Fast green FCF inhibits Aß fibrillogenesis, disintegrates mature fibrils, reduces the cytotoxicity, and attenuates Aß-induced cognitive impairment in mice.

Fast green FCF (FGF) is often used in foods, pharmaceuticals, and cosmetics. However, little is known about the interactions of FGF with amyloid-ß protein (Aß) associated with Alzheimer's disease. In this study, the inhibitory effects of FGF on Aß fibrillogenesis, the disruption of preformed Aß fibrils, the reduction of Aß-induced cytotoxicity, and the attenuation of Aß-induced learning and memory impairments in mice were investigated. FGF significantly inhibited Aß fibrillogenesis and disintegrated the mature fibrils as evidenced by thioflavin T fluorescence and atomic force microscopy studies. Co-incubation of Aß with FGF greatly reduced Aß-induced cytotoxicity in vitro. Moreover, FGF showed a protective effect against cognitive impairment in Aß-treated mice. Molecular dynamics simulations further showed that FGF could synergistically interact with the Aß17-42 pentamer via electrostatic interactions, hydrogen bonds and π-π interactions, which reduced the ß-sheet content, and disordered random coils and bend structures of the Aß17-42 pentamer. This study offers a comprehensive understanding of the inhibitory effects of FGF against Aß neurotoxicity, which is critical for the search of effective food additives that can combat amyloid-associated disease.

Antimicrobial activity of topical dyes used in clinical veterinary ophthalmology.

OBJECTIVE: To evaluate in vitro the antibacterial effects of fluorescein, rose bengal, and lissamine green topical ophthalmic dyes against selected Gram-positive and Gram-negative bacteria, and to evaluate whether preserved or preservative-free fluorescein solutions are able to inhibit or potentiate bacterial growth. PROCEDURES: Susceptibility testing was performed using the Kirby-Bauer disk diffusion method plated with clinical ocular isolates of Staphylococcus aureus, Staphylococcus pseudintermedius, Streptococcus spp., Escherichia coli, and Pseudomonas aeruginosa. Bacterial growth inhibition was evaluated 24 hours following the addition of commercially available fluorescein, rose bengal, and lissamine green sterile strips. Antimicrobial effectiveness testing was performed by inoculation of compounded 1% dye solutions, both with and without preservatives (fluorescein and lissamine contained thiomersal, and rose bengal contained nipagin and nepazol), with the five previously mentioned bacteria. Growth was evaluated at days 7, 14, and 28. RESULTS: All dyes showed antibacterial activity against Gram-positive organisms. Preservative-free compounded 1% fluorescein solution inhibited growth of Gram-positive organisms but not of Gram-negative organisms. Preservative-free rose bengal and lissamine green inhibited growth of both types of organisms. CONCLUSIONS: Preferably, ocular surface samples for antimicrobial culture should be taken prior to the administration of topical dyes, due to their potential antibacterial activity, particularly if undiluted strips are applied directly or commercial fluorescein solutions are used and not immediately rinsed. Ophthalmic dye solutions containing preservative are safe from bacterial growth for up to 28 days if properly handled and stored. The use of preservative-free fluorescein solutions should be avoided and preservative-free rose bengal and lissamine green should be handled carefully.

PCR assessment of HSV-1 corneal infection in animals treated with rose bengal and lissamine green B.

PURPOSE: In vivo, the ophthalmic dye rose bengal displays profound antiviral effects against herpes simplex virus (HSV)-1, thus limiting its utility in diagnosis of epithelial keratitis when used before viral culture is performed. In contrast, lissamine green B does not possess significant antiviral activity in vivo. To determine whether polymerase chain reaction (PCR) could successfully detect HSV-1 DNA in ocular samples that have been exposed to ophthalmic dyes, animal models were used to observe the presence of infectious HSV-1 and viral DNA in eyes treated with rose bengal or lissamine green B. METHODS: Animals were bilaterally infected with HSV-1 strain H129, and at daily intervals up to 16 days post infection (dpi) rose bengal or lissamine green B was instilled in the left eyes. The right eyes were not treated with dyes. Swabs of the dye-treated and untreated eyes were assayed by PCR for viral infectivity by culture and the presence of DNA specific for a fragment of the HSV-1 DNA polymerase gene. RESULTS: A statistically equivalent number of samples from lissamine green B-treated and untreated eyes were positive by both viral culture and PCR. In contrast, rose bengal significantly decreased the infectious virus present in ocular secretions. A total of 44% and 78% of the rose bengal-treated and untreated eye samples, respectively, were positive by culture from 1 through 16 dpi. PCR was more sensitive than culture for detection of HSV-1 in rose bengal-treated eyes, in that 74% of rose bengal-treated samples were positive by PCR compared with 44% that were positive by culture during the 16-day period studied. It was also noted that both rose bengal and lissamine green B treatments slightly prolonged the period during which viral DNA was detectable in ocular secretions by PCR, possibly because the singlet oxygen produced by these photoreactive dyes compromised ocular cellular, humoral, and nonspecific immune factors allowing viral DNA to persist for slightly longer periods. CONCLUSIONS: PCR can successfully detect HSV-1 DNA in ocular samples that are culture negative and contain rose bengal or lissamine green B. Visualization of ocular epithelial defects with lissamine green B does not interfere with detection of infectious virus or HSV-1 DNA.