Amelioration of Ischemic Mitochondrial Injury and Bax‐Dependent Outer Membrane Permeabilization by Mdivi‐1

AIMS: Disturbance of the balance between mitochondrial fission and fusion has been implicated in cerebral ischemia and several neurodegenerative diseases, whereas the underlying mechanisms remain poorly understood. In the present study, we attempted to investigate the role of dynamin-related protein 1 (Drp1), a key mitochondrial fission protein, in the pathogenesis of cerebral ischemia. METHODS: Using Drp1 siRNA or Mdivi-1, a small molecule inhibitor of Drp1, we examined the effect of Drp1 knockdown or inhibition on oxygen-glucose deprivation (OGD)-induced mitochondrial dysfunction and death of SH-SY-5Y cells. Cell death and viability were evaluated with LDH and MTT assays, respectively, and mitochondrial morphology, mitochondrial membrane potential (Δψm), and ATP production were assessed using epifluorescence microscopy, flow cytometry, and HPLC, respectively. Moreover, to examine the effect of Drp1 inhibition on ischemic brain injury, middle cerebral artery occlusion (MCAO) mice were injected (i.p.) with Mdivi1, and blood-brain barrier permeability, brain water content, and cell apoptosis were assessed. RESULTS: Knockdown or inhibition of Drp1 by Mdivi-1 significantly attenuated OGD-induced cell death in SH-SY-5Y cells, associated with reduced morphological change of mitochondria and attenuated Bax insertion,oligomerization. Moreover, treatment of the MCAO mice with Mdivi-1 remarkably reduced the infarct volume and neurological deficits in a dose-dependent manner, associated with marked reduction of mitochondrial fragmentation and BAX expression. CONCLUSIONS: Down-regulation or inhibition of Drp1 may reduce cerebral ischemic damage through maintaining normal mitochondrial morphology and function, and decreasing Bax insertion and oligomerization in mitochondria.