Modulation of Inflammatory and Redox Responses by Saturnia Spa Water and Mud Extract in Human Skin Cell Models

Thermal waters and peloid-derived products have long been used in dermatological and spa treatments, although the cellular mechanisms underlying their biological effects remain incompletely characterized. This study investigated the effects of Saturnia spa water (TW) and an aqueous mud extract (MUD) on inflammatory, redox, and wound-healing responses in human skin cell models.

Human dermal fibroblasts (NHDF) and keratinocytes (HaCaT) were exposed to different concentrations of MUD and TW to assess cell viability by MTT assay. Based on the viability results, 5% MUD and TW were selected for subsequent experiments. TNF-α-stimulated cells were used to investigate inflammatory and oxidative responses by evaluating IL-1β and IL-6 production, inflammatory and cytoprotective gene expression, reactive oxygen species (ROS), superoxide dismutase (SOD) activity, and glutathione (GSH) levels. A scratch assay was performed to evaluate the effects of the treatments on cell migration and wound repair.

MUD and TW showed no marked cytotoxic effects at concentrations up to 5% in either cell model, whereas the undiluted preparations affected cell viability. In TNF-α-stimulated NHDF cells, both MUD and TW significantly reduced IL-1β and IL-6 gene expression (p < 0.001), whereas MUD significantly reduced the secretion of both cytokines. Both treatments also enhanced HO-1 expression and restored the TNF-α-induced reduction in SOD activity, whereas total ROS and GSH levels were not significantly altered. In HaCaT cells, TNF-α approximately doubled ROS levels (p < 0.001), whereas both MUD and TW significantly reduced ROS production (p < 0.01). TNF-α also reduced SOD activity by approximately 50% (p < 0.001), an effect that was restored by both treatments. GSH levels remained unchanged. In the scratch assay, both extracts significantly promoted wound closure at 6 h in NHDF cells (p = 0.002) and in HaCaT cells (MUD p = 0.017 and TW p = 0.027).

Under the experimental conditions tested, Saturnia water and its aqueous mud extract exerted anti-inflammatory and redox-modulating effects in human keratinocytes and dermal fibroblasts, together with a positive effect on in vitro wound closure. These findings support further investigation of these spa-derived preparations as potential complementary agents for skin repair and inflammatory modulation, although their disease-specific effects require validation in more physiologically relevant models.