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

Targeting Fibronectin to Overcome Remyelination Failure in Multiple Sclerosis: The Need for Brain- and Lesion-Targeted Drug Delivery

Multiple sclerosis (MS) is a neuroinflammatory and neurodegenerative disease with unknown etiology that can be characterized by the presence of demyelinated lesions. Prevailing treatment protocols in MS rely on the modulation of the inflammatory process but do not impact disease progression. Remyelination is an essential factor for both axonal survival and functional neurological recovery but is often insufficient. The extracellular matrix protein fibronectin contributes to the inhibitory environment created in MS lesions and likely plays a causative role in remyelination failure. The presence of the blood–brain barrier (BBB) hinders the delivery of remyelination therapeutics to lesions. Therefore, therapeutic interventions to normalize the pathogenic MS lesion environment need to be able to cross the BBB. In this review, we outline the multifaceted roles of fibronectin in MS pathogenesis and discuss promising therapeutic targets and agents to overcome fibronectin-mediated inhibition of remyelination. In addition, to pave the way for clinical use, we reflect on opportunities to deliver MS therapeutics to lesions through the utilization of nanomedicine and discuss strategies to deliver fibronectin-directed therapeutics across the BBB. The use of well-designed nanocarriers with appropriate surface functionalization to cross the BBB and target the lesion sites is recommended.

The interaction of heat shock proteins with cellular membranes: a historical perspective

The interaction of heat shock proteins (HSP) with cellular membranes has been an enigmatic process, initially observed by morphological studies, inferred during the purification of HSP70s, and confirmed after the detection of these proteins on the surface of cancer cells and their insertion into artificial lipid bilayers. Today, the association of several HSP with lipid membranes is well established. However, the mechanisms for membrane insertion have been elusive. There is conclusive evidence indicating that HSP70s have a great selectivity for negatively charged phospholipids, whereas other HSP have a broader spectrum of lipid specificity. HSP70 also oligomerizes upon membrane insertion, forming ion conductance channels. The functional role of HSP70 lipid interactions appears related to membrane stabilization that may play a role during cell membrane biogenesis. They could also play a role as membrane chaperones as well as during endocytosis, microautophagy, and signal transduction. Moreover, HSP membrane association is a key component in the extracellular export of these proteins. The presence of HSP70 on the surface of cancer cells and its interaction with lysosome membranes have been envisioned as potential therapeutic targets. Thus, the biology and function of HSP membrane association are reaching a new level of excitement. This review is an attempt to preserve the recollection of the pioneering contributions of many investigators that have participated in this endeavor.

Functions and Therapeutic Potential of Extracellular Hsp60, Hsp70, and Hsp90 in Neuroinflammatory Disorders

Neuroinflammation is implicated in central nervous system (CNS) diseases, but the molecular mechanisms involved are poorly understood. Progress may be accelerated by developing a comprehensive view of the pathogenesis of CNS disorders, including the immune and the chaperone systems (IS and CS). The latter consists of the molecular chaperones; cochaperones; and chaperone cofactors, interactors, and receptors of an organism and its main collaborators in maintaining protein homeostasis (canonical function) are the ubiquitin–proteasome system and chaperone-mediated autophagy. The CS has also noncanonical functions, for instance, modulation of the IS with induction of proinflammatory cytokines. This deserves investigation because it may be at the core of neuroinflammation, and elucidation of its mechanism will open roads toward developing efficacious treatments centered on molecular chaperones (i.e., chaperonotherapy). Here, we discuss information available on the role of three members of the CS—heat shock protein (Hsp)60, Hsp70, and Hsp90—in IS modulation and neuroinflammation. These three chaperones occur intra- and extracellularly, with the latter being the most likely involved in neuroinflammation because they can interact with the IS. We discuss some of the interactions, their consequences, and the molecules involved but many aspects are still incompletely elucidated, and we hope that this review will encourage research based on the data presented to pave the way for the development of chaperonotherapy. This may consist of blocking a chaperone that promotes destructive neuroinflammation or replacing or boosting a defective chaperone with cytoprotective activity against neurodegeneration.

Focal adhesion ribonucleoprotein complex proteins are major humoral cancer antigens and targets in autoimmune diseases

Despite the accumulating evidences of the significance of humoral cancer immunity, its molecular mechanisms have largely remained elusive. Here we show that B-cell repertoire sequencing of 102 clinical gastric cancers and molecular biological analyses unexpectedly reveal that the major humoral cancer antigens are not case-specific neo-antigens but are rather commonly identified as ribonucleoproteins (RNPs) in the focal adhesion complex. These common antigens are shared as autoantigens with multiple autoimmune diseases, suggesting a direct molecular link between cancer- and auto-immunity on the focal adhesion RNP complex. This complex is partially exposed to the outside of cancer cell surfaces, which directly evokes humoral immunity and enables functional bindings of antibodies to cancer cell surfaces in physiological conditions. These findings shed light on humoral cancer immunity in that it commonly targets cellular components fundamental for cytoskeletal integrity and cell movement, pointing to a novel modality of immunotherapy using humoral immunological reactions to cancers.

Transcriptome analysis of normal-appearing white matter reveals cortisol- and disease-associated gene expression profiles in multiple sclerosis

Inter-individual differences in cortisol production by the hypothalamus–pituitary–adrenal (HPA) axis are thought to contribute to clinical and pathological heterogeneity of multiple sclerosis (MS). At the same time, accumulating evidence indicates that MS pathogenesis may originate in the normal-appearing white matter (NAWM). Therefore, we performed a genome-wide transcriptional analysis, by Agilent microarray, of post-mortem NAWM of 9 control subjects and 18 MS patients to investigate to what extent gene expression reflects disease heterogeneity and HPA-axis activity. Activity of the HPA axis was determined by cortisol levels in cerebrospinal fluid and by numbers of corticotropin-releasing neurons in the hypothalamus, while duration of MS and time to EDSS6 served as indicator of disease severity. Applying weighted gene co-expression network analysis led to the identification of a range of gene modules with highly similar co-expression patterns that strongly correlated with various indicators of HPA-axis activity and/or severity of MS. Interestingly, molecular profiles associated with relatively mild MS and high HPA-axis activity were characterized by increased expression of genes that actively regulate inflammation and by molecules involved in myelination, anti-oxidative mechanism, and neuroprotection. Additionally, group-wise comparisons of gene expression in white matter from control subjects and NAWM from (subpopulations of) MS patients uncovered disease-associated gene expression as well as strongly up- or downregulated genes in patients with relatively benign MS and/or high HPA-axis activity, with many differentially expressed genes being previously undescribed in the context of MS. Overall, the data suggest that HPA-axis activity strongly impacts on molecular mechanisms in NAWM of MS patients, but partly also independently of disease severity.

Fibronectin aggregates promote features of a classically and alternatively activated phenotype in macrophages

BACKGROUND

Means to promote endogenous remyelination in multiple sclerosis (MS) benefit from insights into the role of inhibitory molecules that preclude remyelination. Fibronectin assembles into aggregates in MS, which impair oligodendrocyte differentiation and remyelination. Microglia and macrophages are required for complete remyelination and normally switch from a pro-inflammatory classical phenotype upon demyelination to a supportive alternative phenotype during remyelination. Here, we investigated the role of fibronectin aggregates in modulating microglia and macrophage behavior and phenotypes.

METHODS

Bone marrow-derived macrophages and microglia from newborn rats were exposed to (a) plasma fibronectin coatings; (b) coatings of deoxycholate-insoluble fibronectin aggregates; (c) interferon-γ (IFNγ) treatment, as an inducer of the pro-inflammatory classically activated phenotype; (d) interleukin-4 (IL-4) treatment, to promote the pro-regenerative anti-inflammatory alternatively activated phenotype; or (e) left unstimulated on uncoated plastic. To examine the in vitro effects of the different stimulations on cell behavior and phenotype, proliferation, phagocytosis, morphology, and pro- and anti-inflammatory features were assessed.

RESULTS

In line with a classically activated phenotype, exposure of microglia and macrophages to both plasma fibronectin and fibronectin aggregates induced an amoeboid morphology and stimulated phagocytosis by macrophages. Furthermore, as observed upon IFNγ treatment, coatings of aggregated, but not plasma fibronectin, promoted nitric oxide release by microglia and macrophages. Remarkably, fibronectin aggregates induced nitric oxide release in an integrin-independent manner. In addition, fibronectin aggregates, but not plasma fibronectin, increased the expression of arginase-1, similarly as observed upon treatment with IL-4. Proteomic analysis revealed that aggregates of fibronectin act as a scaffold for other proteins, including Hsp70 and thrombospondin-1, which may clarify the induction of both pro-inflammatory and anti-inflammatory features in macrophages cultured on fibronectin aggregate, but not plasma fibronectin coatings.

CONCLUSIONS

Macrophages and microglia grown on aggregated fibronectin coatings adopt a distinct phenotype compared to plasma fibronectin coatings, showing pro-inflammatory and anti-inflammatory features. Therefore, the pathological fibronectin aggregates in MS lesions may impair remyelination by promoting and/or retaining several classically activated phenotypic features in microglia and macrophages.

Dissociation of eIF4E-binding protein 2 (4E-BP2) from eIF4E independent of Thr37/Thr46 phosphorylation in the ischemic stress response

Eukaryotic initiation factor (eIF) 4E-binding proteins (4E-BPs) are translational repressors that bind specifically to eIF4E and are critical in the control of protein translation. 4E-BP2 is the predominant 4E-BP expressed in the brain, but their role is not well known. Here, we characterized four forms of 4E-BP2 detected by two-dimensional gel electrophoresis (2-DGE) in brain. The form with highest electrophoretic mobility was the main form susceptible to phosphorylation at Thr³⁷/Thr⁴⁶ sites, phosphorylation that was detected in acidic spots. Cerebral ischemia and subsequent reperfusion induced dephosphorylation and phosphorylation of 4E-BP2 at Thr³⁷/Thr⁴⁶, respectively. The induced phosphorylation was in parallel with the release of 4E-BP2 from eIF4E, although two of the phosphorylated 4E-BP2 forms were bound to eIF4E. Upon long-term reperfusion, there was a decrease in the binding of 4E-BP2 to eIF4E in cerebral cortex, demonstrated by cap binding assays and 4E-BP2-immunoprecipitation experiments. The release of 4E-BP2 from eIF4E was without changes in 4E-BP2 phosphorylation or other post-translational modification recognized by 2-DGE. These findings demonstrated specific changes in 4E-BP2/eIF4E association dependent and independent of 4E-BP2 phosphorylation. The last result supports the notion that phosphorylation may not be the uniquely regulation for the binding of 4E-BP2 to eIF4E under ischemic stress.

Hsp90 binds directly to fibronectin (FN) and inhibition reduces the extracellular fibronectin matrix in breast cancer cells

Heat shock protein 90 (Hsp90) has been identified in the extracellular space and has been shown to chaperone a finite number of extracellular proteins involved in cell migration and invasion. We used chemical cross-linking and immunoprecipitation followed by tandem mass spectrometry (MS/MS) to isolate a complex containing Hsp90 and the matrix protein fibronectin (FN) from breast cancer cells. Further analysis showed direct binding of Hsp90 to FN using an in vitro co-immunoprecipitation assay, a solid phase binding assay and surface plasmon resonance (SPR) spectroscopy. Confocal microscopy showed regions of co-localisation of Hsp90 and FN in breast cancer cell lines. Exogenous Hsp90β was shown to increase the formation of extracellular FN matrix in the Hs578T cell line, whilst knockdown or inhibition of Hsp90 led to a reduction in the levels of both soluble and insoluble FN and could be partially rescued by addition of exogenous Hsp90β. Treatment of cells with novobiocin led to internalization of FN into vesicles that were positive for the presence of the lysosomal marker, LAMP-1. Taken together, the direct interaction between FN and Hsp90, as well as the decreased levels of both soluble and insoluble FN upon Hsp90 inhibition or knockdown, suggested that FN may be a new client protein for Hsp90 and that Hsp90 was involved in FN matrix assembly and/or stability. The identification of FN as a putative client protein of Hsp90 suggests a role for Hsp90 in FN matrix stability, which is important for a number of fundamental cellular processes including embryogenesis, wound healing, cell migration and metastasis.

Investigation of autoantibody profiles for cerebrospinal fluid biomarker discovery in patients with relapsing-remitting multiple sclerosis

Using the UNIarray® marker technology platform, cerebrospinal fluid immunoglobulin G reactivities of 15 controls and 17 RRMS patients against human recombinant proteins were investigated. Patient cerebrospinal fluids were oligoclonal band positive and reactivities were compared to that of sex- and age-matched controls. We hereby aimed at the characterization of autoreactivity in patients with RRMS. Differences in autoreactivities between control and RRMS samples were identified comprising autoantigens identified in this study only and previously reported autoantigens as well. A combination of the 10-15 most significant proteins may be investigated further as autoantigens for diagnostic purposes. Additional investigations may include minimizing the number of proteins used in such diagnostic tests.

Identification of in vivo HSP90-interacting proteins reveals modularity of HSP90 complexes is dependent on the environment in psychrophilic bacteria

Heat shock protein 90 (HSP90) is a conserved molecular chaperone that functions as part of complexes in which different client proteins target it to diverse sets of substrates. In this paper, HSP90 complexes were investigated in γ-proteobacteria from mild (Shewanella oneidensis) and cold environments (Shewanella frigidimarina and Psychrobacter frigidicola), to determine changes in HSP90 interactions with client proteins in response to the adaptation to cold environments. HSP90 participation in cold adaptation was determined using the specific inhibitor 17-allylamino-geldanamycin. Then, HSP90 was immunoprecipitated from bacterial cultures, and the proteins in HSP90 complexes were analyzed by two-dimensional gel electrophoresis and identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. According to HSP90-associated protein analysis, only 15 common proteins were found in both species from the same genus, S. oneidensis and S. frigidimarina, whereas a significant higher number of common proteins were found in both psychrophilic species S. frigidimarina and P. frigidicola 21 (p < 0.001). Only two HSP90-interacting proteins, the chaperone proteins DnaK and GroEL, were common to the three species. Interestingly, some proteins related to energy metabolism (isocitrate lyase, succinyl-CoA synthetase, alcohol dehydrogenase, NAD(+) synthase, and malate dehydrogenase) and some translation factors only interacted with HSP90 in psychrophilic bacteria. We can conclude that HSP90 and HSP90-associated proteins might take part in the mechanism of adaptation to cold environments, and interestingly, organisms living in similar environments conserve similar potential HSP90 interactors in opposition to phylogenetically closely related organisms of the same genus but from different environments.

New hierarchical phosphorylation pathway of the translational repressor eIF4E-binding protein 1 (4E-BP1) in ischemia-reperfusion stress

Eukaryotic initiation factor (eIF) 4E-binding protein 1 (4E-BP1) is a translational repressor that is characterized by its capacity to bind specifically to eIF4E and inhibit its interaction with eIF4G. Phosphorylation of 4E-BP1 regulates eIF4E availability, and therefore, cap-dependent translation, in cell stress. This study reports a physiological study of 4E-BP1 regulation by phosphorylation using control conditions and a stress-induced translational repression condition, ischemia-reperfusion (IR) stress, in brain tissue. In control conditions, 4E-BP1 was found in four phosphorylation states that were detected by two-dimensional gel electrophoresis and Western blotting, which corresponded to Thr⁶⁹-phosphorylated alone, Thr⁶⁹- and Thr³⁶/Thr⁴⁵-phosphorylated, all these plus Ser⁶⁴ phosphorylation, and dephosphorylation of the sites analyzed. In control or IR conditions, no Thr³⁶/Thr⁴⁵ phosphorylation alone was detected without Thr⁶⁹ phosphorylation, and neither was Ser⁶⁴ phosphorylation without Thr³⁶/Thr⁴⁵/Thr⁶⁹ phosphorylation detected. Ischemic stress induced 4E-BP1 dephosphorylation at Thr⁶⁹, Thr³⁶/Thr⁴⁵, and Ser⁶⁴ residues, with 4E-BP1 remaining phosphorylated at Thr⁶⁹ alone or dephosphorylated. In the subsequent reperfusion, 4E-BP1 phosphorylation was induced at Thr³⁶/Thr⁴⁵ and Ser⁶⁴, in addition to Thr⁶⁹. Changes in 4E-BP1 phosphorylation after IR were according to those found for Akt and mammalian target of rapamycin (mTOR) kinases. These results demonstrate a new hierarchical phosphorylation for 4E-BP1 regulation in which Thr⁶⁹ is phosphorylated first followed by Thr³⁶/Thr⁴⁵ phosphorylation, and Ser⁶⁴ is phosphorylated last. Thr⁶⁹ phosphorylation alone allows binding to eIF4E, and subsequent Thr³⁶/Thr⁴⁵ phosphorylation was sufficient to dissociate 4E-BP1 from eIF4E, which led to eIF4E-4G interaction. These data help to elucidate the physiological role of 4E-BP1 phosphorylation in controlling protein synthesis.

Heat shock proteins: cellular and molecular mechanisms in the central nervous system

Emerging evidence indicates that heat shock proteins (HSPs) are critical regulators in normal neural physiological function as well as in cell stress responses. The functions of HSPs represent an enormous and diverse range of cellular activities, far beyond the originally identified roles in protein folding and chaperoning. HSPs are now understood to be involved in processes such as synaptic transmission, autophagy, ER stress response, protein kinase and cell death signaling. In addition, manipulation of HSPs has robust effects on the fate of cells in neurological injury and disease states. The ongoing exploration of multiple HSP superfamilies has underscored the pluripotent nature of HSPs in the cellular context, and has demanded the recent revamping of the nomenclature referring to these families to reflect a re-organization based on structure and function. In keeping with this re-organization, we first discuss the HSP superfamilies in terms of protein structure, regulation, expression and distribution in the brain. We then explore major cellular functions of HSPs that are relevant to neural physiological states, and from there we discuss known and proposed HSP impacts on major neurological disease states. This review article presents a three-part discussion on the array of HSP families relevant to neuronal tissue, their cellular functions, and the exploration of therapeutic targets of these proteins in the context of neurological diseases.

Heat shock protein-90 beta is expressed at the surface of multipotential mesenchymal precursor cells: generation of a novel monoclonal antibody, STRO-4, with specificity for mesenchymal precursor cells from human and ovine tissues

Mesenchymal stromal cells (MSCs) and their precursor cells (MPCs) can proliferate and differentiate into multiple mesodermal and some ectodermal and endodermal tissues. Culture-expanded MSCs are currently being evaluated as a possible cell therapy to replace/repair injured or diseased tissues. While a number of mAb reagents with specificity to human MSCs, including STRO-1, STRO-3 (BLK ALP), CD71 (SH2, SH3), CD106 (VCAM-1), CD166, and CD271, have facilitated the isolation of purified populations of human MSCs from primary tissues, few if any mAb reagents have been described that can be used to isolate equivalent cells from other species. This is of particular relevance when assessing the tissue regenerative efficacy of MSCs in large immunocompetent, preclinical animal models of disease. In light of this, we sought to generate novel monoclonal antibodies (mAb) with specific reactivity against a cell surface molecule that is expressed at high levels by MSCs from different species. Using CD106 (VCAM-1)-selected ovine MSCs as an immunogen, mAb-producing hybridomas were selected for their reactivity to both human and ovine MSCs. One such hybridoma, termed STRO-4, produced an IgG mAb that reacted with <5% of human and ovine bone marrow (BM) mononuclear cells. As a single selection reagent, STRO-4 mAb was able to enrich colony-forming fibroblasts (CFU-F) in both human and ovine BM by 16- and 8-folds, respectively. Cells isolated with STRO-4 exhibited reactivity with markers commonly associated with MSCs isolated by plastic adherence including CD29, CD44, and CD166. Moreover, when placed in inductive culture conditions in vitro, STRO-4(+) MSCs exhibited multilineage differentiation potential and were capable of forming a mineralized matrix, lipid-filled adipocytes, and chondrocytes capable of forming a glycosaminoglycan-rich matrix. Biochemical analysis revealed that STRO-4 identified the beta isoform of heat shock protein-90 (Hsp90beta). In addition to identifying an antibody reagent that identifies a highly conserved epitope expressed by MSCs from different species, our study also points to a potential role for Hsp90beta in MSC biology.

Expression of heat shock protein 90 at the cell surface in human neuroblastoma cells

In addition to the activity of heat shock protein 90 (Hsp90/HSPC) as a chaperone, some recent studies have reported expression of Hsp90 at the cell surface in certain types of cancer and nervous system cells. We study the expression of Hsp90 at the cell surface in human neuroblastoma (NB69) cells. Immunofluorescence experiments labeling with anti-Hsp90 antibodies on both nonpermeabilized cells and live cells detected Hsp90 at the cell surface. Hsp90 was also identified in a membrane fraction from subcellular fractionation. Cell-surface Hsp90 was significantly more expressed in undifferentiated proliferative spherical neuroblastoma cells than in differentiated flattened cells. In addition, spherical cells were significantly more sensitive to Hsp90 inhibitor 17-allylamino-17-demethoxygeldanamycin compared to flattened cells. This paper describes the first evidence of cell-surface Hsp90 expression in a cancer cell line from nervous tissue and may indicate a novel target for anti-tumoral agents.

High cytotoxic sensitivity of the oligodendrocyte precursor cells to HSP90 inhibitors in cell cultures

Oligodendrocyte precursor cells (OPCs) are able to proliferate, and most differentiate into post-mitotic oligodendrocytes that contribute to remyelination. We have previously studied the expression of heat shock protein90 (HSP90) in OPCs. The ansamycins, such as geldanamycin and 17-allylamino-17-demethoxygeldanamycin (17-AAG) act as specific HSP90 inhibitors, are potent anti-tumor agents and are currently undergoing clinical trials. This work investigated the effect of HSP90 inhibitors on cultured OPCs. Geldanamycin, 17-AAG and another chemically unrelated HSP90 inhibitor, radicicol, were extremely cytotoxic for OPCs. The IC50 values of geldanamycin, 17-AAG and radicicol for OPCs were 7.1, 10.7 and 137 nM, respectively, compared to 1000-2000 nM for preoligodendrocytes, astrocytes and neurons. Adult OPCs were found to be susceptible to HSP90 inhibitors in a similar fashion to perinatal cells. OPC death induced by these HSP90 inhibitors led to a significant decrease in the oligodendrocyte population. The present results highlight that OPCs are uniquely sensitive to HSP90 inhibitors. Geldanamycin and 17-AAG, which penetrate the blood-brain barrier, are novel cancer chemotherapeutic agents and we noted that, in anti-cancer therapy with these drugs, the OPCs may be compromised.

Therapeutic potential of statins in multiple sclerosis: immune modulation, neuroprotection and neurorepair

Statins as inhibitors of 3-hydroxy-3-methyl glutaryl coenzyme A reductase are widely used as cholesterol-lowering drugs. Recent studies provide evidence that the anti-inflammatory activity of statins, which is independent of their cholesterol-lowering effects, may have potential therapeutic implications for neuroinflammatory diseases such as multiple sclerosis (MS), Alzheimer's disease and brain tumors, as well as traumatic spinal cord and brain injuries. Studies with animal models of MS suggest that, in addition to immunomodulatory activities similar to the ones observed with approved MS medications, statin treatment also protects the BBB, protects against neurodegeneration and may also promote neurorepair. Although the initial human studies on statin treatment for MS are encouraging, prospective randomized clinical studies will be required to evaluate their efficacy in the larger patient population.

Proteomic characterization of protein phosphatase 1 complexes in ischemia-reperfusion and ischemic tolerance

Serine/threonine protein phosphatase 1 (PP1) regulates multiple cellular processes. Protein phosphorylation-dephosphorylation is largely altered during ischemia and subsequent reperfusion. The brain is particularly vulnerable to stress resulting from ischemia-reperfusion (IR), however, the acquisition of ischemic tolerance (IT) protects against IR stress. We studied PP1 complexes in response to IR stress and IT in brain using proteomic characterization of PP1 complexes in animal models of IR and IT. PP1alpha and PP1gamma were immunoprecipitated and resolved by 2-D. DIGE analysis detected 14 different PP1-interacting proteins that exhibited significant changes in their association with PP1alpha or PP1gamma. These proteins were identified by MALDI-TOF MS. Seven had the PP1-binding RVxF motif. IR altered the interaction of heat shock cognate 71 kDa-protein, creatine kinase B, and dopamine- and cAMP-regulated phosphoprotein 32 kDa (DARPP32) with both PP1alpha and PP1gamma, and the interaction of phosphodiesterase-6B, transitional ER ATPase, lamin-A, glucose-regulated 78 kDa-protein, dihydropyrimidinase-related protein-2, gamma-enolase, neurofilament-L, and ubiquitin ligase SIAH2 with PP1gamma. IT prevented most of the IR-induced effects. This study identifies novel PP1alpha- and PP1gamma-interacting proteins and reveals an in vivo modularity of PP1 holoenzymes in response to physiological ischemic stress. It supports a potential role of PP1 in IR stress and as a target of the endogenous protective mechanisms induced by IT.

Multiple sclerosis: Disease biomarkers as indicated by pathophysiology

Multiple sclerosis (MS), the most important human inflammatory demyelinating disease of the central nervous system, is characterized by heterogenous genetic backgrounds and immunopathogenetic subtypes, various clinical disease courses, and inhomogeneous and unpredictable therapeutic effects. Because of this heterogeneity, subtyping of our MS patients by genetical, clinical, neuroradiological, and neuroimmunological parameters will be an urgent need in the near future. Therefore the importance of identifying biological markers for MS has evolved over the past years. Evidence for a possible role of antibodies as biological markers for MS comes from several studies indicating that intrathecal antibody production and the dominance of B-cells are associated with a more progressive disease course. This review summarizes the current status and potential applicability of antibodies as biological markers for the diagnosis, classification, disease activity and prediction of clinical courses in MS. Antibodies (and other molecules) serving as biomarkers will help to establish a differential therapeutic concept in MS, which should allow to treat individuals selectively according to their pathogenetic subtype and disease status.

Detection of anti-heat shock protein 90 beta (Hsp90beta) antibodies in cerebrospinal fluid

Antibodies against heat shock protein 90 beta (Hsp90beta) recognize the antigen on the cell surface of the oligodendrocyte precursor cells and cause a decrease of oligodendrocyte population in cell cultures. These antibodies have been found in patients with multiple sclerosis (MS). This report describes an original and sensitive method to detect anti-Hsp90beta antibodies in cerebrospinal fluid (CSF) using a western blot procedure. We have developed the method for autoantibody detection using Hsp90beta from cell membrane fraction instead of commercial Hsp90beta as antigen. The presence of anti-Hsp90beta antibodies in CSF of MS patients may play a pathogenic role in MS, and a large-scale study is needed to establish a possible diagnostic value of these antibodies in MS patients.

Multiple sclerosis: an infectious syndrome involving Chlamydophila pneumoniae

The concept of autoimmune myelinopathy as the primary pathology in multiple sclerosis (MS) is problematic. Vasculitis is seen in the MS brain, both within lesions and in adjacent normal-appearing white matter. The first observation in acute relapse is the sudden, orderly death of oligodendrocytes; inflammatory removal of unsupported myelin seems to be a secondary process. An alternative explanation for these findings is that oligodendrocyte infection might trigger an inflammatory response. Many pathogens, including Chlamydophila (Chlamydia) pneumoniae, have been associated with MS. MS might be an infectious syndrome in which C. pneumoniae has a role in a subset of patients. Mechanisms by which such a cryptic infection could engender relapsing-remitting and, ultimately, progressive disease patterns are discussed.

Antibodies as biological markers for pathophysiological processes in MS

Multiple sclerosis (MS), the most important human inflammatory demyelinating disease of the central nervous system, is characterized by various clinical disease courses, inhomogeneous and unpredictable therapeutic effects, heterogenous genetic backgrounds and immunopathogenetic subtypes as demonstrated by neuropathology. Because of this heterogeneity of MS, a subtyping of our patients by genetical, clinical, neuroradiological, and neuroimmunological parameters will be necessary in the future. Therefore the importance of identifying biological markers for MS has evolved over the past years. Evidence for a possible role of antibodies as biological markers for MS comes from several studies indicating that intrathecal antibody production and the dominance of B cells are associated with a more progressive disease course. In this review we will give an overview on the current status and potential applicability of antibodies as biological markers for the diagnosis, classification, disease activity and prediction of clinical courses in MS. We will therefore summarize the findings on autoantibodies to myelin and nonmyelin antigens and on viral antigens in MS. We believe that antibodies serving as biomarkers will help to establish a differential therapeutic concept in MS, which will allow to treat individuals selectively according to their pathogenetic subtype and disease status.

Anti-heat shock protein 90 is increased in acute mania

OBJECTIVE

The aim of this work was to examine autoantibodies in patients with bipolar disorder.

METHOD

We enrolled 94 patients with acute bipolar mania, with 37 of them medicated and 57 unmedicated at the time of blood sampling. The samples also consisted of 44 patients in the remission state and another 48 normal controls. We first used human glioblastoma (U373 MG) cell lysate to screen the potential autoantibodies present in sera of bipolar mania patients, and anti-heat shock protein (anti-HSP) 60, 70 and 90 autoantibodies were identified. We then examined the serum levels of these autoantibodies by enzyme-linked immunosorbent assay.

RESULTS

The findings of this study showed that serum anti-HSP90 level was significantly higher in bipolar patients in acute mania than those in remission (p = 0.002).

CONCLUSIONS

The data of this study suggest that increased anti-HSP90 might be a state marker for acute mania in patients with bipolar disorder.

Anti-heat shock protein 90β antibodies decrease pre-oligodendrocyte population in perinatal and adult cell cultures. Implications for remyelination in multiple sclerosis

Lesions in the CNS of patients with multiple sclerosis (MS) often fail to remyelinate, resulting in neurological dysfunction. A key factor seems to be the inefficiency of oligodendrocyte precursor cells (OPCs). We recently reported antibodies against heat shock protein 90beta (Hsp90beta) in MS patients that recognized the antigen on the OPC surface. This study investigates the mechanism and result of anti-Hsp90beta antibody attack. These antibodies induced OPC death in culture in a complement-dependent fashion. Anti-Hsp90beta antibody-induced, complement-mediated OPC death only operated in these cells and caused a significant reduction in the number of O4-positive pro-oligodendrocytes (pre-oligodendrocytes). Adult cultured OPCs also expressed Hsp90beta on their cell surface and were attacked by anti-Hsp90beta antibodies leading to a significant decrease in the pre-oligodendrocyte population. In the presence of low levels of anti-Hsp90beta antibody--i.e. in the range seen in the CSF of MS patients--the complement concentration was critical to reduce the pre-oligodendrocyte population (via attack to OPCs). Higher concentrations of anti-Hsp90beta antibodies and complement became extinct the pre-oligodendrocytes. Complement 1-esterase inhibitor prevented these effects in the pre-oligodendrocyte population. These findings demonstrate, for the first time in vitro, a feasible mechanism to decrease the production of new oligodendrocytes, thus limiting the possibility of remyelination.

Pathogenesis of multiple sclerosis

PURPOSE OF REVIEW

The aim of this article is to describe recent observations regarding the basis for the initiation and disease evolution of multiple sclerosis.

RECENT FINDINGS

A current debate is where and what initiates the neuroinflammatory reaction that characterizes the acute multiple sclerosis lesion. Immune sensitization to neural antigens could develop within the systemic compartment consequent to exposure to cross-reacting, possibly viral derived, peptides (molecular mimicry). Although CD4 T cells are considered central to initiating central nervous system inflammation, the actual extent and specificity of tissue injury reflects the array of adaptive (CD8 T cells and antibody) and innate (microglia/macrophages) immune constituents present in the lesions. Neuropathologic studies indicate that lethal changes in neural cells (oligodendrocytes) could also be the initiating event, reflecting as yet unidentified acquired insults (e.g. exogenous virus or reactivated endogenous retrovirus) or intrinsic abnormalities ('neurodegenerative' hypothesis). Recurrence or persistence of the disease process can reflect events occurring at multiple sites including expansion of the immune repertoire in response to neural antigens transported to regional lymph nodes (determinant spreading), especially if immune regulatory mechanisms are defective; alterations in blood-brain barrier properties consequent to initial cellular transmigration; and participation of endogenous (microglia, astrocytes) or long lived infiltrating cells (macrophages, B cells in ectopic germinal centers) in regulating and effecting immune functions within the central nervous system. Accumulating neurologic deficit reflects the balance between injury and repair; the latter also being negatively or positively (trophic support and clearance of tissue debris) impacted by inflammatory processes.

SUMMARY

Understanding the full spectrum of multiple sclerosis presents a continuing challenge for both immunology and neurobiology.

Promoting repair in multiple sclerosis: problems and prospects

PURPOSE OF REVIEW

Despite recent progress in treating the inflammatory component of multiple sclerosis, current therapies have no clear impact on progression of disability, which closely relates to tissue (myelin and axon) injury. Many scientists now focus their efforts on elucidating the mechanisms that lead to tissue injury, and on developing new strategies for tissue repair. We review recent breakthroughs in this field and discuss their putative applications to therapy.

RECENT FINDINGS

Several hypotheses have been raised to explain the failure of remyelination, including depletion of remyelinating cells, quiescence of oligodendrocyte precursor cells and axonal inhibitory signals. Success in remyelination therapy may be achieved either by enhancing endogenous repair or by grafting exogenous remyelinating cells. Several neurotrophic factors have been shown to enhance endogenous remyelination, and many immature cells have been shown to induce efficient exogenous remyelination in animal models. Although effective remyelination probably represents the best way to prevent neurodegeneration, several alternative neuroprotective strategies are emerging. Statins, cyclins and immunophilin ligands are orally available immunomodulatory agents that may protect neurones. Other promising possibilities include the modulation of excitotoxicity, nitric oxide synthesis, or cationic channels.

SUMMARY

Despite the increasing number of putative therapeutic targets, no treatment to achieve remyelination or neuroprotection has yielded positive clinical results in humans. Forging a link between basic biology and treatment of patients will require us to overcome several challenges, including assessment of efficacy of repair, improving tolerance to and delivery of neurotrophic factors, and better defining the indications for and limitations of transplantation.

Chronic Lyme borreliosis at the root of multiple sclerosis – is a cure with antibiotics attainable?

Apart from its devastating impact on individuals and their families, multiple sclerosis (MS) creates a huge economic burden for society by mainly afflicting young adults in their most productive years. Although effective strategies for symptom management and disease modifying therapies have evolved, there exists no curative treatment yet. Worldwide, MS prevalence parallels the distribution of the Lyme disease pathogen Borrelia (B.) burgdorferi, and in America and Europe, the birth excesses of those individuals who later in life develop MS exactly mirror the seasonal distributions of Borrelia transmitting Ixodes ticks. In addition to known acute infections, no other disease exhibits equally marked epidemiological clusters by season and locality, nurturing the hope that prevention might ultimately be attainable. As minocycline, tinidazole and hydroxychloroquine are reportedly capable of destroying both the spirochaetal and cystic L-form of B. burgdorferi found in MS brains, there emerges also new hope for those already afflicted. The immunomodulating anti-inflammatory potential of minocycline and hydroxychloroquine may furthermore reduce the Jarisch Herxheimer reaction triggered by decaying Borrelia at treatment initiation. Even in those cases unrelated to B. burgdorferi, minocycline is known for its beneficial effect on several factors considered to be detrimental in MS. Patients receiving a combination of these pharmaceuticals are thus expected to be cured or to have a longer period of remission compared to untreated controls. Although the goal of this rational, cost-effective and potentially curative treatment seems simple enough, the importance of a scientifically sound approach cannot be overemphasised. A randomised, prospective, double blinded trial is necessary in patients from B. burgdorferi endemic areas with established MS and/or Borrelia L-forms in their cerebrospinal fluid, and to yield reasonable significance within due time, the groups must be large enough and preferably taken together in a multi-centre study.

Involvement of cell surface HSP90 in cell migration reveals a novel role in the developing nervous system

Heat shock protein HSP90 plays important roles in cellular regulation, primarily as a chaperone for a number of key intracellular proteins. We report here that the two HSP90 isoforms, alpha and beta, also localize on the surface of cells in the nervous system and are involved in their migration. A 94-kDa surface antigen, the 4C5 antigen, which was previously shown to be involved in migration processes during development of the nervous system, is shown to be identical to HSP90alpha using mass spectrometry analysis. This identity is further confirmed by immunoprecipitation experiments and by induction of 4C5 antigen expression in heat shock-treated embryonic rat brain cultures. Moreover, immunocytochemistry on live cerebellar rat cells reveals cell surface localization of both HSP90alpha and -beta. Cell migration from cerebellar and sciatic nerve explants is inhibited by anti-HSP90alpha and anti-HSP90beta antibodies, similarly to the inhibition observed with monoclonal antibody 4C5. Moreover, immunostaining with rhodamine-phalloidin of migrating Schwann cells cultured in the presence of antibodies against both alpha and beta isoforms of HSP90 reveals that HSP90 activity is associated with actin cytoskeletal organization, necessary for lamellipodia formation.