Holger Jahn

Disruption of ClC-3, a Chloride Channel Expressed on Synaptic Vesicles, Leads to a Loss of the Hippocampus

Several plasma membrane chloride channels are well characterized, but much less is known about the molecular identity and function of intracellular Cl- channels. ClC-3 is thought to mediate swelling-activated plasma membrane currents, but we now show that this broadly expressed chloride channel is present in endosomal compartments and synaptic vesicles of neurons. While swelling-activated currents are unchanged in mice with disrupted ClC-3, acidification of synaptic vesicles is impaired and there is severe postnatal degeneration of the retina and the hippocampus. Electrophysiological analysis of juvenile hippocampal slices revealed no major functional abnormalities despite slightly increased amplitudes of miniature excitatory postsynaptic currents. Mice almost lacking the hippocampus survive and show several behavioral abnormalities but are still able to acquire motor skills.

Naturally occurring human urinary peptides for use in diagnosis of chronic kidney disease

Because of its availability, ease of collection, and correlation with physiology and pathology, urine is an attractive source for clinical proteomics/peptidomics. However, the lack of comparable data sets from large cohorts has greatly hindered the development of clinical proteomics. Here, we report the establishment of a reproducible, high resolution method for peptidome analysis of naturally occurring human urinary peptides and proteins, ranging from 800 to 17,000 Da, using samples from 3,600 individuals analyzed by capillary electrophoresis coupled to MS. All processed data were deposited in an Structured Query Language (SQL) database. This database currently contains 5,010 relevant unique urinary peptides that serve as a pool of potential classifiers for diagnosis and monitoring of various diseases. As an example, by using this source of information, we were able to define urinary peptide biomarkers for chronic kidney diseases, allowing diagnosis of these diseases with high accuracy. Application of the chronic kidney disease-specific biomarker set to an independent test cohort in the subsequent replication phase resulted in 85.5% sensitivity and 100% specificity. These results indicate the potential usefulness of capillary electrophoresis coupled to MS for clinical applications in the analysis of naturally occurring urinary peptides.

Executive functioning in obsessive–compulsive disorder, unipolar depression, and schizophrenia

The present study investigated whether schizophrenic, unipolar depressive, and obsessive-compulsive psychiatric patients show a distinguishable profile in tasks considered sensitive to frontal lobe functioning. Three psychiatric samples, each comprising 25 patients with little symptomatic overlap, were compared to 70 healthy controls. Participants completed several executive tasks (Wisconsin Card Sorting Test (WCST), verbal fluency, digit span, Stroop, and Trail-Making). Except for age, which was entered as a covariate, subjects did not differ in any sociodemographic background variable. Healthy controls showed superior performance relative to depressive and schizophrenic patients who exhibited comparable deficits in all tasks. Obsessive-compulsive disorder (OCD) patients revealed dysfunctions in the Trail-Making Tests A and B and in the fluency task. Dysfunctions in the domains of working memory, verbal fluency, distractibility, and concept formation were not confined to a specific psychiatric population.

Amyloid β peptide ratio 42/40 but not Aβ42 correlates with phospho-Tau in patients with low- and high-CSF Aβ40 load

Neurochemical dementia diagnostics (NDD) can significantly improve the clinically based categorization of patients with early dementia disorders, and the cerebrospinal fluid (CSF) concentrations of amyloid β peptides ending at the amino acid position of 42 (Aβx‐42 and Aβ1‐42) are widely accepted biomarkers of Alzheimer’s disease (AD). However, in subjects with constitutively high‐ or low‐CSF concentrations of total Aβ peptides (tAβ), the NDD interpretation might lead to erroneous conclusions as these biomarkers seem to correlate better with the total Aβ load than with the pathological status of a given patient in such cases. In this multicenter study, we found significantly increased CSF concentrations of phosphorylated Tau (pTau181) and total Tau in the group of subjects with high CSF Aβx‐40 concentrations and decreased Aβx‐42/x‐40 concentration ratio compared with the group of subjects with low CSF Aβx‐40 and normal Aβ ratio (p < 0.001 in both cases). Furthermore, we observed significantly decreased Aβ ratio (p < 0.01) in the group of subjects with APOE ε4 allele compared with the group of subjects without this allele. Surprisingly, patients with low‐Aβx‐40 and the decreased Aβ ratio characterized with decreased pTau181 (p < 0.05), and unaltered total Tau compared with the subjects with high Aβx‐40 and the Aβ ratio in the normal range. We conclude that the amyloid β concentration ratio should replace the ‘raw’ concentrations of corresponding Aβ peptides to improve reliability of the neurochemical dementia diagnosis.

Soluble amyloid precursor proteins in the cerebrospinal fluid as novel potential biomarkers of Alzheimer's disease: a multicenter study

In this report, we present the results of a multicenter study to test analytic and diagnostic performance of soluble forms of amyloid precursor proteins α and β (sAPPα and sAPPβ) in the cerebrospinal fluid (CSF) of patients with different forms of dementing conditions. CSF samples were collected from 188 patients with early dementia (mini-mental state examination⩾20 in majority of cases) and mild cognitive impairment (MCI) in 12 gerontopsychiatric centers, and the clinical diagnoses were supported by neurochemical dementia diagnostic (NDD) tools: CSF amyloidβ peptides, Tau and phospho-Tau. sAPPα and sAPPβ were measured with multiplexing method based on electrochemiluminescence. sAPPα and sAPPβ CSF concentrations correlated with each other with very high correlation ratio (R=0.96, P<0.001). We observed highly significantly increased sAPPα and sAPPβ CSF concentrations in patients with NDD characteristic for Alzheimers disease (AD) compared to those with NDD negative results. sAPPα and sAPPβ highly significantly separated patients with AD, whose diagnosis was supported by NDD findings (sAPPα: cutoff, 117.4 ng ml−1, sensitivity, 68%, specificity, 85%, P<0.001; sAPPβ: cutoff, 181.8 ng ml−1, sensitivity, 75%, specificity, 85%, P<0.001), from the patients clinically assessed as having other dementias and supported by NDD untypical for AD. We conclude sAPPα and sAPPβ might be regarded as novel promising biomarkers supporting the clinical diagnosis of AD.

Elevation of beta-amyloid peptide 2-42 in sporadic and familial Alzheimer's disease and its generation in PS1 knockout cells.

Urea-based β-amyloid (Aβ) SDS-polyacrylamide gel electrophoresis and immunoblots were used to analyze the generation of Aβ peptides in conditioned medium from primary mouse neurons and a neuroglioma cell line, as well as in human cerebrospinal fluid. A comparable and highly conserved pattern of Aβ peptides, namely, 1–40/42 and carboxyl-terminal-truncated 1–37, 1–38, and 1–39, was found. Besides Aβ1–42, we also observed a consistent elevation of amino-terminal-truncated Aβ2–42 in a detergent-soluble pool in brains of subjects with Alzheimers disease. Aβ2–42 was also specifically elevated in cerebrospinal fluid samples of Alzheimers disease patients. To decipher the contribution of potential different γ-secretases (presenilins (PSs)) in generating the amino-terminal- and carboxyl-terminal-truncated Aβ peptides, we overexpressed β-amyloid precursor protein (APP)-trafficking mutants in PS1+/+ and PS1−/− neurons. As compared with APP-WT (primary neurons from control or PS1-deficient mice infected with Semliki Forest virus), PS1−/− neurons and PS1+/+ neurons overexpressing APP-Δct (a slow-internalizing mutant) show a decrease of all secreted Aβ peptide species, as expected, because this mutant is processed mainly by α-secretase. This drop is even more pronounced for the APP-KK construct (APP mutant carrying an endoplasmic reticulum retention motif). Surprisingly, Aβ2–42 is significantly less affected in PS1−/− neurons and in neurons transfected with the endocytosis-deficient APP-Δct construct. Our data confirm that PS1 is closely involved in the production of Aβ1–40/42 and the carboxyl-terminal-truncated Aβ1–37, Aβ1–38, and Aβ1–39, but the amino-terminal-truncated and carboxyl-terminal-elongated Aβ2–42 seems to be less affected by PS1 deficiency. Moreover, our results indicate that the latter Aβ peptide species could be generated by a βAsp/Ala-secretase activity.

Biomarker validation of a cued recall memory deficit in prodromal Alzheimer disease

Objective: To compare cued recall measures with other memory and nonmemory tests regarding their association with a biomarker profile indicative of Alzheimer disease (AD) in CSF among patients with mild cognitive impairment (MCI). Methods: Data were obtained by the German Dementia Competence Network. A total of 185 memory clinic patients fulfilling broad criteria for MCI (1 SD deficit in memory tests or in nonmemory tests) were assessed with an extended neuropsychological battery, which included the Free and Cued Selective Reminding Test (FCSRT), the word list learning task from the Consortium to Establish a Registry for Alzheimers Disease neuropsychological battery (CERAD-NP), and the Logical Memory (LM) paragraph recall test from the Wechsler Memory Scale–Revised. CSF was obtained from all patients. Results: A total of 74 out of 185 subjects with MCI (40%) had a CSF profile consistent with AD (Aβ1-42/tau ratio; CSF AD+ group). FCSRT measures reflecting both free and cued recall discriminated best between CSF AD+ and CSF AD− patients, and significantly improved CSF AD classification accuracy, as compared with CERAD delayed recall and LM delayed recall. Conclusions: Cued recall deficits are most closely associated with CSF biomarkers indicative of AD in subjects with MCI. This novel finding complements results from prospective clinical studies and provides further empirical support for cued recall as a specific indicator of prodromal AD, in line with recently proposed research criteria.

Pharmacological Relapse Prevention of Alcoholism: Clinical Predictors of Outcome

Objective: The efficacy of pharmacological relapse prevention in alcoholism with acamprosate and naltrexone has been supported by several controlled trials. It remains uncertain whether any differential indication for treatment exists. Methods: We evaluated outcome data of a controlled trial on acamprosate and naltrexone in patients with low vs. high baseline somatic distress, depression and anxiety (Symptom Checklist-90, SCL-90), low vs. high baseline craving, and according to typological differentiation as proposed by Cloninger and Lesch. These variables have previously been suggested to be predictors of outcome. Results: Comparing the course of abstinence rates, acamprosate was mainly efficacious in patients with low baseline somatic distress, whereas naltrexone was effective especially in patients with high baseline depression. Baseline craving showed no predictive value. Pharmacological treatment was efficacious in type II alcoholics according to Cloninger. Applying Lesch’s typological differentiation, acamprosate was shown to be mainly effective in type I, whereas naltrexone revealed best treatment effects in type III and IV. Conclusion: The study supports the hypothesis that different subgroups of alcohol dependent subjects might benefit from a differential treatment with either naltrexone or acamprosate. Baseline psychopathology and especially typological differentiation might be useful in matching patients to distinct pharmacotherapeutic interventions.

Leptin: a modulator of alcohol craving?

BACKGROUND Leptin has been shown to regulate food intake and energy expenditure. Because leptin acts via regulation of appetite, we studied the hypothesis that suggests leptin modulates craving for alcohol as well. METHODS We studied leptin plasma concentrations (RIA) both in alcoholic subjects during inpatient detoxification (day 1: n = 78, day 14: n = 60) and in healthy control subjects (n = 30). To rule out interference with the activation of the HPA axis during alcohol withdrawal, we also evaluated cortisol plasma levels (RIA). RESULTS We found plasma leptin and cortisol elevated at onset of withdrawal, decreasing significantly up to day 14. Leptin (and the body-mass corrected ratio leptin/BMI) was highly correlated with self-rated craving. No correlations of craving with cortisol and BMI were observed. CONCLUSIONS We suggest that leptin may modulate withdrawal-induced craving in alcoholic subjects.

Modulation of the mineralocorticoid receptor as add-on treatment in depression: A randomized, double-blind, placebo-controlled proof-of-concept study

Preclinical and clinical studies have suggested a role of the mineralocorticoid receptor (MR) in the response to antidepressants. We tested in a proof-of-concept study whether adding fludrocortisone (an MR agonist) or spironolactone (an MR antagonist) accelerates onset of action and improves efficacy of escitalopram in patients with major depression. We included 64 in- and outpatients with major depression (Hamilton Depression Scale-17 score>18) in a double-blind, randomized, placebo-controlled trial. Patients were randomized in a 2:2:1 fashion to fludrocortisone (0.2 mg/d, n=24) or spironolactone (100 mg/d, n=27) or placebo (n=13) for the first 3 weeks during a 5-week treatment with escitalopram. No differences in mean HAMD change scores and in time to response emerged between treatments. However, among the responders, patients treated with fludrocortisone responded faster (Breslow test, p=0.05). The mean number of days to response was 16.0+/-2.6 days vs. placebo 22.2+/-2.0 vs. spironolactone 22.6+/-2.3 (F=3.78, p=0.03). In the whole group, plasma cortisol increased during spironolactone and decreased during fludrocortisone treatment (F=2.4, p=0.04). In patients treated with fludrocortisone, non-responders had elevated cortisol values compared to responders throughout the study period (F=5.1, p=0.04). Stimulation of MR with fludrocortisone as adjunct to escitalopram accelerated the response in the group of responders while no effect emerged in the sample as a whole. A larger randomized controlled trial is warranted.