Plasma CORT Research Articles

Melatonin modulation of the chronic dexamethasone-induced adrenal insufficiency.

Chronic exposure to synthetic glucocorticoids/GCs, widely in use to treat many diseases, may compromise the hypothalamic-pituitary-adrenal/HPA axis leading to a condition of adrenal insufficiency/AI. This study demonstrates the efficacy of the melatonin/MEL in amelioration of chronic dexamethasone (DEX)-induced AI. Mice (Parkes Strain/Male/8 weeks old/30-33 g) were maintained in four groups (10 mice/group) for 30 days: Group 1/Control received intraperitoneal (i.p) vehicle (alcoholic 0.9% normal saline); Group II/DEX (400 µg/kg BW/day/i.p), Group III/(DEX + MEL 750 µg/kg BW/day/subcutaneous), and Group IV received only MEL. Adrenal, pituitary, and blood samples were collected from six mice/groups. Four mice/groups were subjected to the Lipopolysaccharide (LPS) challenge. Adrenal histology, ACTH immunohistochemistry, and plasma ACTH and corticosterone/CORT levels were measured. DEX exposure suppressed the pituitary ACTH expression significantly from control as revealed by morphometry and circulating hormones (Density, p < 0.01; size, immunointensity, plasma ACTH, and CORT; p < 0.001). Increased adrenal histopathology indicated probable AI. MEL co-supplementation significantly increased the corticotropes' density (p < 0.05), size (p < 0.001), immunointensity (<0.01), and plasma level of ACTH (p < 0.01) compared to the DEX group. The adreno-cortical width, zona fasciculata cell density and size, and the plasma CORT level (p < 0.001) were also significantly increased. The enhanced CORT response of the HPA axis in the DEX + MEL group compared to the DEX group on the LPS challenge provides support for the MEL restoration of the HPA axis functioning. Further research on the MEL modulation of the HPA axis may support its role in preventing AI.

Dim blue light at night worsens high-fat diet-induced kidney damage via increasing corticosterone levels and modulating the expression of circadian clock genes.

Obesity is a contributing factor that increases the likelihood of developing chronic kidney disease. In recent years, studies have found that light pollution worldwide promoted obesity, which was known to be a consequence of circadian rhythm disruption. Nevertheless, the impact of light pollution on kidney disease associated with obesity remains mostly unknown, and potential processes have been minimally investigated. Herein, we fed mice a high-fat diet and gave them dim white (dWL), blue (dBL), green (dGL), and red (dRL) light for 12 weeks. Our results showed that both dWL and dBL tended to be more susceptible to damage to kidney dysfunction caused by a high-fat diet compared to LD, with more pronounced changes in dBL. The analysis of kidney found that dBL activated the TGF-β1/Smad signaling pathway to promote epithelial-mesenchymal transition (EMT) in the kidney. Additionally, dBL activated the NF-κB signaling pathway and resulted in elevated protein levels of TLR4, p-IκB, p-P65, and TNF-α. Furthermore, dBL increased BAX protein levels and decreased BCL2 protein levels. At the same time, dBL affected the Keap1/Nrf2/HO-1 signaling pathway, elevating KEAP1 and decreasing NRF2 and HO-1 protein levels. We were surprised to find that dBL altered the expression of the circadian clock genes, resulting in a decrease in the positively regulated genes Bmal1, Clock, and an increase in the negatively regulated genes Per1, Per2, Per3. Mechanistically, dBL increased plasma CORT levels as well as decreased renal GR α expression, and in vitro experiments showed that the circadian clock genes were altered by the addition of CORT and returned to normal levels after the addition of the GR inhibitor RU486. Consequently, dBL can exacerbate renal injury by elevating plasma CORT levels and altering rhythmic changes by acting on the biological clock via GR.

Deleterious effects of social isolation on neuroendocrine-immune status, and cancer progression in rats

Accumulating evidence indicates that social isolation (SI) in humans and rodents is associated with increased cancer incidence and mortality, yet mediating mechanisms remain elusive. Here, we examine the neuroendocrine and immunological consequences of SI and its short- and long-term physiological impacts in naïve and cancer-bearing rats. Findings indicate that isolated animals experienced a significant decrease in weight compared to controls. Specifically, females showed a marked weight decrease during the first week of isolation. Isolated rats had significantly higher numbers of MADB106 experimental pulmonary metastases. Although mortality rates were higher in isolated tumor-bearing rats, unexpectedly, they exhibited a reduced growth rate of orthotopically implanted MADB106 tumors. Transcriptomic analyses of these excised tumors indicated a major downregulation in the expression of various genes, including those associated with pro-metastatic processes (e.g., EMT). In naïve rats (no cancer), levels of IL-6 increased, and total IgG levels decreased under SI conditions. A mixed effect was found for TNFα, which increased in females and decreased in males. In the central nervous system, isolated rats showed altered gene expression in key brain regions associated with stress responses and social behavior. The paraventricular nucleus of the thalamus emerged as a significantly affected region, along with the bed nucleus of the stria terminalis. Changes were observed in the expression of oxytocin, serotonin, and dopamine receptors. Isolated rats also exhibited greater alterations in hypothalamic–pituitary–adrenal (HPA) axis-related regulation and an increase in plasma CORT levels. Our study highlights the profound impact of SI on metastatic processes. Additionally, the potential detrimental effects of SI on thermoregulation were discussed, emphasizing the importance of social thermoregulation in maintaining physiological stability and highlighting the need to avoid single-caging practices in research. We report neuro-immune interactions and changes in brain gene expression, highlighting the need for further research into these underlying processes to improve outcomes in animal models and potential interventions for cancer patients through increased social support.

6826 Mevalonate Treatment Worsened Hypocholesterolemia During Prolonged Sepsis Without Affecting Adrenal And Muscle Function

Abstract Disclosure: L. De Bruyn: None. S. Derde: None. F. Van Beek: None. S. Vander Perre: None. I. Derese: None. L. Pauwels: None. G. Van den Berghe: None. L. Langouche: None. Introduction: Sepsis is hallmarked by an immediate and sustained reduction in total-, HDL- and LDL-cholesterol (-C), associated with illness severity and a potential contributor to the development of adrenal failure and muscle weakness. The underlying mechanisms that might be involved in sepsis-induced hypocholesterolemia are multifactorial and partly understood. We hypothesized that treatment with the cholesterol precursor mevalonate might improve cholesterol availability, thereby improving adrenal gland and skeletal muscle function. Our hypothesis was tested in a validated and clinically relevant mouse model of prolonged sepsis. Methods: In a catheterized mouse model of cecal ligation and puncture-induced, fluid resuscitated and antibiotics treated polymicrobial abdominal sepsis (5 d), septic mice received continuous infusion with either mevalonate (78 mg/d) or placebo solution, whereas healthy mice served as controls (N=50). Plasma total-C (HDL- + LDL-C), CORT and total bile acids were measured, in addition to ex vivo muscle force and adrenocortical cholesterol ester content. Gene expression markers of inflammation (Tnf-α, Il-6) were measured in the adrenal gland, as well as hepatic mRNA expression of cholesterol synthesis enzymes (Hmgcs1, Hmgcr, Fdft1). Metabolites of the mevalonate pathway (mevalonic acid, squalene, lanosterol, desmosterol and (7-dehydro) cholesterol) were quantified in the liver with LC-MS. Results: The sepsis-induced reduction in plasma total-C was further decreased in mevalonate-treated septic mice (26±3 mg/dL) as compared with placebo (53±3 mg/dL) and healthy controls (108±3 mg/dL) (p&amp;lt;0.0001). Metabolites of the mevalonate pathway were all increased in the liver after mevalonate treatment (p&amp;lt;0.01), whereas hepatic cholesterol content was decreased as compared with placebo (p&amp;lt;0.05). Also, gene expression markers of cholesterol synthesis enzymes were further decreased in the liver of mevalonate-treated septic mice as compared with placebo (p&amp;lt;0.05). In the context of the unexpected further reduction in plasma total-C, no additional effect on plasma CORT, total bile acids, and sepsis-induced loss of muscle force and depletion in adrenocortical cholesterol ester content was observed. In addition, the sepsis-induced rise in markers of adrenal inflammation (Tnf-α, Il-6) was not further affected by mevalonate treatment. Conclusion: Mevalonate treatment further reduced the sepsis-induced hypocholesterolemia in prolonged septic mice, potentially due to increased feedback inhibition on hepatic cholesterol biosynthesis, but without further affecting adrenal and muscle function. Other therapies such as substitution with bovine serum HDL-C are currently investigated to improve altered cholesterol availability during sepsis. Presentation: 6/2/2024

Baseline and stress-induced changes in plasma bacterial killing ability against gram-negative bacteria are partially mediated by the complement system in Rhinella diptycha toads

The plasma bacterial killing ability (BKA) is modulated by the stress response in vertebrates, including amphibians. The complement system is an effector mechanism comprised of a set of proteins present in the plasma that once activated can promote bacterial lysis. Herein, we investigated whether changes in plasma BKA as a result of the acute stress response and an immune challenge are mediated by the complement system in Rhinella diptycha toads. Additionally, we investigated whether the observed changes in plasma BKA are associated with changes in plasma corticosterone levels (CORT). We subjected adult male toads to a restraint or an immune challenge (with three concentrations of Aeromonas hydrophila heat inactivated), and then evaluated the plasma BKA against A. hydrophila, in vitro. We determined the complement system activity on plasma BKA, by treating the plasma (baseline, 1 h and 24 h post-restraint, and after the immune challenge) with ethylenediaminetetraacetic acid, heat, or protease. Our results showed increased CORT 1 h and 24 h after restraint and decreased plasma BKA 24 h post-restraint. The inhibitors of the complement system decreased the plasma BKA compared with untreated plasma at all times (baseline, 1 h, and 24 h after restraint), demonstrating that the plasma BKA activity is partially mediated by the complement system. The immune challenge increased CORT, with the highest values being observed in the highest bacterial concentration, compared with control. The plasma BKA was not affected by the immune challenge but was demonstrated to be partially mediated by the complement system. Our results demonstrated that restraint and the immune challenge activated the hypothalamus-pituitary-interrenal axis, by increasing plasma CORT levels in R. diptycha. Also, our results demonstrated the complement system is participative in the plasma BKA for baseline and post-stress situations in these toads.

Chronic exposure to dim artificial light disrupts the daily rhythm in mitochondrial respiration in mouse suprachiasmatic nucleus

ABSTRACT Circadian rhythms of physiology, behavior, and metabolism have an endogenous 24 h period that synchronizes with environmental cycles of light/dark and food availability. Alterations in light cycles are stressful and disrupt such diurnal oscillations. Recently, we witnessed a sudden rise in studies describing the mechanisms behind the interaction between the key characteristics of mitochondrial functions, peripheral clocks, and stress responses. To our knowledge, there is no study in the suprachiasmatic nuclei (SCN) describing the dysregulated mitochondrial bioenergetics under abnormal lighting conditions, which is common in today’s modern world. Thus, we aimed to investigate the existence of daily changes in mitochondrial bioenergetics (respiratory control rate, RCR), mitochondrial abundance (mtDNA/nDNA), plasma corticosterone, and to test whether disturbances in the lighting conditions might influence such rhythms. To confirm this, mice were sacrificed, mitochondria were isolated from the suprachiasmatic nuclei in the brain and blood was collected, every 3 h at various time points zeitgeber time/circadian time, (0, 3, 6, 9, 12, 15, 18, 21, and 24 h) under 12:12 h light-dark (LD, 150 lux L: 0 lux D) cycle and chronic artificial dim lighting (LL, 5 lux: 5lux) conditions, of a 24 h period, respectively. Our results demonstrate the existence of robust daily rhythmicity in RCR, mtDNA/nDNA and plasma CORT under a normal LD cycle. However, these rhythms were significantly disrupted and clock genes expressions were dysregulated under chronic dim LL. Furthermore, mitochondrial abundance was significantly reduced during LL compared to their numbers under LD cycle. Our data demonstrate that the circadian clock regulates mitochondrial functions (RCR, number), essential for accomplishing daily energy demands and supply by the SCN neurons. Abnormal light exposure dysregulates mitochondrial functions in the SCN and may alter metabolism, resulting in obesity, diabetes, and other metabolic disorders. Therefore, properly designing lighting conditions in workplaces is essential to mitigate the adverse consequences of light on humans.

Assay validation of saliva glucocorticoids in Columbia spotted frogs and effects of handling and marking.

Non-invasive methods are important to the field of conservation physiology to reduce negative effects on organisms being studied. Glucocorticoid (GC) hormones are often used to assess health of individuals, but collection methods can be invasive. Many amphibians are imperiled worldwide, and saliva is a non- or semi-invasive matrix to measure GCs that has been partially validated for only four amphibian species. Validation ensures that assays are reliable and can detect changes in saliva corticosterone (sCORT) after exposure to stressors, but it is also necessary to ensure sCORT concentrations are correlated with plasma concentrations. To help validate the use of saliva in assessing CORT responses in amphibians, we captured uniquely marked Columbia spotted frogs (Rana luteiventris) on sequential days and collected baseline and stress-induced (after handling) samples. For a subset of individuals, we collected and quantified CORT in both saliva and blood samples, which have not been compared for amphibians. We tested several aspects of CORT responses and, by collecting across separate days, measured repeatability of CORT responses across days. We also evaluated whether methods common to amphibian conservation, such as handling alone or handling, clipping a toe and tagging elevated sCORT. Similar to previous studies, we show that sCORT is reliable concerning parallelism, recovery, precision and sensitivity. sCORT was weakly correlated with plasma CORT (R2 = 0.21), and we detected elevations in sCORT after handling, demonstrating biological validation. Toe clipping and tagging did not increase sCORT over handling alone, but repeated handling elevated sCORT for ~72hours. However, sCORT responses were highly variable and repeatability was low within individuals and among capture sessions, contrary to previous studies with urinary and waterborne CORT. sCORT is a semi-invasive and rapid technique that could be useful to assess effects of anthropogenic change and conservation efforts, but will require careful study design and future validation.

Effect of increased ventilation during feeding on broiler breeder biochemical, enzymatical, and electrolytes parameters

Breeders exhibit increased heat stress during and after meal feeding, thus increasing ventilation during and immediately post‐feeding may result in improved productivity and health as well as minimizing physiological stress. This study investigated the effect of increased ventilation during feeding on broiler breeder biochemical, enzymatical, and electrolytes parameters. A total of 288 breeder pullets were obtained from a commercial farm at 21 weeks of age (woa) and assigned to 12 pens (24 birds/pen). Each pen was equipped with two tube feeders, nipple drinkers, fresh pine shaving, and LED lighting. Temperature and lighting were adjusted according to primary breeder recommendations. Feed was provided by a commercial feed mill and meal fed once daily, while water was available ad libitum. Feed was presented at 0730 each day concurrently with the beginning of the photoperiod. Treatments included still air (S, negative control), conventional ventilation with no cool‐down (C, positive control), and variable air speed to mimic a cool‐down ventilation program during and immediately post‐feeding (V). Air speed in the V treatment wind tunnel was increased for three hours to offset the increase in metabolic heat production due to feeding and nesting activity, before returning to the baseline ventilation rate. Three sentinel birds in each pen were identified for physiological monitoring at the beginning of the study. On d 21 (start of treatments), 63 (midpoint), and 105 (end of the treatment period), blood samples (3 mL) were collected between 0800 and 0900 h from the brachial wing vein from each of the three sentinel birds into heparinized syringes within 45 s after birds were caught. The collected blood samples were centrifuged to separate the plasma and used to determine the electrolytes levels, concentration of biochemical (ALB, TBILI, BUN, CREAT, TP, UA, CHOL, LDL‐C, HDL, TRIG, GLUC) parameters and enzyme (ALT, ALP, AMYL, AST, CK, GGT, LDH, LIP) activities using an ACE‐AXCEL automatic analyzer. Results show that ALT, BUN, GLUC, and LDL‐C were affected by treatments. However, woa had significant effects on most examined variables along with few interactions. Plasma CORT was not affected by treatments and time, indicating absence of physiological stress. The results are in broad agreement with those reported in the literature and contribute to our knowledge of increasing ventilation during and immediately post‐feeding on blood metabolites variation in broiler breeders.

Relationships of Brain Glucocorticoid Receptors and Commonly Used Stress Parameters with Body Condition of Juvenile American Alligators (Alligator mississippiensis)

Crocodilians in aquacultural settings exhibit variations in growth and condition. The underlying cause of this has yet to be elucidated, but corticosterone (CORT, the main crocodilian stress hormone) is thought to play a role in this. In this study, we measured baseline plasma CORT, heterophil-lymphocyte (H/L) ratios, relative glucocorticoid receptor (GR) levels in the forebrain, and body condition index (BCI) of juvenile American alligators (Alligator mississippiensis). Both univariate and multivariate analyses were used to investigate underlying relationships. In univariate analysis, BCI was negatively related with GR levels, but not by plasma CORT. Multivariate analysis revealed that both relative forebrain GR levels and plasma CORT were negatively related with alligator BCI: alligators with higher body condition had lower levels of CORT and GRs. However, H/L ratios were unrelated to BCI. Our results implicate dysregulation of the hypothalamic-pituitary-adrenal axis as an important factor influencing crocodilian body condition.

Day vs. night variation in the LPS effects on toad's immunity and endocrine mediators

The immune-endocrine interactions following an immune challenge have been demonstrated in amphibians. When considering immune challenges, the immune-endocrine implications can vary with the injection time (day or night), a pattern not explored in amphibians. We investigated the immune response following a lipopolysaccharide - LPS injection, measured as plasma bacterial killing ability - BKA, phagocytosis of blood cells - PP, and neutrophil to lymphocyte ratio - NLR, splenic proinflammatory cytokines mRNA (IL-1β and IL-6), and also endocrine mediators (corticosterone - CORT and melatonin - MEL plasma levels) in Rhinella icterica adult male toads injected at day (10 am) or night (10 pm). LPS induced increases in CORT, NLR, PP, and IL-1β mRNA compared with amphibian phosphate-buffer saline-injected individuals. For plasma CORT, the response was more pronounced during the night. While for the PP and IL-1β mRNA, the effect was more evident during the day. For NLR, the increase happened at both times, day and night, in the LPS-injected toads. Meanwhile, no changes were observed in BKA, IL-6 mRNA, and MEL levels. Overall, our results demonstrated an LPS-induced inflammatory response in R. icterica toads, characterized by higher PP, NLR, and IL-1β mRNA, followed by activation of the hypothalamic-pituitary-interrenal axis (higher CORT levels). The time in which the toads received the LPS injection affected the endocrine and immune mediators. The higher CORT and lower inflammatory response at night suggested a potential functional interaction between CORT and immune reactivity associated with the differences in night vs. day in R. icterica toads. These results highlight the relevance of investigating different injection times and mechanistic pathways to understand LPS-induced immunomodulation in anurans.

Intranasal hydrogel of armodafinil hydroxypropyl-β-cyclodextrin inclusion complex for the treatment of post-traumatic stress disorder

Armodafinil inclusion complex (AIC) hydrogel was prepared and evaluated for its therapeutic effect on Post-traumatic Stress Disorder (PTSD). After computer simulation and physicochemical property investigation, the AIC was formed by lyophilization of armodafinil with ethanol as solvent and hydroxypropyl-beta-cyclodextrin (HP-β-CD) aqueous solution, in which the molar ratio of armodafinil and HP-β-CD was 1–1. The AIC encapsulation efficiency (EE) was (90.98 ± 3.72)% and loading efficiency (LE) was (13.95 ± 0.47)% and it increased the solubility of armodafinil in aqueous solution to 21 times. AIC hydrogel was prepared by adding AIC to methylcellulose (MC) hydrogels (3.33% w/v), and its higher drug release amount and slower release rate were testified by the in-vitro release assay and the rheological test. The mucosa irritation of AIC hydrogel was also evaluated. Healthy group, Model group, Sertraline group with 30 mg/kg sertraline gavage, AIC Hydrogel group with 20 mg/kg AIC hydrogel intranasal administration and AIC Aqueous Solution group with 20 mg/kg AIC aqueous solution gavage were set up for the treatment of mice with PTSD generated from foot shock method. Based on freezing response test in fear-conditioning box and open field test, compared with other groups, PTSD mice in AIC Hydrogel group showed significant improvement in behavioral parameters after 11 days of continuous drug administration and 5 days of drug withdrawal. After sacrifice, the plasma CORT level of PTSD mice in AIC Hydrogel group was elevated compared to Model group. Besides, the western blot (WB) of hippocampal brain-derived neurotrophic factor (BDNF) and amygdala dopamine transporter (DAT) immunohistochemistry sections indicated that AIC hydrogel had a protective effect on the brain tissue of PTSD mice. The brain targeting of intranasal administration was evaluated by fluorescence imaging characteristics of Cy7 hydrogel in the nasal route of drug administration, pharmacokinetics and in-vivo distribution of armodafinil. In short, AIC hydrogel is a promising formulation for the treatment of PTSD based on its high brain delivery and anti-PTSD effect.

Feather, But Not Plasma, Glucocorticoid Response to Artificial Light at Night Differs between Urban and Forest Blue Tit Nestlings.

Urbanization drives phenotypic variation in many animal species. This includes behavioral and physiological traits such as activity patterns, aggression, and hormone levels. A current challenge of urban evolutionary ecology is to understand the environmental drivers of phenotypic variation in cities. Moreover, do individuals develop tolerance to urban environmental factors, which underlie adaptative responses and contribute to the evolution of urban populations? Most available evidence comes from correlative studies and rare experiments where a single urban-related environmental factor has been manipulated in the field. Here we present the results of an experiment in which we tested for differences in the glucocorticoid (CORT) response of urban and rural blue tits nestlings (Cyanistes caeruleus) to artificial light at night (ALAN). ALAN has been suggested to alter CORT response in several animal species, but to date no study has investigated whether this effect of ALAN differs between urban and rural populations. Immediately after hatching, urban and forest broods were either exposed to 2 lux of ALAN (using an LED source mounted inside the nestbox) or received no treatment (dark control). The experiment lasted until the chicks fledged. When the chicks were 13 days old plasma samples were collected to measure baseline CORT concentrations, and feather samples to provide an integrative measure of CORT during growth. Forest birds had higher plasma CORT (pCORT) concentrations than their urban counterparts, irrespective of whether they were exposed to ALAN or not. Conversely, we found population-specific responses of feather CORT to ALAN. Specifically, urban birds that received ALAN had increased feather CORT compared with the urban dark controls, while the opposite was true for the forest birds. pCORT concentrations were negatively associated to fledging success, irrespective of population and treatment, while feather CORT was positively associated to fledging success in broods exposed to ALAN, but negatively in the dark control ones. Our results demonstrate that ALAN can play a role in determination of the glucocorticoid phenotype of wild animals, and may thus contribute to phenotypic differences between urban and rural animals.

Chronic noise exposure has context-dependent effects on stress physiology in nestling Tree Swallows (Tachycineta bicolor)

Anthropogenic noise is increasing in intensity and scope, resulting in changes to acoustic landscapes and largely negative effects on a range of species. In birds, noise can mask acoustic signals used in a variety of communication systems, including parent-offspring communication. As a result, nestling birds raised in noise may have challenges soliciting food from parents and avoiding detection by predators. Given that passerine nestlings are confined to a nest and therefore cannot escape these challenges, noise may also act as a chronic stressor during their development. Here, we raised Tree Swallow (Tachycineta bicolor) nestlings with or without continuous, white noise to test whether noise exposure affected baseline and stress-induced plasma, integrated feather corticosterone levels, and immune function. Stress physiology and immune function may also vary with the competitive environment during development, so we also examined whether noise effects varied with brood size and nestling mass. We found that overall, exposure to noise did not alter nestling stress physiology or immune function. However, light nestlings raised in noise exhibited lower baseline plasma and integrated feather corticosterone than heavy nestlings, suggesting alternative physiological responses to anthropogenic stimuli. Furthermore, light nestlings in larger broods had reduced PHA-induced immune responses compared to heavy nestlings, and PHA-induced immune responses were associated with higher levels of baseline plasma and feather CORT. Overall, our findings suggest that noise can alter the stress physiology of developing birds; however, these effects may depend on developmental conditions and the presence of other environmental stressors, such as competition for resources. Our findings may help to explain why populations are not uniformly affected by noise.

An in vivo explorative study to observe the protective effects of Puerariae flos extract on chronic ethanol exposure and withdrawal male mice

Protective effects of Puerariae flos extract (PFE) on ethanol (EtOH) exposure have been previously verified. This study attempts to explore the protective effects of PEF on EtOH withdrawal models. Sixty male Kunming mice were involved which were randomly divided into five groups (intact control, EtOH group (35-day EtOH exposure), EtOH withdrawal group (28-day exposure + 7-day withdrawal), EtOH withdrawal group + positive control (Deanxit) group, and EtOH withdrawal group + PFE group). The changes of neuropsychological behaviors; hippocampal BDNF expression and CA1 neuronal density; and plasma corticotropin-releasing hormone (CRH), ACTH, and CORT levels were observed. It was found that depression-like behaviors reduced by EtOH exposure and increased by withdrawal under the 28-day EtOH exposure and 7-day withdrawal conditions. In addition, anxiety-like behaviors worsened by EtOH exposure and unchanged by withdrawal. Deanxit and PEF ameliorated such behaviors (vs. withdrawal group). Hippocampal BDNF expression was significantly downregulated by EtOH exposure and upregulated by withdrawal. Deanxit and PEF significantly upregulated the BDNF expression. The hippocampal CA1 neuronal density significantly decreased by EtOH exposure but unchanged by withdrawal and treatments. The plasma CRH, ACTH, and CORT levels show a significant enhancement by EtOH exposure and reduced by withdrawal. They were further reduced by Deanxit and PEF. The protective effects of PEF on EtOH chronic withdrawal mouse models were verified. The results of this study also indicated a complicated scenario of neuropsychological behaviors, hippocampal BDNF expression, and hypothalamic–pituitary–adrenal axis which are affected by the timing of EtOH exposure and withdrawal.

Early life thermal stress modulates hepatic expression of thermotolerance related genes and physiological responses in two rabbit breeds

There are few data about early thermal conditioning (TC) and its effect on later life in rabbits. Therefore, the present study aimed to investigate the impact of exposing two rabbit breeds to early age short-term heat stress (EA-STHS) on physiological parameters and hepatic expression levels of some genes. Rabbits from New Zealand White (NZW) and Baladi Black (BB) rabbit breeds were reared in a controlled environmental chamber (28 ± 2 °C and 40 ± 2% RH). At 42 days of age, rabbits from both breeds were equally divided into two groups; control (untreated) and heat exposed groups (kept at 36 ± 1 °C and 62% RH for 6 h). At 13 weeks of age, rabbits of all groups were re-exposed to acute heat stress (36 ± 1 °C and 62% RH for 6 h). At 13 weeks of age, plasma CORT, plasma MDA, and hepatic MDA had significantly lower levels in the rabbits from the two breeds subjected to EA-STHS than untreated control groups. plasma TAC and the relative hepatic expression of all the studied genes like Hsp70, HspA9, Hsp90α and UCP2 had significantly higher levels in EA-STHS treated NZW and BB rabbits compared with the control groups. In conclusion, the results suggest that EA-STHS has a long-lasting effect on the later life response to acute heat stress in NZW and BB breeds, as indicated by the hepatic expression profile of several genes, corticosterone, and antioxidant parameters. Additionally, each breed had characteristic patterns for the tested parameters at each time point and treatment. HIGHLIGHTS Rabbits are susceptible to thermal stress, which is associated with adverse effects on production and reproduction traits. Early-age thermal conditioning is one of the suggested protective treatments to reduce the heat stress adverse effects. Early age short-term thermal stress may induce thermotolerance ability to later time heat exposure in both rabbit breeds.

Hepatic expression responses of DNA methyltransferases, heat shock proteins, antioxidant enzymes, and NADPH 4 to early life thermal conditioning in broiler chickens

Early-life thermal conditioning (TC) in broiler chickens has long-lasting impacts on later life. Therefore, this study aimed to clarify the molecular mechanism by which TC impacts the hepatic expression heat shock proteins (hsps), antioxidant enzymes, NADPH oxidase 4 (NOX4), glucocorticoid receptor (GR), and DNA methyltransferases genes in broiler chicks at five weeks of age. Two hundred forty one-day-old male broiler chicks of Cobb 500 were allocated into four equal experimental groups. The first group was under the optimal brooding conditions (control), whereas the 2nd, 3rd, and 4th groups were exposed to TC at 39 ± 1 °C for six hours on the third-, fifth- or seventh-day post-hatch, respectively. At 35 days of age, all chicks of four experimental groups were subjected to heat challenge by exposure to 36 ± 1 °C for six hours. Results showed that broilers exposed to TC on the fifth-day post-hatch when exposed to acute heat stress at five weeks of age had the lowest plasma CORT level, the lowest expression (p < .05) for NOX4, GR, SOD, SOD2, and CAT among all groups. The same trend was observed for hsp70, hsp90A, hsp90B, hsp60, and hspA9. In conclusion, early thermal conditioning on the fifth-day post-hatch may improve thermotolerance by decreasing NOX4 and GR expressions, leading to reduced heat shock proteins and antioxidant enzyme gene expression subsequently reduced oxidative stress. Highlights Thermal conditioning is a promising approach to mitigate heat stress in broiler chicks. The optimal age to perform thermal conditioning is a controversial issue. Heat shock proteins gene expression and plasma corticosterone are good indicators for thermotolerance acquisition. Thermal conditioning on the fifth-day post-hatch reduced oxidative stress at five weeks of age.

Baseline corticosterone is associated with parental care in virgin Japanese quail (Coturnix japonica)

Glucocorticoids (GCs) are thought to impact reproductive success, and ultimately fitness. In this study we focus specifically on the relationship between GCs and parental care. Captive bred Japanese quail (Coturnix japonica) do not show spontaneous parental care behavior, however this behavior can be induced through a sensitization procedure. We investigated how the GC status of Japanese quail relates to parental care in animals of both sexes exposed or not to a chick sensitization treatment. To assess GC status, we obtained baseline plasma and feather cort samples, and used the HPA-axis function test to assess stress responsiveness by examining the response to a standardized stressor as well as negative feedback efficacy through dexamethasone injection. Next, birds were either exposed to chicks overnight in a small enclosure (sensitization treatment) or were enclosed but not exposed to chicks (control). The following morning, adult behaviors were filmed in the presence of a fresh set of chicks for 20 min. A final serum GC sample was obtained to assess if exposure to novel chicks was perceived as stressful. In control animals, baseline GCs were associated with increased total parental care duration and decreased latency to first parental care event. Interestingly, the opposite relationship was found in the sensitization group. Finally, exposure to novel chicks was not associated with an increase in corticosterone in either group. Overall it appears that baseline GCs are correlated with parental care in captive bred Japanese quail, and that the relationship changes direction depending on whether or not sensitization has occurred.

Sensitized corticosterone responses do not mediate the enhanced fear memories in chronically stressed rats

Following a stressful event, the hypothalamus-pituitary-adrenal axis mediates the release of the stress hormone cortisol (corticosterone in rodents; CORT). Elevated CORT binds to glucocorticoid receptors to mediate physiological responses including facilitating memory formation. Previous work from our laboratory demonstrated that male rats exposed to chronic stress demonstrate enhanced contextual fear memories and sensitized CORT responses to subsequent stress exposure; however, this is unknown in female rats. The experiments here tested whether chronic stress enhances fear memory formation in female rats and whether the sensitized CORT response in chronic stress rats contributes to their enhanced fear memory. Studies first examined CORT responses to contextual fear conditioning in male and female rats and examined whether chronic stress enhanced the formation of contextual fear memories 24 h later. Studies then used metyrapone, a CORT synthesis inhibitor, to investigate whether blockade of plasma CORT would eliminate the chronic stress-induced enhancement in contextual fear memory. Results show that female rats have greater CORT responses than males, and chronic stress sensitizes the CORT response to fear conditioning in both sexes. However, female rats do not show enhanced contextual fear memory following chronic stress. Chronically stressed male rats show greater memory acquisition and show greater contextual fear memory 24 h later following fear conditioning. Metyrapone dampens contextual fear memory in all rats but does not eliminate the enhancement in freezing behavior in chronic stress rats. Collectively, these studies indicate sensitized CORT responses in chronically stressed rats is likely not the mechanism by which chronic stress facilitates memory formation.

Sex-specific effects of the in ovo environment on early-life phenotypes in eiders

Maternal effects affect offspring phenotype and fitness. However, the roles of offspring sex-specific sensitivity to maternal glucocorticoids and sex-biased maternal investment remain unclear. It is also uncertain whether telomere length (a marker associated with lifespan) depends on early growth in a sex-specific manner. We assessed whether maternal traits including corticosterone (CORT; the main avian glucocorticoid) and in ovo growth rate are sex-specifically related to offspring CORT exposure, relative telomere length (RTL) and body condition in eiders (Somateria mollissima). We measured feather CORT (fCORT), RTL and body condition of newly hatched ducklings, and growth rate in ovo was expressed as tarsus length at hatching per incubation duration. Maternal traits included baseline plasma CORT, RTL, body condition and breeding experience. We found that fCORT was negatively associated with growth rate in daughters, while it showed a positive association in sons. Lower offspring fCORT was associated with higher maternal baseline plasma CORT, and fCORT was higher in larger clutches and in those hatching later. The RTL of daughters was negatively associated with maternal RTL, whereas that of males was nearly independent of maternal RTL. Higher fCORT in ovo was associated with longer RTL at hatching in both sexes. Duckling body condition was mainly explained by egg weight, and sons had a slightly lower body condition. Our correlational results suggest that maternal effects may have heterogeneous and even diametrically opposed effects between the sexes during early development. Our findings also challenge the view that prenatal CORT exposure is invariably associated with shorter telomeres.

Examining the Effects of Chronic Selenium Exposure on Traditionally Used Stress Parameters in Juvenile American Alligators (Alligator mississippiensis).

Environmental contaminants, such as the trace element selenium (Se), are a continuing concern to species worldwide due to their potential pathophysiological effects, including their influence on the stress response mediated through glucocorticoids (GCs; stress hormones). Environmental concentrations of Se are increasing due to anthropogenic activities, including the incomplete combustion of coal and subsequent disposal of coal combustion wastes. However, most studies examining how Se affects GCs have been focused on lower trophic organisms. The objectives of this study were to investigate the effects of long-term Se exposure on traditionally used stress parameters and to identify which of these parameters best indicate Se accumulation in liver and kidney of the American alligator (Alligator mississippiensis), a top trophic carnivore found in the southeastern United States and known to inhabit Se-containing areas. Alligators were divided into three dietary treatments and fed prey spiked with 1000 or 2000ppm of selenomethionine (SeMet) or deionized water (control treatment) for 7weeks. Following the 7-week treatment protocol, blood and tissue samples were obtained to measure plasma corticosterone (CORT; the main crocodilian GC), tail scute CORT, the ratio of peripheral blood heterophils (H) to lymphocytes (L) as H/L ratio, and body condition. To evaluate which parameter best indicated Se accumulation in the liver and kidney, principal component and discriminant analyses were performed. The only parameter significantly correlated with liver and kidney Se concentrations was scute CORT. Our results suggest that measurement of CORT in tail scutes compared with plasma CORT, H/L ratios, and body condition is the best indicator of Se-exposure and accumulation in crocodilians.