Rat and human embryo and post-natal sera contain a potent endogenous competitor of estrogen-rat alpha-fetoprotein interactions

A highly active inhibitor of the binding of estrone and estradiol-17β to rat alpha-fetoprotein is demonstrated for the first time in embryo, immature and adult rat sera as well as in fetal and adult human sera. The competitive character and the narrow specificity of this inhibition effect is shown. The major compound responsible for this activity is isolated by successive column Sephadex LH₂₀ and thin layer chromatography : it is characterized as a nonpolar, nonphenolic, dialysable and thermostable substance, unreactive towards anti-estrone and anti-estradiol-17β anti-bodies. The possible biological role of an endogenous non-estrogen ligand of rodent fetoproteins is discussed.     

Probing the inhibitor selectivity pocket of human 20α-hydroxysteroid dehydrogenase (AKR1C1) with X-ray crystallography and site-directed mutagenesis

Human 20α-hydroxysteroid dehydrogenase (AKR1C1) is an important drug target due to its role in the development of lung and endometrial cancers, premature birth and neuronal disorders. We report the crystal structure of AKR1C1 complexed with the first structure-based designed inhibitor 3-chloro-5-phenylsalicylic acid (K_i = 0.86 nM) bound in the active site. The binding of 3-chloro-5-phenylsalicylic acid to AKR1C1 resulted in a conformational change in the side chain of Phe311 to accommodate the bulky phenyl ring substituent at the 5-position of the inhibitor. The contributions of the nonconserved residues Leu54, Leu306, Leu308 and Phe311 to the binding were further investigated by site-directed mutagenesis, and the effects of the mutations on the K_i value were determined. The Leu54Val and Leu306Ala mutations resulted in 6- and 81-fold increases, respectively, in K_i values compared to the wild-type enzyme, while the remaining mutations had little or no effects.     

The R453Q and D151A polymorphisms of hexose-6-phosphate dehydrogenase gene (H6PD) influence the polycystic ovary syndrome (PCOS) and obesity

Hexose-6-phosphate dehydrogenase (H6PDH) influences 11β-hydroxysteroid dehydrogenase activity, a key enzyme in the peripheral metabolism of cortisol that modulates insulin sensitivity in adipose tissue. To study the associations of R453Q and D151A polymorphisms in the H6PDH gene (H6PD) with polycystic ovary syndrome (PCOS) and their influence on clinical and metabolic variables, we genotyped 237 patients with PCOS and 135 control women for the R453Q (rs6688832) and D151A (rs34603401) variants in H6PD. The R453Q genotypes were distributed differently in patients and controls (χ(2)=9.55, P=0.002). Genotypes of D151A were distributed evenly in women with PCOS and controls, but showed a different distribution in non-obese and obese women (χ(2)=3.95, P=0.047), especially within the PCOS subgroup (χ(2)=4.65, P=0.031). A backward stepwise likelihood ratio logistic regression model (Nagelkerke's R(2)=0.490; χ(2)=164; P<0.0001) retained free testosterone (OR=1.13; 95% CI: 1.10-1.17) and H6PD Q453 alleles (OR=0.46; 95% CI: 0.27-0.79) as statistically significant predictors for PCOS, whereas homeostasis model assessment of insulin resistance and the H6PD D151A variant were excluded by the model. Both H6PD variants were associated with several phenotypic variables, including fasting insulin, homeostasis model assessment of insulin resistance and androstenedione levels. In summary, the R453Q and D151A variants of the H6PD gene are associated with PCOS and obesity, respectively, and may contribute to the PCOS phenotype by influencing obesity, insulin resistance and hyperandrogenism.     

Molecular Screening of the 11β‐HSD1 Gene in Men Characterized by the Metabolic Syndrome

Adipose tissue type 1 11β‐hydroxysteroid dehydrogenase (11β‐HSD1), which generates hormonally active cortisol from inactive cortisone, has been shown to play a central role in adipocyte differentiation and abdominal obesity‐related metabolic complications. The objective was to investigate whether genetic variations in the human 11β‐HSD1 gene are associated with the metabolic syndrome among French‐Canadian men. We sequenced all exons, the exon‐intron splicing boundaries, and 5′ and 3′ regions of the human 11β‐HSD1 gene in 36 men with the metabolic syndrome, as defined by the National Cholesterol Education Program‐Adult Treatment Panel III, and two controls. Three intronic sequence variants were identified: two single‐nucleotide polymorphisms in intron 3 (g.4478T>G) and intron 4 (g.10733G>C) and one insertion in intron 3 (g.4437‐4438insA). The relative allele frequency was 19.6%, 22.1%, and 19.6% for the g.4478G, g.10733C, and g.4438insA alleles, respectively. One single‐nucleotide polymorphism was identified in exon 6 (c.744G>C or G248G). The frequency of the c.744C allele was only 0.46% in a sample of 217 men. Variants were not associated with components of the metabolic syndrome except for plasma apolipoprotein B levels. In conclusion, molecular screening of the 11β‐HSD1 gene did not reveal any sequence variations that can significantly contribute to the etiology of the metabolic syndrome among French‐Canadians.     

Glycyrrhetinic acid as inhibitor or amplifier of permeability transition in rat heart mitochondria

Glycyrrhetinic acid (GE), a hydrolysis product of glycyrrhizic acid, one of the main constituents of licorice root, is able, depending on its concentration, to prevent or to induce the mitochondrial permeability transition (MPT) (a phenomenon related to oxidative stress) in rat heart mitochondria (RHM). In RHM, below a threshold concentration of 7.5 μM, GE prevents oxidative stress and MPT induced by supraphysiological Ca²⁺ concentrations. Above this concentration, GE induces oxidative stress by interacting with a Fe-S centre of Complex I, thus producing ROS, and amplifies the opening of the transition pore, once again induced by Ca²⁺. GE also inhibits Ca²⁺ transport in RHM, thereby preventing the oxidative stress induced by the cation. However, the reduced amount of Ca²⁺ transported in the matrix is sufficient to predispose adenine nucleotide translocase for pore opening. Comparisons between observed results and the effects of GE in rat liver mitochondria (RLM), in which the drug induces only MPT without exhibiting any protective effect, confirm that it interacts in a different way with RHM, suggesting tissue specificity for its action. The concentration dependence of the opposite effects of GE, in RHM but not RLM, is most probably due to the existence of a different, more complex, pathway by means of which GE reaches its target. It follows that high GE concentrations are necessary to stimulate the oxidative stress capable of inducing MPT, because of the above effect, which prevents the interaction of low concentrations of GE with the Fe-S centre. The reported results also explain the mechanism of apoptosis induction by GE in cardiomyocytes.     

Comments on 'Significance of developmental expression of amphioxus Branchiostoma belcheri and zebrafish Danio rerio Hsd17b10 in biological and medical research'

The reported data on the developmental expression of Hsd17b10 gene in Danio rerio is crucial to the utilization of the D. rerio embryo as an animal model for human developmental disorders caused either by mutations on HSD17B10 (formerly HADH2 ) or by defective expression of the gene. Related diseases were summarized, and it was noticed that hyperinsulinaemic hypoglycaemia is not linked to HSD17B10 . This inherited disease is actually caused by a deletion in the HADH gene on chromosome 4. Moreover, it was found by a revision of the reported phylogenetic tree that hydroxyacyl-CoA dehydrogenase II or rather hydroxysteroid (17beta) dehydrogenase 10 (HSD10) of amphioxus Branchiostoma belcheri —occupies a transition position from HSD10 orthologs of invertebrates to those of vertebrates.     

1α,25-Dihydroxyvitamin D3 affects hormone production and expression of steroidogenic enzymes in human adrenocortical NCI-H295R cells

The current study presents data indicating that 1α,25-dihydroxyvitamin D₃ affects the production of hormones and expression of crucial steroidogenic enzymes in the human adrenocortical cell line NCI-H295R. This cell line is widely used as a model for adrenal steroidogenesis. Treatment of the cells with 1α,25-dihydroxyvitamin D₃ suppressed the levels of corticosterone, aldosterone, DHEA, DHEA-sulfate and androstenedione in the culture medium. In order to study the mechanisms behind this suppression of hormone production, we investigated the effects of 1α,25-dihydroxyvitamin D₃ on important genes and enzymes controlling the biosynthesis of adrenal hormones. The mRNA levels were decreased for CYP21A2 while they were increased for CYP11A1 and CYP17A1. No significant changes were observed in mRNA for CYP11B1, CYP11B2 or 3β-hydroxysteroid dehydrogenase (3βHSD). In similarity with the effects on mRNA levels, also the endogenous enzyme activity of CYP21A2 decreased after treatment with 1α,25-dihydroxyvitamin D₃. Interestingly, the two CYP17A1-mediated activities were influenced reciprocally — the 17α-hydroxylase activity increased whereas the 17,20-lyase activity decreased. The current data indicate that the 1α,25-dihydroxyvitamin D₃-mediated decrease in corticosterone and androgen production is due to suppression of the 21-hydroxylase activity by CYP21A2 and the 17,20-lyase activity by CYP17A1, respectively. In conclusion, the current study reports novel findings on 1α,25-dihydroxyvitamin D₃-mediated effects on hormone production and regulation of genes and enzymes involved in steroidogenesis in the adrenocortical NCI-H295R cell line, a model for human adrenal cortex.     

Expression and clinical significance of galectin-3 in osteosarcoma

Galectin-3 is a multifunctional β-galactoside-binding protein which has been shown to play a role in carcinogenesis. However, the involvement of galectin-3 in osteosarcoma remains unclear. In this study, we aimed to examine the serum level of galectin-3 in osteosarcoma patients and healthy controls, and the protein expression of galectin-3 in osteosarcoma tissues and their adjacent non-malignant tissues. We further aimed to investigate the clinical significance of galectin-3 serum and protein expression levels. Galectin-3 serum level was evaluated using ELISA in 132 osteosarcoma patients and 184 healthy controls, while the protein expression of galectin-3 was determined using immunohistochemistry in the malignant and the surrounding non-malignant tissues of the same 132 osteosarcoma patients. Our results showed that the mean galectin-3 serum level was significantly higher in patients than in controls (2.35 ± 0.91 ng/ml vs. 0.86 ± 0.20 ng/ml) (p < 0.0001). Among patients, a higher galectin-3 serum level was significantly associated with the Enneking stage of cancer (p < 0.0001). In addition, we found a significant overrepresentation of high galectin-3 expression in osteosarcoma tissues than in non-malignant tissues (p < 0.0001). Galectin-3 expression in osteosarcoma tissues was also found to be correlated with the Enneking stage of cancer (p < 0.0001) and the occurrence of metastasis (p < 0.0001). In conclusion, galectin-3 could serve as a useful prognostic marker in osteosarcoma.     

The role of lipid second messengers in aldosterone synthesis and secretion

Second messengers are small rapidly diffusing molecules or ions that relay signals between receptors and effector proteins to produce a physiological effect. Lipid messengers constitute one of the four major classes of second messengers. The hydrolysis of two main classes of lipids, glycerophospholipids and sphingolipids, generate parallel profiles of lipid second messengers: phosphatidic acid (PA), diacylglycerol (DAG), and lysophosphatidic acid versus ceramide, ceramide-1-phosphate, sphingosine, and sphingosine-1-phosphate, respectively. In this review, we examine the mechanisms by which these lipid second messengers modulate aldosterone production at multiple levels. Aldosterone is a mineralocorticoid hormone responsible for maintaining fluid volume, electrolyte balance, and blood pressure homeostasis. Primary aldosteronism is a frequent endocrine cause of secondary hypertension. A thorough understanding of the signaling events regulating aldosterone biosynthesis may lead to the identification of novel therapeutic targets. The cumulative evidence in this literature emphasizes the critical roles of PA, DAG, and sphingolipid metabolites in aldosterone synthesis and secretion. However, it also highlights the gaps in our knowledge, such as the preference for phospholipase D-generated PA or DAG, as well as the need for further investigation to elucidate the precise mechanisms by which these lipid second messengers regulate optimal aldosterone production.     

Modulation of synaptic plasticity by brain estrogen in the hippocampus

The hippocampus is a center for learning and memory as well as a target of Alzheimer's disease in aged humans. Synaptic modulation by estrogen is essential to understand the molecular mechanisms of estrogen replacement therapy. Because the local synthesis of estrogen occurs in the hippocampus of both sexes, in addition to the estrogen supply from the gonads, its functions are attracting much attention.