Topic: Potassium Channel

Mechanisms and consequences of cerebrovascular dysfunction in preeclampsia

PROJECT SUMMARY/ABSTRACT Preeclampsia (PE) is a common hypertensive disorder of pregnancy that causes significant maternal and fetal morbidity and mortality worldwide. PE women are at a high risk of stroke, including intracerebral hemorrhage, during the peripartum period, suggesting the sequelae of PE adversely impacts the cerebral circulation to promote hemorrhage. In addition, women with severe early-onset PE are at an 85-fold increased risk of death from intracerebral hemorrhage, importantly suggesting severity of disease promotes greater vulnerability of the cerebral circulation to degradation and rupture. However, the consequences of PE extend far beyond pregnancy and are associated with excessive cardiovascular and cerebrovascular disease risk later in life. Women with previous pregnancy complicated by PE can develop cognitive impairment as early as in their 30’s and 40’s, suggesting PE predisposes the brain to early-onset cognitive impairment. Studies have shown that formerly PE women have changes in gray matter volume and increased white matter lesion burden that occurs as a function of time from pregnancy, suggesting that PE continues to progressively damage the brain long after the affected pregnancy. Thus, our overall goal is to elucidate mechanisms by which women with PE are at risk of intracerebral hemorrhage in pregnancy and cognitive decline later in life. Our preliminary studies found greater vascular degradation, hematoma and cerebral edema in a model of severe PE that was associated with vascular inflammation and microglia activation (neuroinflammation). In addition, we found endothelial dysfunction and diminished neurovascular coupling in PE rats that persisted 5 months postpartum. Impaired neurovascular coupling is well-recognized as an underlying contributor to cognitive decline. These effects in postpartum animals with previous exposure to PE were associated with memory impairment that was not present in the pregnant state, suggesting neurovascular dysfunction precedes cognitive decline. Our central hypothesis is that the sequela of PE accelerates hypertension-induced cerebrovascular dysfunction that predisposes to intracerebral hemorrhage during pregnancy and its persistence postpartum results in early-onset cognitive decline. We will therefore elucidate mechanisms by which PE accelerates vascular degradation and worsens outcome from hemorrhagic stroke, probing pathways involved in oxidative degradative processes using multi-omics and multivariate analysis (Aim 1). We will also determine underlying molecular mechanisms that cause persistent cerebral microvascular dysfunction and cognitive decline postpartum, including oxidative stress-induced BBB leakage and persistent neuroinflammation that drives potassium channel dysfunction, reduced neurovascular coupling and neurovascular uncoupling (Aim 2). We will also use machine learning approaches together with multi-omics and outcome measures to identify factors and cellular pathways that are most impactful for prediction of intracerebral hemorrhage and cognitive impairment. The ability to predict and prevent devasting neurovascular disorders associated with PE has the potential to have long-lasting impacts on the lives of women with PE.

Molecular strategies for resolving differential regulation of dopamine subpopulations

Project Summary/Abstract Dopamine neurons in the ventral tegmental area (VTA) fire action potentials in complex patterns of tonic and phasic activity in response to environmental stimuli and during behavioral tasks. Transcriptomic, anatomical, and functional studies have established that VTA dopamine neurons can be divided into multiple subpopulations with variable gene expression, projection patterns, and response profiles. We recently completed a transcriptomic study that identified genetic markers for three distinct subpopulations of VTA dopamine neurons, and also found evidence for variability in ion channel gene expression between populations that correlated with differences in activity-dependent gene expression. However, much remains unknown regarding how specific genes encoding ion channels, receptors, transcription factors, or other signaling components contribute to the variability in baseline physiological properties observed across the VTA. Here we propose to combine slice electrophysiology recordings of VTA dopamine neurons with post-hoc single-cell sequencing analysis (i.e. patch-seq), which will allow us to directly correlate gene expression and physiological properties in order to identify candidate genes that may be key drivers of the variability between subpopulations. We also propose to validate and utilize a novel dual-recombinase CRISPR/Cas9 system for targeted gene mutagenesis in intersectional neuronal populations, which will provide a mechanism for testing gene function with unprecedented precision. We will use this approach to test the function of two candidate ion channel genes, the potassium channels Kcnh5 and Kcnh7, previously identified in our transcriptomic study as potential contributors to dopamine neuron action potential firing properties. We hypothesize that these genes are important for enabling rapid action potential firing in highly excitable dopamine neurons found in specific subpopulations. As a whole, with this proposal we aim to generate a valuable dataset linking gene expression in VTA dopamine neurons with physiology and subpopulation identification, as well as develop an intersectional gene mutagenesis strategy that can be used throughout the brain to precisely target neuronal subpopulations to test gene function. With this approach, we hope to facilitate future precision targeting of the dopamine system and dopamine-dependent behaviors.

MBI Webinar on preclinical research into brain tumours and neurodegenerative disorders

WEBINAR 1 Breaking the barrier: Using focused ultrasound for the development of targeted therapies for brain tumours presented by Dr Ekaterina (Caty) Salimova, Monash Biomedical Imaging Glioblastoma multiforme (GBM) - brain cancer - is aggressive and difficult to treat as systemic therapies are hindered by the blood-brain barrier (BBB). Focused ultrasound (FUS) - a non-invasive technique that can induce targeted temporary disruption of the BBB – is a promising tool to improve GBM treatments. In this webinar, Dr Ekaterina Salimova will discuss the MRI-guided FUS modality at MBI and her research to develop novel targeted therapies for brain tumours. Dr Ekaterina (Caty) Salimova is a Research Fellow in the Preclinical Team at Monash Biomedical Imaging. Her research interests include imaging cardiovascular disease and MRI-guided focused ultrasound for investigating new therapeutic targets in neuro-oncology. - WEBINAR 2 Disposition of the Kv1.3 inhibitory peptide HsTX1[R14A], a novel attenuator of neuroinflammation presented by Sanjeevini Babu Reddiar, Monash Institute of Pharmaceutical Sciences The voltage-gated potassium channel (Kv1.3) in microglia regulates membrane potential and pro-inflammatory functions, and non-selective blockade of Kv1.3 has shown anti-inflammatory and disease improvement in animal models of Alzheimer’s and Parkinson’s diseases. Therefore, specific inhibitors of pro-inflammatory microglial processes with CNS bioavailability are urgently needed, as disease-modifying treatments for neurodegenerative disorders are lacking. In this webinar, PhD candidate Ms Sanju Reddiar will discuss the synthesis and biodistribution of a Kv1.3-inhibitory peptide using a [64Cu]Cu-DOTA labelled conjugate. Sanjeevini Babu Reddiar is a PhD student at the Monash Institute of Pharmaceutical Sciences. She is working on a project identifying the factors governing the brain disposition and blood-brain barrier permeability of a Kv1.3-blocking peptide.

Acetylcholine modulation of short-term plasticity is critical to reliable long-term plasticity in hippocampal synapses

CA3-CA1 synapses in the hippocampus are the initial locus of episodic memory. The action of acetylcholine alters cellular excitability, modifies neuronal networks, and triggers secondary signaling that directly affects long-term plasticity (LTP) (the cellular underpinning of memory). It is therefore considered a critical regulator of learning and memory in the brain. Its action via M4 metabotropic receptors in the presynaptic terminal of the CA3 neurons and M1 metabotropic receptors in the postsynaptic spines of CA1 neurons produce rich dynamics across multiple timescales. We developed a model to describe the activation of postsynaptic M1 receptors that leads to IP3 production from membrane PIP2 molecules. The binding of IP3 to IP3 receptors in the endoplasmic reticulum (ER) ultimately causes calcium release. This calcium release from the ER activates potassium channels like the calcium-activated SK channels and alters different aspects of synaptic signaling. In an independent signaling cascade, M1 receptors also directly suppress SK channels and the voltage-activated KCNQ2/3 channels, enhancing post-synaptic excitability. In the CA3 presynaptic terminal, we model the reduction of the voltage sensitivity of voltage-gated calcium channels (VGCCs) and the resulting suppression of neurotransmitter release by the action of the M4 receptors. Our results show that the reduced initial release probability because of acetylcholine alters short-term plasticity (STP) dynamics. We characterize the dichotomy of suppressing neurotransmitter release from CA3 neurons and the enhanced excitability of the postsynaptic CA1 spine. Mechanisms underlying STP operate over a few seconds, while those responsible for LTP last for hours, and both forms of plasticity have been linked with very distinct functions in the brain. We show that the concurrent suppression of neurotransmitter release and increased sensitivity conserves neurotransmitter vesicles and enhances the reliability in plasticity. Our work establishes a relationship between STP and LTP coordinated by neuromodulation with acetylcholine.

Autism spectrum disorder-related voltage-gated potassium channel mutation Kv7.3 R2C decreases dopamine neuron excitability and social interaction in mice

Brief ultrasound stimulation induces sustained, reversible modification to neuronal potassium channel function

Deletion of the background potassium channel TWIK-1 increases susceptibility to kainic acid-induced seizure

Design of an Ultrapotent Genetically Encoded Blocker of the Potassium Channel Kv4.2 for Gating Neural Plasticity

On the kinetics of calcium currents and the activation of calcium-activated potassium channels in layer-5 pyramidal neurons

A Kv3.3 voltage-gated potassium channel mutation induces presynaptic hyperexcitability and raises the number of docked vesicles at hippocampal excitatory synapses