title: Avenanthramides Prevent Osteoblast and Osteocyte Apoptosis and Induce Osteoclast Apoptosis in Vitro in an Nrf2-Independent Manner.
abstract: Oats contain unique bioactive compounds known as avenanthramides (AVAs) with antioxidant properties. AVAs might enhance the endogenous antioxidant cellular response by activation of the transcription factor Nrf2. Accumulation of reactive oxygen species plays a critical role in many chronic and degenerative diseases, including osteoporosis. In this disease, there is an imbalance between bone formation by osteoblasts and bone resorption by osteoclasts, which is accompanied by increased osteoblast/osteocyte apoptosis and decreased osteoclast apoptosis. We investigated the ability of the synthethic AVAs 2c, 2f and 2p, to 1-regulate gene expression in bone cells, 2-affect the viability of osteoblasts, osteocytes and osteoclasts, and the generation of osteoclasts from their precursors, and 3-examine the potential involvement of the transcription factor Nrf2 in these actions. All doses of AVA 2c and 1 and 5 µM dose of 2p up-regulated collagen 1A expression. Lower doses of AVAs up-regulated OPG (osteoprotegerin) in OB-6 osteoblastic cells, whereas 100 μM dose of 2f and all concentrations of 2c down-regulated RANKL gene expression in MLO-Y4 osteocytic cells. AVAs did not affect apoptosis of OB-6 osteoblastic cells or MLO-Y4 osteocytic cells; however, they prevented apoptosis induced by the DNA topoisomerase inhibitor etoposide, the glucocorticoid dexamethasone, and hydrogen peroxide. AVAs prevented apoptosis of both wild type (WT) and Nrf2 Knockout (KO) osteoblasts, demonstrating that AVAs-induced survival does not require Nrf2 expression. Further, KO osteoclast precursors produced more mature osteoclasts than WT; and KO cultures exhibited less apoptotic osteoclasts than WT cultures. Although AVAs did not affect WT osteoclasts, AVA 2p reversed the low apoptosis of KO osteoclasts. These in vitro results demonstrate that AVAs regulate, in part, the function of osteoblasts and osteocytes and prevent osteoblast/osteocyte apoptosis and increase osteoclast apoptosis; further, these regulatory actions are independent of Nrf2.
authors.affiliation: Department of Anatomy &amp; Cell Biology, School of Medicine, Indiana University, Indianapolis, IN 46202, USA. gpellegr@iupui.edu.|Roudebush Veterans Administration Medical Center, Indianapolis, IN 46202, USA. gpellegr@iupui.edu.
authors.forename: Gretel G
authors.initials: GG
authors.lastname: Pellegrini
authors.affiliation: Department of Anatomy &amp; Cell Biology, School of Medicine, Indiana University, Indianapolis, IN 46202, USA. moralecy@iupui.edu.
authors.forename: Cynthya C
authors.initials: CC
authors.lastname: Morales
authors.affiliation: Department of Nutrition and Food Studies, George Mason University, Fairfax, VA 22030, USA. taylor.wallace@nof.org.|Think Healthy Group, LLC, Washington, DC 20001, USA. taylor.wallace@nof.org.|National Osteoporosis Foundation, Arlington, VA 22202, USA. taylor.wallace@nof.org.
authors.forename: Taylor C
authors.initials: TC
authors.lastname: Wallace
authors.affiliation: Department of Anatomy &amp; Cell Biology, School of Medicine, Indiana University, Indianapolis, IN 46202, USA. lplotkin@iupui.edu.|Roudebush Veterans Administration Medical Center, Indianapolis, IN 46202, USA. lplotkin@iupui.edu.
authors.forename: Lilian I
authors.initials: LI
authors.lastname: Plotkin
authors.affiliation: Department of Anatomy &amp; Cell Biology, School of Medicine, Indiana University, Indianapolis, IN 46202, USA. tbellido@iupui.edu.|Roudebush Veterans Administration Medical Center, Indianapolis, IN 46202, USA. tbellido@iupui.edu.|Department of Medicine, Division of Endocrinology, School of Medicine, Indiana University, Indianapolis, IN 46202, USA. tbellido@iupui.edu.
authors.forename: Teresita
authors.initials: T
authors.lastname: Bellido
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000138:chemical synthesis / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D018554:Avena / Q000737:chemistry*; D002454:Cell Differentiation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D051267:NF-E2-Related Factor 2 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D010006:Osteoblasts / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D010010:Osteoclasts / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D010011:Osteocytes / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D053244:Osteoprotegerin / Q000235:genetics / Q000378:metabolism; D053245:RANK Ligand / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D062367:ortho-Aminobenzoates / Q000138:chemical synthesis / Q000494:pharmacology*
chemical_list: D000975:Antioxidants; D051267:NF-E2-Related Factor 2; C495636:Nfe2l2 protein, mouse; D053244:Osteoprotegerin; D053245:RANK Ligand; C506031:Tnfrsf11b protein, mouse; C505689:Tnfsf11 protein, mouse; D062367:ortho-Aminobenzoates; C514463:avenanthramide-2C
keywords: apoptosis; avenanthramides; bone cells; gene expression; oxidative stress