Victoria Risbrough, Ph.D. - US grants

[unreadable] DESCRIPTION (provided by applicant): [unreadable] Corticotropin Releasing Factor (CRF) is involved with stress responses and its dysfunction has been indicated in depression, anxiety disorders and drug addiction. CRF has also been implicated in complex interactions with the serotonergic system, which modulates a range of affective functions. The CRF system has significant developmental influences on normal affective functioning. This proposal will examine the respective roles of the CRF1 and CRF2 receptors using novel CRF receptor selective ligands to probe anxiety-like behavior in mice using the acoustic startle reflex (ASR). After determining the roles of each CRF receptor in CRF-potentiated ASR, response to CRF will be examined in serotonin 1A receptor knockout (KO) mice. Because the anxious-like phenotype of these mice is due to the loss of 5-HT1A receptors during development, it is hypothesized that the CRF system is altered in these mice, indicating an important developmental and functional link between these two systems. Preliminary evidence that 5-HT1A mice exhibit more CRF-potentiated ASR than wild-types supports this hypothesis. This project will examine potential mechanisms for the observed hyper-sensitivity to CRF in 5-HT1A KO mice. This information will contribute to knowledge of both normal CRF-5-HT1A receptor interactions in anxiety-like behavior as well as to the understanding of the developmental role of the 5-HT 1A receptor in CRF system function. [unreadable] [unreadable] [unreadable]

[unreadable] DESCRIPTION (provided by applicant): Post-traumatic Stress Disorder (PTSD) is hypothesized to involve disruption of fear extinction processes, perhaps specifically the loss of extinction learning and habituation. Fear extinction is the gradual loss of learned fear responses to conditioned fear stimuli (CS) when the CS is no longer predictive of the noxious or fearful events. Fear extinction requires glutamatergic neurotransmission in the amygdala, and is facilitated by glutamate agonists in both humans and animals. PTSD patients exhibit high levels of corticotropin-releasing factor (CRF) in cerebrospinal fluid. CRF is a neuropeptide that controls behavioral, endocrine, and autonomic responses to stress by activating two known high-affinity CRF receptors: CRF-R1 and CRF-R2. Since CRF concentrations in cerebrospinal fluid are positively associated with the severity of PTSD symptoms, CRF deregulation may be an important pathophysiological substrate for PTSD. Given recent in vitro data indicating that CRF receptors modulate glutamatergic transmission in the amygdala, this R21 application will test a novel model of mechanisms underlying fear extinction deficits in PTSD. The model predicts that the excessive CRF release observed in PTSD patients may disrupt fear extinction via chronic CRF-R1 activation in the amygdala. Hence, the proposed studies in this R21 application will test the hypothesis that acute and chronic CRF receptor activation modulates fear extinction learning. Specific predictions are that: [1] CRF-R1 activation, which reduces glutamatergic transmission in the amygdala, will disrupt fear extinction learning; and [2] CRF-R2 activation, which increases glutamatergic transmission in the amygdala, will enhance fear extinction learning. Aim 1 of this project will use selective CRF-R1 and CRF-R2 ligands during extinction training of fear potentiated startle in normal mice to explore the potentially important and differential influences of CRF receptor subtypes on extinction learning. Aim 2 of this R21 application will explore the validity of mutant mice with CRF-over-expression specifically limited to the central nervous system as a new model with both face and construct validity for PTSD. This aim will test the hypothesis that chronic CRF elevations in CRF-over-expressing mice disrupt fear extinction via the activation of the CRF-R1 receptor. The results of these studies could lead to a new line of investigation involving an innovative combination of pharmacological and experience-based treatments using CRF-R1 antagonists to treat PTSD. [unreadable] [unreadable] [unreadable]

[unreadable] DESCRIPTION (provided by applicant): Post-traumatic Stress Disorder (PTSD) is hypothesized to involve disruption of fear extinction processes, perhaps specifically the loss of extinction learning and habituation. Fear extinction is the gradual loss of learned fear responses to conditioned fear stimuli (CS) when the CS is no longer predictive of the noxious or fearful events. Fear extinction requires glutamatergic neurotransmission in the amygdala, and is facilitated by glutamate agonists in both humans and animals. PTSD patients exhibit high levels of corticotropin-releasing factor (CRF) in cerebrospinal fluid. CRF is a neuropeptide that controls behavioral, endocrine, and autonomic responses to stress by activating two known high-affinity CRF receptors: CRF-R1 and CRF-R2. Since CRF concentrations in cerebrospinal fluid are positively associated with the severity of PTSD symptoms, CRF deregulation may be an important pathophysiological substrate for PTSD. Given recent in vitro data indicating that CRF receptors modulate glutamatergic transmission in the amygdala, this R21 application will test a novel model of mechanisms underlying fear extinction deficits in PTSD. The model predicts that the excessive CRF release observed in PTSD patients may disrupt fear extinction via chronic CRF-R1 activation in the amygdala. Hence, the proposed studies in this R21 application will test the hypothesis that acute and chronic CRF receptor activation modulates fear extinction learning. Specific predictions are that: [1] CRF-R1 activation, which reduces glutamatergic transmission in the amygdala, will disrupt fear extinction learning; and [2] CRF-R2 activation, which increases glutamatergic transmission in the amygdala, will enhance fear extinction learning. Aim 1 of this project will use selective CRF-R1 and CRF-R2 ligands during extinction training of fear potentiated startle in normal mice to explore the potentially important and differential influences of CRF receptor subtypes on extinction learning. Aim 2 of this R21 application will explore the validity of mutant mice with CRF-over-expression specifically limited to the central nervous system as a new model with both face and construct validity for PTSD. This aim will test the hypothesis that chronic CRF elevations in CRF-over-expressing mice disrupt fear extinction via the activation of the CRF-R1 receptor. The results of these studies could lead to a new line of investigation involving an innovative combination of pharmacological and experience-based treatments using CRF-R1 antagonists to treat PTSD. [unreadable] [unreadable] [unreadable]

DESCRIPTION (provided by applicant): A single nucleotide polymorphism (SNP), causing a missense mutation of codon 158 Valine to Methionine in the coding region (termed val158met), exists in the human catechol-o-methyltransferase (COMT) gene. This COMT-Met polymorphism is unique for humans and decreases COMT enzymatic activity 40% in prefrontal cortex tissue. This decrease in enzymatic activity can reduce dopamine clearance in the cortex and enhance dopamine signaling. Since evidence supports a reduction in dopamine signaling in prefrontal cortex in schizophrenia patients, the relationship between the COMT gene and schizophrenia has been extensively studied. Association studies of the COMT val158met SNP with schizophrenia risk are inconsistent, however, and support only a small contribution. Given the complexity and overlapping nature of most neuropsychiatric disorders, it is unlikely that a simple gene to complex trait mechanisms can be identified. Instead, it has been suggested that optimally reduced measures of neuropsychiatric function or "endophenotypes" may be more useful than diagnoses to understand genetic contributions to psychiatric disorders such as schizophrenia. Preliminary data indicate that prepulse inhibition is modulated by the COMT gene in both mice and humans. Prepulse inhibition is an operational measure of sensorimotor gating that is deficient in schizophrenia. Little is known about the functional mechanisms underlying COMT val158met effects on this and other schizophrenia endophenotypes. The COMT SNP is ideally suited for modeling in mice as it is a coding region SNP with a well characterized functional effect on the dopamine metabolism pathway, which is relatively conserved between humans and mice. Indeed, "expressing specific human alleles of interest in mice may help elucidate gene/protein regulation and function, providing novel model systems to study human genes related to brain development, physiology, pharmacology, neurochemistry, and behavior" (RFA NH08-050: Mouse Models Containing Human Alleles: Novel Tools to Study Brain Function). In response to this program announcement, two mutant mouse lines will be created, each carrying a human COMT gene with either the Valine or Methionine polymorphism. Studies will test the hypothesis that similar to humans, mice carrying the COMT-Val allele will show poor prepulse inhibition performance compared to mice carrying the COMT-Met allele. This mouse model of COMT val158met polymorphism could play a critical role in the identification of mechanisms of COMT effects on neuropsychiatric endophenotypes such as sensorimotor gating. In the future, this model can aid in examination of COMT gene vulnerability interactions with other genes or environmental factors relevant to schizophrenia and other neuropsychiatric disorders, such as stress, immune challenge, and developmental insult.

DESCRIPTION (provided by applicant): In response to PA-09-137 Basic and Translational Research in Emotion, this project will use murine models to elucidate the mechanisms underlying the effects of stress and the neuropeptide corticotropin releasing factor (CRF) on anxiety-like behavior related to post-traumatic stress disorder (PTSD). PTSD patients exhibit increases in startle reactivity, exaggerated contextual fear expression, and deficits in information processing. These patients also appear to exhibit pathology in the CRF system, specifically increased CRF concentrations in the cerebrospinal fluid. CRF is a neuropeptide that coordinates many behavioral and neuroendocrine responses to stress via activation of two known receptor subtypes, CRF1 and CRF2. Work funded by this grant has used mouse models to demonstrate that acute activation of both CRF receptor subtypes modulates anxiety-disorder related behaviors, such as exaggerated startle reactivity, increases in context fear-induced startle, and reductions in information processing. Although increased CRF signaling is seen in PTSD patients, it is not known if increased CRF is a pre-exisiting vulnerability factor for development of PTSD after exposure to trauma, or if CRF hypersecretion only manifests as a response to trauma. The overarching hypothesis is that CRF receptor activation is required for enduring effects of trauma on anxiety-like behavior, and that CRF hypersecretion increases the efficacy of predator stress to induce long term anxiety-like responses. To model CRF hypersecretion reported in PTSD subjects, these studies will use a genetic model of increased CRF signaling involving temporal control of CRF over-expression (CRFOE) in the forebrain via doxycycline administration. To model trauma exposure, the feline predator stress model in mice will be used. In this model, single exposure to a feline induces enduring anxiety-like behaviors up to 3 weeks post exposure. This predator stress model has face and predictive validity for PTSD. Aim 1 will examine the relative potency of predator stress to induce PTSD-like symptoms in mice with CRFOE. To test the hypothesis that CRF hypersignaling increases vulnerability to long-term effects of stress we will examine the effects of CRFOE after predator stress across 3 groups: those with CRFOE throughout life, modeling heritable CRF hyper-secretion, CRFOE only in development, modeling effects of childhood trauma on later vulnerability to stress in adulthood, and finally CRFOE only during adulthood to determine if CRFOE for a relatively brief period before and during trauma is sufficient to increase vulnerability to trauma. Aim 2 will identify the contributions of CRF1 and CRF2 signaling to the post-trauma consolidation of predator stress effects on long term anxiety-like behavior in wild- type mice. These studies will provide critical information on two fronts: (1) the verification of CRF hypersignaling as a potential vulnerability factor for development of PTSD-like symptoms after trauma; and (2) the efficacy of CRF receptor ligands to block consolidation of trauma effects. These data will inform clinical studies of possible risk factors for PTSD and help identify novel prophylactic treatment strategies.

RFA-AA-17-016 states that ?Studies examining alcohol related behaviors in current models of PTSD and potentially in novel animal models of PTSD are sought?. Animal models of PTSD are on the cutting edge of exploiting individual differences to understand mechanisms underlying resilience and susceptibility to psychopathology. Validated models of PTSD recapitulate the prevalence of PTSD in trauma-exposed individuals (~15-30% depending on trauma). We will use 2 well-validated animal models of PTSD, social defeat stress and predator stress, to understand in what biological contexts trauma and subsequent enduring stress response provokes drinking behavior. Predator stress models the enduring effects of a severe single traumatic event while social defeat stress models effects of chronic physical and emotional stress. Both models produce variance in enduring response rates to trauma exposure, (30-50% of animals exhibit prolonged behavioral and neurobiological change), providing etiological validity for PTSD. We propose to examine if two highly translatable markers of trauma-symptom development, sleep disturbance and increased peripheral immune signaling, predict development and/or maintenance of drinking after stress in rodents. This approach addresses the RFA mandate to ?identify biomarkers that will predict transition of PTSD to comorbid PTSD-alcohol misuse.? The goal is to (1) develop robust cross-species biomarkers of long term-trauma effects associated with increased alcohol consumption and (2) identify biomarkers that are predictive for treatment response. We will test the hypothesis that sleep and inflammation abnormalities after trauma predict increased drinking and treatment response. To test this hypothesis we will use a large (N=200/model) prospective, longitudinal design based on clinical research approaches. This strategy enables use of sophisticated statistical models to identify biological predictors of drinking behavior. We will assess clinical relevance by comparing these findings to humans by leveraging our clinical database of a prospective, longitudinal study of trauma in active duty service members (N=2600). This database includes data on trauma, PTSD symptoms, alcohol dependence, sleep and peripheral inflammation both before and after a combat deployment. Once validated, sleep and immune biomarkers identified in our animal models and validated in humans can be used to screen for prophylactic and therapeutic treatment effects of novel pharmacotherapies.

Mood and anxiety disorders afflict >20% of adolescents and young adults, with tremendous social and fiscal costs. Late adolescent/young adult service members facing combat are at significant risk for trauma- related disorders, constituting an ideal population to test predictions of the overarching hypothesis driving this Center renewal: that early-life fragmentation/unpredictability (FRAG) is associated with early manifestations of anhedonia and related mental health symptoms via alterations in pleasure-reward circuits which presage increased risk for psychopathology in adulthood. The studies of Project 4, guided by constructive Reviewer suggestions, aim to provide evidence for the role of FRAG-related anhedonia as a novel, unsuspected risk factor for psychopathology in a vulnerable population. We will leverage a large prospective and longitudinal cohort of late-adolescents/young adults recruited in the Marine Resiliency Study (MRS). MRS assessed emotional and cognitive health including anhedonia (within a broad battery of laboratory, self-report and clinical assessments) in young service members before a combat deployment and 3-6 month after it. We will recruit 800-1000 subjects to determine if self-report of early life FRAG is associated with altered mental health trajectories in adulthood. While capitalizing on rich and broad-based assessments of the MRS, we will test three hypotheses: 1) That FRAG, in addition to other established early-life factors, predicts anhedonia during late adolescence / early adulthood. (2) That early-life FRAG and subsequent anhedonia in late adolescence/early adulthood increases risk for adult trauma-related psychopathology. This prediction is supported by preliminary data that pre-deployment anhedonia predicts increased PTS symptoms and increased prevalence for PTSD after deployment (N=1972). This hypothesis will probe the clinical significance and impact of the Center-proposed FRAG and anhedonia risk factors. (3) That FRAG and anhedonia promote trauma-related psychopathology via aberrant pleasure-reward circuitry. A subset of MRS participants identified in Aims 1 & 2 will be recruited into 4 groups with either high or low levels of risk (i.e. combined early-life FRAG and adolescent /early adult anhedonia) and with either high or low levels of PTS symptoms. All will undergo structural MRI, DTI and fMRI and behavioral and cognitive assessments similar to those in Projects 2 and 3 to extend the developmental trajectories of FRAG- associated circuit changes and psychopathology to adulthood. In addition to testing specific Center hypotheses, the broad, longitudinal emotional and cognitive measures within MRS, coupled with data-driven MRI analyses (Imaging core), will enable examination of the role of FRAG in the trajectory of a broad spectrum of adult psychopathology.