Endogenous heme oxygenase induction is a critical mechanism attenuating apoptosis and restoring microvascular perfusion following limb ischemia/reperfusion.
BACKGROUND
A protective role for endogenous heme oxygenase (HO) in the initiation of remote liver injury after limb ischemia/reperfusion has been established. This study expands on our previous work by investigating the role of endogenous HO on hepatocellular injury, hepatocyte death (necrotic and apoptotic), and microvascular perfusion at protracted post-reperfusion times.


METHODS
Remote liver injury was studied after 1 hour of bilateral hind limb ischemia and 3, 6, or 24 hours of reperfusion in male C57BL6 mice. Inhibition of HO was achieved with the use of chromium mesoporphrin (CrMP). Established intravital videomicroscopy techniques were used to evaluate microvascular perfusion and hepatocyte death. Hepatocellular injury was quantified by serum alanine transaminase. Apoptosis was measured by using DNA laddering, Cell Death ELISA, and caspase-3 activity.


RESULTS
Although significant perfusion deficits and hepatocellular injury/death occurred after 3 hours, progression of hepatocellular death beyond 6 hours was not observed. A transient increase in apoptosis was observed at 6 hours. By 24 hours, microvascular perfusion was completely restored. This lack of progression correlated with increased HO activity, observed throughout the protocol. Administration of CrMP reduced HO activity to sham nonstressed levels, and caused increased microvascular perfusion deficits, hepatocellular injury, and hepatocyte death over 24 hours. The transient increase in apoptosis was increased in duration and magnitude in CrMP-treated animals.


CONCLUSIONS
These results suggest that endogenous HO activity prevents the progression of remote liver injury after limb ischemia/reperfusion.
McCarter
Sarah D
SD
Department of Medical Biophysics, University of Western Ontario, and the London Health Science Centre and Lawson Health Research Institute, London, Ontario, Canada.
Akyea
Thelma G
TG
Lu
Xiangru
X
Bihari
Aurelia
A
Scott
Jeffrey R
JR
Badhwar
Amit
A
Dungey
Alison A
AA
Harris
Kenneth A
KA
Feng
Qingping
Q
Potter
Richard F
RF
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006419:Heme Oxygenase (Decyclizing) / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000502:physiology*; D022781:Hepatocytes / Q000187:drug effects / Q000502:physiology; D006614:Hindlimb / Q000098:blood supply; D008107:Liver Diseases / Q000209:etiology*; D008297:Male; D008652:Mesoporphyrins / Q000494:pharmacology; D051379:Mice; D008833:Microcirculation / Q000187:drug effects / Q000503:physiopathology*; D015427:Reperfusion Injury / Q000150:complications / Q000503:physiopathology*
D004791:Enzyme Inhibitors; D008652:Mesoporphyrins; C427471:chromium mesoporphyrin; D006419:Heme Oxygenase (Decyclizing)