Fufang Zhenshu Tiaozhi Capsule Enhances Bone Formation and Safeguards against Glucocorticoid-Induced Osteoporosis through Innovative Mekk2-Mediated β-Catenin Deubiquitination

Abstract

Abstract Background The homeostasis of bone is reliant on the regulation of β-catenin activity in osteoblasts. Glucocorticoids (GC) have been found to reduce β-catenin activity through Wnt pathway signaling, leading to osteoporotic pathology. On the other hand, the activation of β-catenin in osteoblasts can be mediated by mitogen-activated protein kinase kinase kinase 2 (Mekk2), which presents a promising and innovative therapeutic approach to counteract GC-induced osteoporosis (GIOP). The remarkable efficacy of Fufang Zhenshu Tiaozhi (FTZ) capsules in the treatment of GC-induced osteoporosis has been established, although the underlying mechanisms of action have yet to be determined. Methods In this investigation, Mekk2-/- mice were generated utilizing the CRISPR/Cas9 methodology and subjected to Alcian Blue-Alizarin Red staining and immunofluorescence for assessment. To create GIOP models, Mekk2-/- and WT mice were administered dexamethasone (DXMS) and subsequently treated with FTZ. The phenotypic variations in the mice models were analyzed by Micro-CT and histomorphology evaluations. Primary osteoblasts separated from Mekk2−/− and WT mice were subjected to FTZ or WNT3a treatments. Following this, phosphorylation levels of β-catenin and Mekk2, as well as the protein expression of Runx2, were assessed using western blotting and immunoprecipitation methods. C3H10T1/2 cells, which were transfected with TOPflash-luciferase and Renilla, were treated with FTZ and Wnt3a, and β-catenin activity was determined. Results The administration of FTZ in vivo successfully averted GC-induced bone loss. Notably, this protective effect was significantly undermined in Mekk2-deficient mice. Moreover, FTZ was found to effectively promote the process of osteogenic differentiation in primary osteoblasts by modulating the expression of Mekk2. It is noteworthy that the effects of FTZ on Mekk2 are mediated via a mechanism that operates independently of the Wnt signaling pathway. Furthermore, FTZ has been shown to enhance the process of β-catenin deubiquitination, thus further contributing to its beneficial effects on bone health. Conclusions The present study posits that FTZ exerts a remarkable safeguarding effect on bone mass in the context of glucocorticoid-induced osteoporosis (GIOP). The mechanism through which FTZ confers this benefit involves the activation of Mekk2/β-catenin signaling pathways, which represents a promising alternative strategy to counteract the deleterious effects of GIOP by augmenting osteoblastogenesis.