Primary Radiation Stress, Inflammatory Reaction and the Mechanism of Early Postradiation Reparative Processes in Irradiated Tissues

Abstract

The products of radiolysis released from cellular compartment under the influence of ionizing radiation: highly mobile groups of proteins, damaged nuclear and mitochondrial DNA, extracellular ATP and oxidized low density lipoproteins, cause stress activation in irradiated tissues through a pattern of the receptors with start of the cascade r53 and NF-κB of pro-inflammatory ways conducting to an expression of pro-inflammatory genes stimulating synthesis of cytokines of the IL-1 family. Excessive activation of pro-inflammatory way under the influence of a radioactive stress is limited to synthesis, anti-inflammatory cytokines: IL-4, IL-10, IL-11, IL-13 and also antagonists of IL-1 receptor and TGF-β. G-CSF and MG-CSF induced by action of pro-inflammatory cytokines have anti-inflammatory and anti-apoptotic properties decreasing level of pro-inflammatory cytokines IL-6 and TNF. Glucocorticoids participate in regulation of primary radioactive stress, suppressing an excessive expression of genes of pro-inflammatory cytokines. Increased IL-1 level stimulates secretion of corticosteroids through mechanism of feedback. Adrenergic stimulation is capable to raise a gene IL-1β expression. The mechanism of radiation apoptosis of stem cells is implemented through p53-Puma way which blocks interaction anti-apoptotic proteins of Bcl-2 with pro-apoptotic proteins of Bax and Bak. After release from mitochondrion of cytochrome C and apoptosis-inducing factor there is an activation of effector caspases: caspases 3, 6 and 7 through caspase 9, and final cell destruction. Wnt way is crucial for post-radiation repair. Potential of the regenerative response of hemopoietic tissue to radiation injury depends on catenin and ability of Wnt way to stimulate post-radiation bone marrow reparation. Mesenchymal stem cells of bone marrow play a large role in post-radiation regeneration of hemopoietic tissue. Their main action is carried out through TLR2 and TLR4 receptors. Mobilization of hemopoietic stem cells is bound to release proteases from bone marrow, including neutrophil elastase and cathepsin G, and a matrix metalproteinase-9. Radioprotective properties of exogenous IL-1 aren’t limited only by induction of raised G-CSF and GM-CSF production. The larger role in radiation protection is played by the reaction induced by IL-1 in the form of feedback with production anti-apoptotic and anti-inflammatory factors. Primary radioactive stress limits time of radiomitigable effect of IL-1 by 1-2 h after its application after radiation.