Korean Red Ginseng attenuates ultraviolet-mediated inflammasome activation in keratinocytes

Background: Keratinocytes form a physical barrier and act as an innate immune cell in skin. Keratinocytes secrete pro-inflammatory cytokines, such as interleukin (IL)-1 beta, resulting from inflammasome activation when exposed to ultraviolet (UV) irradiation. Korean Red Ginseng extracts (RGE) have been well-studied as modulators of inflammasome activation in immune cells, such as macrophages. In the study, we elucidated the role of RGE on the UV-mediated inflammasome activation in keratinocytes compared with that in macrophages. Methods: Human skin keratinocyte cells (HaCaT), human epidermal keratinocytes (HEK), human monocyte-like cells (THP-1), and mouse macrophages were treated with RGE or a saponin fraction (SF) or non-saponin fraction (NS) of RGE before and after UV irradiation. The secretion levels of IL-1 beta, as an indicator of inflammasome activation, were analyzed. Results: The treatment of RGE or SF in macrophages after UV irradiation inhibited IL-1 beta secretion, but similar treatment in HaCaT cells did not. However, the treatment of RGE or SF in HaCaT cells in the presence of poly I:C, a toll-like receptor (TLR) 3 ligand, before UV exposure elicited the inhibition of the IL-1 beta secretion. The inhibition was caused by the disruption by RGE or SF of the TLR mediating up-regulation of the pro-IL-1 beta and NLRP3 genes during the priming step. Conclusion: RGE and its saponins inhibit IL-1 beta secretion in response to UV exposure in both keratinocytes and macrophages. In particular, RGE treatment interrupted only the priming step in keratinocytes, although it did attenuate both the priming and activation steps in macrophages. (C) 2021 The Korean Society of Ginseng. Publishing services by Elsevier B.V.

Automated summary

The study found that RGE and its saponins can inhibit the secretion of IL-1 beta in response to UV exposure in skin keratinocytes and macrophages, with RGE primarily interrupting the priming step in keratinocytes.