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1.
Study design of Dal-GenE, a pharmacogenetic trial targeting reduction of cardiovascular events with dalcetrapib.
Tardif, JC, Dubé, MP, Pfeffer, MA, Waters, DD, Koenig, W, Maggioni, AP, McMurray, JJV, Mooser, V, White, HD, Heinonen, T, et al
American heart journal. 2020;:157-165
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Abstract
The objectives of precision medicine are to better match patient characteristics with the therapeutic intervention to optimize the chances of beneficial actions while reducing the exposure to unneeded adverse drug experiences. In a retrospective genome-wide association study of the overall neutral placebo-controlled dal-Outcomes trial, the effect of the cholesteryl ester transfer protein (CETP) modulator dalcetrapib on the composite of cardiovascular death, myocardial infarction or stroke was found to be influenced by a polymorphism in the adenylate cyclase type 9 (ADCY9) gene. Whereas patients with the AA genotype at position rs1967309 experienced fewer cardiovascular events with dalcetrapib, those with the GG genotype had an increased rate and the heterozygous AG genotype exhibited no difference from placebo. Measurements of cholesterol efflux and C-reactive protein (CRP) offered directionally supportive genotype-specific findings. In a separate, smaller, placebo-controlled trial, regression of ultrasonography-determined carotid intimal-medial thickness was only observed in dalcetrapib-treated patients with the AA genotype. Collectively, these observations led to the hypothesis that the cardiovascular effects of dalcetrapib may be pharmacogenetically determined, with a favorable benefit-risk ratio only for patients with this specific genotype. We describe below the design of dal-GenE, a precision medicine, placebo-controlled clinical outcome trial of dalcetrapib in patients with a recent acute myocardial infarction with the unique feature of selecting only those with the AA genotype at rs1967309 in the ADCY9 gene.
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Experimental and theoretical validations of a one-pot sequential sensing of Hg2+ and biothiols by a 3D Cu-based zwitterionic metal-organic framework.
Chen, HL, Li, RT, Wu, KY, Hu, PP, Zhang, Z, Huang, NH, Zhang, WH, Chen, JX
Talanta. 2020;:120596
Abstract
A zwitterionic three-dimensional (3D) metal-organic framework (MOF) of {[Cu(Cdcbp)(bipy)]·4H2O}n (1) has been synthesized and characterized (H3CdcbpBr = 3-carboxyl-(3,5-dicarboxybenzyl)-pyridinium bromide; bipy = 4,4'-bipyridine). MOF 1 exhibits a variety of structural traits, such as ligand conjugated, positively charged pyridinium center, and Cu(II) cations that collectively enable its efficient hybridization with the flexible, negatively charged, single-stranded, and thymine-rich (T-rich) DNA. The T-rich DNA is labeled with carboxyfluorescein (FAM) fluorescent probe (characterized as P-DNA), but the resultant MOF 1 - P-DNA hybrid (characterized as P-DNA@1) is non-emissive (off-state) because of the fluorescent quenching by MOF 1. The P-DNA@1 hybrid functions as an effective and selective sensor for Hg2+ due to the formation of rigid hairpin-like T-Hg2+-T double-stranded DNA (ds-DNA@Hg2+) which is subsequently ejected by MOF 1, triggering a recovery of the P-DNA fluorescence (on-state). Subsequent addition of biothiols further sequestrates Hg2+ from the ds-DNA@Hg2+ duplex driven by the stronger Hg-S coordination, thus release the P-DNA and, in turn, resorbed by MOF 1 to regain the initial hybrid (off-state). P-DNA@1 hybrid thus detects Hg2+ and biothiols sequentially via a fluorescence "off-on-off" mechanism. The limits of detection (LOD) for Hg2+, biothiols, including cysteine (Cys), glutathione (GSH) and homocysteine (Hcy) are 3.0, 14.2, 15.1 and 8.0 nM, respectively, with the detection time of 60 min for Hg2+, and instantaneous detection for all the three biothiols. The detection mechanism is further confirmed by circular dichroism (CD), fluorescence anisotropy (FA), binding constant and molecular simulation. This sequential detection of Hg2+ and biothiols counter-proofs the presence of each other and may shed light to the occurrence of related diseases, such as neurodegenerative disorders of Parkinson's disease (PD), and Alzheimer's disease (AD).
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The gut microbiome drives inter- and intra-individual differences in metabolism of bioactive small molecules.
Kerimi, A, Kraut, NU, da Encarnacao, JA, Williamson, G
Scientific reports. 2020;(1):19590
Abstract
The origin of inter-individual variability in the action of bioactive small molecules from the diet is poorly understood and poses a substantial obstacle to harnessing their potential for attenuating disease risk. Epidemiological studies show that coffee lowers the risk of developing type 2 diabetes, independently of caffeine, but since coffee is a complex matrix, consumption gives rise to different classes of metabolites in vivo which in turn can affect multiple related pathways in disease development. We quantified key urinary coffee phenolic acid metabolites repeated three times in 36 volunteers, and observed the highest inter- and intra-individual variation for metabolites produced by the colonic microbiome. Notably, a urinary phenolic metabolite not requiring the action of the microbiota was positively correlated with fasting plasma insulin. These data highlight the role of the gut microbiota as the main driver of both intra- and inter-individual variation in metabolism of dietary bioactive small molecules.
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Measuring Reactive Sulfur Species and Thiol Oxidation States: Challenges and Cautions in Relation to Alkylation-Based Protocols.
Nagy, P, Dóka, É, Ida, T, Akaike, T
Antioxidants & redox signaling. 2020;(16):1174-1189
Abstract
Significance: Redox biology is gaining ground in research related to human physiology (metabolism, signaling), pathophysiology (cancer, cardiovascular disease, neurodegeneration), and toxicology (radiation- or xenobiotic-induced damage). A major hurdle in advancing redox medicine is the current lack of understanding the mechanisms underpinning the observed detrimental or beneficial in vivo effects. To gain deeper insights into the underlying molecular pathways of redox regulation, we need to appreciate the strengths and limitations of the currently available methods. Recent Advances: Reactive sulfur species (RSS), including cysteine derivatives of peptides and proteins along with small molecules such as hydrogen sulfide or inorganic polysulfides, are major players in redox biology. RSS-mediated regulation of protein functions is a widely studied mechanism in the field, and considerable efforts have been devoted to the development of selective detection methods. Critical Issues: A large number of available methods rely on an alkylation step to freeze the dynamism of consecutive oxidation and reduction events among RSS at a particular time point inside the cell. This process uses the assumption that alkylation blocks all redox events instantaneously. We argue that unfortunately this is often not the case, which could have serious impacts on detected sulfur species speciation and confound experimental results. Future Directions: Novel technologies and prudent optimization of existing methods to accurately characterize the dynamic redox status of the thiol proteome as well as detailed understanding of regulatory and signaling capacities of protein polysulfidation are crucial to open new routes toward therapeutic interventions.
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Regulatory thiol oxidation in chloroplast metabolism, oxidative stress response and environmental signaling in plants.
Vogelsang, L, Dietz, KJ
The Biochemical journal. 2020;(10):1865-1878
Abstract
The antagonism between thiol oxidation and reduction enables efficient control of protein function and is used as central mechanism in cellular regulation. The best-studied mechanism is the dithiol-disulfide transition in the Calvin Benson Cycle in photosynthesis, including mixed disulfide formation by glutathionylation. The adjustment of the proper thiol redox state is a fundamental property of all cellular compartments. The glutathione redox potential of the cytosol, stroma, matrix and nucleoplasm usually ranges between -300 and -320 mV. Thiol reduction proceeds by short electron transfer cascades consisting of redox input elements and redox transmitters such as thioredoxins. Thiol oxidation ultimately is linked to reactive oxygen species (ROS) and reactive nitrogen species (RNS). Enhanced ROS production under stress shifts the redox network to more positive redox potentials. ROS do not react randomly but primarily with few specific redox sensors in the cell. The most commonly encountered reaction within the redox regulatory network however is the disulfide swapping. The thiol oxidation dynamics also involves transnitrosylation. This review compiles present knowledge on this network and its central role in sensing environmental cues with focus on chloroplast metabolism.
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Thiol-based redox sensing in the methyltransferase associated sensor kinase RdmS in Methanosarcina acetivorans.
Fiege, K, Frankenberg-Dinkel, N
Environmental microbiology. 2019;(5):1597-1610
Abstract
Organisms have evolved signal transduction systems to quickly adapt their lifestyle to internal and environmental changes. While protein kinases and two-component systems are widely distributed in Bacteria, they are also found in Archaea but are less diversified and abundant. In this work, we analysed the function of the kinase RdmS and its role in a putative two-component system in the methanogenic archaeon Methanosarcina acetivorans. RdmS is encoded upstream of the regulator MsrF, which activates the expression of the corrinoid/methyltransferase fusion protein MtsD. In contrast to a typical bacterial histidine kinase, RdmS lacks a membrane domain and the conserved histidine residue for phosphorylation, indicating a different mechanism of signal transduction in comparison to bacterial counterparts. RdmS covalently binds a heme cofactor and is thereby able to bind small molecules like CO and dimethyl sulfide. Interestingly, RdmS possesses a redox-dependent autophosphorylation activity, which, however, is independent of the bound heme cofactor. In fact, our experimental data suggest a thiol-based redox sensing mechanism by RdmS. Moreover, we were able to show that RdmS interacts with the regulator protein MsrF. From these data, we conclude RdmS to be a thiol-based kinase sensing redox changes and forming an archaeal multicomponent system with the regulators MsrG/F/C.
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7.
The role of thiols in antioxidant systems.
Ulrich, K, Jakob, U
Free radical biology & medicine. 2019;:14-27
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Abstract
The sulfur biochemistry of the thiol group endows cysteines with a number of highly specialized and unique features that enable them to serve a variety of different functions in the cell. Typically highly conserved in proteins, cysteines are predominantly found in functionally or structurally crucial regions, where they act as stabilizing, catalytic, metal-binding and/or redox-regulatory entities. As highly abundant low molecular weight thiols, cysteine thiols and their oxidized disulfide counterparts are carefully balanced to maintain redox homeostasis in various cellular compartments, protect organisms from oxidative and xenobiotic stressors and partake actively in redox-regulatory and signaling processes. In this review, we will discuss the role of protein thiols as scavengers of hydrogen peroxide in antioxidant enzymes, use thiol peroxidases to exemplify how protein thiols contribute to redox signaling, provide an overview over the diverse set of low molecular weight thiol-based redox systems found in biology, and illustrate how thiol-based redox systems have evolved not only to protect against but to take full advantage of a world full of molecular oxygen.
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Loss and formation of malodorous volatile sulfhydryl compounds during wine storage.
Kreitman, GY, Elias, RJ, Jeffery, DW, Sacks, GL
Critical reviews in food science and nutrition. 2019;(11):1728-1752
Abstract
Volatile sulfur compounds (VSCs), particularly low molecular weight sulfhydryls like hydrogen sulfide (H2S) and methanethiol (MeSH), are often observed in wines with sulfurous off-aromas. Recent work has shown both H2S and MeSH can increase up to a few µM (> 40 µg/L) during anoxic storage, but the identity of the latent sources of these sulfhydryls is still disputed. This review critically evaluates the latent precursors and pathways likely to be responsible for the loss and formation of these sulfhydryls during wine storage based on the existing enology literature as well as studies from food chemistry, geochemistry, biochemistry, and synthetic chemistry. We propose that three precursor classes have sufficient concentration and metastability to serve as latent sulfhydryl precursors in wine: 1) transition metal-sulfhydryl complexes, particularly those formed following Cu(II) addition, which are released under anoxic conditions through an unknown mechanism; 2) asymmetric disulfides, polysulfanes, and (di)organopolysulfanes formed through transition-metal mediated oxidation (e.g., Cu(II)) of sulfhydryls or pesticide degradation, and released through sulfitolysis, metal-catalyzed thiol-disulfide exchange or related reactions; 3) S-alkylthioacetates, primarily formed during fermentation, and releasable hydrolytically. Some evidence also exists for S-amino acids serving as precursors. Based on these findings, we propose a "decision tree" approach to choosing appropriate strategies for managing wines with sulfurous off-aromas.
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Coenzyme A: a protective thiol in bacterial antioxidant defence.
Gout, I
Biochemical Society transactions. 2019;(1):469-476
Abstract
Coenzyme A (CoA) is an indispensable cofactor in all living organisms. It is synthesized in an evolutionarily conserved pathway by enzymatic conjugation of cysteine, pantothenate (Vitamin B5), and ATP. This unique chemical structure allows CoA to employ its highly reactive thiol group for diverse biochemical reactions. The involvement of the CoA thiol group in the production of metabolically active CoA thioesters (e.g. acetyl CoA, malonyl CoA, and HMG CoA) and activation of carbonyl-containing compounds has been extensively studied since the discovery of this cofactor in the middle of the last century. We are, however, far behind in understanding the role of CoA as a low-molecular-weight thiol in redox regulation. This review summarizes our current knowledge of CoA function in redox regulation and thiol protection under oxidative stress in bacteria. In this context, I discuss recent findings on a novel mode of redox regulation involving covalent modification of cellular proteins by CoA, termed protein CoAlation.
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Rapid free thiol rebound is a physiological response following cold-induced vasoconstriction in healthy humans, primary Raynaud and systemic sclerosis.
Abdulle, AE, van Roon, AM, Smit, AJ, Pasch, A, van Meurs, M, Bootsma, H, Bakker, SJL, Said, MY, Fernandez, BO, Feelisch, M, et al
Physiological reports. 2019;(6):e14017
Abstract
Raynaud's phenomenon (RP) is often the first sign of systemic sclerosis (SSc). Molecular mechanisms involved are incompletely understood, but reactive oxygen, nitrogen, and sulfur species are thought to play an important role in the pathogenesis of SSc. Free thiol groups play a protective role against oxidative stress and may represent an attractive therapeutic target. We aimed to investigate the effects of hypothermia-induced vasoconstriction on the responsiveness of redox-related markers. Thirty participants (n = 10/group [SSc, primary Raynaud's phenomenon (PRP), healthy controls (HC)]) were included in this study. Fingertip photoelectric plethysmography was performed during a standardized cooling and recovery experiment. Venous blood was collected at four predetermined time points. Free thiols, NO-derived species (nitros(yl)ated species, nitrite, nitrate), sulfate and endothelin-1 were measured. Lower baseline concentrations of free thiols were observed in PRP and SSc patients (HC: 5.87 [5.41-5.99] μmol/g; PRP: 5.17 [4.74-5.61]; SSc 5.28 [4.75-5.80], P = 0.04). Redox-related markers remained unchanged during cooling. However, an unexpected increase in systemic free thiol concentrations was observed in all groups during the recovery phase. The response of this marker differed between groups, with a higher increase found in SSc patients (HC Δ = 1.30 [1.48-1.17]; PRP Δ = 1.04 [1.06-1.03]; SSc Δ = 1.72 [1.13-1.49], P = 0.04). NO-derived species, sulfate and endothelin-1 levels remained unchanged throughout the recovery phase. This exploratory study sheds light on the rapid responsiveness of systemic free thiol concentrations following reperfusion, which may reflect overall redox balance. The robust response to reperfusion in SSc patients suggests that reductive systems involved in this response are functionally intact in these patients.