Estimation of the hypothermic component in neuroprotection provided by cannabinoids following cerebral ischemia

Cannabinoids have neuroprotective potentials, and the expression of endocannabinoids as well as cannabinoid receptors is induced after cerebral ischemia. They also induce hypothermia by lowering the hypothalamic set point. We have estimated the significance of such hypothermia in ischemic neuroprotection following systemic administration of WIN 55,212-2, a synthetic cannabinoid receptor agonist. Results showed that WIN 55,212-2 significantly reduced infarct volumes of rats subjected to focal cerebral ischemia (middle cerebral artery occlusion) and significantly decreased ischemic CA1 damage in rats subjected to global cerebral ischemia (two-vessel occlusion). A significant (approximately 50%) part of this neuroprotection was provided by WIN 55,212-2 induced hypothermia (33.7+/-1.1 degrees C/34.9+/-1.6 degrees C), because prevention of hypothermia by maintaining body core temperatures between 37.0 and 38.0 degrees C dissolved the neuroprotective effect into a hypothermic component and an unidentified component. Finally, the ability of WIN 55,212-2 to reduce levels of the proinflammatory cytokine IFNgamma in the infarcted hemisphere of rats subjected to focal cerebral ischemia required hypothermia. For the cannabinoid WIN 55,212-2, we have isolated and directly demonstrated that hypothermia is only part of, although significant, cannabinoid mediated neuroprotection in both global and focal cerebral ischemia. We conclude that cannabinoids are reliable candidates for drug-induced hypothermia and neuroprotection. These neuroprotective effects of cannabinoids could provide the basis for potential therapeutic uses of cannabinoids and/or endocannabinoids in stroke.     

Emerging Shiga Toxin-Producing Escherichia coli Serotypes in Europe: O100:H- and O127:H40

Novel and as yet rare non-O157 Shiga toxin (Stx)-producing Escherichia coli (STEC) serotypes are emerging in Europe. Two different sorbitol-fermenting STECs, O100:H- carrying the virulence gene stx2 and O127:H40 carrying stx1 and eae genes (found in two related subjects), were isolated from patients’ stool samples. Non-O157 STEC infections in humans are currently under-diagnosed. This report highlights the need for, and importance of, screening for Shiga toxins or serotypes other than just O157.     

Subharmonic microbubble emissions for noninvasively tracking right ventricular pressures

Right heart catheterization is often required to monitor intra-cardiac pressures in a number of disease states. Ultrasound contrast agents can produce pressure modulated subharmonic emissions that may be used to estimate right ventricular (RV) pressures. A technique based on subharmonic acoustic emissions from ultrasound contrast agents to track RV pressures noninvasively has been developed and its clinical potential evaluated. The subharmonic signals were obtained from the aorta, RV, and right atrium (RA) of five anesthetized closed-chest mongrel dogs using a SonixRP ultrasound scanner and PA4-2 phased array. Simultaneous pressure measurements were obtained using a 5-French solid state micromanometer tipped catheter. Initially, aortic subharmonic signals and systemic blood pressures were used to obtain a calibration factor in units of millimeters of mercury per decibel. This factor was combined with RA pressures (that can be obtained noninvasively) and the acoustic data from the RV to obtain RV pressure values. The individual calibration factors ranged from -2.0 to -4.0 mmHg/dB. The subharmonic signals tracked transient changes in the RV pressures within an error of 0.6 mmHg. Relative to the catheter pressures, the mean errors in estimating RV peak systolic and minimum diastolic pressures, and RV relaxation [isovolumic negative derivative of change in pressure over time (-dP/dt)] by use of the subharmonic signals, were -2.3 mmHg, -0.8 mmHg, and 2.9 mmHg/s, respectively. Overall, acoustic estimates of RV peak systolic and minimum diastolic pressures and RV relaxation were within 3.4 mmHg, 1.8 mmHg, and 5.9 mmHg/s, respectively, of the measured pressures. This pilot study demonstrates that subharmonic emissions from ultrasound contrast agents have the potential to noninvasively track in vivo RV pressures with errors below 3.5 mmHg.     

The C-terminal tail of human neuronal calcium sensor 1 regulates the conformational stability of the Ca²⁺₋ activated state

Neuronal calcium sensor 1 (NCS-1) and orthologs are expressed in all organisms from yeast to humans. In the latter, NCS-1 plays an important role in neurotransmitter release and interacts with a plethora of binding partners mostly through a large solvent-exposed hydrophobic crevice. The structural basis behind the multispecific binding profile is not understood. To begin to address this, we applied NMR spectroscopy to determine the solution structure of calcium-bound human NCS-1. The structure in solution demonstrates interdomain flexibility and, in the absence of a binding partner, the C-terminal tail residues occupy the hydrophobic crevice as a ligand mimic. A variant with a C-terminal tail deletion shows lack of a defined structure but maintained cooperative unfolding and dramatically reduced global stability. The results suggest that the C-terminal tail is important for regulating the conformational stability of the Ca(2+)-activated state. Furthermore, a single amino acid mutation that was recently diagnosed in a patient with autistic spectrum disorder was seen to affect the C-terminal tail and binding crevice in NCS-1.     

Modulation of fibrillation of hIAPP core fragments by chemical modification of the peptide backbone

The well-ordered cross β-strand structure found in amyloid aggregates is stabilized by many different side chain interactions, including hydrophobic interactions, electrostatic charge and the intrinsic propensity to form β-sheet structures. In addition to the side chains, backbone interactions are important because of the regular hydrogen-bonding pattern. β-Sheet breaking peptide analogs, such as those formed by N-methylation, interfere with the repetitive hydrogen bonding pattern of peptide strands. Here we test backbone contributions to fibril stability using analogs of the 6-10 residue fibril core of human islet amyloid polypeptide, a 37 amino acid peptide involved in the pathogenesis of type II diabetes. The Phe-Gly peptide bond has been replaced by a hydroxyethylene or a ketomethylene group and the nitrogen-atom has been methylated. In addition, we have prepared peptoids where the side chain is transferred to the nitrogen atom. The backbone turns out to be extremely sensitive to substitution, since only the minimally perturbed ketomethylene analog (where only one of the -NH- groups has been replaced by -CH(2)-) can elongate wildtype fibrils but cannot fibrillate on its own. The resulting fibrils displayed differences in both secondary structure and overall morphology. No analog could inhibit the fibrillation of the parent peptide, suggesting an inability to bind to existing fibril surfaces. In contrast, side chain mutations that left the backbone intact but increased backbone flexibility or removed stabilizing side-chain interactions had very small effect on fibrillation kinetics. We conclude that fibrillation is very sensitive to even small modifications of the peptide backbone.     

Differences in crystalline cellulose modification due to degradation by brown and white rot fungi

Wood-decaying basidiomycetes are some of the most effective bioconverters of lignocellulose in nature, however the way they alter wood crystalline cellulose on a molecular level is still not well understood. To address this, we examined and compared changes in wood undergoing decay by two species of brown rot fungi, Gloeophyllum trabeum and Meruliporia incrassata, and two species of white rot fungi, Irpex lacteus and Pycnoporus sanguineus, using X-ray diffraction (XRD) and ¹³C solid-state nuclear magnetic resonance (NMR) spectroscopy. The overall percent crystallinity in wood undergoing decay by M. incrassata, G. trabeum, and I. lacteus appeared to decrease according to the stage of decay, while in wood decayed by P. sanguineus the crystallinity was found to increase during some stages of degradation. This result is suggested to be potentially due to the different decay strategies employed by these fungi. The average spacing between the 200 cellulose crystal planes was significantly decreased in wood degraded by brown rot, whereas changes observed in wood degraded by the two white rot fungi examined varied according to the selectivity for lignin. The conclusions were supported by a quantitative analysis of the structural components in the wood before and during decay confirming the distinct differences observed for brown and white rot fungi. The results from this study were consistent with differences in degradation methods previously reported among fungal species, specifically more non-enzymatic degradation in brown rot versus more enzymatic degradation in white rot.     

Synthesis and Antiangiogenic Activity of N-Alkylated Levamisole Derivatives

Inhibition of angiogenesis is a promising addition to current cancer treatment strategies. Neutralization of vascular endothelial growth factor by monoclonal antibodies is clinically effective but may cause side effects due to thrombosis. Low molecular weight angiogenesis inhibitors are currently less effective than antibody treatment and are also associated with serious side effects. The discovery of new chemotypes with efficient antiangiogenic activity is therefore of pertinent interest. (S)-Levamisole hydrochloride, an anthelminthic drug approved for human use and with a known clinical profile, was recently shown to be an inhibitor of angiogenesis in vitro and exhibited tumor growth inhibition in mice. Here we describe the synthesis and in vitro evaluation of a series of N-alkylated analogues of levamisole with the aim of characterizing structure–activity relationships with regard to inhibition of angiogenesis. N-Methyllevamisole and p-bromolevamisole proved more effective than the parent compound, (S)-levamisole hydrochloride, with respect to inhibition of angiogenesis and induction of undifferentiated cluster morphology in human umbilical vein endothelial cells grown in co-culture with normal human dermal fibroblasts. Interestingly, the cluster morphology caused by N-methyllevamisole was different than the clusters observed for levamisole, and a third “cord-like” morphology resembling that of the known drug suramin was observed for an aniline-containing derivative. New chemotypes exhibiting antiangiogenic effects in vitro are thus described, and further investigation of their underlying mechanism of action is warranted.     

Spiroindolines identify the vesicular acetylcholine transporter as a novel target for insecticide action

The efficacy of all major insecticide classes continues to be eroded by the development of resistance mediated, in part, by selection of alleles encoding insecticide insensitive target proteins. The discovery of new insecticide classes acting at novel protein binding sites is therefore important for the continued protection of the food supply from insect predators, and of human and animal health from insect borne disease. Here we describe a novel class of insecticides (Spiroindolines) encompassing molecules that combine excellent activity against major agricultural pest species with low mammalian toxicity. We confidently assign the vesicular acetylcholine transporter as the molecular target of Spiroindolines through the combination of molecular genetics in model organisms with a pharmacological approach in insect tissues. The vesicular acetylcholine transporter can now be added to the list of validated insecticide targets in the acetylcholine signalling pathway and we anticipate that this will lead to the discovery of novel molecules useful in sustaining agriculture. In addition to their potential as insecticides and nematocides, Spiroindolines represent the only other class of chemical ligands for the vesicular acetylcholine transporter since those based on the discovery of vesamicol over 40 years ago, and as such, have potential to provide more selective tools for PET imaging in the diagnosis of neurodegenerative disease. They also provide novel biochemical tools for studies of the function of this protein family.     

A steered molecular dynamics study of binding and translocation processes in the GABA transporter

The entire substrate translocation pathway in the human GABA transporter (GAT-1) was explored for the endogenous substrate GABA and the anti-convulsive drug tiagabine. Following a steered molecular dynamics (SMD) approach, in which a harmonic restraining potential is applied to the ligand, dissociation and re-association of ligands were simulated revealing events leading to substrate (GABA) translocation and inhibitor (tiagabine) mechanism of action. We succeeded in turning the transporter from the outward facing occluded to the open-to-out conformation, and also to reorient the transporter to the open-to-in conformation. The simulations are validated by literature data and provide a substrate pathway fingerprint in terms of which, how, and in which sequence specific residues are interacted with. They reveal the essential functional roles of specific residues, e.g. the role of charged residues in the extracellular vestibule including two lysines (K76 (TM1) and K448 (TM10)) and a TM6-triad (D281, E283, and D287) in attracting and relocating substrates towards the secondary/interim substrate-binding site (S2). Likewise, E101 is highlighted as essential for the relocation of the substrate from the primary substrate-binding site (S1) towards the cytoplasm.