S100B is expressed in, and released from, OLN-93 oligodendrocytes: Influence of serum and glucose deprivation

Evaluation of the neuroprotective effect of antipsychotics by serum quantification of protein S100B

OBJECTIVE

This research delves into the intricate interplay between antipsychotic medications and neuroprotection focusing on the S100B protein-a central player in the regulation of neuroapoptotic activity.

METHOD

Blood samples were collected to assess serum S100B protein levels using an immunoassay of immunoelectrochemiluminescence. The first two samples were collected with a 3-month interval between each, and the third sample was obtained 6 months after the previous one. Changes in S100B protein levels throughout the study were assessed using Friedman's ANOVA test. This was followed by the Wilcoxon signed-rank test with Bonferroni correction to account for multiple comparisons.

RESULTS

This study involved 40 patients diagnosed with severe mental disorders (34 schizophrenia, 4 schizoaffective disorder, 1 bipolar disorder, and 1 borderline personality disorder). These patients had been receiving antipsychotic treatment for an average duration of 17 years. The results revealed that the S100B protein remained within physiological levels (median values 39.0 ng/L for the first sample, median values 41.0 ng/L for the second sample, and median values 40.5 ng/L for the third sample) with no significant changes (p = 0.287), with all anti-psychotic medicaments values consistently below 50 ng/L, a lower value compared to maximum range of 105 ng/L. Importantly, there were no significant differences in S100B protein levels between patients on monotherapy and those on combination antipsychotic therapy (p = 0.873), suggesting that combination therapy did not increase neuroapoptotic activity.

CONCLUSIONS

These findings provide compelling evidence for the potential neuroprotective effects of long-term antipsychotic treatment in individuals with severe mental disorders. By maintaining physiological levels of the S100B protein, antipsychotic medications may help protect against neuronal damage and dysfunction. This research contributes valuable insights into the neuroprotective mechanisms of antipsychotic drugs, enhancing our understanding of their potential benefits in the treatment of severe mental disorders.

Mind the Metabolic Gap: Bridging Migraine and Alzheimer's disease through Brain Insulin Resistance

Brain insulin resistance has recently been described as a metabolic abnormality of brain glucose homeostasis that has been proven to downregulate insulin receptors, both in astrocytes and neurons, triggering a reduction in glucose uptake and glycogen synthesis. This condition may generate a mismatch between brain's energy reserve and expenditure, mainly during high metabolic demand, which could be involved in the chronification of migraine and, in the long run, at least in certain subsets of patients, in the prodromic phase of Alzheimer's disease, along a putative metabolic physiopathological continuum. Indeed, the persistent disruption of glucose homeostasis and energy supply to neurons may eventually impair protein folding, an energy-requiring process, promoting pathological changes in Alzheimer's disease, such as amyloid-β deposition and tau hyperphosphorylation. Hopefully, the "neuroenergetic hypothesis" presented herein will provide further insight on there being a conceivable metabolic bridge between chronic migraine and Alzheimer's disease, elucidating novel potential targets for the prophylactic treatment of both diseases.

Astroglial S100B Secretion Is Mediated by Ca2+ Mobilization from Endoplasmic Reticulum: A Study Using Forskolin and DMSO as Secretagogues

S100B, a homodimeric Ca2+-binding protein, is produced and secreted by astrocytes, and its extracellular levels have been used as a glial marker in brain damage and neurodegenerative and psychiatric diseases; however, its mechanism of secretion is elusive. We used primary astrocyte cultures and calcium measurements from real-time fluorescence microscopy to investigate the role of intracellular calcium in S100B secretion. In addition, the dimethyl sulfoxide (DMSO) effect on S100B was investigated in vitro and in vivo using Wistar rats. We found that DMSO, a widely used vehicle in biological assays, is a powerful S100B secretagogue, which caused a biphasic response of Ca2+ mobilization. Our data show that astroglial S100B secretion is triggered by the increase in intracellular Ca2+ and indicate that this increase is due to Ca2+ mobilization from the endoplasmic reticulum. Also, blocking plasma membrane Ca2+ channels involved in the Ca2+ replenishment of internal stores decreased S100B secretion. The DMSO-induced S100B secretion was confirmed in vivo and in ex vivo hippocampal slices. Our data support a nonclassic vesicular export of S100B modulated by Ca2+, and the results might contribute to understanding the mechanism underlying the astroglial release of S100B.

Increased cerebrospinal fluid S100B protein levels in patients with trigeminal neuralgia and hemifacial spasm

BACKGROUND

The pathophysiology of neurovascular compression syndrome has not been fully elucidated, and cerebrospinal fluid levels of nerve tissue-related markers involved in this disorder have not yet been reported.

METHODS

We measured cerebrospinal fluid levels of S100B protein, neuron-specific enolase, and myelin basic protein in 21 patients with trigeminal neuralgia, 9 patients with hemifacial spasms, and 10 patients with non-ruptured intracranial aneurysms (control). Cerebrospinal fluid levels of these markers were determined using commercially available assay kits.

RESULTS

Both trigeminal neuralgia and hemifacial spasm groups showed significantly increased cerebrospinal fluid levels of S100B compared with the control group (1120 [IQR 391-1420], 766 [IQR 583-1500], and 255 [IQR 190-285] pg/mL, respectively; p = 0.001). There were no statistically significant differences in cerebrospinal fluid levels of neuron-specific enolase or myelin basic protein among the groups.

CONCLUSION

Cerebrospinal fluid S100B levels were significantly higher in patients with trigeminal neuralgia and hemifacial spasm than in controls, which suggests the involvement of S100B in the underlying pathophysiology of neurovascular compression syndrome.

Astrocyte Activation Markers

Astrocytes are the most common type of glial cells that provide homeostasis and protection of the central nervous system. Important specific characteristic of astrocytes is manifestation of morphological heterogeneity, which is directly dependent on localization in a particular area of the brain. Astrocytes can integrate into neural networks and keep neurons active in various areas of the brain. Moreover, astrocytes express a variety of receptors, channels, and membrane transporters, which underlie their peculiar metabolic activity, and, hence, determine plasticity of the central nervous system during development and aging. Such complex structural and functional organization of astrocytes requires the use of modern methods for their identification and analysis. Considering the important fact that determining the most appropriate marker for polymorphic and multiple subgroups of astrocytes is of decisive importance for studying their multifunctionality, this review presents markers, modern imaging techniques, and identification of astrocytes, which comprise a valuable resource for studying structural and functional properties of astrocytes, as well as facilitate better understanding of the extent to which astrocytes contribute to neuronal activity.

Molecular Characteristics of RAGE and Advances in Small-Molecule Inhibitors

Receptor for advanced glycation end-products (RAGE) is a member of the immunoglobulin superfamily. RAGE binds and mediates cellular responses to a range of DAMPs (damage-associated molecular pattern molecules), such as AGEs, HMGB1, and S100/calgranulins, and as an innate immune sensor, can recognize microbial PAMPs (pathogen-associated molecular pattern molecules), including bacterial LPS, bacterial DNA, and viral and parasitic proteins. RAGE and its ligands stimulate the activations of diverse pathways, such as p38MAPK, ERK1/2, Cdc42/Rac, and JNK, and trigger cascades of diverse signaling events that are involved in a wide spectrum of diseases, including diabetes mellitus, inflammatory, vascular and neurodegenerative diseases, atherothrombosis, and cancer. Thus, the targeted inhibition of RAGE or its ligands is considered an important strategy for the treatment of cancer and chronic inflammatory diseases.

Increased Expression of S100B and RAGE in a Mouse Model of Bile Duct Ligation-induced Liver Fibrosis

BACKGROUND

Liver fibrosis is defined as the accumulation of the extracellular matrix and scar formation. The receptor for advanced glycation end products (RAGE) has been demonstrated to participate in fibrogenesis. S100B is a ligand of RAGE and exerts extracellular functions by inducing a series of signal transduction cascades. However, the involvement of S100B and RAGE in cholestasis-induced liver fibrosis remains unclear. In this study, we investigated S100B and RAGE expression during liver fibrosis in mice that underwent common bile duct ligation (BDL).

METHODS

BDL was performed in 10-week-old male C57BL/6J mice with sham control (n = 26) and BDL (n = 26) groups. Expression levels of S100B, RAGE and fibrotic markers in the livers from both groups at week 1 and 3 after BDL were examined by western blot and quantitative real-time reverse transcription polymerase chain reaction analysis. Liver fibrotic changes were examined by histological and ultrastructural analysis.

RESULTS

Histological staining with Sirius Red and the evaluation of the messenger RNA expression of fibrotic markers showed noticeable periportal fibrosis and bile duct proliferation. S100B was mainly present in bile duct epithelial cells, and its expression was upregulated in proportion to the ductular reaction during fibrogenesis by BDL. RAGE expression was also increased, and interestingly, triple immunofluorescence staining and transmission electron microscopy showed that both S100B and RAGE were expressed in proliferating bile duct epithelial cells and activated hepatic stellate cells (HSCs) of the BDL livers. In addition, in rat HSCs (HSC-T6), treatment with recombinant S100B protein significantly increased fibrotic markers in a dose-dependent manner, and RAGE small interfering RNA (siRNA) suppressed S100B-stimulated upregulation of fibrotic markers compared with cells treated with scramble siRNA and S100B.

CONCLUSION

These findings suggest that the increased expression of S100B and RAGE and the interaction between S100B and RAGE may play an important role in ductular reaction and liver fibrosis induced by BDL.

Regulation of the tubulin polymerization-promoting protein by Ca2+/S100 proteins

To elucidate S100 protein-mediated signaling pathways, we attempted to identify novel binding partners for S100A2 by screening protein arrays carrying 19,676 recombinant glutathione S-transferase (GST)-fused human proteins with biotinylated S100A2. Among newly discovered putative S100A2 interactants, including TMLHE, TRH, RPL36, MRPS34, CDR2L, OIP5, and MED29, we identified and characterized the tubulin polymerization-promoting protein (TPPP) as a novel S100A2-binding protein. We confirmed the interaction of TPPP with Ca²⁺/S100A2 by multiple independent methods, including the protein array method, S100A2 overlay, and pulldown assay in vitro and in transfected COS-7 cells. Based on the results from the S100A2 overlay assay using various GST-TPPP mutants, the S100A2-binding region was identified in the C-terminal (residues 111-160) of the central core domain of a monomeric form of TPPP that is involved in TPPP dimerization. Chemical cross-linking experiments indicated that S100A2 suppresses dimer formation of His-tagged TPPP in a dose-dependent and a Ca²⁺-dependent manner. In addition to S100A2, TPPP dimerization is disrupted by other multiple S100 proteins, including S100A6 and S100B, in a Ca²⁺-dependent manner but not by S100A4. This is consistent with the fact that S100A6 and S100B, but not S100A4, are capable of interacting with GST-TPPP in the presence of Ca²⁺. Considering these results together, TPPP was identified as a novel target for S100A2, and it is a potential binding target for other multiple S100 proteins, including S100A6 and S100B. Direct binding of the S100 proteins with TPPP may cause disassembly of TPPP dimer formation in response to the increasing concentration of intracellular Ca²⁺, thus resulting in the regulation of the physiological function of TPPP, such as microtubule organization.

Loss of Brain-Derived Neurotrophic Factor (BDNF) Resulting From Congenital- Or Mild Traumatic Brain Injury-Induced Blood-Brain Barrier Disruption Correlates With Depressive-Like Behaviour

Brain-derived neurotrophic factor (BDNF) plays an important role in processes associated with neuroplasticity and neuroprotection. Evidence suggests that decreased BDNF levels in the central nervous system (CNS) represent a mechanism underlying the development of mood disorders. We hypothesize that both congenital and traumatic brain injury (mTBI)-induced blood-brain barrier (BBB) breakdown are responsible for brain BDNF depletion that contributes to the development of depressive-like symptoms. We employed a mouse model of innate differences in BBB integrity with high (HA) and low (LA) permeability. Depressive-like behaviours were determined under chronic mild stress (CMS) conditions or following mTBI using the tail suspension test (TST). Microvascular leakage of the BBB was evaluated using the Evans Blue Dye (EBD) extravasation method. BDNF concentrations in the brain and plasma were measured using the ELISA. Control HA mice with congenitally high BBB permeability showed exacerbated depressive-like behaviours compared with LA mice. In LA mice, with normal BBB function, mTBI, but not CMS, facilitated depressive-like behaviours, which correlated with enhanced BDNF efflux from the brain. In addition, mTBI triggered upregulation of the Bdnf gene in LA mice to compensate for BDNF loss. No alterations in BDNF levels were observed in mTBI and CMS-exposed HA mice. Moreover, CMS did not induce BBB damage or affect depressive-like behaviours in HA mice despite downregulating Bdnf gene expression. To conclude, BDNF efflux through the mTBI-disrupted BBB is strongly linked to the development of depressive-like behaviours, while the depressive phenotype in mice with congenital BBB dysfunction is independent of BDNF leakage.

The trends in nanomaterial-based biosensors for detecting critical biomarkers in stroke

Acute ischemic stroke (AIS), is the second global cause of death after cardiovascular diseases, accounts for 80-85% of cerebrovascular disease. Stroke diagnosis could be challenging in the acute phase. Detection of biomarkers for evaluating the prognosis of diseases is essential for improving personalized treatment and decreasing mortality. At the present time, the absence of a broadly existing and rapid diagnostic test is an important limitation in the evaluation and treatment of diseases. The use of a biomarker-based diagnostic attitude has confirmed very valuable in acute coronary syndromes, which has been promoted in acute stroke to help early management decisions. Over the past decade, different detection procedures have developed for the assessment of human cardiac troponins (cTnI). This review emphasizes on summarizing optical, and electrochemical biosensors for the detection of cTnI, brain natriuretic peptide (BNP), and neuron-specific enolase (NSE) as a critical biomarker in stroke.

Does acute soccer heading cause an increase in plasma S100B? A randomized controlled trial

The purpose of this study was to test the effect of subconcussive head impacts on acute changes in plasma S100B. In this randomized controlled trial, 79 healthy adult soccer players were randomly assigned to either the heading (n = 41) or kicking-control groups (n = 38). The heading group executed 10 headers with soccer balls projected at a speed of 25 mph, whereas the kicking-control group performed 10 kicks. Plasma samples were obtained at pre-, 0h post-, 2h post- and 24h post-intervention and measured for S100B. The primary hypothesis was that there would be a significant group difference (group-by-time interaction) in plasma S100B at 2h post-intervention. Secondary hypotheses included (1) no significant group differences in plasma S100B concentrations at 0h post- and 24h post-intervention; (2) a significant within-group increase in S100B concentrations in the heading group at 2h post-intervention compared to pre-intervention; and (3) no significant within-group changes in plasma S100B in the kicking-control group. Data from 68 subjects were available for analysis (heading n = 37, kicking n = 31). There were no differences in S100B concentrations between heading and kicking groups over time, as evidenced by nonsignificant group-by-time interaction at 2h post-intervention (B = 2.20, 95%CI [-22.22, 26.63], p = 0.86) and at all the other time points (0h post: B = -11.05, 95%CI [-35.37, 13.28], p = 0.38; 24h post: B = 16.11, 95%CI [-8.29, 40.51], p = 0.20). Part of the secondary outcome, the heading group showed elevation in plasma S100B concentrations at 24h post-intervention compared to pre-heading baseline (B = 19.57, 95%CI [3.13, 36.02], p = 0.02), whereas all other within-group comparisons in both remained nonsignificant. The data suggest that 10 bouts of acute controlled soccer headings do not elevate S100B concentrations up to 24-hour post-heading. Further dose-response studies with longer follow-up time points may help determine thresholds of acute soccer heading exposure that are related to astrocyte activation. The protocol was registered under ClinicalTrials.gov (NCT03488381; retrospectively registered.).

Zika virus infection causes widespread damage to the inner ear

Zika virus (ZIKV) has been recently recognized as a causative agent of newborn microcephaly, as well as other neurological consequences. A less well recognized comorbidity of prenatal ZIKV infection is hearing loss, but cases of hearing impairment following adult ZIKV infection have also been recognized. Diminished hearing following prenatal ZIKV infection in a mouse model has been reported, but no cellular consequences were observed. We examined the effects of ZIKV infection on inner ear cellular integrity and expression levels of various proteins important for cochlear function in type I interferon receptor null (Ifnar1^-/-) mice following infection at 5-6 weeks of age. We show that ZIKV antigens are present in cells within the cochlear epithelium, lateral wall, spiral limbus and spiral ganglion. Here we show that ZIKV infection alters cochlear expression of genes that signal cell damage (S100B), transport fluids (AQP1), are gaseous transmitters (eNOs) and modulate immune response (F4/80). Morphological analyses shows that not only are cochlear structures compromised by ZIKV infection, but damage also occurs in vestibular end organs. ZIKV produces a graded distribution of cellular damage in the cochlea, with greatest damage in the apex similar to that reported for cytomegalovirus (CMV) infection. The graded distribution of damage may indicate a differential susceptibility to ZIKV along the cochlear tonotopic axis. Collectively, these data are the first to show the molecular and morphological damage to the inner ear induced by ZIKV infection in adults and suggests multiple mechanisms contributing to the hearing loss reported in the human population.

Modulation of Stem Cells as Therapeutics for Severe Mental Disorders and Cognitive Impairments

Severe mental illnesses (SMI) such as schizophrenia and bipolar disorder affect 2-4% of the world population. Current medications and diagnostic methods for mental illnesses are not satisfying. In animal studies, stem cell therapy is promising for some neuropsychiatric disorders and cognitive/social deficits, not only treating during development (targeting modulation and balancing) but also following neurodegeneration (cell replacement and regenerating support). We believe that novel interventions such as modulation of particular cell populations to develop cell-based treatment can improve cognitive and social functions in SMI. With pathological synaptic/myelin damage, oligodendrocytes seem to play a role. In this review, we have summarized oligodendrogenesis mechanisms and some related calcium signals in neural cells and stem/progenitor cells. The related benefits from endogenous stem/progenitor cells within the brain and exogenous stem cells, including multipotent mesenchymal-derived stromal cells (MSC), fetal neural stem cells (NSC), pluripotent stem cells (PSC), and differentiated progenitors, are discussed. These also include stimulating mechanisms of oligodendrocyte proliferation, maturation, and myelination, responsive to the regenerative effects by both endogenous stem cells and transplanted cells. Among the mechanisms, calcium signaling regulates the neuronal/glial progenitor cell (NPC/GPC)/oligodendrocyte precursor cell (OPC) proliferation, migration, and differentiation, dendrite development, and synaptic plasticity, which are involved in many neuropsychiatric diseases in human. On the basis of numerous protein annotation and protein-protein interaction databases, a total of 119 calcium-dependent/activated proteins that are related to neuropsychiatry in human are summarized in this investigation. One of the advanced methods, the calcium/cation-channel-optogenetics-based stimulation of stem cells and transplanted cells, can take advantage of calcium signaling regulations. Intranasal-to-brain delivery of drugs and stem cells or local delivery with the guidance of brain imaging techniques may provide a unique new approach for treating psychiatric disorders. It is also expected that preconditioning stem cell therapy following precise brain imaging as pathological confirmation has high potential if translated to cell clinic use. Generally, modulable cell transplantation followed by stimulations should provide paracrine protection, synaptic modulation, and myelin repair for the brain in SMI.

Disruption of glial cell development by Zika virus contributes to severe microcephalic newborn mice

The causal link between Zika virus (ZIKV) infection and microcephaly has raised alarm worldwide. Microglial hyperplasia, reactive gliosis, and myelination delay have been reported in ZIKV-infected microcephalic fetuses. However, whether and how ZIKV infection affects glial cell development remain unclear. Here we show that ZIKV infection of embryos at the later stage of development causes severe microcephaly after birth. ZIKV infects the glial progenitors during brain development. Specifically, ZIKV infection disturbs the proliferation and differentiation of the oligodendrocyte progenitor cells and leads to the abolishment of oligodendrocyte development. More importantly, a single intraperitoneal injection of pregnant mice with a human monoclonal neutralizing antibody provides full protection against ZIKV infection and its associated damages in the developing fetuses. Our results not only provide more insights into the pathogenesis of ZIKV infection, but also present a new model for the preclinical test of prophylactic and therapeutic agents against ZIKV infection.

Human Aquaporin 4 Gene Polymorphisms and Haplotypes Are Associated With Serum S100B Level and Negative Symptoms of Schizophrenia in a Southern Chinese Han Population

Background: Aquaporin 4 (AQP4) polymorphism may influence the required dosage of antipsychotic drugs. However, the roles of AQP4 polymorphisms in the blood-brain barrier (BBB) and different neuroprotective effects need further exploration. This study aims to investigate whether the gene polymorphisms and haplotype of AQP4 are associated with serum S100 calcium-binding protein B (S100B) level and clinical symptoms in patients with schizophrenia (SCZ). Methods: We recruited 190 patients with SCZ. They provided demographic data, completed relevant questionnaires, and submitted samples to test for four AQP4 tag single nucleotide polymorphisms (SNPs) and eight haplotypes. The rating scales of Positive and Negative Syndrome Scale (PANSS), Personal and Social Performance (PSP), the Global Assessment of Functioning (GAF), Clinical Global Impression (CGI) were assessed and serum S100B level were measured repeatedly during antipsychotic treatment at weeks 0 (baseline), 3, 6, and 9. Using generalized estimating equation (GEE) analyses, log-transformed S100B (logS100B) level was tested for associations with haplotype and other dependent variables. Results: Discretization via the median split procedure showed that logS100B level >1.78 or ≤ 1.78 had the best discriminant validity to stratify the patients into two groups. After 9 weeks of treatment, the serum S100B level was decreased. The TAA haplotype of AQP4 SNPs was associated with increased serum S100B level (p = 0.006). The PANSS negative subscale (PANSS-N) (p = 0.001) and Clinical Global Impression-Improvement (CGI-I) (p = 0.003) scores had a positive association with S100B level. Conclusion: Patients with the TAA haplotype of the AQP4 polymorphism are likely to have increased serum S100B level, negative symptoms and poor control of neuroinflammation. A logS100B level >1.78 may be sufficiently specific to predict a higher severity of negative symptoms. Further study including healthy controls and patients with first and recurrent episodes under selective AQP4 modulators will be necessary to explore the profound effects on the treatment of patients with SCZ and may positively influence their overall outcome.

Blood biomarkers for brain injury: What are we measuring?

Accurate diagnosis for mild traumatic brain injury (mTBI) remains challenging, as prognosis and return-to-play/work decisions are based largely on patient reports. Numerous investigations have identified and characterized cellular factors in the blood as potential biomarkers for TBI, in the hope that these factors may be used to gauge the severity of brain injury. None of these potential biomarkers have advanced to use in the clinical setting. Some of the most extensively studied blood biomarkers for TBI include S100β, neuron-specific enolase, glial fibrillary acidic protein, and Tau. Understanding the biological function of each of these factors may be imperative to achieve progress in the field. We address the basic question: what are we measuring? This review will discuss blood biomarkers in terms of cellular origin, normal and pathological function, and possible reasons for increased blood levels. Considerations in the selection, evaluation, and validation of potential biomarkers will also be addressed, along with mechanisms that allow brain-derived proteins to enter the bloodstream after TBI. Lastly, we will highlight perspectives and implications for repetitive neurotrauma in the field of blood biomarkers for brain injury.

Serum S100B Is Related to Illness Duration and Clinical Symptoms in Schizophrenia-A Meta-Regression Analysis

S100B has been linked to glial pathology in several psychiatric disorders. Previous studies found higher S100B serum levels in patients with schizophrenia compared to healthy controls, and a number of covariates influencing the size of this effect have been proposed in the literature. Here, we conducted a meta-analysis and meta-regression analysis on alterations of serum S100B in schizophrenia in comparison with healthy control subjects. The meta-analysis followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement to guarantee a high quality and reproducibility. With strict inclusion criteria 19 original studies could be included in the quantitative meta-analysis, comprising a total of 766 patients and 607 healthy control subjects. The meta-analysis confirmed higher values of the glial serum marker S100B in schizophrenia if compared with control subjects. Meta-regression analyses revealed significant effects of illness duration and clinical symptomatology, in particular the total score of the Positive and Negative Syndrome Scale (PANSS), on serum S100B levels in schizophrenia. In sum, results confirm glial pathology in schizophrenia that is modulated by illness duration and related to clinical symptomatology. Further studies are needed to investigate mechanisms and mediating factors related to these findings.

Insulin Stimulates S100B Secretion and These Proteins Antagonistically Modulate Brain Glucose Metabolism

Brain metabolism is highly dependent on glucose, which is derived from the blood circulation and metabolized by the astrocytes and other neural cells via several pathways. Glucose uptake in the brain does not involve insulin-dependent glucose transporters; however, this hormone affects the glucose influx to the brain. Changes in cerebrospinal fluid levels of S100B (an astrocyte-derived protein) have been associated with alterations in glucose metabolism; however, there is no evidence whether insulin modulates glucose metabolism and S100B secretion. Herein, we investigated the effect of S100B on glucose metabolism, measuring D-(3)H-glucose incorporation in two preparations, C6 glioma cells and acute hippocampal slices, and we also investigated the effect of insulin on S100B secretion. Our results showed that: (a) S100B at physiological levels decreases glucose uptake, through the multiligand receptor RAGE and mitogen-activated protein kinase/ERK signaling, and (b) insulin stimulated S100B secretion via PI3K signaling. Our findings indicate the existence of insulin-S100B modulation of glucose utilization in the brain tissue, and may improve our understanding of glucose metabolism in several conditions such as ketosis, streptozotocin-induced dementia and pharmacological exposure to antipsychotics, situations that lead to changes in insulin signaling and extracellular levels of S100B.

The role of autophagy and lipolysis in survival of astrocytes under nutrient deprivation

Astrocytes can survive nutrient deprivation (ND) for days. However, the pro-survival strategy of astrocytes under such a metabolic challenge is still not clear. In the present study, we examined the effects of inhibition of two potential steps in energy acquisition during ND: autophagy (using chloroquine) and lipolysis (using orlistat). The inhibition of autophagy did not show significant effects on cell viability until 8-9h of ND. From that point onwards, the number of dead cells gradually increased, reaching ∼60% between 10 and 12h of ND. In addition, early inhibition of autophagy made astrocytes more vulnerable to the latter ND. The inhibition of lipolysis decreased the viability of cells exposed to ND, but this appeared much later compared to the inhibition of autophagy. The application of orlistat prevented ND-related hyperpolarization of the mitochondrial membrane, and mitochondria became swollen. This study clearly shows that autophagy and lipolysis are essential for the survival of astrocytes under ND conditions, which might be related to their role as neuron-supporting cells.

Immunohistochemical investigation of S100 and NSE in cases of traumatic brain injury and its application for survival time determination

The availability of markers able to provide insight into protein changes in the central nervous system after fatal traumatic brain injury (TBI) is limited. The present study reports on the semi-quantitative assessments of the immunopositive neuroglial cells (both astrocytes and oligodendrocytes) and neurons for S100 protein (S100), as well as neuronal specific enolase (NSE), in the cerebral cortex, hippocampus, and cerebellum with regard to survival time and cause of death. Brain tissues of 47 autopsy cases with TBI (survival times ranged between several minutes and 34 d) and 10 age- and gender-matched controls (natural deaths) were examined. TBI cases were grouped according to their survival time in acute death after brain injury (ABI, n = 25), subacute death after brain injury (SBI, n = 18) and delayed death after brain injury (DBI, n = 4). There were no significant changes in the percentages of S100-stained astrocytes between TBI and control cases. The percentages of S100-positive oligodendrocytes in the pericontusional zone (PCZ) in cases with SBI were significantly lower than in controls (p < 0.05) and in the ABI group (p < 0.05). In the hippocampus, S100-positive oligodendrocytes were significantly lower in cases with ABI and SBI (both, p < 0.05), compared with controls. It is of particular interest that there were also S100-positive neurons in the PCZ and hippocampus in TBI cases after more than 2 h survival but not in ABI cases or controls. The percentages of NSE-positive neurons in the hippocampus were likewise significantly lower in cases with ABI, compared with controls (p < 0.05) but increased in cases with SBI in PCZ (p < 0.05). In conclusion, the present findings emphasize that S100 and NSE-immunopositivity might be useful for detecting the cause and process of death due to TBI. Further, S100-positivity in neurons may be helpful to estimate the survival time of fatal injuries in legal medicine.

Glial cells as key players in schizophrenia pathology: recent insights and concepts of therapy

The past decade has witnessed an explosion of knowledge on the impact of glia for the neurobiological foundation of schizophrenia. A plethora of studies have shown structural and functional abnormalities in all three types of glial cells. There is convincing evidence of reduced numbers of oligodendrocytes, impaired cell maturation and altered gene expression of myelin/oligodendrocyte-related genes that may in part explain white matter abnormalities and disturbed inter- and intra-hemispheric connectivity, which are characteristic signs of schizophrenia. Earlier reports of astrogliosis could not be confirmed by later studies, although the expression of a variety of astrocyte-related genes is abnormal in psychosis. Since astrocytes play a key role in the synaptic metabolism of glutamate, GABA, monoamines and purines, astrocyte dysfunction may contribute to certain aspects of disturbed neurotransmission in schizophrenia. Finally, increased densities of microglial cells and aberrant expression of microglia-related surface markers in schizophrenia suggest that immunological/inflammatory factors are of considerable relevance for the pathophysiology of psychosis. This review describes current evidence for the multifaceted role of glial cells in schizophrenia and discusses efforts to develop glia-directed therapies for the treatment of the disease.

Cranial irradiation alters the brain's microenvironment and permits CCR2+ macrophage infiltration

Therapeutic irradiation is commonly used to treat primary or metastatic central nervous system tumors. It is believed that activation of neuroinflammatory signaling pathways contributes to the development of common adverse effects, which may ultimately contribute to cognitive dysfunction. Recent studies identified the chemokine (C-C motif) receptor (CCR2), constitutively expressed by cells of the monocyte-macrophage lineage, as a mediator of cognitive impairments induced by irradiation. In the present study we utilized a unique reporter mouse (CCR2^RFP/+CX3CR1^GFP/+) to accurately delineate the resident (CX3CR1⁺) versus peripheral (CCR2⁺) innate immune response in the brain following cranial irradiation. Our results demonstrate that a single dose of 10Gy cranial γ-irradiation induced a significant decrease in the percentage of resident microglia, while inducing an increase in the infiltration of peripherally derived CCR2⁺ macrophages. Although reduced in percentage, there was a significant increase in F4/80⁺ activated macrophages in irradiated animals compared to sham. Moreover, we found that there were altered levels of pro-inflammatory cytokines, chemokines, adhesion molecules, and growth factors in the hippocampi of wild type irradiated mice as compared to sham. All of these molecules are implicated in the recruitment, adhesion, and migration of peripheral monocytes to injured tissue. Importantly, there were no measureable changes in the expression of multiple markers associated with blood-brain barrier integrity; implicating the infiltration of peripheral CCR2⁺ macrophages may be due to inflammatory induced chemotactic signaling. Cumulatively, these data provide evidence that therapeutic levels of cranial radiation are sufficient to alter the brain’s homeostatic balance and permit the influx of peripherally-derived CCR2⁺ macrophages as well as the regional susceptibility of the hippocampal formation to ionizing radiation.

Decrease of serum S100B during an oral glucose tolerance test correlates inversely with the insulin response

Increased S100B serum levels have been considered as a marker of glial pathology, brain damage, and blood-brain-barrier impairment. However, S100B expression has also been detected outside the nervous system, suggesting that altered S100B serum levels may not exclusively reflect brain-specific pathologies. Notably, S100B secretion in adipocytes seems to be down-regulated by insulin, and up-regulated by stress and fasting. Therefore, we assumed that dynamic changes of S100B could be observed by challenging healthy subjects with an oral glucose tolerance test (OGTT). OGTT was performed in 17 healthy adult test persons (9 male and 8 female). Apart from S100B, glucose, free fatty acids, insulin, C-peptide, and cortisol were determined in all samples after an overnight fast (0 h), as well as 1h and 2h after ingestion of 75 g glucose. Mean S100B concentrations decreased about 20% during the first hour after glucose ingestion (P<0.001). This decrease of S100B levels was not related to the declining morning peak of cortisol. However, the decrease of serum-S100B 1h after glucose ingestion correlated inversely with the respective changes of serum-insulin (r = -0.484, P=0.049) and serum-C-peptide (r = -0.570, P = 0.017). Our study suggests an inverse correlation between insulin secretion and S100B release after a standardized OGTT. Additional experiments, including the administration of insulin and the measurement of other food intake-related factors are important to ascertain an insulin-regulated S100B release in vivo. To improve comparability between clinical studies assessing conditions with rather mild changes of serum S100B, blood should be taken in a more standardized way (e.g., after fasting overnight).

Pretreatment of aripiprazole and minocycline, but not haloperidol, suppresses oligodendrocyte damage from interferon-γ-stimulated microglia in co-culture model

Recent imaging studies have indicated that the pathophysiology of schizophrenia is closely related to white matter abnormalities and microglial activation. Additionally, recent clinical trials have suggested that atypical antipsychotics may have brain protective properties and that minocycline, an antibiotic with inhibitory effects on microglial activation, improves symptoms of schizophrenia. We have reported that not only atypical antipsychotics with dopamine D2 receptor (D2R) antagonism but also aripiprazole, a unique antipsychotic drug with D2R partial agonism, inhibit microglial activation in vitro. Thus, atypical antipsychotics may exert a beneficial influence on both microglia and oligodendrocytes, while the underlying mechanisms have not been clarified. Here, we investigated whether antipsychotics suppress oligodendrocyte damage by inhibiting microglial activation utilizing a co-culture model with microglia and oligodendrocytes. Pretreatment of aripiprazole and minocycline suppressed apoptosis of oligodendrocytes in the co-culture model with interferon-γ (IFN-γ)-activated microglia, while haloperidol, a traditional antipsychotic drug, did not. Aripiprazole and minocycline inhibited the production of tumor necrosis factor-alpha (TNF-α) from IFN-γ-activated microglia. Moreover, aripiprazole and minocycline attenuated the phosphorylation of signal transducer and activator of transcription 1 (STAT1) in microglia. Overall, our results suggest that aripiprazole and minocycline may have antipsychotic effects through reducing oligodendrocyte damage caused by microglial activation. These results put forward a novel therapeutic hypothesis in schizophrenia research. Future in vivo studies to confirm the present results should be performed.

Functions of S100 proteins

The S100 protein family consists of 24 members functionally distributed into three main subgroups: those that only exert intracellular regulatory effects, those with intracellular and extracellular functions and those which mainly exert extracellular regulatory effects. S100 proteins are only expressed in vertebrates and show cell-specific expression patterns. In some instances, a particular S100 protein can be induced in pathological circumstances in a cell type that does not express it in normal physiological conditions. Within cells, S100 proteins are involved in aspects of regulation of proliferation, differentiation, apoptosis, Ca2+ homeostasis, energy metabolism, inflammation and migration/invasion through interactions with a variety of target proteins including enzymes, cytoskeletal subunits, receptors, transcription factors and nucleic acids. Some S100 proteins are secreted or released and regulate cell functions in an autocrine and paracrine manner via activation of surface receptors (e.g. the receptor for advanced glycation end-products and toll-like receptor 4), G-protein-coupled receptors, scavenger receptors, or heparan sulfate proteoglycans and N-glycans. Extracellular S100A4 and S100B also interact with epidermal growth factor and basic fibroblast growth factor, respectively, thereby enhancing the activity of the corresponding receptors. Thus, extracellular S100 proteins exert regulatory activities on monocytes/macrophages/microglia, neutrophils, lymphocytes, mast cells, articular chondrocytes, endothelial and vascular smooth muscle cells, neurons, astrocytes, Schwann cells, epithelial cells, myoblasts and cardiomyocytes, thereby participating in innate and adaptive immune responses, cell migration and chemotaxis, tissue development and repair, and leukocyte and tumor cell invasion.

Chronic fluoxetine treatment changes S100B expression during postnatal rat brain development

BACKGROUND

Fluoxetine, a selective serotonin reuptake inhibitor, is approved for treatment of childhood depression. In rats, fluoxetine influences neuronal development, but it is unclear whether it also influences glia development. S100B is a glia-derived calcium-binding protein, which may influence the development of serotonergic fibers and, vice versa, serotonin may influence the expression of S100B.

OBJECTIVES

The purpose of this study was to investigate whether fluoxetine treatment influences the expression of S100B during postnatal development, and whether potential changes are regionally dependent upon the time frame of drug administration.

METHODS

S100B gene expression and S100B protein expression in three different brain regions (frontal cortex, hippocampus, and striatum) were studied by real-time polymerase chain reaction (PCR) and immunohistochemistry, respectively. First, a short-term effect, 24 hours after a 14 day fluoxetine treatment (5 mg/kg/bw s.c.) of rats either from postnatal day (PD) 1 to 15, 21 to 35, or 50 to 64, was investigated. Then, the same treatment was used to analyze S100B gene and protein levels at PD 90 (long-term effect).

RESULTS

At PD 90, a significant increase of gene and protein expression was observed in all regions if rats were treated during PDs 21-35, whereas treatment during other periods had no long-term effects. A short-term effect 24 hours after fluoxetine treatment was found for almost all development stages and regions, demonstrated by a significant increase of S100B.

CONCLUSIONS

These results support recent research indicating a highly drug-sensitive period (i.e., periadolescence) of rat brain development. Therefore, further clinical studies should be performed to clarify whether such a sensitive period also exists in children.

Increased nuclear Olig1-expression in the pregenual anterior cingulate white matter of patients with major depression: a regenerative attempt to compensate oligodendrocyte loss?

BACKGROUND

Structural and functional oligodendrocyte deficits as well as impaired myelin integrity have been described in affective disorders and schizophrenia, and may disturb the connectivity between disease-relevant brain regions. Olig1, an oligodendroglial transcription factor, might be important in this context, but has not been systematically studied so far.

METHODS

Nissl- and Olig1-stained oligodendrocytes were quantified in the pregenual anterior cingulate (pACC)/dorsolateral prefrontal cortex (DLPFC), and adjacent white matter of patients with major depressive disorder (MDD, n = 9), bipolar disorder (BD, n = 8), schizophrenia (SZ, n = 13), and matched controls (n = 16). Potential downstream effects of increased Olig1-expression were analyzed. Antidepressant drug effects on Olig1-expression were further explored in OLN-93 oligodendrocyte cultures.

RESULTS

Nissl-stainings of both white matter regions showed a 19-27% reduction of total oligodendrocyte densities in MDD and BD, but not in SZ. In contrast, nuclear Olig1-immunoreactivity was elevated in MDD in the pACC-adjacent white matter (left: p = 0.008; right: p = 0.018); this effect tended to increase with antidepressant dosage (r = 0.631, p = 0.069). This reactive increase of Olig1 was confirmed by partly dose-dependent effects of imipramine and amitriptyline in oligodendrocyte cultures. Correspondingly, MBP expression in the pACC-adjacent white matter tended to increase with antidepressant dosage (r = 0.637, p = 0.065). Other tested brain regions showed no diagnosis-dependent differences regarding Olig1-immunoreactivity.

CONCLUSIONS

Since nuclear Olig1-expression marks oligodendrocyte precursor cells, its increased expression along with reduced total oligodendrocyte densities (Nissl-stained) in the pACC-adjacent white matter of MDD patients might indicate a (putatively medication-boosted) regenerative attempt to compensate oligodendrocyte loss.

Interleukin-6-induced S100B secretion is inhibited by haloperidol and risperidone

Although inflammation may be a physiological defense process, imbalanced neuroinflammation has been associated with the pathophysiology of brain disorders, including major depression and schizophrenia. Activated glia releases a variety of pro-inflammatory cytokines that contribute to neuronal dysfunction. Elevated levels of S100B, a glia derived protein, have been observed in the serum and CSF of schizophrenic patients suggesting a glial role in the disease. We evaluated whether S100B secretion (in C6 glioma cells and hippocampal slices in Wistar rats) could be directly modulated by the main inflammatory cytokines (IL-1β, TNF-α, IL-6 and IL-8) altered in schizophrenia, as well as the possible involvement of mitogen-activated protein kinase (MAPK) pathways in these responses. We also investigated the effects of typical and atypical antipsychotic drugs on glial cytokine-induced S100B release. Our results suggest that S100B secretion is increased by pro-inflammatory cytokines via MAPK and that oxidative stress may be a component of this modulation. These results reinforce the idea that the S100B protein is involved in the inflammatory response observed in many brain diseases, including schizophrenia. Moreover the antipsychotics, haloperidol and risperidone, were able to inhibit the secretion of S100B following IL-6 stimulation in C6 glioma cells.

Os possíveis papéis da S100B na esquizofrenia

CONTEXTO: Evidências científicas do aumento da concentração da proteína S100B no sangue de pacientes esquizofrênicos são muito consistentes. No passado essa informação era principalmente considerada como reflexo da disfunção astroglial ou da barreira hematoencefálica. MÉTODOS: Pesquisa de publicações no PubMed até o dia 15 de junho de 2011 visando estabelecer potenciais ligações entre a proteína S100B e as hipóteses correntes da esquizofrenia. RESULTADOS: A S100B está potencialmente associada com as hipóteses dopaminérgica e glutamatérgica. O aumento da expressão de S100B tem sido detectado em astrócitos corticais em casos de esquizofrenia paranoide, enquanto se observa uma redução da expressão em oligodendrócitos na esquizofrenia residual, dando suporte à hipótese glial. Recentemente, a hipótese da neuroinflamação da esquizofrenia tem recebido atenção crescente. Nesse sentido, a S100B pode funcionar como uma citocina secretada por células gliais, linfócitos CD8+ e células NK, levando à ativação de monócitos e microglia. Além disso, a S100B apresenta propriedades do tipo adipocina e pode estar desregulada na esquizofrenia, devido a distúrbios da sinalização de insulina, levando ao aumento da liberação de S100B e ácidos graxos do tecido adiposo. CONCLUSÃO: A expressão de S100B em diferentes tipos celulares está envolvida em muitos processos regulatórios. Atualmente, não pode ser respondido qual mecanismo relacionado à esquizofrenia é o mais importante.

Increased density of prohibitin-immunoreactive oligodendrocytes in the dorsolateral prefrontal white matter of subjects with schizophrenia suggests extraneuronal roles for the protein in the disease

Prohibitin has previously been implicated in the synaptic pathology of schizophrenia. The recently discovered abundant expression of prohibitin in human prefrontal oligodendrocytes raises the issue, whether this protein might also be part of the well-known white matter abnormalities in schizophrenia. Hence, post-mortem brains of ten patients with schizophrenia and ten matched control cases were investigated. Using a direct, 3D-counting technique we morphometrically analyzed the number and density of prohibitin-immunoreactive oligodendroglial cells in the left and right dorsolateral, anterior cingulate, and orbitofrontal cortex white matter. Additionally, we studied the prohibitin expression in different neuronal and non-neuronal cell populations in rat cell cultures. We could confirm the strong expression of prohibitin in oligodendrocytes. Intracellularly, the protein was localized to mitochondria and some cell nuclei. In schizophrenia, the numerical density of prohibitin-expressing oligodendrocytes was significantly increased in the right dorsolateral white matter area. Taking into consideration the dual intracellular localization of prohibitin in oligodendrocyte mitochondria and cell nuclei, one may suggest an involvement of the protein in mitochondrial dysfunction and/or cycle abnormalities in schizophrenia.

Human eosinophils express RAGE, produce RAGE ligands, exhibit PKC-delta phosphorylation and enhanced viability in response to the RAGE ligand, S100B

This study tested the hypothesis that human eosinophils produce ligands for the receptor for advanced glycation end-products (RAGE), express RAGE and exhibit RAGE-mediated responses. In examining our microarray data, we identified the presence of RAGE and RAGE ligand (S100A4, S100A6, S100A8, S100A9, S100A11, S100P, HMGB1) transcripts. Expression of eosinophil RAGE mRNA was also compared with a known positive control and further assessed via bioinformatics and sequence analysis of RAGE cDNA. Positive and negative controls were used to identify RAGE, S100A8 and S100A9 protein in human primary eosinophils. Immunoblot assessment of eosinophils treated with cytokines (IL-5 or granulocyte macrophage colony-stimulating factor) indicated an up-regulation of S100A8 and S100A9 production, whereas co-treatment of eosinophils with a RAGE ligand and cytokines displayed a down-regulation in the levels of RAGE. Analysis of eosinophil-conditioned media revealed that eosinophils are capable of releasing RAGE, S100A8 and S100A9. To test the eosinophil response to RAGE activation, the most well-characterized RAGE ligand, S100B, was examined. Treatment of eosinophils with S100B resulted in RAGE-mediated PKC-delta phosphorylation, a 3-fold dose-dependent increase in cell survival and an increase in the level of cellular RAGE. Combined, these studies reveal eosinophil expression of RAGE, RAGE ligands and RAGE-mediated responses. The expression of eosinophil RAGE, soluble RAGE and RAGE ligands may be pivotal to the functions of eosinophils in various human diseases involving RAGE and S100 ligands.

Protective effects of haloperidol and clozapine on energy-deprived OLN-93 oligodendrocytes

Magnetic resonance imaging and postmortem studies on schizophrenia provided evidence for compromised myelin integrity and reduced numbers of oligodendrocytes, which may worsen during the disease course. However, it is not clear whether these findings result from disease-inherent oligodendrocyte degeneration or side effects of antipsychotic treatment. Therefore, effects of haloperidol and clozapine on the viability and apoptosis of immature oligodendrocytes (OLN-93 cells, immunopositive for NG2, Olig1, Olig2) have been evaluated in the present study by labeling with propidium iodide and a caspase 3 assay. Given the indications for impaired cerebral energy supply in schizophrenia, a serum and glucose deprivation (SGD) model was chosen in comparison with the basal condition (BC). SGD led to increased necrotic and apoptotic cell death. Haloperidol and clozapine were partially protective in this model and reduced the percentage of propidium iodide-positive cells, while caspase 3 activity was not altered. No significant drug effects were observed under BC. The observed protective effects of haloperidol and clozapine on energy-deprived OLN-93 oligodendrocytes suggest that previously reported reductions in oligodendrocyte density in schizophrenia are rather disease related than a side effect of medication. A new mechanism of antipsychotic action is suggested, which may help to establish new oligodendrocyte-directed therapies of schizophrenia.

Microtubule-associated protein 2, an early blood marker of ischemic brain injury

The aim of this study was to develop a sensitive and rapid blood marker to detect ischemic brain injury, because imaging techniques have a limited capacity to identify lesions during the first crucial hours without massive tissue destruction. Rats were subjected to middle cerebral artery occlusion for various durations (0.5-3 hr), followed by reperfusion. At different time points after ischemia and/or ischemia-reperfusion, the amounts of glial fibrillary acidic protein (GFAP) and microtubule-associated protein 2 (MAP2) in the cerebrospinal fluid (CSF) and serum were analyzed by Western blotting. Brain infarction was observed in an ischemia-duration-dependent manner. GFAP was drastically increased in the CSF 24 and 48 hr after reperfusion, without change in the serum level. Serum levels of MAP2 remarkably increased as early as 0.5 hr of ischemia, much earlier than the observation of minimal tissue injury 3 hr following occlusion. The serum MAP2 level was further increased by a short period (2 hr) of reperfusion, even in 0.5- and 1-hr ischemic rats, despite not observing any typical tissue injuries 24 hr after reperfusion. These results indicate that the MAP2 protein may be able to detect early neuronal injuries, because the level of this protein in the blood spikes before the appearance of visible macrolesions. Therefore, MAP2 could potentially be used as a novel early marker for the detection of a neurotoxic insult.

Human CD8(+) T cells and NK cells express and secrete S100B upon stimulation

Previous studies have demonstrated the utility of S100B as a surrogate marker of brain-related pathologies, e.g. neuropsychiatric disorders, and melanoma progression, which have an inflammatory component. This study addresses the relevance of S100B(+) lymphocytes in mediating such responses. S100B expression was determined in human peripheral blood leukocytes isolated from healthy volunteers using flow cytometry. S100B(+) lymphocytes were characterised for phenotype, cytokine production and S100B secretion. In addition, we investigated whether S100B activates monocytes and neutrophils. S100B(+) cells comprised 2-4% of all lymphocytes and the majority displayed a CD3(+) CD8(+) phenotype; fewer cells were CD3(-) CD56(+) NK lymphocytes. Comparison of S100B(+) and S100B(-) CD3(+) CD8(+) cells revealed no differences in production of interferon gamma (IFNγ) and interleukin-2 (IL-2). Stimulation of S100B(+) CD3(+) CD8(+) lymphocytes with anti-CD3 or phytohaemagglutinin resulted in release of S100B. High concentrations of recombinant human S100B triggered upregulation of CD11b and membrane shedding of CD62L in granulocytes and monocytes. These findings set the stage for a new field of research addressing a S100B-mediated crosstalk between the innate and adaptive immune systems if close proximity of effector and responder cells accomplishes sufficient local S100B levels. In various physiological and pathological conditions S100B might function as an interface to immunological processes, distinct from known cytokine- and chemokine-mediated pathways.

S100B protein in neurodegenerative disorders

"Classic" neurodegenerative disorders, such as Alzheimer's disease and amyotrophic lateral sclerosis share common pathophysiological features and involve progressive loss of specific neuronal populations, axonal or synaptic loss and dysfunction, reactive astrogliosis, and reduction in myelin. Furthermore, despite the absence of astrogliosis, impaired expression of astrocyte- and oligodendrocyte-related genes has been observed in patients with major psychiatric disorders, including schizophrenia and mood disorders. Because S100B is expressed in astrocytes and oligodendrocytes, its concentration in cerebrospinal fluid (CSF) or serum has been considered a suitable surrogate marker for the diagnostic or prognostic assessment of neurodegeneration. This review summarizes previous postmortem, CSF and serum studies regarding the role of S100B in this context. A general drawback is that only small single-center studies have been performed. Many potential confounding factors exist because of the wide extra-astrocytic and extracerebral expression of S100B. Due to lack of disease specificity, reliance on S100B concentrations for differential diagnostic purposes in cases of suspected neurodegenerative disorders is not recommended. Moreover, there is no consistent evidence for a correlation between disease severity and concentrations of S100B in CSF or serum. Therefore, S100B has limited usefulness for monitoring disease progression.

Increased serum S100B in never-medicated and medicated schizophrenic patients

S100B is a calcium-binding protein, which is produced primarily by glial cells. It modulates the proliferation and differentiation of neurons and glia by affecting protective and apoptotic mechanisms. Recently, several studies have shown increased serum S100B levels in patients with schizophrenia, suggesting that S100B might be relevant to the pathophysiology of schizophrenia. S100B levels were assessed using ELISA in the serum of 80 never-medicated early-stage and 82 medicated chronic schizophrenia patients and 97 healthy controls subjects. The psychopathology of schizophrenia was assessed by the Positive and Negative Syndrome Scale (PANSS). Our results showed significantly increased serum S100B levels in both never-medicated and medicated patients compared to normal controls (both p<0.0001). S100B in never-medicated patients was also markedly increased, compared with medicated patients (p<0.0001). S100B changes observed were irrespective of neuroleptic medication, gender, age, and smoking. Increased S100B levels in the early stage of schizophrenia suggest that glial cell activation or structural damage may be part of a neurodegenerative process in schizophrenia. The lower S100B levels in chronic than early-stage patients further suggest that antipsychotic treatment may reduce this neurodegeneration.

S100B Serum Levels in Schizophrenia Are Presumably Related to Visceral Obesity and Insulin Resistance

Elevated blood levels of S100B in schizophrenia have so far been mainly attributed to glial pathology, as S100B is produced by astro- and oligodendroglial cells and is thought to act as a neurotrophic factor with effects on synaptogenesis, dopaminergic and glutamatergic neutrotransmission. However, adipocytes are another important source of S100B since the concentration of S100B in adipose tissue is as high as in nervous tissue. Insulin is downregulating S100B in adipocytes, astrocyte cultures and rat brain. As reviewed in this paper, our recent studies suggest that overweight, visceral obesity, and peripheral/cerebral insulin resistance may be pivotal for at least part of the elevated S100B serum levels in schizophrenia. In the context of this recently identified framework of metabolic disturbances accompanying S100B elevation in schizophrenia, it rather has to be attributed to systemic alterations in glucose metabolism than to be considered a surrogate marker for astrocyte-specific pathologies.

S100b counteracts neurodegeneration of rat cholinergic neurons in brain slices after oxygen-glucose deprivation

Alzheimer's disease is a severe chronic neurodegenerative disorder characterized by beta-amyloid plaques, tau pathology, cerebrovascular damage, inflammation, reactive gliosis, and cell death of cholinergic neurons. The aim of the present study is to test whether the glia-derived molecule S100b can counteract neurodegeneration of cholinergic neurons after oxygen-glucose deprivation (OGD) in organotypic brain slices of basal nucleus of Meynert. Our data showed that 3 days of OGD induced a marked decrease of cholinergic neurons (60% of control), which could be counteracted by 50 μg/mL recombinant S100b. The effect was dose and time dependent. Application of nerve growth factor or fibroblast growth factor-2 was less protective. C-fos-like immunoreactivity was enhanced 3 hours after OGD indicating metabolic stress. We conclude that S100b is a potent neuroprotective factor for cholinergic neurons during ischemic events.

Increased S100B serum levels in schizophrenic patients with tardive dyskinesia: association with dyskinetic movements

Several studies show that calcium-binding protein S100B is increased in schizophrenia and may be involved in the pathogenesis of tardive dyskinesia (TD). We therefore compared serum S100B levels in normal controls (n=60), schizophrenic patients with (n=32) and without TD (n=50). Assessments included the abnormal involuntary movement scale (AIMS) and the positive and negative syndrome scale (PANSS). Serum S100B levels were measured by enzyme-linked immunosorbent assay (ELISA). The results indicated that patients with TD had higher serum S100B levels than normals and those without TD. Serum S100B levels were positively correlated with AIMS scores in patients with TD. These data suggest that increased S100B levels may be related to neuro-degeneration, associated with TD pathophysiology.

The RAGE axis: a fundamental mechanism signaling danger to the vulnerable vasculature

The immunoglobulin superfamily molecule RAGE (receptor for advanced glycation end product) transduces the effects of multiple ligands, including AGEs (advanced glycation end products), advanced oxidation protein products, S100/calgranulins, high-mobility group box-1, amyloid-beta peptide, and beta-sheet fibrils. In diabetes, hyperglycemia likely stimulates the initial burst of production of ligands that interact with RAGE and activate signaling mechanisms. Consequently, increased generation of proinflammatory and prothrombotic molecules and reactive oxygen species trigger further cycles of oxidative stress via RAGE, thus setting the stage for augmented damage to diabetic tissues in the face of further insults. Many of the ligand families of RAGE have been identified in atherosclerotic plaques and in the infarcted heart. Together with increased expression of RAGE in diabetic settings, we propose that release and accumulation of RAGE ligands contribute to exaggerated cellular damage. Stopping the vicious cycle of AGE-RAGE and RAGE axis signaling in the vulnerable heart and great vessels may be essential in controlling and preventing the consequences of diabetes.