Guangxi Key Laboratory of Regenerative Medicine, Orthopaedic Department, The First Affiliated Hospital of Guangxi Medical University, Nanning, 530021, Guangxi, China.
Collaborative Innovation Centre of Regenerative Medicine and Medical BioResource Development and Application Co-constructed by the Province and Ministry, Life Sciences Institute, Guangxi Medical University, Nanning, 530021, Guangxi, China.
J Transl Med. 2023 Nov 22;21(1):839. doi: 10.1186/s12967-023-04706-2.
Activated osteoclasts cause excessive bone resorption, and disrupt bone homeostasis, leading to osteoporosis. The extracellular signal-regulated kinase (ERK) signaling is the classical pathway related to osteoclast differentiation, and mitochondrial reactive oxygen species are closely associated with the differentiation of osteoclasts. Myrislignan (MRL), a natural product derived from nutmeg, has multiple pharmacological activities; however, its therapeutic effect on osteoporosis is unclear. Here, we investigated whether MRL could inhibit osteoclastogenesis and bone mass loss in an ovariectomy mouse model by suppressing mitochondrial function and ERK signaling.
Tartrate-resistant and phosphatase (TRAP) and bone resorption assays were performed to observe the effect of MRL on osteoclastogenesis of bone marrow macrophages. MitoSOX RED and tetramethyl rhodamine methyl ester (TMRM) staining was performed to evaluate the inhibitory effect of MRL on mitochondria. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) assay was performed to detect whether MRL suppressed the expression of osteoclast-specific genes. The impact of MRL on the protein involved in the mitogen-activated protein kinase (MAPK) and nuclear factor-κB pathways was evaluated using western blotting. In addition, a specific ERK agonist LM22B-10, was used to revalidate the inhibitory effect of MRL on ERK. Finally, we established an ovariectomy mouse model to assess the therapeutic effect of MRL on osteoporosis in vivo.
MRL inhibited osteoclast differentiation and the associated bone resorption, by significantly decreasing osteoclastic gene expression. Mechanistically, MRL inhibited the phosphorylation of ERK by suppressing the mitochondrial function, thereby downregulating the nuclear factor of activated T cells 1 (NFATc1) signaling. LM22B-10 treatment further verified the targeted inhibition effect of MRL on ERK. Microscopic computed tomographic and histologic analyses of the tibial tissue sections indicated that ovariectomized mice had lower bone mass and higher expression of ERK compared with normal controls. However, MRL treatment significantly reversed these effects, indicating the anti-osteoporosis effect of MRL.
We report for the first time that MRL inhibits ERK signaling by suppressing mitochondrial function, thereby ameliorating ovariectomy-induced osteoporosis. Our findings can provide a basis for the development of a novel therapeutic strategy for osteoporosis.
活化的破骨细胞引起过度的骨吸收，破坏骨内稳态，导致骨质疏松症。细胞外信号调节激酶（ERK）信号通路是与破骨细胞分化相关的经典通路，线粒体活性氧与破骨细胞的分化密切相关。肉豆蔻烷（MRL）是一种来源于肉豆蔻的天然产物，具有多种药理活性，但它对骨质疏松症的治疗作用尚不清楚。在这里，我们通过抑制线粒体功能和 ERK 信号通路，研究了 MRL 是否可以抑制去卵巢小鼠模型中的破骨细胞生成和骨量丢失。
抗酒石酸酸性磷酸酶（TRAP）和骨吸收试验观察 MRL 对骨髓巨噬细胞破骨细胞生成的影响。MitoSOX RED 和四甲基罗丹明甲酯（TMRM）染色评估 MRL 对线粒体的抑制作用。定量逆转录聚合酶链反应（qRT-PCR）试验检测 MRL 是否抑制破骨细胞特异性基因的表达。用 Western blot 评估 MRL 对丝裂原活化蛋白激酶（MAPK）和核因子-κB 通路相关蛋白的影响。此外，使用特定的 ERK 激动剂 LM22B-10 验证 MRL 对 ERK 的抑制作用。最后，我们建立了去卵巢小鼠模型，在体内评估 MRL 治疗骨质疏松症的疗效。
MRL 通过显著降低破骨细胞基因表达来抑制破骨细胞分化和相关的骨吸收。机制上，MRL 通过抑制线粒体功能抑制 ERK 的磷酸化，从而下调核因子活化 T 细胞 1（NFATc1）信号。LM22B-10 处理进一步验证了 MRL 对 ERK 的靶向抑制作用。胫骨组织切片的显微计算机断层扫描和组织学分析表明，与正常对照组相比，去卵巢小鼠的骨量较低，ERK 表达较高。然而，MRL 治疗显著逆转了这些影响，表明 MRL 具有抗骨质疏松作用。
我们首次报道 MRL 通过抑制线粒体功能抑制 ERK 信号通路，从而改善去卵巢诱导的骨质疏松症。我们的发现可为骨质疏松症的新型治疗策略的发展提供依据。
