Non-ionizing radiation produced by nanosecond pulsed electric fields (nsPEFs) is an alternative to ionizing radiation for cancer treatment. NsPEFs are high power, low energy (non-thermal) pulses that, unlike plasma membrane electroporation, modulate intracellular structures and functions. To determine functions for p53 in nsPEF-induced apoptosis, HCT116p53(+/+) and HCT116p53(-/-) colon carcinoma cells were exposed to multiple pulses of 60 kV/cm with either 60 ns or 300 ns durations and analyzed for apoptotic markers. Several apoptosis markers were observed including cell shrinkage and increased percentages of cells positive for cytochrome c, active caspases, fragmented DNA, and Bax, but not Bcl-2. Unlike nsPEF-induced apoptosis in Jurkat cells (Beebe et al. 2003a) active caspases were observed before increases in cytochrome c, which occurred in the presence and absence of Bax. Cell shrinkage occurred only in cells with increased levels of Bax or cytochrome c. NsPEFs induced apoptosis equally in HCT116p53(+/+) and HCT116p53(-/-) cells. These results demonstrate that non-ionizing radiation produced by nsPEFs can act as a non-ligand agonist with therapeutic potential to induce apoptosis utilizing mitochondrial-independent mechanisms in HCT116 cells that lead to caspase activation and cell death in the presence or absence of p-53 and Bax.
Generation of reactive oxygen species (ROS) during infection is an immediate host defense leading to microbial killing. APE1 is a multifunctional protein induced by ROS and after induction, protects against ROS-mediated DNA damage. Rac1 and NAPDH oxidase (Nox1) are important contributors of ROS generation following infection and associated with gastrointestinal epithelial injury. The purpose of this study was to determine if APE1 regulates the function of Rac1 and Nox1 during oxidative stress. Gastric or colonic epithelial cells (wild-type or with suppressed APE1) were infected with Helicobacter pylori or Salmonella enterica and assessed for Rac1 and NADPH oxidase-dependent superoxide production. Rac1 and APE1 interactions were measured by co-immunoprecipitation, confocal microscopy and proximity ligation assay (PLA) in cell lines or in biopsy specimens. Significantly greater levels of ROS were produced by APE1-deficient human gastric and colonic cell lines and primary gastric epithelial cells compared to control cells after infection with either gastric or enteric pathogens. H. pylori activated Rac1 and Nox1 in all cell types, but activation was higher in APE1 suppressed cells. APE1 overexpression decreased H. pylori-induced ROS generation, Rac1 activation, and Nox1 expression. We determined that the effects of APE1 were mediated through its N-terminal lysine residues interacting with Rac1, leading to inhibition of Nox1 expression and ROS generation. APE1 is a negative regulator of oxidative stress in the gastrointestinal epithelium during bacterial infection by modulating Rac1 and Nox1. Our results implicate APE1 in novel molecular interactions that regulate early stress responses elicited by microbial infections.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.