Skin-Protective Effects of a Rhamnose-Enriched Fraction Isolated from Halocynthia roretzi Tunics Against Particulate Matter-Induced Oxidative and Barrier Damage

Particulate matter (PM) is a major environmental pollutant that induces excessive reactive oxygen species (ROS) production in the skin, leading to inflammatory responses and disruption of skin barrier integrity. The tunic of Halocynthia roretzi, an underutilized marine by-product rich in bioactive polysaccharides, represents a promising sustainable resource for the development of functional biomaterials. In this study, a rhamnose-rich polysaccharide fraction (HTVE-2) was obtained from H. roretzi tunics through enzymatic extraction followed by ethanol fractionation, and its protective effects against PM-induced skin damage were investigated in HaCaT keratinocytes and zebrafish models. In PM-stimulated HaCaT cells, HTVE-2 significantly reduced intracellular ROS production, suppressed inflammatory responses, and restored the expression of skin barrier-related proteins, including tight junction-associated proteins. Notably, PM exposure increased intracellular ROS levels to 279.4% of the control level, whereas treatment with the highest tested concentration of HTVE-2 reduced ROS levels to 184.1%. The protective effects of HTVE-2 were further validated in vivo using zebrafish embryos, in which HTVE-2 exhibited no apparent developmental toxicity and dose-dependently attenuated PM-induced ROS generation. PM exposure increased ROS levels to 236.1% of the control level in zebrafish embryos, while treatment with the highest concentration of HTVE-2 reduced ROS levels to 147.1%. Collectively, these findings demonstrate that the rhamnose-rich HTVE-2 fraction derived from H. roretzi tunics protects against PM-induced oxidative stress, inflammatory responses, and skin barrier dysfunction. These results highlight the potential of HTVE-2 as a marine-derived functional ingredient for protecting the skin against PM-induced damage while providing a value-added approach for the sustainable utilization of H. roretzi tunic by-products.