Schisandrin B regulates MC3T3-E1 subclone 14 cells proliferation and differentiation through BMP2-SMADs-RUNX2-SP7 signaling axis

The role and mechanism of β-catenin-mediated skeletal muscle satellite cells in osteoporotic fractures by Jian-Pi-Bu-Shen formula

Osteoporosis is a metabolic bone disease. β-Catenin is associated with fractures. Jian-Pi-Bu-Shen (JPBS) can promote the healing of osteoporotic fractures (OPF). However, the mechanism of β-catenin-mediated skeletal muscle satellite cells (SMSCs) in OPF by the JPBS is unclear. SMSCs were isolated and divided into five groups. The results showed that the survival rate of SMSCs was significantly higher in the low, medium, and high dose JPBS-containing serum groups after 7 days of incubation. The ALP activity and the number of SMSCs mineralized in the JPBS-containing serum intervention group were elevated. Axin, GSK-3β, β-catenin siRNAs were constructed and transfected into cells. Transfection of siRNAs reduced Axin, GSK-3β, and β-catenin expressions, respectively. β-Catenin-siRNA reversed ALP activity, the number of SMSCs mineralized, and the expression of β-catenin, BMP2, Runx2, COL-I, SP7/Ostrix, Osteocalcin, and BMP-7. Transcriptomic results suggested that the TNF signaling pathway associated with OPF was enriched. SD rats were subjected to the construction of OPF model by removing the ovaries. JPBS decreased the levels of PINP, ALP, CTX, and NTX through β-catenin in OPF rats, while increasing Runx2, β-catenin expressions through β-catenin at the broken end of fractures. Moreover, JPBS decreased BMC, BMD, and BV/TV and improved pathological damage through β-catenin in OPF rats. JPBS decreased the expression of Axin, GSK-3β mRNA, and protein, but increased the expressions of β-catenin, Pax7, COL-II, COL-II, BMP2, and Runx2 through β-catenin in OPF rats. In conclusion, JPBS inhibits Axin/GSK-3β expression, activates the β-catenin signaling, and promotes the osteogenic differentiation of SMSCs.

Modulation of osteoblastogenesis by NRF2: NRF2 activation suppresses osteogenic differentiation and enhances mineralization in human bone marrow-derived mesenchymal stromal cells

Mesenchymal stromal stem cells (MSCs) or skeletal stem cells (SSCs) play a major role in tissue repair due to their robust ability to differentiate into osteoblasts, chondrocytes, and adipocytes. Complex cell signaling cascades tightly regulate this differentiation. In osteogenic differentiation, Runt-related transcription factor 2 (RUNX2) and ALP activity are essential. Furthermore, during the latter stages of osteogenic differentiation, mineral formation mediated by the osteoblast occurs with the secretion of a collagenous extracellular matrix and calcium deposition. Activation of nuclear factor erythroid 2-related factor 2 (NRF2), an important transcription factor against oxidative stress, inhibits osteogenic differentiation and mineralization via modulation of RUNX2 function; however, the exact role of NRF2 in osteoblastogenesis remains unclear. Here, we demonstrate that NRF2 activation in human bone marrow-derived stromal cells (HBMSCs) suppressed osteogenic differentiation. NRF2 activation increased the expression of STRO-1 and KITLG (stem cell markers), indicating NRF2 protects HBMSCs stemness against osteogenic differentiation. In contrast, NRF2 activation enhanced mineralization, which is typically linked to osteogenic differentiation. We determined that these divergent results were due in part to the modulation of cellular calcium flux genes by NRF2 activation. The current findings demonstrate a dual role for NRF2 as a HBMSC maintenance factor as well as a central factor in mineralization, with implications therein for elucidation of bone formation and cellular Ca2+ kinetics, dystrophic calcification and, potentially, application in the modulation of bone formation.

The Lignan-Rich Fraction from Sambucus williamsii Hance Exerts Bone Protective Effects via Altering Circulating Serotonin and Gut Microbiota in Rats

Our previous study revealed that the bone anabolic effects of the lignan-rich fraction (SWCA) from Sambucus williamsii Hance was involved in modulating the metabolism of tryptophan in vivo and inhibiting serotonin (5-HT) synthesis in vitro. This study aimed to determine how SWCA modulates bone metabolism via serotonin in vivo. The effects of SWCA were evaluated by using 4-month-old Sprague-Dawley (SD) ovariectomized rats. The serum levels of 5-HT and kynurenine, the protein expressions of tryptophan hydroxylase 1 (TPH-1) and TPH-2, the genes and proteins related to the 5-HT signaling pathway as well as gut microbiota composition were determined. SWCA treatment alleviated bone loss and decreased serum levels of serotonin, which was negatively related to bone mineral density (BMD) in rats. It suppressed the protein expression of TPH-1 in the colon, and reversed the gene and protein expressions of FOXO1 and ATF4 in the femur in OVX rats, while it did not affect the TPH-2 protein expression in the cortex. SWCA treatment escalated the relative abundance of Antinobacteria and modulated several genera relating to BMD. These findings verified that the bone protective effects of lignans were mediated by serotonin, and provided evidence that lignans might be a good source of TPH-1 inhibitors.

BMP Signaling Pathway in Dentin Development and Diseases

BMP signaling plays an important role in dentin development. BMPs and antagonists regulate odontoblast differentiation and downstream gene expression via canonical Smad and non-canonical Smad signaling pathways. The interaction of BMPs with their receptors leads to the formation of complexes and the transduction of signals to the canonical Smad signaling pathway (for example, BMP ligands, receptors, and Smads) and the non-canonical Smad signaling pathway (for example, MAPKs, p38, Erk, JNK, and PI3K/Akt) to regulate dental mesenchymal stem cell/progenitor proliferation and differentiation during dentin development and homeostasis. Both the canonical Smad and non-canonical Smad signaling pathways converge at transcription factors, such as Dlx3, Osx, Runx2, and others, to promote the differentiation of dental pulp mesenchymal cells into odontoblasts and downregulated gene expressions, such as those of DSPP and DMP1. Dysregulated BMP signaling causes a number of tooth disorders in humans. Mutation or knockout of BMP signaling-associated genes in mice results in dentin defects which enable a better understanding of the BMP signaling networks underlying odontoblast differentiation and dentin formation. This review summarizes the recent advances in our understanding of BMP signaling in odontoblast differentiation and dentin formation. It includes discussion of the expression of BMPs, their receptors, and the implicated downstream genes during dentinogenesis. In addition, the structures of BMPs, BMP receptors, antagonists, and dysregulation of BMP signaling pathways associated with dentin defects are described.

Therapeutic potential of naturally occurring lignans as anticancer agents

Cancer as a long-lasting and dramatic pandemic affects almost a third of the human being worldwide. At present, chemotherapy is the main clinical treatment strategy, but it is difficult to achieve satisfactory efficacy due to drug resistance and side effects. Natural products are becoming increasingly popular in cancer therapy due to their potent broad-spectrum anticancer potency and slight side effects. Lignans are complex diphenolic compounds, comprising a family of secondary metabolites existing widely in plants. Naturally occurring lignans have the potential to act on cancer cells by a range of mechanisms of action and could inhibit the colony formation, arrest the cell cycle in different phases, induce apoptosis, and suppress migration, providing privileged scaffolds for the discovery of novel anticancer agents. In recent five years, a variety of naturally occurring lignans were isolated and screened for their in vitro and/or in vivo anticancer efficacy, and some of them exhibited promising potential. This review has systematically summarized the resources, anticancer activity, and mechanisms of action of naturally occurring lignans, covering articles published between January 2017 and January 2022.

Anti-Cancer Effects of α-Cubebenoate Derived from Schisandra chinensis in CT26 Colon Cancer Cells

α-Cubebenoate derived from Schisandra chinensis has been reported to possess anti-allergic, anti-obesity, and anti-inflammatory effects and to exhibit anti-septic activity, but its anti-cancer effects have not been investigated. To examine the anti-cancer activity of α-cubebenoate, we investigated its effects on the proliferation, apoptosis, and metastasis of CT26 cells. The viabilities of CT26 cells (a murine colorectal carcinoma cell line) and HCT116 cells (a human colon cancer cell line) were remarkably and dose-dependently diminished by α-cubebenoate, whereas the viability of CCD-18Co cells (a normal human fibroblast cell line) were unaffected. Furthermore, α-cubebenoate treatment increased the number of apoptotic CT26 cells as compared with Vehicle-treated cells and increased Bax, Bcl-2, Cas-3, and Cleaved Cas-3 protein levels by activating the MAP kinase signaling pathway. α-Cubebenoate also suppressed CT26 migration by regulating the PI3K/AKT signaling pathway. Furthermore, similar reductions were observed in the expression levels of some migration-related proteins including VEGFA, MMP2, and MMP9. Furthermore, reduced VEGFA expression was found to be accompanied by the phosphorylations of FAK and MLC in the downstream signaling pathway of adhesion protein. The results of the present study provide novel evidence that α-cubebenoate can stimulate apoptosis and inhibit metastasis by regulating the MAPK, PI3K/AKT, and FAK/MLC signaling pathways.