Spatial and Temporal Control of Cavitation Allows High In Vitro Transfection Efficiency in the Absence of Transfection Reagents or Contrast Agents

Sonoporation using low-frequency high-pressure ultrasound (US) is a non-viral approach for in vitro and in vivo gene delivery. In this study, we developed a new sonoporation device designed for spatial and temporal control of ultrasound cavitation. The regulation system incorporated in the device allowed a real-time control of the cavitation level during sonoporation. This device was evaluated for the in vitro transfection efficiency of a plasmid coding for Green Fluorescent Protein (pEGFP-C1) in adherent and non-adherent cell lines. The transfection efficiency of the device was compared to those observed with lipofection and nucleofection methods. In both adherent and non-adherent cell lines, the sonoporation device allowed high rate of transfection of pEGFP-C1 (40–80%), as determined by flow cytometry analysis of GFP expression, along with a low rate of mortality assessed by propidium iodide staining. The transfection efficiency and toxicity of sonoporation on the non-adherent cell lines Jurkat and K562 were similar to those of nucleofection, while these two cell lines were resistant to transfection by lipofection. Moreover, sonoporation was used to produce three stably transfected human lymphoma and leukemia lines. Significant transfection efficiency was also observed in two fresh samples of human acute myeloid leukemia cells. In conclusion, we developed a user-friendly and cost-effective ultrasound device, well adapted for routine in vitro high-yield transfection experiments and which does not require the use of any transfection reagent or gas micro-bubbles.     

Hepatocyte-specific Dyrk1a gene transfer rescues plasma apolipoprotein A-I levels and aortic Akt/GSK3 pathways in hyperhomocysteinemic mice

Hyperhomocysteinemia, characterized by high plasma homocysteine levels, is recognized as an independent risk factor for cardiovascular diseases. The increased synthesis of homocysteine, a product of methionine metabolism involving B vitamins, and its slower intracellular utilization cause increased flux into the blood. Plasma homocysteine level is an important reflection of hepatic methionine metabolism and the rate of processes modified by B vitamins as well as different enzyme activity. Lowering homocysteine might offer therapeutic benefits. However, approximately 50% of hyperhomocysteinemic patients due to cystathionine-beta-synthase deficiency are biochemically responsive to pharmacological doses of B vitamins. Therefore, effective treatments to reduce homocysteine levels are needed, and gene therapy could provide a novel approach. We recently showed that hepatic expression of DYRK1A, a serine/threonine kinase, is negatively correlated with plasma homocysteine levels in cystathionine-beta-synthase deficient mice, a mouse model of hyperhomocysteinemia. Therefore, Dyrk1a is a good candidate for gene therapy to normalize homocysteine levels. We then used an adenoviral construct designed to restrict expression of DYRK1A to hepatocytes, and found decreased plasma homocysteine levels after hepatocyte-specific Dyrk1a gene transfer in hyperhomocysteinemic mice. The elevation of pyridoxal phosphate was consistent with the increase in cystathionine-beta-synthase activity. Commensurate with the decreased plasma homocysteine levels, targeted hepatic expression of DYRK1A resulted in elevated plasma paraoxonase-1 activity and apolipoprotein A-I levels, and rescued the Akt/GSK3 signaling pathways in aorta of mice, which can prevent homocysteine-induced endothelial dysfunction. These results demonstrate that hepatocyte-restricted Dyrk1a gene transfer can offer a useful therapeutic targets for the development of new selective homocysteine lowering therapy.     

Structure des communautés de Phanaeini (Coleoptera : Scarabaeidae) de Guyane : étude par échantillonnage massif au piège d’interception

Summary

Seasonality and community structure of Phanaeini (Coleoptera: Scarabaeidae) in French Guiana : study by mass sampling using large flight interception traps. Phanaeini is a neotropical tribe of scarabs mostly dung or carrion feeders, generally of large size. This paper analyses data collected with large window flight interception traps set on nine forest sites in French Guiana with a primary goal of biotic inventory. The study deals with three main questions: 1) What is the spatial structure of communities and are there some species indicators of secondary forests and others of pristine conditions? 2) What is the temporal structure of the community and is there a stable pattern of seasonality between years and sites? 3) Between close species, is there a temporal asynchrony? Our samples contain more than 9,700 identified specimens, nine complete year series on four sites including a four years continuous survey near Cayenne. We found a significantly lower diversity (Shannon and Simpson index) on the most fragmented and hunted sites. A more equitable repartition of species and a relative abundance of the larger species appear typical of undisturbed sites. Other observations reinforce the hypothesis that there is a fast and huge modification in Phanaeini community structure on the most accessible and disturbed sites. Seasonal pattern shows an abundance peak at the beginning of the rainy season (December or January), a medium abundance during the rainy season with sometimes secondary peaks and a low to very low activity during the dry season. The pattern is rather consistent between years but changes with sampling site. It is however different from the results of other studies using pitfall baited traps in Amazonian and Guyanese forests. These studies show much less clear temporal pattern or no seasonal change. There is no obvious pattern of niche sharing by phenological differences between species. The methodological differences of sampling between baited traps and window flight traps are eventually discussed. Due to its passive way of collecting, interception trap is considered as quite relevant for studying flight activity spatio-temporal patterns of Scarabaeinae. This aspect may explain some differences in seasonality patterns compared to other studies.     

Controlling the stoichiometry and strand polarity of a tetramolecular G-quadruplex structure by using a DNA origami frame

Guanine-rich oligonucleotides often show a strong tendency to form supramolecular architecture, the so-called G-quadruplex structure. Because of the biological significance, it is now considered to be one of the most important conformations of DNA. Here, we describe the direct visualization and single-molecule analysis of the formation of a tetramolecular G-quadruplex in KCl solution. The conformational changes were carried out by incorporating two duplex DNAs, with G–G mismatch repeats in the middle, inside a DNA origami frame and monitoring the topology change of the strands. In the absence of KCl, incorporated duplexes had no interaction and laid parallel to each other. Addition of KCl induced the formation of a G-quadruplex structure by stably binding the duplexes to each other in the middle. Such a quadruplex formation allowed the DNA synapsis without disturbing the duplex regions of the participating sequences, and resulted in an X-shaped structure that was monitored by atomic force microscopy. Further, the G-quadruplex formation in KCl solution and its disruption in KCl-free buffer were analyzed in real-time. The orientation of the G-quadruplex is often difficult to control and investigate using traditional biochemical methods. However, our method using DNA origami could successfully control the strand orientations, topology and stoichiometry of the G-quadruplex.     

Adjuvants and formulations: How to make an immunogen from an antigen

Appropriate adjuvants and formulations improve the immunogenicity of antigens, by increasing both the intensity and duration of immune responses. To that aim, the design and use of adjuvants must obey to the rules regulating physiological responses of the immune system, in particular the long-term development of memory lymphocytes. Here I will briefly discuss the main mechanisms of adjuvanticity at the light of recent knowledge on antigen presentation by B memory lymphocytes, the role of nonspecific stimulation of such cells for memory persistence, and the use of particulate antigens to target B cells, thus facilitating immunological T/B lymphocyte cooperation for getting optimal immune responses.     

Assessing the genetic component of the susceptibility of mice to viral infections.

Laboratory mice often exhibit wide differences in susceptibility when infected experimentally with viruses. Based on such observations, experiments have been designed to investigate the determinism of these differences at the molecular level, and a few genes that play a major role in the innate mechanisms of defence of the species toward viral aggressions have been characterised. For example, the extraordinary resistance of SJL mice to experimental infections with hepatitis virus strain A59 is the consequence of a structural alteration of a cell adhesion molecule which normally binds to the spikes of the virus, allowing its entry into the cells. If the virus cannot bind to the molecule, or if the molecule is absent, epithelial cells of the intestine and liver are not infected and mice are resistant. In the same way, most--not to say all--laboratory strains of mice are susceptible to infections with orthomyxoviruses or flaviviruses because essential molecules, the synthesis of which is normally triggered by interferon, are defective in these mice. Wild mice, by contrast --probably because they are constantly exposed to natural infections--are resistant. Finally, some mouse strains resist experimental infections by the mouse cytomegalovirus 1 (MCMV-1) because, once infected, these mice synthesise a molecule at the surface of infected cells which allows immediate recognition and killing by natural killer (NK) cells. With the exuberant development of mouse genetics and the constant generation of new mutant alleles, it is likely that many more genes with an impact on the phenotype of resistance or susceptibility will be identified in the forthcoming years. These genes are probably numerous, however, and many of them presumably interact with each other and/or have additive effects. This might slow down progress in our understanding of the innate mechanism of defence.     

Effects of arterial wall stress on vasomotion

Smooth muscle and endothelial cells in the arterial wall are exposed to mechanical stress. Indeed blood flow induces intraluminal pressure variations and shear stress. An increase in pressure may induce a vessel contraction, a phenomenon known as the myogenic response. Many muscular vessels present vasomotion, i.e., rhythmic diameter oscillations caused by synchronous cytosolic calcium oscillations of the smooth muscle cells. Vasomotion has been shown to be modulated by pressure changes. To get a better understanding of the effect of stress and in particular pressure on vasomotion, we propose a model of a blood vessel describing the calcium dynamics in a coupled population of smooth muscle cells and endothelial cells and the consequent vessel diameter variations. We show that a rise in pressure increases the calcium concentration. This may either induce or abolish vasomotion, or increase its frequency depending on the initial conditions. In our model the myogenic response is less pronounced for large arteries than for small arteries and occurs at higher values of pressure if the wall thickness is increased. Our results are in agreement with experimental observations concerning a broad range of vessels.     

Early specific free radical-related cytotoxicity of gas phase cigarette smoke and its paradoxical temporary inhibition by tar: An electron paramagnetic resonance study with the spin trap DEPMPO

Electron paramagnetic resonance (EPR) spin trapping studies demonstrated aqueous tar particulate matter (TPM) and gas phase cigarette smoke (GPCS) to behave as different sources of free radicals in cigarette smoke (CS) but their cytotoxic implications have been only assessed in CS due to its relevance to the natural smoking process. Using a sensitive spin trapping detection with 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline-N-oxide (DEPMPO), this study compared the respective roles of CS- and GPCS-derived free radicals on smoke-induced cytotoxicity and lipid peroxidation of filtered and unfiltered, machine-smoked experimental and reference cigarettes yielding a wide range of TPM yields. In buffer bubbled with CS the DEPMPO/superoxide spin adduct was the major detected nitroxide. Use of appropriate control experiments with nitric oxide radical (NO*) or carbonyl sulfide, and a computer analysis of spin adduct diastereoisomery showed that the hydroxyl radical (HO*) adduct of DEPMPO seen in GPCS-bubbled was rather related to metal-catalyzed nucleophilic synthesis than to direct HO* trapping. Unexpectedly a protective effect of TPM on murine 3T3 fibroblasts was observed in early (<3h) free radical-, GPCS-induced cell death, and carbon filtering decreased free radical formation, toxicity and lipid peroxidation in three cell lines (including human epithelial lung cells) challenged with GPCS. These results highlight an acute, free radical-dependent, harmful mechanism specific to the GPCS phase, possibly involving NO* chemistry, whose physical or chemical control may be of great interest with the aim of reducing the toxicity of smoke.