Abrogation of oxidative stress improves insulin sensitivity in the Ren-2 rat model of tissue angiotensin II overexpression

To evaluate the role of renin-angiotensin system (RAS)-mediated oxidative stress in insulin resistance (IR), we compared the effects of the angiotensin II (ANG II) receptor blocker (ARB) valsartan and a superoxide dismutase (SOD) mimetic, tempol, on whole body glucose tolerance and soleus muscle insulin-stimulated glucose uptake in transgenic hypertensive TG(mREN-2)27 (Ren-2) rats. Ren-2 rats and Sprague-Dawley (SD) controls were given valsartan (30 mg/kg) or tempol (1 mmol/l) in their drinking water for 21 days. IR was measured by glucose tolerance testing (1 g/kg glucose ip). IR index (AUC(glucose) x AUC(insulin)) was significantly higher in the Ren-2 animals compared with SD controls (30.5 +/- 7.0 x 10(6) arbitrary units in Ren-2 vs. 10.2 +/- 2.4 x 10(6) in SD, P < 0.01). Both valsartan and tempol treatment normalized Ren-2 IR index. Compared with SD controls (100%), there was a significant increase in superoxide anion production (measured by lucigenin-enhanced chemiluminescence) in soleus muscles of Ren-2 rats (133 +/- 15%). However, superoxide production was reduced in both valsartan- and tempol-treated (85 +/- 22% and 59 +/- 12%, respectively) Ren-2 rats. Insulin (INS)-mediated 2-deoxyglucose (2-DG) uptake (%SD basal levels) was substantially lower in Ren-2 rat soleus muscle compared with SD (Ren-2 + INS = 110 +/- 3% vs. SD + INS = 206 +/- 12%, P < 0.05). However, Ren-2 rats treated with valsartan or tempol exhibited a significant increase in insulin-mediated 2-DG uptake compared with untreated transgenic animals. Improvements in skeletal muscle insulin-dependent glucose uptake and whole body IR in rats overexpressing ANG II by ARB or SOD mimetic indicate that oxidative stress plays an important role in ANG II-mediated insulin resistance.     

MK-8825: a potent and selective CGRP receptor antagonist with good oral activity in rats

Rational modification of the clinically tested CGRP receptor antagonist MK-3207 (3) afforded an analogue with increased unbound fraction in rat plasma and enhanced aqueous solubility, 2-[(8R)-8-(3,5-difluorophenyl)-8-methyl-10-oxo-6,9-diazaspiro[4.5]dec-9-yl]-N-[(6S)-2'-oxo-1',2',5,7-tetrahydrospiro[cyclopenta[b]pyridine-6,3'-pyrrolo[2,3-b]pyridin]-3-yl]acetamide (MK-8825) (6). Compound 6 maintained similar affinity to 3 at the human and rat CGRP receptors but possessed significantly improved in vivo potency in a rat pharmacodynamic model. The overall profile of 6 indicates it should find utility as a rat tool to investigate effects of CGRP receptor blockade in vivo.     

Polar invasion and translocation of Neisseria meningitidis and Streptococcus suis in a novel human model of the blood-cerebrospinal fluid barrier

Acute bacterial meningitis is a life-threatening disease in humans. Discussed as entry sites for pathogens into the brain are the blood-brain and the blood-cerebrospinal fluid barrier (BCSFB). Although human brain microvascular endothelial cells (HBMEC) constitute a well established human in vitro model for the blood-brain barrier, until now no reliable human system presenting the BCSFB has been developed. Here, we describe for the first time a functional human BCSFB model based on human choroid plexus papilloma cells (HIBCPP), which display typical hallmarks of a BCSFB as the expression of junctional proteins and formation of tight junctions, a high electrical resistance and minimal levels of macromolecular flux when grown on transwell filters. Importantly, when challenged with the zoonotic pathogen Streptococcus suis or the human pathogenic bacterium Neisseria meningitidis the HIBCPP show polar bacterial invasion only from the physiologically relevant basolateral side. Meningococcal invasion is attenuated by the presence of a capsule and translocated N. meningitidis form microcolonies on the apical side of HIBCPP opposite of sites of entry. As a functionally relevant human model of the BCSFB the HIBCPP offer a wide range of options for analysis of disease-related mechanisms at the choroid plexus epithelium, especially involving human pathogens.     

Intrinsic flexibility of snRNA hairpin loops facilitates protein binding

Stem–loop II of U1 snRNA and Stem–loop IV of U2 snRNA typically have 10 or 11 nucleotides in their loops. The fluorescent nucleobase 2-aminopurine was used as a substitute for the adenines in each loop to probe the local and global structures and dynamics of these unusually long loops. Using steady-state and time-resolved fluorescence, we find that, while the bases in the loops are stacked, they are able to undergo significant local motion on the picosecond/nanosecond timescale. In addition, the loops have a global conformational change at low temperatures that occurs on the microsecond timescale, as determined using laser T-jump experiments. Nucleobase and loop motions are present at temperatures far below the melting temperature of the hairpin stem, which may facilitate the conformational change required for specific protein binding to these RNA loops.     

Mutational analysis of the stability of the H2A and H2B histone monomers

The eukaryotic histone heterodimer H2A-H2B folds through an obligatory dimeric intermediate that forms in a nearly diffusion-limited association reaction in the stopped-flow dead time. It is unclear whether there is partial folding of the isolated monomers before association. To address the possible contributions of structure in the monomers to the rapid association, we characterized H2A and H2B monomers in the absence of their heterodimeric partner. By far-UV circular dichroism, the H2A and H2B monomers are 15% and 31% helical, respectively—significantly less than observed in X-ray crystal structures. Acrylamide quenching of the intrinsic Tyr fluorescence was indicative of tertiary structure. The H2A and H2B monomers exhibit free energies of unfolding of 2.5 and 2.9 kcal mol^− 1, respectively; at 10 μM, the sum of the stability of the monomers is ∼ 60% of the stability of the native dimer. The helical content, stability, and m values indicate that H2B has a more stable, compact structure than H2A. The monomer m values are larger than expected for the extended histone fold motif, suggesting that the monomers adopt an overly collapsed structure. Stopped-flow refolding—initiated from urea-denatured monomers or the partially folded monomers populated at low denaturant concentrations—yielded essentially identical rates, indicating that monomer folding is productive in the rapid association and folding of the heterodimer. A series of Ala and Gly mutations were introduced into H2A and H2B to probe the importance of helix propensity on the structure and stability of the monomers. The mutational studies show that the central α-helix of the histone fold, which makes extensive intermonomer contacts, is structured in H2B but only partially folded in H2A.     

Non-peptide alpha(v)beta(3) antagonists. Part 3: identification of potent RGD mimetics incorporating novel beta-amino acids as aspartic acid replacements.

Potent non-peptidic alpha(v)beta(3) antagonists have been prepared incorporating various beta-amino acids as aspartic acid mimetics. Modification of the beta-alanine 3-substituents alters the potency and physicochemical properties of these receptor antagonists and in some cases provides orally bioavailable alpha(v)beta(3) inhibitors.     

Quantitative stereochemical analysis of subnanogram amounts of 12-hydroxy-(5,8,10,14)-eicosatetraenoic acid by sequential chiral phase liquid chromatography and stable isotope dilution mass spectrometry

The two enantiomers of 12-hydroxy-(5,8,10,14)-eicosatetraenoic acid (12-HETE) are products of different biosynthetic pathways and have distinct biologic actions. Conventional methods of stereochemical analysis of 12-HETE require multimicrogram amounts of material and cannot be applied to systems where the availability of tissue is limited and only trace quantities of 12-HETE are generated. We have developed a method capable of measuring subnanogram amounts of 12-HETE enantiomers which involves addition of racemic. 18O2-labeled 12-HETE as an internal standard, chiral phase HPLC of the pentafluorobenzyl ester derivative of 12-HETE, and stable isotope dilution gas chromatographic-negative ion chemical ionization mass spectrometric quantitation of the resolved stereoisomers. This method has been employed to determine the stereochemical composition of 12-HETE produced by isolated pancreatic islets.