The hypothalamic-pituitary-adrenal axis and immune-mediated inflammation

Diseases among men 20 years after exposure to severe stress: implications for clinical research and medical care

OBJECTIVE

Epidemiologic studies have linked exposure to severe environmental stress, such as natural disasters and combat operations, to the onset of specific psychiatric disorders. Some research also suggests that these exposures may be associated with the onset of chronic diseases as well. However, these chronic disease outcome studies often have been obscured by bias and confounding.

METHOD

The medical histories of 1399 male Vietnam veterans approximately 20 years after combat exposure (mean years = 17) were analyzed by lifetime posttraumatic stress disorder (PTSD) status (lifetime PTSD = 332 cases). These men were included in a national, random in-person study of United States Army veterans of the Vietnam War (study completion rate = 65%).

RESULTS

After controlling for preservice, in-service, and postservice factors (including intelligence, race, region of birth, enlistment status, volunteer status, Army marital status, Army medical profile, hypochondriasis, age, smoking history, substance abuse, education, and income), associations were found for reported circulatory [odds ratio (OR) = 1.62, p = .007], digestive (OR = 1.47, p = .036), musculoskeletal (OR = 1.78, p = .008), endocrine-nutritional-metabolic (OR = 1.58, p = .10), nervous system (OR = 2.47, p < .001), respiratory (OR = 1.54, p = .042), and nonsexually transmitted infectious diseases (OR = 2.14, p < .004) after military service.

CONCLUSION

Although this study has some limitations, it suggests that there is a direct link between severe stress exposures and a broad spectrum of human diseases. In the future, medical researchers and clinicians should focus more on the medical consequences of exposure to severe environmental stress and seek to better integrate psychobiologic models of disease pathogenesis.

The effect of somatostatin on experimental inflammation in rats

The aim of the present study was to investigate the effect of somatostatin administration on experimentally induced inflammation in rats. Inflammation was induced by the intraplantar injection of carrageenan (50 microL) into the hind paw of the rat. Animals were treated intraplantarly with somatostatin in a volume of 50 microL at different doses (2.5, 25, and 250 ng, 10 microg). The inflammatory response was studied 120, 180, and 240 min after drug administration. The antinociceptive effect of somatostatin was determined by using the Randall and Selitto test and by local production of beta-endorphin from lymphocytes obtained from popliteal lymph nodes. Data show that small doses of somatostatin were the most effective in reducing hyperalgesia. Moreover, our results show that somatostatin treatment significantly increased beta-endorphin in lymphocytes from popliteal lymph nodes. The secretion of opioid peptides, which enhance analgesia, could be stimulated by locally administered somatostatin.

IMPLICATIONS

Acute pain because of intraplantar inflammation induced in rats by carrageenan injection was significantly reduced by small-dose, local administration of somatostatin, which possibly favors beta-endorphin release as a mechanism. These results may have implications regarding treatment of pain conditions associated with an inflammatory response.

Adrenal function predicts demoralization after losses

Stressful experiences can cause disturbances in the hypothalamic-pituitary-adrenocortical axis and the sympathetic-adrenomedullary system. The authors hypothesized that assessments of adrenal function made in the circumstances of stressful losses would predict outcome 1 or 2 years later. The authors collected 24-hour urinary free cortisol, serum cortisol, and 24-hour urinary catecholamines 2 months after intake and used these measures as predictors of depression, anxiety, hopelessness/helplessness, unresolved grief, self-rated health, and help-seeking behavior on follow-up at 13 and 25 months. Adrenal function in the circumstances of a loss predicted only demoralization scores (hopelessness/helplessness) on follow-up.

Does differential neuroendocrine control of cytokine production govern the expression of autoimmune diseases in pregnancy and the postpartum period?

Pregnancy and the postpartum period are associated with significant changes in levels of several hormones, such as estrogen, progesterone, cortisol and possibly catecholamines. Moreover, several autoimmune diseases such as rheumatoid arthritis tend to remit, develop or exacerbate during pregnancy or the postpartum period. Thus, the question arises: are the changes in the hormones and the expression of autoimmune diseases during these periods causally linked, or are these associations an epiphenomenon? Here we suggest that a causal link might be provided through differential neuroendocrine regulation of Th1-type and Th2-type cytokine production.

Glucocorticoids and immune function: unknown dimensions and new frontiers

Despite the importance of glucocorticoids (GCs) to modern medicine, the physiological role of endogenous corticosteroids in immunomodulation is poorly understood. This article discusses evidence suggesting that endogenous GCs not only suppress but also direct and enhance immune functions. These often overlooked actions might well be more important than the inhibitory functions during host defence and the maintenance of homeostasis.

Stress and Critical Illness: The Integrated Immune/Hypothalamic-Pituitary-Adrenal Axis Response

Critical illness leads to a coordinated reaction that is categorized as the stress response; activation of the hypothalamic-pituitary-adrenal (HPA) axis and the sympathetic nervous system leads to metabolic and cardiovascular changes that are generally directed toward maintenance of homeostasis. The HPA axis and the sympathetic nervous system are linked via reciprocally activating brainstem pathways. The immune system acts via cytokines, which are hormones, to activate the HPA axis. Glucocorticoid secretion suppresses immune activity, thus completing an immune-HPA feedback loop. Restraint of immune activity may be a major function of glucocorticoids during stress, thus averting the potential for immune-mediated damage to healthy tissues. Cortisol also acts to produce adaptive metabolic, cardiovascular, and cognitive changes. Activation of the stress system is also associated with inhibition of thyroid, gonadal, and growth axes through neuroendocrine and peripheral mechanisms; such effects can be seen as directed toward conservation of energy. There is growing evidence that hyperfunction and hypofunction of the integrated stress system may lead to a variety of previously unexplained disorders. Recently, a more detailed understanding of the stress system combined with astute clinical observation of critically ill patients has led to promising new avenues for therapeutic investigation.

Interleukin 1 alpha increases serum leptin concentrations in humans

Leptin, the protein product of the ob gene, regulates appetite and body weight in animals. Endotoxin and cytokines, induced by endotoxin, interleukin (IL) 1 and tumor necrosis factor, increase expression of leptin in mice and hamsters. We measured serum leptin concentrations in patients with cancer before and after administration of recombinant human IL-1 alpha. Fourteen patients received IL-1 alpha at one of three dose levels (0.03, 0.1, or 0.3 microgram/kg.day) for 5 days. Serum leptin concentrations increased in all but two patients within 24 h after the first dose. The increase in leptin was correlated directly with IL-1 alpha dose (P = 0.0030). Despite continued administration of IL-1 alpha, serum leptin concentrations returned to pretreatment levels by day 5 of therapy. An increase in serum leptin concentrations may be one mechanism by which anorexia is induced by IL-1 alpha. However, tachyphylaxis of the leptin response suggests that other mechanisms also are involved.

Inhibition of mineralocorticoid and glucocorticoid receptor function by the heat shock protein 90-binding agent geldanamycin

The effects of mineralocorticoids and glucocorticoids are mediated by the intracellular mineralocorticoid glucocorticoid receptor (MR) and glucocorticoid receptor (GR), respectively. Several studies suggest that hormone binding and, thus, receptor activation depend on the association of both MR and GR with the 90-kDa heat shock protein (hsp 90). However, there are few reports analyzing the functional relevance of this association in vivo. The present study was designed to determine how the new hsp 90-binding agent geldanamycin, which was previously shown to disrupt the formation of steroid receptor/hsp complexes, interferes with MR- and GR-mediated transactivation in intact cells. We show that geldanamycin inhibits aldosterone-dependent transactivation of a mineralocorticoid-responsive reporter genes in a concentration-dependent manner. Similar effects were observed for the dexamethasone-activated GR. However, geldanamycin did not affect transcription from a retinoic acid-dependent reporter gene. Inhibition of GR-mediated transactivation was observed both in HeLa cells expressing endogenous GR and in COS-7 cells transfected with a GRa expression vector. Binding studies indicate that geldanamycin disrupts receptor function by reducing hormone binding affinity without lowering intracellular receptor protein levels. Our data support the current model of hsp 90-dependent steroid receptor activation. Furthermore, we show for the first time that MR function also depends on the interaction with hsp 90 in intact cells. Finally, we demonstrate that the function of endogenous is thought to keep the receptor protein in an inactive, yet ligand-activable state (9-17). Ligand binding induces a conformational change in the receptor molecule, which causes it to dissociate from the hsp complex, to translocate to the cell nucleus, and, finally, to interact with specific hormone response elements in the promoter regions of hormone-responsive genes (6-8). Both MR and GR bind as homodimers to identical palindromic sequences on the target DNA, termed glucocorticoid response elements (GREs) (18). The formation of GR/MR heterodimers has also been described (19,20) and may have profound functional consequences (21). The current model of MR and GR function holds that these receptors are unable to bind their respective hormones as long as they are not associated with the hsp complex (9-17). However, experimental support for this model is mainly based on in vitro work. There are few reports analyzing the functional relevance of GR/hsp interactions in mammalian cells. In the most recent study, Whitesell et al. showed that the hspE90-binding agent geldanamycin can specifically disrupt GR/hsp association, thus inhibiting glucocorticoid-mediated transcriptional activation (22). MR is even less well studied in this respect. To our knowledge, there have not been any data supporting a functional role for proper MR/hsp interaction in intact cells. In this study, we show for the first time that MR function depends on the interaction with hsp 90 in intact human cells. Furthermore, we demonstrate that geldanamycin inhibits GR-mediated transcriptional activation in two human cells lines, confirming the results by Whitesell et al. and extending them to transfected as opposed to endogenous GR.

Cytokine-dependent gp130 receptor subunit regulates human fetal pituitary adrenocorticotropin hormone and growth hormone secretion

We have shown recently that leukemia inhibitory factor (LIF) and oncostatin M (OSM), two members of the gp130-dependent cytokine family, stimulate murine proopiomelanocortin (POMC) transcription and adrenocorticotropin hormone (ACTH) secretion. LIF and corticotropin-releasing hormone (CRH) also synergistically induced in vivo ACTH secretion in fetal nonhuman primates. To elucidate the role of the gp130-related cytokines in human pituitary hormone regulation, we tested expression of gp130-related cytokine receptors in human fetal pituitaries. Using RT-PCR, mRNA expression of receptors for LIF, IL-6, and CRH, and the gp130 subunit, were all detected in fetal pituitaries of 18- and 31-wk gestation. Recombinant human IL-6, LIF, and OSM treatments of primary human fetal pituitary cultures (16-31 wk) increased ACTH secretion by up to 48% (P < 0.05) using doses of 1 nM, and when fetal cultures were cotreated with CRH, ACTH was induced five- to sixfold as compared to CRH alone (three- to fourfold; P = 0.01). Incubation with gp130-specific antibody suppressed basal and cytokine-stimulated ACTH secretion (alone or with CRH) from human fetal cells. Human POMC promoter -879/+6 fused to the luciferase reporter gene and transfected into AtT-20 cells, was stimulated by LIF (7-fold), which also exerted strong (22-fold) synergy with CRH on POMC transcription. Growth hormone (GH) release from fetal cultures was modestly stimulated (15-31%, P < 0.05), while other anterior pituitary hormones were not altered by these cytokines. Thus, physiologic concentrations of the gp130-related cytokines have direct effects on ACTH and GH regulation in the human pituitary, indicating that gp130-dependent signals serve as a paracrine system controlling early human pituitary function.

Interleukin-6 and the interleukin-6 receptor in the human adrenal gland: expression and effects on steroidogenesis

Interleukin (IL)-6 is a potent activator of the human hypothalamicpituitary-adrenal axis. After chronic administration of IL-6 in humans, there is a substantial elevation of cortisol, whereas ACTH levels are blunted. Thus, we investigated whether IL-6 and/or the IL-6 receptor (IL-6R) are expressed in the human adrenal gland and whether IL-6 could cause the release of steroid hormones by a direct action on adrenal cells in primary culture. The expression of IL-6 and IL-6R was investigated with RT-PCR and immunohistochemistry, and the effects on human adrenal steroidogenesis were tested with IL-6 in vitro. To avoid effects mediated by macrophages, we depleted adrenal primary cultures from macrophages using specific mouse antihuman CD68 and sheep antimouse IgG conjugated magnetic beads. The results showed that 1): IL-6 and IL-6R are expressed in adrenal cell cultures, including all cell types and those depleted of macrophages; 2) IL-6R is mainly expressed in the zona reticularis and the inner zona fasciculata; positive signals from the zona glomerulosa and the medulla occurred in single cells; and 3) IL-6 regulates adrenal synthesis of mineralocorticoids, glucocorticoids, and androgens in vitro, dependent on time and dose, in the absence of macrophages. After 24 h, aldosterone secretion increased to 172 +/- 28% SEM, cortisol to 177 +/- 27% SEM, and dehydroepiandrosterone to 153 +/- 20% SEM of basal secretion. These findings, in combination with previous investigations, suggest that IL-6 exerts its acute action via the hypothalamus and the pituitary. In the adrenal gland, however, IL-6 seems to be a long-term regulator of stress response, integrating the responses of all cortical zones to stimuli from the immune and endocrine system.

Attenuated free cortisol response to psychosocial stress in children with atopic dermatitis

OBJECTIVE

Atopic dermatitis (AD) is an inflammatory skin disease characterized by a hyperactivity of the humoral immune system with an onset in infancy or early childhood. Although most of the research has focused on the pathophysiological role of the immune system in AD, the impact of endocrine signals in the pathology of AD has received only little attention. However, because the endocrine system may play a regulatory role in immune functioning, it might be of major interest to study endocrine reactivity in AD patients. The present two-part study investigated the relationship between adrenocortical stress response, heart rate response, and psychological parameters in children with AD.

METHOD AND RESULTS

In Study 1, a protocol for induction of psychosocial stress in children aged 8 to 14 years was evaluated. Healthy children (N = 16) were exposed to the Trier Social Stress Test for Children (TSST-C) that mainly consists of public speaking and mental arithmetic tasks in front of an audience. Salivary cortisol was measured 35, 15, and 1 minute before as well as 1, 10, 20, and 30 minutes after the stress; heart rate was monitored continuously. Results showed that the protocol induced a highly significant increase in free cortisol response (p < .001) and heart rate (p < .001). In Study 2, the TSST-C was applied to AD children (N = 15) and age- and sex-matched healthy controls (N = 15). All patients were in remission and medication-free for at least 3 weeks. Again, the stress test induced significant increases in cortisol and heart rate. However, the AD children showed a significantly blunted cortisol response to the stressor compared with the control group (p < .05). Heart rate responses were similar in both experimental groups. Neither subjective stress ratings nor personality traits were related to the blunted cortisol response.

CONCLUSIONS

These findings suggest that the adrenocortical response to stress is attenuated in atopic children. A hyporesponsive hypothalamus-pituitary-adrenal (HPA) axis might explain in part the stress-induced eruptions of AD symptoms.

The hypothalamic-pituitary-adrenal axis and the female reproductive system

The hypothalamic-pituitary-adrenal (HPA) axis and the female reproductive system are intertwined and exhibit a complex relationship. Thus, the HPA axis exerts profound, mostly inhibitory effects, on the reproductive axis, with corticotropin-releasing hormone (CRH) and CRH-induced propiomelanocortin peptides inhibiting hypothalamic GnRH secretion, and with glucocorticoids inhibiting pituitary LH and ovarian estrogen and progesterone secretion and rendering estrogen-target tissues, such as the endometrium, resistant to the gonadal steroid. These effects of the HPA axis are responsible for the "hypothalamic" amenorrhea of stress, depression and eating disorders, and the hypogonadism of Cushing's syndrome. Conversely, estrogen directly stimulates the CRH gene, which may explain the slight hypercortisolism of females and the preponderance of depressive, anxiety, and eating disorders, as well as Cushing's disease in women. Interestingly, several components of the HPA axis and their receptors are present in reproductive tissues, as autocoid regulators of their various functions. These include ovarian and endometrial CRH, which may participate in the inflammatory processes of the ovary, that is, ovulation and luteolysis, and of the endometrium, that is, implantation and menstruation. Finally, the hypercortisolism of the latter half of pregnancy can be explained by high levels of placenta CRH in plasma. This hypercortisolism causes a transient adrenal suppression in the postpartum period, which may explain the postpartum blues/depression and autoimmune phenomena of this period.

Lack of effect of endogenous corticosteroids on the acute inflammatory reaction (edema) induced by Bothrops jararaca venom (BjV) in rats

Intraplantar injection of 5 or 10 micrograms of BjV caused local edema in rats that was not affected by ablation of adrenal glands. In addition, no changes in plasma corticosterone levels were observed. Simultaneous injections of the venom into both hindpaws of normal animals, or injections made at varying intervals, resulted in local inflammatory reactions of comparable time-course development and analogous magnitude. These data might be related to an inability of the venom to evoke secretion of corticosteroids.

The hypothalamic-pituitary-adrenal axis of prairie voles (Microtus ochrogaster): evidence for target tissue glucocorticoid resistance

Basal plasma corticosterone levels in prairie voles (Microtus ochrogaster) are extremely high, in the absence of any apparent negative consequences of glucocorticoid excess. We tested the hypothesis that prairie voles are a novel rodent model of target tissue resistance to glucocorticoids. Prairie voles had a significantly higher adrenal-to-body weight ratio, 5- to 10-fold greater basal plasma corticosterone, and 2- to 3-fold greater basal plasma ACTH concentrations than montane voles (Microtus montanus) and rats. While plasma corticosterone binding globulin (CBG) was 2-fold higher in prairie voles than in rats, both estimated and directly measured plasma free corticosterone were significantly higher in prairie voles than in rats. Plasma corticosterone levels in prairie voles were responsive to both circadian cues and a stressor, but were resistant to suppression by the synthetic glucocorticoid, dexamethasone (DEX). Western blots of brain and liver protein extracts, using a glucocorticoid receptor (GR) antibody, revealed the presence of a approximately 97 kDa immunoreactive band, the expected size for GR. Binding assays revealed significantly lower DEX affinity of corticosteroid receptors (CR) in cytosol of prairie vole brain and liver than that in the same tissues in rats. We conclude that prairie voles are a novel rodent model of glucocorticoid resistance, and that decreased affinity of CR for ligand might be partially responsible for this phenomenon.

Pituitary cytokine and growth factor expression and action

The complex range of pituitary regulatory mechanisms reviewed here underlies the critical function of the pituitary in sustaining all higher life forms. Thus, the ultimate net secretion of pituitary hormones is determined by signal integration from all three tiers of pituitary control. It is clear from our current knowledge that the trophic hormone cells of the anterior pituitary are uniquely specialized to respond to these signals. Unravelling their diversity and complexity will shed light upon the normal function of the master gland. Understanding these control mechanisms will lead to novel diagnosis and therapy of disordered pituitary function (357).

Corticotropin-releasing factor in antinociception and inflammation

Corticotropin-releasing factor (CRF) plays a major role at the level of the hypothalamus and pituitary to control the body's response mechanisms to stressful stimuli. The recent discovery of CRF outside the central nervous system suggests that CRF may well play a similar role in peripheral tissues, most likely in a paracrine manner. While its effects in many other peripheral tissues is not known yet, CRF and its receptors are upregulated in inflammatory pain states pointing to a key role under these circumstances. Indeed, locally expressed CRF seems to act on CRF receptors on immune cells which have migrated into the area of the inflamed tissue, and induce the release of opioid peptides synthesized within these immune cells. These opioids subsequently act on peripheral opioid receptors located on peripheral sensory nerves to inhibit the transmission of painful stimuli. CRF may also affect the inflammatory response; however, these data are still controversial. The peripheral paracrine effects of CRF may be similar to those of hypothalamic CRF, i.e., to counterbalance local stressful events, such as inflammation and pain, so that they do not threaten the homeostasis of the body. Interestingly, CRF-like peptides have been identified not only in mammalians, but also in species such as the frog (Stenzel-Poore et al., 1992, Mol. Endocrinol. 6, 1716) and the teleost fish (Okawara et al., 1988, Proc. Natl. Acad. Sci. USA 85, 8439) indicating that this is a peptide that has been conserved over a long period (200 million years) across species (Lederis et al., 1990, Prog. Clin. Biol. Res. 342, 467) and that the release of ACTH-like peptides by peptides of the CRF family may represent an ancestral type of stress response (Ottaviani et al., 1992, Gen. Comp. Endocrinol. 87, 354; Tran et al., 1990, Gen. Comp. Endocrinol. 78, 351).

Hypercortisolism after stroke--partly cytokine-mediated?

Increased activity of the hypothalamic-pituitary-adrenal (HPA) axis is common early after stroke. Hypercortisolism is a prominent manifestation. Normally the secretion of cortisol is regulated by adrenocorticotrophic hormone (ACTH), but recently an ACTH/cortisol dissociation after stroke was reported. Cytokines may influence the HPA axis, and plasma IL-6 levels are elevated following stroke. We investigated correlations between cortisol, ACTH, and cytokines, and between blood pressure and blood hormone levels early after stroke in seven stroke patients. All had neurological symptoms secondary to brain infarctions. Blood samples for analysis of cortisol, ACTH, IL-6, TNF alpha, norepinephrine, and epinephrine were collected four times daily, and 24-h blood pressure was measured. Plasma IL-6, but not ACTH, correlated significantly to serum cortisol. Catecholamine levels correlated with cytokine and cortisol levels. This study suggests that several routes for HPA-axis dysregulation is present early after stroke. Cytokine release may play an important role in this situation.

A double-blind study of perioperative steroid requirements in secondary adrenal insufficiency

BACKGROUND

Patients treated long-term with supraphysiologic doses of glucocorticoids experience secondary adrenal insufficiency and are routinely given large doses of steroids in the perioperative period to prevent hypotension. Because the dose of steroids required to prevent hypotension is not known, we conducted a randomized, double-blind study to determine whether patients treated long-term with glucocorticoids actually require increased steroids in the perioperative period.

METHODS

Patients who had been taking at least 7.5 mg prednisone daily for several months and had secondary adrenal insufficiency as defined by adrenocorticotropic hormone testing formed the study population. Patients were randomized to two groups. One group received perioperative injections of saline solution alone; the other received perioperative saline solution and cortisol. All patients received their usual daily prednisone dose throughout the study.

RESULTS

Six patients were in the steroid-treated group and 12 were in the saline-treated group. Most subjects underwent major operations such as joint replacements, abdominal operations, and miscellaneous other procedures. Two patients had hypotension, one in each group. Hypotension resolved with volume replacement in both patients. The average pulse rates and blood pressures were similar in both groups during the perioperative period.

CONCLUSIONS

Patients with secondary adrenal insufficiency do not experience hypotension or tachycardia caused by inadequate glucocorticoid levels when given only their daily dose of steroids for surgical procedures.

Neuroimmunomodulation via limbic structures--the neuroanatomy of psychoimmunology

During the last 20 years, mutual communications between the immune, the endocrine and the nervous systems have been defined on the basis of physiological, cellular, and molecular data. Nevertheless, a major problem in the new discipline "Psychoneuroimmunology" is that controversial data and differences in the interpretation of the results make it difficult to obtain a comprehensive overview of the implications of immunoneuroendocrine interactions in the maintenance of physiological homeostasis, as well as in the initiation and the course of pathological conditions within these systems. In this article, we will first discuss the afferent pathways by which immune cells may affect CNS functions and, conversely, how neural tissues can influence the peripheral immune response. We will then review recent data, which emphasize the (patho)physiological roles of hippocampal-amygdala structures and the nucleus accumbens in neuroimmunomodulation. Neuronal activity within the hippocampal formation, the amygdaloid body, and the ventral parts of the basal ganglia has been examined most thoroughly in studies on neuroendocrine, autonomic and cognitive functions, or at the level of emotional and psychomotor behaviors. The interplay of these limbic structures with components of the immune system and vice versa, however, is still less defined. We will attempt to review and discuss this area of research taking into account recent evidences for neuroendocrine immunoregulation via limbic neuronal systems, as well as the influence of cytokines on synaptic transmission, neuronal growth and survival in these brain regions. Finally, the role of limbic structures in stress responses and conditioning of immune reactivity will be commented. Based on these data, we propose new directions of future research.

Glucocorticoid feedback resistance

Glucocorticoid feedback resistance can be inherited or locally acquired. The implications of these two forms of resistance for disease are strikingly different. The inherited form is characterized by enhanced adrenocortical function and hypercorticism to compensate for a generalized deficit in the glucocorticoid receptor gene, but these individuals lack symptoms of Cushing's syndrome. By contrast, resistance acquired at the level of the hypothalamic corticotropin-releasing hormone (CRH) neurons is linked to hypercorticism, which is not compensatory but overexposes the rest of the body and the brain to glucocorticoids. This cell-specific glucocorticoid resistance can be acquired by genetically predisposed individuals failing to cope with (early) life events and causes enhanced vulnerability to disease-specific actions of glucocorticoids. (c) 1997, Elsevier Science Inc. (Trends Endocrinol Metab 1997; 8:26-33).

Presence of functional receptors for corticotropin releasing hormone in caecal circular smooth muscle cells of guinea pig

The presence of specific binding sites for corticotropin releasing hormone (CRH) in caecal circular smooth muscle cells of guinea pig was investigated by binding and pharmacological studies. The specific binding of 125I-CRH to these muscle cells reached an equilibrium after 90 minutes. Several peptides structurally unrelated to CRH did not affect the specific binding of 125I-CRH to these muscle cells. Unlabeled CRH completely inhibited the specific binding of 125I-CRH in a concentration-dependent manner, with an IC50 value of 13.5 nM. A CRH receptor antagonist, alpha-helical CRH (9-41), inhibited the specific binding of 125I-CRH in a concentration-dependent manner with a lower affinity than CRH. In pharmacological study, CRH inhibited the contractile response of these muscle cells to 1 nM cholecystokinin-octapeptide in a concentration-dependent manner, with an IC50 value of 14.1 nM. A CRH receptor antagonist, alpha-helical CRH (9-41), significantly antagonized this inhibitory effect produced by CRH. These results strongly suggest the presence of functional receptors for CRH that mediate relaxation of caecal circular smooth muscle cells of guinea pig.

Does prenatal stress impair coping and regulation of hypothalamic-pituitary-adrenal axis?

Prenatally stressed (PS) human infants and experimental animals show attentional deficits, hyperanxiety and disturbed social behavior. Impaired coping in stressful situations in adult PS monkeys and rodents is associated with dysregulation of the HPA axis, characterized by decreased feedback inhibition of corticotropin-releasing hormone (CRH) and prolonged elevation of plasma glucocorticoids in response to stress. PS rats have higher levels of CRH in the amygdala, fewer hippocampal glucocorticoid receptors and less endogenous opioid and GABA/BDZ (benzodiazepine) inhibitory activity. The mechanisms by which maternal stress induce these long-lasting changes in the developing fetal neuroaxis remain to be elucidated. It is suggested that impaired coping in stressful situations and dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, result from the action of maternal hormones released during stress on the developing fetus. The similarities in coping behavior and dysregulation of the HPA axis in PS animals to those in humans with depression, suggest that gestational stress, at a critical time during fetal development, may increase the propensity to develop this condition.

Immunomodulation of peritoneal macrophages by granulocyte-macrophage colony-stimulating factor in humans

Colony-stimulating factors are growth factors which induce differentiation of the hematopoietic stem cells. Granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulates proliferation and improves functions of neutrophils and monocyte/macrophages. A macrophage submesothelial stratum has been suggested to constitute the first line of peritoneal defense. We have tested whether intraperitoneally administered GM-CSF could increase the number and activation of peritoneal macrophages in peritoneal dialysis patients. Eight stable patients injected 17 micrograms of GM-CSF in each of their four daily CAPD bags over three days. The clinical status, the peritoneal effluent and peripheral blood cell count, membrane receptor expression, phagocytosis activity and cytokine levels were monitored at days 0, 1, 3, 10 and 28. GM-CSF administration caused a large increase in peritoneal macrophage number (89-fold mean increase after 72 hr), returning to baseline seven days after withdrawal. GM-CSF triggered an increase in the expression of CD11b/CD18 (CR3) and its counterreceptor CD54, indicating the cellular progression into a more activated state. Both the number of phagocytic cells (55 +/- 15% to 83 +/- 10%, P < 0.05) and the phagocytic index (137 +/- 29 to 255 +/- 61, P < 0.01) were also augmented. Peritoneal effluent cytokine-chemokine levels demonstrated an increase in IL-6 and MCP-1 levels while TNF-alpha, IL-1, IL-8, MIP-1 alpha and RANTES were not significantly altered. GM-CSF administration did not affect the peritoneal transport of water or solutes. Minor side-effects were registered in two patients. In conclusion, intraperitoneal GM-CSF causes a marked and transient recruitment of primed macrophages into the peritoneum without inducing inflammatory parameters. GM-CSF should improve the peritoneal defensive capacity through potentiation of the effector functions of resident and newly-recruited macrophages.

Binding of alpha-adrenergic receptors stimulates the anti-mycobacterial activity of murine peritoneal macrophages

The effects of adrenergic stimulation of the anti-mycobacterial activity of peritoneal macrophages was investigated. We found that epinephrine and norepinephrine stimulated macrophages to suppress the growth of Mycobacterium avium. Stimulation was mediated by binding to the alpha 2 adrenergic receptor. The addition of the alpha 2 agonist clonidine to cultures resulted in an inhibition of mycobacterial growth and the effect of epinephrine was blocked by the alpha-antagonist phentolamine. Treatment of the macrophages with propranolol, a beta-antagonist, potentiated the effect of epinephrine. Epinephrine mediates its effect by stimulating the expression of macrophage activation genes.

Neuroimmune control of interleukin-6 secretion in the murine spleen. Differential beta-adrenergic effects of electrically released endogenous norepinephrine under various endotoxin conditions

In a previous study we demonstrated a superfusion technique which allows for investigation of nerve-immune cell interaction in murine spleen. We demonstrated that under septic-like conditions in the presence of bacteria and lipopolysaccharide (LPS), electrically induced inhibition of interleukin 6 (IL-6) secretion was attenuated by the beta-adrenergic antagonist propranolol. This effect was now investigated more closely under various endotoxin conditions in order to dissect effects of bacteria and endotoxin: (A) bacteria-rich conditions (without penicillin/streptomycin [P/S] and without LPS), (B) LPS-enriched conditions (with P/S and with LPS), and (C) bacteria-free conditions (with P/S and without LPS). Under bacteria-rich conditions, norepinephrine (Emax = 10(-6) M, p = 0.012) and isoproterenol (Emax = 10(-6) M, p = 0.048) concentration-dependently inhibited IL-6 secretion from murine spleen slices in contrast to bacteria-free conditions. In a bacteria-free environment the beta-adrenergic antagonist propranolol did not attenuate the electrically induced inhibition of splenic IL-6 secretion. The insertion of bacterial filters in front of the superfusion chambers to avoid direct contact between bacteria and cells increased the electrically-induced inhibition of IL-6 secretion (p = 0.0036). Added LPS did not change the electrically-induced release of norepinephrine from presynaptic nerve terminals in murine spleen. The study demonstrates two different beta-adrenergic effects on IL-6 secretion of murine spleen slices under bacteria-rich or bacteria-free conditions.

An open study of pentoxyfylline and thalidomide as adjuvant therapy in the treatment of rheumatoid arthritis

OBJECTIVE

Dysregulation of tumour necrosis factor alpha (TNF alpha) production is thought to be important in rheumatoid arthritis. Since pentoxifylline and thalidomide inhibit endotoxin induced TNF production in vitro, these drugs were tested in an open study in rheumatoid arthritis patients to assess toxicity, the effect on TNF production, and the antiarthritic effects.

METHODS

12 patients with active rheumatoid arthritis were treated with 1200 mg pentoxifylline and 100 mg thalidomide a day during 12 weeks. In addition, TNF production was assessed by ex vivo whole blood cultures stimulated with endotoxin.

RESULTS

Adverse events such as xerostomia, drowsiness, and constipation occurred in almost all patients, which led to discontinuation in three. The drugs halved the TNF production capacity during treatment (ANOVA, P < 0.03) whereas production capacity of interleukin (IL) 6, IL-10, and IL-12 was not affected. Of the nine patients who completed the study, five fulfilled the ACR-20% response criteria after 12 weeks of treatment.

CONCLUSIONS

Although pentoxifylline/thalidomide reduced the production capacity of TNF, the benefit/side effects ratio was poor due to multiple adverse effects, while clinical observation suggests limited efficacy.

Interleukin-6 in the injured patient. Marker of injury or mediator of inflammation?

OBJECTIVE

The effects of interleukin (IL)-6 in the injured patient are examined in an attempt to clarify the potential pathophysiologic role of IL-6 in the response to injury.

SUMMARY BACKGROUND DATA

Interleukin-6 is an integral cytokine mediator of the acute phase response to injury and infection. However, prolonged and excessive elevations of circulating IL-6 levels in patients after trauma, burns, and elective surgery have been associated with complications and mortality. The mechanistic role of IL-6 in mediating these effects is unclear.

METHODS

A review of current literature is performed to summarize the origins, mechanisms of action, and biologic effects of IL-6 and to characterize the IL-6 response to injury.

RESULTS

Interleukin-6 is a multifunctional cytokine expressed by a variety of cells after a multitude of stimuli, under complex regulatory control mechanisms. The IL-6 response to injury is uniquely consistent and related to the magnitude of the insult. Moreover, the early postinjury IL-6 response correlates with complications as well as mortality.

CONCLUSIONS

Interleukin-6 appears to play an active role in the postinjury immune response, making it an attractive therapeutic target in attempts to control hyperinflammatory provoked organ injury.

Regulation of interleukin-10 production by beta-adrenergic agonists

Catecholamines have been shown to inhibit some aspects of macrophage activation through a beta receptor-dependent mechanism. This study was undertaken to analyze the effects of isoproterenol, a specific beta-adrenergic agonist, on the synthesis of interleukin-10 (IL-10), a major macrophage-deactivating factor. Isoproterenol increased IL-10 release from lipopolysaccharide-(LPS)-activated mouse peritoneal macrophages in a dose-dependent manner. A significant effect was already observed with 1 microM isoproterenol, while a 4.5-fold increase was achieved with 10 microM. This increase was observed only if macrophages were exposed to isoproterenol for at least 2 h before LPS challenge. It was apparent within 0.5 h and persisted through 24 h at all the LPS concentrations used. A similar increase was observed at the IL-10 mRNA level, as judged by enzyme-linked immunosorbent assay-polymerase chain reaction. The macrophage response to isoproterenol that led to cyclic AMP accumulation was markedly inhibited by H-89, a potent inhibitor of protein kinase A. These data suggest the involvement of cyclic AMP in the regulation of IL-10 synthesis by isoproterenol. IL-10 was in turn partly responsible for a reduction in tumor necrosis factor-alpha synthesis. In vivo, the administration of oxprenolol, a beta-receptor antagonist, significantly reduced serum IL-10 levels 90 min after LPS challenge. Thus, the present study provides the first evidence that endogenous catecholamines are of critical importance in determining the magnitude of the IL-10 response in experimental endotoxemia.

Direct effects of interleukin-6 on human adrenal cells

Interleukin-6 (IL-6), which is expressed in the human adrenal gland, was found to be a very potent activator of the human HPA axis. So far nothing is known about a local paracrine or autocrine influence of IL-6 within the human adrenal. In this study, the expression of IL-6 and the IL-6 receptor by human adrenal cells in vitro could be demonstrated by immunohistochemistry. Possible effects of IL-6 on steroid release were tested by incubating human adrenal cells in vitro with IL-6 [10(-8) M]. Adrenal steroids were stimulated by IL-6: aldosterone 184 +/- 23, cortisol 198 +/- 19, DHEA 140 +/- 8 and androstenedione 136 +/- 5 (results are means +/- s.e.m. in %). In conclusion, IL-6 can act directly on human adrenal cells and appears to be an important paracrine or autocrine factor.

Early induction of the NGFI-B/Nur77 family genes in nephritis induced by anti-glomerular basement membrane antibody

We recently isolated a novel nuclear receptor NOR-1, which is a member of the steroid/thyroid receptor superfamily, and belongs to the NGFI-B/Nur77 family. In the present study, we examined gene expression of NOR-1 and its closely related members in nephritis induced by anti-glomerular basement membrane (GBM) antibody. The mRNA levels for NOR-1, NGFI-B and RNR-1 increased 24 h after injection of anti-GBM antibody (day 1). Gene expression of NOR-1 and NGFI-B reached maximum levels on day 3, gradually decreased thereafter and returned to control levels on day 28. RNR-1 reached a peak on day 7, and then decreased. Renal injuries were most prominent on day 7 and persisted until day 28, indicating that NOR-1, NGFI-B and RNR-1 genes are induced during the early stage of glomerulonephritis and may be associated with the progression of glomerulonephritis. The induction of the NGFI-B gene was less remarkable than that of NOR-1 and RNR-1. In addition, administration of glucocorticoid hormone suppressed NOR-1 and RNR-1 gene expression to almost normal levels, whereas NGFI-B gene expression was not significantly repressed. These findings also suggest that the NGFI-B/Nur77 family may possess different biological roles and NGFI-B might act as a general transcription factor in cell function.

Leukemia inhibitory factor induces differentiation of pituitary corticotroph function: an immuno-neuroendocrine phenotypic switch

Leukemia inhibitory factor (LIF) promotes differentiated cell function in several systems. We recently reported LIF and LIF receptor expression in human fetal pituitary corticotrophs in vivo and demonstrated LIF stimulation of adrenocorticotrophin (ACTH) transcription in vitro, suggesting a role for LIF in corticotroph development. We therefore assessed the action of LIF on proliferating murine corticotroph cells (AtT20). LIF impairs proliferation of AtT20 cells (25% reduction versus control, P < 0.03), while simultaneously enhancing ACTH secretion (2-fold, P < 0.001) and augmenting ACTH responsiveness to corticotrophin-releasing hormone (CRH) action (4-fold, P < 0.001). This attenuation of cell growth is due to a block of cell cycle progression from G1 into S phase, as measured by flow cytometric analysis (24 +/- 0.8 versus 11.57 +/- 1.5, P < 0.001). Using bromodeoxyuridine incorporation assays, loss of cells in S phase was confirmed (25 +/- 0.08 to 9.4 +/- 1.4, P < 0.008). In contrast, CRH induced the G2/M phase (3.6 +/- 0.2 to 15.4 +/- 3, P < 0.001). This effect was blunted by LIF (P < 0.001 versus CRH alone). Cyclin A mRNA levels, which decline in S phase, were stimulated 3.5-fold by LIF and markedly suppressed by CRH. These results indicate a LIF-induced cell cycle block occurring at G1/S in corticotroph cells. Thus, LIF reduces proliferation, enhances ACTH secretion, and potentiates effects of CRH on ACTH secretion while blocking effects of CRH on the cell cycle. Responses of these three markers of differentiated corticotroph function indicate LIF to be a differentiation factor for pituitary corticotroph cells by preferential phenotypic switching from proliferative to synthetic.

Activation of neurons projecting to the paraventricular hypothalamic nucleus by intravenous lipopolysaccharide

The central nervous system interacts with the immune system to coordinate several components of the acute phase response, although the specific neuroanatomical pathways that mediate these responses are still uncharacterized. However, neurons in both the autonomic and endocrine components of the paraventricular hypothalamic nucleus (PVH) are characteristically activated in different models of immune stimulation. In the current study, we have used intravenous administration of lipopolysaccharide (LPS; 5 or 125 micrograms/kg) to induce the acute phase response. We subsequently coupled immunohistochemistry for Fos (as a marker of neuronal activation) with retrograde transport of the neuroanatomical tracer cholera toxin-b from the PVH. Several of the activated cell groups directly projected to the paraventricular nucleus, including the visceromotor (infralimbic) cortex, median preoptic nucleus, ventromedial preoptic area, bed nucleus of the stria terminalis, parabrachial nucleus, ventrolateral medulla, and nucleus of the solitary tract. These findings indicate that immune system stimulation activates cell groups from multiple nervous system levels that project to the paraventricular nucleus. We hypothesize that the activation of specific autonomic and endocrine elements of the PVH may be due to the activity of distinct afferents that converge on the PVH from multiple components of the central autonomic control system. Our results are consistent with the hypothesis that the PVH plays a key role in integrating diverse physiological cues into the varied manifestations that constitute the cerebral component of the acute phase response.

Dexamethasone suppression test: corticosteroid receptors regulation in mononuclear leukocytes of young and aged subjects

The dexamethasone suppression test (DST) is considered an indicator of the function of the adrenal pituitary axis. The effect of the steroid is mediated by its binding to corticosteroid receptors. We previously suggested that the measurement of corticosteroid receptors in lymphocytes is an index of an analogous pattern in brain. In the present study, corticosteroid Type I and Type II receptors in mononuclear leukocytes were measured in 10 elderly subjects and in 9 young adults, before and after overnight DST (1 mg). Receptors were measured by radioreceptor assay. In all the subjects, dexamethasone was able to suppress plasma cortisol. The number of Type I and Type II receptors before the test was lower in elderly subjects than in adults. In the control group, dexamethasone produced a significant depression of Type I receptors (from 267 +/- 72 to 169 +/- 71 receptors per cell), which can be interpreted as a primary involvement of Type I receptors in the response to dexamethasone; Type II receptors decreased in half the subjects (from 2849 +/- 703 to 2345 +/- 569 receptors per cell). In elderly healthy subjects, Type II receptors were also significantly decreased (from 1796 +/- 671 to 720 +/- 345). We suggest that in young subjects Type II receptors are initially up-regulated by dexamethasone, and then down-regulated, while in aged subjects an up-regulation cannot be achieved, as suggested by the higher values of plasma cortisol usually found in aging subjects.

Selective inhibitors of nitric oxide synthase (NOS) implicate a constitutive isoform of NOS in the regulation of interleukin-1-induced ACTH secretion in rats

Nitric oxide synthase (NOS) exists in at least three distinct isoforms: an inducible NOS (NOS II), and two forms which are constitutively expressed-brain NOS (NOS I) and endothelial NOS (NOS III). We have previously shown that the NOS inhibitor, N(ω)-nitro-L-arginine methyl ester hydrochloride (L-NAME), markedly potentiates and prolongs the increase in plasma adrenocorticotropin (ACTH) concentrations produced by the intravenous injection of interleukin-1β (IL-1β) in the rat. However, the mechanism of action of L-NAME is unknown. The purpose of the present study was to determine the effects on IL-1β-induced ACTH secretion in the rat, of several NOS inhibitors, whose selectivity for the different NOS isoforms has been well characterized, and which lack the muscarinic receptor antagonist properties that have been reported for L-NAME. Subcutaneous (sc) pretreatment with L-NAME (50-300 μmol/kg) produced the expected pronounced exacerbation of the ACTH response to IL-1β. This effect was mimicked by N(G)-nitro-L-arginine, which preferentially inhibits constitutive forms of NOS. In contrast, aminoguanidine, a selective inducible NOS inhibitor at doses up to 3×1.8 mmol/kg, was without effect, suggesting that it is a constitutive form of NOS that regulates the ACTH response to IL-1β. Selective inhibition of brain NOS using either 7-nitro-indazole (administered intraperitoneally) or L-NAME (administered intracerebroventricularly) did not significantly alter ACTH concentrations after IL-1β. Collectively, these data indicate that NO restrains the ACTH response to IL-1β, and that the NO responsible for this effect is generated by a constitutive, most probably endothelial, isoform of NOS.

Anterior pituitary function during critical illness and dopamine treatment

OBJECTIVE

To summarize the available data on anterior pituitary function in critical illness and to focus on the endocrine effects of dopamine infusion. The analogy with anterior pituitary function in the elderly is highlighted, and the potential importance of these observations for recovery from critical illness is discussed.

DATA SOURCES

Computerized search of published research and reference list review.

STUDY SELECTION

Review of 178 citations. Included are seven original studies on the effect of dopamine on pituitary function in adult and pediatric critical illness performed by the authors.

DATA EXTRACTION

Studies on the endocrinology of illness, chronic stress, aging, and dopamine, or on the clinical importance of endocrine changes.

DATA SYNTHESIS

The different pituitary axes are important determinants of normal anabolism and immune function. Continuously increased serum cortisol concentrations, insulin resistance, blunted prolactin release, and attenuated pulsatility of growth hormone and luteinizing hormone secretory patterns, as well as multiple anomalies in the thyroid axis, characterize the endocrine profile of prolonged critical illness. Dopamine, a natural catecholamine with hypophysiotropic properties, which has been used for more than two decades as an inotropic and vasoactive drug in intensive care, suppresses the circulating concentrations of all anterior pituitary-dependent hormones, except for cortisol. Available evidence suggests that the major effect of dopamine administration on the endocrine system is unlikely to be beneficial for the threatened metabolic and immunologic homeostasis of the severely ill patient. This pattern of hypopituitarism induced by chronic, severe illness and exogenous dopamine administration is reminiscent of the hormonal profiles obtained in experimental models of chronic stress, suggesting that endogenous dopamine may play a role in the endocrine and metabolic response to critical illness.

CONCLUSIONS

The dopamine-induced or aggravated pituitary dysfunction in critical illness warrants caution with prolonged infusion of this catecholamine as a so-called supportive agent, particularly in early life. The potential of combined hormonal therapy to improve the metabolic and immune status of the critically ill patient deserves thorough investigation.

Exercise stimulates interleukin-6 secretion: inhibition by glucocorticoids and correlation with catecholamines

In experimental animals, stress and catecholamines stimulate endogenous interleukin-6 (IL-6) secretion, whereas glucocorticoids inhibit it. To examine whether physical stress alters the secretion of IL-6 in humans, and to what extent this is correlated with catecholamines and modified by glucocorticoids, we performed high-intensity treadmill exercise test runs on 15 male volunteers, in a double-blind crossover design, after pretreatment with placebo, hydrocortisone, or dexamethasone. Plasma epinephrine and norepinephrine concentrations peaked 15 min after the start of exercise, whereas plasma IL-6 concentrations peaked twice, 15 min and 45 min after the onset of the test run. There was no difference in either the epinephrine or norepinephrine peaks among the three treatments, but the net area under the curve for IL-6 was smaller after hydrocortisone or dexamethasone than after placebo and smaller after dexamethasone than after hydrocortisone. A positive correlation was observed between peak plasma epinephrine or norepinephrine and IL-6 levels at 15 min. These findings suggest that IL-6 secretion is stimulated during exercise, possibly by catecholamines, whereas exogenous glucocorticoids attenuate this effect without affecting the catecholamine levels.

Effect of cortisol and ACTH on corticosteroid-suppressed peripheral blood natural killer cells from healthy volunteers and patients with Crohn's disease

Recently, we have shown that administration of adrenocorticotropic hormone (ACTH) to corticosteroid-treated Crohn's disease (CD) patients increased the peripheral blood natural killer (NK) cell activity which was suppressed by the corticosteroids. To elucidate this observation we analysed the in vitro effect of budesonide, prednisolone, cortisol, and ACTH on NK cells of healthy volunteers and corticosteroid-treated CD patients. Incubation of peripheral blood mononuclear cells (PBMNC) from healthy volunteers during the cytotoxicity assay caused a dose-dependent inhibition of NK cell activity by the three corticosteroids, while ACTH had hardly any effect. Pre-incubation for 18 h with high and low inhibiting concentrations also showed a significant inhibiting effect on NK cell activity of the corticosteroids. The percentage of CD56+ NK cells tended to increase after pre-incubation with a high inhibiting concentration of budesonide, prednisolone, and cortisol. Incubation of budesonide- or prednisolone-suppressed PBMNC from healthy volunteers and CD patients, with ACTH and/or cortisol, to mimic the in vivo situation, did not restore the corticosteroid-induced suppression of NK cell activity. The increase of the budesonide- or prednisolone-suppressed NK cell activity after in vivo administration of ACTH to the CD patients is therefore probably not a direct effect of cortisol or ACTH. Presumably other factors like cytokines and/or neurohormones must be involved in the in vivo interaction between corticosteroids, ACTH, and NK cells.

Endocrine implications of human immunodeficiency virus infection

Endocrine abnormalities occur frequently in HIV-infected patients. Although the majority of endocrine disorders reflect chronic infection, stress, and malnutrition, some disorders are characteristic of HIV infection or AIDS and deserve particular clinical attention. Identification of HIV patients at risk of frank endocrine disorders, rapid and correct diagnosis, and appropriate management are essential steps to minimize morbidity and mortality. Finally, increasing evidence from in vitro studies suggests that various hormones may influence HIV replication as well as the course of HIV disease and associated disorders. Future studies on the molecular mechanisms of hormones on HIV action and clinical studies on the effects of hormones as adjunctives to established forms of therapy may stimulate development of novel therapeutic strategies that will benefit HIV-infected patients.

Subdiaphragmatic vagotomy inhibits intra-abdominal interleukin-1 beta stimulation of adrenocorticotropin secretion

Although interleukin (IL)-1 beta activates the hypothalamic-pituitary-adrenal (HPA) axis, the mechanisms by which peripheral IL-1 beta acutely stimulates adrenocorticotropin (ACTH) secretion are not clear. Recently, the vagus has been implicated in mediating peripheral cytokine signalling of the brain. To investigate a possible central mechanism for peripheral cytokine stimulation of the HPA axis, we tested the hypothesis that the vagus mediates IL-1 beta activation of the HPA axis by an intra-abdominal stimulus. We studied the effect of subdiaphragmatic vagotomy on plasma ACTH stimulation in rats by intraperitoneal (i.p.) IL-1 beta. Adult male Sprague-Dawley rats underwent subdiaphragmatic vagotomy or sham surgery 1 week prior to study. Rats were killed 1 and 2 h after i.p. saline (control) and low- (4 micrograms/kg) and high-dose (20 micrograms/kg) IL-1 beta. Vagotomy markedly attenuated plasma ACTH secretion at 2 h after high-dose IL-1 beta stimulation and abolished plasma ACTH secretion at 2 h after low-dose IL-1 beta stimulation. At 1 h after low-dose IL-1 beta, stimulation of plasma ACTH in vagotomized animals was also markedly diminished compared to sham animals. However, vagotomy did not alter stimulation of plasma corticosterone at 1 or 2 h after low-dose IL-1 beta or at 2 h after high-dose IL-1 beta. In addition, vagotomy did not alter stimulation of plasma ACTH or corticosterone secretion by insulin-induced hypoglycemia. We conclude that: (1) the vagus plays an important role in stimulation of ACTH secretion by intra-abdominal (i.p.) IL-1 beta; (2) stimulation of corticosterone secretion by i.p. IL-1 beta is not altered by vagotomy; and (3) the inhibitory effect of vagotomy on activation of the HPA axis appears to be specific for immune stimulation by cytokines.

Distribution of Fos-like immunoreactivity in the rat brain following intravenous lipopolysaccharide administration

The central nervous system, particularly the hypothalamus, is intimately involved in the coordination of various aspects of the inflammatory response, including the generation of fever. We used intravenous injections of bacterial cell wall lipopolysaccharide (LPS; 5 or 125 micrograms/kg) to stimulate the acute phase response and mapped the resultant distribution of Fos-like immunoreactivity in the rat brain. In addition, we compared the patterns of Fos distribution with the thermoregulatory responses elicited by the LPS. Administration of LPS resulted in a dose- and time-dependent pattern of Fos-like immunoreactivity throughout the rat brain consistent with a coordinated autonomic, endocrine, and behavioral response to the LPS challenge that was most pronounced 2 hours following injection. Specifically, Fos-like immunoreactivity was observed in key autonomic regulatory nuclear groups, including the insular and prelimbic cortices, paraventricular hypothalamic nucleus, parabrachial nucleus, nucleus of the solitary tract, and the rostral and caudal levels of the ventrolateral medulla. In addition, a significant sustained elevation of Fos-like immunoreactivity was observed in a cell group adjacent to the organum vasculosum of the lamina terminalis, which we termed the ventromedial preoptic area. This sustained elevation of Fos-like immunoreactivity coupled with the alterations in body temperature elicited by LPS leads us to hypothesize that the ventromedial preoptic area may be a key site for the initiation of fever during endotoxemia.