Effects of low dose radiation on human health
It is well known that high doses of ionizing radiation (IR), either as a side effect of therapeutic treatment or through accidental exposure to environmental sources, have a strong genotoxic effect. Normal tissues are extremely vulnerable to the cytotoxicity caused by high doses of IR. For example, IR may alter the functionality of the bone marrow and affect the resident stem cells. Several studies on the effects of IR have focused on its negative influence on hematopoietic stem cells (HSC), while only a few have addressed the effect of IR on the other cell types present in bone marrow, such as mesenchymal stem cells. These cells are of great interest since they differentiate in bone, cartilage, and fat; support hematopoiesis; contribute to the homeostatic maintenance of many organs and tissues, and modulate the inflammatory response.
In recent years, there has been growing evidence that even low doses of radiation (< 500 mGy) may have profound effects on cellular functions. People may be exposed to low dose IR for medical purposes. The effects of low dose radiation related to medical imaging procedures are often not adequately monitored, although these procedures can be frequently repeated on the same individual. A recent study carried out on almost 1,000,000 non-elderly adults in healthcare markets across the United States showed that a consistent number of patients received up to 50 mGy/year.
People may be also unintentionally exposed to low dose IR, such as those who are frequent flyers, those exposed to radiological terrorism and those who live near illegal IR waste dumpsites. For example, in our region, in Southern Italy, years of illegal practices of waste dumping increased risks for liver and lung cancer.
The major target of low dose effects may be stem cells. As result of their long life, stem cells may undergo several rounds of low-level radiation damage that, taken singly, may not have a big impact on cellular physiology, but collectively, these rounds of radiation may severely affect cellular function.
We decided to analyze the effects of low dose radiation on human bone marrow mesenchymal stromal cells (MSC), which contain a subpopulation of stem cells, since to our knowledge there are only a few papers that partially address this topic in spite of the key role of MSC in bone marrow physiology.
1: Alessio N, Del Gaudio S, Capasso S, Di Bernardo G, Cappabianca S, Cipollaro M, Peluso G, Galderisi U. Low dose radiation induced senescence of human mesenchymal stromal cells and impaired the autophagy process. Oncotarget. 2015 Apr 10;6(10):8155-66. PubMed PMID: 25544750; PubMed Central PMCID: PMC4480742.
2: Özcan S, Alessio N, Acar MB, Mert E, Omerli F, Peluso G, Galderisi U. Unbiased analysis of senescence associated secretory phenotype (SASP) to identify common components following different genotoxic stresses. Aging (Albany NY). 2016 Jul;8(7):1316-29. doi: 10.18632/aging.100971. PubMed PMID: 27288264; PubMed Central PMCID: PMC4993333.
3: Alessio N, Esposito G, Galano G, De Rosa R, Anello P, Peluso G, Tabocchini MA, Galderisi U. Irradiation of Mesenchymal Stromal Cells With Low and High Doses of Alpha Particles Induces Senescence and/or Apoptosis. J Cell Biochem. 2017 Sep;118(9):2993-3002. doi: 10.1002/jcb.25961. Epub 2017 May 3. PubMed PMID: 28252222.
4: Alessio N, Capasso S, Di Bernardo G, Cappabianca S, Casale F, Calarco A, Cipollaro M, Peluso G, Galderisi U. Mesenchymal stromal cells having inactivated RB1 survive following low irradiation and accumulate damaged DNA: Hints for side effects following radiotherapy. Cell Cycle. 2017 Feb;16(3):251-258. doi: 10.1080/15384101.2016.1175798. Epub 2016 Apr 28. PubMed PMID: 27124644; PubMed Central PMCID: PMC5323029.
5: Squillaro T, Galano G, De Rosa R, Peluso G, Galderisi U. Concise Review: The Effect of Low-Dose Ionizing Radiation on Stem Cell Biology: A Contribution to Radiation Risk. Stem Cells. 2018 Aug;36(8):1146-1153. doi: 10.1002/stem.2836. Epub 2018 May 17. Review. PubMed PMID: 29664142.