Codonopsis pilosula Lipophilic Extract-Loaded Thermosensitive Nanogel Attenuates Skin Photoaging by Inhibiting the FGFR/PI3K/AKT/mTOR Pathway

Background: Skin photoaging, primarily induced by chronic ultraviolet (UV) radiation exposure, is characterized by dryness, wrinkle formation, pigmentation abnormalities, and reduced skin elasticity, resulting from oxidative stress, inflammation, and degradation of the extracellular matrix. Codonopsis pilosula, a traditional food–medicine homologous plant, is recognized for its anti-aging properties. However, its lipophilic components (designated as CP-L) remain insufficiently explored. Methods: Herein, we developed a thermosensitive nanogel encapsulating CP-L-loaded transferosomes (CP-L nanogel) to enhance topical delivery and evaluated its effects in both a UV-induced photoaging mouse model and UVB-irradiated HaCaT keratinocytes. Results: In UV-induced mice, topical application of the nanogel markedly reduced skin wrinkling and epidermal hyperplasia, with epidermal thickness decreased by 83.2% compared to the model group (p < 0.01), and restored skin elasticity and collagen deposition, as evidenced by a 35.5% increase in collagen area fraction (p < 0.01). Correspondingly, in UVB-irradiated HaCaT cells, it significantly increased cell viability from 53.0 ± 9.6% to 89.4 ± 1.0% (p < 0.01) and suppressed apoptosis from 30.1 ± 0.48% to 12.4 ± 0.66% (p < 0.01). Furthermore, the CP-L nanogel consistently attenuated oxidative stress, with SOD, CAT, and GSH-Px activities increased by 73.1%, 188.1%, and 18.2%, respectively (p < 0.01), and MDA levels reduced by 71.0% (p < 0.01), while inflammatory responses were suppressed, as TNF-α, IL-1α, IL-1β, and IL-6 levels decreased by 28.3%, 22.6%, 12.8% and 31.9%, respectively (p < 0.01). Mechanistically, transcriptomic and molecular analyses revealed that the nanogel potently inhibited the UV-induced activation of the FGFR/PI3K/AKT/mTOR/p70S6K signaling cascade at both transcriptional and protein levels, with the phosphorylation levels of FGFR, PI3K, AKT, mTOR, and p70S6K significantly reduced by 43.9%, 30.9%, 38.8%, 34.9%, and 57.3%, respectively (p < 0.01). Molecular docking and dynamics simulations identified isofuranodienone and aromadendrene oxide-(2) as key constituents with high-affinity, stable binding to FGFR1 and AKT1. The cytoprotective effect of the nanogel was completely abolished by co-treatment with the FGFR inhibitor PD173074, confirming functional reliance on this pathway. Enhanced cellular delivery of the formulation was directly demonstrated by flow cytometry, showing an approximately 1.8-fold increase in cellular uptake compared to the free drug (p < 0.01). Conclusions: Collectively, these results demonstrated that the CP-L nanogel alleviated skin photoaging through a multi-faceted mechanism involving enhanced cellular delivery, potent antioxidant and anti-inflammatory activities, and specific inhibition of the FGFR/PI3K/AKT/mTOR signaling cascade, highlighting its potential as a multitargeted topical agent derived from an edible plant.