Transforming growth factor beta 1: an autocrine regulator of adrenocortical steroidogenesis

Adropin Stimulates Proliferation and Inhibits Adrenocortical Steroidogenesis in the Human Adrenal Carcinoma (HAC15) Cell Line

Adropin is a multifunctional peptide hormone encoded by the ENHO (energy homeostasis associated) gene. It plays a role in mechanisms related to increased adiposity, insulin resistance, as well as glucose, and lipid metabolism. The low adropin levels are strongly associated with obesity independent insulin resistance. On the other hand, overexpression or exogenous administration of adropin improves glucose homeostasis. The multidirectional, adropin-related effects associated with the regulation of metabolism in humans also appear to be attributable to the effects of this peptide on the activity of various elements of the endocrine system including adrenal cortex. Therefore, the main purpose of the present study was to investigate the effect of adropin on proliferation and secretory activity in the human HAC15 adrenal carcinoma cell line. In this study, we obtained several highly interesting findings. First, GPR19, the main candidate sensitizer of adrenocortical cells to adropin, was expressed in HAC15 cells. Moreover, GPR19 expression was relatively stable and not regulated by ACTH, forskolin, or adropin itself. Our findings also suggest that adropin has the capacity to decrease expression levels of steroidogenic genes such as steroidogenic acute regulatory protein (StAR) and CYP11A1, which then led to a statistically significant inhibition in cortisol and aldosterone biosynthesis and secretion. Based on whole transcriptome study and research involving transforming growth factor (TGF)-β type I receptor kinase inhibitor we demonstrated that attenuation of steroidogenesis caused by adropin is mediated by the TGF-β signaling pathway likely to act through transactivation mechanism. We found that HAC15 cells treated with adropin presented significantly higher proliferation levels than untreated cells. Using specific intracellular inhibitors, we showed that adropin stimulate proliferation via ERK1/2 and AKT dependent signaling pathways. We have also demonstrated that expression of GPR19 is elevated in adrenocortical carcinoma in relation to normal adrenal glands. High level of GPR19 expression in adrenocortical carcinoma may constitute a negative prognostic factor of disease progression.

Correlation between selected angiogenic markers and prognosis in pediatric adrenocortical tumors: Angiogenic markers and prognosis in pediatric ACTs

BACKGROUND/PURPOSE

Pediatric adrenocortical tumor (ACT) remains a challenging disease. Tumor weight and disease stage are still the most used indicators to prognosis and guidance of clinical decisions. Histology has not added meaningful data for risk stratification and management. ACT is metabolically active, highly vascularized, locally invasive and has the propensity to produce distant metastasis. Our objective was to correlate the expression of vascular endothelial growth factor (VEGF) and intratumoral microvessel density (MVD) with clinical and prognostic aspects in pediatric ACT.

PROCEDURE

In 27 tumors, immunohistochemical expression of VEGF, CD105 (endoglin) and CD34 was analyzed. MVD was determined by CD34 and CD105 antibodies. MVD and VEGF expression was correlated with clinical characteristics and outcome. Normal pediatric glands were used as controls.

RESULTS

Endoglin MVD was significantly higher and CD34 MVD was significantly lower in ACT than control. The VEGF expression did not differ between groups. Cytoplasmic staining for endoglin was correlated with hypertension in ACT. Endoglin MVD greater than 1 mv/field, CD34 MVD less than 32 mv/field and VEGF expression levels above 4.8% were associated with clinical and biological indicators of poor prognosis.

CONCLUSIONS

Endoglin and CD34 MVD values are potential histological markers to refine the histologic classification of pediatric ACT.

Vascular endothelial growth factor receptor inhibitor SU5416 suppresses lymphocyte generation and immune responses in mice by increasing plasma corticosterone

Inhibitors of vascular endothelial growth factor and its receptors (VEGFRs) are attractive therapeutic candidates for cancer treatment. One such small molecule VEGFR inhibitor, SU5416, limits angiogenesis in vivo and is widely used for investigating VEGFR signaling in tumor pathophysiology. Herein, we describe novel actions of SU5416 on the immune system. Treatment of mice with SU5416 for 3 days induced significant reductions in size and cellularity of peripheral lymph nodes. Interestingly, SU5416 did not affect initial lymphocyte localization to peripheral lymph nodes but did reduce lymphocyte accumulation during long-term migration assays. Treatment with SU5416 also induced severe loss of double-positive thymocytes resulting in thymic atrophy and a reduction in peripheral B cells. Furthermore, immune responses following immunization were reduced in mice treated with SU5416. Findings of thymic atrophy and reduced weight gain during SU5416 treatment suggested elevated corticosterone levels. Indeed, a significant 5-fold increase in serum corticosterone was found 4 hours after treatment with SU5416. Importantly, adrenalectomy negated the effects of SU5416 treatment on primary immune tissues, and partial reversal of SU5416-induced changes was observed following blockade of glucocorticoid receptors. SU5416 has been reported to inhibit the activation of latent transforming growth factor (TGF)-β, a cytokine involved in the regulation of glucocorticoid release by the adrenal glands. Interestingly, treatment with a TGF-β receptor inhibitor, showed a similar phenotype as SU5416 treatment, including elevated serum corticosterone levels and thymic atrophy. Therefore, these results suggest that SU5416 induces glucocorticoid release directly from the adrenal glands, possibly by inhibition of TGF-β activation.

Steroidogenic factor-1 is required for TGF-beta3-mediated 17beta-estradiol synthesis in mouse ovarian granulosa cells

The TGF-β superfamily members are indicated to play key roles in ovarian follicular development, such as granulosa cell proliferation, estrogens, and progesterone production. However, little is known about the roles of TGF-β3 in follicular development. In this study, we found that TGF-β3 was predominantly expressed in granulosa cells of mouse ovarian follicles, and it significantly promoted 17β-estradiol (E(2)) release in a dose-dependent manner. The orphan nuclear receptor steroidogenic factor-1 (SF-1) was required in TGF-β3-induced Cyp19a1 (a key rate-limiting enzyme for estrogen biosynthesis) expression and E(2) release. Additionally, TGF-β3 enhanced the binding of SF-1 to endogenous ovary-specific Cyp19a1 type II promoter, as evidenced by chromatin immunoprecipitation assays. The enhanced effect of SF-1 by TGF-β3 may be mediated through functional interactions between SF-1 and mothers against decapentaplegic homolog (Smad)3 (a mediator of TGF-β signaling pathway), because disruption of the interaction abolished the synergistic effects of SF-1, Smad3, and TGF-β3 on Cyp19a1 mRNA expression. RNA interference and chromatin immunoprecipitation studies also demonstrated that Smad3 was required for SF-1 binding to Cyp19a1 type II promoter and activation of Cyp19a1. Smad3 thus acts as a point of convergence that involves integration of SF-1 and TGF-β signaling in affecting E(2) production. Taken together, our data provide mechanistic insights into the roles of SF-1 in TGF-β3-mediated E(2) synthesis. Understanding of potential cross-points between extracellular signals affecting estrogen production will help to discover new therapeutic targets in estrogen-related diseases.

Adrenocortical carcinoma: a clinician's update

Adrenocortical carcinoma is a rare heterogeneous neoplasm with an incompletely understood pathogenesis and a poor prognosis. Previous studies have identified overexpression of insulin-like growth factor 2 (IGF-2) and constitutive activation of β-catenin as key factors involved in the development of adrenocortical carcinoma. Most patients present with steroid hormone excess, for example Cushing syndrome or virilization, or abdominal mass effects, but a growing proportion of patients with adrenocortical carcinoma (currently >15%) is initially diagnosed incidentally. No general consensus on the diagnostic and therapeutic measures for adrenocortical carcinoma exists, but collaborative efforts, such as international conferences and networks, including the European Network for the Study of Adrenal Tumors (ENSAT), have substantially advanced the field. In patients with suspected adrenocortical carcinoma, a thorough endocrine and imaging work-up is recommended to guide the surgical approach aimed at complete resection of the tumor. To establish an adequate basis for treatment decisions, pathology reports include the Weiss score to assess malignancy, the resection status and the Ki67 index. As recurrence is frequent, close follow-up initially every 3 months is mandatory. Most patients benefit from adjuvant mitotane treatment. In metastatic disease, mitotane is the cornerstone of initial treatment, and cytotoxic drugs should be added in case of progression. Results of a large phase III trial in advanced adrenocortical carcinoma are anticipated for 2011 and will hopefully establish a benchmark therapy. New targeted therapies, for example, IGF-1 receptor inhibitors, are under investigation and may soon improve current treatment options.

Molecular genetics of adrenocortical tumours, from familial to sporadic diseases

Adrenal masses can be detected in up to 4% of the population, and are mostly of adrenocortical origin. Adrenocortical tumours (ACTs) may be responsible for excess steroid production and, in the case of adrenocortical cancers, for morbidity or mortality due to tumour growth. Our understanding of the pathogenesis of ACTs is more limited than that for other tumours. However, studies of the genetics of ACTs have led to major advances in this field in the last decade. The identification of germline molecular defects in the hereditary syndrome responsible for ACTs has facilitated progress. Indeed, similar molecular defects have since been identified as somatic alterations in sporadic tumours. The familial diseases concerned are Li-Fraumeni syndrome, which may be due to germline mutation of the tumour-suppressor gene TP53 and Beckwith-Wiedemann syndrome, which is caused by dys-regulation of the imprinted IGF-II locus at 11p15. ACTs also occur in type 1 multiple endocrine neoplasia (MEN 1), which is characterized by a germline mutation of the menin gene. Cushing's syndrome due to primary pigmented nodular adrenocortical disease (PPNAD) has been observed in Carney complex patients presenting inactivating germline PRKAR1A mutations. Interestingly, allelic losses at 17p13 and 11p15 have been demonstrated in sporadic adrenocortical cancer and somatic PRKAR1A mutations have been found in secreting adrenocortical adenomas. More rarely, mutations in Gs protein (gsp) and the gene for ACTH receptor have been observed in ACTs. The genetics of another group of adrenal diseases that can lead to adrenal nodular hyperplasia -- congenital adrenal hyperplasia (CAH) and glucocorticoid-remediable aldosteronism (GRA) -- have also been studied extensively. This review summarizes recent advances in the genetics of ACTs, highlighting both improvements in our understanding of the pathophysiology and the diagnosis of these tumours.

Transforming growth factor beta2 induced pleurodesis is not inhibited by corticosteroids

BACKGROUND

Talc and tetracyclines induce pleurodesis by directly injuring the pleura. The injury results in intense inflammation which subsequently leads to fibrosis. Corticosteroids can inhibit talc pleurodesis by reducing the inflammatory process. We hypothesised that transforming growth factor beta2 (TGFbeta2), a fibrogenic cytokine with immunomodulatory functions, could induce effective pleurodesis without generating significant pleural inflammation and therefore remain effective despite co-administration of corticosteroids.

METHODS

Thirty rabbits were divided into two groups. Rabbits in the steroid group received weekly intramuscular injections of triamcinolone diacetate (0.8 mg/kg). Ten rabbits in each group were given 5.0 microg TGFbeta2 intrapleurally via a chest tube while the remaining five received 1.7 microg TGFbeta2. Pleurodesis was graded macroscopically after 14 days from 1 (none) to 8 (>50% symphysis).

RESULTS

TGFbeta2 produced excellent pleurodesis at both 5.0 microg and 1.7 microg doses. The pleural effusions produced after the injection were low in all inflammatory markers. No significant differences were seen between the steroid group and controls in macroscopic pleurodesis scores (7.2 (1.3) v 7.1 (1.2)), levels of inflammatory markers in the pleural fluids (leucocyte 1107 (387)/mm(3) v 1376 (581)/mm(3); protein 3.1 (0.3) mg/dl v 2.9 (0.3) mg/dl, and LDH 478 (232) IU/l v 502 (123) IU/l), and the degree of microscopic pleural fibrosis and pleural inflammation.

CONCLUSIONS

TGFbeta2 can induce effective pleurodesis and remains effective in the presence of high dose parenteral corticosteroids.

Transforming growth factor β2 induced pleurodesis is not inhibited by corticosteroids

BACKGROUND

Talc and tetracyclines induce pleurodesis by directly injuring the pleura. The injury results in intense inflammation which subsequently leads to fibrosis. Corticosteroids can inhibit talc pleurodesis by reducing the inflammatory process. We hypothesised that transforming growth factor β2 (TGFβ2), a fibrogenic cytokine with immunomodulatory functions, could induce effective pleurodesis without generating significant pleural inflammation and therefore remain effective despite co-administration of corticosteroids.

METHODS

Thirty rabbits were divided into two groups. Rabbits in the steroid group received weekly intramuscular injections of triamcinolone diacetate (0.8 mg/kg). Ten rabbits in each group were given 5.0 μg TGFβ2 intrapleurally via a chest tube while the remaining five received 1.7 μg TGFβ2. Pleurodesis was graded macroscopically after 14 days from 1 (none) to 8 (>50% symphysis).

RESULTS

TGFβ2produced excellent pleurodesis at both 5.0 μg and 1.7 μg doses. The pleural effusions produced after the injection were low in all inflammatory markers. No significant differences were seen between the steroid group and controls in macroscopic pleurodesis scores (7.2 (1.3)v 7.1 (1.2)), levels of inflammatory markers in the pleural fluids (leucocyte 1107 (387)/mm3v 1376 (581)/mm3; protein 3.1 (0.3) mg/dl v 2.9 (0.3) mg/dl, and LDH 478 (232) IU/l v 502 (123) IU/l), and the degree of microscopic pleural fibrosis and pleural inflammation.

CONCLUSIONS

TGFβ2can induce effective pleurodesis and remains effective in the presence of high dose parenteral corticosteroids.

Pathogenesis of adrenocortical incidentalomas and genetic syndromes associated with adrenocortical neoplasms

The study of genetic syndromes associated with adrenocortical tumors (Beckwith-Wiedemann, Li-Fraumeni, McCune-Albright, Carney, and multiple endocrine neoplasia type 1) has shed light on the molecular basis of tumorigenesis. Abnormalities at the 11p15 locus appear as crucial and frequent events found specifically in malignant, sporadic tumors, leading to overexpression of a growth-promoting factor and loss of expression of tumor suppressor genes. In benign tumors, the cAMP pathway can be exacerbated in an ACTH-independent manner when various membrane receptors of the seven transmembrane superfamily are "illegitimately" expressed.

Different immunohistochemical patterns of TGF-beta1 expression in benign and malignant adrenocortical tumours

OBJECTIVE

Transforming growth-factor beta1 (TGF-beta1) influences a number of specific functions of adrenocortical cells in several animal species. The aim of our study was to evaluate by immunohistochemical analysis the presence and distribution of TGF-beta1 in normal adrenal tissue and in different adrenal tumours.

PATIENTS

We analysed 8 functioning (5 adenomas and 3 carcinomas) and 15 non functioning (6 adenomas and 9 carcinomas) adrenal tumours and 6 normal adrenal glands.

RESULTS

In normal adrenal glands, the glomerulosa and the reticularis zones displayed diffuse cytoplasmic staining, while the fasciculata zone was almost completely negative. Functioning adenomas displayed cytoplasmic staining restricted to compact cells while in nonfunctioning adenomas, prevalently composed by clear cells, no staining was observed. Overall, adrenal carcinomas were characterized by the lack of cytoplasmic positivity and by sporadic positive cells around vessels both in functioning and in nonfunctioning tumours.

CONCLUSIONS

TGF-beta1 expression is associated with active steroid secretion in normal adrenal tissue, as well as in benign cortical adenomas, while this relationship is lost in primary adrenal malignancies. These data provide indirect evidence for a regulatory role played by TGF-beta1 on steroid secretory pathways.

Long-term administration of adrenocorticotropin modulates the expression of IGF-I and TGF-beta 1 mRNAs in the rat adrenal cortex

The effects of long-term adrenocorticotropin (ACTH) therapy on the expression of IGF-I and TGF-beta 1 on rat adrenal cortex was investigated. ACTH (0.1 mg/kg/day) or saline as control was injected intraperitoneally in 5-week-old Wistar rats every day for 4 weeks. ACTH significantly increased adrenal weight (P < 0.05) and serum corticosterone (P < 0.05). Competitive RT-PCR analysis on the adrenocortical mRNA showed increased IGF-I (P < 0.01) at 4 weeks of ACTH and increased TGF-beta 1 (P < 0.01) at 1 week of ACTH compared the control group. ACTH also significantly increased proliferating cell nuclear antigen mRNA level (P < 0.01), at 4 weeks of treatment, which correlated with IGF-I level (P < 0.01), but correlated negatively with ACTH-stimulated TGF-beta 1 level (P < 0.05). There was a weak correlation between IGF-I and serum corticosterone (P < 0.05), and between TGF-beta 1 mRNA levels and serum corticosterone concentration (P < 0.05). Histologically, ACTH induced hypertrophy in the zona fasciculata cells and increased the clear cells containing lipid deposits. Immunohistochemistry showed that IGF-I peptide was mainly expressed in the periphery of the zona fasciculata at 4 weeks of ACTH therapy, while the same therapy caused a slight increase in TGF-beta 1 expression in the same area. Our results show that an increase in adrenocortical growth resulting from ACTH treatment is associated with an increase in IGF-I mRNA expression but only a transient increase in TGF-beta 1 mRNA expression.

Regulation of the hypothalamic-pituitary-adrenal axis by cytokines: actions and mechanisms of action

Glucocorticoids are hormone products of the adrenal gland, which have long been recognized to have a profound impact on immunologic processes. The communication between immune and neuroendocrine systems is, however, bidirectional. The endocrine and immune systems share a common "chemical language," with both systems possessing ligands and receptors of "classical" hormones and immunoregulatory mediators. Studies in the early to mid 1980s demonstrated that monocyte-derived or recombinant interleukin-1 (IL-1) causes secretion of hormones of the hypothalamic-pituitary-adrenal (HPA) axis, establishing that immunoregulators, known as cytokines, play a pivotal role in this bidirectional communication between the immune and neuroendocrine systems. The subsequent 10-15 years have witnessed demonstrations that numerous members of several cytokine families increase the secretory activity of the HPA axis. Because this neuroendocrine action of cytokines is mediated primarily at the level of the central nervous system, studies investigating the mechanisms of HPA activation produced by cytokines take on a more broad significance, with findings relevant to the more fundamental question of how cytokines signal the brain. This article reviews published findings that have documented which cytokines have been shown to influence hormone secretion from the HPA axis, determined under what physiological/pathophysiological circumstances endogenous cytokines regulate HPA axis activity, established the possible sites of cytokine action on HPA axis hormone secretion, and identified the potential neuroanatomic and pharmacological mechanisms by which cytokines signal the neuroendocrine hypothalamus.

Transforming growth factor beta1 decreases cholesterol supply to mitochondria via repression of steroidogenic acute regulatory protein expression

Transforming growth factor-betas (TGF-betas) constitute a family of dimeric proteins that affect growth and differentiation of many cell types. TGF-beta1 has also been proposed to be an autocrine regulator of adrenocortical steroidogenesis, acting mainly by decreasing the expression of cytochrome P450c17. Here, we demonstrate that TGF-beta1 has a second target in bovine adrenocortical cells, namely the steroidogenic acute regulatory protein (StAR). Indeed, supplying cells with steroid precursors revealed that TGF-beta1 inhibited two steps in the steroid synthesis pathway, one prior to pregnenolone production and another corresponding to P450c17. More specifically, TGF-beta1 inhibited pregnenolone production but neither the conversion of 25-hydroxycholesterol to pregnenolone nor P450scc activity. Thus, TGF-beta1 must decrease the cholesterol supply to P450scc. We therefore examined the effect of TGF-beta1 on the expression of StAR, a mitochondrial protein implicated in intramitochondrial cholesterol transport. TGF-beta1 decreased the steady state level of StAR mRNA in a time- and concentration-dependent manner. This inhibition occurs at the level of StAR transcription and depends on RNA and protein synthesis. It is likely that the TGF-beta1-induced decrease of StAR expression that we report here may be expanded to other steroidogenic cells in which a decrease of cholesterol accessibility to P450scc by TGF-beta1 has been hypothesized.

Peptide growth factors and the adrenal cortex

Increasing evidence suggests that the actions of classical stimulants of adrenocortical growth and function, such as ACTH or dietary sodium restriction, may partially be mediated via locally produced regulators. Several peptide growth factors, such as basic fibroblast growth factor, insulin-like growth factors, and transforming growth factor-beta 1, have emerged in recent years as multifunctional molecules that typically play such regulatory roles. Adrenocortical cells are highly responsive to these growth factors, in particular in the regulation of cell growth and differentiated functions, such as steroidogenesis. In addition, growth factor expression in the adrenal cortex has been shown to be regulated by physiological stimulants. The spatial expression, release, and activation of these growth factors may, therefore, locally mediate or amplify the actions of the hypothalamo-pituitary axis and the renin-angiotensin system on adrenocortical proliferation, differentiation, and steroidogenesis.

Repression of transforming growth factor beta 1 protein by antisense oligonucleotide-induced increase of adrenal cell differentiated functions

Transforming growth factor beta 1 (TGF beta 1) is a potent inhibitor of several differentiated functions in bovine adrenal fasciculata cells (BAC). In addition, these cells express and secrete this factor. To determine whether this peptide plays an autocrine role in BAC, cells were transfected with 10 microM unmodified sense (SON) or antisense (AON) oligonucleotide complementary to the translation initiation region of the TGF beta 1 mRNA in an attempt to inhibit TGF beta 1 protein synthesis. We investigated first, the cellular uptake, the stability, and the intracellular distribution of 32P-labeled TGF beta 1 AON and SON; and second, the effects of both oligonucleotides on BAC specific functions. We have demonstrated that in BAC, the TGF beta 1 AON uptake reached a plateau after 8 h of transfection (16% of the radioactivity added) and remained fairly constant for at least 24 h. In contrast, the uptake of TGF beta 1 SON reached a plateau after 2 h of transfection (8% of the radioactivity added), remained stable for only 3 h, and then declined. After 8 h of transfection, followed by 44 h of culture without oligonucleotides, the intracellular level of TGF beta 1 AON was still high with about 8% of the radioactivity added, whereas that of TGF beta 1 SON represented only 1.2%. Moreover, AON was present in the cytoplasmic and nuclear fractions, and it was hybridized in both compartments. However, TGF beta 1 SON was present mainly in the cytoplasmic fraction where it was not hybridized. Neither TGF beta 1 AON nor SON modified TGF beta 1 mRNA levels; however, TGF beta 1 AON, but not SON, caused the disappearance of TGF beta 1 immunoreactivity inside the cells. Finally, the steroidogenic responsiveness of BAC transfected with TGF beta 1 AON increased about 2-fold, and this was associated with a 2-fold increase of the mRNA levels of both cytochrome P450 17 alpha-hydroxylase and 3 beta-hydroxysteroid dehydrogenase. Neither TGF beta 1 SON nor a scrambled oligonucleotide containing the same number of G nucleotides as TGF beta 1 AON had any effect on these parameters. Thus, these studies demonstrate that TGF beta 1 has an autocrine inhibitory effect on BAC differentiated functions, an effect that can be overcome by TGF beta 1 AON.

Regulation of primary response and specific genes in adrenal cells by peptide hormones and growth factors

Using cultured bovine adrenal fasciculata cells (BAC), we investigated the effects of two hormones, corticotropin (ACTH) and angiotensin II (Ang-II) and two growth factors, insulin-like growth factors I (IGF-I) and transforming growth factor beta 1 (TGF beta 1), on the mRNA levels of nuclear proto-oncogenes of the Fos and Jun families and on the mRNA levels of genes expressed in BAC coding for ACTH and AT1 receptors, cytochrome P450scc and P450 17 alpha and 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD). ACTH and IGF-1 increased c-fos and jun-B mRNA levels early with later increases in the levels of mRNA for the ACTH receptor and the three steroidogenic enzymes, and enhanced steroidogenic responses to both ACTH and Ang-II. In contrast, Ang-II increased mRNA coding for the three proto-oncogenes (cfos, c-jun, and jun-B), decreased those for P450 17 alpha and 3 beta-HSD, and caused marked homologous and heterologous steroidogenic desensitization. TGF beta 1 increased only jun-B mRNA and markedly reduced BAC-differentiated functions and steroidogenic responsiveness to both ACTH and Ang-II. The long-term effects of ACTH on human adrenal fasciculata cells were comparable with those observed in BAC, whereas the long term effects of Ang-II and TGF beta 1 were different from those observed in BAC. Whether these species-specific differences are related to a different effect of these factors on proto-oncogene expression is not yet known.

Receptor binding of transforming growth factor-beta by human fetal adrenal cells

We have shown previously that transforming growth factor beta 1 (TGF-beta 1) is antimitotic for human fetal adrenal (HFA) cells in vitro and that this effect can be partially blocked by adrenocorticotropic hormone (ACTH). In the present study, we sought to determine whether ACTH might interfere with TGF-beta 1 action by means of reducing TGF-beta 1 binding to adrenal cells. We incubated adrenal cells with 50 pM 125I-labeled TGF-beta 1 for 15 min to 3 h at 4 degree C and found that the binding of 125I-labeled TGF-beta 1 increased with time and could be inhibited in a dose-dependent manner by non-labeled TGF-beta 1 (0.05-10 nM), but not with other relevant cytokines: IL6, TNF alpha,IGF-I, IGF-II, TGF-alpha, and EGF. Pretreatment of HFA cells with ACTH (0.009-900 nM) for 4-24 h significantly increased specific 125I-labeled TGF-beta 1 binding compared to that in untreated cells; maximal increases in binding were achieved with 0.9 nM ACTH. This effect of ACTH could be mimicked by treatment of adrenal cells with dibutyryl cAMP (1 mM) or forskolin (10 microM). Scatchard analysis of data from ACTH-treated cells suggest the presence of two populations of TGF-beta 1 binding sites with different affinity and capacity of binding for the ligand.(ABSTRACT TRUNCATED AT 250 WORDS)

Type beta 1 transforming growth factor is an inhibitor of 3 beta-hydroxysteroid dehydrogenase isomerase in mouse adrenal tumor cell line Y1

In the Y1 mouse adrenal tumor cell line, the 3 beta-hydroxysteroid dehydrogenase isomerase enzyme (3 beta-HSD) which catalyzes the transformation of 3 beta-hydroxy-5-ene steroids to 3-keto-4-ene steroids is active. The effect of type beta 1 transforming growth factor (TGF beta 1), a potent modulator of adrenocortical differentiated functions, on the 3 beta-HSD enzyme was studied. Four isoforms of 3 beta-HSD yielding proteins of different mobility on SDS-PAGE were previously detected in the mouse; whereas only one form was present in the mouse adrenal, we detected two isoforms in the Y1 cells. An inhibition of the basal enzymatic activity was observed after TGF beta 1 treatment which was correlated with a decrease in 3 beta-HSD protein (both isoforms) and mRNA levels.

Regulation of corticotropin and steroidogenic enzyme mRNAs in human fetal adrenal cells by corticotropin, angiotensin-II and transforming growth factor beta 1

Using cultured human fetal adrenal cells, we have investigated the basal secretion of cortisol and dehydroepiandrosterone sulfate (DHAS) and the effect of corticotropin (ACTH), angiotensin-II (A-II) and transforming growth factor beta 1 (TGF beta 1) on the secretion of these steroids and on the mRNA levels of ACTH receptor (ACTHR), cytochrome P-450scc (cholesterol side-chain cleavage), P450 17 alpha (17 alpha-hydroxylase/17-20 lyase) and 3 beta-HSD (3 beta-hydroxysteroid dehydrogenase). The basal DHAS/cortisol ratio declined progressively between 12.5 and 21 weeks. ACTH treatment enhanced the secretion of cortisol and to a lesser extent that of DHAS, and increased the steroidogenic response to an acute stimulation with ACTH. These changes were associated with increased mRNA levels of ACTHR and of the steroidogenic enzymes. A-II treatment also increased the secretion of both DHAS and cortisol, but less than ACTH, enhanced the responsiveness to ACTH and increased ACTHR, P450scc and P450 17 alpha mRNA levels. In contrast, TGF beta 1 alone or together with ACTH decreased DHAS secretion, but not cortisol secretion. Moreover, TGF beta 1 had no effect on ACTHR and P450scc mRNA levels, decreased by about 50% the mRNA levels of P450 17 alpha both in the absence or presence of ACTH, but enhanced the stimulatory effects of ACTH on 3 beta-HSD mRNA. These results, along with those previously reported, suggest that both A-II and TGF beta may play a role in fetal adrenal function. In addition, they show that the effects of both peptides are qualitatively different from, even sometimes opposite to, those previously reported in bovine and ovine adrenal cells.

Effects of transforming growth factor-beta on human fetal adrenal steroid production

Transforming growth factor-beta (TGF-beta) was found to inhibit basal and ACTH-stimulated steroid production by cultured human fetal adrenal cells. The inhibitory effects of TGF-beta were both time and dose-dependent. Inhibition of basal dehydroepiandrosterone sulfate (DS) production usually was noted only after 3 or more days of treatment with > or = 0.1 ng TGF-beta/ml. The inhibitory effects of 1 ng/ml TGF-beta on ACTH-stimulated DS production were more striking than those on cortisol production by both fetal zone and neocortical cells. TGF-beta also was found to interfere with DS and cortisol production by fetal zone cells in response to forskolin and dibutyryl cAMP. TGF-beta interfered with ACTH stimulation of cytochrome P450(17) alpha mRNA in fetal zone and neocortex cells. These results are suggestive that TGF-beta differentially inhibits DS and cortisol production by human fetal adrenal cells and that the site of TGF-beta action on steroidogenesis may be distal to the generation of cAMP. Such results, along with those of others, are suggestive that TGF-beta may play an autocrine/paracrine role in the human adrenal.

Synergistic induction of alpha 2-macroglobulin synthesis by fibroblast growth factor-2 and transforming growth factor beta 1 in bovine adrenocortical cells

We report here that basic fibroblast growth factor (FGF-2), a potent mitogen for adrenocortical cells, stimulates the expression of alpha 2-macroglobulin by these cells at a transcriptional level and is synergistic with TGF beta 1 for this effect. This is supported by the following observations: (i) Treatment of adrenocortical cells by FGF-2 resulted in a time-dependent and dose-dependent increase of alpha 2M synthesis, (ii) FGF-2 did not modify alpha 2M secretion rate; (iii) The induction of alpha 2M synthesis by FGF-2 was not observed in the presence of the transcription inhibitor DRB; (iv) The amount of alpha 2M mRNA was increased by 2 to 3 fold under either FGF-2 or TGF beta 1 treatment; (v) Optimal doses of TGF beta and FGF-2 synergistically increased alpha 2M synthesis. Since alpha 2M is a growth factor-binding protein, its regulation by FGF-2 may represent an important feedback mechanism controlling the bioactivity of autocrine regulators (FGF-2, TFG beta) of adrenocortical functions.

Transforming growth factor beta 1 and adrenocorticotropin differentially regulate the synthesis of adrenocortical cell heparan sulfate proteoglycans and their binding of basic fibroblast growth factor

Adrenocortical differentiated functions are under the control of both endocrine hormones such as ACTH and local factors such as transforming growth factor beta (TGF beta) or basic fibroblast growth factor (bFGF). Besides their regulatory actions on the synthesis of corticosteroids, these two classes of factors also exert some important effects on the cellular environment. We have examined here the regulation by ACTH and TGF beta of adrenocortical cell proteoglycan synthesis and secretion. Under basal conditions, adrenocortical cells synthesized and secreted several species of sulfated proteoglycans, 80% of them being recovered in solution in the culture medium. When analyzed by ion exchange chromatography, the cell extracts and the media from cells metabolically labeled with 35S-sulfate were found to contain two and three species of radioactive sulfated proteoglycans, respectively. All species were proteoheparan-sulfates. Treatment of adrenocortical cells with TGF beta 1 or ACTH resulted in a significant increase of the incorporation of 35S into both secreted and cell-associated proteoglycans. ACTH stimulated more than three times the amount of secreted proteoglycans eluting from DEAE-Trisacryl as peak B, whereas TGF beta preferentially increased the amount of peak C. No important modification of the size of the synthesized proteoglycans was observed. The subpopulation of heparan sulfate proteoglycans capable to bind bFGF was also largely increased after ACTH or TGF beta treatment and paralleled the variation in overall proteoheparan sulfate synthesis. Thus those effects of TGF beta and ACTH on proteoglycan synthesis may participate in an increased ability of adrenocortical cells to bind and respond to bFGF.

Inhibition of adrenocortical steroidogenesis by alpha 2-macroglobulin is caused by associated transforming growth factor beta

alpha 2-Macroglobulin (alpha 2M) is the major protein secreted by bovine adrenocortical cells in primary culture and its synthesis is stimulated by transforming growth factor beta (TGF beta). We investigated here the effects of alpha 2M on adrenocortical steroidogenesis. We observed that commercial preparations of bovine plasma alpha 2M were able to mimic the inhibitory action of TGF beta on adrenocortical cortisol production, with the same specificity of action directed at the steroid 17 alpha-hydroxylation step. This inhibition was time-dependent and dose-dependent (50% inhibition observed with 2 mg/ml alpha 2M). Acid/ethanol extracts of alpha 2M appeared to retain the full inhibitory activity of alpha 2M. Anti-TGF beta antibodies could reverse the inhibition caused by the acid/ethanol extract but not that caused by native alpha 2M. Taken together, these results indicate that the inhibition of adrenocortical steroidogenesis induced by alpha 2M is caused by associated TGF beta. We estimated that 2 mg of alpha 2M contained approximately 0.1 ng of TGF beta, corresponding to a molar ratio of 1/700,000 between TGF beta and alpha 2M. These results also clearly indicate that the alpha 2M-TGF beta complexes are biologically active on adrenocortical cells, suggesting that these cells possess the enzymatic equipment that can activate the latent alpha 2M-TGF beta complexes.

Growth factor regulation of adrenal cortex growth and function

The control of adrenal cortex growth in vivo during development or under certain stress conditions is still very poorly understood at the molecular level. Some information can be collected however from in vitro experiments. Acidic and basic FGF appear to be the most potent mitogens, so far, for primary cultures of adult adrenocortical cells, whereas EGF can also stimulate growth of fetal cells. Several growth factors have emerged in the recent years as multifunctional molecules that play important regulatory functions on adrenocortical steroidogenesis. These include EGF, IL-1, insulin, IGF-1 and TGF beta. In certain cases (e.g. IGF-1, TGF beta), these factors participate in autocrine loops of regulation. The differential expression, release and activation of these factors might locally regulate the steroidogenic action of the hormonal signals delivered through the hypothalamo-pituitary-adrenal axis.