Long-term immune effects of high-level natural radiation on Yangjiang inhabitants in China

Immune status of people living in the Tande-Tande sub-village (Indonesia), an area with high indoor radon concentration

On Earth, there are significant variations in terms of exposure to naturally occurring radiation among different areas. Radon, a naturally-occurring radioactive gas that is the primary cause of lung cancer in nonsmokers and the second most prevalent cause among smokers, poses a considerable risk. Indoor radon, in particular, constitutes the most substantial source of natural radiation to which individuals are exposed. This study assessed the immune status of a population chronically exposed to high indoor radon concentration in Indonesia. Fifty-seven subjects from the Tande-Tande sub-village (high indoor radon concentration area) were compared to fifty-three participants living in the Topoyo village (low concentration area). We contrasted the immunological conditions of these two populations by measuring levels of tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin-4 (IL-4), and IL-10 in serum. Moreover, we also measured levels of the nuclear factor kappa B (NF-κB), superoxide dismutase (SOD), glutathione peroxidase (GPX), and protein kinase B in its phosphorylated (pAkt) and non-phosphorylated form (Akt) in peripheral blood mononuclear cells (PBMCs) of a subset of participants (31 from each population). TNF-α, IFN-γ, and IL-4 levels in Tande-Tande sub-village inhabitants were significantly lower than those in the control group living in the Topoyo village (p = 0.001, p = 0.017, and p = 0.002). The concentration of IL-10 also tended to be lower in people living in the high indoor radon concentration area, but it did not differ significantly between Tande-Tande sub-village inhabitants and Topoyo inhabitants (p = 0.106). Protein levels of NF-κB, pAkt, and Akt in Tande-Tande sub-village inhabitants also did not differ significantly between Tande-Tande sub-village inhabitants and Topoyo inhabitants (p = 0.234, p = 0.210, and p = 0.657). Similarly, activities of SOD and GPX did not differ significantly between the two populations (p = 0.569 and p = 0.949). Overall, despite their chronic exposure to high indoor radon concentrations, our study revealed no increase in the levels of TNF-α, IFN-γ, IL-10, IL-4, SOD, and GPX in the inhabitants of Tande-Tande sub-village compared with people living in the Topoyo village. Furthermore, our study demonstrated no activation in the Akt pathway, as indicated by the pAkt/Akt ratio observed in PBMC lysates of individuals residing in the Tande-Tande sub-village.

Study of Low-Dose Radiation Workers Ionizing Radiation Sensitivity Index and Radiation Dose-Effect Relationship

BACKGROUND

In the present study, we analyzed radiation injuries to Chinese workers exposed to low-dose radiation. We discuss the relationships between dose and injury.

METHODS

This study randomly selected 976 radiation workers who underwent occupational health monitoring. The radiation workers were divided into 5 different types of work: radiation diagnosis, radiation therapy, interventional therapy, nuclear medicine, and industrial inspection. This research was approved by the Bioethics Committee at the Gansu Provincial Center for Disease Control and Prevention.

RESULTS

The average annual cumulative dose to interventional radiation workers was the highest, i.e., 0.86 mSv. The detection rate of lens opacity was 37%, but 99.70% of lens opacities occurred in the peripheral cortex. Posterior subcapsular opacification was detected less than 1.00% of the time. The rate of chromosomal aberrations was highest for radiological workers with more than 20 years of service. Annual cumulative dose reached 2.04 mSv, and the monitoring dose for 3 months was as high as 1.62 mSv. Dicentric chromosomes were also detected. The manual packaging and drug delivery nuclear medicine staffs totaled 14 individuals. 131 131 was detected in the thyroids of 4 workers (28.57%). The detection rate of thyroid 131 I was higher in the hand-packed and administered group than in the automatic administration group.

CONCLUSION

Radiation workers exposed to low doses of radiation can sustain injuries. Interventional radiology workers receive the highest doses and sustain the most significant effects. This study suggests that chromosome aberration analysis is an important index in occupational health monitoring of radiological workers. Monitoring of internal radiation exposure cannot be ignored for nuclear medicine staff.

Role of low-dose radiation in senescence and aging: A beneficial perspective

Cellular senescence refers to the permanent arrest of cell cycle caused by intrinsic and/or extrinsic stressors including oncogene activation, irradiation, DNA damage, oxidative stress, and certain cytokines (including senescence associated secretory phenotype). Cellular senescence is an important factor in aging. Accumulation of senescent cells has been implicated in the causation of various age-related organ disorders, tissue dysfunction, and chronic diseases. It is widely accepted that the biological effects triggered by low-dose radiation (LDR) are different from those caused by high-dose radiation. Experimental evidence suggests that LDR may promote growth and development, enhance longevity, induce embryo production, and delay the progression of chronic diseases. The underlying mechanisms of these effects include modulation of immune response, stimulation of hematopoietic system, antioxidative effect, reduced DNA damage and improved ability for DNA damage repair. In this review, we discuss the possible mechanisms by which LDR prevents senescence and aging from the perspectives of inhibiting cellular senescence and promoting the removal of senescent cells. We review a wide broad of evidence about the beneficial impact of LDR in senescence and aging models (including cardiovascular diseases, neurological diseases, arthritis and osteoporosis, chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis) to highlight the potential value of LDR in preventing aging and age-related diseases. However, there is no consensus on the effect of LDR on human health, and several important aspects require further investigation.

Biological and cellular responses of humans to high-level natural radiation: A clarion call for a fresh perspective on the linear no-threshold paradigm

There remains considerable uncertainty in obtaining risk estimates of adverse health outcomes of chronic low-dose radiation. In the absence of reliable direct data, extrapolation through the linear no-threshold (LNT) hypothesis forms the cardinal tenet of all risk assessments for low doses (≤ 100 mGy) and for the radiation protection principle of As Low As Reasonably Achievable (ALARA). However, as recent evidences demonstrate, LNT assumptions do not appropriately reflect the biology of the cell at the low-dose end of the dose-response curve. In this regard, human populations living in high-level natural radiation areas (HLNRA) of the world can provide valuable insights into the biological and cellular effects of chronic radiation to facilitate improved precision of the dose-response relationship at low doses. Here, data obtained over decades of epidemiological and radiobiological studies on HLNRA populations is summarized. These studies do not show any evidence of unfavourable health effects or adverse cellular effects that can be correlated with high-level natural radiation. Contrary to the assumptions of LNT, no excess cancer risks or untoward pregnancy outcomes have been found to be associated with cumulative radiation dose or in-utero exposures. Molecular biology-driven studies demonstrate that chronic low-dose activates several cellular defence mechanisms that help cells to sense, recover, survive, and adapt to radiation stress. These mechanisms include stress-response signaling, DNA repair, immune alterations and most importantly, the radiation-induced adaptive response. The HLNRA data is consistent with the new evolving paradigms of low-dose radiobiology and can help develop the theoretical framework of an alternate dose-response model. A rational integration of radiobiology with epidemiology data is imperative to reduce uncertainties in predicting the potential health risks of chronic low doses of radiation.

Ionizing Radiation-Induced Brain Cell Aging and the Potential Underlying Molecular Mechanisms

Population aging is occurring rapidly worldwide, challenging the global economy and healthcare services. Brain aging is a significant contributor to various age-related neurological and neuropsychological disorders, including Alzheimer's disease and Parkinson's disease. Several extrinsic factors, such as exposure to ionizing radiation, can accelerate senescence. Multiple human and animal studies have reported that exposure to ionizing radiation can have varied effects on organ aging and lead to the prolongation or shortening of life span depending on the radiation dose or dose rate. This paper reviews the effects of radiation on the aging of different types of brain cells, including neurons, microglia, astrocytes, and cerebral endothelial cells. Further, the relevant molecular mechanisms are discussed. Overall, this review highlights how radiation-induced senescence in different cell types may lead to brain aging, which could result in the development of various neurological and neuropsychological disorders. Therefore, treatment targeting radiation-induced oxidative stress and neuroinflammation may prevent radiation-induced brain aging and the neurological and neuropsychological disorders it may cause.

Low dose ionizing radiation effects on the immune system

Ionizing radiation interacts with the immune system in many ways with a multiplicity that mirrors the complexity of the immune system itself: namely the need to maintain a delicate balance between different compartments, cells and soluble factors that work collectively to protect, maintain, and restore tissue function in the face of severe challenges including radiation damage. The cytotoxic effects of high dose radiation are less relevant after low dose exposure, where subtle quantitative and functional effects predominate that may go unnoticed until late after exposure or after a second challenge reveals or exacerbates the effects. For example, low doses may permanently alter immune fitness and therefore accelerate immune senescence and pave the way for a wide spectrum of possible pathophysiological events, including early-onset of age-related degenerative disorders and cancer. By contrast, the so called low dose radiation therapy displays beneficial, anti-inflammatory and pain relieving properties in chronic inflammatory and degenerative diseases. In this review, epidemiological, clinical and experimental data regarding the effects of low-dose radiation on the homeostasis and functional integrity of immune cells will be discussed, as will be the role of immune-mediated mechanisms in the systemic manifestation of localized exposures such as inflammatory reactions. The central conclusion is that ionizing radiation fundamentally and durably reshapes the immune system. Further, the importance of discovery of immunological pathways for modifying radiation resilience amongst other research directions in this field is implied.

IL-2 and IL-2R gene polymorphisms and immune function in people residing in areas with high background radiation, Yangjiang, China

PURPOSE

Long-term exposure to low dose radiation may trigger immune response and stimulate hormesis. Interleukin-2 (IL-2) and interleukin-2 receptor (IL-2R) play a crucial role in immune function. We aimed to explore the possible association of IL-2 and IL-2R gene polymorphisms with low dose radiation exposure, as well as the relationship with IL-2 gene expression in people residing in areas with a high background radiation in Yangjiang, China.

MATERIALS AND METHODS

We recruited and assigned 54 native men residing in Yangxi County, Yangjiang city to the high natural background radiation (HNBR) group, and 53 native men residing in Hengpi County, Enping city to the control area (CA) group. All the participants wore a thermoluminescent dosimeter (TLD) for 90 days, and answered questionnaires. The serum levels of IL2, IL4, IL5, sIL2R, and tumor growth factor (TGF), and expression levels of IL2RA, IL2RB, IL2RG, and IL2 were also analyzed. Additionally, we tested 10 polymorphic loci associated with the IL-2 gene.

RESULTS

The annual effective radiation doses in the HNBR and CA groups were 6.24 mSv y^-1 and 1.95 mSv y^-1, respectively. After adjusting for potential confounding factors, the serum levels of IL-2 and IL-5 were higher in the HNBR group than the CA group (p < .05), while the serum level of TGFβ was lower in the HNBR group (p < .05). The IL-2 gene mRNA expression level was higher in the HNBR group than the CA group (p < .05). The IL-2RB rs76206423 AA allele showed significant variations in the HNBR group (p = .0381).

CONCLUSIONS

Long-term exposure to low dose radiation may enhance immune function, and IL-2RB rs76206423 may be related to the expression of IL-2 by other coding variants. Moreover, our data provide a better understanding of the molecular mechanism of the immune response to low dose radiation.

Effects of Radon From Hot Springs on Lymphocyte Subsets in Peripheral Blood

Objective:

To analyze changes in immune functions by detecting lymphocyte subsets in the peripheral blood of residents in the vicinity of radon from hot springs.

Methods:

Two groups were randomly selected; 61 residents in the vicinity of the hot springs were assigned to the radon group, and 51 residents with a similar lifestyle and habits but no contact with hot springs were assigned to the control group. The percentages of lymphocyte subsets (CD3⁺, CD4⁺CD8⁻, CD4⁻CD8⁺, CD4⁺/CD8⁺, and TCR/CD3) in the 2 groups were evaluated on a FACS Aria flow cytometer. The absolute values of lymphocytes (LYMPH#) and percentages of lymphocytes (LYMPH%) were measured by an automatic blood analyzer.

Results:

In the radon group, the numbers of CD3⁺ (Z = −0.140, P > .05) and CD4⁺CD8⁻ (Z = −0.964, P > .05) T cells were higher, as compared with the controls, but this difference was not significant. In addition, the number of CD4⁻CD8⁺ (t = −2.141, P < .05) T cells was significantly lower in the radon group. Furthermore, the average ratios of CD4⁺/CD8⁺ (t = −2.201, P < .05) and TCR/CD3 (t = 2.047, P < .05) cells were significantly higher in the radon group than in the controls. Compared with the control group, the LYMPH# (t = −0.485, P > .05) and LYMPH% (Z = −0.835, P > .05) showed no significant change.

Conclusion:

Radon-rich hot springs could alter the proportions of lymphocyte subsets and possibly affect immunologic functions.