Inhibition of mitochondrial fission inhibits replication of glioblastoma cells and increases mitochondrial mass but has no effect on cell death

PODEROS, JJ; REBAGLIATI, I; CARRERAS, MC; VILLALBA, N; BLANCO, G.A.

Congreso; XI REUNIÓN ANUAL DE LA SOCIEDAD ARGENTINA DE INVESTIGACIÓN CLÍNICA (SAIC); 2016

During cell replication (CR), mitochondria must provide the energeticrequirements of G1 and S phases, and further split between the daughter cells.Thus, blocking fission can have detrimental effects on tumour cellsreplication; while, a persistent mitochondrial fusion can lead to reactiveoxygen species overproduction and initiation of apoptosis. We evaluated theeffect of Mdivi1, a mitochondrial fission inhibitor, on U87 and HeLa cells overCR, mitochondrial mass (MM), and cell death by flow cytometry or fluorescencemicroscopy. CR was evaluated by DNA content with propidium iodide (PI), MM bystaining mitochondrial cardiolipin with nonyl-acridine-orange (NAO),mitochondrial membrane potential with tetra-methyl-rhodamine-esther, and cellviability was determined by staining cells with PI. Mdivi1 at 25-100 μM inducedfusion of the mitochondrial network of U87 cells at 24-72h. The round-shapedmitochondria of untreated cells were progressively lost and replaced withelongated thread-like shapes (p<0.001 for the difference of roundness indexbetween Mdivi1-treated and basal cells). In cells treated with 100μM Mdivi1,donut-shaped mitochondria were also noted. Mdivi1 at 25-75 μM had no effect oncell viability at 48h in U87 or HeLa cells; however, the MM was significantlyincreased (p<0.001). At 72h, while U87 cells showed no change in viability,HeLa cells were all dead. DNA content analysis showed a progressive accumulation of U87 cells in S  and G2/M phases with increasing Mdivi1 doses(5.6 and 18.4%  for basal and 50μM Mdivi1in G2 phase and 33.4% and 42.6% for basal and 50μM Mdivi1 in S phase, respectively). Cells arrested in S andG2 phase showed increased MM. We conclude that blocking of mitochondrialfission in U87 cells inhibits CR probably owing to impairment of the normalsplit of mitochondria to daughter cells. The differential susceptibility between U87 and HeLa cells to theincrease in MM may be due to the different extent of OXPHOS and glycolysis usage