Stimulation Of Corticosterone Secretion Research Articles

Discovery of CRN04894: A Novel Potent Selective MC2R Antagonist.

A novel class of nonpeptide melanocortin type 2 receptor (MC2R) antagonists was discovered through modification of known nonpeptide MC4R ligands. Structure-activity relationship (SAR) studies led to the discovery of 17h (CRN04894), a highly potent and subtype-selective first-in-class MC2R antagonist, which demonstrated remarkable efficacy in a rat model of adrenocorticotrophic hormone (ACTH)-stimulated corticosterone secretion. Oral administration of 17h suppressed ACTH-stimulated corticosterone secretion in a dose-dependent manner at doses ≥3 mg/kg. With its satisfactory pharmaceutical properties, 17h was advanced to Phase 1 human clinical trials in healthy volunteers with the goal of moving into patient trials to evaluate CRN04894 for the treatment of ACTH-dependent diseases, including congenital adrenal hyperplasia (CAH) and Cushing's disease (CD).

Ascorbic Acid Protects Bone Marrow from Oxidative Stress and Transient Elevation of Corticosterone Caused by X-ray Exposure in Akr1a-Knockout Mice.

Bone marrow cells are the most sensitive to exposure to X-rays in the body and are selectively damaged even by doses that are generally considered permissive in other organs. Ascorbic acid (Asc) is a potent antioxidant that is reported to alleviate damages caused by X-ray exposure. However, rodents can synthesize Asc, which creates difficulties in rigorously assessing its effects in such laboratory animals. To address this issue, we employed mice with defects in their ability to synthesize Asc due to a genetic ablation of aldehyde reductase (Akr1a-KO). In this study, concentrations of white blood cells (WBCs) were decreased 3 days after exposure to X-rays at 2 Gy and then gradually recovered. At approximately one month, the recovery rate of WBCs was delayed in the Akr1a-KO mouse group, which was reversed via supplementation with Asc. Following exposure to X-rays, Asc levels decreased in plasma, bone marrow cells, and the liver during an early period, and then started to increase. X-ray exposure stimulated the pituitary gland to release adrenocorticotropic hormone (ACTH), which stimulated corticosterone secretion. Asc released from the liver, which was also stimulated by ACTH, appeared to be recruited to the bone marrow. Since corticosterone in high doses is injurious, these collective results imply that Asc protects bone marrow via its antioxidant capacity against ROS produced via exposure to X-rays and the cytotoxic action of transiently elevated corticosterone.

Fasting-activated ventrolateral medulla neurons regulate T cell homing and suppress autoimmune disease in mice.

Dietary fasting markedly influences the distribution and function of immune cells and exerts potent immunosuppressive effects. However, the mechanisms through which fasting regulates immunity remain obscure. Here we report that catecholaminergic (CA) neurons in the ventrolateral medulla (VLM) are activated during fasting in mice, and we demonstrate that the activity of these CA neurons impacts the distribution of T cells and the development of autoimmune disease in an experimental autoimmune encephalomyelitis (EAE) model. Ablation of VLM CA neurons largely reversed fasting-mediated T cell redistribution. Activation of these neurons drove T cell homing to bone marrow in a CXCR4/CXCL12 axis-dependent manner, which may be mediated by a neural circuit that stimulates corticosterone secretion. Similar to fasting, the continuous activation of VLM CA neurons suppressed T cell activation, proliferation, differentiation and cytokine production in autoimmune mouse models and substantially alleviated disease symptoms. Collectively, our study demonstrates neuronal control of inflammation and T cell distribution, suggesting a neural mechanism underlying fasting-mediated immune regulation.

Extracellular Nampt (eNampt/visfatin/PBEF) directly and indirectly stimulates ACTH and CCL2 protein secretion from isolated rat corticotropes.

Nicotinamide phosphoribosyltransferase (Nampt/visfatin/PBEF) acts both as an enzyme in the nicotinamide adenine dinucleotide (NAD) synthesis pathway as well as an extracellular hormone (eNampt). Among its effects, eNampt exerts potent pro-inflammatory effects. We have recently shown that, in rats, eNampt stimulates corticosterone secretion by acting through the pituitary rather than the hypothalamus. To investigate the mechanism of action of eNampt on the secretion of adrenocorticotropic hormone (ACTH) and chemokine (C-C motif) ligand 2 (CCL2), which are cytokines secreted by pituitary neuroendocrine tumors. The research was carried out on the AtT-20 murine cell line, primary rat pituitary cell culture, isolated pituitary corticotropes, and in vivo. The effects of the performed experiments were examined using the following methods: gene expression profiling using microarrays, quantitative polymerase chain reaction (qPCR) and enzyme-linked immunosorbent assay (ELISA). The results suggest that eNampt stimulates ACTH secretion from rat corticotropes both directly and indirectly. Indirect action most likely occurs through interleukin (IL)-6 secreted by folliculostellate cells of the pituitary gland. In isolated ACTH cells of the rat pituitary gland, eNampt stimulates the expression of genes involved in the immune response. Among them, the protein encoded by the CCL2 gene seems to also be involved in the regulation of corticotropin-releasing hormone (CRH)-dependent metabolism. Unlike rat corticotropes, murine AtT-20 corticotropic cells do not react to either eNampt or Fk866 (the inhibitor of Nampt enzymatic action). The eNampt stimulates the secretion of ACTH from rat corticotropes indirectly and directly, likely by stimulating IL-6 secretion from folliculostellate cells of the pituitary gland. This effect was not observed in the AtT-20 corticotropic cell cancer cell line.

The expression of mimecan in adrenal tissue plays a role in an organism's responses to stress.

Mimecan encodes a secretory protein that is secreted into the human serum as two mature proteins with molecular masses of 25 and 12 kDa. We found 12-kDa mimecan to be a novel satiety hormone mediated by the upregulation of the expression of interleukin (IL)-1β and IL-6 in the hypothalamus. Mimecan was found to be expressed in human pituitary corticotroph cells and was up-regulated by glucocorticoids, while the secretion of adrenocorticotropic hormone (ACTH) in pituitary corticotroph AtT-20 cells was induced by mimecan. However, the effects of mimecan in adrenal tissue on the hypothalamic–pituitary–adrenal (HPA) axis functions remain unknown. We demonstrated that the expression of mimecan in adrenal tissues is significantly downregulated by hypoglycemia and scalded stress. It was down-regulated by ACTH, but upregulated by glucocorticoids through in vivo and in vitro studies. We further found that 12-kDa mimecan fused protein increased the corticosterone secretion of adrenal cells in vivo and in vitro. Interestingly, compared to litter-mate mice, the diurnal rhythm of corticosterone secretion was disrupted under basal conditions, and the response to restraint stress was stronger in mimecan knockout mice. These findings suggest that mimecan stimulates corticosterone secretion in the adrenal tissues under basal conditions; however, the down-regulated expression of mimecan by increased ACTH secretion after stress in adrenal tissues might play a role in maintaining the homeostasis of an organism’s responses to stress.

Effects of Osthole on Progesterone Secretion in Chicken Preovulatory Follicles Granulosa Cells.

Simple SummaryProgesterone produced by granulosa cells regulates the diverse reproductive events in poultry. Osthole is a natural compound extracted from Cnidium. In this study, we confirmed Osthole up-regulated the progesterone secretion though elevating the expression of key proteins in the process of progesterone synthesis. These results indicate Osthole could be used in the pre-peak phase and (or) the peak phase to maximize the output of egg production in laying hens. Moreover, it provided a new idea that natural compounds may be the target library to screen the potential drugs used in poultry to increase the egg quality and yield.Osthole (Ost) is an active constituent of Cnidium monnieri (L.) Cusson which possesses anti-inflammatory and anti-oxidative properties. It also has estrogen-like activity and can stimulate corticosterone secretion. The present study was aimed to check the role of Ost on progesterone (P4) secretion in cultured granulosa cells obtained from hen preovulatory follicles. Different concentrations (5, 2.5, and 1.25 µg/mL) of Ost was added to granulosa cells for 6, 12, 18, and 24 h to investigate the level of progesterone secretions using enzyme linked immunosorbent assay (ELISA). The results showed that progesterone secretion was significantly increased in cells treated with Ost at 2.5 μg/mL. Also, qRT-PCR showed that mRNA expression of steroidogenic acute regulatory protein (StAR) was significantly up-regulated by Ost at 2.5 μg/mL concentration. Cytochrome P450 side-chain cleavage (P450scc) and 3β-hydroxysteroid dehydrogenase (3β-HSD) was significantly up-regulated by Ost. However, no significant differences were observed for the expression of proliferating cell nuclear antigen (PCNA). The protein expression of StAR, P450scc and 3β-HSD were significantly up-regulated by Ost treatment. The concentration of cyclic adenosine monophosphate (cAMP) and protein kinase A (PKA) in cell lysates showed no change with Ost treatment at 2.5 μg/mL by ELISA. An ROS kit showed non-significant difference in the level of reactive oxygen species (ROS). In conclusion, Ost treatment at a concentration of 2.5 μg/mL for 24 h had significantly up-regulated P4 secretion by elevating P450scc, 3β-HSD and StAR at both gene and protein level in granulosa cells obtained from hen preovulatory follicles.

Osthole, a coumadin analog from Cnidium monnieri (L.) Cusson, stimulates corticosterone secretion by increasing steroidogenic enzyme expression in mouse Y1 adrenocortical tumor cells

Ethnopharmacological relevanceOsthole is an O-methylated coumadin, which was isolated and purified from the seeds of Cnidium monnieri (L.) Cusson. Osthole is a commonly used traditional Chinese medicine to treat patients with Kidney-Yang deficiency patients, who exhibit clinical signs similar to those of glucocorticoid withdrawal. However, the mechanism of action of osthole is not fully understood. ObjectiveThis study was designed to reveal the effects of osthole on corticosterone production in mouse Y1 cell. Materials and methodsMouse Y1 adrenocortical cells were used to evaluate corticosterone production, which was quantified by enzyme-linked immunosorbent assay (ELISA) kits. Cell viability was tested using the MTT assay, and the mRNA and protein expression of genes encoding steroidogenic enzymes and transcription factors was monitored by quantitative real-time reverse-transcription polymerase chain reaction (qRT-PCR) and western blotting, respectively. ResultsOsthole stimulated corticosterone secretion from mouse Y1 cells in a dose- and time-dependent manner, and osthole enhanced the effect of dibutyryl-cAMP (Bu2cAMP) on corticosterone production. Further, osthole also increased StAR and CYP11B1 mRNA expression in a dose-dependent manner and enhanced the expression of transcription factors such as HSD3B1, FDX1, POR and RXRα as well as immediate early genes such as NR4A1. Moreover, osthole significantly increased SCARB1(SRB1) mRNA and StAR protein expression in the presence or absence of Bu2cAMP; these proteins are an important for the transport of the corticosteroid precursor cholesterol transport into mitochondria. ConclusionsOur results show that the promotion of corticosterone biosynthesis and secretion is a novel effect of osthole, suggesting that this agent can be utilized for the prevention and treatment of Kidney-Yang deficiency syndrome.

Environmentally relevant bouts of cooling stimulate corticosterone secretion in free-living eastern bluebird (Sialia sialis) nestlings: Potential links between maternal behavior and corticosterone exposure in offspring

In vertebrates, exposure to stressful stimuli or to elevated glucocorticoids early in development can contribute to phenotypic variation that may have significant fitness consequences. In species with altricial young, offspring may be partially buffered from elevations in glucocorticoids by a period of low glucocorticoid responsiveness to stressors coupled with high levels of parental care. Because altricial young depend heavily on their parents for warmth, parental brooding behavior could buffer offspring from glucocorticoid exposure associated with cooling. We studied eastern bluebirds (Sialia sialis) with two goals: (1) to determine whether an experimental drop in body temperature such as that which might occur when a brooding female is off the nest was sufficient to stimulate glucocorticoid secretion in young chicks, and (2) to examine the extent to which chicks experienced such bouts of cooling in the field. We subjected chicks to treatments simulating nest temperatures while females were brooding or absent from the nest. We also recorded chick surface temperatures and ambient temperatures at nests during the first week of the brood period. Reductions of surface temperature of less than 10°C significantly elevated corticosterone secretion in chicks as young as 5days old, and thermal and hormonal responses of chicks to cooling increased in an age-dependent manner. One quarter of broods experienced repeated, natural bouts of cooling of this magnitude or greater in the nest. Our data suggest that natural variations in maternal brooding patterns can result in differential exposure of offspring to glucocorticoids, and this may have important phenotypic consequences later in life.

Effects of Propylthiouracil on the Production of Aldosterone in Rat Zona Glomerulosa Cells

Propylthiouracil (PTU), an anti-thyroid drug, is widely used for the treatment in hyperthyroid patients. Previous studies indicate that thyroxine inhibit the spontaneous and adrenocorticotropin (ACTH)-stimulated corticosterone secretion by acting directly at adrenal glands via decrease cAMP production. It has also been shown that PTU suppresses corticosterone release by male rat zona fasciculata-reticularis cells. However, the direct effects and mechanisms of PTU on the aldosterone production in adrenal zona glomerulosa (ZG) cells are still unclear. ZG cells were prepared from adrenocortical tissues of male rats, and then challenged with or without angiotensin II (10^(-7), 10^(-6) M), ACTH (10^(-9) M), A23187 (10^(-5) M), cyclopiazonic acid (CPA, 10^(-5) M), forskolin (10^(-5) M), 8-Br-cAMP (10^(-5) M), trilostane (10^(-6) M, 3β-HSD inhibitor) or steroidogenic precursors (e.g. 10^(-6) M 25-OH-cholesterol and 10^(-7), 10^(-5) M corticosterone) at 37°C for 1 h. Our results showed that PTU (0-3 mM) dose-dependently decreased the aldosterone release in response to the above hormones, drugs and the steroidogenic precursors in vitro. PTU also decreased steroidogenic acute regulatory (StAR) protein expression, but did not alter the protein expression of P450 side chain cleavage enzyme (P450scc) during steroidogenesis of aldosterone. These results suggested that PTU has a direct inhibitory effect on aldosterone production via cAMP, and Ca^2+ down stream pathway and the steroidogenic enzymes activities including P450scc and aldosterone synthase, as well as StAR protein expression.

Effects of Propylthiouracil on the Production of Aldosterone in Rat Zona Glomerulosa Cells

Propylthiouracil (PTU), an anti-thyroid drug, is widely used for the treatment in hyperthyroid patients. Previous studies indicate that thyroxine inhibit the spontaneous and adrenocorticotropin (ACTH)-stimulated corticosterone secretion by acting directly at adrenal glands via decrease cAMP production. It has also been shown that PTU suppresses corticosterone release by male rat zona fasciculata-reticularis cells. However, the direct effects and mechanisms of PTU on the aldosterone production in adrenal zona glomerulosa (ZG) cells are still unclear. ZG cells were prepared from adrenocortical tissues of male rats, and then challenged with or without angiotensin II (10^(-7), 10^(-6) M), ACTH (10^(-9) M), A23187 (10^(-5) M), cyclopiazonic acid (CPA, 10^(-5) M), forskolin (10^(-5) M), 8-Br-cAMP (10^(-5) M), trilostane (10^(-6) M, 3β-HSD inhibitor) or steroidogenic precursors (e.g. 10^(-6) M 25-OH-cholesterol and 10^(-7), 10^(-5) M corticosterone) at 37°C for 1 h. Our results showed that PTU (0-3 mM) dose-dependently decreased the aldosterone release in response to the above hormones, drugs and the steroidogenic precursors in vitro. PTU also decreased steroidogenic acute regulatory (StAR) protein expression, but did not alter the protein expression of P450 side chain cleavage enzyme (P450scc) during steroidogenesis of aldosterone. These results suggested that PTU has a direct inhibitory effect on aldosterone production via cAMP, and Ca^2+ down stream pathway and the steroidogenic enzymes activities including P450scc and aldosterone synthase, as well as StAR protein expression.

Participation of endocannabinoids in rapid suppression of stress responses by glucocorticoids in neonates

In adult rodents, endocannabinoids (eCBs) regulate fast glucocorticoid (GC) feedback in the hypothalamus–pituitary adrenal (HPA) axis, acting as retrograde messengers that bind to cannabinoid receptors (CB1R) and inhibit glutamate release from presynaptic CRH neurons in the paraventricular nucleus of the hypothalamus (PVN). During the first two weeks of life, rat pups exhibit significant CRH and ACTH responses to stress although the adrenal GC output remains reduced. At the same time, pups also display increased sensitivity to GC feedback, but it is unclear whether eCBs play a role in mediating fast GC feedback in neonatal life. In our studies, we examined the role of eCBs in the rapid suppression of anoxia-induced ACTH release and determined whether eCB action could be modulated by the levels of circulating GCs present at the time of stress. PND8 pups were subjected to 3-min anoxia with AM251, a CB1R blocker, injected 30min prior to stress onset. The effects of either metyrapone (MET) (a steroidogenic 11beta-hydroxylase blocker) or methylprednisolone (PRED) (a synthetic GC) pretreatment on AM251 effect and the stress response were evaluated. Treatment with AM251 before stress onset tended to increase overall ACTH and CORT secretion, and also delayed the return to baseline ACTH. The AM251 effect on ACTH in PND8 pups was lost in MET-treated pups, who exhibited high basal and stimulated ACTH release and no CORT response to stress. Methylprednisolone suppressed ACTH stress responses although AM251 still delayed restoration of ACTH levels to the baseline. This suggests that the eCB effect on ACTH secretion in neonates is most evident when there is a dynamic fluctuation of corticosterone levels. Interestingly, AM251 increased basal and stimulated corticosterone secretion in all treatments including MET, suggestive of a direct action of CB1R blockade on adrenal steroidogenesis.

Neuropeptide W stimulates adrenocorticotrophic hormone release <i>via</i> corticotrophin-releasing factor but not <i>via</i> arginine vasopressin

Neuropeptide W (NPW) was isolated as an endogenous ligand for NPBWR1, an orphan G protein-coupled receptor localized in the rat brain, including the paraventricular nucleus. It has been reported that central administration of NPW stimulates corticosterone secretion in rats. We hypothesized that NPW activates the hypothalamic-pituitary-adrenal (HPA) axis via corticotrophin-releasing factor (CRF) and/or arginine vasopressin (AVP). NPW at 1 pM to 10 nM did not affect basal or ACTH-induced corticosterone release from dispersed rat adrenocortical cells, or basal and CRF-induced ACTH release from dispersed rat anterior pituitary cells. In conscious and unrestrained male rats, intravenous administration of 2.5 and 25 nmol NPW did not affect plasma ACTH levels. However, intracerebroventricular (icv) administration of 2.5 and 5.0 nmol NPW increased plasma ACTH levels in a dose-dependent manner at 15 min after stimulation (5.0 vs. 2.5 nmol NPW vs. vehicle: 1802 ± 349 vs. 1170 ± 204 vs. 151 ± 28 pg/mL, respectively, mean ± SEM). Pretreatment with astressin, a CRF receptor antagonist, inhibited the increase in plasma ACTH levels induced by icv administration of 2.5 nmol NPW at 15 min (453 ± 176 vs. 1532 ± 343 pg/mL, p<0.05) and at 30 min (564 ± 147 vs. 1214 ± 139 pg/mL, p<0.05) versus pretreatment with vehicle alone. However, pretreatment with [1-(β-mercapto-β, β-cyclopentamethylenepropionic acid), 2-(Ο-methyl)tyrosine]-arg-vasopressin, a V1a/V1b receptor antagonist, did not affect icv NPW-induced ACTH release at any time (p>0.05). In conclusion, we suggest that central NPW activates the HPA axis by activating hypothalamic CRF but not AVP.

Galanin enhances corticosterone secretion from dispersed rat adrenocortical cells through the activation of GAL-R1 and GAL-R2 receptors coupled to the adenylate cyclase-dependent signaling cascade

Galanin is a regulatory peptide, which acts via three subtypes of receptors, named GAL-R1, GAL-R2 and GAL-R3. Reverse transcription-polymerase chain reaction demonstrated the expression of GAL-R1 and GAL-R2, but not GAL-R3 mRNAs in dispersed rat adrenal zona fasciculata-reticularis (inner) cells. The immuno-blockade of GAL-R1 and GAL-R2, but not GAL-R3, decreased the binding of [3H]galanin to dispersed cells, a complete inhibition being obtained only by the simultaneous blockade of both receptor subtypes. Galanin stimulated corticosterone and cyclic-AMP release from dispersed inner rat adrenocortical cells, while inositol triphosphate production was not affected. Again these responses to galanin were reversed by both the GAL-R1 and GAL-R2, but not the GAL-R3 immuno-blockade. The adenylate cyclase inhibitor SQ-22536 and the protein kinase (PK) A inhibitor H-89 abolished the corticosterone response of dispersed cells to galanin, while the phospholipase C inhibitor U-73122 and the PKC inhibitor calphostin-C were ineffective. We conclude that rat inner adrenocortical cells express GAL-R1 and GAL-R2 as mRNA and protein, and galanin stimulates corticosterone secretion acting via these receptor subtypes which are both coupled to the adenylate cyclase/PKA-dependent signaling pathway.

Orexins modulate the growth of cultured rat adrenocortical cells, acting through type 1 and type 2 receptors coupled to the MAPK p42/p44- and p38-dependent cascades

Orexin A and B are hypothalamic peptides that act through two subtypes of receptors named OX1-R and OX2-R. The OX1-R almost exclusively binds orexin-A, whereas OX2-R is non-selective for both orexins. We previously found that rat adrenocortical cells express both orexin-receptor subtypes, and orexin-A stimulates corticosterone secretion from dispersed adrenocortical cells acting via the OX1-R. Here, we examined the possibility that orexins, acting through both their receptor subtypes, modulate the growth of adrenocortical cells. Reverse transcription-polymerase chain reaction showed that rat adrenocortical cells cultured in vitro for four days expressed OX1-R and OX2-R mRNAs. Orexin-A increased the proliferation rate (PR) of cultured cells, while orexin-B lowered it. Using selective antibodies, we demonstrated that OX1-R immuno-blockade reversed the proliferogenic action of orexin-A, causing a sizeable decrease in PR. In contrast, OX2-R immuno-blockade magnified the proliferogenic effect of orexin-A and annulled the antiproliferogenic action of orexin-B. The proliferogenic effect of orexin-A in the presence of OX2-R immuno-blockade was abrogated by the MAPK p42/p44 inhibitor PD-98059, while the antiproliferogenic effect of orexin-A in the presence of OX1-R immuno-blockade was annulled by the MAPK p38 inhibitor SB-203580. Neither inhibitor altered per se the basal PR of cultured cells. Taken together, our present findings allow us to conclude that i) orexins modulate the growth of rat adrenocortical cells cultured in vitro, by exerting both proliferogenic and antiproliferogenic effects, which are mediated by OX1-Rs and OX2-Rs, respectively; and ii) OX1-R and OX2-R growth effects involve the activation of the MAPK p42/p44 and p38 signaling cascades, respectively.

Adrenal phenotype in TPIT insufficient animals cannot be restored by short-term treatment with physiological doses of ACTH and N-POMC

Tpit is a positive regulator for late POMC cell differentiation. Accordingly, inactivation of the Tpit gene results in loss of POMC expressing cells in the pituitary while heterozygous mice (Tpit+/–) display a normal adrenal phenotype. Adrenal growth and function is dependent upon hormonal stimulation from the pituitary. While ACTH is a potent stimulator of adrenal steroidogenesis, N-terminal POMC peptides have been implicated to act as potent adrenal mitogens and suppressors of adrenal steroidogenesis. To dissect specific effects of ACTH and N-POMC(1–28) on adrenal function, both peptides were injected over 7 days in Tpit+/– and Tpit–/– mice. In addition, as a model of acute secondary adrenal insufficiency, another group of Tpit+/– mice was pretreated with dexamethasone (dex) over 6 days prior ACTH and N-POMC substitution. Adrenal weight, morphology, and steroid production were assessed. Sham treated Tpit–/– mice had lower adrenal weights (0.9±0.3mg) in comparison to dexa treated Tpit+/– (2.6±0.1mg, p=0.0006) and sham treated Tpit+/– animals (3.6±0.1mg, p<0.0001) with smaller cortical areas and a higher number of cells per HPF indicating cellular hypotrophy. In addition, morphological and immunohistochemical evaluation in Tpit–/– animals revealed a prominent outer zone composed of cells negative for steroidogenic enzymes and SF-1 which was not evident in dexa treated or sham treated Tpit+/– mice. Neither ACTH (at high physiological doses) nor N-POMC substitution had a significant effect on adrenal weight and morphology compared to sham treated animals from each genotype. Although RT-PCR and immunohistochemistry demonstrated expression of ACTH receptor and steroidogenic enzymes (SCC, 3βHSD, StAR) in Tpit–/– adrenals, ACTH treatment did not stimulate corticosterone secretion. Taken together, these results suggest that physiological levels of ACTH cannot restore adrenocortical morphology and function in Tpit–/– mice and treatment with N-POMC does not significantly affect adrenal growth or steroidogenesis in this particular experimental setting.

Endocrine and behavioral response to a decline in habitat quality: effects of pond drying on the slider turtle,Trachemys scripta

The effect of the simulated drying of a pond on the behavior and corticosterone secretion of Trachemys scripta was measured in a field situation. Slider turtles were held in experimental and control ponds (12 x 15 m) enclosed with a drift fence integrated with spring-triggered livetraps. The experimental pond water level was dropped 10 cm per day for 8 d, until water was completely drained. Slider turtles responded to the draining of the pond by the emigration of the majority (75%) of the experimental population. Emigrating turtles had significantly elevated corticosterone at Time 0 (blood sample within 10 min of handling=4.48 ng/mL+/-0.503SE) when compared with turtles captured in a control pond (Time 0=0.954 ng/mL+/-0.121SE), where conditions were held constant. Turtles emigrated during the final 72 hr of pond draining when ponds reached 30 cm depth and lower and water temperature was at least 30.8 degrees C or higher. Additionally, the effect of trapping using spring-activated livetraps was tested. Turtles held in livetraps (n=6) for 45-110 min showed a characteristic corticosterone response (Time 0=0.957 ng/mL+/-0.091SE; Time 30=2.85 ng/mL+/-0.131SE), indicating that this trapping technique alone does not stimulate corticosterone secretion. The findings of the study met our predictions that turtles would respond to the draining of the pond behaviorally by emigrating from the habitat concurrent with an elevated corticosterone concentration. This supports the view that corticosterone is involved in stress avoidance mechanisms that allow organisms to respond to environmental perturbations.

Regulation of hypoxia-induced release of corticotropin-releasing factor in the rat hypothalamus by norepinephrine

Corticotropin-releasing factor (CRF) peptide release was activated by hypoxia in the rat hypothalamus. The mechanisms, however, of the hypoxia-induced CRF release remains unclear. In this study, we demonstrated that the norepinephrine (NE) and its receptors in the paraventricular nucleus (PVN) mediated the CRF release in a simulated altitude hypoxia. When rats were exposed to 5 or 7 km altitude of hypoxia for a short or long term: (1) NE levels in the PVN and the CeA, using the HPLC analysis, were intensity and time course dependently increased, but the increase in the PVN were potential than in the CeA. Restraint-induced NE increase was much higher in both the PVN and the CeA, compared with hypoxia-induced response. (2) Hypoxia and restraint significantly enhanced CRF release in the ME and the PVN but not in the CeA, through RIA assay, which result in stimulating corticosterone secretion. (3) Hypoxia-induced CRF release was reversed by an injection of prazosin (icv), an α-1 adrenoceptor antagonist, while administration of yohimbine (icv), an α-2 receptor antagonist, facilitated further CRF release. These data suggested that hypoxia induced NE activation centrally, via α-1 and -2 receptors, leading to improving hypothalamic CRF release, which in turn stimulated pituitary and adrenal cortex. Restraint presented much potential action on NE activation than hypoxia.

Dietary Ethyl-eicosapentaenoic Acid but not Soybean Oil Reverses Central Interleukin-1-induced Changes in Behavior, Corticosterone and Immune Response in Rats

Omega (n)-3 and n-6 fatty acids are important membrane components of neurons and immune cells, and related to psychiatric and inflammatory diseases. Increased ratio of n-6/n-3 in the blood has been reported in depressed patients and in students following stress exposure. The n-3 fatty acid, eicosapentaenoic acid (ethyl-EPA) suppresses inflammation and has antidepressant properties. Interleukin (IL)-1β can stimulate corticosterone secretion, induce anxiety and stress-like behavior and inflammatory responses. This study was to evaluate the effect of diets enriched with coconut oil, ethyl-EPA and soybean oil on central IL-1β induced stress and anxiety-like behavior, induced changes in the concentration of prostaglandin (PG) E2 and corticosterone and the release of IL-10. Groups of rats were fed with either 5% coconut oil (as control diet), 0.2% EPA with 4.8% coconut oil or 1% EPA with 4% coconut oil and 5% soybean oil for 7 weeks. The central administration of IL-1β induced sickness, stress and anxiety-like behavior as indicated by a reduction in body weight, decreased time spent, and the number of entries, into the open arms of the elevated plus maze and decreased exploration and entry into the central zone of the “open field” apparatus. IL-1β also increased PGE2 and corticosterone concentrations and decreased the release of IL-10 from leucocytes. Food enriched with ethyl-EPA but not soybean oil, significantly attenuated most of these changes. These results demonstrate that ethyl-EPA has anti-inflammatory, anti-stress and anti-anxiety effects in rats.

The effects of acth, isoproterenol and Dexamethasone on the rat adrenal gland response to ethane dimethanesulphonate (Eds): A stereological study

Ethane dimethanesulphonate (EDS), an alkylating agent, caused marked atrophy of the adrenal cortex of adult male rats, in addition to its toxic effect on testicular Leydig cells. The aim of this work was to examine whether a 9-day treatment with ACTH (40 IU/kg/d), isoproterenol (120 mg/kg/d) or dexamethasone (0.25 mg/kg/d), which started 4 days prior to intraperitoneal administration of a single dose of EDS (75 mg/kg), affected the morphological changes in the adrenal cortex evoked by EDS alone. The animals were killed 15 days after EDS injection. Stereological analysis revealed that both ACTH and isoproterenol almost completely prevented cortical atrophy induced by EDS. They also considerably stimulated corticosterone secretion in EDS-injected animals. By contrast, in dexamethasone-suppressed rats, the deleterious effect of EDS on adrenocortical cells was augmented. The volume and cellularity of all cortical zones were reduced, but the remaining cells of the zona reticularis displayed considerable hypertrophy which was probably responsible for the maintenance of corticosterone secretion. These results clearly demonstrate that both ACTH and b adrenoceptor stimulation have protective action against the toxic effects of EDS on rat adrenal cortex, whereas dexamethasone exerts an opposite influence.

Expression of CRHR1 and CRHR2 in mouse pituitary and adrenal gland: implications for HPA system regulation.

Deficiency of corticotropin-releasing hormone receptor I (CRHR1) reduces anxiety-related behavior in mice and severely impairs the stress response of the hypothalamic-pituitary-adrenocortical (HPA) system. Most recently, we could show that severe emotional stressors induce a significant rise in plasma ACTH even in mice deficient for the CRHR1 (Crhr1-1-) which is, however, not accompanied by an increase in plasma corticosterone concentration, suggesting that CRHR1 might be directly involved in the regulation of adrenal corticosterone release. We therefore used the Crhr1-1- mouse model to clarify the potential role of adrenal CRHR1 in the regulation of the HPA system and, in particular, of corticosterone secretion. In Crhr1-/- mice, intravenous ACTH administration failed to stimulate corticosterone secretion despite a significant upregulation of ACTH receptor mRNA levels in the adrenal cortex of these mutants. Further, by means of RT-PCR and in situ hybridization analyses, we could provide first evidence that both CRHR1 and CRHR2 are expressed in the mouse pituitary and adrenal cortex. Stimulation of pituitary CRHR2 does not induce ACTH secretion either in vitro or in vivo. Our data strongly suggest that CRHR1 plays a crucial role in the release of corticosterone from the adrenal cortex, independently of pituitary function. The existence of an intra-adrenal CRH/CRHR1 regulatory system which contributes to the corticosteroid secretory activity adds to the complexity of HPA system regulation and stress hormone homeostasis.