Role of the heat shock protein 90 in immune response stimulation by bacterial DNA and synthetic oligonucleotides

Systems Immunology Analysis Reveals an Immunomodulatory Effect of Snail-p53 Binding on Neutrophil- and T Cell-Mediated Immunity in KRAS Mutant Non-Small Cell Lung Cancer

Immunomodulation and chronic inflammation are important mechanisms utilized by cancer cells to evade the immune defense and promote tumor progression. Therefore, various efforts were focused on the development of approaches to reprogram the immune response to increase the immune detection of cancer cells and enhance patient response to various types of therapy. A number of regulatory proteins were investigated and proposed as potential targets for immunomodulatory therapeutic approaches including p53 and Snail. In this study, we investigated the immunomodulatory effect of disrupting Snail-p53 binding induced by the oncogenic KRAS to suppress p53 signaling. We analyzed the transcriptomic profile mediated by Snail-p53 binding inhibitor GN25 in non-small cell lung cancer cells (A549) using Next generation whole RNA-sequencing. Notably, we observed a significant enrichment in transcripts involved in immune response pathways especially those contributing to neutrophil (IL8) and T-cell mediated immunity (BCL6, and CD81). Moreover, transcripts associated with NF-κB signaling were also enriched which may play an important role in the immunomodulatory effect of Snail-p53 binding. Further analysis revealed that the immune expression signature of GN25 overlaps with the signature of other therapeutic compounds known to exhibit immunomodulatory effects validating the immunomodulatory potential of targeting Snail-p53 binding. The effects of GN25 on the immune response pathways suggest that targeting Snail-p53 binding might be a potentially effective therapeutic strategy.

Tumor-intrinsic and tumor-extrinsic factors impacting hsp90- targeted therapy

In 1994 the first heat shock protein 90 (Hsp90) inhibitor was identified and Hsp90 was reported to be a target for anticancer therapeutics. In the past 18 years there have been 17 distinct Hsp90 inhibitors entered into clinical trial, and the small molecule Hsp90 inhibitors have been highly valuable as probes of the role of Hsp90 and its client proteins in cancer. Although no Hsp90 inhibitor has achieved regulatory approval, recently there has been significant progress in Hsp90 inhibitor clinical development, and in the past year RECIST responses have been documented in HER2-positive breast cancer and EML4-ALK-positive non-small cell lung cancer. All of the clinical Hsp90 inhibitors studied to date are specific in their target, i.e. they bind exclusively to Hsp90 and two related heat shock proteins. However, Hsp90 inhibitors are markedly pleiotropic, causing degradation of over 200 client proteins and impacting critical multiprotein complexes. Furthermore, it has only recently been appreciated that Hsp90 inhibitors can, paradoxically, cause transient activation of the protein kinase clients they are chaperoning, resulting in initiation of signal transduction and significant physiological events in both tumor and tumor microenvironment. An additional area of recent progress in Hsp90 research is in studies of the posttranslational modifications of Hsp90 itself and Hsp90 co-chaperone proteins. Together, a picture is emerging in which the impact of Hsp90 inhibitors is shaped by the tumor intracellular and extracellular milieu, and in which Hsp90 inhibitors impact tumor and host on a microenvironmental and systems level. Here we review the tumor intrinsic and extrinsic factors that impact the efficacy of small molecules engaging the Hsp90 chaperone machine.

A novel putative lipoprotein receptor (CasLpR) in the hemocytes of the blue crab, Callinectes sapidus: cloning and up-regulated expression after the injection of LPS and LTA

The full-length cDNA encoding a putative lipoprotein receptor (CasLpR) was isolated from the hemocytes of Callinectes sapidus using 5' and 3' RACEs. The open reading frame for CasLpR contains a precursor of putative CasLpR consisting of 1710 amino acid residues including 22 amino acid residues of the signal peptide (22 amino acids). Mature CasLpR (1688 amino acids with 5.6% of phosphorylation sites) has multiple, putative functional domains: five low-density lipoprotein receptor domains in the N-terminus, and a G-protein-coupled receptor proteolysis site domain and a 7 transmembrane receptor (secretin family) domain in the C-terminus. To date, there are no proteins with a similar domain structure in the GenBank. The expression pattern of CasLpR was exclusive in hemocytes among all tested tissues obtained from a juvenile female at intermolt stage: brain, eyestalk ganglia, pericardial organs, and thoracic ganglia complex (nervous system); hepatopancreas (digestive system); heart, artery and hemocytes (circulatory system); gill and antennal gland (excretory system), hypodermis; and Y-organ (endocrine organ). There was no CasLpR expression in the ovary of an adult female. A putative function of CasLpR was examined after challenges of lipopolysaccharides (LPS) and lipoteichoic acid (LTA) in vivo using qRT-PCR assays. Animals at 24 h after injection of LPS or LTA up-regulated the expression of CasLpR in hemocytes by ∼3.5 and 1.4 folds, respectively, compared to the controls that received saline injection. LPS challenge also caused the greatest increment (∼55 folds) of heat shock protein 90 (Hsp90) expression in these samples. These data indicate that putative CasLpR and CasHsp90 may be involved in the defense system or the stress response of C. sapidus.

EC144, a synthetic inhibitor of heat shock protein 90, blocks innate and adaptive immune responses in models of inflammation and autoimmunity

Heat shock protein 90 (Hsp90) is a molecular chaperone involved in folding and stabilizing multiple intracellular proteins that have roles in cell activation and proliferation. Many Hsp90 client proteins in tumor cells are mutated or overexpressed oncogenic proteins driving cancer cell growth, leading to the acceptance of Hsp90 as a potential therapeutic target for cancer. Because several signal transduction molecules that are dependent on Hsp90 function are also involved in activation of innate and adaptive cells of the immune system, we investigated the mechanism by which inhibiting Hsp90 leads to therapeutic efficacy in rodent models of inflammation and autoimmunity. EC144, a synthetic Hsp90 inhibitor, blocked LPS-induced TLR4 signaling in RAW 264.7 cells by inhibiting activation of ERK1/2, MEK1/2, JNK, and p38 MAPK but not NF-κB. Ex vivo LPS-stimulated CD11b(+) peritoneal exudate cells from EC144-treated mice were blocked from phosphorylating tumor progression locus 2, MEK1/2, and ERK1/2. Consequently, EC144-treated mice were resistant to LPS administration and had suppressed systemic TNF-α release. Inhibiting Hsp90 also blocked in vitro CD4(+) T cell proliferation in mouse and human MLRs. In vivo, semitherapeutic administration of EC144 blocked disease development in rat collagen-induced arthritis by suppressing the inflammatory response. In a mouse collagen-induced arthritis model, EC144 also suppressed disease development, which correlated with a suppressed Ag-specific Ab response and a block in activation of Ag-specific CD4(+) T cells. Our results describe mechanisms by which blocking Hsp90 function may be applicable to treatment of autoimmune diseases involving inflammation and activation of the adaptive immune response.

Expression and distribution of three heat shock protein genes under heat shock stress and under exposure to Vibrio harveyi in Penaeus monodon

A sudden increase in temperature results in heat shock stress of the cultured shrimp. To cope with the stress, shrimp has to overcome by triggering a response known as heat shock response. To understand the heat shock response in the black tiger shrimp (Penaeus monodon), we examined expression patterns and distribution of three heat shock protein (hsp) genes in P. monodon juveniles. The expression levels of hsp21, hsp70 and hsp90 were determined by quantitative real-time PCR in nine tissues (gill, heart, hepatopancreas, stomach, intestine, eyestalk, pleopod, thoracic ganglia and hemocyte) under untreated and heat shock conditions. Under untreated condition, all three hsp genes were differentially expressed in all examined tissues where the hsp70 transcript showed the highest basal level. Under heat shock condition, only hsp90 was inducible in all nine tissues when comparing to its untreated level. The time-course induction experiment in gill and hepatopancreas revealed that the transcriptional levels of hsp21, hsp70 and hsp90 were inducible under the heat shock condition and in time-dependent manner. To determine the response of the hsp genes upon bacterial exposure, we further determined transcript levels of the hsp genes in gill of P. monodon after Vibrio harveyi injection. The expression levels of hsp70 and hsp90 were significantly increased after a 3-h exposure to V. harveyi where the hsp21 transcript was induced later after a 24-h exposure. This evidence suggests for putative roles and involvement of the hsp genes as a part of immunity response against V. harveyi in P. monodon.

Role of Hsp90 in CpG ODN mediated immunostimulation in avian macrophages

In mammals, CpG mediated immune activation is initiated through toll-like receptor (TLR) 9 and Hsp90 via activation of MAPK/ERK and PI3K/AKT pathways. However, in the absence of TLR9 ortholog in chicken genome, the role of Hsp90 and kinase (MAPK/ERK and PI3K/AKT) pathways in initiating CpG ODN(2007) induced immune activation in chicken is not clear. Using electrophoretic mobility shift assay (EMSA) and selective inhibitors of signal transduction pathways, we determined the role of these pathways in the production of Th1 cytokines/chemokines and nitric oxide (NO) in CpG ODN(2007) treated avian macrophage cells. Hsp90alpha but not Hsp90beta is bound to CpG ODN(2007). Inhibition of Hsp90 with geldanamycin resulted in the inactivation of MAPK/ERK and PI3K/AKT pathways leading to significantly reduced levels of IFN-gamma, IL-6 and NO mRNAs in CpG ODN(2007) stimulated cells. Moreover, inhibition of ERK1/2 and PI3/AKT kinase pathways with PD985009 and LY294002, respectively, suppresses the phosphorylation of ERK2 and AKT leading to the production of decreased amounts of IFN-gamma, IL-6 and NO mRNAs in CpG ODN(2007) stimulated cells. Our results demonstrate that binding of CpG ODN(2007) to Hsp90 induces activation of ERK2 and AKT phosphorylation leading to the production of high levels of IFN-gamma, IL-6, MIP-3alpha and nitric oxide (NO). In contrast to mammals, our results suggest that Hsp90alpha but not Hsp90beta binds with the CpG ODN(2007) and may play a major role in CpG ODN(2007) induced immunoactivation in avian macrophage cells. To our knowledge, this is the first report evaluating the involvement of Hsp90 and kinase (MAPK/ERK and PI3K/AKT) pathways in CpG mediated immunostimulation in avian macrophage cells.

Small molecule inhibitors of Hsp90 potently affect inflammatory disease pathways and exhibit activity in models of rheumatoid arthritis

OBJECTIVE

To evaluate the ability of SNX-7081, a novel small molecule inhibitor of Hsp90, to block components of inflammation, including cytokine production, protein kinase activity, and angiogenic signaling. A close analog was evaluated in preclinical in vivo models of rheumatoid arthritis (RA).

METHODS

SNX-7081 binding to Hsp90 was characterized in Jurkat cells and RA synovial fibroblasts (RASFs). Inhibition of NF-kappaB nuclear translocation was evaluated in cellular systems, using lipopolysaccharide (LPS), tumor necrosis factor alpha, or interleukin-1beta stimulation. Suppression of cytokine production in THP-1 cells, human umbilical vein endothelial cells, and RASFs was studied. Disruption of MAPK signaling cascades by SNX-7081 following growth factor stimulation was assessed. SNX-7081 was tested in 2 relevant angiogenesis assays: platelet-derived growth factor activation of fibroblasts and LPS-induced nitric oxide (NO) release in J774 macrophages. A close analog, SNX-4414, was evaluated in rat collagen-induced arthritis and adjuvant-induced arthritis, following oral treatment.

RESULTS

SNX-7081 showed strong binding affinity to Hsp90 and expected induction of Hsp70. NF-kappaB nuclear translocation was blocked by SNX-7081 at nanomolar concentrations, and cytokine production was potently inhibited. Growth factor activation of ERK and JNK signaling was significantly reduced by SNX-7081. NO production was also sharply inhibited. In animal models, SNX-4414 fully inhibited paw swelling and improved body weight. Scores for inflammation, pannus formation, cartilage damage, and bone resorption returned to normal.

CONCLUSION

The present results demonstrate that a small molecule Hsp90 inhibitor can impact inflammatory disease processes. The strong in vivo efficacy observed with SNX-4414 provides preclinical validation for consideration of Hsp90 inhibitors in the treatment of RA.

TLR9-activating DNA up-regulates ZAP70 via sustained PKB induction in IgM+ B cells

In the past, ZAP70 was considered a T cell-specific kinase, and its aberrant expression in B-CLL cells was interpreted as a sign of malignant transformation and dedifferentiation. It was only recently that ZAP70 was detected in normal human B cells. In this study, we show that TLR9-activated B cells resemble B-cell chronic lymphocytic leukemia cells with regard to CD5, CD23, CD25, and heat shock protein 90 expression. Furthermore, stimulatory CpG and GpC DNA oligonucleotides target CD27(+)IgM(+) and CD27(-)IgM(+) B cells (but not IgM(-) B cells) and enhance ZAP70 expression predominantly in the IgM(+)CD27(+) B cell subset. ZAP70 is induced via activation of TLR-7 or -9 in a MyD88-dependent manner, depends on protein kinase B (PKB)/mammalian target of rapamycin signaling and is rapamycin sensitive. Furthermore, ZAP70 expression levels correlate with induction of cyclin A2, prolonged B cell proliferation, and sustained induction of PKB. These events are not observed upon CD40 ligation. However, this deficit can be overcome by the expression of constitutively active PKB, given that CD40 ligation of PKB-transgenic B cells induces B cell proliferation and ZAP70 expression. These results highlight a major difference between CD40- and TLR-7/9-mediated B cell activation and suggest that ZAP70 expression levels in B cells give an estimate of the proliferative potential and the associated PKB availability.

Cathepsins are required for Toll-like receptor 9 responses

Toll-like receptors (TLR) recognize a variety of microbial products and activate defense responses. Pathogen sensing by TLR2/4 requires accessory molecules, whereas little is known about a molecule required for DNA recognition by TLR9. After endocytosis of microbes, microbial DNA is exposed and recognized by TLR9 in lysosomes. We here show that cathepsins, lysosomal cysteine proteases, are required for TLR9 responses. A cell line Ba/F3 was found to be defective in TLR9 responses despite enforced TLR9 expression. Functional cloning with Ba/F3 identified cathepsin B/L as a molecule required for TLR9 responses. The protease activity was essential for the complementing effect. TLR9 responses were also conferred by cathepsin S or F, but not by cathepsin H. TLR9-dependent B cell proliferation and CD86 upregulation were apparently downregulated by cathepsin B/L inhibitors. Cathepsin B inhibitor downregulated interaction of CpG-B with TLR9 in 293T cells. These results suggest roles for cathepsins in DNA recognition by TLR9.

Mechanisms of Legionella pneumophila-induced interleukin-8 expression in human lung epithelial cells

BACKGROUND

Legionella pneumophila is a facultative intracellular bacterium, capable of replicating within the phagosomes of macrophages and monocytes, but little is known about its interaction with human lung epithelial cells. We investigated the effect of L. pneumophila on the expression of interleukin-8 (IL-8) in human A549 alveolar and NCI-H292 tracheal epithelial cell lines.

RESULTS

Infection of L. pneumophila strain, but not heat-killed strain, resulted in upregulation of IL-8. IL-8 mRNA expression was induced immediately after the infection and its signal became gradually stronger until 24 h after infection. On the other hand, IL-8 expression in A549 cells infected with L. pneumophila lacking a functional type IV secretion system was transient. The IL-8 expression was slightly induced at 16 h and increased at 24 h after infection with flagellin-deficient Legionella. Activation of the IL-8 promoter by L. pneumophila infection occurred through the action of nuclear factor-kappaB (NF-kappaB). Transfection of dominant negative mutants of NF-kappaB-inducing kinase, IkappaB kinase and IkappaB inhibited L. pneumophila-mediated activation of IL-8 promoter. Treatment with hsp90 inhibitor suppressed L. pneumophila-induced IL-8 mRNA due to deactivation of NF-kappaB.

CONCLUSION

Collectively, these results suggest that L. pneumophila induces activation of NF-kappaB through an intracellular signaling pathway that involves NF-kappaB-inducing kinase and IkappaB kinase, leading to IL-8 gene transcription, and that hsp90 acts as a crucial regulator in L. pneumophila-induced IL-8 expression, presumably contributing to immune response in L. pneumophila. The presence of flagellin and a type IV secretion system are critical for Legionella to induce IL-8 expression in lung epithelial cells.

Helicobacter pylori induces CCL20 expression

CCL20 attracts immature dendritic cells and memory T cells and plays a role on mucosal surfaces in inflammation. However, whether Helicobacter pylori infection induces CCL20 in human gastric epithelial cells remains to be determined. The aim of this study was to analyze the molecular mechanism of H. pylori-induced CCL20 expression. Expression of CCL20 mRNA was assessed by reverse transcription-PCR. Five normal and five H. pylori-infected gastric tissue samples were stained immunohistochemically for CCL20. A luciferase assay was used to monitor activation of the CCL20 gene promoter, and an electrophoretic mobility shift assay was used to explore the binding of transcription factors to this promoter. The CCL20 expression in epithelial cells of H. pylori-positive tissues was higher than that in H. pylori-negative tissues. H. pylori induced CCL20 expression in gastric epithelial cell lines, and the induction was dependent on an intact cag pathogenicity island. Activation of the CCL20 promoter by H. pylori occurred through the action of NF-kappaB. Transfection of IkappaB kinase and NF-kappaB-inducing kinase dominant negative mutants inhibited H. pylori-mediated activation of CCL20. Treatment with an inhibitor of Hsp90 suppressed H. pylori-induced CCL20 mRNA due to deactivation of NF-kappaB. Collectively, these results suggest that H. pylori activates NF-kappaB through an intracellular signaling pathway that involves IkappaB kinase and NF-kappaB-inducing kinase, leading to CCL20 gene transcription, and that Hsp90 is a crucial regulator of H. pylori-induced CCL20 expression, presumably contributing to the immune response in H. pylori.

Analysis of gene expression in the tumor-associated macrophage

INTRODUCTION

The tumor-associated macrophage (TAM) is at the front line of the host's defense against malignancy and provides an attractive target for immune-modulatory therapy. However, factors present within the tumor microenvironment can alter macrophage phenotype, preventing its cytotoxic activity and reducing its susceptibility to interferon-gamma and lipopolysaccharide-mediated stimulation.

METHODS

Macrophages were isolated from subcutaneous B16 melanoma tumors implanted in C57 BL/6 mice. Wound macrophages were harvested from subcutaneously-implanted PVA sponges, and resting peritoneal macrophages were harvested by peritoneal lavage. Gene expression was analyzed using an Atlas cDNA array (Clontech, Mountain View, CA).

RESULTS

TAM demonstrated a pattern of gene expression distinct from both wound and peritoneal macrophage. There is an increase in proliferation-associated genes and in genes encoding the ultrastructural proteins cofillin, zyxin, and vimentin more commonly associated with fibroblast-like cells. In addition, an observed decrease in expression of the CD14 gene, and increase in inhibitory pathways including osteopontin and its receptor CD44, the inositol 1,4,5-triphosphate receptor, and the receptors for interleukin-4 and granulocyte monocyte-colony stimulating factor could explain the resistance of TAM to lipopolysaccharide-mediated stimulation. There was also a significant decrease in the expression of the interferon-gamma second messenger, IRF-1.

CONCLUSIONS

This study has identified a number of pathways involved in the suppression of TAM function. Targeting of these pathways may allow for the generation of more effective immune-modulatory anti-neoplastic therapy.

Immunostimulatory oligonucleotides in therapy of allergic diseases

At present, the improvement of hygienic life standards is considered as an environmental condition, increasing the prevalence of allergic diseases, as early contact with some pathogens is, according to the hygiene hypothesis, required for maturation of the immune system. The recognition of microbial components involves acquired and innate immunity mechanisms. Recently, the link between innate and acquired immunity has been discovered. It involves the evolutionarily old Toll-like receptor (TLR) system. Ligands recognised by TLRs include unmethylated deoxycytidil-deoxyguanosine (CpG) motif-containing microbial DNA. TLR-mediated signalling induces expression of cytokines preferentially promoting a Th1-directed response. Therefore, synthetic CpG motif-containing immunostimulatory oligonucleotides could be employed in causal allergy treatment. This review discusses some molecular aspects of the TLR system, as well as results of animal studies and early experiences, including treatment safety, from human clinical trials with immunostimulatory CpG motif-containing oligonucleotides.

Heat shock proteins as endogenous adjuvants in sterile and septic inflammation

Heat shock proteins (HSPs) have been reported to stimulate the immune system via innate receptors. However, the role of HSPs as endogenous adjuvants has been challenged by reports claiming that pure HSPs are not innate ligands; it is only the bacterial molecules trapped by the HSPs that can signal the innate immune system. In this review, we discuss data suggesting that both views, in essence, are correct; pure HSPs are indeed innate immunostimulators, but HSPs can also function as transducers of pathogen signals. In other words, HSPs perform diverse functions in two alternative modes of inflammation: sterile inflammation, which results from endogenous stimuli and is necessary for body maintenance, and septic inflammation, which protects us from environmental pathogens. Endogenous HSPs are key players in the modulation of these two modes of inflammation, and as such, they are potential targets for new and more efficient therapies for cancer, infections, and autoimmunity.

Regulation of Nod1 by Hsp90 chaperone complex

Nod1 and Nod2 proteins play important roles in mammalian innate immune responses as intracellular sensors for bacterial peptidoglycan. Nod1 and Nod2 share structural homology with many R proteins involved in plant disease resistance. It has been demonstrated that plant Hsp90 and its co-chaperone RAR1 are implicated in R-mediated disease resistance. Here the Chp-1 gene encoding a mammalian homologue of plant RAR1 was identified as a new target for transcriptional activation by heat shock factor 1 (HSF1), a stress-responsive HSF isoform. In addition, Nod1 is demonstrated to be a client protein of the Hsp90 chaperone complex containing the Chp-1. Chp-1 interacts with the tetratricopeptide repeat (TPR) domain of protein phosphatase 5 (PP5) and the ATPase domain of Hsp90 via two distinct zinc-binding cysteine and histidine rich domains (CHORDs). These findings suggest a common regulatory mechanism involving the Hsp90 chaperone complex in R-mediated disease resistance in plants and Nod1-mediated innate immune response in mammals.

A Central Role for the Hsp90·Cdc37 Molecular Chaperone Module in Interleukin-1 Receptor-associated-kinase-dependent Signaling by Toll-like Receptors

Toll-like receptors (TLRs) serve crucial roles in innate immunity by mediating the activation of macrophages by microbial pathogens. The protein kinase interleukin-1 receptor associated kinase (IRAK-1) is a key component of TLR signaling pathways via its interaction with TRAF6, which subsequently leads to the activation of MAP kinases and various transcription factors. IRAK-1 is degraded following TLR activation, and this has been proposed to contribute to tolerance in macrophages by limiting further TLR-mediated signaling. Using a mass spectrometric-based approach, we have identified a cohort of chaperones and co-chaperones including Hsp90 and Cdc37, which bind to IRAK-1 but not IRAK-4 in 293T cells. Pharmacologic inhibition of Hsp90 led to a rapid decline in the expression level of IRAK-1, whereas overexpression of Cdc37 enhanced the activation and oligomerization of IRAK-1 in 293T cells. Significantly, the inhibition of Hsp90 in macrophages resulted in the destabilization and degradation of IRAK-1 but not IRAK-4. Concomitant with the loss of IRAK-1 expression was a reduction in the activation of p38 MAP kinase and Erk1/2 following stimulation with the bacterially derived TLR ligands, lipopolysaccharide and CpG DNA. Moreover, TLR ligand-induced expression of proinflammatory cytokines was also reduced. Thus we conclude that the level of on-going support provided to IRAK-1 by the Hsp90-Cdc37 chaperone module directly influences the magnitude of TLR-mediated macrophage activation. In addition, because further TLR signaling depends on the synthesis of new IRAK-1, the Hsp90-Cdc37 chaperone module could also contribute to tolerance in macrophages by controlling the rate at which nascent IRAK-1 is folded into a functional conformation.

Blockage of HSP 90 modulates Helicobacter pylori-induced IL-8 productions through the inactivation of transcriptional factors of AP-1 and NF-kappaB

Helicobacter pylori infection leads to significant inflammations in the gastric mucosa, which is closely associated with development of gastric cancer. Heat shock protein 90 (HSP 90) has been revealed to be critical for intracellular signaling that participates in inflammatory response as well as carcinogenesis. In this study, we investigated a regulatory role of HSP 90 in H. pylori-induced IL-8 production. Our results showed that H. pylori stimulated significant phosphorylation of HSP 90 and the phosphorylation was diminished by administration of HSP 90 inhibitor, geldanamycin (GA). Treatment of GA completely inhibited H. pylori-induced IL-8 production due to deactivation of ERK1/2 and NF-kappaB. These results subsequently lead to inactivation of AP-1 and NF-kappaB, which are known to be major transcriptional factors of IL-8. Our data provide important insights that HSP 90 is involved as a crucial regulator in H. pylori-induced IL-8 production and its inhibitor could be potentially used for the inhibition of H. pylori-provoked inflammation.

CpG DNA-mediated immune response in pulmonary endothelial cells

Although the CpG DNA immune response mediated by Toll-like receptor 9 (TLR9) has been extensively studied in a number of immune cells, the response to CpG DNA in endothelial cells (EC) is not well understood. In this study, we show that both mouse and rat lung EC display constitutive expression of TLR9 mRNA. Exposure to CpG DNA induced a potent proinflammatory response as manifested by an increased expression of IL-8 and ICAM-1 in mouse pulmonary EC. The proinflammatory response was sensitive to chloroquine, consistent with a role of endosomal contribution. A role for p38 MAPK and NF-kappaB pathway was apparent as the response was sensitive to inhibitors of p38 MAPK and NF-kappaB but was not affected by inhibitors of ERK1/2. A synergistic effect of CpG DNA and LPS on the inflammatory response is consistent with multiple TLR interaction in EC. This study suggests a possible role for CpG DNA-mediated EC immune response in the host defense system. It also has important implications in plasmid DNA-mediated pulmonary endothelium gene transfer.

Cytosolic HSP90 associates with and modulates the Arabidopsis RPM1 disease resistance protein

The Arabidopsis protein RPM1 activates disease resistance in response to Pseudomonas syringae proteins targeted to the inside of the host cell via the bacterial type III delivery system. We demonstrate that specific mutations in the ATP-binding domain of a single Arabidopsis cytosolic HSP90 isoform compromise RPM1 function. These mutations do not affect the function of related disease resistance proteins. RPM1 associates with HSP90 in plant cells. The Arabidopsis proteins RAR1 and SGT1 are required for the action of many R proteins, and display some structural similarity to HSP90 co-chaperones. Each associates with HSP90 in plant cells. Our data suggest that (i) RPM1 is an HSP90 client protein; and (ii) RAR1 and SGT1 may function independently as HSP90 cofactors. Dynamic interactions among these proteins can regulate RPM1 stability and function, perhaps similarly to the formation and regulation of animal steroid receptor complexes.

Genistein inhibits herbimycin A-induced over-expression of inducible heat shock protein 70 kDa

It has been shown that expression of heat shock proteins (HSPs) can interfere with the effectiveness of therapeutic cytotoxic drugs. In this study, we investigated the regulation of expression of HSPs in human epidermoid A-431 cells. Two known protein tyrosine kinase inhibitors were studied. Treatment of cells with herbimycin A increased production of inducible HSP 70 kDa (HSP-70i) in a concentration-dependent manner, whereas genistein did not. The increase induced by herbimycin A was observed within 2 h, reached a peak at 6 h, and remained above the basal level 3 days later. Pretreatment with genistein inhibited the herbimycin A-induced increase in HSP-70i. Herbimycin A treatment increased levels of HSP-70i mRNA in cells, suggesting that herbimycin A increases HSP-70i by promoting transcription. Treatment with genistein or genistein combined with herbimycin A did not increase HSP-70i mRNA, suggesting that the inhibitory effect of genistein also occurs at the level of mRNA production. Herbimycin A increased intracellular Ca2+ concentration ([Ca2+]i), but treatment with genistein decreased it. Chelation of [Ca2+]i with BAPTA blocked the herbimycin A-induced increase in HSP-70i mRNA and HSP-70i protein. Herbimycin A induced the phosphorylation of heat shock factor 1 (HSF1), while genistein reduced HSF1 production. The ability of genistein to inhibit the herbimycin A-induced increase in HSP-70i is not associated with genistein's capacity to decrease basal [Ca2+]i, but because it decreases HSFI production. The herbimycin A-induced increase in HSP-70i protected cells from hypoxia injury.

The expression of plasma nucleosomes in mice undergoing in vivo apoptosis

Nucleosomes occur in the blood of patients with systemic lupus erythematosus and are thought to result from in vivo cell death. To determine the conditions for the release of nucleosomes into the blood, normal mice were treated with four agents that have the potential to induce apoptosis or immune cell activation in vivo: LPS, CpG DNA, anti-Fas antibody, and dexamethasone. Blood nucleosomes were measured by a capture ELISA immunoassay, with the DNA component assessed by fluorimetry with the dye PicoGreen. Following treatment with LPS and a monoclonal anti-Fas antibody, nucleosomes and DNA appeared in the plasma in a dose-dependent fashion. In contrast, dexamethasone treatment, despite causing significant thymocyte loss, did not elicit plasma nucleosomes. Similarly, CpG DNA, while inducing an IL-12 response comparable to that of LPS, also did not elicit plasma nucleosomes. These results suggest that plasma nucleosome levels reflect specific patterns of cell death and are not an invariable consequence of in vivo apoptosis or immune cell activation.

Geldanamycin inhibits the production of inflammatory cytokines in activated macrophages by reducing the stability and translation of cytokine transcripts

OBJECTIVE

Heat-shock protein 90 (Hsp90) is critical in the intracellular signaling pathways that promote inflammatory cytokine production. Geldanamycin (GD) is a benzoquinone ansamycin that inhibits the function of Hsp90. GD inhibits the production of tumor necrosis factor alpha (TNFalpha) in activated macrophages and suppresses the progression of adjuvant-induced arthritis and experimental allergic encephalomyelitis in rodents. GD has been used to investigate the mechanisms by which Hsp90 regulates inflammatory cytokine production.

METHODS

The macrophage cell line RAW264.7 (or primary peritoneal macrophages) was activated with lipopolysaccharide in the absence or presence of GD. The effect of GD on the transcription, stability, and translation of inflammatory cytokine messenger RNA (mRNA) was determined using nuclear run-on assays, mRNA decay assays, and sucrose gradient polysome profiles, respectively.

RESULTS

Our data revealed that GD potently inhibits the production of TNFalpha, interleukin-6 (IL-6), and IL-1beta in activated macrophages. Although GD did not significantly reduce the transcription of inflammatory cytokine mRNA, it significantly decreased the stability of these transcripts. Polysome profiles indicated that GD also inhibited the translation of TNFalpha and IL-6 transcripts. These effects may be due, in part, to inhibition of p38 mitogen-activated protein kinase, a kinase known to regulate the stability and translation of inflammatory cytokine transcripts.

CONCLUSION

These results indicate that the function of Hsp90 is important in the posttranscriptional control of inflammatory cytokine production.

CpG ODN activates NO and iNOS production in mouse macrophage cell line (RAW 264.7)

Synthetic CpG containing oligodeoxynucleotide (CpG ODN) is recognized for its ability to activate cells to produce several cytokines, such as IL-12 and TNF-alpha. In the present study we have demonstrated that CpG ODN 1826, known for its immunostimulatory activity in the mouse system could, by itself, induce nitric oxide (NO) and inducible nitric oxide synthase (iNOS) production from mouse macrophage cell line (RAW 264.7). Neutralizing antibody against TNF-alpha was not able to inhibit NO or iNOS production from the CpG ODN 1826-activated macrophages, suggesting that although the TNF-alpha was also produced by CpG ODN-activated macrophages, the production of iNOS was not mediated through TNF-alpha. Although both CpG ODN 1826 and lipopolysaccharide (LPS) were able to stimulate NO and iNOS production, the exposure time required for maximum production of NO and iNOS for the CpG ODN 1826-activated macrophages was significantly longer than those activated with LPS. These results were due probably to a delay of NF-kappaB translocation, as indicated by the delay of IkappaBalpha degradation. Moreover, the fact that chloroquine abolished NO and iNOS production from the cells treated with CpG ODN 1826 but not from those treated with LPS suggested that the induction of NO and iNOS production from the cells stimulated with CpG ODN (1826) also required endosomal maturation/acidification.

Bench-to-bedside review: Toll-like receptors and their role in septic shock

The Toll-like receptors (TLRs) are essential transmembrane signaling receptors of the innate immune system that alert the host to the presence of a microbial invader. The recent discovery of the TLRs has rapidly expanded our knowledge of molecular events that initiate host-pathogen interactions. These functional attributes of the cellular receptors provide insights into the nature of pattern recognition receptors that activate the human antimicrobial defense systems. The fundamental significance of the TLRs in the generation of systemic inflammation and the pathogenesis of septic shock is reviewed. The potential clinical implications of therapeutic modulation of these recently characterized receptors of innate immunity are also discussed.