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

Extracellular vesicle-associated small heat shock proteins as therapeutic agents in neurodegenerative diseases and beyond

Increasing evidence points towards using extracellular vesicles (EVs) as a therapeutic strategy in neurodegenerative diseases such as multiple sclerosis, Parkinson's, and Alzheimer's disease. EVs are nanosized carriers that play an essential role in intercellular communication and cellular homeostasis by transporting an active molecular cargo, including a large variety of proteins. Recent publications demonstrate that small heat shock proteins (HSPBs) exhibit a beneficial role in neurodegenerative diseases. Moreover, it is defined that HSPBs target the autophagy and the apoptosis pathway, playing a prominent role in chaperone activity and cell survival. This review elaborates on the therapeutic potential of EVs and HSPBs, in particular HSPB1 and HSPB8, in neurodegenerative diseases. We conclude that EVs and HSPBs positively influence neuroinflammation, central nervous system (CNS) repair, and protein aggregation in CNS disorders. Moreover, we propose the use of HSPB-loaded EVs as advanced nanocarriers for the future development of neurodegenerative disease therapies.

Different interleukin-17-secreting Toll-like receptor+ T-cell subsets are associated with disease activity in multiple sclerosis

Signalling through Toll-like receptors (TLRs) may play a role in the pathogenesis of autoimmune diseases, such as multiple sclerosis (MS). In the present study, the expression of TLR-2, -4 and -9 was significantly higher on CD4⁺ and CD8⁺ T-cells from MS patients compared to healthy individuals. Following in-vitro activation, the proportion of interleukin (IL)-17⁺ and IL-6⁺ CD4⁺ and CD8⁺ T-cells was higher in the patients. In addition, the proportion of IFN-γ-secreting TLR⁺ CD8⁺ T-cells was increased in MS patients. Among different IL-17⁺ T-cell phenotypes, the proportion of IL-17⁺ TLR⁺ CD4⁺ and CD8⁺ T-cells producing IFN-γ or IL-6 were positively associated with the number of active brain lesions and neurological disabilities. Interestingly, activation of purified CD4⁺ and CD8⁺ T-cells with ligands for TLR-2 (Pam3Csk4), TLR-4 [lipopolysaccharide (LPS)] and TLR-9 [oligodeoxynucleotide (ODN)] directly induced cytokine production in MS patients. Among the pathogen-associated molecular patterns (PAMPs), Pam3Csk4 was more potent than other TLR ligands in inducing the production of all proinflammatory cytokines. Furthermore, IL-6, IFN-γ, IL-17 and granulocyte-macrophage colony-stimulating factor (GM-CSF) levels produced by Pam3Csk4-activated CD4⁺ cells were directly associated with disease activity. A similar correlation was observed with regard to IL-17 levels released by Pam3Csk4-stimulated CD8⁺ T-cells and clinical parameters. In conclusion, our data suggest that the expansion of different T helper type 17 (Th17) phenotypes expressing TLR-2, -4 and -9 is associated with MS disease activity, and reveals a preferential ability of TLR-2 ligand in directly inducing the production of cytokines related to brains lesions and neurological disabilities.

Heat Shock Proteins in Multiple Sclerosis

Multiple sclerosis (MS) is an immune-mediated and neurodegenerative central nervous system disease, mostly affect myelin sheaths. The MS pathogenesis is still under debate. It is influenced by genetic, environment factors. Heat shock proteins (HSPs) are highly conserved proteins seen in all organisms. Not only heat stress but also under many stress conditions they are overexpressed. Their roles in MS pathogenesis are highly correlated with their location (intracellular or extracellular). In this chapter, we will discuss the role of HSP in MS pathogenesis.

Cellular stress and innate inflammation in organ-specific autoimmunity: lessons learned from vitiligo

For decades, research in autoimmunity has focused primarily on immune contributions to disease. Yet recent studies report elevated levels of reactive oxygen species and abnormal activation of the unfolded protein response in cells targeted by autoimmunity, implicating cellular stress originating from the target tissue as a contributing factor. A better understanding of this contribution may help to answer important lingering questions in organ-specific autoimmunity, as to what factors initiate disease and what directs its tissue specificity. Vitiligo, an autoimmune disease of the skin, has been the focus of translational research for over 30 years, and both melanocyte stress and immune mechanisms have been thought to be mutually exclusive explanations for pathogenesis. Chemical-induced vitiligo is a unique clinical presentation that reflects the importance of environmental influences on autoimmunity, provides insight into a new paradigm linking cell stress to the immune response, and serves as a template for other autoimmune diseases. In this review, I will discuss the evidence for cell stress contributions to a number of autoimmune diseases, the questions that remain, and how vitiligo, an underappreciated example of organ-specific autoimmunity, helps to answer them.

Heat shock protein 70 (Hsp70) interacts with the Notch1 intracellular domain and contributes to the activity of Notch signaling in myelin-reactive CD4 T cells

Notch receptors (Notch1-4) are involved in the differentiation of CD4 T cells and the development of autoimmunity. Mechanisms regulating Notch signaling in CD4 T cells are not fully elucidated. In this study we investigated potential crosstalk between Notch pathway molecules and heat shock protein 70 (Hsp70), the major intracellular chaperone involved in the protein transport during immune responses and other stress conditions. Using Hsp70(-/-) mice we found that Hsp70 is critical for up-regulation of NICD1 and induction of Notch target genes in Jagged1- and Delta-like1-stimulated CD4 T cells. Co-immunoprecipitation analysis of wild-type CD4 T cells stimulated with either Jagged1 or Delta-like1 showed a direct interaction between NICD1 and Hsp70. Both molecules co-localized within the nucleus of CD4 T cells stimulated with Notch ligands. Molecular interaction and nuclear colocalization of NICD1 and Hsp70 were also detected in CD4 T cells reactive against myelin oligodendrocyte glycoprotein (MOG)35-55, which showed Hsp70-dependent up-regulation of both NICD1 and Notch target genes. In conclusion, we demonstrate for the first time that Hsp70 interacts with NICD1 and contributes to the activity of Notch signaling in CD4 T cells. Interaction between Hsp70 and NICD1 may represent a novel mechanism regulating Notch signaling in activated CD4 T cells.

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.

Hsp70 regulates immune response in experimental autoimmune encephalomyelitis

Heat shock protein (Hsp)70 is one of the most important stress-inducible proteins. Intracellular Hsp70 not only mediates chaperone-cytoprotective functions but can also block multiple steps in the apoptosis pathway. In addition, Hsp70 is actively released into the extracellular milieu, thereby promoting innate and adaptive immune responses. Thus, Hsp70 may be a critical molecule in multiple sclerosis (MS) pathogenesis and a potential target in this disease due to its immunological and cytoprotective functions. To investigate the role of Hsp70 in MS pathogenesis, we examined its immune and cytoprotective roles using both in vitro and in vivo experimental procedures. We found that Hsp70.1-deficient mice were more resistant to developing experimental autoimmune encephalomyelitis (EAE) compared with their wild-type (WT) littermates, suggesting that Hsp70.1 plays a critical role in promoting an effective myelin oligodendrocyte glycoprotein (MOG)-specific T cell response. Conversely, Hsp70.1-deficient mice that developed EAE showed an increased level of autoreactive T cells to achieve the same production of cytokines compared with the WT mice. Although a neuroprotective role of HSP70 has been suggested, Hsp70.1-deficient mice that developed EAE did not exhibit increased demyelination compared with the control mice. Accordingly, Hsp70 deficiency did not influence the vulnerability to apoptosis of oligodendrocyte precursor cells (OPCs) in culture. Thus, the immunological role of Hsp70 may be relevant in EAE, and specific therapies down-regulating Hsp70 expression may be a promising approach to reduce the early autoimmune response in MS patients.

Up-regulation of inducible heat shock protein-70 expression in multiple sclerosis patients

Inducible heat shock protein (HSP)70 (HSP70-1A and HSP70-1B proteins) is a chaperone responsible for assisting proper protein folding. Following stress conditions, HSP70 is highly up-regulated to mediate cytoprotective functions. In addition, HSP70 is able to trigger innate and adaptive immune responses that promote the immune recognition of antigens and to act as a cytokine when it is released. The data in the literature are controversial with regard to expression studies in peripheral blood mononuclear cells (PBMCs). In the present study, we aimed to examine if alterations of HSP70-1A/B expression are involved in the autoimmune pathogenesis of multiple sclerosis (MS). We determined both mRNA and protein expression in PBMCs of MS patients and healthy donors (HDs). We found a baseline increased expression of the HSPA1A gene in PBMCs from MS patients compared with HDs. Gene expression findings were associated with an increased protein expression of HSP70-1A/B in T lymphocytes (CD4+ and CD8+) and monocytes from MS patients under basal conditions that may reflect the immunological activation occurring in MS patients. We also provided evidence that heat shock (HS) stimulus induced HSP70-1A/B protein expression in HDs and MS patients, and that HS-induced HSP70-1A/B protein expression in monocytes correlated with the number of T2 lesions at baseline in MS patients. However, after lipopolysaccharide inflammatory stimulus, monocytes from MS patients failed to induce HSP70-1A/B protein expression. Our data hint at altered immune responses in MS and may indicate either a state of chronic stress or increased vulnerability to physiological immune responses in MS patients.

Initial immunopathogenesis of multiple sclerosis: innate immune response

Multiple sclerosis (MS) is an inflammatory, demyelinating, and neurodegenerative disease of the central nervous system. The hallmark to MS is the demyelinated plaque, which consists of a well-demarcated hypocellular area characterized by the loss of myelin, the formation of astrocytic scars, and the mononuclear cell infiltrates concentrated in perivascular spaces composed of T cells, B lymphocytes, plasma cells, and macrophages. Activation of resident cells initiates an inflammatory cascade, leading to tissue destruction, demyelination, and neurological deficit. The immunological phenomena that lead to the activation of autoreactive T cells to myelin sheath components are the result of multiple and complex interactions between environment and genetic background conferring individual susceptibility. Within the CNS, an increase of TLR expression during MS is observed, even in the absence of any apparent microbial involvement. In the present review, we focus on the role of the innate immune system, the first line of defense of the organism, as promoter and mediator of cross reactions that generate molecular mimicry triggering the inflammatory response through an adaptive cytotoxic response 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.

Elevated HSP27 levels during attacks in patients with multiple sclerosis

OBJECTIVES

The small heat shock protein, HSP27, has been shown to have a more potent protective effect in the nervous system. However, there is limited information about the behavior of HSP27 in the course of multiple sclerosis (MS). Thus, we investigated the HSP27 levels during relapse and remission phases of MS.

MATERIALS AND METHODS

A total of 50 relapsing-remitting or secondary progressive MS patients and 45 age- and gender-matched controls without any systemic diseases were enrolled. HSP27 levels were serologically detected in serum samples of both controls and MS patients during acute attacks and after a minimum of 2 months of each individual attack.

RESULTS

The mean HSP27 level was 12.41 ± 18.21 ng/ml in the attack phase, 4.58 ± 4.75 ng/ml during remission, and 2.58 ± 3.88 ng/ml in control patients. The heat shock proteins (HSP) levels of MS patients in the attack phase were significantly higher than those obtained in the remission phase (P = 0.005). Moreover, HSP levels in the attack and remission phases of MS patients were also significantly higher when compared to controls (P = 0.001 and P = 0.03, respectively). While there was no correlation between HSP27 levels in the attack phase and age, disease duration, or expanded disability status scale scores (P = 0.69, P = 0.32, and P = 0.91, respectively), a positive correlation was observed between the HSP27 levels and the total attack number (P = 0.001).

CONCLUSIONS

Our findings revealed a marked elevation in HSP27 levels during the relapse phase. Therefore, it can be suggested that elevated HSP27 levels may guide in the accurate detection of an attack in patients with MS.

Heat shock protein 70/peptide complexes: potent mediators for the generation of antiviral T cells particularly with regard to low precursor frequencies

Background

Heat shock protein 70 (HSP70) has gained major attention as an adjuvant capable of inducing antigen-specific CD8⁺ and CD4⁺ T-cell responses. The ability of HSP70/peptide complexes to elicit cytotoxic T-cell (CTL) responses by cross-presentation of exogenous antigens via HLA class I molecules is of central interest in immunotherapy. We examined the role of HSP70/CMVpp65_495-503-peptide complex (HSP70/CMV-PC) in HLA class I-restricted cross-presentation for ex vivo expansion of CMV-specific CTLs.

Methods

CMV-specific T cells generated from PBMCs of HLA-A*02:01/CMV-seropositive donors were stimulated for 21 days with HSP70/CMV-PC and analyzed in functional assays. As a control PBMCs were cultured in the presence of CMVpp65_495-503 peptide or HSP70. Increase of CMV-specific CTLs was visualized by pentameric HLA-A*02:01/CMVpp65_495-503 complex.

Results

About 90% of HSP70/CMV-PC generated T cells were CMV-specific and exhibited significantly higher IFN-γ secretion, cytotoxic activity, and an increased heme oxygenase 1 (HO-1) gene expression as compared to about 69% of those stimulated with CMVpp65_495-503 peptide. We decided to classify the HLA-A*02:01/CMV-seropositive donors as weak, medium, and strong responder according to the frequency of generated A2/CMV-pentamer-positive CD8⁺ T cells. HSP70/CMV-PC significantly induces strong antiviral T-cell responses especially in those donors with low memory precursor frequencies. Blockage of CD91 with α2-macroglobulin markedly reduced proliferation of antiviral T cells suggesting a major role of this receptor in the uptake of HSP70/CMV-PC.

Conclusion

This study clearly demonstrates that HSP70/CMV-PC is a potent mediator to induce stronger T-cell responses compared to antiviral peptides. This simple and efficient technique may help to generate significant quantities of antiviral CTLs by cross-presentation. Thus, we propose HSP70 for chaperoning peptides to reach an efficient level of cross-presentation. HSP70/peptide complexes may be particularly useful to generate stronger T-cell responses in cases of low precursor frequencies and may help to improve the efficiency of antigen-specific T-cell therapy for minor antigens.

Aberrant stress-induced Hsp70 expression in immune cells in multiple sclerosis

Heat shock protein 70 (Hsp70), a prominent member of the heat shock protein family, is a stress-induced chaperone, contributing to the "protein triage" mechanism. However, we and others have previously shown that chaperonin activity of Hsp70 also promotes immune recognition of protein/peptide antigens, including myelin autoantigens. Hsp70 has been strikingly elevated in multiple sclerosis (MS) lesions. In a search for the mechanism of Hsp70 up-regulation in MS, we analyzed Hsp70 expression in peripheral blood mononuclear cells (PBMCs) from MS patients (n = 49), healthy controls (n = 40), and patients with rheumatoid arthritis, (RA; n = 13). Hsp70 was detected by Western blot, and Hsp70 levels were quantified by ELISA. We found that Hsp70 was expressed at low levels in ex vivo PBMCs. However, after heat shock, Hsp70 was up-regulated significantly more (up to sixfold) in MS patients compared with healthy controls. This significant overproduction of Hsp70 was also seen following another stress condition, LPS stimulation. Hsp70 is a product of several independent genes, and we found the HSPA1B gene product to be the major form responsible for Hsp70 protein overexpression in PBMCs. Hsp70 overexpression was preceded by increased nuclear presence of heat shock factor 1 (HSF1). HSF1 activation depends on phosphorylation, and we found that inhibition of the A group of protein kinase C isoenzymes significantly reduced inducible Hsp70 production. These results indicate that immune cells from MS patients are more prone to Hsp70 induction under stress conditions, suggesting a possible link between Hsp70 overexpression and development of autoimmunity.

A novel unbiased proteomic approach to detect the reactivity of cerebrospinal fluid in neurological diseases

Neurodegenerative diseases, such as multiple sclerosis represent global health issues. Accordingly, there is an urgent need to understand the pathogenesis of this and other central nervous system disorders, so that more effective therapeutics can be developed. Cerebrospinal fluid is a potential source of important reporter molecules released from various cell types as a result of central nervous system pathology. Here, we report the development of an unbiased approach for the detection of reactive cerebrospinal fluid molecules and target brain proteins from patients with multiple sclerosis. To help identify molecules that may serve as clinical biomarkers for multiple sclerosis, we have biotinylated proteins present in the cerebrospinal fluid and tested their reactivity against brain homogenate as well as myelin and myelin-axolemmal complexes. Proteins were separated by two-dimensional gel electrophoresis, blotted onto membranes and probed separately with biotinylated unprocessed cerebrospinal fluid samples. Protein spots that reacted to two or more multiple sclerosis-cerebrospinal fluids were further analyzed by matrix assisted laser desorption ionization-time-of-flight time-of-flight mass spectrometry. In addition to previously reported proteins found in multiple sclerosis cerebrospinal fluid, such as αβ crystallin, enolase, and 14-3-3-protein, we have identified several additional molecules involved in mitochondrial and energy metabolism, myelin gene expression and/or cytoskeletal organization. These include aspartate aminotransferase, cyclophilin-A, quaking protein, collapsin response mediator protein-2, ubiquitin carboxy-terminal hydrolase L1, and cofilin. To further validate these findings, the cellular expression pattern of collapsin response mediator protein-2 and ubiquitin carboxy-terminal hydrolase L1 were investigated in human chronic-active MS lesions by immunohistochemistry. The observation that in multiple sclerosis lesions phosphorylated collapsin response mediator protein-2 was increased, whereas Ubiquitin carboxy-terminal hydrolase L1 was down-regulated, not only highlights the importance of these molecules in the pathology of this disease, but also illustrates the use of our approach in attempting to decipher the complex pathological processes leading to multiple sclerosis and other neurodegenerative diseases.

Hsp70 and its molecular role in nervous system diseases

Heat shock proteins (HSPs) are induced in response to many injuries including stroke, neurodegenerative disease, epilepsy, and trauma. The overexpression of one HSP in particular, Hsp70, serves a protective role in several different models of nervous system injury, but has also been linked to a deleterious role in some diseases. Hsp70 functions as a chaperone and protects neurons from protein aggregation and toxicity (Parkinson disease, Alzheimer disease, polyglutamine diseases, and amyotrophic lateral sclerosis), protects cells from apoptosis (Parkinson disease), is a stress marker (temporal lobe epilepsy), protects cells from inflammation (cerebral ischemic injury), has an adjuvant role in antigen presentation and is involved in the immune response in autoimmune disease (multiple sclerosis). The worldwide incidence of neurodegenerative diseases is high. As neurodegenerative diseases disproportionately affect older individuals, disease-related morbidity has increased along with the general increase in longevity. An understanding of the underlying mechanisms that lead to neurodegeneration is key to identifying methods of prevention and treatment. Investigators have observed protective effects of HSPs induced by preconditioning, overexpression, or drugs in a variety of models of brain disease. Experimental data suggest that manipulation of the cellular stress response may offer strategies to protect the brain during progression of neurodegenerative disease.

Molecular architecture of myelinated peripheral nerves is supported by calorie restriction with aging

Peripheral nerves from aged animals exhibit features of degeneration, including marked fiber loss, morphological irregularities in myelinated axons and notable reduction in the expression of myelin proteins. To investigate how protein homeostatic mechanisms change with age within the peripheral nervous system, we isolated Schwann cells from the sciatic nerves of young and old rats. The responsiveness of cells from aged nerves to stress stimuli is weakened, which in part may account for the observed age-associated alterations in glial and axonal proteins in vivo. Although calorie restriction is known to slow the aging process in the central nervous system, its influence on peripheral nerves has not been investigated in detail. To determine if dietary restriction is beneficial for peripheral nerve health and glial function, we studied sciatic nerves from rats of four distinct ages (8, 18, 29 and 38 months) kept on an ad libitum (AL) or a 40% calorie restricted diet. Age-associated reduction in the expression of the major myelin proteins and widening of the nodes of Ranvier are attenuated by the dietary intervention, which is paralleled with the maintenance of a differentiated Schwann cell phenotype. The improvements in nerve architecture with diet restriction, in part, are underlined by sustained expression of protein chaperones and markers of the autophagy-lysosomal pathway. Together, the in vitro and in vivo results suggest that there might be an age-limit by which dietary intervention needs to be initiated to elicit a beneficial response on peripheral nerve health.

A heat shock protein gene (Hsp70.1) is critically involved in the generation of the immune response to myelin antigen

Protracted inflammation has been associated with the generation of autoimmune responses. In this respect, increase in the chaperonin, heat shock protein 70 (hsp70) is an outcome of prolonged inflammatory stress. Previous experiments have shown that overexpression of inducible hsp70 in vitro enhanced myelin autoantigen recognition. To prove the role of hsp70 in myelin-directed responses in vivo, we applied a mouse deficient in the major gene encoding inducible hsp70, hsp70.1. Hsp70.1(-/-) mice sensitized for experimental autoimmune encephalomyelitis (EAE) with myelin oligodendrocyte glycoprotein (MOG) peptide 35-55, displayed almost complete resistance to the disease. This correlated with the loss of T cell proliferation and IFN-gamma production in response to MOG(35-55). T cell transfer experiments as well as antigen presentation assays in vitro demonstrated that hsp70 deficiency was associated with dysfunction in the activation of autoreactive T cells. Moreover, T cell responses to ovalbumin (OVA) peptide 323-339 were altered and CD4(+) T cells were more prone to TCR-induced apoptosis, suggesting broader spectrum of T cell defect in hsp70.1(-/-) mice. These results provide compelling evidence for generalized effect mediated by inducible hsp70 in the recognition of myelin self and non-self antigens that influences the cytokine profile of the immune response affecting autoimmune demyelination.

Pharmacological induction of the heat shock response improves myelination in a neuropathic model

Misexpression and intracellular retention of peripheral myelin protein 22 (PMP22) is associated with hereditary neuropathies in humans, including Charcot-Marie-Tooth disease type 1A (CMT1A). Mice expressing extra copies of the human PMP22, termed C22, display morphologic and behavioral characteristics of CMT1A. In neuropathic Schwann cells, the turnover of the newly-synthesized PMP22 is decreased, leading to the formation of cytosolic protein aggregates. To aid the processing of PMP22 and alleviate the associated myelin defects, we pharmacologically stimulated the expression of protein chaperones by synthetic small-molecule inhibitors of heat shock protein 90 (HSP90). The exposure of Schwann cells to these compounds enhanced the levels of cytosolic chaperones in a time- and dose-dependent manner, with minimal cytotoxicity. Treatment of dorsal root ganglion (DRG) explants from neuropathic mice improved myelin formation and the processing of PMP22. These results warrant further studies with HSP90 inhibitors as potential therapeutic candidates for hereditary demyelinating neuropathies.