Steroidogenic factor 1 gene transcription is inhibited by transforming growth factor beta

Sirtuin 7 is essential for the survival and synthesis of oestrogen in yak (Bos grunniens) cumulus granulosa cells

Cumulus granulosa cells (CGCs) are a type of important ovarian somatic cells that carries out various functions related to oogenesis, follicular development and embryogenesis. The study on the development and function of CGCs facilitates the understanding of reproductive regulation in female animals. Sirtuin 7 (SIRT7) is a member of the sirtuin family of NAD+-dependent deacetylases mediating numerous biological processes. In this study, we detected the localization of SIRT7 in yak ovaries as well as explored the function of SIRT7 in yak CGCs. The results revealed that the SIRT7 protein was mainly localized in the cytoplasm of oocytes, granulosa cells and theca cells. The knockdown of SIRT7 in yak CGCs repressed cell proliferation and impacted the expressions of several apoptosis-related genes. Furthermore, oestrogen synthesis was also inhibited in SIRT7-deficient yak CGCs. The expressions of several sterogenesis-related genes decreased significantly following SIRT7 knockdown. In addition, the lack of SIRT7 in yak CGCs resulted in decreased levels of the TGFB/SMAD family members TGFB1, TGFBR1 SMAD2 and SMAD3. Moreover, the activation of the TGFB/SMAD pathway by adding TGFB/SMAD pathway activator SRI-011381 partially rescued the level of oestrogen secreted by SIRT7-deficient yak CGCs, as well as the expressions of steroidogenesis-related genes NR5A1 and CYP19A1. This research is the first to focus on the role of SIRT7 in yak ovary, and the outcomes offer new insights into the mechanism governing yak reproduction.

Adrenal Cortex Development and Maintenance: Knowledge Acquired From Mouse Models

The adrenal cortex is an endocrine organ organized into concentric zones that are specialized to produce specific steroid hormones essential for life. The development and maintenance of the adrenal cortex are complex, as a fetal adrenal is first formed from a common primordium with the gonads, followed by its separation in a distinct primordium, the invasion of the adrenal primordium by neural crest-derived cells to form the medulla, and finally its encapsulation. The fetal cortex is then replaced by a definitive cortex, which will establish zonation and be maintained throughout life by regeneration relying on the proliferation, centripetal migration, and differentiation of several stem/progenitor cell populations whose activities are sex-specific. Here, we highlight the advances made, using transgenic mouse models, to delineate the molecular mechanisms regulating these processes.

Range of SHH signaling in adrenal gland is limited by membrane contact to cells with primary cilia

The signaling protein Sonic Hedgehog (SHH) is crucial for the development and function of many vertebrate tissues. It remains largely unclear, however, what defines the range and specificity of pathway activation. The adrenal gland represents a useful model to address this question, where the SHH pathway is activated in a very specific subset of cells lying near the SHH-producing cells, even though there is an abundance of lipoproteins that would allow SHH to travel and signal long-range. We determine that, whereas adrenal cells can secrete SHH on lipoproteins, this form of SHH is inactive due to the presence of cosecreted inhibitors, potentially explaining the absence of long-range signaling. Instead, we find that SHH-producing cells signal at short range via membrane-bound SHH, only to receiving cells with primary cilia. Finally, our data from NCI-H295R adrenocortical carcinoma cells suggest that adrenocortical tumors may evade these regulatory control mechanisms by acquiring the ability to activate SHH target genes in response to TGF-β.

TGFB1 represses the expression of SF1 and LRH1 to inhibit E2 production in rat LCs

Leydig cells (LCs) in the adult testis have been identified as the major sites of oestrogen production, which is crucial for mammalian germ cell differentiation. Our previous work showed that transforming growth factor beta 1 (TGFB1) inhibits estradiol (E₂) secretion via down-regulating Cyp19 gene expression in mature rat LCs. However, the mechanism remains unclear. In the present study, the effects of TGFB1 on the expression levels of steroidogenic factor 1 (SF1), liver receptor homolog 1 (LRH1), cAMP response element-binding protein (CREB) and cAMP responsive element modulator (CREM) were evaluated both in primary cultured LCs and in rat testis. The involvement of TGFB1 signalling in the regulation of SF1 and LRH1 expression was then validated by applying the inhibitor of the TGFB type 1 receptor (TGFBR1) SB431542. Moreover, the expression of CYP19 in testicular LCs was investigated and the production of E₂ in testicular interstitial fluid (TIF) was measured. The results showed that TGFB1 especially down-regulated the expression levels of SF1 and LRH1 both in primary cultured LCs and in rat testis. The down-regulations of TGFB1 in the production of E₂ in TIF and the expression of CYP19 in testicular LCs were also observed in vivo These inhibitory effects could be reversed by TGFBR1 inhibitor SB431542. Our findings suggest that TGFB1 may act through the canonical signalling pathway involving ALK5 to restrain SF1 and LRH1 accumulation and eventually attenuate Cyp19 transcription and oestrogen production in LCs.

Transforming growth factor-β1 and diabetic nephropathy

Transforming growth factor-β1 (TGF-β1) is established to be involved in the pathogenesis of diabetic nephropathy. The diabetic milieu enhances oxidative stress and induces the expression of TGF-β1. TGF-β1 promotes cell hypertrophy and extracellular matrix accumulation in the mesangium, which decreases glomerular filtration rate and leads to chronic renal failure. Recently, TGF-β1 has been demonstrated to regulate urinary albumin excretion by both increasing glomerular permeability and decreasing reabsorption in the proximal tubules. TGF-β1 also increases urinary excretion of water, electrolytes and glucose by suppressing tubular reabsorption in both normal and diabetic conditions. Although TGF-β1 exerts hypertrophic and fibrogenic effects in diabetic nephropathy, whether suppression of the function of TGF-β1 can be an option to prevent or treat the complication is still controversial. This is partly because adrenal production of mineralocorticoids could be augmented by the suppression of TGF-β1. However, differentiating the molecular mechanisms for glomerulosclerosis from those for the suppression of the effects of mineralocorticoids by TGF-β1 may assist in developing novel therapeutic strategies for diabetic nephropathy. In this review, we discuss recent findings on the role of TGF-β1 in diabetic nephropathy.

Transforming growth factor beta1 and aldosterone

PURPOSE OF REVIEW

It is well established that blocking the renin-angiotensin-aldosterone system (RAAS) is effective for the treatment of cardiovascular and renal complications in hypertension and diabetes mellitus. Although the induction of transforming growth factor beta1 (TGFbeta1) by components of the RAAS mediates the hypertrophic and fibrogenic changes in cardiovascular-renal complications, it is still controversial as to whether TGFbeta1 can be a target to prevent such complications. Here, we review recent findings on the role of TGFbeta1 in fluid homeostasis, focusing on the relationship with aldosterone.

RECENT FINDINGS

TGFbeta1 suppresses the adrenal production of aldosterone and renal tubular sodium reabsorption. We have generated mice with TGFbeta1 mRNA expression graded in five steps, from 10 to 300% of normal, and found that blood pressure and plasma volume are negatively regulated by TGFbeta1. Notably, the 10% hypomorph exhibits primary aldosteronism and sodium and water retention due to markedly impaired urinary excretion of water and electrolytes.

SUMMARY

These results identify TGFbeta signalling as an important counterregulatory system against aldosterone. Understanding the molecular mechanisms for the suppressive effects of TGFbeta1 on adrenocortical and renal function may further our understanding of primary aldosteronism, as well as assist in the development of novel therapeutic strategies for hypertension.

The role of transforming growth factor β1 in the regulation of blood pressure

Although human association studies suggest a link between polymorphisms in the gene encoding transforming growth factor (TGF) β1 and differing blood pressure levels, a causative mechanism for this correlation remains elusive. Recently we have generated a series of mice with graded expression of TGFβ1, ranging from approximately 10% to 300% compared to normal. We have found that blood pressure and plasma volume are negatively regulated by TGFβ1. Of note, the 10% hypomorph exhibits primary aldosteronism and markedly impaired urinary excretion of water and electrolytes. We here review previous literature highlighting the importance of TGFβ signaling as a natriuretic system, which we postulate is a causative mechanism explaining how polymorphisms in TGFβ1 could influence blood pressure levels.

TGF-β1 regulation of estrogen production in mature rat Leydig cells

BACKGROUND

Besides androgens, estrogens produced in Leydig cells are also crucial for mammalian germ cell differentiation. Transforming growth factor-β1 (TGF-β1) is now known to have multiple effects on regulation of Leydig cell function. The objective of the present study is to determine whether TGF-β1 regulates estradiol (E2) synthesis in adult rat Leydig cells and then to assess the impact of TGF-β1 on Cx43-based gap junctional intercellular communication (GJIC) between Leydig cells.

METHODOLOGY/PRINCIPAL FINDINGS

Primary cultured Leydig cells were incubated in the presence of recombinant TGF-β1 and the production of E2 as well as testosterone (T) were measured by RIA. The activity of P450arom was addressed by the tritiated water release assay and the expression of Cyp19 gene was evaluated by Western blotting and real time RT-PCR. The expression of Cx43 and GJIC were investigated with immunofluorescence and fluorescence recovery after photo-bleaching (FRAP), respectively. Results from this study show that TGF-β1 down-regulates the level of E2 secretion and the activity of P450arom in a dose-dependent manner in adult Leydig cells. In addition, the expression of Cx43 and GJIC was closely related to the regulation of E2 and TGF-β1, and E2 treatment in turn restored the inhibition of TGF-β1 on GJIC.

CONCLUSIONS

Our results indicate, for the first time in adult rat Leydig cells, that TGF-β1 suppresses P450arom activity, as well as the expression of the Cyp19 gene, and that depression of E2 secretion leads to down-regulation of Cx43-based GJIC between Leydig cells.

Knockdown of SF-1 and RNF31 affects components of steroidogenesis, TGFβ, and Wnt/β-catenin signaling in adrenocortical carcinoma cells

The orphan nuclear receptor Steroidogenic Factor-1 (SF-1, NR5A1) is a critical regulator of development and homeostasis of the adrenal cortex and gonads. We recently showed that a complex containing E3 ubiquitin ligase RNF31 and the known SF-1 corepressor DAX-1 (NR0B1) interacts with SF-1 on target promoters and represses transcription of steroidogenic acute regulatory protein (StAR) and aromatase (CYP19) genes. To further evaluate the role of SF-1 in the adrenal cortex and the involvement of RNF31 in SF-1-dependent pathways, we performed genome-wide gene-expression analysis of adrenocortical NCI-H295R cells where SF-1 or RNF31 had been knocked down using RNA interference. We find RNF31 to be deeply connected to cholesterol metabolism and steroid hormone synthesis, strengthening its role as an SF-1 coregulator. We also find intriguing evidence of negative crosstalk between SF-1 and both transforming growth factor (TGF) β and Wnt/β-catenin signaling. This crosstalk could be of importance for adrenogonadal development, maintenance of adrenocortical progenitor cells and the development of adrenocortical carcinoma. Finally, the SF-1 gene profile can be used to distinguish malignant from benign adrenocortical tumors, a finding that implicates SF-1 in the development of malignant adrenocortical carcinoma.

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.

The relation of adiponectin and tumor necrosis factor alpha levels between endothelial nitric oxide synthase, angiotensin-converting enzyme, transforming growth factor beta, and tumor necrosis factor alpha gene polymorphism in adrenal incidentalomas

OBJECTIVE

The aim of our study was to demonstrate demographic characteristics, presence of inflammatory markers, distribution of angiotensin-converting enzyme (ACE), tumor necrosis factor (TNF), endothelial nitric oxide synthase (eNOS) genotypes and relations among these parameters in these patients and control subjects.

RESEARCH DESIGN AND METHODS

Study samples were collected from 50 patients with adrenal mass and 30 control groups. The eNOS, ACE, TNF-alpha, transforming growth factor (TGF)-beta genes polymorphisms, TNF-alpha, adiponectin levels were analysed in 50 unrelated Turkish patients with a diagnosis of adrenal incidentaloma (AI).

RESULTS

There was statistically significant difference between TNF-alpha levels of patient and controls (p=0.048). We have not detected the connection between TGF-beta, TNF-alpha, ACE, eNOS gene polymorphism with serum TNF-alpha and adiponectin levels. In this study, we demonstrated that there were significant differences for ACE genotypes in the patients when compared to the controls (p<0.05). The percentages of the ID, DD, II genotypes for ACE gene polymorphism in the patients group were 30.0, 13.0, 7.0%, respectively.

CONCLUSIONS

According to different cases of eNOS, TGF-beta, ACE, and TNF-alpha gene genotypes; no statistical significant difference was found between basal cortisol, ACTH, DHEAS, metanephrine, renin, aldosterone, normetanephrine, 17-hydroxyprogesterone, 1 mg low-dose dexamethasone suppression test-cortisol response and AI size. In this study, I/D genotype was determined to be statistically higher in ACE gene in patients with AI (p=0.014).

SMAD3 inhibits SF-1-dependent activation of the CYP17 promoter in H295R cells

Cytochrome P450c17, encoded by the CYP17 gene, is a component of 17alpha-hydroxylase/17,20 lyase which catalyses 17alpha-hydroxylation of pregnenolone or progesterone, required for glucocorticosteroid and androgen synthesis. It has been reported that transforming growth factor beta (TGF-beta) decreases both basal and cAMP-stimulated levels of CYP17 mRNA, but the mechanism of TGF-beta action on CYP17 expression remains unknown. We investigated an inhibitory effect of TGF-beta on CYP17 expression in H295R cells using constructs containing the CYP17 promoter region fused with the luciferase gene. In the H295R cells, TGF-beta decreased endogenous SF-1 level and inhibited activity of the 300 bp fragment of CYP17 promoter, which was stimulated by coexpression of SF-1. Overexpression of SMAD3 caused an inhibition of SF-1-stimulated CYP17 promoter activity, whereas overexpression of SMAD7 was ineffective. In conclusion, our results suggest that the inhibitory action of TGF-beta on CYP17 transcription involve at least two mechanisms: SMAD3 dependent inactivation of CYP17 promoter activity and repression of SF-1 expression.