Biology subjects

Khoshbouei, H.

Publications and source records attributed to Khoshbouei, H..

13 recordsLinked to original sources

bioRxiv2025

Parkinson's Paradox: Alpha-synuclein's Selective Strike on SNc Dopamine Neurons over VTA

In synucleinopathies, including Parkinsons disease (PD), dopamine neurons in the substantia nigra pars compacta (SNc) exhibit greater vulnerability to degeneration than those in the ventral tegmental area (VTA). While -synuclein (Syn) pathology is implicated in nigral dopamine neuron loss, the mechanisms by which Syn affects neuronal activity and midbrain dopamine network connectivity prior to cell death remain unclear. This study tested the hypothesis that elevated Syn expression induces pathophysiological changes in firing activity and disrupts network connectivity dynamics of dopamine neurons before neuronal loss. We employed two mouse models of synucleinopathy: preformed Syn fibril (PFF) injection and AAV-mediated expression of human Syn (hSyn) under the control of the tyrosine hydroxylase (TH) promoter, both targeting the VTA and SNc. Four weeks post-injection, brain sections underwent histological, electrophysiological, and network analyses. Immunohistochemistry for TH, hSyn, and phospho-Ser129 Syn assessed Syn expression and dopaminergic neuron alterations. Neuronal viability was evaluated using two complementary approaches: quantification of TH+ or FOX3+ and TUNEL labeling. Importantly, these analyses revealed no significant changes in neuronal counts or TUNEL+ cells at this time point, confirming that subsequent functional assessments captured pre-neurodegenerative, Syn-induced alterations rather than late-stage neurodegeneration. Electrophysiological recordings revealed a differential effect of hSyn expression. SNc dopamine neurons exhibited significantly increased baseline firing rates, whereas VTA dopamine neurons remained unchanged. These findings indicate a region-specific vulnerability to Syn-induced hyperactivity of dopamine neurons. Further analysis revealed impaired homeostatic firing rate regulation in SNc, but not VTA, dopamine neurons, demonstrated by a reduced capacity to recover baseline firing following hyperpolarization. Collectively, our results demonstrate that, prior to neurodegeneration, elevated Syn expression differentially disrupts both basal firing activity and network stability of SNc dopamine neurons, while sparing VTA dopamine neurons. By identifying neurophysiological changes preceding dopaminergic neuron loss, these findings provide critical insights into the pathophysiological mechanisms predisposing SNc neurons to degeneration in Parkinsons disease. Significance StatementA central question in Parkinsons disease research is why dopamine neurons in the substantia nigra pars compacta (SNc) are more vulnerable than those in the ventral tegmental area (VTA). This study reveals that alpha-synuclein (Syn) pathology differentially impacts dopamine neuronal activity and network connectivity, causing changes in the SNc before neuronal loss occurs, but not in the VTA. These findings provide a mechanism to explain the differential resilience of these neighboring dopamine neuron populations and provide insights into Parkinsons disease progression. The methodologies developed in this study establish a foundation for investigating network topology in deep brain structures and its role in neurodegenerative disorders.

neuroscience↗

bioRxiv2024

Brain-body circuit by which midbrain dopamine neuronal activity modulates splenic immunity

Midbrain dopamine neurons are well-known to shape central nervous system function, yet there is growing evidence for their influence on the peripheral immune system. Here we demonstrate that midbrain dopamine neurons form a circuit to the spleen via a multi-synaptic pathway from the dorsal vagal complex (DVC) through the celiac ganglion. Midbrain dopamine neurons modulate the activity of D1- and D2-like dopamine receptor-expressing DVC neurons. In vivo activation of midbrain dopamine neurons induced dopamine release in the DVC and increased immediate early gene expression in both the DVC and celiac ganglion. Activation of this midbrain-to-spleen circuit reduced spleen weight and decreased naive CD4+ T-cell populations without affecting total T-cell numbers. These findings unveil a functional midbrain- DVC-celiac ganglion-spleen pathway, through which midbrain dopamine neurons modulate splenic immunity. These novel insights into the neural regulation of the immune system have important implications for diseases involving altered dopamine neurotransmission and highlight potential targets for immunotherapeutic interventions.

neuroscience↗

bioRxiv2023

Aurora Kinase A Inhibition plus Tumor Treating Fields Suppress Glioma Cell Proliferation in a Cilium-Independent Manner

Tumor Treating Fields (TTFields) have been shown to extend the survival of glioblastoma (GBM) patients. TTFields interfere with a broad range of cellular processes which may contribute to their efficacy. Among these, TTFields disrupt primary cilia stability on GBM cells. Here we asked if concomitant treatment of TTFields with other agents that interfere with GBM ciliogenesis can further suppress GBM cell proliferation in vitro. Aurora Kinase A (AURKA) promotes both cilia disassembly and GBM growth in vitro and in xenograft models. Inhibitors of AURKA such as Alisertib have been previously demonstrated to inhibit cilia disassembly and increase the frequency of cilia in various cell types. However, here we show that physiological concentrations of Alisertib treatment significantly reduced GBM cilia frequency in gliomaspheres across multiple patient derived cell lines, and in patient biopsies treated ex vivo with Alisertib. This activity of Alisertib seems to be glioma cell specific as it did not reduce neuronal or glial cilia frequencies in mixed primary cell cultures from mouse forebrain. Furthermore, Alisertib depletion of glioma cilia appears specific to AURKA inhibition, as a potent AURKB inhibitor, AZD1152, had no effect on GBM ciliary frequency. Treatment of two different GBM patient-derived cell lines with TTFields and Alisertib resulted in a significant reduction in cell proliferation compared to either treatment alone. However, this effect was not cilia-dependent as the combined treatment reduced proliferation in cilia-depleted cell lines lacking, ARL13b, or U87MG cells which are naturally devoid of ARL13B+ cilia. This result is not surprising given the wide range of pathways regulated by AURKA in addition to cilia. Nonetheless, Alisertib-mediated effects on glioma cilia may be a useful biomarker of drug efficacy within tumor tissue. Considering Alisertib has been shown to cross the blood brain barrier and inhibit intracranial growth of xenografted tumor models, our data warrant future studies to explore whether concomitant Alisertib and TTFields exposure prolongs survival of brain tumor-bearing animals in vivo.

cancer biology↗

bioRxiv2023

Complement C1q-dependent engulfment of alpha-synuclein induces ENS-resident macrophage exhaustion and accelerates Parkinsons-like gut pathology

Deposition of misfolded -synuclein (syn) in the enteric nervous system (ENS) is found in multiple neurodegenerative diseases. It is hypothesized that ENS synucleinopathy contributes to both the pathogenesis and non-motor morbidity in Parkinsons Disease (PD), but the cellular and molecular mechanisms that shape enteric histopathology and dysfunction are poorly understood. Here, we demonstrate that ENS-resident macrophages, which play a critical role in maintaining ENS homeostasis, initially respond to enteric neuronal syn pathology by upregulating machinery for complement-mediated engulfment. Pharmacologic depletion of ENS-macrophages or genetic deletion of C1q enhanced enteric neuropathology. Conversely, C1q deletion ameliorated gut dysfunction, indicating that complement partially mediates syn-induced gut dysfunction. Internalization of syn led to increased endo-lysosomal stress that resulted in macrophage exhaustion and temporally correlated with the progression of ENS pathology. These novel findings highlight the importance of enteric neuron-macrophage interactions in removing toxic protein aggregates that putatively shape the earliest stages of PD in the periphery.

neuroscience↗

bioRxiv2023

Inhibition of LRRK2 kinase activity rescues deficits in striatal dopamine dynamics in VPS35 p.D620N knock-in mice

Dysregulation of dopamine neurotransmission profoundly affects motor, motivation and learning behaviors, and is often observed during the prodromal phase of Parkinsons disease (PD). However, the mechanism underlying these pathophysiological changes remains to be elucidated. Mutations in vacuolar protein sorting 35 (VPS35) and leucine-rich repeat kinase 2 (LRRK2) both lead to autosomal dominant PD, and VPS35 and LRRK2 may physically interact to govern the trafficking of synaptic cargos within the endo-lysosomal network in a kinase-dependent manner. To better understand the functional role of VPS35 and LRRK2 on dopamine physiology, we examined Vps35 haploinsufficient (Haplo) and Vps35 p.D620N knock-in (VKI) mice and how their behavior, dopamine kinetics and biochemistry are influenced by LRRK2 kinase inhibitors. We found Vps35 p.D620N significantly elevates LRRK2-mediated phosphorylation of Rab10, Rab12 and Rab29. In contrast, Vps35 haploinsufficiency reduces phosphorylation of Rab12. While striatal dopamine transporter (DAT) expression and function is similarly impaired in both VKI and Haplo mice, that physiology is normalized in VKI by treatment with the LRRK2 kinase inhibitor, MLi-2. As a corollary, VKI animals show a significant increase in amphetamine induced hyperlocomotion, compared to Haplo mice, that is also abolished by MLi-2. Taken together, these data show Vps35 p.D620N confers a gain-of-function with respect to LRRK2 kinase activation, and VPS35 and LRRK2 functionally interact to regulate DAT trafficking and striatal dopamine neurotransmission.

neuroscience↗

bioRxiv2023

Asymmetric control of food intake by left and right vagal sensory neurons

We investigated the lateralization of gut-innervating vagal sensory neurons and their roles in feeding behavior. Using genetic, anatomical, and behavioral analyses, we discovered a subset of highly lateralized vagal sensory neurons with distinct sensory responses to intestinal stimuli. Our results demonstrated that left vagal sensory neurons (LNG) are crucial for distension-induced satiety, while right vagal sensory neurons (RNG) mediate preference for nutritive foods. Furthermore, these lateralized neurons engage different central circuits, with LNG neurons recruiting brain regions associated with energy balance and RNG neurons activating areas related to salience, memory, and reward. Altogether, our findings unveil the diverse roles of asymmetrical gut-vagal-brain circuits in feeding behavior, offering new insights for potential therapeutic interventions targeting vagal nerve stimulation in metabolic and neuropsychiatric diseases. One Sentence SummaryLateralized gut-brain circuits respond to different sensory modalities and control distinct feeding behaviors.

neuroscience↗

bioRxiv2022

Clinical and pathological characterization of Central Nervous System cryptococcosis in an experimental mouse model of stereotaxic intracerebral infection

Infection of the Central Nervous System (CNS) by the encapsulated fungus Cryptococcus neoformans can lead to high mortality meningitis, most commonly in immunocompromised patients. While the mechanisms by which the fungus crosses the blood-brain barrier to initiate infection in the CNS are well recognized, there are still substantial unanswered questions about the disease progression once the fungus is established in the brain. C. neoformans is characterized by a glucuronoxylomannan (GXM)-rich polysaccharide capsule which has been implicated in immune evasion, but its role during the host CNS infection needs further elucidation. Therefore, the present study aims to examine these key questions about the mechanisms underlying cryptococcal meningitis progression and the impact of fungal GXM release by using an intracerebral rodent infection model via stereotaxic surgery. After developing brain infection, we analyzed distinct brain regions and found that while fungal load and brain weight were comparable one-week post-infection, there were region-specific histopathological (with and without brain parenchyma involvement) and disease manifestations. Moreover, we also observed a region-specific correlation between GXM accumulation and glial cell recruitment. Further, mortality was associated with the presence of subarachnoid hemorrhaging and GXM deposition in the meningeal blood vessels and meninges in all regions infected. Our results show that using the present infection model can facilitate clinical and neuropathological observations during the progression of neurocryptococcosis. Importantly, this mouse model can be used to further investigate disease progression as it develops in humans. IMPORTANCECryptococcus neoformans is the causative agent of cryptococcal meningoencephalitis (CME), a severe infection of the central nervous system (CNS) in humans. The high mortality and morbidity rates of this disease in immunosuppressed and HIV+/AIDS-infected individuals necessitate a reliable model for understanding the mechanisms and manifestations of cryptococcosis infection in the CNS. This study presents a mouse model of infection that utilizes a stereotaxic surgical setup to provide a comparative analysis of C. neoformans infection in the brain. Though not typical of infection in humans, this method provides a controlled experimental system to observe the progression of C. neoformans infection in specific regions of the brain. Additionally, this study characterizes murine manifestations of the disease, including GXM deposition in brain tissue and blood vessels, and documents the role of microglia, the resident immune cells of the CNS, in engulfing fungal cells. Depending on the region of the brain infected, distinct disease pathology can be observed with this model, expanding our understanding of cryptococcosis progression in the CNS. The importance of this work extends to the clinical setting, where many questions regarding cerebral cryptococcosis remain unresolved. Utilization of this model to further understand the mechanisms of this pathogen will provide means to develop new therapies to combat infection in humans.

microbiology↗

bioRxiv2021

Tumor Treating Fields Suppression of Ciliogenesis Enhances Temozolomide Toxicity

Tumor Treating Fields (TTFields) are low intensity, alternating intermediate frequency (200kHz) electrical fields that extend survival of glioblastoma patients receiving maintenance temozolomide (TMZ) chemotherapy. How TTFields exert efficacy on cancer over normal cells, or interact with TMZ is unclear. Primary cilia are microtubule-based organelles triggered by extracellular ligands, mechanical and electrical field stimulation, and are capable of promoting cancer growth and TMZ chemoresistance. We found in both low and high grade patient glioma cell lines that TTFields ablated cilia within 24 hours. Halting TTFields treatment led to recovered frequencies of elongated cilia. Cilia on normal primary astrocytes, neurons, and multiciliated/ependymal cells were less affected by TTFields. The TTFields-mediated loss of glioma cilia was partially rescued by chloroquine pretreatment, suggesting the effect is in part due to autophagy activation. We also observed death of ciliated cells during TTFields by live imaging. Notably, TMZ-induced stimulation of ciliogenesis in both adherent cells and gliomaspheres was blocked by TTFields. Moreover, the inhibitory effects of TTFields and TMZ on tumor cell recurrence correlated with the relative timing of TMZ exposure to TTFields and ARL13B+ cilia. Finally, TTFields disrupted cilia in patient tumors treated ex vivo. Our findings suggest TTFields efficacy may depend on the degree of tumor ciliogenesis and relative timing of TMZ treatment.

cancer biology↗

bioRxiv2021

Functional characterization of the biogenic amine transporter system on human macrophages

Monocyte-derived macrophages are key players in tissue homeostasis and disease regulated by a variety of signaling molecules. Recent literature has highlighted the ability for biogenic amines to regulate macrophage functions, but the mechanisms governing biogenic amine signaling on and around immune cells remains nebulous. In the central nervous system, biogenic amine transporters are regarded as the master regulators of neurotransmitter signaling. While we and others have shown macrophages express these transporters, relatively little is known of their function on these cells. To address these knowledge gaps, we interrogated the function of norepinephrine (NET) and dopamine (DAT) transporters on human monocyte-derived macrophages. We found that both NET and DAT are present and can uptake substrate from the extracellular space at baseline. Not only was DAT expressed in cultured macrophages, but it was also detected in a subset of intestinal macrophages in situ. Surprisingly, we discovered a NET-independent, DAT-mediated immuno-modulatory mechanism in response to lipopolysaccharide (LPS). LPS induced reverse transport of dopamine through DAT, engaging autocrine/paracrine signaling loop that regulated the macrophage response. Removing this signaling loop enhanced the pro-inflammatory response to LPS. Finally, we found that this DAT-immune axis was disrupted in disease. Collectively, our data introduce a novel role for DAT in the regulation of innate immunity during health and disease.

neuroscience↗

bioRxiv2021

TNF increases Tyrosine Hydroxylase expression in human monocytes

Most, if not all, peripheral immune cells in humans and animals express tyrosine hydroxylase (TH), the rate limiting enzyme in catecholamine synthesis. Since TH is typically studied in the context of brain catecholamine signaling, little is known about changes in TH production and function in peripheral immune cells. This knowledge gap is due, in part, to the lack of an adequately sensitive assay to measure TH in immune cells expressing lower TH levels compared to other TH expressing cells. Here, we report the development of a highly sensitive and reproducible Bio-ELISA to quantify picogram levels of TH in multiple model systems. We have applied this assay to monocytes isolated from blood of persons with Parkinsons disease (PD) and to age-matched, healthy controls. Our study unexpectedly revealed that PD patients monocytes express significantly higher levels of TH protein in peripheral monocytes relative to healthy controls. Tumor necrosis factor (TNF{delta}), a pro-inflammatory cytokine, has also been shown to be increased in the brains and peripheral circulation in human PD, as well as in animal models of PD. Therefore, we investigated a possible connection between higher levels of TH protein and the known increase in circulating TNF{delta} in PD. Monocytes isolated from healthy donors were treated with TNF{delta} or with TNF{delta} in the presence of an inhibitor. Tissue plasminogen activator (TPA) was used as a positive control. We observed that TNF{delta} stimulation increased both the number of TH+ monocytes and the quantity of TH per monocyte, without increasing the total numbers of monocytes. These results revealed that TNF{delta} could potentially modify monocytic TH production and serve a regulatory role in peripheral immune function. The development and application of a highly sensitive assay to quantify TH in both human and animal cells will provide a novel tool for further investigating possible PD immune regulatory pathways between brain and periphery.

neuroscience↗

bioRxiv2021

Novel insights in the pathophysiology of α-synuclein dysregulation on D2 receptor activity contributing to the vulnerability of dopamine neurons

Pathophysiological damages and loss of function of dopamine neurons precedes their demise and contributes to the early phases of Parkinsons disease. The presence of aberrant intercellular pathological inclusions of the protein -synuclein within ventral midbrain dopaminergic neurons is one of the cardinal features of Parkinsons disease. We employed multiple complementary approaches in molecular biology, electrophysiology, and live-cell imaging to investigate how excessive -synuclein levels alters multiple characteristics of dopaminergic neuronal dynamics and dopamine transmission prior to neuronal demise. These studies demonstrate that -synuclein dysregulation of D2 receptor autoinhibition contributes to the vulnerability of dopaminergic neurons, and that modulation thereof can ameliorate the resulting pathophysiology. These novel findings provide mechanistic insights in the insidious loss of dopaminergic function and neurons that characterize Parkinsons disease progression with significant therapeutic implications.

neuroscience↗

bioRxiv2021

Dopamine transporter is a master regulator of dopaminergic neural network connectivity

Dopaminergic neurons of the substantia nigra (SNC) and ventral tegmental area (VTA) exhibit spontaneous firing activity. The dopaminergic neurons in these regions have been shown to exhibit differential sensitivity to neuronal loss and psychostimulants targeting dopamine transporter. However, it remains unclear whether these regional differences scale beyond individual neuronal activity to regional neuronal networks. Here we utilized live-cell calcium imaging to show that network connectivity greatly differs between SNC and VTA regions with higher incidence of hub-like neurons in the VTA. Specifically, the frequency of hub-like neurons was significantly lower in SNC dopamine neurons than in the adjacent VTA, consistent with the interpretation of a lower network resilience to SNC neuronal loss. We tested this hypothesis when activity of an individual dopaminergic neuron is suppressed, through whole-cell patch clamp electrophysiology, in either SNC, or VTA networks. Neuronal loss in the SNC decreased network clustering, whereas the larger number of hub-neurons in the VTA overcompensated by increasing network clustering in the VTA. We further show that network properties are regulatable via a dopamine transporter but not a D2 receptor dependent mechanism. Our results demonstrate novel regulatory mechanisms of functional network topology in dopaminergic brain regions.

neuroscience↗

bioRxiv2019

Mechanism of manganese dysregulation of dopamine neuronal activity

Manganese exposure produces Parkinsons-like neurological symptoms, suggesting a selective dysregulation of dopamine transmission. It is unknown, however, how manganese accumulates in dopaminergic brain regions or how it regulates the activity of dopamine neurons. Our in vivo studies suggest manganese accumulates in dopamine neurons of the ventral tegmental area and substantia nigra via nifedipine-sensitive Ca2+ channels. Manganese produces a Ca2+ channel-mediated current which increases neurotransmitter release and rhythmic firing activity of dopamine neurons. These increases are prevented by blockade of Ca2+ channels and depend on downstream recruitment of Ca2+-activated potassium channels to the plasma membrane. These findings demonstrate the mechanism of manganese-induced dysfunction of dopamine neurons, and reveal a potential therapeutic target to attenuate manganese-induced impairment of dopamine transmission.\n\nSignificance StatementManganese is a trace element critical to many physiological processes. Overexposure to manganese is an environmental risk factor for neurological disorders such as a Parkinsons disease-like syndrome known as manganism. We found manganese dose-dependently increased the excitability of dopamine neurons, decreased the amplitude of action potentials, and narrowed action potential width. Blockade of Ca2+ channels prevented these effects as well as manganese accumulation in the mouse midbrain in vivo. Our data provide a potential mechanism for manganese-regulation of dopaminergic neurons.

cell biology↗