Chemical synthesis of 16beta-propylaminoacyl derivatives of estradiol and their inhibitory potency on type 1 17beta-hydroxysteroid dehydrogenase and binding affinity on steroid receptors

The 17beta-hydroxysteroid dehydrogenases (17beta-HSDs) are members of a family of enzymes that catalyze the interconversion of weakly active sexual hormones (ketosteroids) and potent hormones (17beta-hydroxysteroids). Among the known isoforms of 17beta-HSD, the type 1 catalyzes the NAD(P)H-mediated reduction of estrone (E(1)) to estradiol (E(2)), a predominant mitogen for the breast cancer cells. Therefore, the inhibition of this particular enzyme is a logical approach to reduce the concentration of estradiol in breast tumors. To develop inhibitors of type 1 17beta-HSD activity, we hypothesized that molecules containing both hydrophobic and hydrophilic components should be interesting candidates for interacting with both the steroid binding domain and some amino acid residues of the cofactor binding domain of the enzyme. Firstly, a conveniently protected 16beta-(3-aminopropyl)-E(2) derivative was synthesized from commercially available E(1). Then, a representative of all class of NHBoc-protected amino acids (basic, acid, aromatic, aliphatic, hydroxylated) were coupled using standard procedures to the amino group of the precursor. Finally, cleavage of all protecting groups was performed in a single step to generate a series of 16beta-propylaminoacyl derivatives of E(2). The enzymatic screening revealed that none of the novel compounds can inhibit the reductive activity of type 1 17beta-HSD. On the other hand, all of these E(2) derivatives did not show any significant binding affinity on four steroid receptors including the estrogen receptor. Additional efforts aimed at improving the inhibitory potency of these steroidal derivatives on type 1 17beta-HSD without providing estrogenic activities is under investigation using a combinatorial chemistry approach.     

Structure-activity relationship of biaryl acylsulfonamide analogues on the human EP(3) prostanoid receptor

Potent and selective ligands for the human EP3 prostanoid receptor are described. Biaryl compounds bearing a tethered ortho substituted acidic moiety were identified as potent EP3 antagonists based on the SAR described herein. The binding affinity of key compounds on all eight human prostanoid receptors is reported.     

Plasma kinetics of VLDL and HDL apoC-I in normolipidemic and hypertriglyceridemic subjects

ApoC-I has several different lipid-regulating functions including, inhibition of receptor-mediated uptake of plasma triglyceride-rich lipoproteins, inhibition of cholesteryl ester transfer activity, and mediation of tissue fatty acid uptake. Since little is known about the rate of production and catabolism of plasma apoC-I in humans, the present study was undertaken to determine the plasma kinetics of VLDL and HDL apoC-I using a primed constant (12 h) intravenous infusion of deuterium-labeled leucine. Data were obtained for 14 subjects: normolipidemics (NL, n = 4), hypertriglyceridemics (HTG, n = 4) and combined hyperlipidemics (CHL, n = 6). Plasma VLDL triglyceride (TG) levels were 0.59 +/- 0.03, 4.32 +/- 0.77 (P < 0.01 vs. NL), and 2.20 +/- 0.39 mmol/l (P < 0.01 vs. NL), and plasma LDL cholesterol (LDL-C) levels were 2.34 +/- 0.22, 2.48 +/- 0.26, and 5.35 +/- 0.48 mmol/l (P < 0.01 vs. NL), respectively. HTG and CHL had significantly (P < 0.05) increased levels of total plasma apoC-I (12.5 +/- 1.2 and 12.4 +/- 1.3 mg/dl, respectively) versus NL (7.9 +/- 0.6 mg/dl), due to significantly (P < 0.01) elevated levels of VLDL apoC-I (5.8 +/- 0.8 and 4.5 +/- 0.8 vs. 0.3 +/- 0.1 mg/dl). HTG and CHL also had increased rates of VLDL apoC-I transport (i.e., production) versus NL: 2.29 +/- 0.34 and 3.04 +/- 0.53 versus 0.24 +/- 0.11 mg/kg.day (P < 0.01), with no significant change in VLDL apoC-I residence times (RT): 1.16 +/- 0.12 versus 0.69 +/- 0.06 versus 0.74 +/- 0.17. Although HDL apoC-I concentrations were not significantly lower in HTG and CHL versus NL, HDL apoC-I rates of transport were inversely related to plasma and VLDL-TG levels (r = -0.63 and -0.62, respectively, P < 0.05). Our results demonstrate that increased levels of plasma and VLDL apoC-I in hypertriglyceridemic subjects (with or without elevated LDL-C levels) are associated with increased levels of plasma VLDL apoC-I production.     

Selection against blue mussels (Mytilus edulis L.) homozygotes under various stressful conditions

Three mussel groups differing in mean multilocus heterozygosity (MLH) were used to examine the MLH-fitness relationship. Mussels were submitted to aerobic and anaerobic stressful conditions in the laboratory, and their LT(50) was measured. Mortality was not random in two of the three groups and affected the homozygous individuals more. This selective mortality caused a significant increase in the mean MLH of the survivors, but only for the two groups characterized by the lowest initial MLH and significant deficits in heterozygotes at the onset of the experiments. While these experiments were ongoing, the same two groups also suffered a 40% mortality rate in lantern nets under field conditions. This mortality also increased the mean MLH in survivors. All groups showed strong inverse relationships between MLH and standard metabolism. Our results suggest that the higher resistance of more heterozygous individuals is related to their lower metabolic needs.     

Weight loss-induced rise in plasma pollutant is associated with reduced skeletal muscle oxidative capacity

In this study, we examined whether weight loss-induced changes in plasma organochlorine compounds (OC) were associated with those in skeletal muscle markers of glycolytic and oxidative metabolism. Vastus lateralis skeletal muscle enzyme activities and plasma OC (Aroclor 1260, polychlorinated biphenyl 153, p,p'-DDE, beta-hexachlorocyclohexane, and hexachlorobenzene) were measured before and after a weight loss program in 17 men and 20 women. Both sexes showed a similar reduction in body weight (approximately 11 kg) in response to treatment, although men lost significantly more fat mass than women (P < 0.05). Enzymatic markers of glycolysis, phosphofructokinase (PFK) activity, and oxidative metabolism, beta-hydroxyacyl-CoA dehydrogenase (HADH), citrate synthase (CS), and cytochrome c oxidase (COX) activities, remained unchanged after weight loss. A significant increase in plasma OC levels was observed in response to weight loss, an effect that was more pronounced in men. No relationship was observed between changes in OC and those in PFK activity in either sex [-0.31 < r < 0.12, not significant (NS)]. However, the greater the increase in plasma OC levels, the greater the reduction in oxidative enzyme (HADH, CS, COX) activities was in response to weight loss in men (-0.75 < r < -0.50, P < 0.05) but not in women (-0.33 < r < 0.33, NS). These results suggest that the weight loss-induced increase in plasma pollutant levels is likely to be associated with reduced skeletal muscle oxidative metabolism in men but not in women.     

RCAS1 is associated with ductal breast cancer progression

RCAS1/EBAG9 (receptor-binding cancer antigen expressed on SiSo cells/ estrogen receptor-binding fragment-associated gene 9), an estrogen-transcribed protein, has been shown to be expressed in a wide variety of cancers, including uterine, ovarian, and lung cancer cells. Soluble and membranous RCAS1 proteins may play a role in the immune escape of tumor cells by promoting T lymphocyte inhibition of growth and apoptosis. In the present report, the presence of RCAS1 was revealed in human ductal breast cancer biopsies by immunohistochemistry. Its cytoplasmic expression was exhibited in cancer cells obtained from tumor biopsies and in breast cancer cell lines. RCAS1 significantly correlated with tumor grade. In addition, RCAS1 was identified in MCF7 culture supernatants. Those observations suggest that RCAS1 is a new marker for breast cancer progression and a possible mechanism for breast cancer immune escape.     

Glycosylation study of the major genetic variants of human alpha1-acid glycoprotein and of their pharmacokinetics in the rat

Human alpha1-acid glycoprotein (AAG) is a mixture of at least two genetic variants, the A variant and the F1 and/or S variant or variants, which are encoded by two different genes. AAG is also an extensively glycosylated protein which possesses five N-linked glycans exhibiting substantial heterogeneity in their structures. The first objective of this study was to investigate the glycosylation of the two major gene products of AAG, i.e. the A variant and a mixture of the F1 and S variants (F1*S). To this end, we combined a chromatographic method for the fractionation of the AAG variants with a lectin-binding assay to characterise the glycosylation of purified glycoproteins. Secondly, because the oligosaccharides can influence the disposition of AAG, a kinetic study of the AAG variants was carried out in the rat. After intravenous administration of whole human AAG, the separation and quantification of the AAG variants in plasma was performed by application of specific methods by isoelectric focusing and immunonephelometry. The binding studies carried out on a panel of lectins showed significant differences in the lectin-binding characteristics of the separated F1*S and A variants, accounting for differences in the degree of branching of their glycan chains and substitution with sialic acid and fucose. The plasma concentration-time profiles of the F1*S and A variants were biphasic, and only small differences were observed between the variants for their initial and terminal half-lives, clearance and distribution volume. This indicates that the structural differences between the two AAG gene products do not affect their pharmacokinetics in the rat. Specific drug transport roles have been previously demonstrated for the F1*S and A variants, calling for further investigations into their effects on the disposition of drugs they bind in plasma. The present study shows that such investigations are possible without being complicated by kinetic differences between these variants.     

Mek2 is dispensable for mouse growth and development

MEK is a dual-specificity kinase that activates the extracellular signal-regulated kinase (ERK) mitogen-activated protein (MAP) kinase upon agonist binding to receptors. The ERK/MAP kinase cascade is involved in cell fate determination in many organisms. In mammals, this pathway is proposed to regulate cell growth and differentiation. Genetic studies have shown that although a single Mek gene is present in Caenorhabditis elegans, Drosophila melanogaster, and Xenopus laevis, two Mek homologs, Mek1 and Mek2, are present in the mammalian cascade. The inactivation of the Mek1 gene leads to embryonic lethality and has revealed the unique role played by Mek1 during embryogenesis. To investigate the biological function of the second homolog, we have generated mice deficient in Mek2 function. Mek2 mutant mice are viable and fertile, and they do not present flagrant morphological alteration. Although several components of the ERK/MAP kinase cascade have been implicated in thymocyte development, no such involvement was observed for MEK2, which appears to be nonessential for thymocyte differentiation and T-cell-receptor-induced proliferation and apoptosis. Altogether, our findings demonstrate that MEK2 is not necessary for the normal development of the embryo and T-cell lineages, suggesting that the loss of MEK2 can be compensated for by MEK1.