Abstract LB135: Effects of acute psychological stress on DNA damage levels in peripheral blood mononuclear cells: An experimental study with healthy human volunteers

Abstract

Abstract Increased levels of DNA damage in human peripheral blood mononuclear cells (PBMC), as indicated by classic alkaline comet and γ-H2AX assays, have been widely used in toxicology and epidemiology studies of potential environmental carcinogens. To date, however, little research has explored the possibility that exposure to acute psychological stresses in daily life may acutely increase levels of DNA damage and thus, much like repeated tobacco use, may cumulatively contribute to lifetime cancer risk. The purpose of the present experimental study was to provide a first critical test of the hypothesis that exposure of healthy humans to a brief psychological stress results in increased levels of DNA damage. We also tested preventative effects of a beta-adrenergic receptor blocker (propranolol), a mechanistic pathway for psychological stress effects on DNA supported by preclinical research. Healthy volunteers were recruited by multiple strategies including targeted outreach (telephone/email), with oversampling for age, sex, and minority status. Eligibility was confirmed by self-report, clinical testing (blood & urine), and MD review. On the experimental day, participants were randomized to receive either a single dose of propranolol (80mg) or a placebo. After a 60 min rest period with video distraction, all participants (n=123; 48.8% ≥ 40yr; 52% women; 52% minority) underwent a well-established, 15-minute stress challenge, a speech task and mental arithmetic (Trier Social Stress Test, TSST), with psychological stress confirmed by visual analog scales. Blood samples were collected (via IV line) immediately before and after the TSST. As the primary study outcome, DNA damage in PBMC was assessed (blind) with Comet IV software (% tail intensity) following single cell gel electrophoresis under alkaline conditions with and without in vitro exposure to 25uM H2O2 (comet assay). For a subset of participants with sufficient frozen PBMC samples available (n=43), levels of pan-nuclear γ-H2AX were determined with a validated, sensitive, immunoblot method that detects H2AX phosphorylation at Ser139, and expresses γ-H2AX as the ratio of p-Ser139-H2AX to total H2AX. Exploratory nonparametric analyses revealed that undergoing the TSST significantly increased levels of DNA damage in PBMC (H2O2 comet assay [p<.001] and γ-H2AX biomarker [p=.03], Wilcoxon tests) in the group of participants that was randomized to pretreatment with placebo. In the group pretreated with propranolol before the TSST, a significant increase in γ-H2AX was not found. Conclusion. Supporting the study hypothesis that acute stress can increase levels of DNA damage, the results of the present study highlight the potential importance of additional research to address the possibility that repeated exposures to acute life stresses may cumulatively contribute to increased lifetime risk of cancer. Citation Format: Dana H. Bovbjerg, John Schmitz, Kurt D. Ackerman, Scott R. Beach, Albert D. Donnenberg, Jessica Manculich, Matthew F. Muldoon, Patricia L. Opresko, Patrick M. Tarwater, Hong Wang, Frank J. Jenkins. Effects of acute psychological stress on DNA damage levels in peripheral blood mononuclear cells: An experimental study with healthy human volunteers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB135.