9. Cross, DJ; Huber, BR; Silverman, MA; Cline, MM; Gill, TB; Cross, CG; Cook, DG; Minoshima, S. (2021) Intranasal Paclitaxel Alters Alzheimer's Disease Phenotypic Features in 3xTg-AD Mice.J. Alzheimers Dis. 83: 379-394 Intranasal Paclitaxel Alters Alzheimer's Disease Phenotypic Features in 3xTg-AD Mice
Alzheimer's disease; axonal transport; cognitive impairment; intranasal drug administration; microtubule stabilization
Background: Microtubule stabilizing drugs, commonly used as anti-cancer therapeutics, have been proposed for treatment of Alzheimer's disease (AD); however, many do not cross the blood-brain barrier. Objective: This research investigated if paclitaxel (PTX) delivered via the intranasal (IN) route could alter the phenotypic progression of AD in 3xTg-AD mice. Methods: We administered intranasal PTX in 3XTg-AD mice (3xTg-AD n = 15, 10 weeks and n = 10, 44 weeks, PTX: 0.6 mg/kg or 0.9%saline (SAL)) at 2-week intervals. After treatment, 3XTg-AD mice underwent manganese-enhanced magnetic resonance imaging to measure in vivo axonal transport. In a separate 3XTg-AD cohort, PTX-treated mice were tested in a radial water tread maze at 52 weeks of age after four treatments, and at 72 weeks of age, anxiety was assessed by an elevated-plus maze after 14 total treatments. Results: PTX increased axonal transport rates in treated 3XTg-AD compared to controls (p <= 0.003). Further investigation using an in vitro neuron model of A beta-induced axonal transport disruption confirmed PTX prevented axonal transport deficits. Confocal microscopy after treatment found fewer phospho-tau containing neurons (5.25 +/- 3.8 versus 8.33 +/- 2.5, p < 0.04) in the CA1, altered microglia, and reduced reactive astrocytes. PTX improved performance of 3xTg-AD on the water tread maze compared to controls and not significantly different from WT (Day 5, 143.8 +/- 43 versus 91.5 +/- 77s and Day 12, 138.3 +/- 52 versus 107.7 +/- 75s for SAL versus PTX). Elevated plus maze revealed that PTX-treated 3xTg-AD mice spent more time exploring open arms (Open arm 129.1 +/- 80 versus 20.9 +/- 31s for PTX versus SAL, p <= 0.05). Conclusion: Taken collectively, these findings indicate that intranasal-administered microtubule-stabilizing drugs may offer a potential therapeutic option for treating AD. DOI PubMed
8. Gomes, LMF; Mahammed, A; Prosser, KE; Smith, JR; Silverman, MA; Walsby, CJ; Gross, Z; Storr, T. (2019) A catalytic antioxidant for limiting amyloid-beta peptide aggregation and reactive oxygen species generation.Chem. Sci. 10 A catalytic antioxidant for limiting amyloid-beta peptide aggregation and reactive oxygen species generation
Alzheimer's disease (AD) is a multifaceted disease that is characterized by increased oxidative stress, metal-ion dysregulation, and the formation of intracellular neurofibrillary tangles and extracellular amyloid-beta (A beta) aggregates. In this work we report the large affinity binding of the iron(III) 2,17-bis-sulfonato-5,10,15-tris(pentafluorophenyl)corrole complex FeL1 to the A beta peptide (K-d similar to 10(-7)) and the ability of the bound FeL1 to act as a catalytic antioxidant in both the presence and absence of Cu(II) ions. Specific findings are that: (a) an A beta histidine residue binds axially to FeL1; (b) that the resulting adduct is an efficient catalase; (c) this interaction restricts the formation of high molecular weight peptide aggregates. UV-Vis and electron paramagnetic resonance (EPR) studies show that although the binding of FeL1 does not influence the A beta-Cu(II) interaction (K-d similar to 10(-10)), bound FeL1 still acts as an antioxidant thereby significantly limiting reactive oxygen species (ROS) generation from A beta-Cu. Overall, FeL1 is shown to bind to the A beta peptide, and modulate peptide aggregation. In addition, FeL1 forms a ternary species with A beta-Cu(II) and impedes ROS generation, thus showing the promise of discrete metal complexes to limit the toxicity pathways of the A beta peptide. DOI PubMed
7. Robinson, BJ; Stanisavljevic, B; Silverman, MA; Scalettar, BA. (2016) Stochastic Subcellular Organization of Dense-Core Vesicles Revealed by Point Pattern Analysis.Biophysical Journal 111: 852-863 Stochastic Subcellular Organization of Dense-Core Vesicles Revealed by Point Pattern Analysis
Dense-core vesicles (DCVs) are regulated secretory organelles found in many types of neurons. In neurons of the hippocampus, their cargo includes proteins that mediate several pivotal processes, including differentiation and synaptic plasticity. Motivated by interest in DCV distribution and its impact on cargo action, we have used fluorescence microscopy and statistical analysis to develop a quantitative model of the subcellular organization of DCVs in hippocampal neurons that are spontaneously active (their most prevalent state). We also have tested the functionally motivated hypothesis that these organelles are synaptically enriched. Variance-to-mean ratio, frequency distribution, and Moran's autocorrelation analyses reveal that DCV distribution along shafts, and within synapses, follows Poisson statistics, establishing that stochastically dictated organization sustains cargo function. Occupancy in boutons exceeds that at nearby extrasynaptic axonal sites by approximately threefold, revealing significant local presynaptic enrichment. Widespread stochastic organization is consistent with the emerging functional importance of synaptically and extrasynaptically localized DCVs. Presynaptic enrichment is consistent with the established importance of protecting presynaptic sites from depletion of DCV cargo. These results enhance understanding of the link between DCV organization and mechanisms of cargo action, and they reinforce the emerging theme that randomness is a prevalent aspect of synaptic organization and composition. DOI
6. Cavolo, SL; Zhou, CM; Ketcham, SA; Suzuki, MM; Ukalovic, K; Silverman, MA; Schroer, TA; Levitan, ES. (2015) Mycalolide B dissociates dynactin and abolishes retrograde axonal transport of dense-core vesicles.Molecular Biology of the Cell 26: 2664-2672 Mycalolide B dissociates dynactin and abolishes retrograde axonal transport of dense-core vesicles
Axonal transport is critical for maintaining synaptic transmission. Of interest, anterograde and retrograde axonal transport appear to be interdependent, as perturbing one directional motor often impairs movement in the opposite direction. Here live imaging of Drosophila and hippocampal neuron dense-core vesicles (DCVs) containing a neuropeptide or brain-derived neurotrophic factor shows that the F-actin depolymerizing macrolide toxin mycalolide B (MB) rapidly and selectively abolishes retrograde, but not anterograde, transport in the axon and the nerve terminal. Latrunculin A does not mimic MB, demonstrating that F-actin depolymerization is not responsible for unidirectional transport inhibition. Given that dynactin initiates retrograde transport and that amino acid sequences implicated in macrolide toxin binding are found in the dynactin component actin-related protein 1, we examined dynactin integrity. Remarkably, cell extract and purified protein experiments show that MB induces disassembly of the dynactin complex. Thus imaging selective retrograde transport inhibition led to the discovery of a small-molecule dynactin disruptor. The rapid unidirectional inhibition by MB suggests that dynactin is absolutely required for retrograde DCV transport but does not directly facilitate ongoing anterograde DCV transport in the axon or nerve terminal. More generally, MB's effects bolster the conclusion that anterograde and retrograde axonal transport are not necessarily interdependent. DOI
5. Ramser, EM; Gan, KJ; Decker, H; Fan, EY; Suzuki, MM; Ferreira, ST; Silverman, MA. (2013) Amyloid-beta oligomers induce tau-independent disruption of BDNF axonal transport via calcineurin activation in cultured hippocampal neurons.Mol. Biol. Cell 24: 2494-2505 Amyloid-beta oligomers induce tau-independent disruption of BDNF axonal transport via calcineurin activation in cultured hippocampal neurons
Disruption of fast axonal transport (FAT) is an early pathological event in Alzheimer's disease (AD). Soluble amyloid-beta oligomers (A beta Os), increasingly recognized as proximal neurotoxins in AD, impair organelle transport in cultured neurons and transgenic mouse models. A beta Os also stimulate hyperphosphorylation of the axonal microtubule-associated protein, tau. However, the role of tau in FAT disruption is controversial. Here we show that A beta Os reduce vesicular transport of brain-derived neurotrophic factor (BDNF) in hippocampal neurons from both wild-type and tau-knockout mice, indicating that tau is not required for transport disruption. FAT inhibition is not accompanied by microtubule destabilization or neuronal death. Significantly, inhibition of calcineurin (CaN), a calcium-dependent phosphatase implicated in AD pathogenesis, rescues BDNF transport. Moreover, inhibition of protein phosphatase 1 and glycogen synthase kinase 3 beta, downstream targets of CaN, prevents BDNF transport defects induced by A beta Os. We further show that A beta Os induce CaN activation through nonexcitotoxic calcium signaling. Results implicate CaN in FAT regulation and demonstrate that tau is not required for A beta O-induced BDNF transport disruption. DOI PubMed
4. Bomfim, TR; Forny-Germano, L; Sathler, LB; Brito-Moreira, J; Houzel, JC; Decker, H; Silverman, MA; Kazi, H; Melo, HM; McClean, PL; Holscher, C; Arnold, SE; Talbot, K; Klein, WL; Munoz, DP; Ferreira, ST; De Felice, FG. (2012) An anti-diabetes agent protects the mouse brain from defective insulin signaling caused by Alzheimer's disease-associated A beta oligomers.Journal of Clinical Investigation 122: 1339-1353 An anti-diabetes agent protects the mouse brain from defective insulin signaling caused by Alzheimer's disease-associated A beta oligomers
Defective brain insulin signaling has been suggested to contribute to the cognitive deficits in patients with Alzheimer's disease (AD). Although a connection between AD and diabetes has been suggested, a major unknown is the mechanism(s) by which insulin resistance in the brain arises in individuals with AD. Here, we show that serine phosphorylation of IRS-1 (IRS-1pSer) is common to both diseases. Brain tissue from humans with AD had elevated levels of IRS-1pSer and activated JNK, analogous to what occurs in peripheral tissue in patients with diabetes. We found that amyloid-beta peptide (A beta) oligomers, synaptotoxins that accumulate in the brains of AD patients, activated the JNK/TNF-alpha pathway, induced IRS-1 phosphorylation at multiple serine residues, and inhibited physiological IRS-1pTyr in mature cultured hippocarnpal neurons. Impaired IRS-1 signaling was also present in the hippocampi of Tg mice with a brain condition that models AD. Importantly, intracerebroventricular injection of A beta oligomers triggered hippocampal IRS-1pSer and JNK activation in cynomolgus monkeys. The oligomer-induced neuronal pathologies observed in vitro, including impaired axonal transport, were prevented by exposure to exendin-4 (exenatide), an anti-diabetes agent. In Tg mice, exendin-4 decreased levels of hippocampal IRS-1pSer and activated JNK and improved behavioral measures of cognition. By establishing molecular links between the dysregulated insulin signaling in AD and diabetes, our results open avenues for the investigation of new therapeutics in AD. DOI
3. Decker, H; Lo, KY; Unger, SM; Ferreira, ST; Silverman, MA. (2010) Amyloid-beta Peptide Oligomers Disrupt Axonal Transport through an NMDA Receptor-Dependent Mechanism That Is Mediated by Glycogen Synthase Kinase 3 beta in Primary Cultured Hippocampal Neurons.Journal of Neuroscience 30: 9166-9171 Amyloid-beta Peptide Oligomers Disrupt Axonal Transport through an NMDA Receptor-Dependent Mechanism That Is Mediated by Glycogen Synthase Kinase 3 beta in Primary Cultured Hippocampal Neurons
Disruption of axonal transport is a hallmark of several neurodegenerative diseases, including Alzheimer's disease (AD). Even though defective transport is considered an early pathologic event, the mechanisms by which neurodegenerative insults impact transport are poorly understood. We show that soluble oligomers of the amyloid-beta peptide (A beta Os), increasingly recognized as the proximal neurotoxins in AD pathology, induce disruption of organelle transport in primary hippocampal neurons in culture. Live imaging of fluorescent protein-tagged organelles revealed a marked decrease in axonal trafficking of dense-core vesicles and mitochondria in the presence of 0.5 mu M A beta Os. NMDA receptor (NMDAR) antagonists, including D-AP5, MK-801, and memantine, prevented the disruption of trafficking, thereby identifying signals for A beta O action at the cell membrane. Significantly, both pharmacological inhibition of glycogen synthase kinase-3 beta (GSK-3 beta) and transfection of neurons with a kinase-dead form of GSK-3 beta prevented the transport defect. Finally, we demonstrate by biochemical and immunocytochemical means that A beta Os do not affect microtubule stability, indicating that disruption of transport involves a more subtle mechanism than microtubule destabilization, likely the dysregulation of intracellular signaling cascades. Results demonstrate that A beta Os negatively impact axonal transport by a mechanism that is initiated by NMDARs and mediated by GSK-3 beta and establish a new connection between toxic A beta oligomers and AD pathology.Website
2.Silverman, MA; Leroux, MR. (2009) Intraflagellar transport and the generation of dynamic, structurally and functionally diverse cilia.Trends Cell Biol. 19: 306-316 Intraflagellar transport and the generation of dynamic, structurally and functionally diverse cilia
Cilia are organelles that project from most eukaryotic organisms and cell types. Their pervasiveness stems from having remarkably versatile propulsive and sensory functions, which in humans are recognized to have essential roles in physiology and development. Under-appreciated, however, are their diverse ultrastructures and typically bipartite organization consisting of doublet and singlet microtubules. Moreover, the overall shapes of the membrane-ensheathed cilia are varied, as exemplified by differences between hair-like olfactory cilia and rod- or cone-shaped photoreceptor connecting cilia-outer segments. Although cell-specific transcriptional programs are evidently crucial in establishing ciliary morphological specialization, few players directly involved in generating such diversity are known. Recent findings suggest that at least two molecular motors (kinesin-II and OSM-3/KIF17) can differentially mobilize the intraflagellar transport machinery required for ciliogenesis and, presumably, different cargo to help generate dynamic, structurally and functionally distinct cilia. DOI PubMed
