A study on the pathogenesis of the radiation pneumonitis. Alterations in pulmonary mRNA encoding adhesion molecules ICAM-1, VCAM-1, and P-selectin following thoracic irradiation in mice

To investigate the role of the adhesion molecules in the pathogenesis of the radiation pneumonitis, we quantified the mRNA expression of the adhesion molecules in the lung by Northern blot method following whole thorax irradiation to C57BL/6J mice. After irradiation of 12 Gy to the whole thorax, there were increase of mRNA for ICAM-1 by 42% at 4 hours (p<0.05), 76% at 24 hours (p<0.01) and 51% at 48 hours (p<0.05) compared with controls. And it returned to control level at 1 week. No significant change was observed thereafter until 8 weeks. The expression of VCAM-1 mRNA were also increased by 49% (p<0.01) at 12 hours and were still increased by 25% at 1 week. P-selectin mRNA as transiently increased by 59% at 12 hours. We examined the relationship between the ICAM-1 induction and the radiation dose, and found that ICAM-1 expression was increased by 3 Gy of irradiation and it was increased in radiation dose dependent manner up to 24 Gy. These early inductions of mRNA for ICAM-1, VCAM-1 and P-selectin in mice lungs following thoracic irradiation were transient but significant, and they were one of the most immediate change reported in vivo. It is suggested that these adhesion molecules are possibly related to the pathogenesis of the radiation pneumonitis. (author)