Interaction of the hydrogen sulfide system with the oxytocin system in the injured mouse heart

Both the hydrogen sulfide/cystathionine-γ-lyase (H2S/CSE) and oxytocin/oxytocin receptor (OT/OTR) systems have been reported to be cardioprotective. H2S can stimulate OT release, thereby affecting blood volume and pressure regulation. Systemic hyper-inflammation after blunt chest trauma is enhanced in cigarette smoke (CS)-exposed CSE−/− mice compared to wildtype (WT). CS increases myometrial OTR expression, but to this point, no data are available on the effects CS exposure on the cardiac OT/OTR system. Since a contusion of the thorax (Txt) can cause myocardial injury, the aim of this post hoc study was to investigate the effects of CSE−/− and exogenous administration of GYY4137 (a slow release H2S releasing compound) on OTR expression in the heart, after acute on chronic disease, of CS exposed mice undergoing Txt.Methods: This study is a post hoc analysis of material obtained in wild type (WT) homozygous CSE−/− mice after 2-3 weeks of CS exposure and subsequent anesthesia, blast wave-induced TxT, and surgical instrumentation for mechanical ventilation (MV) and hemodynamic monitoring. CSE−/− animals received a 50 μg/g GYY4137-bolus after TxT. After 4h of MV, animals were exsanguinated and organs were harvested. The heart was cut transversally, formalin-fixed, and paraffin- embedded. Immunohistochemistry for OTR, arginine-vasopressin-receptor (AVPR), and vascular endothelial growth factor (VEGF) was performed with naïve animals as native controls.Results: CSE−/− was associated with hypertension and lower blood glucose levels, partially and significantly restored by GYY4137 treatment, respectively. Myocardial OTR expression was reduced upon injury, and this was aggravated in CSE−/−. Exogenous H2S administration restored myocardial protein expression to WT levels.Conclusions: This study suggests that cardiac CSE regulates cardiac OTR expression, and this effect might play a role in the regulation of cardiovascular function

The genetic interactome of prohibitins: coordinated control of cardiolipin and phosphatidylethanolamine by conserved regulators in mitochondria

Prohibitin ring complexes in the mitochondrial inner membrane regulate cell proliferation as well as the dynamics and function of mitochondria. Although prohibitins are essential in higher eukaryotes, prohibitin-deficient yeast cells are viable and exhibit a reduced replicative life span. Here, we define the genetic interactome of prohibitins in yeast using synthetic genetic arrays, and identify 35 genetic interactors of prohibitins (GEP genes) required for cell survival in the absence of prohibitins. Proteins encoded by these genes include members of a conserved protein family, Ups1 and Gep1, which affect the processing of the dynamin-like GTPase Mgm1 and thereby modulate cristae morphogenesis. We show that Ups1 and Gep1 regulate the levels of cardiolipin and phosphatidylethanolamine in mitochondria in a lipid-specific but coordinated manner. Lipid profiling by mass spectrometry of GEP-deficient mitochondria reveals a critical role of cardiolipin and phosphatidylethanolamine for survival of prohibitin-deficient cells. We propose that prohibitins control inner membrane organization and integrity by acting as protein and lipid scaffolds

Revisiting the matching function

There is strong empirical evidence for Cobb-Douglas matching functions. We show in this paper that this widely found relation between matches on the one hand and unemployment and vacancies on the other hand can be the result of different underlying mechanisms. Obviously, it can be generated by assuming a Cobb-Douglas matching function. Less obvious, the same relationship results from a vacancy free entry condition and idiosyncratic productivity shocks. A positive aggregate productivity shock leads to more vacancy posting, a shift of the idiosyncratic selection cutoff and thereby more hiring. We calibrate a model with both mechanisms to administrative German labor market data and show that idiosyncratic productivity for new contacts is an important driver of the elasticity of the job-finding rate with respect to market tightness. Accounting for idiosyncratic productivity can explain the observed negative time trend in estimated matching efficiency and asymmetric business cycle responses to large aggregate shocks

Pluripotenzerhaltung von Mausstammzellen in Abhängigkeit des PI3K/Akt Signalwegs

Aufgrund der steigenden Lebenserwartung nehmen degenerative Erkrankungen wie Morbus Parkinson, Morbus Alzheimer oder Diabetes deutlich zu. Momentan können bei diesen Erkrankungen jedoch nur die Symptome, nicht aber deren Ursachen behandelt werden. Ein Forschungsansatz hierzu stellt die regenerative Medizin dar. Diese beschäftigt sich mit der möglichen zellbasierten Ersetzung von beschädigtem Gewebe oder Organen. Hierzu könnten beispielsweise Stammzellen aufgrund ihrer unbegrenzten Teilungsfähigkeit und ihrer Fähigkeit, Zelltypen aller Gewebe ausbilden, einen wichtigen Beitrag leisten. Da die Forschung mit humanen Stammzellen ethisch und rechtlich bedenklich ist, bietet sich das murine Modellsystem für die Erforschung von Stammzelleigenschaften an. Für eine gezielte Differenzierung von Stammzellen ist es wichtig, zuvor grundlegende Eigenschaften wie beispielsweise pluripotenzrelevante Signalwege, genau zu verstehen. Ein wichtiger Signalweg im Zusammenhang mit der Pluripotenzerhaltung in murinen Stammzellen (mES Zellen) stellt der PI3K/Akt Signalweg dar. Bisherige Erkenntnisse zeigen, dass die Inhibition von PI3K den Verlust der pluripotenten Fähigkeit von mES Zellen zur Folge hat. Es gibt Hinweise darauf, dass dies hauptsächlich auf eine Hemmung der Serin/Threonin Kinase Akt zurückgehen soll. Akt soll die Pluripotenz zum einen über die Hochregulation pluripotenzassoziierter Transkriptionsfaktoren und zum anderen durch eine direkte Stabilisierung pluripotenzrelevanter Proteine regulieren. So führt die Aktivierung von Akt beispielsweise zu einer Hochregulation der Transkriptionsfaktoren Tbx3 und Nanog, die wiederum die Expression von Oct4 und Sox2 induzieren. Oct4 und Sox2 können durch die Phosphorylierung durch Akt direkt stabilisiert werden. Da bisher noch nicht bekannt war, ob eine oder mehrere der Akt Isoformen bedeutend für die Pluripotenzerhaltung von mES Zellen ist, sollte dies in der vorliegenden Arbeit genauer untersucht werden. Dafür wurden als erstes mittels der TALEN Technologie Akt1-/- mES Zellen generiert, die erstaunlicher Weise ohne einen Verlust ihrer pluripotenten Fähigkeit kultiviert werden konnten. Um auszuschließen, dass der Verlust von Akt1 durch Akt2 kompensiert wird, wurde in diesen Zellen zusätzlich Akt2 shRNA basiert herunterreguliert. Unerwarteter Weise hatte der Verlust beider Akt Isoformen keinen Effekt auf die Pluripotenzerhaltung in den Stammzellen, was mit verschiedenen Assays, wie der Nachweis der Alkalischen Phosphatase Aktivität, der Expression pluripotenzrelevanter Transkriptionsfaktoren auf mRNA- und Proteinebene, sowie der Differenzierungsfähigkeit in Zellen aller drei Keimblätter, gezeigt werden konnte. Es gab keine Hinweise auf eine mögliche Kompensation des Verlusts der beiden Isoformen durch Akt3 noch durch eine veränderte Regulation der anderen beiden pluripotenzassoziierten Signalwege JAK/STAT und MAPK. Es wurde ebenfalls nachgewiesen, dass der Verlust der Pluripotenz bei der Inhibition von PI3K nicht auf eine verminderte Aktivierung PDK1 zurückzuführen ist, da eine Inhibition von PDK1 oder eine Herunterregulation des Proteins mit shRNA die Pluripotenz der verwendeten mES Zellen nicht beeinträchtigt. Zusätzlich konnte gezeigt werden, dass eine unspezifische Inhibition von mTOR durch einen PI3K Inhibitor ebenfalls nicht für den Verlust der Pluripotenz der Stammzellen verantwortlich ist, da die Inhibition von mTOR mit Rapamycin nur die Proliferation der Zellen beeinflusst. Entgegen der Annahmen in der Literatur wird in dieser Arbeit somit dargelegt, dass der Verlust der Pluripotenz durch eine Inhibition der PI3K in V6.4 mES Zellen nicht auf eine damit einhergehende Inaktivierung der Akt Isoformen 1 und 2 zurück zu führen ist und es somit offen bleibt, wie genau die Inhibition von PI3K einen negativen Effekt auf die Pluripotenzerhaltung der Stammzellen hat

ΔMST and the Regulation of Cardiac CSE and OTR Expression in Trauma and Hemorrhage

Genetic deletion of 3-mercaptopyruvate sulfurtransferase (MST) is known to result in hypertension and cardiac hypertrophy in older mice, and is associated with increased anxiety-like behaviors. Endogenous hydrogen sulfide (H2S) produced by MST in the mitochondria is also known to be involved in physiological and cellular bioenergetics, and its dysfunction associated with depressive behavior and increased cardiovascular morbidity. Interestingly, early life stress has been shown to lead to a significant loss of cystathionine-γ-lyase (CSE) and oxytocin receptor (OTR) expression in the heart. Thus, we were interested in testing the hypothesis of whether genetic MST mutation (ΔMST) would affect cardiac CSE and OTR expression and affect the mitochondrial respiration in a clinically relevant, resuscitated, mouse model of trauma and hemorrhagic shock. In ΔMST mice, we found a reduction of CSE and OTR in both the naive as well as injured state, in contrast to the wild type (wt) controls. Interestingly, the ΔMST showed a different complex IV response to injury than the wt controls, although our claims are based on the non-demonstrated assumption that naive wt and naive ΔMST mice have comparable complex IV activity. Finally, hemorrhagic shock led to a reduction of CSE and OTR, confirming previous results in the injured mouse heart. To date, the exact mechanisms of the cardiac interaction between H2S and OT are not clear, but they point the way to potential cardioprotective therapies

ΔMST and the Regulation of Cardiac CSE and OTR Expression in Trauma and Hemorrhage

Genetic deletion of 3-mercaptopyruvate sulfurtransferase (MST) is known to result in hypertension and cardiac hypertrophy in older mice, and is associated with increased anxiety-like behaviors. Endogenous hydrogen sulfide (H2S) produced by MST in the mitochondria is also known to be involved in physiological and cellular bioenergetics, and its dysfunction associated with depressive behavior and increased cardiovascular morbidity. Interestingly, early life stress has been shown to lead to a significant loss of cystathionine-γ-lyase (CSE) and oxytocin receptor (OTR) expression in the heart. Thus, we were interested in testing the hypothesis of whether genetic MST mutation (ΔMST) would affect cardiac CSE and OTR expression and affect the mitochondrial respiration in a clinically relevant, resuscitated, mouse model of trauma and hemorrhagic shock. In ΔMST mice, we found a reduction of CSE and OTR in both the naive as well as injured state, in contrast to the wild type (wt) controls. Interestingly, the ΔMST showed a different complex IV response to injury than the wt controls, although our claims are based on the non-demonstrated assumption that naive wt and naive ΔMST mice have comparable complex IV activity. Finally, hemorrhagic shock led to a reduction of CSE and OTR, confirming previous results in the injured mouse heart. To date, the exact mechanisms of the cardiac interaction between H2S and OT are not clear, but they point the way to potential cardioprotective therapies

Molecular and functional interactions between AKT and SOX2 in breast carcinoma

The transcription factor SOX2 is a key regulator of pluripotency in embryonic stem cells and plays important roles in early organogenesis. Recently, SOX2 expression was documented in various cancers and suggested as a cancer stem cell (CSC) marker. Here we identify the Ser/Thr-kinase AKT as an upstream regulator of SOX2 protein turnover in breast carcinoma (BC). SOX2 and pAKT are co-expressed and co-regulated in breast CSCs and depletion of either reduces clonogenicity. Ectopic SOX2 expression restores clonogenicity and in vivo tumorigenicity of AKT-inhibited cells, suggesting that SOX2 acts as a functional downstream AKT target. Mechanistically, we show that AKT physically interacts with the SOX2 protein to modulate its subcellular distribution. AKT kinase inhibition results in enhanced cytoplasmic retention of SOX2, presumably via impaired nuclear import, and in successive cytoplasmic proteasomal degradation of the protein. In line, blockade of either nuclear transport or proteasomal degradation rescues SOX2 expression in AKT-inhibited BC cells. Finally, AKT inhibitors efficiently suppress the growth of SOX2-expressing putative cancer stem cells, whereas conventional chemotherapeutics select for this population. Together, our results suggest the AKT/SOX2 molecular axis as a regulator of BC clonogenicity and AKT inhibitors as promising drugs for the treatment of SOX2-positive BC