Characteristics of the response of human adrenocortical cells to ACTH

Metabolic profiling reveals therapeutic biomarkers of processed Aconitum carmichaeli Debx in treating hydrocortisone induced kidney-yang deficiency syndrome rats

ETHNOPHARMACOLOGICAL RELEVANCE

Kidney-yang deficiency syndrome (KYDS) is a diagnostic pattern in traditional Chinese medicine (TCM) and clinical data showed that the unbalance in adrenal cortical hormone is the key issue in KYDS patients. The processed Ranunculaceae aconitum carmichaeli debx (bai-fu-pian in Chinese, BFP) is one of the most commonly used Chinese herbs for treating KYDS. The present study was conducted to explore the therapeutic biomarkers of the BFP in treating hydrocortisone administration induced KYDS rats.

MATERIALS AND METHODS

Thirty male Sprague-Dawley rats were randomly divided into five groups with six in each group. KYDS in rats was induced by i.p. injection of hydrocortisone at the dose of 10mg/kg per day for 15 days as described previously. The rats with KYDS were administered orally, starting from the day of hydrocortisone administration stopped, with BFP extract at the dose of 0.32g/kg, 0.64g/kg and 1.28g/kg per day respectively for 15 days. The blood samples were collected for the liquid chromatography quadruple time-of-flight mass spectrometry (LC-Q-TOF-MS) test, as well as radioimmunoassay to determine the concentrations of cyclic adenosine monophosphate (cAMP), cyclic guanosine monophosphate (cGMP) and adrenocorticotrophic hormone (ACTH). The metabolic responses to BFP administration were investigated by using the principal components analysis (PCA) and orthogonal partial least squares analysis (OPLS). Bioinformatics analyses were performed by using the Ingenuity Pathway Analysis (IPA). Variance analysis and linear regression analysis were used in this study.

RESULTS

The signs and concentrations of cAMP, cGMP and ACTH in the model rats were similar to those previously described about KYDS rats and BFP treatment can reverse the changes. Seventeen significantly changed metabolites among different groups were identified. Thirteen metabolites were identified in the KYDS rats comparing to healthy rats with nine up-regulated and four down-regulated. After BFP treatment at three dosages, five up-regulated metabolites including phosphate, betaine, (4-hydroxyphenyl) acetaldehyde, 5-hydroxyindol-3-acetic acid and 5'-phosphoribosyl-N-formylglycinamide were dose-dependently reversed. The network analysis with IPA showed that four canonical pathways including superpathway of methionine degradation, purine nucleotides de novo biosynthesis II, tyrosine synthesis and serotonin receptor signaling involved the therapeutic mechanism of BFP in treating the KYDS rats.

CONCLUSIONS

Five therapeutic biomarkers (phosphate, betaine, (4-hydroxyphenyl) acetaldehyde, 5-hydroxyindol-3-acetic acid and 5'-phosphoribosyl-N-formylglycinamide) and two corresponding canonical pathways (amino acid metabolism and purine nucleotide metabolism) were identified to be involved in the therapeutic mechanism of BFP treating the KYDS.

The effects of ACTH on steroid metabolomic profiles in human adrenal cells

The adrenal glands are the primary source of mineralocorticoids, glucocorticoids, and the so-called adrenal androgens. Under physiological conditions, cortisol and adrenal androgen synthesis are controlled primarily by ACTH. Although it is well established that ACTH can stimulate steroidogenesis in the human adrenal gland, the effect of ACTH on overall production of different classes of steroid hormones has not been defined. In this study, we examined the effect of ACTH on the production of 23 steroid hormones in adult adrenal primary cultures and 20 steroids in the adrenal cell line, H295R. Liquid chromatography/tandem mass spectrometry analysis revealed that, in primary adrenal cell cultures, cortisol and corticosterone were the two most abundant steroid hormones produced with or without ACTH treatment (48  h). Cortisol production responded the most to ACTH treatment, with a 64-fold increase. Interestingly, the production of two androgens, androstenedione and 11β-hydroxyandrostenedione (11OHA), that were also produced in large amounts under basal conditions significantly increased after ACTH incubation. In H295R cells, 11-deoxycortisol and androstenedione were the major products under basal conditions. Treatment with forskolin increased the percentage of 11β-hydroxylated products, including cortisol and 11OHA. This study illustrates that adrenal cells respond to ACTH through the secretion of a variety of steroid hormones, thus supporting the role of adrenal cells as a source of both corticosteroids and androgens.

The adrenal cortex in ectopic adrenocorticotropic hormone syndrome: A morphological study with histology, transmission and scanning electron microscopy, flow cytometry, and image analysis

The surgically removed adrenal glands of an 83-year-old woman with ectopic adrenocorticotropic hormone syndrome were studied by light microscopy, transmission and scanning electron microscopy, and flow-cytometric and image analyses for DNA ploidy. Light microscopy revealed marked adrenocortical hyperplasia. The majority of the large fasciculata cells were lipid-depleted compact cells, some with large nuclei. By transmission electron microscopy, marked abundance of smooth endoplasmic reticulum was noted. Mitochondria were large, had vesicular or tubulovesicular cristae, and showed focal cavitation in their internal compartments. Lysosomes were numerous in many large cells. Long microvilli were prominent on the cell surfaces and interdigitating with adjacent cells. Scanning electron microscopy disclosed many conspicuous microvilli and small pits on the cell membranes. The microvillous hyperplasia is most likely destined to facilitate uptake of hormone precursors or discharge of synthesized hormones by increasing the cell surface area; the small pits on cell membranes may reflect endocytosis of hormone precursors required for accelerated corticosteroid synthesis. Flow-cytometric and image analysis of the adrenocortical cells showed aneuploid and polyploid DNA populations, providing evidence that aneuploidy and polyploidy may occur not only in neoplastic but also in hyperplastic cells.

The ACTH stimulation test before and after clinical recovery from depression

Excessive cortisol secretion after cosyntropin (adrenocorticotropic hormone; ACTH) infusion in some depressed patients has suggested the possibility that the adrenal cortex may have heightened responsiveness to ACTH, and that this may contribute, in part, to activation of the hypothalamic-pituitary-adrenocortical axis. We administered an ACTH test and dexamethasone suppression test (DST) to 32 patients before and after treatment. Maximal cortisol response to ACTH demonstrated a significant decrease after treatment in the subgroup of melancholic/DST nonsuppressors (p = 0.04). When the cumulative cortisol response (CCR) to ACTH was examined, the DST nonsuppressors had a greater CCR decrease than suppressors (p = 0.03), and the melancholics a greater decrease than nonmelancholics (p = 0.02). The melancholic/DST nonsuppressor subgroup had the largest CCR decrease after treatment (p = 0.03), and these patients may represent a group of depressives with altered adrenocortical function that tends to "normalize" with clinical recovery.

Adrenocortical responsiveness to the ACTH stimulation test in depressed patients and healthy volunteers

Adrenocortical activation in depression has been postulated to result from overactivity of limbic system-hypothalamic function. However, some studies suggest the possibility that excessive secretion of cortisol might result, in part, from a heightened adrenocortical responsiveness to ACTH. To further examine this possibility, we utilized both the ACTH stimulation test and the overnight dexamethasone suppression test (DST) in 72 patients with major depression and 37 age- and gender-matched healthy volunteers. The melancholic/DST-nonsuppressor group had larger mean peak cortisol and cumulative cortisol responses (CCR) than any of the other patients groups or healthy controls. However, the differences failed to reach statistical significance as a result of a relatively large cortisol response variability. Nevertheless, the present findings are in general agreement with previous reports suggesting the possibility of an enhanced adrenocortical responsiveness to ACTH.

Enhanced 17 alpha-hydroxylation of pregnenolone and increased androgen production by rabbit adrenocortical cells stimulated chronically with corticotropin

The postulated chronic stimulatory effect of corticotropin (ACTH) on pregnenolone production and on 17 alpha-hydroxylase activity was evaluated on adrenocortical cells obtained from control and chronically ACTH-treated rabbits. The cells were incubated with various concentrations of ACTH added alone or together with trilostane, so as to inhibit further conversion of pregnenolone and dehydroepiandrosterone. The maximal steroidogenic effect of ACTH (determined in the absence of trilostane) was increased 2-fold in adrenocortical cells from ACTH-treated animals; furthermore, cortisol production was increased whereas that of corticosterone decreased. While the generation of pregnenolone was of comparable magnitude for cells from both experimental groups, chronic in vivo treatment with ACTH was followed by a 40-fold enhancement in 17-hydroxypregnenolone production. Concomitantly, maximal DHEA production documented in the presence of ACTH and trilostane was enhanced more than 200-fold, from 0.45 +/- 0.20 pmol in control rabbits to 147 +/- 67 pmol in cells from ACTH-treated animals. The corresponding values of DHEA-sulphate production were 0.86 +/- 0.12 and 432 +/- 334 pmol, respectively. Thus, a prolonged stimulatory effect of ACTH on rabbit adrenocortical cells consists in an enhancement of the capacity to generate pregnenolone, and to convert this compound into 17-hydroxylated steroids.

Enhanced androgen production by rabbit adrenocortical cells stimulated chronically with corticotropin: evidence for increased 17 alpha-hydroxylase activity

The effects of prolonged treatment with corticotropin (ACTH1-24, 200 micrograms s.c. daily during 12 days) on the production of androgens and glucocorticoids were studied on rabbit dispersed adrenocortical cells. The steroidogenic capacity of adrenocortical cells, expressed in terms of the maximal response to ACTH of glucocorticoid (i.e. corticosterone and cortisol) production, was significantly increased after treatment with ACTH. This was associated with a loss of sensitivity to this peptide: indeed, the concentration of ACTH required to induce a half maximal secretory response was one order of magnitude higher with cells from ACTH-treated animals. Among the C21 steroids measured the changes observed involved the 17 alpha-hydroxylated compounds (cortisol, cortisone, 11-deoxycortisol) while corticosterone production was significantly depressed. This effect of prolonged ACTH treatment on steroidogenic pathways involving 17 alpha-hydroxylation, was further evidenced by a clear-cut enhancement in androgen secretion (dehydroepiandrosterone, androstenedione and testosterone) by adrenocortical cells from ACTH-treated animals. The changes observed after treatment of the animal with ACTH were equally obvious, whether the adrenocortical cells were incubated with ACTH or with dibutyryl-c-AMP.

The enhancement of pregnenolone production as the main mechanism of the prolonged stimulatory effect of ACTH on cortisol production by guinea-pig adrenocortical cells

The prolonged stimulatory influence of corticotropin (ACTH) on the adrenocortical steroidogenic response to ACTH was studied in guinea-pig adrenocortical cells harvested from control and ACTH-treated animals (ACTH1-24, 50 micrograms s.c. twice daily on the day preceding the in vitro experiment). The maximal capacity to produce cortisol in response to ACTH (by 10(5) cells and 2 h incubation) was increased from 341.8 +/- 36.3 ng (control group) to 663.3 +/- 37.6 ng for cells obtained from guinea-pigs treated in vivo with ACTH. In the presence of trilostane, added to the cells in order to block the conversion of pregnenolone to cortisol, the net maximal output of pregnenolone and 17-hydroxypregnenolone in response to ACTH was significantly increased in adrenocortical cells from ACTH-treated animals (449.5 +/- 35.8 ng pregnenolone and 85.7 +/- 10.5 ng 17-hydroxypregnenolone vs 269.1 +/- 36.3 ng pregnenolone and 43.7 +/- 8.51 ng 17-hydroxypregnenolone for cells from control guinea-pigs). It appeared therefore that the total production of pregnenolone (as estimated by the sum of pregnenolone and 17-hydroxypregnenolone produced by the cells incubated with trilostane) nearly reached the level of the maximal production of cortisol in response to ACTH and was also significantly enhanced for cells from ACTH-treated animals (532.2 +/- 38.4 ng vs 312.8 +/- 40.0 ng for cells from control group). By contrast, no effect was documented on 17 alpha-hydroxylase activity since 17 alpha-hydroxylation index was similar for both types of adrenocortical cells (16.3 +/- 2.05% for ACTH-treated animals and 14.2 +/- 2.83% for control group). It was concluded therefore that the prolonged stimulatory influence of ACTH on pregnenolone production is the main mechanism of the enhancement of cortisol synthesis by guinea-pig adrenocortical cells previously stimulated by ACTH.

On the specificity of the inhibitory effect of trilostane and aminoglutethimide on adrenocortical steroidogenesis in guinea pig

The effect of trilostane and aminoglutethimide on steroidogenesis was studied on isolated guinea pig adrenocortical cells in order to verify whether, in addition to the inhibitory influence of trilostane on 3beta-hydroxysteroid dehydrogenase and isomerase and the inhibition by aminoglutethimide of pregnenolone formation, these inhibitors may also affect other enzymatic steps of cortisol synthesis. While trilostane completely abolished cortisol production in response to ACTH with concomitant enhancement in pregnenolone and 17-hydroxypregnenolone formation, the conversion of progesterone, 17-hydroxyprogesterone and 11-deoxycortisol into cortisol was not affected by the presence of the inhibitor. Contrasting with this specific inhibitory effect of trilostane, aminoglutethimide inhibited not only pregnenolone formation but also several other enzymatic steps involved in the conversion of this precursor of steroidogenesis into cortisol. Among these additional effects of aminoglutethimide on steroidogenesis, the inhibition of 11 beta-hydroxylation was clearly demonstrated.

ACTH sensitivity of isolated human pathological adrenocortical cells: variability of responses in aldosterone, corticosterone, deoxycorticosterone and cortisol production

In vitro aldosterone, deoxycorticosterone, corticosterone and cortisol production of human adrenocortical cells derived from adenomas (Conn's syndrome, Cushing's syndrome), from hyperplastic adrenals (Cushing's syndrome) and from adrenals surrounding aldosteronoma are described. Cells from adenomas causing either Cushing's syndrome or Conn's syndrome harboured the highest basal and ACTH-stimulated corticosteroid production. Adrenocortical cells derived from micronodular hyperplasia causing Cushing's syndrome and cells from cortisol producing adenoma displayed predominantly cortisol and corticosterone secretion both under basal conditions and following stimulation with ACTH. Aldosteronoma cells showed highly variable aldosterone, deoxycorticosterone, corticosterone and cortisol response to ACTH. However, in aldosteronoma cell suspensions, the basal and ACTH-stimulated ratios of aldosterone to cortisol were increased when compared to ratios of steroids produced by cells from other adrenal tissues. Chronic treatment with spironolactone of patients with Conn's syndrome before surgery was associated with a decreased ratio of aldosterone to corticosterone, revealing that 18-hydroxylase in aldosteronoma cells may be inhibited during long-term therapy. Non-tumorous cells isolated from adrenals surrounding aldosteronoma displayed less aldosterone prior to and after stimulation with ACTH than aldosteronoma cells.

The prolonged stimulatory effect of ACTH on 11 beta-hydroxylation, and its contribution to the steroidogenic potency of adrenocortical cells

The mechanism of the prolonged stimulatory influence of corticotropin (ACTH) on the capacity of adrenocortical cells to produce cortisol in response to ACTH and more specifically the role of 11 beta-hydroxylation, was studied on guinea-pig adrenocortical cells dispersed from control and ACTH-treated animals. As a result of the previous in vivo exposure to ACTH, the net maximal production of glucocorticoids in response to ACTH (by 10(5) cells and 2 h incubation) increased from 660 +/- 33.9 ng (control group) to 1105 +/- 117.9 ng for cells from ACTH-treated animals (P less than 0.001), whereas the apparent affinity of the steroidogenic response remained unchanged. In addition there occurred an increased conversion of exogenous pregnenolone into cortisol by cells from ACTH-treated animals, indicating a prolonged stimulatory influence of ACTH on the post-pregnenolone pathway of cortisol biosynthesis. The activity of 11 beta-hydroxylation step was therefore examined by incubating the adrenocortical cells from control and ACTH-treated animals in the presence of increasing amounts of 11-deoxycortisol. The maximal capacity of 11-deoxycortisol conversion into cortisol was increased as a result of the in vivo exposure to ACTH, averaging 3423 +/- 211 ng cortisol formed from 5 micrograms 11-deoxycortisol by 10(5) cells from ACTH-treated animals vs 2074 +/- 185 ng for cells from control guinea-pigs (P less than 0.001). However, the conversion of lower amounts of 11-deoxycortisol into cortisol, reproducing quantitatively the maximal effect of ACTH on cortisol biosynthesis, was only barely increased in cells from ACTH-treated animals (P greater than 0.05). Therefore it was concluded that ACTH increases in a lasting way not only the overall steroidogenic capacity of adrenocortical cells but also the maximal efficiency of 11 beta-hydroxylation. Since the latter effect cannot account quantitatively for the magnitude of the lasting effect of ACTH on the maximal capacity of adrenocortical cells to produce cortisol in response to ACTH, it appears that the prolonged influence of ACTH on cortisol biosynthesis should also involve a stimulatory influence of the peptide on earlier step(s) of steroidogenesis.

The stimulatory effect of corticotropin on cortisol biosynthetic pathway in guinea-pig adrenocortical cells

The mechanism of the prolonged stimulatory effect of corticotropin (ACTH) on adrenocortical synthesis of cortisol was studied in guinea-pig adrenocortical cells harvested from control animals and from guinea-pigs submitted 24 h before the sacrifice to a prolonged ether anesthesia in an attempt to induce a release of endogenous ACTH. As a result of this in vivo exposure to endogenous ACTH, the maximal capacity to produce glucocorticoids (by 1 X 10(5) cells incubated during 2 h) in response to ACTH increased from 579 +/- 111 ng (control group) to 915 +/- 143 ng for cells from treated animals, whereas the apparent affinity of the steroidogenic response to ACTH remained unchanged. This hyper-reactivity of cells from anesthetized animals was also evident in the presence of dibutyryl cyclic AMP. Moreover, there was increased conversion of exogenous pregnenolone into cortisol by cells from previously anesthetized animals. It was therefore concluded that ACTH increases in a lasting way the activity of steroidogenic pathway leading to cortisol synthesis by adrenocortical cells at sites distal to cyclic AMP generation. Besides an obvious increase of formation of pregnenolone in response to ACTH, it seems that this ACTH-induced enhancement in the capacity of the steroidogenic response to ACTH also implies a prolonged stimulatory influence of the peptide on the post-pregnenolone steroidogenic pathway leading to cortisol synthesis.

In vitro effects of high molecular weight forms of ACTH on the fetal sheep adrenal

The direct involvement of the pituitary-adrenal axis in birth has been well established, at least in sheep, and its removal prolongs pregnancy. As part of the process the fetal sheep adrenal grows rapidly during the 10-15 d prepartum and is associated with a large rise in the plasma corticosteroid concentration. This does not seem to result from an increased ACTH secretion. The fetal adrenal in vivo seems refractory to circulating ACTH and shows poor response to elevation of plasma concentration. Thus the signal for the adrenal hypertrophy and the initiation of parturition remains unclear. The responsiveness of the fetal adrenal to ACTH has been re-examined using isolated adrenal cells. The study shows that in the fetal sheep these are not inherently unresponsive to ACTH, but that high-molecular-weight forms of ACTH block the action of ACTH. These peptides may be responsible for controlling the activity of the adrenal in situ.