Inhibition of HSP70 and a collagen-specific molecular chaperone (HSP47) expression in rat osteoblasts by microgravity.
Rat osteoblasts were cultured aboard a space shuttle for 4 or 5 days. Cells were exposed to 1alpha, 25 dihydroxyvitamin D(3) during the last 20 h and then solubilized by guanidine solution. The mRNA levels for molecular chaperones were analyzed by semi-quantitative RT-PCR. ELISA was used to quantify TGF-beta1 in the conditioned medium. The HSP70 mRNA levels in the flight cultures were almost completely suppressed, as compared to the ground (1 x g) controls. The inducible HSP70 is known as the major heat shock protein that prevents stress-induced apoptosis. The mean mRNA levels for the constitutive HSC73 in the flight cultures were reduced to 69%, approximately 60% of the ground controls. HSC73 is reported to prevent the pathological state that is induced by disruption of microtubule network. The mean HSP47 mRNA levels in the flight cultures were decreased to 50% and 19% of the ground controls on the 4th and 5th days. Concomitantly, the concentration of TGF-beta1 in the conditioned medium of the flight cultures was reduced to 37% and 19% of the ground controls on the 4th and 5th days. HSP47 is the collagen-specific molecular chaperone that controls collagen processing and quality and is regulated by TGF-beta1. Microgravity differentially modulated the expression of molecular chaperones in osteoblasts, which might be involved in induction and/or prevention of osteopenia in space.
Kumei
Yasuhiro
Y
Graduate School of Tokyo Medical and Dental University, Tokyo 113-8549, Japan. kumei.bch@tmd.ac.jp
Morita
Sadao
S
Shimokawa
Hitoyata
H
Ohya
Kei'ichi
K
Akiyama
Hideo
H
Hirano
Masahiko
M
Sams
Clarence F
CF
Whitson
Peggy A
PA
D000818:Animals; D001483:Base Sequence; D002117:Calcitriol / Q000494:pharmacology; D002478:Cells, Cultured; D003094:Collagen; D017931:DNA Primers; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D050958:HSP47 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics*; D006360:Heat-Shock Proteins / Q000235:genetics*; D008297:Male; D010006:Osteoblasts / Q000187:drug effects / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic / Q000187:drug effects / Q000235:genetics; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D014893:Weightlessness
D017931:DNA Primers; D050958:HSP47 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D012333:RNA, Messenger; C494662:Serpinh1 protein, rat; D016212:Transforming Growth Factor beta; D003094:Collagen; D002117:Calcitriol