Duloxetine suppresses BMP-4-induced release of osteoprotegerin via inhibition of the SMAD signaling pathway in osteoblasts.

Duloxetine, a selective serotonin-norepinephrine reuptake inhibitor, is currently recommended for the treatment of chronic painful disorders such as fibromyalgia, chronic musculoskeletal pain, and diabetic peripheral neuropathy. We previously demonstrated that bone morphogenetic protein-4 (BMP-4) stimulates osteoprotegerin (OPG) production in osteoblast-like MC3T3-E1 cells, and that p70 S6 kinase positively regulates OPG synthesis. The present study aimed to investigate the effect of duloxetine on BMP-4-stimulated OPG synthesis in these cells. Duloxetine dose-dependently suppressed OPG release stimulated by BMP-4. Fluvoxamine, a selective serotonin reuptake inhibitor (SSRI), reduced BMP-4-stimulated OPG release, whereas a selective and specific norepinephrine reuptake inhibitor, reboxetine, failed to affect OPG release. In addition, another SSRI sertraline also inhibited BMP-4-stimulated OPG release. On the other hand, siRNA of SMAD1 reduced the OPG release stimulated by BMP-4, indicating the involvement of the SMAD1/5/8 pathway in OPG release. Rapamycin inhibited BMP-4-stimulated p70 S6 kinase phosphorylation, and compound C suppressed the SMAD1/5/8 phosphorylation stimulated by BMP-4. Duloxetine did not affect BMP-4-induced phosphorylation of p70 S6 kinase but suppressed SMAD1/5/8 phosphorylation. Both fluvoxamine and sertraline also inhibited BMP-4-elicited phosphorylation of SMAD1/5/8. These results strongly suggest that duloxetine suppresses BMP-4-stimulated OPG release via inhibition of the Smad1/5/8 signaling pathway in osteoblasts.

Prunella vulgaris L protects glucocorticoids-induced osteogenesis inhibition in bone marrow mesenchymal stem cells through activating the Smad pathway.

OBJECTIVE: To elucidate the role of Prunella vulgaris L (PVL) in protecting glucocorticoids (GC)-induced osteogenesis inhibition, thereafter, protecting the deterioration of osteoporosis (OP). MATERIALS AND METHODS: Cell Counting Kit-8 (CCK-8) assay was conducted to assess the influence of PVL treatment on MSCs viability. Osteogenesis in MSCs was induced by Dexamethasone (DEX) stimulation. Regulatory effects of PVL on osteogenesis-related gene expressions, ALP activity, and mineralization ability in DEX-induced MSCs were determined. At last, protein levels of p-Smad1/5/9 and total-Smad1/5/9 influenced by DEX and PVL were measured by Western blot. RESULTS: PVL treatment did not pose a time- or dose-dependent influence on MSCs viability. DEX induction in MSCs downregulated ALP, RUNX2, Bglap, and Osterix. ALP activity and mineralization in DEX-induced MSCs were suppressed. Downregulated osteogenesis-related genes decreased ALP activity and mineralization in MSCs undergoing DEX stimulation were partially reversed by PVL treatment. Moreover, the downregulated p-Smad1/5/9 level in DEX-induced MSCs was elevated by PVL treatment, while total-Smad1/5/9 was not affected. CONCLUSIONS: PVL alleviated GC-induced suppression in MSCs osteogenesis by activating the Smad pathway, thereafter, protecting the deterioration of OP.

Bone morphogenetic protein 2 regulates cell-cell communication by down-regulating connexin43 expression in luteinized human granulosa cells.

STUDY QUESTION: Does bone morphogenetic protein 2 (BMP2) regulate connexin43 (Cx43) and modulate cell-cell communication in luteinized human granulosa cells? SUMMARY ANSWER: BMP2 decreases gap junction intercellular communication (GJIC) of luteinized human granulosa cells by down-regulating Cx43 expression through an activin receptor-like kinase (ALK)2/ALK3-mediated Sma- and Mad-related protein (SMAD)-dependent signaling pathway. WHAT IS KNOWN ALREADY: BMP2 and its putative receptors are highly expressed in the human corpus luteum and are involved in the process of luteolysis. Cx43-coupled gap junctions play a critical role in the development and maintenance of corpus luteum. STUDY DESIGN DURATION: This is a laboratory study conducted over a 1-year period. At least three independent experiments with three replicates were conducted and the experimental samples were compared with the appropriate vehicle controls for all of the inhibition-approach, concentration-dependent or time-course studies. PARTICIPANTS/MATERIALS, SETTING, METHODS: SVOG cell line (immortalized human granulosa-lutein cells derived from in vitro fertilization patients in an academic research center) was used as the study model. The changes of Cx43 expression and levels of phosphorylated SMAD1/5/8 protein were evaluated after exposure to recombinant human BMP2. Real-time quantitative PCR and Western blot analysis were used to examine the specific mRNA and protein levels, respectively. The BMP/TGF-ß type I receptor inhibitors (Dorsomorphin, DMH-1 and SB431542) and target depletion small interfering RNAs (ALK2, ALK3, ALK6 and SMAD4) were used to investigate the underlying molecular mechanisms. A scrape loading and dye transfer assay was used to evaluate the GJIC between the SVOG cells. MAIN RESULTS AND THE ROLE OF CHANCE: Treatment with BMP2 down-regulated the expression of Cx43 and decreased the GJIC activity, whereas it increased the phosphorylated SMAD1/5/8 protein in SVOG cells (P < 0.05). These biological effects were abolished by pre-treatment with the BMP type I receptor inhibitors, Dorsomorphin and DMH-1 (P < 0.05), but not SB431542. Additionally, the individual or concomitant small interfering RNA-mediated knockdown of ALK2 and ALK3, but not ALK6 attenuated the BMP2-induced increases in phosphorylated SMAD1/5/8 and down-regulation of Cx43 expression (P < 0.05). The knockdown of SMAD4 completely abolished the BMP2-induced down-regulation of Cx43 expression (P < 0.05). LIMITATIONS REASONS FOR CAUTION: This experimental study was conducted in an in vitro cell culture system, and may not reflect a realistic intra-ovarian environment. WIDER IMPLICATIONS OF THE FINDINGS: Our results suggested that BMP2 may be involved in the local modulation of cell-cell communication in the luteal phase. This study also represents the first comprehensive research of molecular mechanisms of BMP2 in the down-regulation Cx43 in luteinized human granulosa cells. Such data may provide valuable insights into ovarian physiology and benefit the development of potential therapeutic methods for patients suffering from luteal insufficiency. LARGE SCALE DATA: N/A. STUDY FUNDING AND COMPETING INTEREST(s): This research was supported by an operating grant from the China-Canadian Joint Health Research Initiative Grants Program to P.C.K. Leung and J.Z. Sheng. The authors declare no competing interest with the contents of this article.

Exogenous cytochrome c inhibits the expression of transforming growth factor-ß1 in a mouse model of sepsis-induced myocardial dysfunction via the SMAD1/5/8 signaling pathway.

The current study investigated the role of exogenous cytochrome c in sepsis-induced myocardial dysfunction (SIMD) using a mouse model and aimed to elucidate its effect on transforming growth factor-ß1 (TGF-ß1) expression during this process. A total of 75 male Kunming mice were randomly divided into the following five group: Normal (N, n=15); sham-operation (SHAM, n=15); sepsis (CLP, n=15); normal saline (NS, n=15); and cytochrome c (Cytc, n=15). Animals were sacrificed at 0, 6 or 12 h and the samples were analyzed using transmission electron microscopy, histopathological examination, reverse transcription-quantitative polymerase chain reaction, ELISA, protein analysis by western blotting. The SIMD model was developed and a significant downregulation of TGF-ß1 gene expression, in addition to a reduction in the plasma and protein levels of TGF-ß1 as well as the protein levels of TGF-ß1-activated SMAD 1/5/8 were observed in the CLP group. The data from the current study indicate that using exogenous cytochrome c as a therapeutic strategy for SIMD is feasible, and may function via the downregulation of TGF-ß1 expression through the SMAD 1/5/8 signaling pathway.