Lutein Isomers: Preparation, Separation, Structure Elucidation, and Occurrence in 20 Medicinal Plants.

Lutein and its cis-isomers occur in a lot of plants, including a variety of flowers. In this study, lutein isomers were produced via iodine-catalyzed isomerization, and four cis-isomers (9Z-, 9'Z-, 13Z-, and 13Z') were isolated by means of column chromatography and semipreparative HPLC. The structures of the 9'Z- and 13'Z-isomers were elucidated via NMR measurements. These compounds were used as standards for the HPLC-DAD-MS determination of the carotenoid composition of the flowers of 20 plant species, in which lutein and its geometrical isomers are the main components. The flowers showed great variation in their cis- and trans-lutein content, and also in the presence or absence of other carotenoids, such as violaxanthin, neoxanthin, ß-cryptoxanthin, and ß-carotene. Some of the investigated flowers were found to be rich sources of lutein without zeaxanthin.

Analyzing the Carotenoid Composition of Melilot (Melilotus officinalis (L.) Pall.) Extracts and the Effects of Isolated (All-E)-lutein-5,6-epoxide on Primary Sensory Neurons and Macrophages.

Melilotus officinalis is known to contain several types of secondary metabolites. In contrast, the carotenoid composition of this medicinal plant has not been investigated, although it may also contribute to the biological activities of the drug, such as anti-inflammatory effects. Therefore, this study focuses on the isolation and identification of carotenoids from Meliloti herba and on the effect of isolated (all-E)-lutein 5,6-epoxide on primary sensory neurons and macrophages involved in nociception, as well as neurogenic and non-neurogenic inflammatory processes. The composition of the plant extracts was analyzed by high performance liquid chromatography (HPLC). The main carotenoid was isolated by column liquid chromatography (CLC) and identified by MS and NMR. The effect of water-soluble lutein 5,6-epoxide-RAMEB (randomly methylated-ß-cyclodextrin) was investigated on Ca2+-influx in rat primary sensory neurons induced by the activation of the transient receptor potential ankyrin 1 receptor agonist to mustard-oil and on endotoxin-induced IL-1ß release from isolated mouse peritoneal macrophages. (all-E)-Lutein 5,6-epoxide significantly decreased the percent of responsive primary sensory neurons compared to the vehicle-treated stimulated control. Furthermore, endotoxin-evoked IL-1ß release from macrophages was significantly decreased by 100 µM lutein 5,6-epoxide compared to the vehicle-treated control. The water-soluble form of lutein 5,6-epoxide-RAMEB decreases the activation of primary sensory neurons and macrophages, which opens perspectives for its analgesic and anti-inflammatory applications.

Limited Evolutionary Conservation of the Phenotypic Effects of Antibiotic Resistance Mutations.

Multidrug-resistant clinical isolates are common in certain pathogens, but rare in others. This pattern may be due to the fact that mutations shaping resistance have species-specific effects. To investigate this issue, we transferred a range of resistance-conferring mutations and a full resistance gene into Escherichia coli and closely related bacteria. We found that resistance mutations in one bacterial species frequently provide no resistance, in fact even yielding drug hypersensitivity in close relatives. In depth analysis of a key gene involved in aminoglycoside resistance (trkH) indicated that preexisting mutations in other genes-intergenic epistasis-underlie such extreme differences in mutational effects between species. Finally, reconstruction of adaptive landscapes under multiple antibiotic stresses revealed that mutations frequently provide multidrug resistance or elevated drug susceptibility (i.e., collateral sensitivity) only with certain combinations of other resistance mutations. We conclude that resistance and collateral sensitivity are contingent upon the genetic makeup of the bacterial population, and such contingency could shape the long-term fate of resistant bacteria. These results underlie the importance of species-specific treatment strategies.

Phenotypic heterogeneity promotes adaptive evolution.

Genetically identical cells frequently display substantial heterogeneity in gene expression, cellular morphology and physiology. It has been suggested that by rapidly generating a subpopulation with novel phenotypic traits, phenotypic heterogeneity (or plasticity) accelerates the rate of adaptive evolution in populations facing extreme environmental challenges. This issue is important as cell-to-cell phenotypic heterogeneity may initiate key steps in microbial evolution of drug resistance and cancer progression. Here, we study how stochastic transitions between cellular states influence evolutionary adaptation to a stressful environment in yeast Saccharomyces cerevisiae. We developed inducible synthetic gene circuits that generate varying degrees of expression stochasticity of an antifungal resistance gene. We initiated laboratory evolutionary experiments with genotypes carrying different versions of the genetic circuit by exposing the corresponding populations to gradually increasing antifungal stress. Phenotypic heterogeneity altered the evolutionary dynamics by transforming the adaptive landscape that relates genotype to fitness. Specifically, it enhanced the adaptive value of beneficial mutations through synergism between cell-to-cell variability and genetic variation. Our work demonstrates that phenotypic heterogeneity is an evolving trait when populations face a chronic selection pressure. It shapes evolutionary trajectories at the genomic level and facilitates evolutionary rescue from a deteriorating environmental stress.

Correction: Phenotypic heterogeneity promotes adaptive evolution.

[This corrects the article DOI: 10.1371/journal.pbio.2000644.].

Study on the Synthesis, Antioxidant Properties, and Self-Assembly of Carotenoid-Flavonoid Conjugates.

Flavonoids and carotenoids possess beneficial physiological effects, such as high antioxidant capacity, anticarcinogenic, immunomodulatory, and anti-inflammatory properties, as well as protective effects against UV light. The covalent coupling of hydrophobic carotenoids with hydrophilic flavonoids, such as daidzein and chrysin, was achieved, resulting in new amphipathic structures. 7-Azidohexyl ethers of daidzein and chrysin were prepared in five steps, and their azide-alkyne [4 + 2] cycloaddition with pentynoates of 8'-apo-ß-carotenol, zeaxanthin, and capsanthin afforded carotenoid-flavonoid conjugates. The trolox-equivalent antioxidant capacity against ABTS•+ radical cation and self-assembly of the final products were examined. The 1:1 flavonoid-carotenoid hybrids generally showed higher antioxidant activity than their parent flavonoids but lower than that of the corresponding carotenoids. The diflavonoid hybrids of zeaxanthin and capsanthin, however, were found to exhibit a synergistic enhancement in antioxidant capacities. ECD (electronic circular dichroism) and UV-vis analysis of zeaxanthin-flavonoid conjugates revealed that they form different optically active J-aggregates in acetone/water and tetrahydrofuran/water mixtures depending on the solvent ratio and type of the applied aprotic polar solvent, while the capsanthin derivatives showed no self-assembly. The zeaxanthin bis-triazole conjugates with daidzein and with chrysin, differing only in the position of a phenolic hydroxyl group, showed significantly different aggregation profile upon the addition of water.

Indispensability of Horizontally Transferred Genes and Its Impact on Bacterial Genome Streamlining.

Why are certain bacterial genomes so small and compact? The adaptive genome streamlining hypothesis posits that selection acts to reduce genome size because of the metabolic burden of replicating DNA. To reveal the impact of genome streamlining on cellular traits, we reduced the Escherichia coli genome by up to 20% by deleting regions which have been repeatedly subjects of horizontal transfer in nature. Unexpectedly, horizontally transferred genes not only confer utilization of specific nutrients and elevate tolerance to stresses, but also allow efficient usage of resources to build new cells, and hence influence fitness in routine and stressful environments alike. Genome reduction affected fitness not only by gene loss, but also by induction of a general stress response. Finally, we failed to find evidence that the advantage of smaller genomes would be due to a reduced metabolic burden of replicating DNA or a link with smaller cell size. We conclude that as the potential energetic benefit gained by deletion of short genomic segments is vanishingly small compared with the deleterious side effects of these deletions, selection for reduced DNA synthesis costs is unlikely to shape the evolution of small genomes.

The genomic landscape of compensatory evolution.

Adaptive evolution is generally assumed to progress through the accumulation of beneficial mutations. However, as deleterious mutations are common in natural populations, they generate a strong selection pressure to mitigate their detrimental effects through compensatory genetic changes. This process can potentially influence directions of adaptive evolution by enabling evolutionary routes that are otherwise inaccessible. Therefore, the extent to which compensatory mutations shape genomic evolution is of central importance. Here, we studied the capacity of the baker's yeast genome to compensate the complete loss of genes during evolution, and explored the long-term consequences of this process. We initiated laboratory evolutionary experiments with over 180 haploid baker's yeast genotypes, all of which initially displayed slow growth owing to the deletion of a single gene. Compensatory evolution following gene loss was rapid and pervasive: 68% of the genotypes reached near wild-type fitness through accumulation of adaptive mutations elsewhere in the genome. As compensatory mutations have associated fitness costs, genotypes with especially low fitnesses were more likely to be subjects of compensatory evolution. Genomic analysis revealed that as compensatory mutations were generally specific to the functional defect incurred, convergent evolution at the molecular level was extremely rare. Moreover, the majority of the gene expression changes due to gene deletion remained unrestored. Accordingly, compensatory evolution promoted genomic divergence of parallel evolving populations. However, these different evolutionary outcomes are not phenotypically equivalent, as they generated diverse growth phenotypes across environments. Taken together, these results indicate that gene loss initiates adaptive genomic changes that rapidly restores fitness, but this process has substantial pleiotropic effects on cellular physiology and evolvability upon environmental change. Our work also implies that gene content variation across species could be partly due to the action of compensatory evolution rather than the passive loss of genes.

Antagonism between bacteriostatic and bactericidal antibiotics is prevalent.

Combination therapy is rarely used to counter the evolution of resistance in bacterial infections. Expansion of the use of combination therapy requires knowledge of how drugs interact at inhibitory concentrations. More than 50 years ago, it was noted that, if bactericidal drugs are most potent with actively dividing cells, then the inhibition of growth induced by a bacteriostatic drug should result in an overall reduction of efficacy when the drug is used in combination with a bactericidal drug. Our goal here was to investigate this hypothesis systematically. We first constructed time-kill curves using five different antibiotics at clinically relevant concentrations, and we observed antagonism between bactericidal and bacteriostatic drugs. We extended our investigation by performing a screen of pairwise combinations of 21 different antibiotics at subinhibitory concentrations, and we found that strong antagonistic interactions were enriched significantly among combinations of bacteriostatic and bactericidal drugs. Finally, since our hypothesis relies on phenotypic effects produced by different drug classes, we recreated these experiments in a microfluidic device and performed time-lapse microscopy to directly observe and quantify the growth and division of individual cells with controlled antibiotic concentrations. While our single-cell observations supported the antagonism between bacteriostatic and bactericidal drugs, they revealed an unexpected variety of cellular responses to antagonistic drug combinations, suggesting that multiple mechanisms underlie the interactions.

Bacterial evolution of antibiotic hypersensitivity.

The evolution of resistance to a single antibiotic is frequently accompanied by increased resistance to multiple other antimicrobial agents. In sharp contrast, very little is known about the frequency and mechanisms underlying collateral sensitivity. In this case, genetic adaptation under antibiotic stress yields enhanced sensitivity to other antibiotics. Using large-scale laboratory evolutionary experiments with Escherichia coli, we demonstrate that collateral sensitivity occurs frequently during the evolution of antibiotic resistance. Specifically, populations adapted to aminoglycosides have an especially low fitness in the presence of several other antibiotics. Whole-genome sequencing of laboratory-evolved strains revealed multiple mechanisms underlying aminoglycoside resistance, including a reduction in the proton-motive force (PMF) across the inner membrane. We propose that as a side effect, these mutations diminish the activity of PMF-dependent major efflux pumps (including the AcrAB transporter), leading to hypersensitivity to several other antibiotics. More generally, our work offers an insight into the mechanisms that drive the evolution of negative trade-offs under antibiotic selection.

A systematic quantitative approach comprehensively defines domain-specific functional pathways linked to Schizosaccharomyces pombe heterochromatin regulation.

Heterochromatin plays a critical role in regulating gene expression and maintaining genome integrity. While structural and enzymatic components have been linked to heterochromatin establishment, a comprehensive view of the underlying pathways at diverse heterochromatin domains remains elusive. Here, we developed a systematic approach to identify factors involved in heterochromatin silencing at pericentromeres, subtelomeres, and the silent mating type locus in Schizosaccharomyces pombe. Using quantitative measures, iterative genetic screening, and domain-specific heterochromatin reporters, we identified 369 mutants with different degrees of reduced or enhanced silencing. As expected, mutations in the core heterochromatin machinery globally decreased silencing. However, most other mutants exhibited distinct qualitative and quantitative profiles that indicate domain-specific functions. For example, decreased mating type silencing was linked to mutations in heterochromatin maintenance genes, while compromised subtelomere silencing was associated with metabolic pathways. Furthermore, similar phenotypic profiles revealed shared functions for subunits within complexes. We also discovered that the uncharacterized protein Dhm2 plays a crucial role in maintaining constitutive and facultative heterochromatin, while its absence caused phenotypes akin to DNA replication-deficient mutants. Collectively, our systematic approach unveiled a landscape of domain-specific heterochromatin regulators controlling distinct states and identified Dhm2 as a previously unknown factor linked to heterochromatin inheritance and replication fidelity.

Competition between transposable elements and mutator genes in bacteria.

Although both genotypes with elevated mutation rate (mutators) and mobilization of insertion sequence (IS) elements have substantial impact on genome diversification, their potential interactions are unknown. Moreover, the evolutionary forces driving gradual accumulation of these elements are unclear: Do these elements spread in an initially transposon-free bacterial genome as they enable rapid adaptive evolution? To address these issues, we inserted an active IS1 element into a reduced Escherichia coli genome devoid of all other mobile DNA. Evolutionary laboratory experiments revealed that IS elements increase mutational supply and occasionally generate variants with especially large phenotypic effects. However, their impact on adaptive evolution is small compared with mismatch repair mutator alleles, and hence, the latter impede the spread of IS-carrying strains. Given their ubiquity in natural populations, such mutator alleles could limit early phase of IS element evolution in a new bacterial host. More generally, our work demonstrates the existence of an evolutionary conflict between mutation-promoting mechanisms.

Cryptocapsinepoxide-type carotenoids from red mamey, Pouteria sapota.

New carotenoids, cryptocapsin-5,6-epoxide, 3'-deoxycapsanthin-5,6-epoxide, and cryptocapsin-5,8-epoxides, have been isolated from the ripe fruits of red mamey (Pouteria sapota). Cryptocapsin-5,6-epoxide was prepared by partial synthesis via epoxidation of cryptocapsin, and the (5R,6S)- and (5S,6R)-stereoisomers were identified by HPLC-ECD analysis. Spectroscopic data of the natural (anti) and semisynthetic (syn) derivatives obtained by acid-catalyzed rearrangement of cryptocapsin-5,8-epoxide stereoisomers were compared for structural elucidation. Chiral HPLC separation of natural and semisynthetic samples of cryptocapsin-5,8-epoxides was performed, and HPLC-ECD analysis allowed configurational assignment of the separated stereoisomers.

Characterization of antibiotic resistomes by reprogrammed bacteriophage-enabled functional metagenomics in clinical strains.

Functional metagenomics is a powerful experimental tool to identify antibiotic resistance genes (ARGs) in the environment, but the range of suitable host bacterial species is limited. This limitation affects both the scope of the identified ARGs and the interpretation of their clinical relevance. Here we present a functional metagenomics pipeline called Reprogrammed Bacteriophage Particle Assisted Multi-species Functional Metagenomics (DEEPMINE). This approach combines and improves the use of T7 bacteriophage with exchanged tail fibres and targeted mutagenesis to expand phage host-specificity and efficiency for functional metagenomics. These modified phage particles were used to introduce large metagenomic plasmid libraries into clinically relevant bacterial pathogens. By screening for ARGs in soil and gut microbiomes and clinical genomes against 13 antibiotics, we demonstrate that this approach substantially expands the list of identified ARGs. Many ARGs have species-specific effects on resistance; they provide a high level of resistance in one bacterial species but yield very limited resistance in a related species. Finally, we identified mobile ARGs against antibiotics that are currently under clinical development or have recently been approved. Overall, DEEPMINE expands the functional metagenomics toolbox for studying microbial communities.

Synthesis and evaluation of a new class of MIF-inhibitors in activated macrophage cells and in experimental septic shock in mice.

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine with enzymatic activities. Anti-inflammatory effects of MIF enzyme inhibitors indicate a link between its cytokine- and catalytic activities. Herein the synthesis, docking, and bioactivity of substituted benzylidene-1-indanone and -1-tetralone derivatives as MIF-tautomerase inhibitors is reported. Many of these substituted benzylidene-1-tetralones and -indan-1-ones were potent MIF-tautomerase inhibitors (IC50 < 10 µmol/L), and the most potent inhibitors were the 1-indanone derivatives 16 and 20. Some of these compounds acted as selective enolase or ketonase inhibitors. In addition, compounds 16, 20, 26, 37 and 61 efficiently inhibited NO, TNFα and IL-6 production in lipopolysaccharide-induced macrophages. Compound 20, 37 and 61 also inhibited ROS generation, and compound 26 and 37 abolished activation of NF-κB. Compound 37 significantly augmented hypothermia induced by high dose of lipopolysaccharide in mice. The possible mechanisms of action were explored using molecular modelling and docking, as well as molecular dynamics simulations.

Gene loss and compensatory evolution promotes the emergence of morphological novelties in budding yeast.

Deleterious mutations are generally considered to be irrelevant for morphological evolution. However, they could be compensated by conditionally beneficial mutations, thereby providing access to new adaptive paths. Here we use high-dimensional phenotyping of laboratory-evolved budding yeast lineages to demonstrate that new cellular morphologies emerge exceptionally rapidly as a by-product of gene loss and subsequent compensatory evolution. Unexpectedly, the capacities for invasive growth, multicellular aggregation and biofilm formation also spontaneously evolve in response to gene loss. These multicellular phenotypes can be achieved by diverse mutational routes and without reactivating the canonical regulatory pathways. These ecologically and clinically relevant traits originate as pleiotropic side effects of compensatory evolution and have no obvious utility in the laboratory environment. The extent of morphological diversity in the evolved lineages is comparable to that of natural yeast isolates with diverse genetic backgrounds and lifestyles. Finally, we show that both the initial gene loss and subsequent compensatory mutations contribute to new morphologies, with their synergistic effects underlying specific morphological changes. We conclude that compensatory evolution is a previously unrecognized source of morphological diversity and phenotypic novelties.

Proteome-wide landscape of solubility limits in a bacterial cell.

Proteins are prone to aggregate when expressed above their solubility limits. Aggregation may occur rapidly, potentially as early as proteins emerge from the ribosome, or slowly, following synthesis. However, in vivo data on aggregation rates are scarce. Here, we classified the Escherichia coli proteome into rapidly and slowly aggregating proteins using an in vivo image-based screen coupled with machine learning. We find that the majority (70%) of cytosolic proteins that become insoluble upon overexpression have relatively low rates of aggregation and are unlikely to aggregate co-translationally. Remarkably, such proteins exhibit higher folding rates compared to rapidly aggregating proteins, potentially implying that they aggregate after reaching their folded states. Furthermore, we find that a substantial fraction (~ 35%) of the proteome remain soluble at concentrations much higher than those found naturally, indicating a large margin of safety to tolerate gene expression changes. We show that high disorder content and low surface stickiness are major determinants of high solubility and are favored in abundant bacterial proteins. Overall, our study provides a global view of aggregation rates and hence solubility limits of proteins in a bacterial cell.

Novel cyclic C5-curcuminoids penetrating the blood-brain barrier: Design, synthesis and antiproliferative activity against astrocytoma and neuroblastoma cells.

Novel series of cyclic C5-curcuminoids 17a-j and 19-22 were prepared as cytotoxic agents and evaluated against human neuroblastoma (SH-SY5Y) or human grade IV astrocytoma (CCF-STTG1) cell lines in low (∼0.1 nM - 10 nM) concentrations. Among the tested 21 derivatives, 16 displayed potent antiproliferative activity with IC50 values in the low nanomolar to picomolar range (IC50 = 7.483-0.139 nM). Highly active compounds like N-monocarboxylic derivative 19b with IC50 = 0.139 nM value against neuroblastoma and N-alkyl substituted 11 with IC50 = 0.257 nM against astrocytoma proved some degree of selectivity toward non-cancerous astrocytes and kidney cells. This potent anticancer activity did not show a strong correlation with experimental logPTLC values, but the most potent antiproliferative molecules 11-13 and 19-22 are belonging to discrete subgroups of the cyclic C5-curcuminoids. Compounds 12, 17c and 19b were subjected to blood-brain barrier (BBB) penetration studies, too. The BBB was revealed to be permeable for all of them but, as the apparent permeability coefficient (Papp) values mirrored, in different ratios. Lower toxicity of 12, 17c and 19b was observed toward primary rat brain endothelial cells of the BBB model, which means they remained undamaged under 10 µM concentrations. Penetration depends, at least in part, on albumin binding of 12, 17c and 19b and the presence of monocarboxylic acid transporters in the case of 19b. Permeation through the BBB and albumin binding, we described here, is the first example of cyclic C5-curcuminoids as to our knowledge.

Synthesis and study of new paramagnetic resveratrol analogues.

New resveratrol analogues containing five- and six-membered nitroxides and isoindoline nitroxides were synthesized. These new compounds were compared to resveratrol based on their ABTS radical scavenging ability as well on their capacity to suppress inflammatory process in macrophages induced by lipopolysaccharides. The ABTS and ROS scavenging activities of new molecules were the same or weaker than that of resveratrol, but some of paramagnetic resveratrol derivatives suppressed nitrite and TNFα production more efficiently than resveratrol. Based on these results the new nitroxide and phenol containing hybrid molecules can be considered as new antioxidant and anti-inflammatory agents.