DNA Damage Increases Secreted Aß40 and Aß42 in Neuronal Progenitor Cells: Relevance to Alzheimer's Disease.

BACKGROUND: Recent studies suggest a strong association between neuronal DNA damage, elevated levels of amyloid-ß (Aß), and regions of the brain that degenerate in Alzheimer's disease (AD). OBJECTIVE: To investigate the nature of this association, we tested the hypothesis that extensive DNA damage leads to an increase in Aß40 and Aß42 generation. METHODS: We utilized an immortalized human neuronal progenitor cell line (NPCs), ReN VM GA2. NPCs or 20 day differentiated neurons were treated with hydrogen peroxide or etoposide and allowed to recover for designated times. Sandwich ELISA was used to assess secreted Aß40 and Aß42. Western blotting, immunostaining, and neutral comet assay were used to evaluate the DNA damage response and processes indicative of AD pathology. RESULTS: We determined that global hydrogen peroxide damage results in increased cellular Aß40 and Aß42 secretion 24 h after treatment in ReN GA2 NPCs. Similarly, DNA double strand break (DSB)-specific etoposide damage leads to increased Aß40 and Aß42 secretion 2 h and 4 h after treatment in ReN GA2 NPCs. In contrast, etoposide damage does not increase Aß40 and Aß42 secretion in post-mitotic ReN GA2 neurons. CONCLUSION: These findings provide evidence that in our model, DNA damage is associated with an increase in Aß secretion in neuronal progenitors, which may contribute to the early stages of neuronal pathology in AD.

Implications of sequence and timing of exposure for synergy between the pyrethroid insecticide alpha-cypermethrin and the entomopathogenic fungus Beauveria bassiana.

BACKGROUND: Combining low doses of chemical insecticides with entomopathogens constitutes a sustainable pest control method, but the significance of the timing and sequence of exposures needs clarification. We studied lethal effects of combinations of the entomopathogenic fungus Beauveria bassiana (KVL03-122) and the pyrethroid alpha-cypermethrin on the beetle Tenebrio molitor under varying timing and sequence of exposure. Synergy over time was evaluated in relation to the model of independent action (IA). We expected that increased progression of disease caused by B. bassiana would make beetles more susceptible to the insecticide, leading to enhanced synergy. RESULTS: Synergistic effects between B. bassiana and alpha-cypermethrin were observed when B. bassiana was applied first, but only when the interval between applications was >48 h. With 72 h between exposures, mortality had increased to 100% after 8 days, in contrast to the 60% mortality expected. No synergy was observed when the insecticide was applied prior to fungal exposure within 24 h. CONCLUSION: The sequence and timing of exposure do matter to achieve synergistic mortality by combining B. bassiana and alpha-cypermethrin, and the IA model proved to be a strong tool with which to evaluate the interactions of the two stressors over time. Pest control strategies could include B. bassiana followed by low-dose exposures to alpha-cypermethrin after 2-3 days. © 2018 Society of Chemical Industry.

Transcription-coupled homologous recombination after oxidative damage.

Oxidative DNA damage induces genomic instability and may lead to mutagenesis and carcinogenesis. As severe blockades to RNA polymerase II (RNA POLII) during transcription, oxidative DNA damage and the associated DNA strand breaks have a profoundly deleterious impact on cell survival. To protect the integrity of coding regions, high fidelity DNA repair at a transcriptionally active site in non-dividing somatic cells, (i.e., terminally differentiated and quiescent/G0 cells) is necessary to maintain the sequence integrity of transcribed regions. Recent studies indicate that an RNA-templated, transcription-associated recombination mechanism is important to protect coding regions from DNA damage-induced genomic instability. Here, we describe the discovery that G1/G0 cells exhibit Cockayne syndrome (CS) B (CSB)-dependent assembly of homologous recombination (HR) factors at double strand break (DSB) sites within actively transcribed regions. This discovery is a challenge to the current dogma that HR occurs only in S/G2 cells where undamaged sister chromatids are available as donor templates.

Poly(vinyl alcohol) acetoacetate-based tissue adhesives are non-cytotoxic and non-inflammatory.

Polymer-based tissue adhesives composed of poly(vinyl alcohol) acetoacetate (PVOH acac) and cross-linking amines were investigated for their effects on cell survival and inflammatory cell activation using in vitro mouse cell cultures. Cytotoxicity of tissue adhesives was evaluated by placing adhesives in direct contact with 3T3 fibroblast cells. Tissue adhesives formulated from PVOH acac and 3-aminopropyltrialkoxysilane (APS) were non-cytotoxic to fibroblasts; adhesives formulated from PVOH acac and aminated poly(vinyl alcohol) (PVOH amine) were also non-cytotoxic to fibroblasts. In contrast, a commercial adhesive composed of 2-octyl cyanoacrylate was highly cytotoxic to fibroblasts. The inflammatory potential of tissue adhesives was evaluated by exposing J774 macrophage cells to adhesives, and measuring TNF-alpha release from macrophages. PVOH acac-based tissue adhesives did not elicit inflammatory TNF-alpha release from macrophages. These results suggest that PVOH acac-based tissue adhesives are non-cytotoxic and non-inflammatory. Such tissue adhesives represent a promising technology for a variety of medical applications, including surgical wound closure and tissue engineering, and the results are also significant in the design of in vitro cell culture systems to study biomaterials.

Polysaccharide-based tissue adhesives for sealing corneal incisions.

PURPOSE: To investigate the ability of a novel polysaccharide-based tissue adhesive to seal corneal incisions, and to determine the effect of the tissue adhesive on corneal endothelial cells. METHODS: A polysaccharide-based tissue adhesive composed of dextran aldehyde and star PEG amines was applied to a 5-mm corneal incision on an enucleated rabbit eye, and the leak pressure of the eye was measured. The tissue adhesive was additionally incubated in direct contact with bovine corneal endothelial cells to evaluate cytotoxicity. RESULTS: The polysaccharide-based tissue adhesive was successful in sealing corneal incisions to pressures of > 10 psi (500 mmHg). The tissue adhesive was non-cytotoxic to bovine corneal endothelial cells. CONCLUSIONS: Polysaccharide-based tissue adhesives are efficacious in sealing corneal wounds and are non-cytotoxic to corneal endothelial cells. Such adhesives represent a promising new technology for ophthalmic surgery.

Interactions of polysaccharide-based tissue adhesives with clinically relevant fibroblast and macrophage cell lines.

The effects of polysaccharide-based tissue adhesives on cell survival and inflammatory cell activation were determined using in vitro mouse cell cultures. Cytotoxicity of tissue adhesives was evaluated by placing adhesives in direct contact with 3T3 fibroblast cells. Polysaccharide-based tissue adhesives composed of dextran aldehyde and star PEG amine were non-cytotoxic to fibroblasts; in contrast, a commercial adhesive composed of 2-octyl cyanoacrylate was highly cytotoxic to fibroblasts. The inflammatory potential of tissue adhesives was evaluated by exposing J774 macrophage cells to adhesives, and measuring TNF-alpha release from macrophages. Polysaccharide-based tissue adhesives did not elicit inflammatory TNF-alpha release from macrophages. These results suggest that polysaccharide-based tissue adhesives are non-cytotoxic and non-inflammatory; the results are therefore significant in the design of in vitro cell culture systems to study biomaterials.