In vitro modulation of multidrug resistance by pregnane steroids and in vivo inhibition of tumour development by 7α-OBz-11α(R)-OTHP-5β-pregnanedione in K562/R7 and H295R cell xenografts

Synthetic progesterone and 5α/β-pregnane-3,20-dione derivatives were evaluated as in vitro and in vivo modulators of multidrug-resistance (MDR) using two P-gp-expressing human cell lines, the non-steroidogenic K562/R7 erythroleukaemia cells and the steroidogenic NCI-H295R adrenocortical carcinoma cells, both resistant to doxorubicin. The maximal effect in both cell lines was observed for 7α-O-benzoyloxy,11α(R)-O-tetrahydropyranyloxy-5β-pregnane-3,20-dione 4. This modulator co-injected with doxorubicin significantly decreased the tumour size and increased the survival time of immunodeficient mice xenografted with NCI-H295R or K562/R7 cells.

Synthesis of new steroidal inhibitors of P-glycoprotein-mediated multidrug resistance and biological evaluation on K562/R7 erythroleukemia cells

A simple route for improving the potency of progesterone as a modulator of P-gp-mediated multidrug resistance was established by esterification or etherification of hydroxylated 5α/β-pregnane-3,20-dione or 5β-cholan-3-one precursors. X-ray crystallography of representative 7α-, 11α-, and 17α-(2'R/S)-O-tetrahydropyranyl ether diastereoisomers revealed different combinations of axial-equatorial configurations of the anomeric oxygen. Substantial stimulation of accumulation and chemosensitization was observed on K562/R7 erythroleukemia cells resistant to doxorubicin, especially using 7α,11α-O-disubstituted derivatives of 5α/β-pregnane-3,20-dione, among which the 5β-H-7α-benzoyloxy-11α-(2'R)-O-tetrahydropyranyl ether 22a revealed promising properties (accumulation index 2.9, IC50 0.5 μM versus 1.2 and 10.6 μM for progesterone), slightly overcoming those of verapamil and cyclosporin A. Several 7α,12α-O-disubstituted derivatives of 5β-cholan-3-one proved even more active, especially the 7α-O-methoxymethyl-12α-benzoate 56 (accumulation index 3.8, IC50 0.2 μM). The panel of modulating effects from different O-substitutions at a same position suggests a structural influence of the substituent completing a simple protection against stimulating effects of hydroxyl groups on P-gp-mediated transport.

Mitotane has an estrogenic effect on sex hormone-binding globulin and corticosteroid-binding globulin in humans

CONTEXT

Side effects of mitotane (o,p'-DDD) have suggested estrogenic effects.

OBJECTIVE

The objective of the study was to explore o,p'-DDD potential estrogenic effect on SHBG and corticosteroid-binding globulin (CBG).

DESIGN

Human hepatoma cell lines (HepG2), lacking estrogen receptor (ER)-alpha, and Hep89, stably transfected by ERalpha, were used.

SETTING

The study was conducted at an academic research laboratory and medical center.

PATIENTS AND OTHER PARTICIPANTS

The study included 10 male patients with recurrent adrenal carcinoma, receiving mitotane (4-6.5 g daily) for more than 6 months.

MAIN OUTCOME MEASURES

The main outcome measures were SHBG/CBG mRNA levels measured by real-time PCR, culture medium SHBG/CBG concentrations measured by specific immunoassays, and transient transfection experiments with human SHBG proximal promoter reporter constructs.

RESULTS

Increased serum SHBG and CBG concentrations, which exceeded normal male limits, were observed in most mitotane-treated patients. In the HepG2 cell line, 17beta-estradiol (E2) or o,p'-DDD treatment had no effect on mRNA or SHBG/CBG concentrations. In contrast, in the Hep89 cell line, E2 increased concentrations of SHBG (r = 0.44, P < 0.0001) and CBG (r = 0.585, P < 0.0001) secreted into culture media in a dose-dependent manner. o,p'-DDD significantly increased SHBG (150% vs. control, P < 0.05) and CBG (184% vs. control, P < 0.05) production by Hep89 cells, at a concentration of 2 x 10(-5) m. Transient transfection experiments in Hep89 cells showed that E2 or o,p'-DDD treatment did not increase the transcriptional activity of the minimal proximal promoter of human SHBG gene.

CONCLUSIONS

Mitotane increased SHBG/CBG gene expression and liver production by mechanisms requiring the presence of ERalpha.

Corticosteroid Binding Globulin: A New Target for Cortisol-Driven Obesity

We present data suggesting that corticosteroid-binding globulin (CBG) may be the causal gene of a previously identified quantitative trait locus (QTL) associated with cortisol levels, fat, and muscle content in a pig intercross. Because Cbg in human and mouse maps in the region orthologous to the pig region containing this QTL, we considered Cbg as an interesting positional candidate gene because CBG plays a major role in cortisol bioavailability. Firstly, we cloned pig Cbg from a bacterial artificial chromosome library and showed by fluorescent in situ hybridization and radiation hybrid mapping that it maps on 7q26 at the peak of the QTL interval. Secondly, we detected in a subset of the pig intercross progeny a highly significant genetic linkage between CBG plasma binding capacity values and the chromosome 7 markers flanking the cortisol-associated QTL. In this population, CBG capacity is correlated positively to fat and negatively to muscle content. Thirdly, CBG capacity was three times higher in Meishan compared with Large White parental breeds and a 7-fold difference was found in Cbg mRNA expression between the two breeds. Overall, the data accumulated in this study point to Cbg gene as a key regulator of cortisol levels and obesity susceptibility.

Influence of SHBG gene pentanucleotide TAAAA repeat and D327N polymorphism on serum sex hormone-binding globulin concentration in hirsute women

SHBG is the specific plasma transport protein for sex steroid hormones in humans. Plasma SHBG concentration follows a gender dimorphism but varies with nutritional and hormonal status in both sexes. In addition, a genetic influence on SHBG in humans has recently been suggested by family studies. We investigated the relationship between a point mutation (D327N) in SHBG gene exon 8 that delays human SHBG half-life and a pentanucleotide repeat polymorphism [PNRP (TAAAA)(n)] in the SHBG gene 5' untranslated region that influences transcription in vitro, on the one hand, and SHBG levels on the other, in a population of 303 women referred for hirsutism. Of these patients, 154 (51%) met the criteria for polycystic ovary syndrome (PCOS) and 124 (41%) were overweight [body mass index (BMI) > or = 25 kg/m(2)]. The two SHBG gene alleles for D327N substitution, wild-type (W) and variant (v), were identified by restriction fragment length polymorphism in the whole population, and the GeneScan method was used to identify PNRP alleles in 245 subjects. Six alleles of the pentanucleotide motif with six to 11 repeats were present in our population. Plasma SHBG concentration was related to PCOS status, non-SHBG-bound testosterone, BMI, fasting blood glucose level, fasting insulinemia, and D327N allele v. The v allele was associated with higher SHBG levels [36.9 +/- 15.9 nmol/liter for W/v (n = 52) and 43.5 +/- 3.5 nmol/liter for v/v (n = 2)] than was the wild-type W allele [31.1 +/- 16.1 nmol/liter (n = 249); P = 0.039]. Multivariate analysis showed that BMI, PCOS status, and D327N polymorphism influenced plasma SHBG concentrations, each of these parameters contributing independently of the others. Investigating the role of each allele of the TAAAA repeat polymorphism on SHBG levels was more complex because of the number of different genotypes (as many as 18 in our population) and the low frequency of some of them. Moreover, a strong disequilibrium linkage was found between D327N allele v and the eight-TAAAA repeat allele (P < 0.0001). This could mask the effect of the TAAAA repeat polymorphism on SHBG concentration in vivo. Nevertheless, SHBG levels in patients who were homozygous for six repeats (34.9 +/- 16.2 nmol/liter; n = 21) were significantly (P = 0.043) higher than in nine-repeat homozygous patients (21.5 +/- 13.0 nmol/liter; n = 8), and lay between the two for eight-repeat homozygous patients (28.5 +/- 15.8 nmol/liter; n = 44). Delineating the precise role of this PNRP polymorphism will need further investigation in a large healthy population. In summary, although BMI and PCOS status have a major influence on circulating SHBG levels in hirsute women, the present results support the notion that polymorphism(s) within the coding sequence and, potentially, in the regulatory sequence of the SHBG gene are associated with circulating SHBG levels and may represent part of the genetic background of sex steroid hormone activity in humans.

Study of the effect of changing glucose, insulin, and insulin-like growth factor-I levels on serum corticosteroid binding globulin in lean, obese, and obese subjects with glucose intolerance

We have previously described that serum corticosteroid binding globulin (CBG) concentrations are associated with insulin secretion. The present study was designed to evaluate the effects of changing insulin concentrations, both endogenous and after exogenous insulin administration, on circulating CBG levels in vivo. Serum CBG concentrations were measured during an insulin-modified frequently sampled intravenous (IV) glucose tolerance test (FSIVGT) in 14 lean and 19 obese otherwise healthy subjects with varying degrees of glucose tolerance. Acute insulin response to glucose (AIRg) correlated significantly with serum CBG concentrations at time 0 (r = -.38, P =.029), 22 minutes (r = -.41, P =.01), 50 minutes (r = -.41, P =.01), and 180 minutes (r = -.39, P =.02). Insulin sensitivity (S(I)) was not associated with serum CBG concentration at time 0 (r = -.16, P = not significant [NS]), but correlated significantly with CBG concentration at 22 minutes (r = -.41, P =.02) and 50 minutes (r = -.35, P =.048) of the FSIVGT. In lean subjects, serum CBG concentration decreased significantly after IV insulin from 37.9 +/- 5.4 to 35.4 +/- 3 mg/L (P =.02) and returned to basal levels thereafter. In contrast, obese, glucose-tolerant subjects had lower CBG levels than lean and obese glucose intolerant subjects (33.8 +/- 3.0 v 37.9 +/- 5.4 and 39.8 +/- 4.4 mg/L, respectively), and their serum CBG concentrations remained unchanged during FSIVGT. Mean serum-free insulin-like growth factor-I (IGF-I) concentrations steadily declined from 1.21 +/- 0.81 to 0.8 +/- 0.36 microg/L during the FSIVGT, and this effect was restricted to lean subjects. Basal serum-free IGF-I did not correlate with CBG levels at time 0, but correlated inversely with the serum CBG concentrations at 22 minutes (r = -.36, P =.04). Stepwise multivariant analysis showed that AIRg (P =.035) and S(I) (P =.046), but not free IGF-I levels, independently contributed to 28% of CBG variance at 22 minutes. These results suggest that insulin, but not IGF-I, constitutes an important negative regulator of CBG liver synthesis. Endogenous and exogenous insulin do not affect serum CBG concentrations in insulin-resistant obese subjects with preserved or decreased insulin secretion. Obese glucose-tolerant subjects are hypothesized to exhibit tonically inhibited serum CBG levels. In contrast, in lean subjects, the higher the insulin secretion the lower the serum CBG concentration. The mechanisms of this CBG inhibitory effect exerted by insulin and its implication on cortisol homeostasis and fat distribution in humans await further investigations.

Novel human corticosteroid-binding globulin variant with low cortisol-binding affinity

Corticosteroid-binding globulin (CBG) is the plasma transport protein that regulates the access of glucocorticoid hormones to target cells. Genetic deficiencies of CBG are rare, and only a single human CBG variant (Trancortin Leuven) has been related so far to decreased cortisol-binding affinity. We report here on a 43-yr-old woman, referred for chronic asthenia and hypotension, with repeatedly low morning serum cortisol levels (22-61 nmol/L; normal range, 204-546 nmol/L), normal plasma ACTH levels (38-49 pg/mL; normal, <50 pg/mL), and normal urinary cortisol (10-76 nmol/24 h; normal range, 10-105 nmol/24 h). An increased percent-free (dialysable fraction) serum cortisol (8.7-9.7%, normal range, 2.9-3.9%) suggested abnormal CBG binding activity. Indeed, she had a low serum CBG concentration (24 mg/L vs. 44+/-6 mg/L in normal women), and the affinity of her CBG for cortisol was decreased (association constant, Ka = 0.12 L/nmol vs. 0.82+/-0.29 L/nmol). In her immediate family members, the serum CBG concentration and cortisol-binding activity were normal in her husband, but the four living children had slightly lower serum CBG concentrations than the reference ranges for their pre- and postpubertal status. Measurements of cortisol distribution in undiluted serum indicated that an increase in the percentage of nonprotein-bound cortisol offsets the low cortisol levels to give approximately normal concentrations of free cortisol in serum. Direct sequencing of PCR-amplified exons encoding CBG revealed that the proband was homozygous for a polymorphism (GAC-AAC) in the codon for residue 367, which results in a Asp367-->Asn substitution. Her children were heterozygous for this polymorphism. When this nucleotide change was introduced into a normal human CBG complementary DNA, for expression in Chinese hamster ovary cells, Scatchard analysis demonstrated that the Asn367 substitution reduced the affinity of human CBG for cortisol by approximately 4-fold (Ka = 0.15 L/nmol), as compared to normal recombinant CBG (Ka = 0.66 L/nmol). These results suggest that Asp367 is an important determinant of CBG steroid-binding activity and that normal negative regulation of the hypothalamic-pituitary-adrenal axis is maintained by relatively normal serum-free cortisol concentrations, despite a marked reduction in the steroid-binding affinity of this novel human CBG variant, which we have designated as CBG-Lyon.

Decreased corticosteroid-binding globulin in burn patients: relationship with interleukin-6 and fat in nutritional support

OBJECTIVES

To analyze the effect of low-fat nutritional solutions, with or without fish oil, on serum interleukin (IL)-6, and to explore the relationships between IL-6, corticosteroid-binding globulin (CBG; the main cortisol carrier in plasma), and protein metabolism in severely burned adult patients.

DESIGN

Randomized, double-blind study with control and low fat-fed groups.

SETTING

Burn center of Hôtel-Dieu Hospital of Montréal.

PATIENTS

Thirty-seven men and women with thermal burn injury over >20% of body surface area and no other known medical condition.

INTERVENTIONS

Within 24 hrs after admission, nutritional support was started through a gastroenteral tube inserted under endoscopic guidance. The goal for energy intake was calculated using the Curreri formula, and was adjusted with biweekly measurements of resting energy expenditure. Patients were randomly assigned to one of the following groups: control (35% of energy as fat); low fat 1 (15% of energy as fat); and low fat 2 (50% of fat in the form of fish oil).

MEASUREMENTS AND MAIN RESULTS

Tumor necrosis factor (TNF)-alpha and TNF-beta, IL-6, CBG, and cortisol free fraction were measured every 3 days for 28 days. Nitrogen balance and urinary 3-methylhistidine excretion were measured daily. IL-6 concentrations were high in all patients, with the highest value (460 +/- 111 units/mL) observed on day 4. Concentrations of IL-6 were higher in control patients than in low fat-fed patients between days 13 and 28, but not between days 1 and 13. Multivariate analysis showed that IL-6, total body surface area burned, and sepsis scores were independent predictors of CBG between days 1 and 13 (n = 170; p<.00001). High IL-6 concentrations were predictors of low CBG concentrations and high cortisol free fractions. There was no relationship between IL-6, nitrogen balance, and 3-methylhistidine excretion. TNF-alpha and TNF-beta activity measurements by biological assay showed no correlation with other factors measured.

CONCLUSIONS

a) Low-fat feeding, with or without fish oil, does not change the early production of IL-6 after burn injury; b) serum IL-6 is negatively correlated with CBG, which supports the hypothesis that this cytokine inhibits hepatic CBG production; and c) IL-6 does not appear to directly influence protein metabolism in burn patients.

Corticosteroid-binding globulin synthesis regulation by cytokines and glucocorticoids in human hepatoblastoma-derived (HepG2) cells

Plasma corticosteroid-binding globulin (CBG) concentrations decrease dramatically in patients with septic shock or burn injury. This decrease suggests that mediators of the acute phase response, such as cytokines and glucocorticoid hormones, might influence clearance as well as liver synthesis of CBG in humans. The present study investigated the effects of interleukin-6 (IL-6), IL-1 beta, and dexamethasone on CBG synthesis by a clone of human hepatoblastoma-derived (HepG2) cell line. In culture medium from HepG2 cells, the immunoconcentration of CBG and the levels of CBG messenger ribonucleic acid (mRNA) were dose dependently decreased in the presence of IL-6 concentrations ranging from 0.1-10 ng/mL. The percent decrease in CBG immunoconcentration was quantitatively similar to the percent decrease in CBG mRNA levels (29 +/- 6% and 39 +/- 15%, respectively, of control values). In contrast, and as expected, IL-6 dose dependently increased the mRNA levels (164 +/- 22% of control values) of alpha 1-antitrypsin, a positive acute phase protein, but did not affect the immunoconcentration of sex hormone-binding globulin, another liver protein. Dexamethasone alone did not significantly affect CBG secretion or mRNA levels, but did dose-dependently increase tyrosine amino-transferase mRNA levels, which increased to 252 +/- 16% of the control values. However, in combination with IL-6, dexamethasone had a significant additive effect on IL-6 inhibition of CBG secretion and mRNAs in HepG2 cells. IL-1 beta dose-dependently stimulated CBG secretion (156 +/- 10% of control values) with no significant effect on CBG mRNA levels. In addition, IL-1 beta significantly decreased the inhibitory effect of IL-6 on CBG secretion, but had no effect on the inhibitory effect of IL-6 on CBG mRNA levels. These results suggest that IL-1 beta acts on the posttranslation processing and/or secretion mechanisms of CBG in HepG2 cells. Together, the present results strongly support the hypothesis that the decrease in plasma CBG concentrations is associated with the increase in IL-6 and glucocorticoid levels reported in patients with septic shock and burn injury.

Improved clinical status and length of care with low-fat nutrition support in burn patients

BACKGROUND

The optimal amount and type of fat in the nutrition support of burned patients have not been determined. The aim of this study was to test low-fat nutritional solutions, with or without fish oil, on protein metabolism, morbidity, and length of care in severely burned adults.

METHODS

In a prospective randomized clinical trial, 43 patients were assigned to one of the following groups: control (35% fat), low-fat solution (ie, 15% of total calories as fat), low-fat with fish oil, given for 30 days. Nitrogen balance, urinary 3-methylhistidine excretion, urinary cortisol, and clinical status were measured daily. Corticosteroid-binding globulin and total and free serum cortisol were measured every 3 days.

RESULTS

Compared with controls, patients on low-fat support had fewer cases of pneumonia: 3/24 vs 7/13 (p = .02), better respiratory and nutrition status, and shorter time to healing: 1.2 vs 1.8 days/% burned area (p = 0.01). There was no difference in nitrogen balance between groups, and 3-methylhistidine excretion was higher and serum free cortisol was lower in log-fat--fed patients than in controls. There was no difference between the two low-fat groups in any of the parameters measured.

CONCLUSIONS

This study showed that low-fat nutrition support decreases infectious morbidity and shortens length of stay in burn patients. Fish oil does not seem to add clinical benefit to low-fat solutions. In addition, this study provides the first evidence that nutrition intervention modulates cortisol-binding globulin and the concentration of free circulating cortisol after a severe stress.

Effects of drug administration on gonadotropins, sex steroid hormones and binding proteins in humans

The possible mechanisms by which the administration of drugs may alter the gonadal function in humans are considered in this review. Based on personal data, and on data published in the literature, the following events may occur: (1) blockade of gonadal steroidogenesis; (2) interaction of drug(s) with the steroid-binding protein system in plasma, and (3) interference of drug(s) at the level of the feedback control of gonadotropin secretion. Representative examples of the above mechanisms are as following: (1) Ketoconazole possesses inhibitory effects in vitro on cytochrome P-450. When given in adult males, it decreased the plasma concentrations of testosterone (T) and androstenedione and increased 17 alpha-hydroxyprogesterone levels, suggesting that this drug acts in vivo on gonadal steroidogenesis by blocking the 17,20-lyase. (2) Danazol is a progestagen with high affinity for sex steroid-binding protein (SBP); when given in high dosages in normal males, it increased rapidly the dialyzable fraction (percent protein unbound or free fraction) of T. This suggests that by interacting with the binding sites of SBP, danazol and/or its metabolites displace the fraction of T bound to SBP. However, in males as well as in females, the long-term administration of danazol decreased also the binding capacity of SBP, and consequently increased the free fraction of sex steroid hormones. (3) Dihydrotestosterone (DHT), the most active androgen in many target cells, given at therapeutic dosages to adult males, resulted in a decrease in plasma concentrations of luteinizing hormone (LH) and T, without any significant change in the percent of free T, even though the affinity of DHT for SBP is higher than that of T. This suggests that the main effect of DHT is to inhibit gonadotropin secretion at the central level. (4) Flutamide, a nonsteroidal antiandrogen, increased both LH and T levels, demonstrating its pure antiandrogenic activity on gonadotropin secretion. The consequence(s) of the effects of such drugs on the production, the metabolic clearance rate and the bioavailability of sex steroid hormones are discussed.