Novel Proteomic Profiling of Epididymal Extracellular Vesicles in the Domestic Cat Reveals Proteins Related to Sequential Sperm Maturation with Differences Observed between Normospermic and Teratospermic Individuals.

Extracellular vesicles (EVs) secreted by the epididymal epithelium transfer to spermatozoa key proteins that are essential in promoting motility and subsequent fertilization success. Using the domestic cat model, the objectives were to (1) characterize and compare protein content of EVs between segments of the epididymis, and (2) compare EV protein compositions between normo- and teratospermic individuals (producing >60% of abnormal spermatozoa). Epididymal EVs from adult cats were isolated and assessed via liquid chromatography tandem MS. Both male types shared 3008 proteins in total, with 98 and 20 EV proteins unique to normospermic and teratospermic males, respectively. Expression levels of several proteins changed between epididymal segments in both male types. Several proteins in both groups were related to sperm motility (e.g. hexokinase 1, adenylate kinase isoenzyme) and zona pellucida or oolemma binding (e.g. disintegrin and metalloproteinase domain proteins, zona binding proteins 1 and 2). Interestingly, seven cauda-derived EV proteins trended downward in teratospermic compared with normospermic males, which may relate to poor sperm quality. Collective results revealed, for the first time, EV proteins related to sequential sperm maturation with differences observed between normospermic and teratospermic individuals.

Exposure to epididymal extracellular vesicles enhances immature sperm function and sustains vitality of cryopreserved spermatozoa in the domestic cat model.

PURPOSE: Extracellular vesicles (EVs) secreted by the epididymal epithelium transfer key factors to maturing spermatozoa. Using an in vitro system previously developed in our laboratory, the objective was to (1) characterize the impact of EV exposure on the fertilizing ability and developmental potential of immature sperm cells from the caput epididymidis and (2) examine the benefit of EV exposure to restore vitality of mature spermatozoa from the cauda epididymidis after freezing-thawing. METHODS: EVs were isolated from entire epididymides and collected into pellets via ultracentrifugation. Immature spermatozoa from adult cats were isolated from the caput epididymis and incubated with EVs prior to in vitro fertilization. Similarly, mature spermatozoa were isolated from the cauda segment and cryopreserved prior to EV exposure and subsequent analysis of motility and developmental potential after fertilization. RESULTS: EV exposure did not affect the percentage of caput sperm penetration; however, it improved the fertilizing ability (faster pronuclear apposition) and the developmental potential (higher proportions of morula-blastocysts) of those immature sperm cells. While EV exposure was beneficial to the frozen-thawed sperm motility, it did not significantly improve the fertilizing ability and the developmental potential. CONCLUSIONS: Epididymal EVs contain multiple factors contributing to immature sperm function, specifically enhancing the ability to complete a faster pronuclear apposition with subsequently improved early embryonic development. Supplementation was also beneficial to the motility of spermatozoa that had undergone cryopreservation. Those new findings could lead to new options for male fertility treatment in animal models and humans.

An exploratory investigation of brain-selective estrogen treatment in males using a mouse model of Alzheimer's disease.

Estrogens are neuroprotective, and studies suggest that they may mitigate the pathology and symptoms of Alzheimer's disease (AD) in female models. However, central estrogen effects have not been examined in males in the context of AD. The purpose of this follow-up study was to assess the benefits of a brain-selective 17ß-estradiol estrogen prodrug, 10ß,17ß-hydroxyestra-1,4-dien-3-one (DHED), also in the male APPswe/PS1dE9 double-transgenic mouse model of the disease. After continuously exposing 6-month old animals to DHED for two months, their brains showed decreased amyloid precursor and amyloid-ß protein levels. The DHED-treated APPswe/PS1dE9 double transgenic subjects also exhibited enhanced performance in a cognitive task, while 17ß-estradiol treatment did not reach statistical significance. Taken together, data presented here suggest that DHED may also have therapeutic benefit in males and warrant further investigations to fully elucidate the potential of targeted estrogen therapy for a gender-independent treatment of early-stage AD.

Differential expression of hepatic genes with embryonic exposure to an environmentally relevant PCB mixture in Japanese quail (Coturnix japonica).

The upper Hudson River was contaminated with polychlorinated biphenyls (PCB) Aroclor mixtures from the 1940s until the late 1970s. Several well-established biomarkers, such as induction of hepatic cytochrome P450 monooxygenases, were used to measure exposure to PCBs and similar contaminants in birds. In the present study, Japanese quail eggs were injected with a PCB mixture based upon a congener profile found in spotted sandpiper eggs at the upper Hudson River and subsequently, RNA was extracted from hatchling liver tissue for hybridization to a customized chicken cDNA microarray. Nominal concentrations of the mixture used for microarray hybridization were 0, 6, 12, or 49 µg/g egg. Hepatic gene expression profiles were analyzed using cluster and pathway analyses. Results showed potentially useful biomarkers of both exposure and effect attributed to PCB mixture. Biorag and Ingenuity Pathway Analysis® analyses revealed differentially expressed genes including those involved in glycolysis, xenobiotic metabolism, replication, protein degradation, and tumor regulation. These genes included cytochrome P450 1A5 (CYP1A5), cytochrome b5 (CYB5), NADH-cytochrome b5 reductase, glutathione S-transferase (GSTA), fructose bisphosphate aldolase (ALDOB), glycogen phosphorylase, carbonic anhydrase, and DNA topoisomerase II. CYP1A5, CYB5, GSTA, and ALDOB were chosen for quantitative real-time polymerase chain reaction confirmation, as these genes exhibited a clear dose response on the array. Data demonstrated that an initial transcriptional profile associated with an environmentally relevant PCB mixture in Japanese quail occurred.

Key factors enhancing sperm fertilizing ability are transferred from the epididymis to the spermatozoa via epididymosomes in the domestic cat model.

PURPOSE: Spermatozoa undergo critical changes in structure and function during the epididymal transit. Our previous studies in the domestic cat demonstrated that incidence of cenexin-a key protein involved in the centrosomal maturation-progressively increases in sperm cells from caput to cauda epididymidis. The objectives of the study were to (1) characterize mechanisms involved in transferring key factors-using the cenexin as a marker-between the epididymis and maturing sperm cells and (2) demonstrate the impact of such mechanisms on the acquisition of functional properties by spermatozoa. METHODS: Epididymides were dissected from adult cat testes to assess the presence and localization of cenexin in testicular tissues and each epididymal segment (caput, corpus, and cauda) via immunofluorescence, Western blot, and mass spectrometry. RESULTS: Results showed that tissues, luminal fluid, and isolated epididymosomes from each segment contained cenexin. Co-incubation of immature sperm cells for 3 h with luminal fluid or epididymosomes followed by immunostaining revealed that percentages of sperm cells containing cenexin significantly increased in samples co-incubated with epididymosome suspensions. Additionally, epididymosome co-incubation with immature spermatozoa resulted in sustained motility compared to untreated spermatozoa while there was no significant effect on acrosome integrity. CONCLUSIONS: Taken together, these results suggest that epididymosomes play a critical role in epididymal sperm maturation and could be ideal vehicles to assist in the enhancement or suppression of male fertility.

A comparative evaluation of treatments with 17ß-estradiol and its brain-selective prodrug in a double-transgenic mouse model of Alzheimer's disease.

Estrogens are neuroprotective and, thus, potentially useful for the therapy of Alzheimer's disease; however, clinical use of hormone therapy remains controversial due to adverse peripheral effects. The goal of this study was to investigate the benefits of treatment with 10ß,17ß-dihydroxyestra-1,4-dien-3-one (DHED), a brain-selective prodrug of 17ß-estradiol, in comparison with the parent hormone using APPswe/PS1dE9 double transgenic mice to model the pathology of the disease. Ovariectomized and intact females were continuously treated with vehicle, 17ß-estradiol, or DHED via subcutaneous osmotic pumps from 6 to 8months of age. We confirmed that this prolonged treatment with DHED did not stimulate uterine tissue, whereas 17ß-estradiol treatment increased uterine weight. Amyloid precursor protein decreased in both treatment groups of intact, but not in ovariectomized double transgenic females in which ovariectomy already decreased the expression of this protein significantly. However, reduced brain amyloid-ß peptide levels could be observed for both treatments. Consequently, double-transgenic ovariectomized and intact mice had higher cognitive performance compared to untreated control animals in response to both estradiol and DHED administrations. Overall, the tested brain-selective 17ß-estradiol prodrug proved to be an effective early-stage intervention in an Alzheimer's disease-relevant mouse model without showing systemic impact and, thus, warrants further evaluation as a potential therapeutic candidate.

Characterization of multiple pathways modulating aggression in the male clouded leopard (Neofelis nebulosa).

Breeding clouded leopards (Neofelis nebulosa) ex situ has been a challenge, primarily due to extreme and often fatal male aggression toward females. This study's aim was to determine the degree to which two possible mechanisms-serotonergic pathways and circulating testosterone levels-affect aggressive behavior. Male clouded leopard behavioral and hormonal data were collected during a series of behavior tests administered before and after treatment with either an anxiety-reducing tricyclic antidepressant (clomipramine) or a GnRH agonist (deslorelin). Results showed that clomipramine treatment decreased "overall activity" (P = 0.054) and increased "lying down" (P = 0.0043) and hiding in a "nest box" (P = 0.0023). Clomipramine treatment also decreased the incidence of "growling" during a mirror image stimulation test, relative to non-test periods (P < 0.0001 pre-drug treatment; P = 0.242 peri-drug treatment), indicating reduced aggression. Suppression of the reproductive axis via deslorelin treatment resulted in significant decreases in circulating androgen (P < 0.0001) and glucocorticoid (P < 0.0001), accompanied by decreased aggressive behaviors, including "swatting" (P = 0.0476), "tail flicking" (P = 0.0409), and "growling" during the behavior reaction tests: mirror image stimulation (P < 0.0001 pre-drug treatment: P = 0.7098 peri-drug treatment) and unfamiliar people test (P < 0.0001 pre-drug treatment: P = 0.2666 peri-drug treatment) relative to non-test periods. Both drug treatments provide evidence that multiple mechanisms modulate aggressive behavior in the male clouded leopard, suggesting that serotonergic modulation coupled with circulating androgens may aid in the formation of successful breeding pairs. Zoo Biol. 35:474-486, 2016. © 2016 Wiley Periodicals, Inc.

Progestin priming before gonadotrophin stimulation and AI improves embryo development and normalises luteal function in the cat.

Exogenous gonadotrophins administered before AI can adversely alter endocrine dynamics and inhibit embryo development in felids. In the present study, we tested the hypothesis that priming the domestic cat ovary with progestin mitigates the negative influence of gonadotrophin therapy by normalising early embryogenesis and luteal function. Queens were given either: (1) progestin pretreatment plus chorionic gonadotrophins (n=8; primed); or (2) gonadotrophins only (n=8; unprimed). Ovulatory response was assessed laparoscopically, and cats with fresh corpora lutea (CL) were inseminated in utero. Ovariohysterectomy was performed 3 days later to recover intra-oviductal embryos for in vitro culture; one ovary was prepared for histology, and CL from the remaining ovary were excised and assessed for progesterone content and targeted gene expression. Of the six primed and seven unprimed queens inseminated, embryo(s) were recovered from five individuals per group. Embryos from progestin-primed donors more closely simulated normal stage in vivo development (P<0.05). No 2- or 4-cell embryos from either group developed beyond 16-cells in vitro; however, 50% of unprimed and 66.7% of primed (P>0.05) 5-16-cell embryos progressed to morulae or blastocysts by Day 4 of culture. Although histological characteristics were unaffected by progestin priming (P>0.05), luteal progesterone was unusually high (P<0.05) in unprimed compared with primed cats (72.4±5.8 vs. 52.2±5.5 ng mg(-1), respectively). Two genes associated with progesterone biosynthesis (luteinising hormone receptor and 3ß-hydroxysteroid dehydrogenase) were upregulated in unprimed versus primed individuals (P=0.05 and P<0.05, respectively), indicating potential mechanistic pathways for the protective influence of pre-emptive progestin treatment. Building on earlier findings that progestin priming prevents spontaneous ovulation, increases ovarian sensitivity to gonadotrophins and ensures a normative endocrine environment, the present study demonstrates that pretreatment with this steroid also benefits embryo development and normalisation of early luteal function.

Current concepts in neuroendocrine disruption.

In the last few years, it has become clear that a wide variety of environmental contaminants have specific effects on neuroendocrine systems in fish, amphibians, birds and mammals. While it is beyond the scope of this review to provide a comprehensive examination of all of these neuroendocrine disruptors, we will focus on select representative examples. Organochlorine pesticides bioaccumulate in neuroendocrine areas of the brain that directly regulate GnRH neurons, thereby altering the expression of genes downstream of GnRH signaling. Organochlorine pesticides can also agonize or antagonize hormone receptors, adversely affecting crosstalk between neurotransmitter systems. The impacts of polychlorinated biphenyls are varied and in many cases subtle. This is particularly true for neuroedocrine and behavioral effects of exposure. These effects impact sexual differentiation of the hypothalamic-pituitary-gonadal axis, and other neuroendocrine systems regulating the thyroid, metabolic, and stress axes and their physiological responses. Weakly estrogenic and anti-androgenic pollutants such as bisphenol A, phthalates, phytochemicals, and the fungicide vinclozolin can lead to severe and widespread neuroendocrine disruptions in discrete brain regions, including the hippocampus, amygdala, and hypothalamus, resulting in behavioral changes in a wide range of species. Behavioral features that have been shown to be affected by one or more these chemicals include cognitive deficits, heightened anxiety or anxiety-like, sociosexual, locomotor, and appetitive behaviors. Neuroactive pharmaceuticals are now widely detected in aquatic environments and water supplies through the release of wastewater treatment plant effluents. The antidepressant fluoxetine is one such pharmaceutical neuroendocrine disruptor. Fluoxetine is a selective serotonin reuptake inhibitor that can affect multiple neuroendocrine pathways and behavioral circuits, including disruptive effects on reproduction and feeding in fish. There is growing evidence for the association between environmental contaminant exposures and diseases with strong neuroendocrine components, for example decreased fecundity, neurodegeneration, and cardiac disease. It is critical to consider the timing of exposures of neuroendocrine disruptors because embryonic stages of central nervous system development are exquisitely sensitive to adverse effects. There is also evidence for epigenetic and transgenerational neuroendocrine disrupting effects of some pollutants. We must now consider the impacts of neuroendocrine disruptors on reproduction, development, growth and behaviors, and the population consequences for evolutionary change in an increasingly contaminated world. This review examines the evidence to date that various so-called neuroendocrine disruptors can induce such effects often at environmentally-relevant concentrations.

Comparative biology and non-traditional approaches for basic aging research for facilitating translational studies.

As humans, we aspire to healthy aging and ideally reaching our maximal lifespan. That, however, requires optimizing resilience to stressors and minimizing exposure to factors that accelerate aging. Understanding the complexities of aging processes involves characterizing the causal bases of physical, physiological, and cognitive deficits that accumulate over time, eventually culminating in reduced functionality and decreased resistance to disease and environmental stressors. Both the progression of age-related conditions and onset of diseases are affected by environmental stressors; however, the basis for increased susceptibility remains poorly understood. Furthermore, the actions of some environmental stressors, such as endocrine disruptors, can alter both developmental and aging processes, contributing to lifelong issues with inflammatory and neurodegenerative conditions. This manuscript focuses on the comparative biology and evolution of aging and longevity. The status of an array of animal models and potential for specific geroscience translational applications is addressed by asking these questions. What animal models are currently available for aging and translational geroscience? What are the key roadblocks and barriers for studies of healthy aging, and how might specific animal models be useful? Are research tools available? Which vertebrate animal models can specifically address targeted questions in human aging processes? Can information be synthesized for a range of vertebrate species to identify suitable animal models for addressing specific research questions in geroscience, especially relative to basic physiological function, timing and trajectory of disease progression, effects of environmental stressors, and potential for regenerative medicine?

Global challenges in aging: insights from comparative biology and one health.

The well-being of wildlife populations, ecosystem health, and human health are interlinked, and preserving wildlife is crucial for sustaining healthy ecosystems. Wildlife numbers, and in particular avian populations, have steeply declined over the past century, associated with anthropogenic factors originating from industry, urbanization, changing land use, habitat loss, pollution, emerging diseases, and climate change. All these factors combine to exert increasing stress and impair health for both humans and wildlife, with diminished metabolic, immune, and reproductive function, deteriorating overall health, and reduced longevity. The "toxic aging coin" suggests that these stressors may have dual impacts on aging-they can accelerate the aging process, and older individuals may struggle to cope with pollutants compared to younger ones. These responses are reflected in the health and productivity of individuals, and at a larger scale, the health and ability of populations to withstand disturbances. To understand the potential risk to health over the lifespan, it is important to articulate some of these global challenges and consider both their impacts on aging populations and on the aging process. In this review, we use the toxic aging coin and One Health conceptual frameworks to examine the interconnected health of humans, wildlife, and ecosystems. This exploration aims to develop proactive approaches for optimizing wildlife and human health.

Assessing effects of environmental chemicals on neuroendocrine systems: potential mechanisms and functional outcomes.

Environmental pollutants encompass a vast array of compounds. Most studies in birds have focused on toxicological effects, with little attention to non-lethal effects. Consequently, it has proven difficult to assess potential risk associated with exposure to endocrine disrupting chemicals (EDCs). Assessing potential adverse effects due to exposure is further complicated by the great variation that occurs across avian species. These include variations in reproductive strategies, life span, sexual differentiation, and migration. Differences in reproductive strategies, particularly in the developmental patterns and mechanisms for precocial and altricial chicks, predispose birds to wide variations in response to steroids and steroid-like EDCs. We have investigated the effects of EDCs in precocial birds including Japanese quail (Coturnix japonica) and mallard ducks (Anas platyrhynchos) as well as in wild altricial songbirds. Studies in Japanese quail characterized endogenous steroid hormone changes during development and have demonstrated that the developing embryo uses the yolk as a 'steroid hormone depot'. It appears that actual embryonic exposure is quantitatively lower than indicated by the treatment in egg injections and that the true amount of compound necessary for bioactivity may be quite low relative to the actual dosage delivered. Additionally, embryonic exposure to specific EDCs adversely affected sexual differentiation in quail, especially impacting male sexual behavior as well as neural systems, immune response, and thyroid hormones. Many of these studies considered single compounds; however, wild birds are exposed to complex mixtures and multiple compounds. We tested complex mixtures of polychlorinated biphenyls (PCBs) at concentrations that bracketed those found in eggs in contaminated regions. Results indicated that the predictive value of the toxic equivalency (TEQ), based on comparative activation of the aryl hydrocarbon receptor (AhR) relative to dioxin was not as accurate as expected. We discuss the potential of developing an endocrine disruption index (EDI) to bridge the inconsistencies observed between responses predicted by the TEQ and those observed in vivo following exposure to EDCs. Further, we will discuss how an EDI would complement the adverse outcome pathways analyses to consider the range of effects of endocrine disruptors in birds.

Oral progestin priming increases ovarian sensitivity to gonadotropin stimulation and improves luteal function in the cat.

As the only domesticated species known to exhibit both induced and spontaneous ovulation, the cat is a model for understanding the nuances of ovarian control. To explore ovarian sensitivity to exogenous gonadotropins and the influence of progestin priming, we conducted a study of queens that were down-regulated with oral progestin or allowed to cycle normally, followed by low or high doses of equine chorionic gonadotropin (eCG) and human chorionic gonadotropin (hCG). Our metrics included 1) fecal steroid metabolite profiles before and after ovulation induction, 2) laparoscopic examination of ovarian follicles and corpora lutea (CL) on Days 2 and 17 (Day 0 = hCG administration), and 3) ovariohysterectomy (Day 17) to assess CL progesterone concentrations, morphometrics, and histology. Reproductive tracts from time-matched, naturally mated queens (n = 6) served as controls. Every progestin-primed cat (n = 12) produced the desired response of morphologically similar, fresh CL (regardless of eCG/hCG dose) by Day 2, whereas 41.7% of unprimed counterparts (n = 12) failed to ovulate or had variable-aged CL suggestive of prior spontaneous ovulation (P < 0.05). The ovarian response to low, but not high, eCG/hCG was improved (P < 0.05) in primed compared to unprimed cats, indicating increased sensitivity to gonadotropin in the progestin-primed ovary. Progestin priming prevented hyperelevated fecal steroid metabolites and normalized CL progesterone capacity, but only when combined with low eCG/hCG. However, priming failed to prevent ancillary CL formation, smaller CL mass, or abnormal luteal cell density, which were common to all eCG/hCG-treated cats. Thus, the domestic cat exposed to eCG/hCG produces CL with structural and functional aberrations. These anomalies can be partially mitigated by progestin priming, possibly due to a protective effect of progestin associated with enhanced ovarian sensitivity to gonadotropins.

Protracted reproductive seasonality in the male giant panda (Ailuropoda melanoleuca) reflected by patterns in androgen profiles, ejaculate characteristics, and selected behaviors.

The female giant panda (Ailuropoda melanoleuca) experiences a brief (24-72 h) seasonal estrus, occurring once annually in spring (February-May). Our aim was to determine the existence and temporal profile of reproductive seasonality in the male of this species. The study was facilitated by 3 yr of access to eight giant panda males living in a large breeding center in China. Seasonal periods for the male were defined on the basis of female reproductive activity as prebreeding, breeding (early, peak, late), and nonbreeding seasons. Testes size, fecal androgen excretion, ejaculated sperm density, and frequency of reproductive behaviors (i.e., locomotion, scent marking, vocalizations) increased (P < 0.05) from the prebreeding period (October 1-January 31) to the early breeding season (February 1-March 21). Testes volume and sperm concentration were maximal from March 22 through April 15, a period coinciding with maximal female breeding activity. The occurrence of male reproductive behaviors and fecal androgen concentrations began declining during peak breeding and continued from April 16 through May 31 (late breeding period), returning to nadir throughout the nonbreeding interval (June 1-September 30). Reproductive quiescence throughout the latter period was associated with basal testes size/volume and aspermic ejaculates. Our results reveal that testes morphometry, fecal androgen excretion, seminal quality, and certain behaviors integrated together clearly demonstrate reproductive seasonality in the male giant panda. The coordinated increases in testes size, androgen production, sperm density, and sexual behaviors occur over a protracted interval, likely to prepare for and then accommodate a brief, unpredictable female estrus.

Old World Vultures Reflect Effects of Environmental Pollutants Through Human Encroachment.

African wildlife face challenges from many stressors including current and emerging contaminants, habitat and resource loss, poaching, intentional and unintentional poisoning, and climate-related environmental change. The plight of African vultures exemplifies these challenges due to environmental contaminants and other stressors acting on individuals and populations that are already threatened or endangered. Many of these threats emanate from increasing human population size and settlement density, habitat loss from changing land use for agriculture, residential areas, and industry, and climate-related changes in resource availability. Environmental chemicals that are hazardous include legacy chemicals, emerging chemicals of concern, and high-volume-use chemicals that are employed as weed killers and in other agricultural applications. Furthermore, there are differences in risk for species living in close proximity to humans or in areas affected by habitat loss, climate, and industry. Monitoring programs are essential to track the status of nesting pairs, offspring survival, longevity, and lifetime productivity. This is important for long-lived birds, such as vultures, that may be especially vulnerable to chronic exposure to chemicals as obligate scavengers. Furthermore, their position in the food web may increase risk due to biomagnification of chemicals. We review the primary chemical hazards to Old World vultures and the interacting stressors affecting these and other birds. Habitat is a major consideration for vultures, with tree-nesters and cliff-nesters potentially experiencing different risks of exposure to environmental chemicals. The present review provides information from long-term monitoring programs and discusses a range of these threats and their effects on vulture populations. Environ Toxicol Chem 2022;41:1586-1603. © 2022 SETAC.

Integrating Environment and Aging Research: Opportunities for Synergy and Acceleration.

Despite significant overlaps in mission, the fields of environmental health sciences and aging biology are just beginning to intersect. It is increasingly clear that genetics alone does not predict an individual's neurological aging and sensitivity to disease. Accordingly, aging neuroscience is a growing area of mutual interest within environmental health sciences. The impetus for this review came from a workshop hosted by the National Academies of Sciences, Engineering, and Medicine in June of 2020, which focused on integrating the science of aging and environmental health research. It is critical to bridge disciplines with multidisciplinary collaborations across toxicology, comparative biology, epidemiology to understand the impacts of environmental toxicant exposures and age-related outcomes. This scoping review aims to highlight overlaps and gaps in existing knowledge and identify essential research initiatives. It begins with an overview of aging biology and biomarkers, followed by examples of synergy with environmental health sciences. New areas for synergistic research and policy development are also discussed. Technological advances including next-generation sequencing and other-omics tools now offer new opportunities, including exposomic research, to integrate aging biomarkers into environmental health assessments and bridge disciplinary gaps. This is necessary to advance a more complete mechanistic understanding of how life-time exposures to toxicants and other physical and social stressors alter biological aging. New cumulative risk frameworks in environmental health sciences acknowledge that exposures and other external stressors can accumulate across the life course and the advancement of new biomarkers of exposure and response grounded in aging biology can support increased understanding of population vulnerability. Identifying the role of environmental stressors, broadly defined, on aging biology and neuroscience can similarly advance opportunities for intervention and translational research. Several areas of growing research interest include expanding exposomics and use of multi-omics, the microbiome as a mediator of environmental stressors, toxicant mixtures and neurobiology, and the role of structural and historical marginalization and racism in shaping persistent disparities in population aging and outcomes. Integrated foundational and translational aging biology research in environmental health sciences is needed to improve policy, reduce disparities, and enhance the quality of life for older individuals.

Hormonal effects of maltreatment in Nazca booby nestlings: implications for the "cycle of violence".

Non-breeding Nazca booby adults exhibit an unusual and intense social attraction to non-familial conspecific nestlings. Non-parental Adult Visitors (NAVs) seek out and approach unguarded nestlings during daylight hours and display parental, aggressive, and/or sexual behavior. In a striking parallel to the "cycle of violence" of human biology, degree of victimization as a nestling is strongly correlated with frequency of future maltreatment behavior exhibited as an adult. Here, we investigate candidates for permanent organization of this behavior, including immediate and long-term changes in growth and circulating corticosterone and testosterone due to victimization, by protecting some nestlings with portable exclosures that prevented NAV visits and comparing them to controls. During maltreatment episodes, nestlings experience an approximately five-fold increase in corticosterone concentration, and corticosterone remains elevated approximately 2.8-fold until at least the following morning. Our results are consistent with the possibility that repeated activation of the hypothalamic-pituitary-adrenal axis permanently organizes future adult maltreatment behavior. No effect on growth, acute or chronic changes in testosterone, or chronic corticosterone elevation was detected or appeared to be components of an organizational effect. This unusual behavior presents an opportunity to investigate neural, endocrine, and behavioral organization resulting from early social trauma that may be conserved across vertebrate classes.

Neuroendocrine impacts of endocrine-disrupting chemicals in birds: life stage and species sensitivities.

Assessing potential risk associated with exposure to endocrine-disrupting chemicals (EDC) has been difficult due to species specific variation in vulnerability and to both short- and long-term effects produced by EDC. In precocial birds, embryonic exposure to EDC impacts sexual differentiation of neuroendocrine systems and behavior. Often, detectable nonlethal effects of EDC diminish as the organism matures such that the chronic impact of EDC may appear relatively innocuous by the time an individual is sexually mature. In addition, studies have not addressed lifetime effects of EDC exposure on birds. Consequently, it is difficult to assess chronic effects of nonlethal exposure on the fitness of an individual and whether there is a potential risk to a wild population. Assessing behavioral and neuroendocrine consequences of exposure is complicated by individual and species variation in sensitivity as well as exposure to complex mixtures. Our studies are designed to examine effects of individual EDC administered to the embryo as well as in a multigenerational dietary study in which birds received low doses of the pesticide methoxychlor (MXC). The influence of dietary MXC exposure was also compared between Japanese quail and northern bobwhite quail. The effects of dietary exposures to 0.5, 5, or 10 ppm that are relatively environmentally low were determined. The selection of these doses was to mimic levels that might be encountered in the field and higher doses that might potentially reveal effects of exposure at relatively low exposures. These doses were also based on the regulations by the U.S. Environmental Protection Agency that mandate a limit 0.04 ppm MXC in drinking water, with a limit of no more than 0.05 ppm in water that children drink. Further there is a limit of 1-100 ppm for crops and other food for human and livestock consumption; bottled water has a 0.1 ppm limit for MXC content. Our data are discussed in the context of applicability of toxicological yardsticks, including the toxic equivalent (TEQ) and neurotoxic equivalent (NEQ) as predictive indices for short- and long-term outcomes to nonlethal concentrations of EDC. Other approaches have been developed to address inconsistencies in effects and incorporate diverse data into potency estimates. Perhaps it is time to develop a more inclusive estimation method for endocrine and neuroendocrine effects. An endocrine disruption index (EDI) would (1) complement other indices, (2) focus on endocrine disruption, and (3) include effects beyond those mediated by the aryl hydrocarbon receptor (AhR) for a comparative assessment of nonlethal EDC effects.

Understanding Reproductive Aging in Wildlife to Improve Animal Conservation and Human Reproductive Health.

Similar to humans and laboratory animals, reproductive aging is observed in wild species-from small invertebrates to large mammals. Aging issues are also prevalent in rare and endangered species under human care as their life expectancy is longer than in the wild. The objectives of this review are to (1) present conserved as well as distinctive traits of reproductive aging in different wild animal species (2) highlight the value of comparative studies to address aging issues in conservation breeding as well as in human reproductive medicine, and (3) suggest next steps forward in that research area. From social insects to mega-vertebrates, reproductive aging studies as well as observations in the wild or in breeding centers often remain at the physiological or organismal scale (senescence) rather than at the germ cell level. Overall, multiple traits are conserved across very different species (depletion of the ovarian reserve or no decline in testicular functions), but unique features also exist (endless reproductive life or unaltered quality of germ cells). There is a broad consensus about the need to fill research gaps because many cellular and molecular processes during reproductive aging remain undescribed. More research in male aging is particularly needed across all species. Furthermore, studies on reproductive aging of target species in their natural habitat (sentinel species) are crucial to define more accurate reproductive indicators relevant to other species, including humans, sharing the same environment. Wild species can significantly contribute to our general knowledge of a crucial phenomenon and provide new approaches to extend the reproductive lifespan.

Adopting a "Compound" Exposome Approach in Environmental Aging Biomarker Research: A Call to Action for Advancing Racial Health Equity.

BACKGROUND: In June 2020, the National Academies of Sciences, Engineering, and Medicine hosted a virtual workshop focused on integrating the science of aging and environmental health research. The concurrent COVID-19 pandemic and national attention on racism exposed shortcomings in the environmental research field's conceptualization and methodological use of race, which have subsequently hindered the ability of research to address racial health disparities. By the workshop's conclusion, the authors deduced that the utility of environmental aging biomarkers-aging biomarkers shown to be specifically influenced by environmental exposures-would be greatly diminished if these biomarkers are developed absent of considerations of broader societal factors-like structural racism-that impinge on racial health equity. OBJECTIVES: The authors reached a post-workshop consensus recommendation: To advance racial health equity, a "compound" exposome approach should be widely adopted in environmental aging biomarker research. We present this recommendation here. DISCUSSION: The authors believe that without explicit considerations of racial health equity, people in most need of the benefits afforded by a better understanding of the relationships between exposures and aging will be the least likely to receive them because biomarkers may not encompass cumulative impacts from their unique social and environmental stressors. Employing an exposome approach that allows for more comprehensive exposure-disease pathway characterization across broad domains, including the social exposome and neighborhood factors, is the first step. Exposome-centered study designs must then be supported with efforts aimed at increasing the recruitment and retention of racially diverse study populations and researchers and further "compounded" with strategies directed at improving the use and interpretation of race throughout the publication and dissemination process. This compound exposome approach maximizes the ability of our science to identify environmental aging biomarkers that explicate racial disparities in health and best positions the environmental research community to contribute to the elimination of racial health disparities. https://doi.org/10.1289/EHP8392.