Inhibition of activated/memory (CD45RO(+)) T cells by oxidative stress associated with block of NF-kappaB activation

Impaired immune responses in cancer patients have been associated with oxidative stress. Increased levels of reactive oxygen species released from activated, tumor-infiltrating macrophages or granulocytes may therefore constitute a hurdle for effective immunotherapy against cancer. In this study, we investigated functional consequences and molecular events in T cells exposed to low levels of oxidative stress. We observed that cytokine production of human PBMC, upon stimulation with an HLA-A*0201-restricted influenza peptide and nonspecific receptor cross-linking, was reduced after exposure to micromolar levels of H2O2. Functional impairment as measured by IFN-gamma release occurred earlier and at lower doses of exogenously added H2O2 than required to induce apoptosis. This suggests that there is a dose window of oxidative stress leading to T cell unresponsiveness in the absence of apoptosis. The reduction of Th1 cytokines, induced by H2O2, was predominantly observed in memory/effector (CD45RO(+)) T cells and correlated with a block in NF-kappaB activation. IL-10 production was more profoundly influenced by low doses of H2O2 than IFN-gamma, TNF-alpha, and IL-2. The influence of H2O2 on production of IL-10 was not significantly different between memory/activated and naive T cells. These observations suggest that Th1 and Th2 cytokines are differently regulated under conditions of oxidative stress. Taken together, these findings may explain why Ag-experienced, CD45RO(+), T cells found in the tumor milieu are functionally suppressed.

The final phase in acute myeloid leukaemia (AML): a study of cause of death, place of death and type of care during the last week of life

The aim of this study was to increase the knowledge of the final phase in acute myeloid leukaemia (AML), a period which entails many complex medical and psychosocial decisions. Data on cause and place of death were gathered through a retrospective review of medical and nursing records of 106 patients with AML who had died during 1995-1997. We focused on the actual phase of the disease and to what extent the patients were prescribed palliative care. With increased knowledge of the dying process in AML there are options to discuss which approach would be the most preferred final phase for an AML patient.

A mouse model for adenovirus gene delivery

The cellular attachment receptor for adenovirus (Ad), Coxsackie adenovirus receptor (CAR), required for delivery of Ad into primary cells, is not present on all cell types, thus restricting Ad-gene delivery systems. To circumvent this constrain, a transgenic mouse has been generated that expresses a truncated human CAR in all tissues analyzed. These mice allowed efficient in vitro infections at low multiplicities into lymphoid, myeloid, and endothelial cells. Furthermore, in vivo administration of Ad-vectors results in infection of macrophages, lymphocytes, and endothelial cells. In addition, tail vein injection resulted in targeting of virus into previously inaccessible areas, such as the lung and the capillaries of the brain. The CAR transgenic mice will be useful for rapid functional genomic analysis in vivo, for testing the efficacy of gene therapy procedures or as a source of easily transducible cells.

Impact of transcription factors AP-1 and NF-kappaB on the outcome of experimental Staphylococcus aureus arthritis and sepsis

Staphylococcus aureus infection is, despite adequate antibiotic treatment, a disease characterized by high mortality. The bacterium triggers an exaggerated immune response in the host, which on the one hand acts as an efficient defense, but on the other hand gives rise to tissue damage. In this study we have modulated the hosts response to S. aureus by inhibition of nuclear factor kappaB (NF-kappaB) and activator protein-1 (AP-1)-triggered release of pro-inflammatory cytokines and tissue-destructive proteins, respectively. Mice were administered with antisense oligonucleotides (ODN) to the p65 subunit of NF-kappaB and/or a double-stranded oligonucleotide (mCoAP-1) with homology to the murine AP-1 binding site of collagenase IV gene (metalloproteinase-9; MMP-9), solely or in combination with antibiotics. In mice systemically treated with antisense ODN to NF-kappaB p65 alone, the bacterial burden in the kidneys was significantly increased (P = 0.04) The same tendency was seen when mCoAP-1 was administered either alone or in combination with antibiotics. We also found significantly (P = 0.04) elevated levels of IL-6 in p65 antisense treated mice. Surprisingly, this p65 antisense therapy approach, which has turned out to be highly efficient in amelioration of aseptic arthritis and colitis, failed to change the clinical course of either septic arthritis or sepsis. We suggest that interaction with transcription factors leads to increased bacterial burden in vivo, abrogating the potential benefits of the anti-inflammatory properties exerted by these compounds.

Absence of Toll-like receptor 4 explains endotoxin hyporesponsiveness in human intestinal epithelium

BACKGROUND

The Toll protein in Drosophila regulates dorsal ventral patterning during embryogenesis, and participates in antibacterial and antifungal host defense. Mammalian homologues are termed Toll-like receptors and, to date, nine have been cloned (TLRI-9) in humans. They are characterized by extracellular leucine-rich repeats and a cytoplasmic domain similar to the interleukin 1 receptor. Both TLR2 and TLR4 recognize various bacterial cell wall components including lipopolysaccharide (LPS). This results in the activation of the NFkappaB pathway. Peripheral blood mononuclear cells (PBMCs) express both TLR2 and TLR4. The authors hypothesized that the expression of TLR 2 and TLR4 in human intestinal epithelial cells differs from PBMCs because of the abundance of LPS in the intestinal lumen.

METHODS

Epithelial cells were isolated from Caco-2 cells, fetal gut explants, and small bowel resection specimens using Hanks/ethylenediamine tetraacetic acid solution. PBMCs were used as positive controls. Ribonucleic acid (RNA) was isolated using the TRIzol method. Standard reverse transcription-polymerase chain reaction examined TLR2 and TLR4 messenger RNA (mRNA) expression. NFkappaB expression was determined using a luciferase reporter assay.

RESULTS

TLR2 mRNA was highly expressed in PBMCs and was present in all human intestinal epithelial cells. TLR4 mRNA was detected only in PBMCs. TLR4 is not present in epithelium from children with inflammatory bowel disease. In Caco-2 cells, significant NFkappaB activation in response to LPS occurred only in the presence of TLR4 introduced by complementary deoxyribonucleic acid transfection.

CONCLUSION

Absence of TLR4 is associated with endotoxin hyporesponsiveness of intestinal epithelial cells. TLR4 is not directly involved in inflammation of the intestinal epithelium. Although TLR2 is normally present in the epithelial cell, it plays a limited role in inflammation. It may be activated during conditions in which bacterial cell wall concentrations within the intestine are pathologically high.

Hepatic cholesterol metabolism and resistance to dietary cholesterol in LXRbeta-deficient mice

The nuclear oxysterol-receptor paralogues LXRalpha and LXRbeta share a high degree of amino acid identity and bind endogenous oxysterol ligands with similar affinities. While LXRalpha has been established as an important regulator of cholesterol catabolism in cholesterol-fed mice, little is known about the function of LXRbeta in vivo. We have generated mouse lines with targeted disruptions of each of these LXR receptors and have compared their responses to dietary cholesterol. Serum and hepatic cholesterol levels and lipoprotein profiles of cholesterol-fed animals revealed no significant differences between LXRbeta(-/-) and wild-type mice. Steady-state mRNA levels of 3-hydroxy-3-methylglutaryl coenzyme A reductase, farnesyl diphosphate synthase, and squalene synthase were increased in LXRbeta(-/-) mice compared with LXRbeta(+/+) mice, when fed standard chow. The mRNA levels for cholesterol 7alpha-hydroxylase, oxysterol 7alpha-hydroxylase, sterol 12alpha-hydroxylase, and sterol 27-hydroxylase, respectively, were comparable in these strains, both on standard and 2% cholesterol chow. Our results indicate that LXRbeta(-/-) mice - in contrast to LXRalpha(-/-) mice - maintain their resistance to dietary cholesterol, despite subtle effects on the expression of genes coding for enzymes involved in lipid metabolism. Thus, our data indicate that LXRbeta has no complete overlapping function compared with LXRalpha in the liver.

Context-dependent Pax-5 repression of a PU.1/NF-kappaB regulated reporter gene in B lineage cells

Enhancers located in the 3' end of the locus in part regulate immunoglobulin heavy chain (IgH) gene expression. One of these enhancers, HS 1,2, is developmentally regulated by DNA binding proteins like NF-kappaB, Pax-5 and the protein complex NF-alphaP in B lineage cells. Here we report that NF-alphaP is the ets protein PU.1. A glutathione-S-transferase (GST)-pulldown assay demonstrated that PU.1 can physically interact with NF-kappaB in solution. Experiments in COS cells showed that PU.1 and NF-kappaB (p50/c-Rel) can activate transcription of an enhancer linked reporter gene. The paired domain protein Pax-5 has previously been shown to repress enhancer-dependent transcription. Additional co-transfection experiments revealed that PU.1/NF-kappaB dependent transcription could be repressed in a context dependent manner by Pax-5, but not by the paired domain of Pax-5. When the PU.1 binding site was substituted with a binding site for the ets-protein Elf-1, Pax-5 could no longer repress reporter gene activity. Our data indicate a model where Pax-5 mediated repression of the HS 1,2 enhancer requires the recruitment of a co-factor which is dependent on Pax-5/PU.1 but which cannot be recruited by Pax-5/Elf-1.

The lymphoid-specific cofactor OBF-1 is essential for the expression of a V(H) promoter/HS1,2 enhancer-linked transgene in late B cell development

Mice deficient for the lymphoid-specific cofactor OBF-1 display reduced levels of IgG, IgA and IgE. To examine whether the lowered immunoglobulin expression is linked to reduced activity of IgH cis-regulatory elements, OBF-1(-/-) mice were crossed with mice expressing transgenes driven by a V(H) or beta-globin promoter linked to the HS1,2 enhancer. Here we show that OBF-1 is essential for the induced expression of a V(H) promoter-linked transgene, in contrast to a beta-globin promoter-dependent transgene, in LPS/IL-4 or CD40-stimulated splenic B cells. Furthermore, impaired transgene expression is observed in OBF-1(-/-) peritoneal B cells. This deficiency may be linked to OBF-1, as peritoneal cells from normal mice express OBF-1 protein constitutively. Our data link OBF-1 to IgH gene expression in late B lymphoid development.

Salmonella typhimurium mutants that downregulate phagocyte nitric oxide production

To examine the potential and strategies of the facultative intracellular pathogen Salmonella typhimurium to increase its fitness in host cells, we applied a selection that enriches for mutants with increased bacterial growth yields in murine J774-A.1 macrophage-like cells. The selection, which was based on intracellular growth competition, rapidly yielded isolates that out-competed the wild-type strain during intracellular growth. J774-A.1 cells responded to challenge with S. typhimurium by mounting an inducible nitric oxide synthase (iNOS) mRNA and protein expression and a concomitant nitric oxide (NO) production. Inhibition of NO production with the use of the competitive inhibitor N-monomethyl-L-arginine (NMMA) resulted in a 20-fold increase in bacterial growth yield, suggesting that the NO response prevented bacterial intracellular growth. In accordance with this observation, five out of the nine growth advantage mutants isolated inhibited production of NO from J774-A.1 cells, despite an induction of iNOS mRNA and iNOS protein. Accompanying bacterial phenotypes included alterations in lipopolysaccharide structure and in the profiles of proteins secreted by invasion-competent bacteria. The results indicate that S. typhimurium has the ability to mutate in several different ways to increase its host fitness and that inhibition of iNOS activity may be a major adaptation.

The bacterial protein YopJ abrogates multiple signal transduction pathways that converge on the transcription factor CREB

Bacterially encoded proteins are known to affect eukaryotic signalling pathways and thus cell growth and differentiation. The enteric pathogen Yersinia pseudotuberculosis (YP) can translocate Yersinia outer proteins (Yops) into eukaryotic cells. Recently, MKK proteins have been identified as tentative targets of YopJ-mediated inhibition of ligand receptor-dependent signal transduction in mammalian cells. These results prompted us to assess whether multiple signal transduction pathways and their downstream target genes would also be subject to regulation by YopJ. Here, we show that YopJ effectively blocks the lipopolysaccharide (LPS) receptor, the interleukin (IL)-1beta receptor and the UVC-induced activation of the transcription receptor cAMP response element-binding protein (CREB). In addition, by abrogating the phosphorylation of CREB and thus activating protein (AP)-1-dependent transcription, YopJ can block LPS-induced clonal expansion that is associated with an adaptive immune response. Thus, YopJ interferes with multiple pathways converging on the transcription factor CREB. Our data are discussed in the context of YopJ acting as an antagonist to circumvent innate and adaptive immune responses at multiple levels.

Bacterial regulation of intestinal immune responses

If we understand pathological processess within the alimentary tract, it is apparent that the fundamental aspects of microbe-host interactions need to be examined in greater detail. Pathogenic bacteria have evolved strategies to alter and subvert the function of T cels and phagocytes in the gut wall, and exploiting these molecules may lead to new treatments for chronic inflammatory bowel diseases. The adaptation of microbes to their host must involve microbe-mediated interference of the host innate immune response. The recent demonstration that nonpathogenic E. coli have a beneficial effect in ulcerative colitis further supports the notion that normal flora may alter the expression of the innate immune receptors or recognize alternative receptors compared with pathogenic variants. Such differences may conceivably lead to beneficial and protective alterations to the host through cytokine and antimicrobial peptide expression. Perhaps the contact point between microbes and host cells lies with the pattern-recognition receptors such as TLRs. However, although much light has been shed on the downstream consequences of TLR activation, many more questions remain unsolved. For example, little is known about the expression profiles of the different TLRs throughout the gastrointestinal tract. Additionally, ambiguities remain over the natural ligands for TLRs. The discovery that the Drosophila Toll receptor acts downstream of the pathogen recognition event suggests that there are many more twists and turns to be revealed in the story of host-microbe interactions in the gastrointestinal tract.

The Salmonella YopJ-homologue AvrA does not possess YopJ-like activity

The YopJ protein of Yersinia pseudotuberculosis inhibits several eukaryotic signalling pathways that are normally activated in cells following their contact with bacteria. Salmonella encodes a protein, AvrA, that is secreted by the typeIII inv/spa secretion system which is clearly homologous to YopJ (56% identical, 87% similarity). Since AvrA and YopJs similarity also encompassed a region of YopJ that had previously been shown to be critical for its biological activity, we were interested whether AvrA and YopJ provoked similar responses in eukaryotic cells. Two different approaches were used to determine whether AvrA possesses YopJ-like activity in modulating cytokine expression or killing macrophages. An avrA strain of Salmonella dublin was constructed and its activity was compared to an isogenic wildtype counterpart in cellular response assays. In a complementary approach, AvrA was expressed in and delivered into eukaryotic cells by a yopJ strain of Yersinia pseudotuberculosis. We show here that AvrA affects neither cytokine expression or plays a role in macrophage killing when expressed by either Salmonella or Yersinia. Additionally, AvrA does not possess SopB/D-like activity in promoting fluid secretion into infected calf ileal loops. These data indicate that Salmonella and Yersinia trigger and/or modulate eukaryotic cell responses by different typeIII-secreted proteins and suggests that despite their close evolutionary relatedness, AvrA and YopJ perform different functions for Salmonella and Yersinia, respectively.

Bacterial adaptation to host innate immunity responses

Several recent reports show that different bacterial components trigger innate and inflammatory responses in host organisms. In parallel, selected bacterial virulence factors have been identified that interfere with corresponding responses. In many cases, this involves interference with host proinflammatory signal transduction pathways, whereas in selected cases bacterial virulence factors interfere with host antibacterial mechanisms. This indicates that bacteria, besides activating cellular responses, also have the capacity to directly interact with branches of the innate defence.

Cutting edge: Ig heavy chain 3' HS1-4 directs correct spatial position-independent expression of a linked transgene to B lineage cells

The Ig H chain locus is regulated by a set of cis-acting elements. Hypersensitive sites (HS) located 3' of the IgH, HS1-4, has been suggested to act as a locus control region (LCR) in cell lines. To assess the proposed role of HS1-4 acting as an LCR, we generated transgenic mice harboring a VH promoter-beta-globin reporter gene linked to the Ig H chain HS1-4 3'regulatory sequences. Transgene expression is strictly confined to B lymphocytes, with no detectable expression outside the B cell lineage in all transgenic founder lines. Furthermore, reporter gene activity is integration independent but not copy number dependent. Thus, additional sequences are required to allow the HS1-4 regulatory region to act as a classical LCR in mice. Our data are discussed in the context of tissue-specific gene expression in B lineage cells.

Cutting Edge: Ig Heavy Chain 3′ HS1–4 Directs Correct Spatial Position-Independent Expression of a Linked Transgene to B Lineage Cells

The Ig H chain locus is regulated by a set of cis-acting elements. Hypersensitive sites (HS) located 3′ of the IgH, HS1–4, has been suggested to act as a locus control region (LCR) in cell lines. To assess the proposed role of HS1–4 acting as an LCR, we generated transgenic mice harboring a VH promoter-β-globin reporter gene linked to the Ig H chain HS1–4 3′regulatory sequences. Transgene expression is strictly confined to B lymphocytes, with no detectable expression outside the B cell lineage in all transgenic founder lines. Furthermore, reporter gene activity is integration independent but not copy number dependent. Thus, additional sequences are required to allow the HS1–4 regulatory region to act as a classical LCR in mice. Our data are discussed in the context of tissue-specific gene expression in B lineage cells.

Novel Salmonella typhimurium properties in host--parasite interactions

Inflammatory bowel disease (IBD) comprises different diseases in the gastrointestinal tract in human, of which Crohn's disease (CD) and ulcerative colitis (UC) are the most prominent. A key factor in the etiology of IBD is the chronic inflammatory process, and a large body of evidence suggests that the transcription factor nuclear factor-kappa B (NF-kappaB) is the key regulator of responses determining the clinical inflammatory condition. Recent findings using antisense oligonucleotides provide direct evidence that the p65 subunit of NF-kappaB plays a central role in chronic intestinal inflammation. It has previously been shown that the Gram negative bacteria Yersinia pseudotubercolosis targets the eukaryotic signal transduction pathway(s) that lead to NF-kappaB activation (and thus avoid an anti-bacterial inflammatory response). In this paper, growth-based selected Salmonella typhimurium clones have been used to generate a clearer picture of the molecular mechanisms involved in host-parasite interactions. From the results presented here, S. typhimurium and Y. pseudotubercolosis may use the same mechanism to block NF-kappaB activation, following host cell infection. A new adaptational feature could also be shown, where a growth-based selected bacteria avoided the normally induced translocation of NF-kappaB in host cells.

Interference of eukaryotic signalling pathways by the bacteria Yersinia outer protein YopJ

Upon contact with bacteria, eukaryotic cells activates a slurry of defence mechanisms via distinct signalling transduction pathways. However, some bacteria have evolved strategies to escape or inhibit these host defence systems. We have recently shown that the bacteria Yersinia pseudotuberculosis, which encodes the Yersinia outer protein (YopJ) appears to inhibit the activation of NF-kappaB by preventing the phosphorylation of IkappaB. In a subsequent series of experiments it has also been shown that YopJ blocks the phosphorylation of the p38 MAP kinase. Here the regulatory function of YopJ on eukaryotic signal transduction is discussed.

Temporal expression of a V(H) promoter-Cmu transgene linked to the IgH HS1,2 enhancer

Immunoglobulin heavy chain (IgH) gene expression is guided by cis-regulatory elements which direct correct temporal and spatial expression in B lineage cells. One of these cis-acting elements is the IgH HS1,2 enhancer and previous studies in transgenic mice have revealed a temporally restricted activity of an HS1,2 enhancer-linked human beta-globin reporter gene in B lineage cells. To assess whether this enhancer can impose strict temporal regulation onto a V(H)-promoter-Cmu reporter gene, transgenic mice were generated. These mice expressed high serum levels of protein from the transgene. Moreover, high levels of transgene expression were observed in spleen and thymus, while lower expression was found in heart and kidney and no expression was detected in liver and brain. Interestingly, transgene expression was confined to large, activated B cells and peritoneal B cells but not observed in small, resting splenic B cells or activated T cells. However, upon mitogenic stimulation of resting B cells with LPS, high levels of transgene expression was induced. Our data demonstrate that the HS1,2 enhancer can interact with a natural V(H) promoter in a strict temporal fashion and when provided with an appropriate activation signal, this V(H) promoter/enhancer construct can induce transgene expression in resting B, but not T lineage cells. Our data are compatible with a model whereby the regulation of IgH gene expression may be subject to regulation by distinct subsets of cis-regulatory elements acting at different stages of B lymphocyte development. Thus, Ig gene expression may be regulated via an interaction between the V(H) promoter and 3' enhancer elements (here typified by the HS1,2 enhancer) in terminally differentiated B lineage cells.

Cytokine gene transcription by NF-kappa B family members in patients with inflammatory bowel disease

We examined the expression of the transcription factor NF-kappa B, a nuclear trans-acting factor known to play a key role in cytokine gene regulation, in patients with inflammatory bowel disease (IBD). It was found that LP macrophages in Crohn's disease (CD) and ulcerative colitis (UC) display high levels of NF-kappa B DNA-binding activity accompanied by an increased production of interleukin (IL)-1, IL-6, and tumor necrosis factor (TNF) alpha. Western blot studies showed an increased expression of the p50 and c-rel subunits of NF-kappa B; however, the most striking finding was an increased expression level of NF-kappa B p65 in patients with CD and UC. Selective downregulation of p65 in IBD macrophages by a specific antisense phosphorothioate oligonucleotide was sufficient to considerably reduce production of proinflammatory cytokines. These results demonstrate a characteristic increase of NF-kappa B binding levels in patients with IBD. The data suggest that antisense DNA targeting NF-kappa B p65 can be used as a novel molecular approach for the treatment of patients with IBD.

Stone fragmentation pattern of piezoelectric shockwave lithotripsy in vitro

Whole stones (N = 64; largest diameter 5-15 mm) were treated in vitro with piezoelectric shockwaves using the Edap LT-01 lithotripter with 2.5 Hz at either 100% or 54% power. The number of fragments larger than 2 mm was counted after every 30 seconds. The stones were defined as totally broken when all fragments were < 2 mm. Total fragmentation time was correlated with the energy level and the size of the stone. The number of large fragments did not correlate with the energy level but rather with the original size of the stone.