Cytotoxic and Immunomodulatory Effects of Hypericin as a Photosensitizer in Photodynamic Therapy Used on Skin Cell Cultures

Abstract

Determination of the hypericin–photodynamic (HY–PDT) effect on the secretion of cytokines secreted by the skin cells, may be the basis for using the immunomodulatory effect of photodynamic action in the treatment of inflammatory skin diseases. The study aimed to evaluate the cytotoxic and immunomodulatory effects of hypericin (HY) in photodynamic therapy (PDT) performed in vitro on cultures of selected skin cell lines. The study used two human cell lines, primary dermal fibroblast (HDFa) and primary epidermal keratinocytes (HEKa). The MTT test was used to define the metabolic activity of treated cells. Cell supernatants subjected to sublethal PDT were assessed to determine the interleukins: IL-2, IL-8, IL-10, IL-11, IL-19, IL-22, and metalloproteinase 1 (MMP-1). The results confirm the destructive effect of HY–PDT and the immunomodulatory effects of sublethal doses on the selected skin cells, depending on the concentration of HY and the light doses. No statistically significant differences were noted in IL-2 and IL-10 concentration after HY–PDT for HEKa and HDFa lines. After using HY–PDT, the concentration of IL-8, MMP-1, IL-22, and IL-11 significantly decreased in the HEKa line. Moreover, the concentration of IL-19 and MMP-1 significantly decreased in the HDFa line. The concentration of IL-11 in the HDFa line after using only the HY, without the light, increased but decreased after HY–PDT. Our experiment confirmed that HY–PDT has not only a cytotoxic effect but, used in sublethal doses, also presents immunomodulatory properties. These may be an advantage of HY–PDT when used in the treatment of persistent skin inflammation, connected with the release of pro-inflammatory cytokines resistant to conventional treatment methods.