Cerebrospinal fluid somatostatin, mood, and cognition in multiple sclerosis

Identification of potential biomarkers for neuromyelitis optica by quantitative proteomics

OBJECTIVE

Neuromyelitis optica (NMO) was a serious autoimmune inflammatory condition affecting the central nervous system. Currently, there was a lack of diagnostic biomarkers for AQP4-IgG-negative NMO patients.

METHODS

A comparative proteomic analysis was conducted on the CSF of 10 patients with NMO and 10 patients with non-inflammatory neurological disorders (NND) using tandem mass tagging technology. Differentially expressed proteins (DEPs) were analyzed using bioinformatic methods. The candidate proteins were then validated through ELISAs in a subsequent cohort of 160 samples, consisting of paired CSF and plasma samples from 50 NMO patients, CSF samples from 30 NND patients, and plasma samples from 30 healthy individuals.

RESULTS

We identified 389 proteins via proteomics, screening 79 DEPs. NCAM1, SST and AHSG were selected as candidate molecules for further validation. Compared to NND patients, there were decreased levels of AHSG in CSF and increased levels of NCAM1 and SST in NMO patients. The ELISA results revealed significantly higher levels of AHSG, SST and NCAM1 in the CSF of the NMO group compared to the NND group. Similarly, the serum levels of these three proteins were also higher in the NMO group compared to the healthy control group. It was found that serum NCAM1 levels significantly decreased in patients with non-relapsed NMO compared to patients with relapsed NMO and CSF NCAM1 level increased in patients with bilateral NMO compared to patients with unilateral NMO. Furthermore, CSF SST levels increased in AQP4 antibody-positive NMO patients compared to AQP4 antibody-negative patients.

INTERPRETATION

CSF NCAM1, serum NCAM1 and serum SST may serve as potential biomarkers for NMO patients and aid in the diagnosis of AQP4 antibody-negative NMO patients.

Plasma Protein Levels Analysis in Multiple Sclerosis Sardinian Families Identified C9 and CYP24A1 as Candidate Biomarkers

Here we investigate protein levels in 69 multiple sclerosis (MS) cases and 143 healthy controls (HC) from twenty Sardinian families to search for promising biomarkers in plasma. Using antibody suspension bead array technology, the plasma levels of 56 MS-related proteins were obtained. Differences between MS cases and HC were estimated using Linear Mixed Models or Linear Quantile Mixed Models. The proportion of proteins level variability, explained by a set of 119 MS-risk SNPs as to the literature, was also quantified. Higher plasma C9 and CYP24A1 levels were found in MS cases compared to HC (p < 0.05 after Holm multiple testing correction), with protein level differences estimated as, respectively, 0.53 (95% CI: 0.25, 0.81) and 0.42 (95% CI: 0.19, 0.65) times plasma level standard deviation measured in HC. Furthermore, C9 resulted in both statistically significantly higher relapsing-remitting MS (RRMS) and secondary-progressive MS (SPMS) compared to HC, with SPMS showing the highest differences. Instead, CYP24A1 was statistically significantly higher only in RRMS as compared to HC. Respectively, 26% (95% CI: 10%, 44%) and 16% (95% CI: 9%, 39%) of CYP24A1 and C9 plasma level variability was explained by known MS-risk SNPs. Our results highlight C9 and CYP24A1 as potential biomarkers in plasma for MS and allow us to gain insight into molecular disease mechanisms.

Discovery of Novel Biomarkers for Diagnosing and Predicting the Progression of Multiple Sclerosis Using TMT-Based Quantitative Proteomics

Objective

Here, we aimed to identify protein biomarkers that could rapidly and accurately diagnose multiple sclerosis (MS) using a highly sensitive proteomic immunoassay.

Methods

Tandem mass tag (TMT) quantitative proteomic analysis was performed to determine the differentially expressed proteins (DEPs) in cerebrospinal fluid (CSF) samples collected from 10 patients with MS and 10 non-inflammatory neurological controls (NINCs). The DEPs were analyzed using bioinformatics tools, and the candidate proteins were validated using the ELISA method in another cohort comprising 160 samples (paired CSF and plasma of 40 patients with MS, CSF of 40 NINCs, and plasma of 40 healthy individuals). Receiver operating characteristic (ROC) curves were used to determine the diagnostic potential of this method.

Results

Compared to NINCs, we identified 83 CSF-specific DEPs out of a total of 343 proteins in MS patients. Gene ontology (GO) enrichment analysis revealed that these DEPs are mainly involved in platelet degranulation, negative regulation of proteolysis, and post-translational protein modification. Pathway enrichment analysis revealed that the complement and coagulation cascades, Ras signaling pathway, and PI3K-Akt signaling pathway are the main components. Insulin-like growth factor-binding protein 7 (IGFBP7), insulin-like growth factor 2 (IGF2), and somatostatin (SST) were identified as the potential proteins with high scores, degree, and centrality in the protein-protein interaction (PPI) network. We validated the expression of these three proteins using ELISA. Compared to NINCs, the level of CSF IGFBP7 was significantly upregulated, and the level of CSF SST was significantly downregulated in the MS group.

Conclusion

Our results suggest that SST and IGFBP7 might be associated with the pathogenesis of MS and would be helpful in diagnosing MS. Since IGFBP7 was used to classify relapsing remitting MS (RRMS) and secondary progressive MS (SPMS) patients, therefore, it may act as a potential key marker and therapeutic target in MS.

Neurochemical Markers in the Mammalian Brain: Structure, Roles in Synaptic Communication, and Pharmacological Relevance

BACKGROUND

Knowledge of molecular marker (typically protein or mRNA) expression in neural systems can provide insight to the chemical blueprint of signal processing and transmission, assist in tracking developmental or pathological progressions, and yield key information regarding potential medicinal targets. These markers are particularly relevant in the mammalian brain in the light of its unsurpassed cellular diversity. Accordingly, molecular expression profiling is rapidly becoming a major approach to classify neuron types. Despite a profusion of research, however, the biological functions of molecular markers commonly used to distinguish neuron types remain incompletely understood. Furthermore, most molecular markers of mammalian neuron types are also present in other organs, therefore complicating considerations of their potential pharmacological interactions.

OBJECTIVE

Here, we survey 15 prominent neurochemical markers from five categories, namely membrane transporters, calcium-binding proteins, neuropeptides, receptors, and extracellular matrix proteins, explaining their relation and relevance to synaptic communication.

METHOD

For each marker, we summarize fundamental structural features, cellular functionality, distributions within and outside the brain, as well as known drug effectors and mechanisms of action.

CONCLUSION

This essential primer thus links together the cellular complexity of the brain, the chemical properties of key molecular players in neurotransmission, and possible biomedical opportunities.

Somatostatin and Somatostatin-Containing Neurons in Shaping Neuronal Activity and Plasticity

Since its discovery over four decades ago, somatostatin (SOM) receives growing scientific and clinical interest. Being localized in the nervous system in a subset of interneurons somatostatin acts as a neurotransmitter or neuromodulator and its role in the fine-tuning of neuronal activity and involvement in synaptic plasticity and memory formation are widely recognized in the recent literature. Combining transgenic animals with electrophysiological, anatomical and molecular methods allowed to characterize several subpopulations of somatostatin-containing interneurons possessing specific anatomical and physiological features engaged in controlling the output of cortical excitatory neurons. Special characteristic and connectivity of somatostatin-containing neurons set them up as significant players in shaping activity and plasticity of the nervous system. However, somatostatin is not just a marker of particular interneuronal subpopulation. Somatostatin itself acts pre- and postsynaptically, modulating excitability and neuronal responses. In the present review, we combine the knowledge regarding somatostatin and somatostatin-containing interneurons, trying to incorporate it into the current view concerning the role of the somatostatinergic system in cortical plasticity.

Somatostatin preserved blood brain barrier against cytokine induced alterations: possible role in multiple sclerosis

Multiple sclerosis (MS) is an inflammatory neurological disorder associated with demyelination, impaired blood brain barrier (BBB), axonal damage and neuronal loss. In the present study, we measured somatostatin (SST) and tumor necrosis factor-α (TNF-α) like immunoreactivity in CSF samples from MS and non-MS patients. We also examined the role of SST in cytokines and lipopolysaccharide (LPS)-induced damage to the BBB using human brain endothelial cells in culture. Most of the cerebrospinal fluid (CSF) samples studied from definite MS patients exhibited lower somatostatin (SST)-like immunoreactivity and higher expression of TNF-α in comparison to non-MS patients. Treatment of cells with cytokines and LPS blocked SST secretion and decreased SST expression. Human brain endothelial cells expressed all five somatostatin receptors (SSTRs) with increased expression of SSTR2 and 4 upon treatment with cytokines and LPS. Cytokines and LPS-induced disruption of the tight junction proteins Zonula occludens (ZO-1) organization was restored in presence of SST, SSTR2 or SSTR4 selective agonists. Furthermore, inflammation induced changes in extracellular signal-regulated kinases (ERK1/2 and ERK5) signaling and altered expression of endothelial and inducible nitric oxide synthase are modulated in presence of SST. These data indicate that decreased levels of SST contribute to failure of the BBB in MS.

Induction of experimental allergic encephalomyelitis in a low-susceptible Albino Oxford rat strain by somatostatin analogue SMS 201-995

OBJECTIVE

The effect of the somatostatin analogue SMS 201-995 (octreotide; OCT) on the course of experimental allergic encephalomyelitis (EAE) in the relatively resistant Albino Oxford (AO) strain of rats was studied.

METHODS

Animals were actively immunized with bovine brain homogenate in complete Freund's adjuvant. OCT was given subcutaneously in the hind legs on days 7, 8 and 9 after immunization, at a dose of 3 x 5 microg/kg/day. Rats in control groups were treated with saline or were left untreated. EAE was scored clinically and immunophenotypically, estimating by flow cytometry the changes in the popliteal lymph nodes (PLN) and spleen and monitoring immunohistologically the brain sections of rats recovered from disease.

RESULTS

In control AO rats, EAE was induced in only 2 of 22 rats (9%). In OCT-treated rats, however, EAE developed in 11 of 20 rats (55%), in comparison with 3 of 17 saline-treated animals (17%) (p <0.05). In PLN of OCT-treated rats during the clinical course of EAE, a decreased proportion of OX8+ cells was seen, followed by increases in OX39+ and W3/25+ cells on days 17 and 26. In spleen, OCT decreased the proportion of OX1+, OX39+ and OX8+ cells (on days 12 and/or 17), and increased the proportion of OX39+ cells on days 26 and 31. In the brain sections of saline-treated rats recovered from EAE, numerous Mac-1+, Mac-3+ and OX8+ cells were found. These cells were, however, absent in OCT-treated rats; instead, several W3/25+ cells were noticed.

CONCLUSIONS

These data imply that OCT increases the susceptibility of AO rats to EAE, interfering with specific and/or nonspecific defense mechanisms operating in both the initial and recovery phase of EAE.

Low CSF somatostatin associated with response to nimodipine in patents with affective illness

BACKGROUND

In patients with depression, treatment with nimodipine has been shown to increase cerebrospinal fluid (CSF) somatostatin (SRIF) and ameliorate baseline global cerebral hypometabolism. This study was conducted to assess whether a low baseline level of CSF SRIF was associated with response to nimodipine treatment.

METHODS

Twenty-one depressed patients underwent lumbar puncture for analysis of CSF somatostatin-like immunoreactivity (SRIF-LI) during a medication-free period and after at least 6 weeks of nimodipine monotherapy. Twenty-five healthy control subjects were utilized as a comparison group. Clinical improvement was assessed using the Clinical Global Impression Scale for Bipolar Illness.

RESULTS

As predicted, baseline CSF SRIF-LI was significantly lower in eventual nimodipine responders (33.1 +/- 2.8 pg/mol) compared to eventual nonresponders [41.9 +/- 2.6 pg/mL; t(19) = 1.98, p =.03, one-tailed].

CONCLUSIONS

Low baseline CSF somatostatin in depression may be associated with response to nimodipine, which in turn may be related to the ability of nimodipine to increase CSF somatostatin.

Lower levels of the circulating neuropeptide somatostatin in Schistosoma mansoni infected patients may have pathological significance

In recent years, cases of severe morbidity (fibrosis, haematemesis, hepatosplenomegaly, ascites) caused to Schistosoma mansoni infections are on the rise in Northern Senegal. The neuropeptide somatostatin is reported to decrease portal pressure, control variceal bleeding and fibrosis, and reduce Schistosoma-caused clinical morbidity in the rodent model. The aim of this study was to delineate the role of somatostatin in S. mansoni-caused pathogenesis, by studying host levels of somatostatin in the peripheral blood of uninfected and S. mansoni-infected individuals. Subjects from the district dispensary at Richard Toll, in the Medical Region of Saint-Louis, Senegal, infected with S. mansoni and suffering from severe morbidity were selected. A separate group consisted of individuals resident in the same region but uninfected at the time of the study. Significantly lower somatostatin levels were detected in severe morbidity patients, compared with the exposed but uninfected subjects. In patients with schistosomiasis physiological levels of somatostatin may determine disposition of particular individuals towards severe morbidity, as opposed to others. Host pathology can thus be alleviated by the therapeutic ability of somatostatin to treat bleeding oesophageal varices, reduce portal pressure and prevent progression to severe fibrosis.

Deficit of somatostatin-like immunoreactivity in the vitreous fluid of diabetic patients: possible role in the development of proliferative diabetic retinopathy

OBJECTIVE

To evaluate the vitreous levels of somatostatin-like immunoreactivity (SLI) in patients with proliferative diabetic retinopathy (PDR).

RESEARCH DESIGN AND METHODS

A total of 14 diabetic patients with PDR, in whom a vitrectomy was performed, were included in the study. Sixteen nondiabetic patients, with other conditions requiring vitrectomy, served as a control group. Both venous blood and vitreous samples were collected at the time of vitreoretinal surgery. Patients in whom intravitreous hemoglobin was detectable were excluded. In addition, a correction for plasma levels of SLI and intravitreal proteins was performed. SLI was measured by radioimmunoassay and vitreous hemoglobin by spectrophotometry.

RESULTS

SLI in the vitreous fluid was significantly lower in diabetic patients than in the control group (68 +/- 18.7 vs. 193.6 +/- 30.8 pg/ml, P < 0.01). The vitreous SLI-to-plasma SLI ratio was strikingly higher in nondiabetic subjects than in diabetic patients with PDR (5.3 [1.2-71.1] vs. 0.6 [0.03-4.1], P < 0.01). After correcting for total vitreous protein concentration, SLI (pg/mg of proteins) remained significantly higher in nondiabetic control subjects than in diabetic patients with PDR (186 [51-463] vs. 7.5 [0.8-82], P < 0.0001). Remarkably, intravitreous levels of SLI were higher than those obtained in plasma in nondiabetic control subjects (193.6 +/- 30.8 vs. 43.5 +/- 10.7 pg/ml, P < 0.0001). Finally, a lack of relationship between plasma and vitreous levels of SLI was observed in both diabetic patients with PDR and nondiabetic control subjects.

CONCLUSIONS

The significantly higher SLI in the vitreous fluid than in plasma detected in nondiabetic control subjects supports the concept that somatostatin plays a relevant role in retinal homeostasis. In addition, the intravitreous deficit of SLI observed in diabetic patients with PDR suggests that it might contribute to the process of retinal neovascularization.

The relationship between disability and depression in multiple sclerosis: the role of uncertainty, coping, and hope

The relationship between disability and depression was studied in 188 patients with clinically definite multiple sclerosis (MS). Patients were administered the Zung Self-Rating Depression Scale, Ways of Coping, Uncertainty of Illness Scale, and Hope Scale during their regular clinic appointments. Their current level of disability was rated by the attending physician using the Expanded Disability Status Scale. Even when the depression measure was corrected for items overlapping with other symptoms or consequences of MS, depression was correlated with disability. Depression was also correlated with an array of psychological variables, including uncertainty concerning ones illness, hope, and the use of various emotion-centered, though not problem-centered coping strategies. Multiple regression analyses revealed that none of these psychological correlates mediated or moderated the relationship between disability and depression. Instead, disability, uncertainty, hope, and emotion-centered coping were significant independent predictors of depression, together accounting for approximately 40% of the variance in patients' self-reported depression. The relationship between disability and depression in MS is usually interpreted as evidence that depression is psychogenic and reactive to the demands and limitations of this disease. The demonstration that this relationship is not diminished when an array of potentially intervening psychological variables are included in the analysis raises questions concerning the validity of this interpretation.