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

Abstract

Natural mineral (thermal) waters have been used for centuries as treatment for various diseases. However, the scientific background of such therapeutic action is mostly empiric and based on knowledge acquired over time. Among the various types of natural mineral waters, sulfurous thermal waters (STWs) are the most common type in the center of Portugal. STWs are characterized by high pH, poor mineralization, and the presence of several ions and salts, such as bicarbonate, sodium, fluoride, silica, and carbonate. Furthermore, these waters are indicated as a good option for the treatment of various illnesses, namely respiratory diseases (e.g., allergic rhinitis, asthma, and chronic obstructive pulmonary disease). From the sulfide species present in these waters, hydrogen sulfide (H 2 S) stands out due to its abundance. In healthy conditions, H 2 S-related enzymes (e.g., cystathionine β-synthase and cystathionine γ-lyase) are expressed in human lungs, where they have mucolytic, antioxidant, anti-inflammatory, and antibacterial roles, thus contributing to airway epithelium homeostasis. These roles occur mainly through S-sulfhydration, a post-translational modification through which H 2 S is able to change the activity of several targets, such as ion channels, second messengers, proteins, among others. However, in respiratory diseases the metabolism of H 2 S is altered, which seems to contribute somehow to the respiratory deterioration. Moreover, H 2 S has been regarded as a good biomarker of airway dysfunction and severity, and can be measured in serum, sputum, and exhaled air. Hence, in this review we will recapitulate the effects of STWs on lung epithelial-immune crosstalk through the action of its main component, H 2 S.

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

“…Apart from osmolality, which was, in the present study, described by the use of pure water, physiological saline (0.9%) and brine solution (2%), the composition of the inhaled solution also plays a crucial role. There are several types of thermal waters divided according to the composition and described in detail elsewhere [68,69]. In the present study, brine, a thermal water with a prevalence of sodium and chloride ions, was used.…”

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

“…are also required, as long as microbiological analyses to test the absence of parasites or pathogenic micro-organisms. If biological properties of NMSWs on different organ systems are established (e.g., urinary [53], digestive [54], respiratory [55], and gastrointestinal [56] tracts; bone [57]; and skin [58,59]), these must be confirmed by clinical and pharmacological analyses that state them as specific characteristics of each particular NMSW. Several of these parameters contribute to the classification of natural mineral waters: the 180 • C fixed residue, for example, defines the water mineral content (very low: <50 mg/L), low (<500 mg/L), medium (from 500 mg/L to 1500 mg/L) and high (>1500 mg/L).…”

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

“…In the field of BT, tissue explants, primary cells, or immortalized lines can be used to investigate the potential biological effects of a single inorganic molecule (Carbajo and Maraver 2017;Viegas et al 2019;Wallace and Wang 2015), or organic compounds (Gerencsér et al 2019), or a mineral water as a whole (Fioravanti et al 2011;Gálvez et al 2018).…”

“…Among the inorganic molecules, which generally constitute the mineral waters, sulfur has currently been recognized as a crucial element with a wide range of functions, mainly when it was found in the form of hydrogen sulfide (H 2 S) (Carbajo and Maraver 2017;Viegas et al 2019;Wallace and Wang 2015). H 2 S represents the main active molecule of sulfurous mineral-medicine waters; it is a small gaseous molecule traditionally considered as toxic gas, but, in the last years, scientific opinion has changed as more reports on its biological activity were published, and it is now considered a biologically relevant molecule (Carbajo and Maraver 2017;Wallace and Wang 2015).…”