Mitochondrial permeabilization without caspase activation mediates the increase of basal apoptosis in cells lacking Nrf2

Abstract

Nuclear factor E2-related factor-2 (Nrf2) is a cap’n’collar/basic leucine zipper (b-ZIP) transcription factor which acts as sensor of oxidative and electrophilic stress. Low levels of Nrf2 predispose cells to chemical carcinogenesis but a dark side of Nrf2 function also exists because its unrestrained activation may allow the survival of potentially dangerous damaged cells. Since Nrf2 inhibition may be of therapeutic interest in cancer, and a decrease of Nrf2 activity may be related with degenerative changes associated with aging, it is important to investigate how the lack of Nrf2 function activates molecular mechanisms mediating cell death. Murine Embryonic Fibroblasts (MEFs) bearing a Nrf2 deletion (Nrf2KO) displayed diminished cellular growth rate and shortened lifespan compared with wild-type MEFs. Basal rates of DNA fragmentation and histone H2A.X phosphorylation were higher in Nrf2KO MEFs, although steady-state levels of reactive oxygen species were not significantly increased. Enhanced rates of apoptotic DNA fragmentation were confirmed in liver and lung tissues from Nrf2KO mice. Apoptosis in Nrf2KO MEFs was associated with a decrease of Bcl-2 but not Bax levels, and with the release of the mitochondrial pro-apoptotic factors cytochrome c and AIF. Procaspase-9 and Apaf-1 were also increased in Nrf2KO MEFs but caspase-3 was not activated. Inhibition of XIAP increased death in Nrf2KO but not in wild-type MEFs. Mitochondrial ultrastructure was also altered in Nrf2KO MEFs. Our results support that Nrf2 deletion produces mitochondrial dysfunction associated with mitochondrial permeabilization, increasing basal apoptosis through a caspase-independent and AIF-dependent pathway.

Kaempferol increases levels of coenzyme Q in kidney cells and serves as a biosynthetic ring precursor

“…Whole lysates were prepared from cells as described by Ariza et al [21] and steady state protein levels were determined by Western blot (see below). Tissues were obtained from Sirt3 knockout mice and their corresponding genetic background-matched controls bred at the Gladstone Institute (San Francisco, CA, USA).…”

“…The procedure was performed as described by Ariza et al [21] with samples of whole cell extracts (50 μg of protein) applied per gel lane. The following primary antibodies were used: Anti-Sirt3 (Santa Cruz Biotechnology, Inc) at 1:1000 dilution, anti-acetyl lysine (Cell Signaling) at 1:1000 dilution, and anti-Coq2 [25] at 1:1000 dilution.…”

Atorvastatin induces mitochondrial dysfunction and cell apoptosis in HepG2 cells via inhibition of the Nrf2 pathway

“…In addition, activation of the Nrf2/HO‐1 pathway by pinocembrin suppressed H 2 O 2 ‐induced mitochondrial dysfunction in SH‐SY5Y cells by preventing mitochondria‐related redox and bioenergetic impairments (de Oliveira, da Costa Ferreira, Brasil, & Peres, ). Also consistent with the protective efficacy of Nrf2 activation, murine embryonic fibroblasts harboring a Nrf2 deletion (Nrf2 knockout) exhibited increased basal apoptosis associated with reduced Bcl‐2 expression and enhanced release of mitochondrial cytochrome c (Ariza et al, ).…”

Aluminum Exposure from Parenteral Nutrition: Early Bile Canaliculus Changes of the Hepatocyte

“…Oxidative stress is responsible for the production of proinflammatory cytokines, produced by lymphocytes and Kupffer cells, among which tumor necrosis factor alpha, transforming growth factors alpha and beta, interleukins 6 and 8, nuclear factor-kappa B, and adiponectin are prominent. In mitochondrial cardiomyopathies, these cytokines are produced through free radical-mediated mechanisms, by altering mitochondrial membrane permeability and inhibiting the respiratory chain with a mechanism that seems to be ubiquitous for several cell types [ 36 , 37 , 38 , 39 , 40 , 41 , 42 ].…”