Biological Effects of Thermal Water-Associated Hydrogen Sulfide on Human Airways and Associated Immune Cells: Implications for Respiratory Diseases

The Impact of Thermal Water in Asthma and COPD: A Systematic Review According to the PRISMA Statement

BACKGROUND

Asthma and chronic obstructive pulmonary disease (COPD) are global health challenges leading to substantial morbidity and mortality. While existing guidelines emphasize evidence-based treatments, the potential therapeutic role of thermal water (TW) inhalation remains under-investigated.

METHODS

This systematic review followed PRISMA-P guidelines and sought to evaluate the impact of TW in asthma and COPD. A thorough literature search, performed up to May 2023, encompassed in vitro, in vivo, randomized controlled trial (RCT), non-RCT, and observational studies.

RESULTS

The review included 12 studies reporting different findings. In vitro studies suggested TW could enhance antioxidant capacity and cell proliferation. In a murine model of non-atopic asthma, TW inhalation reduced airway hyperresponsiveness and inflammation. RCTs in COPD patients indicated mixed effects, including improved quality of life, reduced airway oxidant stress, and enhanced exercise tolerance. Asthma patients exposed to water aerosols exhibited improved lung function and reduced airway inflammation. Non-RCTs showed improved lung function and antioxidant activity after TW therapy. Additionally, observational studies reported enhanced lung function and reduced airway inflammation.

CONCLUSION

The current evidence suggests potential benefits of TW therapy in asthma and COPD. However, limited high-quality RCTs and concerns regarding occupational TW exposure necessitate further investigation. While TW therapy offers a non-invasive treatment, its therapeutic potential still needs definitive demonstration. Future research should therefore prioritize well-designed RCTs to thoroughly establish the efficacy and safety of TW as a potential therapeutic intervention for asthma and COPD.

A Novel Bionebulizer Approach to Study the Effects of Natural Mineral Water on a 3D In Vitro Nasal Model from Allergic Rhinitis Patients

Sulfurous thermal waters (STWs) are used as a complementary treatment for allergic rhinitis. However, there is scant data on the effects of STW on nasal epithelial cells, and in vitro models are warranted. The main aim of this study was to evaluate the dose and time effects of exposure to 3D nasal inserts (MucilAirTM-HF allergic rhinitis model) with STW or isotonic sodium chloride solution (ISCS) aerosols. Transepithelial electrical resistance (TEER) and histology were assessed before and after nebulizations. Chemokine/cytokine levels in the basal supernatants were assessed by enzyme-linked immunosorbent assay. The results showed that more than four daily nebulizations of four or more minutes compromised the normal epithelial integrity. In contrast, 1 or 2 min of STW or ISCS nebulizations had no toxic effect up to 3 days. No statistically significant changes in release of inflammatory chemokines MCP-1/CCL2 > IL-8/CXCL8 > MIP-1α/CCL3, no meaningful release of "alarmins" (IL-1α, IL-33), nor of anti-inflammatory IL-10 cytokine were observed. We have characterized safe time and dose conditions for aerosol nebulizations using a novel in vitro 3D nasal epithelium model of allergic rhinitis patients. This may be a suitable in vitro setup to mimic in vivo treatments of chronic rhinitis with STW upon triggering an inflammatory stimulus in the future.

Gasotransmitter Research Advances in Respiratory Diseases

Significance: Gasotransmitters are small gas molecules that are endogenously generated and have well-defined physiological functions. The most well-defined gasotransmitters currently are nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S), while other potent gasotransmitters include ammonia, methane, cyanide, hydrogen gas, and sulfur dioxide. Gasotransmitters play a role in various respiratory diseases such as asthma, chronic obstructive pulmonary disease, obstructive sleep apnea, lung infection, bronchiectasis, cystic fibrosis, primary ciliary dyskinesia, and COVID-19. Recent Advances: Gasotransmitters can act as biomarkers that facilitate disease diagnosis, indicate disease severity, predict disease exacerbation, and evaluate disease outcomes. They also have cell-protective properties, and many studies have been conducted to explore their pharmacological applications. Innovative drug donors and drug delivery methods have been invented to amplify their therapeutic effects. Critical Issues: In this article, we briefly reviewed the physiological and pathophysiological functions of some gasotransmitters in the respiratory system, the progress in detecting exhaled gasotransmitters, as well as innovative drugs derived from these molecules. Future Directions: The current challenge for gasotransmitter research includes further exploring their physiological and pathological functions, clarifying their complicated interactions, exploring suitable drug donors and delivery devices, and characterizing new members of gasotransmitters. Antioxid. Redox Signal. 40, 168-185.

External use of radon and sulfide mineral waters in the treat-ment of experimental arthrosis

Abstract: The article presents the results of studies of the effect of radon and sulfide min-eral waters (MW) on Wistar rats with experimental arthrosis. materials and methods. Rats were randomized into 4 groups. Group 1 consisted of intact rats (control group). In the remaining three groups, a model of knee arthrosis was reproduced using dexamethasone injections. Group 2 consisted of rats with untreated pathology. Group 3 consisted of rats using radon MW procedures, and group 4 consisted of rats using sulfide MW. Results. Morphological studies have determined that using radon and sulfide MW has a curative effect on the structural and functional organization of the joint and cartilage - the manifes-tations of inflammation in the knee joints are significantly reduced, dystrophic manifesta-tions disappear, and reparative processes in cartilage improve. There are signs of an im-provement in the state of metabolic processes in the body of rats: the balance in the lipid peroxidation and antioxidant systems is restored, and the indicators of the processes of energy supply of transmembrane transport (according to the activity of magnesium-dependent Na+/K+-ATP-ase and Ca2+-ATP-ase) and protein exchange.Conclusion. Based on the data obtained, it was concluded that both applied MWs have a unidirectional, but somewhat different in strength, curative effect on the course of experimental arthrosis, which is due to different mechanisms of the biological action of radon and hydrogen sul-fide. Keywords: experimental arthrosis; morphological and metabolic indicators; radon; hydrogen sulfide; mineral water.

Utility of NO and H2S donating platforms in managing COVID-19: Rationale and promise

Viral infections are a continuing global burden on the human population, underscored by the ramifications of the COVID-19 pandemic. Current treatment options and supportive therapies for many viral infections are relatively limited, indicating a need for alternative therapeutic approaches. Virus-induced damage occurs through direct infection of host cells and inflammation-related changes. Severe cases of certain viral infections, including COVID-19, can lead to a hyperinflammatory response termed cytokine storm, resulting in extensive endothelial damage, thrombosis, respiratory failure, and death. Therapies targeting these complications are crucial in addition to antiviral therapies. Nitric oxide and hydrogen sulfide are two endogenous gasotransmitters that have emerged as key signaling molecules with a broad range of antiviral actions in addition to having anti-inflammatory properties and protective functions in the vasculature and respiratory system. The enhancement of endogenous nitric oxide and hydrogen sulfide levels thus holds promise for managing both early-stage and later-stage viral infections, including SARS-CoV-2. Using SARS-CoV-2 as a model for similar viral infections, here we explore the current evidence regarding nitric oxide and hydrogen sulfide's use to limit viral infection, resolve inflammation, and reduce vascular and pulmonary damage.

Protective role of Portuguese natural mineral waters on skin aging: in vitro evaluation of anti-senescence and anti-oxidant properties

Natural mineral waters (NMWs) emerge from the earth as springs and their beneficial therapeutic effect has been empirically recognized in different countries. Portugal has diverse NMW resources that are sought for the relief of different afflictions including dermatological complications. However, there is a lack of scientific validation supporting this empiric knowledge. In this study, we aimed to screen the in vitro bioactivity of Portuguese NMWs with different chemical profiles, namely sulfurous/bicarbonate/sodic (SBS), bicarbonate/magnesium, sulfated/calcic, sulfurous/chlorinated/sodic, sulfurous/bicarbonate/fluoridated/sodic, and chlorinated/sodic, focusing on aging-related skin alterations. Mouse skin fibroblasts and macrophages were exposed to culture medium prepared in different NMWs. Cellular viability was evaluated by MTT assay and etoposide-induced senescence was analyzed through the beta-galactosidase staining kit. Wound healing was investigated by the scratch assay, and phototoxicity/photoprotection after UVA irradiation was evaluated using a neutral red solution. ROS production was quantified using the 2'7'-dichlorofluorescin diacetate dye, and the activity of superoxide dismutase (SOD) was analyzed by a commercial kit after lipopolysaccharide exposure. NMWs within the SBS profile demonstrated anti-senescence activity in skin fibroblasts, along with a variable effect on cellular viability. Among the tested NMWs, two decreased cellular senescence and preserved cell viability and were therefore selected for subsequent studies, together with a SBS NMW with therapeutic indications for dermatologic diseases. Overall, the selected NMW promoted wound healing in skin fibroblasts and activated SOD in macrophages, thus suggesting an anti-oxidant effect. None of the NMWs prevented phototoxicity after UV irradiation. Our results shed a light on the anti-aging potential of Portuguese NMW, supporting their putative application in cosmetic or medical products.

Eustachian tube insufflation with thermal water: Effectiveness in the treatment of pediatric otitis media with effusion

PURPOSE

Otitis media with effusion (OME) is the most common ear disease in childhood. The hearing loss associated with OME impacts on children's language development and behavior. Eustachian tube insufflation are among possible treatments for OME, but data regarding their effectiveness are scarce. The aim of this investigation was to analyze the effect of inhalatory thermal therapy and Eustachian tube insufflation in a consecutive cohort of pediatric patients with OME.

MATERIALS AND METHODS

Seventy-four pediatric patients referred for OME to the thermal medical center "La Contea" (Battaglia Terme, Padova, Italy) were considered. Data from tympanometry and pure tone audiometry performed immediately before (T0), at the end of treatment (T1) and at a follow-up control (T2) were analyzed.

RESULTS

Data from 148 ears were available. The pressure values of tympanometry significantly improved from T0 to T1 (p = 0.0001), and further improvement was recorded at T2, when 60.8% of patients had normal tympanograms. A significant gain of the air-conduction threshold in the T0-T2 interval was observed (p = 0.0001). At otoscopy, a significant reduction of tympanic membranes with fluid or air-fluid levels presence (p < 0.00001) and a significant increase of normal tympanic membranes (p = 0.0001) were found.

CONCLUSION

Eustachian tube insufflation represented a well-tolerated and effective treatment in children with OME. Further investigations should deepen these results in randomized, double-blind settings, possibly with long-term follow-up periods. A quality-of-life and cost-effectiveness evaluation of this treatment approach for pediatric OME could be helpful for public health decision-making.

Crenotherapy as a Complementary and Integrative Treatment for Chronic Rhinosinusitis: A Systematic Review and Discussion of Current Evidence Limitations

BACKGROUND

Chronic rhinosinusitis (CRS) is a common condition that affects patients' quality of life. Standard treatments for CRS have known side effects and variable efficacy rates. Thus, complementary and integrative (CIM) treatments for CRS such as crenotherapy, which utilizes high mineral content water or vapor as an inhalation therapy, are of continued interest.

OBJECTIVES

To summarize and evaluate the current research investigating crenotherapy's therapeutic potential and clinical outcomes for the treatment of CRS.

STUDY DESIGN

Systematic review and qualitative analysis.

METHODS

A systematic review was performed, with a comprehensive search strategy applied to 6 databases from inception to March 2021: CINAHL, Cochrane, Embase, PubMed, Scopus, and Web of Science. Studies with at least 10 patients, which investigated crenotherapy as the sole or adjunctive treatment for CRS in humans were included.

RESULTS

In total, 10 articles out of 756 were included. Of these, 6 were randomized controlled trials. The remaining four articles were non-randomized prospective cohort studies. Six studies assessed clinical symptoms in response to crenotherapy, and there were unanimous improvements in Visual Analog Scale (VAS), Sino-Nasal Outcome Test-20 (SNOT-20), and other quality of life metrics. The studies that assessed inflammatory markers, cytology, or other measures showed significant improvement in neutrophil count, spores, ciliary motility, IgE, and manometry. Minimal to no adverse events were reported across all 10 studies.

CONCLUSION

There is limited data to support crenotherapy's effectiveness in treating patients with CRS. However, published studies suggest that for certain patients crenotherapy can both improve CRS symptoms and objective measures of nasociliary function with minimal side effects. Findings must be interpreted with caution due to study heterogeneity, inconsistent use of standard CRS definitions and outcomes measures, as well as other study design flaws. Given these results, as well as a growing interest in CIM, crenotherapy treatments for CRS deserve further investigation.

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.

Reactive Sulfur Compounds in the Fight against COVID-19

The SARS-CoV-2 coronavirus pandemic outbreak in 2019 resulted in the need to search for an effective and safe strategy for treating infected patients, relieving symptoms, and preventing severe disease. SARS-CoV-2 is an RNA virus that can cause acute respiratory failure and thrombosis, as well as impair circulatory system function. Permanent damage to the heart muscle or other cardiovascular disorders may occur during or after the infection. The severe course of the disease is associated with the release of large amounts of pro-inflammatory cytokines. Due to their documented anti-inflammatory, antioxidant, and antiviral effects, reactive sulfur compounds, including hydrogen sulfide (H₂S), lipoic acid (LA), N-acetylcysteine (NAC), glutathione (GSH), and some other lesser-known sulfur compounds, have attracted the interest of scientists for the treatment and prevention of the adverse effects of diseases caused by SARS-CoV-2. This article reviews current knowledge about various endogenous or exogenous reactive sulfur compounds and discusses the possibility, or in some cases the results, of their use in the treatment or prophylaxis of COVID-19.

Health management of patients with COVID-19: is there a room for hydrotherapeutic approaches?

With highly variable types of coronavirus disease 2019 (COVID-19) symptoms in both severity and duration, there is today an important need for early, individualized, and multidisciplinary strategies of rehabilitation. Some patients present persistent affections of the respiratory function, digestive system, cardiovascular function, locomotor system, mental health, sleep, nervous system, immune system, taste, smell, metabolism, inflammation, and skin. In this context, we highlight here that hydrothermal centers should be considered today as medically and economically relevant alternatives to face the urgent need for interventions among COVID-19 patients. We raise the potential benefits of hydrotherapy programs already existing which combine alternative medicine with respiratory care, physical activity, nutritional advice, psychological support, and physiotherapy, in relaxing environments and under medical supervision. Beyond the virtues of thermal waters, many studies reported medical benefits of natural mineral waters through compressing, buoyancy, resistance, temperature changes, hydrostatic pressure, inhalations, or drinking. Thermal institutions might offer individualized follow-up helping to unclog hospitals while ensuring the continuity of health care for the different clinical manifestations of COVID-19 in both post-acute and chronic COVID-19 patients. Our present review underlines the need to further explore the medical effectiveness, clinical and territorial feasibility, and medico-economic impacts of the implementation of post-COVID-19 patient management in hydrotherapeutic establishments.

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

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

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.

Buffering Adaptive Immunity by Hydrogen Sulfide

T cell-mediated adaptive immunity is designed to respond to non-self antigens and pathogens through the activation and proliferation of various T cell populations. T helper 1 (Th1), Th2, Th17 and Treg cells finely orchestrate cellular responses through a plethora of paracrine and autocrine stimuli that include cytokines, autacoids, and hormones. Hydrogen sulfide (H₂S) is one of these mediators able to induce/inhibit immunological responses, playing a role in inflammatory and autoimmune diseases, neurological disorders, asthma, acute pancreatitis, and sepsis. Both endogenous and exogenous H₂S modulate numerous important cell signaling pathways. In monocytes, polymorphonuclear, and T cells H₂S impacts on activation, survival, proliferation, polarization, adhesion pathways, and modulates cytokine production and sensitivity to chemokines. Here, we offer a comprehensive review on the role of H₂S as a natural buffer able to maintain over time a functional balance between Th1, Th2, Th17 and Treg immunological responses.

H2S donating corticosteroids: Design, synthesis and biological evaluation in a murine model of asthma

Introduction

Hydrogen sulfide (H2S) is a fundamental biological endogenous gas-mediator in the respiratory system. It regulates pivotal patho-physiological processes such as oxidative stress, pulmonary circulation, airway tone and inflammation.

Objectives

We herein describe the design and synthesis of molecular hybrids obtained by the condensation of several corticosteroids with different hydrogen sulfide releasing moieties.

Methods

All the molecules are characterized for their ability to release H2S both via amperometric approach and using a fluorescent probe. The chemical stability of the newly synthesized hybrid molecules has been investigated at differing pH values and in human serum.

Results

Prednisone-TBZ hybrid (compound 7) was selected for further evaluations. The obtained results from the in vitro and in vivo studies clearly show evidence in favor of the anti-inflammatory properties of the released H2S.

Conclusions

The protective effect on airway remodeling makes the hybrid Prednisone-TBZ (compound 7) as a promising therapeutic option in reducing allergic asthma symptoms and exacerbations.

Inhalations with thermal waters in respiratory diseases

ETHNOPHARMACOLOGICAL RELEVANCE

Inhalations with thermal waters are an old therapeutic method used in the therapy of respiratory diseases as a treatment of choice showing a long-lasting outcome with no side effects. Paradoxically, there is little well-established research on their mechanisms of action.

AIM OF THE STUDY

The aim of this paper is therefore to summarize the influence of inhalatory treatment with thermal waters on the main symptoms and features of respiratory disorders including allergy-like symptoms, inflammation, oxidant-anti-oxidant balance, cellular influx, disturbed mucus secretions, recurrent infections, pulmonary and nasal function and quality of life. A short history of inhalations is also presented.

MATERIALS AND METHODS

The present paper is a sum-up of research articles on the use of inhalations with thermal waters in respiratory disorders.

RESULTS

According to the herein presented literature, the use of thermal water inhalations is beneficial for almost all manifestations of respiratory diseases. The mode of their action remains still unclear; however, it seems that the most important one relies on the restoration of proper defense mechanisms of the organism.

CONCLUSIONS

Inhalations with thermal waters alleviate symptoms of respiratory diseases. They also improve the quality of life of the patients and seem to be a good add-on therapy in the treatment of disorders of the respiratory system.

Clinical efficacy of medical hydrology: an umbrella review

The aim of this research was to summarize available scientific evidence on the efficacy of medical hydrology for the management of any health condition. The search was conducted on 26th March 2021, in the following databases: Medline (via PubMed), EMBASE, Web of Science, Cochrane Library, and Google Scholar. All relevant literature reviews investigating the clinical efficacy of interventions characterized by the use of natural mineral waters and muds were included. The quality of studies was assessed with the "AMSTAR 2" tool. After article screening, 49 reviews were included in this work. Overall, retrieved scientific evidence suggests that spa therapy is beneficial for patients affected by some specific musculoskeletal conditions, with improvements potentially lasting up to 9 months. Moreover, balneotherapy can be an integrative support for the management of chronic venous insufficiency and some inflammatory skin diseases like psoriasis. The role of spa therapy in rehabilitation appears relevant as well. More limited, although interesting evidence exists for inhalation and hydropinic therapies. Globally, retrieved evidence suggests that, besides individual wellbeing, medical hydrology can be useful for public health. In particular, higher-quality studies seem to support the integrative use of spa-related interventions for conditions like osteoarthritis, fibromyalgia, low back pain of rheumatic origin, and chronic venous insufficiency. However, the body of evidence has some limitations and further clinical trials should be designed for each relevant application to consolidate and expand acquired knowledge.

Hydrogen Sulfide Inhibits TMPRSS2 in Human Airway Epithelial Cells: Implications for SARS-CoV-2 Infection

The COVID-19 pandemic has now affected around 190 million people worldwide, accounting for more than 4 million confirmed deaths. Besides ongoing global vaccination, finding protective and therapeutic strategies is an urgent clinical need. SARS-CoV-2 mostly infects the host organism via the respiratory system, requiring angiotensin-converting enzyme 2 (ACE2) and transmembrane protease serine 2 (TMPRSS2) to enter target cells. Therefore, these surface proteins are considered potential druggable targets. Hydrogen sulfide (H2S) is a gasotransmitter produced by several cell types and is also part of natural compounds, such as sulfurous waters that are often inhaled as low-intensity therapy and prevention in different respiratory conditions. H2S is a potent biological mediator, with anti-oxidant, anti-inflammatory, and, as more recently shown, also anti-viral activities. Considering that respiratory epithelial cells can be directly exposed to H2S by inhalation, here we tested the in vitro effects of H2S-donors on TMPRSS2 and ACE2 expression in human upper and lower airway epithelial cells. We showed that H2S significantly reduces the expression of TMPRSS2 without modifying ACE2 expression both in respiratory cell lines and primary human upper and lower airway epithelial cells. Results suggest that inhalational exposure of respiratory epithelial cells to natural H2S sources may hinder SARS-CoV-2 entry into airway epithelial cells and, consequently, potentially prevent the virus from spreading into the lower respiratory tract and the lung.

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.

The effectiveness of balneotherapy and aquatic exercise on bone metabolism: A systematic review and meta-analysis

OBJECTIVE

To systematically evaluate the effectiveness of balneotherapy and/or aquatic exercise on bone metabolism.

DESIGN

A systematic literature search was conducted from inception to January 4, 2021. Standardized mean differences (SMDs) and 95% confidence intervals (CIs) were calculated using a fixed-effect model according to study heterogeneity.

RESULTS

Seven articles involving 467 participants were selected. Three balneotherapy studies were qualitatively integrated. The results showed that bone resorption slowed down with or without stimulation of bone formation. A pooled meta-analysis of four studies on aquatic exercise showed significant evidence for a reduction in parathyroid hormone (PTH; SMD = -0.71; 95% CI, -1.04 to -0.38; P < 0.001), and a significant increase in osteocalcin (OC; SMD = 0.60; 95% CI, 0.16 to 1.03; P = 0.007) after aquatic exercise.

CONCLUSION

Balneotherapy and aquatic exercise had significant effects on bone metabolism, reducing bone resorption and/or increasing bone formation. This study highlights the importance of balneotherapy and aquatic exercise for bone health.

Are There Benefits from Thermal Bacteria for Health? The Hydrogenome Role

In recent years, natural thermal mineral waters have been gaining the special attention of the scientific community, namely in the prevention and treatment of some diseases, due to the microbial properties that exist in these habitats. The aim of this work was to characterize the physicochemical composition and the microbial taxonomic communities present in three thermal waters of the Galician region in Spain and two samples of the northern region in Portugal. These collected water samples were analyzed for physicochemical characterization and the respective hydrogenome of the waters using next generation sequencing together with 16S rRNA gene sequencing. The sequencing showed a high diversity of microorganisms in all analyzed waters; however, there is a clear bacterial predominance of Proteobacteria phylum, followed by Firmicutes, Deinococcus-Thermus, Aquificae and Nitrospira. The main physicochemical parameters responsible for the clustering within the Spanish waters were sulfur compounds (SO32− and S2−), CO32− and neutral pH, and in the Portuguese waters were Mg, Ca and Sr, nitrogen compounds (NO3− and NH4+), Na, Rb, conductivity and dry residue. This work will allow for a better understanding of the microbial community’s composition and how these microorganisms interfere in the physicochemical constitution of these waters often associated with medicinal properties. Furthermore, the hydrogenome may be used as an auxiliary tool in the practice of medical hydrology, increasing the likelihood of safe use of these unique water types.

The Role of Hydrogen Sulfide in Respiratory Diseases

Respiratory diseases are leading causes of death and disability around the globe, with a diverse range of health problems. Treatment of respiratory diseases and infections has been verified to be thought-provoking because of the increasing incidence and mortality rate. Hydrogen sulfide (H₂S) is one of the recognized gaseous transmitters involved in an extensive range of cellular functions, and physiological and pathological processes in a variety of diseases, including respiratory diseases. Recently, the therapeutic potential of H₂S for respiratory diseases has been widely investigated. H₂S plays a vital therapeutic role in obstructive respiratory disease, pulmonary fibrosis, emphysema, pancreatic inflammatory/respiratory lung injury, pulmonary inflammation, bronchial asthma and bronchiectasis. Although the therapeutic role of H₂S has been extensively studied in various respiratory diseases, a concrete literature review will have an extraordinary impact on future therapeutics. This review provides a comprehensive overview of the effective role of H₂S in respiratory diseases. Besides, we also summarized H₂S production in the lung and its metabolism processes in respiratory diseases.

Understanding hydrogen sulfide signaling in neonatal airway disease

INTRODUCTION

Airway dysfunction leading to chronic lung disease is a common consequence of premature birth and mechanisms responsible for early and progressive airway remodeling are not completely understood. Current therapeutic options are only partially effective in reducing the burden of neonatal airway disease and premature decline of lung function. Gasotransmitter hydrogen sulfide (H2S) has been recently recognized for its therapeutic potential in lung diseases.

AREAS COVERED

Contradictory to its well-known toxicity at high concentrations, H2S has been characterized to have anti-inflammatory, antioxidant, and antiapoptotic properties at physiological concentrations. In the respiratory system, endogenous H2S production participates in late lung development and exogenous H2S administration has a protective role in a variety of diseases such as acute lung injury and chronic pulmonary hypertension and fibrosis. Literature searches performed using NCBI PubMed without publication date limitations were used to construct this review, which highlights the dichotomous role of H2S in the lung, and explores its promising beneficial effects in lung diseases.

EXPERT OPINION

The emerging role of H2S in pathways involved in chronic lung disease of prematurity along with its recent use in animal models of BPD highlight H2S as a potential novel candidate in protecting lung function following preterm birth.

Different Waters for Different Performances: Can We Imagine Sport-Related Natural Mineral Spring Waters?

Preserving the hydration status means to balance daily fluids and salt losses with gains, where the losses depend on several physiological and environmental factors. Especially for athletes, these losses could be relevant and negatively influence the performance: therefore, their hydro-saline status must be preserved with personalized pre- and rehydration plans all along the performance period. Scientific literature in this field is mainly dedicated to artificial sport drinks. Different territories in most world areas are rich in drinking natural mineral spring waters with saline compositions that reflect their geological origin and that are used for human health (often under medical prescription). However, scarce scientific attention has been dedicated to the use of these waters for athletes. We therefore reviewed the existing literature from the innovative viewpoint of matching spring water mineral compositions with different athletic performances and their hydro-saline requirements.

Anti-inflammatory potential of Portuguese thermal waters

In light of Medical Hydrology, thermal waters (TW) are all-natural mineral waters that emerge inside a thermal resort and have therapeutic applications. Their beneficial effect has been empirically recognized for centuries, being indicated for symptom alleviation and/or treatment of several diseases, almost all associated with inflammation. Indeed, an anti-inflammatory effect has been attributed to many different Portuguese TW but there is no scientific validation supporting this empiric knowledge. In the present study, we aimed to investigate the anti-inflammatory properties of 14 TW pertaining to thermal centers located in the Central Region of Portugal, and grouped according to their ionic profile. Mouse macrophage cells stimulated with lipopolysaccharide (LPS), a Toll-like receptor 4 agonist, were exposed to culture medium prepared in TW. Metabolism, nitric oxide (NO) production, inducible nitric oxide synthase (iNOS) expression levels and the scavenging capacity of TW, were investigated in vitro. 11 out of 14 TW reduced NO production and/or iNOS expression, and/or scavenging activity, in macrophages exposed to LPS. The sulphated/calcic TW did not show any effect on at least one of the inflammatory parameters evaluated. Two sulphurous/bicarbonate/sodic TW and the sulphurous/chlorinated/sodic TW promoted an increase in NO production and/or iNOS expression. Our results validate, for the first time, the anti-inflammatory properties of Portuguese TW, supporting their therapeutic use in the treatment of inflammation-related diseases and promoting their putative application in cosmetic products and medical devices.

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.

Balneotherapy and hydrotherapy in chronic respiratory disease

Chronic respiratory diseases (CRD) belong to major noncommunicable diseases (NCD) targeted by World Health Organization (WHO) NCD Action Plan and United Nations (UN) Sustainable Development Goal (STG) 3.4 to achieve 30% decline of mortality by the year 2030. Strong evidence is now available in the literature for therapeutic aquatic exercise interventions in improving health status of chronic obstructive pulmonary diseases (COPD) patients. However, gym-based exercises can be difficult for patients with COPD who are mainly elderly and often have co-morbidities-such as severe arthritis and obesity-which may impair their ability to exercise at an adequate intensity. Besides improving respiratory function and health status in COPD, exercise in water helps overcoming patient's fears and promote socialization, contrasting the risk of depression, which is a major condition often associated with long term COPD condition. Susceptibility to respiratory infections plays a role in exacerbations of COPD. Sulphur-rich water inhalations improve muco-ciliary clearance, reduce inflammatory cytokines production and inflammatory mucosal infiltration, reduce elastase secretion by neutrophils, preserving elastic properties of pulmonary interstitium and thus facilitating expectoration. Repeated cold water stimulations in COPD also reduce frequency of infections. Finally, sauna bathing reduces the risk of pneumonia. On the other side, hydrotherapy/balneotherapy also help obesity control, which is one of the most difficult NCD risk factors to modify and consequently is an important component of the WHO preventive strategy to achieve STG 3.4. Along with high prevalence and mortality, CRD cause increasing pharmaceutical and hospital costs. In this perspective, Health Resort Medicine should not be ignored as a resource in the WHO NCD strategy and Universal Health Coverage, providing a multi-stakeholder platform (including the network of health resorts and their facilities) able to give a real help to the achievement of UN goal STG 3.4 by the year 2030.

Protocols and self-checking plans for the safety of post-COVID-19 balneotherapy

During the COVID-19 pandemics, balneotherapic establishments were closed in Italy like in the rest of Europe. The Italian Foundation for Research in balneotherapy (FoRST) was asked to prepare a safety protocol to be proposed to the National Health Authorities to allow the establishments to restart their activity when possible, under safe conditions (the so-called Phase-2). The group of experts proposed the following hygienic and sanitary protocols of risk management for the initial reopening of the balneology settings in Italy. The plan aims to define the operating procedures to be implemented at the balneology establishments for the beginning of Phase-2 and to keep them constantly updated in the different periods that will characterize Phase-2 in relation to the trends of the disease. To this end the procedures, defined on the basis of the scientific state-of-the-art available today, will be updated and revised from time to time whenever further scientific evidence and directives from the Health Authorities make it necessary and/or useful.

Inhalations with Brine Solution from the 'Wieliczka' Salt Mine Diminish Airway Hyperreactivity and Inflammation in a Murine Model of Non-Atopic Asthma

Inhalations with brine solutions are old but underestimated add-ons to pharmacological treatments of inflammatory lung diseases. Although widely used, not all features underlying their action on the respiratory system have been explored. The aim of the present study was to elucidate the mechanism of the beneficial action of inhalations of brine solution from the 'Wieliczka' Salt Mine, a Polish health resort, in a murine model of non-atopic asthma. Asthma was induced in BALB/c mice by skin sensitization with dinitrofluorobenzene followed by an intratracheal challenge of cognate hapten. All animals underwent 12 inhalation sessions with brine solution, pure water or physiological saline. Control mice were not inhaled. We found that brine inhalations reduced, as compared to non-inhaled mice, the typical asthma-related symptoms, like airway hyperreactivity (AHR), the infiltration of pro-inflammatory cells into the bronchial tree, and the inflammation of the airways at the level of pro-inflammatory cytokines IL-1α, IL-1β and IL-6. The level of the anti-inflammatory IL-10 was elevated in brine-inhaled mice. Inhalations with pure water increased AHR, whereas saline had no influence, either on AHR or cytokine concentrations. These observations indicate that inhalations with a brine solution from the 'Wieliczka' Salt Mine diminish the asthma-related symptoms, mostly by reducing the inflammatory status and by decreasing AHR.

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.