La importancia de evaluar el daño al DNA / The Importance of Assessing DNA Damage

Resumen Se calcula que el cuerpo humano está conformado por billones de células, las cuales sufren cientos de miles de lesiones al día en su DNA. Aunque el DNA no es la única biomolécula que sufre daños, su importancia radica en que es la única que no puede ser sustituida por la célula, así que, cuando esta sufre daños, la célula debe repararlos, tolerarlos o, en el caso extremo, activar las vías que la llevarán a la muerte, ya que lo importante es mantener la integridad celular y la homeostasis del organismo. Hay miles de agentes que pueden dañar al DNA, algunos los produce la misma célula y se les denomina 'agentes endógenos', mientras que otros son agentes externos y se les conoce como 'agentes exógenos'. La célula no puede evitar el daño causado por los agentes endógenos, ya que son productos de la actividad metabólica, por ejemplo; así que, cuando suceden se activan de forma inmediata los mecanismos celulares para mitigarlos. Lo mismo pasa con los daños causados por agentes exógenos, ya que la célula hará todo lo posible por disminuir los efectos adversos que pueden causar. El problema se pone de manifiesto cuando la célula no puede reparar los daños o los repara mal o son tantos que los mecanismos de reparación se ven rebasados, es entonces cuando el daño permanece en el DNA y se genera un estado de inestabilidad cromosómica que puede conducir a la célula a la disfunción y a la malignización. Este estado de inestabilidad cromosómica se puede ver reflejado en el aumento de rompimientos de DNA o de micronúcleos en las células expuestas, lo que se puede cuantificar por medio de métodos especiales como el 'Ensayo Cometa' y el 'Ensayo de Micronúcleos', ya que identificar el daño en el DNA es una forma de evaluar el potencial tóxico que tienen los agentes a los que están expuestas las poblaciones, permite conocer los mecanismos de acción que tienen y, además, ayuda a comprender los factores que influyen en el detrimento de la salud poblacional.

Abstract It is estimated that the human body is made of trillions of cells, which suffer hundreds of thousands of DNA lesions every day. Although DNA is not the only biomolecule that suffers damage, its importance lies in the fact that it is the only biomolecule that cannot be replaced by the cell, so when it suffers damage, the cell must repair it, tolerate or, in a extreme case, activate pathways that will lead to death, since the objective is to maintain cell integrity and the homeostasis of the organism.There are thousands of agents that can damage DNA, some are produced by the cell and are called 'endogenous, while others are external agents and are known as 'exogenous. The cell cannot avoid the damage caused by endogenous agents, since they are products of its metabolic activity, for example, so when they occur, cellular mechanisms are immediately activated to mitigate them. The same happens with the damage caused by exogenous agents, since the cell will do everything possible to diminish the adverse effects they can cause. The problem becomes apparent when the cell is unable to repair the damage or poorly repairs it, or repairs so much that the mechanisms are overwhelmed, when the damage remains in the DNA and a state of chromosomal instability is generated that can lead the cell to dysfunction and malignization. This state of chromosomal instability can be reflected in increased DNA breaks or micronuclei in exposed cells, which can be quantified by special methods such as the 'Comet Assay' and the 'Micronucleus Assay'. Since identifying DNA damage is a way of evaluating the toxic potential of the agents to which populations are exposed, it allows us to know their mechanisms of action and helps to understand the factors that influence the detriment in population's health.

Optimization of comet experiment method and analysis of influencing factors / 安徽医科大学学报

Objective To detect cell DNA damage more effectively by optimizing the influencing factors of Comet assay and establishing a positive control.Methods Based on the traditional alkaline comet assay,the gel prepara-tion method,gel concentration,agarose solvent,lysis time,cell density and electrophoresis voltage were opti-mized.HL-60 cells were induced by hydrogen peroxide(H2O2)as a DNA damage inducer as a positive control.Results The optimized experimental results showed that the gel preparation method improved from three-step meth-od to two-step method.PBS was used as agarose solvent,0.8％normal melting point agarose was used to prepare the bottom layer,and 0.7％low melting point agarose was mixed with cell suspension as the second layer.The gel preparation effect was better,the operation was simpler,the time was saved,and the degumming problem was bet-ter solved.After lysis for 1 h and electrophoresis at 1 V/cm voltage,representative comet images were obtained.The results were easy to interpret and could effectively avoid false positive results.The positive control of comet as-say was successfully established by comparing the DNA damage of HL-60 cells induced by different concentrations of H2 O2.Conclusion Compared with the traditional method,the optimized comet assay method is simpler,faster,more accurate,lower cost and has better repeatability,which can quickly detect DNA damage in cells.

Study on the Mechanism of Hepatotoxicity Induced by Rhubarb Based on Network Pharmacology and Experimental Verification / 世界科学技术-中医药现代化

Objective The potential mechanism of hepatotoxicity induced by rhubarb was preliminarily explored by network pharmacology and verified by cell experiments.Methods Based on network pharmacology,component collection and target prediction are carried out through multiple databases.PPI network construction,GO enrichment analysis and KEGG pathway analysis were combined with software to systematically predict the mechanism of hepatotoxicity induced by rhubarb.The pathway information predicted by network pharmacology was verified by primary hepatocyte experiments and Western blot experiments.Results The results of network pharmacology showed that RH was the main component of hepatotoxicity induced by rhubarb.Seventeen core targets of hepatotoxicity induced by rhubarb were obtained.KEGG results suggested that DNA damage and apoptosis were one of the key mechanisms of hepatotoxicity induced by rhubarb.The results of primary hepatocytes and Western blot showed that RH could inhibit the viability of primary hepatocytes in a time-dose dependent manner.ABT and SFP can significantly reduce the toxicity of RH on primary liver cells in mice,and RFP can increase the toxicity of RH to mouse primary liver cells.Upregulation of γ-H2AX and PARP-1 protein in primary liver cells of mice after treatment with different concentrations of RH.Conclusion RH in rhubarb can significantly inhibit the viability of mouse primary hepatocytes,and its toxicity to mouse primary hepatocytes is mainly caused by the metabolic activation of RH by CYP 2C9.RH can activate PARP-1 protein,phosphorylate H2AX,induce DNA damage and apoptosis in mouse primary hepatocytes.

Expression of TRIP4 and DDIT4 in Glioma Tissue and Their Relationship with Clinical Pathological Parameters and Prognosis / 现代检验医学杂志

Objective To study the expression of thyroid hormone receptor binding protein 4(TRIP4)and DNA damage inducing transcription factor 4(DDIT4)in glioma tissue and their relationship with clinical pathological characteristics and prognosis.Methods 94 glioma patients admitted to the First Hospital of Hebei Medical University from February 2018 to February 2019 were selected as the research subjects.The expression of TRIP4,DDIT4 proteins in tissues were detected by immunohistochemistry.The relationship between the expression of TRIP4,DDIT4 proteins in glioma tissues and clinical pathological characteristics were compared.The differences in survival prognosis of glioma patients with different levels of TRIP4,DDIT4 protein expression were analyzed by Kaplan-Meier survival curve.Univariate and multivariate COX regression analysis was conducted to analyze the factors affecting the survival prognosis of glioma patients.Results The positive rates of TRIP4(68.09%),DDIT4(65.96%)proteins in glioma tissues were higher than those in adjacent tissues(13.83%,10.64%),with statistically significant differences(χ2=57.212,60.866,all P<0.05).There was a significant positive correlation between TRIP4 and DDIT4 protein expression in glioma tissues(r=0.722,P<0.05).The positive rates of TRIP4(83.64%vs 46.15%,80.00%vs 51.28%)and DDIT4(80.00%vs 46.15%,76.36%vs 51.28%)proteins in glioma tissues with tumor diameter≥3cm,WHO grade Ⅲ were significantly higher than those in tissues with tumor diameter＜3cm,WHO grade Ⅰ～Ⅱ(χ2=6.393～14.754,P<0.05).The 3-year overall survival rates of the TRIP4 positive and negative expression groups were 37.50%(24/64)and 66.67%(20/30),respectively.The 3-year cumulative survival of the TRIP4 positive expression group was significantly lower than that in the TRIP4 negative expression group(Log-rank χ2=5.949,P=0.015).The 3-year overall survival rate of DDIT4 positive and negative expression group was 37.10%(23/62)and 70.00%(21/30),respectively.The 3-year cumulative survival of the DDIT4 positive expression group was significantly lower than that in the DDIT4 negative expression group(Log-rank χ2=7.642,P=0.006).Tumor diameter≥3cm(HR=1.614,P=0.000),WHO grade Ⅲ(HR=1.790,P=0.000),positive TRIP4(HR=1.665,P=0.000)and positive DDIT4(HR=1.476,P=0.000)were independent risk factors affecting the survival prognosis of glioma patients.Conclusion The expression of TRIP4 and DDIT4 protein in glioma tissue was increased.Both of them were related to tumor diameter and WHO grade,and are potential tumor markers for survival prognosis of glioma.

Effects of different exercise types on human DNA damage,DNA methylation and telomere length / 中国组织工程研究

BACKGROUND:Exercise is not only an effective means to improve physical and mental health,but also has a good intervention effect on the occurrence and development of metabolic,cardiovascular and cerebrovascular diseases.The reason is related to the epigenetic factors. OBJECTIVE:To summarize the effects of different exercise types on human DNA damage,DNA methylation,and telomere length,and analyze the possible mechanism of exercise regulation epigenetic modification,in order to provide a reference for exercise to improve body function. METHODS:"Exercise,aerobic training,acute exercise,anaerobic training,resistance training,DNA damage,DNA methylation,telomere"were used as the Chinese search terms,and"exercise,sport,aerobic exercise,anaerobic exercise,resistance training,acute exercise,DNA metabolism,DNA damage,telomere"were used as the English search terms.We searched PubMed,Embase,Web of Science,and CNKI databases,and screened articles according to inclusion and exclusion criteria,and finally included 70 articles. RESULTS AND CONCLUSION:(1)Long-term aerobic,resistance,and anaerobic exercises can improve DNA damage.The reason is that exercise can improve the body's antioxidant capacity.Acute exercise can aggravate the degree of DNA damage by up-regulating the expression of reactive oxygen species and reactive nitrogen oxides.(2)Acute exercise,long-term resistance exercise,and anaerobic exercise play a positive role in reducing DNA methylation.The key mechanism may be that exercise-induced reactive oxygen species changes the expression of glutathione oxidized/glutathione,DNA methyltransferase,and 10-11 translocation enzyme.Then it can regulate DNA methylation.(3)Compared with other types of exercise,long-term aerobic exercise may have more potential value in increasing telomere length,and its biological mechanism involves inflammation,oxidative stress,DNA methylation,and regulation of microRNAs(miRNAs)expression.(4)Based on the current literature,aerobic exercise lasting at least 2 years can increase telomere length,and future research should further clarify the optimal exercise duration.

Construction of recombinant adenovirus vector of Uhrf1 gene and its role in DNA damage repair of cardiomyocytes / 中国病理生理杂志

AIM:To construct a recombinant adenovirus vector carrying the mouse ubiquitin-like with plant homeodomain and RING finger domains 1(Uhrf1)gene,validate the expression of Uhrf1 in neonatal mouse cardiomyo-cytes and explored its role in hydrogen peroxide(H2O2)-induced DNA damage.METHODS:The mouse Uhrf1 gene cod-ing sequence was amplified by polymerase chain reaction(PCR),digested,and inserted into the pADM-CMV-C-FH vec-tor to create the recombinant adenoviral plasmid ADM-Uhrf1.Following transfection into HEK293T cells,we generated re-combinant adenoviral particles,amplified,purified,and determined the titer.Neonatal mouse cardiomyocytes were infect-ed at an multiplicity of infection(MOI)of 50,UHRF1 protein expression was validated via Western blot and immunofluo-rescence staining.H2O2-induced DNA damage was explored along with adenovirus-mediated Uhrf1 overexpression to inves-tigate its role in DNA damage repair.RESULTS:ADM-Uhrf1 virus titer,determined by capsid immunofluorescence as-say,was 1.8×1013 pfu/L.Western blot confirmed a significant increase in UHRF1 protein expression(P＜0.05),with im-munofluorescence indicating predominant nuclear localization.Uhrf1 overexpression effectively inhibited the expression of the DNA damage marker,phosphorylated H2AX protein(γH2AX)(P＜0.01).CONCLUSION:We successfully con-structed a recombinant adenoviral vector carrying the mouse Uhrf1 gene,facilitating Uhrf1 overexpression in neonatal mouse cardiomyocytes.Furthermore,this overexpression effectively alleviated DNA damage in cardiomyocytes.

Progress in role of silent information regulator 3 in improving idiopathic pulmonary fibrosis by regulating mitochondrial dysfunction / 中国病理生理杂志

Idiopathic pulmonary fibrosis(IPF)is a chronic progressive interstitial lung disease of unknown etiology,with a rapid disease course,poor prognosis,and the absence of effective therapeutic drugs.Mitochondrial dys-function is one of the crucial causes of inducing IPF.Silent information regulator 3(SIRT3)can restore mitochondrial ho-meostasis by inhibiting mitochondrial oxidative stress,repairing mitochondrial DNA damage,and ameliorating abnormal mitochondrial lipid metabolism.This paper summarizes the role and mechanism of SIRT3 in attenuating mitochondrial dys-function based on delineating the relationship between mitochondrial dysfunction and IPF,aiming to provide references for finding effective treatment methods for IPF.

DNA oxidative damage induced by natural pyrethrins in human liver cells / 环境与职业医学

Background Natural pyrethrins have long been widely used in the fields of environmental and household hygiene. Studies have reported that natural pyrethrins have potential liver toxicity, but their specific mechanisms are still unclear yet. Objective To explore the effect of natural pyrethrins on DNA damage in human liver cells. Methods This study used human liver cell QSG7701 as an in vitro testing model. After exposure to DMSO and a series of concentrations of natural pyrethrins (5, 10, 20, and 40 μg·mL−1) for 6 and 24 h, reactive oxygen species (ROS) was detected by fluorescence microscopy using a fluorescence probe, thiobarbituric acid reactive substance (TBARS) by colorimetric method using a microplate reader, DNA damage by comet assay through observing DNA fragment migration under microscope, and phospho H2AX (γH2AX) and 8-oxoguanine (8-oxoG) by immunofluorescence assay using a laser confocal microscope. Results As the exposure concentration of natural pyrethrins increased, the fluorescence intensity of ROS significantly increased in a concentration-dependent manner. The differences in ROS between the 10 μg·mL−1 and above groups and the control group were statistically significant (P<0.01), and the ROS levels in the 20 μg·mL−1 and 40 μg·mL−1 treatment groups were 2.17 and 3.05 times higher than that in the control group respectively. The TBARS level increased in a concentration-dependent manner in natural pyrethrins treated cells (P<0.01), and the levels in the 20 μg·mL−1 and 40 μg·mL−1 treatment groups were 2.46 and 3.01 times higher than that in the control group respectively. The results of comet assay showed trailing formation of cellular DNA in each dose group; as the exposure concentration of natural pyrethrins increased, indicators such as tail DNA content (TDNA%), tail length (TL), tail moment (TM), and Olive tail moment (OTM) increased in a concentration-dependent manner. Compared with the control group, the differences in the indicators between the 20 μg·mL−1 and above groups and the control group were statistically significant (P<0.01), especially in the 40 μg·mL−1 treatment groups, where TDNA%, TL, TM, and OTM were (46.92 ± 3.52) %, (64.67± 4.16) μm, 30.96 ± 2.94, and 22.64 ± 3.89, respectively. The cellular immunofluorescence results showed that natural pyrethrins induced the formation of γH2AX and 8-oxoG, the fluorescence intensities of γH2AX and 8-oxoG increased in a concentration-dependent manner, and the differences between the 10 μg·mL−1 and above groups and the control group were statistically significant (P<0.01). Conclusion Natural pyrethrins could induce DNA damage in human liver cells, and ROS-mediated oxidative stress may play an important role in its liver cell genotoxicity.

Effects of fractionated low-dose ionizing radiation in the induction of EA.hy926 cell senescence / 中国辐射卫生

Objective To investigate the mechanism of fractionated low-dose ionizing radiation (LDIR) in the induction of EA.hy926 cell senescence. Methods EA.hy926 cells were irradiated with X-ray at 0, 50, 100, and 200 mGy × 4, respectively, and cultured for 24, 48, and 72 h. Several indicators were measured, including the levels of cellular senescence-associated β-galactosidase (SA-β-gal) staining, mRNA levels of senescence-associated cell cycle protein-dependent kinase inhibitor genes CDKN1A and CDKN2A, reactive oxygen species (ROS), total antioxidant capacity (T-AOC), and phosphorylated H2A histone family member X (γ-H2AX). Results After 4 fractionated LDIR, compared with the control group, the treatment groups showed increased nucleus area, blurred cell edge, and increased SA-β-gal positive area (P < 0.05) at 24, 48 and 72 h. After 4 fractionated LDIR, the mRNA level of CDKN1A increased in the 100 and 200 mGy × 4 groups at 24 and 48 h (P < 0.05), and CDKN2A mRNA level increased in the 100 and 200 mGy × 4 groups at 48 and 72 h (P < 0.05). The fluorescence intensity of ROS increased in treatment groups at 24, 48, and 72 h after 4 fractionated LDIR (P < 0.05). After 4 fractionated LDIR, the T-AOC level increased in the 100 and 200 mGy × 4 groups at 24 h (P < 0.05), and T-AOC level increased in all treatment groups at 48 and 72 h (P < 0.05). After 4 fractionated LDIR, γ-H2AX fluorescence intensity increased in all treatment groups at 24 h (P < 0.05), and the fluorescence intensity increased in the 100 and 200 mGy × 4 groups at 48 and 72 h (P < 0.05). Conclusion Fractionated LDIR can induce cellular senescence in EA.hy926 cells by impacting the cellular oxidation-antioxidation and oxidative damage levels, and the effects were relatively evident at 100 and 200 mGy.

Fanconi Anemia: Exploration of DNA Repair Pathways from Genetic Diseases to Cancer and Prospects for Treatment / 肿瘤防治研究

Fanconi anemia (FA) is an inheritable disorder that presents with bone marrow failure, developmental anomalies, and an increased susceptibility to cancer. The etiology of this condition stems from a genetic mutation that disrupts the proper repair of interstrand DNA cross-links (ICLs). The resultant dysregulation of the DNA damage response mechanism can induce genomic instability, thereby elevating the mutation rates and the likelihood of developing cancer. The FA pathway assumes a pivotal role in safeguarding genome stability through its involvement in the repair of DNA cross-links and the maintenance of overall genomic integrity. A mutation in the germ line of any of the genes responsible for encoding the FA protein results in the development of FA. The prevalence of aberrant FA gene expression in somatic cancer, coupled with the identification of a connection between FA pathway activation and resistance to chemotherapy, has solidified the correlation between the FA pathway and cancer. Consequently, targeted therapies that exploit FA pathway gene abnormalities are being progressively developed and implemented. This review critically examines the involvement of the FA protein in the repair of ICLs, the regulation of the FA signaling network, and its implications in cancer pathogenesis and prognosis. Additionally, it explores the potential utility of small-molecule inhibitors that target the FA pathway.

Study on OS-induced DNA damage from X-ray activation and cellular premature aging of HaCaT cells / 中国医学装备

Objective:To explore the changes of oxidative stress(OS),DNA damage and the occurrence of cellular premature aging of human immortalized keratinocytes(HaCaT)after that was radiated by X-ray with different doses.Methods:HaCaT cells were radiated by X-ray,and they were divided into 0 Gy group,5 Gy group and 10 Gy group according to the irradiation dose.The levels of intracellular reactive oxygen species(ROS)were detected by 2,7-Dichlorofluorescein diacetate(DCFH-DA)fluorescent probe,and the intracellular content of malondialdehyde(MDA)of lipid peroxidation products and the activity of superoxide dismutase(SOD)were measured by colorimetry.Immunofluorescence staining was used to detect the phosphorylated histone 2A variant(γ-H2AX)in HaCaT cells that were radiated by X-ray with different doses.Cell count kit-8(CCK-8)was used to detect the effect of X-ray with different doses on the proliferation of HaCaT cells after X-ray with different doses radiated them.β-Galactosidase staining was used to detect the proportion of premature aging cells.The changes of p21 and p53 protein expressions after X-ray irradiation were detected by Western blot.Results:After HaCaT cells were radiated by X-ray for 24h,the fluorescence intensity of 2',7'-Dichlorofluorescein(DCF)in 5 Gy and 10 Gy groups were significantly higher than that in the 0 Gy group,and the MDA contents of them were significantly higher than that in the control group,and the SOD activities of them were significantly lower than that in the control group(F=38.35,92.22,5.22,P<0.05),respectively.The change of γ-H2AX focus showed a dose-dependent significant increase at 1 h after irradiation,and the difference between them and control group was statistically significant(F=129.3,P<0.05).At 6h,24h and 48h after X-ray radiated HaCaT cells,the cell proliferation abilities of 5 Gy group and 10 Gy group were significantly decreased than that of 0 Gy group(F=116.41,62.20,34.29,P<0.01),and the β-Galactosidase activity of the two groups were significantly increased than that of 0 Gy group,and the difference was significant(F=1629.22,P<0.01).At 72h after X-ray with different doses radiated HaCaT cells,the expression levels of p21 and p53 proteins of 5 Gy group and 10 Gy group increased,and the differences of them among three groups were significant(F=104.4,66.69,P<0.01),respectively.Conclusion:Ionizing radiation can induce the occurrences of oxidative stress and DNA damage in HaCaT cells,and cause the occurrence of cellular premature aging.

Research progress in histone acetylation in radiation-related DNA damage / 中华放射肿瘤学杂志

Radiotherapy is a first-line treatment for a variety of malignant tumors by inducing DNA damage to kill tumor cells. However, tumor cells have different sensitivities to radiotherapy, ultimately leading to different therapeutic effects. Histone acetylation, regulated by histone acetyltransferase (HAT) and histone deacetylase (HDAC), is involved in the regulation of cell radiation sensitivity by influencing DNA damage repair. The main mechanisms are recruiting DNA repair related proteins and mediating chromatin dynamic changes. In this article, the role of histone acetylation modification in tumor radiotherapy was reviewed, aming to provide the basis for the radiotherapy sensitization strategy based on histone acetylation.

Protective effects of nicotinamide mononucleotide on ethanol-induced DNA damage in L02 cells / 预防医学

Objective@#To investigate protective effects of nicotinamide mononucleotide (NMN) on ethanol-induced DNA damage in L02 cells, so as to provide the evidence for adjuvant therapy of NMN on alcoholic liver diseases.@*Methods@#L02 cells were pretreated with different concentrations of NMN (0, 1, 2, 4 and 8 mmol/L) for 6 h, and then were exposed to 0.4% ethanol for 12 h. The treated cells were divided into the control group, 0.4% ethanol group and different concentrations of NMN groups. Cell viability was analyzed using trypan blue staining for determining the concentration of NMN as a protective agent. The effects of NMN on ethanol-induced DNA damage in L02 cells were evaluated using immunofluorescence detection and reactive oxygen species (ROS) assay. L02 cells were exposed to 0.4% ethanol for 12 h, cultured in a medium containing a protective concentration of NMN, and divided into PBS group and NMN group. Cell viability was detected at 0, 2, 4, 8, 16 and 32 h, and the effects of NMN on repairing ethanol-induced DNA damage were evaluated by alkaline comet assay.@*Results@#The cell viability was lower in 0.4% ethanol group than than in the control group, and was higher in different concentrations of NMN groups than in 0.4% ethanol group (all P<0.05), with no significant difference in the cells viability between 4 mmol/L and higher concentrations of NMN groups and the control group (all P>0.05). Therefore, 4 mmol/L NMN was selected as a protective agent. The cell tail moments, relative immunofluorescence intensities of γH2AX and relative levels of ROS were higher in 0.4% ethanol group than in the control group, and lower in 4 mmol/L and higher concentrations of NMN groups than in 0.4% ethanol group (all P<0.05). The cell viability was increased and the cell tail moment was shortened with the increase of 4 mmol/L NMN intervention time; and the cell viability in 4 h and more of NMN groups were higher, and the cell tail moment were lower than that in PBS group (all P<0.05).@*Conclusions@#NMN attenuates DNA damage in a dose-dependent manner and promotes the repair of DNA damage in a time-dependent manner. NMN has a protective effect on ethanol-induced DNA damage in hepatocytes.

In vitro assessment of the severity of deoxyribonucleic acid damage in different types of cataracts directly in lens epithelial cells

Purpose: This study aimed to assess the severity of deoxyribonucleic acid (DNA) damage in lens epithelial cells (LECs) of senile cortical, nuclear, and posterior subcapsular cataracts. Methods: LECs were obtained from senile cortical, nuclear, and subcapsular types of cataracts after surgery. DNA damage in the cells was immediately assessed quantitatively using the CometScore™ software. Results: Comets were found in cataractous LECs. The formation of “comets” in the DNA of LECs can be visualized using single?cell gel electrophoresis and indicates DNA strand breaks because the damaged DNA migrates at a different rate than the nondamaged DNA. Maximal damage was observed in Grade 3 cortical, nuclear, and subcapsular forms of cataracts. Statistically significant DNA damage was seen between grades 1 and 3 of cortical type of cataract, grades 1 and 3 of nuclear type of cataract, and grades 2 and 3 and grades 1 and 3 of posterior subcapsular type of cataract. Conclusion: In patients with senile cataract, DNA of LECs was randomly damaged, and this type of damage was possibly caused by reactive oxygen species (ROS). Maximum DNA damage was found in patients with Grade 3 senile cortical, nuclear, and subcapsular type cataracts. The pathogenesis of senile cataracts is multifactorial and includes continuous molecular stress resulting from photooxidative stress, UV irradiation, and oxidative reactions.

Advances of structure and mechanisms of bromodomain-containing protein 4 and its related research in tumors / 生物工程学报

The bromodomain and extraterminal domain (Bet) family are the regulators of the epigenome and also the pivotal driving factors for the expression of tumor related genes that tumor cells depend on for survival and proliferation. Bromodomain-containing protein 4 (Brd4) is a member of the Bet protein family. Generally, Brd4 identifies acetylated histones and binds to the promoter or enhancer region of target genes to initiate and maintain expression of tumor related genes. Brd4 is closely related to the regulation of multiple transcription factors and chromatin modification and is involved in DNA damage repair and maintenance of telomere function, thus maintaining the survival of tumor cells. This review summarizes the structure and function of Brd4 protein and the application of its inhibitors in tumor research.

Establishment of Human Lung Adenocarcinoma Radioresistant Cell Lines and the Mechanism of Radioresistance / 中国肺癌杂志

BACKGROUND@#Radiotherapy is one of the most common treatments for lung cancer, and about 40%-50% of patients after radiotherapy will appear uncontrolled or recurrence in the case of local tumors. Radioresistance is the predominant cause of local therapeutic failure. Nevertheless, the lack of in vitro radioresistance models is an influential factor obstructing the study of its mechanism. Therefore, the establishment of radioresistant cell lines, H1975DR and H1299DR, was beneficial to explore the mechanism of radioresistance in lung adenocarcinoma.@*METHODS@#The radioresistant cell lines of H1975DR and H1299DR were obtained from H1975 and H1299 cells irradiated with equal doses of X-rays; Clonogenic assays were performed to compare the clone-forming ability of H1975 vs H1975DR cells, H1299 vs H1299DR cells, then fitting cell survival curve by linear quadratic model; The comet assay was employed to examine DNA damage repair and calculate the percentage of DNA tails; The optical microscopy, CCK-8, flow cytometry, Transwell invasion assays were used to compare biological characteristics such as cell morphology, cell proliferation, apoptosis level, cycle distribution, cell migration and invasion; Western blot was carried out to measure the protein expression of DNA damage repair factors, such as DNA-PKcs, 53BP1, RAD51, and p-ATM.@*RESULTS@#After five months of continuous irradiation and stable culture, radioresistant cell lines H1975DR and H1299DR were obtained. The cell proliferation activity, clone formation ability and DNA damage repair ability of the two radioresistant cell lines were significantly improved under X-ray irradiation. The proportion of the G2/M phase was markedly decreased and the proportion of the G0/G1 phase was increased. Cell migration and invasion ability were significantly enhanced. Relative expression levels of p-DNA-PKcs (Ser2056), 53BP1 in the nonhomologous end-joining (NHEJ) repair pathway and p-ATM (Ser1981), RAD51 in the homologous recombination (HR) repair pathway were higher than those in H1975 and H1299.@*CONCLUSIONS@#H1975 and H1299 cell lines can be able to differentiate into lung adenocarcinoma radioresistant cell lines H1975DR and H1299DR by equal dose fractional irradiation, which provided an in vitro cytological model for the study of radiotherapy resistance mechanism of lung cancer patients.

Disulfiram enhances the antitumor activity of cisplatin by inhibiting the Fanconi anemia repair pathway / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

A series of chemotherapeutic drugs that induce DNA damage, such as cisplatin (DDP), are standard clinical treatments for ovarian cancer, testicular cancer, and other diseases that lack effective targeted drug therapy. Drug resistance is one of the main factors limiting their application. Sensitizers can overcome the drug resistance of tumor cells, thereby enhancing the antitumor activity of chemotherapeutic drugs. In this study, we aimed to identify marketable drugs that could be potential chemotherapy sensitizers and explore the underlying mechanisms. We found that the alcohol withdrawal drug disulfiram (DSF) could significantly enhance the antitumor activity of DDP. JC-1 staining, propidium iodide (PI) staining, and western blotting confirmed that the combination of DSF and DDP could enhance the apoptosis of tumor cells. Subsequent RNA sequencing combined with Gene Set Enrichment Analysis (GSEA) pathway enrichment analysis and cell biology studies such as immunofluorescence suggested an underlying mechanism: DSF makes cells more vulnerable to DNA damage by inhibiting the Fanconi anemia (FA) repair pathway, exerting a sensitizing effect to DNA damaging agents including platinum chemotherapy drugs. Thus, our study illustrated the potential mechanism of action of DSF in enhancing the antitumor effect of DDP. This might provide an effective and safe solution for combating DDP resistance in clinical treatment.

Effects of niraparib on the radiosensitivity of human esophageal cancer cells and its mechanism / 中华放射肿瘤学杂志

Objective:To evaluate the effect of niraparib, the poly (ADP-ribose) polymerase (PARP) inhibitor, on the radiosensitivity of esophageal squamous cell carcinoma (ESCC) and to preliminarily investigate its mechanism.Methods:Human esophageal squamous cell carcinoma cells ECA-109 and KYSE-150 were divided into the control, niraparib, single irradiation, combined (niraparib+irradiation) groups. Cell proliferation was measured by CCK-8 assay. The changes of cell survival rate were detected by colony formation assay. The changes of cell cycle and apoptosis were analyzed by flow cytometry. The number of γH2AX foci was detected by immunofluorescence, and the expression levels of PARP-1, cleaved-PARP, RAD51, mitogen-activated protein kinase (MAPK) [extracellular signal-regulated kinase 1 and 2 (ERK1/2) ] and p-MAPK (ERK1/2) proteins were determined by Western blot. All data were expressed as Mean±SD. Data between two groups conforming to normal distribution through the normality test were subject to independent sample t-test and multiple groups were analyzed using one-way ANOVA. Results:In human ESCC cells ECA-109 and KYSE-150, the proliferation of ESCC cells was significantly inhibited by niraparib combined with irradiation, and the values of average lethal dose (D 0), quasi-threshould dose(D q), survival fraction after 2 Gy irradiation (SF 2) in the combined group were decreased compared with those in the single irradiation group. The effect of irradiation alone on apoptosis of ECA-109 and KYSE-150 cells was limited. Compared to single irradiation group, irradiation combined with niraparib further increased the apoptosis rate in ESCC cells ( P=0.015, P=0.006). In ECA-109 cells, G 2/M phase arrest was significantly increased in combined group compared with irradiation alone group ( P<0.001). In ECA-109 cells, the number of γH2AX foci in combined group was higher than that in the single irradiation group after 2 h, and showed a significantly slower decay of γH2AX foci ( P<0.001). Moreover, niraparib combined with irradiation enhanced the radiation-induced cleavage of PARP-1 and down-regulated the expression of Rad51 and p-MAPK(ERK1/2). Conclusion:Niraparib can increase the radiosensitivity of esophageal cancer cells by inhibiting cell proliferation, promoting cell apoptosis, inhibiting the repair of DNA damage and regulating the MARK-ERK signaling pathway.

Effect of Paint Exposure Among Paint Workers and DNA Damage: A Scoping Review

@#Paint contains various complex chemical mixtures, such as aliphatic hydrocarbons, aromatic hydrocarbons (primarily toluene), ketones, and benzene as reported at previous studies. Toxicity from some chemicals can cause early DNA damage with various factors. A scoping review was conducted via literature review on relevant studies on the effect of paint exposure on paint workers and DNA damage. A systematic search was conducted in October 2021 via PubMed, Scopus, and Web of Science databases. The key terms used were paint, solvent-based paint, organic solvent, mixed organic solvent, occupational exposure and DNA damage, oxidative stress, genotoxicity on a painter, paint worker. From 561 articles, only 13 articles were finally selected based on the inclusion, exclusion criteria, and eligibility criteria. The literature showed that biomonitoring studies on painters were consistently reporting positive and significant DNA damage due to exposure to different types of compounds mixed in a paint. However, there were fewer studies on paint manufacturing factory workers compared to painters while paint manufacturing workers exposed various chemical everyday during the paint production which potentially susceptible to occupational toxicity. In conclusion, this review suggests that exposure to paints could induce early DNA damage among paint workers and further investigations on paint exposure among paint manufacturing factory workers and the DNA damage were needed in order to improve occupational health among paint workers in the future.

Research progress of DNA-PK inhibitors in the cancer treatment / 药学学报

The most toxic DNA damage is DNA double strand breaks (DSBs), which are mainly repaired by non-homologous end joining (NHEJ). DNA-dependent protein kinase (DNA-PK) belongs to phosphatidylinositol-3-kinase-related protein kinase family (PIKK) and plays a key role in NHEJ. DNA-PK is overexpressed in a variety of cancer cells and is related to the occurrence, development and drug resistance of malignant tumors. In this article, the representative DNA-PK inhibitors with anticancer effects are reviewed, in order to provide a reference to discovery novel DNA-PK inhibitors.