2023, Vol. 27 ›› Issue (10): 1560-1566

Effects of high mobility group box 1 and ERK1/2 pathway on autophagy of human periodontal ligament cells under tensile stress

Zhang Min1, 2, Bai Shulin3, Li Shenghong1, 2, Fan Zhibo1, 2, Xie Yijia1, 2, Xu Xiaomei1, 2   

Abstract: BACKGROUND: The mechanical force signal transduction pathway and its regulation mechanism of bone remodeling after orthodontic tooth movement are hot topics in orthodontic biomechanics and biology. In the present study, the mechanism of complex molecular signal network in the response of periodontal ligament cells to mechanical stimulation during orthodontic tooth movement is not clear.  
OBJECTIVE: To investigate the effect of high mobility group box 1 (HMGB1) and ERK1/2 pathway on autophagy in human periodontal ligament cells under tensile stress during orthodontic tooth movement.
METHODS: The passages 3-5 human periodontal ligament cells were selected and the HMGB1 distribution in the cells was observed by immunofluorescence under cyclic tensile stress. The expression levels of autophagy-associated protein LC3-II, Beclin-1 and HMGB1 were detected by real-time fluorescence quantitative PCR (RT-qPCR) and western blot assay. After tensile stress loading, nuclear and cytoplasmic proteins were extracted respectively. Western blot assay was used to detect HMGB1 protein level in nucleus and cytoplasm. The mechanisms by which HMGBI participated in regulating autophagy were investigated. Cellular autophagy levels were measured by immunofluorescence, RT-qPCR and western blot assay using ethyl pyruvate, a cytosolic inhibitor of HMGB1. Finally, PD98059 was used to inhibit ERK1/2 pathway, and the autophagy level of HMGB1 was detected by RT-qPCR and western blot assay. The mechanism of HMGB1 regulating autophagy through ERK1/2 pathway was explored.  
RESULTS AND CONCLUSION: (1) By external tensile stress loading, the autophagy level and HMGB1 expression of human periodontal ligament cells were increased and HMGB1 translocated from nucleus to cytoplasm. (2) Human periodontal ligament cells participated in the regulation of autophagy induced by tensile stress through HMGB1 nuclear-cytoplasmic translocation. (3) PD98059, an inhibitor of the ERK1/2 pathway, significantly inhibited the autophagy induced by HMGB1 under tensile stress. (4) These findings suggested that under tensile stress, HMGB1 transferred from the nucleus to the cytoplasm, and regulated autophagy by ERK12 pathway to maintain the homeostasis of human periodontal ligament cells and periodontal dynamic equilibrium.
Key words: tensile stress, periodontal ligament cell, orthodontic tooth movement, HMGB1, autophagy, ERK1/2, homeostasis