Elevation of heat shock protein synthesis and hsp gene transcription during monocyte to macrophage differentiation of U937 cells

Cell Surface Hsp90- and αMβ2 Integrin-Mediated Uptake of Bacterial Flagellins to Activate Inflammasomes by Human Macrophages

All-trans retinoic acid (ATRA) is an active metabolite of vitamin A, which plays an important role in the immune function. Here, we demonstrated that ATRA induces the heat shock protein (Hsp) 90 complex on the surface of THP-1 macrophages, which facilitates the internalization of exogenous bacterial flagellins to activate the inflammasome response. Mass spectrometric protein identification and co-immunoprecipitation revealed that the Hsp90 homodimer interacts with both Hsp70 and αMβ2 integrin. ATRA-induced complex formation was dependent on the retinoic acid receptor (RAR)/retinoid X receptor (RXR) pathway and intracellular calcium level and was essential for triggering the internalization of bacterial flagellin, which was clathrin dependent. Notably, in this process, αMβ2 integrin was found to act as a carrier to deliver flagellin to the cytosol to activate the inflammasome, leading to caspase-1 activity and secretion of interleukin (IL)-1β. Our study provides new insights into the underlying molecular mechanism by which exogenous bacterial flagellins are delivered into host cells without a bacterial transport system, as well as the mechanism by which vitamin A contributes to enhancing the human macrophage function to detect and respond to bacterial infection.

Morphometric Characterization of Rat and Human Alveolar Macrophage Cell Models and their Response to Amiodarone using High Content Image Analysis

PURPOSE

Progress to the clinic may be delayed or prevented when vacuolated or "foamy" alveolar macrophages are observed during non-clinical inhalation toxicology assessment. The first step in developing methods to study this response in vitro is to characterize macrophage cell lines and their response to drug exposures.

METHODS

Human (U937) and rat (NR8383) cell lines and primary rat alveolar macrophages obtained by bronchoalveolar lavage were characterized using high content fluorescence imaging analysis quantification of cell viability, morphometry, and phospholipid and neutral lipid accumulation.

RESULTS

Cell health, morphology and lipid content were comparable (p < 0.05) for both cell lines and the primary macrophages in terms of vacuole number, size and lipid content. Responses to amiodarone, a known inducer of phospholipidosis, required analysis of shifts in cell population profiles (the proportion of cells with elevated vacuolation or lipid content) rather than average population data which was insensitive to the changes observed.

CONCLUSIONS

A high content image analysis assay was developed and used to provide detailed morphological characterization of rat and human alveolar-like macrophages and their response to a phospholipidosis-inducing agent. This provides a basis for development of assays to predict or understand macrophage vacuolation following inhaled drug exposure.

Effect of sphingosine kinase modulators on interleukin-1β release, sphingosine 1-phosphate receptor 1 expression and experimental autoimmune encephalomyelitis

BACKGROUND AND PURPOSE

The sphingosine analogue, FTY720 (GilenyaR ), alleviates clinical disease progression in multiple sclerosis. Here, we variously assessed the effects of an azide analogue of (S)-FTY720 vinylphosphonate (compound 5; a sphingosine kinase 1 activator), (R)-FTY720 methyl ether (ROMe, a sphingosine kinase 2 inhibitor) and RB-020 (a sphingosine kinase 1 inhibitor and sphingosine kinase 2 substrate) on IL-1β formation, sphingosine 1-phosphate levels and expression of S1P1 receptors. We also assessed the effect of compound 5 and ROMe in an experimental autoimmune encephalomyelitis (EAE) model in mice.

EXPERIMENTAL APPROACH

We measured IL-1β formation by macrophages, sphingosine 1-phosphate levels and expression levels of S1P1 receptors in vitro and clinical score in mice with EAE and the extent of inflammatory cell infiltration into the spinal cord in vivo.

KEY RESULTS

Treatment of differentiated U937 macrophages with compound 5, RB-020 or sphingosine (but not ROMe) enhanced IL-1β release. These data suggest that these compounds might be pro-inflammatory in vitro. However, compound 5 or ROMe reduced disease progression and infiltration of inflammatory cells into the spinal cord in EAE, and ROMe induced a reduction in CD4+ and CD8+ T-cell levels in the blood (lymphopenia). Indeed, ROMe induced a marked decrease in expression of cell surface S1P1 receptors in vitro.

CONCLUSION AND IMPLICATIONS

This is the first demonstration that an activator of sphingosine kinase 1 (compound 5) and an inhibitor of sphingosine kinase 2 (ROMe, which also reduces cell surface S1P1 receptor expression) have an anti-inflammatory action in EAE.

Effect of ether glycerol lipids on interleukin-1β release and experimental autoimmune encephalomyelitis

We have assessed the effect of two ether glycerol lipids, 77-6 ((2S, 3R)-4-(Tetradecyloxy)-2-amino-1,3-butanediol) and 56-5 ((S)-2-Amino-3-O-hexadecyl-1-propanol), which are substrates for sphingosine kinases, on inflammatory responses. Treatment of differentiated U937 macrophage-like cells with 77-6 but not 56-5 enhanced IL-1β release; either alone or in the presence of LPS. The stimulatory effect of sphingosine or 77-6 on LPS-stimulated IL-1β release was reduced by pretreatment of cells with the caspase-1 inhibitor, Ac-YVAD-CHO, thereby indicating a role for the inflammasome. The enhancement of LPS-stimulated IL-1β release in response to sphingosine, but not 77-6, was reduced by pretreatment of cells with the cathepsin B inhibitor, CA074Me, indicating a role for lysosomal destabilization in the effect of sphingosine. Administration of 56-5 to mice increased disease progression in an experimental autoimmune encephalomyelitis model and this was associated with a considerable increase in the infiltration of CD4(+) T-cells, CD11b(+) monocytes and F4/80(+) macrophages in the spinal cord. 56-5 and 77-6 were without effect on the degradation of myc-tagged sphingosine 1-phosphate 1 receptor in CCL39 cells. Therefore, the effect of 56-5 on EAE disease progression is likely to be independent of the inflammasome or the sphingosine 1-phosphate 1 receptor. However, 56-5 is chemically similar to platelet activating factor and the exacerbation of EAE disease progression might be linked to platelet activating factor receptor signaling.

Dermal exposure to immunostimulants induces changes in activity and proliferation of coelomocytes of Eisenia andrei

Due to the specific habitat conditions in which they live, earthworms are constantly exposed to pathogens. Consequently, they have evolved various immuno-defense mechanisms, including cellular (coelomocytes) and humoral responses, which may help to eliminate deleterious micro-organisms but also repair and/or protect host cells and tissues. Similar to mammalian phagocytes, coelomocytes can kill ingested pathogens with reactive oxygen species (ROS) and nitric oxide. In the present work, we studied the effects of the dermal exposure of Eisenia andrei earthworms to different immuno-stimulants: phorbol-12-myristate-13-acetate (PMA), lipopolysaccharide (LPS) or concanavalin A (ConA). After 3 days of treatment with all immuno-stimulants, decreased numbers and changed composition of the coelomocytes were observed. The immuno-stimulants also induced numerous changes in bactericidal activity, including ROS production. Furthermore, all stimulants increased cell proliferation while only LPS-treatment significantly elevated apoptosis of coelomocytes. These results demonstrate that in vivo treatment of earthworms with immuno-stimulants induces various changes in their coelomocyte response.

The roles of monocytic heat shock protein 60 and Toll-like receptors in the regional inflammation response to wear debris particles

The biological response to orthopaedic wear debris is central to peri-prosthetic tissue inflammation and osteolysis, through mechanisms that include local inflammatory cytokine production. In particular, interleukin-1 beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha|) are generated in high quantities following monocyte accumulation in periprosthetic inflammatory tissue, and these cytokine combine with other inflammatory mediators to trigger osteolysis. Since the precise mechanisms involved in debris-associated inflammation remain unclear, it is important to understand how wear debris particles initially interact with inflammatory cells. We have previously demonstrated that the severity of the inflammation response is influenced by the size, shape, and quantity of particles accumulated in tissues. The current in vitro and in vivo results indicate that heat-shock protein (Hsp) expression is elevated when monocytes are exposed to wear debris particles. We have also addressed the mechanisms by which heat-shock protein 60 (Hsp60) positively modulates inflammatory cytokines via Toll-like receptor-4 (TLR4) signal transduction pathway on mononuclear cells. Furthermore, down-regulation of TLR4 expression using antisense oligonucleotides targeted to TLR4 mRNA suppressed cytokine production in both exogenous Hsp60 and particles stimulated cultures. Collectively, these data indicate that monocytic Hsp60 is an additional inducible immunoregulatory mediator in response to particle-induced cell stress.

Heat Shock Protein 32 in Human Peripheral Blood Mononuclear Cells: Effect of Aging and Inflammation

The purpose of the present study was to assess the influence of age and acute infection on the production of Hsp32 in human peripheral blood cells, using flow cytometry. Thirty-five controls and 31 patients with acute infection participated. We found that the age and inflammatory status correlated positively with Hsp32 levels in both heat shocked (HS) and non-HS monocytes and lymphocytes. In addition, the HS response of Hsp32 was different in these peripheral blood cells; whereas HS exerted an up-regulation in the levels of Hsp32 in monocytes, a significant decrease in Hsp32 levels was noticed for lymphocytes. We found significant relationships between circulating C-reactive protein as well as interleukin-6 and the levels of Hsp32 in cells. We conclude that Hsp32 is up-regulated in the elderly as well as in individuals with inflammation, and that the HS response of Hsp32 is different in monocytes as compared to lymphocytes.

Remodelling of the PDE4 cAMP phosphodiesterase isoform profile upon monocyte-macrophage differentiation of human U937 cells

Monocytes and macrophages provide key targets for the action of novel anti-inflammatory therapeutics targeted at inhibition of PDE4 cAMP-specific phosphodiesterases. PDE4 enzymes provide the dominant cAMP phosphodiesterase activity in U937 human monocytic cells. Differentiation of U937 monocytic cells to a macrophage-like phenotype causes a marked reduction in total cellular PDE4 activity. Monocytic U937 cells express the long PDE4A4, PDE4D5 and PDE4D3 isoforms plus the short PDE4B2 isoform. Differentiation of U937 cells to a macrophage-like phenotype causes a marked downregulation of PDE4D3 and PDE4D5, elicits a marked upregulation of PDE4B2 and induces the novel PDE4A10 long isoform. Comparable patterns are found in human peripheral blood monocytes and macrophages differentiated from them. Immunopurification of PDE4 subfamilies identifies long PDE4D isoforms as providing the major PDE4 activity in U937 monocytic cells. In U937 macrophage-like cells, the activity of the short PDE4B2 isoform predominates. No indication of either the expression or induction of PDE4C was evident. Activation of ERK exerts an inhibitory effect on total PDE4 activity in monocytic U937 cells, where the activity of long PDE4 isoforms predominates. The effect of ERK activation is switched to one of overall stimulation of total PDE4 activity in macrophage U937 cells, where the activity of the short PDE4B2 isoform predominates.10 The profound differentiation-induced changes in PDE4 isoform profile identified here suggests that the development of inhibitors specific for particular PDE4 isoforms may allow for selective effects on monocytes and macrophages to be achieved.

Regulation of Pim-1 by Hsp90

The protooncogene Pim-1 encodes serine/threonine protein kinases that are involved in cytokine-mediated cell proliferation and in lymphoma- and leukemogenesis. It is largely unknown how Pim-1 executes its biological effects. Here we show that Pim-1 physically interacts with heat shock protein 90 alpha and beta (Hsp90alpha and beta). The Hsp90-specific inhibitor geldanamycin (GA) induced a rapid degradation of Pim-1 and reduced its kinase activity. The expression of Hsp90alpha was regulated by a signal from the cytokine receptor gp130, as is Pim-1's expression. These results indicate that Hsp90 is coordinately regulated with Pim-1 and is involved in the stabilization and function of Pim-1.

Annexin I is a stress protein induced by heat, oxidative stress and a sulfhydryl-reactive agent

Annexin I (also called lipocortin 1) is a 37-kDa member of the annexin family of proteins. It has been proposed to be involved in the regulation of cell growth and differentiation, apoptosis, and inflammation. Previously, we have reported that annexin I displays a chaperone-like function (Kim, G.Y., Lee, H.B., Lee, S.O., Rhee, H.J. & Na, D.S. (1997) Biochem. Mol. Biol. Int. 43, 521-528). To determine the possibility that annexin I is a stress protein, we examined whether expression of annexin I and annexin I mRNA increases in response to stresses in A549 and HeLa cells. Treatments of cells with heat, hydrogen peroxide or sodium arsenite resulted in (a) an increase in annexin I and annexin I mRNA and (b) translocation of annexin I from the cytoplasm to the nucleus and perinuclear region. The annexin I gene promoter region, cloned upstream of a reporter gene, was inducible in response to heat, hydrogen peroxide, and sodium arsenite. These results indicate that annexin I serves as a stress protein and annexins may constitute a new class of stress proteins.

Expression of heat shock protein 70 (HSP70) at the interface of polymer-implants in vivo

Synthetic polymer meshes are widely applied in the modern surgical approach for repairing abdominal wall defects. The implanted material is often observed leading to post-operative complications such as deficient abdominal wall mobility and adhesion formation with the abdominal cavity and/or abdominal organs. However, the functioning of the implant is primarily affected by the wound healing process guided by inflammatory events occurring at the tissue-material interface. This could presumably be influenced by the physicochemical properties of the polymer. With regard to it, the cellular and molecular processes involved in the successful restoration of the abdominal wall function are poorly understood. The present in vivo study, therefore, exemplary investigated in a rat model, the commercially available polymer-meshes Prolene (polypropylene, PP), Mersilene (polyester, PE) and Vicryl (polyglactin 910), as well as new mesh variants consisting either of PP (EB) or a combination of PP and polyglactin 910 (A plus or Vypro). The implanted material was evaluated by light and electron microscopy, immunohistochemistry as well as morphometry over an implantation period of 90 days. The data show that polymers induce heat shock protein (HSP)70, and its expression at the interface correlates inversely with the activity of the inflammatory reaction in vivo. Further, an ascent in HSP70 expression parallels the increasing implantation period and evolving foreign-body granulomas. Accordingly, a major role for HSP70 in modulating the local acceptance of polymers and as an additional marker for in vivo testing of polymers is suggestive.

Interleukin-10 activates heat-shock protein 90beta gene expression

Elevated levels of the cytokine interleukin-10 (IL-10) have been reported in patients with active systemic lupus erythematosus (SLE). Any role for IL-10 in the pathogenesis of SLE is likely to involve the activation of expression of specific genes within its target cells. We have previously reported elevated levels of the 90 000 MW heat-shock protein (hsp 90) and autoantibodies to hsp 90 in patients with SLE. Recent studies have shown that the cytokine IL-6 activates hsp 90 gene expression via specific transcription factors that include STAT-3 (signal transducer and activator of transcription 3). In view of the known role of STAT proteins in IL-10 signalling pathways, we have investigated the effect of IL-10 on hsp 90 gene expression. Here we report that IL-10 enhances the expression of hsp 90 in both a human hepatoma cell line (HepG2) stably expressing the human IL-10 receptor and peripheral blood mononuclear cells (PBMC). In reporter gene assays IL-10 is able to activate both the hsp 90alpha and hsp 90beta promoters directly. Furthermore, a short region of the hsp 90beta promoter which is activated in response to IL-10, contains a STAT-3 binding site. This element but not a mutant derivative unable to bind STAT-3, is able to confer a response to IL-10 on a heterologous promoter. These results may be understood in terms of the shared signalling mechanisms of IL-10 and IL-6 and provide evidence of a role for IL-10 in the overexpression of hsp 90 in SLE, with possible pathological consequences.

Protection of neuronal cells from apoptosis by Hsp27 delivered with a herpes simplex virus-based vector

Overexpression of the gene encoding the 70-kDa heat shock protein (hsp70) has previously been shown to protect neuronal cells against subsequent thermal or ischemic stress. It has no protective effect, however, against stimuli that induce apoptosis, although a mild heat shock (sufficient to induce hsp synthesis) does have a protective effect against apoptosis. We have prepared disabled herpes simplex virus-based vectors that are able to produce high level expression of individual hsps in infected neuronal cells without damaging effects. We have used these vectors to show that hsp27 and hsp56 (which have never previously been overexpressed in neuronal cells) as well as hsp70 can protect dorsal root ganglion neurons from thermal or ischemic stress. In contrast, only hsp27 can protect dorsal root ganglion neurons from apoptosis induced by nerve growth factor withdrawal, and hsp27 also protects the ND7 neuronal cell line from retinoic acid-induced apoptosis. However, hsp70 showed no protective effect against apoptosis in contrast to its anti-apoptotic effect in non-neuronal cell types. These results thus identify hsp27 as a novel neuroprotective factor and show that it can mediate this effect when delivered via a high efficiency viral vector.

Signal transducer and activator of transcription-1 and heat shock factor-1 interact and activate the transcription of the Hsp-70 and Hsp-90beta gene promoters

We have previously demonstrated that interleukin-6 (IL-6) increases the levels of the heat shock protein 90 (Hsp-90) and activates the Hsp-90beta promoter via the IL-6-activated transcription factors NF-IL6 and signal transducer and activator of transcription-3 (STAT-3). Here, we show that interferon-gamma (IFN-gamma) treatment increases the levels of Hsp-70 and Hsp-90 and also enhances the activity of the Hsp-70 and Hsp-90beta promoters with these effects being dependent on activation of the STAT-1 transcription factor by IFN-gamma. These effects were not seen in a STAT-1-deficient cell line, indicating that IFN-gamma modulates Hsp induction via a STAT-1-dependent pathway. The effect of IFN-gamma/STAT-1 was mediated via a short region of the Hsp-70/Hsp-90 promoters, which also mediates the effects of NF-IL6 and STAT-3 and can bind STAT-1. This region also contains a binding site for the stress-activated transcription factor HSF-1. We show that STAT-1 and HSF-1 interact with one another via a protein-protein interaction and produce a strong activation of transcription, which is in contrast to our previous finding that STAT-3 and HSF-1 antagonize one another. To our knowledge this is the first report of HSF-1 interacting directly via a protein-protein interaction with another transcription factor. Such protein-protein interactions and the binding of a number of different stress and cytokine-activated transcription factors to a short region of the Hsp-90 and Hsp-70 gene promoters are likely to play a very important role in Hsp gene activation by non-stressful stimuli and the integration of these responses with the stress response of these genes.

The regulation of heat shock proteins and their role in systemic lupus erythematosus

OBJECTIVES

After a serendipitous suggestion, it was established that a significant subset of patients with systemic lupus erythematosus (SLE) overexpress the 90-kD heat shock protein (Hsp90). In this review, we have analyzed our own data and that of others, to explore the link between Hsp90 and SLE.

METHODS

We performed a detailed literature review focusing on the potential role of Hsp in the etiopathogenesis of SLE.

RESULTS

Data are discussed showing surface expression of this Hsp in patients with lupus, a similar overexpression in the splenocytes of MRL/Ipr mice before the onset of disease, the detection of antibodies to Hsp90 in a proportion of both lupus patients and lupus-prone mice, and most recently, an analysis of the transcription factors that regulate the production of this protein and the influence of key cytokines on these factors.

CONCLUSIONS

These observations provide a model to show how a protein with key physiological roles in healthy individuals may, on occasion, become the target of an autoimmune attack with clinical consequences recognized in both mouse and human. Given that up to now, other heat shock proteins are not targeted in a similar fashion, the specificity of these responses is remarkable.

Elevation of IL-6 in transgenic mice results in increased levels of the 90 kDa heat shock protein (hsp90) and the production of anti-hsp90 antibodies

Treatment of human peripheral blood lymphocytes (PBL) in vitro with the cytokine interleukin-6 (IL-6) induces increased levels of the 90 kDa heat shock protein (hsp90). Hsp90 levels are also elevated in PBLs of human patients with systemic lupus erythematosus (SLE) and in MRL/lpr mice with autoimmune disease. Although IL-6 is elevated in both these situations it has not been shown that it is involved in stimulating elevation of hsp90 levels in vivo. Here we show directly that the elevation of IL-6 in vivo either in mice transgenic for the IL-6 gene or in knock-out mice lacking a functional gene for the transcription factor C/EBP beta (NF-IL-6) does indeed result in elevated hsp90 levels. This overexpression is associated with the specific production of autoantibodies to hsp90 in these mice which is also observed in SLE patients and MRL/1pr mice. Hence IL-6 is likely to play a critical role in the regulation of hsp90 levels both in autoimmune disease states and potentially in normal cells in vivo. In turn the elevated levels of hsp90 produced in autoimmune diseases are likely to be responsible for the observed production of anti-hsp90 autoantibodies.

The nuclear factor interleukin-6 (NF-IL6) and signal transducer and activator of transcription-3 (STAT-3) signalling pathways co-operate to mediate the activation of the hsp90beta gene by interleukin-6 but have opposite effects on its inducibility by heat shock

The levels of the 90 kDa heat-shock protein (hsp90) and the activity of the hsp90beta gene promoter are increased in response to treatment by interleukin (IL)-6. The hsp90beta gene promoter contains binding sites for the transcription factors nuclear factor IL-6 (NF-IL6) and signal transducer and activator of transcription 3 (STAT-3), which are activated respectively by the mitogen-activated-protein-kinase and Jak-kinase pathways following IL-6 treatment. Both these factors can activate the hsp90 promoter and have a strong synergistic effect on its activity, which appears to be critical for IL-6-mediated activation of the promoter. Interestingly, the two factors interact differently with the heat-shock factor (HSF) and a heat-shock stress. Thus STAT-3 reduces the stimulatory effect of heat shock whereas NF-IL6 enhances it. When applied together, heat shock and IL-6 produce only weak activation of the hsp90 promoter compared with either stimulus alone, indicating that the inhibitory effect of STAT-3 on HSF predominates under these conditions. In contrast, IL-1, which activates only the NF-IL6 pathway, synergizes with heat shock to produce strong activation of hsp90. These effects are discussed in terms of the multiple stimuli that may regulate the hsp90 promoter in unstressed cells and their interaction with its stress-mediated activation.

Modulation of heat-shock protein 70 (HSP70) gene expression by sodium butyrate in U-937 promonocytic cells: relationships with differentiation and apoptosis

The administration of sodium butyrate at 0.75 mM induced the functional differentiation of U-937 human promonocytic leukemia cells with negligible cell mortality. However, the drug rapidly caused cell death with characteristics of apoptosis when used at concentrations of 5 mM and above. In addition, butyrate stimulated the expression of the stress-responsive heat-shock protein 70 (HSP70) gene when applied at both differentiation-inducing and apoptosis-inducing concentrations. The induction of HSP70 by butyrate was inhibited by the simultaneous addition of cAMP-increasing agents (dibutyryl cAMP or the combination of forskolin plus theophylline). However, these agents did not prevent differentiation and only partially reduced apoptosis. Moreover, the DNA topoisomerase II inhibitor etoposide, which provoked U-937 cell differentiation and apoptosis with the same or greater efficiency than butyrate, failed to stimulate HSP70 expression. Finally, it was observed that cAMP-increasing agents also abrogated the induction of HSP70 and reduced the apoptosis caused by cadmium chloride, a typical inducer of the stress response. Taken together, these results indicate that HSP70 expression is not required for differentiation of promonocytic cells, as earlier proposed, and that butyrate probably triggers the stress response in these cells.

Distribution of HSP70, protein kinase C, and spectrin is altered in lymphocytes during a fever-like hyperthermia exposure

Many B and T lymphocytes display a significant heterogeneity with respect to the subcellular distribution of the cytoskeletal protein spectrin and protein kinase C (PKC), both of which often can be found in a large cytoplasmic aggregate in these cell types. In addition to spectrin and PKC, we recently have reported that HSP70 is also a component of this lymphocyte aggregate. Moreover, these three proteins can undergo dynamic and reversible changes in their localization causing "assembly" of the aggregate in response to various conditions associated with lymphocyte activation, indicating that this naturally occurring aggregate structure is sensitive to activation status. We show here that the same changes in HSP70/spectrin/PKC localization induced by PKC activation also can be caused, in vitro and in vivo, by a mild hyperthermia exposure, as occurs during a natural fever (39.5-40 degrees C, 2-12 hr). This mild heat exposure also triggers the activation of PKC, a major heat shock response, and lymphocyte proliferation. The increase in PKC activity, HSP70-spectrin-PKC aggregate formation, and heat shock protein expression resulting from exposure to fever-like hyperthermia are all inhibited by calphostin C, a specific inhibitor of PKC. These data demonstrate that changes observed during lymphocyte activation could be induced by a mild hyperthermia exposure occurring during a normal febrile episode.

gamma delta T-cell-human glial cell interactions. II. Relationship between heat shock protein expression and susceptibility to cytolysis

gamma delta T-cells have been implicated in the immunopathogenesis of multiple sclerosis (MS), possibly through interaction with heat shock proteins (hsp). We have previously demonstrated that human oligodendrocytes (OGC) express hsp on their surface and induce the proliferation and expansion of gamma delta T-cells. We also showed that gamma delta T-cells are highly cytolytic to OGC in vitro. The current study addresses whether gamma delta T-cell-induced cytotoxicity to OGC involves the recognition of hsp on OGC or some other ligand. We first compared the lytic potential for different human glial cells and found that gamma delta T-cells lysed OGC, microglia and human fetal astrocytes to the same extent, despite the preferential expression of hsp only on OGC. This suggested that either hsp was not involved in cytolytic recognition or that more than one ligand exists. To address this we used cell lines that either shared OGC properties of hsp expression and the ability to stimulate gamma delta T-cells (RPMI 8226, Daudi) or did not (U937) in cold target competition assays with OGC. Results demonstrated that although all the cell lines were effectively killed by gamma delta T-cells, only the RPMI 8226 and Daudi cells were able to effectively compete for lysis with the OGC. These results support the notion that probably more than one ligand for gamma delta T-cell cytotoxic recognition exists but hsp could still be involved in gamma delta T-cell-induced lysis of OGC. Regulating the expression of hsp on OGC might therefore be a way of interfering with potential gamma delta T-cell-induced damage in MS.

Macrophage-lysis mediated by autoantibodies to heat shock protein 65/60

Macrophages in atherosclerotic lesions have been shown to express high amounts of heat shock protein 60 (hsp60), a highly conserved protein. Patients with atherosclerosis have high titers of anti-hsp65/60 antibodies (Ab) recognizing macrophages in the lesions. To elucidate the role of anti-hsp65/60 Ab in macrophage cytotoxicity, human high titer serum and purified anti-hsp65/60 Ab were tested on in vitro heat-stressed cells of a human macrophage cell line (U937) and macrophages derived from peripheral blood. Application of heat stress at 42 degrees C for 30 min resulted in marked upregulation of hsp60 mRNA, followed by increased protein expression as determined by Northern blot and FACS-analysis, respectively. Compared to unstressed cells, high titer serum and anti-hsp65/60 Ab preferentially bound to the surface of stressed U937 macrophages, but not control antibodies. Furthermore, high titer serum and anti-hsp65/60 Ab exerted significant (P < 0.01) complement-mediated cytotoxicity and antibody-dependent cellular cytotoxicity (ADCC) on stressed 51Cr-labelled U937 and peripheral blood derived macrophages. Thus, macrophages expressing hsp60 can be lysed by autoantibodies against hsp65/60, which may contribute to cell death in atherosclerotic plaques in vivo.

Interleukin 6 activates heat-shock protein 90 beta gene expression

The levels of the cytokine interleukin-6 (IL-6) and the heat-shock protein hsp90 have both been reported to be elevated in patients with active systemic lupus erythematosus (SLE). We show that hsp90 protein accumulates to increased levels in both HuH7 hepatoma cells and peripheral blood mononuclear cells (PBMCs) treated with IL-6. In PBMCs this effect occurs without induction of the other hsps, paralleling the specific elevation of hsp90 in SLE. IL-6 is able to activate the hsp90 gene promoter directly; this activation can also be achieved by overexpressing either of the transcription factors NF-IL-6 or NF-IL-6 beta whose synthesis is induced by IL-6 treatment. Hence the induction of hsp90 protein accumulation by IL-6 is likely to be dependent on the enhanced activity of the hsp90 beta gene promoter produced by increased levels of NF-IL-6 and/or NF-IL-6 beta. These effects are discussed in terms of the role of hsp90 in the normal immune system and the mechanism of its activation in patients with SLE.

Focal cerebral ischaemia increases the levels of several classes of heat shock proteins and their corresponding mRNAs

The induction of focal cerebral ischaemia in rats by middle cerebral artery occlusion has previously been shown to increase, over time, the mRNA levels of the heat shock proteins (HSPs) 27 and 70. However, the levels of HSP90 mRNA remain constant. In contrast, during global ischaemia, HSP70 and HSP90 mRNA levels are both raised, particularly in the CA1 neurons in the hippocampus, an area that is resistant to the insult in comparison to the surrounding regions. HSP27 mRNA is raised in the neuroglia in the subregions of the hippocampus. However, the protein levels of HSP27, 70 and 90 have not been characterised in focal ischaemia. With this data in mind, we have carried out a comparative study of HSP27, 56, 60, 70 and 90 mRNA and protein levels during focal cerebral ischaemia in rats, up to 24 h post-occlusion. We have shown that HSP70 and HSP27 mRNA levels are increased and also that HSP60 mRNA levels (which had also not previously been characterised in this model of focal ischaemia) are significantly raised. HSP90 and HSP56 mRNAs were not significantly elevated. On Western blot analysis, the inducible HSP72 protein was first detected at 8 h post-occlusion, HSP27 protein was detected only at 24 h post-occlusion and HSP60 protein, although constitutive, appeared to increase at 24 h post-occlusion. HSP56 protein levels appeared to rise on the occluded side, but HSP90 protein levels remained constant.

Trigeminal ganglion neurons are protected by the heat shock proteins hsp70 and hsp90 from thermal stress but not from programmed cell death following nerve growth factor withdrawal

A prior mild thermal stress (heat shock) can protect neuronal cells against a subsequent exposure to either severe thermal stress or the induction of programmed cell death (apoptosis). By micro-injecting trigeminal ganglion neurons with expression constructs we show that over-expression of the individual heat shock proteins hsp70 and hsp90 can protect these cells against severe thermal stress but not against apoptosis. However, the protective effect of prior heat shock against subsequent apoptosis is dependent upon its ability to induce heat shock protein (hsp) synthesis rather than, for example, the inhibition of other protein synthesis associated with heat shock. The significance of these effects is discussed in terms of the role of different hsps in protecting neuronal cells from distinct stresses.

15-Deoxyspergualin inhibits interleukin 6 production in in vitro stimulated human lymphocytes

Experimental data show that relatively low concentrations of 15-deoxyspergualin (DSG) inhibit the induction of cytotoxic T lymphocytes (CTL) and the generation of antibody-producing cells. Considerably higher concentrations of DSG are required to inhibit proliferative responses. In this in vitro study, the effects of DSG on CTL induction, on proliferative responses induced by different stimuli, and on the production of interleukins IL-1, IL-2 and IL-6 and IFN-gamma (gamma-interferon) were assessed and compared with the effects of CsA (cyclosporine A) and/or FK506. We confirmed the suppressive action of DSG on the generation of CTL. Quite unexpectedly, however, we found that, although DSG did not affect the proliferative response to allogeneic lymphocytes or a superantigen, it did inhibit proliferation of peripheral blood leucocytes (PBL) stimulated with Staphyloccus aureus. DSG was active even when added on day 2 of in vitro culture, suggesting that DSG does not inhibit early events. The fraction of CD3+ lymphoblasts and the CD4/CD8 ratio was lower in cells stimulated by S. aureus in the presence of DSG, showing a selective effect on CD3+CD4+ responder T lymphocytes. The proportion of IL-2 receptor (CD25) positive cells was also reduced by DSG treatment. Moreover, we found that DSG inhibited the proliferation induced by PHA (phytohaemagglutinin) but not by Con A (concanavalin A). This effect of DSG was time-dependent, since PHA induced proliferation was not affected until day 4 after stimulation, and indicated that DSG may inhibit proliferation induced via a CD2- but not via a CD3-mediated pathway. DSG did not influence the production of IL-2 or IFN-gamma or the lipopolysaccharide induced production of IL-2 or IL-6. In contrast, the production of IL-6 was inhibited when cells were stimulated by allogeneic lymphocytes, S. aureus, PHA or Con A. This suggested to us that the DSG-suppressed IL-6 production could be the basis for the other observed effects. We tried to mimic the DSG effects with antibodies and indeed found that the IL-6 specific antibodies had similar effects. Furthermore, recombinant IL-6 completely overcame the suppressive effects of DSG on S. aureus and PHA induced proliferation, whereas addition of IL-6 to DSG treated PBL only partly restored the cytotoxic activity of lymphoblasts induced by allogeneic cells. Thus, the inhibitory effect of DSG on de novo synthesis of IL-6 could explain some of its immunosuppressive effects, but additional DSG-sensitive steps are obviously involved in CTL induction and differentiation.

Heat-shock protein 90 and ubiquitin: developmental regulation during myogenesis

Heat-shock/stress proteins are constitutive and stress-inducible proteins, regulated by a number of factors including developmental processes. The 90-kD heat-shock protein (hsp90) and ubiquitin are up-regulated in regenerating fibers and diseased fibers of Duchenne muscular dystrophy. The aim of the present study was to investigate whether the heat-shock response in regenerating fibers is developmentally regulated or disease-associated. Immunohistochemistry and immunoblot analysis were employed to compare the expression of hsp90 and ubiquitin in normal immature muscle from infants and regenerating fibers in polymyositis and dermatomyositis with the basal expression in normal mature muscle from adults. A significant up-regulation of hsp90 and ubiquitin in regenerating fibers and developing infantile fibers suggests that hsp90 and ubiquitin, during myogenesis, are largely regulated by the activation of developmental mechanisms rather than being primarily disease-related. Modulation of the stress response may promote myogenesis and provide a new therapeutic approach in myopathies.

Interleukin-4 upregulates the heat shock protein Hsp90alpha and enhances transcription of a reporter gene coupled to a single heat shock element

Transcription of the heat shock protein Hsp90alpha was strongly upregulated in human T-cells by interleukin-4 (IL-4) and to a lesser extent by IL-2, reaching peak levels after 2-3 days of stimulation. Heat shock proteins are induced within minutes under stress conditions, via heat shock factors (HSF), which activate heat shock elements (HSE). IL-4, IL-2 and IL-13 upregulated transcription of a reporter gene coupled to a single HSE site and a minimal promoter. HSE may therefore be involved in cytokine induced heat shock gene transcription in the absence of cellular stress.

Relationship of lead-induced proteins to stress response proteins in astroglial cells

Astroglial cells are resistant to cell death and morphologic damage following lead (Pb) exposure at concentrations which elicit detrimental effects in neurons. A possible explanation may be that astroglial cells respond to Pb by increasing the expression of specific proteins, such as heat-shock proteins (HSPs), which confer resistance to low levels of Pb. However, there has been relatively limited information regarding the ability of Pb to evoke the synthesis of HSPs. In the current study, pulse-labeling of cultured astroglial proteins with [3H]-leucine was used to evaluate the nature of Pb-induced changes in protein expression. The effect of Pb on newly synthesized proteins was compared to the response elicited by heat-shock and oxidative injury. Immunoblot analysis was utilized to examine alterations in levels of various stress proteins including HSP27, HSP70, HSP90, and heme oxygenase-1 (HO-1). Even though Pb induced the synthesis of proteins with estimated molecular weights of 23 kDa, 32 kDa, 70 kDa, and 90 kDa, the accumulation of HSPs other than HO-1 was not observed. Hyperthermia and treatment with Na arsenite both resulted in enhanced expression of HSP70 and HO-1. In addition, exposure to hydrogen peroxide (H2O2), cadmium (Cd), and lipopolysaccharide (LPS) stimulated a rise in HO-1 levels. Although cellular insult failed to elicit an increase in either HSP27 or HSP90, cultured astroglia expressed readily detectable levels of both these proteins. Furthermore, Pb exposure resulted in the development of crosstolerance to subsequent injury by treatment with either Cd or H2O2. The results of this study indicate that Pb triggers a less conventional stress response in astroglial cells, which may provide enhanced resistance to the toxic effects of Pb.

Modulation of HSP70 and HSP27 gene expression by the differentiation inducer sodium butyrate in U-937 human promonocytic leukemia cells

The treatment of U-937 human promonocytic cells with the differentiation inducer sodium butyrate (0.75 mM) transiently increased heat-shock protein 70 (HSP70) mRNA levels between 3 and 6 h, and heat-shock protein 27 (HSP27) mRNA levels between 12 and 24 h, as indicated by northern blot assays. Gel retardation assays indicated that butyrate also stimulated heat-shock factor (HSF) binding activity between 3 and 6 h, suggesting that the activation of HSP70 gene expression was mediated by the heat-shock factor DNA response element (HSE). In addition, the treatment provoked a biphasic alteration of the c-fos mRNA level, consisting of a slight increase between 0.5 and 3 h followed by a greater increase between 12 and 48 h, while it caused a single increase between 12 and 48 h in c-jun mRNA level. The possible involvement of the heat-shock protein genes in the butyrate-induced differentiation of U-937 cells is discussed.

cAMP increasing agents prevent the stimulation of heat-shock protein 70 (HSP70) gene expression by cadmium chloride in human myeloid cell lines

Treatment of U-937 human promonocytic cells with the cAMP increasing agents isoproterenol plus theophylline decreased the basal level of heat-shock protein 70 (HSP70) mRNA. In addition, the cAMP increasing agents attenuated the increase in HSP70 mRNA and protein levels produced by cadmium chloride in U-937 and other human myeloid cell lines, reduced the capacity of cadmium treatment to generate stress-tolerance, and attenuated the cadmium-produced stimulation of heat-shock factor (HSF) binding activity. By contrast, isoproterenol plus theophylline failed to attenuate the stimulation of HSP70 gene expression and HSF binding activity caused by heat-shock. Isoproterenol plus theophylline did not prevent the uptake of cadmium into the cells, and increased to a similar extent the intracellular cAMP levels in cadmium- and heat-treated cells. The cAMP increasing agents reduced the induction by cadmium of the HSP27 stress gene, but failed to attenuate other cadmium-elicited stress reactions such as the inhibition of total protein synthesis. It is concluded that cAMP does not inhibit the stress response as a whole, but it interferes with some step of the pathway by which cadmium specifically stimulates HSF binding activity and as a consequence HSP70 gene expression, in human myeloid cell lines.

Differential expression and regulation of hsp70 and hsp90 by phorbol esters and heat shock

Human peripheral blood monocytes (PBM) produce superoxide anions (O2-.) by a process involving electron transfer from NADPH to O2, catalyzed by the respiratory burst enzyme NADPH oxidase. We have previously shown that phagocytosis, while activating NADPH oxidase, induced in PBM the synthesis of heat shock (HS) proteins (HSP). The present study was undertaken to establish whether this increase in HSP expression was related to O2-. and/or to classical second messengers such as protein kinase C (PKC). Thus, the effects of the PKC activator phorbol 12-myristate 13-acetate (PMA) were compared with those of heat shock on the expression, in PBM, of the major HSP, hsp70 and hsp90, using biometabolic labeling, Western and Northern blotting, and gel mobility shift assays. PMA induced the accumulation of mRNA and an increased expression of hsp90 and, to a lesser extent, hsp/hsc70 (hsc is the cognate, constitutive form). This induction was also observed in PBM from patients with chronic granulomatous disease, a genetic defect in NADPH oxidase, and was abolished by the PKC inhibitors staurosporine and H-7. PMA did not cause activation of the HS factor, and the PMA-induced overexpression expression of HSP was not blocked by the transcriptional inhibitor actinomycin D. HSP-specific mRNA stability was increased after PMA exposure as compared with heat shock. These results suggest that O2-. is not involved in the PMA-mediated induction of hsp70 and hsp90 and that, in contrast to HS, PMA increases the expression of HSP as a result of PKC-induced mRNA stabilization rather than of transcriptional activation of HS genes.

Expression and immune recognition of stress proteins in sarcoidosis and other chronic interstitial lung diseases

Stress proteins (SP) are major immunogens in a number of microbial infections and have been implicated in some autoimmune diseases. The aetiology of sarcoidosis, a non-caseating granulomatous disease, remains unknown, but mycobacteria as well as autoimmunity have been considered. In the present study, patients diagnosed with sarcoidosis and other interstitial lung diseases (ILD), as well as healthy volunteers were studied to determine: (i) the level of expression of SP in alveolar macrophages and blood monocytes; (ii) the serum levels of antibodies specific for mycobacterial SP65 and SP70; and (iii) the reactivity of peripheral blood and alveolar lymphocytes to mycobacterial SP65. Our results suggest that SP are expressed constitutively at high levels in alveolar macrophages, retrieved by bronchoalveolar lavage, from all individuals regardless of health status. In contrast, freshly isolated blood monocytes express low levels of SP, which are, however, readily upregulated following exposure to IFN-gamma and TNF-alpha. Lymphocyte reactivity and presence of antibodies against mycobacterial SP may reflect the current state of in vivo inflammation rather than the cause of inflammation.

Differential production of interferon-gamma and interleukin-4 in response to Th1- and Th2-stimulating pathogens by gamma delta T cells in vivo

Exposure to various pathogens can stimulate at least two patterns of cytokine production by CD4-positive T cells. Responses that result in secretion of interferon-gamma (IFN-gamma), lymphotoxin and interleukin-2 (IL-2) are classified as T-helper-1 (Th1); CD4+ T-cell production of IL-4, IL-5, IL-9, IL-10 and IL-13 is called a T-helper-2 response (Th2). Differentiation of CD4+ T cells into either Th1 or Th2 cells is influenced by the cytokine milieu in which the initial antigen priming occurs. Here we use flow cytometry to identify the presence of intracellular cytokines (cytoflow) and analyse T-cell production of IFN-gamma and IL-4 from mice infected with Listeria monocytogenes or Nippostrongylus brasiliensis. We show that T cells bearing gamma delta receptors discriminate early in infection between these two pathogens by producing cytokines associated with the appropriate T-helper response. Our results demonstrate that gamma delta T cells are involved in establishing primary immune responses.

Heat shock protein expression in oral epithelial dysplasia and squamous cell carcinoma

Heat shock protein (HSP) expression is upregulated in tumour cells and, therefore, HSP expression is a likely marker of the malignant potential of oral epithelial lesions. Furthermore, the 70-kDa HSP (HSP 70) is implicated in the degree of tumour differentiation, the rate of tumour proliferation and the magnitude of the anti-tumour immune response. Accordingly, the distribution and intensity of HSP 70 expression was assessed in the epithelial compartment of oral squamous cell carcinoma (SCC, n = 29), dysplastic oral epithelium (n = 18) and benign oral mucosal lesions (n = 22) using avidin-biotin complex immunohistochemistry and microdensitometry under standardised conditions. Staining intensity was recorded in kilo-ohms (k omega). Normal oral mucosa (n = 15) was used for comparison, and results were analysed using Kruskall-Wallis and Fisher's exact tests. The distribution of HSP 70 expression in well differentiated SCC was significantly different from that in poorly differentiated SCC (P < 0.05), the latter demonstrating a more focal staining pattern. Median staining intensity in SCC (6.22 k omega), epithelial dysplasia (9.61 k omega) and the benign oral mucosal lesions (8.28 k omega) was significantly greater than that in normal oral mucosa (5.64 k omega; P < 0.05). Staining intensity in poorly differentiated SCC (7.66 k omega) was greater than that in moderately differentiated SCC (4.77 k omega), although this result just failed to reach statistical significance (P = 0.06). These results suggest that, as employed currently, HSP 70 expression is not a definitive marker of oral malignancy or malignant potential.(ABSTRACT TRUNCATED AT 250 WORDS)