Fluoxetine, not donepezil, reverses anhedonia, cognitive dysfunctions and hippocampal proteome changes during repeated social defeat exposure.

While anhedonia is considered a core symptom of major depressive disorder (MDD), less attention has been paid to cognitive dysfunctions. We evaluated the behavioural and molecular effects of a selective serotonin re-uptake inhibitor (SSRI, fluoxetine) and an acetylcholinesterase inhibitor (AChEI, donepezil) on emotional-cognitive endophenotypes of depression and the hippocampal proteome. A chronic social defeat (SD) procedure was followed up by "reminder" sessions of direct and indirect SD. Anhedonia-related behaviour was assessed longitudinally by intracranial self-stimulation (ICSS). Cognitive dysfunction was analysed by an object recognition test (ORT) and extinction of fear memory. Tandem mass spectrometry (MSE) and protein-protein-interaction (PPI) network modelling were used to characterise the underlying biological processes of SD and SSRI/AChEI treatment. Independent selected reaction monitoring (SRM) was conducted for molecular validation. Repeated SD resulted in a stable increase of anhedonia-like behaviour as measured by ICSS. Fluoxetine treatment reversed this phenotype, whereas donepezil showed no effect. Fluoxetine improved recognition memory and inhibitory learning in a stressor-related context, whereas donepezil only improved fear extinction. MSE and PPI network analysis highlighted functional SD stress-related hippocampal proteome changes including reduced glutamatergic neurotransmission and learning processes, which were reversed by fluoxetine, but not by donepezil. SRM validation of molecular key players involved in these pathways confirmed the hypothesis that fluoxetine acts via increased AMPA receptor signalling and Ca2+-mediated neuroplasticity in the amelioration of stress-impaired reward processing and memory consolidation. Our study highlights molecular mediators of SD stress reversed by SSRI treatment, identifying potential viable future targets to improve cognitive dysfunctions in MDD patients.

Serum biomarkers predictive of depressive episodes in panic disorder.

Panic disorder with or without comorbid agoraphobia (PD/PDA) has been linked to an increased risk to develop subsequent depressive episodes, yet the underlying pathophysiology of these disorders remains poorly understood. We aimed to identify a biomarker panel predictive for the development of a depressive disorder (major depressive disorder and/or dysthymia) within a 2-year-follow-up period. Blood serum concentrations of 165 analytes were evaluated in 120 PD/PDA patients without depressive disorder baseline diagnosis (6-month-recency) in the Netherlands Study of Depression and Anxiety (NESDA). We assessed the predictive performance of serum biomarkers, clinical, and self-report variables using receiver operating characteristics curves (ROC) and the area under the ROC curve (AUC). False-discovery-rate corrected logistic regression model selection of serum analytes and covariates identified an optimal predictive panel comprised of tetranectin and creatine kinase MB along with patient gender and scores from the Inventory of Depressive Symptomatology (IDS) rating scale. Combined, an AUC of 0.87 was reached for identifying the PD/PDA patients who developed a depressive disorder within 2 years (n = 44). The addition of biomarkers represented a significant (p = 0.010) improvement over using gender and IDS alone as predictors (AUC = 0.78). For the first time, we report on a combination of biological serum markers, clinical variables and self-report inventories that can detect PD/PDA patients at increased risk of developing subsequent depressive disorders with good predictive performance in a naturalistic cohort design. After an independent validation our proposed biomarkers could prove useful in the detection of at-risk PD/PDA patients, allowing for early therapeutic interventions and improving clinical outcome.

Discovery of serum biomarkers predicting development of a subsequent depressive episode in social anxiety disorder.

Although social anxiety disorder (SAD) is strongly associated with the subsequent development of a depressive disorder (major depressive disorder or dysthymia), no underlying biological risk factors are known. We aimed to identify biomarkers which predict depressive episodes in SAD patients over a 2-year follow-up period. One hundred sixty-five multiplexed immunoassay analytes were investigated in blood serum of 143 SAD patients without co-morbid depressive disorders, recruited within the Netherlands Study of Depression and Anxiety (NESDA). Predictive performance of identified biomarkers, clinical variables and self-report inventories was assessed using receiver operating characteristics curves (ROC) and represented by the area under the ROC curve (AUC). Stepwise logistic regression resulted in the selection of four serum analytes (AXL receptor tyrosine kinase, vascular cell adhesion molecule 1, vitronectin, collagen IV) and four additional variables (Inventory of Depressive Symptomatology, Beck Anxiety Inventory somatic subscale, depressive disorder lifetime diagnosis, BMI) as optimal set of patient parameters. When combined, an AUC of 0.86 was achieved for the identification of SAD individuals who later developed a depressive disorder. Throughout our analyses, biomarkers yielded superior discriminative performance compared to clinical variables and self-report inventories alone. We report the discovery of a serum marker panel with good predictive performance to identify SAD individuals prone to develop subsequent depressive episodes in a naturalistic cohort design. Furthermore, we emphasise the importance to combine biological markers, clinical variables and self-report inventories for disease course predictions in psychiatry. Following replication in independent cohorts, validated biomarkers could help to identify SAD patients at risk of developing a depressive disorder, thus facilitating early intervention.

[Biomarker research in neuropsychiatry: challenges and potential]. / Biomarkerforschung in der Neuropsychiatrie: Herausforderung und Potenzial.

The introduction of blood-based biomarkers for psychiatric disorders faces numerous challenges. The goal of research efforts is the improvement of the current more or less subjective diagnosis, treatment and patient management. So far attempts to introduce molecular analyses have faced considerable resistance. There is an urgent need for a paradigm shift so that peripheral markers may also deliver insights into pathological states of the brain. Health regulators have called for a reform of research and development approaches, with the goal to enhance the safety and efficiency of future antipsychotic drugs using biomarker-based methods. Here we discuss the potential of the biomarker sector in this context, as exemplified by the recent introduction of Veripsych™, the first blood test aiding the diagnosis of schizophrenia.

Immunochemical characterization of an IgG-binding protein of Streptococcus suis.

Several bacterial species express surface proteins with affinity for the constant region (Fc) of immunoglobulin (Ig) of different animal species. Previous studies from our group have reported the presence of an IgG-binding protein in various serotypes of Streptococcus suis. This molecule was also shown to bind in a non-immune fashion chicken IgY and to our knowledge this characteristic is unique. In the present study, by dot-blotting, we showed that the native protein, obtained by affinity chromatography, reacted more strongly with IgG from various animal species than the denatured material. Using a competitive enzyme-linked immunosorbent assay the affinity of the native 60-kDa protein (previously identified as a 52-kDa protein) towards IgG of various animal species was compared to pig IgG. Bovine, goat and human IgG were able to compete effectively with pig IgG whereas chicken IgY constituted a poor competitor. Peptide mapping analysis using denatured protein indicated that pig and bovine IgG recognized the same proteolytic fragment whereas chicken IgY did not. The smallest proteolytic fragment that retained the binding activity towards the IgG of the different animal species tested had a molecular mass of approximately 40 kDa. Fragments with Mr < 40 kDa showed specific binding activities. That is, the smallest fragment binding pig and bovine IgG had a Mr of 30 kDa whereas for goat and human IgG a fragment of less than 16 kDa still showed binding activity. Finally, we observed that antisera raised against a heat-shock protein of Pseudomonas aeruginosa reacted with the 60-kDa S. suis protein indicating that the S. suis 60-kDa protein is a member of the 60-kDa hsp family that possesses the characteristic of binding in a non-immune way mammalian IgG and chicken IgY.

Identification of a Streptococcus suis 60-kDa heat-shock protein using western blotting.

This study was initiated to investigate the presence of stress or heat shock proteins in Streptococcus suis. SDS-PAGE and Western blotting using polyclonal and monoclonal antibodies directed against different bacterial heat shock proteins demonstrated cross-reactivity with a protein with an apparent molecular mass of 60 kDa in all S. suis serotypes tested. The 60-kDa cross-reactive protein was present in virulent and avirulent strains of S. suis serotype 2 tested. A rabbit antiserum raised against the 60-kDa S. suis protein recognized the 60-65-kDa heat shock proteins in different Gram-positive and Gram-negative bacteria. Finally, the 60-kDa heat shock protein of S. suis was shown to be mostly secreted into the culture supernatant and, to a lesser extent, cell-associated. Growth under heat stress conditions (42 degrees C) increased the expression of the 60-kDa S. suis protein. This protein is, to our knowledge, the first common antigen found in different serotypes of S. suis.

Characterization of Streptococcus suis capsular type 2 haemolysin.

The production of a haemolysin by Streptococcus suis capsular type 2 was investigated. Human group O erythrocytes were the most susceptible, followed by horse, sheep, cow and pig red blood cells, which exhibited similar susceptibilities; rabbit erythrocytes were the least susceptible. The haemolysin was produced at the end of the exponential growth phase. The toxin described in this paper was purified by affinity chromatography using a thiopropyl-Sepharose 6B column. It is an extracellular protein with a molecular mass of 65 kDa. The haemolysin belongs to the family of toxins known as antigenically related cholesterol-binding cytolytic toxins, since it shares common characteristics with other members of this family, such as sensitivity to oxygen and oxidizing agents, activation by reducing agents, inhibition by low concentrations of cholesterol, formation of transmembrane pores and a 'multihit' mechanism of action. In addition, anti-streptolysin antibodies inhibited the haemolytic activity caused by the S. suis haemolysin. Antibodies against the haemolysin could not be detected in pigs experimentally infected with a haemolytic positive strain of S. suis capsular type 2. To our knowledge, this is the only Lancefield group D Streptococcus producing a haemolysin with these characteristics. The role of this haemolysin in the pathogenesis of S. suis infections remains to be investigated.