Effect of irradiation on gene expression of rat liver adhesion molecules: in vivo and in vitro studies.
OBJECTIVE
Migration of leukocytes into tissue is a key element of innate and adaptive immunity. An animal study showed that liver irradiation, in spite of induction of chemokine gene expression, does not lead to recruitment of leukocytes into the parenchyma. The aim of this study was to analyze gene expression of adhesion molecules, which mediate leukocyte recruitment into organs, in irradiated rat liver in vivo and rat hepatocytes in vitro.


METHODS
Rat livers in vivo were irradiated selectively at 25 Gy. Isolated hepatocytes in vitro were irradiated at 8 Gy. RNA extracted within 48 h after irradiation in vivo and in vitro was analyzed by real-time PCR (polymerase chain reaction) and Northern blot. Adhesion molecule concentration in serum was measured by ELISA (enzyme-linked immunosorbent assay). Cryostat sections of livers were used for immunohistology.


RESULTS
Significant radiation-induced increase of ICAM-1 (intercellular adhesion molecule-1), VCAM-1 (vascular cell adhesion molecule-1), JAM-1 (junctional adhesion molecule-1), beta1-integrin, beta2-integrin, E-cadherin, and P-selectin gene expression could be detected in vivo, while PECAM-1 (platelet-endothelial cell adhesion molecule-1) gene expression remained unchanged. In vitro, beta1-integrin, JAM-1, and ICAM-2 showed a radiation-induced increased expression, whereas the levels of P-selectin, ICAM-1, PECAM-1, VCAM-1, Madcam-1 (mucosal addressin cell adhesion molecule-1), beta2-integrin, and E-cadherin were downregulated. However, incubation of irradiated hepatocytes with either tumor necrosis factor-(TNF-)alpha, interleukin-(IL-)1beta, or IL-6 plus TNF-alpha led to an upregulation of P-selectin, ICAM-1 and VCAM-1.


CONCLUSIONS
The findings suggest that liver irradiation modulates gene expression of the main adhesion molecules in vivo and in cytokine-activated hepatocytes, with the exception of PECAM-1. This may be one reason for the lack of inflammation in the irradiated rat liver.
Moriconi
Federico
F
Department of Gastroenterology and Endocrinology, Göttingen University, Göttingen, Germany.
Malik
Ihtzaz
I
Ahmad
Ghayyor
G
Dudas
Joszef
J
Rave-Fränk
Margret
M
Vorwerk
Hilke
H
Hille
Andrea
A
Hess
Clemens Friedrich
CF
Ramadori
Giuliano
G
Christiansen
Hans
H
D000818:Animals; D018821:CD18 Antigens / Q000097:blood / Q000235:genetics; D015820:Cadherins / Q000097:blood / Q000235:genetics; D015815:Cell Adhesion Molecules / Q000097:blood / Q000235:genetics* / Q000528:radiation effects*; D015536:Down-Regulation / Q000528:radiation effects; D005786:Gene Expression Regulation / Q000528:radiation effects*; D022781:Hepatocytes / Q000528:radiation effects*; D066298:In Vitro Techniques; D019012:Integrin beta1 / Q000097:blood / Q000235:genetics; D018799:Intercellular Adhesion Molecule-1 / Q000097:blood / Q000235:genetics; D053583:Interleukin-1beta / Q000494:pharmacology; D015850:Interleukin-6 / Q000494:pharmacology; D008099:Liver / Q000528:radiation effects*; D008297:Male; D020556:Neutrophil Infiltration / Q000528:radiation effects*; D019007:P-Selectin / Q000097:blood / Q000235:genetics; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000097:blood / Q000235:genetics; D011833:Radiation Injuries, Experimental / Q000276:immunology*; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D015854:Up-Regulation / Q000528:radiation effects; D019010:Vascular Cell Adhesion Molecule-1 / Q000097:blood / Q000235:genetics
D018821:CD18 Antigens; D015820:Cadherins; D015815:Cell Adhesion Molecules; C520495:F11r protein, rat; D019012:Integrin beta1; D053583:Interleukin-1beta; D015850:Interleukin-6; D019007:P-Selectin; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D014409:Tumor Necrosis Factor-alpha; D019010:Vascular Cell Adhesion Molecule-1; D018799:Intercellular Adhesion Molecule-1