Howard Mount | University of Toronto (original) (raw)

Papers by Howard Mount

Research paper thumbnail of Reduced tissue levels of biogenic amine transmitters were observed in wild-type malaria exposed, but not in C5a receptor knockout offspring, relative to unexposed controls

<p>Brain tissue level of <b>(a)</b> dopamine (DA) and <b>(b)</b> se... more <p>Brain tissue level of <b>(a)</b> dopamine (DA) and <b>(b)</b> serotonin (5HT) in the frontal cortex, <b>(c)</b> norepinephrine (NE) in the temporoparietal cortex and <b>(d)</b> serotonin (5HT) in the striatum, <b>(e)</b> norepinephrine and <b>(f)</b> serotonin in the cerebellum of wild type malaria exposed offspring (WT EX, n = 15) expressed relative to malaria unexposed wild type offspring and C5a receptor knockout unexposed offspring expressed relative to malaria unexposed <i>C5ar-/-</i> offspring (<i>C5ar-/-</i>EX, n = 15). <i>In utero</i> exposure to EMIP induced dysregulated messenger ribonucleic acid (mRNA) transcription level of BDNF in the fetal brain at gestational day 19. Fetal brain mRNA transcript level expressed as normalized copy number of <b>(g)</b> BDNF. *<i>P</i> < 0.05, **<i>P</i> < 0.01, ***<i>P</i> < 0.005; T-test (a-f) and one-way ANOVA (g). Box plots depict median, 95% confidence interval (box) and range (whiskers).</p

Research paper thumbnail of Viral alpha-synuclein knockdown prevents spreading synucleinopathy

Brain Communications, 2021

The accumulation of aggregated alpha-synuclein (α-syn) in Parkinson's disease, dementia with ... more The accumulation of aggregated alpha-synuclein (α-syn) in Parkinson's disease, dementia with Lewy bodies and multiple system atrophy is thought to involve a common prion-like mechanism, whereby misfolded α-syn provides a conformational template for further accumulation of pathological α-syn. We tested whether silencing α-syn gene expression could reduce native non-aggregated α-syn substrate and thereby disrupt the propagation of pathological α-syn initiated by seeding with synucleinopathy-affected mouse brain homogenates. Unilateral intracerebral injections of adeno-associated virus serotype-1 encoding microRNA targeting the α-syn gene reduced the extent and severity of both the α-syn pathology and motor deficits. Importantly, a moderate 50% reduction in α-syn was sufficient to prevent the spread of α-syn pathology to distal brain regions. Our study combines behavioural, immunohistochemical and biochemical data that strongly support α-syn knockdown gene therapy for synucleinopat...

Research paper thumbnail of Inhibitory and potentiating influences of glycine on N-methyl-D-aspartate-evoked dopamine release from cultured rat mesencephalic cells

Molecular pharmacology, 1991

In the presence of 1.2 mM Mg2+, glycine (30-100 microM) inhibited [3H]dopamine ([3H]DA) release s... more In the presence of 1.2 mM Mg2+, glycine (30-100 microM) inhibited [3H]dopamine ([3H]DA) release stimulated by N-methyl-D-aspartate (NMDA), in fetal rat mesencephalic cell cultures. Strychnine (1 microM) blocked the inhibitory effect of 100 microM glycine, indicating an action via strychnine-sensitive inhibitory glycine receptors. A higher concentration of strychnine (100 microM), by itself, inhibited NMDA-evoked [3H]DA release in the presence or absence of Mg2+. Spontaneous [3H]DA release and [3H]DA release stimulated by kainate and quisqualate were unaffected by glycine (less than or equal to 100 microM) or strychnine (less than or equal to 100 microM), indicating that glycine and strychnine modulatory effects are only associated with the NMDA receptor subtype. [3H]DA release evoked by K+ (56 mM) was unaffected by glycine (less than or equal to 100 microM) but was attenuated by a high concentration of strychnine (100 microM). In the absence of exogenous Mg2+, glycine (30-100 microM...

Research paper thumbnail of Interactions of excitatory amino acids with midbrain dopamine neurons

Schizophrenia Research, 1989

Research paper thumbnail of Mature Glycosylation and Trafficking of Nicastrin Modulate Its Binding to Presenilins

Journal of Biological Chemistry, 2002

Nicastrin is an integral component of the high molecular weight presenilin complexes that control... more Nicastrin is an integral component of the high molecular weight presenilin complexes that control proteolytic processing of the amyloid precursor protein and Notch. We report here that nicastrin is most probably a type 1 transmembrane glycoprotein that is expressed at moderate levels in the brain and in cultured neurons. Immunofluorescence studies demonstrate that nicastrin is localized in the endoplasmic reticulum, Golgi, and a discrete population of vesicles. Glycosidase analyses reveal that endogenous nicastrin undergoes a conventional, trafficking-dependent maturation process. However, when highly expressed in transfected cells, there is a disproportionate accumulation of the endo-␤-N-acetylglucosaminidase H-sensitive, immature form, with no significant increase in the levels of the fully mature species. Immunoprecipitation revealed that presenilin-1 interacts preferentially with mature nicastrin, suggesting that correct trafficking and co-localization of the presenilin complex components are essential for activity. These findings demonstrate that trafficking and post-translational modifications of nicastrin are tightly regulated processes that accompany the assembly of the active presenilin complexes that execute ␥-secretase cleavage. These results also underscore the caveat that simple overexpression of nicastrin in transfected cells may result in the accumulation of large amounts of the immature protein, which is apparently unable to assemble into the active complexes capable of processing amyloid precursor protein and Notch.

Research paper thumbnail of Mammalian Toxicology. Chapter 6

Research paper thumbnail of <i>In utero</i> exposure to EMIP induces a cognitive phenotype in offspring that is rescued by genetic and pharmacological blockade of C5a-C5a receptor signaling

<p><b>(a)</b> Maternal parasitaemia (day one to seven post infection) expressed... more <p><b>(a)</b> Maternal parasitaemia (day one to seven post infection) expressed as percent of infected red blood cells (iRBCs) per total red blood cells counted in wild-type (n = 5) and <i>C5ar-/-</i> dams (n = 5). <b>(b)</b> Weight from one to six weeks of age in wild-type malaria unexposed (n = 14) and wild-type malaria exposed offspring (n = 13), <i>C5ar-/-</i> malaria unexposed (n = 13) and <i>C5ar-/-</i> malaria exposed (n = 14) offspring. <b>(c)</b> Testing Performance (preference ratio) and <b>(d)</b> total exploration time of wild-type unexposed (WT UE, n = 14), wild-type malaria exposed (WT EX, n = 13), C5a receptor knockout unexposed (<i>C5ar-/-</i> UE, n = 13) and <i>C5ar-/-</i> malaria exposed (<i>C5ar-/-</i> EX, n = 14) offspring in the NOR test (<i>P</i> > 0.05). <b>(e)</b> Performance of WT UE (n = 15), WT EX (n = 15), <i>C5ar-/-</i> UE (n = 13) and <i>C5ar-/-</i> EX (n = 15) offspring in the TST test. (<b>f)</b> Testing Performance (preference ratio) and <b>(g)</b> total exploration time of wild-type unexposed (WT UE, n = 11), wild-type malaria exposed (WT EX, n = 12), C5a receptor knockout unexposed (<i>C5ar-/-</i> UE, n = 13) and <i>C5ar-/-</i> malaria exposed (<i>C5ar-/-</i> EX, n = 9) offspring tested at 20 weeks of age in the NOR test. <b>(h)</b> Performance of WT UE (n = 12), WT EX (n = 11), <i>C5ar-/-</i> UE (n = 12) and <i>C5ar-/-</i> EX (n = 10) offspring tested at 20 weeks of age in the TST test. <b>(i)</b> Testing Performance (preference ratio) and <b>(j)</b> total exploration time of UE offspring (n = 11), EX offspring (n = 11), EX offspring of control rabbit antisera treated dams (R-EX, n = 12) and EX offspring of C5a antisera treated dams (αC5a-EX, n = 12) offspring in the NOR test (<i>P</i> > 0.05 for total exploration time). <b>(k)</b> Performance of UE (n = 11), EX (n = 12), R-EX (n = 10) and αC5a EX (n = 12) offspring in the TST test. *<i>P</i> < 0.05, **<i>P</i> < 0.01, ***<i>P</i> < 0.005; one-way ANOVA and post-test. Data are presented as mean +/- SD.</p

Research paper thumbnail of <i>In utero</i> exposure to EMIP is associated with localized changes in tissue levels of major biogenic amines in offspring at 8 weeks of age

<p>Tissue levels of <b>(a)</b> dopamine, and <b>(b)</b> serotonin i... more <p>Tissue levels of <b>(a)</b> dopamine, and <b>(b)</b> serotonin in the frontal cortex, <b>(c)</b> norepinephrine in the temporoparietal cortex, <b>(d)</b> serotonin in the striatum, <b>(e)</b> serotonin and <b>(f)</b> norepinephrine in the cerebellum of unexposed (UE, n = 15) and malaria exposed (EX, n = 15) offspring. * <i>P < 0</i>.<i>05</i>, **<i>P</i> < 0.01, ***<i>P</i> < 0.005; T-Test. Box plots depict median, 95% confidence interval (box) and range (whiskers).</p

Research paper thumbnail of Micro-CT images of fetal cerebral vasculature at gestational day 18

<p>Maximum intensity projection renderings of the axial <b>(a)</b> and sagittal... more <p>Maximum intensity projection renderings of the axial <b>(a)</b> and sagittal <b>(b)</b> view of vasculature from wild-type unexposed offspring, axial <b>(c)</b> and sagittal <b>(d)</b> view of vasculature from wild-type malaria exposed offspring, axial <b>(e)</b> and sagittal <b>(f)</b> view of vasculature from <i>C5ar-/-</i> unexposed offspring and axial <b>(g)</b> and sagittal <b>(h)</b> view of vasculature from <i>C5ar-/-</i> malaria exposed offspring.</p

Research paper thumbnail of RESEARCH ARTICLE Experimental Malaria in Pregnancy Induces Neurocognitive Injury in Uninfected Offspring via a C5a-C5a Receptor Dependent Pathway

The in utero environment profoundly impacts childhood neurodevelopment and behaviour. A substanti... more The in utero environment profoundly impacts childhood neurodevelopment and behaviour. A substantial proportion of pregnancies in Africa are at risk of malaria in pregnancy (MIP) however the impact of in utero exposure to MIP on fetal neurodevelopment is unknown. Complement activation, in particular C5a, may contribute to neuropathology and adverse outcomes during MIP. We used an experimental model of MIP and standardized neurocog-nitive testing, MRI, micro-CT and HPLC analysis of neurotransmitter levels, to test the hypothesis that in utero exposure to malaria alters neurodevelopment through a C5a-C5aR dependent pathway. We show that malaria-exposed offspring have persistent neurocogni-tive deficits in memory and affective-like behaviour compared to unexposed controls. These deficits were associated with reduced regional brain levels of major biogenic amines and BDNF that were rescued by disruption of C5a-C5aR signaling using genetic and functional approaches. Our results demonstrat...

Research paper thumbnail of Acid

The low density lipoprotein receptor is not necessary

Research paper thumbnail of In utero exposure to protease inhibitor-based antiretroviral regimens delays growth and developmental milestones in mice

PLOS ONE, 2020

Antiretroviral therapy (ART) in pregnancy has dramatically reduced HIV vertical transmission rate... more Antiretroviral therapy (ART) in pregnancy has dramatically reduced HIV vertical transmission rates. Consequently, there is a growing number of children that are HIV exposed uninfected (CHEUs). Studies suggest that CHEUs exposed in utero to ART may experience developmental delays compared to their peers. We investigated the effects of in utero ART exposure on perinatal neurodevelopment in mice, through assessment of developmental milestones. Developmental milestone tests (parallel to reflex testing in human infants) are reflective of brain maturity and useful in predicting later behavioral outcomes. We hypothesized that ART in pregnancy alters the in utero environment and thereby alters developmental milestone outcomes in pups. Throughout pregnancy, dams were treated with boosted-atazanavir combined with either abacavir/lamivudine (ATV/r/ABC/3TC), or tenofovir/emtricitabine (ATV/r/TDF/FTC), or water as control. Pups were assessed daily for general somatic growth and on a battery of t...

Research paper thumbnail of A b peptide immunization reduces behavioural impairment and plaques in a model of Alzheimer ' s disease

NATURE | VOL 408 | 21/28 DECEMBER 2000 | www.nature.com 979 14. Chen, K. S. et al. Neurodegenerat... more NATURE | VOL 408 | 21/28 DECEMBER 2000 | www.nature.com 979 14. Chen, K. S. et al. Neurodegenerative Alzheimer-like pathology in PDAPP 717V!F transgenic mice. Prog. Brain Res. 117, 327±334 (1998). 15. Ennaceur, A. & Delacour, J. A new one-trial test for neurobiological studies of memory in rats. 1: Behavioral data. Behav. Brain Res. 31, 47±59 (1988). 16. Tang, Y. P. et al. Genetic enhancement of learning and memory in mice. Nature 401, 63±69 (1999). 17. Chapman, P. F. et al. Impaired synaptic plasticity and learning in aged amyloid precursor protein transgenic mice. Nature Neurosci. 2, 271±276 (1999). 18. Hsiao, K. et al. Correlative memory de®cits, Ab elevation, and amyloid plaques in transgenic mice. Science 274, 99±102 (1996). 19. Johnson-Wood, K. et al. Amyloid precursor protein processing and Ab42 deposition in a transgenic mouse model of Alzheimer disease. Proc. Natl Acad. Sci. USA 94, 1550±1555 (1997). 20. Dodart, J.-C., Mathis, C., Bales, K. R., Paul, S. M. & Ungerer, A. Ear...

Research paper thumbnail of Mount HTJ, Dreyfus CF, Black IBPurkinje cell survival is differentially regulated by metabotropic and ionotropic excitatory amino acid receptors. J Neurosci 13:3173-3179

The Journal of Neuroscience : The Official Journal of the Society for Neuroscience

ABSTRACT

Research paper thumbnail of Genetics, molecular biology, and animal modeling of Alzheimer’s disease

Alzheimer: 100 Years and Beyond, 2006

Research paper thumbnail of Regulation of Dopamine Release from Rat Mesencephalic Cell Cultures by Excitatory Amino Acids

Research paper thumbnail of APH-1 Interacts with Mature and Immature Forms of Presenilins and Nicastrin and May Play a Role in Maturation of Presenilin·Nicastrin Complexes

Journal of Biological Chemistry, 2002

Research paper thumbnail of Carboxyl-terminal Fragments of Alzheimer β-Amyloid Precursor Protein Accumulate in Restricted and Unpredicted Intracellular Compartments in Presenilin 1-deficient Cells

Journal of Biological Chemistry, 2000

Absence of functional presenilin 1 (PS1) protein leads to loss of ␥-secretase cleavage of the amy... more Absence of functional presenilin 1 (PS1) protein leads to loss of ␥-secretase cleavage of the amyloid precursor protein (␤APP), resulting in a dramatic reduction in amyloid ␤ peptide (A␤) production and accumulation of ␣or ␤-secretase-cleaved COOH-terminal fragments of ␤APP (␣-or ␤-CTFs). The major COOH-terminal fragment (CTF) in brain was identified as ␤APP-CTF-(11-98), which is consistent with the observation that cultured neurons generate primarily A␤-(11-40). In PS1 ؊/؊ murine neurons and fibroblasts expressing the loss-offunction PS1 D385A mutant, CTFs accumulated in the endoplasmic reticulum, Golgi, and lysosomes, but not late endosomes. There were some subtle differences in the subcellular distribution of CTFs in PS1 ؊/؊ neurons as compared with PS1 D385A mutant fibroblasts. However, there was no obvious redistribution of full-length ␤APP or of markers of other organelles in either mutant. Blockade of endoplasmic reticulum-to-Golgi trafficking indicated that in PS1 ؊/؊ neurons (as in normal cells) trafficking of ␤APP to the Golgi compartment is necessary before ␣and ␤-secretase cleavages occur. Thus, although we cannot exclude a specific role for PS1 in trafficking of CTFs, these data argue against a major role in general protein trafficking. These results are more compatible with a role for PS1 either as the actual ␥-secretase catalytic activity or in other functions indirectly related to ␥-secretase catalysis (e.g. an activator of ␥-secretase, a substrate adaptor for ␥-secretase, or delivery of ␥-secretase to ␤APP-containing compartments).

Research paper thumbnail of Unesterified docosahexaenoic acid is protective in neuroinflammation

Journal of Neurochemistry, 2013

Docosahexaenoic acid (22:6n-3) is the major brain n-3 polyunsaturated fatty acid and it is possib... more Docosahexaenoic acid (22:6n-3) is the major brain n-3 polyunsaturated fatty acid and it is possible that docosahexaenoic acid is anti-inflammatory in the brain as it is known to be in other tissues. Using a combination of models including the fat-1 transgenic mouse, chronic dietary n-3 polyunsaturated fatty acid modulation in transgenic and wild-type mice, and acute direct brain infusion, we demonstrated that unesterified docosahexaenoic acid attenuates neuroinflammation initiated by intracerebroventricular lipopolysaccharide. Hippocampal neuroinflammation was assessed by gene expression and immunohistochemistry. Furthermore, docosahexaenoic acid protected against lipopolysaccharide-induced neuronal loss. Acute intracerebroventricular infusion of unesterified docosahexaenoic acid or its 12/15-lipoxygenase product and precursor to protectins and resolvins, 17S-hydroperoxy-docosahexaenoic acid, mimics anti-neuroinflammatory aspects of chronically increased unesterified docosahexaenoic acid. LC-MS/MS revealed that neuroprotectin D1 and several other docosahexaenoic acid-derived specialized pro-resolving mediators are present in the hippocampus. Acute intracerebroventricular infusion of 17S-hydroperoxy-docosahexaenoic acid increases hippocampal neuroprotectin D1 levels concomitant to attenuating neuroinflammation. These results show that unesterified docosahexaenoic acid is protective in a lipopolysaccharide-initiated mouse model of acute neuroinflammation, at least in part, via its conversion to specialized pro-resolving mediators; these docosahexaenoic acid stores may provide novel targets for the prevention and treatment(s) of neurological disorders with a neuroinflammatory component. Our study shows that chronically increased brain unesterified DHA levels, but not solely phospholipid DHA levels, attenuate neuroinflammation. Similar attenuations occur with acute increases in brain unesterified DHA or 17S-HpDHA levels, highlighting the importance of an available pool of precursor unesterified DHA for the production of enzymatically derived specialized pro-resolving mediators that are critical in the regulation of neuroinflammation.

Research paper thumbnail of Decreased Brain-Derived Neurotrophic Factor Depends on Amyloid Aggregation State in Transgenic Mouse Models of Alzheimer's Disease

Journal of Neuroscience, 2009

Downregulation of brain-derived neurotrophic factor (BDNF) in the cortex occurs early in the prog... more Downregulation of brain-derived neurotrophic factor (BDNF) in the cortex occurs early in the progression of Alzheimer's disease (AD). Since BDNF plays a critical role in neuronal survival, synaptic plasticity, and memory, BDNF reduction may contribute to synaptic and cellular loss and memory deficits characteristic of AD. In vitro evidence suggests that amyloid-␤ (A␤) contributes to BDNF downregulation in AD, but the specific A␤ aggregation state responsible for this downregulation in vivo is unknown. In the present study, we examined cortical levels of BDNF mRNA in three different transgenic AD mouse models harboring mutations in APP resulting in A␤ overproduction, and in a genetic mouse model of Down syndrome. Two of the three A␤ transgenic strains (APP NLh and TgCRND8) exhibited significantly decreased cortical BDNF mRNA levels compared with wild-type mice, whereas neither the other strain (APP swe / PS-1) nor the Down syndrome mouse model (Ts65Dn) was affected. Only APP NLh and TgCRND8 mice expressed high A␤ 42 /A␤ 40 ratios and larger SDS-stable A␤ oligomers (ϳ115 kDa). TgCRND8 mice exhibited downregulation of BDNF transcripts III and IV; transcript IV is also downregulated in AD. Furthermore, in all transgenic mouse strains, there was a correlation between levels of large oligomers, A␤ 42 /A␤ 40 , and severity of BDNF decrease. These data show that the amount and species of A␤ vary among transgenic mouse models of AD and are negatively correlated with BDNF levels. These findings also suggest that the effect of A␤ on decreased BDNF expression is specific to the aggregation state of A␤ and is dependent on large oligomers.

Research paper thumbnail of Reduced tissue levels of biogenic amine transmitters were observed in wild-type malaria exposed, but not in C5a receptor knockout offspring, relative to unexposed controls

<p>Brain tissue level of <b>(a)</b> dopamine (DA) and <b>(b)</b> se... more <p>Brain tissue level of <b>(a)</b> dopamine (DA) and <b>(b)</b> serotonin (5HT) in the frontal cortex, <b>(c)</b> norepinephrine (NE) in the temporoparietal cortex and <b>(d)</b> serotonin (5HT) in the striatum, <b>(e)</b> norepinephrine and <b>(f)</b> serotonin in the cerebellum of wild type malaria exposed offspring (WT EX, n = 15) expressed relative to malaria unexposed wild type offspring and C5a receptor knockout unexposed offspring expressed relative to malaria unexposed <i>C5ar-/-</i> offspring (<i>C5ar-/-</i>EX, n = 15). <i>In utero</i> exposure to EMIP induced dysregulated messenger ribonucleic acid (mRNA) transcription level of BDNF in the fetal brain at gestational day 19. Fetal brain mRNA transcript level expressed as normalized copy number of <b>(g)</b> BDNF. *<i>P</i> < 0.05, **<i>P</i> < 0.01, ***<i>P</i> < 0.005; T-test (a-f) and one-way ANOVA (g). Box plots depict median, 95% confidence interval (box) and range (whiskers).</p

Research paper thumbnail of Viral alpha-synuclein knockdown prevents spreading synucleinopathy

Brain Communications, 2021

The accumulation of aggregated alpha-synuclein (α-syn) in Parkinson's disease, dementia with ... more The accumulation of aggregated alpha-synuclein (α-syn) in Parkinson's disease, dementia with Lewy bodies and multiple system atrophy is thought to involve a common prion-like mechanism, whereby misfolded α-syn provides a conformational template for further accumulation of pathological α-syn. We tested whether silencing α-syn gene expression could reduce native non-aggregated α-syn substrate and thereby disrupt the propagation of pathological α-syn initiated by seeding with synucleinopathy-affected mouse brain homogenates. Unilateral intracerebral injections of adeno-associated virus serotype-1 encoding microRNA targeting the α-syn gene reduced the extent and severity of both the α-syn pathology and motor deficits. Importantly, a moderate 50% reduction in α-syn was sufficient to prevent the spread of α-syn pathology to distal brain regions. Our study combines behavioural, immunohistochemical and biochemical data that strongly support α-syn knockdown gene therapy for synucleinopat...

Research paper thumbnail of Inhibitory and potentiating influences of glycine on N-methyl-D-aspartate-evoked dopamine release from cultured rat mesencephalic cells

Molecular pharmacology, 1991

In the presence of 1.2 mM Mg2+, glycine (30-100 microM) inhibited [3H]dopamine ([3H]DA) release s... more In the presence of 1.2 mM Mg2+, glycine (30-100 microM) inhibited [3H]dopamine ([3H]DA) release stimulated by N-methyl-D-aspartate (NMDA), in fetal rat mesencephalic cell cultures. Strychnine (1 microM) blocked the inhibitory effect of 100 microM glycine, indicating an action via strychnine-sensitive inhibitory glycine receptors. A higher concentration of strychnine (100 microM), by itself, inhibited NMDA-evoked [3H]DA release in the presence or absence of Mg2+. Spontaneous [3H]DA release and [3H]DA release stimulated by kainate and quisqualate were unaffected by glycine (less than or equal to 100 microM) or strychnine (less than or equal to 100 microM), indicating that glycine and strychnine modulatory effects are only associated with the NMDA receptor subtype. [3H]DA release evoked by K+ (56 mM) was unaffected by glycine (less than or equal to 100 microM) but was attenuated by a high concentration of strychnine (100 microM). In the absence of exogenous Mg2+, glycine (30-100 microM...

Research paper thumbnail of Interactions of excitatory amino acids with midbrain dopamine neurons

Schizophrenia Research, 1989

Research paper thumbnail of Mature Glycosylation and Trafficking of Nicastrin Modulate Its Binding to Presenilins

Journal of Biological Chemistry, 2002

Nicastrin is an integral component of the high molecular weight presenilin complexes that control... more Nicastrin is an integral component of the high molecular weight presenilin complexes that control proteolytic processing of the amyloid precursor protein and Notch. We report here that nicastrin is most probably a type 1 transmembrane glycoprotein that is expressed at moderate levels in the brain and in cultured neurons. Immunofluorescence studies demonstrate that nicastrin is localized in the endoplasmic reticulum, Golgi, and a discrete population of vesicles. Glycosidase analyses reveal that endogenous nicastrin undergoes a conventional, trafficking-dependent maturation process. However, when highly expressed in transfected cells, there is a disproportionate accumulation of the endo-␤-N-acetylglucosaminidase H-sensitive, immature form, with no significant increase in the levels of the fully mature species. Immunoprecipitation revealed that presenilin-1 interacts preferentially with mature nicastrin, suggesting that correct trafficking and co-localization of the presenilin complex components are essential for activity. These findings demonstrate that trafficking and post-translational modifications of nicastrin are tightly regulated processes that accompany the assembly of the active presenilin complexes that execute ␥-secretase cleavage. These results also underscore the caveat that simple overexpression of nicastrin in transfected cells may result in the accumulation of large amounts of the immature protein, which is apparently unable to assemble into the active complexes capable of processing amyloid precursor protein and Notch.

Research paper thumbnail of Mammalian Toxicology. Chapter 6

Research paper thumbnail of <i>In utero</i> exposure to EMIP induces a cognitive phenotype in offspring that is rescued by genetic and pharmacological blockade of C5a-C5a receptor signaling

<p><b>(a)</b> Maternal parasitaemia (day one to seven post infection) expressed... more <p><b>(a)</b> Maternal parasitaemia (day one to seven post infection) expressed as percent of infected red blood cells (iRBCs) per total red blood cells counted in wild-type (n = 5) and <i>C5ar-/-</i> dams (n = 5). <b>(b)</b> Weight from one to six weeks of age in wild-type malaria unexposed (n = 14) and wild-type malaria exposed offspring (n = 13), <i>C5ar-/-</i> malaria unexposed (n = 13) and <i>C5ar-/-</i> malaria exposed (n = 14) offspring. <b>(c)</b> Testing Performance (preference ratio) and <b>(d)</b> total exploration time of wild-type unexposed (WT UE, n = 14), wild-type malaria exposed (WT EX, n = 13), C5a receptor knockout unexposed (<i>C5ar-/-</i> UE, n = 13) and <i>C5ar-/-</i> malaria exposed (<i>C5ar-/-</i> EX, n = 14) offspring in the NOR test (<i>P</i> > 0.05). <b>(e)</b> Performance of WT UE (n = 15), WT EX (n = 15), <i>C5ar-/-</i> UE (n = 13) and <i>C5ar-/-</i> EX (n = 15) offspring in the TST test. (<b>f)</b> Testing Performance (preference ratio) and <b>(g)</b> total exploration time of wild-type unexposed (WT UE, n = 11), wild-type malaria exposed (WT EX, n = 12), C5a receptor knockout unexposed (<i>C5ar-/-</i> UE, n = 13) and <i>C5ar-/-</i> malaria exposed (<i>C5ar-/-</i> EX, n = 9) offspring tested at 20 weeks of age in the NOR test. <b>(h)</b> Performance of WT UE (n = 12), WT EX (n = 11), <i>C5ar-/-</i> UE (n = 12) and <i>C5ar-/-</i> EX (n = 10) offspring tested at 20 weeks of age in the TST test. <b>(i)</b> Testing Performance (preference ratio) and <b>(j)</b> total exploration time of UE offspring (n = 11), EX offspring (n = 11), EX offspring of control rabbit antisera treated dams (R-EX, n = 12) and EX offspring of C5a antisera treated dams (αC5a-EX, n = 12) offspring in the NOR test (<i>P</i> > 0.05 for total exploration time). <b>(k)</b> Performance of UE (n = 11), EX (n = 12), R-EX (n = 10) and αC5a EX (n = 12) offspring in the TST test. *<i>P</i> < 0.05, **<i>P</i> < 0.01, ***<i>P</i> < 0.005; one-way ANOVA and post-test. Data are presented as mean +/- SD.</p

Research paper thumbnail of <i>In utero</i> exposure to EMIP is associated with localized changes in tissue levels of major biogenic amines in offspring at 8 weeks of age

<p>Tissue levels of <b>(a)</b> dopamine, and <b>(b)</b> serotonin i... more <p>Tissue levels of <b>(a)</b> dopamine, and <b>(b)</b> serotonin in the frontal cortex, <b>(c)</b> norepinephrine in the temporoparietal cortex, <b>(d)</b> serotonin in the striatum, <b>(e)</b> serotonin and <b>(f)</b> norepinephrine in the cerebellum of unexposed (UE, n = 15) and malaria exposed (EX, n = 15) offspring. * <i>P < 0</i>.<i>05</i>, **<i>P</i> < 0.01, ***<i>P</i> < 0.005; T-Test. Box plots depict median, 95% confidence interval (box) and range (whiskers).</p

Research paper thumbnail of Micro-CT images of fetal cerebral vasculature at gestational day 18

<p>Maximum intensity projection renderings of the axial <b>(a)</b> and sagittal... more <p>Maximum intensity projection renderings of the axial <b>(a)</b> and sagittal <b>(b)</b> view of vasculature from wild-type unexposed offspring, axial <b>(c)</b> and sagittal <b>(d)</b> view of vasculature from wild-type malaria exposed offspring, axial <b>(e)</b> and sagittal <b>(f)</b> view of vasculature from <i>C5ar-/-</i> unexposed offspring and axial <b>(g)</b> and sagittal <b>(h)</b> view of vasculature from <i>C5ar-/-</i> malaria exposed offspring.</p

Research paper thumbnail of RESEARCH ARTICLE Experimental Malaria in Pregnancy Induces Neurocognitive Injury in Uninfected Offspring via a C5a-C5a Receptor Dependent Pathway

The in utero environment profoundly impacts childhood neurodevelopment and behaviour. A substanti... more The in utero environment profoundly impacts childhood neurodevelopment and behaviour. A substantial proportion of pregnancies in Africa are at risk of malaria in pregnancy (MIP) however the impact of in utero exposure to MIP on fetal neurodevelopment is unknown. Complement activation, in particular C5a, may contribute to neuropathology and adverse outcomes during MIP. We used an experimental model of MIP and standardized neurocog-nitive testing, MRI, micro-CT and HPLC analysis of neurotransmitter levels, to test the hypothesis that in utero exposure to malaria alters neurodevelopment through a C5a-C5aR dependent pathway. We show that malaria-exposed offspring have persistent neurocogni-tive deficits in memory and affective-like behaviour compared to unexposed controls. These deficits were associated with reduced regional brain levels of major biogenic amines and BDNF that were rescued by disruption of C5a-C5aR signaling using genetic and functional approaches. Our results demonstrat...

Research paper thumbnail of Acid

The low density lipoprotein receptor is not necessary

Research paper thumbnail of In utero exposure to protease inhibitor-based antiretroviral regimens delays growth and developmental milestones in mice

PLOS ONE, 2020

Antiretroviral therapy (ART) in pregnancy has dramatically reduced HIV vertical transmission rate... more Antiretroviral therapy (ART) in pregnancy has dramatically reduced HIV vertical transmission rates. Consequently, there is a growing number of children that are HIV exposed uninfected (CHEUs). Studies suggest that CHEUs exposed in utero to ART may experience developmental delays compared to their peers. We investigated the effects of in utero ART exposure on perinatal neurodevelopment in mice, through assessment of developmental milestones. Developmental milestone tests (parallel to reflex testing in human infants) are reflective of brain maturity and useful in predicting later behavioral outcomes. We hypothesized that ART in pregnancy alters the in utero environment and thereby alters developmental milestone outcomes in pups. Throughout pregnancy, dams were treated with boosted-atazanavir combined with either abacavir/lamivudine (ATV/r/ABC/3TC), or tenofovir/emtricitabine (ATV/r/TDF/FTC), or water as control. Pups were assessed daily for general somatic growth and on a battery of t...

Research paper thumbnail of A b peptide immunization reduces behavioural impairment and plaques in a model of Alzheimer ' s disease

NATURE | VOL 408 | 21/28 DECEMBER 2000 | www.nature.com 979 14. Chen, K. S. et al. Neurodegenerat... more NATURE | VOL 408 | 21/28 DECEMBER 2000 | www.nature.com 979 14. Chen, K. S. et al. Neurodegenerative Alzheimer-like pathology in PDAPP 717V!F transgenic mice. Prog. Brain Res. 117, 327±334 (1998). 15. Ennaceur, A. & Delacour, J. A new one-trial test for neurobiological studies of memory in rats. 1: Behavioral data. Behav. Brain Res. 31, 47±59 (1988). 16. Tang, Y. P. et al. Genetic enhancement of learning and memory in mice. Nature 401, 63±69 (1999). 17. Chapman, P. F. et al. Impaired synaptic plasticity and learning in aged amyloid precursor protein transgenic mice. Nature Neurosci. 2, 271±276 (1999). 18. Hsiao, K. et al. Correlative memory de®cits, Ab elevation, and amyloid plaques in transgenic mice. Science 274, 99±102 (1996). 19. Johnson-Wood, K. et al. Amyloid precursor protein processing and Ab42 deposition in a transgenic mouse model of Alzheimer disease. Proc. Natl Acad. Sci. USA 94, 1550±1555 (1997). 20. Dodart, J.-C., Mathis, C., Bales, K. R., Paul, S. M. & Ungerer, A. Ear...

Research paper thumbnail of Mount HTJ, Dreyfus CF, Black IBPurkinje cell survival is differentially regulated by metabotropic and ionotropic excitatory amino acid receptors. J Neurosci 13:3173-3179

The Journal of Neuroscience : The Official Journal of the Society for Neuroscience

ABSTRACT

Research paper thumbnail of Genetics, molecular biology, and animal modeling of Alzheimer’s disease

Alzheimer: 100 Years and Beyond, 2006

Research paper thumbnail of Regulation of Dopamine Release from Rat Mesencephalic Cell Cultures by Excitatory Amino Acids

Research paper thumbnail of APH-1 Interacts with Mature and Immature Forms of Presenilins and Nicastrin and May Play a Role in Maturation of Presenilin·Nicastrin Complexes

Journal of Biological Chemistry, 2002

Research paper thumbnail of Carboxyl-terminal Fragments of Alzheimer β-Amyloid Precursor Protein Accumulate in Restricted and Unpredicted Intracellular Compartments in Presenilin 1-deficient Cells

Journal of Biological Chemistry, 2000

Absence of functional presenilin 1 (PS1) protein leads to loss of ␥-secretase cleavage of the amy... more Absence of functional presenilin 1 (PS1) protein leads to loss of ␥-secretase cleavage of the amyloid precursor protein (␤APP), resulting in a dramatic reduction in amyloid ␤ peptide (A␤) production and accumulation of ␣or ␤-secretase-cleaved COOH-terminal fragments of ␤APP (␣-or ␤-CTFs). The major COOH-terminal fragment (CTF) in brain was identified as ␤APP-CTF-(11-98), which is consistent with the observation that cultured neurons generate primarily A␤-(11-40). In PS1 ؊/؊ murine neurons and fibroblasts expressing the loss-offunction PS1 D385A mutant, CTFs accumulated in the endoplasmic reticulum, Golgi, and lysosomes, but not late endosomes. There were some subtle differences in the subcellular distribution of CTFs in PS1 ؊/؊ neurons as compared with PS1 D385A mutant fibroblasts. However, there was no obvious redistribution of full-length ␤APP or of markers of other organelles in either mutant. Blockade of endoplasmic reticulum-to-Golgi trafficking indicated that in PS1 ؊/؊ neurons (as in normal cells) trafficking of ␤APP to the Golgi compartment is necessary before ␣and ␤-secretase cleavages occur. Thus, although we cannot exclude a specific role for PS1 in trafficking of CTFs, these data argue against a major role in general protein trafficking. These results are more compatible with a role for PS1 either as the actual ␥-secretase catalytic activity or in other functions indirectly related to ␥-secretase catalysis (e.g. an activator of ␥-secretase, a substrate adaptor for ␥-secretase, or delivery of ␥-secretase to ␤APP-containing compartments).

Research paper thumbnail of Unesterified docosahexaenoic acid is protective in neuroinflammation

Journal of Neurochemistry, 2013

Docosahexaenoic acid (22:6n-3) is the major brain n-3 polyunsaturated fatty acid and it is possib... more Docosahexaenoic acid (22:6n-3) is the major brain n-3 polyunsaturated fatty acid and it is possible that docosahexaenoic acid is anti-inflammatory in the brain as it is known to be in other tissues. Using a combination of models including the fat-1 transgenic mouse, chronic dietary n-3 polyunsaturated fatty acid modulation in transgenic and wild-type mice, and acute direct brain infusion, we demonstrated that unesterified docosahexaenoic acid attenuates neuroinflammation initiated by intracerebroventricular lipopolysaccharide. Hippocampal neuroinflammation was assessed by gene expression and immunohistochemistry. Furthermore, docosahexaenoic acid protected against lipopolysaccharide-induced neuronal loss. Acute intracerebroventricular infusion of unesterified docosahexaenoic acid or its 12/15-lipoxygenase product and precursor to protectins and resolvins, 17S-hydroperoxy-docosahexaenoic acid, mimics anti-neuroinflammatory aspects of chronically increased unesterified docosahexaenoic acid. LC-MS/MS revealed that neuroprotectin D1 and several other docosahexaenoic acid-derived specialized pro-resolving mediators are present in the hippocampus. Acute intracerebroventricular infusion of 17S-hydroperoxy-docosahexaenoic acid increases hippocampal neuroprotectin D1 levels concomitant to attenuating neuroinflammation. These results show that unesterified docosahexaenoic acid is protective in a lipopolysaccharide-initiated mouse model of acute neuroinflammation, at least in part, via its conversion to specialized pro-resolving mediators; these docosahexaenoic acid stores may provide novel targets for the prevention and treatment(s) of neurological disorders with a neuroinflammatory component. Our study shows that chronically increased brain unesterified DHA levels, but not solely phospholipid DHA levels, attenuate neuroinflammation. Similar attenuations occur with acute increases in brain unesterified DHA or 17S-HpDHA levels, highlighting the importance of an available pool of precursor unesterified DHA for the production of enzymatically derived specialized pro-resolving mediators that are critical in the regulation of neuroinflammation.

Research paper thumbnail of Decreased Brain-Derived Neurotrophic Factor Depends on Amyloid Aggregation State in Transgenic Mouse Models of Alzheimer's Disease

Journal of Neuroscience, 2009

Downregulation of brain-derived neurotrophic factor (BDNF) in the cortex occurs early in the prog... more Downregulation of brain-derived neurotrophic factor (BDNF) in the cortex occurs early in the progression of Alzheimer's disease (AD). Since BDNF plays a critical role in neuronal survival, synaptic plasticity, and memory, BDNF reduction may contribute to synaptic and cellular loss and memory deficits characteristic of AD. In vitro evidence suggests that amyloid-␤ (A␤) contributes to BDNF downregulation in AD, but the specific A␤ aggregation state responsible for this downregulation in vivo is unknown. In the present study, we examined cortical levels of BDNF mRNA in three different transgenic AD mouse models harboring mutations in APP resulting in A␤ overproduction, and in a genetic mouse model of Down syndrome. Two of the three A␤ transgenic strains (APP NLh and TgCRND8) exhibited significantly decreased cortical BDNF mRNA levels compared with wild-type mice, whereas neither the other strain (APP swe / PS-1) nor the Down syndrome mouse model (Ts65Dn) was affected. Only APP NLh and TgCRND8 mice expressed high A␤ 42 /A␤ 40 ratios and larger SDS-stable A␤ oligomers (ϳ115 kDa). TgCRND8 mice exhibited downregulation of BDNF transcripts III and IV; transcript IV is also downregulated in AD. Furthermore, in all transgenic mouse strains, there was a correlation between levels of large oligomers, A␤ 42 /A␤ 40 , and severity of BDNF decrease. These data show that the amount and species of A␤ vary among transgenic mouse models of AD and are negatively correlated with BDNF levels. These findings also suggest that the effect of A␤ on decreased BDNF expression is specific to the aggregation state of A␤ and is dependent on large oligomers.