Abstract
The purpose of the present study was to explore the efficacy of fermented extract of sea tangle (Laminaria japonica Aresch, FST) with Lactobacillus brevis on DNA damage and apoptosis in hydrogen peroxide (H(2)O(2))-stimulated osteoblastic MC3T3-E1 cells and clarify related signaling pathways. Our results showed that exposure to FST significantly improved cell viability, inhibited apoptosis, and suppressed the generation of reactive oxygen species (ROS) in H(2)O(2)-stimulated cells. In addition, H(2)O(2) triggered DNA damage in MC3T3-E1 cells was markedly attenuated by FST pretreatment. Moreover, H(2)O(2)-induced mitochondrial dysfunctions associated with apoptotic events, including loss of mitochondrial membrane potential (MMP), decreased Bcl-2/Bcl-2 associated x-protein (Bax) ratio, and cytosolic release of cytochrome c, were reduced in the presence of FST. FST also diminished H(2)O(2)-induced activation of caspase-3, which was associated with the ability of FST to protect the degradation of poly (ADP-ribose) polymerase. Furthermore, FST notably enhanced nuclear translocation and phosphorylation of nuclear factor erythroid 2-related factor 2 (Nrf2) in the presence of H(2)O(2) with concomitant upregulation of heme oxygenase-1 (HO-1) expression. However, artificial blockade of this pathway by the HO-1 inhibitor, zinc protoporphyrin IX, greatly abolished the protective effect of FST against H(2)O(2)-induced MC3T3-E1 cell injury. Taken together, these results demonstrate that FST could protect MC3T3-E1 cells from H(2)O(2)-induced damage by maintaining mitochondrial function while eliminating ROS along with activation of the Nrf2/HO-1 antioxidant pathway.