Hesperetin affects osteoclast differentiation via MAPK signaling pathway.

Background: The number and activity of osteoblasts and osteoclasts play an important role in skeletal biology, especially in bone reconstruction. Scientific and rational regulation of osteoclast formation and activity has become a critical strategy aimed at inhibiting the loss of bone mass in the body and alleviating the occurrence of bone diseases. Currently, there are only a few reports related to hesperetin-regulated osteoclast differentiation.

Objectives: To investigate the influence of hesperetin on osteoclast-like cell differentiation and formation, and determine whether the MAPK signaling pathway is involved in the differentiation process.

Material and methods: The RAW264.7 cells were induced and cultured in vitro to promote their differentiation into osteoclast-like cells. Tetrazolium bromide was utilized to determine the effects of different concentrations (100, 200, 400, and 600 μM) of hesperetin on the proliferation of osteoclast-like cell precursors. Osteoclast-like cell differentiation was conducted using tartrate-resistant acid phosphatase (TRAP) staining assay. The status of nuclei and actin filaments of differentiated osteoclast-like cells was observed with the use of 4',6-diamidino-2-phenylindole dihydrochloride (DAPI) and actin-tracker green staining experiments. Changes in key proteins of the MAPK signaling pathway were detected using western blot.

Results: The results of TRAP staining experiments showed that the number of osteoclast-like cells decreased with the increase in hesperetin concentration. The DAPI and actin-tracker green staining demonstrated that the nuclei of differentiated osteoclast-like cells reduced in size with the increase in hesperetin concentration, and the osteoclast-like cells became smaller. Western blot for key MAPK signaling pathway proteins revealed that phospho-ERK and phospho-p38 protein levels were not significantly inhibited, but phospho-JNK protein levels were reduced.

Conclusions: Hesperetin inhibits the differentiation of osteoclast-like cells. Further studies revealed that hesperetin also affects the activation level of phospho-JNK, a key signaling protein of the MAPK signaling pathway, in the induced differentiation of osteoclast-like cells.