Influence of the blood-CSF-barrier function on S100B in neurodegenerative diseases

How S100B crosses brain barriers and why it is considered a peripheral marker of brain injury

S100B is a 21-kDa protein that is produced and secreted by astrocytes and widely used as a marker of brain injury in clinical and experimental studies. The majority of these studies are based on measurements in blood serum, assuming an associated increase in cerebrospinal fluid and a rupture of the blood-brain barrier (BBB). Moreover, extracerebral sources of S100B are often underestimated. Herein, we will review these interpretations and discuss the routes by which S100B, produced by astrocytes, reaches the circulatory system. We discuss the concept of S100B as an alarmin and its dual activity as an inflammatory and neurotrophic molecule. Furthermore, we emphasize the lack of data supporting the idea that S100B acts as a marker of BBB rupture, and the need to include the glymphatic system in the interpretations of serum changes of S100B. The review is also dedicated to valorizing extracerebral sources of S100B, particularly adipocytes. Furthermore, S100B per se may have direct and indirect modulating roles in brain barriers: on the tight junctions that regulate paracellular transport; on the expression of its receptor, RAGE, which is involved in transcellular protein transport; and on aquaporin-4, a key protein in the glymphatic system that is responsible for the clearance of extracellular proteins from the central nervous system. We hope that the data on S100B, discussed here, will be useful and that it will translate into further health benefits in medical practice.

Biofluid markers of blood-brain barrier disruption and neurodegeneration in Lewy body spectrum diseases: A systematic review and meta-analysis

BACKGROUND

Mixed evidence supports blood-brain barrier (BBB) dysfunction in Lewy body spectrum diseases.

METHODS

We compare biofluid markers in people with idiopathic Parkinson's disease (PD) and people with PD dementia (PDD) and/or dementia with Lewy bodies (DLB), compared with healthy controls (HC). Seven databases were searched up to May 10, 2021. Outcomes included cerebrospinal fluid to blood albumin ratio (Q_alb), and concentrations of 7 blood protein markers that also reflect BBB disruption and/or neurodegenerative co-pathology. We further explore differences between PD patients with and without evidence of dementia. Random-effects models were used to obtain standardized mean differences (SMD) with 95% confidence interval.

RESULTS

Of 13,949 unique records, 51 studies were meta-analyzed. Compared to HC, Q_alb was higher in PD (N_PD/N_HC = 224/563; SMD = 0.960 [0.227-1.694], p = 0.010; I² = 92.2%) and in PDD/DLB (N_PDD/DLB/N_HC = 265/670; SMD = 1.126 [0.358-1.893], p < 0.001; I² = 78.2%). Blood neurofilament light chain (NfL) was higher in PD (N_PD/N_HC = 1848/1130; SMD = 0.747 [0.442-1.052], p < 0.001; I² = 91.9%) and PDD/DLB (N_PDD/DLB/N_HC = 183/469; SMD = 1.051 [0.678-1.423], p = 0.004; I² = 92.7%) than in HC. p-tau 181 (N_PD/N_HC = 276/164; SMD = 0.698 [0.149-1.247], p = 0.013; I² = 82.7%) was also higher in PD compared to HC. In exploratory analyses, blood NfL was higher in PD without dementia (N_PDND/N_HC = 1005/740; SMD = 0.252 [0.042-0.462], p = 0.018; I² = 71.8%) and higher in PDD (N_PDD/N_HC = 100/111; SMD = 0.780 [0.347-1.214], p < 0.001; I² = 46.7%) compared to HC. Q_alb (N_PDD/N_PDND = 63/191; SMD = 0.482 [0.189-0.774], p = 0.010; I²<0.001%) and NfL (N_PDD/N_PDND = 100/223; SMD = 0.595 [0.346-0.844], p < 0.001; I² = 3.4%) were higher in PDD than in PD without dementia.

CONCLUSIONS

Biofluid markers suggest BBB disruption and neurodegenerative co-pathology involvement in common Lewy body diseases. Greater evidence of BBB breakdown was seen in Lewy body disease with cognitive impairment.

CSF biomarkers for prion diseases

Recently, clinical trials of human prion disease (HPD) treatments have begun in many countries, and the therapeutic window of these trials focuses mainly on the early stage of the disease. Furthermore, few studies have examined the role of biomarkers at the early stage. According to the World Health Organization, the clinical diagnostic criteria for HPDs include clinical findings, cerebrospinal fluid (CSF) protein markers, and electroencephalography (EEG). In contrast, the UK and European clinical diagnostic criteria include a combination of clinical findings, 14-3-3 protein in the CSF, magnetic resonance imaging-diffusion-weighted imaging (MRI-DWI), and EEG. Moreover, recent advancements in laboratory testing and MRI-DWI have improved the accuracy of diagnostics used for prion diseases. However, according to MRI-DWI data, patients with rapidly progressing dementia are sometimes misdiagnosed with HPD due to the high-intensity areas detected in their brains. Thus, analyzing the CSF biomarkers is critical to diagnose accurately different diseases. CSF biomarkers are investigated using a biochemical approach or the protein amplification methods that utilize the unique properties of prion proteins and the ability of PrP^Sc to induce a conformational change. The biochemical markers include the 14-3-3 and total tau proteins of the CSF. In contrast, the protein amplification methods include the protein misfolding cyclic amplification assay and real-time quaking-induced conversion (RT-QuIC) assay. The RT-QuIC analysis of the CSF has been proved to be a highly sensitive and specific test for identifying sporadic HPD forms; for this reason, it was included in the diagnostic criteria.

Biomarkers of Neurological Outcome After Aneurysmal Subarachnoid Hemorrhage as Early Predictors at Discharge from an Intensive Care Unit

Background

Subarachnoid bleeding is associated with brain injuries and ranges from almost negligible to acute and life threatening. The main objectives were to study changes in brain-specific biomarker levels in patients after an aneurysmal subarachnoid hemorrhage (aSAH) in relation to early clinical findings, severity scores, and intensive care unit (ICU) outcome. Analysis was done to identify specific biomarkers as predictors of a bad outcome in the acute treatment phase.

Methods

Analysis was performed for the proteins of neurofilament, neuron-specific enolase (NSE), microtubule-associated protein tau (MAPT), and for the proteins of glial cells, S100B, and glial fibrillary acidic protein (GFAP). Outcomes were assessed at discharge from the ICU and analyzed based on the grade in the Glasgow Outcome Scale (GOS). Patients were classified into two groups: with a good outcome (Group 1: GOS IV–V, n = 24) and with a bad outcome (Group 2: GOS I–III, n = 31). Blood samples were taken upon admission to the ICU and afterward daily for up to 6 days.

Results

In Group 1, the level of S100B (1.0, 0.9, 0.7, 2.0, 1.0, 0.3 ng/mL) and NSE (1.5, 2.0, 1.6, 1.2, 16.6, 2.2 ng/mL) was significantly lower than in Group 2 (S100B: 4.7, 4.8, 4.4, 4.5, 6.6, 6.8 ng/mL; NSE: 4.0, 4.1, 4.3, 3.8, 4.4, 2.5 1.1 ng/mL) on day 1–6, respectively. MAPT was significantly lower only on the first and second day (83.2 ± 25.1, 132.7 ± 88.1 pg/mL in Group 1 vs. 625.0 ± 250.7, 616.4 ± 391.6 pg/mL in Group 2). GFAP was elevated in both groups from day 1 to 6. In the ROC analysis, S100B showed the highest ability to predict bad ICU outcome of the four biomarkers measured on admission [area under the curve (AUC) 0.81; 95% CI 0.67–0.94, p < 0.001]. NSE and MAPT also had significant predictive value (AUC 0.71; 95% CI 0.54–0.87, p = 0.01; AUC 0.74; 95% CI 0.55–0.92, p = 0.01, respectively). A strong negative correlation between the GOS and S100B and the GOS and NSE was recorded on days 1–5, and between the GOS and MAPT on day 1.

Conclusion

Our findings provide evidence that brain biomarkers such as S100B, NSE, GFAP, and MAPT increase significantly in patients following aSAH. There is a direct relationship between the neurological outcome in the acute treatment phase and the levels of S100B, NSE, and MAPT. The detection of brain-specific biomarkers in conjunction with clinical data may constitute a valuable diagnostic and prognostic tool in the early phase of aSAH treatment.

Is There Any Relevance Between Serum Heavy Metal Concentration and BBB Leakage in Multiple Sclerosis Patients?

Sharp increase in multiple sclerosis (MS) incidence rate has been observed in Iranian people. In addition, it has been suggested that increased S100B level may be useful as an indicative factor of blood-brain barrier disruption. The propose of this study was to measuring blood arsenic, lead, and cadmium concentration and serum S100B concentration in a group of healthy and multiple sclerosis patients in Tehran as the most polluted city in Iran. All subjects were interviewed regarding age, medical history, possible chemical exposure, acute or chronic diseases, smoking, and dietary habits. Blood heavy metal level was measured by an atomic absorption spectrometer (Varian model 220-Z) conjugated with a graphite furnace atomizer (GTA-110). Also, a serum S100B protein concentration was determined using a commercial ELISA kit. It was observed that all male subjects had higher blood metal level in comparison with healthy controls. Also, MS patients had higher arsenic and cadmium blood concentration in comparison with healthy individuals. Regarding the S100B concentration, it was observed that it had a significant relationship with smoking habit (P value = 0.0001). In addition, arsenic had a greater correlation (63%) with increased serum S100B biomarker level among other elements. BBB leakage was higher in multiple sclerosis than in healthy subjects due to increased S100B release. In addition with regard to the heavy metal exposure especially arsenic and cadmium, these are associated with an increased BBB disruption and it is possible to play a crucial role as a developing agent of multiple sclerosis.

Sporadic Creutzfeldt-Jakob disease presenting as dizziness and cognitive decline: A case report

RATIONALE

Creutzfeldt-Jakob disease (CJD) is an infrequent and rapidly fatal neurodegenerative disease without effective cure. Common presentations of CJD include rapidly progressive cognitive decline, behavioral changes, cerebellar dysfunction, and visual disturbances. Since clinicians may see only very few cases during their professional career, it is important to be familiar with the clinical presentation and progression, and allow for quick diagnosis.

PATIENT CONCERNS

We reported an elderly woman had recurrent attacks of dizziness in the preceding month. She began to suffer progression of memory disturbance half a month before admission and was admitted to our department in a coma.

DIAGNOSIS

The accessory examinations of magnetic resonance imaging (MRI), electroencephalography (EEG), 14-3-3 protein in cerebrospinal fluid and S100 protein in serum support the diagnosis of sporadic CJD (sCJD). Combined with this evidence and clinical symptom, we made a clinical diagnosis of sCJD.

INTERVENTIONS

Supportive treatment.

OUTCOMES

After 2 months of active treatment, the patient's condition had not improved, and the patient died 82 days after admission.

LESSONS

Clinicians should attach importance to sCJD, which is significant for the prevention of transmission and treatment.

S100B raises the alert in subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) is a devastating disease with high mortality and mobility, the novel therapeutic strategies of which are essentially required. The calcium binding protein S100B has emerged as a brain injury biomarker that is implicated in pathogenic process of SAH. S100B is mainly expressed in astrocytes of the central nervous system and functions through initiating intracellular signaling or via interacting with cell surface receptor, such as the receptor of advanced glycation end products. The biological roles of S100B in neurons have been closely associated with its concentrations, resulting in either neuroprotection or neurotoxicity. The levels of S100B in the blood have been suggested as a biomarker to predict the progress or the prognosis of SAH. The role of S100B in the development of cerebral vasospasm and brain damage may result from the induction of oxidative stress and neuroinflammation after SAH. To get further insight into mechanisms underlying the role of S100B in SAH based on this review might help us to find novel therapeutic targets for SAH.

CSF tau correlates with CJD disease severity and cognitive decline

BACKGROUND

Creutzfeldt-Jakob disease (CJD) is the most common prion disease in humans. The clinical diagnosis of CJD is supported by a combination of electroencephalogram, MRI, and the presence in the CSF of biomarkers. CSF tau is a marker for neuronal damage and tangle pathology, and is correlated with cognitive status in Alzheimer's disease (AD).

OBJECTIVES

The aim of this study was to test whether tau levels in the CSF also correlate with the degree of the neurological deficit and cognitive decline in patients with CJD as reflected by various clinical scales that assess disease severity and cognitive performance.

METHODS

Consecutive patients with familial CJD (fCJD) were examined by a neurologist who performed several tests including minimental status examination (MMSE), frontal assessment battery (FAB), NIH stroke scale (NIHSS), CJD neurological scale (CJD-NS), and the expanded disability status scale (EDSS). CSF tau was tested as part of the workout, and the correlation was tested using Pearson correlation.

RESULTS

Fifty-two patients with fCJD were recruited to the study (35 males, mean age 59.4 ± 5.7, range 48-75 years). A significant negative correlation was found between CSF tau levels and the cognitive performance of the patients as reflected by their MMSE and FAB scores. In addition, a significant positive correlation was found between tau levels and the clinical disease severity scales of CJD-NS, NIHSS, and EDSS.

CONCLUSION

The correlation between tau levels and the disease severity and degree of cognitive decline in patients with fCJD suggests that tau can be a biomarker reflecting the extent of neuronal damage.