Radiation treatment of acute inflammation in mice

Purpose: Low-dose radiotherapy (RT) has often been used effectively for the treatment of a variety of benign diseases, particularly those with acute inflammatory features. Here we report findings on radiation treatment of acute inflammation using a murine carrageenin air pouch model. Materials and methods: Air pouches raised on the dorsal surface of mice were injected with λ carrageenin and were irradiated 6 h later with doses ranging from 0 - 5 Gy. Treatment success was evaluated at various times thereafter by volume of exudate and number of inflammatory cells, and levels of inflammation-related cytokines tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β) and transforming growth factor beta-1 (TGFβ-1), and expression of inducible nitric oxide synthase (iNOS), heme oxygenase-1 (HO-1), cyclooxygenase-2 (COX-2) and inducible heat shock protein 70 (HSP70) as determined by enzyme-linked immunosorbent assay (ELISA) and Western blotting, respectively. Results: Crude inflammatory parameters such as the amount of exudates and number of inflammatory cells remained largely unaffected by radiation or were even a slightly and transiently increased. However, the expression of iNOS was attenuated by radiation concomitant with an increase in the levels of HO-1 and HSP70. Cytokine levels varied with the radiation dose and the time point. Conclusions: Ionizing radiation, even at low doses, functionally modulates inflammatory cells. Our findings indicate possible mechanisms as to how low-dose radiation may exert anti-inflammatory effects and provide the first evidence that heat shock proteins may be involved in this response.