The deoxyribonucleic acid (DNA) molecule damage simulations with an atom level geometric model use the traversal algorithm that has the disadvantages of quite time-consuming, slow convergence and high-performance computer requirement. Therefore, this work presents a density-based spatial clustering of applications with noise (DBSCAN) clustering algorithm based on the spatial distributions of energy depositions and hydroxyl radicals (·OH). The algorithm with probability and statistics can quickly get the DNA strand break yields and help to study the variation pattern of the clustered DNA damage. Firstly, we simulated the transportation of protons and secondary particles through the nucleus, as well as the ionization and excitation of water molecules by using Geant4-DNA that is the Monte Carlo simulation toolkit for radiobiology, and got the distributions of energy depositions and hydroxyl radicals. Then we used the damage probability functions to get the spatial distribution dataset of DNA damage points in a simplified geometric model. The DBSCAN clustering algorithm based on damage points density was used to determine the single-strand break (SSB) yield and double-strand break (DSB) yield. Finally, we analyzed the DNA strand break yield variation trend with particle linear energy transfer (LET) and summarized the variation pattern of damage clusters. The simulation results show that the new algorithm has a faster simulation speed than the traversal algorithm and a good precision result. The simulation results have consistency when compared to other experiments and simulations. This work achieves more precise information on clustered DNA damage induced by proton radiation at the molecular level with high speed, so that it provides an essential and powerful research method for the study of radiation biological damage mechanism.
Algorithms ; Computer Simulation ; DNA ; radiation effects ; DNA Damage ; Linear Energy Transfer ; Monte Carlo Method ; Protons

The aim of this study was to investigate the relationship between the effects of different doses of X-rays on DNA damage and JAK/STAT signaling pathway activation in A549 cells. The A549 cells were radiated with X-rays at doses of 2, 4, and 8 Gy. The proliferation of A549 cells was detected by CCK8 method. The content of interleukin 6 (IL-6) in culture medium at different time points after irradiation was detected by enzyme-linked immunoassay, and the expression levels of IL-6 receptor (IL-6R) and p53 binding protein 1 (53BP1) were detected by immunofluorescent staining. The expression levels of JAK2, p-JAK2, STAT3 and p-STAT3 were detected by Western blot. The results showed that, compared with the control group, X-ray irradiation reduced the cellular proliferation, up-regulated the expression of 53BP1, increased the IL-6 content in the medium supernatant, and up-regulated the protein expression levels of IL-6R, JAK2, p-JAK2, STAT3, and p-STAT3. The above effects of X-ray irradiation were dose-dependent. These results suggest that the mechanism by which X-rays cause DNA damage in A549 cells may involve activation of the JAK/STAT signaling pathway.
A549 Cells ; DNA Damage ; radiation effects ; Humans ; Janus Kinase 2 ; metabolism ; Receptors, Interleukin-6 ; metabolism ; STAT3 Transcription Factor ; metabolism ; Signal Transduction ; Tumor Suppressor p53-Binding Protein 1 ; metabolism ; X-Rays

Ultraviolet light(UV)-sensitive disorders refer to a group of diseases due to damages to the nucleotide excision repair mechanism which cannot effectively repair DNA damage caused by ultraviolet radiation. The inheritance pattern of such diseases, mainly including xeroderma pigmentosum, Cockayne syndrome and trichothiodystrophy, is autosomal recessive and known to involve 13 genes. As proteins encoded by such genes are involved in DNA repair and transcription pathways. There is overlap between the symptoms of such diseases, and their genotype - phenotype correlations are quite complex. To facilitate genetic and prenatal diagnosis for such diseases, a summary of the research progress is provided, which mainly focused on mutation research and genotype - phenotype correlation studies. We also propose a strategy for their genetic diagnosis based on recent findings of our group.
Biomedical Research ; methods ; trends ; Cockayne Syndrome ; genetics ; DNA Damage ; DNA Repair ; genetics ; Genetic Predisposition to Disease ; genetics ; Humans ; Skin ; metabolism ; pathology ; radiation effects ; Trichothiodystrophy Syndromes ; genetics ; Ultraviolet Rays ; Xeroderma Pigmentosum ; genetics

Inevitable human exposure to ionizing radiation from man-made sources has been increased with the proceeding of human civilization and consequently public concerns focus on the possible risk to human health. Moreover, Fukushima nuclear power plant accidents after the 2011 East-Japan earthquake and tsunami has brought the great fear and anxiety for the exposure of radiation at low levels, even much lower levels similar to natural background. Health effects of low dose radiation less than 100 mSv have been debated whether they are beneficial or detrimental because sample sizes were not large enough to allow epidemiological detection of excess effects and there was lack of consistency among the available experimental data. We have reviewed an extensive literature on the low dose radiation effects in both radiation biology and epidemiology, and highlighted some of the controversies therein. This article could provide a reasonable view of utilizing radiation for human life and responding to the public questions about radiation risk. In addition, it suggests the necessity of integrated studies of radiobiology and epidemiology at the national level in order to collect more systematic and profound information about health effects of low dose radiation.
DNA Damage/drug effects ; Environmental Exposure ; Humans ; Leukemia/epidemiology/etiology ; Neoplasms, Radiation-Induced/epidemiology ; *Radiation Dosage ; Radiation Tolerance ; *Radiation, Ionizing ; Radioactive Hazard Release ; Risk

OBJECTIVEThe present study was designed to investigate the effects of subchronic low level microwave radiation (MWR) on cognitive function, heat shock protein 70 (HSP70) level and DNA damage in brain of Fischer rats.

METHODSExperiments were performed on male Fischer rats exposed to microwave radiation for 90 days at three different frequencies: 900, 1800, and 2450 MHz. Animals were divided into 4 groups: Group I: Sham exposed, Group II: animals exposed to microwave radiation at 900 MHz and specific absorption rate (SAR) 5.953 × 10-4 W/kg, Group III: animals exposed to 1800 MHz at SAR 5.835 × 10-4 W/kg and Group IV: animals exposed to 2450 MHz at SAR 6.672 × 10-4 W/kg. All the animals were tested for cognitive function using elevated plus maze and Morris water maze at the end of the exposure period and subsequently sacrificed to collect brain tissues. HSP70 levels were estimated by ELISA and DNA damage was assessed using alkaline comet assay.

RESULTSMicrowave exposure at 900-2450 MHz with SAR values as mentioned above lead to decline in cognitive function, increase in HSP70 level and DNA damage in brain.

CONCLUSIONThe results of the present study suggest that low level microwave exposure at frequencies 900, 1800, and 2450 MHz may lead to hazardous effects on brain.

Animals ; Cognition ; radiation effects ; DNA Damage ; HSP70 Heat-Shock Proteins ; genetics ; Male ; Microwaves ; adverse effects ; Rats ; Rats, Inbred F344

OBJECTIVETo explore the role of p21 in ionizing radiation-induced changes in protein levels during the G2/M transition and long-term G2 arrest.

METHODSProtein expression levels were assessed by western blot in the human uveal melanoma 92-1 cells after treatment with ionizing radiation. Depletion of p21 was carried out by employing the siRNA technique. Cell cycle distribution was determined by flow cytometry combined with histone H3 phosphorylation at Ser28, an M-phase marker. Senescence was assessed by senescence- associated-β-galactosidase (SA-β-gal) staining combined with Ki67 staining, a cell proliferation marker.

RESULTSAccompanying increased p21, the protein levels of G2/M transition genes declined significantly in 92-1 cells irradiated with 5 Gy of X-rays. Furthermore, these irradiated cells were blocked at the G2 phase followed by cellular senescence. Depletion of p21 rescued radiation-induced G2 arrest as demonstrated by the upregulation of G2/M transition kinases, as well as the high expression of histone H3 phosphorylated at Ser28. Knockdown of p21 resulted in entry into mitosis of irradiated 92-1 cells. However, cells with serious DNA damage failed to undergo cytokinesis, leading to the accumulation of multinucleated cells.

CONCLUSIONOur results indicated that p21 was responsible for the downregulation of G2/M transition regulatory proteins and the bypass of mitosis induced by irradiation. Downregulation of p21 by siRNA resulted in G2-arrested cells entering into mitosis with serious DNA damage. This is the first report on elucidating the role of p21 in the bypass of mitosis.

Cell Cycle Checkpoints ; radiation effects ; Cell Line, Tumor ; Cyclin-Dependent Kinase Inhibitor p21 ; genetics ; metabolism ; DNA Damage ; Down-Regulation ; Fibroblasts ; metabolism ; radiation effects ; Gene Expression Regulation ; radiation effects ; Humans ; Mitosis ; radiation effects ; RNA Interference ; RNA, Small Interfering ; Radiation, Ionizing ; Up-Regulation

OBJECTIVETo investigate the effect of simulated microgravity and carbon ion irradiation (CIR) on spermatogenic cell apoptosis and sperm DNA damage to the testis of male Swiss Webster mice, and assess the risk associated with space environment.

METHODSSperm DNA damage indicated by DNA fragmentation index (DFI) and high DNA stainability (HDS) was measured by sperm chromatin structure assay (SCSA). Apoptosis of spermatogenic cells was detected by annexin V-propidium iodide assay. Bax (the expression levels of p53) and proliferating cell nuclear antigen (PCNA) were measured by immunoblotting; p53 and PCNA were located by immunohistology.

RESULTSHDS, DFI, apoptosis index, and the expression levels of p53 and Bax were detected to be significantly higher in the experimental groups (P<0.05) compared with those in the control group; however, the PCNA expression varied to a certain degree. p53- and PCNA- positive expression were detected in each group, mainly in relation to the spermatogonic cells and spermatocytes.

CONCLUSIONThe findings of the present study demonstrated that simulated microgravity and CIR can induce spermatogenic cell apoptosis and sperm DNA damage. Sperm DNA damage may be one of the underlying mechanisms behind male fertility decline under space environment. These findings may provide a scientific basis for protecting astronauts and space traveler's health and safety.

Animals ; Apoptosis ; radiation effects ; Carbon ; Cell Proliferation ; radiation effects ; DNA Damage ; Heavy Ions ; adverse effects ; Immunohistochemistry ; Male ; Mice ; Random Allocation ; Sperm Count ; Spermatogenesis ; radiation effects ; Spermatozoa ; radiation effects ; Testis ; radiation effects ; Weightlessness Simulation

Radiation and drug resistance remain the major challenges and causes of mortality in the treatment of locally advanced, recurrent and metastatic breast cancer. Dysregulation of phospholipase D (PLD) has been found in several human cancers and is associated with resistance to anticancer drugs. In the present study, we evaluated the effects of PLD inhibition on cell survival, cell death and DNA damage after exposure to ionizing radiation (IR). Combined IR treatment and PLD inhibition led to an increase in the radiation-induced apoptosis of MDA-MB-231 metastatic breast cancer cells. The selective inhibition of PLD1 and PLD2 led to a significant decrease in the IR-induced colony formation of breast cancer cells. Moreover, PLD inhibition suppressed the radiation-induced activation of extracellular signal-regulated kinase and enhanced the radiation-stimulated phosphorylation of the mitogen-activated protein kinases p38 and c-Jun N-terminal kinase. Furthermore, PLD inhibition, in combination with radiation, was very effective at inducing DNA damage, when compared with radiation alone. Taken together, these results suggest that PLD may be a useful target molecule for the enhancement of the radiotherapy effect.
Breast Neoplasms/*drug therapy/*enzymology/pathology ; Cell Death/drug effects/radiation effects ; Cell Line, Tumor ; Cell Proliferation/drug effects/radiation effects ; DNA Damage ; Enzyme Activation/drug effects/radiation effects ; Enzyme Inhibitors/*pharmacology/*therapeutic use ; Extracellular Signal-Regulated MAP Kinases/metabolism ; Female ; Humans ; JNK Mitogen-Activated Protein Kinases/metabolism ; Phospholipase D/*antagonists & inhibitors/metabolism ; Radiation Tolerance/*drug effects ; Radiation, Ionizing ; p38 Mitogen-Activated Protein Kinases/metabolism

OBJECTIVEWe identify ionizing radiation-induced mitochondrial DNA (mtDNA) deletions in human lymphocytes and their distribution in normal populations.

METHODSLong-range polymerase chain reactions (PCR) using two pairs of primers specific for the human mitochondrial genome were used to analyze the lymphoblastoid cell line following exposure to 10 Gy (60)Co γ-rays. Limited-condition PCR, cloning and sequencing techniques were applied to verify the mtDNA deletions detected with long-range PCR. Human peripheral blood samples were irradiated with 0, 2 and 6 Gy (60)Co γ-rays, and real-time PCR analysis was performed to validate the mtDNA deletions. In order to know the distribution of mtDNA deletions in normal population, 222 healthy Chinese adults were also investigated.

RESULTSTwo mtDNA deletions, a 7455-bp deletion (nt475-nt7929 in heavy strand) and a 9225-bp deletion (nt7714 -nt369 in heavy strand), occurring between two 8-bp direct repeats, were identified in lymphoblastoid cells using long-range PCR, limited-condition PCR and sequencing. These results were also observed for (60)Co γ-rays irradiated human peripheral blood cells.

CONCLUSIONTwo novel mtDNA deletions, a 7455-bp deletion and a 9225-bp deletion, were induced by ionizing radiation. The rate of the mtDNA deletions within a normal population was related to the donors' age, but was independent of gender.

Cell Line ; Cloning, Molecular ; Cobalt Radioisotopes ; DNA Damage ; genetics ; radiation effects ; DNA, Mitochondrial ; genetics ; radiation effects ; Gene Deletion ; Genetic Markers ; Humans ; Lymphocytes ; radiation effects ; Radiation, Ionizing ; Real-Time Polymerase Chain Reaction

OBJECTIVEThis paper aims to evaluate the genotoxicity in peripheral blood lymphocytes of rats after exposure to sunlight at different time points of day in a tropical region of Brazil (5 degrees S, 42 degrees W).

MATERIALS AND METHODSThirty Wistar-Hannover rats, three months old, were randomly divided into three groups of 10 animals each: Group I [control, without exposure to ultraviolet (UV) radiation], Group II (exposed to sunlight during 08:00 a.m. to 10:00 a.m.), and Group III (exposed to sunlight during 10:00 a.m. to 12:00 a.m.). After a week of exposure, peripheral blood samples were taken from the tail of these animals to prepare smears on two slides per animal. In 24 h after exposure to sunlight in Group III, a new collection was obtained to observe the repair activity. The alkaline comet assay was used in this study to evaluate the genotoxic activity of sunlight (P < 0.05).

RESULTSThere was no statistical difference between Group I and II (P = 0.672). On the other hand, the exposure to sunlight in Group III showed genotoxic action in comparison to the other groups (P < 0.0001). Also, there was no significant repair in Group III R (P = 0.407).

CONCLUSIONThis study has shown a genotoxic potential of sunlight (UVA-B) in lymphocytes of mammals from 10:00 a.m. to 12:00 a.m., due to a higher intensity of UV in this tropical region.

Animals ; Comet Assay ; DNA Damage ; Lymphocytes ; radiation effects ; Rats ; Rats, Wistar ; Sunlight