A genome-wide screen reveals that Dyrk1A kinase promotes nucleotide excision repair by preventing aberrant overexpression of cyclin D1 and p21.

Nucleotide excision repair (NER) eliminates highly genotoxic solar UV-induced DNA photoproducts that otherwise stimulate malignant melanoma development. Here, a genome-wide loss-of-function screen, coupling CRISPR/Cas9 technology with a flow cytometry-based DNA repair assay, was used to identify novel genes required for efficient NER in primary human fibroblasts. Interestingly, the screen revealed multiple genes encoding proteins, with no previously known involvement in UV damage repair, that significantly modulate NER uniquely during S phase of the cell cycle. Among these, we further characterized Dyrk1A, a dual specificity kinase that phosphorylates the proto-oncoprotein cyclin D1 on threonine 286 (T286), thereby stimulating its timely cytoplasmic relocalization and proteasomal degradation, which is required for proper regulation of the G1-S phase transition and control of cellular proliferation. We demonstrate that in UV-irradiated HeLa cells, depletion of Dyrk1A leading to overexpression of cyclin D1 causes inhibition of NER uniquely during S phase and reduced cell survival. Consistently, expression/nuclear accumulation of nonphosphorylatable cyclin D1 (T286A) in melanoma cells strongly interferes with S phase NER and enhances cytotoxicity post-UV. Moreover, the negative impact of cyclin D1 (T286A) overexpression on repair is independent of cyclin-dependent kinase activity but requires cyclin D1-dependent upregulation of p21 expression. Our data indicate that inhibition of NER during S phase might represent a previously unappreciated noncanonical mechanism by which oncogenic cyclin D1 fosters melanomagenesis.

Varied Photon Radiation Sources Produce Differences in Cellular Response.

In vitro studies allow evaluation of normal or cancer cell responses to radiation, either alone or in combination with agents used to modify these biological responses. Ionizing radiation can be produced by a variety of particles and sources, with varying energy spectra, interaction probabilities, linear energy transfer, dose uniformity, dose rates, and delivery methods. Multiple radiation sources have been used to irradiate cells in the published literature. However, the equivalence of response in cell culture models across radiation sources has not been rigorously established. Moreover, current reporting of radiation source parameters lacks consistency and rigor which may impact the reproducibility of pre-clinical data between laboratories. Relevant choices of radiation source are also of high importance due to growing interest in comparing photon versus particle radiation effect on biological responses. Therefore, this study robustly evaluates the cellular response (cell survival, apoptosis, and DNA damage) of three distinct cell lines using four unique photon generating radiation sources. We hypothesize there may be subtle differences across the radiation sources, without an appreciable difference in cellular response. The four photon irradiation energies investigated, 662 keV, 100 kVp, 220 kVp, 6 MV, did produce subtle differences in DNA damage and cell survival when treating three distinct tumor cell lines. These variations in cellular response emphasize the need to carefully consider irradiation source, energy, and dose rate depending on study goal and endpoint.

Radiosensitization of Breast Cancer Cells with a 2-Methoxyestradiol Analogue Affects DNA Damage and Repair Signaling In Vitro.

Radiation resistance and radiation-related side effects warrant research into alternative strategies in the application of this modality to cancer treatment. Designed in silico to improve the pharmacokinetics and anti-cancer properties of 2-methoxyestradiol, 2-ethyl-3-O-sulfamoyl-estra-1,3,5(10)16-tetraene (ESE-16) disrupts microtubule dynamics and induces apoptosis. Here, we investigated whether pre-exposure of breast cancer cells to low-dose ESE-16 would affect radiation-induced deoxyribonucleic acid (DNA) damage and the consequent repair pathways. MCF-7, MDA-MB-231, and BT-20 cells were exposed to sub-lethal doses of ESE-16 for 24 h before 8 Gy radiation. Flow cytometric quantification of Annexin V, clonogenic studies, micronuclei quantification, assessment of histone H2AX phosphorylation and Ku70 expression were performed to assess cell viability, DNA damage, and repair pathways, in both directly irradiated cells and cells treated with conditioned medium. A small increase in apoptosis was observed as an early consequence, with significant repercussions on long-term cell survival. Overall, a greater degree of DNA damage was detected. Moreover, initiation of the DNA-damage repair response was delayed, with a subsequent sustained elevation. Radiation-induced bystander effects induced similar pathways and were initiated via intercellular signaling. These results justify further investigation of ESE-16 as a radiation-sensitizing agent since pre-exposure appears to augment the response of tumor cells to radiation.

RNF126-Mediated MRE11 Ubiquitination Activates the DNA Damage Response and Confers Resistance of Triple-Negative Breast Cancer to Radiotherapy.

Triple-negative breast cancer (TNBC) has higher molecular heterogeneity and metastatic potential and the poorest prognosis. Because of limited therapeutics against TNBC, irradiation (IR) therapy is still a common treatment option for patients with lymph nodes or brain metastasis. Thus, it is urgent to develop strategies to enhance the sensitivity of TNBC tumors to low-dose IR. Here, the authors report that E3 ubiquitin ligase Ring finger protein 126 (RNF126) is important for IR-induced ATR-CHK1 pathway activation to enhance DNA damage repair (DDR). Mechanistically, RNF126 physically associates with the MRE11-RAD50-NBS1 (MRN) complex and ubiquitinates MRE11 at K339 and K480 to increase its DNA exonuclease activity, subsequent RPA binding, and ATR phosphorylation, promoting sustained DDR in a homologous recombination repair-prone manner. Accordingly, depletion of RNF126 leads to increased genomic instability and radiation sensitivity in both TNBC cells and mice. Furthermore, it is found that RNF126 expression is induced by IR activating the HER2-AKT-NF-κB pathway and targeting RNF126 expression with dihydroartemisinin significantly improves the sensitivity of TNBC tumors in the brain to IR treatment in vivo. Together, these results reveal that RNF126-mediated MRE11 ubiquitination is a critical regulator of the DDR, which provides a promising target for improving the sensitivity of TNBC to radiotherapy.

Inheritance of paternal DNA damage by histone-mediated repair restriction.

How paternal exposure to ionizing radiation affects genetic inheritance and disease risk in the offspring has been a long-standing question in radiation biology. In humans, nearly 80% of transmitted mutations arise in the paternal germline1, but the transgenerational effects of ionizing radiation exposure has remained controversial and the mechanisms are unknown. Here we show that in sex-separated Caenorhabditis elegans strains, paternal, but not maternal, exposure to ionizing radiation leads to transgenerational embryonic lethality. The offspring of irradiated males displayed various genome instability phenotypes, including DNA fragmentation, chromosomal rearrangement and aneuploidy. Paternal DNA double strand breaks were repaired by maternally provided error-prone polymerase theta-mediated end joining. Mechanistically, we show that depletion of an orthologue of human histone H1.0, HIS-24, or the heterochromatin protein HPL-1, could significantly reverse the transgenerational embryonic lethality. Removal of HIS-24 or HPL-1 reduced histone 3 lysine 9 dimethylation and enabled error-free homologous recombination repair in the germline of the F1 generation from ionizing radiation-treated P0 males, consequently improving the viability of the F2 generation. This work establishes the mechanistic underpinnings of the heritable consequences of paternal radiation exposure on the health of offspring, which may lead to congenital disorders and cancer in humans.

The exciting encounter between lncRNAs and radiosensitivity in IR-induced DNA damage events.

Radiation therapy is a commonly used tool in cancer management due to its ability to destroy malignant tumors. Mechanically, the efficacy of radiotherapy mainly depends on the inherent radiosensitivity of cancer cells and surrounding normal tissues, which mostly accounts for molecular dynamics associated with radiation-induced DNA damage. However, the relationship between radiosensitivity and DNA damage mechanism deserves to be further probed. As the well-established RNA regulators or effectors, long noncoding RNAs (lncRNAs) dominate vital roles in modulating ionizing radiation response by targeting crucial molecular pathways, including DNA damage repair. Recently, emerging evidence has constantly confirmed that overexpression or inhibition of lncRNAs can greatly influence the sensitivity of radiotherapy for many kinds of cancers, by driving a diverse array of DNA damage-associated signaling cascades. In conclusion, this review critically summarizes the recent progress in the molecular mechanism of IR-responsive lncRNAs in the context of radiation-induced DNA damage. The different response of lncRNAs when IR exposure. IR exposure can trigger the changes in expression pattern and subcellular localization of lncRNAs that influences the different radiology processes.

Diverse mutational landscapes in human lymphocytes.

The lymphocyte genome is prone to many threats, including programmed mutation during differentiation1, antigen-driven proliferation and residency in diverse microenvironments. Here, after developing protocols for expansion of single-cell lymphocyte cultures, we sequenced whole genomes from 717 normal naive and memory B and T cells and haematopoietic stem cells. All lymphocyte subsets carried more point mutations and structural variants than haematopoietic stem cells, with higher burdens in memory cells than in naive cells, and with T cells accumulating mutations at a higher rate throughout life. Off-target effects of immunological diversification accounted for approximately half of the additional differentiation-associated mutations in lymphocytes. Memory B cells acquired, on average, 18 off-target mutations genome-wide for every on-target IGHV mutation during the germinal centre reaction. Structural variation was 16-fold higher in lymphocytes than in stem cells, with around 15% of deletions being attributable to off-target recombinase-activating gene activity. DNA damage from ultraviolet light exposure and other sporadic mutational processes generated hundreds to thousands of mutations in some memory cells. The mutation burden and signatures of normal B cells were broadly similar to those seen in many B-cell cancers, suggesting that malignant transformation of lymphocytes arises from the same mutational processes that are active across normal ontogeny. The mutational landscape of normal lymphocytes chronicles the off-target effects of programmed genome engineering during immunological diversification and the consequences of differentiation, proliferation and residency in diverse microenvironments.

BmNPV Orf 65 (Bm65) Is Identified as an Endonuclease Directly Facilitating UV-Induced DNA Damage Repair.

Baculoviruses have been used as biopesticides for the control of Lepidoptera larvae. However, solar UV radiation reduces the activity of baculovirus. In this study, an UV endonuclease, Bm65, was found encoded in the genome of Bombyx mori nuclear polyhedrosis virus (BmNPV). Bm65 (the ortholog of AcMNPV orf79) was guided by a key nuclear localization signal to enter the nucleus and accumulated at UV-induced DNA damage sites. Subsequent results further showed that Bm65-mediated DNA damage repair was not the only UV damage repair pathway of BmNPV. BmNPV also used host DNA repair proteins to repair UV-induced DNA damage. In summary, these results revealed that Bm65 was very important in UV-induced DNA damage repair of BmNPV, and BmNPV repaired UV-damaged DNA through a variety of ways. IMPORTANCE Baculovirus biopesticides are environmentally friendly insecticides and specifically infect invertebrates. UV radiation from the sunlight greatly reduces the activity of baculovirus biopesticides. However, the molecular mechanisms of most baculoviruses to repair UV-induced DNA damage remain unclear. Nucleotide excision repair (NER) is a major DNA repair pathway that removes UV-induced DNA lesions. At present, there are few reports about the nucleotide excision repair pathway in viruses. Here, we showed for the first time that the baculovirus Bm65 endonuclease actually cleaved UV-damaged DNA. Meanwhile, we found that BmNPV used both viral-encoded enzymes and host DNA damage repair proteins to reverse UV-induced DNA damage. These results will provide a reference for the research of UV damage repair of other viruses.

A Monte Carlo study of the relative biological effectiveness in surface brachytherapy.

PURPOSE: This work aims to simulate clustered DNA damage from ionizing radiation and estimate the relative biological effectiveness (RBE) for radionuclide (rBT)- and electronic (eBT)-based surface brachytherapy through a hybrid Monte Carlo (MC) approach, using realistic models of the sources and applicators. METHODS: Damage from ionizing radiation has been studied using the Monte Carlo Damage Simulation algorithm using as input the primary electron fluence simulated using a state-of-the-art MC code, PENELOPE-2018. Two 192 Ir rBT applicators, Valencia and Leipzig, one 60 Co source with a Freiburg Flap applicator (reference source), and two eBT systems, Esteya and INTRABEAM, have been included in this study implementing full realizations of their geometries as disclosed by the manufacturer. The role played by filtration and tube kilovoltage has also been addressed. RESULTS: For rBT, an RBE value of about 1.01 has been found for the applicators and phantoms considered. In the case of eBT, RBE values for the Esteya system show an almost constant RBE value of about 1.06 for all depths and materials. For INTRABEAM, variations in the range of 1.12-1.06 are reported depending on phantom composition and depth. Modifications in the Esteya system, filtration, and tube kilovoltage give rise to variations in the same range. CONCLUSIONS: Current clinical practice does not incorporate biological effects in surface brachytherapy. Therefore, the same absorbed dose is administered to the patients independently on the particularities of the rBT or eBT system considered. The almost constant RBE values reported for rBT support that assumption regardless of the details of the patient geometry, the presence of a flattening filter in the applicator design, or even significant modifications in the photon energy spectra above 300 keV. That is not the case for eBT, where a clear dependence on the eBT system and the characteristics of the patient geometry are reported. A complete study specific for each eBT system, including detailed applicator characteristics (size, shape, filtering, among others) and common anatomical locations, should be performed before adopting an existing RBE value.

Genotoxicity Associated with 131I and 99mTc Exposure in Nuclear Medicine Staff: A Physical and Biological Monitoring Study.

Nuclear medicine staff are constantly exposed to low doses of ionizing radiation. This study investigated the level of genotoxic effects in hospital employees exposed to routinely used 131I and 99mTc in comparison with a control group. The study compared the results of physical and biological monitoring in peripheral blood lymphocytes. The effects of confounding factors, such as smoking status and physical activity, were also considered. Physical dosimetry monitoring revealed differences in the individual annual effective dose as measured by finger ring dosimeter and whole-body dosimeter between the 131I- and 99mTc-exposed groups. The DNA damage studies revealed differences between the groups in terms of excess premature chromosome condensation (PCC) fragments and tail DNA. Physical activity and smoking status differentiated the investigated groups. When assessed by the level of physical activity, the highest mean values of tail DNA were observed for the 99mTc group. When assessed by work-related physical effort, excess PCC fragments were significantly higher in the 131I group than in the control group. In the investigated groups, the tail DNA values were significantly different between non-smokers and past or current smokers, but excess PCC fragments did not significantly differ by smoking status. It is important to measure exposure to low doses of ionizing radiation and assess the potential risk from this exposure. Such investigations support the need to continue epidemiological and experimental studies to improve our understanding of the mechanisms of the health effects of radionuclides and to develop predictive models of the behavior of these complex systems in response to low-dose radiation.

The UVSSA protein is part of a genome integrity homeostasis network with links to transcription-coupled DNA repair and ATM signaling.

SignificanceTranscription-coupled repair (TCR) involves four core proteins: CSA, CSB, USP7, and UVSSA. CSA and CSB are mutated in the severe human neurocutaneous disease Cockayne syndrome. In contrast UVSSA is a mild photosensitive disease in which a mutated protein sequence prevents recruitment of USP7 protease to deubiquitinate and stabilize CSB. We deleted the UVSSA protein using CRISPR-Cas9 in an aneuploid cell line, HEK293, and determined the functional consequences. The knockout cell line was sensitive to transcription-blocking lesions but not sensitive to oxidative agents or PARP inhibitors, unlike CSB. Knockout of UVSSA also activated ATM, like CSB, in transcription-arrested cells. The phenotype of UVSSA, especially its rarity, suggests that many TCR-deficient patients and tumors fail to be recognized clinically.

Application of 233 nm far-UVC LEDs for eradication of MRSA and MSSA and risk assessment on skin models.

A newly developed UVC LED source with an emission wavelength of 233 nm was proved on bactericidal efficacy and skin tolerability. The bactericidal efficacy was qualitatively analysed using blood agar test. Subsequently, quantitative analyses were performed on germ carrier tests using the MRSA strain DSM11822, the MSSA strain DSM799, S. epidermidis DSM1798 with various soil loads. Additionally, the compatibility of the germicidal radiation doses on excised human skin and reconstructed human epidermis was proved. Cell viability, DNA damage and production of radicals were assessed in comparison to typical UVC radiation from discharge lamps (222 nm, 254 nm) and UVB (280-380 nm) radiation for clinical assessment. At a dose of 40 mJ/cm2, the 233 nm light source reduced the viable microorganisms by a log10 reduction (LR) of 5 log10 levels if no soil load was present. Mucin and protein containing soil loads diminished the effect to an LR of 1.5-3.3. A salt solution representing artificial sweat (pH 8.4) had only minor effects on the reduction. The viability of the skin models was not reduced and the DNA damage was far below the damage evoked by 0.1 UVB minimal erythema dose, which can be regarded as safe. Furthermore, the induced damage vanished after 24 h. Irradiation on four consecutive days also did not evoke DNA damage. The radical formation was far lower than 20 min outdoor visible light would cause, which is classified as low radical load and can be compensated by the antioxidant defence system.

Global and transcription-coupled repair of 8-oxoG is initiated by nucleotide excision repair proteins.

UV-DDB, consisting of subunits DDB1 and DDB2, recognizes UV-induced photoproducts during global genome nucleotide excision repair (GG-NER). We recently demonstrated a noncanonical role of UV-DDB in stimulating base excision repair (BER) which raised several questions about the timing of UV-DDB arrival at 8-oxoguanine (8-oxoG), and the dependency of UV-DDB on the recruitment of downstream BER and NER proteins. Using two different approaches to introduce 8-oxoG in cells, we show that DDB2 is recruited to 8-oxoG immediately after damage and colocalizes with 8-oxoG glycosylase (OGG1) at sites of repair. 8-oxoG removal and OGG1 recruitment is significantly reduced in the absence of DDB2. NER proteins, XPA and XPC, also accumulate at 8-oxoG. While XPC recruitment is dependent on DDB2, XPA recruitment is DDB2-independent and transcription-coupled. Finally, DDB2 accumulation at 8-oxoG induces local chromatin unfolding. We propose that DDB2-mediated chromatin decompaction facilitates the recruitment of downstream BER proteins to 8-oxoG lesions.

Low-dose but not high-dose γ-irradiation elicits the dominant-negative effect of mutant p53 in vivo.

Contrary to high doses irradiation (HDR), the biological consequences of dose irradiation (LDR) in breast cancer remain unclear due to the complexity of human epidemiological studies. LDR induces DNA damage that activates p53-mediated tumor-suppressing pathways promoting DNA repair, cell death, and growth arrest. Monoallelic p53 mutations are one of the earliest and the most frequent genetic events in many subtypes of cancer including ErbB2 breast cancer. Using MMTV/ErbB2 mutant p53 (R172H) heterozygous mouse model we found differential p53 genotype-specific effect of LDR vs. HDR on mammary tumorigenesis. Following LDR, mutant p53 heterozygous tumor cells exhibit aberrant ATM/DNA-PK signaling with defects in sensing of double-strand DNA brakes and deficient DNA repair. In contrast, HDR-induced genotoxic stress is sufficient to reach the threshold of DNA damage that is necessary for wtp53 induced DNA repair and cell cycle arrest. As a result, mutant p53 endows dominant-negative effect promoting mammary tumorigenesis after low-impact DNA damage leading to the selection of a genetically unstable proliferative population, with negligible mutagenic effect on tumors carrying wtp53 allele.

High-Accuracy Relative Biological Effectiveness Values Following Low-Dose Thermal Neutron Exposures Support Bimodal Quality Factor Response with Neutron Energy.

Theoretical evaluations indicate the radiation weighting factor for thermal neutrons differs from the current International Commission on Radiological Protection (ICRP) recommended value of 2.5, which has radiation protection implications for high-energy radiotherapy, inside spacecraft, on the lunar or Martian surface, and in nuclear reactor workplaces. We examined the relative biological effectiveness (RBE) of DNA damage generated by thermal neutrons compared to gamma radiation. Whole blood was irradiated by 64 meV thermal neutrons from the National Research Universal reactor. DNA damage and erroneous DNA double-strand break repair was evaluated by dicentric chromosome assay (DCA) and cytokinesis-block micronucleus (CBMN) assay with low doses ranging 6-85 mGy. Linear dose responses were observed. Significant DNA aberration clustering was found indicative of high ionizing density radiation. When the dose contribution of both the 14N(n,p)14C and 1H(n,γ)2H capture reactions were considered, the DCA and the CBMN assays generated similar maximum RBE values of 11.3 ± 1.6 and 9.0 ± 1.1, respectively. Consequently, thermal neutron RBE is approximately four times higher than the current ICRP radiation weighting factor value of 2.5. This lends support to bimodal peaks in the quality factor for RBE neutron energy response, underlining the importance of radiological protection against thermal neutron exposures.

Human exposure to low dose ionizing radiation affects miR-21 and miR-625 expression levels.

BACKGROUND: Recently exposure to ionizing radiation driven by artificial radiation sources such as Medical X-rays and Nuclear medicine has increased hastily. Ionizing radiation-induced the DNA damage and activate the DNA damage response signaling pathways. The aim of this study was to evaluate the role of miR-21 and miR-625 in response to low-dose ionizing radiation. MATERIALS AND METHODS: In this study, the blood sample of 38 volunteer patients who underwent Cardiac scans before and after 99mTc-MIBI injection were used. The WBC of patients was used for RNA extraction and after cDNA synthesis by the poly-A method the expression level of miR-21 and miR-625 was evaluated by real-time PCR method. RESULTS: The results of this study indicated that miR-21 and miR- 625 were significantly upregulated under exposure to low-dose ionizing radiation. The expression level of these miRNAs was not significantly correlated with the age and BMI of patients. More ever the bioinformatics analysis indicated that SP1 was a common target of both miRNAs and had the highest degree between hub genes. CONCLUSION: In summary miR-21 and miR-625 can contribute to the response to acute low dose ionizing radiation by targeting the SP1. However further studies should be carried out on the molecular mechanism of effects of miR-21 and miR-625 in response to low dose ionizing radiation by targeting the SP1.

Contribution of NADPH oxidase to the retention of UVR-induced DNA damage by arsenic.

Arsenic is a naturally occurring element present in food, soil and water and human exposure is associated with increased cancer risk. Arsenic inhibits DNA repair at low, non-cytotoxic concentrations and amplifies the mutagenic and carcinogenic impact of other DNA-damaging agents, such as ultraviolet radiation (UVR). Arsenic exposure leads to oxidation of zinc coordinating cysteine residues, zinc loss and decreased activity of the DNA repair protein poly(ADP)ribose polymerase (PARP)-1. Because arsenic stimulates NADPH oxidase (NOX) activity leading to generation of reactive oxygen species (ROS), the goal of this study was to investigate the role of NOX in arsenic-induced inhibition of PARP activity and retention of DNA damage. NOX involvement in the arsenic response was assessed in vitro and in vivo. Keratinocytes were treated with or without arsenite, solar-simulated UVR, NOX inhibitors and/or isoform specific NOX siRNA. Knockdown or inhibition of NOX decreased arsenite-induced ROS, PARP-1 oxidation and DNA damage retention, while restoring arsenite inhibition of PARP-1 activity. The NOX2 isoform was determined to be the major contributor to arsenite-induced ROS generation and DNA damage retention. In vivo DNA damage was measured by immunohistochemical staining and analysis of dorsal epidermis sections from C57BI/6 and p91phox knockout (NOX2-/-) mice. There was no significant difference in solar-simulated UVR DNA damage as detected by percent PH2AX positive cells within NOX2-/- mice versus control. In contrast, arsenite-dependent retention of UVR-induced DNA damage was markedly reduced. Altogether, the in vitro and in vivo findings indicate that NOX is involved in arsenic enhancement of UVR-induced DNA damage.

NMN recruits GSH to enhance GPX4-mediated ferroptosis defense in UV irradiation induced skin injury.

Oxidative stress and lipid peroxidation are major causes of skin injury induced by ultraviolet (UV) irradiation. Ferroptosis is a form of regulated necrosis driven by iron-dependent peroxidation of phospholipids and contributes to kinds of tissue injuries. However, it remains unclear whether the accumulation of lipid peroxides in UV irradiation-induced skin injury could lead to ferroptosis. We generated UV irradiation-induced skin injury mice model to examine the accumulation of the lipid peroxides and iron. Lipid peroxides 4-HNE, the oxidative enzyme COX2, the oxidative DNA damage biomarker 8-OHdG, and the iron level were increased in UV irradiation-induced skin. The accumulation of iron and lipid peroxidation was also observed in UVB-irradiated epidermal keratinocytes without actual ongoing ferroptotic cell death. Ferroptosis was triggered in UV-irradiated keratinocytes stimulated with ferric ammonium citrate (FAC) to mimic the iron overload. Although GPX4 protected UVB-injured keratinocytes against ferroptotic cell death resulted from dysregulation of iron metabolism and the subsequent increase of lipid ROS, keratinocytes enduring constant UVB treatment were markedly sensitized to ferroptosis. Nicotinamide mononucleotide (NMN) which is a direct and potent NAD+ precursor supplement, rescued the imbalanced NAD+/NADH ratio, recruited the production of GSH and promoted resistance to lipid peroxidation in a GPX4-dependent manner. Taken together, our data suggest that NMN recruits GSH to enhance GPX4-mediated ferroptosis defense in UV irradiation-induced skin injury and inhibits oxidative skin damage. NMN or ferroptosis inhibitor might become promising therapeutic approaches for treating oxidative stress-induced skin diseases or disorders.

SERPINE2/PN-1 regulates the DNA damage response and radioresistance by activating ATM in lung cancer.

Although the DNA damage response (DDR) is associated with the radioresistance characteristics of lung cancer cells, the specific regulators and underlying mechanisms of the DDR are unclear. Here, we identified the serine proteinase inhibitor clade E member 2 (SERPINE2) as a modulator of radiosensitivity and the DDR in lung cancer. Cells exhibiting radioresistance after ionizing radiation show upregulation of SERPINE2, and SERPINE2 knockdown improves tumor radiosensitivity in vitro and in vivo. Functionally, SERPINE2 deficiency causes a reduction in homologous recombination repair, rapid recovery of cell cycle checkpoints, and suppression of migration and invasion. Mechanistically, SERPINE2 knockdown inhibits the accumulation of p-ATM and the downstream repair protein RAD51 during DNA repair, and RAD51 can restore DNA damage and radioresistance phenotypes in lung cancer cells. Furthermore, SERPINE2 can directly interact with MRE11 and ATM to facilitate its phosphorylation in HR-mediated DSB repair. In addition, high SERPINE2 expression correlates with dismal prognosis in lung adenocarcinoma patients, and a high serum SERPINE2 concentration predicts a poor response to radiotherapy in non-small cell lung cancer patients. In summary, these findings indicate a novel regulatory mechanism by which SERPINE2 modulates the DDR and radioresistance in lung cancer.

miRNA-Signature of Irradiated Ptch1+/- Mouse Lens is Dependent on Genetic Background.

One harmful long-term effect of ionizing radiation is cataract development. Recent studies have been focused on elucidating the mechanistic pathways involved in this pathogenesis. Since accumulating evidence has established a role of microRNAs in ocular diseases, including cataract, the goal of this work was to determine the microRNA signature of the mouse lens, at short time periods postirradiation, to understand the mechanisms related to radio-induced cataractogenesis. To evaluate the differences in the microRNA profiles, 10-week-old Patched1 heterozygous (Ptch1+/-) mice, bred onto two different genetic backgrounds (CD1 and C57Bl/6J), received whole-body 2 Gy γ-ray irradiation, and 24 h later lenses were collected. Next-generation sequencing and bioinformatics analysis revealed that genetic background markedly influenced the list of the deregulated microRNAs and the mainly predicted perturbed biological functions of 2 Gy irradiated Ptch1+/- mouse lenses. We identified a subset of microRNAs with a contra-regulated expression between strains, with a key role in regulating Toll-like receptor (TLR)-signaling pathways. Furthermore, a detailed analysis of miRNome data showed a completely different DNA damage response in mouse lenses 24 h postirradiation, mainly mediated by a marked upregulation of p53 signaling in Ptch1+/-/C57Bl/6J lenses that was not detected on a CD1 background. We propose a strict interplay between p53 and TLR signaling in Ptch1+/-/C57Bl/6J lenses shortly after irradiation that could explain both the resistance of this strain to developing lens opacities and the susceptibility of CD1 background to radiation-induced cataractogenesis through activation of epithelial-mesenchymal transition.