Long-term Pathway Activation in Cardiac Ventricular Tissues after Gamma and simGCRsim Irradiation

Space radiation represents a significant health risk for deep-space exploration, yet its long-term effects on cardiovascular function remain poorly understood. While our previous studies have highlighted persistent transcriptional changes in left ventricular (LV) and right ventricular (RV) tissues after a single whole-body irradiation in mice, a systems-level understanding of pathway activity deregulation is lacking. To address this gap, we applied the Pathway Signal Flow (PSF) algorithm to analyze long-term pathway activity alterations in LV and RV tissues of C57Bl/6J mice exposed to gamma radiation (100 cGy 137Cs) or the simplified Galactic Cosmic Ray simulation (simGCRsim, 50 cGy 500 MeV/n) composition of ion beams. RNA sequencing data were analyzed to assess pathway activity changes, sex-specific effects, and ventricular differences 440 days post-irradiation. We observed marked sex- and ventricle-specific differences in pathway deregulation. Left ventricular tissues in females exhibited broad signaling pathway alterations after simGCRsim exposure, particularly in immune response, cytoskeletal remodeling, and survival-related pathways (e.g., NF-κB, VEGF, and MAPK). In contrast, male RV tissues demonstrated higher pathway deregulation than LV, particularly in PPAR, NF-κB, and HIF-1 pathways, implicating metabolic disruption and survival adaptations. Furthermore, simGCRsim exposure induced greater long-term pathway perturbations than gamma rays. Our findings suggest that sex-dependent and ventricle-specific signaling alterations contribute to long-term cardiovascular risks following space irradiation. Notably, VEGF and NF-κB signaling emerge as key regulators of cardiac adaptation in females. Future studies in larger cohorts, incorporating early-stage molecular responses and broader pathway analyses, are needed to refine cardiovascular risk assessments for space travel.