Hydrogen sulfide in longevity and pathologies: Inconsistency is malodorous

Hydrogen Sulfide Ameliorates Heart Aging by Downregulating Matrix Metalloproteinase-9

PURPOSE

Aging contributes significantly to cardiovascular diseases and cardiac dysfunction, leading to the upregulation of matrix metalloproteinase-9 (MMP-9) in the heart and a significant decrease in hydrogen sulfide (H2S) content, coupled with impaired cardiac diastolic function. This study explores whether supplementing exogenous hydrogen sulfide during aging ameliorates the decline in H2S concentration in the heart, suppresses MMP-9 expression, and improves the age-associated impairment in cardiac morphology and function.

METHODS

We collected plasma from healthy individuals of different ages to determine the relationship between aging and H2S and MMP-9 levels through Elisa detection and liquid chromatography-tandem mass spectrometry (LC/MC) detection of plasma H2S content. Three-month-old mice were selected as the young group, while 18-month-old mice were selected as the old group, and sodium hydrosulfide (NaHS) was injected intraperitoneally from 15 months old until 18 months old as the old + NaHS group. Plasma MMP-9 content was detected using Elisa, plasma H2S content, cardiac H2S content, and cystathionine gamma-lyase (CSE) activity were detected using LC/MC, and cardiac function was detected using echocardiography. Heart structure was assessed using hematoxylin and eosin staining, Masone staining was used to detect the degree of cardiac fibrosis, while western blot was used to detect the expression of MMP-9, CSE, and aging marker proteins. Knockdown of MMP-9 and CSE in H9c2 cells using small interfering RNA was carried out to determine the upstream-downstream relationship between MMP-9 and CSE.

RESULTS

H2S content in the plasma of healthy individuals decreases with escalating age, whereas MMP-9 level rises with age progression. Aging leads to a decrease in H2S levels in the heart and plasma of mice, severe impairment of cardiac diastolic function, interstitial relaxation, and fibrosis of the heart. Supplementing with exogenous H2S can improve these phenomena.

CONCLUSION

H2S maintains the structure and function of the heart by inhibiting the expression of MMP-9 during the aging process.

Benzylic Trifluoromethyl Accelerates 1,6-Elimination Toward Rapid Probe Activation

Activity-based detection of hydrogen sulfide in live cells can expand our understanding of its reactivity and complex physiological effects. We have discovered a highly efficient method for fluorescent probe activation, which is driven by H2S-triggered 1,6-elimination of an α-CF3-benzyl to release resorufin. In detecting intracellular H2S, 4-azido-(α-CF3)-benzyl resorufin offers significantly faster signal generation and improved sensitivity compared to 4-azidobenzyl resorufin. Computed free energy profiles for the 1,6-elimination process support the hypothesis that a benzylic CF3 group can reduce the activation energy barrier toward probe activation. This novel probe design allows for near-real-time detection of H2S in HeLa cells under stimulation conditions.

Low-Molecular Weight Compounds that Extend the Chronological Lifespan of Yeasts, Saccharomyces cerevisiae, and Schizosaccharomyces pombe

Yeast is an excellent model organism for research for regulating aging and lifespan, and the studies have made many contributions to date, including identifying various factors and signaling pathways related to aging and lifespan. More than 20 years have passed since molecular biological perspectives are adopted in this research field, and intracellular factors and signal pathways that control aging and lifespan have evolutionarily conserved from yeast to mammals. Furthermore, these findings have been applied to control the aging and lifespan of various model organisms by adjustment of the nutritional environment, genetic manipulation, and drug treatment using low-molecular weight compounds. Among these, drug treatment is easier than the other methods, and research into drugs that regulate aging and lifespan is consequently expected to become more active. Chronological lifespan, a definition of yeast lifespan, refers to the survival period of a cell population under nondividing conditions. Herein, low-molecular weight compounds are summarized that extend the chronological lifespan of Saccharomyces cerevisiae and Schizosaccharomyces pombe, along with their intracellular functions. The low-molecular weight compounds are also discussed that extend the lifespan of other model organisms. Compounds that have so far only been studied in yeast may soon extend lifespan in other organisms.

Application of gold nanoclusters in fluorescence sensing and biological detection

Gold nanoclusters (Au NCs) exhibit broad fluorescent spectra from visible to near-infrared regions and good enzyme-mimicking catalytic activities. Combined with excellent stability and exceptional biocompatibility, the Au NCs have been widely exploited in biomedicine such as biocatalysis and bioimaging. Especially, the long fluorescence lifetime and large Stokes shift attribute Au NCs to good probes for fluorescence sensing and biological detection. In this review, we systematically summarized the molecular structure and fluorescence properties of Au NCs and highlighted the advances in fluorescence sensing and biological detection. The Au NCs display high sensitivity and specificity in detecting iodine ions, metal ions, and reactive oxygen species, as well as certain diseases based on the fluorescence activities of Au NCs. We also proposed several points to improve the practicability and accelerate the clinical translation of the Au NCs.

Simultaneous activation of the hydrogen sulfide biosynthesis genes (CBS and CSE) induces sex-specific geroprotective effects in Drosophila melanogaster

Hydrogen sulfide (H₂S) is one of the most important gasotransmitters that affect lifespan and provide resistance to adverse environmental conditions. Here we investigated geroprotective effects of the individual and simultaneous overexpression of genes encoding key enzymes of H₂S biosynthesis - cystathionine-β-synthase (CBS) and cystathionine-γ-lyase (CSE) on D. melanogaster model. Simultaneous overexpression of CBS and CSE resulted in additive (in males) and synergistic (in females) beneficial effects on median lifespan. Individual overexpression of CBS was associated with increased thermotolerance and decreased transcription level of genes encoding stress-responsive transcription factors HIF1 and Hsf, while individual overexpression of CSE was associated with increased resistance to paraquat. Simultaneous overexpression of both genes increased resistance to hyperthermia in old females or paraquat in old males. The obtained results suggest sex-specific epistatic interaction of CBS and CSE overexpression effects on longevity and stress resistance.

The Role of Hydrogen Sulfide Targeting Autophagy in the Pathological Processes of the Nervous System

Autophagy is an important cellular process, involving the transportation of cytoplasmic contents in the double membrane vesicles to lysosomes for degradation. Autophagy disorder contributes to many diseases, such as immune dysfunction, cancers and nervous system diseases. Hydrogen sulfide (H₂S) is a volatile and toxic gas with a rotten egg odor. For a long time, it was considered as an environmental pollution gas. In recent years, H₂S is regarded as the third most important gas signal molecule after NO and CO. H₂S has a variety of biological functions and can play an important role in a variety of physiological and pathological processes. Increasingly more evidences show that H₂S can regulate autophagy to play a protective role in the nervous system, but the mechanism is not fully understood. In this review, we summarize the recent literatures on the role of H₂S in the pathological process of the nervous system by regulating autophagy, and analyze the mechanism in detail, hoping to provide the reference for future related research.

NO, CO and H2S: A Trinacrium of Bioactive Gases in the Brain

Oxygen and carbon dioxide are time honored gases that have direct bearing on almost all life forms, but over the past thirty years, and in large part due to the Nobel Prize Award in Medicine for the elucidation of nitric oxide (NO) as a bioactive gas, the research and medical communities now recognize other gases as critical for survival. In addition to NO, hydrogen sulfide (H₂S) and carbon monoxide (CO) have emerged as a triumvirate or Trinacrium of gases with analogous importance and that serve important homeostatic functions. Perhaps, one of the most intriguing aspects of these gases is the functional interaction between them, which is intimately linked by the enzyme systems that produce them. Despite the need to better understand NO, H₂S and CO biology, the notion that these are environmental pollutants remains ever present. For this reason, incorporating the concept of hormesis becomes imperative and must be included in discussions when considering developing new therapeutics that involve these gases. While there is now an enormous literature base for each of these gasotransmitters, we provide here an overview of their respective physiologic roles in the brain.

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.

Probing the Role of Cysteine Thiyl Radicals in Biology: Eminently Dangerous, Difficult to Scavenge

Thiyl radicals are exceptionally interesting reactive sulfur species (RSS), but rather rarely considered in a biological or medical context. We here review the reactivity of protein thiyl radicals in aqueous and lipid phases and provide an overview of their most relevant reaction partners in biological systems. We deduce that polyunsaturated fatty acids (PUFAs) are their preferred reaction substrates in lipid phases, whereas protein side chains arguably prevail in aqueous phases. In both cellular compartments, a single, dominating thiyl radical-specific antioxidant does not seem to exist. This conclusion is rationalized by the high reaction rate constants of thiyl radicals with several highly concentrated substrates in the cell, precluding effective interception by antioxidants, especially in lipid bilayers. The intractable reactivity of thiyl radicals may account for a series of long-standing, but still startling biochemical observations surrounding the amino acid cysteine: (i) its global underrepresentation on protein surfaces, (ii) its selective avoidance in aerobic lipid bilayers, especially the inner mitochondrial membrane, (iii) the inverse correlation between cysteine usage and longevity in animals, (iv) the mitochondrial synthesis and translational incorporation of cysteine persulfide, and potentially (v) the ex post introduction of selenocysteine into the genetic code.

Effects of Exogenous Hydrogen Sulfide on Diabetic Metabolic Disorders in db/db Mice Are Associated With Gut Bacterial and Fungal Microbiota

The effects of hydrogen sulfide (H2S) on diabetic metabolic disorders are still controversial, and the mechanisms underlying these effects remain largely unknown. This study was conducted to investigate the potential relationship between the gut microbiota and the improvement of diabetic metabolic disorders by exogenous H2S in obese db/db mice. The db/db mice were treated with sodium hydrosulfide (NaHS) (80 μmol/kg), or vehicle for 16 weeks, respectively. We measured the serum H2S, obesity parameters, glucose homeostasis, and triglyceride. The sequencing of bacterial 16S rRNA gene and fungal internal transcribed spacer (ITS) in the cecal contents of NaHS-treated mice was performed to evaluate the gut microbial communities. We found that supplying exogenous H2S for 16 weeks significantly inhibited the increase of serum triglyceride, blood glucose, and insulin levels and altered specifically the gut bacterial microbiota structure in db/db mice. The relative abundance of some bacterial genera was correlated with the H2S or blood glucose level. Indeed, exogenous H2S increased Firmicutes and decreased Bacteroidetes at the phylum level along with changes of abundance of multifarious genera. Among them, Unclassified_Enterobacteriaceae, Prevotella, and Lactobacillus decreased and Unclassified_Ruminococcaceae, Oscillospira, Ruminococcus, Sutterella, and Desulfovibrio increased. For fungi, exogenous H2S decreased the abundance of Candida and Aspergillus. Here we demonstrated that, in diabetes, microbial dysbiosis may not be just limited to bacteria due to the inter-linked metabolic interactions among bacteria and fungi in the gut. The beneficial effects of exogenous H2S on diabetic metabolic disorders are likely associated with the alterations of specific microbiota.

Deletions of the cystathionine-β-synthase (CBS) and cystathionine-γ-lyase (CSE) genes, involved in the control of hydrogen sulfide biosynthesis, significantly affect lifespan and fitness components of Drosophila melanogaster

The gasotransmitter hydrogen sulfide (H₂S) is an important biological mediator, playing an essential role in many physiological and pathological processes. It is produced by transsulfuration - an evolutionarily highly conserved pathway for the metabolism of sulfur-containing amino acids methionine and cysteine. Cystathionine-β-synthase (CBS) and cystathionine-γ-lyase (CSE) enzymes play a central role in cysteine metabolism and H₂S production. Here we investigated the fitness components (longevity, stress resistance, viability of preimaginal stages, and reproductive function parameters) in D. melanogaster lines containing deletions of the CBS and CSE genes. Surprisingly, in most tests, CSE deletion improved, and CBS worsened the fitness. Lines with deletion of both CBS and CSE demonstrated better stress resistance and longevity than lines with single CBS deletion. At the same time, deletion of both CBS and CSE genes causes more serious disturbances of reproductive function parameters than single CBS deletion. Thus, a complex interaction of H₂S-producing pathways and cellular stress response in determining the lifespan and fitness components of the whole organism was revealed.

Mitochondria-Microbiota Interaction in Neurodegeneration

Alzheimer’s and Parkinson’s are the two best-known neurodegenerative diseases. Each is associated with the excessive aggregation in the brain and elsewhere of its own characteristic amyloid proteins. Yet the two afflictions have much in common and often the same amyloids play a role in both. These amyloids need not be toxic and can help regulate bile secretion, synaptic plasticity, and immune defense. Moreover, when they do form toxic aggregates, amyloids typically harm not just patients but their pathogens too. A major port of entry for pathogens is the gut. Keeping the gut’s microbe community (microbiota) healthy and under control requires that our cells’ main energy producers (mitochondria) support the gut-blood barrier and immune system. As we age, these mitochondria eventually succumb to the corrosive byproducts they themselves release, our defenses break down, pathogens or their toxins break through, and the side effects of inflammation and amyloid aggregation become problematic. Although it gets most of the attention, local amyloid aggregation in the brain merely points to a bigger problem: the systemic breakdown of the entire human superorganism, exemplified by an interaction turning bad between mitochondria and microbiota.

One-Carbon Metabolism: Pulling the Strings behind Aging and Neurodegeneration

One-carbon metabolism (OCM) is a network of biochemical reactions delivering one-carbon units to various biosynthetic pathways. The folate cycle and methionine cycle are the two key modules of this network that regulate purine and thymidine synthesis, amino acid homeostasis, and epigenetic mechanisms. Intersection with the transsulfuration pathway supports glutathione production and regulation of the cellular redox state. Dietary intake of micronutrients, such as folates and amino acids, directly contributes to OCM, thereby adapting the cellular metabolic state to environmental inputs. The contribution of OCM to cellular proliferation during development and in adult proliferative tissues is well established. Nevertheless, accumulating evidence reveals the pivotal role of OCM in cellular homeostasis of non-proliferative tissues and in coordination of signaling cascades that regulate energy homeostasis and longevity. In this review, we summarize the current knowledge on OCM and related pathways and discuss how this metabolic network may impact longevity and neurodegeneration across species.

The Dehydrogenation of H-S Bond into Sulfur Species on Supported Pd Single Atoms Allows Highly Selective and Sensitive Hydrogen Sulfide Detection

The supported metal catalysts on scaffolds usually reveal multiple active sites, resulting in the occurrence of side reaction and being detrimental to the achievement of highly consistent catalysis. Single atom catalysts (SACs), possessed with highly consistent single active sites, have great potentials for overcoming such issues. Herein, the authors used SACs to modulate kinetic process of gas sensitive reaction. The supported Pd SACs, established by a metal organic frameworks-templated approach, promoted greatly the detection capacity to hydrogen sulfide (H₂ S) gas with a very high sensitivity and selectivity. Density functional theory calculations show that the supported Pd SACs not only increased the number of electrons transferring from H₂ S molecules to Pd SACs, but strengthened surface affinity to H₂ S. Moreover, the HS bonds of H₂ S molecules absorbed on Pd atomic sites are more likely to be dehydrogenated directly into sulfur species. Significantly, quasi in situ XPS analysis confirmed the presence of sulfur species during H₂ S detection process, which may be a major cause for such detection signal. Based on these results, a suitable sensing principle for H₂ S gas driven by Pd SACs was put forward. This work will enrich catalytic electronics in chemiresistive gas sensing.

NO-HDAC dual inhibitors

HDAC inhibitors and NO donors have both demonstrated independently broad therapeutic potential in a variety of diseases. Borretto et al. presented the topic of NO-HDAC dual inhibitors for the first time in 2013 as an attractive new topic. Here we collected the general structure of all synthesized NO-HDAC dual inhibitors, lead compounds, synthesis methods and biological features of the most potent dual NO-HDAC inhibitor in each category with the intention of assisting in the synthesis and optimization of new drug-like compounds for diverse diseases. Based on studies done so far, NO-HDAC dual inhibitors have displayed satisfactory results against wound healing (3), heart hypertrophy (3), inflammatory, cardiovascular, neuromuscular illnesses (11a-11e) and cancer (6a-6o, 9a-9d, 10a-10d, 16 and 17). NO-HDAC dual inhibitors can have high therapeutic potential for various diseases due to their new properties, NO properties, HDAC inhibitor properties and also due to the effects of NO on HDAC enzymes.

Potential roles of gut microbiota and microbial metabolites in Parkinson's disease

Parkinson's disease (PD) is a complicated neurodegenerative disease attributed to multifactorial changes. However, its pathological mechanism remains undetermined. Accumulating evidence has revealed the emerging functions of gut microbiota and microbial metabolites, which can affect both the enteric nervous system and the central nervous system via the microbiota-gut-brain axis. Accordingly, intestinal dysbiosis might be closely associated with PD. This review explores alterations to gut microbiota, correlations with clinical manifestations of PD, and briefly probes the underlying mechanisms. Next, the highly controversial roles of microbial metabolites including short-chain fatty acids (SCFAs), H₂ and H₂S are discussed. Finally, the pros and cons of the current treatments for PD, including those targeting microbiota, are assessed. Advancements in research techniques, further studies on levels of specific strains and longitudinal prospective clinical trials are urgently needed for the identification of early diagnostic markers and the development of novel therapeutic approaches for PD.

Response to sulfur in Schizosaccharomyces pombe

Sulfur is an essential component of various biologically important molecules, including methionine, cysteine and glutathione, and it is also involved in coping with oxidative and heavy metal stress. Studies using model organisms, including budding yeast (Saccharomyces cerevisiae) and fission yeast (Schizosaccharomyces pombe), have contributed not only to understanding various cellular processes but also to understanding the utilization and response mechanisms of each nutrient, including sulfur. Although fission yeast can use sulfate as a sulfur source, its sulfur metabolism pathway is slightly different from that of budding yeast because it does not have a trans-sulfuration pathway. In recent years, it has been found that sulfur starvation causes various cellular responses in S. pombe, including sporulation, cell cycle arrest at G₂, chronological lifespan extension, autophagy induction and reduced translation. This MiniReview identifies two sulfate transporters in S. pombe, Sul1 (encoded by SPBC3H7.02) and Sul2 (encoded by SPAC869.05c), and summarizes the metabolic pathways of sulfur assimilation and cellular response to sulfur starvation. Understanding these responses, including metabolism and adaptation, will contribute to a better understanding of the various stress and nutrient starvation responses and chronological lifespan regulation caused by sulfur starvation.