Protective effects of rosmarinic acid against hydrogen peroxide‑induced cellular senescence and the inflammatory response in normal human dermal fibroblasts.

Hydrogen peroxide (H2O2) is a reactive oxygen species (ROS) that induces numerous cellular events, including cellular senescence and inflammatory responses. Therefore, the aim of this study was to investigate the protective effect of Rosmarinic acid (RA) in H2O2‑induced oxidative stress in normal human dermal fibroblasts (NHDFs). Cytotoxicity assays were performed using a water‑soluble tetrazolium salt, and senescence‑associated β‑galactosidase activity was determined to investigate the proportion of senescent cells. Antioxidant capacities were evaluated via H2O2‑scavenging activity, reverse transcription‑quantitative polymerase chain reaction, NRF2 luciferase reporter gene activity and intracellular ROS scavenging assays. Cytokine‑coded gene expression analysis and nuclear factor‑κB luciferase activity were determined to verify the anti‑inflammatory effect of RA. As a result, the present study demonstrated that rosmarinic acid inhibited H2O2‑induced oxidative stress and inflammatory responses in normal human dermal fibroblasts. Initially, the doses of RA that exerted minimal cytotoxic effects in NHDFs were determined using a cytotoxicity assay. Subsequently, pretreatment with the appropriate doses of RA significantly reversed the H2O2‑induced decrease in NHDF cell viability and decreased cellular senescence of NHDFs. In addition, RA inhibited H2O2‑induced ROS production in NHDFs, as determined by a ROS scavenging assay. The protective effects of RA were mediated by the inhibition of nuclear factor erythroid‑derived 2‑like 2, a transcription factor that functions as a key regulator of redox sensitivity. Furthermore, RA suppressed H2O2‑induced inflammation in NHDFs and significantly rescued H2O2‑induced downregulation of sirtuin 1. RA also inhibited nuclear factor (NF)‑κB transcriptional activity and the expression of NF‑κB target genes, including tumor necrosis factor‑α and interleukin‑6, in H2O2‑exposed NHDFs. Taken together, these data indicate that RA inhibits H2O2‑induced cellular damage in NHDFs.