Abstract
Radon therapy, which has been performed in Misasa (Japan) and Badgastein (Austria), was found to have a beneficial effect on pain-related diseases. Although several clinical studies of the curative effects on pain related diseases have been reported, the mechanism remains to be incompletely elucidated. In order to further clarify the mechanism, we developed radon exposure systems for small animals. In the present paper, we review several studies on the anti-inflammatory effects of radon inhalation in mice. We first examined whether radon inhalation inhibits carrageenan-induced inflammatory paw in mice. Radon concentration in mouse cage was approximately 2000 Bq/m 3 , which is similar to the level of radon therapy at Misasa Medical Center, Okayama University Hospital. Although carrageenan administration into right hind paw of mice induced paw edema, radon inhalation inhibited the edema. Antioxidants such as superoxide dismutase (SOD) and catalase were significantly higher in the radon-treated mice than in the sham-treated mice. Since the development of carrageenan-induced inflammation is mediated by reactive oxygen species (ROS), the inhibition of paw edema by radon inhalation is probably due to activation of antioxidant functions. We next examined the effects of radon inhalation on dextran sulfate sodium (DSS)-induced colitis in mice. Results showed that radon inhalation suppressed the damage caused by DSS-induced colitis. In addition, the mediators of inflammatory response such as tumor necrosis factor-alpha (TNF-α) were inhibited, and antioxidants such as SOD were increased by radon inhalation. Next, we examined the effects of radon inhalation on formalin-induced inflammatory pain in mice. Results showed that radon inhalation inhibited the licking response time. TNF-α, activated by formalin-induced inflammation, was lower in the radon-treated mice than in the sham-treated mice. Antioxidant activities such as SOD activity were increased in the mice that inhaled radon. These findings suggested that radon inhalation inhibits several types of inflammation in mice due to activation of antioxidant functions.
Highlights
Large numbers of patients are treated with traditional spa therapy in various countries
To assess the effects of radon inhalation on anti-inflammatory responses and antioxidant functions, we examined the levels of nitric oxide (NO), TNF-α, superoxide dismutase (SOD), CAT and lipid peroxide in serum and paw
The migration of inflammatory leukocytes was inhibited by radon inhalation. These results suggested that radon inhalation has a protective effect on carrageenan-induced inflammatory paw edema in mice due to the activation of antioxidant functions following radon inhalation
Summary
Large numbers of patients are treated with traditional spa therapy in various countries. The treatments with radon spa therapy are to drink radon hot spring water, to take radon bath, to walk in radon pool, and to inhale radon gas. The radon concentration in the room for radon inhaled treatment is around 2,000 Bq/m3 and, the room is hot (around 45oC) and humid (around 90%) [1,4]. A similar treatment is performed using health mines in Montana, United States [5]. The concentration of radon is approximately 45,000 Bq/m3, hot (around 40oC) and humid (up to 95%). There is not much difference in the absorbed dose among other organs [13] In any of these cases, the radon therapy treatment is for pain-related diseases such as rheumatism [5,6,7]. The objective of this work was to review the latest knowledge regarding the antiinflammatory effects of radon inhalation
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