Low density lipoprotein and liposome mediated uptake and cytotoxic effect of N4-octadecyl-1-β-D-arabinofuranosylcytosine in Daudi lymphoma cells

Low density lipoprotein (LDL) receptor-mediated uptake and cytotoxic effects of N4-octadecyl-1-beta-D-arabinofuranosylcytosine (NOAC) were studied in Daudi lymphoma cells. NOAC was either incorporated into LDL or liposomes to compare specific and unspecific uptake mechanisms. Binding of LDL to Daudi cells was not altered after NOAC incorporation (K(D) 60 nM). Binding of liposomal NOAC was not saturable with increasing concentrations. Specific binding of NOAC-LDL to Daudi cells was five times higher than to human lymphocytes. LDL receptor binding could be blocked and up- or down-regulated. Co-incubation with colchicine reduced NOAC-LDL uptake by 36%. These results suggested that NOAC-LDL is taken up via the LDL receptor pathway. In an in vitro cytotoxicity test, the IC50 of NOAC-LDL was about 160 microM, whereas with liposomal NOAC the IC50 was 40 microM. Blocking the LDL receptors with empty LDL protected 50% of the cells from NOAC cytotoxicity. The cellular distribution of NOAC-LDL or NOAC-liposomes differed only in the membrane and nuclei fraction with 13% and 6% respectively. Although it is more convenient to prepare NOAC-liposomes as compared to the loading of LDL particles with the drug, the receptor-mediated uptake of NOAC-LDL provides an interesting rationale for the specific delivery of the drug to tumours that express elevated numbers of LDL receptors

Membrane Permeabilization by Oligomeric α-Synuclein: In Search of the Mechanism

Background: \ud The question of how the aggregation of the neuronal protein α-synuclein contributes to neuronal toxicity in Parkinson's disease has been the subject of intensive research over the past decade. Recently, attention has shifted from the amyloid fibrils to soluble oligomeric intermediates in the α-synuclein aggregation process. These oligomers are hypothesized to be cytotoxic and to permeabilize cellular membranes, possibly by forming pore-like complexes in the bilayer. Although the subject of α-synuclein oligomer-membrane interactions has attracted much attention, there is only limited evidence that supports the pore formation by α-synuclein oligomers. In addition the existing data are contradictory.\ud \ud Methodology/Principal Findings:\ud Here we have studied the mechanism of lipid bilayer disruption by a well-characterized α-synuclein oligomer species in detail using a number of in vitro bilayer systems and assays. Dye efflux from vesicles induced by oligomeric α-synuclein was found to be a fast all-or-none process. Individual vesicles swiftly lose their contents but overall vesicle morphology remains unaltered. A newly developed assay based on a dextran-coupled dye showed that non-equilibrium processes dominate the disruption of the vesicles. The membrane is highly permeable to solute influx directly after oligomer addition, after which membrane integrity is partly restored. The permeabilization of the membrane is possibly related to the intrinsic instability of the bilayer. Vesicles composed of negatively charged lipids, which are generally used for measuring α-synuclein-lipid interactions, were unstable to protein adsorption in general.\ud \ud Conclusions/Significance:\ud The dye efflux from negatively charged vesicles upon addition of α-synuclein has been hypothesized to occur through the formation of oligomeric membrane pores. However, our results show that the dye efflux characteristics are consistent with bilayer defects caused by membrane instability. These data shed new insights into potential mechanisms of toxicity of oligomeric α-synuclein species

Computational approaches for modeling human intestinal absorption and permeability

Human intestinal absorption (HIA) is an important roadblock in the formulation of new drug substances. Computational models are needed for the rapid estimation of this property. The measurements are determined via in vivo experiments or in vitro permeability studies. We present several computational models that are able to predict the absorption of drugs by the human intestine and the permeability through human Caco-2 cells. The training and prediction sets were derived from literature sources and carefully examined to eliminate compounds that are actively transported. We compare our results to models derived by other methods and find that the statistical quality is similar. We believe that models derived from both sources of experimental data would provide greater consistency in predictions. The performance of several QSPR models that we investigated to predict outside the training set for either experimental property clearly indicates that caution should be exercised while applying any of the models for quantitative predictions. However, we are able to show that the qualitative predictions can be obtained with close to a 70% success rate

Cephalopod-omics: emerging fields and technologies in cephalopod biology

Few animal groups can claim the level of wonder that cephalopods instill in the minds of researchers and the general public. Much of cephalopod biology, however, remains unexplored: the largest invertebrate brain, difficult husbandry conditions, complex (meta-)genomes, among many other things, have hindered progress in addressing key questions. However, recent technological advancements in sequencing, imaging, and genetic manipulation have opened new avenues for exploring the biology of these extraordinary animals. The cephalopod molecular biology community is thus experiencing a large influx of researchers, emerging from different fields, accelerating the pace of research in this clade. In the first post-pandemic event at the Cephalopod International Advisory Council (CIAC) conference in April 2022, over 40 participants from all over the world met and discussed key challenges and perspectives for current cephalopod molecular biology and evolution. Our particular focus was on the fields of comparative and regulatory genomics, gene manipulation, single cell transcriptomics, metagenomics and microbial interactions. This article is a result of this joint effort, summarizing the latest insights from these emerging fields, their bottlenecks and potential solutions. The article highlights the interdisciplinary nature of the cephalopod -omics community and provides an emphasis on continuous consolidation of efforts and collaboration in this rapidly evolving field

A human colonic cell line sharing similarities with enterocytes as a model to examine oral absorption: advantages and limitations of the Caco-2 model

Caco-2 cell monolayers mimic intestinal absorptive epithelium and represent a very useful tool for studying transepithelial transport. The literature on Caco-2 cells is controversial regarding transepithelial resistance and permeabilities of different marker compounds across monolayers. This paper discusses probable causes for these discrepancies. First, we present the role of culture conditions, such as the nature of the support or the passage number, on cell biology and transport properties. Further, we compare the presence of transport proteins in Caco-2 cells to mammalian intestinal tissue and discuss their implication for drug absorption. We also examine the advantages and disadvantages of systems such as Transwell and side-by-side diffusion chambers. A summary of comparisons between permeabilities across Caco-2 monolayers and mammalian intestinal tissues is provided. We conclude that the origin of Caco-2 cells and the culture conditions are in part responsible for the discrepancies encountered in the literature

WHEAT TRADE AND THE ADOPTION OF ENSO-BASED FORECASTS: DIFFERENT SCENARIOS

Previous climate information studies have used static models to estimate the benefits of using seasonal forecasts. Technology adoption studies, on the other hand, have used dynamic models but have examined the benefits of adoption ex post. The objective of this study is to examine ex ante the effects of climate forecast adoption on the international wheat market over time. Two general sets of scenarios are analyzed. The first set assumes all wheat-producers within a country or set of countries adopt the forecasts, while producers in the remaining country (ies) do not. Next, producers adopt sequentially over time based on S-shaped adoption curves, whose rates vary by country. Welfare implications are examined and compared in the different scenarios. The model simulates wheat production and trade for the three major exporting countries: United States, Canada, and Australia over 20 years using Monte Carlo techniques. Climate forecasts are based on the five phases of the Southern Oscillation Index. Results for each scenario are based on 1000 simulations. This paper illustrates that when producers in one area of the world adopt a new technology, it has worldwide ramifications. In the case of wheat, producers are better off, on average, if everybody adopts climate forecasts. The gains are not distributed evenly, however, and the variability can be quite large. Adoption can, in some years, lead to substantial losses. Results indicate a great advantage to those who adopt first, though this advantage declines rapidly as more producers adopt. Understanding ex ante the likely consequences of using ENSO-based forecasts allows decision-makers to make better choices

WHEAT TRADE AND THE ADOPTION OF ENSO-BASED FORECASTS: DIFFERENT SCENARIOS

Previous climate information studies have used static models to estimate the benefits of using seasonal forecasts. Technology adoption studies, on the other hand, have used dynamic models but have examined the benefits of adoption ex post. The objective of this study is to examine ex ante the effects of climate forecast adoption on the international wheat market over time. Two general sets of scenarios are analyzed. The first set assumes all wheat-producers within a country or set of countries adopt the forecasts, while producers in the remaining country (ies) do not. Next, producers adopt sequentially over time based on S-shaped adoption curves, whose rates vary by country. Welfare implications are examined and compared in the different scenarios. The model simulates wheat production and trade for the three major exporting countries: United States, Canada, and Australia over 20 years using Monte Carlo techniques. Climate forecasts are based on the five phases of the Southern Oscillation Index. Results for each scenario are based on 1000 simulations. This paper illustrates that when producers in one area of the world adopt a new technology, it has worldwide ramifications. In the case of wheat, producers are better off, on average, if everybody adopts climate forecasts. The gains are not distributed evenly, however, and the variability can be quite large. Adoption can, in some years, lead to substantial losses. Results indicate a great advantage to those who adopt first, though this advantage declines rapidly as more producers adopt. Understanding ex ante the likely consequences of using ENSO-based forecasts allows decision-makers to make better choices.Crop Production/Industries,

Implications of seasonal climate forecasts on world wheat trade: a stochastic, dynamic analysis

Improvements in seasonal climate forecasts have potential economic implications for international agriculture. A stochastic, dynamic simulation model of the international wheat economy is developed to estimate the potential effects of seasonal climate forecasts for various countries' wheat production, exports and world trade. Previous studies have generally ignored the stochastic and dynamic aspects of the effects associated with the use of climate forecasts. This study shows the importance of these aspects. In particular with free trade, the use of seasonal forecasts results in increased producer surplus across all exporting countries. In fact, producers appear to capture a large share of the economic surplus created by using the forecasts. Further, the stochastic dimensions suggest that while the expected long-run benefits of seasonal forecasts are positive, considerable year-to-year variation in the distribution of benefits between producers and consumers should be expected. The possibility exists for an economic measure to increase or decrease over a 20-year horizon, depending on the particular sequence of years