Confirmation of efficacy, elucidation of mechanism, and new search for indications of radon therapy

Indications of radon therapy include various diseases related to respiratory, painful, digestive, chronic degenerative, senile, etc. derived from reactive oxygen species, but most are based on empirical prescriptions. For this reason, we have evaluated the relation between the biological response caused by radon and the tissue/organ absorbed dose more quantitatively, and have promoted the elucidation of mechanisms related to the indication and searching newly. As a result, as a mechanism, a series of moderate physiological stimulative effects accompanying a small amount of oxidative stress by radon inhalation are being elucidated. That is, hyperfunction of anti-oxidation/immune regulation/damage repair, promotion of anti-inflammation/circulating metabolism/hormone secretion, induction of apoptosis/heat shock protein, etc. Also, new indications include inflammatory/neuropathic pain, hepatic/renal injury, colitis, type 1 diabetes, complication kidney injury, hyperuricemia, transient cerebral ischemia, and inflammatory edema. Furthermore, we examined the combined antioxidant effect of radon inhalation and antioxidants or therapeutic agents. As a result, it was clear that any combination treatment could enhance the suppression effect of disease. It can be expected that radon therapy can be used effectively by applying it in addition to usual treatment, since reduction in its dosage can also be expected by concomitant use for drugs with strong side effects.

Protective effects of hot spring water drinking and radon inhalation on ethanol-induced gastric mucosal injury in mice

Radon therapy using radon (222Rn) gas is classified into two types of treatment: inhalation of radon gas and drinking water containing radon. Although short- or long-term intake of spa water is effective in increasing gastric mucosal blood flow, and spa water therapy is useful for treating chronic gastritis and gastric ulcer, the underlying mechanisms for and precise effects of radon protection against mucosal injury are unclear. In the present study, we examined the protective effects of hot spring water drinking and radon inhalation on ethanol-induced gastric mucosal injury in mice. Mice inhaled radon at a concentration of 2000 Bq/m3 for 24 h or were provided with hot spring water for 2 weeks. The activity density of 222Rn ranged from 663 Bq/l (start point of supplying) to 100 Bq/l (end point of supplying). Mice were then orally administered ethanol at three concentrations. The ulcer index (UI), an indicator of mucosal injury, increased in response to the administration of ethanol; however, treatment with either radon inhalation or hot spring water inhibited the elevation in the UI due to ethanol. Although no significant differences in antioxidative enzymes were observed between the radon-treated groups and the non-treated control groups, lipid peroxide levels were significantly lower in the stomachs of mice pre-treated with radon or hot spring water. These results suggest that hot spring water drinking and radon inhalation inhibit ethanol-induced gastric mucosal injury.

Difference in the action mechanism of radon inhalation and radon hot spring water drinking in suppression of hyperuricemia in mice

Although radon therapy is indicated for hyperuricemia, the underlying mechanisms of action have not yet been elucidated in detail. Therefore, we herein examined the inhibitory effects of radon inhalation and hot spring water drinking on potassium oxonate (PO)-induced hyperuricemia in mice. Mice inhaled radon at a concentration of 2000 Bq/m(3) for 24 h or were given hot spring water for 2 weeks. Mice were then administrated PO at a dose of 500 mg/kg. The results obtained showed that serum uric acid levels were significantly increased by the administration of PO. Radon inhalation or hot spring water drinking significantly inhibited elevations in serum uric acid levels through the suppression of xanthine oxidase activity in the liver. Radon inhalation activated anti-oxidative functions in the liver and kidney. These results suggest that radon inhalation inhibits PO-induced hyperuricemia by activating anti-oxidative functions, while hot spring water drinking may suppress PO-induced elevations in serum uric acid levels through the pharmacological effects of the chemical compositions dissolved in it.

Study of antioxidative effects and anti-inflammatory effects in mice due to low-dose X-irradiation or radon inhalation

Low-dose irradiation induces various stimulating effects, especially activation of the biological defense system including antioxidative and immune functions. Oxidative stress induced by reactive oxygen species (ROS) can cause cell damage and death and can induce many types of diseases. This paper reviews new insights into inhibition of ROS-related diseases with low-dose irradiation or radon inhalation. X-irradiation (0.5 Gy) before or after carbon tetrachloride (CCl4) treatment inhibits hepatopathy in mice. X-irradiation (0.5 Gy) before ischemia-reperfusion injury or cold-induced brain injury also inhibits edema. These findings suggest that low-dose X-irradiation has antioxidative effects due to blocking the damage induced by free radicals or ROS. Moreover, radon inhalation increases superoxide dismutase activity in many organs and inhibits CCl4-induced hepatic and renal damage and streptozotocin-induced type I diabetes. These findings suggest that radon inhalation also has antioxidative effects. This antioxidative effect against CCl4-induced hepatopathy is comparable to treatment with ascorbic acid (vitamin C) at a dose of 500 mg/kg weight, or α-tocopherol (vitamin E) treatment at a dose of 300 mg/kg weight, and is due to activation of antioxidative functions. In addition, radon inhalation inhibits carrageenan-induced inflammatory paw edema, suggesting that radon inhalation has anti-inflammatory effects. Furthermore, radon inhalation inhibits formalin-induced inflammatory pain and chronic constriction injury-induced neuropathic pain, suggesting that radon inhalation relieves pain. Thus, low-dose irradiation very likely activates the defense systems in the body, and therefore, contributes to preventing or reducing ROS-related injuries, which are thought to involve peroxidation.

Suppression of streptozotocin-induced type-1 diabetes in mice by radon inhalation

We examined the protective effect of radon inhalation on streptozotocin (STZ)-induced type-1 diabetes in mice. Mice inhaled radon at concentrations of 1000, 2500, and 5500 Bq/m3 for 24 hours before STZ administration. STZ administration induced characteristics of type-1 diabetes such as hyperglycemia and hypoinsulinemia; however, radon inhalation at doses of 1000 and 5500 Bq/m3 significantly suppressed the elevation of blood glucose in diabetic mice. Serum insulin was significantly higher in mice pre-treated with radon at a dose of 1000 Bq/m3 than in mice treated with a sham. In addition, superoxide dismutase activities and total glutathione contents were significantly higher and lipid peroxide was significantly lower in mice pre-treated with radon at doses of 1000 and 5500 Bq/m3 than in mice treated with a sham. These results were consistent with the result that radon inhalation at 1000 and 5500 Bq/m3 suppressed hyperglycemia. These findings suggested that radon inhalation suppressed STZ-induced type-1 diabetes through the enhancement of antioxidative functions in the pancreas.