Dmitri Volfson

Evaluation of TrkB and BDNF transcripts in prefrontal cortex, hippocampus, and striatum from subjects with schizophrenia, bipolar disorder, and major depressive disorder.

Brain-derived neurotrophic factor (BDNF) signaling is integral to a range of neural functions, including synaptic plasticity and exhibits activity-dependent regulation of expression. As altered BDNF signaling has been implicated in multiple psychiatric diseases, here we report a quantitative reverse transcription polymerase chain reaction (RT-PCR) analysis of mRNAs encoding TrkB, total BDNF, and the four most abundant BDNF transcripts (I, IIc, IV, and VI) in postmortem tissue from matched tetrads of subjects with schizophrenia, bipolar disorder, or major depressive disorder (MDD) and healthy comparison subjects. In all three regions examined, dorsolateral prefrontal cortex (DLPFC), associative striatum and hippocampus, total BDNF mRNA levels did not differ in any disease state. In DLPFC, BDNF IIc was significantly lower in schizophrenia relative to healthy comparison subjects. In hippocampus, BDNF I, IIc, and VI were lower in subjects with both schizophrenia and bipolar disorder relative to comparison subjects. In striatum, TrkB mRNA was lower in bipolar disorder and MDD, while BDNF IIc was elevated in MDD, relative to comparison subjects. These data highlight potential alterations in BDNF signaling in the corticohippocampal circuit in schizophrenia, and within the striatum in mood disorders. Novel therapies aimed at improving BDNF-TrkB signaling may therefore have potential to impact on a range of psychiatric disorders.

STEP Levels Are Unchanged in Pre-Frontal Cortex and Associative Striatum in Post-Mortem Human Brain Samples from Subjects with Schizophrenia, Bipolar Disorder and Major Depressive Disorder

Increased protein levels of striatal-enriched tyrosine phosphatase (STEP) have recently been reported in postmortem schizophrenic cortex. The present study sought to replicate this finding in a separate cohort of postmortem samples and to extend observations to striatum, including subjects with bipolar disorder and major depressive disorder in the analysis. No statistically significant changes between disease and control subjects were found in STEP mRNA or protein levels in dorsolateral prefrontal cortex or associative striatum. Although samples were matched for several covariates, postmortem interval correlated negatively with STEP protein levels, emphasizing the importance of including these analyses in postmortem studies.

Passive immunotherapy targeting amyloid-β reduces cerebral amyloid angiopathy and improves vascular reactivity.

Prominent cerebral amyloid angiopathy is often observed in the brains of elderly individuals and is almost universally found in patients with Alzheimers disease. Cerebral amyloid angiopathy is characterized by accumulation of the shorter amyloid-β isoform(s) (predominantly amyloid-β40) in the walls of leptomeningeal and cortical arterioles and is likely a contributory factor to vascular dysfunction leading to stroke and dementia in the elderly. We used transgenic mice with prominent cerebral amyloid angiopathy to investigate the ability of ponezumab, an anti-amyloid-β40 selective antibody, to attenuate amyloid-β accrual in cerebral vessels and to acutely restore vascular reactivity. Chronic administration of ponezumab to transgenic mice led to a significant reduction in amyloid and amyloid-β accumulation both in leptomeningeal and brain vessels when measured by intravital multiphoton imaging and immunohistochemistry. By enriching for cerebral vascular elements, we also measured a significant reduction in the levels of soluble amyloid-β biochemically. We hypothesized that the reduction in vascular amyloid-β40 after ponezumab administration may reflect the ability of ponezumab to mobilize an interstitial fluid pool of amyloid-β40 in brain. Acutely, ponezumab triggered a significant and transient increase in interstitial fluid amyloid-β40 levels in old plaque-bearing transgenic mice but not in young animals. We also measured a beneficial effect on vascular reactivity following acute administration of ponezumab, even in vessels where there was a severe cerebral amyloid angiopathy burden. Taken together, the beneficial effects ponezumab administration has on reducing the rate of cerebral amyloid angiopathy deposition and restoring cerebral vascular health favours a mechanism that involves rapid removal and/or neutralization of amyloid-β species that may otherwise be detrimental to normal vessel function.

Computationally efficient permutation-based confidence interval estimation for tail-area FDR

Challenges of satisfying parametric assumptions in genomic settings with thousands or millions of tests have led investigators to combine powerful False Discovery Rate (FDR) approaches with computationally expensive but exact permutation testing. We describe a computationally efficient permutation-based approach that includes a tractable estimator of the proportion of true null hypotheses, the variance of the log of tail-area FDR, and a confidence interval (CI) estimator, which accounts for the number of permutations conducted and dependencies between tests. The CI estimator applies a binomial distribution and an overdispersion parameter to counts of positive tests. The approach is general with regards to the distribution of the test statistic, it performs favorably in comparison to other approaches, and reliable FDR estimates are demonstrated with as few as 10 permutations. An application of this approach to relate sleep patterns to gene expression patterns in mouse hypothalamus yielded a set of 11 transcripts associated with 24 h REM sleep [FDR = 0.15 (0.08, 0.26)]. Two of the corresponding genes, Sfrp1 and Sfrp4, are involved in wnt signaling and several others, Irf7, Ifit1, Iigp2, and Ifih1, have links to interferon signaling. These genes would have been overlooked had a typical a priori FDR threshold such as 0.05 or 0.1 been applied. The CI provides the flexibility for choosing a significance threshold based on tolerance for false discoveries and precision of the FDR estimate. That is, it frees the investigator to use a more data-driven approach to define significance, such as the minimum estimated FDR, an option that is especially useful for weak effects, often observed in studies of complex diseases.

Impaired β-arrestin recruitment and reduced desensitization by non-catechol agonists of the D1 dopamine receptor

Selective activation of dopamine D1 receptors (D1Rs) has been pursued for 40 years as a therapeutic strategy for neurologic and psychiatric diseases due to the fundamental role of D1Rs in motor function, reward processing, and cognition. All known D1R-selective agonists are catechols, which are rapidly metabolized and desensitize the D1R after prolonged exposure, reducing agonist response. As such, drug-like selective D1R agonists have remained elusive. Here we report a novel series of selective, potent non-catechol D1R agonists with promising in vivo pharmacokinetic properties. These ligands stimulate adenylyl cyclase signaling and are efficacious in a rodent model of Parkinsons disease after oral administration. They exhibit distinct binding to the D1R orthosteric site and a novel functional profile including minimal receptor desensitization, reduced recruitment of β-arrestin, and sustained in vivo efficacy. These results reveal a novel class of D1 agonists with favorable drug-like properties, and define the molecular basis for catechol-specific recruitment of β-arrestin to D1Rs.Dopamine receptor agonists are used for the treatment of various psychiatric diseases. Here, the authors screen approximately three million compounds and identify a novel class of D1R agonists that do not have a catechol scaffold and possess promising pharmacokinetic properties.

Abnormal clotting of the intrinsic/contact pathway in Alzheimer disease patients is related to cognitive ability

Alzheimer disease (AD) is a neurodegenerative disorder characterized by extracellular β-amyloid (Aβ) deposition. Although peripheral inflammation and cerebrovascular pathology are reported in AD, there is a lack of plasma biomarkers in this field. Because the contact system is triggered in patient plasma, we hypothesized that the hemostasis profile could be a novel biomarker in AD. Here, we assessed the clotting profile in plasma from AD patients and age-matched controls. Utilizing clinically relevant assays, thromboelastography and activated partial thromboplastin time, we found impaired clot initiation and formation rate in AD patient plasma. These coagulation end points correlated with cerebrospinal fluid neurofilament-light levels and cognition and were more profound in younger AD patients. Ex vivo intrinsic clotting of plasma from AD mice expressing human amyloid precursor protein (APP) was also delayed in an age-dependent manner, suggesting that this phenotype is related to APP, the parent protein of Aβ. Further analysis of coagulation factors in human plasma indicated that endogenous inhibitor(s) of factors XII and XI in AD plasma contribute to this delayed clotting. Together, these data suggest that delayed clotting in young AD patients is a novel biomarker and that therapies aimed to correct this phenotype might be beneficial in this patient population. Follow-up studies in additional AD patient cohorts are warranted to further evaluate these findings.

THE EFFECTS OF A NOVEL NON-CATECHOL DOPAMINE PARTIAL AGONIST ON WORKING MEMORY IN THE AGED RHESUS MONKEY

P2-083 THE EFFECTS OFA NOVEL NONCATECHOL DOPAMINE PARTIAL AGONISTONWORKINGMEMORY IN THE AGED RHESUS MONKEY Tara L. Moore, Rebecca Smith, Bethany Bowley, Ronald Killiany, Dmitri Volfson, David L. Gray, Kari R. Fonseca, Sheri I. Shamblin, Rouba Kozak, Boston University School of Medicine, Boston, MA, USA; Pfizer Inc., Cambridge, MA, USA; Pfizer Inc., Groton, CT, USA. Contact e-mail: Rouba.Kozak@pfizer.com

NOVEL NON-CATECHOL D1 RECEPTOR AGONISTS EXHIBIT SUSTAINED PHARMACOLOGICAL ACTIVITY

Background: Sleep deprivation (SD) has been implicated as a risk factor for various neurodegenerative disorders viz., dementia including Alzheimer’s disease, ultimately leading to cognitive impairment. It has enduring effects on learning and memory, besides hippocampal synaptic plasticity. Although SD is known to result in cognitive impairment, mechanisms underlying this process are still not clear. Angiotensin converting enzyme (ACE) inhibitors has been studied for its neuroprotective effect against Parkinson’s, Alzheimer’s, Cerebral stroke etc., Hence we investigated the effects of Captopril, the first generation drug of ACE inhibitors on sleep deprivation induced cognitive impairment in C57BL/6J mice. Methods: We used Single platform method of Sleep deprivation in C57BL/6J mice for continuous 5 days. Novel object recognition test (NORT) and elevated plus maze (EPM) were used to assess the cognitive enhancing effect of Captopril during SD. Hippocampal synaptic plasticity was investigated using pre and post – synaptic markers such as Synapsin – I and Neurabin. Brain derived neurotrophic factor (BDNF), which is known to play critical role in synaptic transmission was also examined, besides NeuN. Spine density was evaluated by Golgi method and ultra-structural alterations in the hippocampus were studied by Transmission electron microscopy (TEM). Results: SD caused structural and functional alterations in brain that led to severe learning and memory impairment. Mice treated with Captopril during SD, significantly (p<0.01) improved recognition and spatial memory. The Immunohistochemical staining showed decreased expressions of Synapsin I and Neurabin in SD group whereas Captopril treatment exhibited significant (p<0.001) increase of these expressions in the hippocampus tissue. Treatment with Captopril showed substantial (p<0.01) upregulation in the BDNF expression compared to that of SD group which was accompanied by increased number of NeuN positive cells in the treatment group. Similarly the decreased spine density in SD group was moderately restored by Captopril, besides considerable degree of restoration of the hippocampal mitochondria structure revealed by TEM. Conclusions: Results of the present studies for the first time reports that Captopril attenuates sleep deprivation induced cognitive dysfunction bymodulating the synaptic plasticity, thereby improving the learning and memory functions.

IMPROVED VASCULAR REACTIVITY AND REDUCED CEREBRAL AMYLOID ANGIOPATHY FOLLOWING PASSIVE IMMUNOTHERAPY IN TRANSGENIC MICE

Background: Mixed brain pathologies account for most dementia cases in community-dwelling older persons and those with multiple brain pathologies, had greatly increased odds (3 fold) for dementia. Cerebrovascular pathology is common in the elderly and contributes to ischemic stroke, intracerebral hemorrhages (ICHs), microbleeds, and cerebral amyloid angiopathy (CAA). Moreover the common co-occurrence of AD and vascular pathology mesh with epidemiologic data showing that many vascular risk factors are also risk factors for brain atrophy and dementia. The importance of vascular dysfunction/degeneration was recognized at the recent NINDS workshop on Alzheimer’s Disease-Related Dementias where several sessions were devoted to the vascular contribution to dementia (May 1-2, 2013). Thus, there is increasing recognition that dysfunction in the cerebral vasculature can play a significant role in dementia, including AD where approximately 80-95% of the cases have cerebral vascular pathology The deposition of amyloid-b (Ab) peptides in the cerebral vasculature is an important component leading to ICH and potentially cognitive impairment in Alzheimer’s disease (AD). Finally, blood pressure lowering was shown to reduce the risk of CAA-related ICH, suggesting that hypertension is a factor in inducing ICH in patients with CAA. Methods: This study aims to determine the effect of Ab accumulation on acute and chronic hypertension using a transgenic mouse model overexpressing mutant human amyloid precursor protein. Tg2576 mice and non-transgenic (nonTg) littermates were treated with an angiontensin II (AngII) infusion with ALZET Osmotic pumps (1000 ng/kg/min) and L-NAME (100 mg/kg/day) in drinking water to produce chronic hypertension. Oneweek later, transient acute hypertension was induced by AngII injections (0.5 m g/g, twice daily). Results: A similar increase in systolic blood pressure was observed in both Tg2576 and nonTg mice, however, compared with nonTg mice, Tg2576 mice developed signs of ICH with a markedly shorter latency. In addition, there was as an increase in CAA in the hypertensive Tg2576 mice and the number and size of spontaneous microhemorrhages were significantly increased. Conclusions: Our mixed vascular brain pathology model, which utilizes APP transgenic mice in combination with an acute and chronic hypertension protocol, significantly increases both cerebrovascular and AD-like pathologies.