A Marine-Derived Sterol, Ergosterol, Mitigates UVB-Induced Skin Photodamage via Dual Inhibition of NF-κB and MAPK Signaling

Background: Ultraviolet B (UVB) radiation induces oxidative stress, inflammation, and collagen degradation in skin, leading to photodamage. Ergosterol (ERG)—a sterol widely distributed in fungi and algae, including numerous marine species—possesses antioxidant and anti-inflammatory activities, but its photoprotective mechanisms remain unclear. Methods: Using integratedin vitro(UVB-irradiated human keratinocytes) andin vivo(topical ERG in a murine UVB model) approaches, combined with transcriptomic and network pharmacology analyses, we evaluated ERG’s effects on oxidative stress, inflammation, and extracellular matrix integrity. Results: ERG treatment preserved keratinocyte viability, reduced reactive oxygen species, and suppressed pro-inflammatory mediators after UVB exposure. In mice, topical ERG significantly attenuated epidermal hyperplasia, maintained tight-junction integrity, and inhibited collagen matrix degradation. Mechanistically, ERG exerted dual inhibition of the nuclear factor kappa B (NF-κB) pathway, which mediates inflammation, and the mitogen-activated protein kinase (MAPK) pathway, which regulates collagen degradation. Conclusions: These findings identify ERG as a marine-derived sterol with potent photoprotective activity that simultaneously targets oxidative stress, inflammation, and extracellular matrix damage, highlighting its promise as a natural compound for dermatological applications and aligning with ongoing efforts to explore marine-derived agents against skin oxidative stress and inflammation.