维生素D通过NF-κB调节AMPK/mTOR通路激活软骨细胞自噬发挥骨关节炎保护作用

Articular cartilage plays a central role in the progression of osteoarthritis (OA). Vitamin D (VD) has a protective effect on OA, and its mechanism is still unclear. Based on the fact that VD can play a protective role by inducing autophagy in many diseases, the lack of autophagy activation of chondrocytes in OA patients, and vitamin D receptor distribution on the surface of chondrocytes, we propose that VD may play a protective role by activating autophagy of chondrocytes in OA. Our previous studies have confirmed that VD has protective effect in articular cartilage of OA model mice, and VD can induce the expression of autophagy marker protein LC3-II in chondrocytes. Besides, we also found that the addition of VD in chondrocytes can significantly reduce the activation of NF-κB signaling pathway. Based on the fact that inhibition of NF-κB pathway could activate the autophagy in chondrocytes through AMPK/mTOR/autophagy axis, we propose that VD can active autophagy of chondrocytes by AMPK/mTOR/autophagy axis via inhibiting the NF-κB pathway. If the hypothesis were proved, it will be an important complement to the protective mechanisms of VD in OA.

关节软骨细胞在骨关节炎（OA）进展中起核心作用。维生素D（VD）对OA具有保护作用，其机制尚不明确。基于VD可通过诱导细胞自噬在多种疾病中发挥保护作用，以及OA患者关节软骨细胞自噬激活功能缺失、软骨细胞表面有维生素受体分布的事实，我们提出VD可能通过诱导关节软骨细胞自噬在OA中起到保护作用，我们的前期研究已证实VD对OA模型小鼠关节软骨具有保护作用，同时VD可诱导软骨细胞自噬标志蛋白LC3-II表达。在此基础上，我们还发现VD可减少软骨细胞核蛋白中NF-κB，基于抑制OA模型小鼠软骨细胞NF-κB可通过AMPK/mTOR/自噬轴激活自噬的事实，我们提出VD可能通过抑制软骨细胞NF-κB信号通路的激活，进而调节AMPK/mTOR/自噬轴激活自噬的假说，如果假说被证实，将是对VD保护OA作用机制的重要补充和完善。

本课题主要研究维生素D（VD）通过抑制核转录因子κB（NF-κB）信号通路，调控AMPK/mTOR轴激活自噬，从而发挥对骨关节炎（OA）保护作用的机制。本研究以OA患者软骨细胞及OA大鼠模型为研究对象。结果：（1）细胞及动物实验均提示VD能够通过诱导软骨细胞自噬对OA发挥保护作用，其中自噬相关蛋白Beclin1、LC3 II/LC3 I比值表达增强，mRFP-GFP-LC3腺病毒转染实验提示自噬蛋白在核周表达增强，通过透射电镜可以明显观察到核周自噬体表达数量增多，溶酶体活性明显增强。（2）VD抑制软骨细胞MMP13蛋白表达，促进软骨细胞自噬，使bcl-2表达上调，促进二型胶原酶A（COL2A）表达。通过CCK8检测维生素D未对软骨细胞活性造成影响。（3）VD抑制软骨细胞NF-κB入核从而调控AMPK/mTOR自噬轴激活自噬。在VD作用下，NF-κB的核内荧光表达明显降低，促进了AMPK的磷酸化，抑制了自噬调控子mTOR表达。通过探寻VD通过激活自噬对OA软骨细胞的保护机制，为临床治疗提供选择。