Oxidative stress‐induced angiogenesis is mediated by miR‐205‐5p

miR‐205‐5p is known to be involved in VEGF‐related angiogenesis and seems to regulate associated cell signalling pathways, such as cell migration, proliferation and apoptosis. Therefore, several studies have focused on the potential role of miR‐205‐5p as an anti‐angiogenic factor. Vascular proliferation is observed in diabetic retinopathy and the ‘wet’ form of age‐related macular degeneration. Today, the most common treatments against these eye‐related diseases are anti‐VEGF therapies. In addition, both AMD and DR are typically associated with oxidative stress; hence, the use of antioxidant agents is accepted as a co‐adjuvant therapy for these patients. According to previous data, ARPE‐19 cells release pro‐angiogenic factors when exposed to oxidative insult, leading to angiogenesis. Matching these data, results reported here, indicate that miR‐205‐5p is modulated by oxidative stress and regulates VEGFA‐angiogenesis. Hence, miR‐205‐5p is proposed as a candidate against eye‐related proliferative diseases.     

X-Ray Crystallography of Bacteriorhodopsin and Its Photointermediates: Insights into the Mechanism of Proton Transport

In the last few years, detailed structural information from high-resolution x-ray diffraction has been added to the already large body of spectroscopic and mutational data on the bacteriorhodopsin proton transport cycle. Although there are still many gaps, it is now possible to reconstruct the main events in the translocation of the proton and how they are coupled to the photoisomerization of the retinal chromophore. Future structural work will concentrate on describing the details of the individual proton transfer steps during the photocycle.     

Actions of Ca2+ on an Early Stage in Phototransduction Revealed by the Dynamic Fall in Ca2+ Concentration during the Bright Flash Response

To study the actions of Ca²⁺ on “early” stages of the transduction cascade, changes in cytoplasmic calcium concentration (Ca²⁺ _i) were opposed by manipulating Ca²⁺ fluxes across the rod outer segment membrane immediately following a bright flash. If the outer segment was exposed to 0 Ca²⁺/0 Na⁺ solution for a brief period immediately after the flash, then the period of response saturation was prolonged in comparison with that in Ringer solution. But if the exposure to 0 Ca²⁺/0 Na⁺ solution instead came before or was delayed until 1 s after the flash then it had little effect. The degree of response prolongation increased with the duration of the exposure to 0 Ca²⁺/0 Na⁺ solution, revealing a time constant of 0.49 ± 0.03 s. By the time the response begins to recover from saturation, Ca²⁺ _i seems likely to have fallen to a similar level in each case. Therefore the prolongation of the response when Ca²⁺ _i was prevented from changing immediately after the flash seems likely to reflect the abolition of actions of the usual dynamic fall in Ca²⁺ _i on an early stage in the transduction cascade at a site which is available for only a brief period after the flash. One possibility is that the observed time constant corresponds to the phosphorylation of photoisomerized rhodopsin.     

Site of conversion of endogenous all-trans-retinoids to 11-cis-retinoids in the bovine eye

By use of a new high-resolution high-pressure liquid chromatographic method for the separation of isomeric forms of retinol, retinal, retinyl ester and retinal oxime, various retinoids were analyzed in separated retinal pigment epithelial tissue or neural retinal tissue from fresh bleached bovine eyes after incubation in the dark at either 30 or 4°C for 90 min. 11-cis-Retinoids significantly increased during incubation at 30°C, relative to those at 4°C, in the retinal pigment epithelium, but not in the retina. The major forms of vitamin A in incubated retinal pigment epithelium and neural retina were retinyl esters (70%) and all-trans-retinol (69%), respectively. Thus, in keeping with observations on the isomerization of radioactive retinol in homogenates of eye tissues, the retinal pigment epithelium seems to be the primary site of 11-cis-retinoid formation from endogenous all-trans-retinoids in the bovine eye.