On the role of steroid sulfates in hormone biosynthesis

Sex-Dependent Role of Estrogen Sulfotransferase and Steroid Sulfatase in Metabolic Homeostasis

Sulfonation and desulfation are two opposing processes that represent an important layer of regulation of estrogenic activity via ligand supplies. Enzymatic activities of families of enzymes, known as sulfotransferases and sulfatases, lead to structural and functional changes of the steroids, thyroids, xenobiotics, and neurotransmitters. Estrogen sulfotransferase (EST) and steroid sulfatase (STS) represent negative and positive regulation of the estrogen activity, respectively. This is because EST-mediated sulfation deactivates estrogens, whereas STS-mediated desulfation converts the inactive estrogen sulfates to active estrogens. In addition to the known functions of estrogens, EST and STS in reproductive processes, regulation of estrogens and other signal molecules especially at the local tissue levels has gained increased attention in the context of metabolic disease in recent years. EST expression is detectable in the subcutaneous adipose tissue in both obese women and men, and the expression of EST is markedly induced in the livers of rodent models of obesity and type 2 diabetes. STS was found to be upregulated in patients with chronic inflammatory liver diseases. Interestingly, the tissue distribution and the transcriptional regulation of EST and STS exhibit obvious sex and species specificity. EST ablation produces completely opposite metabolic phenotype in female and male obese mice. Adipogenesis is also differentially regulated by EST in murine and human adipocytes. This chapter focuses on the recent progress in our understanding of the expression and regulation EST and STS in the context of metabolic homeostasis.

1Alpha,25-dihydroxyvitamin D3-mediated stimulation of steroid sulphatase activity in myeloid leukaemic cell lines requires VDRnuc-mediated activation of the RAS/RAF/ERK-MAP kinase signalling pathway

1Alpha,25-dihydroxyvitamin D(3) (1alpha,25(OH)(2)D(3)) stimulates the activity of steroid sulphatase (STS) in myeloid cells [Hughes et al., 2001, 2005]. This was attenuated by inhibitors of phospholipase D (PLD) (n-butanol, 2,3-diphosphoglyceric acid, C(2)-ceramide) and phosphatidate phosphohydrolase (PAP) (propranolol and chlorpromazine), but was unaffected by inhibitors of phospholipase C. The 1alpha,25(OH)(2)D(3)-induced STS activity was also attenuated by inhibitors of protein kinase Calpha and protein kinase Cdelta (Go 6976, HBDDE and rottlerin), but not by an inhibitor of protein kinase Cbeta (LY379196). Additionally, 1alpha,25(OH)(2)D(3)-induced STS activity was attenuated by inhibitors of RAS (manumycin A), RAF (GW5074), MEK (PD098059 and U1026) and JNK (SP600125), but not p38 (PD169316). 1alpha,25(OH)(2)D(3) produced a rapid and long lasting stimulation of the ERK-MAP kinase signalling cascade in HL60 myeloid leukaemic cells. This 'non-genomic' effect of 1alpha,25(OH)(2)D(3) blocked by pharmacological antagonists of nuclear vitamin D receptors (VDR(nuc)) and does not appear to require hetero-dimerisation with the retinoid-X receptor (RXR). Inhibitors of the Src tyrosine kinase (PP1), RAS (manumycin A), RAS-RAF interactions (sulindac sulphide and RAS inhibitory peptide), RAF (GW5074 or chloroquine), and protein kinase Calpha (HBDDE) abrogated the 1alpha,25(OH)(2)D(3)-stimulated increase in ERK-MAP kinase activity. Taken together, these results show that 1alpha,25(OH)(2)D(3)/VDR(nuc) activation of the RAS/RAF/ERK-MAP kinase signalling pathway plays an important role in augmenting STS activity in human myeloid leukaemic cell lines.

Tissue steroid sulfatase levels, testosterone and blood pressure

The objective of this study was to examine the response of tissue steroid sulfatase (STS) levels in hypertensive rat strains, when blood pressure (BP) was lowered by different techniques at an early age. A 4x3 factoral design was used, in which males (n=6-8) from four rat strains (WKY, SHR, SHR/a, SHR/y) at 4 weeks of age, were randomly assigned to one of three treatment groups: a hydralazine group, a castration group and a control group. BP was measured by the tail cuff technique and verified by tail catheter at the end of the experiment. BP was significantly reduced by both treatments in the hypertensive strains (SHR, SHR/a, SHR/y) compared to respective control groups. At 15-17 weeks of age, animals were euthanized and heart, kidney, adrenal glands and liver were assayed for STS levels. The major trend in tissue STS was that castration significantly lowered: adrenal, heart and liver STS in specific strains. In conclusion, castration and hydralazine significantly lowered the BP in the hypertensive rat strains, but only castration consistently lowered STS levels across strains implicating testosterone as a regulator of tissue STS.

Environmental temperature and cryptorchidism: effects on pregnenolone-sulfatase of mice testicular tissue

This study examined the capacity of abdominal organs, such as the scrotal testis, exposed to environmental temperature to hydrolyze pregnenolone sulfate. The cryptorchid state of exposure to 34 degrees C during 14 days decreased testis weight by 38 and 23%. But the enzymatic activity (nanomoles of free steroid/testis) was significantly higher (p < .05) compared with the control. Moreover, a rise in the environmental temperature combined with cryptorchidism in mice, two conditions that induced testicular damage, has been related to the elaboration of factors capable of modifying, through paracrine mechanism, the androgen biosynthesis. The presence of this factor could lead to an increase in the hydrolysis of pregnenolone sulfate, but as for cryptorchidism or high environmental temperature exposure, when cryptorchid mice were exposed to temperatures of 34 degrees C an apparent synergism of both conditions produced a decrease of 66% in testis weight. It would appear that the steroid sulfatase is predominantly located in the interstitial epithelium. This study suggests that cryptorchidism and hyperthermia damage the tubular epithelium by different mechanisms.

Hydrolysis of estrone sulfate in uterine minces of the 6-days pregnant rat

In view of the possible participation of estrogen 3-sulfoconjugates in reproductive events, such as reproductive cycles, gestation and parturition, an experiment was carried out where the conversion of labeled estrone sulfate ([3H]E1S) to estrone ([3H]E1) was measured during in vitro incubation with minced uterine tissues representing implantation sites (IS) and non-implanted areas (NIS), from pregnant rats at the time of blastocyst implantation. Significant hydrolysis of the 3-sulfate, by the action of the estrogen sulfatase, was found in both tissues being less in IS than in NIS, when expressed either as pmol of E1 formed/mg wet tissue/h (238 +/- 37 vs 337 +/- 15, respectively) or as pmol of E1 formed/mg protein/h (1278 +/- 198 vs 1773 +/- 81). Both differences are statistically significant at the 0.001 level. The results obtained here suggest that E1S present in uterine fluids may be taken up and hydrolyzed by the sulfatase present in both intrauterine tissues of the 6-days pregnant rat. However, the decreased formation of E1 found in IS suggests that rat blastocyst is able to regulate the local concentration of unconjugated estrogens required at IS by modulating the activity of the estrogen sulfatase.

Effectiveness of calcium and magnesium on testicular sulfatase activity

Nucleotides and calcium ions have been implicated in the regulation of biosynthesis of steroids, although the exact locus of calcium activity is not yet known. The administration of Ca2+ to Leydig cells increases testosterone production. Steroid sulfatase activity is reported to be enhanced by adenine nucleotides. In the present study the testicular sulfatase was evaluated in subcellular fractions by conversion of sulfate to free steroids in the presence or absence of Ca2+ and Mg2+ ions. The specific activity of the enzyme, which was located predominantly in submitochondrial fraction, showed a positive correlation with calcium, increasing 1.5-fold in the presence of 2.54 mM of calcium (62 nmol/h mg protein-1). In contrast, magnesium inhibited the enzymatic activity 1.79-fold in presence of 1.18 mM (23 nmoles/h mg protein-1). It would appear that testicular sulfatase is predominantly located in the mitochondria, which is recognized as one of the major sites of control of intracellular metabolism, and that its enzymatic activity could be modulated by calcium regulating the levels of potentially active androgens.

Uterine estrogen sulfatase activity at the time of blastocyst implantation in the rat

The conversion of estrone sulfate (E1S) to estrone (E1) was measured during the in vitro incubation of the labeled sulfoconjugate with implantation sites (IS) and nonimplanted regions (NIS) of uterine horns from 6-day pregnant rats. Extensive metabolism of E1S occurred in both tissues, being noticeably less (29.31%) in IS than in NIS. Estrogen sulfatase activity present in the uterus of ovariectomized virgin rats was found to be higher than in both uterine regions of the pregnant rats. We suggest that E1S present in uterine fluids may be accessible to be metabolized into unconjugated estrogens by both intrauterine tissues of 6-day pregnant rats. This metabolism could be locally modulated in IS through the participation of the estrogen sulfatase, the activity of which is in turn controlled by the presence of free estrogens, possibly synthesized and/or secreted by the embryo, which has been shown to inhibit the sulfohydrolase activity.

Uterine estrogen sulfatase activity. Influence of steroid hormones and adenine nucleotides

Steroid sulfatase enzymes participate greatly in reproductive events. To date, estrogen sulfatase seems to have a regulatory role in the control of free estrogen levels in target tissues. The present study evaluates the participation of some adenine nucleotides in estrogen sulfatase kinetics. Using ADP, ATP, NAD and the combination of ADP + NAD or ATP + NAD it was found that adding either of the combined cofactors, the enzymatic activity increased more than 2.0 times. In ovariectomized rats, the corresponding mean enzyme activity was found to be higher than in intact rats. It was also found, in ovariectomized rats treated with ovarian hormones, an inhibition that was higher with estradiol-17 beta than with progesterone treatment. This data suggests that the estrogen sulfatase, being a hormone-dependent enzyme, participates in a new control mechanism of estrogen levels in presence of some cofactors and free steroids.

Effect of (1-24)adrenocorticotrophin stimulation on the rate of corticosterone synthesis by the rat adrenal cortex

The rate of corticosterone synthesis by the rat adrenal gland was measured in vitro, using a cell-free system, following the in vivo administration of (1-24)ACTH. The doses of ACTH used were 50, 100 and 250 micrograms ACTH/kg body weight. With all 3 doses of ACTH there was a significant increase in the rate of corticosterone synthesis within the first 5 min; this initial increase in rate did not vary with the dose of ACTH given. With both the 50 and 100 micrograms/kg doses the new rate of synthesis was maintained without further change, up to 30 min post-injection. In the case of the 250 micrograms/kg dose there was a second significant increase in the rate of corticosterone synthesis observed after 20 min. The results are discussed in the light of the hypothesis that the differential response of the adrenal gland represents the binding of ACTH to two receptors; a high affinity receptor of low abundance and a low affinity receptor of greater abundance. The results are consistent with the initial steroidogenic response resulting from binding to the high affinity receptors. Because of their low abundance these receptors may be completely occupied even at low doses of ACTH, thus explaining the dose-independent nature of the initial response to ACTH. Binding to the more abundant low affinity receptors may be associated with the secondary dose-dependent enhanced synthesis rate, a response which may be mediated via c-AMP.

Formation of androgen conjugates by porcine granulosa cells

The relative abilities of isolated and recombined theca and granulosa cells, derived from medium-sized porcine ovarian follicles, to synthesize androgens and estrogens were compared. Isolated thecal preparations produced large amounts of immunoreactive androstenedione and testosterone. When theca was co-cultured with granulosa cells, accumulation of both these androgens was markedly less. Though the co-cultures produced significantly higher amounts of estradiol, this increase did not account for the reduced androgen production. To determine if the lesser androgen accumulation in the combined cultures was due to metabolism by granulosa cells of androgens to other metabolites, the fate of [3H]androstenedione or [3H]testosterone was followed. Whenever granulosa cells were present in the incubation dishes, most of the radioactivity remained in the aqueous fraction after ether extraction. Examination of the aqueous fraction by DEAE-Sephadex A25 demonstrated the presence of androgen sulphates. The results suggest that granulosa cells are the site at which follicular formation of androgen sulphates takes place.

The ichthyoses--pathogenesis and prenatal diagnosis: a review of recent advances

Disturbances in the process of normal cornification leading to pathologic scaling provide the pathophysiologic basis for the ichthyoses. These disturbances may result from either abnormalities in protein metabolism (keratinization) (i.e., the "bricks") or in lipid metabolism (i.e., the "mortar") (Fig. 1). The evidence linking the various ichthyoses to defects in protein or lipid metabolism have been reviewed. It is likely that future advances will lead not only to a more complete understanding of the pathogenesis of these disorders, but also will shed significant light on the normal stratum corneum functions of barrier formation and desquamation, as well as lead the way to more rational and effective therapies. In recent years, prenatal diagnosis has been successfully performed in several of the ichthyoses. It is likely that improvements in our ability to prenatally diagnose those disorders will advance hand-in-hand with further progress in unraveling their underlying causes.