Update on adrenarche.

PURPOSE OF REVIEW: Adrenarche is the pubertal maturation of the innermost zone of the adrenal cortex, the zona reticularis. The onset of adrenarche occurs between 6 and 8 years of age when dehydroepiandrosterone sulfate (DHEAS) concentrations increase. This review provides an update on adrenal steroidogenesis and the differential diagnosis of premature development of pubic hair. RECENT FINDINGS: The complexity of adrenal steroidogenesis has increased with recognition of the alternative 'backdoor pathway' and the 11-oxo-androgens pathways. Traditionally, sulfated steroids such as DHEAS have been considered to be inactive metabolites. Recent data suggest that intracellular sulfated steroids may function as tissue-specific intracrine hormones particularly in the tissues expressing steroid sulfatases such as ovaries, testes, and placenta. SUMMARY: The physiologic mechanisms governing the onset of adrenarche remain unclear. To date, no validated regulatory feedback mechanism has been identified for adrenal C19 steroid secretion. Available data indicate that for most children, premature adrenarche is a benign variation of development and a diagnosis of exclusion. Patients with premature adrenarche tend to have higher BMI values. Yet, despite greater knowledge about C19 steroids and zona reticularis function, much remains to be learned about adrenarche.

In the zone: understanding zona reticularis function and its transformation by adrenarche.

The human adrenal cortex comprises three distinct zones with unique steroid products, namely the zona glomerulosa, which secretes the mineralocorticoids, the zona fasciculate, which secretes the glucocorticoids and the zona reticularis (ZR), which at adrenarche, begins to produce the so-called adrenal androgens. Of all the adrenal zones, we still understand control of ZR emergence the least, and yet the consequences of such dysregulation can be devastating. Premature adrenarche is a growing problem and the correspondingly inappropriate emergence of ZR function can negatively influence puberty and lead to adult infertility. Our understanding is limited and more needs to be done. The purpose of these three reviews is to provide a survey of where we are in our current understanding of what adrenarche is, and indeed if it is unique to humans at all. Furthermore, these reviews describe what is also known of how the functional ZR emerges during adrenarche and what steroids of physiologic relevance result beyond the widely known DHEA and DHEAS elevated at this time. Such advances in human, primate and indeed stem-cell biology are clearly laying the foundation for new directions in the hunt for the factors involved in the regulation and functional emergence of a ZR at the appropriate time, as well as insight into how they may fail. Given support for these new directions, considerable progress can clearly be made.

The steroid metabolome of adrenarche.

Adrenarche is an endocrine developmental process whereby humans and select nonhuman primates increase adrenal output of a series of steroids, especially DHEA and DHEAS. The timing of adrenarche varies among primates, but in humans serum levels of DHEAS are seen to increase at around 6 years of age. This phenomenon corresponds with the development and expansion of the zona reticularis of the adrenal gland. The physiological phenomena that trigger the onset of adrenarche are still unknown; however, the biochemical pathways leading to this event have been elucidated in detail. There are numerous reviews examining the process of adrenarche, most of which have focused on the changes within the adrenal as well as the phenotypic results of adrenarche. This article reviews the recent and past studies that show the breadth of changes in the circulating steroid metabolome that occur during the process of adrenarche.

Adrenarche: a cell biological perspective.

Adrenarche is a cell biological and endocrinological puzzle. The differentiation of the zona reticularis in childhood in humans requires special techniques for study because it is confined to humans and possibly a small number of other primates. Despite the rapid progress in the definition of adrenocortical stem/progenitor cells in the mouse, the factors that cause the differentiation of adrenocortical cells into zonal cell types have not been identified. There are, however, many candidates in the Wnt, Hedgehog, and other families of signaling molecules. A suitable system for identifying authentic stem cells, capable of differentiation into all zones, has yet to be developed. It is proposed here that the in vitro differentiation of pluripotent cells, combined with appropriate in vitro and in vivo methods for validating authentic adrenocortical stem cells, is a promising approach to solving these questions.

T cells affect thymic involution during puberty by inducing regression of the adrenal reticularis.

The thymus involutes after puberty, although the mechanism by which this process occurs remains poorly understood. The profile of thymic involution, which is inversely correlated with an increase in peripheral T cells, may indicate that the accumulation of T cells in the periphery is related to thymic atrophy. In this study, it was shown that the prevention of T cell generation delayed the initiation of thymic involution. The activation of T cells increased the serum concentration of glucocorticoid (GC) and thymic involution, which was completely prevented by adrenalectomy. In the adrenals of growing mice, the activity of the zona fasciculata, which produces GC, increased and plateaued by the weaning period; however, the zona reticularis (ZR), which produces dehydroepiandrosterone (DHEA) that has anti-GC actions, started to decline just before puberty. Thymic atrophy was preceded by the infiltration of activated T cells into the ZR and by the loss of ZR cells. Thus, T cells are involved in thymic involution, a process which was retarded by DHEA administration, through an increase in GC activity due to ZR cell-killing.

IGF-I enhances cortisol secretion from guinea-pig adrenal gland: in vivo and in vitro study.

Insulin-like growth factor (IGF)-I is a ubiquitously synthesized peptide that, along with IGF-II, acts via the IGF-R type I receptor. IGF-I and its receptor are expressed in the adrenal gland of humans and bovines, the secretion of which they seem to stimulate. As in humans and cows, the main glucocorticoid hormone secreted by guinea-pig adrenals is cortisol, and hence we have studied the adrenocortical effects of IGF-I in this species. In vivo experiments showed that prolonged IGF-I administration raised the plasma concentration of cortisol in both normal and dexamethasone/captopril-treated guinea pigs, thereby ruling out the possibility that IGF-I may act by activating the hypothalamic-pituitary-adrenal axis and the renin-angiotensin system. In vitro experiments demonstrated that IGF-I enhanced basal, but not maximally agonist [ACTH and angiotensin-II (Ang-II)]-stimulated, cortisol secretion from freshly dispersed guinea-pig inner adrenocortical cells. The IGF-I immuno-neutralization suppressed the IGF-I secretagogue effect, without altering the cortisol response to both ACTH and Ang-II. IGF-I raised cyclic-AMP and inositol triphosphate release from dispersed guinea-pig cells, and the effect was reversed by the adenylate cyclase inhibitor SQ-22536 and the phospholipase-C (PLC) inhibitor U-73122. SQ-22536, U-73122, the protein kinase (PK) A inhibitor H-89 and the PKC inhibitor calphostin-C decreased by approximately 50% the cortisol response of dispersed cells to IGF-I, and the combined exposure to SQ-22536 and U-73122 abolished it. We conclude that IGF-I stimulates glucocorticoid secretion from guinea-pig adrenocortical cells, acting via selective receptors coupled to both the adenylate cyclase/PKA- and PLC/PKC-dependent signaling cascades.

Expression of the glucocorticoid receptor in the human adrenal cortex.

Glucocorticoids produced in the adrenal cortex act by binding to a specific intracellular protein, the glucocorticoid receptor (GR), which then modulates gene transcription in target tissues. Whether the adrenal cortex itself is a glucocorticoid target tissue has not been analyzed as yet. Since the presence of GR would be a prerequisite for such "intracortical" glucocorticoid action, this study was designed to analyze GR expression in the normal human adrenal gland using RT-PCR, Western blot, and immunohistochemistry. RT-PCR revealed the presence of GR mRNA in adrenal cortex as well as in NCIh295 cells. These results were confirmed at the protein level by Western blot employing a specific anti-human GR antibody. Immunohistochemically, weak GR staining was observed in the adrenal medulla. In contrast, GR was strongly expressed in the adrenal cortex with the zona reticularis showing the most intense staining. Transfection of a GR-responsive luciferase reporter gene into NCIh295 cells resulted in dexamethasone-dependent induction of luciferase activity, indicating that GR is functional in this tissue. In this study, we show for the first time that GR is expressed in the human adrenal cortex. Its preferential expression in the zona reticularis may indicate a functional role in the regulation of adrenal androgen biosynthesis.

Differences between the growth regulatory pathways in primary rat adrenal cells and mouse tumor cell line.

In this study, DNA synthesis, phosphorylation of ERK1/2 and CREB proteins, as well as induction of c-Fos protein, were examined in rat adrenocortical, glomerulosa and fasciculata/reticularis cells, as well as in the Y1 cell line. We found that FGF2 was mitogenic only in glomerulosa cells and although ACTH did not activate ERK1/2, it did activate CREB protein, indicating efficient transduction of signals initiated in the ACTH receptors of rat adrenocortical cells. The FGF2 activated ERK1/2 in rat adrenal cells by a mechanism that might be modulated by upstream PKA pathway phosphorylation of MEK and despite the nonmitogenic effect of ACTH on rat adrenal cells it effectively induces c-Fos protein. The results presented herein describe distinct differences between the ACTH and FGF2 signal transduction mechanisms seen in adrenocortical cells and those observed in the Y1 cell line, indicating that, in vitro, ACTH blockage of the mitogenic effect occurs in normal adrenal cells after induction of c-Fos protein.

Dehydroepiandrosterone sulfate and allopregnanolone directly stimulate catecholamine production via induction of tyrosine hydroxylase and secretion by affecting actin polymerization.

Adrenal cortical cells of zona reticularis produce the neuroactive steroids dehydroepiandrosterone (DHEA), its sulfate ester dehydroepiandrosterone sulfate (DHEAS), and allopregnanolone (ALLO). An interaction between zona reticularis and adrenal medulla has been postulated based on their close proximity and their interwoven borders. The aim of this paper was to examine in vitro the possible paracrine effects of these steroids on catecholamine production from adrenomedullary chromaffin cells, using an established in vitro model of chromaffin cells, the PC12 rat pheochromocytoma cell line. We have found the following: 1) DHEA, DHEAS, and ALLO increased acutely (peak effect between 10-30 min) and dose-dependently (EC50 in the nanomolar range) catecholamine levels (norepinephrine and dopamine). 2) It appears that the acute effect of these steroids involved actin depolymerization/actin filament disassembly, a fast-response cellular system regulating trafficking of catecholamine vesicles. Specifically, 10(-6) m phallacidin, an actin filament stabilizer, completely prevented steroid-induced catecholamine secretion. 3) DHEAS and ALLO, but not DHEA, also affected catecholamine synthesis. Indeed, DHEAS and ALLO increased catecholamine levels at 24 h, an effect blocked by L-2-methyl-3-(-4-hydroxyphenyl)alanine and 3-(hydrazinomethyl)phenol hydrochloride, inhibitors of tyrosine hydroxylase and L-aromatic amino acid decarboxylase, respectively, suggesting that this effect involved catecholamine synthesis. The latter hypothesis was confirmed by finding that DHEAS and ALLO increased both the mRNA and protein levels of tyrosine hydroxylase. In conclusion, our findings suggest that neuroactive steroids exert a direct tonic effect on adrenal catecholamine synthesis and secretion. These data associate the adrenomedullary malfunction observed in old age and neuroactive steroids.

G protein receptors 7 and 8 are expressed in human adrenocortical cells, and their endogenous ligands neuropeptides B and w enhance cortisol secretion by activating adenylate cyclase- and phospholipase C-dependent signaling cascades.

Neuropeptides B and W (NPB and NPW) are regulatory peptides that act via two subtypes of G protein-coupled receptors, named GPR7 and GPR8. RT-PCR demonstrated the expression of these receptors in both zona glomerulosa and zona fasciculata-reticularis (ZF/R) cells of the human adrenal cortex. NPB and NPW did not affect aldosterone secretion from dispersed zona glomerulosa cells but enhanced cortisol production from ZF/R cells, NPB being more effective than NPW. NPB evoked sizable cAMP and inositol triphosphate responses from ZF/R cells, which were abrogated by the adenylate cyclase inhibitor SQ-22536 and the phospholipase C inhibitor U-73122, respectively. Cortisol response to NPB was lowered by either SQ-22536 and the protein kinase (PK) A inhibitor H-89 or U-73122 and the PKC inhibitor calphostin-C and abolished by the simultaneous exposure to H-89 and calphostin-C. NPW elicited only a rise in cAMP production from dispersed ZF/R cells, and its cortisol response was suppressed by both SQ-22536 and H-89. PreproNPB and preproNPW mRNAs were detected in human adrenal cortexes. We conclude that: 1) NPB and NPW exert a secretagogue action on human ZF/R cells, probably acting in an autocrine-paracrine manner; and 2) the effect of NPB is mediated by both the adenylate cyclase/PKA and the phospholipase C/PKC cascades, whereas that of NPW involves only the activation of the former signaling pathway.

Adrenarche - physiology, biochemistry and human disease.

Adrenarche refers to the onset of dehydroepiandrosterone (DHEA) and DHEA-sulphate (DHEA-S) production from the adrenal zona reticularis that can be detected at around 6 years of age. The phenotypic result of adrenarche is pubarche or the development of axillary and pubic hair that occurs in both girls and boys at about age 8. The phenomenon of adrenarche is unique to human beings and to some Old World primates, and a reversal of adrenarche appears to occur in the ageing process. Premature and exaggerated adrenarche can be indicative of future onset of adult diseases, thus increasing the clinical relevance of adrenarche. The physiological triggers of adrenarche and the role(s) of DHEA-S remain speculative. However, the biochemical pathways that define adrenarche have been characterized in detail, and the appearance of key enzymes and cofactors in the adrenal zona reticularis track with the progression of adrenarche. This article reviews the clinical manifestations of adrenarche, the biochemistry of the enzymes involved in DHEA-S production, and the cell biology of the adrenal zona reticularis.

Variations in adrenal androgen production among (nonhuman) primates.

The synthesis and secretion of the adrenal androgens dehydroepiandrosterone (DHEA) and its sulfate (DS) is a phenomenon apparently unique to humans and nonhuman primates. It occurs at three life stages: in utero from the fetal zone (FZ) cells of the developing adrenal cortex, during adolescence with the onset of adrenarche and the development of the zona reticularis (ZR), and in ever decreasing amounts from the ZR with aging (adrenal senescence). Insufficient data exist to know if any single nonhuman primate exactly mirrors human adrenal androgen secretion through all three life stages, and detailed morphological, biochemical, and endocrinologic studies are required to do so. Androgen synthesis requires that cells express three key enzymes, 17alpha-hydroxylase/17,20-lyase cytochrome P450 (P450c17), nicotinamide-adenine dinucleotide phosphate (NADPH)-cytochrome P450 oxidoreductase (CPR), and cytochrome b5, and that they do not express 3beta-hydroxysteroid dehydrogenase (3beta-HSD). Cytochrome b5 has emerged as a particularly useful marker of androgen synthetic potential. Although a reliable index of the rate of adrenal androgen secretion, DS concentrations may not accurately reflect total adrenal androgen output because rates and routes of androgen metabolism may vary greatly among species. Based on the very limited available data, the most promising nonhuman primate models are marmosets for the human FZ, chimpanzees for human adrenarche, and macaques and baboons for mature ZR function that declines with senescence.

The rise in adrenal androgen biosynthesis: adrenarche.

Adrenarche is characterized by the increase in adrenal androgen production, namely dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEAS) that occurs around 6 years of age. These steroids are secreted by the zona reticularis (ZR) of the adrenal gland. This is associated with pubarche or the increase in androgen-dependent hair growth at the time of puberty. The increase in adrenal androgen production can be explained by the increase in the expression of DHEA-synthesizing steroidogenic enzymes in the ZR. Adrenarche is an event independent of gonadarche and is found only in humans and select nonhuman primates. Although numerous prenatal and postnatal factors are important in the onset of adrenarche, a specific adrenal cortical androgen-stimulating hormone has not been identified. Evidence also exists for a role for adrenarche in behavior, skeletal maturation, and postpubertal well-being. Adrenarche is influenced by sex and race, and some of this variation may be related to the insulin and insulin-like growth factor (IGF) signaling pathways. In addition, children with premature and exaggerated adrenarche may be predisposed to certain diseases later in life.

Adrenal androgens and aging.

Dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEAS) are the principal C19 steroids produced by the human adrenals. Their plasma levels decline to less than 20% of their maximal value during aging. Because these steroids appear to play a role in the maintenance of immunity, musculoskeletal integrity, and cardiovascular health, age-associated declines in adrenal androgen production may contribute to decreased immune function, osteoporosis, and atherosclerosis. Production of DHEA and DHEAS has been localized to the zona reticularis (ZR) of the adrenal cortex and can be modulated by intra-adrenal or extra-adrenal modulators. Extra-adrenal modulators include corticotropin-releasing hormone (CRH), adrenocorticotropic hormone (ACTH), insulin, and transforming growth factor beta (TGF-beta). Intra-adrenal regulators include enzymes and proteins involved in the steroidogenic pathway, specifically 17,20 lyase activity and DHEA sulfotransferase (DST). The natural histories of the emergence of adrenal androgen production and the ontogeny of the ZR appear to correlate closely. In addition, aging results in a decline in adrenal androgen production, and our data suggest a parallel diminution in the area represented by the ZR. This decline in the ZR may result from apoptosis, cellular and humoral immunity, or a reduction in the replicative capacity of the cells of the ZR.

Modulación descendente de la información nociceptiva (I) / Descending modulation of nociceptive information (I)

Las regiones cerebrales involucradas en la modulación intrínseca del estímulo doloroso incluyen a la corteza somatosensorial, el hipotálamo, el mesencéfalo, al sustancia gris periacueductal y el rafe magnus. La estimulación eléctrica de estas regiones produce analgesia en animales y en humanos .Desde estas estructuras centrales las fibras descienden por el cordón dorsolateral a la médula espinal, enviando proyecciones a las láminas I y V. La activación del sistema analgésico descendente tiene un efecto directo en la integración y el paso de la información nociceptiva en el asta posterior. El bloqueo del cordón dorsolateral aumenta la respuesta de las neuronas nociceptivas activadas por el estímulo doloroso. El sistema descendente tiene tres componentes mayores, interrelacionados funcionalmente: el sistema opioide, el sistema noradrenérgico y el sistema serotoninérgico. El sistema opioide integrado por los precursores opiáceos y sus respectivos péptidos está presente en la amígdala, el hipotálamo, la sustancia gris periacueductal, el rafe magnus y el asta posterior. Las neuronas noradrenérgicas se proyectan desde el locus coeruleus y otras células noradrenérgicas hasta el asta posterior, a través del cordón dorsolateral. La estimulación de estas áreas produce analgesia, al igual que la administración directa o intratecal de agonistas de los receptores alfa 2. En el sistema serotoninérgico, las neuronas del rafe magnus contienen serotonina y envían sus proyecciones a la médula por el cordón dorsolateral. El bloqueo farmacológico o la lesión del rafe magnus puede reducir los efectos de la morfina y la administración de serotonina en la médula produce analgesia. (AU)

Pituitary adenylate cyclase-activating polypeptide and PACAP receptor expression and function in the rat adrenal gland.

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a basic 38-amino acid peptide, which acts through three main G protein-coupled VIP/PACAP receptor subtypes, called PAC1, VPAC1 and VPAC2. We have investigated the expression and function of PACAP and its receptors in the rat adrenal gland. Reverse transcription (RT)-polymerase chain reaction (PCR) and radioimmune assay (RIA) allowed the detection of PACAP expression as mRNA and protein exclusively in adrenal medulla (AM). RT-PCR and quantitative autoradiography, using [(125)I]PACAP and selective VIP/PACAP receptor ligands, demonstrated the expression of PAC1 only in AM, and VPAC1 and VPAC2 in both AM and zona glomerulosa (ZG), PACAP receptor expression being absent in zona fasciculata/reticularis (ZF/R). PACAP38 concentration-dependently increased aldosterone secretion from dispersed ZG cells and catecholamine secretion from AM tissue, the maximal effective concentration being 10(-7) M. ZF/R cells did not display any secretory response to PACAP38. Aldosterone response of ZG cells to 10(-7) M PACAP38 was unaffected by the PAC1-antagonist (A) PACAP(6-38), and significantly decreased by the VPAC1-A [Ac-His(1),D-Phe(2),Lys(15),Arg(16)]VIP(3-7) GRF(8-27)-NH(2). Catecholamine response of AM tissue to PACAP38 was reduced, but not abolished, by both PAC1-A and VPAC1-A. The VPAC2 agonist (ago) Ro25-1553 elicited sizeable secretory responses from both ZG cells and AM tissue. PACAP38 (10(-7) M) evoked a marked rise in cyclic-AMP (cAMP) and inositol-1,4,5-triphosphate (IP3) production by ZG cells and AM tissue. cAMP response of ZG cells was lowered by VPAC1-A, and that of AM tissue by both PAC1-A and VPAC1-A. IP3 response of ZG cells and AM tissue was unaffected by PAC1-A and decreased by VPAC1-A. VPAC2-ago did not affect cAMP release, but raised IP3 production by both ZG cells and AM tissue. Aldosterone response of ZG cells and catecholamine response of AM tissue to PACAP38 (10(-7) M) were reduced by the adenylate cyclase (AC) and phospholipase-C (PLC) inhibitors (I) SQ-22536 and U-73122, as well as by the protein kinase (PK)A-I H-89 and PKC-I calphostin-C. Conversely, the secretory responses of both ZG and AM preparations to VPAC2-ago were annulled by PLC-I, lowered by PKC-I, and unaffected by either AC-I or PKA-I. Collectively, our findings allow us to conclude that in the rat adrenals: i) PACAP biosynthesis exclusively occurs in the AM; ii) ZG cells are provided with functional VPAC1 and VPAC2 receptors, whose activation by PACAP evokes a moderate aldosterone response; iii) AM cells possess all the subtypes of VIP/PACAP receptors, whose activation by PACAP elicits a marked catecholamine response; and iv) PAC1 receptors are coupled to the AC-dependent cascade, VPAC1 receptors to both the AC- and PLC-dependent cascades, and VPAC2 receptors exclusively to the PLC-dependent cascade.

Aging effects on the secretion of corticosterone in male rats.

BACKGROUND: The effects of aging on zona fasciculatareticularis (ZFR) cell function in male rats were studied. METHODS: Male rats 3, 6, and 22 months of age were divided into three groups, and collagenase-dispersed ZFR cells were isolated and incubated with adrenocorticotropin (ACTH), 8-bromo-adenosine 3':5'-cyclic monophosphate (8-Br-cAMP), ovine prolactin (oPRL), deoxycorticosterone (DOC), or 3-isobutyl-l-methylxanthine (IBMX) at 37 degrees C for 1 hour. Corticosterone concentrations in cell media and cAMP production in ZFR cells were measured by radioimmunoassay. Protein expression of PRL receptor in ZFR cells were analyzed by Western blot. RESULTS: The basal levels of plasma and medium corticosterone were higher in 22-month-old than in 3-month-old rats. In contrast, the release of corticosterone in response to ACTH, 8-Br-cAMP, and DOC was lower in 22-month-old than in 3- and 6-month-old rats. Aging decreased the oPRL-stimulated release of corticosterone but increased the protein expression of PRL receptor in ZFR cells. The basal levels of intracellular cAMP increased with age. However, the ACTH-stimulated production of intracellular cAMP decreased in 22-month-old compared with 3- or 6-month-old rats. The increment of cAMP accumulation in ZFR cells after administration of IBMX was greater in 22-month-old than in 3- or 6-month-old rats. CONCLUSIONS: These results suggest that the aging effects on the production of corticosterone in rat ZFR cells is associated with change of the generation of cAMP, the activity of 11 beta-hydroxylase and the protein expression of PRL receptor.

Interleukin-3 and interleukin-6 stimulate bovine adrenal cortisol secretion through different pathways.

Several interleukins have been reported to play a major role in the regulation of steroid secretion at all three levels of the hypothalamic-pituitary-adrenal axis. The objective of this study was to investigate the effect of interleukin-3 (IL-3) and interleukin-6 (IL-6) on cortisol secretion of bovine adrenocortical cells in primary culture under serum-free conditions. Both IL-3 and IL-6 stimulated basal cortisol secretion dose-dependently to a similar extent at a similar time course. After incubation with IL-3 or IL-6 at concentrations of 100 microg/l, a maximum 4.1-fold increase of the cortisol secretion was reached after 12 h (P<0.01). Coincubation of IL-3 and IL-6 (100 microg/l) revealed no significant synergism. To elucidate a possible involvement of arachidonic acid metabolites in the signal transduction, we coincubated IL-3 or IL-6 together with the cyclo-oxygenase inhibitor indometacin or the lipoxygenase inhibitor nordihydroguaiaretic acid (NDGA). Coincubation with indometacin completely abolished the stimulatory effect of IL-6 but had no effect on IL-3 stimulated cortisol secretion. In contrast, specific inhibition of the lipoxygenase system by nordihydroguaiaretic acid blocked IL-3 stimulated steroidogenesis while the effect of IL-6 was not affected. Neither IL-3 nor IL-6 altered cAMP levels significantly, whereas ACTH significantly induced cAMP levels in parallel to its steroidogenic effect. In conclusion, our data indicate that IL-3 and IL-6 stimulate the steroid secretion of bovine adrenocortical cells to a similar extent and with a similar time course. However, the effects of IL-3 and IL-6 are mediated through different, cAMP-independent pathways. While the stimulatory effect of IL-3 seems to be dependent on the lipoxygenase pathway, the effect of IL-6 on adrenocortical cortisol secretion is mediated through the cyclo-oxygenase pathway.

Lymphocytes stimulate dehydroepiandrosterone production through direct cellular contact with adrenal zona reticularis cells: a novel mechanism of immune-endocrine interaction.

Adrenal androgen production was reduced by 80% in patients receiving T lymphocyte-suppressive medications compared to that in age-matched controls. In vitro, however, neither tacrolimus nor cyclosporin A reduced dehydroepiandrosterone (DHEA) release by adrenocortical cells. Therefore, we examined the potential role of lymphocytes in adrenal androgen production, using cocultures of human T lymphocytes and adrenocortical primary or transformed cells. Co-cultures led to a 4-fold elevation of DHEA levels (490.4 +/- 94.8% over basal), which was greater than the increase observed after the addition of maximal concentrations of ACTH (117.4 +/- 14.8%). Separation of cells by semipermeable membranes abolished this effect, and transfer of leukocyte-conditioned medium had little androgen-stimulating effect. These data suggested that the observed stimulation of androgen secretion required cell contact rather than soluble paracrine factor(s). Furthermore, we examined human adrenal glands for the presence of T lymphocytes and contact between these cells and steroid-secreting cells of the zona reticularis. Indeed, T lymphocytes expressing CD4 and CD8 antigens were present within human adrenal zona reticularis by immunohistochemical subtyping. Electron microscopic analyses demonstrated direct cell-cell contact between T lymphocytes and adrenocortical cells in situ. This study provides evidence for a novel mechanism of immune-endocrine interactions of direct T lymphocyte-adrenocortical cell contact-mediated stimulation of adrenal androgen secretion.