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

A Pathophysiological Approach To Current Biomarkers

Biomarkers are necessary for screening and diagnosing numerous diseases, predicting the prognosis of patients, and following-up treatment and the course of the patient. Everyday new biomarkers are being used in clinics for these purposes. This section will discuss the physiological roles of the various current biomarkers in a healthy person and the pathophysiological mechanisms underlying the release of these biomarkers. This chapter aims to gain a new perspective for evaluating and interpreting the most current biomarkers.

Relations between cortical thickness, serotonin 1A receptor binding, and structural connectivity: A multimodal imaging study

Serotonin 1A (5-HT_1A ) receptors play a direct role in neuronal development, cell proliferation, and dendritic branching. We hypothesized that variability in 5-HT_1A binding can affect cortical thickness, and may account for a subtype of major depressive disorder (MDD) in which both are altered. To evaluate this, we measured cortical thickness from structural magnetic resonance imaging (MRI) and 5-HT_1A binding by positron emission tomography (PET) in an exploratory study. To examine a range of 5-HT_1A binding and cortical thickness values, we recruited 25 healthy controls and 19 patients with MDD. We hypothesized increased 5-HT_1A binding in the raphe nucleus (RN) would be negatively associated with cortical thickness due to reduced serotonergic transmission. Contrary to our hypothesis, raphe 5-HT_1A binding was positively correlated with cortical thickness in right posterior cingulate cortex (PCC), a region implicated in the default mode network. Cortical thickness was also positively correlated with 5-HT_1A in each cortical region. We further hypothesized that the strength of 5-HT_1A -cortical thickness correlation depends on the number of axons between the raphe nucleus and each region. To explore this we related 5-HT_1A -cortical thickness correlation coefficients to the number of tracts connecting that region and the raphe, as measured by diffusion tensor imaging (DTI) in an independent sample. The 5-HT_1A -cortical thickness association correlated significantly with the number of tracts to each region, supporting our hypothesis. We posit a defect in the raphe may affect the PCC within the default mode network in MDD through serotonergic fibers, resulting in increased ruminative processing.

Homocysteine mediates transcriptional changes of the inflammatory pathway signature genes in human retinal pigment epithelial cells

AIM

To test whether homocysteine (Hcy) can influence the transcriptional profile, we hypothesized that Hcy can lead to the induction of proinflammatory molecules in the retinal cells of aging people.

METHODS

An unbiased in vitro inflammatory pathway focused study was designed employing retinal pigment epithelial (RPE) cell line, ARPE-19. Cells were cultured in the presence or absence of Hcy to capture target genes' expression profile. Three different concentrations of Hcy were added in the culture medium of confluent monolayers. cRNAs were made from the isolated total RNAs and the labeled cRNA probes were hybridized to microarrays specific for human disease pathway inflammatory cytokines, chemokines and their receptor gene micro-array panels as per manufacture's recommendations. Two Hcy up-regulated molecules: IL6 and CEBPB were further validated via Western blot analysis. Hcy's effect on ARPE-19 cellular morphology and genomic DNA integrity were also evaluated.

RESULTS

Gene microarray analyses of RPE cells in response to Hcy treatment revealed alterations in the expressions of several inflammatory gene transcripts such as CCL5, CEBPB, IL13RA2, IL15RA, IL6, IL8 and CXCL3 that were up-regulated. The transcripts for C3, CCL2, IL11RA and IL18 genes exhibited down-regulation. The IL6 and CEBPB expressions were subsequently validated at the protein levels. Treatment of the retinal cells with increasing Hcy concentration influenced their density in culture however their morphology and DNA integrity remained unaffected.

CONCLUSION

These findings suggest that Hcy can potentially mediate the expression of chemokines, cytokines and interleukins receptors in the retinal cells without having any debilitating effects on their morphology and the genomic DNA integrity.

A review of the clinical utility of serum S100B protein levels in the assessment of traumatic brain injury

Background

In order to improve injury assessment of brain injuries, protein markers of pathophysiological processes and tissue fate have been introduced in the clinic. The most studied protein “biomarker” of cerebral damage in traumatic brain injury (TBI) is the protein S100B. The aim of this narrative review is to thoroughly analyze the properties and capabilities of this biomarker with focus on clinical utility in the assessment of patients suffering from TBI.

Results

S100B has successfully been implemented in the clinic regionally (1) to screen mild TBI patients evaluating the need to perform a head computerized tomography, (2) to predict outcome in moderate-to-severe TBI patients, (3) to detect secondary injury development in brain-injured patients and (4) to evaluate treatment efficacy. The potential opportunities and pitfalls of S100B in the different areas usually refer to its specificity and sensitivity to detect and assess intracranial injury.

Conclusion

Given some shortcomings that should be realized, S100B can be used as a versatile screening, monitoring and prediction tool in the management of TBI patients.

A review of the clinical utility of serum S100B protein levels in the assessment of traumatic brain injury

BACKGROUND

In order to improve injury assessment of brain injuries, protein markers of pathophysiological processes and tissue fate have been introduced in the clinic. The most studied protein "biomarker" of cerebral damage in traumatic brain injury (TBI) is the protein S100B. The aim of this narrative review is to thoroughly analyze the properties and capabilities of this biomarker with focus on clinical utility in the assessment of patients suffering from TBI.

RESULTS

S100B has successfully been implemented in the clinic regionally (1) to screen mild TBI patients evaluating the need to perform a head computerized tomography, (2) to predict outcome in moderate-to-severe TBI patients, (3) to detect secondary injury development in brain-injured patients and (4) to evaluate treatment efficacy. The potential opportunities and pitfalls of S100B in the different areas usually refer to its specificity and sensitivity to detect and assess intracranial injury.

CONCLUSION

Given some shortcomings that should be realized, S100B can be used as a versatile screening, monitoring and prediction tool in the management of TBI patients.

Effect of staurosporine in the morphology and viability of cerebellar astrocytes: role of reactive oxygen species and NADPH oxidase

Cell death implies morphological changes that may contribute to the progression of this process. In astrocytes, the mechanisms involving the cytoskeletal changes during cell death are not well explored. Although NADPH oxidase (NOX) has been described as being a critical factor in the production of ROS, not much information is available about the participation of NOX-derived ROS in the cell death of astrocytes and their role in the alterations of the cytoskeleton during the death of astrocytes. In this study, we have evaluated the participation of ROS in the death of cultured cerebellar astrocytes using staurosporine (St) as death inductor. We found that astrocytes express NOX1, NOX2, and NOX4. Also, St induced an early ROS production and NOX activation that participate in the death of astrocytes. These findings suggest that ROS produced by St is generated through NOX1 and NOX4. Finally, we showed that the reorganization of tubulin and actin induced by St is ROS independent and that St did not change the level of expression of these cytoskeletal proteins. We conclude that ROS produced by a NOX is required for cell death in astrocytes, but not for the morphological alterations induced by St.

Intraperitoneal treatment with S100B enhances hippocampal neurogenesis in juvenile mice and after experimental brain injury

BACKGROUND

Neurogenesis is documented in adult mammals including humans, is promoted by neurotrophic factors, and constitutes an innate repair mechanism following brain injury. The glial neurotrophic protein S100B is released following various types of brain injuries, enhances hippocampal neurogenesis and improves cognitive function following brain injury in rats when applied intrathecally. The present study was designed to elucidate whether the beneficial effect of S100B on injury-induced neurogenesis can be confirmed in mice when applied intraperitoneally (i.p.), and whether this effect is dose-dependent.

METHODS

Male juvenile mice were subjected to a unilateral parietal cryolesion or sham injury, and treated with S100B at 20nM, 200nM or vehicle i.p. once daily. Hippocampal progenitor cell proliferation was quantified following labelling with bromo-deoxyuridine (BrdU, 50 mg/KG i.p.) in the germinative area of the dentate gyrus, the subgranular zone (SGZ), on day 4 as well as on cell survival and migration to the granular cell layer (GCL) on day 28. Progenitor cell differentiation was assessed following colabelling with the glial marker GFAP and the neuronal marker NeuN.

RESULTS

S100B enhanced significantly the early progenitor cell proliferation in the SGZ as well as cell survival and migration to the GCL, and promoted neuronal differentiation. While these effects were predominately dose-dependent, 200nM S100B failed to enhance the proliferation in the SGZ on day 4 post-injury.

CONCLUSION

We conclude that S100B participates in hippocampal neurogenesis after injury at lower nanomolar concentrations. Therefore S100B may serve as a potential adjunct treatment to promote neuroregeneration following brain damage.

Neuroplasticity in mood disorders

Neuroimaging and neuropathological studies of major depressive disorder (MDD) and bipolar disorder (BD) have identified abnormalities of brain structure in areas of the prefrontal cortex, amygdala, striatum, hippocampus, parahippocampal gyrus, and raphe nucleus. These structural imaging abnormalities persist across illness episodes, and preliminary evidence suggests they may in some cases arise prior to the onset of depressive episodes in subjects at high familial risk for MDD. In other cases, the magnitude of abnormality is reportedly correlated with time spent depressed. Postmortem histopathological studies of these regions have shown abnormal reductions of synaptic markers and glial cells, and, in rare cases, reductions in neurons in MDD and BD. Many of the regions affected by these structural abnormalities show increased glucose metabolism during depressive episodes. Because the glucose metabolic signal is dominated by glutamatergic transmission, these data support other evidence that excitatory amino acid transmission is elevated in limbic-cortical-striatal-pallidal-thalamic circuits during depression. Some of the subject samples in which these metabolic abnormalities have been demonstrated were also shown to manifest abnormally elevated stressed plasma cortisol levels. The co-occurrence of increased glutamatergic transmission and Cortisol hypersecretion raises the possibility that the gray matter volumetric reductions in these depressed subjects are partly accounted for by processes homologous to the dendritic atrophy induced by chronic stress in adult rodents, which depends upon interactions between elevated glucocorticoid secretion and N-meihyl-D-aspartate (NMDA)-glutamate receptor stimulation. Some mood-stabilizing and antidepressant drugs that exert neurotrophic effects in rodents appear to reverse or attenuate the gray matter volume abnormalities in humans with mood disorders. These neurotrophic effects may be integrally related to the therapeutic effects of such agents, because the regions affected by structural abnormalities in mood disorders are known to play major roles in modulating the endocrine, autonomic, behavioral, and emotional experiential responses to stressors.

Antiproliferative and cell apoptosis-inducing activities of compounds from Buddleja davidii in Mgc-803 cells

BACKGROUND

Buddleja davidii is widely distributed in the southwestern region of China. We have undertaken a systematic analysis of B. davidii as a Chinese traditional medicine with anticancer activity by isolating natural products for their activity against the human gastric cancer cell line Mgc-803 and the human breast cancer cell line Bcap-37.

RESULTS

Ten compounds were extracted and isolated from B. davidii, among which colchicine was identified in B. davidii for the first time. The inhibitory activities of these compounds were investigated in Mgc-803, Bcap-37 cells in vitro by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay, and the results showed that luteolin and colchicine had potent inhibitory activities against the growth of Mgc-803 cells. Subsequent fluorescence staining and flow cytometry analysis indicated that these two compounds could induce apoptosis in Mgc-803 cells. The results also showed that the percentages of early apoptotic cells (Annexin V+/PI-, where PI is propidium iodide) and late apoptotic cells (Annexin V+/PI+) increased in a dose- and time-dependent manner. After 36 h of incubation with luteolin at 20 μM, the percentages of cells were approximately 15.4% in early apoptosis and 43.7% in late apoptosis; after 36 h of incubation with colchicine at 20 μM, the corresponding values were 7.7% and 35.2%, respectively.

CONCLUSIONS

Colchicine and luteolin from B. davidii have potential applications as adjuvant therapies for treating human carcinoma cells. These compounds could also induce apoptosis in tumor cells.

Shared features of S100B immunohistochemistry and cytochrome oxidase histochemistry in the ventroposterior thalamus and lateral habenula in neonatal rats

The ventroposterior thalamus and the habenular nuclei of the epithalamus are relevant to the monoaminergic system functionally and anatomically. The glia-derived S100B protein plays a critical role in the development of the nervous system including the monoaminergic systems. In this study, we performed an immunohistochemical study of glia-related proteins including S100B, serotonin transporter, and microtubule-associated protein 2, as well as cytochrome oxidase histochemistry in neonatal rats. Results showed the same findings for S100B immunohistochemistry between the ventroposterior thalamus and the lateral habenula at postnatal day 7: intense staining in cell bodies of astrocytes, diffusely spread immunoproduct in the intercellular space, and S100B-free areas as well as a strong reaction to cytochrome oxidase histochemistry. Further common features were the scarcity of glial fibrillary acidic protein-positive astrocytes and the few apoptotic cells observed. The results of the cytochrome oxidase reaction suggested that S100B is released actively into intercellular areas in restricted brain regions showing high neuronal activity at postnatal day 7. Pathology of the ventroposterior thalamus and the habenula is suggested in mental disorders, and S100B might be a key factor for investigations in these areas.

Colchicine-induced apoptosis in human normal liver L-02 cells by mitochondrial mediated pathways

Colchicine is an alkaloid that has been widely used to treat gout. It also has a curative effect on cancer. Although many studies have shown that its effect on cell apoptosis was mediated by the activation of caspase-3, the pathways involved in the process remained obscure. Here we show some evidence regarding the missing information using human normal liver cells L-02 in our study. The effect of colchicine on apoptosis in L-02 cells and the apoptosis-associated signaling pathways were determined using different tests including cell viability assay, Annexin V and propidium idodide binding, PI staining, Hoechst 33342 staining, mitochondrial membrane potential assay, caspase activity assay and Western blot analysis. We found that colchicine-induced a dose-dependent drop of cell viability in L-02 cells; early apoptosis happened when cells were treated with 0.1μM of colchicine. The colchicine-induced loss of mitochondrial membrane potential, activation of caspase-3 and 9, up-regulation of Bax and down-regulation of Bcl-2 showed an evidence for the colchicine activity on apoptosis, at least, by acting via the intrinsic apoptotic pathway.

Melatonin modulates cytoskeletal organization in the rat brain hippocampus

Melatonin concentration in plasma reaches high levels during the night and synchronizes body rhythms with the photoperiod. Previous evidence obtained in cultured cells suggests that melatonin synchronizes cytoskeletal re-arrangements at nocturnal plasma concentration. In this study, we determined the amount of microtubules and microfilaments in the rat hippocampus as an index of cytoskeletal organization in rats submitted to a photoperiodic regime. Additionally, these parameters were determined in control rats, sham rats, pinealectomized rats, and rats that were pinealectomized and treated with melatonin for 1 week. The results showed an increase in both the amount of microfilaments in the hippocampus of rats sacrificed in the dark phase, and in melatonin levels. In addition, a decrease in both microfilament and microtubule amounts occurred in pinealectomized rats. In contrast, melatonin treatment partially reestablished actin and tubulin proportions organized in microfilaments and microtubules, respectively. The results indicate that actin organization in microfilaments was associated with both the photoperiod and with melatonin levels. Together, the data support that cytoskeletal organization is regulated rhythmically by melatonin in synchrony with the photoperiod.

Haloperidol causes cytoskeletal collapse in N1E-115 cells through tau hyperphosphorylation induced by oxidative stress: Implications for neurodevelopment

Haloperidol a typical antipsychotic commonly used in the treatment of schizophrenia causes neuronal damage and extrapiramidal symptoms after several years of treatment. These symptoms have been associated with increased levels of oxidative stress. Reactive oxygen species produce cytoskeletal collapse and an excessive phosphorylation of tau, a microtubule-associated protein that plays a key role in microtubule stabilization, and in growth cone and neurite formation, which are cytoskeletal phenotypes that participate in neurodevelopment. Thus, we hypothesized that haloperidol produces neurocytoskeletal disorganization by increasing free radicals and tau hyperphosphorylation, and consequently, the loss of neurodevelopmental cytoskeletal phenotypes, neurites and growth cones. The purpose of this work was the characterization of neuronal cytoskeletal changes caused by haloperidol in neuroblastoma N1E-115 cells. We also studied the mechanisms by which haloperidol causes cytoskeletal changes. The results showed that haloperidol at 100microM caused a complete cytoskeleton collapse in the majority of the cells. Melatonin, a free radical scavenger, blocks tau hyperphosphorylation, and microtubule disorganization caused by haloperidol in a dose-response mode. Additionally, the indole blocks lipoperoxide formation in haloperidol treated cells. The results indicate that free radicals and tau hyperphosphorylation produced by haloperidol caused a cytoskeletal collapse and the lost of growth cones and neurites. These effects were blocked by melatonin. Data suggest that extrapiramidal symptoms in schizophrenic patients can be produced by cytoskeletal disorganization during adult brain neurodevelopment after prolonged haloperidol treatment that can be prevented by melatonin.

Comparative effects of microtubules disruption on glucocorticoid receptor functions in proliferating and quiescent cells

We have recently demonstrated that the alkaloid colchicine (COL) inhibits glucocorticoid receptor (GR) transcriptional activity. In addition, we described proteasome-mediated degradation of GR in COL-treated HeLa cells. While these effects were previously attributed to cell cycle arrest in G2/M phase, this explanation is not applicable for nonproliferating cells such as human hepatocytes (HH). In the current study, we compared COL-mediated microtubule disruption and cell cycle arrest with selected GR functions in HeLa cells and HH as models of proliferating and quiescent cells, respectively. Microtubule disruption led to irreversible decrease in GR binding capacity and protein level in HeLa cells. None of the parameters was restored 24 hours after COL withdrawal. In contrast, dexamethasone (DEX) binding was increased in HH at the beginning of the treatment, with following transient activation of extracellular signal-regulated kinase (ERK). The findings of these investigations emphasize the GR-signaling differences between primary and transformed cells.

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.

S100beta upregulation: a possible mechanism of deltamethrin toxicity and motor coordination deficits

Deltamethrin (DLT) is a type II synthetic pyrethroid with insecticidal properties. It has been considered safe to humans. Excessive exposure of DLT is being variously reported, recently, to cause potential neurotoxicity in adults, as characterized by ataxia, loss of coordination, hyperexcitability, convulsions and paralysis. However, limited information is available on its impact at lower/safe to human doses during development. The present study was designed to assess the postnatal (P) exposure of DLT (as low as 0.7 mg/kg, i.p.) on S-100beta expression in developing rat cerebellum and its impact on Purkinje cell morphogenesis and dendritogenesis, and subsequent spontaneous motor activity (SMA) deficits. Wistar rat pups born to healthy mothers were injected with DLT (Sigma) at a dosage of 0.7 mg/kg body wt., i.p. dissolved in DMSO (Sigma) during P0-7th (DLT-I) and P9-13th day (DLT-II). The control pups were injected with equivalent volumes of DMSO. The pups of both the groups were used to assess the spontaneous motor activity P21 onwards. The cryocut sections (30 microm) of the cerebella were used for anti-S-100beta antibody labeling using streptavidin biotin HRP method. An upregulation of S-100beta expression in Bergmann glial fibers was recorded at P12 and P15 day preparations in both DLT-I and DLT-II treated groups. However, such upregulation of S-100beta was more prominent in DLT-II treated group animals with a large number of strongly S-100beta immunopositive astrocytes flanking around the Purkinje neurons. In Golgi preparation the Purkinje neurons in DLT treated groups had reduced dendritic arbor with short primary dendrites and much reduced dendritic branches which appeared stumpy and hypertrophied. The granule cell proliferation and migration as well as Purkinje cell morphogenesis and dendritogenesis are affected following DLT exposure in the present investigation. This may also affect the mossy fiber-granule cell-parallel pathway formation which in turn may decrease the firing of Purkinje cells (GABAergic inhibitory projections) and thus an increase in the output of the neurons in the deep cerebellar nuclei neurons and disturbed motor coordination.

Effects of maintenance electroshock on the oxidative damage parameters in the rat brain

Although several advances have occurred over the past 20 years concerning refining the use and administration of electroconvulsive therapy to minimize side effects of this treatment, little progress has been made in understanding the mechanisms underlying its therapeutic or adverse effects. This work was performed in order to determine the level of oxidative damage at different times after the maintenance electroconvulsive shock (ECS). Male Wistar rats (250-300 g) received a protocol mimicking therapeutic of maintenance or simulated ECS (Sham) and were subsequently sacrificed immediately after, 48 h and 7 days after the last maintenance electroconvulsive shock. We measured oxidative damage parameters (thiobarbituric acid reactive species for lipid peroxidation and protein carbonyls for protein damage, respectively) in hippocampus, cortex, cerebellum and striatum. We demonstrated no alteration in the lipid peroxidation and protein damage in the four structures studied immediately after, 48 h and 7 days after a last maintenance electroconvulsive shock. Our findings, for the first time, demonstrated that after ECS maintenance we did protocol minimal oxidative damage in the brain regions, predominating absence of damage on the findings.

S100B protein is released from rat neonatal neurons, astrocytes, and microglia by in vitro trauma and anti-S100 increases trauma-induced delayed neuronal injury and negates the protective effect of exogenous S100B on neurons

S100B protein is found in brain, has been used as a marker for brain injury and is neurotrophic. Using a well-characterized in vitro model of brain cell trauma, we have previously shown that strain injury causes S100B release from neonatal rat neuronal plus glial cultures and that exogenous S100B reduces delayed post-traumatic neuronal damage even when given at 6 or 24 h post-trauma. The purpose of the current studies was to measure post-traumatic S100B release by specific brain cell types and to examine the effect of an antibody to S100 on post-traumatic delayed (48 h) neuronal injury and the protective effect of exogenous S100B. Neonatal rat cortical cells grown on a deformable elastic membrane were subjected to a strain (stretch) injury produced by a 50 ms displacement of the membrane. S100B was measured with an ELISA kit. Trauma released S100B from pure cultures of astrocytes, microglia, and neurons. Anti-S100 reduced released S100B to below detectable levels, increased delayed neuronal injury in traumatized cells and negated the protective effect of exogenous S100B on injured cells. Heat denatured anti-S100 did not exacerbate injury. These studies provide further evidence for a protective role for S100B following neuronal trauma.

Serotonin 5-HT1A receptor stimulates c-Jun N-terminal kinase and induces apoptosis in Chinese hamster ovary fibroblasts

The 5-HT1A receptor is a prototypical member of the large and diverse serotonin receptor family. One key role of this receptor is to stimulate cell proliferation and differentiation via the extracellular signal regulated protein kinase (ERK) mitogen activated protein (MAP) kinase. There are few reports on the ability of the 5-HT1A receptor to modulate other MAP kinases such as c-Jun N-terminal kinase (JNK), which is activated by various extracellular stimuli, resulting in cell growth, differentiation, and programmed cell death. We report here for the first time that the 5-HT1A receptor stimulates JNK. JNK stimulation was Pertussis toxin-sensitive and was mediated by Rho family low molecular weight GTPases. The 5-HT1A receptor also increased apoptosis, which was mimicked by the MEK inhibitor PD98059, and blocked by the JNK inhibitor SP600125. These results suggest that the 5-HT1A receptor stimulates both ERK-dependent anti-apoptotic pathways and JNK-dependent pro-apoptotic pathways in CHO cells.

5-HT1A receptor-mediated apoptosis: death by JNK?

There is growing interest in the potential use of 5-HT(1A) receptor agonists as neuroprotective agents in stroke and traumatic brain injury. However, a new study using a recombinant 5-HT(1A) receptor cell line suggests that these agonists may promote as well as inhibit apoptotic responses. Because heterologously expressed receptors may couple promiscuously to inappropriate signal transduction pathways, the results should be interpreted with caution.

The neurotrophic protein S100B: value as a marker of brain damage and possible therapeutic implications

We provide a critical analysis of the value of S100B as a marker of brain damage and possible therapeutic implications. The early assessment of the injury severity and the consequent prognosis are of major concern for physicians treating patients suffering from traumatic brain injury (TBI). A reliable indicator to accurately determine the extent of the brain damage has to meet certain requirements: (i) to originate in the central nervous system (CNS) with no contribution from extracerebral sources; (ii) a passive release from damaged neurons and/or glial cells without any stimulated active release; (iii) a lack of specific effects on neurons and/or glial cells interfering with the initial injury; (iv) an unlimited passage through the blood-brain barrier (BBB). The measurement of putative biochemical markers, such as the S100B protein, has been proposed in this role. Over the past decade, numerous studies have reported a positive correlation of S100B serum levels with a poor outcome following TBI. However, some studies raise doubt whether the serum measurement of S100B is a valid biochemical marker of brain damage. We summarize the specific properties of S100B and analyze whether they support or counteract the necessary requirements to designate this protein as an indicator of brain damage. Finally, we report recent experimental findings suggesting a possible therapeutic potential of S100B.

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.

A Critical Analysis of the Role of the Neurotrophic Protein S100B in Acute Brain Injury

We provide a critical analysis of the relevance of S100B in acute brain injury emphazising the beneficial effect of its biological properties. S100B is a calcium-binding protein, primarily produced by glial cells, and exerts auto- and paracrine functions. Numerous reports indicate, that S100B is released after brain insults and serum levels are positively correlated with the degree of injury and negatively correlated with outcome. However, new data suggest that the currently held view, that serum measurement of S100B is a valid "biomarker" of brain damage in traumatic brain injury (TBI), does not acknowlege the multifaceted release pattern and effect of the blood-brain barrier disruption upon S100B levels in serum. In fact, serum and brain S100B levels are poorly correlated, with serum levels dependent primarily on the integrity of the blood-brain barrier, and not the level of S100B in the brain. The time profile of S100B release following experimental TBI, both in vitro and in vivo, suggests a role of S100B in delayed reparative processes. Further, recent findings provide evidence, that S100B may decrease neuronal injury and/or contribute to repair following TBI. Hence, S100B, far from being a negative determinant of outcome, as suggested previously in the human TBI and ischemia literature, is of potential therapeutic value that could improve outcome in patients who sustain various forms of acute brain damage.

Acute and chronic electroconvulsive shock in rats: Effects on peripheral markers of neuronal injury and glial activity

Electroconvulsive therapy is considered one of the most effective treatments of major depression, but controversy still exists on whether it may be brain damaging. The aim of this work was to evaluate the cerebrospinal fluid (CSF) levels of neuron specific enolase (NSE), protein S100B and lactate of rats submitted to acute and chronic models of ECS. Rats were submitted to either one shock (acute) or a series of eight shocks, applied one at every 48 h (chronic). CSF samples were collected at 0, 3, 6, 12, 24, 48 and 72 h after the shock in the acute model and at these same time intervals after the last shock in the chronic model. Both models did not produce significant alterations in the levels of NSE. S100B levels were significantly increased at 6 h in the chronic model (p<0.0001). There was a significant increase in the levels of lactate at 0 h in both models (p<0.001). These results support the proposition that ECS does not produce neural damage, and suggest that the alterations in the levels of S100B and lactate may reflect an astrocytic activity of a protective nature.

Enhanced hippocampal neurogenesis by intraventricular S100B infusion is associated with improved cognitive recovery after traumatic brain injury

Evidence of injury-induced neurogenesis in the adult hippocampus suggests that an endogenous repair mechanism exists for cognitive dysfunction following traumatic brain injury (TBI). One factor that may be associated with this restoration is S100B, a neurotrophic/mitogenic protein produced by astrocytes, which has been shown to improve memory function. Therefore, we examined whether an intraventricular S100B infusion enhances neurogenesis within the hippocampus following experimental TBI and whether the biological response can be associated with a measurable cognitive improvement. Following lateral fluid percussion or sham injury in male rats (n = 60), we infused S100B (50 ng/h) or vehicle into the lateral ventricle for 7 days using an osmotic micro-pump. Cell proliferation was assessed by injecting the mitotic marker bromodeoxyuridine (BrdU) on day 2 postinjury. Quantification of BrdU-immunoreactive cells in the dentate gyrus revealed an S100B-enhanced proliferation as assessed on day 5 post-injury (p < 0.05), persisting up to 5 weeks (p < 0.05). Using cell-specific markers, we determined the relative numbers of these progenitor cells that became neurons or glia and found that S100B profoundly increased hippocampal neurogenesis 5 weeks after TBI (p < 0.05). Furthermore, spatial learning ability, as assessed by the Morris water maze on day 30-34 post-injury, revealed an improved cognitive performance after S100B infusion (p < 0.05). Collectively, our findings indicate that an intraventricular S100B infusion induces neurogenesis within the hippocampus, which can be associated with an enhanced cognitive function following experimental TBI. These observations provide compelling evidence for the therapeutic potential of S100B in improving functional recovery following TBI.

S100B protein is released by in vitro trauma and reduces delayed neuronal injury

S100B protein in brain is produced primarily by astrocytes, has been used as a marker for brain injury and has also been shown to be neurotrophic and neuroprotective. Using a well characterized in vitro model of brain cell trauma, we examined the potential role of exogenous S100B in preventing delayed neuronal injury. Neuronal plus glial cultures were grown on a deformable Silastic membrane and then subjected to strain (stretch) injury produced by a 50 ms displacement of the membrane. We have previously shown that this injury causes an immediate, but transient, nuclear uptake of the fluorescent dye propidium iodide by astrocytes and a 24-48 h delayed uptake by neurons. Strain injury caused immediate release of S100-beta with further release by 24 and 48 h. Adding 10 or 100 nm S100B to injured cultures at 15 s, 6 h or 24 h after injury reduced delayed neuronal injury measured at 48 h. Exogenous S100B was present in the cultures through 48 h. These studies directly demonstrate the release and neuroprotective role of S100B after traumatic injury and that, unlike most receptor antagonists used for the treatment of trauma, S100B is neuroprotective when given at later, more therapeutically relevant time points.

The 5HT1A receptor agonist, 8-OH-DPAT, protects neurons and reduces astroglial reaction after ischemic damage caused by cortical devascularization

Serotonin 1A (5HT1A) receptor agonists have shown neuroprotective properties in different models of central nervous system injury. Activation of neuronal 5HT1A receptors appears to be involved in the neuroprotective effects. It remains to be elucidated if astroglial cells are responsive to the 5HT1A neuroprotective effects. The participation of astroglial S100B trophic factor has been proposed since 5HT1A activation leads to S100B release and nanomolar concentration level of this molecule showed pro-survival activity in neuronal cultures. Using the cortical devascularization model (CD; unilateral pial disruption), a procedure that results in localized ischemia without producing direct physical damage to brain tissue, we tested the effects of a full 5HT1A agonist, 8-OH-DPAT, or the antagonist WAY-100635 on cortical neuronal survival, astroglial cell response and S100B expression. Wistar rats were subjected to CD lesion which consisted of a craniotomy followed by physical damage to the underlying pial blood vessels. Two and twenty-four hours after the CD lesion, animals received intraperitoneally 8-OH-DPAT (1 mg/kg), WAY-100635 (1 mg/kg) or vehicle (sterile saline). At 3, 7 or 14 days post-lesion, animals were sacrificed and their brains processed for immunohistochemistry to detect GFAP, vimentin, MAP-2, S100B and nuclear Hoechst staining. S100B level in the brain cortex and serum was quantified by an ELISA assay. Serum S100B was considered an index of S100B release. 8-OH-DPAT treatment reduced neuronal death, dendrite loss, astroglial hypertrophy and hyperplasia. In contrast, WAY-100635 treatment increased these parameters of damage. S100B intracellular immunoreactivity in astrocytes and total S100B level showed long-lasting changes after the CD lesion and subsequent treatments depending on the 5HT1A activity. The level of serum S100B was increased in 8-OH-DPAT-treated animals. Increased damage observed in WAY-100635-treated animals supports the hypothesis that the protective 8-OH-DPAT action may be mediated by specific 5HT1A receptors. The reduction in astroglial hypertrophy and hyperplasia as well as long-term changes in S100B immunoreactivity and increased S100B release that we observed allows us to hypothesize that astroglial cells may play an important role in 5HT1A-mediated neuroprotection.

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.

The serotonin-1A agonist ipsapirone prevents ethanol-associated death of total rhombencephalic neurons and prevents the reduction of fetal serotonin neurons

Previously, this laboratory showed that in utero and in vitro ethanol exposure significantly reduces developing serotonin (5-HT) neurons and that treatment with a 5-HT1A agonist such as buspirone or ipsapirone prevents the ethanol-associated loss. The present study investigated whether ethanol decreases fetal rhombencephalic neurons, including 5-HT neurons, by causing apoptosis. We also investigated whether ipsapirone prevents the ethanol-associated deficit of fetal rhombencephalic neurons by reducing apoptosis. The results of these studies strongly suggest that the ethanol-associated reduction in fetal rhombencephalic neurons that accompanies both in utero and in vitro exposure to physiological concentrations of ethanol is associated with increased apoptosis in these neurons. A physiological concentration of ethanol (i.e., 50 mM) increases apoptosis in fetal rhombencephalic neurons and decreases the number 5-HT neurons. It also appears that the 5-HT1A agonist ipsapirone provides neuroprotection to these neurons by reducing apoptosis. Another mechanism by which ethanol-associated apoptosis can be blocked is by including serum proteins in the media at a concentration of 1% or higher; this concentration of serum proteins is high in comparison to the protein concentration in cerebrospinal fluid.

Harm avoidance, anxiety, and response to novelty in the adolescent S-100beta transgenic mouse: role of serotonin and relevance to Down syndrome

S-100beta is an astroglial-derived protein, which plays a role in brain development and maintenance, and is known to play a specific role in the regulation of growth of the serotonergic neuronal system. In humans, the gene for S-100beta is found on chromosome 21, within the region that is considered important for the phenotype of Down syndrome (DS). Thus, we have been studying a model of DS, the S-100beta transgenic mouse. In the current study, we have examined anxiety and responses to novelty in adolescent (60-90 days) animals, at a time when we have shown the animals to be relatively lacking in serotonin innervation, compared to their CD-1 nontransgenic controls. In a test for approach/avoidance, the light/dark test, the S-100beta transgenic mice animals showed no differences from control CD-1 mice. However, in the hole-board test for exploratory behavior, the S-100beta animals were found to be less responsive to the inhibiting effects of the serotonin receptor 5-HT1A agonist, buspirone. Three tests were used to measure response to novelty. In the open field, the S-100beta animals showed greater activity longer than the control animals, and in the Y-maze test, the S-100beta animals spent more time in the novel arm. In a test for novelty-induced gnawing, the S-100beta animals were also more active than control animals. All of these suggest that the S-100beta transgenic mice are slower to habituate to novelty than control animals. Finally, we tested the animals in a new procedure that we are proposing as a test for harm avoidance. In this apparatus, the S-100beta animals showed more approaches to a novel and potentially harmful object than the control mice did. These results are discussed in reference to the known lack of serotonin in the animals, and to the behavioral phenotype of DS.

S100B in brain damage and neurodegeneration

S100B is a calcium-binding peptide produced mainly by astrocytes that exert paracrine and autocrine effects on neurons and glia. Some knowledge has been acquired from in vitro and in vivo animal experiments to understand S100B's roles in cellular energy metabolism, cytoskeleton modification, cell proliferation, and differentiation. Also, insights have been gained regarding the interaction between S100B and the cerebral immune system, and the regulation of S100B activity through serotonergic transmission. Secreted glial S100B exerts trophic or toxic effects depending on its concentration. At nanomolar concentrations, S100B stimulates neurite outgrowth and enhances survival of neurons during development. In contrast, micromolar levels of extracellular S100B in vitro stimulate the expression of proinflammatory cytokines and induce apoptosis. In animal studies, changes in the cerebral concentration of S100B cause behavioral disturbances and cognitive deficits. In humans, increased S100B has been detected with various clinical conditions. Brain trauma and ischemia is associated with increased S100B concentrations, probably due to the destruction of astrocytes. In neurodegenerative, inflammatory and psychiatric diseases, increased S100B levels may be caused by secreted S100B or release from damaged astrocytes. This review summarizes published findings on S100B regarding human brain damage and neurodegeneration. Findings from in vitro and in vivo animal experiments relevant for human neurodegenerative diseases and brain damage are reviewed together with the results of studies on traumatic, ischemic, and inflammatory brain damage as well as neurodegenerative and psychiatric disorders. Methodological problems are discussed and perspectives for future research are outlined.

The role of serotonin in early cortical development

The cerebral cortex is widely innervated by serotonin (5-HT)-containing axons originating from neurons in the raphe nuclei. The early development of this monoamine system in the cortex prompted speculation long ago that it has important functions in cortical maturation and plasticity. Here we review evidence, derived from a plethora of studies and from our recent unpublished work, that supports an important role for 5-HT in a number of major events in the developing cortex, especially at the early stages. This evidence points to a regulatory role for 5-HT in neuronal proliferation, migration and differentiation, and in preventing apoptotic cell death.

Effects of thiocolchicine on axonal cytoskeleton of the rat peroneus nerve

Thiocolchicine is a colchicine-derivative used in the therapy of some diseases and extensively studied in the field of oncological research as antimitotic agent. Here we studied the activity of thiocolchicine on the cytoskeleton of the peroneus nerve, performing a histological and ultrastructural analysis. We observed a decrease in mean myelinated fiber area in thiocolchicine-treated rats in comparison to controls; this was due to a decrease in mean axoplasm area, while myelin thickness was constant. In the ultrastructural analysis a decrease in microtubule density and an increase in neurofilaments were found; moreover, the myelinated fibers seemed to be more affected in comparison to the unmyelinated axons. These findings are in agreement with the capability of binding to microtubule skeleton shared by all the colchicinoids.

Cajal's hypotheses on neurobiones and neurotropic factor match properties of microtubules and S-100 beta

Cajal described both the morphology and plasticity of neurons. He summarized the structure of neurons as composed of membrane, protoplasm, Golgi apparatus, nucleus, spongioplasm and neurofibrils (cytoskeleton). He initially considered the cytoskeleton as absorbing excitation energy and forming a "conductive pathway in the protoplasm" within the neuron. Later, he viewed the neurofibrillary threads as independent, living entities and called them neurobiones. Cajal recognized neuroplasticity in development, memory, sleep, injury and dementia, as well as after exposure to cold and starvation. He noted cytoskeletal changes during these events. However, he did not causatively connect the plastic changes in neurons with the changes in cytoskeleton. Finally, Cajal proposed a theory of chemoaffinity in 1892, and modified his neurotropic theory over the next 40 years. Today we accept that changes in the cytoskeleton produce changes in neuronal morphology. The properties of the cytoskeleton and neurobione as described by Cajal are similar to those of microtubules. These long intraneuronal neurofibrils are polymers of the protein tubulin and, whilst not being living entities, are highly dynamic, sensitive to environmental stimuli, and stabilized by microtubule associated proteins (MAPs). Furthermore, Cajal was very specific in his characterization of the neurotropic factor derived from Schwann cells. Initially, he thought the chemicals attracted the axonal fibers, but later he wrote that the factor was not attractant but rather was involved in assimilation, growth and ramifications. The neurotropic hypothesis described by Cajal in Degeneration and Regeneration in the Nervous System is more similar to a neurite extension factor (NEF) than to a neurotrophic growth factor or specific chemoaffinity (attractant) molecule. S-100 beta is the major NEF found in PNS Schwann cells and CNS astroglial cells. In summary, the views of Cajal on neuroplasticity, its frequency and function, agree with the modern hypothesis of neuronal instability. This concept states that MAPs regulate microtubule stability by a S-100 beta sensitive phosphorylation processes. Serotonin, by acting on the astroglial 5-HT1A receptor, releases S-100 beta and regulates neuronal morphology and apoptosis. This neuronal-glial connection provides a fresh view for linking neuroplasticity, mental illness, and memory with changes in the cytoskeleton.

Neuronal instability: implications for Rett's syndrome

The maturational changes in the brain and spinal cord do not linearly proceed from immature in infants to mature in adults. Dendrites dynamically extend or retract as neurotrophic factors fluctuate. In certain cases mature neurons can be seen soon after birth, and in other cases immature neurons can be identified in the aged brain. Monoamine 'neurotransmitter'; such as serotonin (5-HT), dopamine and norepinephrine appear to function as Maintenance Growth Factors since they must be present in order to produce their maturational actions. Serotonin neurons contain TRK-B receptors and are sensitive to availability of the trophic factor, BDNF. 5-HT also functions by promoting the release of the glial extension factor, S-100beta. 5-HT and S-100beta can provide maturational signals to a variety of neurons, in both cortical and subcortical areas, and appear to be involved in regulating the maturation and release of acetylcholine and dopamine. We have shown that activation of the 5-HT1A receptor is particularly effective in inducing growth of stunted neurons. The mechanism of action of the 5-HT1A receptor involves both a direct inhibition on c-AMP and pCREB formation in postsynaptic neurons and a release of S-100beta from glial cells. Both these events are capable of stabilization and elaboration of the cytoskeleton of the neuron and inhibition of apoptosis. 5-HT1A receptors have been shown to effectively reverse stunted neurons and microencephaly produced in animal models of fetal alcohol syndrome and prenatal cocaine administration. I discuss the implications for regressive disorders such as Rett's syndrome and autism, and the feasibility of treatments with 5-HT1A agonists in children with developmental disorders.

Modern views on an ancient chemical: serotonin effects on cell proliferation, maturation, and apoptosis

Evolutionarily, serotonin existed in plants even before the appearance of animals. Indeed, serotonin may be tied to the evolution of life itself, particularly through the role of tryptophan, its precursor molecule. Tryptophan is an indole-based, essential amino acid which is unique in its light-absorbing properties. In plants, tryptophan-based compounds capture light energy for use in metabolism of glucose and the generation of oxygen and reduced cofactors. Tryptophan, oxygen, and reduced cofactors combine to form serotonin. Serotonin-like molecules direct the growth of light-capturing structures towards the source of light. This morphogenic property also occurs in animal cells, in which serotonin alters the cytoskeleton of cells and thus influences the formation of contacts. In addition, serotonin regulates cell proliferation, migration and maturation in a variety of cell types, including lung, kidney, endothelial cells, mast cells, neurons and astrocytes). In brain, serotonin has interactions with seven families of receptors, numbering at least 14 distinct proteins. Of these, two receptors are important for the purposes of this review. These are the 5-HT1A and 5-HT2A receptors, which in fact have opposing functions in a variety of cellular and behavioral processes. The 5-HT1A receptor develops early in the CNS and is associated with secretion of S-100beta from astrocytes and reduction of c-AMP levels in neurons. These actions provide intracellular stability for the cytoskeleton and result in cell differentiation and cessation of proliferation. Clinically, 5-HT1A receptor drugs decrease brain activity and act as anxiolytics. The 5-HT2A receptor develops more slowly and is associated with glycogenolysis in astrocytes and increased Ca(++) availability in neurons. These actions destabilize the internal cytoskeleton and result in cell proliferation, synaptogenesis, and apoptosis. In humans, 5-HT2A receptor drugs produce hallucinations. The dynamic interactions between the 5-HT1A and 5-HT2A receptors and the cytoskeleton may provide important insights into the etiology of brain disorders and provide novel strategies for their treatment.