Constitutive nuclear NFκB/rel DNA-binding activity of rat thymocytes is increased by stimuli that promote apoptosis, but not inhibited by pyrrolidine dithiocarbamate

Abstract

Rat thymocytes spontaneously undergo apoptotic death in cell culture, and are also sensitive to the induction of apoptosis by various stimuli. We show that unstimulated thymocytes constitutively express a p50-containing nuclear factor kappa B (NF kappa B)/rel DNA-binding activity in their nuclei. When the cells were fractionated by density-gradient centrifugation this activity was found to be most pronounced in immature CD4+8+ thymocytes, the cell population that undergoes selection by apoptosis in vivo and that is most sensitive to external inducers of apoptosis in vitro. The intensity of the NF kappa B/rel protein-DNA complex was significantly enhanced 30 min after exposing thymocytes to methylprednisolone or etoposide, two agents well known to induce apoptosis in these cells. Expression of this DNA-binding activity therefore correlates with the subsequent occurrence of apoptosis. By analogy to other systems, it has been suggested that antioxidants such as pyrrolidine dithiocarbamate (PDTC) inhibit thymocyte apoptosis by preventing the activation of an NF kappa B/rel transcription factor. However, we have found that etoposide induces a very similar enhancement of the NF kappa B/rel DNA-binding activity in the presence or absence of PDTC, despite a pronounced inhibition of apoptotic DNA fragmentation in the former situation. Dithiocarbamates therefore do not exert their anti-apoptotic activity in thymocytes by inhibiting the activation of this transcription factor.

AF1q enhancement of γ irradiation-induced apoptosis by up-regulation of BAD expression via NF-κB in human squamous carcinoma A431 cells

“…The expression of BAD was previously reported to be induced by either etoposide or TRAIL which were also shown to increase the transcriptional activity of NF-κB. The detailed mechanism was however not suggested (29)(30)(31)(32). The regulatory effect of NF-κB on BCL-2 family members has been suggested by many investigators.…”

Expression of Nuclear Factor-κB, Tumor Necrosis Factor Receptor Type 1, and c-Myc in Human Astrocytomas

“…Etoposide and vincristine, chemotherapeutic agents that induce apoptotic cell death, also activate NF-kB, although binding to a distinct receptor. 29,36) These anticancer agents may be less effective at inducing apoptotic cell death because of the concomitant activation of NF-kB. 36) Disruption of the protective mechanism induced by NF-kB makes cells much more vulnerable to killing by TNF-a and other chemotherapeutic agents and ionizing radiation.…”

Signaling pathways activated by daunorubicin

“…126 Moreover, mitoxantrone, which is unable to undergo redox cycling, was also found to activate NF-B in a pyrrolidine dithiocarbamate-insensitive manner, suggesting that the inhibitory effect of pyrrolidine dithiocarbamate could not be related to its antioxidant property. 129 CER was also a plausible candidate. Indeed, previous studies have shown that the addition of CER induced NF-B activation.…”

“…88 By using electrophoretic mobility shift assays, it has been shown that NF-B DNA binding activity is stimulated by cytotoxic effectors, including DNA-damaging agents, such as ionizing radiation, alkylating agents, anthracyclines, topoisomerase inhibitors, and cytosine arabinoside. 89,[123][124][125][126][127][128][129][130] However, the fact that nongenotoxic anticancer compounds such as vinca alkaloids and taxanes 125 may also activate NF-B suggests that DNA damage is not necessarily needed for drug-induced NF-B activation. This finding could mean that these drugs share some NF-B-activating signaling pathways that can be generated in the cytosol but not in the nucleus, similar to that observed in the UV response in which NF-B activation was clearly demonstrated to be initiated not in the nucleus but at or near the plasma membrane through a Src-and Ras-dependent mechanism.…”