Effect of extended exposure to low-dose radiation on autoimmune diseases of immunologically suppressed MRL/MpTn-gld/gld mice

Crosstalk between Fas and S1P1 signaling via NF-kB in osteoclasts controls bone destruction in the TMJ due to rheumatoid arthritis

Rheumatoid arthritis (RA) mainly affects various joints of the body, including the temporomandibular joint (TMJ), and it involves an infiltration of autoantibodies and inflammatory leukocytes into articular tissues and the synovium. Initially, the synovial lining tissue becomes engaged with several kinds of infiltrating cells, including osteoclasts, macrophages, lymphocytes, and plasma cells. Eventually, bone degradation occurs. In order to elucidate the best therapy for RA, a comprehensive study of RA pathogenesis needs to be completed. In this article, we discuss a Fas-deficient condition which develops into RA, with an emphasis on the role of sphingosine 1-phosphate (S1P)/S1P receptor 1 signaling which induces the migration of osteoclast precursor cells. We describe that Fas/S1P1 signaling via NF-κB activation in osteoclasts is a key factor in TMJ-RA severity and we discuss a strategy for blocking nuclear translocation of the p50 NF-κB subunit as a potential therapy for attenuating osteoclastogenesis.

Health Impacts of Low-Dose Ionizing Radiation: Current Scientific Debates and Regulatory Issues

Health impacts of low-dose ionizing radiation are significant in important fields such as X-ray imaging, radiation therapy, nuclear power, and others. However, all existing and potential applications are currently challenged by public concerns and regulatory restrictions. We aimed to assess the validity of the linear no-threshold (LNT) model of radiation damage, which is the basis of current regulation, and to assess the justification for this regulation. We have conducted an extensive search in PubMed. Special attention has been given to papers cited in comprehensive reviews of the United States (2006) and French (2005) Academies of Sciences and in the United Nations Scientific Committee on Atomic Radiation 2016 report. Epidemiological data provide essentially no evidence for detrimental health effects below 100 mSv, and several studies suggest beneficial (hormetic) effects. Equally significant, many studies with in vitro and in animal models demonstrate that several mechanisms initiated by low-dose radiation have beneficial effects. Overall, although probably not yet proven to be untrue, LNT has certainly not been proven to be true. At this point, taking into account the high price tag (in both economic and human terms) borne by the LNT-inspired regulation, there is little doubt that the present regulatory burden should be reduced.

Effects of low-dose-gamma rays on the immune system of different animal models of disease

We reviewed the beneficial or harmful effects of low-dose ionizing radiation on several diseases based on a search of the literature. The attenuation of autoimmune manifestations in animal disease models irradiated with low-dose γ-rays was previously reported by several research groups, whereas the exacerbation of allergic manifestations was described by others. Based on a detailed examination of the literature, we divided animal disease models into two groups: one group consisting of collagen-induced arthritis (CIA), experimental encephalomyelitis (EAE), and systemic lupus erythematosus, the pathologies of which were attenuated by low-dose irradiation, and another group consisting of atopic dermatitis, asthma, and Hashimoto's thyroiditis, the pathologies of which were exacerbated by low-dose irradiation. The same biological indicators, such as cytokine levels and T-cell subpopulations, were examined in these studies. Low-dose irradiation reduced inter-feron (IFN)-gamma (γ) and interleukin (IL)-6 levels and increased IL-5 levels and the percentage of CD4(+)CD25(+)Foxp3(+)Treg cells in almost all immunological disease cases examined. Variations in these biological indicators were attributed to the attenuation or exacerbation of the disease's manifestation. We concluded that autoimmune diseases caused by autoantibodies were attenuated by low-dose irradiation, whereas diseases caused by antibodies against external antigens, such as atopic dermatitis, were exacerbated.

Affects of ionizing radiation on T-cell population lymphocyte: a risk factor of irritable bowel syndrome

Irritable bowel syndrome is observed mostly in Ukrainian children and may be related to adverse health effects as a result of the Chernobyl disaster. The aim of this study was to determine status of T-cell population lymphocytes in children with clinical symptom of irritable bowel syndrome. The test population consisted of 95 participants: 75 rural patients aged 4 to 18 who lived in a contaminated area exposed to natural environmental radiation with clinical symptom of irritable bowel syndrome (categorized in three groups) and 20 healthy urban participants from Kiev aged 5 to 15 as control group. Internal radiation activity has been measured by gamma-ray spectrometry. Peripheral blood leukocytes were analyzed for T-lymphocytes subset such as T-lymphocytes (CD3(+)), T-helper (CD4(+)) and T-cytotoxic (CD8(+)) and then CD4/CD8 ratio was calculated. Percentage of CD3(+) and CD4(+) in all study groups decreased significantly in comparison to control group (p < 0.001). Percentage of CD8(+) increased significantly in all study groups in comparison to control group (p < 0.05). The CD4/CD8 ratio decreased significantly all study groups in comparison to control group (p < 0.001). Cellular immune status of study groups that are residing in a contaminated area has changed. Our data have demonstrated that this change may be related to a higher incidence of children with irritable bowel syndrome.

Exacerbation of autoimmune thyroiditis by a single low dose of whole-body irradiation in non-obese diabetic-H2h4 mice

PURPOSE

To evaluate how irradiation affects thyroid autoimmunity in mouse models of Hashimoto's thyroiditis and Graves' hyperthyroidism.

MATERIALS AND METHODS

Non-obese diabetic (NOD)-H2(h4) mice spontaneously develop anti-thyroglobulin (Tg) antibodies and thyroiditis when supplied with sodium iodine (NaI) in the drinking water. BALB/c mice develop anti-thyrotropin receptor (TSHR) antibodies and hyperthyroidism following immunization with adenovirus expressing TSHR (Ad-TSHR). Mice were irradiated as follows: A single whole-body irradiation with 0.05, 0.5 or 3 Gy one week before or after the beginning of NaI or immunization with Ad-TSHR, fractionated whole-body irradiations with 0.05 Gy twice a week or 0.5 Gy once a week from one week before NaI or Ad-TSHR immunization, or a single regional irradiation to the thyroid gland with 0.5 Gy one week before NaI. The effect of a single irradiation with 0.05, 0.5 or 3 Gy on splenocytes was also evaluated.

RESULTS

A single whole-body irradiation with 0.5 Gy one week before NaI exacerbated thyroiditis and increased anti-Tg antibody titers in NOD-H2(h4) mice. In contrast, any irradiation protocols employed did not affect incidence of hyperthyroidism or anti-TSHR antibody titers in BALB/c mice. High-dose irradiation increased the relative ratios of effector T cells to regulatory T cells (an indication of enhanced immune status) but kills most of T cells.

CONCLUSIONS

These results indicate that a single whole-body low-dose irradiation with 0.5 Gy exacerbates thyroiditis in NOD-H2(h4) mice, data consistent with some clinical evidence for increased incidence of thyroid autoimmunity by environmental irradiation.

Repeated 0.5-Gy gamma-ray irradiation attenuates autoimmune manifestations in MRL-lpr/lpr mice

PURPOSE

MRL-lpr/lpr mice, a model for various autoimmune diseases, were repeatedly irradiated with 0.5 Gy of gamma-rays, and changes in their autoimmune manifestations were investigated.

MATERIALS AND METHODS

MRL-lpr/lpr mice at 13 weeks of age were maintained in plastic cages and exposed whole-body to 0.5 Gy gamma-ray irradiation from a 137Cs source 5 times per week for 4 weeks, from the time they were 13 weeks old until they reached 17 weeks old. Changes of autoimmune manifestations were examined 3 weeks later at the 20th week.

RESULTS

Splenomegaly, lymphadenopathy, and proteinuria in MRL-lpr/lpr mice were clearly ameliorated by a total dose of 10 Gy (0.5 Gy/day x 5 days/week for 4 weeks). Histologically severe disease-specific damage to the kidney and the salivary gland, i.e., glomerulonephritis and sialoadenitis, was also improved after irradiation. CD3+ CD4- CD8- CD45R/B220+ T cell numbers, which proliferate abnormally in MRL-lpr/lpr mice, were significantly decreased by the irradiation, possibly through induction of apoptosis. The elevated NO2- and NO3- (NO(x-) production by macrophages of MRL-lpr/lpr mice was lowered by the irradiation. The irradiation also prolonged the life span of MRL-lpr/lpr mice. These phenomena may contribute to the amelioration of autoimmune manifestations in MRL-lpr/lpr mice exposed to repeated small-doses of gamma-rays.

CONCLUSIONS

Repeated small-dose gamma-ray exposure ameliorates the autoimmune manifestations in MRL-lpr/lpr model mice.

Further study of prolongation of life span associated with immunological modification by chronic low-dose-rate irradiation in MRL-lpr/lpr mice: effects of whole-life irradiation

MRL-lpr/lpr mice carry a deletion in the apoptosis-regulating Fas gene that markedly shortens life due to multiple severe diseases. In our previous study (Radiat. Res. 161, 168- 173, 2004), chronic low-dose-rate gamma irradiation of mice at 0.35 or 1.2 mGy/h for 5 weeks markedly prolonged the life span, accompanied by immunological activation. This report shows that extension of the irradiation period to the entire life of the mice at the same dose rates improved survival further. The 50% survival time for untreated mice, 134 days, was prolonged to 502 days by 1.2 mGy/h life-long irradiation. Also obtained were a time course and a radiation dose-rate response for the activation of the immune system as indicated by a significant increase in CD4+ CD8+ T cells in the thymus and CD8+ T cells in the spleen and also by a significant decrease in CD3+ CD45R/B220+ cells and CD45R/B220+ CD40+ cells in the spleen. Drastic ameliorations of multiple severe diseases, i.e. total-body lymphadenopathy, splenomegaly and serious autoimmune diseases including proteinuria, and kidney and brain-central nervous system syndromes, were found in parallel with these immunological activations, with lifelong low-dose-rate irradiation being more effective than 5-week irradiation at low dose rates.