Acetaminophen (
APAP) overdose, which causes liver injury in animals and humans, activates
c-jun N-terminal kinase (JNK). Although it was shown that the JNK inhibitor
SP600125 effectively reduced
APAP hepatotoxicity, the mechanisms of protection remain unclear. C57Bl/6 mice were treated with 10mg/kg
SP600125 or vehicle (8%
dimethylsulfoxide) 1h before 600mg/kg
APAP administration.
APAP time-dependently induced JNK activation (detected by JNK phosphorylation).
SP600125, but not the vehicle, reduced JNK activation, attenuated mitochondrial Bax translocation and prevented the mitochondrial release of
apoptosis-inducing factor at 4-12h. Nuclear DNA fragmentation,
nitrotyrosine staining, tissue
GSSG levels and liver injury (plasma ALT release and
necrosis) were partially attenuated by the vehicle (-65%) and completely eliminated by
SP600125 (-98%) at 6 and 12h. Furthermore,
SP600125 attenuated the increase of
inducible nitric oxide synthase (iNOS)
mRNA and
protein. However,
APAP did not enhance plasma nitrite+nitrate levels (NO formation);
SP600125 had no effect on this parameter. The
iNOS inhibitor L-NIL did not reduce NO formation or injury after
APAP but prevented NO formation caused by
endotoxin. Since
SP600125 completely eliminated the increase in hepatic
GSSG levels, an
indicator of mitochondrial
oxidant stress, it is concluded that the inhibition of
peroxynitrite was mainly caused by reduced
superoxide formation. Our data suggest that the JNK inhibitor
SP600125 protects against
APAP-induced liver injury in part by attenuation of mitochondrial Bax translocation but mainly by preventing mitochondrial
oxidant stress and
peroxynitrite formation and thereby preventing the
mitochondrial permeability transition pore opening, a key event in
APAP-induced cell
necrosis.