Sulfur amino acid metabolism: pathways for production and removal of homocysteine and cysteine

Insight into Cys and its derivatives metabolism in living system with 3D-printed portable smartphone platform via multifunctional fluorescent probe

Cysteine (Cys) is a crucial biological thiol that facilitates broad range of biological circumstances and health conditions. Especially the aberrant Cys level in human serum is an independent risk factor for cardiovascular diseases. What more, Cys metabolism (Cys to SO2) is typically connected with illnesses such as lung cancer, and are recognized as biomarker. Herein, an innovative multifunctional fluorescent probe was rudimentarily designed and utilized, not only for realizing real-time visualization of the metabolism of Cys to SO2 in tumors through two self-sufficient channels without spectral cross-interference, but also for sensitive, real-time, on-site, and quantitative visual recognition of Cys in human serum through 3D-printed smartphone sensing platform. In addition, the probe's unique response to Cys/HSO3- in distinct spectral behaviors, which have been characterized theoretically using UV-Vis, fluorescence, DFT calculations, and 1H NMR. More importantly, the methodology reported herein enables an available pathway for real-time/on-site and visual determination of Cys in human serum and is expected to extend the use of potential cardiovascular disease biomarker studies for initial monitoring and clinical diagnosis.

Charting unknown metabolic reactions by mass spectrometry-resolved stable-isotope tracing metabolomics

Metabolic reactions play important roles in organisms such as providing energy, transmitting signals, and synthesizing biomacromolecules. Charting unknown metabolic reactions in cells is hindered by limited technologies, restricting the holistic understanding of cellular metabolism. Using mass spectrometry-resolved stable-isotope tracing metabolomics, we develop an isotopologue similarity networking strategy, namely IsoNet, to effectively deduce previously unknown metabolic reactions. The strategy uncovers ~300 previously unknown metabolic reactions in living cells and mice. Specifically, we elaborately chart the metabolic reaction network related to glutathione, unveiling three previously unreported reactions nestled within glutathione metabolism. Among these, a transsulfuration reaction, synthesizing γ-glutamyl-seryl-glycine directly from glutathione, underscores the role of glutathione as a sulfur donor. Functional metabolomics studies systematically characterize biochemical effects of previously unknown reactions in glutathione metabolism, showcasing their diverse functions in regulating cellular metabolism. Overall, these newly uncovered metabolic reactions fill gaps in the metabolic network maps, facilitating exploration of uncharted territories in cellular biochemistry.

Bioorthogonal Reactions for Bioactive Sulfur Species Delivery

Bioorthogonal chemistry has emerged as a powerful tool for the development of controllable drug delivery systems. Bioactive sulfur species, which participate in complex sulfur signaling pathways, play crucial roles in various physiological and pathological processes. However, achieving precise and controlled administration of these sulfur species remains challenging due to their unique physicochemical properties. Over the past few years, a growing number of delivery strategies, which are triggered by different stimuli, have been developed to enhance our understanding of sulfur signaling. Bioorthogonal triggers not only offer excellent controllability but also provide advantages such as tunability, targeted delivery, and spatiotemporal feedback. This review highlights representative donors that can be activated through bioorthogonal reactions and their applications in studying the biological mechanisms and therapeutic functions of the bioactive sulfur species.

Cysteine sulfinic acid and sulfinylated peptides

Cysteine sulfinic acid (CSA) is a stable post translational modification in nature. While long considered to be an irreversible by-product of accidental overoxidation of the cysteine sulfur, evidence in the last two decades has accumulated for its role in numerous and tightly regulated mechanisms. Proteomics studies in the last two decades have identified CSA in hundreds of cellular proteins, highlighting its omnipresence at the core of the cysteine redoxome. Elsewhere, structural studies have shed initial light on the molecular mechanisms underlying CSA reduction in vivo by the sulfiredoxin (Srx) enzyme. While peroxiredoxins have for a long time been the only known substrates to be turned over by Srx, recent studies have uncovered a plethora of potential new substrates of Srx, opening new avenues of investigation in fundamental biology, but also possibly opening new opportunities for developing novel medicines targeting the redoxome, especially in cancer and neurodegeneration. This review first summarises important knowledge surrounding the stereo-electronics and biochemical properties of CSA, including how it is reduced by Srx. In a second part, it highlights the chemical methods recently developed for CSA characterisation, with important examples of electrophilic probes for CSA covalent adduct formation. Crucially, in vitro biochemical studies of CSA and its peptides have historically proven difficult, in great part due to the limitations associated with the few existing synthetic methods available. Here, we also provide a summary of synthetic methods currently available for CSA incorporation into peptides, and their current limitations.

Simple Strategy to Develop Multifunctional NIR Fluorescent Probes for Simultaneous Identification of H2S and SO2

H2S and SO2 have been considered as important gaseous signaling molecules in biological systems, functioning as regulatory roles in many physiological processes of organisms. To better understand the crosstalk and synergetic effects between H2S and SO2 in biological systems, developing a single fluorescent probe for dual-channel fast detection of H2S and SO2 is highly urgent. We herein report a simple strategy to develop multifunctional near-infrared (NIR) fluorescent probes for simultaneous identification of H2S and SO2. Based on the idea of modulating the reactivity of the benzopyrylium core with electron donors, two new NIR fluorescent probes (SW1 and SW2) were synthesized and evaluated. The probe SW2 could not only rapidly sense H2S and SO2 with different fluorescence signals but also be used as a reversible probe to investigate the flux of H2O2 and SO2. Moreover, SW2 was successfully applied in visualizing H2S and SO2 in living cells and mice. These results suggest that SW2 could serve as a useful tool in understanding the complex relationships between H2S and SO2 in biological systems.

Disulfidptosis in tumor progression

Disulfidptosis, a regulated cell death modality driven by the cystine transporter solute carrier family 7 member 11 (SLC7A11), is characterized by actin cytoskeleton collapse under glucose starvation. This review systematically elucidates the pivotal role of disulfidptosis in tumor metabolic reprogramming, with a focus on its molecular mechanisms and distinctions from other cell death pathways. The core mechanisms include SLC7A11-mediated cystine overload and NRF2/c-Myc-regulated pentose phosphate pathway activation. By integrating multiomics data and single-cell transcriptomics, we comprehensively decipher the heterogeneous expression patterns of disulfidptosis-related genes (DRGs) and their dynamic interplay with immune microenvironment remodeling. Furthermore, the coexpression networks of DRGs and disulfidptosis-related long noncoding RNAs (DRLs) offer novel insights into tumor diagnosis, prognosis, and targeted therapy. Therapeutically, SLC7A11 inhibitors (e.g., HG106) and glucose transporter inhibitors (e.g., BAY-876) demonstrate efficacy by exploiting metabolic vulnerabilities, whereas natural compounds synergizing with immune checkpoint blockade provide strategies to counteract immunosuppressive microenvironments. Through interdisciplinary collaboration and clinical translation, disulfidptosis research holds transformative potential in redefining precision oncology.

Methionine in embryonic development: metabolism, redox homeostasis, epigenetic modification and signaling pathway

Methionine, an essential sulfur-containing amino acid, plays a critical role in methyl metabolism, folate metabolism, polyamine synthesis, redox homeostasis maintenance, epigenetic modification and signaling pathway regulation, particularly during embryonic development. Animal and human studies have increasingly documented that methionine deficiency or excess can negatively impact metabolic processes, translation, epigenetics, and signaling pathways, with ultimate detrimental effects on pregnancy outcomes. However, the underlying mechanisms by which methionine precisely regulates epigenetic modifications and affects signaling pathways remain to be elucidated. In this review, we discuss methionine and the metabolism of its metabolites, the influence of folate-mediated carbon metabolism, redox reactions, DNA and RNA methylation, and histone modifications, as well as the mammalian rapamycin complex and silent information regulator 1-MYC signaling pathway. This review also summarizes our present understanding of the contribution of methionine to these processes, and current nutritional and pharmaceutical strategies for the prevention and treatment of developmental defects in embryos.

Homocysteine, Nutrition, and Gut Microbiota: A Comprehensive Review of Current Evidence and Insights

Homocysteine, a sulfur-containing amino acid, is an intermediate product during the metabolism of methionine, a vital amino acid. An elevated concentration of homocysteine in the plasma, named hyperhomocysteinemia, has been significantly related to the onset of several diseases, including diabetes, multiple sclerosis, osteoporosis, cancer, and neurodegenerative disorders such as dementia, Alzheimer's and Parkinson's diseases. An interaction between metabolic pathways of homocysteine and gut microbiota has been reported, and specific microbial signatures have been found in individuals experiencing hyperhomocysteinemia. Furthermore, some evidence suggests that gut microbial modulation may exert an influence on homocysteine levels and related disease progression. Conventional approaches for managing hyperhomocysteinemia typically involve dietary interventions alongside the administration of supplements such as B vitamins and betaine. The present review aims to synthesize recent advancements in understanding interventions targeted at mitigating hyperhomocysteinemia, with a particular emphasis on the role of gut microbiota in these strategies. The emerging therapeutic potential of gut microbiota has been reported for several diseases. Indeed, a better understanding of the complex interaction between microbial species and homocysteine metabolism may help in finding novel therapeutic strategies to counteract hyperhomocysteinemia.

The Gordon Memorial Lecture: genotype, phenotype, selection and more: improving the skeletal health of laying hens

1. This review is a comprehensive exploration of the author's work in improving skeletal health in laying hens, focusing on the insights from genetics on nutritional, and environmental factors. It discusses the importance of the large number of disciplines that have contributed to the efforts to tackle bone quality in laying hens, particularly the keel bone.2. The transition from cages to non-cage environments has increased keel bone damage, despite improving overall skeletal health. It is a welfare paradox that improving the hen's environment has often been accompanied by greater skeletal damage.3. The role of genetics has been important in understanding and addressing bone health issues and will be a major factor in their improvement. This includes the identification of specific genes, like cystathionine-β-synthase, which has led to nutritional interventions using betaine supplementation to improve bone quality by targeting the one carbon pathway.4. The role of the timing of puberty and its genetic control is an additional factor in bone health, and new methods of measuring bone density in live birds are now important to monitor potential issues and deliver genetic solutions.5. The review emphasises a multi-faceted approach, combining genetics, nutrition, rearing practices, and housing design is required in order to improve skeletal health and enhance the welfare and sustainable performance in laying hens.

Functional Specialization of S-Adenosylmethionine Synthases Links Phosphatidylcholine to Mitochondrial Function and Stress Survival

S-adenosylmethionine (SAM), produced by SAM synthases, is critical for various cellular regulatory pathways and the synthesis of diverse metabolites. Studies have often equated the effects of knocking down one synthase with broader SAM-dependent outcomes such as histone methylation or phosphatidylcholine (PC) production. Humans and many other organisms express multiple SAM synthases. Evidence in Caenorhabditis elegans , which possesses four SAM synthase genes, suggest that the enzymatic source of SAM impacts its function. For instance, loss of sams-1 leads to enhanced heat shock survival and increased lifespan, whereas reducing sams-4 adversely affects heat stress survival. Here, we show that SAMS-1 contributes to a variety of intermediary metabolic pathways, whereas SAMS-4 is more important to generate SAM for methylation reactions. We demonstrate that loss of sams-1 exerts age-dependent effects on nuclear-encoded mitochondrial gene expression, mitochondrial metabolites, and may induce mitophagy. We propose a mechanistic model where reduced SAM from SAMS-1 acts through PC to impact mitochondria, thereby enhancing survival during heat stress.

A steric hindrance-regulated probe with single excitation dual emissions for self-adaptive detection of biothiols and H2S in human urine samples and living cells

Sulfur-containing small molecules, mainly including cysteine (Cys), homocysteine (Hcy), glutathione (GSH), and hydrogen sulfide (H2S), are crucial biomarkers, and their levels in different body locations (living cells, tissues, blood, urine, saliva, etc.) are inconsistent and constantly changing. Therefore, it is highly meaningful and challenging to synchronously and accurately detect them in complex multi-component samples without mutual interference. In this work, we propose a steric hindrance-regulated probe, NBD-2FDCI, with single excitation dual emissions to achieve self-adaptive detection of four analytes. This probe was meticulously designed and constructed from a pKa-tuned 2FDCI fluorophore and a thiol-specific recognition moiety NBD. Except for 661 nm fluorescence for indicating the total biothiols and H2S, Cys and Hcy could trigger an additional 550 nm fluorescence. Utilizing the distinctive responses, the probe NBD-2FDCI exhibited exclusive linear ranges for GSH, Cys/Hcy, and H2S to avoid high-level component interference. Thus, the probe was then applied for sulfur compound measurements in urine samples, indicating metabolic disorder of Cys and H2S in bladder cancer patients. Moreover, adaptive imaging of probe NBD-2FDCI in cells was performed with the results being consistent with in vitro testing. In a word, spatial hindrance strategy-guided probes may exhibit broader prospects in the detection of similar components in complex samples.

A high biocompatible near-infrared fluorescent probe for tracking cysteine in multi-biosystem and its application in cervical cancer imaging

Cysteine (Cys) plays a crucial role in the biological system and many related diseases. However, the detection of Cys in living organisms are still hindered by shortage of small molecule fluorophores that exhibit excitation and emission in the near-infrared region. Herein, we designed and synthesized a high water-soluble Cys probe (Cy7-SS) based on heptamethine cyanine scaffold. The prepared Cy7-SS displayed an enhanced emission at near-infrared region (NIR) after the recognition of Cys. Moreover, Cy7-SS not only exhibited high selectivity and sensitivity on the detection of in vitro Cys, but also could be used for endogenous Cys in living cells and C.elegans. The prepared strategy for the design of fluorophores expands the in vivo sensing toolkit for the precise analysis in clinical diagnosis.

Hydrogen sulfide mediates the interaction between C. elegans and Actinobacteria from its natural microbial environment

Caenorhabditis elegans proliferates poorly in the presence of abundant Actinobacteria from its natural ecology, but it is unknown why. Here, we show how perturbed levels of hydrogen sulfide modulate the growth rate of both C. elegans and Actinobacteria. From a forward genetic selection, we find C. elegans mutants with faster growth on an Actinobacteria Microbacterium species and mutant alleles of conserved cystathionine gamma-lyase (cth-2/CTH) that improve growth rate. Conversely, null alleles of cth-2 cause developmental arrest of animals grown on Actinobacteria, but not on Proteobacteria, which can be rescued by exogenous H2S. We also find mutations in a leucine-rich-repeat gene that regulates cysteine and H2S production, lrr-2/LRRC58. We place lrr-2 in the animal sulfur metabolism pathway by demonstrating its role in post-translationally regulating levels of cysteine dioxygenase (cdo-1/CDO1). Exogenously supplied H2S inhibits the growth of Actinobacteria but not Proteobacteria. Thus, we conclude that the C. elegans-Actinobacteria interaction is mediated by H2S.

Immunometabolic profiling related with gestational diabetes mellitus: a nested case-control study of CD4+ T cell phenotypes and glycemic traits

AIMS

To investigate immunometabolic associations of CD4+ T cell phenotypes with gestational diabetes mellitus (GDM).

METHODS

A nested case-control study was conducted comprising 53 pairs of GDM patients and matched controls within a prospective cohort. Metabolomic signatures related to both CD4+ T cell phenotypes and glycemic traits among pregnant women were investigated by weighted gene co-expression network analysis (WGCNA). Multivariable-adjusted generalized linear models were used to explore the associations of CD4+ T cell phenotypes and selected metabolites with GDM. Mediation analysis was conducted to evaluate the mediating effect of selected metabolites on the relationship between CD4+ T cell phenotypes and glycemic traits.

RESULTS

Higher levels of Treg cells (OR per SD increment (95%CI): 0.57 (0.34, 0.95), p = 0.031) and increased expression of Foxp3 (OR per SD increment (95%CI): 0.59 (0.35, 0.97), p = 0.039) and GATA3 (OR per SD increment (95%CI): 0.42 (0.25, 0.72), p = 0.002) were correlated with a decreased risk of GDM. Plasma pyruvaldehyde, S-adenosylhomocysteine (SAH), bergapten, and 9-fluorenone mediated the association between Tregs and fasting plasma glucose (FPG), with mediation proportions of 46.9%, 39.6%, 52.4%, and 56.9%, respectively.

CONCLUSIONS

Treg cells and Foxp3 expressions were inversely associated with GDM risk, with potential metabolic mechanisms involving metabolites such as pyruvaldehyde and SAH.

Dynamic Metabolic Characterization of Lung Tissues in Rats Exposed to Whole-Thorax Irradiation Based on GC-MS

An animal model of radiation-induced lung injury (RILI) was established using female rats given sublethal whole-thorax X-ray irradiation (15 Gy) at a dose rate of 2.7 Gy/min. The rats were studied for up to day 45 and compared with sham-irradiated controls. Time-series lung tissue samples during the progression of RILI were collected for dynamic metabolomics studies based on gas chromatography-mass spectrometry (GC-MS). Differential metabolites associated with radiation-induced lung injury were identified, followed by metabolite set enrichment analysis to uncover pathway changes in RILI. The results revealed dynamic metabolic alterations in the progression of RILI, primarily involving in glycine and serine metabolism, the urea cycle, the Warburg effect, glutamate metabolism, arginine and proline metabolism, glucose-alanine cycle, and ammonia recycling. In addition, the potential panel of biomarkers including taurine, lysine, and tyrosine of RILI was selected and then applied to evaluate the diagnostic potential for RILI based on the receiving operator characteristic curve (ROC) at the early-stage of RILI. The better sensitivity, specificity, and accuracy indicate the potential of early diagnosis for RILI. These findings suggest that dynamic metabolomics data could provide new insights into understanding the complex metabolic dysregulation underlying RILI, facilitating the selection of biomarkers for early diagnosis.

Recent advances in reactive oxygen species (ROS)-responsive drug delivery systems for photodynamic therapy of cancer

Reactive oxygen species (ROS)-responsive drug delivery systems (DDSs) have garnered significant attention in cancer research because of their potential for precise spatiotemporal drug release tailored to high ROS levels within tumors. Despite the challenges posed by ROS distribution heterogeneity and endogenous supply constraints, this review highlights the strategic alliance of ROS-responsive DDSs with photodynamic therapy (PDT), enabling selective drug delivery and leveraging PDT-induced ROS for enhanced therapeutic efficacy. This review delves into the biological importance of ROS in cancer progression and treatment. We elucidate in detail the operational mechanisms of ROS-responsive linkers, including thioether, thioketal, selenide, diselencide, telluride and aryl boronic acids/esters, as well as the latest developments in ROS-responsive nanomedicines that integrate with PDT strategies. These insights are intended to inspire the design of innovative ROS-responsive nanocarriers for enhanced cancer PDT.

Epithelial NSD2 maintains FMO-mediated taurine biosynthesis to prevent intestinal barrier disruption

BACKGROUND

Inflammatory bowel disease (IBD) presents a significant challenge due to its intricate pathogenesis. NSD2, a histone methyltransferase responsible for dimethylating histone 3 at lysine 36, is associated with transcriptional activation. NSD2 expression is decreased in both the intestinal epithelial cells (IECs) of IBD patients and the IBD mouse model. However, the precise role of NSD2 in IBD remains unexplored.

METHODS

Colon tissues from IBD mice, SW620 cells and MC38 cells, were used as research subjects. Clinical databases of IBD patients were analysed to investigate whether NSD2 expression is reduced in the occurrence of IBD. NSD2-knockout mice were generated to further investigate the role of NSD2 in IBD. The IECs were isolated for RNA sequencing and chromatin immunoprecipitation sequencing to identify molecular signalling pathways and key molecules leading to IBD in mice. Molecular and cellular experiments were conducted to analyse and validate the role of NSD2 in the development of IBD. Finally, rescue experiments were performed to confirm the molecular mechanism of NSD2 in the development of IBD.

RESULTS

Deficiency of NSD2 in mouse IECs aggravated epithelial barrier disruption and inflammatory response in IBD. Mechanistically, NSD2 loss led to downregulation of H3K36me2 and flavin-containing monooxygenase (FMO) (taurine-synthesis enzyme) mRNA, resulting in decreased taurine biosynthesis in IECs. Significantly, supplementation with taurine markedly alleviated the symptoms of NSD2 deficiency-induced IBD.

CONCLUSIONS

These data demonstrate that NSD2 plays a pivotal role in maintaining FMO-mediated taurine biosynthesis to prevent intestinal inflammation. Our findings also underscore the importance of NSD2-H3K36me2-mediated taurine biosynthesis in maintaining intestinal mucosal barrier homeostasis.

KEY POINTS

In this study, we investigated the role of the histone methyltransferase NSD2 in preventing intestinal barrier disruption by sustaining taurine biosynthesis. NSD2 levels were reduced in both human specimens and mouse models of IBD. We demonstrate that NSD2 loss hinders the process of taurine synthesis in intestinal cells, leading to increased intestinal inflammation. Supplementation with taurine significantly relieved the symptoms caused by NSD2 deficiency. These data suggest that maintenance of NSD2-mediated taurine biosynthesis is vital for preserving the intestinal barrier and attenuating inflammation.

Protective Effects of L-Cysteine Against Cisplatin-Induced Oxidative Stress-Mediated Reproductive Damage

Cisplatin (CIS) is a widely used chemotherapeutic agent, but its side effects, such as oxidative stress, inflammation, and apoptosis, often lead to male reproductive damage. Oxidative stress, primarily caused by the excessive generation of reactive oxygen species (ROS), plays a critical role in disrupting testicular homeostasis, resulting in spermatogenic impairment and tissue injury. L-cysteine (CYS), a semi-essential amino acid with potent antioxidant and anti-inflammatory properties, may offer protection against CIS-induced oxidative damage. This study aimed to assess the protective potential of CYS against CIS-induced male reproductive toxicity using in vivo and in vitro models. In vitro, treatment of TM3 (Leydig) and TM4 (Sertoli) cells with CIS led to increased ROS levels, reduced cell viability, and elevated apoptosis and inflammation, all of which were significantly ameliorated by subsequent CYS exposure. In vivo, CIS-treated male rats displayed heightened oxidative stress, impaired spermatogenesis, and histopathological damage in reproductive organs. However, CYS administration for 21 days significantly reduced oxidative stress, improved sperm viability, and protected testicular tissues from damage. These findings suggest that CYS has a protective effect against CIS-induced oxidative stress and male reproductive damage, making it a promising therapeutic agent for mitigating CIS-induced reproductive toxicity.

A novel theranostic strategy for myocardial infarction through neutralization of endogenous SO2 using an endoplasmic reticulum-targeted fluorescent probe

Myocardial infarction (MI), one of the leading causes of death worldwide, urgently needs further understanding of the pathological process and effective therapies. SO2 in endoplasmic reticulum in several cardiovascular diseases has been reported to be particularly important. However, the role of endogenous SO2 in endoplasmic reticulum in treating myocardial infarction is still ambiguous and needs to be elucidated. Herein, we developed TPA-HI-SO2 as the first endoplasmic reticulum-targeting fluorescent agent for specific imaging and detection of sulfur dioxide derivatives both in vitro and in vivo. TPA-HI-SO2 shows a highly sensitive and selective response to SO2 derivatives over other anions in aqueous solution with a satisfactory response time and detection limit. Furthermore, TPA-HI-SO2 decreased the SO2 concentration in H9C2 cells treated with H2O2 and in an MI mouse model. Most importantly, TPA-HI-SO2 protects H9C2 cells from H2O2-induced apoptosis and obviously protects against myocardial infarction in vivo through neutralization of endogenous SO2. Taken together, we developed the first ER-targeting ratiometric fluorescent probe for endogenous SO2 with excellent biocompatibility, high selectivity and sensitivity in this paper. More importantly, we demonstrated an obvious increase of the endogenous SO2 concentration in a myocardial infarction mouse model for the first time, which suggests that neutralization of endogenous SO2 in endoplasmic reticulum could be a promising therapeutic strategy for myocardial infarction.

Nonlinear amplification of nano bowl surface concavity on the critical response threshold to biosignals

Polymer nanoparticles that can sharply sense and detect biological signals in cells are promising candidates for biomedical and theranostic nanomaterials. However, the response ability of current polymer assemblies poorly matches the requirement of trace concentration level (10-6 ~ 10-9 mol/L) of cellular biosignals due to their linear signal input-to-function output mode, which impedes their practical applications in vivo. Here we report a kind of nanobowl system with pH-tunable invaginated morphology that can nonlinearly amplify the response abilities toward biosignals by modulating the surface concavity. Compared to conventional spherical nanoparticles, nonspherical nanobowls with a specific concave structure reduce the critical response threshold of polymers by up to 5 orders of magnitude, from millimole to nanomole level, covering most of biosignal concentration windows. Moreover, we find that this nonlinear signal gain effect is originated from the collective impact of a single signal on transitioning the polymer chain aggregation state of individual assemblies, rather than just altering a certain unit or chain. This nonlinear signal-to-response mechanism is potential to solve the tricky problems of probing and sensing endogenous signals with trace physiological concentration.

Color-reversible fluorescence tracking for the dynamic interaction of SO2 with Hg2+ in living cells

Mercury ion (Hg2+) is one of the most threatening substances to human health, and the mercury poisoning can damage physiological homeostasis severely in human, even cause death. Intriguingly, Sulfur dioxide (SO2), a gas signal molecule in human, can specifically interact with Hg2+ for relieving mercury poisoning. However, the dynamic interaction of Hg2+ with SO2 at the tempospatial level and the correlation between Hg2+ and SO2 in the pathological process of mercury poisoning are still elusive. Herein, we rationally designed a reversible and dual color fluorescent probe (CCS) for dynamically visualizing Hg2+ and SO2 and deciphering their interrelationship in mercury poisoning. CCS held good sensitivity, selectivity and reversibility to Hg2+ and SO2, that enabled CCS to specifically detect SO2 and Hg2+ via cyan fluorescence channel (centered around 485 nm) and red fluorescence channel (centered around 679 nm), respectively. Notably, the separate fluorescence signal changes of CCS realized the dynamic tracing of Hg2+ and SO2 in living cells, and presented the potential for exploring the correlation between SO2 and Hg2+ in mercury poisoning.

Traditional Korean diet high in one-carbon nutrients increases global DNA methylation: implication for epigenetic diet

PURPOSE

DNA methylation is a major epigenetic phenomenon through which diet affects health and disease. This study aimed to determine the epigenetic influence of the traditional Korean diet (K-diet) on global DNA methylation via one-carbon metabolism.

METHODS

A crossover study was conducted on 52 women. Two diets, a K-diet, high in plant foods and low in calories and animal fat, and a control diet, similar to the diet currently consumed in Korea, were provided to all subjects alternately for 4 weeks with a 4-week washout period. Clinical parameters were measured before and after each dietary intervention. Nutrient intake was calculated by using a computer-aided nutritional analysis program. One-carbon metabolites in the serum and global DNA methylation in peripheral mononuclear cells were determined using ultra-performance liquid chromatography-tandem mass spectrometry.

RESULTS

The K-diet group consumed more folate (669.9 ± 6.7 µg vs. 502.7 ± 3.0, p < 0.001), B6, B12, serine, and choline, and less methionine (992.6 ± 63 vs. 1048.3 mg ± 34.1, p < 0.0001) than the control group did. In the K-diet group, the increment of plasma 5-methyltetrahydrofolate (0.08 µg/mL ± 0.11 vs 0.02 ± 0.10, p < 0.009) and decrement of L-homocysteine (- 70.7 ± 85.0 vs - 39.3 ± 69.4, p < 0.0168) were greater than those of the control group. Global DNA methylation was significantly increased in the K-diet group (6.70 ± 3.02% to 9.45 ± 3.69, p < 0.0001) but not in the control group.

CONCLUSIONS

A K-diet high in one-carbon nutrients can enhance the global DNA methylation status, suggesting an epigenetic mechanism by which the K-diet conveys health effects. Trial registration Korean Clinical Trial Registry (trial number: KCT0005340, 24/08/2020, retrospectively registered).

SLC7A11-mediated cystine import protects against NDUFS7 deficiency-induced cell death in HEK293T cells

Cell models of mitochondrial complex Ⅰ (CⅠ) deficiency display significant elevations in reactive oxygen species (ROS) levels and an increase in cellular apoptosis. However, the underlying mechanisms governing anti-apoptotic processes in CⅠ-deficient cells remain elusive. Here, we introduced a mutation in NDUFS7, a crucial subunit of CI, in HEK293T cells and found that the absence of NDUFS7 resulted in reduced cell proliferation, elevated cell death, and increased susceptibility to oxidative stress. Mechanismly, we revealed that the upregulation of SLC7A11 played a crucial role in mitigating cell death resulting from NDUFS7 deficiency. Specifically, the increased expression of SLC7A11 enhanced cystine import, which subsequently reduced cell death by promoting the biosynthesis of reduced glutathione (GSH). Collectively, our findings suggest that SLC7A11-mediated cystine import, representing a novel pathway independent of NADPH production, plays a vital role in protection against NDUFS7 deficiency-induced cell death. This novel pathway provides potential insights into the understanding of pathogenic mechanisms and the therapeutic management of mitochondrial disorders associated with CⅠ deficiency.

Ribosomal modification protein rimK-like family member A activates betaine-homocysteine S-methyltransferase 1 to ameliorate hepatic steatosis

Nonalcoholic fatty liver disease (NAFLD) is a serious threat to public health, but its underlying mechanism remains poorly understood. In screening important genes using Gene Importance Calculator (GIC) we developed previously, ribosomal modification protein rimK-like family member A (RIMKLA) was predicted as one essential gene but its functions remained largely unknown. The current study determined the roles of RIMKLA in regulating glucose and lipid metabolism. RIMKLA expression was reduced in livers of human and mouse with NAFLD. Hepatic RIMKLA overexpression ameliorated steatosis and hyperglycemia in obese mice. Hepatocyte-specific RIMKLA knockout aggravated high-fat diet (HFD)-induced dysregulated glucose/lipid metabolism in mice. Mechanistically, RIMKLA is a new protein kinase that phosphorylates betaine-homocysteine S-methyltransferase 1 (BHMT1) at threonine 45 (Thr45) site. Upon phosphorylation at Thr45 and activation, BHMT1 eliminated homocysteine (Hcy) to inhibit the activity of transcription factor activator protein 1 (AP1) and its induction on fatty acid synthase (FASn) and cluster of differentiation 36 (CD36) gene transcriptions, concurrently repressing lipid synthesis and uptake in hepatocytes. Thr45 to alanine (T45A) mutation inactivated BHMT1 to abolish RIMKLA's repression on Hcy level, AP1 activity, FASn/CD36 expressions, and lipid deposition. BHMT1 overexpression rescued the dysregulated lipid metabolism in RIMKLA-deficient hepatocytes. In summary, RIMKLA is a novel protein kinase that phosphorylates BHMT1 at Thr45 to repress lipid synthesis and uptake. Under obese condition, inhibition of RIMKLA impairs BHMT1 activity to promote hepatic lipid deposition.

Targeting the sulfur-containing amino acid pathway in leukemia

sulfur-containing amino acids have been reported to patriciate in gene regulation, DNA methylation, protein synthesis and other physiological or pathological processes. In recent years, metabolism-related molecules of sulfur-containing amino acids affecting the occurrence, development and treatment of tumors have been implicated in various disorders, especially in leukemia. Here, we summarize current knowledge on the sulfur-containing amino acid metabolism pathway in leukemia and examine ongoing efforts to target this pathway, including treatment strategies targeting (a) sulfur-containing amino acids, (b) metabolites of sulfur-containing amino acids, and (c) enzymes and cofactors related to sulfur-containing amino acid metabolism in leukemia. Future leukemia therapy will likely involve innovative strategies targeting the sulfur-containing amino acid metabolism pathway.

The metabolites from traditional Chinese medicine targeting ferroptosis for cancer therapy

Cancer is a major disease with ever-increasing morbidity and mortality. The metabolites derived from traditional Chinese medicine (TCM) have played a significant role in combating cancers with curative efficacy and unique advantages. Ferroptosis, an iron-dependent programmed death characterized by the accumulation of lipid peroxide, stands out from the conventional forms of cell death, such as apoptosis, pyroptosis, necrosis, and autophagy. Recent evidence has demonstrated the potential of TCM metabolites targeting ferroptosis for cancer therapy. We collected and screened related articles published in or before June 2023 using PubMed, Google Scholar, and Web of Science. The searched keywords in scientific databases were ferroptosis, cancer, tumor, traditional Chinese medicine, botanical drugs, and phytomedicine. Only research related to ferroptosis, the metabolites from TCM, and cancer was considered. In this review, we introduce an overview of the current knowledge regarding the ferroptosis mechanisms and review the research advances on the metabolites of TCM inhibiting cancer by targeting ferroptosis.

Near-Infrared Fluorescent Probe for the Detection of Cysteine

Hemicyanine dyes are an ideal structure for building near-infrared fluorescent probes due to their excellent emission wavelength properties and biocompatibility in biological imaging field. Developing a near-infrared fluorescent probe capable of detecting cysteine (Cys) was the aim of this study. A novel developed fluorescent probe P showed high selectivity and sensitivity to Cys in the presence of various analytes. The detection limit of P was found to be 0.329 μM. The MTT assay showed that the probe was essentially non-cytotoxic. Furthermore, the probe was successfully used as cysteine imaging in living cells and mice.

Alterations in metabolome and lipidome in patients with in-stent restenosis

CONTEXT

In-stent restenosis (ISR) can lead to blood flow obstruction, insufficient blood supply to the brain, and may even result in serious complications such as stroke. Endothelial cell hyperproliferation and thrombosis are the primary etiologies, frequently resulting in alterations in intravascular metabolism. However, the metabolic changes related to this process are still undermined.

OBJECTIVE

We tried to characterize the serum metabolome of patients with ISR and those with non-restenosis (NR) using metabolomics and lipidomics, exploring the key metabolic pathways of this pathological phenomenon.

RESULTS

We observed that the cysteine and methionine pathways, which are associated with cell growth and oxidative homeostasis, showed the greatest increase in the ISR group compared to the NR group. Within this pathway, the levels of N-formyl-l-methionine and L-methionine significantly increased in the ISR group, along with elevated levels of downstream metabolites such as 2-ketobutyric acid, pyruvate, and taurocholate. Additionally, an increase in phosphatidylcholine (PC) and phosphatidylserine (PS), as well as a decrease in triacylglycerol in the ISR group, indicated active lipid metabolism in these patients, which could be a significant factor contributing to the recurrence of blood clots after stent placement. Importantly, phenol sulfate and PS(38:4) were identified as potential biomarkers for distinguishing ISR, with an area under the curve of more than 0.85.

CONCLUSIONS

Our study revealed significant metabolic alterations in patients with ISR, particularly in the cysteine and methionine pathways, with phenol sulfate and PS(38:4) showing promise for ISR identification.

Hydrogen sulfide and its role in female reproduction

Hydrogen sulfide (H2S) is a gaseous signaling molecule produced in the body by three enzymes: cystathionine-β-synthase (CBS), cystathionine-γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST). H2S is crucial in various physiological processes associated with female mammalian reproduction. These include estrus cycle, oocyte maturation, oocyte aging, ovulation, embryo transport and early embryo development, the development of the placenta and fetal membranes, pregnancy, and the initiation of labor. Despite the confirmed presence of H2S-producing enzymes in all female reproductive tissues, as described in this review, the exact mechanisms of H2S action in these tissues remain in most cases unclear. Therefore, this review aims to summarize the knowledge about the presence and effects of H2S in these tissues and outline possible signaling pathways that mediate these effects. Understanding these pathways may lead to the development of new therapeutic strategies in the field of women's health and perinatal medicine.

Identifying disulfidptosis subtypes in hepatocellular carcinoma through machine learning and preliminary exploration of its connection with immunotherapy

BACKGROUND

Hepatocellular carcinoma (HCC) is a highly prevalent and deadly cancer, with limited treatment options for advanced-stage patients. Disulfidptosis is a recently identified mechanism of programmed cell death that occurs in SLC7A11 high-expressing cells due to glucose starvation-induced disintegration of the cellular disulfide skeleton. We aimed to explore the potential of disulfidptosis, as a prognostic and therapeutic marker in HCC.

METHODS

We classified HCC patients into two disulfidptosis subtypes (C1 and C2) based on the transcriptional profiles of 31 disulfrgs using a non-negative matrix factorization (NMF) algorithm. Further, five genes (NEIL3, MMP1, STC2, ADH4 and CFHR3) were screened by Cox regression analysis and machine learning algorithm to construct a disulfidptosis scoring system (disulfS). Cell proliferation assay, F-actin staining and PBMC co-culture model were used to validate that disulfidptosis occurs in HCC and correlates with immunotherapy response.

RESULTS

Our results suggests that the low disulfidptosis subtype (C2) demonstrated better overall survival (OS) and progression-free survival (PFS) prognosis, along with lower levels of immunosuppressive cell infiltration and activation of the glycine/serine/threonine metabolic pathway. Additionally, the low disulfidptosis group showed better responses to immunotherapy and potential antagonism with sorafenib treatment. As a total survival risk factor, disulfS demonstrated high predictive efficacy in multiple validation cohorts. We demonstrated the presence of disulfidptosis in HCC cells and its possible relevance to immunotherapeutic sensitization.

CONCLUSION

The present study indicates that novel biomarkers related to disulfidptosis may serve as useful clinical diagnostic indicators for liver cancer, enabling the prediction of prognosis and identification of potential treatment targets.

The role of lipoylation in mitochondrial adaptation to methionine restriction

Dietary methionine restriction (MR) is associated with a spectrum of health-promoting benefits. Being conducive to prevention of chronic diseases and extension of life span, MR can activate integrated responses at metabolic, transcriptional, and physiological levels. However, how the mitochondria of MR influence metabolic phenotypes remains elusive. Here, we provide a summary of cellular functions of methionine metabolism and an overview of the current understanding of effector mechanisms of MR, with a focus on the aspect of mitochondria-mediated responses. We propose that mitochondria can sense and respond to MR through a modulatory role of lipoylation, a mitochondrial protein modification sensitized by MR.

Impact of homocysteine on acute ischemic stroke severity: possible role of aminothiols redox status

BACKGROUND

Acute ischemic stroke (AIS) is one of the most common cerebrovascular diseases which accompanied by a disruption of aminothiols homeostasis. To explore the relationship of aminothiols with neurologic impairment severity, we investigated four aminothiols, homocysteine (Hcy), cysteine (Cys), cysteinylglycine (CG) and glutathione (GSH) in plasma and its influence on ischemic stroke severity in AIS patients.

METHODS

A total of 150 clinical samples from AIS patients were selected for our study. The concentrations of free reduced Hcy (Hcy), own oxidized Hcy (HHcy), free reduced Cys (Cys), own oxidized Cys (cysteine, Cyss), free reduced CG (CG) and free reduced GSH (GSH) were measured by our previously developed hollow fiber centrifugal ultrafiltration (HFCF-UF) method coupled with high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The concentration ratio of Hcy to HHcy (Hcy/HHcy), Cys to Cyss (Cys/Cyss) were also calculated. The neurologic impairment severity of AIS was evaluated using National Institutes of Health Stroke Scale (NIHSS). The Spearman correlation coefficient and logistic regression analysis was used to estimate and perform the correlation between Hcy, HHcy, Cys, Cyss, CG, GSH, Hcy/HHcy, Cys/Cyss and total Hcy with NIHSS score.

RESULTS

The reduced Hcy and Hcy/HHcy was both negatively correlated with NIHSS score in AIS patients with P = 0.008, r=-0.215 and P = 0.002, r=-0.249, respectively. There was no significant correlation of Cys, CG, GSH, HHcy, Cyss, Cys/Cyss and total Hcy with NIHSS score in AIS patients with P value > 0.05.

CONCLUSIONS

The reduced Hcy and Hcy/HHcy, not total Hcy concentration should be used to evaluate neurologic impairment severity of AIS patient.

Copper(I)-nitrene platform for chemoproteomic profiling of methionine

Methionine plays a critical role in various biological and cell regulatory processes, making its chemoproteomic profiling indispensable for exploring its functions and potential in protein therapeutics. Building on the principle of rapid oxidation of methionine, we report Copper(I)-Nitrene Platform for robust, and selective labeling of methionine to generate stable sulfonyl sulfimide conjugates under physiological conditions. We demonstrate the versatility of this platform to label methionine in bioactive peptides, intact proteins (6.5-79.5 kDa), and proteins in complex cell lysate mixtures with varying payloads. We discover ligandable proteins and sites harboring hyperreactive methionine within the human proteome. Furthermore, this has been utilized to profile oxidation-sensitive methionine residues, which might increase our understanding of the protective role of methionine in diseases associated with elevated levels of reactive oxygen species. The Copper(I)-Nitrene Platform allows labeling methionine residues in live cancer cells, observing minimal cytotoxic effects and achieving dose-dependent labeling. Confocal imaging further reveals the spatial distribution of modified proteins within the cell membrane, cytoplasm, and nucleus, underscoring the platform's potential in profiling the cellular interactome.

An AND-Gate Photoacoustic Probe for Cys and H2S Precise Photoacoustic Sensing in Localized Tumors

Photoacoustic (PA) tomography has shown many promising aspects in noninvasive and precise imaging of deep-localized biomarkers. However, these traditional single-locked PA probes always face challenges in precise PA imaging with high specificity. Here, we report a novel AND-gate photoacoustic probe, BAE, to improve tumor imaging accuracy via the combination of two tumor-associated biomarkers, cysteine (Cys) and hydrogen sulfide (H2S). Only when Cys and H2S are concurrently introduced into the detection system does the absorption of BAE red-shift from the initial 680 to 810 nm, thereby showing a 5.29-fold enhancement in its PA signal at 810 nm. The good specificity of BAE is proven, since an obvious PA signal could be observed only in the solution containing both Cys and H2S and was not affected by other reactive sulfur species. After being taken up by tumors with the assistance of a nanomicelle, the AND-gate PA probe BAE was applied for dynamic real-time monitoring of Cys and H2S in vivo, achieving precise identification of tumors. This AND-gate PA probe provides a potential technical tool for precise sensing analysis of deep-seated diseases.

Dimethyl Sulfoxide (DMSO) as a Potential Source of Interference in Research Related to Sulfur Metabolism-A Preliminary Study

Dimethyl sulfoxide (DMSO), an organosulfur compound, is widely used as the gold standard solvent in biological research. It is used in cell culture experiments and as a component of formulations in in vivo studies. Unfortunately, parameters related to sulfur metabolism are often not taken into account when using DMSO. Therefore, in this work we aim to show that the addition of DMSO to the culture medium (even in amounts commonly considered acceptable) alters some parameters of sulfur metabolism. For this study, we used three cell lines: a commercially available Caco-2 line (HTB-37, ATCC) and two lines created as part of our early studies (likewise previously described in the literature) to investigate the anomalies of sulfur metabolism in mucopolysaccharidosis. As the negative effects of DMSO on the cell membrane are well known, additional experiments with the partial loading of DMSO into polymerosomes (poly(ethylene glycol) methyl ether-block-poly(lactide-co-glycolide), PEG-PLGA) were performed to eliminate these potentially disruptive effects. The results show that DMSO is a source of interference in studies related to sulfur metabolism and that there are not just simple effects that can be corrected in the final result by subtracting control values, since complex synergisms are also observed.

The Role of One-Carbon Metabolism and Methyl Donors in Medically Assisted Reproduction: A Narrative Review of the Literature

One-carbon (1-C) metabolic deficiency impairs homeostasis, driving disease development, including infertility. It is of importance to summarize the current evidence regarding the clinical utility of 1-C metabolism-related biomolecules and methyl donors, namely, folate, betaine, choline, vitamin B12, homocysteine (Hcy), and zinc, as potential biomarkers, dietary supplements, and culture media supplements in the context of medically assisted reproduction (MAR). A narrative review of the literature was conducted in the PubMed/Medline database. Diet, ageing, and the endocrine milieu of individuals affect both 1-C metabolism and fertility status. In vitro fertilization (IVF) techniques, and culture conditions in particular, have a direct impact on 1-C metabolic activity in gametes and embryos. Critical analysis indicated that zinc supplementation in cryopreservation media may be a promising approach to reducing oxidative damage, while female serum homocysteine levels may be employed as a possible biomarker for predicting IVF outcomes. Nonetheless, the level of evidence is low, and future studies are needed to verify these data. One-carbon metabolism-related processes, including redox defense and epigenetic regulation, may be compromised in IVF-derived embryos. The study of 1-C metabolism may lead the way towards improving MAR efficiency and safety and ensuring the lifelong health of MAR infants.

Glutathione-triggered release of SO2 gas to augment oxidative stress for enhanced chemodynamic and sonodynamic therapy

Recently, gas therapy has emerged as a promising alternative treatment for deep-seated tumors. However, some challenges regarding insufficient or uncontrolled gas generation as well as unclear therapeutic mechanisms restrict its further clinical application. Herein, a well-designed nanoreactor based on intracellular glutathione (GSH)-triggered generation of sulfur dioxide (SO2) gas to augment oxidative stress has been developed for synergistic chemodynamic therapy (CDT)/sonodynamic therapy (SDT)/SO2 gas therapy. The nanoreactor (designed as CCM@FH-DNs) is constructed by employing iron-doped hollow mesoporous silica nanoparticles as carriers, the surface of which was modified with the SO2 prodrug 2,4-dinitrobenzenesulfonyl (DNs) and further coated with cancer cell membranes for homologous targeting. The CCM@FH-DNs can not only serve as a Fenton-like agent for CDT, but also as a sonosensitizer for SDT. Importantly, CCM@FH-DNs can release SO2 for SO2-mediated gas therapy. Both in vitro and in vivo evaluations demonstrate that the CCM@FH-DNs nanoreactor performs well in augmenting oxidative stress for SO2 gas therapy-enhanced CDT/SDT via GSH depletion and glutathione peroxidase-4 enzyme deactivation as well as superoxide dismutase inhibition. Moreover, the doped iron ions ensure that the CCM@FH-DNs nanoreactors enable magnetic resonance imaging-guided therapy. Such a GSH-triggered SO2 gas therapy-enhanced CDT/SDT strategy provides an intelligent paradigm for developing efficient tumor microenvironment-responsive treatments.

Enhanced Reactivity through Equatorial Sulfur Coordination in Nonheme Iron(IV)-Oxo Complexes: Insights from Experiment and Theory

Sulfur ligation in metalloenzymes often gives the active site unique properties, whether it is the axial cysteinate ligand in the cytochrome P450s or the equatorial sulfur/thiol ligation in nonheme iron enzymes. To understand sulfur ligation to iron complexes and how it affects the structural, spectroscopic, and intrinsic properties of the active species and the catalysis of substrates, we pursued a systematic study and compared sulfur with amine-ligated iron(IV)-oxo complexes. We synthesized and characterized a biomimetic N4S-ligated iron(IV)-oxo complex and compared the obtained results with an analogous N5-ligated iron(IV)-oxo complex. Our work shows that the amine for sulfur replacement in the equatorial ligand framework leads to a rate enhancement for oxygen atom and hydrogen atom transfer reactions. Moreover, the sulfur-ligated iron(IV)-oxo complex reacts through a different reaction mechanism as compared to the N5-ligated iron(IV)-oxo complex, where the former reacts through hydride transfer with the latter reacting via radical pathways. We show that the reactivity differences are caused by a dramatic change in redox potential between the two complexes. Our studies highlight the importance of implementing a sulfur ligand into the equatorial ligand framework of nonheme iron(IV)-oxo complexes and how it affects the physicochemical properties of the oxidant and its reactivity.

Unusual cysteine modifications in natural product biosynthesis

l-Cysteine is a highly reactive amino acid that is modified into a variety of chemical structures, including cysteine sulfinic acid in human metabolic pathways, and sulfur-containing scaffolds of amino acids, alkaloids, and peptides in natural product biosynthesis. Among the modification enzymes responsible for these cysteine-derived compounds, metalloenzymes constitute an important family of enzymes that catalyze a wide variety of reactions. Therefore, understanding their reaction mechanisms is important for the biosynthetic production of cysteine-derived natural products. This review mainly summarizes recent mechanistic investigations of metalloenzymes, with a particular focus on recently discovered mononuclear non-heme iron (NHI) enzymes, dinuclear NHI enzymes, and radical-SAM enzymes involved in unusual cysteine modifications in natural product biosynthesis.

Combined effects of copper and cadmium exposure on ovarian function and structure in Nile Tilapia (Oreochromis niloticus)

With the rapid development of industrialization and urbanization, the issue of copper (Cu) and cadmium (Cd) pollution in aquatic ecosystems has become increasingly severe, posing threats to the ovarian tissue and reproductive capacity of aquatic organisms. However, the combined effects of Cu and Cd on the ovarian development of fish and other aquatic species remain unclear. In this study, female Nile tilapia (Oreochromis niloticus) were individually or co-exposed to Cu and/or Cd in water. Ovarian and serum samples were collected at 15, 30, 60, 90, and 120 days, and the bioaccumulation, ovarian development, and hormone secretion were analyzed. Results showed that both single and combined exposure significantly reduced the gonadosomatic index and serum hormone levels, upregulated estrogen receptor (er) and progesterone receptor (pr) gene transcription levels, and markedly affected ovarian metabolite levels. Combined exposure led to more adverse effects than single exposure. The data demonstrate that the Cu and Cd exposure can impair ovarian function and structure, with more pronounced adverse effects under Cu and Cd co-exposure. The Cu and Cd affect the metabolic pathways of nucleotides and amino acids, leading to ovarian damage. This study highlights the importance of considering combined toxicant exposure in aquatic toxicology research and provides insights into the potential mechanisms underlying heavy metal-induced reproductive toxicity in fish.

Versatile roles of cysteine persulfides in tumor biology

Rewiring the transsulfuration pathway is recognized as a rapid adaptive metabolic response to environmental conditions in cancer cells to support their increased cysteine demand and to produce Reactive Sulfur Species (RSS) including hydrogen sulfide (H2S) and cysteine persulfide. This can directly (via RSS) or indirectly (by supplying Cys) trigger chemical or enzyme catalyzed persulfidation on critical protein cysteine residues to protect them from oxidative damage and to orchestrate protein functions, and thereby contribute to cancer cell plasticity. In this review key aspects of persulfide-mediated biological processes are highlighted and critically discussed in relation to cancer cell survival, bioenergetics, proliferation as well as in tumor angiogenesis, adaptation to hypoxia and oxidative stress, and regulation of epithelial to mesenchymal transition.

Detection and discrimination of glutathione among biological thiols based on oxalyl dihydrazide decorated sulfur nanodots

The quantitative detection and discrimination of glutathione (GSH) were achieved based on oxalyl dihydrazide (ODH) decorated sulfur nanodots. ODH resulted in the aggregation and fluorescence quenching of the sulfur nanodots, and GSH selectively triggered fluorescence recovery through forming stronger hydrogen bonds with ODH than other biological thiols.

Molecular subtypes of disulfidptosis-regulated genes and prognosis models for predicting prognosis, tumor microenvironment infiltration, and therapeutic response in hepatocellular carcinoma

Disulfidptosis, a recently identified mode of cellular demise marked by excess SLC7A11-reliant cystine, has been proved to affect the development and resilience of tumor cells through the production of glutathione from cystine. Glutathione synthesis plays a crucial role in chemotherapy resistance and the survival of liver cancer cells. Thus, understanding the relationship between disulfidptosis and hepatocellular carcinoma (HCC) is imperative. A molecular typing approach was employed to classify patients with HCC into two distinct subtypes, namely disulfidptosis and disulfide-homeostasis, based on the expression of genes associated with disulfidptosis. Patients with disulfidptosis exhibited a longer survival time, improved immune status, and heightened sensitivity to conventional chemotherapeutic drugs and immunotherapy. Patients with disulfide-homeostasis demonstrated an immunosuppressive microenvironment, drug resistance, and unfavorable prognosis. A prognostic model was constructed utilizing the significant prognostic variables of the disulfidptosis-regulated genes. A real-world cohort was subjected to multiplex immunofluorescence to validate the clinical outcomes and immune context. Ultimately, our study delved into the prognostic relevance of disulfidptosis in HCC and provides insights into potential avenues for future research.

High-Contrast Photoacoustic Imaging of Localized Cysteine in Orthotopic Breast Cancer Enabled by A Totally-Caged Methylene Blue Probe

High-contrast photoacoustic sensing imaging (PASI) was greatly determined by optical absorption changes of the absorbers usually enabled by activatable probes via controllably converting the absorbed electromagnetic energy to ultrasound waves. However, most of current photoacoustic probes still suffer from limited imaging contrast towards specific species because of their small absorption spectral changes in the near infrared (NIR) region. Herein, we developed a methylene blue-based photoacoustic probe with its NIR optical absorption totally caged, which could afford dramatical "OFF-to-ON" absorption transition for high-contrast photoacoustic imaging towards the localized cysteine. The rationally designed methylene blue-based probe for cysteine (MB-Cys) would keep in off state with almost no absorption in NIR region, while upon activated by cysteine through cyclization reaction with acrylates, it would reconstruct the π-conjugation system to release the free methylene blue with strong absorption centered at 665 nm (>130-fold enhancement). The unique responsive behavior could enable the PASI for photoacoustic mapping the cysteine in orthotopic breast cancer in a high-contrast manner. Therefore, this work established an up-to-date strategy to originally eliminate the background photoacoustic signal for PASI to accurately monitor cysteine in vivo.

Hypoxia-inducible factor induces cysteine dioxygenase and promotes cysteine homeostasis in Caenorhabditis elegans

Dedicated genetic pathways regulate cysteine homeostasis. For example, high levels of cysteine activate cysteine dioxygenase, a key enzyme in cysteine catabolism in most animal and many fungal species. The mechanism by which cysteine dioxygenase is regulated is largely unknown. In an unbiased genetic screen for mutations that activate cysteine dioxygenase (cdo-1) in the nematode Caenorhabditis elegans, we isolated loss-of-function mutations in rhy-1 and egl-9, which encode proteins that negatively regulate the stability or activity of the oxygen-sensing hypoxia inducible transcription factor (hif-1). EGL-9 and HIF-1 are core members of the conserved eukaryotic hypoxia response. However, we demonstrate that the mechanism of HIF-1-mediated induction of cdo-1 is largely independent of EGL-9 prolyl hydroxylase activity and the von Hippel-Lindau E3 ubiquitin ligase, the classical hypoxia signaling pathway components. We demonstrate that C. elegans cdo-1 is transcriptionally activated by high levels of cysteine and hif-1. hif-1-dependent activation of cdo-1 occurs downstream of an H2S-sensing pathway that includes rhy-1, cysl-1, and egl-9. cdo-1 transcription is primarily activated in the hypodermis where it is also sufficient to drive sulfur amino acid metabolism. Thus, the regulation of cdo-1 by hif-1 reveals a negative feedback loop that maintains cysteine homeostasis. High levels of cysteine stimulate the production of an H2S signal. H2S then acts through the rhy-1/cysl-1/egl-9 signaling pathway to increase HIF-1-mediated transcription of cdo-1, promoting degradation of cysteine via CDO-1.

Protein intake affects erythrocyte glutathione synthesis in young healthy adults in a repeated-measures trial

BACKGROUND

In 2005, the Institute of Medicine advised using methods other than nitrogen balance (NB) for determining protein requirements. Since then, protein requirements using indicator amino acid oxidation (IAAO) have been published and are higher than NB. Glutathione (GSH), a tripeptide of cysteine, glutamate, and glycine, is a principal antioxidant that can be used as a functional indicator of protein adequacy.

OBJECTIVES

The aim of this study was to measure changes in erythrocyte GSH kinetics [fractional synthesis rate (FSR) and absolute synthesis rate (ASR)] in healthy adults following a range of protein intakes at and above the current recommendations.

METHODS

Sixteen healthy adults [8 males and 8 females, aged 25.6 ± 0.9 y (mean ± SEM)] were studied at 4 of 6 protein intakes ranging from 0.6 to 1.5 g⋅kg-1⋅d-1. Erythrocyte GSH kinetics were assessed during a 7-h infusion of [U-13C2-15N]glycine following 2 d of adaptation to each protein intake. Blood and urine tests were performed to measure oxidative stress markers, plasma homocysteine, triglycerides, plasma amino acid concentrations, 5-L-oxoproline (5-OP), and urinary sulfate. The protein intake that maximized GSH synthesis was determined using mixed-effect change-point regression in R. Primary and secondary outcomes were analyzed using linear mixed-effects and repeated-measures analysis of variance with Tukey's post hoc test.

RESULTS

The protein intake that maximized GSH FSR at 78%⋅d-1 was 1.0 g⋅kg-1⋅d-1 (95% confidence interval: 0.63, 1.39). GSH ASR was significantly lower at 0.6 and 0.8 g⋅kg-1⋅d-1 than at 1.5 g⋅kg-1⋅d-1 (2.03 and 2.17, respectively, compared with 3.71 mmol⋅L-1⋅d-1). Increasing the protein intake led to increased urinary sulfate but did not affect erythrocyte GSH concentration, plasma oxidative stress markers, triglycerides, homocysteine, or 5-OP.

CONCLUSIONS

A protein intake of 1.0 g⋅kg-1⋅d-1 maximized GSH synthesis, which is in agreement with earlier IAAO-derived protein requirements of 0.93 to 1.2 g⋅kg-1⋅d-1. These findings suggest that recommendations based on NB (0.66 g⋅kg-1⋅d-1) may underestimate protein needs for adequate health. This trial was registered at clinicaltrials.gov as NCT02971046.

Monitoring of taurine dietary supplementation effect on parameters of Duroc boar ejaculate in summer season

The aim of this experiment was to find out whether the taurine supplementation in daily ration had an effect on quantity or quality of Duroc boar ejaculate. The experiment duration was from June to August, when it could assumed the possible occurrence of heat stress. For the study was chosen 12 Duroc boars of approximately the same age and condition. The control group of 6 Duroc boars was fed only by basic diet and the experimental group of 6 Duroc boars was fed by the same basic diet with supplementation of 15 g taurine/boar/day. Ejaculate was collected once a week by hand glowed technique. From ejaculate parameters were monitored volume of ejaculate, sperm concentration, total amount of sperm, morphologically abnormal sperm, taurine concentration and GSH/GSSH concentration. From microscopic analysis, results were statistically significant in motility in June and July (P<0.05). In biochemical results, a significant difference (P<0.05) has been found between the experimental groups in the concentrations of taurine as well as GSH/GSSG in ejaculate which indicates the effect of heat stress on boars during the experimental period.

Equivalent Response Strategy for Sensing Total Biothiols in Human Serums and Living Cells Using a Hemicyanine-Based Self-Immolative Probe

Biothiols including cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) are crucial in maintaining the redox balance in the body, and the metabolism and transportation of biothiols rely on the coreaction of diverse proteins and enzymes. The abnormal concentrations and metabolism of biothiols are closely associated with many diseases. However, due to the same active reaction site of the sulfydryl group in biothiols, it is inevitable to bear a confused signal of mutual influence on both nonselective detection and discriminate detection, which presents a serious challenge of accurately sensing or imaging the three biothiols. By assigning an α,β-unsaturated ketone moiety as a Michael acceptor to trigger thiols to complete the irreversible equivalent domino response processes of nucleophilic addition, olefinic bond migration, and self-immolation, a targeted strategy was rationally pointed out, and herein, a hemicyanine-based probe CyOCy was prepared as a proof of strategy demonstration. The new probe could be equivalently lit up by Cys, Hcy, GSH, and even biothiol combinations (Cys/Hcy, Cys/GSH, Hcy/GSH, or Cys/Hcy/GSH) with unified linear ranges, detection limits, and response times. The probe CyOCy has been successfully used for the accurate quantification of total biothiols in the serum samples of healthy persons and coronary heart disease patients. In addition, the probe has been applied for cell screening, exogenous biothiol imaging, and monitoring drug-induced biothiol fluctuations. The purposive thinking of this work may provide an effective avenue for the accurate sensing of multicomponent samples.

Dynamics of blood Taurine concentration and its correlation with nutritional and physiological status during the fattening period of Japanese black cattle

Taurine, biosynthesized from methionine or cysteine in the liver, plays a crucial regulatory role in bile acid conjugation, antioxidant effects, and glucose and cholesterol metabolism. This may influence the metabolic changes associated with fat accumulation in beef cattle. However, the physiological role of taurine in this species has not been fully elucidated. In this study, we explored the physiological role of taurine in Japanese Black steers (Bos taurus) in different phases during the fattening period. To examine the correlation among plasma taurine concentrations, various physiological parameters, and genes related to taurine synthesis in the liver, we used biopsied liver tissues, blood samples, and rumen fluids collected from 21 steers at three different stages, i.e., early (T1; 13 mo of age), middle (T2; 20 mo of age), and late (T3; 28 mo of age) phases. Additionally, to investigate the regulatory mechanisms underlying the expression profile of taurine synthesis genes, primary bovine hepatocytes obtained from 4-wk-old Holstein calves were treated with palmitate, oleate, acetate, propionate, or β-hydroxybutyrate (BHBA). Plasma taurine and cholesterol concentrations significantly (P < 0.001) increased in the T2 phase, which is potentially attributable to increased energy intake and assimilation induced by increased intake of concentrated feed. Cysteine-sulfinic acid decarboxylase (CSAD) expression significantly increased (P < 0.01) in T2 than in other phases. The expression levels of cysteine dioxygenase type 1 (CDO1) and cholesterol 7 alpha-hydroxylase (CYP7A1) were significantly higher (P < 0.05) in T2 than in T3; moreover, the CDO1/glutamate-cysteine ligase catalytic subunit (GCLC) ratio was higher (P < 0.05) in T2 than in T1. Plasma taurine concentrations were positively correlated with plasma methionine (r = 0.51; P < 0.05) and total cholesterol (r = 0.56; P < 0.05) concentrations at T2. Relative CDO1 mRNA expression was upregulated in cultured bovine hepatocytes treated with oleate and propionate, whereas it was downregulated upon acetate treatment. These findings indicate that the increase in plasma taurine concentrations in the T2 phase is associated with changes in lipid and methionine metabolism in Japanese Black steers.

Identification of a novel enzyme and the regulation of key enzymes in mammalian taurine synthesis

Taurine has many pharmacological roles on various tissues. The maintenance of abundant taurine content in the mammalian body through endogenous synthesis, in addition to exogenous intake, is the essential factor for morphological and functional maintenances in most tissues. The synthesis of taurine from sulfur-containing amino acids is influenced by various factors. Previous literature findings indicate the influence of the intake of proteins and sulfur-containing amino acids on the activity of the rate-limiting enzymes cysteine dioxygenase and cysteine sulfinate decarboxylase. In addition, the regulation of the activity and expression of taurine-synthesis enzymes by hormones, bile acids, and inflammatory cytokines through nuclear receptors have been reported in liver and reproductive tissues. Furthermore, flavin-containing monooxygenase subtype 1 was recently identified as the taurine-synthesis enzyme that converts hypotaurine to taurine. This review introduces the novel taurine synthesis enzyme and the nuclear receptor-associated regulation of key enzymes in taurine synthesis.