Debra A. Bangasser - US grants

[unreadable] DESCRIPTION (provided by applicant): Stress-related mental illnesses, such as depression and anxiety disorders, are more prevalent in women than men. Dysfunctions in corticotropin-releasing factor (CRF), the neuropeptide that orchestrates the stress response, have been linked to depression and anxiety disorders. However, sex differences in the CRF system are not well characterized. Recent work from our laboratory identified sex differences in neuronal responses to CRF. Specifically, postsynaptic sensitivity of locus coeruleus (LC) neurons to CRF was greater in female vs. male rats. Moreover, swim stress sensitized LC neurons to CRF in male rats only. The following proposal will expand on these finding to determine the underlying cellular mechanism of these differences. The specific aims are as follows: 1) Identify sex differences in the coupling and signaling of the CRF receptor. CRF receptor immunoprecipitation will be used to determine whether there are sex differences in coupling of different G-proteins to the CRF receptor under stressed and unstressed conditions. Additionally, sex differences in CRF receptor signaling will be evaluated by using PKA and PKC assays. Preliminary data indicate that the CRF receptor is coupled more strongly to the Gs protein in unstressed females compared to unstressed males. Following swim stress, Gs coupling to the CRF receptor increases in males only. These are the first data to suggest sex differences in the coupling of a receptor to different G-proteins. Sex differences in CRF receptor structure and function may contribute to increased stress-susceptibility in women. 2) Identify sex differences in CRF receptor trafficking following stress. Here we will use immunoprecipitation of the CRF receptor, along with immunoelectron microscopy to determine whether the CRF receptor is trafficked differently in male vs. female rats after stress. Preliminary data suggest that following stress, CRF receptor internalization in females may be comprimised. If supported, this would suggest that female rats lack this compensatory stress response. PUBLIC HEALTH RELEVANCE Women are twice as likely to suffer from stress-related psychiatric disorders, like depression and anxiety disorders, as men. The proposed experiments will identify sex differences in the receptor for CRF, an important neuromodulator of stress, which may underlie the increased vulnerability of females to stress and stress-related pathology. Importantly, because CRF antagonists are being developed to treat depression and anxiety disorders, sex differences in the CRFr could impact the efficacy of these compounds in women. [unreadable] [unreadable] [unreadable]

DESCRIPTION (provided by applicant): Stress-related psychiatric disorders, like depression and post-traumatic stress disorder, are debilitating mental illnesses that affect twice as many women as men. Although the etiology of this disparity remains unknown, it is thought to be due to sex differences in stress responses. Corticotropin-releasing factor (CRF) orchestrates stress responses, in part, by regulating norepinephrine (NE) and serotonin (5-HT) transmission, and CRF is dysregulated in stress-related disorders. The goal of my current research is to identify sex differences in a receptor for CRF (CRF1 subtype) that may account for sex differences in stress responsivity. To date, I found that CRF1 signals and is trafficked differently in female rats in a manner that can account for elevated responses to acute stress and decreased adaptation to chronic stress. In females, CRF1 immunoprecipitation revealed a greater coupling to Gs, the GTP-binding protein that mediates most cellular responses. Additionally, stress-induced CRF1 association with 2-arrestin2, an integral step in receptor internalization, was apparent in males but not females. Immunoelectron microscopy confirmed stress-induced CRF1 internalization in male rats only, suggesting that this adaptive process to compensate for large amounts of CRF, as may be released in depression, is compromised in females. Importantly, sex differences in CRF1 function rendered NE neurons in the locus coeruleus of female rats more sensitive to low levels of CRF and less adaptable to high levels of CRF. However, because this is the first report of sex differences in stress- related neuropeptide receptor, many questions remain unanswered. Aim 1 of this proposal, which will be completed during the mentored phase (K99), investigates why CRF1 binds proteins differently in males vs. females. There are no sex differences in CRF1 structure, so I will learn proteomic approaches to identify whether sex differences in post-translational modifications of CRF1 account for these effects. Aims 2 and 3 will be completed during the independent phase. Aim 2 will identify the hormones that contribute to the sex difference in CRF1. To this end, I will combine previously acquired endocrine techniques with the skills learned during the K99 phase to determine whether ovarian or testicular hormones establish the sex differences. Aim 3 will evaluate whether sex differences extend to the other receptor subtype, CRF2, in the dorsal raphe nucleus. Because CRF1 and CRF2 share a high degree of sequence identity, proteomic approaches are expected to reveal sex differences in the CRF2. CRF2 activation of the dorsal raphe-5-HT system promotes a passive behavioral response strategy to stress that is a risk factor for depression. Thus, sex differences in CRF2 may contribute to the increased vulnerability of females this disorder. By addressing these questions, this proposal will help elucidate the etiology of sex differences in stress-related disorders. Moreover, because CRF antagonists are being developed to treat these illnesses, considering sex differences in CRF receptors may increase the efficacy of these compounds in women. PUBLIC HEALTH RELEVANCE: Women are twice as likely as men to suffer from stress-related psychiatric disorders, such as depression and post-traumatic stress disorder, however the biological basis of this sex difference remains unknown. The proposed research will identify molecular and hormonal changes that increase the function of a critical stress-related neuropeptide in female rats. This project will not only help us understand why women are more vulnerable to stress-related mental illnesses, but it will identify new pharmaceutical targets which can lead to treatments that are efficacious in both men and women.

Opioid use disorder is on the rise and the economic and human cost is staggering. It remains unclear why only a subset of people who take opioids develop dependence, prompting efforts to understand factors that promote vulnerability to opioid misuse. However, it is also critical to identify factors that promote resilience to substance use disorder (SUD). Experiences early in life can alter risk/resilience for the later development of disorders. For example, early life stress that is not overwhelming can have an ?inoculating? effect that promotes the development of resilience in adulthood. Here we use a rat model of early life adversity, the limited bedding and nesting (LBN) model, to assess how this manipulation affects addiction-like phenotypes in adulthood. In LBN, dams and their pups are exposed to a low resource environment during the pups first week of life, which induces stress in the pups. We found that LBN inoculates males against addiction-like behaviors, such that adult male rats exposed to LBN self-administer less morphine and are less motivated to take morphine than adult males raised in a normal, adequately resourced, nesting environment. Impulsive choice, a risk factor for SUD, was also assessed, and LBN reduced impulsive choice in males. LBN had no effect on these behaviors in female rats. This proposal will determine how LBN further alters addition-like behaviors, as well as changes the physiology and the transcriptome of the nucleus accumbens (NAc), a region that critically mediates drug intake and impulsivity. Aim 1 will test the hypothesis that LBN shifts the dose-response curve for morphine self- administration to the right in males. This aim will also determine if LBN reduces both impulsive choice and impulsive action in males. Consistent with our preliminary data, behavioral changes following LBN in females are not expected. Aim 2 will test the hypothesis that LBN reduces glutamatergic transmission in the NAc of males, but not females, an effect that would promote resilience to the reinforcing efficacy of morphine. Prior work has demonstrated that early life experience can reprogram the brain through epigenetic modifications that lead to persistent changes in gene expression and neuronal signaling. Thus, Aim 3 will identify sex-specific changes in gene expression and accompanying chromatin remodeling events in the NAc elicited by LBN. Our preliminary data reveal that LBN reduces the expression of several glutamate signaling genes in males. Certain histone deacetylases (HDACs), enzymes that remove acetyl groups from histone tails, are implicated in these gene changes. We will test the behavioral relevance of these HDACs by manipulating their function within the NAc and determining whether they mediate resilience to addiction-related behavior. Collectively, this proposal will reveal mechanisms by which LBN can inoculate males against addiction-like phenotypes. Notably, our team of investigators is uniquely positioned to assess LBN-induced changes from the behavioral to the molecular level. Moreover, the sex-specificity of the LBN effects will allow us to, by comparing the sexes, identify novel targets that promote resilience to SUD, which may lead to the development of better therapies to reduce opioid misuse.