Lateral Hypothalamus Corticotropin Releasing Hormone Receptor-1 Inhibition Modulates Stress- Induced Anxiety Behavior

Stress is a reaction to unwanted events disturbing body homeostasis which influences its pathways and target areas. Stress affects the brain through the lateral hypothalamic area (LHA) orexinergic system that mediates the effect of corticotropin-releasing hormone (CRH) through CRH receptor type 1 (CRHr1). Therefore, this study explores the outcome of stress exposure on anxiety development and the involvement of the LHA through LHA-CRHr1. Male Wistar rats (220-250g) implanted with a cannula in either side of the LHA received acute or chronic stress. Subsequently, exploratory behavior and anxiety was examined using the open field (OF) and elevated plus maze (EPM), respectively. Prior to sacrifice, the cerebrospinal fluid (CSF) and the blood were sampled. Nissl stain was performed on fixed brain tissues. Acute stress resulted in a decrease of exploration in the OF and an increase of anxiety in the EPM. LHA-CRHr1 inhibition reversed the variables to increase the exploration and decrease the anxiety. In contrast, chronic stress did not show any effect on the anxiety-related behaviors. Chronic stress decreased the cell population in the LHA, which was prevented by the CRHr1 inhibition. However, the CRHr1 inhibition was unable to reverse the chronic stress increase of the CSF orexin level. Furthermore, both acute and chronic stresses increased the plasma corticosterone level and only the CRHr1 inhibition impeded the effect. Our results recognize LHA-CRHr1 as a capable candidate modulating acute stress-induced anxiety development and chronic stress-induced changes in the cellular population of the region.

Orexin A Enhances Pro-Opiomelanocortin Transcription Regulated by BMP-4 in Mouse Corticotrope AtT20 Cells

Orexin is expressed mainly in the hypothalamus and is known to activate the hypothalamic–pituitary–adrenal (HPA) axis that is involved in various stress responses and its resilience. However, the effects of orexin on the endocrine function of pituitary corticotrope cells remain unclear. In this study, we investigated the roles of orexin A in pro-opiomelanocortin (POMC) transcription using mouse corticotrope AtT20 cells, focusing on the bone morphogenetic protein (BMP) system expressed in the pituitary. Regarding the receptors for orexin, type 2 (OXR2) rather than type 1 (OX1R) receptor mRNA was predominantly expressed in AtT20 cells. It was found that orexin A treatment enhanced POMC expression, induced by corticotropin-releasing hormone (CRH) stimulation through upregulation of CRH receptor type-1 (CRHR1). Orexin A had no direct effect on the POMC transcription suppressed by BMP-4 treatment, whereas it suppressed Smad1/5/9 phosphorylation and Id-1 mRNA expression induced by BMP-4. It was further revealed that orexin A had no significant effect on the expression levels of type I and II BMP receptors but upregulated inhibitory Smad6/7 mRNA and protein levels in AtT20 cells. The results demonstrated that orexin A upregulated CRHR signaling and downregulated BMP-Smad signaling, leading to an enhancement of POMC transcription by corticotrope cells.

Urocortins exhibit differential effects on PGE2 and PGF2α output via CRHR2 in human myometrium

Urocortins (UCNs), belonging to corticotropin-releasing hormone (CRH) family, exert their function via CRH receptor type 1(CRHR1) and 2 (CRHR2). Our previous studies have demonstrated that CRH acts on CRHR1 to potentiate prostaglandin (PG) output induced by inflammatory stimuli in myometrial cells. In the present study, we sought to investigate the effects of UCNs on prostaglandin (PG) output via CRHR2 in cultured human uterine smooth muscle cells (HUSMCs) from human term myometrium. We found that UCN and UCN3 treatment promoted PGE2 and PGF2α secretion in a dose-dependent manner. In contrast, UCN2 dose-dependently inhibited PGE2 and PGF2α secretion. Their effects could be reversed by CRHR2 antagonist and CRHR2 siRNA. Mechanically, we showed that UCN and UCN3 suppressed cAMP production and led to Gi activation, while UCN2 promoted cAMP production and activated Gs signaling. Further, UCN and UCN3 could activate NF-κB and MAPK signaling pathways. These effects were dependent on Gi signaling. In contrast, UCN did not activate MAPK and NF-κB signaling. UCN and UCN3 stimulation of PG secretion was dependent on Gi/adenylyl cyclase (AC)/cAMP, NF-κB and MAPK signaling pathways, while UCN2 suppression of PG output was through Gs/AC/cAMP signaling pathways. Our data suggest that UCN, UCN2 and UCN3 can finely regulate the secretion of PGs via CRHR2, which facilities the functional status of uterus during pregnancy.

MON-018 Fertility Rates in Rats Characterized by Increased Hypothalamic CRH Secretion

Certain strains of rats are characterized by hyperactive Hypothalamic-Pituitary-Adrenal axis responses to stress, increased hypothalamic Corticotropin-Releasing Hormone (CRH) production and decreased fertility rates. Activation of the HPA-axis and CRH secretion has been associated with suppression of the Hypothalamic-Pituitary-Ovarian axis primarily as a result of glucocorticoids. Here we examined the hypothesis that Fischer rats have decreased fertility rates because of hypothalamic CRH hypersecretion. Antalarmin, a CRH receptor type 1 antagonist, is known to suppress adrenocorticotropin hormone secretion and other CRH receptor type 1-mediated responses. Adult female Fischer rats were injected with antalarmin or placebo, twice a day, for 16 days. Mating was evidenced by the presence of spermatozoa in the vaginal smear performed every morning. After 16 days, 20% of rats (20%) treated with placebo became pregnant and 55% rats treated with antalarmin became pregnant. We have previously reported that administration of antalarmin after the first day of pregnancy does not affect blastocyst implantation in Fischer rats. Our data suggest that antalarmin improves fertility rates in Fischer rats by antagonizing the direct antireproductive role of hypothalamic CRH.

Regulation des Angstverhaltens — zur Rolle neuronaler Netzwerke

The corticotropin-releasing hormone (CRH) system orchestrates the organism’s stress response including the regulation of adaptive be haviours. Here we describe a novel neuronal circuit, which acts anxiety suppressing and positively modulates dopamine release. This anxiolytic circuit comprises inhibitory CRH-expressing, long-range projection neurons within the extended amygdala. These neurons innervate the ventral tegmental area, a prominent brain reward center that expresses high levels of CRH receptor type 1.

Urocortin 2 But Not Urocortin 3 Promotes the Synaptic Formation in Hipppocampal Neurons via Induction of NGF Production by Astrocytes

CRH family peptides play differential role during various physiological and pathophysiological responses, such as stress. Urocortins (UCNs) have been implicated to play complementary or contrasting actions for the effects of CRH during stress. It has been shown that activation of CRH receptor type 1 (CRHR1) results in decreased synapse formation in hippocampus. We therefore explored the effect of UCN2 and UCN3, the exclusive CRHR2 agonists, on synaptic formation in hippocampus. In hippocampal slices cultures, UCN2 but not UCN3 treatment increased the levels of presynaptic protein synapsinI and postsynaptic protein postsynaptic density 95 (PSD95), which was reversed by CRHR2 antagonist astressin 2B. In isolated hippocampal neurons, however, UCN2 decreased the numbers of synapsinI- and PSD95-labeled terminals/clusters via CRHR2. Treatment of hippocampal neurons with the media of UCN2-treated astrocytes led to an increase in synapsinI- and PSD95-labeled terminals. In neuron-astrocyte cocultures, UCN2 also enhanced the numbers and level of synapsinI- and PSD95-labeled terminals. These effects did not occur if glial cells were transfected with CRHR2 small interfering RNA. UCN2 but not UCN3 treatment induced nerve growth factor (NGF) production in astrocytes via CRHR2. The effects of the media of UCN2-treated glial cells on synapse formation in hippocampal neurons were prevented by administration of NGF receptor antagonists. Our data indicate that UCN2 promotes synapse formation in hippocampus via induction of NGF secretion from astrocytes. CRHR2 in glial cells mediates the stimulatory effects of CRH. Glia-neuron communication is critical for neuronal circuits remodeling and synaptic plasticity in response to neurohormones or neuromodulators.

CRH Activation of Different Signaling Pathways Results in Differential Calcium Signaling in Human Pregnant Myometrium before and during Labor

Context: Our previous study has demonstrated that CRH has differential effects on human uterine contractility before and after onset of labor. Intracellular Ca2+ concentration ([Ca2+]i) mobilization plays an important role in the control of uterine contraction. Objective: Our objective was to investigate the effects of CRH on [Ca2+]i homeostasis in laboring and nonlaboring myometrial cells and determine subsequent signaling involved in [Ca2+]i regulation by CRH. Design: The myometrial tissues were obtained from pregnant women who were undergoing or not undergoing labor at term. [Ca2+]i was determined by Ca2+ imaging system using the fluorescent dye fura-2-acetoxymethyl ester. Western blot analysis, ELISA, and RIA were used to determine the signaling pathways induced by CRH. Results: CRH induced Ca2+ transient in laboring cells, which was blocked by CRH receptor type 1 (CRHR1) antagonist antalarmin. CRHR1 knockdown impaired this effect of CRH. CRH activated Gi protein, decreased cAMP production, and induced phosphorylated phospholipase C-β3 and inositol-1,4,5-triphosphate production. Phospholipase C and inositol-1,4,5-triphosphate receptor inhibitors blocked the CRH-induced Ca2+ transient in laboring cells. CRH did not induce whereas antalarmin induced the Ca2+ transient in nonlaboring cells. Knockdown of CRHR1 impaired the effect of antalarmin. CRH acted on CRHR1 to activate Gs in nonlaboring cells. Forskolin blocked antalarmin-induced Ca2+ transient. Conclusions: CRH acts on CRHR1 to activate different signaling pathways before and after onset of labor, thereby resulting in differential calcium signaling in response to CRH. The signaling pathways of CRHR1 might serve as a target for the development of new therapeutic strategies for preterm birth.

Regulation of Estradiol and Progesterone Production by CRH-R1 and -R2 Is through Divergent Signaling Pathways in Cultured Human Placental Trophoblasts

CRH and its related peptides urocortins (UCN) have been identified in placenta and implicated to play pivotal roles in the regulation of pregnancy and parturition in humans. The objectives of present study were to investigate the effects of endogenous CRH and its related peptides in the regulation of steroid production in placenta. Placental trophoblasts were isolated from term placenta tissues and cultured for 72 h. Estradiol (E2) and progesterone (P4) contents in culture media were determined by radioimmunoassay. Treatment of cultured trophoblasts with CRH or UCNI antibody showed decreased E2, whereas increased P4 production. Treatment of cells with CRH receptor type 1 antagonist antalarmin or CRH receptor type 2 (CRH-R2) antagonist astressin-2b also decreased E2 but increased P4 production. Knockdown of CRH receptor type 1 or CRH-R2 cells showed a decrease in E2 production and an increase in P4 production. In CRH-R2 knockdown cells, CRH stimulated GTP-bound Gαs protein and phosphorylated phospholipase C-β3. Adenylyl cyclase and protein kinase A inhibitors blocked CRH-induced increased E2 production but not decreased P4 production. PLC inhibitor U73122 and protein kinase C inhibitor chelerythrine blocked the effects of CRH on E2 and P4 production in CRH-R2 knockdown cells. UCNIII, the specific CRH-R2 agonist, stimulated GTP-bound Gαi protein and phosphorylated phospholipase C-β3 expression. Both U73122 and chelerythrine blocked UCNIII-induced increased E2 production and decreased P4 production. We suggest that CRH and its related peptides might be involved in changes in the progesterone to estrogen ratio during human pregnancy.

Differential Regulation of Glucose Transporters Mediated by CRH Receptor Type 1 and Type 2 in Human Placental Trophoblasts

Glucose transport across the placenta is mediated by glucose transporters (GLUT), which is critical for normal development and survival of the fetus. Regulatory mechanisms of GLUT in placenta have not been elucidated. Placental CRH has been implicated to play a key role in the control of fetal growth and development. We hypothesized that CRH, produced locally in placenta, could act to modulate GLUT in placenta. To investigate this, we obtained human placentas from uncomplicated term pregnancies and isolated and cultured trophoblast cells. GLUT1 and GLUT3 expressions in placenta were determined, and effects of CRH on GLUT1 and GLUT3 were examined. GLUT1 and GLUT3 were identified in placental villous syncytiotrophoblasts and the endothelium of vessels. Treatment of cultured placental trophoblasts with CRH resulted in an increase in GLUT1 expression while a decrease in GLUT3 expression in a dose-dependent manner. Cells treated with either CRH antibody or nonselective CRH receptor (CRH-R) antagonist astressin showed a decrease in GLUT1 and an increase in GLUT3 expression. CRH-R1 antagonist antalarmin decreased GLUT1 expression while increased GLUT3 expression. CRH-R2 antagonist astressin2b increased the expression of both GLUT1 and GLUT3. Knockdown of CRH-R1 decreased GLUT1 expression while increased GLUT3 expression. CRH-R2 knockdown caused an increase in both GLUT1 and GLUT3 expression. Our data suggest that, in placenta, CRH produced locally regulates GLUT1 and GLUT3 expression, CRHR1 and CRHR2-mediated differential regulation of GLUT1 and GLUT3 expression. Placental CRH may regulate the growth of fetus and placenta by modulating the expression of GLUT in placenta during pregnancy.