Cytoprotective effects of the fermented milk by Streptococcus thermophilus CGMCC 24468 against ROS damage in HaCaT cells

Streptococcus thermophilus is traditionally used as a starter culture in the production of dairy fermented products. Recently this species has highlighted its potential benefits for skin health. This study evaluated the protective effects of S. thermophilus CGMCC 24468 on keratinocytes HaCaT. Co-incubation with the supernatant of sonicated fermented milk lysate (SFML) enhanced the expression of tight junction proteins (CLDN-1, OCLN, and JAM-1) and the transcription of antioxidative enzyme genes (CAT, SOD, and GPX), reducing intracellular ROS levels. Pre-treatment with SFML inhibited the activation of the MAPK pathway and accelerated wound closure. Collectively, these results demonstrated the potential application of S. thermophilus CGMCC 24468 fermented milk as a natural ingredient in cosmetic formulations for preventing ROS-induced skin photoaging. • Streptococcus thermophilus CGMCC24468 possesses a highly potent antioxidant capacity. • The supernatant of sonicated fermented milk lysate (SFML) can strengthen the cell barrier function. • SFML upregulates the transcription of antioxidant enzymes, thereby reducing intracellular reactive oxygen species (ROS). • Inhibiting MAPK pathway activation shields keratinocytes from oxidative harm to prevent skin aging.