Effects of anti-malarial drugs on the electrocardiographic QT interval modelled in the isolated perfused guinea pig heart system

<p>Abstract</p> <p>Background</p> <p>Concern over the potential cardiotoxicity of anti-malarial drugs inducing a prolonged electrocardiographic QT interval has resulted in the almost complete withdrawal from the market of one anti-malarial drug - halofantrine. The effects on the QT interval of four anti-malarial drugs were examined, using the guinea pig heart.</p> <p>Methods</p> <p>The guinea pig heart was isolated, mounted on a Langendorff apparatus, and was then perfused with pyruvate-added Klebs-Henseleit solutions containing graded concentrations of the four agents such as quinidine (0.15 - 1.2 μM), quinine (0.3 - 2.4 μM), halofantrine (0.1 - 2.0 μM) and mefloquine (0.1 - 2.0 μM). The heart rate-corrected QaTc intervals were measured to evaluate drug-induced QT prolongation effects.</p> <p>Results</p> <p>Quinidine, quinine, and halofantrine prolonged the QaTc interval in a dose-dependent manner, whereas no such effect was found with mefloquine. The EC₅₀values for the QaTc prolongation effects, the concentration that gives a half-maximum effect, were quinidine < quinine ≈ halofantrine.</p> <p>Conclusions</p> <p>In this study, an isolated, perfused guinea pig heart system was constructed to assess the cardiotoxic potential of anti-malarial drugs. This isolated perfused guinea pig heart system could be used to test newly developed anti-malarial drugs for their inherent QT lengthening potential. More information is required on the potential variation in unbound drug concentrations in humans, and their role in cardiotoxicity.</p

Mechanical ventilation modulates TLR4 and IRAK-3 in a non-infectious, ventilator-induced lung injury model

<p>Abstract</p> <p>Background</p> <p>Previous experimental studies have shown that injurious mechanical ventilation has a direct effect on pulmonary and systemic immune responses. How these responses are propagated or attenuated is a matter of speculation. The goal of this study was to determine the contribution of mechanical ventilation in the regulation of Toll-like receptor (TLR) signaling and interleukin-1 receptor associated kinase-3 (IRAK-3) during experimental ventilator-induced lung injury.</p> <p>Methods</p> <p>Prospective, randomized, controlled animal study using male, healthy adults Sprague-Dawley rats weighing 300-350 g. Animals were anesthetized and randomized to spontaneous breathing and to two different mechanical ventilation strategies for 4 hours: high tidal volume (V_T) (20 ml/kg) and low V_T(6 ml/kg). Histological evaluation, TLR2, TLR4, <it>IRAK3 </it>gene expression, IRAK-3 protein levels, inhibitory kappa B alpha (IκBα), tumor necrosis factor-alpha (<it>TNF-α</it>) and interleukin-6 (<it>IL6</it>) gene expression in the lungs and TNF-α and IL-6 protein serum concentrations were analyzed.</p> <p>Results</p> <p>High V_Tmechanical ventilation for 4 hours was associated with a significant increase of TLR4 but not TLR2, a significant decrease of <it>IRAK3 </it>lung gene expression and protein levels, a significant decrease of IκBα, and a higher lung expression and serum concentrations of pro-inflammatory cytokines.</p> <p>Conclusions</p> <p>The current study supports an interaction between TLR4 and IRAK-3 signaling pathway for the over-expression and release of pro-inflammatory cytokines during ventilator-induced lung injury. Our study also suggests that injurious mechanical ventilation may elicit an immune response that is similar to that observed during infections.</p

Population Genetic Diversity and Structure of a Naturally Isolated Plant Species, Rhodiola dumulosa (Crassulaceae)

Aims: Rhodiola dumulosa (Crassulaceae) is a perennial diploid species found in high-montane areas. It is distributed in fragmented populations across northern, central and northwestern China. In this study, we aimed to (i) measure the genetic diversity of this species and that of its populations; (ii) describe the genetic structure of these populations across the entire distribution range in China; and (iii) evaluate the extent of gene flow among the naturally fragmented populations. Methods: Samples from 1089 individuals within 35 populations of R. dumulosa were collected, covering as much of the entire distribution range of this species within China as possible. Population genetic diversity and structure were analyzed using AFLP molecular markers. Gene flow among populations was estimated according to the level of population differentiation. Important Findings: The total genetic diversity of R. dumulosa was high but decreased with increasing altitude. Populationstructure analysis indicated that the most closely related populations were geographically restricted and occurred in close proximity to each other. A significant isolation-by-distance pattern, caused by the naturally fragmented population distribution, was observed. At least two distinct gene pools were found in the 35 sampled populations, one composed of populations in northern China and the other composed of populations in central and northwestern China. The calculation of Nei’s gene diversity index revealed that the genetic diversity in the northern China pool (0.1972) was lower than that in th

Tobacco Upregulates P. gingivalis Fimbrial Proteins Which Induce TLR2 Hyposensitivity

Tobacco smokers are more susceptible to periodontitis than non-smokers but exhibit reduced signs of clinical inflammation. The underlying mechanisms are unknown. We have previously shown that cigarette smoke extract (CSE) represents an environmental stress to which P. gingivalis adapts by altering the expression of several virulence factors - including major and minor fimbrial antigens (FimA and Mfa1, respectively) and capsule - concomitant with a reduced pro-inflammatory potential of intact P. gingivalis.We hypothesized that CSE-regulation of capsule and fimbrial genes is reflected at the ultrastructural and functional levels, alters the nature of host-pathogen interactions, and contributes to the reduced pro- inflammatory potential of smoke exposed P. gingivalis. CSE induced ultrastructural alterations were determined by electron microscopy, confirmed by Western blot and physiological consequences studied in open-flow biofilms. Inflammatory profiling of specific CSE-dysregulated proteins, rFimA and rMfa1, was determined by quantifying cytokine induction in primary human innate and OBA-9 cells. CSE up-regulates P. gingivalis FimA at the protein level, suppresses the production of capsular polysaccharides at the ultrastructural level, and creates conditions that promote biofilm formation. We further show that while FimA is recognized by TLR2/6, it has only minimal inflammatory activity in several cell types. Furthermore, FimA stimulation chronically abrogates the pro-inflammatory response to subsequent TLR2 stimulation by other TLR-2-specific agonists (Pam3CSK4, FSL, Mfa1) in an IkappaBalpha- and IRAK-1-dependent manner.These studies provide some of the first information to explain, mechanistically, how tobacco smoke changes the P. gingivalis phenotype in a manner likely to promote P. gingivalis colonization and infection while simultaneously reducing the host response to this major mucosal pathogen

Principles of mRNA transport in yeast

mRNA localization and localized translation is a common mechanism by which cellular asymmetry is achieved. In higher eukaryotes the mRNA transport machinery is required for such diverse processes as stem cell division and neuronal plasticity. Because mRNA localization in metazoans is highly complex, studies at the molecular level have proven to be cumbersome. However, active mRNA transport has also been reported in fungi including Saccharomyces cerevisiae, Ustilago maydis and Candida albicans, in which these events are less difficult to study. Amongst them, budding yeast S. cerevisiae has yielded mechanistic insights that exceed our understanding of other mRNA localization events to date. In contrast to most reviews, we refrain here from summarizing mRNA localization events from different organisms. Instead we give an in-depth account of ASH1 mRNA localization in budding yeast. This approach is particularly suited to providing a more holistic view of the interconnection between the individual steps of mRNA localization, from transcriptional events to cytoplasmic mRNA transport and localized translation. Because of our advanced mechanistic understanding of mRNA localization in yeast, the present review may also be informative for scientists working, for example, on mRNA localization in embryogenesis or in neurons

UBE2O negatively regulates TRAF6-mediated NF-κB activation by inhibiting TRAF6 polyubiquitination

Tumor necrosis factor (TNF) receptor-associated factor 6 (TRAF6) is a key regulator of the activation of transcription factor NF-κB by the interleukin-1 receptor (IL-1R)/Toll-like receptor (TLR) superfamily. Recruitment of TRAF6 to the receptor-associated IRAK1-IRAK4-MyD88 adaptor protein complex induces lysine 63 (K63) autopolyubiquitination of TRAF6, which leads to further recruitment of downstream regulators, such as TAB2/3 and TAK1, and subsequently triggers NF-κB activation. Here, we identified the putative E2 ubiquitin-conjugating (UBC) enzyme UBE2O as a novel negative regulator of TRAF6-dependent NF-κB signaling. We found that UBE2O binds to TRAF6 to inhibit its K63-polyubiquitination, and to prevent the activation of NF-κB by IL-1β and lipopolysaccharides (LPS). We further show that the inhibitory effect of UBE2O is independent of its carboxy-terminal UBC domain. In contrast, we found that UBE2O acts to disrupt the IL-1β-induced association of TRAF6 with MyD88. These results provide novel insight into the regulation of signaling by IL-1R/TLR and TRAF6