Dual Regulation of Spine-Specific and Synapse-to-Nucleus Signaling by PKCδ during Plasticity.

The activity-dependent plasticity of synapses is believed to be the cellular basis of learning. These synaptic changes are mediated through the coordination of local biochemical reactions in synapses and changes in gene transcription in the nucleus to modulate neuronal circuits and behavior. The protein kinase C (PKC) family of isozymes has long been established as critical for synaptic plasticity. However, because of a lack of suitable isozyme-specific tools, the role of the novel subfamily of PKC isozymes is largely unknown. Here, through the development of fluorescence lifetime imaging-fluorescence resonance energy transfer activity sensors, we investigate novel PKC isozymes in synaptic plasticity in CA1 pyramidal neurons of mice of either sex. We find that PKCδ is activated downstream of TrkB and DAG production, and that the spatiotemporal nature of its activation depends on the plasticity stimulation. In response to single-spine plasticity, PKCδ is activated primarily in the stimulated spine and is required for local expression of plasticity. However, in response to multispine stimulation, a long-lasting and spreading activation of PKCδ scales with the number of spines stimulated and, by regulating cAMP response-element binding protein activity, couples spine plasticity to transcription in the nucleus. Thus, PKCδ plays a dual functional role in facilitating synaptic plasticity.SIGNIFICANCE STATEMENT Synaptic plasticity, or the ability to change the strength of the connections between neurons, underlies learning and memory and is critical for brain health. The protein kinase C (PKC) family is central to this process. However, understanding how these kinases work to mediate plasticity has been limited by a lack of tools to visualize and perturb their activity. Here, we introduce and use new tools to reveal a dual role for PKCδ in facilitating local synaptic plasticity and stabilizing this plasticity through spine-to-nucleus signaling to regulate transcription. This work provides new tools to overcome limitations in studying isozyme-specific PKC function and provides insight into molecular mechanisms of synaptic plasticity.

A single-center, nonblinded, clinical trial comparing blood pressures before and after tourniquet application in healthy humans: A study protocol.

INTRODUCTION: Cardiac arrest is the leading cause of natural death in the United States, and most surviving patients suffer from neurological dysfunction. Although this is recognized as a problem, there have been very few changes to the cardiopulmonary resuscitation (CPR) procedure. Tourniquets have been recognized for their ability to increase truncal blood pressure and have been shown to improve CPR outcomes in animal models. However, the relationship between tourniquet application and blood pressure elevation has not been adequately explored in healthy human adults. OBJECTIVES: The objective of this study is to demonstrate that bilateral, non-invasive, peripheral vascular occlusion in the thighs results in an increased proximal systolic blood pressure ≥ 10 mmHg. METHODS: This is a single-center, non-blinded clinical trial. Volunteers will be screened for eligibility at least 24 hours before the day of the trial. On the day of the trial, volunteers will undergo an informed consent process. If they choose to participate in the trial after informed consent, their baseline blood pressure will be measured. Volunteers will then have a Combat Application Tourniquet (CAT) applied to each thigh, and the windlasses will be tightened by IRB-approved personnel. Once no pulse can be felt in the lower extremity, blood pressure will be measured in the arm. This will be replicated three times, and the tourniquets will be loosened between trials to allow the volunteers to rest. Any complications that arise during the trial will be handled by the physician that is present. ANALYSIS: Changes in systolic blood pressure and diastolic blood pressure will be analyzed using a Shapiro-Wilk test. Then, a one-way repeated measures analysis of variance (ANOVA) will be performed with a Holm-Sidak post-hoc test to determine the mean differences. The significance level will be set to 5% for statistical significance. REGISTRY AND REGISTRATION NUMBER: Clinicaltrials.gov, NCT05324306.

Extremity tourniquets raise blood pressure and maintain heart rate.

BACKGROUND: Tourniquets have been modified and used for centuries to occlude blood flow to control hemorrhage. More recently, the occlusion of peripheral vessels has been linked to resultant increases in blood pressure, which may provide additional therapeutic potential, particularly during states of low cardiac output. OBJECTIVE: The objective of this study was to investigate a causal relationship between tourniquet application and blood pressure in healthy adults. METHODS: Healthy adult volunteers were recruited to participate in this IRB-approved study. Each participant met inclusion criteria and demonstrated baseline normotension. Brachial cuff blood pressure and heart rate were recorded pre- and post-tourniquet application to the bilateral legs. RESULTS: Twenty-seven adults aged 22 to 35 years participated and were included in analysis. The average systolic blood pressure was 122 ± 7 mmHg, diastolic blood pressure was 72 ± 9 mmHg, and heart rate was 70 ± 13 bpm. Following bilateral tourniquet application over the femoral vasculature, we observed a statistically significant increase in systolic (7 mmHg, p < 0.001) and diastolic (4 mmHg, p = 0.05) blood pressures with no significant change in heart rate (2 bpm, p > 0.05). CONCLUSIONS: The elevations in systolic and diastolic blood pressures establish a dependent relationship between tourniquet application to the lower extremities and blood pressure elevation. These results may support new indications for tourniquet-use or extremity vessel occlusion in settings of hemodynamic instability.

Peripheral Arterial Compression as a New Adjunct Technique to Cardiopulmonary Resuscitation.

The success of cardiopulmonary resuscitation (CPR) is critically dependent on the maintenance of myocardial and cerebral perfusion; therefore, preferential perfusion of these vital organs over non-vital vascular beds, such as the extremities, is desirable. We propose that compression of the femoral and/or brachial arteries during CPR improves resuscitation outcomes.

Cellular and Molecular Mechanisms of MEK1 Inhibitor-Induced Cardiotoxicity.

Background: Trametinib is a MEK1 (mitogen-activated extracellular signal-related kinase kinase 1) inhibitor used in the treatment of BRAF (rapid accelerated fibrosarcoma B-type)-mutated metastatic melanoma. Roughly 11% of patients develop cardiomyopathy following long-term trametinib exposure. Although described clinically, the molecular landscape of trametinib cardiotoxicity has not been characterized. Objectives: The aim of this study was to test the hypothesis that trametinib promotes widespread transcriptomic and cellular changes consistent with oxidative stress and impairs cardiac function. Methods: Mice were treated with trametinib (1 mg/kg/d). Echocardiography was performed pre- and post-treatment. Gross, histopathologic, and biochemical assessments were performed to probe for molecular and cellular changes. Human cardiac organoids were used as an in vitro measurement of cardiotoxicity and recovery. Results: Long-term administration of trametinib was associated with significant reductions in survival and left ventricular ejection fraction. Histologic analyses of the heart revealed myocardial vacuolization and calcification in 28% of animals. Bulk RNA sequencing identified 435 differentially expressed genes and 116 differential signaling pathways following trametinib treatment. Upstream gene analysis predicted interleukin-6 as a regulator of 17 relevant differentially expressed genes, suggestive of PI3K/AKT and JAK/STAT activation, which was subsequently validated. Trametinib hearts displayed elevated markers of oxidative stress, myofibrillar degeneration, an 11-fold down-regulation of the apelin receptor, and connexin-43 mislocalization. To confirm the direct cardiotoxic effects of trametinib, human cardiac organoids were treated for 6 days, followed by a 6-day media-only recovery. Trametinib-treated organoids exhibited reductions in diameter and contractility, followed by partial recovery with removal of treatment. Conclusions: These data describe pathologic changes observed in trametinib cardiotoxicity, supporting the exploration of drug holidays and alternative pharmacologic strategies for disease prevention.

Specialized coding patterns among dorsomedial prefrontal neuronal ensembles predict conditioned reward seeking.

Non-overlapping cell populations within dorsomedial prefrontal cortex (dmPFC), defined by gene expression or projection target, control dissociable aspects of reward seeking through unique activity patterns. However, even within these defined cell populations, considerable cell-to-cell variability is found, suggesting that greater resolution is needed to understand information processing in dmPFC. Here, we use two-photon calcium imaging in awake, behaving mice to monitor the activity of dmPFC excitatory neurons throughout Pavlovian reward conditioning. We characterize five unique neuronal ensembles that each encodes specialized information related to a sucrose reward, reward-predictive cues, and behavioral responses to those cues. The ensembles differentially emerge across daily training sessions - and stabilize after learning - in a manner that improves the predictive validity of dmPFC activity dynamics for deciphering variables related to behavioral conditioning. Our results characterize the complex dmPFC neuronal ensemble dynamics that stably predict reward availability and initiation of conditioned reward seeking following cue-reward learning.

Smart materials in cardiovascular implants: Shape memory alloys and shape memory polymers.

Smart materials have intrinsic properties that change in a controlled fashion in response to external stimuli. Currently, the only smart materials with a significant clinical impact in cardiovascular implant design are shape memory alloys, particularly Nitinol. Recent prodigious progress in material science has resulted in the development of sophisticated shape memory polymers. In this article, we have reviewed the literature and outline the characteristics, advantages, and disadvantages of shape memory alloys and shape memory polymers which are relevant to clinical cardiovascular applications, and describe the potential of these smart materials for applications in coronary stents and transcatheter valves.