Methylprednisolone-induced expression of mitochondrial heat shock protein 60 protects mitochondrial membrane potential in the hypoxic rat liver.
This study investigated the contribution made by mitochondrial heat shock protein (hsp) 60 to methylprednisolone-mediated protection against mitochondrial membrane depolarization under hypoxic conditions. A low-flow hypoxia model was generated in isolated male, fasted, pathogen-free Sprague-Dawley rat livers by reducing perfusate inflow pressure from 10 to 2.5 cm H2O for 2 h. The effects of methylprednisolone on mitochondrial membrane potential and expression of mitochondrial hsp 60 protein and mRNA were determined. We measured mitochondrial membrane potential by imaging rhodamine 123 fluorescence. Induction of mitochondrial hsp 60 was detected using two different anti-hsp 60 antibodies: one against the N-terminal signal sequence, which reacted exclusively with cytoplasmic hsp 60, and one against a different epitope, which reacted with cytoplasmic and mitochondrial hsp 60. In addition, the distribution of hsp 60 mRNA was examined using in situ hybridization. We found that under hypoxic conditions, there was a significant decline in mitochondrial membrane potential that was accompanied by a mild decline in the level of mitochondrial hsp 60, and that cytosolic hsp 60 was translocated into mitochondria. Pretreatment with methylprednisolone inhibited the declines in mitochondrial membrane potential and hsp 60 protein, as well as the translocation of cytosolic hsp 60. This raises the possibility that one way in which methylprednisolone protects the mitochondrial membrane potential under hypoxic conditions is to induce expression of mitochondrial hsp 60.
Motoyama
Satoru
S
Department of Surgery, Akita University School of Medicine, Akita City, Japan. motoyama@doc.med.akita-u.ac.jp
Saito
Satoshi
S
Itoh
Hideaki
H
Minamiya
Yoshihiro
Y
Maruyama
Kiyotomi
K
Okuyama
Manabu
M
Ogawa
Jun-Ichi
J
D000818:Animals; D002458:Cell Fractionation; D018834:Chaperonin 60 / Q000235:genetics*; D005786:Gene Expression Regulation / Q000187:drug effects; D000860:Hypoxia / Q000503:physiopathology*; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D007425:Intracellular Membranes / Q000187:drug effects / Q000502:physiology; D008297:Male; D008775:Methylprednisolone / Q000494:pharmacology*; D008930:Mitochondria, Liver / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley
D018834:Chaperonin 60; D012333:RNA, Messenger; D008775:Methylprednisolone