title: Transient oxidative stress in SH-SY5Y human neuroblastoma cells results in caspase dependent and independent cell death and tau proteolysis.
abstract: The effects of an oxidative insult on cell survival and tau metabolism were investigated in human neuroblastoma SH-SY5Y cells. In this treatment paradigm cells were exposed to the membrane permeant oxidant tert-butylhydroperoxide (tBHP) for 40 min, returned to fresh media and cell survival/death was monitored during the post-treatment period. Cell viability decreased significantly by 6 hr after tBHP exposure, and by 24 hr lactate dehydrogenase (LDH) release was 40.1 +/- 8.8% in tBHP treated cells compared to 8.1 +/- 4.7% in control cells. This oxidative stress paradigm also resulted in significant activation of caspase-3 by 2 hr post-treatment and nuclear apoptotic morphology. Furthermore, tBHP treatment also resulted in delayed tau proteolysis that was first evident 2 hr post-treatment. Treatment of the cells with the general caspase inhibitor Boc-Asp(OMe)-Fluoromethylketone (BAF) completely inhibited caspase-3 activation in response to tBHP, and delayed, but did not prevent cell death. BAF treatment also decreased tau proteolysis. In vitro, recombinant tau was readily proteolyzed by active recombinant caspase-3 into a stable breakdown product. Further tau in the cell lysates was cleaved by active recombinant caspase-3 at a rate, and to an extent similar to that observed for the well-established caspase-3 substrate poly(ADP-ribose)polymerase (PARP). These results suggest that oxidative stress-induced cell death occurs through both caspase-dependent and-independent pathways, and that tau is likely an in situ substrate of caspase-3.
authors.affiliation: Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, Alabama, USA.
authors.forename: P K
authors.initials: PK
authors.lastname: Krishnamurthy
authors.forename: J L
authors.initials: JL
authors.lastname: Mays
authors.forename: G N
authors.initials: GN
authors.lastname: Bijur
authors.forename: G V
authors.initials: GV
authors.lastname: Johnson
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D002470:Cell Survival / Q000187:drug effects; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D006801:Humans; D006868:Hydrolysis / Q000187:drug effects; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D009336:Necrosis; D009447:Neuroblastoma / Q000378:metabolism* / Q000473:pathology; D018384:Oxidative Stress; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D013379:Substrate Specificity; D014407:Tumor Cells, Cultured; D016875:tau Proteins / Q000378:metabolism*; D020122:tert-Butylhydroperoxide / Q000494:pharmacology
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; C103192:butyloxycarbonyl-O-methyl-aspartyl-fluoromethyl ketone; D016875:tau Proteins; D020122:tert-Butylhydroperoxide; D007770:L-Lactate Dehydrogenase; D011065:Poly(ADP-ribose) Polymerases; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases