Abstract
Radon treatment is used as an established therapy option in chronic painful inflammatory diseases. While analgesic effects are well described, little is known about the underlying molecular effects. Among the suspected mechanisms are modulations of the anti-oxidative and the immune system. Therefore, we aimed for the first time to examine the beneficial effects of radon exposure on clinical outcome as well as the underlying mechanisms by utilizing a holistic approach in a controlled environment of a radon chamber with an animal model: K/BxN serum-induced arthritic mice as well as isolated cells were exposed to sham or radon irradiation. The effects on the anti-oxidative and the immune system were analyzed by flow-cytometry, qPCR or ELISA. We found a significantly improved clinical disease progression score in the mice, alongside significant increase of peripheral blood B cells and IL-5. No significant alterations were visible in the anti-oxidative system or regarding cell death. We conclude that neither cell death nor anti-oxidative systems are responsible for the beneficial effects of radon exposure in our preclinical model. Rather, radon slightly affects the immune system. However, more research is still needed in order to fully understand radon-mediated effects and to carry out reasonable risk-benefit considerations.
Highlights
Clinical score of mice was assessed as described in [31] at multiple time points throughout the experiments which was used to randomly distribute them into two groups at the beginning of the experiments (Figure 1E).When comparing clinical scores of mock treated animals with those that received radon therapy that was set in relation to the clinical score at the time of mock or radon treatment, we found that one in 7 mice from the mock group (Figure 1F) showed an improvement in clinical parameters while 7 in 9 mice from the radon group (Figure 1G) showed an improvement or remained stable in clinical score after radon treatment
While slight modulations were detected in some of the investigated cytokines (slight reduction of IL-16, IL-17A, and IL-22; minor increase in IL-4 (Figure 5C,G–I)), we found a significant increase of IL-5 within the radon group (Figure 5D, p = 0.0229)
Similar to our results in in vivo exposed mice, we found no significant alterations of anti-oxidative enzymes Superoxide Dismutase 1 (SOD1), Glutathione peroxidase 1 (GPx1), catalase, and nuclear factor-erythroid-2-related factor 2 (Nrf2) in ex vivo exposed bone marrow (Figure 8)
Summary
The noble gas radon is a naturally occurring radioactive substance. While it greatly contributes to the exposure from naturally occurring sources of ionizing radiation (IR) it is widely used in the treatment of benign inflammatory and non-inflammatory diseases, in many countries. It is widely accepted that the emitting alpha-particles from radon in these springs are responsible for the main dose and for several beneficial effects [1,2,3]. The analgesic effects of radon therapies are exploited in the form of bathing in water containing radon, drinking radon-infused water or via inhalation therapy in galleries or caves with enhanced radon concentrations [2,3,4,5]
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