Hydrogen sulfide, reactive sulfur species and coping with reactive oxygen species

Chemoselective Proteomics, Zinc Fingers, and a Zinc(II) Model for H2S Mediated Persulfidation

The gasotransmitter hydrogen sulfide (H2S) is thought to be involved in the post-translational modification of cysteine residues to produce reactive persulfides. A persulfide-specific chemoselective proteomics approach with mammalian cells has identified a broad range of zinc finger (ZF) proteins as targets of persulfidation. Parallel studies with isolated ZFs show that persulfidation is mediated by ZnII, O2, and H2S, with intermediates involving oxygen- and sulfur-based radicals detected by mass spectrometry and optical spectroscopies. A small molecule ZnII complex exhibits analogous reactivity with H2S and O2, giving a persulfidated product. These data show that ZnII is not just a biological structural element, but also plays a critical role in mediating H2S-dependent persulfidation. ZF persulfidation appears to be a general post-translational modification and a possible conduit for H2S signaling. This work has implications for our understanding of H2S-mediated signaling and the regulation of ZFs in cellular physiology and development.

Oxidation of Hydrogen Sulfide to Polysulfide and Thiosulfate by a Carbon Nanozyme: Therapeutic Implications with an Emphasis on Down Syndrome

Hydrogen sulfide (H2 S) is a noxious, potentially poisonous, but necessary gas produced from sulfur metabolism in humans. In Down Syndrome (DS), the production of H2 S is elevated and associated with degraded mitochondrial function. Therefore, removing H2 S from the body as a stable oxide could be an approach to reducing the deleterious effects of H2 S in DS. In this report we describe the catalytic oxidation of hydrogen sulfide (H2 S) to polysulfides (HS2+n - ) and thiosulfate (S2 O3 2- ) by poly(ethylene glycol) hydrophilic carbon clusters (PEG-HCCs) and poly(ethylene glycol) oxidized activated charcoal (PEG-OACs), examples of oxidized carbon nanozymes (OCNs). We show that OCNs oxidize H2 S to polysulfides and S2 O3 2- in a dose-dependent manner. The reaction is dependent on O2 and the presence of quinone groups on the OCNs. In DS donor lymphocytes we found that OCNs increased polysulfide production, proliferation, and afforded protection against additional toxic levels of H2 S compared to untreated DS lymphocytes. Finally, in Dp16 and Ts65DN murine models of DS, we found that OCNs restored osteoclast differentiation. This new action suggests potential facile translation into the clinic for conditions involving excess H2 S exemplified by DS.

A human serum albumin-binding-based fluorescent probe for monitoring hydrogen sulfide and bioimaging

In this work, a fluorescent probe, TPABF-HS, was developed for detecting hydrogen sulfide (H2S) using a human serum albumin (HSA)-binding-based approach for amplifying the fluorescence signal and extending the linear correlation range. Compared to the most recent probes for H2S, the most interesting feature of the detection system developed herein was the especially wide linear range (0-1000 μM (0-100 eq.)), which covered the physiological and pathological levels of H2S. TPABF-HS could be used in applications high sensitivity and selectivity with an LOD value of 0.42 μM. Further, site-competition experiments and molecular docking simulation experiments indicated that signal amplification was realized by the binding of the TPABF fluorophore to the naproxen-binding site of HSA. Moreover, the extension of the measurement span could allow for applications in living cells and Caenorhabditis elegans for imaging both exogenous and endogenous H2S. This work brings new information to the strategy of signal processing by exploiting fluorescent probes.

The Networked Interaction between Probiotics and Intestine in Health and Disease: A Promising Success Story

Probiotics are known to promote human health either precautionary in healthy individuals or therapeutically in patients suffering from certain ailments. Although this knowledge was empirical in past tomes, modern science has already verified it and expanded it to new limits. These microorganisms can be found in nature in various foods such as dairy products or in supplements formulated for clinical or preventive use. The current review examines the different mechanisms of action of the probiotic strains and how they interact with the organism of the host. Emphasis is put on the clinical therapeutic use of these beneficial microorganisms in various clinical conditions of the human gastrointestinal tract. Diseases of the gastrointestinal tract and particularly any malfunction and inflammation of the intestines seriously compromise the health of the whole organism. The interaction between the probiotic strains and the host's microbiota can alleviate the clinical signs and symptoms while in some cases, in due course, it can intervene in the underlying pathology. Various safety issues of the use of probiotics are also discussed.

Untargeted polysulfide omics analysis of alternations in polysulfide production during the germination of broccoli sprouts

Higher consumption of broccoli (Brassica oleracea var. italica) is associated with a reduced risk of cardiometabolic diseases, neurological disorders, diabetes, and cancer. Broccoli is rich in various phytochemicals, including glucosinolates, and isothiocyanates. Moreover, it has recently reported the endogenous production of polysulfides, such as cysteine hydropersulfide (CysS2H) and glutathione hydropersulfide (GS2H), in mammals including humans, and that these bioactive substances function as potent antioxidants and important regulators of redox signaling in vivo. However, few studies have focused on the endogenous polysulfide content of broccoli and the impact of germination on the polysulfide content and composition in broccoli. In this study, we investigated the alternations in polysulfide biosynthesis in broccoli during germination by performing untargeted polysulfide omics analysis and quantitative targeted polysulfide metabolomics through liquid chromatography-electrospray ionization-tandem mass spectrometry. We also performed 2,2-diphenyl-1-picrylhydrazyl radical-scavenging assay to determine the antioxidant properties of the polysulfides. The results revealed that the total polysulfide content of broccoli sprouts significantly increased during germination and growth; CysS2H and cysteine hydrotrisulfide were the predominant organic polysulfide metabolites. Furthermore, we determined that novel sulforaphane (SFN) derivatives conjugated with CysS2H and GS2H were endogenously produced in the broccoli sprouts, and the novel SFN conjugated with CysS2H exhibited a greater radical scavenging capacity than SFN and cysteine. These results suggest that the abundance of polysulfides in broccoli sprouts contribute to their health-promoting properties. Our findings have important biological implications for the development of novel pharmacological targets for the health-promoting effects of broccoli sprouts in humans.

Hydrogen Sulfide Ligation in Hemoglobin I of Lucina pectinata─A QM/MM and Local Mode Study

In this study, we investigated the interaction between the H2S ligand and the heme pocket of hemoglobin I (HbI) of Lucina pectinata for the wild-type protein; three known mutations where distal glutamine is replaced by hydrophobic valine (Gln64Val) and hydrophilic histidine in both protonation forms (Gln64Hisϵ and Gln64Hisδ); five known mutations of the so-called phenyl cage, replacing the hydrophobic phenylalanines Phe29 and Phe43 with tyrosine (Tyr), valine (Val), or leucine (Leu); and two additional mutations, Phe68Tyr and Phe68Val, in order to complement previous studies with new insights about the binding mechanism at the molecular level. A particular focus was on the intrinsic strengths of the chemical bonds involved, utilizing local vibrational force constants based on combined quantum mechanical-molecular mechanical calculations. Wild-type protein and mutations clustered into two distinct groups: Group 1 protein systems with a proton acceptor in the distal protein pocket, close to one of the H2S bonds, and Group 2 protein systems without a hydrogen acceptor close by in the active site of the protein. According to our results, the interactions between H2S and HbI of Lucina pectinata involve two important elements, namely, binding of H2S to Fe of the heme group, followed by the proton transfer from the HS bond to the distal residue. The distal residue is additionally stabilized by a second proton transfer from the distal residue to COO- of the propionate group in heme. We could identify the FeS bond as a key player and discovered that the strength of this bond depends on two mutual factors, namely, the strength of the HS bond involved in the proton transfer and the electrostatic field of the protein pocket qualifying the FeS bond as a sensitive probe for monitoring changes in H2S ligation upon protein mutations. We hope our study will inspire and guide future experimental studies, targeting new promising mutations such as Phe68Tyr, Phe68Val, or Phe43Tyr/Phe68Val.

Always enough but never too much: the how and why of downregulating tissue oxygenation

Cardiovascular regulation of tissue oxygenation is generally viewed as an anti-drop process that prevents tissue oxygen concentration from falling below some minimum. I propose that cardiovascular regulation is predominately an anti-rise process designed to downregulate oxygen delivery. This maintains an evolutionarily conserved, reduced intracellular environment to prevent oxidation of redox-sensitive regulatory protein thiols. A number of points support this hypothesis. First, oxygen is the only nutrient with a positive, fourfold diffusion gradient from the environment to systemic tissues, minimizing the likelihood that oxygen delivery is limited. Second, hemoglobin (Hb) retains oxygen unless offloading is absolutely necessary. The allosteric properties of Hb keep oxygen tightly bound until absolutely needed, and the Bohr shift, which favors offloading, is only transient and lost when metabolism is restored. Third, a myoglobin-like Hb (xHb) would offload all of its oxygen and could easily have evolved, but it did not. Fourth, oxygen-sensitive vasoconstrictors and hyperoxic-rarefaction prevent acute and chronic over perfusion. Fifth, Fåhraeus and Fåhraeus-Lindqvist effects reduce capillary hematocrit to minimize microcirculatory oxygen content. Sixth, venous blood remains 75% saturated, wasting 75% of cardiac output were an oxygen reserve not needed. Finally, xHb-containing red blood cells could be considerably smaller and thereby decrease Fåhraeus and Fåhraeus-Lindqvist effects and cardiac load. In summary, the capacity of the cardiovascular system to deliver oxygen to the tissues generally exceeds demand, and although maintenance of an oxygen delivery reserve is important, it is more important to prevent excess oxygen delivery.

Three-Dimensional Regulation of Ferroptosis at the Intersection of Iron, Sulfur, and Oxygen Executing Scrap and Build Toward Evolution

Significance: Iron is an essential element for every life on earth as a primary media for electron flow. Sulfur compounds as sulfhydryls counteract catalytic activity of iron whereas sulfur overdose is also toxic. In aerobic organisms, oxygen is the major media for electron transfer with higher intracellular mobility, which cooperates with the iron system. Based on the importance of iron, there is no active pathway to excrete iron outside the body in higher species. Whereas bacterial infection causes a scramble for iron in situ, cancer can be the outcome of the side effects of long use of iron and oxygen. Recent Advances: Ferroptosis is a recently coined cell death, defined as catalytic Fe(II)-dependent regulated necrosis accompanied by lipid peroxidation. Researchers recently recognized that ferroptosis is involved in a variety of physiological and pathological contexts, including embryonic erythropoiesis, aging, neurodegeneration and cancer cell death. Alternatively, carcinogenesis is a process to obtain iron addiction with ferroptosis-resistance, based on rodent animal studies. Critical Issues: Here we propose that ferroptosis is three-dimensionally regulated by iron, sulfur and oxygen, which correspond to oxidants, antioxidants and membrane fluidity with susceptibility to lipid peroxidation, respectively. Future Directions: Whereas life attempts to prevent ferroptosis, ferroptotic cells eventually emit iron-loaded ferritin as extracellular vesicles to maintain monopoly of iron. Antioxid. Redox Signal. 39, 807-815.

Iron links endogenous and exogenous nanoparticles

Current progress in biology and medical science is based on the observation at the level of nanometers via electron microscopy and computation. Of note, the size of most cells in higher species exists in a limited range from 5 to 50 μm. Recently, it was demonstrated that endogenous extracellular nanoparticles play a role in communication among various cellular types in a variety of contexts. Among them, exosomes in serum have been established as biomarkers for human diseases by analyzing the cargo molecules. No life on the earth can survive without iron. However, excess iron can be a risk for carcinogenesis in rodents and humans. Nano-sized molecules may cause unexpected bioeffects, including carcinogenesis, which is a process to establish cellular iron addiction with ferroptosis-resistance. Asbestos and carbon nanotubes are the typical examples, leading to carcinogenesis by the alteration of iron metabolism. Recently, we found that CD63, one of the representative markers of exosomes, is under the regulation of iron-responsive element/iron-regulatory protein system. This is a safe strategy to share excess iron in the form of holo-ferritin between iron-sufficient and -deficient cells. On the other hand, damaged cells may secrete holo-ferritin-loaded exosomes as in the case of macrophages in ferroptosis after asbestos exposure. These holo-ferritin-loaded exosomes can cause mutagenic DNA damage in the recipient mesothelial cells. Thus, there is an iron link between exogenous and endogenous nanoparticles, which requires further investigation for better understanding and the future applications.

Protection by Means of Perinatal Oral Sodium Thiosulfate Administration against Offspring Hypertension in a Rat Model of Maternal Chronic Kidney Disease

Hydrogen sulfide (H₂S) and related reactive sulfur species are implicated in chronic kidney disease (CKD) and hypertension. Offspring born to CKD-afflicted mothers could develop hypertension coinciding with disrupted H₂S and nitric oxide (NO) signaling pathways as well as gut microbiota. Thiosulfate, a precursor of H₂S and an antioxidant, has shown anti-hypertensive effects. This study aimed to investigate the protective effects of sodium thiosulfate (STS) in a rat model of maternal CKD-induced hypertension. Before mating, CKD was induced through feeding 0.5% adenine chow for 3 weeks. Mother rats were given a vehicle or STS at a dosage of 2 g/kg/day in drinking water throughout gestation and lactation. Perinatal STS treatment protected 12-week-old offspring from maternal CKD-primed hypertension. The beneficial effects of STS could partially be explained by the enhancement of both H₂S and NO signaling pathways and alterations in gut microbiota. Not only increasing beneficial microbes but maternal STS treatment also mediates several hypertension-associated intestinal bacteria. In conclusion, perinatal treatment with STS improves maternal CKD-primed offspring hypertension, suggesting that early-life RSS-targeting interventions have potential preventive and therapeutic benefits, awaiting future translational research.

Organelle-targeting ratiometric fluorescent probes: design principles, detection mechanisms, bio-applications, and challenges

Biological species, including reactive oxygen species (ROS), reactive sulfur species (RSS), reactive nitrogen species (RNS), F-, Pd2+, Cu2+, Hg2+, and others, are crucial for the healthy functioning of cells in living organisms. However, their aberrant concentration can result in various serious diseases. Therefore, it is essential to monitor biological species in cellular organelles such as the cell membrane, mitochondria, lysosome, endoplasmic reticulum, Golgi apparatus, and nucleus. Among various fluorescent probes for species detection within the organelles, ratiometric fluorescent probes have drawn special attention as a potential way to get beyond the drawbacks of intensity-based probes. This method depends on measuring the intensity change of two emission bands (caused by an analyte), which produces an efficient internal referencing that increases the detection's sensitivity. This review article discusses the literature publications (from 2015 to 2022) on organelle-targeting ratiometric fluorescent probes, the general strategies, the detecting mechanisms, the broad scope, and the challenges currently faced by fluorescent probes.

A selective fluorescent probe for hydrogen sulfide from a series of flavone derivatives and intracellular imaging

In this work, through the orthogonal design of two fluorophores and two recognition groups, a series of fluorescent probes were developed from the flavone derivatives for hydrogen sulfide (H₂S). The probe FlaN-DN stood out from the primarily screening on the selectivity and response intensities. It could respond to H₂S with both the chromogenic and fluorescent signals. Among the recent reported probes for the H₂S detection, FlaN-DN indicated the most highlighted advantages including the rapid response (within 200 s) and the high response multiplication (over 100 folds). FlaN-DN was sensitive to the pH condition, thus could be applied to distinguish the cancer micro-environment. Moreover, FlaN-DN suggested practical capabilities including a wide linear range (0-400 μM), a relatively high sensitivity (limit of detection 0.13 μM), and high selectivity towards H₂S. As a low cytotoxic probe, FlaN-DN achieved the imaging in living HeLa cells. FlaN-DN could detect the endogenous generation H₂S and visualize the dose-dependent responses to the exogenous H₂S level. This work provided a typical case of natural-sourced derivatives as functional implements, which might inspire the future investigations.

Discovery of a triphenylamine-benzofuran derivative as fluorescent probe for hydrogen polysulfide in tea samples

In this work, a novel triphenylamine-benzofuran derived fluorescent probe, TBF-SS, was developed for detecting hydrogen polysulfide in tea samples and intracellular imaging. TBF-SS showed the practical advantages including high sensitivity (LOD = 0.01 μM), high selectivity, rapid response (within 15 min), and steadiness in various environmental conditions. The detecting system was steady within pH range of 6.0-11.0 and temperature range of 20-55 °C. The probe TBF-SS could guarantee the stable detection of H₂S_n for 7 d in storage of either solid or solution. In particular, in the application of various tea samples with different brewing times and testing temperatures, the recovery percentages varied in the range of 95.22 % to 105.0 %. Therefore accurate monitoring of H₂S_n could be achieved by using the probe TBF-SS. In addition, TBF-SS could monitor the exogenous level, the β-lapachone-induced generation and the tea-sample-treated introduction of H₂S_n in living MCF-7 cells. This work might inspire the improvement of the serviceability of fluorescent implements.

Free Radicals Mediated Redox Signaling in Plant Stress Tolerance

Abiotic and biotic stresses negatively affect plant cellular and biological processes, limiting their growth and productivity. Plants respond to these environmental cues and biotrophic attackers by activating intricate metabolic-molecular signaling networks precisely and coordinately. One of the initial signaling networks activated is involved in the generation of reactive oxygen species (ROS), reactive nitrogen species (RNS), and reactive sulfur species (RSS). Recent research has exemplified that ROS below the threshold level can stimulate plant survival by modulating redox homeostasis and regulating various genes of the stress defense pathway. In contrast, RNS regulates the stress tolerance potential of crop plants by modulating post-translation modification processes, such as S-nitrosation and tyrosine nitration, improving the stability of protein and DNA and activating the expression of downstream stress-responsive genes. RSS has recently emerged as a new warrior in combating plant stress-induced oxidative damage by modulating various physiological and stress-related processes. Several recent findings have corroborated the existence of intertwined signaling of ROS/RNS/RSS, playing a substantial role in crop stress management. However, the molecular mechanisms underlying their remarkable effect are still unknown. This review comprehensively describes recent ROS/RNS/RSS biology advancements and how they can modulate cell signaling and gene regulation for abiotic stress management in crop plants. Further, the review summarizes the latest information on how these ROS/RNS/RSS signaling interacts with other plant growth regulators and modulates essential plant functions, particularly photosynthesis, cell growth, and apoptosis.

The Effects of Antioxidant Nutraceuticals on Cellular Sulfur Metabolism and Signaling

Significance: Nutraceuticals are ingested for health benefits, in addition to their general nutritional value. These dietary supplements have become increasingly popular since the late 20th century and they are a rapidly expanding global industry approaching a half-trillion U.S. dollars annually. Many nutraceuticals are promulgated as potent antioxidants. Recent Advances: Experimental support for the efficacy of nutraceuticals has lagged behind anecdotal exuberance. However, accumulating epidemiological evidence and recent, well-controlled clinical trials are beginning to support earlier animal and in vitro studies. Although still somewhat limited, encouraging results have been suggested in essentially all organ systems and against a wide range of pathophysiological conditions. Critical Issues: Health benefits of "antioxidant" nutraceuticals are largely attributed to their ability to scavenge oxidants. This has been criticized based on several factors, including limited bioavailability, short tissue retention time, and the preponderance of endogenous antioxidants. Recent attention has turned to nutraceutical activation of downstream antioxidant systems, especially the Keap1/Nrf2 (Kelch like ECH associated protein 1/nuclear factor erythroid 2-related factor 2) axis. The question now becomes, how do nutraceuticals activate this axis? Future Directions: Reactive sulfur species (RSS), including hydrogen sulfide (H2S) and its metabolites, are potent activators of the Keap1/Nrf2 axis and avid scavengers of reactive oxygen species. Evidence is beginning to accumulate that a variety of nutraceuticals increase cellular RSS by directly providing RSS in the diet, or through a number of catalytic mechanisms that increase endogenous RSS production. We propose that nutraceutical-specific targeting of RSS metabolism will lead to the design and development of even more efficacious antioxidant therapeutic strategies. Antioxid. Redox Signal. 38, 68-94.

Reactive Oxygen, Nitrogen, and Sulfur Species (RONSS) as a Metabolic Cluster for Signaling and Biostimulation of Plants: An Overview

This review highlights the relationship between the metabolism of reactive oxygen species (ROS), reactive nitrogen species (RNS), and H₂S-reactive sulfur species (RSS). These three metabolic pathways, collectively termed reactive oxygen, nitrogen, and sulfur species (RONSS), constitute a conglomerate of reactions that function as an energy dissipation mechanism, in addition to allowing environmental signals to be transduced into cellular information. This information, in the form of proteins with posttranslational modifications or signaling metabolites derived from RONSS, serves as an inducer of many processes for redoxtasis and metabolic adjustment to the changing environmental conditions to which plants are subjected. Although it is thought that the role of reactive chemical species was originally energy dissipation, during evolution they seem to form a cluster of RONSS that, in addition to dissipating excess excitation potential or reducing potential, also fulfils essential signaling functions that play a vital role in the stress acclimation of plants. Signaling occurs by synthesizing many biomolecules that modify the activity of transcription factors and through modifications in thiol groups of enzymes. The result is a series of adjustments in plants' gene expression, biochemistry, and physiology. Therefore, we present an overview of the synthesis and functions of the RONSS, considering the importance and implications in agronomic management, particularly on the biostimulation of crops.

A Caveat When Using Alkyl Halides as Tagging Agents to Detect/Quantify Reactive Sulfur Species

Using alkyl halides to tag reactive sulfur species (RSSs) (H2S, per/polysulfide, and protein-SSH) is an extensively applied approach. The underlying supposition is that, as with thiols, RSS reacts with alkyl halides via a nucleophilic substitution reaction. We found that this supposition is facing a challenge. RSS also initiates a reductive dehalogenation reaction, which generates the reduced unloaded tag and oxidized RSS. Therefore, RSS content in bio-samples might be underestimated, and its species might not be precisely determined when using alkyl halide agents for its analysis. To calculate to the extent of this underestimation, further studies are still required.

Synechococcus sp. PCC7002 Uses Peroxiredoxin to Cope with Reactive Sulfur Species Stress

Cyanobacteria are a widely distributed group of microorganisms in the ocean, and they often need to cope with the stress of reactive sulfur species, such as sulfide and sulfane sulfur. Sulfane sulfur refers to the various forms of zero-valent sulfur, including persulfide, polysulfide, and element sulfur (S₈). Although sulfane sulfur participates in signaling transduction and resistance to reactive oxygen species in cyanobacteria, it is toxic at high concentrations and induces sulfur stress, which has similar effects to oxidative stress. In this study, we report that Synechococcus sp. PCC7002 uses peroxiredoxin to cope with the stress of cellular sulfane sulfur. Synechococcus sp. PCC7002 contains six peroxiredoxins, and all were induced by S₈. Peroxiredoxin I (PrxI) reduced S₈ to H₂S by forming a disulfide bond between residues Cys⁵³ and Cys¹⁵³ of the enzyme. A partial deletion strain of Synechococcus sp. PCC7002 with decreased copy numbers of the prxI gene was more sensitive to S₈ than was the wild type. Thus, peroxiredoxin is involved in maintaining the homeostasis of cellular sulfane sulfur in cyanobacteria. Given that peroxiredoxin evolved before the occurrence of O₂ on Earth, its original function could have been to cope with reactive sulfur species stress, and that function has been preserved. IMPORTANCE Cyanobacteria are the earliest microorganisms that perform oxygenic photosynthesis, which has played a key role in the evolution of life on Earth, and they are the most important primary producers in the modern oceans. The cyanobacterium Synechococcus sp. PCC7002 uses peroxiredoxin to reduce high levels of sulfane sulfur. That function is possibly the original role of peroxiredoxin, as the enzyme evolved before the appearance of O₂ on Earth. The preservation of the reduction of sulfane sulfur by peroxiredoxin5-type peroxiredoxins may offer cyanobacteria an advantage in the complex environment of the modern oceans.

Optimization of a Method for Detecting Intracellular Sulfane Sulfur Levels and Evaluation of Reagents That Affect the Levels in Escherichia coli

Sulfane sulfur is a class of compounds containing zero-valent sulfur. Most sulfane sulfur compounds are reactive and play important signaling roles. Key enzymes involved in the production and metabolism of sulfane sulfur have been characterized; however, little is known about how to change intracellular sulfane sulfur (iSS) levels. To accurately measure iSS, we optimized a previously reported method, in which reactive iSS reacts with sulfite to produce thiosulfate, a stable sulfane sulfur compound, before detection. With the improved method, several factors were tested to influence iSS in Escherichia coli. Temperature, pH, and osmotic pressure showed little effect. At commonly used concentrations, most tested oxidants, including hydrogen peroxide, tert-butyl hydroperoxide, hypochlorous acid, and diamide, did not affect iSS, but carbonyl cyanide m-chlorophenyl hydrazone increased iSS. For reductants, 10 mM dithiothreitol significantly decreased iSS, but tris(2-carboxyethyl)phosphine did not. Among different sulfur-bearing compounds, NaHS, cysteine, S₂O₃²⁻ and diallyl disulfide increased iSS, of which only S₂O₃²⁻ did not inhibit E. coli growth at 10 mM or less. Thus, with the improved method, we have identified reagents that may be used to change iSS in E. coli and other organisms, providing tools to further study the physiological functions of iSS.

Progress and perspective on hydrogen sulfide donors and their biomedical applications

Following the discovery of nitric oxide (NO) and carbon monoxide (CO), hydrogen sulfide (H₂ S) has been identified as the third gasotransmitter in humans. Increasing evidence have shown that H₂ S is of preventive or therapeutic effects on diverse pathological complications. As a consequence, it is of great significance to develop suitable approaches of H₂ S-based therapeutics for biomedical applications. H₂ S-releasing agents (H₂ S donors) play important roles in exploring and understanding the physiological functions of H₂ S. More importantly, accumulating studies have validated the theranostic potential of H₂ S donors in extensive repertoires of in vitro and in vivo disease models. Thus, it is imperative to summarize and update the literatures in this field. In this review, first, the background of H₂ S on its chemical and biological aspects is concisely introduced. Second, the studies regarding the H₂ S-releasing compounds are categorized and described, and accordingly, their H₂ S-donating mechanisms, biological applications, and therapeutic values are also comprehensively delineated and discussed. Necessary comparisons between related H₂ S donors are presented, and the drawbacks of many typical H₂ S donors are analyzed and revealed. Finally, several critical challenges encountered in the development of multifunctional H₂ S donors are discussed, and the direction of their future development as well as their biomedical applications is proposed. We expect that this review will reach extensive audiences across multiple disciplines and promote the innovation of H₂ S biomedicine.

Synthesis of Phospholipids Under Plausible Prebiotic Conditions and Analogies with Phospholipid Biochemistry for Origin of Life Studies

Phospholipids are essential components of biological membranes and are involved in cell signalization, in several enzymatic reactions, and in energy metabolism. In addition, phospholipids represent an evolutionary and non-negligible step in life emergence. Progress in the past decades has led to a deeper understanding of these unique hydrophobic molecules and their most pertinent functions in cell biology. Today, a growing interest in "prebiotic lipidomics" calls for a new assessment of these relevant biomolecules.

Persulfide-Responsive Transcription Factor SqrR Regulates Gene Transfer and Biofilm Formation via the Metabolic Modulation of Cyclic di-GMP in Rhodobacter capsulatus

Bacterial phage-like particles (gene transfer agents-GTAs) are widely employed as a crucial genetic vector in horizontal gene transfer. GTA-mediated gene transfer is induced in response to various stresses; however, regulatory mechanisms are poorly understood. We found that the persulfide-responsive transcription factor SqrR may repress the expression of several GTA-related genes in the photosynthetic bacterium Rhodobacter capsulatus. Here, we show that the sqrR deletion mutant (ΔsqrR) produces higher amounts of intra- and extracellular GTA and gene transfer activity than the wild type (WT). The transcript levels of GTA-related genes are also increased in ΔsqrR. In spite of the presumption that GTA-related genes are regulated in response to sulfide by SqrR, treatment with sulfide did not alter the transcript levels of these genes in the WT strain. Surprisingly, hydrogen peroxide increased the transcript levels of GTA-related genes in the WT, and this alteration was abolished in the ΔsqrR strain. Moreover, the absence of SqrR changed the intracellular cyclic dimeric GMP (c-di-GMP) levels, and the amount of c-di-GMP was correlated with GTA activity and biofilm formation. These results suggest that SqrR is related to the repression of GTA production and the activation of biofilm formation via control of the intracellular c-di-GMP levels.

Physiological roles of hydrogen sulfide in mammalian cells, tissues and organs

H2S belongs to the class of molecules known as gasotransmitters, which also includes nitric oxide (NO) and carbon monoxide (CO). Three enzymes are recognized as endogenous sources of H2S in various cells and tissues: cystathionine g-lyase (CSE), cystathionine β-synthase (CBS) and 3-mercaptopyruvate sulfurtransferase (3-MST). The current article reviews the regulation of these enzymes as well as the pathways of their enzymatic and non-enzymatic degradation and elimination. The multiple interactions of H2S with other labile endogenous molecules (e.g. NO) and reactive oxygen species are also outlined. The various biological targets and signaling pathways are discussed, with special reference to H2S and oxidative posttranscriptional modification of proteins, the effect of H2S on channels and intracellular second messenger pathways, the regulation of gene transcription and translation and the regulation of cellular bioenergetics and metabolism. The pharmacological and molecular tools currently available to study H2S physiology are also reviewed, including their utility and limitations. In subsequent sections, the role of H2S in the regulation of various physiological and cellular functions is reviewed. The physiological role of H2S in various cell types and organ systems are overviewed. Finally, the role of H2S in the regulation of various organ functions is discussed as well as the characteristic bell-shaped biphasic effects of H2S. In addition, key pathophysiological aspects, debated areas, and future research and translational areas are identified A wide array of significant roles of H2S in the physiological regulation of all organ functions emerges from this review.

Protective role of hydrogen sulfide against diabetic cardiomyopathy via alleviating necroptosis

Diabetic cardiomyopathy lacks effective and novel methods. Hydrogen sulfide (H₂S) as the third gasotransmitter plays an important role in the cardiovascular system. Our study was to elucidate the protective effect and possible mechanism of H₂S on diabetic cardiomyopathy from the perspective of necroptosis. Leptin receptor deficiency (db/db) mice and streptozotocin (STZ)-induced diabetic cystathionine-γ-lyase (CSE) knockout (KO) mice were investigated. In addition, cardiomyocytes were stimulated with high glucose. We found that plasma H₂S level, myocardial H₂S production and CSE mRNA expression was impaired in the diabetic mice. CSE deficiency exacerbated diabetic cardiomyopathy, and promoted myocardial oxidative stress, necroptosis and inflammasome in STZ-induced mice. CSE inhibitor dl-propargylglycine (PAG) aggravated cell damage and oxidative stress, deteriorated necroptosis and inflammasome in cardiomyocytes with high glucose stimulation. H₂S donor sodium hydrosulfide (NaHS) improved diabetic cardiomyopathy, attenuated myocardial oxidative stress, necroptosis and the NLR family pyrin domain-containing protein 3 (NLRP3) in db/db mice. NaHS also alleviated cell damage, oxidative stress, necroptosis and inflammasome in cardiomyocytes with high glucose stimulation. In Conclusion, H₂S deficiency aggravated mitochondrial damage, increased reactive oxygen species accumulation, promoted necroptosis, activated NLRP3 inflammasome, and finally exacerbated diabetic cardiomyopathy. Exogenous H₂S supplementation alleviated necroptosis to suppress NLRP3 inflammasome activation and attenuate diabetic cardiomyopathy via mitochondrial dysfunction improvement and oxidative stress inhibition. Our study provides the first evidence and a new mechanism that necroptosis inhibition by a pharmacological manner of H₂S administration protected against diabetic cardiomyopathy. It is beneficial to provide a novel strategy for the prevention and treatment of diabetic cardiomyopathy.

A fluorescent probe derived from Berberrubine for detecting hydrogen polysulfide in food samples

In this work, we chose the fluorophore Berberrubine to develop a selective probe for hydrogen polysulfide (H₂S_n), and applied it into the detection in both food samples and living cells. The developed probe, HER9SS, suggested practical steadiness and serviceability, especially for multi-scene detection. The detecting system was stable in relatively wide pH (7.0-11.0) and temperature (25-45 °C) ranges. Both the storage of BER9SS in solid or in solution could maintain the steadiness over 7 d. BER9SS also indicated advantages including rapid response (within 15 min), high sensitivity (LOD = 0.02 μM; LOQ = 0.01 μM), long linear range (0-15.0 equivalent) and high selectivity among competing analytes. The recovery ranging in 95.23% - 104.8% in the applications in food sources samples (including water and plants) and food samples inferred the practical potential of BER9SS. In biological imaging, BER9SS could achieve both the dose-dependent monitoring and the β-lapachone-induced generation of H₂S_n. Therefore, the information in this work might be useful for the development of fluorescent probes from natural products for multi-scene applications in future, especially with the corresponding attentions on the practicability and serviceability.

Lipid peroxidation functional state changes in patients with obstructive jaundice depending on the level of bilirubin in the blood

Obstructive jaundice (OJ) is the most common syndrome among diseases of the hepatopancreatoduodenal region and is found in 12-45% of cases. OJ may be benign and malignant etiology. Despite the evidence of the participation of bilirubin in reducing the bactericidal properties of neutrophils, there are no data currently on changes in the functioning of the antioxidant defense system depending on the level of bilirubin in the blood of patients with OJ of various origins. Research in this direction reveals the possibility for the development of pathogenetic recommendations for influencing these links of the pathogenesis of the disease. The study included men with OJ of non-malignant (OJNMG) (n = 47; mean age - 52.02 ± 5.18 years) and OJ of malignant genesis (OJMG) (I-II stages of the malignant process) (n = 45; mean age - 53.02 ± 4.8 years), divided into three subgroups, depending on the level of bilirubin in the blood. The indicators of practically healthy men as a control (n = 50, average age - 48.7 ± 3.9 years) were used. Spectrophotometric and statistical research methods were used. A statistically significant decrease of superoxide dismutase, glutathione-S-transferase, glutathione-peroxidase, ceruloplasmin, an increase in the values of diene conjugates, malondialdehyde in the group of patients with OJNMG relative to the control was revealed, regardless of the level of bilirubin in the blood. The presence of malignant genesis of the disease with more intense changes in the studied parameters relative to control is accompanied. Comparison of indicators between groups of patients with OJ of different genesis showed a decrease in the values of glutathione-S-transferase and an increase in the level of diene conjugates in patients with OJMG and the level of bilirubin less than 60 μmol / L, as well as an increase in the content of diene conjugates in patients with OJNMG and a level of bilirubin 60- 200 μmol / L in comparison with the corresponding groups of patients with OJNMG. Thus, both in the groups with OJNMG and in the groups with OJMG, there is a significant decrease in the activity of the main antioxidant enzymes and an increase in lipid peroxidation products, regardless of the level of bilirubin in the blood. The presence of malignant genesis is characterized by more intense differences. The revealed changes can serve as additional criteria for optimizing the diagnosis and treatment of this cohort of patients.

Rhodanese Rdl2 produces reactive sulfur species to protect mitochondria from reactive oxygen species

Mitochondria damage is related to a broad spectrum of pathologies including Alzheimer's, Parkinson's disease, and carcinogenesis. Recently, it has been found that reactive sulfur species (RSS) has a close connection with mitochondrial health. However, the enzyme involving in mitochondrial RSS generation and the mechanism of how RSS affects mitochondrial health are not well understood. In this study, we discovered that rhodanese 2 (Rdl2) is the main enzyme responsible for RSS generation in S. cerevisiae mitochondria, in which no sulfide:quinone oxidoreductase (Sqr) is present. Rdl2 releases sulfane sulfur atoms (S⁰) from stable S⁰ carriers (thiosulfate and dialkyl polysulfide) to produce RSS. Rdl2 deletion leads to morphological change, dysfunction, and DNA degradation of mitochondria. Rdl2-generated RSS can protect DNA from HO^• attack. The reaction rate between RSS and HO^• is ∼10¹⁰ M^-1s^-1, two magnitudes higher than that of HO^• reacting with DNA. Surprisingly, hydrogen sulfide (H₂S) promotes HO^• production through stimulating the Fenton reaction, leading to increased DNA damage. This study highlights the antioxidation function of RSS in vivo and sheds a light on the elusive connection between RSS biogenesis and mitochondrial health.

The Reactive Species Interactome in the Brain

Significance: Redox pioneer Helmut Sies attempted to explain reactive species' challenges faced by organelles, cells, tissues, and organs via three complementary definitions: (i) oxidative stress, that is, the disturbance in the prooxidant-antioxidant defense balance in favor of the prooxidants; (ii) oxidative eustress, the low physiological exposure to prooxidants; and (iii) oxidative distress, the supraphysiological exposure to prooxidants. Recent Advances: Identification, concentration, and interactions are the most important elements to improve our understanding of reactive species in physiology and pathology. In this context, the reactive species interactome (RSI) is a new multilevel redox regulatory system that identifies reactive species families, reactive oxygen species (ROS), reactive nitrogen species (RNS), and reactive sulfur species, and it integrates their interactions with their downstream biological targets. Critical Issues: We propose a united view to fully combine reactive species identification, oxidative eustress and distress, and the RSI system. In this view, we also propose including the forgotten reactive carbonyl species, an increasingly rediscovered reactive species family related to the other reactive families, and key enzymes within the RSI. We focus on brain physiology and pathology to demonstrate why this united view should be considered. Future Directions: More studies are needed for an improved understanding of the contributions of reactive species through their identification, concentration, and interactions, including in the brain. Appreciating the RSI in its entirety should unveil new molecular players and mechanisms in physiology and pathology in the brain and elsewhere.

Vitamin C (Ascorbate) and Redox Topics in Cancer

Significance: Vitamin C (ascorbate), in regard to its effectiveness against malignancies, has had a controversial history in cancer treatment. It has been shown that in vitro and in vivo anticancer efficacy of ascorbate relies on its pro-oxidant effect mainly from an increased generation of reactive oxygen species (ROS). A growing understanding of its anticancer activities and pharmacokinetic properties has prompted scientists to re-evaluate the significance of ascorbate in cancer treatment. Recent Advances: A recent resurge in ascorbate research emerged after discovering that, at high doses, ascorbate preferentially kills Kirsten-Ras (K-ras)- and B-raf oncogene (BRAF)-mutant cancer cells. In addition, some of the main hallmarks of cancer cells, such as redox homeostasis and oxygen-sensing regulation (through inhibition of hypoxia-inducible factor-1 alpha [HIF-1α] activity), are affected by vitamin C. Critical Issues: Currently, there is no clear consensus from the literature in regard to the beneficial effects of antioxidants. Results from both human and animal studies provide no clear evidence about the benefit of antioxidant treatment in preventing or suppressing cancer development. Since pro-oxidants may affect both normal and tumor cells, the extremely low toxicity of ascorbate represents a main advantage. This guarantees the safe inclusion of ascorbate in clinical protocols to treat cancer patients. Future Directions: Current research could focus on elucidating the wide array of reactions between ascorbate and reactive species, namely ROS, reactive nitrogen species as well as reactive sulfide species, and their intracellular molecular targets. Unraveling these mechanisms could allow researchers to assess what could be the optimal combination of ascorbate with standard treatments.

Hydrogen sulfide plays a potential alternative for the treatment of metabolic disorders of diabetic cardiomyopathy

Diabetic cardiomyopathy (DCM) is a cardiovascular complication that tends to occur in patients with diabetes, obesity, or insulin resistance, with a higher late mortality rate. Sustained hyperglycemia, increased free fatty acids, or insulin resistance induces metabolic disorders in cardiac tissues and cells, leading to myocardial fibrosis, left ventricular hypertrophy, diastolic and/or systolic dysfunction, and finally develop into congestive heart failure. The close connection between all signaling pathways and the complex pathogenesis of DCM cause difficulties in finding effective targets for the treatment of DCM. It reported that hydrogen sulfide (H₂S) could regulate cell energy substrate metabolism, reduce insulin resistance, protect cardiomyocytes, and improve myocardial function by acting on related key proteins such as differentiation cluster 36 (CD36) and glucose transporter 4 (GLUT4). In this article, the relative mechanisms of H₂S in alleviating metabolic disorders of DCM were reviewed, and how H₂S can better prevent and treat DCM in clinical practice will be discussed.

An evolutionary perspective on the interplays between hydrogen sulfide and oxygen in cellular functions

The physiological effects of the endogenously generated hydrogen sulfide (H2S) have been extensively studied in recent years. This review summarized the role of H2S in the origin of life and H2S metabolism in organisms from bacteria to vertebrates, examined the relationship between H2S and oxygen from an evolutionary perspective and emphasized the oxygen-dependent manner of H2S signaling in various physiological and pathological processes. H2S and oxygen are inextricably linked in various cellular functions. H2S is involved in aerobic respiration and stimulates oxidative phosphorylation and ATP production within the cell. Besides, H2S has protective effects on ischemia and reperfusion injury in several organs by acting as an oxygen sensor. Also, emerging evidence suggests the role of H2S is in an oxygen-dependent manner. All these findings indicate the subtle relationship between H2S and oxygen and further explain why H2S, a toxic molecule thriving in an anoxia environment several billion years ago, still affects homeostasis today despite the very low content in the body.

EPR Study of KO2 as a Source of Superoxide and •BMPO-OH/OOH Radical That Cleaves Plasmid DNA and Detects Radical Interaction with H2S and Se-Derivatives

Superoxide radical anion (O₂^•−) and its derivatives regulate numerous physiological and pathological processes, which are extensively studied. The aim of our work was to utilize KO₂ as a source of O₂^•− and the electron paramagnetic resonance (EPR) spin trapping 5-tert-butoxycarbonyl-5-methyl-1-pyrroline N-oxide (BMPO) technique for the preparation of ^•BMPO-OOH and/or ^•BMPO-OH radicals in water solution without DMSO. The method distinguishes the interactions of various compounds with ^•BMPO-OOH and/or ^•BMPO-OH radicals over time. Here, we show that the addition of a buffered BMPO-HCl mixture to powdered KO₂ formed relatively stable ^•BMPO-OOH and ^•BMPO-OH radicals and H₂O₂, where the ^•BMPO-OOH/OH ratio depended on the pH. At a final pH of ~6.5–8.0, the concentration of ^•BMPO-OOH radicals was ≥20 times higher than that of ^•BMPO-OH, whereas at pH 9.0–10.0, the ^•BMPO-OH radicals prevailed. The ^•BMPO-OOH/OH radicals effectively cleaved the plasmid DNA. H₂S decreased the concentration of ^•BMPO-OOH/OH radicals, whereas the selenium derivatives 1-methyl-4-(3-(phenylselanyl) propyl) piperazine and 1-methyl-4-(4-(phenylselanyl) butyl) piperazine increased the proportion of ^•BMPO-OH over the ^•BMPO-OOH radicals. In conclusion, the presented approach of using KO₂ as a source of O₂^•−/H₂O₂ and EPR spin trap BMPO for the preparation of ^•BMPO-OOH/OH radicals in a physiological solution could be useful to study the biological effects of radicals and their interactions with compounds.

Analysis of neutrophils functional activity in men with mechanical jaundice of various genesis

Obstructive jaundice (OJ) or blockage of the bile duct code K83.1 (according to ICD 10), occurs in approximately 45-50% of cases of all varieties of jaundice, it can be both non-tumor and tumor genesis. The functional pathway plays a special role in the genesis of complications of breast the activity of neutrophils as key effector cells responsible for the development of the inflammatory process in the breast. Investigation of the metabolic mechanisms of the functioning of neutrophils allows us to identify intracellular targets, when exposed to It was possible to modulate the level of cell reactivity.The study used data from 47 men with obstructive jaundice of non-tumor origin and 45 men with obstructive jaundice of tumor origin (stage I-II of the tumor process). As a control, data from 100 practically healthy men were used. A pronounced change in the kinetics of the chemiluminescent response of neutrophils in men with obstructive jaundice was found, consisting in an increase in the time to reach the maximum intensity, maximum intensity, area under the curve and activation index for both spontaneous and luminol-dependent induced chemiluminescence. The development of the tumor process in this category of patients was accompanied by a decrease in the area parameter under the curve during spontaneous and induced reactions, time to maximum, intensity maximum and activation index during spontaneous chemiluminescence. The data obtained indicate a marked increase in the values of the functional activity of neutrophils in patients with obstructive jaundice of benign origin, as well as a sharp decrease in their values in the presence of a pathological process of malignant origin.

A near-infrared fluorescent probe that can image endogenous hydrogen polysulfides in vivo in tumour-bearing mice

Hydrogen polysulfides (H₂S_n, n > 1), which are important reactive sulfur species, play crucial roles in H₂S-related bioactivities, including antioxidation, cytoprotection, activation of ion channels, transcription factor functions and tumour suppression. Monitoring H₂S_nin vivo is of significant interest for exploring the physiological roles of H₂S_n and the exact mechanisms of H₂S_n-related diseases. Herein, we conceive a novel near-infrared fluorescent probe, NIR-CPS, that is used to detect H₂S_n in living cells and in vivo. With the advantages of high sensitivity, good selectivity and a remarkably large Stokes shift (100 nm), NIR-CPS was successfully applied in visualizing H₂S_n in living cells and mice. More importantly, NIR-CPS monitored H₂S_n stimulated by lipopolysaccharide in tumour-bearing mice. These results demonstrate that the NIR-CPS probe is a potentially powerful tool for the detection of H₂S_nin vivo, thus providing a valuable approach in H₂S_n-related medical research.

Evaluation of Cysteine Metabolism in the Rat Liver and Kidney Following Intravenous Cocaine Administration and Abstinence

Many toxic effects of cocaine are attributed to reactive oxygen species (ROS) generated during its metabolism. Recently, it has been suggested that the biological action of ROS is often confused with endogenously generated reactive sulfur species (RSS). The aim of this study was to evaluate the impact of cocaine on thiols and RSS in the rat liver and kidney in the drug self-administration (SA) paradigm and the cocaine yoked delivery model (YC) followed by drug abstinence with extinction training. The level of thiols as well as RSS formed during anaerobic metabolism of cysteine and sulfate were assayed. In addition, the activity of enzymes involved in RSS formation and glutathione metabolism were determined. In the liver, following direct cocaine administration (SA and YC), the RSS levels decreased, while in the kidneys, cocaine increased the RSS contents in both groups. These changes were maintained in these tissues during drug abstinence. The level of sulfates was changed by cocaine only in the liver. In the kidney, cocaine shifted cysteine metabolism towards an anaerobic pathway. Our study demonstrates for the first time the changes in cysteine metabolism and thiol levels in the liver and kidney of rats after cocaine self-administration and abstinence.

Are Reactive Sulfur Species the New Reactive Oxygen Species?

Significance: Oxidative stress in moderation positively affects homeostasis through signaling, while in excess it is associated with adverse health outcomes. Both activities are generally attributed to reactive oxygen species (ROS); hydrogen peroxide as the signal, and cysteines on regulatory proteins as the target. However, using antioxidants to affect signaling or benefit health has not consistently translated into expected outcomes, or when it does, the mechanism is often unclear. Recent Advances: Reactive sulfur species (RSS) were integral in the origin of life and throughout much of evolution. Sophisticated metabolic pathways that evolved to regulate RSS were easily "tweaked" to deal with ROS due to the remarkable similarities between the two. However, unlike ROS, RSS are stored, recycled, and chemically more versatile. Despite these observations, the relevance and regulatory functions of RSS in extant organisms are generally underappreciated. Critical Issues: A number of factors bias observations in favor of ROS over RSS. Research conducted in room air is hyperoxic to cells, and promotes ROS production and RSS oxidation. Metabolic rates of rodent models greatly exceed those of humans; does this favor ROS? Analytical methods designed to detect ROS also respond to RSS. Do these disguise the contributions of RSS? Future Directions: Resolving the ROS/RSS issue is vital to understand biology in general and human health in particular. Improvements in experimental design and analytical methods are crucial. Perhaps the most important is an appreciation of all the attributes of RSS and keeping an open mind.

Endosymbionts of Metazoans Dwelling in the PACManus Hydrothermal Vent: Diversity and Potential Adaptive Features Revealed by Genome Analysis

Deep-sea hydrothermal vents are dominated by several invertebrate species. The establishment of symbiosis has long been thought to be the key to successful colonization by these sedentary species in such harsh environments. However, the relationships between symbiotic bacteria and their hosts and their role in environmental adaptations generally remain unclear. In this paper, we show that the distribution of three host species showed characteristic niche partitioning in the Manus Basin, giving us the opportunity to understand how they adapt to their particular habitats. This study also revealed three novel genomes of symbionts from the snails of A. boucheti. Combined with a data set on other ectosymbiont and free-living bacteria, genome comparisons for the snail endosymbionts pointed to several genetic traits that may have contributed to the lifestyle shift of Epsilonproteobacteria into the epithelial cells. These findings could increase our understanding of invertebrate-endosymbiont relationships in deep-sea ecosystems.

Deep-sea hydrothermal vent communities are dominated by invertebrates, namely, bathymodiolin mussels, siboglinid tubeworms, and provannid snails. Symbiosis is considered key to successful colonization by these sedentary species in such extreme environments. In the PACManus vent fields, snails, tubeworms, and mussels each colonized a niche with distinct geochemical characteristics. To better understand the metabolic potentials and genomic features contributing to host-environment adaptation, we compared the genomes of the symbionts of Bathymodiolus manusensis, Arcovestia ivanovi, and Alviniconcha boucheti sampled at PACManus, and we discuss their environmentally adaptive features. We found that B. manusensis and A. ivanovi are colonized by Gammaproteobacteria from distinct clades, whereas endosymbionts of B. manusensis feature high intraspecific heterogeneity with differing metabolic potentials. A. boucheti harbored three novel Epsilonproteobacteria symbionts, suggesting potential species-level diversity of snail symbionts. Genome comparisons revealed that the relative abundance of gene families related to low-pH homeostasis, metal resistance, oxidative stress resistance, environmental sensing/responses, and chemotaxis and motility was the highest in A. ivanovi’s symbiont, followed by symbionts of the vent-mouth-dwelling snail A. boucheti, and was relatively low in the symbiont of the vent-periphery-dwelling mussel B. manusensis, which is consistent with their environmental adaptations and host-symbiont interactions. Gene families classified as encoding host interaction/attachment, virulence factors/toxins, and eukaryotic-like proteins were most abundant in symbionts of mussels and least abundant in those of snails, indicating that these symbionts may differ in their host colonization strategies. Comparison of Epsilonproteobacteria symbionts to nonsymbionts demonstrated that the expanded gene families in symbionts were related to vitamin B₁₂ synthesis, toxin-antitoxin systems, methylation, and lipopolysaccharide biosynthesis, suggesting that these are vital to symbiont establishment and development in Epsilonproteobacteria.

IMPORTANCE Deep-sea hydrothermal vents are dominated by several invertebrate species. The establishment of symbiosis has long been thought to be the key to successful colonization by these sedentary species in such harsh environments. However, the relationships between symbiotic bacteria and their hosts and their role in environmental adaptations generally remain unclear. In this paper, we show that the distribution of three host species showed characteristic niche partitioning in the Manus Basin, giving us the opportunity to understand how they adapt to their particular habitats. This study also revealed three novel genomes of symbionts from the snails of A. boucheti. Combined with a data set on other ectosymbiont and free-living bacteria, genome comparisons for the snail endosymbionts pointed to several genetic traits that may have contributed to the lifestyle shift of Epsilonproteobacteria into the epithelial cells. These findings could increase our understanding of invertebrate-endosymbiont relationships in deep-sea ecosystems.

Green tea polyphenolic antioxidants oxidize hydrogen sulfide to thiosulfate and polysulfides: A possible new mechanism underpinning their biological action

Matcha and green tea catechins such as (−)-epicatechin (EC), (−)-epigallocatechin (EGC) and (−)-epigallocatechin gallate (EGCG) have long been studied for their antioxidant and health-promoting effects. Using specific fluorophores for H₂S (AzMC) and polysulfides (SSP4) as well as IC-MS and UPLC-MS/MS-based techniques we here show that popular Japanese and Chinese green teas and select catechins all catalytically oxidize hydrogen sulfide (H₂S) to polysulfides with the potency of EGC > EGCG >> EG. This reaction is accompanied by the formation of sulfite, thiosulfate and sulfate, consumes oxygen and is partially inhibited by the superoxide scavenger, tempol, and superoxide dismutase but not mannitol, trolox, DMPO, or the iron chelator, desferrioxamine. We propose that the reaction proceeds via a one-electron autoxidation process during which one of the OH-groups of the catechin B-ring is autooxidized to a semiquinone radical and oxygen is reduced to superoxide, either of which can then oxidize HS⁻ to thiyl radicals (HS^•) which react to form hydrogen persulfide (H₂S₂). H₂S oxidation reduces the B-ring back to the hydroquinone for recycling while the superoxide is reduced to hydrogen peroxide (H₂O₂). Matcha and catechins also concentration-dependently and rapidly produce polysulfides in HEK293 cells with the potency order EGCG > EGC > EG, an EGCG threshold of ~300 nM, and an EC₅₀ of ~3 μM, suggesting green tea also acts as powerful pro-oxidant in vivo. The resultant polysulfides formed are not only potent antioxidants, but elicit a cascade of secondary cytoprotective effects, and we propose that many of the health benefits of green tea are mediated through these reactions. Remarkably, all green tea leaves constitutively contain small amounts of H₂S₂.

Symmetry Breaking of Phospholipids

Either stereo reactants or stereo catalysis from achiral or chiral molecules are a prerequisite to obtain pure enantiomeric lipid derivatives. We reviewed a few plausibly organic syntheses of phospholipids under prebiotic conditions with special attention paid to the starting materials as pro-chiral dihydroxyacetone and dihydroxyacetone phosphate (DHAP), which are the key molecules to break symmetry in phospholipids. The advantages of homochiral membranes compared to those of heterochiral membranes were analysed in terms of specific recognition, optimal functions of enzymes, membrane fluidity and topological packing. All biological membranes contain enantiomerically pure lipids in modern bacteria, eukarya and archaea. The contemporary archaea, comprising of methanogens, halobacteria and thermoacidophiles, are living under extreme conditions reminiscent of primitive environment and may indicate the origin of one ancient evolution path of lipid biosynthesis. The analysis of the known lipid metabolism reveals that all modern cells including archaea synthetize enantiomerically pure lipid precursors from prochiral DHAP. Sn-glycerol-1-phosphate dehydrogenase (G1PDH), usually found in archaea, catalyses the formation of sn-glycerol-1-phosphate (G1P), while sn-glycerol-3-phosphate dehydrogenase (G3PDH) catalyses the formation of sn-glycerol-3-phosphate (G3P) in bacteria and eukarya. The selective enzymatic activity seems to be the main strategy that evolution retained to obtain enantiomerically pure lipids. The occurrence of two genes encoding for G1PDH and G3PDH served to build up an evolutionary tree being the basis of our hypothesis article focusing on the evolution of these two genes. Gene encoding for G3PDH in eukarya may originate from G3PDH gene found in rare archaea indicating that archaea appeared earlier in the evolutionary tree than eukarya. Archaea and bacteria evolved probably separately, due to their distinct respective genes coding for G1PDH and G3PDH. We propose that prochiral DHAP is an essential molecule since it provides a convergent link between G1DPH and G3PDH. The synthesis of enantiopure phospholipids from DHAP appeared probably firstly in the presence of chemical catalysts, before being catalysed by enzymes which were the products of later Darwinian selection. The enzymes were probably selected for their efficient catalytic activities during evolution from large libraries of vesicles containing amino acids, carbohydrates, nucleic acids, lipids, and meteorite components that induced symmetry imbalance.

Interplay between hydrogen sulfide and methylglyoxal initiates thermotolerance in maize seedlings by modulating reactive oxidative species and osmolyte metabolism

Hydrogen sulfide (H₂S) and methylglyoxal (MG) were supposed to be novel signaling molecules in plants. However, whether interplay between H₂S and MG can initiate thermotolerance in maize seedlings and in relation to metabolism of reactive oxygen species (ROS) and osmolytes is little known. In this study, watering with MG and NaHS (H₂S donor) alone or in combination elevated survival and tissue vigor of maize seedlings under heat stress and coped with an increase in the biomembrane injury (as indicated in membrane lipid peroxidation and electrolyte leakage). The above-mentioned effects were separately weakened by MG scavengers (N-acetyl cysteine: NAC; aminoguanidine: AG) and H₂S inhibitor (DL-propargylglycine, PAG) and scavenger (hypotaurine, HT). These suggested that the interplay between H₂S and MG initiated the thermotolerance in maize seedlings. The further data indicated that, under non-heat stress and heat stress conditions, MG and NaHS alone or in combination modulated ROS metabolism by regulating the activities of antioxidant enzymes (catalase, ascorbate peroxidase, guaiacol peroxidase, glutathione reductase, monodehydroascorbate reductase, and dehydroascorbate reductase) and the contents of non-enzymatic antioxidants (ascorbic acid, glutathione, flavonoids, and carotenoids) in maize seedlings. In addition, MG and NaHS alone or in combination also separately modulated the metabolism of osmolytes (proline, trehalose, glycine betaine, and total soluble sugar), H₂S (L-cysteine desulfhydrase and O-acetylserine (thione) lyase), and MG (glyoxalase I, glyoxalase II, and MG reductase). These physiological effects also were separately impaired by NAC, AG, PAG, and HT. The current data illustrated that the interplay between H₂S and MG initiated the thermotolerance in maize seedlings by modulating ROS, osmolyte, H₂S, and MG metabolism.

Hydrogen Sulfide: From a Toxic Molecule to a Key Molecule of Cell Life

Hydrogen sulfide (H2S) has always been considered toxic, but a huge number of articles published more recently showed the beneficial biochemical properties of its endogenous production throughout all regna. In this review, the participation of H2S in many physiological and pathological processes in animals is described, and its importance as a signaling molecule in plant systems is underlined from an evolutionary point of view. H2S quantification methods are summarized and persulfidation is described as the underlying mechanism of action in plants, animals and bacteria. This review aims to highlight the importance of its crosstalk with other signaling molecules and its fine regulation for the proper function of the cell and its survival.

Plant Peroxisomes: A Factory of Reactive Species

Plant peroxisomes are organelles enclosed by a single membrane whose biochemical composition has the capacity to adapt depending on the plant tissue, developmental stage, as well as internal and external cellular stimuli. Apart from the peroxisomal metabolism of reactive oxygen species (ROS), discovered several decades ago, new molecules with signaling potential, including nitric oxide (NO) and hydrogen sulfide (H2S), have been detected in these organelles in recent years. These molecules generate a family of derived molecules, called reactive nitrogen species (RNS) and reactive sulfur species (RSS), whose peroxisomal metabolism is autoregulated through posttranslational modifications (PTMs) such as S-nitrosation, nitration and persulfidation. The peroxisomal metabolism of these reactive species, which can be weaponized against pathogens, is susceptible to modification in response to external stimuli. This review aims to provide up-to-date information on crosstalk between these reactive species families and peroxisomes, as well as on their cellular environment in light of the well-recognized signaling properties of H2O2, NO and H2S.

Endogenous hydrogen sulfide sulfhydrates IKKβ at cysteine 179 to control pulmonary artery endothelial cell inflammation

BACKGROUND

Pulmonary artery endothelial cell (PAEC) inflammation is a critical event in the development of pulmonary arterial hypertension (PAH). However, the pathogenesis of PAEC inflammation remains unclear.

METHODS

Purified recombinant human inhibitor of κB kinase subunit β (IKKβ) protein, human PAECs and monocrotaline-induced pulmonary hypertensive rats were employed in the study. Site-directed mutagenesis, gene knockdown or overexpression were conducted to manipulate the expression or activity of a target protein.

RESULTS

We showed that hydrogen sulfide (H2S) inhibited IKKβ activation in the cell model of human PAEC inflammation induced by monocrotaline pyrrole-stimulation or knockdown of cystathionine γ-lyase (CSE), an H2S generating enzyme. Mechanistically, H2S was proved to inhibit IKKβ activity directly via sulfhydrating IKKβ at cysteinyl residue 179 (C179) in purified recombinant IKKβ protein in vitro, whereas thiol reductant dithiothreitol (DTT) reversed H2S-induced IKKβ inactivation. Furthermore, to demonstrate the significance of IKKβ sulfhydration by H2S in the development of PAEC inflammation, we mutated C179 to serine (C179S) in IKKβ. In purified IKKβ protein, C179S mutation of IKKβ abolished H2S-induced IKKβ sulfhydration and the subsequent IKKβ inactivation. In human PAECs, C179S mutation of IKKβ blocked H2S-inhibited IKKβ activation and PAEC inflammatory response. In pulmonary hypertensive rats, C179S mutation of IKKβ abolished the inhibitory effect of H2S on IKKβ activation and pulmonary vascular inflammation and remodeling.

CONCLUSION

Collectively, our in vivo and in vitro findings demonstrated, for the first time, that endogenous H2S directly inactivated IKKβ via sulfhydrating IKKβ at Cys179 to inhibit nuclear factor-κB (NF-κB) pathway activation and thereby control PAEC inflammation in PAH.

The Roles of NO and H2S in Sperm Biology: Recent Advances and New Perspectives

After being historically considered as noxious agents, nitric oxide (NO) and hydrogen sulfide (H2S) are now listed as gasotransmitters, gaseous molecules that play a key role in a variety of cellular functions. Both NO and H2S are endogenously produced, enzymatically or non-enzymatically, and interact with each other in a range of cells and tissues. In spite of the great advances achieved in recent decades in other biological systems, knowledge about H2S function and interactions with NO in sperm biology is in its infancy. Here, we aim to provide an update on the importance of these molecules in the physiology of the male gamete. Special emphasis is given to the most recent advances in the metabolism, mechanisms of action, and effects (both physiological and pathophysiological) of these gasotransmitters. This manuscript also illustrates the physiological implications of NO and H2S observed in other cell types, which might be important for sperm function. The relevance of these gasotransmitters to several signaling pathways within sperm cells highlights their potential use for the improvement and successful application of assisted reproductive technologies.

Oxidative-Antioxidant Imbalance and Impaired Glucose Metabolism in Schizophrenia

Schizophrenia is a neurodevelopmental disorder featuring chronic, complex neuropsychiatric features. The etiology and pathogenesis of schizophrenia are not fully understood. Oxidative-antioxidant imbalance is a potential determinant of schizophrenia. Oxidative, nitrosative, or sulfuric damage to enzymes of glycolysis and tricarboxylic acid cycle, as well as calcium transport and ATP biosynthesis might cause impaired bioenergetics function in the brain. This could explain the initial symptoms, such as the first psychotic episode and mild cognitive impairment. Another concept of the etiopathogenesis of schizophrenia is associated with impaired glucose metabolism and insulin resistance with the activation of the mTOR mitochondrial pathway, which may contribute to impaired neuronal development. Consequently, cognitive processes requiring ATP are compromised and dysfunctions in synaptic transmission lead to neuronal death, preceding changes in key brain areas. This review summarizes the role and mutual interactions of oxidative damage and impaired glucose metabolism as key factors affecting metabolic complications in schizophrenia. These observations may be a premise for novel potential therapeutic targets that will delay not only the onset of first symptoms but also the progression of schizophrenia and its complications.

Reactive oxygen species or reactive sulfur species: why we should consider the latter

The biological effects of oxidants, especially reactive oxygen species (ROS), include signaling functions (oxidative eustress), initiation of measures to reduce elevated ROS (oxidative stress), and a cascade of pathophysiological events that accompany excessive ROS (oxidative distress). Although these effects have long been studied in animal models with perturbed ROS, their actions under physiological conditions are less clear. I propose that some of the apparent uncertainty may be due to confusion of ROS with endogenously generated reactive sulfur species (RSS). ROS and RSS are chemically similar, but RSS are more reactive and versatile, and can be stored and reused. Both ROS and RSS signal via oxidation reactions with protein cysteine sulfur and they produce identical effector responses, but RSS appear to be more effective. RSS in the form of persulfidated cysteines (Cys-S-S) are produced endogenously and co-translationally introduced into proteins, and there is increasing evidence that many cellular proteins are persulfidated. A number of practical factors have contributed to confusion between ROS and RSS, and these are discussed herein. Furthermore, essentially all endogenous antioxidant enzymes appeared shortly after life began, some 3.8 billion years ago, when RSS metabolism dominated evolution. This was long before the rise in ROS, 600 million years ago, and I propose that these same enzymes, with only minor modifications, still effectively metabolize RSS in extant organisms. I am not suggesting that all ROS are RSS; however, I believe that the relative importance of ROS and RSS in biological systems needs further consideration.

Synechococcus sp. Strain PCC7002 Uses Sulfide:Quinone Oxidoreductase To Detoxify Exogenous Sulfide and To Convert Endogenous Sulfide to Cellular Sulfane Sulfur

Eutrophication and deoxygenation possibly occur in coastal waters due to excessive nutrients from agricultural and aquacultural activities, leading to sulfide accumulation. Cyanobacteria, as photosynthetic prokaryotes, play significant roles in carbon fixation in the ocean. Although some cyanobacteria can use sulfide as the electron donor for photosynthesis under anaerobic conditions, little is known on how they interact with sulfide under aerobic conditions. In this study, we report that Synechococcus sp. strain PCC7002 (PCC7002), harboring an sqr gene encoding sulfide:quinone oxidoreductase (SQR), oxidized self-produced sulfide to S0, present as persulfide and polysulfide in the cell. The Δsqr mutant contained less cellular S0 and had increased expression of key genes involved in photosynthesis, but it was less competitive than the wild type in cocultures. Further, PCC7002 with SQR and persulfide dioxygenase (PDO) oxidized exogenous sulfide to tolerate high sulfide levels. Thus, SQR offers some benefits to cyanobacteria even under aerobic conditions, explaining the common presence of SQR in cyanobacteria.IMPORTANCE Cyanobacteria are a major force for primary production via oxygenic photosynthesis in the ocean. A marine cyanobacterium, PCC7002, is actively involved in sulfide metabolism. It uses SQR to detoxify exogenous sulfide, enabling it to survive better than its Δsqr mutant in sulfide-rich environments. PCC7002 also uses SQR to oxidize endogenously generated sulfide to S0, which is required for the proper expression of key genes involved in photosynthesis. Thus, SQR has at least two physiological functions in PCC7002. The observation provides a new perspective for the interplays of C and S cycles.