Gene expression profiling in human fibroblast after low-LET irradiation

Exposure to radiation provokes cellular responses controlled in part by gene expression networks. MicroRNAs (miRNAs) are small non-coding RNAs which mostly regulate gene expression by degrading the messages or inhibiting translation. Here we investigated changes in miRNA expression patterns after low (0.1 Gy) and high (2.0 Gy) doses of X-ray in human fibroblasts. At early (0.5 h) and late (6 and 24 h) time points irradiation caused qualitative and quantitative differences in the down-regulation of miRNA levels including miR-92b 137 660 and 656. A transient up-regulation of miRNAs was observed after 2 h post-irradiation following high doses of radiation including miR-558 and 662. MicroRNA levels were inversely correlated with targets from mRNA and proteomic profiling after 2.0 Gy of radiation. MicroRNAs miR-579 608 548-3p and 585 are noted for targeting genes involved in radioresponsive mechanisms such as cell cycle checkpoint and apoptosis. We suggest here a model in which miRNAs may act as hub regulators of specific cellular responses immediately down-regulated so as to stimulate DNA repair mechanisms followed by up-regulation involved in suppressing apoptosis for cell survival. Taken together miRNAs may mediate signaling pathways in sequential fashion in response to radiation and may serve as biodosimetric markers of radiation exposure. Overall design: The gene expression patterns in human fibroblasts after 2.0 Gy of low-LET radiation was determined at 2 and 24 hrs post-irradiation time in technical triplicates. Control non-irradiated samples were also prepared in triplicates.