Many layered crystal phases can be exfoliated or assembled into ultrathin 2D nanosheets with novel properties not achievable by particulate or fibrous nanoforms. Among these 2D materials are ...manganese dioxide (MnO2) nanosheets, which have applications in batteries, catalysts, and biomedical probes. A novel feature of MnO2 is its sensitivity to chemical reduction leading to dissolution and Mn2+ release. Biodissolution is critical for nanosafety assessment of 2D materials, but the timing and location of MnO2 biodissolution in environmental or occupational exposure scenarios are poorly understood. This work investigates the chemical and colloidal dynamics of MnO2 nanosheets in biological media for environmental and human health risk assessment. MnO2 nanosheets are insoluble in most aqueous phases, but react with strong and weak reducing agents in biological fluid environments. In vitro, reductive dissolution can be slow enough in cell culture media for MnO2 internalization by cells in the form of intact nanosheets, which localize in vacuoles, react to deplete intracellular glutathione, and induce cytotoxicity that is likely mediated by intracellular Mn2+ release. The results are used to classify MnO2 nanosheets within a new hazard screening framework for 2D materials, and the implications of MnO2 transformations for nanotoxicity testing and nanosafety assessment are discussed.
Manganese dioxide (MnO2) nanosheets undergo complex reductive dissolution in the presence of diverse biomolecular reducing agents. When dissolution in cell culture media is slow, intact nanosheets can enter cells, where they can deplete intracellular glutathione and induce cytotoxicity through intracellular Mn2+ release. The results are used to classify MnO2 nanosheets within a new biopersistence‐based hazard screening framework for 2D materials.
Genomic instability is one of the primary models of carcinogenesis and a feature of almost all cancers. Homologous recombination (HR) repair protects against genomic instability by maintaining high ...genomic fidelity during the repair of DNA double strand breaks. The defining step of HR repair is the formation of the Rad51 nucleofilament, which facilitates the search for a homologous sequence and invasion of the template DNA strand. Particulate hexavalent chromium (Cr(VI)), a human lung carcinogen, induces DNA double strand breaks and chromosome instability. Since the loss of HR repair increases Cr(VI)-induced chromosome instability, we investigated the effect of extended Cr(VI) exposure on HR repair. We show acute (24 h) Cr(VI) exposure induces a normal HR repair response. In contrast, prolonged (120 h) exposure to particulate Cr(VI) inhibited HR repair and Rad51 nucleofilament formation. Prolonged Cr(VI) exposure had a profound effect on Rad51, evidenced by reduced protein levels and Rad51 mislocalization to the cytoplasm. The response of proteins involved in Rad51 nuclear import and nucleofilament formation displayed varying responses to prolonged Cr(VI) exposure. BRCA2 formed nuclear foci after prolonged Cr(VI) exposure, while Rad51C foci formation was suppressed. These results suggest that particulate Cr(VI), a major chemical carcinogen, inhibits HR repair by targeting Rad51, causing DNA double strand breaks to be repaired by a low fidelity, Rad51-independent repair pathway. These results further enhance our understanding of the underlying mechanism of Cr(VI)-induced chromosome instability and thus, carcinogenesis.
Chromosome instability, a hallmark of lung cancer, is a driving mechanism for hexavalent chromium Cr(VI) carcinogenesis in humans. Cr(VI) induces structural and numerical chromosome instability in ...human lung cells by inducing DNA double-strand breaks and inhibiting homologous recombination repair and causing spindle assembly checkpoint (SAC) bypass and centrosome amplification. Great whales are long-lived species with long-term exposures to Cr(VI) and accumulate Cr in their tissue, but exhibit a low incidence of cancer. Data show Cr(VI) induces fewer chromosome aberrations in whale cells after acute Cr(VI) exposure suggesting whale cells can evade Cr(VI)-induced chromosome instability. However, it is unknown if whales can evade Cr(VI)-induced chromosome instability. Thus, we tested the hypothesis that whale cells resist Cr(VI)-induced loss of homologous recombination repair activity and increased SAC bypass and centrosome amplification. We found Cr(VI) induces similar amounts of DNA double-strand breaks after acute (24 h) and prolonged (120 h) exposures in whale lung cells, but does not inhibit homologous recombination repair, SAC bypass, or centrosome amplification, and does not induce chromosome instability. These data indicate whale lung cells resist Cr(VI)-induced chromosome instability, the major driver for Cr(VI) carcinogenesis at a cellular level, consistent with observations that whales are resistant to cancer.
The development and production of engineered 2D nanomaterials are expanding exponentially, increasing the risk of their release into the aquatic environment. A recent study showed 2D MnO
2
...nanosheets, under development for energy and biomedical applications, dissolve upon interaction with biological reducing agents, resulting in depletion of intracellular glutathione levels within fish gill cells. However, little is known concerning their toxicity and interactions with subcellular organelles. To address this gap, we examined cellular uptake, cytotoxicity and mitochondrial effects of 2D MnO
2
nanosheets using an in vitro fish gill cell line to represent a target tissue of rainbow trout, a freshwater indicator species. The data demonstrate cellular uptake of MnO
2
nanosheets into lysosomes and potential mechanisms of dissolution within the lysosomal compartment. MnO
2
nanosheets induced severe mitochondrial dysfunction at sub-cytotoxic doses. Quantitative, single cell fluorescent imaging revealed mitochondrial fission and impaired mitochondrial membrane potential following MnO
2
nanosheet exposure. Seahorse analyses for cellular respiration revealed that MnO
2
nanosheets inhibited basal respiration, maximal respiration and the spare respiratory capacity of gill cells, indicating mitochondrial dysfunction and reduced cellular respiratory activity. MnO
2
nanosheet exposure also inhibited ATP production, further supporting the suppression of mitochondrial function and cellular respiration. Together, these observations indicate that 2D MnO
2
nanosheets impair the ability of gill cells to respond to energy demands or prolonged stress. Finally, our data demonstrate significant differences in the toxicity of the 2D MnO
2
nanosheets and their microparticle counterparts. This exemplifies the importance of considering the unique physical characteristics of 2D nanomaterials when conducting safety assessments.
To evaluate whether topical acrizanib (LHA510), a small-molecule vascular endothelial growth factor receptor inhibitor, could suppress the need for anti–vascular endothelial growth factor therapy ...over a 12-week period in patients with neovascular age-related macular degeneration.
A phase 2 multicenter randomized double-masked, vehicle-controlled proof-of-concept study.
Trial includes n = 90 patients with active choroidal neovascularization due to neovascular age-related macular degeneration and under anti–vascular endothelial growth factor treatment. All patients received an intravitreal injection of ranibizumab at baseline and were retreated when there was evidence of disease recurrence (rescue). Patients were randomized 1:1 to receive topical LHA510 or vehicle for 12 weeks. Drops were administered twice a day for 8 weeks and then 3 times a day for the last 4 weeks.
The primary outcome was the number of patients requiring rescue over 84 days of topical dosing. Key secondary outcome measures were time to first rescue, total number of ranibizumab injections, changes in central subfield thickness, and changes of visual acuity from baseline to day 84.
The extended per protocol set included 70 patients of whom 25 of 33 patients in the LHA510 group (75.8%) and 25 of 37 patients in the placebo group (67.6%) required rescue by day 84 (P = .8466). Secondary and subgroup analysis did not support evidence of efficacy. Twenty-one of 46 patients administered LHA510 developed a reversible corneal haze that resolved with cessation of treatment and did not recur in patients restarted at once daily frequency.
In spite of extensive optimization for topical efficacy, LHA510 failed to demonstrate clinical efficacy.
Chromosome instability is a common feature of cancers that forms due to the misrepair of DNA double strand breaks. Homologous recombination (HR) repair is a high fidelity DNA repair pathway that ...utilizes a homologous DNA sequence to accurately repair such damage and protect the genome. Prolonged exposure (>72h) to the human lung carcinogen, particulate hexavalent chromium (Cr(VI)), inhibits HR repair, resulting in increased chromosome instability in human cells. Comparative studies have shown acute Cr(VI) exposure induces less chromosome damage in whale cells than human cells, suggesting investigating the effect of this carcinogen in other species may inform efforts to prevent Cr(VI)-induced chromosome instability. Thus, the goal of this study was to determine the effect of prolonged Cr(VI) exposure on HR repair and clastogenesis in North Atlantic right whale (Eubalaena glacialis) lung cells. We show particulate Cr(VI) induces HR repair activity after both acute (24h) and prolonged (120h) exposure in North Atlantic right whale cells. Although the RAD51 response was lower following prolonged Cr(VI) exposure compared to acute exposure, the response was sufficient for HR repair to occur. In accordance with active HR repair, no increase in Cr(VI)-induced clastogenesis was observed with increased exposure time. These results suggest prolonged Cr(VI) exposure affects HR repair and genomic stability differently in whale and human lung cells. Future investigation of the differences in how human and whale cells respond to chemical carcinogens may provide valuable insight into mechanisms of preventing chemical carcinogenesis.
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•Sister chromatid exchanges increased after acute and prolonged chromate exposure.•Acute chromate exposure induced more RAD51 foci formation than prolonged exposure.•Acute and prolonged chromate exposure are comparably genotoxic to right whale cells.
One Environmental Health has emerged as an important area of research that considers the interconnectedness of human, animal and ecosystem health with a focus on toxicology. The great whales in the ...Gulf of Maine are important species for ecosystem health, for the economies of the Eastern seaboard of the United States, and as sentinels for human health. The Gulf of Maine is an area with heavy coastal development, industry, and marine traffic, all of which contribute chronic exposures to environmental chemicals that can bioaccumulate in tissues and may gradually diminish an individual whale's or a population's fitness. We biopsied whales for three seasons (2010–2012) and measured the levels of 25 metals and selenium in skin biopsies collected from three species: humpback whales (Megaptera novaeangliae), fin whales (Balaenoptera physalus), and a minke whale (Balaenoptera acutorostrata). We established baseline levels for humpback and fin whales. Comparisons with similar species from other regions indicate humpback whales have elevated levels of aluminum, chromium, iron, magnesium, nickel and zinc. Contextualizing the data with a One Environmental Health approach finds these levels to be of potential concern for whale health. While much remains to understand what threats these metal levels may pose to the fitness and survival of these whale populations, these data serve as a useful and pertinent start to understanding the threat of pollution.
•Gulf of Maine whales exhibited metal levels in their skin tissues.•Chromium levels in the whales were similar to levels reported in exposed workers.•Nickel levels in the whales were similar to levels reported in exposed workers.
The aim of this study was to focus on hexavalent chromium, Cr(VI), a chemical carcinogen and major public health concern, and consider its ability to impact DNA double strand break repair. We further ...focused on particulate Cr(VI), because it is the more potent carcinogenic form of Cr(VI). DNA double strand break repair serves to protect cells against the detrimental effects of DNA double strand breaks. For particulate Cr(VI), data show DNA double strand break repair must be overcome for neoplastic transformation to occur. Acute Cr(VI) exposures reveal a robust DNA double strand break repair response, however, longer exposures have not been considered. Using the comet assay, we found longer exposures to particulate zinc chromate induced concentration-dependent increases in DNA double strand breaks indicating breaks were occurring throughout the exposure time. Acute (24 h) exposure induced DNA double strand break repair signaling by inducing Mre11 foci formation, ATM phosphorylation and phosphorylated ATM foci formation, Rad51 protein levels and Rad51 foci formation. However, longer exposures reduced the Rad51 response. These data indicate a major chemical carcinogen can simultaneously induce DNA double strand breaks and alter their repair and describe a new and important aspect of the carcinogenic mechanism for Cr(VI).
Many layered crystal phases can be exfoliated or assembled into ultrathin 2D nanosheets with novel properties not achievable by particulate or fibrous nanoforms. Among these 2D materials are ...manganese dioxide (MnO
) nanosheets, which have applications in batteries, catalysts, and biomedical probes. A novel feature of MnO
is its sensitivity to chemical reduction leading to dissolution and Mn
release. Biodissolution is critical for nanosafety assessment of 2D materials, but the timing and location of MnO
biodissolution in environmental or occupational exposure scenarios are poorly understood. This work investigates the chemical and colloidal dynamics of MnO
nanosheets in biological media for environmental and human health risk assessment. MnO
nanosheets are insoluble in most aqueous phases, but react with strong and weak reducing agents in biological fluid environments. In vitro, reductive dissolution can be slow enough in cell culture media for MnO
internalization by cells in the form of intact nanosheets, which localize in vacuoles, react to deplete intracellular glutathione, and induce cytotoxicity that is likely mediated by intracellular Mn
release. The results are used to classify MnO
nanosheets within a new hazard screening framework for 2D materials, and the implications of MnO
transformations for nanotoxicity testing and nanosafety assessment are discussed.
Previous evidence suggests soy genistein may be protective against prostate cancer, but whether this protection involves an estrogen receptor (ER)-dependent mechanism is unknown. To test the ...hypothesis that phytoestrogens may act through ERα or ERβ to play a protective role against prostate cancer, we bred transgenic mice lacking functional ERα or ERβ with transgenic adenocarcinoma of mouse prostate (TRAMP) mice. Dietary genistein reduced the incidence of cancer in ER wild-type (WT)/transgenic adenocarcinoma of mouse prostate mice but not in ERα knockout (KO) or ERβKO mice. Cancer incidence was 70% in ERWT mice fed the control diet compared with 47% in ERWT mice fed low-dose genistein (300 mg/kg) and 32% on the high-dose genistein (750 mg/kg). Surprisingly, genistein only affected the well differentiated carcinoma (WDC) incidence but had no effect on poorly differentiated carcinoma (PDC). No dietary effects have been observed in either of the ERKO animals. We observed a very strong genotypic influence on PDC incidence, a protective effect in ERαKO (only 5% developed PDC), compared with 19% in the ERWT, and an increase in the incidence of PDC in ERβKO mice to 41%. Interestingly, immunohistochemical analysis showed ERα expression changing from nonnuclear in WDC to nuclear in PDC, with little change in ERβ location or expression. In conclusion, genistein is able to inhibit WDC in the presence of both ERs, but the effect of estrogen signaling on PDC is dominant over any dietary treatment, suggesting that improved differential targeting of ERα vs. ERβ would result in prevention of advanced prostate cancer.
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