Prostaglandin expression profile in hypoxic osteoblastic cells.
Conditions such as fracture and unloading have been shown to be associated with tissue and cellular hypoxia in bone. The effects of hypoxia on bone cell physiology and ultimately its impact on bone tissue repair and remodeling are not well understood. In this study, we investigated the role of hypoxia on prostaglandin release from osteoblastic cells cultured in 2% (hypoxia), 5% (potentially cellular normoxia), and 21% (normoxia for standard cell culture conditions) oxygen for up to 24 h. We quantified the effects of reduced oxygen tension on the release of prostaglandin (PG)E(2), PGF(2alpha), PGD(2), and PGI(2). The mechanism by which hypoxia increases PG production was investigated by examining the various regulatory components of the PG biosynthetic pathway. Our data show that PGE(2) levels alone are significantly elevated under hypoxic conditions. Also, we show that cyclooxygenase (COX)-1 and COX-2 play an important role in hypoxia-induced PGE(2) production, possibly via a mechanism involving changes in their respective activity levels under low oxygen conditions. The effect of hypoxia on PGE(2) levels was mimicked by dimethyloxaloglycine, a known activator of the HIF pathway. In addition, we confirmed that HIF-1alpha was stabilized in osteoblastic cells under hypoxia. Taken together these data suggest a role for the HIF pathway in regulation of PGE(2) levels under hypoxic conditions. Previous studies have detected release of prostaglandins from areas of damaged bone, such as a fracture site, and our data may contribute to an understanding of how this release is regulated.
Lee
Christina M
CM
Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California Davis, 1321 Haring Hall, One Shields Ave, Davis, CA 95616, USA.
Genetos
Damian C
DC
Wong
Alice
A
Yellowley
Clare E
CE
D000818:Animals; D016723:Bone Remodeling / Q000502:physiology; D015687:Cell Hypoxia; D002460:Cell Line; D017077:Culture Media, Conditioned / Q000737:chemistry; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D015237:Dinoprost / Q000032:analysis / Q000378:metabolism; D015232:Dinoprostone / Q000032:analysis / Q000378:metabolism*; D011464:Epoprostenol / Q000032:analysis / Q000378:metabolism; D006911:Hydroxyprostaglandin Dehydrogenases / Q000235:genetics / Q000378:metabolism; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000819:agonists / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D010006:Osteoblasts / Q000378:metabolism / Q000502:physiology*; D010100:Oxygen / Q000502:physiology*; D054467:Phospholipases A2 / Q000235:genetics / Q000378:metabolism; D016133:Polymerase Chain Reaction; D015230:Prostaglandin D2 / Q000032:analysis / Q000378:metabolism; D012333:RNA, Messenger; D013997:Time Factors
D017077:Culture Media, Conditioned; D016861:Cyclooxygenase Inhibitors; C497443:Hif1a protein, mouse; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D012333:RNA, Messenger; D015237:Dinoprost; D011464:Epoprostenol; D006911:Hydroxyprostaglandin Dehydrogenases; C035859:15-hydroxyprostaglandin dehydrogenase; D054467:Phospholipases A2; D015232:Dinoprostone; D015230:Prostaglandin D2; D010100:Oxygen