Abstract:

To investigate the regulatory effect and molecular mechanism of xylooligosaccharides （XOS） on skin barrier immune function, we systematically evaluated two HaCaT cell models: ultraviolet B （UVB） -induced injury and Staphylococcus aureus culture supernatant （SA-CS） -induced inflammation. In the UVB injury model, HaCaT cells were irradiated with 30 mJ/cm² UVB and then treated with low, medium and high doses of XOS （50, 100, 200 μg/mL） and an Nrf2 inhibitor （ML385） for 24 h. In the SA-CS inflammation model, cells were treated with 20% SA-CS for 24 h, with low, medium and high doses of XOS and a TLR4 agonist （LPS） added simultaneously. Each group consisted of six replicate wells. Cell viability, apoptosis rate （TUNEL assay）, mRNA levels of apoptosis-related genes （Bax, Bcl-2）, transepithelial electrical resistance （TEER） value, mRNA levels of barrier-related proteins （FLG, Claudin-1/4）, oxidative stress indicators （ROS, MDA, SOD）, proteins of the Nrf2/Keap1 pathway, inflammatory factors （IL-1β, IL-8, TNF-α, etc.） and protein levels of the TLR4/NF-κB pathway were measured. The results show that UVB irradiation significantly decreases cell viability and TEER value, downregulates mRNA expression of barrier-related proteins, promotes cell apoptosis, induces oxidative stress and inhibits Nrf2 nuclear translocation in HaCaT cells. XOS reverses these injuries in a dose-dependent manner, an effect that can be blocked by ML385. SA-CS treatment significantly reduces cell viability and TEER value, downregulates mRNA expression of barrier-related proteins, promotes cell apoptosis, and increases the levels of inflammatory factors and protein expression of TLR4 and p-NF-κB p65. XOS also ameliorates these injuries in a dose-dependent manner, while LPS reverses this effect. In summary, XOS antagonizes UVB-induced oxidative damage in skin cells by activating the Nrf2 pathway, and alleviates SA-CS-mediated inflammatory damage by inhibiting the TLR4/NF-κB pathway, thereby protecting skin barrier function. This study provides experimental evidence and theoretical support for the development of cosmetic raw materials with skin barrier protection, antioxidant and anti-inflammatory effects.

Key words: prebiotics, xylooligosaccharides （XOS）, daily chemical products, skin barrier, immune function, oxidative stress