當蝕骨的溶蝕作用大於造骨細胞時就會產生骨質疏鬆症這類病徵。而許多研究已經證明，一些相關的發炎因子會在蝕骨細胞分化的進程中發揮重要作用。樺木酸是傳統中藥連翹的主要成分，具有一些抗氧化的活性。我們的研究發現，核因子Kappa B受體活化因子配體（RANKL）所誘導RAW264.7 macrophage分化成蝕骨細胞的情況會受到樺木酸明顯的抑制。而抗酒石酸酸性磷酸酶（TRAP）染色的結果顯示樺木酸在抑制蝕骨細胞分化的方面，隨著劑量上升也越來越明顯。RAW264.7巨噬細胞給予 RANKL的刺激後，會誘發細胞外訊號調節激酶（ERK），p38和c-Jun的N-末端激酶（JNK）的磷酸化。我們的實驗中發現RANKL所誘發的ERK，p38和JNK磷酸化情形會因為加入樺木酸而被抑制下來。因此，我們的實驗結果顯示出樺木酸可以透過降低RANKL所誘發ERK、p38和JNK的磷酸化情形進而抑制蝕骨細胞分化，並且保護骨質因蝕骨細胞而流失。
Osteoporosis can occur when osteoclasts dissolve more bone than what the osteoblasts are able to replace.
Many studies have proved that some inflammatory cytokines play an important role in the progression of osteoclastic differentiation. Betulinic acid, a main compound of traditionally used Chinese herb forsythia, has anti-inflammatory activity.
Our study found that the betulinic acid markedly inhibited the receptor activator of nuclear factor kappa B ligand (RANKL) induced osteoclastic differentiation from RAW264.7macrophage cells. Tartrate-resistant acid phosphatase (TRAP) staining demonstrated that differentiation of osteoclast-like cells was inhibited in the presence of betulinic acid in a dose-dependent manner.
Treatment of RAW264.7 macrophages with RANKL induced extracellular signal-regulated kinases (ERK), p38 and c-Jun N-terminal kinase (JNK) phosphorylation. We found RANKL-induced ERK, p38 and JNK was attenuated by betulinic acid. Our data suggest that betulinic acid inhibits osteoclastogenesis from macrophage cells via attenuated of RANKL-induced ERK, p38 and JNK activation, which may protect bone loss from osteoclastogenesis.
