Aging exacerbates negative remodeling and impairs endothelial regeneration after balloon injury

Many older patients, because of their high prevalence of coronary artery disease, are candidates for percutaneous coronary interventions (PCI), but the effects of vascular aging on restenosis after PCI are not yet well understood. Balloon injury to the right carotid artery was performed in adult and old rats. Vascular smooth muscle cell (VSMC) proliferation, apoptotic cell death, together with Akt induction, telomerase activity, p27kip1, and endothelial nitric oxide synthase (eNOS) expression was assessed in isolated arteries. Neointima hyperplasia and vascular remodeling along with endothelial cell regeneration were also measured after balloon injury. Arteries isolated from old rats exhibited a significant reduction of VSMC proliferation and an increase in apoptotic death after balloon injury when compared with adult rats. In the vascular wall of adult rats, balloon dilation induced Akt phosphorylation, and this was barely present in old rats. In arteries from old rats, Akt-modulated cell cycle check points like telomerase activity and p27kip1 expression were decreased and increased, respectively, compared with adults. After balloon injury, old rats showed a significant reduction of neointima formation and an increased vascular negative remodeling compared with adults. These results were coupled by a marked delay in endothelial regeneration in aged rats, partially mediated by a decreased eNOS expression and phosphorylation. Interestingly, chronic administration of L-arginine prevented negative remodeling and improved reendothelialization after balloon injury in aged animals. A decreased neointimal proliferation, an impaired endothelial regeneration, and an increase in vascular remodeling after balloon injury were observed in aged animals. The molecular mechanisms underlying these responses seem to be a reduced Akt and eNOS activity.     

Toxic HypF-N Oligomers Selectively Bind the Plasma Membrane to Impair Cell Adhesion Capability

The deposition of fibrillar protein aggregates in human organs is the hallmark of several pathological states, including highly debilitating neurodegenerative disorders and systemic amyloidoses. It is widely accepted that small oligomers arising as intermediates in the aggregation process, released by fibrils, or growing in secondary nucleation steps are the cytotoxic entities in protein-misfolding diseases, notably neurodegenerative conditions. Increasing evidence indicates that cytotoxicity is triggered by the interaction between nanosized protein aggregates and cell membranes, even though little information on the molecular details of such interaction is presently available. In this work, we propose what is, to our knowledge, a new approach, based on the use of single-cell force spectroscopy applied to multifunctional substrates, to study the interaction between protein oligomers, cell membranes, and/or the extracellular matrix. We compared the interaction of single Chinese hamster ovary cells with two types of oligomers (toxic and nontoxic) grown from the N-terminal domain of the Escherichia coli protein HypF. We were able to quantify the affinity between both oligomer type and the cell membrane by measuring the mechanical work needed to detach the cells from the aggregates, and we could discriminate the contributions of the membrane lipid and protein fractions to such affinity. The fundamental role of the ganglioside GM1 in the membrane-oligomers interaction was also highlighted. Finally, we observed that the binding of toxic oligomers to the cell membrane significantly affects the functionality of adhesion molecules such as Arg-Gly-Asp binding integrins, and that this effect requires the presence of the negatively charged sialic acid moiety of GM1.     

High-resolution molecular epidemiology and evolutionary history of HIV-1 subtypes in Albania

Background

HIV-1 epidemic in Western Europe is largely due to subtype B. Little is known about the HIV-1 in Eastern Europe, but a few studies have shown that non-B subtypes are quite common. In Albania, where a recent study estimated a ten-fold increase of AIDS incidence during the last six years, subtype A and B account for 90% of the know infections.

Methodology/Principal Findings

We investigated the demographic history of HIV-1 subtype A and B in Albania by using a statistical framework based on coalescent theory and phylogeography. High-resolution phylogenetic and molecular clock analysis showed a limited introduction to the Balkan country of subtype A during the late 1980s followed by an epidemic outburst in the early 1990s. In contrast, subtype B was apparently introduced multiple times between the mid-1970s and mid-1980s. Both subtypes are growing exponentially, although the HIV-1A epidemic displays a faster growth rate, and a significantly higher basic reproductive number R₀. HIV-1A gene flow occurs primarily from the capital Tirane, in the center of the country, to the periphery, while HIV-1B flow is characterized by a balanced exchange between center and periphery. Finally, we calculated that the actual number of infections in Albania is at least two orders of magnitude higher than previously thought.

Conclusions/Significance

Our analysis demonstrates the power of recently developed computational tools to investigate molecular epidemiology of pathogens, and emphasize the complex factors involved in the establishment of HIV-1 epidemics. We suggest that a significant correlation exists between HIV-1 exponential spread and the socio-political changes occurred during the Balkan wars. The fast growth of a relatively new non-B epidemic in the Balkans may have significant consequences for the evolution of HIV-1 epidemiology in neighboring countries in Eastern and Western Europe.     

Specific sensing of poly G by the aluminum-salophen complex

The Al(III)-salophen complex 1 exhibited strong spectroscopic changes specifically upon addition of polyG and GpG, while double stranded DNA and RNA, and single stranded polyA, polyU and polyC induced negligible spectral changes of 1. Titrations with mono-nucleotides yielded no spectroscopic changes, revealing that there must be at least two consecutive guanines in single stranded oligonucleotide structure for a measurable spectroscopic change of 1. Preliminary results show that 1 has moderate antiproliferative effect on a number of human tumour cell lines.     

Diverging effects of human recombinant anti-hepatitis C virus (HCV) antibody fragments derived from a single patient on the infectivity of a vesicular stomatitis virus/HCV pseudotype

Hepatitis C virus (HCV) is the major causative agent of blood-borne non-A, non-B hepatitis. Although a strong humoral response is detectable within a few weeks of primary infection and during viral persistence, the role played by antibodies against HCV envelope glycoproteins in controlling viral replication is still unclear. We describe how human monoclonal anti-HCV E2 antibody fragments isolated from a chronically HCV-infected patient differ sharply in their abilities to neutralize infection of HepG2 cells by a vesicular stomatitis virus pseudotype bearing HCV envelope glycoproteins. Two clones were able to neutralize the pseudotype virus at a concentration of 10 micro g/ml, while three other clones completely lacked this activity. These data can explain the lack of protection and the possibility of reinfection that occur even in the presence of a strong antiviral antibody response.     

Fusicoccin stimulates the production of H2O2 in sycamore cell cultures and induces alternative respiration and cytochrome c leakage from mitochondria

Fusicoccin (FC) is a well known toxin acting as a 14-3-3 protein-mediated activator of the plasma membrane H⁺-ATPase and it has been widely used to study the regulatory mechanism and the physiological role of this enzyme's activity. Recently, FC has been shown to induce other responses similar to those occurring under a stress condition, perhaps not strictly dependent on the activation of proton extrusion. In this paper we report that in cultured sycamore ( Acer pseudoplatanus L.) cells FC induces H₂O₂ overproduction as well as other novel, presumably related responses, such as the activation of the alternative oxidase and the leakage of cytochrome c from the mitochondria, accompanied by a decrease of the cytochrome pathway capacity. The relationship between H₂O₂ production and other phenomena has also been studied by means of exogenously added H₂O₂.     

Heregulin targets gamma-catenin to the nucleolus by a mechanism dependent on the DF3/MUC1 oncoprotein

The DF3/MUC1 transmembrane oncoprotein is aberrantly overexpressed in most human breast carcinomas and interacts with the Wnt effector gamma-catenin. Here, we demonstrate that MUC1 associates constitutively with ErbB2 in human breast cancer cells and that treatment with heregulin/neuregulin-1 (HRG) increases the formation of MUC1-ErbB2 complexes. The importance of the MUC1-ErbB2 interaction is supported by the demonstration that HRG induces binding of MUC1 and gamma-catenin and targeting of the MUC1-gamma-catenin complex to the nucleolus. Significantly, nucleolar localization of gamma-catenin in response to HRG is dependent on MUC1 expression. Moreover, mutation of a RRK motif in the MUC1 cytoplasmic domain abrogates HRG-induced nucleolar localization of MUC1 and gamma-catenin. In concert with these results, we show nucleolar localization of MUC1 and gamma-catenin in human breast carcinomas but not in normal mammary ductal epithelium. These findings demonstrate that MUC1 functions in cross talk between ErbB2 and Wnt pathways by acting as a shuttle for HRG-induced nucleolar targeting of gamma-catenin.     

Nitric oxide signaling in plant-pathogen interactions

Nitric oxide (NO), first characterized as an endothelium-derived relaxation factor, is involved in diverse cellular processes including neuronal signaling, blood pressure homeostasis, and immune response. Recent studies have also revealed a role for NO as a signaling molecule in plants. As a developmental regulator, NO promotes germination, leaf extension and root growth, and delays leaf senescence and fruit maturation. Moreover, NO acts as a key signal in plant resistance to incompatible pathogens by triggering resistance-associated hypersensitive cell death. In addition, NO activates the expression of several defense genes (e.g. pathogenesis-related genes, phenylalanine ammonialyase, chalcone synthase) and could play a role in pathways leading to systemic acquired resistance.