Gene expression analyses of the small intestine of pigs in the ex-evacuation zone of the Fukushima Daiichi Nuclear Power Plant

Abstract

BackgroundAfter the accident at the Fukushima Daiichi Nuclear Power Plant, radioactive contaminants were released over a widespread area. Monitoring the biological effects of radiation exposure in animals in the ex-evacuation zone should be continued to understand the health effects of radiation exposure in humans. The present study aimed to clarify the effects of radiation by investigating whether there is any alteration in the morphology and gene expressions of immune molecules in the intestine of pigs and inobuta (wild boar and domestic pig hybrid) in the ex-evacuation zone in 2012. Gene expression analysis was performed in small intestine samples from pigs, which were collected from January to February 2012, in the ex-evacuation zone. Pigs lived freely in this zone, and their small intestine was considered to be affected by the dietary intake of radioactive contaminants.ResultsSeveral genes were selected by microarray analysis for further investigation using real-time polymerase chain reaction. IFN-γ, which is an important inflammatory cytokine, and TLR3, which is a pattern recognize receptor for innate immune system genes, were highly elevated in these pigs. The expressions of the genes of these proteins were associated with the radiation level in the muscles. We also examined the alteration of gene expressions in wild boars 5 years after the disaster. The expression of IFN-γ and TLR3 remained high, and that of Cyclin G1, which is important in the cell cycle, was elevated.ConclusionsWe demonstrated that some changes in gene expression occurred in the small intestine of animals in the ex-evacuation zone after radiation. It is difficult to conclude that these alterations are caused by only artificial radionuclides from the Fukushima Daiichi Nuclear Power Plant. However, the animals in the ex-evacuation zone might have experienced some changes owing to radioactive materials, including contaminated soil, small animals, and insects. We need to continue monitoring the effects of long-term radiation exposure in living things.

The Effect of Radiation on the Immune System in Pigs Affected by the Fukushima Daiichi Nuclear Power Plant Accident

“…We have already reported that some of the selected genes did not show any changes; however, some showed significant differences. As previously reported [16], the expression levels of the AIFM1, IFN-γ and TLR3 genes were significantly higher in abandoned pigs than in control pigs. However, the expression levels of cyclin G1, GADD45A, XRCC1, Smad7, XAB2, XPC, OGG1 and EPHX2 were similar in both groups.…”

“…As we previously reported that there were no remarkable changes including fibrosis in the intestinal tissues of abandoned pigs [16]. Despite the highly elevated IFN-γ gene expression, there were no pathological or morphological changes in both the abandoned and the non-affected control groups (Fig.11.4).…”

“…Therefore, we next focused on the relationship between gene expression and 137 Cs concentration because if radiation causes inflammation through oxidative stress, the elevation of IFN-γ expression might be related to the level of radiation exposure of each pig. Figure 11.2b is a modified version of a figure from our previous report [16]. IFN-γ gene expression was associated with 137 Cs concentration in the muscle (y = 0.3687 × 10 −6 ± 0.1342 × 10 −6 x + 0.05727 ± 0.002299 [R 2 = 0.3502]).…”

“…cDNA samples were analyzed using a microarray (three pigs of control vs three abandoned pigs in the ex-evacuation zone) (V1: 4 × 44K; Agilent Technologies, Palo Alto, CA, USA), and IFN-γ gene expression was assessed by real-time PCR. Primer sequences were designed using Primer-BLAST with sequences obtained from GenBank [16].…”

“…The number of differentially expressed genes with a ≥2-fold change was 5,135. Various immune-related genes were up-regulated in abandoned pigs caught in 2012 [16]. Table 11.1 shows upregulated genes that are involved in NF-κB activation, oxidative stress and inflammatory immune responses.…”