Journal of Cell Science & Therapy
Open Access
ISSN: 2157-7013
+44 1300 500008
ISSN: 2157-7013
+44 1300 500008
Stephen J. Beebe
Scientific Tracks Abstracts: J Cell Sci Ther
Nanosecond pulsed electric fi eld (nsPEF) ablation induces apoptosis markers in several cell types, but cell death pathways have not been fully defi ned. To defi ne extrinsic or intrinsic apoptosis mechanisms we investigated wildtype human Jurkat cells (WT) and mutants with defi ciencies in FADD or caspase-8. While Fas receptor activation resulted in cell death in WT only, nsPEFs induced cell death (~90%) in these clones with identical electric fi eld dependences. Under lethal conditions there were immediate (≤1 min) increases in propidium iodide uptake, Annexin-V-binding, calcium mobilization and a decrease in mitochondria membrane potential (ΔΨm). Th e ΔΨm occurred even with absences of calcium or sodium ions and was insensitive to overexpression of Bcl-2 or Bcl-xl. Bid cleavage, but not cytochrome c release, was attenuated by inhibition of caspases and calpains. Caspase isozymes were selectively activated (-9>-3>>-8) and late appearances of Histone 2AX phosphorylation and TUNEL-positive cells were caspase- dependent. Electric fi eld-dependent cell death was attenuated in APAF-1 defi cient Jurkat cells, which did not express active caspase-9 or -3 or exhibit DNA damage, but was unaff ected by cathepsin B inhibitors. Taken together, these data indicate that mitochondria are primary targets of nsPEFs, which immediately decrease ΔΨm, leading to cytochrome c release, intrinsic apoptosome-mediated caspase activation with down-stream calpain- and caspase-mediated Bid cleavage and caspase-dependent DNA damage. Th ese results indicate an unabated impact of nsPEFs on Jurkat cell mitochondria and caspase-dependent cell demise at lower electric fi elds with additional, undefi ned cell death mechanisms at higher electric fi elds. Th ese fi ndings have important implication for nsPEF ablation of cancer.
Stephen J. Beebe received his PhD (1982) in Medical Sciences from the Medical College of Ohio, (now University of Toledo- College of Medicine). He was a post-doctoral fellow at the Howard Hughes Medical Institute and Department of Molecular Physiology and Biophysics at Vanderbilt University, Nashville. He was Fulbright and Marshall Scholar at the University of Oslo, Department of Medical Biochemistry and National Hospital before becoming an Assistant and Associate Professor in Department of Physiological Sciences and Pediatrics at Eastern Virginia Medical School in Norfolk, Virginia. He is now a Professor at Old Dominion University in the Frank Reidy Research Center for Bioelectrics in Norfolk