The third gas: H2S regulates perfusion pressure in both the isolated and perfused normal rat liver and in cirrhosis

A pyrene-based fluorescent probe for H2S detection and cellular imaging

Hydrogen sulfide (H2S) is a significant reactive sulfur species (RSS) involved in various human diseases, also playing an important role in many physiological and pathological processes. Thus, the development of an effective method for detecting H2S in mammalian cells is of great importance. In this study, we present the synthesis of a novel pyrene-based fluorescent probe, DPP, specifically designed for the selective detection of H2S. The DPP exhibits remarkable sensitivity, with a low detection limit of 0.63 µM, and demonstrates high selectivity for H2S in the presence of various interfering species. Additionally, the probe has demonstrated rapid detection of H2S in less than 6 min. The detection mechanism was thoroughly validated using 1H NMR, FT-IR, UV and fluorescence spectra. Moreover, the applicability of DPP was successfully demonstrated in both in vitro and in vivo settings using HeLa cells, confirming its potential as a powerful tool for monitoring H2S in biological systems. Additionally, the probe exhibited excellent performance in detecting H2S in water samples and in paper strip-based assays, further highlighting its versatility and practical utility for environmental monitoring and on-site applications.

S-Allyl-Cysteine Ameliorates Cirrhotic Portal Hypertension by Enhancing Lymphangiogenesis via a VEGF-C-Independent Manner

BACKGROUND AND AIMS

Lymphangiogenesis is enhanced during the development of liver cirrhosis and portal hypertension (PHT). However, hepatic lymphatic vascular system is understudied in liver cirrhosis and PHT. Hydrogen sulfide (H2S) and related compounds have potential prolymphangiogenic effects besides its previously reported vascular-protective effects. Therefore, we aimed to investigate the effects of endogenous H2S donor S-allyl-cysteine (SAC) on bile duct ligation (BDL)-induced liver cirrhosis and PHT.

METHODS

BDL rats with cholestatic liver cirrhosis and PHT were orally administrated with SAC at 100 or 200 mg/kg/day, as well as DL-propargylglycine (PAG) or MAZ-51 injections. Hemodynamic parameters were determined, and subsequent evaluations of liver fibrosis, intrahepatic vascular resistance (IHVR) and lymphangiogensis were performed. Human lymphatic endothelial cells (hLECs) were used for in vitro verification of prolymphangiogenic effects of SAC.

RESULTS

SAC treatment significantly decreased PP and promoted endogenous H2S production. Liver fibrosis and IHVR were also ameliorated. Hepatic and mesenteric lymphangiogenesis were enhanced in BDL rats and further promoted by SAC despite a significant downregulation of hepatic VEGF-C. Inhibition of H2S production by PAG significantly reduced lymphatic vessels, while inhibition of lymphangiogensis by MAZ-51 reversed the protective effects of SAC against PHT. SAC enhanced lymphangiogenic functions in vitro by promoting cellular H2S production and activating Akt phosphorylation without altering VEGF-C/D, which were reversed by PAG and MAZ-51.

CONCLUSIONS

SAC significantly alleviated BDL-induced liver cirrhosis and PHT. Meanwhile, elevated H2S induced by SAC facilitated lymphangiogenesis via a VEGF-C-independent manner, which contributed to the alleviation of PHT.

Highly selective dual-signal readout H2S probe: Applications in monitoring of water samples, food spoilage and live cell imaging

We present a new probe (DN) for colorimetric and fluorimetric detecting hydrogen sulfide (H2S) on the basis of the H2S-triggered thiolysis of 4-nitro-2,1,3-benzoxadiazoyl (NBD) ether. In H2O/DMSO medium (9/1, v/v, pH 7.4), the aryl ether bond in DN was cleaved by H2S via nucleophilic aromatic substitution to yield a phenolate product with lighting up red fluorescence accompanied with a distinguished color transformation from yellow to pink. Probe DN features near-infrared emission (660 nm), large Stokes Shift (168 nm), good sensitivity (LOD: 15.1 nM) and relative fast response time (5 min) for specific sensing of H2S. Conveniently, a paper strips-based test kit was developed for tracking and assessing meat freshness by monitoring the release of H2S. What is more, DN is demonstrated to image both exogenous and endogenous H2S in live cells with relative short analysis time (30-60 min), providing a new research tool for exploring the relationship between H2S and clinical diseases.

Role of 3-mercaptopyruvate sulfurtransferase in cancer: Molecular mechanisms and therapeutic perspectives

The occurrence and development of tumor is mediated by a wide range of complex mechanisms. Subsequent to nitric oxide and carbon monoxide, hydrogen sulfide (H2S) holds the distinction of being the third identified gasotransmitter. Alternation of H2S level has been widely demonstrated to induce an array of disturbances in important cancer cell signaling pathways. As a result, the effects of H2S-catalyzing enzymes in cancers also attract widspread attention. 3-mercaptopyruvate sulfurtransferase (3-MST) is privileged to be one of them. In fact, 3-MST is overexpressed in many tumors including human colon cancer, lung adenocarcinoma, and bladder urothelial carcinoma. But it is also lowly expressed in hepatocellular carcinoma. In this review, we focus on the generation of endogenous H2S and polysulfides, facilitated by 3-MST. Additionally, we delve deeply into the potential role of 3-MST in tumorigenesis and development. The impact of 3-MST inhibition on the development of tumors and its potential for tumor therapy are also highlighted.

Research progress of hydrogen sulfide fluorescent probes targeting organelles

Hydrogen sulfide (H2S) is implicated in numerous physiological and pathological processes in living organisms. Abnormal levels of H2S can result in various physiological disorders, highlighting the crucial need for effective identification and detection of H2S at the organellar level. Although numerous H2S fluorescent probes targeting organelles have been reported, a comprehensive review of these probes is required. This review focuses on the strategic selection of organelle-targeting groups and recognition sites for H2S fluorescent probes. This review examines H2S fluorescent probes that can specifically target lysosomes, mitochondria, endoplasmic reticulum, Golgi apparatus, and lipid droplets. These fluorescent probes have been meticulously classified and summarized based on their distinct targets, emphasizing their chemical structure, reaction mechanisms, and biological applications. We carefully designed fluorescent probes to efficiently enhance their ability to recognize target substances and exhibit significant fluorescence variations. Furthermore, we discuss the challenges inherent in the development of fluorescent probes and outline potential future directions for this exciting field.

A polymer deposition-mediated surface-charge reformation strategy: reversing the MOF biomineralization behavior

Biomineralization of a porous metal-organic framework (MOF) shell onto biomacromolecule templates is a burgeoning strategy to construct robust biocatalysts. However, it strongly relies on the interfacial interaction between MOF precursors and enzyme surface, significantly limiting the generalization of this nanotechnology. Herein, we identify polymers that are well-suited for deposition onto target biomacromolecules via supramolecular interactions and introduce a polymer deposition-mediated surface-charge reformation strategy to facilitate the biomineralization of porous MOFs, including ZIF-8, ZIF-90, and ZIF-zni onto enzymes. We investigate nine commercially available polymers to find that those with dense -SO3H and -COOH groups effectively regulate the surface-charge properties of the enzymes that are unfavorable for biomineralization. The polymer-enzyme complex thus formed retains its original bioactivity and offers significantly elevated sites to accumulate metal precursors, triggering the in-place MOF biomineralization. We demonstrate that this approach allows access to diverse MOF biocatalysts independent of the enzyme surface chemistry, which are difficult to be synthesized by previous biomineralization methods. Given the highly specific bioactivity and structural stability of the MOF biocatalysts, a chemiluminiscence sensor platform is developed for the sensitive detection of hydrogen sulfide (H2S) biomarkers, with a low limit of detection of 0.09 nM that is superior to most of the reported methods. This study provides an effective and universal strategy for MOF biomineralization using fragile enzymes as biotemplates and offers new insights into accessing multifunctional MOF hybrid biocatalysts.

Single Side-Chain-Modulatory of Hemicyanine for Optimized Fluorescence and Photoacoustic Dual-Modality Imaging of H2S In Vivo

Near-infrared fluorescence (NIRF)/photoacoustic (PA) dual-modality imaging integrated high-sensitivity fluorescence imaging with deep-penetration PA imaging has been recognized as a reliable tool for disease detection and diagnosis. However, it remains an immense challenge for a molecule probe to achieve the optimal NIRF and PA imaging by adjusting the energy allocation between radiative transition and nonradiative transition. Herein, a simple but effective strategy is reported to engineer a NIRF/PA dual-modality probe (Cl-HDN3) based on the near-infrared hemicyanine scaffold to optimize the energy allocation between radiative and nonradiative transition. Upon activation by H2S, the Cl-HDN3 shows a 3.6-fold enhancement in the PA signal and a 4.3-fold enhancement in the fluorescence signal. To achieve the sensitive and selective detection of H2S in vivo, the Cl-HDN3 is encapsulated within an amphiphilic lipid (DSPE-PEG2000) to form the Cl-HDN3-LP, which can successfully map the changes of H2S in a tumor-bearing mouse model with the NIRF/PA dual-modality imaging. This work presents a promising strategy for optimizing fluorescence and PA effects in a molecule probe, which may be extended to the NIRF/PA dual-modality imaging of other disease-relevant biomarkers.

Nanozymes in Alzheimer's disease diagnostics and therapy

Alzheimer's disease (AD) is a progressive neurodegenerative condition that has become an important public health problem of global concern, and the early diagnosis and etiological treatment of AD are currently the focus of research. In the course of clinical treatment, approved clinical drugs mainly serve to slow down the disease process by relieving patients' clinical symptoms. However, these drugs do not target the cause of the disease, and the lack of specificity of these drugs has led to undesirable side effects in treatment. Meanwhile, AD is mainly diagnosed by clinical symptoms and imaging, which does not have the advantage of early diagnosis. Nanozymes have been extensively investigated for the diagnosis and treatment of AD with high stability and specificity. Therefore, this review summarizes the recent advances in various nanozymes for AD diagnosis and therapy, including with peroxidase-like-activity gold nanozymes, iron nanozymes, superoxide dismutase-like- and catalase-like-activity selenium dioxide nanozymes, platinum nanozymes, and peroxidase-like palladium nanozymes, among others. A comprehensive analysis was conducted on the diagnostic and therapeutic characteristics of nanozyme therapy for AD, as well as the prospects and challenges of its clinical application. Our goal is to advance this emerging topic by building on our own work and the new insights we have learned from others. This review will assist researchers to quickly understand relevant nanozymes' therapeutic and diagnostic information and further advance the field of nanozymes in AD.

Self-immolative poly(thiocarbamate) with localized H2S signal amplification for precise cancer imaging and therapy

Hydrogen sulfide is essential in numerous physiological and pathological processes and has emerged as a promising cancer imaging and signaling molecule and a potentially versatile therapeutic agent. However, the endogenous levels of hydrogen sulfide remain insufficient to perform its biological functions, and thus, developing novel strategies that amplify hydrogen sulfide signals at lesion sites is of increasing interest. In this work, a nanoplatform (SNP) based on hydrogen sulfide-responsive self-immolative poly(thiocarbamate) with localized hydrogen sulfide signal amplification capability is developed to encapsulate a hydrogen sulfide-responsive fluorescent probe (e.g., hemicyanine dye; p-Cy) or an anticancer prodrug (e.g., doxorubicin; p-DOX) to form a nanoprobe (SNPp-Cy) or nanomedicine (SNPp-DOX) for cancer imaging and therapy, respectively. SNPp-Cy exhibits a low detection limit for hydrogen sulfide, enabling ultrasensitive detection of small (<2 mm) tumors in female mice. In addition, SNPp-DOX can effectively inhibit the growth of DOX-resistant human breast cancer xenograft, lung metastasis, and patient-derived xenograft tumors in female mice.

Imidazole Compounds: Synthesis, Characterization and Application in Optical Analysis

Imidazole is a five-membered heterocyclic ring containing three carbon atoms, two nitrogen atoms, and two double bonds. Among two nitrogen atoms, one of which carries with a hydrogen atom is a pyrrole-type nitrogen atom, another is a pyridine type nitrogen atom. Hence, the imidazole ring belongs to the π electron-rich aromatic ring and can accept strong suction to the electronic group. Moreover, the nitrogen atom of the imidazole ring is coordinated with metal ions to form metal-organic frameworks. In recent years, because of imidazole compounds' unique optical properties, their applications have attracted more and more attention in optical analysis. Thus, this review has summarized the synthesis, characterization, and application with emphasis on the research progress of imidazole compounds in optical analysis, including fluorescence probe, colorimetric probe, electrochemiluminescence sensor, fiber optical sensor, surface plasmon resonance, etc. This paper will suggest the direction for the development of imidazole-containing sensors with high sensitivity and selectivity.

Smartphone Imaging Device for Multimodal Detection of Hydrogen Sulfide Using Cu-Doped MOF Sensors

Multimodal sensing platforms may offer reliable, fast results, but it is still challenging to incorporate biosensors with high discriminating ability in complex biological samples. Herein, we established a highly sensitive dual colorimetric/electrochemical monitoring approach for the detection of hydrogen sulfide (H2S) utilizing Cu-doped In-based metal-organic frameworks (Cu/In-MOFs) combined with a versatile color selector software-based smartphone imaging device. H2S can result in the enhancement of the electrochemical signal because of the electroactive substance copper sulfide (CuxS), the decrease of the colorimetric signal of the characteristic absorption response caused by the strong coordination effect on Cu/In-MOFs, and the obvious changes of red-green-blue (RGB) values of images acquired via an intelligent smartphone. Attractively, the Cu/In-MOFs-based multimodal detection guarantees precise and sensitive detection of H2S with triple-signal detection limits of 0.096 μM (electrochemical signals), 0.098 μM (colorimetric signals), and 0.099 μM (smartphone signals) and an outstanding linear response. This analytical toolkit provides an idea for fabricating a robust, sensitive, tolerant matrix and reliable sensing platform for rapidly monitoring H2S in clinical disease diagnosis and visual supervision.

Hydrogen sulfide and its role in female reproduction

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

Elucidating the Molecular Pathways and Therapeutic Interventions of Gaseous Mediators in the Context of Fibrosis

Fibrosis, a pathological alteration of the repair response, involves continuous organ damage, scar formation, and eventual functional failure in various chronic inflammatory disorders. Unfortunately, clinical practice offers limited treatment strategies, leading to high mortality rates in chronic diseases. As part of investigations into gaseous mediators, or gasotransmitters, including nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S), numerous studies have confirmed their beneficial roles in attenuating fibrosis. Their therapeutic mechanisms, which involve inhibiting oxidative stress, inflammation, apoptosis, and proliferation, have been increasingly elucidated. Additionally, novel gasotransmitters like hydrogen (H2) and sulfur dioxide (SO2) have emerged as promising options for fibrosis treatment. In this review, we primarily demonstrate and summarize the protective and therapeutic effects of gaseous mediators in the process of fibrosis, with a focus on elucidating the underlying molecular mechanisms involved in combating fibrosis.

The role and mechanism of hydrogen sulfide in liver fibrosis

Hydrogen sulfide (H2S) is the third new gas signaling molecule in the human body after the discovery of NO and CO. Similar to NO, it has the functions of vasodilation, anti-inflammatory, antioxidant, and regulation of cell formation. Enzymes that can produce endogenous H2S, such as CSE, CSB, and 3-MST, are common in liver tissues and are important regulatory molecules in the liver. In the development of liver fibrosis, H2S concentration and expression of related enzymes change significantly, which makes it possible to use exogenous gases to treat liver diseases. This review summarizes the role of H2S in liver fibrosis and its complications induced by NAFLD and CCl4, and elaborates on the anti-liver fibrosis effect of H2S through the mechanism of reducing oxidative stress, inhibiting inflammation, regulating autophagy, regulating glucose and lipid metabolism, providing theoretical reference for further research on the treatment of liver fibrosis with H2S.

A purine-based fluorescent probe for H2S detection and imaging of cells

Hydrogen sulfide (H2S) is a gas with a toxic odor that plays an irreplaceable role in physiological activities within the mammalian body. Therefore, it is important to do the distribution and quantitative detection of H2S in mammalian cells. In this paper, a fluorescence probe (EDPH) based on purine scaffold was designed and synthesized with high sensitivity and good selectivity. H2S induced ether bond breakage in EDPH, resulting in a significant redshift of the absorption band (from 370 nm to 500 nm) with a Stokes shift of 130 nm. After the addition of H2S, the fluorescence intensity of EDPH showed a good linear correlation with the concentration of H2S, which enabled the quantitative detection of H2S with a low limit of detection (41 nM). Finally, the EDPH was applied to the cellular Hele, and the probe has good cellularity imaging capability for the detection of H2S in living systems.

Pathophysiology of Hepatorenal Syndrome

Hepatorenal syndrome type 1 (HRS-1) is a unique form of acute kidney injury that affects individuals with decompensated cirrhosis with ascites. The primary mechanism leading to reduction of kidney function in HRS-1 is hemodynamic in nature. Cumulative evidence points to a cascade of events that led to a profound reduction in kidney perfusion. A state of increased intrahepatic vascular resistance characteristic of advanced cirrhosis and portal hypertension is accompanied by maladaptive peripheral arterial vasodilation and reduction in systemic vascular resistance and mean arterial pressure. As a result of a fall in effective arterial blood volume, there is a compensatory activation of the sympathetic nervous system and the renin-angiotensin system, local renal vasoconstriction, loss of renal autoregulation, decrease in renal blood flow, and ultimately a fall in glomerular filtration rate. Systemic release of nitric oxide stimulated by the fibrotic liver, bacterial translocation, and inflammation constitute key components of the pathogenesis. While angiotensin II and noradrenaline remain the critical mediators of renal arterial and arteriolar vasoconstriction, other novel molecules have been recently implicated. Although the above-described mechanistic pathway remains the backbone of the pathogenesis of HRS-1, other noxious elements may be present in advanced cirrhosis and likely contribute to the renal impairment. Direct liver-kidney crosstalk via the hepatorenal sympathetic reflex can further reduce renal blood flow independently of the systemic derangements. Tense ascites may lead to intraabdominal hypertension and abdominal compartment syndrome. Cardio-hemodynamic processes have also been increasingly recognized. Porto-pulmonary hypertension, cirrhotic cardiomyopathy, and abdominal compartment syndrome may lead to renal congestion and complicate the course of HRS-1. In addition, a degree of ischemic or toxic (cholemic) tubular injury may overlap with the underlying circulatory dysfunction and further exacerbate the course of acute kidney injury. Improving our understanding of the pathogenesis of HRS-1 may lead to improvements in therapeutic options for this seriously ill population.

Metabolism-related signalling pathways involved in the pathogenesis and development of metabolic dysfunction-associated steatotic liver disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) which formerly known as non-alcoholic fatty liver disease (NAFLD) is one of the causes of liver cirrhosis. Currently, a growing number of liver cirrhosis cases develop on the basis of MASLD, and the pathogenesis of MASLD remains unclear. This paper reviews the research progress on the involvement of different metabolism-related signalling pathways in the pathogenesis and development of MASLD.

Hydrogen Sulfide and Liver Health: Insights into Liver Diseases

Significance: Hydrogen sulfide (H2S) is a recently recognized gasotransmitter involved in physiological and pathological conditions in mammals. It protects organs from oxidative stress, inflammation, hypertension, and cell death. With abundant expression of H2S-production enzymes, the liver is closely linked to H2S signaling. Recent Advances: Hepatic H2S comes from various sources, including gut microbiota, exogenous sulfur salts, and endogenous production. Recent studies highlight the importance of hepatic H2S in liver diseases such as nonalcoholic fatty liver disease (NAFLD), liver injury, and cancer, particularly at advanced stages. Endogenous H2S production deficiency is associated with severe liver disease, while exogenous H2S donors protect against liver dysfunction. Critical Issues: However, the roles of H2S in NAFLD, liver injury, and liver cancer are still debated, and its effects depend on donor type, dosage, treatment duration, and cell type, suggesting a multifaceted role. This review aimed to critically evaluate H2S production, metabolism, mode of action, and roles in liver function and disease. Future Direction: Understanding H2S's precise roles and mechanisms in liver health will advance potential therapeutic applications in preclinical and clinical research. Targeting H2S-producing enzymes and exogenous H2S sources, alone or in combination with other drugs, could be explored. Quantifying endogenous H2S levels may aid in diagnosing and managing liver diseases. Antioxid. Redox Signal. 40, 122-144.

Novel salicylic acid derivatives connecting to five-membered cycle through an acyl hydrazone bond as multi-stimuli responsive fluorescent smart materials with photoswitching properties

In order to exploit novel multi-stimuli responsive fluorescent materials, a series of novel fluorescent molecules of salicylic acid derivatives were designed and synthesized via introducing pyrazole or cyclopentane to the salicylic acid scaffold through a special Schiff base-acylhydrazone, and the molecular structures of representative compounds A2 and A4 were verified via single crystal X-ray diffraction. All title molecules could exhibit obvious solvatofluorochromism from cyan to indigo in several solutions with different polarity. The fluorescence titration data exhibited compound A2 and complex A2-Cu2+ with prime detection limits to Cu2+ (0.24 μM) and S2- ions (2.83 μM). The sensitive recognition of A2 to trifluoroacetic (TFA) and A2-TFA to triethylamine (TEA) were also confirmed via fluorescent titration experiments in various solutions, respectively. What's more, the 1H NMR and UV/Vis absorption spectra further explained the mechanism between molecules and ions or molecules and TFA/TEA. Besides, the photoswitching properties of the compounds A2 and A3 could be demonstrated via the irradiation of special wavelength light or heating accompanied with changes in quantum yields. In addition, these phenomena of multiple responses were explained via Density Functional Theory (DFT) based on the Gaussian calculations. Thus, this work provided a preliminary basis for the research of multi-stimuli responsive fluorescent molecules with photoswitching properties.

A turn-on fluorescent probe for selective detection of H2S in environmental samples and bio-imaging in human breast cancer cells

A triphenylamine-benzothaizole-based turn-on fluorescent probe TPB-NO2 was designed and synthesized for tracking H2S in both environmental and biological samples depending upon the sensing strategy of thiolysis of 2,4-dinitrophenyl (DNP) ether. Due to PET (photoinduced electron transfer), occurring from donor triphenylamine moiety to acceptor DNP moiety, the probe TPB-NO2 itself is very weakly fluorescent and colorless in DMSO/H2O solution (1 : 1, v/v; 10 mM HEPES buffer, pH 7.4). But the addition of H2S leads to thiolysis of 2,4-dinitrophenyl ether to block the initial PET process and hence it exhibits naked eye detectable turn-on response with bright cyan fluorescence and intense brown color. Not only that, the probe exhibits excellent selectivity over other bio-thiols like Cysteine (Cys), homocysteine (Hcy), and glutathione (GSH), fast response time (<2 min), and high sensitivity with a detection limit of 9.81 nM. Moreover, to explore the practical applicability of our probe we employed it to monitor H2S successfully in environmental water samples, solid-state TLC strip study, Quantitative determination of H2S in eggs, and in the bioimaging of human breast cancer cells (MDA-MB 231).

Construction of a novel chitosan-based macromolecular nanoprobe for specific fluorescent detection of H2S in live animals

H2S is one of the signal molecules in live organisms and a poisonous gas, which is closely related to our life. The traditional synthetic small molecular organic probes often have the disadvantages of low biocompatibility. In this paper, a fluorescent nanoprobe for detecting H2S in live organisms was constructed based on chitosan. The structure of CH-CN was characterized by infrared spectroscopy, nuclear magnetic resonance, x-ray photoelectron spectroscopy (XPS), XRD and scanning electron microscope (SEM). In the presence of Na2S, the fluorescence intensity at 560 nm was significantly enhanced, and showed high selectivity and sensitivity toward H2S. Based on the good fluorescence response of CH-CN, the probe was also successfully applied to H2S imaging in HepG2 cells and zebrafish. These experimental results indicate that the probe has lower cytotoxicity and excellent stability. The present research shows a typical example of construction of chitosan-based macromolecular fluorescent materials and their bio-imaging application.

A highly sensitive and low toxicity cellulose-based fluorescent polymer for H2S detection in cells, zebrafish and food samples

A cellulose based polymer probe (HC-HS) was prepared for the detection of H2S. HC-HS can be applied to fluorescence imaging of H2S in living cells and zebrafish, and HC-HS was made into test strips to detect H2S produced in the process of food corruption.

Development of novel hydrogen sulfide depletion aided platform for photodynamic therapy with enhanced anticancer performance

Hydrogen sulfide (H₂S) as a key fundamental gasotransmitter regulates various biological processes, and the incontrollable H₂S is essentially associated with the occurrence and development of multiple diseases, including cancers. Photodynamic therapy (PDT), as an invasive tumor treatment technology, has also attracted great attentions. Due to the key role of elevated H₂S in cancers, integrating H₂S depletion/recognition and PDT should be an effective strategy to enhance anticancer performance. In this work, we report a H₂S depletion aided PDT platform (3RAX-NBD) by the chemical ligation of 3RAX and NBD. 3RAX-NBD can react rapidly with H₂S and generate a novel 3RAX derivative compound 3 with increased fluorescence in vitro and in vivo. More notably, 3RAX-NBD can effectively kill multiple cancer cells through in situ irradiation, and 3RAX-NBD also has prominent anticancer effects on 4 T1 tumor-bearing BALB/c female mice with no notably toxic side effects. We believe that our H₂S depletion aided PDT platform may provide a powerful tool for studying the key roles of H₂S in diseases, and also give another promising candidate for cancer treatment.

An ESIPT-based reversible ratiometric fluorescent sensor for detecting HClO/H2S redox cycle in living cells

HClO and H₂S, as two kinds of crucial small biomolecules, are endowed various roles in biological organisms. The redox balance between HClO and H₂S is closely related to the physiological and pathological processes. Thus, it is significant to monitor the redox process between HClO and H₂S. Inspired by the advantages of ratiometric fluorescent probes, we firstly developed a reversible ratiometric fluorescent probe (BT-Se) for HClO and H₂S via combination of phenyl selenide as the response group and 2-(2'-hydroxyphenyl)benzothiazole dye as the fluorophore. The proposed probe BT-Se could detect HClO with well-separated dual emission (110 nm), fast response, good selectivity and sensitivity owing to the oxidation reaction of the Se atom induced by HClO. Moreover, only H₂S could effectively recover the fluorescence of the detection system to the original state via H₂S induced-reduction of selenoxide. Cell imaging studies demonstrated that the probe BT-Se was capable of ratiometric monitoring the changes of intracellular HClO/H₂S, which suggested that it has great potential for researching the biological functions of HClO and H₂S.

Rational development of an ESIPT-based fluorescent probe with large Stokes shift for imaging of hydrogen sulfide in live cells

It is crucial to monitor hydrogen sulfide (H2S) because H2S plays a vital role in the regulation of many physiology and pathology processes. Many evidences indicate that endogenous H2S is closely associated with many diseases such as inflammation and cancers. Herein, we reported a novel fluorescent probe BTDI to monitor the fluctuation of H2S based on the excited-state intramolecular proton transfer (ESIPT) mechanism both ex vivo and in vivo. The selectivity of BTDI for H2S is significantly higher than that for biothiols and other potential anions. After the probe responded to H2S, the nucleophilic addition reaction of the H2S with probe BTDI resulted the shifting of maximum emission peak from 630 nm to 542 nm and the fluorescent signals change from red to green emission along with a large Stokes shift (240 nm). Moreover, BTDI can be successfully applied to detect extracellular and endogenous H2S in living cells through fluorescent cell-imaging, which provides a promising tool for the specific recognition of H2S in complex biological systems.

A biocompatible ratiometric fluorescent nanoprobe for intracellular hydrogen sulfide accurate detection based on rare earth nanoparticle

Hydrogen sulfide (H₂S) is an important signal molecule involved in intracellular activities. To understand the role of H₂S in cellular physiological and pathological process, the development of sensitive and selective methods, especially biocompatible assays, for efficient monitoring the level of H₂S is necessary. Herein, we modified novel rare earth element europium (EU) based fluorescent nanospheres with azide (-N₃) based sensor to construct an ingenious ratiometric fluorescent nanoprobe EU-N3. This nanoprobe showed excellent water solubility and high biocompatibility for intracellular H₂S accurate detection. Nanoprobe EU-N3 had two obvious emission peaks, the green fluorescence peak at 540 nm increased according to the increasing of H₂S concentration and the red fluorescence peak at 616 nm was stable as ratiometric reference. The fluorescence intensity ratio (I₅₄₀/I₆₁₆) displayed good linear response (R = 0.99136) in H₂S range of 0.5 ∼ 30 μM. The analytes response assay demonstrated that the nanoprobe EU-N3 possessed a better specificity for H₂S, compared with other 9 anions and 3 cations. The cell viability assay indicated the nanoprobe EU-N3 had an excellent biocompatibility. The cell imaging showed that the proposed nanoprobe could be applied for detecting the intracellular H₂S changes accurately in live cells. Such nanoprobe provided a safe and accurate strategy for intracellular H₂S detection, which is helpful for the real-time H₂S visualization in the live cell activities.

An ESIPT-based fluorescent turn-on probe with isothiocyanate for detecting hydrogen sulfide in environmental and biological systems

A probe with an isothiocyanate group was synthesized and evaluated for its H₂S sensing ability. Upon addition of H₂S, the probe exhibited ratiometric properties during absorption with a red-shift. The probe exhibited fluorescent off-on responses towards H₂S via the ESIPT process, due to the conversion of isocyanate into amine. UV-vis, fluorescence, and ¹H NMR spectroscopic analyses were performed to investigate the sensing mechanism. The probe has a large Stokes shift, short response time, and low detection limit. It can be used to estimate H₂S levels within the range of 0-36 nM. The practical applicability of the probe was demonstrated using water samples and living cells.

Influence of Gut–Liver Axis on Portal Hypertension in Advanced Chronic Liver Disease: The Gut Microbiome as a New Protagonist in Therapeutic Management

Clinically significant portal hypertension is associated with most complications of advanced chronic liver disease (ACLD), including variceal bleeding, ascites, spontaneous bacterial peritonitis, hepatorenal syndrome, and hepatic encephalopathy. Gut dysbiosis is a hallmark of ACLD with portal hypertension and consists of the overgrowth of potentially pathogenic bacteria and a decrease in autochthonous bacteria; additionally, congestion makes the intestinal barrier more permeable to bacteria and their products, which contributes to the development of complications through inflammatory mechanisms. This review summarizes current knowledge on the role of the gut–liver axis in the pathogenesis of portal hypertension, with a focus on therapies targeting portal hypertension and the gut microbiota. The modulation of the gut microbiota on several levels represents a major challenge in the upcoming years; in-depth characterization of the molecular and microbiological mechanisms linking the gut–liver axis to portal hypertension in a bidirectional relationship could pave the way to the identification of new therapeutic targets for innovative therapies in the management of ACLD.

Design strategy for an analyte-compensated fluorescent probe to reduce its toxicity

During biological detection, the toxicity caused by probes to living organisms is neglected. In this study, an analyte-compensated fluorescent probe (NP-SN₃) was constructed for the detection of H₂S. Through experiments with HepG2 cells and zebrafish embryos and larvae, the NP-SN₃ probe showed no significant difference in imaging performance compared with the traditional probe (NP-N₃) but exhibited lower detection-induced toxicity in the imaging of liver fibrosis in activated HSC-T6 cells. During the development of zebrafish embryos and continuous administration in rats, NP-SN₃ showed a lower death rate, higher hatchability and lower malformation in zebrafish embryos and milder pathological symptoms in stained rat tissues.

A nitrobenzoxadiazole-based near-infrared fluorescent probe for the specific imaging of H2S in inflammatory and tumor mice

As a common gaseous signaling molecule, hydrogen sulfide (H₂S) plays a vital role in physiology and pathology. The development of fluorescent probes for detecting H₂S has attracted widespread attention. However, most of the reported fluorescent probes with nitrobenzoxadiazole (NBD) as the recognition group have been widely used to simultaneously detect biothiols and H₂S, instead of specifically detecting H₂S. Herein, a novel NBD-based near-infrared (NIR) fluorescent probe named CX-N for the detection of H₂S is synthesized. The selectivity of CX-N for H₂S is significantly higher than that for biothiols and other potential interferences. After reacting with H₂S, CX-N shows a significant increase in NIR fluorescence (75-fold), large Stokes shift (155 nm) and fast response (4 min). And the possible response mechanism of CX-N to H₂S is given and confirmed by HPLC and HRMS. Based on the low cytotoxicity of CX-N, it has been used for H₂S imaging in live cells and zebrafish. More importantly, CX-N has also been successfully applied for the real-time imaging of H₂S in inflammatory and tumor mice based on its NIR emission, which provides a reliable platform for the specific recognition of H₂S in complex biological systems.

TLRs-JNK/ NF-κB Pathway Underlies the Protective Effect of the Sulfide Salt Against Liver Toxicity

Hydrogen sulfide (H₂S) is an endogenously gas transmitter signaling molecule with known antioxidant, anti-inflammatory, and cytoprotective properties. Although accumulating evidence shows the therapeutic potential of H₂S in various hepatic diseases, its role in cyclophosphamide (CP)-induced hepatotoxicity remains elusive. The present study was undertaken to investigate the impact of endogenous and exogenous H₂S on toll-like receptors (TLRs)-mediated inflammatory response and apoptosis in CP-induced hepatotoxicity. Either an H₂S donor (NaHS (100 μM/kg) or an H2S blocker [dl-propargylglycine (PAG) (30 mg/kg, i. p.)], was administered for 10 days before a single ip injection of CP (200 mg/kg). NaHS attenuated conferred hepatoprotection against CP-induced toxicity, significantly decreasing serum hepatic function tests and improving hepatic histopathology. Additionally, NaHS-treated rats exhibited antioxidant activity in liver tissues compared with the CP group. The upregulated hepatic levels of TLR2/4 and their downstream signaling molecules including c-Jun N-terminal kinase (JNK) and nuclear factor-kappa B (NF-κB) were also suppressed by NaHS protective treatment. NaHS showed anti-inflammatory and antiapoptotic effects; reducing hepatic level tumor necrosis factor-alpha (TNF-α) and caspase-3 expression. Interestingly, the cytotoxic events induced in CP-treated rats were not significantly altered upon the blocking of endogenous H₂S. Taken together, the present study suggested that exogenously applied H₂S rather than the endogenously generated H₂S, displayed a hepatoprotective effect against CP-induced hepatotoxicity that might be mediated by TLRs-JNK/NF-κB pathways.

BODIPY-NBD dyad for highly selective and sensitive detection of hydrogen sulfide in cells and zebrafish

Hydrogen sulfide (H₂S) has been regarded as the third endogenous gas signaling molecule. The development of suitable tools for H₂S detection in vitro and in vivo has always been a focus of research. In this work, three BODIPY-NBD dyads (o/m/p-BNP) were designed and synthesized using BODIPY and NBD as the fluorophore and quencher, respectively. The position of the NBD moiety in the probe showed different fluorescence quenching abilities. All probes showed highly selective to H₂S. Probe o-BNP displayed the maximum fluorescence enhancement (c.a. 1300-fold) and the lowest detection limit (105 nM). Probe o-BNP can visualize the production of endogenous H₂S in HeLa cells and zebrafish.

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

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

A hydrogen sulphide-responsive and depleting nanoplatform for cancer photodynamic therapy

Hydrogen sulfide (H₂S) as an important biological gasotransmitter plays a pivotal role in many physiological and pathological processes. The sensitive and quantitative detection of H₂S level is therefore crucial for precise diagnosis and prognosis evaluation of various diseases but remains a huge challenge due to the lack of accurate and reliable analytical methods in vivo. In this work, we report a smart, H₂S-responsive and depleting nanoplatform (ZNNPs) for quantitative and real-time imaging of endogenous H₂S for early diagnosis and treatment of H₂S-associated diseases. We show that ZNNPs exhibit unexpected NIR conversion (F₁₀₇₀→ F₇₂₀) and ratiometric photoacoustic (PA₆₈₀/PA₉₀₀) signal responsiveness towards H₂S, allowing for sensitive and quantitative visualization of H₂S in acute hepatotoxicity, cerebral hemorrhage model as well as colorectal tumors in living mice. ZNNPs@FA simultaneously scavenges the mitochondrial H₂S in tumors leading to significant ATP reduction and severe mitochondrial damage, together with the activated photodynamic effect, resulting in efficient suppression of colorectal tumor growth in mice. We believe that this platform may provide a powerful tool for studying the vital impacts of H₂S in related diseases.

Engineered lanthanide-doped upconversion nanoparticles for biosensing and bioimaging application

Various fluctuations of intracellular ions, biomolecules, and other conditions in the physiological environment play crucial roles in fundamental biological processes. These factors are of great importance for analysis in biomedical detection. Nevertheless, developments of the simple, rapid, and accurate proof for specific detection still encounter major challenges. Upconversion nanoparticles (UCNPs), which could absorb multiple low-energy near-infrared light (NIR) photon excitation and emits high-energy photons caused by anti-Stokes shift, show unique upconversion luminescence (UCL) properties, for example, sharp emission band, high physicochemical stability like near-zero photobleaching, photo blinking in biological tissues, and long luminescence lifetime. Furthermore, the NIR used for the light source to excite UCNPs enable lower photo-damage effect and deeper penetration of tissue, and in the meantime, it can avoid the auto-fluorescence and light scattering from biological tissue interference. Thus, the lanthanide-doped UCNP-based functional platform with controlled structure, crystalline phase, size, and multicolor emission has become an appropriate nanomaterial for bioapplications such as biosensing, bioimaging, drug release, and therapies. In this review, the recent progress about synthesis and biomedical applications of UCNPs related to sensing and bioimaging is summarized. Firstly, the different luminescence mechanisms of the upconversion process are presented. Secondly, four of the most common methods for synthesizing UCNPs are compared as well as the advantages and disadvantages of these synthetic routes. Meanwhile, the surface modification of lanthanide-doped UCNPs was introduced to pave the way for their biochemistry applications. Next, this review detailed the biological applications of lanthanide-doped UCNPs, particularly in bioimaging, including UCL and multi-modal imaging and biosensing (monitoring intracellular ions and biomolecules). Finally, the challenges and future perspectives in materials science and biomedical fields of UCNPs are concluded: the low quantum yield of the upconversion process should be considered when they are executed as imaging contrast agents. And the biosafety of lanthanide-doped UCNPs needs to be evaluated.

An ESIPT-based fluorescent probe with fast-response for detection of hydrogen sulfide in mitochondria

Excited-state intramolecular proton transfer (ESIPT) has recently received considerable attention due to its dual fluorescent changes and large Stokes shift. Hydrogen sulfide (H₂S) is a gas signal molecule that plays important roles in modulating the functions of different systems. Herein, by modifying 2-(2́-hydroxyphenyl) benzothiazole (HBT) scaffold, a novel near-infrared mitochondria-targeted fluorescent probe HBTP-H₂S has been rationally designed based on excited-state intramolecular proton transfer (ESIPT) effect. The nucleophilic addition reaction of the H₂S with probe HBTP-H₂S caused the break of the conjugated skeleton, resulting the shifting of maximum emission peak from 658 nm to 470 nm. HBTP-H₂S showed fast-response response time, good selectivity and a large Stokes shift (188 nm) toward H₂S. Most importantly, inspired by the inherent advantages of the probe, HBTP-H₂S was successfully employed to monitor mitochondrial H₂S in HepG2 cells.

An aggregation-induced emissive pyridoxal derived tetradentate Schiff base for the fluorescence turn-off sensing of copper(ii) in an aqueous medium

An aggregation-induced emissive pyridoxal derived tetradentate Schiff base was developed for the fluorescence sensing of copper(ii) and sulphide ions.

Highly Selective Fluorescent Probe Design for Visualizing Hepatic Hydrogen Sulfide in the Pathological Progression of Nonalcoholic Fatty Liver

Hydrogen sulfide (H₂S), emerging as an important gaseous signal, has attracted more and more attention for its key role in chronic fatty liver diseases. However, lacking tools for H₂S-specific in situ detection, the changes of endogenous hepatic H₂S levels in the pathological progression of chronic liver diseases are still unclear. To this end, we adopted a strategy of combining molecular probe design and nanofunctionalization to develop a highly selective near-infrared (NIR) fluorescent probe, which allows in vivo real-time monitoring of hepatic H₂S levels in the process of nonalcoholic fatty liver disease (NAFLD). As a proof of strategy demonstration, we first designed NIR molecular probes for H₂S sensing through chemical design and probe screening and then loaded molecular probes into mesoporous silicon nanomaterials (MSNs) with surface encapsulation using poly(ethylene glycol) to construct a highly selective probe MSN@CSN@PEG, with significantly improved selectivity and photostability. Moreover, MSN@CSN@PEG exhibited high selectivity and sensitivity for endogenous H₂S in cells and tumors in vivo, eliminating the interference of a high concentration of biothiols and sulfhydryl proteins. Furthermore, the probe was applied to in situ intravital imaging and systematic assessment of hepatic H₂S levels in different stages of NAFLD for the first time, which may offer a promising tool for the future study of fatty liver diseases and other chronic liver diseases.

A phenothiazine-based turn-on fluorescent probe for the selective detection of hydrogen sulfide in food, live cells and animals

In this work, a phenothiazine-based fluorescent probe (PR) has been developed for the selective detection of hydrogen sulfide (H₂S) in biosystems and monitoring H₂S produced in the food spoilage process. The nucleophilic attack of H₂S on the CC double bond of PRvia a Michael addition interdicted the ICT process to trigger 34-fold enhancement of the fluorescence emission. PR featured high selectivity and sensitivity (1.8 μM), low cytotoxicity and reliability at physiological pH. "Naked-eye" monitoring of H₂S produced in the food spoilage process using PR was successfully accomplished. The preliminary fluorescence imaging studies showed that PR is suitable for the visualization of exogenous and endogenous H₂S in living cells and live animals. Moreover, PR has been successfully applied to the visualization of H₂S generation in an inflammation model. The results indicated that PR is an effective tool to monitor H₂S production in the fields of biomedicine and food safety.

Iodide-enhanced Co/Fe-MOFs nanozyme for sensitively colorimetric detection of H2S

In this paper, a simple, rapid, and low-cost colorimetric method was designed based on Co/Fe-MOFs-iodide composite for the quantitative detection of H₂S. It is know that iodide can improve the catalytic activity of bimetallic porous material Co/Fe-MOFs via adsorption into the framework of MOFs. Herein, we demonstrate a novel strategy to enhance the peroxidase-like activity of MOFs. Compared to horseradish peroxidase (HRP), the kinetic measurement results show that Co/Fe-MOFs-iodide exhibits excellent affinity to substrates, promoting electron transfer. Due to the synergetic effect of Co/Fe-MOFs and iodide, and rapid electron transfer process, Co/Fe-MOFs-iodide demonstrates improved peroxidase-like activity. As a proof-of-concept application, a novel, highly sensitive H₂S colorimetric method is established with a detection limit (LOD) of 0.33 nM. In the absence of iodide, LOD is approx. 200-fold higher than that of the amplified colorimetric assay. The proposed method can also accurately detect traces of H₂S in serum samples.

Plasma Hydrogen Sulfide Is Positively Associated With Post-operative Survival in Patients Undergoing Surgical Revascularization

Objective: Hydrogen sulfide (H₂S) is a gaseous signaling molecule and redox factor important for cardiovascular function. Deficiencies in its production or bioavailability are implicated in atherosclerotic disease. However, it is unknown if circulating H₂S levels differ between vasculopaths and healthy individuals, and if so, whether H₂S measurements can be used to predict surgical outcomes. Here, we examined: (1) Plasma H₂S levels in patients undergoing vascular surgery and compared these to healthy controls, and (2) the association between H₂S levels and mortality in a cohort of patients undergoing surgical revascularization.

Methods: One hundred and fifteen patients undergoing carotid endarterectomy, open lower extremity revascularization or lower leg amputation were enrolled at a single institution. Peripheral blood was also collected from a matched control cohort of 20 patients without peripheral or coronary artery disease. Plasma H₂S production capacity and sulfide concentration were measured using the lead acetate and monobromobimane methods, respectively.

Results: Plasma H₂S production capacity and plasma sulfide concentrations were reduced in patients with PAD (p < 0.001, p = 0.013, respectively). Patients that underwent surgical revascularization were divided into high vs. low H₂S production capacity groups by median split. Patients in the low H₂S production group had increased probability of mortality (p = 0.003). This association was robust to correction for potentially confounding variables using Cox proportional hazard models.

Conclusion: Circulating H₂S levels were lower in patients with atherosclerotic disease. Patients undergoing surgical revascularization with lower H₂S production capacity, but not sulfide concentrations, had increased probability of mortality within 36 months post-surgery. This work provides insight on the role H₂S plays as a diagnostic and potential therapeutic for cardiovascular disease.