No indications of an enhanced UV-light-induced unscheduled DNA synthesis in splenocytes of mice following a low-dose irradiation in vivo or in vitro

Enhanced nucleotide excision repair in human fibroblasts pre-exposed to ionizing radiation

Cellular protection against deleterious effects of DNA damaging agents requires an intricate network of defense mechanisms known as the DNA damage response (DDR). Ionizing radiation (IR) mediated activation of the DDR induces a transcriptional upregulation of genes that are also involved in nucleotide excision repair (NER). This suggests that pre-exposure to X-rays might stimulate NER in human cells. Here, we demonstrate in normal human fibroblasts that UV-induced NER is augmented by pre-exposure to IR and that this increased repair is accompanied by elevated mRNA and protein levels of the NER factors XPC and DDB2. Furthermore, when IR exposure precedes local UV irradiation, the presence of XPC and DDB2 at the sites of local UV damages is increased. This increase might be p53 dependent, but the mechanism of X-ray specific stabilization of p53 is unclear as both X-rays and UV stabilize p53.

Low-dose whole-body irradiation induces alteration of protein expression in mouse splenocytes

In previous studies, the stimulatory effect on immunological function and adaptive response in splenocytes were found after exposure of mice to low-dose whole-body irradiation (LD-WBI). Protein synthesis was found to be required for these responses. The present study, therefore, attempts to investigate the protein changes in mouse splenocytes after exposure to LD-WBI. Two-dimensional gel electrophoresis was used to show the alterations of proteins in nuclei, cytoplasm and extracellular fluid of the splenocytes at 4 h after mice exposed to 75 mGy X-rays. As compared to control, changed expressions of 20, 15 and 6 proteins, in sizes ranging from 10 to 69 kDa with pI of 5.0-8.2, were found in the nuclei, cytoplasm and extracellular fluid of splenocytes, respectively. One protein, shown in the cytoplasm of splenocytes of control mice, appeared in extracellular fluid of splenocytes after LD-WBI. Two proteins, shown in cytoplasm, and one protein, shown in extracellular fluid of splenocytes in control mice, appeared in the nuclei after LD-WBI. Time-course of protein synthesis varied in different proteins after LD-WBI. These results suggest that alterations of protein expressions and redistribution of proteins between intracellular and extracellular compartments occurred in the splenocytes after LD-WBI. Protein extract from LD-WBI splenocytes was fractionated by Sephadex G-100. Fractions 61-80 contained proteins able to protect lymphocytes in vitro from radiation-induced chromosome aberrations. These findings are of importance in elucidating mechanisms of immuno-enhancement and adaptive response induced by low-dose radiation. although the features and the functions of these proteins remain to be elucidated in future studies.