Radiation Bystander Effects Mechanism
Introduction: Radiation Induced Bystander Effect (RIBE) which cause radiation effects in non-irradiated cells, has challenged the principle according to which radiation traversal through the nucleus of a cell is necessary for producing biological responses. What is the mechanism of this phenomenon? To have a better understanding of this rather ambiguous concept substantial number of original and reviewed article were carefully examined. Results: Irradiated cells release molecules which can propagate in cell environment and/or transmit through gap junction intercellular communication. These molecules can reach to non-irradiated cells and transmit bystander signals. In many investigations, it has been confirmed that these molecules are growth factors, cytokines, nitric oxide and free radicals like reactive oxygen species (ROS). Transmission of by stander signal to neighboring cells persuades them to produce secondary growth factors which in their turn cause further cell injuries. Some investigators suggest, organelles other than nucleus (mitochondria and cell membrane) are the origin of these signals. There is another opinion which suggests double strand breaks (DSB) are not directly generated in bystander cells, rather they are due to smaller damage like single strand breaks which accumulate and end up to DSB. Although bystander mechanisms have not been exactly known, it can be confirmed that multiple mechanisms and various pathways are responsible for this effect. Cell type, radiation type, experimental conditions and end points identify the dominant mechanism. Conclusion: Molecules and pathways which are responsible for RIBE, also cause systemic responses to other non-irradiation stresses. So RIBE is a kind of systemic stress or innate immune responses, which are performed by cell microenvironment. Irradiated cells and their signals are components of microenvironment for creating bystander effects.
introduction: radiation induced bystander effect (ribe) which cause radiation effects in non-irradiated cells, has challenged the principle according to which radiation traversal through the nucleus of a cell is necessary for producing biological responses. what is the mechanism of this phenomenon? to have a better understanding of this rather ambiguous concept substantial number of original an...متن کامل
The radiation-induced bystander effect represents a paradigm shift in our understanding of the radiobiological effects of ionizing radiation, in that extranuclear and extracellular events may also contribute to the final biological consequences of exposure to low doses of radiation. Although radiation-induced bystander effects have been well documented in a variety of biological systems, the me...متن کامل
Introduction: Radiation effects observed in cells that are not irradiated are known as non-targeted effects. Radiation induced bystander effect (RIBE) as a kind of non-targeted effect has been introduced in recent years. RIBE occurs in unexposed cells which are related to adjacent or distant irradiated cells. RIBE contradict with "target theory" which necessitates radiation tr...متن کامل
Although radiation-induced bystander effects have been well described over the past decade, the mechanisms of the signaling processes involved in the bystander phenomenon remain unclear. In the present study, using the Columbia University charged particle microbeam, we found that mitochondrial DNA–depleted human skin fibroblasts (R) showed a higher bystander mutagenic response in confluent mono...متن کامل
Exposure of GM10115 hamster-human hybrid cells to X-rays can result in the induction of chromosomal instability in the progeny of surviving cells. This instability manifests as the dynamic production of novel sub-populations of cells with unique cytogenetic rearrangements involving the "marker" human chromosome. We have used the comet assay to investigate whether there was an elevated level of ...متن کامل
A classical paradigm [correction of paradym] of radiation biology asserts that all radiation effects on cells, tissues and organisms are due to the direct action of radiation. However, there has been a recent growth of interest in the indirect actions of radiation including the radiation-induced adaptive response, the bystander effect, low-dose hypersensitivity, and genomic instability, which a...متن کامل
دوره 6 شماره 2
صفحات 81- 95
تاریخ انتشار 2009-06-01
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