Regional distribution of urocortin-like immunoreactivity and expression of urocortin mRNA in the human brain

Glucocorticoids and cognitive function: a walkthrough in endogenous and exogenous alterations

PURPOSE

The hypothalamic-pituitary-adrenal (HPA) axis exerts many actions on the central nervous system (CNS) aside from stress regulation. Glucocorticoids (GCs) play an important role in affecting several cognitive functions through the effects on both glucocorticoid (GR) and mineralocorticoid receptors (MR). In this review, we aim to unravel the spectrum of cognitive dysfunction secondary to derangement of circulating levels of endogenous and exogenous glucocorticoids.

METHODS

All relevant human prospective and retrospective studies published up to 2022 in PubMed reporting information on HPA disorders, GCs, and cognition were included.

RESULTS

Cognitive impairment is commonly found in GC-related disorders. The main brain areas affected are the hippocampus and pre-frontal cortex, with memory being the most affected domain. Disease duration, circadian rhythm disruption, circulating GCs levels, and unbalanced MR/GR activation are all risk factors for cognitive decline in these patients, albeit with conflicting data among different conditions. Lack of normalization of cognitive dysfunction after treatment is potentially attributable to GC-dependent structural brain alterations, which can persist even after long-term remission.

CONCLUSION

The recognition of cognitive deficits in patients with GC-related disorders is challenging, often delayed, or mistaken. Prompt recognition and treatment of underlying disease may be important to avoid a long-lasting impact on GC-sensitive areas of the brain. However, the resolution of hormonal imbalance is not always followed by complete recovery, suggesting irreversible adverse effects on the CNS, for which there are no specific treatments. Further studies are needed to find the mechanisms involved, which may eventually be targeted for treatment strategies.

The Role of Corticotropin-Releasing Factor (CRF) and CRF-Related Peptides in the Social Behavior of Rodents

Since the corticotropin-releasing factor (CRF) was isolated from an ovine brain, a growing family of CRF-related peptides has been discovered. Today, the mammalian CRF system consists of four ligands (CRF, urocortin 1 (Ucn1), urocortin 2 (Ucn2), and urocortin 3 (Ucn3)); two receptors (CRF receptor type 1 (CRF1) and CRF receptor type 2 (CRF2)); and a CRF-binding protein (CRF-BP). Besides the regulation of the neuroendocrine, autonomic, and behavioral responses to stress, CRF and CRF-related peptides are also involved in different aspects of social behavior. In the present study, we review the experiments that investigated the role of CRF and the urocortins involved in the social behavior of rats, mice, and voles, with a special focus on sociability and preference for social novelty, as well as the ability for social recognition, discrimination, and memory. In general, these experiments demonstrate that CRF, Ucn1, Ucn2, and Ucn3 play important, but distinct roles in the social behavior of rodents, and that they are mediated by CRF1 and/or CRF2. In addition, we suggest the possible brain regions and pathways that express CRF and CRF-related peptides and that might be involved in social interactions. Furthermore, we also emphasize the differences between the species, strains, and sexes that make translation of these roles from rodents to humans difficult.

Dynamic Expression and Regulation of Urotensin I and Corticotropin-Releasing Hormone Receptors in Ovary of Olive Flounder Paralichthys olivaceus

Urotensin I (UI), a fish corticotropin-releasing hormone (CRH) like peptide, has been found throughout vertebrate species that has great effects on adaptive physiology comprising stress-related responses, and osmotic regulation by binding with CRH type I receptor (CRHR1) and CRH type II receptor (CRHR2) in fish. Dynamic expression and regulation of UI and CRH receptors in the olive flounder ovarian follicle were studied so as to make further efforts to understand the role of UI in the development of teleost ovary. The results showed that stage-specific change in UI mRNA levels in ovarian follicles of olive flounder. UI and CRHR1 mRNA levels were higher in stage III follicles (300∼500 μm diameter) compared to stage II (90∼300 μm diameter) and IV (500∼800 μm diameter) follicles, however, the levels of CRHR2 mRNA were decreased in line with the ovarian development from stage II to stage IV. A strong signal of UI protein was observed in the follicular cells and oocyte in stage III and IV follicles by immunohistochemistry. In vitro treatment of olive flounder ovarian follicles with human chorionic gonadotropin (hCG) showed that the mRNA expression of UI increased significantly at low concentration and decreased at high concentration at 6 h, but the CRHR1 and CRHR2 mRNA did not change obviously. In addition, the results of incubation with 17α, 20β-dihydroxy-4-oregnen-3-one (DHP) show that UI and CRHR1 mRNA expression were elevated with increasing concentrations at 9 h. All above results indicated that UI and CRH receptors may have a vital effect on olive flounder ovarian development.

An Update on CRF Mechanisms Underlying Alcohol Use Disorders and Dependence

Alcohol is the most commonly used and abused substance worldwide. The emergence of alcohol use disorders, and alcohol dependence in particular, is accompanied by functional changes in brain reward and stress systems, which contribute to escalated alcohol drinking and seeking. Corticotropin-releasing factor (CRF) systems have been critically implied in the transition toward problematic alcohol drinking and alcohol dependence. This review will discuss how dysregulation of CRF function contributes to the vulnerability for escalated alcohol drinking and other consequences of alcohol consumption, based on preclinical evidence. CRF signaling, mostly via CRF1 receptors, seems to be particularly important in conditions of excessive alcohol taking and seeking, including during early and protracted withdrawal, relapse, as well as during withdrawal-induced anxiety and escalated aggression promoted by alcohol. Modulation of CRF1 function seems to exert a less prominent role over low to moderate alcohol intake, or to species-typical behaviors. While CRF mechanisms in the hypothalamic-pituitary-adrenal axis have some contribution to the neurobiology of alcohol abuse and dependence, a pivotal role for extra-hypothalamic CRF pathways, particularly in the extended amygdala, is well characterized. More recent studies further suggest a direct modulation of brain reward function by CRF signaling in the ventral tegmental area, nucleus accumbens, and the prefrontal cortex, among other structures. This review will further discuss a putative role for other components of the CRF system that contribute for the overall balance of CRF function in reward and stress pathways, including CRF2 receptors, CRF-binding protein, and urocortins, a family of CRF-related peptides.

Role of urocortin in pregnancy: An update and future perspectives

The activities of corticotropin-releasing factor (CRF) and related peptides are mediated a number of receptors with seven transmembrane domains that are coupled to the Gs and Gq proteins. These receptors are known as CRF-Rs. In vitro studies have evidenced that urocortin (UCN) and CRF provoke an increase in the contractility of the uterus which is induced by endometrial prostaglandin F2a. Furthermore, through trophoblasts, it stimulates the secretion of adrenocorticotropic hormone (ACTH) and prostaglandin PGE2 and has a vasodilatory effect on the placenta. While it is well known that the placenta produces considerable quantities of CRF, several studies have, however, excluded that the placenta can generate significant quantities of UCN. In the short term, the human fetal adrenal gland produces more cortisol and dehydroepiandrosterone sulfate. The gestational tissues express UCN3 and UCN2 mRNA in cytotrophoblast and syncytiotrophoblast cells, while UCN2 is only to be found in the maternal and fetal vessels and amniotic cells. Nevertheless, gestational tissues express UCN2 and UCN3 differentially and do not stimulate placental ACTH secretion. In term pregnancies, maternal plasma levels of CRF and UCN are lower than at the beginning of pregnancy and are correlated to labor onset. Conversely, they do not decrease in post-term pregnancies. This evidence would seem to indicate that the fine-regulated expression of these neuropeptides is important in determining the duration of human gestation. In this scenario, low concentrations of UCN in the amniotic fluid at mid-term may be considered a sign of predisposition to preterm birth.

Urocortin 1 expression and secretion by human umbilical vein endothelial cells: In vitro effects of interleukin 8, interferon γ, lipopolysaccharide, endothelin 1, prostaglandin F-2α, estradiol, progesterone and dexamethasone

Urocortin 1 (Ucn1) is a 40-amino-acid peptide that has vasodilatory activity and displays immunomodulatory and antioxidant properties. Maternal and cord plasma Ucn1 levels are increased in preeclampsia and preterm labor, but the mechanisms of such increase are poorly known. Thus, we investigated Ucn1 localization in human umbilical cord and assessed some potential stimuli to Ucn1 release by human umbilical vein endothelial cells (HUVEC). Human umbilical cords were obtained at uncomplicated term pregnancy (n=11). Ucn1 localization was assessed by immunohistochemistry and quantified. HUVEC were grown in vitro to confluence, then incubated with serial concentrations of interleukin (IL)-8, interferon (INF)-γ, lipopolysaccharide (LPS), endothelin (ET)-1, prostaglandin (PG)F-2α, estradiol, progesterone and dexamethasone and Ucn1 concentrations were measured in the supernatants. Ucn1 was immunolocalized with similar intensity in umbilical cord arteries, vein and Wharton's jelly. Ucn1 mRNA was detected in all HUVEC cultures and Ucn1 peptide was detectable in culture medium from untreated cells at different time points. Incubation with IFN-γ increased Ucn1 secretion in a dose-dependent manner. Treatments with IL-8, LPS, ET-1 and dexamethasone were able to increase three to fourfold Ucn1 release from cultured endothelial cells. In conclusion, umbilical vessels express Ucn1 and may be a contributive source of Ucn1 release into fetal-placental circulation. IL-8, IFN-γ, LPS, ET-1 and dexamethasone promote Ucn1 secretion from cultured HUVEC.

The effect of urocortin 1 on motility in isolated, vascularly perfused rat colon

BACKGROUND/AIMS

Urocortin 1, a corticotropin-releasing factor related peptide, increases colonic motility under stressful conditions. We investigated the effect of urocortin 1 on colonic motility using an experimental model with isolated rat colon in which the blood flow and intestinal nerves were preserved. Furthermore, we assessed whether this effect was mediated by adrenergic or cholinergic nerves.

METHODS

Colonic motility was measured in the proximal and distal parts of resected rat colon. The colon resected from the peritoneum was stabilized, and then urocortin 1 (13.8, 138, 277, and 1,388 pM) was administered via a blood vessel. Motility index was measured in the last 5 min of the 15 min administration of urocortin 1 and expressed as percentage change from baseline. Subsequently, the change in motility was measured by perfusing urocortin 1 in colons pretreated with phentolamine, propranolol, hexamethonium, atropine, or tetrodotoxin.

RESULTS

At concentrations of 13.8, 138, 277, and 1,388 pM, urocortin 1 increased the motility of proximal colon (20.4 ± 7.2%,48.4 ± 20.9%, 67.0 ± 25.8%, and 64.2 ± 20.9%, respectively) and the motility of distal colon (3.3 ± 3.3%, 7.8 ± 7.8%, 71.1 ± 28.6%,and 87.4 ± 32.5%, respectively). The motility induced by urocortin 1 was significantly decreased by atropine to 2.4 ± 2.4% in proximal colon and 3.4 ± 3.4% in distal colon (p <œ 0.05). However, tetrodotoxin, propranolol, phentolamine, and hexamethonium did not inhibit motility.

CONCLUSIONS

Urocortin 1 increased colonic motility and it is considered that this effect was directly mediated by local muscarinic cholinergic receptors.

Nuclear overexpression of urocortin discriminates primary brain tumors from reactive gliosis

The role of urocortin (UCN) is still ambiguous in human cancers. We tested the hypothesis that using UCN expression discriminates reactive gliosis from primary brain tumors (PBTs). Immunohistochemical analysis of UCN was performed in six reactive gliosis and 99 PBTs. The immunostain scores of UCN were calculated as the degree of intensity multiplied by the percentage of expressed tumor cells. Nuclear staining of UCN revealed weak intensity and small portion of positively stained cells in reactive gliosis. However, comparing with non-neoplastic tissues, higher immunostain scores of UCN were identified in each WHO grade of astrocytomas and meningiomas. Finally, neither WHO grade nor overall survival rate did not significantly correlate with UCN expression in astrocytomas and meningiomas. Our findings demonstrate for the first time that the application of UCN might be a novel biomarker for not only discriminating reactive gliosis from PBTs, but also deciding where the clear surgical margin was.

Chronic and acute effects of stress on energy balance: are there appropriate animal models?

Stress activates multiple neural and endocrine systems to allow an animal to respond to and survive in a threatening environment. The corticotropin-releasing factor system is a primary initiator of this integrated response, which includes activation of the sympathetic nervous system and the hypothalamic-pituitary-adrenal (HPA) axis. The energetic response to acute stress is determined by the nature and severity of the stressor, but a typical response to an acute stressor is inhibition of food intake, increased heat production, and increased activity with sustained changes in body weight, behavior, and HPA reactivity. The effect of chronic psychological stress is more variable. In humans, chronic stress may cause weight gain in restrained eaters who show increased HPA reactivity to acute stress. This phenotype is difficult to replicate in rodent models where chronic psychological stress is more likely to cause weight loss than weight gain. An exception may be hamsters subjected to repeated bouts of social defeat or foot shock, but the data are limited. Recent reports on the food intake and body composition of subordinate members of group-housed female monkeys indicate that these animals have a similar phenotype to human stress-induced eaters, but there are a limited number of investigators with access to the model. Few stress experiments focus on energy balance, but more information on the phenotype of both humans and animal models during and after exposure to acute or chronic stress may provide novel insight into mechanisms that normally control body weight.

The cytokine ciliary neurotrophic factor (CNTF) activates hypothalamic urocortin-expressing neurons both in vitro and in vivo

Ciliary neurotrophic factor (CNTF) induces neurogenesis, reduces feeding, and induces weight loss. However, the central mechanisms by which CNTF acts are vague. We employed the mHypoE-20/2 line that endogenously expresses the CNTF receptor to examine the direct effects of CNTF on mRNA levels of urocortin-1, urocortin-2, agouti-related peptide, brain-derived neurotrophic factor, and neurotensin. We found that treatment of 10 ng/ml CNTF significantly increased only urocortin-1 mRNA by 1.84-fold at 48 h. We then performed intracerebroventricular injections of 0.5 mg/mL CNTF into mice, and examined its effects on urocortin-1 neurons post-exposure. Through double-label immunohistochemistry using specific antibodies against c-Fos and urocortin-1, we showed that central CNTF administration significantly activated urocortin-1 neurons in specific areas of the hypothalamus. Taken together, our studies point to a potential role for CNTF in regulating hypothalamic urocortin-1-expressing neurons to mediate its recognized effects on energy homeostasis, neuronal proliferaton/survival, and/or neurogenesis.

Is it really a matter of simple dualism? Corticotropin-releasing factor receptors in body and mental health

Physiological responses to stress coordinated by the hypothalamo-pituitary-adrenal axis are concerned with maintaining homeostasis in the presence of real or perceived challenges. Regulators of this axis are corticotrophin releasing factor (CRF) and CRF related neuropeptides, including urocortins 1, 2, and 3. They mediate their actions by binding to CRF receptors (CRFR) 1 and 2, which are located in several stress-related brain regions. The prevailing theory has been that the initiation of and the recovery from an elicited stress response is coordinated by two elements, viz. the (mainly) opposing, but well balanced actions of CRFR1 and CRFR2. Such a dualistic view suggests that CRF/CRFR1 controls the initiation of, and urocortins/CRFR2 mediate the recovery from stress to maintain body and mental health. Consequently, failed adaptation to stress can lead to neuropathology, including anxiety and depression. Recent literature, however, challenges such dualistic and complementary actions of CRFR1 and CRFR2, and suggests that stress recruits CRF system components in a brain area and neuron specific manner to promote adaptation as conditions dictate.

Distribution of urocortins and corticotropin-releasing factor receptors in the cardiovascular system

Urocortins are human homologues of urotensin I, a fish corticotropin-releasing-factor- (CRF-) like peptide secreted from the urophysis. There are three urocortins: urocortin 1, urocortin 2, and urocortin 3 in mammals. We have shown that urocortin 1 and urocortin 3 are endogenously synthesized in the myocardial cells of human heart and may act on CRF type 2 receptor (CRFR2) expressed in the heart. Expression levels of urocortin 1 in the heart and plasma urocortin 1 levels are elevated in patients with heart failure. Recent studies have shown that urocortins have various biological actions in the cardiovascular system, such as a vasodilator action, a positive inotropic action, a cardioprotective action against ischemia/reperfusion injury, and suppressive actions against the renin angiotensin system and the sympathetic nervous system. Urocortins and CRFR2 may therefore be a potential therapeutic target for cardiovascular diseases, such as congestive heart failure, hypertension, and myocardial infarction.

Urocortin 1 modulates immunosignaling in a rat model of colitis via corticotropin-releasing factor receptor 2

Urocortins (UCNs) and their receptors are potent immunoregulators in the gastrointestinal (GI) tract, where they can exert both pro- and anti-inflammatory effects. We examined the contribution of Ucn1 and its receptors to the pathogenesis, progression, and resolution of colitis. Trinitrobenzene sulfonic acid was used to induce colitis in rats. Ucn1 mRNA and immunoreactivity (IR) were ubiquitously expressed throughout the GI tract under basal conditions. During colitis, Ucn1 mRNA levels fell below basal levels on day 1 then increased again by day 6, in association with an increase in the number of Ucn1-IR inflammatory cells. Ucn1-IR cells were also numerous in proliferating granulation tissue. In contrast to Ucn1 expression, average phosphorylated ERK1/2 (pERK1/2) expression rose above controls levels on day 1 and was very low on day 6 of colitis. Knockdown of corticotropin-releasing factor 2 (CRF(2)) but not CRF(1) by RNA interference during colitis significantly decreased the macroscopic lateral spread of ulceration compared with uninjected controls or animals with CRF(1) knockdown. After knockdown of CRF(2), but not of CRF(1) during colitis, edema resolution assessed microscopically was slowed, and myeloperoxidase activity remained elevated even at day 6. Ucn1 and TNF-α mRNA peaked earlier, whereas pERK1/2 activation was attenuated after CRF(2) knockdown. Thus we conclude that local CRF(2) and pERK1/2 activation is pivotal for macroscopic spread of colitis and resolution of edema. Elimination of CRF(2), but not CRF(1), results in uncoordinated immune and pERK1/2 signaling responses.

ACTH response to desmopressin in a patient with acromegaly; expression of corticotropin-releasing factor, urocortins and vasopressin V1b receptor in GH-producing pituitary adenoma

GH-producing pituitary adenomas frequently co-produce other certain anterior pituitary hormones, such as prolactin (PRL). In contrast, GH-producing adenomas which express all of corticotropin-releasing factor (CRF), urocorin1 (Ucn1) and urocortin3 (Ucn3) have not been reported. A 39-year-old woman was admitted for evaluation of the pituitary tumor. The diagnosis of acromegaly was confirmed by elevated serum GH and IGF-I levels, and the absence of GH suppression by oral glucose tolerance test. ACTH response to desmopressin (DDAVP) was observed (plasma ACTH levels increased from 13.9 to 50.4 pg/ml at 90 min). Although it is known that ACTH response to DDAVP is considerably useful for the diagnosis of ACTH-dependent Cushing's syndrome, the diagnosis of Cushing's disease was not supported by the criteria. The patient underwent transsphenoidal resection of the pituitary tumor. Immunohistological examination confirmed a GH- and PRL-producing adenoma, whereas ACTH was negative. ACTH response to DDAVP disappeared after tumor removal. To determine the cause of preoperative ACTH response to DDAVP, we examined expression of CRF family peptides and vasopressin V1b receptor in the pituitary adenoma by immunohistochemistry. Immunohistochemistry revealed positive immunostaining for CRF, Ucn1, Ucn3 and vasopressin V1b receptor in the adenoma. These observations raised the possibility that DDAVP caused an ACTH response, perhaps via the paracrine effects of tumor-derived CRF and Ucn1. When ACTH response to DDAVP is observed in patients with pituitary tumor, not only the direct effect of DDAVP on ACTH secretion, but also a possible involvement of CRF and/or urocortins expressed in the pituitary adenoma, should be considered.

The corticotropin releasing factor system in cancer: expression and pathophysiological implications

Malignant tumors express multiple factors that have some role in the regulating networks supporting their ectopic growth. Recently, increased interest has been developing in the expression and biological role of the neuropeptides and receptors of the corticotropin releasing factor (CRF) system, the principal neuroendocrine mediator of the stress response, especially in the light of several R&D programs for small molecule antagonists that could present some anticancer therapeutic benefit. In the present article, we review the literature suggesting that the CRF system could be involved in the regulation of human cancer development. Potential implication in growth, metastasis, angiogenesis, or immune parameters via activation of locally expressed receptors could be clinically exploited by presenting targets of new therapeutic approaches.

Peripheral and central administration of exogenous urocortin 1 disrupts the fasted motility pattern of the small intestine in rats via the corticotrophin releasing factor receptor 2 and a cholinergic mechanism

BACKGROUND AND AIM

The action of the corticotrophin releasing factor (CRF) receptor on the small intestinal motility has been rarely investigated. The present study aimed to determine the effects of urocortin 1 on small intestinal motility in rats and the CRF receptor subtypes and autonomic pathways mediating the effects.

METHODS

Fasted or fed rats were used to investigate the effect of intravenous or intracerebroventricular urocortin 1 on duodenum and jejunum motility. NBI-27914 and astressin(2)-B (CRF receptor 1 and 2 antagonists, respectively), atropine (an M-receptor antagonist), phentolamine (an alpha-receptor antagonist), propranolol (a beta-receptor antagonist) and N(omega)-Nitro-L-arginine (a nitric oxide synthase [NOS] inhibitor) were applied to determine the involved CRF receptor subtypes and autonomic pathways.

RESULTS

In fasted rats, intravenous or intracerebroventricular injection of urocortin 1 disrupted duodenal and jejunal migrating myoelectric complex pattern, leading to an irregular spiking activity similar to the fed motility pattern. When urocortin 1 was given in the fed state, the fed motility pattern remained unchanged. In addition, urocortin 1 also inhibited small intestinal transit function. Astressin(2)-B injected intraperitoneally or intracerebroventricularly blocked urocortin 1-induced change, while NBI-27914 had no effect. The disruption of migrating myoelectric complex induced by urocortin 1 was abolished by atropine, but not affected by phentolamine, propranolol and N(omega)-Nitro-L-arginine.

CONCLUSION

Intravenous or intracerebroventricular injection of urocortin 1 acts, respectively, on peripheral and central CRF receptor 2 to disrupt the intestinal migrating myoelectric complex through an M-receptor-dependent mechanism, and such change has an inhibitory effect as proved by measuring the small intestinal transit function.

A case of multiple endocrine neoplasia type II accompanied by thyroid medullary carcinoma and pheochromocytomas expressing corticotropin-releasing factor and urocortins

A 38-year-old woman with RET gene mutation presented with tumors in her thyroid and bilateral adrenal glands. I-metaiodobenzylguanidine scintigraphy revealed accumulation of the radioisotope in both adrenal glands. Both plasma adrenaline and noradrenaline levels were elevated. The circadian rhythms for plasma adrenocorticotropic hormone (ACTH) and cortisol levels were disturbed. Plasma ACTH and cortisol levels failed to be suppressed by an overnight dexamethasone test, suggesting autonomic secretion of ACTH and cortisol, although the patient had no typical Cushingoid features, hypertension, or impaired glucose tolerance. Pathological examination showed that these tumors were pheochromocytoma and thyroid medullary carcinoma, respectively, both of which highly expressed corticotropin-releasing factor, urocortin1, and urocortin3. Together with the endocrinological and pathological observations, the patient was diagnosed as multiple endocrine neoplasia type II with corticotropin-releasing factor- and urocortin-producing tumors that stimulated ACTH and glucocorticoid secretion.

Urocortin and the brain

Urocortin is a member of the corticotropin-releasing hormone (CRH) family of peptides. In the brain, its potent suppression of food intake is mediated by CRH receptors (CRHR). Urocortin also participates in the regulation of anxiety, learning, memory, and body temperature, and it shows neuroprotection. This review will summarize the location of urocortin-producing neurons and their projections, the pharmacological evidence of its actions in the CNS, and information acquired from knockout mice. Urocortin interacts with leptin, neuropeptide Y, orexin, and corticotropin in the brain. Also produced by the GI tract, heart, and immune cells, urocortin has blood concentrations ranging from 13 to 152 pg/ml. Blood-borne urocortin stimulates the cerebral endothelial cells composing the blood-brain barrier and crosses the blood-brain barrier by a unique transport system. Overall, urocortin acts on a broad neuronal substrate as a neuromodulator important for basic survival.

The corticotrophin-releasing factor-like peptide urocortin reverses key deficits in two rodent models of Parkinson's disease

The potential neuroprotective action of the corticotrophin-releasing factor-related peptide urocortin (UCN) was investigated in the rat 6-hydroxydopamine (6-OHDA) and lipopolysaccharide (LPS) paradigms of Parkinson's disease. UCN (20 fmol) was either given at the same time as (T = 0) or 7 days after (T = +7) intracerebral 6-OHDA or LPS injection. At 14 days after 6-OHDA or LPS injection, circling behaviour was measured following apomorphine challenge. Circling was significantly lower in rats given UCN at either T = 0 or T = +7 compared with animals given 6-OHDA or LPS and vehicle. Sham-treated rats showed no circling. Consistent with these observations, striatal dopamine concentrations were markedly higher in 6-OHDA/LPS + UCN rats vs. 6-OHDA/LPS + vehicle groups. Additionally, L-dihydroxyphenylalanine production by tyrosine hydroxylase was greatly reduced in the striata of 6-OHDA/LPS + vehicle rats, whereas this was not the case in rats coadministered UCN. Finally, the numbers of tyrosine hydroxylase-positive cells recorded in the substantia nigra of 6-OHDA/LPS + vehicle-treated animals were markedly lower than those of sham-operated or 6-OHDA/LPS + UCN rats. Critically, UCN was effective in reversing lesion-induced deficits when given either at the same time as or 7 days after the neurotoxic insult. To our knowledge, this is the first time that such an effect has been demonstrated in vivo. The apparent ability of UCN to arrest the progression of or even reverse nigral lesions once established suggests that pharmacological manipulation of this system could have substantial therapeutic utility.

Urocortin I is present in the enteric nervous system and exerts an excitatory effect via cholinergic and serotonergic pathways in the rat colon

Corticotropin-releasing factor (CRF) and urocortin I (UcnI) have been shown to accelerate colonic transit after central nervous system (CNS) or peripheral administration, but the mechanism of their peripheral effect on colonic motor function has not been fully investigated. Furthermore, the localization of UcnI in the enteric nervous system (ENS) of the colon is unknown. We investigated the effect of CRF and UcnI on colonic motor function and examined the localization of CRF, UcnI, CRF receptors, choline acetyltransferase (ChAT), and 5-HT. Isometric tension of rat colonic muscle strips was measured. The effect of CRF, UcnI on phasic contractions, and electrical field stimulation (EFS)-induced off-contractions were examined. The effects of UcnI on both types of contraction were also studied in the presence of antalarmin, astressin2-B, tetrodotoxin (TTX), atropine, and 5-HT antagonists. The localizations of CRF, UcnI, CRF receptors, ChAT, and 5-HT in the colon were investigated by immunohistochemistry. CRF and UcnI increased both contractions dose dependently. UcnI exerted a more potent effect than CRF. Antalarmin, TTX, atropine, and 5-HT antagonists abolished the contractile effects of UcnI. CRF and UcnI were observed in the neuronal cells of the myenteric plexus. UcnI and ChAT, as well as UcnI and 5-HT, were colocalized in some of the neuronal cells of the myenteric plexus. This study demonstrated that CRF and UcnI act on the ENS and increase colonic contractility by enhancing cholinergic and serotonergic neurotransmission. These peptides are present in myenteric neurons. CRF and, perhaps, to a greater extent, UcnI appear to act as neuromodulators in the ENS of the rat colon.

Urocortin 2 expression in the rat gastrointestinal tract under basal conditions and in chemical colitis

It is becoming increasingly evident that the urocortins (Ucns) and their receptors are involved in the initiation and development of inflammation in the gastrointestinal (GI) tract. There has not been a systematic study of the basal expression of Ucns or their receptors in the GI tract. Here, we examined basal expression of Ucn 2 and its high-affinity receptor, CRF-R2 in the rat GI tract. Ucn 2 mRNA was expressed throughout the small and large intestine. Surprisingly, CRF-R2 mRNA expression was detected in only a subset of GI regions that expressed Ucn 2. Immunohistochemical study showed that both Ucn 2 immuno-reactivity (Ucn 2-IR) and CRF-R2-IR were consistently seen in the neurons of the myenteric plexus and the nerve fibers innervating the circular muscle. By and large, Ucn 2-IR was detected in all layers, including the mucosal and the submucosal layers throughout the GI regions. In contrast, CRF-R2-IR was very low or undetectable in the mucosal layers of all regions examined. The role of Ucn 2 and CRF-R2 was then examined in a rat model of chemically-induced colitis. In the early phase of colitis, Ucn 2 mRNA levels peaked, whereas, in striking contrast, CRF-R2 mRNA expression decreased approximately 2.5-fold below control levels. At the peptide level, Ucn 2-IR was specifically induced in a large population of immune cells that infiltrated the lamina propria and submucosa of the distal colon, whereas CRFR2-IR was detected in only a small fraction of infiltrated immune cells. CRF-R2-IR was dramatically reduced in the neurons of the myenteric plexus. Thus, we show, for the first time, that in the acute phase of inflammation, Ucn 2 levels are increased whereas expression levels of its only identified receptor, CRF-R2, are decreased. This suggests that Ucn 2 exerts its effects only in part via CRF-R2.

Cardioprotective action of urocortin in early pre- and postconditioning

Pre- and postconditioning are powerful endogenous adaptive phenomenon of the organism whereby different stimuli enhance the tolerance against various types of stress. Urocortin (Ucn), member of the corticotropin-releasing factor (CRF) family has potent effects on the cardiovascular system. The aim of this article was to investigate the action of Ucn on cultured cardiomyocytes in the process of pre- and postconditioning. Isolated neonatal rat ventricular myocytes were preconditioned with adenosine, simulated ischemia, and Ucn (10-min treatment followed by 10-min reperfusion/recovery). For detecting the effect of alternative types of preconditioning, necrosis enzyme (lactate dehydrogenase [LDH]) release, vital staining (trypan blue), and ratio of apoptosis/necrosis were examined after cardiac cells were exposed to 3-h sustained ischemia and 2-h reperfusion. Same parameters were measured in the postconditioned groups (30- or 60-min ischemia followed by postconditioning with 10-min ischemic stimulus or Ucn and 2-h reperfusion). Cells exposed to 3-h ischemia followed by 2-h reperfusion were shown as control. Our results show that LDH release a number of trypan blue-stained dead cells and the ratio of apoptotized and necrotized cells was decreased in all preconditioned groups compared with control group. In postconditioned groups LDH content of culture medium, trypan blue-positive cardiomyocytes, and the rate of apoptotic/necrotic cells was reduced contrasted with non-postconditioned group. We can conclude that preconditioning with Ucn induced such a powerful cell protective effect as adenosine and ischemia. Furthermore, postconditioning with Ucn after 60-min ischemia was more cardioprotective than ischemic postconditioning.

Evidence for the presence of the type 2 corticotropin releasing factor receptor in the rodent cerebellum

Corticotropin releasing factor (CRF), localized in afferent inputs to the cerebellum, binds to two receptors defined as the Type 1 (CRF-R1) and the Type 2 (CRF-R2alpha). CRF-R1 has been localized to the cerebellum, as has a truncated isoform of CRF-R2alpha. Evidence for the presence of the full length isoform of CRF-R2alpha in the cerebellum is conflicting. We used RT-PCR, immunohistochemical, and physiologic techniques to resolve this conflict. RT-PCR data show low levels of CRF-R2alpha in the vermis and hemisphere of the cerebellum. These observations were confirmed by the Gene Expression Nervous System Atlas (GENSAT) database. A CRF-R2alpha antibody was used to determine the cellular distribution of the receptor in the cerebellum. The vast majority of the receptors are localized to Bergmann glial cells located throughout the cerebellum, as well as astrocytes in the granule cell layer. Neuronal labeling is present in sub-populations of Purkinje cells, Golgi cells, basket cells, and cerebellar nuclear neurons. Physiologic data show that urocortin II, which binds selectively to CRF-R2alpha, increases the firing rate of both Purkinje cells and nuclear neurons; this response can be blocked by the CRF-R2alpha-specific antagonist, antisauvagine-30. The present results confirm that CRF-R2alpha is present in the cerebellum and functions in circuits that modulate the firing rate of Purkinje cells and cerebellar nuclear neurons. A comparative analysis showed that the patterns of distribution of CRF-R1, CRF-R2alpha and CRF-R2alpha-tr are distinct. These data indicate that the CRF family of peptides modulates cerebellar output by binding to multiple CRF receptors.

Corticotropin releasing factor (CRF) receptor signaling in the central nervous system: new molecular targets

Corticotropin-releasing factor (CRF) and the related urocortin peptides mediate behavioral, cognitive, autonomic, neuroendocrine and immunologic responses to aversive stimuli by activating CRF(1) or CRF(2) receptors in the central nervous system and anterior pituitary. Markers of hyperactive central CRF systems, including CRF hypersecretion and abnormal hypothalamic-pituitary-adrenal axis functioning, have been identified in subpopulations of patients with anxiety, stress and depressive disorders. Because CRF receptors are rapidly desensitized in the presence of high agonist concentrations, CRF hypersecretion alone may be insufficient to account for the enhanced CRF neurotransmission observed in these patients. Concomitant dysregulation of mechanisms stringently controlling magnitude and duration of CRF receptor signaling also may contribute to this phenomenon. While it is well established that the CRF(1) receptor mediates many anxiety- and depression-like behaviors as well as HPA axis stress responses, CRF(2) receptor functions are not well understood at present. One hypothesis holds that CRF(1) receptor activation initiates fear and anxiety-like responses, while CRF(2) receptor activation re-establishes homeostasis by counteracting the aversive effects of CRF(1) receptor signaling. An alternative hypothesis posits that CRF(1) and CRF(2) receptors contribute to opposite defensive modes, with CRF(1) receptors mediating active defensive responses triggered by escapable stressors, and CRF(2) receptors mediating anxiety- and depression-like responses induced by inescapable, uncontrollable stressors. CRF(1) receptor antagonists are being developed as novel treatments for affective and stress disorders. If it is confirmed that the CRF(2) receptor contributes importantly to anxiety and depression, the development of small molecule CRF(2) receptor antagonists would be therapeutically useful.

Plasma urocortin 1 in sheep: regional sampling and effects of experimental heart failure

Although urocortin 1 (Ucn-1) has been reported to circulate in human plasma and be raised in heart failure, little, if any, information is available regarding the source of circulating Ucn-1. Accordingly, we have performed trans-organ arteriovenous sampling for measurement of Ucn-1 concentration in anesthetized sheep before and after development of pacing-induced heart failure. Arterial plasma Ucn-1 levels measured 15.2 +/- 0.5 pmol/L in normal sheep and increased significantly following development of heart failure to 19.1 +/- 1.6 (p < 0.05). Small but significant positive arteriovenous gradients were observed across the hepatic and renal tissue beds in both states, with rises across the hind limb significant in normal animals and across the head in heart failure. This is the first report identifying sources of circulating Ucn-1.

Expression of urocortin 3/stresscopin in human adrenal glands and adrenal tumors

Urocortin 3 (Ucn 3)/stresscopin (SCP) is a novel peptide of the corticotropin-releasing factor (CRF) family and is a specific ligand for the CRF type 2 receptor. In the present study, we studied expression of Ucn3/SCP in the normal adrenal and adrenal tumors by radioimmunoassay and reverse transcriptase-polymerase chain reaction (RT-PCR). High concentrations of immunoreactive (IR)-Ucn3 were present in the normal portions of adrenal glands (4.2+/-0.51 pmol/g wet weight, mean+/-S.E.M., n = 14), and the levels were higher than those in the brain. IR-Ucn3 was also detected in the tumor tissues of aldosterone-secreting adenomas (6.2+/-0.6 pmol/g wet weight, n = 10), cortisol-secreting adenomas (5.0+/-1.2 pmol/g wet weight, n = 4), and pheochromocytomas (1.9+/-0.4 pmol/g wet weight, n = 7). Reverse phase high performance liquid chromatography showed that IR-Ucn3 in normal portions of adrenal glands and aldosterone-secreting adenomas was eluted mainly in the positions of Ucn3 and SCP with several minor peaks eluting earlier. The RT-PCR showed expression of Ucn3 mRNA in normal portions of adrenal gland (positive ratio; 4/4), aldosterone-secreting adenomas (3/4), cortisol-secreting adenomas (1/3) and pheochromocytomas (6/7). These findings indicate that Ucn3 is produced in normal adrenal and adrenal tumors (both adrenocortical tumors and pheochromocytomas), and suggest that Ucn3 acts as an autocrine or paracrine regulator in normal adrenal and adrenal tumors.

Regulation of Synaptic Transmission by CRF Receptors

Corticotropin-releasing factor (CRF or CRH) and its family of related peptides have long been recognized as hypothalamic-pituitary-adrenal (HPA) axis peptides that function to regulate the release of other hormones, e.g., ACTH. In addition, CRF acts outside the HPA axis not as a hormone, but as a regulator of synaptic transmission, pre- and post-synaptically, within specific CNS neuronal circuits. Synaptic transmission within the nervous system is today understood to be a more complex process compared to the concepts associated with the term 'synapse' introduced by Sherrington in 1897. Based on more than a century of progress with modern cellular and molecular experimental techniques, prior definitions and functions of synaptic molecules and their receptors need to be reconsidered (see Glossary and Fig. 1), especially in light of the important roles for CRF, its family of peptides and other potential endogenous regulators of neurotransmission, e.g., vasopressin, NPY, etc. (see Glossary). In addition, the property of 'constitutive activity' which is associated with G-protein coupled receptors (GPCRs) provides a persistent tonic mechanism to fine-tune synaptic transmission during both acute and chronic information transfer. We have applied the term 'regulator', adapted from the hormone literature, to CRF, as an example of a specific endogenous substance that functions to facilitate or depress the actions of neuromodulators on fast and slow synaptic responses. As such, synaptic neuroregulators provide a basic substrate to prime or initiate silently plastic processes underlying neurotransmitter-mediated information transfer at CNS synapses. Here we review the role of CRF to regulate CNS synaptic transmission and also suggest how under a variety of allostatic changes, e.g., associated with normal plasticity, or adaptations resulting from mental disorders, the synaptic regulatory role for CRF may be 'switched' in its polarity and/or magnitude in order to provide a coping mechanism to deal with daily and life-long stressors. Thus, a prominent role we assign to non-HPA axis CRF, its family of peptides, and their receptors, is to maintain both acute and chronic synaptic stability.

Endothelial urocortin has potent antioxidative properties and is upregulated by inflammatory cytokines and pitavastatin

BACKGROUND

Urocortin, a neuropeptide discovered in the midbrain, is a member of the corticotropin-releasing factor family and is expressed in heart tissues. Urocortin exerts potent cardioprotective effects under various pathological conditions including ischemia/reperfusion. However, the regulation and function of vascular urocortin are unknown.

METHODS AND RESULTS

Immunohistochemistry showed definitive expression of urocortin in endothelial cells of coronary large arteries and microvessels from autopsied hearts. RT-PCR confirmed the expression of urocortin in human umbilical vein endothelial cells (HUVECs). Urocortin (10(-8) M) potently suppressed the generation of angiotensin II-induced reactive oxygen species (ROS) in HUVECs. Tumor necrosis factor-alpha and interferon-gamma increased the urocortin mRNA levels and its release from HUVECs. Incubation with pitavastatin (0.1-3.0 microM) significantly increased the urocortin mRNA levels and its release from HUVECs. Furthermore, treatment with pitavastatin (2 mg/day) for 4 weeks increased the serum urocortin level from 11.0 +/- 6.5 to 16.4 +/- 7.3 ng/ml in healthy volunteers.

CONCLUSION

Endothelial urocortin was upregulated by inflammatory cytokines and pitavastatin and suppressed ROS production in endothelial cells. Treatment with pitavastatin increased the serum urocortin level in human subjects. Thus, endothelial urocortin might protect cardiomyocytes in inflammatory lesions. Urocortin might partly explain the mechanisms of various pleiotropic effects of statins.

Effect of urocortin 1 infusion in humans with stable congestive cardiac failure

In sheep with HF (heart failure), Ucn1 (urocortin 1) decreases total peripheral resistance and left atrial pressure, and increases cardiac output in association with attenuation of vasopressor hormone systems and enhancement of renal function. In a previous study, we demonstrated in the first human studies that infusion of Ucn1 elevates corticotropin (‘ACTH’), cortisol and ANP (atrial natriuretic peptide), and suppresses the hunger-inducing hormone ghrelin in normal subjects. In the present study, we examined the effects of Ucn1 on pituitary, adrenal and cardiovascular systems in the first Ucn1 infusion study in human HF. In human HF, it is proposed that Ucn1 would augment corticotropin and cortisol release, suppress ghrelin and reproduce the cardiorenal effects seen in animals with HF. On day 3 of a controlled metabolic diet, we studied eight male volunteers with stable HF (ejection fraction <40%; New York Heart Association Class II–III) on two occasions, 2 weeks apart, receiving 50 μg of Ucn1 or placebo intravenously over 1 h in a randomized time-matched cross-over design. Neurohormones, haemodynamics and urine indices were recorded. Ucn1 infusion increased plasma Ucn1, corticotropin (baseline, 5.9±0.9 pmol/l; and peak, 7.2±1.0 pmol/l) and cortisol (baseline, 285±42 pmol/l; and peak, 310±41 pmol/l) compared with controls (P<0.001, 0.008 and 0.047 respectively). The plasma Ucn1 half-life was 54±3 min. ANP and ghrelin were unchanged, and no haemodynamic or renal effects were seen. In conclusion, a brief intravenous infusion of 50 μg of Ucn1 stimulates corticotropin and cortisol in male volunteers with stable HF.

Urocortin 1, urocortin 3/stresscopin, and corticotropin-releasing factor receptors in human adrenal and its disorders

CONTEXT

Urocortin 1 (Ucn1) and urocortin 3 (Ucn3)/stresscopin are new members of the corticotropin-releasing factor (CRF) neuropeptide family. Ucn1 binds to both CRF type 1 (CRF1) and type 2 receptors (CRF2), whereas Ucn3 is a specific agonist for CRF2. Recently, direct involvement of the locally synthesized CRF family in adrenocortical function has been proposed.

OBJECTIVE, DESIGN, AND SETTING

We examined in situ expression of Ucn and CRF receptors in nonpathological human adrenal gland and its disorders using immunohistochemistry and mRNA in situ hybridization.

RESULTS

Ucn immunoreactivity was localized in the cortex and medulla of nonpathological adrenal glands. Ucn1 immunoreactivity was marked in the medulla, whereas Ucn3 was immunostained mostly in the cortex. Both CRF type 1 and CRF2 were expressed in the cortex, particularly in the zonae fasciculata and reticularis but very weakly or undetectably in the medulla. Immunohistochemistry in serial tissue sections with mirror images revealed that both Ucn3 and CRF2 were colocalized in more than 85% of the adrenocortical cells. mRNA in situ hybridization confirmed these findings above. In fetal adrenals, Ucn and CRF receptors were expressed in both fetal and definitive zones of the cortex. Ucn and CRF receptors were all expressed in the tumor cells of pheochromocytomas, adrenocortical adenomas, and carcinomas, but its positivity was less than that in nonpathological adrenal glands, suggesting that Ucn1, Ucn3, and CRF receptors were down-regulated in these adrenal neoplasms.

CONCLUSIONS

Ucn1, Ucn3, and CRF receptors are all expressed in human adrenal cortex and medulla and may play important roles in physiological adrenal functions.

Urocortin 3/stresscopin in human colon: possible modulators of gastrointestinal function during stressful conditions

Urocortin 3 (Ucn 3) or stresscopin (SCP) is a new member of the corticotropin-releasing factor (CRF) neuropeptide family and is a specific ligand for CRF type 2 receptor (CRF2). CRF receptors are known to be expressed in the gastrointestinal tract and are considered to play pathophysiological roles, for example, in gastrointestinal motility under stress. We, therefore, examined Ucn 3 expression in the normal human large intestine obtained from surgery and autopsy in order to clarify this local response to stress in human intestine. Both immunohistochemistry and mRNA in situ hybridization demonstrated Ucn 3 expression in myenteric and submucosal nervous plexus, in vascular endothelial cells (VECs) and vascular smooth muscle cells (VSMCs) of blood vessels in subserosa, in smooth muscle layers of the large intestine, and in enterochromaffin cells. In contrast to Urocortin 1 (Ucn 1), Ucn 3 was hardly detected in lamina propria (LP) inflammatory cells in colonic mucosa. In addition, immunohistochemistry demonstrated CRF2 expression in myenteric and submucosal nervous plexus, in smooth muscle layers, in VECs, in VSMCs and in lamina propria inflammatory cells. Immunoreactive Ucn 3 was also detected in the large intestine by RIA, with high concentrations detected in the rectum (15.4+/-9.5 pmol/g wet weight, mean+/-SEM, n=3) and sigmoid colon (6.5+/-3.5 pmol/g wet weight, n=5). Reverse-phase HPLC of the human large intestine disclosed peaks eluting in the position of synthetic Ucn 3 or SCP. These findings all suggest that Ucn 3 plays some physiological or pathological roles in the modulation of gastrointestinal functions during stressful conditions in different manners from Ucn 1.

Physiological roles of urocortins, human homologues of fish urotensin I, and their receptors

Urocortin 1, a human homologue of fish urotensin I, together with its related-compounds (urocortins 2 and 3), comprises a distinct family of stress peptides. Urocortin 1 has a high affinity for both corticotropin-releasing factor (CRF) type 1 receptor (CRF1) and CRF type 2 receptor (CRF2), and urocortins 2 and 3 have a high affinity for CRF2, while CRF has a low affinity for CRF2 and a high affinity for CRF1. These differences of the binding affinity with receptors make the biological actions of these peptides. Besides the binding affinity with receptors, the limited overlap of the distribution of CRF and urocortins may also contribute to the differences of physiological roles of each peptide. Urocortins show 'stress-coping' responses such as anxiolysis and dearousal in the brain. In the periphery, recent studies show the potent effects of urocortins on the cardiovascular and immune systems. In this review article, we take a look over the series of peptides included in this family, especially in terms of the versatility of biological actions, along with the various characters of the receptors.

Localization and physiological roles of urocortin

Urocortin, a 40 amino acid peptide, is a corticotropin-releasing factor (CRF) related peptide, and can bind to all three types of CRF receptors (CRF type 1, type 2a and type 2b receptors) with higher affinities for these receptors than CRF. Immunoreactivity of urocortin is widely distributed in central nervous, digestive, cardiovascular, reproductive, immune and endocrine systems. Urocortin plays important roles in appetite-suppression, immunomodulation, steroidogenesis in the ovary, maintenance of the placental function, labor, and cardioprotection via CRF receptors. Although urocortin has potent adrenocorticotropin (ACTH) releasing activity in vitro, endogenous urocortin does not act on pituitary ACTH secretion in vivo.

Urocortins as cardiovascular peptides

Urocortins (Ucn) 1, 2 and 3, human homologues of fish urotensin I, form the corticotropin-releasing factor (CRF) family, together with CRF, urotensin I and sauvagine. Ucn 3 is a novel member of this family and is a specific ligand for CRF type 2 receptor. CRF type 2 receptor is thought to mediate the stress-coping responses, such as anxiolysis, anorexia, vasodilatation, a positive inotropic action on myocardium and dearousal. Endogenous ligands for the CRF type 2 receptor expressed in the cardiovascular tissues, such as the myocardium, have long been unknown. We have shown expression of Ucn 3 as well as Ucn 1 in the human heart. Ucn 3 is also expressed in the kidney, particularly distal tubules. Studies in various rat tissues showed that high concentrations of immunoreactive Ucn 3 were found in the pituitary gland, adrenal gland, gastrointestinal tract, ovary and spleen in addition to the brain, heart and kidney. These observations suggest that Ucn 3 is expressed in various tissues including heart and kidney, and may regulate the circulation in certain aspects of stress and diseases, such as inflammation. Ucn 1 and 3 appear to have important pathophysiological roles in some cardiovascular diseases.

Translational medicine in fish-derived peptides: from fish endocrinology to human physiology and diseases

Recent studies have revealed the importance of fish-derived peptide hormones to human endocrinology. These peptides include melanin-concentrating hormone (MCH), urocortins (human urotensin-I), and urotensin-II. MCH, a hypothalamic peptide, is a potent stimulator on appetite. Urocortins, e.g. urocortin 1 and urocortin 3 (stresscopin), are endogenous ligands for the corticotropin-releasing factor (CRF) receptors, particularly CRF type 2 receptor, that mediates a vasodilator action, a positive inotropic action and a central appetite-inhibiting action. These actions mediated by CRF type 2 receptor may ameliorate the stress response. Human urotensin-II is a potent vasoconstrictor peptide, while it acts as a vasodilator on some arteries. Human urotensin-II is expressed in various types of cells and tissues, including cardiovascular tissues, as well as many types of tumor cells. Thus, these fish-derived peptides appear to play important roles in human physiology, such as appetite regulation, stress response and cardiovascular regulation, and also in diseases, for example, obesity, cardiovascular diseases and tumors. Development of antagonists/agonists against the receptors for these peptides may open new strategies for the treatment of various diseases, including obesity-related diseases, hypertension, heart failure and malignant tumors.

Colocalization of urocortin and neuronal nitric oxide synthase in the hypothalamus and Edinger-Westphal nucleus of the rat

Different lines of studies suggest that both the corticotropin-releasing hormone-related peptide Urocortin I (Ucn) and the neuromodulator nitric oxide (NO) are involved in the regulation of the complex mechanisms controlling feeding and anxiety-related behaviors. The aim of the present study was to investigate the possible interaction between Ucn and NO in the hypothalamic paraventricular nucleus (PVN), an area known to be involved in the modulation of these particular behaviors. Therefore, we mapped local mRNA and peptide/protein presence of both Ucn and the NO producing neuronal NO synthase (nNOS). This investigation was extended to include the hypothalamic supraoptic nucleus (SON) and the Edinger-Westphal nucleus area (EW), the latter being one of the major cellular Ucn-expressing sites. Furthermore, we compared the two predominantly used laboratory rat strains, Wistar and Sprague-Dawley. Ucn mRNA and immunoreactivity were detected in the SON and in the EW. A significant difference between Wistar and Sprague-Dawley rats was found in mRNA levels in the EW. nNOS was detected in all brain areas analyzed, showing a significantly lower immunoreactivity in the PVN and EW of Sprague-Dawley versus Wistar rats. Contrary to some previous reports, no Ucn mRNA and only a very low immunoreactivity were detectable in the PVN of either rat strain. Interestingly, double-labeling immunofluorescence revealed that in the SON approximately 75% of all cells immunoreactive for Ucn were colocalized with nNOS, whereas in the EW only approximately 2% of the Ucn neurons were found to contain nNOS. These findings suggest an interaction between Ucn and NO signaling within the SON, rather than the PVN, that may modulate the regulation of feeding, reproduction, and anxiety-related behaviors.

Urocortin in the central nervous system of a primate (Cebus apella): sequencing, immunohistochemical, and hybridization histochemical characterization

The urocortin (UCN)-like immunoreactivity and UCN mRNA distribution in various regions of the nonprimate mammalian brain have been reported. However, the Edinger-Westphal nucleus (EW) appears to be the only brain site where UCN expression is conserved across species. Although UCN peptides are present throughout vertebrate phylogeny, the functional roles of both UCN and EW remain poorly understood. Therefore, a study focused on UCN system organization in the primate brain is warranted. By using immunohistochemistry (single and double labeling) and in situ hybridization, we have characterized the organization of UCN-expressing cells and fibers in the central nervous system and pituitary of the capuchin monkey (Cebus apella). In addition, the sequence of the prepro-UCN was determined to establish the level of structural conservation relative to the human sequence. To understand the relationship of acetylcholine cells in the EW, a colocalization study comparing choline acetyltransferase (ChAT) and UCN was also performed. The cloned monkey prepro-UCN is 95% identical to the human preprohormone across the matched sequences. By using an antiserum raised against rat UCN and a probe generated from human cDNA, we found that the EW is the dominant site for UCN expression, although UCN mRNA is also expressed in spinal cord lamina IX. Labeled axons and terminals were distributed diffusely throughout many brain regions and along the length of the spinal cord. Of particular interest were UCN-immunoreactive inputs to the medial preoptic area, the paraventricular nucleus of the hypothalamus, the oral part of the spinal trigeminal nucleus, the flocculus of the cerebellum, and the spinal cord laminae VII and X. We found no UCN hybridization signal in the pituitary. In addition, we observed no colocalization between ChAT and UCN in EW neurons. Our results support the hypothesis that the UCN system might participate in the control of autonomic, endocrine, and sensorimotor functions in primates.

The effect of urocortin on ingestive behaviours and brain Fos immunoreactivity in mice

The influence of urocortin (UCN) on ingestive behaviours and brain neural activity, as measured immunohistochemically by the presence of Fos protein, was determined in mice. Rat UCN was administered by continuous intracerebroventricular (ICV) or subcutaneous (SC) infusion. ICV infusion of UCN (100 ng/h, 14 days) transiently reduced daily food and water intakes (days 1-4) but body weight was reduced from day 2 into the post-infusion period. Sodium intake was reduced from day 3 to the end of infusion. SC infusion of UCN caused similar but smaller reductions in food and water intakes and body weight, without change in sodium intake. In separate experiments, Fos immunoreactivity was increased in several brain nuclei known to be involved in the control of body fluid and energy homeostasis, e.g. central nucleus of the amygdala, median preoptic nucleus, bed nucleus of the stria terminalis and arcuate nucleus. Increased Fos expression was similar for ICV and SC infusions when measured on days 2-3 or 6-7 of infusion. In conclusion, increases of brain activity by UCN may be associated with stimulation of adrenocorticotrophic hormone release and sympathetic nervous activity, but increases may also indicate suppression of ingestive behaviours by stimulating central inhibitory mechanisms located in areas known to control body fluid and energy homeostasis.

Localization of corticoliberin receptors in the rat brain

In situ hybridization was used to study the distribution of corticoliberin receptors of subtypes 1 and 2 (CL-R1 and CL-R2 respectively) in different structures of the rat brain. Levels of CL-R1 mRNA in the brain were significantly greater than levels of CL-R2 mRNA, and the most intense expression of the CL-R1 gene was seen in forebrain structures, especially various neocortical, archicortical, and paleocortical regions in the cerebellar cortex. In addition, significant levels of CL-R1 mRNA expression were noted in the red nucleus and the reticular nucleus of the tegmentum. Intense expression of CL-R2 mRNA was observed in structures of the olfactory system, corticomedial parts of the amygdala, fields CA1-CA4 of the hippocampus, the ventromedial hypothalamus, and several brain stem nuclei. Moderate levels of CL-R2 mRNA were seen in the dorsolateral neostriatum. These results provide evidence that corticoliberin receptors of both subtypes are widespread in the brain. The different patterns of expression of CL-R1 and CL-R2 in the brain probably provide the basis for the functional specificity of action of corticoliberin in brain structures.

Regional haemodynamic effects of urocortin in the anaesthetized rat

Urocortin is an endogenous vasodilator peptide that is related to corticotrophin-releasing factor. We examined the haemodynamic effects of urocortin in thiobutabarbital-anaesthetized rats, via the triple-isotope microspheres technique. Urocortin (3 nmol/kg, i.v. bolus) reduced mean arterial pressure (-25 mm Hg) through a decrease in total peripheral resistance (-43%). This was associated with an increase in cardiac output (+24%) and vasodilatation of the following tissues: heart and stomach (approximately 300% of baseline); liver, intestine, caecum/colon, skeletal muscle and skin (approximately 200%); and testes (approximately 150%). Arterial conductances of the kidneys, spleen and brain were unaffected by urocortin. Neither the vehicle (0.9% NaCl) nor a low dose of urocortin (0.3 nmol/kg) altered any measurements. Therefore, urocortin causes generalized vasodilatation as follows: heart and stomach>liver, intestine, caecum/colon, skeletal muscle and skin>testes.

Corticotropin-releasing factor receptor type 2 messenger ribonucleic acid in rat pituitary: localization and regulation by immune challenge, restraint stress, and glucocorticoids

CRF receptor 2 (CRF R2) has been identified in the rat pituitary. However, the cell types that express the receptor remained to be determined. In the present study, we localized CRF R2 mRNA in gonadotropes of the anterior pituitary. Ribonuclease protection assays of anterior pituitary mRNA further showed that the dominant receptor type is CRF R2alpha. We also demonstrated that the expression of CRF R2 in the pituitary is sensitive to alterations to the hypothalamic-pituitary-adrenal axis as CRF R2 mRNA levels in the anterior pituitary of male rats were significantly decreased 6 h after bacterial endotoxin lipopolysaccharide (LPS) injection or restraint stress. Subcutaneous corticosterone injections also resulted in significant suppression of CRF R2 mRNA levels in the pituitary, suggesting that glucocorticoids are involved in modulating CRF R2 mRNA levels in the pituitary under stress. LPS administration still caused a significant suppression of CRF R2 mRNA levels in the anterior pituitary of adrenalectomized rats. This suggests that one or more additional factors is involved in the regulation of CRF R2 expression in the anterior pituitary. Taken together, these data suggest that CRF R2alpha in the anterior pituitary might be involved in the regulation of gonadal functions under stress.

The localisation of urocortin in the adult rat cerebellum: a light and electron microscopic study

Light and electron microscopic immunocytochemistry was used to identify the cellular and subcellular localisation of urocortin in the adult rat cerebellum. Urocortin immunoreactivity (UCN-ir) was visualised throughout the cerebellum, yet predominated in the posterior vermal lobules, especially lobules IX and X, the flocculus, paraflocculus and deep cerebellar nuclei. Cortical immunoreactivity was most evident in the Purkinje cell layer and molecular layer. Reaction product, though sparse, was found in the somata of Purkinje cells, primarily in the region of the Golgi apparatus. Purkinje cell dendritic UCN-ir was compartmentalised, with it being prevalent in proximal regions especially where climbing fibres synapsed, yet absent in distal regions where parallel fibres synapsed. In the Purkinje cell layer, the labelling was also contained in axonal terminals, synapsing directly on Purkinje cell somata. These were identified as axon terminals of basket cells based on their morphology. Terminals of stellate cells in the upper molecular layer also expressed the peptide. Whilst somata of inferior olivary neurones showed intense immunoreactivity, axonal labelling was indistinct, with only the terminals of climbing fibres containing reaction product. UCN-ir in the mossy fibre-parallel fibre system was restricted to mossy fibre rosettes of mainly posterior lobules and the varicose terminals of parallel fibres. Furthermore, labelling also was prevalent in glial perikarya and their sheaths. The current study shows, firstly, that urocortin enjoys a close ligand-receptor symmetry in the cerebellum, probably to a greater degree than corticotropin-releasing factor since corticotropin-releasing factor itself is found exclusively in the two major cerebellar afferent systems. Its congregation in excitatory and inhibitory axonal terminals suggests a significant degree of participation in the synaptic milieu, perhaps in the capacity as a neurotransmitter or effecting the release of co-localised neurotransmitters. Finally, its unique distribution in the Purkinje cell dendrite might serve as an anatomical marker of discrete populations of dendritic spines.

Cutaneous expression of corticotropin-releasing hormone (CRH), urocortin, and CRH receptors

Studies in mammalian skin have shown expression of the genes for corticotropin-releasing hormone (CRH) and the related urocortin peptide, with subsequent production of the respective peptides. Recent molecular and biochemical analyses have further revealed the presence of CRH receptors (CRH-Rs). These CRH-Rs are functional, responding to CRH and urocortin peptides (exogenous or produced locally) through activation of receptor(s)-mediated pathways to modify skin cell phenotype. Thus, when taken together with the previous findings of cutaneous expression of POMC and its receptors, these observations extend the range of regulatory elements of the hypothalamic-pituitary-adrenal axis expressed in mammalian skin. Overall, the cutaneous CRH/POMC expression is highly reactive to common stressors such as immune cytokines, ultraviolet radiation, cutaneous pathology, or even the physiological changes associated with the hair cycle phase. Therefore, similar to its central analog, the local expression and action of CRH/POMC elements appear to be highly organized and entrained, representing general mechanism of cutaneous response to stressful stimuli. In such a CRH/POMC system, the CRH-Rs may be a central element.

Expression of urotensin II and urotensin II receptor mRNAs in various human tumor cell lines and secretion of urotensin II-like immunoreactivity by SW-13 adrenocortical carcinoma cells

Urotensin II is the most potent vasoconstrictor peptide identified so far. Expression of urotensin II and urotensin II receptor mRNAs was studied in various human tumor cell lines by reverse transcriptase polymerase chain reaction (PCR) method. Secretion of urotensin II by these tumor cells was studied by radioimmunoassay. The tumor cell lines studied were T98G glioblastoma cells, IMR-32 neuroblastoma cells, NB69 neuroblastoma cells, BeWo choriocarcinoma cells, SW-13 adrenocortical carcinoma cells, DLD-1 colorectal adenocarcinoma cells and HeLa cervical cancer cells. Urotensin II mRNA was expressed in 6 tumor cell lines except for NB69 neuroblastoma cells. Urotensin II receptor mRNA was expressed in all 7 tumor cell lines. A significant amount of urotensin II-like immunoreactivity was detected only in the culture medium of SW-13 adrenocortical carcinoma cells by radioimmunoassay. Sephadex G-50 column chromatography showed that the urotensin II-like immunoreactivity in the culture medium extract was eluted earlier than synthetic human urotensin II, suggesting that SW-13 cells secreted higher molecular weight materials, perhaps partially processed forms of the urotensin II precursor. Reverse phase high-performance liquid chromatography (HPLC) showed three immunoreactive peaks, one of which was eluted in the position of urotensin II. The present study has shown for the first time expression of urotensin II and urotensin II receptor mRNAs in various tumor cell lines and the secretion of urotensin II-like immunoreactivity by SW-13 adrenocortical carcinoma cells.

Urocortin hyperpolarizes stomach smooth muscle via activation of Ca2+-sensitive K+ currents

The effect of urocortin (Uro), a recently discovered neuropeptide with selectivity towards corticotropin-releasing hormone type 2 receptor, was tested on whole cell currents expressed by guinea-pig gastric antrum smooth muscle cells. Uro (1 pmol/l-1 nmol/l) caused a concentration-dependent increase of Ca2+-sensitive K currents (I(K)) up to 500% as compared to control currents and did not affect the kinetics and voltage-dependence of inward Ca2+ currents. The I(K)-increasing effect of Uro was fully antagonized by preliminary emptying of intracellular Ca2+ stores with ryanodine and cyclopiazonic acid, as well as by bath application of selective blockers of adenylyl cyclase and cAMP-dependent protein kinase (PKA), but not by inhibitors of guanylyl cyclase, cGMP-dependent protein kinase, and protein kinase C. Comparable I(K) increase was obtained by forskolin (activator of adenylyl cyclase), Sp-cAMPS (activator of PKA), or by intracellular application of the catalytic subunit of PKA. It was concluded that Uro binds to a selective receptor in antral smooth muscle cells where it stimulates I(K) via PKA-dependent increase of Ca2+ concentration near the plasma membrane due to enhanced release from intracellular calcium stores.

Cellular localization of corticotropin releasing factor receptors in the adult mouse cerebellum

Corticotropin releasing factor is a 41 amino acid peptide that is present in afferent systems that project to the cerebellum. In the adult, this peptide modulates the activity of Purkinje cells by enhancing their responsiveness to excitatory amino acids. Two different types of corticotropin releasing factor receptors, designated type 1 and type 2, have been identified. The purpose of this study is to use immunohistochemistry to identify which corticotropin releasing factor receptors are present in the cerebellum of the adult mouse and to determine their cellular distribution. Receptor type 1 immunostaining is present throughout all lobules of the cerebellar cortex. Distinct labeling is present over the somas of most, if not all, Purkinje cells as well as the primary dendrites of Purkinje cells located at the base of vermal folia. In vermal lobules V, VI, VIII and IX numerous glial fibrillary acidic protein immunoreactive processes, oriented radially in the molecular layer, also are immunoreactive for receptor type 1. In the granule cell layer, scattered type 1 immunoreactive puncta are present throughout most cerebellar lobules. Receptor type 2 immunoreactive puncta are present throughout the molecular layer in all lobules. In addition, scattered basket and/or stellate cells, identified with a GABA antibody, are immunopositive for the type 2 receptor. In the Purkinje cell layer, the type 2 receptor immunolabeling is confined to the basal pole of the Purkinje cell including the initial axonal segment. In the granule cell layer, labeling is present over large cell bodies, and their initial axonal segments. These are likely to be Golgi cells, based on their co-staining with GABA. Finally, numerous elongated processes within the white matter, which are likely to be axons, also are type 2 immunoreactive. These data indicate that both types of corticotropin releasing factor receptor are present in the mouse cerebellum. However, the unique distribution of the two types of receptor strongly suggests a differential role for corticotropin releasing factor in modulating the activity of neurons, axons and glial cells via cell-specific ligand-receptor interactions.

Urocortin and corticotropin-releasing factor receptor expression in the human colonic mucosa

Urocortin is a newly identified member of the CRF neuropeptide family. Urocortin has been found to bind with high affinity to CRF receptors. The present study investigated urocortin and CRF receptor expression in human colonic mucosa. Non-pathologic sections of adult colorectal tissues were obtained from patients with colorectal cancer at surgery. Urocortin expression was examined using immunohistochemistry and messenger (m) RNA in situ hybridization. Isolated lamina propria mononuclear cells (LPMC) and epithelial cells were also analyzed by flow cytometry for the characterization of urocortin-positive cells, and by RT-PCR for detection of urocortin, CRF, and CRF receptor mRNA. Urocortin peptide distribution at various stages of human development (n = 35, from 11 weeks of gestation to 6 years of age) was examined by immunohistochemistry using surgical and autopsy specimens. Immunoreactive urocortin and urocortin mRNA were predominantly detected in lamina propria macrophages. Urocortin peptide expression was detected from as early as three months of age, but not before birth or in neonates. Urocortin, CRF receptor type 1 and type 2 alpha mRNA were detected in LPMC. CRF receptor type 2 beta mRNA, a minor isoform in human tissues, was also detected in LPMC, but at lower levels. Urocortin is locally synthesized in lamina propria macrophages and may act on lamina propria inflammatory cells as an autocrine/paracrine regulator of the mucosal immune system. The appearance of urocortin after birth indicates that the exposure to dietary intake and/or luminal bacteria after birth may contribute to the initiation of urocortin expression in human gastrointestinal tract mucosa.

Activation of urocortin transport into brain by leptin

There are several transport systems for peptides and polypeptides at the blood-brain barrier (BBB) which facilitate the passage of bioactive substances from blood to brain or from brain to blood. Nonetheless, it would be a novel concept for one peptide or polypeptide to activate the transport of another peptide with a similar function but unrelated structure. In this study, we report the first observation of such a phenomenon: activation of a urocortin transport system at the BBB by leptin. Urocortin, a corticotropin-releasing factor (CRF)-related neuropeptide, is a more potent suppressor of food intake than leptin or CRF when injected peripherally. Radiolabeled urocortin ((125)I-urocortin) was used for these in vivo studies in mice; it remained stable and intact during the experimental period. Unlike CRF, urocortin was not saturably transported out of the brain. There was no substantial entry of (125)I-urocortin into brain as determined by sensitive multiple-time regression analysis after iv bolus injection. Addition of leptin, however, caused a dose-related increase in the influx of (125)I-urocortin and greatly facilitated its entry into brain parenchyma; this effect disappeared at higher doses of leptin. Moreover, in the presence of an activating dose of leptin, the entry of (125)I-urocortin into brain was saturable. The results indicate that the presence of leptin contributes to the potent satiety effects of urocortin after peripheral administration. Thus, the action of leptin in the periphery extends beyond its direct passage across the BBB and involves acute modulation of an inert transport system. We believe that these findings have broad physiological implications and indicate a unique function of the BBB as a regulatory interface.