Pharmacologically targeting fatty acid synthase-mediated de novo lipogenesis alleviates osteolytic bone loss...

Pharmacologically targeting fatty acid synthase-mediated de novo lipogenesis alleviates osteolytic bone loss by directly inhibiting osteoclastogenesis through suppression of STAT3 palmitoylation and ROS signaling

AUTHORS

Chunmei Xiu, Lei Zhang, Chenxi Zhang, Yuannan Zhang, Xi Luo, Ziyi Zhang, Hangkai Zhao, Kaizhong Ji, Zhiyuan Chen, Guangxu He, Jianquan Chen

ABSTRACT

Aberrant increases in osteoclast formation and/or activity are the underlying cause of bone loss in a variety of osteolytic diseases. Fatty acid synthase (Fasn)-mediated de novo lipogenesis (DNL) is one of the major lipid metabolic pathways and has been shown to play critical roles in diverse physiological and pathological processes. However, little is known about its role in osteoclastogenesis. Here, we investigate the direct role of DNL in osteoclastogenesis and its therapeutic potential in osteolytic diseases. We found that Fasn expression and DNL levels are upregulated during receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclastogenesis. Inhibition of Fasn by shRNA knockdown or its pharmacological inhibitors (ASC40 and trans-C75) impairs osteoclast differentiation in vitro. Mechanistically, pharmacological inhibition of Fasn suppresses RANKL-induced c-Fos/NFATc1 expression and thus osteoclastogenesis partly by disrupting STAT3 palmitoylation, while promoting ROS scavenging to impair mitogen-activated protein kinase (MAPK) signaling. Finally, the therapeutic potential of ASC40 for the treatment of osteolytic bone loss is tested in two mouse models of osteolytic diseases, i.e. ovariectomy (OVX)-induced osteoporosis and titanium nanoparticle-induced calvarial osteolysis. The results show that ASC40 significantly attenuates bone loss and osteoclastogenesis in both models. In conclusion, our results demonstrate that Fasn-mediated DNL is a novel positive regulator of osteoclastogenesis and may serve as a promising therapeutic target for the treatment of osteoclast-driven osteolytic bone diseases.

Targeting the osteoclastogenic cytokine IL-9 as a novel immunotherapeutic strategy in mitigating inflammatory bone loss in post-menopausal osteoporosis

AUTHORS

Leena Sapra, Chaman Saini, Shivani Sharma, Dibyani Nanda, Aishwarya Nilakhe, Naibedya Chattopadhyay, Avtar Singh Meena, Pradyumna K Mishra, Sarika Gupta, Bhavuk Garg, Vikrant Manhas, Rupesh K Srivastava

ABSTRACT

Recent discoveries have established the pivotal role of IL-9-secreting immune cells in a wide spectrum of inflammatory and autoimmune diseases. However, little is known about how IL-9 contributes to the etiology of inflammatory bone loss in PMO. We observed that IL-9 has a pathological impact on inflammatory bone loss in ovariectomized (Ovx) mice. Our in vivo temporal kinetics analysis revealed that estrogen deprivation enhanced the production of IL-9 from Th cells (majorly Th9 and Th17). Both our ex vivo and in vivo studies corroborated these findings in Ovx mice, as estrogen diminishes the potential of Th9 cells to produce IL-9. Mechanistically, Th9 cells in an IL-9-dependent manner enhance osteoclastogenesis and thus could establish themselves as a novel osteoclastogenic Th cell subset. Therapeutically neutralizing/blocking IL-9 improves bone health by inhibiting the differentiation and function of osteoclasts, Th9, and Th17 cells along with maintaining gut integrity in Ovx mice. Post-menopausal osteoporotic patients have increased IL-9-secreting Th9 cells, which may suggest a potential role for IL-9 in the development of osteoporosis. Collectively, our study identifies IL-9-secreting Th9 cells as a driver of bone loss with attendant modulation of gut-immune-bone axis, which implies IL-9-targeted immunotherapies as a potential strategy for the management and treatment of inflammatory bone loss observed in PMO.

Catharanthine tartrate ameliorates osteoclastogenesis by destabilizing HIF-1α

AUTHORS

Luqiong Cai, Chenxin Yu, Binli Zhao, Qihang Wu, Haibo Liang, Meng Zhou, Jiansen Miao, Jiangtao Luo, Jiake Xu, Haiming Jin, Youjin Pan

ABSTRACT

With the aging population, postmenopausal osteoporosis (PMOP), clinically manifested by reduced bone density, weakened skeletal strength, and compromised skeletal microstructure, has become the most prevalent type. The decline in estrogen levels fosters oxidative stress and osteoclastogenesis, which significantly enhance the activity of osteoclasts. Current treatments prefer to adopt relevant strategies to inactivate osteoclasts but come with unavoidable side effects. In our study, Catharanthine Tartrate (CAT), a derivative of the alkaloid catharanthine found in Catharanthus roseus, promised to be an effective therapy for PMOP. CAT inhibited RANKL-induced osteoclast differentiation and bone resorption in vitro. Moreover, CAT inhibited osteoclast activity by enhancing the ubiquitination-mediated proteasomal degradation of HIF-1α, which reduced oxidative stress and subsequently suppressed osteoclast activity. The inhibitory effects of CAT on osteoclast function and oxidative stress were reversed by DMOG, a known inhibitor of HIF-1α degradation. Next, an in vivo mouse experiment using the Ovariectomized (OVX) model to induce osteoporosis indicated that CAT enhanced bone mass density, bone structure, and bone remodeling. Our findings revealed that CAT inhibits PMOP through facilitating HIF-1α ubiquitination and degradation, suggesting a promising therapeutic approach for this disorder.

Dimeric R25CPTH(1–34) activates the parathyroid hormone-1 receptor in vitro and stimulates bone formation in osteoporotic female mice

AUTHORS

Minsoo Noh, Xiangguo Che, Xian Jin, Dong-Kyo Lee, Hyun-Ju Kim, Doo Ri Park, Soo Young Lee, Hunsang Lee, Thomas J Gardella, Je-Yong Choi, Sihoon Lee

ABSTRACT

Osteoporosis, characterized by reduced bone density and strength, increases fracture risk, pain, and limits mobility. Established therapies of parathyroid hormone (PTH) analogs effectively promote bone formation and reduce fractures in severe osteoporosis, but their use is limited by potential adverse effects. In the pursuit of safer osteoporosis treatments, we investigated R25CPTH, a PTH variant wherein the native arginine at position 25 is substituted by cysteine. These studies were prompted by our finding of high bone mineral density in a hypoparathyroidism patient with the R25C homozygous mutation, and we explored its effects on PTH type-1 receptor (PTH1R) signaling in cells and bone metabolism in mice. Our findings indicate that R25CPTH(1–84) forms dimers both intracellularly and extracellularly, and the synthetic dimeric peptide, R25CPTH(1–34), exhibits altered activity in PTH1R-mediated cyclic AMP (cAMP) response. Upon a single injection in mice, dimeric R25CPTH(1–34) induced acute calcemic and phosphaturic responses comparable to PTH(1–34). Furthermore, repeated daily injections increased calvarial bone thickness in intact mice and improved trabecular and cortical bone parameters in ovariectomized (OVX) mice, akin to PTH(1–34). The overall results reveal a capacity of a dimeric PTH peptide ligand to activate the PTH1R in vitro and in vivo as PTH, suggesting a potential path of therapeutic PTH analog development.

Tumor-derived exosomal lncRNA-MIR193BHG promotes bone metastasis of breast cancer by targeting the miR-489-3p/DNMT3A signaling axis in osteoclasts

AUTHORS

Xiaoya Liu, Rui Ma, Feng Wei, Maihuan Wang, Yiwei Jiang, Peng Zheng, Zhen Cao

ABSTRACT

Background

Breast cancer exhibits high incidence and mortality among women, with distant metastasis, especially bone metastasis, being the leading cause of death. Despite advances in adjuvant therapies, bone metastasis remains a challenge for patient survival and quality of life. Exosomes, small vesicles capable of mediating intercellular communication, play a crucial role in tumor metastasis.

Results

This study investigated the role of tumor-derived exosomal long noncoding RNA (lncRNA)-MIR193BHG in breast cancer bone metastasis. LncRNA-MIR193BHG was delivered to osteoclasts via exosomes and promoted osteoclast formation and activity by targeting the miR-489-3p/DNA methyltransferase 3A (DNMT3A) signaling axis, thereby accelerating breast cancer-induced osteolysis. Knockdown experiments demonstrated that reducing the levels of exosomal lncRNA-MIR193BHG significantly inhibited osteoclast differentiation and bone resorption, which was confirmed both in vitro and in vivo. Additionally, mechanistic studies revealed that lncRNA-MIR193BHG acted as a competitive endogenous RNA (ceRNA) interacting with miR-489-3p, regulating DNMT3A expression and subsequently affecting osteoclast differentiation.

Conclusions

These findings suggest that lncRNA-MIR193BHG plays a critical regulatory role in breast cancer bone metastasis, and the lncRNA-MIR193BHG/miR-489-3p/DNMT3A signaling axis could be a potential target for the treatment of breast cancer bone metastasis. Future studies should further explore the broader applicability of this mechanism and its clinical feasibility.

Aflatoxin B1 contamination reduces the saponins content and anti-osteoporosis efficacy of the traditional medicine Radix Dipsaci

AUTHORS

Shuqin Lu, Qingsong Yuan, Lulu Wang, Dapeng Su, Min Hu, Lanping Guo, Chuanzhi Kang, Tao Zhou, Jinqiang Zhang

ABSTRACT

Ethnopharmacological relevance

The Radix Dipsaci, a traditional Chinese medicine with a history spanning over 2000 years in China, is widely recognized for its hepatorenal tonic properties, musculoskeletal fortifying effects, fracture healing capabilities, and its frequent application in the treatment of osteoporosis. Like many traditional Chinese herbal medicines, preparations from Radix Dipsaci are at risk of contamination by harmful mycotoxins such as aflatoxin B1.

Aims of the study

This study aims to evaluate the impact of aflatoxin B1 contamination on Radix Dipsaci in terms of changes in quality, efficacy of anti-osteoporosis and hepatorenal toxicity.

Materials and methods

The contamination rates and levels of major mycotoxins were determined in 45 batches of Radix Dipsaci samples using UPLC-MS/MS analysis. The total saponin content and the levels of akebia saponin D in Radix Dipsaci and its decoctions were evaluated through high-performance liquid chromatography (HPLC) analysis. Differences in secondary metabolites between samples without any mycotoxin contamination (N-RD) and those contaminated solely by aflatoxin B1 (AFB1-RD) were compared using metabolomics sequencing and analysis. The anti-osteoporotic efficacy of Radix Dipsaci contaminated with aflatoxin B1 was assessed in a murine model of retinoic acid-induced osteoporosis by quantifying bone mineral content and bone mineral density using dual-energy X-ray absorptiometry. Additionally, the hepatorenal toxicity of Radix Dipsaci contaminated with aflatoxin B1 was evaluated using hematoxylin-eosin staining and enzyme-linked immunosorbent assay (ELISA).

Results

The results indicated that aflatoxin B1 (AFB1) was the most frequently detected mycotoxin, found in 37.7% of the Radix Dipsaci samples. AFB1 contamination significantly altered the secondary metabolites of Radix Dipsaci. Specifically, there was a notable decrease in the levels of total saponins and akebia saponin D in the AFB1-contaminated samples, which exhibited a negative correlation with the levels of AFB1 contamination. However, the administration of a water decoction from AFB1-contaminated Radix Dipsaci did not result in significant improvements in bone mineral density, bone mineral salt content, the trabecular number, trabecular area, proportion of trabecular bone volume/tissue volume and trabecular separation in an osteoporosis mouse model. Additionally, we observed that approximately 16.04% of AFB1 could migrate from the raw herbs into the decoction, leading to hepatocyte and kidney cell damage, as well as increased levels of the oxidative stress molecule malondialdehyde and pro-inflammatory cytokines in the liver and kidney tissues of the osteoporosis model mice.

Conclusion

In summary, Radix Dipsaci is highly susceptible to mycotoxin contamination, particularly aflatoxin B1. The contamination of Radix Dipsaci with AFB1 not only impacts their saponin content and anti-osteoporosis effect but also induces hepatotoxicity and nephrotoxicity.