Sunitinib is a multitargeted tyrosine kinase inhibitor associated with idiosyncratic hepatotoxicity. The mechanisms of this toxicity are unknown. We hypothesized that sunitinib undergoes metabolic ...activation to form chemically reactive, potentially toxic metabolites which may contribute to development of sunitinib-induced hepatotoxicity. The purpose of this study was to define the role of cytochrome P450 (P450) enzymes in sunitinib bioactivation. Metabolic incubations were performed using individual recombinant P450s, human liver microsomal fractions, and P450-selective chemical inhibitors. Glutathione (GSH) and dansylated GSH were used as trapping agents to detect reactive metabolite formation. Sunitinib metabolites were analyzed by liquid chromatography–tandem mass spectrometry. A putative quinoneimine–GSH conjugate (M5) of sunitinib was detected from trapping studies with GSH and dansyl–GSH in human liver microsomal incubations, and M5 was formed in an NADPH-dependent manner. Recombinant P450 1A2 generated the highest levels of defluorinated sunitinib (M3) and M5, with less formation by P450 3A4 and 2D6. P450 3A4 was the major enzyme forming the primary active metabolite N-desethylsunitinib (M1). In human liver microsomal incubations, P450 3A inhibitor ketoconazole reduced formation of M1 by 88%, while P450 1A2 inhibitor furafylline decreased generation of M5 by 62% compared to control levels. P450 2D6 and P450 3A inhibition also decreased M5 by 54 and 52%, respectively, compared to control. In kinetic assays, recombinant P450 1A2 showed greater efficiency for generation of M3 and M5 compared to that of P450 3A4 and 2D6. Moreover, M5 formation was 2.7-fold more efficient in human liver microsomal preparations from an individual donor with high P450 1A2 activity compared to a donor with low P450 1A2 activity. Collectively, these data suggest that P450 1A2 and 3A4 contribute to oxidative defluorination of sunitinib to generate a reactive, potentially toxic quinoneimine. Factors that alter P450 1A2 and 3A activity may affect patient risk for sunitinib toxicity.
In humans, the attitude toward risk is not neutral and is dissimilar between bets involving gains and bets involving losses. The existence and prevalence of these decision features in non-human ...primates are unclear. In addition, only a few studies have tried to simulate the evolution of agents based on their attitude toward risk. Therefore, we still ignore to what extent Prospect theory's claims are evolutionarily rooted. To shed light on this issue, we collected data from nine macaques that performed bets involving gains or losses. We confirmed that their overall behaviour is coherent with Prospect theory's claims. In parallel, we used a genetic algorithm to simulate the evolution of a population of agents across several generations. We showed that the algorithm selects progressively agents that exhibit risk-seeking, and has an inverted S-shape distorted perception of probability. We compared these two results and found that monkeys' attitude toward risk is only congruent with the simulation when they are facing losses. This result is consistent with the idea that gambling in the loss domain is analogous to deciding in a context of life-threatening challenges where a certain level of risk-seeking behaviour and probability distortion may be adaptive. This article is part of the theme issue 'Existence and prevalence of economic behaviours among non-human primates'.
Cellular exposure to cigarette smoke leads to an array of complex responses including apoptosis, cellular senescence, telomere dysfunction, cellular aging, and neoplastic transformation. To study the ...cellular response to cigarette smoke, a common in vitro model exposes cultured cells to a nominal concentration (i.e. initial concentration) of soluble cigarette smoke extract (CSE). However, we report that use of the nominal concentration of CSE as the only measure of cellular exposure is inadequate. Instead, we demonstrate that cellular response to CSE exposure is dependent not only on the nominal concentration of CSE, but also on specific experimental variables, including the total cell number, and the volume of CSE solution used. As found in other similar xenobiotic assays, our work suggests that the effective dose of CSE is more accurately related to the amount of bioavailable chemicals per cell. In particular, interactions of CSE components both with cells and other physical factors limit CSE bioavailability, as demonstrated by a quantifiably reduced cellular response to CSE that is first modified by such interactions. This has broad implications for the nature of cellular response to CSE exposure, and for the design of in vitro assays using CSE.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Salmonella
hijack host machinery in order to invade cells and establish infection. While considerable work has described the role of host proteins in invasion, much less is known regarding how ...natural variation in these invasion-associated host proteins affects
Salmonella
pathogenesis. Here we leveraged a candidate cellular GWAS screen to identify natural genetic variation in the
ARHGEF26
(
Rho Guanine Nucleotide Exchange Factor 26
) gene that renders lymphoblastoid cells susceptible to
Salmonella
Typhi and Typhimurium invasion. Experimental follow-up redefined ARHGEF26’s role in
Salmonella
epithelial cell infection. Specifically, we identified complex serovar-by-host interactions whereby ARHGEF26 stimulation of
S
. Typhi and
S
. Typhimurium invasion into host cells varied in magnitude and effector-dependence based on host cell type. While ARHGEF26 regulated SopB- and SopE-mediated
S
. Typhi (but not
S
. Typhimurium) infection of HeLa cells, the largest effect of ARHGEF26 was observed with
S
. Typhimurium in polarized MDCK cells through a SopB- and SopE2-independent mechanism. In both cell types, knockdown of the ARHGEF26-associated protein DLG1 resulted in a similar phenotype and serovar specificity. Importantly, we show that ARHGEF26 plays a critical role in
S
. Typhimurium pathogenesis by contributing to bacterial burden in the enteric fever murine model, as well as inflammation in the colitis infection model. In the enteric fever model, SopB and SopE2 are required for the effects of
Arhgef26
deletion on bacterial burden, and the impact of
sopB
and
sopE2
deletion in turn required ARHGEF26. In contrast, SopB and SopE2 were not required for the impacts of
Arhgef26
deletion on colitis. A role for ARHGEF26 on inflammation was also seen in cells, as knockdown reduced IL-8 production in HeLa cells. Together, these data reveal pleiotropic roles for ARHGEF26 during infection and highlight that many of the interactions that occur during infection that are thought to be well understood likely have underappreciated complexity.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Surface Enhanced Raman spectroscopy (SERS) technique was developed to provide a high enhancement of Raman scattering from molecules adsorbed on nanostructured noble metal surfaces. This technique has ...gained tremendous interest in the past few years for the detection, identification and quantification of bacteria. Indeed, compared to the standard methods based on bacteria culture, SERS has many advantages in particular in terms of analysis time, sensitivity and sample preparation. The aim of this review is to provide an overview and a discussion of the SERS methods developed for bacteria analysis over the last 20 years. To well assess the technical issues of such developments, this literature review is presented after having described the physical and chemical phenomena involved in the Raman scattering enhancement as well as the different types of noble metal substrates that can be used.
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Having previously highlighted the gelation of pectin with chlorhexidine (CX), pectinate microparticles were prepared here by vibrational prilling using CX, not only as an active ...ingredient encapsulated but also as a cross-linking agent. CX amount required for pectin gelation was smaller than usual dications (Ca2+, Zn2+) used as cross-linking agent for pectin ionotropic gelation: CX seemed to bind more easily to pectin chains that could be explained by its large molecular size. Three batches of CX microparticles with different mean size were prepared. Whatever the droplet mean diameter, similar particle characteristics in terms of encapsulation efficiency, CX encapsulation yield and drug release were observed. The encapsulation efficiency was about 5.5%, the CX encapsulation yield was approximately 44% and the maximal amount of CX released after 6 h was about 7%. Finally, zinc diacetate was added to the formulation as a competitive pectin cross-linking agent in order to limit CX binding to pectin and to improve CX release. The influence of CX and Zn2+ concentrations on the particles properties was studied by the means of a Doehlert design. Results showed the interest of such a mixture since the competition between both cations led to more or less structured and large microparticles, some of them having promoted the quantity of CX released.
A planar rod model with flexible cross-section has been proposed and discussed recently in literature (Guinot et al., 2012; Picault et al., 2014). This 1D model is especially suitable for the ...modeling of tape springs, which develop localized folds through the flattening of the cross-section, and represents a good alternative to 2D shell models which are numerically hard to perform. However, due to its planar nature, it does not account for the coupling between bending and twisting that is noticed experimentally. In this context, we propose an extension of this rod model to 3D motions that includes torsional warping of the cross-section, based on postulated assumptions that are approximations. Starting from a complete non-linear elastic shell model, we introduce an original kinematics inspired from the elastica model and from Vlassov’s theory (Vlassov, 1962) in order to describe in-plane and out-of-plane changes of the cross-section shape with few parameters. In the specific case of shallow tape springs, approximate expressions of the strain and kinetic energies are derived by performing an analytical integration over the cross-section. The 1D tape spring rod model eventually involves only eight kinematic variables: seven to describe the translation and the rotation of the cross-section (parameterized by a unit quaternion) and one for the shape of the cross-section which is assumed to remain circular. Expressions of the potential and kinetic energies are then introduced in a suitable finite element software that can perform an automatic differentiation to solve the problem. Two static cases are treated. The first one, a tape spring clamped at one end and submitted at the other end to a follower twisting moment, shows that the model account for the bending-twisting couplings in large displacements and large rotations. The second one, a novel test named the transverse bending test, illustrates the ability of the model to account for complex scenarios of 3D foldings, involving bending and twisting as well as the creation of folds, their migration along the tape and their duplication. Quantitative comparisons to numerical results obtained with a shell finite element model are shown.
Despite being in a golden age of bacterial epigenomics, little work has systematically examined the plasticity and functional impacts of the bacterial DNA methylome. Here, we leveraged ...single-molecule, real-time sequencing (SMRT-seq) to examine the m
A DNA methylome of two Salmonella enterica serovar Typhimurium strains: 14028s and a Δ
mutant with derepressed methionine metabolism, grown in Luria broth or medium that simulates the intracellular environment. We found that the methylome is remarkably static: >95% of adenosine bases retain their methylation status across conditions. Integration of methylation with transcriptomic data revealed limited correlation between changes in methylation and gene expression. Further, examination of the transcriptome in Δ
bacteria lacking the m
A methylase with the most dynamic methylation pattern in our data set revealed little evidence of YhdJ-mediated gene regulation. Curiously, despite G(m
A)TC motifs being particularly resistant to change across conditions, incorporating
mutants into our analyses revealed two examples where changes in methylation and transcription may be linked across conditions. This includes the novel finding that the Δ
motility defect may be partially driven by hypermethylation of the chemotaxis gene
. Together, these data redefine the
Typhimurium epigenome as a highly stable system that has rare but important roles in transcriptional regulation. Incorporating these lessons into future studies will be critical as we progress through the epigenomic era.
While recent breakthroughs have enabled intense study of bacterial DNA modifications, limitations in current work have potentiated a surprisingly untested narrative that DNA methylation is a common mechanism of the bacterial response to environmental conditions. Essentially, whether epigenetic regulation of bacterial transcription is a common, generalizable phenomenon is a critical unanswered question that we address here. We found that most DNA methylation is static in Salmonella enterica serovar Typhimurium, even when the bacteria are grown under dramatically different conditions that cause broad changes in the transcriptome. Further, even when the methylation of individual bases change, these changes generally do not correlate with changes in gene expression. Finally, we demonstrate methods by which data can be stratified in order to identify coupled changes in methylation and gene expression.
Summary
Background
Stopping nucleos(t)ide analogues (NA) after hepatitis B e antigen (HBeAg) seroconversion is associated with high relapse rates in Asian patients, but data in Caucasian cohorts are ...scarce. Clinical course, outcomes and immunological aspects of chronic hepatitis B infections differ substantially between distinct ethnicities.
Aim
The aim of this study was to determine relapse rates, factors predicting relapse and clinical outcomes after nucleos(t)ide analogue cessation in a large, predominantly Caucasian cohort of chronic hepatitis B patients with nucleos(t)ide analogue‐induced HBeAg seroconversion.
Methods
This is a nationwide observational cohort study including HBeAg positive, mono‐infected chronic hepatitis B patients with nucleos(t)ide analogue‐induced HBeAg seroconversion from 18 centres in Belgium.
Results
A total of 98 patients with nucleo(s)tide analogue‐induced HBeAg seroconversion were included in the study. Of the 62 patients who stopped treatment after a median consolidation treatment of 8 months, 30 relapsed. Higher gamma‐glutamyl transferase levels at both treatment initiation (HR 1.004; P = 0.001 per unit increment) and HBeAg seroconversion (HR 1.006; P = 0.013 per unit increment) were associated with an increased risk of clinically significant relapse in a multivariate Cox regression model. Treatment cessation led to liver‐related death in 2 patients, of whom one showed a severe flare. Of the patients who continued treatment after HBeAg seroconversion, none relapsed or developed severe hepatic outcomes.
Conclusion
Treatment withdrawal in Caucasian chronic hepatitis B patients after nucleos(t)ide analogue‐induced HBeAg seroconversion results in viral relapses in more than half of patients with potential fatal outcomes. These real‐world data further lend support to preferentially continue NA treatment after HBeAg seroconversion until HBsAg loss.
Linked ContentThis article is linked to Ingiliz and Canbay paper. To view this article visit https://doi.org/10.1111/apt.14649.
The gap state that appears upon reduction of TiO2 plays a key role in many of titania's interesting properties but its origin and spatial localization have remained unclear. In the present work, the ...TiO2(110) surface is reduced in a chemically controlled way by sodium adsorption. By means of resonant photoelectron diffraction, excess electrons are shown to be distributed mainly on subsurface Ti sites strikingly similar to the defective TiO2(110) surface, while any significant contribution from interstitial Ti ions is discarded. In agreement with first principles calculations, these findings demonstrate that the distribution of the band gap charge is an intrinsic property of TiO2(110), independent of the way excess electrons are produced.
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