Rationale: Growing evidence indicates that intracellular reactive oxygen species (ROS) accumulation is a critical factor in the development of osteoporosis by triggering osteoclast formation and function. Pseurotin A (Pse) is a secondary metabolite isolated from Aspergillus fumigatus with antioxidant properties, recently shown to exhibit a wide range of potential therapeutic applications. However, its effects on osteoporosis remain unknown. This study aimed to explore whether Pse, by suppressing ROS level, is able to inhibit osteoclastogenesis and prevent the bone loss induced by estrogen-deficiency in ovariectomized (OVX) mice.

Rationale: Osteoporosis is a severe bone disorder that is a threat to our aging population. Excessive osteoclast formation and bone resorption lead to changes in trabecular bone volume and architecture, leaving the bones vulnerable to fracture. Therapeutic approaches of inhibiting osteoclastogenesis and bone resorption have been proven to be an efficient approach to prevent osteoporosis. In our study, we have demonstrated for the first time that Loureirin B (LrB) inhibits ovariectomized osteoporosis and explored its underlying mechanisms of action in vitro. Methods: We examined the effects of LrB on RANKL-induced osteoclast differentiation and bone resorption, and its impacts on RANKL-induced NFATc1 activation, calcium oscillations and reactive oxygen species (ROS) production in osteoclasts in vitro. We assessed the in vivo efficacy of LrB using an ovariectomy (OVX)-induced osteoporosis model, which was analyzed using micro-computed tomography (micro-CT) and bone histomorphometry. Results: We found that LrB represses osteoclastogenesis, bone resorption, F-actin belts formation, osteoclast specific gene expressions, ROS activity and calcium oscillations through preventing NFATc1 translocation and expression as well as affecting MAPK-NFAT signaling pathways in vitro. Our in vivo study indicated that LrB prevents OVX-induced osteoporosis and preserves bone volume by repressing osteoclast activity and function. Conclusions: Our findings confirm that LrB can attenuate osteoclast formation and OVX-induced osteoporosis. This novel and exciting discovery could pave the way for the development of LrB as a potential therapeutic treatment for osteoporosis.

We show that in solutions of human hemoglobin (Hb)—oxy- and deoxy-Hb A or S—of near-physiological pH, ionic strength, and Hb concentration, liquid–liquid phase separation occurs reversibly and reproducibly at temperatures between 35 and 40°C. In solutions of deoxy-HbS, we demonstrate that the dense liquid droplets facilitate the nucleation of HbS polymers, whose formation is the primary pathogenic event for sickle cell anemia. In view of recent results that shifts of the liquid–liquid separation phase boundary can be achieved by nontoxic additives at molar concentrations up to 30 times lower than the protein concentrations, these findings open new avenues for the inhibition of the HbS polymerization.

Osteoporosis is a bone disease characterized by increasing osseous fragility and fracture due to the reduced bone mass and microstructural degradation. Primary pharmacological strategies for the treatment of osteoporosis, hormone replacement treatment (HRT), and alendronate therapies may produce adverse side-effects and may not be recommended for long-term usage. Some classic and bone-specific natural Chinese medicine are very popularly used to treat osteoporosis and bone fracture effectively in clinical with their potential value in bone growth and development, but with few adverse side-effects. Current evidence suggests that the treatments appear to improve bone metabolism and attenuate the osteoporotic imbalance between bone formation and bone resorption at a cellular level by promoting osteoblast activity and inhibiting the effects of osteoclasts. The valuable therapies might, therefore, provide an effective and safer alternative to primary pharmacological strategies. Therefore, the purpose of this article is to comprehensively review these classic and bone-specific drugs in natural Chinese medicines for the treatment of osteoporosis that had been deeply and definitely studied and reported with both bone formation and antiresorption effects, including Gynochthodes officinalis (F.C.How) Razafim. & B.Bremer (syn. Morinda officinalis F.C.How), Curculigo orchioides Gaertn., Psoralea corylifolia (L.) Medik Eucommia ulmoides Oliv., Dipsacus inermis Wall. (syn. Dipsacus asperoides C.Y.Cheng & T.M.Ai), Cibotium barometz (L.) J. Sm., Velvet Antler, Cistanche deserticola Ma, Cuscuta chinensis Lam., Cnidium monnieri (L.) Cusson, Epimedium brevicornum Maxim, Pueraria montana (Lour.) Merr. and Salvia miltiorrhiza Bunge., thus providing evidence for the potential use of alternative Chinese medicine therapies to effectively treat osteoporosis.

Steroid-induced osteonecrosis of the femoral head (ONFH) is a progressive bone disorder which typically results in femoral head collapse and hip joint dysfunction. It is well-accepted that abnormal osteoclast activity contributes to loss of bone structural integrity and subchondral fracture in ONFH. However, the pathophysiologic mechanisms underlying the recruitment and hyperactivation of osteoclasts in ONFH remain incompletely understood. We assessed the changes of reactive oxygen species (ROS) level and subsequent osteoclast alterations in steroid-induced osteonecrotic femoral heads from both patients and rat ONFH models. When compared with healthy neighboring bone, the necrotic region of human femoral head was characterized by robust up-regulated expression of osteoclast-related proteins [cathepsin K and tartrate-resistant acid phosphatase(TRAP)] but pronounced down-regulation of antioxidant enzymes (catalase, γ-glutamylcysteine synthetase [γ-GCSc], and superoxide dismutase 1 [SOD1]). In addition, the ratio of TNFSF11 (encoding RANKL)/TNFRSF11B (encoding OPG) was increased within the necrotic bone. Consistently, in rat ONFH models induced by methylprednisolone (MPSL) and imiquimod (IMI), significant bone loss in the femoral head was observed, attributable to increased numbers of TRAP positive osteoclasts. Furthermore, the decreased expression of antioxidant enzymes observed by immunoblotting was accompanied by increased ex-vivo ROS fluorescence signals of dihydroethidium (DHE) in rat ONFH models. Therefore, this study lends support to the rationale that antioxidant agents may be a promising therapeutic avenue to prevent or mitigate the progression of steroid-induced ONFH by inhibiting ROS level and hyperactive osteoclasts.