Antidepressant activated biochemical pathways and biomarker candidates

Most of the commonly used antidepressants block monoamine reuptake transporters to enhance serotonergic or noradrenergic neurotransmission. Effects besides or downstream of increased monoaminergic neurotransmission are poorly understood and yet presumably important for the drugs’ mode of action. In my PhD thesis I employed proteomics and metabolomics technologies combined with in silico analyses and identified cellular pathways affected by antidepressant drug treatment. DBA/2 mice were treated with paroxetine as a representative Selective Serotonin Reuptake Inhibitor (SSRI). Hippocampal protein levels were compared between chronic paroxetine- and vehicle-treated animals using in vivo 15N metabolic labeling combined with mass spectrometry. I also studied chronic changes in the hippocampus using unbiased metabolite profiling and the time course of metabolic changes with the help of a targeted polar metabolomics profiling platform. I identified profound alterations related to hippocampal energy metabolism. Glycolytic metabolite levels acutely increased while Krebs cycle metabolite levels decreased upon chronic treatment. Changes in energy metabolism were influenced by altered glycogen metabolism rather than by altered glycolytic or Krebs cycle enzyme levels. Increased energy levels were reflected by an increased ATP/ADP ratio and by increased ratios of high-to-low energy purines and pyrimidines. Paralleling the shift towards aerobic glycolysis upon paroxetine treatment I identified decreased levels of Krebs cycle and oxidative phosphorylation enzyme levels upon the antidepressant-like 15N isotope effect in high-anxiety behavior mice. In the course of my analyses I also identified GABA, galactose-6-phosphate and leucine as biomarker candidates for the assessment of chronic paroxetine treatment effects in the periphery and myo-inositol as biomarker candidate for an early assessment of chronic treatment effects. The identified antidepressant drug treatment affected molecular pathways and novel SSRI modes of action warrant consideration in antidepressant drug development efforts

Tau deletion prevents stress-induced dendritic atrophy in prefrontal cortex: role of synaptic mitochondria

Tau protein in dendrites and synapses has been recently implicated in synaptic degeneration and neuronal malfunction. Chronic stress, awell-known inducer of neuronal/synaptic atrophy, triggers hyperphosphorylation of Tau protein and cognitive deficits. However, the cause–effect relationship between these events remains to be established. To test the involvement of Tau in stress-induced impairments of cognition,we investigated the impact of stress on cognitive behavior, neuronal structure, and the synaptic proteome in the prefrontal cortex (PFC) of Tau knock-out (Tau-KO) and wild-type (WT) mice. Whereas exposure to chronic stress resulted in atrophy of apical dendrites and spine loss in PFC neurons as well as significant impairments in working memory in WT mice, such changes were absent in Tau-KO animals. Quantitative proteomic analysis of PFC synaptosomal fractions, combined with transmission electron microscopy analysis, suggested a prominent role for mitochondria in the regulation of the effects of stress. Specifically, chronically stressed animals exhibit Tau-dependent alterations in the levels of proteins involved in mitochondrial transport and oxidative phosphorylation aswell as in the synaptic localization of mitochondria in PFC. These findings provide evidence for a causal role of Tau in mediating stress-elicited neuronal atrophy and cognitive impairment and indicate that Tau may exert its effects through synaptic mitochondria.This work was funded by the Portuguese Foundation for Science & Technology (FCT, grant number NMC-113934 to I.S.), the EU Consortium Switchbox (grant number Health-FP7-2010-259772 to O.F.X.A. and N.S.), the Deutsche Forschungsgemeinschaft (grant number FI 1895/1-1 to M.D.F.) and the Max Planck Society (M.D.F., G.M., C.W.T., and O.F.X.A.). In addition, this workwas also co-financed by the Portuguese North Regional Operational Program (ON.2 – O Novo Norte) under the National Strategic Reference Framework (QREN), through the European Regional Development Fund (FEDER) (N.S.). S.L. and I.S. are holders of FCT Fellowships. J.V-S. is a recipient of a PhD fellowship (PD/ BD/105938/2014) of the University of Minho MD/PhD Program funded by FCT.info:eu-repo/semantics/publishedVersio

Ketamine's antidepressant effect is mediated by energy metabolism and antioxidant defense system.

Fewer than 50% of all patients with major depressive disorder (MDD) treated with currently available antidepressants (ADs) show full remission. Moreover, about one third of the patients suffering from MDD does not respond to conventional ADs and develop treatment-resistant depression (TRD). Ketamine, a non-competitive, voltage-dependent N-Methyl-D-aspartate receptor (NMDAR) antagonist, has been shown to have a rapid antidepressant effect, especially in patients suffering from TRD. Hippocampi of ketamine-treated mice were analysed by metabolome and proteome profiling to delineate ketamine treatment-affected molecular pathways and biosignatures. Our data implicate mitochondrial energy metabolism and the antioxidant defense system as downstream effectors of the ketamine response. Specifically, ketamine tended to downregulate the adenosine triphosphate (ATP)/adenosine diphosphate (ADP) metabolite ratio which strongly correlated with forced swim test (FST) floating time. Furthermore, we found increased levels of enzymes that are part of the 'oxidative phosphorylation' (OXPHOS) pathway. Our study also suggests that ketamine causes less protein damage by rapidly decreasing reactive oxygen species (ROS) production and lend further support to the hypothesis that mitochondria have a critical role for mediating antidepressant action including the rapid ketamine response

at the Ludwig-Maximilians-University Munich

Most of the commonly used antidepressants block monoamine reuptake transporters to enhance serotonergic or noradrenergic neurotransmission. Effects besides or downstream of increased monoaminergic neurotransmission are poorly understood and yet presumably important for the drugs ’ mode of action. In my PhD thesis I employed proteomics and metabolomics technologies combined with in silico analyses and identified cellular pathways affected by antidepressant drug treatment. DBA/2 mice were treated with paroxetine as a representative Selective Serotonin Reuptake Inhibitor (SSRI). Hippocampal protein levels were compared between chronic paroxetine- and vehicle-treated animals using in vivo 15 N metabolic labeling combined with mass spectrometry. I also studied chronic changes in the hippocampus using unbiased metabolite profiling and the time course of metabolic changes with the help of a targeted polar metabolomics profiling platform. I identified profound alterations related to hippocampa

Variability assessment of ¹⁵N metabolic labeling-based proteomics workflow in mouse plasma and brain

Repeatability of the 15N metabolic labeling workflow for quantitative proteomics in mouse plasma and brain specimens.</p

Leg Dominance Is a Risk Factor for Noncontact Anterior Cruciate Ligament Injuries in Female Recreational Skiers

Background: In recreational alpine skiing, the knee joint accounts for about one third of all injuries in male and female skiers. However, female recreational skiers have twice the knee injury incidence of male skiers, and the anterior cruciate ligament (ACL) injury risk is 3 times greater in female skiers. Purpose: To evaluate whether leg dominance is a risk factor for noncontact ACL injuries in female recreational skiers. Study Design: Cohort study; Level of evidence, 3. Methods: The relationships between leg dominance, side of knee injury, and gender were analyzed in 65 male and 128 female skiers suffering from a noncontact ACL rupture. Results: Anterior cruciate ligament ruptures of the left knee occurred more frequently in female than in male recreational skiers (68% vs 48%, P = .006). For both genders, in 90%, the right leg was the preferred kicking leg. With regard to leg dominance, female skiers suffered more often from ACL ruptures of their nondominant leg than male skiers (63% vs 45%, P = .020). An adjusted odds ratio of 2.0 (95% confidence interval, 1.0-3.8) was calculated. Conclusion: Female skiers showed a 2-fold higher risk of suffering from an ACL rupture on their nondominant leg. Therefore, leg dominance seems to be a risk factor for noncontact ACL injuries in female recreational skiers. </jats:p

Proteome Scale Turnover Analysis in Live Animals Using Stable Isotope Metabolic Labeling

At present most quantitative proteomics investigations are focused on the analysis of protein expression differences between two or more sample specimens. With each analysis a static snapshot of a cellular state is captured with regard to protein expression. However, any information on protein turnover cannot be obtained using classic methodologies. Protein turnover, the result of protein synthesis and degradation, represents a dynamic process, which is of equal importance to understanding physiological processes. Methods employing isotopic tracers have been developed to measure protein turnover. However, applying these methods to live animals is often complicated by the fact that an assessment of precursor pool relative isotope abundance is required. Also, data analysis becomes difficult in case of low label incorporation, which results in a complex convolution of labeled and unlabeled peptide mass spectrometry signals. Here we present a protein turnover analysis method that circumvents this problem using a 15N-labeled diet as an isotopic tracer. Mice were fed with the labeled diet for limited time periods and the resulting partially labeled proteins digested and subjected to tandem mass spectrometry. For the interpretation of the mass spectrometry data, we have developed the ProTurnyzer software that allows the determination of protein fractional synthesis rates without the need of precursor relative isotope abundance information. We present results validating ProTurnyzer with Escherichia coli protein data and apply the method to mouse brain and plasma proteomes for automated turnover studies