The effect of Nrf2 on bone resorption in chronic apical periodontitis

Nuclear factor E2-related factor 2 (Nrf2) is responsible for regulating and maintaining the transcription of cytoprotective genes under conditions of stress and the destruction of redox homeostasis. This study aimed to elucidate the role of Nrf2 in the bone resorption of chronic apical periodontitis (CAP). We used immunohistochemical staining, western blotting and real‐time quantitative polymerase chain reaction (RT‐qPCR) to clarify the expression of Nrf2 in the normal human periodontal ligament and in CAP. A mouse model of apical periodontitis was established by root canal exposure to the oral cavity, and hematoxylin and eosin (HE) staining was used to observe the progress of apical periodontitis. Immunohistochemical staining was used to detect the expression of Nrf2 in different stages of apical periodontitis. An Escherichia coli lipopolysaccharide (LPS) mediated inflammatory environment was also established at the osteoclast and osteoblast levels, and the role of Nrf2 in proliferation and differentiation of osteoblasts and osteoclasts was examined by downregulating Nrf2 expression. The expression of Nrf2 in CAP was higher in the apical periodontitis group than that in healthy periodontal ligament tissue. The expression of Nrf2 increased with the progression of inflammation in mouse apical periodontitis model. In the inflammatory environment mediated by LPS, downregulation of Nrf2 promoted the proliferation and differentiation of osteoclasts and osteoblasts. Nrf2 is involved in the disease process of CAP and may participate in the occurrence and development of bone destruction in CAP by regulating the proliferation and differentiation of osteoclasts and osteoblasts.