Chlorogenic acid mitigates glucocorticoid-induced osteoporosis via modulation of HER2/AKT/mTOR signaling pathway.

Objective: Glucocorticoid-induced osteoporosis (GIOP) is a common complication of prolonged glucocorticoid therapy. Chlorogenic acid (CGA), a polyphenol with antioxidant properties that is extracted from traditional Chinese medicines such as Eucommiae Cortex, has potential anti-osteoporotic activity. This study aimed to investigate the possible effects of CGA on GIOP in mice and murine long bone osteocyte Y4 (MLO-Y4) cells and explore the underlying molecular mechanisms.

Methods: The protective effects of CGA were initially evaluated in the GIOP mouse model induced by dexamethasone (Dex). The micro-computed tomography, hematoxylin-eosin staining, silver nitrate staining, and serum detection were used to assess the efficacy of CGA for improving bone formation in vivo. Then, network pharmacology analysis was used to predict the potential targets and molecular mechanisms underlying the therapeutic efficacy of CGA against GIOP. After that, 2',7'-dichlorofluorescein diacetate staining, flow cytometry, real-time quantitative reverse transcription polymerase chain reaction, and Western blotting were used to verify the mechanisms of CGA against GIOP in vitro.

Results: Animal experiments showed that CGA treatment effectively attenuated Dex-induced decreases in bone mass and strength and improved disrupted osteocyte morphology in mice. The protein-protein interaction analysis highlighted erb-b2 receptor tyrosine kinase (ERBB2), which is also known as human epidermal growth factor receptor 2 (HER2), caspase-3, kinase insert domain receptor, matrix metallopeptidase 9, matrix metallopeptidase 2, proto-oncogene tyrosine-protein kinase Src, and epidermal growth factor receptor as core targets. The Kyoto Encyclopedia of Genes and Genomes analysis revealed several significantly enriched pathways (P < 0.05), including the ERBB, phosphoinositide 3 kinase-AKT serine/threonine kinase 1 (AKT), and mechanistic target of rapamycin kinase (mTOR) pathways. Cellular experiments verified that CGA enhanced bone formation and promoted autophagy while inhibiting apoptosis in MLO-Y4 cells exposed to Dex, which was associated with the upregulated expression of HER2 and activation of the HER2/AKT/mTOR signaling pathway.

Conclusion: CGA exerted anti-osteoporotic effects against GIOP, partially through targeting osteocytes and modulating the HER2/AKT/mTOR signaling pathway. Please cite this article as: Xie AN, Zhang SZY, Zhang Y, Cao JL, Wang CL, Wang LB, Wu HJ, Zhang J, Dai WW. Chlorogenic acid mitigates glucocorticoid-induced osteoporosis via modulation of HER2/AKT/mTOR signaling pathway. J Integr Med. 2025; Epub ahead of print.