Osteoporosis is a systemic metabolic disease characterized by disrupted bone formation/resorption and homeostasis. Flavonoids extracted from traditional Chinese medicinal plants regulate bone homeostasis by intervening in differentiating bone marrow mesenchymal stem cells, balancing the bone immune system, inhibiting oxidative stress response, and reversing iron overload. The target molecules and signaling pathways, such as Wnt/β-catenin and OPG/RANKL/RANK, directly affect osteoblast/osteoclast activity, exhibiting significant potential in the treatment of OP. Therefore, this study presents a systematic review of the recent literature to provide comprehensive information on the traditional Chinese medicine flavonoids involved in the regulation of bone homeostasis. Also, the molecular mechanisms and pharmacological uses of these metabolites are summarized, and their clinical translation and development potential are discussed.

Danshen (Salvia miltiorrhiza) is a traditional Chinese medicine herb that can alleviate the symptoms of osteoarthritis (OA) (Söder et al. 2006) in animals. However, the underlying mechanisms remain poorly understood and require further investigation. In this study, rabbits with experimentally induced OA were given an intra-articular injection of danshen (0.7 mL/day) for 5 weeks. In addition to attenuating the cartilage degeneration of OA in the rabbits, danshen decreased the expression and activity of matrix metalloproteinase 9 (MMP-9) and MMP-13, and increased the expression of their natural inhibitors: tissue inhibitor of matrix metalloproteinase 1 (TIMP-1) and TIMP-2. Apoptosis in osteoarthritic cartilage tissues was attenuated by danshen, accompanied with increased expression of B cell lymphoma 2 (Bcl-2) and decreased levels of Bcl-2-associated X protein (Bax). Further, danshen inhibited the nuclear accumulation of nuclear factor kappa-B (NF-κB) p65 in osteoarthritic cartilage. The therapeutic effects of danshen in vivo were comparable to that of sodium hyaluronate, which is a drug used clinically for the treatment OA. In vitro, sodium nitroprusside (SNP) was used to stimulate apoptosis in primary rabbit chondrocytes. We found that the SNP-induced apoptosis was mitigated by danshen. BAY11-7028, an inhibitor of the NF-κB pathway, augmented danshen’s anti-apoptotic effects in cells exposed to SNP. When these results are considered together, they indicate that danshen alleviates the cartilage injury in rabbit OA through inhibition of the NF-κB signaling pathway.

Purpose: Laryngeal cancer is the most prevalent tumor type in head and neck cancers. Early diagnosis is considered as an important strategy for improving prognosis. The lncRNA DLX6-AS1 has been shown to modulate tumor phenotypes in several types of cancer, but the role of DLX6-AS1 in laryngeal cancer and its concrete mechanisms are not clear. Methods: Tissue samples from laryngeal cancer patients and corresponding clinical data were used for detailed analysis. The laryngeal cancer cell lines HEp-2 and Tu-177 were studied. Cell proliferation, ROS production, mitochondrial respiratory function, intracellular and mitochondrial calcium influx were assessed. Western blotting, quantitative RT-PCR and luciferase assays were used to analyze the interactions. A xenografted tumor model was established to analyze the effects of DLX6-AS1 on tumor growth in vivo. Results: lncRNA DLX6-AS1 had increased expression in tumor tissues compared with adjacent normal tissues and in higher clinical stages compared with lower stages, which was associated with poor prognosis. In detail, DLX6-AS1 knockdown decreased cell proliferation and affected key mitochondrial metabolic parameters in both HEp-2 and Tu-177 cells. Moreover, DLX6-AS1 knockdown suppressed TRPC3-mediated mitochondrial calcium uptake and ROS production. Furthermore, miR-26a functioned as a link between these two molecules, as it could be absorbed by DLX6-AS1 and thus regulated the levels of TRPC3. Finally, the DLX6-AS1/miR-26a/TRPC3 axis modulated laryngeal cancer proliferation both in vitro and in vivo. Conclusion: This study provides new evidence that a novel lncRNA, DLX6-AS1, regulates mitochondrial calcium homeostasis, respiration and tumor proliferation via modulating the miR-26a/TRPC3 axis in laryngeal cancer.

Steroid-induced osteonecrosis of the femoral head (SIONFH) is a frequent orthopedic disease caused by long-term or high-dose administration of corticosteroids. Tanshinone I (TsI), a flavonoid compound isolated from Salvia miltiorrhiza Bunge, has been reported to inhibit osteoclastic differentiation in vitro. This study aimed to investigate whether TsI can ameliorate SIONFH. Herein, SIONFH was induced by intraperitoneal injection of 20μg/kg lipopolysaccharide every 24h for 2 days, followed by an intramuscular injection of 40mg/kg methylprednisolone every 24h for 3 days. Four weeks after the final injection of methylprednisolone, the rats were intraperitoneally administrated with low-dose (5mg/kg) and high-dose (10mg/kg) TsI once daily for 4 weeks. Results showed that TsI significantly alleviated osteonecrotic lesions of the femoral heads as determined by micro-CT analysis. Furthermore, TsI increased alkaline phosphatase activity and expressions of osteoblastic markers including osteocalcin, type I collagen, osteopontin, and Runt-related transcription factor 2 and decreased tartrate-resistant acid phosphatase activity and expressions of osteoclastic markers including cathepsin K and acid phosphatase 5. TsI also reduced inflammatory response and oxidative stress and activated the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway in the femoral heads. Taken together, our findings show that TsI can relieve SIONFH, indicating that it may be a candidate for preventing SIONFH.

Background: Emerging evidence has correlated the human antigen R (HuR) with the low-density lipoprotein receptor-related protein 6 (LRP6) gene, an important therapeutic target for osteoporosis. Herein, we sought to probe the regulatory role of HuR in the LRP6 gene and their interaction in the progression of osteoporosis. Methods: HuR and downstream potential target genes were predicted by bioinformatics analysis to identify their potential functions in bone metabolism following osteoporosis. The effect of HuR on the osteoblastic differentiation and viability and apoptosis of mouse embryo osteoblast precursor cells (MC3T3-E1) was evaluated after artificial modulation of HuR expression. Results: Bone phenotypes were observed in ovariectomized mice in response to adenovirus-mediated HuR overexpression. Poor expression of HuR was identified in the bone tissues of ovariectomized mice. Silencing of HuR inhibited the osteoblastic differentiation of MC3T3-E1 cells, as evidenced by decreased expression of Runx2 and Osterix along with reduced ALP activity. Mechanistically, HuR stabilized LRP6 mRNA and promoted its translation by binding to the 3'UTR of LRP6 mRNA, leading to activation of the downstream Wnt pathway. By this mechanism, osteoblastic differentiation of MC3T3-E1 cells was induced. In ovariectomized mice, overexpression of HuR alleviated osteoporosis-related phenotypes. Conclusion: Overall, these data together support the promoting role of HuR in the osteoblastic differentiation, highlighting a potential novel strategy for osteoporosis treatment.