Biology subjects

Hashemi, P.

Publications and source records attributed to Hashemi, P..

6 recordsLinked to original sources

bioRxiv2026

Focal Neurostimulation of Calcium Signaling and Dopamine Release in Human Dopaminergic Neurons Using Megahertz-range Single-Pulse Focused Ultrasound

Focused Ultrasound (FUS) neurostimulation has increasingly attracted attention given its ability for localized targeting and non- to minimally-invasive capacity. However, the understanding of the biological and neurochemical mechanisms triggered by this neurostimulation modality remains limited. Indeed, further progress of this technology could benefit from spatiotemporal evaluation of neurotransmitter secretory activity resulting from FUS stimulation. Recently, we demonstrated in-vitro the ability of FUS to evoke calcium (Ca2+) waves, in a mixture of human neuronal and glial cells (standard cells), with single-pulse megahertz-range FUS compatible with a transdural approach relying on an intracranial FUS implant. In the present work, we investigated the ability to evoke Ca2+ signaling and dopamine (DA) release by single-pulse megahertz-range FUS stimulation of cultured human dopaminergic neurons in-vitro. A hybrid-platform integrating a custom-made FUS implant prototype (concave spherical transducer, O and focal distance: 15 mm) with real-time Ca2+ fluorescence microscopy imaging (FMI), and fast scan cyclic voltammetry (FSCV) was constructed to evaluate FUS-evoked Ca2+ signaling and concurrent DA release. Ca2+ and DA releases evoked by FUS on dopaminergic neurons (DA neurons) were compared to those evoked in standard cells. Application of single-pulse FUS (frequency: 5.11 MHz, pulse duration: 700 {micro}s, spatial average pulse average intensity, Isapa: 19.59 {+/-} 4.12 W.cm-2) was shown to causally mobilize Ca2+ dynamics in both cell types. Immediate (< 1 s) responses were focally evoked in cell clusters of 290 {micro}m in diameters; corresponding to the -3 dB FUS focal diameter. However, while standard cells exhibited continuous and omnidirectional delayed propagating dynamics following FUS stimulation, DA neurons showed more spatially sparse responses. The FUS-induced Ca2+ activity in DA neurons was accompanied by DA release detected by FSCV, but not in standard cells. This study demonstrates that single-pulse megahertz-range FUS induced with an intracranial implant prototype smaller than conventionally used FUS devices (transcranial applications) can evoke in-vitro intracellular Ca2+ activity while stimulating DA release from dopaminergic neurons, underscoring its potential as a neuro-stimulation/-modulation tool for targeting dopaminergic circuits in various pathologies.

bioengineering↗

bioRxiv2024

Measurement of Real Time Serotonin Dynamics from Human Derived Gut Organoids

The importance of the gut in regulating the brain-body-immune axis is becoming increasingly evident. Interestingly, the brain and gut share many common signalling molecules, with serotonin being one of the most notable. In fact, the gut is the primary source of serotonin in the body. However, studying serotonin dynamics in a human-specific context remains a challenge. Human stem cell-derived models provide a promising avenue for studying signal transmission in well-controlled, in vitro environments. In this study, we report the first fast-scan cyclic voltammetry (FSCV) measurements of serotonin signalling in a newly developed enterochromaffin cell (ECC)-enriched gut organoid model. First, we characterize the stem cell-derived gut organoids and confirmed they are enriched with ECCs - the key cell type responsible for producing and releasing serotonin in the gut. We then optimize an in vitro buffer that maintains cell viability while supporting FSCV measurements. Using this system, we detect spontaneous release events, which increase in frequency and amplitude following stimulation with forskolin (FSK) and 3-isobutyl-1-methylxanthine (IBMX). Finally, we confirm the identity of the signal as serotonin by using a selective serotonin reuptake inhibitor (SSRI), which significantly delayed the reuptake profile. Our study introduces the first real time measurement of serotonin signalling in a human-derived gut model. We believe this system will be essential for future research on serotonins role in the gut and for potential novel drug target identification.

bioengineering↗

bioRxiv2024

Mapping the druggable targets displayed by human colonic enteroendocrine cells

Enteroendocrine cells (EECs) are specialized intestinal hormone-secreting cells that play critical roles in metabolic homeostasis, digestion, and gut-brain communication. They detect diverse stimuli including endocrine, immune, neuronal, microbial, and dietary signals, through a complex array of receptors, ion channels, and transporters, to modulate the release of over 20 hormones. These molecular sensors serve as potential drug targets to modulate hormone secretion, but until recently, catalogues of such targets in human colonic EECs have not been produced. To address this gap, we performed bulk and single-cell RNA sequencing on fluorescently labelled EECs isolated from human colonic organoids, identifying and cataloguing potential druggable targets. This catalogue includes receptors, orphan GPCRs, transporters, and hormones not previously reported in human colonic EECs. Comparison with murine EECs highlighted interspecies similarities and differences, key data to facilitate the design and optimise the predictive accuracy of pre-clinical models. We also functionally validated two receptors not previously identified in human EECs: IL-13R1, was expressed in both peptide-producing EECs and serotonin producing Enterochromaffin cells (ECs), and its ligand IL-13 stimulated the secretion of glucagon-like peptide-1 (GLP-1) and serotonin measured in real-time, and GPR173, which was selectively expressed in ECs and, when activated by its agonist Phoenixin-20, also promoted serotonin release. These analyses provide a valuable resource for therapeutic interventions aimed at modulating gut hormone secretion, with potential applications in treating gastrointestinal, metabolic, and other related disorders.

cell biology↗

bioRxiv2023

Histamine originating from the BNST modulates corticostriatal synaptic transmission during early postnatal development

The neuromodulator histamine regulates key processes in many regions of both the adult and developing brain including the striatum. However, striatal innervation by histaminergic afferents is very sparse making the physiological sources of histamine controversial. Here potential sources of striatal histamine were investigated during early postnatal development and specifically in the second postnatal week, in acute mouse brain slices. Firstly, a combination of whole-cell patch-clamp recordings and optogenetic stimulation demonstrates that during this period exogenously applied histamine modulates the intrinsic properties of developing D1 and D2 striatal spiny projection neurons (SPNs) as well as synaptic transmission at afferents coming from the mPFC and visual cortex. Secondly, immunohistochemistry for histamine reveals a brain region proximal and caudal to striatum densely innervated by histaminergic axons and corresponding to the oval nucleus of the bed nucleus of stria terminalis (ovBNST). Thirdly, direct electrical stimulation of the ovBNST leads to significant and detectable levels of histamine in the striatum, as assessed by both fast scan cyclic voltammetry and fluorescent histamine sensors. Lastly, electrical stimulation of the ovBNST nucleus, at frequencies mimicking active histaminergic neurons, can release sufficient levels of histamine to modulate excitatory synaptic transmission from mPFC onto striatal SPNs by acting at histamine H3 receptors. Together, these results provide evidence for the existence of the ovBNST as an extrastriatal source of histamine during early brain development and postulates a new view of the modus operandi of histamine in that it can cross anatomical boundaries and act as a paracrine neuromodulator. Significance statementHistamine is synthesized by neurons in the hypothalamic tuberomammillary nucleus (TMN) and released from their axons in many brain regions controlling key physiological processes. When dysregulated this can result in neurological and neurodevelopmental disorders such as Tourettes syndrome and OCD. To understand the physiological roles for histamine and to facilitate the generation of new therapeutic interventions it is key to define the sources of histamine and its mode of action. Here we provide evidence, using the developing striatum as an exemplar, that sources of histamine can lie beyond anatomical boundaries with histamine acting as a paracrine neuromodulator. This also has potential implications for our mechanistic understanding of deep brain stimulation of the BNST in treating severe Tourettes syndrome and OCD.

neuroscience↗

bioRxiv2023

3D Printed Ti3C2Tx MXene/PCL Scaffolds for Guided Neuronal Growth and Photothermal Stimulation

The exploration of neural circuitry is essential for understanding the computational mechanisms and physiology of the brain. Despite significant advances in materials and fabrication techniques, controlling neuronal connectivity and response in three dimensions continues to present a formidable challenge. Here, we present a method for engineering the growth of three-dimensional (3D) neural circuits with the capability for optical stimulation. We fabricated bioactive interfaces by melt electrospinning writing (MEW) of 3D printed polycaprolactone (PCL) scaffolds followed by coating with titanium carbide (Ti3C2Tx MXene). Beyond enhancing hydrophilicity, cell adhesion, and electrical conductivity, the Ti3C2Tx MXene coating enabled optocapacitance-based neuronal stimulation due to illumination-induced local temperature increases. This work presents a strategy for additive manufacturing of neural tissues with optical control for functional tissue engineering and neural circuit computation.

bioengineering↗

bioRxiv2021

Novel, User-friendly Experimental and Analysis Strategies for Fast Voltammetry: 1. The Analysis Kid for FSCV

Fast-scan cyclic voltammetry at carbon fiber microelectrodes measures low concentrations of analytes in biological systems. There are ongoing efforts to simplify FSCV analysis and several custom platforms are available for filtering and multi-modal analysis of FSCV signals but there is no single, easily accessible platform that has capacity for all these features. Here we present The Analysis Kid: a free, open-source cloud application that does not require a specialized runtime environment and is easily accessible via common browsers. We show that a user-friendly interface can analyze multi-platform file formats to provide multimodal visualization of FSCV color plots with digital background subtraction. We highlight key features that allow interactive calibration and parametric analysis via peak finding algorithms to automatically detect the maximum amplitude, area under the curve and clearance rate of the signal. Finally, The Analysis Kid enables semi-automatic fitting of data with Michaelis Menten kinetics with single or dual reuptake models. The Analysis Kid can be freely accessed at https://analysis-kid.herokuapp.com/. The web application code is found, under an MIT license, at https://github.com/sermeor/The-Analysis-Kid.

neuroscience↗