Expression Of Urocortin Research Articles

Urocortin stimulates tyrosine hydroxylase activity via the cAMP/protein kinase A pathway in rat Pheochromocytoma PC12 cells

Urocortin is a novel mammalian member of the corticotrophin releasing factor (CRF)-related peptides. We have investigated the expression, mechanism of action and second messenger for urocortin in rat pheochromocytoma PC12 cells. We initially confirmed the expression of urocortin and CRF-R2β, which is thought to be an endogenous receptor for urocortin, in PC12 cells. We also demonstrate that urocortin (≥1 nM) significantly elevates the level of cAMP in these cells. Moreover, α-helical CRF-(9-41), a more specific antagonist of CRF-R2 than CRF-R1 and the adenylate cyclase inhibitor SQ22536, inhibited the urocortin-induced increase in the level of cAMP. Thus, urocortin may exert its physiological role in chromaffin cells via CRF-R2β coupling to adenylate cyclase. Urocortin (≥1 nM) significantly increased the mRNA level and activity of tyrosine hydroxylase (TH), a rate-limiting enzyme in the biosynthesis of catecholamine. Furthermore, urocortin-induced changes in TH-mRNA and activity were inhibited by H89 (a PKA inhibitor) and SQ22536 as well as α-helical CRF-(9-41). However, urocortin did not affect DNA synthesis or catecholamine secretion in these cells. In conclusion, we have demonstrated that urocortin stimulates catecholamine biosynthesis via the cAMP/protein kinase A pathway in PC12 cells, where both urocortin and its receptor, CRF-R2, are expressed.

Urocortins: take them to heart.

The urocortins, together with corticotropin releasing hormone (CRH), have a long evolutionary pedigree. In the brain, CRH largely mediates anxiogenic effects associated with the stress response, while the urocortins are concerned with adaptive and coping behaviour. The urocortins, in particular, are also expressed in peripheral sites, including the heart. Here, they may play an autocrine/paracrine role, since CRH-R2 receptor subtypes, which preferentially bind the urocortins, are also expressed in the heart. Endogenous cardiac urocortin expression is enhanced by ischaemia/reperfusion injury in vitro, and addition of exogenous urocortins reduces cell death caused by ischaemia/reperfusion in vitro, ex vivo and in vivo. In the isolated perfused heart, urocortin improves haemodynamic recovery, and partially prevents the reduction in high energy phosphates following ischaemia/reperfusion. Urocortin-mediated cardioprotection involves several mechanisms, including increased expression of Kir6.1 K(ATP) channels and HSP90, although other as yet poorly understood mechanisms have also been implicated. Moreover, there is early data suggesting that urocortin has beneficial haemodynamic effects in an ovine model of heart failure, and further studies of the value of both endogenous and exogenous urocortins in the compromised heart are clearly needed. In man, there is suggestive, though indirect, data, that urocortin may also provide an endogenous myocyte salvage mechanism against iatrogenic ischaemia/reperfusion injury associated with bypass surgery. These experimental studies suggest that assessment of the clinical use of urocortins as direct and/or cardioplegic therapies in ischaemia/reperfusion, and maybe heart failure, should be actively pursued.

Warm blood cardioplegic arrest induces mitochondrial-mediated cardiomyocyte apoptosis associated with increased urocortin expression in viable cells

ObjectivesThis study assesses the mechanisms of apoptosis in patients after on-pump coronary artery bypass graft surgery and the potential involvement of the endogenous cardiac peptide urocortin as a cardiomyocyte salvage mechanism. We have previously described the mechanisms of apoptosis after ischemia-reperfusion injury in the rat heart and shown that endogenous urocortin is cardioprotective. Here we extend these findings to the human heart exposed to ischemic-reperfusion injury. MethodsTwo sequential biopsy specimens were obtained from the right atriums of 24 patients undergoing coronary artery bypass grafting at the start of grafting and 10 minutes after release of the aortic clamp. Apoptosis was identified by means of immunocytochemical colocalization between terminal deoxynucleotidyl transferase–mediated nick end-labeling positivity and active caspase-3. Immunostaining for active caspase-9 and caspase-8 was performed to identify the pathways of apoptosis induction. Urocortin and adenosine triphosphate–dependent potassium channel expression was also assessed by means of immunocytochemistry. ResultsMyocyte apoptosis (<0.1% before coronary artery bypass grafting) was increased after coronary artery bypass grafting and reperfusion and was greater in patients with longer periods of cardioplegic arrest (3.3% ± 0.5% with <55 minutes and 5.1% ± 0.9% with 85-100 minutes, P < .001). Processing of caspase-9 was always more pronounced than that of caspase-8 (P < .05). Cardioplegic arrest was also associated with increased urocortin expression (up to 29% ± 3.5% vs <3% in samples obtained before coronary artery bypass grafting, P < .001) but only in nonapoptotic myocytes. These and surrounding viable myocytes also showed increased Kir6.1 adenosine triphosphate–dependent potassium channel expression. ConclusionsCardioplegic arrest and subsequent reperfusion result in cardiomyocyte apoptosis, largely through mitochondrial injury, as well as exclusive urocortin expression in viable cells. This finding might suggest a cardioprotective role for endogenous urocortin in human subjects.

CRH peptides modulate proliferation, melanogenesis and dendri‐city in human follicular melanocytes

Corticotropin‐releasing hormone (CRH) is the most proximal element of the hypothalamic‐pituitary‐adrenal axis (HPA) and is the chief regulator of pituitary POMC gene expression and the subsequent production and secretion of POMC peptides. Previously, our laboratories documented cutaneous expression of CRH, urocortin and functional CRH receptors (CRH‐Rs), suggesting their role in skin physiology and pathology. Human skin predominately expressed CRH‐R1 with CRH‐R2 being expressed primarily in the adnexal structures. While CRH‐R activity has been implicated in the regulation of epidermal cell function, a role for these receptors in human hair biology has not yet been demonstrated. This study was designed to investigate the effects of modified CRH peptides (D‐Glu20)‐CRH, (D‐Pro5)‐CRH and (D‐Pro4)‐urocortin with respective selectivity for CRH‐R1 and CRH‐R2 on behaviour of cultured hair follicle melanocytes (HFMs) derived from scalp of seven normal individuals. HFMs were stimulated with these peptides (10−7−10−10 m) for 72 h. (D‐Glu20)‐CRH (10−8 m) and (D‐Pro5)‐CRH (10−9 and 10−10 m) markedly increased cell dendricity, melanogenesis and proliferation (P &lt; 0.01) compared with unstimulated levels. While (D‐Pro4)‐urocortin failed to stimulate cell dendricity, this peptide did stimulate melanogenesis (10−8 m) (P &lt; 0.01) and exhibited a biphasic proliferative response; stimulating pigment cell division at 10−7 and 10−8 m (P &lt; 0.01) but inhibiting proliferation at 10−9 and 10−10 m (P &lt; 0.01). Here, we demonstrate the existence of functionally active CRH‐Rs in cultured human scalp HFM and show that signalling via these receptors modulates follicular melanocyte dendricity, melanogenesis and proliferation. Thus, activation of CRH‐Rs may have a pivotal role in the regulation of follicular melanocyte homeostasis.

Effect of hypoxia on urocortin production in human gestational trophoblasts in vitro.

Urocortin is produced by the placenta throughout pregnancy but its regulation remains unknown. The effect of hypoxia on placental urocortin production is not known. The aim of this study was to determine the effect of in vitro hypoxia on human trophoblastic urocortin production. Placental explants and primary cultures were incubated in anaerobe hypoxic bags for 24 h in a humidified incubator. Urocortin peptide secretion and mRNA (messenger RNA) production was determined by enzyme-linked immunosorbent assay and reverse transcription-polymerase chain reaction, respectively. Morphological and functional integrity was verified by immunohistochemical analysis of urocortin expression. Vascular endothelial growth factor expression was used to verify the generation of cellular hypoxia in our in vitro system. Hypoxia did not affect urocortin secretion or mRNA expression in explant and single-cell cultures. Production was greater from first trimester than term explants and from single-cell primary cultures more than from explant cultures. Hypoxia does not influence human placental urocortin secretion or mRNA expression in vitro.

MRNA expression profiles for corticotrophin-releasing hormone, urocortin, CRH-binding protein and CRH receptors in human term gestational tissues determined by real-time quantitative RT-PCR.

Increasing maternal plasma levels of corticotrophin-releasing hormone (CRH) during the last weeks of pregnancy suggest that this stress hormone plays an important role in the control of human parturition. Little is known about the quantitative contribution of gestational tissues (other than placenta) to intrauterine formation of CRH, urocortin and CRH-binding protein (CRH-BP), or about the distribution of CRH receptors within the uterus. We have investigated the mRNA expression of CRH, urocortin, CRH-BP and CRH receptors 1 and 2 (CRH-R1 and -R2) in gestational tissues by real-time RT-PCR. Placenta, myometrium and choriodecidua were collected after uncomplicated pregnancies at term, before the onset of labour. Distribution of CRH-R1 and CRH-R2 protein was also investigated by immunostaining with receptor subtype-specific antibodies. The placenta was identified as the main site of CRH and CRH-BP mRNA expression, displaying mRNA levels >1000 and >20 times higher than those found in the myometrium and choriodecidua respectively (P<0.05 in each case). mRNA expression of urocortin was low in all tissues investigated. Myometrium and choriodecidua expressed relevant amounts of both receptor subtypes, whereas the CRH receptor population in placenta consisted mainly of CRH-R2. The high expression of CRH in placenta and the substantial expression of CRH receptors in choriodecidua and myometrium suggested that CRH derived from placenta exerts direct or indirect actions on these tissues. Neither CRH produced by myometrium or choriodecidua nor urocortin from other intrauterine sources seem to play a major role in the control of labour.

Urocortin expression in the Edinger-Westphal nucleus is down-regulated in transgenic mice over-expressing neuronal corticotropin-releasing factor

In recent years a large body of evidence has emerged linking chronic stress with increased vulnerability for depression and anxiety disorders. As corticotropin-releasing factor (CRF) is hypersecreted under these psychological conditions, we used our CRF-overexpressing (CRF-OE) mouse line to study underlying brain mechanisms possibly causing these disorders. Urocortin (Ucn), a recently discovered member of the CRF peptide family may play a role in the pathophysiology of stress-induced disorders. Stressors recruit Ucn-immunoreactive neurons in the Edinger-Westphal nucleus (E-WN), which is the major site of Ucn expression. Furthermore, E-WN Ucn mRNA levels are upregulated in CRF-deficient mice. Based on these findings, we hypothesized the down-regulation of E-WN Ucn in CRF-OE mice and consequently, altered responsiveness to stressful stimuli. Our results support this hypothesis as we found weaker immunohistochemical labeling with anti-Ucn and a six times weaker Ucn mRNA signal in E-WN in CRF-OE mice. Moreover, E-WN Ucn-expressing neurons mounted a response to acute challenge in CRF-OE mice too. From these results it is concluded that the CRF and E-WN Ucn neuronal systems work in concert in response to acute challenges, but are inversely regulated in their activities during chronic hyperactivity of the hypothalamo–pituitary–adrenal axis.

Urocortin II is expressed in human pregnant myometrial cells and regulates myosin light chain phosphorylation: potential role of the type-2 corticotropin-releasing hormone receptor in the control of myometrial contractility.

The family of CRH-related peptides are suggested to play important roles in the control of myometrial contractility during pregnancy and labor. In this study we investigated the expression of urocortin II (UCN II) in human myometrium and its ability to phosphorylate intracellular components that can be involved in modulating myometrial contractility. Using RT-PCR and fluorescent in situ hybridization, we demonstrated that UCN II and type-2 CRH receptor (CRH-R2) mRNAs were expressed in human nonpregnant and pregnant myometrium. Immunofluorescent studies confirmed protein expression of UCN II in human pregnant myometrial cells, whereas chemical cross-linking studies with radiolabeled UCN II confirmed the presence of CRH-R2 sites with an apparent molecular mass of 50 kDa. Treatment of primary human myometrial cells with UCN II to specifically activate CRH-R2 resulted in a dose-dependent increase of myosin light chain (MLC(20)) phosphorylation. Activation of protein kinase C (PKC) and ERK1/2 was required for the UCN II-induced activation of MLC(20), because treatment of myometrial cells with inhibitors of MAPK kinase 1 (U0126) and PKC (bisindolylmaleimide) inhibited the UCN II-induced phosphorylation of MLC(20). Furthermore, the UCN II effect on MLC(20) was dependent on RhoA translocation to the membrane and subsequent activation of RhoA-associated kinase, as shown by the use of the specific inhibitors exoenzyme C3 and Y27632. Collectively, our data suggest a distinctive role for CRH-R2- specific agonists like UCN II in the control of myometrial contractility during human pregnancy involving sequential activation of PKC, MAPK kinase 1, ERK1/2, RhoA, and RhoA-associated kinase, leading to the MLC(20) phosphorylation.

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.

Cardiac expression of urocortin (Ucn) in diseased heart; preliminary results on possible involvement of Ucn in pathophysiology of cardiac diseases.

Recently, several studies reported that urocortin (Ucn) had beneficial effects on cardiovascular system and was expressed both in the normal heart and in the heart of dilated cardiomyopathy (DCM), yet the relationship between high expression of Ucn and pathophysiology of Ucn in diseased heart has been discussed. Thus, the present study was designed to elucidate the expression of Ucn in the diseased heart by immunohistochemical approach using endomyocardial biopsy specimens. The involvement of immunoreactive Ucn in pathophysiology of cardiac disease was evaluated using endomyocardial biopsy specimens obtained from the patients with some heart diseases, including DCM and hypertrophic cardiomyopathy (HCM). Ucn was detected in all endomyocardial biopsy specimens of ventricular tissue obtained from the patients with such cardiac diseases, a specimens of atrial tissue, and normal heart specimens obtained from autopsy cases. In DCM patients, left ventricular end-diastolic pressure significantly elevated in severely stained group. On the contrary, in HCM patients, left ventricular ejection fraction was higher in the severely stained group. Ucn was expressed more abundantly in the diseased heart, especially in HCM and DCM, than in the normal heart. In conclusion, such close relationship between Ucn expression in the heart and cardiac function indicated that clinical features of Ucn resembled those of norepinephrine and Ucn could play a certain pathophysiological roles in the cardiac diseases.

Strain differences in urocortin expression in the Edinger–Westphal nucleus and its relation to alcohol-induced hypothermia

The Edinger–Westphal nucleus is the primary source of urocortin in rodent brain. Mapping of inducible transcription factors has shown that the Edinger–Westphal nucleus is preferentially sensitive to ethanol self-administration. In the present study we have immunohistochemically compared expression of urocortin and c-Fos in naive and ethanol-treated C57BL/6J and DBA/2J mouse inbred strains. We found that C57BL/6J mice possess significantly higher numbers of urocortin-expressing cells in the Edinger–Westphal compared to DBA/2J mice. Subsequent histological analysis confirmed a lower number of large neurons in the DBA/2J Edinger–Westphal nucleus. Surprisingly, despite the differences in structure, no strain differences were observed in the number of c-Fos-containing cells after acute (0.6–4.8 g/kg, i.p.) and repeated (2.4 g/kg, 14 days, one injection/day) administration of ethanol. Double-label immunohistochemistry showed that ethanol-induced c-Fos expression is present in different sets of Edinger–Westphal cells between the strains. Specifically, expression of c-Fos in C57BL/6J mice is preferentially induced in urocortin cells, while c-Fos in DBA/2J mice occurs in a mixed population of cells. Behavioral analysis of the B6D2 F2 intercross, a heterogeneous mouse strain, showed that the number of urocortin cells is positively correlated with basal temperatures and ethanol-induced hypothermia. Involvement of the Edinger–Westphal in alcohol-induced hypothermia is further confirmed by analysis of urocortin cells in the HOT/COLD selected lines. These results provide evidence that C57BL/6J and DBA/2J mice have structural differences in the Edinger–Westphal that can result in activation of different populations of neurons upon alcohol intoxication contributing to differential thermoregulation between these inbred strains.

Expression of urocortin mRNA and peptide in the human prostate and in prostatic adenocarcinoma.

Urocortin (UCN) is a recently described neuropeptide member of the CRF family, responsible for the secretion of the proopiomelanocortin-derived peptides from the pituitary gland. Although previous results have demonstrated the synthesis of several neuroendocrine factors in the prostate, no studies have been carried out on the expression of UCN in the human gland. UCN expression was evaluated in benign prostatic hyperplasia and prostatic tumor tissues by RT-PCR and immunohistochemistry. UCN mRNA and peptide were demonstrated in all specimens tested. In nonneoplastic tissues, UCN was localized in the secretory luminal epithelial and basal layer cells, in the smooth muscle component of the stroma, and in lymphoid infiltrates. An intense immunostaining was evident in prostate adenocarcinoma cells. The results of the present study demonstrate for the first time UCN expression in the human prostate and in prostate cancer, and suggest a potential involvement of UCN in prostate physiopathology.

Identification of urocortin mRNA and peptide in the human endometrium.

Urocortin is a 40-amino acid peptide belonging to the corticotropin-releasing factor (CRF) family. In human reproductive tissues, urocortin expression has been previously demonstrated in the ovary, in the placenta and fetal membranes and in pregnant uterine tissues, while no data are available on the expression of the peptide in the nonpregnant uterus. In this study, urocortin expression was evaluated by both immunohistochemistry and reverse transcription-polymerase chain reaction, in human uterine tissues and cells at different phases of the menstrual cycle. Urocortin was immunolocalized in endometrial epithelial and stromal cells, as well as in the myometrium, and in vascular smooth muscle cells. No differences between proliferative and secretory phase were observed. These results were confirmed by reverse transcription-polymerase chain reaction analysis of isolated endometrial epithelial and stromal cells, and myometrial specimens. These findings open new questions on the roles played by urocortin in the human uterus.

Distribution of urocortin in the rat’s gastrointestinal tract and its colocalization with tyrosine hydroxylase

Urocortin (Ucn), a newly identified member of the corticotropin-releasing factor (CRF) family, is not only expressed in the brain, but also abundantly present in the peripheral tissues, especially in the gastrointestinal tract (GI) as determined by radioimmuoassay. In order to determine the precise localization of urocorin in the GI, we mapped the distribution of urocortin-like immunoreactivity (ir) in the GI of the rat using an immunofluorescence histochemical technique. Ucn, both in the brain and the peripheral tissues, is involved in the regulatory control of host-defense mechanism during stress. In order to study the possible involvement of the sympathetic system in the expression of GI urocortin in response to stress, we examined the effect of chemical sympathectomy on urocortin-ir and its colocalization with tyrosine hydroxylase (TH). UCn was expressed in all parietal cells of the stomach, myenteric and submucosal plexuses as well as in cells in Lieberkühn crypts of the small and large intestine. Most of the acid secreting parietal cells contained both Ucn and TH. Chemical sympathectomy did not affect Ucn immunoreactivity of parietal cells.

Expression of urocortin and corticotropin-releasing factor receptor subtypes in the human heart.

Urocortin (Ucn) is a new member of the corticotropin-releasing factor (CRF) neuropeptide family and has positive inotropic actions and protective effects against ischemia in the rat heart. Ucn binds with very high affinity to both CRF receptor type 1 (CRF-R1) and CRF receptor type 2 (CRF-R2). However, to date, endogenous ligand(s) for CRF receptors expressed in the human heart have yet to be elucidated. In this study, we therefore examined the expression of Ucn and CRF receptors in human heart obtained at autopsy by RT-PCR, immunohistochemistry, and RIA. RT-PCR analysis demonstrated that Ucn and CRF-R2alpha mRNAs were detected in all four chambers. CRF-R1 mRNA was weakly present in some left atria, left ventricles, and in one right ventricle. CRF-R2beta mRNA was detected predominantly in the left atrium. CRF mRNA was not detected in any of the four chambers. Immunostaining for both Ucn and CRF receptors was detected in cardiac myocytes in all four chambers. Ucn-like immunoreactivity was detected in all four chambers by RIA, with the highest concentrations in the left ventricle (1.90 +/- 0.5 pmol/g wet weight, mean +/- SEM; n = 4). On the other hand, CRF-like immunoreactivity was very low or undetectable in the human heart. Sephadex G-50 column chromatography demonstrated that most of the Ucn-like immunoreactivity in the human heart was eluting earlier than the standard Ucn, with one minor peak in the position for Ucn. Ucn immunoreactivity was not detected in skeletal muscle by immunohistochemistry or RIA. These results suggest that Ucn is produced in the human heart and stored there mainly in the larger molecular weight forms. Endogenously produced Ucn may therefore exert its effects mostly through CRF-R2 in an autocrine and/or paracrine manner in the human heart.

Expression of Urocortin and Corticotropin-Releasing Factor Receptor Subtypes in the Human Heart

Expression of Urocortin and Corticotropin-Releasing Factor Receptor Subtypes in the Human Heart

Urocortin in the synovial tissue of patients with rheumatoid arthritis

Urocortin is a newly identified member of the corticotropin-releasing factor (CRF) neuropeptide family, and is known to be involved in the modulation of the inflammatory process. We examined the expression of urocortin, CRF and their receptors (CRF receptor; CRF-R) in the synovial tissue of patients with rheumatoid arthritis (RA) in order to study the possible biological roles of urocortin. Synovial tissues/fluids were obtained from 38 patients with RA, nine patients with osteoarthritis and four with trauma. We studied the concentration of urocortin in the synovial fluid using RIA, and the expression of urocortin in synovial tissue using immunohistochemistry, mRNA in situ hybridization and reverse transcriptase-PCR (RT-PCR). In addition, we examined the immunolocalization of CRF and the expression of CRF-R1, -R2-alpha and -R2-beta mRNAs utilizing RT-PCR in these synovial tissues. Urocortin concentrations in synovial fluid were higher in RA patients (79.8+/-154 pg/ml) than in control patients (12.3+/-4.8 pg/ml; P< or =0.05). Urocortin immunoreactivity and mRNA signals were both detected in synovial cells, lymphocytes, fibroblasts and macrophages. The number of urocortin-positive cells in the synovium was significantly higher in RA (73.1+/-32.1 cells per high-power field) than in control (18.4+/-10.4 cells per high-power field) patients. In addition, both urocortin immunoreactivity and mRNA signals in the synovium reached maximum levels in the active stage of RA inflammation. Moreover, the number of immunoreactive urocortin-positive cells was significantly correlated with the urocortin concentration in synovial fluid (r=0.705; P<0.001) and with histologically defined local inflammatory activity (r=0.641; P<0.001). The distribution and number of immunoreactive CRF-positive cells in synovial tissue were similar to those of urocortin-positive cells (r=0.701; P<0.001). Urocortin, CRF-R1 and CRF-R2-alpha mRNAs detected by RT-PCR were expressed in in the synovium of 10/10, 10/10 and 2/10 RA patients respectively, but CRF-R2-beta was not expressed. Urocortin was actively synthesized in the synovium of RA patients. The present study suggests that urocortin may play an important role as an autocrine and/or paracrine regulator of synovial inflammation in RA.

Expression of corticotropin releasing factor (CRF), urocortin and CRF type 1 receptors in hypothalamic-hypophyseal systems under osmotic stimulation.

The expression of corticotropin releasing factor (CRF) and urocortin in hypothalamic magnocellular neurones increases in response to osmotic challenge. To gain a better understanding of the physiological roles of CRF and urocortin in fluid homeostasis, CRF, urocortin and CRF type 1 receptor (CRFR-1) gene expression was examined in the hypothalamic-hypophyseal system usingin situ and double-label in situ hybridization following chronic salt loading. CRFR-1 expression was further examined by immunohistochemistry and receptor binding. Ingestion of hypertonic saline by Sprague-Dawley rats for 7 days induced CRF mRNA exclusively in the oxytocin neurones of the magnocellular paraventricular nucleus (PVN) and the supraoptic nucleus (SON), but induced CRFR-1 mRNA in both oxytocin and vasopressin-containing magnocellular neurones. Hypertonic saline treatment also increased urocortin mRNA expression in the PVN and the SON. In the SON, urocortin was localized to vasopressin and oxytocin neurones but was rarely seen in CRF-positive cells. Changes in CRFR-1 mRNA expression in magnocellular neurones by hypertonic saline treatment were accompanied by changes in CRFR-1 protein levels and receptor binding. Hypertonic saline treatment increased CRFR-1-like immunoreactivity in the magnocellular PVN and SON, and decreased it in the parvocellular PVN. CRF receptor binding in the PVN and SON was also increased in response to osmotic stimulation. Finally, hypertonic saline treatment increased CRFR-1 mRNA, CRFR-1-like immunoreactivity and CRF receptor binding in the intermediate pituitary. These results demonstrate that the increase in the expression of CRF and urocortin message in magnocellular neurones induced by salt loading is accompanied by an increase in CRF receptor levels and binding in the hypothalamus and intermediate pituitary. Thus, CRF and urocortin may exert modulatory effects locally within magnocellular neurones as well as at the pituitary gland in response to osmotic stimulation.

Urocortin and corticotropin-releasing factor receptor expression in normal cycling human ovaries.

Urocortin is a member of the CRF neuropeptide family and has a 43% homology to CRF in amino acid sequence. Urocortin has been found to bind with high affinity to CRF receptors. CRF has been detected in the human ovary and has been demonstrated to suppress ovarian steroidogenesis in vitro. In this study we examined urocortin and CRF receptor expression in normal cycling human ovaries, using immunohistochemistry and RT-PCR. Normal cycling human ovaries were obtained at oophorectomy and hysterectomy from patients who underwent surgery for cervical cancer or myoma uteri. Intense urocortin immunoreactivity was detected in luteinized thecal cells of regressing corpora lutea, in which only luteinized thecal cells have the capacity for steroidogenesis. Immunoreactive urocortin was also detected in luteinized granulosa and thecal cells of functioning corpora lutea, in which both cell components are capable of producing steroids. RT-PCR analyses revealed that messenger ribonucleic acid levels for urocortin, CRF, and CRF receptor type 1 and type 2alpha were significantly higher in the regressing corpus luteum than in the functioning corpus luteum. The spatial and temporal immunolocalization patterns of CRF receptor were similar to those of urocortin. These results suggest that urocortin is locally synthesized in steroidogenic luteal cells and acts on them as an autocrine and/or paracrine regulator of ovarian steroidogenesis, especially during luteal regression.

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 2α mRNA were detected in LPMC. CRF receptor type 2β 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.