The urine proteome as a radiation biodosimeter

The global rise in terrorism has increased the risk of radiological events aimed at creating chaos and destabilization, although they may cause relatively limited number of immediate casualties. We have proposed that a self-administered test would be valuable for initial triage following terrorist use of nuclear/radiological devices. The urine proteome may be a useful source of the biomarkers required for developing such a test. We have developed and extensively used a rat model to study the acute and late effect of total body (TBI) and partial body irradiation on critical organ systems. This model has proven valuable for correlating the structural and functional effects of radiation with molecular changes. Results show that nephron segments differ with regard to their sensitivity and response to ionizing radiation. The urine proteome was analyzed using LC-MS/MS at 24 h after TBI or local kidney irradiation using a 10 Gy single dose of X rays. LC-MS/MS data were analyzed and grouped under Gene Ontology categories Cellular Localization, Molecular Function and Biological Process. We observed a decrease in urine protein/creatinine ratio that corroborated with decreased spectral counts for urinary albumin and other major serum proteins. Interestingly, TBI caused greater decline in urinary albumin than local kidney irradiation. Analysis of acute-phase response proteins and markers of acute kidney injury showed increased urinary levels of cystatin superfamily proteins and alpha-1-acid glycoprotein. Among proteases and protease inhibitors, levels of Kallikrein 1-related peptidase b24, precursor and products of chymotrypsin-like activity, were noticeably increased. Among the amino acids that are susceptible to oxidation by free radicals, oxidized histidine levels were increased following irradiation. Our results suggest that proteomic analysis of early changes in urinary proteins will identify biomarkers for developing a self-administered test for radiation biodosimetry.