Characterization and purification of bile salt hydrolase from Lactobacillus sp. strain 100-100.

We have characterized and purified the bile salt hydrolase from Lactobacillus sp. strain 100-100. Bile salt hydrolase from cells of the strain was purified with column and high-performance liquid chromatography. The activity was assayed in whole cells and cell-free extracts with either a radiochemical assay involving [14C]taurocholic acid or a nonradioactive assay involving trinitrobenzene sulfonate. The activity was detectable only in stationary-phase cells. Within 20 min after conjugated bile acids were added to stationary-phase cultures of strain 100-100, the activity in whole cells increased to levels three- to fivefold higher than in cells from cultures grown in medium free of bile salts. In cell-free extracts, however, the activity was about equal, 1.41 and 1.53 mumol/min per mg of protein, respectively, whether or not the cells have been grown with bile salts present. When supernatant solutions from cultures grown in medium containing taurocholic acid were used to suspend cells grown in medium free of the bile salt, the bile salt hydrolase activity detected in whole cells increased two- to threefold. Two forms of the hydrolase were purified from the cells and designated hydrolases A and B. They eluted from anion-exchange high-performance liquid chromatography in two sets of fractions, A at 0.15 M NaCl and B at 0.18 M NaCl. Their apparent molecular weights in nondenaturing polyacrylamide gel electrophoresis were 115,000 and 105,000, respectively. However, discrepancies existed in the apparent molecular weights and number of peptides detected in sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the two forms. Both had similar substrate specificities, highest on taurodeoxycholic and glycocholic acid, and pH optima between 3.8 and 4.5. The kinetic properties were also similar, with Vmaxs of 17 and 53 micromoles/min per mg of protein and Kms of 0.76 and 0.95 mM taurocholic acid for A and B, respectively. Therefore, whether the enzyme exists in two forms in the cells remains to be determined.     

Insight from molecular modeling into different conformation and SAR of natural steroids and unnatural 7-oxa-steroids

Replacement of the 7-CH2 group of natural steroid with an oxygen atom led to identification of unnatural 7-oxa-steroids as potent and selective progesterone receptor antagonists. The unnatural 7-oxa-steroids exhibited a different structure-activity relationship (SAR) from natural steroids. Molecular modeling demonstrated that the switch of carbon to oxygen in the B-ring results in a subtle conformational change of the tetracyclic skeleton and induces a remarkable spatial shift at the terminal end of the side chain of the D-ring. This shift causes the phenyl ring on the D-ring to form a perfect parallel-displaced form of pi-pi interaction with the phenyl ring of Phe794. The unnatural 7-oxa-steroids were orally active in a rat complement C3 assay and showed comparable pharmacokinetic and metabolic profiles to those of the natural steroid, mifepristone.     

Dual binding site inhibitors of B-RAF kinase

Computer aided modeling guided the design of a series of diarylimidazole compounds (11–22) intended to interact with both the ATP and adjacent allosteric binding domains of B-RAF kinase. Their ability to inhibit the function of B-RAF kinase and intracellular ERK1/2 phosphorylation were evaluated.     

Novel 5-aryl-1,3-dihydro-indole-2-thiones. potent,orally active progesterone receptor agonists

During the course of our studies on 3,3-disubstituted-5-aryloxindoles derived progesterone receptor (PR) antagonists we discovered that changing the amide funtionality to a thio-amide resulted in compounds displaying potent PR agonist activity. In this communication, the synthesis, structure activity relationships (SAR) and in vivo activity of various 5-arylthio-oxindoles will be discussed.     

Selective estrogen receptor modulators protect hippocampal neurons from kainic acid excitotoxicity: differences with the effect of estradiol

Neuroprotective effects of estradiol are well characterized in animal experimental models. However, in humans, the outcome of estrogen treatment for cognitive function and neurological diseases is very controversial. Selective estrogen receptor modulators (SERMs) may represent an alternative to estrogen for the treatment or the prevention of neurodegenerative disorders. SERMs interact with the estrogen receptors and have tissue-specific effects distinct from those of estradiol, acting as estrogen agonists in some tissues and as antagonists in others. In this study we have assessed the effect of tamoxifen, raloxifene, lasofoxifene (CP-336,156), bazedoxifene (TSE-424), and 17beta-estradiol on the hippocampus of adult ovariectomized rats, after the administration of the excitotoxin kainic acid. Administration of kainic acid induced the expression of vimentin in reactive astroglia and a significant neuronal loss in the hilus. SERMs did not affect vimentin immunoreactivity in the hilus, while 17beta-estradiol significantly reduced the surface density of vimentin immunoreactive profiles. Estradiol, tamoxifen (0.4-2 mg/kg), raloxifene (0.4-2 mg/kg), and bazedoxifene (2 mg/kg) prevented neuronal loss in the hilus after the administration of kainic acid. Lasofoxifene (0.4-2 mg/kg) was not neuroprotective. These findings indicate that SERMs present different dose-dependent neuroprotective effects. Furthermore, the mechanisms of neuroprotection by SERMs and estradiol are not identical, because SERMs do not significantly affect reactive gliosis while neuroprotection by estradiol is associated with a strong down-regulation of reactive astroglia.     

The Transmembrane Helices of Beef Heart Cytochrome Oxidase

The locations of the transmembrane helices in the 12 subunits of beef heart cytochrome oxidase were predicted with a modified form of the von Heijne-Blomberg hydrophobicity scale. Based on ~20 residues per transmembrane helix, about 480 of the estimated 660 helical residues (36.8% of 1,793 total residues) are expected to be in transmembrane helices that have their axes tilted by a small angle α from the normal to the plane of the membrane. This angle is calculated to be ~30°, based on the observed overall tilt angle θ of 39° obtained from circular dichroism (CD) measurements on multilamellar films, or about 25°, based on the observed tilt angle θ of 36° obtained from the infrared linear dichroism of films. For 21 residues per transmembrane helix, the calculated values of α become 32° and 28°, respectively, depending upon the value of θ used. Thus, a transmembrane helical tilt angle of ~30° accounts for the predicted transmembrane stretches in cytochrome oxidase if 20-21 residues are sufficient to span the membrane. Additional helical residues in the lipid head region may deviate by a larger angle from the normal to the plane of the membrane in cytochrome oxidase.     

Tumor cell surface expression of granulocyte-macrophage colony-stimulating factor elicits antitumor immunity and protects from tumor challenge in the P815 mouse mastocytoma tumor model.

A novel membrane-bound form of GM-CSF (mbGM-CSF) was expressed on the surface of the mouse mastocytoma cell line P815 to target tumor cell-associated Ags to epidermal Langerhans cells. Transfected clones stimulated the proliferation of syngeneic bone marrow cells, indicating that mbGM-CSF is biologically active. We evaluated the in vivo effects of mbGM-CSF by comparing the growth of mbGM-CSF cells (termed 1D6.1E5) to that of wild-type P815 cells in DBA/2 mice. The growth rates of tumors initiated by P815 and 1D6.1E5 were similar until day 12, after which P815 tumors grew to large sizes while 1D6. 1E5 tumors were rejected. In contrast, the growth of both tumors was unimpeded when injected into nude mice, suggesting that a T cell-dependent antitumor response was induced by 1D6.1E5 in normal mice. Lymphocytes from 1D6.1E5-vaccinated mice were able to kill 51Cr-labeled P815 cells in a dose-dependent fashion that was inhibited by anti-CD8 Abs, suggesting that the antitumor response involved CD8+ CTL. We then tested whether vaccination with these cells would elicit a protective antitumor response by injecting mice with either irradiated 1D6.1E5 or P815 cells and challenging them with nonirradiated P815 cells. 1D6.1E5-treated mice grew small tumors that soon disappeared in all animals. In contrast, the majority of animals receiving the irradiated wild-type tumor vaccine grew large tumors, and 50% died. These data demonstrate that mbGM-CSF expressed on the surface of tumor cells is biologically active and elicits protective antitumor immunity.     

The discovery of a potent orally efficacious indole androgen receptor antagonist through in vivo screening

A series of novel 2-(1H-indol-2-yl)-propan-2-ols have been designed, synthesized, and screened for their ability to inhibit testosterone-induced prostate weight increases in immature rats. Through the use of this paradigm, we were able to identify compounds that exhibited in vivo potency equal to that of the marketed antiandrogen Casodex when orally administered.     

Synthesis and identification of novel 11beta-aryl-4',5'-dihydrospiro[estra-4,9-diene-17beta,4'-oxazole] analogs with dissociated antiprogesterone activities

A series of novel 11beta-aryl-4',5'-dihydrospiro[estra-4,9-diene-17beta,4'-oxazole] analogs have been evaluated for their antagonist hormonal properties using the T47D cell-based alkaline phosphatase assay and the A549 cell-based functional assay. Some of the compounds showed highly potent, and more selective antiprogestational activity against antiglucocorticoid activity than mifepristone (RU 486).     

Discovery of novel phosphorus-containing steroids as selective glucocorticoid receptor antagonist

Mifepristone is a non-selective antagonist of 3-oxosteroid receptors with both abortifacient and anti-diabetic activities. For glucocorticoid receptor (GR) program, we sought an unexplored, synthetically accessible phosphorus-containing steroidal mimetic of mifepristone, suitable for parallel synthesis of analogues. One compound 4a, with high oral bioavailability (59%) in rat, exhibited functional antagonism of GR in oral glucose tolerance test (OGTT). Thus this series of compounds might be potentially useful for the treatment of type II diabetes.