Abstract 18559: Inhibition of Mitochondrial Fission as a Novel Molecular Target to Attenuate Myocardial Ischemia-Reperfusion Injury: Critical Importance of the Timing of Treatment
Background: Mitochondrial fragmentation (i.e., fission) has been implicated as: (i) a critical determinant of myocyte viability and, thus (ii) a potential molecular target for novel cardioprotective therapies. This concept is based on evidence that inhibition of fission, achieved by pharmacologic or genetic manipulation of DRP1 (dynamin-related protein 1: the key molecular regulator of fission) attenuates lethal myocardial ischemia-reperfusion injury. However, all studies have implemented treatment/genetic silencing as a pre-treatment; the effect of inhibition of fission, initiated in a therapeutically relevant manner (at reoxygenation) has, to date, not been explored.
Methods: To address this issue, cultured HL-1 cells underwent 2 hrs of hypoxia + reoxygenation (R). Cells were given: (i) mdivi-1 (specific DRP1 inhibitor; 50 μM) 1 hr before hypoxia (pre-treat); (ii) mdivi-1 (50 μM) at reoxygenation (post-treatment); or (iii) vehicle. Time-matched normoxic cells served as controls. Endpoints included: (i) translocation of DRP1 to mitochondria, assessed at 2 hrs post-R; (ii) expression of cleaved caspase 3 (harbinger of apoptosis), assessed at 2 hrs post-R; and (iii) cell viability quantified by trypan blue staining at 20 hrs post-R.
Results: As expected, pre-treatment with mdivi-1 inhibited translocation of DRP1 to the mitochondria (not shown), attenuated the cleavage of caspase 3 (right: p<0.05), and preserved cell viability (left: p<0.05 vs vehicle). Post-treatment with mdivi-1 had a similar, favorable effect on caspase 3 cleavage (right: p<0.05), but, in contrast, exacerbated cell death (left: p<0.0001 vs vehicle).
Conclusion: We report novel evidence that mdivi-1, given at reoxygenation, has a paradoxical and dissociative effect on apoptotic vs necrotic cell death. Moreover, these data provide initial insight into an apparently complex temporal relationship between inhibition of mitochondrial fission and cardioprotection.
- © 2013 by American Heart Association, Inc.