Sulfur metabolic response in macrophage limits excessive inflammatory response by creating a negative feedback loop

Oxygen needs sulfur, sulfur needs oxygen: a relationship of interdependence

Oxygen and sulfur, both members of the chalcogen group (group 16 elements), play fundamental roles in life. Ancient organisms primarily utilized sulfur for energy metabolism, while the rise in atmospheric oxygen facilitated the evolution of aerobic organisms, enabling highly efficient energy production. Nevertheless, all modern organisms, both aerobes and anaerobes, must protect themselves from oxygen toxicity. Interestingly, aerobes still rely on sulfur for survival. This dependence has been illuminated by the recent discovery of supersulfides, a novel class of biomolecules, made possible through advancements in technology and analytical methods. These breakthroughs are reshaping our understanding of biological processes and emphasizing the intricate interplay between oxygen and sulfur in regulating essential redox reactions. This review summarizes the latest insights into the biological roles of sulfur and oxygen, their interdependence in key processes, and their contributions to adaptive responses to environmental stressors. By exploring these interactions, we aim to provide a comprehensive perspective on how these elements drive survival strategies across diverse life forms, highlighting their indispensable roles in both human health and the sustenance of life.

Targeting Glutamate transport: A breakthrough in mitigating sepsis lung injury

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) can result from various factors, including sepsis, one of the high-risk causes of ALI/ARDS. Recent research emphasizes the role of Glutamate metabolism in ALI/ARDS. Our study found a strong correlation between the difference in serological Glutamate levels of arterial vs venous blood and the progression of lung injury. High arterial - venous (A-V) Glutamate discrepancies were significantly associated with severity in ALI/ARDS patients. Additionally, the subunit of Glutamate transporter system XC- was notably elevated in mouse lungs affected by sepsis and LPS-induced macrophages. Pharmacological inhibition of system XC- or knocking down xCT worsened sepsis-related lung injury in mice. We also showed that xCT in macrophages is essential for activating system XC- for Glutamate transport, offering protection against sepsis-related ALI. Our findings highlight the therapeutic potential of Glutamate transport in mitigating lung injury and provide a promising approach for predicting ALI/ARDS prognosis.

Supersulfide donors and their therapeutic targets in inflammatory diseases

Inflammation is one defense mechanism of the body that has multiple origins, ranging from physical agents to infectious agents including viruses and bacteria. The resolution of inflammation has emerged as a critical endogenous process that protects host tissues from prolonged or excessive inflammation, which can become chronic. Failure of the inflammation resolution is a key pathological mechanism that drives the progression of numerous inflammatory diseases. Owing to the various side effects of currently available drugs to control inflammation, novel therapeutic agents that can prevent or suppress inflammation are needed. Supersulfides are highly reactive and biologically potent molecules that function as antioxidants, redox regulators, and modulators of cell signaling. The catenation state of individual sulfur atoms endows supersulfides with unique biological activities. Great strides have recently been made in achieving a molecular understanding of these sulfur species, which participate in various physiological and pathological pathways. This review mainly focuses on the anti-inflammatory effects of supersulfides. The review starts with an overview of supersulfide biology and highlights the roles of supersulfides in both immune and inflammatory responses. The various donors used to generate supersulfides are assessed as research tools and potential therapeutic agents. Deeper understanding of the molecular and cellular bases of supersulfide-driven biology can help guide the development of innovative therapeutic strategies to prevent and treat diseases associated with various immune and inflammatory responses.

Supersulfides: A Promising Therapeutic Approach for Autoinflammatory Diseases

Supersulfides are molecular species characterized by catenated sulfur moieties, including low-molecular-weight and protein-bound supersulfides. Emerging evidence suggests that these molecules, abundantly present in diverse organisms, play essential roles far beyond their chemical properties, such as functions in energy metabolism, protein stabilization, and antiviral defense. Recent studies highlight their regulatory effects on pattern-recognition receptors (PRRs) and associated signaling pathways-such as nucleotide oligomerization domain-like receptor signaling, toll-like receptor signaling, and type I interferon receptor signaling-critical for innate immunity and inflammatory responses. Dysregulation of these pathways is implicated in a heterogeneous group of autoinflammatory diseases, including inflammasomopathies, relopathies, and type I interferonopathies, respectively. Notably, both endogenous and synthetic supersulfide donors have recently shown promising inhibitory effects on PRR signaling, offering their potential as targeted therapies for managing autoinflammatory conditions. This review summarizes the fundamental biology of supersulfides and typical autoinflammatory diseases, focusing on their roles in innate immune and inflammatory responses, while exploring their therapeutic potential in these diseases.

Macrophages hijack carbapenem-resistance hypervirulent Klebsiella pneumoniae by blocking SLC7A11/GSH-manipulated iron oxidative stress

Infection with carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKP) is life-threatening because of its pronounced virulence and antibiotic resistance. Recent studies revealed that iron and ROS enhance the ability of macrophages to eliminate intracellular pathogenic bacteria. However, whether and how iron-related oxygen stress responses in macrophages elicit a protective role against CR-hvKP infection remains largely unknown. In a mouse model of CR-hvKP pulmonary infection, the production of the Solute Carrier Family 7 member 11 (SLC7A11) was increased. Treatment with the ferroptosis agonist Erastin or Sorafenib decreased the SLC7A11 expression and the bacterial load in infected lung tissues, alleviating CR-hvKP-induced acute lung injury, increasing the content of TLR4, ROS and LPO. In vitro experiments showed that CR-hvKP infection resulted in a remarkable time-dependent changes in the expression of SLC7A11, GSH, ferrous iron, ROS and LPO in MH-S cells. Mechanically, blocking the expression of SLC7A11 in CR-hvKP-infected MH-S cells increased iron and ROS, improving the ability of macrophages to clear CR-hvKP in an LPO-dependent manner. Taken together, our study reveals that improving iron-related oxygen stress via blocking the SLC7A11/GSH pathway promoting the macrophages to phagocytose and eliminate CR-hvKP, which provides a new promising strategy against CR-hvKP infection.

Metabolic Reprogramming in Primary Microglial Cell and Extracellular Vesicle Triggered by Aβ Exposure

Microglia, key immune cells in the brain, play a pivotal role in brain homeostasis and immune responses. Emerging evidence suggests their critical involvement in Alzheimer's disease (AD) pathogenesis and propagation. The propagation of AD pathology is related to the extracellular matrix of microglia, including extracellular vesicles (EV). Recently, microglia-derived EVs are implicated in inflammatory processes and neuronal death. This study aimed to extensively profile and propose the metabolic role of microglial EVs in AD. Accordingly, we determined the significant alterations of the EV metabolome associated with the metabolites in primary microglial cells. Aβ exposure induced significant metabolic alteration of 39, 18, and 28 metabolites in microglial cells, cultured media, and EVs, respectively. Aβ exposure triggered common alteration of key metabolic pathways between microglial cells and EVs, including purine, amino acid, and fatty acid metabolisms. While most of the common metabolites showed the same directional changes among the microglial system, N-acetyl aspartic acid displayed the opposite directional change in EVs. N-acetyl aspartic acid decreased 2.3-fold and twofold in microglial cells and media, respectively, but increased 3.5-fold in EVs under Aβ exposure. Moreover, mediation analysis proposed key EV metabolites that were directly affected by the metabolic dysregulation of Aβ-exposed microglial cells. The up-regulation of cysteic acid in EVs was mediated by up-regulated IMP in microglial cells. The down-regulation of 1-16:0-lysoPE in EVs was mediated by stearoyl-L-carnitine in microglial cells. Our study sheds new light on the role of microglia and EVs in neurodegenerative diseases, offering promising avenues for future therapeutic interventions.

Biliary-intestinal anastomosis leads to alterations in intestinal flora and its flora metabolites and increases the risk of long-term postoperative complications: a case-control study

Objective

Pancreaticoduodenectomy (PD) is a major surgical intervention that encompasses the resection of multiple organs and the reconstruction of the digestive tract, with reconstructive procedures including pancreatico-enteric, bilioenteric, and gastroenteric anastomoses. Prior research has documented a high incidence of long-term complications following PD, which significantly impact patient prognosis and survival, however, the underlying mechanisms remain elusive. Evidence from previous studies suggests that biliary-intestinal anastomosis modifies biliary tract anatomy, altering bile flow into the gut and potentially affecting the gut microbiota and its metabolites. Given the close association between biliary tract infections and alterations in gut microbiota, we hypothesize that changes in intestinal flora and its metabolites post-PD may be a critical factor in the development of long-term complications. The objective of this study is to investigate whether biliary-intestinal anastomosis during PD induces changes in the intestinal microbiota and its metabolites, which in turn may increase the risk of long-term postoperative complications.

Methods

This study included 17 patients who underwent the procedure (group T) and 20 sex- and age-matched controls who did not (group N), patients in group T were stratified into those with (complication group) and without (non-complication group) long-term postoperative complications. Faecal samples were collected from all subjects and DNA was extracted from the samples using 16S rRNA gene sequencing to analyse the composition of the faecal flora and detect flora metabolites.

Results

1. Alpha diversity analysis of the two sample groups indicated a trend towards lower microbial abundance in Group T relative to Group N, however, no significant differences were observed in the Shannon and Simpson diversity indices. 2. At the genus level, Group T patients exhibited markedly higher levels of Escherichia-Shigella, Veillonella, and Enterobacter, while showing significantly lower abundance of Blautia and Bifidobacterium compared to Group N subjects. Analysis of Spearman's correlation and degree of correlation between genera showed a significant negative correlation between Escherichia shigella and Blautia. Veillonella showed a significant positive correlation with both Escherichia shigella and Enterobacter. In addition, Blautia and Bifidobacterium showed a significant positive correlation with each other. 3. Subsequent comparative analysis of the bacterial flora between the complication and non-complication groups revealed a significantly elevated abundance of Escherichia-Shigella in the complication group as compared to the non-complication group. 4. Faecal metabolomic analysis revealed that L-palmitoylcarnitine, arachidic acid and PG 13:0_15:0 were significantly increased in the T group compared to the N group, whereas 3-isopropylmalic acid was significantly decreased in the T group. 5. KEGG pathway analysis identified nine crucial metabolic pathways associated with these microbial shifts: alterations in starch and sucrose metabolism, steroid hormone biosynthesis, caffeine metabolism, the citric acid cycle, riboflavin metabolism, sulfur metabolism, and the biosynthesis of valine, leucine, and isoleucine, as well as pyruvate metabolism and ABC transporter protein pathways.

Conclusion

1. The biliary-intestinal anastomosis, which is performed as part of a pancreaticoduodenectomy, induces significant shifts in the intestinal flora. 2. Increased abundance of Escherichia-Shigella may promote long-term complications after biliary-intestinal anastomosis. 3. Biliary-intestinal anastomosis leads to alterations in the metabolites of the patient's intestinal flora. 4. Intestinal flora and their metabolites in patients after biliary-intestinal anastomosis may contribute to the development of long-term complications through nine metabolic pathways.

Colon-Targeting Supersulfide Donor-Drug Conjugates Align Forces against Inflammation

Supersulfides are rising stars in regulating redox. Their distinctive redox biological functions are becoming increasingly evident with the advancement of supersulfide donors. However, most existing donors are limited to releasing hydropersulfide (RSSH) only, and in addition, there is still a knowledge gap in translating supersulfides into therapeutic molecules. To this end, in this work, we devised and synthesized a supersulfide donor-drug conjugate, RSSS-ASA, containing an azo moiety. This bifunctional prodrug enables the production of hydrotrisulfide (RSSSH) catalyzed by intestinal azoreductase, accompanied by the release of the anti-inflammatory molecule 5-aminosalicylic acid (ASA). Notably, the corelease of the supersulfides with ASA exhibited colonic-targeting attributes, thereby synergistically contributing to the potent anti-inflammatory and antioxidant activities observed in cellular and animal models. This prodrug design is worthy of further development and translation in donor development and disease treatment.

The Therapeutic Potential of Supersulfides in Oxidative Stress-Related Diseases

Oxidation-reduction (redox) reactions are fundamental to sustaining life, with reactive oxygen and nitrogen species playing pivotal roles in cellular signaling and homeostasis. However, excessive oxidative stress disrupts redox balance, contributing to a wide range of diseases, including inflammatory and pulmonary disorders, neurodegeneration, and cancer. Although numerous antioxidant therapies have been developed and tested for oxidative stress-related diseases, their clinical efficacy remains limited. Here, we introduce the emerging concept of 'supersulfides', a class of redox molecule species with unique antioxidant and nucleophilic properties, which have recently been recognized as crucial regulators of cellular redox homeostasis. Unlike traditional antioxidants, supersulfides offer novel mechanisms of action that directly target the underlying processes of oxidative stress. This review summarizes current knowledge on supersulfides, highlighting their roles in oxidative stress and associated diseases, as well as the mechanisms underlying oxidative stress-related pathology. The therapeutic potential of synthetic supersulfides for treating oxidative stress-related diseases is also discussed. A comprehensive understanding of the molecular and cellular basis of redox biology can help to guide the development of innovative redox-based therapeutic strategies aimed at preventing and treating diseases associated with disturbed redox regulation.

Understanding Polysulfide-Mediated Papain Inhibition and Differentiating between Disulfide vs Persulfide Formation

Protein cysteine residues are sensitive to redox-regulating molecules, including reactive sulfur species (RSS). As an important member of the RSS family, polysulfides are known to react with protein cysteines to form persulfides and disulfides, both affecting protein functions. In this work, we studied how polysulfides could impact cysteine proteases through careful mechanistic and kinetic studies. The model protein papain was treated with different polysulfides to elucidate the efficacy of polysulfides as inhibitors for this protein. We also explored the effects of different reductants that could regenerate papain activity after polysulfide-mediated inhibition. A triarylphosphine reagent, TXPTS, was found to be efficient in differentiating between papain persulfidation and disulfide formation.

Role of gut microbial-derived metabolites and other select agents on adipocyte browning

AIMS

Metabolic disease is a multifaceted condition characterized by the disruption of numerous metabolic parameters within the host. Its prevalence has surged significantly in recent years and it has become a prominent non-communicable disease worldwide. The effect of gut microbiota on various beige fat induction is well studied, while the mechanisms behind the link remain unclear. Given that gut microbiota-derived metabolites (meta-metabolites) secreted in the gut serve as a key mode of communication with their host through direct circulation or indirect host physiology modification, understanding the effect of meta-metabolites on adipose tissue is essential.

METHODOLOGY

In our previous in-vivo studies, we observed a correlation between gut microbiota and the formation of beige fat. In this study, we further aimed to validate this correlation by treating the adipocyte cell line (3T3-L1) with meta-metabolites collected from the cecum of mice exhibiting beige adipose tissue formation. Additionally, we treated the adipocyte cell line with known beige fat inducers (L-Rhamnose and Ginsenoside) to assess meta-metabolites' efficacy on beige fat formation.

KEY FINDINGS

Upon treatment with the meta-metabolites from the antibiotic-treated mice, we observed a significant increase in lipid metabolism and beige-specific gene expression. Analyzing the metabolites in these cells revealed that a set of metabolites potentially govern adipocytes, contributing to a metabolically active state. These effects were at par or even better than those of cells treated with L-Rhamnose or Ginsenoside.

SIGNIFICANCE

This research sheds light on the intricate interplay between microbial metabolites and adipose tissue, offering valuable clues for understanding and potentially manipulating these processes for therapeutic purposes.

Supersulphides suppress type-I and type-II interferon responses by blocking JAK/STAT signalling in macrophages

Interferons (IFNs) are cytokines produced and secreted by immune cells when viruses, tumour cells, and so forth, invade the body. Their biological effects are diverse, including antiviral, cell growth-inhibiting, and antitumour effects. The main subclasses of IFNs include type-I (e.g. IFN-α and IFN-β) and type-II (IFN-γ), which activate intracellular signals by binding to type-I and type-II IFN receptors, respectively. We have previously shown that when macrophages are treated with supersulphide donors, which have polysulphide structures in which three or more sulphur atoms are linked within the molecules, IFN-β-induced cellular responses, including signal transducer and activator of transcription 1 (STAT1) phosphorylation and inducible nitric oxide synthase (iNOS) expression, were strongly suppressed. However, the subfamily specificity of the suppression of IFN signals by supersulphides and the mechanism of this suppression are unknown. This study demonstrated that supersulphide donor N-acetyl-L-cysteine tetrasulphide (NAC-S2) can inhibit IFN signalling in macrophages stimulated not only with IFN-α/β but also with IFN-γ. Our data suggest that NAC-S2 blocks phosphorylation of Janus kinases (JAKs), thereby contributing to the inhibition of phosphorylation of STAT1. Under the current experimental conditions, the hydrogen sulphide (H2S) donor NaHS failed to inhibit IFN signalling. Similar to NAC-S2, the carbohydrate-based supersulphide donor thioglucose tetrasulphide (TGS4) was capable of strongly inhibiting tumour necrosis factor-α production, iNOS expression, and nitric oxide production from macrophages stimulated with lipopolysaccharide. Further understanding of the molecular mechanisms by which supersulphide donors exhibit their inhibitory actions towards JAK/STAT signalling is a necessary basis for the development of supersulphide-based therapeutic strategy against autoimmune disorders with dysregulated IFN signalling.

New aspects of redox signaling mediated by supersulfides in health and disease

Oxygen molecules accept electrons from the respiratory chain in the mitochondria and are responsible for energy production in aerobic organisms. The reactive oxygen species formed via these oxygen reduction processes undergo complicated electron transfer reactions with other biological substances, which leads to alterations in their physiological functions and cause diverse biological and pathophysiological consequences (e.g., oxidative stress). Oxygen accounts for only a small proportion of the redox reactions in organisms, especially under aerobic or hypoxic conditions but not under anaerobic and hypoxic conditions. This article discusses a completely new concept of redox biology, which is governed by redox-active supersulfides, i.e., sulfur-catenated molecular species. These species are present in abundance in all organisms but remain largely unexplored in terms of redox biology and life science research. In fact, accumulating evidence shows that supersulfides have extensive redox chemical properties and that they can be readily ionized or radicalized to participate in energy metabolism, redox signaling, and oxidative stress responses in cells and in vivo. Thus, pharmacological intervention and medicinal modulation of supersulfide activities have been shown to benefit the regulation of disease pathogenesis as well as disease control.

Ferroptosis in health and disease

Ferroptosis is a pervasive non-apoptotic form of cell death highly relevant in various degenerative diseases and malignancies. The hallmark of ferroptosis is uncontrolled and overwhelming peroxidation of polyunsaturated fatty acids contained in membrane phospholipids, which eventually leads to rupture of the plasma membrane. Ferroptosis is unique in that it is essentially a spontaneous, uncatalyzed chemical process based on perturbed iron and redox homeostasis contributing to the cell death process, but that it is nonetheless modulated by many metabolic nodes that impinge on the cells' susceptibility to ferroptosis. Among the various nodes affecting ferroptosis sensitivity, several have emerged as promising candidates for pharmacological intervention, rendering ferroptosis-related proteins attractive targets for the treatment of numerous currently incurable diseases. Herein, the current members of a Germany-wide research consortium focusing on ferroptosis research, as well as key external experts in ferroptosis who have made seminal contributions to this rapidly growing and exciting field of research, have gathered to provide a comprehensive, state-of-the-art review on ferroptosis. Specific topics include: basic mechanisms, in vivo relevance, specialized methodologies, chemical and pharmacological tools, and the potential contribution of ferroptosis to disease etiopathology and progression. We hope that this article will not only provide established scientists and newcomers to the field with an overview of the multiple facets of ferroptosis, but also encourage additional efforts to characterize further molecular pathways modulating ferroptosis, with the ultimate goal to develop novel pharmacotherapies to tackle the various diseases associated with - or caused by - ferroptosis.

Integrated metabolomics and network pharmacology approach to exploring the anti-inflammatory mechanisms of Chuanwang xiaoyan capsules

Chuanwang xiaoyan capsules (CWXYC) have anti-inflammatory and detoxification effect, are used in the treatment of acute and chronic tonsillitis, pharyngitis and other inflammation-related diseases clinically. However, the anti-inflammatory mechanisms have not been elucidated. This study aimed to investigate the anti-inflammatory mechanisms of CWXYC using cell metabolomics and network pharmacology strategy. Specifically, CWXYC could efficiently reduce the content of nitric oxide (NO), the cytokines Interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) in LPS-induced RAW264.7 cells. Furthermore, metabolomics was performed to achieve 23 differential metabolites and 9 metabolic pathways containing glutamate metabolism, glutathione metabolism, arginine and proline metabolism, urea cycle, malate-aspartate shuttle, phosphatidylcholine biosynthesis, transfer of acetyl groups into mitochondria, cysteine metabolism and ammonia recycling. The results of network pharmacology showed that CWXYC could treat inflammation through 10 active components, 10 key targets and 55 pathways. Then the results of molecular docking also approved that there existed strong binding energy between the active components and the key targets. Finally, metabolomics and network pharmacology were integrated to get core targets AKT1, SRC and EGFR. Western blot experiments verified that CWXYC could exert anti-inflammatory effect by down-regulating the activated Akt1 and Src proteins. This study demonstrated that CWXYC exerted effects against inflammation, and the potential mechanisms were elucidated. These novel findings will provide an important basis for further mechanism investigations.

Nicotine promotes Staphylococcus aureus-induced osteomyelitis by activating the Nrf2/Slc7a11 signaling axis

Although smoking is a significant risk factor for osteomyelitis, there is limited experimental evidence that nicotine, a key tobacco constituent, is associated with this condition, leaving its mechanistic implications uncharacterized. This study revealed that nicotine promotes Staphylococcus aureus-induced osteomyelitis by increasing Nrf2 and Slc7a11 expression in vivo and in vitro. Inhibition of Slc7a11 using Erastin augmented bacterial phagocytosis/killing capabilities and fortified antimicrobial responses in an osteomyelitis model. Moreover, untargeted metabolomic analysis demonstrated that Erastin mitigated the effects of nicotine on S. aureus-induced osteomyelitis by altering glutamate/glutathione metabolism. These findings suggest that nicotine aggravates S. aureus-induced osteomyelitis by activating the Nrf2/Slc7a11 signaling pathway and that Slc7a11 inhibition can counteract the detrimental health effects of nicotine.

Widespread S-persulfidation in activated macrophages as a protective mechanism against oxidative-inflammatory stress

Acute inflammatory responses often involve the production of reactive oxygen and nitrogen species by innate immune cells, particularly macrophages. How activated macrophages protect themselves in the face of oxidative-inflammatory stress remains a long-standing question. Recent evidence implicates reactive sulfur species (RSS) in inflammatory responses; however, how endogenous RSS affect macrophage function and response to oxidative and inflammatory insults remains poorly understood. In this study, we investigated the endogenous pathways of RSS biogenesis and clearance in macrophages, with a particular focus on exploring how hydrogen sulfide (H2S)-mediated S-persulfidation influences macrophage responses to oxidative-inflammatory stress. We show that classical activation of mouse or human macrophages using lipopolysaccharide and interferon-γ (LPS/IFN-γ) triggers substantial production of H2S/RSS, leading to widespread protein persulfidation. Biochemical and proteomic analyses revealed that this surge in cellular S-persulfidation engaged ∼2% of total thiols and modified over 800 functionally diverse proteins. S-persulfidation was found to be largely dependent on the cystine importer xCT and the H2S-generating enzyme cystathionine γ-lyase and was independent of changes in the global proteome. We further investigated the role of the sulfide-oxidizing enzyme sulfide quinone oxidoreductase (SQOR), and found that it acts as a negative regulator of S-persulfidation. Elevated S-persulfidation following LPS/IFN-γ stimulation or SQOR inhibition was associated with increased resistance to oxidative stress. Upregulation of persulfides also inhibited the activation of the macrophage NLRP3 inflammasome and provided protection against inflammatory cell death. Collectively, our findings shed light on the metabolism and effects of RSS in macrophages and highlight the crucial role of persulfides in enabling macrophages to withstand and alleviate oxidative-inflammatory stress.

PNPO-PLP axis senses prolonged hypoxia in macrophages by regulating lysosomal activity

Oxygen is critical for all metazoan organisms on the earth and impacts various biological processes in physiological and pathological conditions. While oxygen-sensing systems inducing acute hypoxic responses, including the hypoxia-inducible factor pathway, have been identified, those operating in prolonged hypoxia remain to be elucidated. Here we show that pyridoxine 5'-phosphate oxidase (PNPO), which catalyses bioactivation of vitamin B6, serves as an oxygen sensor and regulates lysosomal activity in macrophages. Decreased PNPO activity under prolonged hypoxia reduced an active form of vitamin B6, pyridoxal 5'-phosphate (PLP), and inhibited lysosomal acidification, which in macrophages led to iron dysregulation, TET2 protein loss and delayed resolution of the inflammatory response. Among PLP-dependent metabolism, supersulfide synthesis was suppressed in prolonged hypoxia, resulting in the lysosomal inhibition and consequent proinflammatory phenotypes of macrophages. The PNPO-PLP axis creates a distinct layer of oxygen sensing that gradually shuts down PLP-dependent metabolism in response to prolonged oxygen deprivation.

Advances in Metabolic Regulation of Macrophage Polarization State

Macrophages are significant immune-related cells that are essential for tissue growth, homeostasis maintenance, pathogen resistance, and damage healing. The studies on the metabolic control of macrophage polarization state in recent years and the influence of polarization status on the development and incidence of associated disorders are expounded upon in this article. Firstly, we reviewed the origin and classification of macrophages, with particular attention paid to how the tricarboxylic acid cycle and the three primary metabolites affect macrophage polarization. The primary metabolic hub that controls macrophage polarization is the tricarboxylic acid cycle. Finally, we reviewed the polarization state of macrophages influences the onset and progression of cancers, inflammatory disorders, and other illnesses.

Supersulfide biology and translational medicine for disease control

For decades, the major focus of redox biology has been oxygen, the most abundant element on Earth. Molecular oxygen functions as the final electron acceptor in the mitochondrial respiratory chain, contributing to energy production in aerobic organisms. In addition, oxygen-derived reactive oxygen species including hydrogen peroxide and nitrogen free radicals, such as superoxide, hydroxyl radical and nitric oxide radical, undergo a complicated sequence of electron transfer reactions with other biomolecules, which lead to their modified physiological functions and diverse biological and pathophysiological consequences (e.g. oxidative stress). What is now evident is that oxygen accounts for only a small number of redox reactions in organisms and knowledge of biological redox reactions is still quite limited. This article reviews a new aspects of redox biology which is governed by redox-active sulfur-containing molecules-supersulfides. We define the term 'supersulfides' as sulfur species with catenated sulfur atoms. Supersulfides were determined to be abundant in all organisms, but their redox biological properties have remained largely unexplored. In fact, the unique chemical properties of supersulfides permit them to be readily ionized or radicalized, thereby allowing supersulfides to actively participate in redox reactions and antioxidant responses in cells. Accumulating evidence has demonstrated that supersulfides are indispensable for fundamental biological processes such as energy production, nucleic acid metabolism, protein translation and others. Moreover, manipulation of supersulfide levels was beneficial for pathogenesis of various diseases. Thus, supersulfide biology has opened a new era of disease control that includes potential applications to clinical diagnosis, prevention and therapeutics of diseases.