Comparison of a specific two-site immunoradiometric assay with radioimmunoassay for rat/human CRF-41

Sex-dependent behavior, neuropeptide profile and antidepressant response in rat model of depression

A plethora of animal models of depression is described in the literature, aiming at mimicking different aspects of depression. Understanding the link between depression and stress has been and remains a major focus area for development of animal models, but lines of research with a more mechanistic focus targeting deficiencies in neurotransmitter systems or dysfunctional neuronal circuitries and neuroinflammation are also pursued vigorously. The main objectives of the present study were systematically to evaluate strain and sex characteristics of a genetic animal model, the Flinders Sensitive Line (FSL)/ Flinders Resistant Line (FRL), by applying behavioral, molecular and pharmacological measures relevant to depression, and compare it with the outbred Sprague Dawley rat. In addition, we aimed at comparing across strains and sex the expression of NPY, CRF, CGRP in brain regions critically involved in mood regulation, and investigating the responses to escitalopram. In line with the comparisons of FSL and FRL rats, the FSL rats weighed significantly less than SD rats. Overall, escitalopram treatment for 5-6 weeks did not have a major impact on weight, but displayed a significant antidepressant-like effect, however without any changes in NPY, CRH and CGRP expression. Our comparative study of FSL and SD rat with respect to behavioral characteristic, neuropeptide levels in various brain regions (protein and mRNA levels), and response to long-term antidepressant treatment revealed that female FSL rats showed the most pronounced depressive-like phenotype and response to SSRI treatment. However, these findings were not paralleled by changes in measures of NPY, CRH and CGRP function.

Sex differences in stress-related receptors: ″micro″ differences with ″macro″ implications for mood and anxiety disorders

Stress-related psychiatric disorders, such as unipolar depression and post-traumatic stress disorder (PTSD), occur more frequently in women than in men. Emerging research suggests that sex differences in receptors for the stress hormones, corticotropin releasing factor (CRF) and glucocorticoids, contribute to this disparity. For example, sex differences in CRF receptor binding in the amygdala of rats may predispose females to greater anxiety following stressful events. Additionally, sex differences in CRF receptor signaling and trafficking in the locus coeruleus arousal center combine to make females more sensitive to low levels of CRF, and less adaptable to high levels. These receptor differences in females could lead to hyperarousal, a dysregulated state associated with symptoms of depression and PTSD. Similar to the sex differences observed in CRF receptors, sex differences in glucocorticoid receptor (GR) function also appear to make females more susceptible to dysregulation after a stressful event. Following hypothalamic pituitary adrenal axis activation, GRs are critical to the negative feedback process that inhibits additional glucocorticoid release. Compared to males, female rats have fewer GRs and impaired GR translocation following chronic adolescent stress, effects linked to slower glucocorticoid negative feedback. Thus, under conditions of chronic stress, attenuated negative feedback in females would result in hypercortisolemia, an endocrine state thought to cause depression. Together, these studies suggest that sex differences in stress-related receptors shift females more easily into a dysregulated state of stress reactivity, linked to the development of mood and anxiety disorders. The implications of these receptor sex differences for the development of novel pharmacotherapies are also discussed.

The neuroendocrinology of childhood trauma in personality disorder

BACKGROUND

Childhood trauma has been associated with elevated central corticotropin releasing hormone (CRH) drive in adults meeting general DSM-IV criteria for personality disorder. It is not clear how this may be related to pituitary or adrenal responsiveness in personality disorder. It was hypothesized that high levels of childhood trauma would be associated with blunted cortisol and adrenocorticotropin releasing hormone (ACTH) response to the combined dexamethasone(DEX)/CRH test in adults meeting general DSM-IV criteria for personality disorder.

METHOD

24 healthy, medication free adults with personality disorder (N=16) and a group of healthy controls (N=8) underwent semi-structured diagnostic interviews and completed the Childhood Trauma Questionnaire (CTQ). Across two separate study sessions separated by at least a week, cerebrospinal fluid (CSF) was sampled by lumbar puncture for measurement of CRH concentration (N=17), and peripheral blood cortisol and ACTH levels were measured after challenge with DEX/CRH (N=24).

RESULTS

As hypothesized, high CTQ score was associated with a blunted cortisol and ACTH response to DEX/CRH challenge. Indices of cortisol and ACTH response (peak level and area under the curve (AUC)) to DEX/CRH were in turn significantly negatively correlated with CSF CRH concentration.

CONCLUSION

Childhood trauma in adults with personality disorder is associated with blunted cortisol and ACTH secretion following DEX/CRH challenge. These effects are independent of depression or posttraumatic stress disorder. Previous work would suggest that blunted pituitary-adrenal response is related to elevated central CRH drive. Corroborating this, CSF CRH levels were significantly and negatively correlated with peak level and AUC of both cortisol and ACTH.

Topiramate normalizes hippocampal NPY-LI in flinders sensitive line 'depressed' rats and upregulates NPY, galanin, and CRH-LI in the hypothalamus: implications for mood-stabilizing and weight loss-inducing effects

Topiramate is currently used in the treatment of epilepsy, but this anticonvulsant drug has also been reported to exert mood-stabilizing effects and induce weight loss in patients. Neuropeptide Y (NPY) is abundantly and widely distributed in the mammalian central nervous system and centrally administered NPY markedly reduces pharmacologically induced seizures and induces antidepressant-like activity as well as feeding behavior. Two other peptides, galanin and corticotropin-releasing hormone (CRH), have also been proposed to play a modulatory role in mood, appetite, and seizure regulation. Consequently, we investigated the effects of single and repeated topiramate (10 days, once daily: 40 mg/kg i.p.) or vehicle treatment in 'depressed' flinders sensitive line (FSL) and control Flinders resistant line (FRL) rats on brain regional peptide concentrations of NPY, galanin, and CRH. The handling associated with repeated injections reduced hippocampal levels of NPY- and galanin-like immunoreactivities (LI) while NPY- and CRH-LI levels were increased in the hypothalamus, regardless of strain or treatment. In the hippocampus, concentrations of NPY-LI, galanin-LI, and CRH-LI were lower in FSL than FRL animals. Repeated topiramate treatment selectively normalized NPY-LI in this region in the FSL animals. In the hypothalamus, galanin-LI was reduced in FSL compared to FRL animals. Topiramate elevated the hypothalamic concentrations of NPY-LI, CRH-LI, and galanin-LI in both strains. Furthermore, topiramate elevated serum leptin but not corticosterone levels. The present findings show that topiramate has distinct effects on abnormal hippocampal levels of NPY, with possible implications for its anticonvulsant and mood-stabilizing effects. Furthermore, stimulating hypothalamic NPY-LI, CRH-LI and galanin-LI as well as serum leptin levels may be associated with the weight loss-inducing effects of topiramate.

Peripheral corticotropin-releasing hormone and urocortin in the control of the immune response

Immunological and cellular stress signals trigger the release of corticotropin-releasing hormone (CRH) from the spleen, thymus and inflamed tissue. In vivo and in vitro studies generally suggest that peripheral, immune CRH has pro-inflammatory effects and acts in a paracrine manner by binding to CRH-R1 and CRH-R2 receptors on neighboring immune cells. However, it now seems likely that some of the suggested pro-inflammatory actions of CRH may be attributed to novel CRH-like peptides or to the related peptide, urocortin, which is also present in immune cells and has especially high affinity for CRH-R2 receptors.

Induction of preeclampsia like phenomena by stimulation of sympathetic nerve with cold and fasting stress

The purpose of this study was to examine the effect of cold-stress, fasting stress and cold plus fasting stress on the sympathetic nerve activity. Pregnant and nonpregnant rats were kept in cold environment (0 degrees C), or fasting condition (12 h), and cold plus fasting condition for 2 weeks. Their plasma corticotrophin releasing factor (CRF), catecholamines, insulin levels, and platelets were measured, and histological examinations were performed. In cold plus fasting stress rats, a significant increased CRF, epinephrine (E), norepinephrine (NE), and insulin levels with decreased platelet count (P<0.0001) were observed compared with control. Histological study revealed that diffused enlarged glomeruli with fibrin deposition in the kidney, hemostasis, ischemic necrosis and fibrin deposition in liver and swelling along with hemorrhagic necrosis in adrenal gland of cold plus fasting stress rats. The biochemical and histological changes in cold plus fasting, cold-stressed or fasting rats were similar to human preeclampsia. The findings observed in cold plus fasting stress rats were more pronounced either than cold-stressed or fasting group. These results demonstrate that cold plus fasting stress is an intense stimulator of sympathetic nervous system than either cold stress or fasting.

Procorticotrophin-releasing hormone: endoproteolytic processing and differential release of its derived peptides within AtT20 cells

Procorticotrophin-releasing hormone (proCRH) is expressed mainly in the hypothalamus and in the placenta, where it undergoes tissue-specific endoproteolysis. Our results show that within stably transfected AtT20/D16V cells proCRH is cleaved to generate two fragments of approximately 8 and 3 kDa which could account for proCRH(125-194) and proCRH(125-151), respectively, and a 4.5 kDa product which could account for mature IR-CRH(1-41). The immunofluorescence staining patterns for IR-CRH and IR-ACTH and their response of secretagogues indicate targeting of proCRH and POMC to the secretory pathway in transfected AtT20 cells. In this work, we have used a unique set of specific RIAs and IRMAs to the full length POMC and proCRH molecules and several products of endoproteolytic processing to assess if they could be released differentially in response to stimulation. Although the release of both IR-ACTH and IR-CRH peptides from transfected AtT20 cells is stimulated in response to exposure to high potassium stimulation (51 mM KCl/SmM CaCl2), the sorting index (SI) suggests that mature ACTH is sorted to the regulated secretory pathway 2.1-fold more efficiently than mature CRH(1-41). Mature ACTH is also sorted to the regulated secretory pathway 9-fold more efficiently than IR-proCRH(125-151). Also, mature CRH(1-41) is sorted to the regulated secretory pathway 3-fold more efficiently than IR-proCRH(125-151). These results therefore indicate that the intracellular mechanisms for the storage and release of POMC, proCRH and their endoproteolytic products differ and would sustain the hypothesis that within mammalian peptidergic cells, different biologically active peptides originating from the same or different precursor molecules, could be differentially released in response to specific stimuli. This would give these cells the capacity to finely regulate neurotransmitter release in response to environmental and physiological demands.

Corticotropin releasing factor and its binding protein

Although the lack of ACTH releasing activity of the high peripheral plasma levels of corticotropin releasing factor (CRF) of human placental origin can now be accounted for by the action of a specific sequestering plasma binding protein (pBP), there are many regions of the brain where the BP is found with little or no overlap with CRF. The existence of a mechanism promoting the rapid disappearance of pBP following bolus injection of exogenous CRF into normal individuals, which is triggered by the formation of a dimer complex (BP2/CRF2), and the elevation of pBP levels found in inflammatory disease, coupled with the lack of unequivocal evidence for endogenous CRF in many of these situations, suggests a role for pBP interaction with ligands other than CRF. We have searched for novel BP ligands in the brain and periphery and have found evidence for them in extracts of sheep brain and in synovial fluid collected from the joints of arthritic patients. These novel BP ligands could, thus, be the peptides responsible for many of the roles currently assigned to brain, peripheral, or immune CRF.

Corticotropin-releasing factor and its binding protein: maternal serum levels in term and preterm deliveries

OBJECTIVE

The primary objective of this investigation was to evaluate whether maternal serum corticotropin-releasing factor levels during pregnancy were predictive of spontaneous preterm delivery.

STUDY DESIGN

Maternal serum levels of corticotropin-releasing factor and its binding protein were measured from 20 weeks of gestation in a cross-sectional study of 396 asymptomatic women at high risk for preterm delivery.

RESULTS

Gestational age-specific corticotropin-releasing factor levels were not consistently or substantially increased for preterm compared with term deliveries, whether preterm delivery was due to preterm labor or preterm premature rupture of membranes. The binding protein for corticotropin-releasing factor did not vary according to gestational age until term, when it dropped substantially.

CONCLUSION

Serum corticotropin-releasing factor levels do not appear to be an important predictor of preterm birth in asymptomatic patients who subsequently have either preterm labor or preterm premature rupture of membranes. Nevertheless, the drop in the corticotropin-releasing factor binding protein level at term suggests that the bioavailability of corticotropin-releasing factor increases as parturition approaches.

Co-localisation of autoimmune antibodies specific for double stranded DNA with procorticotrophin-releasing hormone within the nucleus of stably transfected CHO-K1 cells

Human autoantibodies and corticotrophin-releasing hormone (CRH)-specific antibodies have been used in a double-labelling immunofluorescence technique to demonstrate that immunoreactive CRH structures are co-localised with immunostaining produced by double stranded DNA-specific human autoantibodies within the nucleus of cultured ovarian cells of Chinese hamsters (CHO-K1). This co-localisation was confirmed using confocal microscopy. A metabolic labelling technique was used to investigate the role of the cytoskeleton in mediating nuclear translocation of proCRH within stably transfected CHO-K1 cells and showed that microtubule and actin disrupting agents had no effect upon the nuclear translocation of proCRH. These results, therefore, suggest that nuclear translocation of proCRH is not affected by drugs which disrupt the cytoskeleton and, consequently, modify the diameter of the nuclear pores.

Expression of biologically active procorticotrophin-releasing hormone (proCRH) in stably transfected CHO-K1 cells: characterization of nuclear proCRH

Corticotrophin-releasing hormone (CRH) is a 41 amino acid neuropeptide which is cleaved at a pair of dibasic amino acids from a larger precursor molecule (pre-proCRH) by the action of endopeptidases. In cells possessing a regulated secretory pathway, sorting of proneuropeptides and prohormones occurs within the trans-Golgi network, where they are finally packaged into secretory vesicles to be released in response to an external stimulus. Such cells also possess a constitutive secretory pathway, and neuropeptides are also translocated into this subcellular compartment. We have recently established stably transfected CHO-K1 cells expressing the rat pre-proCRH cDNA, and shown that proCRH was localized within the secretory pathway and the nucleus of transfected cells. Both the cytoplasmic and nuclear species of IR-CRH displayed an apparent molecular weight approximately 19 kDa, consistent with the size of the uncleaved CRH precursor molecule. In this paper, we further characterized the bitopological, i.e. nuclear and cytoplasmic localization of proCRH within transfected CHO-K1 cells. Immunoreactive nuclear CRH was not extractable using detergents (Triton X-100 and CHAPS), 10 mM salt washes or RNase digestion but could be abolished by digestion with DNase I. These results therefore suggest that nuclear proCRH is in close association with DNA/chromatin. Treatment of transfected cells with inhibitors of protein and RNA synthesis for up to 24 h had no effect upon immunoreactive nuclear CRH, indicating that it is very stable with a long half life. Brefeldin A treatment had no effect upon the nuclear translocation of newly synthesized proCRH, suggesting that late stages of the secretory pathway (i.e. post rough endoplasmic reticulum compartments) of the transfected cells do not play a role in proCRH nuclear transport. We also demonstrate that proCRH synthesized within stably transfected CHO-K1 cells is capable of stimulating ACTH release from primary cultures of anterior pituitary cells, therefore showing for the first time that the intact precursor is also biologically active and could act as an ACTH secretagogue in-vivo.

Corticotrophin-releasing factor antagonist inhibits neuronal damage induced by focal cerebral ischaemia or activation of NMDA receptors in the rat brain

This study investigated the involvement of corticotrophin-releasing factor (CRF) in acute neuronal damage induced by focal cerebral ischaemia or pharmacological activation of NMDA receptors in the rat brain. Intracerebroventricular injection of a CRF receptor antagonist (alpha-helical CRF9-41), markedly inhibited ischaemic (61%) and excitotoxic (41%) brain damage. Peripheral injection of a glucocorticoid antagonist (RU38486) did not affect ischaemic damage. Ischaemic and excitotoxic damage caused increased hypothalamic concentrations of CRF. These data indicate that CRF mediates ischaemic and excitotoxic neuronal damage in the rat, but that this effect is not dependent on glucocorticoids.

High sensitivity two-site immunoradiometric and immunochemiluminometric assays for rat growth hormone-releasing hormone. Development of an acridinium ester based chemiluminescence assay for the avidin-coated bead system

High sensitivity two-site immunoradiometric and immunochemiluminometric assays were developed for the direct measurement of rat GHRH in perifusate of hypothalamic fragments and in hypophysial portal plasma. A solid phase immunoradiometric assay was developed initially using avidin-coated polystyrene beads and radioimmunoassay quality polyclonal antibodies to N-terminal and C-terminal fragments of GHRH. Immunoaffinity purification of the high affinity antibodies required a strong eluant, 1 M acetic acid with 10% dioxane. For high sensitivity, the affinity-purified C-terminal signal antibody was iodinated by the lactoperoxidase-glucose oxidase method and absorbed with avidin-BSA-IgG conjugated matrix. Conversion to an acridinium ester based immunochemiluminometric assay required substantial modifications to optimize performance. For both assays, the innovative modification of delayed addition of the bead enhanced assay performance by two-fold. By precision profile analysis the sensitivity of the immunochemiluminiometric assay (0.035 pg/tube) was two-fold better than the sensitivity of the immunoradiometric assay (0.066 pg/tube). These assays, 4-7-fold more sensitive than a highly optimized radioimmunoassay (0.26 pg/tube), were validated for direct unextracted measurement of GHRH in perifusate and in hypophysial portal plasma. They have significant advantages for biological measurements, reducing the number of hypothalami per perifusion chamber and enabling measurement of low concentrations of plasma GHRH not previously possible. The avidin-coated bead system can be flexibly used to develop high sensitivity two-site peptide assays using polyclonal antibodies. Further, this system has been extended to acridinium ester based immunochemiluminometric assays with improvement of assay performance.

Histones and related preparations interfere with immunoassays for peptide hormones

We report here that histones and certain related preparations generate a consistent interference with radioimmuno (RIA), immunoradiometric (IRMA), and enzyme-linked immunosorbent (ELISA) assays for a number of peptide hormones. Histones H1, H2A, H2B, H3, HIIA, HIIS, protamine, and the related preparations homeostatic thymus hormone and peptide MB35 generated a dose-dependent signal in both the human corticotropin-releasing hormone (CRH) and the human adrenocorticotropic hormone (ACTH) IRMA. This signal was not affected when the linker antiserum was removed from the IRMA reagent mixture, thus proving that the signal was not due to cross-reaction or sample contamination with CRH or ACTH. The above histone preparations, as well as protamine, but not ubiquitin, also generated a strong negative interference with RIAs for ACTH, CRH, rat growth hormone (rGH), and rat prolactin (rPRL). In an ELISA system for the thymic peptide facteur thymique sérique, histones and protamine again showed a strong interfering activity. When known amounts of rGH, rPRL, and hACTH were dissolved in charcoal-washed horse serum or supernatants from rat liver homogenates (centrifuged 1 h at 10,000 x g), and the corresponding RIAs and IRMA (for ACTH) were performed in the absence or presence of histones HIIA and HIIS (at 1 mg/ml level), an interfering activity of histones was again observed. We conclude that histones and some related peptide preparations have, when present in biologic fluids, a significant capacity to interfere with peptide immunoassays.

Development of a two-site immunoradiometric assay for rat/human corticotrophin-releasing factor. Application to the measurement of interleukin-1 beta-stimulated production of hypothalamic CRF in vitro

The hypothalamic hormone corticotrophin-releasing factor (CRF) is a highly conserved, 41-residue peptide, the N terminal region of which rarely induces antibody production, which has hindered the development of two-site immunometric assays. A synthetic N terminal peptide, CRF1-20-Cys-Tyr-NH2, was conjugated to bovine serum albumin through the cysteine thiol group, and used to prepare N terminal directed CRF-specific antibodies. The same peptide, conjugated through the cysteine thiol group to activated thiol-Sepharose, was used to affinity purify N terminal CRF-specific antibodies, and these were used in conjunction with a radioiodinated C terminal directed monoclonal anti-CRF antibody for the development of a specific, sensitive two-site immunoradiometric assay for CRF. To test the utility of the assay, hypothalami were stimulated in vitro with interleukin-1 beta, a putative regulator of CRF secretion, and CRF was measured in hypothalamic homogenates and conditioned media. Interleukin-1 beta dose-dependently stimulated synthesis and secretion of CRF, demonstrating the applicability of the immunoradiometric assay, and confirming previous reports that interleukin-1 beta can directly stimulate CRF secretion from the rat hypothalamus in vitro.

Prediction of protein antigenic sites in human corticotrophin-releasing hormone precursor

1. The primary structure of human corticotrophin-releasing hormone precursor (h pre-proCRH) has been analysed using a number of computer algorithms to identify the areas of highest predicted antigenicity. 2. These results were correlated with crossreactivity data obtained from studies of antibodies produced in rabbits by immunizing with h pre-proCRH, and a number of related peptides. 3. Six areas of high predicted antigenicity were identified in h pre-proCRH by the prediction routines utilized. Two of these corresponded almost exactly to the two putative cleavage sites of the prohormone, and a third lay within the C-terminal region of one of the products of post-translational processing of the prohormone, i.e. CRH(1-41). 4. Experimental crossreactivity data also indicated that a number of structural factors (e.g. Omega loops, peptide conformation) may also be involved in recognition of peptide fragments by antibodies.

Hypothalamic corticotropin-releasing hormone and opioid peptide neurons: functional changes after adrenalectomy and/or castration

The influences of short- and long-term castration and adrenalectomy (or both) upon corticotropin-releasing hormone (CRH) mRNA levels, CRH peptide levels, and endogenous opioid peptide (EOP) content in the hypothalamus, and basal and CRH-stimulated EOP release in vitro, were examined. Gonadal and adrenal steroids regulated the function of these hypothalamic peptidergic systems in terms of peptide synthesis, storage pools, and secretion. The steroids were also found to alter the sensitivity of EOPergic neurons to CRH. In some cases, evidence was obtained for an interaction between gonadal and adrenal steroids in determining neuronal function (seen as additive or counteractive effects). A finding of major importance was that the response of these peptidergic systems was markedly influenced by the duration of steroid deprivation, the results of chronic treatment often being opposite to those of acute treatment. Lastly, inspection of the data on peptide synthesis, storage and release, revealed that there was no simple relationship between these three parameters even within a single type of peptidergic neuron.

Neocortical concentrations of neuropeptides in senile dementia of the Alzheimer and Lewy body type: comparison with Parkinson's disease and severity correlations

Corticotropin releasing hormone (CRH), somatostatin (SRIF), and arginine vasopressin (AVP) concentrations were estimated using radioimmunoassay in the temporal and occipital cortices in postmortem brain from patients clinically and neuropathologically diagnosed as senile dementia of the Lewy body type (SDLT), senile dementia of the Alzheimer type (SDAT), and Parkinson's disease (PD) and from neurologically normal controls. The concentration of temporal and occipital neocortical CRH was diminished in both SDAT and SDLT compared to control values, whereas SRIF was reduced only in temporal cortex in both these conditions. In contrast, the concentrations of both CRH and SRIF were unaltered in PD. The concentrations of AVP in SDLT, SDAT, and PD were similar to those found in the control groups. The decrement in SRIF, but not CRH, was found to be correlated with some indices of severity of illness in SDAT; a similar but nonsignificant trend for SRIF was observed in SDLT.

Corticotrophin-releasing factor-41 in the human and rat-utility of a highly sensitive enzyme amplified immunometric assay

Abstract We have developed a highly sensitive and specific immunoassay for human/rat corticotrophin-releasing factor-41 (CRF-41) to enable determination of immunoreactive CRF-41 levels in biological samples. To achieve high specificity, sensitivity and speed we have used two antisera in a sandwich enzyme immunoassay combined with enzyme amplification. The assay has a sensitivity of 0.08 fmol/well compared with radioimmunoassay sensitivities of 0.5 fmol/tube and is highly specific for the intact CRF-41 molecule. Measurement of samples is complete within 24 h compared with the 5 days required to obtain sensitive radioimmunoassay measurement. The assay has been used to measure both rat hypothalamic CRF-41 tissue content and release in vitro with good correlation when compared to radioimmunoassay measurement using antisera rC70 (0.983) or R1 (0.953). The assay only measures immunoreactive CRF-41 coeluting with human/rat CRF-41 and its oxidized form Met [O(21,38)]CRF-41 in human and rat tissue extracts separated by high-performance liquid chromatography. The ability to measure immunoreactive CRF-41 in unextracted plasma allows rapid measurement and eliminates multiple extraction steps.

Cortical concentrations of corticotropin-releasing hormone and its receptor in Alzheimer type dementia and major depression

Corticotropin-releasing hormone-immunoreactivity (CRH-IR) and CRH receptors (binding capacity and affinity) were measured in postmortem cortical areas from depressed subjects, two groups of senile dementia of the Alzheimer type (SDAT), and age-, sex-, and postmortem-delay-matched controls. No difference in CRH-IR and CRH receptor status between depressed subjects and controls was noted. CRH-IR was decreased in all cortical areas in SDAT, with a corresponding increase in CRH receptor binding capacity (with no change in affinity) in occipital cortex. No effects of postmortem delay were seen. It is suggested that the increase in CRH receptor numbers in SDAT is related to the degree of distribution of pathological involvement in specific regions.

Anatomical Localization of Corticotropin-Releasing Factor and Arginine Vasopressin in the Human Hypothalamus; the Effect of Corticosteroids on their Concentrations in Human and Rat Hypothalami

Abstract In this study, we have determined the distribution of corticotropin-releasing factor and vasopressin in the human hypothalamus, and investigated the effect of glucocorticoid administration on the concentrations of both peptides. Corticotropin-releasing factor and vasopressin were measured by a two-site immunoradiometric assay and/or radioimmunoassay. The presence of both peptides was studied in extracts of eleven areas of the human hypothalamus as well as in the pituitary stalk from autopsied patients who had been free of chronic steroid administration (n = 14) or had received Corticosteroids (n = 5). Unlike vasopressin, corticotropin-releasing factor was detected in all extracts: the highest concentration was found in the pituitary stalk, whilst the lowest detectable amounts occurred in the supraoptic and lateral areas and in the mammillary bodies. This pattern of distribution is similar to that reported for the rat hypothalamus. The excellent correlation (R = 0.994) between corticotropin-releasing factor data obtained by immunoradiometric assay and by radioimmunoassay renders the presence of a corticotropin-releasing factor precursor molecule in the extracts highly unlikely. In the human brain extracts, glucocorticoid treatment affected neither the content, nor the distribution of corticotropin-releasing factor and vasopressin. In the rats, dexamethasone administration produced a 50% decrease in the vasopressin content (P < 0.05) of the basomedial and dorsal parts of the hypothalamus and had no effect on the corticotropin-releasing factor content of these areas. These results show that the distribution of corticotropin-releasing factor is similar in both human and rat hypothalami. The rat data suggest that negative feedback effects of glucocorticoids involve changes in hypothalamic vasopressin content.

Expression of biologically active human pre-procorticotropin releasing hormone in E. coli: characterization and purification

1. Human pre-procorticotropin releasing hormone (CRH) was expressed in E. coli strain TG2 as a fusion protein with beta-galactosidase. 2. A 140 kDa band which corresponded to beta-galactosidase pre-proCRH fusion protein was identified in lysates of TG2 cells harbouring the recombinant plasmid pre-proCRH (10-196) [ph PPC (10-196)] after sodium dodecyl sulphate-polyacrylamide gel electrophoresis and Coomassie Blue staining. The identity of the fusion protein was confirmed by Western blotting and a two-site immunoradiometric assay. 3. Purification of the fusion protein from isolated, washed and solubilized inclusion bodies was achieved by ion-exchange chromatography in the presence of 8 M urea. 4. When comparing the adrenocorticotropin-releasing activity on a molar basis, the potency of the chimeric CRH precursor was 4% of that of synthetic r/h CRH (1-41).

Peptides in the neocortex in Alzheimer's disease and ageing

Studies which have examined neuropeptides in Alzheimer's disease (AD) and normal ageing are reviewed. A marked specificity and selectivity is noted: most neuropeptides are normal, and the only two peptides consistently altered are somatostatin (SRIF) and corticotropin releasing hormone (CRH). Binding sites for CRH are increased in number in a reciprocal fashion to the reduction in CRH. These findings (1) provide evidence for selective vulnerability within the cortex in AD, (2) suggest that the primary site of pathology in AD may be cortical, and (3) indicate that the pathological process of AD is distinct from that of normal ageing.

Osmotic stimulation affects neurohypophysial corticotropin releasing factor-41 content: effect of dexamethasone

In this study we examined the effects of 2% saline loading (S), partial restriction of water consumption (R) or a combination of S or R with dexamethasone (DEX) treatment for 14 days on corticotropin releasing factor (CRF)-41 content of the neurointermediate lobe (NIL) and supraoptic nuclei (SON) of male Wistar rats. Arginine vasopressin (AVP) and oxytocin (OXY) contents of the NIL and SON were also assayed as well as plasma corticosterone, ACTH, [Na+] and [Cl-] concentrations. S or R for 14 days resulted in an increase in CRF-41 content and a concomitant drop in AVP and OXY contents of the NIL. Dexamethasone treatment enhanced the effect of S but not of R on NIL CRF-41 content. Dexamethasone treatment abolished the decrease in the AVP content and partially reversed the decrease in the OXY content of the NIL in response to S but not in response to R. No changes were observed in CRF-41, AVP and OXY content of the SON. Unstressed plasma corticosterone concentrations were not changed in S rats but were elevated in R rats; DEX did not prevent this elevation. Plasma ACTH concentrations were low in all groups examined. Plasma [Na+] and [Cl-] increased in response to both S and R. Increases in [Na+] and [Cl-] evoked by S but not R were prevented by DEX treatment. The results show that in the NIL, osmotic stimulation decreases AVP and OXY content, while it increases the CRF-41 content.

Central activation of thermogenesis and fever by interleukin-1 beta and interleukin-1 alpha involves different mechanisms

Interleukin-1 exists in two forms (alpha and beta) which are assumed to act on the same receptor. Both forms of the molecule stimulated fever and thermogenesis in the rat when injected into the brain, but interleukin-1 beta was more effective, and combined injection of alpha and beta elicited additive responses. The actions of interleukin-1 beta were inhibited by pretreatment of the animals with either a receptor antagonist or monoclonal antibody to corticotrophin releasing factor. The effects of interleukin-1 alpha were unaltered by these treatments. The results indicate that brain corticotrophin releasing factor mediates thermogenesis and fever induced by interleukin-1 beta but not by interleukin-1 alpha.

A specific carrier substance for human corticotrophin releasing factor in late gestational maternal plasma which could mask the ACTH-releasing activity

Late gestational maternal plasma contains a carrier substance for corticotrophin releasing factor (CRF-41) with a molecular weight in the region of 40,000. Using gel chromatography and CRF-41 immunoradiometric assay (IRMA), we show that binding of the peptide to its plasma carrier can be disrupted by treatment with urea. The binding capacity of the carrier substance is not saturated, since time-dependent incorporation of synthetic CRF-41 occurs at 4 degrees C. The carrier substance is also present in normal male plasma. It is specific for human CRF-41, not binding to ACTH, GnRH, vasopressin or ovine CRF-41. Most of the high concentration of CRF-41 in late gestational maternal plasma is bound to the carrier. Dilutions of pooled fractions containing carrier-bound CRF-41 after chromatography of maternal plasma had ACTH-releasing activity as did the synthetic peptide. However, the more concentrated chromatographic fractions at the apex of the carrier-bound CRF-41 peak showed reduced bioactivity, indicating that the higher concentrations of carrier in the original maternal plasma could mask the ACTH-releasing activity of CRF-41.

Corticotropin-releasing factor immunoreactivity in post-mortem brain from depressed suicides

Corticotropin-releasing factor immunoreactivity (CRF-I) was measured in cortical brain tissue obtained at post-mortem from 12 suicide victims with clear evidence of depressive illness and 12 age-matched and sex-matched control subjects dying by natural causes. There were no significant differences in mean CRF-I concentrations in frontal, temporal, motor and parietal cortex between the total suicide group, or the eight drug-free suicides and their matched controls. These findings suggest that cortical CRF-I concentrations are unaltered in depressive illness and are discussed in relation to recent reports of elevated CRF-I con centrations in the cerebrospinal fluid of depressed patients.

Posttranslational processing of corticotropin-releasing factor in the ovine tuberoinfundibular system and pituitary

The present studies were undertaken to characterize the immunoreactive-corticotropin-releasing factor (ir-CRF) in two areas of the ovine tuberoinfundibular system, hypophysial portal blood, and pituitary. With an antiserum raised against synthetic ovine (o)CRF(1-41) and 125I-Tyro-oCRF(1-41) as the tracer, concentrations of ir-CRF (pg/mg wet weight, n = 5) were: paraventricular hypothalamus (PVN), 11.7 +/- 2.5; median eminence (ME), 2276 +/- 296; anterior pituitary (AP), less than 0.5; posterior pituitary (PP), 10.0 +/- 2.2. Analysis of the ir-CRF in these areas on G-75 Sephadex chromatography revealed two main peaks--a 'major' peak which coeluted with synthetic oCRF(1-41) and a 'minor' peak which eluted eight fractions later. These two immunoreactive species of CRF were also found in hypophysial portal blood. When ME extract was analyzed by reverse-phase high performance liquid chromatography (HPLC), the 'minor' peak of ir-CRF eluted before that of CRF(1-41). Since CRF contains Arg35-Lys36 within its sequence, we tested the hypothesis that the 'minor' peak of ir-CRF represented a fragment, or fragments, of the molecule derived by proteolytic cleavage at this site. Tyro-oCRF(34-41) was digested with trypsin and the reaction products were identified by amino acid analysis. Two of these products were CRF(36-41) and CRF(37-41), and both migrated in the 'minor' peak area on G-75 Sephadex chromatography and HPLC. In the CRF(1-41) RIA, serial dilution of both fragments yielded nonparallel displacement curves. However, with 125I-Tyro-oCRF(34-41) as the radiolabeled ligand and Tyro-oCRF(34-41) as the standard, serial dilutions of CRF(1-41), CRF(36-41), and CRF(37-41) generated parallel displacement curves, and the molar cross-reactivities were 90%, 45% and 10% respectively. When the ir-CRF in HPLC fractions of ovine ME was measured in the Tyro-oCRF(34-41) RIA, the molar abundance of the hexapeptide and pentapeptide could be obtained. Calculations based on the premise that the 'minor' peak was solely composed of either the hexapeptide or pentapeptide indicated that CRF(36-41) could account for up to 37% of the total ir-CRF, or that CRF(37-41) could account for up to 73% of the total immunoreactivity. On more discriminating HPLC systems, immunoreactive (ir-) oCRF in the sheep median eminence (ME) could be resolved into five different molecular forms. On three distinct chromatographic systems, four of these immunoreactive species shared retention characteristics identical with synthetic oCRF(37-41), oCRF(36-41), oCRF(16-41) and oCRF(1-41), with the fifth immunoreactive peak as yet unidentified.(ABSTRACT TRUNCATED AT 400 WORDS)

Distribution of corticotropin-releasing factor-like immunoreactivity in human brain

We have measured corticotropin-releasing factor (CRF)-like immunoreactivity in the brain of 3 humans who had died of natural causes using a radioimmunoassay for human CRF. The peptide was widely and heterogeneously distributed and showed interspecies differences when compared with rat and rabbit. The highest concentrations were in hypothalamus, with substantial concentrations in cortex, and low or undetectable concentrations in several basal ganglia, cerebellum and hippocampus.