Biology subjects

Brenner, D. J.

Publications and source records attributed to Brenner, D. J..

13 recordsLinked to original sources

bioRxiv2024

Extending the Acute Skin Response Spectrum to Include the Far-UVC

Guidance on maximal limits for ultraviolet (UV) exposure has been developed by national and international organizations to protect against adverse effects on human skin and eyes. These guidelines consider the risk of both acute effects (i.e. erythema and photokeratitis) and delayed effects (e.g., skin and ocular cancers) when determining exposure limits, and specify the dose a person can safely receive during an 8-hour period without harmful effects. The determination of these exposure limits relies on the action spectra of photobiological responses triggered by UV radiation that quantify the effectiveness of each wavelength at eliciting each of these effects. With growing interest in using far-UVC (200-235 nm) radiation to control the spread of airborne pathogens, recent arguments have emerged about revisiting exposure limits for UV wavelengths. However, the standard erythema action spectra, which provides some of the quantitative basis for these limits, has not been extended below 240 nm. This study assists to expand the erythema action spectrum to far-UVC wavelengths using a hairless albino mice model. We estimate that inducing acute effects on mouse skin with 222 nm radiation requires a dose of 1,162 mJ/cm2, well above the current ACGIH skin exposure limit of 480 mJ/cm2.

biophysics↗

bioRxiv2024

Multiwell-based G0-PCC assay for radiation biodosimetry

In cytogenetic biodosimetry, assessing radiation exposure typically requires over 48 hours for cells to reach mitosis, significantly delaying the administration of crucial radiation countermeasures needed within the first 24 hours post-exposure. To improve medical response times, we incorporated the G0-Premature Chromosome Condensation (G0-PCC) technique with the Rapid Automated Biodosimetry Tool-II (RABiT-II), creating a faster alternative for large-scale radiation emergencies. Our findings revealed that using a lower concentration of Calyculin A (Cal A) than recommended effectively increased the yield of highly-condensed G0-PCC cells (hPCC). However, integrating recombinant CDK1/Cyclin B kinase, vital for chromosome condensation, proved challenging due to the properties of these proteins affecting interactions with cellular membranes. Interestingly, Cal A alone was capable of inducing chromosome compaction in some G0 cells even in the absence of mitotic kinases, although these chromosomes displayed atypical morphologies. This suggests that Cal A mechanism for compacting G0 chromatin may differ from condensation driven by mitotic kinases. Additionally, we observed a correlation between radiation dose and extent of hPCC chromosome fragmentation, which allowed us to automate radiation damage quantification using a Convolutional Neural Network (CNN). Our method can address the need for a same-day cytogenetic biodosimetry test in radiation emergency situations.

cell biology↗

bioRxiv2022

Ocular and Facial Far-UVC Doses from Ceiling-Mounted 222 nm Far-UVC Fixtures

Far-UVC radiation, commonly defined as wavelengths from 200 nm - 235 nm, is a promising tool to help prevent the spread of disease. The unique advantage of far-UVC technology over traditional ultraviolet germicidal irradiation lies in the potential for direct application of far-UVC into occupied spaces since antimicrobial doses of far-UVC are significantly below the recommended daily safe exposure limits. This study used a ceiling-mounted far-UVC fixture emitting at 222 nm to directly irradiate an indoor space and then evaluated the doses received upon a manikin. Radiation sensitive film was affixed to the head, nose, lip, and eyes of the manikin, and the 8-hour equivalent exposure dose was determined. Variables examined included manikin height (sitting or standing position), manikin offset from directly below the fixture, tilt of the manikin, the addition of glasses, the addition of hair, and different anatomical feature sizes. Importantly, at the manikin position with the highest dose to eyes, the average eye dose was only 5.8% of the maximum directly measured dose. These results provide the first experimental analysis of possible exposure doses a human would experience from an indoor far-UVC installation.

bioengineering↗

bioRxiv2022

No evidence of induced skin cancer or other skin abnormalities after long term (66 week) chronic exposure to 222-nm far-UVC radiatio

Far-UVC radiation, typically defined as 200-235 nm, has similar or greater anti-microbial efficacy compared to conventional 254-nm germicidal radiation. In addition, biophysical considerations of the interaction of far-UVC with tissue, as well as multiple short-term safety studies in animal models and humans, suggest that far-UVC exposure may be safe for skin and eye tissue. Nevertheless, the potential for skin cancer after chronic long-term exposure to far-UVC has not been studied. Here, we assessed far-UVC induced carcinogenic skin changes and other pathological dermal abnormalities in 96 SKH-1 hairless mice of both sexes that were exposed to average daily dorsal skin doses of 396 mJ/cm2, 126 mJ/cm2 or 56 mJ/cm2 of 222 nm far-UVC radiation for 66 weeks, 5 days per week, 8 hours per day, as well as similarly-treated unexposed controls. No evidence for increased skin cancer, abnormal skin growths, or incidental skin pathology findings was observed in the far-UVC exposed mice. In addition, there were no significant changes in morbidity or mortality. The findings from this study support the long-term safety of long-term chronic exposure to far-UVC radiation, and therefore its potential suitability as a practical anti-microbial approach to reduce airborne viral and bacterial loads in occupied indoor settings.

cancer biology↗

bioRxiv2022

LET-dependence of radiation-induced makers of Immunogenic Cell Death in human cancer cell lines

PurposeIt has been suggested that heavy-ion radiation therapy may contribute to the control of distal metastases. These distant responses may include immune cell activation. Immunostimulation resulting from radiation-induced immunogenic cell death (ICD) of cancer cells, leads to the recruitment of anti-tumor T cells. Specific markers of ICD include translocation of calreticulin (CRT) and extracellular release of high mobility group box 1 protein (HMGB1), and ATP. However, the LET dependence of these effects remains unknown. Materials and MethodsExpression of the molecular indicators described above were tested in a panel of human cancer cell lines, that included pancreatic cancer (Panc1 and Paca2), glioblastoma (U87 and LN18) and melanoma (HTB129 and SK-Mel5). Cells were irradiated with 5 Gy of particles spanning a range of LETs, from 10 KeV/m to 150 KeV/m and assayed for relocalization of calreticulin and release of HMGB1 and ATP were assayed 24 hours later. ResultsIn the pancreatic cancer cell lines (Panc1 and Paca2) there was a continued increase in the membrane relocalization of calreticulin as a function of increasing LET up to 150 KeV/m. The melanoma cell lines, HTB129 and Sk-Mel5 showed similar patterns. In contrast, calreticulin levels were higher, but not LET-dependent, in irradiated U87 and LN18 (glioblastoma) lines. With the exception of the response in Paca2, increases in LET correlated with increases in HMGB1 that seemed to peak at 100 KeV/m and then either remain unchanged or decrease at 150 KeV/m. while the ATP levels were elevated in media from some of the irradiated groups, there were no clear patterns either by cell type or LET. ConclusionsOur results indicate that at equal doses, although there is an overall trend of increases in the responses to increasing LETs, there are significant cell line-specific differences in the patterns of expression of these key ICD markers.

cell biology↗

bioRxiv2021

Wavelength-dependent DNA photodamage in a 3-D human skin model over the far-UVC and germicidal-UVC wavelength ranges from 215 to 255 nm

The effectiveness of UVC to reduce airborne-mediated disease transmission is well-established. However conventional germicidal UVC (~254 nm) cannot be used directly in occupied spaces because of the potential for damage to the skin and eye. A recently studied alternative with the potential to be used directly in occupied spaces is far-UVC (200 to 235 nm, typically 222 nm), as it cannot penetrate to the key living cells in the epidermis. Optimal far-UVC use is hampered by limited knowledge of the precise wavelength dependence of UVC-induced DNA damage, and thus we have used a monochromatic UVC exposure system to assess wavelength-dependent DNA damage in a realistic 3-D human skin model. We exposed a 3-D human skin model to mono-wavelength UVC exposures of 100 mJ/cm2, at UVC wavelengths from 215 to 255 nm (5-nm steps). At each wavelength we measured yields of DNA-damaged keratinocytes, and their distribution within the layers of the epidermis. No increase in DNA damage was observed in the epidermis at wavelengths from 215 to 235 nm, but at higher wavelengths (240-255 nm) significant levels of DNA damage were observed. These results support use of far-UVC light to safely reduce the risk of airborne disease transmission in occupied locations.

biophysics↗

bioRxiv2019

DNA damage response in peripheral mouse blood leukocytes in vivo after variable, low-dose rate exposure

Environmental contamination and ingestion of the radionuclide Cesium-137 (137Cs) is a large concern in fallout from a nuclear reactor accident and improvised nuclear device and highlights the need to develop biological assays for low dose rate, internal emitter radiation. To mimic low dose rates attributable to fallout, we have developed a VAriable Dose-rate External 137Cs irradiatoR (VADER), which can provide arbitrarily varying and progressive low dose rate irradiations in the range of 1.2 to 0.1 Gy/day, while circumventing the complexities of dealing with radioactively-contaminated biomaterials. We investigated the kinetics of mouse peripheral leukocytes DNA damage response in vivo after variable, low-dose rate 137Cs exposure. C57BL/6 mice were placed in the VADER over 7 days with total accumulated dose up to 2.7 Gy. Peripheral blood response including the leukocytes depletion, apoptosis signal protein p53 and DNA repair biomarker {gamma}-H2AX were measured. The results illustrated that blood leukocyte count had significantly dropped by days 7. P53 levels peaked at day 2 (total dose=0.91Gy) and then declined whereas {gamma}-H2AX yields generally increased with accumulated dose and peaked at day 5 (total dose=2.08Gy). ROC curve analysis for {gamma}-H2AX provided a good discrimination of accumulated dose < 2 Gy and [≥] 2 Gy, highlighting the potential of {gamma}-H2AX as a biomarker dosimetry in a protracted, environmental exposure scenario.

cell biology↗

bioRxiv2019

New High Throughput Approaches to Detect Partial-body and Neutron Exposures on an Individual Basis

Biodosimetry-based discrimination between homogeneous total-body photon exposure and complex irradiation scenarios (partial-body shielding and/or neutron + photon mixtures) can improve treatment decisions after mass-casualty radiation-related incidents. Our study objective was to use high-throughput biomarkers to: a) detect partial-body and/or neutron exposure on an individual basis, and b) estimate separately the photon and neutron doses in a mixed exposure. We developed a novel approach, where metrics related to the shapes of micronuclei distributions per binucleated cell in ex-vivo irradiated human lymphocytes (variance/mean, kurtosis, skewness, etc.) served as predictors in machine learning or parametric analyses of the following scenarios: (A) Homogeneous gamma-irradiation, mimicking total-body exposures, vs. mixtures of irradiated blood with unirradiated blood, mimicking partial-body exposures. (B) X rays vs. various neutron + photon mixtures. Classification of samples as homogeneously vs. heterogeneously irradiated (scenario A) achieved a receiver operating characteristic curve area (AUROC) of 0.931 (uncertainty range of 0.903-0.951), and R2 for actual vs. reconstructed mean dose was 0.87. Detection of samples with [≥]10% neutron contribution (scenario B) achieved AUROC of 0.916 (0.893-0.943), and R2 for reconstructing photon-equivalent dose was 0.77. These encouraging findings demonstrate a proof-of-principle for the proposed approach of analyzing micronuclei/cell distributions to detect clinically-relevant complex radiation exposure scenarios.

biophysics↗

bioRxiv2019

New Approaches for Quantitative Reconstruction of Radiation Dose in Human Blood Cells

In the event of a nuclear attack or radiation event, there would be an urgent need for assessing and reconstructing the dose to which hundreds or thousands of individuals were exposed. These measurements would need a rapid assay to facilitate triage and medical management for individuals based on dose. Our approaches to development of rapid assays for reconstructing dose, using transcriptomics, have led to identification of gene sets that have potential to be used in the field; but need further testing. This was a proof-of-principle study for new methods using radiation-responsive genes to generate quantitative, rather than categorical, radiation-dose reconstructions based on a blood sample. We used a new normalization method to reduce effects of variability of gene signals in unirradiated samples across studies; developed a quantitative dose-reconstruction method that is generally under-utilized compared to categorical methods; and combined these to determine a gene-set as a reconstructor. Our dose-reconstruction biomarker was trained on two data sets and tested on two independent ones. It was able to predict dose up to 4.5 Gy with root mean squared error (RMSE) of {+/-} 0.35 Gy on test datasets (same platform), and up to 6.0 Gy with RMSE of 1.74 Gy on another (different platform).

genomics↗

bioRxiv2019

Development of a high-throughput γ-H2AX assay based on imaging flow cytometry

BackgroundMeasurement of {gamma}-H2AX foci formation in cells provides a sensitive and reliable method for quantitation of the radiation-induced DNA damage response. The objective of the present study was to develop a rapid, high-throughput {gamma}-H2AX assay based on imaging flow cytometry (IFC) using the ImageStream(R)X Mk II (ISX MKII) platform to evaluate DNA double strand break (DSB) repair kinetics in human peripheral blood cells after exposure to ionizing irradiation.\n\nMethodsThe {gamma}-H2AX protocol was optimized for small volumes (100 {micro}l) of blood in Matrix 96-tube format and blood cell lymphocytes were identified and captured by ISX INSPIRE software and analyzed by Data Exploration and Analysis Software.\n\nResultsPresented here are: 1) dose response curves based on {gamma}-H2AX fluorescence intensity and foci number, 2) measurements of DNA repair kinetics up to 24 h after exposure to 4 Gy {gamma} rays and, 3) a mathematical approach for modeling DNA DSB rejoining kinetics using two key parameters a) rate of {gamma}-H2AX decay, and b) yield of residual unrepaired breaks.\n\nConclusionsThe results indicate that the IFC-based {gamma}-H2AX protocol may provide a practical, high-throughput and inexpensive platform for measurements of individual global DSB repair capacity and facilitate the prediction of precision medicine concepts.

cell biology↗

bioRxiv2019

The use of a centrifuge-free RABiT-II system for high-throughput micronucleus analysis

The cytokinesis-block micronucleus (CBMN) assay is considered as the most suitable biodosimetry method for automation. Previously, we automated this assay on a commercial robotic biotech high-throughput system (RABiT-II) adopting both a traditional and an accelerated micronucleus protocol, both using centrifugation steps for lymphocyte harvesting and washing, after whole blood culturing. Here we describe further development of our accelerated CBMN assay protocol for using on High Throughput/High Content Screening (HTS/HCS) robotic systems without a centrifuge. This opens the way for implementation of the CBMN assay on a wider range of commercial automated HTS/HCS systems and thus increases the potential capacity of dose estimates following a mass-casualty radiological event.

cell biology↗

bioRxiv2019

A new approach to automated CBMN scoring following high doses

In recent years we have automated the CBMN assay using microvolumes of blood, processed in multiwell plates. We have seen that at doses above 6 Gy the detected yield of micronuclei actually declines with dose, likely because of mitotic delay, preventing cells from forming micronuclei and also, when using one color imaging, resulting in many false binucleated cells, consisting of two randomly-adjacent nuclei. By using the inverse mitotic index (the ratio of mononuclear to binuclear cells) to adjust the micronucleus yield we were able to obtain a monotonic increasing dose response curve at doses of up to at least 10 Gy from the same samples which generated dose-response curve with a peak near 6 Gy, when scored using the traditional micronucleus yield.

cell biology↗

bioRxiv2017

Far-UVC light: A new tool to control the spread of airborne-mediated microbial diseases

Airborne-mediated microbial diseases such as influenza and tuberculosis represent major public health challenges. A direct approach to prevent airborne transmission is inactivation of airborne pathogens, and the airborne antimicrobial potential of UVC ultraviolet light has long been established; however, its widespread use in public settings is limited because conventional UVC light sources are both carcinogenic and cataractogenic. By contrast, we have previously shown that far-UVC light (207-222 nm) efficiently kills bacteria without harm to exposed mammalian skin. This is because, due to its strong absorbance in biological materials, far-UVC light cannot penetrate even the outer (non living) layers of human skin or eye; however, because bacteria and viruses are of micrometer or smaller dimensions, far-UVC can penetrate and inactivate them. We show for the first time that far-UVC efficiently kills airborne aerosolized viruses, a very low dose of 2 mJ/cm2 of 222-nm light inactivating >95% of aerosolized H1N1 influenza virus. Continuous very low dose-rate far-UVC light in indoor public locations is a promising, safe and inexpensive tool to reduce the spread of airborne-mediated microbial diseases.

bioengineering↗