Autophagy negative-regulating Wnt signaling enhanced inflammatory osteoclastogenesis from Pre-OCs in vitro

Abstract

Periodontitis thereby the alveolar bone loss induced by inflammation, is a wide-spread phenomenon around the world. It is an ongoing challenge faced by clinicians worldwide. This study aimed to identify the effects of lipopolysaccharide (LPS) on osteoclasts (OCs) differentiation in vitro and to investigate its molecular mechanism. For bone marrow derived macrophages (considered as Pro-OCs), LPS impaired their differentiation into OCs in a dose-dependent manner. In contrast, it promoted Pre-OCs (referred to receptor activator of nuclear factor-κB ligand (RANKL) pretreated Pro-OCs) and differentiated to OCs with increased maximum diameter, quantity, the covering area and the fusion index in vitro. It also facilitated OCs proliferation, bone resorption and OCs related genes expression. Furthermore, it was revealed that LPS enhanced OCs genesis from Pre-OCs via activating autophagy pathway consequently elevated the accumulation of TRAP, Cts K and NFATC1, specific genes of OCs. The members of Wnt signaling were expressed as at lower states during the LPS induced OCs formation, but they could be rescued in the presence of autophagy inhibitor. The most promising observation was the direct interaction of LC3B and Dvl2, indicating that the crosstalk between above pathways existed in OCs. Taken together, we consider that LPS activates autophagy which negatively regulates Wnt signaling via autophagic degradation of Dvl2 is significant for osteoclastogenesis from Pre-OCs in vitro. Our study sheds light on the fact that autophagy inhibitors will become a new, potentially applicable therapeutic option in the treatment of periodontal bone loss.