Nobiletin, a NF-κB signaling antagonist, promotes BMP-induced bone formation

Nobiletin ameliorates hormone-induced osteoblast apoptosis by modulating JAK2/STAT3 signaling

Our paper aimed to disclose the effects of nobiletin (NOB) on hormone-induced osteoblast apoptosis and potential action mechanism. MC3T3-E1 cells were randomly separated into normal group, glucocorticoid (GC) group, L-NOB group, M-NOB group, H-NOB group, and Colivelin group (Colivelin: JAK2/STAT3 activator). CCK-8 was applied to ascertain the activity of MC3T3-E1 cells. FITC-Annexin V/PI method was applied to measure cell apoptosis. Alkaline phosphatase (ALP) assay kit was applied to measure ALP activity. Enzyme linked immunosorbent assay (ELISA) was implemented to ascertain the levels of IL-6, IL-1β, TNF-α, and ROS. Western blotting was implemented to distinguish the expressions of JAK2/STAT3 pathway proteins. The viability of MC3T3-E1 cells, ALP activities, and bcl-2 protein level were considerably decreased, while the apoptotic rate, the levels of TNF-α, IL-1β, IL-6, ROS, and the expressions of pJAK2/JAK2, pSTAT3/STAT3, Caspase-3, and bax proteins were greatly increased in each group after GC treatment. In comparison with GC group, MC3T3-E1 cell viability, ALP activity, and bcl-2 protein level in the L-NOB group, M-NOB group, and H-NOB group were greatly increased. Conversely, the apoptotic rate, the levels of TNF-α, IL-1β, IL-6, ROS, and the expressions of pJAK2/JAK2, pSTAT3/STAT3, Caspase-3, and bax proteins were markedly reduced. In contrast to H-NOB group, the apoptotic rate, the levels of TNF-α, IL-1β, IL-6, ROS, and the expressions of pJAK2/JAK2, pSTAT3/STAT3, Caspase-3, and bax proteins in Colivelin group were considerably enhanced, while MC3T3-E1 cell viability, ALP activity, and bcl-2 protein level were greatly declined. NOB ameliorates hormone-induced osteoblast apoptosis by reducing JAK2/STAT3 signaling activity.

Polymethoxyflavones and Bone Metabolism

Phytochemicals, such as flavonoids, are bioactive compounds produced by plants, including citrus fruits, that exhibit antioxidant effects on mammalian cells and tissues. Polymethoxyflavones (PMFs) are a family of flavonoids found in the pulp and peel of citrus fruits, and have been reported to have potent antioxidant activity implicated in the prevention of human diseases. Several studies have shown that PMFs have a protective effect on bone resorption in mouse models of diseases, including osteoporosis, rheumatoid arthritis, and periodontal disease. PMFs significantly suppressed the differentiation of osteoclasts (bone resorptive cells) through indirect and direct mechanisms. The indirect effect of PMFs is the suppression of inflammatory mediator production, such as prostaglandin E2 (PGE2), and the reduction of osteoclastic inducers, such as the receptor activator of NF-κB ligand (RANKL), in osteoblasts (bone-forming cells). The direct effect of PMF suppresses osteoclast differentiation and function by inhibiting the NF-κB signaling pathway. In silico molecular docking studies indicated that PMFs target the ATP-binding pocket of IKKβ and inhibit the NF-κB signaling pathway. These findings suggest that PMFs protect against bone destruction by interfering with the NF-κB pathway in osteoblasts and osteoclasts. In this review, we summarize the latest findings regarding the effects of PMFs on various bone resorption-related diseases in mouse models.

Lutein Maintains Bone Mass In Vitro and In Vivo Against Disuse-Induced Bone Loss in Hindlimb-Unloaded Mice

BACKGROUND

Lutein, a carotenoid, exhibits various biological activities such as maintaining the health of the eye, skin, heart, and bone. Recently, we found that lutein has dual roles in suppressing bone resorption and promoting bone formation. In this study, we examined the effects of lutein in a disuse-induced osteoporosis model using hindlimb-unloaded (HLU) mice.

METHODS

Osteoclast differentiation was assessed by coculturing mouse primary osteoblasts and bone marrow cells or culturing a mouse osteoclast precursor cell line. The bone-resorbing activity was determined by mouse calvarial organ cultures. An in situ docking simulation was conducted to reveal the interaction of lutein and IκB kinase (IKK) β protein. HLU mice were fed a 1% lutein-containing diet for two weeks, and the femoral bone mass was measured by μCT.

RESULTS

Osteoclast differentiation is significantly inhibited by lutein, astaxanthin, and β-cryptoxanthin. In contrast, only lutein promoted osteoblastic calcified bone nodule formation. To elucidate the molecular role of lutein, we functionally analyzed the NF-κB complex, a molecule involved in bone metabolism, especially in osteoclasts. Docking simulations showed that lutein binds to IKK, thus inhibiting the activation of NF-κB. In a cell culture analysis, the phosphorylation of p65, the active form of NF-κB in osteoblasts, was suppressed by lutein treatment. In vivo, a μCT analysis of the bone microarchitecture showed that lutein improves several bone parameters while maintaining bone mass.

CONCLUSIONS

Lutein is effective in maintaining bone mass by controlling both bone resorption and formation, which is applied to prevent disuse-induced osteoporosis.

Drug delivery systems based on polyethylene glycol hydrogels for enhanced bone regeneration

Drug delivery systems composed of osteogenic substances and biological materials are of great significance in enhancing bone regeneration, and appropriate biological carriers are the cornerstone for their construction. Polyethylene glycol (PEG) is favored in bone tissue engineering due to its good biocompatibility and hydrophilicity. When combined with other substances, the physicochemical properties of PEG-based hydrogels fully meet the requirements of drug delivery carriers. Therefore, this paper reviews the application of PEG-based hydrogels in the treatment of bone defects. The advantages and disadvantages of PEG as a carrier are analyzed, and various modification methods of PEG hydrogels are summarized. On this basis, the application of PEG-based hydrogel drug delivery systems in promoting bone regeneration in recent years is summarized. Finally, the shortcomings and future developments of PEG-based hydrogel drug delivery systems are discussed. This review provides a theoretical basis and fabrication strategy for the application of PEG-based composite drug delivery systems in local bone defects.