Visible blue light inhibits infection and replication of SARS-CoV-2 at doses that are well-tolerated by human respiratory tissue.

The delivery of safe, visible wavelengths of light can be an effective, pathogen-agnostic, countermeasure that would expand the current portfolio of SARS-CoV-2 intervention strategies beyond the conventional approaches of vaccine, antibody, and antiviral therapeutics. Employing custom biological light units, that incorporate optically engineered light-emitting diode (LED) arrays, we harnessed monochromatic wavelengths of light for uniform delivery across biological surfaces. We demonstrated that primary 3D human tracheal/bronchial-derived epithelial tissues tolerated high doses of a narrow spectral band of visible light centered at a peak wavelength of 425 nm. We extended these studies to Vero E6 cells to understand how light may influence the viability of a mammalian cell line conventionally used for assaying SARS-CoV-2. The exposure of single-cell monolayers of Vero E6 cells to similar doses of 425 nm blue light resulted in viabilities that were dependent on dose and cell density. Doses of 425 nm blue light that are well-tolerated by Vero E6 cells also inhibited infection and replication of cell-associated SARS-CoV-2 by > 99% 24 h post-infection after a single five-minute light exposure. Moreover, the 425 nm blue light inactivated cell-free betacoronaviruses including SARS-CoV-1, MERS-CoV, and SARS-CoV-2 up to 99.99% in a dose-dependent manner. Importantly, clinically applicable doses of 425 nm blue light dramatically inhibited SARS-CoV-2 infection and replication in primary human 3D tracheal/bronchial tissue. Safe doses of visible light should be considered part of the strategic portfolio for the development of SARS-CoV-2 therapeutic countermeasures to mitigate coronavirus disease 2019 (COVID-19).

Multi-scaled Monte Carlo calculation for radon-induced cellular damage in the bronchial airway epithelium.

Radon is a leading cause of lung cancer in indoor public and mining workers. Inhaled radon progeny releases alpha particles, which can damage cells in the airway epithelium. The extent and complexity of cellular damage vary depending on the alpha particle's kinetic energy and cell characteristics. We developed a framework to quantitate the cellular damage on the nanometer and micrometer scales at different intensities of exposure to radon progenies Po-218 and Po-214. Energy depositions along the tracks of alpha particles that were slowing down were simulated on a nanometer scale using the Monte Carlo code Geant4-DNA. The nano-scaled track histories in a 5 µm radius and 1 µm-thick cylindrical volume were integrated into the tracking scheme of alpha trajectories in a micron-scale bronchial epithelium segment in the user-written SNU-CDS program. Damage distribution in cellular DNA was estimated for six cell types in the epithelium. Deep-sited cell nuclei in the epithelium would have less chance of being hit, but DNA damage from a single hit would be more serious, because low-energy alpha particles of high LET would hit the nuclei. The greater damage in deep-sited nuclei was due to the 7.69 MeV alpha particles emitted from Po-214. From daily work under 1 WL of radon concentration, basal cells would respond with the highest portion of complex DSBs among the suspected progenitor cells in the most exposed regions of the lung epithelium.

Long-term results of elective mucosal irradiation for head and neck cancer of unknown primary in Chinese population: The EMICUP study.

OBJECTIVE: Controversy still exists regarding the volume of radiation for head and neck cancer of unknown primary (HNCUP). Theoretically, elective mucosal irradiation (EMI) should achieve a balance between survival and toxicity. This prospective study was conducted to evaluate the long-term benefit of EMI in Chinese HNCUP patients. METHODS: A phase II, single-arm trial was performed at two centers in China. HNCUP patients with pathologically confirmed metastatic squamous cell carcinoma or poorly differentiated carcinoma were enrolled. Patients with metastatic lymph nodes limited to level IV and/or the supraclavicular fossa were excluded. The EMI approach was specifically customized to Chinese patients by differentiating HNCUP as putative nasopharyngeal carcinoma (NPC) or non-putative NPC. The primary endpoint was 3-year mucosal recurrence-free survival (MRFS). RESULTS: A total of 48 patients were enrolled between 02/02/2010 and 08/01/2018; 46 patients were analyzed, including 24 putative NPC and 22 non-putative NPC patients. No primary recurrence was observed during a median follow-up period of 70 months, and only 1 patient experienced out of field recurrence in the contralateral neck. The 3-year MRFS was 90.6% (95%CI: 76.4%-96.4%). The 5-year MRFS, regional-recurrence free survival (RRFS) and overall survival (OS) were 90.6% (95%CI: 76.4%-96.4%), 86.0% (95%CI: 71.1%-93.7%), and 90.6% (95%CI: 76.4%-96.4%), respectively. No grade 4 acute or late toxicities occurred, and the most frequent grade 3 acute toxicity was oral mucositis (45.7%). CONCLUSION: To the best of our knowledge, this is the first prospective study to evaluate the long-term outcomes of EMI in Chinese HNCUP patients. Excellent MRFS and OS rates were observed. Further randomized studies are warranted.

Inhibition of Radiation-Induced Ccl2 Signaling Protects Lungs from Vascular Dysfunction and Endothelial Cell Loss.

Aims: Radiation-induced normal tissue toxicity often precludes the application of curative radiation doses. Here we investigated the therapeutic potential of chemokine C-C motif ligand 2 (Ccl2) signaling inhibition to protect normal lung tissue from radiotherapy (RT)-induced injury. Results: RT-induced vascular dysfunction and associated adverse effects can be efficiently antagonized by inhibition of Ccl2 signaling using either the selective Ccl2 inhibitor bindarit (BIN) or mice deficient for the main Ccl2 receptor CCR2 (KO). BIN-treatment efficiently counteracted the RT-induced expression of Ccl2, normalized endothelial cell (EC) morphology and vascular function, and limited lung inflammation and metastasis early after irradiation (acute effects). A similar protection of the vascular compartment was detected by loss of Ccl2 signaling in lungs of CCR2-KO mice. Long-term Ccl2 signaling inhibition also significantly limited EC loss and accompanied fibrosis progression as adverse late effect. With respect to the human situation, we further confirmed that Ccl2 secreted by RT-induced senescent epithelial cells resulted in the activation of normally quiescent but DNA-damaged EC finally leading to EC loss in ex vivo cultured human normal lung tissue. Innovation: Abrogation of certain aspects of the secretome of irradiated resident lung cells, in particular signaling inhibition of the senescence-associated secretory phenotype-factor Ccl2 secreted predominantly by RT-induced senescent epithelial cells, resulted in protection of the endothelial compartment. Conclusions: Radioprotection of the normal tissue via Ccl2 signaling inhibition without simultaneous protection or preferable radiosensitization of tumor tissue might improve local tumor control and survival, because higher doses of radiation could be used.

Cytotoxicity and genotoxicity of light emitted by incandescent, halogen, and LED bulbs on ARPE-19 and BEAS-2B cell lines.

LED technology has the extraordinary ability to reduce energy consumption, constituting an economic and ecological advantage, so it is planned to replace incandescent, halogen and other inefficient bulbs for public and domestic lighting with LEDs. LEDs present specific spectral and energetic characteristics compared with those of other domestic light sources, so the potential risks for human health of these bulbs need to be explored. The aim of this study was to assess cytotoxicity and genotoxicity of light emitted by different commercial light bulbs: incandescent, halogen, and two LED bulbs with different correlated color temperatures. The evaluation was done on ARPE-19 as a specific cell model for eye toxicity and on BEAS-2B as a good cell model for toxicology tests. Light induced mainly cytotoxic effects on ARPE-19 and DNA damage on BEAS-2B, so different cell lines showed different biological responses. Moreover, our findings indicate that among the four bulbs, cold LED caused the highest cytotoxic effect on ARPE-19 and the highest genotoxic and oxidative effect on BEAS-2B. Cold LED is probably able to cause more cellular damage because it contains more high-energy radiations (blue). These results suggest that LED technology could be a safe alternative to older technologies, but the use of warm LED should be preferred to cold LED, which can potentially cause adverse effects on retinal cells.

Loss of Nrf2 promotes alveolar type 2 cell loss in irradiated, fibrotic lung.

The development of radiation-induced pulmonary fibrosis represents a critical clinical issue limiting delivery of therapeutic doses of radiation to non-small cell lung cancer. Identification of the cell types whose injury initiates a fibrotic response and the underlying biological factors that govern that response are needed for developing strategies that prevent or mitigate fibrosis. C57BL/6 mice (wild type, Nrf2 null, Nrf2flox/flox, and Nrf2Δ/Δ; SPC-Cre) were administered a thoracic dose of 12Gy and allowed to recover for 250 days. Whole slide digital and confocal microscopy imaging of H&E, Masson's trichrome and immunostaining were used to assess tissue remodeling, collagen deposition and cell renewal/mobilization during the regenerative process. Histological assessment of irradiated, fibrotic wild type lung revealed significant loss of alveolar type 2 cells 250 days after irradiation. Type 2 cell loss and the corresponding development of fibrosis were enhanced in the Nrf2 null mouse. Yet, conditional deletion of Nrf2 in alveolar type 2 cells in irradiated lung did not impair type 2 cell survival nor yield an increased fibrotic phenotype. Instead, radiation-induced ΔNp63 stem/progenitor cell mobilization was inhibited in the Nrf2 null mouse while the propensity for radiation-induced myofibroblasts derived from alveolar type 2 cells was magnified. In summary, these results indicate that Nrf2 is an important regulator of irradiated lung's capacity to maintain alveolar type 2 cells, whose injury can initiate a fibrotic phenotype. Loss of Nrf2 inhibits ΔNp63 stem/progenitor mobilization, a key event for reconstitution of injured lung, while promoting a myofibroblast phenotype that is central for fibrosis.

Cytoplasmic Irradiation Induces Metabolic Shift in Human Small Airway Epithelial Cells via Activation of Pim-1 Kinase.

The unique cellular and molecular consequences of cytoplasmic damage caused by ionizing radiation were studied using a precision microbeam irradiator. Our results indicated that targeted cytoplasmic irradiation induced metabolic shift from an oxidative to glycolytic phenotype in human small airway epithelial cells (SAE). At 24 h postirradiation, there was an increase in the mRNA expression level of key glycolytic enzymes as well as lactate secretion in SAE cells. Using RNA-sequencing analysis to compare genes that were responsive to cytoplasmic versus nuclear irradiation, we found a glycolysis related gene, Pim-1, was significantly upregulated only in cytoplasmic irradiated SAE cells. Inhibition of Pim-1 activity using the selective pharmaceutic inhibitor Smi-4a significantly reduced the level of lactate production and glucose uptake after cytoplasmic irradiation. In addition, Pim-1 also inhibited AMPK activity, which is a well-characterized negative regulator of glycolysis. Distinct from the glycolysis induced by cytoplasmic irradiation, targeted nuclear irradiation also induced a transient and minimal increase in glycolysis that correlated with increased expression of Hif-1α. In an effort to explore the underline mechanism, we found that inhibition of mitochondria fission using the cell-permeable inhibitor mdivi-1 suppressed the induction of Pim-1, thus confirming Pim-1 upregulation as a downstream effect of mitochondrial dysfunction. Our data show and, for the first time, that cytoplasmic irradiation mediate expression level of Pim-1, which lead to glycolytic shift in SAE cells. Additionally, since glycolysis is frequently linked to cancer cell metabolism, our findings further suggest a role of cytoplasmic damage in promoting neoplastic changes.

Elucidation of changes in molecular signalling leading to increased cellular transformation in oncogenically progressed human bronchial epithelial cells exposed to radiations of increasing LET.

The early transcriptional response and subsequent induction of anchorage-independent growth after exposure to particles of high Z and energy (HZE) as well as γ-rays were examined in human bronchial epithelial cells (HBEC3KT) immortalised without viral oncogenes and an isogenic variant cell line whose p53 expression was suppressed but that expressed an active mutant K-RAS(V12) (HBEC3KT-P53KRAS). Cell survival following irradiation showed that HBEC3KT-P53KRAS cells were more radioresistant than HBEC3KT cells irrespective of the radiation species. In addition, radiation enhanced the ability of the surviving HBEC3KT-P53RAS cells but not the surviving HBEC3KT cells to grow in anchorage-independent fashion (soft agar colony formation). HZE particle irradiation was far more efficient than γ-rays at rendering HBEC3KT-P53RAS cells permissive for soft agar growth. Gene expression profiles after radiation showed that the molecular response to radiation for HBEC3KT-P53RAS, similar to that for HBEC3KT cells, varies with radiation quality. Several pathways associated with anchorage independent growth, including the HIF-1α, mTOR, IGF-1, RhoA and ERK/MAPK pathways, were over-represented in the irradiated HBEC3KT-P53RAS cells compared to parental HBEC3KT cells. These results suggest that oncogenically progressed human lung epithelial cells are at greater risk for cellular transformation and carcinogenic risk after ionising radiation, but particularly so after HZE radiations. These results have implication for: (i) terrestrial radiation and suggests the possibility of enhanced carcinogenic risk from diagnostic CT screens used for early lung cancer detection; (ii) enhanced carcinogenic risk from heavy particles used in radiotherapy; and (iii) for space radiation, raising the possibility that astronauts harbouring epithelial regions of dysplasia or hyperplasia within the lung that contain oncogenic changes, may have a greater risk for lung cancers based upon their exposure to heavy particles present in the deep space environment.

The differential role of human macrophage in triggering secondary bystander effects after either gamma-ray or carbon beam irradiation.

The abscopal effect could be an underlying factor in evaluating prognosis of radiotherapy. This study established an in vitro system to examine whether tumor-generated bystander signals could be transmitted by macrophages to further trigger secondary cellular responses after different irradiations, where human lung cancer NCI-H446 cells were irradiated with either γ-rays or carbon ions and co-cultured with human macrophage U937 cells, then these U937 cells were used as a bystander signal transmitter and co-cultured with human bronchial epithelial cells BEAS-2B. Results showed that U937 cells were only activated by γ-irradiated NCI-H446 cells so that the secondary injuries in BEAS-2B cells under carbon ion irradiation were weaker than γ-rays. Both TNF-α and IL-1α were involved in the γ-irradiation induced secondary bystander effect but only TNF-α contributed to the carbon ion induced response. Further assay disclosed that IL-1α but not TNF-α was largely responsible for the activation of macrophages and the formation of micronucleus in BEAS-2B cells. These data suggest that macrophages could transfer secondary bystander signals and play a key role in the secondary bystander effect of photon irradiation, while carbon ion irradiation has conspicuous advantage due to its reduced secondary injury.

Long-term low-dose α-particle enhanced the potential of malignant transformation in human bronchial epithelial cells through MAPK/Akt pathway.

Since the wide usage of ionizing radiation, the cancer risk of low dose radiation (LDR) (<0.1 Gy) has become attractive for a long time. However, most results are derived from epidemiologic studies on atomic-bomb survivors and nuclear accidents surrounding population, and the molecular mechanism of this risk is elusive. To explore the potential of a long-term LDR-induced malignant transformation, human bronchial epithelial cells Beas-2B were fractionally irradiated with 0.025 Gy α-particles for 8 times in total and then further cultured for 1-2 months. It was found that the cell proliferation, the abilities of adhesion and invasion, and the protein expressions of p-ERK, p-Akt, especially p-P38 were not only increased in the multiply-irradiated cells but also in their offspring 1-2 months after the final exposure, indicating high potentiality of cell malignant transformation. On opposite, the expressions of p-JNK and p-P66 were diminished in the subcultures of irradiated cells and thus may play a role of negative regulation in canceration. When the cells were transferred with p38 siRNA, the LDR-induced enhancements of cell adhesion and invasion were significantly reduced. These findings suggest that long-term LDR of α-particles could enhance the potential of malignant transformation incidence in human bronchial epithelial cells through MAPK/Akt pathway.

Modulation of wireless (2.45 GHz)-induced oxidative toxicity in laryngotracheal mucosa of rat by melatonin.

It is well known that oxidative stress induces larynx cancer, although antioxidants induce modulator role on etiology of the cancer. It is well known that electromagnetic radiation (EMR) induces oxidative stress in different cell systems. The aim of this study was to investigate the possible protective role of melatonin on oxidative stress induced by Wi-Fi (2.45 GHz) EMR in laryngotracheal mucosa of rat. For this purpose, 32 male rats were equally categorized into four groups, namely controls, sham controls, EMR-exposed rats, EMR-exposed rats treated with melatonin at a dose of 10 mg/kg/day. Except for the controls and sham controls, the animals were exposed to 2.45 GHz radiation during 60 min/day for 28 days. The lipid peroxidation levels were significantly (p < 0.05) higher in the radiation-exposed groups than in the control and sham control groups. The lipid peroxidation level in the irradiated animals treated with melatonin was significantly (p < 0.01) lower than in those that were only exposed to Wi-Fi radiation. The activity of glutathione peroxidase was lower in the irradiated-only group relative to control and sham control groups but its activity was significantly (p < 0.05) increased in the groups treated with melatonin. The reduced glutathione levels in the mucosa of rat did not change in the four groups. There is an apparent protective effect of melatonin on the Wi-Fi-induced oxidative stress in the laryngotracheal mucosa of rats by inhibition of free radical formation and support of the glutathione peroxidase antioxidant system.

Radon-induced reduced apoptosis in human bronchial epithelial cells with knockdown of mitochondria DNA.

Radon and radon progeny inhalation exposure are recognized to induce lung cancer. To explore the role of mitochondria in radon-induced carcinogenesis in humans, an in vitro partially depleted mitochondrial DNA (mtDNA) cell line (ρ-) was generated by treatment of human bronchial epithelial (HBE) cells (ρ+) with ethidium bromide (EB). The characterization of ρ- cells indicated the presence of dysfunctional mitochondria and might thus serve a reliable model to investigate the role of mitochondria. In a gas inhalation chamber, ρ- and ρ+ cells were exposed to radon gas produced by a radium source. Results showed that apoptosis was significantly increased both in ρ- and ρ+ cells irradiated by radon. Moreover, apoptosis in ρ- cells showed a lower level than in ρ+ cells. Radon was further found to depress mitochondrial membrane potential (MMP) of HBE cells with knockdown mtDNA. Production of reactive oxygen species (ROS) was markedly elevated both in ρ- and ρ+ cells exposed to radon. The distribution of phases of cell cycle was different in ρ- compared to ρ+ cells. Radon irradiation induced a rise in G2/M and decrease in S phase in ρ+ cells. In ρ- cells, G1, G2/M, and S populations remained similar to cells exposed to radon. In conclusion, radon-induced changes in ROS generation, MMP and cell cycle are all attributed to reduction of apoptosis, which may trigger and promote cell transformation, leading to carcinogenesis. Our study indicates that the use of the ρ- knockdown mtDNA HBE cells may serve as a reliable model to study the role played by mitochondria in carcinogenic diseases.

Acute mucosal radiation reactions in patients with head and neck cancer. Patterns of mucosal healing on the basis of daily examinations.

PURPOSE: The goal of this research was to evaluate the healing processes of acute mucosal radiation reactions (AMRR) in patients with head and neck cancer. MATERIALS AND METHODS: In 46 patients with oral and oropharyngeal cancer patients irradiated with conventional (n = 25) and accelerated (n = 21) dose fractionation AMRR was evaluated daily during and after radiotherapy. Complex of morphological and functional symptoms according to the Dische score were collected daily until complete healing. RESULTS: Duration of healing after the end of radiotherapy ranged widely (12-70 days). It was on the average 8 days longer for accelerated than for conventional radiotherapy (p = 0.016). Duration of dysphagia was also longer for accelerated irradiation (11 days, p = 0.027). Three types of morphological symptoms were observed as the last symptom at the end of AMRR healing: spotted and confluent mucositis, erythema, and edema. Only a slight correlation between healing duration and area of irradiation fields (r = 0.23) was noted. In patients with confluent mucositis, two morphological forms of mucosal healing were observed, i.e., marginal and spotted. The spotted form was noted in 71% of patients undergoing conventional radiotherapy and in 38% of patients undergoing accelerated radiotherapy. The symptoms of mucosal healing were observed in 40% patients during radiotherapy. CONCLUSION: The wide range of AMRR healing reflects individual potential of mucosa recovery with longer duration for accelerated radiotherapy. Two morphological forms of confluent mucositis healing were present: marginal and spotted. Healing of AMRR during radiotherapy can be observed in a significant proportion of patients.

ERK/GSK3ß/Snail signaling mediates radiation-induced alveolar epithelial-to-mesenchymal transition.

Radiotherapy is one of the major treatment regimes for thoracic malignancies, but can lead to severe lung complications including pneumonitis and fibrosis. Recent studies suggest that epithelial-to-mesenchymal transition (EMT) plays an important role in tissue injury leading to organ fibrosis. To investigate whether radiation can induce EMT in lung epithelial cells and also to understand the potential mechanism(s) associated with this change, rat alveolar type II lung epithelial RLE-6TN cells were irradiated with 8 Gy of (137)Cs γ-rays. Western blot and immunofluorescence analyses revealed a time-dependent decrease in E-cadherin with a concomitant increase in α-smooth muscle actin (α-SMA) and vimentin after radiation, suggesting that the epithelial cells acquired a mesenchymal-like morphology. Protein levels and nuclear translocation of Snail, the key inducer of EMT, were significantly elevated in the irradiated cells. Radiation also induced a time-dependent inactivation of glycogen synthase kinase-3ß (GSK3ß), an endogenous inhibitor of Snail. A marked increase in phosphorylation of ERK1/2, but not JNK or p38, was observed in irradiated RLE-6TN cells. Silencing ERK1/2 using siRNAs and the MEK/ERK inhibitor U0126 attenuated the radiation-induced phosphorylation of GSK3ß and altered the protein levels of Snail, α-SMA, and E-cadherin in RLE-6TN cells. Preincubating RLE-6TN cells with N-acetylcysteine, an antioxidant, abolished the radiation-induced phosphorylation of ERK and altered protein levels of Snail, E-cadherin, and α-SMA. These findings reveal, for the first time, that radiation-induced EMT in alveolar type II epithelial cells is mediated by the ERK/GSK3ß/Snail pathway.

Effect of site-specific bronchial radon progeny deposition on the spatial and temporal distributions of cellular responses.

Inhaled short-lived radon progenies may deposit in bronchial airways and interact with the epithelium by the emission of alpha particles. Simulation of the related radiobiological effects requires the knowledge of space and time distributions of alpha particle hits and biological endpoints. Present modelling efforts include simulation of radioaerosol deposition patterns in a central bronchial airway bifurcation, modelling of human bronchial epithelium, generation of alpha particle tracks, and computation of spatio-temporal distributions of cell nucleus hits, cell killing and cell transformation events. Simulation results indicate that the preferential radionuclide deposition at carinal ridges plays an important role in the space and time evolution of the biological events. While multiple hits are generally rare for low cumulative exposures, their probability may be quite high at the carinal ridges of the airway bifurcations. Likewise, cell killing and transformation events also occur with higher probability in this area. In the case of uniform surface activities, successive hits as well as cell killing and transformation events within a restricted area (say 0.5 mm(2)) are well separated in time. However, in the case of realistic inhomogeneous deposition, they occur more frequently within the mean cycle time of cells located at the carinal ridge even at low cumulative doses. The site-specificity of radionuclide deposition impacts not only on direct, but also on non-targeted radiobiological effects due to intercellular communication. Incorporation of present results into mechanistic models of carcinogenesis may provide useful information concerning the dose-effect relationship in the low-dose range.

Reirradiation of head and neck cancer with high-dose-rate brachytherapy: a customizable intraluminal solution for postoperative treatment of tracheal mucosa recurrence.

PURPOSE: Delivering adequate dose to tracheal mucosa recurrence after multiple prior courses of surgery and radiation presented a challenge for radiation delivery. Tumor bed location and size, combined with previous doses to surrounding areas, complicated the use of external beam therapy with either photons or electrons. High-dose-rate (HDR) brachytherapy was explored to provide sufficient dose coverage. METHODS AND MATERIALS: A 45-year-old gentleman presented with recurrent head and neck cancer. After undergoing additional excision of gross tumor in the tracheal region, radiation was recommended to improve local control. The region of residual tumor was confined to a small superficial lesion at the posterior-superior aspect of the trachea, involving mucosa located along the bend of the trachea, immediately deep to the stoma. External beam treatment was discussed but was not recommended based on recurrence location in the prior radiation field and patient's flexed chin position. HDR technique with a custom applicator was preferred. RESULTS: A three-dimensional HDR plan based on computed tomography used a single catheter optimized to cover gross tumor volume as delineated by physician. Prescribed dose was 5 Gy/fraction for six fractions (two fractions/wk). The applicator position was verified daily with computed tomography and physician setup approval before treatment. The patient was positioned on a wing board to allow access to the stoma. HDR brachytherapy was well tolerated. CONCLUSIONS: Intraluminal HDR brachytherapy is a viable option for providing dose to region inside tracheal stoma. Advantages over photon and electron beam therapy include reduced dose to surrounding tissues previously irradiated, skin dose, and reproducibility of treatment delivery.

Screening of differential expressive genes in murine cells following radon exposure.

This study was designed to construct and identify the subtracted cDNA library in peripheral blood cells of BALB/c mice and tracheal-bronchial epithelial cells of Wistar rats following exposure to radon inhalation. Two groups of the animals were exposed in a radon chamber at an accumulative dose of 100 WLM, while control animals were housed in a room at a background dose of 1 WLM. To construct a subtracted cDNA library enriched with differentially expressed genes, the SMART technique and suppression subtractive hybridization (SSH) assay were performed. The obtained forward and reverse cDNA fragments were directly inserted into a pMD-18 vector and transformed into Escherichia coli JM109. In total, 593 white bacterial clones were selected from both forward- and reverse-subtracted libraries. Among them, 81 clones were chosen for their differential expressions based on reverse Northern blot. Portions of these cDNA clones were also verified by a quantitative real-time polymerase chain reaction (PCR). The screening resulted in 14 upregulative and 8 downregulative known function/annotation genes, which were revealed to be functionally related to cell proliferation, cell oxidative and DNA damage, apoptosis, and tumor promotion. Access numbers were obtained from the GenBank for 11 unknown expressed sequence tags (EST). Analysis of biological roles of these cDNA fragments may provide further insight into mechanisms underlying adverse molecular events induced by high-dose radon exposure.

[Comparative characteristic of fatty acid content of lipids from expired air condensate in children with recurrent bronchitis residing in radiative contaminated territories and "clear" regions concerning radionuclide contamination].

The differences in the fat acid spectrum of expired air condensate in children with recurrent bronchitis who are residents of the radiation contaminated territories and children with analogous diagnosis living in the "clear" region regarding the radionuclide contamination consisted in the increased saturation of lipid complex indices against the decrease in content of polyunsaturated fat acids, antioxidant properties of pulmonary surfactant and activity of adaptation-compensatory processes in lipid bilayer of its membrane structures.

Radon carcinogenesis: risk data and cellular hits.

Abundant epidemiological data are now available (2008) on the human lung cancer response for lifetime radon gas exposure to residential concentrations of 100 Bq m(-3), equal to 22 working level months over 40 y. We combined published pooled epidemiological data and dosimetric calculations of alpha particle hits to target basal or mucous cell nuclei in bronchial epithelium. This yields an estimate that about 10,000 basal nuclei (target) cell hits per cm2 per person over a lifetime are involved in radon-related lung cancer. The DNA target cell area (cross section) for a hit is about 2 bp. The present epidemiology indicates that 1000 persons need to be exposed to this hit rate for observable cancers to be detected. The mechanism proposed is that the extensive prior DNA damage in smokers, followed by alpha particle damage to a critical site in checkpoint genes, accounts for the greater lung cancer response in smokers.

Absorbed fractions for electrons and beta particles in sensitive regions of human respiratory tract.

The absorbed fractions (AF) of electrons in sensitive layers of human respiratory tract were calculated in this paper. For that purpose the source code for simulation package PENELOPE, based on Monte Carlo method, was developed. The human respiratory tract was modeled according to ICRP66 publication, where AF of electrons was calculated using EGS4 simulation software. Some approximations used in ICRP66 were corrected in this work, and new values of AF for radon progeny are given. Minimal energy (EABS) that electron can have during transport through material is 1 keV in ICRP66, while it is set as low as 100 eV in the presented work. Lowering value of EABS gives more accurate results for AF when initial energy of electrons is below 50 keV. To represent tissue, water is used in ICRP66, while in this work epithelia tissue is used.