Effects of cholinergic agonists and antagonists on interleukin-2-induced corticotropin-releasing hormone release from the mediobasal hypothalamus

The Role of ACTH and Corticosteroids for Sepsis and Septic Shock: An Update

Sepsis is a common disorder associated with high morbidity and mortality. It is now defined as an abnormal host response to infection, resulting in life-threatening dysfunction of organs. There is evidence from in vitro and in vivo experiments in various animal models and in patients that endotoxin or sepsis may directly and indirectly alter the hypothalamic-pituitary-adrenal response to severe infection. These alterations may include necrosis or hemorrhage or inflammatory mediator-mediated decreased ACTH synthesis, steroidogenesis, cortisol delivery to tissues, clearance from plasma, and decreased sensitivity of tissues to cortisol. Disruption of the hypothalamic-pituitary-adrenal axis may translate in patients with sepsis into cardiovascular and other organ dysfunction, and eventually an increase in the risk of death. Exogenous administration of corticosteroids at moderate dose, i.e., <400 mg of hydrocortisone or equivalent for >96 h, may help reversing sepsis-associated shock and organ dysfunction. Corticosteroids may also shorten the duration of stay in the ICU. Except for increased blood glucose and sodium levels, treatment with corticosteroids was rather well tolerated in the context of clinical trials. The benefit of treatment on survival remains controversial. Based on available randomized controlled trials, the likelihood of survival benefit is greater in septic shock versus sepsis patients, in sepsis with acute respiratory distress syndrome or with community-acquired pneumonia versus patients without these conditions, and in patients with a blunted cortisol response to 250 μg of ACTH test versus those with normal response.

Cholinergic regulation of keratinocyte innate immunity and permeability barrier integrity: new perspectives in epidermal immunity and disease

Several cutaneous inflammatory diseases and their clinical phenotypes are recapitulated in animal models of skin disease. However, the identification of shared pathways for disease progression is limited by the ability to delineate the complex biochemical processes fundamental for development of the disease. Identifying common signaling pathways that contribute to cutaneous inflammation and immune function will facilitate better scientific and therapeutic strategies to span a variety of inflammatory skin diseases. Aberrant antimicrobial peptide (AMP) expression and activity is one mechanism behind the development and severity of several inflammatory skin diseases and directly influences the susceptibility of skin to microbial infections. Our studies have recently exposed a newly identified pathway for negative regulation of AMPs in the skin by the cholinergic anti-inflammatory pathway via acetylcholine (ACh). The role of ACh in AMP regulation of immune and permeability barrier function in keratinocytes is reviewed, and the importance for a better comprehension of cutaneous disease progression by cholinergic signaling is discussed.

Nitrous oxide-induced analgesia does not influence nitrous oxide's immobilizing requirements

BACKGROUND

Nitrous oxide (N(2)O) acts on supraspinal noradrenergic neurons to produce analgesia, but it is unclear if analgesia contributes to N(2)O's immobilizing effects. We tested the hypothesis that N(2)O minimum alveolar anesthetic concentration (MAC) is unchanged after selective ablation of supraspinal noradrenergic neurons, or in naïve animals at N(2)O exposure timepoints when analgesia is absent.

METHODS

We determined tailflick latency (TFL) and hindpaw withdrawal latency (HPL) under 70% N(2)O, N(2)O MAC, and isoflurane MAC before and after intracerebroventricular injections of anti-dopamine-beta hydroxylase conjugated to saporin (SAP-DBH; n = 7), or a control antibody conjugated to saporin (n = 5). In a separate group of naive rats (n = 8), N(2)O MAC was determined at 25-45 min after initiation of N(2)O exposure (during peak analgesia) and again at 120-140 min (after TFL and HPL returned to baseline).

RESULTS

After 30 min of N(2)O exposure, TFL and HPL increased significantly but declined back to baseline within 120 min. N(2)O did not produce analgesia in rats that received SAP-DBH. However, N(2)O and isoflurane MAC were not significantly different between SAP-DBH and control-injected animals (Mean +/- sd for N(2)O: 1.7 +/- 0.1 atm vs 1.7 +/- 0.2 atm; isofurane: 1.6 +/- 0.2% vs 1.7 +/- 0.2%). In naïve animals, N(2)O MAC was not different at the 30 min period compared with the 120 min period (1.8 +/- 0.1 atm vs 1.8 +/- 0.2 atm).

CONCLUSIONS

Destroying brainstem noradrenergic neurons or prolonged exposure to N(2)O removes its analgesic effects, but does not change MAC. The immobilizing mechanism of N(2)O is independent from its analgesic effects.

Comparative analysis of the expression of c-Fos and interleukin-2 proteins in hypothalamus cells during various treatments

The aim of the present work was to perform a combined analysis of the degree of activation of the anterior hypothalamus of the rat and expression of the interleukin-2 gene during treatments of different types: mild stress ("handling") and adaption to it, as well as intranasal administration of physiological saline and the peptides Vilon (Lys-Glu) and Epitalon (Ala-Glu-Asp-Gly). Changes in the numbers of c-Fos-and IL-2-positive cells in structures of the lateral area (LHA) and anterior (AHN), supraoptic (SON), and paraventricular (PVN) nuclei of the hypothalamus in Wistar rats. Ratios of the quantities of c-Fos-and IL-2-positive cells were determined in intact animals and after activation of brain cells initiated by different treatments; the influences of adaptation to handling on the nature of changes in the expression of these proteins was also studied. Combined analysis of the intensity of expression of these two proteins - c-Fos, a marker of neuron activation and a trans-factor for the IL-2 cytokine gene and other inducible genes, and IL-2 - in intact animals and after various treatments showed that the process of cell activation in most of the hypothalamic structures studied correlated with decreases in the quantity of IL-2-positive cells in these structures; different patterns of changes in the numbers of c-Fos-and IL-2-positive cells were seen in response to different treatments in conditions of stress and adaptation to it.

Metabolism modulators in sepsis: the abnormal pituitary response

OBJECTIVE

Summarize the current knowledge on the role of the hypothalamic pituitary axis in the development of sepsis.

DESIGN

Review article.

METHOD

We systematically searched for relevant articles in MEDLINE and Embase (up to December 2006) using the following search terms: sepsis or septic shock or septicemia or endotoxemia and pituitary gland or hypothalamus. We also retrieved relevant references from selected articles.

RESULTS

During sepsis, the pituitary gland is activated via blood-borne proinflammatory cytokines and through a complex interaction between the autonomic nervous system and the immune cells. Sepsis elicits a very reproducible pattern of pituitary hormone secretion, with plasma adrenocorticotropin and prolactin increasing within a few minutes following the insult, and with a rapid inhibition of secretion of luteinizing and thyroid-stimulatory hormone but not of follicle-stimulating hormone. Growth hormone secretion also is stimulated. Nitric oxide is a key mediator in the activation of the hypothalamic-pituitary axis and in excess nitric oxide is the main factor accounting for abnormal pituitary response. Low adrenocorticotropin and vasopressin levels are likely the most deleterious consequences of the abnormal pituitary response, because they will contribute to shock and progression of inflammation with subsequent multiple organ failure and death.

CONCLUSIONS

Sepsis is associated with major changes in the hypothalamic-pituitary axis. The manipulation of the pituitary function during sepsis is a major challenge for the next decade.

Sequence of pituitary–adrenal cortical hormone responses to low-dose physostigmine administration in young adult women and men

We previously demonstrated greater HPA axis activation in adult men compared to adult women following low-dose administration of the anticholinesterase inhibitor, physostigmine (PHYSO). Because blood sampling was done infrequently following PHYSO, the rise times of AVP, ACTH1-39, and cortisol could not be determined. In the present study, we determined the sequence of hormone increases by frequent blood sampling following PHYSO. Twelve adult women and 12 adult men underwent three test sessions 5-7 days apart: PHYSO, saline control, and repeat PHYSO. As in the earlier study, PHYSO produced no side effects in half the subjects and mild side effects in the other half, with no significant female-male differences. None of the hormone responses was significantly correlated with the presence or absence of side effects. In both women and men, the AVP increase preceded the ACTH1-39 increase, which in turn preceded the cortisol increase. The AVP and ACTH AUCs were significantly positively correlated in both women and men, supporting AVP as an acute stimulus to ACTH secretion. Also as in the earlier study, the AVP response to PHYSO was more than twice as great in men as in women, but the difference was not statistically significant. We therefore analyzed the results of both studies combined (N=26 women and 26 men). The men had a significantly greater AVP response and a trend toward a greater ACTH1-39 response compared to the women. These findings further support the concept of sexual diergism (functional sex difference) in the influence of CNS cholinergic systems on HPA hormone secretion.

Immune modulation of the hypothalamic-pituitary-adrenal (HPA) axis during viral infection

Compelling data has been amassed indicating that soluble factors, or cytokines, emanating from the immune system can have profound effects on the neuroendocrine system, in particular the hypothalamic- pituitary-adrenal (HPA) axis. HPA activation by cytokines (via the release of glucocorticoids), in turn, has been found to play a critical role in restraining and shaping immune responses. Thus, cytokine-HPA interactions represent a fundamental consideration regarding the maintenance of homeostasis and the development of disease during viral infection. Although reviews exist that focus on the bi-directional communication between the immune system and the HPA axis during viral infection (188,235), others have focused on the immunomodulatory effects of glucocorticoids during viral infection (14,225). This review, however, concentrates on the other side of the bi-directional loop of neuroendocrine-immune interactions, namely, the characterization of HPA axis activity during viral infection and the mechanisms employed by cytokines to stimulate glucocorticoid release.

Interleukin-2 given to asymptomatic HIV-infected individuals leads to an exaggerated response of the pituitary gland to the action of CRH

BACKGROUND AND AIMS

Studies investigating the impact of interleukin-2 (IL-2) on the corticotroph axis have shown that IL-2 can stimulate cortisol and ACTH secretion. However, the site, the time course and the mechanisms of IL-2 stimulation of the corticotroph axis are still not known. The aim of this study was to gain insight into the mechanisms of IL-2 stimulation of the corticotroph axis.

PATIENTS AND METHODS

A total of 9 x 10(6) IU/day IL-2 were given to 18 male HIV-infected patients treated with a combination of HIV antiviral drugs (usually two reverse-transcriptase inhibitors and one protease-inhibitor) over a course of 4-5 days. Seven of these 18 patients received a second course of IL-2.

RESULTS

Cortisol levels increased significantly (P < 0.001) from baseline levels (427 +/- 118 nmol/l) to 746 +/- 132 nmol/l after 4 days of IL-2 therapy with a gradual decrease to baseline within 10 days after the end of therapy. ACTH showed a similar pattern rising from 5.9 +/- 1.9 pmol/l at baseline to 12.4 +/- 4.6 pmol/l on day 4 (P < 0.001). The cortisol response after CRH application (carried out at 15.00 h) was significantly more pronounced at the end of IL-2 application (CRH test B, baseline: 330 +/- 59 nmol/l, peak 774 +/- 134 nmol/l, 135% increase) when compared to pretreatment (CRH test A, baseline: 226 +/- 73 nmol/l, peak 459 +/- 103 nmol/l, 103% increase, P </= 0.0001). The cortisol response 9 days after the end of IL-2 administration showed a similar pattern when compared to pretreatment values. The ACTH response after CRH was essentially paralleled by the cortisol response (CRH test B, baseline: 6.1 +/- 2.8 pmol/l, peak 16.0 +/- 4.4 pmol/l, 170% increase; CRH test A, baseline: 4.3 +/- 1.9 pmol/l, peak 9.2 +/- 3.1 pmol/l, 110% increase, P = 0.0005). Furthermore, we observed higher ACTH and cortisol concentrations in the morning when compared to late afternoon values during treatment with IL-2 [cortisol: baseline: 426 +/- 73 nmol/l (8.00 h); 226 +/- 73 nmol/l (15.00 h)]; day 4: [746 +/- 132 nmol/l (8.00 h); 339 +/- 59 nmol/l (15.00 h)]; ACTH: baseline: [5.9 +/- 1.9 pmol/l (8.00 h); 4.3 +/- 1.9 pmol/l (15.00 h)]; day 4: [12.4 +/- 4.7 pmol/l (8.00 h); 6.1 +/- 2.8 pmol/l (15.00 h)].

CONCLUSION

The data from this in vivo study suggest that IL-2 most likely resulted in corticotroph hyperplasia leading to an exaggerated response of the pituitary gland to the action of CRH.

Corticotropin releasing factor antagonist, alpha-helical CRF(9-41), reverses nicotine-induced conditioned, but not unconditioned, anxiety

RATIONALE

Unconditioned anxiogenic effects of nicotine have been observed in the social interaction (SI) test 5 min after injection of a low dose and both 5 min and 30 min after injection of a high dose. Conditioned anxiety has also been observed 24 h after testing in the SI with a high dose of nicotine.

OBJECTIVES

In order to determine whether these three anxiogenic effects shared a common mechanism, we investigated the role of corticotropin releasing factor (CRF). We therefore examined whether the CRF antagonist alpha-helical CRF(9-41) could block these three anxiogenic effects of nicotine.

METHODS

To test the unconditioned anxiogenic effects, pairs of male rats were tested in SI 5 min after s.c. vehicle or nicotine (0.1 mg/kg) or 30 min after s.c. vehicle or nicotine (0.45 mg/kg), and 30 min after i.c.v. artificial cerebrospinal fluid (aCSF) or alpha-helical CRF(9-41). To test conditioned anxiety, rats were exposed to the SI test on day 1, 5 min after vehicle or nicotine (0.1 mg/kg). On day 2, they were re-tested in SI 30 min after i.c.v. aCSF or alpha-helical CRF(9-41) (5 microg).

RESULTS

alpha-Helical CRF(9-41) did not block the unconditioned anxiogenic effect of either dose of nicotine. Nicotine (0.1 mg/kg, 5 min) elicited a conditioned anxiogenic response that was significantly reversed by alpha-helical CRF(9-41). The CRF antagonist alone had no effect.

CONCLUSIONS

CRF is an important mediator of the conditioned anxiety to nicotine, but may not play a role in mediating the acute anxiogenic effects.

Post-traumatic stress disorder: advances in psychoneuroimmunology

Exposure to trauma can result in immune dysregulation, and increasing evidence suggests that there are immune alterations associated with post-traumatic stress disorder (PTSD). However, the exact nature of these immune findings in PTSD has not been defined. The study of psychoneuroimmunology in PTSD is relevant not only for understanding the biological underpinnings of this disorder, but also for establishing the nature of the associations between PTSD and other medical and psychiatric illnesses.

The mechanism of action of cytokines to control the release of hypothalamic and pituitary hormones in infection

During infection, bacterial and viral products, such as bacterial lipopolysaccharide (LPS), cause the release of cytokines from immune cells. These cytokines can reach the brain by several routes. Furthermore, cytokines, such as interleukin-1 (IL-1), are induced in neurons within the brain by systemic injection of LPS. These cytokines determine the pattern of hypothalamic-pituitary secretion that characterizes infection. IL-2, by stimulation of cholinergic neurons, activates neural nitric oxide synthase (nNOS). The nitric oxide (NO) released diffuses into corticotropin-releasing hormone (CRH)-secreting neurons and releases CRH. IL-2 also acts in the pituitary to stimulate adrenocorticotropic hormone (ACTH) secretion. On the other hand, IL-1 alpha blocks the NO-induced release of luteinizing hormone-releasing hormone (LHRH) from LHRH neurons, thereby blocking pulsatile LH but not follicle-stimulating hormone (FSH) release and also inhibiting sex behavior that is induced by LHRH. IL-1 alpha and granulocyte macrophage colony-stimulating factor (GMCSF) block the response of the LHRH terminals to NO. The mechanism of action of GMCSF to inhibit LHRH release is as follows. It acts on its receptors on gamma-aminobutyric acid (GABA)ergic neurons to stimulate GABA release. GABA acts on GABAa receptors on the LHRH neuronal terminal to block NOergic stimulation of LHRH release. IL-1 alpha inhibits growth hormone (GH) release by inhibiting GH-releasing hormone (GHRH) release, which is mediated by NO, and stimulating somatostatin release, also mediated by NO. IL-1 alpha-induced stimulation of PRL release is also mediated by intrahypothlamic action of NO, which inhibits release of the PRL-inhibiting hormone dopamine. The actions of NO are brought about by its combined activation of guanylate cyclase-liberating cyclic guanosine monophosphate (cGMP) and activation of cyclooxygenase (COX) and lipoxygenase (LOX) with liberation of prostaglandin E2 and leukotrienes, respectively. Thus, NO plays a key role in inducing the changes in release of hypothalamic peptides induced in infection by cytokines. Cytokines, such as IL-1 beta, also act in the anterior pituitary gland, at least in part via induction of inducible NOS. The NO produced inhibits release of ACTH. The adipocyte hormone leptin, a member of the cytokine family, has largely opposite actions to those of the proinflammatory cytokines, stimulating the release of FSHRF and LHRH from the hypothalamus and FSH and LH from the pituitary directly by NO.

Induction of c-fos and interleukin-2 genes expression in the central nervous system following stressor stimuli

An injection of 5% mustard in vegetable oil, an injection of vegetable oil and needle prick into a rat leg gastrocnemius muscle were selected as stressor stimuli. Expression of c-fos mRNA and interleukin-2 (IL-2) mRNA was measured using digoxigenin labeled cDNA probe. C-fos-like proteins were determined by an immunochemical method with anti-c-fos polyclonal antibodies. Thirty min after the injection of 5% mustard in vegetable oil, c-fos mRNA synthesis was shown in the sacral segments of the spinal cord. Many c-fos mRNA labeled cells were noted also in the hypothalamus (paraventricular nucleus, dorsomedial nucleus, and the lateral hypothalamic area), thalamus, hippocampus, nucleus caudatum, sensori-motor zone of the brain cortex and the amygdaloid complex. Expression of c-fos-like proteins was shown after the injection of vegetable oil and 5% mustard in vegetable oil (within 2 h) in the spinal cord structures, the maximum quantity of the labeled cells was found in the I and II sacral segments (in the superficial lamina of the gray matter of the dorsal horns in the ipsilateral side), the minimum in the IV and V lumbar segments (in the intermediate zone of the gray matter at the level of the central canal). When c-fos-like proteins expression were analyzed in the CNS, c-fos-labeled cells were detected in the same structures where c-fos mRNA was also shown. The IL-2 mRNA synthesis was shown within 2 h after the stimulus in the same brain structures as c-fos mRNA. It is always difficult to destinguish the effect of stress as sensory stimuli or as general stimuli. The c-fos immunoreactivity appeared mostly in the contralateral side of the hypothalamus, therefore maybe in our investigation the mechanism of sensory stimuli mostly results in the changes that have been obtained. The information of applied stimuli arrived in the spinal cord, and is transmitted to the brain where it activates certain brain structures inducing c-fos and IL-2 genes expression. The most important conclusion is that the used stress stimuli induced not only c-fos gene but also IL-2 gene expression in the brain. The synthesis of both mRNA takes place in the same brain structures.