Olive Leaf Extract Suppresses Sebogenesis and Inflammation via AKT/ERK and SREBP-1/PPAR-γ Signaling in Human Sebocytes.

This study evaluated olive leaf extract (OLE) as a multifunctional dermocosmetic candidate for sebum-related and inflammatory responses relevant to oily and acne-prone skin using an axis-aligned in vitro panel: (i) sebocyte lipogenesis, (ii) inflammatory mediator production in keratinocytes, and (iii) fibroblast-mediated collagen gel contraction. In addition, supportive mechanistic evidence for the sebum-related effects of OLE was obtained by examining signaling proteins associated with sebocyte lipogenesis, including PPAR-γ and SREBP-1. As a result, OLE significantly inhibited linoleic acid-induced lipid accumulation in SEB-1 sebocytes without cytotoxicity. In HaCaT keratinocytes, OLE significantly reduced the production of pro-inflammatory cytokines, including IL-8, TNF-α, and PGE2, induced by Cutibacterium acnes or UVB. In dermal fibroblast-containing collagen gels, OLE enhanced fibroblast-mediated gel contraction. Additionally, analysis of the main mechanisms of lipid inhibition using SEB-1 sebocytes revealed that OLE exerts a dual regulatory role in lipid synthesis and inflammation by downregulating AKT and ERK phosphorylation and inhibiting PPAR-γ and SREBP-1 expression. Furthermore, among the tested extracts, the 70% ethanol extract (OLE70) exhibited the strongest antioxidant activity, the greatest gel contraction response, and the highest content of oleuropein, a major bioactive phenolic compound derived from olive. Like OLE, oleuropein also showed sebum-regulatory activity by reducing lipid accumulation in SEB-1 sebocytes, an inhibitory effect on IL-8 expression in HaCaT keratinocytes, and an inhibitory effect on the expression of PPAR-γ and SREBP-1, which are involved in sebum secretion. Taken together, these findings suggest that OLE and its major phenolic constituent, oleuropein, may modulate sebum-related, inflammatory, oxidative, and dermal remodeling-associated responses in skin cell models. These results should be interpreted as exploratory and provide a basis for further mechanistic and translational investigation.