Medical Neurobiology Commons^™

Loss-Of-Function KCa2.2 Mutations Abolish Channel Activity, Young-Woo Nam, Mohammad Asikur Rahman, Grace Yang, Razan Orfali, Meng Cui, Miao Zhang

Pharmacy Faculty Articles and Research

Small-conductance Ca²⁺-activated potassium channels subtype 2 (K_Ca2.2, also called SK2) are operated exclusively by a Ca²⁺-calmodulin gating mechanism. Heterozygous genetic mutations of K_Ca2.2 channels have been associated with autosomal dominant neurodevelopmental disorders including cerebellar ataxia and tremor in humans and rodents. Taking advantage of these pathogenic mutations, we performed structure-function studies of the rat K_Ca2.2 channel. No measurable current was detected from HEK293 cells heterologously expressing these pathogenic K_Ca2.2 mutants. When co-expressed with the K_Ca2.2_WT channel, mutations of the pore-lining amino acid residues (I360M, Y362C, G363S …

Ciliogenesis Mechanisms Mediated By Pak2-Arl13b Signaling In Brain Endothelial Cells Is Responsible For Vascular Stability, Karthikeyan Thirugnanam, Shubhangi Prabhudesai, Emma Van Why, Amy Pan, Ankan Gupta, Koji Foreman, Rahima Zennadi, Kevin R. Rarick, Surya M. Nauli, Sean P. Palacek, Ramani Ramchandran

Pharmacy Faculty Articles and Research

In the developing vasculature, cilia, microtubule-based organelles that project from the apical surface of endothelial cells (ECs), have been identified to function cell autonomously to promote vascular integrity and prevent hemorrhage. To date, the underlying mechanisms of endothelial cilia formation (ciliogenesis) are not fully understood. Understanding these mechanisms is likely to open new avenues for targeting EC-cilia to promote vascular stability. Here, we hypothesized that brain ECs ciliogenesis and the underlying mechanisms that control this process are critical for brain vascular stability. To investigate this hypothesis, we utilized multiple approaches including developmental zebrafish model system and primary cell culture systems. …

Full- Versus Sub-Regional Quantification Of Amyloid-Beta Load On Mouse Brain Sections, Yuu Ohno, Riley Murphy, Matthew Choi, Weijun Ou, Rachita K. Sumbria

Pharmacy Faculty Articles and Research

Extracellular accumulation of amyloid-beta (Aβ) plaques is one of the major pathological hallmarks of Alzheimer's disease (AD), and is the target of the only FDA-approved disease-modifying treatment for AD. Accordingly, the use of transgenic mouse models that overexpress the amyloid precursor protein and thereby accumulate cerebral Aβ plaques are widely used to model human AD in mice. Therefore, immunoassays, including enzyme-linked immunosorbent assay (ELISA) and immunostaining, commonly measure the Aβ load in brain tissues derived from AD transgenic mice. Though the methods for Aβ detection and quantification have been well established and documented, the impact of the size of the …

A Comparison Of Calcium Aggregation And Ultracentrifugation Methods For The Preparation Of Rat Brain Microsomes For Drug Metabolism Studies, Barent N. Dubois, Farideh Amirrad, Reza Mehvar

Pharmacy Faculty Articles and Research

Preparation of brain microsomes by the calcium chloride aggregation method has been suggested as an alternative to the ultracentrifugation method. However, the effects of the calcium chloride concentration on the quality of the microsomal fractions are not known. Brain microsomes were prepared from the adult rat brains using the high-speed ultracentrifugation and low-speed calcium chloride (10–100 mM) aggregation methods (n = 5–6 per group). The microsomal protein yield (spectrometry), the cytochrome P450 reductase (CPR) activity (spectrometry), and the monooxygenase activities (UPLC-MS/MS) of CYP2D and CYP2E1 were determined in the obtained fractions. Increasing the concentrations of calcium chloride progressively increased …

Insights Into The Mechanisms Of Brain Endothelial Erythrophagocytosis, Jiahong Sun, Prema Vyas, Samar Mann, Annlia Paganini-Hill, Ane C. F. Nunes, Wei Ling Lau, David H. Cribbs, Mark J. Fisher, Rachita K. Sumbria

Pharmacy Faculty Articles and Research

The endothelial cells which form the inner cellular lining of the vasculature can act as non-professional phagocytes to ingest and remove emboli and aged/injured red blood cells (RBCs) from circulation. We previously demonstrated an erythrophagocytic phenotype of the brain endothelium for oxidatively stressed RBCs with subsequent migration of iron-rich RBCs and RBC degradation products across the brain endothelium in vivo and in vitro, in the absence of brain endothelium disruption. However, the mechanisms contributing to brain endothelial erythrophagocytosis are not well defined, and herein we elucidate the cellular mechanisms underlying brain endothelial erythrophagocytosis. Murine brain microvascular endothelial cells (bEnd.3 …

Acute And Chronic Dosing Of A High-Affinity Rat/Mouse Chimeric Transferrin Receptor Antibody In Mice, Demi M. Castellanos, Jiahong Sun, Joshua Yang, Weijun Ou, Alexander C. Zambon, William M. Pardridge, Rachita K. Sumbria

Pharmacy Faculty Articles and Research

Non-invasive brain delivery of neurotherapeutics is challenging due to the blood-brain barrier. The revived interest in transferrin receptor antibodies (TfRMAbs) as brain drug-delivery vectors has revealed the effect of dosing regimen, valency, and affinity on brain uptake, TfR expression, and Fc-effector function side effects. These studies have primarily used monovalent TfRMAbs with a human constant region following acute intravenous dosing in mice. The effects of a high-affinity bivalent TfRMAb with a murine constant region, without a fusion partner, following extravascular dosing in mice are, however, not well characterized. Here we elucidate the plasma pharmacokinetics and safety of a high-affinity bivalent …

Targeting The Transferrin Receptor To Develop Erythropoietin For Alzheimer’S Disease, Rachita K. Sumbria

Pharmacy Faculty Articles and Research

"Alzheimer’s disease (AD) is the sixth leading cause of death in the United States with approximately 5.8 million Americans currently living with AD. Due to the lack of a disease modifying treatment for AD and the aging baby boomer generation, this number is projected to grow to 13.8 million by 2050 (Gaugler et al., 2019). Amyloid-beta (Aβ) plaque accumulation, one of the major pathological hallmarks of AD, can begin > 20 years before clinical symptoms of AD. By the time AD is clinically diagnosed, neuronal loss and neuropathological lesions (Aβ plaques and tau tangles) have already occurred in many brain regions …

Effects Of Dabigatran In Mouse Models Of Aging And Cerebral Amyloid Angiopathy, Neethu Michael, Mher Mahoney Grigoryan, Kelley Kilday, Rachita K. Sumbria, Vitaly Vasilevko, Joanne Van Ryn, David H. Cribbs, Annlia Paganini-Hill, Mark J. Fisher

Pharmacy Faculty Articles and Research

Oral anticoagulants are a critical component of stroke prevention, but carry a risk of brain hemorrhage. These hemorrhagic complications tend to occur in elderly individuals, especially those with predisposing conditions such as cerebral amyloid angiopathy (CAA). Clinical evidence suggests that non-vitamin K antagonist oral anticoagulants are safer than traditional oral anticoagulants. We analyzed whether the anticoagulant dabigatran produces cerebral microhemorrhage (the pathological substrate of MRI-demonstrable cerebral microbleeds) or intracerebral hemorrhage in aged mice with and without hemorrhage-predisposing angiopathy. We studied aged (22 months old) Tg2576 (a model of CAA) and wild-type (WT) littermate mice. Mice received either dabigatran etexilate (DE) …

The Promises And Challenges Of Erythropoietin For Treatment Of Alzheimer's Disease, Jiahong Sun, Jan Michelle Martin, Victoria Vanderpoel, Rachita K. Sumbria

Pharmacy Faculty Articles and Research

Alzheimer’s disease (AD) is the most prevalent neurodegenerative disorder in the world, and intracellular neurofibrillary tangles and extracellular amyloid-beta protein deposits represent the major pathological hallmarks of the disease. Currently available treatments provide some symptomatic relief but fail to modify primary pathological processes that underlie the disease. Erythropoietin (EPO), a hematopoietic growth factor, acts primarily to stimulate erythroid cell production, and is clinically used to treat anemia. EPO has evolved as a therapeutic agent for neurodegeneration and has improved neurological outcomes and AD pathology in rodents. However, penetration of the blood–brain barrier (BBB) and negative hematopoietic effects are the two …

Hematologic Safety Of Chronic Brain-Penetrating Erythropoietin Dosing In App/Ps1 Mice, Jiahong Sun, Joshua Yang, Kathrine Whitman, Charlene Zhu, David H. Cribbs, Ruben J. Boado, William M. Pardridge, Rachita K. Sumbria

Pharmacy Faculty Articles and Research

Introduction: Low blood-brain barrier (BBB) penetration and hematopoietic side effects limit the therapeutic development of erythropoietin (EPO) for Alzheimer's disease (AD). A fusion protein of EPO and a chimeric monoclonal antibody targeting the mouse transferrin receptor (cTfRMAb) has been engineered. The latter drives EPO into the brain via receptor-mediated transcytosis across the BBB and increases its peripheral clearance to reduce hematopoietic side effects of EPO. Our previous work shows the protective effects of this BBB-penetrating EPO in AD mice but hematologic effects have not been studied. Herein, we investigate the hematologic safety and therapeutic effects of chronic cTfRMAb-EPO dosing, …

Brain Endothelial Erythrophagocytosis And Hemoglobin Transmigration Across Brain Endothelium: Implications For Pathogenesis Of Cerebral Microbleeds, Rudy Chang, Juan Castillo, Alexander C. Zambon, Tatiana B. Krasieva, Mark J. Fisher, Rachita K. Sumbria

Pharmacy Faculty Articles and Research

Peripheral endothelial cells are capable of erythrophagocytosis, but data on brain endothelial erythrophagocytosis are limited. We studied the relationship between brain endothelial erythrophagocytosis and cerebral microhemorrhage, the pathological substrate of MRI-demonstrable cerebral microbleeds. To demonstrate the erythrophagocytic capability of the brain endothelium, we studied the interactions between brain endothelial cells and red blood cells exposed to oxidative stress in vitro, and developed a new in vitro cerebral microbleeds model to study the subsequent passage of hemoglobin across the brain endothelial monolayer. Using multiple approaches, our results show marked brain endothelial erythrophagocytosis of red blood cells exposed to oxidative stress compared …

Aging Exacerbates Development Of Cerebral Microbleeds In A Mouse Model, Rachita K. Sumbria, Mher Mahoney Grigoryan, Vitaly Vasilevko, Annlia Paganini-Hill, Kelley Kilday, Ronald Kim, David H. Cribbs, Mark J. Fisher

Pharmacy Faculty Articles and Research

Background: Cerebral microhemorrhages (CMH) are commonly found in the aging brain. CMH are also the neuropathological substrate of cerebral microbleeds (CMB), demonstrated on brain MRI. Recent studies demonstrate the importance of systemic inflammation in CMH development, but the relationships among inflammation, aging, and CMH development are not well-defined. In the current study, we hypothesized that the pathogenesis of inflammation-induced CMH in mice differs by age.

Methods: We studied young (3 months, n = 20) and old (18 months, n = 25) C57BL/6 mice injected with low-dose lipopolysaccharide (LPS; 1 mg/kg, i.p.) or saline at 0, 6, and 24 …

Role Of Microglial Amylin Receptors In Mediating Beta Amyloid (Aβ)-Induced Inflammation, Wen Fu, Vlatka Vukojevic, Aarti Patel, Rania Soudy, David Mactavish, David Westaway, Kamaljit Kaur, Valeri Goncharuk, Jack Jhamandas

Pharmacy Faculty Articles and Research

Background: Neuroinflammation in the brain consequent to activation of microglia is viewed as an important component of Alzheimer’s disease (AD) pathology. Amyloid beta (Aβ) protein is known to activate microglia and unleash an inflammatory cascade that eventually results in neuronal dysfunction and death. In this study, we sought to identify the presence of amylin receptors on human fetal and murine microglia and determine whether Aβ activation of the inflammasome complex and subsequent release of cytokines is mediated through these receptors.

Methods: The presence of dimeric components of the amylin receptor (calcitonin receptor and receptor activity modifying protein 3) …

Trkb-Enhancer Facilitates Functional Recovery After Traumatic Brain Injury, John Marshall, Joanna Szmydynger-Chodobska, Mengia S. Rioult-Pedotti, Kara Lau, Andrea T. Chin, Siva K. Reddy Kotla, Rakesh Tiwari, Keykavous Parang, Steven W. Threlkeld, Adam Chodobski

Pharmacy Faculty Articles and Research

Brain-derived neurotrophic factor (BDNF), a key player in regulating synaptic strength and learning, is dysregulated following traumatic brain injury (TBI), suggesting that stimulation of BDNF signaling pathways may facilitate functional recovery. This study investigates whether CN2097, a peptidomimetic ligand which targets the synaptic scaffold protein, postsynaptic density protein 95, to enhance downstream signaling of tropomyosin-related kinase B, a receptor for BDNF, can improve neurological function after TBI. Moderate to severe TBI elicits neuroinflammation and c-Jun-N-terminal kinase (JNK) activation, which is associated with memory deficits. Here we demonstrate that CN2097 significantly reduces the post-traumatic synthesis of proinflammatory mediators and inhibits the …

Efficient Synthesis Of Cn2097 Using In Situ Activation Of Sulfhydryl Group, Shaban Darwish, Keykavous Parang, John Marshall, Dennis J. Goebel, Rakesh Tiwari

Pharmacy Faculty Articles and Research

CN2097 (R₇Cs-sCYK[KTE(β-Ala)]V) is a rationally designed peptidomimetic that shows effectiveness in preclinical models for the treatment of neurological disorders, such as Angelman syndrome, traumatic brain injury (TBI), and stroke. Because of its potential therapeutic activity for the treatment of human CNS disorders, there was an urgent need to develop an efficient strategy for large-scale synthesis of CN2097. The synthesis of CN2097 was accomplished using Fmoc/tBu solid phase chemistry in multiple steps. Two different peptide fragments (activated polyarginine peptide Npys-sCR₇ and CYK[KTE(β-Ala)]V) were synthesized, followed by solution phase coupling in water. Activation of the polyarginine (CR₇) …

Effects Of Phosphodiesterase 3a Modulation On Murine Cerebral Microhemorrhages, Rachita K. Sumbria, Vitaly Vasilevko, Mher Mahoney Grigoryan, Annlia Paganini-Hill, Ronald Kim, David H. Cribbs, Mark J. Fisher

Pharmacy Faculty Articles and Research

Background: Cerebral microbleeds (CMB) are MRI-demonstrable cerebral microhemorrhages (CMH) which commonly coexist with ischemic stroke. This creates a challenging therapeutic milieu, and a strategy that simultaneously protects the vessel wall and provides anti-thrombotic activity is an attractive potential approach. Phosphodiesterase 3A (PDE3A) inhibition is known to provide cerebral vessel wall protection combined with anti-thrombotic effects. As an initial step in the development of a therapy that simultaneously treats CMB and ischemic stroke, we hypothesized that inhibition of the PDE3A pathway is protective against CMH development.

Methods: The effect of PDE3A pathway inhibition was studied in the inflammation-induced and …

Tumor Necrosis Factor Α Inhibition For Alzheimer's Disease, Rudy Chang, Kei-Lwun Yee, Rachita K. Sumbria

Pharmacy Faculty Articles and Research

Tumor necrosis factor α (TNF-α) plays a central role in the pathophysiology of Alzheimer’s disease (AD). Food and Drug Administration–approved biologic TNF-α inhibitors are thus a potential treatment for AD, but they do not cross the blood-brain barrier. In this short review, we discuss the involvement of TNF-α in AD, challenges associated with the development of existing biologic TNF-α inhibitors for AD, and potential therapeutic strategies for targeting TNF-α for AD therapy.

A Murine Model Of Inflammation-Induced Cerebral Microbleeds, Rachita K. Sumbria, Mher Mahoney Grigoryan, Vitaly Vasilevko, Tatiana B. Krasieva, Miriam Scadeng, Alexandra K. Dvornikova, Annlia Paganini-Hill, Ronald Kim, David H. Cribbs, Mark J. Fisher

Pharmacy Faculty Articles and Research

Background: Cerebral microhemorrhages (CMH) are tiny deposits of blood degradation products in the brain and are pathological substrates of cerebral microbleeds. The existing CMH animal models are β-amyloid-, hypoxic brain injury-, or hypertension-induced. Recent evidence shows that CMH develop independently of hypoxic brain injury, hypertension, or amyloid deposition and CMH are associated with normal aging, sepsis, and neurodegenerative conditions. One common factor among the above pathologies is inflammation, and recent clinical studies show a link between systemic inflammation and CMH. Hence, we hypothesize that inflammation induces CMH development and thus, lipopolysaccharide (LPS)-induced CMH may be an appropriate model to …

Effects Of Pde4 Pathway Inhibition In Rat Experimental Stroke, Fan Yang, Rachita K. Sumbria, Dong Xue, Chuanhui Yu, Dan He, Shuo Liu, Annlia Paganini-Hill, Mark J. Fisher

Pharmacy Faculty Articles and Research

PURPOSE: The first genomewide association study indicated that variations in the phosphodiesterase 4D (PDE4D) gene confer risk for ischemic stroke. However, inconsistencies among the studies designed to replicate the findings indicated the need for further investigation to elucidate the role of the PDE4 pathway in stroke pathogenesis. Hence, we studied the effect of global inhibition of the PDE4 pathway in two rat experimental stroke models, using the PDE4 inhibitor rolipram. Further, the specific role of the PDE4D isoform in ischemic stroke pathogenesis was studied using PDE4D knockout rats in experimental stroke. METHODS: Rats were subjected to either the …

Pharmacokinetics And Brain Uptake In The Rhesus Monkey Of A Fusion Protein Of Arylsulfatase A And A Monoclonal Antibody Against The Human Insulin Receptor, Ruben J. Boado, Jeff Zhiqiang Lu, Eric Ka-Wai Hui, Rachita K. Sumbria, William M. Pardridge

Pharmacy Faculty Articles and Research

Metachromatic leukodystrophy (MLD) is a lysosomal storage disorder of the brain caused by mutations in the gene encoding the lysosomal sulfatase, arylsulfatase A (ASA). It is not possible to treat the brain in MLD with recombinant ASA, because the enzyme does not cross the blood-brain barrier (BBB). In the present investigation, a BBB-penetrating IgG-ASA fusion protein is engineered and expressed, where the ASA monomer is fused to the carboxyl terminus of each heavy chain of an engineered monoclonal antibody (MAb) against the human insulin receptor (HIR). The HIRMAb crosses the BBB via receptor-mediated transport on the endogenous BBB insulin receptor, …

Ginkgo Extract Egb761 Confers Neuroprotection By Reduction Of Glutamate Release In Ischemic Brain, Alexander Mdzinarishvili, Rachita K. Sumbria, Dorothee Lang, Jochen Klein

Pharmacy Faculty Articles and Research

Purpose - Ginkgo extract EGb761 has shown anti-edema and anti-ischemic effects in various experimental models. In the present study, we demonstrate neuroprotective effects of EGb761 in experimental stroke while monitoring brain metabolism by microdialysis. Methods - We have used oxygen-glucose deprivation in brain slices in vitro and middle cerebral artery occlusion (MCAO) in vivo to induce ischemia in mouse brain. We used microdialysis in mouse striatum to monitor extracellular concentrations of glucose and glutamate. Results - In vitro, EGb761 reduced ischemia-induced cell swelling in hippocampal slices by 60%. In vivo, administration of EGb761 (300 mg/kg) reduced cell degeneration and edema …

Neuroprotective Effects Of Bilobalide Are Accompanied By A Reduction Of Ischemia-Induced Glutamate Release In Vivo, Dorothee Lang, Cornelia Kiewert, Alexander Mdzinarishvili, Tina Maria Schwarzkopf, Rachita K. Sumbria, Joachim Hartmann, Jochen Klein

Pharmacy Faculty Articles and Research

Neuroprotective properties of bilobalide, a specific constituent of Ginkgo extracts, were tested in a mouse model of stroke. After 24 h of middle cerebral artery occlusion (MCAO), bilobalide reduced infarct areas in the core region (striatum) by 40–50% when given at 10 mg/kg 1 h prior to MCAO. Neuroprotection was also observed at lower doses, or when the drug was given 1 h past stroke induction. Sensorimotor function in mice was improved by bilobalide as shown by corner and chimney tests. When brain metabolism in situ was monitored by microdialysis, MCAO caused a rapid disappearance of extracellular glucose in the …

Unifying The Mathematical Modeling Of In Vivo And In Vitro Microdialysis, Peter M. Bungay, Rachita K. Sumbria, Ulrich Bickel

Pharmacy Faculty Articles and Research

A unifying approach is presented for developing mathematical models of microdialysis that are applicable to both in vitro and in vivo situations. Previous models for cylindrical probes have been limited by accommodating analyte diffusion through the surrounding medium in the radial direction only, i.e., perpendicular to the probe axis, or by incomplete incorporation of diffusion in the axial direction. Both radial and axial diffusion are included in the present work by employing two-dimensional finite element analysis. As in previous models, the nondimensional clearance modulus (Θ) represents the degree to which analyte clearance from the external medium influences diffusion through the …