Modeling menopause: The utility of rodents in translational behavioral endocrinology research

Sex differences in age-associated neurological diseases-A roadmap for reliable and high-yield research

Once taken into consideration, sex differences in neurological diseases emerge in abundance: (i) Stroke severity is significantly higher in females than in males, (ii) Alzheimer's disease (AD) pathology is more pronounced in females, and (iii) conspicuous links with hormonal cycles led to female-specific diagnoses, such as catamenial migraines and epilepsy. While these differences receive increasing attention in isolation, they likely link to similar processes in the brain. Hence, this review aims to present an overview of the influences of sex chromosomes, hormones, and aging on male and female brains across health and disease, with a particular focus on AD and stroke. The focus here on advancements across several fields holds promise to fuel future research and to lead to an enriched understanding of the brain and more effective personalized neurologic care for all.

Androgens Enhance Recognition Memory and Dendritic Spine Density in the Hippocampus and Prefrontal Cortex of Ovariectomized Female Rats

Estrogen replacement has been repeatedly shown to enhance memory and increase dendritic spine density in the hippocampus and prefrontal cortex of ovariectomized (OVX) female rats. Given the potential deleterious effects of chronic estrogen administration, the present study assessed cognitive function using recognition memory tasks and measured dendritic spine density in the CA1 region of the hippocampus and medial prefrontal cortex after subchronic androgen replacement to adult OVX female rats. All androgens enhanced recognition memory in OVX rats, but object placement (OP) and object recognition (OR) results differed. Only testosterone enhanced OR. Testosterone had no effect on OP while dehydroepiandrosterone (DHEA), dihydrotestosterone (DHT) and androstenedione (AD) enhanced OP. Dendritic spine density was increased by both TP and DHEA in both brain areas (DHT and AD were not tested). Lastly, we used the aromatase inhibitor, letrozole, to discriminate between potential androgenic and estrogenic effects of androgens on behavior. Letrozole alone did not alter recognition memory in OVX rats and did not block the effects of either TP or DHEA on recognition memory suggesting that effects were mediated via androgenic mechanisms. The present results expand previous information on gonadal hormone actions and show that, in addition to estrogens, androgens also improve memory and increase spine density in brains of OVX female rats. While requiring further investigation, these observations provide a basis for therapeutic interventions in the treatment of menopausal, age or disease related memory loss.

Advancing age and sex modulate antidyskinetic efficacy of striatal CaV1.3 gene therapy in a rat model of Parkinson's disease

We previously demonstrated that viral vector-mediated striatal CaV1.3 calcium channel downregulation in young adult (3mo) male parkinsonian rats provides uniform, robust protection against levodopa-induced dyskinesias (LID). Acknowledging the association of PD with aging and incidence in male and female sexes, we have expanded our studies to include rats of advancing age of both sexes. The current study directly contrasts age and sex, determining their impact on efficacy of intrastriatal AAV-CaV1.3-shRNA to prevent LID induction, removing the variable of levodopa-priming. Considering both sexes together, late-middle-aged ('aged'; 15mo) parkinsonian rats receiving AAV-CaV1.3-shRNA developed significantly less severe LID compared control AAV-scramble(SCR)-shRNA rats, however therapeutic benefit was significantly less robust than observed in young males. When considered separately, females showed significantly less therapeutic benefit than males. Furthermore, aged non-cycling/proestrous-negative female rats were refractory to LID induction, regardless of vector. This study provides novel insight into the impact of age and sex on the variable antidyskinetic responses of CaV1.3-targeted gene therapy, highlighting the importance of including clinically relevant age and sex populations in PD studies.

Sex Chromosomes and Sex Hormones: Dissecting the Forces That Differentiate Female and Male Hearts

The heart is a highly sex-biased organ, as sex shapes innumerable aspects of heart health and disease. Sex chromosomes and sex hormones -testosterone, progesterone, and estrogen- establish and perpetuate the division between male and female myocardium. Of these differentiating factors, the insulating effects of estrogen have been rigorously interrogated and reviewed, whereas the influence of sex chromosomes, testosterone, and progesterone remains in dispute or ill-defined. Here, we synthesize growing evidence that sex chromosomes and sex hormones substantially bias heart form, function, and dysfunction in a context-dependent fashion. The discrete protective functions ascribed to each of the 3 estrogen receptors are also enumerated. Subsequently, we overview obstacles that have historically discouraged the inclusion of female subjects in basic science such as the impact of the female estrus cycle and reproductive senescence on data reliability and reproducibility. Furthermore, we weigh the utility of several common strategies to intercept and rescue sex-specific protection. Last, we warn of common compounds in animal chow and cell culture that interfere with estrogen signaling. In sum, we survey the controversies and challenges that stem from sex-inclusive cardiovascular research, comparing the possible causes of cardiac sex bias, elucidating sex chromosome or hormone-dependent processes in the heart, describing common lapses that imperil female and male cell and animal work, and illuminating facets of the female heart yet unexplored or still uncertain.

The Human Cerebello-Hippocampal Circuit Across Adulthood

Direct communication between the hippocampus and cerebellum has been shown via coactivation and synchronized neuronal oscillations in animal models. Further, this novel cerebello-hippocampal circuit may be impacted by sex steroid hormones. The cerebellum and hippocampus are dense with estradiol and progesterone receptors relative to other brain regions. Females experience up to a 90% decrease in ovarian estradiol production after the menopausal transition. Postmenopausal women show lower cerebello-cortical and intracerebellar FC compared to reproductive aged females. Sex hormones are established modulators of both memory function and synaptic organization in the hippocampus in non-human animal studies. However, investigation of the cerebello-hippocampal (CB-HP) circuit has been limited to animal studies and small homogeneous samples of young adults as it relates to spatial navigation. Here, we investigate the CB-HP circuit in 138 adult humans (53% female) from 35-86 years of age, to define its FC patterns, and investigate its associations with behavior, hormone levels, and sex differences therein. We established robust FC patterns between the CB and HP in this sample. We predicted and found negative relationships between age and CB-HP FC. As expected, estradiol levels exhibited positive relationships with CB-HP. We found lower CB-HP FC with higher levels of progesterone. We provide the first characterization of the CB-HP circuit across middle and older adulthood and demonstrate that connectivity is sensitive to sex steroid hormone levels. This work provides the first clear CB-HP circuit mapping in the human brain and serves as a foundation for future work in neurological and psychiatric diseases.

Longitudinal Decline of Exercise Capacity in Male and Female Mice

The population of older adults is exponentially expanding. Alongside aging comes the onset of chronic disease, decline of functional capacity, and reduced quality of life. Thus, this population increase will stress the capacity and financial viability of health and long-term care systems. Developing preclinical models for age-related functional decline is imperative to advancing therapies that extend healthspan and prolong independence. Previously in a cross-sectional study, we established a powerful composite scoring system we termed CFAB (Comprehensive Functional Assessment Battery). CFAB measures physical function and exercise capacity using well-validated determinants to measure overall motor function, fore-limb strength, four-limb strength/endurance, aerobic capacity, and volitional exercise/activity rate. In the current work, we used CFAB to track cohorts of male and female C57BL/6 mice over the lifespan (measuring CFAB at 6, 12, 18, 24, and 28 months of age). Overall, we found statistically significantly declining function as the mice aged, with some differences between males and females in trajectory and slope. We also determined that body mass changes presented differently between sexes, and tracked body composition (fat percentage, using magnetic resonance imagery) in females. In a subset of mice, we tracked in vivo contractile physiology noting declines in plantar flexor maximum isometric torque. In summary, our data suggest that males and females declined at different rates. We confirmed the efficacy of CFAB to track longitudinal changes in exercise capacity and physical fitness in both males and females, further validating the system to track age-related functional decline.

Effects of exercise and transient estradiol exposure in middle-aged female rats

The benefits of estrogen treatment on cognition in middle-aged and older women are dependent on many factors, including the timing of treatment. Moreover, the potential interactive effects with other lifestyle factors, such as exercise, are poorly understood. In this study, we tested for lasting benefits of independent and combined treatment with estrogen and voluntary exercise initiated in midlife, using a rat model of menopause. Twelve-month-old, retired female breeders were bilaterally ovariectomized and received six weeks of 17β-estradiol (E2) treatment via subcutaneous implant, with or without access to running wheels. After E2 treatment, animals in the exercise groups had running wheel access for seven additional weeks, including a two-week period of cognitive and affective testing. Thereafter, hippocampal neuronal and cellular plasticity were assessed. E2 and exercise independently exerted effects on behavioral and cellular outcome measures. Transient E2 treatment enduringly increased motor output, lowered body weight, and increased behavioral plasticity. Exercise decreased total hippocampal microglia number and increased brain weight. No additive effects of exercise and E2 treatment were observed. E2 treatment may provide a means by which to enduringly increase physical activity in middle age, but combined E2 and exercise do not produce additive benefits on hippocampal behavioral or cellular plasticity.

Blockade of A2AR improved brain perfusion and cognitive function in a mouse model of Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder that affects more than 6.2 million Americans aged 65 and older, particularly women. Along with AD's main hallmarks (formation of β-amyloid plaques and tau neurofibrillary tangles), there are vascular alterations that occurs in AD pathology. Adenosine A2 receptor (A2AR) is one of the key factors of brain vascular autoregulation and is overexpressed in AD patients. Our previous findings suggest that protein arginine methyltransferase 4 (PRMT4) is overexpressed in AD, which leads to decrease in cerebral blood flow in aged female 3xTg mice. We aimed to investigate the mechanism behind A2AR signaling in the regulation of brain perfusion and blood-brain barrier integrity in age and sex-dependent 3xTg mice, and if it is related to PRMT4. Istradefylline, a highly selective A2AR antagonist, was used to modulate A2AR signaling. Aged female 3xTg and C57BL/6 J mice were evaluated for brain perfusion (via laser speckle) and cognitive function (via open field, T-maze and novel object recognition). Our results suggest that modulation of A2AR signaling in aged female 3xTg increased cerebral perfusion by decreasing PRMT4 expression, restored the levels of APP and tau, maintained blood-brain barrier integrity by maintaining the expression of tight junction proteins, and preserved functional learning/memory.

Regulation of Age-Related Lipid Metabolism in Ovarian Cancer

The mortality rate of ovarian cancer (OC) remains the highest among female gynecological malignancies. Advanced age is the highest risk factor for OC development and progression, yet little is known about the role of the aged tumor microenvironment (TME). We conducted RNA sequencing and lipidomic analysis of young and aged gonadal adipose tissue from rat xenografts before and after OC formation. The rates of tumor formation (p = 0.047) and tumor volume (p = 0.002) were significantly higher in the aged rats than in their young counterparts. RNA sequencing data showed significant differences in gene expression profiles between the groups of young and aged rat adipose tissues (p < 0.05), including S100a8, S100a9, Il1rl1, Lcn2, C3, Hba-a1, Fcna, and Pnpla3. At the time of tumor generation, there were also changes in the lipid components within the gonadal adipose tissues of young and aged rats, with higher levels of free fatty acids (FFAs) and triglycerides (TGs) in aged rats. Furthermore, the aged TME showed changes in immune cell composition, especially inflammation-related cells, including neutrophils, myeloid dendritic cells, CD4+ T cells (non-regulatory), and mast cell activation (p < 0.05). The correlation between S100a8, S100a9, neutrophil, and omega-5, FFA 18:3 levels was also determined. Additionally, omega-5, which is downregulated in aged rats, inhibited OC cell proliferation in vitro (p < 0.001). Our study suggests that the aged TME promotes OC proliferation resulting from age-related changes in gene/pathway expression, lipid metabolism, and immune cell distribution. Targeting the aging adipose microenvironment, particularly lipid metabolism, is a promising therapeutic strategy for OC and warrants further investigation. Significance: The aging microenvironment contributes to OC development and progression because of changes in the immune response regulatory genes S100a8 and S100a9, secreted by adipocytes, preadipocytes, or neutrophils, and by altering omega-5 metabolism.

Menopause-induced 17β-estradiol and progesterone loss increases senescence markers, matrix disassembly and degeneration in mouse cartilage

Female individuals who are post-menopausal present with higher incidence of knee osteoarthritis (KOA) than male counterparts; however, the mechanisms underlying this disparity are unknown. The most commonly used preclinical models lack human-relevant menopausal phenotypes, which may contribute to our incomplete understanding of sex-specific differences in KOA pathogenesis. Here we chemically induced menopause in middle-aged (14-16 months) C57/BL6N female mice. When we mapped the trajectory of KOA over time, we found that menopause aggravated cartilage degeneration relative to non-menopause controls. Network medicine analyses revealed that loss of 17β-estradiol and progesterone with menopause enhanced susceptibility to senescence and extracellular matrix disassembly. In vivo, restoration of 17β-estradiol and progesterone in menopausal mice protected against cartilage degeneration compared to untreated menopausal controls. Accordingly, post-menopausal human chondrocytes displayed decreased markers of senescence and increased markers of chondrogenicity when cultured with 17β-estradiol and progesterone. These findings implicate menopause-associated senescence and extracellular matrix disassembly in the sex-specific pathogenesis of KOA.

Preventive Effects of Resistance Training on Hemodynamics and Kidney Mitochondrial Bioenergetic Function in Ovariectomized Rats

Menopause occurs due to the depletion of the ovarian reserve, leading to a progressive decline in estrogen (E2) levels. This decrease in E2 levels increases the risk of developing several diseases and can coexist with chronic kidney disease (CKD). Arterial hypertension (AH) is another condition associated with menopause and may either contribute to or result from CKD. Ovariectomy (OVX) induces hypoestrogenism, which can lead to mitochondrial bioenergetic dysfunction in the kidneys. Previous studies have suggested that exercise training has beneficial effects on adults with CKD and AH. To investigate the effects of OVX and resistance training (RT) on hemodynamic parameters and mitochondrial bioenergetic function of the kidney, female Wistar rats were divided into ovariectomized (OVX) and intact (INT) groups. These rats were either kept sedentary (SED) or subjected to RT for thirteen weeks. The RT involved climbing a vertical ladder with a workload apparatus. Hemodynamic parameters were assessed via tail plethysmography. Mitochondrial respiratory function was evaluated with high-resolution respirometry. Gene expression related to the electron transport chain (ETC) and oxidative phosphorylation (OXPHOS) was evaluated by real-time qPCR. At week 13, key hemodynamic parameters (systolic blood pressure and mean arterial pressure) were significantly elevated in the OVX-SED group. Compared with those in the other groups, mitochondrial bioenergetics were impaired in the OVX-SED group. In contrast, the trained groups presented improved mitochondrial bioenergetic function compared with the sedentary groups. OVX led to reduced gene expression related to the mitochondrial ETC and OXPHOS, whereas RT both prevented this reduction and increased gene expression in the trained groups. Our results indicate that hypoestrogenism significantly decreases OXPHOS and ETC capacity in the kidneys of sedentary animals. However, RT effectively increased the expression of genes related to mitochondrial ETC and OXPHOS, thereby counteracting the effects of OVX.

Nicotine is an Immunosuppressant: Implications for Women's Health and Disease

A plethora of evidence supports that nicotine, the primary alkaloid in tobacco products that is generally accepted for maintaining use, is immunoregulatory and may function as an immunosuppressant. Women have unique experiences with use of nicotine-containing products and also undergo significant reproductive transitions throughout their lifespan which may be impacted by nicotine use. Within the extant literature, there is conflicting evidence that nicotine may confer beneficial health effects in specific disease states (e.g., in ulcerative colitis). Use prevalence of nicotine-containing products is exceptionally high in individuals presenting with some comorbid disease states that impact immune system health and can be a risk factor for the development of diseases which disproportionately impact women; however, the mechanisms underlying these relationships are largely unclear. Further, little is known regarding the impacts of nicotine's immunosuppressive effects on women's health during the menopausal transition, which is arguably an inflammatory event characterized by a pro-inflammatory peri-menopause period. Given that post-menopausal women are at a higher risk than men for the development of neurodegenerative diseases such as Alzheimer's disease and are also more vulnerable to negative health effects associated with diseases such as HIV-1 infection, it is important to understand how use of nicotine-containing products may impact the immune milieu in women. In this review, we define instances in which nicotine use confers immunosuppressive, anti-inflammatory, or pro-inflammatory effects in the context of comorbid disease states, and focus on how nicotine impacts neuroimmune signaling to maintain use. We posit that regardless of potential health benefits, nicotine use cessation should be a priority in the clinical care of women. The synthesis of this review demonstrates the importance of systematically defining the relationships between volitional nicotine use, immune system function, and comorbid disease states in women to better understand how nicotine impacts women's health and disease.

Overcoming challenges in the management of recurrent urinary tract infections

INTRODUCTION

Urinary tract infection (UTI) is a major global health concern. While acute UTIs can usually be effectively treated, recurrent UTIs (rUTIs) impact patients for years, causing significant morbidity and can become refractory to front-line antibiotics.

AREAS COVERED

This review discusses the risk factors associated with rUTI, current rUTI treatment paradigms, prophylactic strategies, and challenges in rUTI diagnostics. We specifically discuss common risk factors for rUTI, including biological sex, age, menopause status, and diabetes mellitus. We also review recently available evidence for commonly used treatments, from oral antibiotic therapy to intravesical antimicrobials, electrofulguration of chronic cystitis, and the last-resort treatment, cystectomy. We discuss the most current literature evaluating prophylactic strategies for rUTI including long-term antibiotic prophylaxis, estrogen hormone therapy, and dietary supplements. Finally, we address the important role of UTI diagnostics in effective rUTI management and review the strengths and limitations of both current and emerging UTI diagnostic platforms as well as their ability to operate at point-of-care.

EXPERT OPINION

We discuss the current challenges faced by clinicians in managing rUTI in women and the steps that should be taken so that clinicians, scientists, and patients can work together to better understand the disease and develop better strategies for its management.

Ovariectomy drives increase of an ECM transcription signature in the posterior eye and retina

Increased risk of developing glaucoma has recently been associated with early age of menopause. Here, we examined how age and surgically-induced menopause via ovariectomy (OVX) impacted gene expression in gene pathways previously linked to glaucoma, such as extracellular matrix (ECM) remodeling and TGF-β signaling. Using bulk RNA sequencing, we analyzed changes in young (3-4 months) and middle-aged (9-10 months) Long-Evans rats. We focused on posterior pole tissues (sclera and optic nerve head) but also examined the retina to compare observed changes across different tissue regions. Our results demonstrated that aging and OVX significantly alter gene expression in the sclera and optic nerve head. Generally, OVX triggered the enrichment of immune-related processes. However, OVX in young rats also led to significant enrichment of ECM and TGF-β gene sets. At the same time, these effects were diminished in middle-aged rats, indicating an age dependency of the effects of OVX on matrix-related pathways. Notably, the transcriptional factor Fos was downregulated in the posterior eye and retina in aged and OVX animals. Fos is a major regulator of cell proliferation and survival, and its dysregulation may play an important role in aging and menopause for women. These findings underscore the important role of menopause timing in modulating molecular pathways associated with glaucoma, which is consistent with clinical studies showing that early menopause may heighten the risk of developing this condition. This study also highlights the importance of considering women's health factors, such as menopause, in understanding and managing glaucoma risk.

Hallmarks of female reproductive aging in physiologic aging mice

The female reproductive axis is one of the first organ systems to age, which has consequences for fertility and overall health. Here, we provide a comprehensive overview of the biological process of female reproductive aging across reproductive organs, tissues and cells based on research with widely used physiologic aging mouse models, and describe the mechanisms that underpin these phenotypes. Overall, aging is associated with dysregulation of the hypothalamic-pituitary-ovarian axis, perturbations of the ovarian stroma, reduced egg quantity and quality, and altered uterine morphology and function that contributes to reduced capacity for fertilization and impaired embryo development. Ultimately, these age-related phenotypes contribute to altered pregnancy outcomes and adverse consequences in offspring. Conserved mechanisms of aging, as well as those unique to the reproductive system, underlie these phenotypes. The knowledge of such mechanisms will lead to development of therapeutics to extend female reproductive longevity and support endocrine function and overall health.

Research progress on the correlation between estrogen and estrogen receptor on postmenopausal sarcopenia

Estrogen is a necessary sex steroid and potent neuroprotective hormone. It plays a multifaceted role beyond the reproductive system, extending its influence to the brain, skeletal muscle, and other organs. Estrogen's role in cognition, mood, autonomic regulation, and neuroprotection involves interactions with neurotransmitters, neuromodulators in a distributed manner. Notably, the impact of estrogen on mitochondrial metabolism in skeletal muscle is particularly significant due to a unique modulated bioenergetic profiles, synaptic plasticity, and neuronal health. The deficiency of estrogen in menopause has been linked to changes in brain structure, connectivity, energy metabolism. Therewith, these are crucial factors in cognitive function and the risk of Alzheimer's diseases. Besides, it leads to endocrine and metabolic dysfunction, resulting in osteoporosis, metabolic syndrome, and a tendency toward decreased muscle mass and strength. Estrogen's influence on mitochondrial function is particularly relevant to aging, as it affects the production of ATP and the overall metabolic health of the brain. Estrogen decline in women skeletal muscle mass is usually related to sarcopenia, a prevalent disease observed in vulnerable elderly individuals. Therefore, estrogen is considered to play a crucial role in skeletal muscle homeostasis and motor ability, although the exact mechanism remains unclear. This paper reviews the literature on the impact of estrogen on postmenopausal skeletal muscle diseases and the underlying molecular mechanisms, especially in terms of mitochondrial metabolism. In summary, estrogen plays an important role in the health of skeletal muscle in postmenopausal women, and its impact on mitochondrial function and homeostasis offers potential targets for the development of new strategies to treat sarcopenia.

The Interaction Of Diet-Induced Obesity And Chronic Stress In A Mouse Model Of Menopause

Menopause is characterized by the cessation of ovarian hormone production. During postmenopause, cisgender women face increased risks of obesity, cognitive decline, and mood disorder. Mood disorders are associated with exposure to chronic stress. We investigated the combined effects of a high-fat diet (HFD) and chronic stress exposure in a mouse model of menopause using 4-vinylcyclohexene diepoxide (VCD), a selective ovotoxicant that gradually depletes ovarian follicles and hormones. Starting at 6 months, 82 female WT C57BL/6J mice received saline or VCD (130 mg/kg i.p.) 5 days per week for 3 weeks. One month after injection, mice were fed either low-fat diet (LFD) or HFD for 8 weeks followed by 6 weeks of chronic variable mild stress (CVMS). Post-CVMS, mice were either processed for gene expression of the anterodorsal BNST or behavior tests to assess cognitive and anxiety-related behaviors. Plasma samples were collected to analyze metabolic hormones and corticosterone levels. VCD-treated HFD-fed mice had higher fat and body mass, and elevated fasting glucose levels compared to controls and more pronounced avoidance behaviors and cognitive impairments. LFD-fed, VCD-treated mice exhibited less exploration of novel objects and open spaces compared to OIL and HFD counterparts. VCD elevated corticosterone levels on LFD and increased BNST Pacap gene expression on HFD. These findings highlight cognitive repercussions of estrogen deficiency and suggest a potential protective effect of a HFD against some of the adverse outcomes associated with menopause. Our study emphasizes the importance of considering dietary and hormonal interactions in the development of therapeutic strategies.

Spatial learning and memory impairment at the post-follicular depletion state is associated with reduced hippocampal glucose uptake

The menopausal transition is a complex neuroendocrine aging process affecting brain structure and metabolic function. Such changes are consistent with neurological sequelae noted following the menopausal transition, including cognitive deficits. Although studies in rodent models of the menopause revealed changes in learning and memory, little is known about the structural and metabolic changes in the brain regions serving the cognitive function in these models. The administration 4-vinylcyclohexene diepoxide (VCD) in laboratory animals results in follicular depletion, and thus, is a powerful translational tool that models the human menopause. In the studies presented here, we evaluated behavior, brain structure, and metabolism in young female rats administered with either VCD or vehicle for 15 days across the early, mid, and post-follicular depletion states at 1-, 2-, and 3-months post-final injection, respectively. Additionally, we evaluated the serum hormonal profile and ovarian follicles based on the estrous cycle pattern. Positron emission tomography (PET) was utilized to determine regional brain glucose metabolism in the hippocampus, medial prefrontal cortex, and striatum. Subsequently, the rats were euthanized for ex-vivo magnetic resonance imaging (MRI) to assess regional brain volumes. VCD-induced rats at the post-follicular depleted time points had diminished spatial learning and memory as well as reduced hippocampal glucose uptake. Additionally, VCD-induced rats at post-follicular depletion time points had marked reductions in estradiol, progesterone, and anti-mullerian hormone with an increase in follicle-stimulating hormone. These rats also exhibited fewer ovarian follicles, indicating that substantial ovarian function loss during post-follicular time points impairs the female rats' spatial learning/memory abilities and triggers the metabolic changes in the hippocampus.

BT-11 repurposing potential for Alzheimer's disease and insights into its mode of actions

Neuroinflammation is a key pathological hallmark of Alzheimer's disease (AD). Investigational and FDA approved drugs targeting inflammation already exist, thus drug repurposing for AD is a suitable approach. BT-11 is an investigational drug that reduces inflammation in the gut and improves cognitive function. BT-11 is orally active and binds to lanthionine synthetase C-like 2 (LANCL2), a glutathione-s-transferase, thus potentially reducing oxidative stress. We investigated the effects of BT-11 long-term treatment on the TgF344-AD rat model. BT-11 reduced hippocampal-dependent spatial memory deficits, Aβ plaque load and neuronal loss in males, and mitigated microglia numbers in females. BT-11 treatment led to hippocampal transcriptomic changes in signaling receptor, including G-protein coupled receptor pathways. We detected LANCL2 in hippocampal nuclear and cytoplasmic fractions with potential different post-translational modifications, suggesting distinct functions based on its subcellular localization. LANCL2 was present in oligodendrocytes, showing a role in oligodendrocyte function. To our knowledge, these last two findings have not been reported. Overall, our data suggest that targeting LANCL2 with BT-11 improves cognition and reduces AD-like pathology by potentially modulating G-protein signaling and oligodendrocyte function. Our studies contribute to the field of novel immunomodulatory AD therapeutics, and merit further research on the role of LANCL2 in this disease.

Enhancing translation: A need to leverage complex preclinical models of addictive drugs to accelerate substance use treatment options

Preclinical models of addictive drugs have been developed for decades to model aspects of the clinical experience in substance use disorders (SUDs). These include passive exposure as well as volitional intake models across addictive drugs and have been utilized to also measure withdrawal symptomatology and potential neurobehavioral mechanisms underlying relapse to drug seeking or taking. There are a number of Food and Drug Administration (FDA)-approved medications for SUDs, however, many demonstrate low clinical efficacy as well as potential sex differences, and we also note gaps in the continuum of care for certain aspects of clinical experiences in individuals who use drugs. In this review, we provide a comprehensive update on both frequently utilized and novel behavioral models of addiction with a focus on translational value to the clinical experience and highlight the need for preclinical research to follow epidemiological trends in drug use patterns to stay abreast of clinical treatment needs. We then note areas in which models could be improved to enhance the medications development pipeline through efforts to enhance translation of preclinical models. Next, we describe neuroscience efforts that can be leveraged to identify novel biological mechanisms to enhance medications development efforts for SUDs, focusing specifically on advances in brain transcriptomics approaches that can provide comprehensive screening and identification of novel targets. Together, the confluence of this review demonstrates the need for careful selection of behavioral models and methodological parameters that better approximate the clinical experience combined with cutting edge neuroscience techniques to advance the medications development pipeline for SUDs.

Activity of the hypothalamic neuropeptide Y increases in adult and decreases in old rats

Middle-aged obesity and aging anorexia with muscle loss (sarcopenia) of old people present public health burden. These alterations may appear both in humans and rodents suggesting the role for regulatory alterations. Previously, we demonstrated that biphasic changes in the weight-reducing (catabolic) effects of neuropeptides of the hypothalamus-adipose tissue axis (e.g. leptin) may contribute to both trends. With regard to the anabolic effects of the hypothalamic neuropeptide Y (NPY) inhibited by leptin, we hypothesized non-linear age-related changes with shifts in the opposite directions. We investigated the orexigenic and hypometabolic effects of intracerebroventricularly administered NPY (hyperphagia induced by NPY injection or changes in food intake, body weight, heart rate, body temperature, locomotor activity during a 7-day NPY infusion), the immunoreactivity and gene expression of NPY in the hypothalamic arcuate nucleus of male Wistar rats of five age groups from young to old. The orexigenic/hypometabolic efficacy and the immunoreactivity of NPY increased in middle-aged animals preceding the peak of adiposity observed in aging rats, then decreased preceding anorexia and weight loss in old rats. These shifts may contribute to the development of both age-related obesity and aging anorexia, sarcopenia, and should be considered in future drug development targeting the NPY system.

Regulation of Age-Related Lipid Metabolism in Ovarian Cancer

Although a lot of effort has been dedicated to ovarian cancer (OC) research, the mortality rate is still among the highest in female gynecologic malignancies. The effects of the aged tumor microenvironment are still being undermined despite age being the highest risk factor in ovarian cancer development and progression. In this study, we have conducted RNA sequencing and lipidomics analysis of gonadal adipose tissues from young and aged rat xenografts before and after ovarian cancer formation. We have found significantly higher tumor formation rates and volumes in aged OC xenograft rat models compared to their young counterparts (p<0.05), suggesting the aged adipose microenvironment (AME) is more susceptible to OC outgrowth. We have revealed significant shifts in the gene expression enrichment from groups of young vs. aged rats before tumor formation, groups of young vs. aged rats when the tumor formed, and groups of aged rats before and after tumor formation. We also observed shifts in the lipid components of the gonadal adipose tissues between young and aged rat xenografts when tumors were generated. Additionally, we found that the aged AME was associated with age-related changes in the immune cell composition, especially inflammation-related cells. The top hits showing the most differences between aged and young adipose tissues were eight genes including S100a8, S100a9, Il1rl1, Lcn2, C3, Hba-a1, Fcna, and Pnpla3, 22 lipids including multiple isoforms of free fatty acids (FFA) and triglyceride (TG), as well as four immune cells including neutrophil, myeloid dendritic cell, T cell CD4+ (non-regulatory), and mast cell activation. The functional correlation among S100a8, S100a9, neutrophil, and FFA (18:3) was also determined. Furthermore, FFA (18:3), which was shown to be downregulated in aged xenograft rats, was capable of inhibiting OC cell proliferation. In conclusion, our study suggested that aging promoted OC proliferation through changes in genes/pathways, lipid metabolism, and immune cells. Targeting the aging adipose microenvironment, particularly lipid metabolism reprogramming, holds promise as a therapeutic strategy for OC, which warrants further investigation.

Significance

Aging microenvironment of OC may be regulated by S100a8 and S100a9 secreted by adipocytes, preadipocytes, or neutrophils through affecting the lipid metabolism, such as FFA (18:3).

Insomnia-related rodent models in drug discovery

Despite the widespread prevalence and important medical impact of insomnia, effective agents with few side effects are lacking in clinics. This is most likely due to relatively poor understanding of the etiology and pathophysiology of insomnia, and the lack of appropriate animal models for screening new compounds. As the main homeostatic, circadian, and neurochemical modulations of sleep remain essentially similar between humans and rodents, rodent models are often used to elucidate the mechanisms of insomnia and to develop novel therapeutic targets. In this article, we focus on several rodent models of insomnia induced by stress, diseases, drugs, disruption of the circadian clock, and other means such as genetic manipulation of specific neuronal activity, respectively, which could be used to screen for novel hypnotics. Moreover, important advantages and constraints of some animal models are discussed. Finally, this review highlights that the rodent models of insomnia may play a crucial role in novel drug development to optimize the management of insomnia.

Acute sleep deprivation-induced hepatotoxicity and dyslipidemia in middle-aged female rats and its amelioration by butanol extract of Tinospora cordifolia

BACKGROUND

Sleep deprivation (SD) due to an unhealthy lifestyle poses an oxidative challenge and is closely associated with an increased risk and prevalence of different metabolic disorders. Although the negative consequences of SD are well reported on mental health little is known about its detrimental effects on liver function and lipid metabolism. Tinospora cordifolia is reported for its hepatoprotective activity in different pre-clinical model systems. The current study was designed to elucidate the cumulative effects of aging and acute SD on liver functions, oxidative stress, and lipid metabolism, and their management by butanol extract of T. cordifolia (B-TCE) using middle-aged female acyclic rats as the model system.

RESULTS

Rats were divided into 4 groups: (1) Vehicle-undisturbed (VUD) (2) Vehicle-sleep deprived (VSD) (3) B-TCE pre-treated sleep-deprived (TSD) (4) B-TCE pre-treated undisturbed sleep (TUD). TSD and TUD groups were given 35 mg/kg of B-TCE once daily for 15 days followed by 12 h of sleep deprivation (6 a.m.-6 p.m.) of VSD and TSD group animals using the gentle-handling method while VUD and TUD group animals were left undisturbed. SD of VSD group animals increased oxidative stress, liver function disruption, and dyslipidemia which were ameliorated by B-TCE pre-treatment. Further, B-TCE was observed to target AMPK and its downstream lipid metabolism pathways as well as the p-Akt/cyclinD1/p-bad pathway of cell survival as possible underlying mechanisms of its hepatoprotective activity.

CONCLUSIONS

These findings suggest that B-TCE being a multi-component extract may be a potential agent in curtailing sleep-related problems and preventing SD-associated hepatotoxicity and dyslipidemia in postmenopausal women.

Treatment with brain specific estrogen prodrug ameliorates cognitive effects of surgical menopause in mice

Menopause is an endocrine shift leading to increased vulnerability for cognitive impairment and dementia risk factors, in part due to loss of neuroprotective circulating estrogens. Systemic replacement of estrogen post-menopause has limitations, including risk for estrogen-sensitive cancers. A promising therapeutic approach therefore might be to deliver estrogen only to the brain. We examined whether we could enhance cognitive performance by delivering estrogen exclusively to the brain in ovariectomized mice (a surgical menopause model). We treated mice with the prodrug 10β,17β-dihydroxyestra-1,4-dien-3-one (DHED), which can be administered systemically but is converted to 17β-estradiol only in the brain. Young and middle-aged C57BL/6 J mice received ovariectomy and subcutaneous implant containing vehicle or DHED and underwent cognitive testing to assess memory after 1-3.5 months of treatment. Low and medium doses of DHED did not alter metabolic status in middle-aged mice. In both age groups, DHED treatment improved spatial memory in ovariectomized mice. Additional testing in middle-aged mice showed that DHED treatment improved working and recognition memory in ovariectomized mice. These results lay the foundation for future studies determining if this intervention is as efficacious in models of dementia with comorbid risk factors.

Longitudinal Decline of Exercise Capacity in Male and Female Mice

The population of older adults is exponentially expanding. Alongside aging comes the onset of chronic disease, decline of functional capacity, and reduced quality of life. Thus, this population increase will stress the capacity and financial viability of health and long-term care systems. Developing pre-clinical models for age-related functional decline is imperative to advancing therapies that extend healthspan and prolong independence. Previously in a cross-sectional study, we established a powerful composite scoring system we termed CFAB (comprehensive functional assessment battery). CFAB measures physical function and exercise capacity using well-validated determinants to measure overall motor function, fore-limb strength, four-limb strength/endurance, aerobic capacity, and volitional exercise/activity rate. In the current work, we used CFAB to track cohorts of male and female C57BL/6 mice over the lifespan (measuring CFAB at 6, 12, 18, 24, and 28 months of age). Overall, we found statistically significantly declining function as the mice aged, with some differences between males and females in trajectory and slope. We also determined that body mass changes presented differently between sexes, and tracked body composition (fat percentage, using magnetic resonance imagery) in females. In a subset of mice, we tracked in vivo contractile physiology noting declines in plantar flexor maximum isometric torque. In summary, our data suggest that males and females declined at different rates. We confirmed the efficacy of CFAB to track longitudinal changes in exercise capacity and physical fitness in both males and females, further validating the system to track age-related functional decline.

The intersection between menopause and depression: overview of research using animal models

Menopausal women may experience symptoms of depression, sometimes even progressing clinical depression requiring treatment to improve quality of life. While varying levels of estrogen in perimenopause may contribute to an increased biological vulnerability to mood disturbances, the effectiveness of estrogen replacement therapy (ERT) in the relief of depressive symptoms remains controversial. Menopausal depression has a complex, multifactorial etiology, that has limited the identification of optimal treatment strategies for the management of this psychiatric complaint. Nevertheless, clinical evidence increasingly supports the notion that estrogen exerts neuroprotective effects on brain structures related to mood regulation. Indeed, research using preclinical animal models continues to improve our understanding of menopause and the effectiveness of ERT and other substances at treating depression-like behaviors. However, questions regarding the efficacy of ERT in perimenopause have been raised. These questions may be answered by further investigation using specific animal models of reduced ovarian function. This review compares and discusses the advantages and pitfalls of different models emulating the menopausal stages and their relationship with the onset of depressive-like signs, as well as the efficacy and mechanisms of conventional and novel ERTs in treating depressive-like behavior. Ovariectomized young rats, middle-to-old aged intact rats, and females treated with reprotoxics have all been used as models of menopause, with stages ranging from surgical menopause to perimenopause. Additionally, this manuscript discusses the impact of organistic and therapeutic variables that may improve or reduce the antidepressant response of females to ERT. Findings from these models have revealed the complexity of the dynamic changes occurring in brain function during menopausal transition, reinforcing the idea that the best approach is timely intervention considering the opportunity window, in addition to the careful selection of treatment according to the presence or absence of reproductive tissue. Additionally, data from animal models has yielded evidence to support new promising estrogens that could be considered as ERTs with antidepressant properties and actions in endocrine situations in which traditional ERTs are not effective.

The Protective Role of Magnoliae Flos in Preventing Ovotoxicity and Managing Ovarian Function: An In Vitro and In Vivo Study

Magnoliae Flos (MF) is a medicinal herb widely employed in traditional medicine for relieving sinusitis, allergic rhinitis, headaches, and toothaches. Here, we investigated the potential preventive effects of MF extract (MFE) against 4-vinylcyclohexene diepoxide (VCD)-induced ovotoxicity in ovarian cells and a mouse model of premature ovarian insufficiency (POI). The cytoprotective effects of MFE were assessed using CHO-K1 or COV434 cells. In vivo, B6C3F1 female mice were intraperitoneally injected with VCD for two weeks to induce POI, while MFE was orally administered for four weeks, beginning one week before VCD administration. VCD led to a significant decline in the viabilities of CHO-K1 and COV434 cells and triggered excessive reactive oxygen species (ROS) production and apoptosis specifically in CHO-K1 cells. However, pretreatment with MFE effectively prevented VCD-induced cell death and ROS generation, while also activating the Akt signaling pathway. In vivo, MFE increased relative ovary weights, follicle numbers, and serum estradiol and anti-Müllerian hormone levels versus controls under conditions of ovary failure. Collectively, our results demonstrate that MFE has a preventive effect on VCD-induced ovotoxicity through Akt activation. These results suggest that MFE may have the potential to prevent and manage conditions such as POI and diminished ovarian reserve.

Estrogen counteracts age-related decline in beige adipogenesis through the NAMPT-regulated ER stress response

Thermogenic beige adipocytes are recognized as potential therapeutic targets for combating metabolic diseases. However, the metabolic advantages that they offer are compromised with aging. Here we show that treating mice with estrogen (E2), a hormone that decreases with age, can counteract the age-related decline in beige adipogenesis when exposed to cold temperature while concurrently enhancing energy expenditure and improving glucose tolerance in mice. Mechanistically, we found that nicotinamide phosphoribosyl transferase (NAMPT) plays a pivotal role in facilitating the formation of E2-induced beige adipocytes, which subsequently suppresses the onset of age-related endoplasmic reticulum (ER) stress. Furthermore, we found that targeting NAMPT signaling, either genetically or pharmacologically, can restore the formation of beige adipocytes by increasing the number of perivascular adipocyte progenitor cells. Conversely, the absence of NAMPT signaling prevents this process. Together, our findings shed light on the mechanisms regulating the age-dependent impairment of beige adipocyte formation and underscore the E2-NAMPT-controlled ER stress pathway as a key regulator of this process.

Combined supplementation with hesperidin, phytosterols and curcumin decreases adiposity and improves metabolic health in ovariectomized rats

In recent years many women have looked for alternative therapies to address menopause. Hesperidin, phytosterols and curcumin are bioactive compounds that can ameliorate some cardiovascular risk factors associated with menopause, although there are no data concerning the effects of their combined supplementation. We used ovariectomized (OVX) rats, a postmenopausal model with oestrogen deficiency, to evaluate whether supplementation with a multi-ingredient (MI) including hesperidin, phytosterols and curcumin for 57 days would display beneficial effects against fat mass accretion and metabolic disturbances associated with menopause. Twenty OVX rats were orally supplemented with either MI (OVX-MI) or vehicle (OVX). Furthermore, 10 OVX rats orally received the vehicle along with subcutaneous injections of 17β-oestradiol biweekly (OVX-E2), whereas 10 rats were sham operated and received oral and injected vehicles (control group; SH). MI supplementation partly counteracted the fat mass accretion observed in OVX animals, which was evidenced by decreased total fat mass, adiposity index, the weight of retroperitoneal, inguinal and mesenteric white adipose tissue (MWAT) depots and MWAT adipocyte hypertrophy. These effects were accompanied by a significant decrease in the circulating levels of leptin and the mRNA levels of the fatty acid uptake-related genes Lpl and Cd36 in MWAT. These results were very similar to those observed in OVX-E2 animals. OVX-MI rats also displayed a higher lean body mass, lean/fat mass ratio, adiponectin-to-leptin ratio and insulin sensitivity than their OVX counterparts. Our findings can pave the way for using this MI formulation as an alternative therapy to manage obesity and to improve the cardiometabolic health of menopausal women.

Metabolic Profiling in Plasma and Brain Induced by 17β-Estradiol Supplementation in Ovariectomized Mice

17β-Estradiol is an ovarian hormone that regulates energy circulation and storage by acting on the central nervous system. However, the metabolic differences between the blood and brain when stimulated by 17β-estradiol are poorly understood. Moreover, research using menopause-induced models to investigate primary metabolites in the blood and brain is limited. Thus, this study aimed to identify metabolic changes in the plasma and brain resulting from 17β-estradiol supplementation in an estrogen-deficient mouse model. Three groups of mice were utilized: sham-operated mice (Sham), ovariectomized mice (OVX), and ovariectomized mice that received a weekly supplementation of 17β-estradiol (E2). Plasma and brain samples from these mice were subjected to metabolic analysis using gas chromatography-time-of-flight-mass spectrometry. Compared with the plasma samples from the Sham and OVX groups, the plasma samples from the E2 group contained higher contents of branched-chain amino acids (BCAAs), such as valine, isoleucine, and leucine. Meanwhile, the brain samples from the E2 group contained higher contents of most metabolites, including BCAAs, neurotransmitters, tricarboxylic acid cycle intermediates, and fatty acids, than those from the two other groups. This study is the first to reveal differences in energy metabolism induced by 17β-estradiol supplementation through brain metabolic profiling of ovariectomized mice, emphasizing the importance of brain metabolic profiling in menopausal hormone research.

Microdose lithium improves behavioral deficits and modulates molecular mechanisms of memory formation in female SAMP-8, a mouse model of accelerated aging

Alzheimer's disease (AD) is the most common neuronal disorder that leads to the development of dementia. Until nowadays, some therapies may alleviate the symptoms, but there is no pharmacological treatment. Microdosing lithium has been used to modify the pathological characteristics of the disease, with effects in both experimental and clinical conditions. The present work aimed to analyze the effects of this treatment on spatial memory, anxiety, and molecular mechanisms related to long-term memory formation during the aging process of a mouse model of accelerated aging (SAMP-8). Female SAMP-8 showed learning and memory impairments together with disruption of memory mechanisms, neuronal loss, and increased density of senile plaques compared to their natural control strain, the senescence-accelerated mouse resistant (SAMR-1). Chronic treatment with lithium promoted memory maintenance, reduction in anxiety, and maintenance of proteins related to memory formation and neuronal density. The density of senile plaques was also reduced. An increase in the density of gamma-aminobutyric acid A (GABAA) and α7 nicotinic cholinergic receptors was also observed and related to neuroprotection and anxiety reduction. In addition, this microdose of lithium inhibited the activation of glycogen synthase kinase-3beta (GSK-3β), the classical mechanism of lithium cell effects, which could contribute to the preservation of the memory mechanism and reduction in senile plaque formation. This work shows that lithium effects in neuroprotection along the aging process are not related to a unique cellular mechanism but produce multiple effects that slowly protect the brain along the aging process.

Micro-ultrasound based characterization of cerebrovasculature following focal ischemic stroke and upon short-term rehabilitation

Notwithstanding recanalization treatments in the acute stage of stroke, many survivors suffer long-term impairments. Physical rehabilitation is the only widely available strategy for chronic-stage recovery, but its optimization is hindered by limited understanding of its effects on brain structure and function. Using micro-ultrasound, behavioral testing, and electrophysiology, we investigated the impact of skilled reaching rehabilitation on cerebral hemodynamics, motor function, and neuronal activity in a rat model of focal ischemic stroke. A 50 MHz micro-ultrasound transducer and intracortical electrophysiology were utilized to characterize neurovascular changes three weeks following focal ischemia elicited by endothelin-1 injection into the sensorimotor cortex. Sprague-Dawley rats were rehabilitated through tray reaching, and their fine skilled reaching was assessed via the Montoya staircase. Focal ischemia led to a sustained deficit in forelimb reaching; and increased tortuosity of the penetrating vessels in the perilesional cortex; with no lateralization of spontaneous neuronal activity. Rehabilitation improved skilled reaching; decreased cortical vascularity; was associated with elevated peri- vs. contralesional hypercapnia-induced flow homogenization and increased perilesional spontaneous cortical neuronal activity. Our study demonstrated neurovascular plasticity accompanying rehabilitation-elicited functional recovery in the subacute stage following stroke, and multiple micro-ultrasound-based markers of cerebrovascular structure and function modified in recovery from ischemia and upon rehabilitation.

VCD-induced menopause mouse model reveals reprogramming of hepatic metabolism

OBJECTIVE

Menopause adversely impacts systemic energy metabolism and increases the risk of metabolic disease(s) including hepatic steatosis, but the mechanisms are largely unknown. Dosing female mice with vinyl cyclohexene dioxide (VCD) selectively causes follicular atresia in ovaries, leading to a murine menopause-like phenotype.

METHODS

In this study, we treated female C57BL6/J mice with VCD (160 mg/kg i.p. for 20 consecutive days followed by verification of the lack of estrous cycling) to investigate changes in body composition, energy expenditure (EE), hepatic mitochondrial function, and hepatic steatosis across different dietary conditions.

RESULTS

VCD treatment induced ovarian follicular loss and increased follicle-stimulating hormone (FSH) levels in female mice, mimicking a menopause-like phenotype. VCD treatment did not affect body composition, or EE in mice on a low-fat diet (LFD) or in response to a short-term (1-week) high-fat, high sucrose diet (HFHS). However, the transition to a HFHS lowered cage activity in VCD mice. A chronic HFHS diet (16 weeks) significantly increased weight gain, fat mass, and hepatic steatosis in VCD-treated mice compared to HFHS-fed controls. In the liver, VCD mice showed suppressed hepatic mitochondrial respiration on LFD, while chronic HFHS resulted in compensatory increases in hepatic mitochondrial respiration. Also, liver RNA sequencing revealed that VCD promoted global upregulation of hepatic lipid/cholesterol synthesis pathways.

CONCLUSION

Our findings suggest that the VCD-induced menopause model compromises hepatic mitochondrial function and lipid/cholesterol homeostasis that sets the stage for HFHS diet-induced steatosis while also increasing susceptibility to obesity.

A Pilot Systematic Review and Meta-analysis of Neuroprotective Studies in Female Rodent Models of Ischemic Stroke

Most ischemic stroke (IS) patients go untreated due to limited treatment windows, restrictive eligibility criteria, and poor availability of current clinical therapies. Neuroprotective treatments targeting protracted neurodegeneration are needed yet keep failing in clinical trials. Over half of IS patients are female, and the scarcity of neuroprotective studies using female animals hinders translational success. This pilot review and meta-analysis assessed the relationship between the risk of bias and efficacy of studies testing post-ischemic neuroprotective therapies using female rodent models of IS. We carried out a systematic search of the PubMed database for studies published between 1999 and May 2022, used the CAMARADES checklist to evaluate study quality, and extracted data pertaining to lesion volume and behavioral assessment. We found that 34 studies met our inclusion criteria, with pooled effect sizes depicting a significant treatment effect. However, researchers used mostly healthy young females, administered therapies within short time windows, ignored hormonal influences, and did not assess long-term outcomes. Interestingly, studies failing to report factors impacting internal validity, such as blinding and random allocation, had inflated effect sizes or did not reach statistical significance. There was also a relationship between low study quality and larger effect sizes for functional outcome, stressing the need to follow the existing translational design, reporting, and data analysis guidelines. In this review, we cover previous recommendations and offer our own in hopes that rigorous and meticulous research using female animal models of IS will increase our chances of successful bench-to-bedside translation.

Linking alterations in estrogen receptor expression to memory deficits and depressive behavior in an ovariectomy mouse model

The high risk of neurological disorders in postmenopausal women is an emerging medical issue. Based on the hypothesis of altered estrogen receptors (ERα and β) after the decline of estrogen production, we investigated the changes in ERs expressions across brain regions and depressive/amnesic behaviors. C57BL/6J female mice were ovariectomized (OVX) to establish a menopausal condition. Along with behavior tests (anxiety, depression, and memory), the expression of ERs, microglial activity, and neuronal activity was measured in six brain regions (hippocampus, prefrontal cortex, striatum, raphe nucleus, amygdala, and hypothalamus) from 4 to 12 weeks after OVX. Mice exhibited anxiety- and depressive-like behaviors, as well as memory impairment. These behavioral alterations have been linked to a suppression in the expression of ERβ. The decreased ERβ expression coincided with microglial-derived neuroinflammation, as indicated by notable activations of Ionized calcium-binding adapter molecule 1 and Interleukin-1beta. Additionally, the activity of brain-derived neurotrophic factor (BDNF), particularly in the hippocampus, decreased in a time-dependent manner from 4 to 12 weeks post-OVX. Our study provides evidence shedding light on the susceptibility to memory impairment and depression in women after menopause. This susceptibility is associated with the suppression of ERβ and alteration of ERα in six brain regions.

A coming-of-age story: adult neurogenesis or adolescent neurogenesis in rodents?

It is surprising that after more than a century using rodents for scientific research, there are no clear, consensual, or consistent definitions for when a mouse or a rat becomes adult. Specifically, in the field of adult hippocampal neurogenesis, where this concept is central, there is a trend to consider that puberty marks the start of adulthood and is not uncommon to find 30-day-old mice being described as adults. However, as others discussed earlier, this implies an important bias in the perceived importance of this trait because functional studies are normally done at very young ages, when neurogenesis is at its peak, disregarding middle aged and old animals that exhibit very little generation of new neurons. In this feature article we elaborate on those issues and argue that research on the postnatal development of mice and rats in the last 3 decades allows to establish an adolescence period that marks the transition to adulthood, as occurs in other mammals. Adolescence in both rat and mice ends around postnatal day 60 and therefore this age can be considered the onset of adulthood in both species. Nonetheless, to account for inter-individual, inter-strain differences in maturation and for possible delays due to environmental and social conditions, 3 months of age might be a safer option to consider mice and rats bona fide adults, as suggested by The Jackson Labs.

Sex- and age-dependent susceptibility to ventricular arrhythmias in the rat heart ex vivo

The incidence of life-threatening ventricular arrhythmias, the most common cause of sudden cardiac death (SCD), depends largely on the arrhythmic substrate that develops in the myocardium during the aging process. There is a large deficit of comparative studies on the development of this substrate in both sexes, with a particular paucity of studies in females. To identify the substrates of arrhythmia, fibrosis, cardiomyocyte hypertrophy, mitochondrial density, oxidative stress, antioxidant defense and intracellular Ca2+ signaling in isolated cardiomyocytes were measured in the hearts of 3- and 24-month-old female and male rats. Arrhythmia susceptibility was assessed in ex vivo perfused hearts after exposure to isoproterenol (ISO) and hydrogen peroxide (H2O2). The number of ventricular premature beats (PVBs), ventricular tachycardia (VT) and ventricular fibrillation (VF) episodes, as well as intrinsic heart rate, QRS and QT duration, were measured in ECG signals recorded from the surfaces of the beating hearts. After ISO administration, VT/VFs were formed only in the hearts of males, mainly older ones. In contrast, H2O2 led to VT/VF formation in the hearts of rats of both sexes but much more frequently in older males. We identified several components of the arrhythmia substrate that develop in the myocardium during the aging process, including high spontaneous ryanodine receptor activity in cardiomyocytes, fibrosis of varying severity in different layers of the myocardium (nonheterogenic fibrosis), and high levels of oxidative stress as measured by nitrated tyrosine levels. All of these elements appeared at a much greater intensity in male individuals during the aging process. On the other hand, in aging females, antioxidant defense at the level of H2O2 detoxification, measured as glutathione peroxidase expression, was weaker than that in males of the same age. We showed that sex has a significant effect on the development of an arrhythmic substrate during aging. This substrate determines the incidence of life-threatening ventricular arrhythmias in the presence of additional stimuli with proarrhythmic potential, such as catecholamine stimulation or oxidative stress, which are constant elements in the pathomechanism of most cardiovascular diseases.

Use of Quantitative Electroencephalography to Inform Age- and Sex-Related Differences in NMDA Receptor Function Following MK-801 Administration

Sex- and age-related differences in symptom prevalence and severity have been widely reported in patients with schizophrenia, yet the underlying mechanisms contributing to these differences are not well understood. N-methyl-D-aspartate (NMDA) receptor hypofunction contributes to schizophrenia pathology, and preclinical models often use NMDA receptor antagonists, including MK-801, to model all symptom clusters. Quantitative electroencephalography (qEEG) represents a translational approach to measure neuronal activity, identify targetable biomarkers in neuropsychiatric disorders and evaluate possible treatments. Abnormalities in gamma power have been reported in patients with schizophrenia and correspond to psychosis and cognitive impairment. Further, as gamma power reflects cortical glutamate and GABA signaling, it is highly sensitive to changes in NMDA receptor function, and NMDA receptor antagonists aberrantly increase gamma power in rodents and humans. To evaluate the role of sex and age on NMDA receptor function, MK-801 (0.03-0.3 mg/kg, SC) was administered to 3- and 9-month-old male and female Sprague-Dawley rats that were implanted with wireless EEG transmitters to measure cortical brain function. MK-801-induced elevations in gamma power were observed in 3-month-old male and female and 9-month-old male rats. In contrast, 9-month-old female rats demonstrated blunted maximal elevations across a wide dose range. Importantly, MK-801-induced hyperlocomotor effects, a common behavioral screen used to examine antipsychotic-like activity, were similar across all groups. Overall, sex-by-age-related differences in gamma power support using qEEG as a translational tool to evaluate pathological progression and predict treatment response across a heterogeneous population.

The impact of 17β-estradiol on the estrogen-deficient female brain: from mechanisms to therapy with hot flushes as target symptoms

Sex steroids are essential for whole body development and functions. Among these steroids, 17β-estradiol (E2) has been known as the principal "female" hormone. However, E2's actions are not restricted to reproduction, as it plays a myriad of important roles throughout the body including the brain. In fact, this hormone also has profound effects on the female brain throughout the life span. The brain receives this gonadal hormone from the circulation, and local formation of E2 from testosterone via aromatase has been shown. Therefore, the brain appears to be not only a target but also a producer of this steroid. The beneficial broad actions of the hormone in the brain are the end result of well-orchestrated delayed genomic and rapid non-genomic responses. A drastic and steady decline in circulating E2 in a female occurs naturally over an extended period of time starting with the perimenopausal transition, as ovarian functions are gradually declining until the complete cessation of the menstrual cycle. The waning of endogenous E2 in the blood leads to an estrogen-deficient brain. This adversely impacts neural and behavioral functions and may lead to a constellation of maladies such as vasomotor symptoms with varying severity among women and, also, over time within an individual. Vasomotor symptoms triggered apparently by estrogen deficiency are related to abnormal changes in the hypothalamus particularly involving its preoptic and anterior areas. However, conventional hormone therapies to "re-estrogenize" the brain carry risks due to multiple confounding factors including unwanted hormonal exposure of the periphery. In this review, we focus on hot flushes as the archetypic manifestation of estrogen deprivation in the brain. Beyond our current mechanistic understanding of the symptoms, we highlight the arduous process and various obstacles of developing effective and safe therapies for hot flushes using E2. We discuss our preclinical efforts to constrain E2's beneficial actions to the brain by the DHED prodrug our laboratory developed to treat maladies associated with the hypoestrogenic brain.

Thrombin-activatable fibrinolysis inhibitor and sex modulate thrombus stability and pulmonary embolism burden in a murine model

BACKGROUND

Thrombin-activatable fibrinolysis inhibitor (TAFI) levels are positively correlated with the risk of thrombosis. The mechanism of how TAFI affects venous thromboembolism (VTE) remains uncertain. In addition, the role of sex on the risk of VTE has also been studied. However, their association also remains unclear.

OBJECTIVES

To investigate how TAFI and/or sex affect venous thrombus stability and consequent pulmonary embolism (PE).

METHODS

Ferric chloride-induced thrombi were formed within the femoral veins of male and female wild-type (WT) or TAFI-knockout (Cpb2-/-) mice. Thrombi were imaged over 2 hours using intravital videomicroscopy to quantify embolization and thrombus size over time. Lungs were examined by immunohistochemistry to quantify (a) emboli and (b) fibrin composition of these emboli.

RESULTS

Embolization events in female mice were higher than in males (7.9-fold in WT and 3.1-fold in Cpb2-/- mice). Although the maximal thrombus sizes were not different across groups, Cpb2-/- mice had thrombi that were, on average, 24% smaller at the end of the 2-hour experiment than WT mice. Loss of TAFI led to a 4.0- and 2.8-fold increase in PE burden in males and females, respectively, while sex had no influence. Pulmonary emboli in Cpb2-/- mice had higher fibrin composition compared with WT mice.

CONCLUSION

Female mice had less stable venous thrombi than male mice, suggesting a higher risk of PE in females with deep vein thrombosis. Mice lacking TAFI had more thrombus degradation and higher PE burden than WT mice. These results confirm the role of TAFI in venous thrombosis.

Practical solutions for including sex as a biological variable (SABV) in preclinical neuropsychopharmacological research

Recently, many funding agencies have released guidelines on the importance of considering sex as a biological variable (SABV) as an experimental factor, aiming to address sex differences and avoid possible sex biases to enhance the reproducibility and translational relevance of preclinical research. In neuroscience and pharmacology, the female sex is often omitted from experimental designs, with researchers generalizing male-driven outcomes to both sexes, risking a biased or limited understanding of disease mechanisms and thus potentially ineffective therapeutics. Herein, we describe key methodological aspects that should be considered when sex is factored into in vitro and in vivo experiments and provide practical knowledge for researchers to incorporate SABV into preclinical research. Both age and sex significantly influence biological and behavioral processes due to critical changes at different timepoints of development for males and females and due to hormonal fluctuations across the rodent lifespan. We show that including both sexes does not require larger sample sizes, and even if sex is included as an independent variable in the study design, a moderate increase in sample size is sufficient. Moreover, the importance of tracking hormone levels in both sexes and the differentiation between sex differences and sex-related strategy in behaviors are explained. Finally, the lack of robust data on how biological sex influences the pharmacokinetic (PK), pharmacodynamic (PD), or toxicological effects of various preclinically administered drugs to animals due to the exclusion of female animals is discussed, and methodological strategies to enhance the rigor and translational relevance of preclinical research are proposed.

VCD-induced menopause mouse model reveals reprogramming of hepatic metabolism

Menopause adversely impacts systemic energy metabolism and increases the risk of metabolic disease(s) including hepatic steatosis, but the mechanisms are largely unknown. Dosing female mice with vinyl cyclohexene dioxide (VCD) selectively causes follicular atresia in ovaries, leading to a murine menopause-like phenotype. In this study, we treated female C57BL6/J mice with VCD (160mg/kg i.p. for 20 consecutive days followed by verification of the lack of estrous cycling) to investigate changes in body composition, energy expenditure (EE), hepatic mitochondrial function, and hepatic steatosis across different dietary conditions. VCD treatment induced ovarian follicular loss and increased follicle-stimulating hormone (FSH) levels in female mice, mimicking a menopause-like phenotype. VCD treatment did not affect body composition, or EE in mice on a low-fat diet or in response to a short-term (1-week) high-fat, high sucrose diet (HFHS). However, the transition to a HFHS lowered cage activity in VCD mice. A chronic HFHS diet (16 weeks) significantly increased weight gain, fat mass, and hepatic steatosis in VCD-treated mice compared to HFHS-fed controls. In the liver, VCD mice showed suppressed hepatic mitochondrial respiration on LFD, while chronic HFHS diet resulted in compensatory increases in hepatic mitochondrial respiration. Also, liver RNA sequencing revealed that VCD promoted global upregulation of hepatic lipid/cholesterol synthesis pathways. Our findings suggest that the VCD- induced menopause model compromises hepatic mitochondrial function and lipid/cholesterol homeostasis that sets the stage for HFHS diet-induced steatosis while also increasing susceptibility to obesity.

Aged and induced-premature ovarian failure mouse models affect diestrus profile and ovarian features

Sex hormones exert a wide influence on several systems of the human body, especially in women, who undergo intense changes in the trans and postmenopausal periods. Different experimental models are used to mimic these conditions; however, the impact on hormonal profile may be different. This study aimed to analyze and compare vaginal cytology of different post-estropausal mice models, along with their microscopical ovarian features. Forty-six C57BL/6J female mice with the ages of 4, 6 and 18 months at the beginning of the experiment, weighing about 25-28 grams, constituted five groups: NC-(negative control) animals with no treatment, OVX-SHAM-sham ovariectomized, OVX-ovariectomized, VCD-medicated with 160 mg/kg/day of 4-vinylcyclohexene diepoxide via IP for 20 consecutive days, and Aged-senescent mice under physiological estropause. Euthanasia was performed at different periods for the removal of the ovaries, and after diestrus was confirmed by vaginal cytology for 10 consecutive days. For daily vaginal cytology, morphological and histomorphometric microscopic analyzes were performed. Aged mice presented significant increased neutrophils when compared to VCD group, as well as increased cornified epithelial cells when compared to OVX mice, and also increased nucleated epithelial cells when compared to VCD and OVX. NC and OVX-SHAM ovaries presented innumerous follicles at different stages of development, while VCD showed marked follicular atresia, depleted of primordial or developing follicles and a predominance of interstitial cells. The ovaries of aged mice were predominantly constituted by corpus luteum degenerated into corpus albicans, with rare antral follicles. All analyzed models led to different permanent diestrus profiles caused by each model, as indicated by ovarian features. This should be carefully considered when choosing a post-estropausal experimental model, in order to better correlate this challenging phase of female's life with physiological/pathological conditions.

Female aging: when translational models don't translate

For many pathologies associated with aging, female patients present with higher morbidity and more frequent adverse events from treatments compared to male patients. While preclinical models are the foundation of our mechanistic understanding of age-related diseases, the most common models fail to recapitulate archetypical female aging trajectories. For example, while over 70% of the top age-related diseases are influenced by the systemic effects of reproductive senescence, we found that preclinical studies that include menopausal phenotypes modeling those seen in humans make up <1% of published aging biology research. The long-term impacts of pregnancy, birthing and breastfeeding are also typically omitted from preclinical work. In this Perspective, we summarize limitations in the most commonly used aging models, and we provide recommendations for better incorporating menopause, pregnancy and other considerations of sex in vivo and in vitro. Lastly, we outline action items for aging biology researchers, journals, funding agencies and animal providers to address this gap.

Estrogen dysregulation, intraocular pressure, and glaucoma risk

Characterized by optic nerve atrophy due to retinal ganglion cell (RGC) death, glaucoma is the leading cause of irreversible blindness worldwide. Of the major risk factors for glaucoma (age, ocular hypertension, and genetics), only elevated intraocular pressure (IOP) is modifiable, which is largely regulated by aqueous humor outflow through the trabecular meshwork. Glucocorticoids such as dexamethasone have long been known to elevate IOP and lead to glaucoma. However, several recent studies have reported that steroid hormone estrogen levels inversely correlate with glaucoma risk, and that variants in estrogen signaling genes have been associated with glaucoma. As a result, estrogen dysregulation may contribute to glaucoma pathogenesis, and estrogen signaling may protect against glaucoma. The mechanism for estrogen-related protection against glaucoma is not completely understood but likely involves both regulation of IOP homeostasis and neuroprotection of RGCs. Based upon its known activities, estrogen signaling may promote IOP homeostasis by affecting extracellular matrix turnover, focal adhesion assembly, actin stress fiber formation, mechanosensation, and nitric oxide production. In addition, estrogen receptors in the RGCs may mediate neuroprotective functions. As a result, the estrogen signaling pathway may offer a therapeutic target for both IOP control and neuroprotection. This review examines the evidence for a relationship between estrogen and IOP and explores the possible mechanisms by which estrogen maintains IOP homeostasis.

Safety of Innovative Nanotechnology Oral Formulations Loaded with Bioactive Menopause Molecules: Influence of Genotoxicity and Biochemical Parameters on a Menopausal Rat Model

In recent years, nanoparticles have gained significant importance due to their unique properties, such as pharmacological, electrical, optical, and magnetic abilities, contributing to the growth of the science and technology sector. Particular naturally derived biomolecules with beneficial effects on menopause disorder have been the subject of studies of pharmaceutical formulation to obtain alternative pharmaceutical forms with increased bioavailability and without side effects, as in nanostructured lipid carriers (NLCs) loaded with such active ingredients. In the present study, one stage of a broader project, we have performed pharmacotoxicology studies for six combinatory innovative nanocapsule pharmaceutical forms containing active natural biomolecules before considering them as oral formulas for (1) in vitro toxicity studies on culture cells and (2) in vivo preclinical studies on a surgically induced menopause model of Wistar female rats, and the influence of the NLCs on key biochemical parameters: lipid profile (TG, Chol, HDL), glycemic markers (Gli), bone markers (Pac, Palc, Ca, phosphorus), renal markers (Crea, urea, URAC), inflammation (TNF), oxidative stress (GSH, MDA), and estrogen-progesterone hormonal profile. The micronucleus test did not reveal the genotoxicity of the tested compounds; the menopause model showed no significant safety concerns for the six tested formulas evaluated using the blood biochemical parameters; and the results showed the potential hypoglycemic, hypolipidemic, hypouricemic, and antioxidant potential of one of the tested formulas containing nano diosgenin and glycyrrhizic acid.

Murine Orchiectomy and Ovariectomy to Reduce Sex Hormone Production

Sex hormone signaling plays a critical role in multiple organ systems as well as in the progression of various diseases, including neurodegenerative disease. The manipulation of sex hormone levels in the murine model system allows for the study of their impact on organs/tissues and within disease progression. Orchiectomy - the surgical removal of the testes - and ovariectomy - the surgical removal of the ovaries - provide a method to deplete the endogenous sex hormones so that the precise hormone levels can be provided through drug or other delivery methods. Here, we provide rapid and minimally invasive methods for both orchiectomy and ovariectomy in the murine model system for the reduction of sex hormones. This protocol details the surgical preparation and excision of the testes through the scrotal sac, and excision of the ovaries via two incisions in the right and left lateral dorsum.

Sex differences in microglia function in aged rats underlie vulnerability to cognitive decline

Aging is associated with a significant shift in immune system reactivity ("inflammaging"), as basal inflammation increases but protective responses to infection are compromised. The immune system exhibits considerable sex differences, which may influence the process of inflammaging, including immune cell activation and behavioral consequences of immune signaling (i.e., impaired memory). Here, we test the hypothesis that sex differences in immune aging may mediate sex differences in cognitive decline. Aged male and female rats received peripheral immune stimulation using lipopolysaccharide (LPS), then molecular, cellular, and behavioral outcomes were assessed. We observed that LPS-treated aged male rats showed cognitive impairment and increased neuroinflammatory responses relative to adult males. In contrast, aged female rats did not display these aging-related deficits. Using transcriptomic and flow cytometry analyses, we further observed significant age- and sex- dependent changes in immune cell populations in the brain parenchyma and meninges, indicating a broad shift in the neuroinflammatory environment that may potentiate these behavioral effects. Ovariectomized aged female rats were also resistant to inflammation-induced memory deficits, indicating that ovarian hormones are not required for the attenuated neuroinflammation in aged females. Overall, our results indicate that males have amplified inflammatory priming with age, which contributes to age-associated cognitive decline. Our findings highlight sexual dimorphism in mechanisms of aging, and suggest that sex is a crucial consideration for identifying therapies for aging and neuroinflammation.