Imidazo[1,2-a]pyridines: a potent and selective class of cyclin-dependent kinase inhibitors identified through structure-based hybridisation

High-throughput screening identified the imidazo[1,2-a]pyridine and bisanilinopyrimidine series as inhibitors of the cyclin-dependent kinase CDK4. Comparison of their experimentally-determined binding modes and emerging structure-activity trends led to the development of potent and selective imidazo[1,2-a]pyridine inhibitors for CDK4 and in particular CDK2.     

N-isonicotinoyl-(L)-4-aminophenylalanine derivatives as tight binding VLA-4 antagonists

A series of isonicotinoyl-(L)-aminophenylalanine derivatives was prepared and evaluated as VLA-4 antagonists. These compounds exhibit subnanomolar binding affinity to VLA-4 and significant off-rates. The interplay between off-rate, protein binding and pharmacokinetics is discussed.     

Amount-dependent temporal discounting?

Amount-dependent temporal discounting has been demonstrated for human choice between outcomes differing in amount and delay. In the only study to date with non-humans, Grace reported no evidence for amount-dependent temporal discounting with pigeons in a concurrent-chains procedure. The present experiments repeated Grace's procedure but with modifications to enhance the discrimination between small and large magnitude outcomes. In Experiment 1, sensitivity of pigeons' initial-link choice to the terminal link delay ratio was greater with large reinforcer durations in the terminal links than with small reinforcer durations. This result is consistent with a greater rate of temporal discounting for larger reinforcers (the reverse of the result for humans), but can also be explained as enhanced discrimination of delay ratios with larger reinforcer durations. The results of a second experiment supported Grace's conclusion that amount-dependent temporal discounting does not characterize pigeons' choice in concurrent chains. Because reinforcer amount was held constant between choice alternatives in the present experiments and that of Grace, but varied in the human studies, our results question whether prior demonstrations of amount-dependent discounting reflect the effects of reinforcer delay or of reinforcer amount. Differences in the procedures used to study discounting in humans (titration procedures) and non-humans (concurrent chains) may contribute to the divergent results across species.     

Aldosterone modulates neural vasomotor response in hypertension: role of calcitonin gene-related peptide

Objective: We analyse the effect of aldosterone on vasomotor response induced by electrical field stimulation (EFS) in mesenteric arteries from Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR). Results: Aldosterone (0.001–1 μM) reduced vasoconstrictor response to EFS in a dose- and time-dependent manner only in SHR. Thus, the rest of experiments were performed only in SHR. Aldosterone did not affect either noradrenaline response or release. Effect of aldosterone (1 μM) on EFS response was not affected by N^G-nitro-arginine-methyl esther (100 μM), and was abolished by capsaicin (0.5 μM) and the calcitonin gene-related peptide antagonist (CGRP 8–37, 0.5 μM). Calcitonin gene-related peptide (0.1 nM–0.1 μM) induced a concentration-dependent relaxation, which was enhanced by aldosterone (1 μM). Incubation with either spironolactone (1 μM), glibenclamide (10 μM), RU 486 10 μM, ODQ (10 μM) or cycloheximide (10 μM) significantly reduced the enhancement of CGRP-relaxation produced by aldosterone, while remained unmodified by SQ 22,536. Conclusions: Aldosterone decreases the vasoconstrictor response to EFS in mesenteric arteries from SHR but not from WKY. This effect is mediated by an increased response to the sensory neurotransmitter CGRP, substantially, through glucocorticoid receptors activation. Furthermore, this effect is mediated by an increase of cGMP synthesis and ATP-dependent potassium channel activation.     

Control of the reactivation kinetics of homodimeric triosephosphate isomerase from unfolded monomers

Homodimeric triosephosphate isomerases from Trypanosoma cruzi (TcTIM) and Trypanosoma brucei (TbTIM) have markedly similar catalytic properties and 3-D structures; their overall amino acid sequence identity is 68% and 85% in their interface residues. Nonetheless, active dimer formation from guanidinium chloride unfolded monomers is faster and more efficient in TcTIM than in TbTIM. The enzymes thus provide a unique opportunity for exploring the factors that control the formation of active dimers. The kinetics of reactivation at different protein concentrations showed that the process involved three reactions: monomer folding, association of folded monomers, and a transition from inactive to active dimers. The rate constants of the reactions indicated that, at relatively low protein concentrations, the rate-limiting step of reactivation was the association reaction; at high protein concentrations the transition of inactive to active dimers was rate limiting. The rates of the latter two reactions were higher in TcTIM than in TbTIM. Studies with a mutant of TcTIM that had the interface residues of TbTIM showed that the association rate constant was similar to that of TbTIM. However, the rate of the transition from inactive to active dimers was close to that of TcTIM; thus, this transition depends on the noninterfacial portion of the enzymes. When unfolded monomers of TcTIM and TbTIM were allowed to reactivate together, TcTIM, the hybrid, and TbTIM were formed in a proportion of 1:0.9:0.2. This distribution suggests that, in the hybrid, the characteristics of the TcTIM monomers influence the properties of TbTIM monomers.     

Purification and characterization of three members of the photolyase/cryptochrome family blue-light photoreceptors from Vibrio cholerae

The sequence of Vibrio cholerae genome revealed three genes belonging to the photolyase/cryptochrome blue-light photoreceptor family. The proteins encoded by the three genes were purified and characterized. All three proteins contain folate and flavin cofactors and have absorption peaks in the range of 350-500 nm. Only one of the three, VcPhr, is a photolyase specific for cyclobutane pyrimidine dimers. The other two are cryptochromes and were designated VcCry1 and VcCry2, respectively. Mutation of phr abolishes photoreactivation of UV-induced killing, whereas mutations in cry1 and cry2 do not affect photorepair activity. VcCry1 exhibits some unique features. Of all cryptochromes characterized to date, it is the only one that contains stoichiometric amounts of both chromophores and retains its flavin cofactor in the two-electron reduced FADH2 form. In addition, VcCry1 exhibits RNA binding activity and co-purifies with an RNA of 60-70 nucleotides in length.     

Kaempferol-induced growth inhibition and apoptosis in A549 lung cancer cells is mediated by activation of MEK-MAPK

A vast variety of naturally occurring substances have been shown to protect against experimental carcinogenesis and an increasing amount of evidence suggests that kaempferol may have cancer chemopreventative properties. However, the precise underlying protective mechanisms are poorly understood. To elucidate these mechanisms, we challenged human lung cancer cell line A549 with kaempferol and investigated its effects upon cellular growth and signal transduction pathways. Treatment of A549 cells with kaempferol resulted in a dose- and time-dependent reduction in cell viability and DNA synthesis with the rate of apoptosis equivalent to 0.9+/-0.5, 5.2+/-1.5, 16.8+/-2.0, 25.4+/-2.6, and 37.8+/-4.5% on treatment with 0, 17.5, 35.0, 52.5, and 70.0 microM kaempferol, respectively. Concomitantly, kaempferol treatments led to a 1.2-, 2.7-, 3.3-, and 3.4-fold increase in Bax. Similar elevations were also observed in Bad which increased 1.2-, 3.3-, 3.7-, and 4.7-fold, respectively, as compared to control. Bcl-2 and Bcl-xL expression were inhibited in a dose-dependent fashion. While the Akt-1 and phosphorylated Akt-1 were inhibited, the mitogen-activated protein kinase (MAPK) was activated upon kaempferol treatment. Kaempferol induced apoptosis was associated with the cleavage of caspase-7 and poly ADP-ribose polymerase (PARP). Inhibition of MEK1/2 but not PI-3 kinase blocked kaempferol-induced cleavage of caspase-7, PARP cleavage, and apoptosis. The results suggest that inactivation of Akt-1 and alteration of Bcl-2 family of proteins are not sufficient for kaempferol to induce apoptosis and activation of MEK-MAPK is a requirement for kaempferol-induced cell death machinery in A549 cells.     

Deaza- and deoxyadenosine derivatives: synthesis and inhibition of animal viruses as human infection models

N6-Cycloalkyl-2',3'-dideoxyadenosine derivatives and (2-chloro)-N6-cycloheptyl-3-deazaadenosine have been synthesized and tested, along with other (deaza)purine (deoxy)nucleosides from our chemical library, as inhibitors of virus replication against Bovine Herpes Virus 1 (BHV-1) and sheep Maedi/Visna Virus (MVV). Most compounds demonstrated good antireplicative activity against MVV, showing also low cell toxicity.     

New fluorinated derivatives as esterase inhibitors. Synthesis,hydration and crossed specificity studies

A variety of new fluorinated chemicals have been prepared for the first time and tested as inhibitors of esterases, one of the main enzymes involved in pheromone catabolism, in two economically important pests, the Egyptian armyworm Spodoptera littoralis (SL) and the Mediterranean corn borer Sesamia nonagrioides (SN). Using the respective major component of the pheromone as substrate, the K(m) and V(max) of the antennal esterase of both insects resulted to be 5.66 x 10(-4) M and 8.47 x 10(-6) Mmin(-1) for SL and 1.61 x 10(-7) M and 1.25 x 10(-7) Mmin(-1) for SN, pointing out that SN esterase has a higher affinity for its corresponding substrate than SL. In general, the trifluoromethyl ketones (TFMKs) exhibited higher inhibitory potency than the corresponding difluoromethyl ketones (DFMKs) or difluoroaldehydes (DFAs). The compounds appeared to hydrate differently in aqueous solution, the extent of hydration following the order: alpha,alpha-DFMKs相似文献   

Novel cell line selectively expressing neuropeptide Y-Y2 receptors

Neuropeptide Y (NPY) recognition by the human neuroblastoma cell lines SiMa, Kelly, SH-SY5Y, CHP-234, and MHH-NB-11 was analyzed in radioactive binding assays using tritiated NPY. For the cell lines CHP-234 and MHH-NB-11 binding of [3H]propionyl-NPY was observed with Kd-values of 0.64 +/- 0.07 nM and 0.53 +/- 0.12 nM, respectively, determined by saturation analysis with non-linear regression. The receptor subtype was determined by competition analysis using the subtype selective NPY analogues [Leu31, Pro34]-NPY (NPY-Y1, NPY-Y5), [Ahx(5-24)]-NPY (NPY-Y2), [Ala31, Aib32]-NPY (NPY-Y5), NPY [3-36] (NPY-Y2, NPY-Y5), and NPY [13-36] (NPY-Y2). Both cell lines, CHP-234 and MHH-NB-11, the latter one being characterized for NPY receptors for the first time, showed exclusive expression of NPY-Y2 receptors. In both cell lines binding of NPY induced signal transduction, which was monitored as reduction of forskolin-induced cAMP production in an ELISA.