Saponin from Tea (Camellia sinensis) Seed Meal Attenuates Cortisol-Induced Lipogenesis and Inflammation in Human Cells

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Abstract
A fast-paced lifestyle contributes to heightened emotional stress, driving the demand for milder and safer cosmetic ingredients that can counteract stress-induced skin damage—a focus of cutting-edge research in the field. Aim: The aim was to elucidate the role and mechanistic basis of tea (Camellia sinensis) seed meal saponin (Sap) in regulating stress-induced sebum overproduction and inflammatory responses. Methods: The composition and chemical structure of Sap were analyzed using UV-vis absorption spectroscopy, Fourier-transform infrared spectroscopy (FT-IR), and ultra-high-performance liquid chromatography–mass spectrometry (UHPLC-MS). In vitro models of cortisone-induced excessive lipid accumulation and the tumor necrosis factor-alpha (TNF-α)-stimulated inflammatory models were established on sebaceous gland cells (SZ95) and normal human epidermal keratinocytes (NHEKs), respectively. Cortisol and inflammatory cytokine secretion levels in cells were detected using ELISA. Additionally, the signaling pathways were revealed by Western blot (WB) and real-time quantitative polymerase chain reaction (RT-PCR). Results: Five saponins were identified in the Sap extract, all belonging to the oleanolic-acid-type pentacyclic triterpenes. Sap treatment significantly attenuated cortisone-induced cortisol secretion and lipid accumulation in SZ95 sebocytes. Mechanistically, Sap inhibited the 11β-HSD1/SREBP-1 pathway, which mediates its sebosuppressive effects, while concurrently down-regulating the mRNA expression of key downstream transcription factors and enzymes, including SREBP-1, FAS, and ACC. Additionally, Sap treatment significantly attenuated TNF-α-stimulated cortisol secretion and inflammatory cytokine (IL-1β, IL-6, and IL-8) production in NHEK cells through the inhibition of the 11β-HSD1/TLR2/NF-κB signaling pathway. Conclusion: Sap demonstrated dual inhibitory effects, suppressing both emotional-stress-induced sebum overproduction and inflammatory cytokines secretion.

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