Modelling the potential spread of Hyalomma marginatum ticks in Europe by migratory birds

This study modelled the probability of introduction of Hyalomma marginatum into Europe by predicting the potential migratory routes of 28 bird species and the probability to carry immatures of the tick. Flyways were modelled as a spatio-temporal feature, at weekly intervals, using satellite-derived data of temperature and vegetal phenology, together with cost surfaces derived from speed and direction of the wind (years 2002–2018). The expected period of activity of tick immatures defined the probability of ticks being carried by birds along the modelled flyways. The probability of moulting of the engorged nymphs was modelled as a linear relationship of the daily sum of temperatures after tick introduction by birds. Positive probabilities of tick introduction extend the known northern range of permanent populations to central and western France, and large portions of central Europe. The flight of birds into an area and thence the risk of introduction of H. marginatum is very heterogeneous, with sites receiving “waves” of different bird species at diverse times of the year. Therefore, there is not a clear period of time for introduction, as it depends on the modelled behaviour of the bird species. The probability of introduction into Baltic and Nordic countries is small. We hypothesise that conditions of a warmer climate might support permanent populations of H. marginatum if a high number of immatures is introduced. Active surveys in risky territories, where the tick is not yet established, are advisable for rapid intervention.     

Ceramide is the key mediator of oxidative stress-induced apoptosis in retinal photoreceptor cells

Nitric oxide and reactive oxygen species play a critical role in photoreceptor apoptosis. However, the exact molecular mechanisms triggered by oxidative stress in photoreceptor cell death remain undefined. Here, we demonstrate that the sphingolipid ceramide is the key mediator of oxidative stress-induced apoptosis in 661W retinal photoreceptor cells. Treatment of 661W cells with the nitric oxide donor, sodium nitroprusside, activates acid sphingomyelinase. As a result, sphingomyelin is hydrolysed, which leads to an increase in the concentration of ceramide. We also show that ceramide is responsible for the activation of the mitochondrial apoptotic pathway in 661W photoreceptor cells and subsequent activation of the caspase cascade. Furthermore, we show for the first time that ceramide is responsible for the increased Ca2+ levels in the mitochondria and cytosol that precedes activation of the calpain-mediated apoptotic pathway. Additionally, we provide evidence that ceramide also activates the endolysosomal protease cathepsin D pathway. In summary, our findings show that ceramide controls the cell death decisions in photoreceptor cells and highlight the relevance of acid sphingomyelinase as a potential therapeutic target for the treatment of retinal pathologies.     

Multilocus Sequence Analysis of the Marine Bacterial Genus Tenacibaculum Suggests Parallel Evolution of Fish Pathogenicity and Endemic Colonization of Aquaculture Systems

The genus Tenacibaculum, a member of the family Flavobacteriaceae, is an abundant component of marine bacterial ecosystems that also hosts several fish pathogens, some of which are of serious concern for marine aquaculture. Here, we applied multilocus sequence analysis (MLSA) to 114 representatives of most known species in the genus and of the worldwide diversity of the major fish pathogen Tenacibaculum maritimum. Recombination hampers precise phylogenetic reconstruction, but the data indicate intertwined environmental and pathogenic lineages, which suggests that pathogenicity evolved independently in several species. At lower phylogenetic levels recombination is also important, and the species T. maritimum constitutes a cohesive group of isolates. Importantly, the data reveal no trace of long-distance dissemination that could be linked to international fish movements. Instead, the high number of distinct genotypes suggests an endemic distribution of strains. The MLSA scheme and the data described in this study will help in monitoring Tenacibaculum infections in marine aquaculture; we show, for instance, that isolates from tenacibaculosis outbreaks in Norwegian salmon farms are related to T. dicentrarchi, a recently described species.     

Impaired Ca2+ handling in penile arteries from prediabetic Zucker rats: involvement of Rho kinase

Diabetes is associated with an increased vascular tone usually involved in the pathogenesis of diabetic cardiovascular complications such as hypertension, stroke, coronary artery disease, or erectile dysfunction (ED). Enhanced contractility of penile erectile tissue has been associated with augmented activity of the RhoA/Rho kinase (RhoK) pathway in models of diabetes-associated ED. The present study assessed whether abnormal vasoconstriction in penile arteries from prediabetic obese Zucker rats (OZRs) is due to changes in the intracellular Ca(2+) concentration ([Ca(2+)](i)) and/or in myofilament Ca(2+) sensitivity. Penile arteries from OZRs and lean Zucker rats (LZRs) were mounted on microvascular myographs for simultaneous measurements of [Ca(2+)](i) and tension. The relationships between [Ca(2+)](i) and contraction for the α(1)-adrenergic vasoconstrictor phenylephrine (PE) were left shifted and steeper in OZRs compared with LZRs, although the magnitude of the contraction was similar in both groups. In contrast, the vasoconstriction induced by the thromboxane A(2) receptor agonist U-46619 was augmented in arteries from OZRs, and this increase was associated with an increase in both the sensitivity and maximum responses to Ca(2+). The RhoK inhibitor Y-27632 (10 μM) reduced the vasoconstriction induced by PE to a greater extent in OZRs than in LZRs, without altering Ca(2+). Y-27632 inhibited with a greater potency the contraction elicited by high KCl in arteries from OZRs compared with LZRs without changing [Ca(2+)](i). RhoK-II expression was augmented in arteries from OZRs. These results suggest receptor-specific changes in the Ca(2+) handling of penile arteries under conditions of metabolic syndrome. Whereas augmented vasoconstriction upon activation of the thromboxane A(2) receptor is coupled to enhanced Ca(2+) entry, a RhoK-mediated enhancement of myofilament Ca(2+) sensitivity is coupled with the α(1)-adrenergic vasoconstriction in penile arteries from OZRs.     

Alpha-amylase from Bacillus licheniformis mutants near to the catalytic site: effects on hydrolytic and transglycosylation activity

The alpha-amylase from Bacillus licheniformis is the most widely used enzyme in the starch industry owing to its hyperthermostability, converting starch to medium-sized oligosaccharides. Based on sequence alignment of homologous amylases, we found a semi-conserved sequence pattern near the active site between transglycosidic and hydrolytic amylases, which suggested that hydrophobicity may play a role in modifying the transglycosylation/hydrolysis ratio. Based on this analysis, we replaced residue Val286 by Phe and Tyr in Bacillus licheniformis alpha-amylase. Surprisingly, the two resultant mutant enzymes, Val286Phe and Val286Tyr, showed two different behaviors. Val286Tyr mutant was 5-fold more active for hydrolysis of starch than the wild-type enzyme. In contrast, the Val286Phe mutant, differing only by one hydroxyl group, was 3-fold less hydrolytic than the wild-type enzyme and apparently had a higher transglycosylation/hydrolysis ratio. These results are discussed in terms of affinity of subsites, hydrophobicity and electrostatic environment in the active site. The engineered enzyme reported here may represent an attractive alternative for the starch transformation industries as it affords direct and substantial material savings and requires no process modifications.     

Regulation of Coagulation Factor XI Expression by MicroRNAs in the Human Liver

High levels of factor XI (FXI) increase the risk of thromboembolic disease. However, the genetic and environmental factors regulating FXI expression are still largely unknown. The aim of our study was to evaluate the regulation of FXI by microRNAs (miRNAs) in the human liver. In silico prediction yielded four miRNA candidates that might regulate FXI expression. HepG2 cells were transfected with miR-181a-5p, miR-23a-3p, miR-16-5p and miR-195-5p. We used mir-494, which was not predicted to bind to F11, as a negative control. Only miR-181a-5p caused a significant decrease both in FXI protein and F11 mRNA levels. In addition, transfection with a miR-181a-5p inhibitor in PLC/PRF/5 hepatic cells increased both the levels of F11 mRNA and extracellular FXI. Luciferase assays in human colon cancer cells deficient for Dicer (HCT-DK) demonstrated a direct interaction between miR-181a-5p and 3′untranslated region of F11. Additionally, F11 mRNA levels were inversely and significantly correlated with miR-181a-5p levels in 114 healthy livers, but not with miR-494. This study demonstrates that FXI expression is directly regulated by a specific miRNA, miR-181a-5p, in the human liver. Future studies are necessary to further investigate the potential consequences of miRNA dysregulation in pathologies involving FXI.