The S-100 protein causes an increase of intracellular calcium and death of PC12 cells

Cerebrospinal Fluid C18 Ceramide Associates with Markers of Alzheimer's Disease and Inflammation at the Pre- and Early Stages of Dementia

Background:

Understanding how dysregulation in lipid metabolism relates to the severity of Alzheimer‘s disease (AD) pathology might be critical in developing effective treatments.

Objective:

To identify lipid species in cerebrospinal fluid (CSF) associated with signature AD pathology and to explore their relationships with measures reflecting AD-related processes (neurodegeneration, inflammation, deficits in verbal episodic memory) among subjects at the pre- and early symptomatic stages of dementia.

Methods:

A total of 60 subjects that had been referred to an Icelandic memory clinic cohort were classified as having CSF AD (n = 34) or non-AD (n = 26) pathology profiles. Untargeted CSF lipidomic analysis was performed using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS) for the detection of mass-to-charge ratio (m/z) features. CSF proteins reflecting neurodegeneration (neurofilament light [NFL]) and inflammation (chitinase-3-like protein 1 [YKL-40], S100 calcium-binding protein B [S100B], glial fibrillary acidic protein [GFAP]) were also measured. Rey Auditory Verbal Learning (RAVLT) and Story tests were used for the assessment of verbal episodic memory.

Results:

Eight out of 1008 features were identified as best distinguishing between the CSF profile groups. Of those, only the annotation of the m/z feature assigned to lipid species C18 ceramide was confirmed with a high confidence. Multiple regression analyses, adjusted for age, gender, and education, demonstrated significant associations of CSF core AD markers (Aβ₄₂: st.β= –0.36, p = 0.007; T-tau: st.β= 0.41, p = 0.005) and inflammatory marker S100B (st.β= 0.51, p = 0.001) with C18 ceramide levels.

Conclusion:

Higher levels of C18 ceramide associated with increased AD pathology and inflammation, suggesting its potential value as a therapeutic target.

Elevation of gene expression of calcineurin, calmodulin and calsyntenin in oxidative stress induced PC12 cells

In normal physiological conditions, reactive oxygen and nitrogen species are used as important signaling molecules in the cell. However, in excess it causes the disruption of cell resulting in their death. Oxidative stress causes influx in intracellular calcium levels leading to higher concentrations of calcium in the cell. This accelerated calcium affects both the mitochondria and nuclei leading to excitotoxicity in neurons. Intracellular calcium levels are controlled by voltage dependent calcium channels located in the plasma membrane, calcium stores like endoplasmic/sarcoplasmic reticulum and majorly by calcium binding proteins. Our study was aimed at analyzing the gene expression of major calcium binding proteins namely calcineurin, calmodulin, calreticulin, synaptotagamin and calsyntenin in stress induced PC 12 cells. Rotenone (1 μM), Peroxynitrite (10 μM), H2O2 (100 μM) and High glucose (33 mM) were used to induce oxidative stress in PC12 cells. Results obtained from the study suggest that calcineurin, calmodulin and calsyntenin gene expression were enhanced compared to the control due to oxidative stress. However, synaptotagmin and calreticulin gene expression were down regulated. Further, Akt protein expression (stress marker) was enhanced in PC12 cells with all other stress inducers except in hyperglycemic condition.

Arundic Acid (ONO-2506), an Inhibitor of S100B Protein Synthesis, Prevents Neurological Deficits and Brain Tissue Damage Following Intracerebral Hemorrhage in Male Wistar Rats

Stroke is one of the leading causes of mortality and neurological morbidity. Intracerebral hemorrhage (ICH) has the poorest prognosis among all stroke subtypes and no treatment has been effective in improving outcomes. Following ICH, the observed high levels of S100B protein have been associated with worsening of injury and neurological deficits. Arundic acid (AA) exerts neuroprotective effects through inhibition of astrocytic synthesis of S100B in some models of experimental brain injury; however, it has not been studied in ICH. The aim of this study was to evaluate the effects of intracerebroventricular (ICV) administration of AA in male Wistar rats submitted to ICH model assessing the following variables: reactive astrogliosis, S100B levels, antioxidant defenses, cell death, lesion extension and neurological function. Firstly, AA was injected at different doses (0.02, 0.2, 2 and 20 μg/μl) in the left lateral ventricle in order to observe which dose would decrease GFAP and S100B striatal levels in non-injured rats. Following determination of the effective dose, ICH damage was induced by IV-S collagenase intrastrial injection and 2 μg/μl AA was injected through ICV route immediately before injury. AA treatment prevented ICH-induced neurological deficits and tissue damage, inhibited excessive astrocytic activation and cellular apoptosis, reduced peripheral and central S100B levels (in striatum, serum and cerebrospinal fluid), improved neuronal survival and enhanced the antioxidant defences after injury. Altogether, these results suggest that S100B is a viable target for treating ICH and highlight AA as an interesting strategy for improving neurological outcome after experimental brain hemorrhage.

Post-Operative Cognitive Dysfunction: An exploration of the inflammatory hypothesis and novel therapies

Post-Operative Cognitive Dysfunction (POCD) is a highly prevalent condition with significant clinical, social and financial impacts for patients and their communities. The underlying pathophysiology is becoming increasingly understood, with the role of neuroinflammation and oxidative stress secondary to surgery and anaesthesia strongly implicated. This review aims to describe the putative mechanisms by which surgery-induced inflammation produces cognitive sequelae, with a focus on identifying potential novel therapies based upon their ability to modify these pathways.

Cerebrospinal Fluid Proteins as Regulators of Beta-amyloid Aggregation and Toxicity

Amyloid disorders, such as Alzheimer's, are almost invariably late-onset diseases. One defining diagnostic feature of Alzheimer's disease is the deposition of beta-amyloid as extracellular plaques, primarily in the hippocampus. This raises the question: are there natural protective agents that prevent beta-amyloid from depositing, and is it loss of this protection that leads to onset of disease? Proteins in cerebrospinal fluid (CSF) have been suggested to act as just such natural protective agents. Here, we describe some of the early evidence that led to this suggestion, and we discuss, in greater detail, two CSF proteins that have garnered the bulk of the attention.

S100B and Glial Fibrillary Acidic Protein as Indexes to Monitor Damage Severity in an In Vitro Model of Traumatic Brain Injury

Traumatic brain injury (TBI) is a leading and rising cause of death and disability worldwide. There is great interest in S100B and Glial Fibrillary Acid Protein (GFAP) as candidate biomarkers of TBI for diagnosis, triage, prognostication and drug development. However, conflicting results especially on S100B hamper their routine application in clinical practice. To try to address this question, we mimicked TBI damage utilizing a well-validated, simplified in vitro model of graded stretch injury induced in rat organotypic hippocampal slice cultures (OHSC). Different severities of trauma, from mild to severe, have been tested by using an equi-biaxial stretch of the OHSCs at a specified Lagrangian strain of 0 (controls), 5, 10, 20 and 50 %. OHSC were analysed at 3, 6, 18, 24, 48 and 96 h post-injury. Cell death, gene expressions and release into the culture medium of S100B and GFAP were determined at each time point. Gene expression and release of S100B slightly increased only in 20 and 50 % stretched OHSC. GFAP over-expression occurred in 10, 20 and 50 % and was inversely correlated with time post-injury. GFAP release significantly increased with time at any level of injury (p < 0.01 with respect to controls). Consequently, the total amount of GFAP released showed a strong linear relationship with the severity of injury (R(2) = 0.7662; p < 0.001). Under these experimental conditions, S100B seems to be useful in diagnosing only moderate to severe TBI-like injuries. Differently, GFAP demonstrates adequate biomarker requisites since its cellular release is affected by all grades of injury severity.

Central nervous system effects of prenatal selective serotonin reuptake inhibitors: sensing the signal through the noise

RATIONALE

Women are increasingly prescribed selective serotonin reuptake inhibitors (SSRIs) during pregnancy, with potential implications for neurodevelopment. Whether prenatal SSRI exposure has an effect on neurodevelopment and behavior in the offspring is an important area of investigation.

OBJECTIVES

The aim of this paper was to review the existing preclinical and clinical literature of prenatal SSRI exposure on serotonin-related behaviors and markers in the offspring. The goal is to determine if there is a signal in the literature that could guide clinical care and/or inform research.

RESULTS

Preclinical studies (n = 4) showed SSRI exposure during development enhanced depression-like behavior. Half of rodent studies examining anxiety-like behavior (n = 13) noted adverse effects with SSRI exposure. A majority of studies of social behavior (n = 4) noted a decrease in sociability in SSRI exposed offspring. Human studies (n = 4) examining anxiety in the offspring showed no adverse effects of prenatal SSRI exposure. The outcome of one study suggested that children with autism were more likely to have a mother who was prescribed an SSRI during pregnancy.

CONCLUSIONS

Preclinical findings in rodents exposed to SSRIs during development point to an increase in depression- and anxiety-like behavior and alteration in social behaviors in the offspring, though both the methods used and the findings were not uniform. These data are not robust enough to discourage use of SSRIs during human pregnancy, particularly given the known adverse effects of maternal mental illness on pregnancy outcomes and infant neurodevelopment. Future research should focus on consistent animal models and prospective human studies with larger samples.

Effects of S100B on Serotonergic Plasticity and Neuroinflammation in the Hippocampus in Down Syndrome and Alzheimer's Disease: Studies in an S100B Overexpressing Mouse Model

S100B promotes development and maturation in the mammalian brain. However, prolonged or extensive exposure can lead to neurodegeneration. Two important functions of S100B in this regard, are its role in the development and plasticity of the serotonergic neurotransmitter system, and its role in the cascade of glial changes associated with neuroinflammation. Both of these processes are therefore accelerated towards degeneration in disease processes wherein S100B is increased, notably, Alzheimer's disease (AD) and Down syndrome (DS). In order to study the role of S100B in this context, we have examined S100B overexpressing transgenic mice. Similar to AD and DS, the transgenic animals show a profound change in serotonin innervation. By 28 weeks of age, there is a significant loss of terminals in the hippocampus. Similarly, the transgenic animals show neuroinflammatory changes analogous with AD and DS. These include decreased numbers of mature, stable astroglial cells, increased numbers of activated microglial cells and increased microglial expression of the cell surface receptor RAGE. Eventually, the S100B transgenic animals show neurodegeneration and the appearance of hyperphosphorylated tau structures, as seen in late stage DS and AD. The role of S100B in these conditions is discussed.

S100B Protein, A Damage-Associated Molecular Pattern Protein in the Brain and Heart, and Beyond

S100B belongs to a multigenic family of Ca(2+)-binding proteins of the EF-hand type and is expressed in high abundance in the brain. S100B interacts with target proteins within cells thereby altering their functions once secreted/released with the multiligand receptor RAGE. As an intracellular regulator, S100B affects protein phosphorylation, energy metabolism, the dynamics of cytoskeleton constituents (and hence, of cell shape and migration), Ca(2+) homeostasis, and cell proliferation and differentiation. As an extracellular signal, at low, physiological concentrations, S100B protects neurons against apoptosis, stimulates neurite outgrowth and astrocyte proliferation, and negatively regulates astrocytic and microglial responses to neurotoxic agents, while at high doses S100B causes neuronal death and exhibits properties of a damage-associated molecular pattern protein. S100B also exerts effects outside the brain; as an intracellular regulator, S100B inhibits the postinfarction hypertrophic response in cardiomyocytes, while as an extracellular signal, (high) S100B causes cardiomyocyte death, activates endothelial cells, and stimulates vascular smooth muscle cell proliferation.

Neonatal S100B protein levels after prenatal exposure to selective serotonin reuptake inhibitors

OBJECTIVE

This study investigated neonatal S100B levels as a biomarker of prenatal selective serotonin reuptake inhibitor (SSRI) exposure.

METHODS

Maternal (delivery; N = 53) and neonatal (cord; N = 52) serum S100B levels were compared between prenatally SSRI-exposed (maternal, N = 36; neonatal, N = 37; duration: 230 +/- 71 days) and nonexposed (maternal, N = 17; neonatal, N = 15) groups. Measures of maternal depression and anxiety symptoms were assessed during the third trimester (33-36 weeks), and neonatal outcomes, including Apgar scores, birth weight, gestational age at birth, and symptoms of poor neonatal adaptation, were recorded.

RESULTS

S100B levels were significantly lower in prenatally SSRI-exposed neonates than in nonexposed neonates, controlling for gestational age and third-trimester maternal mood (P = .036). In contrast, SSRI-exposed mothers had significantly higher maternal serum S100B levels, compared with nonexposed mothers (P = .014), even controlling for maternal mood in the third trimester. S100B levels were not associated with maternal or neonatal drug levels, duration of prenatal exposure, demographic variables, or risk for poor neonatal adaptation.

CONCLUSIONS

Prenatal SSRI exposure was associated with decreased neonatal serum S100B levels, controlling for prenatal maternal mood. Neonatal S100B levels did not reflect neonatal behavioral outcomes and were not related to pharmacologic indices. These findings are consistent with prenatal alcohol and cocaine exposures, which also alter central serotonin levels.

S100B's double life: intracellular regulator and extracellular signal

The Ca2+-binding protein of the EF-hand type, S100B, exerts both intracellular and extracellular functions. Recent studies have provided more detailed information concerning the mechanism(s) of action of S100B as an intracellular regulator and an extracellular signal. Indeed, intracellular S100B acts as a stimulator of cell proliferation and migration and an inhibitor of apoptosis and differentiation, which might have important implications during brain, cartilage and skeletal muscle development and repair, activation of astrocytes in the course of brain damage and neurodegenerative processes, and of cardiomyocyte remodeling after infarction, as well as in melanomagenesis and gliomagenesis. As an extracellular factor, S100B engages RAGE (receptor for advanced glycation end products) in a variety of cell types with different outcomes (i.e. beneficial or detrimental, pro-proliferative or pro-differentiative) depending on the concentration attained by the protein, the cell type and the microenvironment. Yet, RAGE might not be the sole S100B receptor, and S100B's ability to engage RAGE might be regulated by its interaction with other extracellular factors. Future studies using S100B transgenic and S100B null mice might shed more light on the functional role(s) of the protein.

S100A6 (calcyclin) enhances the sensitivity to apoptosis via the upregulation of caspase-3 activity in Hep3B cells

S100A6 (calcyclin) is a small calcium-binding protein which has been implicated in several cellular processes such as cell cycle progression, cytoskeleton rearrangement, and exocytosis. Also the upregulation of S100A6 has been reported in a variety of tumors and linked to metastasis. However, exact intracellular roles of S100A6 related with apoptosis have not been clarified yet. Here we demonstrated that the upregulation of S100A6 enhances the cell death rate compared to the control under the apoptotic conditions. In exogenously S100A6 induced Hep3B cells, cell viability was significantly decreased compared with mock and S100A6-knockdown cells under calcium ionophore A23187 treatment. The exogenously introduced S100A6 significantly affected the caspase-3-like activity in programmed cell death through the enhanced caspase-3 expression, which was verified by promoter assay in wild or mutant S100A6-transfected Hep3B cells. Next, the promoter activity of caspase-3 was increased by 2.5-folds in wild-type S100A6-transfected cells compared to mutant 2 (E67K, mutant of EF-hand motif) or control. Our results suggest that S100A6 might be involved in the processing of apoptosis by modulating the transcriptional regulation of caspase-3.

Protein S-100 and neuropsychological functioning following severe traumatic brain injury

PRIMARY OBJECTIVE

To examine the relationship between serum concentrations of protein S-100beta and neuropsychological functioning following severe traumatic brain injury.

DESIGN

Matched control group.

METHODS

Blood samples were taken within 12 hours of injury and then daily up to 7 days post-injury (n=23). Within 2 weeks of emerging from post-traumatic amnesia (PTA), participants completed a battery of neuropsychological measures. These results were compared with a matched sample of healthy controls.

RESULTS

Early measurement of S-100 not only reflected overall brain injury severity, but also related to neuropsychological deficits, with higher serum concentrations associated with poorer performance across most cognitive domains. PTA duration, measured by the Westmead PTA Scale, was found to be the strongest predictor of S-100 concentration (R2=0.59, p<0.001).

CONCLUSIONS

These findings show that measurement of serum protein S-100 may further aid in the identification of individuals with severe TBI who are likely to experience cognitive difficulties.

Prenatal stress reduces S100B in the neonatal rat hippocampus

Prenatal stress has been shown to disturb neonatal rat brain development. The astroglial-specific neurotrophic factor S100B is known to play an important role in normal brain development. In the present study, we investigated the effects of prenatal stress on S100B concentrations in the hippocampus of 1-day-old Fischer 344 rats. Overall, prenatal stress resulted in a 25% reduction in hippocampal S100B content. Further, male hippocampal S100B content was negatively correlated with plasma corticosterone levels. Positive correlations were found between female S100B levels and fetal growth, and hippocampal brain-derived neurotrophic factor content. In conclusion, the observed reduction in neonatal hippocampal S100B levels, as a consequence of prenatal stress, may be involved in affecting postnatal brain development.

The astroglial-derived S100beta protein stimulates the expression of nitric oxide synthase in rodent macrophages through p38 MAP kinase activation

S100beta is an astroglial-derived Ca2+ -binding protein having neurotrophic role on neurons and glial cells. An aberrant S100beta production has been observed in neurodegenerative disease, as Alzheimer's disease and Down syndrome. S100beta is responsible to start up a gliotic reaction by the release of pro-inflammatory mediators, including nitric oxide (NO) and cytokines from microglia and astrocytes, which are, in turn, deleterious for neurons. Interestingly, pro-inflammatory effect of S100beta seems not be restricted into the brain. Macrophages play a pivotal role in inflammatory diseases, occurring both in the brain and in the periphery. In this study, we tested the hypothesis that S100beta may affect macrophage functions, amplifying thus the inflammatory process. Our results demonstrate that S100beta stimulates both NO production and iNOS protein transcription and expression in J774 and rat peritoneal macrophages. NO production was concentration and time-dependently inhibited by two iNOS inhibitors, L-NAME and SMT. We also demonstrated that S100beta induced oxidative stress by increasing H2O2 production and lipid peroxidation of cell membrane in both macrophage types. The pro-oxidant potential of S100beta activates p38 MAP kinase (MAPK), which has been described to directly activate NF-kappaB. In our study, SB203580, a p38 MAPK inhibitor, and two NF-kappaB inhibitors, TLCK and BAY 11-7082, decreased both NO production and iNOS protein transcription and expression in S100beta-stimulated J774 and peritoneal rat macrophages. Moreover, additional studies demonstrated that S100beta affected also TNF-alpha protein expression in J774 macrophages. In conclusion, our results highlight the potential role of S100beta during an inflammatory scenario identifying macrophages as a novel S100beta-responsive cell-type.

Novel role for gabapentin in neuroprotection of central nervous system in streptozotocine-induced diabetic rats

AIM

To investigate the effect of gabapentin on neural [neuron-specific enolase (NSE)] and glial markers [glial fibrillary acidic protein (GFAP) and S100B] in different brain regions of diabetic rats.

METHODS

Diabetes was induced by a single intraperitoneal injection of streptozotocine (50 mg/kg body weight). Rats in one diabetic group received gabapentin (50 mg.kg(-1).d(-1)) and rats in the other diabetic group received vehicle only for 6 weeks. The levels of GFAP, S100B, and NSE were determined by immunoblotting in the hippocampus, cortex, and cerebellum. Lipid peroxidation (LPO as malondialdehyde+ 4-hydroxyalkenals) and glutathione (GSH) levels were also determined in the same brain parts.

RESULTS

Total and degraded GFAP content and S100B protein expression in different areas of brain tissues significantly increased in diabetic rats compared to control rats. Similarly, NSE levels were also significantly elevated in hyperglycemic rats. In addition, there was a significant increase in LPO levels in the diabetic rat brain compared to control rat brains. Pretreatment with gabapentin prevented the upregulation of GFAP, S100B, and NSE in all brain regions of diabetic rats. The level of LPO was reduced, but not completely halted, by treatment with gabapentin.

CONCLUSION

These results suggest that diabetes causes glial and neuronal injury, possibly as a result of elevated oxidative stress, and that gabapentin protects neurons and glial cells. Thus, we predict that gabapentin treatment will attenuate the hippo-campal and cortical neurodegeneration observed during diabetes mellitus in rats.

Identification of differentially expressed genes in scrapie-infected mouse brains by using global gene expression technology

The pathogenesis of prion diseases, a class of transmissible fatal neurodegenerative diseases in humans and animals, is still unclear. The aim of this study was to identify the differentially regulated genes that correlate with the development of prion diseases for a better understanding of their pathological mechanisms. We employed Affymetrix Mouse Expression Arrays 430A containing >22,000 transcripts and compared the global gene expression profiles from brains of mice who were intracerebrally inoculated with scrapie strains ME7 and RML with those from brains of uninfected and mock-infected mice. The microarray data were analyzed by Significance Analysis of Microarrays, revealing 121 genes whose expression increased at least twofold in both ME7- and RML-infected mouse brains, with an estimated false discovery rate of < or =5%. These genes encode proteins involved in proteolysis, protease inhibition, cell growth and maintenance, the immune response, signal transduction, cell adhesion, and molecular metabolism. The time course of expression generally showed up-regulation of these genes from 120 days postinoculation (dpi) for ME7-inoculated mouse brains and from 90 dpi for RML-inoculated mouse brains. The onset of elevated expression correlated temporally with the onset of PrP(Sc) accumulation and the activation of glia, which may have contributed to neuronal cell death. Among the differentially regulated genes reported in the present study, the emergence of genes for several cathepsins and S100 calcium binding proteins was conspicuous. These and other genes reported here may represent novel potential diagnostic and therapeutic targets for prion disease.

Expression levels of cytoskeletal proteins indicate pathological aging of S100B transgenic mice: an immunohistochemical study of MAP-2, drebrin and GAP-43

S100B is a calcium-binding protein found within astroglial cells. When released, S100B has extracellular neurotrophic effects involving the neuronal cytoskeleton. The gene for S100B is located on chromosome 21 and levels of the protein are elevated in Down Syndrome (DS) and Alzheimer's Disease (AD). Thus, overexpression of S100B may be related to the cytoskeletal abnormalities seen in these disorders. Transgenic mice overexpressing human S100B were examined for cytoskeletal changes as young (70 days) and aged (200 days) adults, using immunochemical staining of the dendritic associated protein, MAP-2, the growth-associated protein-43 (GAP-43) and the dendritic spine marker, drebrin. As young adults, the S100B transgenic mice exhibited significantly greater MAP-2-immunoreactivity in the hippocampus, however as older adults, the animals exhibited less staining. In both the CD1 control animals and the S100B animals, the immunoreactivity of drebrin increased with age, however there were no significant between group differences. Finally, the older S100B animals showed more GAP-43 staining than the control animals, suggesting that synaptic remodeling could take place, possibly in response to the loss of MAP-2-ir dendrites. Overall, the data suggest that S100B overexpression leads to changes in cytoskeletal markers. The longitudinal effects of S100B overexpression are discussed with relevance to aging and pathology.

Trisomy 21 and the brain

In fetuses with Down syndrome, neurons fail to show normal dendritic development, yielding a "tree in winter" appearance. This developmental failure is thought to result in mental retardation. In adults with Down syndrome, neuronal loss is dramatic and neurofibrillary and neuritic Abeta plaque pathologies are consistent with Alzheimer disease. These pathological changes are thought to underlie the neuropsychological and physiological changes in older individuals with Down syndrome. Two chromosome 21-based gene products, beta-amyloid precursor protein (betaAPP) and S100B, have been implicated in these neuronal and interstitial changes. Although not necessary for mental retardation and other features, betaAPP gene triplication is necessary, although perhaps not sufficient, for development of Alzheimer pathology. S100B is overexpressed throughout life in Down patients, and mice with extra copies of the S100B gene have dendritic abnormalities. S100B overexpression correlates with Alzheimer pathology in post-adolescent Down syndrome patients and has been implicated in Abeta plaque pathogenesis. Interleukin-1 (IL-1) is a non-chromosome-21-based cytokine that is also overexpressed throughout life in Down syndrome. IL-1 upregulates betaAPP and S100B expression and drives numerous neurodegenerative and self-amplifying cascades that support a neuroinflammatory component in the pathogenesis of sporadic and Down syndrome-related Alzheimer disease.

Increased clusterin expression in old but not young adult S100B transgenic mice: evidence of neuropathological aging in a model of Down Syndrome

S100B is a calcium-binding protein, localized to astroglial cells, which has a variety of neurotrophic functions, including roles in serotonergic neuronal growth, synaptogenesis dendritic branching and apoptosis. In humans, the gene for S100B is found on chromosome 21, within what is considered the obligate region for Down Syndrome (DS) and levels of S100B are increased in brain of both DS and Alzheimer's Disease (AD). We have been characterizing a transgenic mouse overexpressing this protein and have previously found evidence of pathological changes in brains of the mice. In the current study, we have examined the expression of clusterin, a protein expressed in aging neurons, in the mice at two ages. Our findings show increased clusterin expression in the aged S100B mice compared to their CD-1 controls, a finding we have interpreted as further evidence of pathological brain aging.

Low molecular weight phosphotyrosine protein phosphatase from PC12 cells. Purification, some properties and expression during neurogenesis in vitro and in vivo

The purification and partial characterization of low molecular weight phosphotyrosine phosphatase (LMW-PTP) was reported for the first time in PC12 cells. In addition, the expression levels during neuronal phenotype induction by nerve growth factor (NGF) and during neurogenesis in chick embryos were investigated. LMW-PTP was purified to homogeneity and showed a single band of about 18 kDa with sodium dodecyl sulfate polyacrylamide gel electrophoresis. A native molecular mass of 20.1 kDa was determined by gel filtration on Sephadex G-75 column. The LMW-PTP from PC12 cells displays structural and biochemical characteristics similar to the enzyme isolated for normal tissues. It was specifically immunoprecipitated by an affinity purified antibody directed against the bovine liver enzyme. The enzyme is present in the cytosolic and cytoskeletal cell compartment where is tyrosine phosphorylated. Time course expression of LMW-PTP in PC12 cells was investigated after NGF treatment and showed an increase of about 30% in the basal level of LMW-PTP from 0 to 72 h. These changes were related to the appearance in PC12 cells of neuronal processes and to a decrease in cell proliferation. An increase of the LMW-PTP expression was also observed in vivo during chick embryo neurogenesis from 8-day-old embryos to adult chicks. The protein level, assayed by immunoblotting, increases from 14-day-old embryos to the hatched chicks reaching the adult levels within the first week after birth. These data indicate that the neurogenesis process is accompanied by a physiological increment of LMW-PTP expression in vitro and in vivo.

Studies of the brain specificity of S100B and neuron-specific enolase (NSE) in blood serum of acute care patients

Laboratory monitoring with damage markers of brain and of non-nervous tissues in blood serum of 401 acute care patients showed increased contents of neuron-specific enolase (NSE) and S100B besides raised levels of markers of heart, skeletal muscle, bile duct, liver, prostate, kidney, salivary gland damage or of inflammatory stress to varying frequencies. Correlation between raised NSE and S100B contents ascertained brain damage. Correlation between raised NSE and troponin I (cTnI) values indicated brain damage induced by heart failure (probably caused by hypoxia and anemia); this was assessed with correlations between NSE and other heart markers, e.g. creatine kinase (CK) isoenzymes, alpha-hydroxybutyrate dehydrogenase. S100B did not show such correlations: data indicated S100B release from non-nervous tissues having high S100B content, e.g. fat, cartilage, skin. S100B release might be triggered by inflammatory stress and tissue damage. This was further supported by low NSE/S100B concentration ratios in serum compared to cerebrospinal fluid (CSF) of patients with comatose state, convulsive status, or intracerebral hemorrhage. Our data revealed CSF to be the relevant sample to monitor brain damage with NSE and S100B, whereas in serum raised S100B levels together with normal NSE levels indicated release from non-nervous tissues of acute care patients pointing out multi-organ dysfunction.

Cytosine arabinofuranoside-induced activation of astrocytes increases the susceptibility of neurons to glutamate due to the release of soluble factors

Activation of astrocytes occurs during many forms of CNS injury, but its importance for neuronal survival is poorly understood. When hippocampal cultures of neurons and astrocytes were treated from day 2-4 in vitro (DIV 2-4) with 1 microM cytosine arabinofuranoside (AraC), we observed a stellation of astrocytes, an increase in glial fibrillary acidic protein (GFAP) level as well as a higher susceptibility of the neurons to glutamate compared with cultures treated from DIV 2-4 with vehicle. To find out whether factors released into the culture medium were responsible for the observed differences in glutamate neurotoxicity, conditioned medium of AraC-treated cultures (MCMAraC) was added to vehicle-treated cultures and conditioned medium of vehicle-treated cultures (MCMvh) was added to AraC-treated cultures 2 h before and up to 18 h after the exposure to 1mM glutamate for 1 h. MCMAraC increased glutamate neurotoxicity in vehicle-treated cultures and MCMvh reduced glutamate neurotoxicity in AraC-treated cultures. Heat-inactivation of MCMvh increased, whereas heat-inactivation of MCMAraC did not affect glutamate toxicity suggesting that heat-inactivation changed the proportion of factors in MCMvh inhibiting and exacerbating the excitotoxic injury. Similar findings were obtained using conditioned medium of pure astrocyte cultures of DIV 12 treated from DIV 2-4 with vehicle or 1 microM AraC suggesting that heat-sensitive factors in MCMvh were mainly derived from astrocytes. Treatment of hippocampal cultures with 1mM dibutyryl-cAMP for 3 days induced an activation of the astrocytes similar to AraC and increased neuronal susceptibility to glutamate. Our findings provide evidence that activation of astrocytes impairs their ability to protect neurons after excitotoxic injury due to changes in the release of soluble and heat-sensitive factors.

Effects of ethanol and 5-HT1A agonists on astroglial S100B

Previous studies from this and another laboratory demonstrated that in utero ethanol exposure reduces 5-HT neurons and S100B-immunopositive glia that are proximal to these neurons. Our laboratory also found that these effects are prevented by maternal treatment with a 5-HT(1A) agonist. Because of S100B's important role in the development of 5-HT neurons, the present study used both in vivo and in vitro models to investigate the potential involvement of S100B with the damaging effects of ethanol and with the protective effects of 5-HT(1A) agonists. We used in situ hybridization to address whether a 5-HT(1A) agonist could potentially affect S100B mRNA in vivo. Maternal treatment with buspirone between gestation days 13 and 20 significantly increased S100B mRNA in neuroepithelium of G20 offspring of control (40%) and ethanol-fed dams (20%). However, S100B mRNA was not altered in neuroepithelium from ethanol-exposed offspring. In astroglial cultures, we examined whether ethanol reduces the release of S100B and whether a 5-HT(1A) agonist could stimulate the release of this protein. We also evaluated the effects of ethanol and ipsapirone on astroglial content of S100B. Neither the concentration of S100B in astroglial media nor astroglial content of S100B were affected by ethanol. However, treatment with 100 nM ipsapirone, a 5-HT(1A) agonist, between the 6th and 7th day in vitro, increased astroglial release of S100B 2- to 3-fold. Thus, the protective effects of a 5-HT(1A) agonist on ethanol-treated 5-HT neurons might be associated with the ability of these drugs to release the neurotrophic factor S100B from astrocytes.

Utility of immunostaining for S-100 protein subunits in gonadal sex cord-stromal tumors, with emphasis on the large-cell calcifying Sertoli cell tumor of the testis

This study concerns the immunohistochemical localization of S-100 alpha, S-100 beta, and whole brain S-100 (wbS-100) in testicular large-cell calcifying Sertoli cell tumor (LCCSCT). We examined 8 LCCSCTs (7 benign and 1 malignant), 6 Sertoli cell tumors not otherwise specified (SCTs-NOS), 6 Leydig cell tumors (LCTs), 5 ovarian Sertoli-Leydig cell tumors (SLCTs), and 7 gonadoblastomas (GBLs). The 8 LCCSCTs showed immunoreactivity for S-100 alpha, S-100 beta, and wbS-100. Five of the 6 LCTs and the Leydig cell components in the ovarian SLCTs stained positively for S-100 alpha and wbS-100 but were negative for S-100 beta. SCTs-NOS and the Sertoli cell components in the SLCTs occasionally showed focal and weak/moderate positivity for S-100 alpha, S-100 beta, and wbS-100. Sex cord cells of the GBLs were positive for S-100 beta and wbS-100 and negative for S-100 alpha. Germ cell elements of the GBLs were negative for S-100 alpha, S-100 beta, and wbS-100. In nonneoplastic testicular parenchyma adjacent to the above-mentioned tumors, there was S-100 alpha reactivity in Leydig cells, rete testis, and a few Sertoli cells. S-100 beta reactivity was seen in a few Sertoli cells, Schwann cells, and some endothelial cells. WbS-100 reactivity was present in Leydig cells, a few Sertoli cells, rete testis, Schwann cells, and some endothelial cells. The results indicate that S-100 alpha and S-100 beta can potentially be used as immunohistochemical markers for LCCSCT, especially when differentiating it from LCT, which may mimic LCCSCT on routine histopathology. Although the biological significance of both S-100 subunits expression in LCCSCT remains unknown, these notable calcium-binding proteins may be associated with the characteristic calcification in LCCSCT through regulation of calcium levels in the tumor cells.

Colchicine-induced cytoskeletal collapse and apoptosis in N-18 neuroblastoma cultures is rapidly reversed by applied S-100beta

Brain connections depend on a stable association between dendrites and axons whose cytoskeleton is stabilized by the proteins MAP-2 and tau, respectively. The glial protein S-100beta inhibits the phosphorylation by PKC of these two microtubule-associated proteins. In order to determine if exogenous S-100beta can directly influence the cytoskeleton of living cells, cultures of N-18 cells (neuroblastoma clonal cell line) are treated for 30 min in serum-free medium with 10(-6) M colchicine. In normal media, colchicine induces a rapid retraction of processes, membrane blebbing, nuclear collapse, and cell death. The observed cellular changes, due to cytoskeletal collapse after exposure to colchicine, are similar and consistent with the loss of processes and cytoplasmic blebbing seen in cells undergoing apoptosis. The addition of 20 ng/ml of S-100beta after the initial 30-min exposure to colchicine prevents apoptosis, nuclear collapse and induces the regrowth of retracted processes. Cells were treated with the Hoechst Stain, a fluorescent marker that binds to nuclear material, to determine the occurrence of apoptosis in our cultures. In our control cultures, receiving no drugs, we found that 15.1% of the cells were apoptotic. When colchicine was added to the culture medium we found that 31.6% of the cells became apoptotic. However, when colchicine was followed by exposure to S-100beta we found that only 5.4% of the cells were apoptotic. Our results suggest that extracellular application of the glial protein S-100beta is sufficient to reverse colchicine-induced cytoskeletal collapse and prevent the resultant apoptosis of the cells. The increased levels of S-100beta seen after brain injury and in certain neurological and psychiatric disorders may be considered as beneficial for brain recovery.

Astrocytes contribute to neuronal impairment in beta A toxicity increasing apoptosis in rat hippocampal neurons

Astrocytosis is a common feature of amyloid plaques, the hallmark of Alzheimer's disease (AD), along with activated microglia, neurofibrillary tangles, and beta-amyloid (beta A) deposition. However, the relationship between astrocytosis and neurodegeneration remains unclear. To assess whether beta A-stimulated astrocytes can damage neurons and contribute to beta A neurotoxicity, we studied the effects of beta A treatment in astrocytic/neuronal co-cultures, obtained from rat embryonic brain tissue. We found that in neuronal cultures conditioned by beta A-treated astrocytes, but not directly in contact with beta A, the number of apoptotic cells increased, doubling the values of controls. In astrocytes, beta A did not cause astrocytic cell death, nor did produce changes in nitric oxide or prostaglandin E(2) levels. In contrast, S-100 beta expression was remarkably increased. Our data show for the first time that beta A--astrocytic interaction produces a detrimental effect on neurons, which may contribute to neurodegeneration in AD.

New structural analogues of Tubulozole induce apoptosis, [Ca2+]i modifications and cytoskeletal disorganization in glial (GL15) and neuronal-like (PC12) cell lines

The synthesis and the biological activity of (+/-)-cis- and (+/-)-trans-[4-[[2-(1,1'-biphenyl-4-yl)-2-(1H-imidazol-1-ylmethyl)-1, 3-dioxolan-4-yl]methylthio]phenyl]carbamic acid ethyl esters (2a and 2b) are discussed. They were designed as structural analogues of Tubulozole, a synthetic tubulin polymerisation inhibitor with antimitotic properties. Biological tests were carried out on PC12, a neuronal-like cell line derived from rat pheochromocytoma, and on GL15, a cell line derived from human glioblastoma. The exposure (from 5 to 20 h) of GL15 and PC12 cells to different concentrations (0.1-1000 microM; IC50 approximately 1 microM) of 2a or 2b resulted in a drastic decrease in the number of viable cells without an apparent effect on the cell distribution in the various phases of the cell cycle. Compound 2a or 2b (10 microM) induced cell death by activating apoptosis. This was correlated with the activation of an oscillating Ca(2+)-dependent mechanism which increased the intracellular calcium concentration ([Ca2+]i) via Ca(2+)-release from internal stores. Moreover, 2a (10 microM) also induced severe damage of cytoskeletal F-actin filaments after a 5 h incubation in GL15 cells. This was also observed but to a smaller extent, for 2b. Under the same experimental conditions, PC12 cells showed similar actin deregulation.

Serum S100 protein as a marker of cerebral damage during cardiac surgery

The identification of a serum marker to assist in the diagnosis of cerebral injury after cardiac surgery is potentially useful. S100 protein is an early marker of cerebral damage. It is released after cardiac surgery performed under cardiopulmonary bypass (CPB). Its level is correlated with the duration of CPB, deep circulatory arrest and aortic cross-clamping. Increased levels of S100 protein are correlated with the age of the patient and the number of microemboli, especially during aortic cannulation. Perioperative cerebral complications such as stroke, delayed awakening and confusion are associated with increased levels of S100 protein directly after bypass and from 15 to 48 h after it. In addition, increased levels of S100 protein are related to neuropsychological dysfunction after cardiac surgery. S100 protein has early and late release patterns after CPB; the early pattern may be due to sub-clinical brain injury. The late release pattern may be due to perioperative cerebral complications. Patients undergoing intracardiac operations combined with coronary artery bypass surgery are more susceptible to brain injury and have higher levels of S100 after CPB. Furthermore, adults and children undergoing deep circulatory arrest are more susceptible to brain injury, in terms of higher S100 protein release after CPB. Serum S100 protein levels are reduced after using arterial line filtration and covalent-bonded heparin to coat the inner surface of the CPB circuit.

S-100beta protects cultured neurons against glutamate- and staurosporine-induced damage and is involved in the antiapoptotic action of the 5 HT(1A)-receptor agonist, Bay x 3702

The serotonin (5-HT)(1A) receptor agonists have already been shown to protect cultured neurons from excitotoxic as well as from apoptotic damage [B. Ahlemeyer, J. Krieglstein, Stimulation of 5-HT(1A) receptors inhibits apoptosis induced by serum deprivation in cultured neurons from chick embryo, Brain Res. 777 (1997) 179-186. ; B. Ahlemeyer, A. Glaser, C. Schaper, I. Semkova, J. Krieglstein, The 5-HT(1A) receptor agonist, Bay x 3702, inhibited apoptosis induced by serum deprivation in cultured neurons, Eur. J. Pharmacol. 370 (1999) 211-216.; J.H.M. Prehn, M. Welsch, C. Backhauss, J. Nuglisch, F. Ausmeier, C. Karkoutly, J. Krieglstein, Effects of serotonergic drugs in experimental brain ischemia: evidence for a protective role of serotonin in cerebral ischemia, Brain Res. 630 (1993) 110-120.; I. Semkova, P. Wolz, J. Krieglstein, Neuroprotective effect of 5-HT(1A) receptor agonist, Bay x 3702, demonstrated in vitro and in vivo, Eur. J. Pharmacol. 359 (1998) 251-260.; B. Suchanek, H. Struppeck, T. Fahrig, The 5-HT(1A) receptor agonist, Bay x 3702, prevents staurosporine-induced apoptosis, Eur. J. Pharmacol. 355 (1998) 95-101.] and to increase the release of the neurotrophic protein, S-100beta [P.M. Whitaker-Azmitia, R. Murphy, E.C. Azmitia, Stimulation of astroglial 5-HT(1A) receptors releases the serotonergic growth factor, protein S-100, and alters astroglial morphology, Brain Res. 497 (1989) 80-86. ; P.M. Whitaker-Azmitia, R. Murphy, E.C. Azmitia, S-100 protein is released from astroglial cells by stimulation of 5-HT(1A) receptors, Brain Res. 528 (1990) 155-158.]. In this study, we tried to find out whether S-100beta can protect cultured neurons from glutamate- and staurosporine-induced damage and whether the neuroprotective activity of the highly selective 5-HT(1A) receptor agonist, Bay x 3702, is mediated by an induction of S-100beta. Extracellularly added S-100beta (1-10 ng/ml) reduced staurosporine-induced damage in pure neuronal cultures from chick embryo telencephalon as well as in mixed neuronal/glial cultures from neonatal rat hippocampus. In addition, S-100beta (1 ng/ml) reduced neuronal death induced by exposure to glutamate (0.25 mM, 30 min) in mixed neuronal/glial cultures from neonatal rat hippocampus. In cultured rat cortical astrocytes, a 24 h-treatment with Bay x 3702 (1 nM) increased the S-100beta content in the culture medium from 2.2+/-0.3 (controls) to 6.2+/-0.7 ng/ml. In the adult rat, a 4 h-infusion of 4 microg/kg Bay x 3702 (i.v.) was found to increase the S-100beta content in the striatum 6 h after the beginning of the infusion to 153+/-37 microg/g compared with 60+/-20 microg/g in vehicle-treated rats. Bay x 3702 had no effect on the S-100beta content in the rat hippocampus. Finally, we tried to block the protective effect of Bay x 3702 against staurosporine-induced damage in mixed neuronal/glial cultures from rat neonatal hippocampus by anti-S-100beta antibodies. We found only a partial blockade, although the antibodies fully blocked the antiapoptotic effect of S-100beta itself demonstrating that the antibody was effective in blocking neuroprotection by S-100beta. Thus, we conclude that S-100beta was able to protect cultured neurons against glutamate- and staurosporine-induced damage. Furthermore, S-100beta mediated partially the protective effect of the 5-HT(1A) receptor agonist, Bay x 3702, against staurosporine-induced apoptosis in mixed neuronal/glial cultures from neonatal rat hippocampus.

Structural basis of the Ca(2+)-dependent association between S100C (S100A11) and its target, the N-terminal part of annexin I

BACKGROUND

S100C (S100A11) is a member of the S100 calcium-binding protein family, the function of which is not yet entirely clear, but may include cytoskeleton assembly and dynamics. S100 proteins consist of two EF-hand calcium-binding motifs, connected by a flexible loop. Like several other members of the family, S100C forms a homodimer. A number of S100 proteins form complexes with annexins, another family of calcium-binding proteins that also bind to phospholipids. Structural studies have been undertaken to understand the basis of these interactions.

RESULTS

We have solved the crystal structure of a complex of calcium-loaded S100C with a synthetic peptide that corresponds to the first 14 residues of the annexin I N terminus at 2.3 A resolution. We find a stoichiometry of one peptide per S100C monomer, the entire complex structure consisting of two peptides per S100C dimer. Each peptide, however, interacts with both monomers of the S100C dimer. The two S100C molecules of the dimer are linked by a disulphide bridge. The structure is surprisingly close to that of the p11-annexin II N-terminal peptide complex solved previously. We have performed competition experiments to try to understand the specificity of the S100-annexin interaction.

CONCLUSIONS

By solving the structure of a second annexin N terminus-S100 protein complex, we confirmed a novel mode of interaction of S100 proteins with their target peptides; there is a one-to-one stoichiometry, where the dimeric structure of the S100 protein is, nevertheless, essential for complex formation. Our structure can provide a model for a Ca(2+)-regulated annexin I-S100C heterotetramer, possibly involved in crosslinking membrane surfaces or organising membranes during certain fusion events.

Differential expression of S100B and S100A6(1) in the human fetal and aged cerebral cortex

S100B and S100A6 (calcylin) are two members of the S100 Ca(2+)-binding protein family and have been localized in the mammalian nervous system. However, information on their distribution in the human nervous system, especially in the developing human fetal brain, is scarce. In the present study, an immunocytochemical method was used to examine the spatio-temporal protein expression patterns of S100B and S100A6 in normal human fetal hippocampus, entorhinal cortex and occipital cortex. Normal aged adult human brain specimens were also included for comparison. From week 15 onwards, an increase with advancing gestation age in both the number and staining intensity of S100B positive, astrocyte-like cells was found in the pyramidal layer of the hippocampus, while both the molecular and polymorphic layers showed similar S100B immunoreactivities at all stages examined. A decrease in the immunoreactivities was found in the molecular layer of the aged adult hippocampus while other layers exhibited immunoreactivities similar to those of the late fetus. At week 15, the molecular, pyramidal and ganglionic/multiform layers of the entorhinal cortex also showed positive S100B immunoreactivities which were maintained throughout the rest of the gestation and in adult specimens. In the occipital cortex, the numbers of positive cells for all layers were about twofold higher than those found in the hippocampus and entorhinal cortex, and immunoreactivities detected in the granular layer increased from week 21, reaching a plateau at around week 27. S100B positive fibers were also found at week 30 but were not observed in aged adult specimens. S100A6 positive cells were on the whole fewer in number than those of S100B in the brain regions examined. The S100A6 immunoreactivities which were localized in some pyramidal neuron-like and some glial-like cells of the pyramidal and molecular layers of the hippocampus increased by midgestation and became weak in the late fetus and in aged adult specimens. Weakly stained S100A6 positive cells were also observed in the entorhinal cortex throughout the gestation and in aged adult cortex. S100A6 immunoreactivities were weak in the fetal occipital cortex. They were also localized in the glial-like cells of the aged adult occipital cortex. The differential spatio-temporal expression of S100B and S100A6 proteins suggests that the proteins play different roles in different brain regions during development and in adulthood.

Modulation of glial activation by astrocyte-derived protein S100B: differential responses of astrocyte and microglial cultures

The astrocyte-derived protein S100B stimulates production of inducible nitric oxide synthase and nitric oxide (NO) in astrocytes [Hu et al., 1996, J. Biol. Chem. 271:2543], but its effect on microglia is not known. In addition, S100B's ability to modulate the activity of other glial activating agents has not been defined. In this study, we compared the ability of S100B to stimulate NO in cultures of rat primary astrocytes and the BV-2 murine microglial cell line, and investigated the effect of the combined action of S100B and other stimuli known to activate glial cells. S100B itself stimulated the production of NO in astrocytes, and did not modify or potentiated only weakly the NO production induced by interleukin-1 beta, tumor necrosis factor alpha, dibutyryl cyclic AMP, zymosan A or lipid A. In contrast, S100B alone did not induce NO in BV-2 cells but strongly potentiated NO production in the presence of lipid A but not zymosan A. The deletion of eight C-terminal amino acid residues in S100B leads to a loss of the effect of S100B on microglia but not on astrocytes. These results demonstrate that responses of glial cells to extracellular S100B can vary depending on the cell type, and suggest that different structural features of S100B are important for the protein's effects on microglia and astrocytes.

Bcl-2 expression regulates cell sensitivity to S100beta-mediated apoptosis

The S100beta protein is overexpressed in the brain of patients with Alzheimer's disease and Down's syndrome and is able to induce apoptosis in neurons at high concentrations. The intracellular events that regulate the apoptotic effect are largely unknown. This study investigates the roles of the bcl-2 proto-oncogene, one of the best-defined apoptotic genes, on cell death induced by S100beta. Human neuronal precursor NT2/D1 cells showed a high degree of cell death by apoptosis after exposure to 2 microM S100beta in serum-free medium. Death was preceded by a down-regulation of the Bcl-2 protein. Gene transfer with a full-length bcl-2 cDNA under the control of a constitutive promoter in NT2 cells elevated Bcl-2 protein levels and repressed S100beta-mediated cell death. When exposed to retinoic acid, the NT2/D1 cells differentiated into a neuronal phenotype. The differentiated cells up-regulated their levels of Bcl-2 and became resistant to S100beta-induced cell death. Downregulation of Bcl-2 by an antisense oligonucleotide in the differentiated cells, however, increased their susceptibility to S100beta-related cytotoxicity. Therefore, apoptosis induced through S100beta signaling is subject to regulation by Bcl-2. A combined alteration such as up-regulation of S100beta together with down-regulation of Bcl-2 may be important in the pathogenesis of Alzheimer's disease and Down's syndrome.

Rapid desensitization of PC12 cells stimulated with high concentrations of extracellular S100

Undifferentiated PC12 cells undergo apoptosis, via a calcium-induced calcium release mechanism, when the calcium-binding protein purified from bovine brain (native S100) is present in micromolar concentration in the medium. This process begins when S100 binds to specific membrane binding sites and involves up to 50% of the cell population. In the experiments reported here, we demonstrate that, by utilizing [3H]S100, the S100 protein can be displaced from its binding sites only during the first 10 min of incubation. This fact is due to an internalization mechanism, having a time-course with a plateau after 10-20 min of incubation. The native form of S100 is a mixture of two different S100 isoforms: S100A1 (20%) and S100B (80%). Using confocal microscopy and monoclonal antibodies, we demonstrated that only one of these isoforms, S100A1, was autoexpressed in more than 50% of the PC12 cells analysed. After cell incubation with 2 microM native S100, S100B also appears in PC12 cells, with a maximum presence after 10 min of incubation. This fact seems to indicate that this isoform, at least, is effectively translocated when stimulated with external native S100. From the data reported, it is possible to hypothesize that, in PC12 cells, a possible homeostatic mechanism is present that can counteract the effect of a continuously applied lethal stimulus (stimuli) on cell viability.

Calcium and S100B regulation of p53-dependent cell growth arrest and apoptosis

In glial C6 cells constitutively expressing wild-type p53, synthesis of the calcium-binding protein S100B is associated with cell density-dependent inhibition of growth and apoptosis in response to UV irradiation. A functional interaction between S100B and p53 was first demonstrated in p53-negative mouse embryo fibroblasts (MEF cells) by sequential transfection with the S100B and the temperature-sensitive p53Val135 genes. We show that in MEF cells expressing a low level of p53Val135, S100B cooperates with p53Val135 in triggering calcium-dependent cell growth arrest and cell death in response to UV irradiation at the nonpermissive temperature (37.5 degreesC). Calcium-dependent growth arrest of MEF cells expressing S100B correlates with specific nuclear accumulation of the wild-type p53Val135 conformational species. S100B modulation of wild-type p53Val135 nuclear translocation and functions was confirmed with the rat embryo fibroblast (REF) cell line clone 6, which is transformed by oncogenic Ha-ras and overexpression of p53Val135. Ectopic expression of S100B in clone 6 cells restores contact inhibition of growth at 37.5 degreesC, which also correlates with nuclear accumulation of the wild-type p53Val135 conformational species. Moreover, a calcium ionophore mediates a reversible G1 arrest in S100B-expressing REF (S100B-REF) cells at 37.5 degreesC that is phenotypically indistinguishable from p53-mediated G1 arrest at the permissive temperature (32 degreesC). S100B-REF cells proceeding from G1 underwent apoptosis in response to UV irradiation. Our data support a model in which calcium signaling and S100B cooperate with the p53 pathways of cell growth inhibition and apoptosis.

Cerebral emboli and serum S100beta during cardiac operations

BACKGROUND

The glial protein S100beta has been used to estimate cerebral damage in a number of clinical settings. The purpose of this investigation was to determine the correlation between cerebral microemboli and S100beta levels during cardiac operations.

METHODS

Transcranial Doppler ultrasonography was used to measure emboli in the right middle cerebral artery. Emboli counts (n = 111) were divided into five time periods: (1) incision to aortic cannulation; (2) aortic cannulation to cross-clamp onset; (3) cross-clamp onset to cross-clamp release; (4) cross-clamp release to decannulation; and (5) decannulation to chest closure. The level of S100beta (n = 156) was measured at baseline, at the end of cardiopulmonary bypass, then 150 and 270 minutes after cross-clamp release.

RESULTS

The level of S100beta correlated with age, cardiopulmonary bypass time, cross-clamp time, and number of emboli at time period 2. Although cardiopulmonary bypass time was univariately associated with S100beta level, it became nonsignificant in a multivariable model that included age and cross-clamp time.

CONCLUSIONS

The correlation of S100beta level with emboli measured during cannulation (time period 2) supports the hypothesis that cannulation is a high-risk time period for cerebral injury.

Kinetical analysis of tumor cell death-inducing mechanism by polymorphonuclear leukocyte-derived calprotectin: involvement of protein synthesis and generation of reactive oxygen species in target cells

We have previously shown that calprotectin, the most abundant cytosolic protein existing in polymorphonuclear leukocytes (PMNs), induces apoptotic cell death in various tumor cells, suggesting that calprotectin is an effector molecule against tumor cells in PMNs. To explore the cell death-inducing mechanism of the factor, we examined the involvement of target protein synthesis and generation of reactive oxygen species (ROS) in the reaction. Calprotectin induced cell death in MM46 mouse mammary carcinoma cells after a 14-16 hr lag time. When the factor was removed from the medium up to about 12 hr after culturing, the effect was diminished. The induction of cell death by calprotectin was markedly inhibited by the presence of the RNA synthesis inhibitor actinomycin D or the protein synthesis inhibitor cycloheximide. However, the addition of these inhibitors after 12 hr of culturing was unable to inhibit the reaction. Up to 12 hr of culturing, the net protein synthesis of MM46 cells was augmented by the presence of calprotectin, but thereafter was impaired. The induction of cell death was also inhibited by the antioxidative reagents N-acetyl-L-cysteine (NAC) or propyl gallate. The addition of NAC even 15 hr later significantly attenuated the calprotectin effect. Flow cytometry analysis showed that calprotectin began to increase the ROS content in MM46 cells after 8-12 hr of culturing, and that the increase was abrogated by the antioxidants. Thus, protein synthesis and ROS generation may be essential elements in the early or later phases of the cell death-inducing reaction of calprotectin, respectively.

S-100 proteins in trimethyltin-induced neurodegeneration in the rat hippocampus. An immunochemical and immunocytochemical study

After acute trimethyltin (TMT) intoxication (21 d after a single i.p. injection at a dose of 8 mg/kg) the histological, immunohistochemical, and immunochemical investigation of adult rat hippocampus showed a distinct pattern of neuronal loss, and an increase in both glial fibrillary acidic protein- (GFAP) immunoreactive cells and GFAP concentration, as expected. S-100-immunoreactive cells also increased markedly, whereas the concentration of S-100 increased even more than that of GFAP. The data show that S-100 is an index of glial reaction to damage after TMT intoxication and suggest the potential usefulness of exploring the possibility that it may play a role in induced neurodegenerative processes.

Nerve growth factor inhibits apoptosis induced by S-100 binding in neuronal PC12 cells

When grown for seven days in a medium containing nerve growth factor (100 ng/ml), 10% horse serum and 5% fetal bovine serum PC12 cells stopped dividing, extended neurites and assumed a neuronal phenotype. Withdrawal of nerve growth factor from these cells resulted in loss of neurites and apoptotic changes in many cells. The apoptotic changes were exacerbated if the cells were also exposed to 1-2 microM S-100, a calcium binding protein purified from bovine brain. After exposure to S-100, the PC12 cells underwent characteristic apoptotic changes. Within 2 in neurites retracted, the cell body shrunk and submembranous accumulation of condensed cytoplasmic material was observed. DNA ladders were present after 24-48 h and 60% of the cells became hypodiploid after 72 h. S-100 induced apoptosis by binding to specific sites (Kd = 189 nM) on PC12 cells and this caused a rise in [Ca2+]i due to a transmembrane capacitative flux followed by the depletion of internal stores. This increase was reversed if 5 microM nifedipine, a specific L-type Ca2+ channel inhibitor, was added to the medium after S-100 and completely abolished if the cells were pretreated with 5 microM thapsigargin, an inhibitor of endoplasmic reticulum Ca(2+)-ATPase. The presence of nerve growth factor in the culture medium completely blocked the apoptotic changes induced by S-100, probably due to interaction of nerve growth factor and S-100 at the same binding sites. These data indicate that nerve growth factor not only prevents apoptosis during cell development, but also apoptosis induced by endogenous substances such as S-100.

Amyloid in Alzheimer's disease and prion-related encephalopathies: studies with synthetic peptides

Deposition of amyloid-beta protein (beta A) in brain parenchyma and vessel walls is a major pathological feature of Alzheimer's disease (AD). In prion-related encephalopathies (PRE), too, an altered form of prion protein (PrPsc) forms amyloid fibrils and accumulates in the brain. In both conditions the amyloid deposition is accompanied by nerve cell loss, whose pathogenesis and molecular basis are not understood. Neuropathological, genetic and biochemical studies indicate a central role of beta A in the AD pathogenesis. Synthetic peptides homologous to beta A and its fragments contribute to investigate the mechanisms of beta A deposit formation and the role played by beta A in AD pathogenesis. The physicochemical studies on the beta-sheet conformation and self-aggregation properties of beta A peptides indicate the conditions and the factors influencing the formation of beta A deposits. The neurotoxic activity of beta A and its fragments support the causal relationship between beta A deposits and the neuropathological events in AD. Numerous studies were performed to clarify the mechanism of neuronal death induced by exposure to beta A peptides. A similar approach has been used to investigate the role of PrPsc in PRE; in these diseases, the association between accumulation of PrPsc and neuropathology is evident and numerous data indicate that PrPsc itself might be the infectious agent responsible for disease transmission. Thus, PrP peptides were used to investigate the pathogenic role of PrPsc in PRE and the conformational change responsible for the conversion PrPc to PrPsc that makes the molecule apparently infectious. In particular, we synthesized a peptide homologous to residues 106-126, an integral part of all abnormal PrP isoforms that accumulate in the brain of subjects' PRE. This peptide is fibrillogenic, has secondary structure largely composed of beta-sheet and proteinase-resistant properties, is neurotoxic and induces astrogliosis. In this review, we summarize and compare the data obtained with beta A and PrP peptides and analyze the significance in terms of amyloidogenic proteins and neurodegeneration.

A decreased incidence of neuroblastomas in Down's syndrome and overproduction of S-100 b protein

Neuroblastoma, one of the most frequent solid tumors found in childhood, is very rare in Down's syndrome subjects. This lack could possibly be due to overproduction of S-100 b protein for the following reasons: 1) the gene coding for S-100 b protein is situated on chromosome 21, and the protein is overproduced via a gene dosage effect; 2) S-100 b protein is found in glial cells and Schwann cells of the central and peripheral nervous system and has been shown to have a differentiating effect on normal neural cells; 3) neuroblastomas with a stroma rich in S-100 protein have a good prognosis. Preliminary studies demonstrated an inhibition of growth of two human neuroblastoma cell lines in the presence of S-100 b protein compared to controls. It is postulated that S-100 b protein may inhibit the development of neuroblastomas in Down's syndrome either antenatally, or after birth and may be a therapeutic agent against neuroblastoma.

S100 beta stimulates inducible nitric oxide synthase activity and mRNA levels in rat cortical astrocytes

The glia-derived, neurotrophic protein S100 beta has been implicated in development and maintenance of the nervous system. However, S100 beta has also been postulated to play a role in mechanisms of neuropathology, because of its specific localization and selective overexpression in Alzheimer's disease. To begin to address the question of whether S100 beta can induce potentially toxic signaling pathways, we examined the effects of the protein on nitric oxide synthase (NOS) activity in cultures of rat cortical astrocytes. S100 beta treatment of astrocytes induced a time- and dose-dependent increase in accumulation of the NO metabolite, nitrite, in the conditioned medium. The S100 beta- stimulated nitrite production was blocked by cycloheximide and by the NOS inhibitor N-nitro-L-arginine methylester, but not by the inactive D-isomer of the inhibitor. Direct measurement of NOS enzymatic activity in cell extracts and analysis of NOS mRNA levels showed that the NOS activated by S100 beta addition is the calcium-independent, inducible isoform. Furthermore, the specificity of the effects of S100 beta on activation of NOS was demonstrated by the inability of S100 alpha and calmodulin to induce an increase in nitrite levels. Our data indicate that S100 beta can induce a potent activation of inducible NOS in astrocytes, an observation that might have relevance to the role of S100 beta in neuropathology.

beta-Amyloid regulates gene expression of glial trophic substance S100 beta in C6 glioma and primary astrocyte cultures

S100 beta, a calcium-binding protein synthesized by CNS astrocytes, has trophic effects in vitro (neurite extension and glial proliferation). In Alzheimer's disease and Down's syndrome, severely afflicted brain regions exhibit up to 20-fold higher levels of S100 beta protein, and astrocytes surrounding neuritic plaques exhibit highly elevated levels of S100 beta immunostaining. A major constituent of plaques, beta-amyloid, has been reported to have neurotoxic and neurotrophic effects in vitro. In our study we examined the responses of CNS glia to beta-amyloid. C6 glioma cells and primary rat astrocyte cultures were treated with beta A(1-40) peptide at doses up to 1 microM. Weak mitogenic activity, measured by [3H]thymidine incorporation, was observed. Northern blot analysis revealed increases of S100 beta mRNA within 24 h in a dose-dependent manner. Nuclear run-off transcription assays showed that beta A(1-40) specifically induced new synthesis of S100 beta mRNA in cells maintained in serum, but under serum-free conditions, there was a general elevation of several mRNA species. Corresponding increases of S100 beta protein synthesis were observed by immunoprecipitation of 35S-labeled cellular proteins. To evaluate whether this effect of beta-amyloid was mediated via neurokinin receptors or by calcium fluxes, various agonists and antagonists were tested and found to be ineffective at stimulating S100 beta synthesis. In sum, these in vitro data suggest that in neuropathological conditions, beta-amyloid itself is an agent which may provoke chronic gliosis and the production of trophic substances by astrocytes.

Double effect of ethanol on intracellular Ca2+ levels in undifferentiated PC12 cells

In PC12, a cellular line derived from a rat pheochromocytoma, ethanol (EtOH) induces a different effect depending on the concentration used. When resting cells are incubated with an alcohol concentration less than or equal to 120 mM, the [Ca2+]i increased with a double phase pattern. If the alcohol concentration was increased over 120-160 mM, EtOH reversed its effect and the [Ca2+]i decreased. This decrease was strongly inhibited if KCl-depolarized cells were used and was completely abolished if the substrate constituted EtOH-chronically treated cells. The Ca2+ increase is the consequence of an activation of L-type voltage-activated channels, while the other voltage-dependent channels (N-type), the receptor-operated channels and the Ca2+ extrusion pump present in these cells are not involved in EtOH action. These findings indicate that EtOH can induce (by different mechanisms) both potentiating and inhibiting effects on [Ca2+]i in PC12 cells in relation to the alcohol dose effectively present in the suspension medium.

The S-100: a protein family in search of a function

The S-100 is a group of low molecular weight (10-12 kD) calcium-binding proteins highly conserved among vertebrates. It is present in different tissues as dimers of homologous or different subunits (alpha, beta). In the nervous system, the S-100 exists as a mixture composed of beta beta and alpha beta dimers with the monomer beta represented more often. Its intracellular localisation is mainly restricted to the glial cytoplasmic compartment with a small fraction bound to membranes. In this compartment the S-100 acts as a potent inhibitor of phosphorylation on several substrates including the synaptosomal C-Kinase and Tau, a microtubule-associated protein. The S-100 in particular conditions, after binding with specific membrane sites (Kd = 0.2 microM; Bmax = 4.5 nM), is able to modify the activity of adenylate cyclase, probably via G-proteins. In addition, the Ca2+ homeostasis is also modulated by S-100 via an increase of specific membrane conductance and/or Ca2+ release from intracellular stores. "In vitro" and "in vivo" experiments showed that lower (nM) concentrations of extracellular S-100 beta act on glial and neuronal cells as a growth-differentiating factor. On the other hand, higher concentrations of the protein induce apoptosis of some cells such as the sympathetic-like PC12 line. Finally, data obtained from physiological (development, ageing) or pathological (dementia associated with Down's syndrome, Alzheimer's disease) conditions showed that a relationship could be established between the S-100 levels and some aspects of the statii.

S100 beta protects hippocampal neurons from damage induced by glucose deprivation

S100 beta is a calcium-binding protein elevated in Down's syndrome and Alzheimer's disease. Previous studies have demonstrated that S100 beta is trophic for several neuronal populations. We tested the influence of S100 beta on hippocampal neurons. The initial response included a rapid increase in [Ca2+]i similar to that elicited by S100 beta in other populations. S100 beta also substantially decreased cell death and loss of mitochondrial function resulting from glucose deprivation. Therefore, S100 beta exerts a neuroprotective influence on CNS neurons, suggesting that its elevation in neurological disorders may be a compensatory response.

The S100 protein family: history, function, and expression

The S100 family of calcium binding proteins contains approximately 16 members each of which exhibits a unique pattern of tissue/cell type specific expression. Although the distribution of these proteins is not restricted to the nervous system, the implication of several members of this family in nervous system development, function, and disease has sparked new interest in these proteins. We now know that the original two members of this family, S100A1 and S100B, can regulate a diverse group of cellular functions including cell-cell communication, cell growth, cell structure, energy metabolism, contraction and intracellular signal transduction. Although some members of the family may function extracellularly, most appear to function as intracellular calcium-modulated proteins and couple extracellular stimuli to cellular responses via interaction with other cellular proteins called target proteins. Interaction of these proteins with target proteins appear to involve cysteine residues (one in S100A1 and two in S100B), as well as a stretch of 13 amino acids, in the middle of the molecule called the linker region, which connects the two EF-hand calcium binding domains. In addition to the amino acid sequence and secondary structures of these proteins, the structures of the genes encoding these proteins are highly conserved. Studies on the expression of these proteins have demonstrated that a complex mixture of transcriptional and postranscriptional mechanisms regulate S100 expression. Further analysis of the function and expression of these proteins in both nervous and nonnervous tissues will provide important information regarding the role of altered S100 expression in nervous system development, function and disease.

The brain protein S-100ab induces apoptosis in PC12 cells

Incubation of PC12 cells with S-100 protein induces a rapid (0.5-1.0 min) rise of intracellular Ca2+ which lasts for the whole period of incubation. This effect is abolished in a Ca(2+)-free medium or in the presence of 1.0 microM Ni2+, an inhibitor of calcium channels. The rise in intracellular Ca2+ is followed by a progressive increase of cells undergoing degeneration and death. This event is accompanied by the appearance of apoptotic bodies and DNA fragmentation typical of the process known as apoptosis. S-100-induced cell death is prevented by 1 microM Ni2+ or by 0.1 nM cycloheximide, suggesting the involvement of new protein synthesis. It is postulated that the binding of S-100ab to specific sites present in PC12 cells is followed by the formation of Ca2+ channels and/or the stimulation of pre-existing ones with consequent increase of Ca2+ influx and activation of a process of cell death.