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Although extracorporeal membrane ventilation offers the possibility for low-frequency ventilation, protocols commonly used in patients with acute respiratory distress syndrome (ARDS) and treated with extracorporeal membrane oxygenation (ECMO) vary largely. Whether strict adherence to low-frequency ventilation offers benefit on important outcome measures is poorly understood. Background/Objectives: This pilot clinical study investigated the efficacy of low-frequency ventilation on ventilator-free days (VFDs) in patients suffering from ARDS who were treated with ECMO therapy. Methods: In this single-center randomized controlled trial, 44 (70% male) successive ARDS patients treated with ECMO (aged 56 ± 12 years, SAPS III 64 (SD ± 14)) were randomly assigned 1:1 to the control group (conventional ventilation) or the treatment group (low-frequency ventilation during first 72 h on ECMO: respiratory rate 4–5/min; PEEP 14–16 cm H2O; plateau pressure 23–25 cm H2O, tidal volume: <4 mL/kg). The primary endpoint was VFDs at day 28 after starting ECMO treatment. The major secondary endpoint was ICU mortality, 28-day mortality and 90-day mortality. Results: Twenty-three (52%) patients were successfully weaned from ECMO and were discharged from the intensive care unit (ICU). Twelve patients in the treatment group and five patients in the control group showed more than one VFD at day 28 of ECMO treatment. VFDs were 3.0 (SD ± 5.5) days in the control group and 5.4 (SD ± 6) days in the treatment group (p = 0.117). Until day 28 of ECMO initiation, patients in the treatment group could be successfully weaned off of the ventilator more often (OR of 0.164 of 0 VFDs at day 28 after ECMO start; 95% CI 0.036–0.758; p = 0.021). ICU mortality did not differ significantly (36% in treatment group and 59% in control group; p = 0.227). Conclusions: Low-frequency ventilation is comparable to conventional protective ventilation in patients with ARDS who have been treated with ECMO. However, low-frequency ventilation may support weaning from invasive mechanical ventilation in patients suffering from ARDS and treated with ECMO therapy. [ABSTRACT FROM AUTHOR]

Oxygen conditions in the lung determine downstream organ functionality by setting the partial pressure of oxygen, regulating the redox homeostasis and by activating mediators in the lung that can be propagated in the blood stream. Examples for such mediators are secreted soluble or vesicle-bound molecules (proteins and nucleic acids) that can be taken up by remote target cells impacting their metabolism and signaling pathways. MicroRNAs (miRNAs) have gained significant interest as intercellular communicators, biomarkers and therapeutic targets in this context. Due to their high stability in the blood stream, they have also been attributed a role as "memory molecules" that are able to modulate gene expression upon repeated (stress) exposures. In this study, we aimed to identify and quantify released miRNAs from lung microvascular endothelial cells in response to different oxygen conditions. We combined next-generation sequencing (NGS) of secreted miRNAs and cellular mRNA sequencing with bioinformatic analyses in order to delineate molecular events on the cellular and extracellular level and their putative interdependence. We show that the identified miRNA networks have the potential to co-mediate some of the molecular events, that have been observed in the context of hypoxia, hyperoxia, intermittent hypoxia and intermittent hypoxia/hyperoxia. [ABSTRACT FROM AUTHOR]

Fast synaptic inhibition in the brain is largely mediated by [gamma]aminobutyric acid receptors (GABAAR). While the pharmacological manipulation of GABAAR function by therapeutic agents, such as benzodiazepines can have profound effects on neuronal excitation and behavior, the endogenous mechanisms neurons use to regulate the efficacy of synaptic inhibition and their impact on behavior remains poorly understood. To address this issue, we created a knock-in mouse in which tyrosine phosphorylation of the GABAARs [gamma]2 subunit, a posttranslational modification that is critical for their functional modulation, has been ablated. These animals exhibited enhanced GABAAR accumulation at postsynaptic inhibitory synaptic specializations on pyramidal neurons within the CA3 subdomain of the hippocampus, primarily due to aberrant trafficking within the endocytic pathway. This enhanced inhibition correlated with a specific deficit in spatial object recognition, a behavioral paradigm dependent upon CA3. Thus, phospho-dependent regulation of GABAAR function involving just two tyrosine residues in the [gamma]2 subunit provides an input-specific mechanism that not only regulates the efficacy of synaptic inhibition, but has behavioral consequences. cognition/GABAA receptor/inhibitory synapses doi/10.1073/pnas.0908840106

The regulation of the number of [gamma]2-subunit-containing GAB[A.sub.A] receptors (GAB[A.sub.A]RS) present at synapses is critical for correct synaptic inhibition and animal behavior. This regulation occurs, in part, by the controlled removal of receptors from the membrane in clathrin-coated vesicles, but it remains unclear how clathrin recruitment to surface [gamma]2-subunit-containing GAB[A.sub.A]RS is regulated. Here, we identify a [gamma]2-subunit-specific Yxx[phi]-type-binding motif for the clathrin adaptor protein, AP2, which is located within a site for [gamma]2-subunit tyrosine phosphorylation. Blocking GAB[A.sub.A]R-AP2 interactions via this motif increases synaptic responses within minutes. Crystallographic and biochemical studies reveal that phosphorylation of the Yxx[phi] motif inhibits AP2 binding, leading to increased surface receptor number. In addition, the crystal structure provides an explanation for the high affinity of this motif for AP2 and suggests that [gamma]2-subunit-containing heteromeric GAB[A.sub.A]RS may be internalized as dimers or multimers. These data define a mechanism for tyrosine kinase regulation of GAB[A.sub.A]R surface levels and synaptic inhibition. endocytosis | phosphorylation | structure | synaptic transmission | tyrosine kinase

[gamma]-Aminobutyric acid type A receptors ([GABA.sub.A]RS) are the major sites of fast synaptic inhibition in the brain. An essential determinant for the efficacy of synaptic inhibition is the regulation of [GABA.sub.A]R cell surface stability. Here. we have examined the regulation of [GABA.sub.A]R endocytic sorting, a critical regulator of cell surface receptor number. In neurons, rapid constitutive endocytosis of [GABA.sub.A]RS was evident. Internalized receptors were then either rapidly recycled back to the cell surface, or on a slower time scale, targeted for lysosomal degradation. This sorting decision was regulated by a direct interaction of [GABA.sub.A]RS with Huntingtin-associated protein 1 (HAP1), HAP1 modulated synaptic [GABA.sub.A]R number by inhibiting receptor degradation and facilitating receptor recycling. Together these observations have identified a role for HAP1 in regulating [GABA.sub.A]R sorting, suggesting an important role for this protein in the construction and maintenance of inhibitory synapses.

[Gamma]-Aminobutyric acid (GABA) type A receptors mediate fast inhibitory synaptic transmission and have been implicated in responses to sedative/hypnotic agents (including neuroactive steroids), anxiety, and learning and memory. Using gene targeting technology, we generated a strain of mice deficient in the ~ subunit of the GABA type A receptors. In vivo testing of various behavioral responses revealed a strikingly selective attenuation of responses to neuroactive steroids, but not to other modulatory drugs. Electrophysiological recordings from hippocampal slices revealed a significantly faster miniature inhibitory postsynaptic current decay time in null mice, with no change in miniature inhibitory postsynaptic current amplitude or frequency. Learning and memory assessed with fear conditioning were normal. These results begin to illuminate the novel contributions of the [Delta] subunit to GABA pharmacology and sedative/hypnotic responses and behavior and provide insights into the physiology of neurosteroids.

Glutamic acid decarboxylase of 65 kDa (GAD65) antibodies have been reported in a variety of neurological disorders such as stiff-person syndrome (SPS), sporadic ataxia and some cases of epilepsy. Since the target is believed to be the cytoplasmic enzyme GAD65, the key enzyme of g-aminobutyric acid (GABA) synthesis, the pathophysiological role of these antibodies is poorly understood. Here, we stereotactically injected human cerebrospinal fluid (CSF) containing GAD65-antibodies into the hippocampus of rats in vivo and then prepared hippocampal slices 1-2 days after post-operative recovery. We characterized both evoked and spontaneous GABAergic transmission in vitro using sharp microelectrode and patch-clamp recordings in CA1 neurons. Intracellular recordings with sharp microelectrodes from CA1 neurons showed that evoked GABAARor GABABR-mediated inhibitory postsynaptic potentials (IPSP) remained unaltered in anti-GAD65 tissue. These results were confirmed with patch-clamp recordings showing no difference in evoked gabazine-sensitive inhibitory postsynaptic currents (IPSCs). In addition, spontaneous IPSCs also showed no difference between anti-GAD65 tissue and controls with respect to the mean frequency, the mean amplitude and the sIPSC distribution. In conclusion, stereotactic injection of GAD65-antibodies into the hippocampus leaves evoked and spontaneous GABAergic synaptic transmission intact. Hence, dysfunction of the inhibitory GABAergic system does not appear to be the major mechanism of epileptogenicity in this disease. [ABSTRACT FROM AUTHOR]