Transcriptional Upregulation of DNA Damage Response Genes in Bank Voles (Myodes glareolus) Inhabiting the Chernobyl Exclusion Zone

Abstract

Exposure to ionizing radiation (IR) from radionuclides released into the environment can damage DNA. An expected response to exposure to environmental radionuclides, therefore, is initiation of DNA damage response (DDR) pathways. Increased DNA damage is a characteristic of many organisms exposed to radionuclides but expression of DDR genes of wildlife inhabiting an area contaminated by radionuclides is poorly understood. We quantified expression of five central DDR genes Atm, Mre11, p53, Brca1, and p21 in the livers of the bank vole Myodes glareolus that inhabited areas within the Chernobyl Exclusion Zone (CEZ) that differed in levels of ambient radioactivity, and also from control areas outside the CEZ (i.e., sites with no detectable environmental radionuclides) in Ukraine. Expression of these DDR genes did not significantly differ between male and female bank voles, nor among sites within the CEZ. We found a near two-fold upregulation in the DDR initiators Mre11 and Atm in animals collected from the CEZ compared with samples from control sites. As Atm is an important regulator of oxidative stress, our data suggest that antioxidant activity may be a key component of the defense against exposure to environmental radioactivity.

Infection Load and Prevalence of Novel Viruses Identified from the Bank Vole Do Not Associate with Exposure to Environmental Radioactivity

“…The following are available online at http://www.mdpi.com/1999-4915/12/1/44/s1: Figure S1: Pairwise correlation of plasma virus particle amounts in males and females; Figure S2: Virus amounts in Swedish bank vole spleen transcriptome samples; Table S1: Bank vole females collected on October 2016 used for NGS, Table S2: Female bank vole samples used in virus qPCR analysis; Table S3: Male bank vole samples used in virus qPCR analysis; Table S4: Pairwise comparisons of virus amounts between females of Chernobyl exclusion zone and control populations; Table S5: Pairwise comparisons between absorbed dose rates and virus amounts; Table S6: Virus-specific qPCR primers used in this study. where: D int is the absorbed dose rate due to internal exposure from 137 Cs (mGy/day); A is the activity of 137 Cs incorporated in the animal body (Bq/kg); C u is the unit conversion coefficient; φ i is the absorbed fractions for electron, positron or photon of the specific energy line E i self-absorption in tissue for the 137 Cs source which is uniformly distributed throughout homogeneous sphere of mass 20 g of unit density and tissue-equivalent composition (Stabin et al, 2000); f i is the intensity (or emission frequency) of the specific energy line E i (MeV) emitted per decay of 137 Cs and it daughter radionuclide 137 mBa (ICRP Publication 38,1983), the sum is taken over all electron, positron and photon energies E i of 137 Cs spectrum (see also Chesser et al, 2000).…”

“…Virus activation by irradiation may be facilitated by radiation-mediated immunosuppression that makes the host more susceptible to virus infection and replication [33][34][35], or by radiation-induced activation of the DNA repair proteins that some viruses utilize in their replication [36,37]. Wild bank voles exposed to chronic low-dose (up to 20 µGy/h) environmental radiation show activated transcription of DNA repair proteins [38] and inhibited apoptosis [39], and show signs of immunosuppression [40]. As these processes may support virus replication, we predicted an elevated viral load in bank voles inhabiting areas contaminated by radionuclides compared with uncontaminated areas.…”

Exposure to environmental radionuclides is associated with altered metabolic and immunity pathways in a wild rodent

“…While exposure to environmental radionuclides impacts gene expression, it is hard to identify a general response of organisms because studies typically quantify expression of candidate genes from DNA repair and oxidative stress pathways. For example, the level of soil radionuclides within and around the CEZ is associated with the activity of some candidate radical scavenging and DNA damage response genes in plants (Kovalchuk, ) and in a rodent, the bank vole Myodes glareolus (Jernfors et al, ). Away from Chernobyl, increased DNA damage and elevated expression of selected DNA damage and repair candidate genes were observed in European wood mice ( Apodemus sylvaticus ) exposed to uranium mining waste (Lourenço, Pereira, Gonçalves, & Mendo, ) and marine mussels ( Mytilus sp.)…”

Ecological mechanisms can modify radiation effects in a key forest mammal of Chernobyl

“…Certainly, bank voles inhabiting areas contaminated by radionuclides derived from the former Chernobyl NPP show signs of molecular stress, such as upregulation of some DNA damage response genes (Jernfors et al. ) and altered telomere homeostasis (Kesäniemi et al. ).…”