Sex, age, and hunger regulate behavioral prioritization through dynamic modulation of chemoreceptor expression.

BACKGROUND: Adaptive behavioral prioritization requires flexible outputs from fixed neural circuits. In C. elegans, the prioritization of feeding versus mate searching depends on biological sex (males will abandon food to search for mates, whereas hermaphrodites will not) as well as developmental stage and feeding status. Previously, we found that males are less attracted than hermaphrodites to the food-associated odorant diacetyl, suggesting that sensory modulation may contribute to behavioral prioritization. RESULTS: We show that somatic sex acts cell autonomously to reconfigure the olfactory circuit by regulating a key chemoreceptor, odr-10, in the AWA neurons. Moreover, we find that odr-10 has a significant role in food detection, the regulation of which contributes to sex differences in behavioral prioritization. Overexpression of odr-10 increases male food attraction and decreases off-food exploration; conversely, loss of odr-10 impairs food taxis in both sexes. In larvae, both sexes prioritize feeding over exploration; correspondingly, the sexes have equal odr-10 expression and food attraction. Food deprivation, which transiently favors feeding over exploration in adult males, increases male food attraction by activating odr-10 expression. Furthermore, the weak expression of odr-10 in well-fed adult males has important adaptive value, allowing males to efficiently locate mates in a patchy food environment. CONCLUSIONS: We find that modulated expression of a single chemoreceptor plays a key role in naturally occurring variation in the prioritization of feeding and exploration. The convergence of three independent regulatory inputs--somatic sex, age, and feeding status--on chemoreceptor expression highlights sensory function as a key source of plasticity in neural circuits.

Early oligodendrocyte/myelin pathology in Alzheimer's disease mice constitutes a novel therapeutic target.

The detection of myelin disruptions in Alzheimer's disease (AD)-affected brain raises the possibility that oligodendrocytes undergo pathophysiological assault over the protracted course of this neurodegenerative disease. Oligodendrocyte compromise arising from direct toxic effects imparted by pathological amyloid-beta peptides and/or through signals derived from degenerating neurons could play an important role in the disease process. We previously demonstrated that 3xTg-AD mice, which harbor the human amyloid precursor protein Swedish mutant transgene, presenilin knock-in mutation, and tau P301L mutant transgene, exhibit significant alterations in overall myelination patterns and oligodendrocyte status at time points preceding the appearance of amyloid and tau pathology. Herein, we demonstrate that Abeta(1-42) leads to increased caspase-3 expression and apoptotic cell death of both nondifferentiated and differentiated mouse oligodendrocyte precursor (mOP) cells in vitro. Through use of a recombinant adeno-associated virus serotype-2 (rAAV2) vector expressing an Abeta(1-42)-specific intracellular antibody (intrabody), oligodendrocyte and myelin marker expression, as well as myelin integrity, were restored in the vector-infused brain regions of 3xTg-AD mice. Overall, this work provides further insights into the impact of Abeta(1-42)-mediated toxicity on the temporal and spatial progression of subtle myelin disruption during the early presymptomatic stages of AD and may help to validate new therapeutic options designed to avert these early impairments.

Abeta-directed single-chain antibody delivery via a serotype-1 AAV vector improves learning behavior and pathology in Alzheimer's disease mice.

Alzheimer's disease (AD) is a progressive dementing disorder characterized by age-related amyloid-beta (Abeta) deposition, neurofibrillary tangles, and synapse and neuronal loss. It is widely recognized that Abeta is a principal pathogenic mediator of AD. Our goal was to develop an immunotherapeutic approach, which would specifically lead to the clearance and/or neutralization of Abeta in the triple transgenic mouse model (3xTg-AD). These mice develop the amyloid and tangle pathologies and synaptic dysfunction reminiscent of human AD. Using a human single-chain variable fragment (scFv) antibody phage display library, a novel scFv antibody specific to Abeta was isolated, its activity characterized in vitro, and its open reading frame subsequently cloned into a recombinant adeno-associated virus (rAAV) vector. Three-month-old 3xTg-AD mice were intrahippocampally infused with serotype-1 rAAV vectors encoding Abeta-scFv or a control vector using convection-enhanced delivery (CED). Mice receiving rAAV1-Abeta-scFv harbored lower levels of insoluble Abeta and hyperphosphorylated tau, and exhibited improved cognitive function as measured by the Morris Water Maze (MWM) spatial memory task. These results underscore the potential of gene-based passive vaccination for AD, and provide further rationale for the development of Abeta-targeting strategies for this debilitating disease.

An improved method for generating consistent soluble amyloid-beta oligomer preparations for in vitro neurotoxicity studies.

Soluble Abeta oligomers are recognized as playing a key role in Alzheimer's disease (AD) pathophysiology. Despite their significance, many investigators encounter difficulty generating reliable preparations for in vitro and in vivo experiments. Solutions of Abeta are often unstable and soluble conformer profiles inconsistent. In this study we describe detailed methods for preparing Abeta oligomers that are stable for several weeks and are enriched for low and high molecular weight oligomeric forms, including the 56-kDa form, a conformer implicated in AD-related cognitive impairment. We characterize their structural and functional properties using Western blot, dot blot, atomic force microscopy, Thioflavine T fluorescence, and primary neuronal culture toxicity assays. These synthetic preparations should prove valuable to many studying Abeta-mediated mechanisms underlying AD.

Effects of herpes simplex virus amplicon transduction on murine dendritic cells.

The herpes simplex virus (HSV)-based amplicon is a versatile vaccine platform that has been preclinically vetted as a gene-based immunotherapeutic for cancer, HIV, and neurodegenerative disorders. Although it is well known that injection of dendritic cells (DCs) transduced ex vivo with helper virus-free HSV amplicon vectors expressing disease-relevant antigens induces antigen-specific immune responses, the cellular receptor(s) by which the amplicon virion gains entry into DCs, as well as the effects that viral vector transduction impinges on the physiological status of these cells, is less understood. Herein, we examine the effects of amplicon transduction on mouse bone marrow-derived DCs. We demonstrate that HSV-1 cellular receptors HveC and HveA are expressed on the cell surface of murine DCs, and that HSV amplicons transduce DCs at high efficiency (>90%) with minimal effects on cell viability. Transduction of dendritic cells with amplicons induces a transient DC maturation phenotype as represented by self-limited upregulation of MHCII and CD11c markers. Mature DCs are less sensitive to HSV amplicon transduction than immature DCs regarding DC-related surface marker maintenance. From this and our previous work, we conclude that HSV amplicons transduce DCs efficiently, but impart differential and transient physiological effects on mature and immature DC pools, which will facilitate fine-tuning of this vaccination platform and further exploit its potential in immunotherapy.

Potential of chemo-immunotherapy and radioimmunotherapy in relapsed primary central nervous system (CNS) lymphoma.

Five patients with relapsed PCNSL were given chemo-immunotherapy (rituximab followed by carboplatin and methotrexate) with osmotic blood-brain barrier (BBB) opening. Four patients achieved CR and one patient had stable disease. Two patients (2/5) had durable responses (survival: 230+, 122+, 82, 42, 38 weeks). One patient later received Indium-111-ibritumomab tiuxetan and Yttrium-90-ibritumomab tiuxetan intravenous, without BBB opening. There was good uptake of Indium-111 ibritumomab tiuxetan in tumor on SPECT scan after 48 h. Estimated radiation doses to brain around and distant from tumor were within safe limits. After Ytrium-90 ibritumomab tiuxetan there was CR in enhancing tumor where the BBB was leaky, but lesions occurred in other brain regions, where the BBB was intact during Yttrium-90 ibritumomab tiuxetan infusion. Imaging and dosimetry with Indium-111 ibritumomab tiuxetan and efficacy with Yttrium-90 ibritumomab tiuxetan suggest the need for future enhanced CNS delivery when using monoclonal or radiolabeled antibodies, as intravenous delivery alone may provide modest clinical benefit due to limited BBB permeability.

Alterations in striatal dopamine catabolism precede loss of substantia nigra neurons in a mouse model of juvenile neuronal ceroid lipofuscinosis.

Batten disease, or juvenile neuronal ceroid lipofuscinosis (JNCL), results from mutations in the CLN3 gene. This disorder presents clinically around the age of 5 years with visual deficits progressing to include seizures, cognitive impairment, motor deterioration, hallucinations, and premature death by the third to fourth decade of life. The motor deficits include coordination and gait abnormalities, myoclonic jerks, inability to initiate movements, and spasticity. Previous work from our laboratory has identified an early reduction in catechol-O-methyltransferase (COMT), an enzyme responsible for the efficient degradation of dopamine. Alterations in the kinetics of dopamine metabolism could cause the accumulation of undegraded or unsequestered dopamine leading to the formation of toxic dopamine intermediates. We report an imbalance in the catabolism of dopamine in 3 month Cln3(-/-) mice persisting through 9 months of age that may be causal to oxidative damage within the striatum at 9 months of age. Combined with the previously reported inflammatory changes and loss of post-synaptic D1alpha receptors, this could facilitate cell loss in striatal projection regions and underlie a general locomotion deficit that becomes apparent at 12 months of age in Cln3(-/-) mice. This study provides evidence for early changes in the kinetics of COMT in the Cln3(-/-) mouse striatum, affecting the turnover of dopamine, likely leading to neuron loss and motor deficits. These data provide novel insights into the basis of motor deficits in JNCL and how alterations in dopamine catabolism may result in oxidative damage and localized neuronal loss in this disorder.

Translational considerations for CNS gene therapy.

Gene transfer is being rigorously evaluated in the laboratory in the preparation for the development of clinical therapies. Many CNS diseases, which have proved more challenging to treat than peripheral disorders, are prime candidates for gene therapy. However, there are numerous considerations in the development of gene therapy, including delivery, maintenance of expression, transgene level regulation, toxicity of the viral vector system and safety of the gene product. The authors review these issues and discuss various approaches used in preclinical studies. Alzheimer's and Parkinson's disease are employed as models, in which much research has already been performed, to address disease-specific questions about gene therapy approaches.