The New Synthetic HS-Releasing SDSS Protects MC3T3-E1 Osteoblasts against HO-Induced Apoptosis by Suppressing Oxidative Stress, Inhibiting MAPKs, and Activating the PI3K/Akt Pathway.

Reactive oxygen species (ROS) are important in osteoporosis development. Oxidative stress induces apoptosis of osteoblasts and arrest of their differentiation. Both Danshensu (DSS) and hydrogen sulfide (HS) produce significant antioxidant effect in various systems. In this study, we synthesized SDSS, a novel HS-releasing compound derived from DSS, and studied its antioxidant effect in an HO-induced MC3T3-E1 osteoblastic cell injury model. We first characterized the HS releasing property of SDSS in both and models. HPLC chromatogram showed that intravenous injection of SDSS in adult rats released ADT-OH, a well proved HS sustained-release moiety, within several minutes in the rat plasma. Using an HS selective fluorescent probe, we further confirmed that SDSS released HS in MC3T3-E1 osteoblastic cells. Biological studies revealed that SDSS had no significant toxic effect but produced protective effects against HO-induced MC3T3-E1 cell apoptosis. SDSS also reversed the arrest of cell differentiation caused by HO treatment. This was caused by the stimulatory effect of SDSS on bone sialoprotein, runt-related transcription factor 2, collagen expression, alkaline phosphatase activity, and bone nodule formation. Further studies revealed that SDSS reversed the reduced superoxide dismutase activity and glutathione content, and the increased ROS production in HO treated cells. In addition, SDSS significantly attenuated HO-induced activation of p38-, ERK1/2-, and JNK-MAPKs. SDSS also stimulated phosphatidylinositol 3-kinase/Akt signaling pathway. Blockade of this pathway attenuated the cytoprotective effect of SDSS. In conclusion, SDSS protects MC3T3-E1 cells against HO-induced apoptosis by suppressing oxidative stress, inhibiting MAPKs, and activating the phosphatidylinositol 3-kinase/Akt pathway.