Role of Epithelium Sodium Channel in Bone Formation

OBJECTIVE: To review the recent developments in the mechanisms of epithelium sodium channels (ENaCs) induced bone formation and regulation. DATA SOURCES: Studies written in English or Chinese were searched using Medline, PubMed and the index of Chinese-language literature with time restriction from 2005 to 2014. Keywords included ENaC, bone, bone formation, osteonecrosis, estrogen, and osteoporosis. Data from published articles about the structure of ENaC, mechanism of ENaC in bone formation in recent domestic and foreign literature were selected. STUDY SELECTION: Abstract and full text of all studies were required to obtain. Studies those were not accessible and those did not focus on the keywords were excluded. RESULTS: ENaCs are tripolymer ion channels which are assembled from homologous α, β, and γ subunits. Crystal structure of ENaCs suggests that ENaC has a central ion-channel located in the central symmetry axis of the three subunits. ENaCs are protease sensitive channels whose iron-channel activity is regulated by the proteolytic reaction. Channel opening probability of ENaCs is regulated by proteinases, mechanical force, and shear stress. Several molecules are involved in regulation of ENaCs in bone formation, including nitride oxide synthases, voltage-sensitive calcium channels, and cyclooxygenase-2. CONCLUSION: The pathway of ENaC involved in shear stress has an effect on stimulating osteoblasts even bone formation by estrogen interference.