In this study, we evaluated the effect of spa spring water from Yong-gung oncheon on cells related to the skin immune reaction. The treatment of spa spring water from Yong-gung oncheon decreased the expression of proinflammatory cytokines under TLR stimulation to the HaCaT cells and APCs. In addition, spa spring water attenuated the differentiation process of subsets of T helper cells, i.e., Th1, Th2 and Th17 cells.
The therapeutic mechanism of spa spring water in dermatologic diseases can be divided into three categories: active ingredient, thermal effects and mechanical effects. Minerals in spa spring water, such as sulfur, magnesium, calcium or selenium induce anti-inflammatory, keratolytic, antibacterial or antifungal effects6
. For anti-inflammatory effects, the inhibition of Th1 differentiation, inhibition of cytokine production from keratinocytes, and modulatory effects on epidermal Langerhans cells have been reported10
. In this study, we observed the significant inhibitory effect on the secretion of pro-inflammatory cytokines, including IL-6, IL-8, IL-1α, TNFα and GM-CSF from keratinocytes (). In addition, we observed the differentiation of Th1, Th2, or Th17, but not of Foxp3+
cells under the treatment with water from Yong-gung oncheon ().
Th17 cells are related to the autoimmunity or inflammatory skin disease, such as psoriasis or atopic dermatitis via IL-17 and IL-22 secretion. IL-17 acts directly on keratinocytes and induces the production of MIP-3α, IL-8 and β-defensin, whereas, IL-22 regulates the keratinocyte differentiation11,12
. In addition, IL-17 promotes the neutrophil recruitment by inducing the neutrophil-attracting chemokines (CXCL1, CXCL2, CXCL5, and CXCL8) and stimulates neutrophil production by inducing granulopoiesis factors (G-CSF or GM-CSF)13
. In case of Staphylococcus aureus
infection, the role of Th17 was reported to be critical: in mice bacterial clearance was impaired in IL-17R-deficient mice, and in human hyper immunoglobulin E syndrome, atopic dermatitis, human immunodeficiency virus/acquired immune deficiency syndrome or mucocutaneous candidiasis, in which there is a common deficiency of Th17 cells. These IL-17-mediated defenses against S. aureus
infection are involved with promotion of neutrophil recruitment via cytokines, chemokines or adhesion molecules and production of antimicrobial peptides. In this context, reduced Th17 cell differentiation, by spa spring water, implies that spa spring water may reduce the immune reaction in the epidermal layer, partly by affecting the antimicrobial peptide production and epidermal differentiation irrespective of antibacterial effect of IL-17.
Regulatory T cells (Treg
cells) mediate immunosuppression and tolerogenic responses through contact-dependent or -independent mechanisms14-16
produce IL-10 or TGF-β as effector molecules, and the balance between Treg
cells and effector T cells is crucial for the maintenance of homeostasis and self-tolerance17
. In this study, spa spring water from Yong-gung oncheon treatment induced Foxp3+
cell differentiation in vitro
, implying that the immune modulatory effect of spa spring water also includes Treg
cell-induced immune suppressive effects.
TLRs are a type of pattern recognition receptor, which recognize microbial products known as pathogen-associated molecular patterns, i.e., bacterial lipoproteins, zymosan, LPS, flagellin, ssRNA, dsRNA, and unmethylated CpG DNA. TLRs are transmembrane receptors and present on the cell surface or on the surface of endosomal compartments. It was reported that TLR3 ligand poly (I : C) was the most potent stimulator of IL-8, IL-6 and TNFα secretion18
in the primary keratinocyte and HaCaT cell lines. In this experiment, we used TLR1 to TLR6 agonists to activate the HaCaT cells inducing pro-inflammatory cytokines. We observed that spa spring water treatment led to reduced IL-6, IL-8, TNF-α, IL-1α, and GM-CSF from the HaCaT cells, following TLR ligand treatments, and spa spring water from Yong-gung oncheon suppressed the expression of IL-6, TNF-α and class II MHC expression of APC in this experiment (). In case of atopic asthma, IL-5, IL-13, IL-1β, IFN-γ, IL-12, GM-CSF, IL-4, and IL-10 were elevated, compared with those of the non-atopic patients19
. Further studies are required to compare the cytokine profile in non-atopic and atopic dermatitis patients after a spa treatment.
These results showed that spa spring water treatment suppressed the inflammatory cytokines production, and also modulated differentiation of CD4+ T cells into Th1, Th2, and Th17 cells, but not Tregs cells. With these experimental protocols, we can evaluate and compare the efficacy of spa spring waters in Korea, immunologically. Furthermore, we would define immune-active ingredient from this spa spring water to reveal immune modulatory mechanism of spa spring waters in Korea.