The Adverse Effects of Auditory Stress on Mouse Uterus Receptivity and Behaviour

Elephant Gestation: Insights Into Idiopathic Abortions and Stillbirth

The declining African and Asian elephant populations emphasize the importance of a backup population. Successful reproduction in captivity plays a key role in maintaining such a genetically diverse ex situ population but is challenged by reproductive loss in the form of abortions and stillbirths. The elephants' biphasic prolactin pattern led us to predict a higher incidence of abortions during the time of reduced prolactin concentrations. Therefore, this study focuses on the identification of months during elephant gestation which are prone to loss of pregnancy. A metric was developed to identify the fetal age of aborted calves based on the fetal mass using a regression model. Data on idiopathic abortions in captive and wild elephants collected from zoos, tourist camps, semi-captive, and free-ranging populations since 1974 were analyzed, revealing a significantly higher prevalence of abortions during the 15th and 17th month of gestation. Additionally, the prevalence of stillbirths in the 22nd month of gestation between 2000 and 2023 was assessed. Although stillbirths showed a declining trend over time, the average prevalence between 2019 and 2023 was still 2.8%. Consequently, the 15th, 17th, and 22nd month of gestation were identified as stages prone to pregnancy loss. These findings underscore the necessity of researching risk factors and preventative measures for pregnancy loss in these 3 months, especially exploring a possible link with prolactin during the 15th and 17th month of gestation. The identification of stages prone to fetal loss is a key step towards enhancing elephant reproductive success and welfare.

Health position paper and redox perspectives - Disease burden by transportation noise

Transportation noise is a ubiquitous urban exposure. In 2018, the World Health Organization concluded that chronic exposure to road traffic noise is a risk factor for ischemic heart disease. In contrast, they concluded that the quality of evidence for a link to other diseases was very low to moderate. Since then, several studies on the impact of noise on various diseases have been published. Also, studies investigating the mechanistic pathways underlying noise-induced health effects are emerging. We review the current evidence regarding effects of noise on health and the related disease-mechanisms. Several high-quality cohort studies consistently found road traffic noise to be associated with a higher risk of ischemic heart disease, heart failure, diabetes, and all-cause mortality. Furthermore, recent studies have indicated that road traffic and railway noise may increase the risk of diseases not commonly investigated in an environmental noise context, including breast cancer, dementia, and tinnitus. The harmful effects of noise are related to activation of a physiological stress response and nighttime sleep disturbance. Oxidative stress and inflammation downstream of stress hormone signaling and dysregulated circadian rhythms are identified as major disease-relevant pathomechanistic drivers. We discuss the role of reactive oxygen species and present results from antioxidant interventions. Lastly, we provide an overview of oxidative stress markers and adverse redox processes reported for noise-exposed animals and humans. This position paper summarizes all available epidemiological, clinical, and preclinical evidence of transportation noise as an important environmental risk factor for public health and discusses its implications on the population level.

Noise and mental health: evidence, mechanisms, and consequences

The recognition of noise exposure as a prominent environmental determinant of public health has grown substantially. While recent years have yielded a wealth of evidence linking environmental noise exposure primarily to cardiovascular ailments, our understanding of the detrimental effects of noise on the brain and mental health outcomes remains limited. Despite being a nascent research area, an increasing body of compelling research and conclusive findings confirms that exposure to noise, particularly from sources such as traffic, can potentially impact the central nervous system. These harms of noise increase the susceptibility to mental health conditions such as depression, anxiety, suicide, and behavioral problems in children and adolescents. From a mechanistic perspective, several investigations propose direct adverse phenotypic changes in brain tissue by noise (e.g. neuroinflammation, cerebral oxidative stress), in addition to feedback signaling by remote organ damage, dysregulated immune cells, and impaired circadian rhythms, which may collectively contribute to noise-dependent impairment of mental health. This concise review linking noise exposure to mental health outcomes seeks to fill research gaps by assessing current findings from studies involving both humans and animals.

Effects of Refined Handling on Reproductive Indices of BALB/cJ and CD-1 IGS Mice

Current mouse handling methods during cage change procedures can cause stress and potentially compromise animal welfare. Our previous study of breeding C57BL/6J mice found modest increases in pup production and a significant reduction in preweaning litter losses when mice were handled using a tunnel as compared with a tail-lift with padded forceps. The current study evaluated how these 2 handling methods affected reproduction by 2 additional mouse strains, BALB/cJ (a low- to intermediate-fecundity strain) and CD-1 IGS (a high-fecundity stock). We predicted that refined handling would have minimal effects on the high-fecundity line with a satisfactory production rate and greater effects on the low-fecundity line. Handling method (tunnel compared with tail-lift) was randomly assigned to monogamous breeding pairs of mice. Reproductive metrics (litter size at birth and weaning, numbers of litters, litter attrition, between-litter intervals, pup wean- ing weight, and sex ratio) were prospectively monitored for 80 BALB/cJ and 77 CD-1 pairs that were bred continuously for 6 mo. Both strains of mice were highly productive, exceeding previously published breeding data. However, neither strain demonstrated operational or statistically significant differences between handling methods for any reproduction metric. As we detected no negative effects in these 2 strains and the benefits are clear in other strains, refined handling should be considered for all breeding mice.

A Review of the Effects of Some Extrinsic Factors on Mice Used in Research

Animals have been used in research for over 2,000 y. From very crude experiments conducted by ancient scholars, animal research, as a science, was refined over hundreds of years to what we know it as today. However, the housing conditions of animals used for research did not improve significantly until less than 100 years ago when guidelines for housing research animals were first published. In addition, it was not until relatively recently that some extrinsic factors were recognized as a research variable, even when animals were housed under recommended guidelines. For example, temperature, humidity, light, noise, vibration, diet, water, caging, bedding, etc., can all potentially affect research using mice, contributing the inability of others to reproduce published findings. Consequently, these external factors should be carefully considered in the design, planning, and execution of animal experiments. In addition, as recommended by others, the housing and husbandry conditions of the animals should be described in detail in publications resulting from animal research to improve study reproducibility. Here, we briefly review some common, and less common, external factors that affect research in one of the most popular animal models, the mouse.

Early tactile stimulation influences the development of Alzheimer's disease in gestationally stressed APP NL-G-F adult offspring NL-G-F/NL-G-F mice

Alzheimer's disease (AD) is associated with cerebral plaques and tangles, reduced synapse number, and shrinkage in several brain areas and these morphological effects are associated with the onset of compromised cognitive, motor, and anxiety-like behaviours. The appearance of both anatomical and behavioural symptoms is worsened by stress. The focus of this study was to examine the effect of neonatal tactile stimulation on AD-like behavioural and neurological symptoms on APP NL-G-F/NL-G-F mice, a mouse model of AD, who have been gestationally stressed. Our findings indicate that neonatal tactile stimulation improves cognition, motor skills, and anxiety-like symptoms in both gestationally stressed and non-stressed adult APP mice and that these alterations are associated with reduced Aβ plaque formation. Thus, tactile stimulation appears to be a promising non-invasive preventative strategy for slowing the onset of dementia in aging animals.

Prenatal immobility stress: Relationship with oxidative stress, inflammation, apoptosis, and intrauterine growth restriction in rats

BACKGROUND

Prenatal stress is a significant risk factor affecting pregnant women and fetal health. In the present study, we aimed to investigate the effect of immobility stress at different periods of pregnancy on oxidative stress, inflammation, placental apoptosis and intrauterine growth retardation in rats.

METHODS

Fifty adult virgin female Wistar albino rats were used. Pregnant rats were exposed to 6 h/day immobilization stress in a wire cage at different stages of pregnancy. Groups I and II (Day 1-10 stress group) were sacrificed on the 10th day of pregnancy, and Group III, Group IV (10-19th-day stress group), and Group V (1-19th-day stress group) were sacrificed on the 19th day of pregnancy. Inflammatory cytokines, including interleukin-6 (IL-6) and interleukin-10 (IL-10), serum corticotropin-releasing hormone (CRH), and corticosterone levels were measured by enzyme-linked immunosorbent assay. Malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT) levels in the placenta were spectrophotometrically measured. Histopathological analyses of the placenta were evaluated by hematoxylin and eosin staining. Tumor necrosis factor-alpha (TNF-α) and caspase-3 immunoreactivity in placenta tissues were determined by the indirect immunohistochemical method. Placental apoptosis was determined by the TUNEL staining method.

RESULTS

We found that the immobility stress during pregnancy significantly increased serum corticosterone levels. Our results showed that the immobility stress diminished the number and weight of fetuses in rats compared to the non-stress group. The immobility stress caused significant histopathological changes in the connection zone and labyrinth zone and increased placental TNF-α and caspase-3 immunoreactivity and placental apoptosis. In addition, immobility stress significantly increased the levels of pro-inflammatory IL-6 and MDA and caused a significant decrease in the levels of antioxidant enzymes such as SOD, CAT, and anti-inflammatory IL-10.

CONCLUSIONS

Our data suggest that immobility stress causes intrauterine growth retardation by activating the hypothalamic-pituitary-adrenal axis and deteriorating placental histomorphology and deregulating inflammatory and oxidative processes.

Developmental Programming in Animal Models: Critical Evidence of Current Environmental Negative Changes

The Developmental Origins of Health and Disease (DOHaD) approach answers questions surrounding the early events suffered by the mother during reproductive stages that can either partially or permanently influence the developmental programming of children, predisposing them to be either healthy or exhibit negative health outcomes in adulthood. Globally, vulnerable populations tend to present high obesity rates, including among school-age children and women of reproductive age. In addition, adults suffer from high rates of diabetes, hypertension, cardiovascular, and other metabolic diseases. The increase in metabolic outcomes has been associated with the combination of maternal womb conditions and adult lifestyle-related factors such as malnutrition and obesity, smoking habits, and alcoholism. However, to date, "new environmental changes" have recently been considered negative factors of development, such as maternal sedentary lifestyle, lack of maternal attachment during lactation, overcrowding, smog, overurbanization, industrialization, noise pollution, and psychosocial stress experienced during the current SARS-CoV-2 pandemic. Therefore, it is important to recognize how all these factors impact offspring development during pregnancy and lactation, a period in which the subject cannot protect itself from these mechanisms. This review aims to introduce the importance of studying DOHaD, discuss classical programming studies, and address the importance of studying new emerging programming mechanisms, known as actual lifestyle factors, during pregnancy and lactation.

Local immune recognition of trophoblast in early human pregnancy: controversies and questions

The role of the maternal immune system in reproductive success in humans remains controversial. Here we focus on the events that occur in the maternal decidua during the first few weeks of human pregnancy, because this is the site at which maternal leukocytes initially interact with and can recognize fetal trophoblast cells, potentially involving allorecognition by both T cells and natural killer (NK) cells. NK cells are the dominant leukocyte population in first-trimester decidua, and genetic studies point to a role of allorecognition by uterine NK cells in establishing a boundary between the mother and the fetus. By contrast, definitive evidence that allorecognition by decidual T cells occurs during the first trimester is lacking. Thus, our view is that during the crucial period when the placenta is established, damaging T cell-mediated adaptive immune responses towards placental trophoblast are minimized, whereas NK cell allorecognition contributes to successful implantation and healthy pregnancy.

An Inexpensive Open-Source Chamber for Controlled Hypoxia/Hyperoxia Exposure

Understanding hypoxia/hyperoxia exposure requires either a high-altitude research facility or a chamber in which gas concentrations are precisely and reproducibly controlled. Hypoxia-induced conditions such as hypoxic-ischemic encephalopathy (HIE), obstructive or central apneas, and ischemic stroke present unique challenges for the development of models with acute or chronic hypoxia exposure. Many murine models exist to study these conditions; however, there are a variety of different hypoxia exposure protocols used across laboratories. Experimental equipment for hypoxia exposure typically includes flow regulators, nitrogen concentrators, and premix oxygen/nitrogen tanks. Commercial hypoxia/hyperoxia chambers with environmental monitoring are incredibly expensive and require proprietary software with subscription fees or highly expensive software licenses. Limitations exist in these systems as most are single animal systems and not designed for extended or intermittent hypoxia exposure. We have developed a simple hypoxia chamber with off-the-shelf components, and controlled by open-source software for continuous data acquisition of oxygen levels and other environmental factors (temperature, humidity, pressure, light, sound, etc.). Our chamber can accommodate up to two mouse cages and one rat cage at any oxygen level needed, when using a nitrogen concentrator or premixed oxygen/nitrogen tank with a flow regulator, but is also scalable. Our system uses a Python-based script to save data in a text file using modules from the sensor vendor. We utilized Python or R scripts for data analysis, and we have provided examples of data analysis scripts and acquired data for extended exposure periods (≤7 days). By using FLOS (Free-Libre and open-source) software and hardware, we have developed a low-cost and customizable system that can be used for a variety of exposure protocols. This hypoxia/hyperoxia exposure chamber allows for reproducible and transparent data acquisition and increased consistency with a high degree of customization for each experimenter’s needs.

Cerebral consequences of environmental noise exposure

The importance of noise exposure as a major environmental determinant of public health is being increasingly recognized. While in recent years a large body evidence has emerged linking environmental noise exposure mainly to cardiovascular disease, much less is known concerning the adverse health effects of noise on the brain and associated neuropsychiatric outcomes. Despite being a relatively new area of investigation, indeed, mounting research and conclusive evidence demonstrate that exposure to noise, primarily from traffic sources, may affect the central nervous system and brain, thereby contributing to an increased risk of neuropsychiatric disorders such as stroke, dementia and cognitive decline, neurodevelopmental disorders, depression, and anxiety disorder. On a mechanistic level, a significant number of studies suggest the involvement of reactive oxygen species/oxidative stress and inflammatory pathways, among others, to fundamentally drive the adverse brain health effects of noise exposure. This in-depth review on the cerebral consequences of environmental noise exposure aims to contribute to the associated research needs by evaluating current findings from human and animal studies. From a public health perspective, these findings may also help to reinforce efforts promoting adequate mitigation strategies and preventive measures to lower the societal consequences of unhealthy environments.

Impact of Chronic Prenatal Stress on Maternal Neuroendocrine Function and Embryo and Placenta Development During Early-to-Mid-Pregnancy in Mice

Psychological stress, both leading up to and during pregnancy, is associated with increased risk for negative pregnancy outcomes. Although the neuroendocrine circuits that link the stress response to reduced sexual motivation and mating are well-described, the specific pathways by which stress negatively impacts gestational outcomes remain unclear. Using a mouse model of chronic psychological stress during pregnancy, we investigated 1) how chronic exposure to stress during gestation impacts maternal reproductive neuroendocrine circuitry, and 2) whether stress alters developmental outcomes for the fetus or placenta by mid-pregnancy. Focusing on the stress-responsive neuropeptide RFRP-3, we identified novel contacts between RFRP-3-immunoreactive (RFRP-3-ir) cells and tuberoinfundibular dopaminergic neurons in the arcuate nucleus, thus providing a potential pathway linking the neuroendocrine stress response directly to pituitary prolactin production and release. However, neither of these cell populations nor circulating levels of pituitary hormones were affected by chronic stress. Conversely, circulating levels of steroid hormones relevant to gestational outcomes (progesterone and corticosterone) were altered in chronically-stressed dams across gestation, and those dams were qualitatively more likely to experience delays in fetal development. Together, these findings suggest that, up until at least mid-pregnancy, mothers appear to be relatively resilient to the effects of elevated glucocorticoids on reproductive neuroendocrine system function. We conclude that understanding how chronic psychological stress impacts reproductive outcomes will require understanding individual susceptibility and identifying reliable neuroendocrine changes resulting from gestational stress.

Corneal Changes and Strategies to Improve Survival of Hypomorphic Collagen VII-Deficient Mice for the Study of Ocular Dystrophic Epidermolysis Bullosa

Ophthalmic study of collagen CVII hypomorphic mice is uniquely challenging due to the strain's published survival rate to weaning of 24%. Because chronic ocular fibrosis requires time to develop, optimizing the survival rate is of critical importance.In this study, standard husbandry practices were enhanced by the addition of sterilized diet and drug delivery gels, acidified water, irradiated food pellets, cellulose fiber bedding, minimal handling, removal of siblings within 2-3 wk from birth, and a preferred housing location. Survival rates per breeding cycle, sex, weight, and cause of early euthanasia were recorded and analyzed over 43 mo. Overall, 49% of mice survived to weaning and 76% of weaned mice survived to 20 wk of age. Corneal opacities were seen in 65% of mice by 20 wk, but only 10% of eyes showed the sustained opacification that was indicative of fibrosis. Corneal opacities occurred at the same rate as in humans with epidermolysis bullosa. 66% of the mice showed weight loss at 11 wk. Males required early euthanasia 4 times more often than did females. Euthanasia was required for urinary obstruction due to penile prolapse in 88% of males. With our enhanced care protocol, hypomorphic mice in our colony survived at twice the published rate. With this revised husbandry standard, experiments planned with termination endpoints of 14 wk for males and 17 wk for females are more likely to reach completion.

Vitamin D2 protects acute and repeated noise stress induced behavioral, biochemical, and histopathological alterations: Possible antioxidant effect

Noise is an environmental stressor which causes distress and hearing loss in individuals residing in urban areas. Psychological deficits such as anxiety, depression, impaired memory and cognitive decline are caused by noise stress. Different vitamins have been used as a potential antioxidant for neuronal protection. In this study we investigate the anxiolytic, antidepressant and memory enhancing effect of vitamin D2 (Vit D2) following noise stress. Thirty-six albino rats were randomly divided into six groups. (i) Unstressed + corn oil (ii) Unstressed + Vit D2 (iii) Acute noise stress + corn oil (iv) Acute noise stress + Vit D2 (v) Repeated noise stress + corn oil (vi) Repeated noise stress + Vit D2. 600 IU/kg body weight of Vit D2 dosage was prepared in corn oil. Corn oil is used as vehicle and all the drugs administered via oral gavage till end of the experiment (day 16). Recorded sound of generator which was amplified by speakers and had 100 dB intensity was used as noise stress. Repeated stressed animals were exposed to noise (4-hrs) daily for 14 days, while acute stressed animals were exposed to noise (4-hrs) once after 14 days. Behavioral tests (elevated plus maze, light dark box, tail suspension test and Morris water maze) of all groups were performed after15 days treatment period. After behavioral tests rats received their last dosage and decapitated after 1-hr. Brain of all animals was removed and used for biochemical (oxidative stress biomarker, antioxidant enzymes and acetylcholinesterase) and histopathological estimations. Results show that Vit D2 decreased time spent in light box and open arm of light dark activity box and elevated plus maze test respectively (used for anxiety evaluation), decreased immobility time in tail suspension test (for depression) and improved cognitive ability evaluated by Morris water maze test in acute and repeated noise stressed rats. Furthermore, increased antioxidant enzymes activity, decreased lipid peroxidation and acetylcholinesterase activity were also observed in Vit D2 treated animals following acute and repeated noise stress. Normalization in histopathological studies was also observed in Vit D2 treated following acute and repeated noise stress. It is concluded that Vit D2 protects from noise stress induced behavioral, biochemical and histopathological impairment through its antioxidant potential.

Insight on Polyunsaturated Fatty Acids in Endometrial Receptivity

Endometrial receptivity plays a crucial role in fertilization as well as pregnancy outcome in patients faced with fertility challenges. The optimization of endometrial receptivity may help with normal implantation of the embryo, and endometrial receptivity may be affected by numerous factors. Recently, the role of lipids in pregnancy has been increasingly recognized. Fatty acids and their metabolites may be involved in all stages of pregnancy and play a role in supporting cell proliferation and development, participating in cell signaling and regulating cell function. Polyunsaturated fatty acids, in particular, are essential fatty acids for the human body that can affect the receptivity of the endometrium through in a variety of methods, such as producing prostaglandins, estrogen and progesterone, among others. Additionally, polyunsaturated fatty acids are also involved in immunity and the regulation of endometrial decidualization. Fatty acids are essential for fetal placental growth and development. The interrelationship of polyunsaturated fatty acids with these substances and how they may affect endometrial receptivity will be reviewed in this article.

Prenatal stress dysregulates resting-state functional connectivity and sensory motifs

Prenatal stress (PS) can impact fetal brain structure and function and contribute to higher vulnerability to neurodevelopmental and neuropsychiatric disorders. To understand how PS alters evoked and spontaneous neocortical activity and intrinsic brain functional connectivity, mesoscale voltage imaging was performed in adult C57BL/6NJ mice that had been exposed to auditory stress on gestational days 12-16, the age at which neocortex is developing. PS mice had a four-fold higher basal corticosterone level and reduced amplitude of cortical sensory-evoked responses to visual, auditory, whisker, forelimb, and hindlimb stimuli. Relative to control animals, PS led to a general reduction of resting-state functional connectivity, as well as reduced inter-modular connectivity, enhanced intra-modular connectivity, and altered frequency of auditory and forelimb spontaneous sensory motifs. These resting-state changes resulted in a cortical connectivity pattern featuring disjoint but tight modules and a decline in network efficiency. The findings demonstrate that cortical connectivity is sensitive to PS and exposed offspring may be at risk for adult stress-related neuropsychiatric disorders.

Prenatal stress and increased susceptibility to anxiety-like behaviors: role of neuroinflammation and balance between GABAergic and glutamatergic transmission

Neuroplasticity during the prenatal period allows neurons to regenerate anatomically and functionally for re-programming the brain development. During this critical period of fetal programming, the fetus phenotype can change in accordance with environmental stimuli such as stress exposure. Prenatal stress (PS) can exert important effects on brain development and result in permanent alterations with long-lasting consequences on the physiology and behavior of the offspring later in life. Neuroinflammation, as well as GABAergic and glutamatergic dysfunctions, has been implicated as potential mediators of behavioral consequences of PS. Hyperexcitation, due to enhanced excitatory transmission or reduced inhibitory transmission, can promote anxiety. Alterations of the GABAergic and/or glutamatergic signaling during fetal development lead to a severe excitatory/inhibitory imbalance in neuronal circuits, a condition that may account for PS-precipitated anxiety-like behaviors. This review summarizes experimental evidence linking PS to an elevated risk to anxiety-like behaviors and interprets the role of the neuroinflammation and alterations of the brain GABAergic and glutamatergic transmission in this phenomenon. We hypothesize this is an imbalance in GABAergic and glutamatergic circuits (as a direct or indirect consequence of neuroinflammation), which at least partially contributes to PS-precipitated anxiety-like behaviors and primes the brain to be vulnerable to anxiety disorders. Therefore, pharmacological interventions with anti-inflammatory activities and with regulatory effects on the excitatory/inhibitory balance can be attributed to the novel therapeutic target for anxiety disorders.

Traffic noise exposure, cognitive decline, and amyloid-beta pathology in an AD mouse model

Concerns are growing that exposure to environmental pollutants, such as traffic noise, might cause cognitive impairments and predispose individuals toward the development of Alzheimer's disease (AD) dementia. In this study in a knock-in mouse model of AD, we investigated how chronic traffic noise exposure (CTNE) impacts cognitive performance and amyloid-beta (Aβ) pathology. A group of APP^{NL-G-F/NL-G-F} mice was exposed to CTNE (70 dB_A , 8 hr/day for 1 month) and compared with nonexposed counterparts. Following CTNE, an increase in hypothalamic-pituitary-adrenal (HPA) axis responsivity was observed by corticosterone assay of the blood. One month after CTNE, the CTNE group demonstrated impairments in cognitive and motor functions, and indications of anxiety-like behavior, relative to the control animals. The noise-exposed group also showed elevated Aβ aggregation, as inferred by a greater number of plaques and larger average plaque size in various regions of the brain, including regions involved in stress regulation. The results support that noise-associated dysregulation of the neuroendocrine system as a potential risk factor for developing cognitive impairment and Aβ pathology, which should be further investigated in human studies.

Gestational Stress Augments Postpartum β-Amyloid Pathology and Cognitive Decline in a Mouse Model of Alzheimer's Disease

Besides well-known risk factors for Alzheimer's disease (AD), stress, and in particular noise stress (NS), is a lifestyle risk factor common today. It is known that females are at a significantly greater risk of developing AD than males, and given that stress is a common adversity in females during pregnancy, we hypothesized that gestational noise exposure could exacerbate the postpartum development of the AD-like neuropathological changes during the life span. Pregnant APPNL-G-F/NL-G-F mice were randomly assigned to either the stress condition or control group. The stress group was exposed to the NS on gestational days 12-16, which resulted in a markedly higher hypothalamic-pituitary-adrenal (HPA) axis responsivity during the postpartum stage. Higher amyloid-β (Aβ) deposition and larger Aβ plaque size in the olfactory area were the early onset impacts of the gestational stress (GS) seen at the age of 4 months. This pattern of increased Aβ aggregation and larger plaque size were observed in various brain areas involved in both AD and stress regulation, especially in limbic structures, at the age of 6 months. The GS also produced anxiety-like behavior, deficits in learning and memory, and impaired motor coordination. The findings suggest that environmental stresses during pregnancy pose a potential risk factor in accelerating postpartum cognitive decline and AD-like neuropathological changes in the dams (mothers) later in life.

RNASeq analysis reveals upregulation of complement C3 in the offspring gut following prenatal stress in mice

Dysregulated activation of inflammatory signaling by the immature neonatal immune system could lead to the development of many pediatric diseases including necrotizing enterocolitis (NEC). While the mechanism(s) of pathogenesis is unknown, NEC is believed to have multifactorial causes. Microbial dysbiosis and intestinal immaturity have been implicated as potential triggers for this disease. We hypothesized that psychological stress during pregnancy negatively impacts the development of intestinal tissues in offspring and contributes to development of NEC. Consistent with this hypothesis, we previously observed shorter villi and a decrease in total surface area in the small intestine of pups derived from mice that were chronically stressed during gestation. In this study, we performed RNASeq analysis to determine the gene expression changes in the offspring gut following prenatal stress in pregnant mice and identified several differentially expressed genes (DEGs) and biological pathways. Notably, C3 was upregulated in the small intestine and contributed to a higher tissue injury score in a mesenteric ischemia model compared to unstressed controls. We discuss the potential implications of these stress-induced genes expression changes and their contribution to development of intestinal inflammation.

Prenatal Maternal Stress Causes Preterm Birth and Affects Neonatal Adaptive Immunity in Mice

Maternal stress is a well-established risk factor for preterm birth and has been associated with adverse neonatal outcomes in the first and subsequent generations, including increased susceptibility to disease and lasting immunological changes. However, a causal link between prenatal maternal stress and preterm birth, as well as compromised neonatal immunity, has yet to be established. To fill this gap in knowledge, we used a murine model of prenatal maternal stress across three generations and high-dimensional flow cytometry to evaluate neonatal adaptive immunity. We report that recurrent prenatal maternal stress induced preterm birth in the first and second filial generations and negatively impacted early neonatal growth. Strikingly, prenatal maternal stress induced a systematic reduction in T cells and B cells, the former including regulatory CD4+ T cells as well as IL-4- and IL-17A-producing T cells, in the second generation. Yet, neonatal adaptive immunity gained resilience against prenatal maternal stress by the third generation. We also show that the rate of prenatal maternal stress-induced preterm birth can be reduced upon cessation of stress, though neonatal growth impairments persisted. These findings provide evidence that prenatal maternal stress causes preterm birth and affects neonatal immunity across generations, adverse effects that can be ameliorated upon cessation.

Life-Course Contribution of Prenatal Stress in Regulating the Neural Modulation Network Underlying the Prepulse Inhibition of the Acoustic Startle Reflex in Male Alzheimer's Disease Mice

The prepulse inhibition (PPI) of the acoustic startle reflex (ASR), as an index of sensorimotor gating, is one of the most extensively used paradigms in the field of neuropsychiatric disorders. Few studies have examined how prenatal stress (PS) regulates the sensorimotor gating during the lifespan and how PS modifies the development of amyloid-beta (Aβ) pathology in brain areas underlying the PPI formation. We followed alternations in corticosterone levels, learning and memory, and the PPI of the ASR measures in APPNL-G-F/NL-G-F offspring of dams exposed to gestational noise stress. In-depth quantifications of the Aβ plaque accumulation were also performed at 6 months. The results indicated an age-dependent deterioration of sensorimotor gating, long-lasting PS-induced abnormalities in PPI magnitudes, as well as deficits in spatial memory. The PS also resulted in a higher Aβ aggregation predominantly in brain areas associated with the PPI modulation network. The findings suggest the contribution of a PS-induced hypothalamic-pituitary-adrenal (HPA) axis hyperactivity in regulating the PPI modulation substrates leading to the abnormal development of the neural protection system in response to disruptive stimuli. The long-lasting HPA axis dysregulation appears to be the major underlying mechanism in precipitating the Aβ deposition, especially in brain areas contributed to the PPI modulation network.

Effects of stress on the auditory system: an approach to study a common origin for mood disorders and dementia

The concept of stress is a fundamental piece to understand how organisms can adapt to the demands produced by a continuously changing environment. However, modern lifestyle subjects humans to high levels of negative stress or distress, which increases the prevalence of mental illnesses. Definitely, stress has become the pandemic of the 21st century, a fact that demands a great intellectual effort from scientists to understand the neurobiology of stress. This review proposes an innovative point of view to understand that mood disorders and dementia have a common etiology in a stressful environment. We propose that distress produces sensory deprivation, and this interferes with the connection between the brain and the environment in which the subject lives. The auditory system can serve as an example to understand this idea. In this sense, distress impairs the auditory system and induces hearing loss or presbycusis at an early age; this can increase the cognitive load in stressed people, which can stimulate the development of dementia in them. On the other hand, distress impairs the auditory system and increases the excitability of the amygdala, a limbic structure involved in the emotional processing of sounds. A consequence of these alterations could be the increase in the persistence of auditory fear memory, which could increase the development of mood disorders. Finally, it is important to emphasize that stress is an evolutionary issue that is necessary to understand the mental health of humans in these modern times. This article is a contribution to this discussion and will provide insights into the origin of stress-related neuropsychiatric disorders.

Chronic traffic noise stress accelerates brain impairment and cognitive decline in mice

Although traffic noise exposure is a well-known environmental pollutant whose negative health effect has been discussed in different aspects of the human life, only a few animal studies have tackled this issue as a cohort study, which is not feasible to be addressed in human studies. In addition to the deleterious impact of the daytime noise on well-being, chronic nocturnal noise can also disturb sleep and affects physical and mental health, but to date, little research has examined the neurobiological effects of light/dark cycles of traffic noise exposure. We investigated the effects of light/dark cycles and sex on the impact of chronic traffic noise exposure on mouse brain structure-function. The mice were randomly assigned to either one of two stress conditions or a control condition. Animals were exposed to traffic noise on either the light-cycle (LC) or dark-cycle (DC) for 30 days. Traffic noise exposure caused the hypothalamic-pituitary-adrenal (HPA) axis hyperactivity, anxiety-like behavior, impairments in learning and memory, dysfunction in balance and motor coordination, and a reduction in variety of brain measures including a brain volume, medial prefrontal cortex (mPFC) area, cortical thickness, hippocampal volume, amygdala area, and the neural density in mPFC and dentate gyrus. All behavioral and brain measures revealed adverse effects of the chronic noise stress irrespective of the LC/DC exposure or sex. Our findings were a re-emphasis on the significance of noise prevention and mitigation strategies for public health.

Stress and the HPA Axis: Balancing Homeostasis and Fertility

An organism’s reproductive fitness is sensitive to the environment, integrating cues of resource availability, ecological factors, and hazards within its habitat. Events that challenge the environment of an organism activate the central stress response system, which is primarily mediated by the hypothalamic–pituitary–adrenal (HPA) axis. The regulatory functions of the HPA axis govern the cardiovascular and metabolic system, immune functions, behavior, and reproduction. Activation of the HPA axis by various stressors primarily inhibits reproductive function and is able to alter fetal development, imparting a biological record of stress experienced in utero. Clinical studies and experimental data indicate that stress signaling can mediate these effects through direct actions in the brain, gonads, and embryonic tissues. This review focuses on the mechanisms by which stress activation of the HPA axis impacts fertility and fetal development.

Prenatal noise stress impairs HPA axis and cognitive performance in mice

Noise stress is a common environmental pollutant whose adverse effect on offspring performance has been less studied. This study was novel in terms of using “noise” as a prenatal stress compared with physical stress to explore the effect of stress during gestation on HPA axis activation, cognitive performance, and motor coordination, as well as in investigating the effect of behavioral assessments on the corticosterone (CORT) levels. Three groups of C57BL/6 mice with a gestational history of either noise stress (NS), physical stress (PS), or no stress were examined in several behavioral tests. Plasma CORT level was significantly higher before starting the behavioral tests in NS group than the two other groups. It was significantly increased after the behavioral tests in both prenatal stressed groups relative to the controls. Stress caused anxiety-like behavior and reduced learning and memory performance in both stressed groups compared to the controls, as well as decreased motor coordination in the NS group relative to the other groups. The findings suggested that: prenatal NS severely changes the HPA axis; both prenatal stressors, and particularly NS, negatively impair the offspring’s cognitive and motor performance; and, they also cause a strong susceptibility to interpret environmental experiences as stressful conditions.

Corticosterone response to gestational stress and postpartum memory function in mice

Maternal stress is a common adversity during pregnancy. Gestational corticosterone alternations are thought to contribute to the etiology of postpartum behavioral disturbances. However, the impact of stress during pregnancy, in particular noise exposure, on gestational corticosterone fluctuations and spatial cognition in postpartum mice has not been fully understood yet. We hypothesized that noise exposure during pregnancy negatively affects gestational corticosterone levels and postpartum memory function in the dams similar to the physical stressors. Pregnant C57BL/6 mice were randomly assigned to either one of two stress conditions or a control condition. The noise stress (NS) was induced by presenting a loud intermittent 3000 Hz frequency on gestational days (GDs) 12, 14, and 16 for 24 hours, whereas the physical stress (PS) consisted of restraint and exposure to an elevated platform on GDs 12–16. Plasma corticosterone level was collected on GDs 11 and 17, and Morris water task (MWT) was carried out 30 days after parturition. Compared to the control group, the level of corticosterone in the stressed groups was significantly increased on GD17 relative to GD11. Significantly longer swim time and lower swim speed were observed in both stressed groups relative to the control group. Probe time was significantly shorter in the NS group than the other groups. The delta corticosterone level was significantly correlated with the swim time as well as the probe time in the three groups. Given the results, the adverse effects of gestational noise exposure on the hypothalamic pituitary-adrenal (HPA) axis activation and postpartum spatial learning and memory function were as large as/ or a bit stronger than the physical stresses. The findings suggest the significance of conservation against loud noise exposure in daily living, as well as need to further notice to the different aspects of gestational stress in mothers’ behavior like offspring.