title: HIF-1α-induced HSP70 regulates anabolic responses in articular chondrocytes under hypoxic conditions.
abstract: We assessed whether heat shock protein 70 (HSP70) is involved in hypoxia inducible factor 1 alpha (HIF-1α)-dependent anabolic pathways in articular chondrocytes under hypoxic conditions. Primary rabbit chondrocytes were cultured under normoxia (20% oxygen condition) or hypoxia (1% oxygen condition). Alternatively, cells cultured under normoxia were treated with CoCl2 , which induces HIF-1α, to simulate hypoxia, or transfected with siRNAs targeting HIF-1α (si-HIF-1α) and HSP70 (si-HSP70) under hypoxia. HSP70 expression was enhanced by the increased expression of HIF-1α under hypoxia or simulated hypoxia, but not in the presence of si-HIF-1α. Hypoxia-induced overexpression of ECM genes was significantly suppressed by si-HIF-1α or si-HSP70. Cell viability positively correlated with hypoxia, but transfection with si-HIF-1α or si-HSP70 abrogated the chondroprotective effects of hypoxia. Although LDH release from sodium nitroprusside-treated cells and the proportion of TUNEL positive cells were decreased under hypoxia, transfection with si-HIF-1α or si-HSP70 almost completely blocked these effects. These findings indicated that HIF-1α-induced HSP70 overexpression increased the expression levels of ECM genes and cell viability, and protected chondrocytes from apoptosis. HIF-1α may regulate the anabolic effects of chondrocytes under hypoxic conditions by regulating HSP70 expression.
authors.affiliation: Department of Orthopaedics, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan.
authors.forename: Shinji
authors.initials: S
authors.lastname: Tsuchida
authors.forename: Yuji
authors.initials: Y
authors.lastname: Arai
authors.forename: Kenji A
authors.initials: KA
authors.lastname: Takahashi
authors.forename: Tsunao
authors.initials: T
authors.lastname: Kishida
authors.forename: Ryu
authors.initials: R
authors.lastname: Terauchi
authors.forename: Kuniaki
authors.initials: K
authors.lastname: Honjo
authors.forename: Shuji
authors.initials: S
authors.lastname: Nakagawa
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Inoue
authors.forename: Kazuya
authors.initials: K
authors.lastname: Ikoma
authors.forename: Keiichiro
authors.initials: K
authors.lastname: Ueshima
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Matsuki
authors.forename: Osam
authors.initials: O
authors.lastname: Mazda
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Kubo
mesh_terms: D000332:Aerobiosis / Q000187:drug effects; D000818:Animals; D002358:Cartilage, Articular / Q000187:drug effects / Q000378:metabolism; D015687:Cell Hypoxia / Q000502:physiology*; D002470:Cell Survival; D002478:Cells, Cultured; D019902:Chondrocytes / Q000187:drug effects / Q000378:metabolism*; D003035:Cobalt / Q000494:pharmacology; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000096:biosynthesis / Q000502:physiology*; D008297:Male; D034741:RNA, Small Interfering / Q000494:pharmacology; D011817:Rabbits
chemical_list: D018840:HSP70 Heat-Shock Proteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D034741:RNA, Small Interfering; D003035:Cobalt; C018021:cobaltous chloride
keywords: apoptosis; extracellular matrix; heat shock protein 70; hypoxia; hypoxia-inducible factor-1α