Natalie R. Gassman

Induction of oxidative stress by bisphenol A and its pleiotropic effects

Bisphenol A (BPA) has become a target of intense public scrutiny since concerns about its association with human diseases such as obesity, diabetes, reproductive disorders, and cancer have emerged. BPA is a highly prevalent chemical in consumer products, and human exposure is thought to be ubiquitous. Numerous studies have demonstrated its endocrine disrupting properties and attributed exposure with cytotoxic, genotoxic, and carcinogenic effects; however, the results of these studies are still highly debated and a consensus about BPAs safety and its role in human disease has not been reached. One of the contributing factors is a lack of molecular mechanisms or modes of action that explain the diverse and pleiotropic effects observed after BPA exposure. The increase in BPA research seen over the last ten years has resulted in more studies that examine molecular mechanisms and revealed links between BPA‐induced oxidative stress and human disease. Here, a review of the current literature examining BPA exposure and the induction of reactive oxygen species (ROS) or oxidative stress will be provided to examine the landscape of the current BPA literature and provide a framework for understanding how induction of oxidative stress by BPA may contribute to the pleiotropic effects observed after exposure. Environ. Mol. Mutagen. 58:60–71, 2017.

Application of Laser Micro-irradiation for Examination of Single and Double Strand Break Repair in Mammalian Cells

Highly coordinated DNA repair pathways exist to detect, excise and replace damaged DNA bases, and coordinate repair of DNA strand breaks. While molecular biology techniques have clarified structure, enzymatic functions, and kinetics of repair proteins, there is still a need to understand how repair is coordinated within the nucleus. Laser micro-irradiation offers a powerful tool for inducing DNA damage and monitoring the recruitment of repair proteins. Induction of DNA damage by laser micro-irradiation can occur with a range of wavelengths, and users can reliably induce single strand breaks, base lesions and double strand breaks with a range of doses. Here, laser micro-irradiation is used to examine repair of single and double strand breaks induced by two common confocal laser wavelengths, 355 nm and 405 nm. Further, proper characterization of the applied laser dose for inducing specific damage mixtures is described, so users can reproducibly perform laser micro-irradiation data acquisition and analysis.

Broad spectrum detection of DNA damage by Repair Assisted Damage Detection (RADD)

Environmental exposures, reactive by-products of cellular metabolism, and spontaneous deamination events result in a spectrum of DNA adducts that if un-repaired threaten genomic integrity by inducing mutations, increasing instability, and contributing to the initiation and progression of cancer. Assessment of DNA adducts in cells and tissues is critical for genotoxic and carcinogenic evaluation of chemical exposure and may provide insight into the etiology of cancer. Numerous methods to characterize the formation of DNA adducts and their retention for risk assessment have been developed. However, there are still significant drawbacks to the implementation and wide-spread use of these methods, because they often require a substantial amount of biological sample, highly specialized expertise and equipment, and depending on technique, may be limited to the detection and quantification of only a handful of DNA adducts at a time. There is a pressing need for high throughput, easy to implement assays that can assess a broad spectrum of DNA lesions, allowing for faster evaluation of chemical exposures and assessment of the retention of adducts in biological samples. Here, we describe a new methodology, Repair Assisted Damage Detection (RADD), which utilizes a DNA damage processing repair enzyme cocktail to detect and modify sites of DNA damage for a subsequent gap filling reaction that labels the DNA damage sites. This ability to detect and label a broad spectrum of DNA lesions within cells, offers a novel and easy to use tool for assessing levels of DNA damage in cells that have been exposed to environmental agents or have natural variations in DNA repair capacity.

College tanning behaviors, attitudes, beliefs, and intentions: A systematic review of the literature

Despite well-established links between exposure to ultraviolet radiation (UVR) and skin cancer, UVR-based tanning behaviors persist among college students. Understanding tanning motivations, perceptions, barriers, and demographic characteristics of this population is critical to modifying these behaviors, but is limited by variability in study design, sample size, and outcomes measured in the current literature. To help clarify the tanning behaviors of this population and provide a concise reference for future studies, this review examines existing reports to determine the comparability of tanning behaviors across multiple U.S. college populations. A systematic review of the literature was performed in July 2016 to identify studies investigating tanning behaviors among U.S. college students. Twenty-three studies met inclusion criteria. High rates of indoor tanning (IT) and outdoor tanning (OT) were found among college students. Key motivators included appearance, emotion, health perceptions, and the influence of parents, peers, and the media. Misconceptions regarding skin protection, low rates of sun protective behaviors, and tanning dependence were barriers against safe UVR exposure. Understudied demographic factors may account for variance in observed tanning behaviors, emphasizing the need for standardization efforts to consistently identify trends associated with geographical region, age, year in college, and sex. The findings presented in this review reaffirm that college students are at high risk for tanning-associated skin cancer, emphasizing the critical need for effective, targeted interventions. Improved interventions will reduce the burden of skin cancer within this group, ultimately contributing to longer, healthier lives.

High prevalence of combination tanning among undergraduates: Survey at a southeastern US university

patients taking NOACs, the incidence of infection during MMS and cutaneous surgeries is low (2.3%) and more commonly seen in ear procedures and with large postoperative defects. Although grafts and second-stage interpolation flaps can be associated with a higher rate of perioperative complications, all cases of bleeding and infection in this study were in patients who had intermediate layer closures.

Targets for repair: detecting and quantifying DNA damage with fluorescence-based methodologies

Detection and characterization of DNA damage is essential for evaluating genotoxicity, monitoring DNA repair, developing biomarkers for exposures, and evaluating the efficacy of chemotherapies. These diverse applications for DNA damage measurements have spurred the continual development and refinement of methodologies for detecting, characterizing, and quantifying DNA damage from isolated DNA and in cells and tissues. Current damage detection methods cover a wide range of techniques from radiolabeling to mass spectrometry, and use of these techniques varies widely based on expense, expertise, and knowledge of adduct formation. More generalizable, easy-to-use methods for detecting and quantifying DNA damage are needed, and there has been an emergence of fluorescence-based methodologies to address this need. Developments in these fluorescence-based strategies are reviewed here.

Variations in nuclear localization strategies among pol X family enzymes

Despite the essential roles of pol X family enzymes in DNA repair, information about the structural basis of their nuclear import is limited. Recent studies revealed the unexpected presence of a functional nuclear localization signal (NLS) in DNA polymerase β, indicating the importance of active nuclear targeting, even for enzymes likely to leak into and out of the nucleus. The current studies further explore the active nuclear transport of these enzymes by identifying and structurally characterizing the functional NLS sequences in the three remaining human pol X enzymes: terminal deoxynucleotidyl transferase (TdT), DNA polymerase mu (pol μ) and DNA polymerase lambda (pol λ). NLS identifications are based on Importin α (Impα) binding affinity determined by fluorescence polarization of fluorescein‐labeled NLS peptides, X‐ray crystallographic analysis of the Impα∆IBB•NLS complexes and fluorescence‐based subcellular localization studies. All three polymerases use NLS sequences located near their N‐terminus; TdT and pol μ utilize monopartite NLS sequences, while pol λ utilizes a bipartite sequence, unique among the pol X family members. The pol μ NLS has relatively weak measured affinity for Impα, due in part to its proximity to the N‐terminus that limits non‐specific interactions of flanking residues preceding the NLS. However, this effect is partially mitigated by an N‐terminal sequence unsupportive of Met1 removal by methionine aminopeptidase, leading to a 3‐fold increase in affinity when the N‐terminal methionine is present. Nuclear targeting is unique to each pol X family enzyme with variations dependent on the structure and unique functional role of each polymerase.

A truly safer alternative? Sunless tanning products and the unknown

Ultraviolet radiation (UVR) exposure is increasingly appreciated as a significant risk factor for the development skin cancers. Exposure to UVR through tanning behaviors, particularly the use of indoor tanning (IT) lamps or bed, has been attributed to the increasing incidence of skin cancer among adolescents and young adults (AYA), with individuals who initiate IT before the age of 35, significantly increasing their risk of developing skin cancer (Wehner et al., 2012). These findings have prompted age restriction legislation in a number of states and recommendations by the FDA for uniform, national legislation restricting sunlamp product use to individuals ≥18 years and requiring adult users to sign a risk acknowledgment statement before their first IT session and every six months following.(FDA, 2015) There is some evidence that rigorous IT policies and restrictions reduce the prevalence of IT among AYA females (Guy et al., 2014a; Guy et al., 2014b; Hester et al., 2005). However, compliance with tanning restrictions are highly varied from state to state, so the efficacy of these restrictions is hard to gauge (Williams et al., 2018). AYAs feel societal pressure to be tan due to the value of tanned appearance as a firmly established social norm (Dennis et al., 2009; Lazovich and Forster, 2005). Particularly in modern Western culture, tanned skin is frequently synonymous with attractiveness or healthiness, a concept consistently reinforced by media and peer influences (Dennis et al., 2009; Lazovich and Forster, 2005; Fogel and Krausz, 2013). AYAs are especially vulnerable to these influences, and while legislation may restrict their access to UV tanning options such as IT, it will likely have no bearing on their desire to achieve and maintain a tanned appearance (Hillhouse et al., 2009; Stapleton et al., 2008; Cafri et al., 2008; Banerjee et al., 2015). Consequently, many AYAs are likely to turn to other methods of tanning their skin, particularly those who are disinclined to tan naturally (Quinn et al., 2015). For these individuals, sunless tanning products (STPs) are an increasingly attractive and easily accessible alternative to IT and outdoor tanning (Quinn et al., 2015; Sheehan and Lesher, 2005; Mahoney et al., 2012; Sahn et al., 2012; Russo et al., 2012). STPs, which include spray tanning and the use of gels, foams, creams, and/or lotions, provide a tanned appearance without UV exposure. Most over-the-counter STPs contain dihydroxyacetone (DHA), the most popular and longest-used FDA-approved browning agent. DHA is a keto sugar that undergoes a Maillard-like reaction with the amines in the skins surface to produce a brown color within 3 h of application (Johnson and Fusaro, 1998). Darker skin is achieved by increasing the percentage of DHA in the STP (typically between 2 and 15%) and by increasing the frequency of application. There has been a prevailing attitude that DHA is “safe,” largely because it is a common by-product in carbohydrate metabolism and because its absorption has been thought to be limited to the keratinized outer layer of the epidermis, the stratum corneum. However, several reports have now shown that up to 20% of an applied 5% dose of DHA penetrates into and remains within the underlying viable layers of the epidermis and dermis (Yourick et al., 2004). This penetration into viable skin raises concerns about the safety of DHA. Surprisingly, there is a lack of literature examining exposures to DHA, particularly aerosolized exposures, such as would be experienced by spray tanning. DHA has been found to be cytotoxic to keratinocyte and melanoma cell models (Petersen et al., 2004; Smith et al., 2018), and co-exposure of DHA with UV has been shown to increase the formation of free radicals in ex vivo skin (Jung et al., 2008). While these results may not directly reflect potential biological effects of DHA in the complex skin microenvironment, they raise concerns about exposures to DHA, particularly through internal exposures from inhalation, absorption into mucous membranes, or through broken skin. Additionally, they raise fundamental questions about how these products are used. Despite their promotion in recent years by some as a safer alternative to UV tanning, there are limited data available on the use of STPs (Pagoto et al., 2010). Several surveys have measured sunless tanning

Analysis of single, cisplatin-induced DNA bends by atomic force microscopy and simulations

Bent DNA, or DNA that is locally more flexible, is a recognition motif for many DNA binding proteins. These DNA conformational properties can thus influence many cellular processes, such as replication, transcription, and DNA repair. The importance of these DNA conformational properties is juxtaposed to the experimental difficulty to accurately determine small bends, locally more flexible DNA, or a combination of both (bends with increased flexibility). In essence, many current bulk methods use average quantities, such as the average end‐to‐end distance, to extract DNA conformational properties; they cannot access the additional information that is contained in the end‐to‐end distance distributions. We developed a method that exploits this additional information to determine DNA conformational parameters. The method is based on matching end‐to‐end distance distributions obtained experimentally by atomic force microscopy imaging to distributions obtained from simulations. We applied this method to investigate cisplatin GG biadducts. We found that cisplatin induces a bend angle of 36° and softens the DNA locally around the bend.

Significant Engagement in Tanning Behaviors by Men at a U.S. University

Adolescent and young adult men are a potentially overlooked population with respect to risky tanning behaviors. This study sought to determine the prevalence of various modes of tanning and associated variables among young men in a university setting in the southeastern United States. Undergraduate students at a public institution in Mobile, Alabama were surveyed electronically in March 2016. Of the 818 undergraduate men surveyed, over 90% reported tanning behaviors, with 37% reporting engaging in indoor tanning. Additionally, over 25% reported engaging in two or more types of tanning concurrently. These findings indicate that early intervention efforts targeting young men are needed to reduce risky tanning behaviors and associated negative health outcomes.