Lipocortin-1 is an endogenous inhibitor of ischemic damage in the rat brain.

Lipocortin-1 (annexin-1) is an endogenous peptide with antiinflammatory properties. We have previously demonstrated lipocortin immunoreactivity in certain glial cells and neurons in the rat brain (Strijbos, P.J.L.M., F.J.H. Tilders, F. Carey, R. Forder, and N.J. Rothwell. 1990. Brain Res. In press.), and have shown that an NH2-terminal fragment (1-188) of lipocortin-1 inhibits the central and peripheral actions of cytokines on fever and thermogenesis in the rat in vivo (Carey, F., R. Forder, M.D. Edge, A.R. Greene, M.A. Horan, P.J.L.M. Strijbos, and N.J. Rothwell. 1990. Am. J. Physiol. 259:R266; and Strijbos, P.J.L.M., J.L. Browning, M. Ward, R. Forder, F. Carey, M.A. Horan, and N.J. Rothwell. 1991. Br. J. Pharmacol. In press.). We now report that intracerebroventricular administration of lipocortin-1 fragment causes marked inhibition of infarct size (60%) and cerebral edema (46%) measured 2 h after cerebral ischemia (middle cerebral artery occlusion) in the rat in vivo. The lipocortin-1 fragment was effective when administered 10 min after induction of ischemia. Ischemia caused increased expression of lipocortin-1 around the area of infarction as demonstrated by immunocytochemistry. Intracerebroventricular injection of neutralizing antilipocortin-1 fragment antiserum increased the size of infarct (53%) and the development of edema (29%). These findings indicate that lipocortin-1 is an endogenous inhibitor of cerebral ischemia with considerable therapeutic potential.

A single exposure to amphetamine is sufficient to induce long-term behavioral, neuroendocrine, and neurochemical sensitization in rats.

Repeated treatment with psychostimulant drugs causes long-lasting behavioral sensitization and associated neuroadaptations. Although sensitization induced by a single psychostimulant exposure has also been reported, information on the behavioral and neurochemical consequences of a single psychostimulant exposure is sparse. Therefore, to evaluate whether behavioral sensitization evoked by single and repeated psychostimulant pretreatment regimens represent the same neurobiological phenomenon, the time-dependent expression of behavioral, neurochemical, and neuroendocrine sensitization after a single exposure to amphetamine was investigated in rats. A single exposure to amphetamine (5 mg/kg, i.p.) caused context-independent sensitization of the locomotor effects of amphetamine, which intensified over time. Thus, sensitization to amphetamine was marginal at 3 d after treatment and more evident after 1 week, whereas 3 weeks after treatment, profound sensitization, as well as cross-sensitization, to cocaine was observed. Amphetamine pretreatment caused an increase in the electrically evoked release of [(3)H]dopamine from nucleus accumbens, caudate putamen, and medial prefrontal cortex slices and of [(14)C]acetylcholine from accumbens and caudate slices. The hyperreactivity of dopaminergic nerve terminals appeared to parallel the development of locomotor sensitization, i.e., whereas hyperreactivity of accumbens dopaminergic terminals increased between 3 d and 3 weeks after treatment, the hyperreactivity of medial prefrontal dopaminergic terminals decreased. Pre-exposure to amphetamine also sensitized the hypothalamus-pituitary-adrenal axis response to amphetamine at 1 and 3 weeks, but not at 3 d after treatment. Because these data closely resemble those reported previously for repeated amphetamine pretreatment, it is concluded that a single exposure to amphetamine is sufficient to induce long-term behavioral, neurochemical, and neuroendocrine sensitization in rats.

Nitric oxide synthase expression and apoptotic cell death in brains of AIDS and AIDS dementia patients.

OBJECTIVES: To determine the occurrence and cellular localization of inducible nitric oxide synthase (iNOS), NOS activity and its association with cell death in brains of AIDS and AIDS dementia complex (ADC) patients. DESIGN AND METHODS: Post-mortem cerebral cortex tissue of eight AIDS patients, eight ADC patients and eight control subjects was processed for iNOS immunocytochemistry, NADPH-diaphorase activity staining as an index of NOS activity, and in situ end-labelling to detect cell death. RESULTS: iNOS-positive cells were present in the white matter of 14 out of 16 AIDS and ADC patients, whereas two out of eight control subjects showed iNOS-positive cells. iNOS immunoreactivity was exclusively localized in activated macrophages and microglial cells that both showed NADPH-diaphorase activity. In addition, NADPH-diaphorase activity, not related to iNOS immunoreactivity, was observed in astrocytes in both white and grey matter of AIDS and ADC patients. All AIDS and ADC patients, and only one control subject showed characteristic features of apoptotic cell death. CONCLUSIONS: Different forms of NOS are present in microglial cells and astrocytes of AIDS and ADC patients but are largely absent in control subjects. Although more NOS-expressing cells occur in ADC than in AIDS patients, apoptotic cell death was found in both patient groups to the same extent. We postulate that NO production in brains of AIDS patients results in cumulative cortical cell loss, which becomes neurologically evident at later stages of disease and is expressed as ADC.

Hypothalamic lesions in multiple sclerosis.

Demyelinating lesions of fiber bundles in and adjacent to the hypothalamus (i.e. the fornix. anterior commissure, internal capsule, and optic system) may be the basis for autonomic and endocrine alterations in multiple sclerosis (MS) patients. Therefore we investigated the presence and immunological activity of lesions in hypothalamic fiber bundles of 17 MS patients and 14 controls. In the MS group, 16 of 17 patients showed demyelinated lesions. The incidence of active lesions was high (60%) and outnumbered chronic inactive lesions in the internal capsule (p = 0.005). In 4 of 17 MS patients, axonal damage was observed and in 3 of 17 MS patients grey matter lesions were apparent. Duration of MS was inversely related to the active hypothalamic MS lesion score (r = -0.72, p = 0.001). Since comparison of hypothalamic lesions with MS lesions in other areas of the brain in the same patients (n = 7) showed a great similarity both as stage and appearance was concerned, this negative relation in all likelihood reflects the clinical consequences of high disease activity throughout the whole brain. In controls no demyelinating lesions were seen but in 11 control cases HLA expression was observed that was lower than that present in MS patients (p = 0.02). In the median eminence region that lacks a blood-brain barrier, all controls showed a strong HLA expression around the blood vessels. We conclude that systematic pathological investigation of the hypothalamus in MS patients reveals an unexpected high incidence of active lesions that may impact on hypothalamic functioning.

Adrenergic mechanisms involved in the control of pituitary-adrenal activity in the rat: a beta-adrenergic stimulatory mechanism.

Epinephrine or isoproterenol was infused into a lateral tail vein of female Wistar rats under Nembutal anesthesia. After 20 min of diffusion, trunk blood was collected for the determination of plasma corticosterone (B) and ACTH immunoreactivity (ACTHi). Infusion of l-epinephrine resulted in a dose-related increase in plasma ACTHi and B. Maximal levels were similar to those observed during ether stress. The pituitary-adrenal system appeared more sensitive than the cardiovascular system to epinephrine, since the ED50 values of epinephrine for its effects on ACTHi and heart rate were 165 and 840 ng/kg . min, respectively. The effect of epinephrine on pituitary-adrenal activity could be mimicked by the beta-adrenergic agonist l-isoproterenol and could be blocked by the beta-adrenergic antagonist l-propranolol, whereas d-propranolol was ineffective. The response of the pituitary-adrenal system to epinephrine was not caused by effects on peripheral parameters such as the distribution or clearance of ACTH or B but was mediated by an increase in ACTH release. The pituitary-adrenal response to epinephrine and isoproterenol was not related to changes in heart rate, blood pressure, or vasopressin secretion. Infusion of epinephrine at a dose that induced a maximal increase in plasma ACTHi and B (1000 ng/kg . min) resulted in a circulating epinephrine concentration of 11 pmol/ml, which is within the physiological range. From these data we conclude that 1) circulating epinephrine can stimulate pituitary-adrenocortical activity, 2) this action is mediated by a beta-adrenergic receptor mechanism, and 3) such a mechanism may be involved in the response of the pituitary-adrenal axis during certain forms of stress.

Diurnal variation in resting levels of corticosterone is not mediated by variation in adrenal responsiveness to adrenocorticotropin but involves splanchnic nerve integrity.

To study possible mechanisms controlling diurnal changes in corticosterone (CORT) levels, we tested the CORT responses to ACTH in the morning (AM) and evening (PM) in male Wistar and Sprague-Dawley rats. Rat ACTH-(1-39) or human ACTH-(1-24) (3.75-15 ng/rat) was given as an iv bolus or an intraarterial infusion to (un)anesthetized rats treated with dexamethasone (0.1-0.5 mg/kg, 2-6 h before ACTH). In all conditions studied, no AM/PM differences in CORT responses were found when ACTH was given in vehicle (pH 4.3-7). This contrasts with earlier studies in which ACTH was given in a strongly acid vehicle (pH 1-1.9). Administration of ACTH in such acid vehicle confirmed the reported AM/PM differences in CORT responses (P < 0.05). Because alterations in splanchnic nerve activity can modulate ACTH-induced CORT secretion, we studied the effect of splanchnic nerve transection (SPLNX) on the diurnal change in resting CORT levels in unilaterally adrenalectomized rats. SPLNX reduced resting CORT concentrations in the PM (approximately 50%; P < 0.05), but not in the AM. SPLNX did not abolish the acid vehicle-associated AM/PM differences in CORT responses to ACTH. We conclude that 1) diurnal variation in adrenal responsiveness to ACTH per se does not exist in this rat model; 2) the strongly acid vehicle interacts with ACTH-induced CORT secretion; 3) the PM rise in plasma CORT depends on the integrity of the sympathetic neural input to the adrenal gland.

Subdiaphragmatic vagotomy suppresses endotoxin-induced activation of hypothalamic corticotropin-releasing hormone neurons and ACTH secretion.

In order to assess the possibility that endotoxin-induced activation of the hypothalamus-pituitary-adrenal (HPA) axis is mediated by vagal afferents, we studied the effects of transection of the vagal nerves on endotoxin-induced Fos expression in hypothalamic corticotropin-releasing hormone (CRH) neurons and plasma ACTH and corticosterone responses. Groups of rats were subjected to sham surgery, complete subdiaphragmatic vagotomy (SVGX), or selective transection of the hepatic branch (HVGX). Two weeks after surgery, endotoxin or saline was injected i.p. and rats were sacrificed by decapitation two hours later. SVGX blocked or attenuated the ACTH response to 20 and 250 micrograms/kg endotoxin, respectively. HVGX did not suppress the ACTH response to either endotoxin dose. In addition, corticosterone responses were not affected by SVGX or HVGX. The endotoxin-induced Fos expression in CRH neurons was suppressed in SVGX, but not in HVGX animals. These observations lead us to postulate that the CRH and ACTH responses to a low dose of endotoxin are mediated by vagal afferents. The responses to a high dose of endotoxin involve additional neuronal or humoral pathways.

Antibodies in passive immunization studies: characteristics and consequences.

Antibodies to neuropeptides or hormones are frequently used in passive immunization studies to unravel their physiological role in signal transfer. In such in vivo experiments antibodies are considered to bind and thereby to biologically inactivate the endogenous substance during its journey from its site of secretion to its site of action (signalling time). However, little is known about the mechanism of action and characteristics of antibodies that determine such biological activity. Since the signalling time in neuronal and hormonal communication is short, the kinetics of antibody binding is an important feature. Here, we present a theoretical framework to describe antibody binding kinetics which can contribute to the design of passive immunization protocols. The specific effects of variation in antibody concentration, dissociation constant, and on-rate constant on these binding kinetics are demonstrated. Simple methods are described to determine these parameters, which may guide the selection of antibodies for passive immunization studies. When time is limited, the on-rate constant and the local antibody concentration are the most important determinants. Several points are illustrated for CRF signal transfer in the rat. CRF signalling time in the hypothalamo-pituitary complex, as established from dye transport experiments, was 3-7 sec. Based on parameters measured for a rat monoclonal antibody to CRF (PFU 83), we computed that half-maximal and full blockades of ether-induced ACTH secretion were associated with approximately 85% and more than 99% binding of CRF, respectively. From the theoretical framework presented in this study we conclude that, in general, the kinetics of antigen binding are sufficiently fast for antibodies to interfere with hormonal and probably nonsynaptic neuronal signal transfer. However, interference with fast signalling processes (less than 10 msec), which may occur in the brain, is unlikely.

Human recombinant interleukin-1 receptor antagonist prevents adrenocorticotropin, but not interleukin-6 responses to bacterial endotoxin in rats.

The present study was designed to analyze the role of endogenous interleukin-1 (IL-1) in the ACTH, corticosterone (CORT), and IL-6 responses of rats to bacterial endotoxin. Recombinant rat IL-1 beta (rIL-1 beta) when given ip resulted in dose-dependent increases in plasma ACTH, CORT, and IL-6 concentrations. Plasma ACTH and CORT responses could be induced by low rIL-1 beta doses that did not elevate plasma IL-6 levels. The half-maximally effective dose of rIL-1 beta was less than 0.6 microgram/kg for the ACTH and CORT responses and higher than 2.5 micrograms/kg for the IL-6 response. Time-course studies indicated that plasma ACTH and CORT concentrations were already elevated 30 min after the injection of rIL-1 beta (2.5 micrograms/kg, ip), with peak values after 1-2 h, followed by a subsequent decline. In contrast, plasma IL-6 concentrations became elevated 2 h after the injection of rIL-1 beta. In another set of experiments, the administration of endotoxin resulted in a dose-dependent elevation of the plasma ACTH, CORT, and IL-6 concentrations. The dose-response characteristics for ACTH, CORT, and IL-6 were different. The half-maximally effective dose for the ACTH and CORT, and IL-6 responses were approximately 2.5 micrograms/kg and more than 10 micrograms/kg, respectively. Time courses of plasma ACTH, CORT, and IL-6 responses to endotoxin (2.5 micrograms/kg, ip) were similar, with peak values measured after 2 h. When given alone, the human IL-1 receptor antagonist (IL-1RA; 1 or 2.5 mg/kg, ip) did not affect resting plasma ACTH and CORT concentrations and reduced plasma IL-6 concentrations in one experiment. At a dose of 1 mg/kg, IL-1RA inhibited ACTH and IL-6 responses to rIL-1 beta (2.5 micrograms/kg, ip) by 75% and 90%, respectively. Administration of IL-1RA (2.5 mg/kg, ip) 30 min after endotoxin (2.5 micrograms/kg, ip) completely prevented the ACTH response and partially inhibited the CORT response, but did not affect the IL-6 response measured 2.5 h after endotoxin administration. We conclude that 1) IL-1 receptors are involved in the ACTH and IL-6 responses to rat IL-1 beta; 2) the ACTH response, but not the IL-6 response, to a low dose dose of endotoxin in rats requires IL-1 receptor activation by endogenous produced IL-1; and 3) circulating IL-6 is not a prime mediator involved in ACTH and CORT responses to low doses of rIL-1 beta and endotoxin.

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.

Chronic psychosocial stress enhances vasopressin, but not corticotropin-releasing factor, in the external zone of the median eminence of male rats: relationship to subordinate status.

Male Wistar rats living in hierarchically structure male/female colonies were used to investigate the effects of chronic psychosocial stress on the hypothalamus-pituitary-adrenal system. Colony-housed subordinates were compared to control rats housed in male-female pairs. Classical parameters of chronic stress (thymus involution, impaired somatic growth, and elevated resting plasma corticosterone level) were found in all subordinate rats. Changes in vasopressin (AVP) and CRF stored in the external zone of the median eminence (ZEME) were measured by quantitative immunocytochemistry. Chronic psychosocial stress for 19-28 days increased AVP immunostaining in the ZEME to 160-190% of that in pair-housed controls, whereas CRF immunostaining in the ZEME remained unchanged. Within colonies, subordinates differed in avoidance behavior and aggression received (subordinate status). This intracolony subordination rank was correlated with AVP in the ZEME (P less than 0.01). Although resting corticosterone was elevated in subordinate rats (P less than 0.01), the increase in AVP was not associated with detectable secretion of AVP and/or CRF from the ZEME, as measured after blockade of axonal transport. In control rats, interaction with a dominant male increased plasma ACTH and corticosterone levels and caused depletion of AVP, but not CRF, from the ZEME. Subordinates showed suppressed hypothalamic (AVP depletion), pituitary (plasma ACTH) and adrenal (plasma corticosterone) responses to interaction with the dominant male, which may reflect suppressive actions of elevated corticosterone on CRF neurons or suprahypothalamic centers.

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.

Stress-induced increase in vasopressin and corticotropin-releasing factor expression in hypophysiotrophic paraventricular neurons.

The concerted action of CRF and vasopressin (VP) plays a critical role in regulating ACTH release from anterior pituitary cells. In this study, we have explored the expression of these neurohormones in hypophysiotropic paraventricular neurons after repeated exposure of rats to immobilization stress. Cell by cell quantitative in situ hybridization was used to evaluate the steady state level of mRNAs coding for VP and CRF. We found that 16 daily stress exposures resulted in a significant increase in the average cellular level of CRF and VP mRNAs (150% and 200% of control levels, respectively). Moreover, in the repeatedly stressed group, the number of VP-expressing parvicellular neurons was approximately doubled relative to the control value. Using quantitative immunoelectron microscopy, VP- and CRF-immunoreactive sites were assessed in the dense core vesicle compartment of CRF axon terminals in the external zone of the median eminence. We found that after repeated stress, the immunolabeling of VP was augmented, while that of CRF was slightly decreased. Concurrently, we observed a significant increase in the proportion of CRF nerve terminals that were VP positive (from 50% in controls to 90% in stressed animals). We conclude that the observed changes in CRF neurons may represent a physiological response to increased functional demand and may lead to alterations in the composition of the ACTH-releasing signal.

Selective depletion of macrophages prevents pituitary-adrenal activation in response to subpyrogenic, but not to pyrogenic, doses of bacterial endotoxin in rats.

The mechanisms by which bacterial endotoxin [lipopolysaccharide (LPS)] stimulates the hypothalamo-pituitary-adrenal axis (HPAA) have not been elucidated. The present study was designed to investigate the involvement of macrophages in plasma ACTH and corticosterone responses to LPS administration in rats using selective in vivo macrophage depletion. Intraperitoneal administration of subpyrogenic doses of LPS to normal rats resulted in elevated plasma ACTH and corticosterone concentrations, measured 2 h later. The response showed a remarkable steep dose relationship, with minimal effective doses between 0.5-1.5 micrograms (ACTH) and 0.5 micrograms or less (corticosterone)/kg BW. Plasma PRL, LH, and catecholamine (norepinephrine, epinephrine) levels were not significantly changed under the conditions used. Only at 6 h after LPS administration was a small elevation of norepinephrine noted. To deplete macrophages, rats were injected with liposomes encapsulated with dichloromethylene diphosphonate (Cl2MDP). Histochemical (acid phosphatase) and immunocytochemical techniques (monoclonal antibodies to rat macrophages coded ED1 and ED3) were applied to examine the efficiency of macrophage elimination by the Cl2MDP liposomes in cytospins of peritoneal exudates and in sections of the liver and spleen. Since cells of the macrophage lineage are considered to be the main source of IL-1 in the circulation, we also measured circulating levels of immunoreactive interleukin-1 beta (IL-1) concentrations in control and Cl2MDP liposome-treated rats by the use of a newly developed RIA. Reduced numbers of macrophages were seen in peritoneal lavages of Cl2MDP liposome-treated animals, whereas the morphological appearance and numbers of mast cells, granulocytes, and T-cells were unaffected. Similarly, macrophages were effectively eliminated in the spleen, mesenteric lymph nodes, and liver, as inferred from the reduction of macrophage staining in these organs. Plasma IL-1 concentrations could only be detected in response to a pyrogenic (2.5 mg/kg, iv) and not to a subpyrogenic (0.025 mg/kg, ip) dose of LPS. The increase in plasma IL-1 concentrations in response to the pyrogenic dose of LPS, reaching levels of 20-40 ng/ml in control rats, was blunted in animals treated with the Cl2MDP liposomes. Macrophage depletion by Cl2MDP liposomes did not affect either resting plasma corticosterone levels or the corticosterone response to ether exposure. At subpyrogenic doses of LPS, plasma ACTH and corticosterone responses were completely prevented by macrophage depletion. In contrast, at pyrogenic doses of LPS, plasma ACTH and corticosterone responses were not significantly affected by depleting macrophages. These data demonstrate that activation of the HPAA by a subpyrogenic dose of LPS is macrophage dependent. However, macrophage-independent mechanisms mediate activation of the HPAA in response to a pyrogenic dose of LPS.

Physiological role of corticotropin-releasing factor in the control of adrenocorticotropin-mediated corticosterone release from the rat adrenal gland.

Marked fluctuations in adrenal sensitivity to ACTH have been reported under both physiological (e.g. diurnal) and experimental conditions. Recently, we reported that immunoneutralization of CRF reduces resting corticosterone (cort) levels in rats without inducing concomitant reductions in plasma ACTH. We postulated an endogenous CRF mechanism that controls the adrenal sensitivity to ACTH. In the present study, this hypothesis was tested by iv infusion of human ACTH (0, 1, 3, and 10 ng/kg.min for 60 min) into dexamethasone-treated anaesthetized male Wistar rats. Serial blood samples were taken for the determination of ACTH and corticosterone by RIA (ACTHi, corti). Infusion of ACTH resulted in dose-dependent steady state plasma ACTHi levels, ranging from 50-600 pg/ml, which were not affected by prior administration of a rat monoclonal antibody to rat CRF (PFU 83). As expected, infusion of ACTH resulted in a dose-dependent increase in plasma corti. In PFU 83-treated rats, preinfusion plasma corti levels were reduced compared to those of rat immunoglobulin G-treated controls (7.8 +/- 1.2 vs 25.3 +/- 3.2 ng/ml). In addition, the corti responses to infusion of 1 and 3 ng/kg.min ACTH were suppressed by PFU 83. However, at a (near) maximally effective dose of ACTH (10 ng/kg.min), no differences in plasma corti were found between PFU 83 and immunoglobulin G-treated rats. These findings suggest that immunoneutralization of endogenous CRF results in a 3-fold reduction of the adrenal sensitivity to ACTH. Subsequently, we studied the possible effects of exogenous CRF on the isolated perfused adrenal gland in situ. In this preparation, CRF alone (1-100 pmol) or ACTH alone (5 fmol) did not affect the corti secretion rate or the flow rate of the perfusion medium through the gland. However, when given together a marked (up to 3.2 times) CRF dose-dependent stimulation of corti secretion and an increase (up to 1.7 times) in adrenal flow rate were obtained. In experiments with freshly dispersed adrenal cells in vitro, PFU 83 (1 microM) or CRF (0.1-10 nM) did not influence corti secretion when given alone and did not affect ACTH-induced corti secretion. It is unlikely, therefore, that CRF acts directly on the steroid-producing cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Domains of rat interleukin 1 beta involved in type I receptor binding.

In the present study the inhibitory effects of a panel of 21 monoclonal antibodies (moabs) to rat interleukin 1 beta (rIL-1 beta) on the binding of 125I-labeled rIL-1 beta to murine type I IL-1 receptors on EL4 cells were investigated. Furthermore, the epitopes of these moabs were determined by the use of the pepscan technique, and these epitopes were visualized on a three-dimensional model of rIL-1 beta. Some moabs (SILK 3, 4, 5, 6, and 22) inhibited receptor binding of radioiodinated rIL-1 beta at concentrations that are similar to the dissociation constant values of antibody-rIL-1 beta binding. Another group of moabs (SILK 7, 11, 20, 21, and 23) also inhibited receptor binding but only at concentrations that are 10-150 times higher than their dissociation constants. A large group of moabs did not affect receptor binding in the concentration range tested, and two moabs enhanced the binding of rIL-1 beta to type I receptors. The result of pepscan analysis shows that the moabs bound to one or more of the amino acid sequences 35-49, 66-85, 78-97, 106-124, and 123-143 of mature rIL-1 beta. Modeling of rIL-1 beta shows that the binding domains of SILK 4, 5, 6, and 22 (sequence 123-143) is located at the closed end of the molecule, indicating that this part of rIL-1 beta harbors domains that are crucial for type I receptor binding. The binding domain of SILK 3 (sequence 66-85) is also located at this end of the molecule. In contrast, the binding domains of SILK 7, 11, 20, 21, and 23 (sequence 78-97) are located at the open end of the molecule, which is at the same face as the amino- and carboxy-terminals. The binding domain of SILK 16 (sequence 106-124) is positioned at the center of the molecule. It is concluded that the closed end of rIL-1 beta contains sequences that are crucial for its binding to type I receptors on murine EL4 cells. Because of the high concentrations of antibodies to residues 78-97 of rIL-1 beta that are needed to interfere with receptor binding, the importance of these domains in binding to type I receptors remains uncertain.

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.

Disease progression in chronic relapsing experimental allergic encephalomyelitis is associated with reduced inflammation-driven production of corticosterone.

In this study, we demonstrate that disruption of neuroendocrine signaling is a major factor driving disease progression in myelin oligodendrocyte glycoprotein-induced chronic relapsing experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis. Although the initial episode of chronic relapsing experimental autoimmune encephalomyelitis is associated with a robust hypothalamic-pituitary-adrenocortical axis response, we show that subsequent disease progression is associated with a selective desensitization of hypothalamic-pituitary-adrenocortical responsiveness to inflammatory mediators. Inflammatory activity in the central nervous system during relapse is therefore unable to produce an endogenous immunosuppressive corticosterone response, and disease progresses into an ultimately lethal phase. However, disease progression is inhibited if the circulating corticosterone level is maintained at levels seen during the initial phase of disease. The effect of hypothalamic-pituitary-adrenocortical axis desensitization on the clinical course of experimental autoimmune encephalomyelitis is aggravated by a marked reduction in proinflammatory cytokine synthesis in the central nervous system in the later stages of disease, reflecting an increasing involvement of antibody, rather than T cell-dependent effector mechanisms, in disease pathogenesis, with time. Thus, our data indicate that distinct immune-endocrine effects play a decisive role in determining disease progression in multiple sclerosis, a concept supported by reports that a subpopulation of multiple sclerosis patients shows evidence of hypothalamic-pituitary-adrenocortical axis desensitization.

The major immunoreactive alpha-melanocyte-stimulating hormone (alpha MSH)-like substance found in human fetal pituitary tissue is not alpha MSH but may be desacetyl alpha MSH (adrenocorticotropin1-13NH2).

Pituitary glands were obtained from human abortuses during the second half of gestation. Acid extracts were made from the anterior and neurointermediate lobes, and alpha MSH immunoreactivity (alpha MSHi) was quantified by RIA. alpha MSHi was found in both lobes of the pituitary gland, with 20-80% of the total pituitary alpha MSHi being present in extracts of the anterior lobe. Anterior and neurointermediate lobe extracts subjected to gel filtration on Sephadex G-50 revealed one peak of alpha MSHi having an elution profile identical to those of alpha MSH and desacetyl alpha MSH (ACTH1-13NH2). To characterize further the alpha MSHi extracts were subjected to high pressure liquid chromatography. No alpha MSH could be identified in extracts of the anterior lobe, and most of the alpha MSHi had an elution profile identical to that of desacetyl alpha MSH. Although small amounts of alpha MSH might be present in the neurointermediate lobe, most of the alpha MSHi in this lobe coeluted with desacetyl alpha MSH. Since alpha MSH was not converted to desacetyl alpha MSH during the extraction and chromatographic procedures, we hypothesize that the predominant form of alpha MSH-like material in the human fetal pituitary gland may be desacetyl alpha MSH.

Direct measurement of human plasma corticotropin-releasing hormone by "two-site" immunoradiometric assay.

A "two-site" immunoradiometric assay (IRMA) which allows the direct estimation of human CRH (hCRH) in plasma is described. Using this IRMA, basal levels of CRH in normal subjects ranged from 2-28 pg/mL [mean, 15 +/- 7 (+/- SD) pg/mL; n = 58]. Values in men and women were similar. Plasma CRH values within this range were also found in patients with Cushing's syndrome, Addison's disease, and Nelson's syndrome, with no correlation between plasma CRH and ACTH levels in these patients. Elevated plasma CRH levels were found in pregnant women near term [1462 +/- 752 (+/- SD) pg/mL; n = 55], and the dilution curve of this CRH-like immunoreactivity paralleled the IRMA standard curve. After its immunoadsorption from maternal plasma, this CRH-like material eluted on reverse phase high performance liquid chromatography with a retention time identical to that of synthetic CRH and had equipotent bioactivity with the synthetic peptide in the perfused anterior pituitary cell bioassay. Circulating CRH was not detected in Wistar rats, even after adrenalectomy and subsequent ether stress. Synthetic hCRH was degraded by fresh human plasma relatively slowly; 65% of added CRH remained after 1 h of incubation at 37 C. Degradation was inhibited by heat treatment (54 C; 1 h), cold treatment (4 C; 4 h), or freezing and thawing. Loss of synthetic rat CRH occurred more rapidly when fresh rat plasma was used; only 20% of added CRH remained under the same conditions. The inability to measure CRH in peripheral rat plasma may be due to the presence of active CRH-degrading enzymes which fragment the CRH molecule into forms not recognized by the CRH IRMA.