Abstract
Introduction: Understanding the molecular mechanism of chronic low-dose ionizing radiation (LDIR) effects on the human body is the subject of many research studies. Several aspects of cell function such as cell proliferation, apoptosis, inflammation, and tumorigenesis are affected by LDIR. Detection of the main biological process that is targeted by LIDR via network analysis is the main aim of this study.
Methods: GSE66720 consisting of gene expression profiles of human umbilical vein endothelial cells (HUVECs) (a suitable cell line to be investigated), including irradiated and control cells, was downloaded from Gene Expression Omnibus (GEO). The significant differentially expressed genes (DEGs) were determined and analyzed via protein-protein interaction (PPI) network analysis to find the central individuals. The main cell function which was related to the central nodes was introduced.
Results: Among 64 queried DEGs, 48 genes were recognized by the STRING database. C-X-C motif chemokine ligand 8 (CXCL8), intercellular adhesion molecule 1 (ICAM1), Melanoma growth-stimulatory activity/growth-regulated protein α (CXCL1), vascular cell adhesion molecule 1 (VCAM-1), and nerve growth factor (NGF) were introduced as hub nodes.
Conclusion: Findings indicate that inflammation is the main initial target of LDIR at the cellular level which is associated with alteration in the other essential functions of the irradiated cells.
Keywords: Radiation, Gene expression, Inflammation, Network analysis, Central node
Introduction
The effect of long-term low-dose ionizing radiation (LDIR)on the radiated cells indicates that the immune system is the target of radiation.1 Investigations have revealed that chronic low-dose γ-radiation induces cytokine profile change in irradiated mice.2Several other biological effects of chronic low-dose of ionizing radiation are reported by researchers.3 Proteomics as a high throughput method is applied to study the biological effects of chronic LDIR. Based on the literature, the glycolysis pathway and pyruvate dehydrogenase availability are inhibited by low and moderate radiation doses in the liver of the radiated mice. Another effect is significant long-term alterations in lipid metabolism in the liver of the tested animals.4,5
Genomics is used to detect the molecular mechanism of chronic LDIR. Based on genomics findings, dissimilar appearances of LDIR-induced cellular responses may have diverse signal transduction pathways.6 Like proteomics and genomics, bioinformatics is a method that is applied to investigate the molecular mechanism after radiation and LDIR on the different types of tested biological samples.7,8 Network analysis is a method that is useful to identify the significant differentially expressed genes (DEGs) or differentially expressed proteins (DEPs). Several gene profiles and also protein profiles after radiation are analyzed via network analysis.9,10
Protein-protein interaction (PPI) network analysis is a method which is based on interactions between a set of genes or proteins that may construct a network. Since the properties of elements of the network are not similar, the importance of each node may differ from the other nodes to form the network. The crucial nodes in the network are known as central nodes. One critical central node is a hub node. A hub node is connected to most nodes of the studied network.11,12
In the present study, gene expression profiles of human umbilical vein endothelial cells (HUVECs) in the absence and presence of 4.66 mGy/h for 6 hours by using cesium-137 were downloaded from Gene Expression Omnibus (GEO), and the significant DEGs were determined to find the crucial dysregulated genes among large numbers of DEGs. The identified significant DEGs were screened via PPI network analysis to introduce the limited numbers of DEGs that were targeted by LDIR and induced the main alteration in the function of the radiated cells.
Methods
Data of GSE66720 that is related to the cultured HUVECs was downloaded from GEO (https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=gse66720). The cells were synchronized in G1 cell cycle phase. Four gene expression profiles in GSE66720 which are characterized as GSM1630524 and GSM1630531 relative to the gene expression profiles of the control cells and GSM1630530 and GSM1630537 of the cells that were exposed to 4.66 mGy/h for 6 hours by using cesium-137 were selected to be analyzed.
The gene expression profiles were analyzed by using GEO2R to match the sample statistically via volcano plot, meandiff plot, expression plot, and box plot. The dysregulated genes that were characterized by FC > 1.5 and P value < 0.05 were selected as the significant DEGs.
The significant DEGs were imported in Cytoscape software13 via the “protein query” of the STRING database to construct a PPI network. The queried DEGs were connected to each other via undirected edges. Since most of the queried DEGs were isolated, 70 first neighbors were added to the DEGs from the STRING database and the main connected component of the formed network was analyzed by the “NetworkAnalyzer” application of Cytoscape. Four centrality parameters including degree value, betweenness centrality, closeness centrality, and stress were determined for the nodes of the main connected component. Five top nodes among the queried DEGs based on the degree value were identified as queried DEGs hubs. Similarly, five first neighbors’ hubs were introduced. The biological roles of the hub nodes were searched and discussed to find a new perspective on chronic ionizing radiation effects on the cultured cells.
Results
As it is shown in Figure 1, volcano plot analysis revealed that the gene expression profiles of the treated cells versus the control cells are significantly discriminated. A considerable number of the genes are significantly up-regulated and down-regulated. Considering -0.6 > log2FC > 0.6 which refers to fold change (FC) > 1.5, distribution of log2expression of the significant DEGs is presented in Figure 2. As it is depicted in Figure 3, the gene expression profiles of the control cells and the radiated cell are comparable. The distribution boxes are central median and the frequency of the expressed points is limited to nearly equal ranges. Based on the curves in Figure 4, the density of the genes with zero intensity is the maximum and the dysregulated genes are characterized by fewer values of density. The curves in Figure 4 are similar and comparable, but they are not unique based on the types of proteins. A list of 64 significant DEGs is presented in Table 1. 25 upregulated DEGs versus 39 downregulated individuals are introduced.
Figure 1.
Volcano Plot, Representation of -log10(P Value) Versus log2FC for Gene Expression Profiles of the Radiated Cells Relative to the Control Cells. P-adjective < 0.05 was considered
Figure 2.
Meandiff Plot, Representation of log2FC Versus log2 Expression for Gene Expression Profiles of the Radiated Cells Relative to the Control Cells. P-adjective < 0.05 was considered
Figure 3.
Box Plot Representation of Expression Distribution for Gene Expression Profiles of the Two Radiated Cell Samples Relative to the Control Cells. Four quarters are shown for each gene expression profile
Figure 4.
Expression PlotRepresentation of Density Versus Intensity of Expression for Four Gene Expression Profiles of the Radiated Cell Samples Relative to the Control Cells
Table 1. List of 64 significant DEGs which discriminate the radiated cells from the controls .
| Gene Title | Gene Symbol | LogFC | P Value |
|---|---|---|---|
| Cytochrome P450 family 1 subfamily A member 1 | CYP1A1 | -1.473 | 0.00 |
| Vascular cell adhesion molecule 1 | VCAM1 | -1.424 | 0.00 |
| Phospholipase A2 group IVC | PLA2G4C | -1.243 | 0.00 |
| Intercellular adhesion molecule 1 | ICAM1 | -1.113 | 0.00 |
| Histone deacetylase 9 | HDAC9 | -1.107 | 0.00 |
| Selectin E | SELE | -1.06 | 0.00 |
| Cerebellin 2 precursor | CBLN2 | -1.02 | 0.00 |
| Myozenin 2 | MYOZ2 | -0.848 | 0.01 |
| C-X-C motif chemokine ligand 8 | CXCL8 | -0.847 | 0.00 |
| F-box protein 32 | FBXO32 | -0.838 | 0.00 |
| Intercellular adhesion molecule 1 | ICAM1 | -0.803 | 0.00 |
| Interleukin 4 induced 1 | IL4I1 | -0.735 | 0.01 |
| G-patch domain containing 2 like | GPATCH2L | -0.713 | 0.02 |
| PDZ and LIM domain 5 | PDLIM5 | -0.685 | 0.00 |
| Neural precursor cell expressed, developmentally down-regulated 4-like, E3 ubiquitin protein ligase | NEDD4L | -0.684 | 0.01 |
| CD274 molecule | CD274 | -0.68 | 0.01 |
| Rho GTPase activating protein 6 | ARHGAP6 | -0.676 | 0.01 |
| Nerve growth factor | NGF | -0.675 | 0.02 |
| Retinol dehydrogenase 13 | RDH13 | -0.674 | 0.01 |
| Nuclear paraspeckle assembly transcript 1 (non-protein coding) | NEAT1 | -0.666 | 0.02 |
| NFKB inhibitor zeta | NFKBIZ | -0.656 | 0.00 |
| Microtubule associated protein 2 | MAP2 | -0.651 | 0.01 |
| Glycerophosphocholine phosphodiesterase 1 | GPCPD1 | -0.647 | 0.00 |
| TOLLIP antisense RNA 1 (head to head) | TOLLIP-AS1 | -0.645 | 0.02 |
| Myozenin 2 | MYOZ2 | -0.642 | 0.01 |
| SPOC domain containing 1 | SPOCD1 | -0.64 | 0.01 |
| PDZ and LIM domain 5 | PDLIM5 | -0.638 | 0.01 |
| Small integral membrane protein 10 like 2B///small integral membrane protein 10 like 2A | SMIM10L2B///SMIM10L2A | -0.625 | 0.01 |
| Exosome component 7///C-type lectin domain family 3 member B | EXOSC7///CLEC3B | -0.624 | 0.01 |
| Sulfotransferase family 1C member 4 | SULT1C4 | -0.616 | 0.00 |
| C-X-C motif chemokine ligand 1 | CXCL1 | -0.616 | 0.00 |
| Apoptosis associated transcript in bladder cancer | AATBC | -0.607 | 0.00 |
| Peptidoglycan recognition protein 1 | PGLYRP1 | -0.606 | 0.01 |
| Transmembrane p24 trafficking protein 10 | TMED10 | -0.605 | 0.02 |
| Neuronal PAS domain protein 2 | NPAS2 | -0.604 | 0.01 |
| cAMP responsive element binding protein 5 | CREB5 | -0.602 | 0.00 |
| Neural precursor cell expressed, developmentally down-regulated 4-like, E3 ubiquitin protein ligase | NEDD4L | -0.601 | 0.00 |
| Carnitine O-octanoyltransferase | CROT | 0.612 | 0.01 |
| Zinc fingers and homeoboxes 3 | ZHX3 | 0.614 | 0.00 |
| FOXF1 adjacent non-coding developmental regulatory RNA | FENDRR | 0.615 | 0.01 |
| Neuronal growth regulator 1 | NEGR1 | 0.615 | 0.02 |
| Angiopoietin 2 | ANGPT2 | 0.623 | 0.01 |
| Sphingosine-1-phosphate receptor 3 | S1PR3 | 0.63 | 0.00 |
| S-phase kinase-associated protein 2, E3 ubiquitin protein ligase | SKP2 | 0.63 | 0.01 |
| Homeobox A11 | HOXA11 | 0.631 | 0.00 |
| Ecotropic viral integration site 2B | EVI2B | 0.643 | 0.00 |
| TLR4 interactor with leucine rich repeats | TRIL | 0.645 | 0.02 |
| Fanconi anemia complementation group A | FANCA | 0.66 | 0.01 |
| Coxsackie virus and adenovirus receptor | CXADR | 0.663 | 0.00 |
| BBSome interacting protein 1 | BBIP1 | 0.67 | 0.01 |
| Angiopoietin 2 | ANGPT2 | 0.674 | 0.00 |
| Syntrophin beta 2 | SNTB2 | 0.674 | 0.01 |
| TLR4 interactor with leucine rich repeats | TRIL | 0.677 | 0.00 |
| TIMP metallopeptidase inhibitor 3 | TIMP3 | 0.698 | 0.00 |
| Centrosomal protein 350 | CEP350 | 0.706 | 0.01 |
| Mannosidase alpha class 1C member 1 | MAN1C1 | 0.711 | 0.00 |
| Zinc finger CCCH-type containing 11A | ZC3H11A | 0.712 | 0.01 |
| Lipase E, hormone sensitive type | LIPE | 0.732 | 0.00 |
| Pleckstrin and Sec7 domain containing 3 | PSD3 | 0.762 | 0.01 |
| ATP2A1 antisense RNA 1 | ATP2A1-AS1 | 0.804 | 0.01 |
| Coxsackie virus and adenovirus receptor | CXADR | 0.858 | 0.01 |
| Nuclear receptor subfamily 1 group D member 2 | NR1D2 | 0.985 | 0.01 |
Among the 64 introduced DEGs, 48 individuals were recognized by the STRING database and the network was constructed by Cytoscape software (see Figure 5). Only 27% of the 48 recognized DEGs including 13 genes were included in the main connected component by 27 connections. When 70 first neighbors were added to the 48 queried DEGs, the main connected component including 70 first neighbors and 34 queried DEGs (equal to 71% of the queried DEGs) was formed by 2729 links between the nodes. The main connected component which is constructed from first neighbors and the related queried DEGs is shown in Figure 6. The nodes of the network are laid out based on the degree value.
Figure 5.
The 48 Recognized DEGs Including 31 Isolated Genes, 4 Paired Genes, and a Main Connected Component. The 13 nodes of the main connected component are connected to each other by 27 edges
Figure 6.
The main connected component including 104 nodes and 2729 links is presented and the related nodes are laid out by the degree value
Results of the main connected component including four centrality parameters such as degree value, betweenness centrality (BC), closeness centrality (CC), and stress are tabulated in Table 2. The 5 top queried hubs and also 5 top first neighbor hubs are determined and shown in Table 3.
Table 2. The 104 Nodes of the Main Connected Component and the Relative Central Parameters .
| No. | Display Name | Query Term | Degree | Betweenness Centrality | Closeness Centrality | Stress |
|---|---|---|---|---|---|---|
| 1 | AKT1 | 87 | 0.043 | 0.866 | 3496 | |
| 2 | ACTB | 86 | 0.040 | 0.858 | 3232 | |
| 3 | GAPDH | 83 | 0.013 | 0.831 | 2366 | |
| 4 | IL6 | 82 | 0.010 | 0.824 | 2166 | |
| 5 | TNF | 82 | 0.010 | 0.824 | 2166 | |
| 6 | CXCL8 | CXCL8 | 80 | 0.006 | 0.811 | 1796 |
| 7 | IL1B | 80 | 0.006 | 0.811 | 1796 | |
| 8 | JUN | 78 | 0.010 | 0.798 | 1638 | |
| 9 | STAT3 | 78 | 0.016 | 0.805 | 1776 | |
| 10 | ALB | 77 | 0.007 | 0.780 | 1406 | |
| 11 | MMP9 | 77 | 0.006 | 0.780 | 1362 | |
| 12 | CASP3 | 76 | 0.006 | 0.780 | 1268 | |
| 13 | IL10 | 76 | 0.006 | 0.774 | 1232 | |
| 14 | INS | 76 | 0.018 | 0.780 | 1862 | |
| 15 | PTGS2 | 76 | 0.012 | 0.780 | 1520 | |
| 16 | TP53 | 76 | 0.010 | 0.786 | 1668 | |
| 17 | VEGFA | 76 | 0.003 | 0.786 | 1196 | |
| 18 | CCL2 | 75 | 0.003 | 0.763 | 1006 | |
| 19 | EGF | 75 | 0.004 | 0.774 | 1228 | |
| 20 | MAPK3 | 75 | 0.020 | 0.780 | 1898 | |
| 21 | TLR4 | 75 | 0.010 | 0.769 | 1634 | |
| 22 | FN1 | 74 | 0.006 | 0.763 | 1194 | |
| 23 | PPARG | 74 | 0.012 | 0.774 | 1776 | |
| 24 | CD4 | 73 | 0.002 | 0.757 | 800 | |
| 25 | EGFR | 73 | 0.007 | 0.769 | 1414 | |
| 26 | HIF1A | 73 | 0.005 | 0.769 | 1218 | |
| 27 | ICAM1 | ICAM1 | 73 | 0.002 | 0.757 | 756 |
| 28 | SRC | 73 | 0.007 | 0.769 | 1428 | |
| 29 | CD44 | 72 | 0.002 | 0.757 | 886 | |
| 30 | CD8A | 72 | 0.002 | 0.752 | 778 | |
| 31 | CXCR4 | 72 | 0.004 | 0.752 | 890 | |
| 32 | CXCL1 | CXCL1 | 71 | 0.002 | 0.736 | 744 |
| 33 | CXCL12 | 71 | 0.002 | 0.746 | 746 | |
| 34 | IFNG | 71 | 0.001 | 0.746 | 600 | |
| 35 | IL2 | 71 | 0.001 | 0.741 | 592 | |
| 36 | CSF2 | 70 | 0.001 | 0.741 | 614 | |
| 37 | IL4 | 70 | 0.001 | 0.736 | 494 | |
| 38 | ITGAM | 70 | 0.001 | 0.736 | 558 | |
| 39 | PTPRC | 70 | 0.015 | 0.736 | 1522 | |
| 40 | VCAM1 | VCAM1 | 70 | 0.001 | 0.736 | 616 |
| 41 | MMP2 | 69 | 0.021 | 0.736 | 2140 | |
| 42 | TLR2 | 69 | 0.005 | 0.736 | 1038 | |
| 43 | CCL5 | 68 | 0.001 | 0.720 | 440 | |
| 44 | FGF2 | 68 | 0.003 | 0.736 | 880 | |
| 45 | IL17A | 68 | 0.002 | 0.725 | 612 | |
| 46 | IL1A | 68 | 0.003 | 0.725 | 776 | |
| 47 | NFKBIA | 68 | 0.010 | 0.741 | 1620 | |
| 48 | NGF | NGF | 67 | 0.005 | 0.725 | 782 |
| 49 | TNFRSF1A | 67 | 0.004 | 0.715 | 762 | |
| 50 | CTNNB1 | 66 | 0.005 | 0.730 | 1018 | |
| 51 | NOTCH1 | 66 | 0.010 | 0.730 | 1314 | |
| 52 | PECAM1 | 66 | 0.001 | 0.720 | 532 | |
| 53 | SELE | SELE | 66 | 0.001 | 0.720 | 624 |
| 54 | CSF3 | 65 | 0.001 | 0.705 | 392 | |
| 55 | IGF1 | 65 | 0.003 | 0.715 | 612 | |
| 56 | CD34 | 64 | 0.001 | 0.710 | 392 | |
| 57 | MYD88 | 64 | 0.004 | 0.705 | 902 | |
| 58 | IL13 | 63 | 0.001 | 0.696 | 282 | |
| 59 | LEP | 63 | 0.003 | 0.710 | 720 | |
| 60 | CXCL10 | 62 | 0.000 | 0.691 | 260 | |
| 61 | IL18 | 62 | 0.000 | 0.691 | 258 | |
| 62 | RELA | 62 | 0.003 | 0.701 | 838 | |
| 63 | CD40 | 61 | 0.002 | 0.687 | 530 | |
| 64 | CCL3 | 60 | 0.000 | 0.682 | 228 | |
| 65 | HRAS | 60 | 0.022 | 0.701 | 2828 | |
| 66 | IKBKB | 60 | 0.008 | 0.696 | 1242 | |
| 67 | ESR1 | 58 | 0.006 | 0.691 | 1000 | |
| 68 | SERPINE1 | 58 | 0.006 | 0.682 | 868 | |
| 69 | NOS3 | 57 | 0.022 | 0.682 | 2874 | |
| 70 | CD274 | CD274 | 56 | 0.000 | 0.660 | 234 |
| 71 | KDR | 56 | 0.003 | 0.673 | 462 | |
| 72 | HSP90AA1 | 53 | 0.018 | 0.665 | 1372 | |
| 73 | CXCL2 | 52 | 0.001 | 0.636 | 194 | |
| 74 | NFKB1 | 51 | 0.002 | 0.648 | 566 | |
| 75 | EP300 | 44 | 0.025 | 0.624 | 3588 | |
| 76 | CREBBP | 37 | 0.025 | 0.595 | 3380 | |
| 77 | ITGB2 | 36 | 0.005 | 0.579 | 524 | |
| 78 | ANGPT2 | ANGPT2 | 33 | 0.000 | 0.572 | 56 |
| 79 | TIMP3 | TIMP3 | 25 | 0.000 | 0.545 | 4 |
| 80 | SKP2 | SKP2 | 19 | 0.000 | 0.534 | 8 |
| 81 | NFKBIZ | NFKBIZ | 16 | 0.000 | 0.500 | 4 |
| 82 | CYP1A1 | CYP1A1 | 14 | 0.000 | 0.512 | 18 |
| 83 | LIPE | LIPE | 11 | 0.000 | 0.505 | 0 |
| 84 | HDAC9 | HDAC9 | 10 | 0.000 | 0.502 | 0 |
| 85 | MAP2 | MAP2 | 10 | 0.000 | 0.495 | 0 |
| 86 | FBXO32 | FBXO32 | 9 | 0.000 | 0.495 | 0 |
| 87 | S1PR3 | S1PR3 | 7 | 0.000 | 0.488 | 2 |
| 88 | PGLYRP1 | PGLYRP1 | 6 | 0.000 | 0.462 | 0 |
| 89 | CREB5 | CREB5 | 5 | 0.000 | 0.488 | 0 |
| 90 | FANCA | FANCA | 5 | 0.000 | 0.484 | 0 |
| 91 | NEDD4L | NEDD4L | 5 | 0.000 | 0.481 | 2 |
| 92 | NPAS2 | NPAS2 | 5 | 0.001 | 0.464 | 156 |
| 93 | TRIL | TRIL | 5 | 0.000 | 0.460 | 0 |
| 94 | PDLIM5 | PDLIM5 | 4 | 0.019 | 0.484 | 644 |
| 95 | CXADR | CXADR | 2 | 0.000 | 0.470 | 0 |
| 96 | EVI2B | EVI2B | 2 | 0.000 | 0.435 | 0 |
| 97 | NR1D2 | NR1D2 | 2 | 0.000 | 0.389 | 0 |
| 98 | PLA2G4C | PLA2G4C | 2 | 0.000 | 0.452 | 0 |
| 99 | TMED10 | TMED10 | 2 | 0.000 | 0.456 | 0 |
| 100 | ARHGAP6 | ARHGAP6 | 1 | 0.000 | 0.414 | 0 |
| 101 | CEP350 | CEP350 | 1 | 0.000 | 0.375 | 0 |
| 102 | HOXA11 | HOXA11 | 1 | 0.000 | 0.426 | 0 |
| 103 | MYOZ2 | MYOZ2 | 1 | 0.000 | 0.327 | 0 |
| 104 | SNTB2 | SNTB2 | 1 | 0.000 | 0.407 | 0 |
Table 3. The 5 Top Added First Neighbor Hubs and 5 Top Queried DEGs Hubs .
| No. | Display Name | Query Term | Degree | Betweenness Centrality | Closeness Centrality | Stress |
| 1 | AKT1 | 87 | 0.043 | 0.866 | 3496 | |
| 2 | ACTB | 86 | 0.040 | 0.858 | 3232 | |
| 3 | GAPDH | 83 | 0.013 | 0.831 | 2366 | |
| 4 | IL6 | 82 | 0.010 | 0.824 | 2166 | |
| 5 | TNF | 82 | 0.010 | 0.824 | 2166 | |
| 6 | CXCL8 | CXCL8 | 80 | 0.006 | 0.811 | 1796 |
| 7 | ICAM1 | ICAM1 | 73 | 0.002 | 0.757 | 756 |
| 8 | CXCL1 | CXCL1 | 71 | 0.002 | 0.736 | 744 |
| 9 | VCAM1 | VCAM1 | 70 | 0.001 | 0.736 | 616 |
| 10 | NGF | NGF | 67 | 0.005 | 0.725 | 782 |
Note. The nodes are picked based on the degree value.
Discussion
Network analysis as a useful method is applied to describe the molecular mechanism due to radiation at the cellular level.14 Here, the gene expression alteration of HUVECs after radiation of 4.66 mGy/h for 6 hours by using cesium-137 was studied via PPI network analysis. Results from Figures 1-4 indicate that there are significant DEGs that discriminate the radiated cells from the controls. As it is depicted in Table 1, 64 significant DEGs were selected to be analyzed. In the first step of the analysis, 16 DEGs were not included for more investigation because they were not recognized in the STRING database.
As it is shown in Figure 5, the recognized DEGs cannot form an informative PPI network and there are a weak number of connections between the studied DEGs. Adding proper numbers of the first neighbors to the queried DEGs is a suitable method that leads to the construction of an appropriate PPI network for investigation.15 The network including the recognized DEGs and added individuals is shown in Figure 6. Analysis of the constructed network led to the introduction of 5 queried DEGs as hubs and also five hub nodes among the added first neighbors. However, the other centrality parameters such as betweenness centrality, closeness centrality, and stress for the hub nodes were significant. As shown in Table 3, all first neighbor hubs are characterized by a higher value of degree relative to the DEGs hubs.
AKT1, ACTB, GAPDH, IL6, and TNF are the first neighbor hubs, while the queried DEGs hubs are CXCL8, ICAM1, CXCL1, VCAM1, and NGF. The role of AKT1 in the radiated sample is investigated by several researchers. As it is reported, AKT1 plays a role in the suppression of apoptosis in the radiated germ cells in vivo. Activation of AKT1 and radiosensitivity have been investigated to show the role of this gene in DNA double-strand break repair.16,17 Both ACTB and GAPDH are considered control genes in radiotherapy investigation.18 Inducing the expression of IL6 by ionizing radiation in the human fibroblasts is a well-studied subject by researchers.19 The role of TNF-α in the modulation of cell responses to ionizing radiation is discussed in a study by Pal et al.20
C-X-C motif chemokine ligand 8 (CXCL8) which is known as IL8 is involved in the tumor microenvironment. As it is reported by investigators, CXCL8 initiates leucocyte infiltration and neovascularization, which precedes invasion and metastasis in tumor progression.21 Intercellular adhesion molecule 1 (ICAM1) is responsible for several immune functions such as response to inflammatory mediators and different stimuli.22 Melanoma growth-stimulatory activity/growth-regulated protein α (CXCL1) is an important player in angiogenesis, inflammation, tumorigenesis, and wound healing processes.23 Investigations indicate that silencing of vascular cell adhesion molecule 1 (VCAM-1) leads to inflammation and apoptosis inhibition.24 As it is reported, nerve growth factor (NGF) is associated with several processes such as differentiation, proliferation, protection, and survival of peripheral sensory and sympathetic neurons. This gene plays a crucial role in the translation of various environmental stimuli into pathological and physiological feedback. It is shown that NGF levels are related to stressful events.25 When the five queried hubs (CXCL8, ICAM1, CXCL1, VCAM1, and NGF) are investigated together, a document about the progression of oral squamous cell carcinoma appears, reflecting the tumorigenesis property of the applied radiation.26
Findings indicate that the main target of chronic ionizing radiation is the activation of the inflammatory system which can lead to the initiation of related processes such as apoptosis, cell differentiation and proliferation, angiogenesis, invasion and metastasis in tumor progression. An investigation indicated that chronic low-dose-rate ionizing radiation induced the upregulation of the genes against oxidative stress in the human fibroblast cells.27
Conclusion
It can be concluded that the targets of chronic low-dose-rate ionizing radiation are different genes; however, the genes related to the inflammatory system are the crucial ones. It seems the inflammatory system is the main gate of damages that end in tumorigenesis and metastasis.
Acknowledgment
Shahid Beheshti University of Medical Sciences supported this research.
Conflicts of Interest
All authors declare they have no conflicts of interest.
Ethical Considerations
This project was approved by Shahid Beheshti University of Medical Sciences (No. IR.SBMU.RETECH.REC.1400.889).
Please cite this article as follows: Ansari M, Rezaei-Tavirani M, Hamzeloo-Moghadam M, Razzaghi M, Arjmand B, Zamanian Azodi M, et al. Investigation into chronic low-dose ionizing radiation effect on gene expression profile of human HUVECs cells. J Lasers Med Sci. 2022;13:e35. doi:10.34172/jlms.2022.35.
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