title: Inhibition of NADPH oxidases prevents chronic ethanol-induced bone loss in female rats.
abstract: Previous in vitro data suggest that ethanol (EtOH) activates NADPH oxidase (Nox) in osteoblasts leading to accumulation of reactive oxygen species (ROS). This might be a mechanism underlying inhibition of bone formation and increased bone resorption observed in vivo after EtOH exposure. In a rat model in which cycling females were infused intragastrically with EtOH-containing liquid diets, EtOH significantly decreased bone formation and stimulated osteoblast-dependent osteoclast differentiation. These effects were reversed by exogenous 17-β-estradiol coadministration. Moreover, coadministration of N-acetyl cysteine (NAC), an antioxidant, or diphenylene iodonium (DPI), a specific Nox inhibitor, also abolished chronic EtOH-associated bone loss. EtOH treatment up-regulated mRNA levels of Nox1, 2, 4, and the receptor activator of nuclear factor-κB ligand (RANKL), an essential factor for differentiation of osteoclasts in bone. Protein levels of Nox4, a major Nox isoform expressed in nonphagocytic cells, was also up-regulated by EtOH in bone. 17-β-Estradiol, NAC, and DPI were able to normalize EtOH-induced up-regulation of Nox and RANKL. In vitro experiments demonstrated that EtOH directly up-regulated Nox expression in osteoblasts. Pretreatment of osteoblasts with DPI eliminated EtOH-induced RANKL promoter activity. Furthermore, EtOH induced RANKL gene expression, and RANKL promoter activation in osteoblasts was ROS-dependent. These data suggest that inhibition of Nox expression and activity may be critical for prevention of chronic EtOH-induced osteoblast-dependent bone loss.
authors.affiliation: Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, AR, USA.
authors.forename: Jin-Ran
authors.initials: JR
authors.lastname: Chen
authors.forename: Oxana P
authors.initials: OP
authors.lastname: Lazarenko
authors.forename: Kartik
authors.initials: K
authors.lastname: Shankar
authors.forename: Michael L
authors.initials: ML
authors.lastname: Blackburn
authors.forename: Charles K
authors.initials: CK
authors.lastname: Lumpkin
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Badger
authors.forename: Martin J J
authors.initials: MJ
authors.lastname: Ronis
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology / Q000627:therapeutic use; D000818:Animals; D001862:Bone Resorption / Q000139:chemically induced / Q000201:enzymology* / Q000517:prevention & control*; D002460:Cell Line; D004791:Enzyme Inhibitors / Q000494:pharmacology / Q000627:therapeutic use; D004958:Estradiol / Q000494:pharmacology / Q000627:therapeutic use; D000431:Ethanol / Q000633:toxicity*; D005260:Female; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D009861:Onium Compounds / Q000494:pharmacology / Q000627:therapeutic use; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D009861:Onium Compounds; D017382:Reactive Oxygen Species; D000431:Ethanol; D004958:Estradiol; C007517:diphenyleneiodonium; D019255:NADPH Oxidases; D000111:Acetylcysteine