Effects of Hydrogen Sulfide on Autophagy and Hippo-Yes-Associated Protein Pathway of Orthodontic Periodontal Ligament Cells in Mice

Abstract

Background: The mechanical force signal transduction pathway and its regulation mechanism of orthodontic tooth movement and bone remodeling are the focus of orthodontic biomechanics and biology research. hydrogen sulfide (H₂S) inhibits bone resorption and conducts an important role in osteogenesis and osteoblastogenesis in bone tissue. This study aims to investigate the effects of H₂S and the Hippo-Yes-associated protein (YAP) pathway on autophagy of mouse periodontal ligament cells (mPDLCs) during orthodontic tooth movement. Methods: The orthodontic tooth movement model of C57BL6/J mice was established. Third to fifth-generation mPDLCs with good growth conditions were selected. They were divided into H₂S alone groups (control (H₂S = 0 mM), 0.01 mM, 0.05 mM, 0.1 mM, 0.5 mM); Apply tension group (control (Apply tension = 0 h), 1 h, 3 h, 6 h); Apply tension for 1 h + H₂S (control, 0.01 mM, 0.05 mM, 0.1 mM; 0.5 mM); Apply tension for 3 h + H₂S (control, 0.01 mM, 0.05 mM, 0.1 mM, 0.5 mM); Apply tension for 6 h + H₂S (control, 0.01 mM, 0.05 mM, 0.1 mM, 0.5 mM). The morphology of mPDLCs was observed by immunofluorescence. Sodium hydrosulfide (NaHS) was used as the donor of exogenous H₂S. The levels of bone plastic proteins, containing receptor activator of nuclear factor kappa-B ligand (RANKL) and Osteoprotegerin (OPG), autophagy-related proteins, containing Autophagy Related Protein 5 (Atg5), Autophagy Related Protein 7 (Atg7), and coiled-coil, myosin-like BCL2 interacting protein (Beclin-1), and the Hippo pathway protein (active-YAP) were assessed by western blot. Results: All experimental rats showed tooth movement, and the experimental modeling was successful. The level of RANKL increased and OPG declined after the application of tension and reached the most significant difference at 6 h of stress (p < 0.05). When the concentration of H₂S was 0.5 mM, the increase of RANKL and the decrease of OPG were the most significant (p < 0.05), regardless of whether tension was applied or not. When tension was applied for 6 h and H₂S was 0.5 mM, the level of active-YAP was significantly increased (p < 0.05). HY-101275, an inhibitor of the Hippo pathway, reversed the promoting effects of H₂S and tension on bone remodeling and autophagy of mPDLCs (p < 0.05). Conclusions: Under the action of orthodontic force, H₂S can increase the level of autophagy in mPDLCs. The Hippo-YAP signaling pathway is involved in the process of H₂S-induced increase of mPDLCs autophagy.