High concentrations of hydrogen sulphide elevate the expression of a series of pro-inflammatory genes in fibroblast-like synoviocytes derived from rheumatoid and osteoarthritis patients

Hydrogen Sulfide: A Versatile Molecule and Therapeutic Target in Health and Diseases

In recent years, research has unveiled the significant role of hydrogen sulfide (H2S) in many physiological and pathological processes. The role of endogenous H2S, H2S donors, and inhibitors has been the subject of studies that have aimed to investigate this intriguing molecule. The mechanisms by which H2S contributes to different diseases, including inflammatory conditions, cardiovascular disease, viral infections, and neurological disorders, are complex. Despite noteworthy progress, several questions remain unanswered. H2S donors and inhibitors have shown significant therapeutic potential for various diseases. This review summarizes our current understanding of H2S-based therapeutics in inflammatory conditions, cardiovascular diseases, viral infections, and neurological disorders.

Therapeutic potential of hydrogen sulfide in osteoarthritis development

The pathological mechanisms and treatments of osteoarthritis (OA) are critical topics in medical research. This paper reviews the regulatory mechanisms of hydrogen sulfide (H2S) in OA and the therapeutic potential of H2S donors. The review highlights the importance of changes in the endogenous H2S pathway in OA development and systematically elaborates on the role of H2S as a third gaseous transmitter that regulates inflammation, oxidative stress, and pain associated with OA. It also explains how H2S can lessen bone and joint inflammation by inhibiting leukocyte adhesion and migration, reducing pro-inflammatory mediators, and impeding the activation of key inflammatory pathways such as nuclear factor kappa B (NF-κB) and mitogen-activated protein kinase (MAPK). Additionally, H2S is shown to mitigate mitochondrial dysfunction and endoplasmic reticulum stress, and to modulate Nrf2, NF-κB, PI3K/Akt, and MAPK pathways, thereby decreasing oxidative stress-induced chondrocyte apoptosis. Moreover, H2S alleviates bone and joint pain through the activation of Kv7, K-ATP, and Nrf2/HO-1-NQO1 pathways. Recent developments have produced a variety of H2S donors, including sustained-release H2S donors, natural H2S donors, and synthetic H2S donors. Understanding the role of H2S in OA can lead to the discovery of new therapeutic targets, while innovative H2S donors offer promising new treatments for patients with OA.

Triangular-shaped homologous heterostructure as photocatalytic H2S scavenger and macrophage modulator for rheumatoid arthritis therapy

Rheumatoid arthritis (RA) is a chronic arthropathy causing cartilage destruction, bone erosion, and even disability. Although some advances in RA treatment have been made based on inflammatory cytokine inhibition, long-term treatment and drug effect have been restrained by severe side effects. Herein, we developed a resveratrol (RSV)-loaded Ag/Ag₂S triangular-shaped homologous heterostructure with polyethylene glycol/folic acid (PEG/FA) modification (Ag/Ag₂S-PEG-FA/RSV NTs) to simultaneously suppress inflammatory cytokine over-expression through photocatalytic H₂S scavenging and macrophage polarization stimulation. On one hand, the over-expressed H₂S, which acted as a pro-inflammatory mediator to activate the MAPK/ICAM-1 pathway and exacerbate inflammation, was eliminated through photocatalysis. The homologous Ag and Ag₂S of the heterostructure enhanced electron separation and transfer by acting as a charge acceptor and electron generator, respectively, which restrained electron/hole recombination and promoted photocatalysis efficiency. Additionally, the intrinsic superoxide dismutase (SOD) and catalase (CAT) activity of Ag decomposed the reactive oxygen species (ROS) over-expressed in the RA microenvironment, which supplied O₂ for the photocatalytic H₂S scavenging progress. On the other hand, RSV, a natural product with anti-inflammatory activity, could be delivered to the inflammatory joint by the targeting effect of PEG-FA, thus inhibiting the IκB/NF-κB pro-inflammatory pathway to induce macrophage interconversion balance from M1 to M2. As expected, the Ag/Ag₂S-PEG-FA/RSV NTs exhibited H₂S scavenging capacity and modulated macrophage polarization to reduce the inflammatory cytokine level and halt RA progression in vitro and in vivo. Overall, this study revealed a therapeutic strategy with high efficacy, which opens broad prospects for RA treatment.

Clinical Impact of Balneotherapy and Therapeutic Exercise in Rheumatic Diseases: A Lexical Analysis and Scoping Review

To review the evidence regarding the clinical effect of spa therapy for rheumatic diseases, with particular attention given to association protocols between balneotherapy and rehabilitation interventions, and to support the literature research and studies’ selection with lexical analysis. Methods: A lexical analysis was performed considering a list of words representing diseases and outcome measures linked to the theme studied in our review. Then, two independent researchers conducted a literature search on PubMed using the string employed for lexical analysis, including Randomized Controlled Trials regarding spa therapy’s clinical effects on patients affected by rheumatic diseases published in the last 30 years. After the exclusion of works that did not meet the eligibility criteria, 14 studies were included in the final scoping review. Results: Spa therapy has shown a favourable effect on pain, function and quality of life in patients with Osteoarthritis, Fibromyalgia and Rheumatoid Arthritis. Different treatment modalities and types of water have demonstrated beneficial long-term clinical improvement. Furthermore, the association between thermal therapy and rehabilitation treatments has shown better clinical outcomes, probably due to the synergistic effect between the peculiar properties of the thermal waters and the therapeutic exercise program, if conducted in the same context. Conclusions: The combination of balneotherapy and rehabilitative interventions seems to be effective in ameliorating several outcomes in patients with rheumatic diseases. However, due to the wide variety of methodologies and interventions employed, these findings need to be further investigated. The lexical analysis should represent an auxiliary support for an extensive evaluation of scientific literature.

Recent Advances in Molecular Research on Hydrogen Sulfide (H2S) Role in Diabetes Mellitus (DM)-A Systematic Review

Abundant experimental data suggest that hydrogen sulfide (H₂S) is related to the pathophysiology of Diabetes Mellitus (DM). Multiple molecular mechanisms, including receptors, membrane ion channels, signalingmolecules, enzymes, and transcription factors, are known to be responsible for the H₂S biological actions; however, H₂S is not fully documented as a gaseous signaling molecule interfering with DM and vascular-linked pathology. In recent decades, multiple approaches regarding therapeutic exploitation of H₂S have been identified, either based on H₂S exogenous apport or on its modulated endogenous biosynthesis. This paper aims to synthesize and systematize, as comprehensively as possible, the recent literature-related data regarding the therapeutic/rehabilitative role of H₂S in DM. This review was conducted following the “Preferred reporting items for systematic reviews and meta-analyses” (PRISMA) methodology, interrogating five international medically renowned databases by specific keyword combinations/“syntaxes” used contextually, over the last five years (2017–2021). The respective search/filtered and selection methodology we applied has identified, in the first step, 212 articles. After deploying the next specific quest steps, 51 unique published papers qualified for minute analysis resulted. To these bibliographic resources obtained through the PRISMA methodology, in order to have the best available information coverage, we added 86 papers that were freely found by a direct internet search. Finally, we selected for a connected meta-analysis eight relevant reports that included 1237 human subjects elicited from clinical trial registration platforms. Numerous H₂S releasing/stimulating compounds have been produced, some being used in experimental models. However, very few of them were further advanced in clinical studies, indicating that the development of H₂S as a therapeutic agent is still at the beginning.

Balneotherapy year in review 2021: focus on the mechanisms of action of balneotherapy in rheumatic diseases

Balneotherapy (BT) is one of the most commonly used non-pharmacologic complementary therapies for different rheumatic diseases. Its beneficial properties probably derived from a combination of mechanical, thermal, and chemical effects, but the exact mechanism of action is not elucidated. This review aimed at summarizing the current knowledge about the effects of BT, and identifying its possible mechanism of action in different rheumatic diseases. Pubmed and Scopus were used to perform a search of the literature to extract articles including terms related to BT and rheumatic diseases published in the period from 2010 to 2021. We selected pre-clinical studies, randomized controlled trials, and clinical trials. The results of clinical studies confirmed the beneficial properties on different mediators and factors of inflammation, oxidative stress, cartilage metabolism, and humoral and cellular immune responses in patients affected by chronic degenerative musculoskeletal disorders. The data derived from OA and RA-induced murine models revealed the efficacy of different BT treatments in decreasing pain, inflammation, and improving mobility, as well as in reducing the expression of matrix-degrading enzymes and markers of oxidative stress damage. Different in vitro studies analyzed the potential effect of a mineral water, as a whole, or of a mineral element, demonstrating their anti-inflammatory, antioxidant, and chondroprotective properties in OA cartilage, synoviocytes and chondrocytes, and osteoblast and osteoclast cultures. The presented data are promising and confirm BT as an effective complementary approach in the management of several low-grade inflammation, degenerative, and stress-related pathologies, as rheumatic diseases.

Cinnamic Aldehyde, the main monomer component of Cinnamon, exhibits anti-inflammatory property in OA synovial fibroblasts via TLR4/MyD88 pathway

Cinnamon is a wildly used traditional Chinese herbal medicine for osteoarthritis (OA) treatment, but the underlying mechanism remains ambiguous. The purpose of this study is to explore the mechanism of cinnamic aldehyde (CA), a bioactive substance extracted from Cinnamon, on synovial inflammation in OA. A total of 144 CA-OA co-targeted genes were identified by detect databases (PubChem, HIT, TCMSP, TTD, DrugBank and GeneCards). The results of GO enrichment analysis indicated that these co-targeted genes have participated in many biological processes including 'inflammatory response', 'cellular response to lipopolysaccharide', 'response to drug', 'immune response', 'lipopolysaccharide-mediated signalling pathway', etc. KEGG pathway analysis showed these co-targeted genes were mainly enriched in 'Toll-like receptor signalling pathway', 'TNF signalling pathway', 'NF-kappa B signalling pathway', etc. Molecular docking demonstrated that CA could successfully bind to TLR2 and TLR4. The results of in vitro experiments showed no potential toxicity of 10, 20 and 50 μM/L CA on human OA FLS, and CA can significantly inhibit the inflammation in LPS-induced human FLS. Further experimental mechanism evidence confirmed CA can inhibited the inflammation in LPS-induced human OA FLS via blocking the TLR4/MyD88 signalling pathway. Our results demonstrated that CA exhibited strong anti-inflammation effect in OA FLS through blocking the activation of TLR4/MyD88 signalling pathway, suggesting its potential as a hopeful candidate for the development of novel agents for the treatment of OA.

Hydrogen sulfide (H2S) - therapeutic relevance in rehabilitation and balneotherapy Systematic literature review and meta-analysis based on the PRISMA paradig

Background. An active molecule in sulfurous mineral - therapeutic waters and also in sapropelic mud is H2S, a hormetic gaseous molecule that can actively penetrate the skin. While high levels of H2S are extremely toxic, low levels are tolerated and have potential cytoprotective effects, with anti-inflammatory and antioxidant applications. Objective. This systematic review aims to rigorously select related articles and identify within their content the main possible uses of hydrogen sulfide from balneary sources and to explain its physiological mechanisms and therapeutic properties. Methods. To elaborate our systematic review, we have searched for relevant open access articles in 6 international databases: Cochrane , Elsevier , NCBI/PubMed , NCBI/PMC , PEDro , and ISI Web of Knowledge/Science , published from January 2016 until July 2021. The contextually quested keywords combinations/ syntaxes used are specified on this page. The eligible articles were analyzed in detail regarding pathologies addressed by hydrogen sulfide. All articles with any design (reviews, randomized controlled trials, non-randomized controlled trials, case-control studies, cross-sectional studies), if eligible according to the above-mentioned selection methodology, containing in the title the selected combinations, were included in the analysis. Articles were excluded in the second phase if they did not reach the relevance criterion. Results. Our search identified, first, 291 articles. After eliminating the duplicates and non-ISI articles, remained 121 papers. In the second phase, we applied a PEDro selection filter, resulting in 108 articles that passed the relevance criterion and were included in this systematic review. Conclusions. H2S biology and medical relevance are not fully understood and used adequately for sanogenic or medical purposes. More research is needed to fully understand the mechanisms and importance of this therapeutic gase. The link between balneotherapy and medical rehabilitation regarding the usage of hydrogen sulfide emphasises the unity for this medical speciality.

New Therapeutic Approaches Using Hydrogen Sulfide Donors in Inflammation and Immune Response

Significance: Inflammation and immune response are associated with many pathological disorders, including rheumatoid arthritis, lupus, heart failure, and cancer(s). In recent times, important roles of hydrogen sulfide (H₂S) have been evidenced by researchers in inflammatory responses, as well as immunomodulatory effects in several disease models. Recent Advances: Numerous biological targets, including cytochrome c oxidase, various kinases, enzymes involved in epigenetic changes, transcription factors, namely nuclear factor kappa B and nuclear factor erythroid 2-related factor 2, and several membrane ion channels, are shown to be sensitive to H₂S and have been widely investigated in various preclinical models. Critical Issues: A complete understanding of the effects of H₂S in inflammatory and immune response is vital in the development of novel H₂S generating therapeutics. In this review, the biological effects and pharmacological properties of H₂S in inflammation and immune response are addressed. The review also covers some of the novel H₂S releasing prodrugs developed in recent years as tools to study this fascinating molecule. Future Directions: H₂S plays important roles in inflammation and immunity-related processes. Future researches are needed to further assess the immunomodulatory effects of H₂S and to assist in the design of more efficient H₂S carrier systems, or drug formulations, for the management of immune-related conditions in humans. Antioxid. Redox Signal. 35, 341-356.

Effects of sulphur-containing mineral water intake on oxidative status and markers for inflammation in healthy subjects

CONTEXT

Sulphurous mineral waters (SMW) have a wide range of applications. Sulphur content of mineral waters is considered as possible determinant for their anti-inflammatory or pro-inflammatory effects.

OBJECTIVE

To explore the healing properties of Varna basin mineral water by analysing possible antioxidative and anti-inflammatory effects.

MATERIALS AND METHODS

An intervention with Varna SMW intake was performed with healthy volunteers. Total thiols, total glutathione and its fractions, reactive oxygen metabolites, malondialdehyde, intracellular adhesion molecule (ICAM-1) and vascular cell adhesion molecule (VCAM-1) were measured. Expression of γ-gluthamyl-cysteinyl ligase (GCL) and sICAM-1 genes was also analysed.

RESULTS

A significantly increased total glutathione and total thiols were observed at the end of the intervention. GCL and sICAM-1 gene expressions were increased after the intervention.

CONCLUSION

SMW consumption improved redox status of the body. We suggested that these beneficial effects may be attributed to the established high levels of sulphur-containing compounds in Varna mineral water.

Hydrogen Sulfide in Inflammation: A Novel Mediator and Therapeutic Target

Significance: Inflammation is a normal response to injury, but uncontrolled inflammation can lead to several diseases. In recent years, research has shown endogenously synthesized hydrogen sulfide (H₂S) to be a novel mediator of inflammation. This review summarizes the current understanding and recent advances of H₂S role with respect to inflammation in different diseases. Recent Advances: Promising early results from clinical studies suggest an important role of H₂S in human inflammatory disease. Critical Issues: Defining the precise mechanism by which H₂S contributes to inflammation is a complex challenge, and there is active ongoing research that is focused on addressing this question. Most of this work has been conducted on animal models of human disease and isolated/cultured cells, and its translation to the clinic is another challenge in the area of H₂S research. Future Directions: Defining the mechanism by which H₂S acts as an inflammatory mediator will help us better understand different inflammatory diseases and help develop novel therapeutic approaches for these diseases.

The Fibroblast-Like Synoviocyte Derived Exosomal Long Non-coding RNA H19 Alleviates Osteoarthritis Progression Through the miR-106b-5p/TIMP2 Axis

Osteoarthritis (OA) is a common degenerative joint disease that affects people worldwide. The interaction between fibroblast-like synoviocytes (FLSs) and chondrocytes may play a vital role in OA disease pathology. However, the underlying mechanisms by which FLSs exert regulatory effects on chondrocytes still need to be elucidated. Exosomes, small membrane vesicles secreted from living cells, are known to play a variety of roles in mediating cell-to-cell communication through the transferring of biological components such as non-coding RNAs and proteins. Here, we investigate the cellular processes of chondrocytes regulated by FLS-derived exosomes and the mechanisms of action underlying the functions of exosomes in OA pathogenesis. We observed that exosome-mediated cartilage repair was characterized by increased cell viability and migration as well as alleviated matrix degradation. Using chondrocyte cultures, the enhanced cellular proliferation and migration during exosome-mediated cartilage repair was linked to the exosomal lncRNA H19-mediated regulation of the miR-106b-5p/TIMP2 axis. Transfection of miR-106-5p mimics in chondrocytes significantly decreased cell proliferation and migration, promoted matrix degradation characterized by elevated MMP13 and ADAMTS5 expression, and reduced the expression of COL2A1 and ACAN in chondrocytes. Furthermore, we found that TIMP2 was directly regulated by miR-106-5p. Co-transfections of miR-106-5p mimics and TIMP2 resulted in higher levels of COL2A1 and ACAN, but lower levels of MMP13 and ADAMTS5. Together, these observations demonstrated that the lncRNA H19 may promote chondrocyte proliferation and migration and inhibit matrix degradation in OA possibly by targeting the miR-106b-5p/TIMP2 axis. In the future, H19 may serve as a potential therapeutic target for the treatment of OA.

From in vitro research to real life studies: an extensive narrative review of the effects of balneotherapy on human immune response

Purpose

The biologic mechanisms by which balneotherapy (BT) alleviates symptoms of different diseases are still poorly understood. Recently, preclinical models and clinical trials have been developed to study the effects of BT on the immune system. This review summarizes the currently available evidence regarding the effects of spa therapy on the immune response, to confirm the role of BT in the enhancement of immune system and open interesting research fields.

Methods

PubMed and Google Scholar were searched from 1997 up to June 2020, with search criteria including terms related to BT and immune system. We selected only in vitro research, randomized controlled trials (RCTs) or clinical trials.

Results

In vitro studies on human and animal samples have demonstrated that thermal waters exert anti-inflammatory and immunomodulatory effects. In particular, H₂S donors seem to counteract the inflammatory processes in psoriatic lesions, arthritic fibroblast-like synoviocytes and chondrocytes, and regulate important factors implicated in osteoarthritis pathogenesis and progression. RCTs and clinical trials revealed, after BT, a reduction in circulating levels of pro-inflammatory molecules, such as TNF-α, IL-1β, and C-reactive protein, and an increase in anti-inflammatory molecules such as the IGF-1 growth factor especially in musculoskeletal diseases.

Conclusion

Further preclinical studies and RCTs could help to exploit BT in real life for preventive and therapeutic treatments.

Hydrogen Sulfide: a Novel Immunoinflammatory Regulator in Rheumatoid Arthritis

Hydrogen sulfide (H₂S), an endogenous, gaseous, signaling transmitter, has been shown to have vasodilative, anti-oxidative, anti-inflammatory, and cytoprotective activities. Increasing evidence also indicates that H₂S can suppress the production of inflammatory mediators by immune cells, for example, T cells and macrophages. Inflammation is closely related to an immune response in several diseases such as rheumatoid arthritis (RA), multiple sclerosis (MS), systemic lupus erythematosus (SLE), and cancer. Considering these biological effects of H₂S, a potential role in the treatment of immune-related RA is being exploited. In the present review, we will provide an overview of the therapeutic potential of H₂S in RA treatment.

Hydrogen Sulfide and its Interaction with Other Players in Inflammation

Hydrogen sulfide (H₂S) plays a vital role in human physiology and in the pathophysiology of several diseases. In addition, a substantial role of H₂S in inflammation has emerged. This chapter will discuss the involvement of H₂S in various inflammatory diseases. Furthermore, the contribution of reactive oxygen species (ROS), adhesion molecules, and leukocyte recruitment in H₂S-mediated inflammation will be discussed. The interrelationship of H₂S with other gasotransmitters in inflammation will also be examined. There is mixed literature on the contribution of H₂S to inflammation due to studies reporting both pro- and anti-inflammatory actions. These apparent discrepancies in the literature could be resolved with further studies.

Hydrogen sulfide: An endogenous regulator of the immune system

Hydrogen sulfide (H₂S) is now recognized as an endogenous signaling gasotransmitter in mammals. It is produced by mammalian cells and tissues by various enzymes - predominantly cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST) - but part of the H₂S is produced by the intestinal microbiota (colonic H₂S-producing bacteria). Here we summarize the available information on the production and functional role of H₂S in the various cell types typically associated with innate immunity (neutrophils, macrophages, dendritic cells, natural killer cells, mast cells, basophils, eosinophils) and adaptive immunity (T and B lymphocytes) under normal conditions and as it relates to the development of various inflammatory and immune diseases. Special attention is paid to the physiological and the pathophysiological aspects of the oral cavity and the colon, where the immune cells and the parenchymal cells are exposed to a special "H₂S environment" due to bacterial H₂S production. H₂S has many cellular and molecular targets. Immune cells are "surrounded" by a "cloud" of H₂S, as a result of endogenous H₂S production and exogenous production from the surrounding parenchymal cells, which, in turn, importantly regulates their viability and function. Downregulation of endogenous H₂S producing enzymes in various diseases, or genetic defects in H₂S biosynthetic enzyme systems either lead to the development of spontaneous autoimmune disease or accelerate the onset and worsen the severity of various immune-mediated diseases (e.g. autoimmune rheumatoid arthritis or asthma). Low, regulated amounts of H₂S, when therapeutically delivered by small molecule donors, improve the function of various immune cells, and protect them against dysfunction induced by various noxious stimuli (e.g. reactive oxygen species or oxidized LDL). These effects of H₂S contribute to the maintenance of immune functions, can stimulate antimicrobial defenses and can exert anti-inflammatory therapeutic effects in various diseases.

A comprehensive analysis to understand the mechanism of action of balneotherapy: why, how, and where they can be used? Evidence from in vitro studies performed on human and animal samples

Balneotherapy (BT) is one of the most commonly used complementary therapies for many pathological conditions. Its beneficial effects are related to physical and chemical factors, but the exact mechanism of action is not fully understood. Recently, there has been an increased interest in the use of preclinical models to investigate the influence of BT on inflammation, immunity, and cartilage and bone metabolism. The objective of this comprehensive analysis was to summarize the current knowledge about the in vitro studies in BT and to revise the obtained results on the biological effects of mineral waters. Special attention has been paid to the main rheumatological and dermatological conditions, and to the regulation of the immune response. The objective of this review was to summarize the in vitro studies, on human and animal samples, investigating the biological effects of BT. In particular, we analyzed the properties of a thermal water, as a whole, of an inorganic molecule, such as hydrogen sulfide in different cell cultures (keratinocytes, synoviocytes, chondrocytes, and peripheral blood cells), or of the organic component. The results corroborated the scientific value of in vitro studies in demonstrating the anti-inflammatory, antioxidant, chondroprotective, and immunosuppressive role of BT at the cellular level. However, the validity of the cell culture model is limited by several sources of bias, as the differences in experimental procedures, the high heterogeneity among the available researches, and the difficulties in considering all the chemical and physical factors of BT. We would like to stimulate the scientific community to standardize the experimental procedures and enhance in vitro research in the field of BT.

Glutathione-Allylsulfur Conjugates as Mesenchymal Stem Cells Stimulating Agents for Potential Applications in Tissue Repair

The endogenous gasotransmitter H₂S plays an important role in the central nervous, respiratory and cardiovascular systems. Accordingly, slow-releasing H₂S donors are powerful tools for basic studies and innovative pharmaco-therapeutic agents for cardiovascular and neurodegenerative diseases. Nonetheless, the effects of H₂S-releasing agents on the growth of stem cells have not been fully investigated. H₂S preconditioning can enhance mesenchymal stem cell survival after post-ischaemic myocardial implantation; therefore, stem cell therapy combined with H₂S may be relevant in cell-based therapy for regenerative medicine. Here, we studied the effects of slow-releasing H₂S agents on the cell growth and differentiation of cardiac Lin⁻ Sca1⁺ human mesenchymal stem cells (cMSC) and on normal human dermal fibroblasts (NHDF). In particular, we investigated the effects of water-soluble GSH–garlic conjugates (GSGa) on cMSC compared to other H₂S-releasing agents, such as Na₂S and GYY4137. GSGa treatment of cMSC and NHDF increased their cell proliferation and migration in a concentration dependent manner with respect to the control. GSGa treatment promoted an upregulation of the expression of proteins involved in oxidative stress protection, cell–cell adhesion and commitment to differentiation. These results highlight the effects of H₂S-natural donors as biochemical factors that promote MSC homing, increasing their safety profile and efficacy after transplantation, and the value of these donors in developing functional 3D-stem cell delivery systems for cardiac muscle tissue repair and regeneration.

Hydrogen Sulfide as Potential Regulatory Gasotransmitter in Arthritic Diseases

The social and economic impact of chronic inflammatory diseases, such as arthritis, explains the growing interest of the research in this field. The antioxidant and anti-inflammatory properties of the endogenous gasotransmitter hydrogen sulfide (H₂S) were recently demonstrated in the context of different inflammatory diseases. In particular, H₂S is able to suppress the production of pro-inflammatory mediations by lymphocytes and innate immunity cells. Considering these biological effects of H₂S, a potential role in the treatment of inflammatory arthritis, such as rheumatoid arthritis (RA), can be postulated. However, despite the growing interest in H₂S, more evidence is needed to understand the pathophysiology and the potential of H₂S as a therapeutic agent. Within this review, we provide an overview on H₂S biological effects, on its role in immune-mediated inflammatory diseases, on H₂S releasing drugs, and on systems of tissue repair and regeneration that are currently under investigation for potential therapeutic applications in arthritic diseases.

Exogenous hydrogen sulfide prevents lipopolysaccharide-induced inflammation by blocking the TLR4/NF-κB pathway in MAC-T cells

Mastitis impairs animal health and results in economic loss. Lipopolysaccharide (LPS) may cause immune response and inflammation in the bovine mammary gland. Hydrogen sulfide (H₂S) is the third gasotransmitter that acts as an anti-inflammation regulator in many cells. Despite the importance of H₂S in regulating inflammation, the effect and mechanism of exogenous H₂S on LPS-induced inflammation in bovine mammary epithelial cells are unknown. In the present study, with NaHS as a donor of H₂S, the bovine mammary epithelial cell line (MAC-T) was applied as an in vitro model to study the role of H₂S on LPS-induced MAC-T cells. The results verified that the cell viability was diminished by LPS but restored by exogenous H₂S at a physiologically relevant concentration (10 μM). Additionally, the production of H₂S was mitigated in the LPS-induced MAC-T cells. Meanwhile, exogenous H₂S decreased the intracellular ROS production and mRNA expression levels of the pro-inflammatory cytokines, TNF-α, IL-1β, IL-8, and IL-6. Furthermore, exogenous H₂S inhibited the mRNA expression of TLR4 and activation of NF-κB signaling pathway. In summary, exogenous H₂S exerts anti-inflammatory effects through attenuating oxidative stress and blocking the TLR4/NF-κB pathway in the LPS-induced bovine mammary epithelial cells. Our findings might clarify new prophylactic approaches for mastitis.

Hydrogen sulfide exposure triggers chicken trachea inflammatory injury through oxidative stress-mediated FOS/IL8 signaling

Hydrogen sulfide (H₂S) is well known to cause irritation and damage to airway following inhalation, but the mechanism by which H₂S contributes to airway toxicity is unclear. In order to assess the respiratory toxicity of H₂S inhalation in chicken trachea, we investigated the change of oxidative stress parameters, tracheal tissue structure and transcriptome profiles of chicken trachea exposed to H₂S for 42 days. The results showed H₂S exposure induced oxidative stress and inflammation in trachea. The ultrastructural analysis revealed loss of cilia and accumulation of mucus in tracheal epithelium. Differentially expressed genes (DEGs) analysis indicated 454 genes were significantly changed, including 136 genes upregulated and 318 genes downregulated. Gene ontology and KEGG analysis showed many genes involved in response to oxidative stress, inflammatory and immune response, which might contribute to H₂S-induced tracheal inflammatory injury. Among those genes, N-acetyl-L-cysteine (NAC) treatment blocked the H₂S-triggered expression of FOS and IL8. Silencing FOS by siRNA inhibited H₂S-induced expression of IL8. Taken together, we concluded that H₂S induced oxidative stress leads to tracheal inflammation through FOS/IL8 signaling, leading to excessive mucus secretion and absence of cilia. These results provide new insights for unveiling the biological effects of H₂S in vivo and in vitro.

Upregulation of stanniocalcin-1 inhibits the development of osteoarthritis by inhibiting survival and inflammation of fibroblast-like synovial cells

OBJECTIVE

Osteoarthritis (OA) is a progressive and disabling disorder, characterized by synovial inflammation and joint effusion. This study aimed to explore the role of stanniocalcin-1 (STC1) in the development of OA by regulating the survival and inflammation of fibroblast-like synovial (FLS) cells.

METHODS

Microarray analyses were adopted to screen differentially expressed genes (DEGs) related to OA, and regulatory microRNA (miR) was also identified. Synovial tissue samples from patients with OA and healthy individuals were obtained to determine the expression levels of miR-454, STC1, IL-6, IL-8, and MMP3/13. The targeted relationship between miR-454 and STC1 was verified by dual-luciferase reporter gene assay. With the treatment of miR-454 mimic and STC1 overexpression vector, the effect of miR-454 and STC1 on FLS cell viability and apoptosis as well as production of inflammatory cytokines were tested.

RESULTS

STC1 with aberrant low expression was screened from GSE1919 profile in OA. STC1 was found to be downregulated in OA-FLS tissues and cells. STC1 overexpression inhibited OA-FLS cell viability but induced apoptosis of OA-FLS cells. Moreover, STC1 overexpression decreased levels of IL-6, IL-8, and MMP3/13, suggesting that STC1 overexpression suppressed inflammatory reactions. In addition, miR-454 blocked the inhibitory effects of STC1 overexpression on OA-FLS cell viability and inflammatory reaction and exerted a promotion effect of STC1 overexpression on apoptosis of OA-FLS cells.

CONCLUSIONS

Taken together, the results revealed that upregulation of STC1 could repress proliferation of OA-FLS cells and inflammatory reaction, and enhance apoptosis of OA-FLS cells, which was negatively regulated by miR-454.

Intra-articular injection of hydrogen sulfide decreased the progression of gonarthrosis

Hydrogen sulfide (H₂S) is found in both the plasma and synovial fluid of patients with gonarthrosis. In the present study, we investigated whether intra-articular injection of sodium hydrosulfide (NaSH) (1 mM, 30 μL), a H₂S donor, might affect gonarthrosis in rats. Gonarthrosis was induced surgically in the left knees of rats and left for 6 weeks for the development of disease. Then, intra-articular injections of NaSH or methylprednisolone (1 mg/kg, 30 μL) were administered to rats. Half of each group was sacrificed at the end of the first day and the other half was sacrificed at the end of 4 weeks to evaluate early and later effects of injections on gonarthrosis. The injury induced by anterior cruciate ligament resection and medial meniscectomy in rats caused the development of gonarthrosis. As the duration lengthened after gonarthrosis induction, the progression of the disease continued. According to the modified Mankin Scoring System, intra-articular injection of NaSH histopathologically slowed the progression of gonarthrosis, whereas methylprednisolone was ineffective. In addition, NaSH decreased apoptosis in rat knees with gonarthrosis. Each treatment did not cause injury to healthy knees. Our results lead to the consideration that intra-articular NaSH administration may be effective in the progression of gonarthrosis.

Spa therapy adjunct to pharmacotherapy is beneficial in rheumatoid arthritis: a crossover randomized controlled trial

This study aims to investigate whether 2-week spa therapy, as an adjunct to usual pharmacological therapy, has any beneficial effect in patients with rheumatoid arthritis (RA). In this single-blind crossover study, 50 patients were randomly assigned in a 1:1 manner to receive usual pharmacological therapy plus 2-week spa therapy or usual pharmacological therapy alone (period 1.6 months); after a 9-month washout, patients were crossed over to the opposite assignment (period 2.6 months). Spa therapy program included a daily saline balneotherapy session at 36-37 °C for 20 min except Sundays. The clinical outcomes were evaluated at baseline, after spa therapy (2 weeks) and 3 and 6 months after the spa therapy in both period and were pain (Visual Analogue Scale (VAS)), patient and physician global assessments (VAS), Health Assessment Questionnaire (HAQ), and Disease Activity Score (DAS28). Spa therapy was superior to control therapy in improving all the assessed clinical outcomes at the end of the spa therapy. This superiority persisted significantly in physician global assessment (p = 0.010) and with a trend in favor of spa group in patient global assessment (p = 0.058), function (p = 0.092), and disease activity (p = 0.098) at 3 months. Statistically significant improvements were found in spa therapy compared to control in disease activity (p = 0.006) and patient (p = 0.020) and physician global (p = 0.011) assessments, and a trend toward improvements in pain (p = 0.069) and swollen joints (p = 0.070) at 6 months. A 2-week spa therapy adjunct to usual pharmacological therapy provided beneficial clinical effects compared to usual pharmacological therapy alone, in RA patients treated with traditional disease-modifying antirheumatic drugs. These beneficial effects may last for 6 months.

Icariin Regulates Cellular Functions and Gene Expression of Osteoarthritis Patient-Derived Human Fibroblast-Like Synoviocytes

Synovial inflammation plays an important role in the pathogenesis and progress of osteoarthritis (OA). There is an urgent need to find safe and effective drugs that can reduce the inflammation and regulate the pathogenesis of cytokines of the OA disease. Here, we investigated the effect of icariin, the major pharmacological active component of herb Epimedium on human osteoarthritis fibroblast-like synoviocytes (OA–FLSs). The OA–FLSs were isolated from patients with osteoarthritis and cultured in vitro with different concentrations of icariin. Then, cell viability, proliferation, and migration were investigated; MMP14, GRP78, and IL-1β gene expression levels were detected via qRT-PCR. Icariin showed low cytotoxicity to OA–FLSs at a concentration of under 10 μM and decreased the proliferation of the cells at concentrations of 1 and 10 μM. Icariin inhibited cell migration with concentrations ranging from 0.1 to 1 μM. Also, the expression of three cytokines for the pathogenesis of OA which include IL-1β, MMP14 and GRP78 was decreased by the various concentrations of icariin. These preliminary results imply that icariin might be an effective compound for the treatment of OA disease.

H2S protects lipopolysaccharide-induced inflammation by blocking NFκB transactivation in endothelial cells

Hydrogen sulfide (H₂S) is a novel gasotransmitter and acts as a multifunctional regulator in various cellular functions. Past studies have demonstrated a significant role of H₂S and its generating enzyme cystathionine gamma-lyase (CSE) in the cardiovascular system. Lipopolysaccharide (LPS), a major pathogenic factor, is known to initiate the inflammatory immune response. The cross talk between LPS-induced inflammation and the CSE/H₂S system in vascular cells has not yet been elucidated in detail. Here we showed that LPS decreased CSE mRNA and protein expression in human endothelial cells and blocked H₂S production in mouse aorta tissues. Transfection of the cells with TLR4-specific siRNA knockdown TLR4 mRNA expression and abolished the inhibitory role of LPS on CSE expression. Higher dose of LPS (100μg/ml) decreased cell viability, which was reversed by exogenously applied H₂S at physiologically relevant concentration (30μM). Lower dose of LPS (10μg/ml) had no effect on cell viability, but significantly induced inflammation gene expressions and cytokines secretion and stimulated cell hyper-permeability. H₂S treatment prevented LPS-induced inflammation and hyper-permeability. Lower VE-cadherin expression in LPS-incubated cells would contribute to cell hyper-permeability, which was reversed by H₂S co-incubation. In addition, H₂S treatment blocked LPS-induced NFκB transactivation. We further validated that LPS-induced hyper-permeability was reversed by CSE overexpression but further deteriorated by CRISPR/Cas9-mediated knockout of CSE. In vivo, deficiency of CSE sensitized the mice to LPS-induced inflammation in vascular tissues. Take together, these data suggest that CSE/H₂S system protects LPS-induced inflammation and cell hyper-permeability by blocking NFκB transactivation.

Cystathionine-gamma-lyase deficient mice are protected against the development of multiorgan failure and exhibit reduced inflammatory response during burn

Considering the role of H₂S in critical illness, the aim of this study was to compare the outcome of burn in wild-type mice and in mice deficient in CSE, one of the principal mammalian H₂S-generating enzymes. Animals were subjected to scald burn. Outcome variables included indices of organ injury, clinical chemistry parameters and plasma levels of inflammatory mediators. Plasma levels of H₂S significantly increased in response to burn in wild-type mice, but remained unchanged in CSE^-/- mice. Expression of the three H₂S-producing enzymes (CSE, CBS and 3-MST) in the lung and liver, and the capacity of tissue homogenates to produce H₂S, however, was not affected by burn. In CSE deficient mice there was a significant amelioration of burn-induced accumulation of myeloperoxidase levels in heart, lung, liver and kidney and significantly lower degree of malon dialdehyde accumulation in the heart, lung and kidney than in wild-type mice. CSE deficient mice, compared to wild-type mice, showed a significant attenuation of the burn-induced elevation in circulating alkaline aminotransferase and blood urea nitrogen and creatinine levels, indicative of protective effects of CSE deficiency against burn-induced hepatic, and renal functional impairment. Multiple burn-induced inflammatory mediators (TNF-α, IL-1β, IL-4, IL-6, IL-10 and IL-12) were significantly lower in the plasma of CSE^-/- animals after burn than in the plasma of wild-type controls subjected to burns. In conclusion, CSE deficiency improves organ function and attenuates the inflammatory response in a murine model of burn.

Effect of spa therapy with saline balneotherapy on oxidant/antioxidant status in patients with rheumatoid arthritis: a single-blind randomized controlled trial

Oxidative stress has been shown to play a contributory role in the pathogenesis of rheumatoid arthritis (RA). Recent studies have provided evidence for antioxidant properties of spa therapy. The purpose of this study is to investigate whether spa therapy with saline balneotherapy has any influence on the oxidant/antioxidant status in patients with RA and to assess clinical effects of spa therapy. In this investigator-blind randomized controlled trial, we randomly assigned 50 patients in a 1:1 ratio to spa therapy plus standard drug treatment (spa group) or standard drug treatment alone (control group). Spa group followed a 2-week course of spa therapy regimen consisting of a total of 12 balneotherapy sessions in a thermal mineral water pool at 36-37 °C for 20 min every day except Sunday. All clinical and biochemical parameters were assessed at baseline and after spa therapy (2 weeks). The clinical parameters were pain intensity, patient global assessment, physician global assessment, Health Assessment Questionnaire disability index (HAQ-DI), Disease Activity Score for 28-joints based on erythrocyte sedimentation rate (DAS28-4[ESR]). Oxidative status parameters were malondialdehyde (MDA), nonenzymatic superoxide radical scavenger activity (NSSA), antioxidant potential (AOP), and superoxide dismutase (SOD). The NSSA levels were increased significantly in the spa group (p = 0.003) but not in the control group (p = 0.509); and there was a trend in favor of spa therapy for improvements in NSSA levels compared to control (p = 0.091). Significant clinical improvement was found in the spa group compared to the control in terms of patient global assessment (p = 0.011), physician global assessment (p = 0.043), function (HAQ-DI) (p = 0.037), disease activity (DAS28-4[ESR]) (0.044) and swollen joint count (0.009), and a trend toward improvement in pain scores (0.057). Spa therapy with saline balneotherapy exerts antioxidant effect in patients with RA as reflected by the increase in NSSA levels after spa therapy; whether this antioxidant effect contributes to the clinical improvements observed remains to be verified.

D-Penicillamine modulates hydrogen sulfide (H2S) pathway through selective inhibition of cystathionine-γ-lyase

BACKGROUND AND PURPOSE

Hydrogen sulfide (H2S) is a gasotransmitter produced from L-cysteine through the enzymatic action of cystathionine-γ-lyase (CSE) and/or cystathionine-β-synthase. D-Penicillamine is the d isomer of a dimethylated cysteine and has been used for the treatment of rheumatoid arthritis. AsD-penicillamine is structurally very similar to cysteine, we have investigated whether D-penicillamine, as a cysteine analogue, has an effect on the H2 S pathway.

EXPERIMENTAL APPROACH

We tested the effect of D-penicillamine (0.01-1 mM) in mouse aortic rings mounted in isolated organ baths and determined whether it could affect H2 S biosynthesis. In particular, we investigated any possible inhibitor or donor behaviour by using recombinant enzyme-based assays and an in vivo approach.

KEY RESULTS

D-Penicillamine, per se, showed little or no vasodilator effect, and it cannot be metabolized as a substrate in place of l-cysteine. However, d-penicillamine significantly reduced L-cysteine-induced vasodilatation in a concentration-dependent manner through inhibition of H2 S biosynthesis, and this effect occurred at concentrations 10 times lower than those needed to induce the release of H2 S. In particular, D-penicillamine selectively inhibited CSE in a pyridoxal-5'-phosphate-dependent manner.

CONCLUSIONS AND IMPLICATIONS

Taken together, our results suggest that D-penicillamine acts as a selective CSE inhibitor, leading to new perspectives in the design and use of specific pharmacological tools for H2 S research. In addition, the inhibitory effect of D-penicillamine on CSE could account for its beneficial action in rheumatoid arthritis patients, where H2 S has been shown to have a detrimental effect.

H2S and Inflammation: An Overview

Inflammation is a response to traumatic, infectious, post-ischemic, toxic, or autoimmune injury. However, uncontrolled inflammation can lead to disease, and inflammation is now believed to be responsible for several disease conditions. Research in our laboratory has shown that hydrogen sulfide (H2S) acts as a novel mediator of inflammation. At present, work in several research groups worldwide is focused on determining the role of H2S in inflammation. H2S has been implicated in different inflammatory conditions. Most of this research involved working with animal models of disease and in vitro systems. Recent research, however, points to a role of H2S in clinical inflammatory disease as well. This chapter describes our current understanding of the role of H2S in inflammation.

An evolutionary perspective on the immunomodulatory role of hydrogen sulphide

Most preclinical studies on endogenous hydrogen sulphide signalling have given little consideration to the fact that the human body contains more bacterial cells than human cells, and that evolution provides the context for all biology. Whether hydrogen sulphide is pro or anti-inflammatory is heavily debated within the literature, yet researchers have not fully considered that invasive bacteria produce hydrogen sulphide, often at levels far above the endogenous levels of the host. Here I argue that if hydrogen sulphide is an endogenous signalling molecule with immunomodulatory functions, then it must have evolved in the presence of virulent bacteria which produce hydrogen sulphide. This context leads to two competing theories about the evolution of endogenous hydrogen sulphide signalling. The detectable emission theory proposes that bacteria produce hydrogen sulphide as part of normal metabolism and hosts which evolved to detect and respond to this hydrogen sulphide would gain a selective survival advantage. This predicts that the endogenous production of hydrogen sulphide is a mechanism which amplifies the bacterial hydrogen sulphide signal. The opposing protective agent theory predicts that bacterial hydrogen sulphide is an effective defence against the bactericidal mechanisms of the host's immune response. In this case, endogenous hydrogen sulphide production is either at inconsequential levels to alter the immune response, or is involved in the inflammation resolution process. Evidence suggests that the direct interactions of hydrogen sulphide with the bactericidal mechanisms of the innate immune system are most congruent with the protective agent theory. Therefore, I argue that if hydrogen sulphide is an immunomodulatory endogenous signalling molecule its effects are most likely anti-inflammatory.

Selective modulation of MAPKs contribute to the anti-proliferative and anti-inflammatory activities of 1,7-dihydroxy-3,4-dimethoxyxanthone in rheumatoid arthritis-derived fibroblast-like synoviocyte MH7A cells

ETHNOPHARMACOLOGICAL RELEVANCE

1,7-Dihydroxy-3,4-dimethoxyxanthone (XAN) is an antirheumatic agent isolated from traditional Chinese medicine Securidaca inappendiculata Hassk. This study was designed to investigate its anti-proliferative and anti-inflammatory activities on rheumatoid arthritis derived fibroblast-like synoviocyte cell line MH7A, and explore the underlying mechanism of action.

METHODS

The anti-proliferative activity of XAN on MH7A cells was assessed by an MTT method. Its pro-apoptotic and cell cycle arrest activities were analyzed by flow cytometry. W-B method was employed to investigate hallmark kinases involved in the course. Pro-inflammatory cytokines in culture supernatant of MH7A cells were determined by an ELISA method.

RESULTS

The results showed XAN efficiently suppressed the proliferation and secretion of IL-1β and IL-6 of MH7A cells in a concentration-dependent manner. Co-treatment with MAPKs inhibitors U0126, SB202190 and SP600125 indicated JNK and p38 pathways were involved in the course. Up-regulation of p-p38, p-ERK, bax and p21, and down-regulation of p-JNK, cyclin D1 and bcl-2 were observed upon the treatment with XAN. SB202190 partly reversed the modulatory effects. The results suggested XAN inhibited the proliferation of MH7A cells mainly via cell cycle arrest at G1/S phase, and the activity was due to the up-regulation of p-p38, which led to the modulation of p21 and cyclin D1. The down-regulation of p-JNK by XAN suppressed the secretion of pro-inflammatory cytokines, which was beneficial to the anti-proliferative activity of MH7A cells.

CONCLUSION

XAN selectively modulated MAPKs signaling, and exerted the subsequent anti-proliferative and anti-inflammatory activities on MH7A cells.

Hydrogen sulfide attenuates IL-1β-induced inflammatory signaling and dysfunction of osteoarthritic chondrocytes

Inflammatory cytokines are crucial factors in the onset of osteoarthritis (OA). The pro-inflammatory cytokine, interleukin-1β (IL-1β), is capable of stimulating a few cartilage degradation mediators and is of importance to the pathogenesis of OA. It has been demonstrated that hydrogen sulfide (H2S) exerts an inhibitory effect on inflammation. Thus, in the present study, we aimed to investigate the therapeutic effects of H2S in OA. For this purpose, an in vitro model of cartilage inflammation was created. Human OA chondrocytes were cultured and pre-treated with H2S (0.06-1.5 mM) with or without IL-1β (10 ng/ml) and then Griess reagent was used to quantify the production of nitric oxide (NO). Using enzyme-linked immunosorbent assay, we quantified the production of prostaglandin E2 (PGE2) and matrix metalloproteinase-13 (MMP-13). In addition, we determined the gene expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) and MMP-13 using reverse transcription-quantitative polymerase chain reaction and the expression of signaling molecules related to mitogen-activated protein kinases (MAPKs) and nuclear factor-κB (NF-κB) by western blot analysis. Our results revealed that H2S markedly reversed the effects of IL-1β on the gene expression of COX-2, MMP-13 and iNOS and on the production of MMP-13, PGE2 and NO. In addition, H2S inhibited the activation of the extracellular signal-regulated kinase (ERK)/IκBα/NF-κB pathway which was induced by IL-1β. On the whole, the results of the present study suggest that H2S exerts chondroprotective effects. Thus, H2S may have potential for use in the treatment of patients suffering from OA.

Phosphinodithioate and Phosphoramidodithioate Hydrogen Sulfide Donors

Hydrogen sulfide is rapidly emerging as a key physiological mediator and potential therapeutic tool in numerous areas such as acute and chronic inflammation, neurodegenerative and cardiovascular disease, diabetes, obesity and cancer. However, the vast majority of the published studies have employed crude sulfide salts such as sodium hydrosulfide (NaSH) and sodium sulfide (Na2S) as H2S "donors" to generate H2S. Although these salts are cheap, readily available and easy to use, H2S generated from them occurs as an instantaneous and pH-dependent dissociation, whereas endogenous H2S synthesis from the enzymes cystathionine γ-lyase, cystathionine-β-synthase and 3-mercaptopyruvate sulfurtransferase is a slow and sustained process. Furthermore, sulfide salts are frequently used at concentrations (e.g. 100 μM to 10 mM) far in excess of the levels of H2S reported in vivo (nM to low μM). For the therapeutic potential of H2S is to be properly harnessed, pharmacological agents which generate H2S in a physiological manner and deliver physiologically relevant concentrations are needed. The phosphorodithioate GYY4137 has been proposed as "slow-release" H2S donors and has shown promising efficacy in cellular and animal model diseases such as hypertension, sepsis, atherosclerosis, neonatal lung injury and cancer. However, H2S generation from GYY4137 is inefficient necessitating its use at high concentrations/doses. However, structural modification of the phosphorodithioate core has led to compounds (e.g. AP67 and AP105) with accelerated rates of H2S generation and enhanced biological activity. In this review, the therapeutic potential and limitations of GYY4137 and related phosphorodithioate derivatives are discussed.

Hydrogen sulphide decreases IL-1β-induced activation of fibroblast-like synoviocytes from patients with osteoarthritis

Balneotherapy employing sulphurous thermal water is still applied to patients suffering from diseases of musculoskeletal system like osteoarthritis (OA) but evidence for its clinical effectiveness is scarce. Since the gasotransmitter hydrogen sulphide (H₂S) seems to affect cells involved in degenerative joint diseases, it was the objective of this study to investigate the effects of exogenous H₂S on fibroblast-like synoviocytes (FLS), which are key players in OA pathogenesis being capable of producing pro-inflammatory cytokines and matrix degrading enzymes. To address this issue primary FLS derived from OA patients were stimulated with IL-1β and treated with the H₂S donor NaHS. Cellular responses were analysed by ELISA, quantitative real-time PCR, phospho-MAPkinase array and Western blotting. Treatment-induced effects on cellular structure and synovial architecture were investigated in three-dimensional extracellular matrix micromasses. NaHS treatment reduced both spontaneous and IL-1β-induced secretion of IL-6, IL-8 and RANTES in different experimental settings. In addition, NaHS treatment reduced the expression of matrix metallo-proteinases MMP-2 and MMP-14. IL-1β induced the phosphorylation of several MAPkinases. NaHS treatment partially reduced IL-1β-induced activation of several MAPK whereas it increased phosphorylation of pro-survival factor Akt1/2. When cultured in spherical micromasses, FLS intentionally established a synovial lining layer-like structure; stimulation with IL-1β altered the architecture of micromasses leading to hyperplasia of the lining layer which was completely inhibited by concomitant exposure to NaHS. These data suggest that H₂S partially antagonizes IL-1β stimulation via selective manipulation of the MAPkinase and the PI3K/Akt pathways which may encourage development of novel drugs for treatment of OA.

Hydrogen sulfide acts as a pro-inflammatory mediator in rheumatic disease

OBJECTIVE

Hydrogen sulfide (H₂ S) is a gaseous mediator produced in the body. In experimental models, endogenously produced H₂ S has been shown to have pro-inflammatory effects. The aim of this study was to investigate whether H₂ S is present in three common rheumatic diseases, rheumatoid arthritis (RA), gout and osteoarthritis (OA) and to determine if H₂ S levels correlate with disease activity.

METHODS

Patients with RA, gout, OA, and healthy controls (n = 30 each) were recruited. Plasma and where possible, synovial fluid (SF), were obtained. Levels of H₂ S and interleukin-6 (IL-6) (a known inflammatory marker as a positive control) were determined and assessed for their relationship with disease activity.

RESULTS

SF-H₂ S levels were significantly elevated in both RA and gout when compared to respective plasma levels. Plasma levels of H₂ S were not different from those in healthy controls in patients with either RA or gout. In OA, plasma levels of H₂ S were significantly elevated compared to healthy controls. In RA, SF-H₂ S levels correlated with Disease Activity Score (DAS)-28 and tender joint count.

CONCLUSION

H₂ S is present in the joint and acts as a pro-inflammatory mediator in rheumatic diseases. H₂ S may be a novel therapeutic target for these conditions.

Effect of hydrogen sulfide sources on inflammation and catabolic markers on interleukin 1β-stimulated human articular chondrocytes

OBJECTIVE

Hydrogen sulfide (H2S), the third gasotransmitter together with NO and CO, is emerging as a regulator of inflammation. To test if it might offer therapeutic value in the treatment of osteoarthritis (OA) we evaluated the effects of two exogenous sources of H2S, NaSH and GYY4137, on inflammation and catabolic markers that characterize OA.

METHOD

Human chondrocytes (CHs) were isolated from OA tissue. Cells were stimulated with a pro-inflammatory cytokine (interleukin-1β, IL1β, 5 ng/ml) and the ability of the two H2S sources to ameliorate its effects on the cells was tested. Nitric oxide (NO) production was quantified through the Griess reaction. Protein levels of inducible NO synthase (NOS2) and matrix metalloproteinase 13 (MMP13) were visualized through immunocytochemistry (ICC). Relative mRNA expression was quantified with qRT-PCR. Prostaglandin-2 (PGE-2), interleukin 6 (IL6) and MMP13 levels were measured with specific EIAs. NFκB nuclear translocation was visualized with immunofluorescence.

RESULTS

Both H2S sources led to significant reductions in NO, PGE-2, IL6 and MMP13 released by the cells and at the protein level. This was achieved by downregulation of relevant genes involved in the synthesis routes of these molecules, namely NOS2, cyclooxigenase-2 (COX2), prostaglandin E synthase (PTGES), IL6 and MMP13. NFκB nuclear translocation was also reduced.

CONCLUSION

NaSH and GYY4137 show anti-inflammatory and anti-catabolic properties when added to IL1β activated osteoarthritic CHs. Supplementation with exogenous H2S sources can regulate the expression of relevant genes in OA pathogenesis and progression, counteracting IL1β pro-inflammatory signals that lead to cartilage destruction in part by reducing NFκB activation.

Connective tissue growth factor promotes interleukin-1β-mediated synovial inflammation in knee osteoarthritis

Connective tissue growth factor (CTGF), also known as CCN2, is a key proinflammatory mediator. In the present study, the involvement of the CTGF signaling pathway in human knee osteoarthritis (OA) fibroblast-like synoviocytes (FLSs) was investigated. FLSs were isolated from human OA synovium and incubated with CTGF in the absence or presence of interleukin‑1β (IL‑1β). The expression of relevant genes and proteins was analyzed by qPCR, western blotting and enzyme-linked immunosorbent assay (ELISA). Matrix metalloproteinase (MMP) activity and nuclear factor (NF)-κB activation were also evaluated. CTGF stimulation resulted in the significant production of IL-6, IL-8, C-C motif ligand 2 (CCL2), CCL20, MMP-1 and MMP-3 in FLSs in the presence, but not in the absence, of IL-1β. CTGF also enhanced the levels of phosphorylated extracellular signal-related kinase 1/2 (ERK1/2) and p38. In addition, CTGF at 25 ng/ml, in the presence of IL‑1β, significantly potentiated NF-κB activation. The results indicated that CTGF interacted with IL‑1β in FLSs to promote the inflammatory response in the synovium, leading to the initiation of the inflammatory cascade. These results support the proinflammatory role of CTGF in synovitis and joint destruction in OA.

Role of hydrogen sulfide in the pathology of inflammation

Hydrogen sulfide (H2S) is a well-known toxic gas that is synthesized in the human body from the amino acids cystathionine, homocysteine, and cysteine by the action of at least two distinct enzymes: cystathionine-γ-lyase and cystathionine-β-synthase. In the past few years, H2S has emerged as a novel and increasingly important biological mediator. Imbalances in H2S have also been shown to be associated with various disease conditions. However, defining the precise pathophysiology of H2S is proving to be a complex challenge. Recent research in our laboratory has shown H2S as a novel mediator of inflammation and work in several groups worldwide is currently focused on determining the role of H2S in inflammation. H2S has been implicated in different inflammatory conditions, such as acute pancreatitis, sepsis, joint inflammation, and chronic obstructive pulmonary disease (COPD). Active research on the role of H2S in inflammation will unravel the pathophysiology of its actions in inflammatory conditions and may help develop novel therapeutic approaches for several, as yet incurable, disease conditions.