Browsing by Author "Friguet, Bertrand"
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- ItemAdvanced Glycation Endproducts Induce Photocrosslinking and Oxidation of Bovine Lens Proteins Through Type-I Mechanism(2009) Fuentealba Patiño, Denis Alberto; Friguet, Bertrand; Silva Stevens, Eduardo Andrés
- ItemAutosensitized oxidation of glycated bovine lens proteins irradiated with UVA-visible light at low oxygen concentration(2008) Ávila, Felipe; Matus, Alex; Fuentealba Patiño, Denis Alberto; Lissi, Eduardo; Friguet, Bertrand; Silva Stevens, Eduardo Andrés
- ItemOxidative modifications in crystallin proteins and lens epithelial cells associated with photosensitized reactions mediated by the major chromophore arising from glucose degradation(2016) Vargas Brancoli, Francisco José; Becker C., María Inés; Friguet, Bertrand; Silva S., E.
- ItemPhotosensitized reactions mediated by the major chromophore arising from glucose decomposition, result in oxidation and cross-linking of lens proteins and activation of the proteasome(ELSEVIER SCIENCE BV, 2012) Avila, Felipe; Trejo, Sebastian; Baraibar, Martin A.; Friguet, Bertrand; Silva, EduardoGlucose solutions incubated at low oxygen concentration gave rise to the appearance of an absorption band in the UVA-visible region after 10 days. Further characterization evidenced that this band was composed by a single chomophore with maximum absorption bands at 335 and 365 nm. HPLC/MS and UV spectroscopy assays indicated that this product is composed by five unities of furan. Importantly, the presence of a compound with identical spectral and chromatographic properties was observed in the water-soluble fraction of cataractous human eye lenses. The photo-biological effects of this glucose-derived chromophore (GDC) have been addressed using targets of biological relevance, such as water-soluble proteins from eye lens and the proteasome present in this protein mixture. Increased protein oxidation and protein crosslinking was observed when lens proteins were exposed to UVA-visible light in the presence of GDC under a 5% and 20% oxygen atmosphere. In addition, an increased proteasome peptidase activity was also observed. However, the use of D2O resulted in decreased proteasome activity, suggesting that singlet oxygen promotes the impairment of proteasome activity. Our results suggest that the species generated by Type I and Type II mechanisms have opposite effects on proteasome activity, being Type I a positive activator while Type II lead to impairment of proteasome function. (C) 2011 Elsevier B.V. All rights reserved.
- ItemPhotosensitizing activity of endogenous eye lens chromophores : an attempt to unravel their contributions to photo‐aging and cataract disease(2015) Ávila, Felipe; Friguet, Bertrand; Silva Stevens, Eduardo Andrés
- ItemSimultaneous chemical and photochemical protein crosslinking induced by irradiation of eye lens proteins in the presence of ascorbate: the photosensitizing role of an UVA-visible-absorbing decomposition product of vitamin C(ROYAL SOC CHEMISTRY, 2010) Avila, Felipe; Friguet, Bertrand; Silva, EduardoExposure to light has been implicated as a risk factor during aging of the eye lens and in cataract generation. In order to visualize the actual effect of UVA-visible light on this tissue, we incubated water-soluble eye lens proteins with ascorbate in the presence and absence of UVA-visible light for 3, 6 and 9 days at low oxygen concentration. The samples incubated in the presence of light were characterized by an initially small but continuous increase over time of the protein crosslinking. This was not the result of more extensive glycation because the decrease in amino group content of the proteins and the decomposition of ascorbate was the same in both irradiated and unirradiated samples. The augmented crosslinking capacity observed in the presence of UVA-visible light is due to the generation of a chromophore from the decomposition of ascorbate. This chromophore, obtained after 3, 6 and 9 days of incubation of solutions containing only ascorbate, induces both protein-crosslinking and oxidation after exposure to UVA-visible light in the presence of lens proteins. The extent of the crosslinking was proportional to the amount of the chomophore present in the solution. The presence of this chromophore was also determined when ascorbate was incubated with four-fold higher concentrations of N-alpha-acetyl lysine and N-alpha-acetyl arginine. When these samples were used as photosensitizers, the crosslinking degree was conditioned by the presence of this chromophore; nonetheless, the ascorbate-mediated advanced glycation end product (AGE) generation also made a contribution. The results of this work indicate that ascorbate oxidation, which generates the AGEs responsible for the chemical crosslinking of the lens proteins, also simultaneously produces a chromophore that can act as a photosensitizer, further increasing the protein crosslinking.