Herman Beerman lecture. Mechanisms of steroid hormone action

Osteogenic Differentiation of Adipose-Derived Stromal Cells: From Bench to Clinics

In addition to mesenchymal stem cells, adipose-derived stem/stromal cells (ASCs) are an attractive source for a large variety of cell-based therapies. One of their most important potential applications is related to the regeneration of bone tissue thanks to their capacity to differentiate in bone cells. However, this requires a proper control of their osteogenic differentiation, which depends not only on the initial characteristics of harvested cells but also on the conditions used for their culture. In this review, we first briefly describe the preclinical and clinical trials using ASCs for bone regeneration and present the quantitative parameters used to characterize the osteogenic differentiation of ASCs. We then focus on the soluble factors influencing the osteogenic differentiation of ACS, including the steroid hormones and various growth factors, notably the most osteoinductive ones, the bone morphogenetic proteins (BMPs). Impact statement Adipose-derived stromal/stem cells are reviewed for their use in bone regeneration.

Estrogen evokes a rapid effect on intracellular calcium in neurons characterized by calcium oscillations in the arcuate nucleus

Rapid estrogen effects became an interesting topic to explain estrogen effects not associated with the classical nuclear pathway. The rapid estrogen effect on intracellular calcium oscillations was characterized in neurons of the arcuate nucleus. Ratiometric calcium imaging (fura-2AM) was used to measure intracellular calcium in brain slices of female Swiss Webster mice (median of age 27 days p.n.). Calcium oscillations were dependent on intracellular calcium and also on calcium influx from the extracellular space. The perfusion of slices with calcium-free solution inhibited spontaneous calcium oscillations. The metabotropic glutamate receptor agonist t-ACPD (5 microM) and low concentrated ryanodine (100 nM) induced intracellular calcium release when slices were perfused with calcium-free solution. 17beta-estradiol (10 nM) also induced intracellular calcium release in calcium-free ACSF. This effect was inhibited by the preceding administration of thapsigargin (2 microM) indicating the association of the rapid estrogen effect with intracellular calcium stores. The administration of the non-selective phospholipase C-inhibitor ET-18 (30 microM), but not U73122 (10 microM), and the inhibition of protein kinase A by H-89 (0.25 microM) suppressed the rapid estrogen effect. Analyses indicated a qualitative, but not quantitatively significant effect of 17beta-estradiol on calcium oscillations.

Interruption of estradiol signal transduction by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) through disruption of the protein phosphorylation pathway in adipose tissues from immature and mature female rats

At doses of 10-115 microg/kg, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) decreased body and adipose tissue weights of mature female rats. Doses below 10 microg TCDD/kg decreased body and adipose tissue weights of immature, but not mature females. Doses of 2 and 10 microg TCDD/kg decreased adipose tissue epidermal growth factor receptor (EGFR) binding activity 5 and 7 days later in immature and mature females, respectively. At these times, there was a decrease in the activities of tyrosine kinase (TK), mitogen-activated protein kinase (MAP2K), and protein kinase A (PKA). In mature females, estradiol (E2, 15 microg/kg) increased TK and PKA activities and decreased MAP2K activity. In immature females, E2 decreased TK and PKA activities but not MAP2K activity. TCDD abolished the stimulatory effect of E2 on TK and PKA in mature females, and in immature females TCDD potentiated the negative effect of E2 on all three kinases. TCDD decreased binding of [3H]E2 to cytosolic and nuclear estrogen receptors (ERs) of mature and immature females, and antagonized the stimulatory effect of E2 on ER binding activity. E2 increased DNA binding activity of the estrogen response element (ERE) and activator protein-1, and TCDD antagonized this effect. Geldanamycin, an inhibitor of Src tyrosine kinase, reduced the effects of TCDD on body and adipose tissue weights. Geldanamycin antagonized the effects of TCDD on EGFR binding activity and TK activity. In cell-free preparations, TCDD antagonized E2 action on TK activity in mature females, as well as E2 action on PKA activity in immature females. We hypothesize that TCDD antagonizes E2 action in female adipose tissues through disruption of common cytosolic signal transduction pathways.

Female sex hormone stimulates cultured human keratinocyte proliferation and its RNA- and protein-synthetic activities

The present study was carried out to assess the effect of female sex hormones, i.e., estrogen and progesterone, on human keratinocyte proliferation, and its RNA- and protein-synthetic activities in a culture system. The presence of receptors for estrogen and progesterone and their messenger ribonucleic acids (mRNAs) in the cultured cells was also investigated. Human keratinocytes were cultured in the experimental DMEM-Ham's F12 medium containing various concentrations of estrogen or progesterone, which was followed by determining cell yields and [3H]thymidine incorporation. The keratinocytes were also tested for RNA- and protein-synthetic activities by measuring [3H]uridine and [3H]leucine incorporation. Both estrogen and progesterone receptors were determined by the enzyme immunoassay method using monoclonal antibodies, and mRNA expression for these hormone receptors was detected by in situ hybridization. Cell yields and [3H]thymidine incorporation increased gradually until 3 x 10(-10) M of both estrogen and progesterone, decreased thereafter until 3 x 10(-7) M, and peaked at 3 x 10(-10) M. [3H]Uridine and [3H]leucine uptake followed almost the same pattern as the cell proliferation, peaking at 3 x 10(-10) M of both hormones. Small amounts of estrogen and progesterone receptors were present in the cultured cells, and their mRNAs were found to be present in the cell cytoplasm. These results clearly suggest that sex hormones play an important role in human keratinocyte proliferation, and its RNA- and protein-synthetic activities, at least in part, via their hormone receptors.

Sex steroid hormones and cell dynamics in the periodontium

The biological changes that occur in tissues of the periodontium during puberty, the menstrual cycle, pregnancy, menopause, and oral contraceptive use have heightened interest in the relationship between sex steroid hormones and periodontal health. These clinical observations coupled with tissue specificity of hormone localization, identification of hormone receptors, as well as the metabolism of hormones have strongly suggested that periodontal tissues are targets for androgens, estrogens, and progestins. The etiologies of periodontal endocrinopathies are diverse; nonetheless, periodontal pathologies may be a consequence of the actions and interactions of sex steroid hormones on specific cells found in the periodontium.

Physiological implications of estrogen receptor modulation by 2,3,7,8-tetrachlorodibenzo-p-dioxin

The interactions of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) with hormones and hormone receptors have important implications for TCDD toxicity. Evidence suggests that TCDD modulates receptors for glucocorticoids, prolactin, thyroxine, low density lipids, epidermal growth factor, and estrogens. Estrogen receptor modulation and the animal's physiological responses to this modulation appear to be particularly important effects and can explain much of the toxicity observed in TCDD-treated animals. Susceptibility of different species to TCDD correlates with their steroid glucuronidation capacity. Because of the close interactions and interdependent regulation of hormonal systems, other hormones may have a similar role in TCDD toxicity.

Pharmacology and pharmacokinetics of estrogens

The primary source of estrogen, ovarian 17 beta-estradiol, is normally converted to estrone and estriol, both of which are metabolized to their sulfate and glucuronide forms, as well as oxidated to nonestrogens. In postmenopausal women, the primary sources of estrogen are nonovarian, including the production of androstenedione from the adrenal cortex and its metabolism to estrone by the liver, adipose tissue, skeletal muscle, kidney, brain, and hair follicles. Estrogen circulates bound to sex hormone-binding globulin and albumin. The sulfate form may be a storage form of this hormone and is freely converted back to estrone and estriol. The glucuronide and sulfate forms have limited cell penetration; they are excreted mainly in the kidney, with little tubular reabsorption. Several theories have been advanced to explain the effects of estrogens on the basis of their receptors. A consideration of pharmacologic and pharmacokinetic characteristics reveals specific advantages and disadvantages of the preparations currently available for estrogen replacement therapy. Oral agents have the disadvantage of being subject to a considerable first-pass hepatic effect, resulting in their conversion to estriol, oxidation to nonestrogens, and conjugation to sulfate and glucuronide salts. These preparations can also be associated with poor patient compliance, as can injectable, topical, or suppository preparations. On the other hand, transdermal patches are not subject to a first-pass hepatic effect, provide relatively uniform serum levels, and may help alleviate the problem of noncompliance.

Safety and efficacy of topical minoxidil in the management of androgenetic alopecia

Of 149 subjects with androgenetic alopecia, 102 completed 1 year of a double-blind, randomized study comparing 2% minoxidil and 3% minoxidil solutions for safety and efficacy. One third of the subjects used a vehicle placebo for the first 4 months and then switched to 3% minoxidil. At 12 months the 2% minoxidil group switched to a 3% solution. During months 5 to 12 a steady increase in terminal hair counts occurred to an equal degree within the 2% and 3% minoxidil groups and the 3% treatment group switched from placebo. Total hair counts at 12 months increased from a baseline mean of 63.5 to 180.6 in the 2% treatment group, from 61.0 to 179.9 in the 3% group, and from 65.0 to 191.1 in the placebo to 3% crossover group. Although all 102 subjects completing 12 months of the study thought that visible hair growth had resulted, 89 were considered by the investigators to have visible growth. Dense hair growth, defined as hair long enough to cut or comb, was present in 48 subjects by their own evaluation and in 33 subjects by investigator evaluation. There were no serious side effects. Two instances of allergic contact dermatitis and four of pruritus were attributed to use of the drug. Two individuals complained of impotence, which disappeared within a few days of discontinuation of topical minoxidil. This effect has not been reported during the use of minoxidil in its oral form (Loniten) for the treatment of hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

Glucocorticoids: binding affinity and lipophilicity

The relative binding affinity of 35 steroids for the glucocorticoid receptor was determined in experiments in which the competition of various unlabeled steroids with either [6,7-3H]dexamethasone or [1,2-3H]hydrocortisone for the cytosolic glucocorticoid receptor of cultured human keratinocytes was measured. The data obtained were correlated with steroid lipophilicity, measured as the partition coefficient of the steroid between 1-octanol and pH 7.4 aqueous buffer. The introduction of various substituents on the steroid molecule induced changes in the binding affinity and was associated in some cases with concomitant changes in steroid lipophilicity. The substitution by a 17 alpha-OH or 21-OH group leads in all cases to a decrease in steroid lipophilicity and to an increase in affinity. In contrast, 17 alpha-OAc and especially 21-OAc substitution on hydrocortisone and betamethasone causes a decrease in the steroid affinity for the receptor and an increase in steroid lipophilicity. The elongation of the ester chain from acetate to valerate in both position C-17 and C-21 leads to the increase in both the binding affinity for the receptor and the lipophilicity of steroids. However, all 21-esters showed lower binding affinity than the parent alcohol. The binding affinity of the highly lipophilic 17 alpha, 21-diester was found to be lower than that of the 17 alpha-ester but higher than that of the 21-ester or of the parent alcohol. Only in the series of 17 alpha- and 21-esters is there a correlation between the binding affinity of steroids for the glucocorticoid receptor and their lipophilicity.

Angiotensin-1-converting enzyme activity of murine macrophages isolated from granulomas elicited by eggs of Schistosoma mansoni

Angiotensin-1-converting enzyme (A1CE) activity was assessed in macrophages isolated from hepatic egg granulomas at 7 and 20 weeks after the infection of mice with Schistosoma mansoni. At 2 h after isolation, granuloma macrophages (GM) from chronically infected mice (20 weeks) displayed significantly higher levels of A1CE than did GM from mice 7 weeks after infection; both of the values were significantly higher than control peritoneal resident macrophages from normal mice. A1CE activity in GM and their respective culture supernatants declined over a 72-h period of in vitro cultivation; however, the decline was abrogated with the addition of dexamethasone to the culture medium. GM from athymic mice displayed significantly higher A1CE activity than did those from normal controls. Our data confirm and extend previous findings of others that GM are a major source of A1CE in murine schistosomiasis and that lymphocyte function may regulate GM A1CE production.

Steroid hormone receptors and their relevance for sebum production in the sebaceous gland ear model of the Syrian hamster

We determined the capacity of steroid hormone receptors in the sebaceous glands of intact nontreated, castrated, with testosterone substituted castrated male, intact female, and intact with testosterone substituted female animals using the animal ear model of the Syrian hamster. The steroid hormone binding capacity was compared with the sebaceous gland areas and sebogenesis. Intact male animals showed large sebaceous follicles, a high sebogenesis rate, and high capacity for sexual hormone binding proteins. In castrated males, the sebaceous gland areas and sebogenesis were both diminished, and androgen and estrogen receptors were decreased. When the castrated males were substituted with testosterone propionate, the sebaceous glands showed large volumes, high sebum production, and androgen binding activity again. In female animals having small sebaceous follicles and a low rate of sebogenesis, testosterone propionate enlarged the sebaceous glands and increased sebogenesis and the capacity of androgen binding. One can conclude from these data that testosterone is not only the main hormone for sebum production but also induces the synthesis of its own receptor.

Histochemically demonstrable enzyme activities and their independence of the hormone receptor content in female breast carcinoma

Acid phosphatase, leucine aminopeptidase, monoamine oxidase and non specific esterase activities were histochemically demonstrated in specimens derived from 15 infiltrating ductal carcinomas of female breast. The relative areas occupied by the enzyme-positive carcinoma cells were visually estimated and, in the cases of leucine aminopeptidase, assessed morphometrically. All enzyme activities were found to be subject to major variations within a single carcinoma and between individual carcinomas, and the activity of any single enzyme was independent of that of three others. None of the enzyme activities correlated with the estrogen and progesterone receptor values, nor the histological grade of malignancy of the tumour. Thus, histochemically demonstrable enzyme activities seem to be of no use in predicting the hormone receptor content in infiltrating ductal carcinomas of the female breast.

Corticoids and human skin fibroblasts: intracellular specific binding in relation to growth inhibition

The binding of 3H-triamcinolone acetonide to soluble macromolecules of cultured human skin fibroblasts was studied in an attempt to explain the mechanism underlying the inhibitory effects of glucocorticoids on cell growth. The results were as follows: Cultured human skin fibroblasts contain in cytosol a high affinity binding system for glucocorticoids. Various glucocorticoid derivatives competed for specific binding of 3H-triamcinolone acetonide. In some but not all instances this competition was related to the clinical efficacy of the derivatives under study and to their potency for the inhibition of cell growth. A specific glucocorticoid binding system was detectable in steroid-sensitive, low-density cell cultures (apparent Bmax = 200 fmoles/mg protein). The number of steroid binding sites was lower in high-density cell cultures (apparent Bmax = 125 fmoles/mg protein). The sensitivity to growth inhibition by glucocorticoids was markedly decreased in the high-density cell cultures. There were no differences in the affinity constants between these cell cultures (Kdiss. = 3.3 X 10-9 M). When cells were grown in medium containing glucocorticoid, renewal of the incubation medium led to disappearance of the growth-inhibitory effects, whereas specific binding was not affected. Nandrolone, an inhibitor of cell growth, abolished the growth-inhibitory effects of glucocorticoids but did not displace 3H-triamcinolone acetonide from its binding sites. The results suggest that in addition to a mechanism mediated by a glucocorticoid binding system with receptor like properties also other factors as well appear of relevance for the control of cell growth. These factors may be beyond the actual binding process of steroid and involve the action at the level of genomic expression of the cell.

Photocontact dermatitis to hydrocortisone

A patient was found to have a delayed positive patch test to hydrocortisone on multiple testing. This proved to be due to a photoallergy with an action spectrum in the UV-A range. The patient coincidently had a polymorphous light eruption in the UV-B range.