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Anti-inflammatory effects of low-dose radiotherapy in an experimental model of systemic inflammation in mice
Meritxell Arenas1, Fèlix Gil, Meritxell Gironella
1Department of Radiation Oncology, Hospital Clínic de Barcelona, Institut de Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), University of Barcelona, Barcelona, Spain.
Purpose:
The aim of this study was to determine the effects of low-dose radiotherapy (LD-RT) on the inflammatory response and to characterize the potential mechanisms underlying these effects.
Methods And Materials:
Mice were irradiated with 0.1, 0.3, 0.6 Gy, or sham radiation before lipopolysaccharide (LPS) challenge. Leukocyte-endothelial cell interactions in intestinal venules were assessed using intravital microscopy. Intercellular adhesion molecule-1 (ICAM-1) expression was determined using radiolabeled antibodies 5 h after irradiation. Production of transforming growth factor-beta1 (TGF-beta1) was measured by enzyme-linked immunosorbent assay and its in vivo functional relevance by immunoneutralization.
Results:
Compared with vehicle treated animals, LPS induced a marked increase in leukocyte adhesion (0.13+/-0.59 vs. 5.89+/-1.03, p<0.0001) in intestinal venules. The number of adherent leukocytes was significantly reduced by the 3 doses of LD-RT tested; the highest inhibition was observed with 0.3 Gy (0.66+/-1.96, p<0.0001). LPS-induced ICAM-1 upregulation was not modified by LD-RT. Circulating levels of TGF-beta1 were significantly increased in response to LD-RT in controls and LPS challenged animals. Neutralization of TGF-beta1 partially restored LPS-induced adhesion (4.83+/-1.41, p<0.05).
Conclusions:
LD-RT has a significant anti-inflammatory effect, inhibiting leukocyte recruitment, which is maximal at 0.3 Gy. This effect results in part from increased TGF-beta1 production and is not related to modulation of ICAM-1 expression.