Exopolysaccharide from Lacticaseibacillus rhamnosus IR06 as a potential postbiotics attenuates photoaging through regulation of MAPK and NF-κB signaling.

Exopolysaccharides (EPSs) are widely used in the food industry as stabilizers, viscosity enhancers, and thickeners due to their rheology-improving properties. Beyond food applications, EPSs have gained attention for their diverse biological effects, including antioxidant, anti-inflammatory, and anticancer activities. Ultraviolet B (UVB) radiation induces the production of intracellular reactive oxygen species (ROS), leading to skin damage such as epithelial barrier dysfunction, wrinkle formation, and inflammation. In this study, we investigated the protective effects of EPS derived from a potential probiotic lactic acid bacterium. The EPS from Lacticaseibacillus rhamnosus IR06 (EPS-IR06) exhibited notable in vitro protection against photoaging and inflammation. Characterization identified EPS-IR06 as a heteropolysaccharide with a glucose-branched galactomannan structure, with a molecular weight ranging from 3.9 × 10⁴ to 5.8 × 10⁵ Da. Treatment with EPS-IR06 on a UVB-induced 3D human skin model reduced epidermal damage and increased biomarkers associated with epidermal barrier function. Furthermore, EPS-IR06 effectively scavenged intracellular ROS and restored the balance of Nrf2-mediated antioxidant response in UVB-induced human epidermal keratinocytes. EPS-IR06 significantly reduced the expression of matrix metalloproteinases and pro-inflammatory mediators by modulating the MAPK and NF-κB signaling pathways. These findings suggest that EPS-IR06 could serve as a novel protective agent against UVB-induced skin damage, with potential applications in cosmetics and food industries.