Quantifying clustered DNA damage induction and repair by gel electrophoresis, electronic imaging and number average length analysis

Assessing DNA damage induction, repair and consequences of such damages requires measurement of specific DNA lesions by methods that are independent of biological responses to such lesions. Lesions affecting one DNA strand (altered bases, abasic sites, single strand breaks (SSB)) as well as damages affecting both strands (clustered damages, double strand breaks) can be quantified by direct measurement of DNA using gel electrophoresis, gel imaging and number average length analysis. Damage frequencies as low as a few sites per gigabase pair (10(9)bp) can be quantified by this approach in about 50ng of non-radioactive DNA, and single molecule methods may allow such measurements in DNA from single cells. This review presents the theoretical basis, biochemical requirements and practical aspects of this approach, and shows examples of their applications in identification and quantitation of complex clustered damages.     

Bifunctional agents for reperfusion arrhythmias: novel hybrid vitamin E/class I antiarrhythmics

We have synthesized a series of hybrid compounds combining the pharmacophoric redox moieties of vitamin E and key features responsible for the antiarrhythmic properties of the class I antiarrhythmics procainamide and lidocaine. Procainamide analogue (2a) and lidocaine analogues (14a) and (14b) are very strong inhibitors of lipid peroxidation. All analogues tested at 100 or 30 microM enhanced the post ischemic recovery without inducing ventricular fibrillations while there was no evidence in our experiments for drug-induced pro-arrhythmia. In addition, they induced a widening of the QRS intervals. Our data suggest that the efficacy of the new compounds in preventing reperfusion arrhythmias could be attributed to their combined effects involving inhibition of free radical mediated damage coupled with antiarrhythmic properties.     

Imaging the Brain Marijuana Receptor: Development of a Radioligand that Binds to Cannabinoid CB1 Receptors In Vivo

Abstract: The major active ingredient of marijuana, (−)-Δ⁹-tetrahydrocannabinol, exerts its psychoactive effects via binding to cannabinoid CB1 receptors, which are widely distributed in the brain. Radionuclide imaging of CB1 receptors in living human subjects would help explore the presently unknown physiological roles of this receptor system, as well as the neurochemical consequences of marijuana dependence. Currently available cannabinoid receptor radioligands are exceedingly lipophilic and unsuitable for in vivo use. We report the development of a novel radioligand, [¹²³I]AM281{ N -(morpholin-4-yl)-5-(4-[¹²³I]iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1 H -pyrazole-3-carboxamide}, that is structurally related to the CB1-selective antagonist SR141716A [ N -(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1 H -pyrazole-3-carboxamide]. Baboon single photon emission computed tomography studies, mouse brain dissection studies, and ex vivo autoradiography in rat brain demonstrated rapid passage of [¹²³I]AM281 into the brain after intravenous injection, appropriate regional brain specificity of binding, and reduction of binding after treatment with SR141716A. AM281 has an affinity in the low nanomolar range for cerebellar binding sites labeled with [³H]SR141716A in vitro, and binding of [¹²³I]AM281 is inhibited by several structurally distinct cannabinoid receptor ligands. We conclude that [¹²³I]AM281 has appropriate properties for in vivo studies of cannabinoid CB1 receptors and is suitable for imaging these receptors in the living human brain.     

Mapping the binding domains of the alpha(IIb) subunit. A study performed on the activated form of the platelet integrin alpha(IIb)beta(3).

alpha(IIb)beta(3), a member of the integrin family of adhesive protein receptors, is the most abundant glycoprotein on platelet plasma-membranes and binds to adhesive proteins via the recognition of short amino acid sequences, for example the ubiquitous RGD motif. However, elucidation of the ligand-binding domains of the receptor remains controversial, mainly owing to the fact that integrins are conformationally labile during purification and storage. In this study, a detailed mapping of the extracellular region of the alpha(IIb) subunit is presented, using overlapping 20-peptides, in order to identify the binding sites of alpha(IIb) potentially involved in the platelet-aggregation event. Regions alpha(IIb) 313-332, alpha(IIb) 265-284 and alpha(IIb) 57-64 of alpha(IIb)beta(3) were identified as putative fibrinogen-binding domains because the corresponding peptides inhibited platelet aggregation and antagonized fibrinogen association, possibly by interacting with this ligand. The latter is further supported by the finding that the above peptides did not interfere with the binding of PAC-1 to the activated form of alpha(IIb)beta(3). Furthermore, alpha(IIb) 313-332 was found to bind to fibrinogen in a solid-phase binding assay. It should be emphasized that all the experiments in this study were carried out on activated platelets and consequently on the activated form of this integrin receptor. We hypothesize that RAD and RAE adhesive motifs, encompassed in alpha(IIb) 313-332, 265-284 and 57-64, are capable of recognizing complementary domains of fibrinogen, thus inhibiting the binding of this ligand to platelets.     

Preparation of optically pure 4-(hydroxymethyl)-2-pentadecyl-1,3-dioxolanes and their corresponding phosphodiester ether lipid derivatives.

Semi-preparative HPLC on a chiral stationary phase (Chiracel OD) was utilized in the course of this synthesis to separate the four possible diastereomers [cis-(2R,4S)-2a, trans-(2S,4S)-2b, cis-(2S,4R)-2a', and trans-(2R,4R)-2b'] of a 2,4-disubstituted-1,3-dioxolane into optically pure forms (100% de, 100% ee). The syntheses of phosphodiester head group derivatives from each of these four conformationally constrained diastereomeric dioxolanes gave phospholipids which are monocyclic ether lipid analogs. First, the series of four [[(2-pentadecyl-1,3-dioxolan-4-yl)methyl]oxy]phosphocholines 5 were synthesized to give optically pure conformationally constrained analogues of ET-16-OCH(3). A head group variation was also demonstrated by the syntheses of the four diastereomeric [[(2-pentadecyl-1,3-dioxolan-4-yl)-methyl]oxy]phospho-beta-(N-methylmorpholino)ethanols 6.     

Visualization by live-cell microscopy of disruption of ND10 during herpes simplex virus type 1 infection

ND10 structures are disrupted during herpes simplex virus type 1 (HSV-1) infection by viral regulatory protein ICP0. The significance of this effect remains controversial, partly because of a report that high-level expression of the major ND10 promyelocytic leukemia (PML) protein precludes ND10 disruption yet does not inhibit HSV-1 infection. Here we demonstrate dramatic reorganization of ND10 during HSV-1 infection by live-cell microscopy, even in the presence of overexpressed PML.     

Engineering lipid vesicles of enhanced intratumoral transport capabilities: correlating liposome characteristics with penetration into human prostate tumor spheroids

Liposomes have been widely used delivery systems, particularly relevant to the development of cancer therapeutics. Numerous liposome-based drugs are in the clinic or in clinical trials today against multiple tumor types; however, systematic studies of liposome interactions with solid or metastatic tumor nodules are scarce. This study is describing the in vitro interaction between liposomes and avascular human prostate (LNCaP-LN3) tumor spheroids. The ability of fluorescently labelled liposomal delivery systems of varying physicochemical characteristics to penetrate within multicellular tumor spheroids has been investigated by confocal laser scanning microscopy. A variety of liposome characteristics and experimental parameters were investigated, including lipid bilayer composition, duration of liposome-spheroid interaction, mean liposome size, steric stabilization of liposomes. Electrostatic binding between cationic liposomes and spheroids was very efficient; however, it impeded any significant penetration of the vesicles within deeper layers of the tumor spheroid. Small unilamellar liposomes of neutral surface character did not bind as efficiently but exhibited enhanced penetrative transport capabilities closer to the tumor core. Polymer-coated (sterically stabilised) liposomes exhibited almost no interaction with the spheroid, indicating that their limited diffusion within avascular tissues may be a limiting step for their use against micrometastases. Multicellular tumor spheroids were used as models of solid tumor interstitium relevant to delivery systems able to extravasate from the microcapillaries or as models of prevascularized micrometastases. This study illustrates that interactions between liposomes and other drug delivery systems with multicellular tumor spheroids can offer critically important information with respect to optimizing solid or micrometastatic tumor delivery and targeting strategies.