Importin α7 Is Essential for Zygotic Genome Activation and Early Mouse Development

Importin α is involved in the nuclear import of proteins. It also contributes to spindle assembly and nuclear membrane formation, however, the underlying mechanisms are poorly understood. Here, we studied the function of importin α7 by gene targeting in mice and show that it is essential for early embryonic development. Embryos lacking importin α7 display a reduced ability for the first cleavage and arrest completely at the two-cell stage. We show that the zygotic genome activation is severely disturbed in these embryos. Our findings indicate that importin α7 is a new member of the small group of maternal effect genes

Ein genetisches System zur Untersuchung der Permeabilitätsbarriere des Kernporenkomplexes der Hefe Saccharomyces cerevisiae

Kernporenkomplexe (NPCs) verbinden das Zytoplasma mit dem Nukleoplasma. Ein unkontrollierter Austausch von Molekülen zwischen diesen Kompartimenten wird durch die Permeabilitätsbarriere der Kernporenkomplexe verhindert. Diese supprimiert einerseits die Passage von inerten Makromoleküle, andererseits aber fördert sie den Transport von Molekülen soweit diese im Komplex mit Kern-Transport-Rezeptoren (NTRs) vorliegen. Ungefähr ein Drittel der Proteine, die den NPC bilden, enthalten so genannte FG Domänen. Diese FG Domänen bilden die Permeabilitätsbarriere. NTRs binden an einzelne FG Motive dieser Domänen und diese Interaktion ist essentiell für die Passage von NTR-Molekül-Komplexen durch den NPC. Auf welche Art und Weise diese Interaktion den beschleunigten Transport von NTR-Molekül-Komplexen durch den NPC ermöglicht, ist jedoch rätselhaft. FG Domänen sind sehr verschiedenartig. Sie unterscheiden sich in ihrer Kohäsionskraft, in ihren FG Motiven, ihrer Länge, der Ladungsverteilung sowie der Sequenz zwischen einzelnen FG Motiven. Die biophysikalischen und biochemischen Eigenschaften einzelner FG Domänen wurden gut in vitro analysiert. Dennoch ist die in vivo Bedeutung der Eigenschaften einzelner FG Domänen für die Funktionalität der Permeabilitätsbarriere nach wie vor ungeklärt. Bisher wurde versucht Fragen nach der in vivo Bedeutung einzelner FG Domänen zu beantworten, indem mehrere FG Domänen in verschiedenen Kombinationen gleichzeitig in S. cerevisiae deletiert und daraus resultierende Phänotypen analysiert wurden. Wir konnten zeigen, dass bisher berichtete letale Phänotypen in mehrfach FG deletierten Stämmen nicht ausschließlich durch den Mangel an FG Domänen verursacht werden, sondern sich vor allem aufgrund der angewandten Deletionsstrategie ausprägen. Mit einer alternativen Deletionsstrategie können wir nun vielmehr zeigen, dass S. cerevisiae mehr Deletionen von FG Domänen toleriert als vormals angenommen. Der Schwerpunkt dieser Arbeit lag darin zu eruieren welche Eigenschaften von FG Domänen für die in vivo Funktionalität der Permeabilitätsbarriere essentiell sind. Dafür haben wir ein in vivo System etabliert, dass es uns erlaubt die Funktionalität einzelner FG Domänen zu untersuchen, in dem wir die Auswirkungen von Mutationen, Deletionen oder eines Domänenaustausches auf die Lebensfähigkeit von S. cerevisiae analysieren. Mit diesem System können wir zeigen, dass die besonders kohäsiven FG Domänen von Nup100p und Nup116p eine besondere Rolle im Erhalt der Permeabilitätsbarriere spielen und dass sie funktionell nicht durch beliebige FG Domänen ersetzt werden können. Diese Tatsache deutet darauf hin, dass die Fähigkeit zur Bindung von NTRs alleine nicht ausreichend ist um die Funktionsweise der Permeabilitätsbarriere zu erklären. Darüber hinaus legen wir dar, dass die einzelnen Ankerpunkte der FG Domänen in der Kernpore nicht gleichwertig sind. Unsere Ergebnisse stützen jene Modelle, die zur Erklärung der Funktionalität der Permeabilitätsbarriere die kohäsiven Eigenschaften von FG Domänen heranziehen. Allerdings nehmen wir auf Grund unserer Ergebnisse an, dass sowohl eine exzessive Präsenz von kohäsiver FG Masse als auch deren Abwesenheit zum Zelltod führt

Pharmacokinetic interactions between clozapine and sertraline in smokers and non‐smokers

Clozapine is an effective antipsychotic drug for treatment-resistant schizophrenia. Sertraline is a widely prescribed antidepressant and often concomitantly applied to address negative symptoms or depression. However, data on interactions between clozapine and sertraline are inconsistent. The aim of our study was to evaluate pharmacokinetic interactions between clozapine and sertraline analysing a therapeutic drug monitoring database of 1644 clozapine-medicated patients. We compared four groups: non-smokers (n = 250) and smokers (n = 326) with co-medication without known effects on cytochrome P450 and without sertraline, and non-smokers (n = 18) and smokers (n = 17) with sertraline co-medication. Measured and dose-corrected concentrations (C/D) of clozapine were compared between the groups using non-parametrical tests with a significance level of 0.05. Post hoc analyses included pairwise comparisons to account for smoking status. Although we detected significant differences for clozapine levels and C/D values between study groups (P .05 for Mann-Whitney U test in both cases). A negative correlation between the sertraline dose and the clozapine concentration was found in non-smokers (Spearman's rank correlation, rs = -0.535, P = .048). A potential pharmacokinetic interaction between clozapine and a standard therapeutic sertraline dose seems to be of minor clinical importance

Cytochrome P450-mediated inhibition of venlafaxine metabolism by trimipramine

Objective The aim of this study was to ensure patients' safety and to enhance treatment efficacy, knowledge about pharmacokinetic interactions even in complex clinical situations of polypharmacy is invaluable. This study is to uncover the potential of pharmacokinetic interactions between venlafaxine and trimipramine in a naturalistic sample. Methods Out of a therapeutic drug monitoring database with plasma concentrations of venlafaxine (VEN) and O-desmethylvenlafaxine (ODV), we considered two groups of patients receiving venlafaxine without known cytochrome P450 confounding medications, taking solely venlafaxine: V-0 (n = 905), and a group of patients co-medicated with trimipramine, V-TRIM (n = 33). For VEN, ODV and active moiety (sum of VEN + ODV) plasma concentrations and dose-adjusted concentrations as well as ODV/VEN ratios were compared between groups using the Mann-Whitney U test with a significance level of 0.05. Results Patients co-medicated with trimipramine had higher plasma concentrations of VEN (183.0 vs. 72.0, +154%, P = 0.002) and AM (324.0 vs. 267.5, +21%, P = 0.005) and higher dose adjusted plasma concentrations than patients in the control group (P = 0.001 and P = 0.003). No differences were found for ODV and C/D ODV (P < 0.05 for both comparisons). The metabolite to parent ratio, ODV/VEN, was significantly lower in the V-TRIM group (1.15 vs. 2.37, P = 0.012). Conclusion Findings suggest inhibitory effects of trimipramine on venlafaxine pharmacokinetics most likely via an inhibition of CYP 2D6 or by saturated enzyme capacity. The lack of in vitro data hampers the understanding of the exact mechanisms. Clinicians should be aware of drug-drug interactions when combining these agents. Therapeutic drug monitoring helps to ensure treatment efficacy and patients' safety

Pharmacokinetic correlates of venlafaxine: associated adverse reactions

To address the potential correlation between plasma concentrations of venlafaxine (VEN), its active metabolite O-desmethylvenlafaxine (ODVEN) and the active moiety, AM, (ODVEN + VEN) and adverse drug reactions (ADR) in a large naturalistic sample of in- and outpatients. We compared plasma concentrations of VEN, ODVEN and AM and dose-adjusted (C/D) levels as well the ODVEN/VEN ratios between patients complaining ADRs, following the Udvalg for Kliniske Undersogelser side effect rating scales (UKU) (n = 114) and patients without ADRs (control group, n = 688) out of a naturalistic database. We also investigated potential pharmacokinetic correlates of the four UKU categories by comparing patients complaining ADRs with those who did not. Based on previous literature we applied different ODVEN/VEN ratio values as cut-offs to split our sample into two groups at a time and compare frequencies of ADRs between the groups. No differences for demographic and pharmacokinetic variables including plasma and C/D concentrations as well as ODVEN/VEN ratios were observed between study groups. Neither the comparisons between females and males nor between elderly and non-elderly patients revealed significant differences (p > 0.05 in all cases). No differences were also reported exploring the patients complaining ADRs from the 4 UKU categories separately. After applying various ODVEN/VEN cut-offs, groups did not display differences in frequencies of ADRs (p > 0.05 in all cases). Our findings do not demonstrate a direct link between venlafaxine metabolism measures and ADRs. Therefore, additional dimensions are needed to be considered in future trials aiming to disentangle the involved aspects of ADRs in patients receiving venlafaxine

Lack of Smoking Effects on Pharmacokinetics of Oral Paliperidone-analysis of a Naturalistic Therapeutic Drug Monitoring Sample

Introduction Major smoking effects have been reported for a series of psychotropic agents, mainly including substrates of CYP450 1A2, although smoking may also affect alternative metabolic pathways. To our knowledge, smoking effects on paliperidone pharmacokinetics have not been assessed yet. Methods We compared plasma concentrations of paliperidone as well as dose-corrected-plasma concentrations (C/D) from a naturalistic database between smokers and nonsmokers using nonparametrical tests, such as the Mann-Whitney U-test (MWU). Additionally, we compared light and heavy smokers with nonsmokers separately. Results Comparing 55 smokers with 37 nonsmokers treated with oral paliperidone, no differences in the percentage of females, age, body weight, body mass index, and daily paliperidone dose were reported (p=0.709 for chi (2) , p=0.26, p=0.38, p=0.67, and p=0.8 for MWU). No differences were detected in plasma concentrations or C/D values (p=0.50 and p=0.96 for MWU). Likewise, differences in daily dose, plasma concentrations, or C/D values were not significant between light smokers (n=17) and nonsmokers (p=0.61, p=0.81, and p=0.33 for MWU) or heavy smokers (n=22) and nonsmokers (p=0.874, p=0.38, and p=0.59; MWU in all cases). Discussion Paliperidone is not affected by smoking, and paliperidone dose-adjustments in smokers may not be necessary. This may be seen as an essential difference to risperidone, whose cytochrome-mediated metabolism might be affected by smoking

Pharmacokinetics of venlafaxine in treatment responders and non-responders: a retrospective analysis of a large naturalistic database

PurposeTo assess in a large naturalistic sample, whether clinical response to a treatment with venlafaxine is associated with different patterns of plasma concentrations of active moiety, AM (sum of venlafaxine (VEN) and its active metabolite O-desmethylvenlafaxine (ODVEN)).MethodsApplying a regression model, plasma concentrations and plasma concentrations corrected-by-dosage (C/D) for AM were included as independent variable with Clinical Global Impressions-Improvement (CGI-I) scale ratings as dependent variable. Moreover, AM, VEN, and ODVEN were compared between treatment responders and non-responders, defining response as much or very much improved on the CGI-I scale based on the non-parametric Mann-Whitney U (M-W-U) test with a significance level of 0.05.ResultsNo correlations were found between AM and C/D AM plasma concentrations and CGI-I ratings (regression coefficient 0.0, CI 0.000, 0.001, p=0.492 for AM and 0.047, CI -0.065, 0.159, p=0.408 for C/D AM). Venlafaxine daily dosage did not differ between responders and non-responders (217.776.9 vs. 222.0 +/- 72.7mg/day, p=0.45 for M-W-U). Responders displayed lower ODVEN (p=0.033) and AM (p=0.031) plasma concentrations than non-responders (p=0.033 and 0.031, respectively for M-W-U). No other differences were detected. Using a cut-off level of 400ng/mL for AM concentrations, a higher percentage of responders was reported in the group of patients with AM400ng/mL (8%) (p=0.038).Conclusions Higher ODVEN and AM concentrations in non-responders than in responders indicate that treatment escalation above upper thresholds of therapeutic reference ranges of venlafaxine is not promising. Hence, the therapeutic reference range for venlafaxine can help in improving outcomes in a measurement-based care model that takes advantage of therapeutic drug monitoring