Physical properties and surface activity of surfactant-like membranes containing the cationic and hydrophobic peptide KL4

Surfactant-like membranes containing the 21-residue peptide KLLLLKLLLLKLLLLKLLLLK (KL4), have been clinically tested as a therapeutic agent for respiratory distress syndrome in premature infants. The aims of this study were to investigate the interactions between the KL4 peptide and lipid bilayers, and the role of both the lipid composition and KL4 structure on the surface adsorption activity of KL4-containing membranes. We used bilayers of three-component systems [1,2-dipalmitoyl-phosphatidylcholine/1-palmitoyl-2-oleoyl-phosphatidylglycerol/palmitic acid (DPPC/POPG/PA) and DPPC/1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC)/PA] and binary lipid mixtures of DPPC/POPG and DPPC/PA to examine the specific interaction of KL4 with POPG and PA. We found that, at low peptide concentrations, KL4 adopted a predominantly alpha-helical secondary structure in POPG- or POPC-containing membranes, and a beta-sheet structure in DPPC/PA vesicles. As the concentration of the peptide increased, KL4 interconverted to a beta-sheet structure in DPPC/POPG/PA or DPPC/POPC/PA vesicles. Ca2+ favored alpha<-->beta interconversion. This conformational flexibility of KL4 did not influence the surface adsorption activity of KL4-containing vesicles. KL4 showed a concentration-dependent ordering effect on POPG- and POPC-containing membranes, which could be linked to its surface activity. In addition, we found that the physical state of the membrane had a critical role in the surface adsorption process. Our results indicate that the most rapid surface adsorption takes place with vesicles showing well-defined solid/fluid phase co-existence at temperatures below their gel to fluid phase transition temperature, such as those of DPPC/POPG/PA and DPPC/POPC/PA. In contrast, more fluid (DPPC/POPG) or excessively rigid (DPPC/PA) KL4-containing membranes fail in their ability to adsorb rapidly onto and spread at the air-water interface.     

Synthesis,semipreparative HPLC separation,biological evaluation,and 3D-QSAR of hydrazothiazole derivatives as human monoamine oxidase B inhibitors

The present study reports on synthesis in high yields (70–99%), HPLC enantioseparation, inhibitory activity against human monoamino oxidases, and molecular modeling including 3D-QSAR studies, of a large series of (4-aryl-thiazol-2-yl)hydrazones (1–45). Most of the synthesized compounds proved to be potent and selective inhibitors of hMAO-B isoform in the micromolar or nanomolar range, thus demonstrating that hydrazothiazole could be considered a good pharmacophore to design new hMAO-B inhibitors. Due to the presence in some derivatives of a chiral center, we also performed a semipreparative chromatographic enantioseparation of these compounds obtained by a stereoconservative pattern. The separated enantiomers were submitted to in vitro biological evaluation to point out the stereorecognition of the active site of the enzyme towards these structures. Finally, a 3D-QSAR study was carried out using Comparative Molecular Field Analysis (CoMFA), aiming to deduce rational guidelines for the further structural modification of these lead compounds.     

Antiviral activity of benzimidazole derivatives. II. Antiviral activity of 2-phenylbenzimidazole derivatives

Seventy-six 2-phenylbenzimidazole derivatives were synthesized and evaluated in cell-based assays for cytotoxicity and antiviral activity against a panel of 10 RNA and DNA viruses. The most commonly affected viruses were, in decreasing order, CVB-2, BVDV, Sb-1, HSV-1, and YFV, while HIV-1 and VSV were not affected, and RSV, VV and Reo-1 were only susceptible to a few compounds. Thirty-nine compounds exhibited high activity (EC₅₀ = 0.1–10 μM) against at least one virus, and four of them were outstanding for their high and selective activity against VV (24, EC₅₀ = 0.1 μM) and BVDV (50, 51, and 53 with EC₅₀ = 1.5, 0.8, and 1.0 μM, respectively). The last compounds inhibited at low micromolar concentrations the NS5B RdRp of BVDV and also of HCV, the latter sharing structural similarity with the former. The considered compounds represent attractive leads for the development of antiviral agents against poxviruses, pestiviruses and even HCV, which are important human and veterinary pathogens.     

Non-additive effects of RBP4, ESR1 and IGF2 polymorphisms on litter size at different parities in a Chinese-European porcine line

Background

The aim of this work was to study the effects on litter size of variants of the porcine genes RBP4, ESR1 and IGF2, currently used in genetic tests for different purposes. Moreover, we investigated a possible effect of the interaction between RBP4-MspI and ESR1-PvuII polymorphisms. The IGF2-intron3-G3072A polymorphism is actually used to select lean growth, but other possible effects of this polymorphism on reproductive traits need to be evaluated.

Methods

Detection of polymorphisms in the genomic and cDNA sequences of RBP4 gene was carried out. RBP4-MspI and IGF2-intron3-G3072A were genotyped in a hyperprolific Chinese-European line (Tai-Zumu) and three new RBP4 polymorphisms were genotyped in different pig breeds. A bivariate animal model was implemented in association analyses considering the number of piglets born alive at early (NBA₁₂) and later parities (NBA₃₊ ) as different traits. A joint analysis of RBP4-MspI and ESR1-PvuII was performed to test their possible interaction. In the IGF2 analysis, paternal or maternal imprinting effects were also considered.

Results

Four different RBP4 haplotypes were detected (TGAC, GGAG, GAAG and GATG) in different pig breeds and wild boars. A significant interaction effect between RBP4-MspI and ESR1-PvuII polymorphisms of 0.61 ± 0.29 piglets was detected on NBA₃₊. The IGF2 analysis revealed a significant increase on NBA₃₊ of 0.74 ± 0.37 piglets for the paternally inherited allele A.

Conclusions

All the analyzed pig and wild boar populations shared one of the four detected RBP4 haplotypes. This suggests an ancestral origin of the quoted haplotype. The joint use of RBP4-MspI and ESR1-PvuII polymorphisms could be implemented to select for higher prolificacy in the Tai-Zumu line. In this population, the paternal allele IGF2-intron3-3072A increased litter size from the third parity. The non-additive effects on litter size reported here should be tested before implementation in other pig breeding schemes.     

Voltage‐dependent κ‐opioid modulation of action potential waveform‐elicited calcium currents in neurohypophysial terminals

Release of neurotransmitter is activated by the influx of calcium. Inhibition of Ca²⁺ channels results in less calcium influx into the terminals and presumably a reduction in transmitter release. In the neurohypophysis (NH), Ca²⁺ channel kinetics, and the associated Ca²⁺ influx, is primarily controlled by membrane voltage and can be modulated, in a voltage‐dependent manner, by G‐protein subunits interacting with voltage‐gated calcium channels (VGCCs). In this series of experiments we test whether the κ‐ and µ‐opioid inhibition of Ca²⁺ currents in NH terminals is voltage‐dependent. Voltage‐dependent relief of G‐protein inhibition of VGCC can be achieved with either a depolarizing square pre‐pulse or by action potential waveforms. Both protocols were tested in the presence and absence of opioid agonists targeting the κ‐ and µ‐receptors in neurohypophysial terminals. The κ‐opioid VGCC inhibition is relieved by such pre‐pulses, suggesting that this receptor is involved in a voltage‐dependent membrane delimited pathway. In contrast, µ‐opioid inhibition of VGCC is not relieved by such pre‐pulses, indicating a voltage‐independent diffusible second‐messenger signaling pathway. Furthermore, relief of κ‐opioid inhibition during a physiologic action potential (AP) burst stimulation indicates the possibility of activity‐dependent modulation in vivo. Differences in the facilitation of Ca²⁺ channels due to specific G‐protein modulation during a burst of APs may contribute to the fine‐tuning of Ca²⁺‐dependent neuropeptide release in other CNS terminals, as well. J. Cell. Physiol. 225: 223–232, 2010. © 2010 Wiley‐Liss, Inc.