The rapid release of corticosterone from the adrenal induced by ACTH is mediated by nitric oxide acting by prostaglandin E2

Improving survival rates in two models of spontaneous postoperative metastasis in mice by combined administration of a beta-adrenergic antagonist and a cyclooxygenase-2 inhibitor

Clinical practice does not consider perioperative paracrine and neuroendocrine stress responses as risk factors for cancer recurrence, although recent animal studies provided supportive evidence. Suggested mechanisms include the effects of stress-hormones on tumor cells and on host physiology. In this study, in mice undergoing primary tumor excision, we tested the survival-enhancing potential of perioperative blockade of catecholamines and prostaglandins, and studied potential mediating mechanisms. C57BL/6J mice were inoculated intrafootpad with syngeneic B16F10.9-melanoma or Lewis lung carcinoma, and the paw was amputated when a developing tumor exceeded 100 microl. The clinically used beta-adrenergic antagonist propranolol, and/or the cyclooxygenase-2 inhibitor etodolac, were administered once before amputation, and recurrence-free survival was monitored. In different studies, NK cytotoxicity, leukocytes' molecular functional markers, and vascular endothelial growth factor secretion by tumor cells were studied in the context of surgery and drug treatments. The findings indicated that the combination of propranolol and etodolac, but neither drug alone, significantly and markedly improved survival rates in both tumor models, and was as effective as established immunostimulatory agents (IL-12 and polyinosinic-polycytiylic acid). Surgery markedly reduced NK cytotoxicity and NK cell expression of Fas ligand and CD11a, reduced all circulating lymphocyte-subtype concentrations, and increased corticosterone levels. Propranolol and etodolac administration counteracted these perturbations. B16 and 3LL secreted vascular endothelial growth factor in vitro, but secretion was not affected by catecholamine agonists, prostaglandins, corticosterone, propranolol, or etodolac. Overall, propranolol and etodolac administration, which could be applied perioperatively in most cancer patients with minimal risk and low cost, has counteracted several immunologic and endocrinologic perturbations and improved recurrence-free survival rates in mice undergoing primary tumor excision.

Oleoyl-estrone increases adrenal corticosteroid synthesis gene expression in overweight male rats

Oleoyl-estrone (OE) induces a marked loss of body fat in rats by maintaining energy expenditure, body protein and blood glucose despite decreasing food intake. OE increases glucocorticoids, but they arrest OE lipid-mobilization. We studied here whether OE induces a direct effect on adrenal glands function as part of this feedback regulation. Dietary overweight male rats were given oral 10nmol/g OE gavages for ten days. A group (PF) of pair-fed to OE rats, and controls received vehicle-only gavages. OE rats lost slightly more body than PF, but had larger adrenal glands. Tissue corticosterone levels, and gene expressions for glucocorticoid-synthesizing enzymes were increased in OE versus controls and PF; thus, we assumed that adrenal growth affected essentially its cortex since OE also lowered the expression of the medullar catecholamine synthesis enzyme genes. Serum corticosterone was higher in PF than in OE and controls, but liver expression of corticosteroid-disposing steroid 5alpha-reductase was 3x larger in OE than PF and controls. Circulating glucocorticoids changed little under OE, in spite of higher adrenal gland and liver content, hinting at modulation of glucocorticoid turnover as instrumental in their purported increased activity. In conclusion, we have observed that OE considerable enhanced the expression of the genes controlling the synthesis of glucocorticoids from cholesterol in the rat and increasing the adrenal glands' corticosterone, size and cellularity, but also the liver disposal of corticosteroids, suggesting that OE increases corticosterone synthesis and degradation (i.e. serum turnover), a process not driven by limited energy availability but directly related to the administration of OE.

Acute and chronic estradiol replacements differentially alter corticosterone and COX-mediated responses to an inflammatory stimulus in female rats

INTRODUCTION

This study aimed to determine whether the previously reported differential effects of estradiol on inflammation-induced behavioral responses are in part explained through differential activation of the corticosterone-cyclooxygenase (CORT-COX) regulatory pathway.

METHODS

Prostaglandin E2 (PGE2), COX, and CORT levels were analyzed before and after a formalin administration (1% vs. 5%, representing different intensities of inflammatory stimuli).

RESULTS

In vehicle-treated rats, chronic estradiol administration increased corticosterone, and decreased COX and PGE2. After acute estradiol administration, although corticosterone serum levels were increased, COX protein levels were unchanged. In rats treated with formalin, PGE2 serum levels were higher in rats administered 5% formalin than vehicle- and 1%-treated rats. Significant correlations were observed between PGE2 serum levels, CORT serum levels, and COX protein levels.

CONCLUSIONS

Our results suggest that the administration of exogenous estradiol may mediate inflammatory responses by regulating the levels of PGE2 and/or CORT release, thereby mediating the nociceptive response to an inflammatory stimulus.

Aldo keto reductase 1B7 and prostaglandin F2alpha are regulators of adrenal endocrine functions

Prostaglandin F_2α (PGF_2α), represses ovarian steroidogenesis and initiates parturition in mammals but its impact on adrenal gland is unknown. Prostaglandins biosynthesis depends on the sequential action of upstream cyclooxygenases (COX) and terminal synthases but no PGF_2α synthases (PGFS) were functionally identified in mammalian cells. In vitro, the most efficient mammalian PGFS belong to aldo-keto reductase 1B (AKR1B) family. The adrenal gland is a major site of AKR1B expression in both human (AKR1B1) and mouse (AKR1B3, AKR1B7). Thus, we examined the PGF_2α biosynthetic pathway and its functional impact on both cortical and medullary zones. Both compartments produced PGF_2α but expressed different biosynthetic isozymes. In chromaffin cells, PGF_2α secretion appeared constitutive and correlated to continuous expression of COX1 and AKR1B3. In steroidogenic cells, PGF_2α secretion was stimulated by adrenocorticotropic hormone (ACTH) and correlated to ACTH-responsiveness of both COX2 and AKR1B7/B1. The pivotal role of AKR1B7 in ACTH-induced PGF_2α release and functional coupling with COX2 was demonstrated using over- and down-expression in cell lines. PGF_2α receptor was only detected in chromaffin cells, making medulla the primary target of PGF_2α action. By comparing PGF_2α-responsiveness of isolated cells and whole adrenal cultures, we demonstrated that PGF_2α repressed glucocorticoid secretion by an indirect mechanism involving a decrease in catecholamine release which in turn decreased adrenal steroidogenesis. PGF_2α may be regarded as a negative autocrine/paracrine regulator within a novel intra-adrenal feedback loop. The coordinated cell-specific regulation of COX2 and AKR1B7 ensures the generation of this stress-induced corticostatic signal.

Normal responses to restraint stress in mice lacking the gene for neuronal nitric oxide synthase

The hormonal changes associated with immobilization stress (IMO) include a swift increase in corticosterone (CORT) concentration and a decrease in circulating testosterone (T) levels. There is evidence that the production of the short-lived neuromodulator nitric oxide (NO) is increased during stress in various tissues, including the brain. NO also suppresses the biosynthesis of T. Both the inducible and the neuronal isoforms of NO synthase (iNOS and nNOS, respectively) have been implicated in this suppression, but the evidence has not been conclusive. We used adult wild-type (WT) and nNOS knockout male mice (nNOS-/-) to assess the respective roles of CORT and nNOS-derived NO in stress mediated inhibition of T production. Animals were assigned to either basal control or 3-hour IMO groups. No difference in basal plasma and testicular T levels were observed between WT and nNOS-/-, although testicular weights of mutant mice were slightly lower compared to WT animals. The plasma contents of luteinizing hormone (LH) and CORT in unstressed mice of both genotypes were similar. Exposure to 3 hours of IMO increased plasma CORT and decreased T concentrations in mice of both genotypes. However, comparable levels of plasma LH and testicular nitrite and nitrate (NOx), NO stable metabolites, were detected in control and stressed WT and nNOS-/- mice. Adrenal concentrations of NOx declined after IMO, but the reduction was not statistically significant. These findings implicate CORT rather than NO generated by nNOS in the rapid stress-induced suppression of circulating T.

Systemic immune challenge activates an intrinsically regulated local inflammatory circuit in the adrenal gland

There is evidence from in vitro studies that inflammatory messengers influence the release of stress hormone via direct effects on the adrenal gland; however, the mechanisms underlying these effects in the intact organism are unknown. Here we demonstrate that systemic inflammation in rats elicited by iv injection of lipopolysaccharide results in dynamic changes in the adrenal immune cell population, implying a rapid depletion of dendritic cells in the inner cortical layer and the recruitment of immature cells to the outer layers. These changes are accompanied by an induced production of IL-1beta and IL-1 receptor type 1 as well as cyclooxygenase-2 and microsomal prostaglandin E synthase-1 in these cells, implying local cytokine-mediated prostaglandin E(2) production in the adrenals, which also displayed prostaglandin E(2) receptors of subtypes 1 and 3 in the cortex and medulla. The IL-1beta expression was also induced by systemically administrated IL-1beta and was in both cases attenuated by IL-1 receptor antagonist, consistent with an autocrine signaling loop. IL-1beta similarly induced expression of cyclooxygenase-2, but the cyclooxygenase-2 expression was, in contrast, further enhanced by IL-1 receptor antagonist. These data demonstrate a mechanism by which systemic inflammatory agents activate an intrinsically regulated local signaling circuit that may influence the adrenals' response to immune stress and may help explain the dissociation between plasma levels of ACTH and corticosteroids during chronic immune perturbations.

Plasma aldosterone response to the low-dose adrenocorticotrophin (ACTH 1-24) stimulation test

BACKGROUND

Endocrine tests for adrenal insufficiency use pharmacological doses of stimulant such as ACTH. More physiological tests have often used high-dose protocols for sampling frequency.

AIMS

To evaluate the response of plasma aldosterone concentration to low doses (125, 250 and 500 ng/m(2) body surface area) of synthetic ACTH.

DESIGN

A randomised trial in six normal adult males aged 18-27 years.

MATERIALS AND METHODS

Aldosterone concentration was measured by radioimmunoassay in serum from blood samples taken at 10 min intervals for 90 min.

RESULTS

All three doses produced a significant rise in plasma aldosterone concentration (125 ng/m(2), P = 0.003; 250 ng/m(2), P < 0.001; 500 ng/m(2), P < 0.001) but there was no effect of dose on either the peak or incremental plasma aldosterone concentration. Mean time to peak was similar between the doses and the two higher doses were associated with a longer secretory profile (125 ng/m(2) 56 (26 SD) mins, 250 ng/m(2) 74 (19) mins, 500 ng/m(2) 77 (21) mins; F = 3.39; P = 0.04). Peaks of 100% were detected within 30 min of drug administration and peak response was associated with the prestimulation plasma aldosterone concentration (r = 0.45; P = 0.003). The between- and within-individual coefficients of variation for prestimulation concentrations were 37.0% and 32.8%, and for the peak response were 27.2% and 27.2%, respectively.

CONCLUSIONS

The response of plasma aldosterone concentrations to low-dose ACTH administration requires a blood sampling protocol of 0, 10, 20 and 30 min to capture concentrations near the peak response. The high-dose protocol would have missed the response. Over the dose range studied no dose-response was observed so the selection of dose should be based on the dose effective to release steroids in the glucocorticoid pathway if this study is to be used in conjunction with such evaluation.

HYPOTHERMIA DURING ENDOTOXEMIC SHOCK IN FEMALE MICE LACKING INDUCIBLE NITRIC OXIDE SYNTHASE

The present study was undertaken to evaluate: (1) whether lipopolysaccharide LPS-induced hypothermic responses may be altered during two estrous cycle phases, proestrus and diestrus, and after ovariectomy, followed by hormonal supplementation and (2) whether nitric oxide (NO) plays a role on LPS-induced hypothermia responses in female mice. Experiments were performed on adult female wild-type (WT) C57BL and inducible NO synthase knockout (KO) mice weighing 18 to 30 g. Endotoxemia was induced by intraperitoneal LPS administration from Escherichia coli at a nonlethal dose of 10 mg/kg, and body temperature was measured by biotelemetry. Hormonal replacement was performed in ovariectomized mice through 17beta-estradiol Silastic capsules (100 mug) and s.c. injection of progesterone (0.5 mg per animal). We observed that during the diestrus phase, mice presented more intensive hypothermia than during proestrus phase, and hormonal supplementation with 17beta-estradiol and progesterone attenuated hypothermia in ovariectomized mice. During diestrus and ovariectomy, KO mice had higher hypothermic response when compared with the WT group. During proestrus, the lack of statistical difference between KO and WT mice could be consequent of lower ovarian hormones plasma levels. After hormonal replacement, hypothermia was reverted in KO groups probably because of higher ovarian hormonal levels. In summary, the results demonstrated that NO release by inducible NO synthase has an important thermoregulatory role in LPS-induced hypothermia in female mice. Besides, this involvement is directly dependent on the presence of ovarian hormones and their respective levels.

Human adrenal glands secrete vitamin C in response to adrenocorticotrophic hormone

BACKGROUND

When vitamin C intake is from foods, fasting plasma concentrations do not exceed 80 micromol/L. We postulated that such tight control permits a paracrine function of vitamin C.

OBJECTIVE

The purpose of this study was to determine whether paracrine secretion of vitamin C from the adrenal glands occurs.

DESIGN

During diagnostic evaluation of 26 patients with hyperaldosteronism, we administered adrenocorticotrophic hormone intravenously and measured vitamin C and cortisol in adrenal and peripheral veins.

RESULTS

Adrenal vein vitamin C concentrations increased in all cases and reached a peak of 176 +/- 71 micromol/L at 1-4 min, whereas the corresponding peripheral vein vitamin C concentrations were 35 +/- 15 micromol/L (P<0.0001). Mean adrenal vein vitamin C increased from 39 +/- 15 micromol/L at 0 min, rose to 162 +/- 101 micromol/L at 2 min, and returned to 55 +/- 16 micromol/L at 15 min. Adrenal vein vitamin C release preceded the release of adrenal vein cortisol, which increased from 1923 +/- 2806 nmol/L at 0 min to 27 191 +/- 16 161 nmol/L at 15 min (P<0.0001). Peripheral plasma cortisol increased from 250 +/- 119 nmol/L at 0 min to 506 +/- 189 nmol/L at 15 min (P<0.0001).

CONCLUSIONS

Adrenocorticotrophic hormone stimulation increases adrenal vein but not peripheral vein vitamin C concentrations. These data are the first in humans showing that hormone-regulated vitamin secretion occurs and that adrenal vitamin C paracrine secretion is part of the stress response. Tight control of peripheral vitamin C concentration is permissive of higher local concentrations that may have paracrine functions.

Polyunsaturated fatty acids in male and female reproduction

In Westernized societies, average consumption of n-6 polyunsaturated fatty acids (PUFAs) far exceeds nutritional requirements. The ratio of n-6 to n-3 PUFAs is generally >10:1 whereas on a primitive human diet it was closer to 1:1. Diets fed to intensively farmed livestock have followed a similar trend. Both n-6 and n-3 PUFAs can influence reproductive processes through a variety of mechanisms. They provide the precursors for prostaglandin synthesis and can modulate the expression patterns of many key enzymes involved in both prostaglandin and steroid metabolism. They are essential components of all cell membranes. The proportions of different PUFAs in tissues of the reproductive tract reflect dietary consumption. PUFA supplements (particularly n-3 PUFAs in fish oil) are promoted for general health reasons. Fish oils may also benefit fertility in cattle and reduce the risk of preterm labor in women, but in both cases current evidence to support this is inconclusive. Gamma-linolenic acid containing oils can alter the types of prostaglandins produced by cells in vitro, but published data to support claims relating to effects on reproductive health are lacking. Spermatozoa require a high PUFA content to provide the plasma membrane with the fluidity essential at fertilization. However, this makes spermatozoa particularly vulnerable to attack by reactive oxygen species, and lifestyle factors promoting oxidative stress have clear associations with reduced fertility. Adequately powered trials that control for the ratios of different PUFAs consumed are required to determine the extent to which this aspect of our diets does influence our fertility.

Endothelial cell-mediated regulation of aldosterone release from human adrenocortical cells

Endothelial cells play an important role in the development and functioning of endocrine tissue and endothelial cell-derived factors have been shown to regulate mineralocorticoid release in bovine adrenal cells. In the present study, we analysed the role of human endothelial cells in the synthesis and release of aldosterone from adrenocortical cells (NCI-H295R). Endothelial cell-induced aldosterone release was rapid and lasted as a long-term effect over a period of 48 h. This stimulant effect was influenced by the duration of endothelial cell conditioning and decreased linearly with increasing dilutions of the conditioned medium. At the molecular level, an increase in the mRNA transcripts of aldosterone synthase and StAR could be observed. Cellular interaction with endothelial cell-factors enhanced the activation of CRE, and the promoter activity of both StAR and SF-1 reporter genes. In conclusion, human endothelial cells are important intra-adrenal regulators of human aldosterone synthesis and release.

From Neuroendocrinology to Neuroimmunomodulation - a tribute to Prof. Dr. Samuel McCann

One of the leading experts in the field of Neuroendocrinology and Neuroimmunmodulation, Samuel Mac Donald McCann, known by all his friends as 'Don', passed away in 2007. This article pays tribute to his outstanding scientific contribution and a glimpse on his fascinating personality. A member of the National Academy of Sciences of the United States and pioneer in the field of neuroendocrine regulation, he identified numerous hormones and peptides and set the stage for basic concepts in physiology and clinical medicine.

Nitric oxide impairs baroreflex gain during acute psychological stress

Psychological stress can suppress baroreflex function, but the mechanism has not been fully elucidated. Nitric oxide in the brain and in the adrenal cortex, as well as plasma glucocorticoids, increases during stress and has been shown to suppress reflex gain in unstressed animals. Therefore, the purpose of this study was to test the hypothesis that stress, caused by exposure to a novel environment, decreases baroreflex gain in rabbits through the actions of nitric oxide to increase corticosterone release. Baroreflex control of heart rate and plasma corticosterone levels was quantified before and after blockade of nitric oxide synthase (NOS) with N(omega)-nitro-L-arginine (L-NNA; 20 mg/kg iv) in conscious rabbits exposed to a novel environment and in the same rabbits once they had been conditioned to the environment. Stress significantly reduced baroreflex gain from -23.4 +/- 2 to -12.2 +/- 1.6 beats x min(-1) x mmHg(-1) (P < 0.05) and increased plasma corticosterone levels from 5.4 +/- 0.7 to 15.5 +/- 5.0 ng/ml (P < 0.05). NOS blockade increased gain in stressed animals (to -27.2 +/- 5.4 beats x min(-1) x mmHg(-1), P < 0.05) but did not alter gain in unstressed rabbits (-26.8 +/- 4.9 beats x min(-1) x mmHg(-1)) such that gain was equalized between the two states. NOS blockade increased plasma corticosterone levels in unstressed animals (to 14.3 +/- 2.1 ng/ml, P < 0.05) but failed to significantly alter levels in stressed rabbits (14.0 +/- 3.9 ng/ml). In conclusion, psychological stress may act via nitric oxide, independently of increases in corticosterone, to decrease baroreflex gain.

In vitro effects of crude extracts of Parkia biglobosa (Mimosaceae), Stereospermum kunthianum (Bignoniaceae) and Biophytum petersianum (Oxalidaceae) on corticosteroid secretion in rat

Previous studies conducted in guinea pig, rat and rabbit have revealed that crude extracts from Parkia biglobosa, Stereospermum kunthianum and Biophytum petersianum exert hypotensive and/or hypoglycemic activities. Since corticosteroids are involved in the control of arterial blood pressure and glycemia, we have investigated the possible effects of these plant extracts on rat adrenal tissue in vitro. Short-term administration of crude semi-ethanolic extracts of P. biglobosa and S. kunthianum to perifused rat adrenal tissue did not induce any significant changes in corticosteroid output. Conversely, the B. petersianum extract caused a dose-dependent increase in corticosterone and aldosterone secretion. Repeated infusions or prolonged administration of B. petersianum extract did not produce any apparent attenuation of the steroid response. Altogether, these data indicate that a semi-ethanolic extract of B. petersianum dose-dependently stimulates corticosterone and aldosterone secretion in rat without any desensitization phenomenon.

Protective effect of naproxen (non-selective COX-inhibitor) or rofecoxib (selective COX-2 inhibitor) on immobilization stress-induced behavioral and biochemical alterations in mice

Chronic stress precipitates many neuropsychiatric disorders and alters the various oxidative stress parameters in brain. Cyclooxygenase (COX) is reported to play an important role in pathogenesis of various neurodegenerative disorders including stroke and seizures. In the present study, we examined the effect of naproxen (non-selective COX-inhibitor having much potency towards COX-I isoform) or rofecoxib (a selective COX-2 inhibitor) in subchronic immobilization stress. Mice were subjected to immobilized stress for 6 h daily for a period of seven days. Naproxen (7 mg/kg, i.p.) or rofecoxib (2 mg/kg, i.p.) was administered daily for 7 days before challenging them to immobilization stress. Behavioral analysis revealed the hyperlocomotor activity and increased anxiety response. Subchronic stress decreased percent retention of memory and also caused hyperalgesia in mice. Biochemical analysis revealed that chronic immobilization stress significantly increased lipid peroxidation and nitrite levels and decreased the reduced glutathione and adrenal ascorbic acid levels. Chronic treatment with naproxen or rofecoxib significantly attenuated the immobilization stress-induced behavioral and biochemical alterations. These results suggested that the use of COX-inhibitors (naproxen or rofecoxib) could be a useful neuroprotective strategy in the treatment of stress.