Antioxidant effect of phenolic compounds (PC) at different concentrations in IEC-6 cells: A spectroscopic analysis.

Phenolic compounds (PC) have been proposed as natural antioxidant agents that protect cells against oxidative stress-related diseases. Nonetheless, their low bioavailability forecasts controversy about mechanisms on their in vivo scavenging activity against reactive oxygen species (ROS). It has been proposed that PC reduce directly ROS concentration. An alternative or complementary action of PC could be the activation of the cell's antioxidant pathway, involving the regulation of gene expression, like that initiated by the Nrf2 transcription factor. To date there is not enough experimental data to support or discard this possibility. In the present study, we evaluated the use of several PC to prevent peroxidation of macromolecules and to elicit the activation of the Nrf2 transcription factor in H2O2-stresed IEC-6 enterocytic cell line. Synchrotron microspectroscopy demonstrated that PC compounds protected proteins, lipids and nucleic acids against oxidation induced by H2O2. Immunofluorescence results showed that treatment with quercetin (Qc), catechin (Cat) and capsaicin (Cap) induced the translocation of Nrf2 into the nucleus, at the same level as did H2O2 treatment, thus mimicking the action of the endogenous cell response to peroxidation. Even though the detailed mechanism still needs to be elucidated, we demonstrated the activation of Nrf2 by PCs in response to oxidative stress.

Analysis of melanopsin gene expression in the rabbit retina at different ages.

Melanopsin is the photopigment of intrinsically photosensitive retinal ganglion cells that mediate non-visual responses to light. The aim of this study was to describe and analyze melanopsin gene expression in the rabbit retina at different ages and compare its expression with the prototypic gene of retinal ganglion cells (Thy-1 gene). Expression levels of OPN4, Thy-1, and GADPH genes were measured by real-time PCR at 3, 4, 8, 11, 12, 17, 19, 20, 23, 27, 32, and 47 postnatal days. We also regrouped the days before and after day 12 of life (pre-photic and post-photic stage, respectively). Average expression of the OPN4 gene between days was similar (P = 0.713), but was statistically different in the Thy-1 gene (P = 0.004). Also, no significant differences were found in OPN4 gene expression pre-photic and post-photic stage (P = 0.629); however, Thy-1 expression was higher in the pre-photic stage, almost double, than in the post-photic stage, with significant differences (P = 0.001). This is the first report describing OPN4 gene expression in the rabbit retina at different ages. We demonstrated that the OPN4 gene is constantly expressed at all early stages, even before the onset of photoentrainment by the pups and that Thy-1 and OPN4 gene expressions are out of phase.

Different specific binding sites of [3H]glycine and [3H]strychnine in synaptosomal membranes isolated from frog retina.

Synaptosomal fractions were isolated from frog retina: a fraction enriched in photoreceptor terminals (P1) and a second one (P2) containing interneurons terminals. We compared the binding of [3H]glycine and [3H]strychnine to membranes of these synaptosomes. The binding of both radioactive ligands was saturable and Na(+)-independent. [3H]Glycine bound to a single site in P1 and P2 synaptosomal fractions, with KD = 12 and 82 nM and BMax = 3.1 and 3.06 pmol/mg protein respectively. [3H]Strychnine bound to two sites in each one of the synaptosomal fractions. For P1 KD values were 3.9 and 18.7 nM, and BMax values were 1.1 and 7.1 pmol/mg protein, respectively. Membranes from the P2 synaptosomal fraction showed KD's of 0.6 and 48 nM and BMax's of 0.4 and 4.5 pmol/mg. Specific [3H]glycine binding was displaced by beta-alanine, 1-serine, d-serine and HA966, but not by strychnine, 7-chlorokynurenic or 5,7-dichloro-kynurenic acids. Specific [3H]strychnine binding was partially displaced by glycine and related amino acids and totally displaced only by 2-NH2-strychnine. Our results indicate the presence of high affinity binding sites for glycine and strychnine in frog retinal synaptosomal membranes. The pharmacological binding pattern indicates the presence of the strychnine sensitive glycine receptor as well as other sites. These might not include the NMDA receptor-associated glycine site.