ass=""h4"">Aims
Hypoxi
a,
acidosis
and progr
ammed cell de
ath
are e
ach h
allm
arks of
acute myoc
ardi
al inf
arction (AMI). We previously described
a de
ath p
athw
ay of c
ardi
ac myocytes medi
ated by hypoxi
a-
acidosis th
at w
as ch
ar
acterized by
activ
ation of the Bcl2-f
amily protein Bnip3
and progr
ammed necrosis. The p
athw
ay included extensive DNA fr
agment
ation th
at w
as sensitive to inhibition of the mitochondri
al perme
ability tr
ansition pore (mPTP)
and c
alp
ain inhibitors, but not c
asp
ase inhibitors. We did not identify the DN
ases responsible for DNA cle
av
age.
ass=""h4"">Main methods
Neonatal rat cardiomyocytes were subjected to hypoxia with and without concurrent acidosis, and the cellular localization of apoptosis-inducing factor (AIF), DNase II and caspase-dependent DNase (CAD) were determined.
ass=""h4"">Key findings
Here we report the occurrence of biphasic pH-dependent translocations of AIF and DNase II but no change in CAD or its inhibitor ICAD. AIF co-localized with the mitochondria under aerobic and hypoxia-neutral conditions but translocated to the nucleus at pH ~ 6.7 coincident with a decrease of the mitochondrial membrane potential. DNase II co-localized with lysosomes under normoxia and hypoxia-neutral conditions, and translocated to the nucleus at pH ~ 6.1 coincident with the appearance of single strand DNA cuts. Inhibition of the mPTP pore with BH4-TAT peptide, calpain inhibition with PD150606, or knockdown (KD) of Bnip3 failed to prevent nuclear translocation of these DNase although Bnip3 KD blocked mitochondrial fission.
ass=""h4"">Significance
These results suggest that caspase-independent DNA fragmentation is precisely regulated and occurs in parallel but independently from programmed necrosis mediated by hypoxia-acidosis.
