host exacerbated underlying lung injury (Blood 1996; 88: 3230).

METHODS

Lethally irradiated CBA mice received BMT from allogeneic (B10.BR) or syngeneic (CBA) donors. The role of TNFalpha in the exacerbation of pulmonary toxicity caused by LPS injection and in the evolution of IPS after allogeneic BMT was examined by neutralizing TNFalpha after BMT using a soluble binding protein (rhTNFR:Fc).

RESULTS

Five weeks after BMT, administration of rhTNFR:Fc dramatically reduced mortality and prevented the exacerbation of lung injury caused by LPS administration. This protective effect was associated with preservation of pulmonary function and with marked reductions of cells, neutrophils, and LPS in the BAL fluid of treated animals. TNFalpha neutralization from week 4 to 6 after allogeneic BMT effectively halted the progression of systemic GVHD and significantly reduced, but did not prevent lung injury that developed during the treatment period.

CONCLUSIONS

We conclude that TNFalpha is central to early LPS induced toxicity in this model and is a significant, but not the exclusive contributor to the development of IPS after allogeneic BMT.

Genomic and functional changes induced by the activation of the peripheral cannabinoid receptor CB2 in the promyelocytic cells HL-60. Possible involvement of the CB2 receptor in cell differentiation

The function of the peripheral cannabinoid receptor (CB2), which is mainly expressed on hematopoietic cells, remains an enigma. In an attempt to decipher its role, we used Affymetrix DNA chips to investigate the gene expression profile of the promyelocytic cells HL-60 transfected with the CB2 receptor and activated with the cannabinoid agonist CP 55,940. Agonist exposure of these cells led to an activation of a mitogen-activated protein kinase cascade and a receptor desensitization, indicating a functional coupling of the transfected receptors. At the genomic level, activation of the CB2 receptors induced an up-regulation of nine genes involved in cytokine synthesis, regulation of transcription, and cell differentiation. A majority of them are under the control of the transcription factor NF-kappaB, whose nuclear translocation was demonstrated. Many features of the transcriptional events, reported here for the first time, appeared to be related to an activation of a cell differentiation program, suggesting that CB2 receptors could play a role in the initialization of cell maturation. Moreover, we showed that CB2-activated wild-type HL-60 cells developed properties usually found in host defense effector cells such as an enhanced release of chemotactic cytokines and an increased motility, characteristic of more mature cells of the granulocytic-monocytic lineage.