Marcus C. Rosenhagen

Polymorphisms in the Drug Transporter Gene ABCB1 Predict Antidepressant Treatment Response in Depression

The clinical efficacy of a systemically administered drug acting on the central nervous system depends on its ability to pass the blood-brain barrier, which is regulated by transporter molecules such as ABCB1 (MDR1). Here we report that polymorphisms in the ABCB1 gene predict the response to antidepressant treatment in those depressed patients receiving drugs that have been identified as substrates of ABCB1 using abcb1ab double-knockout mice. Our results indicate that the combined consideration of both the medications capacity to act as an ABCB1-transporter substrate and the patients ABCB1 genotype are strong predictors for achieving a remission. This finding can be viewed as a further step into personalized antidepressant treatment.

Essential role of the unusual DNA-binding motif of BAG-1 for inhibition of the glucocorticoid receptor.

The co-chaperone BAG-1 is involved in the regulation of steroid hormone receptors, including the glucocorticoid receptor (GR). More recently, BAG-1 was found in the nucleus where it decreases GR transactivation. Moreover, nonspecific DNA binding of BAG-1 has been reported. We discovered that of the N-terminal part of BAG-1M, the first 8 amino acids are sufficient for DNA binding, containing a stretch of three lysines and a stretch of three arginines. Changing the spacing between these stretches had no effect on DNA binding. Surprisingly, this small, nonsequence-specific DNA binding domain was nonetheless necessary for the inhibitory function of BAG-1 for GR-dependent transcription, whereas the following serine- and threonine-rich E2 X 4 repeat domain was not. Mutational analysis of these two domains revealed that only mutants retaining DNA binding capability were able to down-regulate GR-mediated transactivation. Intriguingly, lack of DNA binding could not be functionally rescued by BAG-1M harboring a point mutation abolishing interaction with hsp70. Thus, DNA binding and hsp70 interaction are required in cis. We propose that the nonsequence-specific DNA-binding protein BAG-1 acts at specific chromosomal loci by interacting with other proteins.

Off-line memory consolidation impairments in multiple sclerosis patients receiving high-dose corticosteroid treatment mirror consolidation impairments in depression

BACKGROUND Sleep supports the consolidation of procedural memory, however patients with major depression show impaired motor memory performance after a night of sleep. It was hypothesized that this impairment is related to hypothalamic-pituitary-adrenal (HPA) axis dysfunction. We tested if high-dose administration of corticosteroids impairs off-line motor memory consolidation in patients with multiple sclerosis (MS). METHODS Nine patients with MS receiving high-dose corticosteroid therapy (methylprednisolone) and nine MS patients receiving alternative therapy (mitoxantrone) were assessed using a sequential finger tapping task before and after a night with polysomnography. In addition, nine patients with major depression (MD) receiving antidepressants and nine healthy controls were assessed. RESULTS Although the four groups did not differ in practice-dependent learning, healthy subjects and MS patients receiving mitoxantrone showed markedly overnight-improvements in tapping performance of 17% and 24% while MS patients receiving high-dose corticosteroid therapy and depressed patients showed -9% and -10% overnight decrease. MS patients with and without corticosteroid therapy did not differ in their amount of REM sleep, nor did MD patients and healthy controls. In addition, we did not find any correlation between REM sleep and memory consolidation. CONCLUSION Our results show that a strong intervention into the HPA system like in MS high-dose corticosteroid therapy impairs off-line motor memory consolidation comparable to the impairments seen in depressed patients. We propose therefore that depression-related changes in plasma corticosteroid levels rather than in sleep per se underlie off-line memory consolidation impairments in MD.

The anti-Parkinson drug budipine is exported actively out of the brain by P-glycoprotein in mice

P-glycoprotein, a product of the ABCB1 gene, is a plasma membrane transporter that exports certain drugs as well as endogenous substances against a concentration gradient in the intestines, kidney and testes. It also constitutes an important part of the blood-brain barrier, where it exports its substrates out of the brain back into the circulation. To investigate whether the uptake of the anti-Parkinson drug budipine into the brain is mediated by P-glycoprotein, abcb1ab(-/-) double knock-out mice and wild-type control mice received budipine continuously over 11 days via implanted osmotic infusion pumps at the rate of 30ug over 24h. Concentrations of the drug in plasma, brain, and organs were measured with HPLC. Budipine concentrations in the abcb1ab knock-out animals were 3.1 times higher than in control mice. This study confirms the important role P-gp plays at the blood-brain barrier and shows that budipine is a substrate of P-gp.

Synergistic inhibition of the glucocorticoid receptor by radicicol and benzoquinone ansamycins.

Abstract Radicicol (RAD) and the benzoquinone ansamycin geldanamycin (GA) are potential anticancer drugs known to inhibit heat shock protein 90 (hsp90) and, therefore, the activation of proteins dependent on its function such as protooncogenic kinases and nuclear receptors. Using the glucocorticoid receptor (GR) as a model system we analysed the effects of RAD and various benzoquinone ansamycins. All compounds efficiently abolished GRdependent transactivation. Surprisingly, whenever one of the ansamycins was applied in combination with RAD, synergistic inhibition of GRdependent transcription and of hormone binding of GR was observed. In contrast, combination of two ansamycins showed no synergy. These findings suggest synergism within the hsp90 dimer and may open new ways to explore hsp90 as therapeutic target.

The clinical impact of ABCB1 polymorphisms on the treatment of psychiatric diseases.

Polymorphisms in the drug transporter gene ABCB1 account for differences in the clinically efficacy of the most drugs, most likely by influencing their access to the brain. The majority proportion of depressed patients, given a regular dose, do not respond properly or experience severe side effects. One explanation may be the polymorphisms in the drug transporter gene ABCB1, which account for differences in the clinical efficacy of antidepressants, neuroleptics or mood stabilizers most likely by influencing their access to the brain. If patients are treated with a substrate of P-gp, functionally relevant genetic variants in the ABCB1 transporter could influence intracerebral drug concentrations and, thereby, clinical response. The review shows recently investigated clinical impact of ABCB1 variants including the three most important SNPs rs1045642, rs2032582, and rs2032583. In the paper, with respect not to go beyond the scope of this review, we will focus on these three SNPs. The final goal of pharmacogenetics is to help clinicians to choose the best treatment for each individual patient. >From the evidence reviewed in this publication, it is likely that combination of metabolizing and drug target polymorphisms will produce the best prediction for the selection of the optimal dose and optimal drug as a function of the individual` s genetic profile.

In-depth analysis of the human CSF proteome using protein prefractionation

The identification of disease markers in human body fluids requires an extensive and thorough analysis of its protein constituents. In the present study, we have extended our analysis of the human cerebrospinal fluid (CSF) proteome using protein prefractional followed by shotgun mass spectrometry. After the removal of abundant protein components from the mixture with the help of immunodepletion affinity chromatography, we used either anion exchange chromatography or sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) to further subfractionate the proteins present in CSFs. Each protein subfraction was enzyme digested and analyzed by tandem mass spectrometry and the resulting data evaluated using the Spectrum Mill software. Different subfractionation methods resulted in the identification of a grant total of 259 proteins in CSF from a patient with normal pressure hydrocephalus. The greatest number of protein, 240 in total, were identified after prefractionating the CSF proteins by immunodepletion and SDS-PAGE. Immuno-depletion combined with anion exchange fractionation resulted in 112 proteins and 74 proteins were found when only immunodepletion of the CSF samples was carried out. All methods used showed a significant increase in the number of identified proteins as compared with nondepleted and unfractionated CSF sample analysis, which yielded only 38 protein identifications. The present work establishes a platform for future studies aimed at a detailed comparative proteome analysis of CSFs from different groups of patients suffering from various psychiatric and neurological disorders.

P-glycoprotein has negligible effects on estradiol and testosterone in mice.

P-glycoprotein (P-gp) is an important factor at the blood-brain barrier preventing passage of a wide variety of substances into the brain. Several studies have provided evidence that some drugs and certain steroid hormones are substrates or inhibitors of P-gp. However, the situation is unclear with regard to gonadal steroids, which have considerable central nervous effects. In vitro, experiments on the relationship between estradiol and P-gp are equivocal. We used abcb1ab knock-out mice and wild-type mice to determine the uptake of [3H]-17-beta-estradiol and [3H]-testosterone into the cerebrum and other organs after subcutaneous administration. The organ/plasma quotients showed no significant group effects. We concluded that P-gp does not influence the penetration of testosterone and estradiol to a biologically significant extent.

P01-03 - Biomarkers for changes in self-regulation through cognitive behavioral therapy for depression

Depressed patients show a disturbed hypothalamic-pituitary-adrenal (HPA) axis regulation, resulting in increased cortisol levels, inadequate cortisol suppression following a low dose of dexamethasone, increased concentrations of corticotropin releasing hormone (CRH) in the cerebrospinal fluid, and a blunted adrenocorticotropic hormone (ACTH) response following CRH administration. Treatment with antidepressants, but seemingly also cognitive behavioral therapy (CBT), is associated with an improvement of a disturbed HPA-axis regulation, which can be most sensitively evaluated with the combined dexamethasone (dex)/CRH test. Favorable response to antidepressant treatment can be predicted at an early stage by determining the degree of normalization of HPA-axis function under treatment in a second dex/CRH test. We report about the predictive validity of HPA-axis normalization on the favorable response of CBT in medicated depressed patients. Medicated depressed patients receiving CBT at the Max-Planck-Institute of Psychiatry in Munich are studied using the State-Trait-Angstinventar (STAI), Beck Depression Inventory (BDI), Volitional-Components-Questionnaire (VCQ-3), Emotion-Regulation Questionnaire (EPQ) and the Self-Control and Self-Management Scale (SCMS). Neuroendocrine parameters including measures of HPA-axis regulation are measured before and after therapy via dex/CRH test. Up to the present moment data for N=38 depressed patients have been collected (N=21 male, 25-78 years; N=17 female, 21-80 years). The mean level of depression and anxiety showed a significant decrease between pre- and post-treatment measurement. Measures of perceived self-regulation and self-estimation increased and measures of perceived self-inhibition and inhibition of will decreased. The expected changes in depression, anxiety and self-regulation after treatment with antidepressants and CBT were observed. Endocrine data are currently under analysis.