Anabolic and Antiresorptive Modulation of Bone Homeostasis by the Epigenetic Modulator Sulforaphane, a Naturally Occurring Isothiocyanate

Abstract

Bone degenerative pathologies like osteoporosis may be initiated by age-related shifts in anabolic and catabolic responses that control bone homeostasis. Here we show that sulforaphane (SFN), a naturally occurring isothiocyanate, promotes osteoblast differentiation by epigenetic mechanisms. SFN enhances active DNA demethylation via Tet1 and Tet2 and promotes preosteoblast differentiation by enhancing extracellular matrix mineralization and the expression of osteoblastic markers (Runx2, Col1a1, Bglap2, Sp7, Atf4, and Alpl). SFN decreases the expression of the osteoclast activator receptor activator of nuclear factor-B ligand (RANKL) in osteocytes and mouse calvarial explants and preferentially induces apoptosis in preosteoclastic cells via up-regulation of the Tet1/Fas/Caspase 8 and Caspase 3/7 pathway. These mechanistic effects correlate with higher bone volume (ϳ20%) in both normal and ovariectomized mice treated with SFN for 5 weeks compared with untreated mice as determined by microcomputed tomography. This effect is due to a higher trabecular number in these mice. Importantly, no shifts in mineral density distribution are observed upon SFN treatment as measured by quantitative backscattered electron imaging. Our data indicate that the food-derived compound SFN epigenetically stimulates osteoblast activity and diminishes osteoclast bone resorption, shifting the balance of bone homeostasis and favoring bone acquisition and/or mitigation of bone resorption in vivo. Thus, SFN is a member of a new class of epigenetic compounds that could be considered for novel strategies to counteract osteoporosis.

Histone H4 Methyltransferase Suv420h2 Maintains Fidelity of Osteoblast Differentiation

“…Consistent with its functional role in bone cell differentiation, Suv420h2 depletion by siRNA suppresses the maturation potential of MC3T3-E1 pre-osteoblastic cells by reducing Alp activity, ECM mineralization, as well as the expression of osteoblast-related biomarkers (e.g., Ibsp , Col1a1 or Sp7 ). Our finding that Suv420h2 is a positive regulator of osteoblast differentiation complements our previous studies that established the importance of other epigenetic regulators, including the H3K27 methyl transferase EZH2 (4, 5), DNA hydroxymethylases TET1 and TET2 (2, 3), DNA methyl-transferases (29, 30) and histone deacetylases (31). Interestingly, each of these epigenetic regulators are enzymes whose activity can be modulated by natural or synthetic inhibitors that strongly affect the differentiation potential of osteoblasts (2, 3, 6, 12).…”

“…These enzymes may function as pharmacological targets and thus present an enticing opportunity for manipulation of the biological properties of cells during cell growth and differentiation. Recently, we have shown that natural compounds can alter chromatin via active DNA demethylation (2, 3) and that drug-induced inhibition of the H3K27 methyltransferase Ezh2 significantly supports osteoblastic differentiation and bone formation in vitro and in vivo (4, 5). These studies provide proof-of-concept that the activity of epigenetic regulators (EpiRegs) can be leveraged to promote osteogenic lineage progression (6-8), and provide the rationale for investigating the roles of other EpiRegs during osteoblast differentiation.…”

Profiling of human epigenetic regulators using a semi-automated real-time qPCR platform validated by next generation sequencing

“…For example, modulating the activity of histone deacetylases (HDACs), the WD-repeat domain protein WDR5, which is associated with a histone 3 lysine 4 (H3K4) methyltransferase complex, and the H3K9 methyl transferase SUV420H2 can stimulate osteogenic differentiation of MSCs and/or pre-osteoblasts [Di Bernardo et al, 2009; Dudakovic et al, 2013; Farzaneh et al, 2016; Gordon et al, 2015; Gori et al, 2001; Gori et al, 2006; Lee et al, 2009; Schroeder and Westendorf, 2005]. Other studies have demonstrated that suppression of histone 3 lysine 27 trimethylation (H3K27me3) or altering CpG methylation can significantly enhance osteogenic differentiation and inhibit adipogenic differentiation of MSCs [Dudakovic et al, 2016; Dudakovic et al, 2015b; Hemming et al, 2014; Jing et al, 2015; Thaler et al, 2016; Wei et al, 2011]. These studies demonstrate that the epigenetic landscape is deformable to favor selective commitment of mesenchymal stromal/stem cells to the osteogenic lineage.…”

Monocrotaline Suppresses RANKL-Induced Osteoclastogenesis In Vitro and Prevents LPS-Induced Bone Loss In Vivo

“…RANKL is a member of the tumor necrosis factor (TNF) family [11]. Binding of RANKL to RANK results in the recruitment of the TNF receptor-associated factor 6 (TRAF6).…”