Location: Arkansas Children's Nutrition CenterTitle: A crucial role for ethanol-induced oxidative stress in controlling lineage commitment of mesenchymal stromal cells through Inhibition of Wnt / Beta-catenin Signaling Author
Submitted to: American Society for Bone and Mineral Research
Publication Type: Abstract Only
Publication Acceptance Date: 7/9/2009
Publication Date: 9/17/2009
Citation: Chen, J., Lazarenko, O.P., Shankar, K., Blackburn, M.L., Badger, T.M., Ronis, M.J. 2009. A crucial role for ethanol-induced oxidative stress in controlling lineage commitment of mesenchymal stromal cells through inhibition of Wnt / beta-catenin signaling [abstract]. Journal of Bone and Mineral Research. 24(Suppl 1). Available: http://www.asbmr.org/Meetings/AnnualMeeting/AbstractDetail.aspx?aid=51d4e88b-f79d-47e2-a15b-134f0c57b52e. Program No. SA 0191. Interpretive Summary:
Technical Abstract: The mechanisms by which chronic ethanol intake induces bone loss remain largely unclear. Especially in females, skeletal response to ethanol may vary depending on the physiologic status (viz. cycling, pregnancy, lactation). Nonetheless, ethanol-induced oxidative stress appears to be the key event leading to skeletal toxicity. In the current study, we chronically infused EtOH-containing liquid diets (12 g/kg/day) to post-lactational female Sprague-Dawley rat dams for 4 weeks beginning at weaning using total enteral nutrition. EtOH consumption dramatically decreased bone mineral density (BMD) compared to control animals during this period of post-lactational bone rebuilding. EtOH-induced bone loss was completely blocked by co-administration of the antioxidant N-acetylcysteine (NAC) at 1.2 g/kg/d. NAC was able to prevent down-regulation of circulating bone formation markers alkaline phosphatase and osteocalcin in serum and their mRNA expression in bone tissue. PCR array based analyses of Wnt signaling from bone tissue revealed that the majority of Wnt signaling components were down-regulated by chronic EtOH feeding. Real-time PCR confirmed down-regulated mRNA expression in a subset of the Wnt signaling components by EtOH. However, the Wnt antagonist DKK1 was up-regulated by EtOH. Western blot analyses showed that protein expression of the key canonical Wnt signaling molecule, beta-catenin was inhibited while glycogen synthase kinase-3-beta was de-phosphorylated by EtOH in bone and pre-osteoblastic cells. These actions of EtOH were blocked by NAC. Further, our findings indicate that EtOH trans-inactivated TCF/LEF target gene transcription and eliminated beta-catenin nuclear translocation in osteoblasts. Finally, we showed that EtOH reciprocally suppressed osteoblastogenesis and enhanced adipogenesis. All of these effects of EtOH on lineage commitment of mesenchymal stromal cells were eliminated by NAC pre-treatment. These observations suggest that EtOH inhibits bone formation through its novel effects on stimulating oxidative stress leading to suppressed Wnt/beta-catenin signaling, in female post-lactational rats.