Specific Corticotropin-releasing Hormone Receptor Research Articles

A CRHR1 antagonist prevents synaptic loss and memory deficits in a trauma-induced delirium-like syndrome

Older patients with severe physical trauma are at high risk of developing neuropsychiatric syndromes with global impairment of cognition, attention, and consciousness. We employed a thoracic trauma (TxT) mouse model and thoroughly analyzed age-dependent spatial and temporal posttraumatic alterations in the central nervous system. Up to 5 days after trauma, we observed a transient 50% decrease in the number of excitatory synapses specifically in hippocampal pyramidal neurons accompanied by alterations in attention and motor activity and disruption of contextual memory consolidation. In parallel, hippocampal corticotropin-releasing hormone (CRH) expression was highly upregulated, and brain-derived neurotrophic factor (BDNF) levels were significantly reduced. In vitro experiments revealed that CRH application induced neuronal autophagy with rapid lysosomal degradation of BDNF via the NF-κB pathway. The subsequent synaptic loss was rescued by BDNF as well as by specific NF-κB and CRH receptor 1 (CRHR1) antagonists. In vivo, the chronic application of a CRHR1 antagonist after TxT resulted in reversal of the observed histological, molecular, and behavioral alterations. The data suggest that neuropsychiatric syndromes (i.e., delirium) after peripheral trauma might be at least in part due to the activation of the hippocampal CRH/NF-κB/BDNF pathway, which results in a dramatic loss of synaptic contacts. The successful rescue by stress hormone receptor antagonists should encourage clinical trials focusing on trauma-induced delirium and/or other posttraumatic syndromes.

MiR-34b attenuates trauma-induced anxiety-like behavior by targeting CRHR1.

Exposure to trauma is a potential contributor to anxiety; however, the molecular mechanisms responsible for trauma-induced anxiety require further clarification. In this study, in an aim to explore these mechanisms, we observed the changes in the hypothalamic pituitary adrenal (HPA) axis using a radioimmunoassay and the changes in anxiety-like behavior using the open field test and elevated plus maze test in a rat model following intervention with NBI-27914, a specific corticotropin-releasing hormone receptor 1 (CRHR1) antagonist. CRHR1 was found to be involved in trauma-induced anxiety. We then applied bioinformatic analysis to screen microRNAs (miRNAs or miRs) that target CRHR1, and miR-34b was determined to negatively regulate CRHR1 mRNA in primary hypothalamic neurons. The overexpression of miR-34b in the paraventricular nucleus (PVN) by a miRNA agomir using a drug delivery system decreased the hyperactivity of the HPA axis and anxiety-like behavior. Overall, the involvement of the HPA axis in trauma-induced anxiety was demonstrated, and trauma-induced anxiety was attenuated by decreasing the hyperactivity of the HPA axis via miR-34b by targeting CRHR1.

CRH-R1 and CRH-R2 differentially modulate dendritic outgrowth of hippocampal neurons

Corticotropin-releasing hormone (CRH) has been implicated to be involved in the development of dendrites in brain. In the present study, we examined the effect of CRH on dendrite outgrowth in primary cultured hippocampal neurons and defined the specific CRH receptor subtype involved. Treatment of neurons with increasing concentration of CRH resulted in an increase in the total dendritic branch length (TDBL) of neurons compared with untreated neurons over 2-4days period of treatment. These effects can be reversed by the specific CRH-R1 antagonist antalarmin but not by the CRH-R2 antagonist astressin 2B. Treatment of neurons with urocortin II, the exclusive CRH-R2 agonist, significantly decreased TDBL of the cultured neurons. These effects can be reversed by the CRH-R2 antagonist astressin 2B. Our results suggest that CRH-R1 and CRH-R2 differentially modulate the dendritic growth of hippocampal neurons in culture.

The CRH-R1 receptor mediates luteinizing hormone, prolactin, corticosterone and progesterone secretion induced by restraint stress in estrogen-primed rats

Acute stress has been shown to modify hypothalamus–pituitary–gonadal (HPG) axis activity. Corticotropin-releasing hormone (CRH), the principal regulator of the hypothalamus–pituitary–adrenal (HPA) axis, has been implicated as a mediator of stress-induced effects on the reproductive axis. The role of the specific CRH receptor subtypes in this response is not completely understood. In the current study, we investigated the role of the CRH-R1 receptor on luteinizing hormone (LH), follicle-stimulating hormone (FSH), prolactin (PRL), progesterone (P) and corticosterone (CT) secretion in stress-induced responses under the influence of estrogen (E2). Estrogen-primed ovariectomized rats (estradiol cypionate, 10μg sc) received an i.v. administration of antalarmin (0.1 or 1mg/kg), a selective CRH-R1 antagonist, or vehicle before restraint stress for 40min. Seven blood samples were collected from two experimental groups (one from 10:00h to 14:00h and the other from 10:00h to 18:00h). An increase of plasma LH induced by restraint acute-stress was followed by alteration of the secretion pattern in the estrogen-induced afternoon surge. In a similar manner, we observed a suppression of the afternoon surge in plasma FSH, a delay of E2-induced PRL secretion, and an increase in plasma P and CT. Antalarmin attenuated stress-induce LH increase, decreased CT and P secretion and blocked the stress effects on PRL secretion. These findings suggest that CRH-R1 mediates, at least in part, the restraint stress effects on the HPA, PRL, and reproductive axes.

The anorexigenic effect of cholecystokinin octapeptide in a goldfish model is mediated by the vagal afferent and subsequently through the melanocortin- and corticotropin-releasing hormone-signaling pathways

We have been extensively investigating the mechanisms by which neuropeptides regulate feeding behavior by using a goldfish ( Carassius auratus) model. In this species, the anorexigenic action of melanocortin peptide is centrally mediated via the corticotropin-releasing hormone (CRH)/CRH receptor neuronal system, whereas sulfated cholecystokinin octapeptide (CCK-8s) is involved in the appetite regulation as a peripheral anorexigenic factor. The aim of the present study was to identify the mechanism of the anorexigenic effect of peripherally injected CCK-8s, which has not yet been identified in goldfish. Co-administration of capsaicin, a neurotoxin that destroys primary sensory afferents, at 100 nmol/g BW, blocked the anorexigenic action of intraperitoneally injected CCK-8s (100 pmol/g BW), whereas the anorexigenic action of intracerebroventricularly injected CCK-8s (5 pmol/g BW) was not blocked by co-administration of capsaicin. Pre-treatment with a specific CRH receptor antagonist, α-helical CRH (9–41), attenuated the anorexigenic action of CCK-8s. The expression level of CRH mRNA in the diencephalic tissue of the CCK-8s-injected group was not changed, but the level of proopiomelanocortin mRNA was significantly increased at 1 h after treatment. Therefore, we have identified for the first time that the reduction of appetite induced by peripherally injected CCK-8s in goldfish appears to be mediated by the vagal afferent and subsequently through the melanocortin- and corticotropin-releasing hormone-signaling pathways.

Possible Actions of Corticotropin-Releasing Hormone in Regulating Porcine Corpus Luteum Function

The objective of the present study was to determine whether corticotropin-releasing hormone (CRH) influences porcine corpus luteum function. The gene expressions of CRH receptors (CRH-R) were determined in the CLs of Chinese Meishan pigs during the estrous cycle. The effects of CRH on progesterone (P), estradiol-17β (E) and prostaglandin (PG) F(2α) secretion by cultured luteal cells were also investigated. Messenger RNAs of the CRH-R were clearly expressed in the CL throughout the estrous cycle, and the mRNA level was higher at the regressed stage than at the other stages (P<0.05). When the cultured luteal cells obtained from the mid-luteal stage CL (days 8-11) were exposed to CRH (50-5000 ng/ml), P secretion by the cells was significantly reduced at the highest dose (P<0.05), whereas CRH had no effect on E and PGF(2α) secretion by the cells. The overall results suggest that CRH inhibits local P production from luteal cells via its specific CRH-R, implying that CRH plays some roles in regulating porcine CL function during the estrous cycle, especially in the period of luteolysis.

Corticotropin-Releasing Hormone Receptor 1 Antagonist Blocks Brain–Gut Activation Induced by Colonic Distention in Rats

The corticotropin-releasing hormone receptor 1 mediates stress-induced changes in colonic motor activity and emotion. We tested the hypothesis that pretreatment with JTC-017, a specific corticotropin-releasing hormone receptor 1 antagonist, blocks colorectal distention-induced hippocampal noradrenaline release and visceral perception in rats. We also investigated whether pretreatment with JTC-017 blocks acute or chronic colorectal distention-induced adrenocorticotropic hormone release, anxiety, and stress-induced changes in colonic motility. Rats were pretreated intrahippocampally with alpha-helical corticotropin-releasing hormone (1.25 microg/kg; vehicle), a nonspecific corticotropin-releasing hormone receptor antagonist, or intraperitoneally with JTC-017 (10 mg/kg). Hippocampal noradrenaline release after microdialysis and the frequency of abdominal contractions were measured in response to acute colorectal distention. Plasma adrenocorticotropic hormone levels, anxiety-related behavior, and stress-induced changes in colonic motility were evaluated after acute or chronic colorectal distention followed by exposure to an elevated plus maze. Administration of alpha-helical corticotropin-releasing hormone or JTC-017 significantly attenuated hippocampal noradrenaline release and reduced the frequency of abdominal contractions induced by acute distention. In addition, JTC-017 significantly reduced plasma adrenocorticotropic hormone and anxiety after acute distention. After chronic distention, changes in plasma adrenocorticotropic hormone and anxiety were not significant because of habituation. In contrast, a significant increase in fecal pellet output during the elevated plus maze was observed after chronic distention. This increase in fecal pellet output was blocked by pretreatment with JTC-017. Our results suggest that JTC-017, a specific corticotropin-releasing hormone receptor 1 antagonist, attenuates hippocampal noradrenaline release, visceral perception, adrenocorticotropic hormone release, and anxiety after acute colorectal distention in rats. In addition, JTC-017 blocks stress-induced changes in colonic motility after chronic colorectal distention in rats.

Maternal and Fetal Hypothalamic‐Pituitary‐Adrenal Axes During Pregnancy and Postpartum

The principal modulators of the hypothalamic-pituitary-adrenal (HPA) axis are corticotropin-releasing hormone (CRH) and arginine-vasopressin (AVP). Corticotropin-releasing hormone is not exclusively produced in the hypothalamus. Its presence has been demonstrated at peripheral inflammatory sites. Ovulation and luteolysis bear characteristics of an aseptic inflammation. CRH was found in the theca and stromal cells as well as in cells of the corpora lutea of human and rat ovaries. The cytoplasm of the glandular epithelial cells of the endometrium has been shown to contain CRH and the myometrium contains specific CRH receptors. It has been suggested that CRH of fetal and maternal origin regulates FasL production, thus affecting the invasion (implantation) process through a local auto-paracrine regulatory loop involving the cytotrophoblast cells. Thus, the latter may regulate their own apoptosis. During pregnancy, the plasma level of circulating maternal immunoreactive CRH increases exponentially from the first trimester of gestation due to the CRH production in the placenta, decidua, and fetal membranes. The presence in plasma and amniotic fluid of a CRH-binding protein (CRHbp) that reduces the bioactivity of circulating CRH by binding is unique to humans. Maternal pituitary ACTH secretion and plasma ACTH levels rise during pregnancy-though remaining within normal limits-paralleling the rise of plasma cortisol levels. The maternal adrenal glands during pregnancy gradually become hypertrophic. Pregnancy is a transient, but physiologic, period of hypercortisolism. The diurnal variation of plasma cortisol levels is maintained in pregnancy, probably due to the secretion of AVP from the parvicellular paraventricular nuclei. CRH is detected in the fetal hypothalamus as early as the 12th week of gestation. CRH levels in fetal plasma are 50% less than in maternal plasma. The circulating fetal CRH is almost exclusively of placental origin. The placenta secretes CRH at a slower rate in the fetal compartment. AVP is detected in some neurons of the fetal hypothalamus together with CRH. AVP is usually detectable in the human fetal neurohypophysis at 11 to 12 weeks gestation and increases over 1000-fold over the next 12 to 16 weeks. The role of fetal AVP is unclear. Labor appears to be a stimulus for AVP release by the fetus. The processing of POMC differs in the anterior and intermediate lobes of the fetal pituitary gland. Corticotropin (ACTH) is detectable by radioimmunoassay in fetal plasma at 12 weeks gestation. Concentrations are higher before 34 weeks gestation, with a significant fall in late gestation. The human fetal adrenal is enormous relative to that of the adult organ. Adrenal steroid synthesis is increased in the fetus. The major steroid produced by the fetal adrenal zone is sulfoconjugated dehydroepiandrosterone (DHEAS). The majority of cortisol present in the fetal circulation appears to be of maternal origin, at least in the nonhuman primate. The fetal adrenal uses the large amounts of progesterone supplied by the placenta to make cortisol. Another source of cortisol for the fetus is the amniotic fluid where cortisol converted from cortisone by the choriodecidua, is found. In humans, maternal plasma CRH, ACTH, and cortisol levels increase during normal labor and drop at about four days postpartum; however, maternal ACTH and cortisol levels at this stage are not correlated. In sheep, placental CRH stimulates the fetal production of ACTH, which in turn leads to a surge of fetal cortisol secretion that precipitates parturition. The 10-day-long intravenous administration of antalarmin, a CRH receptor antagonist, significantly prolonged gestation compared to the control group of animals. Thus, CRH receptor antagonism in the fetus can also delay parturition. The HPA axis during the postpartum period gradually recovers from its activated state during pregnancy. The adrenals are mildly suppressed in a way analogous to postcure Cushing's syndrome. Provocation testing has shown that hypothalamic CRH secretion is transiently suppriently suppressed at three and six weeks postpartum, normalizing at 12 weeks.

The role of CRH in behavioral responses to stress

Corticotropin-releasing hormone (CRH) and urocortin in the central nervous system affect behavior and can enhance behavioral responses to stressors. The action of CRH-related peptides is mediated through multiple receptors that differ markedly in their pharmacological profiles and anatomical distribution. Comparative pharmacology of CRH receptor agonists suggests that CRH, urocortin, sauvagine and urotensin consistently mimic, and CRH receptor antagonists consistently lessen, functional consequences of stressor exposure. Recently, important advances have been made in understanding the CRH system and its role in behavioral responses to stress by the development of specific CRH receptor antagonists, application of antisense oligonucleotides and development of transgenic mice lacking peptides and functional receptors. This review summarizes recent findings with respect to components of the CRH system and their role in stress-induced behavioral responses.

Pituitary CRH Receptor Blockade Reduces Waking in the Rat

We have previously hypothesized that corticotropin-releasing hormone (CRH) is involved in the regulation of physiological waking. Central administration of CRH receptor antagonists reduces spontaneous waking in the rat. Some of the responses to central administration of CRH receptor antagonists may be mediated by mechanisms involving the hypothalamic–pituitary–adrenal axis, either by direct actions on the hypothalamus or by actions at the level of the pituitary due to leakage of the antagonists from the cerebrospinal fluid to blood. To further clarify the role of the hypothalamic–pituitary–adrenal axis as a mediator of responses to CRH receptor blockade, we administered intravenously into freely behaving rats in their home recording cages two specific CRH receptor antagonists, astressin or α-helical CRH 9–41, and determined subsequent changes in waking and sleep. Our results indicate that both antagonists reduce spontaneous waking, but with different time courses. Astressin, a potent antagonist of pituitary CRH receptors, reduces waking during postinjection hours 9–10, whereas high doses of α-helical CRH 9–41 reduce waking only during the first postinjection hour. These results indicate that some effects of CRH on sleep–wake behavior may be meditated by pituitary CRH receptors.

Evidence that corticotropin-releasing hormone acts as a growth hormone-releasing factor in a primitive teleost, the European eel (Anguilla anguilla).

The inhibitory control of growth hormone (GH) release by somatostatin (SRIH) has been conserved throughout vertebrate evolution. In contrast, the neuropeptides involved in the stimulatory control of GH vary according to species and/or physiological situations. We investigated the direct pituitary regulation of GH release in a primitive teleost, the European eel (Anguilla anguilla L.) at the juvenile stage. Short-term serum-free primary cultures of dispersed pituitary cells were used, and GH release was measured by an homologous radioimmunoassay. Whereas growth hormone-releasing hormone (GHRH), gonadotropin-releasing hormone (GnRH), thyrotropin-releasing hormone (TRH), neuropeptide Y (NPY) and cholecystokinin (CCK) failed to induce any change in GH release, corticotropin-releasing hormone (CRH) dose-dependently stimulated GH release with a significant effect at 1 nM and a maximal effect (> or =400% of controls at 24 h) at 100 nM. In agreement with our previous studies, PACAP also stimulated GH release but its maximal effect was lower than that of CRH. Proopiomelanocortin (POMC)-peptides, corticotropin (ACTH), melanotropin (alpha-MSH), beta-endorphin) had no effect on GH release, at any dose tested (0.1-1000 nM), indicating that the stimulatory effect of CRH on GH release by somatotrophs was not mediated by CRH-induced release of POMC-peptides from corticotrophs and melanotrophs. The CRH antagonist, alpha-helical CRH(9-41), significantly inhibited the stimulatory effect of CRH on GH release, suggesting the implication of specific CRH receptors related to mammalian ones. The stimulatory effect of CRH on GH release was reduced after 24 h of incubation, indicating a desensitization. In contrast, no desensitization to the inhibitory effect of SRIH was observed. SRIH inhibited CRH action in a dose-dependent manner. The effect of SRIH was overriding, 1 nM SRIH being able to abolish the effect of 1000 nM CRH. In conclusion, in the eel, CRH stimulates GH release directly at the pituitary cell level. GH and cortisol secretions could interact in controlling several physiological functions such as metabolism and ion exchange. This study suggests that CRH may have played an important early role in vertebrates co-ordinating the activation of various endocrine axes involved in metamorphosis, osmoregulation, stress and fasting. The stimulatory role of CRH on GH release may have been partially conserved during evolution, as it is found in some human physio-pathological situations such as stress, fasting and depression.

Effect of intracerebroventricular administration of alpha-helical CRH (9-41) on the sleep/waking cycle in rats under normal conditions or after subjection to an acute stressful stimulus.

It has been shown in a previous study that specific lesioning of the noradrenergic system of the locus coeruleus abolished the sleep increase induced by immobilization stress. Given the fact that brain corticotropin-releasing hormone (CRH) acts as a neurotransmitter in the locus coeruleus under stress conditions, the present study was designed to investigate the involvement of CRH in the sleep increase seen after immobilization stress and on the spontaneous wake/sleep cycle. One hundred micrograms of the specific CRH receptor antagonist alpha-helical CRH (9-41), or vehicle alone was injected into the right lateral ventricle 30 min either before subjecting the animals to immobilization stress or before the spontaneous sleep-waking recordings onset. A single intracerebroventricular (i.c.v.) injection of alpha-helical CRH (9-41) had no effect on spontaneous paradoxical sleep but abolished the stress-induced increase, while wakefulness and slow-wave sleep were unchanged under both normal and stressful conditions. We therefore report that the involvement of endogenous CRH in the paradoxical sleep mechanism is dependent on the environmental conditions and suggest that, while the paradoxical sleep increase induced by immobilization stress may be mediated by endogenous corticotropin-releasing hormone, other mechanisms, either CRH-independent or situated at a distance from antagonist activity, may be involved in spontaneous paradoxical sleep. These results show, for the first time, that endogenous CRH may be involved in sleep-waking mechanisms only under stressful conditions and, in particular, as a fundamental component of the paradoxical sleep increase.

Identification of a novel murine receptor for corticotropin-releasing hormone expressed in the heart.

Corticotropin-releasing hormone (CRH) is the principal regulator of the stress response. CRH stimulates production of ACTH via specific CRH receptors located on pituitary corticotropes. In addition to pituitary and central nervous system effects, peripheral effects of CRH have been observed involving the immune and cardiovascular systems. Specific CRH binding studies in several peripheral organs, as well as functional studies, have implied the existence of peripheral CRH receptors. Although a pituitary/brain CRH receptor has recently been identified, it is expressed at very low levels in peripheral sites where CRH effects have been observed. We report here the identification of a novel murine CRH receptor that is highly expressed in the heart. The newly cloned CRH receptor cDNA (CRH-R2) was isolated from a mouse heart cDNA library and encodes a 430-amino acid protein containing seven putative transmembrane domains characteristic of G protein-coupled receptors. CRH-R2 is 69% identical with the previously identified murine pituitary CRH receptor and is encoded by a distinct gene. In addition to a high level of expression in the heart, weak expression was also observed in the brain and lungs. Functional studies using CRH-R2-transfected cells indicate that CRH and the CRH-related amphibian peptide, sauvagine, bind with high affinity to CRH-R2 and stimulate intracellular accumulation of cAMP.(ABSTRACT TRUNCATED AT 250 WORDS)

G protein-coupled corticotropin-releasing hormone receptors in rat retina

The presence of corticotropin-releasing hormone (CRH) receptors in rat retinal membranes was investigated by using [ 125I-Tyr o]-ovine CRH ([ 125I]oCRH) as radioligand. The receptor binding was rapid, reversible, saturable and specific. The [ 125I]oCRH binding was completely displaced by different CRH-related peptides with a rank order of potency similar to that displayed in stimulating rat retinal adenylyl cyclase activity. Two populations of binding sites were detected: one with high affinity ( K d = 1.7 nM) and the other with low-affinity ( K d = 130 nM). The GTP analogue guanosine 5′- O-(3′-thiotriphosphate) reduced the high-affinity binding and increased the relative proportion of sites with low-affinity. Incubation of rat retinal membranes with the RM/1 antibody, which recognizes the carboxyl-terminus of the α subunit of the G protein Gs, prevented the CRH stimulation of adenylyl cyclase. In immunoblots, the RM/1 antibody recognized an immunoreactive protein band of 45 kDa and a protein with a similar electrophoretic mobility was ADP-ribosylated by cholera toxin. These data provide evidence for the presence of specific CRH receptors in rat retina and contribute to define the CRH signalling system in this tissue.

Coupling of corticotropin-releasing hormone receptors to adenylyl cyclase in human Y-79 retinoblastoma cells.

In human Y-79 retinoblastoma cells, corticotropin-releasing hormone (CRH) stimulates adenylyl cyclase activity and increases cyclic AMP accumulation. Different CRH analogues mimic the CRH stimulation of adenylyl cyclase and show similar sensitivity to the CRH receptor antagonist alpha-helical CRH9-41. Vasoactive intestinal peptide (VIP) also increases the enzyme activity but less potently than CRH, and its effect is counteracted by the VIP receptor antagonist [D-p-Cl-Phe6,Leu17]VIP. The VIP antagonist does not affect the response to CRH. The CRH-stimulated adenylyl cyclase activity is amplified by Mg2+, is inhibited by submicromolar concentrations of Ca2+, and requires GTP. Moreover, the CRH stimulation is reduced by pretreatment of cells with cholera toxin and by incubation of membranes with the RM/1 antibody, which recognizes the C-terminus of the alpha subunit of Gs. In immunoblots, the RM/1 antibody identifies a doublet of 45 and 52 kDa. Two proteins of similar molecular weights are ADP-ribosylated by cholera toxin. These data demonstrate that in human Y-79 retinoblastoma cells, specific CRH receptors stimulate cyclic AMP formation by interacting with Gs and by affecting a Ca(2+)-inhibitable form of adenylyl cyclase.