Sulphurous Mineral Waters: New Applications for Health

Abstract

Sulphurous mineral waters have been traditionally used in medical hydrology as treatment for skin, respiratory, and musculoskeletal disorders. However, driven by recent intense research efforts, topical treatments are starting to show benefits for pulmonary hypertension, arterial hypertension, atherosclerosis, ischemia-reperfusion injury, heart failure, peptic ulcer, and acute and chronic inflammatory diseases. The beneficial effects of sulphurous mineral waters, sulphurous mud, or peloids made from sulphurous mineral water have been attributed to the presence of sulphur mainly in the form of hydrogen sulphide. This form is largely available in conditions of low pH when oxygen concentrations are also low. In the organism, small amounts of hydrogen sulphide are produced by some cells where they have numerous biological signalling functions. While high levels of hydrogen sulphide are extremely toxic, enzymes in the body are capable of detoxifying it by oxidation to harmless sulphate. Hence, low levels of hydrogen sulphide may be tolerated indefinitely. In this paper, we review the chemistry and actions of hydrogen sulphide in sulphurous mineral waters and its natural role in body physiology. This is followed by an update of available data on the impacts of exogenous hydrogen sulphide on the skin and internal cells and organs including new therapeutic possibilities of sulphurous mineral waters and their peloids.

Figure 1

Hydrogen sulphide concentrations versus pH. According to the pH (7.04 or 11.96), sulphurous derivatives occur in saline (HS⁻ and S²⁻) or gaseous (H₂S) solution. On the skin (pH < 6), hydrogen sulphide is mainly present as gas (H₂S), whereas, at physiological pH, (7.2–7.4) only one-third exists as gas (H₂S) and it is mainly found in saline solution (HS⁻).

Figure 2

Mechanism of endothelial cell proliferation through hydrogen sulphide activity and NO production by the H₂S pathway. An increase in vessel formation is produced that is significantly attenuated through NO production blockade by nitro-L-arginine methyl ester (L-NAME).

Figure 3

Mechanisms of action of hydrogen sulphide on bonds between corneocytes. Sulphur can be transformed into pentathionic acid and/or produce H₂S, transforming cystine into cysteine (keratolytic effect). In some situations, hydrogen sulphide can convert cysteine into cystine (keratoplastic effect).

Figure 4

Cellular uptake of hydrogen sulphide according to pH and temperature. In cells, sulphur is mostly absorbed as bisulphide salt, while, on skin, hydrogen sulphide is the main molecule involved in the absorption and release of sulphur.

Figure 5

Hydrogen sulphide has a dual effect on keratinocytes: at low concentrations, it induces their proliferation, while, at high concentrations, it exerts a cytostatic effect on these cells and reduces VEGF release via the ERK pathway.