Cerebrospinal fluid and serum levels of neuron-specific enolase in patients with schizophrenia

Biomarkers in the cerebrospinal fluid of patients with psychotic disorders compared to healthy controls: a systematic review and meta-analysis

Psychotic disorders are severe mental disorders with poorly understood etiology. Biomarkers in the cerebrospinal fluid (CSF) could provide etiological clues and diagnostic tools for psychosis; however, an unbiased overview of CSF alterations in individuals with psychotic disorders is lacking. The objective of this study was to summarize all quantifiable findings in CSF from individuals with psychotic disorders compared to healthy controls (HC). Studies published before January 25th, 2023 were identified searching PubMed, EMBASE, Cochrane Library, Web of Science, ClinicalTrials.gov, and PsycINFO. Screening, full-text review, data extraction, and risk of bias assessments were performed by two independent reviewers following PRISMA guidelines. Findings in patients and healthy controls were compared and summarized using random-effects analyses and assessment of publication bias, subgroup and sensitivity analyses were performed. 145 studies, covering 197 biomarkers, were included, of which 163 biomarkers have not previously been investigated in meta-analyses. All studies showed some degree of bias. 55 biomarkers measured in CSF were associated with psychosis and of these were 15 biomarkers measured in ≥2 studies. Patients showed increased levels of noradrenaline (standardized mean difference/SMD, 0.53; 95% confidence interval/CI, 0.16 to 0.90) and its metabolite 3-methoxy-4-hydroxyphenylglycol (SMD, 0.30; 95% CI: 0.05 to 0.55), the serotonin metabolite 5-hydroxyindoleacetic acid (SMD, 0.11; 95% CI: 0.01 to 0.21), the pro-inflammatory neurotransmitter kynurenic acid (SMD, 1.58; 95% CI: 0.34 to 2.81), its precursor kynurenine (SMD,0.99; 95% CI: 0.60 to 1.38), the cytokines interleukin-6 (SMD, 0.58; 95% CI: 0.39 to 0.77) and interleukin-8 (SMD, 0.43; 95% CI: 0.24 to 0.62), the endocannabinoid anandamide (SMD, 0.78; 95% CI: 0.53 to 1.02), albumin ratio (SMD, 0.40; 95% CI: 0.08 to 0.72), total protein (SMD, 0.29; 95% CI: 0.16 to 0.43), immunoglobulin ratio (SMD, 0.45; 95% CI: 0.06 to 0.85) and glucose (SMD, 0.48; 95% CI: 0.01 to 0.94). Neurotensin (SMD, -0.67; 95% CI: -0.89 to -0.46) and γ-aminobutyric acid (SMD, -0.29; 95% CI: -0.50 to -0.09) were decreased. Most biomarkers showed no significant differences, including the dopamine metabolites homovanillic acid and 3,4-dihydroxyphenylacetic acid. These findings suggest that dysregulation of the immune and adrenergic system as well as blood-brain barrier dysfunction are implicated in the pathophysiology of psychotic disorders.

Lower circulating neuron-specific enolase concentrations in adults and adolescents with severe mental illness

BACKGROUND

Both neurodegenerative and neurodevelopmental abnormalities have been suggested to be part of the etiopathology of severe mental illness (SMI). Neuron-specific enolase (NSE), mainly located in the neuronal cytoplasm, may indicate the process as it is upregulated after neuronal injury while a switch from non-neuronal enolase to NSE occurs during neuronal maturation.

METHODS

We included 1132 adult patients with SMI [schizophrenia (SZ) or bipolar spectrum disorders], 903 adult healthy controls (HC), 32 adolescent patients with SMI and 67 adolescent HC. Plasma NSE concentrations were measured by enzyme immunoassay. For 842 adults and 85 adolescents, we used total grey matter volume (TGMV) based on T1-weighted magnetic resonance images processed in FreeSurfer v6.0. We explored NSE case-control differences in adults and adolescents separately. To investigate whether putative case-control differences in NSE were TGMV-dependent we controlled for TGMV.

RESULTS

We found significantly lower NSE concentrations in both adult (p < 0.001) and adolescent patients with SMI (p = 0.007) compared to HC. The results remained significant after controlling for TGMV. Among adults, both patients with SZ spectrum (p < 0.001) and bipolar spectrum disorders (p = 0.005) had lower NSE than HC. In both patient subgroups, lower NSE levels were associated with increased symptom severity. Among adults (p < 0.001) and adolescents (p = 0.040), females had lower NSE concentrations than males.

CONCLUSION

We found lower NSE concentrations in adult and adolescent patients with SMI compared to HC. The results suggest the lack of progressive neuronal injury, and may reflect abnormal neuronal maturation. This provides further support of a neurodevelopmental rather than a neurodegenerative mechanism in SMI.

Altered Expression of Glucocorticoid Receptor and Neuron-Specific Enolase mRNA in Peripheral Blood in First-Episode Schizophrenia and Chronic Schizophrenia

INTRODUCTION

It is well-known that altered hypothalamus-pituitary-adrenal (HPA) axis process has an important role in the neurodegenerative process in schizophrenia (SZ). However, this neurodegenerative mechanism has not been clarified in SZ. Therefore, the main purpose of this study was to determine HPA axis damage in the first-episode, unmedicated schizophrenia (FES) patients and chronic schizophrenia (CSZ) patients in comparison with healthy controls (HC) by means of quantitative analysis of the peripheral blood mRNA expression of glucocorticoid receptor (GR), GR transcripts containing exons 1B (GR-1B), and neuron specific enolase (NSE) genes and serum cortisol and NSE, a specific serum marker for neuronal damage.

METHODS

In the present study, 43 FES patients, 39 CSZ, and 47 HC were included. The peripheral blood mRNA expressions for GR, GR-1B, and NSE genes were determined by real-time quantitative polymerase chain reaction (RT-qPCR). Serum cortisol and NSE were analyzed by electrochemiluminescence immunoassay technique.

RESULTS

Levels of GR mRNA were significantly lower in FES and CSZ than that in HC. The expression of GR-1B mRNA was significantly decreased in CSZ when compared with that in FES. Levels of NSE mRNA were significantly lower in CSZ than that in FES patients or HC patients. CSZ patients showed significantly lower cortisol concentrations than FES and HC patients. FES patients showed significantly higher NSE concentrations than CSZ and HC.

CONCLUSION

Our findings support that there is disrupted HPA axis system in the SZ and suggest that CSZ patients suffer a greater HPA axis damage than FES patients. Our research implicated underlying GR mRNA dysregulation in SZ and the potential importance of the functional GR-1B transcription in CSZ.

Neuron-Specific Enolase

The clinical value of neuron-specific enolase as a marker in small cell lung cancer, neuroblastoma, melanoma and seminoma has been reviewed The role of serum and cerebrospinal NSE in benign and malignant disease of the central nervous sytem is discussed.

Neuron-Specific Enolase as a Biomarker: Biochemical and Clinical Aspects

Neuron-specific enolase (NSE) is known to be a cell specific isoenzyme of the glycolytic enzyme enolase. In vertebrate organisms three isozymes of enolase, expressed by different genes, are present: enolase α is ubiquitous; enolase β is muscle-specific and enolase γ is neuron-specific. The expression of NSE, which occurs as γγ- and αγ-dimer, is a late event in neural differentiation, thus making it a useful index of neural maturation.NSE is a highly specific marker for neurons and peripheral neuroendocrine cells. As a result of the findings of NSE in specific tissues under normal conditions, increased body fluids levels of NSE may occur with malignant proliferation and thus can be of value in diagnosis, staging and treatment of related neuroendocrine tumours (NETs).NSE is currently the most reliable tumour marker in diagnosis, prognosis and follow-up of small cell lung cancer (SCLC), even though increased levels of NSE have been reported also in non-small cell lung cancer (NSCLC). The level of NSE correlates with tumour burden, number of metastatic sites and response to treatment.NSE can be also useful at diagnosis of NETs and gastroenteropancreatic (GEP)-NETs.Raised serum levels of NSE have been found in all stages of neuroblastoma, although the incidence of increased concentration is greater in widespread and metastatic disease. Moreover, NSE determination in cord blood offers an early postnatal possibility of confirming the diagnosis of neuroblastoma in newborns.NSE has been demonstrated to provide quantitative measures of brain damage and/or to improve the diagnosis and the outcome evaluation in ischaemic stroke, intracerebral hemorrhage, seizures, comatose patients after cardiopulmonary resuscitation for cardiac arrest and traumatic brain injury.Increased NSE serum levels have also been found associated with melanoma, seminoma, renal cell carcinoma, Merkel cell tumour, carcinoid tumours, dysgerminomas and immature teratomas, malignant phaechromocytoma, Guillain-Barré syndrome and Creutzfeldt-Jakob disease.

Cerebrospinal fluid biomarker candidates of schizophrenia: where do we stand?

Here, we review the cerebrospinal fluid (CSF) candidate markers with regard to their clinical relevance as potential surrogates for disease activity, prognosis assessment, and predictors of treatment response. We searched different online databases such as MEDLINE and EMBASE for studies on schizophrenia and CSF. Initial studies on cerebrospinal fluid in patients with schizophrenia revealed increased brain-blood barrier permeability with elevated total protein content, increased CSF-to-serum ratio for albumin, and intrathecal production of immunoglobulins in subgroups of patients. Analyses of metabolites in CSF suggest alterations within glutamatergic neurotransmission as well as monoamine and cannabinoid metabolism. Decreased levels of brain-derived neurotrophic factor and nerve growth factor in CSF of first-episode patients with schizophrenia reported in recent studies point to a dysregulation of neuroprotective and neurodevelopmental processes. Still, these findings must be considered as non-specific. A more profound characterization of the particular psychopathological profiles, the investigation of patients in the prodromal phase or within the first episode of schizophrenia promoting longitudinal investigations, implementation of different approaches of proteomics, and rigorous adherence to standard procedures based on international CSF guidelines are necessary to improve the quality of CSF studies in schizophrenia, paving the way for identification of syndrome-specific biomarker candidates.

Construction and analysis of the protein-protein interaction networks for schizophrenia, bipolar disorder, and major depression

BACKGROUND

Schizophrenia, bipolar disorder, and major depression are devastating mental diseases, each with distinctive yet overlapping epidemiologic characteristics. Microarray and proteomics data have revealed genes which expressed abnormally in patients. Several single nucleotide polymorphisms (SNPs) and mutations are associated with one or more of the three diseases. Nevertheless, there are few studies on the interactions among the disease-associated genes and proteins.

RESULTS

This study, for the first time, incorporated microarray and protein-protein interaction (PPI) databases to construct the PPI network of abnormally expressed genes in postmortem brain samples of schizophrenia, bipolar disorder, and major depression patients. The samples were collected from Brodmann area (BA) 10 of the prefrontal cortex. Abnormally expressed disease genes were selected by t-tests comparing the disease and control samples. These genes were involved in housekeeping functions (e.g. translation, transcription, energy conversion, and metabolism), in brain specific functions (e.g. signal transduction, neuron cell differentiation, and cytoskeleton), or in stress responses (e.g. heat shocks and biotic stress).The diseases were interconnected through several "switchboard"-like nodes in the PPI network or shared abnormally expressed genes. A "core" functional module which consisted of a tightly knitted sub-network of clique-5 and -4s was also observed. These cliques were formed by 12 genes highly expressed in both disease and control samples.

CONCLUSIONS

Several previously unidentified disease marker genes and drug targets, such as SBNO2 (schizophrenia), SEC24C (bipolar disorder), and SRRT (major depression), were identified based on statistical and topological analyses of the PPI network. The shared or interconnecting marker genes may explain the shared symptoms of the studied diseases. Furthermore, the "switchboard" genes, such as APP, UBC, and YWHAZ, are proposed as potential targets for developing new treatments due to their functional and topological significance.

Neuron-specific enolase is unaltered whereas S100B is elevated in serum of patients with schizophrenia--original research and meta-analysis

Previous studies reported altered levels of the astrocytic marker S100B in schizophrenia. To clarify mechanisms, we measured weekly serum levels of S100B together with the neuronal marker neuron-specific enolase in 20 patients with schizophrenia and 19 age- and gender-matched control subjects. S100B was elevated at admission and discharge in schizophrenic patients compared with control subjects, whereas there were no significant differences for neuron-specific enolase. Treatment had no impact on either S100B or neuron-specific enolase. A systematic, quantitative meta-analysis of all published studies involving 380 patients and 358 control subjects revealed elevated serum S100B in schizophrenia without any effect of antipsychotic treatment. Results suggest that increases of serum S100B are related to active secretion of S100B by astrocytes in combination with blood-brain barrier dysfunction in schizophrenia.

Increased lipid peroxidation and neuron specific enolase in treatment refractory schizophrenics

It is well-known that increased lipid peroxidation and failure of antioxidant mechanisms leads to neuronal damage in schizophrenic patients. However, this neurodegenerative mechanism has not been studied in treatment refractory schizophrenics (TRS). Therefore, the main purpose of this study was to determine neuronal damage in TRS in comparison to non-refractory schizophrenics (NRS) by means of quantitative analysis of lipid peroxidation and neuron specific enolase (NSE) related to the psychopathology severity. Two groups of paranoid schizophrenics, TRS and NRS, and a group of healthy controls (CO) were assembled (n=13). Lipid peroxidation was analyzed through spectrophotometry for quantification of malonaldehyde (MDA) and 4-hydroxynonenal (4-HNE) serum concentrations. As well, serum NSE was quantified by radioimmunoassay (ELSA). Psychopathology was evaluated using the brief psychiatric rating scale (BPRS) and the positive and negative symptoms scale (PANSS). TRS showed significant higher concentrations of lipoperoxides by-products and NSE, than NRS and CO. Clinical scores also revealed a more severe pathology in TRS, than in NRS. Raised lipoperoxidation correlated with higher delusions and emotional withdrawal symptoms, and increased NSE correlated with a lower flow of the conversation and lack of spontaneity. All these results together suggest that TRS patients suffer a greater lipid peroxidation and neuronal damage than NRS, apparently related to worsening of some of the psychiatric symptoms.

Oxidative stress parameters in unmedicated and treated bipolar subjects during initial manic episode: A possible role for lithium antioxidant effects

Studies have proposed the involvement of oxidative stress and neuronal energy dysfunctions in the pathophysiology of bipolar disorder (BD). This study evaluates plasma levels of the oxidative/energy metabolism markers, thiobarbituric acid reactive substances (TBARS), superoxide dismutase (SOD), catalase (CAT), and neuron-specific enolase (NSE) during initial episodes of mania compared to controls in 75 subjects. Two groups of manic subjects (unmedicated n=30, and lithium-treated n=15) were age/gender matched with healthy controls (n=30). TBARS and antioxidant enzymes activity (SOD and CAT) were increased in unmedicated manic patients compared to controls. Conversely, plasma NSE levels were lower during mania than in the controls. In contrast, acute treatment with lithium showed a significant reduction in both SOD/CAT ratio and TBARS levels. These results suggest that initial manic episodes are associated with both increased oxidative stress parameters and activated antioxidant defenses, which may be related to dysfunctions on energy metabolism and neuroplasticity pathways. Antioxidant effects using lithium in mania were shown, and further studies are necessary to evaluate the potential role of these effects in the pathophysiology and therapeutics of BD.

Increased serum S100B protein in schizophrenia: a study in medication-free patients

S100B protein, a calcium binding protein produced and released by glial cells, has been used as a sensitive marker of brain damage. Previous studies have found alterations in peripheral S100B levels in schizophrenic patients on medication. We compared serum S100B levels of 20 medication-free DSM-IV schizophrenic patients and 20 age-gender matched healthy controls. Schizophrenic patients presented higher serum S100B levels (mean 0.120 ng/ml+/-S.D. 0.140) compared to controls (mean 0.066 ng/ml+/-S.D. 0.067; P=0.014) and there was a negative correlation with illness duration (r=-0.496, P=0.031). The results of this study indicate that serum S100B levels may be a state marker of a limited neurodegenerative process, particularly in the early course of schizophrenia or, at least, in a subgroup of schizophrenic patients.

Developmental trajectory and disease progression in schizophrenia: the conundrum, and insights from a 12-year prospective study in the Monaghan 101

Though conceptualised originally as a deteriorating disorder, some contemporary studies have been interpreted as challenging these foundations; more radically, it has been proposed that schizophrenia may be a 'static encephalopathy' of neurodevelopmental origin. The argument offered here is that schizophrenia is indeed a neurodevelopmental disorder, but that this is not in itself antithetical to later disease progression. Rather, the onset of psychosis may reflect the maturationally-mediated triggering of an active disease process that is associated with progressive deterioration unless attenuated by antipsychotic drugs. A developmental trajectory is proposed to link first or early second trimester dysplasia to the chronic course of the illness; from this, it is argued that schizophrenia is inherently a progressive disorder but that antipsychotic drugs may act to ameliorate this progressive component and thus confer on the disease course some of the characteristics of a 'static encephalopathy'. The 'true' natural history of an illness cannot be determined from studies in treated populations.

Neuron specific enolase in cerebrospinal fluid: a biochemical marker for neuronal degeneration in dementia disorders?

Alzheimer's disease (AD) is the most common disease causing dementia. Today the clinical diagnosis of AD is made by way of exclusion, and no biochemical markers are available to assist the clinical diagnosis. We examined the potential of neuron-specific enolase (NSE) in cerebrospinal fluid (CSF) as a diagnostic marker for AD. NSE was determined with a monoclonal antibody two-site immunoradiometric assay (IRMA) in serum (S) and cerebrospinal fluid (CSF) samples from 45 patients with "probable Alzheimer's disease (AD)", 19 patients with vascular dementia (VAD) and 33 age-matched healthy individuals. There was no significant correlation between S-NSE and CSF-NSE, or between CSF/S albumin ratio and CSF-NSE, findings suggesting that the major portion of CSF-NSE is intrathecally produced and that analysis of CSF-NSE alone (without accompanying analysis of serum) is sufficient. CSF-NSE was significantly higher in the AD group (4.7 +/- 2.7 ng/mL; p < 0.0001) and in VAD group (4.5 +/- 2.5 ng/mL; p < 0.001) as compared with the control group (2.2 +/- 1.0 ng/mL), while it did not differ significantly between the AD and the VAD group. These findings suggest that CSF-NSE have a potential as a non-disease specific marker for the neuronal degeneration in dementia disorders.