Natural UV-protective organic matter in thermal water
Introduction
The basis of the “organic hypothesis” of medical balneology is that medicinal waters, especially thermal spa and hot spring waters, contain a high variability of organic components with possible biological effects [1], [2], [3]. If exact evidence supported this concept, it could initiate a paradigm shift of healing exclusively by the salts and gases of spa waters, in the classical hypothesis. Simple gas chromatographic (GC) measurements – together with studies on therapeutic/toxic characteristics – may provide scientific bases for new classifications of medicinal spa waters [1], [4]. Previously, the spa waters of the Carpathian Basin, in Central Europe, were sampled and studied by GC, and volatile organics were abundant [3], [5]. Several mineral springs and spas have been known since the Roman era in the region, involving the Pannonia Superior, Pannonia Inferior, and, in part, Dacia provinces. This area involves the territory of Hungary, Slovakia, Transcarpathia (Ukraine), and Transylvania (Romania), at present. Since the basin is very rich in thermal waters containing high amounts of dissolved organic materials, as indicated by chemical oxygen demand or total organic carbon measurements [6], these samples are especially suitable to test the organic hypothesis.
However, because of the abundance and variety of organics, the only strategy to study these organic mixtures, including possible interactions, is determination of their biological activities in different tests. It has been already reported [5], [7], [8], [9] that some typical spa waters and peloids (muds), selected by hydrogeological origin, have measurable biological effects. The most informative results were obtained from the Comet Assay (single-cell microgel electrophoresis for DNA damage) and the Salmonella Ames mutagenicity studies with the different chemical fractions of waters and peloids.
In this study, we present a new application of the Salmonella TA strains originally engineered for the Ames mutagenicity test [10], [11]. These mutant strains differ from the wild-type S. typhimurium, inter alia, in their UV sensitivity. Only well-defined UV intensity proved to be lethal to these mutant cells; therefore, their alteration upon the presence of organic fractions isolated from the water samples may be a suitable model of possible photobiological effects.
Section snippets
Description of sampled spa waters
Five different spa waters were sampled, concentrated, and used in our tests. “Hévíz”: The largest surface warm-water medicinal lake of Europe, supplied by thermal-karstic water (filtered by a peat sediment), which does not rise directly from the Triassic dolomite but rather from the Pannonian conglomerate and sandstone (Sample No. 1).
“Hajdúszoboszló”: The upper-Pannonian aquifer yields 73–78 °C hot water rich in minerals: alkali-chlorides and bicarbonates, iodide, bromide, and fluoride. Its
Results
The standard spontaneous reversion rates in the plate incorporation test are about 120–200 (for TA100) and 20–40 (for TA98). A sample shows mutagenicity in the Salmonella test if it doubles (TA100) or triples (TA98) the mean number of spontaneous revertant colonies [11]. The specific lethal UV dose had to be determined first for the two TA strains respectively, under the experimental conditions (Table 1). A 2s irradiation with the lamp killed the TA98 cells but at least 4 s were needed for
Discussion
Organic isolates prepared from five thermal spa waters were tested for possible interactions with photobiological mechanisms, namely the modification of the UV sensitivity of mutant bacteria. The idea of possible protecting or sensitizing effects of thermal waters, in general, is based upon two facts: (i) effectiveness of balneotherapy-associated phototherapy in psoriasis treatment [12], [13], and (ii) the result of the single study on interactions of UV irradiation and peloid treatment
Conflict of interest
All authors declare that there is not any actual or potential conflict of interest including any financial, personal, or other relationships with other people or organizations within three years of beginning the submitted work that could inappropriately influence, or be perceived to influence, their work.
Acknowledgement
This work was supported by the Faculty of Medicine, University of Pécs (Grant No. PTE ÁOK KA 2013/13-29).
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