Bcl‐2 protects TK6 cells against hydroquinone‐induced apoptosis through PARP‐1 cytoplasm translocation and stabilizing mitochondrial membrane potential

Abstract

B cell leukemia/lymphoma-2 (Bcl-2) suppresses apoptosis by binding the BH3 domain of proapoptotic factors and thereby regulating mitochondrial membrane potential (MMP). This study aimed to investigate the role of Bcl-2 in controlling the mitochondrial pathway of apoptosis during hydroquinone (HQ)-induced TK6 cytotoxicity. In this study, HQ, one metabolite of benzene, decreased the MMP in a concentration-dependent manner and induced the generation of reactive oxygen species (ROS), the activation of the DNA damage marker g-H2AX, and production of the DNA damage-responsive enzyme poly(ADP-ribose)polymerase-1 (PARP-1). Exposure of TK6 cells to HQ leads to an increase in Bcl-2 and colocalization with PARP-1 in the cytoplasm. Inhibition of Bcl-2 using the BH3 mimetic, ABT-737, suppressed the PARP-1 nuclear to cytoplasm translocation and sensitized TK6 cells to HQ-induced apoptosis through depolarization of the MMP. Western blot analysis indicated that ABT-737 combined with HQ increased the levels of cleaved PARP and g-H2AX, but significantly decreased the level of P53. Thus, ABT-737 can influence PARP-1 translocation and induce apoptosis via mitochondria-mediated apoptotic pathway, independently of P53. In addition, we found that knockdown of PARP-1 attenuated the HQ-induced production of cleaved PARP and P53. These results identify Bcl-2 as a protective mediator of HQ-induced apoptosis and show that upregulation of Bcl-2 helps to localize PARP-1 to the cytoplasm and stabilize MMP. Environ. Mol. Mutagen. 59:49-59, 2018.V C 2017 Wiley Periodicals, Inc.

Apoptosis regulation by subcellular relocation of caspases

“…3a , cyt). These translocation events have already been reported in response to a range of apoptotic, as wells as other, stress stimuli 27 , 39 – 50 .…”

“…In response to cisplatin, TNFα/CHX and staurosporine, in addition to caspase entry into the nucleus, we detected the cytoplasmic translocation of the apoptotic 89-kDa fragment of PARP1, which is plausible since caspase-mediated cleavage of PARP1 removes its DNA binding domain and disrupts its NLS. Previously, this translocation event has already been described in response to different apoptotic stimuli, including TNFα and DNA-damaging agent etoposide 45 – 50 . Moreover, we observed the nuclear accumulation of GAPDH and hexokinase II during cisplatin-induced apoptosis.…”

Reactive Oxygen Species Regulate Endoplasmic Reticulum Stress and ER‐Mitochondrial Ca2+ Crosstalk to Promote Programmed Necrosis of Rat Nucleus Pulposus Cells under Compression

“…PARP, located at the mitochondrial outer membrane, is an important protein that regulates energy metabolism and mitochondrial membrane potential [24]. Activated PARP leads to continued nicotinamide adenine dinucleotide (NAD + ) depletion and loss of mitochondrial membrane potential, which then triggered AIF translocation from the mitochondria to the nucleus to cause chromatin condensation and DNA fragmentation, which leads to programmed necrosis of cells [25].…”

Flow Cytometry Reveals the Nature of Oncotic Cells

“…The expression of pH2AX and cleaved PARP in the four identified phenotypes in live and dead cells are resting, early or late apoptotic, RIP1-dependent apoptosis, and DN, the incidence of which is modified by the action of the two drugs used in this study and can be further manipulated by blockade of ACD and RCD processes by zVAD and Nec-1 (Figure 6D,E) [22,23,24,25]. In the first instance live resting cells, the main phenotype of untreated Jurkat cells express RIP3 with a high degree of DDR (37%), whereas resting DN cells showed little DDR (2%) but a high degree of cleaved PARP (39%) in the absence of caspase-3 [25].…”