Action Of Adrenocorticotropic Hormone Research Articles

Identification of a novel specific small-molecule melanocortin-2-receptor antagonist.

The overproduction of adrenocorticotropic hormone (ACTH), in conditions such as Cushing's disease and congenital adrenal hyperplasia (CAH), leads to significant morbidity. Current treatment with glucocorticoids does not adequately suppress plasma ACTH, resulting in excess adrenal androgen production. At present, there is no effective medical treatment in clinical use that would directly block the action of ACTH. Such a therapy would be of great clinical value. ACTH acts via a highly selective receptor, the melanocortin-2 receptor (MC2R) associated with its accessory protein MRAP. ACTH is the only known naturally occurring agonist for this receptor. This lack of redundancy and the high degree of ligand specificity suggest that antagonism of this receptor could provide a useful therapeutic strategy in the treatment of conditions of ACTH excess. To this end, we screened an extensive library of low-molecular-weight drug-like compounds for MC2R antagonist activity using a high-throughput homogeneous time-resolved fluorescence cAMP assay in Chinese hamster ovary cells stably co-expressing human MC2R and MRAP. Hits that demonstrated MC2R antagonist properties were counter-screened against the β2 adrenergic receptor and dose-response analysis undertaken. This led to the identification of a highly specific MC2R antagonist capable of antagonising ACTH-induced progesterone release in murine Y-1 adrenal cells and having selectivity for MC2R amongst the human melanocortin receptors. This work provides a foundation for the clinical investigation of small-molecule ACTH antagonists as therapeutic agents and proof of concept for the screening and discovery of such compounds.

Repository Corticotropin Injections Promote Clinical Remission and Regulatory T Cell Expansion in Membranous Nephropathy

Repository Corticotropin Injections Promote Clinical Remission and Regulatory T Cell Expansion in Membranous Nephropathy

Decisive evidence of direct effect of ACTH treatment in West syndrome: A case report

In patients with West syndrome, the administration of exogenous adrenocorticotropic hormone (ACTH) is considered a potent and effective treatment [1]. Exogenously administered ACTH hyperactivates the hypothalamic-pituitary-adrenal axis (Fig. 1A); however, the resulting hormonal changes cannot fully account for the therapeutic effect of ACTH. Indeed, the administration of corticosteroids to patients with West syndrome failed to provide an anti-epileptic effect comparable to that of ACTH [1]. Thus, the antiepileptic effect of ACTH in West syndrome has been postulated to involve a direct action of ACTH on the central nervous system (i.e., a “direct pathway”) that occurs independently of the hypothalamic-pituitary-adrenal axis (i.e., an “indirect pathway”).

Effects of CRN04894, a Nonpeptide Orally Bioavailable ACTH Antagonist, on Corticosterone in Rodent Models of ACTH Excess

CRN04894 is an orally administered nonpeptide that is a potent and selective antagonist for adrenocorticotropic hormone (ACTH) acting at the melanocortin 2 receptor (MC2R) and is currently under development for the treatment of diseases of ACTH excess such as Cushing’s disease, congenital adrenal hyperplasia, and ectopic ACTH-secreting tumors. Cushing’s disease results from an adenoma derived from pituitary corticotropic cells that secrete excess ACTH, whereas ectopic ACTH syndrome arises from nonpituitary ACTH secreting tumors. Congenital adrenal hyperplasia is a genetic disease that results in cortisol deficiency leading to high levels of ACTH and adrenal androgens. Each of these indications is characterized by high ACTH levels that act on MC2R expressed in the adrenal cortex to drive pathological elevations of adrenally derived steroid hormones. CRN04894 blocks the action of ACTH at MC2R, providing a potential novel treatment for these diseases. Preclinical models of chronic hypercortisolemia include implantation of ACTH-secreting pituitary tumor cells in mice and continuous administration of ACTH via subcutaneously implanted osmotic pumps in rats. These models induce features consistent with human diseases of ACTH excess including hypercortisolemia and hypertrophy of the adrenal glands. We employed both rodent models to examine the pharmacodynamic effects of CRN04894 on corticosterone levels and adrenal gland morphology. In the mouse pituitary tumor model, subcutaneous inoculation of the ACTH-secreting mouse pituitary tumor cell line, AtT-20, into immunodeficient mice resulted in formation of tumors and increased plasma ACTH and corticosterone levels. Repeated daily oral administration of CRN04894 for 14 days dose-dependently and robustly suppressed plasma corticosterone levels in mice with AtT-20 tumors. In the rat model, subcutaneous implantation of osmotic pumps delivering ACTH resulted in increased corticosterone levels, reduction in body weight, and hypertrophy of the adrenal glands after 7 days. Daily oral administration of CRN04894 over 7 days dose-dependently suppressed corticosterone levels, mitigated the effect of ACTH excess on body weight, and rescued the adrenal gland hypertrophy. These findings provide evidence that CRN04894 functions as an effective ACTH antagonist at MC2R to suppress adrenal corticosterone secretion in both mouse and rat models of ACTH excess and hypercortisolemia, thus providing a strong rationale for its potential therapeutic utility in diseases of ACTH excess. This work was supported in part by an SBIR grant from the NIH awarded to Dr. Struthers (R43- DK115245)

The role of inflammatory cytokines in anemia and gastrointestinal mucosal injury induced by foot electric stimulation

Foot electrical stimulation (FES) has been considered as a classic stressor that can disturb homeostasis. Acute anemia was observed in the model induced by FES. The aim of this study was to explore the role of inflammatory cytokines underlying the acute anemia and gastrointestinal (GI) mucosal injury in the FES. Twenty-four male Kunming mice (20 ± 2 g) were randomly divided into control group and experimental group. The mice were placed in a footshock chamber that can generate 0.5 mA electrical impulse periodically for 0.5 h. After the process, red blood cell count, hemoglobin concentration and hematocrit, the levels of corticotropin releasing hormone (CRH) in serum and hypothalamus, and adrenocorticotropic hormone (ACTH) in serum and pituitary were detected separately. In addition, we investigated the expressions of inflammatory cytokines (IL-1, IL-6, TNF-α, iNOS, and IL-10) in the hypothalamus and duodenum by Polymerase Chain Reaction (PCR). Results showed that this FES model induced anemia, increased CRH and ACTH activity in the serum after the FES. Moreover, the expressions of IL-1β, IL-6, TNF-α, and iNOS were significantly increased following the process, while IL-10 was not activated. These findings suggest that anemia, the inflammatory cytokines in the hypothalamus and duodenum of the mice in the model induced by FES is closely related to GI mucosal injury/bleeding. Taken together, these results underscore the importance of anemia, GI mucosal injury/bleeding and stress, future studies would be needed to translate these findings into the benefit of affected patients.

OR19-03 Effects of Nonpeptide Orally Bioavailable ACTH Antagonists on Adrenal Gland Size and Function in Rats

Cushing’s disease (CD) and Ectopic ACTH syndrome (EAS) stem from excess circulating adrenocorticotropic hormone (ACTH) and resulting hypercortisolemia. In CD, excess ACTH is secreted from pituitary tumors, whereas excess ACTH in EAS arises from nonpituitary tumors. ACTH acts on the adrenal melanocortin type 2 (MC2) receptor to control the synthesis and secretion of adrenal hormones, including the stress hormone cortisol (corticosterone in rats) which accounts for the comorbidities of CD and EAS. Availability of a potent ACTH antagonist that can normalize cortisol in patients with diseases of excess ACTH will be a major advance in endocrinology. Additionally, an ACTH antagonist will have utility in congenital adrenal hyperplasia (CAH) because of its ability to block production of excess adrenal androgens.Crinetics is evaluating and developing ACTH antagonists for the treatment of diseases of excess ACTH. To our knowledge, these compounds represent the first potent nonpeptide ACTH antagonists to demonstrate in vitro potency and in vivo efficacy. As a result, the direct effects of sustained MC2 receptor blockade on the structure and function of the adrenal gland have never been able to be assessed. We examined the effects of several orally bioavailable ACTH antagonists across a range of doses on Sprague-Dawley rat adrenal gland weight, histology, and hormone levels in repeat dosing (7-14 days) studies. Sustained MC2 receptor antagonism dose dependently blocked activity of ACTH at the level of the adrenal gland and reduced plasma corticosterone levels. In the normal rat, this resulted in dose-dependent atrophy of the adrenal gland as assessed by organ weights and microscopically. The atrophy was primarily observed in the cortisol producing zona fasciculata, as well as in the zona reticularis, with smaller reductions noted in the aldosterone producing zona glomerulosa. Additionally, hypertrophy of the adrenal glands caused by continuous subcutaneous administration of exogenous ACTH was reversed by treatment with an ACTH antagonist. The adrenal effects were accompanied by expected changes in corticosterone levels. These preclinical findings demonstrate the therapeutic potential of ACTH antagonism and provide a strong rationale for development of an orally bioavailable drug that can be used to combat CD, EAS, and CAH.

SAT-364 Nonpeptide Orally-Bioavailable ACTH Antagonists: Suppression of ACTH-Induced Corticosterone Secretion and Adrenal Hypertrophy in Rats

Cushing’s disease is most commonly the result of a microadenoma derived from pituitary corticotrophic cells that secretes excess adrenocorticotropic hormone (ACTH). ACTH is an important modulator of steroidal hormone synthesis and secretion from the adrenal gland and its selective activity at the melanocortin type 2 receptor (MC2) dictates the synthesis and secretion of cortisol (corticosterone in rats). The resulting hypercortisolemia in Cushing’s patients presents in a myriad of symptoms that include growth of fat pads, excessive sweating, dilation of capillaries, thinning of the skin, muscle weakness, hirsutism, depression/anxiety, hypertension, osteoporosis, insulin resistance, hyperglycemia, and heart disease, among others that result in high morbidity. We hypothesize that blocking ACTH action directly via a selective MC2 receptor antagonist may provide an important new therapeutic mechanism to help better manage Cushing’s disease in patients. To test this hypothesis, we launched an iterative medicinal chemistry program to identify potent and selective nonpeptide MC2 receptor antagonists with pharmaceutical and safety characteristics suitable for evaluation in human clinical trials. Unlike most other G protein coupled receptors, MC2 requires the presence of an accessory protein (MRAP) for cell surface expression and recognition of ACTH and our effort led to small molecule nonpeptides with antagonist activity in CHO-K cells stably expressing the MC2-MRAP complex. Iterative optimization led rapidly to the discovery of multiple chemical classes of highly potent, nonpeptide MC2 selective antagonist leads, which were then further optimized for drug-like characteristics. We have identified multiple compounds that exhibit high potency for human and rat MC2 receptors (hMC2 Kb <1 nM), while having little activity at the MC1, MC3, MC4, or MC5 receptors. In rat and dog pharmacokinetic studies, many of these selective MC2 antagonists exhibit good oral bioavailability. In rat models to probe their efficacy, these selective MC2 antagonists acutely suppress corticosterone secretion in an ACTH-challenge model in male Sprague-Dawley rats and the degree of suppression is proportional to their activity at the rat MC2 receptor. In a 7-day hypercortisolemia model in which rats receive an implanted minipump that continually secretes ACTH, corticosterone levels were decreased, and body weight loss and adrenal hypertrophy were prevented. To our knowledge, these compounds represent the first potent nonpeptide MC2 receptor antagonists to demonstrate in vitro potency and in vivo efficacy and we are actively pursuing preclinical safety and toxicology studies to select the optimal molecule(s) suitable for evaluation in human clinical trials.

Hypercorticism during streptozotocin diabetes and mifepristone administration: the role of cyclic adenosine monophosphate

It was studed basal and ACTH-stimulated production of cyclic adenosine monophosphate (cAMP) and corticosteroid hormones (progesterone and corticosterone) in rat adrenals in vitro under streptozotocin diabetes, in conditions of mifepristone administration and their combination. It was shown that in streptozotocin diabetes animals, both the basal and adrenocorticotropic hormone (ACTH) stimulated cAMP production significantly increased; this was accompanied by the increase in basal and ACTH-stimulated progesterone and corticosterone production in rat adrenals in vitro. Repeated administration of mifepristone to control and diabetic rats caused an increase mainly in ACTH-stimulated production of the main glucocorticoid hormone, corticosterone, without additional changes in the cAMP level. The results obtained suggest activation of two mechanisms of steroidogenesis enhancement in experimental animals. In rats with streptozotocin diabetes, both basal and ACTH-stimulated activity of all stages of steroidogenesis increase, which is mediated by the increased formation of cAMP as second messenger mediating the ACTH action on adrenocortical cells. Prolonged administration of mifepristone to control and diabetic rats resulted in increased activity of only late stages of steroidogenesis with predominant elevation of synthesis of physiologically active hormone corticosterone without additional changes in cAMP production level.

The impact of acute PAH exposure on the toadfish glucocorticoid stress response

The objective of the present study was to determine whether the polycyclic aromatic hydrocarbons (PAHs) associated with the Deepwater Horizon (DWH) oil spill impacted the stress response of teleost fish. The hypothesis was that intraperitoneal (IP) treatment with PAHs associated with the DWH oil spill or waterborne exposure to DWH oil high energy water-accommodated fraction (HEWAF) would result in the downregulation of the stress response of Gulf toadfish, Opsanus beta, a benthic marine teleost fish that resides in the Gulf of Mexico. In vivo plasma cortisol levels and adrenocorticotropic hormone (ACTH)-mediated cortisol secretion by in vitro isolated kidney tissue were measured. Toadfish at rest IP-treated with naphthalene had higher plasma cortisol compared to fluorene-treated and control fish; phenanthrene-treated fish tended to have higher plasma cortisol levels that fluorene-treated and controls. When subjected to an additional crowding stress, naphthalene and phenanthrene-treated fish were no longer able to mount a stress response compared to fluorene-treated and control fish, suggesting exhaustion of the stress response. Supporting this in vivo data, there tended to be less cortisol released by the kidney in vitro from naphthalene and phenanthrene-treated fish in response to ACTH compared to controls. In contrast, toadfish at rest exposed to 3% Slick A HEWAF did not have significantly different plasma cortisol levels compared to controls. But, exposed fish did have significantly less cortisol released by the kidney in vitro in response to ACTH. When toadfish were subjected to an additional stress, there were no significant differences in plasma cortisol or ACTH, suggesting the action of a secondary secretagogue to maintain plasma cortisol in vivo. Combined, these data suggest that in response to acute PAH exposure, there may be internalization or downregulation of the melanocortin 2 receptor (MC2R) that mediates the action of ACTH.

Effect of adrenocorticotropic hormone on UCP1 gene expression in brown adipocytes.

Like other tissues, adrenocorticotropic hormone (ACTH) can produce its effect on brown adipose tissue (BAT). This study was taken to understand the direct effect of ACTH action on thermogenin gene expression and possible relation with α receptors and caffeine with this hormone. Brown fat precursor cells were isolated from interscapular BAT of young mice and grown in culture. The cells were exposed to norepinephrine (NE) and other agents. Total RNA was isolated after harvesting the cells, and northern blot analysis was performed. Hybridization was performed with nick translated cDNA probes. Filters were exposed to film, and results were evaluated by scanning. Cyclic adenosine monophosphate (cAMP) was measured by using Amersham assay kit. ACTH stimulates thermogenin gene expression in brown adipocytes. Initiation and maximum stimulations are observed with 0.01 μM and 10 μM (about 45%) of ACTH, respectively, in comparison to 0.1 μM of NE. Maximum response of cAMP is also observed with 10 μM of ACTH (about 64%). Studies with cirazoline and ACTH show that UCP1 mRNA expression is increased significantly with 10 μM of ACTH, whereas cAMP generation is decreased. In the presence of caffeine, ACTH increases cAMP generation and UCP1 gene expression more than twofold. ACTH stimulates thermogenin gene expression in cultured brown adipocytes. The complex interrelationship of ACTH with cirazoline indicates the possibility of relation between the activity of ACTH and α receptors in brown adipocytes. Further stimulation of cAMP generation and thermogenin gene expression is possible with ACTH in conjugation with caffeine and RO 20-1724.

60 YEARS OF POMC: Adrenal and extra-adrenal functions of ACTH.

The pituitary adrenocorticotropic hormone (ACTH) plays a pivotal role in homeostasis and stress response and is thus the major component of the hypothalamo-pituitary-adrenal axis. After a brief summary of ACTH production from proopiomelanocortin (POMC) and on ACTH receptor properties, the first part of the review covers the role of ACTH in steroidogenesis and steroid secretion. We highlight the mechanisms explaining the differential acute vs chronic effects of ACTH on aldosterone and glucocorticoid secretion. The second part summarizes the effects of ACTH on adrenal growth, addressing its role as either a mitogenic or a differentiating factor. We then review the mechanisms involved in steroid secretion, from the classical Cyclic adenosine monophosphate second messenger system to various signaling cascades. We also consider how the interaction between the extracellular matrix and the cytoskeleton may trigger activation of signaling platforms potentially stimulating or repressing the steroidogenic potency of ACTH. Finally, we consider the extra-adrenal actions of ACTH, in particular its role in differentiation in a variety of cell types, in addition to its known lipolytic effects on adipocytes. In each section, we endeavor to correlate basic mechanisms of ACTH function with the pathological consequences of ACTH signaling deficiency and of overproduction of ACTH.

Adrenocorticotropic hormone gel in patients with refractory rheumatoid arthritis: a case series

While many patients with rheumatoid arthritis respond to treatment with disease-modifying antirheumatic drugs, some patients have refractory disease. The mechanism of action of adrenocorticotropic hormone (ACTH) gel and its direct action on melanocortin receptors is thought to result in steroid-independent anti-inflammatory and immunomodulatory effects, in addition to steroidogenic effects. ACTH gel may provide efficacy for patients who previously failed treatment with prednisone or disease-modifying antirheumatic drugs. In this case series, we report five patients with refractory rheumatoid arthritis on ACTH gel who have failed up to five previous treatments. In these patients, ACTH gel provided improvements in inflammatory markers and/or patient-reported symptoms in each case.

Effect of Trilostane on Hormone and Serum Electrolyte Concentrations in Dogs with Pituitary‐Dependent Hyperadrenocorticism

BackgroundThe effects of trilostane on key hormones and electrolytes over 24 hours in dogs with pituitary‐dependent hyperadrenocorticism (PDH) are unknown.ObjectivesTo determine the plasma concentration of cortisol, endogenous adrenocorticotropic hormone (ACTH), aldosterone, sodium, potassium, and ionized calcium concentrations, and plasma renin activity over a 24‐hour period after administration of trilostane to dogs with well‐controlled PDH.AnimalsNine dogs (mean age 9.3 ± 0.67 years, mean weight 31.9 ± 6.4 kg) with confirmed PDH.MethodsProspective study. Thirty days after the first administration of trilostane, blood samples were taken at −30, 0 (baseline), 15, 30, 60, and 90 minutes, and 2, 3, 4, 6, 8, 12, 16, 20, and 24 hours after administration of trilostane and plasma concentration of cortisol, endogenous ACTH, aldosterone, sodium, potassium, ionized calcium, and renin activity were determined.ResultsCortisol concentrations decreased significantly (P < .001) 2–4 hours after trilostane administration. From baseline, there was a significant (P < .001) increase in endogenous ACTH concentrations between hours 3–12, a significant increase (P < .001) in aldosterone concentration between hours 16–20, and a significant (P < .001) increase in renin activity between hours 6–20. Potassium concentration decreased significantly (P < .05) between hours 0.5–2.Conclusion and Clinical ImportanceTreatment with trilostane did not cause clinically relevant alterations in plasma aldosterone and potassium concentration. Results suggest that in dogs with PDH, the optimal time point for an ACTH‐stimulation test to be performed is 2–4 hours after trilostane dosing. Future studies are necessary to establish interpretation criteria for a 2‐ to 4‐hour postpill ACTH‐stimulation test.

ACTH promotes chondrogenic nodule formation and induces transient elevations in intracellular calcium in rat bone marrow cell cultures via MC2-R signaling

Adrenocorticotropic hormone (ACTH) is among several melanocortin peptide hormones that are derived from proopiomelanocortin (POMC). ACTH has been found to enhance osteogenesis and chondrogenesis. We show that, in the presence of dexamethasone, ACTH dose-dependently increases chondrogenic nodule formation in bone marrow stromal cells (BMSC) from the Wistar Kyoto (WKY) rat. The nodules consist in condensed cells highly expressing alkaline phosphatase, Sox9 and type II collagen transcripts and a proteoglycan-rich matrix. Immunoblot analysis of crude membrane fractions has shown that these cells express three melanocortin receptors (MC-R), namely MC2-R, MC3-R and MC5-R and the melanocortin 2-receptor accessory protein (MRAP). To determine which of these receptors mediate ACTH-induced effects, we have used MC-R-specific peptides and the known agonist profiles of the receptors. Neither α-MSH, a strong agonist of MC5-R, nor γ2-MSH, a strong agonist of MC3-R, duplicates ACTH effects in rat BMSC. In addition, calcium flux has been examined as a mechanism for ACTH action at the MC2-R. Consistent with MC2-R and MRAP expression patterns in the BMSC cultures, ACTH-induced transient increases in intracellular calcium are increased with dexamethasone treatment. Neither α-MSH nor γ2-MSH affects calcium flux. Dexamethasone increases MC2-R and MRAP expression and POMC peptide expression and cleavage increasing the production of the lipolytic β-lipotropic hormone product. Therefore, the effects of ACTH in rat BMSC enriched for mesenchymal progenitors are consistent with an MC2-R signaling mechanism, with dexamethasone being capable of regulating components of the melanocortin system in these cells.

Multiple Sclerosis, Relapses, and the Mechanism of Action of Adrenocorticotropic Hormone

Relapses in multiple sclerosis (MS) are disruptive and frequently disabling for patients, and their treatment is often a challenge to clinicians. Despite progress in the understanding of the pathophysiology of MS and development of new treatments for long-term management of MS, options for treating relapses have not changed substantially over the past few decades. Corticosteroids, a component of the hypothalamic-pituitary-adrenal axis that modulate immune responses and reduce inflammation, are currently the mainstay of relapse treatment. Adrenocorticotropic hormone (ACTH) gel is another treatment option. Although it has long been assumed that the efficacy of ACTH in treating relapses depends on the peptide’s ability to increase endogenous corticosteroid production, evidence from research on the melanocortin system suggests that steroidogenesis may only partly account for ACTH influences. Indeed, the melanocortin peptides [ACTH and α-, β-, γ-melanocyte-stimulating hormones (MSH)] and their receptors (Melanocortin receptors, MCRs) exert multiple actions, including modulation of inflammatory and immune mediator production. MCRs are widely distributed within the central nervous system and in peripheral tissues including immune cells (e.g., macrophages). This suggests that the mechanism of action of ACTH includes not only steroid-mediated indirect effects, but also direct anti-inflammatory and immune-modulating actions via the melanocortin system. An increased understanding of the role of the melanocortin system, particularly ACTH, in the immune and inflammatory processes underlying relapses may help to improve relapse management.

Cytokines in cerebrospinal fluid of children with West syndrome

In this study we aimed to determine the levels of tumor necrosis factor beta (TNF-b), interleukin (IL) 1-beta (IL-1b), IL-5, IL-10, and interferon gamma (IFN-g ) in CSF from children during the onset of West syndrome (WS). We observed elevated levels of IL-1b and IFN-g correlated to clinical, EEG, therapeutic response, and follow-up suggesting the involvement of immune response in WS. These results suggest that inflammatory and immunologic mediators may play a role in the pathophysiologic mechanisms of infantile spasms. Our findings may explain the perfusion and cognitive disfunctions and actions of adrenocorticotropic hormone (ACTH), corticosteroids, and intravenous immunoglobulin (IVIg) observed in WS. In conclusion, WS results from association of neurophysiological mechanisms and structural abnormalities with participation of cytokines mainly in symptomatic group.

Direct actions of ACTH on ovarian function of pseudopregnant rabbits

The present study sought to assess whether the receptors for adrenocorticotropic hormone (ACTH), MC2R, and for glucocorticoid (GR) are expressed in corpora lutea (CL) of pseudopregnant rabbits and whether ACTH and cortisol exert any direct action on luteal function. By immunohistochemistry, positive reaction for MC2R and GR was detectable within luteal cells of CL. The MC2R mRNA levels were five-fold less abundant in day 9 than in day 4 CL (P<0.01). At both stages, ACTH agonist (ACTH 1-24) increased progesterone and prostaglandin (PG) E2 (PGE2) (P<0.01), but reduced PGF2α releases (P<0.01) in vitro. ACTH 1-24 injection increased plasma cortisol levels within 4h (P<0.01), but decreased (P<0.01) progesterone 24h later and for the following two days. ACTH administration to estrous rabbits caused a transitory increase in blood progesterone concentrations (P<0.01). Daily injections of ACTH did not modify progesterone profile following ovulation. In conclusion, ACTH directly up-regulates CL progesterone production in vitro via MC2R, but indirectly hampers luteal function via cortisol-GR associated mechanism.

Melanocortin receptor subtypes in interrenal cells and corticotropic activity of α-melanocyte-stimulating hormones in barfin flounder, Verasper moseri

The aim of this study was to characterize the pituitary–interrenal axis in barfin flounder, a flatfish. Adrenocorticotropic hormone (ACTH) and melanocortin 2 receptor (MC2R) have been shown to be indispensable substances in pituitary and interrenal cells for cortisol release, respectively. We previously identified ACTH in the pars distalis of the barfin flounder pituitary gland, and detected transcripts of Mc1r, Mc4r, and Mc5r in the head kidney wherein interrenal cells are located. We have now demonstrated the presence of MC2R, which is a specific receptor for ACTH, in interrenal cells by molecular cloning of Mc2r cDNA and in situ hybridization, and confirmation of the in vitro cortisol-releasing activity of ACTH. These results show the presence of a classical pituitary–interrenal axis in this fish. We also evaluated the role of α-melanocyte-stimulating hormone (α-MSH) and its related peptides. In situ hybridization was used to demonstrate the expression of Mc5r in interrenal cells; both desacetyl-α-MSH and diacetyl-α-MSH showed in vitro cortisol-releasing activities, while the activity of α-MSH was negligible. These findings indicate the presence of an additional pituitary–interrenal axis consisting of α-MSH-like peptides secreted from the neurointermediate lobe of the pituitary and MC5R in the interrenal cells. The cortisol-releasing activity of desacetyl-α-MSH and diacetyl-α-MSH, compared with the low activity of α-MSH, suggest a unique and specific functional role of these forms of MSH peptides. The interrenal co-expression of two subtypes of Mcrs may play a role in this specialization.

The genetics of familial glucocorticoid deficiency

Familial glucocorticoid deficiency is an autosomal recessive disorder resulting from defects in the action of adrenocorticotropic hormone (ACTH) to stimulate glucocorticoid synthesis in the adrenal. Production of mineralocorticoids by the adrenal is normal. Patients present in early life with low or undetectable cortisol and--because of the failure of the negative feedback loop to the pituitary and hypothalamus--grossly elevated ACTH levels. About half of all cases result from mutations in the ACTH receptor (melanocortin 2 receptor) or from mutations in the melanocortin 2 receptor accessory protein (MRAP), but other genetic causes of this potentially lethal disorder remain to be discovered.

Stress activation of cellular markers of inflammation in rheumatoid arthritis: Protective effects of tumor necrosis factor α antagonists

Psychological stress is thought to aggravate disease activity in rheumatoid arthritis (RA), although the physiologic mechanisms are unclear. Tumor necrosis factor alpha (TNFalpha) is an inflammatory cytokine involved in the exacerbation of RA, and TNFalpha antagonists have emerged as efficacious treatments. The purpose of this study was to determine whether RA patients show increased monocyte production of TNFalpha following acute psychological stress and whether such responses are abrogated in RA patients taking TNFalpha antagonists. A standardized stress task was administered to 3 groups of subjects: RA patients taking TNFalpha antagonists, RA patients not taking such medications, and healthy controls. Lipopolysaccharide-stimulated monocyte production of inflammatory cytokines was repeatedly measured using intracellular staining and flow cytometry. Subjective stress, cardiovascular responses, adrenocorticotropic hormone (ACTH) levels, and cortisol levels were also measured. The stress task induced increases in subjective stress, cardiovascular activity, and levels of ACTH and cortisol, with similar responses in the 3 groups. In addition, the stress task induced a significant increase (P < 0.001) in monocyte production of TNFalpha among RA patients who were not taking TNFalpha antagonists. However, monocyte production of TNFalpha did not change following psychological stress in RA patients taking TNFalpha antagonists or in healthy controls. Brief psychological stress can trigger increased stimulated monocyte production of TNFalpha in RA patients. The use of TNFalpha antagonists protects against stress activation of cellular markers of inflammation in RA patients.