Flavonoid-rich Phyla nodiflora fraction promotes Keap1 degradation and Nrf2/HO-1 activation to attenuate particulate matter-induced oxidative stress in human keratinocytes.
Lin Chia-Hsuan, Wu Jin-Ye, Gu Andrea, Wu Ho-Cheng, Chen Yih-Fung, Ko Horng-Huey
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE: Phyla nodiflora (L.) Greene (PN) has been traditionally used in Asia for the treatment of inflammatory and dermatological conditions. Its pharmacological activities are largely attributed to flavonoids with antioxidant and anti-melanogenic effects. Given these traditional and pharmacological properties, it is plausible that PN may protect the skin cells against airborne stressors, such as particulate matter (PM). AIM OF THE STUDY: To evaluate a flavonoid-rich fraction of PN derived from the solvent-free microwave hydrodiffusion and gravity extraction (PN Fr. 5) for its protective effects against PM-induced oxidative damage. MATERIALS AND METHODS: Human keratinocytes (HaCaT cells) were exposed to urban dust PM (NIST® SRM® 1649b). PN antioxidant activity was evaluated by measuring PM-induced intracellular reactive oxygen species (ROS), and mechanisms were examined via the Keap1-Nrf2/HO-1 pathway using Western blotting, RT-qPCR, and cycloheximide chase assays. Feature-based molecular networking and docking were used to prioritize putative active compounds. RESULTS: PN Fr. 5 showed the strongest activity among preparations, reducing PM-induced ROS and upregulating AQP3 without cytotoxicity. Mechanistically, PN Fr. 5 accelerated Keap1 degradation, stabilizing Nrf2 and upregulating downstream antioxidant proteins, including HO-1. Molecular networking identified jaceosidin, isokaempferide, eupafolin, and chrysosplenol D as the major flavonoids, with docking studies suggesting that these compounds, particularly jaceosidin, may collectively contribute as non-electrophilic modulators of the Keap1-Nrf2 protein-protein interaction, thereby enhancing Nrf2/HO-1 signaling. CONCLUSIONS: The flavonoid-rich fraction of P. nodiflora (PN Fr. 5) exhibited potent antioxidant activity through Keap1-Nrf2/HO-1 activation, supporting its traditional dermatological use and potential as a plant-based protective agent against PM-induced oxidative damage in keratinocytes.
Key Findings
- Phyla nodiflora flavonoid-rich fraction (PN Fr. 5) reduces particulate matter-induced reactive oxygen species (ROS) in human keratinocytes without cytotoxicity.
- PN Fr. 5 promotes Keap1 degradation, stabilizes Nrf2, and upregulates downstream antioxidant proteins including HO-1, enhancing the Keap1-Nrf2/HO-1 pathway.
- Major flavonoids such as jaceosidin, isokaempferide, eupafolin, and chrysosplenol D may act as non-electrophilic modulators of Keap1-Nrf2 interaction, contributing to antioxidant effects.
Clinical Significance
The study supports the potential use of Phyla nodiflora flavonoid-rich extracts as plant-based protective agents against oxidative damage caused by airborne particulate matter, which may benefit skin health and inflammatory conditions.
Citation
Lin Chia-Hsuan, Wu Jin-Ye, Gu Andreaet al.. Flavonoid-rich Phyla nodiflora fraction promotes Keap1 degradation and Nrf2/HO-1 activation to attenuate particulate matter-induced oxidative stress in human keratinocytes. Journal of ethnopharmacology. 2026-Apr-06.