Biological and immunological characterization of corticotropin-releasing activity in the bovine adrenal medulla

Short treatment with antalarmin alters adrenal gland receptors in the rat model of endometriosis

Endometriosis is a chronic inflammatory disorder in which endometrial tissue is found outside the uterine cavity. Previous reports suggest that there is a dysregulation of the hypothalamic pituitary adrenal axis during the progression of endometriosis. Our previous report showed that a short-term treatment with antalarmin, a corticotrophin releasing hormone receptor type 1 (CRHR1) antagonist decreases the number and size of endometriotic vesicles in the auto-transplantation rat model of endometriosis. Our current goal was to examine the mRNA expression of intra-adrenal receptors to better understand the mechanisms of the hypothalamic pituitary adrenal (HPA) axis involvement in endometriosis. We used two groups of female rats. The first received sham surgery or endometriosis surgery before collecting the adrenals after 7 days of the disease progression. The second group of animals received endometriosis surgery and a treatment of either vehicle or antalarmin (20 mg/kg, i.p.) during the first 7 days after endometriosis induction and then the disease was allowed to progress until day 60. Rats with sham surgery served as controls. Results showed that the mRNA expression of the mineralocorticoid (MRC2) receptor was lower in the rats after 7 days of endometriosis surgery and in rats with endometriosis that received antalarmin. In addition, the CRHR1 was significantly elevated in animals that received antalarmin and this was counteracted by a non-significant elevation in CRHR2 mRNA. The glucocorticoid receptor mRNA within the adrenals was not affected by endometriosis or antalarmin treatment. This report is one of the first to explore intra-adrenal mRNA for receptors involved in the HPA axis signaling as well as in the sympatho-adrenal signaling, calling for additional research towards understanding the role of the adrenal glands in chronic inflammatory diseases such as endometriosis.

Expression of urocortin and corticotropin-releasing hormone receptors in the bovine adrenal gland

Urocortin (UCN), a 40 amino acid peptide, is a corticotrophin-releasing hormone (CRH)-related peptide. The biological actions of CRH family peptides are mediated via two types of G protein-coupled receptors, CRH type 1 receptor (CRHR1) and CRH type 2 receptor (CRHR2). The aim of the present study was to investigate the expression of UCN, CRHR1 and CRHR2 by immunohistochemistry, western blot and real-time RT-PCR in the bovine adrenal gland to clarify the mechanisms of the intra-adrenal CRH-based regulatory system. The results showed that UCN, CRHR1 and CRHR2 were expressed in both the cortex and medulla. Specifically, UCN-immunoreactivity (IR) was distributed in the outer part of the zona fasciculata and in the zona reticularis of the cortex and in the medulla. UCN and CRHR2 mRNA expression levels were higher in the cortex than in the medulla, while CRHR1 mRNA levels were undetectable in the cortex. These results suggest that UCN, CRHR1 and CRHR2 are expressed in the bovine adrenal gland and that UCN might play a role in the intra-adrenal CRH-based regulatory system through an autocrine mechanism.

A specific CRH antagonist attenuates ACTH-stimulated cortisol secretion in ovine adrenocortical cells

Corticotropin releasing hormone (CRH) has been detected in the adrenal gland of many species and may be involved in regulation of glucocorticoid secretion. In cultured human fetal adrenal definitive/transitional zone cells, CRH upregulates the adrenocorticotropic hormone (ACTH) receptor and steroidogenic enzymes and is blocked by the selective CRH type 1 receptor (CRH(1)) antagonist, antalarmin. Based on these findings and evidence that antalarmin infusion into sheep suppressed prepartum increases in cortisol, we hypothesized that antalarmin would influence adrenal cortisol secretion. Antalarmin strongly attenuated ACTH and forskolin (FSK)-stimulated cortisol and cyclic adenosine monophosphate (cAMP) release from cultured ovine adrenocortical cells but did not prevent ACTH binding to cells or ACTH-induced proliferation in adult cells. Corticotropin releasing hormone was minimally effective as a secretagogue but increased the cortisol response to subsequent ACTH. These results suggest that antalarmin attenuates ACTH-induced cortisol secretion from cultured ovine adrenal cortical cells at a site distal to the ACTH receptor. Although CRH may modulate the secretory response to ACTH, it is probably not a direct cortisol secretagogue in the sheep.

Influence of Stress and Nutrition on Cattle Immunity

Today, the scientific community readily embraces the fact that stress and nutrition impact every physiologic process in the body. At last, the specific mechanisms by which stress and nutrition affect the immune function are being elucidated. The debate among animal scientists concerning the definition and quantification of stress as it relates to animal productivity and well-being is ongoing. However, an increased appreciation and understanding of the effects of stress on livestock production has emerged throughout the scientific community and with livestock producers. The intent of this article is to provide an overview of the general concepts of stress and immunology, and to review the effects of stress and nutrition on the immune system of cattle.

Distribution of corticotropin releasing hormone in the fetus, newborn, juvenile, and adult baboon

Corticotropin releasing hormone (CRH) has previously been identified in extrahypothalamic tissues and may act in a paracrine fashion within these tissues. To date, CRH production and its role in the fetus and newborn have not been investigated. The aim of this study was to explore the distribution and ontogeny of CRH in extrahypothalamic tissues of the fetus, newborn, juvenile, and adult baboon. Pituitary, adrenal, kidney, liver, and lung tissues from baboons at 125 d gestation, 140 d gestation, 185 d gestation (term), juveniles, and adults were obtained at necropsy. The tissues were quantified for protein and immunoreactive CRH was determined by a RIA. CRH levels were normalized to the protein content of each tissue. CRH was present in all tissues and varied over a 100-fold range according to tissue type. The highest concentration of CRH was found in the pituitary, which did not differ with the gestation and/or age of the animal. In the lung tissues of 125- and 140-d gestation animals, CRH was greater than the term, juvenile, and adult lung (p < 0.02). CRH in the adrenal gland of the 125-d samples was greater than the other four ages tested (p < 0.02). Liver CRH levels were higher in the term animals compared with the juvenile baboons. Our study documents the existence of CRH in extrahypothalamic tissues of the baboon from 125 d of gestation to adulthood. Given its presence and distribution, we speculate that CRH may exert ongoing paracrine and/or autocrine actions in these tissues from the time of intrauterine life throughout adulthood.

Corticotropin-releasing hormone induces Fas ligand production and apoptosis in PC12 cells via activation of p38 mitogen-activated protein kinase

Recent experimental findings involve corticotropin-releasing hormone (CRH) in the cellular response to noxious stimuli and possibly apoptosis. The aim of the present work was to examine the effect of CRH on apoptosis and the Fas/Fas ligand system in an in vitro model, the PC12 rat pheochromocytoma cell line, which is widely used in the study of apoptosis and at the same time expresses the CRH/CRH receptor system. We have found the following. CRH induced Fas ligand production and apoptosis. These effects were mediated by the CRH type 1 receptor because its antagonist antalarmin blocked CRH-induced apoptosis and Fas ligand expression. CRH activated p38 mitogen-activated protein kinase, which was found to be essential for CRH-induced apoptosis and Fas ligand production. CRH also promoted a rapid and transient activation of ERK1/2, which, however, was not necessary for either CRH-induced apoptosis or Fas ligand production. Thus, CRH promotes PC12 apoptosis via the CRH type 1 receptor, which induces Fas ligand production via activation of p38.

Corticotropin-releasing hormone stimulates steroidogenesis in cultured human adrenal cells

The effects of corticotropin releasing hormone (CRH) on steroid production by cultures of human fetal adrenal cells was investigated. We found that CRH, at concentrations that have been reported to exist in human fetal serum, stimulated dehydroepiandrosterone sulfate (DS) and cortisol production by cultured fetal zone and neocortical zone cells. A dose-dependent increase in secretion of both steroids was noted, with the cortisol pathway being preferentially enhanced by CRH at high concentrations. Pretreatment of adrenal cells for 3 days made them more responsive to ACTH stimulation and such effects were dose-dependent also. Inclusion of the antagonist, alpha-helical CRH (9-41) blocked CRH-induced stimulation of DS and cortisol over a broad dose range and also interfered with the augmentation of cortisol secretion noted after ACTH in CRH treated cells. CRH had no effects on adrenal cell proliferation or total cell protein. These studies are suggestive that CRH, either of systemic origin or else produced within the adrenal itself, has the potential to be a modulator of adrenal steroid production in the human.

Adrenomedullectomy prevents the suppression of pulsatile luteinising hormone release during fasting in female rats

Fasting inhibits the pulsatile secretion of luteinising hormone (LH) in female rats, an effect which is potentiated by the presence of oestradiol (E2). We have previously described various pharmacological or surgical treatments that can rapidly restore the pulses in a fasting animal. Nevertheless, the central and peripheral mechanisms that mediate this suppression of the pulses remain unclear. We have recently shown that adrenomedullectomy prevents the suppression of LH pulses by insulin-induced hypoglycaemia, a state which activates the sympathoadrenal axis. The present study was undertaken to establish whether this axis might contribute to the loss of the pulses that occurs in ovariectomised E2-treated rats that have been fasted for 48 h. Following sham adrenomedullectomy LH pulses were observed in animals fed ad libitum; after 48 h of fasting the animals that had received this sham procedure showed a significant suppression of LH levels and LH pulse frequency. In contrast, adrenomedullectomy prevented the inhibition of the pulses by 48 h of fasting; it had no effect on the pulses in the absence of fasting. These results suggest that adrenomedullary activity plays a significant role in the fasting-induced suppression of LH pulses in rats.

KAT45, a noradrenergic human pheochromocytoma cell line producing corticotropin-releasing hormone

KAT45 cells were derived from a human pheochromocytoma, which also caused ectopic Cushing's syndrome, and developed into a cell line spontaneously after the continuous primary culture of the tumor cells. These human pheochromocytoma cells were compared with the extensively characterized PC12 rat pheochromocytoma cell line. KAT45 cells resembled PC12 cells in morphology, proliferation rate, response to cholinergic stimuli, and the development of dendrite-like projections after exposure to nerve growth factor. They produced norepinephrine and epinephrine in a ratio of 50:1, as opposed to production of dopamine by PC12 cells, in amounts 1 order of magnitude higher compared with PC12. Because of the ectopic Cushing's syndrome in our patient, her normal ACTH level, and the knowledge that PC12 cells and even normal rat chromaffin cells appear to produce CRH, we examined whether KAT45 cells also produced this neuropeptide. Indeed, KAT45 cells released authentic CRH and contained an apparently intact CRH transcript. Nicotine and KCl depolarization stimulated the secretion of CRH, whereas interleukin-1beta, glucocorticoids, and nerve growth factor stimulated its synthesis. In addition to the potential systemic effects of CRH, which in our patient produced ectopic Cushing's syndrome, CRH can exert paracrine effects within normal or tumoral adrenals. We used KAT45 cells as a model for the study of the local role of CRH. CRH affected several parameters of KAT45 cell metabolism, including their proliferation rate, synthesis of catecholamines, and production of POMC-derived peptides. KAT45 cells, in addition to the data they provided regarding the in vitro profile of a human CRH-producing pheochromocytoma, may prove to be a valuable auxiliary to the PC12 cell line.

Comparative study between normal rat chromaffin and PC12 rat pheochromocytoma cells: production and effects of corticotropin-releasing hormone

The adrenal medulla of several species and some human pheochromocytomas contain CRH. The first aim of the present work was to find out whether normal rat adrenal chromaffin cells and the PC12 rat pheochromocytoma cell line produce CRH in vitro and what regulates its production. CRH was measured and characterized in the media of both types of chromaffin cells under basal conditions and after exposure to K+, nicotine, interleukin-1 beta, and nerve growth factor (NGF). The second aim was to examine the biological effect of exogenous CRH (and of its antagonist) on the production of catecholamines from these two types of cells. Our results are as follows: 1) Both types of chromaffin cells contained and secreted comparable amounts of immunoreactive-CRH under basal conditions and after K(+)-induced depolarization, nicotine, and interleukin-1 beta; 2) the physicochemical characteristics of the immunoreactive-CRH in the cells and the media were identical to the putative CRH peptide on both sieve chromatography and RP-HPLC; 3) synthetic CRH induced the production of catecholamines from both cell types in a dose- and time-dependent manner; this effect was abolished by the antagonist, alpha helical CRH; 4) exposure of PC12 cells to NGF (for 1 week) resulted in their neuronal differentiation and the stimulation of their production of CRH by 30 times and of dopamine by 10 times, compared with parallel controls; this effect of NGF was abolished by alpha helical CRH. In conclusion, our data suggest that the production of CRH by PC12 cells represents the preservation of a normal chromaffin cell characteristic rather than a tumor-induced ectopic phenomenon.

Mifepristone modulation of ACTH and CRH regulation of bovine adrenocorticosteroidogenesis in vitro

Mifepristone (RU486), bovine corticotropin-releasing hormone (CRH), arginine vasopressin (VP), adrenocorticotropin (ACTH1-24), and protein kinase activators (forskolin, [FSK]; phorbol 12-myristate 13-acetate [PMA]) were used in vitro to investigate their direct effect on adrenocorticosteroidogenesis. Bovine adrenocortical fasciculata/reticularis cells (2 x 10(5) viable cells/well) were cultured for 3 d in medium supplemented with 10% fetal calf serum. After incubation for an additional 24 hr in serum-free medium, cells were treated with serum-free medium alone (Control) or various concentrations of ACTH, CRH, VP, FSK, PMA, RU486, and/or various concentrations for 1, 2, 4, or 24 hr. Medium content of cortisol and progesterone were determined by radioimmunoassays. ACTH, CRH, FSK, and PMA each stimulated (P < 0.05) secretion of cortisol in time- and dose-related manners. Although these agents stimulated (P < 0.05) secretion of progesterone in a dose-related manner, medium content of progesterone declined (P < 0.05) over time. The minimal effective doses of ACTH and CRH required to stimulate (P < 0.05) secretion of cortisol relative to the Control over a 4-hr culture period were 0.01 nM and 3 nM, respectively. Relative to observations at 1 hr posttreatment, 24-hr treatment with ACTH or CRH increased the medium content of cortisol by an additional 19.8- and 48-fold, respectively (whereas content of progesterone declined over that time period). VP-stimulated secretion of cortisol was time- (P < 0.05) but not dose-related. Specifically, by 24-hr posttreatment, the medium content of cortisol was increased (P < 0.05) 4.6-fold relative to the quantity of cortisol secreted by 1-hr postaddition of VP (0.01 to 1 microM). Co-treatment with RU486 (1 microM) decreased (p < 0.05) FSK-, ACTH- and CRH-stimulated secretion of cortisol by 77, 27, and 56%, respectively. Similarly, the stimulatory effects of ACTH and CRH on progesterone secretion were reduced (P < 0.05) by 40 and 22%, respectively, by co-addition of RU486. The inhibitory action of RU486 on production of cortisol was no longer apparent by 24 hr after treatment. These observations indicate that RU486 can act as a steroid agonist and as well as an antagonist. These data characterize time- and dose-related direct actions of ACTH, CRH, and RU486 on adrenocorticosteroidogenesis. This information will assist efforts to clarify complex intra-adrenal interactions of neurohormones, growth factors, and endogenous steroids.

Corticotropin-releasing hormone-like axons in the adrenal glands of fetal and postnatal sheep

The presence of corticotropin-releasing hormone outside of the brain suggests that it may have functional roles besides the stimulation of pituitary adrenocorticotropin. The purpose of the present study was to determine immunohistochemically, the ontogeny of corticotropin-releasing hormone-like immunoreactivity in sheep adrenals from fetal day 100 to adult. Adrenal corticotropin-releasing hormone-like immunoreactivity: 1) was found in all animals examined, 2) existed as clusters of darkly beaded axon-like fibers over medullary cells at the medullary-cortical interface or over islands of medullary cells surrounded by cortex or rays of medullary cells extending into the cortex, 3) showed a definite increase with age, 4) was depleted in newborns < 12 h old, and 5) was found in pre- and postnatal splanchnic nerves. In conclusion, corticotropin-releasing hormone-like immunopositive fibers are present in the ovine adrenal medulla at various stages of development, supporting the concept that corticotropin-releasing hormone in pre- and postnatal sheep may play a direct local part in the regulation of adrenal function.

Evidence that an extrahypothalamic pituitary corticotropin-releasing hormone (CRH)/adrenocorticotropin (ACTH) system controls adrenal growth and secretion in rats

Within two weeks, hypophysectomy induced in rats a striking decrease in the level of circulating ACTH (the concentration of which was at the limit of sensitivity of our assay system), coupled with a net reduction in the plasma corticosterone concentration and an evident adrenal atrophy. Zona fasciculata, the main producer of glucocorticoids, was decreased in volume, due to a lowering in both the number and average volume of its parenchymal cells. Subcutaneous ACTH infusion (0.1 pmol.min-1), administered during the last week following hypophysectomy, restored the normal blood level of ACTH and completely reversed all effects of hypophysectomy on the adrenals. Subcutaneous infusion for one week with alpha-helical-CRH or corticotropin-inhibiting peptide (1 nmol.min-1), which are competitive inhibitors of CRH and ACTH, evoked a further significant lowering of plasma corticosterone concentration and markedly enhanced adrenal atrophy in hypophysectomized rats. These findings strongly suggest that an extrahypothalamic pituitary CRH/ACTH system may be involved in the maintenance of the growth and steroidogenic secretory activity of the rat adrenal cortex.

Structure and dynamics of adrenal mitochondria following stimulation with corticotropin releasing hormone

The mitochondria of rat adrenals were investigated qualitatively and quantitatively in different functional states of the adrenal cortex. Following stimulation of the animals with corticotropin releasing hormone (CRH), the corticosterone serum levels reached a maximum 1 hour after stimulation with CRH. The amount of inner mitochondrial membrane within the zona fasciculata increased showing a biphasic time course, with a first maximum 2 hours and a second maximum 8 hours after stimulation. In contrast, a significant rise of mitochondrial volume occurred only 24 hours after CRH stimulation. Therefore, the dense vesicularization of mitochondrial cristae may constitute an early process to enhance the steroidogenic capacity of these cells. Within cells of the transition zone between zona glomerulosa and zona fasciculata, we could depict a special type of mitochondria with characteristic crescent-like cristae only seen after stimulation with CRH. This type of mitochondria may represent an intermediate form between mitochondria of zona glomerulosa and zona fasciculata underlining the impressive transformational capacity of adrenocortical mitochondria. After hypophysectomy, zona fasciculata cells contained mitochondria with tubular inner membranes, representing a hypofunctional state. In contrast, the hypofunctional state after hypophysectomy and the hyperfunctional state after stimulation of the adrenal cortex via CRH injection did not appear to correlate with the morphology of mitochondria from the zona reticularis and adrenal medulla.

A novel 1745-dalton pyroglutamyl peptide derived from chromogranin B is in the bovine adrenomedullary chromaffin vesicle

1. Following the recent demonstration of a glutaminyl cyclase activity localized in adrenomedullary chromaffin vesicles, an assay was developed to isolate and characterize posttranslationally modified peptides from this tissue which contain pyroglutamate. This assay consisted of spectrometric identification of peptides before and after enzymatic removal of pyroglutamyl residues. 2. Using this procedure, a pyroglutamyl peptide (BAM-1745) was isolated and sequenced and was shown to be a significant component of adrenomedullary secretory vesicles. 3. A computer search through the Swiss-Prot protein sequence database revealed a 93% identity of BAM-1745 and a fragment of human chromogranin B (Gln580-Tyr593).