Cysteine dioxygenase: a robust system for regulation of cellular cysteine levels

Taurine ameliorates cellular senescence associated with an increased hydrogen sulfide and a decreased hepatokine, IGFBP-1, in CCl4-induced hepatotoxicity in mice

This study investigated the protective effects of taurine against cellular senescence and hepatokine secretion in a mouse model of carbon tetrachloride (CCl4)-induced chronic liver injury. Oral taurine administration by tap water containing 3 % taurine significantly attenuated liver damage, as evidenced by reduced serum AST, ALT level and hepatic lipid peroxidation. Importantly, hepatic taurine level is reduced in CCl4-induced injury model, while taurine administration recovered it. Moreover, taurine administration decreased the numbers of p21-positive senescent cells in liver tissue of CCl4-treated mice. Taurine increases hydrogen sulfide (H2S) in liver of normal mice, suggesting anti-oxidative role through H2S production by taurine. Furthermore, inhibition of CTH, which is an enzyme responsible for H2S production from cysteine, by propagylglycine attenuated malondialdehyde-lowering effect of taurine in liver of CCl4-treated mice. Moreover, we found taurine treatment lowers insulin-like growth factor binding protein-1 (IGFBP-1) in liver of normal mice. Importantly, while chronic CCl4 injection caused an induction of IGFBP-1, taurine administration blocked it. These findings suggest that taurine exerts its protective effects by attenuating cellular senescence, which is associated with enhancing H2S production and inhibiting IGFBP-1 expression. This study highlights the potential of taurine as a therapeutic strategy for mitigating chronic liver injury by producing H2S and targeting IGFBP1.

The cystathionine-γ-lyase inhibitor DL-propargylglycine augments the ability of L-cysteine ethyl ester to overcome the adverse effects of morphine on breathing

l-cysteine ethyl ester (l-CYSee) overcomes adverse effects elicited by systemic injection of morphine on ventilatory parameters and arterial blood-gas chemistry in rats. l-CYSee or l-cysteine, resulting from the deesterification of l-CYSee, may enter enzymatic cascades that produce the ventilatory stimulant molecule, hydrogen sulfide (H2S). dl-propargylglycine (dl-PROP) is an inhibitor of cystathionine-γ-lyase (CSE)-mediated conversion of l-cysteine to H2S and has been widely used in vivo. We examined whether l-CYSee (2 injections × 500 µmol/kg, IV)-induced reversal of the changes in ventilation elicited by morphine (10 mg/kg, IV) in freely moving male Sprague Dawley rats was altered by prior administration of dl-PROP (25 mg/kg, IV). The major findings were 1) the effects of morphine on ventilatory parameters were not affected by subsequent injection of dl-PROP; 2) first injection of l-CYSee elicited a prompt reversal of the adverse effects of morphine that was more pronounced in dl-PROP-treated than vehicle-treated rats; and 3) the actions of the second injection of l-CYSee were dramatically augmented in dl-PROP-treated rats. In addition, the changes in many of the ventilatory parameters during a subsequent hypoxic-hypercapnic (HH) gas challenge were augmented substantially by dl-PROP. This study demonstrates that 1) inhibition of CSE with dl-PROP does not affect the ventilatory actions of morphine, 2) reversal effects of l-CYSee were augmented by blockade of CSE, and 3) blockade of CSE augments the ventilatory responses to HH gas challenge in morphine-treated rats. These unexpected findings suggest that the CSE-dependent production of H2S from l-CYSee countermands l-CYSee reversal of morphine-induced respiratory depression in rats.NEW & NOTEWORTHY The ability of l-cysteine ethyl ester (l-CYSee) to overcome the adverse effects of morphine on breathing is exaggerated by inhibition of cystathionine-γ-lyase (CSE), suggesting that conversion of l-CYSee or l-cysteine to H2S countermands the effects of l-CYSee against morphine.

An mRNA-display derived cyclic peptide scaffold reveals the substrate binding interactions of an N-terminal cysteine oxidase

N-terminal cysteine oxidases (NCOs) act as enzymatic oxygen (O2) sensors, coordinating cellular changes to hypoxia in animals and plants. They regulate the O2-dependent stability of proteins bearing an N-terminal cysteine residue through the N-degron pathway. Despite their important role in hypoxic adaptation, which renders them potential therapeutic and agrichemical targets, structural information on NCO substrate binding remains elusive. To overcome this challenge, we employed a unique strategy by which a cyclic peptide inhibitor of the mammalian NCO, 2-aminoethanethiol dioxygenase (ADO), was identified by mRNA display and used as a scaffold to graft substrate moieties. This allowed the determination of two substrate analogue-bound crystal structures of ADO. Key binding interactions were revealed, including bidentate coordination of the N-terminal residue at the metal cofactor. Subsequent structure guided mutagenesis identified aspartate-206 as an essential catalytic residue, playing a role in reactive oxygen intermediate orientation or stabilisation. These findings provide fundamental information on ADO substrate interactions, which can elucidate enzyme mechanism and act as a platform for chemical discovery.

Major Oxidative and Antioxidant Mechanisms During Heat Stress-Induced Oxidative Stress in Chickens

Heat stress (HS) is one of the most important stressors in chickens, and its adverse effects are primarily caused by disturbing the redox homeostasis. An increase in electron leakage from the mitochondrial electron transport chain is the major source of free radical production under HS, which triggers other enzymatic systems to generate more radicals. As a defense mechanism, cells have enzymatic and non-enzymatic antioxidant systems that work cooperatively against free radicals. The generation of free radicals, particularly the reactive oxygen species (ROS) and reactive nitrogen species (RNS), under HS condition outweighs the cellular antioxidant capacity, resulting in oxidative damage to macromolecules, including lipids, carbohydrates, proteins, and DNA. Understanding these detrimental oxidative processes and protective defense mechanisms is important in developing mitigation strategies against HS. This review summarizes the current understanding of major oxidative and antioxidant systems and their molecular mechanisms in generating or neutralizing the ROS/RNS. Importantly, this review explores the potential mechanisms that lead to the development of oxidative stress in heat-stressed chickens, highlighting their unique behavioral and physiological responses against thermal stress. Further, we summarize the major findings associated with these oxidative and antioxidant mechanisms in chickens.

Comprehensive analysis and experimental validation of disulfidptosis-associated prognostic signature and immune microenvironment characterization of gastric cancer

BACKGROUND

Gastric cancer (GC) is one of the most common causes of cancer-related death worldwide. As a novel form of programmed cell death, disulfidptosis is characterized by excessive cysteine accumulation, disulfide stress and actin destruction. There is evidence that targeting disulfidptosis is a promising anticancer strategy. Further improvement of GC risk stratification based on disulfidptosis has positive clinical significance.

METHODS

We analyzed the expression levels of disulfidptosis-associated genes (DPAGs) in normal and GC tissues and characterized the molecular subtypes of GC patients. Based on the characteristics of DPAG subtypes, differentially expressed prognosis-related genes were selected by LASSO-univariate Cox analysis and multivariate Cox analysis analyzed to establish a prognostic model. Using single-cell sequencing analysis reveals the cell subpopulation for GC. The function of the selected target in GC was verified by in vitro experimental means, including siRNA, qRT-PCR, Western blot, CCK-8, and Transwell assay.

RESULTS

DPAG score was verified to be an independent prognostic factor of GC and was significantly associated with poor prognosis of gastric cancer. Subsequent studies on subgroup immunoinfiltration characteristics, drug sensitivity analysis, immunotherapy response and somatic mutation characteristics of DPAG score comprehensively confirmed the potential guiding significance of DPAG score for individualized treatment of gastric cancer patients. Single-cell sequencing analysis revealed the expression characteristics of DPAG-related prognostic signatures across cell subpopulations. In vitro experiments showed APC11, as one of the selected DPAGs, was highly expressed in gastric cancer, and knockdown of APC11 could significantly inhibit the proliferation and migration of GC cells, demonstrating the reliability of bioinformatics results.

CONCLUSION

The results of this study provide a new perspective for exploring the role of disulfidptosis in the occurrence and development of GC.

Glutathione Contributes to Caloric Restriction-Triggered Shift in Taurine Homeostasis

BACKGROUND/OBJECTIVES

Previously, we found that caloric restriction (CR) in mice increases taurine levels by stimulating hepatic synthesis, secretion into the intestine and deconjugation of taurine-conjugated bile acids (BA). Subsequently, in the intestine, taurine conjugates various molecules, including glutathione (GSH). The current study explores the mechanisms behind forming taurine-GSH conjugate and its consequences for taurine, other taurine conjugates, and BA in order to improve understanding of their role in CR.

METHODS

The non-enzymatic conjugation of taurine and GSH was assessed and the uptake of taurine, GSH, and taurine-GSH was verified in five sections of the small intestine. Levels of taurine, gavaged 13C labeled taurine, taurine conjugates, taurine-GSH, and GSH were measured in various tissues of ad libitum and CR mice. Next, the taurine-related CR phenotype was challenged by applying the inhibitors of taurine transporter (SLC6A6) and GSH-S transferases (GST).

RESULTS

The CR-related increase in taurine in intestinal mucosa was accompanied by the uptake and distribution of taurine towards selected organs. A unique composition of taurine conjugates characterized each tissue. Although taurine-GSH conjugate could be formed in non-enzymatic reactions, GST activity contributed to taurine-related CR outcomes. Upon SLC6A6 and GST inhibition, the taurine-related parameters were affected mainly in the ileum rather than the liver. Meanwhile, BA levels were somewhat affected by GST inhibition in the ileum and in the liver by SLC6A6 inhibitor.

CONCLUSIONS

The discovered CR phenotype involves a regulatory network that adjusts taurine and BA homeostasis. GSH supports these processes by conjugating taurine, impacting taurine uptake from the intestine and its availability to form other types of conjugates.

Gut microbiota, dietary taurine, and fiber shift taurine homeostasis in adipose tissue of calorie-restricted mice to impact fat loss

Previously, we demonstrated that caloric restriction (CR) stimulates the synthesis, conjugation, secretion, and deconjugation of taurine and bile acids in the intestine, as well as their reuptake. Given taurine's potent antiobesogenic properties, this study aimed to assess whether the CR-induced shift in taurine homeostasis contributes to adipose tissue loss. To verify that, male C57Bl/6 mice were subjected to 20% CR or ad libitum feeding, with variations in cage bedding and gut microbiota conditions. Additional groups received taurine supplementation or were fed a low-taurine diet (LTD). The results showed that in CR animals, taurine derived from the intestine was preferentially trafficked to epididymal white adipose tissue (eWAT) over other tested organs. Besides increased levels of taurine transporter TauT, gene expression of Cysteine dioxygenase (Cdo) involved in taurine synthesis was upregulated in CR eWAT. Taurine concentration in adipocytes was inversely correlated with fat pad weight of CR mice. Different types of cage bedding did not impact eWAT taurine levels; however, the lack of bedding and consumption of a diet high in soluble fiber did. Depleting gut microbiota with antibiotics or inhibiting bile salt hydrolase (BSH) activity reduced WAT taurine concentration in CR mice. Taurine supplementation increased taurine levels in WAT and brown adipose tissue (BAT), promoting fat loss in CR animals. LTD consumption blunted WAT loss in CR animals, with negligible impact on BAT. This study provides multiple insights into taurine's role in CR-triggered fat loss and describes a novel communication path between the liver, gut, microbiota, and WAT, with taurine acting as a messenger.

Integration of epigenomic and transcriptomic profiling uncovers EZH2 target genes linked to cysteine metabolism in hepatocellular carcinoma

Enhancer of zeste homolog 2 (EZH2), a key protein implicated in various cancers including hepatocellular carcinoma (HCC), is recognized for its association with epigenetic dysregulation and pathogenesis. Despite clinical explorations into EZH2-targeting therapies, the mechanisms underlying its role in gene suppression in HCC have remained largely unexplored. Here, we integrate epigenomic and transcriptomic analyses to uncover the transcriptional landscape modulated by selective EZH2 inhibition in HCC. By reanalyzing transcriptomic data of HCC patients, we demonstrate that EZH2 overexpression correlates with poor patient survival. Treatment with the EZH2 inhibitor tazemetostat restored expression of genes involved in cysteine-methionine metabolism and lipid homeostasis, while suppressing angiogenesis and oxidative stress-related genes. Mechanistically, we demonstrate EZH2-mediated H3K27me3 enrichment at cis-regulatory elements of transsulfuration pathway genes, which is reversed upon inhibition, leading to increased chromatin accessibility. Among 16 EZH2-targeted candidate genes, BHMT and CDO1 were notably correlated with poor HCC prognosis. Tazemetostat treatment of HCC cells increased BHMT and CDO1 expression while reducing levels of ferroptosis markers FSP1, NFS1, and SLC7A11. Functionally, EZH2 inhibition dose-dependently reduced cell viability and increased lipid peroxidation in HCC cells. Our findings reveal a novel epigenetic mechanism controlling lipid peroxidation and ferroptosis susceptibility in HCC, providing a rationale for exploring EZH2-targeted therapies in this malignancy.

The distinct mechanism regulating taurine homeostasis in mice: Nutrient availability affects taurine levels in the liver and energy restriction influences it in the intestine

AIMS

Our previous findings indicate that caloric restriction (CR) stimulates the production and secretion of taurine-conjugated bile acids in mice. Subsequent processing by gut microbiota leads to increased levels of deconjugated bile acids, taurine, and various taurine conjugates in the intestine. Furthermore, we demonstrated that carbohydrate restriction and protein restriction, to a smaller extent, mirror the impact of CR in terms of hepatic production of bile acids but not their secretion. We hypothesized that modulating dietary macronutrient levels would influence taurine homeostasis in the liver and intestine of ad libitum-fed and CR animals.

MATERIALS AND METHODS

Ad libitum-fed male mice were allocated to receive either a control, low-protein (LP), low-fat (LF), or low-carbohydrate (LC) diet. Meanwhile, CR groups were given 80 % of their regular voluntary food intake as a control, high-protein (HP), high-fat (HF), or high-carbohydrate (HC) diet.

KEY FINDINGS

While CR did not affect the taurine levels and its conjugates in the liver, alteration in carbohydrates and protein intake impacted it. Conversely, in the intestine, CR increased the amount of free and conjugated taurine, whereas the various diets did not affect it or disrupt the CR-specific phenotype. Notably, variations in diet composition impacted the expression of the taurine transporter (Slc6a6) and glutathione-S transferases (GST) in the intestine as well as cysteine dioxygenase (Cdo) in the liver.

SIGNIFICANCE

The liver and the intestine show distinct responses to dietary interventions, with hepatic taurine being affected by the diet composition, while intestinal taurine is governed by energy availability.

Betaine Supplementation Into High-Carbohydrate Diets Improves Feed Efficiency and Liver Health of Megalobrama amblycephala by Increasing Taurine Synthesis

Dietary betaine supplementation has been reported to alleviate the adverse effects of high-carbohydrate diets on Megalobrama amblycephala, while the regulatory mechanism remains largely unknown. In the present study, a 79-day feeding trial was conducted with 450 juvenile Megalobrama amblycephala (average weight 6.75 ± 0.10 g), which were fed with five high-carbohydrate diets (43%) supplementing betaine at 0% (CD group), 0.2% (0.2Bet group), 0.4% (0.4Bet group), 0.8% (0.8Bet group), and 1.6% (1.6Bet group), respectively. Results showed M. amblycephala in 0.8Bet group exhibited the best growth performance, indicated by the largest weight gain ratio (142.88%) and least feed conversion ratio (1.63). Moreover, liver health was promoted in 0.8Bet group, with decreased number of non-nucleated cells and less lipid accumulation, which was accompanied by the lowest hepatosomatic index (1.38%). In order to further illustrate the regulatory mechanism, metabolites assay indicated that dietary betaine supplementation significantly increased plasma contents of methionine, serine, hypotaurine, and taurine, but did not affect plasma contents of cystathionine, cystine, or cysteic acid. Accordingly, the mRNA expressions of cysteine sulfinate decarboxylase in cysteine sulfinic acid pathway and cysteamine dioxygenase (ADO) in sulfinic acid (CS) pathway, which were both involved in taurine synthesis, were also upregulated in the liver. Meanwhile, the microbial communities in M. amblycephala intestine were more stable and uniform with betaine supplementation. Therefore, dietary betaine supplementation may exert its protective roles in improving feed efficiency and liver health of M. amblycephala via promoting de novo taurine synthesis and stabilizing intestinal microbial communities.

Ala-Cys-Cys-Ala dipeptide dimer alleviates problematic cysteine and cystine levels in media formulations and enhances CHO cell growth and metabolism

Cysteine and cystine are essential amino acids present in mammalian cell cultures. While contributing to biomass synthesis, recombinant protein production, and antioxidant defense mechanisms, cysteine poses a major challenge in media formulations owing to its poor stability and oxidation to cystine, a cysteine dimer. Due to its poor solubility, cystine can cause precipitation of feed media, formation of undesired products, and consequently, reduce cysteine bioavailability. In this study, a highly soluble cysteine containing dipeptide dimer, Ala-Cys-Cys-Ala (ACCA), was evaluated as a suitable alternative to cysteine and cystine in CHO cell cultures. Replacing cysteine and cystine in basal medium with ACCA did not sustain cell growth. However, addition of ACCA at 4 mM and 8 mM to basal medium containing cysteine and cystine boosted cell growth up to 15% and 27% in CHO-GS and CHO-K1 batch cell cultures respectively and led to a proportionate increase in IgG titer. 13C-Metabolic flux analysis revealed that supplementation of ACCA reduced glycolytic fluxes by 20% leading to more efficient glucose metabolism in CHO-K1 cells. In fed-batch cultures, ACCA was able to replace cysteine and cystine in feed medium. Furthermore, supplementation of ACCA at high concentrations in basal medium eliminated the need for any cysteine equivalents in feed medium and increased cell densities and viabilities in fed-batch cultures without any significant impact on IgG charge variants. Taken together, this study demonstrates the potential of ACCA to improve CHO cell growth, productivity, and metabolism while also facilitating the formulation of cysteine- and cystine-free feed media. Such alternatives to cysteine and cystine will pave the way for enhanced biomanufacturing by increasing cell densities in culture and extending the storage of highly concentrated feed media as part of achieving intensified bioproduction processes.

The epigenetic signatures of opioid addiction and physical dependence are prevented by D-cysteine ethyl ester and betaine

We have reported that D,L-thiol esters, including D-cysteine ethyl ester (D-CYSee), are effective at overcoming opioid-induced respiratory depression (OIRD) in rats. Our on-going studies reveal that co-injections of D-CYSee with multi-day morphine injections markedly diminish spontaneous withdrawal that usually occurs after cessation of multiple injections of morphine in rats. Chronically administered opioids are known (1) to alter cellular redox status, thus inducing an oxidative state, and (2) for an overall decrease in DNA methylation, therefore resulting in the transcriptional activation of previously silenced long interspersed elements (LINE-1) retrotransposon genes. The first objective of the present study was to determine whether D-CYSee and the one carbon metabolism with the methyl donor, betaine, would maintain redox control and normal DNA methylation levels in human neuroblastoma cell cultures (SH-SY5Y) under overnight challenge with morphine (100 nM). The second objective was to determine whether D-CYSee and/or betaine could diminish the degree of physical dependence to morphine in male Sprague Dawley rats. Our data showed that overnight treatment with morphine reduced cellular GSH levels, induced mitochondrial damage, decreased global DNA methylation, and increased LINE-1 mRNA expression. These adverse effects by morphine, which diminished the reducing capacity and compromised the maintenance of the membrane potential of SH-SY5Y cells, was prevented by concurrent application of D-CYSee (100 µM) or betaine (300 µM). Furthermore, our data demonstrated that co-injections of D-CYSee (250 μmol/kg, IV) and to a lesser extent, betaine (250 μmol/kg, IV), markedly diminished the development of physical dependence induced by multi-day morphine injections (escalating daily doses of 10-30 mg/kg, IV), as assessed by the lesser number of withdrawal phenomena elicited by the injection of the opioid receptor antagonist, naloxone (1.5 mg/kg, IV). These findings provide evidence that D-CYSee and betaine prevent the appearance of redox alterations and epigenetic signatures commonly seen in neural cells involved in opioid physical dependence/addiction, and lessen development of physical dependence to morphine.

Deciphering pathophysiological mechanisms underlying cystathionine beta-synthase-deficient homocystinuria using targeted metabolomics, liver proteomics, sphingolipidomics and analysis of mitochondrial function

BACKGROUND

Cystathionine β-synthase (CBS)-deficient homocystinuria (HCU) is an inherited disorder of sulfur amino acid metabolism with varying severity and organ complications, and a limited knowledge about underlying pathophysiological processes. Here we aimed at getting an in-depth insight into disease mechanisms using a transgenic mouse model of HCU (I278T).

METHODS

We assessed metabolic, proteomic and sphingolipidomic changes, and mitochondrial function in tissues and body fluids of I278T mice and WT controls. Furthermore, we evaluated the efficacy of methionine-restricted diet (MRD) in I278T mice.

RESULTS

In WT mice, we observed a distinct tissue/body fluid compartmentalization of metabolites with up to six-orders of magnitude differences in concentrations among various organs. The I278T mice exhibited the anticipated metabolic imbalance with signs of an increased production of hydrogen sulfide and disturbed persulfidation of free aminothiols. HCU resulted in a significant dysregulation of liver proteome affecting biological oxidations, conjugation of compounds, and metabolism of amino acids, vitamins, cofactors and lipids. Liver sphingolipidomics indicated upregulation of the pro-proliferative sphingosine-1-phosphate signaling pathway. Liver mitochondrial function of HCU mice did not seem to be impaired compared to controls. MRD in I278T mice improved metabolic balance in all tissues and substantially reduced dysregulation of liver proteome.

CONCLUSION

The study highlights distinct tissue compartmentalization of sulfur-related metabolites in normal mice, extensive metabolome, proteome and sphingolipidome disruptions in I278T mice, and the efficacy of MRD to alleviate some of the HCU-related biochemical abnormalities.

Programming a Ferroptosis-to-Apoptosis Transition Landscape Revealed Ferroptosis Biomarkers and Repressors for Cancer Therapy

Ferroptosis and apoptosis are key cell-death pathways implicated in several human diseases including cancer. Ferroptosis is driven by iron-dependent lipid peroxidation and currently has no characteristic biomarkers or gene signatures. Here a continuous phenotypic gradient between ferroptosis and apoptosis coupled to transcriptomic and metabolomic landscapes is established. The gradual ferroptosis-to-apoptosis transcriptomic landscape is used to generate a unique, unbiased transcriptomic predictor, the Gradient Gene Set (GGS), which classified ferroptosis and apoptosis with high accuracy. Further GGS optimization using multiple ferroptotic and apoptotic datasets revealed highly specific ferroptosis biomarkers, which are robustly validated in vitro and in vivo. A subset of the GGS is associated with poor prognosis in breast cancer patients and PDXs and contains different ferroptosis repressors. Depletion of one representative, PDGFA-assaociated protein 1(PDAP1), is found to suppress basal-like breast tumor growth in a mouse model. Omics and mechanistic studies revealed that ferroptosis is associated with enhanced lysosomal function, glutaminolysis, and the tricarboxylic acid (TCA) cycle, while its transition into apoptosis is attributed to enhanced endoplasmic reticulum(ER)-stress and phosphatidylethanolamine (PE)-to-phosphatidylcholine (PC) metabolic shift. Collectively, this study highlights molecular mechanisms underlying ferroptosis execution, identified a highly predictive ferroptosis gene signature with prognostic value, ferroptosis versus apoptosis biomarkers, and ferroptosis repressors for breast cancer therapy.

A Nonheme Iron(III) Superoxide Complex Leads to Sulfur Oxygenation

A new alkylthiolate-ligated nonheme iron complex, FeII(BNPAMe2S)Br (1), is reported. Reaction of 1 with O2 at -40 °C, or reaction of the ferric form with O2•- at -80 °C, gives a rare iron(III)-superoxide intermediate, [FeIII(O2)(BNPAMe2S)]+ (2), characterized by UV-vis, 57Fe Mössbauer, ATR-FTIR, EPR, and CSIMS. Metastable 2 then converts to an S-oxygenated FeII(sulfinate) product via a sequential O atom transfer mechanism involving an iron-sulfenate intermediate. These results provide evidence for the feasibility of proposed intermediates in thiol dioxygenases.

Taurine deficiency associated with dilated cardiomyopathy and aging

Taurine (2-aminoethanesulfonic acid) is a free amino acid found ubiquitously and abundantly in mammalian tissues. Taurine content in the heart is approximately 20 mM, which is approximately 100 times higher than plasma concentration. The high intracellular concentration of taurine is maintained by the taurine transporter (TauT; Slc6a6). Taurine plays various roles, including the regulation of intracellular ion dynamics, calcium handling, and acting as an antioxidant in the heart. Some species, such as cats and foxes, have low taurine biosynthetic capacity, and dietary taurine deficiency can lead to disorders such as dilated cardiomyopathy and blindness. In humans, the relationship between dietary taurine deficiency and cardiomyopathy is not yet clear, but a genetic mutation related to the taurine transporter has been reported to be associated with dilated cardiomyopathy. On the other hand, many studies have shown an association between dietary taurine intake and age-related diseases. Notably, it has recently been reported that taurine declines with age and is associated with lifespan in worms and mice, as well as healthspan in mice and monkeys. In this review, we summarize the role of dietary and genetic taurine deficiency in the development of cardiomyopathy and aging.

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.

L-cysteine ethylester reverses the adverse effects of morphine on breathing and arterial blood-gas chemistry while minimally affecting antinociception in unanesthetized rats

L-cysteine ethylester (L-CYSee) is a membrane-permeable analogue of L-cysteine with a variety of pharmacological effects. The purpose of this study was to determine the effects of L-CYSee on morphine-induced changes in ventilation, arterial-blood gas (ABG) chemistry, Alveolar-arterial (A-a) gradient (i.e., a measure of the index of alveolar gas-exchange), antinociception and sedation in male Sprague Dawley rats. An injection of morphine (10 mg/kg, IV) produced adverse effects on breathing, including sustained decreases in minute ventilation. L-CYSee (500 μmol/kg, IV) given 15 min later immediately reversed the actions of morphine. Another injection of L-CYSee (500 μmol/kg, IV) after 15 min elicited more pronounced excitatory ventilatory responses. L-CYSee (250 or 500 μmol/kg, IV) elicited a rapid and prolonged reversal of the actions of morphine (10 mg/kg, IV) on ABG chemistry (pH, pCO2, pO2, sO2) and A-a gradient. L-serine ethylester (an oxygen atom replaces the sulfur; 500 μmol/kg, IV), was ineffective in all studies. L-CYSee (500 μmol/kg, IV) did not alter morphine (10 mg/kg, IV)-induced sedation, but slightly reduced the overall duration of morphine (5 or 10 mg/kg, IV)-induced analgesia. In summary, L-CYSee rapidly overcame the effects of morphine on breathing and alveolar gas-exchange, while not affecting morphine sedation or early-stage analgesia. The mechanisms by which L-CYSee modulates morphine depression of breathing are unknown, but appear to require thiol-dependent processes.

Dietary sulfur amino acid restriction in humans with overweight and obesity: a translational randomized controlled trial

BACKGROUND

Dietary sulfur amino acid restriction (SAAR) improves metabolic health in animals. In this study, we investigated the effect of dietary SAAR on body weight, body composition, resting metabolic rate, gene expression profiles in white adipose tissue (WAT), and an extensive blood biomarker profile in humans with overweight or obesity.

METHODS

N = 59 participants with overweight or obesity (73% women) were randomized stratified by sex to an 8-week plant-based dietary intervention low (~ 2 g/day, SAAR) or high (~ 5.6 g/day, control group) in sulfur amino acids. The diets were provided in full to the participants, and both investigators and participants were blinded to the intervention. Outcome analyses were performed using linear mixed model regression adjusted for baseline values of the outcome and sex.

RESULTS

SAAR led to a ~ 20% greater weight loss compared to controls (β 95% CI - 1.14 (- 2.04, - 0.25) kg, p = 0.013). Despite greater weight loss, resting metabolic rate remained similar between groups. Furthermore, SAAR decreased serum leptin, and increased ketone bodies compared to controls. In WAT, 20 genes were upregulated whereas 24 genes were downregulated (FDR < 5%) in the SAAR group compared to controls. Generally applicable gene set enrichment analyses revealed that processes associated with ribosomes were upregulated, whereas processes related to structural components were downregulated.

CONCLUSION

Our study shows that SAAR leads to greater weight loss, decreased leptin and increased ketone bodies compared to controls. Further research on SAAR is needed to investigate the therapeutic potential for metabolic conditions in humans.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT04701346, registered Jan 8th 2021, https://www.

CLINICALTRIALS

gov/study/NCT04701346.

Low feed intake at weaning reduces intestinal glutathione levels and promotes cysteine oxidation to taurine in pigs

Weaning stress in pigs is associated with low feed intake and poor nutrient utilization. Cysteine is a sulfur amino acid with key roles in pig production, but how cysteine metabolism and requirements are affected by weaning stress should be better defined. The objective of this study was to determine the collective impact of weaning and feed restriction on tissue cysteine metabolism. Pigs were weaned at 21-d age without access to feed (W; 6.90 ± 0.81 kg; n = 9; reflecting acute nutritional stress) or were not weaned and remained with the sow (nonweaned [NW]; 6.81 ± 0.65 kg; n = 8). At euthanasia (23-d age), blood, bile, liver, jejunum, and ileum tissues were collected. Plasma, bile, and tissue amino acid and amino thiol concentrations were analyzed by HPLC. The activity of glutamate cysteine ligase (GCL) and glutathione synthetase (GSS), enzymes needed for glutathione (GSH) production, and cysteine dioxygenase 1 (CDO1) were determined with activity assays followed by HPLC analysis of reaction products. Plasma (271 vs. 192 ± 19 µmol/L; P < 0.001) and liver (417 vs. 298 ± 33 nmol/g; P < 0.05) Cys concentrations were increased in W compared to NW pigs. Despite greater plasma Cys, jejunum and ileum Cys content were not affected by weaning (P > 0.10), whereas γ-glutamylcysteine (γ-GlyCys), the immediate precursor of GSH, declined in both jejunum (14.3 vs. 9.7 ± 1.4 nmol/g; P < 0.01) and ileum (11.2 vs. 6.4 ± 0.8 nmol/g; P < 0.001) in W pigs. Glutathione content was lower in the jejunum (1,379 vs. 1,720 ± 70 nmol/g; P < 0.05) and ileum (1,497 vs. 1,740 ± 74 nmol/g; P < 0.05) in W pigs. In the jejunum, GCL activity tended to be greater (0.56 vs. 0.39 ± 0.07 nmol γ-GluCys • mg-1 • min-1; P < 0.10), whereas GSS activity tended to be lower (1.11 vs. 1.38 ± 0.10 nmol GSH • mg-1 • min-1; P < 0.10) in W compared to NW pigs. In the ileum, the activities of GCL and GSS were not affected by weaning (P > 0.10). Although liver CDO1 activity was not different between groups (P < 0.10), liver taurine was greater in W compared to NW pigs (5,115 vs. 2,336 ± 912 nmol/g; P = 0.001). Bile concentrations of Cys (1,203 vs. 279 ± 103 µmol/L; P < 0.001) and cysteinylglycine (203 vs. 117 ± 33 µmol/L; P < 0.10), the direct product of GSH degradation, were greater in W compared to NW pigs. Collectively, these results suggest that systemic Cys is not effectively utilized for gut GSH production in newly weaned pigs; instead, it is oxidized to taurine and eliminated in bile.

Ferroptosis resistance in cancer: recent advances and future perspectives

Ferroptosis is an iron-dependent, non-apoptotic form of regulated cell death and has been implicated in the occurrence and development of various diseases, including heart disease, nervous system diseases and cancer. Ferroptosis induction recently emerged as an attractive strategy for cancer therapy. Ferroptosis has become a potential target for intervention in these diseases or injuries in relevant preclinical models. This review summarizes recent progress on the mechanisms of ferroptosis resistance in cancer, highlights redox status and metabolism's role in it. Combination therapy for ferroptosis has great potential in cancer treatment, especially malignant tumors that are resistant to conventional therapies. This review will lead us to have a comprehensive understanding of the future exploration of ferroptosis and cancer therapy. A deeper understanding of the relationship between ferroptosis resistance and metabolism reprogramming may provide new strategies for tumor treatment and drug development based on ferroptosis.

Function of taurine and its synthesis-related genes in hypertonic regulation of Sinonovacula constricta

Salinity changes affect the osmotic gradient across the gill epithelium of marine species. Taurine is an important osmoregulator with a crucial role in osmoregulation in marine bivalves. This study determined the osmolality, taurine content, key enzymes involved in taurine synthesis (cysteine dioxygenase (CDO), cysteine sulfinic acid decarboxylase (CSAD), and taurine transporter (TauT)) and related gene expression in razor clam Sinonovacula constricta in response to high salt stress [high salt seawater (S30) versus high salt seawater with taurine supplementation (S30T) versus natural salinity control]. The data were recorded at 0, 6, 12, 24, 48, 72 h. Serum osmolality significantly increased under high salt conditions compared with the control group (P < 0.05). When serum osmolality had stabilized (after 48 h), there was no significant difference in serum osmolality between the S30T and control groups (P > 0.05), but serum osmolality was significantly lower in the S30 versus control group (P < 0.05). Taurine content significantly increased under high salt stress and remained high (P < 0.05). CSAD and CDO content was higher in S30 than in S30T, whereas TauT was significantly lower in S30 than in the control group eventually (P < 0.05). Expression of CDO and CSAD in the S30 and S30T groups was significantly higher than in control animals (P < 0.05), with that in S30 being higher than in S30T. By contrast, TauT expression peaked 6 h after stress in S30 and S30T, but was lower in S30 than in the control group (P < 0.05). These results demonstrate that S. constricta is an osmoconformer, with exogenous taurine relieving the stress of osmoregulation caused by insufficient endogenous taurine in cells. These findings further enhance our understanding of the regulatory mechanisms underlying the response of S. constricta to high salinity stress.

L-cysteine ethyl ester prevents and reverses acquired physical dependence on morphine in male Sprague Dawley rats

The molecular mechanisms underlying the acquisition of addiction/dependence on morphine may result from the ability of the opioid to diminish the transport of L-cysteine into neurons via inhibition of excitatory amino acid transporter 3 (EAA3). The objective of this study was to determine whether the co-administration of the cell-penetrant L-thiol ester, L-cysteine ethyl ester (L-CYSee), would reduce physical dependence on morphine in male Sprague Dawley rats. Injection of the opioid-receptor antagonist, naloxone HCl (NLX; 1.5 mg/kg, IP), elicited pronounced withdrawal phenomena in rats which received a subcutaneous depot of morphine (150 mg/kg) for 36 h and were receiving a continuous infusion of saline (20 μL/h, IV) via osmotic minipumps for the same 36 h period. The withdrawal phenomena included wet-dog shakes, jumping, rearing, fore-paw licking, 360° circling, writhing, apneas, cardiovascular (pressor and tachycardia) responses, hypothermia, and body weight loss. NLX elicited substantially reduced withdrawal syndrome in rats that received an infusion of L-CYSee (20.8 μmol/kg/h, IV) for 36 h. NLX precipitated a marked withdrawal syndrome in rats that had received subcutaneous depots of morphine (150 mg/kg) for 48 h) and a co-infusion of vehicle. However, the NLX-precipitated withdrawal signs were markedly reduced in morphine (150 mg/kg for 48 h)-treated rats that began receiving an infusion of L-CYSee (20.8 μmol/kg/h, IV) at 36 h. In similar studies to those described previously, neither L-cysteine nor L-serine ethyl ester (both at 20.8 μmol/kg/h, IV) mimicked the effects of L-CYSee. This study demonstrates that 1) L-CYSee attenuates the development of physical dependence on morphine in male rats and 2) prior administration of L-CYSee reverses morphine dependence, most likely by intracellular actions within the brain. The lack of the effect of L-serine ethyl ester (oxygen atom instead of sulfur atom) strongly implicates thiol biochemistry in the efficacy of L-CYSee. Accordingly, L-CYSee and analogs may be a novel class of therapeutics that ameliorate the development of physical dependence on opioids in humans.

Molecular Mechanisms of Ferroptosis and Its Role in Viral Pathogenesis

Ferroptosis is a novelty form of regulated cell death, and it is mainly characterized by iron accumulation and lipid peroxidation in the cells. Its underlying mechanism is related to the amino acid, iron, and lipid metabolisms. During viral infection, pathogenic microorganisms have evolved to interfere with ferroptosis, and ferroptosis is often manipulated by viruses to regulate host cell servicing for viral reproduction. Therefore, this review provides a comprehensive overview of the mechanisms underlying ferroptosis, elucidates the intricate signaling pathways involved, and explores the pivotal role of ferroptosis in the pathogenesis of viral infections. By enhancing our understanding of ferroptosis, novel therapeutic strategies can be devised to effectively prevent and treat diseases associated with this process. Furthermore, unraveling the developmental mechanisms through which viral infections exploit ferroptosis will facilitate development of innovative antiviral agents.

Longitudinal dynamics of the tumor hypoxia response: From enzyme activity to biological phenotype

Poor oxygenation (hypoxia) is a common spatially heterogeneous feature of human tumors. Biological responses to tumor hypoxia are orchestrated by the decreased activity of oxygen-dependent enzymes. The affinity of these enzymes for oxygen positions them along a continuum of oxygen sensing that defines their roles in launching reactive and adaptive cellular responses. These responses encompass regulation of all steps in the central dogma, with rapid perturbation of the metabolome and proteome followed by more persistent reprogramming of the transcriptome and epigenome. Core hypoxia response genes and pathways are commonly regulated at multiple inflection points, fine-tuning the dependencies on oxygen concentration and hypoxia duration. Ultimately, shifts in the activity of oxygen-sensing enzymes directly or indirectly endow cells with intrinsic hypoxia tolerance and drive processes that are associated with aggressive phenotypes in cancer including angiogenesis, migration, invasion, immune evasion, epithelial mesenchymal transition, and stemness.

Targeted demethylation of the CDO1 promoter based on CRISPR system inhibits the malignant potential of breast cancer cells

BACKGROUND

Cysteine dioxygenase 1 (CDO1) is frequently methylated, and its expression is decreased in many human cancers including breast cancer (BC). However, the functional and mechanistic aspects of CDO1 inactivation in BC are poorly understood, and the diagnostic significance of serum CDO1 methylation remains unclear.

METHODS

We performed bioinformatics analysis of publicly available databases and employed MassARRAY EpiTYPER methylation sequencing technology to identify differentially methylated sites in the CDO1 promoter of BC tissues compared to normal adjacent tissues (NATs). Subsequently, we developed a MethyLight assay using specific primers and probes for these CpG sites to detect the percentage of methylated reference (PMR) of the CDO1 promoter. Furthermore, both LentiCRISPR/dCas9-Tet1CD-based CDO1-targeted demethylation system and CDO1 overexpression strategy were utilized to detect the function and underlying mechanism of CDO1 in BC. Finally, the early diagnostic value of CDO1 as a methylation biomarker in BC serum was evaluated.

RESULTS

CDO1 promoter was hypermethylated in BC tissues, which was related to poor prognosis (p < .05). The CRISPR/dCas9-based targeted demethylation system significantly reduced the PMR of CDO1 promotor and increased CDO1 expression in BC cells. Consequently, this leads to suppression of cell proliferation, migration and invasion. Additionally, we found that CDO1 exerted a tumour suppressor effect by inhibiting the cell cycle, promoting cell apoptosis and ferroptosis. Furthermore, we employed the MethyLight to detect CDO1 PMR in BC serum, and we discovered that serum CDO1 methylation was an effective non-invasive biomarker for early diagnosis of BC.

CONCLUSIONS

CDO1 is hypermethylated and acts as a tumour suppressor gene in BC. Epigenetic editing of abnormal CDO1 methylation could have a crucial role in the clinical treatment and prognosis of BC. Additionally, serum CDO1 methylation holds promise as a valuable biomarker for the early diagnosis and management of BC.

The transcription factor HBP1 promotes ferroptosis in tumor cells by regulating the UHRF1-CDO1 axis

The induction of ferroptosis in tumor cells is one of the most important mechanisms by which tumor progression can be inhibited; however, the specific regulatory mechanism underlying ferroptosis remains unclear. In this study, we found that transcription factor HBP1 has a novel function of reducing the antioxidant capacity of tumor cells. We investigated the important role of HBP1 in ferroptosis. HBP1 down-regulates the protein levels of UHRF1 by inhibiting the expression of the UHRF1 gene at the transcriptional level. Reduced levels of UHRF1 have been shown to regulate the ferroptosis-related gene CDO1 by epigenetic mechanisms, thus up-regulating the level of CDO1 and increasing the sensitivity of hepatocellular carcinoma and cervical cancer cells to ferroptosis. On this basis, we constructed metal-polyphenol-network coated HBP1 nanoparticles by combining biological and nanotechnological. MPN-HBP1 nanoparticles entered tumor cells efficiently and innocuously, induced ferroptosis, and inhibited the malignant proliferation of tumors by regulating the HBP1-UHRF1-CDO1 axis. This study provides a new perspective for further research on the regulatory mechanism underlying ferroptosis and its potential role in tumor therapy.

A Single DNA Point Mutation Leads to the Formation of a Cysteine-Tyrosine Crosslink in the Cysteine Dioxygenase from Bacillus subtilis

Cysteine dioxygenase (CDO) is a non-heme iron-containing enzyme that catalyzes the oxidation of cysteine (Cys) to cysteine sulfinic acid (CSA). Crystal structures of eukaryotic CDOs revealed the presence of an unusual crosslink between the sulfur of a cysteine residue (C93 in Mus musculus CDO, MmCDO) and a carbon atom adjacent to the phenyl group of a tyrosine residue (Y157). Formation of this crosslink occurs over time as a byproduct of catalysis and increases the catalytic efficiency of CDO by at least 10-fold. Interestingly, in bacterial CDOs, the residue corresponding to C93 is replaced by a highly conserved glycine (G82 in Bacillus subtilis CDO, BsCDO), which precludes the formation of a C-Y crosslink in these enzymes; yet bacterial CDOs achieve turnover rates paralleling those of fully crosslinked eukaryotic CDOs. In the present study, we prepared the G82C variant of BsCDO to determine if a single DNA point mutation could lead to C-Y crosslink formation in this enzyme. We used gel electrophoresis, peptide mass spectrometry, electron paramagnetic resonance spectroscopy, and kinetic assays to characterize this variant alongside the natively crosslinked wild-type (WT) MmCDO and the natively non-crosslinked WT BsCDO. Collectively, our results provide compelling evidence that the G82C BsCDO variant is indeed capable of C-Y crosslink formation. Our kinetic studies indicate that G82C BsCDO has a reduced catalytic efficiency compared to WT BsCDO and that activity increases as the ratio of crosslinked to non-crosslinked enzyme increases. Finally, by carrying out a bioinformatic analysis of the CDO family, we were able to identify a large number of putatively crosslinked bacterial CDOs, the majority of which are from Gram-negative pathogenic bacteria.

Critical Roles of the Cysteine-Glutathione Axis in the Production of γ-Glutamyl Peptides in the Nervous System

γ-Glutamyl moiety that is attached to the cysteine (Cys) residue in glutathione (GSH) protects it from peptidase-mediated degradation. The sulfhydryl group of the Cys residue represents most of the functions of GSH, which include electron donation to peroxidases, protection of reactive sulfhydryl in proteins via glutaredoxin, and glutathione conjugation of xenobiotics, whereas Cys-derived sulfur is also a pivotal component of some redox-responsive molecules. The amount of Cys that is available tends to restrict the capacity of GSH synthesis. In in vitro systems, cystine is the major form in the extracellular milieu, and a specific cystine transporter, xCT, is essential for survival in most lines of cells and in many primary cultivated cells as well. A reduction in the supply of Cys causes GPX4 to be inhibited due to insufficient GSH synthesis, which leads to iron-dependent necrotic cell death, ferroptosis. Cells generally cannot take up GSH without the removal of γ-glutamyl moiety by γ-glutamyl transferase (GGT) on the cell surface. Meanwhile, the Cys-GSH axis is essentially common to certain types of cells; primarily, neuronal cells that contain a unique metabolic system for intercellular communication concerning γ-glutamyl peptides. After a general description of metabolic processes concerning the Cys-GSH axis, we provide an overview and discuss the significance of GSH-related compounds in the nervous system.

Insights into the keratin efficient degradation mechanism mediated by Bacillus sp. CN2 based on integrating functional degradomics

BACKGROUND

Keratin, the main component of chicken feather, is the third most abundant material after cellulose and chitin. Keratin can be converted into high-value compounds and is considered a potential high-quality protein supplement; However, its recalcitrance makes its breakdown a challenge, and the mechanisms of action of keratinolytic proteases-mediated keratinous substrates degradation are not yet fully elucidated. Bacillus sp. CN2, having many protease-coding genes, is a dominant species in keratin-rich materials environments. To explore the degradation patterns of feather keratin, in this study, we investigated the characteristics of feather degradation by strain CN2 based on the functional-degradomics technology.

RESULTS

Bacillus sp. CN2 showed strong feather keratin degradation activities, which could degrade native feathers efficiently resulting in 86.70% weight loss in 24 h, along with the production of 195.05 ± 6.65 U/mL keratinases at 48 h, and the release of 0.40 mg/mL soluble proteins at 60 h. The extracellular protease consortium had wide substrate specificity and exhibited excellent biodegradability toward soluble and insoluble proteins. Importantly, analysis of the extracellular proteome revealed the presence of a highly-efficient keratin degradation system. Firstly, T3 γ-glutamyltransferase provides a reductive force to break the dense disulfide bond structure of keratin. Then S8B serine endopeptidases first hydrolyze keratin to expose more cleavage sites. Finally, keratin is degraded into small peptides under the synergistic action of proteases such as M4, S8C, and S8A. Consistent with this, high-performance liquid chromatography (HPLC) and amino acid analysis showed that the feather keratin hydrolysate contained a large number of soluble peptides and essential amino acids.

CONCLUSIONS

The specific expression of γ-glutamyltransferase and co-secretion of endopeptidase and exopeptidase by the Bacillus sp. CN2 play an important role in feather keratin degradation. This insight increases our understanding of the keratinous substrate degradation and may inspire the design of the optimal enzyme cocktails for more efficient exploration of protein resources in industrial applications.

New Methylcitrate Synthase Inhibitor Induces Proteolysis, Lipid Degradation and Pyruvate Excretion in Paracoccidioides brasiliensis

BACKGROUND

Paracoccidioidomycosis is a systemic mycosis caused by the inhalation of conidia of the genus Paracoccidioides. During the infectious process, fungal cells use several carbon sources, leading to the production of propionyl-CoA. The latter is metabolized by the methylcitrate synthase, a key enzyme of the methylcitrate cycle. We identified an inhibitor compound (ZINC08964784) that showed antifungal activity against P. brasiliensis.

METHODS

This work aimed to understand the fungal metabolic response of P. brasiliensis cells exposed to ZINC08964784 through a proteomics approach. We used a glucose-free medium supplemented with propionate in order to simulate the environment found by the pathogen during the infection. We performed pyruvate dosage, proteolytic assay, dosage of intracellular lipids and quantification of reactive oxygen species in order to validate the proteomic results.

RESULTS

The proteomic analysis indicated that the fungal cells undergo a metabolic shift due to the inhibition of the methylcitrate cycle and the generation of reactive species. Proteolytic enzymes were induced, driving amino acids into degradation for energy production. In addition, glycolysis and the citric acid cycle were down-regulated while ß-oxidation was up-regulated. The accumulation of pyruvate and propionyl-CoA led the cells to a state of oxidative stress in the presence of ZINC08964784.

CONCLUSIONS

The inhibition of methylcitrate synthase caused by the compound promoted a metabolic shift in P. brasiliensis damaging energy production and generating oxidative stress. Hence, the compound is a promising alternative for developing new strategies of therapies against paracoccidioidomycosis.

TP73 Isoform-specific disruption reveals a critical role of TAp73beta in growth suppression and inflammatory response

TP73 is expressed as multiple N- and C-terminal isoforms through two separate promoters or alternative splicing. While N-terminal p73 isoforms have been well studied, very little is known about p73 C-terminal isoforms. Thus, CRISPR was used to delete TP73 Exon13 (E13-KO) to induce p73α to p73β isoform switch. We showed that E13-KO led to decreased cell proliferation and migration and sensitized cells to ferroptosis, which can be reverted by knockdown of TAp73β in E13-KO cells. To understand the biological function of p73β in vivo, we generated a mouse model in that the Trp73 E13 was deleted by CRISPR. We showed that p73α to p73β isoform switch led to increased cellular senescence in mouse embryonic fibroblasts. We also showed that E13-deficient mice exhibited shorter life span and were prone to spontaneous tumors, chronic inflammation and liver steatosis as compared to WT mice. Additionally, we found that the incidence of chronic inflammation and liver steatosis was higher in E13-deficient mice than that in Trp73-deficient mice, suggesting that p73β is a strong inducer of inflammatory response. Mechanistically, we showed that TAp73β was able to induce cysteine dioxygenase 1 (CDO-1), leading to cysteine depletion and subsequently, enhanced ferroptosis and growth suppression. Conversely, knockdown of CDO-1 was able to alleviate the growth suppression and ferroptosis in E13-KO cells. Together, our data suggest that at a physiologically relevant level, TAp73β is a strong inducer of growth suppression but insufficient to compensate for loss of TAp73α in tumor suppression due to aberrant induction of inflammatory response and liver steatosis.

Unique features of regulation of sulfate assimilation in monocots

Sulfate assimilation is an essential pathway of plant primary metabolism, regulated by the demand for reduced sulfur (S). The S-containing tripeptide glutathione (GSH) is the key signal for such regulation in Arabidopsis, but little is known about the conservation of these regulatory mechanisms beyond this model species. Using two model monocot species, C3 rice (Oryza sativa) and C4Setaria viridis, and feeding of cysteine or GSH, we aimed to find out how conserved are the regulatory mechanisms described for Arabidopsis in these species. We showed that while in principle the regulation is similar, there are many species-specific differences. For example, thiols supplied by the roots are translocated to the shoots in rice but remain in the roots of Setaria. Cysteine and GSH concentrations are highly correlated in Setaria, but not in rice. In both rice and Setaria, GSH seems to be the signal for demand-driven regulation of sulfate assimilation. Unexpectedly, we observed cysteine oxidation to sulfate in both species, a reaction that does not occur in Arabidopsis. This reaction is dependent on sulfite oxidase, but the enzyme(s) releasing sulfite from cysteine still need to be identified. Altogether our data reveal a number of unique features in the regulation of S metabolism in the monocot species and indicate the need for using multiple taxonomically distinct models to better understand the control of nutrient homeostasis, which is important for generating low-input crop varieties.

L-cysteine methyl ester overcomes the deleterious effects of morphine on ventilatory parameters and arterial blood-gas chemistry in unanesthetized rats

We are developing a series of thiolesters that produce an immediate and sustained reversal of the deleterious effects of opioids, such as morphine and fentanyl, on ventilation without diminishing the antinociceptive effects of these opioids. We report here the effects of systemic injections of L-cysteine methyl ester (L-CYSme) on morphine-induced changes in ventilatory parameters, arterial-blood gas (ABG) chemistry (pH, pCO₂, pO₂, sO₂), Alveolar-arterial (A-a) gradient (i.e., the index of alveolar gas-exchange within the lungs), and antinociception in unanesthetized Sprague Dawley rats. The administration of morphine (10 mg/kg, IV) produced a series of deleterious effects on ventilatory parameters, including sustained decreases in tidal volume, minute ventilation, inspiratory drive and peak inspiratory flow that were accompanied by a sustained increase in end inspiratory pause. A single injection of L-CYSme (500 μmol/kg, IV) produced a rapid and long-lasting reversal of the deleterious effects of morphine on ventilatory parameters, and a second injection of L-CYSme (500 μmol/kg, IV) elicited pronounced increases in ventilatory parameters, such as minute ventilation, to values well above pre-morphine levels. L-CYSme (250 or 500 μmol/kg, IV) also produced an immediate and sustained reversal of the deleterious effects of morphine (10 mg/kg, IV) on arterial blood pH, pCO₂, pO₂, sO₂ and A-a gradient, whereas L-cysteine (500 μmol/kg, IV) itself was inactive. L-CYSme (500 μmol/kg, IV) did not appear to modulate the sedative effects of morphine as measured by righting reflex times, but did diminish the duration, however, not the magnitude of the antinociceptive actions of morphine (5 or 10 mg/kg, IV) as determined in tail-flick latency and hindpaw-withdrawal latency assays. These findings provide evidence that L-CYSme can powerfully overcome the deleterious effects of morphine on breathing and gas-exchange in Sprague Dawley rats while not affecting the sedative or early stage antinociceptive effects of the opioid. The mechanisms by which L-CYSme interferes with the OR-induced signaling pathways that mediate the deleterious effects of morphine on ventilatory performance, and by which L-CYSme diminishes the late stage antinociceptive action of morphine remain to be determined.

Effects of dietary L-Proline and L-Alanine on growth performance, and flesh quality of common carp (Cyprinus carpio) juveniles

The purpose of the present study was to investigate the effects of amino acids L-Proline and LAlanine on growth performance, amino acid, and fatty acid levels in the fillet of juvenile common carp. 450 juvenile common carp were randomly distributed in 30 tanks and fed with three levels of proline (5 [P5], 10 [P10], and 15 [P15] g/kg), three levels of Alanine [A] (5 [A5], 10 [A10], and 15 [A15] g/kg), three levels of proline-alanine combination [PA] (2.5 + 2.5 [2.5PA], 5 + 5 [5PA], 7.5 + 7.5 [7.5PA] g/kg feed) and basal diet (control). The highest body weight gain (25.85 ± 0.1 g) and survival rate (91.11 ± 3.84) were observed in 7.5 PA treatment. The highest protein content (64.58 ± 0.49) was noticed in 2.5 PA; however, compared to combined treatments (5 PA and 2.5 PA), it did not show any significant difference (p<0.05). The highest total amount of essential amino acids (48.30 ± 48.3) were observed in 7.5 PA treatment. The highest amount of DHA (5.65 ± 0.08), total EPA, and DHA (8.91 ± 0.13) were in 7.5 PA treatment. Finally, it can be concluded that two amino acids of L-Proline and L-Alanine at the combined level of 5 PA can improve the growth performance, survival, and fillet composition in the juvenile common carp.

System Xc−/GSH/GPX4 axis: An important antioxidant system for the ferroptosis in drug-resistant solid tumor therapy

The activation of ferroptosis is a new effective way to treat drug-resistant solid tumors. Ferroptosis is an iron-mediated form of cell death caused by the accumulation of lipid peroxides. The intracellular imbalance between oxidant and antioxidant due to the abnormal expression of multiple redox active enzymes will promote the produce of reactive oxygen species (ROS). So far, a few pathways and regulators have been discovered to regulate ferroptosis. In particular, the cystine/glutamate antiporter (System Xc−), glutathione peroxidase 4 (GPX4) and glutathione (GSH) (System Xc−/GSH/GPX4 axis) plays a key role in preventing lipid peroxidation-mediated ferroptosis, because of which could be inhibited by blocking System Xc−/GSH/GPX4 axis. This review aims to present the current understanding of the mechanism of ferroptosis based on the System Xc−/GSH/GPX4 axis in the treatment of drug-resistant solid tumors.

Metabolic profile of exhaled breath condensate from the pneumonia patients

PURPOSE OF THE STUDY

Exhaled breath condensate (EBC) is increasingly being used for disease diagnosis and environmental exposure assessment as a noninvasive method reducing the risk of exposure. The purpose of this study was to investigate the application of a new sample type of EBC in pneumonia by metabolomics and to explore differential metabolites and potential metabolic pathways.

MATERIALS AND METHODS

A case-control study was performed at the Peking University Third Hospital from August to December 2020. C-MS/MS analyses were performed on EBC samples using a UHPLC system.

RESULTS

Totally 22 patients with pneumonia and 24 healthy controls were recruited. Using untargeted metabolomics based on LC-MS/MS analysis, 25 kinds of differential metabolites were found. Through a comprehensive analysis of the pathways in which the differential metabolites were located, the key pathway with the highest correlation with the difference of metabolites was taurine and hypotaurine metabolism.

CONCLUSIONS

The study implicates that the hypotaurine/taurine metabolic pathway may play a role on the development of pneumonia through metabolism analysis on EBC and the 3-Sulfinoalanine may be used as a biomarker in the diagnosis of pneumonia.

A Resourceful Race: Bacterial Scavenging of Host Sulfur Metabolism during Colonization

Sulfur is a requirement for life. Therefore, both the host and colonizing bacteria must regulate sulfur metabolism in a coordinated fashion to meet cellular demands. The host environment is a rich source of organic and inorganic sulfur metabolites that are utilized in critical physiological processes such as redox homeostasis and cellular signaling. As such, modulating enzymes dedicated to sulfur metabolite biosynthesis plays a vital role in host fitness. This is exemplified from a molecular standpoint through layered regulation of this machinery at the transcriptional, translational, and posttranslational levels. With such a diverse metabolite pool available, pathogens and symbionts have evolved multiple mechanisms to exploit sulfur reservoirs to ensure propagation within the host. Indeed, characterization of sulfur transporters has revealed that bacteria employ multiple tactics to acquire ideal sulfur sources, such as cysteine and its derivatives. However, bacteria that employ acquisition strategies targeting multiple sulfur sources complicate in vivo studies that investigate how specific sulfur metabolites support proliferation. Furthermore, regulatory systems controlling the bacterial sulfur regulon are also multifaceted. This too creates an interesting challenge for in vivo work focused on bacterial regulation of sulfur metabolism in response to the host. This review examines the importance of sulfur at the host-bacterium interface and the elegant studies conducted to define this interaction.

Metabolic Basis and Clinical Evidence for Skin Lightening Effects of Thiol Compounds

Melanin pigment is a major factor in determining the color of the skin, and its abnormal increase or decrease can cause serious pigmentation disorders. The melanin pigment of the skin is divided into light pheomelanin and dark eumelanin, and a big difference between them is whether they contain sulfur. Melanin synthesis starts from a common reaction in which tyrosine or dihydroxyphenylalanine (DOPA) is oxidized by tyrosinase (TYR) to produce dopaquinone (DQ). DQ is spontaneously converted to leukodopachrome and then oxidized to dopachrome, which enters the eumelanin synthesis pathway. When DQ reacts with cysteine, cysteinyl dopa is generated, which is oxidized to cysteinyl DQ and enters the pheomelanin synthesis pathway. Therefore, thiol compounds can influence the relative synthesis of eumelanin and pheomelanin. In addition, thiol compounds can inhibit enzymatic activity by binding to copper ions at the active site of TYR, and act as an antioxidant scavenging reactive oxygen species and free radicals or as a modulator of redox balance, thereby inhibiting overall melanin synthesis. This review will cover the metabolic aspects of thiol compounds, the role of thiol compounds in melanin synthesis, comparison of the antimelanogenic effects of various thiol compounds, and clinical trials on the skin lightening efficacy of thiol compounds. We hope that this review will help identify the advantages and disadvantages of various thiol compounds as modulators of skin pigmentation and contribute to the development of safer and more effective strategies for the treatment of pigmentation disorders.

Cysteine as a Multifaceted Player in Kidney, the Cysteine-Related Thiolome and Its Implications for Precision Medicine

In this review encouraged by original data, we first provided in vivo evidence that the kidney, comparative to the liver or brain, is an organ particularly rich in cysteine. In the kidney, the total availability of cysteine was higher in cortex tissue than in the medulla and distributed in free reduced, free oxidized and protein-bound fractions (in descending order). Next, we provided a comprehensive integrated review on the evidence that supports the reliance on cysteine of the kidney beyond cysteine antioxidant properties, highlighting the relevance of cysteine and its renal metabolism in the control of cysteine excess in the body as a pivotal source of metabolites to kidney biomass and bioenergetics and a promoter of adaptive responses to stressors. This view might translate into novel perspectives on the mechanisms of kidney function and blood pressure regulation and on clinical implications of the cysteine-related thiolome as a tool in precision medicine.

Modulation of Human Hydrogen Sulfide Metabolism by Micronutrients, Preliminary Data

BACKGROUND

Hydrogen sulfide (H2S) is a pivotal gasotransmitter networking with nitric oxide (NO) and carbon monoxide (CO) to regulate basic homeostatic functions. It is released by the alternative pathways of transulfuration by the enzymes Cystathionine Beta Synthase (CBS) and Cystathionine Gamma Lyase (CSE), and by Cysteine AminoTransferase (CAT)/ 3-Mercaptopyruvate Sulfur Transferase (3MPST). A non-enzymatic, intravascular release is also in place. We retrospectively investigated the possibility to modulate the endogenous H2S release and signaling in humans by a dietary manipulation with supplemented micronutrients (L-cystine, Taurine and pyridoxal 5-phopsphate/P5P).

METHODS

Patients referring for antiaging purposes underwent a 10-day supplementation. Blood was collected at baseline and after treatment and the metabolome was investigated by mass spectrometry to monitor the changes in the metabolites reporting on H2S metabolism and related pathways.

RESULTS

Data were available from 6 middle aged subjects (2 women). Micronutrients increased 3-mercaptopyruvate (P = .03), reporting on the activity of CAT that provides the substrate for H2S release within mitochondria by 3MPST, decreased lanthionine (P = .024), reporting the release of H2S from CBS, and had no significant effect of H2S release from CSE. This is compatible with a homeostatic balancing. We also recorded a strong increase of reporters of H2S-induced pathways including 5-MethylTHF (P = .001) and SAME (P = .022), reporting on methylation capacity, and of BH4 (P = .021) and BH2 (P = .028) reporting on nitric oxide metabolism. These activations may be explained by the concomitant induction of non-enzymatic release of H2S.

CONCLUSIONS

Although the current evidences are weak and will need to be confirmed, the effect of micronutrients was compatible with an increase of the H2S endogenous release and signaling within the control of homeostatic mechanisms, further endorsing the role of feeding in health and disease. These effects might result in a H2S boosting effect in case of defective activity of pathologic origin, which should be checked in duly designed clinical trials.

High cysteine diet reduces insulin resistance in SHR-CRP rats

Increased plasma total cysteine (tCys) has been associated with obesity and metabolic syndrome in human and some animal studies but the underlying mechanisms remain unclear. In this study, we aimed at evaluating the effects of high cysteine diet administered to SHR-CRP transgenic rats, a model of metabolic syndrome and inflammation. SHR-CRP rats were fed either standard (3.2 g cystine/kg diet) or high cysteine diet (HCD, enriched with additional 4 g L-cysteine/kg diet). After 4 weeks, urine, plasma and tissue samples were collected and parameters of metabolic syndrome, sulfur metabolites and hepatic gene expression were evaluated. Rats on HCD exhibited similar body weights and weights of fat depots, reduced levels of serum insulin, and reduced oxidative stress in the liver. The HCD did not change concentrations of tCys in tissues and body fluids while taurine in tissues and body fluids, and urinary sulfate were significantly increased. In contrast, betaine levels were significantly reduced possibly compensating for taurine elevation. In summary, increased Cys intake did not induce obesity while it ameliorated insulin resistance in the SHR-CRP rats, possibly due to beneficial effects of accumulating taurine.

N-Acetylcysteine and Hydrogen Sulfide in Coronavirus Disease 2019

Significance: Hydrogen sulfide (H₂S) is one of the three main gasotransmitters that are endogenously produced in humans and are protective against oxidative stress. Recent findings from studies focusing on coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), shifted our attention to a potentially modulatory role of H₂S in this viral respiratory disease. Recent Advances: H₂S levels at hospital admission may be of importance since this gasotransmitter has been shown to be protective against lung damage through its antiviral, antioxidant, and anti-inflammatory actions. Furthermore, many COVID-19 cases have been described demonstrating remarkable clinical improvement upon administration of high doses of N-acetylcysteine (NAC). NAC is a renowned pharmacological antioxidant substance acting as a source of cysteine, thereby promoting endogenous glutathione (GSH) biosynthesis as well as generation of sulfane sulfur species when desulfurated to H₂S. Critical Issues: Combining H₂S physiology and currently available knowledge of COVID-19, H₂S is hypothesized to target three main vulnerabilities of SARS-CoV-2: (i) cell entry through interfering with functional host receptors, (ii) viral replication through acting on RNA-dependent RNA polymerase (RdRp), and (iii) the escalation of inflammation to a potentially lethal hyperinflammatory cytokine storm (toll-like receptor 4 [TLR4] pathway and NLR family pyrin domain containing 3 [NLRP3] inflammasome). Future Directions: Dissecting the breakdown of NAC reveals the possibility of increasing endogenous H₂S levels, which may provide a convenient rationale for the application of H₂S-targeted therapeutics. Further randomized-controlled trials are warranted to investigate its definitive role.

A Case for Hydrogen Sulfide Metabolism as an Oxygen Sensing Mechanism

The ability to detect oxygen availability is a ubiquitous attribute of aerobic organisms. However, the mechanism(s) that transduce oxygen concentration or availability into appropriate physiological responses is less clear and often controversial. This review will make the case for oxygen-dependent metabolism of hydrogen sulfide (H₂S) and polysulfides, collectively referred to as reactive sulfur species (RSS) as a physiologically relevant O₂ sensing mechanism. This hypothesis is based on observations that H₂S and RSS metabolism is inversely correlated with O₂ tension, exogenous H₂S elicits physiological responses identical to those produced by hypoxia, factors that affect H₂S production or catabolism also affect tissue responses to hypoxia, and that RSS efficiently regulate downstream effectors of the hypoxic response in a manner consistent with a decrease in O₂. H₂S-mediated O₂ sensing is then compared to the more generally accepted reactive oxygen species (ROS) mediated O₂ sensing mechanism and a number of reasons are offered to resolve some of the confusion between the two.

Extracellular cystine influences human preadipocyte differentiation and correlates with fat mass in healthy adults

Plasma cysteine is associated with human obesity, but it is unknown whether this is mediated by reduced, disulfide (cystine and mixed-disulfides) or protein-bound (bCys) fractions. We investigated which cysteine fractions are associated with adiposity in vivo and if a relevant fraction influences human adipogenesis in vitro. In the current study, plasma cysteine fractions were correlated with body fat mass in 35 adults. Strong positive correlations with fat mass were observed for cystine and mixed disulfides (r ≥ 0.61, P < 0.001), but not the quantitatively major form, bCys. Primary human preadipocytes were differentiated in media containing cystine concentrations varying from 10-50 μM, a range similar to that in plasma. Increasing extracellular cystine (10-50 μM) enhanced mRNA expression of PPARG2 (to sixfold), PPARG1, PLIN1, SCD1 and CDO1 (P = 0.042- < 0.001). Adipocyte lipid accumulation and lipid-droplet size showed dose-dependent increases from lowest to highest cystine concentrations (P < 0.001), and the malonedialdehyde/total antioxidant capacity increased, suggesting increased oxidative stress. In conclusion, increased cystine concentrations, within the physiological range, are positively associated with both fat mass in healthy adults and human adipogenic differentiation in vitro. The potential role of cystine as a modifiable factor regulating human adipocyte turnover and metabolism deserves further study.

Gene expression of intracortical bone demonstrates loading-induced increases in Wnt1 and Ngf and inhibition of bone remodeling processes

Osteocytes are the primary mechanosensitive cells in bone. However, their location in mineralized matrix has limited the in vivo study of osteocytic genes induced by mechanical loading. Laser Capture Microdissection (LCM) allows isolation of intracortical bone (Intra-CB), enriched for osteocytes, from bone tissue for gene expression analysis. We used microarray to analyze gene expression from mouse tibial Intra-CB dissected using LCM 4 h after a single loading bout or after 5 days of loading. Osteocyte enrichment was supported by greater expression of Sost, Dmp1, Dkk1, and Mepe in Intra-CB regions vs. Mixed regions containing periosteum and muscle (fold-change (FC) = 3.4, 2.2, 5.1, 3.0, respectively). Over 150 differentially expressed genes (DEGs) due to loading (loaded vs. contralateral control) in Intra-CB were found on Day 1 and Day 5, but only 10 genes were differentially expressed on both days, including Ngf (Day 1 FC = 13.5, Day 5 FC = 11.1) and Wnt1 (Day 1 FC = 1.5, Day 5 FC = 5.1). The expression of Ngf and Wnt1 within Intra-CB was confirmed by in situ hybridization, and a significant increase in number of Wnt1 mRNA molecules occurred on day 1. We also found changes in extracellular matrix remodeling with Timp1 (FC = 3.1) increased on day 1 and MMP13 (FC = 0.3) decreased on day 5. Supporting this result, IHC for osteocytic MMP13 demonstrated a marginal decrease due to loading on day 5. Gene Ontology (GO) biological processes for loading DEGs indicated regulation of vasculature, neuronal and immune processes while cell-type specific gene lists suggested regulation of osteoclast, osteoblast, and endothelial related genes. In summary, microarray analysis of microdissected Intra-CB revealed differential regulation of Ngf, Wnt1, and MMP13 due to loading in osteocytes.