Faculty Bibliography

Depression has been linked to Alzheimer's disease as either an increased risk factor for its development or as a prodromal symptom. The neurobiological basis for such an association, however, remains poorly understood. Numerous studies have examined whether changes in amyloid beta (Abeta) metabolism, which are implicated in the pathogenesis of Alzheimer's disease, are also found in depression. In this paper, we investigated the relationship between depressive symptoms and cerebrospinal fluid (CSF) Abeta indices in otherwise healthy, cognitively normal elderly with late-life major depression (LLMD) and controls using a longitudinal approach, which is a novel contribution toward the literature. Significantly lower levels of CSF Abeta42 were observed in the LLMD group at baseline and were associated with more severe depressive symptoms. During longitudinal follow-up, the depressed group remained cognitively unchanged, but was significantly less depressed than at baseline. A greater improvement in depressive symptoms was associated with increases in CSF Abeta42 levels in both groups. Increases in CSF Abeta42 and Abeta40 were also associated with increased CSF total-tau levels. Our results suggest that LLMD may be associated with state-dependent effects of CSF Abeta42 levels. Future studies should determine whether the association reflects state-dependent changes in neuronal activity and/or brain amyloid burden in depression.

Because of an extra copy of the Abeta precursor protein gene on chromosome 21, Down syndrome (DS) individuals develop high levels of Abeta peptides and Alzheimer disease-like brain amyloidosis early in life. Here we show that the gamma-secretase activating protein (GSAP), a key enzyme in amyloidogenesis, is increased in DS brains and specifically regulated at the transcriptional level by GATA1 transcription factor. The discovery of this novel pathway has translational implications for DS, because pharmacological inhibition of GSAP is an attractive and viable Abeta-lowering therapeutic strategy for this disorder. ANN NEUROL 2016;79:138-143.

Pathological accumulation of abnormally phosphorylated tau protein in astrocytes is a frequent, but poorly characterized feature of the aging brain. Its etiology is uncertain, but its presence is sufficiently ubiquitous to merit further characterization and classification, which may stimulate clinicopathological studies and research into its pathobiology. This paper aims to harmonize evaluation and nomenclature of aging-related tau astrogliopathy (ARTAG), a term that refers to a morphological spectrum of astroglial pathology detected by tau immunohistochemistry, especially with phosphorylation-dependent and 4R isoform-specific antibodies. ARTAG occurs mainly, but not exclusively, in individuals over 60 years of age. Tau-immunoreactive astrocytes in ARTAG include thorn-shaped astrocytes at the glia limitans and in white matter, as well as solitary or clustered astrocytes with perinuclear cytoplasmic tau immunoreactivity that extends into the astroglial processes as fine fibrillar or granular immunopositivity, typically in gray matter. Various forms of ARTAG may coexist in the same brain and might reflect different pathogenic processes. Based on morphology and anatomical distribution, ARTAG can be distinguished from primary tauopathies, but may be concurrent with primary tauopathies or other disorders. We recommend four steps for evaluation of ARTAG: (1) identification of five types based on the location of either morphologies of tau astrogliopathy: subpial, subependymal, perivascular, white matter, gray matter; (2) documentation of the regional involvement: medial temporal lobe, lobar (frontal, parietal, occipital, lateral temporal), subcortical, brainstem; (3) documentation of the severity of tau astrogliopathy; and (4) description of subregional involvement. Some types of ARTAG may underlie neurological symptoms; however, the clinical significance of ARTAG is currently uncertain and awaits further studies. The goal of this proposal is to raise awareness of astroglial tau pathology in the aged brain, facilitating communication among neuropathologists and researchers, and informing interpretation of clinical biomarkers and imaging studies that focus on tau-related indicators.

Alzheimer's disease (AD) is the most common form of dementia worldwide. It is characterized by an imbalance between the production and clearance of amyloid beta (Abeta) and tau proteins. In AD these normal proteins accumulate, leading to aggregation and a conformational change forming oligomeric and fibrillary species with a high beta-sheet content. Active and passive immunotherapeutic approaches result in dramatic reduction of Abeta pathology in AD animal models. However, there is much more limited evidence in human studies of significant clinical benefits from these strategies and it is becoming apparent that they may only be effective very early in AD. Vaccination targeting only tau pathology has shown benefits in some mouse studies but human studies are limited. Greater therapeutic efficacy for the next generation of vaccine approaches will likely benefit from specifically targeting the most toxic species of Abeta and tau, ideally simultaneously.

Cerebrospinal fluid (CSF) measures of phosphorylated-tau (P-tau) 231 and P-tau181 are two biomarkers for the identification of tau pathology as related to Alzheimer's disease (AD). While both are pathologically validated, their relative diagnostic performances are not well known. This cross-sectional diagnostic study of 87 normal (NL) subjects and 28 AD subjects compared CSF P-tau231 with CSF P-tau181. Logistic regression modeling demonstrated that the P-tau231 was superior to the P-tau181 in the diagnostic classifications. At a fixed 85% sensitivity cutoff, the ROC analysis shows that P-tau231 has greater overall specificity than P-tau181. While both P-tau analytes demonstrated equivalent negative predictive accuracies, P-tau231 yielded significantly fewer false positives. Moreover, P-tau231, but not P-tau181, demonstrated sensitivity to the E4 genotype. A postmortem validation with 9 AD subjects confirmed the superiority of the CSF P-tau231 specificity. This study suggests that P-tau231 has the potential to improve the CSF tau biomarker diagnosis of AD.

INTRODUCTION: Characterization of the type and topography of structural changes and their alterations throughout the lifespan of individuals with autism is essential for understanding the mechanisms contributing to the autistic phenotype. The aim of this stereological study of neurons in 16 brain structures of 14 autistic and 14 control subjects from 4 to 64 years of age was to establish the course of neuronal nuclear and cytoplasmic volume changes throughout the lifespan of individuals with autism. RESULTS: Our data indicate that a deficit of neuronal soma volume in children with autism is associated with deficits in the volume of the neuronal nucleus and cytoplasm. The significant deficits of neuronal nuclear and cytoplasmic volumes in 13 of 16 examined subcortical structures, archicortex, cerebellum, and brainstem in 4- to 8-year-old autistic children suggest a global nature of brain developmental abnormalities, but with region-specific differences in the severity of neuronal pathology. The observed increase in nuclear volumes in 8 of 16 structures in the autistic teenagers/young adults and decrease in nuclear volumes in 14 of 16 regions in the age-matched control subjects reveal opposite trajectories throughout the lifespan. The deficit in neuronal nuclear volumes, ranging from 7% to 42% in the 16 examined regions in children with autism, and in neuronal cytoplasmic volumes from 1% to 31%, as well as the broader range of interindividual differences for the nuclear than the cytoplasmic volume deficits, suggest a partial distinction between nuclear and cytoplasmic pathology. CONCLUSIONS: The most severe deficit of both neuronal nucleus and cytoplasm volume in 4-to 8-year-old autistic children appears to be a reflection of early developmental alterations that may have a major contribution to the autistic phenotype. The broad range of functions of the affected structures implies that their developmental and age-associated abnormalities contribute not only to the diagnostic features of autism but also to the broad spectrum of clinical alterations associated with autism. Lack of clinical improvement in autistic teenagers and adults indicates that the observed increase in neuron nucleus and cytoplasm volume close to control level does not normalize brain function.

INTRODUCTION: In vivo profiles of aldosterone synthase inhibitors (ASIs) have been investigated utilizing various rodent models. Due to lack of CYP17 activity, rodents produce corticosterone rather than cortisol as that of humans, which raised concern to their effectiveness in translational pharmacological characterization of ASI. METHODS: A rhesus monkey model that combines a low sodium diet with adrenocorticotropin (ACTH) treatment was developed. Plasma concentrations of steroid metabolites associated with reactions catalyzed by CYP11B2 and CYP11B1 were measured concurrently by a UPLC/MS method. RESULTS: Plasma concentration of aldosterone in regular diet fed rhesus monkeys was low at 109pg/mL. Aldosterone concentrations were increased to 252pg/mL when animals were maintained on a low sodium diet for 3weeks, and to 300pg/mL with ACTH treatment at 0.3mg/kg. The combination of low sodium diet with ACTH treatment further increased plasma concentration of aldosterone to 730pg/mL and other steroid metabolites at various levels. Intravenous administration of ASI, fadrozole (0.001-1mg/kg) or LCI699 (0.003-3mg/kg), led to dose-dependent reductions in aldosterone and 18-hydroxycorticosterone, increases in 11-deoxycorticosterone and 11-deoxycortisol, and bell-shaped changes in cortisol and corticosterone. In vivo selectivity of CYP11B2/CYP11B1 for fadrazole was 26-fold and LCI-699 was 27-fold, which was consistent with relative selectivity using in vitro values from recombinant cells transfected with rhesus monkey CYP11B2 and CYP11B1. DISCUSSION: This model enables concurrent characterization of pharmacokinetics, pharmacodynamics and selectivity of CYP11B2 over CYP11B1 inhibition in the same animal. It may be used as a translational model for pharmacological characterization of ASI.

Background: Immunomodulation is a promising therapeutic approach for Alzheimer's disease (AD); however, major drawbacks are cerebral microhemorrhages associated with increased cerebral amyloid angiopathy (CAA) and excessive inflammation. Our initial findings indicate that stimulation of TLR9 signaling with CpG oligodeoxynucleotide (ODN) is effective against CAA without inducing toxicity in AD mouse models. To further assess potential human use of CpG ODN we advanced our studies using a well-established non-human primate model of sporadic CAA, squirrel monkey (Saimiri Boliviensis). Methods: Safety and efficacy assessment studies were first performed in young squirrel monkeys (SQM). Elderly female monkeys were subcutaneously injected either with the most effective and non-toxic dosages of the class B CpG ODN containing a primate specific immunostimulatory sequence or saline. Both age groups were subjected to behavioral testing. Plasma taken during the course of treatment was analyzed to identify immune responses and AD biomarkers. Fluidigm RT-PCR was used to evaluate mRNA levels of cytokines in SQM PBMCs. Results: CpG ODN elevated the levels of various Th1/Th2 cytokines in plasma from old monkeys. Upregulation of cytokines in CpG ODN group was further confirmed by RTPCR. Pre-treatment behavioral assessment in our aged monkeys demonstrated cognitive deficits on the Inhibitory Control of Behavior and Delayed Response tests. Age effect on cognitive abilities was observed as the young group performed with overall lower session error rates compared to old animals. Post-treatment behavioral testing in our aged monkeys is ongoing. Here we report the first pyroglutamate (pE3) immunohistochemistry of aged Saimiri Boliviensis. In addition to 6E10/4G8 As-positive plaques, pyroglutamate As-positive deposits in the form of CAA and parenchymal plaques were detected. Our preliminary biomarker analyses revealed a noticeable increase in As40, As42 and AspE3 plasma levels in CpG ODN-treated group. Further longitudinal assessment of potential AD biomarkers is currently in progress. Conclusions: The presented studies represent the first trial of specifically targeting CAA in non-human primates. We hope that our research will validate this novel approach of immunomodulation as a safer method to successfully ameliorate AD related pathologies and provide critical data for potential clinical use of CpG ODN in AD patients

Background: We have previously demonstrated that immuno-intervention in AD animal models can lead to prevention of some pathology through innate immune system stimulation via TLR9 induced by CpG ODN (Scholtzova et al 2014) or the modulation of the adaptive immune system through active vaccination with the beta-sheet oligomeric form of the polymerized Bri peptide (Goni et al 2014). A challenge to therapeutic immune stimulation of old AD Tg animals, with preexisting extensive pathology, is senescence of the immune system. We have now vaccinated old 3xTg AD animals with both Abeta and tau pathology, with the pBri as a conformational antigen and CpGODNas an immune stimulator. Methods: Two groups of at least 15 months old 3xTg AD animals were inoculated four times over a period of two months with either vehicle or oligomeric pBri in Alum as previously described. Another group was inoculated from 12 to 17 month old with five doses of pBri or CpG ODN in alternate weeks as reported. Behavioral and locomotor tests were performed after the 17 month of age. The animals were then euthanized, followed by histological and biochemical analyses. Results: We show that old animals still could mount a conformational immune response that results in diminished pathology, as well as rescue of cognitive function. Both groups vaccinated with pBri and pBri-CpG ODN showed behavioral rescue when compared to age matched controls. Biochemistry and immuno-histology showed improvements of some pathological features; importantly including diminished oligomeric Abeta and tau. Conclusions: The active immunomodulation using polymerized beta-sheet oligomeric pBri can elicit a conformational antibody response even in old animals. These antibodies directed to beta-sheet conformation can retard the progression and reverse some preexisting pathology. The use of CpG ODN can help to boost the innate immune system, in senescent animals, to help establish the subsequent adaptive conformational response