The anti-inflammatory effect of low-dose radiation therapy involves a diminished CCL20 chemokine expression and granulocyte/endothelial cell adhesion.
OBJECTIVE
Low-dose radiotherapy (LD-RT) is known to exert an anti-inflammatory effect, however, the underlying molecular mechanisms are not fully understood. The manipulation of polymorphonuclear neutrophil (PMN) function and/or recruitment may be one mechanism. Chemokines contribute to this process by creating a chemotactic gradient and by activating integrins. This study aimed to characterize the effect of LD-RT on CCL20 chemokine production and PMN/endothelial cell (EC) adhesion.


METHODS
The EC line EA.hy.926 was irradiated with doses ranging from 0 to 3 Gy and was co-cultured with PMNs from healthy donors either by direct cell contact or separated by transwell membrane chambers. CXCL8, CCL18, CCL20 chemokine and tumor necrosis factor-(TNF-)alpha cytokine levels in supernatants were determined by ELISA and adhesion assays were performed. The functional impact of the cytokines transforming growth factor-(TGF-)beta(1) and TNF-alpha and of the intercellular adhesion molecule-(ICAM-)1 on CCL20 expression was analyzed by using neutralizing antibodies.


RESULTS
As compared to CXCL8 and CCL18, CCL20 chemokine secretion was found to be exclusively induced by a direct cell-cell contact between PMNs and EA.hy.926 ECs in a TNF-alpha-dependent, but ICAM-1-independent manner. Furthermore, irradiation with doses between 0.5 and 1 Gy resulted in a significant reduction of CCL20 release which was dependent on TGF-beta(1) (p < 0.01). The decrease of CCL20 paralleled with a significant reduction in PMN/EA.hy.926 EC adhesion (p < 0.001).


CONCLUSIONS
The modulation of CCL20 chemokine expression and PMN/EC adhesion adds a further facet to the plethora of mechanisms contributing to the anti-inflammatory efficacy of LD-RT.
Rödel
Franz
F
Department of Radiotherapy and Oncology, University of Frankfurt/Main, Germany.
Hofmann
Dorothée
D
Auer
Judith
J
Keilholz
Ludwig
L
Röllinghoff
Martin
M
Sauer
Rolf
R
Beuscher
Horst Ulrich
HU
D002448:Cell Adhesion / Q000528:radiation effects*; D002460:Cell Line; D054418:Chemokine CCL20 / Q000378:metabolism; D018925:Chemokines / Q000378:metabolism*; D019742:Chemokines, CC / Q000378:metabolism; D002634:Chemotaxis, Leukocyte / Q000528:radiation effects*; D019583:Dose Fractionation, Radiation; D004730:Endothelium, Vascular / Q000528:radiation effects; D006801:Humans; D006822:Hybrid Cells / Q000528:radiation effects; D066298:In Vitro Techniques; D016023:Integrins / Q000378:metabolism*; D016209:Interleukin-8 / Q000378:metabolism; D019402:Macrophage Inflammatory Proteins / Q000378:metabolism; D020556:Neutrophil Infiltration / Q000528:radiation effects*; D009504:Neutrophils / Q000276:immunology / Q000528:radiation effects*; D011879:Radiotherapy Dosage; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
C111792:CCL18 protein, human; C108355:CCL20 protein, human; D054418:Chemokine CCL20; D018925:Chemokines; D019742:Chemokines, CC; D016023:Integrins; D016209:Interleukin-8; D019402:Macrophage Inflammatory Proteins; D014409:Tumor Necrosis Factor-alpha