Gemma Casadesus, PhD, Tufts University - US grants

[unreadable] DESCRIPTION (provided by applicant): Estrogen is thought to play an important role in age-related cognitive decline, neuronal plasticity, as well as the pathogenesis of Alzheimer disease (AD). Epidemiological evidence linked decreased incidence of AD and cognitive decline in women previously exposed to hormone (estrogen) replacement therapy (HRT). Further, clinical data correlates estrogen deficiency to the etiology of AD, yet initiating HRT in elderly (age 65 and over) post-menopausal women failed to improve cognitive performance. These findings have led many in the field, including us, to re-examine the role of estrogen in cognition and AD and to look beyond the direct effects of estrogen to more indirect, though perhaps no less important, effects. To this end, declining levels of sex steroids in women and men, albeit to a lesser degree, result in increases in gonadotropins such as luteinizing hormone (LH) through loss of feedback inhibition. LH, like estrogen, is modulated by HRT and serum levels of LH are higher in AD patients compared to aged-matched controls. Moreover, recent published and preliminary data, including our own studies, show that LH is capable of modulating cognitive behavior and associated neuronal plasticity markers, is present in the brain, has the highest levels of receptors in the hippocampus, is increased in the AD brain, and is capable of altering amyloid-b protein precursor processing. In this proposal, our goal is to dissect the hormonal contributions and interactions of estrogen and LH on cognition, synaptic plasticity, and AD pathogenesis using animal models of menopause and AD. Specifically, we propose to measure cognitive behavior [Morris Water Maze (MWM) task], neuronal plasticity as measured by structural and functional changes in synaptic remodeling, and cognitive decline (MWM) and amyloid-b synthesis and deposition in female C57/BLJ6 and AD transgenic mice (Tg2576) after ovariectomy and thereafter assess the effect of a "critical window" of efficacy of pharmacological manipulation of estrogen and LH levels, either singly or in combination. This systematic analysis will not only address the importance of hormonal action in cognition but will also begin to dissect the individual contributions of estrogen and LH and how these aspects are affected by the post-menopausal timing of HRT. PUBLIC HEALTH RELEVANCE: Postmenopausal changes in HPG-axis hormones, in particular estrogen, is tightly linked to cognitive impairment in older individuals and development of AD. This proposal trascends beyond the study of estrogen to determine the influence of other HPG-axis hormones. Specifically, the objective of this body of work is to investigate whether luteinizing hormone is a central mediator of such impairment, independently or in conjunction with estrogen. Outcomes of the proposal are not only important from a scientific perspective but could lead to immediate novel therapeutic regimens. [unreadable] [unreadable] [unreadable]

DESCRIPTION (provided by applicant): Estrogen is thought to play an important role in age-related cognitive decline, neuronal plasticity, as well as the pathogenesis of Alzheimer disease (AD). Epidemiological evidence linked decreased incidence of AD and cognitive decline in women previously exposed to hormone (estrogen) replacement therapy (HRT). Further, clinical data correlates estrogen deficiency to the etiology of AD, yet initiating HRT in elderly (age 65 and over) post-menopausal women failed to improve cognitive performance. These findings have led many in the field, including us, to re-examine the role of estrogen in cognition and AD and to look beyond the direct effects of estrogen to more indirect, though perhaps no less important, effects. To this end, declining levels of sex steroids in women and men, albeit to a lesser degree, result in increases in gonadotropins such as luteinizing hormone (LH) through loss of feedback inhibition. LH, like estrogen, is modulated by HRT and serum levels of LH are higher in AD patients compared to aged-matched controls. Moreover, recent published and preliminary data, including our own studies, show that LH is capable of modulating cognitive behavior and associated neuronal plasticity markers, is present in the brain, has the highest levels of receptors in the hippocampus, is increased in the AD brain, and is capable of altering amyloid-b protein precursor processing. In this proposal, our goal is to dissect the hormonal contributions and interactions of estrogen and LH on cognition, synaptic plasticity, and AD pathogenesis using animal models of menopause and AD. Specifically, we propose to measure cognitive behavior [Morris Water Maze (MWM) task], neuronal plasticity as measured by structural and functional changes in synaptic remodeling, and cognitive decline (MWM) and amyloid-b synthesis and deposition in female C57/BLJ6 and AD transgenic mice (Tg2576) after ovariectomy and thereafter assess the effect of a critical window of efficacy of pharmacological manipulation of estrogen and LH levels, either singly or in combination. This systematic analysis will not only address the importance of hormonal action in cognition but will also begin to dissect the individual contributions of estrogen and LH and how these aspects are affected by the post-menopausal timing of HRT. PUBLIC HEALTH RELEVANCE: Postmenopausal changes in HPG-axis hormones, in particular estrogen, is tightly linked to cognitive impairment in older individuals and development of AD. This proposal trascends beyond the study of estrogen to determine the influence of other HPG-axis hormones. Specifically, the objective of this body of work is to investigate whether luteinizing hormone is a central mediator of such impairment, independently or in conjunction with estrogen. Outcomes of the proposal are not only important from a scientific perspective but could lead to immediate novel therapeutic regimens.

Principal Investigator/Program Director (Last, first, middle): Casadesus, Gemma Project Summary Estrogen is thought to play an important role in age-related cognitive decline, neuronal plasticity, as well as the pathogenesis of Alzheimer disease (AD). Epidemiological evidence linked decreased incidence of AD and cognitive decline in women previously exposed to hormone (estrogen) replacement therapy (HRT). Further, clinical data correlates estrogen deficiency to the etiology of AD, yet initiating HRT in elderly (age 65 and over) post-menopausal women failed to improve cognitive performance. These findings have led many in the field, including us, to re-examine the role of estrogen in cognition and AD and to look beyond the direct effects of estrogen to more indirect, though perhaps no less important, effects. To this end, declining levels of sex steroids in women and men, albeit to a lesser degree, result in increases in gonadotropins such as luteinizing hormone (LH) through loss of feedback inhibition. LH, like estrogen, is modulated by HRT and serum levels of LH are higher in AD patients compared to aged-matched controls. Moreover, recent published and preliminary data, including our own studies, show that LH is capable of modulating cognitive behavior and associated neuronal plasticity markers, is present in the brain, has the highest levels of receptors in the hippocampus, is increased in the AD brain, and is capable of altering amyloid-¿ protein precursor processing. In this proposal, our goal is to dissect the hormonal contributions and interactions of estrogen and LH on cognition, synaptic plasticity, and AD pathogenesis using animal models of menopause and AD. Specifically, we propose to measure cognitive behavior [Morris Water Maze (MWM) task], neuronal plasticity as measured by structural and functional changes in synaptic remodeling, and cognitive decline (MWM) and amyloid-¿ synthesis and deposition in female C57/BLJ6 and AD transgenic mice (Tg2576) after ovariectomy and thereafter assess the effect of a critical window of efficacy of pharmacological manipulation of estrogen and LH levels, either singly or in combination. This systematic analysis will not only address the importance of hormonal action in cognition but will also begin to dissect the individual contributions of estrogen and LH and how these aspects are affected by the post- menopausal timing of HRT. Project Description Page 6

? DESCRIPTION (provided by applicant): Preventative and disease modifying therapies for Alzheimer's disease represent a large unmet medical need and therapies addressing aspects beyond targeting pathology are urgently needed. To this end, epidemiologic studies have linked metabolic changes and diseases including obesity, insulin resistance, and diabetes with Alzheimer's disease, and increasing therapeutic emphasis is being placed on metabolic hormones to combat the pathogenic aspects of this disease. To this end we have and others found that a novel hormone, amylin, which critical in the regulation of insulin sensitivity and glucose homeostasis in the periphery affords cognitive benefits and regulates AD-related pathogenic aspects. However, the mechanisms underlying the benefits of amylin on the AD behavioral and cellular phenotype remain unknown. Similarly whether these benefits are mediated directly through the activation of the amylin receptor or indirectly through improving overall metabolic tone is also unknown. To address these questions, we propose to address the specificity of amylin effects on cognition and AD-related aspects such as amyloid-beta and tau pathology, AD-related signaling and oxidative stress by determining: 1) whether CNS blockade of amylin receptor signaling exacerbates the AD behavioral and cellular phenotype 2) whether amylin administration normalizes or slows down accelerated cognitive decline and AD-related parameters observed in diet-induced insulin resistant APP/PS1 mice and whether these are associated with changes in central and peripheral insulin related parameters and 3) based on the fact that amylin signaling occurs via two different calcitonin-ramp receptor complexes (CLT-RAMP1 and CLT-RAMP3), we seek to also determine which receptor complex is more important in regulating AD pathology, AD-related signaling, and oxidative stress under normal and insulin-resistant conditions in vitro. Together these studies will allow us to better understan the underlying mechanisms of amylin on AD and potentially develop novel more targeted therapies for this disease.

Project Summary To date there is no clear physiological event that is associated with the development of sporadic AD. However, reproductive hormones are known to be critical modulators of cognition and neuronal function. Their deregulation, particularly in women, is a significant physiological senescence milestone with a clear impact on cognition and AD development. Estrogen (E2) has been the focus of hormone-based therapies for cognition and AD, however, with the failure of hormone replacement therapy (HRT) to improve function and protect from AD development in elderly women, focus has expanded to others that become equally deregulated during aging; one such group of hormones are gonadotropins such as LH. To this end, we and others, both at a clinical and basic level, have shown that increased peripheral levels luteinizing hormone (LH) that result from loss of E2 during menopause are an important contributor of cognitive dysfunction in women and a potential risk factor for AD. For example, we have published data demonstrating that reducing levels of peripheral LH is as effective as HRT at improving OVX and AD related cognitive and spine density loss, even beyond the critical period of ET effectiveness. However, the mechanisms that underlie these effects are unknown. We have now determined that LH is endogenously produced in the brain and that their levels are inversely correlated to levels in the periphery. This suggests that endogenous LH could have a role in the modulation of cognition and spine formation/remodeling. This is supported by findings that peripheral LH reductions, increases brain LH and leads to activation of signaling cascades associated with LH receptor (LHR) signaling that drive both cognition associated signaling and spine remodeling. Therefore, the goal of this proposal is to determine the involvement of the LH system on cognitive and spine density loss associated reproductive senescence (menopause) and whether dysregulation of LHR signaling drives AD development. To address this we will determine whether direct LH administration ICV under conditions of low brain LH (ovariectomy (OVX) and AD) rescue OVX and AD associated cognitive and spine density loss in normal and the APP/PS1 mouse model (AIM1). Further, to address whether brain-derived LH or LHR are involved in regulating cognition, spine density and AD pathology we will knockdown LH and LHR in brain using the CRISPR/Cas9 system and AAV 2/9 delivery of sgRNA (AIM 2). Lastly, given that LHR activation of several cascades associated with cognition and neuronal plasticity (Gs & Gq) we will determine the involvement of such cascades in regulating neuronal plasticity and AD related pathology in vitro using primary neuronal culture of B6J and APP/PS1 under basal and LHR knockdown and under inhibition of specific cascades after LH treatment (AIM 3). Together, these aims will provide the first and critical step to understanding how LH regulates cognitive and neuronal function in health and disease.

Project Summary Metabolic resistance (METS) and type II diabetes (T2D) hold one of the strongest associations with AD development, however, we know little in terms of how, at a precise mechanistic level, this prodromal metabolic phenotype actually leads to neurodegenerative changes that ultimately result in AD. We know equally little about how sex contributes in accelerating or slowing this progression and how known sex-specific differences for METS/T2D and AD affect this relationship. Given that the incidences of both diseases are skyrocketing, understanding these aspects is critical to develop optimal early/preventative therapeutic interventions for individuals with METS/T2D, at high risk for AD. However, addressing these questions using single targeted hypothesis-based approaches is difficult given the multifactorial nature of potential interactions (multiple disease factors, time, and sex) and is further confounded by changing/incomplete experimental designs across animal studies. To address these challenges, we seek to study the relationship between METS/T2D progression and AD in a more global genome-wide manner, coupled with powerful statistics and biochemical measurements to gain a clearer picture of the METS/T2D-AD relationship. Specifically, we propose to determine alterations in transcriptome, AD and METS-related mitochondrial, metabolic, and pathology changes, in both sexes, over time. We will use bioinformatics and large-scale statistical analysis tools to identify associations across these variables, in addition to sex hormone levels, and time. We will couple these observations with modifications of mitochondrial and metabolic genes (affected early in both diseases) and novel ones discovered via RNA seq to interrogate these relationships mechanistically in vitro.