Ionizing radiation mediates expression of cell adhesion molecules in distinct histological patterns within the lung.

Inflammatory cell infiltration of the lung is a predominant histopathological change that occurs during radiation pneumonitis. Emigration of inflammatory cells from the circulation requires the interaction between cell adhesion molecules on the vascular endothelium and molecules on the surface of leukocytes. We studied the immunohistochemical pattern of expression of cell adhesion molecules in lungs from mice treated with thoracic irradiation. After X-irradiation, the endothelial leukocyte adhesion molecule 1 (ELAM-1; E-selectin) was primarily expressed in the pulmonary endothelium of larger vessels and minimally in the microvascular endothelium. Conversely, the intercellular adhesion molecule 1 (ICAM-1; CD54) was expressed in the pulmonary capillary endothelium and minimally in the endothelium of larger vessels. Radiation-mediated E-selectin expression was first observed at 6 h, whereas ICAM-1 expression initially increased at 24 h after irradiation. ICAM-1 and E-selectin expression persisted for several days. P-selectin is constitutively expressed in Weibel-Palade bodies in the endothelium, which moved to the vascular lumen within 30 min after irradiation. P-selectin was not detected in the pulmonary endothelium at 6 h after irradiation. The radiation dose required for increased cell adhesion molecule expression within the pulmonary vascular endothelium was 2 Gy, and expression increased in a dose-dependent manner. These data demonstrate that ICAM-1 and E-selectin expression is increased in the pulmonary endothelium following thoracic irradiation. The pattern of expression of E-selectin, P-selectin, and ICAM-1 is distinct from one another.

Irradiation induces increase of adhesion molecules and accumulation of beta2-integrin-expressing cells in humans.

PURPOSE: The purpose of our investigation was to describe the dose- and time-dependent histomorphologic alterations of the irradiated tissue, the composition of the infiltrate, and the expression patterns of various adhesion molecules. METHODS AND MATERIALS: We analyzed immunohistochemically alterations in oral mucosa in 13 head and neck cancer patients before radiotherapy and with 30 Gy and 60 Gy. All had oral mucosa irradiation, with a final dose of 60 Gy using conventional fractionation. Snap-frozen specimens were stained using the indirect immunperoxidase technique. Histomorphology was studied in paraffin-embedded sections. In addition, we determined the clinical degree of oral mucositis. RESULTS: Histomorphologic evaluation showed no vascular damage. Irradiation caused a steep increase of beta2-integrin-bearing cells (p < 0.01), whereas the percentage of beta1-integrin-positive cells remained at low levels. Additionally we found an increase in the expression of endothelial intercellular adhesion molecule-1 (ICAM-1) (p < 0.01) and E-selectin (p < 0.05), while endothelial vascular cell adhesion molecule-1 (VCAM-1) expression remained at very low levels. CONCLUSION: Our findings indicate that in radiation-induced oral mucositis there is no marked vascular damage until the end of radiotherapy. For recruitment of leukocytes, beta2 is more involved than beta1. Pharmaceuticals that block leukocyte adhesion to E-selectin or ICAM-1 may prevent radiation-mediated inflammation in oral mucosa.

Gamma knife irradiation increases cerebral endothelial expression of intercellular adhesion molecule 1 and E-selectin.

OBJECTIVE: Alterations in multiple functions of the microvasculature occur in response to gamma irradiation and are thought to contribute to radiation-induced end organ damage by inducing inflammatory responses, particularly leukocyte infiltration into the affected area. Endothelial cell adhesion molecules (ECAMs) mediate leukocyte adhesion and migration. Here, we validate a method to study the effect of Leksell gamma knife stereotactic radiosurgery on the expression of ECAMs on human cerebral endothelium at 0, 24, 48, and 72 hours after irradiation. METHODS: A human brain endothelial cell line (IHEC) was cultured on 12-mm coverslips and subjected to 50 Gy of collimated gamma irradiation with the Leksell gamma knife (Elekta Instruments, Inc., Atlanta, GA). Lactate dehydrogenase release was measured at 24, 48, and 72 hours after irradiation and caspase-3 at 24, 48, 72, 96, and 120 hours. ECAM expression was measured at postirradiation intervals of 0, 24, 48, and 72 hours by cell enzyme-linked immunoabsorbent assay. We used a cell irradiator composed of two chambers. The upper chamber holds the coverslips firmly in place while they are immersed in media. The lower chamber is connected to a peristaltic pump, which pumps water into the chamber and maintains the media in the upper chamber at 37 degrees C through convection. RESULTS: None of the ECAMs tested was significantly elevated compared with the control basally. Twenty-four hours after irradiation, intercellular adhesion molecule 1 was significantly elevated on brain endothelial cells but there was no significant elevation of E-selectin. Vascular cell adhesion molecule 1 was increased slightly but not significantly and decreased at 48 hours. At 72 hours, E-selectin expression was significantly increased; intercellular adhesion molecule 1 and vascular cell adhesion molecule 1 were not altered relative to sham controls. CONCLUSION: Increased ECAM expression and lactate dehydrogenase release support the idea that the cerebral microvasculature undergoes an inflammatory response after Leksell gamma knife stereotactic radiosurgery.

Comparison of changes in endothelial adhesion molecule expression following UVB irradiation of skin and a human dermal microvascular cell line (HMEC-1).

We have assessed the pattern of dermal endothelial adhesion molecule expression following broadband UVB irradiation in vivo and in vitro. Skin biopsies were taken from 4 human volunteers at baseline and at 4, 8 and 24 h post-irradiation with 2.5 minimal erythema doses of UVB. Sections were stained immunohistochemically for E-selectin, intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1). CD31 and neutrophil elastase. The effect of direct UVB irradiation on E-selectin, ICAM-1 and VCAM-1 was examined in a human dermal microvascular endothelial cell line, HMEC-1. Cultured HMEC-1 were irradiated with 2.5-40 mJ/cm2 of UVB, and assessed for adhesion molecule expression by immunofluorescence microscopy and fluorescence-activated cell sorter analysis. In vivo, E-selectin was minimally expressed on EC at baseline and was induced by 4 h following irradiation, P < 0.01. ICAM-1 was moderately expressed at baseline and appeared mildly induced at 24 h, although this did not reach statistical significance. VCAM-1 was weakly expressed in unirradiated skin while CD31 was moderately expressed, but neither was induced by UVB irradiation. A significant neutrophilic infiltrate appeared by 8 h and was maximal at 24 h, P < 0.05. Neutrophil infiltration correlated with E-selectin expression, r = 0.96. In HMEC-1, ICAM-1 was upregulated at 24 h post-irradiation, with an increase in mean channel fluorescence from 100% at baseline to 145 (SD12)% at 24 h, P < 0.05. No change was seen in expression of E-selectin, VCAM-1 or CD31. These studies support the involvement of endothelial adhesion molecules E-selectin and ICAM-1 in UVB-induced inflammation. Whereas ICAM-1 is upregulated by direct irradiation of endothelial cells, E-selectin stimulation appears to be an indirect effect.