Prodrugs of hydrogen sulfide and related sulfur species: recent development

Advancements in increasing efficiency of hydrogen sulfide in therapeutics: Strategies for targeted delivery as prodrugs

Hydrogen sulfide (H2S) has emerged as a potent therapeutic agent with diverse physiological functions, including vasodilation, anti-inflammation, and cytoprotection. However, its clinical application is limited due to its volatility and potential toxicity at high concentrations. To address these challenges, researchers have developed various H2S prodrugs that release H2S in a controlled and targeted manner. The review underscores the importance of targeting and delivery strategies in maximizing the therapeutic potential of H2S, a gasotransmitter with diverse physiological functions and therapeutic effects. By summarizing recent advancements, the review provides valuable insights for researchers and clinicians interested in harnessing the therapeutic benefits of H2S while minimizing off-target effects and toxicity. The integration of novel targeting and delivery approaches not only enhances the efficacy of H2S-based therapeutics but also expands the scope of potential applications, offering promising avenues for the development of new treatments for a variety of diseases and disorders.

Gas-Responsive and Gas-Releasing Polymer Assemblies

In order to explore the unique physiological roles of gas signaling molecules and gasotransmitters in vivo, chemists have engineered a variety of gas-responsive polymers that can monitor their changes in cellular milieu, and gas-releasing polymers that can orchestrate the release of gases. These have advanced their potential applications in the field of bio-imaging, nanodelivery, and theranostics. Since these polymers are of different chain structures and properties, the morphology of their assemblies will manifest distinct transitions after responding to gas or releasing gas. In this review, we summarize the fundamental design rationale of gas-responsive and gas-releasing polymers in structure and their controlled transition in self-assembled morphology and function, as well as present some perspectives in this prosperous field. Emerging challenges faced for the future research are also discussed.

Activatable Probes for Ratiometric Imaging of Endogenous Biomarkers In Vivo

Dynamic variations in the concentration and abnormal distribution of endogenous biomarkers are strongly associated with multiple physiological and pathological states. Therefore, it is crucial to design imaging systems capable of real-time detection of dynamic changes in biomarkers for the accurate diagnosis and effective treatment of diseases. Recently, ratiometric imaging has emerged as a widely used technique for sensing and imaging of biomarkers due to its advantage of circumventing the limitations inherent to conventional intensity-dependent signal readout methods while also providing built-in self-calibration for signal correction. Here, the recent progress of ratiometric probes and their applications in sensing and imaging of biomarkers are outlined. Ratiometric probes are classified according to their imaging mechanisms, and ratiometric photoacoustic imaging, ratiometric optical imaging including photoluminescence imaging and self-luminescence imaging, ratiometric magnetic resonance imaging, and dual-modal ratiometric imaging are discussed. The applications of ratiometric probes in the sensing and imaging of biomarkers such as pH, reactive oxygen species (ROS), reactive nitrogen species (RNS), glutathione (GSH), gas molecules, enzymes, metal ions, and hypoxia are discussed in detail. Additionally, this Review presents an overview of challenges faced in this field along with future research directions.

Fluorimetric Reusable Polymeric Sensor for Hydrogen Sulfide Detection

In this study, with the help of reactive monomers, crosslinkers, and photoinitiator that detect H2S in various matrices, an H2S sensitive fluorescence sensor polymerizes under ultraviolet (UV) light was developed. To this goal, a polymeric membrane was prepared, and the characterization of the membrane was carried out with Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) methods. Afterward, appropriate conditions were identified, the excitation wavelength was determined as 370 nm, and the emission wavelength was determined as 425 nm. It was established that the fluorescence intensity of the prepared polymeric membrane decreased in the presence of H2S. A detailed analysis was executed to determine the sensor's most suitable pH value and time. It was found that the optimum pH was 8.0, and the optimal duration was 15 s. It has been calculated that the linear range of the developed method is 2.19 × 10-8- 6.25 × 10-7 M, and the detection limit (LOD) is 7.37 × 10-9 M. The effect of some possible interfering ions was investigated, and it determined that the sensor had excellent selectivity. In addition, the sensor used to determine H2S can be used at least 100 times. The recovery percentages were 102.1%-103.2%, and 104.6%, using tap water samples. In terms of providing reliable, fast results, high sensitivity, reusable, low cost, and ease of use, the developed fluorimetric sensor, compared to standard methods, has become more advantageous.

Reactive sulfur species and their significance in health and disease

Reactive sulfur species (RSS) have been recognized in the last two decades as very important molecules in redox regulation. They are involved in metabolic processes and, in this way, they are responsible for maintenance of health. This review summarizes current information about the essential biological RSS, including H₂S, low molecular weight persulfides, protein persulfides as well as organic and inorganic polysulfides, their synthesis, catabolism and chemical reactivity. Moreover, the role of RSS disturbances in various pathologies including vascular diseases, chronic kidney diseases, diabetes mellitus Type 2, neurological diseases, obesity, chronic obstructive pulmonary disease and in the most current problem of COVID-19 is presented. The significance of RSS in aging is also mentioned. Finally, the possibilities of using the precursors of various forms of RSS for therapeutic purposes are discussed.

Progress and perspective on hydrogen sulfide donors and their biomedical applications

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

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.

Gasping for Sulfide: A Critical Appraisal of Hydrogen Sulfide in Lung Disease and Accelerated Aging

Hydrogen sulfide (H₂S) is a gaseous signaling molecule involved in a plethora of physiological and pathological processes. It is primarily synthesized by cystathionine-β-synthase, cystathionine-γ-lyase, and 3-mercaptopyruvate sulfurtransferase as a metabolite of the transsulfuration pathway. H₂S has been shown to exert beneficial roles in lung disease acting as an anti-inflammatory and antiviral and to ameliorate cell metabolism and protect from oxidative stress. H₂S interacts with transcription factors, ion channels, and a multitude of proteins via post-translational modifications through S-persulfidation ("sulfhydration"). Perturbation of endogenous H₂S synthesis and/or levels have been implicated in the development of accelerated lung aging and diseases, including asthma, chronic obstructive pulmonary disease, and fibrosis. Furthermore, evidence indicates that persulfidation is decreased with aging. Here, we review the use of H₂S as a biomarker of lung pathologies and discuss the potential of using H₂S-generating molecules and synthesis inhibitors to treat respiratory diseases. Furthermore, we provide a critical appraisal of methods of detection used to quantify H₂S concentration in biological samples and discuss the challenges of characterizing physiological and pathological levels. Considerations and caveats of using H₂S delivery molecules, the choice of generating molecules, and concentrations are also reviewed. Antioxid. Redox Signal. 35, 551-579.