Transplanting old organs promotes senescence in young recipients.

In clinical organ transplantation, donor and recipient ages may differ substantially. Old donor organs accumulate senescent cells that have the capacity to induce senescence in naïve cells. We hypothesized that the engraftment of old organs may induce senescence in younger recipients, promoting age-related pathologies. When performing isogeneic cardiac transplants between age-mismatched C57BL/6 old donor (18 months) mice and young and middle-aged C57BL/6 (3- or 12- month-old) recipients , we observed augmented frequencies of senescent cells in draining lymph nodes, adipose tissue, livers, and hindlimb muscles 30 days after transplantation. These observations went along with compromised physical performance and impaired spatial learning and memory abilities. Systemic levels of the senescence-associated secretory phenotype factors, including mitochondrial DNA (mt-DNA), were elevated in recipients. Of mechanistic relevance, injections of mt-DNA phenocopied effects of age-mismatched organ transplantation on accelerating aging. Single treatment of old donor animals with senolytics prior to transplantation attenuated mt-DNA release and improved physical capacities in young recipients. Collectively, we show that transplanting older organs induces senescence in transplant recipients, resulting in compromised physical and cognitive capacities. Depleting senescent cells with senolytics, in turn, represents a promising approach to improve outcomes of older organs.

High-Energy, Whole-Body Proton Irradiation Differentially Alters Long-Term Brain Pathology and Behavior Dependent on Sex and Alzheimer's Disease Mutations.

Whole-body exposure to high-energy particle radiation remains an unmitigated hazard to human health in space. Ongoing experiments at the NASA Space Radiation Laboratory and elsewhere repeatedly show persistent changes in brain function long after exposure to simulations of this unique radiation environment, although, as is also the case with proton radiotherapy sequelae, how this occurs and especially how it interacts with common comorbidities is not well-understood. Here, we report modest differential changes in behavior and brain pathology between male and female Alzheimer's-like and wildtype littermate mice 7-8 months after exposure to 0, 0.5, or 2 Gy of 1 GeV proton radiation. The mice were examined with a battery of behavior tests and assayed for amyloid beta pathology, synaptic markers, microbleeds, microglial reactivity, and plasma cytokines. In general, the Alzheimer's model mice were more prone than their wildtype littermates to radiation-induced behavior changes, and hippocampal staining for amyloid beta pathology and microglial activation in these mice revealed a dose-dependent reduction in males but not in females. In summary, radiation-induced, long-term changes in behavior and pathology, although modest, appear specific to both sex and the underlying disease state.

Long-Term Sex- and Genotype-Specific Effects of 56Fe Irradiation on Wild-Type and APPswe/PS1dE9 Transgenic Mice.

Space radiation presents a substantial threat to travel beyond Earth. Relatively low doses of high-energy particle radiation cause physiological and behavioral impairments in rodents and may pose risks to human spaceflight. There is evidence that 56Fe irradiation, a significant component of space radiation, may be more harmful to males than to females and worsen Alzheimer's disease pathology in genetically vulnerable models. Yet, research on the long-term, sex- and genotype-specific effects of 56Fe irradiation is lacking. Here, we irradiated 4-month-old male and female, wild-type and Alzheimer's-like APP/PS1 mice with 0, 0.10, or 0.50 Gy of 56Fe ions (1GeV/u). Mice underwent microPET scans before and 7.5 months after irradiation, a battery of behavioral tests at 11 months of age and were sacrificed for pathological and biochemical analyses at 12 months of age. 56Fe irradiation worsened amyloid-beta (Aß) pathology, gliosis, neuroinflammation and spatial memory, but improved motor coordination, in male transgenic mice and worsened fear memory in wild-type males. Although sham-irradiated female APP/PS1 mice had more cerebral Aß and gliosis than sham-irradiated male transgenics, female mice of both genotypes were relatively spared from radiation effects 8 months later. These results provide evidence for sex-specific, long-term CNS effects of space radiation.

σ1 receptor ligands control a switch between passive and active threat responses.

Humans and many animals show 'freezing' behavior in response to threatening stimuli. In humans, inappropriate threat responses are fundamental characteristics of several mental illnesses. To identify small molecules that modulate threat responses, we developed a high-throughput behavioral assay in zebrafish (Danio rerio) and evaluated 10,000 compounds for their effects on freezing behavior. We found three classes of compounds that switch the threat response from freezing to escape-like behavior. We then screened these for binding activity across 45 candidate targets. Using target profile clustering, we identified the sigma-1 (σ1) receptor as having a role in the mechanism of behavioral switching and confirmed that known σ1 ligands also disrupt freezing behavior. Furthermore, mutation of the gene encoding σ1 prevented the behavioral effect of escape-inducing compounds. One compound, which we call finazine, potently bound mammalian σ1 and altered threat-response behavior in mice. Thus, pharmacological and genetic interrogation of the freezing response revealed σ1 as a mediator of threat responses in vertebrates.

Zebrafish behavioral profiling identifies multitarget antipsychotic-like compounds.

Many psychiatric drugs act on multiple targets and therefore require screening assays that encompass a wide target space. With sufficiently rich phenotyping and a large sampling of compounds, it should be possible to identify compounds with desired mechanisms of action on the basis of behavioral profiles alone. Although zebrafish (Danio rerio) behavior has been used to rapidly identify neuroactive compounds, it is not clear what types of behavioral assays would be necessary to identify multitarget compounds such as antipsychotics. Here we developed a battery of behavioral assays in larval zebrafish to determine whether behavioral profiles can provide sufficient phenotypic resolution to identify and classify psychiatric drugs. Using the antipsychotic drug haloperidol as a test case, we found that behavioral profiles of haloperidol-treated zebrafish could be used to identify previously uncharacterized compounds with desired antipsychotic-like activities and multitarget mechanisms of action.

Disruption of the ATP/adenosine balance in CD39-/- mice is associated with handling-induced seizures.

Seizures are due to excessive, synchronous neuronal firing in the brain and are characteristic of epilepsy, the fourth most prevalent neurological disease. We report handling-induced and spontaneous seizures in mice deficient for CD39, a cell-surface ATPase highly expressed on microglial cells. CD39-/- mice with handling-induced seizures had normal input-output curves and paired-pulse ratio measured from hippocampal slices and lacked microgliosis, astrogliosis or overt cell loss in the hippocampus and cortex. As expected, however, the cerebrospinal fluid of CD39-/- mice contained increased levels of ATP and decreased levels of adenosine. To determine if immune activation was involved in seizure progression, we challenged mice with lipopolysaccharide (LPS) and measured the effect on microglia activation and seizure severity. Systemic LPS challenge resulted in increased cortical staining of Iba1/CD68 and gene array data from purified microglia predicted increased expression of interleukin-8, triggering receptor expressed on myeloid cells 1, p38, pattern recognition receptors, death receptor, nuclear factor-κB , complement, acute phase, and interleukin-6 signalling pathways in CD39-/- versus CD39+/+ mice. However, LPS treatment did not affect handling-induced seizures. In addition, microglia-specific CD39 deletion in adult mice was not sufficient to cause seizures, suggesting instead that altered expression of CD39 during development or on non-microglial cells such as vascular endothelial cells may promote the seizure phenotype. In summary, we show a correlation between altered extracellular ATP/adenosine ratio and a previously unreported seizure phenotype in CD39-/- mice. This work provides groundwork for further elucidation of the underlying mechanisms of epilepsy.

Complement C3-Deficient Mice Fail to Display Age-Related Hippocampal Decline.

The complement system is part of the innate immune response responsible for removing pathogens and cellular debris, in addition to helping to refine CNS neuronal connections via microglia-mediated pruning of inappropriate synapses during brain development. However, less is known about the role of complement during normal aging. Here, we studied the role of the central complement component, C3, in synaptic health and aging. We examined behavior as well as electrophysiological, synaptic, and neuronal changes in the brains of C3-deficient male mice (C3 KO) compared with age-, strain-, and gender-matched C57BL/6J (wild-type, WT) control mice at postnatal day 30, 4 months, and 16 months of age. We found the following: (1) region-specific and age-dependent synapse loss in aged WT mice that was not observed in C3 KO mice; (2) age-dependent neuron loss in hippocampal CA3 (but not in CA1) that followed synapse loss in aged WT mice, neither of which were observed in aged C3 KO mice; and (3) significantly enhanced LTP and cognition and less anxiety in aged C3 KO mice compared with aged WT mice. Importantly, CA3 synaptic puncta were similar between WT and C3 KO mice at P30. Together, our results suggest a novel and prominent role for complement protein C3 in mediating aged-related and region-specific changes in synaptic function and plasticity in the aging brain. Significance statement: The complement cascade, part of the innate immune response to remove pathogens, also plays a role in synaptic refinement during brain development by the removal of weak synapses. We investigated whether complement C3, a central component, affects synapse loss during aging. Wild-type (WT) and C3 knock-out (C3 KO) mice were examined at different ages. The mice were similar at 1 month of age. However, with aging, WT mice lost synapses in specific brain regions, especially in hippocampus, an area important for memory, whereas C3 KO mice were protected. Aged C3 KO mice also performed better on learning and memory tests than aged WT mice. Our results suggest that complement C3, or its downstream signaling, is detrimental to synapses during aging.

Regulator of G protein signaling 4 [corrected] is a crucial modulator of antidepressant drug action in depression and neuropathic pain models.

Regulator of G protein signaling 4 (Rgs4) is a signal transduction protein that controls the function of monoamine, opiate, muscarinic, and other G protein-coupled receptors via interactions with Gα subunits. Rgs4 is expressed in several brain regions involved in mood, movement, cognition, and addiction and is regulated by psychotropic drugs, stress, and corticosteroids. In this study, we use genetic mouse models and viral-mediated gene transfer to examine the role of Rgs4 in the actions of antidepressant medications. We first analyzed human postmortem brain tissue and found robust up-regulation of RGS4 expression in the nucleus accumbens (NAc) of subjects receiving standard antidepressant medications that target monoamine systems. Behavioral studies of mice lacking Rgs4, including specific knockdowns in NAc, demonstrate that Rgs4 in this brain region acts as a positive modulator of the antidepressant-like and antiallodynic-like actions of several monoamine-directed antidepressant drugs, including tricyclic antidepressants, selective serotonin reuptake inhibitors, and norepinephrine reuptake inhibitors. Studies using viral-mediated increases in Rgs4 activity in NAc further support this hypothesis. Interestingly, in prefrontal cortex, Rgs4 acts as a negative modulator of the actions of nonmonoamine-directed drugs that are purported to act as antidepressants: the N-methyl-D-aspartate glutamate receptor antagonist ketamine and the delta opioid agonist (+)-4-[(αR)-α-((2S,5R)-4-Allyl-2,5-dimethyl-1-piperazinyl)-3-methoxybenzyl]-N,N-diethylbenzamide. Together, these data reveal a unique modulatory role of Rgs4 in the brain region-specific actions of a wide range of antidepressant drugs and indicate that pharmacological interventions at the level of RGS4 activity may enhance the actions of such drugs used for the treatment of depression and neuropathic pain.

LRP1 in GABAergic neurons is a key link between obesity and memory function.

OBJECTIVE: Low-density lipoprotein receptor-related protein-1 (LRP1) regulates energy homeostasis, blood-brain barrier integrity, and metabolic signaling in the brain. Deficiency of LRP1 in inhibitory gamma-aminobutyric acid (GABA)ergic neurons causes severe obesity in mice. However, the impact of LRP1 in inhibitory neurons on memory function and cognition in the context of obesity is poorly understood. METHODS: Mice lacking LRP1 in GABAergic neurons (Vgat-Cre; LRP1loxP/loxP) underwent behavioral tests for locomotor activity and motor coordination, short/long-term and spatial memory, and fear learning/memory. This study evaluated the relationships between behavior and metabolic risk factors and followed the mice at 16 and 32 weeks of age. RESULTS: Deletion of LRP1 in GABAergic neurons caused a significant impairment in memory function in 32-week-old mice. In the spatial Y-maze test, Vgat-Cre; LRP1loxP/loxP mice exhibited decreased travel distance and duration in the novel arm compared with controls (LRP1loxP/loxP mice). In addition, GABAergic neuron-specific LRP1-deficient mice showed a diminished capacity for performing learning and memory tasks during the water T-maze test. Moreover, reduced freezing time was observed in these mice during the contextual and cued fear conditioning tests. These effects were accompanied by increased neuronal necrosis and satellitosis in the hippocampus. Importantly, the distance and duration in the novel arm, as well as the performance of the reversal water T-maze test, negatively correlated with metabolic risk parameters, including body weight, serum leptin, insulin, and apolipoprotein J. However, in 16-week-old Vgat-Cre; LRP1loxP/loxP mice, there were no differences in the behavioral tests or correlations between metabolic parameters and cognition. CONCLUSIONS: Our findings demonstrate that LRP1 from GABAergic neurons is important in regulating normal learning and memory. Metabolically, obesity caused by GABAergic LRP1 deletion negatively regulates memory and cognitive function in an age-dependent manner. Thus, LRP1 in GABAergic neurons may play a crucial role in maintaining normal excitatory/inhibitory balance, impacting memory function, and reinforcing the potential importance of LRP1 in neural system integrity.

Gabrb3 endothelial cell-specific knockout mice display abnormal blood flow, hypertension, and behavioral dysfunction.

Our recent studies uncovered a novel GABA signaling pathway in embryonic forebrain endothelial cells that works independently from neuronal GABA signaling and revealed that disruptions in endothelial GABAA receptor-GABA signaling from early embryonic stages can directly contribute to the origin of psychiatric disorders. In the GABAA receptor ß3 subunit endothelial cell conditional knockout (Gabrb3ECKO) mice, the ß3 subunit is deleted selectively from endothelial cells, therefore endothelial GABAA receptors become inactivated and dysfunctional. There is a reduction in vessel densities and increased vessel morphology in the Gabrb3ECKO telencephalon that persists in the adult neocortex. Gabrb3ECKO mice show behavioral deficits such as impaired reciprocal social interactions, communication deficits, heightened anxiety, and depression. Here, we characterize the functional changes in Gabrb3ECKO mice by evaluating cortical blood flow, examine the consequences of loss of endothelial Gabrb3 on cardiac tissue, and define more in-depth altered behaviors. Red blood cell velocity and blood flow were increased in the cortical microcirculation of the Gabrb3ECKO mice. The Gabrb3ECKO mice had a reduction in vessel densities in the heart, similar to the brain; exhibited wavy, myocardial fibers, with elongated 'worm-like' nuclei in their cardiac histology, and developed hypertension. Additional alterations in behavioral function were observed in the Gabrb3ECKO mice such as increased spontaneous exploratory activity and rearing in an open field, reduced short term memory, decreased ambulatory activity in CLAMS testing, and altered prepulse inhibition to startle, an important biomarker of psychiatric diseases such as schizophrenia. Our results imply that vascular Gabrb3 is a key player in the brain as well as the heart, and its loss in both organs can lead to concurrent development of psychiatric and cardiac dysfunction.

Focused ultrasound with anti-pGlu3 Aß enhances efficacy in Alzheimer's disease-like mice via recruitment of peripheral immune cells.

Pyroglutamate-3 amyloid-ß (pGlu3 Aß) is an N-terminally modified, pathogenic form of amyloid-ß that is present in cerebral amyloid plaques and vascular deposits. Here, we used focused ultrasound (FUS) with microbubbles to enhance the intravenous delivery of an Fc-competent anti-pGlu3 Aß monoclonal antibody, 07/2a mAb, across the blood brain barrier (BBB) in an attempt to improve Aß removal and memory in aged APP/PS1dE9 mice, an Alzheimer's disease (AD)-like model of amyloidogenesis. First, we demonstrated that bilateral hippocampal FUS-BBB disruption (FUS-BBBD) led to a 5.5-fold increase of 07/2a mAb delivery to the brains compared to non-sonicated mice 72 h following a single treatment. Then, we determined that three weekly treatments with 07/2a mAb alone improved spatial learning and memory in aged, plaque-rich APP/PS1dE9 mice, and that this improvement occurred faster and in a higher percentage of animals when combined with FUS-BBBD. Mice given the combination treatment had reduced hippocampal plaque burden compared to PBS-treated controls. Furthermore, synaptic protein levels were higher in hippocampal synaptosomes from mice given the combination treatment compared to sham controls, and there were more CA3 synaptic puncta labeled in the APP/PS1dE9 mice given the combination treatment compared to those given mAb alone. Plaque-associated microglia were present in the hippocampi of APP/PS1dE9 mice treated with 07/2a mAb with and without FUS-BBBD. However, we discovered that plaque-associated Ly6G+ monocytes were only present in the hippocampi of APP/PS1dE9 mice that were given FUS-BBBD alone or even more so, the combination treatment. Lastly, FUS-BBBD did not increase the incidence of microhemorrhage in mice with or without 07/2a mAb treatment. Our findings suggest that FUS is a useful tool to enhance delivery and efficacy of an anti-pGlu3 Aß mAb for immunotherapy either via an additive effect or an independent mechanism. We revealed a potential novel mechanism wherein the combination of 07/2a mAb with FUS-BBBD led to greater monocyte infiltration and recruitment to plaques in this AD-like model. Overall, these effects resulted in greater plaque removal, sparing of synapses and improved cognitive function without causing overt damage, suggesting the possibility of FUS-BBBD as a noninvasive method to increase the therapeutic efficacy of drugs or biologics in AD patients.

Cis P-tau underlies vascular contribution to cognitive impairment and dementia and can be effectively targeted by immunotherapy in mice.

Compelling evidence supports vascular contributions to cognitive impairment and dementia (VCID) including Alzheimer's disease (AD), but the underlying pathogenic mechanisms and treatments are not fully understood. Cis P-tau is an early driver of neurodegeneration resulting from traumatic brain injury, but its role in VCID remains unclear. Here, we found robust cis P-tau despite no tau tangles in patients with VCID and in mice modeling key aspects of clinical VCID, likely because of the inhibition of its isomerase Pin1 by DAPK1. Elimination of cis P-tau in VCID mice using cis-targeted immunotherapy, brain-specific Pin1 overexpression, or DAPK1 knockout effectively rescues VCID-like neurodegeneration and cognitive impairment in executive function. Cis mAb also prevents and ameliorates progression of AD-like neurodegeneration and memory loss in mice. Furthermore, single-cell RNA sequencing revealed that young VCID mice display diverse cortical cell type-specific transcriptomic changes resembling old patients with AD, and the vast majority of these global changes were recovered by cis-targeted immunotherapy. Moreover, purified soluble cis P-tau was sufficient to induce progressive neurodegeneration and brain dysfunction by causing axonopathy and conserved transcriptomic signature found in VCID mice and patients with AD with early pathology. Thus, cis P-tau might play a major role in mediating VCID and AD, and antibody targeting it may be useful for early diagnosis, prevention, and treatment of cognitive impairment and dementia after neurovascular insults and in AD.

Exercise hormone irisin is a critical regulator of cognitive function.

Identifying secreted mediators that drive the cognitive benefits of exercise holds great promise for the treatment of cognitive decline in ageing or Alzheimer's disease (AD). Here, we show that irisin, the cleaved and circulating form of the exercise-induced membrane protein FNDC5, is sufficient to confer the benefits of exercise on cognitive function. Genetic deletion of Fndc5/irisin (global Fndc5 knock-out (KO) mice; F5KO) impairs cognitive function in exercise, ageing and AD. Diminished pattern separation in F5KO mice can be rescued by delivering irisin directly into the dentate gyrus, suggesting that irisin is the active moiety. In F5KO mice, adult-born neurons in the dentate gyrus are morphologically, transcriptionally and functionally abnormal. Importantly, elevation of circulating irisin levels by peripheral delivery of irisin via adeno-associated viral overexpression in the liver results in enrichment of central irisin and is sufficient to improve both the cognitive deficit and neuropathology in AD mouse models. Irisin is a crucial regulator of the cognitive benefits of exercise and is a potential therapeutic agent for treating cognitive disorders including AD.

The prototoxin lynx1 acts on nicotinic acetylcholine receptors to balance neuronal activity and survival in vivo.

Nicotinic acetylcholine receptors (nAChRs) affect a wide array of biological processes, including learning and memory, attention, and addiction. lynx1, the founding member of a family of mammalian prototoxins, modulates nAChR function in vitro by altering agonist sensitivity and desensitization kinetics. Here we demonstrate, through the generation of lynx1 null mutant mice, that lynx1 modulates nAChR signaling in vivo. Its loss decreases the EC(50) for nicotine by approximately 10-fold, decreases receptor desensitization, elevates intracellular calcium levels in response to nicotine, and enhances synaptic efficacy. lynx1 null mutant mice exhibit enhanced performance in specific tests of learning and memory. Consistent with reports that mutations resulting in hyperactivation of nAChRs can lead to neurodegeneration, aging lynx1 null mutant mice exhibit a vacuolating degeneration that is exacerbated by nicotine and ameliorated by null mutations in nAChRs. We conclude that lynx1 functions as an allosteric modulator of nAChR function in vivo, balancing neuronal activity and survival in the CNS.

RGS9-2: probing an intracellular modulator of behavior as a drug target.

Regulators of G-protein signaling (RGS proteins) comprise a large family of signal transduction molecules that modulate G-protein-coupled-receptor (GPCR) function. Among the RGS proteins expressed in the brain, RGS9-2 is very abundant in the striatum, a brain region involved in movement, motivation, mood and addiction. This protein negatively modulates signal transduction thus playing a key part in striatal function and resultant behavioral responses. In particular, there is evidence of important interactions with mu-opioid- and dopamine D(2)-receptor signaling pathways. Several studies indicate that manipulations of RGS9-2 levels in the striatum might greatly affect pharmacological responses. These findings indicate that treatment strategies targeting RGS9-2 levels or activity might be used to enhance responses to drugs acting at GPCRs and/or prevent undesired drug actions.

The novel triple reuptake inhibitor JZAD-IV-22 exhibits an antidepressant pharmacological profile without locomotor stimulant or sensitization properties.

Triple reuptake inhibitors (TRIs) that block the dopamine transporter (DAT), norepinephrine transporter, and serotonin transporter are being developed as a new class of antidepressant that may have better efficacy and fewer side effects compared with traditional antidepressants. We describe a novel TRI, 2-[4-(4-chlorophenyl)-1-methylpiperidin-3-ylmethylsulfanyl]-1-(3-methylpiperidin-1-yl)-ethanone (JZAD-IV-22), that inhibits all three monoamine transporters with approximately equal potency in vitro. (+/-)-1-(3,4-dichlorophenyl)-3-azabicyclo-[3.1.0]hexane hydrochloride (DOV 216,303), a TRI shown to be an effective antidepressant in a clinical trial, shows reuptake inhibition similar to that of JZAD-IV-22 in vitro. Furthermore, both JZAD-IV-22 and DOV 216,303 increase levels of dopamine, norepinephrine, and serotonin in the mouse prefrontal cortex when administered by peripheral injection. JZAD-IV-22 and DOV 216,303 exhibited antidepressant-like efficacy in the mouse forced-swim and tail-suspension tests at doses that increased neurotransmitter levels. Because development of DAT inhibitors could be hindered by abuse liability, both JZAD-IV-22 and DOV 216,303 were compared in two assays that are markers of abuse potential. Both JZAD-IV-22 and DOV 216,303 partially substituted for cocaine in a drug discrimination assay in rats, and high doses of DOV 216,303 produced locomotor sensitization in mice. JZAD-IV-22 showed no evidence of sensitization at any dose tested. These results demonstrate that JZAD-IV-22 is a TRI with antidepressant-like activity similar to that of DOV 216,303. The striking feature that distinguishes the two TRIs is that locomotor sensitization, a common underlying feature of drugs of abuse, is seen with DOV 216,303 but is completely lacking in JZAD-IV-22. These findings may have implications for the potential for abuse liability in humans.

Effector function of anti-pyroglutamate-3 Aß antibodies affects cognitive benefit, glial activation and amyloid clearance in Alzheimer's-like mice.

BACKGROUND: Pyroglutamate-3 Aß (pGlu-3 Aß) is an N-terminally truncated and post-translationally modified Aß species found in Alzheimer's disease (AD) brain. Its increased peptide aggregation propensity and toxicity make it an attractive emerging treatment strategy for AD. We address the question of how the effector function of an anti-pGlu-3 Aß antibody influences the efficacy of immunotherapy in mouse models with AD-like pathology. METHODS: We compared two different immunoglobulin (Ig) isotypes of the same murine anti-pGlu-3 Aß mAb (07/1 IgG1 and 07/2a IgG2a) and a general N-terminal Aß mAb (3A1 IgG1) for their ability to clear Aß and protect cognition in a therapeutic passive immunotherapy study in aged, plaque-rich APPSWE/PS1ΔE9 transgenic (Tg) mice. We also compared the ability of these antibodies and a CDC-mutant form of 07/2a (07/2a-k), engineered to avoid complement activation, to clear Aß in an ex vivo phagocytosis assay and following treatment in APPSLxhQC double Tg mice, and to activate microglia using longitudinal microPET imaging with TSPO-specific 18F-GE180 tracer following a single bolus antibody injection in young and old Tg mice. RESULTS: We demonstrated significant cognitive improvement, better plaque clearance, and more plaque-associated microglia in the absence of microhemorrhage in aged APPSWE/PS1ΔE9 Tg mice treated with 07/2a, but not 07/1 or 3A1, compared to PBS in our first in vivo study. All mAbs cleared plaques in an ex vivo assay, although 07/2a promoted the highest phagocytic activity. Compared with 07/2a, 07/2a-k showed slightly reduced affinity to Fcγ receptors CD32 and CD64, although the two antibodies had similar binding affinities to pGlu-3 Aß. Treatment of APPSLxhQC mice with 07/2a and 07/2a-k mAbs in our second in vivo study showed significant plaque-lowering with both mAbs. Longitudinal 18F-GE180 microPET imaging revealed different temporal patterns of microglial activation for 3A1, 07/1, and 07/2a mAbs and no difference between 07/2a-k and PBS-treated Tg mice. CONCLUSION: Our results suggest that attenuation of behavioral deficits and clearance of amyloid is associated with strong effector function of the anti-pGlu-3 Aß mAb in a therapeutic treatment paradigm. We present evidence that antibody engineering to reduce CDC-mediated complement binding facilitates phagocytosis of plaques without inducing neuroinflammation in vivo. Hence, the results provide implications for tailoring effector function of humanized antibodies for clinical development.

Traumatic Brain Injury-related voiding dysfunction in mice is caused by damage to rostral pathways, altering inputs to the reflex pathways.

Brain degeneration, including that caused by traumatic brain injury (TBI) often leads to severe bladder dysfunction, including incontinence and lower urinary tract symptoms; with the causes remaining unknown. Male C57BL/6J mice underwent repetitive moderate brain injury (rmdTBI) or sham injury, then mice received either cis P-tau monoclonal antibody (cis mAb), which prevents brain degeneration in TBI mice, or control (IgG). Void spot assays revealed age-dependent incontinence in IgG controls 8 months after injury, while cis mAb treated or sham mice showed no dysfunction. No obvious bladder pathology occurred in any group. Urodynamic cystometry in conscious mice revealed overactive bladder, reduced maximal voiding pressures and incontinence in IgG control, but not sham or cis mAb treated mice. Hyperphosphorylated tau deposition and neural tangle-like pathology occurred in cortical and hippocampal regions only of IgG control mice accompanied with post-traumatic neuroinflammation and was not seen in midbrain and hindbrain regions associated with bladder filling and voiding reflex arcs. In this model of brain degeneration bladder dysfunction results from rostral, and not hindbrain damage, indicating that rostral brain inputs are required for normal bladder functioning. Detailed analysis of the functioning of neural circuits controlling bladder function in TBI should lead to insights into how brain degeneration leads to bladder dysfunction, as well as novel strategies to treat these disorders.

Space-like 56Fe irradiation manifests mild, early sex-specific behavioral and neuropathological changes in wildtype and Alzheimer's-like transgenic mice.

Space travel will expose people to high-energy, heavy particle radiation, and the cognitive deficits induced by this exposure are not well understood. To investigate the short-term effects of space radiation, we irradiated 4-month-old Alzheimer's disease (AD)-like transgenic (Tg) mice and wildtype (WT) littermates with a single, whole-body dose of 10 or 50 cGy 56Fe ions (1 GeV/u) at Brookhaven National Laboratory. At ~1.5 months post irradiation, behavioural testing showed sex-, genotype-, and dose-dependent changes in locomotor activity, contextual fear conditioning, grip strength, and motor learning, mainly in Tg but not WT mice. There was little change in general health, depression, or anxiety. Two months post irradiation, microPET imaging of the stable binding of a translocator protein ligand suggested no radiation-specific change in neuroinflammation, although initial uptake was reduced in female mice independently of cerebral blood flow. Biochemical and immunohistochemical analyses revealed that radiation reduced cerebral amyloid-ß levels and microglia activation in female Tg mice, modestly increased microhemorrhages in 50 cGy irradiated male WT mice, and did not affect synaptic marker levels compared to sham controls. Taken together, we show specific short-term changes in neuropathology and behaviour induced by 56Fe irradiation, possibly having implications for long-term space travel.

Decreased synaptic vesicle recycling efficiency and cognitive deficits in amphiphysin 1 knockout mice.

The function of the clathrin coat in synaptic vesicle endocytosis is assisted by a variety of accessory factors, among which amphiphysin (amphiphysin 1 and 2) is one of the best characterized. A putative endocytic function of amphiphysin was supported by dominant-negative interference studies. We have now generated amphiphysin 1 knockout mice and found that lack of amphiphysin 1 causes a parallel dramatic reduction of amphiphysin 2 selectively in brain. Cell-free assembly of endocytic protein scaffolds is defective in mutant brain extracts. Knockout mice exhibit defects in synaptic vesicle recycling that are unmasked by stimulation and suggest impairments at multiple stages of the cycle. These defects correlate with increased mortality due to rare irreversible seizures and with major learning deficits, suggesting a critical role of amphiphysin for higher brain functions.