CR2 units of CR2 complexes are possibly associated with nucleophilic agents through reactive covalent links

The human complement receptor type 2 (CR2/CD21), a transmembrane glycoprotein, associates with a variety of surface antigens and proteins in the cell membrane. We examined the possibilities that the CR2 units of CR2 complexes are associated through internal covalent links reactive with nucleophilic agents, e.g. H(2)O or methylamine, and that CR2-positive cells process anti-CR2 monoclonal antibodies (MoAbs). Data from immunoblotting and cytofluorimetry with CR2-binding site-specific MoAbs show that: (i) CR2-positive Raji cells release soluble CR2 isoforms into the medium when incubated in phosphate buffered saline; (ii) despite affecting the detection of one soluble CR2 isoform, methylamine treatment of soluble CR2 allows the detection of another of its isoforms; (iii) limited pre-treatment of cells with methylamine reveals a more heterogeneous CR2-positive cell population or enhances the detection of CR2; (iv) cell treatment with CR2-binding site-specific MoAbs enhances the detection of CR2 isoform(s). The data suggest that CR2 is shed mainly as a soluble CR2 complex, in which the CR2 units link covalently and react with nucleophilic agents. Raji cells may process bound fragments (145 kDa) that are recognised by and become bound by anti-CR2 MoAb.     

Increased resistance to oxidation of betalain-enriched human low density lipoproteins

Betalains are natural pigments recently considered as compounds with potential antioxidative properties. In this work, ex vivo plasma spiking of pure either betanin or indicaxanthin, followed by isolation of low density lipoprotein (LDL), and measurement of its resistance to copper-induced oxidation, has been used to research if these betalains can bind to LDL and prevent oxidation of LDL lipids. When pooled human plasma from 10 healthy volunteers was incubated in the presence of 25-100 μM either betanin or indicaxanthin, incorporation of both compounds in LDL was observed, with a maximum binding of 0.52±0.08, and 0.51±0.06 nmoles of indicaxanthin and betanin, respectively, per mg LDL protein. Indicaxanthin-enriched and betanin-enriched LDL were more resistant than homologous native LDL to copper-induced oxidation, as assessed by the elongation of the induction period. The incorporated indicaxanthin, however, appeared twice as effective as betanin in increasing the length of the lag phase, while both compounds did not affect the propagation rate. Both betalains were consumed during the inhibition period of lipid oxidation, and delayed consumption of LDL-beta carotene. Indicaxanthin, but not betanin, prevented vitamin E consumption at the beginning of LDL oxidation, and prolonged the time of its utilization. The resistance of LDL to oxidation when vitamin E and indicaxanthin acted separately in a sequence, was lower than that measured when they were allowed to act in combination, indicating some synergistic interaction between the two molecules. No prooxidant effect over a large concentration range of either betanin or indicaxanthin was observed, when either betalain was added to the LDL system undergoing a copper-induced oxidation.

These results show than indicaxanthin and betanin may bind to LDL, and are highly effective in preventing copper-induced lipid oxidation. Interaction with vitamin E appears to add a remarkable potential to indicaxanthin in the protection of LDL. Although molecular mechanisms remain uncompletely understood, various aspects of the action of betanin and indicaxanthin in preventing LDL lipid oxidation are discussed.     

Optimization of a higher throughput microsomal stability screening assay for profiling drug discovery candidates

Metabolic stability plays an important role in the success of drug candidates. First-pass metabolism is one of the major causes of poor oral bioavailability and short half-life. Traditionally, metabolic stability was evaluated at a later stage of drug discovery and required laborious manual manipulations. With the advance of high-throughput screening, combinatorial chemistry, and early profiling of drug-like properties, automated and rapid stability assays are needed to meet the increasing demand of throughput, speed, and reproducibility at earlier stages of drug discovery. The authors describe optimization of a simple, robust, high-throughput microsomal stability assay developed in a 96-well format. The assay consists of 2 automated components: robotic sample preparation for incubation and cleanup and rapid liquid chromatography/mass spectrometry/mass spectrometry (LC/MS/MS) analysis to determine percent remaining of the parent compound. The reagent solutions and procedural steps were optimized for automation. Variables affecting assay results were investigated. The variability introduced by microsome preparations from different sources (various vendors and batches) was studied and indicates the need for careful control. Quality control and normalization of the stability results are critical when applying the screening data, generated at different times or research sites, to discovery projects.     

New solid supports linking nucleoside scaffolds

An easy and efficient strategy to obtain new nucleoside based solid supports in which the nucleoside moieties have been anchored to the solid support through the nucleobase is here proposed. A simple and efficient solid-phase synthesis of 5' and 3'-derivatized uridine analogues has so been developed, following methodologies well established in organic chemistry.     

Vgamma9/Vdelta2 T lymphocytes in Italian patients with Behçet's disease: evidence for expansion,and tumour necrosis factor receptor II and interleukin-12 receptor beta1 expression in active disease

Beh?et's disease is a multisystem disease in which there is evidence of immunological dysregulation. It has been proposed that gamma/delta T cells are involved in its pathogenesis. The aim of the present study was to assess the capacity of gamma/delta T cells with phenotype Vgamma9/Vdelta2, from a group of Italian patients with Beh?et's disease, to proliferate in the presence of various phosphoantigens and to express tumour necrosis factor (TNF) and IL-12 receptors. Twenty-five patients and 45 healthy individuals were studied. Vgamma9/Vdelta2 T cells were analyzed by fluorescence activated cell sorting, utilizing specific monoclonal antibodies. For the expansion of Vgamma9/Vdelta2 T cells, lymphocytes were cultured in the presence of various phosphoantigens. The expression of TNF receptor II and IL-12 receptor beta1 was evaluated with the simultaneous use of anti-TNF receptor II phycoerythrin-labelled (PE) or anti-IL-12 receptor beta1 PE and anti-Vdelta2 T-cell receptor fluorescein isothiocyanate. There was a certain hierarchy in the response of Vgamma9/Vdelta2 T cells toward the different phosphoantigens, with the highest expansion factor obtained with dimethylallyl pyrophosphate and the lowest with xylose 1P. The expansion factor was fivefold greater in patients with active disease than in those with inactive disease or in control individuals. TNF receptor II and IL-12 receptor beta1 expressions were increased in both patients and control individuals. The proportion of Vgamma9/Vdelta2 T cells bearing these receptors was raised in active disease when Vgamma9/Vdelta2 T cells were cultured in the presence of dimethylallyl pyrophosphate. These results indicate that Vgamma9/Vdelta2 T cell activation is correlated with disease progression and probably involved in the pathogenesis.     

Use of a novel triple-tracer approach to assess postprandial glucose metabolism

Numerous studies have used the dual-tracer method to assess postprandial glucose metabolism. The present experiments were undertaken to determine whether the marked tracer nonsteady state that occurs with the dual-tracer approach after food ingestion introduces error when it is used to simultaneously measure both meal glucose appearance (R(a meal)) and endogenous glucose production (EGP). To do so, a novel triple-tracer approach was designed: 12 subjects ingested a mixed meal containing [1-(13)C]glucose while [6-(3)H]glucose and [6,6-(2)H(2)]glucose were infused intravenously in patterns that minimized the change in the plasma ratios of [6-(3)H]glucose to [1-(13)C]glucose and of [6,6-(2)H(2)]glucose to endogenous glucose, respectively. R(a meal) and EGP measured with this approach were essentially model independent, since non-steady-state error was minimized by the protocol. Initial splanchnic glucose extraction (ISE) was 12.9% +/- 3.4%, and suppression of EGP (EGPS) was 40.3% +/- 4.1%. In contrast, when calculated with the dual-tracer one-compartment model, ISE was higher (P < 0.05) and EGPS was lower (P < 0.005) than observed with the triple-tracer approach. These errors could only be prevented by using time-varying volumes different for R(a meal) and EGP. Analysis of the dual-tracer data with a two-compartment model reduced but did not totally avoid the problems associated with marked postprandial changes in the tracer-to-tracee ratios. We conclude that results from previous studies that have used the dual-tracer one-compartment model to measure postprandial carbohydrate metabolism need to be reevaluated and that the triple-tracer technique may provide a useful approach for doing so.     

Desialylated N-CAM and chromatin-derived acidic peptide effects in the hypothalamus

Chromatin-derived acidic peptides (ACPs) have been shown to acutely modulate hypothalamic catecholamine release. To investigate whether this effect is mediated through membrane polysialylated neural-cell adhesion molecule (PSA-N-CAM), we pretreated rat hypothalamic synaptosomes with neuraminidase enzyme, which partially cleaves sialic acid residues from N-CAM, and perfused them with ACP-1 (Asp-Asp-Ser-Asp-Glu-Glu-Asn) or a more lipophilic derivative, ACP-2 ([Ala-Ile-Ser-Pro]-Asp-Asp-Ser-Asp-Glu-Glu-Asn). We have found that neuraminidase completely abolish the inhibitory effect of ACP-1 on dopamine release, while the inhibitory activity of ACP-1 on norepinephrine release is partially lost. On the other hand, ACP-2 inhibition of dopamine release is not modified by neuraminidase pretreatment.     

Myogenic potential of mouse primordial germ cells

Primordial germ cells are the only stem cells that retain true developmental totipotency after gastrulation, express markers typical of totipotent/pluripotent status and are able both in vivo and in vitro to give rise to pluripotent stem cells as EC and EG cells. We have therefore explored the possibility of the trans-differentiation of mouse PGCs to a myogenic lineage by transplanting them directly or after in vitro culture into a regenerating muscle and by culturing them on monolayers of differentianting muscle cells. The results obtained suggest that mouse PGCs may trans-differentiate into myogenic cells, provided that their somatic environment is preserved. This occurs at an estimated frequency of 0.01%, which is no higher than that reported for stem cells of adult tissues.