Citron Essential Oils Alleviate the Mediators Related to Rosacea Pathophysiology in Epidermal Keratinocytes

BACKGROUND: Citron is well known for an abundance of antioxidative and anti-inflammatory ingredients such as vitamin C, polyphenol compounds, flavonoids, and limonoids. OBJECTIVE: In this study, we aimed to evaluate the effects of citron essential oils on rosacea mediators in activated keratinocytes in vitro. METHODS: Normal human epidermal keratinocytes (NHEKs) were stimulated with 1α, 25-dihydroxyvitamin D(3) (VD(3)) and interleukin 33 (IL-33) with LL-37 to induce rosacea mediators such as kallikrein 5 (KLK5), cathelicidin, vascular endothelial growth factor (VEGF), and transient receptor potential vanilloid 1 (TRPV1). These mediators were analyzed by performing reverse-transcription polymerase chain reaction (PCR), quantitative real-time PCR, immunocytofluorescence and enzyme-linked immunosorbent assay after NHEKs were treated with citron seed and unripe citron essential oils. RESULTS: The messenger RNA (mRNA) and protein levels of KLK5 and LL-37 induced by VD(3) were suppressed by citron seed and unripe citron essential oils. Furthermore, the mRNA and protein levels of VEGF and TRPV1 induced by IL-33 with LL-37 were also suppressed by citron essential oils. CONCLUSION: These results show that citron essential oils have suppressive effects on rosacea mediators in activated epidermal keratinocytes, which indicates that the citron essential oils may be valuable adjuvant therapeutic agents for rosacea.