Induction of heat-shock gene expression in postischemic pig liver depends on superoxide generation.
OBJECTIVE
Both hemorrhagic and cardiogenic shock are associated with hepatic shock gene expression at resuscitation. This study investigated the potential role of intravascular superoxide anion as a proximal trigger of heat shock protein gene expression.


METHODS
Preanesthetized pigs were subjected to 120 m of total warm hepatic ischemia. The survival model consisted of warm, total hepatic ischemia and reperfusion (with active portal-systemic bypass) followed by reperfusion and survival for 3 days. Serial hepatic biopsy samples were evaluated for the expression of heat shock protein 72 (HSP-72) messenger RNA (mRNA) by Northern and Western analysis and by in situ RNA hybridization. The possible role of intravascular O2- as a mediator of heat shock response was evaluated by its specific inhibition by the intravenous infusion of recombinant human superoxide dismutase (SOD).


RESULTS
Ischemia for 120 minutes followed by 60 minutes of reperfusion caused accumulation of HSP-72 mRNA. Transcripts were localized to hepatocytes. HSP-72 mRNA was detected neither following ischemia alone nor when SOD was infused for 15 minutes at reperfusion. Three days later, transcripts were not detectable, but HSP-72 protein accumulated irrespective of SOD administration.


CONCLUSIONS
Warm hepatic ischemia induces the hepatocyte expression of HSP-72 at reperfusion by a mechanism that is dependent upon the superoxide anion, probably generated intravascularly. However, the transient dismutation of superoxide is insufficient to suppress subsequent accumulation of HSP-72.
Schoeniger
L O
LO
Department of Surgery, Johns Hopkins Medical Institutions, Baltimore, Maryland.
Andreoni
K A
KA
Ott
G R
GR
Risby
T H
TH
Bulkley
G B
GB
Udelsman
R
R
Burdick
J F
JF
Buchman
T G
TG
D000818:Animals; D001483:Base Sequence; D005786:Gene Expression Regulation; D006360:Heat-Shock Proteins / Q000235:genetics*; D007511:Ischemia / Q000235:genetics* / Q000378:metabolism* / Q000628:therapy; D008099:Liver / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D008102:Liver Circulation; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D015424:Reperfusion; D013481:Superoxides / Q000378:metabolism*; D013552:Swine; D014158:Transcription, Genetic
D006360:Heat-Shock Proteins; D015345:Oligonucleotide Probes; D012333:RNA, Messenger; D013481:Superoxides