Differential expression of heat shock proteins by human glial cells

The immunology of multiple sclerosis

Our incomplete understanding of the causes and pathways involved in the onset and progression of multiple sclerosis (MS) limits our ability to effectively treat this complex neurological disease. Recent studies explore the role of immune cells at different stages of MS and how they interact with cells of the central nervous system (CNS). The findings presented here begin to question the exclusivity of an antigen-specific cause and highlight how seemingly distinct immune cell types can share common functions that drive disease. Innovative techniques further expose new disease-associated immune cell populations and reinforce how environmental context is critical to their phenotype and subsequent role in disease. Importantly, the differentiation of immune cells into a pathogenic state is potentially reversible through therapeutic manipulation. As such, understanding the mechanisms that provide plasticity to causal cell types is likely key to uncoupling these disease processes and may identify novel therapeutic targets that replace the need for cell ablation.

Positive or negative involvement of heat shock proteins in multiple sclerosis pathogenesis: an overview

Multiple sclerosis (MS) is the most diffuse chronic inflammatory disease of the central nervous system. Both immune-mediated and neurodegenerative processes apparently play roles in the pathogenesis of this disease. Heat shock proteins (HSPs) are a family of highly evolutionarily conserved proteins; their expression in the nervous system is induced in a variety of pathologic states, including cerebral ischemia, neurodegenerative diseases, epilepsy, and trauma. To date, investigators have observed protective effects of HSPs in a variety of brain disease models (e.g. of Alzheimer disease and Parkinson disease). In contrast, unequivocal data have been obtained for their roles in MS that depend on the HSP family and particularly on their localization (i.e. intracellular or extracellular). This article reviews our current understanding of the involvement of the principal HSP families in MS.

Heat shock protein 70: roles in multiple sclerosis

Heat shock proteins (HSP) have long been considered intracellular chaperones that possess housekeeping and cytoprotective functions. Consequently, HSP overexpression was proposed as a potential therapy for neurodegenerative diseases characterized by the accumulation or aggregation of abnormal proteins. Recently, the discovery that cells release HSP with the capacity to trigger proinflammatory as well as immunoregulatory responses has focused attention on investigating the role of HSP in chronic inflammatory autoimmune diseases such as multiple sclerosis (MS). To date, the most relevant HSP is the inducible Hsp70, which exhibits both cytoprotectant and immunoregulatory functions. Several studies have presented contradictory evidence concerning the involvement of Hsp70 in MS or experimental autoimmune encephalomyelitis (EAE), the MS animal model. In this review, we dissect the functions of Hsp70 and discuss the controversial data concerning the role of Hsp70 in MS and EAE.

γδ T cells and multiple sclerosis: Friends, foes, or both?

Multiple sclerosis (MS) is a debilitating CNS disease characterized by demyelination and neuro-axonal loss. Though the exact etiology is still unknown, accumulated evidence points to the immune system being involved in the MS disease-process. Both ill-fated adaptive and innate immune responses can potentially contribute to the etiopathogenesis. We have been interested in deciphering how innate immunity might be involved; in particular, the role of γδ T cells. In this review, we discuss the current understanding about γδ T cells and describe the evidence implicating them in myelin injury, neurotoxicity, and immunoregulation in the development of MS.

Cerebral neurons and glial cell types inducing heat shock protein Hsp70 following heat stress in the rat

In this chapter, the distribution of Hsp70 in brain cell types following whole body hyperthermia is reviewed. The prevalence of Hsp70 expression in oligodendrocytes, microglia, and vascular cells in this type of stress contrasts with scarcity of Hsp70 induction in astrocytes and most neurons of the hyperthermic brain. However, a similarity between hyperthermic- and arsenite-induced brain patterns of Hsp70 expression supports the view that denaturation of specific proteins plays a major role in the selectivity of glial/vascular expression also during hyperthermia in vivo. The mechanism of neuronal Hsp70 non-responsiveness in heat stress despite their ability to use Hsc70 in a partial heat stress response remains to be elucidated.

Association of MBP peptides with Hsp70 in normal appearing human white matter

Multiple Sclerosis is an autoimmune disease directed against myelin proteins. The etiology of MS is poorly defined though, with no definitive causative agent yet identified. It has been hypothesized that MS may be a multifactorial disease resulting in the same end product: the destruction of myelin by the immune system. In this report we describe a potential role for heat shock proteins in the pathogenesis of MS. We isolated Hsp70 from the normal appearing white matter of both MS and normal human brain and found this was actively associated with, among other things, immunodominant MBP peptides. Hsp70-MBP peptide complexes prepared in vitro were shown to be highly immunogenic, with adjuvant-like effects stimulating MBP peptide-specific T cell lines to respond to normally sub-optimal concentrations of peptide. This demonstration of a specific interaction between Hsp70 and different MBP peptides, coupled with the adjuvanticity of this association is suggestive of a possible role for Hsp70 in the immunopathology associated with MS.

Induction of endothelial cell apoptosis by the binding of anti-endothelial cell antibodies to Hsp60 in vasculitis-associated systemic autoimmune diseases

OBJECTIVE

Anti-endothelial cell antibodies (AECAs), which recognize a number of endothelial antigens, are seen in patients with systemic autoimmune diseases, more often in the presence of vasculitis than in its absence. Some AECAs induce apoptosis of endothelial cells (ECs), but their target antigens remain unknown. The aim of this study was to determine whether Hsp60 is a target antigen and whether AECAs induce apoptosis in ECs.

METHODS

Two-dimensional electrophoresis and conventional Western blotting techniques were used to characterize AECA targets. Hsp60 reactivity was determined by enzyme-linked immunosorbent assay.

RESULTS

Hsp60 was shown to be targeted by a proportion of AECAs. The level of reactivity was higher in patients with systemic autoimmune disease and vasculitis than in those without vasculitis and in patients with systemic lupus erythematosus than in patients with other systemic autoimmune diseases. Hsp60 was expressed on the plasma membrane of heat-stressed ECs, and this followed Hsp60 messenger RNA transcription, confinement of the protein to the cytoplasm, and translocation of the protein to the surface. Shedding of Hsp60 from ECs was induced by stress and resulted in the binding of soluble Hsp60 to the surface of ECs, particularly stressed ECs. Apoptosis of ECs was triggered by anti-Hsp60-containing AECA-positive sera and was inhibited by preincubation of the ECs with recombinant Hsp60.

CONCLUSION

Our data support the notion that Hsp60 is an important target for AECAs and that such an interaction contributes to pathogenic effects, especially in vasculitis-associated systemic autoimmune disease.

Heat shock proteins in autoimmune diseases

Heat shock proteins (hsp's) are among the most conserved proteins in evolution. They have been identified as important pathogen-related antigens as well as autoantigens suitable for construction of novel vaccines. The high evolutionary homology of hsp's has raised the question about the safety of such vaccines. Experimental and clinical observations have confirmed that hsp proteins are involved in the regulation of some autoimmune disease such as autoimmune arthritis, type 1 diabetes mellitus, atherosclerosis, multiple sclerosis, and other autoimmune reactions. It has been shown in experimental animals that some hsp proteins (especially hsp60, hsp70, and hsp10) can either induce or prevent autoimmune reactions depending on the circumstances. This article discusses the involvement of hsp proteins in the etiology of autoimmune diseases and it presents promising experimental data on the effects of immunization with hsp proteins in the prevention and therapy of autoimmune diseases.

Antibodies reactive to heat shock protein 90 induce oligodendrocyte precursor cell death in culture. Implications for demyelination in multiple sclerosis

Oligodendrocyte precursor cells (OPCs) are extremely efficient at remyelination. These cells persist in the adult human central nervous system and can proliferate. However, the failure to remyelinate is a pathological characteristic of the human demyelinating disease multiple sclerosis (MS), which suggests that these cells are ineffective in this disorder. This paper reports that IgG antibodies in the cerebrospinal fluid (CSF) of MS patients specifically recognize an antigen on OPCs in culture. Control patients were found not to possess these antibodies. The antigen was immunoprecipitated in cell extracts from cultures with purified IgG from MS CSF. Peptide mass fingerprinting identified it as the beta type of heat shock protein 90 (Hsp90). Two-dimensional electrophoresis and immunoblot showed that this antigen in fact corresponds to two specific isoforms of Hsp90beta. Several control assays using monoclonal and polyclonal anti-Hsp90 antibodies confirmed the specific expression of Hsp90 on OPCs. Labeling OPCs in vivo with MS CSF and anti-Hsp90 antibodies and subsequent immunofluorescence confocal microscopy located the antigen on the cell surface. The binding of CSF antibodies from MS patients to the OPC surface led to complement activation and significant extinction of the OPC population. These results suggest that OPCs may be a target of anti-Hsp90 antibodies in MS patients and that this could prevent remyelination.

Identification of cerebral neurons and glial cell types inducing heat shock protein Hsp70 following heat stress in the rat

Heat shock proteins were recently recognized as molecular chaperones that besides their chaperoning function were also involved in processes of cell death and survival. Many types of neural cells were reportedly capable of expressing heat shock protein Hsp70 following heat stress in vitro. However, identification of cell types inducing Hsp70 protein in the hyperthermic brain is not clear. In this study, cerebral Hsp70 distribution was evaluated in anesthetized adult rats (urethane, 1.5 g/kg, i.p.) subjected to short-term hyperthermia (41.5 degrees C for 30 min). Detection of Hsp70 was achieved by an ABC technique in vibratome or paraffin sections combined with specific markers of glial cell types. Hsp70 appeared by 90 min, mainly in glial and vascular cells, with enhanced immunostaining by 4 h following hyperthermia. Higher numbers of Hsp70-positive cells were detected in the white matter and diencephalic region than in the cerebral cortex, especially over the shorter interval. Hsp70 was localized in many oligodendrocytes, double-labeled with lectin GSII, and some vessels. Microglia showed apparently less Hsp70/OX-42 double-labeled cells than the previous two cell types. In contrast, only a few Hsp70-stained cells were positive for astrocyte marker GFAP. In addition to glial/vascular Hsp70 staining, neuronal Hsp70 induction was observed only in discrete regions including the paraventricular, supraoptic, suprachiasmatic and other hypothalamic nuclei, and in amygdala. Prevailing heat-stress expression of Hsp70 in oligodendrocytes and vascular cells might render them less susceptible to the consequences of other types of cell stress and could be exploited to increase selectively their survival in pathological situations.

In vitro injury model for oligodendrocytes: development, injury, and recovery

In this study we investigated the effects of severe hypothermia (cryoinjury) on oligodendrocyte (OL) cell marker expression and morphological features. We used a chemically defined cell culture medium, glial development medium (GDM), which favored the optimal expression of the OL phenotype in CG4 cells. Experiments using CG4 cells cultured in 2% serum or in GDM were conducted in parallel. After severe hypothermia, cells were reanimated at 37 degrees C and 4.5% CO(2) and cultured in either GDM or in medium supplemented with 2% serum. In either medium, around 70% of the total number of cells detached within 2 to 4 hours following reanimation. Oligodendroglial markers such as A2B5, O4, Tf, ferritin, tubulin, and MBP were examined by double and triple immunofluorescence. All of these markers except MBP re-appeared at different times during the recovery period for up to 48 hours. Glial fibrillary acidic protein (GFAP) and heat shock protein 60 (HSP-60) were used as injury markers. The presence of serum induced HSP-60 expression, while GDM did not. All CG4 cells expressed HSP-60 in response to hypothermia independently of the cell culture medium used. Cryoinjury induced a spectrum of morphological changes in CG4 cells. The expression of OL specific markers was also influenced by hypothermia. Moreover both, serum and cryoinjury induced the expression of HSP-60 that colocalized with OL and myelin markers. The expression of GFAP by injured cells but not by normal cells corroborated the state of injury of CG4 cells.

Fatal hyperthermia secondary to sunbathing in a patient with multiple sclerosis

A 27-year-old white woman with a history of multiple sclerosis was found dead lying on a lounger, clad in a bathing suit. She had been sunbathing for 4 hours. Significant autopsy findings consisted of numerous variably sized demyelinated plaques involving the periventricular cerebral white matter and cerebellum. Elevation of core temperature in patients with multiple sclerosis leading to transient or permanent adverse neurologic signs and symptoms has been documented for more than 60 years. This case illustrates that a modestly increased core body temperature, even from a usually innocuous activity such as sunbathing, may be fatal in patients with multiple sclerosis.

Differential expression of stress proteins in human adult astrocytes in response to cytokines

Various lines of evidence suggest a close relationship between heat shock proteins (hsp) and several autoimmune diseases such as arthritis, diabetes and multiple sclerosis. While enhanced expression of hsp in autoimmune diseases is often regarded as a non-specific bystander effect of the inflammatory process, surprisingly little is known on hsp regulation by inflammatory mediators such as cytokines. In this study cytokine-induced expression of hsp60, hsp27 and alphaB-crystallin was studied in cultures of primary human adult astrocytes at the mRNA as well as at the protein level. We show differential hsp expression patterns in response to pro-inflammatory and immunoregulatory cytokines. Hsp60 expression was found to be enhanced in response to cytokines as diverse as IL-1beta, TNF-alpha, IL-4, IL-6 and IL-10. Upregulation of hsp27, however, was primarily induced by immunoregulatory cytokines like IL-4, IL-6 and TGF-beta whereas alphaB-crystallin expression was found to be enhanced by the pro-inflammatory cytokine TNF-alpha only. None of the cytokines studied was able to enhance expression of all three hsp simultaneously. These results show that in human astrocytes induced expression of hsp27 and alphaB-crystallin is dependent on the presence of a defined set of stimuli, while induced expression of hsp60 is a much less selective event. This highly differential pattern of hsp expression in response to inflammatory mediators known to play an important role in the pathogenesis of autoimmune diseases indicates that hsp responses are specific rather than non-specific bystander responses.

High prevalence of anti-alpha-crystallin antibodies in multiple sclerosis: correlation with severity and activity of disease

INTRODUCTION

The presence of T-cell reactivity to alphaB-crystallin in patients with multiple sclerosis (MS) has suggested that this small molecular weight heat shock protein (Hsp) may be an autoantigen in MS.

MATERIAL AND METHODS

We have tested the serum of patients with clinically definite MS (n=30), other inflammatory neurological disease (n=22), non-inflammatory neurological disease (n=42) and healthy individuals (n=23) for systemic humoral responses to bovine alphaB-crystallin, to the homologous chaperone protein, alphaA-crystallin, and to another small Hsp, Hsp 27.

RESULTS

Sixty-three percent of MS patients exhibited immunoreactivity to alpha-crystallin and this was present in all 4 of 4 non-ambulatory patients with MS. In contrast, serum concentrations in MS patients of antibodies to the small Hsp, Hsp27, and to myelin basic protein were negligible (P<0.001). Serum anti-alpha-crystallin immune responses were detected in significantly lower percentages of patients with other inflammatory neurological diseases (32%, P<0.025), and with non-inflammatory neurological diseases (12%, P<0.001). None of the healthy control individuals showed anti-alpha-crystallin reactivity. The concentration of anti-alpha-crystallin antibodies in patients with MS correlated with severe disease (P<0.05) and with active disease (P<0.025).

CONCLUSION

Our observations support the notion that anti-alpha-crystallin autoimmune responses may contribute to pathogenicity in MS and may represent a mechanism of how recurrent attacks of MS develop subsequent to an isolated demyelinating episode.

Cell surface colligin/Hsp47 associates with tetraspanin protein CD9 in epidermoid carcinoma cell lines

Hsps expressed on the cell surface have been associated with tumor invasiveness and used as targets for molecular surveillance. The present study utilized four human oral squamous cell carcinoma cells lines, SCC-4, SCC-9, SCC-15, SCC-25, the murine epidermoid carcinoma cell line LL/2, and primary cultures of human gingival fibroblasts to assess the cell surface expression of colligin/Hsp47, a proposed marker for malignancy. Immunoprecipitation studies following protein crosslinking revealed that Hsp47 was associated with a number of membrane proteins including the tetraspanin CD9. Cytometric analyses were performed to determine the distribution of cell surface colligin/Hsp47 during the phases of the cell cycle. These studies showed that colligin/Hsp47 was not limited to any phase of the cell cycle in epidermoid carcinoma cells. Boyden chamber tumor invasion assays and colloidal gold migration assays utilizing a reconstituted basement membrane (Matrigel), collagen type I, and laminin-5 substrates revealed that cell lines expressing constitutive high levels of colligin/Hsp47 manifested the lowest invasion and migration indices. The incorporation of antibodies against Hsps into the migration and invasion assays, likewise, increased the invasion indices and the phagokinetic migration indices. These data indicate that colligin/Hsp47 is anchored to the cell membrane in a complex with CD9 where it moderates tumor cell invasion and motility possibly by acting as a serpin protein inhibitor or as a receptor for collagen.

Immunity to heat shock proteins and neurological disorders of women

Stress or heat shock proteins are constitutively expressed in normal CNS tissues in a variety of cell types (oligodendrocytes, astrocytes, and neurons). Their presence may protect cells from various stresses, such as hypoxia, anoxia, and excessive excitatory stimulation. Increased amounts of hsp are expressed in various cells of the CNS during acute toxic-metabolic states and in chronic degenerative and inflammatory diseases. Increased expression of hsp may lead to immune responses to these proteins. Antibodies to mycobacterial hsp bind to normal human myelin and to oligodendrocytes in regions of MS demyelination. Cellular immune responses to hsp occur with increased frequency and magnitude in persons with MS, especially those with recent onset of disease. In addition, there are populations of T cells expressing gamma/delta T cells in the brains and spinal fluids of persons with MS, suggesting an in situ immune response to hsps. Humoral immune responses to hsp are found in CSF, but no disease specificity has been documented. Some myelin proteins have sequence homology with particular hsps. One instance is the homology between a peptide of mycobacterial Hsp65 and the myelin protein CNP. Our data on EAE suggest that immune responses to either cross-reactive hsp epitopes or whole hsp can modify the course of both acute and chronic relapsing EAE. In addition, the severity and frequency of environmental exposure to infectious agents can modify the course of EAE, possibly by altering the patterns of immune response to hsp. Finally, tolerance to the small hsp, alpha B-crystallin, a putative autoantigen in persons with MS, alters the course of relapsing EAE, supporting its role in chronic, autoimmune CNS disease. Modifying immune responses to hsp may be a potential new treatment option for persons with MS.

Role of heat shock proteins in protection from and pathogenesis of infectious diseases

Increased synthesis of heat shock proteins (hsp) occurs in prokaryotic and eukaryotic cells when they are exposed to stress. By increasing their hsp content, cells protect themselves from lethal assaults, primarily because hsp interfere with the uncontrolled protein unfolding that occurs under stress. However, hsp are not produced only by stressed cells; some hsp are synthesized constitutively and perform important housekeeping functions. Accordingly, hsp are involved in the assembly of molecules which play important roles in the immune system. It is not surprising that due to their wide distribution and their homology among different species, hsp represent target antigens of the immune response. Frequent confrontation of the immune system with conserved regions of hsp which are shared by various microbial pathogens can potentiate antimicrobial immunity. However, long-term confrontation of the immune system with hsp antigens which are similar in the host and invaders may convert the immune response against these host antigens and promote autoimmune disease. This review provides an overview of the role of hsp in immunity with a focus on infectious and autoimmune diseases.

Heat shock proteins and experimental autoimmune encephalomyelitis. II: environmental infection and extra-neuraxial inflammation alter the course of chronic relapsing encephalomyelitis

We wished to study how infections might trigger relapses of autoimmune diseases such as multiple sclerosis (MS) and encephalomyelitis (EAE). We hypothesized that immune responses to heat shock proteins (hsp) induced by an infection could modulate responses to autoantigens. We induced extra-neuraxial inflammation in SJL mice housed either in specific-pathogen free (SPF) or conventional facilities. Mice in conventional housing are continuously exposed to large numbers of infectious agents. Spleen cell proliferative responses to human HSP60 and bacterial HSP65 were measured as were numbers of cells secreting IFN-gamma or IL-5. Proliferative responses to HSP60 were increased in conventionally housed mice compared to SPF mice and this was associated with skewing of secreted cytokines toward a Th2 pattern. Skewing toward a Th1 pattern was noted in SPF mice. Acute and relapsing EAE was induced in both groups of mice. Acute EAE was, in general, equivalent in all groups. However, SPF mice had more severe relapses than did conventionally housed animals and these differences were amplified by extra-neuraxial inflammation. Immunocytochemical analyses of brains from mice with relapsing EAE showed that increased numbers of brain gamma/delta cells were associated with disease remission. Our data suggest that frequent exposure to infectious agents leads to a relative Th2 skewing of immune responses to hsp and that this is associated with milder, less frequent relapses of EAE. They also support the concept that immune responses to hsp are of potential importance in exacerbating and perpetuating organ-restricted autoimmune diseases.

T-cell responses to myelin antigens in multiple sclerosis; relevance of the predominant autoimmune reactivity to myelin oligodendrocyte glycoprotein

Until recently, the search for the 'culprit' autoantigen towards which deleterious autoimmunity is directed in multiple sclerosis (MS) centered mostly on myelin basic protein (MBP) and proteolipid (PLP), the two most abundant protein components of central nervous system (CNS) myelin, the target tissue for the autoimmune attack in MS. Although such research has yielded important data, furthering our understanding of the disease and opening avenues for possible immune-specific therapeutic approaches, attempts to unequivocally associate MS with MBP or PLP as primary target antigens in the disease have not been successful. This has led in recent years to a new perspective in MS research, whereby different CNS antigens are being investigated for their possible role in the initiation or progression of MS. Interesting studies in laboratory animals show that T-cells directed against certain non-myelin-specific CNS antigens are able to cause inflammation of the CNS, albeit without expression of clinical disease. However, reactivity to these antigens by MS T-cells has not been demonstrated. Conversely, reactivity by MS T-cells to non-myelin-specific antigens such as heat shock proteins, could be observed, but the pathogenic potential of such reactivity has not been corroborated with the encephalitogenicity of the antigen. More relevant to MS pathogenesis may be, as we outlined in this review, the autoimmune reactivity directed against minor myelin proteins, in particular the CNS-specific myelin oligodendrocyte glycoprotein (MOG). Here, we review the current knowledge gathered on T-cell reactivity to possible target antigens in MS in the context of their encephalitogenic potential, and underline the facets which make MOG a highly relevant contender as primary target antigen in MS, albeit not necessarily the only one.

Humoral immune response to mycobacterial heat shock protein (hsp)65 in the cerebrospinal fluid of neuro-Behçet patients

Although systemic immune reactivity to 65-kD mycobacterial hsp65 (m-hsp65) has been shown previously in Behçet's disease (BD), local immune response was not investigated. We studied anti-m-hsp65 IgG, IgM and IgA antibodies in the serum and cerebrospinal fluid (CSF) of 25 BD patients with cerebral parenchymal involvement (p-NBD), seven BD patients with intracranial hypertension (ih-NBD), eight BD patients without central nervous system (CNS) involvement, 30 patients with multiple sclerosis (MS) and 24 patients with non-inflammatory CNS disorders (NIC). Significantly higher CSF IgG responses were detected in p-NBD patients (ELISA ratio 1.3 +/- 0.9) compared with NIC (0.7 +/- 0.4, P < 0.01). In p-NBD patients' IgG, IgM or IgA CSF anti-m-hsp65 positivity rate was 48% (12/25); this was significantly higher when compared with MS (3/30; P < 0.03) and NIC (3/24; P < 0.01). CSF anti-m-hsp65 IgG ratios correlated with the duration of BD (r = 0.4, P < 0.04) but not with the duration of neurological involvement. Serum IgM and IgA responses were elevated in ih-NBD, suggesting a different type of involvement than p-NBD. These results implicate an increased local humoral response to m-hsp65 in the CSF of p-NBD patients, which might be related to the pathogenesis of neurological involvement.

Mechanism of gammadelta T cell-induced human oligodendrocyte cytotoxicity: relevance to multiple sclerosis

Gammadelta T cells may contribute to the pathogenesis of Multiple Sclerosis (MS) via cytotoxicity directed at the myelin-oligodendrocyte unit. We have previously demonstrated that peripheral blood-derived gammadelta T cells lyse fresh human oligodendrocytes in vitro. The present work extends these observations to gammadelta T cells derived from both peripheral blood (PBL) and cerebrospinal fluid (CSF) of MS and non-MS neurological disease controls and addresses the mechanism of cellular cytotoxicity. We found that MS patients contained increased proportions of Vdelta1+ gammadelta T cells in both CSF and PBL samples compared to other neurological disease (OND) controls. Although gammadelta T cells from all patients were cytotoxic towards Daudi, RPMI 8226, U937, Jurkat, oligodendroglioma and fresh human oligodendrocyte targets, OND-derived, Vdelta2+ rich, populations derived from the CSF exhibited greater cytotoxicity towards cell lines (Daudi, RPMI 8226) known to express high levels of heat shock proteins (hsp). To clarify the mechanism(s) of cytotoxicity used by gammadelta T cells, we first showed that cell-target contact was necessary by the use of physical barriers (transwells), which reduced target cell lysis by at least 75%. The use of Ca2+-free media reduced lysis by up to 50%, but fully blocking gammadelta T cell Perforin release and function by either Ca2+ chelation (Mg2EGTA) or the H+-ATPase inhibitor Concanamycin-A (CMA), completely abrogated the lysis of Fas-/hsp60high expressing targets (Daudi, U937). However, additional treatment with Brefeldin A was required for the complete inhibition of gammadelta T cell mediated killing of Fas+ expressing Jurkat targets and fresh human brain-derived oligodendrocytes. Inhibition of granzyme activity by an isocoumarin compound reduced cytolysis only slightly. The use of either Brefeldin A or an anti-Fas antibody alone did not significantly affect lysis. These findings suggest that in MS, gammadelta T cells may utilize either the Fas-mediated or Perforin-based cell cytotoxicity pathways in exerting oligodendrocyte damage, though the Perforin pathway is predominant.

Heat shock or stress proteins and their role as autoantigens in multiple sclerosis

Stress or heat shock proteins are constitutively expressed in normal CNS tissues, in a variety of cell types (oligodendrocytes, astrocytes, and neurons). Their presence may protect cells from various stresses, such as hypoxia, anoxia, and excessive excitatory stimulation. Increased amounts of hsp are expressed in various cells of the CNS during acute toxic-metabolic states and in chronic degenerative and inflammatory diseases. Increased expression of hsp may lead to immune responses to these proteins. Antibodies to mycobacterial hsp bind to normal human myelin and to oligodendrocytes in regions of MS demyelination. Cellular immune responses to hsp occur with increased frequency and magnitude in persons with MS, especially those with recent onset of disease. In addition, there are populations of T cells expressing gamma/delta antigen receptors in the brains and spinal fluids of persons with MS, suggesting an in situ immune response to hsp. Humoral immune responses to hsp are found in CSF, but no disease specificity has been documented. Some myelin proteins have sequence homology with particular hsp. One instance is the homology between a peptide of mycobacterial HSP 65 and the myelin protein CNP. Our data in EAE suggest that immune responses to either cross-reactive epitopes or whole hsp can modify the course of both acute and chronic relapsing EAE. These data support the hypothesis that an immune response to an infectious agent's hsp could result in a cross-reactive immune response to CNS myelin, or to responses to endogenous, CNS-expressed hsp, resulting in demyelination. This may be an important mechanism in the pathogenesis of MS.

Gamma delta cells regulate autoimmunity

Gamma delta cells are attractive candidates for mediators of autoimmune disease. They can expand in germ-free mice, probably through recognition of autoantigens, and gamma delta-cell-deficient mice, unlike mice deficient in alpha beta T cells or B cells, show no severe defects in the immune response to foreign antigen challenge. A capacity of gamma delta cells to effect or regulate tissue damage is also plausible, given their ready localization to tissues, and their myriad of effector functions. Added to this, attempts to reconstruct the physiological course of autoimmune diseases with only autoreactive alpha beta T cells seem invariably to fall short for lack of other unidentified players. Gamma delta cells and their putative ligands have been linked to autoimmune conditions, and recent experiments confirm that gamma delta cells play a significant role in autoimmune disease in vivo.

Expression of alphaB-crystallin in glia cells during lesional development in multiple sclerosis

The small heat shock protein alphaB-crystallin was recently identified as a dominant human T-cell antigen in myelin derived from multiple sclerosis (MS) patients. Using immunohistochemical techniques, oligodendrocytes as well as astrocytes in MS lesions were shown to express alphaB-crystallin. In the present study we examined the expression of alphaB-crystallin, human natural killer cell marker (HNK-1; as a marker for immature oligodendrocytes) and heat shock protein 60 (hsp60) in glia cells at different stages of MS lesion development i.e. in early active lesions, late active lesions and inactive lesions. The results demonstrate that already at the earliest stages of lesional development a subpopulation of oligodendrocytes express detectable levels of alphaB-crystallin. In active lesions about 5-10% of all oligodendrocytes were found to express alphaB-crystallin, whereas in inactive lesions the relative number of alphaB-crystallin-expressing oligodendrocytes was approximately tenfold less. For astrocytes the relative number of alphaB-crystallin-expressing cells was 40-50% for all three types of lesions. Also, alphaB-crystallin-expressing oligodendrocytes and astrocytes displayed different patterns of distribution in lesional areas. These data suggest different regulatory pathways for alphaB-crystallin expression in either type of glia cell. No correlation was found between expression patterns of HNK-1 and alphaB-crystallin indicating that the subpopulation of alphaB-crystallin-expressing oligodendrocytes consisted of both mature and immature oligodendrocytes. In addition, no correlation was found between expression of hsp60 and alphaB-crystallin in MS lesions suggesting different regulatory pathways for either hsp.

The Norton Lecture: a review of the oligodendrocyte in the multiple sclerosis lesion

The mechanisms involved in the elimination of oligodendrocytes and myelin from the demyelinated plaque of multiple sclerosis (MS) are inextricably intertwined and yet most investigations tend to consider them separately. This short review revisits the problem of oligodendrocyte pathology in MS and attempts to put the topic into perspective by examining the numerous immunologically-active molecules associated with the oligodendrocyte, some, but not all, cross-reactive with myelin. The consensus of opinion is that myelin is the primary target in MS but that oligodendrocytes are eventually lost from the lesion. Reappraisal of recent and past works brings into focus a possible key role for soluble mediators, in particular antibody and the pro-inflammatory cytokine, TNF alpha, in oligodendrocyte loss and myelin in MS. Despite extensive neuropathologic investigation by a number of laboratories, no evidence has yet been found to support the concept that apoptosis might account for oligodendrocyte depletion in MS, even though molecules belonging to the apoptotic cascade can be expressed by oligodendrocytes in and around lesions. Indeed, abundant evidence has been presented to show that oligodendrocytes initially respond to the demyelinating insult in MS by proliferating and elaborating new myelin but, no doubt due to the relentless progression of inflammatory events, the cells are eventually lost, probably via a cytolytic pathway. Strategies to block the progression of CNS inflammation in EAE and MS appear to promote the survival of oligodendrocytes and to enhance remyelination. Such strategies appear to hold much promise for the MS patient.

Differential induction of heat shock mRNA in oligodendrocytes, microglia, and astrocytes following hyperthermia

A time course analysis of hsp70 mRNA induction in response to a physiologically relevant increase in body temperature of 2.6 degrees C was performed in the rabbit forebrain. A protocol that combined in situ hybridization and cytochemistry on the same tissue section was employed to identify reactive glial cell types. Cytochemical markers for astrocytes, microglia, and oligodendrocytes were utilized in combination with a DIG-labelled hsp70 riboprobe, which permitted mRNA localization at high resolution. Four glial cell body-enriched regions of the rabbit forebrain were examined, namely, cortical layer 1, hippocampal fissure, corpus callosum, and fimbria. Maximal hsp70 mRNA induction was observed in 2 and 3 h hyperthermic animals. The colocalization analysis demonstrated that hsp70 mRNA was induced in oligodendrocytes and microglia, but not in forebrain GFAP positive astrocytes. In addition, cell counts were performed which showed that almost all oligodendrocytes induced hsp70 mRNA while a subpopulation of microglial cells responded. These data are consistent with the notion that oligodendrocytes, microglia, and astrocytes exhibit distinct thresholds for activation of the heat shock response following a physiologically relevant increase in body temperature.

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.

gamma delta T-cell-human glial cell interactions. I. In vitro induction of gammadelta T-cell expansion by human glial cells

gamma delta T-cells are found in increased proportion in multiple sclerosis (MS) white matter plaque infiltrates compared with peripheral blood or spleen, raising the possibility that they are either specifically attracted to lesion sites or, once present, are stimulated to expand. We have previously shown that human oligodendrocytes (OGC) preferentially express heat shock proteins (hsp), molecules to which gamma delta T-cells have been known to react and that in vitro expanded gamma delta T-cells can lyse OGC. We therefore investigated whether human glial cells, that differentially express hsp, could stimulate gamma delta T-cell expansion from peripheral blood. We compared the glial cell-induced expansion to cell lines which also differentially express hsp and have been shown to selectively stimulate gamma delta T-cell expansion (e.g. RPMI 8226, Daudi). We found that both OGC and human fetal astrocytes (hFA) expressed hsp and stimulated the preferential expansion of gamma delta T-cells to about the same extent as the hsp expressing cell lines RPMI 8226 or Daudi, in the presence of exogenous interleukin-2 (IL-2) but without any T-cell mitogen. Furthermore, the type of gamma delta T-cells expanded were of the V delta 2 subtype known to be particularly reactive to hsp. Microglia, U937 cell lines or purified myelin membranes, which express little or no hsp, did not support gamma delta T-cell growth. These results therefore suggest that OGC may contribute to the local expansion of gamma delta T-cells within MS plaques. Potential harmful effects of gamma delta T-cells on OGC may thereby contribute to the immunopathogenesis of MS demyelination.

The role of molecular chaperones in mitochondrial protein import and folding

Molecular chaperones play a critical role in many cellular processes. This review concentrates on their role in targeting of proteins to the mitochondria and the subsequent folding of the imported protein. It also reviews the role of molecular chaperons in protein degradation, a process that not only regulates the turnover of proteins but also eliminates proteins that have folded incorrectly or have aggregated as a result of cell stress. Finally, the role of molecular chaperones, in particular to mitochondrial chaperonins, in disease is reviewed. In support of the endosymbiont theory on the origin of mitochondria, the chaperones of the mitochondrial compartment show a high degree of similarity to bacterial molecular chaperones. Thus, studies of protein folding in bacteria such as Escherichia coli have proved to be instructive in understanding the process in the eukaryotic cell. As in bacteria, the molecular chaperone genes of eukaryotes are activated by a variety of stresses. The regulation of stress genes involved in mitochondrial chaperone function is reviewed and major unsolved questions regarding the regulation, function, and involvement in disease of the molecular chaperones are identified.

Differential expression of heat shock 70 proteins in primary cultures from rat cerebellum

While a number of studies have described the heat shock response in established cell lines and in primary cultures of cells derived from the nervous system, there has been no systematic analysis comparing expression and localization of the inducible heat shock 70 (hsp70) proteins and the constitutively synthesized members of the family (hsc70) in neurons and glia. In the present communication, we utilized specific probes to compare the expression of hsp70 and hsc70 mRNAs and proteins in two types of primary cultures, astroglial and neuro-astroglial, from postnatal rat cerebellum. Conditions were adjusted to maintain physiological numbers of microglia in both types of culture, and cultures were analyzed at a number of different time points following a precisely defined heat shock. The northern, in situ hybridization and immunohistochemical analyses resulted in a number of novel observations concerning the nature of the heat shock response in these neuronal and glial cells. In postnatal day 4-5 cultures, hsp70 mRNA levels were elevated for at least 10 h in both types of culture, but in situ hybridization analysis showed no evidence for hsp70 mRNAs in neurons. Microglia were the only cell type in which hsp70 was detected in non-stressed cultures and this cell type contained the highest concentrations of hsp70 proteins in stressed cultures. Hsc70 mRNA levels were also increased after heat shock, but the increase was more transient. Hsc70 mRNAs and proteins were present in all cell types, again with the highest concentrations being present in microglia. Hsc70 mRNAs and proteins were localized in the cytoplasm at all time points examined, with hsc70 protein also being localized in nucleoli. Hsp70 mRNAs and proteins were diffusely localized over nuclei of astrocytes, as well as of most microglia. Hsp70, but not hsc70, was localized on chromosomes in glia once they had resumed cell division after heat shock, suggesting a role for hsp70 either in targeting damaged chromosomal proteins or in cell division. Some cytoplasmic hsp70 was observed in astrocytes of the mixed neuro-astroglial cultures and a delayed hsp70 immunoreactivity was observed in granule neurons in these cultures, suggesting either that translation of low levels of hsp70 mRNAs was more efficient in neurons, or that glial-neuronal translocation of hsp70 proteins had taken place. These results suggest that metabolism and functions of different heat shock protein family members may not always be identical and that care must be taken in extrapolation of results from one cell type to another.

Tumor-specific cell surface expression of the-KDEL containing, endoplasmic reticular heat shock protein gp96

Heat shock protein (HSP) gp96/grp94 contains a signal peptide at the amino terminus and a -KDEL sequence at the carboxy terminus and is a major component of the lumen of the mammalian endoplasmic reticulum (ER). We show, by a number of immunolocalization methods using light and electron microscopy, that a significant proportion of intact gp96 molecules is also expressed on the cell surface. Surface gp96 molecules truly represent surface expression and do not result from adventitious deposition of gp96 released by dead cells on to the live cells in culture. Cell surface expression of gp96 is enhanced by heat shock and exposure to reducing agents. Gp96 molecules are not released from plasma membranes by repeated salt washes, and gp96 is not an integral membrane protein. Our observations suggest that gp96 and perhaps other HSPs are anchored to the cell surface as part of larger molecular complexes, which also transport them to the cell surface.

Gamma delta + T cells in Wilson's disease

Little is currently known about the role of gamma delta + T cells in disease pathogenesis. We have demonstrated elevated levels of gamma delta + T cells in the peripheral blood and cerebrospinal fluid of patients with Wilson's disease compared with other neurological diseases. The percentage of V delta 1 +/ gamma delta + T cells was between 20% and 50% in all patient groups; gamma delta + T cells in blood correlated with copper concentrations. The antigen reactivity of gamma delta + T cells and how the antigens relate to the gamma delta + T cells found in WD remains unknown. It remains unclear whether there is a direct reason for the elevated gamma delta + T cells population found in WD. Immunohistochemistry of frozen autopsy material from brain and liver of WD patients could allow exact localization of gamma delta + T cells and heat shock proteins in future studies.

A role of Hsp60 in autoimmune diabetes: analysis in a transgenic model

A pathogenic role for self-reactive cells against the stress protein Hsp60 has been proposed as one of the events leading to autoimmune destruction of pancreatic beta cells in the diabetes of nonobese diabetic (NOD) mice. To examine this hypothesis, we generated transgenic NOD mice carrying a murine Hsp60 transgene driven by the H-2E alpha class II promoter. This would be expected to direct expression of the transgene to antigen-presenting cells including those in the thymus and so induce immunological tolerance by deletion. Detailed analysis of Hsp60 expression revealed that the endogenous gene is itself expressed strongly in thymic medullary epithelium (and weakly in cortex) yet fails to induce tolerance. Transgenic mice with retargeted Hsp60 showed overexpression of the gene in thymic cortical epithelium and in bone marrow-derived cells. Analysis of spontaneous T-cell responses to a panel of self and heterologous Hsp60 antigens showed that tolerance to the protein had not been induced, although responses to an immunodominant 437-460 epitope implicated in disease were suppressed, probably indicating an epitope shift. This correlated with changes in disease susceptibility: insulitis in transgenic mice was substantially reduced so that pathology rarely progressed beyond periislet infiltration. This was reflected in a substantial reduction in hyperglycemia and disease. These data indicate that T cells specific for some epitopes of murine Hsp60 are likely to be involved in the islet-cell destruction that occurs in NOD mice.

Expression of human heat-shock protein 70 antigens and gamma/delta T-cell receptor antigens in human central nervous tissue

The human gamma delta T cell receptor is normally expressed on lymphoid tissue. Because expression of different molecules of the T-cell system has been described on human brain cells, we examined the expression of T-cell receptor gamma delta antigens with a panel of various anti-gamma/delta TCR mAbs using immunohistochemistry on different regions of frozen human postmortem tissue of five different brains. We found expression of gamma/delta TCR antigens on brain tissue in different regions of the brain, probably on neurons. Using mAbs against the 70-kd human heat-shock-protein (hsp 70), immunohistochemistry showed staining of microglia. A polymerase chain reaction analysis using a highly sensitive primer sequence against the constant region delta sequence supports the notion that the gamma/delta TCR is expressed in human brain; however, the sequence cannot be assigned to a specific tissue with this method. Both heat shock proteins and the gamma/delta TCR seem to be involved in autoimmune processes, and their expression on colocalizing structures in human CNS may play a role in triggering neuropsychiatric autoimmune disorders.

HSP72 induction by heat stress in human neurons and glial cells in culture

Expression of 72-kDa heat shock protein (HSP72) induced by heat stress was investigated in cultured neurons and glial cells isolated from fetal human brains using immunoblotting and immunocytochemistry. Under the unstressed condition, a low level of HSP72 expression was observed in astrocytes, microglia, oligodendrocytes, and neurons. Under the heat-stressed condition, an increased expression of HSP72 was observed in all cell types with specific location in the nuclear and cytoplasmic regions. Following heat stress, HSP72 was expressed intensely in more than 50% of astrocytes and microglia during 8-24 h post-recovery, while it was detectable in only 9% of oligodendrocytes and 3% of neurons at 48 h post-recovery. These results indicate that heat stress induces a predominant expression of HSP72 in astrocytes and microglia, and more limited HSP72 expression in oligodendrocytes and neurons in fetal human neural cells in culture. The differential patterns of HSP72 induction in human neural cells by heat stress suggest that cellular mechanisms by which the heat shock response is regulated are different among various cell types in the human central nervous system.

Cytokine induction of heat shock protein expression in human oligodendrocytes: an interleukin-1-mediated mechanism

In this study, we examined the role of cytokines, known to be in elevated levels in multiple sclerosis (MS) plaques, in regulating oligodendrocyte (ODC) expression of heat shock protein (hsp) in human brain-derived glial cell cultures. Using dual-stain immunohistochemistry, we initially compared the ability of a mixture of cytokines (IL-1 alpha, IL-1 beta, IL-2, IL-6, IL-8, TNF-alpha, TNF-beta, IFN-beta and IFN-gamma) with that of physical stimuli such as heat shock and peroxide, to increase cellular expression of the mainly inducible hsp72 species in mixed glial cell cultures (containing ODC, astrocytes and microglia). Similar to heat shock and peroxide, the cytokine mixture induced hsp72 expression only in ODC (70 +/- 5% vs. a baseline of 3 +/- 1% positive cells). When used individually, however, only IL-1 alpha (79 +/- 3%), IFN-gamma (70 +/- 2%) and TNF-alpha (65 +/- 5%) induced ODC hsp72 expression in mixed glial cell cultures. In purified ODC preparations, only IL-1 alpha induced hsp72 expression (84 +/- 4%). An IL-1 receptor antagonist (IL-1ra), abrogated hsp72 induction by IL-1 alpha (16 +/- 3%) as well as that due to IFN-gamma (14 +/- 1%) and TNF-alpha (13 +/- 2%) in mixed glial cell cultures. Furthermore, ODC express IL-1 receptors, detected by confocal laser scanning microscopy. Our data indicate that cytokines mediate hsp induction in ODC possibly via a final common pathway involving IL-1 binding to its receptor on ODC. Such interaction could enhance any putative ODC-immune interactions which are dependent on hsp molecule recognition.

V delta 1 gene usage, interleukin-2 receptors and adhesion molecules on gamma delta+ T cells in inflammatory diseases of the nervous system

This study investigates the expression of T cell receptor V delta 1 chain, interleukin-2 receptor alpha-chain (CD25) and adhesion molecules ICAM-1 (CD54), LFA-1 (CD11a/18) and CD44 on gamma delta+ T cells by three-color flow cytometry on cerebrospinal fluid (CSF) and blood cells in patients with multiple sclerosis (MS), other inflammatory neurological diseases (OIND) and other neurological diseases (OND). Of gamma delta + T cells in CSF and blood, 20-40% belonged to the 'epithelial' V delta 1 subtype. MS patients had the lowest levels in both CSF and blood, but the differences between the patient groups were not significant. The activation markers CD25 and CD54 were expressed by only a small proportion of gamma delta+ T cells and in a minority of patients. Although the occurrence of CD25+ and CD54+ gamma delta+ T cells was somewhat higher in CSF than in blood and in inflammatory diseases than in controls, the small numbers of CD25+ and CD54+ gamma delta+ T cells preclude establishing differences amongst compartments and patient groups. The adhesion molecules CD11a/18 and CD44 were constitutively expressed on all T cells. Therefore, we compared the relative antigen density per cell as measured by the relative fluorescence index (RFI) between CSF and blood, between the patient groups and between gamma delta+ and total T cells. The only difference encountered was a slightly higher expression of adhesion molecules on gamma delta+ compared to total T cells, with preference to MS patients. In conclusion, the V delta 1+ subtype of gamma delta+ T cells does not dominate in the CSF compartment.(ABSTRACT TRUNCATED AT 250 WORDS)