FoxO-mediated defense against oxidative stress in osteoblasts is indispensable for skeletal homeostasis in mice.
Aging increases oxidative stress and osteoblast apoptosis and decreases bone mass, whereas forkhead box O (FoxO) transcription factors defend against oxidative stress by activating genes involved in free radical scavenging and apoptosis. Conditional deletion of FoxO1, FoxO3, and FoxO4 in 3-month-old mice resulted in an increase in oxidative stress in bone and osteoblast apoptosis and a decrease in the number of osteoblasts, the rate of bone formation, and bone mass at cancellous and cortical sites. The effect of the deletion on osteoblast apoptosis was cell autonomous and resulted from oxidative stress. Conversely, overexpression of a FoxO3 transgene in mature osteoblasts decreased oxidative stress and osteoblast apoptosis and increased osteoblast number, bone formation rate, and vertebral bone mass. We conclude that FoxO-dependent oxidative defense provides a mechanism to handle the oxygen free radicals constantly generated by the aerobic metabolism of osteoblasts and is thereby indispensable for bone mass homeostasis.
Division of Endocrinology and Metabolism, Center for Osteoporosis and Metabolic Bone Diseases, University of Arkansas for Medical Sciences and the Central Arkansas Veterans Healthcare System, Little Rock, AR 72205, USA.
Elena
E
Ambrogini
Maria
M
Almeida
Marta
M
Martin-Millan
Ji-Hye
JH
Paik
Ronald A
RA
Depinho
Li
L
Han
Joseph
J
Goellner
Robert S
RS
Weinstein
Robert L
RL
Jilka
Charles A
CA
O'Brien
Stavros C
SC
Manolagas
D000818:Animals; D017209:Apoptosis; D018797:Cell Cycle Proteins; D002478:Cells, Cultured; D000071161:Forkhead Box Protein O1; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000235:genetics* / Q000378:metabolism*; D017353:Gene Deletion; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism*; D018384:Oxidative Stress; D019076:Transgenes; D015854:Up-Regulation
D018797:Cell Cycle Proteins; C499517:FOXO3 protein, human; D000071161:Forkhead Box Protein O1; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; C474033:FoxO3 protein, mouse; C525394:FoxO4 protein, mouse; C467200:Foxo1 protein, mouse