Gene Expression Profiles in Radiation Workers Occupationally Exposed to Low Levels of Ionizing Radiation in Al-Tuwaitha Site in Baghdad

Ionizing radiation (IR) imposes risks to human health and the environment. IR at low doses and low dose rates has the potency to initiate carcinogenesis. Genotoxic environmental agents such as IR trigger a cascade of signal transduction pathways for cellular protection. Physical dosimeter records indicated that the total accu mulated radiation doses in these individuals varied from 0.696 to 39.088 mSv. In this study, using cDNA Real time polymerase chain reaction (RT-PCR) technique, we monitored the gene expression profiles in lymphocytes derived from 20 male radiation workers occupationally exposed to low ionizing radiation as well as 10 male blood samples as control. Total RNA was isolated using Trizol method from blood for the study groups mentioned. The RNA concentration was determined spectrophotometrically by measuring their absorbance using Nano- drop spectrophotometer that dependent on the ratio A260/A280 of the wavelength which lead to the determination of RNA purity, it ranged from 1.79-2.1 in all groups. RNA integrity and quality were confirmed by agarose gel electrophoresis. Three bands such as 28s, 18s and 5s appeared in a visible manner. This study involved the reverse transcription (RT) of the RNA for the manufacture of complementary DNA (cDNA) using the polymerase chain reaction (PCR) for investigation on above –mentioned groups of study. Complementary DNA was used in amplification of genes used in the present study, three types of specialized primer genes were selected for the genes such as RHOA, CDKN1A and GADD45A, which have a relation with ionizing radiation in addition to the primers for internal control (β-actin) gene. All of these genes play an important role in the organization of the Cell cycle/proliferation and DNA repair. Therefore, the study was contributed to the possibility of using it as a biological evidence for the detection of radiation exposure or contamination and thus may contribute to understand some of unknown mechanisms that may occur during the process of cancer formation perhaps caused by radiation.The optimal conditions for PCR were determined using a dye ( SYBR® Green 1).This should be done before using the device quantitative real time-PCR (QRT-PCR) in experiments. The products of replicated specialized primers for the genes concerned and the cDNA for the studied samples were electrophoretically separated in agarose gels .The banding profiles were visualized by ethidium bromide staining, as the molecular weight were 135 bp , 165 bp and 185 , bp, ( nitrogen-base pair) for RHOA ,CDKN1A, GADD45A genes , respectively.Gene expression analysis revealed statistically significant transcriptional changes in a 3 genes (RHOA, GADD45A up-regulated and CDKN1A down-regulated) . Some of the genes that showed altered expression profiles in this study can be used as biomarkers for monitoring the chronic low level exposure in humans. Additionally, alterations in gene expression patterns observed in chronically exposed radiation workers reinforces the need for defining the effective radiation dose that causes immediate genetic damage as well as the long-term effects on genomic instability, including cancer.