Anti-α-synuclein c-terminal antibodies block PFF uptake and accumulation of phospho-synuclein in preclinical models of Parkinson's disease.

Parkinson's disease (PD), a neurodegenerative disease affecting dopaminergic (DA) neurons, is characterized by decline of motor function and cognition. Dopaminergic cell loss is associated with accumulation of toxic alpha synuclein aggregates. As DA neuron death occurs late in the disease, therapeutics that block the spread of alpha synuclein may offer functional benefit and delay disease progression. To test this hypothesis, we generated antibodies to the C terminal region of synuclein with high nanomolar affinity and characterized them in in vitro and in vivo models of spread. Interestingly, we found that only antibodies with high affinity to the distal most portion of the C-terminus robustly reduced uptake of alpha synuclein preformed fibrils (PFF) and accumulation of phospho (S129) alpha synuclein in cell culture. Additionally, the antibody treatment blocked the spread of phospho (S129) alpha synuclein associated-pathology in a mouse model of synucleinopathy. Blockade of neuronal PFF uptake by different antibodies was more predictive of in vivo activity than their binding potency to monomeric or oligomeric forms of alpha synuclein. These data demonstrate that antibodies directed to the C-terminus of the alpha synuclein have differential effects on target engagement and efficacy. Furthermore, our data provides additional support for the development of alpha synuclein antibodies as a therapeutic strategy for PD patients.

Genetic ablation of Gpnmb does not alter synuclein-related pathology.

The gene GPNMB is known to play roles in phagocytosis and tissue repair, and is upregulated in microglia in many mouse models of neurodegenerative disease as well as in human patients. Nearby genomic variants are associated with both elevated Parkinson's disease (PD) risk and higher expression of this gene, suggesting that inhibiting GPNMB activity might be protective in Parkinson's disease. We tested this hypothesis in three different mouse models of neurological diseases: a remyelination model and two models of alpha-synuclein pathology. We found that Gpnmb deletion had no effect on histological, cellular, behavioral, neurochemical or gene expression phenotypes in any of these models. These data suggest that Gpnmb does not play a major role in the development of pathology or functional defects in these models and that further work is necessary to study its role in the development or progression of Parkinson's disease.

Micro-CT imaging and structural analysis of glomeruli in a model of Adriamycin-induced nephropathy.

Glomeruli number and size are important for determining the pathogenesis of glomerular disease, chronic kidney disease, and hypertension. Moreover, renal injury can occur in specific cortical layers and alter glomerular spatial distribution. In this study, we present a comprehensive structural analysis of glomeruli in a model of Adriamycin (doxorubicin) nephropathy. Glomeruli are imaged (micro-CT at 10 × 10 × 10 µm3) in kidney specimens from C57Bl/6 mouse cohorts: control treated with saline ( n = 9) and Adriamycin treated with 20 mg/kg Adriamycin ( n = 7). Several indices were examined, including glomerular number, glomerular volume, glomerular volume heterogeneity, and spatial density at each glomerulus and in each cortical layer (superficial, midcortical, and juxtamedullary). In the Adriamycin-treated animals, glomerular number decreased significantly in the left kidney [control: 8,298 ± 221, Adriamycin: 6,781 ± 630 (mean ± SE)] and right kidney (control: 7,317 ± 367, Adriamycin: 5,522 ± 508), and glomerular volume heterogeneity increased significantly in the left kidney (control: 0.642 ± 0.015, Adriamycin: 0.786 ± 0.018) and right kidney (control: 0.739 ± 0.016, Adriamycin: 0.937 ± 0.023). Glomerular spatial density was not affected. Glomerular volume heterogeneity increased significantly in the superficial and midcortical layers of the Adriamycin cohort. Adriamycin did not affect glomerular volume or density metrics in the juxtamedullary region, suggesting a compensatory mechanism of juxtamedullary glomeruli to injury in the outer cortical layers. Left/right asymmetry was observed in kidney size and various glomeruli metrics. The methods presented here can be used to evaluate renal disease models with subtle changes in glomerular endowment locally or across the entire kidney, and they provide an imaging tool to investigate diverse interventions and therapeutic drugs.

Genetic inactivation of RIP1 kinase does not ameliorate disease in a mouse model of ALS.

RIP1 kinase is proposed to play a critical role in driving necroptosis and inflammation in neurodegenerative disorders, including Amyotrophic Lateral Sclerosis (ALS). Preclinical studies indicated that while pharmacological inhibition of RIP1 kinase can ameliorate axonal pathology and delay disease onset in the mutant SOD1 transgenic (SOD1-Tg) mice, genetic blockade of necroptosis does not provide benefit in this mouse model. To clarify the role of RIP1 kinase activity in driving pathology in SOD1-Tg mice, we crossed SOD1-Tgs to RIP1 kinase-dead knock-in mice, and measured disease progression using functional and histopathological endpoints. Genetic inactivation of the RIP1 kinase activity in the SOD1-Tgs did not benefit the declining muscle strength or nerve function, motor neuron degeneration or neuroinflammation. In addition, we did not find evidence of phosphorylated RIP1 accumulation in the spinal cords of ALS patients. On the other hand, genetic inactivation of RIP1 kinase activity ameliorated the depletion of the neurotransmitter dopamine in a toxin model of dopaminergic neurodegeneration. These findings indicate that RIP1 kinase activity is dispensable for disease pathogenesis in the SOD1-Tg mice while inhibition of kinase activity may provide benefit in acute injury models.

Ocular phenotypes in a mouse model of impaired glucocerebrosidase activity.

Mutations in the GBA1 gene encoding glucocerebrosidase (GCase) are linked to Gaucher (GD) and Parkinson's Disease (PD). Since some GD and PD patients develop ocular phenotypes, we determined whether ocular phenotypes might result from impaired GCase activity and the corresponding accumulation of glucosylceramide (GluCer) and glucosylsphingosine (GluSph) in the Gba1D409V/D409V knock-in (Gba KI/KI; "KI") mouse. Gba KI mice developed age-dependent pupil dilation deficits to an anti-muscarinic agent; histologically, the iris covered the anterior part of the lens with adhesions between the iris and the anterior surface of the lens (posterior synechia). This may prevent pupil dilation in general, beyond an un-responsiveness of the iris to anti-muscarinics. Gba KI mice displayed atrophy and pigment dispersion of the iris, and occlusion of the iridocorneal angle by pigment-laden cells, reminiscent of secondary open angle glaucoma. Gba KI mice showed progressive thinning of the retina consistent with retinal degeneration. GluSph levels were increased in the anterior and posterior segments of the eye, suggesting that accumulation of lipids in the eye may contribute to degeneration in this compartment. We conclude that the Gba KI model provides robust and reproducible eye phenotypes which may be used to test for efficacy and establish biomarkers for GBA1-related therapies.

Antibody semorinemab reduces tau pathology in a transgenic mouse model and engages tau in patients with Alzheimer's disease.

Tau has become an attractive alternative target for passive immunotherapy efforts for Alzheimer's disease (AD). The anatomical distribution and extent of tau pathology correlate with disease course and severity better than other disease markers to date. We describe here the generation, preclinical characterization, and phase 1 clinical characterization of semorinemab, a humanized anti-tau monoclonal antibody with an immunoglobulin G4 (igG4) isotype backbone. Semorinemab binds all six human tau isoforms and protects neurons against tau oligomer neurotoxicity in cocultures of neurons and microglia. In addition, when administered intraperitoneally once weekly for 13 weeks, murine versions of semorinemab reduced the accumulation of tau pathology in a transgenic mouse model of tauopathy, independent of antibody effector function status. Semorinemab also showed clear evidence of target engagement in vivo, with increases in systemic tau concentrations observed in tau transgenic mice, nonhuman primates, and humans. Higher concentrations of systemic tau were observed after dosing in AD participants compared to healthy control participants. No concerning safety signals were observed in the phase 1 clinical trial at single doses up to 16,800 mg and multiple doses totaling 33,600 mg in a month.

Cerebrovascular dysfunction in amyloid precursor protein transgenic mice: contribution of soluble and insoluble amyloid-beta peptide, partial restoration via gamma-secretase inhibition.

The contributing effect of cerebrovascular pathology in Alzheimer's disease (AD) has become increasingly appreciated. Recent evidence suggests that amyloid-beta peptide (Abeta), the same peptide found in neuritic plaques of AD, may play a role via its vasoactive properties. Several studies have examined young Tg2576 mice expressing mutant amyloid precursor protein (APP) and having elevated levels of soluble Abeta but no cerebral amyloid angiopathy (CAA). These studies suggest but do not prove that soluble Abeta can significantly impair the cerebral circulation. Other studies examining older Tg2576 mice having extensive CAA found even greater cerebrovascular dysfunction, suggesting that CAA is likely to further impair vascular function. Herein, we examined vasodilatory responses in young and older Tg2576 mice to further assess the roles of soluble and insoluble Abeta on vessel function. We found that (1) vascular impairment was present in both young and older Tg2576 mice; (2) a strong correlation between CAA severity and vessel reactivity exists; (3) a surprisingly small amount of CAA led to marked reduction or complete loss of vessel function; 4) CAA-induced vasomotor impairment resulted from dysfunction rather than loss or disruption of vascular smooth muscle cells; and 5) acute depletion of Abeta improved vessel function in young and to a lesser degree older Tg2576 mice. These results strongly suggest that both soluble and insoluble Abeta cause cerebrovascular dysfunction, that mechanisms other than Abeta-induced alteration in vessel integrity are responsible, and that anti-Abeta therapy may have beneficial vascular effects in addition to positive effects on parenchymal amyloid.

Anti-Abeta antibody treatment promotes the rapid recovery of amyloid-associated neuritic dystrophy in PDAPP transgenic mice.

Neuritic plaques are a defining feature of Alzheimer disease (AD) pathology. These structures are composed of extracellular accumulations of amyloid-beta peptide (Abeta) and other plaque-associated proteins, surrounded by large, swollen axons and dendrites (dystrophic neurites) and activated glia. Dystrophic neurites are thought to disrupt neuronal function, but whether this damage is static, dynamic, or reversible is unknown. To address this, we monitored neuritic plaques in the brains of living PDAPP;Thy-1:YFP transgenic mice, a model that develops AD-like pathology and also stably expresses yellow fluorescent protein (YFP) in a subset of neurons in the brain. Using multiphoton microscopy, we observed and monitored amyloid through cranial windows in PDAPP;Thy-1:YFP double-transgenic mice using the in vivo amyloid-imaging fluorophore methoxy-X04, and individual YFP-labeled dystrophic neurites by their inherent fluorescence. In vivo studies using this system suggest that amyloid-associated dystrophic neurites are relatively stable structures in PDAPP;Thy-1:YFP transgenic mice over several days. However, a significant reduction in the number and size of dystrophic neurites was seen 3 days after Abeta deposits were cleared by anti-Abeta antibody treatment. This analysis suggests that ongoing axonal and dendritic damage is secondary to Abeta and is, in part, rapidly reversible.

Posterior localization of dynein and dorsal-ventral axis formation depend on kinesin in Drosophila oocytes.

To establish the major body axes, late Drosophila oocytes localize determinants to discrete cortical positions: bicoid mRNA to the anterior cortex, oskar mRNA to the posterior cortex, and gurken mRNA to the margin of the anterior cortex adjacent to the oocyte nucleus (the "anterodorsal corner"). These localizations depend on microtubules that are thought to be organized such that plus end-directed motors can move cargoes, like oskar, away from the anterior/lateral surfaces and hence toward the posterior pole. Likewise, minus end-directed motors may move cargoes toward anterior destinations. Contradicting this, cytoplasmic dynein, a minus-end motor, accumulates at the posterior. Here, we report that disruption of the plus-end motor kinesin I causes a shift of dynein from posterior to anterior. This provides an explanation for the dynein paradox, suggesting that dynein is moved as a cargo toward the posterior pole by kinesin-generated forces. However, other results present a new transport polarity puzzle. Disruption of kinesin I causes partial defects in anterior positioning of the nucleus and severe defects in anterodorsal localization of gurken mRNA. Kinesin may generate anterodorsal forces directly, despite the apparent preponderance of minus ends at the anterior cortex. Alternatively, kinesin I may facilitate cytoplasmic dynein-based anterodorsal forces by repositioning dynein toward microtubule plus ends.

Antibody-Mediated Targeting of Tau In Vivo Does Not Require Effector Function and Microglial Engagement.

The spread of tau pathology correlates with cognitive decline in Alzheimer's disease. In vitro, tau antibodies can block cell-to-cell tau spreading. Although mechanisms of anti-tau function in vivo are unknown, effector function might promote microglia-mediated clearance. In this study, we investigated whether antibody effector function is required for targeting tau. We compared efficacy in vivo and in vitro of two versions of the same tau antibody, with and without effector function, measuring tau pathology, neuron health, and microglial function. Both antibodies reduced accumulation of tau pathology in Tau-P301L transgenic mice and protected cultured neurons against extracellular tau-induced toxicity. Only the full-effector antibody enhanced tau uptake in cultured microglia, which promoted release of proinflammatory cytokines. In neuron-microglia co-cultures, only effectorless anti-tau protected neurons, suggesting full-effector tau antibodies can induce indirect toxicity via microglia. We conclude that effector function is not required for efficacy, and effectorless tau antibodies may represent a safer approach to targeting tau.

Use of YFP to study amyloid-beta associated neurite alterations in live brain slices.

Neuritic plaques are one of the defining neuropathological features of Alzheimer's disease (AD). These structures are composed of a buildup of fibrils of the amyloid-beta (Abeta) peptide (amyloid) surrounded by activated glial cells and degenerating nerve processes (dystrophic neurites). To study neuritic plaques and possible abnormalities associated with dendrites, axons, and synaptic structures, we have developed an acute slice preparation model using PDAPP, yellow fluorescent protein (YFP) double transgenic mice (a mouse model with AD-like pathology that stably expresses YFP in a subset of neurons in the brain). With laser scanning confocal microscopy, we have imaged living brain slices from PDAPP, YFP double transgenic mice as old as 20 months and have been able to visualize axons, dendrites, dendritic spines, and dystrophic neurites for many hours. Our initial studies suggest that dystrophic axons and dendrites within neuritic plaques are fairly stable structures in the absence of exogenous perturbations. This acute slice preparation model should prove to be a useful tool to explore the pathophysiology of Abeta-related axonal, dendritic, and synaptic dysfunction.

PDAPP; YFP double transgenic mice: a tool to study amyloid-beta associated changes in axonal, dendritic, and synaptic structures.

Neuritic plaques are one of the stereotypical hallmarks of Alzheimer's disease (AD) pathology. These structures are composed of extracellular accumulations of fibrillar forms of the amyloid-beta peptide (Abeta), a variety of other plaque-associated proteins, activated glial cells, and degenerating nerve processes. To study the neuritic toxicity of different structural forms of Abeta in the context of regional connectivity and the entire cell, we crossed PDAPP transgenic (Tg) mice, a model with AD-like pathology, to Tg mice that stably express yellow fluorescent protein (YFP) in a subset of neurons in the brain. In PDAPP; YFP double Tg mice, markedly enlarged YFP-labeled axonal and dendritic varicosities were associated with fibrillar Abeta deposits. These varicosities were absent in areas where there were nonfibrillar Abeta deposits. Interestingly, YFP-labeled varicosities revealed changes that corresponded with changes seen with electron microscopy and the de Olmos silver staining technique. Other silver staining methods and immunohistochemical localization of phosphorylated neurofilaments or phosphorylated tau were unable to detect the majority of these dystrophic neurites. Some but not all synaptic vesicle markers accumulated abnormally in YFP-labeled varicosities associated with neuritic plaques. In addition to the characterization of the effects of Abeta on axonal and dendritic structure, YFP-labeled neurons in Tg mice should prove to be a valuable tool to interpret the localization patterns of other markers and for future studies examining the dynamics of axons and dendrites in a variety of disease conditions in living tissue both in vitro and in vivo.

Amyloid-beta immunotherapies in mice and men.

Given the compelling genetic and biochemical evidence that has implicated amyloid-beta (Abeta) in the pathogenesis of Alzheimer's disease, many studies have focused on ways to inhibit Abeta production, to reverse or impede the formation of toxic forms of Abeta, or to facilitate the clearance of Abeta from the brain, in the hope of developing viable treatments for the disease. Using transgenic mouse models of Alzheimer's disease, many advances have been made in methodologies using different immunization techniques designed to clear soluble and aggregated forms of Abeta from the brain. We have highlighted how data derived from studies using transgenic mouse models have shaped our understanding of immunization-dependent Abeta clearance mechanisms and how these studies have influenced the development of anti-Abeta immunotherapies in humans.

Diffusion tensor imaging detects age-dependent white matter changes in a transgenic mouse model with amyloid deposition.

Increasing evidence demonstrates that there is marked damage and dysfunction not only in the gray matter but also in the white matter in Alzheimer's disease (AD). In this study, transgenic mice overexpressing beta-amyloid precursor protein (APP) under control of the platelet-derived growth factor promoter (PDAPP mice) were examined using diffusion tensor magnetic resonance imaging (DTI) to evaluate the extent of white matter injury before and following the development of AD-like pathology. The profile of DTI parameters was significantly different in old PDAPP mice compared to that of old control mice following the development of AD-like pathology. No difference in DTI parameters was observed between the young PDAPP and control mice. Our results suggest that as amyloid beta (Abeta) deposition and levels increase over time in PDAPP mice, these changes lead to primary or secondary white matter injury that can be detected by DTI.