Neuroendocrinology of interleukin-1.
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Animals↗
Biomedical subjects
F Berkenbosch
Publications and source records attributed to F Berkenbosch.
Induction of beta-endorphin secretion by lymphocytes after subcutaneous administration of corticotropin-releasing factor.
Cells of the immune system can be stimulated to secrete POMC-derived peptides such as beta-endorphin and ACTH. Recently, it has been reported that CRF induces beta-endorphin secretion by human peripheral blood mononuclear cells in vitro (1). It has been shown that interleukin-1 (IL-1) mediates the CRF-induced secretion of beta-endorphin by lymphocytes in vitro. In the present report it is demonstrated that sc administration of CRF to rats can also induced beta-endorphin secretion by lymphocytes from spleen and mesenteric lymph nodes. Moreover, this CRF-induced secretion of beta-endorphin coincides with enhanced secretion of IL-1 by macrophages. Previously, we reported that IL-1 can activate CRF neurons in the hypothalamus of the brain. Our data indicate the existence of an intricate relationship between CRF and IL-1, peptides that can be viewed as playing a pivotal role in the interaction between the central nervous system and the immune system.
Animals↗
Neuroendocrine, sympathetic and metabolic responses induced by interleukin-1.
Effects on turnover of vasopressin (AVP) in the hypothalamus and on secretion of pituitary hormones, catecholamines and insulin after intraperitoneal injection of recombinant interleukin-1 (beta) (IL-1) were investigated in male wistar rats. Intraperitoneal administration of IL-1 in a dose (1 microgram) that maximally activated pituitary-adrenal activity failed to alter plasma concentrations of prolactin, luteinizing hormone and melanocyte-stimulating hormone. Rats chronically cannulated in the right jugular veins showed a time-related increase in plasma corticosterone concentrations in response to intraperitoneal administration of IL-1 that lasted up to 4 h. In the same rats, plasma epinephrine (E) and norepinephrine (NE) concentrations were only slightly elevated (2-fold increase) at 30 min and at 1 h after IL-1 administration. Unlike in endotoxin-resistant C3H/HeJ mice, where IL-1 induces hypoglycemia, IL-1 did not affect plasma concentrations of glucose and insulin in Wistar rats. In the zona externa of the median eminence, IL-1 stimulated corticotropin-releasing factor (CRF) turnover at an approximate rate of 15%/h, but did not cause a concomitant change in AVP turnover as can be observed after insulin-induced hypoglycemia. Since half of the hypothalamic CRF neurons have been shown to costore AVP, the data favor the view of a selective effect of IL-1 on a subtype of CRF neurons. We conclude that pituitary-adrenal activation in response to Il-1 is caused by CRF secretion from a subtype of CRF neurons (not storing AVP) in the rat hypothalamus.(ABSTRACT TRUNCATED AT 250 WORDS)
Adrenocorticotropic Hormone↗
Characterization and biological activity of a rat monoclonal antibody to rat/human corticotropin-releasing factor.
To produce a rat monoclonal antibody directed to rat CRF (rCRF), female Wistar rats were actively immunized with a rCRF-bovine thyroglobulin conjugate. Immunization resulted in the formation of CRF antibodies, as indicated by binding of [125I]iodo-rCRF and attenuation of the plasma corticosterone responses to ether stress. Rat spleen cells were fused with mouse myeloma P3 cells, and a hybridoma clone (PFU 83) was selected according to its capacity to bind [125I]iodo-rCRF and inhibit rCRF-induced ACTH release from cultured rat pituitary cells. PFU 83 antibodies (IgG2a subclass) are directed to the extreme C-terminal part (amino acids 38-39) of rCRF and bind with an affinity constant of 21 nM. In vitro, PFU 83 causes a parallel shift to the right of the rCRF dose-ACTH response curve, with an apparent affinity of 10 nM. PFU 83 neither binds nor blocks the ACTH-releasing activity of oCRF. Intravenous administration of PFU 83 ascites (generated in nude mice) to Wistar rats caused a dose-dependent inhibition of ether-induced ACTH secretion. Full blockade of the ACTH response to ether was found at a dose of 10 nmol PFU 83/rat. Based on the dynamics of rCRF binding and its in vitro and in vivo effects, we conclude that the rCRF-blocking bioactivity of PFU 83 is due to binding of PFU 83 to native rCRF and formation of a biologically inactive complex. Finally, we found that PFU 83 did not affect resting or ether-induced alpha MSH secretion, indicating that CRF does not play a major role in the control of alpha MSH secretion.
Adrenocorticotropic Hormone↗
Hypoglycemia enhances turnover of corticotropin-releasing factor and of vasopressin in the zona externa of the rat median eminence.
Insulin administration to overnight fasted rats causes a dose-dependent decline in plasma glucose concentrations and a dose-dependent increase in plasma ACTH concentrations. The ACTH response, but not the glucose response, was blocked by treatment with chlorpromazine-morphine-pentobarbital, indicating that the main factors triggering the ACTH response are of central, rather than peripheral, origin. To study whether insulin affected the turnover of CRF and vasopressin (AVP) in the zona externa of the median eminence (ZEME), we determined the rate of decline of both hypophysiotropic factors in rats with or without blockade of axonal transport by colchicine. In the ZEME, the concentrations of CRF and AVP were assessed by quantitative immunocytochemistry (QICC) in tissue sections or by RIA in median eminence extracts. QICC allows selective quantification of AVP and other peptides within the ZEME. The changes in the CRF content, as measured by QICC and RIA, were linearly correlated (r = 0.99), demonstrating that changes in peptide-staining intensity reflect changes in peptide content. Colchicine, when given intracisternally in a nontoxic dose of 5 micrograms, had no marked effect on resting plasma levels of ACTH and only slightly reduced the ACTH response to insulin-induced hypoglycemia. In the ZEME, CRF and AVP concentrations at rest were not affected by colchicine. In colchicine-treated rats insulin-induced hypoglycemia resulted in a prominent decline in CRF and AVP concentrations in the ZEME. The CRF concentration declined at a rate of 23%/h over a period of 3 h. The AVP concentration declined to a similar extent as CRF over the first hour, but tended to fall at the later time points. We conclude that hypoglycemia increases turnover of both CRF and AVP in the ZEME. However, the turnover rates of both hypophysiotropic peptides do not appear to be quantitatively coupled.
Adrenocorticotropic Hormone↗
Effect of axonal transport blockade on corticotropin-releasing factor immunoreactivity in the median eminence of intact and adrenalectomized rats: relationship between depletion rate and secretory activity.
Male Wistar rats were anaesthetized, injected intracisternally (i.c.) with saline or colchicine and were decapitated at various time intervals. Trunk blood was collected for the determination of immunoreactive adrenocorticotropic hormone (ACTHi) by radioimmunoassay (RIA) and of corticosterone by a fluorometric assay. Changes in corticotropin-releasing factor (CRF) content of the median eminence (ME) were assessed by quantitative immunocytochemistry (QICC) on cryostat sections of ME preparations or by RIA of CRF in ME-extracts. Administration of colchicine resulted in a long-lasting and dose-dependent stimulation of ACTHi secretion. At a dose of 25 micrograms, high plasma ACTHi levels were found for up to 24 h. A dose of 5 micrograms per rat, that has been reported to effectively block vasopressin transport in paraventricular-neurohypophyseal neurons, resulted in a small elevation of plasma ACTHi. In intact rats, i.c. administration of saline of saline containing 5 micrograms of colchicine had no effect on the CRF content in the ME. In contrast, colchicine caused a depletion of the CRF stores in the ME of 1-week adrenalectomized (ADX) rats. The disappearance rate was 9.2%/h as measured by RIA and 11.2%/h as measured by QICC. When plasma corticosterone and ACTHi were normalized by giving ADX rats corticosterone in drinking water, the colchicine-induced depletion of the CRF stores was fully prevented. We conclude that the rate of decline of CRF in the ME of rats treated with a non-toxic dose of colchicine to block axonal transport is positively correlated to the secretory activity of CRF neurons of the paraventricular-infundibular system.
Adrenalectomy↗
Immunohistochemical localization of monoamines and cyclic nucleotides. Their application in quantitative immunofluorescence studies and tracing monoaminergic neuronal connections.
We have described immunocytochemical methods for the direct visualization of monoamine- and cGMP-containing neurons, using antibodies to the primary or secondary messengers themselves. The specificity and affinity of these antibodies were determined using quantitative immunofluorescence of gelatin models, as non-biological models, to which the native substances and their possibly cross-reacting compounds were incorporated. The use of retro- and anterograde tracers both in conjunction with immunohistochemical procedures provides the possibility to characterize transmitter specifically afferent and efferent pathways. With the presented double-label immunocytochemical procedures it is feasible to visualize and trace a projection between two brain areas, and in addition to specify the transmitters which are involved in their afferents and efferents and their target neurons and neurons of origin. Using the SCG, as a biological model, we could demonstrate that cGMP levels in individual cells could be elevated by cholinergic agonists. Moreover, using quantitative immunofluorescence of cGMP as a post- or presynaptic marker we have the possibility to measure the post-/presynaptic effects of monoamines or neuropeptides in individual neurons.
Animals↗
Corticotropin-releasing factor-producing neurons in the rat activated by interleukin-1.
Intraperitoneal administration of human recombinant interleukin-1 (IL-1) to rats can increase blood levels of corticosterone and adrenocorticotropic hormone (ACTH). The route by which IL-1 affects pituitary-adrenal activity is unknown. That the IL-1-induced pituitary-adrenal activation involves an increased secretion of corticotropin-releasing factor (CRF) is indicated by three lines of evidence. First, immunoneutralization of CRF markedly attenuated the IL-1-induced increase of ACTH blood levels. Second, after blockade of fast axonal transport in hypothalamic neurons by colchicine, IL-1 administration decreased the CRF immunostaining in the median eminence, indicating an enhanced release of CRF in response to IL-1. Third, IL-1 did not stimulate ACTH release from primary cultures of anterior pituitary cells. These data further support the notion of the existence of an immunoregulatory feedback circuit between the immune system and the brain.
Adrenal Glands↗
Histamine-immunostaining in the rat median eminence: an unexpected form of cross-reactivity with LH-RH.
By use of two antisera (alpha HA-1, alpha HA-2) raised to histamine (HA) a similar distribution of HA-positive cell bodies and fibres in the rat brain has been demonstrated, except for a dense plexus in the median eminence which was only found with alpha HA-1. The HA-immunostaining in the median eminence was similar in distribution to that of luteinizing hormone-releasing hormone (LH-RH). In gelatin models containing LH-RH a concentration-dependent increase in immunofluorescence intensity (range: 0.01-10 microM) was found with alpha HA-1 but not with alpha HA-2. To evaluate the significance of the cross-reaction of alpha HA-1 with LH-RH, antero- or postero-lateral deafferentations of the rat mediobasal hypothalamus were made to discriminate between LH-RH and HA projections to the median eminence. The LH-RH- and HA-immunostaining in the median eminence was not affected by posterolateral deafferentations but was abolished in rats with an anterolateral lesion. We conclude that the HA-immunostaining in the rat median eminence is due to a cross-reaction of alpha HA-1 with LH-RH.
Animals↗
A quantitative approach to cross-reaction problems in immunocytochemistry.
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Animals↗
Sympathoadrenal activity facilitates beta-endorphin and alpha-MSH secretion but does not potentiate ACTH secretion during immobilization stress.
The potential involvement of the sympathoadrenal system in stress-induced secretion of peptides from the intermediate lobe of the pituitary gland and the activation of the pituitary-adrenal axis was studied. Male Wistar rats were subjected to control procedures, to sympathectomy by chronic administration (8 weeks) of guanethidine and/or to medullectomy by adrenal enucleation 9 weeks prior to exposure to forced immobilization stress for various periods of time. In intact or sham-operated rats, immobilization caused a prompt increase of circulating norepinephrine, epinephrine (EPI), corticosterone and of immunoreactive adrenocorticotropic hormone (ACTHi), alpha-melanocyte-stimulating hormone (alpha-MSHi) and beta-endorphin (beta-ENDi). Peak levels of pituitary hormones were found after 10 min of stress exposure, but fell to less than 30% of these levels after 2.5 h of immobilization. Adrenal medullectomy, which abolished the stress-induced release of EPI, reduced the acute increase of plasma alpha-MSHi and beta-ENDi, but did not influence the acute increase of plasma ACTHi during immobilization stress. Also in medullectomized plus sympathectomized rats, the initial stress response of circulating ACTHi was not different from that of controls. Adrenal medullectomy with or without additional sympathectomy caused a marked increase in plasma ACTHi concentrations after prolonged stress exposure. We conclude that: catecholamines originating from the adrenalmedulla facilitate the stress-induced secretion of intermediate lobe peptides (alpha-MSHi, beta-ENDi); catecholamines from the sympathoadrenomedullary system do not contribute to the acute release of ACTH during immobilization stress; the sympathoadrenomedullary system is involved in the secondary reduction of circulating ACTHi levels seen during prolonged stress.
Adrenal Medulla↗
Corticotropin-releasing factor immunostaining in the rat spinal cord and medulla oblongata: an unexpected form of cross-reactivity with substance P.
By use of two antisera (alpha-CRFA, alpha-CRFB) raised against conjugates of o-CRF and bovine thyroglobulin, cryostat sections of formaldehyde-fixed gelatin models containing o-CRF can be stained. The staining intensity was quantitated by use of an automated microfluorimeter and was shown to be dependent on the concentration of o-CRF (1-300 microM) added to the gel. Determination of the CRF staining intensity after incorporation of o-CRF-related peptides and fragments indicated that both antisera reacted with the C-terminal region of o-CRF. They showed poor cross reactivity with r-CRF fixed in the gel. In the same models, r-CRF could be immunostained efficiently by use of an antiserum (alpha-CRFC) raised to a conjugate of r-CRF and thyroglobulin. This antiserum reacted with the N-terminal and midportion parts but not with the C-terminal fragment of o-CRF fixed in the gels. By use of both o-CRF antisera nerve fibers can be stained in the rat hypothalamus (median eminence) and in the medulla oblongata (spinal trigeminal tract and nucleus) and spinal cord (dorsal horn). Immunoinhibition experiments showed that o-CRF caused a concentration-dependent quenching (0.001-1 microM) of the immunostaining of o-CRF-containing models, rat median eminence and medulla oblongata preparations. alpha-CRFC also stained CRF immunoreactive (CRFi) fibers in the rat hypothalamus with an equal distribution to that found with the o-CRF antisera. However, no immunostaining was found in the spinal trigeminal nucleus and tract and in the dorsal horn, indicating that these fibers store different CRF-related products from those found in the hypothalamus. The CRFi in the medulla oblongata and spinal cord induced by alpha-CRFA was completely abolished 1 week after treatment of adult rats with capsaicin, a substance known to deplete Substance P (SP) from those areas. Gels incorporated with SP showed a concentration-dependent increase (range 10-1000 microM) in immunostaining with both o-CRF sera but not with the r-CRF antiserum. In addition, incubation of o-CRF sera with SP caused a concentration-dependent quenching (range 10-100 microM) of immunostaining in SP-containing models. SP at a concentration of 100 microM was also effective in quenching the CRFi in the dorsal horn and spinal trigeminal area. Quenching was also obtained with the C-terminal part of o-CRF (range 0.002-0.1 microM), which indicates that both CRF antisera contain an immunoglobulin which recognizes determinants on CRF as well as on SP.(ABSTRACT TRUNCATED AT 400 WORDS)
Amino Acid Sequence↗
Colocalization of peptide histidine isoleucine amine and corticotropin-releasing factor immunoreactivity in neurons of the rat hypothalamus: a surprising artefact.
Indirect immunocytochemistry of corticotropin-releasing factor (CRF) and peptide histidine isoleucine amide (PHI) was performed by the use of antibodies raised to CRF and PHI. The staining intensity was quantitated by using an automated microfluorimeter. CRF and PHI immunoreactive fibres showed a similar pattern of distribution in the zona externa of the median eminence of the rat hypothalamus. Administration of colchicine (50 micrograms i.c.v.) resulted in the appearance of PHI and CRF immunoreactive cell bodies in the parvocellular part of the paraventricular nucleus. The PHI immunoreactive cell bodies were of low intensity and less abundant than those stained with the CRF antisera. Microfluorimetric measurements of the immunostaining in the median eminence showed parallel changes of PHI and CRF immunostaining after adrenalectomy, administration of reserpine and/or pargyline. In order to evaluate whether these data demonstrate that PHI and CRF are colocalized in hypothalamic neurons, we studied the specificity of PHI immunostaining by the use of a nonbiological gelatin model. Although CRF and PHI do not show structural homologies, the PHI antisera caused staining of PHI containing gels (range: 0.001-1 microM) but also of rat CRF (rCRF)-containing gels (range: 10-300 microM). In addition, preincubation of one of the PHI antisera with PHI or rCRF both caused a concentration-dependent quenching of the immunostaining in PHI- and CRF-containing gels and in preparations of the median eminence. Again, higher concentrations of rCRF (100 microM) than PHI (0.1 microM) were needed to show immunoinhibition, suggesting that the PHI antiserum has much lower avidity for native and fixed rCRF than for native and fixed PHI.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
CRF and catecholamines; their place in the central and peripheral regulation of the stress response.
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Adrenal Medulla↗
Stress-induced secretion of adrenocorticotropin in rats is inhibited by administration of antisera to ovine corticotropin-releasing factor and vasopressin.
Intact handled rats were pretreated with the immunoglobulin G fractions from normal rabbit serum or antisera to ovine corticotropin-releasing factor (CRF) and/or vasopressin and subjected to restraint or formalin stress. The formalin-induced rise in plasma ACTH was reduced to 28% in rats pretreated with anti-CRF, to 53% in those pretreated with antivasopressin, and to 16% in rats given both antibodies. Pretreatment of animals with anti-CRF, antivasopressin, or a combination of both antibodies also attenuated the ACTH response to restraint stress to 13%, 37%, and 12%, respectively, of those in normal rabbit serum-treated rats. Antiserum pretreatment did not reduce the restraint- or formalin-induced rise in plasma PRL in the same animals, however. We conclude, therefore, that both vasopressin and an ovine CRF-like peptide are physiologically relevant peptides involved in stress-induced ACTH release.
Adrenocorticotropic Hormone↗
Role of epinephrine and vasopressin in the control of the pituitary-adrenal response to stress.
In addition to corticotropin-releasing factor (CRF) and structurally related peptides, arginine vasopressin (AVP), oxytocin, angiotensin II, vasoactive intestinal polypeptide, peptide histidine isoleucinamide, epinephrine (E), and norepinephrine induce secretion of adrenocorticotropin (ACTH) from corticotropic cells in vitro. The apparent affinity and intrinsic ACTH-releasing activity of these substances are lower than those of CRF. These substances can also act synergistically with CRF. In this paper the role of catecholamines and AVP in the control of ACTH release is discussed. Infusion i.v. of E increases plasma ACTH and corticosterone to levels that are normally found during stress. E-induced stimulation of pituitary-adrenal activity is mediated by beta adrenoceptors and involves release of CRF, because it can be prevented by beta-adrenoceptor blockers and by destruction of CRF neurons (hypothalamic lesions), blockade of CRF release (chlorpromazine, morphine, and Nembutal), or administration of CRF antiserum. Although stress can cause a vast increase in plasma E, circulating E is not essential for the acute stress-induced release of ACTH because blockade of beta (or alpha) adrenoceptors, administration of chlorisondamine, or extirpation of the adrenal medulla and sympathectomy do not prevent the pituitary-adrenal response to stress. In contrast, circulating E plays a major role in the release of intermediate-lobe peptides during emotional stress. Studies of the role of AVP in pituitary-adrenal control by the use of pressor receptor (V1) antagonists are not valuable because of the ineffectiveness of such antagonists in blocking AVP-induced release of ACTH from corticotropic cells in vitro. Treatment of rats with an antiserum to AVP reduces the ACTH response to stress. We conclude that AVP has an important role in stress-induced activation of the pituitary-adrenal system, possibly by potentiating the effects of CRF.
Adrenocorticotropic Hormone↗
The beta-adrenoceptor-blocking drug propranolol prevents secretion of immunoreactive beta-endorphin and alpha-melanocyte-stimulating hormone in response to certain stress stimuli.
Handled female Wistar rats were exposed to one of the following stress stimuli: restraint, electric foot shocks, passive avoidance situation, ether, or nembutal anesthesia followed by ip formalin or laparotomy. Trunk blood was collected 2-4 min after initiation of the stress stimulus for the determination of immunoreactive beta-endorphin (beta-ENDi), ACTH (ACTHi), and alpha-MSH (alpha-MSHi). All stressors evoked a rapid increase of circulating beta-ENDi to 0.75-2.10 ng/ml. All except passive avoidance situation also induced a rapid increase of plasma ACTHi to 0.45-0.70 ng/ml, whereas plasma alpha-MSHi increased after ether and restraint to 0.18-0.40 ng/ml but was not affected by formalin stress. To study the involvement of a beta-adrenoceptor mechanism in stress-induced peptide secretion, rats were treated with D-propranolol or L-propranolol 40 min before stress exposure. Propranolol did not prevent the increase of plasma ACTHi to any of the stressors studied. L-Propranolol but not its inactive D-isomer reduced (restraint, passive avoidance) or abolished (electric foot shocks) the increase in plasma beta-ENDi but did not affect the beta-ENDi response to other stressors (ether, formalin, laparotomy). Similarly, L-propranolol attenuated the alpha-MSHi response to restraint but not to ether stress. To discriminate between corticotroph or melanotroph origin of beta-ENDi released during stress, rats were treated with dexamethasone or were subjected to neurointermediate lobectomy (4 weeks). Neurointermediate lobectomy did not affect basal or stress-induced plasma ACTHi but resulted in undetectable alpha-MSHi levels. It largely prevented the beta-ENDi response to restraint stress (propranolol sensitive) but had little effect on the beta-ENDi response to formalin stress (propranolol insensitive). Conversely, dexamethasone prevented stress-induced ACTHi response without affecting plasma alpha-MSHi. The beta-ENDi response to restraint stress (propranolol sensitive) was not changed but the response to formalin stress (propranolol insensitive) was largely prevented by dexamethasone. These results show that the intermediate lobe is the main source of beta-ENDi secreted during exposure to stressors with a high emotional impact. Since intermediate lobe peptide secretion induced by such stimuli can be prevented by beta-adrenoceptor blockade, we speculate that stress-induced discharge of catecholamines, possibly from the adrenal medulla, is the trigger signal for peptide secretion from the melanotrophs during this type of stress.
Adrenocorticotropic Hormone↗
The intestinal peptide PHI-27 potentiates the action of corticotropin-releasing factor on ACTH release from rat pituitary fragments in vitro.
Effects of rat corticotropin releasing factor (r-CRF) and of natural and synthetic porcine PHI-27 on ACTH release were studied by using freshly prepared anterior pituitary fragments of rats that were superfused with Krebs Ringer bicarbonate buffer (KRB). ACTH was measured in effluent medium samples by RIA. Superfusion with r-CRF-containing KRB caused a concentration-dependent (range 0.2-10 mM) increase of ACTH release. PHI alone did not alter the spontaneous release of ACTH at concentrations of up to 700 nM, but 2000 nM of natural or synthetic porcine PHI-27 enhanced the release rate of ACTH to 180 and 150% of basal ACTH release respectively. Addition of a subeffective concentration of PHI (300nM) to r-CRF containing KRB strongly potentiated its ACTH-releasing effect. Since PHI immunoreactive material is present in nerve fibres located in the external zone of the median eminence, we suggest that PHI or related products may play a physiological role in the control of ACTH secretion.
Adrenocorticotropic Hormone↗