TGF-beta1 stimulates expression of the aromatase (CYP19) gene in human osteoblast-like cells and THP-1 cells

A Role for TGFβ Signaling in Preclinical Osteolytic Estrogen Receptor-Positive Breast Cancer Bone Metastases Progression

While tumoral Smad-mediated transforming growth factor β (TGFβ) signaling drives osteolytic estrogen receptor α-negative (ER-) breast cancer bone metastases (BMETs) in preclinical models, its role in ER+ BMETs, representing the majority of clinical BMETs, has not been documented. Experiments were undertaken to examine Smad-mediated TGFβ signaling in human ER+ cells and bone-tropic behavior following intracardiac inoculation of estrogen (E2)-supplemented female nude mice. While all ER+ tumor cells tested (ZR-75-1, T47D, and MCF-7-derived) expressed TGFβ receptors II and I, only cells with TGFβ-inducible Smad signaling (MCF-7) formed osteolytic BMETs in vivo. Regulated secretion of PTHrP, an osteolytic factor expressed in >90% of clinical BMETs, also tracked with osteolytic potential; TGFβ and E2 each induced PTHrP in bone-tropic or BMET-derived MCF-7 cells, with the combination yielding additive effects, while in cells not forming BMETs, PTHrP was not induced. In vivo treatment with 1D11, a pan-TGFβ neutralizing antibody, significantly decreased osteolytic ER+ BMETs in association with a decrease in bone-resorbing osteoclasts at the tumor-bone interface. Thus, TGFβ may also be a driver of ER+ BMET osteolysis. Moreover, additive pro-osteolytic effects of tumoral E2 and TGFβ signaling could at least partially explain the greater propensity for ER+ tumors to form BMETs, which are primarily osteolytic.

Estrogen disorders: Interpreting the abnormal regulation of aromatase in granulosa cells (Review)

Ovarian granulosa cells (GCs) are the most important source of estrogen. Therefore, aromatase (estrogen synthase), which is the key enzyme in estrogen synthesis, is not only an important factor of ovarian development, but also the key to estrogen secretion by GCs. Disorders of the ovarian estrogen secretion are more likely to induce female estrogen-dependent diseases and fertility issues, such as ovarian cancer and polycystic ovary syndrome. Hence, aromatase is an important drug target; treatment with its inhibitors in estrogen-dependent diseases has attracted increasing attention. The present review article focuses on the regulation and mechanism of the aromatase activity in the GCs, as well as the specific regulation of aromatase promoters. In GCs, follicle-stimulating hormone (FSH) is dependent on the cyclic adenosine monophosphate (cAMP) pathway to regulate the aromatase activity, and the regulation of this enzyme is related to the activation of signaling pathways, such as phosphatidylinositol 3-kinase (PI3K) and extracellular signal-regulated kinase (ERK). In addition, endocrine-disrupting substance and other related factors affect the expression of aromatase, which eventually create an imbalance in the estrogen secretion by the target tissues. The present review highlights these useful factors as potential inhibitors for target therapy.

Platelets induce increased estrogen production through NF-κB and TGF-β1 signaling pathways in endometriotic stromal cells

Endometriosis is estrogen-dependent disorder. Two theories provide the explanations for the increased estrogen production. One is the feed-forward loop model linking inflammation and estrogen production. The more recent model evokes the tissue hypoxia resulting from endometrial debris detached and then regurgitated to the peritoneal cavity. Both models tacitly assume that everything occurs within the endometriotic stromal cells, seemingly without the need for exogenous factors. This study was undertaken to investigate as whether platelets may be responsible for local estrogen overproduction. We employed in vitro experimentation that evaluated the 17β-estradiol (E₂) levels in endometriotic stromal cells treated with activated platelets, and the genes and protein expression levels of StAR, HSD3B2, aromatase, and HSD17B1, as well as their upstream genes/proteins such as NF-κB, TGF-β1, HIF-1α, SF-1 and phosphorylated CREB. In addition, we conducted 2 animal experimentations using platelet depletion/infusion and also neutralization of NF-κB and TGF-β1, followed by immunohistochemistry analysis of involved in StAR, HSD3B2, aromatase, and HSD17B1, as well as SF-1 and p-CREB. We found that treatment of endometriotic stromal cells by activated platelets increase the E₂ production by 4.5 fold, and concomitant with increased gene and protein expression of StAR, HSD3B2, aromatase, and HSD17B1, the four genes/enzymes important to estrogen synthesis, along with their upstream genes HIF-1α, SF-1 and phosphorylated CREB. Moreover, platelets activate these genes through the activation of NF-κB and/or TGF-β1, and antagonism of either signaling pathway can abolish the induction of the 4 genes and thus increased estrogen production. The two animal experimentations confirmed these changes. Thus, platelets increase the E₂ production in endometriotic stromal cells through upregulation of StAR, HSD3B2, aromatase, and HSD17B1 via the activation of NF-κB and/or TGF-β1. These findings provide a yet another compelling piece of evidence that endometriotic lesions are indeed wounds undergoing repeated tissue injury and repair. They strongly indicate that non-hormonal therapeutics for endometriosis is theoretically viable, with anti-platelet therapy being one promising avenue.

Estrogen receptor beta in prostate cancer: friend or foe?

Prostate cancer is the commonest, non-cutaneous cancer in men. At present, there is no cure for the advanced, castration-resistant form of the disease. Estrogen has been shown to be important in prostate carcinogenesis, with evidence resulting from epidemiological, cancer cell line, human tissue and animal studies. The prostate expresses both estrogen receptor alpha (ERA) and estrogen receptor beta (ERB). Most evidence suggests that ERA mediates the harmful effects of estrogen in the prostate, whereas ERB is tumour suppressive, but trials of ERB-selective agents have not translated into improved clinical outcomes. The role of ERB in the prostate remains unclear and there is increasing evidence that isoforms of ERB may be oncogenic. Detailed study of ERB and ERB isoforms in the prostate is required to establish their cell-specific roles, in order to determine if therapies can be directed towards ERB-dependent pathways. In this review, we summarise evidence on the role of ERB in prostate cancer and highlight areas for future research.

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.

Blockade of transforming growth factor-beta (TGFβ) signaling inhibits osteoblastic tumorigenesis by a novel human prostate cancer cell line

BACKGROUND

The skeleton is the most common site of prostate cancer metastasis, which often results in osteoblastic lesions. The role of transforming growth factor-beta (TGFβ) signaling in prostate cancer-induced osteoblastic metastasis is not clear. We investigated the role of TGFβ signaling in prostate cancer-induced bone metastasis using a novel human prostate cancer cell line, PacMetUT1.

METHODS

We injected PacMetUT1/Luc-GFP cells in male nude mice by intracardiac and intratibia injections and then investigated the effect of TGFβ signaling abrogation on osteoblastic tumor growth and incidence in vivo by using fluorescence and bioluminescence imaging analysis and quantifying bone and tumor volume by histomorphometry analysis. Osteoclasts were counted using TRAP assay.

RESULTS

Osteoblastic bone metastasis in skull, rib, and femur was detected after 10-16 weeks of intracardiac injection of the PacMetUT1 cells. Stable knockdown of TGFβ1 with an shRNA resulted in decreased tumor incidence and bone formation when the cells were directly injected into the tibiae. Systemic administration of either a small inhibitor of TGFβ type I receptor kinase or a pan TGFβ binding protein (BG(E) RII) also decreased bone tumor growth and osteoblastic bone formation in vivo after 7 weeks of treatment.

CONCLUSIONS

Our results for the first time indicate that blockade of TGFβ signaling in the PacMetUT1 model significantly inhibits osteoblastic bone formation and tumor incidence. Thus, TGFβ signaling pathway may be a viable target for the prevention and treatment of prostate cancer-induced bone metastasis.

Insulin-like growth factor I enhances the expression of aromatase P450 by inhibiting autophagy

Aromatase, a key enzyme of estrogen biosynthesis, is transcriptionally regulated by many growth factors. IGF-I enhances aromatase activity in a variety of cells, but the mechanism of action has not been determined. We herein report our finding of a novel mechanism of action for IGF-I. IGF-I enhanced the dexamethasone (DEX)-induced aromatase activity by 30% in serum-starved THP-1 cells. The increase was associated with a corresponding increase in the level of aromatase protein but not with any change in the mRNA level. Metabolic labeling experiments revealed that IGF-I inhibited the degradation of aromatase. We identified pepstatin A as the most effective inhibitor of aromatase degradation by in vitro assay. Using a nontoxic concentration of pepstatin A, we examined IGF-I's action on aromatase distribution in microsomes and lysosomes. In the presence of pepstatin A, DEX caused an increase in the amount of aromatase in both microsomes and lysosomes, and IGF-I attenuated the DEX-induced accumulation of aromatase in lysosomes and, conversely, enhanced its accumulation in the microsomes. The addition of serum abolished the IGF-I-induced changes. The transport from microsome to lysosome was fluorescently traced in cells using a recombinant aromatase. IGF-I selectively reduced the aromatase signal in the lysosomes. Finally, we observed that IGF-I enhanced the aromatase activity by 50% as early as 1 h after treatment; furthermore, rapamycin, an enhancer of autophagy, completely negated the effect of IGF-I on the enzyme. These results indicate that IGF-I enhances aromatase by the inhibition of autophagy.

The gene for aromatase, a rate-limiting enzyme for local estrogen biosynthesis, is a downstream target gene of Runx2 in skeletal tissues

The essential osteoblast-related transcription factor Runx2 and the female steroid hormone estrogen are known to play pivotal roles in bone homeostasis; however, the functional interaction between Runx2- and estrogen-mediated signaling in skeletal tissues is minimally understood. Here we provide evidence that aromatase (CYP19), a rate-limiting enzyme responsible for estrogen biosynthesis in mammals, is transcriptionally regulated by Runx2. Consistent with the presence of multiple Runx2 binding sites, the binding of Runx2 to the aromatase promoter was demonstrated in vitro and confirmed in vivo by chromatin immunoprecipitation assays. The bone-specific aromatase promoter is activated by Runx2, and endogenous aromatase gene expression is upregulated by Runx2 overexpression, establishing the aromatase gene as a target of Runx2. The biological significance of the Runx2 transcriptional control of the aromatase gene is reflected by the enhanced estrogen biosynthesis in response to Runx2 in cultured cells. Reduced in vivo expression of skeletal aromatase gene and low bone mineral density are evident in Runx2 mutant mice. Collectively, these findings uncover a novel link between Runx2-mediated osteoblastogenic processes and the osteoblast-mediated biosynthesis of estrogen as an osteoprotective steroid hormone.

Transforming growth factor-beta inhibits aromatase gene transcription in human trophoblast cells via the Smad2 signaling pathway

BACKGROUND

Transforming growth factor-beta (TGF-beta) is known to exert multiple regulatory functions in the human placenta, including inhibition of estrodial production. We have previously reported that TGF-beta1 decreased aromatase mRNA levels in human trophoblast cells. The objective of this study was to investigate the molecular mechanisms underlying the regulatory effect of TGF-beta1 on aromatase expression.

METHODS

To determine if TGF-beta regulates aromatase gene transcription, several reporter constructs containing different lengths of the placental specific promoter of the human aromatase gene were generated. JEG-3 cells were transiently transfected with a promoter construct and treated with or without TGF-beta1. The promoter activity was measured by luciferase assays. To examine the downstream signaling molecule mediating the effect of TGF-beta on aromatase transcription, cells were transiently transfected with dominant negative mutants of TGF-beta type II (TbetaRII) and type I receptor (ALK5) receptors before TGF-beta treatment. Smad2 activation was assessed by measuring phophorylated Smad2 protein levels in cytosolic and nuclear fractions. Smad2 expression was silenced using a siRNA expression construct. Finally, aromatase mRNA half-life was determined by treating cells with actinomycin D together with TGF-beta1 and measuring aromatase mRNA levels at various time points after treatment.

RESULTS AND DISCUSSION

TGF-beta1 inhibited the aromatase promoter activity in a time- and dose-dependent manner. Deletion analysis suggests that the TGF-beta1 response element resides between -422 and -117 nucleotides upstream from the transcription start site where a Smad binding element was found. The inhibitory effect of TGF-beta1 was blocked by dominant negative mutants of TbetaRII and ALK5. TGF-beta1 treatment induced Smad2 phosphorylation and translocation into the nucleus. On the other hand, knockdown of Smad2 expression reversed the inhibitory effect of TGF-beta1 on aroamtase transcription. Furthermore, TGF-beta1 accelerated the degradation of aromatase mRNA.

CONCLUSION

Our results demonstrate that TGF-beta1 exerts regulatory effects on aromatase gene at both transcriptional and post-transcriptional levels. The transcriptional regulation of aromatase gene by TGF-beta1 is mediated by the canonical TGF-beta pathway involving TbetaRII, ALK5 and Smad2. These findings further support the role of TGF-beta1 in regulating human placental functions and pregnancy.

A new SNP in a negative regulatory region of the CYP19A1 gene is associated with lumbar spine BMD in postmenopausal women

Osteoporosis is a common disease of bone possessing a strong genetic component. Cytochrome P450 aromatase, which is encoded by the CYP19A1 gene, converts androgens to estradiol. Considerable evidence suggests that extragonadal estrogens play an important role in determining bone mineral density (BMD) in postmenopausal women, and, among them, those synthesized in bone cells may also be important for the determination of bone phenotype. Therefore, CYP19A1 is an excellent candidate gene for osteoporosis. Since a region upstream of exon I.3, including exon I.6, was identified as containing repressor elements of promoter pII, we conducted a search for SNPs in this region of CYP19A1. Two SNPs [Aro1(rs4775936) and Aro2] located in exon I.6 and promoter I.6, respectively, were identified and their association with BMD analyzed in a cohort of 256 Spanish postmenopausal women. Aro1(rs4775936), but not Aro2, was associated with lumbar spine BMD (P = 0.029). Homozygotes AA (16% of the women) exhibited significantly higher lumbar spine BMD, compared with GG or GA individuals. Therefore, this study describes the Aro1 polymorphism which lies within a regulatory region and which may be a functional polymorphism, partially responsible for the bone phenotype it is associated with.

Aromatase and regulation of bone remodeling

Estrogens play a key role in regulating bone mineralization. Bone tissue expresses the enzymes that metabolize estrogens, as well as the alpha and beta receptors that mediate responses to estrogens. After the menopause, estrogen secretion by the ovaries is promptly replaced by production within tissues, which occurs chiefly via aromatization of adrenal steroids. Therefore, aromatase activity is a major determinant of estrogen activity in postmenopausal women. Studies are beginning to shed light on the mechanisms by which aromatase activity influences bone remodeling.

Aromatase in testis: expression and role in male reproduction

The mammalian testis serves two main functions: production of spermatozoa and synthesis of steroids, among them estrogens are the end products obtained from the irreversible transformation of androgens by aromatase (P450arom). In the rat the pattern of P450arom expression differs among the testicular somatic cell types according to age; in addition, we have shown that gonocytes, spermatogonia, spermatocytes (preleptotene, pachytene), spermatids and spermatozoa, represent an important source of estrogens; the expression of aromatase is three-fold higher in pachytene spermatocyte (PS) compared to gonocytes. In man both Leydig cells and immature germ cells (PS and round spermatids, RS) as well as ejaculated spermatozoa expressed a biologically active aromatase revealed as a single band of 49 kDa on western blots. Up today P450arom has been demonstrated in male germ cells of all mammals so far studied (mice, bank vole, bear and monkey). The aromatase gene is highly conserved and is unique in humans; its expression is regulated in a cell-specific manner via the alternative use of various promoters located in the first exon. Nevertheless, data concerning the regulation of P450arom especially in germ cells are scarce. We have demonstrated that TGFbeta inhibits the expression of Cyp19 in PS and RS via the SMAD pathway although TNFalpha exerts a stimulatory role in PS, which is amplified in presence of dexamethasone. It is noteworthy that dexamethasone alone exerts a positive effect on Cyp19 expression in PS and a negative one in RS. Cyclic AMP is also a positive regulator of P450arom gene expression in germ cells. In addition, we have shown that androgens and estrogens modulate Cyp19 gene expression, whatever the testicular cell type studied, which favored the presence of androgens and estrogens responsive elements on the Cyp19 gene promoter(s). Moreover, in presence of seminiferous tubules conditioned media, the amount of aromatase transcripts is increased in Leydig cells, therefore, suggesting that other locally produced modulators are involved in the regulation of the aromatase gene expression and among them the liver receptor homolog-1 (LRH-1) from germ cells origin is concerned. Using RACE-PCR we have confirmed that promoter II directs the expression of aromatase gene, whatever the testicular cell type studied in the rat but the involvement of another promoter, such as PI.4 is suggested. Finally, the aromatase gene is constitutively expressed both in somatic and germ cells of the testis and the identification of the promoter(s) concerned as well as their detailed regions which direct(s) the expression of Cyp19 gene is obviously very important but largely unknown especially according to the ontogeny of the male gonad.

Inhibition of ossification in vivo and differentiation of osteoblasts in vitro by tributyltin

Tributyltin is ubiquitous in the environment and an endocrine disruptor for many wildlife species. However, minimal information is available regarding the effect of this chemical on bone formation. When tributyltin chloride (TBT) (1mg/kg body weight) was administered subcutaneously to pregnant mice at 10, 12, and 14 days post coitus (dpc), fetuses at 17.5 days post coitus revealed the inhibition of calcification of supraoccipital bone. In contrast, 1mg/kg body weight monobutyltin trichloride (MBT) did not affect the fetal skeleton. Therefore, we examined the effects of TBT and its metabolites (dibutyltin dichloride, DBT, and MBT) on bone metabolism using rat calvarial osteoblast-like cells (ROB cells). The viability of ROB cells was not affected by the exposure of the cells to 10(-10) to 10(-7)M TBT. However, TBT reduced the activity of alkaline phosphatase (ALPase) and the rate of deposition of calcium of ROB cells. In addition, the expression levels of mRNA for ALPase and osteocalcin, which are markers of osteoblastic differentiation, were depressed by the treatment with TBT. TBT inhibited ALPase activity and the deposition of calcium to a greater extent than did DBT. MBT had no effect on the osteoblast differentiation of ROB cells. Tributyltin is known to inhibit the activity of aromatase. However, the aromatase inhibitor aminoglutethimide did not reproduce the inhibitory effects of TBT on osteoblast differentiation. Our findings indicate that TBT might have critical effects on the formation of bone both in vivo and in vitro although its action mechanism is not clarified.

Regulation of aromatase gene expression in Leydig cells and germ cells

The ability of the testis to convert irreversibly androgens into estrogens is related to the presence of a microsomal enzymatic complex named aromatase. Although somatic cells and germ cells (GC) have the capacity to produce estrogens the regulation of the CYP19 gene expression in adult rat testicular cells and specially in freshly purified Leydig cells, pachytene spermatocytes (PS) and round spermatids (RS) is not fully understood. In the present study we have analyzed the putative effects of steroid hormones, transforming growth factor beta (TGFbeta), cytokine (tumor necrosis factor alpha, TNFalpha) and dexamethasone (Dex) on CYP19 expression in these purified testicular cells from adult rat. In parallel the biological role of seminiferous tubules and Sertoli cells conditioned media on the expression of aromatase was studied. Using a highly specific quantitative competitive RT-PCR we established that testosterone (T) enhances CYP19 gene expression in Leydig cells and germ cells, and augments the estradiol outputs. The non-aromatizable androgen 5alpha-DHT induces the same effect as T on P450 aromatase (P450arom) gene expression but was inefficient on the estradiol output. In PS and RS an inhibitory effect on CYP19 gene transcription was observed with TGFbeta (1 ng/ml) alone or in combination with T. Conversely, the addition of TNFalpha (20 ng/ml) increases the P450arom transcription in PS although an inhibitory effect is observed in RS. Together with T, TNFalpha decreases the amount of P450arom mRNA in PS and RS. In PS we found that Dex regulates positively CYP19 expression and negatively in RS. Furthermore in PS a synergistic effect of Dex and TNFalpha on P450arom mRNA expression was observed whereas an additive one was recorded for RS. Therefore in germ cells TNFalpha likely enhances expression of aromatase through promoter PI.4 in PS, possibly via an AP1 site upstream the GAS element, while in RS TNFalpha requires glucocorticoids as a co-stimulator to increase CYP19 gene expression. Finally in presence of seminiferous tubules or Sertoli cell conditioned media, the amount of aromatase transcripts is increased in both Leydig cells and germ cells therefore suggesting that other locally produced modulators, yet unknown, but from Sertoli cell origin, are concerned in the regulation of the aromatase gene expression in rat testicular cells. In summary, using an in vitro model of mature rat Leydig cells, pachytene spermatocytes and round spermatids, we have shown that several factors direct the expression of the aromatase gene and it is obvious that not only promoter PII but also promoter PI.4 are concerned.

Regulation of aromatase gene expression in purified germ cells of adult male rats: effects of transforming growth factor beta, tumor necrosis factor alpha, and cyclic adenosine 3',5'-monosphosphate

Estrogens are key regulators of sexual differentiation and development in vertebrates. The P450 aromatase (P450arom) is the steroidogenic enzyme responsible for the synthesis of estrogens from androgens. In the adult rat testis, aromatase transcripts and activity have been observed in somatic cells and germ cells, including pachytene spermatocytes (PS) and round spermatids (RS), but little is known concerning regulation of the aromatase gene expression, especially in germ cells. The quality of germ cell preparations was assessed by the absence of androgen-binding protein and stem cell factor transcripts, two specific markers for Sertoli cells. By employing a competitive quantitative reverse transcriptase-polymerase chain reaction technique, we confirmed that germ cells contained P450arom transcripts and demonstrated that the aromatase gene was up-regulated by cAMP. Conversely, transforming growth factor (TGF) beta1 inhibited Cyp19 gene expression in a dose- and a time-dependent manner in both PS and RS. The addition of tumor necrosis factor (TNF) alpha to purified germ cells induced an increase of the amount of P450arom mRNA in PS, although an inhibitory effect was observed in RS. When PS were treated with dexamethasone (Dex), a similar enhancement of the aromatase transcript level was observed, whereas an inhibitory effect was recorded for RS. Furthermore, in either TGFbeta1- or TNFalpha-treated germ cells, the addition of Dex stimulated the aromatase gene transcription. Experiments using 5' rapid amplification of cDNA ends suggested that promoter PII is mainly concerned in the regulation of the aromatase gene expression in germ cells of adult male rats; however, the presence of other promoters could not be excluded.

Aromatase expression and role of estrogens in male gonad : a review

The ability of the testis to convert irreversibly androgens into estrogens is related to the presence of a microsomal enzymatic complex named aromatase, which is composed of a specific glycoprotein, the cytochrome P450 aromatase (P450arom) and an ubiquitous reductase. The aromatase gene is unique in humans and contained 18 exons, 9 of them being translated. In the rat testis we have immunolocalized the P450arom not only in Leydig cells but also in germ cells and especially in elongated spermatids. Related to the stage of germ cell maturation, we have shown that the level of P450arom mRNA transcripts decreases, it is much more abundant in pachytene spermatocytes and round spermatids than in mature germ cells whereas the aromatase activity is 2-4 fold greater in spermatozoa when compared to the younger germ cells. Using a highly specific quantitative competitive RT-PCR method we have evidenced that several factors direct the expression of the aromatase gene in Leydig cells, Sertoli cells, pachytene spermatocytes and round spermatids, and it is obvious that promoter PII is the main one but other promoters could be concerned. In the bank-vole testis we have observed a positive correlation between a fully developed spermatogenesis and a strong immunoreactivity for both P450arom and estrogen receptor beta not only in Sertoli cells but also in pachytene spermatocytes and round spermatids. Our recent data obtained from ejaculated human spermatozoa demonstrate the presence of aromatase both in terms of mRNA and protein, and in addition, we suggest that aromatase could be involved in the acquisition of sperm motility. Indeed in men the congenital aromatase deficiency is associated with severe bone maturation problems and sterility. Together with the widespread distribution of estrogen receptors in testicular cells these data clearly show that estrogens play a physiological role in the regulation of spermatogenesis in mammals.

New perspectives on growth factor-sex steroid interaction in the prostate

Many organs respond to both sex steroids and growth factors. Regulation of these pathways is integral to cell-cell communications during development and aberrant changes cause disease pathogenesis. Traditionally, paracrine and endocrine actions of growth factors and steroid hormones are considered independently. Recently, new data indicated that activin/TGFbeta and sex steroid signalling are linked; explicitly, that the pathways cross-talk intracellularly. Here we present new perspectives on these interactions, using examples predominantly from the prostate, as it is a well-characterised organ in this context. While this information provides insight to the potential mechanisms behind these interactions, it also presents a new challenge; the action of any of these factors cannot be considered exclusively without considering the impact on the other biological pathways.

Response of normal female human osteoblasts (NHOst) to 17beta-estradiol is modulated by implant surface morphology

Titanium (Ti) surfaces with rough microtopographies enhance osteogenic differentiation, local factor production, and response to osteogenic agents in vitro and increase pullout strength of dental implants in vivo. Estrogens regulate bone formation, resorption, and remodeling in females and may be important in implant success. Here, we tested the hypothesis that estrogen modulates osteoblast response to implant surface morphology. Primary female human osteoblasts were cultured to confluence on three Ti surfaces (pretreatment, PT - R(a) 0.60 microm; sandblasted and acid-etched, SLA - R(a) 3.97 microm; and Ti plasma-sprayed, TPS - R(a) 5.21 microm) and treated for 24 h with 10(-7) or 10(-8) M 17beta-estradiol (E(2)). Cell number decreased with increasing surface roughness, but was not sensitive to E(2). Alkaline phosphatase specific activity of isolated cells and cell layer lysates was lower on rough surfaces. E(2) increased both parameters on smooth surfaces, whereas on rough surfaces, the stimulatory effect of E(2) on alkaline phosphatase was evident only when measuring cell layer lysates. Osteocalcin levels were higher in the conditioned media of cells grown on rough surfaces; E(2) had no effect in cultures on the plastic surfaces, but increased osteocalcin production on all Ti surfaces. TGF-beta1 and PGE(2) production was increased on rough surfaces, and E(2) augmented this effect in a synergistic manner; on smooth surfaces, there was no change in production with E(2). The response of osteoblasts to surface topography was modulated by E(2). On smooth surfaces, E(2) affected only alkaline phosphatase, but on rough surfaces, E(2) increased levels of osteocalcin, TGF-beta1, and PGE(2). These results show that normal adult human female osteoblasts are sensitive to surface microtopography and that E(2) can alter this response.

Rat costochondral chondrocytes produce 17beta-estradiol and regulate its production by 1alpha,25(OH)(2)D(3)

Prior studies have shown that 17beta-estradiol (17beta-E(2)) regulates growth plate chondrocyte maturation and differentiation. This study examines the hypothesis that 17beta-E(2) is a local regulator of rat costochondral growth plate chondrocytes by determining whether these cells express aromatase mRNA and enzyme activity, produce 17beta-E(2), and regulate 17beta-E(2) production by vitamin D(3) metabolites in a gender-specific and cell-maturation-dependent manner. Aromatase gene expression was assessed by reverse transcription-polymerase chain reaction (RT-PCR) and northern analysis of total RNA from male and female chondrocytes. Aromatase specific activity was measured in cell layer lysates of confluent male and female rat costochondral resting zone (RC) and growth zone (GC) cartilage cells that had been treated for 24 h with 1alpha, 25(OH)(2)D(3), 24R,25(OH)(2)D(3), or transforming growth factor (TGF)-beta1. 17beta-E(2) released into the culture media of treated cells was measured by radioimmunoassay (RIA). Female RC cells expressed the highest levels of aromatase mRNA compared with male RC cells and both male and female GC cells. Aromatase activity was present in male and female cells and was 1.6 times greater in female RC cells than female GC cells; male RC and GC cells displayed comparable levels. All cultures produced 17beta-E(2), with a 2.5-fold greater production by female RC cells than female GC cells or either cell type from male rats. Treatment of cultures with 1alpha,25(OH)(2)D(3) caused a dose-dependent increase in 17beta-E(2) production by female RC (1.5-fold greater than control cells) and female GC (threefold greater than control cells) cells. In contrast, 1alpha,25(OH)(2)D(3) had no effect on male GC cells and increased production in male RC cells by only 10% at the highest concentration of 1alpha,25(OH)(2)D(3) used. Neither 24R, 25(OH)(2)D(3) nor TGF-beta1 had an effect on 17beta -E(2) production. These results support our hypothesis and indicate that 17beta-E(2) is most likely a local regulator of rat costochondral growth plate chondrocytes.

Stepwise estrogen suppression manipulating the estrostat

Estrogen suppression is an effective endocrine treatment option in pre- as well as postmenopausal breast cancer patients. The fact that it produces clinical benefits not only in these two groups of patients that differ significantly with respect to plasma estrogen levels but also among patients with very low plasma estrogen levels due to previous hypophysectomy, adrenalectomy or treatment with first/second generation aromatase inhibitors, suggests estrogen deprivation to work independent of pretreatment plasma estrogen levels. Interestingly, in vitro studies have revealed MCF-7 cells to respond to estrogen deprivation by sensitization, causing maximum estradiol stimulation at a concentration 10(-5) to 10(-4) the concentration needed in wild-type cells. While results from recent phase III studies comparing novel aromatase inhibitors and inactivators to conventional therapy have suggested that a more effective hormone ablation may be translated into an improved clinical efficacy, the biochemical rationale for lack of complete cross-resistance between aromatase inhibitors and inactivators or aromatase inhibitors and megestrol acetate remains to be explained. Interestingly, patients becoming resistant to estrogen deprivation may still respond to estrogens administered in pharmacological doses. Future studies are warranted to explore alterations in gene expression and signaling mechanisms in response to different therapies in tumor tissue in vivo.

Regulation of aromatase activity in bone-derived cells: possible role of mitogen-activated protein kinase

Fetal human osteoblast-like cells and the THP-1 cell line that differentiates into macrophage/osteoblast-like cells in the presence of Vitamin D3 and which possesses high aromatase activity, constitute a useful model with which to study the regulation of aromatase in bone. We showed that dexamethasone (DEX)-induced aromatase activity in the THP-1 cell line is completely suppressed by forskolin and by dibutyryl cAMP. We therefore investigated the contribution of mitogen-activated protein kinase (MAPK) to the regulation of aromatase, because cAMP inhibits MAPK in many cells. We examined the role of MAPK on aromatase activity using PD98059, a selective inhibitor of MEK-1. PD98059 (100 microM) reduced DEX+interleukin (IL)-1beta-induced aromatase activity in human osteoblast-like cells by more than 90%, whereas 50% of the aromatase mRNA concentration was retained compared with the control incubated with DEX+IL-1beta. PD98059 (50 microM) reduced the activity of aromatase in THP-1 cells by 80% without significantly affecting the mRNA level. These results indicated that MAPK plays an important role in aromatase activation at the post-transcriptional level.

Molecular mechanisms of TGF-(beta) antagonism by interferon (gamma) and cyclosporine A in lung fibroblasts

Lung fibrosis is a fatal condition of excess extracellular matrix (ECM) deposition associated with increased transforming growth factor beta (TGF-beta) activity. Although much is known about its pathological features, our understanding of the signal transduction pathways resulting in increased ECM and collagen deposition in response to TGF-beta is still incompletely defined. We have previously reported that a JunD homodimer of the transcription factor AP-1 is specifically activated by TGF-beta in lung fibroblasts. Here we demonstrate that JunD is also specifically required for TGF-beta-induced effects. Antisense against JunD, but not c-fos or c-jun, significantly inhibited collagen deposition in response to TGF-beta in primary human lung fibroblasts. We then investigated the ability of pharmacological agents to inhibit TGF-beta-induced signaling and collagen deposition. Cs-A and IFN-gamma, but not glucocorticoids, cyclophosphamide, or azathioprine, inhibited TGF-beta-induced signaling, as assessed by luciferase reporter gene assays, and collagen deposition. TGF-beta antagonism by Cs-A was associated with direct inhibition of JunD activation, as demonstrated by electrophoretic mobility shift analyses. In contrast, the effects of IFN-gamma required signal transducer and activator of transcription (STAT)-1. We thus identify the JunD isoform of AP-1 as an essential mediator of TGF-beta-induced effects in lung fibroblasts. TGF-beta-induced signaling and collagen deposition are efficiently antagonized by Cs-A and IFN-gamma treatment, both of which exhibit distinct molecular mechanisms of action. These observations therefore offer novel targets for future therapy of fibrotic lung disease.

Cytokines and hormones with anti-inflammatory effects: new tools for therapeutic intervention

The inflammation that is involved in the development of glomerulonephritis is tightly regulated by the expression of anti-inflammatory factors. These include circulating hormones, such as glucocorticoids, and mediators that are produced by intrinsic cells and infiltrating leucocytes. The present review focuses on these anti-inflammatory factors, summarizing in particular their activities in existing models of glomerulonephritis. In addition, experimental evidence is presented that anti-inflammatory mediators are able to increase glucocorticoid binding or signalling in target cells. These data help to explain the in-vivo efficacy of anti-inflammatory mediators, and offer a promising new avenue for therapeutic intervention.