Perturbations of arginine vasopressin secretion during inflammatory stress. Pathophysiologic implications

Validity of mental and physical stress models

Different stress models are employed to enhance our understanding of the underlying mechanisms and explore potential interventions. However, the utility of these models remains a critical concern, as their validities may be limited by the complexity of stress processes. Literature review revealed that both mental and physical stress models possess reasonable construct and criterion validities, respectively reflected in psychometrically assessed stress ratings and in activation of the sympathoadrenal system and the hypothalamic-pituitary-adrenal axis. The findings are less robust, though, in the pharmacological perturbations' domain, including such agents as adenosine or dobutamine. Likewise, stress models' convergent- and discriminant validity vary depending on the stressors' nature. Stress models share similarities, but also have important differences regarding their validities. Specific traits defined by the nature of the stressor stimulus should be taken into consideration when selecting stress models. Doing so can personalize prevention and treatment of stress-related antecedents, its acute processing, and chronic sequelae. Further work is warranted to refine stress models' validity and customize them so they commensurate diverse populations and circumstances.

Systematic analysis between inflammation-related index and sex hormones in American adults: cross-sectional research based NHANES 2013-2016

Background

A series of novel inflammation-related indexes has been confirmed to be efficient indicators of human immune and inflammatory status, with great potential as predictors for a variety of diseases. However, the association between inflammation-related indexes and sex hormones in the general population remained uncertain.

Methods

We incorporated data from the NHANES 2013-2016 survey of American adults. On the basis of distribution and comparison analysis, we chose to undertake separate analyses of men and women (including premenopausal and postmenopausal groups). Multivariable weighted linear regression models, eXtreme Gradient Boosting (XGBoost) models, generalized linear analysis, stratified models, logistic regression models and sensitivity analysis were utilized to assess the relationships between inflammation-related indexes and sex hormones.

Results

Total 9372 participants out of 20146 were fitted into our research. We conducted separate gender analysis due to different distribution. Multivariable weighted linear regression indicated every component of the inflammation-related index was negatively correlated with at least one component of the male hormone indexes. However, SII, NLR, PPN, and NC were associated positively with female estradiol. XGBoost identify SII, PLR and NLR were the critical indexes on sex hormones. Inflammation-related indexes was associated with Testosterone deficiency in male and postmenstrual group and associated with Excessive Estradiol in premenstrual group. Finally, the subgroup analysis revealed that the association between sex hormones and inflammatory indicators was prominent in American adults over the age of 60 or those with BMI (>28 kg/m²).

Conclusion

In all, inflammation-related indexes act as independent risks associated with sex hormone alterations and metabolic disorder in both genders. Using multiple models, we revealed the relative importance of inflammation-related indexes. Subgroup analysis also identified the high-risk population. More prospective and experimental research should be conducted to validate the results.

High salt induced augmentation of angiotensin II mediated hypertension is associated with differential expression of tumor necrosis factor-alpha receptors in the kidney

Aim: Chronic high salt (HS) intake causes minimal changes in blood pressure (BP) but it induces augmented hypertensive response to angiotensin II (AngII) administration in rodents. The mechanism of this augmentation is not clearly understood. As tumor necrosis factor-alpha (TNF-α) induces natriuresis by activating TNF-α receptor type 1 (TNFR1) but not type 2 (TNFR2), we hypothesize that TNFR1 activity is reduced when HS is given in combination of AngII that leads to enhanced sodium retention and thus, causing augmented hypertension. The aim of this study is to examine the responses to chronic HS intake and AngII administration on the renal tissue protein expressions of TNFR1 and TNFR2 in mice. Methods: Different groups of mice (n = 6–7 in each group) chronically treated with or without AngII (25 ng/min; implanted minipump) for 4 weeks which were fed either normal salt (NS; 0.4% NaCl) or high salt (HS; 4% NaCl) diets. Systemic BP was measured by tail-cuff plethysmography. At the end of treatment period, kidneys were harvested after sacrificing the mice with euthanasia. Immuno-histochemical analysis of TNFR1 and TNFR2 proteins in renal tissues was performed by measuring the staining area and the intensity of receptors’ immunoreactivities using NIS-Elements software. The results were expressed in percent area of positive staining and the relative intensity. Results: HS intake alone did not alter mean BP (HS; 77 ± 1 vs. NS; 76 ± 3 vs. mmHg; tail-cuff plethysmography) but AngII induced increases in BP were augmented in HS group (104 ± 2 vs. 95 ± 2 mmHg; P < 0.05). The area of TNFR1 staining was higher in HS than NS group (6.0 ± 0.9% vs. 3.2 ± 0.7%; P < 0.05) but it was lower in AngII + HS than in AngII + NS group (5.0 ± 0.7% vs. 6.3 ± 0.7%; P = 0.068). TNFR2 immunoreactivity was minimal in NS and HS groups but it was high in AngII + NS and even higher in AngII + HS group. Conclusions: These data suggest that the HS induced increased TNFR1 activity that facilitates enhanced sodium excretion is compromised in elevated AngII condition leading to salt retention and augmented hypertension.

Stress and the "extended" autonomic system

This review updates three key concepts of autonomic neuroscience-stress, the autonomic nervous system (ANS), and homeostasis. Hans Selye popularized stress as a scientific idea. He defined stress variously as a stereotyped response pattern, a state that evokes this pattern, or a stimulus that evokes the state. According to the "homeostat" theory stress is a condition where a comparator senses a discrepancy between sensed afferent input and a response algorithm, the integrated error signal eliciting specific patterns of altered effector outflows. Scientific advances since Langley's definition of the ANS have incited the proposal here of the "extended autonomic system," or EAS, for three reasons. (1) Several neuroendocrine systems are bound inextricably to Langley's ANS. The first to be described, by Cannon in the early 1900s, involves the hormone adrenaline, the main effector chemical of the sympathetic adrenergic system. Other neuroendocrine systems are the hypothalamic-pituitary-adrenocortical system, the arginine vasopressin system, and the renin-angiotensin-aldosterone system. (2) An evolving body of research links the ANS complexly with inflammatory/immune systems, including vagal anti-inflammatory and catecholamine-related inflammasomal components. (3) A hierarchical network of brain centers (the central autonomic network, CAN) regulates ANS outflows. Embedded within the CAN is the central stress system conceptualized by Chrousos and Gold. According to the allostasis concept, homeostatic input-output curves can be altered in an anticipatory, feed-forward manner; and prolonged or inappropriate allostatic adjustments increase wear-and-tear (allostatic load), resulting in chronic, stress-related, multi-system disorders. This review concludes with sections on clinical and therapeutic implications of the updated concepts offered here.

Activation of hypothalamic AMPK ameliorates metabolic complications of experimental arthritis

OBJECTIVE

To investigate whether thermogenesis and the hypothalamus may be involved in the physiopathology of experimental arthritis (EA).

METHODS

EA was induced in Lewis male rats by intradermal injection of Freund's complete adjuvant (FCA). Food intake, body weight, plasma cytokines, thermographic analysis, gene and protein expression of thermogenic markers in brown (BAT) and white (WAT) adipose tissue and hypothalamic AMP-activated protein kinase (AMPK) were analyzed. Virogenetic activation of hypothalamic AMPK was performed.

RESULTS

We first demonstrate that EA is associated with increased BAT thermogenesis and browning of subcutaneous WAT (sWAT) leading to elevated energy expenditure. Moreover, rats suffering EA show inhibition of hypothalamic AMPK, a canonical energy sensor modulating energy homeostasis at central level. Notably, specific genetic activation of AMPK in the ventromedial nucleus of the hypothalamus (VMH; a key site modulating energy metabolism) reverses the effect of EA on energy balance, brown fat and browning, as well as promoting an amelioration of the inflammatory status.

CONCLUSION

Overall, these data indicate that EA promotes a central catabolic state that can be targeted and reversed by the activation of hypothalamic AMPK. This might open new therapeutic alternatives to treat rheumatoid arthritis (RA)-associated metabolic comorbidities, improving RA-patients overall prognosis.

Copeptin response to hypoglycemic stress is linked to prolactin activation in children

PURPOSE

The physiological role of arginine vasopressin (AVP) in the acute stress response in humans and especially in children is unclear. The aim of this study was to explore the interaction between copeptin, a well-established surrogate marker of AVP release, and anterior pituitary hormone activation in response to acute hypoglycemic stress in children and adolescents.

METHODS

We conducted an exploratory single center study involving 77 children and adolescents undergoing insulin-induced hypoglycemia. Blood levels of copeptin, ACTH, cortisol, GH, prolactin, interleukin-6 (IL-6), adrenaline and noradrenaline were determined at baseline and after insulin-induced hypoglycemia.

RESULTS

Basal plasma levels of copeptin (median: 5.2 pmol/L) increased significantly after hypoglycemia (median 9.7 pmol/L; P < 0.0001). Subjects with insufficient HPA axis response or severe GH deficiency had lower hypoglycemia-induced copeptin increase (median: 2.3 pmol/L) compared with individuals with intact pituitary response (median: 5.2 pmol/L, P = 0.02). Copeptin increase correlated significantly with the maximal increase of ACTH (r_s = 0.30; P = 0.010), cortisol (r_s = 0.33; P = 0.003), prolactin (r_s = 0.25; P = 0.03), IL-6 (r_s = 0.35; P = 0.008) and with BMI-SDS (r_s = - 0.28, P = 0.01). In multivariate regression analysis, prolactin increase was the only independent variable associated with copeptin increase (P = 0.0004).

CONCLUSION

Our data indicate that: (1) hypoglycemic stress elicits a marked copeptin response in children and adolescents, pointing out its role as an acute stress marker in this population; (2) stress-induced AVP/copeptin release is associated with anterior pituitary activation, mainly a prolactin response.

The extended autonomic system, dyshomeostasis, and COVID-19

The pandemic viral illness COVID-19 is especially life-threatening in the elderly and in those with any of a variety of chronic medical conditions. This essay explores the possibility that the heightened risk may involve activation of the “extended autonomic system” (EAS). Traditionally, the autonomic nervous system has been viewed as consisting of the sympathetic nervous system, the parasympathetic nervous system, and the enteric nervous system. Over the past century, however, neuroendocrine and neuroimmune systems have come to the fore, justifying expansion of the meaning of “autonomic.” Additional facets include the sympathetic adrenergic system, for which adrenaline is the key effector; the hypothalamic-pituitary-adrenocortical axis; arginine vasopressin (synonymous with anti-diuretic hormone); the renin-angiotensin-aldosterone system, with angiotensin II and aldosterone the main effectors; and cholinergic anti-inflammatory and sympathetic inflammasomal pathways. A hierarchical brain network—the “central autonomic network”—regulates these systems; embedded within it are components of the Chrousos/Gold “stress system.” Acute, coordinated alterations in homeostatic settings (allostasis) can be crucial for surviving stressors such as traumatic hemorrhage, asphyxiation, and sepsis, which throughout human evolution have threatened homeostasis; however, intense or long-term EAS activation may cause harm. While required for appropriate responses in emergencies, EAS activation in the setting of chronically decreased homeostatic efficiencies (dyshomeostasis) may reduce thresholds for induction of destabilizing, lethal vicious cycles. Testable hypotheses derived from these concepts are that biomarkers of EAS activation correlate with clinical and pathophysiologic data and predict outcome in COVID-19 and that treatments targeting specific abnormalities identified in individual patients may be beneficial.

Oxytocin and Vasopressin Systems in Obesity and Metabolic Health: Mechanisms and Perspectives

PURPOSE OF REVIEW

The neurohypophysial endocrine system is identified here as a potential target for therapeutic interventions toward improving obesity-related metabolic dysfunction, given its coinciding pleiotropic effects on psychological, neurological and metabolic systems that are disrupted in obesity.

RECENT FINDINGS

Copeptin, the C-terminal portion of the precursor of arginine-vasopressin, is positively associated with body mass index and risk of type 2 diabetes. Plasma oxytocin is decreased in obesity and several other conditions of abnormal glucose homeostasis. Recent data also show non-classical tissues, such as myocytes, hepatocytes and β-cells, exhibit responses to oxytocin and vasopressin receptor binding that may contribute to alterations in metabolic function. The modulation of anorexigenic and orexigenic pathways appears to be the dominant mechanism underlying the effects of oxytocin and vasopressin on body weight regulation; however, there are apparent limitations associated with their use in direct pharmacological applications. A clearer picture of their wider physiological effects is needed before either system can be considered for therapeutic use.

Copeptin as a novel marker predicting prognosis of liver cirrhosis and its major complications

OBJECTIVES

The aim of the work was to assess the level of copeptin as a surrogate marker predicting the severity of liver diseases and its major complications.

PATIENTS AND METHODS

This was a cross-sectional study that included 40 patients and 10 controls and was performed in Tanta University Hospital between June 2016 and November 2016. The studied cases were divided into five groups: group I (10 patients): compensated cirrhosis; group II (10 patients): cirrhosis with gastrointestinal hemorrhage due to portal hypertension; group III (10 patients): cirrhosis with hepatorenal syndrome; group IV (10 patients): cirrhosis with liver cell failure; and group V (10 controls): normal healthy individuals.

RESULTS

Regarding serum copeptin in the studied groups, copeptin showed a significant decrease in group I vs group II' group I vs group III, and group I vs group IV; and there was a significant increase in group II vs group III' group II vs group IV' group II vs control' group III vs control, and group IV vs control. No significance was detected between group I vs control and group III vs group IV.

CONCLUSIONS

Copeptin is a novel marker for the determination of prognosis of liver cirrhosis. There is significant association between serum level of copeptin and complications of liver cirrhosis.

Expression of Proinflammatory Cytokines Is Upregulated in the Hypothalamic Paraventricular Nucleus of Dahl Salt-Sensitive Hypertensive Rats

Accumulating evidence indicates that inflammation is implicated in hypertension. However, the role of brain proinflammatory cytokines (PICs) in salt sensitive hypertension remains to be determined. Thus, the objective of this study was to test the hypothesis that high salt (HS) diet increases PICs expression in the paraventricular nucleus (PVN) and leads to PVN neuronal activation. Eight-week-old male Dahl salt sensitive (Dahl S) rats, and age and sex matched normal Sprague Dawley (SD) rats were divided into two groups and fed with either a HS (4% NaCl) or normal salt (NS, 0.4% NaCl) diet for 5 consecutive weeks. HS diet induced hypertension and significantly increased cerebrospinal fluid (CSF) sodium concentration ([Na⁺]) in Dahl S rats, but not in normal SD rats. In addition, HS diet intake triggered increases in mRNA levels and immunoreactivities of PVN PICs including TNF-α, IL-6, and IL-1β, as well as Fra1, a chronic marker of neuronal activation, in Dahl S rats, but not in SD rats. Next, we investigated whether this increase in the expression of PVN PICs and Fra1 was induced by increased CSF [Na⁺]. Adult male SD rats were intracerebroventricular (ICV) infused with 8 μl of either hypertonic salt (4 μmol NaCl), mannitol (8 μmol, as osmolarity control), or isotonic salt (0.9% NaCl as vehicle control). Three hours following the ICV infusion, rats were euthanized and their PVN PICs expression was measured. The results showed that central administration of hypertonic saline in SD rats significantly increased the expression of PICs including TNF-α, IL-6, and IL-1β, as well as neuronal activation marker Fra1, compared to isotonic NaCl controls and osmolarity controls. Finally, we tested whether the increase in PICs expression occurred in neurons. Incubation of hypothalamic neurons with 10 mM NaCl in a culture medium for 6 h elicited significant increases in TNF-α, IL-6, and Fra1 mRNA levels. These observations, coupled with the important role of PICs in modulating neuronal activity and stimulating vasopressin release, suggest that HS intake induces an inflammatory state in the PVN, which, may in turn, augments sympathetic nerve activity and vasopressin secretion, contributing to the development of salt sensitive hypertension.

Elevated vasopressin in pregnant mice induces T-helper subset alterations consistent with human preeclampsia

The pathogenesis of preeclampsia (PreE), a hypertensive disorder of pregnancy, involves imbalanced T helper (TH) cell populations and resultant changes in pro- and anti-inflammatory cytokine release. Elevated copeptin (an inert biomarker of arginine vasopressin (AVP)), secretion precedes the development of symptoms in PreE in humans, and infusion of AVP proximal to and throughout gestation is sufficient to initiate cardiovascular and renal phenotypes of PreE in wild-type C57BL/6J mice. We hypothesize that AVP infusion in wild-type mice is sufficient to induce the immune changes observed in human PreE. AVP infusion throughout gestation in mice resulted in increased pro-inflammatory interferon γ (IFNg) (TH1) in the maternal plasma. The TH17-associated cytokine interleukin (IL)-17 was elevated in the maternal plasma, amniotic fluid, and placenta following AVP infusion. Conversely, the TH2-associated anti-inflammatory cytokine IL-4 was decreased in the maternal and fetal kidneys from AVP-infused dams, while IL-10 was decreased in the maternal kidney and all fetal tissues. Collectively, these results demonstrate the sufficiency of AVP to induce the immune changes typical of PreE. We investigated if T cells can respond directly to AVP by evaluating the expression of AVP receptors (AVPRs) on mouse and human CD4+ T cells. Mouse and human T cells expressed AVPR1a, AVPR1b, and AVPR2. The expression of AVPR1a was decreased in CD4+ T cells obtained from PreE-affected women. In total, our data are consistent with a potential initiating role for AVP in the immune dysfunction typical of PreE and identifies putative signaling mechanism(s) for future investigation.

Pathophysiology of copeptin in kidney disease and hypertension

Copeptin is derived from the cleavage of the precursor of arginine vasopressin (AVP), produced in an equimolar ratio in hypothalamus and processed during axonal transport AVP is an unstable peptide and has a short half-life of 5-20 min. Unlike AVP, copeptin is a stable molecule and can easily be measured. Recent evidence suggest that increased copeptin levels have been associated with worse outcomes in various clinical conditions including chronic kidney disease (CKD) and hypertension. In this review, the data regarding copeptin with kidney function (evaluated as glomerular filtration rate, increased albumin/protein excretion or both) and hypertension with regard to performed studies, prognosis and pathogenesis was summarised.

Liver cirrhosis reversion is improved in hamsters with a neurointermediate pituitary lobectomy

Regulating mechanisms of fibrosis is an important goal in the treatment of fibrosis and liver cirrhosis. The role of arginine vasopressin (AVP) in promoting fibrosis in several organs has been well documented. However, the result of an AVP deficiency during liver fibrosis has not been reported. We herein study the effects of an AVP deficiency, which was induced by neurointermediate pituitary lobectomy (NIL), on liver cirrhosis and liver cirrhosis reversion. Hamsters were intact (control) or underwent CCl₄-induced cirrhosis, the latter animals divided into four groups: Cirrhotic, NIL-cirrhotic, Cirrhotic-reversion (R) and NIL-cirrhotic-R. Liver function, liver histopathology (including the fibrosis area and collagen types) and liver expression of MMP-13 and TIMP-2 were assessed. Results show that the AVP deficiency decreased the levels of alkaline phosphatase in serum and the expression of type I collagen and TIMP-2, and increased type III collagen deposition, MMP-13 expression and the size of regeneration nodules in NIL-cirrhotic and NIL-cirrhotic-R animals. A significantly greater recovery was found in the NIL-cirrhotic-R than the Cirrhotic-R group. We conclude that an AVP deficiency participates importantly in hamster liver regeneration by: 1) prompting the fibroblasts to produce type III collagen deposit, 2) influencing the activity of AP from bile duct cells, and 3) inhibiting TIMP-2 expression while favoring the fibrolytic activity of MMP-13.

[Vasopressors and inotropes: use in paediatrics]

The cardiovascular system is a dynamic system, which is required to ensure adequate delivery of oxygen, nutrients, and hormones to the tissues that are necessary for cell metabolism. It also synthesises and modifies the vasoactive components that regulate vascular tone and myocardial function. These vasoactive components have demonstrated their beneficial effects in the management of paediatric patients in a critical condition with heart failure and shock. However, their use and abuse brings harmful effects, increases mortality, and is associated with arrhythmias. An increase in myocardial oxygen consumption favours the presence of ischaemia, therefore it is necessary to know the mechanism of action and indications of these drugs to minimise their harmful effects. The purpose of this review is to describe the pharmacology and clinical applications of inotropic and vasopressor agents in the paediatric patient in acritical condition.

Vasopressin in Septic Shock; Assessment of Sepsis Biomarkers: A Randomized, Controlled Trial

Background and Aims:

Vasopressin (VP) in sepsis apart from vasoconstrictive effect may have some immunomodulatory effects. The aim of this study was to evaluate the effect of VP on different aspect of sepsis by measuring of sepsis biomarkers.

Materials and Methods:

In this trial, a total number of 42 septic shock patients were included. The first group received norepinephrine (NE) infusion to reach the target mean arterial pressure (MAP) of ≥ 65 mm Hg and the second group received arginine vasopressin (AVP) infusion in addition to NE. Serum lactate, C-reactive protein (CRP), interleukin-6 (IL-6), IL-10, pentraxin 3 (PTX3), angiopoietin 1 and 2 (Ang 1 and 2) levels were assessed.

Results:

Level of IL-6 and IL-10 decreased, but there was no significant difference between the two groups after 48 h. CRP and PTX3 levels were not also significantly different between groups. Although Angs were not statistically different, there was a trend toward higher Ang-1 in and lower Ang 2 in AVP group after 24 and 48 h. In addition, lactate level did not differ between NE and AVP groups. There was no interaction between VP and hydrocortisone use on IL-6, IL-10, and PTX3, but a significant statistical interaction on Ang 1 and Ang 2 were observed.

Conclusions:

Although analysis of sepsis biomarkers showed no significant difference between two groups, no immunomodulatory effect for VP alone, subgroup analysis of hydrocortisone used in this study showed that the combination of glucocorticoids and AVP had a significant effect on Angs level which eventually causes less endothelial permeability and higher MAP in this group of patients.

Incidence of Exercise-Associated Hyponatremia and Its Association With Nonosmotic Stimuli of Arginine Vasopressin in the GNW100s Ultra-endurance Marathon

OBJECTIVES

(1) To examine the incidence of exercise-associated hyponatremia (EAH) during and after an ultramarathon and (2) to evaluate hypothesized nonosmotic stimuli [interleukin-6 (IL-6), hypoglycemia, ambient temperature] with arginine vasopressin (AVP) concentrations in hyponatremic versus normonatremic runners.

DESIGN

Prospective cohort study.

SETTING

The Great North Walk 100s ultramarathons.

PARTICIPANTS

Fifteen runners participated in either 103.7- or 173.7-km ultramarathons.

MAIN OUTCOME MEASURES

Serum sodium concentration ([Na]) and AVP concentration. Secondary outcome measures included IL-6, blood glucose, ambient temperature, weight change, fluid consumption, and use of nonsteroidal anti-inflammatory drugs (NSAIDs).

RESULTS

Postrace EAH incidence was 4 of 15 runners, whereas EAH incidence at any point during the race was in 10 of 15 runners. A significant positive correlation was noted between AVP and IL-6 (r = 0.31, P < 0.05) but not between AVP and blood glucose (r = 0.09, nonsignificant) or ambient temperature (r = -0.12, NS). Subgroup analysis revealed that the correlation between AVP and IL-6 was significant in hyponatremic (r = 0.37, P < 0.05) but not normonatremic runners (r = 0.31, NS). Hyponatremic runners lost less weight than normonatremic runners (2.5 vs. 3.7 kg, P < 0.05, respectively) despite similar fluid consumption. Seven of 10 hyponatremic runners consumed NSAIDs versus 0 of 5 normonatremic runners.

CONCLUSIONS

Exercise-associated hyponatremia incidence mid-race is higher than postrace, suggesting that 40% of runners are able to self-correct low serum [Na] status during an ultramarathon. Interleukin-6 seems to be the main nonosmotic stimulus associated with AVP in hyponatremic runners. Nonsteroidal anti-inflammatory ingestion is more common in hyponatremic versus normonatremic runners.

CLINICAL RELEVANCE

Exercise-associated hyponatremia associated with nonosmotic AVP secretion may be more common during ultramarathon races without discriminatory clinical symptomatology.

Vasopressin in preeclampsia: a novel very early human pregnancy biomarker and clinically relevant mouse model

Preeclampsia, a cardiovascular disorder of late pregnancy, is characterized as a low-renin hypertensive state relative to normotensive pregnancy. Because other nonpregnant low-renin hypertensive disorders often exhibit and are occasionally dependent on elevated arginine vasopressin (AVP) secretion, we hypothesized a possible use for plasma AVP measurements in the prediction of preeclampsia. Copeptin is an inert prosegment of AVP that is secreted in a 1:1 molar ratio and exhibits a substantially longer biological half-life compared with AVP, rendering it a clinically useful biomarker of AVP secretion. Copeptin was measured throughout pregnancy in maternal plasma from preeclamptic and control women. Maternal plasma copeptin was significantly higher throughout preeclamptic pregnancies versus control pregnancies. While controlling for clinically significant confounders (age, body mass index, chronic essential hypertension, twin gestation, diabetes mellitus, and history of preeclampsia) using multivariate regression, the association of higher copeptin concentration and the development of preeclampsia remained significant. Receiver operating characteristic analyses reveal that as early as the sixth week of gestation, elevated maternal plasma copeptin concentration is a highly significant predictor of preeclampsia throughout pregnancy. Finally, chronic infusion of AVP during pregnancy (24 ng per hour) is sufficient to phenocopy preeclampsia in C57BL/6J mice, causing pregnancy-specific hypertension, renal glomerular endotheliosis, proteinuria, and intrauterine growth restriction. These data implicate AVP release as a novel predictive biomarker for preeclampsia very early in pregnancy, identify chronic AVP infusion as a novel and clinically relevant model of preeclampsia in mice, and are consistent with a potential causative role for AVP in preeclampsia in humans.

Plasma copeptin, a possible prognostic marker in cirrhosis

BACKGROUND & AIM

Copeptin, secreted stoichiometrically with vasopressin, demonstrated its prognostic role in various diseases other than cirrhosis.

METHODS

We investigated the association between severity of cirrhosis and plasma concentrations of copeptin, and the prognostic value of copeptin in 95 non-septic cirrhotic patients (34 Child-Pugh A, 29 CP-B, 32 CP-C), 30 septic patients with a Child-Pugh >8 ('group D'), and 16 healthy volunteers. Patients were followed for at least 12 months to assess the composite endpoint death/liver transplantation.

RESULTS

Median copeptin concentrations (interquartile range) increased through healthy volunteers group [5.95 (3.76-9.43) pmol/L] and 'group D' patients [18.81 (8.96-36.66) pmol/L; P < 0.001)]. During a median follow-up of 11.0 ± 6.1 months, 28 non-transplanted patients died and eight were transplanted. In receiver operated characteristic curves analysis, the area under the curve values were as follows: Child-Pugh score 0.80 (95% CI: 0.71-0.86), model of end-stage liver disease (MELD) score 0.80 (0.70-0.86), C-reactive protein (CRP) 0.71 (0.60-0.80) and copeptin 0.70 (0.57-0.79). By stratifying the values of these variables into tertiles, the risk of death/liver transplantation for patients belonging to the highest tertile of copeptin (>13 pmol/L) was high (Log-rank test: P = 0.0002) and 2.3-fold higher than for patients with lower concentrations after adjusting for MELD score (>21) and CRP (>24 mg/L) in a Cox model. Other potential predictors (age, total cholesterol, natraemia and serum free cortisol) did not reach a significant level.

CONCLUSION

In cirrhotic patients, copeptin concentrations increased along with the severity of liver disease. In our cohort, the 1-year mortality or liver transplantation was predicted by high MELD score and high concentrations of CRP and copeptin.

Regulation of intestinal immune response by selective removal of the anterior, posterior, or entire pituitary gland in Trichinella spiralis infected golden hamsters

The influence of anterior pituitary hormones on the gastrointestinal tract of humans and animals has been previously reported. Hypophysectomy (HYPOX) in the rat causes atrophy of the intestinal mucosa, and reduction of gastric secretion and intestinal absorption, as well as increased susceptibility to bacterial and viral infections. However, to our knowledge, no findings have been published concerning the immune response following HYPOX during worm infection, particularly that which is caused by the nematode Trichinella spiralis. The aim of this work was to analyze the effects of total or partial HYPOX on colonization of T. spiralis in the intestinal lumen, together with duodenal and splenic cytokine expression. Our results indicate that 5 days post infection, only neurointermediate pituitary lobectomy (NIL) reduces the number of intestinally recovered T. spiralis larvae. Using semiquantitative inmunofluorescent laser confocal microscopy, we observed that the mean intensity of all tested Th1 cytokines was markedly diminished, even in the duodenum of infected controls. In contrast, a high level of expression of these cytokines was noted in the NIL infected hamsters. Likewise, a significant decrease in the fluorescence intensity of Th2 cytokines (with the exception of IL-4) was apparent in the duodenum of control and sham infected hamsters, compared to animals with NIL surgeries, which showed an increase in the expression of IL-5 and IL-13. Histology of duodenal mucosa from NIL hamsters showed an exacerbated inflammatory infiltrate located along the lamina propria, which was related to the presence of the parasite. We conclude that hormones from each pituitary lobe affect the gastrointestinal immune responses to T. spiralis through various mechanisms.

Effects of neurointermediate pituitary lobectomy and desmopressin on acute experimental autoimmune encephalomyelitis in Lewis rats

OBJECTIVE

The role of arginine vasopressin (AVP) as a direct immune regulator has not yet been clarified, and more work is needed to assess its involvement in the immunoneuroendocrine network. In the present study, the effects of neurointermediate pituitary lobectomy (NIL) and desmopressin (DP), an agonist of AVP, on acute experimental autoimmune encephalomyelitis (EAE) in female Lewis rats were evaluated. The activity of the hypothalamic-pituitary-adrenocortical (HPA) axis was also assessed.

METHODS

Five groups of rats were used, as follows: (1) sham-operated (SHAM) rats, (2) SHAM + DP rats, (3) NIL rats, (4) NIL + DP rats and (5) untreated normal control rats. DP treatment started 2 weeks after surgery, and immunization to induce EAE was carried out 1 week later.

RESULTS

SHAM rats developed full-blown clinical and histological signs of EAE and activation of the HPA axis. SHAM + DP animals had mild clinical signs of EAE, inflammatory infiltrations in the spinal cord and an activated HPA axis. NIL animals developed minimal EAE, scanty spinal cord inflammation and no changes in HPA axis activity. NIL + DP rats developed severe clinical signs of EAE, extensive spinal cord inflammatory infiltrations and marked activation of the HPA axis.

CONCLUSIONS

NIL decreased the cell-mediated immune response, while DP in NIL animals restored the immune response. AVP is directly involved in the maintenance of immune competence.

The Sequential Organ Failure Assessment score and copeptin for predicting survival in ventilator-associated pneumonia

INTRODUCTION

Ventilator-associated pneumonia remains the most common nosocomial infection in the critically ill and contributes to significant morbidity. Eventual decisions regarding withdrawal or maximal therapy are demanding and rely on physicians' experience. Additional objective tools for risk assessment may improve medical judgement. Copeptin, reflecting vasopressin release, as well as the Sequential Organ Failure Assessment (SOFA) score, reflecting the individual degree of organ dysfunction, might qualify for survival prediction in ventilator-associated pneumonia. We investigated the predictive value of the SOFA score and copeptin in ventilator-associated pneumonia.

METHODS

One hundred one patients with ventilator-associated pneumonia were prospectively assessed. Death within 28 days after ventilator-associated pneumonia onset was the primary end point.

RESULTS

The SOFA score and the copeptin levels at ventilator-associated pneumonia onset were significantly elevated in nonsurvivors (P = .002 and P = .017, respectively). Both markers had different time courses in survivors and nonsurvivors (P < .001 and P = .006). Mean SOFA (average SOFA of 10 days after VAP onset) was superior in predicting 28-day survival as compared with SOFA and copeptin at ventilator-associated pneumonia onset (area under the curve, 0.90 vs 0.73 and 0.67, respectively).

CONCLUSIONS

The predictive value of serial-measured SOFA significantly exceeds those of single SOFA and copeptin measurements. Serial SOFA scores accurately predict outcome in ventilator-associated pneumonia.

Arginine vasopressin, fluid balance and exercise: is exercise-associated hyponatraemia a disorder of arginine vasopressin secretion?

The ability of the human body to regulate plasma osmolality (POsm) within a very narrow and well defined physiological range underscores the vital importance of preserving water and sodium balance at rest and during exercise. The principle endocrine regulator of whole body fluid homeostasis is the posterior pituitary hormone, arginine vasopressin (AVP). Inappropriate AVP secretion may perpetuate either slow or rapid violation of these biological boundaries, thereby promoting pathophysiology, morbidity and occasional mortality. In the resting state, AVP secretion is primarily regulated by changes in POsm (osmotic regulation). The osmotic regulation of AVP secretion during exercise, however, may possibly be enhanced or overridden by many potential non-osmotic factors concurrently stimulated during physical activity, particularly during competition. The prevalence of these highly volatile non-osmotic AVP stimuli during strenuous or prolonged physical activity may reflect a teleological mechanism to promote water conservation during exercise. However, non-osmotic AVP secretion, combined with high fluid availability plus sustained fluid intake (exceeding fluid output), has been hypothesized to lead to an increase in both the incidence and related deaths from exercise-associated hyponatraemia (EAH) in lay and military populations. Inappropriately, high plasma AVP concentrations ([AVP](p)) associated with low blood sodium concentrations facilitate fluid retention and sodium loss, thereby possibly reconciling both the water intoxication and sodium loss theories of hyponatraemia that are currently under debate. Therefore, given the potential for a variety of exercise-induced non-osmotic stimuli for AVP secretion, hydration strategies must be flexible, individualized and open to change during competitive events to prevent the occurrence of rare, but life-threatening, EAH. This review focuses on the potential osmotic and non-osmotic stimuli to AVP secretion that may affect fluid homeostasis during physical activity. Recent laboratory and field data support: (i) stimulatory effects of exercise intensity and duration on [AVP](p); (ii) possible relationships between changes in POsm with changes in both sweat and urinary osmolality; (iii) alterations in the AVP osmoregulatory set-point by sex steroid hormones; (iv) differences in [AVP](p) in trained versus untrained athletes; and (v) potential inter-relationships between AVP and classical (aldosterone, atrial natriuretic peptide) and non-classical (oxytocin, interleukin-6) endocrine mediators. The review concludes with a hypothesis on how sustained fluid intakes beyond the capacity for fluid loss might possibly facilitate the development of hyponatraemia if exercise-induced non-osmotic stimuli override 'normal' osmotic suppression of AVP when hypo-osmolality exists.

Use of the dexamethasone-corticotrophin releasing hormone test to assess hypothalamic-pituitary-adrenal axis function in rheumatoid arthritis

Objectives. Hypothalamic-Pituitary-Adrenal axis function may be abnormal in rheumatoid arthritis (RA). A pilot study in 7 patients suggested impaired glucocorticoid feedback in some patients after the dexamethasone-corticotrophin releasing hormone (CRH) test. This study aimed to investigate the dexamethasone-corticotrophin releasing factor test in a larger group of patients and relate the results to characteristics of the disease. Methods. Outpatients with active RA (>/=3 swollen and tender joints and C-reactive protein > 10 mg/L) took dexamethasone (1.5 mg) at 23:00 hour in the evening. Next day, baseline saliva and plasma samples were collected, CRH was infused at 11:00 hour, and 4 serial blood and saliva samples were collected. Plasma samples were stored at -80 degrees C and a radioimmunoassay performed for saliva and plasma cortisol. Results. All 20 participants showed normal dexamethasone suppression and mounted no response to the CRH challenge. In samples with measurable cortisol, there was a strong correlation between saliva and plasma values (r = 0.876, n = 26, P < .01). Conclusion. No abnormalities were found in the Dexamethasone-CRH test in RA patients in contrast to a previous pilot study. Salivary cortisol measurement may offer an alternative noninvasive technique to plasma cortisol in RA patients in future studies.

Vasopressin in the pediatric cardiac intensive care unit: Myth or reality

Pediatric cardiac surgery is undergoing a metamorphosis, with more and more critical patients being operated in our country today. Although the principles of physiology have not changed, it is imperative that care providers continue to stay abreast with developments and newer drugs that may help modify the outcome. The team dynamics have also become more complex, which necessitates the need for all care providers (surgeons, cardiologists, anesthesiologists, and intensivists) to better understand the interactions and benefits of newer drugs. Vasopressin has been used in our adult patients for more than a decade and recently has found its rightful place in the pediatric armoury. The objective of this article is to review the physiology of vasopressin and the rationale of its use in critically ill children with shock, in context of the available published data.

Biomarkers in Peripheral Blood Associated with Vascular Injury in Sprague-Dawley Rats Treated with the Phosphodiesterase IV Inhibitors SCH 351591 or SCH 534385

Drug-associated vascular injury can be caused by phosphodiesterase (PDE) IV inhibitors and drugs from several other classes. The pathogenesis is poorly understood, but it appears to include vascular and innate immunological components. This research was undertaken to identify changes in peripheral blood associated with vascular injury caused by PDE IV inhibitors. We evaluated twelve proteins, serum nitrite, and leukocyte populations in peripheral blood of rats treated with experimental PDE IV inhibitors. We found that these compounds produced histological microvascular injury in a dose- and time-dependent manner. Measurement of these serum proteins showed changes in eight of the twelve examined. Changes were seen in the levels of: tissue inhibitor of metalloproteinase-1, α1-acid glycoprotein, GRO/CINC-1, vascular endothelial growth factor, C-reactive protein, haptoglobin, thrombomodulin, and interleukin-6. No changes were seen in levels of tumor necrosis factor-α, hepatocyte growth factor, nerve growth factor, and granulocyte-monocyte colony stimulating factor. Serum levels of nitrite were also increased. Circulating granulocyte numbers were increased, and lymphocyte numbers were decreased. The changes in these parameters showed both a dose- and time-dependent association with histopathologic changes. These biomarkers could provide an additional tool for the nonclinical and clinical evaluation of investigational compounds.

Fitness alters fluid regulatory but not behavioural responses to hypohydrated exercise

Dehydration is typical during prolonged exercise. Because training stimulates numerous adaptations, some involving fluid regulation, it is conceivable that training involves adaptations to dehydration. This study tested the hypothesis that trained individuals have altered fluid regulatory, but not behavioural or perceptual responses to exercise when hypohydrated. Six trained (V.O2 peak: 65+/-8 mL kg(-1) min(-1)) and six untrained (V.O2 peak: 45+/-4 mL kg(-1) min(-1)) males cycled for 40 min at 70%V.O2 peak, once whilst euhydrated (EUH) and once whilst hypohydrated by ~2% body mass (HYPO), before a 40-min performance trial with euhydration (in EUH) or ad libitum drinking (in HYPO), in temperate conditions (24.3 degrees C, 50% rh). Baseline hydration was achieved by complete or partial rehydration from exercise+heat stress on the previous evening. Body mass was reduced (-1.8+/-0.1%) and plasma osmolality was increased (5+/-1 mosmol kg(-1)) similarly between fitness groups in HYPO compared to EUH (P<0.05). During exercise, plasma [AVP] rose more in HYPO than EUH; the elevation was greater in the Untrained (4.1+/-1.7 vs. 2.0+/-0.8 pmol L(-1), P<0.01) than Trained (1.4+/-0.6 vs. 1.1+/-0.5 pmol L(-1), P<0.01; P=0.02). Increases in plasma [AVP] relative to osmolality were higher in Untrained than Trained (0.47+/-0.06 vs. 0.025+/-0.05 pmol mosmol(-1), P=0.03). Fitness groups had equivalent thirst ratings during fixed exercise but Trained were thirstier than Untrained when self regulating in HYPO (4.0+/-1.5 vs. 2.7+/-1.2; P=0.05); thus Trained tended to consume more fluid (1.20+/-0.16 vs. 0.88+/-0.16 L; P=0.19), but maintained similar hypohydration consistent with their greater sweat rate during HYPO. In conclusion, aerobic fitness attenuates the neuroendocrine ([AVP]) response to hypohydrated exercise, but not perceptual (thirst) or behavioural (ad libitum drinking) responses.

Vasopressin in pediatric shock and cardiac arrest

OBJECTIVE

To review the physiology and the published literature on the role of vasopressin in shock in children.

DATA SOURCE

We searched MEDLINE (1966-2007), EMBASE (1980-2007), and the Cochrane Library, using the terms vasopressin, terlipressin, and shock and synonyms or related terms for relevant studies in pediatrics. We searched the online ISRCTN-Current Controlled Trials registry for ongoing trials. We reviewed the reference lists of all identified studies and reviews as well as personal files to identify other published studies.

RESULTS

Beneficial effects have been reported in vasodilatory shock and asystolic cardiac arrest in adults. Solid evidence for vasopressin use in children is scant. Observational studies have reported an improvement in blood pressure and rapid weaning off catecholamines during administration of low-dose vasopressin. Dosing in children is extrapolated from adult studies.

CONCLUSIONS

Vasopressin offers promise in shock and cardiac arrest in children. However, in view of the limited experience with vasopressin, it should be used with caution. Results of a double-blind, randomized controlled trial in children with vasodilatory shock will be available soon.

Hyponatremia in marathon runners due to inappropriate arginine vasopressin secretion

PURPOSE

Exercise-associated hyponatremia (EAH), as defined by a blood sodium concentration [Na+] less than 135 mmol/L, may lead to hypotonic encephalopathy with fatal cerebral edema. Understanding the pathogenetic role of antidiuresis may lead to improved strategies for prevention and treatment.

METHODS

Normonatremic marathon runners were tested pre- and post-race for creatine kinase, interleukin-6, cortisol, prolactin, and arginine vasopressin. Similar testing also was carried out in runners with encephalopathy caused by EAH, including 2 cases with fatal cerebral edema.

RESULTS

Normonatremic runners (n = 33; 2001) with a mean 3% decrease in body weight showed a 40-fold increase in interleukin-6 (66.6 +/- 11.9 pg/mL from 1.6 +/- 0.5 pg/mL, P = .001), which was significantly correlated with increases in creatine kinase (r = 0.88, P = <.0001), cortisol (r = 0.70, P = .0003), and prolactin (r = 0.67, P <.007), but not arginine vasopressin (r = 0.44, P = .07). Collapsed runners with EAH (n = 22; 2004) showed a mean blood urea nitrogen less than 15 mg/dL with measurable plasma levels of arginine vasopressin (>0.5 pg/mL) in 43% of cases. Two marathon runners with fatal cerebral edema additionally showed less than maximally dilute urines (>100 mmol/kg/H2O) and urine [Na+] greater than 25 mEq/L.

CONCLUSIONS

Cases of EAH fulfill the essential diagnostic criteria for the syndrome of inappropriate antidiuretic hormone secretion (SIADH). Runners with hypotonic encephalopathy at subsequent races were treated with intravenous hypertonic (3%) saline on the basis of this paradigm, which resulted in rapid clinical improvement without adverse effects. Release of muscle-derived interleukin-6 may play a role in the nonosmotic secretion of arginine vasopressin, thereby linking rhabdomyolysis to the pathogenesis of EAH.

Circulating levels of copeptin, a novel biomarker, in lower respiratory tract infections

BACKGROUND

Vasopressin has haemodynamic as well as osmoregulatory effects, and reflects the individual stress response. Copeptin is co-synthesized with vasopressin, directly mirroring vasopressin levels, but is more stable in plasma and serum. Both levels are increased in patients with septic shock. Lower respiratory tract infections (LRTI) are a precursor of sepsis. Thus, we investigated circulating levels and the prognostic use of copeptin for the severity and outcome in patients with LRTI.

MATERIALS AND METHODS

Five hundred and forty-five consecutive patients with LRTI and 50 healthy controls were evaluated. Serum copeptin levels were measured with a new chemiluminescent sandwich immunoassay.

RESULTS

Of the 545 patients, 373 had community-acquired pneumonia (CAP), 60 acute exacerbations of chronic obstructive pulmonary disease (COPD), 59 acute bronchitis, 13 exacerbations of asthma and 40 other final diagnoses. Copeptin levels were significantly higher in patients with LRTI as compared to controls (P < 0.001) with highest levels in patients with CAP. Copeptin levels increased with increasing severity of CAP, as classified by the pneumonia severity index (PSI) (P < 0.001). In patients who died, copeptin levels on admission were significantly higher as compared to levels in survivors [70.0 (28.8-149.0) vs. 24.3 (10.8-43.8) pmol L(-1), P < 0.001]. The area under the receiver operating curve (AUC) for survival was 0.75 for copeptin, which was significantly higher as compared to C-reactive protein (AUC 0.61, P = 0.01), leukocyte count (AUC 0.59, P = 0.01) and similar to procalcitonin (AUC 0.68, P = 0.21).

CONCLUSIONS

Copeptin levels are increased with increasing severity of LRTI namely in patients with CAP and unfavourable outcome. Copeptin levels, as a novel biomarker, might be a useful tool in the risk stratification of patients with LRTI.

Vasopressin during cardiopulmonary resuscitation and different shock states: a review of the literature

Vasopressin administration may be a promising therapy in the management of various shock states. In laboratory models of cardiac arrest, vasopressin improved vital organ blood flow, cerebral oxygen delivery, the rate of return of spontaneous circulation, and neurological recovery compared with epinephrine (adrenaline). In a study of 1219 adult patients with cardiac arrest, the effects of vasopressin were similar to those of epinephrine in the management of ventricular fibrillation and pulseless electrical activity; however, vasopressin was superior to epinephrine in patients with asystole. Furthermore, vasopressin followed by epinephrine resulted in significantly higher rates of survival to hospital admission and hospital discharge. The current cardiopulmonary resuscitation guidelines recommend intravenous vasopressin 40 IU or epinephrine 1mg in adult patients refractory to electrical countershock. Several investigations have demonstrated that vasopressin can successfully stabilize hemodynamic variables in advanced vasodilatory shock. Use of vasopressin in vasodilatory shock should be guided by strict hemodynamic indications, such as hypotension despite norepinephrine (noradrenaline) dosages >0.5 mug/kg/min. Vasopressin must never be used as the sole vasopressor agent. In our institutional routine, a fixed vasopressin dosage of 0.067 IU/min (i.e. 100 IU/50 mL at 2 mL/h) is administered and mean arterial pressure is regulated by adjusting norepinephrine infusion. When norepinephrine dosages decrease to 0.2 microg/kg/min, vasopressin is withdrawn in small steps according to the response in mean arterial pressure. Vasopressin also improved short- and long-term survival in various porcine models of uncontrolled hemorrhagic shock. In the clinical setting, we observed positive effects of vasopressin in some patients with life-threatening hemorrhagic shock, which had no longer responded to adrenergic catecholamines and fluid resuscitation. Clinical employment of vasopressin during hemorrhagic shock is experimental at this point in time.

Exercise-associated hyponatremia: role of cytokines

Exercise-associated hyponatremia (EAH) has emerged in recent years as a life-threatening complication of endurance sports that may lead to fatal cerebral and pulmonary edema. Defined as a serum sodium concentration <135 mEq/L (1 mEq/L = 1 mmol/L), symptomatic EAH is a dilutional hyponatremia with abnormal fluid retention mediated by decreased urine production, which is a variant of the syndrome of inappropriate antidiuretic hormone secretion. Strategies for prevention and treatment must take into account the pathophysiology underlying this dominant clinical paradigm. Beyond educating runners to drink moderately, monitoring changes in body weight during endurance sports may facilitate the early detection of positive fluid balance characteristic of symptomatic cases. Rapid diagnosis by point-of-care testing indicates the need for fluid restriction in mild cases and emergent treatment with hypertonic (3%) NaCl to reverse acute hypotonic encephalopathy. The efficacy of arginine vasopressin V(2) receptor antagonists warrants study as an alternative treatment to loop diuretics for volume overload in these patients. Nonosmotic stimulation of arginine vasopressin secretion may be mediated in part by enhanced release of muscle-derived interleukin-6 during glycogen depletion, linking exertional rhabdomyolysis to the pathogenesis of EAH.

Effects of arginine-vasopressin and parathyroid hormone-related protein (1-34) on cell proliferation and production of YKL-40 in cultured chondrocytes from patients with rheumatoid arthritis and osteoarthritis

OBJECTIVE

Both arg-vasopressin (AVP) and parathyroid hormone-related protein (PTHrP) may act as proinflammatory hormones. In addition, they have been suggested to be involved in the pathophysiology of rheumatoid arthritis (RA). We therefore investigated the effects of AVP and PTHrP (1-34) on cell proliferation and secretion of the glycoprotein YKL-40 in human chondrocytes derived from healthy subjects as well as from patients with RA or osteoarthritis (OA).

METHOD

Primary cultures of human chondrocytes were incubated with AVP (1-100 pmol/l) or PTHrP (1-34) (0.1-100 nmol/l). Cell proliferation was measured as [3H]thymidine incorporation. Intracellular cAMP and YKL-40 in cell medium were determined by commercially available kits.

RESULTS

AVP and PTHrP (1-34) increased proliferation in chondrocytes derived from healthy donors as well as from RA and OA patients. PTHrP (1-34), but not AVP, increased intracellular levels of cAMP. PTHrP (1-34) did not change the amount of YKL-40 in chondrocytes from healthy subjects or patients with OA. AVP tended to decrease the secretion of YKL-40 from healthy chondrocytes. Both PTHrP (1-34) and AVP increased YKL-40 secretion from RA chondrocytes. In contrast, AVP decreased the secretion of YKL-40 in chondrocytes from patients with OA.

CONCLUSION

AVP and PTHrP (1-34) stimulated proliferation in human chondrocytes derived from healthy subjects as well as from patients with RA or OA. However, the effects of AVP and PTHrP (1-34) on YKL-40 secretion varied depending on the origin of the chondrocytes.

Hypophysectomy and neurointermediate pituitary lobectomy reduce serum immunoglobulin M (IgM) and IgG and intestinal IgA responses to Salmonella enterica serovar Typhimurium infection in rats

The influence of anterior pituitary hormones on the gastrointestinal tract of humans and animals has been reported. Hypophysectomy (HYPOX) in the rat causes atrophy of the intestinal mucosa, reduction of gastric secretion and intestinal absorption, and increased susceptibility to infections. To our knowledge, there are no studies on the humoral immune response of the gut-associated lymphoid tissue after HYPOX. We have reported that decreased secretion of vasopressin and oxytocin due to neurointermediate pituitary lobectomy (NIL) diminishes humoral and cell-mediated immune responses. However, no data have been published on whether NIL can affect intestinal immune responses. We analyzed the effects of HYPOX and NIL on bacterial colonization of the intestinal lumen, Peyer's patches, and spleen as well as the serum immunoglobulin G (IgG) and IgM and specific intestinal IgA levels in response to Salmonella enterica serovar Typhimurium oral infection. Results showed the following: (i) Salmonella serovar Typhimurium was eliminated from the intestinal lumen at the same rate in rats that underwent a sham operation, HYPOX, and NIL; (ii) Salmonella serovar Typhimurium colonization of Peyer's patches and spleen was significantly higher in both HYPOX and NIL rats than in sham-operated rats; (iii) serum IgG and IgM and intestinal IgA against surface proteins of Salmonella serovar Typhimurium were significantly lower in HYPOX and NIL rats than in sham-operated rats; and (iv) compared to NIL rats, higher Peyer's patch and spleen bacterial colonization and decreased IgG, IgM, and IgA production were observed in HYPOX rats. We conclude that hormones from each pituitary lobe affect the systemic and gastrointestinal humoral immune responses through different mechanisms.

Stress in Autoimmune Disease Models

The release of endogenous glucocorticoids is critical in regulating the severity of disease activity in patients with inflammatory conditions such as rheumatoid arthritis (RA). Blocking cortisol production results in a flare-up in disease activity in RA patients, and surgical removal of the adrenals in patients with Cushing's disease has been reported to exacerbate autoimmune disease. In adjuvant-induced arthritis (AA; a rat model of RA), there is an activation of the hypothalamo-pituitary-adrenal (HPA) axis associated with the development of inflammation. In addition, there are profound changes in peptides within the paraventricular nucleus, which are responsible for regulating the HPA axis. These changes have profound implications on the ability of AA rats to respond to acute stress. Understanding the regulation of the HPA axis in health and disease holds out the promise of targeted therapy to alleviate inflammatory conditions. This article will consider the impact of stress on an individual and his or her susceptibility to inflammation. We wish to question the idea that stress is "all bad." As we shall see, exposure to a single acute stressor can alter the phenotype of the rat to change it from being susceptible to resistant in autoimmune disease models. This alteration in susceptibility takes days to manifest itself, but can last for weeks, suggesting beneficial effects of exposure to an acute stressor.

The safety and efficacy of the use of vasopressin in sepsis and septic shock

Sepsis remains a significant problem and cause of morbidity and mortality in intensive care. Vasopressin infusions are currently used as rescue therapy for the treatment of vasodilatory, catecholamine-resistant septic shock. At present, there are no large randomised, controlled trials in the literature investigating vasopressin in this role, although two such studies are currently ongoing in Canada. This review outlines the pathophysiology of sepsis and that of vasopressin in sepsis and reviews the available evidence for the use of vasopressin in sepsis and septic shock. A review of the safety data for vasopressin in this indication is included. Recommendations for the use of vasopressin in septic shock, along with suggestions for the direction of further work in the field are presented.

Glucocorticoids down-regulate lipopolysaccharide-induced de novo production of neurotensin mRNA in the rat hypothalamic, paraventricular, corticotrophin-releasing hormone neurons

OBJECTIVE

Intraperitoneal injection of the endotoxin lipopolysaccharide (LPS) produces inflammation accompanied by activation of the immune system and the secretion of cytokines. Cytokines stimulate the hypothalamo-pituitary-adrenal (HPA) axis to release the anti-inflammatory corticosterone which controls its own production by acting on the HPA axis. Upstream in the HPA axis are neuroendocrine corticotrophin-releasing hormone (CRH) neurons located in the paraventricular nucleus (PVN), whose multipeptidergic phenotype changes during inflammation: while CRH mRNA is up-regulated in these conditions, neurotensin (NT) mRNA expression is induced de novo. The negative feedback control of glucocorticoids on CRH production is well documented; however, their action on NT production in the PVN of the hypothalamus is poorly documented. The aim of this study was to determine if glucocorticoids modulate the de novo production of NT during inflammation.

METHODS

Using quantitative in situ hybridization histochemistry, we examined whether the absence (adrenalectomy) or excess (corticosterone implants) of glucocorticoids modulate de novo production of NT mRNA in the PVN during inflammation induced by LPS treatment.

RESULTS

A relatively low dose of LPS (50 microg/kg) that is not efficient to induce NT mRNA production in the PVN becomes efficient after adrenalectomy. Moreover, corticosterone excess reduces LPS-induced production of NT mRNA in the PVN.

CONCLUSION

Glucocorticoids exert a negative control on NT mRNA production in the PVN of the hypothalamus, and this effect requires that NT mRNA production be triggered, such as during inflammation.

Low plasma vasopressin/norepinephrine ratio predicts septic shock

To evaluate if low plasma vasopressin and high norepinephrine concentrations predict grave prognosis of sepsis, a prospective sample of consecutive patients visiting the emergency department of a university teaching hospital who met the American College of Chest Physicians criteria of sepsis or severe sepsis was enrolled. Besides septic workup, we measured serum vasopressin and norepinephrine concentrations to correlate the impending outcome. One hundred eighty-two patients aged 27 to 99 years met the inclusive criteria and were classified as those with septic shock (n = 72), severe sepsis (n = 56), and those with sepsis only (n = 54) according to the outcome within 6 hours. Thirty healthy subjects were included as control. The plasma vasopressin level at baseline was significantly lower for those who finally developed septic shock (septic shock group, 3.6 +/- 2.5 pg/mL; 95% confidence interval [CI], 3.0-4.2 pg/mL; severe sepsis group, 21.8 +/- 4.1 pg/mL, 95% CI, 20.7-22.9 pg/mL; sepsis group, 10.6 +/- 6.5 pg/mL, 95% CI, 8.8-12.4 pg/mL, P < .001), whereas the norepinephrine level was highest for the same group (septic shock group, 3650 +/- 980 pg/mL, 95% CI, 3420-3880 pg/mL; severe sepsis group, 3600 +/- 1000 pg/mL, 95% CI, 3330-3870 pg/mL; sepsis group, 1720 +/- 320 pg/mL, 95% CI, 1630-1810 pg/mL). The vasopressin/norepinephrine ratio was significantly lower for the patients with final diagnosis of septic shock (P < .001). The mean interval between the time of samples drawn and the time of the most severe occurring sequelae was 2.4 +/- 0.8 hours. Receiver operating characteristic analysis revealed that the vasopressin/norepinephrine ratio 1 x 10(-3) had a sensitivity of 97% (95% CI, 90%-99%) and a specificity of 85% (95% CI, 78%-91%) for detecting impending septic shock. Low serum vasopressin/norepinephrine ratio can predict impending septic shock.

Effect of inflammation on lacrimal gland function

The lacrimal gland is the main contributor to the aqueous layer of the tear film. It secretes proteins, electrolytes and water, which helps to nourish and protect the ocular surface. Lacrimal gland secretion is primarily under neural control, which is achieved through a neural reflex arc. Stimuli to the ocular surface activate afferent sensory nerves in the cornea and conjunctiva. This in turn activates efferent parasympathetic and sympathetic nerves in the lacrimal gland to stimulate secretion. Sex steroid hormones are also important regulators of lacrimal gland functions. A decrease or lack of lacrimal gland secretion is the leading cause of aqueous tear deficient dry eye syndrome (DES). It has been suggested that DES is an inflammatory disorder that affects the ocular surface and the lacrimal gland. In several pathological instances, the lacrimal gland can become a target of the immune system and show signs of inflammation. This can result from autoimmune diseases (Sjögren's syndrome), organ transplantation (graft versus host disease), or simply as a result of aging. The hallmarks of lacrimal gland inflammation are the presence of focal lymphocytic infiltrates and increased production of proinflammatory cytokines. The mechanisms leading to lacrimal gland dysfunction are still poorly understood. Apoptosis, production of autoantibodies, hormonal imbalance, alterations in signaling molecules, neural dysfunction, and increased levels of proinflammatory cytokines have been proposed as possible mediators of lacrimal gland insufficiency in disease states.

The Neuroendocrine–Immune Interactions in Systemic Lupus Erythematosus: A Basis for Understanding Disease Pathogenesis and Complexity

Much progress has been made in the understanding of the impact of the neuroendocrine immune interactions and the pathogenic role in systemic lupus erythematosus, clinically and at the molecular level. This article focuses on the intertwining networks that involve the hypothalamic-pituitary-adrenal axis, cytokines within the central nervous system, and the sympathetic system. Hormones (estrogen, prolactin, gonadotropin-releasing hormone, and leptin) play an important role as immunomodulatory agents.

Hypothalamic-pituitary-adrenal axis function in ankylosing spondylitis

OBJECTIVE

To assess basal function and responsiveness of the hypothalamic-pituitary-adrenal (HPA) axis in patients with ankylosing spondylitis during dynamic testing.

METHODS

Insulin induced hypoglycaemia (IIH) (Actrapid HM 0.1 IU/kg, as intravenous bolus) was induced in 17 patients and 11 healthy controls matched for age, sex, and body mass index. Concentrations of glucose, adrenocorticotrophic hormone (ACTH), cortisol, insulin, dehydroepiandrosterone sulphate (DHEAS), 17alpha-hydroxyprogesterone, interleukin 6 (IL-6), and tumour necrosis factor alpha (TNFalpha) were determined in plasma.

RESULTS

Comparable basal cortisol levels were found in the two groups, with a trend to be lower in ankylosing spondylitis. In the ankylosing spondylitis group, there were higher concentrations of IL-6 (mean (SEM): 16.6 (2.8) pg/ml v 1.41 (0.66) pg/ml in controls; p<0.001) and TNFalpha (8.5 (1.74) pg/ml v 4.08 (0.42) pg/ml in controls; p<0.01). Glucose, insulin, ACTH, DHEAS, and 17alpha-hydroxyprogesterone did not differ significantly from control. The IIH test was carried out successfully in 11 of the 17 patients with ankylosing spondylitis, and the ACTH and cortisol responses were comparable with control. General linear modelling showed a different course of glycaemia (p = 0.041) in the ankylosing spondylitis patients who met the criteria for a successful IIH test compared with the controls.

CONCLUSIONS

The results suggest there is no difference in basal HPA axis activity and completely preserved responsiveness of the HPA axis in patients with ankylosing spondylitis. The interpretation of the different course of glycaemia during IIH in ankylosing spondylitis requires further investigation.

Hypothalamo-pituitary-adrenal axis dysfunction as a contributory factor to chronic pain and depression

Chronic pain and depressive illness are variably resistant to treatment with current pharmacologic therapies. Pain as a reflex sensory response is accompanied by a fast autonomic and delayed neuroendocrine response mediated by the sympathoadrenal and hypothalamo-pituitary-adrenal (HPA) axis, respectively. The emotional aspect of the pain response is encoded by corticolimbic systems (including the HPA axis) to encapsulate the relationship between pain, memory, and mood. These same systems contribute to the symptomatology of depression, a common symptom of which is pain. Conversely, many chronic pain patients may suffer from depressive illness, which appears to develop as a consequence of chronic pain. A comparison of key changes in HPA function after chronic stress in animals with clinical depression in humans, reveals some striking similarities. In this article, the role of the HPA axis in the etiology of chronic pain and depression is discussed.

Leukemia inhibitory factor stimulates vasopressin release in rats

Leukemia inhibitory factor (LIF) is a cytokine of the interleukin-6 family exhibiting diverse physiological functions during inflammatory stress. It is well known that syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is often associated with inflammatory disease, and cytokines produced at inflammatory foci are thought to stimulate arginine vasopressin (AVP) release. In the present study, we investigated the effects of centrally administered LIF on AVP release in conscious rats. Intracerebroventricular administration of LIF (0.01-1.0 microg/rat) significantly increased the plasma AVP concentration, and its effect was observed from 5 to 60 min after the injection. LIF did not cause significant changes in plasma Na+, total protein and blood pressure. There were no significant changes in the plasma AVP concentration after intravenous injection of LIF (1.0, 3.0 microg/rat). These results indicate that LIF plays a stimulatory role in the regulation of AVP release, and suggest the possibility that LIF may be involved in the pathogenesis of SIADH.

Hypothalamic-pituitary cytokine network

Cytokines expressed in the brain and involved in regulating the hypothalamus-pituitary-adrenal (HPA) axis contribute to the neuroendocrine interface. Leukemia inhibitory factor (LIF) and LIF receptors are expressed in human pituitary cells and murine hypothalamus and pituitary. LIF potently induces pituitary proopiomelanocortin (POMC) gene transcription and ACTH secretion and potentiates CRH induction of POMC. In vivo, LIF, along with CRH, enhances POMC expression and ACTH secretion in response to emotional and inflammatory stress. To further elucidate specific roles for both CRH and LIF in activating the inflammatory HPA response, double-knockout mice (CRH/LIFKO) were generated by breeding the null mutants for each respective single gene. Inflammation produced by ip injection of lipopolysaccharide (1 microg/mouse) to double CRH and LIF-deficient mice elicited pituitary POMC induction similar to wild type and markedly higher than in single null animals (P<0.0.01). Double-knockout mice also demonstrated robust corticosterone response to inflammation. High pituitary POMC mRNA levels may reflect abundant TNFalpha, IL-1beta, and IL-6 activation observed in the hypothalamus and pituitary of these animals. Our results suggest that increased central proinflammatory cytokine expression can compensate for the impaired HPA axis function and activates inflammatory ACTH and corticosterone responses in mice-deficient in both CRH and LIF.

Hypothalamo-pituitary-adrenal axis and chronic immune activation

Corticosteroids have potent immunosuppressive and anti-inflammatory effects. Although corticosteroids are an important weapon in the clinical arsenal for treating inflammatory episodes, the mechanisms underlying the actions and regulation of endogenous corticosteroids remain obscure. In the late 1980s and early 1990s, a hypothesis was proposed that suggested that susceptibility to autoimmune disease was linked to a hypoactive hypothalamo-pituitary-adrenal (HPA) axis. It was further suggested that this defect in regulation of the HPA axis was situated at the level of the hypothalamus. This compelling hypothesis directly linked control of the HPA axis with susceptibility to disease rather than just severity of inflammation. The initial findings acted as a stimulus to further research, and over the next decade the hypothesis was tested. Recent studies suggest that the original hypothesis is in need of modification and that susceptibility is more complex and requires the involvement of more than a single parameter. These data are discussed together with recent developments concerning regulation of the HPA in disease in preclinical models and patients with rheumatoid arthritis. The latter studies in patients with rheumatoid arthritis provide evidence for the existence of a subpopulation of these patients with altered negative feedback regulation of the HPA axis.

Management of vasodilatory shock: defining the role of arginine vasopressin

The rationale for an arginine vasopressin (argipressin) infusion was put forward after it was discovered that patients in shock states might have an endogenous arginine vasopressin deficiency. Subsequently, several investigations impressively demonstrated that arginine vasopressin can successfully stabilise haemodynamics even in advanced vasodilatory shock. We report on physiological and pharmacological aspects of arginine vasopressin, and summarise current clinical knowledge on employing a continuous arginine vasopressin infusion in critically ill patients with catecholamine-resistant vasodilatory shock of different aetiologies. In view of presented experimental evidence and current clinical experience, a continuous arginine vasopressin infusion of approximately 2 to approximately 6 IU/h can be considered as a supplemental strategy to vasopressor catecholamines in order to preserve cardiocirculatory homeostasis in patients with advanced vasodilatory shock. Because data on adverse effects are still limited, arginine vasopressin should be reserved for patients in whom adequate haemodynamic stabilisation cannot be achieved with conventional vasopressor therapy or who have obvious adverse effects of catecholamines that result in further significant haemodynamic deterioration. For the same reasons, arginine vasopressin should not be used as a single, alternative vasopressor agent instead of catecholamine vasopressors. Future prospective studies will be necessary to define the exact role of arginine vasopressin in the therapy of vasodilatory shock.

Neuroendocrinology of autoimmunity

The HPA axis is fundamental for long-term survival and protection from the ravages of autoimmune disease. Continuing investigations suggest that the hypothesis linking susceptibility to autoimmune disease and a hyporesponsive HPA axis is somewhat simplistic. Instead, data from a number of different human diseases and from preclinical studies in a variety of models have suggested a more complicated picture. Alterations in the diurnal rhythms of ACTH, cortisol, and immune parameters appear to be linked to severity of disease. The use of low doses of steroids timed to target disrupted diurnal immune system changes in patients with RA may reduce the unfortunate side effects of long-term steroid use. Studies in cancer patients have related alterations in diurnal cortisol to survival. Whether differences in individual cortisol profiles are predictive of a deterioration in symptoms of autoimmune disease remains to be established. Responsiveness of the HPA axis to subtle challenges such as the dexamethasone suppression test and the related dexamethasone-CRF test suggest that there are different sub-populations of patients with RA and MS and these may have confounded earlier, apparently contradictory, studies. These different responses may be related to the severity of the disease. That these HPA axis differences can be altered beneficially through the use of antidepressants, as has been shown in MS, may impact on future health care strategies. However, reports of negative developments in arthritis associated with SSRI use suggest that the SSRIs may be unsuitable under some circumstances. The link of behavioral differences to alterations in neurotransmitter changes associated with disease is intriguing and opens new avenues of research. These future studies will require input from neuroscientists, neuroendocrinologists, psychologists, and immunologists working with the clinical specialties already involved in treating patients with autoimmune disease. These multidisciplinary studies reflecting the increased importance of hormonal and neurotransmitter involvement with the immune system hold great promise for the future.

Central mineralocorticoid receptor blockade decreases plasma TNF-alpha after coronary artery ligation in rats

The Randomized Aldactone Evaluation Study (RALES) demonstrated a substantial clinical benefit to blocking the effects of aldosterone (Aldo) in patients with heart failure. We recently demonstrated that the enhanced renal conservation of sodium and water in rats with heart failure can be reduced by blocking the central nervous system effects of Aldo with the mineralocorticoid receptor (MR) antagonist spironolactone (SL). Preliminary data from our laboratory suggested that central MR might contribute to another peripheral mechanism in heart failure, the release of proinflammatory cytokines. In the present study, SL (100 ng/h for 21 days) or ethanol vehicle (Veh) was administered via the 3(rd) cerebral ventricle to one group of rats after coronary ligation (CL) or sham CL (Sham) to induce congestive heart failure (CHF). In Veh-treated CHF rats, tumor necrosis factor-alpha (TNF-alpha) levels increased during day 1 and continued to increase throughout the 3-wk observation period. In CHF rats treated with SL, started 24 h after CL, TNF-alpha levels rose initially but retuned to control levels by day 5 after CL and remained low throughout the study. These findings suggest that activation of MR in the central nervous system plays a critical role in regulating TNF-alpha release in heart failure rats. Thus some of the beneficial effect of blocking MR in heart failure could be due at least in part to a reduction in TNF-alpha production.

Heart failure and the brain: new perspectives

Despite recent therapeutic advances, the prognosis for patients with heart failure remains dismal. Unchecked neurohumoral excitation is a critical element in the progressive clinical deterioration associated with the heart failure syndrome, and its peripheral manifestations have become the principal targets for intervention. The link between peripheral systems activated in heart failure and the central nervous system as a source of neurohumoral drive has therefore come under close scrutiny. In this context, the forebrain and particularly the paraventricular nucleus of the hypothalamus have emerged as sites that sense humoral signals generated peripherally in response to the stresses of heart failure and contribute to the altered volume regulation and augmented sympathetic drive that characterize the heart failure syndrome. This brief review summarizes recent studies from our laboratory supporting the concept that the forebrain plays a critical role in the pathogenesis of ischemia-induced heart failure and suggesting that the forebrain contribution must be considered in designing therapeutic strategies. Forebrain signaling by neuroactive products of the renin-angiotensin system and the immune system are emphasized.