CD40L参与模拟失重促进破骨细胞分化的骨免疫机制研究

Bone-immune system dysregulation induced by weight loss leads to bone absorption resulting in weightless bone loss, which seriously endangers the health of astronauts. However, the mechanism is still unclear. CD40L participants in osteoclast differentiation by regulating the expression of M-CSF and RANKL. Our team found that bone-immune system dysregulation induced by simulated weightlessness increased CD40L expression in T cells and promoted the osteoclast differentiation. Besides, T cells with high CD40L expression enhance the osteoclast differentiation. Therefore, CD40L may regulate osteoclast differentiation through M-CSF and RANKL, thus participating in promoting bone resorption under simulated weightlessness conditions. The following research areas will be involved in this project: (1) Changes in CD40L expression during the process of osteoclast differentiation promoted by simulated weightlessness; (2) The effects of simulated weightlessness or high/low CD40L expression or CD40L-/- T cells on osteoclast differentiation and the expression of M-CSF and RANKL; the effects of simulated weightlessness or CD40L-/- on bone resorption in mice; (3) The screening of natural products targeting on CD40L and their function against weightlessness bone loss. This project offers a theoretical basis for further understanding of the mechanism of weightless bone loss in space and provides new potential natural products and lead compounds for the prevention and therapy of osteoporosis diseases.

失重引起骨免疫失衡促进骨吸收，导致失重性骨质流失，严重危害航天员健康，但是其具体机制尚不明确。CD40L通过调节M-CSF和RANKL的表达参与破骨细胞分化和骨吸收。申请者发现：模拟失重条件下免疫失衡，T细胞中CD40L表达上调，破骨细胞分化增强；且高表达CD40L的T细胞促进破骨细胞分化。因此提出：T细胞中CD40L可能通过M-CSF和RANKL调控破骨细胞分化参与模拟失重促进骨吸收。本项目拟研究：(1)模拟失重促进破骨细胞分化过程中，T细胞中CD40L表达变化；(2)模拟失重条件下，CD40L高/低表达及CD40L-/-的T细胞对破骨细胞分化及M-CSF和RANKL表达的影响；模拟失重或CD40L-/-对小鼠骨吸收的影响；(3)靶向于CD40L的活性天然产物筛选及其抗失重性骨质流失的功能研究。为深入理解空间失重性骨质流失的发生机制提供理论基础，并为骨质疏松症的防治提供新的候选天然药物。

失重引起骨免疫失衡促进骨吸收，导致失重性骨质流失，严重危害航天员健康，但是其具体机制尚不明确。CD40L通过调节M-CSF和RANKL的表达参与破骨细胞分化和骨吸收。本项目中我们采用体外、体内模拟失重条件，从分子-细胞-动物不同层次深入研究CD40L作为关键骨免疫调节因子，通过激活基质细胞产生M-CSF和RANKL，促进破骨细胞分化，参与模拟失重条件促进骨吸收的骨免疫作用机制。.本研究在细胞和分子水平，研究模拟失重条件下对T 细胞分泌的CD40L的变化，阐明了CD40L对基质细胞产生M-CSF和RANKL的影响及其对破骨细胞分化的作用；在动物水平，研究模拟失重条件对大鼠T 细胞中CD40L 表达及其对破骨细胞分化与骨吸收的影响；单细胞组学分析骨髓细胞发现，由尾悬吊引起的大鼠T淋巴细胞和B淋巴细胞占比的降低，失重条件下，T淋巴细胞活化异常促进CD40L表达从而导致骨质流失；细胞通讯分析表明在失重条件下，骨髓腔中T淋巴细胞对巨噬细胞有调节作用，促进破骨细胞分化及骨吸收；进一步通过系统药理学ADME模型筛选靶向于CD40L的天然活性产物，异鼠李素和毛蕊异黄酮，体外实验发现，20 μM异鼠李素和毛蕊异黄酮可有效抑制破骨细胞分化，异鼠李素抑制破骨细胞分化的能力优于毛蕊异黄酮。Docking结果表明这两种化合物有效成分均通过氢键和疏水作用与骨免疫相关靶点蛋白具有良好的结合活性。进一步通过单细胞组学分析，分析T细胞CD40L对破骨细胞分化的作用途径和机制，阐明这些天然产物在模拟失重条件下通过抑制CD40L/ ITGA5和ITGB1抑制破骨细胞分化的机制。.综上所述，本研究从骨免疫新视角阐明了失重性骨质流失的新机制，采用系统药理学方法分析，筛选出抗失重性骨质流失的活性天然产物。为深入理解空间失重性骨质流失的发生机制提供理论基础，并为骨质疏松症的防治提供新的候选天然药物。