GSK3β-Cyclophilin D-mPTP信号轴在氧化应激诱导成骨细胞凋亡中的作用和机制研究

Osteoporosis, a highly prevalent disease, results in massive costs to the patients as well as the whole society, while its etiopathogenesis is complicated. Oxidative stress induced osteoblast apoptosis was recognized as a crucial initiating factor in the development and progression of osteoporosis, however, the underlying mechanisms are not well understood. Mitochondrial permeability transition pore (mPTP) is regarded as “a master regulator of cell death (apoptosis and necrosis）” in diverse diseases, while Cyclophilin D (CypD), a crucial component for mPTP formation, would facilitate an opening of the mPTP. Increasing evidence demonstrated that glycogen synthase kinase-3β (GSK3β) could favor mPTP opening through phosphorylation, mitochondrial translocation and interaction with CypD, which finally triggered the cell death in response to oxidative stress. Our preliminary study revealed that target protein of CypD significantly increased along with a significantly decreased GSK3β phosphorylation in oxidative stress induced osteoblast apoptosis model. Thus, we hypothesized that “GSK3β-CypD-mPTP signaling axis would play an important role in the osteoblast apoptosis caused by oxidative stress in the pathology of osteoporosis”. In order to verify the hypothesis and explore the mechanism, a classical osteoblast apoptosis model induced by H2O2 will be set up. Target gene overexpression plasmid, RNA interfering and inhibition reagent will be applied to adjust the expression and function of GSK3β, CypD and mPTP in this model. Through this comprehensive study, it will not only provide new insights into oxidative stress induced osteoporosis, but also make a solid foundation for the development of new therapeutic approaches in prevention or treatment of osteoporosis.

骨质疏松发病率高、危害大且病因复杂；氧化应激介导的成骨细胞凋亡是骨质疏松发生的病理基础，但其确切机制未完全阐明。mPTP在细胞凋亡与坏死中扮演着关键角色，CypD是mPTP的直接调控者。氧化应激病理状态下，GSK3β通过磷酸化、线粒体易位结合CypD介导mPTP开放，诱发细胞死亡。课题组前期探索性研究发现，在H2O2诱导成骨细胞凋亡模型中GSK3β磷酸化水平降低，CypD表达增加；故提出“GSK3β-CypD-mPTP信号轴在氧化应激诱导的成骨细胞凋亡中发挥重要调控作用”的假设。为此，本项目拟构建H2O2诱导成骨细胞凋亡模型，通过基因过表达、RNA干扰及拮抗剂作用，调控GSK3β、CypD及mPTP的表达及功能，正反双重验证GSK3β-CypD-mPTP信号轴在氧化应激诱导成骨细胞凋亡中的调控作用。本研究结果将进一步丰富骨质疏松发病机制的理论体系，也为建立新的防治策略提供线索和理论基础。

骨质疏松发病率高、危害大且病因复杂；氧化应激介导的成骨细胞凋亡是骨质疏松发生的病理基础，但其确切机制未完全阐明。本项目采用过氧化氢（H2O2）构建氧化应激诱导成骨细胞凋亡模型，通过基因过表达、RNA干扰及拮抗剂作用，调控GSK3β、CypD及mPTP的表达及功能，正反双重验证GSK3β-CypD-mPTP信号轴在氧化应激诱导成骨细胞凋亡中的调控作用。实验结果显示：1、H2O2诱导成骨细胞凋亡模型中，线粒体膜电位明显下降，细胞内Ca2+水平显著增加，提示细胞mPTP开放；2、CypD在H2O2诱导的成骨细胞凋亡中起着关键作用，抑制CypD表达可调控mPTP开放进而缓解H2O2诱导的成骨细胞氧化应激损伤，其表达增加会加剧H2O2诱导的成骨细胞凋亡发生；3、GSK3β在H2O2诱导成骨细胞凋亡发生中的起着关键作用，抑制GSK3β活性可减弱H2O2诱导的成骨细胞氧化应激损伤；4、GSK3β可作为CypD的上游调控H2O2诱导的成骨细胞凋亡。上述结果证实GSK3β-CypD-mPTP信号轴在氧化应激诱导的成骨细胞凋亡中发挥重要调控作用。该结论将进一步丰富骨质疏松发病机制的理论体系，也为建立新的防治策略提供线索和理论基础。