Oxidative stress triggers neuronal caspase-independent death: Endonuclease G involvement in programmed cell death-type III

Abstract

To characterize neuronal death, primary cortical neurons (C57/Black 6 J mice) were exposed to hydrogen peroxide (H2O2) and staurosporine. Both caused cell shrinkage, nuclear condensation, DNA fragmentation and loss of plasma membrane integrity. Neither treatment induced caspase-7 activity, but caspase-3 was activated by staurosporine but not H2O2. Each treatment caused redistribution from mitochondria of both endonuclease G (Endo G) and cytochrome c. Neurons knocked down for Endo G expression using siRNA showed reduction in both nuclear condensation and DNA fragmentation after treatment with H2O2, but not staurosporine. Endo G suppression protected cells against H2O2-induced cell death, while staurosporine-induced death was merely delayed. We conclude that staurosporine induces apoptosis in these neurons, but severe oxidative stress leads to Endo G-dependent death, in the absence of caspase activation (programmed cell death-type III). Therefore, oxidative stress triggers in neurons a form of necrosis that is a systematic cellular response subject to molecular regulation.

Oxidative stress impairs autophagic flux in prion protein-deficient hippocampal cells

“…This result is somewhat consistent with the previous finding that H 2 O 2 treatment leads to ENDOG-dependent death but not CASP3 activation at an early time point in primary cortical neurons. 56 Unexpectedly, we found that Prnp 0/0 cells were less sensitive to apoptosis at later time points after treatment with H 2 O 2 than Prnp +/+ cells. This result suggests that the presence of PrP C may promote CASP3-dependent apoptosis during H 2 O 2 -induced oxidative stress.…”

Repeated mild traumatic brain injury: potential mechanisms of damage

“…122 Acute increases in protein nitration 125 and DNA damage 123 can also occur following TBI, while excessive ROS may also trigger caspase-dependent 126 and -independent cell death pathways. 127 In a repeated moderate WD study, increases in reduced glutathione/oxidized glutathione, and nitrate and nitrite stressors, together with decreases in the antioxidant ascorbic acid were observed 48 h after final injury, when 2 moderate TBIs were given 1-3, but not 5 d apart. 119 While studies are limited, these findings provide further support for an acute temporal period of compromised cellular defenses in the brain, with modulation of oxidative and nitrosative stressors by injury interval and a cumulative effect of increased ROS production following repeated moderate TBI implicating oxidative stress in the proposed window of vulnerability.…”

Oxidative Stress: Emerging Mitochondrial and Cellular Themes and Variations in Neuronal Injury

“…B) Under chronic oxidative stress, at relatively low intensity, neurons tend to undergo apoptosis, while autophagy proceeds it is not necessarily liked to the death outcome, but rather is a cellular defense mechanism. This condition can be replicated by treatment of cells with standard apoptosis inducers such as staurosporine (Higgins GC and Nagley P, unpublished observations) C) Under acute oxidative stress at moderate intensity cells undergo programmed necrosis [87], as well as autophagy that in part contributes to the death outcome. Note that the autophagic pathways in conditions B and C may not be mechanistically identical.…”

“…Knockdown of these proteins via short interfering RNA (siRNA) protects these cells from paraquat treatment. Translocation of Bax and Bak to the OMM initiates outer mitochondrial membrane permeabilization (OMMP), resulting in the redistribution of pro-apoptotic factors from the mitochondrial IMS, such as cyt c, Smac/DIABLO and HtrA2/Omi which are essential for the activation of downstream effector caspase-3 and caspase-7, ultimately leading to neuronal cell death [86][87][88].…”