Recent advances in the role of hydrogen sulfide in age-related diseases

In recent years, the impact of age-related diseases on human health has become increasingly severe, and developing effective drugs to deal with these diseases has become an urgent task. Considering the essential regulatory role of hydrogen sulfide (H2S) in these diseases, it is regarded as a promising target for treatment. H2S is a novel gaseous transmitter involved in many critical physiological activities, including anti-oxidation, anti-inflammation, and angiogenesis. H2S also regulates cell activities such as cell proliferation, migration, invasion, apoptosis, and autophagy. These regulatory effects of H2S contribute to relieving and treating age-related diseases. In this review, we mainly focus on the pathogenesis and treatment prospects of H2S in regulating age-related diseases.

Strategies for gaseous neuromodulator release in chemical neuroscience: Experimental approaches and translational validation

Gasotransmitters are a group of short-lived gaseous signaling molecules displaying diverse biological functions depending upon their localized concentration. Nitric oxide (NO), hydrogen sulfide (H2S), and carbon monoxide (CO) are three important examples of endogenously produced gasotransmitters that play a crucial role in human neurophysiology and pathogenesis. Alterations in their optimal physiological concentrations can lead to various severe pathophysiological consequences, including neurological disorders. Exogenous administration of gasotransmitters has emerged as a prominent therapeutic approach for treating such neurological diseases. However, their gaseous nature and short half-life limit their therapeutic delivery. Therefore, developing synthetic gasotransmitter-releasing strategies having control over the release and duration of these gaseous molecules has become imperative. However, the complex chemistry of synthesis and the challenges of specific quantified delivery of these gases, make their therapeutic application a challenging task. This review article provides a focused overview of emerging strategies for delivering gasotransmitters in a controlled and sustained manner to re-establish neurophysiological homeostasis.

Chemistry of Hydrogen Sulfide-Pathological and Physiological Functions in Mammalian Cells

Hydrogen sulfide (H2S) was recognized as a gaseous signaling molecule, similar to nitric oxide (-NO) and carbon monoxide (CO). The aim of this review is to provide an overview of the formation of hydrogen sulfide (H2S) in the human body. H2S is synthesized by enzymatic processes involving cysteine and several enzymes, including cystathionine-β-synthase (CBS), cystathionine-γ-lyase (CSE), cysteine aminotransferase (CAT), 3-mercaptopyruvate sulfurtransferase (3MST) and D-amino acid oxidase (DAO). The physiological and pathological effects of hydrogen sulfide (H2S) on various systems in the human body have led to extensive research efforts to develop appropriate methods to deliver H2S under conditions that mimic physiological settings and respond to various stimuli. These functions span a wide spectrum, ranging from effects on the endocrine system and cellular lifespan to protection of liver and kidney function. The exact physiological and hazardous thresholds of hydrogen sulfide (H2S) in the human body are currently not well understood and need to be researched in depth. This article provides an overview of the physiological significance of H2S in the human body. It highlights the various sources of H2S production in different situations and examines existing techniques for detecting this gas.

Multiple Actions of H2S-Releasing Peptides in Human β-Amyloid Expressing C. elegans

Alzheimer's disease (AD) is a debilitating progressive neurodegenerative disorder characterized by the loss of cognitive function. A major challenge in treating this ailment fully is its multifactorial nature, as it is associated with effects like deposition of Aβ plaques, oxidative distress, inflammation of neuronal cells, and low levels of the neurotransmitter acetylcholine (ACh). In the present work, we demonstrate the design, synthesis, and biological activity of peptide conjugates by coupling a H₂S-releasing moiety to the peptides known for their Aβ antiaggregating properties. These conjugates release H₂S in a slow and sustained manner, due to the formation of self-assembled structures and delivered a significant amount of H₂S within Caenorhabditis elegans. These conjugates are shown to target multiple factors responsible for the progression of AD: notably, we observed reduction in oxidative distress, inhibition of Aβ aggregation, and significantly increased ACh levels in the C. elegans model expressing human Aβ.

On-demand therapeutic delivery of hydrogen sulfide aided by biomolecules

Hydrogen sulfide (H₂S), known as the third gasotransmitter, exerts various physiological functions including cardiac protection, angiogenesis, anti-inflammatory, and anti-cancer capability. Given its promising therapeutic potential as well as severe perniciousness if improper use, the sustained and tunable H₂S delivery systems are highly required for H₂S-based gas therapy with enhanced bioactivity and reduced side effects. To this end, a series of stimuli-responsive compounds capable of releasing H₂S (termed H₂S donors) have been designed over the past two decades to mimic the endogenous generation of H₂S and elucidate the biological functions. Further to improve the stability of H₂S donors and achieve the targeted delivery, various delivery systems have been constructed. In this review, we focus on the recent advances of an emerging subset, biomolecular-based H₂S delivery systems, which combine H₂S donors with biomolecular vectors including polysaccharide, peptide, and protein. We demonstrated their basic structures, building strategies, and therapeutic applications respectively to unfold their inherent merits endued by biomolecules including biocompatibility, biodegradability as well as expansibility. The varied development potentials of biomolecular-based H₂S delivery systems based on their specific properties are also discussed. At the end, brief future outlooks and upcoming challenges are presented as well.

A naphthalimide-based peptide conjugate for concurrent imaging and apoptosis induction in cancer cells by utilizing endogenous hydrogen sulfide

The excessive production of endogenous hydrogen sulfide (H2S) in cancer cells leads to enhanced tumor growth and metastasis. On the other hand, decreased endogenous H2S suppresses tumor growth. The reported approaches for inhibiting tumor growth are selective silencing of the tumor-promoting genes and pharmacological inhibition of these proteins. To enhance the antitumor efficacy of frontline chemotherapeutic agents, herein, we synthesized a highly sensitive endogenous H2S responsive fluorescent probe, i.e., a hydrogen sulfide-sensing naphthalimide-based peptide conjugate (HSNPc), which showed selective inhibition of proliferation of cancer cells due to apoptosis induction. Furthermore, HSNPc suppressed the glycolytic reserve, a critical energy source for the proliferation of cancer cells. HSNPc also decreased the Young's modulus of HeLa cells compared to the control cells, which demonstrated a direct relation between cell apoptosis and cell stiffness. Taken together, we demonstrated the dual function of detection and killing of cancer cells by HSNPc that can be likened to a theranostic role.

Photothermally Activated Coacervate Model Protocells as Signal Transducers Endow Mammalian Cells with Light Sensitivity

The development of a novel photothermally activated coacervate model protocell is reported as a signal transducer to endow mammalian cells with light sensitivity. In this system, near-infrared light irradiation triggers H₂ S release in coacervate model protocells, leading to modulation of the behavior of living cells. The functional coacervate model protocells are prepared by loading metal-alloyed plasmonic nanoparticles and an H₂ S donor into the liquid coacervate microdroplets. Upon light irradiation, the H₂ S signal messenger is released through the photothermal effect of plasmonic nanoparticles and photothermal mediated pyrolysis of the H₂ S donor. The H₂ S signal is delivered to the mammalian cell community to trigger depletion of reactive oxygen species, reduce the activity of lactate dehydrogenase and improve cell viability. This study provides a new approach to the implementation of chemical signaling in artificial cell colonies and protocell/living cell consortia. The photothermal protocell system offers a powerful platform for light modulation of the behavior of mammalian cells and shows great promise for biomedical applications.

Hydrogen sulfide enhances adult neurogenesis in a mouse model of Parkinson's disease

Hydrogen sulfide (H₂S) is regarded to be a protectant against diseases of the central nervous system and cardiovascular system. However, the mechanism by which H₂S elicits neuroprotective effects in the progression of Parkinson's disease (PD) remains unclear. To investigate the role of H₂S in delaying the pathological process of PD, we used the most common sodium hydrosulfide (NaHS) as an H₂S donor and established a mouse model of PD induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine/probenecid (MPTP/p) in the present study. Our results show that H₂S reduced neuronal loss during the progression of PD. Notably, we found that H₂S exhibited protective effects on dopaminergic neurons. Excitingly, H₂S also increased the proliferation of neural stem cells in the subventricular zone. Next, we evaluated whether the neuroprotective effects of H₂S on dopaminergic neurons in PD are dependent on adult nerve regeneration by treating primary adult neural stem cells cultured ex vivo with 1-methyl-4-phenylpyridine. Our results show that H₂S could prevent nerve injury induced by 1-methyl-4-phenylpyridine, promote the growth of neurospheres, and promote neurogenesis by regulating Akt/glycogen synthase kinase-3β/β-catenin pathways in adult neural stem cells. These findings confirm that H₂S can increase neurogenesis in an adult mouse model of PD by regulating the Akt/glycogen synthase kinase-3β/β-catenin signaling pathway. This study was approved by the Animal Care and Use Committee of Nanjing Medical University, China (IACUC Approval No. 1601153-3).

NaSH increases SIRT1 activity and autophagy flux through sulfhydration to protect SH-SY5Y cells induced by MPP~

Parkinson's disease (PD) is one of the most prevailing aging diseases around the world. The present study was to investigate the potential effect of hydrogen sulfide (H2S) and silent mating type information regulation 2 homolog 1 (SIRT1) in MPP~+ induced SH-SY5Y cells and its underlying mechanisms in PD. SH-SY5Y cells were induced by MPP~+ and treated with the H2S donor NaHS to detect the effect of H2S on the molecular behaviors of MPP~+ induced SH-SY5Y cells. NaHS reduced the apoptosis rate and expressions of MDA, 4-HNE and p62, while increased cell viability, autophagy flux and expressions of LC3 II/I and Beclin1 in MPP~+ induced SH-SY5Y cells. Then, levels of autophagy-related proteins and inflammation-related proteins (TNF-α, IL-Iβ) were detected, indicating that Chloroquine and Sirtinol reversed the protective effect of H2S on SH-SY5Y cells induced by MPP~+. We further explored the particular function of H2S, SH-SY5Y cells treated with MPP~+, NaHS chloroquine, and SIRT1 inhibitor (Sirtinol). The results showed that H2S increased SIRT1 expression and sulfhydration. Finally, a PD mouse model verified the above results. In a word, H2S ameliorated SIRT1 activity through acceleration of SIRT1 sulfhydration to increase the autophagy flux and attenuate damage of SH-SY5Y cells induced by MPP~+. H2S and SIRT1 activator might be a target in the treatment of PD patients.