Serum Lipocalin2 is a potential biomarker of liver irradiation damage

IL-6 - IL-1- lipocalin2 (LCN2) - liver irradiation - oxidative stress - TNF-a Lipocalin2 (LCN2) is an acute phase protein. The source of its increased serum level in oxidative stress conditions (ROS) remains still unknown. We prospectively evaluate the serum LCN2 increase after single dose liver irradiation along with hepatic LCN2 gene and protein expression.

A single dose of 25 Gray was administered percutaneously to the liver of randomly paired rats after a planning CT scan. Male Wistar rats were sacrificed 1, 3, 6, 12, 24 and 48 h after irradiation along with sham-irradiated controls. ELISA, RT-PCR, Western blot and immunofluorescence staining was performed. Furthermore, hepatocytes, myofibroblasts and Kupffer cells were isolated from the liver of healthy rats and irradiated ex-vivo.

After liver irradiation, LCN2 serum levels increased significantly up to 2.7 μg/ml within 6 h and stayed elevated over 24 h. LCN2 specific transcripts increased significantly up to 552 ± 109-fold at 24 h after liver irradiation, which was further confirmed at protein level. α2-macroglobulin and hemoxygenase-1 also showed an increase, but the magnitude was less as compared to LCN2. LCN2+ granulocytes were detected within 1 h after irradiation around central and portal fields and remained high during the course of study. Ex-vivo irradiated hepatocytes (2.4 ± 0.6-fold) showed a higher LCN2 gene expression as compared to myofibroblasts and Kupffer cells. IL-1β treatment further increased LCN2 gene expression in cultured hepatocytes.

Single dose liver irradiation induces a significant increase in LCN2 serum levels, comparable to the induction of acute phase proteins. We suggest LCN2 as marker for the early phase of radiation-induced tissue damage.