Serum steroid sulphates in ichthyosis

Steroid Sulfatase Deficiency and Androgen Activation Before and After Puberty

CONTEXT

Steroid sulfatase (STS) cleaves the sulfate moiety off steroid sulfates, including dehydroepiandrosterone (DHEA) sulfate (DHEAS), the inactive sulfate ester of the adrenal androgen precursor DHEA. Deficient DHEA sulfation, the opposite enzymatic reaction to that catalyzed by STS, results in androgen excess by increased conversion of DHEA to active androgens. STS deficiency (STSD) due to deletions or inactivating mutations in the X-linked STS gene manifests with ichthyosis, but androgen synthesis and metabolism in STSD have not been studied in detail yet.

PATIENTS AND METHODS

We carried out a cross-sectional study in 30 males with STSD (age 6-27 y; 13 prepubertal, 5 peripubertal, and 12 postpubertal) and 38 age-, sex-, and Tanner stage-matched healthy controls. Serum and 24-hour urine steroid metabolome analysis was performed by mass spectrometry and genetic analysis of the STS gene by multiplex ligation-dependent probe amplification and Sanger sequencing.

RESULTS

Genetic analysis showed STS mutations in all patients, comprising 27 complete gene deletions, 1 intragenic deletion and 2 missense mutations. STSD patients had apparently normal pubertal development. Serum and 24-hour urinary DHEAS were increased in STSD, whereas serum DHEA and testosterone were decreased. However, total 24-hour urinary androgen excretion was similar to controls, with evidence of increased 5α-reductase activity in STSD. Prepubertal healthy controls showed a marked increase in the serum DHEA to DHEAS ratio that was absent in postpubertal controls and in STSD patients of any pubertal stage.

CONCLUSIONS

In STSD patients, an increased 5α-reductase activity appears to compensate for a reduced rate of androgen generation by enhancing peripheral androgen activation in affected patients. In healthy controls, we discovered a prepubertal surge in the serum DHEA to DHEAS ratio that was absent in STSD, indicative of physiologically up-regulated STS activity before puberty. This may represent a fine tuning mechanism for tissue-specific androgen activation preparing for the major changes in androgen production during puberty.

The Regulation of Steroid Action by Sulfation and Desulfation

Steroid sulfation and desulfation are fundamental pathways vital for a functional vertebrate endocrine system. After biosynthesis, hydrophobic steroids are sulfated to expedite circulatory transit. Target cells express transmembrane organic anion-transporting polypeptides that facilitate cellular uptake of sulfated steroids. Once intracellular, sulfatases hydrolyze these steroid sulfate esters to their unconjugated, and usually active, forms. Because most steroids can be sulfated, including cholesterol, pregnenolone, dehydroepiandrosterone, and estrone, understanding the function, tissue distribution, and regulation of sulfation and desulfation processes provides significant insights into normal endocrine function. Not surprisingly, dysregulation of these pathways is associated with numerous pathologies, including steroid-dependent cancers, polycystic ovary syndrome, and X-linked ichthyosis. Here we provide a comprehensive examination of our current knowledge of endocrine-related sulfation and desulfation pathways. We describe the interplay between sulfatases and sulfotransferases, showing how their expression and regulation influences steroid action. Furthermore, we address the role that organic anion-transporting polypeptides play in regulating intracellular steroid concentrations and how their expression patterns influence many pathologies, especially cancer. Finally, the recent advances in pharmacologically targeting steroidogenic pathways will be examined.

High levels of oxysterol sulfates in serum of patients with steroid sulfatase deficiency

Steroid sulfatase (STS) deficiency is the underlying cause of the skin condition known as recessive X-linked ichthyosis (RXLI). RXLI patients show scales on their skin caused by high concentrations of cholesterol sulfate (CS), as they are not capable of releasing the sulfate group from its structure to obtain free cholesterol. CS has been reported, so far, as the sole sulfated steroid with increased concentrations in the blood of RXLI patients. A non-targeted LC-MS approach in negative mode detection (LC-MS precursor ion scan mode) was applied to serum samples of 12 RXLI patients and 19 healthy males. We found that CS was not the only sulfated compound consistently elevated in RXLI patients, because a group of compounds with a m/z of 481 was found in high concentrations too. Further LC-MS/MS demonstrated that the main contributor to the m/z 481 signal in RXLI serum is 27-hydroxycholesterol-3-sulfate (27OHC3S). Accordingly, a new method for 27OHC3S quantification in the context of RXLI has been developed and validated. Other hydroxycholesterol sulfate compounds were elevated as well in RXLI patients.

Increased levels of DHEAS in serum of patients with X-linked ichthyosis

The metabolic basis of X-linked ichthyosis is a deficiency of steroid sulphatase, a microsomal enzyme which removes sulphate groups from sulphated steroids. We report on a carefully controlled group of 15 patients with recessive X-linked ichthyosis, selected in a narrow age range (22-33 years), in whom, through the use of gas chromatographic analysis and conventional radioimmunoassay, we have measured not only elevated serum cholesterol sulphate levels but also significantly elevated serum dehydroepiandrosterone sulphate levels. The latter finding has been controversial in previous reports. We believe that the radioimmunoassay procedure generally used should be held responsible for such controversy since it often gives rise to false positive and/or false negative values. Gas chromatography, although more exacting, appears to be far more reliable for the assessment of elevated serum dehydroepiandrosterone.

Cholesterol sulphate levels in the hair and nails of patients with recessive X-linked ichthyosis

Cholesterol sulphate (CS) has been suggested as an intercellular glue for corneocyte-corneocyte cohesion from studies on patients with recessive X-linked ichthyosis (RXLI). Pathological stratum corneum of RXLI patients was found to show a significant elevation of CS. In the present study hair and nails, unaffected keratinized tissues in RXLI patients, were examined for CS levels. The results demonstrated significantly elevated CS levels in both tissues in RXLI patients (P less than 0.001). In particular the mean CS level in the hair of RXLI patients was five times greater than normal. The present study suggests that hair is a useful material for the diagnosis of RXLI.

Simplified determination of serum cholesterol sulfate by gas-liquid chromatography combined with cyclohexylsilane-bonded phase column purification

A new gas-liquid chromatographic (GLC) determination of cholesterol sulfate (CS) and dehydroepiandrosterone sulfate (DHEAS) for a biochemical diagnosis of recessive X-linked ichthyosis (RXLI) is described. Although the GLC method for determination of CS is known to be more sensitive than the thin layer chromatographic (TLC) method, the former method has not been widely employed because of its complicated pre-purification steps. The present method allows us to measure the serum levels of CS and DHEAS without tedious purification steps such as multiple conventional column chromatography and preoperative thin layer chromatography. Sulfated steroids are rapidly purified with a commercially available mini disposable cyclohexylsilane-bonded phase (CH) column, CH BOND ELUT, and the purified steroids after desulfation are converted to water-resistant tert-butyldimethylsilyl ether derivative for the GLC analysis on dual 2m glass columns packed with 2% XE-60 on Chromosorb W. By the present method, serum CS concentrations in RXLI patients were shown to be about 10 times higher than those in patients with ichthyosis vulgaris, carriers of RXLI, and healthy subjects. This method is more suitable not only for a biochemical diagnosis of RXLI but also for studies on the metabolism of sulfated steroids than the previous time-consuming GLC methods.

Metabolism of 3H-dehydroepiandrosterone sulphate by subjects with steroid sulphatase deficiency

Patients with steroid sulphatase deficiency develop ichthyosis with accumulation of cholesterol sulphate in plasma and in the stratum corneum. The present study was undertaken to determine whether desulphation of the C19 steroid DHEAS is also impaired. The mean plasma concentrations of DHEA and androstenedione were significantly lower for patients than for controls (p less than 0.02 and 0.001) while the mean concentration of DHEAS was higher (p less than 0.002). Following intravenous administration of 3H-DHEAS, one patient failed to desulphate 3H-DHEAS as evidenced by an absence of urinary 3H-glucuronides. A second produced normal amounts of urinary 3H-glucuronides (indicative of desulphation capacity) in a baseline study but did not desulphate 3H-DHEAS following ampicillin treatment to alter gut microflora. A third patient had consistent sulphatase activity with and without ampicillin.

Simplified method of determination of serum cholesterol sulfate by reverse phase thin-layer chromatography

A new method for determination of cholesterol sulfate (CS) and dehydroepiandrosterone sulfate (DHEAS) from 1 ml serum by reverse phase thin-layer chromatography (TLC) is described. The method comprises an isolation step of sulfated steroids by means of octadecylsilane-bonded (C18) reverse phase column chromatography, a solvolysis step for desulfation of sulfated steroids, and a C18 TLC step for measurement on a photodensitometer. This method is much simpler and more rapid than the methods previously reported, since neither a radioisotope is needed, nor any steps of saponification, derivatization, tedious scraping from a TLC plate, and time-consuming conventional column chromatography are not required. The present method allowed us to distinguish recessive X-linked ichthyosis (RXLI) very easily from ichthyosis vulgaris (IV) by the size and gradation of clearly visible blue chromogen derived from CS on a TLC plate in RXLI. By photodensitometer scanning, the CS levels in patients with RXLI were about 10 times higher than those of patients with IV and healthy subjects, whereas the DHEAS level was normal in the RXLI patients. The present simplified method proved to be useful in diagnosis of RXLI.

Regulation of serum testosterone in men with steroid sulfatase deficiency: response to human chorionic gonadotropin

Human chorionic gonadotropin (hCG; 5000 IU) was administered to 6 control men and 6 patients with recessive x-linked ichthyosis (RXLI) with verified 3 beta-hydroxysteroid sulfate sulfatase (3 beta-HSS) deficiency in their skin biopsy samples. Concentrations of steroids and their sulfate conjugates were determined in peripheral serum specimens collected a day before and 4 days after hCG administration. Testosterone concentrations were identical in patients and controls. Baseline serum LH concentrations were also identical in the 2 groups showing that there were no major differences in the regulation of the hypothalamic-pituitary-gonadal axis. The significantly increased (31-82%) serum concentrations of sulfated pregnenolone, 17-hydroxypregnenolone, dehydroepiandrosterone and 5-androstene-3 beta,17 beta-diol in patients compared with controls indicated that their circulating concentrations were regulated by 3 beta-HSS. This is in line with the fact that the baseline concentrations of the same unconjugated steroids were significantly lower (32-90%) in patients with RXLI, suggesting that a proportion of these circulating steroids were derived from the corresponding sulfated precursors. The response patterns and actual concentrations of testosterone, 17-hydroxyprogesterone and estradiol were similar in the patients and the controls after hCG. The decreased concentrations of testosterone sulfated at carbon 17 under baseline conditions and after hCG in patients with RXLI remains enigmatic. In conclusion, testosterone production and the response to hCG seem to be identical in patients with RXLI and controls despite the fact that significant differences were observed in the circulating concentrations of several unconjugated and sulfated testosterone precursors.

Abnormal androgen and oestrogen metabolism in men with steroid sulphatase deficiency and recessive X-linked ichthyosis

Serum levels of sex hormone binding globulin (SHBG), testosterone, free testosterone, dihydrotestosterone, androstenedione, dehydroepiandrosterone sulphate, oestradiol, oestrone, oestrone sulphate, FSH, and LH were measured in 20 steroid sulphatase-deficient men with recessive X-linked ichthyosis and in normal men. The serum oestrone sulphate level was significantly higher than normal in the patients (P less than 0.0001). In affected men, there was a tendency towards higher dehydroepiandrosterone sulphate levels and no decline with age was seen in the patients as opposed to normal men (interaction: P less than 0.025). Serum androstenedione, and oestradiol levels were lower than normal in the patients (P less than 0.0005 and P = 0.055, respectively), while their LH level was higher than normal (P less than 0.0005). The serum levels of SHBG, total and free testosterone, dihydrotestosterone, oestrone, and FSH were not significantly different from normal in the icthyotic patients. We suggest that the observed abnormalities in these patients are a consequence of the enzyme deficiency which severely impairs the ability of tissues to hydrolyse steroid sulphates.

Stratum corneum lipids in disorders of cornification. Steroid sulfatase and cholesterol sulfate in normal desquamation and the pathogenesis of recessive X-linked ichthyosis

The pathological scaling in recessive x-linked ichthyosis is associated with accumulation of abnormal quantities of cholesterol sulfate in stratum corneum (J. Clin. Invest. 68:1404-1410, 1981). To determine whether or not cholesterol sulfate accumulates in recessive x-linked ichthyosis as a direct result of the missing enzyme, steroid sulfatase, we quantitated both steroid sulfatase and its substrate, we quantitated both steroid sulfatase and its substrate, cholesterol sulfate, in different epidermal strata, as well as within stratum corneum subcellular fractions obtained from normal human and neonatal mouse epidermis and from patients with recessive x-linked ichthyosis. In normal human and mouse epidermis, steroid sulfatase activity peaked in the stratum granulosum and stratum corneum, and negligible activity was detectable in lower epidermal layers. In contrast, in recessive x-linked ichthyosis epidermis, enzyme levels were virtually undetectable at all levels. In normal human stratum corneum, up to 10 times more steroid sulfatase activity was present in purified peripheral membrane preparations than in the whole tissue. Whereas in normal human epidermis cholesterol sulfate levels were lowest in the basal/spinous layer, and highest in the stratum granulosum, in recessive x-linked ichthyosis the levels were only slightly higher in the lower epidermis, but continued to climb in the stratum corneum. In both normal and in recessive x-linked ichthyosis stratum corneum, cholesterol sulfate appeared primarily within membrane domains, paralleling the pattern of steroid sulfatase localization. Finally, the role of excess cholesterol sulfate in the pathogenesis of recessive x-linked ichthyosis was directly tested by topical applications of this substance, which produced visible scaling in hairless mice in parallel to an increased cholesterol sulfate content of the stratum corneum. These results demonstrate an intimate relationship between steroid sulfatase and cholesterol sulfate in normal epidermis: both are concentrated in the outer epidermis (stratum corneum and stratum granulosum), and both are localized to membrane domains. Presumably, as a result of this distribution pattern, continued enzymatic degradation of substrate occurs in normal epidermis, thereby preventing excessive accumulation of cholesterol sulfate. In contrast, in recessive x-linked ichthyosis, degradation of cholesterol sulfate does not occur and cholesterol sulfate accumulates specifically in the stratum corneum, where it produces visible scale.

Cholesterol sulphate in the microsomal sulphatase deficient placenta

Placental sulphatase deficiency (PSD) and recessive X-linked ichthyosis (RXLI) are known as a nosological entity, due to deficiency of the enzyme, steroid sulphatase. Prior studies have demonstrated high urinary excretion and some accumulation of sulphated steroids prenatally, and of accumulation of cholesterol sulphate postnatally. This study was undertaken to investigate the level of cholesterol sulphate in the sulphatase deficient placenta. Whereas cholesterol sulphate levels are elevated in blood, erythrocyte membrane and stratum corneum of patients with RXLI, cholesterol sulphate content of four investigated sulphatase deficient placentas was normal in comparison to six normal male controls and four male controls with low oestrogen excretion in the third trimester of pregnancy but with normal placental sulphatase activity. The explanation for normal cholesterol sulphate content of sulphatase deficient placentas is unknown but may be due to placental transport, rapid metabolism to other sulphated steroids or age-related differences in residual enzyme activities.

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.

A new method for the determination of steroid sulphatase activity in leukocytes in X-linked recessive ichthyosis

The diagnosis of X-linked ichthyosis can now be reliably established by using a non-radioactive method to detect steroid sulphatase deficiency in leukocytes. This new method yields the same results with leukocytes as with cultured fibroblasts. The second type of microsomal arylsulphatase previously described in cultured fibroblasts is also present in leukocytes.

Stratum corneum lipids in disorders of cornification: increased cholesterol sulfate content of stratum corneum in recessive x-linked ichthyosis

Activity of the microsomal enzyme, steroid sulfatase, is absent in keratinocytes, fibroblasts, and leukocytes of patients with recessive x-linked ichthyosis. This study was undertaken to determine if cholesterol sulfate, a substrate of this enzyme, accumulates in the pathological scale of these patients. Scales from 8 patients with recessive x-linked ichthyosis, 10 patients with other forms of ichthyosis, and normal human outer stratum corneum were extracted with chloroform/water (1:2:0.8 by vol) and lipids were fractionated by quantitative, sequential thin-layer chromatography. Cholesterol sulfate was identified by cochromatography in several solvent systems, by its staining characteristics, by biochemical analysis, and by mass spectrometry. The mean cholesterol sulfate content of recessive x-linked ichthyotic scale was 12.5 +/- 0.8% of the total lipid, a fivefold increase over normal (P less than 0.0025), whereas the cholesterol sulfate content of other ichthyotic scale was normal. This increase in cholesterol sulfate content was accompanied by a decrease in total neutral lipids (P less than 0.0025) and free sterols (P less than 0.025) but no change in sterol esters or total sterols. These results demonstrate that deficiency of steroid sulfatase in recessive x-linked ichthyosis results in excessive accumulation of a substrate, cholesterol sulfate, in the pathologic scale, which may underly the pathogenesis of the scaling in this disorder. Measurement of cholesterol sulfate content in scale provides an alternative method to enzymatic assay for the diagnosis of this form of ichthyosis.

X-linked ichthyosis: increased blood cholesterol sulfate and electrophoretic mobility of low-density lipoprotein

Plasma cholesterol sulfate concentration is increased in patients with recessive X-linked ichthyosis, a disease in which steroid sulfatase activity is absent. In these patients, cholesterol sulfate is found primarily in the low-density lipoprotein fraction of plasma, and the electrophoretic mobility of these lipoproteins is greatly increased.

Steroid sulphatase activity in the skin biopsies of various types of ichthyosis

A simple method was developed for the determination of steroid sulphatase activity in a skin biopsy for routine use. In this method, 6 mg of minced tissue is incubated in 1 ml of Krebs-Ringer bicarbonate buffer with radioactive dehydroepiandrosterone sulphate (20,000 c.p.m., S.A. 1.1 Ci/mmol) for 4 h. After the incubation the liberated unconjugated dehydroepiandrosterone and its possible metabolites are separated from the conjugated compound by extraction with ethyl acetate-ethyl ether 10:90 (v/v). The organic phase is counted in a scintillation counter. The results are expressed as c.p.m. values per 6 mg tissue wet weight. Steroid sulphatase activity was measured in skin biopsies from nine control subjects and from thirteen patients with various types of ichthyosis. In the different groups studied, the ranges of the c.p.m. values were as follows: controls (n = 9) 377-1802; X-linked ichthyosis (n = 5) 140-214; ichthyosis vulgaris (n = 5) 607-1320; ichthyosiform erythroderma (n = 2) 2146-2214; lamellar ichthyosis (n = 1) 2185. The reagent blank varied from 180 to 259 c.p.m. In X-linked ichthyosis the c.p.m. values were always less than in the corresponding reagent blank, indicating that no enzyme activity was present in the tissue. In other types of ichthyosis, steroid sulphatase activity was normal. The method described is easy to accomplish in any clinical laboratory where scintillation counting is possible.