Prevention of radiation-induced bystander effects by agents that inactivate cell-free chromatin released from irradiated dying cells

Abstract

Radiation-induced bystander effect (RIBE) is a poorly understood phenomenon wherein non-targeted cells exhibit effects of radiation. We have reported that cell-free chromatin (cfCh) particles that are released from dying cells can integrate into genomes of surrounding healthy cells to induce DNA damage and inflammation. This raised the possibility that RIBE might be induced by cfCh released from irradiated dying cells. When conditioned media from BrdU-labeled irradiated cells were passed through filters of pore size 0.22 µm and incubated with unexposed cells, BrdU-labeled cfCh particles could be seen to readily enter their nuclei to activate H2AX, active Caspase-3, NFκB, and IL-6. A direct relationship was observed with respect to activation of RIBE biomarkers and radiation dose in the range of 0.1–50 Gy. We confirmed by FISH and cytogenetic analysis that cfCh had stably integrated into chromosomes of bystander cells and had led to extensive chromosomal instability. The above RIBE effects could be abrogated when conditioned media were pre-treated with agents that inactivate cfCh, namely, anti-histone antibody complexed nanoparticles (CNPs), DNase I and a novel DNA degrading agent Resveratrol-copper (R-Cu). Lower hemi-body irradiation with γ-rays (0.1–50 Gy) led to activation of H2AX, active Caspase-3, NFκB, and IL-6 in brain cells in a dose-dependent manner. Activation of these RIBE biomarkers could be abrogated by concurrent treatment with CNPs, DNase I and R-Cu indicating that activation of RIBE was not due to radiation scatter to the brain. RIBE activation was seen even when mini-beam radiation was delivered to the umbilical region of mice wherein radiation scatter to brain was negligible and could be abrogated by cfCh inactivating agents. These results indicate that cfCh released from radiation-induced dying cells are activators of RIBE and that it can be prevented by treatment with appropriate cfCh inactivating agents.

The Nanomaterial-Induced Bystander Effects Reprogrammed Macrophage Immune Function

“…Studies on bystander responses suggest that bystander signals may be transferred to neighboring cells either by gap junctional intercellular communication or by the production of exosomes or soluble extracellular signaling factors released from stressed targeted cells [3,13,16,17]. Soluble extracellular signaling factors such as ROS, nitric oxide (NO), extracellular DNA, and cytokines including TGF-β have been found to play an important role in multiple stressor-induced bystander effects [37,38,39,40]. Cell viability was the main cell response regulated by the bystander effect veri ed by the inhibitors (Fig.…”

RADIATION-INDUCED BYSTANDER EFFECT – MODELING, MANIFESTATION, MECHANISMS, PERSISTENCE, CANCER RISKS (literature review)

“…Studies ful filled by I. Mittra show that the new class of phys iological mobile genetic elements is nucleic acids released from both healthy and damaged (inclu ding cancer / irradiated) cells [50,51]. S. Kirolikar et al found that such non cellular chromatin (cfCh) particles released due to the apoptosis of Jurkat cells (human lymphoblastic leukemia) irra diated at 15,0 Gy were integrated into the genomes of surrounding intact mouse fibroblasts (NIH3T3 cells) and induced in them bystander effect (acti vation of H2AX, caspase 3, NFκB and IL 6) under joint incubation for 24 hours [52].…”

“…В дослідженнях I. Mittra зі співавторами показано, що новим класом фізіоло гічних мобільних генетичних елементів є нуклеїнові кислоти, вивільнені як зі здорових, так і з пошкодже них (у тому числі, ракових чи опромінених) клітин [50,51]. S. Kirolikar з колегами встановлено, що безклітинні хроматинові (cfCh) частинки, вивільнені внаслідок апоптозу Jurkat клітинами (лімфобластної лейкемії людини), опроміненими в дозі 15,0 Гр, інтег рувались в геноми оточуючих інтактних фібробластів миші (NIH3T3 клітин) та індукували в них ефект свідка (активація H2AX, каспази 3, NFκB і IL 6 ) при спільній інкубації протягом 24 год [52].…”

“…S. Kirolikar et al conducted an experiment with the irradiation of the mice umbilical region dia meter of 1 cm at a dose of 2000 cGy using platform for radiotherapy Varian/BrainLAB Novalis Tx™ and adhering to the conditions excluded disper sion of the active doses of radiation [52]. In the non irradiated brain cells of mice induction of bystander effect was recorded which was manifest ed in increasing levels of γH2AX, Caspase 3, NFκB, IL 6.…”

“…S. Kirolikar з колегами провели експеримент з оп роміненням пупочної області мишей діаметром 1 см в дозі 2000 сГр з використанням платформи для проме невої терапії Varian/BrainLAB Novalis Tx™ і дотриман ням умов, що виключили розсіювання діючої дози радіації [52]. При цьому в неопромінених клітинах го ловного мозку мишей було зареєстровано індукцію ефекту свідка, що проявлялась у підвищенні рівнів γH2AX, Caspase 3, NFκB, IL 6.…”