Enhancing versus suppressive effects of stress on immune function: implications for immunoprotection and immunopathology

Cost of a deprived environment - increased intraspecific aggression and susceptibility to pathogen infections

A lack of environmental enrichment can be severely detrimental to animal welfare. For terrestrial species, including humans, barren environments are associated with reduced cognitive function and increased stress responses and pathology. Despite a clear link between increased stress and reduced immune function, uncertainty remains on how enrichment might influence susceptibility to disease. For aquatic vertebrates, we are only now beginning to assess enrichment needs. Enrichment deprivation in fish has been linked to increased stress responses, agonistic behaviour, physiological changes and reduced survival. Limited data exist, however, on the impact of enrichment on disease resistance in fish, despite infectious diseases being a major challenge for global aquaculture. Here, using a model vertebrate host-parasite system, we investigated the impact of enrichment deprivation on susceptibility to disease, behaviour and physiology. Fish in barren tanks showed significantly higher infection burdens compared with those in enriched enclosures and they also displayed increased intraspecific aggression behaviour. Infections caused hosts to have significantly increased standard metabolic rates compared with uninfected conspecifics, but this did not differ between enriched and barren tanks. This study highlights the universal physiological cost of parasite infection and the biological cost (increased susceptibility to infection and increased aggression) of depriving captive animals of environmental enrichment.

Stress and coping in women with breast cancer:unravelling the mechanisms to improve resilience

Breast cancer diagnosis, surgery, adjuvant therapies and survivorship can all be extremely stressful. In women, concerns about body image are common as a result of the disease and can affect interpersonal relationships, possibly leading to social isolation, increasing the likelihood for mood disorders. This is particularly relevant as women are at greater risk to develop anxiety and depressive symptoms in response to highly stressful situations. Here we address the mechanisms and the pathways activated as a result of stress and contributing to changes in the pathophysiology of breast cancer, as well as the potential of stress management factors and interventions in buffering the deleterious effects of chronic stress in a gender perspective. An improved understanding of the biological mechanisms linking stress-management resources to health-relevant biological processes in breast cancer patients could reveal novel therapeutic targets and help clarifying which psychosocial interventions can improve cancer outcomes, ultimately offering a unique opportunity to improve contemporary cancer treatments.

C-type lectin-mediated microbial homeostasis is critical for Helicoverpa armigera larval growth and development

The immune system of a host functions critically in shaping the composition of the microbiota, and some microbes are involved in regulating host endocrine system and development. However, whether the immune system acts on endocrine and development by shaping the composition of the microbiota remains unclear, and few molecular players or microbes involved in this process have been identified. In the current study, we found that RNA interference of a C-type lectin (HaCTL3) in the cotton bollworm Helicoverpa armigera suppresses ecdysone and juvenile hormone signaling, thus reducing larval body size and delaying pupation. Depletion of HaCTL3 also results in an increased abundance of Enterocuccus mundtii in the hemolymph, which may escape from the gut. Furthermore, HaCTL3 and its controlled antimicrobial peptides (attacin, lebocin, and gloverin) are involved in the clearance of E. mundtii from the hemolymph via phagocytosis or direct bactericidal activity. Injection of E. mundtii into larval hemocoel mimics HaCTL3-depleted phenotypes and suppresses ecdysone and juvenile hormone signaling. Taken together, we conclude that HaCTL3 maintains normal larval growth and development of H. armigera via suppressing the abundance of E. mundtii in the hemolymph. Our results provide the first evidence of an immune system acting on an endocrine system to modulate development via shaping the composition of microbiota in insect hemolymph. Thus, this study will deepen our understanding of the interaction between immunity and development.

Considering that a large number of hemocytes and multiple soluble effectors are present in insect hemolymph, it is conventionally believed that healthy insect hemolymph is a hostile environment for bacteria and is, therefore, sterile. However, increasing evidences disprove this opinion, although the interactive mechanism between hemolymph microbiota and insect host, as well as the function of hemolymph microbiota, remain unclear. C-type lectin (CTL), as pattern recognition receptor (PRR), plays important roles in defending against various pathogens. Here we found that various bacteria colonized the hemolymph of the cotton bollworm Helicoverpa armigera. We first reported that an H. armigera CTL (HaCTL3) was involved in modulating larval growth and development. Further study indicated that HaCTL3-mediated homeostasis of Enterocuccus mundtii in the hemolymph is critical for normal larval growth and development. Our study demonstrated that this PRR modulated insect development through shaping hemolymph microbiota, which may represent a novel mechanism of immune system regulation during insect development.

Biomarkers Suggesting Favorable Prognostic Outcomes in Sudden Sensorineural Hearing Loss

Sudden sensorineural hearing loss (SSNHL) is a medical emergency, making detailed examination to determine possible causes and early treatment important. However, etiological examinations in SSNHL do not always reveal a cause, and several factors have been found to affect treatment outcomes. Various studies are being performed to determine the prognosis and effects of treatment in patients who experience sudden hearing loss, and to identify biomarkers associated with this condition. Embase, PubMed, and the Cochrane database were searched using the key words SSNHL, prognostic, and biomarker. This search identified 4 articles in Embase, 28 articles in PubMed, and 36 in the Cochrane database. Of these 68 articles, 3 were duplicates and 37 were unrelated to the research topic. After excluding these articles, the remaining 28 articles were reviewed. Factors associated with SSNHL were divided into six categories: metabolic, hemostatic, inflammatory, immunologic, oxidative, and other factors. The associations between these factors with the occurrence of SSNHL and with patient prognosis were analyzed. Low monocyte counts, low neutrophil/lymphocyte ratio (NLR) and monocyte/high-density lipoproteins (HDL) cholesterol ratio (MHR), and low concentrations of fibrinogen, platelet glycoprotein (GP) IIIa, and TNF-α were found to be associated with good prognosis. However, these factors alone could not completely determine the onset of and recovery from SSNHL, suggesting the need for future basic and clinical studies.

Retrospective analysis of the lifetime endocrine response of southern right whale calves to gull wounding and harassment: A baleen hormone approach

Physiological measurements are informative in assessing the relative importance of stressors that potentially impact the health of wildlife. Kelp Gulls, Larus dominicanus (KG), resident to the region of Península Valdés, Argentina, have developed a unique behavior of landing on the backs of southern right whale adults and calves, Eubalaena australis (SRW), where they feed on their skin and blubber. This parasitic behavior results in large open wounds on the dorsal surface of the whale. Coincidently, the SRW population off the coast of Península Valdés has experienced elevated calf mortality. We quantified levels of glucocorticoids and thyroid hormone extracted from baleen of dead calves to evaluate, retrospectively, the endocrine response of whale calves to gull wounding and harassment. Baleen accumulates hormones as it grows, allowing evaluation of long-term trends in physiological condition. While glucocorticoids (GCs) are known to increase in response to stressors such as disturbance, the metabolic hormone triiodothyronine (T₃) has been shown to decrease under sustained food deprivation but is largely unaffected by disturbance stress. We quantified lifetime patterns of GCs and T₃ in baleen recovered at necropsy from 36 southern right whale calves with varying severity of wounding from KGs. GC levels in baleen correlated positively with the degree of wounding, while T₃ levels remained stable irrespective of the severity of the wounding. Our results suggest no evidence of malnutrition in low vs. severely wounded whales. However, the positive correlation of GCs with wound severity indicates that heavily wounded calves are suffering high levels of physiological stress before they die. This suggests that KG wounding may have contributed to the high southern right whale calf mortality observed in the Península Valdés region of Argentina.

On the winter enhancement of adaptive humoral immunity: hypothesis testing in desert hamsters (Phodopus roborovskii: Cricetidae, Rodentia) kept under long-day and short-day photoperiod

We tested the winter immunity enhancement hypothesis (WIEH) on male desert hamsters (Phodopus roborovskii) kept under long-day (LD) and short-day (SD) photoperiods. We assumed that under SD in a laboratory, the adaptive humoral immune responsiveness to the antigenic challenge would be enhanced due to the lack of winter physical stressors and food shortages and/or because of the action of an endogenous winter bolstering mechanism, while under LD the immune responsiveness would be suppressed by the activity of the reproductive system. The results support the WIEH in part. We did not find a difference in antibody production in response to sheep erythrocytes between SD and LD hamsters, but SD males had the lower number of granulocytes and the higher number of lymphocytes in white blood cell counts. Reproductive activity was lower in SD males. These males demonstrated an increase in their mass-specific resting metabolic rate, their mass-specific maximal metabolic rate and their level of cortisol. The result of a generalized linear model analysis indicates the negative effect on secondary immunoresponsiveness to sheep erythrocytes of mid-ventral gland size, the organ characterizing individual reproductive quality, and designates a tradeoff between antibody production and reproductive effort. The mass-independent maximal metabolic rate also negatively affected antibody production, indicating a tradeoff between maximal aerobic performance and the adaptive immune function. The higher stress in SD males seems to be the most likely reason for the lack of the effect of daylight duration on antibody production.

Modulating offspring responses: concerted effects of stress and immunogenic challenge in the parental generation

The perception, processing and response to environmental challenges involves the activation of the immuno-neuroendocrine (INE) interplay. Concerted environmental challenges might induce trade-off when resource allocation to one trait occurs at the expense of another, also producing potential transgenerational effects in the offspring. We evaluated whether concerted challenges, in the form of an immune inoculum against inactivated Salmonella enteritidis (immune challenge, ICH) and a chronic heat stress (CHS) exposure on adult Japanese quail, modulate the INE responses of the parental generation and their offspring. Adults were inoculated and later exposed to a CHS along nine consecutive days. For the last 5 days of the CHS, eggs were collected for incubation. Chicks were identified according to their parental treatments and remained undisturbed. Induced inflammatory response, heterophil/lymphocyte (H/L) ratio and specific humoral response against sheep red blood cells (SRBC) were evaluated in both generations. Regardless of the ICH, stressed adults showed a reduced inflammatory response and an elevated H/L ratio compared with controls. In offspring, the inflammatory response was elevated and the specific SRBC antibody titres were diminished in those chicks prenatally exposed to CHS, regardless of the ICH. No differences were found in the H/L ratio of the offspring. Together, our results suggest that CHS exposure influences the INE interplay of adult quail, establishing trade-offs within their immune system. Moreover, CHS not only affected parental INE responses but also modulated their offspring INE responses, probably affecting their potential to respond to future challenges. The adaptability of the developmental programming of offspring would depend on the environment encountered.

Reflections on Bruce S. McEwen's contributions to stress neurobiology and so much more

The authors highlight, from a firsthand perspective, Bruce S. McEwen's seminal influence on the field of stress neurobiology and beyond, and how these investigations have yielded important insights, principles and critical questions that continue to guide stress research today. Featured are discussion of: 1) the important inverted-U relationship between stress/glucocorticoids and optimal physiological function, 2) stress adaptation and the role of adaptive stress responses, 3) mechanisms by which the short-term stress response promotes heightened immune function and immunity, and 4) the far reaching impact of the theoretical framework of allostasis and allostatic load-concepts that have created new bridges between stress physiology, biomedical sciences, health psychology and sociology.

Predictive value of preoperative and postoperative peripheral lymphocyte difference in hepatitis B virus-related hepatocellular cancer patients: Based on the analysis of dynamic nomogram

BACKGROUND

Inflammation plays an important role in the progression and prognosis of hepatocellular carcinoma (HCC). Our aim is to explore the prognostic value of preoperative and postoperative peripheral lymphocyte differences and to develop a dynamic prognosis nomogram in hepatitis B virus-related HCC patients.

METHODS

Important indicators related to overall survival (OS) are screened out by Cox proportional hazard models. The receiver operating characteristic curves, decision curve analysis curves, net reclassification improvement, and integrated discrimination improvement were used to evaluate the performance of the model.

RESULTS

Lymphocyte (L) difference was an independent risk factor. It was further verified that the performance of the nomogram was significantly improved after the L difference was incorporated into the nomogram. The nomogram generated had the area under curves of 0.779, 0.775, and 0.793 at 3, 5, and 7 years after surgery, respectively. Our nomogram models showed significantly better performance in predicting the HCC prognosis compared to other models. And online webserver and scoring system table was built based on the proposed nomogram for convenient clinical use.

CONCLUSIONS

It is newly found that L difference is an effective predictor of OS, and the nomogram based on this indicator can accurately predict the prognosis of HCC patients.

[The Role of Personal Resources in Coping]

BACKGROUND

Stress reactions can be a result of occupational and everyday stress, which are perceived individually. The insufficient compensation of stress can lead to various diseases. Personality traits play an important role in this. Stress reactions can lead to health problems and diseases. Therefore it is important to reduce stress. The aim of this study was to examine the role of personality traits in dealing with stress perception and coping.

MATERIAL AND METHOD

The questionnaire on Differential stress inventory (DSI) differentiated 217 subjects into 5 types of DSI. The survey compared these 5 types along their personality traits via the Freiburg Personality Inventory (FPI-R).

RESULTS

The DSI types showed significant differences in the expression of the personality traits. This applies the everyday stress, professional and private interactions with other people and the existential and future fears. People with pronounced physical disorders in the FPI showed physical and/or emotional-cognitive stress manifestation as well as a sense of helplessness. Life satisfaction is negatively related to stressors, for example through everyday life.

CONCLUSION

The survey revealed the importance of personality traits in coping with job strain. Occupational health diagnostics should be integrated in occupational health care and prevention. The occupational physician or the prevention team appear here to be significant, as they see workers falling through the classic family doctor model. In the prevention team, personality traits can be supplemented by psychologists. Personal resources can be imparted or reinforced to prevent physical disorders.

Effects of elevated corticosterone on humoral innate and antibody-mediated immunity in southern leopard frog (Lithobates sphenocephalus) tadpoles

As a free-living larval stage of a vertebrate, tadpoles are good subjects for the study of the development of physiological systems and the study of evolutionarily conserved, context-dependent responses to variable environments. While the basic components of innate and adaptive immune defenses in tadpoles are known, the impact of glucocorticoids on immune defenses in tadpoles is not well-studied. We completed four experiments to assess effects of elevation of corticosterone on humoral innate defenses and antibody-mediated immunity in southern leopard frog tadpoles (Lithobates sphenocephalus). To test humoral innate defense within the tadpoles exposed to short-term and long-term elevation of glucocorticoids, we exposed tadpoles to exogenous corticosterone for different lengths of time in each experiment (0-84 days). We used bacterial killing assays to assess humoral innate immune defense. To test antibody-mediated immune responses, we again exposed tadpoles to exogenous corticosterone, while also exposing them to Aeromonas hydrophila. We used A. hydrophila ELISA comparing IgM and IgY responses among groups. Plasma from corticosterone-dosed tadpoles killed more A. hydrophila than control tadpoles each following a short-term (14 day) and long-term (56 day) exposure to exogenous corticosterone. Conversely, corticosterone-dosed tadpoles had significantly lower IgM and IgY against A. hydrophila after 12 weeks. Our fourth experiment revealed that the lower IgY response is a product of weaker, delayed isotype switching compared with controls. These results show that elevated corticosterone has differential effects on innate and acquired immunity in larval southern leopard frogs, consistent with patterns in more derived vertebrates and in adult frogs.

Immune dysregulation in depression: Evidence from genome-wide association

A strong body of evidence supports a role for immune dysregulation across many psychiatric disorders including depression, the leading cause of global disability. Recent progress in the search for genetic variants associated with depression provides the opportunity to strengthen our current understanding of etiological factors contributing to depression and generate novel hypotheses. Here, we provide an overview of the literature demonstrating a role for immune dysregulation in depression, followed by a detailed discussion of the immune-related genes identified by the most recent genome-wide meta-analysis of depression. These genes represent strong evidence-based targets for future basic and translational research which aims to understand the role of the immune system in depression pathology and identify novel points for therapeutic intervention.

Differential associations of proinflammatory and anti-inflammatory cytokines with depression severity from noncancer status to breast cancer course and subsequent chemotherapy

Background

In this study, we examined the differential associations of various proinflammatory and anti-inflammatory cytokines with depression severity from the development of breast cancer to subsequent chemotherapy treatment.

Methods

A cross-sectional study was conducted on a sample of 116 women: 29 controls without cancer, 55 patients with breast cancer who were not receiving chemotherapy, and 32 patients with breast cancer who were receiving chemotherapy. Blood samples were assayed to evaluate serum levels of the following cytokines: interferon-γ, interleukin (IL)-12 (p70), IL-1β, IL-2, tumor necrosis factor (TNF)-α, IL-4, IL-5, IL-10, IL-13, IL-6, and IL-17A. Depression severity was assessed using the Patient Health Questionnaire.

Results

After adjustment for sociodemographics, consistent patterns of the association between cytokine and depression were noted in the different groups. No significant associations were observed in the controls. Inverse associations were observed between cytokines levels and depression severity in patients with breast cancer who were not receiving chemotherapy, whereas positive associations were noted in patients with breast cancer who were receiving chemotherapy. Specific differential relationships between IL-5 levels and depression severity were found between patients with breast cancer who were receiving and not receiving chemotherapy.

Conclusions

Our study revealed differential relationships between cytokine levels and depression severity with the development of cancer. Immunostimulation and immunosuppression in breast cancer and cancer treatment may account for the differential responses with the development of breast cancer.

The Impact of Dental Environment Stress on Dentition Status, Salivary Nitric Oxide and Flow Rate

Aim:

This study aimed to assess the dental caries experience among dental students with different levels of dental environment stress in relation to salivary nitric oxide (NO) and flow rate of whole unstimulated saliva.

Materials and Methods:

The study involved 300 dental students. They were classified into three categories (mild stress, moderate stress, and severe stress) according to dental environment stress questionnaire (DESQ); clinical examination for dental caries was carried out. Unstimulated salivary samples were collected from the mild and severe stress groups for measuring the salivary flow rate. Estimation of salivary NO was carried out by using salivary NO test strips. All data were analyzed using the Statistical Package for the Social Sciences software, version 21.0 (SPSS, Chicago, Illinois).

Results:

Dental caries experience was higher among severe and moderate stress groups with nonsignificant differences (P > 0.05). Mean value of salivary flow rate was lower among severe stress group with nonsignificant differences (P > 0.05). NO was significantly higher among severe stress group (P < 0.05). Flow rate was weak negatively correlated with caries experience among both mild and severe stress groups except for the decay surface (DS), which was weak positive among mild stress group. NO was weak negatively correlated with DS among both mild and severe stress groups. All these correlations were statistically not significant (P > 0.05).

Conclusion:

Dental environment stress appears to affect oral health, shown by higher dental caries among dental students with severe dental environment stress by affecting the normal level of salivary flow rate and NO.

Impact of Housing Environment on the Immune System in Chickens: A Review

During their lifespan, chickens are confronted with a wide range of acute and chronic stressors in their housing environment that may threaten their welfare and health by modulating the immune system. Especially chronic stressful conditions can exceed the individual's allostatic load, with negative consequences for immunity. A fully functional immune system is mandatory for health and welfare and, consequently, also for high productivity and safe animal products. This review provides a comprehensive overview of the impact of housing form, light regime as well as aerial ammonia and hydrogen sulfide concentrations on the immune system in chickens. Certain housing conditions are clearly associated with immunological alterations which potentially impair the success of vaccinations or affect disease susceptibility. Such poor conditions counteract sustainable poultry production. This review also outlines current knowledge gaps and provides recommendations for future research.

Analyzing Stress as a Multivariate Phenotype

The stress phenotype is multivariate. Recent advances have broadened our understanding beyond characterizing the stress response in a single dimension. Simultaneously, the toolbox available to ecophysiologists has expanded greatly in recent years, allowing the measurement of multiple biomarkers from an individual at a single point in time. Yet these advances-in our conceptual understanding and available methodologies-have not yet been combined in a unifying multivariate statistical framework. Here, we offer a brief review of the multivariate stress phenotype and describe a general statistical approach for analysis using nonparametric multivariate analysis of variance with residual randomization in permutation procedures (RRPP) implemented using the "RRPP" package in R. We also provide an example illustrating the novel insights that can be gained from a holistic multivariate approach to stress and provide a tutorial for how we analyzed these data, including annotated R code and a guide to interpretation of outputs (Online Appendix 1). We hope that this statistical methodology will provide a quantitative framework facilitating the unification of our theoretical understanding and empirical observations into a quantitative, multivariate theory of stress.

The cortisol burden in elderly subjects with metabolic syndrome and its association with low-grade inflammation

BACKGROUND

Elderly people are exposed to an increased load of stressful events and neuro-hormonal stimulation is a key finding in metabolic syndrome and its related disorders.

AIMS

To determine the role of cortisol in elderly subjects, with or without metabolic syndrome (MetS), by means of a national multicentre observational study, AGICO (AGIng and Cortisol).

METHODS

From 2012 to 2017, the AGICO study enrolled n.339 subjects (aged > 65), after obtaining their informed consent. The investigators assessed a cardio-metabolic panel (including electrocardiogram, carotid ultrasonography and echocardiography), the presence of MetS (on Adult Treatment Panel III criteria), a neurological examination (including brain imaging), and cortisol activity (using a consecutive collection of diurnal and nocturnal urine).

RESULTS

In the patients presenting with MetS, the standardized diurnal and nocturnal cortisol excretion rates were 210.7 ± 145.5 and 173.7 ± 118.1 (mean ± standard deviation) μg/g creatinine/12 h; in those without MetS, the standardized diurnal and nocturnal cortisol excretion rates were 188.7 ± 92.7 and 144.1 ± 82.3 μg/g creatinine/12 h, respectively (nocturnal urinary cortisol in patients with MetS versus those without MetS p = 0.05, female patients with MetS vs female patients without MetS, p < 0.025). A significant positive correlation was found between the CRP levels and both the diurnal and nocturnal urinary cortisol levels with r = 0.187 (p < 0.025) and r = 0.411 (p < 0.00000001), respectively.

DISCUSSION

The elderly patients with MetS showed a trend towards increased standardized nocturnal cortisol excretions, with particular regard to the female subjects.

CONCLUSION

The positive correlation between cortisol excretion and low-grade inflammation suggests a common mechanism driving both hormonal and inflammatory changes.

Restraint stress increased the permeability of the nasal epithelium in BALB/c mice

Stress seems to affect the onset and evolution of diverse illnesses with an inflammatory substrate. Whether physiological or psychological, stress increases epithelial permeability. In the mucosa of the nasal cavity and upper respiratory tract, the epithelial barrier is regulated in large part by bicellular and tricellular tight junctions (bTJs and tTJs, respectively). The junctional complexes are composed of multiple membrane proteins: claudins, tight-junction-associated MARVEL proteins (TAMs: occludin, tricellulin and marvelD3), and scaffolding proteins such as ZO-1, -2 and -3. The aim of the present study was to examine the possible modification of nasal permeability and TJ protein expression in a mouse model of acute psychological stress (a 4-h immobility session). Serum corticosterone was quantified from plasma samples to verify the onset of stress. Evaluation was made of the relative concentration of key proteins in nasal mucosa by using Western blot, and of changes in permeability by analyzing FITC-Dextran leakage from the nose to the blood. Compared to the control, the stressed group showed a greater epithelial permeability to FITC-Dextran, a reduced expression of occludin and tricellulin, and an elevated expression of ZO-2 and claudin-4. This evidence points to increased paracellular flow of large molecules through an altered structure of tTJs. Apparently, the structure of bTJs remained unchanged. The current findings could provide insights into the relation of stress to the onset/exacerbation of respiratory infections and/or allergies.

Illuminating Neuroimmunity: A Humoral Brain

The hypothalamic-pituitary-adrenal axis modulates immunity in response to stress. In a recent report in the May 14, 2020 issue of Nature, Zhang et al. use optogenetic tools to investigate whether the splenic immune response is directly controlled by descending neuronal circuits activated in response to stress.

Stress and immunity: Field comparisons among populations of invasive cane toads in Florida

Cane toads (Rhinella marina) were introduced worldwide and have become invasive in multiple locations, representing a major driver of biodiversity loss through competition (food, shelter, territory), predation, and the poisoning of native species. These toads have been used in Australia as a model for studies concerning invasion biology and ecoimmunology, as longer-established (core) and invasion front (edge) populations show altered stress and immune response profiles. Although cane toads were also introduced into the United States in the 1950s, these patterns have yet to be evaluated for the populations spanning Florida. Toads introduced into Florida have dispersed primarily northward along a latitudinal gradient, where they encounter cooler temperatures that may further impact stress and immune differences between core and edge populations. In this study, we sampled cane toads from nine different locations spanning their invasion in Florida. Cane toads from southern populations showed higher plasma bacterial killing ability and natural antibody titers than the toads from the northern populations, indicating they have a better immune surveillance system. Also, southern toads were more responsive to a novel stressor (1 hr restraint), showing a higher increase in corticosterone levels. These results indicate that possible trade-offs have occurred between immune and stress responses as these toads have become established in northern cooler areas in Florida.

The fatty acid amide hydrolase inhibitor URB597 modulates splenic catecholamines in chronically stressed female and male rats

The changes in sympathetic innervations in lymphoid organs could be a key factor in immune dysregulation. The endocannabinoid system has been shown to exhibit potent immunomodulatory effects that may differ between males and females, representing a potential therapeutic target for peripheral and central inflammatory disorders. Thus, in the present study, an examination was made of the effect of fatty acid amide hydrolase inhibitor URB597 treatment on splenic catecholamine content, synthesis, uptake and degradation in chronically unpredictably stressed (CUS) female and male rats. The results show that CUS increases anxiety-like behaviors and that URB597 had an anxiolytic effect on chronically stressed animals of both sexes. CUS induced the expression of plasma interleukin - 6 (IL-6), interleukin - 10 (IL-10) and IL-6 in the spleen, whereas the expression of IL-10 was reduced in the spleen of both sexes. URB597 treatment did not cause changes in IL-6 in plasma or the spleen, whereas it increased IL-10 in the spleen in CUS animals of both sexes. CUS caused a significant depletion of noradrenaline content in the spleen of female rats and a reduction in noradrenaline uptake in the spleen of female rats, while stressed males had a small but insignificant decrease of splenic noradrenaline levels and an enhanced uptake. The FAAH inhibitor URB597 enhances reduced noradrenaline content, affecting its uptake directly at the level of the spleen. It gives rise to the possibility that endocannabinoids exert a neurorestorative effect on the sympathetic nerve system and cell-mediated immune responses in the spleen of chronically stressed rats.

Abd-Elhakim Y. Saussurea lappa Ethanolic Extract Attenuates Triamcinolone Acetonide-Induced Pulmonary and Splenic Tissue Damage in Rats via Modulation of Oxidative Stress, Inflammation, and Apoptosis

Background: In this era, worldwide interest has been directed towards using natural antioxidants to guard against drug side effects. Saussurea lappa is a famous medicinal plant with many biologically active compounds. Triamcinolone acetonide (TA) is an extensively used glucocorticoid. Hence, this study explored, for the first time, the possible beneficial effects of S. lappa ethanolic extract on TA-induced oxidative damage in the lung and spleen of rats. Methods: Five experimental groups were used: control group, S. lappa-treated group (600 mg/kg/day, orally), TA-treated group (40 mg/kg/twice/week I/P), S. lappa + TA co-treated group, and S. lappa/TA prophylactic group. Results: TA exposure significantly induced leukocytosis and neutrophilia. In addition, TA significantly reduced the levels of C-reactive protein, interleukin-12, tumor necrosis factor α, and immunoglobulins. Lung Caspase-3 overexpression and splenic CD8⁺ downregulation were also noted in the TA group. TA treatment significantly increased malondialdehyde concentration but reduced superoxide dismutase and glutathione peroxidase activities. S. lappa counteracted the TA oxidative and apoptotic effects. The best results were recorded in the prophylactic group. Conclusions:S. lappa has a remarkable protective effect via its anti-inflammatory, anti-apoptotic, and antioxidant capacity. Thus, it could be a candidate as a natural antioxidant to face glucocorticoid’s harmful side effects.

Can melatonin reduce the severity of COVID-19 pandemic?

The current COVID-19 pandemic is one of the most devastating events in recent history. The virus causes relatively minor damage to young, healthy populations, imposing life-threatening danger to the elderly and people with diseases of chronic inflammation. Therefore, if we could reduce the risk for vulnerable populations, it would make the COVID-19 pandemic more similar to other typical outbreaks. Children don't suffer from COVID-19 as much as their grandparents and have a much higher melatonin level. Bats are nocturnal animals possessing high levels of melatonin, which may contribute to their high anti-viral resistance. Viruses induce an explosion of inflammatory cytokines and reactive oxygen species, and melatonin is the best natural antioxidant that is lost with age. The programmed cell death coronaviruses cause, which can result in significant lung damage, is also inhibited by melatonin. Coronavirus causes inflammation in the lungs which requires inflammasome activity. Melatonin blocks these inflammasomes. General immunity is impaired by anxiety and sleep deprivation. Melatonin improves sleep habits, reduces anxiety and stimulates immunity. Fibrosis may be the most dangerous complication after COVID-19. Melatonin is known to prevent fibrosis. Mechanical ventilation may be necessary but yet imposes risks due to oxidative stress, which can be reduced by melatonin. Thus, by using the safe over-the-counter drug melatonin, we may be immediately able to prevent the development of severe disease symptoms in coronavirus patients, reduce the severity of their symptoms, and/or reduce the immuno-pathology of coronavirus infection on patients' health after the active phase of the infection is over.

Reprogramming of the Immune System by Stress and Faulty Hormonal Imprinting

PURPOSE

Hormonal imprinting is taking place perinatally at the first encounter between the developing hormone receptors and their target hormones. However, in this crucial period when the developmental window for physiological imprinting is open, other molecules, such as synthetic hormones and endocrine disruptors can bind to the receptors, leading to faulty imprinting with life-long consequences, especially to the immune system. This review presents the factors of stress and faulty hormonal imprinting that lead to reprogramming of the immune system.

METHODS

Relevant publications from Pubmed since 1990 were reviewed and synthesized.

FINDINGS

The developing immune system is rather sensitive to hormonal effects. Faulty hormonal imprinting is able to reprogram the original developmental program present in a given cell, with lifelong consequences, manifested in alteration of hormone binding by receptors, susceptibility to certain (non-infectious) diseases, and triggering of other diseases. As stress mobilizes the hypothalamic-pituitary-adrenal axis if it occurred during gestation or perinatally, it could lead to faulty hormonal imprinting in the immune system, manifested later as allergic and autoimmune diseases or weakness of normal immune defenses. Hormonal imprinting is an epigenetic process and is carried to the offspring without alteration of DNA base sequences. This means that any form of early-life stress alone or in association with hormonal imprinting could be associated with the developmental origin of health and disease (DOHaD). As puberty is also a period of reprogramming, stress or faulty imprinting can change the original (developmental) program, also with life-long consequences.

IMPLICATIONS

Considering the continuous differentiation of immune cells (from blast-cells) during the whole life, there is a possibility of late-imprinting or stress-activated reprogramming in the immune system at any periods of life, with later pathogenetic consequences.

Chronic Stress Contributes to Osteosarcopenic Adiposity via Inflammation and Immune Modulation: The Case for More Precise Nutritional Investigation

Chronic stress and low-grade chronic inflammation (LGCI) are key underlying factors formany diseases, including bone and body composition impairments. Objectives of this narrativereview were to examine the mechanisms by which chronic stress and LGCI may influenceosteosarcopenic adiposity (OSA) syndrome, originally named as ostoesarcopenic obesity (OSO).We also examined the crucial nutrients presumed to be affected by or cause of stress andinflammation and compared/contrasted them to those of our prehistoric ancestors. The evidenceshows that stress (particularly chronic) and its related inflammatory processes, contribute toosteoporosis, sarcopenia, and adiposity ultimately leading to OSA as a final and most derangedstate of body composition, commencing at the mesenchymal cell lineage disturbance. Thefoods/nutrients consumed by modern humans, as well as their altered lifestyle, also contribute tostress, LGCI and subsequently to OSA. The processes can also go in opposite direction when stressand inflammation impact nutritional status, particularly some micronutrients' levels. Whilenutritional management of body composition and LGCI have been studied, the nutrients (and theirquantities) most affected by stressors and those which may act toward the alleviation of stressfulstate, ultimately leading to better body composition outcomes, need to be elucidated.

Chronic isolation stress is associated with increased colonic and motor symptoms in the A53T mouse model of Parkinson's disease

BACKGROUND

Chronic stress exacerbates motor deficits and increases dopaminergic cell loss in several rodent models of Parkinson's disease (PD). However, little is known about effects of stress on gastrointestinal (GI) dysfunction, a common non-motor symptom of PD. We aimed to determine whether chronic stress exacerbates GI dysfunction in the A53T mouse model of PD and whether this relates to changes in α-synuclein distribution.

METHODS

Chronic isolation stress was induced by single-housing WT and homozygote A53T mice between 5 and 15 months of age. GI and motor function were compared with mice that had been group-housed.

KEY RESULTS

Chronic isolation stress increased plasma corticosterone and exacerbated deficits in colonic propulsion and whole-gut transit in A53T mice and also increased motor deficits. However, our results indicated that the novel environment-induced defecation response, a common method used to evaluate colorectal function, was not a useful test to measure exacerbation of GI dysfunction, most likely because of the reported reduced level of anxiety in A53T mice. A53T mice had lower corticosterone levels than WT mice under both housing conditions, but single-housing increased levels for both genotypes. Enteric neuropathy was observed in aging A53T mice and A53T mice had a greater accumulation of alpha-synuclein (αsyn) in myenteric ganglia under both housing conditions.

CONCLUSIONS & INFERENCES

Chronic isolation stress exacerbates PD-associated GI dysfunction, in addition to increasing motor deficits. However, these changes in GI symptoms are not directly related to corticosterone levels, worsened enteric neuropathy, or enteric αsyn accumulation.

Transportation and Routine Veterinary Interventions Alter Immune Function in the Dog

Rapid activation of the hypothalamic pituitary adrenal axis and the sympathetic nervous system are hallmarks of the acute stress response and these systems interact with the immune system by signaling though glucocorticoid and adrenergic receptors on immune cells. There is limited information about the effect of these physiologic responses on immunologic parameters of pet dogs enrolled in clinical studies. The objective of this study was to evaluate how travel, instrumentation, and hospitalization alter immunologic parameters in pet dogs. Blood was collected from healthy dogs in a home environment and from healthy dogs at the time of presentation to the hospital and after instrumentation and 24 hours of hospitalization. We found that lipopolysaccharide (LPS)-induced downregulation of toll like receptor 4 (TLR4) was blunted in dogs exposed to stress. Neutrophil and monocyte major histocompatibility complex class II (MHCII) expression increased after transportation to the veterinary hospital but then became similar to that of the control dogs at the end of hospitalization. Peripheral blood mononuclear cell cytotoxicity function was blunted in dogs exposed to the stress of transportation as well as hospitalization. Neutrophil apoptosis was greater in dogs exposed to stress compared to controls although this effect significantly decreased after hospitalization stress. Conversely, stress did not alter induced or spontaneous cytokine production from leukocytes, neutrophil or monocyte expression of TLR4, LPS-induced downregulation of monocyte TLR4, LPS-induced neutrophil and monocyte expression of MHCII or peripheral blood lymphocyte phenotype. Transportation and instrumentation/hospitalization stress should be considered when interpreting immunologic studies in pet dogs.

Immunosuppressive effect and global dysregulation of blood transcriptome in response to psychosocial stress in vervet monkeys (Chlorocebus sabaeus)

Psychosocial stressors - life events that challenge social support and relationships - represent powerful risk factors for human disease; included amongst these events are relocation, isolation and displacement. To evaluate the impact of a controlled psychosocial stressor on physiology and underlying molecular pathways, we longitudinally studied the influence of a 28-day period of quarantine on biomarkers of immune signalling, microbial translocation, glycaemic health and blood transcriptome in the wild-born vervet monkey. This event caused a coordinated, mostly transient, reduction of circulating levels of nine immune signalling molecules. These were paralleled by a massive dysregulation of blood transcriptome, including genes implicated in chronic pathologies and immune functions. Immune and inflammatory functions were enriched among the genes downregulated in response to stress. An upregulation of genes involved in blood coagulation, platelet activation was characteristic of the rapid response to stress induction. Stress also decreased neutrophils and increased CD4 + T cell proportions in blood. This model of psychosocial stress, characterised by an immune dysregulation at the transcriptomic, molecular and cellular levels, creates opportunities to uncover the underlying mechanisms of stress-related diseases with an immune component, including cardiovascular diseases and susceptibility to infections.

Ancestral stress programs sex-specific biological aging trajectories and non-communicable disease risk

The incidence of non-communicable diseases (NCDs) is rising globally but their causes are generally not understood. Here we show that cumulative ancestral stress leads to premature aging and raises NCD risk in a rat population. This longitudinal study revealed that cumulative multigenerational prenatal stress (MPS) across four generations (F0-F3) raises age- and sex-dependent adverse health outcomes in F4 offspring. MPS accelerated biological aging processes and exacerbated sex-specific incidences of respiratory and kidney diseases, inflammatory processes and tumors. Unbiased deep sequencing of frontal cortex revealed that MPS altered expression of microRNAs and their target genes involved in synaptic plasticity, stress regulation, immune function and longevity. Multi-layer top-down deep learning metabolite enrichment analysis of urine markers revealed altered metabolic homeodynamics in MPS males. Thus, peripheral metabolic signatures may provide sensitive biomarkers of stress vulnerability and disease risk. Programming by MPS appears to be a significant determinant of lifetime mental health trajectories, physical wellbeing and vulnerability to NCDs through altered epigenetic regulation.

A Proteomic View of the Cross-Talk Between Early Intestinal Microbiota and Poultry Immune System

Proteomics has been used to investigate cross-talk between the intestinal microbiome and host biological processes. In this study, an in ovo technique and a proteomics approach was used to address how early bacterial colonization in the gastrointestinal tract (GIT) could modulate inflammatory and immune responses in young broilers. Embryos at 18 embryogenic days were inoculated with saline (S), 102 CFU of Citrobacter freundii (CF), Citrobacter species (C2), or lactic acid bacteria mixture (L) into the amnion. At 10 days posthatch, ileum samples from 12 birds per treatment were selected for tandem mass spectrometry analysis. Our further findings indicated that treatment-specific influences on early GIT microbiota resulted in different immune responses in mature broilers. Predicted functional analyses revealed activation of inflammation pathways in broilers treated in ovo with L and CF. Exposure to L enhanced functional annotation related to activation, trafficking of immune cells, and skeletal growth based-network, while CF inhibited biological functions associated with immune cell migration and inflammatory response. These results highlighted that proper immune function was dependent on specific GIT microbiota profiles, in which early-life exposure to L-based probiotic may have modulated the immune functions, whereas neonatal colonization of Enterobacteriaceae strains may have led to immune dysregulation associated with chronic inflammation.

Premature birth stunts early growth and is a possible driver of stress-induced maternal effects in the guppy Poecilia reticulata

We tested the effects of gestational stress, principally in the form of alarm cue extracted from the skin of conspecifics, on reproduction in female guppies (Poecilia reticulata) and the growth and behaviour of their offspring. Offspring from mothers exposed to alarm cue exhibited stunted growth in the first few days post-partum, which appeared to be mediated by shortening of the gestation period, the length of which directly correlated with growth rate within the first 6 days post-partum. Mature offspring did not differ in behaviour or stress responses compared with controls and so the effects of maternal predation stress did not appear to persist into adulthood. A different form of gestational stress, dietary restriction, did not significantly affect offspring growth, though brood size was reduced, suggesting that the effects of predation stress were not mediated by differences in resource demand or consumption.

Non-invasive stress evaluation in domestic horses (Equus caballus): impact of housing conditions on sensory laterality and immunoglobulin A

The study aimed to evaluate sensory laterality and concentration of faecal immunoglobulin A (IgA) as non-invasive measures of stress in horses by comparing them with the already established measures of motor laterality and faecal glucocorticoid metabolites (FGMs). Eleven three-year-old horses were exposed to known stressful situations (change of housing, initial training) to assess the two new parameters. Sensory laterality initially shifted significantly to the left and faecal FGMs were significantly increased on the change from group to individual housing and remained high through initial training. Motor laterality shifted significantly to the left after one week of individual stabling. Faecal IgA remained unchanged throughout the experiment. We therefore suggest that sensory laterality may be helpful in assessing acute stress in horses, especially on an individual level, as it proved to be an objective behavioural parameter that is easy to observe. Comparably, motor laterality may be helpful in assessing long-lasting stress. The results indicate that stress changes sensory laterality in horses, but further research is needed on a larger sample to evaluate elevated chronic stress, as it was not clear whether the horses of the present study experienced compromised welfare, which it has been proposed may affect faecal IgA.

Impact of high dietary plant protein with or without marine ingredients in gut mucosa proteome of gilthead seabream (Sparus aurata, L.)

The digestive tract, particularly the intestine, represents one of the main sites of interactions with the environment, playing the gut mucosa a crucial role in the digestion and absorption of nutrients, and in the immune defence. Previous researches have proven that the fishmeal replacement by plant sources could have an impact on the intestinal status at both digestive and immune level, compromising relevant productive parameters, such as feed efficiency, growth or survival. In order to evaluate the long-term impact of total fishmeal replacement on intestinal mucosa, the gut mucosa proteome was analysed in fish fed with a fishmeal-based diet, against plant protein-based diets with or without alternative marine sources inclusion. Total fishmeal replacement without marine ingredients inclusion, reported a negative impact in growth and biometric parameters, further an altered gut mucosa proteome. However, the inclusion of a low percentage of marine ingredients in plant protein-based diets was able to maintain the growth, biometrics parameters and gut mucosa proteome with similar values to FM group. A total fishmeal replacement induced a big set of underrepresented proteins in relation to several biological processes such as intracellular transport, assembly of cellular macrocomplex, protein localization and protein catabolism, as well as several molecular functions, mainly related with binding to different molecules and the maintenance of the cytoskeleton structure. The set of downregulated proteins also included molecules which have a crucial role in the maintenance of the normal function of the enterocytes, and therefore, of the epithelium, including permeability, immune and inflammatory response regulation and nutritional absorption. Possibly, the amino acid imbalance presented in VM diet, in a long-term feeding, may be the main reason of these alterations, which can be prevented by the inclusion of 15% of alternative marine sources. SIGNIFICANCE: Long-term feeding with plant protein based diets may be considered as a stress factor and lead to a negative impact on digestive and immune system mechanisms at the gut, that can become apparent in a reduced fish performance. The need for fishmeal replacement by alternative ingredients such as plant sources to ensure the sustainability of the aquaculture sector has led the research assessing the intestinal status of fish to be of increasing importance. This scientific work provides further knowledge about the proteins and biologic processes altered in the gut in response to plant protein based diets, suggesting the loss of part of gut mucosa functionality. Nevertheless, the inclusion of alternative marine ingredients was able to reverse these negative effects, showing as a feasible option to develop sustainable aquafeeds.

Batrachochytrium salamandrivorans ELICITS ACUTE STRESS RESPONSE IN SPOTTED SALAMANDERS BUT NOT INFECTION OR MORTALITY

The emerging fungal pathogen Batrachochytrium salamandrivorans (Bsal) is a major threat to amphibian species worldwide with potential to infect many species if it invades salamander biodiversity hotspots in the Americas. Bsal can cause the disease chytridiomycosis, and it is important to assess the risk of Bsal-induced chytridiomycosis to species in North America. We evaluated the susceptibility to Bsal of the common and widespread spotted salamander, Ambystoma maculatum, across life history stages and monitored the effect of Bsal exposure on growth rate and response of the stress hormone, corticosterone. We conclude that spotted salamanders appear resistant to Bsal because they showed no indication of disease or infection, and experienced minor effects on growth upon exposure. While we focused on a single population for this study, results were consistent across conditions of exposure including high or repeated doses of Bsal, life-stage at exposure, environmental conditions including two temperatures and two substrates, and promoting pathogen infectivity by conditioning Bsal cultures with thyroid hormone. Exposure to high levels of Bsal elicited an acute but not chronic increase in corticosterone in spotted salamanders, and reduced growth. We hypothesize that the early acute increase in corticosterone facilitated mounting an immune response to the pathogen, perhaps through immunoredistribution to the skin, but further study is needed to determine immune responses to Bsal. These results will contribute to development of appropriate Bsal management plans to conserve species at risk of emerging disease.

The relationship between stress and vitiligo: Evaluating perceived stress and electronic medical record data

Vitiligo is a T-cell mediated skin disorder characterized by progressive loss of skin color. In individuals genetically predisposed to the disease, various triggers contribute to the initiation of vitiligo. Precipitating factors can stress the skin, leading to T-cell activation and recruitment. Though hereditary factors are implicated in the pathogenesis of vitiligo, it is unknown whether precipitating, stressful events play a role in vitiligo. To understand this, we utilized a validated perceived stress scale (PSS) to measure this parameter in vitiligo patients compared to persons without vitiligo. Additionally, we probed a clinical database, using a knowledge linking software called ROCKET, to gauge stress-related conditions in the vitiligo patient population. From a pool of patients in an existing database, a hundred individuals with vitiligo and twenty-five age- and sex-matched comparison group of individuals without vitiligo completed an online survey to quantify their levels of perceived stress. In parallel, patients described specifics of their disease condition, including the affected body sites, the extent, duration and activity of their vitiligo. Perceived stress was significantly higher among vitiligo individuals compared to those without vitiligo. ROCKET analyses suggested signs of metabolic-related disease (i.e., ‘stress’) preceding vitiligo development. No correlation was found between perceived stress and the stage or the extent of disease, suggesting that elevated stress may not be a consequence of pigment loss alone. The data provide further support for stress as a precipitating factor in vitiligo development.

Investigating the relationship between corticosterone and glucose in a reptile

The glucocorticoid hormone corticosterone (CORT) has classically been used in ecophysiological studies as a proxy for stress and energy mobilization, but rarely are CORT and the energy metabolites themselves concurrently measured. To examine CORT's role in mobilizing glucose in a wild reptile, we conducted two studies. The first study measured natural baseline and stress-induced blood-borne CORT and glucose levels in snakes during spring emergence and again when snakes return to the denning sites in autumn. The second study manipulated the hypothalamic-pituitary-adrenal (HPA) axis in male snakes in the autumn by taking a baseline blood sample, then subjecting individuals to one of five treatments (no injection, saline, CORT, adrenocorticotropin hormone and metyrapone). Subsequent samples were taken at 30 and 60 min. In both studies, we found that glucose levels do increase with acute stress, but that the relationship was not directly related to CORT elevation. In the second study, we found that none of the HPA axis manipulations directly affected blood glucose levels, further indicating that CORT may play a complex but not direct role in glucose mobilization in snakes. This study highlights the need for testing mechanisms in wild organisms by combining in situ observations with manipulative studies.

A tale of two islands: evidence for impaired stress response and altered immune functions in an insular pit viper following ecological disturbance

The frequency and intensity of ecological perturbations affecting wild animal populations is expected to increase in the future with animals facing numerous global threats. Seahorse Key is a continental island off mainland Florida that has historically been a major rookery for several species of waterbirds. As a result of an unknown disturbance, the entire rookery abandoned Seahorse Key in April 2015 and shifted nesting activities to nearby Snake Key, resulting in an influx of food resources in the form of fish carrion to resident Florida cottonmouth snakes (Agkistrodon conanti), while snakes on Seahorse Key experienced a drastic reduction in food resources. Our objective was to assess plasma corticosterone concentrations, corticosterone negative feedback using dexamethasone, blood glucose, body condition, packed cell volume, natural antibody agglutination, white blood cell counts and ratios and erythrocyte sedimentation rate to characterize the long-term effects of differential resource availability in these two snake populations 3 years after this major ecological disturbance. We collected blood samples at three time points from cottonmouths on Seahorse Key (n = 6 individuals) and Snake Key (n = 13 individuals) in fall 2018. In due consideration of the small sample size, our study shows evidence that 3 years after the shift in waterbird nesting Seahorse Key cottonmouths exhibit a dampened acute stress response and presumptive impaired innate immune functions relative to cottonmouths on Snake Key. These results highlight the context-dependent nature of biomarkers and implicate the significant decrease in food resources on Seahorse Key in altering hormonal stress responses and innate immune functions, possibly leading to unknown long-term downstream effects. This study assessed the response of a wild population of pit viper to ecological disturbance in situ with the aim to improve our understanding of how animals cope with such perturbations and improve our capacity to make informed decisions for conservation.

Artificial Light at Night (ALAN): A Potential Anthropogenic Component for the COVID-19 and HCoVs Outbreak

The origin of the coronavirus disease 2019 (COVID-19) pandemic is zoonotic. The circadian day-night is the rhythmic clue to organisms for their synchronized body functions. The "development for mankind" escalated the use of artificial light at night (ALAN). In this article, we tried to focus on the possible influence of this anthropogenic factor in human coronavirus (HCoV) outbreak. The relationship between the occurrences of coronavirus and the ascending curve of the night-light has also been delivered. The ALAN influences the physiology and behavior of bat, a known nocturnal natural reservoir of many Coronaviridae. The "threatened" and "endangered" status of the majority of bat species is mainly because of the destruction of their proper habit and habitat predominantly through artificial illumination. The stress exerted by ALAN leads to the impaired body functions, especially endocrine, immune, genomic integration, and overall rhythm features of different physiological variables and behaviors in nocturnal animals. Night-light disturbs "virus-host" synchronization and may lead to mutation in the genomic part of the virus and excessive virus shedding. We also proposed some future strategies to mitigate the repercussions of ALAN and for the protection of the living system in the earth as well.

Relationships between glucocorticoids and infection with Batrachochytrium dendrobatidis in three amphibian species

It is often hypothesized that organisms exposed to environmental change may experience physiological stress, which could reduce individual quality and make them more susceptible to disease. Amphibians are amongst the most threatened taxa, particularly in the context of disease, but relatively few studies explore links between stress and disease in amphibian species. Here, we use the fungal pathogen Batrachochytrium dendrobatidis (Bd) and amphibians as an example to explore relationships between disease and glucocorticoids (GCs), metabolic hormones that comprise one important component of the stress response. While previous work is limited, it has largely identified positive relationships between GCs and Bd-infection. However, the causality remains unclear and few studies have integrated both baseline (GC release that is related to standard, physiological functioning) and stress-induced (GC release in response to an acute stressor) measures of GCs. Here, we examine salivary corticosterone before and after exposure to a stressor, in both field and captive settings. We present results for Bd-infected and uninfected individuals of three amphibian species with differential susceptibilities to this pathogen (Rana catesbeiana, R. clamitans, and R. sylvatica). We hypothesized that prior to stress, baseline GCs would be higher in Bd-infected animals, particularly in more Bd-susceptible species. We also expected that after exposure to a stressor, stress-induced GCs would be lower in Bd-infected animals. These species exhibited significant interspecific differences in baseline and stress induced corticosterone, though other variables like sex, body size, and day of year were usually not predictive of corticosterone. In contrast to most previous work, we found no relationships between Bd and corticosterone for two species (R. catesbeiana and R. clamitans), and in the least Bd-tolerant species (R. sylvatica) animals exhibited context-dependent differences in relationships between Bd infection and corticosterone: Bd-positive R. sylvatica had significantly lower baseline and stress-induced corticosterone, with this pattern being stronger in the field than in captivity. These results were surprising, as past work in other species has more often found elevated GCs in Bd-positive animals, a pattern that aligns with well-documented relationships between chronically high GCs, reduced individual quality, and immunosuppression. This work highlights the potential relevance of GCs to disease susceptibility in the context of amphibian declines, while underscoring the importance of characterizing these relationships in diverse contexts.

Contrasting Responses of Lizards to Divergent Ecological Stressors Across Biological Levels of Organization

It is frequently hypothesized that animals employ a generalized "stress response," largely mediated by glucocorticoid (GC) hormones, such as corticosterone, to combat challenging environmental conditions. Under this hypothesis, diverse stressors are predicted to have concordant effects across biological levels of an organism. We tested the generalized stress response hypothesis in two complementary experiments with juvenile and adult male Eastern fence lizards (Sceloporus undulatus). In both experiments, animals were exposed to diverse, ecologically-relevant, acute stressors (high temperature or red imported fire ants, Solenopsis invicta) and we examined their responses at three biological levels: behavioral; physiological (endocrine [plasma corticosterone and blood glucose concentrations] and innate immunity [complement and natural antibodies]); and cellular responses (gene expression of a panel of five heat-shock proteins in blood and liver) at 30 or 90 min post stress initiation. In both experiments, we observed large differences in the cellular response to the two stressors, which contrasts the similar behavioral and endocrine responses. In the adult experiment for which we had innate immune data, the stressors affected immune function independently, and they were correlated with CORT in opposing directions. Taken together, these results challenge the concept of a generalized stress response. Rather, the stress response was context specific, especially at the cellular level. Such context-specificity might explain why attempts to link GC hormones with life history and fitness have proved difficult. Our results emphasize the need for indicators at multiple biological levels and whole-organism examinations of stress.

Gender and Age Differences in the Suppressive Effect of a 50 Hz Electric Field on the Immobilization-Induced Increase of Plasma Glucocorticoid in Mice

We developed an experimental system to characterize the suppressive effect of extremely low-frequency (ELF) electric fields (EFs) on the stress response. We assessed differences in the EF effects by age and gender. Control, EF-alone, immobilization-alone, and co-treated groups were subjected to an EF (50 Hz, 10 kV/m). Co-treated mice were exposed to the EF for 60 min, with immobilization during the latter half. Our results indicate that the suppressive effects of ELF EFs on the stress response in immobilized mice occur regardless of gender or age. As stress plays an important role in the onset and progression of various diseases, these findings may have broad implications for understanding the efficacy of EFs in animal, and perhaps human, health. Bioelectromagnetics. 2020;41:156-163. © 2019 Bioelectromagnetics Society.