Design, synthesis and structure-activity relationship of a series of arginine aldehyde factor Xa inhibitors. Part 1: structures based on the (D)-Arg-Gly-Arg tripeptide sequence

A series of arginine aldehyde inhibitors was designed as transition state (TS) analogues based on the known factor Xa specific substrate Cbz-D-Arg-Gly-Arg-pNA. BnSO2-(D)Arg-Gly-Arg-H (20) was found to be the most potent and selective inhibitor of factor Xa and prothrombinase activity in this series.     

A CD91-positive subset of CD11c+ blood dendritic cells: characterization of the APC that functions to enhance adaptive immune responses against CD91-targeted antigens

Dendritic cells (DC) and other APCs rely on a number of specialized receptors to facilitate the uptake and intracellular accumulation of Ags. In this capacity, APCs use receptor-mediated endocytosis to enhance Ag presentation and the stimulation of Ag-specific T cells. Studies have demonstrated that the targeted delivery of Ags in vivo to CD91/the low-density lipoprotein receptor-related protein (CD91/LRP) induces enhanced activation of the adaptive immune system. However, the APC that mediates these augmented, Ag-specific responses remains to be characterized. In this study, we show that a subset of CD11c(+) lineage-negative (lin(-)) DC expresses the scavenger receptor CD91/LRP and that these rare APC are primarily responsible for the T cell activation that occurs following CD91/LRP-mediated Ag uptake in whole blood. The targeting of Ags to CD91/LRP results in enhanced receptor-mediated uptake within both lin(-) DCs and monocytes, and this uptake results in markedly increased T cell activation. Finally, purified cellular populations were used to demonstrate that CD11c(+) lin(-) DC, but not monocytes, are capable of stimulating T cell activation following CD91/LRP-mediated Ag uptake. Therefore, CD11c(+) lin(-) DC use CD91/LRP to facilitate the uptake and subsequent presentation of an array of Ags complexed within the CD91/LRP ligand, the activated form of alpha2-macroglobulin (alpha2M*).     

Multiple and additive functions of ALDH3A1 and ALDH1A1: cataract phenotype and ocular oxidative damage in Aldh3a1(-/-)/Aldh1a1(-/-) knock-out mice

ALDH3A1 (aldehyde dehydrogenase 3A1) is abundant in the mouse cornea but undetectable in the lens, and ALDH1A1 is present at lower (catalytic) levels in the cornea and lens. To test the hypothesis that ALDH3A1 and ALDH1A1 protect the anterior segment of the eye against environmentally induced oxidative damage, Aldh1a1(-/-)/Aldh3a1(-/-) double knock-out and Aldh1a1(-/-) and Aldh3a1(-/-) single knock-out mice were evaluated for biochemical changes and cataract formation (lens opacification). The Aldh1a1/Aldh3a1- and Aldh3a1-null mice develop cataracts in the anterior and posterior subcapsular regions as well as punctate opacities in the cortex by 1 month of age. The Aldh1a1-null mice also develop cataracts later in life (6-9 months of age). One- to three-month-old Aldh-null mice exposed to UVB exhibited accelerated anterior lens subcapsular opacification, which was more pronounced in Aldh3a1(-/-) and Aldh3a1(-/-)/Aldh1a1(-/-) mice compared with Aldh1a1(-/-) and wild type animals. Cataract formation was associated with decreased proteasomal activity, increased protein oxidation, increased GSH levels, and increased levels of 4-hydroxy-2-nonenal- and malondialdehyde-protein adducts. In conclusion, these findings support the hypothesis that corneal ALDH3A1 and lens ALDH1A1 protect the eye against cataract formation via nonenzymatic (light filtering) and enzymatic (detoxification) functions.     

Glycation of low-density lipoprotein results in the time-dependent accumulation of cholesteryl esters and apolipoprotein B-100 protein in primary human monocyte-derived macrophages

Nonenzymatic covalent binding (glycation) of reactive aldehydes (from glucose or metabolic processes) to low-density lipoproteins has been previously shown to result in lipid accumulation in a murine macrophage cell line. The formation of such lipid-laden cells is a hallmark of atherosclerosis. In this study, we characterize lipid accumulation in primary human monocyte-derived macrophages, which are cells of immediate relevance to human atherosclerosis, on exposure to low-density lipoprotein glycated using methylglyoxal or glycolaldehyde. The time course of cellular uptake of low-density lipoprotein-derived lipids and protein has been characterized, together with the subsequent turnover of the modified apolipoprotein B-100 (apoB) protein. Cholesterol and cholesteryl ester accumulation occurs within 24 h of exposure to glycated low-density lipoprotein, and increases in a time-dependent manner. Higher cellular cholesteryl ester levels were detected with glycolaldehyde-modified low-density lipoprotein than with methylglyoxal-modified low-density lipoprotein. Uptake was significantly decreased by fucoidin (an inhibitor of scavenger receptor SR-A) and a mAb to CD36. Human monocyte-derived macrophages endocytosed and degraded significantly more (125)I-labeled apoB from glycolaldehyde-modified than from methylglyoxal-modified, or control, low-density lipoprotein. Differences in the endocytic and degradation rates resulted in net intracellular accumulation of modified apoB from glycolaldehyde-modified low-density lipoprotein. Accumulation of lipid therefore parallels increased endocytosis and, to a lesser extent, degradation of apoB in human macrophages exposed to glycolaldehyde-modified low-density lipoprotein. This accumulation of cholesteryl esters and modified protein from glycated low-density lipoprotein may contribute to cellular dysfunction and the increased atherosclerosis observed in people with diabetes, and other pathologies linked to exposure to reactive carbonyls.     

Regulation of phosphoenolpyruvate carboxykinase (GTP) in adipose tissue in vivo by glucocorticoids and insulin.

1. The regulation of the synthesis of phosphoenolpyruvate carboxykinase (GTP) (EC 4.1.1.32) in epididymal adipose tissue, liver and kidney in vivo was studied immunochemically. 2. Phosphoenolpyruvate carboxykinase (GTP) synthesis in adipose tissue is increased by starvation, diabetes and noradrenaline, and decreased by re-feeding and insulin. These changes were also seen in adrenalectomized rats and are qualitatively similar to those observed for the liver enzyme. This indicates the involvement of cyclic AMP as an inducer and insulin as a de-inducer in the regulation of phosphoenolpyruvate carboxykinase (GTP) in both tissues. (Induction and de-induction are defined as selective increase and decrease respectively in the rate of enzyme synthesis, regardless of the mechanism involved.)3. Adrenalectomy had little effect on phosphoenolpyruvate carboxykinase (GTP) synthesis in liver and kidney, but increased the synthesis rate of the adipose-tissue enzyme. Starvation and adrenalectomy had additive effects in increasing the synthesis rate of adipose-tissue phosphoenolpyruvate carboxykinase (GTP). In adrenalectomized diabetic rats glucocorticoids increased phosphoenolpyruvate carboxykinase (GTP) synthesis in liver and kidney while decreasing enzyme synthesis in adipose tissue. De-induction of adipose tissue phosphoenolpyruvate carboxykinase (GTP) is therefore regulated independently by glucocorticoids and insulin. 4. Although liver, kidney and adipose-tissue phosphoenolpyruvate carboxykinases (GTP) are seemingly identical, there is an apparent tissue-specific differentiation in regulatory systems for the enzyme.     

An entirely cell-based system to generate single-chain antibodies against cell surface receptors

The generation of recombinant antibodies (Abs) using phage display is a proven method to obtain a large variety of Abs that bind with high affinity to a given antigen. Traditionally, the generation of single-chain Abs depends on the use of recombinant proteins in several stages of the procedure. This can be a problem, especially in the case of cell-surface receptors, because Abs generated and selected against recombinant proteins may not bind the same protein expressed on a cell surface in its native form and because the expression of some receptors as recombinant proteins is problematic. To overcome these difficulties, we developed a strategy to generate single-chain Abs that does not require the use of recombinant protein at any stage of the procedure. In this strategy, stably transfected cells are used for the immunization of mice, measuring Ab responses to immunization, panning the phage library, high-throughput screening of arrayed phage clones, and characterization of recombinant single-chain variable regions. This strategy was used to generate a panel of single-chain Abs specific for the innate immunity receptor Toll-like receptor 2. Once generated, individual single-chain variable regions were subcloned into an expression vector allowing the production of recombinant Abs in insect cells, thus avoiding the contamination of recombinant Abs with microbial products. This cell-based system efficiently generates Abs that bind to native molecules on the cell surface, bypasses the requirement of recombinant protein production, and avoids risks of microbial component contamination.     

Characterization of golimumab,a human monoclonal antibody specific for human tumor necrosis factor α

We prepared and characterized golimumab, a human IgG1 tumor necrosis factor alpha (TNFα) antagonist monoclonal antibody chosen for clinical development based on its molecular properties. Golimumab was compared with infliximab, adalimumab and etanercept for affinity and in vitro TNFα neutralization. The affinity of golimumab for soluble human TNFα, as determined by surface plasmon resonance, was similar to that of etanercept (18 pM versus 11 pM), greater than that of infliximab (44 pM) and significantly greater than that of adalimumab (127 pM, p = 0.018). The concentration of golimumab necessary to neutralize TNFα-induced E-selectin expression on human endothelial cells by 50% was significantly less than those for infliximab (3.2-fold; p = 0.017) and adalimumab (3.3-fold; p = 0.008) and comparable to that for etanercept. The conformational stability of golimumab was greater than that of infliximab (primary melting temperature [Tm] 74.8°C vs. 69.5°C) as assessed by differential scanning calorimetry. In addition, golimumab showed minimal aggregation over the intended shelf life when formulated as a high concentration liquid product (100 mg/mL) for subcutaneous administration. In vivo, golimumab at doses of 1 and 10 mg/kg significantly delayed disease progression in a mouse model of human TNFα-induced arthritis when compared with untreated mice, while infliximab was effective only at 10 mg/kg. Golimumab also significantly reduced histological scores for arthritis severity and cartilage damage, as well as serum levels of pro-inflammatory cytokines and chemokines associated with arthritis. Thus, we have demonstrated that golimumab is a highly stable human monoclonal antibody with high affinity and capacity to neutralize human TNFα in vitro and in vivo.Key words: TNF, golimumab, neutralization, affinity, bioassay, arthritis, stability, solubility     

Retrograde transport of neurotrophins: fact and function

Retrograde signals generated by nerve growth factor (NGF) and other neurotrophins promote the survival of appropriately connected neurons during development, and failure to obtain sufficient retrograde signals may contribute to neuronal death occurring in many neurodegenerative diseases. The discovery over 25 years ago that NGF supplied to the axon terminals is retrogradely transported to the cell bodies suggested that NGF must reach the cell body to promote neuronal survival. Research during the intervening decades has produced a refinement of this hypothesis. The current hypothesis is that NGF bound to TrkA at the axon terminal is internalized into signaling endosomes, with NGF in their lumens bound to phosphorylated TrkA in their membranes, which are retrogradely transported to the cell bodies, where TrkA activates downstream signaling molecules that promote neuronal survival and regulate many aspects of neuronal gene expression. This model has been extrapolated to retrograde signaling by all neurotrophins. We consider the evidence for this model, focusing on results of experiments with neurons in compartmented cultures. Results to date indicate that while the transport of signaling endosomes containing NGF bound to TrkA may carry retrograde signals, retrograde survival signals can be carried by another mechanism that is activated by NGF at the axon terminal surface and travels to the cell body unaccompanied by the NGF that initiated it. It is hypothesized that multiple mechanisms of retrograde signaling exist and function under different circumstances. The newly discovered potential for redundancy in retrograde signaling mechanisms can complicate the interpretation of experimental results.     

Breeding durations as estimators of adult sex ratios and population size

Adult sex ratios (ASRs) and population size are two of the most fundamental parameters in population biology, as they are the main determinants of genetic and demographic viability, and vulnerability of a population to stochastic events. Underpinning the application of population viability analysis for predicting the extinction risk of populations is the need to accurately estimate parameters that determine the viability of populations (i.e. the ASR and population size). Here we demonstrate that a lack of temporal information can confound estimation of both parameters. Using acoustic telemetry, we compared differences in breeding durations of both sexes for a giant Australian cuttlefish Sepia apama breeding aggregation to the strongly male-biased operational sex ratio (4:1), in order to estimate the population ASR. The ratio of breeding durations between sexes was equal to the operational sex ratio, suggesting that the ASR is not strongly male-biased, but balanced. Furthermore, the short residence times of individuals at the breeding aggregation suggests that previous density-based abundance estimates have significantly underestimated population size. With the current wide application of population viability analysis for predicting the extinction risk of populations, tools to improve the accuracy of such predictions are vital. Here we provide a new approach to estimating the fundamental ASR parameter, and call for temporal considerations when estimating population size.