S100B protein: general characteristics and pathophysiological implications in the Central Nervous System

Diverse role of S100 calcium-binding protein B in alzheimer's disease: pathological mechanisms and therapeutic implications

S100 calcium-binding protein B, a member of the S100 protein family, plays an important role in the pathogenesis of Alzheimer's disease. Alzheimer's disease, a neurodegenerative disorder, is characterized by amyloid-beta plaques, neurofibrillary tangles, progressive dementia, and severe neuroinflammation. S100 calcium-binding protein B, predominantly secreted by astrocytes, exhibits a dual role in Alzheimer's disease, where at low (nanomolar) concentrations, it exhibits neurotrophic and neuroprotective effects and enhances synaptic plasticity, while at higher concentrations, it contributes to neuroinflammation and neuronal damage. In addition to its pathological roles in Alzheimer's disease, S100 calcium-binding protein B is also considered a potential biomarker, as increased levels correlate with cognitive decline and disease progression in cerebrospinal fluid. Targeting S100 calcium-binding protein B and/or its interaction with the receptor for advanced glycation end-products seems to be a potential target for therapeutic intervention. The development of multiple treatment approaches, such as pharmacological inhibitors, immunotherapy, and modulation of S100 calcium-binding protein B / receptor for advanced glycation end-products signalling pathways, might help to reduce neuroinflammation and amyloid-beta deposition effectively. This review aims to provide an overview of the role of S100 calcium-binding protein B in Alzheimer's disease and to explore its potential as a treatment target, well-grounded in its dual nature. Understanding S100 calcium-binding protein B's involvement in the pathogenesis of Alzheimer's disease may advance its application as a biomarker and help in the development of new treatment strategies, ultimately improving patients' quality of life.

Potential effects of induced focal ischemia in the motor cortex of rats undergoing experimental periodontitis

Stroke is a severe medical condition resulting from an interruption in the blood supply to the brain, ultimately compromising tissue homeostasis. Currently, stroke stands as the second leading cause of death worldwide and the third leading cause when considering both mortality and disability together. Periodontitis is characterized by persistent inflammation in hard and soft tissues which support the teeth, primarily caused by bacterial biofilms, and is one of the most common causes of tooth loss in adults and can contribute to a systemic inflammatory burden. In the light of this, the present study investigated the effects of inducing focal ischemia in the motor cortex in rats undergoing experimental periodontitis. Adult Wistar rats were divided into four groups (control, ischemia, periodontitis, and periodontitis + ischemia) and were evaluated for motor performance, basic histology, and the volume and microarchitecture of alveolar bone. The results showed that the comorbidity between ischemia and periodontitis aggravates the spontaneous locomotion of rats, although the motor performance of adult rats had not been altered. Nonetheless, they revealed significant tissue impairment in the motor cortex. Additionally, there was a meaningful alteration in both the volume and microarchitecture of alveolar bone in this group. Our results indicate that the model of comorbidity between ligature-induced experimental periodontitis and focal ischemia was capable of inducing greater neurological impairment and alveolar bone loss in rats, attributable to diminished bone quality, when compared to each condition individually.

Expression of S100β during mouse cochlear development

In the present study, the expression of S100β was examined in the mouse cochlea from embryonic day 17 (E17) to postnatal day 32 (P32) using immunofluorescence, aiming to explore its possible role in auditory system. At E17, S100β expression was not detected, except in the external cochlear wall. Starting at E18.5, S100β staining appeared in the organ of Corti and the stria vascularis. In the E18.5 and P1 organ of Corti, S100β was confined to the developing pillar cells. By P6, cytoplasmic staining of S100β was evident in the inner and outer pillar cells, forming the tunnel of Corti. Additionally, S100β expression extended medially into the three rows of Deiter's cells, with labeling of their phalangeal processes. At P8, S100β continued to be expressed in the heads, bodies, and feet of the two pillar cells, as well as in the soma and phalangeal processes of the three rows of Deiter's cells. In the lateral wall of the P8 cochlea, S100β was expressed not only in the stria vascularis but also in the spiral ligament. Between P10 and P12, S100β expression was maintained in the Deiter's cells and pillar cells of the organ of Corti, as well as in the lateral wall, and spiral limbus. From P14 onwards, S100β expression ceased in the stria vascularis, though it persisted in the spiral ligament and spiral limbus into adulthood. Within the P14 and P21 organ of Corti, S100β remained in the Deiter's and pillar cells. S100β immunostaining was not observed in the phalangeal processes of Deiter's cells but was specifically present in the Deiter's cell cups at P21. In the adult cochlea (P28 and P32), S100β expression declined in both Deiter's and pillar cells. The dynamic spatiotemporal changes in S100β expression during cochlear ontogeny suggest its role in cochlear development and hearing function.

The relationship between inflammatory markers, clinical characteristics, and cognitive performance in drug-naïve patients with schizophrenia

Increasing evidence implicates that inflammatory factors do play a crucial role in the pathophysiology of schizophrenia. However, the association between inflammatory markers and different symptom dimensions and cognitive function of schizophrenia remains unclear. A total of 140 drug-naïve patients with schizophrenia and 69 healthy controls matched for age and gender were enrolled. Peripheral blood plasma concentrations of S-100 calcium-binding protein B (S100B), neutrophil gelatinase-associated lipocalin (NGAL), and interferon-γ (IFN-γ) were detected by enzyme-linked immunosorbent assay (ELISA). Psychotic symptoms were measured using the Positive and Negative Syndrome Scale (PANSS), and cognitive function was assessed by the MATRICS Consensus Cognitive Battery (MCCB). Compared with healthy controls, patients with schizophrenia had significantly worse cognitive function and lower levels of NGAL and IFN-γ (P < 0.001). In schizophrenia, plasma NGAL and IFN-γ levels negatively correlated with positive symptom scores (all P < 0.05). There was a positive correlation between plasma levels of NGAL and IFN-γ with visual learning, neurocognition, and MCCB total score (all P < 0.05). We found that NGAL levels (β = 0.352, t = 5.553, 95% CI 0.228-0.477, P < 0.001) and negative symptoms subscale scores (β = - 0.321, OR = 0.725, 95% CI 648-0.811, P < 0.001) were independently associated with the MCCB total score. Further, binary logistic regression analysis indicated that the concentrations of NGAL (β = - 0.246, OR = 0.782, 95% CI 0.651-0.939, P = 0.008) were independently associated with the diagnosis of schizophrenia. There was a positive correlation between NGAL and IFN-γ levels and MCCB total score in schizophrenia. NGAL level was an independent protective factor for cognitive function and an independent risk factor for the diagnosis of schizophrenia.

S100B actions on glial and neuronal cells in the developing brain: an overview

The S100B is a member of the S100 family of "E" helix-loop- "F" helix structure (EF) hand calcium-binding proteins expressed in diverse glial, selected neuronal, and various peripheral cells, exerting differential effects. In particular, this review compiles descriptions of the detection of S100B in different brain cells localized in specific regions during the development of humans, mice, and rats. Then, it summarizes S100B's actions on the differentiation, growth, and maturation of glial and neuronal cells in humans and rodents. Particular emphasis is placed on S100B regulation of the differentiation and maturation of astrocytes, oligodendrocytes (OL), and the stimulation of dendritic development in serotoninergic and cerebellar neurons during embryogenesis. We also summarized reports that associate morphological alterations (impaired neurite outgrowth, neuronal migration, altered radial glial cell morphology) of specific neural cell groups during neurodevelopment and functional disturbances (slower rate of weight gain, impaired spatial learning) with changes in the expression of S100B caused by different conditions and stimuli as exposure to stress, ethanol, cocaine and congenital conditions such as Down's Syndrome. Taken together, this evidence highlights the impact of the expression and early actions of S100B in astrocytes, OL, and neurons during brain development, which is reflected in the alterations in differentiation, growth, and maturation of these cells. This allows the integration of a spatiotemporal panorama of S100B actions in glial and neuronal cells in the developing brain.

The Role of S100b Protein Biomarker in Brain Death: A Literature Review

Brain death (BD) represents the irreversible loss of all brain functions, including the brainstem, and is equivalent to clinical death established by neurological criteria. However, clinical diagnosis, mainly based on the absence of primary reflexes post-acute brain injury, remains a challenge in hospital settings. The S100 calcium-binding protein beta (S100b) is used to monitor brain injuries, as recommended by neurotrauma care guidelines in some countries. Its levels are associated with severity and mortality, particularly after traumatic brain injury (TBI) and cerebral hemorrhage. The evaluation of S100b levels in investigating brain death is promising; however, aspects such as cutoff values remain to be elucidated. This paper reviews the literature on the use of S100b as a biomarker in diagnosing brain death. It is noteworthy that there is still no defined cutoff for S100b levels in confirming brain death. Additionally, when considering the use of S100b in emergency situations, a point-of-care methodology should be established to support clinical decision-making quickly and easily in the early identification of patients who are more likely to progress to brain death. In this context, S100b levels may assist in establishing the diagnosis of brain death, complementing existing clinical evidence. This, in turn, can optimize and qualify the organ donation process, reducing costs with ineffective therapies and minimizing the suffering of the families involved.

Cellular and Molecular Pathophysiology of Traumatic Brain Injury: What Have We Learned So Far?

Traumatic brain injury (TBI) is one of the leading causes of long-lasting morbidity and mortality worldwide, being a devastating condition related to the impairment of the nervous system after an external traumatic event resulting in transitory or permanent functional disability, with a significant burden to the healthcare system. Harmful events underlying TBI can be classified into two sequential stages, primary and secondary, which are both associated with breakdown of the tissue homeostasis due to impairment of the blood-brain barrier, osmotic imbalance, inflammatory processes, oxidative stress, excitotoxicity, and apoptotic cell death, ultimately resulting in a loss of tissue functionality. The present study provides an updated review concerning the roles of brain edema, inflammation, excitotoxicity, and oxidative stress on brain changes resulting from a TBI. The proper characterization of the phenomena resulting from TBI can contribute to the improvement of care, rehabilitation and quality of life of the affected people.

Circulating S100B levels at birth and risk of six major neuropsychiatric or neurological disorders: a two-sample Mendelian Randomization Study

Circulating levels of the astrocytic marker S100B have been associated with risk of neuropsychiatric or neurological disorders. However, reported effects have been inconsistent, and no causal relations have yet been established. We applied two-sample Mendelian Randomization (MR) on the association statistics from genome-wide association studies (GWAS) for circulating S100B levels measured 5-7 days after birth (the iPSYCH sample) and in an older adult sample (mean age, 72.5 years; the Lothian sample), upon those derived from major depression disorder (MDD), schizophrenia (SCZ), bipolar disorder (BIP), autism spectral disorder (ASD), Alzheimer's disease (AD), and Parkinson's disease (PD). We studied the causal relations in the two S100B datasets for risk of these six neuropsychiatric disorders. MR suggested increased S100B levels 5-7 days after birth to causally increase the risk of MDD (OR = 1.014; 95%CI = 1.007-1.022; FDR-corrected p = 6.43×10-4). In older adults, MR suggested increased S100B levels to have a causal relation to the risk of BIP (OR = 1.075; 95%CI = 1.026-1.127; FDR-corrected p = 1.35×10-2). No significant causal relations were found for the other five disorders. We did not observe any evidence for reverse causality of these neuropsychiatric or neurological disorders on altered S100B levels. Sensitivity analyses using more stringent SNP-selection criteria and three alternative MR models suggested the results are robust. Altogether, our findings imply a small cause-effect relation for the previously reported associations of S100B and mood disorders. Such findings may provide a novel avenue for the diagnosis and management of disorders.

Brain damage serum biomarkers induced by COVID-19 in patients from northeast Brazil

Neurological symptoms have been often reported in COVID-19 disease. In the present study, we evaluated brain damage associated with the increase of serum levels of neurological biomarkers S100B and neuron-specific enolase (NSE) induced by SARS-CoV-2 infection, in a population from Northeastern Brazil. Thirty-six healthy control (G1) individuals and 141 patients with confirmed COVID-19 were enrolled in this study. Positive-COVID-19 patients were divided into two groups according to the severity of illness by the National Institute of Health (NIH) criteria, 76 patients with mild symptoms for COVID-19 and (G2) and 65 with acute respiratory conditions requiring supplemental oxygenation via intensive care unit (ICU) admission (G3). A follow-up study was conducted with 23 patients from G2 14 (D14) and 21 (D21) days after the onset of symptoms. Serum levels of NSE and S100B were measured using the enzyme-linked immunoassay method (ELISA). Results revealed a significant positive association between G3 patients and S100B serum expression (p = 0.0403). The serum levels of NSE were also significantly enhanced in the G3 group compared to the control (p < 0.0001) and G2 group (p < 0.0001). In addition, clinical features such as symptoms and oxygenation status were not correlated with NSE or S100B serum expression. The follow-up study demonstrated a decrease over time (21 days) in NSE serum expression (p < 0.0001). These results suggest that brain damage is followed by acute virus exposure, with no long-term effects. Future work examining COVID-19 recovery will shed light on chronic neurological damage of SARS-CoV-2 infection.

Differential proteomic profile of lumbar and ventricular cerebrospinal fluid

BACKGROUND

Pathological cerebral conditions may manifest in altered composition of the cerebrospinal fluid (CSF). Although diagnostic CSF analysis seeks to establish pathological disturbances in the brain proper, CSF is generally sampled from the lumbar compartment for reasons of technical ease and ethical considerations. We here aimed to compare the molecular composition of CSF obtained from the ventricular versus the lumbar CSF compartments to establish a relevance for employing lumbar CSF as a proxy for the CSF bathing the brain tissue.

METHODS

CSF was collected from 46 patients with idiopathic normal pressure hydrocephalus (iNPH) patients during their diagnostic workup (lumbar samples) and in connection with their subsequent CSF diversion shunt surgery (ventricular samples). The mass-spectrometry-based proteomic profile was determined in these samples and in addition, selected biomarkers were quantified with ELISA (S100B, neurofilament light (NfL), amyloid-β (Aβ₄₀, Aβ₄₂), and total tau (T-tau) and phosphorylated tau (P-tau) forms). The latter analysis was extended to include paired porcine samples obtained from the lumbar compartment and the cerebromedullary cistern closely related to the ventricles.

RESULTS

In total 1231 proteins were detected in the human CSF. Of these, 216 distributed equally in the two CSF compartments, whereas 22 were preferentially (or solely) present in the ventricular CSF and four in the lumbar CSF. The selected biomarkers of neurodegeneration and Alzheimer's disease displayed differential distribution, some with higher (S100B, T-tau, and P-tau) and some with lower (NfL, Aβ₄₀, Aβ₄₂) levels in the ventricular compartment. In the porcine samples, all biomarkers were most abundant in the lumbar CSF.

CONCLUSIONS

The overall proteomic profile differs between the ventricular and the lumbar CSF compartments, and so does the distribution of clinically employed biomarkers. However, for a range of CSF proteins and biomarkers, one can reliably employ lumbar CSF as a proxy for ventricular CSF if or a lumbar/cranial index for the particular molecule has been established. It is therefore important to verify the compartmental preference of the proteins or biomarkers of interest prior to extrapolating from lumbar CSF to that of the ventricular fluid bordering the brain.

Correlation Between Cognitive Impairment and Homocysteine and S100B Protein in Patients with Progressive Ischemic Stroke

PURPOSE

This study aimed to investigate the relationship between cognitive impairment and homocysteine (Hcy) and S100B protein in patients with progressive ischemic stroke (PIS).

PATIENTS AND METHODS

A total of 158 patients with PIS hospitalized in the Department of Neurology in Taixing People's Hospital from January 2020 to March 2022 were enrolled in the study. After 90 days of follow-up, the patients were divided into two groups according to the MoCA score-99 cases with cognitive impairment group (observation group) and 59 cases with cognitive normal group (control group). Causal diagram was drawn to assess the association between risk factors and PIS with observation group. The risk factors indicators of cognitive impairment in patients with PIS were screened. The related predictive indicators were screened by multivariate logistic regression analysis, and Pearson correlation analysis. The predictive value was analyzed by Receiver Operating Characteristic (ROC) curve.

RESULTS

Multivariate logistic regression analysis showed that age, hypertension, lesion position, Hcy and S100B protein were related risk factors for cognitive impairment in patients with PIS. Pearson correlation analysis was conducted between Hcy and S100 B protein and MoCA score, and revealed that Hcy and S100 B protein were negatively correlated with MoCA score. ROC curve analysis showed that the Area Under the Curve (AUC) of S100 B protein and Hcy in identifying cognitive impairment after PIS was 0.709 and 0.673, respectively, and the combined AUC of Hcy and S100B protein in predicting cognitive impairment after PIS was 0.739.

CONCLUSION

Hcy and S100B protein are related risk factors for cognitive impairment in patients with PIS, and may be used as in a prediction model to predict cognitive impairment after PIS in the future.

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.

Effect of senescence on the tyrosine hydroxylase and S100B immunoreactivity in the nigrostriatal pathway of the rat

Senescence is a natural and progressive physiological event that leads to a series of morphophysiological alterations in the organism. The brain is the most vulnerable organ to both structural and functional changes during this process. Dopamine is a key neurotransmitter for the proper functioning of the brain, directly involved in circuitries related with emotions, learning, motivation and reward. One of the main dopamine- producing nuclei is the substantia nigra pars compacta (SNpc), which establish connections with the striatum forming the so-called nigrostriatal pathway. S100B is a calcium binding protein mainly expressed by astrocytes, involved in both intracellular and extracellular processes, and whose expression is increased following injury in the nervous tissue, being a useful marker in altered status of central nervous system. The present study aimed to analyze the impact of senescence on the cells immunoreactive for tyrosine hydroxylase (TH) and S100B along the nigrostriatal pathway of the rat. Our results show an decreased expression of S100B⁺ cells in SNpc. In addition, there was a significant decrease in TH immunoreactivity in both projection fibers and TH⁺ cell bodies. In the striatum, a decrease in TH immunoreactivity was also observed, as well as an enlargement of the white matter bundles. Our findings point out that senescence is related to the anatomical and neurochemical changes observed throughout the nigrostriatal pathway.

A novel prognostic 6-gene signature for osteoporosis

INTRODUCTION

The incidence of osteoporosis (OP) keeps increasing due to global aging of the population. Therefore, identifying the diagnostic and prognostic biomarkers of OP is of great significance.

METHODS

mRNA data from OP and non-OP samples were obtained from GEO database, which were divided into training set (GSE35959) and testing sets (GSE7158, GSE62402, GSE7429 and GSE56815). Gene modules most significantly related to OP were revealed using weighted gene co-expression network analysis (WGCNA) and differentially expressed genes (DEGs) between OP and normal samples in training set were identified using limma R package. Thereafter, above two gene sets were intersected to obtain the genes potentially related to OP. Protein-protein interaction (PPI) pairs were screened by STRING database and visualized using Cytoscape, while the plug-in cytoHubba was used to screen hub genes by determining their topological parameters. Afterwards, a diagnostic model was constructed using those hub genes, whose creditability was further evaluated by testing sets.

RESULTS

The results of WGCNA analysis found the Black module was most significantly related to OP, which included altogether 1286 genes. Meanwhile, 2771 DEGs were discovered between OP patients and the normal controls. After taking the intersection, 479 genes were identified potentially correlated with the development of OP. Subsequently, six hub genes were discovered through PPI network construction and node topological analysis. Finally, we constructed a support vector machine model based on these six genes, which can accurately classified training and testing set samples into OP and normal groups.

CONCLUSION

Our current study constructed a six hub genes-based diagnostic model for OP. Our findings may shed some light on the research of the early diagnosis for OP and had certain practical significance.

'A picture is worth a thousand words': The use of microscopy for imaging neuroinflammation

Since the first studies of the nervous system by the Nobel laureates Camillo Golgi and Santiago Ramon y Cajal using simple dyes and conventional light microscopes, microscopy has come a long way to the most recent techniques that make it possible to perform images in live cells and animals in health and disease. Many pathological conditions of the central nervous system have already been linked to inflammatory responses. In this scenario, several available markers and techniques can help imaging and unveil the neuroinflammatory process. Moreover, microscopy imaging techniques have become even more necessary to validate the large quantity of data generated in the era of 'omics'. This review aims to highlight how to assess neuroinflammation by using microscopy as a tool to provide specific details about the cell's architecture during neuroinflammatory conditions. First, we describe specific markers that have been used in light microscopy studies and that are widely applied to unravel and describe neuroinflammatory mechanisms in distinct conditions. Then, we discuss some important methodologies that facilitate the imaging of these markers, such as immunohistochemistry and immunofluorescence techniques. Emphasis will be given to studies using two-photon microscopy, an approach that revolutionized the real-time assessment of neuroinflammatory processes. Finally, some studies integrating omics with microscopy will be presented. The fusion of these techniques is developing, but the high amount of data generated from these applications will certainly improve comprehension of the molecular mechanisms involved in neuroinflammation.